Synergistic effects of co-combustion of sewage sludge and corn stalk and the resulting gas emission characteristics

Increasing discharge of sewage sludge is a threat to the ecological environment, and sludge treatment via combustion is the most feasible alternative. However, the low calorific value and high-water content of raw sludge results in poor firing performance and increases the risk of environmental pollution. Recently, co-combustion has emerged as a more environment-friendly technology. Herein, the combustion behaviours of sewage sludge, corn stalk and their mixture at four heating rates were studied via thermogravimetric experiments. Results yielded the division of weight loss into three stages for corn stalk: dehydration, combustion of volatiles and combustion of fixed carbon; four stages were identified for sewage sludge and the mixture of sludge and stalk: dehydration, combustion of volatiles, combustion of fixed carbon and thermal decomposition of a small amount of minerals. Synergistic analyses found that with a 60% blending ratio of sewage sludge, interaction between the components in the high-temperature range was greatly promoted. Gas emission characteristics showed that CO(2)was the main product during (co-)combustion, while the NO(x)emissions at low (or high) temperatures for the blend were higher (or lower) than the theoretical values. Temperature had little effect on H2S emissions, though it significantly affected SO(2)emissions during co-combustion.