造纸专业英语2.ppt

Lesson13Pulpbleaching Bleachingisthetreatmentofwoodandotherlignocellulosicpulpswithchemicalagentstoincreasetheirbrightness Brightnessisincreasedbydecolorizingordissolvingthecoloredcomponentsinpulp primarilylignin Twoapproachesareusedinthechemicalbleachingofpulps bleachv 漂白lignocellulosic木质纤维素的agent 化学 药剂brightness亮度decolorizevt 使脱色dissolvevt 使溶解componentn 组分 Lesson13Pulpbleaching Oneistoalmosttotallyremoveresiduallignin whichisusedforbleachingofchemicalpulpsandleadstogreaterfiber fiberbondingstrengthinpaperbutweakerfibersduetothestrongchemicalusedtodecreasethelengthofcellulosemolecules Theotherapproachistoutilizechemicalsthatselectivelydestroysomeofthechromophoricgroupsinmechanicalpulps whichisreferredtoaslignin preservingorbrightening residual残余的 剩余的bondv结合 使粘合strength强度chemical化学药品molecule分子chromophoric发色的 发色团的group基团 基mechanicalpulp机械浆brightening显白 显亮 Lesson13Pulpbleaching Sinceligninisacomplexmoleculewithdifferentlinkages thebreakageofvarioustypesofbondsrequirestheuseofdifferentchemicals Therefore allthecoloredmaterialinpulpscannotbeeliminatedbyanysinglechemicalandbleachingisamulti stepprocess complex复杂的 多元的linkage 化 键合 成键 Lesson13Pulpbleaching Theprincipalcommercialbleachingchemicalsconsistsoftheoxidants chlorine C oxygen O hypochlorite H chlorinedioxide D hydrogenperoxide P andozone Z theonlyreductant hydrosulfite andtheonlyalkali sodiumhydroxide E orcausticextraction oxidant氧化剂chlorine氯oxygen氧气hypochlorite 化 次氯酸盐chlorinedioxide二氧化氯hydrogenperoxide过氧化氢ozone 化 臭氧reductant还原剂hydrosulfite 化 亚硫酸氢盐alkali碱sodiumhydroxide氢氧化钠causticextraction碱抽提 Lesson13Pulpbleaching Itispossibletorankeachoftheoxidizingchemicalsforeconomy selectivity andparticlebleaching althoughitmustberememberedthattheparticularconditionsofusewillgreatlyeffectonranking Therankingsare Economy O C D H P Z Selectivity DelignificationD C O ZBrightening D P HParticlebleaching D H C O P Z delignification脱木素作用 Lesson13Pulpbleaching Becauseoftheirgreatereconomy chlorineandoxygenareusedintheearlystagesofbleachingforligninremoval butcannotbeusedformoreextensivetreatmentbecausetheirpoorselectivityresultsincellulosedegradation Chlorinedioxide hypochlorite andperoxidecanbeusedinthelaterstageduetotheirselectivityandalsotheirhighercost Selectivity选择性degradation降解作用 Lesson13Pulpbleaching Wecandividebleachingsequencesintotwoparts delignificationandbrightening Inthedelignificationpart ligninremovalistheobjectiveandkappanumberisusedastheprincipalcontrolparameter Inthebrighteningpart higherbrightnessistheobjectiveandbrightnessisthemaincontrolparameter OxygencanbeusedeitherbeforechlorinationorafterasanadditivetotheEstage Eo Inthedelignificationpartofthesequence 80 85 oftheresiduallignininunbleachedpulpisremoved kappanumber卡伯值parameter参数chlorination 化 氯化 作用 additive添加的 附加的 添加物unbleached未漂的 Lesson13Pulpbleaching Thebrighteningpartofthesequencecanbesinglestage i e Htoreach70 brightness Orthispartcanbe3or4stagestoreach90 brightness Hypochloriteandchlorinedioxidearetheprincipalbleachingagentsinthispart Sequencesmoretypicalofmodernmillsforbleachingsoftwoodkraftpulpare D C E O DEDandO D C E O D Themostwidelyadoptedshortsequenceis D C EO D Inmostcases eachbleachingstageisfollowedbyawashingstagetoremovereactionproducts Lesson13Pulpbleaching Sulfiteandhardwoodkraftpulpsare easierbleaching thansoftwoodkraftpulps Bothhavelowerlignincontent andtheligninresiduesinsulfitepulpsarepartiallysulfonatedandthereforemorereadilysolubilized Consequently asomewhatsimplerprocesscanbeusedtoachieveacomparablebrightnesslevel sulphonate磺酸盐 使磺化solubilizev 溶解 Lesson13Pulpbleaching Formechanicalpulpbleachingorpulpbrightening inordertoretaintheadvantageofhighyield pulpsmustbedecoloredorbrightenedbymethodsthatdonotsolubilizeanyappreciableamountoflignin Commerciallyusedchemicalsforthispurposetodayaresodiumhydrosulfitewhichhasareductiveaction andhydrogenperoxideswhichhaveanoxidativeaction Single stagetreatmentsaresufficientforimprovingtheeyeappealofnewspri