影响DHX工艺C_3收率因素分析及工艺完善

Influencing factors analysis of the C_3 yield and optimization of light hydrocarbon recovery unit with DHX process

对国内某120×10~4 m^3/d轻烃回收装置典型的DHX工艺C_3收率影响因素进行分析,在不改变现有装置的前提下,借助流程模拟软件Aspen HYSYS对工艺全流程建模。对主要操作参数进行分析,权衡C_3收率与装置的能耗关系。根据分析结果得出,在现有装置条件下,低温分离器最佳操作温度为-42℃、重接触塔最佳回流温度为-70℃。另外,膨胀机的膨胀比是影响C_3收率的关键,但是在不新增原料气压缩机、外输天然气压缩机的前提下,不宜对膨胀机的膨胀比进行调整。同时通过对脱乙烷塔塔顶至重接触塔管线的计算,确定管线中气液两相混输是造成脱乙烷塔塔顶温度波动、管线积液甚至断流现象的主要原因。基于以上分析结果,提出增加C_3收率的3种措施:1通过增大低温分离器入口换热器的换热面积,降低低温分离器的操作温度;2调整重接触塔进料流程,降低重接触塔塔顶C_3的损失;3增加脱乙烷塔塔顶物流气液分离罐,避免管线中气液两相混输,降低管线压力损失。C_3收率可由当前的67.1%提升至82.3%,同时有效解决脱乙烷塔温度波动幅度大、管线积液甚至断流的现象,增强了装置的安全性和稳定性。

The influencing factors of C3 yield were analyzed on a domestic 1 200 X 103 m^3/d light hydrocarbon recovery unit with direct heat exchange （DHX） process. Under the condition of existing equipment, the simulation was done by Aspen HYSYS. The sensitivity of the key parameters was analyzed, which weighed the relationship between C3 yield and energy consumption. According to the analysis results, some conclusions were obtained： the optimum operating temperature was -42 °C for low temperature separator,the optimum operating temperature was -70℃ for the reflux of DHX tower. Furthermore, the expansion ratio of expander is a key factor to affect the yield of C3 , but it is unfavorable to adjust the expansion ratio of expander without new feed gas compressor or outlet natural gas compressor. The main reason of temperature fluctuation, pipeline effusion, even cut-out of C2 tower was found by the calculation of the pipeline from C2 tower to DHX tower. Based on the results of the above analysis, three measures were proposed to improve the C3 yield, which included increasing the heat exchanger area to reduce the operating temperature of low temperature separator,adjusting DHX tower feeding process to reduce loss of C3 , adding gas-liquid separating pot to avoid gas-liquid two-phase flow boosting, and decreasing the pressure loss. The C3 yield could be raised from 67. 1% to 82. 3%, and the temperature fluctuation, pipeline effusion, even cut-out of C2 tower could be effectively solved. The security and stability of unit were enhanced.