Screw conveyors, solids transport

The cattle manure with about 25 p.c. dry matter content and the litter is transported by trailer to the reception hopper for manure and solid organic wastes. From here manure will be delivered by a bucket elevator, with the help of feed screw conveyor into the digester tower made of anticorrosive steel. The slurry and the sewage water mixed with faeces will be pumped into the digester. 

A third way to transport the solid fuel through the conversion system is to apply screw technology [19]. Figure 23 shows an example of a conversion applying screw conveyor technology [31]. The screw technology is an especially common conversion... 

Screw conveyors are suited to transport of even sticky and abrasive solids up inclines of 20° or so. They are limited to distances of 150 ft or so because of shaft torque strength. A 12 in. dia conveyor can handle 1000-3000 cuft/hr, at speeds ranging from 40 to 60 rpm. 

Most nuclear wastes are in liquid or solid form. If the waste is solid, it may be transported by various methods in drums using forklifts, on conveyor belts, suspended in gases in pneumatic conveyors, suspended in liquids as slurries, in screw conveyors, in bucket elevators, etc. 

Another type of stationary bed extractor is shown in Figure 5.5. This Hildebrand extractor consists of a U-shaped screw conveyor with a separate auger, or screw, mechanism in each section to transport the solids through the U. Each auger rotates at a different speed to control compaction of the solids. Solids are fed into one end of the U and solvent into the other to provide countercurrent flow. 

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. 

Solid transport Continuous Screw conveyor, vacuum-pressure lock... 

Allowable torque also limits screws to a maximum of 500-600 mm in diameter. Screw conveyors are used for nearly horizontal transport. While they are able to lift solids at an angle, the particles begin to fall back along the flights of the screw, and efficiency drops off rapidly as the slope increases. At an inclination of 15-20°, the capacity of a screw can be cut by 50%. Specially designed units can operate vertically. These can replace short elevators in small plants. 

---