Abstract
The length and pattern of air–fuel mixing plays a significant role in the uniformity, flame temperature, and emission characteristics, which can lead to a superior product quality in a non-oxidizing direct fired burner for a cold-rolled steel plate furnace. In this study, a diffusion-flame-type burner and partially-premixed-type burner were experimentally investigated to understand their effects on flame shape, flame temperature, and exhaust gas characteristics. With this aim, fuel nozzle size, nozzle hole number, fuel injection angle, and mixing distance of fuel and air were varied during the experiments. Computational fluid dynamics simulations were also performed to investigate the air–fuel mixing state for a nozzle-mixed burner and a partially-premixed burner. The results show that the flame temperature of the partially-premixed burner increases by up to 26 °C on average compared to that of the nozzle-mixed burner. It is also shown that the mixing distance plays an important role in the flame temperature of the partially-premixed burner. In addition, the residual oxygen concentration and volume ratio of CO/CO2 in the flue gas of the partially-premixed burner exhibit lower concentrations compared to those of the diffusion flame burner.
Highlights
The heating method in this heat treatment process is mainly divided into an indirect heating method, whereby a radiant tube is used, and a direct heating method, which uses a direct firing flame
The main function of the non-oxidizing direct fired furnace used in the heat treatment process of the cold-rolled steel plate is to prevent the excessive oxidation of the surface of steel and heat it up to 700–760 ◦ C for steel moving at a constant line speed while maintaining the furnace temperature of 1100–1300 ◦ C
In terms of modeling and from a practical perspective, this study addresses the pressing need for the heat treatment industry to adopt air staging, air swirling, and plasma-assisted combustion in the radiant tube burner, which processes can ensure high heat recovery efficiency and low Premixed burners and nozzle-mixed burners have been generally used for the direct heating method
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Zadghaffari et al [6] investigated burner configuration to minimize pollutant emissions using numerical method They presented computational fluid dynamics model of a non-premixed burner and focused on the study of the angle of gas, which was injected through the burner tip to the combustion zone. Lee et al [12] performed the combustion characteristics of a porous media burner (PMB) with a large surface area for application in a non-oxidizing annealing furnace using a model furnace. In terms of modeling and from a practical perspective, this study addresses the pressing need for the heat treatment industry to adopt air staging, air swirling, and plasma-assisted combustion in the radiant tube burner, which processes can ensure high heat recovery efficiency and low NOx emissions. In this study, the effect of the nozzle-mixed burner and partially-premixed burner on air–fuel mixing, flame temperature, mixing with ambient gas, and exhaust gas were experimentally investigated
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