Zinc Ferrite-based Sorbent For Medium-high Temperature Coal Gas Desulfurization

Zinc ferrite-based sorbentsfor medium-high temperature coal gas desulfurization were developed at the temperature range of300～550℃. Three methods for zinc ferrite preparation, including coprecipitaion method, homogeneous precipitation method, sol-gel method, are summarized and compared in this paper. The influences of additives on zinc ferrite-based sorbent desulfurization properties werestudied. Effects of operational conditions such as reaction pressure, reaction atmosphere and regeneration temperature on sorbents performance were also investigated. At the same time, the feasibility of using haydite as the carrier of Cu-Zn-Fesorbent for the removal of H2S from coal gas were analyzed.Zinc ferrite sorbents were prepared and optimized by coprecipitaion method, homogeneous precipitation method and sol-gel method. The results indicated that the sorbent exhibited a higher sulfur capacity when using coprecipitaion method at the condition thatthe total metal ion concentration was0.6mol/L, the precipitation temperature was80℃and the calcination temperature was600℃. When using homogeneous precipitation method, the sorbent exhibited a higher sulfur capacity at thecondition thatthe calcination temperature was500℃and the ratio of urea solution and nitrate concentration is1:10. When using sol-gel method, the sorbent exhibited a higher sulfur capacity at the condition that the calcination temperature was600℃and reaction pH is1:10. The sulfur capacity of the sorbents prepared by coprecipitaion method, homogeneous precipitation method and sol-gel methodat the optimized condition were38.8,31.2and25.4g S/100g sorbent respectively, and the results indicated that coprecipitaion method is thebetter method for the preparation of desulfurizer.The influences of Cu、Mn、Co、Ni and Ce additives on zinc ferrite-based sorbent desulfurization properties were studied, and the results indicated that the sorbent exhibited a higher sulfur capacity of41.2g S/100g sorbent at the condition that the additive was10%Cu. The results of XRD and SEM showed that the assistance Cu could prevent the aggregation of ZnFe2O4crystals with the presence of a little ZnO and CuO, improve the dispersion of the active ZnFe2O4component, and avoid the formation of more product layers which would result the lower utilization of the desulfurizer. The experimental results provide a theoretical basis for the preparation of Cu-Zn-Fe sorbents with good desulfurization performance. Takes the ZFDCu10-sorbent as an example, effects of operational conditions such as reaction pressure, reaction atmosphere and regeneration temperature on sorbents performance were investigated. The results indicated that pressure and CO have positive effect on desulfurization process, while H2S and H2have no significant influence and600℃is a better regeneration temperature at the temperature range of510～600℃.The feasibility of using haydite as the carrier of Cu-Zn-Fe sorbent for the removal of H2S from coal gas were analyzed,and haydite carried sorbent were modified by orthogonal experiment.The results showed that desulfurization activity of modified haydite desulfurizers were affected by various factors:pseudo-boehmite/haydite ratio>sodium aluminate/haydite ratio>ZFDCulO/haydite ratio>haydite size. The optimum conditions for preparation of haydite desulfurizers are0.0%of pseudo-boehmite/haydite ratio,27%of sodium aluminate/haydite ratio,33%of ZFDCu10/haydite ratio and0.3-0.5mm of haydite size. The sorbent made by the optimum conditions have a sulfur capacity of8.1g S/100g sorbent and the abrasive featureof the sorbentin fluidization is not ideal. The results of SEM and EDS showed that the haydite has abundant aperture and it is an appropriate carrier, uneven distribution of particles on the surface of E3desulfurizer may cause by the surface reunion of pseudo-boehmite, which would result the unevenness distribution of active constituent on the desulfurizer.