Tangential flow cyclones

Figure 1.115 Top photographs of vortex-flow pattern formation at various flow rates when contacting water and dyed water (acid blue) solutions in the tangential-flow cyclone micro mixer. Bottom comparison of the experimentally derived image of one vortex pattern with the predicted image by CFD simulation [131] (source IMM).

There are a number of different forms of cyclone but the reverse flow cyclone represented in Fig. 1 is the most common design used in the industry. The cyclone consists of four main parts the inlet, the separation chamber, the dust chamber and the vortex finder. Tangential inlets are preferred for the separation of solid particles from gases [1]. In this study, the numerical simulation deals with the standard case of reverse flow cyclone with a tangential rectangular inlet. Cyclone dimension used in this simulation are as shown in Table 1. 

Figure 38 (Liu et al., 1990b) shows a four-inlet cyclone. Solids tend to be densified around the inlet region as the vertically entering solids-laden streams are suddenly diverted toward tangential flow in a horizontal plane. At inlet velocities exceeding 8.5 m/s, the overall separation efficiency for a typical FCC catalyst was found to be consistently above 99%, as shown in Fig. 39. This design, however, resulted in relatively high pressure drop unless the inlets were appropriately enlarged. The efficiency and pressure drop of this type of multi-inlet cyclones could be approximated by modifying the single-inlet cyclone expressions (Kou, 1987 Shi et al., 1987) ...

The most commonly used design is the reverse-flow cyclone, as shown in Figure 10.43 other configurations are used for special purposes. In a reverse-flow cyclone, the gas enters the top chamber tangentially and spirals down to the apex of the conical section it then moves upward in a second, smaller-diameter spiral, and... 

In the cyclonic spray chamber droplets are discriminated according to their size by means of a vortex produced by the tangential flow of the nebulizer. Smaller droplets are transferred with the sample aerosol into the ICP-MS, while the larger droplets collide with the walls and exit by gravity via a drain tube. If compared to the Scott design, the cyclonic spray chamber typically shows higher sensitivity. 

There are two primary types of cyclones the reverse-flow cyclone and the uniflow cyclone. The reverse-flow (Fig. 1) is by far the most common. It is called a reverse-flow cyclone because the gas-solids mixture enters the cyclone tangentially at its periphery, spirals around the barrel, and then the gas reverses flow and exits through a gas outlet tube (also called the vortex finder or the vortex tube) at the top of the cyclone. The solids spiral down around the barrel of the cyclone at an angle of approximately 15 degrees and enter the cyclone cone attached to the bottom of the barrel. The solids exit the reverse-flow cyclone at the bottom of the cyclone cone. 

Over the decades that cyclones have been used, many different reverse-flow cyclone geometries have been tried to improve efficiency, prevent particle attrition, prevent erosion of the cyclone wall, or prevent particle buildup on the cyclone surfaces. However, there are a few basic types that have emerged as the most popular over the years. Some of these cyclone types are shown in Fig. 3. The cyclones shown in this figure are the tangential inlet cyclone, the volute Met cyclone, and the axial inlet cyclone. This last type of cyclone uses axial swirl vanes to impel the gas solids mixture into rotary centrifugal motion. 

In a tangential-inlet reverse-flow cyclone, the cyclone inlet translates the linear inlet gas flow into a rotating vortex flow. As shown in Fig. 1, the gas solids mixture enters an annulus region between the outer wall of the cyclone and the outer wall of the gas outlet tube. As the gas solids mixture spirals downwards, it sets up a vortex with an axial direction downward toward the solids outlet. 

Fig. 3.1.1. Sketch of a tangential-inlet cyclone with the flow pattern indicated. The coordinate directions are shown, normally the 2-axis coincides with the axis of the cyclone or swirl tube. To the right, the radial distributions of the axial and tangential gas velocity components are sketched. It is understood that the dust outlet may be the Uquid outlet for the case of a demisting cyclone...

Flow Pattern In a cyclone the gas path involves a double vortex with the gas spiraling downward at the outside and upward at the inside. When the gas enters the cyclone, its velocity undergoes a redistribution so that me tangential component of velocity increases with decreasing radius as expressed by The spiral velocity in a... 

The complex three-dimensional flow pattern within the cyclone is dominated by the radial (Fr) and tangential (V0) velocity components. The vertical component is also significant but plays only an indirect role in the separation. The tangential velocity in the vortex varies with the distance from the axis in a complex manner, which can be described by the equation... 

---