Abstract:

The amount of CO₂ emitted from fossil fuel combustion emissions accounts for 75% of total CO₂ emissions. In order to alleviate the global greenhouse effect caused by CO₂, CO₂ in CO₂/N₂ must be separated. Hydrate-based gas separation is an efficient, low-energy consumption CO₂/N₂ separation technology. In this paper, the relationship between CO₂ volume fraction, reaction conditions and reaction characteristics in the process of CO₂/N₂ separation by hydrate-based gas separation is studied. The CPA-SRK equation and Chen-Guo model are used to process simulation and analysis. It is found by calculation that the CO₂ volume fraction of the feed dry base has a great influence on the reaction pressure and the equilibrium level of the CO₂/N₂ separation process by the hydrate-based gas separation. With the increase of CO₂ volume fraction, the reaction pressure decreases, and the decrease decreases with the increase of volume fraction. When the CO₂ volume fraction of feed is less than 20%, the decrease is faster. When the volume fraction is greater than 50%, the pressure decrease becomes smaller. When the temperature is 277K and the CO₂ volume fraction is less than 10%, the four hydrate equilibrium stages are needed to obtain the required gas sample. At the same temperature, when the CO₂ volume fraction is 10%—20%, the three hydrate equilibrium stages are needed, and when the CO₂ volume fraction is greater than 30%, the separation needs two hydrate equilibrium stages. Temperature has a great influence on the reaction pressure of hydration separation, but it has little effect on the number of separation stages required. As the temperature increases, the hydration reaction pressure increases, and the increase decreases with the increase of the feed dry CO₂ volume fraction. For the gas sample studied, three hydrate equilibrium stages are required at different temperatures to achieve the process requirements.

Key words: hydrate-based gas separation, process simulation and analysis, separation stages, equilibrium stage

摘要：

化石燃料燃烧排放烟气中CO₂的量占CO₂总排放量的75%，为了缓解CO₂导致的全球温室效应，需将CO₂/N₂中的CO₂分离出来。水合物法分离是一种高效、低能耗的CO₂/N₂分离技术。本文研究了水合物法平衡级分离CO₂/N₂过程中，进料CO₂体积分数、反应条件与反应特性三者间的关系，利用CPA-SRK方程+Chen-Guo模型对其进行平衡级分离流程模拟分析。经计算发现，进料干基CO₂体积分数对水合物法分离CO₂/N₂工艺的反应压力、平衡级级数均有较大影响。随着体积分数的增加，反应压力呈减小趋势，减小幅度随体积分数增加而减小，当进料CO₂体积分数小于20%时，压力下降较快，当体积分数大于50%时，压力降低幅度变小。温度为277K时，CO₂体积分数小于10%时，需四个水合物平衡级分离才能得到满足要求的气样；当体积分数为10%~20%时，需三个水合物平衡级分离；体积分数大于30%时为两个水合物平衡级分离。温度对水合分离的反应压力有较大影响，但对所需平衡级分离级数的影响并不大。随着温度的升高，水合反应压力呈增加趋势，增加幅度随进料干基CO₂体积分数的增加而降低。针对所研究气样，在不同温度下，均需三个水合物平衡级分离才能达到工艺要求。

关键词: 水合物法气体分离, 流程模拟分析, 分离级, 平衡级