The Aggregation Simulation Of The Coal-fired Ultrafine Particulate

The coal-fired power plant is the most concentrated place where emit ultrafine particulate. The particulate aggregation technology is a effective method to gather ultrafine particulate dust. During the simulation of the particulate aggregation, the key job is to research the aggregation mechanism.The flow field of the turbulence coalescence device is simulated by FLUENT, and the results show that both big and small vortex chips are good at producing vortices, which could creat favorable conditions for the collisions and coalescence of the ultrafine particle. The simulation of the ultrafine particles trajectories which carried out at diffierent velocity, different size and charged or not, lead to a regular conclution:The faster the velocity is, the larger particles affected by the turbulence, and it is easier for the collisions and coalescence;large particles are less effected by the turbulence, while the small ones are effected more,so there is an apparent relative motion between them; the attractive force between particles increases as the partticles are charged, which make it easier for the collisions and coalescence.The main coalescence form in the device are:thermal coalescence, Coulomb coalescence, Brown coalescence and turbulence coalescence. Different coalescence models were calculated by coupling turbulent two-fluid model and population balance model, it turns out that turbulence coalescence is the most common form, Brown coalescence and thermal coalescence have smaller effect to the whole coalescence which could be eliminated; Coulomb coalescence has a significantly promote influence to the turbulence coalescence, therefore, particles should be pre-charged before the aggregation device to improve the effect of particle coalescence; thermal coalescence also has a significant effect to the coalescence in practical power station smoke temperature conditions, so it should be considered in power station.The ultrafine particles turbulent coalescence model framework was established in turbulent coalescence device, and the turbulence coalescence kernel function of inertial particles in full range was introduced. Coupled two-fluid model and particle population balance model by using the discrete method. Compared the calculated results with the experimental, illustrated that the rationality of the model and the feasibility of turbulence clustering effectively, and found that the coalescence effect improved as velocity increase.With the k-e and LES model, the3D flow field and the particle trajectories of the turbulence coalescence device is simulated. With the LES model, the flow field and the particle trajectories can be descripted detailed, and it is the superiority of the LES model.