# Study on the Ash Deposition Characteristics for Co-Combustion of Zhundong Coal with Cotton Stalk
## 3 Results and Discussion
### Effect of Tangential Circle Diameter on the Ash Fusion Process  
As previously established, avoiding the impact of molten particles on the wall's surface can effectively alleviate the slagging on the heating surface. Therefore, by reducing the diameter of the theoretical tangential circle diameter, more ash particles are gathered in the center of the furnace to reduce the impact of ash particles on the wall. In this study, the theoretical tangential circle diameter was reduced from 1600 to 1200, 800, and 400 mm, and the influence of the tangential circle diameter on the ash deposition characteristics was analyzed. Figure 4: Temperature distribution at different heights of the furnace under different blending ratios. Figure 5: Average ash deposition rate on the burner wall under different blending ratios. The temperature distribution in the furnace under different tangential circle diameters is shown in Figure 6. It can be seen that with the decrease in the theoretical tangential circle diameter, the temperature of the main combustion zone and the burnout zone increased gradually. When the theoretical tangential circle diameter was reduced to 400 mm, the maximum temperature in the main combustion zone reached above 1700 K. At the height of the furnace, about 28 m, due to the filling of the exhaust air, the fuel was completely burned to release additional heat, and the furnace temperature rose slightly. The distribution of flue gas components in the furnace under different tangential circle diameters is shown in Figure 7, and the concentration trends of CO and O\({}_{2}\) were basically the same. The temperature distribution at different heights of the furnace under different tangential circle diameters is shown in Figure 8. It can be seen that, with the decrease in the tangential circle diameter, the furnace section temperature increased, which was consistent with the results in Figure 7. In addition, the high-temperature area of the main combustion zone gradually migrated to the central area of the furnace, and the temperature near the wall decreased by 300-400 K accordingly. To analyze the particle trajectories under different tangential circle diameters, the particle motion trajectory of the first layer primary air was analyzed, as illustrated in Figure 9. The results revealed significant changes in particle motion patterns as the tangential circle diameter decreased. With a larger tangential circle diameter, particles rapidly approached the wall after injection and subsequently adhered closely to the wall's surface. This phenomenon facilitates the combustion-generated ash particles' collision and adherence to high-temperature walls, forming deposit layers. As the tangential circle diameter decreased,  
Figure 6: Temperature distribution in the furnace under different tangential circle diameters. Figure 7: Distribution of flue gas components under different tangential circle diameters. the particles entering the furnace exhibited a stronger tendency toward the central region, with their trajectories deviating from the walls. Ash particles instead rotated with flue gas in the central furnace area, significantly reducing their likelihood of wall collisions and adhesion. However, it should be noted that when the tangential circle diameter was too small, the airflow directly impinged on the central furnace region, creating a substantial angle with the actual flue-gas flow direction. This configuration induced localized recirculation phenomena in the burner zone, causing some coal ash particles to collide and adhere to walls near the burners. This mechanism may lead to severe slagging issues in the burner region. Figure 10 illustrates the ash deposition patterns on the walls under different tangential circle diameters. As shown, the ash deposition in the main combustion zone improved with a decreasing tangential circle diameter. At a tangential circle diameter of 1600 mm, the ash deposits exhibited a band-shaped distribution, primarily concentrated on the walls surrounding the main combustion zone.