De invloed van de samenstelling van binaire mengsels op het schotelrendement in rectificatiekolommen

The effect of composition on plate efficiencies for binary mixtures of ethanol and water, n-heptane and methylcyclohexane, and methylcyclohexane and toluene was studied experimentally in an adiabatic distillation column of 3.8 cm internal diameter containing 9 sieve plates. Accurate data concerning the vapour-liquid equilibrium curves were required for the calculation of Murphree plate and point efficiencies. This led to the use of the test for internal consistency of vapour-liquid equilibrium data as introduced by Harington, which was extended to P constant, T variable and corrected for differences from an ideal gas of the vapour phase. An exact graphic method to evaluate the vapour-liquid equilibrium from boiling point composition data of binary mixtures was derived.

The observed point efficiencies on overall gas basis seemed to vary markedly with composition in low and high concentrations. It was demonstrated that these variations could not be attributed to lack of precision in the equiibrium data, interference with the column operation by sampling, variation in physical properties with composition, or a variation in stripping or rectifying factor mV/L with concentration.

The point efficiencies at total reflux seemed to be a function of the corresponding driving forces for mass transfer in the gas phase.