Study on characteristics, hydrogen-rich gas, bio-oil production, and process optimization of co-pyrolysis of sewage sludge and wheat straw

Sewage sludge (SS) and wheat straw (WS) are wastes that need to be treated urgently. In this research, the co-pyrolysis of SS and WS was investigated utilizing a thermogravimetric analyzer (TG) and a fixed bed. Using the Coats-Redfern approach, the effects of the mix ratio and the interactions of the SS and WS were investigated, and the effects of mix ratio, N2 flow rate, and pyrolysis temperature were examined for fixed bed pyrolysis. The response surface method (RSM) was applied in fixed bed pyrolysis to optimize the process. Increasing WS ratio can reduce pyrolysis residual rate to 23.8% for TG analysis. The reaction activation energy (E) increased with WS ratio. For the co-pyrolysis, there were substantial interactions between 200 and 400°. For fixed bed pyrolysis, syngas and bio-oil yields were mainly affected by N2 flow rate and pyrolysis temperature. The components with the highest amount in bio-oil gradually changed from aliphatic to aromatic hydrocarbons as the WS proportion grew, demonstrating that WS pyrolysis produced mostly aromatic compounds whereas SS pyrolysis produced more aliphatic compounds. Temperature 600 °C, sludge mixing ratio 32%, flow rate 2.5L/min, anticipated maximum H2 0.0421 m3/kg, and maximum bio-oil of 50.7114 g/kg are the best circumstances according to RSM.