Ash formation and deposition from a Victorian brown coal—modelling and prevention

Abstract

Experiments were conducted in a drop-tube furnace to determine the ash character and to measure ash deposition for Loy Yang brown coal and the same coal treated with aluminium lactate. A series of experiments on sized fractions, using the same stoichiometry (20% excess air), gas temperatures (1000–1250°C) and surface temperatures of the deposition probe (500–800°C) allowed direct comparison of results for the treated and untreated coals. The results show that treatment with aluminium reduces the amount of sodium-rich fine ash and also causes an overall reduction in the ash-size distribution when compared to the untreated coal. The treated coal was markedly less fouling and slagging, particularly at a deposit probe temperature of 700°C. Thermodynamic calculations and experimental data (XRD, FTIR) indicate that the added aluminium in the treated coal led to the formation of aluminium-rich phases such as MgAl 2O 4 and sodium aluminosilicates. The reduction in fouling and slagging is probably due to the decrease in the sodium chloride and the formation of aluminium-rich phases.