Direct Combustion of Fine Coal from Coal Waste

Fine coal is a coal waste generated by washing the coal at the mines, and contains 30~55 wt% water after thickening via gravity settling/filtration. Due to the lack of cost effective approaches to remove the water from fine coal, needed in order to burn it in a conventional boiler, the coal producers often choose to discard the fine coal. There is already approximately 4 billion tons of fine coal waste in the U.S. and another 70~90 million tons is being produced every year. A unique process for the direct combustion of the wet fine coal, without further dewatering, is developed. Bench-scale testing has already been conducted in the Phase I and Phase II projects. Pilot-scale demonstrations will be conducted and the process’s economic advantages will be quantified in Phase IIA. In Phase II, a pumpable coal water slurry with 62.5% solid loading was prepared from real fine coal and slurry production was scaled up by a factor of 12. A burner designed for this process and a bench-scale combustor were constructed in the lab. In the combustion tests, a 17-kW self- sustained slurry flame burned stably in air and the fuel burnout was 95%. A computational fluid dynamics model was developed to simulate the slurry combustion process. With a newly constructed burner, this technology will be further demonstrated at the 100-kW level at an existing pilot-scale facility. The computational fluid dynamics model of the slurry combustion process will be updated after the pilot data is acquired. Furthermore, a techno-economic analysis of retrofitting a circulating fluidized bed boiler with this technology will be conducted to show the cost benefits. This technology can be applied to retrofit existing power plants or build new power plants at location close to the fine coal. With this new technology, the 4 billion tons of currently unusable fuel can be turned into electricity and its negative effect on environment is minimized.