Numerical studies of pulverized coal combustion in a tubular coal combustor with slanted oxygen jet

A pure two-fluid model for turbulent reacting gas-particle flow of coal particles is developed using a unified Eulerian treatment of both the gas and particle phases. The particles' history caused by mass transfer due to moisture evaporation, devolatilization and char reaction is described. Both velocity and temperature of the coal particles and the gas phase are predicted by solving the momentum and energy equations of the gas and particle phases, respectively. A k-s-kk two-phase turbulence model, EBU-Arrhenius turbulent combustion model and fourflux radiation heat transfer model are incorporated into a comprehensive model. The above comprehensive mathematical model is used to simulate two-dimensional gas-particle flows and pulverized coal combustion in a newly designed tubular oxygen-coal combustor of blast furnace. Predicted results of isothermal gas-particle flows are in good agreement with those obtained by measurements. The results also show that the proposed tubular oxygen-coal combustor prolongs the coal particle residence time and enhances the mixing of coal and oxygen. Results indicate that smaller coal particles of 10 mum. diameter are heated and devolatilized rapidly and have volatile combustion in the combustor, while larger coal particles of 40 and 70 mum in diameter are heated but not devolatilized, and combustion of such particles does not occur in the tubular combustor. (C) 2002 Elsevier Science Ltd. All rights reserved.