Numerical Simulation Of A 75t/h Circulationfluidized Bed Boiler Of Power Plant

The merits of circulation fluidized bed boiler have been discussed in many papers and literatures. Circulation fluidized bed has already been used in many field such as energy, environment etc. Numerical simulation is a very powerful method assistant to the test method in research of multiphase flow so basic theory of numerical simulation , the motive and possibility of simulation to a 75t/h circulation fluidized bed boiler in combustion characteristic were introduced firstly.Secondly ,the model of this numerical simulation is expatiated .This simulation is based on a structured mesh with boundary fitted coordinates, 3D steady numerical approach is used, SIMPLE method is used in (solving N-S equations) flow field prediction; RNG k- e model is used as closure of turbulent Reynolds equations. Lagrangian particle trajectory is traced,.During travelling through gas and interacting with gas, coal particles devolatilize and undergo char combustion, creating a source of fuel for reaction in gas phase, where two-competing-rates devolatilization model and kinetics/diffusion-limited char combustion model are used.PI model is employed to simulate radiation heat transfer. Species and chemical reactions are modeled using the mixture-fraction/PDF approach and the full equilibrium chemistry, where the turbulence chemistry interaction is modeled using a double-delta probability density function(PDF). NOx, including thermal NOx and fuel NOx, are post-processed from combustion. FLUENT6.0 is used in total simulation.Last ,The paper shows the results of numerical simulation and analyse it. The results showed pay special attention to the following points :the boiler furnace temperature distributions; oxygen species concentrations,carbon monoxide concentrations,carbon dioxide species concentrations; particle track; Nox(NO) emission. Further more the discussion is made in following tasks: the speed range of the first air and second air and which ratio should be controlled; the fitting volume and fitting particle diameter of feed carbon; controlling the ash volume of extern heatresults indicates this simulation is pretty reasonable and thus the conclusions can be used to guide the design and operation of circulation fluidized bed boiler similar.