Improving the efficency of pellet hot water boilers

The article considers the design features and operating modes of KVM-4.0D hot water boilers, analyzes their technical, economic and environmental indicators when changing the heat output in the range from 0.32 to 1.15 of the nominal value. The fractional composition of fuels, ash and slag has been investigated. Durability of the pellets have been tested as well as its change when the granules pass through the fuel supply system. The content of combustible substances in ash and slag and the effect of underburning of combustible substances in various fractions of combustion residues on the carbon loss have been determined. Thermal analysis of wood pellets was carried out. The components of the heat balance have been determined. Recommendations for further improving the energy and environmental performance of hot water boilers are proposed, which create the basis for improving the designs of heat-generating plants operating on wood pellets. After constructive revision associated with the installation of an additional line for recirculation of exhaust flue gases under the grate, the KVm-4,0D boilers ensured efficient combustion of wood pellets with technical, economic and environmental indicators exceeding those of Austrian hot water boilers of the same capacity. Considering that the focal residues of these boilers contain a significant amount of CaO and a large amount of fine particles less than 45 microns in size, these dust particles have an increased health hazard for the boiler house operator. To maintain high technical, economic and environmental performance of the boilers, it is necessary to ensure periodic monitoring of the density of all elements of the gas path and the ash removal system, as well as regular cleaning of industrial premises. The studies carried out have shown that these boilers are not recommended for long-term use in operating modes with low load, since such modes are accompanied by increased values of carbon monoxide emission, and, consequently, heat losses with chemical incompleteness of combustion due to high air excess ratios.

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