Cylinder-on-cone

CFD simulation results in a cylinder-on-cone geometry (a) airflow pattern (b) velocity vector (different levels) (c) particle... 

A cylinder-on-cone short-form pilot-scale spray dryer with cocurrent flow of drying air and spray of droplets (Figure 10.3) is adopted from the literature [30]. The diameter and position of air outlet pipe are assumed to be equal to the corresponding data published by Huang et al. [31]. 

A sketch of a standard reverse-flow, cylinder-on-cone cyclone with a tangential, slot-type inlet is shown in Fig. 1.3.1. 

The cylinder-on-cone cyclone with a tangential entry is the industry standard design for centrifugal dedusting or demisting devices. Even so, wide varieties of other configurations are in use and some of these will be discussed in the chapters that follow. We now proceed to look at some of these configurations. 

The fourth type of inlet we wish to describe is that of swirl vanes. As shown in Fig. 1.3.8 d, a swirl-vane assembly allows the gas to enter the cyclone parallel to the axis of the cyclone The swirl-vane assembly is positioned between the vortex finder (or, in case of a straight-through device, see below, a central solid body) and the outer (body) wall of the cyclone. This type of inlet is often inserted in cylindrical-bodied cyclones rather than in cylinder-on-cone or conical-bodied geometries. When it is, we refer to the separator as a swirl tube. Swirl tubes are often of small size (by commercial standards) and are most commonly arranged in a parallel array on a common tube-sheet within a pressure-retaining vessel. They are normally fed from, and discharge into, common, but separate overflow and underflow plenums. 

Another assumption made in the models is that the swirl velocity profile (its radial distribution) in the cyclone is constant axially. Figure 4.4.2 shows LDA measurements of the radial profiles of the tangential velocity at a series of axial stations in a cylinder-on-cone cyclone with a conventional slot-type inlet. Figure 4.4.3 shows a similar plot for a swirl tube with a cylindrical body. 

The figures show that the profile of the dimensionless tangential velocity is constant at all axial positions in the cylinder-on-cone cyclone, even until deep in the conical section. In the swirl tube there is a slight tendency for the tangential velocity to decrease as we move down. Overall, the measurements confirm the validity of this model assumption at least for geometries most commonly found in commercial service. 

A third assumption made in cyclone performance models is that the radial velocity is uniform over CS. The radial velocity is the smallest velocity component, and it is more difficult to measure with LDA than the other components. We can again resort to CFD to get an impression of the flow pattern. Figure 4.4.4 shows profile plots of the radial velocity distribution in both a cylindrical swirl tube and a cylinder-on-cone cyclone with slot inlet. 

Fig. 4.4.4. Profile plots from CFD simulations of the radial velocity distribution in a cylindrical swirl tube and a cylinder-on-cone cyclone. The main difference between the two is that the radial flow from the outer to the inner vortex is more uniformly distributed axially in the cyclone than in the swirl tube...

The picture is not quite fair . Although the lip leakage appears to be much less of a dominant feature in the cylinder-on-cone cyclone, the maximum... 

Meissner/Loffler Cylinder-on-cone cyclones with slot inlets at low solids loading Considers the frictional losses in the body. The friction factors on the cylindrical wall, the conical wall and the roof can in principle be different. The authors themselves did not relate / to the solids loading. 

Obviously this model has some restrictions in its range of applications. As the model stands, it is only suitable for cyclones with slot inlet and a low loading. This is because the effect of the dust on the wall on the friction factors is not reliably quantified as the authors state. If the effect of the solids is to be accounted for, the friction factors at the different walls are likely to differ. Another restriction is that it is only applicable to the conventional cylinder-on-cone cyclone design, and therefore not to cylindrical swirl tubes. 

Rietema Cylinder-on-cone cyclones with slot inlets. ... 

In this section we will present formulas required to design or evaluate a conventional cylinder-on-cone or a predominately cylindrical type of cyclone geometry. In doing so, we shall follow closely the methods of Muschelknautz (1970, for example) and, to some extent, those of Muschelknautz and Trefz (1990, 1991, 1992). Some departures from the MM will be worked into the development that follow the writers own experiences and preferences. 

Fig. 6.1.1. Elevation views of a typical cylinder-on-cone cyclone showing various dimensional notations used herein...

Although this seems to be approximately true in swirl tubes with a cylindrical body, experimental results indicate that the separation performance of cylinder-on-cone cyclones is reduced more than would be expected from the reduction of their effective length when the vortex ends within the conical section. One example is the dramatic reduction in separation efficiency (corresponding to an increase in cut diameter) for the longest cyclone length... 

Storch and Pojar (1970) performed an interesting and rare study of erosive wear within a variety of steel cylinder-on-cone cyclones with tangential inlets. Erosion rates in each cyclone s cylinder and cone sections were measured as a function of gas inlet velocity and solids concentration for two different types of abrasive dust. The experimental results are illustrated in Fig. 12.1.1, frames a through d. The wear reported is that after exposing the cyclone to a fixed total quantity of dust. 

Cylinder-on-Cone Cyclones with Tangential Inlet... 

In this section we concentrate on cylinder-on-cone cyclones with tangential inlets. To give a feel for the range of Viable designs we list some frequently used designs. We then proceed to give some specific design and construction advice. 

Cylinder-on-Cone Cyclones with Tangential Inlet 349 15.1.3 Design of the Cone Section... 

This completes our look at the design of cylinder-on-cone cyclones with tangential inlets. In the following section we discuss the design of cylindrical swirl tubes with swirl vanes. In this discussion, we concentrate on the aspects that are specific to swirl tubes. For the aspects shared between swirl tubes and tangential entry cyclones, much of the discussion above is equally valid for swirl tubes, such as the discussion pertaining to vortex finder configurations. 

The design of swirl tubes features much less prominently in the hteratme than cylinder-on-cone cyclones. The main design features specific to swirl tubes are the inlet vanes, the length of the swirl tube body and the configuration of the... 

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