Effect of hydrothermal treatment on co-combustion of paper sludge with coal: thermal behavior, NO emissions, and slagging/fouling tendency

ABSTRACTIn this study, the effect of hydrothermal treatment (HTT) on co-combustion of paper sludge with subbituminous coal was investigated. The paper sludge was treated by the hydrothermal pilot plant at a temperature of 197°C and a pressure of 1.9 MPa for 30 min. Thermal degradation during co-combustion was studied by thermogravimetric analysis. When burning hydrothermally treated paper sludge (HTT-PS) with coal, multiple decomposition behaviors were observed. The ignition temperature of the mixture was reduced since the paper sludge was more reactive than coal. NO emissions performance was tested by a batch-type fixed bed combustor. Results showed that the NO emissions could be reduced by 26–31% and, therefore, the mixture of coal and HTT-PS yielded lower NO emissions compared to the original mixture. NO conversion of HTT-PS was also lower. X-ray photoelectron microscopy suggested that HTT dissolved or protonated amide and simultaneously condensed the nitrogen functional compounds resulting in lower NO...