Study On Char-supported Fe-Zn Sorbents And Application

In this study, three lignite char-supported Fe-Zn sorbents were prepared by impregnationof different amount of iron and zinc. The experiments of sulfur removal properties of thesorbents were carried out using a fixed-bed quartz reactor at the temperature range of200℃to400℃using simulated coal gases (with3540ppmv H2S and148ppmv COS) conditionswith a space velocity of1000h-1. The concentrations of H2S and COS in the coke oven gasstream at the reactor outlet were analyzed by using a gas chromatographer equipped with aTCD and a FPD. Morphology and structure of the sorbent samples were analyzed using avariety of analytical methods and the mechanism of sulfidation was also discussed.The results of desulfurization experiments showed that activated lignite char itself canremove H2S and COS and the breakthrough time was35minutes at200℃. The mechanismof the sulfur uptake was physical or physiochemical absorption. The breakthrough time of thesorbent containing10.8%iron were110minutes、265minutes、560minutes at200℃,300℃,400℃, respectively. Char-supported iron-based sorbent added zinc to improve thedesulfurization precision and sulfur capacity; The breakthrough time, sulfur capacity,desulfurization efficiency was1020minutes,9.44%and99.63%, respectively. Theimprovement of properties of the iron-based sorbents during desulfurization was not obviouswhen the zinc content is further increased to above10%(wt).XRD and SEM analysis showed that the iron in the char-supported single Fe sorbentsexisted as Fe3O4.In Fe-Zn sorbents, Fe existed as ZnFe2O4before desulfurization. Aftersulfidation, iron and zinc oxides were transformed into FeS, Fe(1-X)S and ZnS, respectively.SEM showed clearly that iron and zinc were highly distributed in the char surface beforedesulfurization leading to a high reactivity of the sorbents.