Air conveyor

Bins may be located inside or outside and the material transferred by bucket elevator, screw, or air conveyors. Ferric sulfate stored in bins usually absorbs some moisture and forms a thin protective crust which retards further absorption until the crust is broken. 

Despite their disadvantages, suction skimmers are the most economical of all skimmers. Their compactness and shallow draft make them particularly useful in shallow water and in confined spaces. They operate best in calm water with thick slicks and no debris. Very large vacuum pumps, called air conveyors, and suction... 

Milling.—The first operation at the distillery is the preparation of the grain and malt. These are elevated to hoppers and passed over magnetic separators to remove tramp iron, etc., which might injure the crushers. The cereals are then fed to grinders of the type commonly used for flour milling, and reduced to meal. The separate meals are then elevated to receivers and hoppers by means of air conveyors, and fed to their respective storage bins. 

The main individual sources of noise in chemical and petrochemical plants are burners (process furnaces, steam boilers, and flares), fans, compressors, blowers, pumps, electric motors, steam turbines, gears, valves, exhausts to open air, conveyors and silos, airborne splash noise from cooling towers, coal mills, and loading and unloading of raw and finished materials. 

Air conveyors or pneumatic conveyors have been developed considerably in recent years and are most suitable for finely divided or light materials. An air system, produced by blowing at one end of a pipe, and sometimes sucking at the discharge end or both, entrains the solid particles and carries them along the pipe. 

The hopper loader is effective in minimizing contamination, reducing spilling, and eliminating hand operations. Most loaders work on the air conveyor principle which employs tubes and a venturi jet to transfer the pellets from the carton to the hopper. The level of plastic pellets in the hopper is maintained automatically. 

Tunnel dryers are shown in Fig. 3.15a. Wet material on trays or a conveyor belt is passed through a tunnel, and drying takes place by hot air. The airflow can be countercurrent, cocurrent, or a mixture of both. This method is usually used when the product is not free flowing. 

In the spunbond process (Fig. 10), an aspiratory is used to draw the fibers in spinning and directiy deposit them as a web of continuous, randomly oriented filaments onto a moving conveyor belt. In the meltblown process (Fig. 11), high velocity air is used to draw the extmded melt into fine-denier fibers that are laid down in a continuous web on a collector dmm. 

In the spunbond process, the fiber is spun similarly to conventional melt spinning, but the fibers are attenuated by air drag appHed at a distance from the spinneret. This allows a reasonably high level of filament orientation to be developed. The fibers are directly deposited onto a moving conveyor belt as a web of continuous randomly oriented filaments. As with meltblown webs, the fibers are usually thermal bonded or needled (53). 

Assemblies of small disks are rotated in a planetary movement around a central screw conveyor. The disks are mounted on six hoUow axles and the axles revolve on overhanging bearings from the gearbox at one end of the vessel where they are driven, via a drive shaft, by an electric motor. The filtrate is collected from the disks via the hoUow shafts and a filter valve into a large collecting pipe. The hoUow shafts also collect the water and air from the dewatering process, in another part of the rotational cycle. The number of disks mounted on the shafts can be adjusted for different materials, depending on the required capacity and the cake thickness to be used. 

After the resin is appHed to the paper, the wet treated web enters a drying oven where most of the solvent is evaporated off. Modem treaters, such as that shown in Figure 1, have air flotation ovens so that the web is never touched by hot conveyor bars that may cause streaks noticeable in the final product. 

The high lead slag from the smelting furnace is tapped continuously and transferred down a heated launder directly into the reduction furnace through a port in the side of the vessel. Lump coal for reduction is fed continuously to the furnace by conveyor and dropped direcdy into the bath. Heating for the endothermic reduction reactions is provided by oil injected down the lance. The combustion air stoichiometry is set at 95% of that required for complete oil combustion. Air is injected into the top of the furnace to afterbum the volatile materials from the coal and provide additional heat to the top of the furnace. Reduction temperatures range from 1170 to 1200°C to maintain slag duidity. 

Transportation. For short distances from the mine, transportation (qv) is by tmck or conveyor belt. Rail transportation is generally used for greater distances. Slurry pipelines (qv) ate being considered as an alternative. Rail transport over hundreds of kilometers results in loss of surface material in uncovered cats and a tendency to overheat in bottom-dumping tail cats owing to air infiltration around the cracks (31). Proper sealing and covets permit shipping over hundreds of kilometers. 

Cmshed stone is conveyed by a mbber-belt conveyor and bucket elevator. Fine stone and dust are conveyed by enclosed screw conveyors, air slides, or pneumatic air systems into storage bins and tank tmcks for shipment. For screening, changeable vibratory screens predominate for all sizes from 23 cm to 0.074 mm (200 mesh). Most stone is stored uncovered on the ground in conical stockpiles, suppHed by radial belt conveyors. Such a conveyor can maintain four stockpiles of different sized stone. Large commercial plants typically stockpile stone in 10 sizes ... 

Containerized ice cream is hardened on a stationary or continuous refrigerated plate-contact hardener or by convection air blast as the product is carried on a conveyor or through a tunnel. Air temperatures for hardening are —40 to —50° C. The temperature at the center of the container as well as the storage temperature should be <—26°C. Approximately one-half of the heat is removed at the freezer and the remainder in the hardening process. 

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