Application of Organic Fuel Additives to Enhance Coal Combustion Efficiency

Abstract

The results from numerical and experimental investigations into the influence of organic fuel additives (OFAs) on the efficiency of combusting high-ash Ekibastuz coal are presented. Technology and a special combustion chamber equipped with a plasma-assisted startup system are proposed. The thermodynamic and kinetic parameters of cocombustion of coal with OFA are numerically analyzed, as a result of which the optimum process temperatures, air-to-coal mass consumption ratios, and combustion chamber geometrical parameters have been selected. Thermodynamic analyses of the coal combustion process have shown that 7 kg of air is required to burn 1 kg of coal. A tendency toward increasing the concentrations of CO2 and Н2О and, accordingly, toward decreasing the concentrations of NO, СО, and O2 in the coal combustion products in using OFA has been revealed. The kinetic analysis results have shown that the coal combustion process with a consumption rate of 10 kg/h is fully completed in a combustion chamber 0.2 m in diameter and 0.9 m in height. A series of experiments on cocombustion of Ekibastuz coal with OFA was carried out. The investigation results made it possible to evaluate the effectiveness of Omstar-DX1 and Open Flame OFAs, which are prepared as mixtures of light ethers. Comparative experiments of coal combustion with and without OFAs in different concentrations (0–5 cm3 per kg of coal) have shown that the OFAs increase the flame temperature in the combustion chamber’s initial part and decrease this temperature at the chamber’s outlet. This means that the air–coal mixture takes less time to ignite and, accordingly, it burns out more rapidly. The introduction of OFAs results in a noticeably more efficient combustion of low-grade coal, in smaller emissions of CO and NO, and in an increased concentration of CO2, which points to the more complete combustion of fuel.