Numerical Simulation on Improving NO_x Reduction Efficiency of SNCR by Regulating the 3-D Temperature Field in a Furnace

Abstract:

The optimum temperature within the reagent injection zone is between 900 and 1150°C for the NO_X reduction by SNCR (selective non-catalytic reduction) in coal-fired utility boiler furnaces. As the load and the fuel property changes, the temperature within the reagent injection zone will bias from the optimum range, which will reduces significantly the de-NO_X efficiency, and consequently the applicability of SNCR technology. An idea to improve the NO_X reduction efficiency of SNCR by regulating the 3-D temperature field in a furnace is proposed in this paper. In order to study the new method, Computational fluid dynamics (CFD) model of a 200 MW multi-fuel tangentially fired boiler have been developed using Fluent 6.3.26 to investigate the three-fuel combustion system of coal, blast furnace gas (BFG), and coke oven gas (COG) with an eddy-dissipation model for simulating the gas-phase combustion, and to examine the NO_X reduction by SNCR using urea-water solution. The current CFD models have been validated by the experimental data obtained from the boiler for case study. The results show that, with the improved coal and air feed method, average residence time of coal particles increases 0.3s, burnout degree of pulverized coal increases 2%, the average temperature at the furnace nose decreases 61K from 1496K to 1435K, the NO emission at the exit (without SNCR) decreases 58 ppm from 528 to 470 ppm, the SNCR NO removal efficiency increases 10% from 36.1 to 46.1%. The numerical simulation results show that this combustion adjustment method based on 3-D temperature field reconstruction measuring system in a 200 MW multi-fuel tangentially fired utility boiler co-firing pulverized coal with BFG and COG is timely and effective to maintain the temperature of reagent injection zone at optimum temperature range and high NO_X removal efficiency of SNCR.

• Periodical: Advanced Materials Research (Volumes 807-809)
• Pages: 1505-1513
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.807-809.1505
• Online since: September 2013
• Authors: Amir A.B. Musa, Xiong Wei Zeng, Qing Yan Fang, Huai Chun Zhou
• Keywords: 3-Dimensional Temperature Field Technique, Multi-Fuel Combustion, NO_X Removal Efficiency, Numerical Simulation, Pulverized Coal, SNCR

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