Abstract
The paper presents verification of the mathematical model and the results of a numerical research of the influence of operating conditions on the formation of nitrogen oxides during the combustion of coal-water fuel in a promising low-capacity boiler. For the numerical simulation of turbulent flow of an incompressible liquid, we used the approach of Reynolds-averaged Navier-Stokes equations (RANS) taking into account the interfacial interactions. To solve the equation of thermal radiation transfer, the P1 approximation of spherical harmonics method was employed. The optical properties of gases were described based on the sum of gray gases model. To describe the motion of coal particles we used the method of Lagrange multipliers. The combustion process of coal-water fuel is considered in terms of the following consecutive steps: evaporation of the water part of the droplet, evaporation of moisture from the fuel, devolatilization and the combustion of the volatile components, and the combustion of the coke residue. Comparative analysis has shown that the selection of the operating conditions of the boiler has a significant influence on the oxygen concentration in combustion chamber and the temperature of the flue gases. This leads to significant differences in the formation of nitrogen oxides during the combustion of coal-water fuel.
Highlights
The improvement of technologies for the use of various fuels for the development of the energy sector is an important task
Comparative analysis has shown that the selection of the operating conditions of the boiler has a significant influence on the oxygen concentration in combustion chamber and the temperature of the flue gases
We investigated the effect of the amount and temperature of the supply air on the nitrogen oxides formation during the combustion of coal-water fuel
Summary
The improvement of technologies for the use of various fuels for the development of the energy sector is an important task. One of the ways to ensure large-scale involvement of coal, at least in low-capacity energy, can be the use of coal combustion technology in the form of a coal-water suspension (coal-water fuel, CWF) [1,2,3,4]. The technology of coal combustion in the form of CWF is one of the most environmentally friendly, economically viable and promising. It allows the use of low-calorie and lean coals and by-product coal for the preparation of CWF, as well as the creation of composite water-peat-coal, water-oil-coal and other fuel compositions on their basis. Mathematical description of coal-water fuel combustion includes a set of interrelated models describing turbulent gas motion, the transfer of thermal and radiant energy, combustion, movement of the coal particles, etc
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