Study Of CO₂ Separation Methods And Characteristics In SNG

In the present SNG process, Rectisol technology was generally used for CO2 gas removal. However, the limit of the Sulfur-content in acid gases and refrigerating capacity in the technology harmed the removal effect. Therefore, it is necessary to research on the characteristics of CO2 gas removal methods existing, to provide some theoretical and data support for looking for a more safe and effective method to alternate Rectisol. In this dissertation, the characteristics and theoretical analysis of membrane separation method and MEA chemical absorption are studied, based on this, a new type method for CO2 separation, called membrane separationchemical absorption combination is presented and studied. The results of the study are as follows:Membrane separation coefficient is an important parameter to measure polymer membrane gas separation performance, for air intake, the greater the volume flow rate, the higher the pressure, and the lower the temperature, then the greater the membrane separation coefficient, the greater the membrane permeated side CO2 gas concentration. Generon210 membrane has a greater separation coefficient than the Prism, but the separation performance of the latter is more stable when intake air condition change. When the condition of the intake air is 0.9 MPa, 25℃, 60L/min, Generon210 membrane separation has the result that: permeated side CO2 concentration is 63.4%, the separation efficiency is 63.27%, CH4 recovery rate is 93.55%, the concentration is 95.5%. The greater the MEA solution flow rate and the temperature, the greater CO2 absorption amount is. When the MEA solution concentration becomes more than 30%, due to the solution viscosity increase, the CO2 absorption amount decreases. When use the 30%,55℃,15L/h MEA solution to absorb the 60L/min、15%CO2 intake gas, separation efficiency can reach more than 99%, recycled CH4 concentration is above 99%; When use 6m3/h steamto desorb the 30%,100 ℃ MEA rich-solution, the highest desorption rate can be obtained which is 72.52%. The mechanism of amphoteric ion can accurately describe the MEA chemical absorption and desorption process, the dynamic model based on the mechanism can be used to calculate the MEA absorption rate in the process of chemical absorption and desorption rate at any moment in the process of desorption. The CO2 separation process of combination method is influenced by the intake gas pressure, volume flow rate, temperature and MEA concentration, flow rate, temperature. To achieve an ideal separation effect, the MEA must be adjusted to make sure that the MEA/CO2 moore ratio reaches more than 1.15, in the condition, the separation efficiency is 81% and the concentration of recycled CH4 concentration is 95.5%. Combination method is beneficial to greatly reduce the amount of the MEA solution required in chemical absorption process greatly. Therefore the method is suitable for large volume process, and can be used as an alternative method of rectisol technology.