A Quantitative Method for Determining the Primary Air Ratio in Coal-Fired Power Plant
In a long-term time, the primary air ratio (PAR) is determined based on the empirical data in coal-fired power plants and lack of theory. With the TG-DSC experiment of three different rank coals, a new method is proposed for quantitatively determining the
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Abstract
In a long-term time, the primary air ratio (PAR) is determined based on the empirical data in coal-fired power plants and lack of theory. With the TG-DSC experiment of three different rank coals, a new method is proposed for quantitatively determining the PAR in coal-fired power plant in terms of the theory of intensive ignition at the initial stage of coal combustion, at which only the rate of heat released from coal oxidation is not less than that of heat loss in combustion system; the fuel is initially ignited (ignition temperature, Ti), until the heat flow is accelerated to the value of inflection point; i.e., the intensive ignition temperature of Tig by the combustion of active components; the chars are fully ignited, the corresponding conversion ratio is determined at temperature Tig, and PAR can be calculated. The results of TG-DSC test showed the conversion ratio at the intensive ignition temperature of JWY anthracite which is 22 %, higher than the volatile matter content (12.3 %) of parent coal; it is further stated that the homogeneous and heterogeneous ignition of anthracite simultaneously takes place; however, the conversion ratios of ZCY bituminous coal and SLH lignite at Tig were 24 and 43 %, respectively, and were close to or less than the volatile matter content of parent coals; it indicates that the ignition is attributed to parts of volatile matter burning homogeneously with air. The PAR calculated based on TG-DSC experiment data is in the range of the proposal value of handbook and close to the less value, but is slightly greater than that of coal-fired power plant for anthracite and bituminous coal combustion and has a more wider adjustable range for lignite combustion in initial stage for the requirement of controlling slagging and NOx production, so it provides a upper limit of PAR for the coal-fired boiler.
Keywords
TG-DSC
1
Primary air ratio
Introduction
In the past ten years, more than 80 % of Chinese electricity production comes from burning coal, biomass, nature gas, petroleum coke, and oil, among them, burning coal based, and this trend will continue in the coming decades. For the consideration of efficient and environmentally acceptable use B. Zhang F. Yue Y. Liu P. Fu (&) State Key Lab of Coal Combustion, Huazhong University of Science and Technology, Wu Han 430074, China e-mail: [email protected]
Ignition temperature
Coal combustion
Boiler
of coal, many efforts have being invested [1]. With the purpose of optimizing the combustion processes, many studies have been developed by research departments and industrial companies, such as air staging combustion, which is conducive to reduce the emission of pollutants and facilitate flame stability of coal combustion. Primary air velocity, which corresponds to the primary air ratio (PAR) under the condition of a certain operating burner, has an important influence on the ignition and burnout of pulverized coal [2] and the NOx formation especially for the combustion of high volatile coal [3]. The bulk airflow rat
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