Calculation On Vapor-liquid Phase Equilibrium In Separation Process Of Natural Gas

In order to optimize flow in separation process of natural gas further and reduce energy consumption, the whole flow is needed to be simulated, and the calculation of phase equilibrium in the flow is the foundation of the whole calculation. The study of phase equilibrium is the basic method of separation of natural gas, which provides necessary property data for the exploitation and utilization of natural gas. Through the study of the subject can be measured accurately in accordance with the experimental data to balance the product of natural gas separation and the promotion of the forecast conditions. We can better master gas separation process. In the research and production of gas separation technology has academic value and practical significance.In this paper, we supplicate SRK equation parameters the by using material critical compression factor, and establish improved m-expression, and use the improved SRK equation to calculate the separation of natural gas in the vapor-liquid equilibrium calculation.The results show that without taking into account the mole fraction of gas in less than 3% of the group of circumstances, gas component mole fraction of SRK equation is that average relative error is 3.78%, and liquid component mole fraction is that average relative error is 2.16%, and phase equilibrium constant is that average relative error is 4.90%. Mole fraction of gas component, liquid component mole fraction, the phase equilibrium constant relative error of the mean value of three is 3.61%, the SRK equation of improved gas composition mole fraction is that average relative error is 1.30%, liquid components mole fraction is that average relative error is 0.52%, the phase equilibrium constant is that average relative error is 4.90%. Mole fraction of gas component, liquid component mole fraction, the phase equilibrium constant relative error of the mean value of three is 2.24%. Using SRK equation and improved SRK equation to calculate simple one-component gas phase equilibrium which can meet the accuracy requirements, however, the improved SRK equation have better accuracy.Calculating in the balance of natural gas system data, the smallest error of improved SRK equation is 0.082%, and the biggest error is 16.67%, and average error was less than 5%; the original SRK equation of the minimum error is 0.411 percent, and the biggest error is 25.00%, average error of less than 10%.To sum up: In this paper, we improve calculation results of the SRK equation, which is better than the original equation, and we improve the calculation is that does not increase the complexity. The improved SRK equation of state is better than PR, PT. It is wide, accuracy, and relative error is small. The improved SRK equation should be considered firstly, when we calculate light hydrocarbon of gas and outside the gas composition of recovery, light hydrocarbon recovery and constitution.