Pre-separation Characteristics Study Of The Economizer Hopper In A Pulverized Coal Fired Boiler

Recently, more and more attention were paid on environmental protection. A large number of emissions, including Nitrogen oxides, Sulfur oxides and fly ash, were produced during Coal-fired power stations operation. The power plants were the sources of particle pollution. The electrostatic precipitator (ESP) was widely used in power plant. But the ESP has low efficiency and needs more energy when it dealt with flue without precollection. In order to increase the separation efficiency and reduce the wear and of air preheater, one easy way is the precollection of fly ash before ESP by adding ash-hoppers downstream the economizer.To obtain higher separate efficiency with lower pressure loss, it is necessary to optimize the ash-hopper's structure to find reasonable arrangements for the baffles which were used to change the flow direction of flow gas in the flue. The results of system performance were obtained from the iso-thermal experiments and simulation. There were some advises mentioned for the iso-thermal model experiment, and the rationalization of the simulation result were verified by the iso-thermal experiments. The Euler similarity criterion was adopted in experiment, so the iso-thermal experiments could enter the second self-modeling region to be similar to the flow characteristics of prototype. In this case, less energy was needed for the power of experiment and less air from fans.The numerical simulation was carried out by the commercial CFD software, Fluent. It was found that the system structure, especially the baffles and the baffle arrangements, is important to the performance. The most suitable structure was found through simulation results including the velocity and pressure fields of gas phase, the pathlines of particles, the pressure drop and the separation efficiency. The diameter and the release location of particles had great influence to their pathlines. Particles far from the exit and with large diameter were easily trapped. The baffles could used to optimize the velocity field, decreasing the wear of flue from particles. The angles, arrangement, quantity of baffles were all important for the system performance. There were some laws for the system performance when they changed. Though the laws, the most valuable structure was picked quickly.