大学课件-化工原理下册-萃取小结english.ppt

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1、LIQUID-LIQUID EXTRACTION （brief summary）,1 unit operation- to separate components in a liquid mixture,2 difference in solubility,3 solvent is added to change solubility,4 Steps Involved In Extraction,solute : A original solvent : B solvent : S,B ,S immiscible S, A (Extract) B, A (Raffinate) B ,S par

2、tially miscible S,A(B) (Extract) B,A(S) (Raffinate),Removal and recovery of solvent from each phase,Extract Extract liquid E y（A+（S、B）,Raffinate Raffinate liquid R x(B+（A、S）,after extraction process,supercritical-liquid as solvent (last decade) Liquid-like density Gas-like diffusivity exhibit enhanc

3、ed solvating Gas-like viscosity power,Non-toxic Environmentally acceptable,CO2 is very attractive alternative,A,B,R,E,M,M is addition point,S,E is difference point,the level law,right-angled isosceles triangular diagram,A,B,S,R0,E0,M,R1,E1,R2,E2,En,Rn,K,solubility curve,3) conjugate phases,1）solubil

4、ity curve,2）tie line,4) plait point,Auxiliary curve,distribution curve and distribution coefficient,abscissa：Solute concentration xA in Raffinate coordinate：Solute concentration yA in Extract,distribution coefficient,distribution coefficient for original solvent,Calculation of L-L Extraction,Number

5、of stages: N Efficiency: ,A,B,S,F,M,E,R,Single-stage Extraction with Partially Miscible Solvent,A,B,R,R,E,F,M,S,extract liquid and raffinate liquid,A,B,S,F,M,E,R,E,R,B,F,S,E1,R1,R2,E2,A,amount of solvent,yAmax,A,B,S,yAmax,E,R,F,M,yA,Multiple Contact,co-current flowsheet,counter-current flowsheet,co-

6、current flowsheet,A,B,S,F,M1,R1,E1,M2,R2,E2,M3,R3,E3,R3,counter-current flowsheet,1）mass balance,E1 、 RN not conjugate phases,Dummy flow D ：rightleft,A,F,M,RN,RN,E1,D,B,S,2）mass balance over every stage,3）graphic method,Equilibrium relation： Ei , Ri Operating relation： Ei+1 , Ri,A,F,M,RN,RN,E1,D,R1,

7、E2,F S RN E1 D,F S M RN E1 R1,E2, xn xN,N= n,E1 、D ,R1(in Equilibrium),D E2 (Operating relation),F,S,Rn ,S/F ， D , D= F- E1 D- left of triangular diagram ， Dummy flow D from left to right,(S/F) affect separating operation,(S/F) addition point M and difference point D N,S/F （S/F）min D= Dmin N ,S/F y1

8、 slope of operating line ,Dmin,F、DminE1,F,E1,RNE1, FS M,M,B,S completely immiscible mixture,S、 B are const over extraction process,Ratio of solute to solvent: X-kg(A) / kg (B) Y-kg(A) / kg (S),single-stage extraction,Y,X,0,Distribution curve,XF,Y0,C,slope（-mB/mS）,Operation ope.,D,X,Y,co-current flow

9、sheet,X,Y,0,XF,Y0,-mB/mS,X1,X2,X4,X3,Y1,Y2,Y3,Y4,counter-current flowsheet,(mS/mB) affect separating operation,(S/B) (S/B) min N ,suitable solvent for extraction,Selectivity,Selectivity coefficient,B,S completely immiscible, good for separation,Recovery of solvent,Physical properties,kA ， ，good for

10、separation, good separation ability, =1, extraction can not utilized to separate mixture,STAGE-WISE EQUIPMENT FOR EXTRACTION DIFFERENTIAL CONTACT EQUIPMENT FOR EXTRACTION 1.differential contactors-continuous variation on C stage-wise contactors-C 2. external work 3. tower / combined units,The Mixer-settler,Spray Column,Scheibel Column,Packing column,Baffle-plate columns,转盘萃取塔,搅拌填料塔,Centrifugal extractors,