How to select the type of sludge transfer pump
The flow rate of the concentrated sludge in the water purification plant is generally not too large, the sludge concentration is high, and it contains fine particles. When air flotation is used in the concentration process, there are a lot of air bubbles in the sludge. In order to improve the effect of sludge dewatering, it is often necessary to add flocculants. In order to protect the flocs from being destroyed, high-speed rotation or large shearing force should not be generated during the conveying process.
In addition, the choice of sludge pump should also be adapted to the type of dehydrator. For example, when a plate and frame filter press is used, the pressure during the mud feeding process changes from low to high, and the flow changes from large to small.
Why is the screw pump suitable for conveying sludge?
Judging from the current use of pump types, centrifugal pumps have a wide range of applications, but they have a large shear force on the conveying medium. Diaphragm pumps are mostly used in corrosive media and dosing systems. Plunger pumps are expensive and are mostly used in situations with very high-pressure requirements. The screw pump and lobe pump can transport the medium continuously and evenly without turbulence, agitation, pulsation, and shearing phenomenon, especially suitable for pumping thickened sludge, maintaining the sludge properties to the greatest extent, and protecting the flocs from being damaged, thereby Get the best dehydration results. Therefore, it is advisable to use a screw pump or cam rotor pump for sludge discharge from the water purification plant to concentrate sludge.
Compare the performance of the sludge pump
Screw pumps are mostly eccentric single screw pumps in the sludge treatment system of water purification plants, which are composed of stators, rotors, universal joints, drive devices, and frames. Due to the difference in the number of threads of the rotor and the stator, a closed volume cavity is created between the rotor and the stator surface. The suction end to the discharge end is continuously sent out. There is continuous interference contact between the rotor and the stator of the screw pump, forming a reliable sealing line between the suction end and the discharge end so that the screw pump can not only pump higher pressure but also have a certain self-priming ability.
Single screw pumps can be used to transport liquids containing solid particles, acid-base salt liquids, and liquids of different viscosity, such as pulp, ointment, sewage oil, sewage, mud, jam, etc. It is widely used in environmental protection, biological engineering, sewage treatment, mining, petrochemical, food, sugar, pharmaceutical, paper, dyes, construction, agriculture, and other industrial sectors, etc.
The cam rotor pump is also a positive displacement pump. Its working principle is similar to that of the Roots blower. The two rotor impellers are arranged in parallel, and a cavity is formed between the two rotor impellers and between the rotor and the pump casing. The sludge is sucked and discharged to achieve the purpose of conveying the sludge. The rotor impeller has 2-leaf and 3-leaf, 4-leaf and 6-leaf structures.
The characteristics and working conditions of the rotary lobe pump have many similarities with the screw pump. The features are:
(1) The distance that the medium is conveyed in the cam rotor pump is relatively short, unlike the screw pump, which has a long contact line, so the particle passing capacity is large, the structure size is small, the footprint is small, the efficiency is high, and the required maintenance space is small. , Good anti-corrosion performance, low maintenance, and maintenance costs.
(2) The cam rotor pump can transport the medium in reverse and can withstand dry operation for a short time without the pump being damaged.
(3) The linear cam rotor pump will have large pressure fluctuations during operation. The use of the helical rotor impeller can solve this problem, reduce the pulsation to a minimum, and basically realize the pulsation-free conveying of the medium. The cam rotor pump also has the self-priming ability, but the self-priming performance is not as good as that of the screw pump. Due to structural reasons, the price of rotary lobe pumps is higher than that of screw pumps when the size of the pump is small. The smaller the size, the bigger the price difference. On the contrary, when the size of the pump is larger, the larger the size, the lower the price is compared with the screw pump. Generally, if the flow rate of a single pump is above 70m3/h, a cam rotor pump should be selected. If the flow rate of a single pump is below 40m3/h, a screw pump should be selected.
When the screw pump is used as the mud feed pump, the centrifugal dehydrator can be equipped with a single-stage screw pump, and the plate and frame dehydrator should choose a multi-stage screw pump under the condition of high pressure. In the sludge treatment system, the cam rotor pump is suitable for conveying sludge with a solid content of less than 6%. For dewatered sludge, screw conveyors are generally used. However, under special working conditions, such as long distances, large vertical height differences, pressure conveying requirements, or small equipment installation space, screw mud cake pumps can be used.