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CONVERSION OF LOW AND MEDIUM POWER BOILERS FOR COMBUSTION OF SOLID FUEL BIOMASS

The paper analyzes the existing fleet and the possibilities of replacing anthracite and natural gas boilers of low and medium capacity and substantiates that the reconstruction with conversion to biomass is appropriate for boilers with a thermal capacity of more than 5 MW. The main problem is the reduction of heat perception of furnace screens and increase of heat removal to the convective pass due to the increased specific yield of biomass combustion products. Based on the analysis of changes in the nature of combustion processes and redistribution of heat exchange in the boiler, it was determined the criteria for the possibility of converting boilers from fossil fuels to biomass with maximum use of available equipment and the most acceptable fuel for this - agricultural pellets and wood waste. Technical solutions for the reconstruction of a boiler with a dense bed with a steam capacity of 20 t/h on anthracite (24 t/h on natural gas) have been developed and calculated with transfer to burning of granules of biomass and/or gas coal without change of dimensions of a fire chamber and without loss of thermal power due to compensation of the lowered heat absorption of a fire chamber by increase of a surface of a water economizer with corresponding decrease in an air heater. Technical solutions were used during the reconstruction of 4 boilers "Babcock-Wilcox" of Khorostkiv Sugar Plant. Co-combustion of biofuel pellets with coal is implemented in the range of components share from 0 to 100%. When burning granules, underburning in the fly ash is almost absent, ash deposits on convective surfaces are self-cleaning for several hours of work on gas coal. The solutions developed allowed to solve the problem of renovation of old boilers with the expansion of their fuel base and improvement of environmental performance through the use of biomass. Bibl. 18, Fig. 3, Tab. 4.