Abstract
This paper presents new results of computational experiments on the implementation of Overfire Air (OFA) technologies using an example of a combustion chamber of the BKZ-75 boiler of the Shakhtinskaya power plant (Shakhtinsk, Kazakhstan) burning high-ash Karaganda coal. The effect of mass air flow through special nozzles located above the burner level on the flow aerodynamics, temperature fields, concentration fields of carbon monoxide CO and nitrogen NO over the entire volume of the combustion chamber was studied. The studied characteristics were compared for various percentages of supplying additional air through OFA injectors: OFA is 0% (basic version), 10% and 18 %. It was shown that the installation of OFA injectors leads to a change in the field of the total velocity vector, temperature, and concentrations of carbon oxides and nitrogen. An increase in the percentage of air supplied through OFA injectors to 18% leads to a decrease in the concentrations of carbon monoxide CO by about 36% and nitrogen oxide NO by 25% compared with the base case. The obtained results will optimize the process of burning pulverized fuel in the combustion chamber of the BKZ-75 boiler, increase the efficiency of fuel burnout, reduce harmful emissions and introduce OFAtechnology at other coal-burning thermal power plants.
Highlights
In most economically developed countries of the world, as in Kazakhstan, a significant amount of thermal and electric energy is generated at thermal power plants (TPPs) burning organic fuel
An analysis of the figures shows that for these two investigated percentages of air supply through Overfire Air (OFA) nozzles, the torch core is located in the centre of the combustion chamber and is determined by the region of the collision of flows from the burners
This is due to the fact that with the OFA, the area around the burners is depleted in oxygen, which leads to a decrease in the coefficient of excess air
Summary
In most economically developed countries of the world, as in Kazakhstan, a significant amount of thermal and electric energy is generated at thermal power plants (TPPs) burning organic fuel. The share of emissions from sources of the energy complex of Kazakhstan with its high dependence on coal as the main source of energy is 43.7 % of all emissions of pollutants into the air in Central Asia. For this purpose, the development and implementation of environmentally friendly technologies for the combustion of solid fuels in the furnaces of boilers of Kazakhstan TPPs are relevant [16–20]
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