The Research About Xi’an Concentrated Heating Flue Gas Emission And Diffusion

In recent years, the city’s central heating business is developing at an unprecedented rate,including the scattered coal-fired boilers being replced by the construction of thermal powerplants and large regional boiler rooms. Since central heating needs large coal-fired heat source,compared with the the dispersed small heating coal-fired boiler in the same heat supply,central heating will reduce the emission of flue gas pollutants and the air pollution of the city.But we are facing another problem that, with the expansion of the city, while the heatingcapacity increases, the corresponding smoke extraction volume will increase. What this paperis exploring is that how the development of cenral heating impacts the atmosphericenvironment of the city and how to coordinate the development of central heating andatmospheric environment.There are a certain amount of SO₂, CO₂, NO_x, soot and other pollutants in the flue gas,so this article mainly studies the emissions and diffusion of major pollutants such as SO₂, NO_x,etc.The SO₂diffusion characteristic of a chimney in large space is been calculated bymulti-component flow model, so the impaction of the size of the wind speed on the floormaximum concentration and distance can be obtained by this numerical analysis method. Thesame numerical analysis method is used to simulate atmospheric diffusion of major pollutantssuch as NO_xand SO₂for the flue gas emission of the13heat stations in Xi’an the beltwaywithin the region. The dispersion characteristic of the multi-point pollutants is analyzed, andthe situation that may aggravate the pollution being caused by the flue gas superposition ofmulti-point sources is studied on this basis. The results show that the degree of dispersion ofpollutants is very low when the wind speed is smaller, and when the wind speed is greater, thepollutant concentration will diffuse faster with the air diffusion, which will make lessenvironmental pollution of the ground. Because multiple chimneys smoke at the same time,there will be superposition of flue gas from multiple chimneys when flue gas transfers underthe direction of the wind, and the pollutant concentration of superposition place is higher thanelsewhere. The smaller the wind speed, the higher the pollutant concentration of superpositionplace. In addition, there is a direct relationship between diffusion superposition of the flue gas and arrange layout of the chimney. When the arrangement of chimneys is parallel to thedirection of wind, the smaller the chimneys’ distance, the higher the concentration of thesuperimposed region. When the arrangement of chimneys is vertical to the direction of thewind, the smaller the chimneys’ distance, the larger the superimposed region.In this paper, the development of Xi’an central heating in recent years for theimprovement of the urban atmospheric environment is analyzed, and the first time this paperpresents that the whole field of Numerical Analysis can be used to analyze the atmosphericdispersion characteristics of the multi-point exhaust NO_xand SO₂of the urban central heating.The diffusion law of different heights and different wind and the situation that may aggravatethe pollution being caused by the flue gas superposition of multiple chimneys are also studiedin this paper. The purpose of this paper is to provide the theory help for the coordination ofurban central heating and atmospheric environment, and the sustainable development.