How to control and reduce the generation of CO2 has become an important focus in science and industry. In this work, a circulating fluidized coal gasifier is numerically simulated to optimally produce more hydrogen and reduce CO2 by carbonation of CaO powder simultaneously. The Eulerian-Lagrangian method was used to simulate the circulating fluidized bed reactor. The gas phase turbulence was described with Reynold Stress Model, the movement of the solid particles and the interactions between gas phase and solid particle were represented by Discrete Phase Model, Tturbulent-chemistry interaction is described by EDC(Eddy-Dissipation-Concept)model, which includes the detailed chemical reaction mechanism in turbulence. The reaction network including 9 reactions was established, and the parameters of apparent carbonation kinetics were determined by fitting against the available TGA carbonation experiment data. The flow field parameters such as gas temperature distributions, pressure distribution, the components distributions of gas phase, particle movement properties including particle trajectories, particle residue time and particle velocity, and carbon conversion and products composition distributions at different operating conditions were obtained. These simulated results are in good agreement with the experimental data, which provides indispensable micro-structure and interaction information for optimal design and operation of the coal gasification process. The effects of the factors such as temperature, pressure, gas velocity and the content of CaO in solid feed on the hydrogen and CO2 concentration in coal gasifier were presented. It can be found that the flow field parameters show a significant asymmetric distribution at the nozzle inlet. The temperature increases more rapidly with the inlet temperatureat increasing in the relative lower part of the reactor. The isomolar-fraction lines of CO and H2 are coincident with the isotherm lines; the region of higher temperature is responsible for the higher molar fractions of CO and H2. CO and H2. With the pressure increasing from 0.1MPa to 2MPa, the char conversion rate increases rapidly to 100%, while the CO2 molar fraction of CO2 increases gently at the exit of the reactor. The increase of the content of CaO in solid feed can substantially increase hydrogen production ratio and in-situ fixation of CO2 effectively.

Keywords: coal gasification, numerical simulation, CO2 removal, hydrogen production