Raschepkin V. Processes of fine fly ash particles removal in the thermal power plants particulate control equipment

The thesis is devoted to searching the ways of a more efficient capturing of the fine fly ash particles in particulate control equipment of coal firing thermal power stations. Efficiency of the existing particulate control devices and physical mechanisms which contribute to better capturing of the fine fly ash particles in flue gas of coal firing thermal power stations are analysed. Efficiency of various mechanisms of particles and droplets coagulation has been assessed in the medium and parameters typical for the flue gas ducts of thermal power stations; the problem is solved of the fine dust particles settling at the evaporating droplets, to form solid agglomerates via Brownian diffusion mechanism. Evolution of the drop-size distribution function is studied for droplets evaporating in the atmosphere of the hot flue gas. An improved engineering model and analysis techniques are developed, of fly ash particles coagulation with droplets in Venturi tube, based on spatial variation of the collection efficiency of particles on an individual droplets, accounting spray water flow polydispersity and particle size distribution, which allows to define optimal droplets size and spray water flow rate at different modes of thermal power units operation. The mathematical model is developed of the fly ash particles precharging upstream the electrostatic precipitators. It is shown that installation of the additional corona electrodes at the gas distribution grate of electrostatic precipitators provides reduction of dust particles penetration through the electrostatic filters at excess speeds of flue gas, thus mitigating negative impact of corona discharge blockage at high concentrations of fly ash particles in flue gas, and adds to improvement of the overall efficiency of dust collection by the electrostatic precipitators.