Reactor CE12500

Reactor CE12500 is an industrial size vessel with torospherical bottom, equipped with a retreated curved blade impeller. The shaft of the impeller enters the vessel from above and the nominal capacity of the vessel is 12450 kg. In the simulated configuration, the impeller is in the curved part of the tank, near the bottom. Two beaver tail baffles are placed near the wall of the tank (angular position $\theta=0$ and $\theta=165^o$) to improve the circulation. The geometrical dimensions of the reactor are reported in Table 4.5.  

Table 4.5: Geometrical dimensions of the industrial vessel CE12500.

Vessel diameter	D	2.348 m
Vessel height	H	3.133 m
Baffle width	$B_w$	0.17 m
Number of baffles	$n_B$	2
Impeller diameter	d	1.35 m
Blade width	b	0.17 m
Number of blades	$n_b$	3

Figures 4.15 and 4.16 show the computational domain adopted for the numerical simulation of reactor CE12500. The number of finite volumes in the computational domain is 136592. A regular meshing is used for the discretization of the cylindrical body of the tank. The number of cells in the azimuthal direction is increased as the radial distance from the rotation axis becomes larger to maintain the volume of computational cells almost constant (see Figure 4.16). Distortion of the grid is locally produced to simulate accurately the shape of the baffles, as shown in Figure 4.16 and  4.17. A distorted grid is also required in the bottom of the vessel (purple part in Figure 4.17) to reproduce the curvature and to model the shape of the impeller. A detailed view of the impeller is shown in Figure 4.18. The rounded shape of the blades and their inclination with respect to the horizontal plane and the radial direction are accurately reproduced. The impeller rotation is counter-clockwise.

Figure 4.15: Front view of CE12500.

Figure 4.16: Top view of CE12500.

Figure 4.17: Detailed view of the bottom of CE12500.

Figure 4.18: Impeller shape for CE12500.

Simulations made on this model are aimed at assessing scale-up possibilities. For this reason, numerical simulations are made to explore the behavior of the industrial size reactor in the same range of Reynolds numbers considered for investigation of the laboratory reactor. Table 4.6 gathers the simulations made for the CE12500. Fluid properties and angular velocities are selected to obtain values of the Reynolds number in the range $[30:3 \cdot 10^6]$. Simulations S3 and S4 are made at the same Reynolds number to determine the response of CFD simulations when fluids very different for viscosity are considered. To obtain the same Reynolds number, the angular velocity is varied according with the selected fluid viscosity.

Table 4.6: Simulations made for CE12500.

Ref	Density $[kg/m^3]$	Viscosity $[Pa \cdot s]$	RPM
S1	10.	1.	100
S2	1000.	5.	50
S3	1000.	0.001	0.1
S4	1000.	1.	100
S5	1.4	$1.8 \cdot 10^{-5}$	100
S6	1000.	0.001	100

Simulations are full transient and start from fluid at rest in the tank. The sliding mesh is used to account for the relative motion of impeller and vessel. Boundary conditions are the same used for the laboratory vessel and are shown in Figure 4.19. No slip condition is used for the wall of the vessel ($\bf {v}=0$), and for the surface of the impeller ( $v_{\theta}(r)=\omega r$). Free shear condition is used at the top of the vessel to simulate the flat free surface.

Figure 4.19: Boundary conditions for the simulations.