Streszczenie: Waste heat recovery technologies to remove heat and harmful pollution from exhaust gas-vapor mixtures re-main a general trend in enhancing the efficiency of power plants. The exhaust gases from combustion engines when water-fuel emulsion (WFE) combustion contain a large amount of solid particles, deposition of which on the heating surfaces of the exhaust gas boilers (EGB) can degrade their heat transfer performance and shorten the service life. The processes of pollution deposition from exhaust gases on the economizer condensing heat ex-change surface (CHES) of the EGB were studied, and their effect on the CHES heat and mass transfer character-istics was assessed. It is found that increasing the water content in the WFE to 30% enhances the intensity of acid mass transfer due to decreasing the low-temperature corrosion rate with reaching the maximum-intensity at wall temperatures of 110…120 °C against 140…150 °C in conventional practice, which allows deeper exhaust heat utilization and increasing boiler heat productivity by about 30%. At a water content of 30% the sulfuric ac-id concentration was 57%, which confirms the hypothesis about the passage of the nitrous mechanism of sulfuric acid formation in the condensate on CHES. The optimized CHES cleaning periodicity values corresponding to the smallest fouling coefficient and the highest heat transfer were determined. The correlations for determining the fouling, heat transfer and thermal efficiency coefficients for the CHES of the EGB when WFE combustion are provided. They are helpful for designing the economizer CHES of EGB.
Abstract: Waste heat recovery technologies to remove heat and harmful pollution from exhaust gas-vapor mixtures re-main a general trend in enhancing the efficiency of power plants. The exhaust gases from combustion engines when water-fuel emulsion (WFE) combustion contain a large amount of solid particles, deposition of which on the heating surfaces of the exhaust gas boilers (EGB) can degrade their heat transfer performance and shorten the service life. The processes of pollution deposition from exhaust gases on the economizer condensing heat ex-change surface (CHES) of the EGB were studied, and their effect on the CHES heat and mass transfer character-istics was assessed. It is found that increasing the water content in the WFE to 30% enhances the intensity of acid mass transfer due to decreasing the low-temperature corrosion rate with reaching the maximum-intensity at wall temperatures of 110…120 °C against 140…150 °C in conventional practice, which allows deeper exhaust heat utilization and increasing boiler heat productivity by about 30%. At a water content of 30% the sulfuric ac-id concentration was 57%, which confirms the hypothesis about the passage of the nitrous mechanism of sulfuric acid formation in the condensate on CHES. The optimized CHES cleaning periodicity values corresponding to the smallest fouling coefficient and the highest heat transfer were determined. The correlations for determining the fouling, heat transfer and thermal efficiency coefficients for the CHES of the EGB when WFE combustion are provided. They are helpful for designing the economizer CHES of EGB.
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