Co-thermal degradation characteristics of rice straw and sewage sludge

Co-thermal treatment of binary biomass mixture is an alternative to enhance the refractory decomposition of biomass thermal degradation efficiency resulted in the synergistic reaction. Rice straw (RS) containing a large amount of fixed carbon (FC) is quite difficult to thermally decompose at a lower temperature. Considering the RS and sewage sludge (SS), co-thermal treatment for enhancing energy conversion efficiency was feasible. This study investigates the kinetic behaviors and gas evolution of RS, SS, and their blends under co-thermal decomposition processes using Thermogravimetric analysis combined with Fourier-Transform Infrared Spectroscopy (FTIR). The experimental results indicate that SS could enhance the volatile matter decomposition in RS co-thermal process at lower temperatures. Activation energy decreases from 53 to 49 kJ mol^{− 1} with an increase in SS addition from 50 to 80% under pyrolysis conditions. The major volatile components were aliphatic chains with double bonds, as well as carbonyl, hydroxyl, and C–H groups in organic compounds by FTIR identification. The tested materials characteristics in terms of volatile matter (VM)-to-FC ratio significantly affected the thermal degradation performance. Activation energy was decreased with increasing the VM/FC ratio. It implied that co-thermal reaction could be accelerated. In summary, the results could provide the important information for co-thermal treatment of SS and RS in application for commercial-scale plant design.