Thermodynamic Calculation And Optimization Research Of Combustion Gas Component On Oxy-coal Fired Boiler

Currently oxy-fuel technology is gradually developed, the scope of itsapplication is expanding, the remould of existing coal-fired boiler appliedoxy-fuel technology has been more and more concerned. Thermalcalculation is the fundamental basis of boiler design. Under oxy-fuelcombustion process, the recycled flue gas and the oxygen concentrationof combustion gas will cause the changes in the components of flue gas,the enthalpy of flue gas and the heat transfer coefficient. These changeswill have important impact on the thermodynamic calculation and thearrangement of the heating surfaces in oxygen-enriched coal-fired boiler.In this sense, investigation on oxygen-enriched coal-fired boiler thermalcalculation process and the relationship between the layout of heatingsurface and the change of oxygen concentration in combustion gas is ofgreat significance for the practice and application of oxygen-enrichedcoal-fired boiler.On the basis of a supercritical600MW coal-fired boiler, in accordance with the characteristics of the process of the flue gasrecirculation under oxy-fuel combustion, a calculation model ofwas applied, some key parameters about the combustion products wasdetailed calculated. Variation of these related parameters at differentmode of flue gas recirculation and air leakage coefficient was obtained.After establishing a stable flue gas recirculation, combining with thestandard of conventional coal-fired boiler thermal calculation and theimprovement of some key parameters in the critieria used foroxygen-enriched coal-fired boiler, a suitable method was proposed for theoxygen-enriched coal-fired boiler. The new thermal calculation methodwas used for the analysis, which focus on the relationship between theheating surface layout and the change of oxygen concentration incombustion gas. The aim is to provide guidance to the design ofoxygen-enriched coal-fired boiler for power plant.Analyzed from the calculation results, the volume of recycled flue gas,the components of nitrogen and oxygen in the combustion productsincreases with increasing air leakage coefficient, while the carbon dioxideand water vapor decreases with air leakage coefficient. The portion ofnitrogen and oxygen was mainly affected by the impact of the air leakagecoefficient, the portion of carbon dioxide and water vapor was mainlyinfluenced by the mode of fuel gas recirculation. Compared with the conventional boiler, the heat transfer coefficient increases, while the heattransfer area decreases, in accord with economic operation indicators ofoxygen-enriched coal-fired boiler. In order to keep the same furnace size,The recommended oxygen concentration for dry flue gas recirculation isaround26%and for wet flue gas recirculation is around28%.