Abstract:

Fischer-Tropsch synthetic water contains a variety of high value-added oxygen-containing organic compounds such as alcohols, ketones, and acids. However, due to the large amount of water and the complex azeotrope system, it is usually necessary to perform preliminary separation first. In this study, four alternative preliminary separation processes, direct two-column distillation, pervaporation-two-column distillation, direct dividing wall column distillation, and pervaporation-dividing wall column distillation, were designed first. According to the pervaporation experimental data, the pervaporation process model was constructed and simulated in Aspen Plus, and the optimal process parameters and simulation results of the distillation process were obtained through sensitivity analysis. The energy consumption and effective energy loss of the four processes were compared. The results show that the pervaporation-dividing wall column distillation process has obvious energy-saving advantages. Compared with direct two-column distillation, the energy consumption could be reduced by 15.85%, and the effective energy loss could be reduced by 45.74%. After pre-concentration by the pervaporation membrane, the concentration of the solution could enter the appropriate separation concentration range of the dividing wall column, so as to give full play to the advantages of the dividing wall column. Since the energy required for pervaporation could be provided by low-grade heat sources such as waste heat, the loss of effective energy could be significantly reduced in the coal chemical industry with sufficient waste heat. For this process, when the price of pervaporation membrane is lower than 438 CNY/m², the coupled process of pervaporation-dividing wall column distillation would show higher economy.

Key words: Fischer-Tropsch synthetic water, separation, membranes, pervaporation, distillation, DWC

摘要：

费托合成水中含有醇、酮、酸等多种高附加值含氧有机物可提取出来作为高附加值产品，但由于费托合成水处量大，共沸体系复杂，通常需要首先对其进行初步分离。设计了直接两塔精馏、渗透汽化-两塔精馏、直接隔壁塔精馏、渗透汽化-隔壁塔精馏四种可供选择的初步分离工艺。根据渗透汽化实验数据在Aspen Plus中构建渗透汽化过程模型并进行模拟，结合灵敏度分析得到精馏过程的最佳工艺参数和模拟结果，并对四种工艺的能耗和有效能损失进行对比。结果表明，渗透汽化-隔壁塔精馏工艺具有明显的节能优势，其能耗较直接两塔精馏可降低15.85%，有效能损失降低45.74%。经渗透汽化膜预浓缩后，溶液的浓度可进入隔壁塔的适宜分离浓度区间，以充分发挥隔壁塔优势。由于渗透汽化所需能量可由余热等低品位热源提供，在余热充足的煤化工领域中可显著降低有效能损失。对于该过程而言，当渗透汽化膜价格低于438元/m²时，渗透汽化-隔壁塔精馏耦合工艺将会表现出较高的经济性。

关键词: 费托合成水, 分离, 膜, 渗透汽化, 精馏, 隔壁塔