SE542991C2 - A method and a system for extracting hydrolysate in a continuous cooking process for producing pulp - Google Patents

A method and a system for extracting hydrolysate in a continuous cooking process for producing pulp

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Publication number
SE542991C2
SE542991C2 SE1950386A SE1950386A SE542991C2 SE 542991 C2 SE542991 C2 SE 542991C2 SE 1950386 A SE1950386 A SE 1950386A SE 1950386 A SE1950386 A SE 1950386A SE 542991 C2 SE542991 C2 SE 542991C2
Authority
SE
Sweden
Prior art keywords
prehydrolysis
hydrolysate
vessel
vesse1
content
Prior art date
Application number
SE1950386A
Other languages
Swedish (sv)
Other versions
SE1950386A1 (en
Inventor
Hunphrey Landman
Lari Lammi
Magnus Hägglund
Original Assignee
Valmet Oy
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Valmet Oy filed Critical Valmet Oy
Priority to SE1950386A priority Critical patent/SE542991C2/en
Priority to PCT/SE2020/050285 priority patent/WO2020204783A1/en
Priority to EP20782621.5A priority patent/EP3947808A4/en
Priority to CN202080025300.9A priority patent/CN113646481B/en
Priority to BR112021013052-7A priority patent/BR112021013052A2/en
Publication of SE1950386A1 publication Critical patent/SE1950386A1/en
Publication of SE542991C2 publication Critical patent/SE542991C2/en
Priority to ZA2021/04457A priority patent/ZA202104457B/en

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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
    • D21C7/00—Digesters
    • 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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • 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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/02—Pretreatment of the finely-divided materials before digesting with water or steam
    • 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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/04—Pretreatment of the finely-divided materials before digesting with acid reacting compounds
    • 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
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/0007—Recovery of by-products, i.e. compounds other than those necessary for pulping, for multiple uses or not otherwise provided for
    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/22—Other features of pulping processes
    • D21C3/24—Continuous processes
    • 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
    • D21C7/00—Digesters
    • D21C7/08—Discharge devices
    • 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
    • D21C7/00—Digesters
    • D21C7/12—Devices for regulating or controlling
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P2201/00—Pretreatment of cellulosic or lignocellulosic material for subsequent enzymatic treatment or hydrolysis

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  • Extraction Or Liquid Replacement (AREA)
  • Paper (AREA)
  • Polysaccharides And Polysaccharide Derivatives (AREA)

Abstract

A method and a hydrolysate extracting arrangement in a continuous cooking process for producing pulp, said method comprising the steps of:(e) cooling a content in a prehydrolysis vessel (5a; 5b; 5c; 5d) of a continuous pulp production system such that the content has been cooled down when the content arrives at a hydrolysis outlet (9) of the prehydrolysis vessel (5a; 5b; 5c; 5d) on its way from an inlet (13) provided in one end of the prehydrolysis vessel to an outlet (15) provided in an opposite end of the prehydrolysis vessel;(f) removing a hydrolysate of said content through the hydrolysate outlet (9) of the prehydrolysis vessel,wherein said content in the prehydrolysis vessel is cooled to such a degree that the removed hydrolysate has a temperature between 70°C and 130°C .

Description

A method and a system for extracting hydrolysate in a continuous cooking process for producing pulp TECHNICAL FIELD The present invention relates to a method for extracting hydrolysate in a continuous cooking process for producing pulp. The invention further relates to a prehydrolysis vessel system.
BACKGROUND In some pulp production, for example in dissolving pulp production, a lignocellulose rawmaterial is first subject to a hydrolysis before an alkaline cooking is performed. Thehydrolysis is norrnally performed by adding steam or liquid to the lignocellulo se raw material.During the hydrolysis the hemicellulose, mainly C5 sugars, are degraded and released fromthe Wood. If the sugars should be extracted a hydrolysate comprising the dissolved sugarsneeds to be removed from a vessel Where the hydrolysis is performed before the pH ischanged and an alkaline cooking is performed. In the alkaline cooking process the dissolved sugars after the hydrolysis are broken-down to non-valuable components.
Handling of hydrolysate may be problematic due to its very sticky consistence and tendencyto create scaling for example in pipes, screens and on tank surfaces. Hydrolysate can beremoved through screens provided in the prehydrolysis vessel in a continuous cookingsystem. However, due to the sticky consistence of the hydrolysate and its tendency to createscaling there Will be problems With scaling in the screens. Hereby the screens need to becleaned and the production efficiency may be decreased. In the Worst case the productioneven needs to be stopped during cleaning. Any need for cleaning and any interruption in production processes are of course negative.
SUMMARY An object of the present invention is to improve production efficiency in a continuous pulp production process.
A further object of the present invention is to improve hydrolysate extraction efficiency in a continuous pulp production system.
This is achieved by a method for extracting hydrolysate in a continuous cooking system forproducing pulp and by a prehydrolysis vessel in a continuous cooking system for producing pulp according to the independent claims.
According to one aspect of the invention, a method for extracting hydrolysate in a continuous cooking process for producing pulp is provided, said method comprising the steps of: - cooling a content in a prehydrolysis vessel of a continuous pulp production system suchthat the content has been cooled down when the content arrives at a hydrolysis outlet of theprehydrolysis vessel on its way from an inlet provided in one end of the prehydrolysisvessel to an outlet provided in an opposite end of the prehydrolysis vessel; - removing a hydrolysate of said content through the hydrolysate outlet of the prehydrolysisvessel, wherein said content in the prehydrolysis vessel is cooled to such a degree that ahydrolysate removed through the hydrolysate outlet has a temperature between 70 °C and130 °C, wherein said cooling comprises circulating a part of the removed hydrolysatethrough a heat exchanger for cooling it down to a temperature between 20 °C and 100 °Cand adding the cooled hydrolysate to the content of the prehydrolysis vessel.
According to another aspect of the invention, a prehydrolysis vessel system in a continuous pulp production system is provided, wherein said prehydrolysis vessel system comprises: (a) a prehydrolysis vessel comprising: - an inlet provided in one end of the prehydrolysis vessel for receiving a content to be treatedin the prehydrolysis vessel; - an outlet provided in an opposite end of the prehydrolysis vessel; and - a hydrolysis outlet; and (b) a hydrolysate extracting arrangement connected to the prehydrolysis vessel, said hydrolysate extracting arrangement comprising: - a hydrolysate removing conduit comprising a prehydrolysis vessel connector which isconnected to the hydrolysate outlet of the prehydrolysis vessel; and - at least one cooling device which is provided to the prehydrolysis vessel such that it can cool down a content of the prehydrolysis vessel such that the content has been cooled 2 down when the content arrives at the hydrolysis outlet of the prehydrolysis vessel on itsway from the inlet of the prehydrolysis vessel to the outlet of the prehydrolysis vessel,wherein said cooling device is configured for cooling down the content in theprehydrolysis vessel to such a degree that a hydrolysate removed through the hydrolysateoutlet has a temperature between 70 °C and 130 °C, and wherein said at least one coolingdevice comprises a hydrolysate circulation arrangement which is configured to circulate apart of the hydrolysate removed through the hydrolysate removing conduit through a heatexchanger for cooling it down to a temperature between 20 °C and 100 °C and add thecooled hydrolysate to the content of the prehydrolysis vessel, wherein said prehydrolysisvessel comprises a cooling section in which cooling section said cooling of the content bythe cooling device is performed, which cooling section is a length section of theprehydrolysis vessel, in which length section the hydrolysis outlet is provided and whichlength section is less than l/3 or less than l/5 of a total length of the prehydrolysis vesseland wherein said cooling section is closer to the outlet than to the inlet of the prehydrolysis vessel.
Hereby a method and a system for extraction of hydrolysate in a pulp production system isprovided which is more effective and reliable than prior art systems. Thanks to the cooling ofthe hydrolysate before it is removed through a hydrolysate outlet of the prehydrolysis vesselthe tendency of the hydrolysate to create scaling, for example in the hydrolysate outlet whichcan be one or more screens, is much decreased. When cooling the hydrolysate the furfuralformation is reduced and also the lignin degradation is reduced. This will reduce the tendencyto build scaling. Furthermore the stability of the sugar solution is radically improved due tolowering the sugar degradation rate and a more effective sugar extraction from thehydrolysate can be provided. A more reliable process is provided thanks to less scaling andless need for cleaning of the system and a better sugar yield can be provided thanks to reduced sugar degradation.
In one embodiment of the invention said cooling of a content in the prehydrolysis vesselcomprises cooling the content to such a degree that the removed hydrolysate has atemperature between 70°C and l20°C or between 90°C and ll0°C. In this embodiment of the invention the cooling device is configured to cool the content to such a degree that the removed hydrolysate has a temperature between 70°C and 120°C or between 90°C and110°C.
In one embodiment of the invention said cooling comprises adding liquid with a temperaturebetween 20 °C and 100 °C or a temperature between 30 °C and 80 °C or a temperaturebetween 40 °C and 70 °C to the content in the prehydrolysis vessel. In this embodiment thecooling device comprises a liquid adding device which is conf1gured to add a liquid having atemperature between 20 °C and 100 °C or a temperature between 30 °C and 80 °C or a temperature between 40 °C and 70 °C to the content of the prehydrolysis vessel.
In one embodiment of the invention said cooled hydrolysate is added into the prehydrolysisvessel through nozzles provided around a periphery of an enclosing wall of the prehydrolysis vessel.
In one embodiment of the invention at least a part of said cooled hydrolysate is added to thecontent of the prehydrolysis vessel through an outlet of a liquid adding pipe protruding intothe prehydrolysis vessel, wherein said outlet is positioned closer to a central axis of the prehydrolysis vessel than to an enclo sing wall.
In one embodiment of the invention the step of removing a hydrolysate comprises removingthe hydrolysate through at least one screen provided in an enclosing wall of the prehydrolysis vessel, wherein said at least one screen is the hydrolysate outlet.
In one embodiment of the invention the step of removing a hydrolysate comprises displacingthe hydrolysate out through the hydrolysate outlet by adding a liquid into the prehydrolysis vessel from a bottom part of the prehydrolysis vessel.
In one embodiment of the invention the method further comprises the step of extracting sugar from the removed hydrolysate.
In one embodiment of the invention the continuous cooking process is a process for producing dissolving pulp.
Further embodiments of the invention are described in dependent claims and in the detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS Figures 1a-1d are schematic illustrations of different embodiments of prehydrolysis vesselsystems comprising a hydrolysate extracting arrangement connected to a prehydrolysis vessel in a continuous cooking system according to the invention.
Figure 2 is a floW chart of a method for extracting hydrolysate according to one embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS Figures 1a-1d are schematic illustrations of different embodiments of prehydrolysis vesselsystems la, lb, 1c, ld comprising a hydrolysate extracting arrangement Sa, 3b, 3c, 3dconnected to a prehydrolysis vessel 5a, 5b, 5c, 5d in a continuous cooking system accordingto the invention. Some of the components are the same in all embodiments and Will also be given the same or corresponding reference numbers.
Common for all the embodiments is that the hydrolysate extracting arrangement Sa; 3b; 3c; 3dcomprises a hydrolysate removing conduit 7 comprising a prehydrolysis vessel connector 8Which is arranged for being connected to a hydrolysate outlet 9 of the prehydrolysis vessel 5a;5b; 5c; 5d. The hydrolysate outlet 9 can for example be one or more screens provided in anenclosing Wall 21 of the prehydrolysis vessel. A reason for removing hydrolysate from theprehydrolysis vessel can be that the hydrolysate can be used in some Way, for example forextraction of sugar. Another reason for removing the hydrolysate is that less alkali Will beneeded in the next step of the pulp production process if at least some of the hydrolysate isremoved because the hydrolysate is acidic. Such a prehydrolysis vessel is a pressurized vessel.
The continuous cooking process of the invention can be a process for producing dissolving pulp.
The hydrolysate extracting arrangement 3a; 3b; 3c; 3d comprises furtherrnore at least onecooling device 11a, 11b; 11b°; 11c, 11c", 11c"; 11d configured such that it can be provided tothe prehydrolysis vessel 5a; 5b; 5c; 5d and such that it can cool down a content of theprehydrolysis vessel such that the content has been cooled down When the content arrives atthe hydrolysis outlet 9 of the prehydrolysis vessel on its Way from an inlet 13 provided in one end of the prehydrolysis vessel 5a; 5b; 5c; 5d to an outlet 15 provided in an opposite end of the prehydrolysis vessel. A scraper 16 is often provided in the bottom part of theprehydrolysis vessel. The cooling device lla, llb; 1lb°; llc, 1lc°, 11c"; 11d is configured tocool down the content in the prehydrolysis vessel to such a degree that a hydrolysate removedthrough the hydrolysate outlet 9 has a temperature less than 130 °C. For example, atemperature between 70 °C and 130 °C. In one embodiment of the invention the coolingdevice lla, llb; 11b"; 11c, 11c°, 11c"; 11d is configured for cooling down the content in theprehydrolysis vessel to such a degree that a hydrolysate removed through the hydrolysateoutlet 9 has a temperature less than 120 °C or between 70 °C and 120 °C and in anotherembodiment the cooling device lla, llb; l1b°; llc, 1lc°, 1lc"; 11d is configured for coolingdown the content in the prehydrolysis vessel to such a degree that a hydrolysate removedthrough the hydrolysate outlet 9 has a temperature less than 110 °C or between 90 °C and 110°C.
The hydrolysate outlet 9 can be provided in the enclosing wall 21of the prehydrolysis vesselsomewhere between the inlet 13 and the outlet 15 of the prehydrolysis vessel and can asmentioned above suitably be one or more screens provided in the enclosing wall. Thehydrolysate outlet 9 can be provided closer to the outlet 15 than the inlet 13 of the prehydrolysis vessel.
A normal temperature of the content in the prehydrolysis vessel 5a; 5b; 5c; 5d (i.e. before thecooling according to the invention) can for example be around 160-180 °C. At thattemperature the hydrolysate is very sticky and difficult to handle. For example heavy scalingis easily produced in components such as tank walls, tubes and screens coming into contactwith the hydrolysate. Hereby there are often problems related to scaling in equipment used forremoving the hydrolysate. The sticky consistence of the hydrolysate and its tendency toprovide scaling is probably due to furfural which is produced from the dissolved sugars andalso due to lignin. The furfural production is a fianction of time, i.e. longer exposure time ofsugars in such conditions leads to higher furfural concentration in the solution. Lignin contentalso increases during the hydrolysis time. Scaling consists much of lignin and furfuraltogether with sugars. Surprisingly it has been found that by cooling down the hydrolysate tofor example less than around 130 °C or less than 120 °C or less than 110 °C the stickyconsistence and tendency to provide scaling is greatly decreased and extraction of hydrolysisfrom a pulp production process can be much improved. Hereby also extraction of sugars froma hydrolysate can be improved. The positive effect of the cooling, i.e. the reduction of scaling, is surprisingly high also for relatively small temperature reductions. By cooling the content 6 down before a hydrolysate is removed from the prehydrolysis vessel of a continuous pulpproduction system according to the invention a much more effective extraction of thehydrolysate will be achieved thanks to less problem with scaling. Hereby the system forcontinuous production of pulp can also be operated in a more effective way when the problem with scaling is reduced.
Furthermore in these types of cooking systems for producing pulp it is traditionally veryimportant to keep up the high temperatures of the material in order to avoid energy loss.Hereby it would not be obvious for a skilled person to adopt this solution to cool down thecontent in the prehydrolysis vessel before a hydrolysate is removed as elevated temperature is required for the alkaline lignin removal step after the hydrolysis.
Also common for all the embodiments as shown in Figures 1a-1d is that said at least onecooling device lla, llb; 11b°; llc, 11c", 11c"; 11d is conf1gured such that it can provide acooling effect to a content in the prehydrolysis vessel 5a; 5b; 5c; 5d in a cooling section 23 ofsaid prehydrolysis vessel when the cooling device is provided to the prehydrolysis vessel. Thecooling section 23 is a length section of the prehydrolysis vessel, in which length section thehydrolysis outlet 9 is provided. Said length section is in one embodiment of the invention lessthan 1/3 of a total length of the prehydrolysis vessel and in one embodiment less than 1/5 of atotal length of the prehydrolysis vessel. Said cooling section 23 is positioned closer to theoutlet 15 than to the inlet 13 of the prehydrolysis vessel. The cooling of the content in theprehydrolysis vessel 5a; 5b; 5c; 5d is suitably performed in the vicinity of the hydrolysateoutlet 9. The cooling section 23 can be defined as a length section of the prehydrolysis vesselwhich length section comprises a part of the enclosing wall 21 and the space inside theenclosing wall 21 within this length section. The hydrolysis outlet 9 is positioned within thislength section. The cooling is performed somewhere within this cooling section 23 and herebythe cooling is performed in vicinity of the hydrolysate outlet 9. The cooling can be performedin a number of different ways and the cooling device can be embodied in a number ofdifferent ways which will be further described in relation to Figures la-ld. These differentcooling methods can also be combined in different ways which are all covered by this invention.
The removing of a hydrolysate from the prehydrolysis vessel 5a; 5b; 5c; 5d according to theinvention can comprise displacing the hydrolysate out through the hydrolysate outlet 9 byadding a liquid into the prehydrolysis vessel from a bottom part 25 of the prehydrolysis vessel. Therefore said prehydrolysis vessel 5a; 5b; 5c; 5d can comprise a liquid adding device27 which is conf1gured for adding liquid to the bottom part 25 of the prehydrolysis vessel fordisplacing cooled hydrolysate out through the hydrolysate outlet 9. The liquid that is addedcan be for example cooking liquor, such as white or black liquor and it can be added fromnozzles in the enclosing wall 2l in the bottom part 25 and/or from a central tube 27" providedinto the vessel through a bottom 26 of the vessel as shown in Figures la-ld. Such a liquidadding device 27 is norrnally provided in this type of prehydrolysis vessel for allowingtransfer of the material out through the outlet 15 of the prehydrolysis vessel. The central tube27" of the liquid adding device 27 is provided according to the invention for providing the further effect of displacing the cooled hydrolysate out through the hydrolysate outlet 9.
The hydrolysate extracting arrangement 3a; 3b; 3c; 3d can in some embodiments furthercomprise a sugar extracting arrangement 3l (only shown in Figure la, but it can be providedin all embodiments of the invention). The sugar extracting arrangement is connected to thehydrolysate removing conduit 7 and is arranged for extracting sugar from the hydrolysate.Sugar extraction will be more effective compared to in prior art because of the lowertemperature of the hydrolysate. Sugar degradation reaction is reduced in the hydrolysatethanks to the lower temperature of the hydrolysate and a total sugar yield can hereby be improved.
Figure la shows one embodiment of a prehydrolysis vessel system la according to theinvention. A hydrolysate extracting arrangement 3a which is connected to the prehydrolysisvessel 5a comprises in this embodiment a hydrolysate removing conduit 7 and a coolingdevice lla. The cooling device lla is in this embodiment a liquid adding device which isconf1gured for adding a liquid having a temperature between 20 °C and 100 °C or atemperature between 30 °C and 80 °C or a temperature between 40 °C and 70 °C to thecontent of the prehydrolysis vessel 5a. The liquid can be for example water or washing liquidor another liquid and should be provided to the prehydrolysis vessel 5a inside the coolingsection 23. The liquid can suitably have a pH around 7 or can be slightly acid or slightlyalkaline. In this embodiment a liquid adding pipe 33a is provided to the prehydrolysis vessel5a. Said liquid adding pipe 33a is protruding into the prehydrolysis vessel 5a and has an outlet34a positioned within the cooling section 23 and suitably closer to a central axis A of theprehydrolysis vessel than an enclosing wall 2l of the prehydrolysis vessel, i.e. centered withinthe prehydrolysis vessel 5a in vicinity of the hydrolysate outlet 9. The cooling device lla of the hydrolysate extracting arrangement 3a can therefore be connected to the liquid adding 8 pipe 33 for providing a liquid into the prehydrolysis vessel for cooling the content of theprehydrolysis vessel. Hereby the content inside the prehydrolysis vessel 5a can be cooleddown in vicinity of the hydrolysate outlet 9 and a hydrolysate removed through thehydrolysate outlet 9 can have a lower temperature than without this cooling. The temperatureof the removed hydrolysate can be measured, and a temperature of the liquid added throughthe liquid adding pipe 33 can be controlled such that a suitable temperature of the removedhydrolysate is achieved, such as for example less than 130 °C or less than 120 °C or less than 110 °C, as discussed above.
Figure 1b shows another embodiment of a prehydrolysis vessel system 1b according to theinvention. A hydrolysate extracting arrangement 3b which is connected to a prehydrolysisvessel 5b comprises in this embodiment a hydrolysate removing conduit 7 and a coolingdevice 11b, 11b". The cooling device comprises in this embodiment two parts. A first part 11bcan be connected to a liquid adding pipe 33b provided to the prehydrolysis vessel 5b. Saidliquid adding pipe 33b is protruding into the prehydrolysis vessel 5b and has an outlet 34bpositioned within the cooling section 23 and suitably closer to a central axis A of theprehydrolysis vessel than an enclosing wall 21 of the prehydrolysis vessel, i.e. centered withinthe prehydrolysis vessel 5b in vicinity of the hydrolysate outlet 9. The second part 11b" of thecooling device is in this embodiment configured for adding a cooling liquid into theprehydrolysis vessel 5b through nozzles 37 provided around a periphery of an enclosing wall21 of the prehydrolysis vessel 5b. Said nozzles 37 are provided within the cooling section 23of the prehydrolysis vessel 5b, i.e. in vicinity of the hydrolysate outlet 9. Hereby a coolingliquid can be both added into the prehydrolysis vessel 5b from the enclosing wall 21 and beadded to the content in the prehydrolysis vessel from a central place within the prehydrolysisvessel in vicinity of the hydrolysate outlet 9. Hereby the hydrolysate can be effectivelydisplaced and cooled down. Said nozzles 37 can be provided such that they direct a coolingliquid into the prehydrolysis vessel. Nozzles 37" can however also be provided within anouter compartment 38 which is provided outside the prehydrolysis vessel such that itsurrounds the screen 9 (the prehydrolysis outlet) provided in the enclosing wall 21 of theprehydrolysis vessel. Hereby cooling liquid can be added to the hydrolysate when it has beenremoved out from the prehydrolysis vessel through the screen 9 and when the hydrolysate is provided in said outer compartment 38.
In the embodiment as shown in Figure lb the hydrolysate extracting arrangement 3b comprises further a hydrolysate circulation arrangement 39. The hydrolysate circulation 9 arrangement 39 is configured for circulating a part of the hydrolysate removed through thehydrolysate removing conduit 7 through a heat exchanger 41 for cooling it down to atemperature between 20 °C and 100 °C or a temperature between 30 °C and 80 °C or atemperature between 40 °C and 70 °C and adding the cooled hydrolysate to the content of theprehydrolysis vessel 5b through the first and/or the second part llb, llb" of the coolingdevice. In another embodiment the cooling device may comprise only one of the first andsecond parts llb, llb". The hydrolysate circulation arrangement 39 hereby connects thehydrolysate removing conduit 7 with the first and/or second parts llb, llb" of the coolingdevice through a heat exchanger 41 and transfers a part of the removed hydrolysate from thehydrolysate removing conduit 7, through the heat exchanger 41 and to the cooling device 1 lb,llb" for adding it to the cooling section 23 of the prehydrolysis vessel 5b when thehydrolysate extracting arrangement 3b is connected to the prehydrolysis vessel 5b. Thecooling provided by the heat exchanger 41 to the circulated hydrolysate can be controlled independence of a measured temperature of the removed hydrolysate. As discussed above atemperature of the removed hydrolysate should be controlled to be less than 130 °C or less than 120 °C or less than 110 °C.
Recirculation of the hydrolysate may be advantageous because no additional liquid fromoutside the system need to be added into the prehydrolysis vessel for providing the coolingand hereby unnecessary dilution of the hydrolysate is avoided. However in some processes itmay be suitable to add some extra liquid as shown in the embodiment in Figure la. Forexample hydrolysis extraction yield may be improved by the addition of some extra liquid. Itmay be suitable to have a system where both these altematives can be utilized in combination or independently. One such system is shown in Figure lc.
Figure lc shows another embodiment of a prehydrolysis vessel system lc according to theinvention. A hydrolysate extracting arrangement 3c which is connected to a prehydrolysisvessel 5c comprises in this embodiment a hydrolysate removing conduit 7 and a coolingdevice llc, llc°, llc". The cooling device comprises in this embodiment three parts,whereof a first part llc and a second part 11c" are identical to the first and second parts llb,llb" as described above in relation to Figure lb and will not be described in detail again. Thefirst and second part llc, llc" are hereby connected to a hydrolysate circulation arrangement39 and to a liquid adding pipe 33b and to nozzles 37 as described above. The third part llc"is identical to the cooling device lla as described in relation to Figure la and will not be described in detail. The third part llc" of the cooling device is connected to a liquid adding pipe 33a and can add a cooling liquid to the content of the prehydrolysis vessel 5c. Hereby, inthis embodiment these three alternative ways of cooling the content in the prehydrolysisvessel 5c can be combined for an optimal cooling effect. Altematively an operator of thesystem can choose one or more of the separate parts llc, llc°, llc" of the cooling device forcooling the content. The temperature of the added liquid (either circulated hydrolysate orother liquid added through the third part llc") can be controlled such that the removed hydrolysate has a suitable temperature such that scaling is minimized.
Figure ld shows another embodiment of a prehydrolysis vessel system ld according to theinvention. A hydrolysate extracting arrangement 3d which is connected to a prehydrolysisvessel 5d comprises in this embodiment a hydrolysate removing conduit 7 and a coolingdevice lld. It comprises furtherrnore a hydrolysate circulation arrangement 39 as describedabove in relation to Figure lb. The hydrolysate circulation arrangement 39 is conf1gured forcirculating a part of the hydrolysate removed through the hydrolysate removing conduit 7through a heat exchanger 4l for cooling it down to a temperature between 20 °C and 100 °Cor a temperature between 30 °C and 80 °C or a temperature between 40 °C and 70 °C andadding the cooled hydrolysate to the content of the prehydrolysis vessel 5d through thecooling device lld. The cooling device lld transfers the cooled circulated hydrolysate to anumber of nozzles 37. The nozzles 37 are in this embodiment distributed not only around theperiphery of the enclosing wall 2l but also distributed along the length of the prehydrolysisvessel 5b within the cooling section 23. In this embodiment the prehydrolysis vessel 5dcomprises a number of screens 51 which are provided in sections and nozzles 37 are providedin between said screens 51. Hereby the cooled hydrolysate can be more effectively distributedover the screens and prevent scaling in the screens. The prehydrolysis vessel system ldaccording to this embodiment can also be provided with another cooling device lla, which is adding another cooling liquid as described in relation to Figure la.
Figure 2 is a flow chart of the method for extracting hydrolysate in a continuous cookingprocess for producing pulp according to one embodiment of the invention. The steps are described in order below: Sl: Cooling a content in a prehydrolysis vessel of a continuous pulp production system suchthat the content has been cooled down when the content arrives at a hydrolysis outlet of theprehydrolysis vessel on its way from an inlet provided in one end of the prehydrolysis vessel to an outlet provided in an opposite end of the prehydrolysis vessel. Said cooling is suitably 11 performed in a cooling section of said prehydrolysis vessel, which cooling section is a lengthsection of the prehydrolysis vessel, in which length section the hydrolysis outlet is providedSaid length section is in one embodiment of the invention less than 1/3 of a total length of theprehydrolysis vessel and in one embodiment less than 1/5 of a total length of theprehydrolysis vessel. Said cooling section is closer to the outlet than to the inlet of theprehydrolysis vessel. The cooling can be provided by adding liquid with a temperaturebetween 20 °C and 100 °C or a temperature between 30 °C and 80 °C or a temperaturebetween 40 °C and 70 °C to the content in the prehydrolysis vessel. The liquid can be for example water or washing liquid or circulated hydrolysate as described above.
S2: Removing a hydrolysate of said content through the hydrolysate outlet of the prehydrolysis vessel.
Said content in the prehydrolysis vessel is cooled to such a degree that the removedhydrolysate has a temperature less than 130 °C or less than 120 °C or less than 110 °C asdescribed above. This can also be described as in interval between 70 °C and 130 °C or 120 °C or 110 °C.The method can optionally also comprise a further step: S3: Extracting sugar from the removed hydrolysate. Thanks to the cooling of the content inthe prehydrolysis vessel the sugar degradation is reduced and the sugar extraction yield can be increased. 12

Claims (9)

1. A method for extracting hydrolysate in a continuous cooking process for producingpu1p, said method comprising the steps of: - coo1ing a content in a prehydrolysis vesse1 (5a; 5b; 5c; 5d) of a continuous pu1pproduction system such that the content has been coo1ed down when the contentarrives at a hydrolysate out1et (9) of the prehydrolysis vesse1 (5a; 5b; 5c; 5d) onits way from an in1et (13) provided in one end of the prehydrolysis vesse1 (5a;5b; 5c; 5d) to an out1et (15) provided in an opposite end of the prehydrolysisvesse1 (5a; 5b; 5c; 5d); - removing a hydrolysate of said content through the hydrolysate out1et (9) of theprehydrolysis vesse1(5a; 5b; 5c; 5d), characterized in that said content in the prehydrolysis vesse1 (5a; 5b; 5c; 5d) is coo1edto such a degree that a hydrolysate removed through the hydrolysate out1et (9) has atemperature between 70 °C and 130 °C, and that said coo1ing comprises circu1ating apart of the removed hydrolysate through a heat exchanger (41) for coo1ing it down to atemperature between 20 °C and 100 °C and adding the coo1ed hydro 1ysate to the contentof the prehydrolysis vesse1 (5a; 5b; 5c; 5d).
2. Method according to c1aim 1, characterized in that said coo1ing is performed in acoo1ing section (23) of said prehydrolysis vesse1 (5a; 5b; 5c; 5d), which coo1ing section(23) is a 1ength section of the prehydrolysis vesse1 (5a; 5b; 5c; 5d), in which 1engthsection the hydrolysate out1et (9) is provided and which 1ength section is 1ess than 1/ 3or 1ess than 1/ 5 of a tota1 1ength of the prehydro 1ysis vesse1 (5 a; 5b; 5c; 5d) and whereinsaid coo1ing section (23) is c1oser to the out1et (15) than to the in1et (13) of the prehydrolysis vesse1(5a; 5b; 5c; 5d).
3. Method according to c1aim 1 or 2, characterized in that said coo1ing of a content in theprehydrolysis vesse1 (5a; 5b; 5c; 5d) comprises coo1ing the content to such a degree thatthe removed hydrolysate has a temperature between 70 °C and 120 °C or between 90°C and 110 °C.
4. Method according to any one of the preceding c1aims, characterized in that said coo1ing comprises adding liquid with a temperature between 20 °C and 100 °C or a temperature 13 10. 11. between 30 °C and 80 °C or a temperature between 40 °C and 70 °C to the content in the prehydrolysis vessel (5a; 5b; 5c; 5d). Method according to any one of the preceding claims, characterized in that said coolingcomprises circulating a part of the removed hydrolysate through a heat exchanger (41)for cooling it down to a temperature between 30 °C and 80 °C or a temperature between40 °C and 70 °C and adding the cooled hydrolysate to the content of the prehydrolysisvessel (5a; 5b; 5c; 5d). Method according to claim 5, characterized in that said cooled hydrolysate is addedinto the prehydrolysis vessel (5b; 5c; 5d) through nozzles (37) provided around aperiphery of an enclosing wall (21) of the prehydrolysis vessel (5b; 5c; 5d). Method according to any one of the claims 5-6, characterized in that at least a part ofsaid cooled hydrolysate is added to the content of the prehydrolysis vessel (5b; 5c)through an outlet (34b) of a liquid adding pipe (33b) protruding into the prehydrolysisvessel (5b; 5c), wherein said outlet (34b) is positioned closer to a central axis (A) of the prehydrolysis vessel (5b; 5c) than to an enclosing wall (21). Method according to any one of the preceding claims, characterized in that the step ofremoving a hydrolysate comprises removing the hydrolysate through at least one screen(9; 51) provided in an enclosing wall (21) of the prehydrolysis vessel (5a; 5b; 5c; 5d), wherein said at least one screen is the hydrolysate outlet (9). Method according to any one of the preceding claims, characterized in that the step ofremoving a hydrolysate comprises displacing the hydrolysate out through thehydrolysate outlet (9) by adding a liquid into the prehydrolysis vessel (5a; 5b; 5c; 5d)from a bottom part (25) of the prehydrolysis vessel (5a; 5b; 5c; 5d). Method according to any one of the previous claims, characterized in that the method further comprises the step of extracting sugar from the removed hydrolysate. Method according to any one of the preceding claims, characterized in that the continuous cooking process is a process for producing dissolving pulp. 14 12. A prehydrolysis vesse1 system in a continuous pu1p production system, wherein saidprehydrolysis vesse1 system (1a; 1b; 1c; 1d) comprises:(a) a prehydrolysis vesse1 (5a; 5b; 5c; 5d) comprising:- an in1et (13) provided in one end of the prehydrolysis vesse1 (5a; 5b; 5c; 5d) forreceiving a content to be treated in the prehydrolysis vesse1 (5a; 5b; 5c; 5d);- an out1et (15) provided in an opposite end of the prehydrolysis vesse1 (5a; 5b;5c; 5d); and- a hydro1ysate out1et (9); and(b) a hydro1ysate extracting arrangement (3a; 3b; 3c; 3d) connected to the prehydrolysisvesse1 (5a; 5b; 5c; 5d), said hydro1ysate extracting arrangement (3a; 3b; 3c; 3d)comprising:- a hydro1ysate removing conduit (7) comprising a prehydro 1ysis vesse1 connector(8) which is connected to the hydro1ysate out1et (9) of the prehydrolysis vesse1(5a; 5b; 5c; 5d); and- at 1east one coo1ing device (11a, 11b; 11b°; 11c, 11c”, 11c”; 11d) which isprovided to the prehydrolysis vesse1(5a; 5b; 5c; 5d) such that it can coo1 downa content of the prehydrolysis vesse1 (5a; 5b; 5c; 5d) such that the content hasbeen coo1ed down when the content arrives at the hydro1ysate out1et (9) of theprehydrolysis vesse1 (5a; 5b; 5c; 5d) on its way from the in1et (13) of theprehydrolysis vesse1 (5a; 5b; 5c; 5d) to the out1et (15) of the prehydrolysis vesse1(5a; 5b; 5c; 5d), characterized in that said coo1ing device (11a, 11b; 11b°; 11c, 11c°, 11c”; 11d) isconfigured for coo1ing down the content in the prehydro 1ysis vesse1 (5 a; 5b; 5c; 5d)to such a degree that a hydro1ysate removed through the hydro1ysate out1et (9) hasa temperature between 70 °C and 130 °C, and that said at 1east one coo1ing device(11a, 11b; 11b”; 11c, 11c°, 11c”; 11d) comprises a hydro1ysate circu1ationarrangement (3 9) which is configured to circu1ate a part of the hydro1ysate removedthrough the hydro1ysate removing conduit (7) through a heat exchanger (41) forcoo1ing it down to a temperature between 20 °C and 100 °C and add the coo1edhydro1ysate to the content of the prehydro 1ysis vesse1 (5 a; 5b; 5c; 5d), and that saidprehydrolysis vesse1 (5a; 5b; 5c; 5d) comprises a coo1ing section (23) in whichcoo1ing section (23) said coo1ing of the content by the coo1ing device (11a, 11b; 11b°; 11c, 11c”, 11c”; 11d) is performed, which coo1ing section (23) is a 1ength 13. 14. 1
5. 1
6. section of the prehydrolysis vessel (5a; 5b; 5c; 5d), in which length section thehydrolysate outlet (9) is provided and which length section is less than 1/3 or lessthan 1/5 of a total length of the prehydrolysis vessel (5a; 5b; 5c; 5d) and whereinsaid cooling section (23) is closer to the outlet (15) than to the inlet (13) of the prehydrolysis vessel (5a; 5b; 5c; 5d). Prehydrolysis vessel system according to claim 12, characterized in that the coolingdevice (1 la, llb; 11b°; 11c, 11c°, 11c”; 11d) is configured to cool the content to sucha degree that the removed hydrolysate has a temperature between 70 °C and 120 °C orbetween 90 °C and 110 °C. Prehydrolysis vessel system according to any one of the claims 12-13, characterizedin that said at least one cooling device (1 la, llb; 11b°; 11c, 11c°, 11c”; 11d) comprisesa liquid adding device (1 la) which is configured to add a liquid having a temperaturebetween 20 °C and 100 °C or a temperature between 30 °C and 80 °C or a temperature between 40 °C and 70 °C to the content of the prehydrolysis vessel (5a; 5b; 5c; 5d). Prehydrolysis vessel system according to any one of the claims 12-14, characterizedin that said hydrolysate circulation arrangement (3 9) is configured to circulate a part ofthe hydrolysate removed through the hydrolysate removing conduit (7) through a heatexchanger (41) for cooling it down to a temperature between 30 °C and 80 °C or atemperature between 40 °C and 70 °C and add the cooled hydrolysate to the content ofthe prehydrolysis vessel (5b; 5c; 5d). Prehydrolysis vessel system according to any one of the claims 12-15, characterizedin that the prehydrolysis vessel (5b; 5c; 5d) comprises nozzles (37) provided around aperiphery of an enclosing wall (21) of the prehydrolysis vessel (5b; 5c; 5d), whereinsaid at least one cooling device (11b; 11b°; 11c, 11c°, 11c”; 11d) of the hydrolysateextracting arrangement (3b; 3c; 3d) can be connected to the nozzles (3 7) for providinga liquid into the prehydrolysis vessel (5b; 5c; 5d) for cooling the content of theprehydrolysis vessel (5b; 5c; 5d). 16 1
7. 1
8. 1
9. Prehydrolysis vessel system according to any one of the claims 12-16, comprising atleast one liquid adding pipe (33a; 33b) protruding into the prehydrolysis vessel (5a; 5b;5c) and having an outlet (34a; 34b) positioned closer to a central axis (A) of theprehydrolysis vessel (5a; 5b; 5c) than to an enclosing Wall (21) of the prehydrolysisvessel (5a; 5b; 5c), characterized in that said at least one cooling device (lla, llb;11b°; 11c, 11c°, 11c”) ofthe hydrolysate extracting arrangement (3a; Sh; 3c) can beconnected to the at least one liquid adding pipe (33a; 33b) for providing a liquid intothe prehydrolysis vessel (5a; 5b; 5c) for cooling the content of the prehydrolysis vessel(5a; 5b; 5c). Prehydrolysis vessel system according to any one of the claims 12-17, characterizedin that said prehydrolysis vessel (5a; 5b; 5c; 5d) comprises a liquid adding device (27)conf1gured for adding liquid to a bottom part (25) of the prehydrolysis vessel (5a; 5b;5c; 5d) for displacing hydrolysate out through the hydrolysate outlet (9). Prehydrolysis vessel system according to any one of the claims 12-18, characterizedin that said hydrolysate outlet (9) of the prehydrolysis vessel (5a; 5b; 5c; 5d) is at leastone screen (9; 51) provided in an enclosing Wall (21) of the prehydrolysis vessel (5a; 5b; 5c; 5d). 17
SE1950386A 2019-03-29 2019-03-29 A method and a system for extracting hydrolysate in a continuous cooking process for producing pulp SE542991C2 (en)

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SE1950386A SE542991C2 (en) 2019-03-29 2019-03-29 A method and a system for extracting hydrolysate in a continuous cooking process for producing pulp
PCT/SE2020/050285 WO2020204783A1 (en) 2019-03-29 2020-03-18 A method and arrangement in a continuous pulp production process
EP20782621.5A EP3947808A4 (en) 2019-03-29 2020-03-18 A method and arrangement in a continuous pulp production process
CN202080025300.9A CN113646481B (en) 2019-03-29 2020-03-18 Method and arrangement in a continuous pulp production process
BR112021013052-7A BR112021013052A2 (en) 2019-03-29 2020-03-18 METHOD FOR EXTRACTING HYDROLYZE IN A CONTINUOUS COOKING PROCESS TO PRODUCE PULP, PRE-HYDROLYSIS VESSEL SYSTEM IN A CONTINUOUS PULP PRODUCTION SYSTEM, HYDROLYZATE EXTRACTION DISPOSITION
ZA2021/04457A ZA202104457B (en) 2019-03-29 2021-06-28 A method and arrangement in a continuous pulp production process

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US3530034A (en) 1969-05-16 1970-09-22 Itt Rayonier Inc Continuous aqueous prehydrolysis of wood chips
US4436586A (en) * 1982-01-22 1984-03-13 Kamyr, Inc. Method of producing kraft pulp using an acid prehydrolysis and pre-extraction
US20070131363A1 (en) * 2005-10-24 2007-06-14 Andritz Inc. Fiberline systems, processes and methods
BRPI0505212A (en) * 2005-11-01 2007-08-07 Dedini Sa Ind De Base improvements in fast acid hydrolysis process of lignocellulosic material and hydrolysis reactor
FI123036B (en) * 2006-02-10 2012-10-15 Metso Paper Inc Method for recovering hydrolysis products
US8734610B2 (en) * 2007-05-23 2014-05-27 Andritz Inc. Two vessel reactor system and method for hydrolysis and digestion of wood chips with chemical enhanced wash method
US9260818B2 (en) 2007-05-23 2016-02-16 Andritz Inc. Single vessel reactor system for hydrolysis and digestion of wood chips with chemical enhanced wash method
EP2212467B1 (en) * 2007-11-01 2014-06-11 Eau-Viron Incorporated Methods and apparatus for hydrolyzing cellulosic material
US8192549B2 (en) 2008-06-10 2012-06-05 Andritz Inc. Apparatus and method for hydrolysis of cellulosic material in a two-step process
JP5378306B2 (en) * 2010-06-15 2013-12-25 月島機械株式会社 Biomass processing apparatus and processing method
CN103687990B (en) * 2011-05-13 2016-03-30 维美德公司 Manufacture the compact method of prehydrolyzed pulp
WO2016112203A1 (en) * 2015-01-07 2016-07-14 Andritz Inc. System and method for monitoring and control of multiple processing zones within pressurized vessels
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