Study Of Sulfur-resistant HI Decomposition Catalyst And Pilot System Design And Commissioning In Sulfur-Iodine Cycle For Hydrogen Production

Hydrogen is a new and efficient energy source with the characteristics of storage and transportation.Today's environmental pollution and fossil energy crisis have caused more and more people to pay attention to hydrogen energy.Therefore,large-scale hydrogen production is the trend of the times.There are many methods for hydrogen production.Among them,thermochemical sulfur iodine cycly is an ideal choice for hydrogen production because of its high efficiency,low cost,and large-scale industrialization.The SI cycle consists of the following three-step thermochemical reactions:Bunsen reaction:2H2O+I2+SO2?H2SO4+2HIHI catalytic decompostion reaction:2HI?H2+I2H2SO4 catalytic decompostion reaction:H2SO4?H2O+SO2+1/2O2For the thermochemical sulfur-iodine cycle,although it has been studied for several decades,there are still many difficulties in its large-scale application.This paper is devoted to the screening of sulfur-resistant for HI decomposition catalysts and corrosion-resistant materials in sulfur-iodine cycle and the design,construction,commissioning and amplification of the pilot sulfur-iodine system.Residual H2SO4 could not be avoided in the SI cycle because of incomplete purification.The H2SO4 present in the HI feeding stream may lead to the poisoning of HI decomposition catalysts.In this study,the activity and sulfur poisoning of Ru and Ni catalysts loaded on carbon and alumina,respectively,were investigated at 500?.HI conversion efficiency markedly decreased from 21%to 10%with H2SO4(3000ppm)present,which was reversible when H2SO4 was withdrawn in the case of Ru/C.In the case of Ru/C and Ni/Al2O3,catalyst deactivation depends on the concentration of H2SO4;the higher the concentration of H2SO4,the greater the severity of deactivation.Catalysts before and after sulfur poisoning were characterized by transmission electron microscopy(TEM),energy-dispersive X-Ray spectroscopy(EDX),X-ray photoelectron spectroscopy(XPS),and X-ray diffraction(XRD).Experimental results and characterization of poisoned and fresh catalysts indicate that the catalyst deactivation could be ascribed to the competitive adsorption of sulfur species and change in its surface properties.The residual sulfuric acid adsorption capacity in the HI feed is stronger than the HI molecule and is the most important factor in producing a competitive adsorption effect.The competitive adsorption effect has a great influence on the conversion rate of HI decomposition,and the proper ratio of the catalyst to the feeding can effectively reduce the impact of the competitive adsorptionNi-Ru/SiO2 catalysts showed excellent catalytic activity without sulfur-poisoning and exhibited superior catalytic performance after poisoning compared to the Ru-free catalyst.The effect of Ru on the improvement in sulfur resistance over Ni-based catalysts was attributed to electronic factors,as evidenced by theory modeling analyses.As a result,bimetallic Ni-Ru catalysts possessed a better catalytic and sulfur-tolerant performance than Ni catalyst in H2SO4-containing HI decomposition reactions.The addition of Ru to the Ni-based catalyst could substantially improve the sulfur-tolerance,which provides new insights for maintaining greater activity during HI decomposition in the presence of sulfurThe construction of the pilot test of hydrogen production system was completed,and the commissioning and optimization of the main sub-modules of the pilot test system were carried out.Then,the linkage operation of the whole process is carried out,and the operability and operability of the pilot test system are introduced from the preliminary experimental results of the closed full cycle.The results and analysis of the pilot test system provide a reliable basis for the construction and operation of the sulphur-iodine cycle hydrogen production.Under the support of this data,this paper further designed a larger hydrogen production system with 5000L/h hydrogen production capacity,and introduced the parameters of the simulation calculation results of the material flow after the system amplification and the whole set.