UNIFAC-DMD法预测烷烃-氨的汽液相平衡

UNIFAC-DMD models in predicting vapor-liquid equilibrium of ammonia-alkanes binary system

烷烃-氨的汽液相平衡模型是计算爱因斯坦制冷循环的重要数据。然而在设计氨-水-异戊烷的爱因斯坦制冷循环的过程中,从文献中查阅不到异戊烷-氨的相平衡数据。采用商业软件中基团贡献法UNIFAC-DMD自带的数据库所预测的结果也不尽人意,不能得到特征的蝶形相图。本文利用基团贡献法的原理,通过使用模拟软件,应用文献中得到的丙烷-氨和正丁烷-氨体系的相平衡数据,拟合基团贡献法UNIFAC-DMD中的CH_2、NH_3的含对温度修正的基团交互参数a_(CH_2NH_3,1)/K,a_(CH_2NH_3,2),a_(CH_2NH_3,3)/K^(-1)和a_(NH_3CH_3,1)/K,a_(NH_3CH_3,2),a_(NH_3CH_3,3)/K^(-1)。拟合得到上述基团交互参数值分别为-1 995.4,18.51,-0.037,11 565.3,-68.98,和0.111 4。将此组新参数替换原有基团贡献法的数据库参数,重新预测烷烃-氨的相平衡,成功预测得到了蝶形相图。

UNIFAC-DMD group interactive parameters provided by ASPEN failed to give the right phase diagram prediction of ammo- nia-alkanes binary systems which are believed to be in the characteristic butterfly shape. Experimental binary VLE data of ammoniapropane and ammonia-butane from the literature were used for the assessment of the right UNIFAC-DMD CHa-NH3 group interactive parameters of αCH2NH3,1/K,αCH2NH3.2,αCH2NH3,3/K-1和αNH3CH3,1/K,αNH3CH3,2,αNH3CH3,3/K^-1.The values obtained were - 1 995.4,18.51, - 0. 037, 11 565.3, - 68.98 and 0. 111 4, respectively. With this new set of parameters, good results were obtained, which can be used for ammonia-water-isopentane and similar Einstein refrigeration cycles studies.