Research On Carbon Dioxide Snowed Separation Technology

The CO₂ content in the currently mined natural gas is getting higher,and the drawbacks of the traditional alcoholamine method are becoming prominent.The paper proposes a carbon dioxide snowed separation technology,not only obtain the product gas that meets the requirements（ie,the CO₂ content is less than 3%）,but also achieve capture and recovery of CO₂ products.The paper explores both theoretical calculations and experimental design.The phase equilibrium calculation of CO₂-N2 binary system is carried out by using PR equation and SRK equation respectively.Comparing the results obtained by the equation with the existing literature data,the accuracy of the phase equilibrium calculation of CO₂-N2 binary system by PR equation is higher than that of SRK Equation,so it is applied to the calculation of freezing point and dew point of CO₂-N2 binary system.At the same time,HYSYS software is used to calculate the phase equilibrium data of the CO₂-N2 binary system,mainly to calculate the freezing point,and compared with the theoretical calculation value of PR equation.The absolute value of the average relative error is small,which can be directly calculated by HYSYS software.Drawing the three-dimensional map of the CO₂-N2 binary system,and we can obtain the application conditions of the CO₂ snowed separation technology,including the snowing temperature,the interval size and the maximum CO₂ content in the mixed gas.As the operating pressure continues to decrease,the temperature required for CO₂ snow separation is getting lower,but the temperature range for CO₂ snow separation is getting larger,and the more CO₂ can be allowed in the mixture gas.In order to facilitate the subsequent experimental application,the formula for the temperature required for CO₂ snow separation technology and the maximum content of CO₂ in the permitted mixture is fitted,and the calculation accuracy meets the practical application requirements.The CO₂ snow separation system was developed to achieve the snow separation of CO₂ under laboratory conditions.Under the pressure of 0.5MPa,the "local low temperature,condensation tuberculosis" scheme was selected for the CO₂ snowed separation test.As a result,the CO₂ concentration of the products at the top and bottom outlets,as well as the production rate of CO₂ products and the top gas recovery rate were all consistent with the theory.At the same time,it also summarizes the shortcomings of the test experiment and proposes to improve the operating pressure or continue to improve the insulation performance of the device to remove CO₂ well.Finally,three different operating pressures（1.2 MPa,1.0 MPa,0.7 MPa）were used for CO₂ snowed separation experiments,and good results were obtained.The CO₂ concentration in the bottom product can reach 100%;the CO₂ concentration in the top product gas is also less than the predetermined target of 3%.Meanwhile,the gas recovery rate at the top outlet is maintained above 94%,and the CO₂ product enters the CO₂ collection tank for storage and utilization.It laid a good foundation for further research on CO₂ snow separation technology.