Free counters!

Saturday, September 21, 2013

Stoichiometry Problem - Material Balance, 12

Category: Chemical Engineering Math, Algebra

"Published in Suisun City, California, USA"

Soya bean seeds are extracted with hexane in batch extractors. The flaked seeds are found to contain 18.6% oil, 69% solids, and 12.4% moisture by weight. At the end of the extraction process, cake (meal) is separated from hexane-oil mixture. The cake is analyzed to contain 0.8% oil, 87.7% solids, and 11.5% moisture by weight. Find the percentage recovery of oil. 

Solution:

The given word problem is about extraction of soya bean with hexane to collect soya bean oil 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 given problem, it is better to draw the flow diagram as follows

Photo by Math Principles in Everyday Life

Basis: 100 kg of Flaked Seeds

Let x = be the amount of Hexane
      y = be the amount of Cake
      z = be the amount of Hexane-Oil

Overall Material Balance of Batch Extractors:


Material Balance of Solids:




The amount of oil in cake is calculated as follows




If we know the amount of oil in flaked seeds and cake, then we can calculate the amount of oil recovered or extracted as follows






Therefore,