基于三种状态方程计算CO_2-nC_4H_(10)气液相平衡

Gas-Liquid Phase Equilibrium of CO_2-nC_4H_(10) Calculated by Three State Equations

利用三种状态方程对二氧化碳-正丁烷体系(CO_2-nC_4H_(10))气液相平衡的总压和CO_2的气相组成进行计算,得到计算值与实验值的偏差。三种状态方程计算的CO_2气相组成的平均标准偏差均小于1.5%,总压的平均标准偏差均小于2.5%。三种状态方程计算精度接近,计算可靠,相比于SRK方程,PR、PT方程在计算二元体系相平衡时相对精度较高。在273.15 K温度、全液相分数范围内,PT方程适用的范围更广。对273.15 K、293.15 K温度下的全液相组成计算表明:随着CO_2液相组成的增大,气液相平衡时总压逐渐增大,气相组成先陡增,后缓慢增大;随着温度的升高,要达到相同的CO_2液相组成,所需的总压逐渐升高,CO_2的气相组成降低。

The total pressure of the gas-liquid phase equilibrium of carbon dioxide-normal butane system and the gas phase composition of carbon dioxide are calculated by using three state equations,and the error between the calculated value and the experimental value is obtained.The average standard deviations of CO2 gas phase composition calculated by three state equations are all less than 1.5%,and the average standard deviations of the total pressure are all less than 2.5%.The calculation accuracies of the three state equations are close and the calculation is reliable.Compared with the SRK equation,the accuracy of the PR and PT equation is relatively higher when calculating the phase equilibrium of binary system.Under the temperature of 273.15 K whole liquid phase fraction,the application scope of the PT equation is broader.By calculating the composition of the whole liquid phase under the temperature of 273.15 K and 293.15 K,it is shown the total pressure of gas-liquid phase equilibrium increases with the increase of the liquid phase of CO2,and the gas phase composition firstly increase abruptly and then slowly;as the temperature goes up,in order to achieve the same CO2 liquid phase composition,the total pressure required should be go up gradually and the gas phase composition of CO2 should decrease.