Sludge thickening with Klein belt thickener type SNP

Process Description:

Advantages of the belt filter press type SNP

• robust and compact frame construction with easily detachable stainless steel covers, easy to operate and to maintain
  
• particularly large filter area for predewatering
  
• high pressure zone containing 12 (or 10) press rollers
  
• high dewatering performance by favourable roller arrangement and a pressure of 8 – 10 bar
  
• low operation and maintenance costs
  
• separation of filtrate and wash water
  
• water requirement for belt cleaning can be supplemented by filtrate
  
• low-wear and low-noise operation
  
• continuous and fully-automatic operation
  
• high volume reduction of the sludge to reduce the transport costs for sludge disposal
  
• maximum dry solids concentration in the presscake
  
• the press cake is ideally suitable for further treatment (drying, transport, storage etc.)
  
• corrosion protection by stainless steel design, special coatings or hot-galvanizing of the components

 Sludge Conditioning

The sludge to be dewatered is delivered to the belt filter press by means of an infinitely variable sludge feeding pump (eccentric screw pump), which is working without blockage due to its special design and operation mode.

The sludge passes through a mixer with an integrated weight-loaded non-return valve. Here the sludge is mixed with a polymer solution (0,1 % concentration).

The integrated non-return valve ensures an optimal mixing energy depending on the sludge flow.

The sludge flakes stabilize in the subsequent pipe and are fed onto the belt filter press in an optimal dewatering condition.

Dewatering Process

The sludge passes the following dewatering zones:

1. Predewatering Zone
   
   A statical thickening of the flocculated sludge is effected in the predewatering zone.
   
   Rows of ploughs which are situated on the sieve belt guarantee an optimal circulation of the sludge so that the free water on the sludge surface can be drained off quickly.
   
   The careful treatment of the sludge produces a filtrate which is nearly free of solids and which is collected in a filtrate tank. The filtrate is drained off into the foundation below the machine or can be used as flushing water for belt cleaning.
   
2. Wedge Zone
   
   The sieve belts with the prethickened sludge are guided over a perforated, curved plate which causes a continuously increasing pressure onto the sludge cake. By the slow and careful pressure increase the sludge becomes solid and is compacted in a way that it can be treated with maximum pressure in the following press zone.
   
3. Press Zone
   
   In the press zone the sieve belts are conducted over 12 (or 10) press rollers which are decreasing in diameter and thus generate an increasing pressure.The first press roller is designed as perforated roller in order to drain off the filtrate.
   
   The sieve belts pass the rollers with a large grip angle, resulting in a long-lasting pressure onto the press cake. The pressure generated between the sieve belts causes an optimal dewatering in exactly defined pressure stages, and in addition shear forces are generated caused by a cross movement of the sieve belts.

The press rollers are running in self-aligning roller bearings, which are sealed with a grease chamber, an oil seal and a triple labyrinth.

All rollers and bearings are overdimensioned in order to guarantee a long operating life and a wear-free operation.

Drive

The drive of the sieve belts is executed by means of rubber-coated drive rollers which are connected synchronously to gear wheels and which are driven by an infinitely adjustable geared motor. All parts which contact the product are made of stainless steel, hot-galvanized or rubber-coated steel and are resistant to corrosion. The machine is an open construction and all parts are easily accessible for operation, maintenance and cleaning.

Discharge

The dewatered presscake is discharged in a height of approx. 970 mm. Thus it is possible to apply all kinds of conveying systems. The press cake is removed from the sieve belt by means of adjustable plastic scrapers. The scrapers are designed in a way that they can be lifted and cleaned easily.

Belt Cleaning

After having passed the press zone the sieve belts are conducted through a high-pressure cleaning device which operates with spray nozzles at a pressure of 6 – 8 bar. A special cleaning brush incorporated in the spray bar ensures an optimal cleaning of the spray nozzles.

The flushing water of the upper belt is collected separately from the filtrate and is drained off into the foundation below the machine. The flushing water from the lower belt is drained off directly below the machine.

Belt Tension and Belt Tracking

The belt tension is generated separately for the upper and lower belt by means of pneumatic cylinders.

The actually set pressure remains constant in all operation modes.

Tracking rollers which are activated by pneumatic cylinders guarantee the centric run of the sieve belts.

The pneumatic cylinders receive their signals by gas-tight casted electronic proximity switches which scan the belt track.

The application of a pneumatic system for belt tension and belt tracking results in a smooth adjustment of the optimal operation mode, as the compressibility of the air causes a smooth and slightly delayed regulation which minimizes the belt wear.

An environmental pollution which may happen in case of leakages in hydraulic systems is impossible.

Design of the belt filter press SNP

All components for drive, control, cleaning and tension of the sieve belts are arranged in a way that they will not come into contact with the filtrate or material to be dewatered.

Special importance has been attached to corrosion protection.

In standard design the machine frame is made of hot-galvanized steel. The machine can also be supplied in stainless steel or with special coatings. The feeding area of the press and the filtrate tanks are made of stainless steel.

Our delivery scope comprises the engineering, delivery, assembly and commissioning of complete plants incl. the necessary accessories, polymer preparation system and fully-automatic control. Especially maintenance and service are our primary concern.