Question

Sugar solution needs to be concentrated to 55 wt.% in order to produce sugar crystal. Double effect evaporator with reverse feed configuration was used for this purpose. 5000 kg/h of 15 wt% sugar feed solution enters the second evaporator at 30°C. The absolute pressure in the second evaporator is 12.35 kPa. Saturated steam at 313 kPa enters the first evaporator and the vapor from this evaporator is used to heat the second evaporator. The overall coefficients are U1 = 2500 and U2 = 1800 W/m2 .K. The heating areas for both evaporators are equal. The boiling point rise of the solutions can be estimated from BPR (°C) = 1.78 X + 6.22 X2 . The heat capacity of the liquid solution is cp (kJ/kg.K) = 4.19 -2.35 X (where X is the weight %.). Calculate the steam consumption in kg/hr and evaporator area. (Note: The difference between the assumed and calculated values less than 15% is acceptable).

Answer 1