TGA-FTIR analysis of co-pyrolysis characteristics of hydrochar and paper sludge

•The pyrolysis of paper sludge could be improved by blending hydrochar.•The synergistic effect occurred during co-pyrolysis of the blends.•Kinetic parameters were calculated by using model-fitting method.•The evolution and distribution of gaseous products were studied.•The option co-pyrolysis effectiveness index was obtained when the ratio between hydrochar and paper sludge was 9:1.

The co-pyrolysis characteristics for hydrochar, paper sludge and their blends were investigated by TG-FTIR technique. The pyrolysis of paper sludge and hydrochar could be divided into three stages and one stage respectively. The model-fitting method was adopted to investigate the kinetic parameters of pyrolysis process, and the n-th order reaction model matched the pyrolysis process well. The activation energy was determined by the composition of the feedstocks and the stages of the pyrolysis. TG- FTIR indicated that CO2, H2O, CO, CH, CO, CO and CC groups were the main gases released from the pyrolysis process. There existed a coupling synergistic effect between these two feedstocks. The evolution of the gaseous products was consistent with the weight loss of the mixtures during co-pyrolysis. The co-pyrolysis effectiveness index was calculated. When the mass proportion of hydrochar was 90%, most desired products could be obtained.