Ca ion-exchanged coal char as H 2S sorbent

Abstract

H 2S removal using Ca ion-exchanged coal char was studied in a fixed bed reactor at a temperature of 900°C. Yallourn, an Australian brown coal was used for ion exchange. The CaO obtained from the pyrolysis of Ca ion-exchanged coal was finely dispersed in the char and much more reactive toward H 2S than that from limestone. Ca ion-exchanged coal char showed high H 2S capture and almost no emission of H 2S was observed in the earlier reaction stage. At a reaction time of 100 min, the S/Ca atomic ratio in Ca ion-exchanged coal char increased to 1.2. This was due to H 2S capture capacity of both the coal char itself and the CaO distributed in the char. The sorption capacity of char was determined as 1.5 mmol-H 2S/g-char. The desulfurization characteristics of calcined limestone strongly depended on the particle size, whereas those of Ca ion-exchanged coal char was almost independent of the char particle size.