Desulfurization Capacity of Iron Oxide Minerals for High Temperature Removal of H2S and its Relation to Their Physical Properties
Satoshi KUSHIYAMA, Yutaka KOINUMA, Satoru KOBAYASHI, Reiji AIZAWA, Koichi MIZUNO
SYNOPSIS: - H2S desulfurization capacity was compared between the sorbents of 0.59/0.84 mm particle size prepared from iron oxide minerals, i. e. ochers, red clays and iron ores. Reactions were carried out using a packed-bed microreactor with a 0.5 % H2S-20 % H2-N2 gas mixture at the condition of; temperature 500°C, GHSV 10, 000 h-1, pressure 1.4 kgf/cm2. Among the sorbents tested, ochers showed remarkably high capacity. Observations of sulfided sorbent particles by secondary electron microscopy (SEM) together with the measurements of surface area, Fe2O3 crystallite size and pore size distribution led to the conclusions as in the followings;
1) Under the reaction condition utilized, the capacity is strongly controlled by intraparticle diffusion. Only a little influence was observed of the surface area and/or the Fe2O3 crystallite size.
2) Pore size distribution is an important factor governing the capacity, namely, the larger the macropore volume, the higher the capacity. However, it is the most critical whether or not the dense layer of pyrrhotite is formed on the outer surface of sorbent particles in the course of desulfurization.
3) Examination by SEM revealed that no such dense layer was formed for the sorbents prepared from ochers, while it was clearly seen for the other sorbents. This is very likely the reason of the markedly high performance exhibited by ochers.