Thickening equipment is usually used for concentrating and tailings dewatering before filting in mineral processing plant. It can also be widely used for concentration and purification of solid slurry in industries such as coal, chemical industry, building materials and water and sewage treatment. The thickening equipment include center drive type and traction type thickener.
2.Working principle of thickener
The thickener is mainly consists of a circular thickening tank and thickener rake scraper. The settlement of solid particles suspended in a slurry concentrated pool under the action of gravity, the upper is clear water, the solid-liquid separation. In the bottom of the concentrated pool of slime deposited by rake scraper continuously scraping set to the bottom center of the discharge port of discharge, and the clean water is concentrated along the overflow pool. The working principle is shown in Figure 1.
The area of A is a clarification area. The solid particles content is low, and the cohesive force between particles is small. The B area is the settlement area, and its concentration is the same as the suspension before settling. The increase of solid particle content in the range of cohesive force between each other is greater than the resistance of solid particles by sedimentation; C area is the transition zone, increase the cohesive force of solid particles in the area between the solid particle content increased; D area is compression zone cohesion between solids larger, higher concentration the particles also increases. With the process of precipitation, the D region and the A region gradually increase, while the B region gradually decreases and even vanishes, and the C region is also disappearing. At this time, the pulp is at the critical point of the settlement process. After the critical point, only the A and D areas are left.
3. Center drive type thickener
The Center drive thickener specifications are relatively small, generally less than 20m in diameter. In the case of the diameter below 12m, the manual raking method is generally adopted, and the automatic raking method is generally adopted in the case of the diameter above the 12m. Center drive type thickener is mainly composed of thickening pool, rake frame, transmission device, rake lifting device, feeding device, discharge device and signal safety device etc.. The structure is shown in Figure 2.
Figure2. Center drive type thickener
1. trusses; 2. transmission; 3. rake lifting device; 4. feeding tube; 5. rake frame; 6. tilted plate; 7. thickening pool; 8. ring overflow chute; 9. vertical shaft; 10. discharging hopper.
A cylindrical thickening ppool 7 is made of cement or steel plate (small size), and the bottom of the pool is slightly conical or flat. In the bottom of the pool, there is a discharge hopper 10 to discharge the concentrated product, and a ring overflow chute 8 on the upper part of the pool. In a concentrated tank has a vertical shaft 9 at the distal end of the shaft, fixed with a cross shaped rake frame 5 is arranged below the scraper frame. The rake frame and the horizontal plane are 8 -15 degrees. The vertical shaft is rotated by a cylindrical gear reducer, a middle gear and a worm gear reducer, which is fixed on the truss 1. As the shaft rotates, the pulp flows along the trusses of the trusses into the feeder 4 in the center of the pool and flows around the concentrating pool. The solid particles in the pulp gradually settle down to the bottom of the concentration pool, and the scrapers under the rake rack are scraped into the discharge hopper in the center of the pool and are discharged with a slurry pump. The water clarified above is efflux from the ring overflow chute 8 at the upper part of the pool. In order to improve the thickening efficiency, an tilted plate 6 is installed around the pool in the lower part of the clarification area of the thickening pool. The slurry flow moves along the spatial syncline of the tilted plate, and the solid particles settle vertically between the two tilted plates, so that the settlement distance is shortened and the time is reduced. The fine particles settling on the inclined plate are gathered together and slide along the inclined plate, and the settlement speed is quickened. Installation of the inclined plate also increases the natural sedimentation area of thickener. As a general thickener concentrates before filtration or as tailings dewatering. Used as a thickener concentrates, its products are discharged from the discharge port at the bottom of the concentrate, the concentration index is below 75%. Used as a thickener dewatering of tailings, it is the product of overflow water discharged from the upper overflow groove, the solid content index is less than 0.5%, and the sludge discharge index of 20%-30%.
4. Traction type thickener
Traction type thickener series, general diameter 15-100m, shrinkage pool made of concrete, the center has a reinforced concrete pillar, with the help of the end of the harrow frame bearing at the center pillar special, and the other end of the drive car is connected by roller supporting carriage on the rail track along the concentrated pool laying on the circumference. The roller is driven by a motor fixed on a transmission car through a reducer and gear rack transmission device, so that it rolls on the track and drives the rake rack to rotate to scrape the sediment. The structure is shown in Figure 3.
Figure3. Traction type thickener
1. rack; 2. track; 3. overflow tank; 4. concentrating pool; 5. bracket; 6. feeding slot; 7. electric unit; 8. unloading port; 9. rake frame; 10. scraper; 11. drive car; 12. roller; 13. gear
Traction thickener is large, suitable for processing large amount of applications, mainly used to concentrate and tailings Concentrate Dewatering, can be widely used in condensed liquid containing solid particles of coal, chemical industry, building materials, water and wastewater treatment industry and purification.
5.Main parts of traction type thickener
5.1. Thickening pool
The pool structure according to its specifications, to the thickener operation requirements of material properties, the underflow discharging and terrain conditions, can be made of steel, concrete or masonry lining with matter in the earth. The wall and bottom of the groove can be made of the same or different material (or masonry). In order to prevent corrosion, the inner wall of the groove can be painted or lined with rubber or plastic.
5.2. Feeding way of traction type thickener
This thickener generally uses the center feed, slurry was sent to the center for ore thickener pool, and then slowly into the settlement area. In addition, there are around feeding and feeding at the bottom of the thickener. The surrounding material thickener to pulp distributor immersed in the pulp, installed in the thickener surrounding a certain depth from the overflow weir. Compared with the center feed, the feed processing amount is large.
Overload protection device and signal are important measures to ensure the normal operation of the large-scale thickener. At present, there are three types, hydraulic pressure, mechanical and electronic control safety protection device.
5.4. The transmission mechanism of thickener
Because of fine material settling speed is slow, in order to reduce the settlement process of interference, the rake type thickener rake arm speed must be slow, so the transmission speed ratio is large. General use of worm gear and three gear reducer can meet the requirements; in order to ensure the safe operation of the transmission mechanism of thickener, there must be a safety device to prevent precipitation too thick or excessive feeding and mechanical damage or motor.
6.specification of thickener
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Simple and convenient installation & maintenance.
The simple internal structure is convenient for the layout of hydraulic and electric control system.
Control the speed of rake by regulating oil volume of oil pump, so as to achieve the best state.
Automatic rake lifting and dropping.
Can be equipped with automatic reagent dosing system.
NXZ thickener is composed of bridge frames, scraping rake, steady flowing barrels, transmission part, lifting rake part, railings, steel tank and others. Bridge frames are fixed to the supporting frames of thickening tank to bear the total loading of equipment and offer access for working staff to enter the concentrator’s center; vertical transmission using direct-cycloid reducer drive, through the gear pair driving large slewing ring gear which is installed in transmission, thereby stimulating the central axis of rotation, scraping rake frame and scraper system are connected with the central axis, through the rotation of the scraper to promote and realize the concentration of sediment material to the collection center of the pool.