Abstract:

Reducing CO₂ emissions is particularly important for environmental protection. In conventional Rectisol process, a large amount of CO₂, absorbed by poor methanol, is diluted by N₂ and directly discharged into the atmosphere as tail gas. In order to explore the space for process improvement, a conventional Rectisol process was simulated based on Aspen Plus. The physical property method selected the CPA (Cubic-Plus-Association) model, and the binary interaction coefficient of the model was corrected, and then compared with the practical data to ensure the accuracy of the model. For process improvement, firstly, the first improvement, based on the conventional Rectisol process, was proposed by combining four-stage pressurized hot flash and depressurized flash for CO₂ capture, and the related parameters were optimized to further reduce the system utilities consumption. The result showed that although the CO₂ production of the first improvement process was 3.3 times that of the conventional process, the system energy consumption increased by 2.12%, and the system exergy consumption increased by 17.81%. Next, further energy saving improvement was made on the basis of the first improvement process by adopting the combined technology of "semi-lean solution + turbine recovery". The CO₂ production of the second improvement process was not only equivalent to the first improvement process, but also the system energy consumption and exergy consumption reduce by 17.16% and 5.85% respectively compared with the conventional Rectisol process.

Key words: Rectisol process, simulated, CPA model, CO₂ capture, energy saving

摘要：

减少CO₂排放对环境保护尤为重要。传统低温甲醇洗工艺中大量被贫甲醇吸收的CO₂由于被N₂稀释而直接作为尾气排放进大气中。为探究工艺改进空间，本研究基于Aspen Plus对一传统低温甲醇洗工艺进行模拟，物性方法选用CPA（Cubic-Plus-Association）模型并对该模型的二元交互系数进行回归修正，后与实际数据进行对比确保模型的准确性。对于工艺改进，首先在传统低温甲醇洗工艺的基础上采用四级增压热闪蒸和降压闪蒸相结合的方式进行一次改进以用于CO₂捕集，并对相关参数进行优化以进一步降低系统公用工程消耗。结果显示，虽然一次改进工艺的CO₂产量是传统工艺的3.3倍，但系统能量消耗增加了2.12%，系统㶲消耗增加了17.81%。接着，在一次改进工艺的基础上采用“半贫液+透平回收”相结合技术进一步进行节能改进，二次改进工艺的CO₂产量不仅与一次改进工艺相当，系统能量消耗和系统㶲消耗相比于传统低温甲醇洗工艺也分别降低了17.16%和5.85%。

关键词: 甲醇洗工艺, 模拟, CPA模型, CO₂捕集, 节能