Question

A Bean company carried out process to extract oil from fresh soybean containing 21 wt% soy oil. The extraction is using pure hexane, targeted to remove 90 % of the oil in a countercurrent multistages leaching process. The company prepare 1000 kg fresh soybean per hour and the final exit overflow solution is to contain 65 wt% soy oil. The slurry underflow is assumed N = -0.5 yA + 2. a) Calculate LO, LN, V1 and VN+1. b) Determine the total number of theoretical stages

Answer 1

Hexane V(N+1) y(N+1) = V1= y1= 0 wt% 65 wt% N-1 LN= xN= LO (Soyabene) = x0= 1000 kg/h 21 wt% Feed rate fresh Soyabene LO= Soya oil contained in feed x0= Hence total Soya oil in feed (L0* X0Y/100= 1000 kg/h 21 wt% 210 kg/h Target removal of Soya oil from feed= Hence total recovered Soya oil in overflow (210 * 90/100)= In overflow V1 * y1= Given y1= Hence V1=(189*100/65)= 90 % 189 kg/h 189 kg/h 65 wt% 291 kg/h So Hence flow rate of V1= 291 kg/h Fresh hexane flow rate (V(N+1))= V1-V1*y1 V(N+1)= 102 kg/h Fresh feed Lo= 1000 kg/h LN=LO + V(N+1)-V1 Overall mass balance LN= xN= 811 kg/h 2.59 wt% Slurry under flow is assumed as N = -0.5*yA +2 A =(y(N+1)-1)/(y*(N+1)-y*1) y*(N+1) = xN= y*1=x0= value of factor A= 2.59 wt% 21 wt% -3.53 y = y1= 65 wt% Hence total nos of theoretical stages will be N= 3.15 4 approx