Flow Field Characteristics Of Wet Stack And Optimization Of Inlet Structure

Coal- generating electricity is the major power generation method in china. Combustion of coal with sulfur in organic as well as inorganic form, leads to high emission of sulfur dioxide,which is the main component causing air pollution and acid rain. Therefore, flue gas desulfurization(FGD) is essential. Limestone-gypsum wet flue gas desulfurization(WFGD) is widely used in coal-firing units because of its high desulfurization efficiency, mature technology and low operating cost. Considering corrosion and plugging problems, most of power plant uninstall the gas heat exchanger devices(GGH). Wet stack emission without GGH will reduce the temperature and lifting height of the flue gas, which lead to the phenomenon of “gypsum rain”. Gypsum rain has a negative impact not only on the environment but also on human life.Currently, most of studies on gypsum rain are concentrated on optimization of flow field in spray tower and improving the efficiency of mist eliminator. The researches on optimization of stack structure to reduce gypsum droplets emission are very few. In this paper, the Euler-Lagrange method is applied to study the gas–liquid two-phase flow in chimney. The main achievements made in this paper are as follows:(1) Physical and mathematical model of original chimney is built and solved numerically. Flow field of flue gas was analyzed under different mass flow of flue gas. The influence of mass flow on gypsum droplets adsorption has been investigated. The relationship between flue gas flow field and gypsum droplets adsorption has been studied.(2) The scale of chimney is huge,and number of grid is very large. Computers in college fail to meet the requirements of calculation. The simplified model was proposed and proved to be useful by compared with flow field of original chimney.(3) Staggered inlets model was proposed and proved to be beneficial for formation of single large whirlpool in stack. With the increase in staggered distance of inlet, gypsum droplets adsorption ratio is increased, but the flow resistance increased first, then decreased.(4) The effect of baffle plate's height and angle on gypsum droplets adsorption was investigated. The results show that reducing the height of baffle plate has a significantly effect on gypsum droplets adsorption, but the angle of baffle plate doesn't. With the decrease of height of baffle plate, flue gas distributed uniformly, gypsum droplets adsorption ratio and flow resistance is increased.