Conveyor vanes

FIG. 21-1 Typical feed arrangements for screw conveyors, a) Plain spouts of chutes, (h) Rotary cutoff valve, (c) Rotary-vane feeder, (d) Bin gate, (e) Side inlet gate. (FMC Corporation, Matetial Handling Systems Division. )... 

A manufacturer s or vendor s inquiry form is a questionnaire whose completion will give him the information on which to base a specific recommendation of equipment and a price. General information about the process in whieh the proposed equipment is expected to function, amounts and appropriate properties ol the streams involved, and the required performance arc basic. The nature of additional information vanes from case to case foi instance, being different for fillets than for pneumatic conveyors. Individual suppliers have specific inquiry forms. A representative selection is in Appendix C. 

Figure 3.7. Solids feeders with variable speed drives, (a) Rotary vane (star) feeder with variable speed drive, (b) Horizontal screw feeder, (c) Belt feeder taking material from a bin with an adjustable underflow weir, (d) Rotary plate feeder Rate of discharge is controlled by the rotation speed, height of the collar, and the position of the plow, (e) Continuously weighing feeder with variable speed belt conveyor.

In a full-scroll centrifuge (Fig. 30.44) the liquid flows in a spiral path against the motion of the conveyor. Under these conditions the boundary layer is as much as 10 times as thick as it is when the layer flows only in an axial direction. Furthermore, spiral flow induces eddies and turbulence in the boundary layer, impeding sedimentation with axial flow the boundary layer is in laminar flow, and sedimentation is unimpeded. Willis and Shapiro give E values for axial-flow centrifuges. The addition of vanes can increase E by 3 to 4 times. 

FIGURE 43.15 Fluidized bed dryers (a) with heating tubes (b) with superheated steam heating, 1—screw conveyor 2—stationary hlade 3—cylinder 4—side cyclone 5—ejector 6—stationary vanes 7—superheater, 8— impeller, 9—top outlet 10—screw conveyor (Courtesy of Niro A/S) (c) rotary kiln dryer using sands heated in a fluidized hed humer. (Adapted from Isheim, M.C., US Patent 4,248,164, 1981.)... 

FIGURE 53.11 Superheated steam fluid-bed dryer (1) screw feeder (2) stationary blades (3) cylinder (4) cyclone (5) ejector (6) vanes (7) heat exchanger (8) impeller (9) top outlet and (10) screw conveyor. (Courtesy of Niro, Inc., Columbia, MD.)... 

The spreaders mounted to the truck usually contain augers to distribute aggregate and provide better control of the rate of spread compared to vane spreaders. The self-propelled spreaders have a receiving hopper and belt conveyors to carry the aggregate to the hopper spreader and offer high daily production rates. 

This feature has the same function as the quasi-axial How. In this design, longitudinal radial vanes are welded to the conveyor hub. say 6 to 12 in number, and a ribbon flight is welded on the outer edge of the vanes. The vanes extend from the feed zone to the front hub. 

One problem with this dcxdce is the possible uneven distribution of flow between the vanes. To overcome this, a small number of holes in the vanes will allow some flow between the channels. It is important to make the number of channels match the number of feed ports in the conveyor. 

In design this is similar to the fully axial conveyor, except that the vanes arc angled to the radii and there are many tiiore of them. In present designs the number of vanes are 48 to 9h or more depending upon the siKe of decanter. They extend from just forward of the feed zone to the front hub. 

Theoretically the clarification capacity of a vaned conveyor can be doubled or increased even more. In practice the increase is somew hat less due to channelling of the centrate. and its not passing through the vanes with a uniform velocity distribution. 

A decanter conveyor with a disc stack [10] has the same function as a conveyor with angled vanes. The disc stack comprises a stack of say 50-100 conical discs very much the same as a stack of discs in a disc centrifuge. The... 

The use of conical discs, or angled vanes, on the conveyor will theoretically enhance the Sigma value, the clarification capacity, of the centrifuge. To estimate the Sigma value of a stack of conical discs, the formula used for disc stack centrifuges may be employed [11] ... 

A conveyor which has no central hub. or just a very small diameter one. The flights are held on radial vanes joined onto a small diameter pipe support... 

A dimensionless group, used in fluid dynamics, heat and mass transfer A flight of small height, welded to pillars or vanes attached to the conveyor hub Metal strips sometimes welded, or spot-welded, axially to the bowl or beach, or onto a liner thereon. Used sometimes in place of grooves... 

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