Characteristics of coal partial gasification experiments on a circulating fluidized bed reactor under CO2O2 atmosphere

Highlights: • CO₂-coal gasification results in high-efficiency CO₂ capture and storage. • When the oxygen-coal ratio is 0.57, the concentration of CO + H₂ reaches the maximum value. • The pores of char are getting opened as the reactant gas enters the inside of char. • New O-containing functional group and more aromatic rings are generated. - Abstract: Coal partial gasification experiments are carried out on a self-designed circulating fluidized bed (CFB) gasifier under CO₂O₂ atmosphere. The CFB gasifier system is mainly composed of a ceramic furnace, auger screw conveyor, gas supplier, gas-solid separation unit, temperature and pressure measuring system, and Distributed Control System (DCS). The experiments are conducted at temperatures between 800 and 930 °C. The coal with particle size of 0.45–0.9 mm is selected for experiments. Mixture of CO₂ and O₂ is adopted as reactant gas. The oxygen-coal ratio varies from 0.38 to 0.8. The results show that as oxygen-coal ratio increases, the concentration of CO + H₂ first goes up and then declines. When the oxygen-coal ratio is 0.57, the concentration of CO + H₂ reaches the maximum value. To a certain extent, the higher oxygen-coal ratio results in better gas composition. The volume fraction of combustible gas and the lower calorific value reach ∼40% and 5.58 MJ/Nm³. To explore the variety of char structure features, the Scanning Electron Microscope (SEM) and Raman Spectrometer are adopted. The results show that the pores of char are getting opened as the reactant gas enters the inside of char and new O-containing functional group and more aromatic rings are generated. It makes the chars become more disordered.