化學反應工程原理課件 1-1

1緒論化工生產(chǎn)過程

用化學方法將原料加工成產(chǎn)品的生產(chǎn)過程。pretreatmentphysicaltreatmentsteps

separationphysicaltreatmentstepsrawmaterialsrecycleproductschemicaltreatmentsteps化學工程：

工程技術的一個分支，探討化工生產(chǎn)過程的規(guī)律性，并根據(jù)對其規(guī)律性的認識來解決化工生產(chǎn)中的問題。pretreatmentphysicaltreatmentsteps

separationphysicaltreatmentstepsrawmaterialsrecycleproductschemicaltreatmentsteps1.1ChemicalReactionEngineeringconcernedwiththeexploitationofchemicalreactionsonanindustrialscale.engineeringaspectofchemicalreactionindustrialreactorsTheresearchesonchemicalprocesses:

before1920s

forproductionofspecificproducts

1920s

unitoperations

1960

transportphenomena

1957

reactionengineering

engineeringscience1.1.1研究對象

對于化學變化的研究，有：尺度基礎研究對象量子量子力學分子間化學變化的微觀規(guī)律分子動力學或化學動態(tài)學分子經(jīng)典力學眾多分子間化學變化的宏觀規(guī)律微團或設備化學動力學傳遞理論工業(yè)反應器中的化學變化規(guī)律化學動力學化學反應工程－工業(yè)反應過程1.1.2Objectives(1)

developmentofreactiontechnology(2)

optimizationofoperatingcondition(3)design,scale-up,andanalysisofreactor,

predictionofreactorperformance1.1.3Context

Kineticsmechanismandrateofreaction

Foracertainreactionsystem,therateofreactionisusuallyexpressedas

r=f(c,T,p)Modeloftransportphenomena

v,p,c,T=f(x,y,z,t)

effectoftransportprocessesontherateofreaction

optimizedoperationcondition,

themostappropriatetypeandstructureofreactor（三傳一反）（反應器設計與分析）Oxidationofammoniaonacatalyst:

Chemicalandphysicalprocessesoccursimultaneously.NH3O2NOH2OQ4NH3+5O2

4NO+6H2OHr

reactionheatandmasstransfermomentum,1.1.4Methodmathematicalmodeling

resolutionofproblemchemicalreactionphysicalprocessesreactionkineticsmodeloftransportcombinationMathematicalmodeling:過程實驗與觀察過程的分析研究計算機模擬物理模型數(shù)學模型用于反應器設計、放大與分析與實驗結果比較否模型參數(shù)(實驗)合理簡化是理論、實驗和計算的結合1.2ConversionandYieldofReaction1.2.1Extentofreaction

Areactionis

AA+BB

RR(1.1)whereisthestoichiometriccoefficient,

for

reactant(A,B),isnegative;

for

product(R),ispositive.

initialmoles:nA0,nB0,nR0

attheendofreaction:nA

,nB

,nR

Theratio

Foranycomponenti,

ni

ni

0=i

(1.3)IfcomponentiinvolvesinMreactions,isapositiveconstant,=

(1.2)theextentofreaction.(1.4)1.2.2ConversionInitialcondition:continuousatthe

inletofthereactorbatch

atthebeginningofthereactionItisthefractionofareactantconverted,amountofreactantconverted

initial

amountofthereactantX=(1.5)Conversion:Calculationsareusuallybasedontheconversionofkeycomponent,e.g.,Aisusuallythemostexpensivereactant,soitsamountinthemixtureislimited.thevalueofXreflectstheeconomy;themaximumvalueofXis100%.amountofreactantconverted

initial

amountofthereactantX=(1.5)TherelationbetweenconversionXand

is

(1.6)1.2.3Yieldandselectivity

TheyieldisdefinedforreactionproductR,whereAisusuallythekeycomponent.amountofRformed

initialamountofA

(1.7)orYR=

molesofAconsumedforR

molesofAfedtothesystem(1.8)Formultiplereactions,theselectivityisoftenused,definedas(1.11)TherelationbetweenconversionX,yieldY,andselectivitySis

Y=SX(1.12)S=molesofAconsumedfordesiredproduct

molesofAconvertedExample1.2

inlet

outlet

C2H41515x

y/2O277x/23y/2

C2H4O0xCO21010+yH2O0

y

Ar

1212

N2

56

56.

total100100x/2Theequationsforconcentrationsattheexit:

ethyleneoxygenx,y

separationrawmaterialsproductsreactorrecycleConversion:單程轉化率separationrawmaterialsproductsreactorrecycle全程轉化率amountofreactantconverted

initial

amountofthereactantX=(1.5)Exercises:Chap.1:1,21.3ClassificationofReactionsandReactors1.3.1Classificationofreactions

homogeneoussystems:

gas,liquidheterogeneoussystems:

gas-solid,gas-liquid,liquid-liquid,liquid-solid,gas-liquid-solid

1.3.2TypesofreactorsAccordingtotheconstructionofreactors,wehave(1)tubularreactor

(2)stirredtankreactor(3)towerreactorGLGLGLGLplatetowerpackedtowerbubblecolumnspraytower(4)fixedbedreactorpackedtubularreactor(5)fluidizedbedreactor

G(L)G(6)movingbedreactorSG(7)tricklebedreactorL

G1.4ModeofOperation1.Batchoperation

nomaterialentersorleavesthereactorduringreaction.

Feature:

closing

usuallyconstant-volume

unsteady-state

cRcAtcA00Itisusuallyinastirredtankreactorforslowreactionandsmallamountofoutput.reactionA

R:2.Continuousoperationreactantsenterandproductsleavethereactorcontinuously.

Feature:

open

steady-state

usuallyconstantpressureLz0cALcRLcRcAcA0e.g.,reactionA

Rinatubularreactor:3.Semi-batchoperation

Atleastoneofthereactantsorproductsisfedinortakenoutcontinuously,andothersarechargedordischargedinbatchmode,whichmaybeusedtotreatagaswithaliquid,tocontrolahighlyexothermicreaction,toimproveproductyield.1.5DesignandScale-upofReactorsObjectives:selectthetypeofreactordeterminetheoptimumoperatingconditiondeterminethesizeofreactor1.5.1Generalprocedureforreactordesign

Generalrequirements:

inchemistry:sufficientreactiontime

inmasstransfer:

inheattransfer:

insafety:Generalprocedure:(1)forallreactions,collectthedataonkineticsandthermodynamicsundertheoperatingcondition;(2)collectthephysicalpropertiesneeded;(3)determinetheratecontrollingprocessandselectthetypeofreactor;(4)determinetheoperatingcondition;(5)calculatethesizeofreactor;(6)selectappropriateconstructionmaterial;(7)carryoutinitialmechanicaldesign;(8)evaluatethecapitalandoperationcostsofvariousdesignsandassesstheeconomicoptimumdesign.1.5.2BasicequationsforreactordesignreactorsizeV

rateofreactionrA(c,T,p)

c,T,p=f(x,y,z,t)Basicequations:(1)materialbalanceforanycomponent

ci

(x,y,z,t)(2)energybalance

T(x,y,z,t)(