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② Plate and frame filter press
.
Mainly by filtration plate and frame filter, filter box, filter cloth and so on
Figure 11-26 Filter frame, filter plate, filter cloth
The characteristics of the plate and frame filter press are: simple structure, easy operation, stable operation, few failures, convenient maintenance, long service life of the machine; large filtering driving force, low cake moisture content; filtering and root selection range is relatively small, and the unit The filtration area occupies a small area; it has strong adaptability to materials and is suitable for all kinds of sludge; the filtrate has a high recovery rate of clarified solid phase
.
The main disadvantages are: intermittent operation, small processing capacity, low yield, high labor intensity, and high filter cloth consumption
(3) Centrifugal dewatering The equipment used for centrifugal dewatering of sludge is a centrifuge
.
According to its separation factors, centrifuges can be divided into high-speed centrifuges (separation factor a is 3000), medium-speed centrifuges, (separation factor a is 150-300), and low-speed centrifuges (separation factor a is 1000-1500); The geometric shapes are divided into drum centrifuges, disc centrifuges, and plate centrifuges
Figure 11-27 Schematic diagram of the combination of filter frame, filter plate and filter cloth
The rotating drum centrifuge is mainly composed of rotating drum, screw conveyor and hollow shaft, as shown in Figure 11-28
.
The screw conveyor and the rotating drum are driven by a driving device and rotate in the same direction.
However, there is a small speed difference between the two.
Relying on the effect of this speed difference, the conveyor can slowly convey the concentrated mud cake and the sewage.
Figure 11-28 Rotary drum centrifuge
1- gearbox; 2- drum: 3- cover; 4- screw conveyor belt; 5- bearing; 6-hollow shaft; 7- driving wheel
When the sludge inlet direction is consistent with the sludge solid conveying direction, that is, when the sludge inlet and the sludge outlet are at both ends of the drum, it is called a downstream centrifugal dehydrator; when the sludge inlet direction is the same as the sludge solid conveyance When the direction is opposite, that is, the mud inlet and the mud outlet are on the same side of the drum, it is called a countercurrent centrifugal dehydrator
.
Down-flow centrifugal dewatering machine and counter-flow centrifugal dewatering machine have their own advantages and disadvantages.
Because the sludge changes direction in the middle of the counter-flow centrifugal dewatering machine, the flow state in the drum is agitated hydraulically, so under the same conditions, the solid content of the mud cake Slightly lower than the co-current type, the solid content of the separated liquid is slightly higher, and the overall dehydration efficiency is lower than that of the co-current type; but the wear degree of the counter-current type is lower than that of the co-current type
Regardless of sludge concentration or sludge dewatering, in order to ensure continuous production, convenient operation, automatic control, and good sanitary conditions, polymer polyelectrolytes are often used as coagulants, and polyacrylamide (PAM) is usually used
Related Links: Sludge Dewatering Equipment (1)