Numerical Simulation Of Combusting Coal-bed Methane In Coal-fired Boiler And Experimental Study On Combustion Stability

Calorific value of coal-bed methane that contains 30% methane concentration is lower. Greenhouse effect of methane is 20 times as carbon dioxide, damaging the ozone layer is 7 times more than carbon dioxide. Thus, for industrial development and utilization of coal-bed methane, not only can effectively alleviate the country's natural gas supply current and future conflicts, but also has good social and environmental benefits of coal mine production safety, saving resources and protecting the environment, have far-reaching significance. Escalating tensions in the energy situation, the low efficiency coal-fired industrial boilers burning coal bed methane in the vicinity of coal mines is a good change of energy saving measures to reduce emissions.Firstly, the article present the domestic and international use status of coal-bed methane, summarizes the use of several low concentration of coal-bed methane utilization obstacles; and also outlines the current situation of low calorific value gas combustion research, analysis of the low calorific value methane ignition performance, flame stability of various factors, which provided the theoretical basis for industrial applications for the coal fired boiler converting to burn low heat value coal-bed methane.Secondly, based on standard k-εturbulence model, finite rate model and the P-1 radiation heat transfer model, three-dimensional and PDF model, numerical simulation is conducted to analyze the in-boiler flow and combustion process after coal fired boiler furnace converted to burn low heat value coal-bed methane. Furnace flow field, temperature and species concentration distribution field and NOx emission characteristics are predicted. Simulation results show that: the absolute velocity along central axis of the burner exist a largest value. With the reduction of heat load, the peaks of temperature and velocity is gradually decreases, and the peaks move forward significantly. NOx formation is mainly in the rear of the furnace hot zone, and the maximum generating capacity along after the highest temperature region.Finally, the experiment of influence of geometrical parameters on flame stability characteristics of low calorific value coal-bed methane is carried on, which analysis the effects of the structure and installation location of swirling slice on combustion of low calorific value coal bed methane. The experimental study results show that: the best combustion condition is obtained when the location of N3 swirling slice away from the swirl burner 30mm, which has the maximum flame temperature, and not prone to occur burning off , blowout and other instability factors,...