CA2121807A1 - Method and apparatus for controlling liquid level in a knot drainer - Google Patents
Method and apparatus for controlling liquid level in a knot drainerInfo
- Publication number
- CA2121807A1 CA2121807A1 CA002121807A CA2121807A CA2121807A1 CA 2121807 A1 CA2121807 A1 CA 2121807A1 CA 002121807 A CA002121807 A CA 002121807A CA 2121807 A CA2121807 A CA 2121807A CA 2121807 A1 CA2121807 A1 CA 2121807A1
- Authority
- CA
- Canada
- Prior art keywords
- accepts
- liquid level
- knot
- chamber
- level
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C40—COMBINATORIAL TECHNOLOGY
- C40B—COMBINATORIAL CHEMISTRY; LIBRARIES, e.g. CHEMICAL LIBRARIES
- C40B40/00—Libraries per se, e.g. arrays, mixtures
- C40B40/02—Libraries contained in or displayed by microorganisms, e.g. bacteria or animal cells; Libraries contained in or displayed by vectors, e.g. plasmids; Libraries containing only microorganisms or vectors
-
- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
- C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
- C12N15/09—Recombinant DNA-technology
- C12N15/10—Processes for the isolation, preparation or purification of DNA or RNA
- C12N15/1034—Isolating an individual clone by screening libraries
- C12N15/1037—Screening libraries presented on the surface of microorganisms, e.g. phage display, E. coli display
-
- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
- C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
- C12N9/0002—Antibodies with enzymatic activity, e.g. abzymes
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K38/00—Medicinal preparations containing peptides
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2333/00—Assays involving biological materials from specific organisms or of a specific nature
- G01N2333/90—Enzymes; Proenzymes
- G01N2333/901—Antibodies with enzymatic activity; e.g. abzymes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/30—Against vector-borne diseases, e.g. mosquito-borne, fly-borne, tick-borne or waterborne diseases whose impact is exacerbated by climate change
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S424/00—Drug, bio-affecting and body treating compositions
- Y10S424/805—Drug, bio-affecting and body treating compositions involving IgE or IgD
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S424/00—Drug, bio-affecting and body treating compositions
- Y10S424/81—Drug, bio-affecting and body treating compositions involving autoimmunity, allergy, immediate hypersensitivity, delayed hypersensitivity, immunosuppression, immunotolerance, or anergy
Abstract
A screen aperture blinding prevention and liquid overflow prevention and level control apparatus for a knot drainer (100) senses liquid level (77) within the knot drainer (100) and compares the sensed level to a setpoint level. Differences in the two levels generate control signals of appropriate magnitude and direction, and those control signals are transmitted to a valve (140) whose degree of responsiveness and openness is adjusted to change the outflow rate of accepts liquor from the accepts chamber (80) of the rejects separator. In addition, passive level control is provided in the discharge line for establishing accept flooded screen apertures (61) regardless of variations of inflow and outflow rates during operation while active level control to create accept flow rate greater than, less than, or equal to inlet flow rate is provided by the combination of siphonic loop (170), barometric leg (55) and control. Continuous flow of fiber and liquid through separating screen apertures is appropriately supervised by monitoring accepts chamber (80) pressure.
Description
WO93/08518 2121~ 0 7 P~/US92/086~1 .
M~ETHOD AND APPARATUS ~OR CONTROLLING
LIQU~D LEVEL lN A KNOT DRAINER
BACK~ROUND OF THE ~NVENI101~
This invention relates generally to rejects separators for fibrous slurries produced by cooking cellulose material such as wood and more particularly to liquid level control method and apparatus for sealed knot separators and knot drainers in a paper pulpmaking operation.
ln a pulp mill, a small fraction of the pulp stream consists of undi~ested wood chips called knots. These knots must be remo~ed from the pulp durin~ processing to negate contamination of the finished pulp with undesirable woody type material. For this purpose, a knot separator is used which may be a one stage system for a lowcapacity mill or, more commonly, since hi~h capacity knotters reject a considerable amount of ~ood fiber with the knots~ a two stage system wherein the rejected knots and~fiber rom the first stage hi~h capacity knotters are separated again in thesecondary or reject sta~e knot drainer. The two stage svstem perrnits a higher capacity operatlon while, at the same time, irnproving the efficiency of knot separation from good fiber and knot removal. This improved accuracy results in a decrease in theamount~ o f pulp liquor and fiber being dischar~ed with the knots.
:, ~ , The prlmary high capacity knotter operates under pressure. It removes the knots from ~the main pulp stream and concentrates them in a relatively low volume, I ow consisiency reJects flow of concentrated kno~s with fiber and liquor. The second stage rejects separator drains the pulp fiber and liquor away from the knots, washes adhered fiber off the k~nots, and rejects fiber free damp knots to a knot tanl;. This simplifies knot reprocessing or disposal and conserves pulp fiber, liquor and contained chemicals and minimizes undesirable environmental dischar~es.
A secondary rejects separator or knot drainer is open to the atmosphere throu~h the rejects dischar~e outlet. Feed rate to the knot drajner ;s determined by the knot 2121807 '` ` ' content of the cooked pulp and the operation of the pulp system and is subject to wide fluctuations. It is, therefore~ possible for the knot drainer to over~low or "run dry"~
depending upon the feed flow rate of knots~ andior fiber, and/or liquor in combination.
T~}e knot drainer does not actually run dry, but this terrninology is used to describe a corldition which occurs due to the differential pressure (i.e., delta P) across the screen basket reaching a level at which the inlet side of the apertures in the screen basket are incipiently blinded over and thus fiber and/or li~uor incipiently ceases to flow through the apertures at which point the liquid level in the accepts chamber of the knot drainer mav, if not maintained full, fall below the top of the separating screen basket and allow the ingress of air into the accepts compartment therebv maximizino delta P.
This may cause blinding off of the separating screen basket apertures and mav require shutdown of the knot drainer for cleanout and the shutdown of the entire pulping line during the cleanout penod. The loss of production due to running dry and the loss of fiber and pulp liquor due to overflow are significant economic risks.
:
The ~foregoing illusrrates li~nita~ions known tO exist in present devices and methods. Thus~ it is~ apparent that it would be advantageous to provide an alternative directed to overcoming onè or~ more of the limitations set forth above. Accordingly a suitable ~alternative Is ~provided includln~ features more fully disclosed hereinafter.
SUMMARY OF THE II~VE?~ION
In one aspect of the present invention, this is accornplished by providing a liquid level control apparatus for a knot drainer which provides for sensing apparent inlet liquid level withinj the knot drainer. for comparin~ the sensed inlet liquid level to a set~ point inlet liquid level, and ~or transmitting a signal having an appropriate sign : ~ , ~ and a magnitude proportional to the difference~ if any between the sensed level and : :
the set point level~ an apparatus, responsive to the transmitted signal, for regulating the outflow rate of accepts liquor from the knot drainer and an accepts dischar~e line havin~ a siphonic loop for establishin a minimum liquid level within sand knot ~ ~ : SVB~ UTES&~EET
~,r ~
~ 212~`~Q7 2a drainer and a barometrlcally positioned downstream of the accepts chamber outlet for providing a vacuum action fo~ rapid absorption of flow surges.
:
:
O
-3 ~T~
:
WO g3/08518 PCr/VS92/08651 ; 2121~
The foregoing and o~her aspects will become apparerlt from the following detailed descnption of the invention when considered in conjunction with the accompanying drawing figures.
. , .
BRlEF DESCRIPTION OF THE DRAWlNGS
Fig. 1 is a schematic cross sectional elevation view showing the ~eneral layout of an advanced desi~n rqects separator incorporatin~ features of the present invention;
Fi~. 2 is a schematic dia,~ram indicatlng interconnection of sensing and controlfeatures of the present invention ' ETAILED DES~RlPTlO~
Referring to Fig. 1, operation of a rejects, or knot, drainer 100 can be understood. The example shown is a vertical drainer in which the knot bearin~ slulTy is ~ed into the knot drainer 100 through feed inlet ~0. lt passes axially upward throu~h screening chamber 58 in which~the majority fraction of the acceptable fiber passes throu~h apertures 61 of coarse screen 60 into accepts chamber ~0 from which it is discharged throu~h accepts dischar~e outlet 54. At the same time~ the kllOtS~ unable to pass~through~ screen apenures 61, encounter convevor screw flight 70 which is rotating with shaft 59 and which propels the knots upward through a washing region 76 which lies between screening chamber 58 and liquid level vortex 77. Preferably, just below the surfac of liquid leYel ~voreex 77 are knot washing liquor injection nozzles 75, which introduce fiber free~wash liquor. This liquor removes any adherin~ fiber from the knots by liquid scouring due to the relative motion between knot and wash liquor.
Once above liquid level vortex 77, the knots are further drained of liquid by centrifu~al force and ~ravity and are finallv swept into knot dischar~e outlet 53 and - may be. for example, collected in a knot tank which is not shown. To this point, the description has been of the operation of a standard advanced design rejects separator.
WO 93/08518 pcr/us92/o86~1 21218~7 ~
Foatures of the screen basket aperture blinding prevention and overflow control system of the present invention applicable to the advanced design rejects separator and other similar, generally vertical, cylindrical screenplate, knot conveyor type separators are best illustrated by reference to Figs. 1 and 2.
; Liquid level in a rejects drainer is a function of feed flow rate, knot washing liquid flow rate, accepts discharge flow rate, accepts pressure, screen aperture entrance blinding, and knot discharge. ~eed flow rate is determined by the operating characteristics of the pulp line in whlch the rejects separator is located. Therefore, feed~ flow ~rate to the~ reJects separator is subject to wide fluctuation and cannot be ; ~ constrained~ wlthout a ~danger ~of upsetnng the pulp line operation. Knot washing or elutriation flow rate is manually set in order to assure effectiveness in removin~ fiber from the upwardly travelling knots. ~Knot discharge varies with the degree and horoughness of ~the cooking process and excluding hard cooks (excessive knot content) and othèr than~in the case of excessive and;abnonnally hlgh knot content in the ;digested~pulp due to cooking~upset, has very little effect on liquid level within the réJects~drainer. Therefore,~ the~ most~ practical ~neans for maintaining the accept side of the~ screen~apertures 61~flooded~ withiD a reJects drainer is by controlling the accepts chamber submergence by level;~ànd1or pressure and the accepts discharge flow rate.
Ievel~ control ~system~of `the present invention provides a liquid level limiterthe~n of ~a~siphomc loop~170 which provides for flooding the accept side of the screen by~means~of en~surir~g~a~minimum~ liquid~level during startup and other transient flow operatmg condltions. ~ s~ operates similarly to a drain trap and is a passive or static level limiting device;but an active inlet flow surge absorbing devlce when m combination~with barometrlc leg~55 which can provide a "liquid plunger" effect creating a rapid pressure: decrease in accepts chamber 80 in response to increases in openness of valve 140.
, .~ W~93/08518 PCI~US92/û8651 .~ ~
~121~07 A liquid level sensor 110 is mounted on or near the bottom of the housin,~ of the rejects separator ~00 on the inlet side of the screen 60 for example against shaft base 58. Sensor 11û monitors the apparent level of liquid level vortex 77 and transits a signal of appropriate magnitude~through wires 112 to liquid level control si~nal prooessor 130. Accepts chamber preissure sensor 120 monitors pressure and provides ~; an indication of the apparent liquid level within the accepts chamber 80. Accepts pressure sensor 120 transmits a signal through wires 122 to signal processor 130.
Llquid level control si~nal processor 130 transmits control si~nals throu~h contral si~nal w~res 1~32 and 162. These si~nals actuate and re~ulate the degree of openness of accepts outflow control ;valve ~40~ and. when appropriate, trigger accepts chamber low level alarm 160.
The combination of slphonic loop ~70, barometric leg ~ and accepts outflow ontrol valve 140 mamtains~accepts chamber 80 flooded while preventing overflow of the~3eparator by rapidly absorblng inlet flow surges. Since accepts outflow capacity exceeàs;inlet~low capacity, ~adjus~nénts of openness of valve l~0 in response tosense'd apparent inlet ~llquid~ level~ changes result in immediate increase or decrease of à~pts ~c~hamber pressure due to~ increa~sed or decreased slphonin~ ac~ion caused b~
increaséd~or decreàsed~fluid flow through valve ~40 and barometric leg 5~.
The barometnc~ piping of accepts; discharge 55 has a higher flow capacity capabili~y~ than does ~feed~flow~inlet SO and; is sized to create relatively iow accept c hamber pressure surges~ to enhance the~ absorption of increased inlet flow sur~es while maintaining the screen flooded. This assures that there is sufficient accepts flow capacity to handle anv instantaneous increased feed flow which may come from thepulp line. This "excess" ;flow absorption capability permits accepts outflow control valve 140 to be operated; at a partially open condition and to increase or decrease its openness in response to increases or decreases of hquid level 77, as sensed by liquid level sensor 110. Thus, liquid inlet level control is primarily achieved throu~h ~he , ~
WO 93/08518 ~ l 2 l ~ ~ 7 PCr/US92/086~1 combination of siphonic loop 170, barometric leg 5~, and accepts outflow controlvalve 140 whose openness is modulated in response to signals from liquid level si~na]
processor 130 which counteract liquid level changes as measured and signalled b~level sensor 110. Knot washing or elutriation flow rate is determined by the requirements for fiber removal and is not adjustable for liquid level control purposes.
Accepts chamber 80 must be maintained full of liquid at all times. This is to avoid an excessive pressure drop across screen 60 due to the accepts side of apertures 6I not being flooded~ which could result in blinding the inlet side of the screen apertures 61 with an impenneable mat of pulp and knots due to centrifuging effect.
Such blinding would? in the majority of instances, require shutdown of the separator for cleanout of the screen. Consequently, accepts chamber pressure sensor 120 monitors pressure in accepts chamber 80 and transmits si~nals through signal leads 122 to si~nal processor 130. Wher~ever the apparent liquid level in accepts chamber 80 falls to a preestablished level, immediately before the top of accept side of the screen 60 can begin to become ~nflooded. the si~nal is preferably used for triggering alarm 160 through leads 16Z and for alerting an operator of the discrepant operating condition so that appropriate corrective action can be taken. However it may also be used to trig~er backwash flbw through screen apertures 61 from backwash nozzles 64 or to tcmporarily override, through leads ~2, the norrnal control si~nals to accepts outflow control vaive 140 causing it to close. Thus, accepts chamber low level alarm 160, shown schematically in Fig. 2, may produce an audio/visual alarrn and/or a control signal t~ backwash nozzles 64 and to accepts outflow control valve 140 to eliminate screen blinding, if ~any, ~and to bring the accepts chamber and the screen basket 60 back to a flooded condition thereby eliminating excessive pressure drop across screen 60 attributable to non-balanced centrifu~al force.
The invention described provides real time dynamic control of screening charnber liquid level in rejects separators in response to chan~es in feed flow rate and in response to partial blinding of openings of screen apertures 61 Overflows to the .
.
.
WO 93/0~518 ~ JS92/0~651 ~1~1807 knot discharge chute are prevented as well as blinding of screen apertures induced by low liquid level and non-flooded screen apertures 61 on the accepts side of the screen 60.
:~
,.
:
.
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~,
M~ETHOD AND APPARATUS ~OR CONTROLLING
LIQU~D LEVEL lN A KNOT DRAINER
BACK~ROUND OF THE ~NVENI101~
This invention relates generally to rejects separators for fibrous slurries produced by cooking cellulose material such as wood and more particularly to liquid level control method and apparatus for sealed knot separators and knot drainers in a paper pulpmaking operation.
ln a pulp mill, a small fraction of the pulp stream consists of undi~ested wood chips called knots. These knots must be remo~ed from the pulp durin~ processing to negate contamination of the finished pulp with undesirable woody type material. For this purpose, a knot separator is used which may be a one stage system for a lowcapacity mill or, more commonly, since hi~h capacity knotters reject a considerable amount of ~ood fiber with the knots~ a two stage system wherein the rejected knots and~fiber rom the first stage hi~h capacity knotters are separated again in thesecondary or reject sta~e knot drainer. The two stage svstem perrnits a higher capacity operatlon while, at the same time, irnproving the efficiency of knot separation from good fiber and knot removal. This improved accuracy results in a decrease in theamount~ o f pulp liquor and fiber being dischar~ed with the knots.
:, ~ , The prlmary high capacity knotter operates under pressure. It removes the knots from ~the main pulp stream and concentrates them in a relatively low volume, I ow consisiency reJects flow of concentrated kno~s with fiber and liquor. The second stage rejects separator drains the pulp fiber and liquor away from the knots, washes adhered fiber off the k~nots, and rejects fiber free damp knots to a knot tanl;. This simplifies knot reprocessing or disposal and conserves pulp fiber, liquor and contained chemicals and minimizes undesirable environmental dischar~es.
A secondary rejects separator or knot drainer is open to the atmosphere throu~h the rejects dischar~e outlet. Feed rate to the knot drajner ;s determined by the knot 2121807 '` ` ' content of the cooked pulp and the operation of the pulp system and is subject to wide fluctuations. It is, therefore~ possible for the knot drainer to over~low or "run dry"~
depending upon the feed flow rate of knots~ andior fiber, and/or liquor in combination.
T~}e knot drainer does not actually run dry, but this terrninology is used to describe a corldition which occurs due to the differential pressure (i.e., delta P) across the screen basket reaching a level at which the inlet side of the apertures in the screen basket are incipiently blinded over and thus fiber and/or li~uor incipiently ceases to flow through the apertures at which point the liquid level in the accepts chamber of the knot drainer mav, if not maintained full, fall below the top of the separating screen basket and allow the ingress of air into the accepts compartment therebv maximizino delta P.
This may cause blinding off of the separating screen basket apertures and mav require shutdown of the knot drainer for cleanout and the shutdown of the entire pulping line during the cleanout penod. The loss of production due to running dry and the loss of fiber and pulp liquor due to overflow are significant economic risks.
:
The ~foregoing illusrrates li~nita~ions known tO exist in present devices and methods. Thus~ it is~ apparent that it would be advantageous to provide an alternative directed to overcoming onè or~ more of the limitations set forth above. Accordingly a suitable ~alternative Is ~provided includln~ features more fully disclosed hereinafter.
SUMMARY OF THE II~VE?~ION
In one aspect of the present invention, this is accornplished by providing a liquid level control apparatus for a knot drainer which provides for sensing apparent inlet liquid level withinj the knot drainer. for comparin~ the sensed inlet liquid level to a set~ point inlet liquid level, and ~or transmitting a signal having an appropriate sign : ~ , ~ and a magnitude proportional to the difference~ if any between the sensed level and : :
the set point level~ an apparatus, responsive to the transmitted signal, for regulating the outflow rate of accepts liquor from the knot drainer and an accepts dischar~e line havin~ a siphonic loop for establishin a minimum liquid level within sand knot ~ ~ : SVB~ UTES&~EET
~,r ~
~ 212~`~Q7 2a drainer and a barometrlcally positioned downstream of the accepts chamber outlet for providing a vacuum action fo~ rapid absorption of flow surges.
:
:
O
-3 ~T~
:
WO g3/08518 PCr/VS92/08651 ; 2121~
The foregoing and o~her aspects will become apparerlt from the following detailed descnption of the invention when considered in conjunction with the accompanying drawing figures.
. , .
BRlEF DESCRIPTION OF THE DRAWlNGS
Fig. 1 is a schematic cross sectional elevation view showing the ~eneral layout of an advanced desi~n rqects separator incorporatin~ features of the present invention;
Fi~. 2 is a schematic dia,~ram indicatlng interconnection of sensing and controlfeatures of the present invention ' ETAILED DES~RlPTlO~
Referring to Fig. 1, operation of a rejects, or knot, drainer 100 can be understood. The example shown is a vertical drainer in which the knot bearin~ slulTy is ~ed into the knot drainer 100 through feed inlet ~0. lt passes axially upward throu~h screening chamber 58 in which~the majority fraction of the acceptable fiber passes throu~h apertures 61 of coarse screen 60 into accepts chamber ~0 from which it is discharged throu~h accepts dischar~e outlet 54. At the same time~ the kllOtS~ unable to pass~through~ screen apenures 61, encounter convevor screw flight 70 which is rotating with shaft 59 and which propels the knots upward through a washing region 76 which lies between screening chamber 58 and liquid level vortex 77. Preferably, just below the surfac of liquid leYel ~voreex 77 are knot washing liquor injection nozzles 75, which introduce fiber free~wash liquor. This liquor removes any adherin~ fiber from the knots by liquid scouring due to the relative motion between knot and wash liquor.
Once above liquid level vortex 77, the knots are further drained of liquid by centrifu~al force and ~ravity and are finallv swept into knot dischar~e outlet 53 and - may be. for example, collected in a knot tank which is not shown. To this point, the description has been of the operation of a standard advanced design rejects separator.
WO 93/08518 pcr/us92/o86~1 21218~7 ~
Foatures of the screen basket aperture blinding prevention and overflow control system of the present invention applicable to the advanced design rejects separator and other similar, generally vertical, cylindrical screenplate, knot conveyor type separators are best illustrated by reference to Figs. 1 and 2.
; Liquid level in a rejects drainer is a function of feed flow rate, knot washing liquid flow rate, accepts discharge flow rate, accepts pressure, screen aperture entrance blinding, and knot discharge. ~eed flow rate is determined by the operating characteristics of the pulp line in whlch the rejects separator is located. Therefore, feed~ flow ~rate to the~ reJects separator is subject to wide fluctuation and cannot be ; ~ constrained~ wlthout a ~danger ~of upsetnng the pulp line operation. Knot washing or elutriation flow rate is manually set in order to assure effectiveness in removin~ fiber from the upwardly travelling knots. ~Knot discharge varies with the degree and horoughness of ~the cooking process and excluding hard cooks (excessive knot content) and othèr than~in the case of excessive and;abnonnally hlgh knot content in the ;digested~pulp due to cooking~upset, has very little effect on liquid level within the réJects~drainer. Therefore,~ the~ most~ practical ~neans for maintaining the accept side of the~ screen~apertures 61~flooded~ withiD a reJects drainer is by controlling the accepts chamber submergence by level;~ànd1or pressure and the accepts discharge flow rate.
Ievel~ control ~system~of `the present invention provides a liquid level limiterthe~n of ~a~siphomc loop~170 which provides for flooding the accept side of the screen by~means~of en~surir~g~a~minimum~ liquid~level during startup and other transient flow operatmg condltions. ~ s~ operates similarly to a drain trap and is a passive or static level limiting device;but an active inlet flow surge absorbing devlce when m combination~with barometrlc leg~55 which can provide a "liquid plunger" effect creating a rapid pressure: decrease in accepts chamber 80 in response to increases in openness of valve 140.
, .~ W~93/08518 PCI~US92/û8651 .~ ~
~121~07 A liquid level sensor 110 is mounted on or near the bottom of the housin,~ of the rejects separator ~00 on the inlet side of the screen 60 for example against shaft base 58. Sensor 11û monitors the apparent level of liquid level vortex 77 and transits a signal of appropriate magnitude~through wires 112 to liquid level control si~nal prooessor 130. Accepts chamber preissure sensor 120 monitors pressure and provides ~; an indication of the apparent liquid level within the accepts chamber 80. Accepts pressure sensor 120 transmits a signal through wires 122 to signal processor 130.
Llquid level control si~nal processor 130 transmits control si~nals throu~h contral si~nal w~res 1~32 and 162. These si~nals actuate and re~ulate the degree of openness of accepts outflow control ;valve ~40~ and. when appropriate, trigger accepts chamber low level alarm 160.
The combination of slphonic loop ~70, barometric leg ~ and accepts outflow ontrol valve 140 mamtains~accepts chamber 80 flooded while preventing overflow of the~3eparator by rapidly absorblng inlet flow surges. Since accepts outflow capacity exceeàs;inlet~low capacity, ~adjus~nénts of openness of valve l~0 in response tosense'd apparent inlet ~llquid~ level~ changes result in immediate increase or decrease of à~pts ~c~hamber pressure due to~ increa~sed or decreased slphonin~ ac~ion caused b~
increaséd~or decreàsed~fluid flow through valve ~40 and barometric leg 5~.
The barometnc~ piping of accepts; discharge 55 has a higher flow capacity capabili~y~ than does ~feed~flow~inlet SO and; is sized to create relatively iow accept c hamber pressure surges~ to enhance the~ absorption of increased inlet flow sur~es while maintaining the screen flooded. This assures that there is sufficient accepts flow capacity to handle anv instantaneous increased feed flow which may come from thepulp line. This "excess" ;flow absorption capability permits accepts outflow control valve 140 to be operated; at a partially open condition and to increase or decrease its openness in response to increases or decreases of hquid level 77, as sensed by liquid level sensor 110. Thus, liquid inlet level control is primarily achieved throu~h ~he , ~
WO 93/08518 ~ l 2 l ~ ~ 7 PCr/US92/086~1 combination of siphonic loop 170, barometric leg 5~, and accepts outflow controlvalve 140 whose openness is modulated in response to signals from liquid level si~na]
processor 130 which counteract liquid level changes as measured and signalled b~level sensor 110. Knot washing or elutriation flow rate is determined by the requirements for fiber removal and is not adjustable for liquid level control purposes.
Accepts chamber 80 must be maintained full of liquid at all times. This is to avoid an excessive pressure drop across screen 60 due to the accepts side of apertures 6I not being flooded~ which could result in blinding the inlet side of the screen apertures 61 with an impenneable mat of pulp and knots due to centrifuging effect.
Such blinding would? in the majority of instances, require shutdown of the separator for cleanout of the screen. Consequently, accepts chamber pressure sensor 120 monitors pressure in accepts chamber 80 and transmits si~nals through signal leads 122 to si~nal processor 130. Wher~ever the apparent liquid level in accepts chamber 80 falls to a preestablished level, immediately before the top of accept side of the screen 60 can begin to become ~nflooded. the si~nal is preferably used for triggering alarm 160 through leads 16Z and for alerting an operator of the discrepant operating condition so that appropriate corrective action can be taken. However it may also be used to trig~er backwash flbw through screen apertures 61 from backwash nozzles 64 or to tcmporarily override, through leads ~2, the norrnal control si~nals to accepts outflow control vaive 140 causing it to close. Thus, accepts chamber low level alarm 160, shown schematically in Fig. 2, may produce an audio/visual alarrn and/or a control signal t~ backwash nozzles 64 and to accepts outflow control valve 140 to eliminate screen blinding, if ~any, ~and to bring the accepts chamber and the screen basket 60 back to a flooded condition thereby eliminating excessive pressure drop across screen 60 attributable to non-balanced centrifu~al force.
The invention described provides real time dynamic control of screening charnber liquid level in rejects separators in response to chan~es in feed flow rate and in response to partial blinding of openings of screen apertures 61 Overflows to the .
.
.
WO 93/0~518 ~ JS92/0~651 ~1~1807 knot discharge chute are prevented as well as blinding of screen apertures induced by low liquid level and non-flooded screen apertures 61 on the accepts side of the screen 60.
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.
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Claims (8)
- What is claimed is:
A liquid level control apparatus for a knot drainer (100) having at least a screening chamber (58) and an accepts chamber (80) separated by a screening means (60) andcharacterized in that said apparatus comprises:
means for establishing an inlet liquid set point;
means (110) for sensing apparent inlet liquid level within said knot drainer;
means for comparing said inlet liquid level set point to said sensed inlet liquid level, and for transmitting a signal having an appropriate sign and a magnitude proportional to a difference, if any, between said liquid level set point and said sensed liquid level;
means (140), responsive to said transmitted signal, for regulating an accepts outflow rate from said knot drainer;
pressure sensing means (120)in the accepts chamber (80) for monitoring apparent accepts chamber liquid level and for thereby detecting incipient blinding of perforations of said rejects separation screen bounding said accepts chamber;
an accepts discharge line having a siphonic loop means (170) for establishing a minimum liquid level within the knot drainer; and a barometric leg means (55) positioned downstream of the accepts chamber outlet for providing a vacuum action for rapid absorption of flow surges. - 2. The liquid level control apparatus for a knot drainer as recited in claim 1 wherein said means for regulating said accepts outflow rate is a valve means (140).
- 3. The level control apparatus for a knot drainer as recited in either claim 1 or claim 2 wherein said pressure sensing means in the accepts chamber generates a signal which, after appropriate processing, may be used to activate an audio/visual alarm (160), to activate flow of backwashing liquid through the rejects separating screen, and/or to temporarily override the level control signal to the means regulating the accept outflow rate from the knot drainer.
- 4. The level control apparatus of claim 1,wherein said accepts line is capable of generating a flow rate capacity which exceeds the flow rate capacity of a feed flow line for rejects-bearing pulp slurry.
- 5. A method for controlling liquid level in a knot drainer, including the steps of:
establishing an acceptable liquid level setpoint for said knot drainer;
monitoring and sensing liquid level in the knot drainer;
comparing the liquid level setpoint and the sensed liquid level, and generating a control signal having an appropriate sign and a magnitude proportional to the difference, if any, between the levels;
providing, in an accepts discharge line, means for maintaining a minimum liquid level in the knot drainer irrespective of variations of liquid feed flow and accepts liquid outflow; and adjusting a valve means in an accepts discharge line, said valve means being responsive to said control signal, for regulating outflow of accepts liquid from an accepts chamber of said knot drainer and for thereby controlling liquid level therein. - 6. The method of claim 5, including the further step of:
providing, in said accepts chamber, pressure sensing means for detecting apparent liquid level in said accepts chamber and for thereby detecting incipient blinding of perforations of a rejects separating screen bounding said accepts chamber. - 7. The method of claim 6, wherein said accepts chamber pressure sensing means provides a signal which activates an alarm.
- 8. The method of claim 6, including the further step of:
providing signal processing means for receiving signals from said liquid level sensing means, and from said accepts chamber pressure sensing means, for converting said signals to appropriate control and alarm signals, and for retransmitting said control and alarm signals to an accepts outflow valve in said accepts discharge line and an accepts chamber low level alarm, respectively.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US780,765 | 1991-10-21 | ||
| US07/780,765 US5258289A (en) | 1990-09-05 | 1991-10-22 | Method for the selecting of genes encoding catalytic antibodies |
| PCT/US1993/003408 WO1994024278A1 (en) | 1991-10-22 | 1993-04-09 | Selecting genes encoding catalytic antibodies |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2121807A1 true CA2121807A1 (en) | 1993-04-29 |
Family
ID=26786671
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002121807A Abandoned CA2121807A1 (en) | 1991-10-21 | 1992-10-12 | Method and apparatus for controlling liquid level in a knot drainer |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US5258289A (en) |
| CA (1) | CA2121807A1 (en) |
| WO (1) | WO1994024278A1 (en) |
Families Citing this family (47)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9015198D0 (en) * | 1990-07-10 | 1990-08-29 | Brien Caroline J O | Binding substance |
| US6916605B1 (en) * | 1990-07-10 | 2005-07-12 | Medical Research Council | Methods for producing members of specific binding pairs |
| US7063943B1 (en) | 1990-07-10 | 2006-06-20 | Cambridge Antibody Technology | Methods for producing members of specific binding pairs |
| DK1024191T3 (en) | 1991-12-02 | 2008-12-08 | Medical Res Council | Preparation of autoantibodies displayed on phage surfaces from antibody segment libraries |
| US5455221A (en) * | 1994-04-29 | 1995-10-03 | The United States Of America As Represented By The Secretary Of Agriculture | Botcinolide: a natural product herbicide which is a hydroxylated monalactone |
| WO1993019170A1 (en) * | 1992-03-16 | 1993-09-30 | Jacob Nathaniel Wohlstadter | Selection methods |
| US5648458A (en) * | 1992-05-06 | 1997-07-15 | Affymax Technologies N.V. | Peptides and compounds that bind to ELAM-1 |
| US5728802A (en) * | 1992-05-06 | 1998-03-17 | Affymax Technologies N.V. | Peptides and compounds that bind selectins including endothelium leukocyte adhesion molecule 1 (ELAM-1) |
| US5643873A (en) * | 1992-05-06 | 1997-07-01 | Affymax Technologies N.V. | Peptides and compounds that bind selectins including endothelial leukocyte adhesion molecule 1 |
| AU695406B2 (en) * | 1994-03-30 | 1998-08-13 | Igen International, Inc. | The isolation and production of catalytic antibodies using phage technology |
| US6846628B1 (en) * | 1994-04-29 | 2005-01-25 | Jacob Nathaniel Wohlstadter | Selection methods |
| US6063562A (en) * | 1994-09-16 | 2000-05-16 | Sepracor, Inc. | In vitro method for predicting the evolutionary response of HIV protease to a drug targeted thereagainst |
| US5766842A (en) * | 1994-09-16 | 1998-06-16 | Sepracor, Inc. | In vitro method for predicting the evolutionary response of a protein to a drug targeted thereagainst |
| US5602021A (en) * | 1994-12-29 | 1997-02-11 | Catalytic Antibodies, Inc. | Method for generating proteolytic enzymes specific against a selected peptide sequence |
| US6329139B1 (en) | 1995-04-25 | 2001-12-11 | Discovery Partners International | Automated sorting system for matrices with memory |
| US5741462A (en) * | 1995-04-25 | 1998-04-21 | Irori | Remotely programmable matrices with memories |
| US5751629A (en) | 1995-04-25 | 1998-05-12 | Irori | Remotely programmable matrices with memories |
| US6331273B1 (en) | 1995-04-25 | 2001-12-18 | Discovery Partners International | Remotely programmable matrices with memories |
| US6017496A (en) | 1995-06-07 | 2000-01-25 | Irori | Matrices with memories and uses thereof |
| US5874214A (en) | 1995-04-25 | 1999-02-23 | Irori | Remotely programmable matrices with memories |
| US6416714B1 (en) | 1995-04-25 | 2002-07-09 | Discovery Partners International, Inc. | Remotely programmable matrices with memories |
| DE69718150T3 (en) | 1996-03-01 | 2009-03-05 | Novartis Ag | PEPTIDE IMMUNOGENES FOR THE PROTECTION AGAINST THE TREATMENT OF ALLERGIES |
| US6699658B1 (en) | 1996-05-31 | 2004-03-02 | Board Of Trustees Of The University Of Illinois | Yeast cell surface display of proteins and uses thereof |
| US6300065B1 (en) | 1996-05-31 | 2001-10-09 | Board Of Trustees Of The University Of Illinois | Yeast cell surface display of proteins and uses thereof |
| US6696251B1 (en) | 1996-05-31 | 2004-02-24 | Board Of Trustees Of The University Of Illinois | Yeast cell surface display of proteins and uses thereof |
| AU729035B2 (en) | 1997-06-12 | 2001-01-25 | Novartis Ag | Artificial antibody polypeptides |
| IT1293511B1 (en) * | 1997-07-30 | 1999-03-01 | Gentili Ist Spa | MONOCLONAL CATALYTIC ANTIBODIES WITH PROTEASIC ACTIVITY FOR THE SELECTIVE LYSIS OF THE PROTEIN COMPONENT OF PLATES AND RELATED AGGREGATES |
| US6759243B2 (en) | 1998-01-20 | 2004-07-06 | Board Of Trustees Of The University Of Illinois | High affinity TCR proteins and methods |
| US7236888B2 (en) * | 1998-03-06 | 2007-06-26 | The Regents Of The University Of California | Method to measure the activation state of signaling pathways in cells |
| ES2564161T3 (en) | 2000-07-11 | 2016-03-18 | Research Corporation Technologies, Inc | Artificial antibody polypeptides |
| AU2002213091A1 (en) * | 2000-10-20 | 2002-05-06 | Igen International, Inc. | Methods and compositions for modifying biologically active target molecules |
| WO2002042732A2 (en) * | 2000-11-22 | 2002-05-30 | The Regents Of The University Of California | A method to measure the activation state of signaling pathways in cells |
| WO2002046400A2 (en) * | 2000-12-08 | 2002-06-13 | The Board Of Trustees Of The University Of Illinois | Mutated class ii major histocompatibility proteins |
| ATE455857T1 (en) | 2001-05-09 | 2010-02-15 | Monsanto Technology Llc | METABOLITE TRANSPORTERS |
| EP1950305A1 (en) | 2001-05-09 | 2008-07-30 | Monsanto Technology, LLC | Tyr a genes and uses thereof |
| US7919309B2 (en) | 2001-09-13 | 2011-04-05 | California Institute Of Technology | Method for expression of small antiviral RNA molecules within a cell |
| US7737124B2 (en) * | 2001-09-13 | 2010-06-15 | California Institute Of Technology | Method for expression of small antiviral RNA molecules with reduced cytotoxicity within a cell |
| US20040072276A1 (en) * | 2002-05-10 | 2004-04-15 | Direvo BioTech AG. | Process for generating sequence-specific proteases by directed evolution and use thereof |
| AU2003243436A1 (en) | 2002-06-06 | 2003-12-22 | Shohei Koide | Reconstituted polypeptides |
| US20050002897A1 (en) * | 2003-06-18 | 2005-01-06 | Ulrich Haupts | Biological entities and the pharmaceutical or diagnostic use thereof |
| ATE526399T1 (en) * | 2003-06-18 | 2011-10-15 | Bayer Pharma AG | NEW BIOLOGICAL UNITS AND THEIR USE |
| AU2005227313A1 (en) | 2004-03-19 | 2005-10-06 | Amgen Inc. | Reducing the risk of human and anti-human antibodies through V gene manipulation |
| US7674621B2 (en) | 2004-05-21 | 2010-03-09 | The United States Of America As Represented By The Department Of Health And Human Services | Plasmids and phages for homologous recombination and methods of use |
| WO2009079618A1 (en) * | 2007-12-18 | 2009-06-25 | Cytodesign, Inc. | Enzyme engineering systems and methods |
| PE20142330A1 (en) * | 2008-12-09 | 2015-01-14 | Pfizer Vaccines Llc | IGE CH3 PEPTIDE VACCINE |
| EP2442824A2 (en) | 2009-06-19 | 2012-04-25 | MedImmune, LLC | Protease variants |
| US9200251B1 (en) | 2011-03-31 | 2015-12-01 | David Gordon Bermudes | Bacterial methionine analogue and methionine synthesis inhibitor anticancer, antiinfective and coronary heart disease protective microcins and methods of treatment therewith |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4336186A (en) * | 1978-08-03 | 1982-06-22 | Gargiulo Robert J | Analytical fluorogenic substrates for proteolytic enzymes |
| US5037750A (en) * | 1984-11-27 | 1991-08-06 | Igen, Inc. | Method for producing antibodies which catalyze chemical reactions |
| ATE78158T1 (en) * | 1985-05-22 | 1992-08-15 | Liposome Technology Inc | METHOD AND SYSTEM FOR INHALATION OF LIPOSOMES. |
| US5096815A (en) * | 1989-01-06 | 1992-03-17 | Protein Engineering Corporation | Generation and selection of novel dna-binding proteins and polypeptides |
-
1991
- 1991-10-22 US US07/780,765 patent/US5258289A/en not_active Expired - Fee Related
-
1992
- 1992-10-12 CA CA002121807A patent/CA2121807A1/en not_active Abandoned
-
1993
- 1993-04-09 WO PCT/US1993/003408 patent/WO1994024278A1/en active IP Right Grant
Also Published As
| Publication number | Publication date |
|---|---|
| US5258289A (en) | 1993-11-02 |
| WO1994024278A1 (en) | 1994-10-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |