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Address: Lixing Industrial Park, Xueguan road, Zhucheng.
Phone：0536－6557999 （marketing）
0536－6557998 (after-sale)
0536－6557996 （fax）
Mobile：13721950199
Website：http//www.zcqj.com
Network real name：Zhucheng Light Machine
E-mail：zcqjwhf@126.com
Operator：Wang Huanfan |
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| Main point of sludge dewatering equipments choosing |
Lots of sludge is produced after precipitation treatment of sewage. Though through thickening and digestive treatment, water ratio is 96%. It is too big to be treated. So dewatering treatment is necessary and solid sludge rate of sludge mess should be increased to reduce occupied place by sludge.
The large and medium-sized sewage treatment companies always use mechanical dewatering. There are lots kinds of dewater machines. They can separated into vacuum filter dewater machines, filter press machines, and centrifugal dewatering machines. In this article, Main point of sludge dewatering equipments choosing and working principles of common filter press machines will be introduced. (includes belt filter press machine and plank filter press machines)
1. Belt filter press dewatering machine
Belt filter press dewatering machine’s working principle: sludge is hold between two tense filter belts, and it goes through the regular rolling cylinders. The route is just like “S”. The pressure is from the belt, and water is separated out from the sludge. Then the sludge mess is formed. This is the dewatering principle.
The following points should be considered when choosing model:
(1) Belt. It should have features of good tension ability, bending resistance, acid and base resistance and temperature shift resistance. At the same time, real character of sludge should also be considered. Proper texture is important because proper texture is helpful for ventilation property and tiny sludge stopping.
(2) Offset system of rolling cylinder relies on air power sets.
(3) Tension system of filter belt always is controlled by air power sets. Tension range is 0.3－0.7MPa. The most common value is 0.5MP.
(4) Belt speed control. Different sludge needs different speed because there is a best speed range for each kind of sludge. In this range, both treatment capability and high quality sludge mess are ensured.
Sludge weight has little affects on belt filter press dewatering machines. It has the following features: filter mess has low water ratio; works steadily; has low consumption; it’s easy to manage and control; has little demand for the operator. At the same time, there’re many domestic producers, because it was imported very early. In engineering construction plans, it should be considered to save money. At present, our county has many companies that use it, like Beijing Gaobeidian Sewage Treatment Plant. This machine was used in the first-stage construction, and it worked very well, so the plant chose it in the second-stage too.
2. Centrifugal dewatering machine
Centrifugal dewatering machine is mainly made up with rotating load and spiral conveyer with hollow rotating shaft. Sludge enters the rotor after it enters cylinder from hollow rotating shaft under the centrifugal force made by high speed rotating. More sludge, bigger centrifugal force. It forms solid sludge staying on the inner wall; less water, smaller centrifugal force. Liquid layer is formed inside the solid layer. Solid sludge is transmitted into the rotating load by spiral conveyer and get out from the exits around the rotating load, while liquid gather in the rotating load and finally flow out.
The key part of centrifugal dewatering machine is the rotor. Bigger diameter, stronger dewatering capability it has. But running cost is very high. Longer rotating load, higher solid sludge rate will appear. Cost performance will be reduced if the rotating load is too long. Rotating load speed is an important controlling parameter. Whether both the solid sludge rate and running cost are well controlled is the key point. Now low speed centrifugal machine is widely use. There’re special demands for the wheels and spires. Because their margin is easily broke. The margin of spire on new type centrifugal machine is made to assembled block, so it can be replaced easily. The material is tungsten carbide which is very expensive.
Big noise, high cost and low treating ability are disadvantages of centrifugal dewatering machine. Little domestic companies can produce small-sized centrifugal machine. We can only get big-sized centrifugal machine from abroad. At the same time, sludge weight has big affect on centrifugal machine, and it has high level demands for the operator. Little factory uses this kind of machine. But centrifugal machine technology abroad has developed a lot.
3. Plank filter press dewatering machine
Water is separated out under the pressure of planks. It is consisted of filter board, frame, auto-air power closing system, side board suspending system; filter board shacking system, air press set, filter fabric washing set, and photo electricity protection set. When you make a choice the following items should be considered:
（1）Demands for solid sludge rate of filter mess.
（2）Material of frame.
（3）Material of filter board and filter fabric. They should be corrosion resistant. The filter fabric must have good tensile resistance.
（4）Moving method of filter board. It should be done through hydraulic pressure-air power full automatically or semi automatically to reduce the operator’s works.
（5） Filter fabric shaking set makes sludge mess fall easily. Compared with other filter press machines, the biggest advantage of plank filter press machine is occupying much space. Now lets make a comparison on the belt filter press machine used in the first-stage of Beijing Gaobeidian Sewage Treatment Plant and the plank filter press machine used by anshan industrial sewage treatment plant: sewage quantity of the former one is 500000 t／d, sludge output: 1852．5m3/d, dry matter: 92．63t／d. Five Germany KLEIN－KS30 type belt filter press machines were used. Area for each one is 2750*3500mm. Sewage quantity of anshan industrial sewage treatment plant is 22t/d, dry matter: 275t/d. Six plank filter press machines were used. Area for each one is 2400*12000mm. At the same time, little plants use it now, because it works discontinuously, has low efficiency and cause pollution. At present, because technology is developed, it becomes more proper for modern sewage treatment plants. (it runs full automatically because of PLC system; lots of process can be done by the PLC control like filtering, pressing, filter board removing, filter fabric shacking, press air supporting, filter fabric washing and sludge entering ) Lots of labor power is saved.
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