化工原理下冊重點(中英文)

一、傳質(zhì)過程導(dǎo)論

ntroductionofmasstransferrocess

物質(zhì)在相際間的轉(zhuǎn)移屬于物質(zhì)傳質(zhì)過程

Substancetransferbetween

phasesbelongstothemasstransfer

process

這類單元操作在化工生產(chǎn)中應(yīng)用甚廣

Thiskindofunitoperationiswidely

usedinchemicalproduction

Inthispartwemainlylearn

（一）相組成的表示方法representingmethodof

phasecomposition

對于混合物，一個相的組成可以用多種方

法表示/

Forthemixture,aphasecomposition

canbeexpressedinavarietyofways,

1.質(zhì)量分數(shù)與摩爾分數(shù)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.質(zhì)量比與摩爾比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.氣體總壓與理想氣體中組分的分壓

Totalpressureandpartialpressureofcomponentinideal

gas:

a

MoleratioY-partialpressure:

a

massratio-partialpressure:

a

molarconcentrationCA-PA:

a

massconcentrationCA-PA:

a

（二）、擴散原理principleofdiffusion

1、Ficklaw:溫度、總壓一定，組分A在擴散方向上任一

點處的擴散通量與該處A的濃度梯度成正比。

Underacertaintemperature,total

pressure,diffusionfluxofcomponentA

onthedirectionofdiffusionis

proportionaltoconcentrationgradient

a

[dcA/dz-concentrationgradient;

DAB-DiffusioncoefficientofAinB,m2/s]

PS:1、負號表示方向相反minussignmeansJAandgradientare

intheoppositedirection

2、Ficklawdescribestherule

ofdiffusionrate

分子擴散兩種形式Moleculardiffusionintwo

forms:

二、吸收Absorption

（一）、吸收的基本理論Thebasictheoryof

absorption

L利用不同氣體組分在液體溶劑中的溶解度差異，對其進行選擇

性溶解，從而將氣體混合物進行組分分離的傳質(zhì)過程稱為吸收

UsetheSolubilitydifferenceofdifferentgas

componentsinliquidsolvents,

dissolvethecomponentselectivelyzThemass

transferprocessofgasmixtureseparation

iscalledtheabsorption

在工業(yè)上的應(yīng)用有：原料氣的凈化、某些

產(chǎn)品的制取、廢氣的治理等

theindustryapplicationispurificationof

feedgas,preparationofsomeproducts,

improvementofexhaustgas.

2、氣液相平衡gas-liquidequilibrium

在溶質(zhì)A與溶劑接觸、進行溶解度的過程中，隨著濃度cA

的逐漸增大，傳質(zhì)速率將逐漸減慢,最后降到零，cA達到一最大限

度cA*.這時稱氣液達到了相平衡，

intheprocessofAcontactingwithsolutesolubilityin

solvent,withtheincreasingofconcentration,themass

transferratewillgraduallyslowdown,finallyreducedtozero,

cAreachedamaximumcA*oThenitiscalled

gas-liquidphaseequilibrium.

亨利定律henry'slaw:

總壓不高時，在一定溫度下，稀溶液上方氣相中溶質(zhì)的平衡

分壓與溶質(zhì)在液相中的摩爾分率成正比。

Whenthetotalpressureisnothigh,atacertain

temperature,equilibriumpartialpressureofthe

solute\ntheqasphaseabovethedilute

solutionisproportionaltotheMole

Fractionofsoluteintheliquidphase.

a

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

C-液相總濃度theliquidphasetotal

concentration;

H-溶解度系數(shù)solubility

coefficient】

（二）、吸收傳質(zhì)速率masstransferrateofabsorption

①雙膜模型doublemembrancemodel

1）氣液兩相存在一個穩(wěn)定的相界面，界面兩側(cè)存在穩(wěn)定的氣膜和液

膜，膜內(nèi)為分子擴散

wesuppose,Thereisastablegas-liquidinterface,stablegas

filmandliquidexistonbothsidesoftheinterface,inthefilm

thereismoleculardiffusion

2)相界面處兩相達平衡Twophaseachievebalanceatphase

interface.

a

為吸收速率的計算提供了依據(jù)Providethebasisforthe

calculationofabsorptionrate

②相際傳質(zhì)速率方程masstransferingrateequation

1、Gasmembraneabsorptionrateequations:

NA=RG(pc-pi)

【I<G-氣膜吸收系數(shù)Gasmembraneabsorption

coefficient;]

當氣相的組成以摩爾分率表示時

Whenthegasphasecompositionusethemolefractionto

express:

a

[ky-表示以摩爾分數(shù)差為推動力的氣膜吸收系數(shù)

Gasmembraneabsorptioncoefficientthat

usedifferenceofmolefraction8Sdrivingforce]

2、liquidmembraneabsorptionrate

equations:

NA=RL(G-CL)

[ki-liquidmembraneabsorption

coefficient;]

當液相的組成以摩爾分率表示時

Whentheliquidphasecompositionusethe

molefractiontoexpress:

a

【kx-表示以摩爾分數(shù)差為推動力的液膜吸收系數(shù)

liquidmembraneabsorptioncoefficient

thatusedifferenceofmolefraction8Sdrivingforce]

3、總吸收系數(shù)及相應(yīng)的吸收速率方程式

①氣相總分壓差為推動力的傳質(zhì)速率方程

equationthatusedifferenceofgasphaseoverallpartial

pressureasdrivingforce.

NA=KG(pG-pL*)

【KG一氣相總傳質(zhì)系數(shù)Thegas

phaseoverallmasstransfercoefficient

PL*-與液相主體濃度成平衡的氣相分

壓,Pa

gasphasepartial

pressurethatisinbalance

withconcentration

ofliquidphase；

PG-gasphasepartial

pressure]

以摩爾分率表示時usethemolefractiontoexpress:

a

[Ky—以,為推動力的氣相總傳質(zhì)系數(shù)

gasphaseoverallmass

transfercoefficientthatuseAyasdriving

force

y*-與液相組成成平衡的氣相組

成，摩爾分數(shù)

Gascompositionthatisin

balancewithliquidcomposition,mole

fraction]

②以液相總濃度差為推動力的傳質(zhì)速率方程

equationthatusedifferenceofliquidphase

overallconcentrationasdrivingforce.

NA=KL(CG*-CL)

【CG*-與氣相分壓PG呈平衡的液相濃度，

liquidconcentrationthatisin

balancewithgasphasepartialpressure]

3

ps:總系數(shù)與分系數(shù)的關(guān)系Theoverallcoefficientandpartial

coefficient

a

a

Respectivelyaretotalresistanceandgasfilmresistanceand

liquidfilmresistance

a

3

氣膜控制：gasfilmcontrol:

溶解度很大時的易溶氣體，傳質(zhì)阻力主要集中在氣相。稱為氣膜控制

物系。

Asforthesolublegaswithlargesolubility,meansH（溶解度

系數(shù)

solubilitycoefficient)islarge,sothemasstransferresistance

ismainlyconcentratedinthegasphase.Knownasthegas

filmcontrolsystem.

a

a

a

a

（三）、吸收（或脫吸）塔的計算Thecalculationofabsorption

tower

1、物料衡算與操作線方程materialbalance、operatingline

equation

a

Ga、Gb——氣體組分（A+B）出塔、入塔的流率，kmol/

m2s

exit、enterflowrateofgas

component

La、Lb——液體組分（A+B）出塔、入塔的流率

G、L——通過塔此截面的氣、液流率，

Thegasandliquidflowrateof

acrosssectionofthetower

ya、yb——出塔、入塔氣體的摩爾分數(shù)，

exit、entermolefractionofgas

component

x、y——塔一截面處氣、液的摩爾分數(shù)

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)

(解釋：氣體溶質(zhì)被吸收，y、G不斷減小，以不變的量

作為基準,即惰性氣體B的流率和溶劑S的流率

Thegassoluteisabsorbed,y,G

decreasecontinuously,

useinvariantasthebenchmark,

theinertgasBflowrateGBandthe

solventSflowrateLs]

藍色的通常是已知的，如果再知道Ls、Xb

之一，就可求出另一個量

GB、Yb、Ya、Xaareusually

known,ifweknowoneofLSZ

Xbzandthenwecanfindanother

quantity.

為求得任意截面上的氣液組成關(guān)系，可以對塔頂

與此截面間作物料衡算，

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

平衡線

ABisLS/GB,OE-lineofbalanceo

AnypiontPontheoperatingline,

PQ-以氣相摩爾比之差表示的推動力driving

forceexpressedbydifferenceofgasphase

moleratio(Y-Y*),PR-driving

forceexpressedbydifferenceofliquid

phasemoleratio(X*-X).

whenLsdecreases

,slopedecreasesaswellz

LimitoperationisBmeetingOEatC,soC

-drivingforceis0zandmasstransferrateis

also0.

liquid-gasratiointhissituationis

calledminimumliquidgasratio,

a

應(yīng)用啥的：關(guān)于溶劑的用量，希望流率要小來

降低消耗，但限于溶解度，不能太小，所以實際

采用液氣比常在最小值的L1至2倍內(nèi)選.

Abouttheamountofsolvent,wewantflow

ratecanbesmallertoreducethe

consumption,butduetothelimited

solubility,itcannotbetoosmall,sothe

liquidgasratioisalwayschoosed1.1to2

timesoftheminimumvalue

(四)、填料層高度的計算heightoffillinglayer

它應(yīng)保證其中有效氣液接觸面積能滿足傳質(zhì)的需求

Itshouldensuretheeffectivegas-liquidcontact

areacanmeetthedemandofmasstransfer

A=aV=a(nD2/4)h

L對數(shù)平均推動力法logarithmicaveragedriving

force

a

【Kya-氣相總體積吸收系數(shù)gasphase

overallvolumeabsorptioncoefficient;

A

①findym：

a

△ya=ya-mxaallwillbe

giveno

2、吸收因數(shù)法AbsorptionNumberMethod

①液氣比liquid-gasratio:

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

②吸收因素absorptionfactorA:

A=L/mG

S。脫吸因素Desorptionfactor:

S=l/A

③吸U攵要求Absorptionrequirements:

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

(4)useS、?lookatgraph,getNOG

h=NOG*HOG

傳質(zhì)單元TransferUnit

氣相總傳質(zhì)單元數(shù)gasphaseoverall

transferunit:NOG

為了便于分析，把整個填料層分為若干段,

Inordertofacilitatetheanalysis,thefiller

layerisdividedintoseveralsegments,

傳質(zhì)單元高度heightoftransferunitHOG：

a

同理還有液相總傳質(zhì)單元數(shù)Similarly,NOLHOL

（五）、塔板數(shù)platenumber

板式塔和填料塔的區(qū)別在于，氣液兩相

的接觸是在塔板上進行的，故組成沿塔高呈階躍

式變化而不是連續(xù)式變化。所以得求塔板數(shù)。

thedifferencebetweenplate

columnandpackedcolumnisthatthe

gas-liquidcontactisoncolumnplate,so

thecompositionalongthetowerhigh

issteptypechangeinsteadofcontinuous

change.Soweshouldfindplatenumber.

a

a

N-理論板數(shù)numberoftheoreticalplates

總板效率overallplateefficiencyEO:

E0=N/Ne

Ne-實際板數(shù)actualnumberplate

三、蒸儲distillation

利用混合物在一定壓力下各組分相對揮發(fā)度(沸點)的不同進

行分離的一種單元操作。Usethedifferenceofrelative

volatility(BP)

betweencomponentsofmixtureundercertain

pressure,toseparatemixedliquids0

第一節(jié)二元物系的汽液相平衡

顯然，氣液兩相呈平衡時的組成差別越大，越有利于蒸播

分離。因此這里需研究相平衡關(guān)系。

Obviously,themorebiggerthedifference

ofcompositionofagas-liquid(whichisin

equilibrium)is,theeasierthedistillationis.Soheretostudy

phaseequilibrium.

(一)、理想溶液idealsolution

若溶液中的各個組分在全部濃度范圍內(nèi)都服從拉烏爾定

律，稱為理想溶液。

ifeachcomponentinthesolutioninthe

wholeconcentrationrangeobeysRaoul's

law,knownastheidealsolution

a

3

a

-純液體的蒸氣壓Thepure

liquidvaporpressure

x-易揮發(fā)組分A的摩爾分數(shù)The

molarfractionofvolatilecomponents

a

a

so,液相組成liquidcomposition:

a

泡點方程bubble-point

equation0

a

（解釋：

Dependsonthetemperaturesolutionbegantoboil)

means一定總壓下液相組成與泡點的關(guān)系

Underacertaintotalpressure

relationshipbetweenliquidphasecomposition

andthebubblepoint。

a

露點方程

Dew-pointequationo

means一定總壓下氣相組成與開始冷凝時的溫度的關(guān)

系

Underacertaintotalpressurethe

relationshipbetweengasphasecompositionand

temperaturegasbegantocondensate

氣液相平衡圖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）揮發(fā)度和相對揮發(fā)度Volatilityand

relativevolatility

1、Volatility:對純液體，揮發(fā)度指該液體在

定溫度下的飽和蒸汽壓

Forthepureliquid,volatilityrefersto

thesaturatedvapourpressureofsaturatedunderacertain

temperature

a

對混合液，揮發(fā)度為組分在蒸氣中分壓和與之平衡的液相中的摩爾分

率之比

Forthepureliquid,volatilityreferstotheratiobetween

Componentpartialpressureinthevapourandmole

fractionintheliquidphase

a

2.relativevolatility:溶液中易揮發(fā)組分的揮發(fā)度與難揮發(fā)組分的

揮發(fā)度之比，用a表示。Theratioofvolatility

betweenvolatilecomponentsandICSSVolatile

componentsinthesolution,

a

a

道爾頓分Dalton'sLawofPartialPressure

a

a

a

3

_______________________________________Gas

liquidequilibriumequation,

canbeusedtofindGas-liquidCompositiononceweare

givena

第二節(jié)蒸儲方式

—、簡單蒸儲Simpledistillation

流程圖如下flowchart:

a

混合液在蒸儲釜中逐漸汽化，產(chǎn)生的蒸汽進入冷凝器，儲出液進入

容器中。

Themixtureinthedistillationkettlegraduallyvaporized,

thegenerated

vaporenteringthecondenser,

thedistillateintothecontainer.

Afteradifferentialtimedt,Residual

liquiddecreasedbydW,Liquidphase

compositiondecreasedbydx,

對易揮發(fā)組分，出前后的微分進行物料衡算為:

tovolatilecomponents,carriedouta

materialbalance,

a

[W——某一瞬間釜內(nèi)

的液量，Theamountofliquidinkettleata

moment,kmol]

a

a

將上式積分integrateit,

a

[Wl.W2——釜內(nèi)的料液量和殘液量Amol

Theamountofmaterial

liquidandresidualliquidinsidethekettle

xl、x2——料液和殘液中易揮發(fā)組分組成

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、平衡蒸儲Equilibriumdistillation

分離效果不好，只能作為原料的初步分離Separationeffectisnot

good,canonlybeusedaspreliminaryseparationofraw

materials

a

使混合液體部分氣化，并使氣液兩相處于平衡狀態(tài)，然后將氣液

兩相分開，分別從頂部和底部排出。

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

—汽液相平衡組成的物料

衡算關(guān)系

materialbalance

relationshipofvaporliquidequilibrium

YD、XwcanbecomputedbymixedGasliquid

equilibriumequationandbalancedequations

第三節(jié)二元連續(xù)精微的分析和計算

（一）、精儲原理principleofrectification

a

將原料液進入的那層板稱為加料板，加料板以上稱為精微段，作用是

使上升氣流中易揮發(fā)組分的濃度逐板增加，從而在塔頂?shù)玫胶细竦囊?/p>

揮發(fā)產(chǎn)品；

Theplatethatrawmaterialliquidenterintois

calledfeedboard,Thefeedboardaboveiscalled

therectifyingsection,theroleisincreaseingconcentration

ofvolatile['valntl]componentsintherisingairstepby

step,togetaqualifiedvolatileproductsat

thetopofthetower;

加料板以下稱為提儲段，作用是使下流液體中易

揮發(fā)組分逐板減少，從而在塔底得到合格的難揮

發(fā)產(chǎn)品

Thefeedboardbelowiscalledthe

strippingsection,theroleis

reduceingvolatilecomponentsin

defluentliquidstepbystep,togeta

qualifiedlessvolatileproductsin

bottomofthetower

（二）、計算

1、全塔物料衡算Overallmaterialbalance

a

fortotal

a

material:

a

forvolatilecomponents:_________________

【F-料液流率flowrateofMaterial

liquid,kmol/h；

D-塔頂產(chǎn)品流率flowrateoftop

product；

W-塔底產(chǎn)品流率....bttomproduct;

xF-易揮發(fā)組分的摩爾分數(shù)mole

fractionofvolatilecomponent]

一般是給出F、xFDW,求D,W

generallyF,xFDWwillbegiventofindD,W

（不講！塔頂易揮發(fā)組分回收率recoveryrateofvolatile

componentsattoptower：

a

)

2、精微段操作線方程operatinglineequationofRectifying

section

a

(這個圖不是很懂談。。。。畫的時候不寫yl，直接上y(n+1)

fortotal

a

material:

forvolatile

3

components:

【V-離開的汽流量removedvapourflow；L-回流液

量theamountofrefluxliquid;

D-儲出液量Distillateamount;

a

a

精福段操

作線方程

a

回流比refluxratio

3、提微段操作線方程

a

fortotal

a

material:

forvolatile

a

components:

[L'-becauseofinputatfeedborad,與L不同

a

提微段操作線方程

4、進料熱狀態(tài)feedthermalcondition

q-進料液相分率Feedliquidfraction

a

L'=L+qF

V'=V-(1-q)F

熱量衡算heatbalance

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

ip---進料的烙enthalpyoffeedstock

3

a

1）過冷液體subcooledliquid

a

q>i

2）對于泡點進料bubblepointfeed（飽和液體

saturatedliquid）

a

，q=i

3）汽液混合物進料liquid-vapormixture

a

q

a

4）對于飽和蒸汽進料saturatedvapor

a

q=0

5）過熱蒸汽進料superheatedvapor

a

a

a

a

5、理論塔板層數(shù)的求法Theoreticalplate

layers【甩】

Stage-by-stagecalculation、graphic

method

1）操作線:

a

c)q線方程Qlineequation

a

a

第四節(jié)其它蒸儲方式

甩甩甩

四、萃取extraction

（一）、基本概念concept

分離液體混合物的工業(yè)過程除蒸儲外，應(yīng)用較廣的還有萃取。

Inadditiontothedistillation,extractioniswidelyused

toseparateliquidmixturesinindustrialprocess.

利用混合液中各組分在溶劑中溶解度的差異而實現(xiàn)分離的一

種單元操作。

it'saunitoperationbyusingthedifferenceof

solubilitybetweeneachcompositioninsolventstoachieve

separation.

a

SshouldhasabigdissolvingcapacitytoA,doesnotdissolve

B

使液相分成兩層Maketheliquidphaseisdividedintotwo

layerSo

onelayerisE,includesAS

theotherisraffinate,B

（二）、組成在三角形相圖上的表示方法triangularphase

diagram

A-溶質(zhì)soluteB-original