A New Clean Coal Technology by Mild Modification at Low Temperature

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In order to develop a new method for producing a high performance absorbent of H_2S based on the waste and low rank coal, we performed the following items:(1) Proposal of a new preparation method of absorbent.(2) Performance of the removal of H_2S by a new absorbent.(3) Application of iron wastes in steel factory.First, we tried a new method to produce an absorbent of H_2S as follows: The low rank coal was oxidized for 2 h at 70 ℃ by nitric acid to introduce a large amount of carboxyl functional group and was exchanged by Fe ion. The Fe-exchanged coal was pyrolyzed at 500 ℃ and gasified at 800 ℃ under steam. Though the treatment the type of Fe changed into FeC after pyrolysis and Fe_3O_4 after gasification. The weight content of Fe after gasification was ca. 80 %. We found that the Fe_3O_4 particles of 20-50 nm in size were highly dispersed in the Fe/carbon complex from the observation by SEM. Thus, an attractive Fe/carbon complex was successfully produced.Next, we examined the performance of Fe/carbon complex as a absorbent of H_2S. We compared the de-H_2S profiles of new and conventional absorbents. A absorbent prepared by the proposed method had a high performance of desulfurization. From the X-ray analysis the Fe_3O_4 was converted into FeS after exposing by H_2S. It was supposed that the high performance of a new absorbent was brought about by physical (the highly dispersed nano particles) and chemical (pure Fe_3O_4) properties of Fe/carbon complex.Finally, we applied the proposed method to iron wastes in steel factory such as iron sludge and dust. It was found that these wastes were significantly absorbed H2S. Furthermore, we confirmed that the adsorbent prepared by the proposed method form these wastes had a high de-H_2S performance. Thus it was clarified that the proposed method is effective for producing a high performance absorbent of H_2S.