A 2D dynamicmodel for a bubbling fluidized bed (BFB) combustor has been developed for simulating the coal and biomass cofiring\nprocess under 21% O2/79% CO2 atmosphere in a 6 kWth bubbling fluidized bed, coupled with the Euler-Euler two-phase flow\nmodel. The kinetic theory of binary granular mixtures is employed for the solid phase in order to map the effect of particle size and\ndensity. The distribution of temperature, volume fraction, velocity, gas species concentration, and reaction rates are studied with\nnumerical calculations. The simulated temperature distribution along the height of the combustor and outlet gas concentrations\nshow good agreement with experimental data, validating the accuracy and reliability of the developed cofiring simulation model.\nAs indicated in the results, there are two high temperature zones in the combustor, which separately exist at the fuel inlet and dilute\nphase. The reaction rates are related to the species concentration and temperature.The higher concentration and temperature lead\nto the larger reaction rates. It can be seen that all of the homogeneous reaction rates are larger at the fuel inlet region because of\nrich O2 and volatiles. High mass fraction of volatile gas is found at the fuel inlet, and the main reburning gas at the dilute phase is\nCH4.The mass fraction distribution of CO is related to the volume fraction of fuel which is due to the fact that the source of CO\nis not only from the devolatilization but also from the gasification. On the basis of this theoretical study, a better understanding of\nflow and combustion characteristics in biomass and coal cofiring under oxy-fuel atmospheres could be achieved.
Loading....