Advantages comparison between screw sludge dehydrator and belt filter press

 

The screw sludge dehydrator and belt filter press, both of which are widely used in the sludge dewatering field, can operate continuously. In many cases, they can replace each other.

Working principle of screw sludge dehydrator:

The main body of the screw sludge dehydrator is overlapped by a fixed ring and a movable ring, and the spiral shaft runs through it, integrating concentration and dehydration. The front section is the concentration section, and the rear section is the dehydration section.

1) Concentration: When the spiral shaft rotates, a plurality of fixed and movable laminations around the spiral shaft move relative. Under the action of gravity, sewage is filtered out from the relatively moving lamination gap to achieve rapid concentration.

2) Dewatering: the concentrated sludge moves forward with the rotation of the spiral shaft; Along the outlet direction of mud cake, the pitch of spiral shaft decreases gradually, the gap between rings also decreases gradually, and the volume of spiral cavity decreases continuously; Under the action of the outlet back pressure plate, the internal pressure gradually increases. Driven by the continuous operation of the spiral drive shaft in turn, the water in the sludge is squeezed out, and the solid content of the filter cake increases continuously, finally realizing the continuous dehydration of the sludge.

3) Self cleaning: The rotation of the spiral shaft promotes the continuous rotation of the traveling ring. The equipment realizes continuous self-cleaning process by relying on the movement between the fixed ring and the moving ring, ingeniously avoiding the common blockage problem of the traditional dehydrator.

Working principle of belt filter press:

The belt filter press is a kind of filter equipment which is made up of two annular filter belts wound on a series of drums arranged in sequence with different sizes, and uses the squeezing and shearing action between filter belts to remove the water in the slurry.

1. In the pretreatment stage, the solid content of the original slurry is generally very low. In order to reduce the treatment cost, gravity sedimentation or other means should be used to increase the slurry concentration. The common pretreatment method of belt filter is: the thickened sludge is mixed with high polymer flocculant, under the action of flocculant, the fine particles are agglomerated and preliminarily precipitated, which is the preparation condition for sludge dewatering.

2. In the gravity dewatering stage, the belt filter adds the sludge after flocculation pretreatment to the filter belt. Under the action of gravity, the free water outside the floc is filtered out through the filter belt, thus reducing the water content of the sludge.

3. In the wedge pre press dewatering stage, after gravity dewatering, the sludge starts to enter the wedge press section, and the gap between the filter belts gradually decreases, so that it starts to be squeezed and sheared by the action and dehydrated again. After this stage, the fluidity of the sludge is almost completely lost, so as to ensure that the sludge will not be squeezed out in the press dehydration section under normal conditions.

4. In the press and dewatering stage, the belt filter repeatedly presses and shears the sludge through the carefully designed press roll system to remove a large amount of capillary water, so that the water content of the sludge is gradually reduced and the sludge filter cake is formed. The filter cake is scraped off by the discharge scraper at the separation of the gravity concentration filter belt, and the discharged filter cloth enters the next cycle after cleaning.

Advantages of the screw sludge dehydrator:

1. The screw sludge dehydrator is applicable to the dehydration of high and low concentration sludge. It does not need to build a thickener, reducing the construction cost, phosphorus release and odor generation.

2. It does not block, reduces flushing water consumption, saves water charges, and reduces the internal circulation burden caused by the backflow of cleaning water.

3. The electric control cabinet, flocculation mixing tank and dehydration main body are integrated to reduce the floor area, and the installation is simple and convenient.

4. Fully automatic 24-hour operation is realized to reduce the labor intensity of operators.

5. The running speed of the spiral shaft is low, 2-3 revolutions per minute, low power consumption, and there is basically no vibration and noise on site.

6. The body is almost made of stainless steel, which can greatly extend the service life.

Advantages of filter press:

1. Low power consumption and large processing capacity.

2. High dehydration efficiency and high solid content of mud cake.

3. Simple operation management and easy maintenance.

4. High degree of automation and continuous production.

5. Low noise, long service life.

6. It can treat inorganic sludge.

 

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