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

本文的目的是阐明为什么说烃-水体系的脱水蒸馏效率极低。现将迄今为止所取得的研究成果归纳如下。1.单塔板精馏实验对苯-水、甲苯-水、己烷-水三个体系进行了脱水精馏实验，结果表明，在较高的水浓度范围内，塔板效率可达庚烷-甲苯体系的塔板效率（70%左右），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.在这个实验中，我们通过测量每个塔板上的水浓度来检查五塔板塔中的浓度分布。结果表明，在塔顶三、四级以下的塔板上，水的浓度基本不变，存在脱水极限，塔板效率随塔板高度的增加而提高 ...更多信息 上述第1项中的cy是基于在相对高的水浓度范围内获得的汽液平衡（VLE）关系的计算结果，其中假设VLE比恒定。还考虑到上述结果，认为效率下降的原因可能主要是由于在低水浓度范围内的VLE关系，这还没有被测量。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.低水含量范围内汽液平衡关系的测定用分子筛作脱水剂的五层塔底液，可测定含水量达2 wt-ppm左右的汽液平衡关系。对于苯-水和己烷-水体系，在水含量大于100 wt-ppm的范围内，汽液平衡比几乎不变，但在较低的水含量范围内，汽液平衡比随水含量的降低而逐渐减小，在低于5 wt-ppm时，汽液平衡比突然趋于1。根据该汽液平衡数据计算出的塔板效率值比第1项中得到的值高，但在低水浓度范围内仍为低值。因此，不能将效率下降的原因仅仅归结为汽液平衡关系。因此，我们打算日后澄清这一点。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