A stream of 220kmol/h of a binary mixture containing benzene and toluene (45 mol% benzene) needs to be distilled to provide its components in high purity. A column of dishes with reflux (fractional distillation) will be used for the service. It is desired to obtain 97.5% pure benzene as the top product and 98% toluene in the bottom product (data on a molar basis). Benzene and toluene form an ideal liquid solution, the column will be operated at about 1atm, with relative volatility corresponds to 2.5. A reflux ratio of 3.5mol for each mole of distillate (3.5:1) will be used. The latent heats of benzene and toluene at the specified pressure are 7.38 and 7.96 cal/mol, respectively. a – Justify why, in this case, we can use the assumption of constant molar flow rate for each region of the column (enrichment and depletion) separately. b – What is the expected distillate and bottom product production? c – Is it possible to obtain high purity toluene as a top product and benzene as a bottom product? Justify. d – Calculate the number of equilibrium stages necessary for the operation of the column, considering that the feeding is made with liquid at the bubble point (saturated liquid). With graphics .
A stream of 220kmol/h of a binary mixture containing benzene and toluene (45 mol% benzene) needs to be distilled to provide its components in high purity. A column of dishes with reflux (fractional distillation) will be used for the
service. It is desired to obtain 97.5% pure benzene as the top product and 98% toluene in the bottom product (data on a molar basis). Benzene and toluene form an ideal liquid solution, the column will be operated at about 1atm, with relative volatility
corresponds to 2.5. A reflux ratio of 3.5mol for each mole of distillate (3.5:1) will be used. The latent heats of benzene and toluene at the specified pressure are 7.38 and 7.96 cal/mol, respectively.
a – Justify why, in this case, we can use the assumption of constant molar flow rate for each region of the column (enrichment and depletion) separately.
b – What is the expected distillate and bottom product production?
c – Is it possible to obtain high purity toluene as a top product and benzene as a bottom product? Justify.
d – Calculate the number of equilibrium stages necessary for the operation of the column, considering that the feeding is made with liquid at the bubble point (saturated liquid). With graphics .
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