ASH FORMATION AND DEPOSITION FROM A VICTORIAN BROWN-COAL - MODELING AND PREVENTION

Experiments were conducted in a drop-tube furnace to determine the ash character and to measure ash deposition for Loy Yang brown coal and t he same coal treated with aluminium lactate, A series of experiments o n sized fractions, using the same stoichiometry (20% excess air), gas temperatures (1000-1250 degrees C) and surface temperatures of the dep osition probe (500-800 degrees 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 cau ses an overall reduction in the ash-size distribution when compared to the untreated coal, The treated coal was markedly less fouling and sl agging, particularly at a deposit probe temperature of 700 degrees C. Thermodynamic calculations and experimental data (XRD, FTIR) indicate that the added aluminium in the treated coal led to the formation of a luminium-rich phases such as MgAl2O4 and sodium aluminosilicates. The reduction in fouling and slagging is probably due to the decrease in t he sodium chloride and the formation of aluminium-rich phases. (C) 199 8 Elsevier Science B.V.