SE539449C2 - Method for heating cellulosic material to full cooking temperature in digesters - Google Patents

Method for heating cellulosic material to full cooking temperature in digesters Download PDF

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Publication number
SE539449C2
SE539449C2 SE1551483A SE1551483A SE539449C2 SE 539449 C2 SE539449 C2 SE 539449C2 SE 1551483 A SE1551483 A SE 1551483A SE 1551483 A SE1551483 A SE 1551483A SE 539449 C2 SE539449 C2 SE 539449C2
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Sweden
Prior art keywords
digester
steam
liquor
heated
heating
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SE1551483A
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Swedish (sv)
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SE1551483A1 (en
Inventor
Olsson Krister
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Valmet Oy
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Application filed by Valmet Oy filed Critical Valmet Oy
Priority to SE1551483A priority Critical patent/SE539449C2/en
Priority to EP16866744.2A priority patent/EP3377696A4/en
Priority to PCT/SE2016/051013 priority patent/WO2017086856A1/en
Publication of SE1551483A1 publication Critical patent/SE1551483A1/en
Publication of SE539449C2 publication Critical patent/SE539449C2/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
    • D21C7/10—Heating 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
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/10—Concentrating spent liquor by evaporation
    • 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
    • D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate 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
    • 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
    • D21C7/14—Means for circulating the lye
    • 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
    • D21C11/0085—Introduction of auxiliary substances into the regenerating system in order to improve the performance of certain steps of the latter, the presence of these substances being confined to the regeneration cycle
    • D21C11/0092—Substances modifying the evaporation, combustion, or thermal decomposition processes of black liquor
    • 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

Abstract

13 ABSTRACTThe invention relates to an improved method for generating steam in a digester plantof a chemical pulp mill. 5 A mixture of alkaline cooking liquor and black liquor is before charge to the digestersystem heated in a reboiler producing black liquor steam used to heat the cellulosicfeed material in digester top reaching full cooking temperature. By this method couldaddition of clean steam condensate to cooking liquor be avoided, and problems likelignin precipitation in black liquor heaters as well as alkaline corrosion in cooking 10 liquor heaters may be totally avoided. (Figz) KST15003SE Abstract.docx

Description

1/13 METOD FOR HEATING CELLULOSIC MATERIAL TO FULL COOKINGTEMPERATURE IN DIGESTERS BACKCERGUNÜ OF ENVENTEONThe present iiiventien reiates te a inethed ter generating steam in a digester piant et a shemieai puip miii.
Conventienaiiy, in eider tiberiine systems have a ship bin and a suhseduent steamingvessei been used ter steaming/heating ot wood chips er ether eeiiuiese materiai.initiai stearning in chip bin has used tresh iew pressure steam, reaehing atemperature in the range eti-ttithtl. The supseeuent stearning in steaming vesseiiiermaiiy used tiasheei steam trern biaek iieuer tiash tanke, reaehing a temperature ettGGIiZtDPC., The steamed chips are thereatter siurried in seeking er impregnatioitiieuor. First in digester tep has the chips er siurry been heated to tuii digestertemperature, iying in the range et t30~t80°tl using expensive medium pressuresteam trem the steam net it the ehips are te be heated to tuii seeking temperature ina steam phase digester. in case et a hydrauiie digester, the heating is made using aheating eirsuiatien. in these systems has a voiume et spent het biaek iieuor (typicaiiyat tuii seeking temperature et t3tli~t80° C.) been withdrawn trem the seeking systern.The heat vaiue in the het biaek iiquer voiume is used initiaiiy te generate steam tersteaming vessei and heat white iiquer, er aiternative iieuid veiumes eharged te theseeking systems. The spent het ieiaek iieuer is typieatiy sent tirst te two er more tiashtanks connected in series where steam traetiens are produced at sueeessiveiy towertemperature and pressure as the iieuer is tiashed in stages to temperatures etappreximateiy 954 'it)° C. Finaiiy the biaek iieuer is sent te the evaperater system in the reeevery isiand. iiewever, in recent state et the art digester systems has the digester system beenimproved and simpiitied sensiderapiy and in digester systems with Compact CookingGZW, soid by Vattnet, is a singie tirst impregnatien vessei, irnpBinW, repiaeing aiiprevious chip pins, steaming vessei and irnpregnatien vesset. in such impBin vesseiis the ehips steamed and impregnated with hot biaek iieuor that is suppiied tremdigester, and when added to impBin is aiiewed te tiash ett steam ter steaming and KST15003SE_text.dOcx 2/13 using the residuai hiack iiuuer as the irnpregnation iiduor.
Different concepts have heen proposed where the heating to tuii digestertemperature is repiacing the additien ot ciean steani into digester to usage ot tiashsteant trern hiack iiduor. Ciean cendensate wiii thus not he iost in digester, andcoeking iiduors wiii not he diiuted with ciean water that increase evaperation work inthe recevery operations.
One ot the first patents diseiosing a rehoiier producing dirty stearn ter heating indigester top is shewn in Vairnet ABs SE 453ß73. Here is dirty het stearn producedin a steani converter (reieoiier) using the heat vaiue in hot hiach iiduor as heatingrnediurn in the steani converter.
Another systeni is disciosed in US 43441540, where the heat vaiue in hot hiack iiouoris recovered in 3 seriaiiy connected evaporation stages. Stearn trern the evaporationstages are directiy intreduced te the irnpregnation and cooiting zenes in a digester terheating the tiprous rnateriai.
Yet a systern has been proposed in US ßJiTdQYt, hut ter the generation et purestearn to he used in the chip pin er chip tube. iriere is the ciean stearn obtained trernthe repoiier pressurized petore added to the chip hin. it an educator is used driven hytresh steain, ceuid a tower pressure he estahiished in the rehoiier and inore heatvaiue he extracted trern the hot piack iiduor. in US 2tliO7/0i3i363 is disciosed a coinpiex systern where the hot hiack iiduor is sentto an evaperation stage ii and vapour trern evaperatien stage iii is returned to chipein tor heating. Sšerne et the heat vaiue in the ieiack iieuer is used in pre~heatersheating white iiduors exciusiveiy. in US85t25t4 is disciesed a cernpiex duai heat recevery systern, using a firstevaporator to generate toui steam ter heating in digester tep using a tirst extractiontievv frorn digester, and a second heat exchanger for producing ciean stearn trern asecond extractioii tiow troni digester.
Uåâšeëitiriâ concerns a rnethod using the Crossillirct” concept pronioted hy VairnetAB, in the Cressílirc concept is het hiaek iiduer added directiy into the transfersystem in erder te reduce steani censurnption in digester top ter reaching tuii coekingternperature. in this patent is a reoeiier aiso used te recover residuai heat vaiue in the return KST15003SE_text.dOcx 3/13 iidtior withdrawn in the top separator, and this rehoiier is producing ciean steam forchip bin steaming. in US88Q8498 is yet another system discioeed where fiash steam from hiaok iiotiorheats white iiduor, and the fiashed hiack iiduor is used in a second heat exchanger inorder to heat white iiouor.
The known soititions provide different systems for orodtioing steam for heating needsin the digester oiant and for imoroving the energy eoonorny of the onto rniii. t-iowever,rnost systern faiis to take a common aooroaoh for heating aii feed fiows to digester,and inciudee coinoiex systeins with muitioie heat exchange apoaratoses.SUMMARY OF ittt/ENTEON The inventive method is deveiooed for generating steam in a digester oiant of achernicai otiip miii comprisiitg; extracting a voiume of hot hiack iigtior (Het) at ftiii Cooking temperature from thedigester (Diç adding a charge of aikaiine cooking iigdor (MIL) to the hot hiack iigtior forrning amixed tioner (WLt-Hstšš geherating vanor hy evaporating the mixed iiddor hy heating the mixed iiodorindirectiy with fresh steam (STMP), wherein an evaporated mixed iigdor fiow (X) isseparated from the vaoor; heating oeiitiiosic feed materiai in the digester with the generated vaoor (STBL)separated from the evaporated mixed iiooor, and adding the heated evaoorated mixed iiduor to the digester giant (Xxm or Xxtrz orXxtts ) for heating the ceiiuiosio feed materiai in or before the digester (D). in a preferred emhodiment is the evaoorated mixed iiotior used as irnpregnationiiouid in eariy chip treatment systems, i.e. hiack iidttor imoregnatioh, which isadvantageous from an emission point as the evaoorated mixed iiddor has a towercontent of rnaiodorotis gases than the content of rnaiodorode gases in the voitime ofhot hiack iiddor yvhen extracted from digester The inventive method rnay aiso further invoive that the evaooration of the mixediiotior takes oiace in a reooiier (Rett) and the charge of aikaiine cooking iigtior (Vt/L) isintroduced into the hot hiack iiqtior in or before the rehoiier where adeouate rhixingtakes piaoe during the hoiiiitg conditions prevaiiing in the rehoiier.
KST15003SE_text.dOcx 4/13 The inventive method may aieo further invoive that said evaporated mixed iiduorobtaining a iovver dry matter content than the hot biaok iiduor and a toweroonoentratioh of aiitaii than the fresh aiitaiine Cooking iiduor.
The inventive method may ateo further invoive vvherein a oieah steam oondeneate ieobtained trom the indireot heating in the reboiier and this oiean oondensate ie usedae heating medium in a preheater, preheating the aiitaiine oooiting iiduor or the mixediiduor before being fed to the reboiier.
The inventive method may aieo further invoive vvherein the heated evaporated mixediiquor 'iiovv (X) ie heated to a temperature above the prevaiiing tuii Cookingtemperature, and oharged at ieast in part to the top of the digester (Qi-ord vvhere the heated evaporated mixed iiduor generates steam as weii as hot booking iiduor.
The inventive method may aiso further invoive wherein the heated evaporated mixediiduor ie heated to a temperature above the prevaiiing fuii oooiting temperature, andoharged at ieast in part to a preoedihg impregnation vessei (EB), preferahiy at end ofthe impregnation veeeei and preferabiy direotiy ahead of transfer ot the oeiiuioeiefeed materiai to the digester (Ü).
The inventive method may aiso turther invoive wherein the heated evaporated mixediiduor fiovi/ (X) is heated to a temperature above the prevaiiing tuti Cookingtemperature, and oharged at ieaet in part to a preoeding impregnation vessei (EB),preferabiy at start of the impregnation vessei and more preferabiy direotiy into a ohipvoiume eetabiished over a iiduid ievei (Liet) in said impregnation vessei, suoh thatsteam reieased from the heated evaporated mixed iiduor vviii steam the oeiiuiosiofeed materiai before impregnation.
The advantages with these atternativee vviii pe expiained in more detaii in connection with the detaiied description toiiovving beiovv.
KST15003SE_text.dOcx /13 SUMMARY GF Ti-tE QRAWENGS iïitå. t shovvs schematicaiiy a state ot the art digester system; Figí shows a moditication ot the digester system in Fig “i where the ihventive steamgeneration system is instaiied; Figß shows e deteii view ot the steam generating system, with identified processparameters disciosed. ÜEÉTAiLEÜ DESCRWTEON FiG. t iiiustrates a state ot the ert digester system ot the Compact Cooking GZWconcept, soid py Vaimet. "the Compact Cooking GZWi concept inciudes a singie tirstatmospheric impregnation vessei iB, impBinW, repiacihg aii previous chip pins,steaming vessei and impregnation vessei. in such impßin vessei is the chips (Ii-tittsteamed and impregnated with hot oiack iiouor TSRET that is suppiieci trom digesterD. and when added to iß/ irnpBin is aiiowed to tiash ett steam tor steaming and usingthe residuai piack iiouor as the impregnation iiouortorming e iiouor ievei Liet heiowthe steam tiash ett position. "the system inciudes the Crosstflirctiri concept promotedpy Vaimet AB. where hot hiaek iiouor HBL tyithdrawn trom digester is added ciirectiyinto the trehster system in order to reduce steam consumption in digester top toreievating the temperature. Finai heating is ohtained hy en additionai heating withinediuin pressure steam Step reaching tuii cooiring temperature in digester top. Atirst heating ot the chips towards tuii cooiting temperature then takes piece during thetransfer to the top separator TS. and the excess transport iiouor Tårta is withdrayvnin the top separator and used as the tiashing impregnation iiduor. in mostinstaiiations in warmer ciimetes is the steam tiashed ett trom the hot biack iiduor inthe atmospheric tmpBin vessei enough tor tuii steaming ot chips and purging ot airpound in the chips. Need tor additionai iow pressure steam tor steaming chips mayhe totaiiy avoided, put tor extreme conditions during winter time when chips may bedeep trozen. As indicated, the extraetion position tor the hot hiacit iiduor at tuiicooiring temperature may he iocated anywhere in the digester, i.e. within theindicated zone A. As shown here is a dedicated heater used tor the white iiciuor Wi.charge, and the addition to digester top is conventionaiiy made using a white iiouorheader distriputor (not shown) that sprays the white iiouor into the top. i-iowever,handiing conceritrated white iiduor et tuii cooking temperature invoives increased KST15003SE_text.dOcx 6/13 eorresien expostire, and the heaters may he stipieeted te aikaii corrosiori even it theheater is made in stainiess steei needing even hetter and mere expensive materiai inthe heater. Aise the spraying et eeneentrated hot white iiquor into radiaiiy directednezzies tewards inside it digester sheii may expese the digester sheii te aikaiieorresien, which has heen seen in digesters rnade in carbon steei materiai. Additionet het aikaiirie iieuer inte digester tep may not he ideai ter a perteet rnixing inte thechips, as the eniy mixing etteet is trem the tree taii et chips passing the aikaiine sprays.
FEG. 2 iiiustrates an improvement et the Compact Ceeking GZW concept as shown intigure t, and inciudes a steam generatien system eperating according te theinventive method. in the inventive concept is at ieast a part et the het hiaek iieuerHat, heiding tuii seeking temperature which in this exampie is ”i4t°(3, instead sent toa reheiier Rep ter turther heating. As shewn may aise the het piaek iieuer ite.. heheated in preheater t-iE hetere being charged te the reieoiier, and this aiterhative wiiiee mere described in teiiewing Fig. 3. Aise, a charge et tresh aikaiine seeking iiduer,typicaiiy white iideor put any kind et aikaiine seeking iiduor may he used, is ehargedinte the het eiaek iiduer and preterahiy hetere the preheater HE. "typicaiiy the aikaiineCooking iiduor heids a ternperature peiow 'ittttïï and stored in atmospheric tanks,and hence the mixed iideor Win-HBL tft/iii reach a tower temperature at aeedt tïštiïï. ita preheater HE is used this temperature may ee increased te about t34°t3 peterecharged to the reheiier Rep. “the repeiier heids ot veieme et mixed iideor Wise-istand a ceii er pipiitg ter heating media is instaiied in this iieeer veiume, in this case theheating media is medium pressure steam Stifp. i-tence, the heating et the mixediieuerwiii he done indirectiy, and ciean steam cendensate wiii not he test in themixed iidtier and diiute it. "the eeii is suppiied with medium pressure steam Stivia anda cendensate Str; is extracted trem the heating eeii. The heating in the reheiierresuits in heavy iooiiing and the added aikaiine iieuer wiii pe perteetiy mixed with thehot hiack iideer, and a hiaek iieuer steam STBL is hoiied ett trem the mixed iieeer. Thehiaek iieeer steam Stat tseiied ett is ied te the tep et the digester, and this veiume otsteam may totaiiy repiace the cenventienai charge et eieah medium pressure steamte digester top.
Set/erat pesitive etteets et this inventive heat treatment et the mixed iieuer areeetained.
KST15003SE_text.dOcx 7/13 First, the heated hot hiaok iiouor is eievated to ternperatures above tuiioooking temperature, and the heat vaiue in this hot hiaok iiouor increases, and thatwithout diiution ot ciean stearn oondensate.
Seoondiy, hoth the addition ot aikaii and heating have positive etieots onthe content otdissoived hentioeiiuiose in the hiack iiduor, that need tirne, ternperatureand high aikaii oonoentration in order to increase oieavage rate on end groups ot thehernioeiiuiose. tft/hen the cieavage etteot has reached a oriticai order oouid thehernioeiiuiose start to preoipitate onto ceiiuiose and increase yieid trorn the oook. Theadditionai retentiori tirne in the repoiier, the heating and the aikaii addition aiicontribute synergistioaiiy in increased cieavage rate, Thirdiy, the oonfirnon heating ot ooth oiaok iiduor and aiitaiine Cookingiiouor in a iiduor ntixture in one singie heating apparatus avoids hoth iigninpreoipitation risks in a rehoiier ted vvith hiaok iiouor With high soiids content and iovvaikaii ievei oiose to iignin preoipitation ievei as wei! as avoids aikaii oorrosion risks indedicated heaters tor oonoentrated cooking iiduor.
Fourthiy, the content ot rnaiodorous gases in the hiaok iiduor vviii pereduced, such as suitur and rnethyirneroaptans, as they vviii hoii ett to a iarge extentWith the hiaok iiciuor stearri as they have a iovver ooiiing point. it/tost ot thesernaiodorous gases, espeeiaiiy ntethyirneroaptans, has vveii knovvn deiignitioationetteots irnproving the deiignitioatioit rate in the digester.
The heated hot hiaok iiouor Wind-ist rnay reaoh a temperature vveii over the tuiioooking ternperature, and this tiovv X rriay be used in severai aiternative routes,either tor exoiusive use or in oornhinations.
First option given priority to reduce need tor rnediurn pressure stearnaddition to digester top invoives routing the tiow X to digester top at the indicatedposition XALi-i. "the overheated rriixed iiouor tyiii then tiash ott additionai stearn as weiias suppiy ot both aikaii artd ioiack iiquor to eook at tuii seeking temperature.
Second option given priority to reduce need tor medium pressure stearnaddition to digester top hy heating the oeiiuiosit: rriateriai aiready in transteroirouiation invoives routing the tiow X at end of irnpregnation vessei iB and preterahiydirectiy ahead ot the transfer systern at the indioated position XAm. The overheated rnixed iiouor wiii heat the siurry vvith oeiiuiosic rnateriai When rnixed into this siurry.
KST15003SE_text.dOcx 8/13 Third eption given priority te increase steaming etiect in tep etimpregnatien vessei inveives reuting the tiew X at tep et irnpregnatien vessei EB, andpreterahiy inte the return tiew TSRET trom the tep separetor at the indieated positienXAt-rß., The everheated mixed iiduer wiii heat the return iiduer when mixed inte it andmere steam wiii tee tieshed ett when tinaiiy dumpad inte the veiume et eeid ehipsiying aheve the iiguer ievei Liet. This option may he preterred in miiis eperating inceid eiimate and ted with deep trezen chips.
These 3 eptiens may he cernpined with the erdinary withdrawai et het hiack tieuerHat as shewn in Figt, hatch-marked tiew in Figß, and aiternative or cempiementingwithdrawats et het piaek iieuer He, iewer dewn in the digester, aise shewn as hateh-marked tiew in Figí, Gptiens 2 and 3 ter the X tievif are speeiticaiiy adapted ter a Compact Ceekingw*system with an impišin, hut eptien t may he used in any digester system eperatingwith cenventionai pressurized impregnatien vesseis as weii as using other chippretreatment systems with dedicated ship pins and steaming vesseis. (Dptien 2 mayaise he used in cenventienai E-vesset digester systems where heating is te he ehtained in tirst vessei., in tigure 3 is disciesed an emhedirnent et the inventien in a Compact Ceeitingtittsystern with an irnpBirt impiemented aecording te the tirst eptien.
The hasie parameters ter the digester systern are as teiiews: ß Digester capacity: 4090 edt/d a Steam te digester: Iššt) kgfadt, and 16,2 kg/sß Steam pressure te digester tep: 4,5 hartg) v» MP steam pressure etter centret vaive: ttlš hade) ß ivtP steam temperature: ”iåšßßïï o BL+WL itew: 4,6 mïtiedt a Btfitnli. temperature: 139%) ß Fuii ceoking temperature: 141%) The pasic parameters ter the Repeiier (Rep) are as teiiews:o Effective heat exchange area:754 m2 - itmvsiue: tsss w/(m-t ~ m) KST15003SE_text.dOcx 9/13 Û ATIQQ: e Cohdehsate temp. decrease: 5,G°C 29,3°C The hasic parameters tor the Preheater (HE) are as toiiows: o Ettective heat exchehge areaztšíà m21835 Wítmg ~ “Ct282%? o ievaiue:ß ATI As seeh ih this emhodimerit are hoth a rehoiier Reh ahd a oreheater HE ihstaiied, asthe cohdehsete STC trom the rehoiier stiii has e cohsiderahie heat vaiue thet couid heused ih a preheeter. But the ihvehtioh do hot require the preheater tor ohtaihihg thehuik voiuhie ot heated hiaok iiouor steam STBL. Fractieaiiy the ihstaiiatioh ot aoreheater may he motivated it there is e shortege ih medium pressure steam, and/orthe investment costs tor the hreheater motivetes ihstaiiatioh compared to savihgs ihooeratihg oosts (ie. cost tor medium pressure steam). it is cieariy seeh ih thisexampie that the hiack iiouor steam Stat is heated to töäjt “(3 ahd at a heat vaiue otâïäß ittiiitg. Aiso the overheeted mixed iiouor Wifi-tät from the rehoiier hoicis sametemperature ot tdšfi “(1 Ghce the overheated mixed iiduor is added to the digestertoh is ah adciitiohei amouht ot steam reieesed at a rete ot 4,4 kg/s, vvhich is aimost4Q% ot the hiaok iiduor steam Stat rate trom the rehoiier, virhiie the cookihg iiouorWifiriiat is charged at tuii cooitihg temperature.
White the ihvehtioh has heeh described ih cohhectioh with ihstaiiatioh ih a CompactCookihgtt" system, it is to he uhderstood thet the ihvehtioh is hot to he iimited to thedisciosed emhodimerit, hut the ihveritive method is ihtehded to cover variousimoiemehtetiohs ih dittereht digester systems such es cohvehtioitai cookihg,ooerated with iTC, EAPC, Lo~Soiids or simiiar oookihg iiouor routihg. "the hasic orihcioies are that hoth the eikeiirie cooitihg iiduor ahd hiack iiouor as emixed iiduor is heated ih ohe commoh ihciirect heat exehahger, that couid avoidcohdehsetioh ot cieah steam oohdehsate ih the mixed iiduor, hut stiii ohtaihs ediiutioh ettect ot the hiaok iiduor hy eikeii edditioh.
The ihcreased tiow rete ot iiouor oessihg the ihdirect heet exohahger ihcreaseheatihg ettioiehcy.
KST15003SE_text.dOcx /13 Biack iidtior typicaiiy has a dry rnatter content exceeding that ot trash cooking iiduorhy at ieast š-EOÉ/tt, so the diiutioit hy tresh cooking iidtior improves tiowcharacteristics troiigh the indirect heat exchanger and reduce scaiing tendencies,that otten are seen in evaooration stages as a tar iiite deposition in the evaoorationstages, where sirniiar increase ot dry rnatter content ot ondiitited hiack iioiior isobtained. in a cost reduction aiternative rnay the entire heating ot the rnixed iiduor, te. taiackiiduor and white iidtior, hy obtained in the indirect heatet betore charging to digester,vifhich rriean that the white iiduor charge to digester too needs no dedicated whiteiidtior heater, which save investment costs tor such heater, and ehahie downscaiingot any additionai white iiquor heater tor other charges to the process. tndirect heaterstor concentrateci white iidtior are dee to working conditions, heat and aikaiiconcentration, rnost expensive as they need to he ntade in high aiioy corrosive resistant steei.
The totai charge ot aiitaiine Cooking iidtior needed tor the entire cook rnay hecharged to the rehoiier, or at ieast 2ß~ 5022» ot the totai necessary charge.
KST15003SE_text.dOcx

Claims (6)

1. A method for generating steam in a digester plant of a chemical pulp millcomprising; extracting a volume of hot black liquor (HBL) at full cooking temperature fromthe digester (D); adding a charge of alkaline cooking liquor (WL) to the hot black liquor forminga mixed liquor (WL+HBL); generating vapor by evaporating the mixed liquor by heating the mixed liquorindirectly with fresh steam (STMP), wherein an evaporated mixed liquor flow (X)is separated from the vapor and the evaporated mixed liquor has a lowercontent of malodorous gases than the content of malodorous gases in thevolume of hot black liquor when extracted from digester; heating cellulosic feed material in the digester with the generated vapor (STBL)separated from the evaporated mixed liquor, and adding the heated evaporated mixed liquor to the digester plant (XAm orXAuz or XALTa ) for heating the cellulosic feed material in or before the digester(D)-
2. The method according to claim 1 wherein the evaporation of the mixedliquor takes place in a reboiler (Reb) and the charge of alkaline cooking liquor(WL) is introduced into the hot black liquor in or before the reboiler where adequate mixing takes place during the boiling conditions prevailing in the reboiler. §4. The method according to claim 2 wherein a clean steam condensate isobtained from the indirect heating in the reboiler and this clean condensate isused as heating medium in a preheater, preheating the alkaline cooking liquor or the mixed liquor before being fed to the reboiler. gå. The method according to claim 1 wherein the heated evaporated mixed liquor flow (X) is heated to a temperature above the prevailing full cookingtemperature, and charged at least in part to the top of the digester (Drop)where the heated evaporated mixed liquor generates steam as well as hot cooking liquor. Qê. The method according to claim 1 wherein the heated evaporated mixedliquor is heated to a temperature above the prevailing full cookingtemperature, and charged at least in part to a preceding impregnation vessel(IB), preferably at end of the impregnation vessel and preferably directly ahead of transfer of the cellulosic feed material to the digester (D). Qi. The method according to claim 1 wherein the heated evaporated mixedliquor flow (X) is heated to a temperature above the prevailing full cookingtemperature, and charged at least in part to a preceding impregnation vessel(IB), preferably at start of the impregnation vessel and more preferably directlyinto a chip volume established over a liquid level (LiqL) in said impregnationvessel, such that steam released from the heated evaporated mixed liquor will steam the cellulosic feed material before impregnation.
SE1551483A 2015-11-16 2015-11-16 Method for heating cellulosic material to full cooking temperature in digesters SE539449C2 (en)

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SE1551483A SE539449C2 (en) 2015-11-16 2015-11-16 Method for heating cellulosic material to full cooking temperature in digesters
EP16866744.2A EP3377696A4 (en) 2015-11-16 2016-10-18 Method for heating cellulosic material to full cooking temperature in digesters
PCT/SE2016/051013 WO2017086856A1 (en) 2015-11-16 2016-10-18 Method for heating cellulosic material to full cooking temperature in digesters

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SE545465C2 (en) * 2019-12-02 2023-09-19 Valmet Oy Method and arrangement for adding treatment liquors to cellulose raw material in a continuous process using down flow vessels

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CA1097465A (en) * 1976-11-30 1981-03-17 James R. Prough Black liquor energy recovery
SE453673B (en) * 1985-07-02 1988-02-22 Kamyr Ab SEE CONTINUOUS COOKING TO HEAT THE FIBER MATERIAL AT THE COOKER'S TOP
US4897157A (en) * 1986-07-08 1990-01-30 Kamyr, Inc. Make-up liquor and black liquor evaporating processing during pulp production
US5213662A (en) * 1991-08-14 1993-05-25 Kamyr, Inc. Treatment of chips with high temperature black liquor to reduce black liquor viscosity
US6306252B1 (en) * 1995-04-10 2001-10-23 Andritz-Ahlstrom Inc. Heat recovery from spent digester cooking liquor
JP2005256224A (en) * 2004-03-12 2005-09-22 Daio Paper Corp Method of digestion using columnar vessel type continuous digester
FI120547B (en) * 2004-10-04 2009-11-30 Metso Paper Inc Alkaline cooking process and pulp making plant
SE0502851L (en) * 2005-12-21 2006-12-19 Kvaerner Pulping Tech Systems and process for the generation of steam in a boiler for the production of chemical cellulose pulp
SE530332C2 (en) * 2006-11-07 2008-05-06 Metso Fiber Karlstad Ab Process for energy-efficient production of cellulose pulp in a continuous cookery
FI122983B (en) * 2009-02-09 2012-09-28 Andritz Inc A process for steam generation at a pulp mill digester
US8986504B1 (en) * 2013-10-25 2015-03-24 International Paper Company Digester apparatus
FI127386B (en) * 2014-03-05 2018-04-30 Andritz Oy A process for steam generation at a pulp mill digester

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SE1551483A1 (en) 2017-05-17

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