Calculation And Analysis Of Flue Gas Moisture Content And Research On The Characteristics Of Wet Emission In Coal Fired Power Plant

High moisture content of the flue gas from the boiler in coal-fired power plant is easy to result in corrosion of pipeline at the end of the boiler and equipments,and excessive moisture emission to the atmosphere may cause acid rain, haze problems. In this research, flue gas moisture content-related processes in coal-fired power plant are the main study object, for the source of the moisture content of the flue gas, flue gas moisture content quantification calculations, diffusion characteristics rear of the boiler flue gas moisture stack emissions were studied through data research, theoretical analysis and numerical simulation analysis method. The main work is as follows:(1)Theoretical calculation and analysis of moisture content balance of the boiler combustion system in coal-fired power plant. Establish a basic model of moisture content calculation of boiler combustion system through exploring the sources of moisture content of wet flue gas in coal-fired boiler system. The calculated method of moisture content of coal-fired boiler system is derived from the basic principles of thermodynamics and mass balance principle. It is found that burning less moisture content coal can reduce the moisture content of wet flue gas through comparing the result of moisture content of actual operating parameters of boiler combustion system with different coal.(2) Theoretical calculation and analysis of moisture content balance of the wet flue gas desulfurization process. Establish a basic model of moisture content calculation of wet desulfurization system. According to the basic principle of thermodynamics and the principle of conservation of materials, the calculation method of wet flue gas desulfurization process is given. Using this method to calculate and analyze the actual running data of 6 different capacity units, the main source of the wet weight of the flue gas emissions is the wet desulphurization process.(3) Theoretical calculation and analysis of the amount of water vapor condensation to the environment. The calculated method of moisture content of wet flue gas condensation in the chimney and emissions into the environment is derived from the basic principles of thermodynamics and mass balance principle. Use this method to calculate the amount of the wet environment emissions for a 600 MW coal-fired boiler flue gas unit in the spring, summer, autumn and winter four seasons. Based on the results of the analysis, the results show that: More than 80% of the wet saturated moisture content in the flue gas will be emitted into the atmosphere, the relationship of how much water vapor discharge into the environment in different seasons is winter> spring> autumn> summer. The moisture content emission to the environment will make environmental air humidity rises, a part of moisture content will form fog, in this case it will create favorable conditions for haze and acid rain, combined with the relationship of how many days haze occurs is winter> spring> autumn> summer. It is found that the moisture content of wet flue gas discharged into the environment contribute to the generation of haze.(4) Theoretical calculation and analysis of moisture content of boiler flue gas from coal-fired power plant in Shanghai area discharged into environment. According to the basic principles of thermodynamics, it is calculated that the moisture content from coal-fired power plant discharge into the atmosphere in Shanghai in one year, comparative analysis moisture content, the amount of soot, sulfur dioxide and nitrogen oxide emissions to the environment from 2006 to 2013 in Shanghai coal-fired power plant. The results showed that: the amount of smoke, sulfur dioxide, nitrogen oxide discharged from coal-fired power plants in Shanghai is decreasing year by year, but the amount of Wet emissions is increase. Combined with frequent fog and haze in recent years, it can be known that the amount of moisture in the flue gas emission from the coal fired power plant to the environment creates the condition of fog.(5) CFD numerical simulation of diffusion characteristics of wet flue gas stacks emissions. Using Gambit software build a model of the wet flue gas flow discharged from smokestack of coal-fired power plant, and simulate temperature and velocity field at different exhaust air speeds and different environmental air velocities using Fluent software. Analyzing the results of the simulation results showed that: flue gas velocity from stack emissions is constant, and within a certain range of ambient wind speed, the lateral transmission distance of the wet flue gas is proportional to the wind speeds, while the lifting height of the wet flue gas is inversely proportional to the ambient wind speeds;When the wind speed is relatively large, the wet flue gas emissions need to have enough momentum.