# Effect of Furnace Structure on Burden Distribution and Gas Flow in Sinter Vertical Cooling Furnace
## 4 Results and Discussion
### Gas Velocity Distribution of Sinter Layer  
The distribution of the cooling gas in a vertical cooling furnace has an important influence on the adequacy of gas-solid heat transfer. Figure 6 shows the vector distribution of the cooling gas velocity in the two types of furnaces. In the existing furnace type, the cooling gas flow direction only changed significantly in the vent cowl section. After entering the rectangular section, the cooling gas almost always flowed upward along the vertical direction. Only when it was near the surface of the burden did the gas in the middle area gradually turn to the sidewall area and the center area with less resistance. When adopting the Venturi furnace type, the cooling gas flow first formed a vertical-outward-inclined flow direction in the original vent cowl section as the furnace cavity width gradually increased. Then, the cooling gas flowed into the expansion part of the variable-diameter section. The expansion part was actually a contraction structure for the cooling gas; therefore, the cooling gas near the wall also generated partial velocity of the transverse flow while flowing upward, making the gas flow direction become vertical-inward-inclined. When the cooling gas passed through the vertical part of the variable-diameter section and entered the contraction part (expanding for the gas), the gas flow direction was inclined again due to the expansion of the wall, forming a vertical-outward-inclined flow direction again. After entering the vertical section, the gas flow direction was the same as that in the existing furnace. By comparing the flow direction of the cooling gas in the two types of furnaces, it can be observed that the gas flow direction in the Venturi furnace was more complex. While the cooling gas moved vertically  
Figure 5: Voidage distribution of sinter layer. (**a**) Voidage distribution map. (**b**) Voidage distribution at line V1. upward, it also generated lateral movement in some areas of the furnace cavity. On one hand, it was conducive to weakening the gas pipeline path in the burden, thus avoiding the direct escape of the cooling gas from the pipeline and improving the utilization rate of the cooling gas. On the other hand, it could force the cooling gas near the wall to enter the burden laterally, thus increasing the contact area with high-temperature sinter and improving the gas-solid contact heat transfer. Figure 7 shows the cloud diagram of the gas velocity distribution in the existing furnace type and the Venturi furnace type. For incompressible gas, according to the continuity equation, the smaller the cross section of the gas flow channel, the greater the gas velocity. In the variable-diameter section of the Venturi furnace, the width of the furnace cavity was relatively narrow, making the color of the gas velocity mainly red (\(>\)2.75 m/s), and the average velocity was 3.52 m/s. On the corresponding position of the existing furnace, except for the vent cowl section, the width of the furnace cavity was relatively wide, making the color of gas velocity mainly a yellow-green color (\(\sim\)2.0 m/s), and the average velocity was 2.04 m/s. It can be seen that the gas velocity increased by 72.55%. In the vertical section of the Venturi furnace, the color of the gas velocity was mainly yellow (\(\sim\)2.25 m/s), and the average velocity was 2.34 m/s. However, the corresponding position of the existing furnace was basically green (\(\sim\)1.75 m/s), with an average velocity of 1.79 m/s. It can be seen that the gas velocity increased by 30.73%. This shows that the Venturi furnace could improve the cooling gas velocity as a whole and realize the secondary acceleration of the cooling gas after it entered the variable-diameter section, making the cooling gas velocity higher. The increase in the cooling gas velocity means an increase in the gas-solid relative velocity, which was beneficial for improving the gas-solid convective heat transfer coefficient and then improving the gas-solid heat transfer efficiency.