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

Abstract

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 ( τ 0) 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 SO 2, NO x , 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.