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Contents
1. 348 164 SE 5 219226 A 6 1993 pendant tube cleaning and operating systems 5 355 845 A 10 1994 5 368 471 A 11 1994 12 Claims 8 Drawing Sheets 80 79 90 76 75 70 S N N N N N N S N N 96 65 U S Patent Oct 14 2008 Sheet 1 of 8 US 7 437 025 B2 35 35 Kraft Chemical Recovery Boiler 37 37 47 Distributed Control System Fig 1 U S Patent Oct 14 2008 Sheet 2 of 8 35 60 55 Fig 2 US 7 437 025 B2 U S Patent Oct 14 2008 Sheet 3 of 8 US 7 437 025 B2 SE wo eo ILLIC CL XSXSSIXXXXXJ y U S Patent Oct 14 2008 Sheet 4 of 8 US 7 437 025 B2 98 85 Fig4 55 97 99 US 7 437 025 B2 Sheet 5 of 8 Oct 14 2008 U S Patent e GD 9 D L Du ee Se 2 L i D GE EE 2 NLL EE 2 TLETT WA d WEE U S Patent 70 Oct 14 2008 Sheet 6 of 8 s v diii S N E E ad 80 e oO oo N C r CN E Lr 65 US 7 437 025 B2 Fig 8 US 7 437 025 B2 Sheet 7 of 8 Oct 14 2008 U S Patent ei suosi uUyBuapeneny 8 e Ued ur 0L 46402063 uj uojssjuSue1 0 s i z o a e p o 8 0 8 0 1 UOISSIWSUEJ US 7 437 025 B2 Sheet 8 of 8 Oct 14 2008 U S Patent SEIS pue au SZ Jejog Aaen BJE S Je og BuipuejsJepur eDeu sejeuns 3 uonisodeq eBeu Se Ser pejueufegs 001 uoneueuibes e2. image formed by the video data input is captured and includes a low pass filter for performing noise filtering of said video input It also includes an image compensation system for array compensation to correct for pixel variation and dead US 2005 0220331 A1 Oct 6 2005 51 Int CI cells etc and for correcting geometric distortion An image G06K 9 20 2006 01 segmentation module receives a cleaned image from the G06K 9 00 2006 01 image pre processing circuit for separating the image of the 32 US CL teh t ti trieste 382 312 382 154 recovery boiler interior into background pendant tubes and 58 Field of Classification Search 382 100 deposition It also accomplishes thresholding clustering on 382 141 154 173 224 264 285 312 431 12 gray scale texture and makes morphological transforms to 431 13 75 110 186 234 162 30 1 30 11 smooth regions and identifies regions by connected compo 250 316 1 330 333 nents An image understanding unit receives a segmented See application file for complete search history image sent from the image segmentation module and matches 56 References Cited derived regions to a3 D model of said boiler It derives a3 D structure the deposition on pendant tubes in the boiler and U S PATENT DOCUMENTS provides the information about deposits to the plant distrib uted control system for more efficient operation of the plant 4 539 588 A 9 1985 Ariessohn et al
3. likely to decline as new processes come on line it is expected that well over 50 of wood pulp production will still be produced in 2020 using the Kraft process In the Kraft pulp production process a fibrous material most commonly wood chips are broken down into pulp ina digester under pressure in a steam heated aqueous solution of sodium hydroxide and sodium sulfide called white liquor After cooking in the digester the pulp is separated from the residual liquid called black liquor Black liquor is an aqueous solution containing wood lignins organic material and inor ganic compounds oxidized in the digester during the cooking process It is concentrated and then burned in a recovery boiler to generate steam which is used in the pulp mill for pulp cooking and drying and other energy requirements The material remaining after combustion of the black liquor called smelt is collected in a molten bed at the bottom of the boiler and discharged to a dissolving tank to be recycled into new white liquor Kraft chemical and energy recovery boilers in which the black liquor is burned are large and expensive with capaci ties installed in the last 30 years for pulp mills typically exceeding 1000 tons of pulp per day It is difficult economi cally to add small incremental units of boiler capacity so the capacity of the chemical recovery boiler is often the factor limiting the capacity of the entire pulp mill The effective burning capacity
4. of recover boilers is fre quently determined by the processes governing the deposi tion of fume intermediate sized particles and carryover of partially burnt liquor smelt drops on heat transfer surfaces of the steam and water tubes in the boiler and the attendant plugging of gas passages between and around those pendant steam and water tubes Much effort has been made and con tinues to be made to improving the understanding of the mechanism of particulate and vapor deposition on the tubes However there are still no reliable on line methods for sys tematically detecting the presence and build up rates ofthese deposits 25 40 55 2 Various efforts to control the rate and quantity of deposits on the pendant tubes in the boiler have been undertaken in the past These include adjustments to conditions of combustion such as the nozzles that spray the black liquor into the com bustion chamber and the way air is introduced into the com bustion chamber They also include systems such as soot blowers for removing deposits on the tubes before they seri ously impact the operation ofthe boiler These control efforts are most effective when they are immediately correlated to the results they produce but heretofore there has been no reliable method of determining directly the amount of depos its on the pendant tubes Such control efforts have therefore necessarily been based on indirect measurements and consid erations and have usua
5. the depositions on recovery boiler pendant tubes The invention includes a focal plane array camera capable of creating images in a particular range of infrared radiation that has low absorption by molecules in the gas stream in a chemical recovery boiler and is not scattered significantly by particles normally present in the boiler gas stream Another aspect of the invention is a system of one or more deposit monitoring sensors feeding signals to a data processing sys tem under control of a distributed control system Preferably the deposit monitoring sensors include focal plane array cam eras operating in the mid infra red band in the region of about 4 12 microns wavelength Clear images can be obtained at a low cost of the boiler interior and particularly of the pendant water and steam tubes in the boiler to enable for the first time a visual real time inspection of the condition of the tubes and depositions thereon so that control schemes can be implemented DESCRIPTION OF THE DRAWINGS The invention and its many attendant features and advan tages will become clear upon reading the following detailed description ofthe preferred embodiment in conjunction with the following drawings wherein FIG 1 is a schematic diagram of the invention installed in a Kraft recovery boiler US 7 437 025 B2 3 FIG 2 is a schematic elevation of a monitoring sensor shown in FIG 1 FIG 3 is an elevation of a hand held sensor in accordance wit
6. 2 358 A 10 1995 Werner 5 578 995 A 11 1996 Bryant et al 37 Weyerhaeuser Co Maintenance and Installation Manual Version 2 0 High Temperature Imaging System VIS Pub lished by Sensor amp Simulation Products Tacoma Washing ton 98477 Nov 30 1988 Continued Primary Examiner Deandra M Hughes 57 ABSTRACT A system for detection and control of deposition on pendant tubes in recovery and power boilers includes one or more deposit monitoring sensors operating in infrared regions of about 4 or 8 7 microns and directly producing images of the interior of the boiler or producing feeding signals to a data processing system for information to enable a distributed control system by which the boilers are operated to operate said boilers more efficiently The data processing system includes an image pre processing circuit in which a 2 D image formed by the video data input is captured and includes a low pass filter for performing noise filtering of said video input It also includes an image compensation system for array compensation to correct for pixel variation and dead cells etc and for correcting geometric distortion An image segmentation module receives a cleaned image from the image pre processing circuit for separating the image of the recovery boiler interior into background pen dant tubes and deposition It also accomplishes thresholding clustering on gray scale texture and makes morphological transforms to smooth
7. The sensor 35 shown in more detail in FIGS 2 and 5 7 converts the acquired infrared data to electrical signals which are conducted via electrical lines 37 to a sensor data process ing system 40 shown in more detail in FIG 10 and described in detail below The hand held sensor 36 shown in FIG 3 converts the acquired infrared data directly to an image that is viewed on a display inside a hood 42 at the viewer end of a camera body 44 A distributed control system 45 which is the computer system used by paper mill or power plant operators for con trolling the operation of the plant is connected to the sensor data processing system 40 by a link 47 for advanced control of the boiler operations in accordance with the information sup plied by the sensor data processing system 40 with operator judgement and analysis where necessary to minimize depo sition of the pendant steam tubes 49 and otherwise maximize plant efficiency Turning now to FIG 2 one embodiment of the deposit monitoring sensor 35 is shown having a focal plane array camera 50 and a lens tube 55 connected to the camera 50 by way of a spectral band pass filter 60 that limits the light admitted into the camera 50 to a particular band in the mid IR spectrum The imaging optics consist ofthe double layered steel lens tube 55 shown in FIGS 5 7 containing a train of ZnSe or amorphous silicon lenses 65 The front lens 70 serves as the objective and has a field of view of at lea
8. US007437025B2 az United States Patent 10 Patent No US 7 437 025 B2 Kychakoff et al 45 Date of Patent Oct 14 2008 54 SENSING SYSTEM FOR DETECTION AND 5 462 358 A 10 1995 Werner sissie 374 124 CONTROL OF DEPOSITION ON PENDANT 5 578 995 A 11 1996 Bryant etal 340 627 TUBES IN RECOVERY AND POWER 5 646 338 A 7 1997 Mercusot et al 73 86 BOILERS 6 560 966 B1 5 2003 Fetescu etal 60 775 76 Inventors George Kychakoff 23618 SE 25 St cited by examiner Maple Valley WA US 98038 Martin A Afromowitz 4429 Forest Ave Mercer Island WA US 98040 Richard 57 ABSTRACT E Hogle 12424 Littlerock Rd Olympia WA US 98512 Primary Examiner Yon Couso A system for detection and control of deposition on pendant tubes in recovery and power boilers includes one or more deposit monitoring sensors operating in infrared regions of about 4 or 8 7 microns and directly producing images of the interior of the boiler or producing feeding signals to a data Notice Subject to any disclaimer the term of this J y patent is extended or adjusted under 35 U S C 154 b by 633 days processing system for information to enable a distributed DT SPEO 117137087 control system by which the boilers are operated to operate 22 Filed May 24 2005 said boilers more efficiently The data processing system includes an image pre processing circuit in which a 2 D 65 Prior Publication Data
9. a distributed control system by which said boilers are operated to operate said boilers more efficiently
10. beu abew uea D SOL or OL 614 DEL Jo 3u025 JeMo g Wea S SPUBWILUOD Jewo g 96 06 BuisseooJd ad eDeuJJ OSDIA US 7 437 025 B2 1 SENSING SYSTEM FOR DETECTION AND CONTROL OF DEPOSITION ON PENDANT TUBES IN RECOVERY AND POWER BOILERS The U S Government has a paid up license in this inven tion and the right in limited circumstances to require the patent owner to license others on reasonable terms as pro vided for by the terms of Contract No DE FC36 99G010375 by the Department of Energy This is related to U S Provisional Application No 60 170 839 filed on Dec 14 1999 and to PCT US00 33879 filed on Dec 14 2000 and further to U S Ser No 10 168 277 filed on Jun 14 2002 all entitled Sensing System for Detection and Control of Deposition on Pendant Tubes in Recovery and Power Boilers This invention pertains to a sensing system for detection and control of deposition on pendant tubes in Kraft recovery boilers and more particularly to a mid band infra red imag ing system that is tuned to a particular spectrum of infra red radiation to see into the otherwise visually impenetrable inte rior of a recovery boiler in operation to provide information about the condition of pendant steam tubes in the boiler BACKGROUND OF THE INVENTION In 1995 about 82 of the wood pulp consumed at US paper and paperboard plants was produced using the Kraft process Although the proportion of pulp from this source is
11. coma WA 98477 copyright 1989 RCA Closed Circuit Video Equipment TC1005 01 Cam eras Installation and Operating Instructions Serial No 005838 and up New Holland Ave Lancaster PA 17604 3140 USA Apr 1984 RCA Closed Circuit Video Equipment DXC 101 102 Sony Service Manual Apr 1984 SYN FAB Inc High Temperature amp Industrial CCTV Equipment SF12 Solid State High Temperature Camera System Specifications Mobile Alabama Jul 1995 cited by examiner US 7 437 025 C1 1 EX PARTE REEXAMINATION CERTIFICATE ISSUED UNDER 35 U S C 307 THE PATENT IS HEREBY AMENDED AS INDICATED BELOW Matter enclosed in heavy brackets appeared in the patent but has been deleted and is no longer a part of the patent matter printed in italics indicates additions made to the patent AS A RESULT OF REEXAMINATION IT HAS BEEN DETERMINED THAT Claims 1 3 and 8 11 are cancelled Claims 4 7 and 12 are determined to be patentable as amended 4 A deposit monitoring sensor according to claim 1 5 wherein said optic elements comprise zinc selenide or amorphous silicon materials 5 A deposit monitoring sensor according to claim 1 for monitoring deposits on pendant tubes in a Kraft recovery boiler or a power boiler comprising an elongated lens tube containing high IR transmissivity optic elements and a spec tral band pass filter for passing radiation in a preferred wavelength band coupled to a camera sensitive to said wa
12. ent calibration and is relatively inexpensive However it does use a semi transpar ent chopper wheel to limit the intensity of the light to the array The chopper wheel introduces its own set of problems such as the superimposition of artifacts such as curved lines across the image These problems can be addressed by chang ing required solutions to achieve satisfactory images The PtSi array camera requires cryogenic cooling and is quite expensive making it a less preferred version of the usable cameras The microbolometer array camera does not require cryogenic cooling and does not use a chopper It also has significantly greater dynamic range than the ferroelectric array camera However it may require frequent once a day re calibration to produce acceptable images and is signifi cantly more expensive than the ferroelectric array camera The preferred camera is a ferroelectric array camera modi fied to view infrared radiation in a wavelength band of about 3 5 4 0 microns preferably about 3 9 microns or infrared radiation in a wavelength band of about 8 5 9 0 microns preferably about 8 7 microns This camera produces clear images in the system outlined above and is inexpensive enough to be affordable for pulp mills to purchase and use We anticipate that other imaging arrays usable in our camera will be developed that will be usable in the system shown in FIG 1 The sensor shown in FIG 3 includes the camera body 44 connected t
13. h this invention FIG 4 is an elevation of the hand held sensor of FIG 3 showing the air flow system for the lens tube FIG 5 is a sectional end elevation of the a monitoring sensors shown in FIG 2 FIG 6 is a sectional elevation of the a monitoring sensor shown in FIG 3 along lines 6 6 in FIG 4 FIG 7 is an enlarged sectional elevation of the distal end of the a monitoring sensor shown in FIG 6 FIG 8 is a schematic diagram ofthe optical elements in the sensor shown in FIG 3 FIG 9 is a graph showing the light transmission over a range of wavelengths in a recovery boiler and FIG 10 is a schematic flow diagram of the process of receiving data from the monitoring sensors in FIGS 1 and 3 to data input to the distributed control system in FIG 1 for control of deposition control systems in the boiler DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the drawings and more particularly to FIG 1 thereof a deposition detection system in accordance with this invention is shown installed in a Kraft recovery boiler 30 The deposition detection system includes one or several monitoring sensors 35 described in detail below which acquire data in the midband infra red spectrum within a par ticular field of view from the interior of the recovery boiler The monitoring sensors 35 could be fixed in position to per manently monitor particular areas within the boiler or could be integrated hand held units 36 shown in FIG 3
14. lly yielded unsatisfactory results The severe environment of boilers namely the high tem perature turbulent gas flow particle laden atmosphere and intensity of radiation have made it difficult to develop a sens ing system for detection and control of deposition on pendant tubes in Kraft recovery boilers that would be economically viable as a commercial product Attempts to use near IR cameras for direct monitoring of pendant tube deposits have failed to reliably produce good images over the span of large boilers and devices operating at longer wavelengths have been impractical for boiler side use because of prohibitive expense and the need for reliable cryogenic cooling U S Pat No 4 539 588 entitled Imaging of Hot Infrared Emitting Surfaces Obscured by Particulate Fume and Hot Gasses issued on Sep 3 1985 to Peter C Ariessohn and R K James discloses an improvement in the technology of the time but operated in a wavelength region of 1 5 1 8 micron which has a relatively high susceptibility to light scattering by particles in the boiler gas stream Thus there has long been a serious need for a deposition detection system for recovery boiler pendant tubes to solve the unfulfilled requirement to monitor the degree and distri bution of fume intermediate sized particles and carryover particle depositions on recovery boiler tubes SUMMARY OF THE INVENTION Accordingly this invention provides a method of directly monitoring
15. ntrol of the steam cleaning sys tem for the pendant tubes 49 in the boiler A control scheme is envisioned that utilizes the informa tion from the deposition detection system to control or mini mize further deposition or optimize deposit removal pro cesses From the processed images the system identifies the location of deposits and activates the steam cleaners or soot blowers that are most appropriate to clean the affected loca tion and prevent pluggage Currently the soot blowers are operated blind on a timed cycle Operating only the soot blowers only where and when there are deposits needing removal will minimize the steam usage as well as tube wear caused by unnecessary over cleaning Moreover it is now possible for the first time to accurately relate the deposition rate to the liquor burning parameters so the boiler operation can be optimized to minimize deposits on the pendant tubes Obviously numerous modifications and variations of the preferred embodiment described above are possible and will become apparent to those skilled in the art in light of this specification For example many functions and advantages are described for the preferred embodiment but in some uses of the invention not all of these functions and advantages would be needed Therefore we contemplate the use of the invention using fewer than the complete set of noted functions and advantages Moreover several species and embodiments
16. o the lens tube 65 by way of an intermediate structure 85 The intermediate structure 85 includes an adjust able iris 90 and the lens 60 which is axially movable to give the lens train the ability of focus in a low light wide aperture condition The hand held unit 37 has a power switch 94 and an electrical connector 96 which provides the ability to con nect electronically into the distributed control system 45 The lens tube 55 is connected to a source 98 of air pressure through a pressure regulator 97 and a flexible air hose 99 The graph on FIG 9 illustrates the benefits of operating in the regions of about 4 and 8 7 microns As illustrated there are several windows available to viewing the interior of a chemical recovery boiler by virtue of the light absorption characteristics of the gas and vapors in the gas stream of a chemical recovery boiler for a pulp mill The visibility of the boiler interior at these wavelengths is also influenced by the scattering effect of the particles in the boiler gas The effec tiveness of this particle scattering is greatly decreased at longer wavelengths and for wavelengths in excess of 3 microns does not significantly degrade images of recovery boiler interiors in the upper furnace and convection pass sec tions By operating an a region of low absorption and low scatter of the gas molecules and particles respectively in the US 7 437 025 B2 5 boiler gas stream the resolution of the images
17. of the invention are disclosed herein but not all are specifi cally claimed although all are covered by generic claims Nevertheless it is our intention that each and every one of these species and embodiments and the equivalents thereof be encompassed and protected within the scope ofthe follow ing claims and no dedication to the public is intended by virtue of the lack of claims specific to any individual species Accordingly we expressly intend that all these embodiments species modifications and variations and the equivalents thereof are to be considered within the spirit and scope ofthe invention as defined in the following claims wherein we claim The invention claimed is 1 A deposit monitoring sensor for monitoring deposits on pendant tubes in a Kraft recovery boiler or a power boiler comprising 25 30 40 45 65 6 an elongated lens tube containing high IR tranamissivity optic elements and a spectral band pass filter for passing radiation in a preferred wavelength band coupled to a camera sensitive to said wavelength band said lens tube having a cooling channel to prevent excessive heating of said optic elements from the boiler 2 A deposit monitoring sensor as in claim 1 wherein said cooling channel comprises an inner wall of said lens tube in which lenses are mounted and an outer wall surrounding said inner wall an inlet fluid coupling at one end of said outer tube for delivering a flow of co
18. oling fluid between said inner wall and said outer wall of said tube an outlet in said outer tube for conveying said cooling fluid out of said outer tube through said outlet for cooling to prevent excessive heating from the boiler 3 A deposit monitoring sensor as in claim 1 wherein said cooling channel comprises an inner wall of said lens tube has in which lenses are mounted and an outer wall surrounding said inner wall said outer wall having an open distal end anaircoupling for connection to a source of air pressure for delivering a flow of cooling air between said inner wall and said outer wall of said tube and for discharging said cooling air flow out through said opening at said distal end of said outer wall whereby a flow of cooling air is established along said lens tube for cooling to prevent excessive heating from the boiler 4 A deposit monitoring sensor according to claim 1 wherein said optic elements comprise zinc selenide or amorphous silicon materials 5 A deposit monitoring sensor according to claim 1 wherein said preferred wavelength band is in the region of 4 microns 6 A deposit monitoring sensor according to claim 1 wherein said preferred wavelength band is in the region of 8 7 microns 7 A deposit monitoring sensor according to claim 1 wherein said camera includes a focal plane array 8 A deposit monitoring sensor according to claim 1 wherein said cooling channel in said lens tube includes an inne
19. r wall and an outer wall surrounding and spaced from said inner wall and defining therebetween an annular space for flow of cooling fluid for conveying heat from said outer wall and protecting said inner wall and said lens tube from excessive heating from hot gasses in said boiler 9 A deposit monitoring sensor according to claim 8 wherein said cooling channel in said lens tube includes a coupling for connecting a source of air pressure to said lens tube for establishing a flow of cooling air around said inner tube 10 A deposit monitoring sensor according to claim 8 wherein said cooling fluid is water 11 A deposit monitoring sensor according to claim 9 wherein said cooling channel in said lens tube includes an opening at the distal end of said tube through which said cooling fluid exits said lens tube 12 A deposit monitoring sensor for monitoring deposits on pendant tubes in a Kraft recovery boiler or a power boiler comprising US 7 437 025 B2 7 at least one deposit monitoring sensor having an elongated lens tube containing high IR transmissivity optic ele ments and a spectral band pass filter for passing radia tion in a preferred wavelength band coupled to a camera sensitive to said wavelength bandfeeding signals for 5 producing an image for sending to a data processing 8 system for generating information about deposition on said pendant tubes to enable a distributed control system by which said boilers are ope
20. rated to operate said boilers more efficiently US007437025C1 a z EX PARTE REEXAMINATION CERTIFICATE 7594th United States Patent 10 Number US 7 437 025 C1 Kychakoff et al 45 Certificate Issued Jul 6 2010 54 SENSING SYSTEM FOR DETECTION AND 5 615 953 A 4 1997 Moskal CONTROL OF DEPOSITION ON PENDANT 5 646 338 A 7 1997 Mercusot et al TUBES IN RECOVERY AND POWER 5 724 180 A 3 1998 Wellman etal 359 359 BOILERS 6 560 966 Bl 5 2003 Fetescu et al OTHER PUBLICATIONS 76 Inventors George Kychakoff 23618 SE 25 St Maple Valley WA US 98038 Martin A Afromowitz 4429 Forest Ave Mercer Island WA US 98040 Richard E Hogle 12424 Littlerock Rd Olympia WA US 98512 Reexamination Request No 90 010 515 May 18 2009 Reexamination Certificate for Patent No 7 437 025 Issued Oct 14 2008 Appl No 11 137 089 Filed May 24 2005 51 Int CI G06K 9 20 2006 01 G06K 9 00 2006 01 52 US CL inmitten 382 312 382 154 58 Field of Classification Search None See application file for complete search history 56 References Cited U S PATENT DOCUMENTS 3 021 386 A 2 1962 Clark 3 609 236 A 9 1971 Heilman 4 005 327 A 1 1977 Roosild et al 4 539 588 A 9 1985 Ariessohn et al 4 679 891 A 7 1987 Roberts 4 709 381 A 11 1987 Beaudet 5 096 502 A 3 1992 Carter et al 5 219 226 A 6 1993 James 5 355 845 A 10 1994 Burgess et al 5 368 471 A 11 1994 Kychakoff et al 5 46
21. regions and identifies regions by connected components An image understanding unit receives a segmented image sent from the image seg mentation module and matches derived regions to a 3 D model of said boiler It derives a 3 D structure the deposition on pendant tubes in the boiler and provides the information about deposits to the plant distributed control system for more efficient operation of the plant pendant tube cleaning and operating systems 35 37 US 7 437 025 C1 Page2 OTHER PUBLICATIONS Weyerhaeuser Co Maintenance and Installation Manual Version 2 0 High Temperature Imaging System IR Pub lished by Sensor amp Simulation Products Tacoma Washing ton 98477 copyright 1989 Weyerhaeuser Co High temperature Imaging Sensor Lens Tube User Guide and Installation Manual Published by Sensor amp Simulation Products Tacoma Washington 98477 Tul 1 1992 Weyerhaeuser Co High Temperature Imaging System Lens Tube 2 13 Dia Lens Tubes Maintenance Manual Version 1 0 Published by Sensor amp Simulation Products Tacoma WA 98477 copyright 1989 Weyerhaeuser Co High Temperature Imaging System Lens Tube 1 50 Dia Lens Tubes Maintenance Manual Version 1 0 Published by Sensor amp Simulation Products Tacoma WA 98477 copyright 1989 Weyerhaeuser Co High Temperature Imaging System Lens Tube 1 75 Dia Lens Tubes Maintenance Manual Version 1 1 Published by Sensor amp Simulation Products Ta
22. st 20 Three other lenses 75 76 and 77 serve as transfer optics transporting the image formed by the objective onto the focal plane array 78 of the camera 50 The electrical signals from the imaging array 78 are processed in the electronic circuitry 79 and transmitted to a remote processing system in the case of the monitoring system shown in FIG 2 or displayed on a display such as an 20 30 35 40 45 50 55 65 4 LCD display screen 80 in the case of the hand held unit shown in FIG 3 The total length of the lens tube is about 36 inches permitting the focal plane to be located remotely from the boiler port The lens tube 55 is cooled and purged by a constant stream of air supplied at about 30 psi through a gas coupling 81 into the space between the inner and outer tubes of the double layered lens tube 55 through which the air flows and exits out through an axial opening 85 at the distal end of the lens tube 65 Several camera models could be used a ferroelectric array camera a PtSi camera and a Si microbolometer array cam era Also an InSb array camera operating in the 3 9 micron wavelength region has produced adequate images but was determined to be impractical because of its cost and the lim ited lifetime of the necessary low temperature cooling sys tems required for operation of the camera The ferroelectric array camera is attractive because it does not require cryo genic cooling does not require frequ
23. that are pos sible by infrared imaging in the chemical recovery boiler is maximized Turning now to FIG 10 an image processing system 40 and a link to one version of the distributed control system is shown having a video input 90 from the camera 50 to an image pre processing circuit 95 in which the 2 D image is captured and noise filtering is performed in a low pass filter Array compensation is accomplished to correct for pixel variation and dead cells etc and geometric distortion is corrected by image system compensation A cleaned image 100 is sent from the image pre processing circuit to an image segmentation module 105 where the image of the recovery boiler interior is separated into background pendant tubes and deposition Thresholding clustering on gray scale texture is accomplished and morphological transforms to smooth regions are made Regions are identified by connected com ponents The segmented image 110 is sent from the image segmentation module 105 to an image understanding unit 115 where derived regions are matched to a 3 D model of the recovery boiler and a 3 D structure 120 of the deposition is inferred Those deposition estimates can be provided to the distributed control system to update the computer model and state 125 of the recovery boiler which is fed back in a closed loop to continually update the image understanding unit 115 The deposition estimates 120 are fed to the soot blower control 130 for optimized co
24. velength band said lens tube having a cooling channel to prevent excessive heating of said optic elements from the 20 25 30 2 boiler wherein said preferred wavelength band is in the region of 4 microns 6 A deposit monitoring sensor according to claim 1 for monitoring deposits on pendant tubes in a Kraft recovery boiler or a power boiler comprising an elongated lens tube containing high IR transmissivity optic elements and a spectral band pass filter for pass ing radiation in a preferred wavelength band coupled to a camera sensitive to said wavelength band said lens tube having a cooling channel to prevent excessive heating of said optic elements from the boiler wherein said preferred wavelength band is in the region of 8 7 microns 7 A deposit monitoring sensor according to claim 1 5 wherein said camera includes a focal plane microbolometer array 12 A deposit monitoring sensor for monitoring deposits on pendant tubes in a Kraft recovery boiler or a power boiler comprising at least one deposit monitoring sensor having an elon gated lens tube containing high IR transmissivity optic elements and a spectral band pass filter for passing radiation in a preferred wavelength band iz the region of 4 microns coupled to a camera sensitive to said wavelength bandfeeding signals for producing an image for sending to a data processing system for gen erating information about deposition on said pendant tubes to enable
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