## 3 Results and Discussion  
### Particle Distributions with No Deflector  
Figure 8 illustrates the velocity distribution at plane 1. The corresponding relative standard deviation (RSD) is 9.93% and the total pressure loss is 513.90 Pa, including the two catalyst layers of 420 Pa. Figure 9 shows the velocity distribution of the central section for the SCR-deNO\({}_{x}\) facility. As can be seen, the blue gas gathers towards the right-side wall of the vertical duct. The high-speed areas locate in the bottom side of the sloped duct and in the lower side of the vertical duct. Figure 7: The sketch map of the detection spots over the perforated plate. Figure 10a,b show the general ash particle distributions of plane 1 and plane 2 with no deflector installed. The corresponding histogram graphs of ash particle distributions along the X-direction and Z-direction are presented in Figures 11 and 12, respectively. Figure 8: Contours of gas velocity at plane 1 with no deflector (unit: m/s). Figure 9: Contours of gas velocity at the central section (unit: m/s). Figure 10: Contours of particle concentration: (**a**) plane 1, (**b**) plane 2 (unit: g/m\({}^{3}\)). As shown in Figure 11, there are 10 columns in both the X-direction and the Z-direction. It is indicated that the ash particle distribution is generally homogeneous in the Z-direction. Although the numbers of ash particles near the wall are relatively small, most of the percentages are close to the average level of 10%. However, an obviously inhomogeneous distribution of ash particle is observed along the X-direction. The deviation between the maximum and the minimum is about 20 percentage points. It is revealed that the ash particles are accumulated near the central area of the plane, especially in the fifth column. On the contrary, the amount of ash particles is quite small in the first and second columns, indicating that few ash particles are accumulated near the left-side wall, which is corresponding to the inner side of the wedge-shaped turning. Similarly, for the ash particles at plane 2, the distribution is relatively homogeneous along the Z-direction while it is quite inhomogeneous along the X-direction. According to Figure 12a, a severe accumulation of ash particles occurs near the right-side wall along the X-direction, which may lead to a drastic impact on the AIG and the support structure. Figure 11: Histogram graphs of particle distributions at plane 1: (**a**) along the X-direction, (**b**) along the Z-direction. A further investigation is conducted on the distributions of ash particles with different diameters. According to Table 1, the ash particles are classified into four classes based on the diameters: the small-sized particles (\(\mathbf{\Phi}\leq 6.3\times 10^{-2}\) mm), the medium-sized particles (\(6.3\times 10^{-2}\) mm \(<\mathbf{\Phi}\leq 8.8\times 10^{-2}\) mm), the large-sized particles (\(8.8\times 10^{-2}\) mm \(<\mathbf{\Phi}\leq 0.15\) mm) and the extra-large-sized particles (\(\mathbf{\Phi}>0.15\) mm). Since the diameter distribution follows the Rosin-Rammler rule, the proportion of the particle numbers for the three groups is about 4:2:3:1. Figure 13 illustrates the distributions of the four classes of particles at plane 1 with no deflector installed. According to Figure 13, it is indicated that the small-sized particles, which is shown in black dash, are well dispersed. Meanwhile, there is a similar tendency between the distributions of the large-sized and extra-large-sized particles, which are illustrated in blue and magenta, respectively. These two classes of ash particles perform extremely nonuniform distributions, especially for the extra-large-sized particles, the severest accumulation accounts for nearly 40% of the total amount. Moreover, few ash particles are accumulated near the left-side wall of plane 1.