Analyses of coal and sewage sludge co-combustion using Coats-Redfern model

The co-combustibility of coal and sludge was investigated with thermogravimetric analysis. The results show that the burning process of sludge can be divided into three phases: water evaporation, volatile matter volatilization and combustion, fixed carbon combustion and burning out. The ignition temperature of sludge is only 260 degree centigrade at the beginning of volatile matter combustion. The addition of wet sludge or dried sludge will reduce the burning velocity of coal, and also decrease the ignition temperature. However the blend of coal and sludge has not an obvious stage of the volatile matter volatilization and combustion. The activation energy of the sludge is lower than that of the coal. The addition of wet sludge or dried sludge will decrease the activation energy of the blend fuel, and improve the fire behavior. On the whole, the sludge addition has little influence on the combustion of the coal when the addition ratio is lower than 10%.