Performance Evaluation of a Laboratory Scale Sieve Plate Distilling Column

Author : Hernandez, Mae Beth L.
Major Adviser : Alcanzare, Edilberto A.; Demafelis, Rex B.
Committee Members : Arquiza, Apollo C.; Manoto, Russel D.; Abrigo Jr., Casiano S. 
Year : 1994
Month : April
Type : Thesis
Degree: (select one) MS/BS/PhD
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The performance of the distilling column, containing 11 plates was tested to get the time required to attain steady state condition both at total reflux and during feeding. A feed of ethanol-water mixture with a composition of 8.17 mole percent ethanol was used. Total reflux was done for 7 hours, and feeding was done for 3 hours.

Steady state was not attained but was however approached during the run. Analysis of the liquid samples taken at the end of the total reflux from the eighth, ninth and tenth segments showed that their compositions are 69.65, 66.26, and 57.04 mole percent ethanol respectively.

Feeding started on the 7th hour and on the 10th hour the distillate formed was 73.35% by mole ethanol and the bottoms was 2.24% by mole ethanol. The reflux ratio was 3.13. Feeding was done on top of the ninth plate, and this was found out to be the correct feed plate as based on 73.35% by mole ethanol distillate recovery of the enriching section. A graphical solution using the McCabe-Thiele method showed that the equilibrium plates required for the separation is 4.5, thus the column has an overall efficiency of 40.91%.

To be able to improve the performance of the distilling column, there must be a constant vapor production in the reboiler and this will happen if the steam supplied is steady. The cooling water rate must be properly controlled. There should also be proper instrumentation for the equipment. In addition, because the liquid hold up in the reboiler is very large as compared to that contained in the column, the mixture that must be fed at total reflux must have a concentration lower than the actual feed.

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