Belt conveyors, solids transport

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. 

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... 

Most powder systems are transported at some time during their manufacture as flowing streams Hoppers are emptied by screw or belt conveyors, powders are transferred to bagging operations by screw or pneumatic conveyors and many solids are transported through pipes. A general rule in all sampling is that whenever possible the sample should be taken when the powder is in motion. This is usually easy with... 

Another example of the application of encapsulated sources of radioactive radiation in technical installations is the control of material transport on conveyor belts. The counting rate of the ratemeter is a measure of the thickness or the density, respectively, of the material transported by the belt. By multiplication by the velocity of the conveyor belt, the mass of the transported material is obtained. In the same way, solids transported with gas streams can be determined. 

Chipping, the process of reducing a log to chips of about 2.5 x 2.5 x 0.5 cm thick is a common preliminary to all pulping methods except stone groundwood. Wood chips are more convenient and uniform for solids transport within the mill complex by conveyor belt or pneumatic delivery systems than are whole logs. Also a chip format is more amenable to direct physical conversion to fibers because of the much easier and more uniform penetration of heat and moisture through the thin sections of wood. 

CONVEYORS. Pneumatic conveyors for solids are described in Chap. 7. Other common devices for transportation include belt conveyors and bucket elevators, closed-belt conveyors with zipperlike fasteners, and various kinds of drag and flight conveyors. These all include a return leg that carries the empty belt or chain back from the discharge to the loading point. Vibrating conveyors and screw conveyors have no return leg but only operate over relatively short distances. Pneumatic conveyors also have no return leg and are not so limited as to distance of travel. Conveyors for solids are discussed in Ref. 9a. 

Percolation extractor with solids transport by a belt conveyor from chamber to chamber countercurrently to the solvent. Solvent is sprayed on the solids by means of feed pumps, increase of extraction yield possible by increasing solvent supply and if the solvent is circulated before it is passed to the next stage. 

A. Belt Conveyors. Belt conveyors are sometimes used to transport solids over quite long distances. They are used mostly for horizontal transport and are also capable of moving material at angles up to about 20° above the horizontal. 

Use a more cost-effective materials transport system for example, pump solid material as a slurry instead of handling it dry with a succession of belt conveyors when the material is slurried ( re-pulped )... 

The issues listed above are some of the important considerations when laying out a plant incorporating belt conveyors, or in deciding whether a belt conveyor or system of conveyors is the best solution for a given application of bulk solids transport. The following alternative devices are often worthy of consideration. 

A.W. Roberts, A. Harrison, and J.W. Hayes, Economic Factors Relating to the Design of Belt Conveyors for Long Distance Transportation of Bulk Solids, Bulk Solids Handling. Vol. 5, No. 6, pp.l 143-1149,1985... 

A.W. Roberts, Mechanical Transport in Bulk Solids Processing and Handling, Proc.Intl Symposium, Reliable Flow of Particulate Solids HI, pp.567-616, 1999 Belt Conveyors for Bulk Materials. Conveyor Equipment Manufacturers Association (CEMA). USA... 

Continuous transport of the solids against the solution is employed in several kinds of equipment, including screw, perforated belt, and bucket conveyors. One operation carries a bed of seeds 3-4 ft thick on a perforated belt that moves only a few feet per minute. Fresh solvent is applied 1/5 to 1/3 of the distance from the discharge, percolates downward, is collected in pans, and is redistributed by pumps countercurrently to the travel of the material. 

Estimate the power required for a conveyor belt system transporting 2.5 tons per hour of radioactive contaminated solids from a location in a utility to a storage bin. The process unit end of the conveyor is at ground level while the top of the storage bin is 25 ft high. The total length of the belt system is 75 ft. Typical power requirements for flat conveyors of this capacity may be assumed to be 2.13 hp per 100 ft. Assume a safety factor of 10%. 

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