Abstract
Using numerical methods, studies have been carried out to determine the effect of the introduction of the technology of two-stage combustion of high-ash Karaganda coal on the main characteristics of heat and mass transfer processes in the furnace of the BKZ-75 boiler at Shakhtinskaya TPP (Kazakhstan). Various regimes of supplying additional air into the combustion space, the volume of which varied from 0% (traditional basic version) to 30% of the total volume of air required for fuel combustion, have been investigated using 3D computer modeling methods. The performed computational experiments made it possible to obtain the distributions of the total velocity vector, temperature fields, concentration fields of carbon monoxide CO and nitrogen dioxide NO2 over the entire volume of the furnace and at the outlet from it. The introduction of the two-stage combustion technology made it possible to optimize the combustion of high-ash coal, since in this case there is an increase in the temperature in the torch core and a decrease in it at the outlet from the furnace, which has a significant effect on the chemical processes of the formation of combustion products. Based on the results obtained, it can be concluded that an increase in the percentage of air supplied through additional injectors to 18% leads to a decrease in the concentrations of carbon monoxide CO by about 36%, and nitrogen dioxide NO2 by 25% compared to the base case. A further increase in the volume of additional air leads to a deterioration in these indicators. The results obtained will make it possible to optimize the combustion of low-grade fuel in the furnace of the BKZ-75 boiler, increase the efficiency of fuel burnout, reduce harmful emissions into the atmosphere, and introduce a two-stage combustion technology at other coal-fired TPPs.
Highlights
Thermal power engineering is the leading branch of the global energy sector and plays a major role in the development of industry in many countries of the world, but it exceeds all other industries in terms of emissions of pollutants into the atmosphere
As a result of numerical experiments on the implementation of two-stage combustion of high-ash Karaganda coal, an aerodynamic flow pattern, temperature and concentration fields of carbon monoxide CO and nitrogen dioxide NO2 were obtained throughout the volume and at the outlet of the furnace of the BKZ-75 boiler
Overall, the flow pattern changes with additional air supply through the injectors, the aerodynamic characteristics of the combustion of a pulverized coal flame when two-stage combustion is introduced differ from the base case
Summary
Thermal power engineering is the leading branch of the global energy sector and plays a major role in the development of industry in many countries of the world, but it exceeds all other industries in terms of emissions of pollutants into the atmosphere (ash particles, sulfur dioxide, nitrogen and carbon oxides). The main fuel for Kazakh thermal power plants, which generate up to 85% of electricity, is low-grade coal with high ash content. Its use as the main energy source leads to problems in flame stabilization, slagging of convective heating surfaces, air pollution with fly ash, carbon and nitrogen oxides, hydrocarbons, and other combustion products. According to the latest data provided by the energy agency, Kazakhstan carries out 43.7% of emissions of pollutants into the atmospheric air of Central Asia, while CO2 emissions reached 12.8 tons per capita [2,3,4]
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