Dynamics Analysis Of The Behavior Of Fine Particulate Matter In Pulverized Coal Combustion

The absorbable particulate matters in the atmosphere have become a very important problem of pollution and many countries pay more and more intention on it. To know how the particulate matters generates and grows in the combustion process is the premise to control and prevent them. And one of the core problems is the dynamic analysis of behavior of fine particulate matter. However, condensation, Brownian coagulation and the diffusion of fine particles to the surface of the coarse particles are very important to the change of particle size distribution. To simulate and predict these processes is the hotspot of the aerosol studies nowadays. Here in this article we firstly summarize the study evolution and models about particle condensation, Brownian coagulation and the diffusion of fine particles to the surface of the coarse particles, then give a reasonable initial log-normal size distribution to the particle system, using moment method finally simulate these processes in the poly-disperse system with different initial condition: condensation alone, Brownian coagulation alone, condensation along with Brownian coagulation and the diffusion of fine particles to the surface of the coarse particles. Compared with the references, the results accord with the analytical solution well. Further more, the simulation results of condensation and Brownian coagulation shows obvious self-persevere character. According to the simulation results; and the initial poly-disperse character can change the coagulation rate in the early coagulation stage and the final particle diameter. The final particle system will still be poly disperse and obtain self-persevere state. So it can be conclude that when considering the model of particles in combustion, it is necessary to consider poly-disperse character. However when it comes to the particles in flues, we can assume it has enough time to obtain a self-persevere state. And to the particle system that has a typical bimodal size distribution, it shows that the diffusion process have strong effects on the final size, number, disperse character of the fine particles; and with the increase of portion of fine particles, the decay rate of number density increase obviously, so it can be indicated that the initial evaporation mass of mineral matter has little effect on the final quantity that fine particle emitted; when mass load is the same, the more the coarse particle size, the better the effect of diffusion process. Finally, the change of particle size distribution under conditions of different initial fine particle dispersed character when diffusion works alone was studied. It is show most parameters do not show the self-preserved character except particle number. It can be conclude, if it is particle volume and dispersed character that were mainly considered, when there is mass loss, the suppose of particle initial size distribution may not be appropriate. These study result, provide a base for the construction of mode for the transfer of ultra-fine particles during coal combustion and show that the initial poly-disperse character, the diffusion process and so on are all the principle factor that must be considered.