Numerical Simulation Of Flow And Combustion Pollutants Formation In MSW Fluidized Bed Incinerator

With the development of economic and the living standard of the people, more and more municipals solid wastes will result in the environmental, social and ecological problems and great environmental pressure on the sustainable development of the society. For the advantages of incineration on the volume reduction, resource utilization and disposal in a sound manner other than the landfill or compost, incineration technology has got widely application in developed countries, especially for the technology of fluidized bed incinerator for its advantages of compact structure, high efficiency of combustion and low pollutants emission.Base on the over-review on the multiphase flow on the gas solid fluidized bed, numerical simulation of the bubbling fluidize bed, circulating fluidized bed and fluidize bed with pipe distributor were carried out using Euler-Euler two fluid model. The simulation results show that the drag force model and restitution coefficient show more effects on the simulation results. Comparisons of simulation results were presented under different cases including the simulation of two and three dimensions. The numerical results of circulating fluidized bed using Ergun drag force model agree well with the experimental data, together with the annular-core structure of radial distribution of particles. Based on the kinetic theory of granular flow and PC-SIMPLE algorithm, the gas-solid flow hydrodynamic characteristics of fluidized bed with pipe distributor were obtained, including the bubble formation, growth and disappearance process in different cases. The effect of the orifice velocity and the horizontal pitch of the pipes on the fluidization quality were also discussed. The numerical simulation results show that such new type fluidized bed partly shares the same hydrodynamics of the ICFB (internally circulating fluidized bed), the initial bubbles are almost symmetric and the adjacent bubbles will merge with the time increasing. Bad fluidization quality may occur with decreasing the orifice velocity or increasing the horizontal pitch of the pipes in the middle dense zone of the fluidized bed and the critical ratio of the dimension between the two pipes with the pipe diameter was supposed to be 0.25. The numerical simulation of the two rows of pipe air distributor show that the air supply have more effects on the fluidization between the zone of the two rows of the pipes. In addition, segregation phenomena was obtained through the simulation of the binary mixtures of two types of particle.According to the elementary mechanisms of nitrogen oxide formation, its formation characteristics in different combustion condition were presented using chemical reaction kinetic in this paper. The investigation results show that the prediction data using GRI-Mech2.11 mechanism are more precise than GRI-Mech3.0. With the increase of strain rate and decrease of the combustion equivalent ratio, the ignition point of methane occurred ahead and the NO mole fraction of the former got decreased, but no obvious change with the latter. Kinetic simulation of the NO formation under different cases was presented, including the effects of the bed temperature, excess air HCN content. The results agree well with the trends of the experiment.Experiment of HC1 emission characteristics was carried out in a lab scale fluidized bed, including the effect of the bed temperature, MSW percentage on the HC1 emission and the inhibition effect of HC1 on the NO and SO₂ emission. According to the kinetic simulation results of the pollutants interaction in the flue gas, HC1 has the inhibition effects on the oxidation of CO and CO. With the incensement of NO...