| In this paper,the flue gas desulphurisation process of coal-fired boilers is optimised to enhance the efficiency of flue gas desulphurisation;at the same time,the hot flue gas evaporation capacity of the desulphurisation unit is used to concentrate the magnesium sulphate solution in the desulphurisation slurry,thus achieving waste water emission reduction and reducing water recharge;the concentrated desulphurisation waste water is evaporated and crystallised to obtain a pure and qualified magnesium sulphate product in heptahydrate,which can achieve the purpose of emission reduction and efficiency enhancement.The main work includes:（1）The MgO wet desulphurisation tower was used as a research object to examine the design of the desulphurisation system in terms of prevention and scale prevention,to investigate the effects of SO2concentration,flue gas volume,p H and liquid to gas ratio on the desulphurisation efficiency,to determine the optimum desulphurisation conditions and to analyse the operation of the plant and its economic and social benefits.When SO2 concentration is 500-4000 mg/m3,p H is 5-7,and liquid-gas ratio is 4-6,the desulfurization efficiency can be maintained above 95%.（2）The impact of high humidity flue gas on the environment was analysed by testing and analysing high humidity flue gas through enthalpy and humidity diagrams;simulated flue gas emission tests were conducted to investigate the relationship between shading and average particle size and plume height,ambient temperature,ambient moisture content,flue gas temperature and flue gas superheat;analysis and comparison were carried out based on existing technologies at home and abroad to understand the characteristics and applicable features of each technology;according to the actual operating parameters,the heat exchange path of highly humid flue gas is optimised and the optimal process route is determined;the flue gas spray cooling condensation+MGGH technology route is adopted,the structure and parameters of the spray condensation system,MGGH heat exchanger,flue gas bundle condenser and flue gas bundle steam heater are studied,and the selection of pumps,fans and other ancillary equipment is carried out,forming a complete set of deep flue gas reduction technology for highly humid flue gas.（3）The catalytic oxidation method is used to efficiently oxidize the boiler magnesium flue gas desulfurization wastewater,and the optimal catalyst and optimal catalytic reaction process are selected.The hot flue gas evaporation capacity of the desulphurisation unit is used to concentrate the magnesium sulphate solution in the desulphurisation slurry to reduce the discharge of the wastewater.The purity of magnesium sulfate heptahydrate product is 99.16%,higher than the national standard HG-T2680-1995 industrial magnesium sulfate heptahydrate 98%of the first grade. |
