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

•Integrated CO2/sludge gasification was explored using the waste heat from slags.•The characteristics and the mechanism of syngas release were identified.•The hot slags acted as not only good heat carrier but also effective SO2 fixation.•A conceptual model of CO2/sludge gasification with multi-system was designed.

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 0.022 kg/kgsludge at 500 °C to 0.422 kg/kgsludge at 900 °C; meanwhile, the SO2 concentration at 900 °C remarkably reduced from 164 ppm to 114 ppm by blast furnace slags (BFS) and 93 ppm 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.

Graphical abstractSyngas production was achieved using an integrated method of CO2/sludge gasification using hot slags from the steel industry. This method mainly involved a rotary cup atomizer (RCA) system and a gasifying system.Figure optionsDownload full-size imageDownload as PowerPoint slide