Solid belt conveyors

A safe estimate of power requirement for double drum dryers is approx 0.67 HP/(rpm)(100 sqft of surface). Maintenance can be as high as 10%/yr of the installed cost. Knives last from 1 to 6 months depending on abrasiveness of the slurry. Competitors for drum dryers are solid belt conveyors that can can handle greater... 

C202 1 Hydrolysate washed solid belt conveyor 116,103... 

Solids (belt conveyor— bulk or discrete flow, pneumatic conveyor—bulk or discrete flow, screw conveyor—bulk or discrete flow, bucket elevator—bulk or discrete flow)... 

Several plants employ cooled-belt flakers. These consist of flexible steel belts, ca 1-m wide and up to 50-m long, that have short mbber skirting at the edges. Molten pitch flows from a thermostatically controlled tank over a weir to give a flat thin sheet on the belt, which is cooled from below by water sprays. At the end of the belt, the solid pitch is broken up by rotating tines. The pitch flakes are drained and transported to a covered storage silo by belt conveyor, during which time the surface moisture evaporates. 

Example 7 Cross-Belt Sampbng of Solids from Conveyors. 

In addition to secondarv resistance control, other devices such as reactors and thyristors (solid-state controllable rectifiers) are used to control wound-rotor motors. Fixed secondary reactors combined with resistors can provide veiy constant accelerating torque with a minimum number of accelerating steps. The change in slip frequency with speed continually changes the effective reac tance and hence the value of resistance associated with the reactor. The secondaiy reactors, resistors, and contacts can be varied in design to provide the proper accelerating speed-torque curve for the protection of belt conveyors and similar loads. 

Use of enclosed belt conveyors, chutes or pneumatic conveyors for solids. 

Cake disposal is relatively straightforward. Cakes may be discharged into bins that are trucked away or transported with a belt conveyor. With very large filter presses a well formed cake may weigh 200-300 kg per chamber and when it falls into a bin or onto a belt conveyor in one solid piece the impact is very high. Hence, special measures are required to break and de-lump the sole hard cake and, for belt conveyors, it is also recommended to increase the number of belt support rollers below the discharge chute at the point of impact. 

Belt conveyors are the most commonly used type of equipment for the continuous transport of solids. They can carry a wide range of materials economically over long and short distances both horizontally or at an appreciable angle, depending on the angle of repose of the solids. A belt conveyor consists of an endless belt of a flexible material, supported on rollers (idlers), and passing over larger rollers at each end, one of which is... 

Screw conveyors, also called worm conveyors, are used for materials that are free flowing. The basic principle of the screw conveyor has been known since the time of Archimedes. The modem conveyor consists of a helical screw rotating in a U-shaped trough. They can be used horizontally or, with some loss of capacity, at an incline to lift materials. Screw conveyors are less efficient than belt conveyors, due to the friction between the solids and the flights of the screw and the trough, but are cheaper and easier to maintain. They are used to convey solids over short distances, and when some elevation (lift) is required. They can also be used for delivering a metered flow of solids. 

There are many other different types of solids-handling devices, ranging from dumpsters to screw and belt conveyors and bucket elevators. The range and variety of equipment make this subject too large to be adequately covered by this book. The reader is referred to the voluminous literature on the subject. For sizing equipment the most helpful source is often the manufacturers manuals. 

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.

Equipment developed essentially for movement of granular solids has been adapted to drying. Screw conveyors, for instance, have been used but are rarely competitive with belt conveyors,... 

Feed material, consisting of fresh and recycled particles, may be introduced by a belt conveyor, a chute, pipe or similar devices. Liquid phase may be introduced either before or immediately after the solids enter the cylinder. In iron ore balling, premoistened wet filter cake usually constitutes the feed but water sprays may also be located inside the drum for moisture addition to aid balling control. Although water is the usual wetting agent, various solutions and slurries may be used in mixed fertilizer granulation. These may... 

Continuous Percolators Coarse solids are also leached by percolation in moving-bed equipment, including single-deck and multideck rake classifiers, bucket-elevator contactors, and horizontal-belt conveyors. 

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