Abstract:

The energy consumption of crude methanol distillation is one of the key factors affecting the production cost of methanol. Although five-column multi-effect distillation can reduce the energy consumption of the distillation process, there is still a considerable amount of low temperature waste heat. In order to further reduce the energy consumption, a mechanical vapor recompression (MVR) heat-pump and an assisted reboiler in the stripping section of the atmospheric column were added to form the novel methanol distillation process combining heat pump and multi-effect process. Based on the whole process simulation data, the rationality of the heat pump setting was analyzed through pinch technology. The energy consumption, the coefficient of performance (COP) and total annual cost (TAC) was used to evaluate the process performance. The results showed that the heat pump setting was reasonable in the novel methanol distillation process. The condenser duty and the total reboiler duty were 24.7MW and 22.25MW， respectively, and the COP was 22.5. The condenser duty, heat duty and TAC were reduced by 33.76%, 32.64% and 26.97%, respectively compared with the five-column multi-effect distillation process. The energy saving effect was significant for the novel methanol distillation process combining heat pump and multi-effect process.

Key words: methanol distillation, five-column multi-effect process, heat-pump assisted distillation, low temperature thermal utilization, economic evaluation

摘要：

粗甲醇精馏的能耗是影响甲醇生产成本的关键因素之一。虽然五塔多效精馏可以降低精馏过程能耗，但仍存在相当的低品位余热未利用，为进一步降低五塔多效精馏工艺的能耗，本研究引入机械蒸汽再压缩式（MVR）热泵，在常压塔提馏段增设辅助再沸器，形成热泵耦合多效甲醇精馏新工艺。基于新工艺的全流程模拟数据，文章利用夹点技术对热泵设置的合理性进行分析，采用能耗、效能系数（COP）和年总成本（TAC）等指标对新工艺过程进行评价。结果表明：热泵耦合多效甲醇精馏新工艺中热泵设置合理，冷负荷为24.7MW，再沸器总热负荷为22.25MW，COP为22.5，相比五塔多效精馏工艺，冷负荷、热负荷以及TAC分别降低33.76%、32.64%和26.97%。热泵耦合多效甲醇精馏新工艺节能效果显著。

关键词: 甲醇精馏, 五塔多效工艺, 热泵辅助精馏, 低温余热利用, 经济评价