氧燃烧方式下煤粉锅炉辐射传热特性分析

Thermodynamic Calculation of Radiative Heat Transfer in a Coal-fired Boiler under an Oxygen Combustion Mode

氧燃烧方式是一种能综合控制燃煤污染物排放的新型洁净燃烧技术,有关该方式下煤粉锅炉传热特性的研究对于老机组改造及新机组的重建具有非常重要的意义。以某电厂300MW燃煤锅炉为例,针对氧燃烧方式下燃烧介质的物理特性发生变化,通过引入循环率的概念,提出并发现了氧燃烧方式下必须考虑CO2、H2O、O2、H2的5种高温分解反应,在此基础上修正并发展了新的适用于氧燃烧方式下绝热火焰温度、锅炉辐射传热的计算方法。结果表明,修正后的辐射传热计算公式在氧燃烧方式下具有良好的通用性,在干、湿两种烟气循环方式下,绝热火焰温度随循环率的增加非线性降低;当干烟气、湿烟气的循环率分别在0.71和0.67附近时,获得与常规燃烧方式相同的烟气平均温度和辐射传热量。

Oxygen combustion mode is a new type of clean combustion technology for the comprehensive control of pollutant emis-sions from coal-combustion. The investigation of the heat transfer characteristics of a coal-fired boiler under the mode men-tioned earlier is of the utmost importance for the reconstruction of old thermal power plants and retrofitting of new ones. With a 300 MW coal-fired boiler in a power plant serving as an example,in the light of changes occurring to the physical properties of combustion media under the new combustion mode and through an introduction of the concept of circulating rate,proposed and identified were five pyrolysis reactions of CO2,H2O,O2 and H2 necessary to be taken into account un-der the combustion mode in question. On this basis,corrected and developed was a new method for calculating the adia-batic flame temperature and radiative heat transfer suitable for the combustion mode. The research results show that the corrected radiative heat transfer calculation formulae display a good universality under the oxygen combustion mode. Under the two types of dry and wet flue gas circulating mode,the adiabatic flame temperature decreases nonlinearly with an in-crease of the circulating rate. When the circulating rates of the dry and wet flue gases are around 0.71 and 0.67 respec-tively ,flue-gas average temperature and radiative heat-transfer rate are obtained,which are identical to those of a conven-tional combustion mode.