Study On The Optimization Of Technology Process And Gas Distribution In Natural Gas Purification System

With the extension of the service life of purification system,the natural gas temperament of the raw material,the handling capacity of the devices and the operating conditions have changed significantly compared with the original design value.This leads to the purification of the product gas exceeding the national standard of second grade.Aiming at the key problem that need to be solved urgently,particularly control the CO2 content in 3%（V/V）,the optimization of technology process and gas distribution schemes were systematically studied based on the operating conditions of the existing devices.The results are as follows:（1）A set of desulfurization and decarbonization device was self designed and built to simulate on the spot and obtained the type of formula amine solution is MDEA+DEA.Taking the removal rate of CO2 as the response value,the proportion of formula amine solution and the absorption process conditions were optimized by Design Expert software.The results showed that the optimal concentration of formula amine solution is MDEA:DEA:H2O =42.17%:5.00%:52.83%,the optimum absorption temperature is 34.66℃,the optimum operating pressure is 4.78 MPa,and the optimum absorption time is 12.96 min.The desorption rate of formula amine solution is 90%⁹3%.（2）The mass transfer model for absorption of CO2 in formula amine solution was established,which based on the double-film theory.The experimental results showed that this process belongs to a first-order reaction and the reaction rate equation is -dc_CO2/dt=1.0010c_CO2¹.0063.The enhancement factor is 45.57 and the mass transfer rate equation is NA = 144.12c1.The interaction coefficient is 0.1635,which indicates that the effect of absorption is enhanced.（3）The natural gas desulfurization,decarbonization and dehydration process was simulated by Aspen HYSYS.The results showed that the optimum formula amine solution and the best absorption process can make the natural gas quality qualified,and the gas volume increased by 6.4%.The energy and heat transfer network of the process was analyzed and optimized by Aspen Energy Analyzer.The results showed that the optimum pinch temperature difference is 5 with the total cost index as the target value.The temperatures of cold and heat flow pinch are 122.9℃ and 127.9℃ respectively.The cold and thermal utilities with the minimum number of heat exchangers and the highest economic benefits were2.437×106 k J/h and 6.077×106 k J/h respectively.The total annual cost index is 7.431×10-3.The above three data are reduced by 30.59%,15.03%,and 4.47% compared with thesimulated values.At the same time,the thermal utility under the pinch point is eliminated,and the energy is allocated and utilized reasonably.（4）The gas distribution model was established without changing the formula amine solution and the source code of the valve was compiled based on genetic algorithm.The results showed that the total gas volume can reach 1045.4587×104 m3/d on the premise of guaranteeing the quality of the product,which increased by 4.87% before optimization.Meanwhile,the different gas distribution schemes were obtained.