Thermal and kinetic analysis of pressurized oxy-fuel combustion of pulverized coal: An interpretation of combustion mechanism

Abstract

• Pressurized oxy-fuel combustion performance of a typical bituminous coal is investigated. • The thermodynamics parameters and the most probabilistic kinetic model for the pressurized oxy-fuel combustion process are analyzed. • Elevating pressure can significantly improve the combustion performance of coal but the promotion effect gradually alleviates. • The ignition mechanism transforms from heterogeneous to homogeneous when the oxygen concentration reaches 50% at 0.5 MPa. Pressurized oxy-fuel combustion is one of the emerging clean technologies that can efficiently separate and recover CO 2 , and this combustion mechanism differs significantly from atmospheric air combustion. In this paper, the effects of reaction conditions such as total pressure, oxygen concentration and atmosphere gas composition on the combustion characteristics of Xinjiang Bostan coal were investigated using thermogravimetric methods. Furthermore, the thermodynamics parameters and the most probabilistic kinetic model for the pressurized oxy-fuel combustion process were explored. The results showed that the system pressure rising from 0.1 to 1 MPa could enhance the combustion process of coal; however, when the system pressure exceeds 0.5 MPa, the promoting effect is clearly weakened. The ignition mechanism transforms from heterogeneous to homogeneous when the oxygen concentration reaches 50% at 0.5 MPa. The mechanism functions of pressurized oxy-fuel combustion reaction varied as the reaction progressed. In addition, the rise of pressure and oxygen concentration correspond to the higher chemical reaction order of pulverized coal combustion and the pressure has less influence on the reaction mechanism than oxygen concentration. The results obtained may assist with the optimization of pressurized oxy-fuel combustion and guide its industrial applications.