Integrated carbon dioxide/sludge gasification using waste heat from hot slags: Syngas production and sulfur dioxide fixation

Abstract

The integrated CO2/sludge gasification using the waste heat in hot slags, was explored with the aim of syngas production, waste heat recovery and sewage sludge disposal. The results demonstrated that hot slags presented multiple roles on sludge gasification, i.e., not only a good heat carrier (500–950°C) but also an effective desulfurizer (800–900°C). The total gas yields increased from 0.022kg/kgsludge at 500°C to 0.422kg/kgsludge at 900°C; meanwhile, the SO2 concentration at 900°C remarkably reduced from 164ppm to 114ppm by blast furnace slags (BFS) and 93ppm by steel slags (SS), respectively. A three-stage reaction was clarified including volatile release, char transformation and fixed carbon using Gaussian fittings and the kinetic model was analyzed. Accordingly, a decline process using the integrated method was designed and the optimum slag/sludge ratio was deduced. These deciphered results appealed potential ways of reasonable disposal of sewage sludge and efficient recovery of waste heat from hot slags.