The Clean Energy Technology Development Center of Southern Research Institute in Durham, North Carolina, has developed a technology that combines both coal and biomass feedstocks for use in Integrated Gasification Combined Cycle systems. Use of biomass—as a supplement to coal—could allow power stations to take credit for the carbon dioxide that plants and trees take out of the atmosphere as they grow and mature. The program was sponsored by the U.S. Department of Energy (DOE), with additional financial support from Southern Research and TK Energi.
In contrast to bulky and expensive lockhoppers, the prototype feeder creates a highly-compressed "plug" of coal and biomass, so dense that the high pressure inside commercial-scale gasifiers is held back as the material is pushed into the gasifier. A primary challenge related to biomass utilization in IGCC power plants has been the inability to reliably feed a variety of biomass feedstocks to the gasifier as biomass-coal mixtures. Southern Research and TK Energi have shown this challenge can be overcome.
"When we reached 450 pounds per square inch of pressure, and the feeder was still holding back pressure and increasing in feed rate, we knew we had a winner. There was a lot of high-fiving going on," said Santosh Gangwal, Ph.D. project leader for Southern Research.
The prototype piston-driven plug feed system was demonstrated using a blend of two coal types (bituminous and lignite) and three biomass feedstocks (woody biomass, prairie grass, and corn stover) fed into a pressurized simulated gasifier environment up to 450 pounds per square inch.