Hopper erosion

Solid Feeders. A solids feeder is any device that will maintain a reasonably uniform flow of bulk material, implying a metering function. It deals with solids in bulk, solid-liquid, and solid-gas mixtures which may be free-flowing, lumpy, sticky, corrosive, erosive, fluidizable, hot, plastic, or pasty. It deals with feeding against pressure or vacuum, with feeding where precision is required, as well as with more usual conditions. Finally, since many materials tend to hang up in bins and hoppers, and... 

A screen with openings of 100/150 x 100/150 mm below the feed hopper should be provided to prevent big lumps from getting loaded on the belt as these can spill or cause erosion (can peel off upper layers of belt and damage it) due to their concentrated weight at one spot. 

One also has to inspect any access or inspection hatches, light and sight ports, and any flanges for the possibility of gas leaking into the cyclone. This is especially true if such features are located in the lower cone, hopper or dipleg regions. Obviously, holes resulting from erosion or corrosion should be repaired as soon as conditions permit. 

As shown in Figs. 12.1.1 and 12.1.2 later in this section, several zones within a typical cyclone are especially vulnerable to erosive attack. These include the inlet Target area , the lower cone and the dust hopper and/or upper dipleg (if present). We will discuss each of these areas separately below. 

Fig. 12,1.10. A commercial installation consisting of a parallel arrangement of two cyclones sharing a common underflow hopper and overflow plenum (or header ). Note blower in bottom left-hand side of image pulls gas through the cyclones. Also note the specially designed erosion-resistant elbow just ahead of the cyclones. Courtesy Fisher-Klosterman Inc.

New material on the end-of-vortex phenomenon in reverse flow cyclones and swirl tubes is given in Chapter 9. Chapters 10 and 11 emphasize the importance of base-line performance of a new cyclone, tracer measurements, and post-separation problems including hopper design. Prudent advice is given regarding suggested focus on underflow mechanics when operational problems arise. Substantial changes were made in Chapter 12, with new material and illustrations added on erosion of the vortex finder s outer wall in view of recent CFD results, and use of wetted walls, sprays, and electrostatic fields in cyclones. 

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