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Introduction about Differential Speed of Decanter Centrifuge

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The differential of the screw speed and bowl speed in the decanter centrifuge directly affects the slag discharge capacity, the degree of muddy dryness, and the quality of the filtrate. It is one of the important parameters in the decanter centrifuge that needs to be adjusted according to the operating situation.

Increasing the differential speed is conducive to improving the slag discharge capacity, but the dewatering time of the sediment will be shortened, and the moisture content of the mud cake will be large after dehydration. Decreasing the differential speed will increase the thickness of the sediment, the sediment dewatering time will increase, and the moisture content of the mud cake will decrease after dehydration. At the same time, the spiral will have less disturbance to the material in the clarification zone, and the quality of the filtrate will be relatively better. To prevent the slag discharge from reducing the material blocking phenomenon caused by the sediment in the centrifuge can not be discharged in a timely manner, to prevent a large amount of mud in the filtrate, then you must reduce the amount of feed or increase the differential speed.

Some types of equipment have the function of speeding up slag discharge automatically. After the set torque reaches a certain limit value, the equipment will automatically reduce the amount of mud and medicine, increase the differential speed, and quickly push out the accumulated mud ring layer. After the torque is reduced to a certain value, the flow and difference Degrees automatically return to normal. This is a measure to effectively protect the decanter centrifuge. However, in the long-term operation, this situation should be avoided frequently, because it is easy to make the decanter centrifuge often in an condition of unstable flow and unstable differential speed. The fluctuations in the process will affect the processing effect and reduce the processing capacity. 

Therefore, the differential speed should be determined according to the nature of the material, the amount of processing capacity, the processing requirements and the structural parameters of the decanter centrifuge. To put it simply: there is a contradiction between the processing capacity and the processing effect. To increase the processing capacity of the decanter centrifuge, it is necessary to increase the differential speed ratio, but the degree of muddy biscuits may be reduced. Capacity, so the on-site debugging work is to find the best equipment operating conditions parameters that meet the actual sludge properties of the respective site, in order to achieve the dual purpose of the highest equipment operating efficiency and the best treatment effect. There is no simple data to calculate, only rely on long-term actual debugging to accumulate experience, and adjust in time according to changes.

At the same time, within a certain range, the control of the degree of speed difference and the control of the amount of flocculant dosing complement each other. When a certain degree of muddy dryness is required, if the degree of difference is reduced, the amount of flocculant dosing can be saved. To put it simply, increasing the pressure of equipment treatment will reduce the pressure of using flocculant. Therefore, the proper use of the lowest possible difference can reduce the consumption of flocculant to a certain extent. As the saying goes, "If the equipment works well, the medicine is saved, and if the decanter centrifuge is not well operated, the medicine is spent." It depends on the design and processing accuracy of the equipment itself, and it also involves the control of the operating parameters of the equipment.

For decanter centrifuges with automatic adjustment of differential degrees, the parameter settings of differential degrees should be determined in combination with long-term use, and amended in time according to various changes that may occur.

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Solids Liquid Separation Small Decantr Centrifuge For South America Client

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Solids Liquid Separation Small Decantr Centrifuge For South America Client

GN exported Solids Liquid Separation Small Decantr Centrifuge For South America Client on 17th Mar 2020. The model is specially designed for this client, meeting every requirements of the project.

It's very important to choose the right model, so hereby we'd like to share some points of view about how to analyze for choosing the proper decanter centrifuge from the nature of the material.

 
I. Consider from the nature and composition of materials
 
 
The primary basis for selection is the type of heterogeneous system that is separated. For example, for the separation of emulsions in a liquid-liquid system, the first consideration is to use a centrifugal separator. For liquid-solid systems, when the liquid phase of the suspension is a loose material with a low degree of solidity, large solid phase concentration, and coarse particle size (> 100um), various filter centrifuges can be considered. Generally speaking, this kind of centrifuge can get drier filter residue and better washing conditions. Secondly, it is necessary to further select the appropriate form for specific conditions.
 
If the suspension is a material with a large liquid phase viscosity and a fine solid particle size, it is easy to block the filter cloth or screen, but it is difficult to regenerate. Therefore, a centrifugal sedimentation centrifuge should be used. When the solid phase concentration is large (5% to 10%), a spiral discharge decanter centrifuge can be used. If the solid phase concentration is less than 1%, a tubular high-speed centrifuge or a chamber centrifuge can be used. If the solid phase concentration is 1% --- 5%, a disc centrifuge can be used. The automatic slag-discharging dish centrifuge can obtain flowing concentrated sediment, so it is often used for solid-phase concentration. For liquid-liquid-solid three-phase systems, generally the solid content is not high, you can use a dish centrifuge.
 
 
 
2. From the technical requirements of the separation process
 
 
The process requirements of the separation process directly affect the selection of the centrifuge. For example, the separation process requires intermittent or continuous operation. The minimum particle size of the separation, the liquid content of the filter residue, the clarity of the filtrate, the discharge method, whether the solid particles are allowed to be destroyed, and washed Requirements, the length of the operating cycle and whether automatic control is required, the degree of automatic control, etc.
 
 
In addition, there are aslo some requirements for sealing, anti-corrosion and explosion-proof.
In short, it is necessary to choose a centrifuge that is inexpensive, applicable (that is, in line with process requirements), simple to manufacture, and easy to maintain. Choose according to the main contradictions that need to be resolved and make economic comparisons. Both technical possibilities and economic rationality must be considered. Of course, according to human operation, there are also manual operation and automatic operation. Users can choose according to their needs.

 

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Key points for Selection and Use of Polymer Flocculants in Sludge Treatment

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Key points for Selection and Use of Polymer Flocculants in Sludge Treatment
 
In the process of sludge treatment we do not only need the equipment such as decanter centrifuge but also need flocculanats. It's very important to select and make good use the right polymer flocculant, otherwise the result of sludge treatment will not be ideal. Here are some key points from GN Separation about the selection and use of polymer flocculants:
 
 
 
① Selection of species: The action mechanism of flocculants is charge neutralization polymer bridge, so anionic and cationic flocculants should be selected according to the charge characteristics of the separated materials.
② Selection of dosage: The best dosage of flocculant is that the flocculant is completely adsorbed on the surface of the solid phase particles and the flocculation sedimentation speed reaches the maximum. When the flocculant exceeds the optimal amount, the flocculation effect will decrease.
③ Selection of molecular weight: The larger the molecular weight of the flocculant, the stronger the capture power of solid particles, and the better the flocculation effect. If the molecular weight of the flocculant is too small. No flocculation effect will be achieved. For sludge dewatering, the selected molecular weight must be ≥ 3 million.
④ Shear strength of flocculant: Flocculants used in belt filter presses and decanter centrifuges have different shear strength requirements. High for general decanter centrifuges. And in the small sample test, you need to use a stirrer to verify the intensity of different stirring.
⑤ Selection of the feeding position; after flocculant is added, the flocculation settling speed is faster. If it is transported through a long-distance pipeline, it will easily cause pipeline blockage. According to tests, it is best to dissolve the flocculant solution with good solubility. Add at the decanter centrifuge inlet
⑥ Dissolving method of flocculant: High-speed mechanical stirrer cannot be used to dissolve the polymer flocculant, because the strong mechanical stirring will destroy the molecular chain of the flocculant, and the effect of the flocculant will be significantly reduced. Generally, the stirring speed of the dissolving flocculant is less than 50 rpm, and it is appropriate to divide it. The blade of the mixer should be as wide as possible. Studies have shown that the flocculant is 0.4 to 0 after being added to water. 6MPa compressed air bubbling is the best method to dissolve the flocculant-the dissolution is very uniform and the dissolution rate is extremely fast.
 
 
We hope the key points above can be helpful to the clients in treatment of sludge. GN can not only provide users with Decanter Centrifuges, but also provide users with turnkey solutions for dewatering process, including solutions for material transportation, classification and dewatering. Rely on GN’s rich production line of separation and conveying equipment, more and more reliable and advanced equipment will be manufactured for users all over the world.
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Some Advice on The Operation Process of Decanter Centrifuge

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Some Advice on The Operation Process of Decanter Centrifuge

In order to achieve a better performance during the separation process of decanter centrifuge, the following advice are provided by GN :

(1) In order to make the decanter centrifuge as stable as possible, it is required to keep the flow, concentration and temperature of the supply stable. This is very important for the continuous running process. The decanter centrifuge feed is stable and the clarification of its outlet The flow and concentration of liquid and solid residue can be kept constant, and the process equipment connected to the decanter centrifuge can also work in a stable state, which can ensure the stability of the entire system. In order to achieve this purpose, the materials must enter a storage tank with a stirrer before entering the decanter centrifuge. The solid-liquid is made homogeneous by stirring, and then the feed liquid is quantitatively fed into the decanter centrifuge through a flow meter by a screw pump.

(2) For those materials that are highly abrasive to equipment, it is recommended to remove coarse particles first, which can greatly improve the wear on equipment. In order to prevent decanter centrifuge from blocking, coarse particles larger than the required diameter should be removed before entering the decanter centrifuge. In order to prevent the fibrous material from entering the decanter centrifuge and blocking the material port, which will cause the machine to vibrate, in the sludge dewatering process of urban sewage treatment, a sludge cutter is installed in the decanter centrifuge feed pipe, so that the pipe and screw The clogging of pumps and decanter centrifuges has basically improved.

(3) A flexible connection must be used between the pipeline connected to the inlet and outlet of the decanter centrifuge to prevent the vibration transmission.

 

(4) Before the decanter centrifuge is stopped, the remaining material in the drum must be cleaned to prevent the drum from being out of balance due to the presence of the residual material, which will cause the excitation vibration at the next stop. Therefore, a water inlet must be configured at the machine inlet to facilitate cleaning when the machine is stopped.

(5) Lifting tools need to be installed in the decanter centrifuge operation workshop for easy maintenance. The control instrument of the decanter centrifuge should be placed in a room with better conditions to ensure the normal operation of the instrument.

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GN Released Updated TBM Slurry Separation Plant

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What is a TBM Slurry Separation Plant?
 
TBM slurry separation plant is to separate and remove the excavated solids from the bentonite suspension - a mixture of water and thixotropic clay. The cleaned liquid is then returned to the slurry circulation.
20200228-GN-TBM-500M
GN Solids Control uses shale shaker, desander, desilter and decanter centrifuge to form the TBM slurry separation plant. An efficient TBM slurry separation plant is the basis for the successful use of sludge-assisted tunnel boring machines (TBM). 
The GN Slurry Separation Plant is popular for projects by AVN Machines, Mix Shields or Shaft Sinking Machines. With 12 years development, GN has made great progress in this field and an updated TBM Slurry Separation Plant has been released recently.
 
Available Models of GN TBM Slurry Separation Plant 
 
Standardized mud-water separation system, including:
1.GNTBM-240M, capacity:240m3/h 
2.GNTBM-360M, capacity:360m3/h
3.GNTBM-500M, capacity:500m3/h
4.GNTBM-1000M, capacity:1000m3/h
Larger capacity systems can also be designed for customers requirement.
 
In addition, GN can also provide a shield dewatering centrifuge:TBM dewatering decanter centrifuge
20200228--Dewatering-Decanter-Centrifuge
GN Manufactures decanter centrifuges of various sizes for the TBM dewatering treatment. The 22-inch GNLW553C-VFD and 30-inch GNLW764A large bowl decanter are popular for TBM sludge treatment. GN delivers the dewatering centrifuge to the customer together with the chemical dosing unit as a complete package. 
 
Features of GN TBM Slurry Separation Plant:
1.OEM for the entire line of shaker, desander, desilter and decanter centrifuges.
2.Customized construction system with standard equipment for your conditions.
3.Worldwide support from our branches and partners around the world.
    4.High-power shale shaker and high-speed decanter centrifuge for high efficient slurry separation.
5.Double deck shale shaker can increase the capacity while taking up less space.
6.Modular structure for fast movements.
 
20200228-GNTBM-360M
TBM slurry separation plant process
1.A coarse slate shaker removes large particles from the TBM slurry.
2.A centrifugal pump bakes the slurry and conveys coarse hydrocyclones.
3.A dewatering shaker below the coarse hydrocyclones dries the solids.
4.The other centrifugal pump pumps the slurry into fine hydrocyclones to separate solids over 20 microns.
5.The fine shaker dewaters the solids released from the fine hydrocyclones.
6.Decanter centrifuge separates solids over 2-5 microns without chemicals.
7.The chemically improved decanter centrifuge separates solids over 1 micron.