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

这项工作的目的是澄清为什么说烃-水系统的脱水蒸馏效率极低的原因。到目前为止所取得的研究成果总结如下。1.单塔板精馏实验对苯-水、甲苯-水和正己烷-水三种体系的脱水精馏实验表明，在较高的水浓度范围内，塔板效率可达到与庚烷-甲苯体系相同的水平(约70%)，但在较低的水浓度范围内，塔板效率随水浓度的降低而降低。2.五盘塔精馏实验在本实验中，我们通过测量每一级的水浓度，考察了五盘塔内的浓度分布。结果表明，从塔顶算起第三、四级以下的水浓度不变，存在脱水极限。塔板效率…在上述第1项中，更多的是基于在相对较高的水浓度范围内获得的汽液平衡(VLE)关系的计算结果，其中VLE比率被假定为恒定。考虑到上述结果，认为效率下降的原因很大程度上可能是由于尚未测量到的低含水率范围内的汽液平衡关系所致。因此，我们主要在该范围内对汽液平衡关系进行了仔细的测量。3.测定低水浓度范围内的汽液平衡关系。用五盘塔底级液体和分子筛作为脱水剂，可测得水含量高达2wt-ppm的汽液平衡关系。对于苯-水和正己烷-水体系，发现在水含量高于100wt-ppm的范围内，汽液平衡比几乎是恒定的，但在较低的浓度范围内，它随着水浓度的降低而逐渐减小，并在5wt-ppm以下突然趋于1。基于该汽液平衡数据的塔板效率计算值高于项目1中的计算值，但在低含水浓度范围内仍处于较低值。因此，我们不能将效率下降的原因仅仅归结为汽液平衡关系。因此，我们打算在未来澄清这一点。较少

The purpose of this work is to clarify the reason why it is said that the efficiency of dehydrating distillation in hydrocarbon-water system is extremely low. The research results obtained so far are summarized as follows. 1.Distillation experiment with a single-tray column In dehydrating distillation experiments for three systems of benzene-water,toluene-water,and hexane-water,it was shown that in a range of relatively high water concentration the tray efficiency reached as high as those for heptane-toluene system(about 70%),but in a low water concentration range the efficiency became low as the water concentration decreases. 2.Distillation experiment with a five-tray column In this experiment,we examined a concentration profile in a five-tray column by measuring the water concentration on each stage. The results showed that the water concentration below the third or fourth stage from the top of the column does not change and hence the limit of the dehydration exists.The tray efficien … More cy in item 1 above is the calculated result based on the vapor-liquid equilibrium (VLE) relation obtained in a range of relatively high water concentration,where the VLE ratio was assumed to be constant. Taking into account also the above results,it was considered that the reason of the efficiency drop may be largely due to the VLE relation in a range of low water concentration, which have not been yet measured. Therefore we conducted careful measurement of the VLE relation mainly in that range. 3.Measurement of the VLE relation in a range of low water concentration Using the liquid on the bottom stage of the five-tray column and molecular sieves as a dehydrating agent,we could measure the VLE relation up to about 2wt-ppm in water content. For benzene-water and hexane-water systems it was found that in a range above 100wt-ppm in water content the VLE ratio is almost constant,but in a range of the lower concentration it decreases gradually with decrease of the water concentration and tends to approach unity abruptly below 5wt-ppm. The calculated values of the tray efficiency based on this VLE data became higher than those obtained in item 1, but still gave its low value in a low water concentration range. Consequently,we could not reduce the reason of the efficiency drop to the VLE relation only. So we intend to clarify this questionable point in future. Less