In recent years, domestic refining and chemical enterprises have paid more and more attention to the efficient comprehensive utilization of refinery dry gas. Many units have been built to recover and separate C₂, C₃ and other components from dry gas as raw materials for ethylene production. These units mostly adopt the shallow cold oil absorption process. The composition of refinery dry gas varies greatly, especially the hydrogen content. Aiming at the C₄ absorption and desorption section of the C₂ recovery unit using the shallow cold oil absorption method, this paper analyzes the single-stage equilibrium process of C₄ absorption in refinery dry gas, compares the solubility of C₂ and C₃ components in C₄ absorbent and the separation factor of methane and ethane at different hydrogen concentrations, and compares the circulation amount of absorbent in the multi-stage absorption and desorption process of the actual unit, as well as the heat supply in the C₄ absorption and desorption process. When the hydrogen content in refinery dry gas increases, the solubility of C₂ and C₃ components in C₄ absorbent increases slightly, the separation difficulty decreases, and the amount of absorbent consumed and the heat supply for absorption and desorption required to recover a unit mass of product gas are reduced. At the same time, the average molecular weight of refinery dry gas decreases significantly. In the design of new units, the selection of dry gas compressor should consider the change of gas molecular weight. For the units that have been put into use, it is necessary to evaluate the operating characteristics of the dry gas compressor.

margin:0px 0px 16px, padding:0px, border:0px, font-size:16px, vertical-align:baseline, color:rgba(0, 0, 0, 0.9), background-color:#FFFFFF, "> hydrogen content, C? recovery unit, C? absorption, separation factor, solubility, absorbent, reboiler, compressor

近年来国内炼化企业对炼厂干气的高效综合利用越来越重视，建设了多套装置回收分离干气中的碳二、碳三等组分作为乙烯生产的原料，此类装置多采用浅冷油吸收的工艺方法。炼厂干气的组成差异较大，尤其是氢气含量。针对采用浅冷油吸收法的碳二回收装置中碳四吸收解吸部分，分析了炼厂干气碳四吸收的单级平衡过程，对比了不同氢气浓度时碳二和碳三组分在碳四吸收剂中的溶解度、甲烷和乙烷的分离因子，并对比了实际装置的多级吸收解吸过程中吸收剂的循环量，以及碳四吸收和解吸过程中的供热量。炼厂干气中氢气含量增加时，碳二、碳三组分在碳四吸收剂中的溶解度有小幅增加，分离的难度有所降低，回收单位质量的产品气所消耗的吸收剂量和吸收解吸供热量降低。同时炼厂干气的平均分子量明显变小，在新装置设计时干气压缩机选型需考虑气体分子量变化的因素；对已投用装置，需对干气压缩机运行特性进行评估。