| After desulfurized flue gas is discharged through high chimneys in coal-fired power plants,in order to solve the situation of "gypsum rain" due to the increase in flue gas humidity,it is necessary to increase the flue gas reheating system,which not only increases investment but also leads to complex systems and frequent failures.With the development of coal-fired power generation technology and the gradual improvement of environmental protection requirements,the adoption of smoke exhaust cooling tower technology in coal-fired power plants in northern China can eliminate the formation of "gypsum rain" and can also eliminate chimneys and their flue gas reheating systems and reduce the failure of environmental protection facilities.Savings on investment.The advantage of the exhaust cooling tower is that under normal environmental conditions,the use of huge heat in the tower to reheat the wet flue gas after combustion desulphurization of the boiler can obtain a higher lifting height than the use of chimney discharge.So that the flue gas in the atmosphere environment to obtain better diffusion effects.However,under extremely extreme environmental wind speed conditions,the discharge and diffusion conditions of flue gas through the cooling tower deteriorated,and the wind direction under the cooling tower formed a cavity area(ie,a negative pressure area).The concentration of pollutants near the ground in the cavity area exceeded the standard,causing environmental problems.In order to further study the influence of smoke discharged from smoke discharge cooling towers on the surrounding environment in coal-fired power plants,this paper has carried out wind tunnel experiment and model data analysis of smoke discharge cooling towers in a coal-fired power plant project,applying the theory of aerodynamics,fluid mechanics and computer simulation.The mechanism of flue gas diffusion was verified,the dynamics of flue gas discharge from smoke cooling towers were mastered,the size of the air direction cavity area under the smoke cooling tower and the concentration of smoke pollutants on the ground were determined,and the distance of the air environment protection zone was delineated.It provides a reliable basis for the environmental impact evaluation of coal fired power plants using smoke cooling tower technology.This paper mainly carried out the following research and achieved some important results:1.Through the analysis of the formation process of smoke diffusion and the analysis of the flow distribution characteristics of the exhaust cooling tower cavity area,it is verified that the formation mechanism of the exhaust cooling tower cavity area is:steady current-relatively fixed vortex-alternating vortex street-alternating vortex-cavity area-turbulent flow.2.Based on the theories of aerodynamics,fluid mechanics and computer simulation,an experimental platform for environmental wind tunnel of smoke exhaust cooling tower in a coal-fired power plant was built.According to the theoretical requirements such as similar geometry,similar boundary conditions,and similar motion of two kinds of flows,Hedongli's similarity is used to determine the model ratio of wind tunnel simulation experiments.Based on the comparison and analysis of wind tunnels of various forms,the experimental platform is reasonably built,and the environmental wind tunnel of the direct-suction double experimental section suitable for the atmospheric pollution experiment simulation is optimized,which is used in this experiment and is improved appropriately.It is determined that the basic parameters of this experimental wind tunnel are:3.5 m wide,2.2 m high and 20 m long.The wind speed adjustment range is 0.1 to 6.4 m/s.The measurement instrument is optimized to ensure the accuracy and reliability of the test parameters.3.The wind tunnel experiment and model data of smoke exhaust cooling tower were carried out,the smoke diffusion and cavitation formation mechanism were verified,and the law of smoke diffusion concentration and smoke distance between smoke cooling tower and smoke tower was obtained.Through the experimental analysis and research,with the gradual increase of environmental wind speed,the negative pressure reflux phenomenon occurred on the back surface of the exhaust cooling tower,and the floating dead zone was partially formed.The smoke plume appeared in the downward clamping state,which verified the existence of the cooling tower cavity area.The flue gas concentration in the cavitation area and the lower wind direction has obvious boundary effect within the distance of the tower edge,and gradually weakens until it disappears with the increase of the distance.Under the vertical windward condition of the two towers,the highest concentration and the low temperature difference in summer are the factors that are most detrimental to the diffusion of smoke.4.The atmospheric environmental protection distance in the vicinity of the smoke tower was studied,and the atmospheric environmental protection distance in the vicinity of the smoke tower was determined through the analysis of the size and smoke concentration of the cavity area under different wind direction conditions.This experiment measured two towers of vertical windward wind direction(NE wind direction),two towers of lateral windward wind direction(SE wind direction),two towers of the center connection and wind direction into 45 degrees(S wind direction)three types of wind down cavity area size.The concentration of S02,N02,and PM10 at different distances from the lower wind direction under different wind speeds was simulated in the most unfavorable working conditions-the minimum temperature difference between the flue gas temperature and the ambient temperature in summer,and the smoke concentration was superimposed by the size of the cavity area and the smoke concentration analysis.The final determination of the atmospheric protection scope of the project:is to use the cooling tower as the center,a radius of 415m to draw a circle,and a height of 1500m within the close range area. |
PDF Full Text Request