Clean Coal Technologies, Coal

Scientist believes his zinc pellets can aid gasification plants

Issue 10 and Volume 100.

Scientist believes his zinc pellets can aid gasification plants

An Illinois scientist believes he has found a way to help coal gasification power plants remove sulfur emissions while significantly cutting capital costs and increasing power plant revenues. Jim Swisher, E&A Associates chief scientist and partner, expects to know for sure this fall when 7 tons of his zinc titanate pellets–a sulfur absorber that can be cleaned and reused up to 1,000 times–receive long-term performance testing at a General Electric (GE) coal gasifier in Schenectady, N.Y.

Coal gasification, one of the nation`s most promising clean coal technologies, turns high-sulfur coal into low-sulfur coal gas. One problem with the process is that the coal gas, produced at temperatures exceeding 2,300 F, must be cooled to about 70 F before the sulfur can be removed. Zinc titanate can remove the sulfur at about 1,000 F. Coal gasification plants using this sorbent would have much smaller cooling systems and could use the remaining thermal energy to produce power more efficiently.

“Hot gas clean up using zinc titanate works just as well as cold gas clean up. The advantages come into play when power companies spend less building gasification plants and profit from the higher energy efficiencies to generate electricity,” Swisher said. He estimates that hot gas clean up can increase power generation revenues by 3 to 4 percent.

If the GE tests are successful, then 70 tons of Swisher`s pellets, each the size of a BB, may be put to work in a 260 MW Tampa Electric coal gasification power plant in Lakeland, Fla.

“Technologies like this will help eliminate any disadvantage Illinois coal has by making coal gasification plants more profitable,” said Richard Shockley, director of the Illinois Clean Coal Institute, which is funding Swisher`s research. The U.S. Department of Energy estimates that by 2040 coal gasification will supply 130 GW of electricity and use more than 427 million tons of coal annually.

Swisher has been studying zinc titanate for four years and believes he has succeeded in finding a formulation of zinc titanate durable enough to withstand 1,000 cycles of sulfur exposure and cleaning. Other researchers have run into problems with the zinc titanate, with the pellets disintegrating in a few days, months before the zinc wears out.

Swisher solved the strength problem by increasing the amount of titanium oxide, which gives the zinc titanate structural strength, and by adjusting the manufacturing process.

United Catalysts Inc., a Louisville, Ky., chemical firm, is producing the pellets for the GE test for $7.60/lb, but the cost could fall to $5/lb if the pellets are produced in greater quantities.