A single effect evaporator is fed with 10000 kg / h of weak liquor containing 15 % caustic by weight and is concentrated to get thick liquor containing 40 % by weight caustic. Calculate: (i) kg / h of water evaporated and (ii) kg / h of thick liquor

A single effect evaporator is fed with 10000 kg / h of weak liquor containing 15 % caustic by weight and is concentrated to get thick liquor containing 40 % by weight caustic. Calculate: (i) kg / h of water evaporated and (ii) kg / h of thick liquor Correct Answer 6250 kg/h, 3750 kg/h

10000 kg / h of weak liquor. Let x be the kg / h thick liquor obtained and y be the kg / h water evaporated. Overall Material balance: Total mass Input = Total mass output kg / h weak liquor = kg / h water evaporated + kg / h thick liquor 10000 = x + y Material Balance of NaOH: NaOH in the liquid stream = NaOH in output stream NaOH in the weak liquor = NaOH in thick liquor 0.15 × 10000 = 0.40x x = 3750 kg/hr Hence, y= 6250 kg/hr Water evaporated = 6250 kg/h Thick liquor obtained = 3750 kg/h