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SCHX4011 CHEMCAD LAB

1. Job CHEMCAD TUTORIAL Date 01 17 2005 Time 12 07 59 T O amp on on 2 a 150 100 d 0 240 230 220 210 200 190 180 170 160 150 140 130 120 110 100 30 80 70 60 50 40 30 20 10 05 15 Temp F t Bubble e Dew a Vf 0 25000 e f 0 50000 e Critical Point For Help press F1 Logic 1110 741 Dev 624 447 Scale 0 768 Mode Simulation Steady State K PR H PR 12 08 PM You are now in a plot window and your available commands have changed Actually this window can be thought of as a plot edit window because it is the same for every plot It has the following commands File This command is for file management and print control as it is in every CHEMCAD window Edit Contains the undo cut copyand paste commands 31 View Controls the Toolbar and Status Bar display status Graph Provides access to zoom editing and data transfer facilities Window For arranging windows and icons Help Provides access to the on line help facility At this point let s make note of a few important items regarding CHEMCAD plots 1 To zoom in on a certain section of the plot point to one corner of the area that you want to zoom in on then click and drag i e hold down the left mouse button while you are moving the cursor to the opposite corner of that area When you release the mouse button the program will zoom in on the boxed in area To re
2. e The Stream Name field can display a stream label of up to 16 alphanumeric characters This field is optional and you can use any label you like e The next four fields Temp F Pres psia Vapor Fraction and Enthalpy MMBtu h are the thermodynamic properties of the stream According to the Gibbs Phase Rule once a mixture s composition is given specifying any two of these four thermodynamic properties will define the other two As such defining the composition temperature and pressure for a mixture uniquely defines its vapor fraction and enthalpy Alternatively defining the composition pressure and enthalpy will uniquely define the mixture s temperature and vapor fraction Since enthalpies are calculated relative to a datum the calculation of any given stream enthalpy is an involved process which is prone to errors For this reason CHEMCAD does not permit you to enter stream enthalpy as a constraint In addition to defining the stream s composition you must define exactly two of the following properties temperature pressure and vapor fraction The two variables that you specify will display as red text while the third variable and the value enthalpy will be displayed in black when you flash the stream An exception to this convention allows you to add heat duty with an empty stream If you specify a total component flow rate of zero you may specify a temperature pressure and enthalpy rate A stream defined this way is
3. Cp Cv Cp Cv Ideal M Vap 2 factor Yap viscosity Yap thm cond Liquid Mole flow rate I Mass flow rate M Lig enth M Liq entropy M Molecular wt M Lig act dens M Liq act vol I Lig Std Liq M Lig Std Yap Liquid Cp Liq Z factor I Liq viscosity M Lig them cond M Lig surf tens Latent heat PH value Cancel This dialog box is used to select which items for each stream are to be included in the databox Items are selected by clicking the small box next to them A checkmark indicates that the item will be included An empty box indicates that the box will not be included in the databox For the purposes of this demonstration let s accept the default settings Therefore please click the OK button to close this dialog box and save its current settings 4 You will now see the Data Box Settings dialog box This dialog box looks like this 42 E Data Box Settings Obviously this dialog box is used to make format settings for the databox For simplicity accept the default settings by pressing the OK button now The stream databox will appear in the upper left hand corner of the PFD 6 Now let s move the databox so that it fits along the bottom of our PFD To do this move the cursor until it is over the databox Then while holding down the left button move the mouse around until the databox is in the bottom center of the PFD like so oe ait KE fR amna T alo
4. The steps do not have to be performed in this order nor do all of them have to be done for each flowsheet All should be considered for each problem There are a series of Help facilities available throughout the program The bottom line of the screen provides a one sentence description of the current highlighted item The Help command provides access to the On line Manual which contains comprehensive technical information The F1 key provides context sensitive help place the cursor in a specific field and press the F1 key Use of these help facilities will ease your way through the program CHEMCAD is object oriented Therefore most input and editing can be done by double clicking or right clicking the object of the operation as well as by using the menu commands All stream and unit operations specifications input are accomplished using dialog boxes These dialog boxes are context specific and employ some combination of character fields combo boxes choice boxes and check boxes A DESCRIPTION OF THE TUTORIAL PROBLEM The problem to be solved in this tutorial is illustrated in Figure 1 below It is a condensate stabilizer plant Gas enters the system with the feed conditions shown It is our job to take this existing unit and determine new operating conditions and any necessary modifications The design requirements are as follows 1 The cricondotherm highest possible dew point of the product gas must be 20 F or less 2 Th
5. difficult The issues involved and the proper techniques for selection are described in the Thermodynamics section of the on line manual In addition CHEMCAD has a system available to assist the user in making this choice This feature called the Thermo Wizard is also described in the Thermodynamics section of the on line manual Because the issues involved in making thermodynamic selections and in using the Thermo Wizard are beyond the scope of this tutorial let s assume we know that we want to use the Peng Robinson method for both the K value and enthalpy calculations In this case we would proceed as given below First we need to accept the default temperature pressure values for the ThermoWizard The Wizard will recommend using SRK please accept this message box Then let us now make our own selection in the K value Options dialog box In the upper left corner of this screen will be a combo box labeled Global K value Option which is currently highlighted Please open this window by clicking on it First we need to select our K value models by pointing and clicking on the K values option on the menu displayed Please do this now The K value Options dialog box will be displayed In the upper left corner of this screen will be a combo box labeled Global K value Option which is currently highlighted Please open this window by clicking on it Your screen should look like this 20 E K Value Options Global K Value Option Global Ph
6. select the Format command either by pressing ALT M or by clicking it with the mouse The following menu will appear 4 CHEMCAD 5 0 Tutod coe I Ble Edt View Foret Pun Simun The Ci Hli Ergeesenng Uris Bring bo Erori Send lo Pack Ed Faiten Pen Siye e AS LokH Ford pgi Import Boman sae et ete Sat Now select the Engineering Units option by clicking on it with the mouse The following dialog box will appear RE Engineering Unit Selection Time Mass Mole Temperature Pressure Enthalpy Work Liquid Yolume Liquid Vol Rate Units selection Crude Flow Rate BPSD F Vapor Volume Vapor Vol Rate ft3 ai ft3 hr x Options and references Liquid Density lbzft3 v Viscosity Vapor Density ibvte3 v Suf Tension dyne cm v Thickness ft Solubility Par cal ec 0 5 Y Diameter ft v Dipole Moment debyes X Length ft Cake Resistance ft lb X Velocity ft sec Packing DP in water ft X Area ft2 v Currency Heat Capacity Btu lbmolF v Currency factor 1 Specific Heat Btu lbmol v Heat Trans Coeff Btuzhr ft2 F v ENGLISH Save Profile Therm Conduct Btu hr ft F x Load Profile English Alt SI Sl Metric LoadDefault SaveDefault Cancel OK The ENGLISH unit s option is the default and is currently highlighted You may change the engineering units system by clicking any one of the four buttons English Alt SI SI or Metric or you can change any
7. Click the Add Stream Box option on the Format Menu The Select Streams dialog box will appear E Select Streams T Print all streams Select streams from flowsheet Enter the stream ID s i 5 E E i E E E _ E E p _ E E E E E E E __ E E E E E E i E E E _ E E E Ee S E E g 3 5 a 7y Normally this dialog box would be used to list the streams which are to be included in the streams databox In our case however we will include all the streams in the databox so we don t have to list the streams The default is to include all streams Therefore click the OK button to close the dialog box The PFD Property Options dialog box will open 3 The PFD Property Options dialog box looks like this 41 General Max no of streams in a row Mass flow rate Temperature Pressure Mole vap frac Mass vap frac Enthalpy Entropy Critical Tc Critical Pe Sg wtr base iv Vv v v B E a C a a E a Sq air base API gravity M Molecular wt Total act dens E Databox Property Options Crude Solid m Overall M Total act vol Total Std Lig Total Std Yap Heating value Reid vap pres Vapor pressure Composition Option Std liquid vol v Include all components C Select components Vapor Mole flow rate M Mass flow rate M Yap enth M Yap entropy M Molecular wt I Yap Act dens M Yap Act vol M Yap Std Lig M Yap Std Yap M Yap Cp
8. Dew e Ve 02300 eo w 05000 Critical Port Figure 14 Zoomed in plot result 60 5 As this view shows the highest dewpoint of this mixture is a little less than 20 F so the cricondentherm dewpoint is indeed within the target product gas specification Right click the mouse anywhere in the plot window to return to the full plot view 6 To print the phase envelope plot click the Print button and then follow any prompts from your printer 7 You can also try the following to practice working with plots in CHEMCAD e Edit the text of the plot title in this case Phase Envelope for Stream 5 or the graph axis labels by selecting Chart gt Edit Titles In the Chart Titles dialog box make any desired changes and then click OK to view the updated chart e Select Chart gt Edit to open the Chart Explorer which provides access to settings for color size layout and various other aspects of the plot presentation 8 Return to the main simulation window by clicking the chart tab s red x button or leave the chart window open and click the main simulation tab at the bottom left of the CHEMCAD workspace Checking the Bottoms Stream Purity This problem also requires that the percent of propane in stream 9 be 1 You can check to see if you ve achieved this specification by checking the stream composition report available on the Report menu First though youll need to set the flow units for the stream composition 1 Select Report g
9. N pentane 14 N hexane 14 Save this stream information by pointing to the OK button in the upper left corner of the dialog box We are now ready to input the equipment parameters INPUTTING EQUIPMENT PARAMETERS Specifying the first heat exchanger In a fashion similar to streams equipment parameters may be input using either the Specifications command on the menu bar or by double clicking directly on the UnitOp we wish to specify Again the latter is easier therefore please point and double click on the first heat exchanger now An equipment specific input dialog box will appear 23 R Heat Exchanger HTXR Misc Settings Cost Estimations Calculation Modes Simulation mode 0 Enter specifications CHEMCAD simulation ba Pressure Drops defaults 0 Backcale mode for Autocalc 0 No back calculation be Stream 1 Utility option 0 Utility Option Off v Stream 4 Enter one specification only Temperature stream 2 F Delta temperature specifications Temperature stream 5 Min delta temperature Vapor fraction stream 2 Hot outlet cold inlet Vapor fraction stream 5 Hot inlet cold outlet Subcooling stream 2 Stream 2 stream 5 Superheat stream 2 Stream 5 stream 4 F Subcooling stream 5 F Stream 2 stream 1 F F Superheat stream 5 Heat duty MMBtu h Heat transfer coeff and area specification Heat transfer coeff U Btuzhr ft2 F Area shell t2 Data entry screens can be more than one page long The
10. Report Writer dialog box From here you can specify exactly what you want to include in your report 2 Start by specifying which streams you want to include Click the Select Streams amp UnitOps tab and check the Select Streams Override Defaults box This provides access to the other stream selection settings 3 Click the Select From Flowsheet button which brings up the Select Streams dialog box Either type in the numbers 1 5 8 and 9 or click the corresponding streams on the flowsheet to add the numbers Click OK to return to the Select Streams amp UnitOps tab 63 4 The All UnitOps option is selected by default In this case you do want to include all UnitOps in the report so leave the settings on the right side of the tab as they are 5 Click Stream Properties in the left column to view the stream properties options Then click the Properties tab which lists a collapsed list of all available stream properties You can check the Stream Properties Override Defaults box to explore the various properties and see which ones are selected but for the purpose of this tutorial use the default settings on this tab 6 Click Stream Composition in the left column to view the stream composition options Then click the Stream Compositions tab which lists available and selected flow options Click the Stream Composition Override Defaults box to gain access to these options Keep the Mass Flow Rate option and double click Mole Fra
11. The first time you change directions of a stream CHEMCAD will let you do so without any problem Every additional time you change directions you must first press the left button on the mouse to identify the longitude or latitude through which you want the stream to pass Doing this will create an anchor point to fix the longitude or latitude on the screen 9 You may cancel the stream drawing action by double clicking the left button during the stream drawing process With these rules in mind let us now connect the UnitOps with streams Click the Streams icon box on the palette The palette will disappear and the crosshairs cursor will appear Move the cursor close to the tip of the feed arrow When the cursor switches to a black arrow press the left button on the mouse Draw the stream over to the right with your mouse When the label for left most inlet arrow on the first heat exchanger appears press the left button on the mouse CHEMCAD will draw the stream directly to that point and will place a stream ID number on the flowsheet CHEMCAD issues ID numbers sequentially so this ID will be Number 1 You may change it using the EDIT STREAM menu invoked by right clicking the stream if you would like to do so Let s draw the second stream Move the cursor to the right most point of the first heat exchanger When you are close enough to the unit outlet point the cursor will switch over to the black arrow again Press the left button on the mo
12. and drag on one of these boxes The icon will grow or shrink according to the mouse movements Now let s place the two heat exchangers on the flowsheet Please follow the procedure given below 1 Point to the heat exchanger box and let the cursor stay there until the message label appears Using this label make sure you are pointing to the heat exchanger box 2 Right click the box The heat exchanger icon sub palette should appear 3 Now point to the two sided heat exchanger icon as indicated below Two sided heat exchanger 4 Left click on this icon The palettes will disappear and the small square cursor will reappear 5 Locate the cursor about one and a half 1 5 inch directly to the right of the feed icon Then left click again The heat exchanger icon will be displayed on the flowsheet and the palettes will reappear 6 Now point to the icon for a horizontally oriented one sided heat exchanger as indicated below One sided heat exchanger 7 Left click on this icon The palettes will disappear and the small square cursor will reappear 10 8 Locate the cursor about one and a half 1 5 inch directly to the right of the first heat exchanger icon Then left click again The heat exchanger icon will be displayed on the flowsheet and the palettes will reappear 9 Now close the sub palette by right clicking on the heat exchanger icon box on the main palette Your flowsheet should now look something like t
13. buttons called Specifications Misc Settings and Cost Estimations indicate the pages for this dialog box You may browse through them by clicking on the tab NOW LET S FILL IN THE SCREEN Pressure drop for both sides of the exchanger is 5 psi Enter a 5 for both pressure drop fields We need to specify the first stream outlet to be at its dewpoint We do this by specifying an outlet vapor fraction of 1 Therefore move to the Vapor Fraction stream 2 field either by tabbing down to it or by clicking on it Then enter 1 This completes the input for this unit We now need to save this information and close the dialog box You do this by clicking on the OK button Specifying the second heat exchanger We can now select the next unit for data input Move the cursor to the second heat exchanger and double click The menu for a single sided heat exchanger will appear 24 E Simple Heat Exchanger HTXR Specifications Utility Rating Cost Estimations Pressure drop 5 psi For design mode enter only ONE of the following Temperature of stream 3 4 39999 F Vapor fraction of stream 3 ray Subcooling stream 3 eat IP Supetheat stream 3 a F Heat Duty MMB Delta T stream 3 stream 2 a IF Backcale Mode for Autocalc fo No back calculation Calculated Heat Duty 2 83774 MMBtu h LMTD End points LMTD Corr Factor Utility Flowrate see Rating Case The outlet temperature from this heat exchanger will determi
14. checkmark in the box next to them will not be printed The user may turn these options on off by pointing and clicking with the arrow For the purpose of this demonstration we will use the default settings for stream properties output Therefore please exit this menu by pointing and clicking on CANCEL in the upper portion of the screen This will return you to the Report Menu Let s select which pieces of equipment or unit operations we want to include in our output report To do this select the Select Unit Operations option on the menu Please do this now The Select Unit Operations data dialog box will appear As you can see this dialog box is very similar to the Select Streams dialog box which we encountered earlier In the default condition all unit operations are output If the user chooses to override this default he she may do so by either entering the unit operations numbers in the column at the bottom of the screen using the keyboard or by clicking on the Select from flowsheet graphics option on the screen Then the select cursor will appear and unit operations will be selected in precisely the same manner as streams selected earlier In our case we are going to print all the unit operations Since this is the default we will make no changes Please point and click on OK For our final selection we are going to specify which information is going to be printed for the condensate stabilizer distillation column To do this please s
15. given specifying any two of the four thermodynamic properties of a mixture will define the other two Thus defining the composition temperature and pressure uniquely defines the vapor fraction and enthalpy as well again this is for a mixture only Alternately defining the composition pressure and enthalpy will uniquely define temperature and vapor fraction CHEMCAD however by convention does not permit this much freedom Since enthalpies are calculated relative to a datum the calculation of any given stream enthalpy is an involved process that is prone to errors For this reason CHEMCAD does not permit you to enter stream enthalpy There is one exception to this rule when the total component flowrate of a stream is zero entering an enthalpy in a stream may serve as an alternative way of adding a heat duty to a unit Therefore to uniquely define any stream in CHEMCAD the user must define the composition of that stream and any two of temperature pressure and vapor fraction This is for a mixture For pure component all three thermodynamic properties are sometimes required The fields Total Flow Units and Comp Units work together to provide the user with a variety of ways to define stream compositions If the Comp Units are set to mole mass or volume fraction which can be done globally or locally then the Total Flow Units combo box will become available If Comp Units is set as a flow or amount option then the total flowrate
16. job Report For generating tabular hardcopy outputs Main PFD For producing and editing the primary first process flow diagram 35 New PED For producing additional process flow diagrams Open PFD For editing process flow diagrams other than the main PFD Let s choose the Report option by pressing the R key This will cause the Report Menu to appear E Report Menu Report Formats Select Streams Select Unit Operations Stream Properties Stream Flowrate Compositions Distillation Summaries Batch Dynamic Results Miscellaneous Steam Eowats Conpotione ___Disiton Summaries Heating Curves Bahmane Meos Erano End Report For the purpose of this demonstration let s assume we want to print out the following information 1 For Streams 1 5 8 and 9 let s print the stream composition in mass flowrates and mole fractions as well as the default stream properties 2 The equipment summaries for every piece of equipment in the flowsheet 3 Tower profiles for the condensate stabilizer We will begin with Item 1 above We must first specify which streams we want to print out To do this use the Select Streams option on the Report Menu Please point and click on this option now The Select Streams dialog box will appear and will permit you to identify the desired streams either with the use of the mouse or by entering the stream ID numbers in the boxes provided Using the mouse employs the
17. key several times until you arrive at the Nitrogen field Note Before you continue verify that the Comp unit field is set to Ibmol h 3 Type 100 19 in the Nitrogen field and then in similar fashion type the following numbers in the corresponding fields e Methane 4505 48 Ethane 514 e Propane 214 I Butane 19 2 N Butane 18 18 e I Pentane 26 4 e N Pentane 14 N Hexane 14 4 Click OK to save this stream information and return to the main CHEMCAD workspace Enter UnitOp Parameters Now that you ve specified your feed stream properties it s time to specify the characteristics of your UnitOps The following sections address each UnitOp in turn Note As with streams you can enter UnitOp parameters in various ways but for the purposes of this tutorial we ll use the quickest and simplest method double clicking each UnitOp to access its specification dialog box First Heat Exchanger 1 Double click the flowsheet icon for the first heat exchanger The Heat Exchanger dialog box will appear as shown in Figure 10 55 R Heat Exchanger HTXR Misc Settings Cost Estimations Calculation Modes Simulation mode 0 Enter specifications CHEMCAD simulation V Pressure Drops defaults 0 Backcalc mode for Autocalc Stream 1 Utity option 0 Utilty Option Off v Stream 4 Enter one specification only Temperature stream 2 Delta temperature specifications Temperature
18. may also be selected by double clicking on them The selected component will appear in the list displayed in the Selected Components Area Insert button This button is used to insert a component somewhere in the component list rather than appending to the end of the list Clear button The Clear button is used to delete the entire component list When this button is Clicked all of the components listed in the Selected Component Area will be erased Delete button The Delete button is used to delete individual components from the component list To use this option highlight the component in the Selected Components Area and click the Delete button Copy Components from another job The Copy Components button is used to import the component list from another CHEMCAD job When this button is clicked the user is prompted to browse for the location of the CHEMCAD job from which the components will be imported These components are then added to the Selected Components Area To show how a component is selected let s select Nitrogen First click on the Selection String Field and then type in the string Nitrogen As you build the string the program will locate and highlight the component nitrogen To add it to the component list double click on it Or click on the Add button The component will appear in the Selected Components Area Nitrogen could just as easily been located by entering the string N2 in the field The same thing could ha
19. stream 5 Minimum delta temperature Vapor fraction stream 2 Hot outlet cold inlet Subcooling stream 2 stream 2 stream 5 Subcooling stream 5 stream 2 stream 1 Vapor fraction stream 5 Hot inlet cold outlet Superheat stream 2 stream 5 stream 4 Superheat stream 5 SS Heat transfer coefficient and area specification Heat duty specified MMBtu h Specifying both U and counts as a single thermal specification Heat transfer coefficient U Btu hr ft2 F Area per shell ft2 Figurel0 The Heat Exchanger dialog box 2 As with many types of UnitOps the dialog box for specifying a heatexchanger consists of multiple tabbed pages You can browse through theSpecifications Misc Settings and Cost Estimations tabs by clicking eachtab in turn 3 The pressure drop on both sides of this exchanger is 5 psi On the Specifications tab find the Pressure Drops area and enter 5 in both the Stream 1 and Stream 4 fields 4 The first stream outlet must be at its dewpoint so you ll need to specify an outlet vapor pressure of 1 In the field next to Vapor fraction stream 2 enter 1 5 Click OK to save the specifications for this UnitOp and close the dialog box Second Heat Exchanger 1 Double click the flowsheet icon for the second heat exchanger The Simple Heat Exchanger dialog box will appear 2 The outlet temperature from this heat exchanger will determine how much of the liquid is removed in
20. the cricondentherm dewpoint 3 Click OK to continue CHEMCAD perform the required flash calculations to generate the specified phase envelope Phase envelope results are produced in two formats e A numerical tabulation table of the temperature pressure vapor fraction vapor compressibility factor and the liquid compressibility factor e A graphical plot of temperature and pressure for each vapor fraction line requested The tabular results will appear first since you re interested in the graphical results close the window displaying the table The screen will now look similar to Figure 13 Note that the main CHEMCAD button toolbar is largely unavailable now and the menu items have changed 59 FA RSRESSSSESSEESESSESEE m HHHH apii E pufisstisssavasees dorn BERW 4m SBS BD Gt a ER sssr sss sn tay CETE EEES EREHE eS tf 4 Bee Eee ao HHHH HHH ttt Figure 13 Phase envelope plot results 4 To determine whether the cricondentherm dewpoint of stream 5 is 20 F or less zoom in on the far right portion of the dewpoint curve To do this click and drag with your mouse to highlight that portion of the graph approximately 400 to 1000 psi and 0 to 30 F When you release the mouse button the selected area will fill the entire plot window giving you a closeup view of specific data points Phase Envelope for Stream 5 Job CHEMCAD nanan hir 3551 Press psia Temp F e Bubble e
21. the flash drum This in turn will determine the cricondentherm dewpoint of the product gas Therefore this specification is one of the key parameters of this process As a first attempt use an outlet temperature of 5 F Enter 5 in the Pressure drop field and 5 in the Temperature of stream 3 field 56 E Simple Heat Exchanger HTXR Specifications Utility Rating Cost Estimations Pressure drop 5 i psi For design mode enter only ONE of the following Temperature of stream 3 Vapor fraction of stream 3 Subcooling stream 3 F Superheat stream 3 oo F Heat Duty MMBtu h Delta T stream 3 stream 2 o i F Backcale Mode for Autocalc 0 No back calculation Calculated Heat Duty MMBtu h LMTD End points F LMTD Corr Factor Utility Flowrate see Rating Case Ib h Figure 11 Setting up the second heat exchanger Flash Drum In this simulation the flash drum is a vapor liquid separator and requires no specification Valve 1 Double click the valve flowsheet icon to bring up the Valve dialog box 2 The outlet pressure for this unit is 125 psia so enter 125 in the Outlet pressure field 3 Click OK to save the specifications for this UnitOp and close the dialog box Stabilizer Tower 1 Double click the tower icon to open the TOWR Distillation Column dialog box Note that the settings for this UnitOp are divided into five tabs 2 On the General tab enter the following e Co
22. unit individually by clicking on the individual item and then selecting from the list presented For this tutorial we will use English engineering units therefore just exit the dialog box by clicking the Cancel button DRAWING THE FLOWSHEET To draw the flow sheet you will be working with the flowsheet palette which looks like this XOAN TAN Please note the following about the flow sheet palette The first box re invokes the arrow cursor when needed e The second box enables the user to rotate objects on the flowsheet e The next five boxes reading horizontally enable the user to draw the indicated primitive on the flowsheet Box number eight the ab box is used to put text on the drawing Box number nine is for drawing process streams streams must connect unit operations The remaining boxes each represent one of the unit operations in the CHEMCAD library Pointing to a box with the cursor will cause a small descriptive label to appear which will indicate what each box represents Pointing to a box and clicking with the left button of the mouse will activate the corresponding function Pointing to a box and clicking with the right button of the mouse will cause a sub palette of icon options to be displayed Right clicking again on the same master palette box will cause the sub palette to disappear Multiple sub palettes may be displayed simultaneously The master palette may be switched on and off us
23. warranty of any kind either expressed or implicd This explicitly excludes any implicd warrantics of merchantability or fitness for a particular purpose or use The entire risk as to the quality and performance of this software is assumed by the user Chemstations shall have no liability in excess of the total amount pald to Chemstatlons under the Program License Agreement for this software In no event will Chemstations Inc be liable to the user for any lost profits or other incidental or consequential damages arising aut of the use or inability to use this software even it Chemstations Inc has been advised as to the possibility of such damages For Help press Fi 02 04 PM The top line is called the Title Bar It contains the CHEMCAD logo and name on the left side and the WINDOWS minimize tile and close buttons on the right side The next line is called the Menu Bar This bar contains the top level commans for CUEMC AD ky ae This command is used to define File output formats open jobs print and obtain general information about CHEMCAD License This command is used to configure license update dongles and authorize special licenses View This command enables the user to toggle the Tool bar and Status bar on and off Help This function allows the user to call the on line Help facility STARTING A NEW JOB THE SIMULATION WINDOW Let s start by opening a new job and giving it a job name The File command is used f
24. 22 becomes the sum of the component flow rates and the Total Flow Units combo box will not be available for editing If the Comp Units is set to an amount flow unit as opposed to mole mass or volume fractions then as the component flow rate values are entered they are automatically summed and the current sum is displayed in the field labeled Total Flow In the upper right hand corner of the dialog box is the Flash button Clicking this button at anytime will cause the program to perform a flash calculation using the currently specified composition and thermodynamic properties This allows quick flash calculations to be made without exiting the dialog box Fractions that do not sum to 1 0 are automatically normalized upon flashing or exiting the dialog box Now let s enter the data Let s start with temperature Please move to the temperature field by clicking on it Once the highlight is on the proper field type 75 down arrow When you press the down arrow key the highlight will move down to the pressure field Please enter 200 in this field Next let s move down to the Nitrogen field Please move the cursor down until it points to the field to the right of Nitrogen and click the left button on the mouse Please enter 100 19 in this field In a similar fashion please enter the following numbers in their corresponding fields Methane 4505 48 Ethane 514 Propane 214 I butane 19 2 N butane 18 18 I pentane 26 4
25. 2786 Pres psia 130 0000 Enth MMBtu h 2 0871 Vapor mole fraction 0 00000 Total lbmol fh 30 0001 Total lbfh 2187 0605 Total std L t3 hr 55 8464 Total std V scfh 11384 41 Component mole Nitrogen 0 000000 Methane 0 000000 Ethane 0 000196 Propane 8 156643 I Butane 5 551371 H Butane 8 035712 I Pentane 26 602361 H Pentane 16 393609 N Hexane 35 260105 Para obtener Ayuda presione F1 If the default Flowsheet Quickview option of the View menu is check marked you may also place the cursor on stream 9 and a summary for the stream will be displayed We can see from this display that propane is far below our 1 specification This means our design is too conservative To correct this let s go back and re specify the column to produce precisely 1 propane in the bottom Please click the close button once RE RUNNING THE SIMULATION Let s re run the stabilizer specifying that we want 1 propane in the bottom To do this please double click on the Tower UnitOp The TOWR Distillation Column data entry dialog box for the stabilizer should reappear Now let s click on the Specifications page of the dialog box We want to change our specification from Bottom mole flowrate to a purity specification Therefore we must start by changing the mode of the specification To do this please point and click on the field below the Select reboiler mode option and select Mode 6 This field should now read 6 Bottom component mole fraction To co
26. CHEMCAD USER MANUAL Table of Contents Welcome to the CHEMCAD A DESCRIPTION OF THE TUTORIAL PROBLEM GETTING STARTED STARTING A NEW JOB THE SIMULATION WINDOW SELECTING ENGINEERING UNITS DRAWING THE FLOWSHEET PUTTING STREAMS ON THE FLOWSHEET SELECTING COMPONENTS SELECTING THERMODYNAMIC OPTIONS DEFINING THE FEED STREAMS INPUTTING EQUIPMENT PARAMETERS RUNNING THE SIMULATION REVIEWING THE RESULTS INTERACTIVELY RE RUNNING THE SIMULATION PRODUCING A REPORT GENERATING THE PROCESS FLOW DIAGRAM SUMMARY CHEMCAD TUTORIAL Welcome to the CHEMCAD This tutorial provides basic input skills for operating CHEMCAD CHEMCAD is a very easy program to learn and the best way to master it is by using it Here we provide a step by step description of how to solve the condensate stabilizer problem given below The input procedure is simple and straightforward It is designed to be intuitive for a chemical engineer familiar with the Windows environment However for the sake of clarity and for those new to Windows a review of some of the basic rules for using CHEMCAD is given BASIC STEPS The following ten basic steps are used to run a flow sheet simulation in CHEMCAD e Starting a new job e Selecting engineering units e Creating a flow sheet e Selecting components e Selecting thermodynamics options e Defining the feed streams e Input equipment parameters e Running the simulation e Reviewing the results e Generating hardcopy output
27. K button This completes the input for the valve unit Specifying the stabilizer tower Now double click tower unit The TOWR Distillation Column dialog box will appear There are five pages to this screen as indicated by the tabs On the first page we need to enter the top pressure which is 125 psia the column pressure drop which is 5 psi the number of stages which is 12 and the feed stage location which is stage number 1 Therefore please complete your screen as shown below E TOWR Distillation Column General Specifications Convergence Cost Estimation 1 Cost Estimation 2 General Model Parameters ak ia Condenser type fo Total or no condenser v Ambient heat transfer Subcooled temp F Heat transfer area stage ft2 Heat transfer coeff U Btu hr ft2 F Ambient temperature F Top pressure psia Cond press drop psi Colm press drop psi Reflux pump pout Bottom pump pout No of stages Feed stages Feed tray for stream Cancel OK Let s continue our data input on the next page Please click on the Specifications tab We make our specifications for the column on this screen We have no condenser or side streams on this column so we will only be making specifications for the reboiler First we need to specify our reboiler mode In order to determine what our options are please point the arrow to the field below the label Select Reboiler Mode and click the left button on the mouse A list shou
28. Options dialog box will be displayed You will notice on this screen that the Peng Robinson method has already been chosen The program automatically makes this the enthalpy model when you have chosen the Peng Robinson K value method If this assumption is erroneous you may override it at this time In our case we would like to use the Peng Robinson model so let s point and click on the OK button in the upper right portion of the screen This will close the Enthalpy Options dialog box saving the currently displayed options For the purpose of our tutorial the thermodynamic selections are now complete 21 DEFINING THE FEED STREAMS We are now in a position to define the feed streams This can be done by using the Specifications command on the menu bar or by double clicking directly on the stream we wish to specify Double click stream 1 The Edit Streams dialog box will appear like this Flach Comp Let Cnc oF Please note the following points about this dialog box The first field called Stream Name allows you to enter a stream label or name This name may be up to 16 alphanumeric characters and will appear on the flowsheet when you close this dialog box Note Entering and or editing such steam labels can also be done a number of other ways The next four fields temperature pressure vapor fraction and enthalpy are the thermodynamic properties of the stream According to the Gibbs Phase Rule once the composition is
29. a feed stream or any UnitOp icon you can click the icon to display the black sizing handles at each corner With the icon selected this way you can click the icon and drag it to a new location or click any sizing handle and drag it outward or inward to resize the icon 2 Now place the two heat exchangers on the flowsheet On the All UnitOps palette point to the Heat Exchanger icon until its pop up label appears see Figure 1 ci h a g d Heat exchanger 1 IE Cy z Figure 1 The pop up label that identifies the UnitOp icon 3 Click the lower right corner of the Heat Exchanger icon on the black triangle to open the sub palette Select the two sided heat exchanger icon as shown in Figure 2 The icon that you clicked in the sub palette now appears on the main All UnitOps palette to represent the Heat Exchanger UnitOp E A or f A A Figure 2 Selecting the two sided heat exchanger icon Select Default 47 4 Point the mouse cursor about an inch to the right of the feed icon and click A two sided heat exchanger icon appears on the flowsheet where you clicked Note The UnitOp ID label of 1 should appear in a circle next to the heat exchanger icon For each subsequent UnitOp that you draw CHEMCAD will assign an ordinal number in this way to uniquely identify each piece of equipment on the flowsheet 5 Return to the All UnitOps palette and again click the Heat Exchanger icon s black triangle To swit
30. ach unit has inlet and outlet positions These are established when the symbol is created The program always snaps streams to these positions During the simulation a process stream always flows from an outlet position on a source unit to an inlet position on a destination unit but when drawing the flowsheet a stream may be drawn in any direction that is from an inlet position to an outlet position as well as from an outlet position to an inlet position 3 When starting a stream the cursor will be a small cross When the cursor gets near an outlet position it will convert to a black arrow When this occurs you should left click the mouse to start the stream if that is the starting position you desire 4 When completing the stream to a unit the cursor will remain as a black arrow When the cursor is near an inlet or outlet position a label will appear indicating the location and number of the position 5 Once the desired position has been located as indicated by the appearance of the label you should left click the mouse to complete the stream 6 While drawing a stream the palette will disappear It will reappear only when you left click somewhere on the flowsheet which is not a UnitOp inlet or outlet point You are not required to click the stream link icon square each time you begin a stream 7 You can alternate between placing UnitOps on the screen and connecting them with streams as long as the above rules are followed 8
31. ase Option 7 Vapor Liquid Soid Ethane Ethylene Propane Propylene C Vapor Liquid Liquid S olid Regular SAK PR Bips Water Hydrocarbon Solubility C Special SRK PR Bips Miscible Vapor Phase Association mmiscible No Vapor Phase Association tlean piociel San Vapor Phase Association No of BIP sets Default BIP set Vapor Fugacity Poynting Correction C Correction No Correction F Clear all local K models BIPs I Set local K models BIPs Set tray BIPs Set Henry components SRK PR Alpha function Standard SRK PR C Boston Mathias extrapolation Help Options in gray are not applicable for this k value option ance OK You will notice the presence of a Scroll Bar at the right of this list indicating that all of the available options could not fit into this area Therefore the user may scroll through them using any of the methods previously described in this tutorial We would like to use the Peng Robinson method To make this choice please scroll up through list point the arrow to the Peng Robinson option and click the left button on the mouse The box will close and Peng Robinson will now be displayed in the field let s save our selection by pointing and clicking the OK button in the upper left corner This will return you to the Simulation Menu Bar Now let s select our enthalpy model Do this by again clicking the ThermoPhysical command then clicking the Enthalpy option The Enthalpy
32. ation and can normally be ignored therefore please click YES now This will return you to the Simulation Window All of the data entry for the flowsheet is now complete RUNNING THE SIMULATION To run the simulation point and click on the RUN command on the menu bar This will cause the RUN Menu to open up like this t CHEMCAD 5 0 Tutort_ocs Ele Ed View nia Edt Flomuheet ThemoPhyica Specticatios Aun Reayts Pit Dipt Song Took window Help lej x We want to run a steady state analysis so select the Run All option The program will first recheck the data and list any errors and or warnings on the screen In this case we should have no errors although we will have warnings saying we have not given certain estimates We can ignore these warnings and proceed by clicking the YES button The calculation will then proceed Upon finishing the CC5 Message Box will appear with the message Recycle calculation has converged To close this dialog box and clear the screen you must click on the OK button 28 REVIEWING THE RESULTS INTERACTIVELY Now that the simulation is complete we will want to review the results before printing a hardcopy We do this using the Results and Plot commands on the menu bar With these commands let s check whether we have met our design criteria Checking the cricondentherm dewpoint If we have chosen the proper outlet temperature for heat exchanger number 2 the cricondentherm dew
33. ch from the two sided model to a single sided model you ll need to select the appropriate icon see Figure 3 from the Heat Exchanger sub palette He v A am m f A i Figure 3 Switching to the single sided heat exchanger icon E S G g a 6 Again move the cursor to the workspace this time about an inch to the right of the first heat exchanger and click the mouse A single sided heat exchanger icon appears on the flowsheet where you clicked Your flowsheet so far should look something like Figure 4 m Figure 4 The flowsheet so far 7 Add the Flash and Valve UnitOp icons to your flowsheet using the standard icons 8 For the condensate stabilizer use a distillation column Multiple distillation UnitOps are available but for now assume that the module you want to use is the rigorous distillation model called Tower Yovu ll need a Tower icon with trays and a reboiler but no condenser this is different from the default Tower UnitOp icon Click the lower right corner of the Tower icon s box to view the sub palette then select the icon shown in Figure 5 48 aT TIED e Fh p a ED Co uD F p e Figure 5 Selecting the appropriate Tower UnitOp icon 9 Now that you have selected the appropriate Tower icon add this UnitOp to the flowsheet 10 Place three Product icons on the flowsheet one for each product stream You can quickly place three identical icons simply by clicking r
34. ctions in the left column to add this option to the list of selected flow options at right 7 Finally verify that the Tray profile report section is included in the Consolidated Report You can also delete any report sections that you don t need and re order the desired sections to suit your needs 8 Click Generate to run and display the report You can now review the results re run if desired save the report for later use and print the report as needed 9 When you finish reviewing and working with the report click Cancel to close the Report Writer dialog box and return to the main CHEMCAD workspace Generating a Process Flow Diagram As you know the streams and UnitOps on a flowsheet only tell part of the story of your process Fortunately CHEMCAD provides many features to help you add the extra content needed to turn a plain flowsheet into a full fledged process flow diagram PFD for others to review and use To prepare your finished simulation to be printed as a PFD you ll add a stream databox containing the heat and material balance for the entire flowsheet You ll place that databox underneath the flowsheet diagram and then add a title to the area above the flowsheet Finally you will create a new layer in this simulation and assign the PFD specific items to that layer so that you can hide them from view when working and display them again quickly for printing Follow these steps to prepare and print the PFD 1 Star
35. d the Tower dialog box we selected the Tower UnitOp UnitOp No 5 When we closed that dialog box UnitOp No 5 remained selected even though its dialog box was closed Therefore when we told the program to Run selected units it immediately ran UnitOp No 5 because it was selected Selected objects are indicated by the four corner boxes which surround them When the calculation is finished the message Calc Unit 5 TOWR will appear to the left on the bottom line of the CHEMCAD window This should happen almost immediately since the stabilizer runs very fast We now want to insure that we have 1 propane in the bottom stream We will again do this with the Results command Please point and click on the Results command on the menu bar This will cause the Results Menu to appear Now highlight the Stream Compositions option and display Stream 9 using the following steps 1 Point and click on the Select Streams option 2 Move the cursor to Stream 9 then press the left mouse button 3 Click OK Stream 9 should now be displayed in a Notepad Window We can see that propane is now 1 as desired Now click the Notepad close box to close the stream composition display PRODUCING A REPORT To produce a hardcopy output of any kind use the Output option on the menu bar Click Output or press ALT O The OUTPUT MENU will appear and you will have the following options Job Note For including and storing comments on the simulation
36. del is required i e equation of state activity model etc 2 Second it looks at temperature and pressure ranges that you provide and decides which equation within a given category is best at the limits of those ranges 3 If the method is an activity model the program then looks at the BIP database to see which model has the most data sets for the current problem It then calculates the fractional completeness of the BIP matrix If that fraction is greater than the BIP threshold parameter it uses the chosen activity method if not it uses UNIFAC 51 The Thermodynamics Wizard is no replacement for engineering judgment This tool uses an algorithm based on general rules and is therefore fallible The suggested model might not always be the best model for the system Selecting thermodynamic options basically means selecting a model or method for calculating vapor liquid or vapor liquid liquid phase equilibrium called the Kvalue model and selecting a method or model for calculating the heat balance called the enthalpy model The commands for these selections are located on the Thermophysical menu CHEMCAD has a library of dozens of K value models with a variety of options and about 12 enthalpy models Making the proper selection from these libraries can sometimes be difficult For the purposes of this tutorial assume that you want to use the Peng Robinson method for both the K value and enthalpy calculations Follow these steps to sel
37. e PFD palette click on the Data Box command on the menu bar then select the Palette command at the bottom of the Data Box Menu A small PFD Palette will appear at the bottom left of the window Text can be created and placed on the PFD using the ab square at the far right of the palette Please click on this square now The palette will disappear and the text cursor will appear Locate the cursor towards the top left of the PFD in a position appropriate for a title then press the left mouse button Now type the PFD title Condensate Stabilizer PFD When finished double click on some vacant spot The palette will reappear We now have a complete process flow diagram We can generate a hardcopy of this PFD by clicking the Print button To close CHEMCAD click on the Close in the upper right hand corner of the window When you do this CHEMCAD might ask you if you want to exit CHEMCAD Please answer yes We are now finished with our demonstration SUMMARY During this tutorial we have accomplished the following things 1 Set up a new problem Drawn our flowsheet Interactively prepared our input Run the simulation Interactively changed our input Rerun the simulation Plotted and viewed the results interactively Produced a tabulated report of results MONI DUABwWDN Produced a process flow diagram These are the major functions within the process simulation portion of CHEMCAD 44 CHEMCAD Tutoria
38. e stabilized condensate Stream 9 must have maximum propane content of 1 yoga j ae 3 El Tol TE O Figure 1 Condensate Stabilizer Feed HX 1 HX 2 Valve Stabilizer T 75 F P drop 1 5 psi Pdrop 5psi Pout 125 12 stages psia P 200 psia P drop 2 5 psi T out 5 F Feed stage 1 N2 100 19 Ib mol hr Vap Frac 1 Bottom draw 30 lb moles hr Column P drop 5 psi C1 4505 48 C2 514 00 C3 214 00 iC4 19 20 nC4 18 18 iC5 26 40 nCs5 14 00 nC6 14 00 2 GETTING STARTED The first time you run CHEMCAD the Top Level Window will appear on your screen Please maximize this window that is zoom it to fill in the screen by clicking the Maximize button in the upper right hand corner of the CHEMCAD window This will cause CHEMCAD to fill your screen and your display should look something like this CHEMCAD 5 4 3 File License View Help Ofer iet Slej Se This proprietary software is the property of Chemstations Inc and is provided to the user pursuant to a Chemstations Program License Agreement containing restrictions to its use This software contains the valuable trade secrets and proprictary information of Chemstations Inc and is protected by Federal copyright law It may not be copied or distributed in any torm or medium disclosed to third parties of used in any manner except as expressly permitted by the Chemstations Program License Agreement This software Is provided without
39. ect your thermophysical options 1 Accept the default temperature and pressure ranges in the Thermodynamics Wizard and click OK 2 Click OK again to accept the wizard s suggested method of SRK 3 When the Thermodynamic Settings dialog box opens find the Global KValue Model selection in the upper left corner of the K Value Models tab The current setting is SRK but for the purposes of the tutorial you ll need to select the Peng Robinson model Click the down arrow at the right end of the selection box to view a long list of K value choices then click Peng Robinson EE Thermodynamic Settings Kyalue Models Enthalpy Models Transport Properties Global K Value Model Global Phase Option Peng Robinson b v Ethane Ethylene Propane Propylene Vapor Liquid Liquid Solid Regular SRK PR Bips Water Hydrocarbon Solubility C Special SRK PR Bips C Miscible Vapor Liquid Solid Vapor Phase Association immiscible No Vapor Phase Association mrpr ee Vapor Phase Association No of BIP sets Vapor Fugacity Poynting Correction Correction Default BIP set No Correction M Set Henry components SRK PR Alpha function Set local thermodynamics Standard SRK PR Clear all local thermodynamics C Boston Mathias extrapolation Reflash input streams for local H models Special PSRK Gas Physical Solvent Package Options in gray are not applicable for this k value option Cancel OK Figu
40. elect the Distillation Summaries option on the menu The Distillation Options dialog box will appear and will permit you to do the following things 1 Tray profile Print a tabular summary of the tray profiles for the column i e for each stage the program will print the temperature pressure vapor flowrate liquid flowrate and any feeds and products going to or from the stage 38 2 Tray properties A tabular summary of the transport properties of the vapor and the liquid on each stage of the column 3 Tray sizing Results of tray sizing calculations for each stage of the column The user may select from valve sieve or bubble cap trays 4 Packed column sizing Packed column sizing and pressure drop calculation results 5 Tray compositions Tray compositions may be printed in mole or mass flowrates as well as mole or mass fractions Only one may be selected We are going to print only the tray profiles described in Item 1 above As you can see from the checkmark on the dialog box this is the default option Therefore please click OK to return to the Report Menu We are now ready to generate our report Please point and click on the option which says Calculate and Give Results When you do this the report will be displayed in a Word window It will be formatted exactly as it would on paper To print this report click the Print button on the toolbar Once we are finished with the report close the Word wind
41. epeatedly in a slightly different location When you ve clicked to create the third Product icon right click to turn off the Product drawing tool Drawing Streams Now that all of the UnitOps are in place select the Stream tool and connect the various UnitOps as appropriate Remember that each stream must start at a red outlet point on the upstream UnitOp and end at a blue inlet point on the downstream UnitOp To avoid having to re select the Stream tool each time make sure that as soon as you click to complete one stream you move the cursor to the next location and click to start the next stream Draw streams to connect the following e Feed stream to first heat exchanger s left side inlet e First heat exchanger s right side outlet to second heat exchanger s left side inlet e Second heat exchanger s right side outlet to flash inlet of your choice e Flash top outlet to first heat exchanger s top inlet e First heat exchanger s bottom outlet to nearest product icon e Flash bottom outlet to valve inlet e Valve outlet to tower inlet of your choice e Tower top outlet to nearest product icon e Tower bottom reboiler outlet to nearest product icon As you draw streams CHEMCAD assigns stream IDs just as it assigned UnitOp IDs when you created those items The labels for stream IDs are displayed in squares to distinguish them from the UnitOp IDs displayed in circles 49 Selecting Components Now you need to identify
42. general type of model is required i e equation of state activity model etc 19 2 Next it looks at the temperature and pressure ranges input by the user and decides which equation within a given category is best at the limits of those ranges 3 If the method is an activity model the program then looks at the BIP database to see which model has the most data sets for the current problem It then calculates the fractional completeness of the BIP matrix If that fraction is greater than the BIP threshold parameter it uses the chosen activity method if not it uses UNIFAC The K Value Wizard is no replacement for engineering judgment The Wizard uses an algorithm based on general rules and might not always be correct The suggested model might not be the best model for the system Selecting thermodynamic options basically means selecting a model or method for calculating vapor liquid or vapor liquid liquid phase equilibrium called the K value option and selecting a method or model for calculating the heat balance called the enthalpy option You do this using the ThermoPhysical command located on the menu bar This is the same command you used to access the Component List above Please click this option now The ThermoPhysical menu should appear as before CHEMCAD has a library of about 50 K value models with a variety of options and about twelve enthalpy models Making the proper selection from these libraries can sometimes be
43. his 1 CHEMCAD 5 4 3 D VOCSDATA new new ccx Jita x EEE Er e e ot Gal e al 8 A A AInehe i fT Fohe j gt Loge 404 418 Oev 404 418 Scale 1 000 Mode Flowshect Steady State 2 14 PM For convenience move the palette to one side by clicking and dragging on the brown bar at the top of the palette Now follow the procedure outlined above to place the flash tank and the valve unit operations on the screen 11 1 CHEMCAD 5 4 3 D VOCSDATA new new ccx D fe Edt View Format Mode ThemoPhyscal Soecfcaticns Run Resuts Pot Outrut Sng Tools Window Help FX Olsa zae B WARAN R iz fE Mowshet Kere Rae jj caf RGhoOseaReaee fkEF 4a 7 4 Yioteociaad bo Tt foo ge Loge 575 145 Oev S75 145 Scale 1 000 Mode Flowshect Steady State For the condensate stabilizer itself we want to use a distillation column module You might notice from the palette that there are multiple distillation modules available in CHEMCAD An explanation of each of these options is given in the on line Help manual You can access this manual at any time by clicking the Help command on the menu bar For now however let s accept that the module we want to use is the rigorous distillation model called Tower This UnitOp is found on your palette as shown below ROLIONL NL F amp Bo F Seon Stee Raa TES Rona ee a Ve we be eee de el ae Since we want to use a Tower icon that has a reboiler b
44. ing the View Main Palette command by selecting between the Flowsheet Simulation options on the Mode command or by selecting between the Simulation Flowsheet options on the Change Mode combo box on the tool bar The size and shape of the main palette can be controlled using the View Palette Settings commands On the icon display inlets are indicated by small blue squares and outlets by small brown squares Our purpose now is to set up the flowsheet topology Creating a flowsheet is the process of placing unit operations icons on the screen connecting them with streams and then adding various graphical objects to enhance the drawing All of these things may be done using the palette Feed We will start by placing unit operations icons on the flowsheet By convention CHEMCAD requires that every stream come from a unit operation and go to a unit operation Therefore we must place a Feed icon on the flowsheet to serve as the source unit for the feed stream This is a good place to start so point to the Feed box like so Fead Hi1 for more click onthe right mous button 1I me OY BE amp C fy be Please follow the procedure given below 1 Right click the feed icon box The Feed sub palette will appear Now right click the feed icon box on the main palette again The sub palette will disappear This is how you call and close UnitOp icon sub palettes 2 Now left click on the feed icon on the main palette The pale
45. ld open displaying the available options 27 As indicated in Figure 1 we need to specify the bottom flowrate for this unit which is Mode No 4 Therefore please point the cursor to 4 Bottom mole flowrate and click the left button on the mouse The list will close and the field should now read 4 Bottom mole flowrate Now we need to specify the numeric value of that flowrate This is done in the field immediately to the right which opens after we make our mode selection Please point the arrow to that field and click the left button on the mouse This field should be highlighted and we can enter a value of 30 Now let s move to the last page of this data entry screen by clicking the Convergence tab As you can see from the screen all of the entries on this page are optional However for the purpose of demonstration let s enter an estimate of 50 F for the top temperature and 150 F for the bottom temperature Please point and click on the T top field and enter a value of 50 in this field Now move to the field labeled T bottom immediately below Please enter a value of 150 in this field Now we have completed the data input for the tower unit Let s save this data by pointing and clicking on the OK button When you do this you will get a warning message saying you have not entered an estimate for the distillation rate In a dialog box the program will ask you if you want to ignore this warning Warning messages are for your inform
46. lm press drop 5 e No of stages 12 e Feed tray for stream 1 57 3 Click the Specifications tab to make specifications for the column This column has no condenser or side streams so you will only be making specifications for the reboiler Drop down the list of options for Select reboiler mode and select the mode called 4 Bottom mole flowrate 4 Now you need to specify the numeric value of the reboiler flow rate In the Specification field immediately to the right of your reboiler mode selection enter a value of 30 5 Click OK to save the specifications for this UnitOp and return to the main CHEMCAD workspace All of the data entry for the flowsheet is now complete Before you continue you should save your simulation As noted earlier it s a good idea to do this periodically as you build the simulation but completion of your UnitOp specifications is a particularly good time to stop and save Run the Simulation To run the simulation click the Run All button on the toolbar The program first rechecks the data and lists any errors and warnings in the Messages pane In this case you should have no errors although you will have warnings about estimates you have not given You can ignore these warnings and proceed by clicking Yes The calculation will then proceed When the run finishes a message box appears Recycle calculation has converged To close this dialog box and clear the screen click OK Review the Results and Prin
47. lowrate to a purity specification Click the Select reboilers mode drop down list and select 6 Bottom component mole fraction 3 With this change of mode you need to specify the desired purity and the component for which it is being specified In the Specification field enter 01 In the Component drop down list select 4 Propane 4 Click OK to save your changes and return to the main CHEMCAD workspace 5 You can now re run the calculations for the condensate stabilizer While you could accomplish this using the Run All command it s more efficient to rerun only the UnitOp that you have changed The quickest way to do this is to right click the UnitOp icon on the flowsheet and select Run this UnitOp Run the Tower UnitOp using this method As soon as you see the Run finished message in the bottom left corner of the CHEMCAD window you can check on the propane content of the bottom stream You ve already seen how to get a detailed Stream Composition report you can also use the Flowsheet Quickview feature to get instant stream information without even clicking the mouse Find the Flowsheet Quickview button at the far right end of the CHEMCAD toolbar If this button is not currently activated with a thin outline and a white button background click the button to turn on this feature R Figure 16 Turning on the Flowsheet Quickview feature With Flowsheet Quickview turned on point your mouse cursor at stream 9 on the flowsheet Afte
48. ls Although the simulations stored in your Examples directory are useful for many scenarios the best way to learn to use CHEMCAD is to create and run simulations yourself The tutorials in this chapter walk you through basic simulation building step by step using a realistic example problem that will help prepare you for your own simulations The first tutorial is for a simple steady state simulation which is then used as the basis for the second tutorial in which you ll learn to use the CC THERM module to rate a heat exchanger CC STEADY STATE Tutorial This tutorial creates a basic steady state simulation for a condensate stabilizer plant In this plant gas enters the system with the feed conditions shown in the following diagram Condenser Stabilizer HX 1 HX 2 Valve Stabilizer P drop 1 5 psi P drop 5 psi P out 125 psia 12 stages P drop 2 5 psi T out 5 F Feed stage 1 Vapor fraction 1 1 0 Bottom draw 30 lbemol h 8 gt 4 TH Feed gt 0 z AE T 75 F P 200 psi N 100 19 lbemol h 6 3 gt 1 propane C 4505 48 lbemol h C 514 00 lbemol h C 214 lbemol h E Cricondentherm iC 19 20 lbemol h nC 18 18 lbemol h iC 26 40 lbemol h nC 14 00 lbemol h nC 14 00 lbemol h dewpoint 20 F Your job is to determine new operating conditio
49. mplete our specifications we must identify what that purity is and for which component it is being specified In the Specification field to the right we want to enter 01 instead of the present 30 Please do this now Next we must identify the component for which we are making a purity specification To do this click on the component field A list of all of the components in the component list will open Click on propane The list will close 34 Please click on the third page of the screen Since we have run this condensate stabilizer before we want to instruct the program to pick up where it left off at the end of the last simulation We do this by making the proper selection in the field labeled Initial flag under Convergence parameters Please click on this option A list will open displaying the available options The option we want is option number one Reload column profile We have now made all the changes required to rerun the condensate stabilizer Let s save them by pointing and clicking on the OK button Please point and click on the Run option on the menu bar This will cause the Run Menu to reappear Please note at this point that since the only unit affected by our changes is the condensate stabilizer itself it is not necessary to rerun the entire flowsheet Therefore let s only rerun Unit 5 the condensate stabilizer We do this by pointing and clicking on the Run selected Units option Please do this now When we opene
50. n information from an Excel data sheet into the drawing Again the style but not the content unless modified from the Excel file of these databoxes is within the user s control 4 Adding text to the drawing Using the text facility of CHEMCAD Titles notes and various other text can be placed on the PFD 5 Placing symbols in the PFD The user can create and store symbols such as company logos in a symbols library for later retrieval and placement on CHEMCAD drawings 6 Drawing primitive i e simple objects A variety of 2D objects are available to the user for freehand object creation To see how these work let s draw the PFD In order to have adequate space to place additional information on the PFD the first thing we need to do is reduce the size of the flowsheet Please click on the Zoom Out option located on the tool bar CHEMCAD 5 4 3 D CC5DATA new new ccx H Fie Edit Yiew Format Mode ThermoPhysical Specifications Run Results Plot Output Sizing Tools Window Help G x osa e S AJA aE ea Manero Rolf R O e s ele eE The flowsheet will shrink in the middle of the screen Creating a stream databox Now let s place the heat and material balance for the flowsheet on the screen This information is contained in a Stream Databox A stream databox is created using the following process 1 Click the Format command on the menu bar The Format Box Menu will appear 40 2
51. n to the normal phase envelope boundaries Therefore complete the dialog box as shown 29 E Phase Envelope Estimations optional Bubble point T Dew point T Vapor fractions optional Vapor fraction Vapor fraction Vapor fraction Vapor fraction Starting press OK Now click the OK button to save these entries CHEMCAD will perform the required flash calculations necessary to generate the phase envelope as specified above Phase envelope results are produced in two formats 1 A numerical tabulation table of the temperature pressure vapor fraction vapor compressibility factor and the liquid compressibility factor 2 A plot of temperature and pressure for each vapor fraction line requested The former is displayed in a Notepad Window the latter in a Plot Window Since data for these windows is generated simultaneously both windows are opened Therefore when the calculations are complete CHEMCAD quickly displays the Plot Window then it displays the Notepad Window Since we are not going to use the tabulated results please close the Notepad Window now Your screen will then look like this 30 CHEMCAD 5 4 3 ChartA2 BAE File Edit View Graph Window Help x osa eel S e r Phase Envelope for Stream 5
52. ne how much of the liquid is removed in the flash drum This in turn will determine the cricondotherm dewpoint of the product gas Therefore this specification is one of the key parameters of our design As a first attempt let s estimate an outlet temperature of 5 F Therefore please enter 5 in the Pressure Drop field and a 5 in the Temperature of Stream 3 field Point and click on the OK button to save the data and close the dialog box Specifying the flash drum In our example the flash drum is a vapor liquid separator and requires no specification Therefore we do not need to enter any input for this unit Specifying the valve Let s enter the outlet pressure for the valve Please move the cursor to the valve and double click The Valve dialog box will appear Since our outlet pressure for this unit is 125 psia please enter 125 in the Pressure Out field then point and click on the OK button This completes the input for the valve unit 25 Specifying the stabilizer tower Now double click tower unit The TOWR Distillation Column dialog box will appear There are five pages to this screen as indicated by the tabs On the first page we need to enter the top pressure which is 125 psia the column pressure drop which is 5 psi the number of stages which is 12 and the feed stage location which is stage number 1 Therefore please complete your screen as shown below EE Simple Heat Exchanger HTXR S
53. ns for this existing plant along with any necessary modifications The design requirements are as follows e The cricondentherm dewpoint of the product gas must be 20 F or less A cricondentherm dewpoint is the highest temperature for two phase coexistence of a mixture As long as the stream temperature stays above the cricondentherm dewpoint the stream contents will not condense 45 e The stabilized condensate must have maximum propane content of 1 Overview Running a flowsheet simulation in CHEMCAD is essentially a nine step procedure Start a new simulation Select engineering units Create a flowsheet Select components Select thermodynamics options Define the feed streams Enter UnitOp parameters Run the simulation Review the results and print as needed OANANINNBWN KR The steps do not have to be performed in this order nor do all of them have to be done for each flowsheet but you should consider all steps for each problem Starting a New Simulation Start by creating a new simulation and giving it a name To do this launch CHEMCAD and then Select File gt Save to open the Save As dialog box Navigate to the directory where you want to store the simulation try My Simulations located under My Documents and give your simulation a name leaving the type as CHEMCAD 6 cc6 Then click Save to create the file and return to the main CHEMCAD window Note Instead of saving all changes in
54. ok Window Help 2x olsa hle Bl KAAJA i Ef Fow ker RIA aE KODONLN LY fee 4a Fd Vio te ci l b a Tm l a O poeet oady ate 03 26 PM lt If you need to delete or reroute a stream right click on the stream to call the Edit Stream menu Use the Delete and Re draw commands as needed When all streams are satisfactorily drawn double click on a vacant spot on the flowsheet and the palette will reappear 16 We are now finished drawing our flowsheet To move on we need to activate the Simulation mode Therefore at this time click on the Mode command on the menu bar and select the Simulation option The palette will close and the input functions will become available SELECTING COMPONENTS Next let s identify which components are to be used in this simulation Selecting the ThermoPhysical command does this Again this may be done by pressing ALT L or by clicking with the mouse Do this now please The following menu will open up 4 CHENMCAD 5 0 Tutor ccx Tj fle Edt Yew Fost Edt Pomheet ThemoPhysica Specticaten Pun Reads Git Qupa Sting Joos Wrdw Help ETE olsa ope S Ha gt ROLY Raela os e CD To choose components from the standard CHEMCAD databank click the Component List option with the mouse The following Component Selection dialog box will appear This dialog box is organized as indicated below E Component Selection Selected Components Component Databank 1 Hyd
55. ontrol control For modifying various aspects of the flowsheet and its presentation Edit functions include Redraw Undo Redo Cut Copy Paste Delete Flip and Rotate 90 among others For controlling various display and drawing options For selecting engineering units setting graphics options and importing bit maps To switch back and forth between the Flowsheet mode and the Simulation mode For selecting components K Value method s and enthalpy method s for the current job as well as viewing and editing the CHEMCAD databanks setting up distillation curves and defining solids For entering editing and manipulating stream and unit operations data This may also be done by double clicking the stream or UnitOp directly on the flowsheet For running the simulations as well as for defining calculation order s Results For reviewing calculated results Plot For displaying calculated results graphically Output For preparing reports and Process Flow Diagrams PFD s Sizing For performing sizing and rating calculations for various types of equipment Tools For performing various activities associated with simulation These include data regression CO2 solids and hydrates prediction TOD COD calculations and others Window For arranging windows and icons display Help For invoking the CHEMCAD help system SELECTING ENGINEERING UNITS To select engineering units for this flow sheet
56. or this To open the File menu click on the word File on the menu bar Now choose the New Job option by clicking on it o HA a ea Heb i opii giac _ senza FesdChargelicnn COM ip C Sial Conin pb C Satish Liesi EJ mm o Siva ark Lupe hob Fies cca Cancel The following dialog box will open This dialog box is prompting you to enter a name and folder for the new job Let s use the name TUTORI Please enter this name in the field labeled File Name Then close the dialog box by clicking the Save button You will be taken into the main working window of CHEMCAD 1 CHEMCAD 5 4 3 D VOCSDATA g g cex x Fle Edt View Format Mode ThermoPhysical Specfications Run Resuts Pot Outret Siting Tool Window Help x olsa ej amp HAJAJAJR R iz f Fow E Rae af SoS Seb s Loge 14 618 Oev 714 618 Scale 1 000 Mode Flowsheet Ready Relota Part 02 06 PM The major features of this window are labeled above as described below The top line called the Title Bar now contains the CHEMCAD logo and the current job name as well as the minimize title and close buttons which are always present on the left side The Menu Bar follows the Title Bar and consists of fifteen For file management and print commands in addition to the Help command These commands are File Edit View Fomat Mode ThermoPhysical Specifications Run For file management and print c
57. out in units of molar flowrate For Tutorl we do not want mole flowrates we want mass flowrates and mole fractions Therefore we first need to turn the Mole flow rate off You can do this by pointing and clicking on the box to the left of the label This box currently contains a checkmark indicating that at this time mole flowrates is an active selection Please point and click this box now Now let s turn the mass flowrate option on Please point and click on the Mass flowrate box now Finally let s turn the Mole Fractions option on by pointing and clicking on that option Your screen should look like this 37 E Flow Composition Options Select options to display Mole flow rate jv Mole fractions M Mole Mass fractions Mass F Std lig vol flow Std lig vol frac Std lig vol Std vap vol flow Std vap vol frac Std vap vol Cancel OK Please save these entries by pointing and clicking on OK in the bottom right corner of the dialog box This will return you to the Report Menu Now let s select stream properties Please select the Stream Properties option on the Report Menu The Property Options dialog box will appear Please note this dialog box has two pages You will also notice this is an on off selection screen similar to the Flowrate Composition options dialog box Whichever options have a checkmark in the box next to them will be printed Whichever options do not have a
58. ow by clicking the close button The Report Menu will reappear You can now return to the main CHEMCAD window GENERATING THE PROCESS FLOW DIAGRAM Another way to obtain a hardcopy output is to create a process flow diagram PFD Select the Main PFD option on the Output Menu Optionally the user might either choose the Main PFD option from the Change Mode combo box on the tool bar or select the Main PFD option from the Mode command The program will go into PFD mode which means it will open up certain commands and features that up to now have been unavailable These are Add Stream Box The Add Stream Box command is used to create stream data boxes Stream data boxes can be used to display the heat and material balance and stream properties As many stream data boxes as desired can be placed on a PFD This command is located on the Format menu Add UnitOp Box The Add UnitOp Box command is used to create unit operation data boxes Unit operation data boxes can be used to display the input and or output of UnitOps on the flowsheet As many UnitOp data boxes as desired can be placed on a PFD This command is located on the Format menu Add TP Box The Add TP Box command is used command is used to display the temperature pressure and or flowrate of a stream in small boxes attached to the relevant stream This command is located on the Format menu Add Excel Range The Add Excel Range command is used to easily display simulation da
59. pecifications Utility Rating Cost Estimations Pressure drop 5 psi For design mode enter only ONE of the following Temperature of stream 3 4 99999 F Vapor fraction of stream 3 a Subcooling stream 3 ssid F Superheat stream 3 oOo F Heat Duty MMB Delta T stream 3 stream 2 hh P Backcalc Mode for utocalc fo No back calculation T Calculated Heat Duty 2 83774 MMBtu h LMTD End points LMTD Corr Factor Utility Flowrate see Rating Case The outlet temperature from this heat exchanger will determine how much of the liquid is removed in the flash drum This in turn will determine the cricondotherm dewpoint of the product gas Therefore this specification is one of the key parameters of our design As a first attempt let s estimate an outlet temperature of 5 F Therefore please enter 5 in the Pressure Drop field and a 5 in the Temperature of Stream 3 field Point and click on the OK button to save the data and close the dialog box 26 Specifying the flash drum In our example the flash drum is a vapor liquid separator and requires no specification Therefore we do not need to enter any input for this unit Specifying the valve Let s enter the outlet pressure for the valve Please move the cursor to the valve and double click The Valve dialog box will appear Since our outlet pressure for this unit is 125 psia please enter 125 in the Pressure Out field then point and click on the O
60. point for the product gas stream Stream 5 will be 20 F or less The cricondentherm dewpoint you will remember is the highest dewpoint temperature a mixture will ever see at any pressure The simplest way for us to identify the highest dewpoint temperature of the product gas is to plot all of the dewpoint temperatures of the product gas i e to plot a phase envelope Let s do that now To plot anything inside CHEMCAD we must start with the Plot command on the menu bar Please select this option by clicking on it When you do this the PLOT MENU will appear On this menu you will see a list of the general categories of plots available within CHEMCAD Please select Envelopes by clicking on it or by pressing the E key The Select streams dialog box will appear Move the cursor to stream 5 the product gas stream leaving the bottom of heat exchanger number 1 and click it once The number 5 will appear in the dialog box field Now click OK to close the streams selection process The Phase Envelope Options dialog box will appear EE Phase Envelope Estimations optional Bubble point T Dew point T Vapor fractions optional Vapor fraction Vapor fraction Vapor fraction Vapor fraction Cancel Starting press No entries on this screen are required since we only need to look at the dew point line However to make the plot more interesting let s display the 0 25 and the 0 5 vapor fraction lines in additio
61. r a moment a pop up information window appears listing stream properties including composition The value for propane should be 1 or very close to 1 as shown in Figure 17 62 Streas No 9 Strean Nare Teap 238 8567 es psia 130 0000 Enth KMBtu h 1 9058 Vapor sole fraction 6 00000 Total lbmol h 27 1644 Total lbh 2045 0244 Total std L ft3 hr 51 6274 Total std V scth 10308 30 Component sole X Nitrogen 0 000000 Methane 0 000000 Ethene 0 000017 Propane 1 000131 I Butane 5 663057 N Butane 8 416503 I Penteane 28 606650 N Pentane 17 601676 W Hexane 38 629970 Figure 17 Checking the propane content of stream 9 Now that you have achieved the results that you set out to produce save the simulation using either File gt Save or the Save button on the toolbar Producing a Text Report The Report menu offers a broad array of text reports as described in Chapter 8 Output and Reports For the purpose of this tutorial assume that you want to view and print out a report with the following information e For Streams 1 5 8 and 9 the stream composition in mass flow rates and mole fractions as well as the default stream properties e The equipment summaries for every piece of equipment in the flowsheet e Tower tray profiles for the condensate stabilizer Because you want a report with a broad range of information about your simulation use the Consolidated Report option 1 Select Report gt Consolidated Report to bring up the
62. re 8 The new K value selection in the Thermodynamic Settings dialog box 52 4 Now click the Enthalpy Models tab The Peng Robinson method has already been entered as the Global Enthalpy Model selection this was done automatically because you chose Peng Robinson as your K value method While you do have the option to override this choice in this case you ll need to keep the Peng Robinson model leave all settings as they are and click OK to return to the main CHEMCAD workspace For the purpose of this tutorial the thermodynamic selections are now complete Note While you are not required to use the Thermodynamics Wizard you should know how to use it if only as a starting point for your simulations You can revisit the wizard at any time by selecting Thermophysical gt Thermodynamics Wizard Defining the Feed Streams Now it s time to define your simulation s feed stream There are several ways that you can do this but the quickest and most efficient way to define a single stream is to double click the stream line Note Before you proceed verify that your engineering units are set to English in the Engineering Unit Selection dialog box as described earlier in this tutorial Double click the line for stream 1 your feed stream to bring up the Edit Streams dialog box E Edit Streams I Pentane N Pentane Figure 9 The Edit Streams dialog box 53 You will specify the feed stream according to the following rules
63. rialaGEMGADT Tutorial CHEMCAD TUTORIAL cen 106274 6226 106274 6326 106274 6226 102632 0000 102623 0000 2641 6797 2641 6797 454 6191 2187 0505 75 0000 22 0622 5 0000 5 0000 47 9082 5 0000 8 5561 71 5064 214 2786 200 0000 195 0000 190 0000 190 0000 185 0000 190 0000 125 0000 125 0000 120 0000 gt gt BOXSET my Logic 989 793 Dev 531 560 Scale 0 768 Mode PFD Steady State K PR H PR 01 39 PM 7 Now let s resize the databox Point the cursor to one of the small black squares at the corners or the databox Then while holding down the left mouse button roll the mouse around As you do so the databox will change size Move the mouse until the databox is the correct size then release the mouse 43 Our stream databox has been successfully completed You can put as many stream databoxes on a PFD as you desire Thus one databox might contain the heat and material balance while another contains the stream transport properties Alternately one databox might contain stream one through twenty while another contains streams thirty through fifty The system is extremely flexible UnitOp databoxes can be created using the same process outlined above These databoxes can contain input and or output information for any selected UnitOp on the flowsheet Placing text on the PFD xGOONLCA Text and other symbols and objects can be put on the PFD also using the PFD palette To call th
64. rogen o gt B A Methane Ethane Propane I Butane 2 Methylpropane Isobutane N Butane I Pentane 2 Methylbutane Isopentane N Pentane i Delete Clear Add Insert Search for Copy components from another job 17 Selected Components area The current list of selected components will be displayed in this area Component Databank area All components stored in the databank s are listed here Components are listed in order of their ID numbers When this area is active a blue highlight will identify one of the components Selection string field This field is used to locate a component in the databank Once the desired component has been located it is added to the flowsheet component list by double clicking on it or by highlighting it and then clicking on the Add button The program locates components by matching the string entered in this field The string can be any alphanumeric combination The string will be matched to any part of an ID numbers formula or synonym component name listed in the databank As you type in the string the program automatically finds and highlights the closest match As the string changes the highlighted component changes Next button If the current match is not the component you are looking for click the Next button to find the next matching string Add button Clicking on the Add button will add the currently highlighted component to the end of the flowsheet component list Components
65. same stream selection procedure illustrated above therefore let s type in the desired stream numbers this time To do this follow the procedure given below 1 Select No in the small box next to the label Print ALL streams 2 Select Yes in the field labeled Select from flowsheet graphic 3 Now we need to identify streams 1 5 8 and 9 as the selected streams First click on the stream ID box in the upper left hand corner under the label Enter the stream ID s 36 4 Type the number 1 into the field 5 Now click on another field and type the number 5 It does not matter which box you select Any box will do even if it is not contiguous to the first box 6 Select boxes for the other streams and enter the numbers 8 and 9 7 To close the Select Streams dialog box click on the Save button We should now be back on the Report Menu Our next step will be to select the flow units for the stream compositions print out To do this we use the Stream Flowrate Composition option on the Report Menu Please select this option now Your screen should look like this RE Flow Composition Options Select options to display WV Mole flow rate M Mole fractions M Mole Mass fractions Mass Std lig vol flow Std lig vol frac Std lig vol M Std vap vol flow Std vap vol frac M Std vap vol Cancel OK You will notice that in the default condition the stream compositions will be printed
66. stantly CHEMCAD now saves your simulation only when you use the Save command This provides you with greater flexibility and gives you more control over your simulations but it also means that you should save your work frequently This is a sound practice for working in any software application as it can help you avoid losing work in the event of a power problem or computer glitch Selecting Engineering Units Select Format gt Engineering Units to open the Engineering Unit Selection dialog box The English units option is the default and is currently highlighted To change the engineering units system you would click the Alt SI SI or Metric button you could then change any of the individual units as well For this tutorial you will use English units so click Cancel to exit this dialog box without making changes Drawing the Flowsheet Creating a flowsheet is a matter of placing UnitOp icons on the screen connecting them with streams and then adding various graphical objects to enhance the drawing Placing UnitOps 1 Start your flowsheet by adding an icon to represent the initial feed stream In the All UnitOps palette find the Feed icon which is an arrow pointing to theright Click the 46 Feed icon then click in the workspace where you want to place the feed stream When the feed stream arrow appears go ahead and turn off the Feed drawing tool by right clicking any blank area of the workspace Note At any time after drawing
67. store the original sized click on the Graph command on the menu bar then click on the Zoom Out command 2 The plot title text in this case Phase Envelope for Stream 5 can be edited using the Chart Explorer facility within CHEMCAD This is accessed by clicking on the Graph command then selecting the Edit option 3 The color size layout and various other aspects of the plot presentation can also be edited using the Chart Explorer function 4 A hardcopy of this plot can be obtained by clicking the Print button Let s use some of these features to see how they work First remembering that we are trying to determine if the cricondentherm dewpoint of Stream 5 is 20 F or less let s zoom in on the graph around the right most area of the curve a Point the cursor to a point around the 1000 psia 0 F coordinate on the graph b Now push down the left button of the mouse and hold it down while you drag the cursor to the approximate location of the 400 psia 30 F coordinate c Release the left button The program will zoom in on the selected area and you screen should look something like this 32 Vim Hiei betes HT ene a COTO From this we can see the highest dewpoint of this mixture is a little less that 20 F Therefore the cricondentherm dewpoint of this mixture is indeed at or less than our product gas specification Our plot is now finished To print the display click the Print button This finishes our plo
68. t Set Flow Units to bring up the View Flow Rate Unit dialog box Click the Mole button and then click OK to apply this selection and close the dialog box 2 Now select Report gt Stream Compositions gt Select Streams In the Select Streams dialog box type 9 and then click OK to continue 3 The resulting tabular data window shows that propane is greater than the 1 specification see Figure 15 This means that the initial design is too conservative To correct this you can go back and re specify the column to produce precisely 1 propane in the bottom Simulation CHEMCAD Tutorial FLOW SUMMARIES Stream No 9 Stream Name Temp F 228 7404 Pres psia 130 0000 Enth MMBtu h 2 0944 Vapor mole frac 0 00000 Total lbmol h 30 0000 Total lb h 2221 0918 Total std L t3 hr 56 3867 Total std V scfh 11384 34 Component mole Nitrogen 0 000000 Methane 0 000000 Ethane 0 000069 Propane 4 175568 I Butane 5 468059 N Butane 7 966615 I Pentane 28 739998 N Pentane 18 414593 N Hexane 35 235101 Figure 15 Stream Composition report for stream 9 61 4 Return to the main simulation window by clicking the report tab s red x button Re running the Simulation You can now re run the stabilizer specifying that you want 1 propane in the bottom 1 Double click the Tower UnitOp to bring up the TOWR Distillation Column dialog box for the stabilizer 2 Click the Specifications tab You need to change the reboiler mode from 4 Bottom mole f
69. t as Needed Before running and printing reports and plots you should review the simulation to verify whether it meets the design criteria set out for this problem Checking the Cricondentherm Dewpoint If you have chosen the proper outlet temperature for the second heat exchanger the cricondentherm dewpoint for the product gas stream stream 5 will be 20 F or less The cricondentherm dewpoint you will recall is the highest dewpoint temperature a mixture will ever see at any pressure The simplest way to identify the highest dewpoint temperature of the product gas is to plot all of the dewpoint temperatures of the product gas i e to plot a phase envelope 1 Start with the Plot menu which provides access to all types of graphical reports Select Plot gt Phase Envelopes In the Select Streams dialog box specify stream 5 then click OK to bring up the Phase Envelope dialog box 2 No entries are required on this screen since you only need to look at the dewpoint line but to make the plot more interesting display the 0 25 and the 0 5 vapor fraction lines in addition to the normal phase envelope boundaries Complete the dialog box as shown in Figure 12 58 E Phase Envelope Estimations optional Bubble point T Dew point T Vapor fractions optional Vapor fraction 25 k Vapor fraction a Vapor fraction Vapor fraction Starting press Cancel Figure 12 Plotting vapor fraction lines along with
70. t by zooming out to give yourself more workspace If you use a mouse that is equipped with a scroll wheel between the mouse buttons you can point at the center of your flowsheet and roll the scroll wheel down a few clicks to zoom out If you don t have a scroll wheel you can select View gt Zoom Options gt Out 64 2 Now place the databox containing the heat and material balance for this flowsheet Select Format gt Add Stream Box to bring up the Select Streams dialog box Because you want to include all streams leave the settings the way they are and click OK to continue 3 In the Databox Property Options dialog box review the default selections indicated by checked boxes For the purposes of this tutorial leave the selections as they are and click OK to continue 4 In the Databox Settings dialog box you can indicate whether to use dividing lines within the box Accept the default settings here and click OK 5 The stream databox appears in the upper left corner of the CHEMCAD workspace but you want to place it below the flowsheet The databox is already selected so point your mouse cursor anywhere inside the box and then click and drag to reposition it Move the databox until it is centered below the flowsheet diagram Note You can also resize a databox by selecting the box and then clicking and dragging any of the sizing handles at the corners Drag in to make the databox smaller or out to make it larger notice that the
71. t exercise Please return to the main window by closing the current window Therefore please click the XI button on the right hand side of the second bar This will return you to the main CHEMCAD window Checking the bottoms stream purity Our second specification requires that the percent of propane in Stream 9 is to be 1 We can check and see if we have achieved this specification by using the Results command Please point and click on the Results command or press ALT U now When you do this the Results menu will appear We want to check stream compositions and we want to do it in mole percent Therefore we must first set our flow units Please point and click on the Set Flow Units option now The View Flow Rate Unit dialog box will appear Please point and click on the option which says Mole Then click OK You will be returned to the Main CHEMCAD Window Now click Results again On the Results Menu highlight Stream Compositions On the STREAM COMPOSITIONS MENU which appears click on Select Streams The Select Streams dialog box will appear As before use the mouse to point to stream 9 and click once Now click OK The following display will appear 33 CHEMCAD_TUTORIAL4 doc WordPad Archivo Edici n Yer Insertar Formato Ayuda Del Shk B Courier New v i0 v vii Nix s 2 2 CHEMCAD 5 4 3 Page 1 Job Hame CHEMCAD TUTORIAL Date 01 17 2005 Time 12 21 49 Stream Ho 9 Stream Name Temp F 214
72. ta from Excel Data Sheets that your computer has access to It is updated after a new run is made This command is located on the Format menu 39 Refresh Data Boxes The Refresh Data Boxes command is used to update the stream and UnitOp data boxes after a new run has been made It is located on the View menu The PFD palette The PFD palette is a small palette which contains only those graphics functions which are relevant to creating a PFD The are the select rotate rectangle ellipse line multiline text and Job box functions These are described below and in the Drawing with the Palette and How to put text on a drawing sections of this User s Guide Other commands not consistent with the creation of PFD will gray out or become unavailable until we switch back into simulation mode The process of creating PFD s consist of the following activities 1 Creating and placing Stream Databoxes on the drawing Stream databoxes are framed tabulations of the heat and material balance and stream properties The content and style of these databoxes is within the user s control 2 Creating and placing Unit Operation Databoxes on the drawing Unit Operations databoxes are framed tabulations of selected input and output values for each unit operation on the flowsheet Again the style and content of these databoxes is within the user s control 3 Displaying simulation data on the drawing The user may paste relevant simulatio
73. text adjusts in size to fit the box 6 Now place a title on the PFD to describe the process In the All UnitOps or Drawing Symbols palette find and select the Text tool 7 Move the cursor to a point somewhere above the flowsheet and click the primary mouse button A vertical insertion point line begins to blink where you have clicked Type the words Condensate Stabilizer PFD and then click any blank spot on the CHEMCAD workspace 8 To make this text larger select Format gt Font In the Font dialog box change the Size setting to 18 and then click OK 9 Click and drag the new heading to center it above the flowsheet diagram 10 Finally set up a layer for your stream databox and title so that you can display or hide these items as a single unit At the bottom of the CHEMCAD Explorer pane click the Simulation tab then right click the Layers item and select New 65 Ce Components Y Thermodynamics t Flowsheet f Sensitivity Studies a Data Maps N Saved Charts Groups ER Qj Le o Remo N elected from All Figure 18 Creating a new layer using the CHEMCAD Explorer 11 In the New Layer dialog box type a name for the new layer For this example name the layer PFD Elements then click OK to create the layer 12 Now add the two PFD elements to the layer Click the title that you placed above the flowsheet then hold down the SHIFT key and click inside the stream databox that you placed belo
74. the components to be used in this simulation Start by selecting Thermophysical gt Select Components This brings up the Select Components dialog box shown in Figure 6 E Select Components Available Components Selected Components ID Name CAS Name CAS Last Modi Hydrogen 1333 74 0 Methane 74 82 68 Ethane 74 84 0 Propane 74 98 6 Isobutane 75 28 5 l Butane 75 28 5 2 Methylpropane 75 28 5 N Butane 106 97 8 Pentane 78 78 4 lsopentane 78 78 4 2 Methylbutane 78 78 4 N Pentane 109 66 0 2 2 Dimethylpropane 463 82 1 Neopentane 463 82 1 N Hexane 110 54 3 he Eotom x E Copy From Another Simulation 1 2 3 4 5 5 5 6 7 7 7 8 g 9 1 lt Figure 6 The Select Components dialog box For this example you ll choose components from the standard CHEMCAD database In the Select Components dialog box find and add each needed component beginning with nitrogen 1 In the Search box start typing the word nitrogen 2 As soon as you ve typed ni you should see 46 Nitrogen N2 highlighted in the Available Components area Click the right arrow button to add nitrogen to your simulation 3 Use the scroll bar in the Available Components area to return to the top of the component list 4 Hold down the CTRL key on your keyboard as you click each of the following components in turn e 2 Methane e 3 Ethane e 4 Propane e 5 I Butane e 6 N Butane 50 5 Click the right arrow b
75. treated as a heat duty and is added to the heat balance of the unit The temperature and pressure are arbitrary for this situation e The Total flow unit and Comp unit fields work together to provide a variety of ways to define stream compositions If the selected comp unit is mole mass or volume fraction either globally or locally then the Total flow unit selection is available If the selected comp unit is a flow or amount option then the total flow rate becomes the sum of the component flow rates and the Total flow unit selection is not available e If the Comp unit field selection is an amount flow unit as opposed to a fractional unit then the component flow rate values are automatically added as you enter them The current sum is displayed in the Total flow field e You can click the Flash button at any time to perform a flash calculation using the currently specified composition and thermodynamic properties This enables you to obtain flash calculations quickly and without leaving the dialog box e Fractions that do not add up to 1 0 are automatically normalized when you either click Flash or exit the dialog box With these rules and behaviors in mind enter the data for your feed stream 54 1 Begin with the stream temperature Click the Temp F label then click the empty field to its right Type 75 and then press the down arrow key on your keyboard to continue 2 Type 200 in the Pres psia field then press the down arrow
76. tte will disappear and a small square box will appear on the screen This is the cursor used to position and place UnitOp icons on the flowsheet 3 Move the cursor to a position that is approximately on the left center of the screen Then left click the mouse The feed icon will appear on the flowsheet and the palette will reappear Notice that since we selected our feed icon from the main palette the icon displayed is the same one displayed on the main palette To choose a different feed icon we would have had to select from the feed icon sub palette This completes the placement of the UnitOp Feed For purposes of instruction let s explore some of the options associated with the Feed icon a To move the symbol e Place the mouse arrow on the icon e Hold down the left button on the mouse The four windows object boxes will appear e With the left mouse button held down drag the icon up about one inch then release the left button of the mouse The icon position has been changed b It may be necessary to move the palette out of the way in order to have access to the icon You can do this by clicking and dragging on the brown bar at the top of the palette c To view the object editing options place the mouse arrow on the icon on the flowsheet not on the palette and press the right button on the mouse d To move or stretch an object left click on the icon so that the four object boxes are displayed around the icon Then click
77. use Draw the stream over to the inlet position on the second heat exchanger and when the label appears press the left button on the mouse again This should complete Stream 2 Next let s draw the stream from the second heat exchanger to the flash tank Locate the right most outlet point on the Heat Exchanger unit When the black arrow appears click the left 15 mouse button Now draw the stream over to the flash tank until the first inlet label appears Press the left button on the mouse to complete Stream 3 Let s draw Stream 4 from the top of the flash tank Move the cursor near the top of the flash tank until the black arrow appears Press the left button on the mouse Now draw the stream up about an inch and over to the left until it is directly over the first heat exchanger then try to draw the stream down You will notice you cannot do it the entire line moves down with you What we need to do is fix horizontal latitude to which that line is pegged before we make our turn To do this select your horizontal elevation for your cross stream and press the left button on the mouse Now draw the steam down to the top of the heat exchanger When that inlet label appears press the left button on the mouse Using this procedure complete the rest of the streams until your flowsheet looks like this 1 CHEMCAD 5 4 3 D VOCSDATA new new ccx Fie Edt View Format Mode TheemoPhysical Specifications Run Results Pit Outret Sing To
78. ut no condenser we must use the sub palette to select the proper icon Therefore right click on the Tower icon box The sub palette will appear Select the Tower icon indicated below by left clicking on it Now add it to the flowsheet 12 1 CHEMCAD 5 4 3 D VOCSDATA new new ccx File Edt View Format Mode ThermoPhyskcal Spedfications Run Resuts Pkt Oust Sang Took Window Help 82 xXx Ojo ea ze S WAAR ie Cafe Fom Rere Raela ae fe F ae Yor a Ew FG so Vt i oo4 s Tower 4 Logic 168 120 Oev 168 120 Scale 1 000 Mode Flowihent Steady State 02 21 PM Close the sub palette by right clicking on the Tower icon box on the main palette Finally we must put three Product icons on the flowsheet one for each product stream The Product icon is located slightly to the right and down from the center of the palette as shown When you are finished you screen should look something like this CHEMCAD 5 4 3 D VOCSDATA new new cex Fie Ed View Format Mode ThermoPiysical Specifications Run Resits Plot Output Siting Toots Window Help olsa tlel B AALAN lis Cf Fow fe Raa o gt Streams It s now time to connect the UnitOps with streams To do this click the Streams icon box on the main palette There are a few general rules to remember when we are drawing streams on the flowsheet 1 Each stream goes from a source unit to a destination unit 2 E
79. utton located to the right of the Available Components area to add all of the selected components to your simulation 6 Now add the following components by double clicking each one in turn e 7 J Pentane e 8 N Pentane e 10 N Hexane E Select Components Available Components Selected Components ID Name CAS Formula Name CAS Last Modified Hydrogen 1333 74 0 E Nitrogen 772 02 27 08 10 46 Methane 74 82 8 Methane 74 8 02 27 08 10 46 Ethane 74 84 0 Ethane 74 8 02 27 08 10 46 Propane 74 98 6 Propane 74 9 02 27 08 10 46 Isobutane 75 28 5 l Butane 75 2 02 27 08 10 46 l Butane 75 28 5 N Butane 106 02 27 08 10 46 2 Methylpropane 75 28 5 l Pentane 78 7 02 27 08 10 46 N Butane 106 97 8 N Pentane 109 02 27 08 10 46 Pentane 78 78 4 N Hexane 110 02 27 08 10 46 lsopentane 78 78 4 2 Methylbutane 78 78 4 N Pentane 109 66 0 2 2 Dimethylpropane 463 82 1 Neopentane 463 82 1 N Hexane 110 64 3 n w Boton 1 2 3 4 5 5 5 6 7 7 7 8 9 l 1 lt Figure 7 The completed Select Components dialog box 7 Save your component selections by clicking OK Selecting Thermodynamic Options As soon as you have finished component selection the Thermodynamics Wizard appears This tool can suggest thermodynamics options to use with this simulation CHEMCAD s Thermodynamics Wizard works like this 1 First it looks at the component list and decides what general type of mo
80. ve been done with the string 46 which is the ID number for nitrogen Strings which comprise only part of the word number or formula can also be used It is also possible to highlight the desired component by clicking on it directly and then clicking the Add button 18 Now select the remaining components in the component list Remember if the first search does not locate the desired component click the Next button to find the next matching string Now find the following components and add them to the component list 2 Methane 3 Ethane 4 Propane 5 I butane 6 N butane 7 I pentane 8 N pentane 10 N hexane The dialog box should now look like this EE Component Selection Selected Components Component Databank Nitrogen Methane Ethane Propane I Butane N Butane I Pentane N Pentane Propane I Butane 2 Methylpropane Isobutane N Butane I Pentane 2 Methylbutane Isopentane N Pentane Neopentane 2 2 Dimethylpropane 4 5 5 5 6 7 a 7 8 9 9 0 Delete Clear Add Insert Search for Next Copy components from another job Cancel OK Let s now save our list by clicking the OK button SELECTING THERMODYNAMIC OPTIONS After the user first selects components the ThermoWizard will appear The ThermoWizard is a system available in the CHEMCAD Suite to assist the user in making K value and enthalpy choices The system works like this 1 First it looks at the component list and decides what
81. w the flowsheet Both items should now be selected with small black boxes visible in each corner 13 In the CHEMCAD Explorer pane double click the Layers item to expand it then right click on your newly created PFD Elements layer and click Add Selected w Leg uivupS Add Selected N Remove Selected Figure 19 Adding selected items to your new layer 66 14 The title and stream databox are now part of the PFD Elements layer This layer is visible as indicated by the green check mark on its icon Click this icon or the name PFD Elements to toggle the layer off causing the title and stream databox to disappear then click again to make them visible 15 With the PFD elements visible select View gt Zoom Options gt Zoom to Fit This custom fits the entire PFD to the available workspace for optimal printing To print you can either select File gt Print or click the Print button on the main CHEMCAD toolbar Follow the prompts for your printer tocomplete the printing process 16 To close CHEMCAD select File gt Close or click the Close button in the upper right comer of the CHEMCAD window Click Yes at the message asking whether you want to exit CHEMCAD then click Yes again to save changes to the simulation 67

SCHX4011 CHEMCAD LAB

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