Abstract:

CO₂ capture is imperative currently, cryogenic separation is one of the important methods of CCS(carbon dioxide capture and storage). The accuracy of CO₂-N₂ phase equilibrium property is related to the liquefied CO₂ recovery and recycling purity in cryogenic method, and it will affect the choice of the system and energy consumption analysis further. N₂-CO₂ phase equilibria calculation based on several state equation models were made in this article. The calculation results show that the PR state equation combined with Vdw mixing rules is most suitable for N₂-CO₂ phase equilibrium calculation, the maximum deviation is 7.37%, the average deviation is about 3%. Then the CO₂ bubble point, dew point and the temperature of sublimation at the condition of 2 MPa with the PR equation model were calculated. An energy consumption analysis about cryogenic system was made, the results show that the method combined liquefaction and sublimation achieved higher recovery and recycling purity, and compared with sublimation separation method, the former method reduce energy consumption by more than 9%. At last, an analysis about the impact of O₂ on the CO₂-N₂ phase equilibrium property was made.

Key words: CO₂ capture, phase equilibria, equation of state, mixing rules, energy consumption analysis

摘要：

当前CO₂捕获日益迫切,低温捕集CO₂是其中的重要方法,而N₂-CO₂相平衡计算的准确程度关系到低温捕集中CO₂的液化回收率以及回收纯度的分析,并影响系统形式的选择及能耗分析。通过不同状态方程及混合规则进行相平衡计算方法的对比选择,结果显示结合Vdw混合规则的PR状态方程计算N₂/O₂相平衡特性时精度最高,最大偏差为7.37%,平均偏差在3%左右,理想方程偏差最大;之后利用PR方程进行2 MPa压力下泡露点以及凝华温度的计算,并采用液化结合凝华的方法进行系统能耗分析,结果显示此方法能达到较高回收率及回收纯度,并与仅使用凝华方法分离相比,能耗降低9%以上;此外研究了O₂对N₂-CO₂二元系统的相平衡特性的影响。

关键词: 二氧化碳捕集, 相平衡, 状态方程, 混合规则, 能耗分析