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  5. Principle of Drum Thickening-Dewatering Belt Filter Press

Principle of Drum Thickening-Dewatering Belt Filter Press

1. Conditioning Tank for Agitation
After the sludge and polymer injected are mixed evenly in the conditioning tank, floc granules are formed and flow into a drum for sludge-water separation.

The conditioning tank of our drum thickening-dewatering belt filter press is constructed from stainless steel. It is designed with open structure, thus providing operators much convenience for observing the conditioning process and the dosage of polymer.

2. Semi-Centrifugal Type Sludge-Water Separation and Thickening System
The conditioned sludge is sent to the fine screen of the separation drum of our drum thickening-dewatering belt filter press. Then, it is slowly rotated by a centrifugal screening machine, so as to remove a large amount of supernatant free water by filtration. In this way, the sludge is effectively thickened. Additionally, the processing capacity of our machine is improved, and the operating time is greatly shortened.

The separated sludge helps reduce the water load of the belt vastly. At the same time, the sludge features stable structure. No sheetflood or side overflow phenomenon occurs. As a result, the dewatering efficiency of the posterior-segment roller is improved, and the water content of the filter cake is reduced.

After separation, the solids content in free water ranges from 0.5‰ to 1‰, which is related with both dosage and type of the polymer.

3. Centralized Sludge Distribution Device
The sludge is basically distributed in the center of the belt of our drum thickening-dewatering belt filter press. The width of the distributed sludge can be adjusted to make both roller and belt suffer the uniform extrusion force, and also prevent the occurrence of lateral leakage.

4. Sludge Dewatering Unit
a. Gravity Dehydration
After the screening process is finished, the sludge with low solids content is uniformly distributed on the filter belt at the operating speed ranging from 1 to 7m/min. While the filter belt runs, a large proportion of free water is gradually removed by gravity. Also, a small part of water is naturally eliminated by gravity through the mesh of the belt.
b. Pressurized Dewatering
After gravity dehydration, the sludge group is sent to the belt through a concave inlet of our drum thickening-dewatering belt filter press. It is restrained by the predetermined width of the filter belt under condition of the thickened sludge cake and no side leakage. Simultaneously, the sludge passes through a series of fixed-size rollers step by step. The force of extruding the sludge is gradually enhanced to achieve the dehydration effect.

After being initially extruded and dehydrated, the sludge is allowed to enter a series of fixed-size main roller and sub-roller. By increasing the sludge extrusion force each time, our drum thickening-dewatering belt filter press can realize the high-efficiency dewatering process. Then, the sludge depends on the proper variation of pressure gradient in the high-pressure shear zone, so as to reduce the water content of the sludge cake. In this zone, the sludge forces the residual water in the sludge cake to be thoroughly discharged, so as to obtain the lower water content of sludge cake. The pressure of an air compressor can serve as the power, and it can be arbitrarily adjusted in accordance with the actual requirements for operation.

5. Belt Cleaning Device
The nozzle is utilized to be well distributed and fixed on the sealed cleaning device of our drum thickening-dewatering belt filter press. This device can be maintained and cleaned easily. Additionally, it does not splatter any rinse water to wet the sludge cake. The nozzle can jet out clean water with the hydraulic pressure ranging from 4 to 5kg/cm2.

The lower and upper belts are washed in two directions. The ejected water creates a fan-shaped angle of 60 degrees, which is conducive to the reduction of hydraulic pressure loss. The ejection speed and water volume can be adjusted arbitrarily in compliance with the actual requirements for operation, so that the remaining dirt can be completely removed from the mesh of the belt.

Beyond that, the hydraulic cleaning method allows the belt to keep permeable to water. It can lower the water content rate of the filter cake, and also extend the service life of the belt. In addition, it can avoid lateral leakage resulted from the serious blockage of the belt.

The cleaning device comes with a filtrate receiver for recycling the filtrate.

6. Removal of Sludge Cake
The upper and lower belts are respectively mounted with a doctor blade, for the purpose of eliminating the sludge by adjusting the tightness of spring.

Performance Characteristics
1. Our drum thickening-dewatering belt filter press can run smoothly without any impact, vibration, or abnormal noise.
2. This machine is made from SUS304 stainless steel. Due to the adoption of TIG welding reinforcement technology, the weld joints are flat and smooth without any defect. Moreover, our equipment is surfaced with the finishing coat, thus offering nice appearance and protective effect. Its structure is firm and highly resistant to chemical corrosion.
3. The drum thickening-dewatering belt filter press also gives the function of limiting and regulating the thickness of the sludge layer.
4. The conditioning tank adopts three spiral blades for cross-rotation and agitation, which allows the polymer and thickened sludge to be entirely mixed.
5. The speed of our machine is stable and adjustable. The speed indicated by our system conforms to the actual mechanical speed.
6. The upper and lower belts are driven synchronously with the traveling speed ranging from 1 to 7m/min. The belt is made from polyester fiber in Sweden or Germany. Its service life can reach over 8,000 hours.
7. Furthermore, this drum thickening-dewatering belt filter press is driven by a motor. Its output speed can be adjusted. All moving parts can operate smoothly. The noise is at most 65dB (A). Our roller is imported from Japan, and it features superior quality.
8. The cleaning system is composed of the spray pipe and the SUS316 stainless steel spray nozzle. The spray range covers the whole belt width. Each nozzle can be replaced.
9. Both structure and performance of the water pump can meet the needs for cleaning the belt.
10. Last but not least, the drum thickening-dewatering belt filter press is provided with the automatic control and protective function. It will stop working or give an alarm, in case of various abnormal situations including the insufficient sludge, deficient polymer, filter-belt tracking failure, ultra-low hydraulic pressure, external signal instructions, ultra low pressure of compressed air, and more.

Accessory Equipment
The whole sludge dehydration system consists of several parts including the sludge pump, air compressor, control cabinet, sludge dewatering equipment, clean-water booster pump, as well as the flocculant preparation and dosing system. A positive displacement pump is recommended as the sludge pump or flocculant dosing pump. Our company can provide clients with a full set of sludge dewatering system.

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