Research On The Kinetics Of Zn/Mn/Cu Sorbents Loaded On Semi-coke Support To Remove H2S From Hot Coal Gas

Sulphides (mainly, H2S, COS and CS2) contained in crude gas not only erode pipelines and reduce facility lifetime to result in the increase of production cost, but also make the catalyst used for synthetizing chemicals from syngas poison and inactivate to affect the quality and yield of the final product and result in the waste of resources. H2S accounts for about90%in the total amounts of sulphides, so the removal of H2S from coal gas has been considered as one of key techniques of coal cleaning conversion.Based on the basis of the research group’s preliminary work, Z20SC, Z20M4SC, Z20C6SC and Z20M4C6SC sorbents were prepared by high-pressure impregnation with semi-coke support and the precursors of Zn(NO3)2, Mn(NO3)2and Cu(NO3)2active components in this paper. The sulfidation performances and desulfurization kinetics of the prepared sorbents were researched in a fixed-bed reactor in two different atmospheres of H2S/N2and H2/CO/H2S/N2. The equivalent grain model was used to analyze experimental data and estimate their desulfurization kinetics parameters. The results may provide the theoretical basis for the industrial application of the sorbent. The main research conclusions are shown as follows.1) The semi-coke support in sorbent prepared by high-pressure impregnation hardly presents desulfurization capacity and the active component is mainly the metal oxide loaded on it. The desulfurization capacity of Z20M4SC and Z20C6SC sorbents is nearly the summation of Z20SC and M4SC or C6SC sorbent, respectively. But the desulfurization capacity of Z20M4C6SC is obviously bigger than the accumulated value of three single metal oxide sorbent, which shows that the Mn and Cu existed simultaneously in sorbent can improve the sulfidation reaction of sorbent.2) The optimum operating conditions optimized by the kinetic researches of sorbent sulfidation reaction are the gas volumetric flow rate of500ml/min, particle size of0.125-0.150mm, sulfidation temperature500℃and500ppmv H2S content in inlet gas for prepared Z20SC, Z20M4SC, Z20C6SC and Z20M4C6SC sorbents. In these conditions, the equivalent grain model can be used to describe the sulfidation reaction process of sorbents prepared by high-pressure impregnation.3) The desulfurization kinetics of Z20SC, Z20M4SC, Z20C6SC and Z20M4C6SC sorbents in H2S/N2show that their desulfurization reactions are controlled by the surface reaction zone in the initial20min, and by the diffusion through the reacted layers after20min. The activation energy Ea in the zone controlled by surface reaction is8.270,7.193,5.011and4.491kJ/mol for Z20SC, Z20M4SC, Z20C6SC and Z20M4C6SC sorbent, respectively. The activation energy Ep in the zone controlled by diffusion through reacted layers is15.220,21.913,13.748and14.435kJ/mol for Z20SC, Z20M4SC, Z20C6SC and Z20M4C6SC sorbent, respectively. Ep is greater than Ea, so we consider that the desulfurization reaction is mainly controlled by the diffusion through the reacted layers.4) The desulfurization kinetics of Z20SC, Z20M4SC, Z20C6SC and Z20M4C6SC sorbents in H2/CO/H2S/N2show that their desulfurization reactions are controlled by the surface reaction controlled zone in initial20min, and by the diffusion through the reacted layers after20min. The activation energy Ea in the zone controlled by surface reaction is8.131,7.999,4.816and 5.788kJ/mol for Z20SC, Z20M4SC, Z20C6SC and Z20M4C6SC sorbent, respectively. The activation energy Ep is36.057,40.496,15.422and12.634kJ/mol in the diffusion through reacted layers for Z20SC, Z20M4SC, Z20C6SC and Z20M4C6SC sorbent, respectively.5) H2and CO introduced into H2S and N2inlet gas present an effect of weakening desulfurization capacity of sorbent, which is related to the change of activation energy Ea and Ep. The changes of Ea for Z20SC、Z20M4SC and Z20C6SC sorbents are not significant, but Ep increases obviously. The activation energy of Z20M4C6SC sorbent in the zone controlled by diffusion through reacted layers has also a notable increase.6) The effect of Mn added in Zn-based sorbent on its activation energy is small, and Cu added in Zn-based sorbent presents the effect of reducing Ea and Ep, especially for the sorbent contained Mn together with Cu.