Numerical Simulation and Air Distribution Parameters Optimization for Pulverized Coal Burner of Aggregate Drying

doi:10.3901/JME.2024.20.289

Abstract

Abstract: Oil and gas are mostly used as fuel for aggregate drying. Compared with oil and gas, the pulverized coal is also suitable for aggregate drying as the operating costs is dramatically reduced. In order to improve the combustion efficiency of pulverized coal and reduce NO_Xemissions, the benign development of pulverized coal combustion behavior needed to be effectively controlled. So the grading air distribution was applied to the pulverized coal combustion system of aggregate drying. The LB2000 aggregate drying equipment was taken as a study case, and the numerical model of the pulverized coal combustion system for aggregate drying was established. The influence of graded air distribution parameters on the combustion efficiency and NO_Xemissions was investigated. A response surface model was proposed, the graded air distribution parameters were comprehensively optimized by means of non-dominated sorting genetic algorithm II (NSGA-II). The results indicated that the pulverized coal combustion can be promoted and the NO_X emission can be regulated when the air supply is increased properly. The highest temperature zone is cooled down and the temperature of back of the drying drum is rose with better aggregate drying effect and quality, and an anoxic environment is formed in local area of the combustion zone, which reduced the amount of NO_X production with the increase of over-fire air within limits. Appropriate air staging depth is in favor to slowing down the combustion of pulverized coal. In addition, the mixing effect of pulverized coal and air can be improved by secondary air, so as to the full combustion of pulverized coal can be promote. The value ranges of the graded air distribution parameters are achieved according to the combustion efficiency and emission characteristics, which excess air coefficient is 1.25～1.35, over-fire air rate is 0.6～0.7, air staging depth is 0.4～0.6. The excess air coefficient is 1.337 5, the over-fire air rate is 0.647 7, and the air staging depth is 0.599 9 through optimization.

Key words: pulverized coal combustion, graded air distribution, combustion efficiency, emission characteristics, aggregate drying

CLC Number:

TQ534

CHENG Haiying, LI Xuan, ZHANG Yong. Numerical Simulation and Air Distribution Parameters Optimization for Pulverized Coal Burner of Aggregate Drying[J]. Journal of Mechanical Engineering, 2024, 60(20): 289-299.

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