Pressurized oxy-fuel combustion performance of pulverized coal for CO2 capture

Pulverized coal combustion in pressurized oxy-fuel (or O-2/CO2) atmosphere is widely accepted as a clean technique for energy conversion with respect to the NOx emission reduction and CO2 capture. The combustion performance of two pulverized coals, including the ignition and burnout, char structure transformation, and ash formation, was investigated, and the effects of system pressure, oxygen concentration, and coal type were explored. Results showed that system pressure had positive effects on the combustion performance of DT coal and SH coal within a range. The best pressure in this work was 1 MPa. The increase of oxygen concentration was more effective for the ignition temperature reduction at elevated pressure. Increasing the pressure affected the release of carbon functional groups on char surface, especially the aromatic and aliphatic carbon, which was least at 1 MPa, indicating the lowest graphitization degree and ignition temperature. A pressurized condition also promoted fragmentation of coal during the devolatilization, and thus enlarged the available surface area for char reaction with O-2, leading to an earlier ignition. The SEM morphologies of ash generated at different pressures identified the enhanced formation of finer ash under pressurized conditions. Results are feasible for optimizing the pressurized oxy-fuel combustion in the future. (C) 2016 Elsevier Ltd. All rights reserved.