Subtopic: Concentration and drying of liquid foods – evaporators, tray, drum and spray dryers
Question Statement:
A double-effect forward-feed evaporator concentrates $9000\text{ kg/h}$ of fruit juice from $10\%$ total solids to $45\%$ total solids. If the overall steam economy of the double-effect evaporator system is $1.60\text{ kg water evaporated/kg steam fed}$, the required steam consumption in $\text{kg/h}$ is ________ (answer in integer).
Answer Key:
4375
Step-by-Step Solution & Explanation
1. Solid balance across evaporator system:
$F \times x_F = P \times x_P$
$9000 \times 0.10 = P \times 0.45 \implies 900 = 0.45 P \implies P = 2000\text{ kg/h}$
2. Total water evaporated $W$:
$W = F - P = 9000 - 2000 = 7000\text{ kg/h}$
3. Steam consumption $S$ with steam economy $SE = 1.60$:
$SE = \frac{W}{S} \implies S = \frac{W}{SE} = \frac{7000}{1.60} = 4375\text{ kg/h}$