Mine-mouth power and process steam generation using fine coal waste fuel

The techno-economic feasibility of mine-mouth power generation using processed fine coal refuse fuel has been evaluated. Fine coal processing studies were conducted on the −100 mesh fine coal refuse of a central Illinois coal mine. On-site column froth flotation testing using a 15-cm diameter (7 kg/h) laboratory Jameson cell produced a 30 175 kJ/kg and 2.85% sulfur product at a combustible recovery of 75%. The mean particle size of the product was 60 μm. The product was dewatered in a Technicas Hidraulicas filter press to a 21% total moisture content filter cake from a 27% solids slurry at 6–10 min cycle times and at 99.5% solids capture efficiency. Material handling tests involving pumpability of the fine coal fuel established the feasibility of pumping this fuel to a fluidized bed boiler. For a 44% moisture content slurry, rheological measurements indicated a yield stress (τ0) value of 275 Pa and viscosity (η) of 0.795 Pa s. Based on these measurements a hydraulically driven piston pump was determined to be appropriate for this application. Bench-scale combustion tests, conducted at Canadian Energy Technology Center, using a 100-mm diameter, 5 m high circulating fluidized bed combustor demonstrated the feasibility of achieving sustained combustion of the fine coal slurry containing up to 51% moisture content. High combustion efficiency and low emission levels were achieved for SO2, NOx, and mercury. CO emissions were high, but in an industrial unit with longer particle residence time and a hotter cyclone, lower emission levels can be expected. Engineering economics for the project indicate feasibility. Conservative estimates of profitability indicate potential to provide a return on investment in the range of 20–25%. A 40% return on investment is projected if the Coal Industrial Park includes production and captive use of process steam.