化工原理下册重点(中英文)

一、传质过程导论

ntroductionofmasstransferrocess

物质在相际间的转移属于物质传质过程

Substancetransferbetween

phasesbelongstothemasstransfer

process

这类单元操作在化工生产中应用甚广

Thiskindofunitoperationiswidely

usedinchemicalproduction

Inthispartwemainlylearn

（一）相组成的表示方法representingmethodof

phasecomposition

对于混合物，一个相的组成可以用多种方

法表示/

Forthemixture,aphasecomposition

canbeexpressedinavarietyofways,

1.质量分数与摩尔分数Themassfractionand

themolefraction

i

refersthefractionthatacomponent

massaccountforo>\totalmass

massfraction:WA

a

a

[WA-massfractionofcomponent

A】

molefraction:XA

gas

a

phase:

a

liquidphase:

a

a

relationshipWA-XA:

a

a

—>

a

[MA-molarmass,kg/kmol]

2.质量比与摩尔比massratio、molarratio

a

massratio:

a

molarratio:X

gas

phase：

a

liquidphase：

a

a

relationshipw-

a

a

relationshipx-X:

a

a

3、concentration:

Massconcentration:CA

a

molarconcentration:CA

a

relationshipCA-WA：

a

relationshipcA-xA:

a

4.气体总压与理想气体中组分的分压

Totalpressureandpartialpressureofcomponentinideal

gas:

a

MoleratioY-partialpressure:

a

massratio-partialpressure:

a

molarconcentrationCA-PA:

a

massconcentrationCA-PA:

a

（二）、扩散原理principleofdiffusion

1、Ficklaw:温度、总压一定，组分A在扩散方向上任一

点处的扩散通量与该处A的浓度梯度成正比。

Underacertaintemperature,total

pressure,diffusionfluxofcomponentA

onthedirectionofdiffusionis

proportionaltoconcentrationgradient

a

[dcA/dz-concentrationgradient;

DAB-DiffusioncoefficientofAinB,m2/s]

PS:1、负号表示方向相反minussignmeansJAandgradientare

intheoppositedirection

2、Ficklawdescribestherule

ofdiffusionrate

分子扩散两种形式Moleculardiffusionintwo

forms:

二、吸收Absorption

（一）、吸收的基本理论Thebasictheoryof

absorption

L利用不同气体组分在液体溶剂中的溶解度差异，对其进行选择

性溶解，从而将气体混合物进行组分分离的传质过程称为吸收

UsetheSolubilitydifferenceofdifferentgas

componentsinliquidsolvents,

dissolvethecomponentselectivelyzThemass

transferprocessofgasmixtureseparation

iscalledtheabsorption

在工业上的应用有：原料气的净化、某些

产品的制取、废气的治理等

theindustryapplicationispurificationof

feedgas,preparationofsomeproducts,

improvementofexhaustgas.

2、气液相平衡gas-liquidequilibrium

在溶质A与溶剂接触、进行溶解度的过程中，随着浓度cA

的逐渐增大，传质速率将逐渐减慢,最后降到零，cA达到一最大限

度cA*.这时称气液达到了相平衡，

intheprocessofAcontactingwithsolutesolubilityin

solvent,withtheincreasingofconcentration,themass

transferratewillgraduallyslowdown,finallyreducedtozero,

cAreachedamaximumcA*oThenitiscalled

gas-liquidphaseequilibrium.

亨利定律henry'slaw:

总压不高时，在一定温度下，稀溶液上方气相中溶质的平衡

分压与溶质在液相中的摩尔分率成正比。

Whenthetotalpressureisnothigh,atacertain

temperature,equilibriumpartialpressureofthe

solute\ntheqasphaseabovethedilute

solutionisproportionaltotheMole

Fractionofsoluteintheliquidphase.

a

[E-Henry'sconstant,kpaE=C/H;

C-液相总浓度theliquidphasetotal

concentration;

H-溶解度系数solubility

coefficient】

（二）、吸收传质速率masstransferrateofabsorption

①双膜模型doublemembrancemodel

1）气液两相存在一个稳定的相界面，界面两侧存在稳定的气膜和液

膜，膜内为分子扩散

wesuppose,Thereisastablegas-liquidinterface,stablegas

filmandliquidexistonbothsidesoftheinterface,inthefilm

thereismoleculardiffusion

2)相界面处两相达平衡Twophaseachievebalanceatphase

interface.

a

为吸收速率的计算提供了依据Providethebasisforthe

calculationofabsorptionrate

②相际传质速率方程masstransferingrateequation

1、Gasmembraneabsorptionrateequations:

NA=RG(pc-pi)

【I<G-气膜吸收系数Gasmembraneabsorption

coefficient;]

当气相的组成以摩尔分率表示时

Whenthegasphasecompositionusethemolefractionto

express:

a

[ky-表示以摩尔分数差为推动力的气膜吸收系数

Gasmembraneabsorptioncoefficientthat

usedifferenceofmolefraction8Sdrivingforce]

2、liquidmembraneabsorptionrate

equations:

NA=RL(G-CL)

[ki-liquidmembraneabsorption

coefficient;]

当液相的组成以摩尔分率表示时

Whentheliquidphasecompositionusethe

molefractiontoexpress:

a

【kx-表示以摩尔分数差为推动力的液膜吸收系数

liquidmembraneabsorptioncoefficient

thatusedifferenceofmolefraction8Sdrivingforce]

3、总吸收系数及相应的吸收速率方程式

①气相总分压差为推动力的传质速率方程

equationthatusedifferenceofgasphaseoverallpartial

pressureasdrivingforce.

NA=KG(pG-pL*)

【KG一气相总传质系数Thegas

phaseoverallmasstransfercoefficient

PL*-与液相主体浓度成平衡的气相分

压,Pa

gasphasepartial

pressurethatisinbalance

withconcentration

ofliquidphase；

PG-gasphasepartial

pressure]

以摩尔分率表示时usethemolefractiontoexpress:

a

[Ky—以,为推动力的气相总传质系数

gasphaseoverallmass

transfercoefficientthatuseAyasdriving

force

y*-与液相组成成平衡的气相组

成，摩尔分数

Gascompositionthatisin

balancewithliquidcomposition,mole

fraction]

②以液相总浓度差为推动力的传质速率方程

equationthatusedifferenceofliquidphase

overallconcentrationasdrivingforce.

NA=KL(CG*-CL)

【CG*-与气相分压PG呈平衡的液相浓度，

liquidconcentrationthatisin

balancewithgasphasepartialpressure]

3

ps:总系数与分系数的关系Theoverallcoefficientandpartial

coefficient

a

a

Respectivelyaretotalresistanceandgasfilmresistanceand

liquidfilmresistance

a

3

气膜控制：gasfilmcontrol:

溶解度很大时的易溶气体，传质阻力主要集中在气相。称为气膜控制

物系。

Asforthesolublegaswithlargesolubility,meansH（溶解度

系数

solubilitycoefficient)islarge,sothemasstransferresistance

ismainlyconcentratedinthegasphase.Knownasthegas

filmcontrolsystem.

a

a

a

a

（三）、吸收（或脱吸）塔的计算Thecalculationofabsorption

tower

1、物料衡算与操作线方程materialbalance、operatingline

equation

a

Ga、Gb——气体组分（A+B）出塔、入塔的流率，kmol/

m2s

exit、enterflowrateofgas

component

La、Lb——液体组分（A+B）出塔、入塔的流率

G、L——通过塔此截面的气、液流率，

Thegasandliquidflowrateof

acrosssectionofthetower

ya、yb——出塔、入塔气体的摩尔分数，

exit、entermolefractionofgas

component

x、y——塔一截面处气、液的摩尔分数

gas,liquidmolefractionof

across-sectionofthetower

全塔物料衡算Overallmaterial

balance:

GB=G(1-y),Ls=L(l-x)

Y=y/l-y,X=x/l-x

GB(Yb-Ya)=Ls(Xb-Xa)

(解释：气体溶质被吸收，y、G不断减小，以不变的量

作为基准,即惰性气体B的流率和溶剂S的流率

Thegassoluteisabsorbed,y,G

decreasecontinuously,

useinvariantasthebenchmark,

theinertgasBflowrateGBandthe

solventSflowrateLs]

蓝色的通常是已知的，如果再知道Ls、Xb

之一，就可求出另一个量

GB、Yb、Ya、Xaareusually

known,ifweknowoneofLSZ

Xbzandthenwecanfindanother

quantity.

为求得任意截面上的气液组成关系，可以对塔顶

与此截面间作物料衡算，

Inordertoobtaingasandliquid

compositionrelationshiponanysection,

wecanmakematerialbalancebetween

thetopofthetowerandthecross

section

GB(Y-Ya)=Ls

(X-Xa)

operatinglineequation

or,Y=LS/GB-X+(Ya-LS/GB

.Xa)

a

accordingtoit,wecanalsodrawathemoleratioof

coordinatesystem,AB-operatingline,slopeofline

平衡线

ABisLS/GB,OE-lineofbalanceo

AnypiontPontheoperatingline,

PQ-以气相摩尔比之差表示的推动力driving

forceexpressedbydifferenceofgasphase

moleratio(Y-Y*),PR-driving

forceexpressedbydifferenceofliquid

phasemoleratio(X*-X).

whenLsdecreases

,slopedecreasesaswellz

LimitoperationisBmeetingOEatC,soC

-drivingforceis0zandmasstransferrateis

also0.

liquid-gasratiointhissituationis

calledminimumliquidgasratio,

a

应用啥的：关于溶剂的用量，希望流率要小来

降低消耗，但限于溶解度，不能太小，所以实际

采用液气比常在最小值的L1至2倍内选.

Abouttheamountofsolvent,wewantflow

ratecanbesmallertoreducethe

consumption,butduetothelimited

solubility,itcannotbetoosmall,sothe

liquidgasratioisalwayschoosed1.1to2

timesoftheminimumvalue

(四)、填料层高度的计算heightoffillinglayer

它应保证其中有效气液接触面积能满足传质的需求

Itshouldensuretheeffectivegas-liquidcontact

areacanmeetthedemandofmasstransfer

A=aV=a(nD2/4)h

L对数平均推动力法logarithmicaveragedriving

force

a

【Kya-气相总体积吸收系数gasphase

overallvolumeabsorptioncoefficient;

A

①findym：

a

△ya=ya-mxaallwillbe

giveno

2、吸收因数法AbsorptionNumberMethod

①液气比liquid-gasratio:

L/G=(yb-ya)/(xb-xa)

②吸收因素absorptionfactorA:

A=L/mG

S。脱吸因素Desorptionfactor:

S=l/A

③吸U攵要求Absorptionrequirements:

(yb-mxa)/(ya-mxa)=?

(4)useS、?lookatgraph,getNOG

h=NOG*HOG

传质单元TransferUnit

气相总传质单元数gasphaseoverall

transferunit:NOG

为了便于分析，把整个填料层分为若干段,

Inordertofacilitatetheanalysis,thefiller

layerisdividedintoseveralsegments,

传质单元高度heightoftransferunitHOG：

a

同理还有液相总传质单元数Similarly,NOLHOL

（五）、塔板数platenumber

板式塔和填料塔的区别在于，气液两相

的接触是在塔板上进行的，故组成沿塔高呈阶跃

式变化而不是连续式变化。所以得求塔板数。

thedifferencebetweenplate

columnandpackedcolumnisthatthe

gas-liquidcontactisoncolumnplate,so

thecompositionalongthetowerhigh

issteptypechangeinsteadofcontinuous

change.Soweshouldfindplatenumber.

a

a

N-理论板数numberoftheoreticalplates

总板效率overallplateefficiencyEO:

E0=N/Ne

Ne-实际板数actualnumberplate

三、蒸储distillation

利用混合物在一定压力下各组分相对挥发度(沸点)的不同进

行分离的一种单元操作。Usethedifferenceofrelative

volatility(BP)

betweencomponentsofmixtureundercertain

pressure,toseparatemixedliquids0

第一节二元物系的汽液相平衡

显然，气液两相呈平衡时的组成差别越大，越有利于蒸播

分离。因此这里需研究相平衡关系。

Obviously,themorebiggerthedifference

ofcompositionofagas-liquid(whichisin

equilibrium)is,theeasierthedistillationis.Soheretostudy

phaseequilibrium.

(一)、理想溶液idealsolution

若溶液中的各个组分在全部浓度范围内都服从拉乌尔定

律，称为理想溶液。

ifeachcomponentinthesolutioninthe

wholeconcentrationrangeobeysRaoul's

law,knownastheidealsolution

a

3

a

-纯液体的蒸气压Thepure

liquidvaporpressure

x-易挥发组分A的摩尔分数The

molarfractionofvolatilecomponents

a

a

so,液相组成liquidcomposition:

a

泡点方程bubble-point

equation0

a

（解释：

Dependsonthetemperaturesolutionbegantoboil)

means一定总压下液相组成与泡点的关系

Underacertaintotalpressure

relationshipbetweenliquidphasecomposition

andthebubblepoint。

a

露点方程

Dew-pointequationo

means一定总压下气相组成与开始冷凝时的温度的关

系

Underacertaintotalpressurethe

relationshipbetweengasphasecompositionand

temperaturegasbegantocondensate

气液相平衡图Gasliquidequilibriumgraph

a

ADB-dew-pointline,t-y;ACB-bubble-pointline,

t-x;

whent=100,drawalinemeett-yatD,meett-xatC,

CDmeansGas-liquidtwophasecompositionx=,

y=

drawAvertical,F-bubble-point(whenx=),

E-dew-point

onlyinthe2phaseregion,

componentcanbeseparated

（二）挥发度和相对挥发度Volatilityand

relativevolatility

1、Volatility:对纯液体，挥发度指该液体在

定温度下的饱和蒸汽压

Forthepureliquid,volatilityrefersto

thesaturatedvapourpressureofsaturatedunderacertain

temperature

a

对混合液，挥发度为组分在蒸气中分压和与之平衡的液相中的摩尔分

率之比

Forthepureliquid,volatilityreferstotheratiobetween

Componentpartialpressureinthevapourandmole

fractionintheliquidphase

a

2.relativevolatility:溶液中易挥发组分的挥发度与难挥发组分的

挥发度之比，用a表示。Theratioofvolatility

betweenvolatilecomponentsandICSSVolatile

componentsinthesolution,

a

a

道尔顿分Dalton'sLawofPartialPressure

a

a

a

3

_______________________________________Gas

liquidequilibriumequation,

canbeusedtofindGas-liquidCompositiononceweare

givena

第二节蒸储方式

—、简单蒸储Simpledistillation

流程图如下flowchart:

a

混合液在蒸储釜中逐渐汽化，产生的蒸汽进入冷凝器，储出液进入

容器中。

Themixtureinthedistillationkettlegraduallyvaporized,

thegenerated

vaporenteringthecondenser,

thedistillateintothecontainer.

Afteradifferentialtimedt,Residual

liquiddecreasedbydW,Liquidphase

compositiondecreasedbydx,

对易挥发组分，出前后的微分进行物料衡算为:

tovolatilecomponents,carriedouta

materialbalance,

a

[W——某一瞬间釜内

的液量，Theamountofliquidinkettleata

moment,kmol]

a

a

将上式积分integrateit,

a

[Wl.W2——釜内的料液量和残液量Amol

Theamountofmaterial

liquidandresidualliquidinsidethekettle

xl、x2——料液和残液中易挥发组分组成

volatilecomponents

ofmaterialliquidandresidualliquid]

Foridealsolution

a

可由WLX1,加上W2X2之一，求W2X2,

accordingtoWi、Xi,addW2orX2,canfindX2orW2

fortotalmaterial:WD=WI-W2

forvolatilecomponents:WDXD=WIXI-W2X2

二、平衡蒸储Equilibriumdistillation

分离效果不好，只能作为原料的初步分离Separationeffectisnot

good,canonlybeusedaspreliminaryseparationofraw

materials

a

使混合液体部分气化，并使气液两相处于平衡状态，然后将气液

两相分开，分别从顶部和底部排出。

partgasifythemixedliquid,enablethe

gas-liquidintheequilibriumstate,

thenseparategas-liquidtwo-phase,they

aredischargedrespectivelyfromthetop

andbottomo

materialbalance:

fortotalmaterial:V+L=F

forvolatilecomponents:

VyD+Lxw=FxF

vy

XW=FX

D+(F-V)F

令液相分率supposeliquidfractionL/F=q,

sogasfractionV/F=l-q

a

—汽液相平衡组成的物料

衡算关系

materialbalance

relationshipofvaporliquidequilibrium

YD、XwcanbecomputedbymixedGasliquid

equilibriumequationandbalancedequations

第三节二元连续精微的分析和计算

（一）、精储原理principleofrectification

a

将原料液进入的那层板称为加料板，加料板以上称为精微段，作用是

使上升气流中易挥发组分的浓度逐板增加，从而在塔顶得到合格的易

挥发产品；

Theplatethatrawmaterialliquidenterintois

calledfeedboard,Thefeedboardaboveiscalled

therectifyingsection,theroleisincreaseingconcentration

ofvolatile['valntl]componentsintherisingairstepby

step,togetaqualifiedvolatileproductsat

thetopofthetower;

加料板以下称为提储段，作用是使下流液体中易

挥发组分逐板减少，从而在塔底得到合格的难挥

发产品

Thefeedboardbelowiscalledthe

strippingsection,theroleis

reduceingvolatilecomponentsin

defluentliquidstepbystep,togeta

qualifiedlessvolatileproductsin

bottomofthetower

（二）、计算

1、全塔物料衡算Overallmaterialbalance

a

fortotal

a

material:

a

forvolatilecomponents:_________________

【F-料液流率flowrateofMaterial

liquid,kmol/h；

D-塔顶产品流率flowrateoftop

product；

W-塔底产品流率....bttomproduct;

xF-易挥发组分的摩尔分数mole

fractionofvolatilecomponent]

一般是给出F、xFDW,求D,W

generallyF,xFDWwillbegiventofindD,W

（不讲！塔顶易挥发组分回收率recoveryrateofvolatile

componentsattoptower：

a

)

2、精微段操作线方程operatinglineequationofRectifying

section

a

(这个图不是很懂谈。。。。画的时候不写yl，直接上y(n+1)

fortotal

a

material:

forvolatile

3

components:

【V-离开的汽流量removedvapourflow；L-回流液

量theamountofrefluxliquid;

D-储出液量Distillateamount;

a

a

精福段操

作线方程

a

回流比refluxratio

3、提微段操作线方程

a

fortotal

a

material:

forvolatile

a

components:

[L'-becauseofinputatfeedborad,与L不同

a

提微段操作线方程

4、进料热状态feedthermalcondition

q-进料液相分率Feedliquidfraction

a

L'=L+qF

V'=V-(1-q)F

热量衡算heatbalance

FiF=(qF)iL+(1-q)Fiv

ip---进料的烙enthalpyoffeedstock

3

a

1）过冷液体subcooledliquid

a

q>i

2）对于泡点进料bubblepointfeed（饱和液体

saturatedliquid）

a

，q=i

3）汽液混合物进料liquid-vapormixture

a

q

a

4）对于饱和蒸汽进料saturatedvapor

a

q=0

5）过热蒸汽进料superheatedvapor

a

a

a

a

5、理论塔板层数的求法Theoreticalplate

layers【甩】

Stage-by-stagecalculation、graphic

method

1）操作线:

a

c)q线方程Qlineequation

a

a

第四节其它蒸储方式

甩甩甩

四、萃取extraction

（一）、基本概念concept

分离液体混合物的工业过程除蒸储外，应用较广的还有萃取。

Inadditiontothedistillation,extractioniswidelyused

toseparateliquidmixturesinindustrialprocess.

利用混合液中各组分在溶剂中溶解度的差异而实现分离的一

种单元操作。

it'saunitoperationbyusingthedifferenceof

solubilitybetweeneachcompositioninsolventstoachieve

separation.

a

SshouldhasabigdissolvingcapacitytoA,doesnotdissolve

B

使液相分成两层Maketheliquidphaseisdividedintotwo

layerSo

onelayerisE,includesAS

theotherisraffinate,B

（二）、组成在三角形相图上的表示方法triangularphase

diagram

A-溶质soluteB-original