# Effect of Furnace Structure on Burden Distribution and Gas Flow in Sinter Vertical Cooling Furnace
## 4 Results and Discussion
### Particle Size Distribution of Sinter Layer  
The sinter distribution in the two furnace types during the discharging process is shown in Figure 3. It can be seen that the burden distribution in the two furnace types after discharging for 900 s was similar to that at 800 s. After 100 s of continuous discharging, the burden distribution still had only a slight change. Therefore, it was considered that the burden in the furnace basically reached a stable state after discharging for 900 s. Next, the burden distribution characteristics in this state were further studied. Figure 4a shows the particle size distribution of the existing furnace type and Venturi furnace type when the sinter distribution was stable. It can be seen that for the two furnace types, most of the large particles were gathered in the middle area, and a certain ratio of large particles was also distributed in the sidewall area and the center area. Small particles were mainly concentrated in the sidewall-to-middle transition zone and the middle-to-center transition zone. The difference was that the number of large particles was less near the surface of the center vent cowl but more near the top of the edge vent cowl, in the Venturi furnace. This was because the width of the vertical part of the variable-diameter section of the Venturi furnace type was 1200 mm, which was greater than the 950 mm of the existing furnace type. This was equivalent to increasing the size of the discharge port, which  
Figure 2: Influence of gas velocity on pressure drop. was beneficial for reducing or even eliminating burden arching. In addition, the contraction angle of the contraction part of the variable-diameter section was 20\({}^{\circ}\), which meant the half top angle was 20\({}^{\circ}\), which was smaller than the 30\({}^{\circ}\) of the existing furnace type and was conducive to reducing the resistance of the inclined wall to the downward movement of the burden. The above phenomena all contributed to improving the downward movement of the burden in the furnace, thereby alleviating the accumulation of large particles near the center vent cowl. However, the top area of the edge vent cowl was far away from the material flow, making it difficult for large particles to merge into the mainstream area of the furnace cavity after entering this area. Therefore, with discharge, large particles were gradually enriched in this area. Figure 4: Distribution of particle size and \(D_{\text{nv}}\) in the existing furnace type and Venturi furnace type. (**a**) Particle size distribution. (**b**) \(D_{\text{nv}}\) distribution. Figure 3: Particle distribution during the discharging process. (**a**) Existing furnace type. (**b**) Venturi furnace type. The number-volume average diameter \(D_{\text{nv}}\) was introduced to quantitatively describe the particle size distribution in the furnace, and its calculation formula is as follows:  
\[D_{\text{nv}}=\sqrt[3]{\frac{\sum\limits_{i=1}^{n}d_{i}^{3}}{n}} \tag{6}\]  
\(D_{\text{nv}}\) is the average particle size of a certain number of sinter particles in a local area of the vertical cooling furnace, which reflects the segregation distribution of particle size. Figure 4b shows the \(D_{\text{nv}}\) distribution of the existing furnace type and the Venturi furnace type when the distribution of sinter was stable. For comparison, the upper limit was set to 0.04 m in the legend. It can be observed that when the Venturi furnace was adopted, first, the high \(D_{\text{nv}}\) channel (\(D_{\text{nv}}>0.033\) m) was no longer vertically distributed upward of the existing furnace but inclined in the variable-diameter section. This served to guide the cooling gas to change its flow direction and prevent it from escaping directly from the sidewall area and the center area.