Numerical Simulation On Low NO_x Emission Modification Of A 300MW Tangentially Coal-fired Boiler

Coal is China’s most important primary energy, however, coal combustion caused great damage to the environment, with the combustion process producing of dust, sulfur oxides and nitrogen oxides are the main source of air pollution in our country. Power plant boiler coal accounts for more than half of the total coal consumption, therefore, clean and efficient combustion of power plant boiler has become the top priority of China’s energy conservation and emissions reduction work. During the period of "10th five-year plan",we solved the problem of pulverized coal power plant boiler in low-load stable combustion; During the period of "11th five-year plan",we focused on solving the problem of flue gas desulfurization, ignition start-up with less oil; During the period of "12th five-year plan" will focus on solving the problem of NO_x emissions. There are many kinds of methods about reducing NO_x emission, including low NO_x combustion technology and catalytic reduction denitration technology, etc. In comprehensive consideration among modification cost, denitration efficiency and operating cost, low NO_x combustion technology is preliminary measures that plant should be adopted. In the context, the article used a 300 MW tangential lean coal boiler as the research object, using Fluent calculated the predicting the flow, heat transfer and combustion in the furnace before and after the modification of low nitrogen combustion.Firstly, this article simply introduces the development of low nitrogen combustion technology between domestic and abroad, concluded a possible plan for the boiler. Secondly, introduces the application of mathematical model in numerical calculation. Then, using Fluent calculated 100% load, 80% load and 60% load condition before and after reconstruction, study the flow field, the temperature field and the distribution of the group of breakout, confirmed the feasibility of retrofit scheme through analyzing the results of preliminary test and calculation. The studies show that the results of numerical calculation meets well with the preliminary performance test results. After the low NO_x combustion modification, the problems of low boiler combustion, high carbon concentration of fly ash and NO_x emission are improved significantly. Meanwhile the negative effects such as superheated steam temperature instability and de-superheating water flow have no obvious change. Finally, calculated on 300 MW load under different operating conditions, the results show that under different coal mill the boiler operate on stable situation; the waisting type air distribution is a better mode for reformed boiler running; excess air coefficient on 1.2, SOFA rate on18%, the boiler runs better.