Recovery of combustibles from electrostatic precipitator discharge

Coal is the main fuel for the direct reduced iron (DRI) plants of India, which are one of the major sources of fly ash generation. The generation of fly ash and its disposal has raised concern because of the environmental impacts. In the present study, two different fly ash samples were investigated to explore the scope of recovery of combustibles. One did not show any recovery potential. The second sample indicated that about 40% of material could be recovered, with 35% fixed carbon and 10,841 kJ kg(-1) gross calorific value. This can be used as a fuel blend in standard fluidised bed combustion boilers efficiently burning inferior coal. A process flowsheet has been suggested for the recovery purpose. It was estimated that for a small 0.2 million tonnes per year (Mtpy) capacity DRI plant, approximately 3.4 ha of land could thus annually be saved from dumping of the generated fly ash, while recovering 1.83 MW of electrical energy.