二氧化碳在CH4-CO2二元体系中的冰点预测

Prediction of CO2 freezing point temperature in CH4-CO2 binary system

关键词:  天然气  CO₂  冰点  HYSYS  Aspen Plus  关联式

Key words:  natural gas  CO₂  freezing  HYSYS  Aspen Plus  correlation

摘要:

采用深冷工艺回收天然气中的乙烷时,脱甲烷塔塔顶及冷箱处的温度较低,容易发生CO₂冻堵。研究固体CO₂在CH₄-CO₂二元体系中的形成规律,有助于优化深冷分离工艺,避免CO₂冻堵,同时降低冷能消耗。修正了纯组分CO₂的饱和蒸气压的通用关联式,以预测二元气相体系中固体CO₂的形成温度,并与陈赓良-朱利凯模型关联式计算、HYSYS软件计算及Aspen Plus软件计算的CO₂固体形成温度进行了比较。结果 表明,修正后的计算模型准确度较高,与Agrawal的实验数据的平均偏差在2 ℃以内。同时,根据Kurata实验数据拟合出CH₄-CO₂二元液相体系中CO₂固体形成温度关联式,并与文献经验公式、HYSYS软件计算及Aspen Plus软件计算的CO₂固体形成温度进行了比较。结果 表明,该计算模型与实验数据吻合度非常高,与Kurata的实验数据的平均偏差在1 ℃以内,且具有广泛的通用性。 

Abstract:

During recoverying ethane from natural gas in cryogenic process, CO₂ in natural gas mixtures easily forms into frost and causes plugging problems due to the low temperature in top of the demethanizer and the cold box. Regularity for the freezing point temperature of CO₂ in CH₄-CO₂ binary system is studied and it can help engineers to optimize the cryogenic separation process and avoid CO₂ freezing, and then reduce consumption of cold energy. For this propose, the saturated vapor pressure correlation of pure component CO₂ is modified to predict the temperature of CO₂ freezing point in vapor phase. The calculation results using the literature correlation, HYSYS software, Aspen Plus software, and correlation raised in this paper are compared with the Agrawal experimental data. The results show that this correlation has higher accuracy which the average deviation is within 2 ℃. In addition, a correlation for CO₂ solid formation temperature in the CH₄-CO₂ binary liquid system is given. Compared with Kurata experimental data, the correlation has the highest accuracy which the average deviation is within 1 ℃, and has wide generality.