"Published in Suisun City, California, USA"
A single effect evaporator is fed with 10,000 kg/hr of weak liquor containing 15% caustic by weight and is concentrated to get thick liquor containing 40% by weight caustic. Calculate (a) kg/hr of water evaporated, and (b) kg/hr of thick liquor obtained.
Solution:
The given word problem is about the evaporation of caustic liquid from weak liquor to thick liquor which involves the principles of Stoichiometry. The total amount of a substance in the reactants or incoming ingredients must be equal to the total amount of a substance in the final products. In short, the Law of Conservation of Mass must be followed all the time. To illustrate the problem, it is better to draw the flow diagram as follows
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| Photo by Math Principles in Everyday Life |
Basis: 10,000 kg/hr of weak liquor
Let x = be the amount of thick liquor
y = be the amount of water evaporated
Overall Material Balance of Evaporator:
Material Balance of NaOH:
Substitute the value of x to the first equation, we have
Therefore,
Amount of Thick Liquor = 3,750 kg/hr
Amount of Water Evaporated = 6,250 kg/hr