【作者】 荆树宏；

【导师】 郑丹星；

【作者基本信息】 北京化工大学 ， 化学工程， 2008， 硕士

【摘要】 炼厂干气中乙烯含量高达14%～22%。然而,我国目前大部分炼厂中干气都作为燃料气被烧掉。分离回收其中的乙烯具有显著的节能减排意义。本课题主要针对乙烯气体物理吸收的方法进行了汽液相平衡研究。首先,本文选择最大超额Gibbs函数法作为吸收剂的评价方法,利用化工流程模拟软件ASPEN PLUS,选择UNIFAC活度系数模型,计算了乙烯与近20种醇类、醚类、芳烃类等溶剂的活度系数和GEmax,分析结果认为芳烃与C2H4的二元体系GEmax数值相对小。收集了C2H4与一些溶剂的VLE数据,比较分析中发现,分子结构对溶剂吸收性能有一定影响,即：溶剂分子结构对称,乙烯在其中的溶解度越大。据此,选择芳环上甲基结构对称的1,3,5-三甲苯(C9H12)为C2H4的适宜吸收剂。然后,以提高汽液相平衡实验数据测定精度为目的,提出了两点取样管路的改进,实验结果表明改进有效良好。利用该装置测定了C2H4+C9H12二元体系在温度253.15K～333.15K,压力0.5MPa～3.0MPa范围内的汽液相平衡数据。采用PR状态方程对此二元体系的VLE数据进行关联,得到该方程的二元交互作用参数kij。实验数据取得了良好的热力学一致性。结果表明PR状态方程能较好的描述C2H4+C9H12二元体系的汽液相平衡行为。C2H4+C9H12二元体系的VLE实验数据表明,C2H4在C9H12中的溶解度普遍比较高,并且随温度变化,液相中的C2H4浓度变化显著。通过比较C2H4+C7H8体系的实验数据,结果可以看出1,3,5-三甲苯作为乙烯吸收剂效果要明显优于甲苯,表明1,3,5-三甲苯具有作为一种新的乙烯吸收剂的研究与开发潜力。本研究为进一步的工艺应用开发提供了热力学数据和模型基础。另一方面,研究结果也验证了GE max判据作为吸收剂判据正确性。更多还原

【Abstract】 The mass fraction of C2H4in the refinery dry gas is very high, which is between14%-22%. However, the gas is burned as fuel gas in most of refineries in our country. The separation and recovery of ethylene has remarkable significance on energy-saving and CO2emission reduction. This paper studied vapor-liquid equilibrium for ethylene absorption on physical method.First, the method excess Gibbs energy was used to evaluate absorbing performance of solvents in this paper. Twenty ethylene and solvents (alcohols, ethers, aromatics) binary system were selected approximately. Their activity coefficients and the maximal excess Gibbs energies were calculated using the software ASPEN PLUS and UNIFAC model (activity coefficient model). The results showed that GEmax of C2H4+aromatics binary system are smaller than others.The VLE data of C2H4and some solvents were collected. The rule that solvents’formula structure could affect their absorbing performance was found in the solvents comparison. In the same temperature and pressure, the more symmetric formula structure is, the higher solubility is. Mesitylene, which formula is C9H12and methyl groups distributed in the aromatic ring symmetrically, was selected to be C2H4absorbent by the method of excess Gibbs energy.Then, the paper put forward two point improvements on the high-pressure VLE apparatus. Experiments show that the improvements are effective. Vapor-Liquid Equilibrium data for ethylene and mesitylene were measured at temperature range from253.15K to333.15K and pressures range from0.5MPa to3.0MPa with the improved high pressure VLE apparatus. The VLE data were correlated with the Peng-Robinson equations of state. The binary interaction parameter kij is also obtained. The experimental data passed the thermodynamics consistency test. The results showed that PR equation of state can better describe the vapor-liquid behaviors of the C2H4+C9H12binary system.VLE experimental data of C2H4+C9H12binary system showed that, on one hand, the solubility of ethylene in the mesitylene was very high in a wide temperature range. Solubility is greatly affected by temperature. It shows that absorbing performance of mesitylene was better than toluene for C2H4while comparing with the VLE data for C2H4+C7H8binary system. So, mesitylene has considerable potential as a new ethylene absorbent and is worthy of research. This study support advanced process application development with VLE data and model foundation. On the other hand, the experimental results show the GEmax criterion, which is used to evaluate solvents, is correct.更多还原