Study Of Oxygen-enhanced Combustion Of Low Volatile Coal

There are a lot of low volatile coal such as lean coal and anthracite coal in our country. The combustion of low volatile coal in power station has a large proportion in China's existing coal units. During the start,stop and low load operation process, it is always required to inject lots of light diesel oil to provide heat and support combustion, which results in a large number of fuel consumption. The fuel consumption will be higher when the boilers burn low volatile pulverized coal. Oxygen-enriched environment at the outlet of the burner can be achieved by using the oxygen-enhanced combustion technology, which can reduce the ignition temperature of the pulverized coal, make the coal fire as soon as possible, strengthen and stabilize combustion. Besides, this technology also can reduce fuel consumption during the start,stop and low load operation process, so that the fuel consumption is reduced. This paper makes the experimental studies and the numerical simulation studies on the oxygen-enhanced technology.On the basis of laboratory equipment, this paper took oxygen-enhanced transformation of the bluff body burner and took model experiment on the cold test bench. Numerical simulation using the same working conditions of the model experiment was carried out. The results of both model experiment and numerical simulation indicated that oxygen-enhanced transformation had not changed the flow field structure of the burner, and the low velocity flow field became longer with the increasing of oxygen concentration, which is better for the ignition of coal. And then, for the 200 MW anthracite burner, hot state numerically simulate was carried out under different primary air fractions(15, 20 and 25 %) and a certain air-fuel ratio, and changing the increasing-oxygen concentration(not increasing, 40, 60, 80 and 100 %). The outlet temperature field of the burner and the concentration distribution of NOx were investigated. The results showed that oxygen-enhanced combustion technology can increase the combustion temperature of low volatile pulverized coal to accelerate the reaction rate,which is great promotion for low volatile pulverized coal to combustion in advance and full combustion. Oxygen concentration of oxygen-enhanced combustion should be controlled below 60%. Comprehensive comparison, each combustion parameters of the 9th working condition(combustion temperature, high temperature zone of distance from the bluff body, NOX concentration) is the most reasonable one among the 11 working conditions studied. The simulation results had a very good guidance function to the practical of oxygen-enhanced combustion process of low volatile coal.On the basis of the above research, hot state numerical simulation was carried out on the 200 MW tangentially-fired boiler under 100% and 75% load respectively with the oxygen-enhanced combustion technology and without the technology. The results obtained that, with the oxygen-enhanced combustion technology, the area of high temperature zone in the main combustion zone of the furnace was increased, the efficiency of the boiler was improved, the carbon content in fly ash was reduced, the outlet temperature was raised, and won't lead the increase of NOX emissions. In summary, oxygen-enhanced combustion technology is beneficial to boiler combustion.