Endless belt

A typical up-draft sinter machine (Fig. 2) has an endless belt of malleable iron pallets with grate bottoms upon which the charge is evenly spread. Beneath the pallets, wind boxes produce an up-draft of air through the charge. At the feed end, an ignition box starts the roasting. The combustion products, mostly SO2 and SO, are collected, usually for sulfuric acid production (see Sulfuric acid and sulfur trioxide). 

Molten materials can also be cooled to soHd products on endless-belt systems, as shown in Figure 12. Some typical materials treated, product and feed characteristics, and capacities of belt cooling systems are given in Table 5. 

Fig. 12. (a) Typical-feeding and (b) discharge systems for endless-belt cooling of molten materials. Courtesy of Sandvik Process Systems Canada Ltd. 

Active Dry Yeast (ADY). The production of active dry yeast is very similar to the production of compressed yeast. However, a different strain of yeast is used and the nitrogen content is reduced to 7% of soHds compared with 8—9% for compressed yeast. The press cake made with the active dry yeast strain is extmded through a perforated plate in the form of thin strands with a diameter of 2—3 mm and a length of 3—10 mm. The strands are dried on endless belts of steel mesh in drying chambers (a continuous process) or in roto-louvre dryers (a batch process), with the temperature kept below 40°C. Drying time in drying chambers is 3—4 h and in roto-louvre dryers is 6 h or more. The final moisture level attained is 7.5—8%. 

Bucket Elevators. In a bucket elevator, a series of buckets attached to an endless belt or chain are filled with material and lifted vertically to a head pulley or sprocket, where the material is dumped. The buckets are then returned back down to a tail pulley or sprocket at the bottom. Bucket elevators are not self-feeding. They must be fed at a controlled rate to avoid overfilling the buckets and damagiag the machinery. In the usual arrangement of a bucket elevator, the chain or belt path is vertical or steeply inclined ia a single plane. Special chain supported bucket systems that can travel ia two and three planes have been developed. 

The endless-belt percolator (Wakeman, loc. cit.) is similar in principle, but the successive feed, solvent spray, drainage, and dumping stations are hnearly rather than circulany disposed. Examples are the de Smet belt extractor (uncompartmented) and the Lurgi frame belt (compartmented), the latter being a kind of linear equivalent of the Rotocel. Horizontal-belt vacuum filters, which resemble endless-belt extractors, are sometimes used for leaching. 

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... 

The paper or paperboard manufacturing process is similar for all types of pulp. Pulp is spread out as extremely dilute slurry on a moving endless belt of filtering fabric. Water is removed by gravity and vacuum, and the resulting web of fibers is passed through presses to remove more water and consolidate the web. Paper and paperboard manufacturers use nearly identical processes, but paper-board is thicker (more than 0.3 mm). 

Pastes and melts are spread as a thin film on a surface where they are dried and cooled, respectively. Subsequently scraped off to yield solid product. Drum drying, flaking, melt cooling, endless belt processing, slating, pastille formation. Drum dryers, drum flakers, endless belt systems... 

Figure 11 Schematic diagram of continuous extraction of uranium from seawater with polyamidoxime/polyhydroxamic acid fiber cloth used as an endless belt" (needs permission from Reactive Polymers).

Pulp is continuously fed into the fourdrinier machine on the surface of a moving endless belt of fine mesh screening, usually made of nylon. Deckle straps prevent the liquid pulp from slopping over the sides. The screening is shaken from side to side as it moves forward to help drain the water. Suction boxes below the screening pull more water through, as a wire-mesh-covered cylinder presses on the web of pulp from above. The cylinder may be covered with a plain wire cloth to impart a wove effect, or with wire in a ladder pattern to produce a laid effect. To produce a watermark, the paper-maker attaches a wire design to the cylinder. 

The now very soggy paper is placed on an endless belt of wool felt that carries it between a series of rollers... 

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