Transcription of CHE 31. INTRODUCTION TO CHEMICAL ENGINEERING …
1 CHE 31. INTRODUCTION TO CHEMICAL ENGINEERING CALCULATIONSL ecture 12 recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os LECTURE 12. recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE2 recycle StreamRecycle stream is a term denoting a process stream that returns material from downstream of a process unit back to the process 12. recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE3 Bypass StreamBypass stream is a stream that skips one or more stages of the process and goes directly to another downstream 12.
2 recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE4 purge StreamPurge stream is a stream bled off to remove an accumulation of inertsor unwanted material that might otherwise build up in the recycle 12. recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE5 Example 12-1. Distillation of Benzene and TolueneA distillation column separates 10,000 kg/hr of a mixture containing equal mass of benzene and toluene. The product D recovered from the condenser at the top of the column contains 95% benzene, and the bottom W from the column contains 96% vapor V entering the condenser from the top of the column is 8000 kg/hr.
3 A portion of the product from the condenser is returned to the column as reflux R, and the rest is withdrawn as the final product D. Assume that V, R, and D are identical in composition since V is condensed the ratio of the amount refluxed R to the product withdrawn 12. recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE6 Example 12-1. Distillation of Benzene and TolueneLECTURE 12. recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE7 Example 12-1. Distillation of Benzene and TolueneOverall ProcessTotal Balance:10,000 = D + WBenzene Balance:10,000( ) = D( ) + W( )Solving simultaneously, D = 5050 kg/hr ; W = 4950 kg/hrTotal balance around the separator:8000 = R + DR = 2950 kg/hrRatio (R/D) = (2950/5050) = 12.
4 recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE8 Example 12-2. Conversion of Sucrose to Glucose and FructoseRefined sugar (sucrose) can be converted to glucose and fructose by the inversion processC12H22O11+ H2O =======>C6H12O6(G) + C6H12O6(F)The combined glucose and fructose is called inversion sugar. If 90% conversion of sucrose occurs on one pass through the reactor, what would be the recycle stream flow per 100 lbm fresh feed of sucrose? What is the concentration of inversion sugar in the recycle and product streams? Assume that the two streams are identical in composition.
5 Refer to the flowchart for the other details of the 12. recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE9 Example 12-2. Conversion of Sucrose to Glucose and FructoseLECTURE 12. recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE10 Overall and Single Pass Conversion PROCESSREACTORI nput-Output100 - 0 Overall Conv. of A == 100 = 100%Input100 Input-Output100 - 25 Single Pass Conv. of A == 100 = 75%Input100 LECTURE 12. recycle , Bypass, & purge CalculationsProf.
6 Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE11 Example 12-2. Conversion of Sucrose to Glucose and FructoseSolution:Basis: 100 lbm of fresh feedOverall Process1. Total Balance:P = 100 lbmMixing Point2. Total Balance:100 + R = T3. Sucrose Balance:100( ) + R(xS)R= T(xS)T4. Inv. Sugar Balance:(0) + R(xI)R= T( )LECTURE 12. recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE12 Example 12-2. Conversion of Sucrose to Glucose and FructoseReactor + Separator5. Sucrose Balance:T(xS)T T(xS)T( ) = (R + 100)(xS)RCalculate for the pound of water consumed per pound of sucrose consumed: 1 mol W1 mol S18 lbm Wlbm W = 1 mol lbm S1 mol Wlbm S6.
7 H2O Balance:T(xW)T T(xS)T( )( ) = (R + 100)(xW)R7. xR:(xS)R+ (xI)R+ (xW)R= xT:(xS)T+ + (xW)T= 12. recycle , Bypass, & purge CalculationsProf. Manolito E Bambase Jr. Department of CHEMICAL ENGINEERING . University of the Philippines Los Ba os SLIDE13 Example 12-2. Conversion of Sucrose to Glucose and FructoseSolving equations 2-8 simultaneously:R = lbmT = lbm(xW)T= (xS)T= (xW)R= (xS)R= (xI)R=
