Intensified effect of K adhering to hematite involved in the sulfurous chemical looping gasification

Abstract

When sulfur in petroleum coke (petcoke) converts to H2S instead of SO2, it is the resource which can be recovered by Claus process. Chemical looping gasification (CLG) is capable of achieving petcoke conversion and sulfur recovery. To simultaneously overcome the obstacles of low gasification reactivity and improve H2 and H2S production, hematite modified by K as oxygen carrier (OC) was involved in the high-sulfur system to investigate the effect on sulfur conversion via batch fluidized bed in petcoke CLG process. K enhanced H2 generation beyond expectation because K not only improved the petcoke gasification but also enhanced the steam oxidation of deep reductive OC. Especially when using 10 % KNO3-hematite, H2 yield increased by 3.9 times as compared to 0 % K, with the carbon conversion efficiency of 99.92 % in the 22nd minute. The different K sources had a different H2 selectivity. The sulfur fate had been originally studied using K-modified hematite OC. H2S was the main phase of sulfur release and the high H2 yield also assisted H2S production. Introducing K contributed to in-situ sulfur capture forming K-Fe-S compounds in the OCs due to the deep reduction of Fe. 10 % KNO3-hematite exhibited excellent cyclic stability with a H2 volume fraction of more than 65 % in 21 cycles. Furthermore, the mechanism of hematite modified by K involved in sulfur-containing system was summarized in petcoke CLG process.