Effect of Furnace Structure on Burden Distribution and Gas Flow in Sinter Vertical Cooling Furnace

Abstract

Sinter sensible heat recovery via a vertical cooling furnace is a new type of waste heat recovery process proposed based on coke dry quenching. However, the segregation of the burden in a vertical cooling furnace is serious, resulting in a large amount of cooling gas escaping from the short-circuit channel of the vertical cooling furnace, which seriously affects the uniform gas–solid heat transfer in the furnace. To improve the burden distribution and gas flow in such a furnace, this paper proposes a Venturi-type vertical cooling furnace. Based on the single silo of a vertical cooling furnace in Meishan Steel, a slot model was established, and the improvement effect of the Venturi furnace structure on the burden distribution and gas flow was studied using the DEM–CFD coupling method. The results show that compared with the existing furnace type, the inclined wall of the Venturi furnace changed the direction of the high Dnv (average diameter) channel from vertical to inclined-vertical and reduced the Dnv from >0.033 m to 0.028~0.03 m in the vertical part of the variable-diameter section, thus reducing the influence area of the high Dnv channel. The minimum and average values of the voidage in the contraction part of the variable-diameter section increased from 0.28 and 0.315 to 0.31 and 0.33, respectively, which caused the voidage distribution to change from U-shaped to W-shaped along the longitudinal direction while simultaneously reducing the longitudinal fluctuation range of the voidage from 0.28~0.39 to 0.298~0.37. The gas flow direction changed from vertical-upward to vertical-inclined-upward, which increased the gas–solid contact. The gas velocity increased significantly. In the vertical section, the average gas velocity was 2.34 m/s, which was 30.73% higher than the velocity of 1.79 m/s of the existing furnace type. In the variable-diameter section, the average gas velocity was 3.52 m/s, which was 72.55% higher than the velocity of 2.04 m/s of the existing furnace type. The high-speed gas channel basically only existed in the sidewall area and the center area of the vertical section, and the length was reduced from 3.11 m to 2.52 m, which reduced the influence area. In the variable-diameter section, the high-speed gas channel disappeared, and the uniformity of the gas velocity distribution was greatly improved. The gas pressure drop increased from 4140 Pa to 6410 Pa, with an increase of 54.83%. Therefore, when designing the Venturi furnace type, it was necessary to take into consideration the improvement in the gas velocity distribution and the increase in the pressure drop. The research results of this paper can provide guidance for the structure optimization of the sinter vertical cooling furnace.