Preparation and Reactivity test of Nano Size ZnO for Removal of H_2S and COS in a Gasified Fuel Gas

摘要

A nano-size zinc oxide was formulated for the effective removal of a very low concentration of sulfur compounds (H_2S, COS) contained in a gasified fuel gas and their reactivity was also investigated in this study. They were prepared by a matrix-assisted method with various precursors. An active carbon was used for a matrix and zinc nitrate, zinc chloride, and zinc sulfate were selected as precursors. Zinc nitrate was the best precursor for the formulation of the nano-size zinc oxide in the experiments. The size of the formulated nano-size zinc oxides was in the range of 20-30 nm and its surface area was about 56.2 m~2/g. From TGA(thermal gravity analysis) test, it was found that its sulfur capacity was about 5.83 gS/100 g-sorbent and sulfur absorption rate was about 0.363 gS/min·100 g-sorbent. Their reactivity increased with the smaller size and the larger surface area of the sorbents. Most prepared nano-size zinc oxides showed an excellent performance for the removal of not only H_2S but also COS. Their absorption rate was faster than commercial zinc oxides. In order to investigate the sulfur absorption characteristics of zinc oxide, a experiments for the nano-size zinc oxides formulated from zinc nitrate precursors were carried out in a packed-bed reactor system over the temperature of 500 °C. It was concluded that the zinc oxide prepared by zinc nitrate as a precursor showed the highest sulfur removing capacity.