Prediction of NOx emission and aerodynamic parameter effects in jet precombustor burner
- Chinese Academy of Sciences, Beijing (China). Inst. of Engineering Thermophysics
Precombustion chamber is a development for NOx control technology. The precombustion chamber is a staged combustion technique capable of achieving low NOx emission and high combustion efficiency. EPA and International Flame Research Foundation have developed the precombustion chamber technique, and while the precombustion chamber has been demonstrated successfully in pilot and full scale tests, its large size and heavy refractory composition make it impractical for most boiler retrofit applications. A new precombustor burner using multiple opposed jets was developed in China. Such jets establish an excellent recirculation zone in the flowfield, different from that associated with swirl and bluff bodies. The burner has excellent combustion characteristics and flexibility in the choice of coal. The small size burner without a refractory wall may satisfy the requirements relating to retrofit of existing burners. This paper reports the potential of mathematical flame models to predict flow patterns, particles trajectories, gas concentration, temperature distribution, NOx emission and aerodynamic parameter effect in this new burner. The conservation equations for the turbulent gas field are derived for time-averaged dependent variables and k-e turbulence model is used. All the equations are solved using the SIMPLE algorithm. The particle trajectories are calculated by a Lagrangian solution of the momentum equations. And a stochastic particle tracking method is used. The global features of fuel-NO formation mechanism proposed by De Soete are included into the coal combustion model. The prediction of temperature and NO contours is basically coincident with experimental results. The particles trajectories illustrate that most particles travel within the recirculation zone and a have long residence time of 45--77ms. The distribution of volatile , CO and O{sub 2} concentrations have shown that devolatilization has been completed and partial char combustion occurs in the burner. The burner works under fuel-rich condition. Low NOx characteristics are predicted by distribution of HCN and NO concentration. Five aerodynamic parameters were studied in this paper. They are stoichiometry in primary zone and secondary zone, secondary air swirling number, the velocity ratio of opposed jets to the primary air and the location of multiple opposed jets ring. Their influence on NOx emission and combustion stability were evaluated. Based on these results, optimal operating conditions for jet precombustor burner can be recommended.
- OSTI ID:
- 349170
- Report Number(s):
- CONF-980985--; ISBN 1-890977-15-2
- Country of Publication:
- United States
- Language:
- English
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