LIGNIN ADSORPTION AND KAPPA NUMBER IN ETHANOL PULPING

JOURNAL OFApTIANJIN UNTVERSITY OF SCIENCE AND TECHNOLOGYVol 19 SuppLIGNIN ADSORPTION ANDprogress about EW pulping technology for woodfiber materials had been made in Canada, while theKAPPA NUMBER IN ETHANOL research on EW pulping for non-wood fiber materialsPULPINGhas seen the remarkable progress. The studyindicated that the technology has much advantagesYongjian Xu, Xinping Licompared to the conventional chemical pulpingprocess such as lower investment, lower cost,Meiyun Zhangexcellent strength propcrty, lower pollution, noSchool of Papermaking Engineering,silicon interfering that existed in chemical recovcry,Shaanxi Province Key Laboratory of Papermaking more flexibility for non-wood fiber material such asShaanxi University of Science and Technologywheat, bagasse, hemp etc 3-s.Therefore theTechnology and Specialty Paper( 712081)technology will resolve many problems inEmail: xyj4922(@sinconventional chemical pulping with non-wood fibermaterials, especially in chemical recovery and wasteABSTRACTwater reuse. 67. At the same time, a phenomenon wasdiscovered in the ethanol pulping that the kappaThe effect of washing temperature, washing stages number was higher but the pulp was easy to bleachresults preliminarily showed that the dissolved lignin lower kappa numo ggeand the cooking operation on the ethanol pulp had :417 This paper mainly studied the reason why thebeen investigated, and the reason for higher kappa ethanol pulp had higher kappa number and alsonumber of the ethanol pulp was discussed. Thebrought forth ways and means to obtain pulp withcould re-adsorb to fiber surface by means of fiberclassification technology and explained the questions EXPERIMENTALfound during the study. Some measures were taken toreduce the kappa number, the results had shown that In the experiment, the wheat straw was obtained fromere was obvious absorption in the ethanol pulping; Xianyang Paper Mill and cut into length oflignin remained in the pulp could easily be dissolved 20mm-30mm manually, the impurity was removedand the pulp with lower kappa number could be and the moisture was equilibrated too. Ethanol wasbtained at a higher temperature; the kappa n could water (EW) arranged 50%60%concentrationnumber industrial ethanol collected from market. The ethanolcould reduce by increasing washing timeenable dissolved lignin to separate out from the Pulping equipments with 15 and 2 volumes workedethanol pulp and restrain the lignin absorption by under the pressures of kgf/cm? and 25 kgf/cmblowing cooking liquid at high temperaturerespectively were designed and made by ShaanxiUniversity of Science and Technology. The oil wasKEYWORDS: ethanol pulping kappa numbecharged into the 15-liter-degester and heated up to acertain temperature first when cooking. And then the2-liter-reactor charged with certain straw were putArticle Il:16726510(2004)supp-0144-04into the oil bath and continually heated up to thecooking temperature after 30 minute. wheat strawINTRODUCTION(100g) was pulped in 2-liter reactor with EW 1: 1(volume)with a liquor to straw rate of 1: 8 at pIt was reported that organic-solvent pulping process temperature of 195C, reaction time was 70 mt pulpinggmin delignfied in the cooking was soluble in the process in water-bathing or oil-bathing with theethanol water(EW) more than in the ethanol only, temperature of 100t(100 degrees centigrade )andobtained a correlative patent in 1932. Diebold who 140C, EW concentration was 50% and 70%, the pulpworked in Paper association of Canada prompted the had 1%-2% consistencies, Each washing stage hadprocess, and pronounced a patent in the 1978-. In been for 30 minutes. The washed and screened pulpaddition, non-wood fiber material occupies a much was stored in the desiccatorshigher proportion to the material used inpapermaking of china, so low pollution-pulping RESULTS AND DISCUSSIONprocesses for non-wood fiber materials seemportant especially and have been devoted to Eff中国煤化工mberesearch in our country. Thed pulp 's hige and ethanolproperties attract papermaker,'s attention. And a contYHCNMHG-14Vol 19 SuppJournal of Tianjin Uninersity of Science an TechnologyResults of pulp-washing were shown in table I where cellulose bonds. And salvation and diffusion of ligninthe pulp was washed at the different temperature of out of cell wall matrix play a significant role 9100 Cand 140C with EW concentration of 55% and Therefore the higher the ethanol concentration, the70%.The kappa number decreased by ten at 140c higher the ethanol content in the liquid phase in thethan at 100%C with the other conditions keeping the digester is, which made more lignin dissolved intosame, so temperature plays an important role in pulp the liquor and the kappa number reduced. the resultwashing. While the difference between EW pulping showed that 70% EW had higher dissolvable abilityand conventional chemical pulping consists in that at the temperature of 140C and the low kappalignin dissolved in the EW liquor through theber pulp was obtainedhydrolysis of alpha - aryl-ether and lignin -hemTable 1 Effeet of washing temperature on kappa numberWash Kappa Yield Decrease in kappaEW阳% Temperature/estages number / nnumber/%54.0614082597Note: wash time at each stage is 30min; unwashed pulp kappa number is 129.Effect of washing stages on kappa numberhorizontal level. But it indicates that the residualThe number of washing stages has greater influence lignin of wheat straw ethanol pulp is difficult toon cleanliness in traditional chemical pulping and dissolve comparatively, and washing repeatedly canalso on ethanol pulping. For many decades, the have the kappa number much more reducedstandard method of washing was to employ a series However even if through 4-stage washing process,of washers operating in a countercurrent flow the fine pulp's kappa number was to be still as high aspulp from wheat straw in order to discuss the effect stages can,'t obtain ethanol pulp with lower kappaof wash stages on kappa number. The result was number. What's more the micro-fine fibers floweshowed in table 2 where the kappa number suffered into washing liquor and the yield was influence withfrom the increase of wash stages and inclined to a the increasing of wash stagesTable 2 Effect of wash stages on kappa numberEw TemperatureWash stages Kappa number Yield Decrease in kappanumber70140267.547.6714060.6530214055.75682Note: wash time at each stage is 30min; unwashed pulp kappa number is 129Effect of blow cooking liquor and fast cooling results were shown in Table 3 where the differenceThe reason for high kappa number may be that lignin fast was obvious. And the kappa number of pulp lipkappa numberbetween by blowing cooking liquor and by coolingdissolved into the EW liquor adsorbed onto fiber lower by 4.8 unites in the former than in the latter,again. And then how to separate dissolved lignin which indicated that the lignin dissolved in twofrom the pulp fiber is to be considered and discussed different manners behaved in a specified wayas a hot problem? So some measures such as blowing Re-d occurring in fastooking liquor and fast cooling after reaction were cool中国煤化工 Ived rushed out oftaken to solve it. It is expected that the method couldreduce the kappa number of wheat straw pulp. The andCNMHthe ew solutionb on the fiberJournal of Tianjin Uinirersity of Science and TechnologyVol19 sTherefore if displacement cooking and washing separated from pulp and the low kappa number pulpprocess was adopted, the lignin was effectively was obtainedTable 3 Effect of the discharging manner on kappa numberEW Temperature Wash KaYield Decrease in kRemarksstagesnumbernumber59.646095384Cooling fast5752Blowing cooking47.7Table 4 The results of fiber classificationPulp(two-stage washed)Pulp(four-stage washed)Soda pulpmeshes kappa numberYield /2kappa number Yield/% KMnO4 Yield /%4946.6714-2848.719.0217.6181.674747.848-1002l433542>100300755213.43surface area comparing with fiber cell, so theirThe analysis to high kappa numberadsorption of lignin is more strong and can explainthe portion of ethanol wheat straw pulp washed by 2For comparison purpose, the EW pulp and soda pulp stages after 100 mash-wire has 92.5 kappa number. Inwere treated into some portions by fiber classification addition, each of the portions before 100 mash-wirestechnology. And each of their proportion to all and has the nearly the same kappa number as otherkappa number were measured. The results were portion washing by four stages comparable to by twoshown in table 4 where different portion had different stages. The loss of micro fines is to be considered askappa number. After multi-stage EW solution the reason for above in the course of washing. Andwashing, the kappa number for tiny portion in the the micro fines after 100 mesh-wire accounts for30.7% when washed by 2 stages process, while onlyThe permanganate number of portions of soda pulp 17.2% by 4 stages process. That the permanganateafter 28 mesh-wires was nearly the same as each number of the micro fines of soda pulp after 100other, while the permanganate number of portions of mash-wires is higher than that between 28 and 100soda pulp before 28 mesh-wires was higher. The mash-wires proves that there is a phenomenon ofresults indicated that there were some not fully adsorption in the alkaline pulping, but it is not just asseparated fiber fascicules. This is not different from serious as that of ethanol pulp. In addition, theEW pulp. The soluble ability of EW suffered from content of micro fines of ethanol wheat straw pulpthe temperature falling in the course of cooking, remained between 48 and 100 mash-wires has aboutwashing and cooling of the ethanol pulp. So there 50%only, while the soda pulp has up to 65%.Andwas some re-abortion of lignin to the fiber after the lignin that ethanol pulp adsorbed mostly may bereaction in blow cooking liquor or fast cooling. That attach to the surface of fiber, this can explain that EWto say abortion phenomenon may be responsible pulp is good in strength and it is apt to be bleachedfor the reason of eW pulp higher kappa numbertooFrom physical -chemical principle, the bigger thespecific surface is, the stronger the ability of中国煤化工adsorption is. And there were plenty of non-fibrouscells in the pulp of wheat straw which has largeoHCNMHGpulp at a relatively146Vol 19 SupJournal of Tianjin (intersity of Science and Technologyhigher temperature. while the pulp of lower kappaStraw-Wheat Alcohol Pulping", Thesis of master degreenumber obtainedof Northwest Institute of Light Industry. 1997.7The kappa number can be reduced in the multi-washing 5. Dokki and Cario, "Organosov Pulping-Alcohol Pulpingocess to some extent, but the increase of fiber's loss willof Bagasse", Ccllulose Chem [J]. Techno. 29, 615-629ccurred with the washing stages incrcasing;1995)The results of fiber classification proved that there was 6. Zhang zhi cheng, "Organic solvent system thick liquid-aobvious adsorption in the EW pulping and washingkind of method that apply tostem thick liquidprocess to a certain extent:forcign papermaking[ (2),Lignin could be dissoived more into EW liquor and be 7. Ressell D, etc OptimizaOrganosolv Processfor While Birch" SolventSymposium, 73-78(1992)REFERENCESStudy on bleaching technology andnechanism of auto-catalyze ethanol pulp of1. Sal manOrganosolv Pulping", Tappi. [] 72(3),rush", the Master dissertatiele Shaanxi169-175(1989university of science and technology 2000Kleinert, paper, 1974, 11-14ELENA PEREIRA, MARIO F.OLIBEIRAEthanol system thick liquid and its course ofISABEL MIRANDA. " Kinetics of ethanol-waterElecting"C.E.P],76(2),62·67(1980and pulp properties of eucalyptus globules Lab?pu4. Xu Yongjian, "Study on Technics and Mechanism of中国煤化工CNMHG147