Investigation on co-firing of coal mine waste residues in pulverized coal combustion systems

Millions of tonnes of coal mine waste residues are piled up in dumping sites, causing serious environmental problems. Co-combustion in fluidized bed facilities is the most widespread alternative for the energy utilization of these by-products. However, no experiences have been so far reported of coal mine waste residues co-firing under pulverized fuel combustion technology. This work proves the technical feasibility of co-firing coal with up to 20% coal mine waste residues and investigates the impacts of transferring this co-firing alternative into a commercial unit. Experimental co-firing tests of coal mine waste residues were conducted on a 500 kWth pulverized fuel pilot plant. Regulated emissions (CO, CO2, SO2 and NOx) and visible flame radiation were monitored, obtaining regular and stable flicker and acceptable emissions levels for CO (200 mg/m3N) and NOx (700-800 mg/m3N). Finally, the impact analysis of co-firing coal mine waste residues in a full-scale pulverized fuel plant was performed by simulating the power cycle and combustion process in a 160 MWe pulverized coal combustion unit. Simulation results show the viability of this alternative in terms of plant efficiency, increase in power consumptions of auxiliary equipment and pollutant emissions for co-firing ratios under 10% in energy basis.