Modeling and optimization of currently in operation natural gas desulfurization process using adsorption separation method

摘要

The simulation of an industrial adsorption cycle including six different steps is presented in this paper. The process consists of five parallel beds containing the zeolite 13X molecular sieve as an adsorbent in such a way that three beds are in the adsorption stage and two beds in the regeneration stage. The regeneration stage is performed in three steps depressurizing from 64.4 bar to 21 bar and heating in 210 degrees C and 310 degrees C. Dynamic simulation for this process consists of mass balance, energy balance, and momentum balance. Simulation accuracy in this case is high compared to industrial data. The feed gas pressure, feed gas temperature, bed height, regeneration step pressure, and first heating and second heating temperatures, all of them considered as effective parameters and mercaptan mole fractions in the outlet flow (which should be less than 15 ppm according to the environmental standards), are investigated by changing them. The results show that the process is regenerated well if the regeneration gas flow rate decreases from 0.35 kmol s(-1) to 0.2 kmol s(-1) and the regeneration step pressure is to be set at less than 27 bar. Moreover, 225 degrees C (as regeneration temperature) is enough to regenerate the mercaptan in the second regeneration step.