ATTRITION-RESISTANT ZINC TITANATE SORBENT FOR SULFUR

For new coal gasification systems, zinc titanate sorbents are being developed to remove sulfur from the hot product gas prior to its use in combined cycle turbines and high-temperature fuel cells. The properties of zinc titanate for this application are very attractive. However, there is still a concern about durability over many sulfidation-regeneration cycles. The approach to the problem taken in this project was to contain the zinc titanate in a structural matrix of excess titania. Fifteen sorbent formulations were evaluated in a screening study to obtain a good compromise between mechanical properties and chemical reactivity. Then, the two best formulations were evaluated in ten-cycle fluidized bed and fixed bed tests. One of these was shown to be outstanding in resistance to attrition and decrepitation during the tests. It had the composition 33.5% zinc oxide and 66.5% titania, was prepared from 2 mu m powders, and was sintered at 1000 degrees C. The crush strength of this sorbent was approximately a factor of 10 higher than values reported by other investigators. Its chemical reactivity was good, and improvement should be possible with minor changes in preparation procedures. The results of complementary research on improving sorbent regeneration procedures and on activation pretreatments are reported, also.