MODEL OF VAPOR LIQUID EQUILIBRIA FOR AQUEOUS ACID GAS ALKANOLAMINE SYSTEMS USING THE ELECTROLYTE NRTL EQUATION
MODEL OF VAPOR LIQUID EQUILIBRIA FOR AQUEOUS ACID GAS ALKANOLAMINE SYSTEMS USING THE ELECTROLYTE NRTL EQUATION
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DOI：
10.1021/ie00091a028
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发表时间：
1989-07-01
影响因子：
4.2
通讯作者：
CHEN, CC
中科院分区：
文献类型：
--
作者：
AUSTGEN, DM;ROCHELLE, GT;CHEN, CC
开发了用于表示酸性气体（H2S，CO2）-烷醇胺-水体系中的汽液平衡的热力学一致模型。该模型以严格的方式解释化学平衡。活度系数的代表，与电解质NRTL方程处理所有真正的液相物种之间的远程离子-离子相互作用和本地的相互作用。水和链烷醇胺都作为溶剂处理。可调参数的电解质NRTL方程，代表短程二元相互作用，拟合二元和三元系统的汽液平衡数据。在25-120 ℃的温度范围内，计算的H2S和CO2平衡与大多数报道的单一酸性气体在单乙醇胺（MEA）和二乙醇胺（DEA）中的水溶液的实验数据非常一致。在不拟合额外参数的情况下，H2S和CO2混合物在MEA或DEA水溶液中的实验平衡表现良好。烷醇胺水溶液广泛用于吸收/汽提操作，以去除酸性气体，主要是硫化氢（H2S）和二氧化碳（CO2）从各种源气体中。H2S和CO2存在于天然气、合成气、烟道气和各种炼油厂物流中，并且CO2是氨和氢制造的副产物。该方法的特征在于通过化学反应增强传质;酸性气体直接反应或通过酸碱缓冲机制与烷醇胺反应以形成非挥发性离子物质。因此，链烷醇胺的存在提高了酸性气体在平衡分压恒定值下在水相中的溶解度。气体处理操作的设计需要了解含水酸性气体-烷醇胺体系的汽液平衡（VLE）。文献中报道了大量酸性气体-醇胺水溶液体系的汽液平衡实验数据。这些数据通常限于高酸性气体负荷;在低酸性气体压力范围内报告的汽液平衡数据很少，而在低酸性气体压力范围内，汽液平衡数据可能是最重要的。这些实验数据的表示是必要的，以便设计工程师可以自信和系统地内插和外推可用的数据。不幸的是，气体处理操作的过程模拟和设计由于缺乏用于准确地表示浓缩电解质水溶液的热力学性质的相关性而受到阻碍。因此，设计计算通常基于经验方法。最近的研究已经导致了几个半经验的过剩吉布斯能模型或活度系数模型的水电解质系统有效的离子强度代表在工业应用中发现的。其中包括Pitzer（1973）、Meissner和Tester（1972）、Bromley（1973）、Cruz和Renon（1978）、Ball等的模型。（1985），Chen et al.（1982），Chen和Evans（1986），以及Christensen et al.（1983年）。Sander等人（1986）提出了一个过量吉布斯能模型来描述盐对混合溶剂体系汽液平衡的影响。模拟
A thermodynamically consistent model was developed for representing vapor-liquid equilibria in the acid gas (H2S, C02)-alkanolamine-water system. The model accounts for chemical equilibria in a rigorous manner. Activity coefficients are represented, with the Electrolyte-NRTL equation treating both long-range ion-ion interactions and local interactions between all true liquid-phase species. Both water and alkanolamine are treated as solvents. Adjustable parameters of the Electrolyte-NRTL equation, representing short-range binary interactions, were fitted on binary and ternary system VLE data. Calculated H2S and C02 equilibria are in good agreement with most of the reported experimental data for aqueous solutions of a single acid gas in monoethanolamine (MEA) and diethanolamine (DEA) in the temperature range 25-120 C. Without fitting additional pa-rameters, representation of experimental equilibria for mixtures of H2S and C02 in aqueous solutions of MEA or DEA is good.Aqueous solutionsof alkanolamines are widely used in absorption/stripping operations to remove acid gases, primarily hydrogen sulfide (H2S) and carbondioxide (C02), from a variety of source gases. H2S and C02 are present in natural gas, synthesis gas, flue gas, and various refinery streams, and C02 is a byproduct of ammonia and hydrogen manufacture. The process is characterized as mass transfer enhanced by chemical reaction; the acid gases either react directly or react through an acid-base buffer mechanism with the alkanolamines to form nonvolatile ionic species. The presence of an alkanolamine, therefore, enhances the solubility of an acid gas in the aqueous phase at a constant value of the equilibrium partial pressure. Design of gas-treating operations requires knowledge of the vapor-liquid equilibria (VLE) of the aqueous acid gas-alkanolamine system. A large body of experimental vapor-liquid equilibria data for aqueous acid gas-alka-nolamine systemshas been reported in the literature. The data are generally limited to high acid gas loadings; little VLE data are reported in the low acid gas pressure range where it is perhaps most important. Representation of these experimental data is needed so that thedesign en-gineer can confidently and systematically interpolate and extrapolate the available data. Unfortunately, process simulation and design of gas-treating operations has been hindered by the lack of a correlation for accurately rep-resenting thermodynamic properties of concentrated aqueous electrolyte solutions. Design calculations are, therefore, often based upon empirical methods. Recent research has led to several semiempirical excess Gibbs energy models or activity coefficient models for aqueous electrolyte systems valid to ionic strengths rep-resentative of those found in industrial applications. Among them are the models of Pitzer (1973), Meissner and Tester (1972), Bromley (1973), Cruz and Renon (1978), Ball et al.(1985), Chen et al.(1982), Chen and Evans (1986), and Christensen et al.(1983). Sander et al.(1986) developed an excess Gibbs energy model to represent the salt effect on the VLE of mixed solvent systems. Mock