The Study Of The Thermal Performance And Design Method For An Oxy-fuel Boiler

Currently, the CO2emissions are mainly from the large coal-fired boilers in China. Itis significant to research and develop the Carbon Capture and Storage (CCS) technologyfor power generating industry. The oxy-fuel technology can not only capture efficientlyCO2existing in flue gas, but also reduce the NOxand dust emissions. It can realize the aimthat so called “Near Zero Emissions”, evently. However, the oxy-fuel combustion for CO2capture research and development is still on Laboratory-scale or pilot-scale plant, it isurgent to develop the commercial-scale oxy-fuel systems.In this study, four types of boiler are selected for calculation, including: themedium-pressure boiler (38.5t/h), high-pressure boiler (220t/h), super pressure boiler (695t/h) and the supercritical boiler (2019t/h). By the results of thermodynamic calculation onthe boilers, we can analyze and obtain the amplification rule of the oxy-fuel boiler.According to it, the design principle and methods of oxy-fuel boiler are extracted finally.Firstly, the thermodynamic calculations of four boilers has been conducted both on theair-firing and oxy-firing conditions. The calculation results show that the flue gas volumeand flow rate is reduced remarkable. Meanwhile the heat capacity of cross-section andvolumetric became smaller, the radiant heat transfer changes very little in furnace. We canfigure out the design method of building a new oxy-fuel boiler based on the analysis.Secondly, thermodynamic calculations has been carried out for the new oxy-fuel boiler.The results show that the flue gas flow rate and the hear transfer on respective surface isable to get the similar result in oxy-firing and air-firing conditions; the heat transfercoefficient on oxy-firing is higher than air-firing. All these turned out that design method isfeasible and correctly.Finally, base on the analysis of optimization process, the change rule of oxy-fuel boiler structure and heart transfer surface has been concluded. The results show that the flowsection area in oxy-fuel combustion boiler is reduced about21%than air-firing boiler. It’ssimilar to the reduction ratio of flue gas volume; the heat transfer surface is obviouslydecreased. With increasing furnace size, the he heat transfer surface reduction increases. Bymeans of the analysis, the design principle and methods of oxy-fuel boiler are extractedevently, it will provide foundation to the oxy-fuel boiler designing and application.