Distillation Efficiency for Removal of Solved Minute Water in a Light Hydrocarbon

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The purpose of this investigation is to make clear the reason why it is said that the efficiency of dehydrating distillation in light hydrocarbon-water system is extremely low. The research results obtained so far are as follows.1. Investigation to past works The head investigator examined relevant literatures and reanalyzed the experimental data in them under taking into account uncertainty of vapor-liquid equilibrium (VLE) relation as well as heat balance, then pointed out the distillation efficiency depends largely upon the estimated value of the VLE relation.2. Measuremen of the VLF relation and examination to the result We examined into experimental apparatus to obtain the VLF data where the condensate of vapor forms two liquid phases, and using a means of providing a liquid decanter within a return pipe of the condensate, measured the VLE relation for three systems of benzene-water, hexane-water, and toluene-water over a wide range in concentration. The values of VLE ratio came u … More p to 2-5 times the data of Lino et. al. Which had been obtained in a range of low water concentration, but agreed fairly well with the values estimated by means of a modified UNIFAC equation.3. Distillation experiment with a packed column and examination to the result Using the Sulzer packing known as a "high efficiency" packing, we conducted a distillation experiment for the three kinds of systems described above. The HETP values obtained were, in contrast to 2-4cm for the heptane-toluene system. 30-40cm for the three hydrocarbon-water systems. This means a remarkable drop in distillation efficiency. Thus we suspected existence of some additional resistance for mass transfer in the change-of-state process between gas and liquid phases and schemed the next experiment with the intention of making use of active agents which can be expected to present catalytic action.4. Distillation experiment with a single stage column and examination to the result At first we conducted a distillation experiment without setting any active agent. Then, in a range of relatively high water concentration, the values of tray efficiency reached as high as those for heptane-toluene system (about 70%) but in a low water concentration range the efficiency became extremely low. This is the calculated result based on the VLE data obtained in item 2 above, and if the VLE ratios in a range of low water concentration diminish abruptly, it can not be said that this efficiency drop is to occur. Hence we consider that, in order to clarify this questionable respect prior to the aforementioned supposition of additional mass transfer resistance, it is necessary to conduct careful measurement of the VLE relations in a range of low water concentration. Less