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.

Automated summary

Co-thermal treatment of binary biomass mixtures can enhance the thermal degradation efficiency through a synergistic reaction. Adding sewage sludge (SS) to rice straw (RS) lowers the activation energy and improves volatile matter decomposition during pyrolysis. This study provides important insights for the commercial-scale plant design of SS and RS co-thermal treatment.