Combustion of bituminous coal loaded with copper salts

Abstract

In the present study, the combustion process of coal samples loaded with three different copper salts (Cu(NO3)2, CuSO4, and Cu(CH3COO)2) was studied. The deposition of Cu salts (5 wt%) on the coal powders was implemented by an incipient wetness impregnation. The experiments on the self-ignition and combustion of the coal samples were carried out in a combustion chamber with a temperature of heating medium of 500–700 °C. The composition of the gas-phase combustion products was determined using a mass-spectroscopic gas analyzer. It was found that the ignition delay time for the modified samples was lower than for the reference sample by 45%. With an increase of the heating medium temperature, a significant decrease in the minimum ignition temperature was observed for all the samples. The maximal difference in the ignition delay time between the reference sample and the sample modified by Cu(NO3)2 was obtained at 500 °C. High-speed video imaging revealed microexplosions of samples with Cu(NO3)2 and Cu(CH3COO)2 additives at the early stage of combustion. Depending on the sample moisture content, the explosions were located on both the inner part and surface of the samples. The introduction of additive resulted in the reduction of fuel underburning; the maximum change was obtained at 600 °C for the sample modified by Cu(NO3)2. Using a gas analyzer it was found that the activation of the combustion process by copper salts significantly reduced the amount of CO formed, thus providing more complete oxidation of the fuel with the formation of CO2.