Mathematical Model of Natural Gas Desulfurization Based on Membrane Absorption

摘要

Models of mass transfer kinetics combined with mass transfer differential equation and mass transfer resistance equation were established on the basis of double-film theory. Mass transfer process of H2 S absorption by means of polypropylene hydrophobic microporous hollow fiber membrane contactor was simulated using MDEA(N-methyldiethanolamine) as the absorption liquid and corresponding experiments of natural gas desulfurization were performed. The simulation results indicated that the removal rate of hydrogen sulfide showed positive dependence on the absorption liquid concentration and gas pressure. However, the desulfurization rate showed negative dependence on gas flow. The simulated values were in good agreement with the experimental results. The in-tube concentration of hydrogen sulfide at the same point increased with increase in the gas velocity. Axial concentration of hydrogen sulfide decreased rapidly at the beginning, and the decrease saw a slowdown during the latter half period. Hydrogen sulfide concentration dropped quickly in the radial direction, and the reduction in the radial direction was weakened with the increase of axial length due to the gradual reduction of hydrogen sulfide concentration along the tube. The desulfurization rate under given operating conditions can be predicted by this model, and the theoretical basis for membrane module design can also be provided.