The replacement of coal in medium to full-scale combined heat and power plants (CHP) using renewable biomass fuels can contribute to decrease the emitted amount of fossil carbon dioxide. Ash related problems limits the use of biomass as fuel in pulverized-fuel boilers. The use of additives such as coal fly ash or kaolin, acting as alkali capture sorbents, represents a promising approach to decrease the formation of combustion aerosols. Besides the aerosol reduction effect the chemical composition of the formed fine particles are influenced by the use of additives leading to less deposit build-up and corrosion in the boiler. As consequence the efficiency and availability of the power plant can be increased.
In this comparative study fine particles and fly ash were sampled at the reheater section of a wood fired full-scale power plant boiler using two different coal fly ash injection techniques. Therefore, two measurement campaigns were conducted at the tangentially-fired 800 MWth boiler at Avedøre Power Station Unit 2 (AVV2) in 2019 and 2022. The first measurement campaign was performed while the coal fly ash was injected with the over burner air into the boiler. During the second measurement campaign the coal fly ash was premixed with the wood pellets before milling.
The particle size distributions of the combustion aerosols were measured by an electrical low-pressure impactor (ELPI). The collected fine particles were analyzed for their chemical composition in a scanning electron microscope by energy dispersive X-ray spectroscopy (SEM/EDX). Additionally, the sampled fly ash and its composition was evaluated by XRF. The results showed an impact of the additive insertion technique on the aerosol quantitiy and chemical composition. The PM1 concentration during the premixed coal fly ash addition was with 105.8 mg/Nm3 almost double as high than with the additive insertion via the over burner air with 54.5 mg/Nm3 at 1.00 and 0.94 wt% additive load respectivley. At higher additive loads (2.42/2.50 wt%) the influence of the insertion mode is less pronounced.
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The replacement of coal in medium to full-scale combined heat and power plants (CHP) using renewable biomass fuels can contribute to decrease the emitted amount of fossil carbon dioxide. Ash related problems limits the use of biomass as fuel in pulverized-fuel boilers. The use of additives such as coal fly ash or kaolin, acting as alkali capture sorbents, represents a promising approach to decrease the formation of combustion aerosols. Besides the aerosol reduction effect the chemical compositio...
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