CA1173603A - Pressure diffuser controlling - Google Patents
Pressure diffuser controllingInfo
- Publication number
- CA1173603A CA1173603A CA000392616A CA392616A CA1173603A CA 1173603 A CA1173603 A CA 1173603A CA 000392616 A CA000392616 A CA 000392616A CA 392616 A CA392616 A CA 392616A CA 1173603 A CA1173603 A CA 1173603A
- Authority
- CA
- Canada
- Prior art keywords
- pulp
- liquid
- withdrawn
- slurry
- flow
- 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.)
- Expired
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Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/02—Washing ; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents
Abstract
ABSTRACT OF THE DISCLOSURE
A method for maintaining all pulp flows in and out of pressurized diffusers constant, continuous, and of stabilized consistency The method comprises feeding the pulp stream through the pulp inlet into the diffuser, withdrawing the treated pulp through the pulp outlet, governing the pulp withdrawal flow rate through the pulp outlet by controlling the pulp feed flow rate into the pulp inlet, establishing a consistency control over pulp withdrawn through the pulp outlet by controlling the li-quid flow rate from the liquid outlet. This facilitates the incorporation of such diffusers into a more efficient pulp mill process.
A method for maintaining all pulp flows in and out of pressurized diffusers constant, continuous, and of stabilized consistency The method comprises feeding the pulp stream through the pulp inlet into the diffuser, withdrawing the treated pulp through the pulp outlet, governing the pulp withdrawal flow rate through the pulp outlet by controlling the pulp feed flow rate into the pulp inlet, establishing a consistency control over pulp withdrawn through the pulp outlet by controlling the li-quid flow rate from the liquid outlet. This facilitates the incorporation of such diffusers into a more efficient pulp mill process.
Description
3l~736g~3 PRESSUE~E DIFFUSER CONTROl[.LER
BACKGROUND AND SIJMMARY OF THE INVENTION
This invention rela ces to a method for maintaining all flows in and out of pressurized 5 diffuser machines constant and continuous and of stabilized consistency thereby facilitating incorporation of such a machine or machines in a pulp mill process.
Conventional dewatering machines based on the rotating drum principle, such as vacuum washers, ai~
pressure washers, drum presses, wash presses and the like, share the co~mon drawbacks that the outlet consistency is undstermined and that the filtrates must exit into atmospheric filtrate tanks. The outlet consistency varies as a result of temperture fluctuations, changes in the production flow xate, variances in pulp drainage characteristics and mechanical factors associated with the process machinery.
To compensate for these problems, the conventional methods employed filtrate tanks as surge absorbers beca~se the exiting filtrate flow varied with its discharging consistency. These large filtrate tanks must be equipped with level recorders. The tanks must be of considerable dimensions to absorb the mentioned fluctuations and to allow suff icient deaeration of the liquor. As a further drawbac~, the large size resuits in significant heat losses.
The conventional filtrate tanks also require adequate pump caparity and pressure head controls to both dilute the incoming stock and circulate the e~cess (surplus) liquor countercurrently back into the 361~3 process. Considerable pressure head on the pump or pumps is required sinre the pressure process i5 conventionally kept we~l above the static head of the filtrate tank which was exposed to the atmosphere.
Introduction of a continuous diffuser which did not require any dilution of the incoming stock of medium consistency coupled with some control over outlet consistency by adjusting the extraction flow relative to wash liquor flow marked an improvement over the conventional processes. However, problems with pressure loss in the stock flow and air extrainment in the stock flow remained~ Since pulp su~pensions of~en contain liquids with fairly high surface tensions, the entrained air causes the suspension to become foamy, elastic, to emit smelly gases and hard to dewater causing treatment problems in succeeding process machinery. Stacking a series of diffusers in ~tages within a common tower casing was only a partial soluton because of practical limitations on the number of stages in one tower.
Additionally, the filtrate flow or extraction flow from the conventional diffusers remained intermittent because of the operating principle of the machine. The intermittent flow required periodic injection of li~uor to the interior oE the diffuser screens. Conventional systems consequently needed adequate liquor tanks, level recorders, pumps and other equipment.
Furthermore, the conventional diffusers needed extraction liquor flow control and separate wash liquor flow control to the preceding stage in multi-stage arrangements.
According to the method of the present invention, all flows in and out of the diffus~r are kept constant and continuous to eliminate the problems ~7~;36~3 commonly associated with diffusers. Consequently, pressurized diffusers may now be easily incorporated in a pressuri~ed system thereby eliminating the need for intermediate ~urge tank~, reducing pump power demand to a minimum, and totally eliminating the air entrainment and gas emission problems since the present invention no longer requires atmospheric disc~arge~ Level controllers will no longer be required and the number of flow controllers is almost halved since the extraction controller for one stage now concurrently serves as th2 wash liquor controller for the preceding stage~ Variat;ons in pulp charac-teristics, production rate and temperature will not af~ect pulp consistency since they will be governed purely through flow control using straightforward instrumentation regulatorsD
According to the pres:ent invention, there is provided a method of treating cellulosic pulp suspensions flowing in a relatively continuous stream through.
pressurized diffusers equipped with pulp inlets and outlets along with treatment liquid inlets and outlets, which method comprises feeding the pulp stream through the pulp inlet into the diffuser, withdrawing the trea-ted pulp through the pulp outlet, governing the pulp withdrawal flow rate through the pulp outlet by controlling the pulp feed flow rate into the pulp inlet, es-tablishing consistency control over pulp withdrawn through the pulp outlet by controlllng the liquid flow rate from the liquid outlet.
Additional cellulosic flow treatment comprises feeding treatment liquid through the liquid inlet and may also include chemical .~73~
admission and/or temperature control over the treatment (wash-displacement) liquid relative to the characteristics of ~he pulp withdrawn through the pulp outlet. Moreover, adapting the method to a multi-s~age pressurized diffuser system comprises connectingthe desired number o such diffusers in serie5 using the pulp withdrawn from one diffuser as the pulp eed f or the 5 uc~eeding diffuser with optional interme~iate temperature and chemical control of the treatment liquid relative to the pulp flow ~hrough the pulp outlet. Further, passing the pulp through an enlarged portion of the feed pipe or a vessel between the diffusers provides a desired retention time between liquid extractions. The agitator in the outlet end of the first diffuser in series measures pulp concentration.
BRIEF DESCRIPTION OF' THE DRAWINGS
For the purposes of description, the method for maintaining constant conti~uous cellulosic flows is shown schematically in the accompanying drawings:
FIGURE 1 is a side view, partly in cross-section and partly in elevation, of details of an exemplary diffuser apparatus utilizable in practicing the method of the invention;
FIGURE 2 is illustrative of a single pressurized diffuser stage showing the flow control method;
FIGURE 3 is a drawing vf the flow control process with independent control of screen speed;
'1~7~ 3 FIGUR~ 4 is a drawing of the control process with independent screen speed, temperature and chemical addltion control and i5 shown on the sheet illus-trating figure 6;
FIGURE ~ is a drawing of a multiple stage arrangement using the flow control method; and FIGURE 6 is a drawing of a multi-stage arrangement with flow control showing intermediate chemical admission, heating and cooling control, and retention~
DETAI~ED D~SCRIPTION OF THE DRAWINGS
The present inventive method maintaining constant and c~ntinuous all pulp or cellulosic flows in and out of a pressurized diffuser. An exemplary diffuser utilizable ;n practicing the present invention is illustrated in FIGURE 1.
The exemplary diffuser 10 illustrated in FIGURE 1 comprises a conical housing 11 with top part 11' and bottom part 11'' having a pulp inlet 12 and outlet 13, with a powered rotatable scraper 14 mounted in the bottom of housing 11 facilitating discharge o~
pulp from the ho~sing 11 after treat~lent. A withdrawn liquid outlet 17 extends from the top part of the ho~sing 11. A screen body 18 is mounted inside and substantially concentric with the housiny 11, the body 18 having per~rations or apertures formed therein to allow passage of liquid therethrough but prevent the passage of suspended solids therethrough. The bearings 19 and 19' are provided between the body 18 and housing 11 to allow relative linear movement of screen 18 with respect to housing 11 in dimension ~A", 3~i~3 The screen 18 is rigidly attached to one end thereo~ to a reciprocal sbaf~ 23, which shaf~c 23 passes through a seal 24 at the top o the housing 11. A conventional drive device 25 (such as shown in U.S. Patent 4,041,560) reciprocates the shaft 23 in dimension A. Normally, drive 25 will operate to move the screen 18 downwardly at about the same speed as the pulp flow from inlet 12 to outlet 13, and ~hen move it upwardly much more quickly, and then restart the downward movement. The speed and nature of operation of the drive 25 may be varied as desired to accomplish the objectives of the present invention, as may be the details, dimensions, and relative spacings, of the housing 11 and screen 18.
For treatment of suspension passing through the housing 11, a treatment liquid inelt 26 is provided~ Treatment liquid introduced through inlet 26 is spread out by baffles 27 arranged circumferen-tially around a concentric li~uid distribution body 15 fastened to the housing part 11'' by ~.hree arms 15' of which one is hollow and in connection with inlet ~6.
As shown in FIGURE 2, e~emplary apparatus utilizable in prac~icing the method of the invention includes pressurized diuser 10/ and associated inlet and outlet flow controls and the lîke. The pulp flow ~slurry) from a continuous digester, a storage tower or the like enters pipeline 28, flows through stock pump 29 (which alternatively may comprise a valve), and enters the top of the vertically aligned pressurized diffuser 10 and flows pa~t movable screen 18 therein. The pulp flow ent~ring pressurized diffuser 10, possibly of varying consistency/ is stabiliz~d in consistency under its passage through the diffuser 10 by means of fine adjustment o ~he extraction flow 30 through outlet 17 relative to wash 73~V~
li~uor flow 31 into inlets 26 of said pressurized diffuser 10. The bottom discharging agitator 14 of pressurized diffuser 10 gives a very reliable output signal for consistency control to a consistency controller 22 and control ratio relay 33. ~his signal adjusts the set point of control ratio relay 33 between the wash liquor flow control FIC 34 and the extraction liquor flow control FIC 35. Control ratio relay 33 may have a limited range, for example, 0.9-1.3, to keep extraction flow deviations within the desired tolerances.
The discharge flow 3~ from outlet 13 is measured by pulp discharge flow monitor 37 and a signal is transmitted to pre-set pulp flow controller FIC 38 which controls the stock pump 29 feeding the diffuser 10 [or controls a valve, depending on the pressure in the preceding vessel and the pressure demand for succeeding processes]. From pulp f low controller FIC 38, a proportional signal is transmitted to pulp flow ratio relay 39 which in turn controls the set point of the wash liquor controller FIC 34 which governs the wash liquid flow to the pressure difuser lOo Wash (or displacement) liquor flow controller FIC 34 receives signals from wash l.iquor sensing means 40 and pulp flow ratio relay 39 to send a composite signal to control ratio relay 33. The composite signal through wash li~uor controller FIC 34 governs the flow of wash liquor to the pressurized diffuser 10 through wash liquor control means 41~
The composite signal is sent from wash liquor controller ~IC 34 to control ratio relay 33. A signal is then transmitted from control ratio relay 33 to extraction flow controller FIC 35. The combination of the signals from extraction flow sensing means 42 and t~360~3 rom the control ratio relay 33 through extraction flow con~roller FIC 35 governs the extraction flow control means 43.
Thus simultaneous pulp flow and consistency con~rol is achieved by regulating the extraction liquor flow relative to the wash liquor flow wi~h reference to the pulp discharge flow, which in turn governs inlet pulp flow and wash liquor flow. That is, i~ the consistency of the incoming pulp stream tends to drop, the extraction flow will increase to maintain constant discharge consistency, while the pulp flow entering the diffuser will increase correspondingly so as to maintain a constant ~iber flow discharging from the diffuser.
In FIGURE 3, the flow control system operates generally according to the descript;on of FIGURE 2, moreover to op~imize performance of pressuriz~d diffuser 10, the speed of screen 18 may be automatically adjusted to match that of the average pulp stream speed through pressurized diffuser 10 by means of a pressure differential control PDC 44 which regulates the drive 25 (e.g. t regulates the flow of oil when drive 25 is a hydraulic cylinder) relative to the pressure differential between the top and bottom of diffuser 10, taken at point~ 45, 46. The optimization process is independent of the flow and consistency control system described in FIGURE 2.
FIGURE ~ shows the 10w and consistency control system as shown in FIGURE 2 and the pressure differential control PDC 44 optimization method ~hown in FIGURE 3 with the addition of chemical admission controller FIC 47 and stock temperature controler TIC
48 which are connected to the wash liquor line 31 just prior to the wash liquor control 41. Displacement or wash liquor enters pipeline 49 and chemical additions ~3L736~
made at point 50 are controlled by chemical admission controller FIC 47 which receives the necessary data, or example, on p~ or conductivity, from transmitter 51 which may be located directly in the discharging pulp stream 36. The chemical admission controller combines the signal f om transmitter 51 with one from chemical flow sensor means 52 to determine the ~mount of chemical admissions through chemical flow control 53 (which may be a valve or pump)~ Passing wash (displacement) liquor through heat exchanger 54 permits the indirect heating or cooling of the pulp stream itself passing ~hrough the pressurized diffuser 10~ The temperature of the heat exchange medium is regulated through temperature controller TIC 4B and attendant flow control 55 wherein the temperature data transmitter 56 may be located in the discharging pulp stream 36. The location of the temperature data transmitter 56 allows automatic temperature control of the pulp stream entering succeediny treatment steps by controlling the temperature of the pulp stream discharging from the preceding diffuser.
A multi-stage pressure diffuser arrangement employing the flow control method can be understood with reference to FIGURB 5. While FIGURE 2 illustrate6 in detail the flow control system of a single diffuser, FIGURE 5 illustrates a multi-stage arrangement. The wash liquid flow controller 34 of Section A becomes the extraction flow controller for diffuser 10' of Section B, and similarly the wash liquid flow controller 34' of Section B becomes the extraction flow controller for diffuser lQI' of Section C. Via control line 57, the ratio relay 39 sends identical signals to the subsequent flow controllers 34', 34'~, so that they are automatically set at the same flow rate.
~7~61)3 Note the absence in FIGURE 5 of any intermediate liquor or surge tanks. There~ore, the smaller boos~er pumps 58, 58', 58 " only have pres~ure heads sufficient to compensate for decreases in pressure through, or example, control valves 41, 41' and 41'' and pipings. For example, booster pumps 58, 58', 58l' can raise the wash (displacement) liquor pressure from diffuser 10' to that in the preceding diffuser 10. This additional pressure head need ba~sically correspond to pulp line friction losses between the diffusers.
Since all wash (displacement) and extraction liquor flows should be of constant magnitude in a multi-stage arrangement, the extraction flow 30 from the first pressurized diffuser 10 which governs the pulp flow consistency of the system should be free of surge effects. To this end, extraction flow 30 from diffuser 10 should enter a surge or liquor tank 59.
Tank 59, the only one required in the flow control system, may be pressurized if the diffusers 10, 10', 10 " are connected in the blow line from a pressurized vessel (e.g., continuous digester or oxygen reactor).
A vapor or gas cushion 60 acting on the gas relief flow 61 through valve 62 enables tank 59 to absorb surges. Gas analy2ers 63 may be incorporated in the gas relief line 61 if desired. This prevents surge flow variances from affecting succeeding process steps. The other constant flow and consistency effects are obtained according to the steps described with FIGURE 2.
In section C of FIGURE 5, the dischar~ing pulp stream 36'' ~rom the final diffuser 10'' may flow directly to any final treatment or processing stage or into a storage tower. Should pressure diffusers be utilized for high temperature washing (above 100C)~ a ~36~3 discharge pressure control PIC 64 governs the pressure of the discharging stream 36'' relative to that oE
final pressure diffuser 10l' by controlling valve 65. It is understood that the pres~nt invention is not limited to a three-stage system.
A multiple ~tage arrangement employing the flow control method with intermediate chemical admission to the wash ~displacement) liquor is illustrated in FIGURE 6. In principle, the chemical admission controller 47' operates in a similar manner to that described with FIGURE 4. The indireck heating and cooling of the wash (displacement) liquor in the heat exchange 54, and associated components also operate in the same manner as in FIGURE 4.
Utilization of the optional hydraulically filled retention vessel 66, however, necessitates that the chemical admission controller FIC 47' combines the signals received from transmitter 52 and ratio relay 67 which in turn receives a signal proportional to the pulp flow in line 36. A change in the pulp flow will thus result in an immediate and proportional change in chemical admission flow. In due time a possible ine correction in the setting of the ratio relay 67 will take place throu~h the incoming signal from the chemical sensor 51 located in the pulp discharge line from retention vessel 6S. The effect of additional retention time on the chemical properties of the pulp will thus be detected and compensated Eor.
In tne multiple stage arrangement as illustrated in FIGURE 6, it is p.referable to maintain all flows in and out of the diffusers constant in order not to induce any chan~es in consistency throughout the sy~tem once stabilized in the ~irst stageO Since the system according to FIGURE 6 incorporates the addition of a smaller flow of ~73~
chemical solution to the displacement liquid, an equal small flow o extraction liquid from a succeeding s~age is bypassed and introduced with the chemical additions to the displacement liquid to any preceding stage of a corresponding pH-rating. This consistency preserving extraction liquor bleed is controlled by flow controller FIC 69 with flow sensor 70 and control valve 710 The flow through line 72 is kept identical to that through line 49 by means of ratio relay 68 transmitting a 1:1 relay signal from flow controller 47' to flow controller 69.
All intermediate stages will have arrangements similar to that described above whenever additives come into the picture. This also applies to the system illustrated in FIGURE 4.
The systems as described above are capable o~
practicing the method of the invention so that the flow rate of the pulp being withdrawn through the pulp outlet 36 by controlling the flow rate (by conrol oE
pump ?9) of pulp fed into the first stage difuser 10;
and are capable of setting and controlling the consistency of the pulp being withdrawn through outlets 36, 36', 36'' by controlling the flow rate (via flow controller 35) of withdrawn liquid rom outlet 17 of first stage diffuser 10 through conduit 30. The nature of the pulp treatment and the qualities o~ the pulp withdrawn from each stage are controlled by adding desired chemicals to the treatment liquids introduced into inlets 26, 26'; 26' 3 through lines 31, 31', 32'', and controlling the temperature o the treatment liquid via tempe~ature controllers 48, 48', 48l' and associated heat exchangers 54, 54', 54 " , The qualities o~ ~he withdrawn pulp in lines 36, 367, 36'' are sensed (by components 51, 51', 51~' and 56, 56', 56''), ~nd 360~
~3 control of the treatmen~ liquid chemical addition and temperature is effected in response to such ~ensing.
While the invention has been herein shown and described in what is presently conceived to be the most preferred and practical embodi~ent thereof, it will be apparent to those of ordinary skill in the art that many modifications may be made thereof within the scope of the invention, which scope is to be accorded the broadest interpretation of the appended claims as to encompass all equivalent methods and procedures.
BACKGROUND AND SIJMMARY OF THE INVENTION
This invention rela ces to a method for maintaining all flows in and out of pressurized 5 diffuser machines constant and continuous and of stabilized consistency thereby facilitating incorporation of such a machine or machines in a pulp mill process.
Conventional dewatering machines based on the rotating drum principle, such as vacuum washers, ai~
pressure washers, drum presses, wash presses and the like, share the co~mon drawbacks that the outlet consistency is undstermined and that the filtrates must exit into atmospheric filtrate tanks. The outlet consistency varies as a result of temperture fluctuations, changes in the production flow xate, variances in pulp drainage characteristics and mechanical factors associated with the process machinery.
To compensate for these problems, the conventional methods employed filtrate tanks as surge absorbers beca~se the exiting filtrate flow varied with its discharging consistency. These large filtrate tanks must be equipped with level recorders. The tanks must be of considerable dimensions to absorb the mentioned fluctuations and to allow suff icient deaeration of the liquor. As a further drawbac~, the large size resuits in significant heat losses.
The conventional filtrate tanks also require adequate pump caparity and pressure head controls to both dilute the incoming stock and circulate the e~cess (surplus) liquor countercurrently back into the 361~3 process. Considerable pressure head on the pump or pumps is required sinre the pressure process i5 conventionally kept we~l above the static head of the filtrate tank which was exposed to the atmosphere.
Introduction of a continuous diffuser which did not require any dilution of the incoming stock of medium consistency coupled with some control over outlet consistency by adjusting the extraction flow relative to wash liquor flow marked an improvement over the conventional processes. However, problems with pressure loss in the stock flow and air extrainment in the stock flow remained~ Since pulp su~pensions of~en contain liquids with fairly high surface tensions, the entrained air causes the suspension to become foamy, elastic, to emit smelly gases and hard to dewater causing treatment problems in succeeding process machinery. Stacking a series of diffusers in ~tages within a common tower casing was only a partial soluton because of practical limitations on the number of stages in one tower.
Additionally, the filtrate flow or extraction flow from the conventional diffusers remained intermittent because of the operating principle of the machine. The intermittent flow required periodic injection of li~uor to the interior oE the diffuser screens. Conventional systems consequently needed adequate liquor tanks, level recorders, pumps and other equipment.
Furthermore, the conventional diffusers needed extraction liquor flow control and separate wash liquor flow control to the preceding stage in multi-stage arrangements.
According to the method of the present invention, all flows in and out of the diffus~r are kept constant and continuous to eliminate the problems ~7~;36~3 commonly associated with diffusers. Consequently, pressurized diffusers may now be easily incorporated in a pressuri~ed system thereby eliminating the need for intermediate ~urge tank~, reducing pump power demand to a minimum, and totally eliminating the air entrainment and gas emission problems since the present invention no longer requires atmospheric disc~arge~ Level controllers will no longer be required and the number of flow controllers is almost halved since the extraction controller for one stage now concurrently serves as th2 wash liquor controller for the preceding stage~ Variat;ons in pulp charac-teristics, production rate and temperature will not af~ect pulp consistency since they will be governed purely through flow control using straightforward instrumentation regulatorsD
According to the pres:ent invention, there is provided a method of treating cellulosic pulp suspensions flowing in a relatively continuous stream through.
pressurized diffusers equipped with pulp inlets and outlets along with treatment liquid inlets and outlets, which method comprises feeding the pulp stream through the pulp inlet into the diffuser, withdrawing the trea-ted pulp through the pulp outlet, governing the pulp withdrawal flow rate through the pulp outlet by controlling the pulp feed flow rate into the pulp inlet, es-tablishing consistency control over pulp withdrawn through the pulp outlet by controlllng the liquid flow rate from the liquid outlet.
Additional cellulosic flow treatment comprises feeding treatment liquid through the liquid inlet and may also include chemical .~73~
admission and/or temperature control over the treatment (wash-displacement) liquid relative to the characteristics of ~he pulp withdrawn through the pulp outlet. Moreover, adapting the method to a multi-s~age pressurized diffuser system comprises connectingthe desired number o such diffusers in serie5 using the pulp withdrawn from one diffuser as the pulp eed f or the 5 uc~eeding diffuser with optional interme~iate temperature and chemical control of the treatment liquid relative to the pulp flow ~hrough the pulp outlet. Further, passing the pulp through an enlarged portion of the feed pipe or a vessel between the diffusers provides a desired retention time between liquid extractions. The agitator in the outlet end of the first diffuser in series measures pulp concentration.
BRIEF DESCRIPTION OF' THE DRAWINGS
For the purposes of description, the method for maintaining constant conti~uous cellulosic flows is shown schematically in the accompanying drawings:
FIGURE 1 is a side view, partly in cross-section and partly in elevation, of details of an exemplary diffuser apparatus utilizable in practicing the method of the invention;
FIGURE 2 is illustrative of a single pressurized diffuser stage showing the flow control method;
FIGURE 3 is a drawing vf the flow control process with independent control of screen speed;
'1~7~ 3 FIGUR~ 4 is a drawing of the control process with independent screen speed, temperature and chemical addltion control and i5 shown on the sheet illus-trating figure 6;
FIGURE ~ is a drawing of a multiple stage arrangement using the flow control method; and FIGURE 6 is a drawing of a multi-stage arrangement with flow control showing intermediate chemical admission, heating and cooling control, and retention~
DETAI~ED D~SCRIPTION OF THE DRAWINGS
The present inventive method maintaining constant and c~ntinuous all pulp or cellulosic flows in and out of a pressurized diffuser. An exemplary diffuser utilizable ;n practicing the present invention is illustrated in FIGURE 1.
The exemplary diffuser 10 illustrated in FIGURE 1 comprises a conical housing 11 with top part 11' and bottom part 11'' having a pulp inlet 12 and outlet 13, with a powered rotatable scraper 14 mounted in the bottom of housing 11 facilitating discharge o~
pulp from the ho~sing 11 after treat~lent. A withdrawn liquid outlet 17 extends from the top part of the ho~sing 11. A screen body 18 is mounted inside and substantially concentric with the housiny 11, the body 18 having per~rations or apertures formed therein to allow passage of liquid therethrough but prevent the passage of suspended solids therethrough. The bearings 19 and 19' are provided between the body 18 and housing 11 to allow relative linear movement of screen 18 with respect to housing 11 in dimension ~A", 3~i~3 The screen 18 is rigidly attached to one end thereo~ to a reciprocal sbaf~ 23, which shaf~c 23 passes through a seal 24 at the top o the housing 11. A conventional drive device 25 (such as shown in U.S. Patent 4,041,560) reciprocates the shaft 23 in dimension A. Normally, drive 25 will operate to move the screen 18 downwardly at about the same speed as the pulp flow from inlet 12 to outlet 13, and ~hen move it upwardly much more quickly, and then restart the downward movement. The speed and nature of operation of the drive 25 may be varied as desired to accomplish the objectives of the present invention, as may be the details, dimensions, and relative spacings, of the housing 11 and screen 18.
For treatment of suspension passing through the housing 11, a treatment liquid inelt 26 is provided~ Treatment liquid introduced through inlet 26 is spread out by baffles 27 arranged circumferen-tially around a concentric li~uid distribution body 15 fastened to the housing part 11'' by ~.hree arms 15' of which one is hollow and in connection with inlet ~6.
As shown in FIGURE 2, e~emplary apparatus utilizable in prac~icing the method of the invention includes pressurized diuser 10/ and associated inlet and outlet flow controls and the lîke. The pulp flow ~slurry) from a continuous digester, a storage tower or the like enters pipeline 28, flows through stock pump 29 (which alternatively may comprise a valve), and enters the top of the vertically aligned pressurized diffuser 10 and flows pa~t movable screen 18 therein. The pulp flow ent~ring pressurized diffuser 10, possibly of varying consistency/ is stabiliz~d in consistency under its passage through the diffuser 10 by means of fine adjustment o ~he extraction flow 30 through outlet 17 relative to wash 73~V~
li~uor flow 31 into inlets 26 of said pressurized diffuser 10. The bottom discharging agitator 14 of pressurized diffuser 10 gives a very reliable output signal for consistency control to a consistency controller 22 and control ratio relay 33. ~his signal adjusts the set point of control ratio relay 33 between the wash liquor flow control FIC 34 and the extraction liquor flow control FIC 35. Control ratio relay 33 may have a limited range, for example, 0.9-1.3, to keep extraction flow deviations within the desired tolerances.
The discharge flow 3~ from outlet 13 is measured by pulp discharge flow monitor 37 and a signal is transmitted to pre-set pulp flow controller FIC 38 which controls the stock pump 29 feeding the diffuser 10 [or controls a valve, depending on the pressure in the preceding vessel and the pressure demand for succeeding processes]. From pulp f low controller FIC 38, a proportional signal is transmitted to pulp flow ratio relay 39 which in turn controls the set point of the wash liquor controller FIC 34 which governs the wash liquid flow to the pressure difuser lOo Wash (or displacement) liquor flow controller FIC 34 receives signals from wash l.iquor sensing means 40 and pulp flow ratio relay 39 to send a composite signal to control ratio relay 33. The composite signal through wash li~uor controller FIC 34 governs the flow of wash liquor to the pressurized diffuser 10 through wash liquor control means 41~
The composite signal is sent from wash liquor controller ~IC 34 to control ratio relay 33. A signal is then transmitted from control ratio relay 33 to extraction flow controller FIC 35. The combination of the signals from extraction flow sensing means 42 and t~360~3 rom the control ratio relay 33 through extraction flow con~roller FIC 35 governs the extraction flow control means 43.
Thus simultaneous pulp flow and consistency con~rol is achieved by regulating the extraction liquor flow relative to the wash liquor flow wi~h reference to the pulp discharge flow, which in turn governs inlet pulp flow and wash liquor flow. That is, i~ the consistency of the incoming pulp stream tends to drop, the extraction flow will increase to maintain constant discharge consistency, while the pulp flow entering the diffuser will increase correspondingly so as to maintain a constant ~iber flow discharging from the diffuser.
In FIGURE 3, the flow control system operates generally according to the descript;on of FIGURE 2, moreover to op~imize performance of pressuriz~d diffuser 10, the speed of screen 18 may be automatically adjusted to match that of the average pulp stream speed through pressurized diffuser 10 by means of a pressure differential control PDC 44 which regulates the drive 25 (e.g. t regulates the flow of oil when drive 25 is a hydraulic cylinder) relative to the pressure differential between the top and bottom of diffuser 10, taken at point~ 45, 46. The optimization process is independent of the flow and consistency control system described in FIGURE 2.
FIGURE ~ shows the 10w and consistency control system as shown in FIGURE 2 and the pressure differential control PDC 44 optimization method ~hown in FIGURE 3 with the addition of chemical admission controller FIC 47 and stock temperature controler TIC
48 which are connected to the wash liquor line 31 just prior to the wash liquor control 41. Displacement or wash liquor enters pipeline 49 and chemical additions ~3L736~
made at point 50 are controlled by chemical admission controller FIC 47 which receives the necessary data, or example, on p~ or conductivity, from transmitter 51 which may be located directly in the discharging pulp stream 36. The chemical admission controller combines the signal f om transmitter 51 with one from chemical flow sensor means 52 to determine the ~mount of chemical admissions through chemical flow control 53 (which may be a valve or pump)~ Passing wash (displacement) liquor through heat exchanger 54 permits the indirect heating or cooling of the pulp stream itself passing ~hrough the pressurized diffuser 10~ The temperature of the heat exchange medium is regulated through temperature controller TIC 4B and attendant flow control 55 wherein the temperature data transmitter 56 may be located in the discharging pulp stream 36. The location of the temperature data transmitter 56 allows automatic temperature control of the pulp stream entering succeediny treatment steps by controlling the temperature of the pulp stream discharging from the preceding diffuser.
A multi-stage pressure diffuser arrangement employing the flow control method can be understood with reference to FIGURB 5. While FIGURE 2 illustrate6 in detail the flow control system of a single diffuser, FIGURE 5 illustrates a multi-stage arrangement. The wash liquid flow controller 34 of Section A becomes the extraction flow controller for diffuser 10' of Section B, and similarly the wash liquid flow controller 34' of Section B becomes the extraction flow controller for diffuser lQI' of Section C. Via control line 57, the ratio relay 39 sends identical signals to the subsequent flow controllers 34', 34'~, so that they are automatically set at the same flow rate.
~7~61)3 Note the absence in FIGURE 5 of any intermediate liquor or surge tanks. There~ore, the smaller boos~er pumps 58, 58', 58 " only have pres~ure heads sufficient to compensate for decreases in pressure through, or example, control valves 41, 41' and 41'' and pipings. For example, booster pumps 58, 58', 58l' can raise the wash (displacement) liquor pressure from diffuser 10' to that in the preceding diffuser 10. This additional pressure head need ba~sically correspond to pulp line friction losses between the diffusers.
Since all wash (displacement) and extraction liquor flows should be of constant magnitude in a multi-stage arrangement, the extraction flow 30 from the first pressurized diffuser 10 which governs the pulp flow consistency of the system should be free of surge effects. To this end, extraction flow 30 from diffuser 10 should enter a surge or liquor tank 59.
Tank 59, the only one required in the flow control system, may be pressurized if the diffusers 10, 10', 10 " are connected in the blow line from a pressurized vessel (e.g., continuous digester or oxygen reactor).
A vapor or gas cushion 60 acting on the gas relief flow 61 through valve 62 enables tank 59 to absorb surges. Gas analy2ers 63 may be incorporated in the gas relief line 61 if desired. This prevents surge flow variances from affecting succeeding process steps. The other constant flow and consistency effects are obtained according to the steps described with FIGURE 2.
In section C of FIGURE 5, the dischar~ing pulp stream 36'' ~rom the final diffuser 10'' may flow directly to any final treatment or processing stage or into a storage tower. Should pressure diffusers be utilized for high temperature washing (above 100C)~ a ~36~3 discharge pressure control PIC 64 governs the pressure of the discharging stream 36'' relative to that oE
final pressure diffuser 10l' by controlling valve 65. It is understood that the pres~nt invention is not limited to a three-stage system.
A multiple ~tage arrangement employing the flow control method with intermediate chemical admission to the wash ~displacement) liquor is illustrated in FIGURE 6. In principle, the chemical admission controller 47' operates in a similar manner to that described with FIGURE 4. The indireck heating and cooling of the wash (displacement) liquor in the heat exchange 54, and associated components also operate in the same manner as in FIGURE 4.
Utilization of the optional hydraulically filled retention vessel 66, however, necessitates that the chemical admission controller FIC 47' combines the signals received from transmitter 52 and ratio relay 67 which in turn receives a signal proportional to the pulp flow in line 36. A change in the pulp flow will thus result in an immediate and proportional change in chemical admission flow. In due time a possible ine correction in the setting of the ratio relay 67 will take place throu~h the incoming signal from the chemical sensor 51 located in the pulp discharge line from retention vessel 6S. The effect of additional retention time on the chemical properties of the pulp will thus be detected and compensated Eor.
In tne multiple stage arrangement as illustrated in FIGURE 6, it is p.referable to maintain all flows in and out of the diffusers constant in order not to induce any chan~es in consistency throughout the sy~tem once stabilized in the ~irst stageO Since the system according to FIGURE 6 incorporates the addition of a smaller flow of ~73~
chemical solution to the displacement liquid, an equal small flow o extraction liquid from a succeeding s~age is bypassed and introduced with the chemical additions to the displacement liquid to any preceding stage of a corresponding pH-rating. This consistency preserving extraction liquor bleed is controlled by flow controller FIC 69 with flow sensor 70 and control valve 710 The flow through line 72 is kept identical to that through line 49 by means of ratio relay 68 transmitting a 1:1 relay signal from flow controller 47' to flow controller 69.
All intermediate stages will have arrangements similar to that described above whenever additives come into the picture. This also applies to the system illustrated in FIGURE 4.
The systems as described above are capable o~
practicing the method of the invention so that the flow rate of the pulp being withdrawn through the pulp outlet 36 by controlling the flow rate (by conrol oE
pump ?9) of pulp fed into the first stage difuser 10;
and are capable of setting and controlling the consistency of the pulp being withdrawn through outlets 36, 36', 36'' by controlling the flow rate (via flow controller 35) of withdrawn liquid rom outlet 17 of first stage diffuser 10 through conduit 30. The nature of the pulp treatment and the qualities o~ the pulp withdrawn from each stage are controlled by adding desired chemicals to the treatment liquids introduced into inlets 26, 26'; 26' 3 through lines 31, 31', 32'', and controlling the temperature o the treatment liquid via tempe~ature controllers 48, 48', 48l' and associated heat exchangers 54, 54', 54 " , The qualities o~ ~he withdrawn pulp in lines 36, 367, 36'' are sensed (by components 51, 51', 51~' and 56, 56', 56''), ~nd 360~
~3 control of the treatmen~ liquid chemical addition and temperature is effected in response to such ~ensing.
While the invention has been herein shown and described in what is presently conceived to be the most preferred and practical embodi~ent thereof, it will be apparent to those of ordinary skill in the art that many modifications may be made thereof within the scope of the invention, which scope is to be accorded the broadest interpretation of the appended claims as to encompass all equivalent methods and procedures.
Claims (17)
1. A method of treating cellulosic pulp flowing in a substantially continuous stream utilizing a pressure-tight vessel having a pulp inlet and pulp outlet, and treatment liquid inlet and liquid extraction outlet comprising the steps of:
(a) feeding a stream of pulp into the vessel pulp inlet at a particular flow rate;
(b) withdrawing treated pulp through the pulp outlet at a particular flow rate;
(c) setting and controlling the flow rate of pulp being withdrawn through the pulp outlet by controlling the flow rate of the pulp being fed into the pulp inlet;
(d) withdrawing liquid through the liquid outlet at a particular flow rate; and (e) setting and controlling the consistency of the pulp being withdrawn through the pulp outlet by controlling the flow rate of liquid from the liquid outlet.
(a) feeding a stream of pulp into the vessel pulp inlet at a particular flow rate;
(b) withdrawing treated pulp through the pulp outlet at a particular flow rate;
(c) setting and controlling the flow rate of pulp being withdrawn through the pulp outlet by controlling the flow rate of the pulp being fed into the pulp inlet;
(d) withdrawing liquid through the liquid outlet at a particular flow rate; and (e) setting and controlling the consistency of the pulp being withdrawn through the pulp outlet by controlling the flow rate of liquid from the liquid outlet.
2. A method as recited in claim 1 comprising the further step of:
(f) feeding treatment liquid into the liquid inlet.
(f) feeding treatment liquid into the liquid inlet.
3. A method as recited in claim 2 comprising the further steps of:
(g) controlling the nature of the pulp treatment and the qualities of the pulp withdrawn in step (b), by adding desired chemicals to the liquid added in step (f), and controlling the temperature of the liquid added in step (f);
(h) sensing the qualities of the pulp withdrawn in step (b), and (i) controlling the chemical addition and temperature of the liquid introduced in step (f ) in response to the sensing results obtained in step (h).
(g) controlling the nature of the pulp treatment and the qualities of the pulp withdrawn in step (b), by adding desired chemicals to the liquid added in step (f), and controlling the temperature of the liquid added in step (f);
(h) sensing the qualities of the pulp withdrawn in step (b), and (i) controlling the chemical addition and temperature of the liquid introduced in step (f ) in response to the sensing results obtained in step (h).
4. A method as recited in claim 3 comprising the further step of:
(j) introducing the pulp withdrawn in step (b) into a second subsequent treatment apparatus.
(j) introducing the pulp withdrawn in step (b) into a second subsequent treatment apparatus.
5. A method as recited in claim 4 comprising the further step of:
(k) introducing the pulp withdrawn from the second apparatus into a third subsequent apparatus so that the liquid withdrawn in step (d) serves as the input liquid in step (fl to the preceding apparatus
(k) introducing the pulp withdrawn from the second apparatus into a third subsequent apparatus so that the liquid withdrawn in step (d) serves as the input liquid in step (fl to the preceding apparatus
6. A process according to claim 4 or 5 further comprising the step of:
(1) retaining the pulp withdrawn in step (b) prior to introducing said pulp into a subsequent apparatus in step (j).
(1) retaining the pulp withdrawn in step (b) prior to introducing said pulp into a subsequent apparatus in step (j).
7. A method as recited in claim 1 comprising the further step of.
(m) measuring the pulp concentration withdrawn in step (b)
(m) measuring the pulp concentration withdrawn in step (b)
8. A method as recited in claim 2 comprising the further steps of:
(n 1 controlling the flow rate of pulp withdrawn in step (b);
(o) controlling the flow rate of liquid entering and leaving the apparatus, and (p) controlling the concentration of pulp withdrawn in step (b).
(n 1 controlling the flow rate of pulp withdrawn in step (b);
(o) controlling the flow rate of liquid entering and leaving the apparatus, and (p) controlling the concentration of pulp withdrawn in step (b).
9. A method as recited in claim 8 comprising the further steps of:
(q) providing a fixed ratio between the discharging pulp stream in step (d) and the treatment liquid introduced in step (f); and (r) adjusting the flow rate of the liquid withdrawn in step (d) relative to the flow rate of liquid introduced in step (f) to compensate for variations in pulp concentration.
(q) providing a fixed ratio between the discharging pulp stream in step (d) and the treatment liquid introduced in step (f); and (r) adjusting the flow rate of the liquid withdrawn in step (d) relative to the flow rate of liquid introduced in step (f) to compensate for variations in pulp concentration.
10. A method of treating cellulosic fibers in a slurry flow substantially by displacement utilizing a pressure tight vessel having a slurry inlet, a movable screen within the vessel adjacent to the slurry inlet, a slurry outlet, a treatment liquid inlet, and a liquid extraction outlet, comprising the steps of:
(a) introducing the slurry into the vessel to flow alongside the movable screen;
(b) withdrawning treated slurry from the vessel through the slurry outlet;
(c) introducing treatment liquid into the vessel through the liquid inlet;
(d) withdrawing displaced liquid from the vessel through the liquid extraction outlet;
(e) measuring the flow rate and consistency of slurry withdrawn in step (b);
(f) stabilizing and controlling the consistency of slurry withdrawn in step (b) by controlling the liquid extraction relative to the treatment liquid introduction of steps (d) and (c) in response to consistency measurements determined in step (e); and (g) controlling the flow rate of slurry into the vessel inlet in step (a) in response to measure-ments of the withdrawn and consistency stabilized slurry flow rate determined in step (e).
(a) introducing the slurry into the vessel to flow alongside the movable screen;
(b) withdrawning treated slurry from the vessel through the slurry outlet;
(c) introducing treatment liquid into the vessel through the liquid inlet;
(d) withdrawing displaced liquid from the vessel through the liquid extraction outlet;
(e) measuring the flow rate and consistency of slurry withdrawn in step (b);
(f) stabilizing and controlling the consistency of slurry withdrawn in step (b) by controlling the liquid extraction relative to the treatment liquid introduction of steps (d) and (c) in response to consistency measurements determined in step (e); and (g) controlling the flow rate of slurry into the vessel inlet in step (a) in response to measure-ments of the withdrawn and consistency stabilized slurry flow rate determined in step (e).
11. A method as recited in claim 10 comprising the further steps of:
(h) interconnecting a plurality of the pressure-tight slurry treatment vessels together;
(i) introducing the slurry withdrawn in step (b) into the next slurry inlet; and (j) introducing liquid withdrawn in step (d) into the preceding stage liquid inlet.
(h) interconnecting a plurality of the pressure-tight slurry treatment vessels together;
(i) introducing the slurry withdrawn in step (b) into the next slurry inlet; and (j) introducing liquid withdrawn in step (d) into the preceding stage liquid inlet.
12. A method as recited in claim 11 comprising the further step of:
(k) cancelling surge effects in the liquid withdrawn in step (d) from the first stage.
(k) cancelling surge effects in the liquid withdrawn in step (d) from the first stage.
13. A method as recited in claim 11 comprising the further step of:
(1) maintaining identical and constant flows and consistency as stabilized in steps (f) and (g) throughout all succeeding stages by means of proportional flow control system and forward bleed corresponding to chemical additive solution flow for each stage.
(1) maintaining identical and constant flows and consistency as stabilized in steps (f) and (g) throughout all succeeding stages by means of proportional flow control system and forward bleed corresponding to chemical additive solution flow for each stage.
14. A method as recited in claim 11 or 13 comprising the further step of.
(m) maintaining the same flow rate for liquid introduced in step (c).
(m) maintaining the same flow rate for liquid introduced in step (c).
15 A method as recited in claim 10, comprising the further steps of:
(n) measuring the characteristics of the slurry withdrawn in step (b);
(o) adjusting the temperature of the cellulose fiber slurry flow undergoing treatment by indirectly heating or cooling the liquid introduced in step (c);
(p) controlling the chemical characteristics of the slurry by introducing chemical additives into the liquid introduced in step (c); and (g) controlling the chemical addition and temperature of the liqu;d introduced in step (c) in response to measurements obtained in step (n)
(n) measuring the characteristics of the slurry withdrawn in step (b);
(o) adjusting the temperature of the cellulose fiber slurry flow undergoing treatment by indirectly heating or cooling the liquid introduced in step (c);
(p) controlling the chemical characteristics of the slurry by introducing chemical additives into the liquid introduced in step (c); and (g) controlling the chemical addition and temperature of the liqu;d introduced in step (c) in response to measurements obtained in step (n)
16. A method of treating cellulosic fiber in a slurry flow according to claims 10, 11, or 12 comprising the further step of:
(r) matching the screen speed in the direction of slurry flow with that of the average speed of the cellulose fiber slurry flow undergoing treatment.
(r) matching the screen speed in the direction of slurry flow with that of the average speed of the cellulose fiber slurry flow undergoing treatment.
17. A method of treating cellulosic fiber in a s]urry flow according to claim 15 comprising the further step of:
(s) matching the screen speed in the direction of slurry flow with that of the average speed of the cellulose fiber slurry flow undergoing treatment.
(s) matching the screen speed in the direction of slurry flow with that of the average speed of the cellulose fiber slurry flow undergoing treatment.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US22181280A | 1980-12-31 | 1980-12-31 | |
| US221,812 | 1980-12-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1173603A true CA1173603A (en) | 1984-09-04 |
Family
ID=22829494
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000392616A Expired CA1173603A (en) | 1980-12-31 | 1981-12-18 | Pressure diffuser controlling |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0055701B1 (en) |
| JP (1) | JPS57133292A (en) |
| AT (1) | ATE16614T1 (en) |
| BR (1) | BR8108558A (en) |
| CA (1) | CA1173603A (en) |
| DE (1) | DE3173030D1 (en) |
| FI (1) | FI69139C (en) |
| NO (1) | NO157626C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5021127A (en) * | 1987-12-01 | 1991-06-04 | Kamyr, Inc. | Extended delignification in pressure diffusers |
| US5066362A (en) * | 1987-12-01 | 1991-11-19 | Kamyr, Inc. | Extended delignification in pressure diffusers |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4793161A (en) * | 1987-11-27 | 1988-12-27 | Kamyr Ab | Effective diffuser/thickener screen backflushing |
| US4908896A (en) * | 1987-11-27 | 1990-03-20 | Kamyr Ab | Backflushing pressure diffuser screens |
| SE462435B (en) * | 1988-11-11 | 1990-06-25 | Kamyr Ab | MAKE STABILIZING THE PRESSURE AND LIQUIDIZATION COUNTRIES IN A SILVER AND SILVER DEVICE |
| US4975148A (en) * | 1988-12-06 | 1990-12-04 | Ahlstromforetagen Svenska Ab | Cold blow system for batch production of pulp |
| FI82082C (en) * | 1989-03-29 | 1991-12-10 | Ahlstroem Oy | FOERFARANDE OCH ANORDNING FOER BEHANDLING AV MASSA. |
| US5538632A (en) * | 1993-10-28 | 1996-07-23 | Beloit Technologies, Inc. | Multiple filter dynamic washer |
| JPWO2015080190A1 (en) * | 2013-11-29 | 2017-03-16 | 三菱化学株式会社 | Slurry cleaning apparatus and cleaning system |
| FI130499B (en) * | 2021-03-25 | 2023-10-10 | Metsae Fibre Oy | Method and apparatus for treating mixtures of liquids and solids |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE312269B (en) * | 1964-12-17 | 1969-07-07 | T Aremaa | |
| FR1468440A (en) * | 1965-02-17 | 1967-02-03 | Kamyr Ab | Process for acting on the consistency of cellulose pulp in bleaching plants |
| US3807202A (en) * | 1969-09-30 | 1974-04-30 | K Gunkel | Continuous washing apparatus for pulp stock and the like |
| SE394821B (en) * | 1975-04-15 | 1977-07-11 | Kamyr Ab | METHOD AND DEVICE FOR DRAINING MOVEMENT SUSPENSIONS |
| GB1566099A (en) * | 1976-11-11 | 1980-04-30 | Largo Lintec Ltd | Pulping cellulosic material |
| US4212239A (en) * | 1979-02-15 | 1980-07-15 | Hobart Corporation | Method and apparatus for removing moisture from wet pulp |
-
1981
- 1981-12-18 AT AT81890204T patent/ATE16614T1/en not_active IP Right Cessation
- 1981-12-18 CA CA000392616A patent/CA1173603A/en not_active Expired
- 1981-12-18 EP EP81890204A patent/EP0055701B1/en not_active Expired
- 1981-12-18 DE DE8181890204T patent/DE3173030D1/en not_active Expired
- 1981-12-28 FI FI814173A patent/FI69139C/en not_active IP Right Cessation
- 1981-12-28 NO NO814440A patent/NO157626C/en not_active IP Right Cessation
- 1981-12-30 BR BR8108558A patent/BR8108558A/en not_active IP Right Cessation
- 1981-12-31 JP JP56216193A patent/JPS57133292A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5021127A (en) * | 1987-12-01 | 1991-06-04 | Kamyr, Inc. | Extended delignification in pressure diffusers |
| US5066362A (en) * | 1987-12-01 | 1991-11-19 | Kamyr, Inc. | Extended delignification in pressure diffusers |
Also Published As
| Publication number | Publication date |
|---|---|
| FI69139C (en) | 1985-12-10 |
| ATE16614T1 (en) | 1985-12-15 |
| EP0055701B1 (en) | 1985-11-21 |
| NO157626B (en) | 1988-01-11 |
| FI69139B (en) | 1985-08-30 |
| EP0055701A1 (en) | 1982-07-07 |
| JPS57133292A (en) | 1982-08-17 |
| DE3173030D1 (en) | 1986-01-02 |
| BR8108558A (en) | 1982-10-19 |
| FI814173L (en) | 1982-07-01 |
| NO157626C (en) | 1988-04-20 |
| NO814440L (en) | 1982-07-01 |
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