News from GN company this week: Recently, 2 sets of Fifth Generation Decanter centrifuges has been manufactured and are ready to start serving for an Overseas Wastewater treatment project.

Model: GNLW454ET-VFD, 2sets.

The relevant situations are as follows:

Equipment technical requirements:

1. Material information: Municipal sewage treatment, solid content 2-3%.
2. Treatment capacity 30-40 cubic meters per hour

3. Main motor: 45kw, Back motor: 15kw

4.Material: Bowl SS2205, Screw SS2205

Collection Box SS304, Base: Carbon Steel

5. Wear protection:

Carbide sleeve protection for material distribution port of screw pusher Carbide sleeve protection for slag discharge port

Spiral blade carbide sheet protection

6. Sensors: including 2 temperature sensors and 1 vibration sensor

7. Slag discharge device: a closed rectangular tube slag discharge groove connecting the slag discharge port of the centrifuge collection box and the inlet of the screw conveyor, the size of the inlet and outlet is the same, and its height is 500mm

To make sure the Decanter centrifuges will provide a reliable performance and the parts and components of all the equipment will run smoothly for a long term operation, our technical department, production department and quality control department have paid a lot of attention to the material selection, material preparation, every step of production and the inspection for this set of equipment in each step.

If you need any support about the operation and maintenance of GN’s equipment like Decanter centrifuge, please feel free to contact GN company for our engineers’ best experience and knowledge in the relevant industry. We will do our best to assist your project because just in this way we can establish a stable and long term cooperation. And we can provide on-line support and site instruction for specific situation if needed.

As a leading manufacturer of separation equipment and conveying equipment, GN always pay high attention to the product quality and consider the long-term benefits for our users. We would also like to introduce GN as a professional manufacturer in decanter centrifuge field, GN pays a lot of attention in the selection of raw materials, high-quality centrifugal casting or forging stainless steel materials are used, and for wearing parts, hard alloy protection is used.

By the way, if you are interested in our products, please check the following items of our company on Alibaba:

Decanter centrifuge

3–Phase Disc centrifuge

Sludge dewatering Screw press

Oil water separator

Centrifugal pump

Vacuum Pump

Submersible pump

Since the belt  filter machine was the mainstream of sludge dewatering in sewage treatment plants in the past, the advantages of the centrifuge are shown in the treatment effect and comparison with the belt  filter machine. The Decanter centrifuge has the following advantages for the belt  filter machine:

①The Decanter centrifuge uses the principle of centrifugal sedimentation to separate the solid and liquid. Because the filter has a filter screen, it will not cause clogging. The belt machine uses the belt filter machine to separate the solid and liquid.

②The Decanter centrifuge is suitable for the concentration and dewatering of various types of sludge, and the belt filter machine is also suitable for various types of sludge, but the remaining activated sludge needs a large amount of medicine and the dehydration is difficult;

③When the feed concentration changes during the dehydration process of the Decanter centrifuge , the slip and torque of the drum and the screw will be automatically tracked and adjusted, so there is no need for a special person to operate, and when the feed concentration changes during the dehydration process, the belt filter machine speed, belt tension, dosing amount and flushing water pressure all need to be adjusted, and the operation requirements are high;

④In the Decanter centrifuge, fine sludge can also be separated from water, so the dosage of flocculant is small. Generally, the dosage of mixed sludge during dewatering is: 1.2kg / t [dry sludge], sludge recovery The rate is above 95%, the moisture content of the mud cake after dehydration is about 65% -75%, and the belt filter machine cannot be woven too densely because of the filter belt. In order to prevent the small sludge from leaking, more flocculant needs to be added In order to make the sludge form larger flocs, the dosage of mixed sludge during dehydration is generally greater than 3kg / L [dry sludge], the sludge recovery rate is about 90%, and the moisture content of the sludge cake after dehydration is about 80%;

⑤The power consumption per cubic meter of sludge dewatering of the centrifuge is 1.2kw / m3, the noise during operation is 76-80db, 24 hours a day continuous operation except the shutdown, no washing water is needed during operation; The power consumption is 0.8kw / m3, the noise during operation is 70-75db, the filter cloth needs to be relaxed and maintained. Generally only two shifts are arranged every day, and the filter cloth needs to be continuously washed with high-pressure water during operation;

⑥The Decanter centrifuge takes up little space, the installation and commissioning are simple, the supporting equipment is only the dosing and feeding and discharging conveyors, the whole machine is fully sealed, and the workshop environment is good; while the belt machine covers a large area, the supporting equipment is not only dosing and feeding and discharging Outside the machine, a flushing pump, air compressor, sludge conditioner, etc. are needed. The whole machine has poor sealing performance. High-pressure cleaning water mist and odor pollute the environment. If the management is not good, it will cause mud overflow;

⑦ The wearing parts of centrifuges are bearings and seals, and the maintenance cycle of the discharge screw is generally more than 3a; while the wearing parts of the machine, in addition to bearings and seals, the belt filter machine also needs to be replaced, which is expensive

News from GN company this week: Recently, 1 set of Decanter Centrifuge and 1 set of 3–Phase Disc stack centrifuge have been manufactured and are ready to start serving for a Kazakstan Client.

To make sure the Decanter Centrifuge and 3–Phase Disc stack centrifuge will provide a reliable performance and the parts and components of all the equipment will run smoothly for a long term operation, our technical department, production department and quality control department have paid a lot of attention to the material selection, material preparation, every step of production and the inspection for this set of equipment in each step.

If you need any support about the operation and maintenance of Decanter Centrifuge and 3–Phase Disc stack centrifuge, please feel free to contact GN company for our engineers’ best experience and knowledge in the relevant industry. We will do our best to assist your project because just in this way we can establish a stable and long term cooperation. And we can provide on-line support and site instruction for specific situation if needed.

As a leading manufacturer of separation equipment and conveying equipment, GN always pay high attention to the product quality and consider the long-term benefits for our users. We would also like to introduce GN as a professional manufacturer in decanter centrifuge field, GN pays a lot of attention in the selection of raw materials, high-quality centrifugal casting or forging stainless steel materials are used, and for wearing parts, hard alloy protection is used.

By the way, if you are interested in our products, please check the following items of our company on Alibaba:

Decanter centrifuge

3–Phase Disc centrifuge

Sludge dewatering Screw press

Oil water separator

Centrifugal pump

Vacuum Pump

Submersible pump

The mechanical dewatering of sludge is an important condition for further disposal. If incineration or other heat treatment is used as the ultimate disposal method, the dewatering power of the Decanter centrifuge is required to be as high as possible, because mechanical dewatering requires 1-2kwh of energy (electric energy) for each ton of water sludge disposal, and not only electric energy, and A lot of heat energy is needed for the evaporation of water.

In most cases, the increase in the rate of mechanical dehydration and dehydration is critical to the reduction of the subsequent disposal and disposal costs of sludge. The principle of separating sodium sulfate in the crystallization process is that the solubility of sodium sulfate in sodium thiocyanate solution is very low, and crystals are easy to form, so the concentrated sodium thiocyanate solution is settled through the settling tank to make sodium sulfate Grain gradually grows at the bottom of the settling tank (sodium sulfate content is about 13% to 15%).

 The role of the  Decanter centrifuge  is to separate the sodium sulfate crystals in the bottom solution (only a small part of them are beaten to evaporate the five effects as seed crystals). The resin is replaced and adsorbs sodium thiocyanate in between, and the waste liquid is discharged. If the separation effect of the centrifuge is not good, the content of sodium thiocyanate in the solid phase separator is too high, which exceeds the adsorption capacity of the sewage resin, and environmental protection requires that the content of sodium thiocyanate in the discharged sewage should not exceed 200ppm, the workshop has to Sodium thiocyanate with concentrated sodium sulfate is poured into the system and concentrated from the beginning to recover. The sodium sulfate content will accumulate in the system, which will eventually lead to unsteady production of the two systems of evaporation and crystallization, and then affect the normal production operation of the equipment.

Nearly 90% of sodium sulfate is separated from sodium thiocyanate in the crystallization separation step. The balance of sodium sulfate must be completed by the separation effect of the centrifuge, so in all recovery equipment, the  Decanter centrifuge  plays a crucial role. The important role is to clean impurities and ensure the clean circulation of blood, just like a human kidney. The separation function of the centrifuge directly affects the smooth production and long-term operation of the entire workshop and even the whole plant.

Two important factors that affect the consumption of flocculant during the sewage treatment process by Decanter centrifuge or other centrifugal sludge dewatering equipment are sludge properties and sludge concentration. When the sludge property changes greatly, it is necessary to adjust the applicable flocculant in time to match the sludge dewatering operation; when the sludge concentration changes, it is necessary to adjust the flocculant supply flow in a timely manner, so that it can meet the treatment effect and Prevent wastage.

     The specific method is to often observe the mud effect, and then appropriately reduce the supply flow of the flocculant working fluid. You can reduce the frequency of the flocculant dosing pump every time by about 0.5-1.0Hz, and observe the mud cake and supernatant status and torque data after a few minutes , According to the situation, decide whether to continue to reduce the dosing pump frequency until the most economical dosing pump operating frequency is found. Or you can increase the frequency of the mud pump about 0.5-1.0Hz each time to observe and adjust. Conversely, when the sludge concentration increases, the adjustment is made in the opposite direction.

In addition, because the Decanter centrifuge‘s structure determines the high requirements for the quality of the mud feed, there should not be a large amount of large-sized particulate matter and fibrous material in the mud feed, otherwise it will easily cause equipment clogging, increased vibration, and affect the treatment efficiency. Therefore, the sludge must be crushed and cut before entering the centrifuge.

Any centrifugal sludge dehydrator has a maximum processing capacity requirement. This requirement has two aspects of data reference guidance:

A. The maximum load of dry solids that can be processed is the maximum weight of non-volatile solids processed per hour, expressed in KGDS (dry solids) / h;

B. The maximum treatable hydraulic load, that is, the sludge flow into the equipment, is expressed in m3 / h, and the product of the sludge concentration (solid content) is the dry solid load.

      Under the condition of normal sludge concentration, it should be ensured that the maximum treatment dry solid load is 70% -90% of the theoretical load set by the equipment factory trademark. It is necessary to avoid the equipment utilization rate being too low, or the equipment loss caused by long-term operation under high load. Speed ​​up and shorten the maintenance cycle. In the case of excessive equipment load, any increase in the amount of flocculant will not improve the treatment effect. It is manifested as unsatisfactory mud biscuits. The supernatant carries high solids and the recovery rate decreases. Sediment overflow causes equipment wear, dynamic balance damage and increased vibration. Sometimes, due to the increase in sludge concentration, when the sludge is fed according to the original flow rate, the actual sludge load exceeds the acceptable load index of the equipment, and the treatment effect decreases. At this time, it is necessary to gradually reduce the frequency of mud feed and observe the effect. After the effect is stabilized, continue to try to control the flow rate of the flocculant to the most economical dosage. Conversely, when the concentration of sludge decreases, the flow of sludge should be gradually increased, and the flow rate of the dosing pump should be adjusted at the same time. If the concentration of influent sludge is too low, although the dry solid load of the equipment is not high, the hydraulic load is very large. Under the high hydraulic load, the incoming low-concentration sludge cannot form a mud ring layer of uniform thickness, and the settled solids will be heavily The supernatant carries overflow, which directly affects the treatment effect and treatment efficiency.

Important factors for the Decanter centrifuge Selection

1.1 Differential ratio

The settling velocity of solids in different media is different, and the degree of aggregation is different, so different differential speed ratios should be used. When the other parameters remain unchanged, the differential speed is large, the solid material is pushed out faster, the amount increases, and the liquid content increases, the shaft power generally decreases, but the separation effect will decrease, that is, the solid content in the filtered liquid Will increase. As the differential speed increases, it actually acts as a stirrer in the drum. Choosing the right differential ratio is the first factor to consider when choosing a model.

1.2 Length-to-diameter ratio

The aspect ratio is the ratio of the axial length of the Decanter centrifuge‘s drum to its diameter. The working area of the Decanter Centrifuge is divided into several areas such as feeding, sedimentation, drying, and unloading. The length of the settlement area is the main parameter that determines the separation effect. The longer the settlement area, the greater the aspect ratio, the better the separation effect, but the greater the shaft power. Different length-to-diameter ratios should be selected according to different media properties (mainly settlement performance), and should be considered in combination with differential speed ratios.

1.3 Power

The use of larger power can improve the processing capacity, especially when the settlement performance of the medium is very good. The user has certain difficulty in choosing the model. In the face of new media or media without successful use experience, relevant tests should be conducted.

2 Determination of operating parameters

2.1 Adjustment of overflow diameter

There are four options for the overflow diameter of the general Decanter Centrifuge. The larger the diameter of the overflow, the longer the drying zone, and the lower the water content of the filter cake, but the higher the solid content of the filtered liquid, so the appropriate overflow diameter should be adjusted. For the “three mud” that is not easy to settle, it should be smaller, and for the medium that is easy to settle, such as TA residue, it should be larger.

2.2 speed

According to the working principle of the Decanter Centrifuge, the higher the speed, the better the separation effect, the dryer the filter cake, the clearer the filtered liquid, and the greater the shaft power. This is an important parameter in actual operation, but it is not that the higher the speed, the better the effect. Generally speaking, for the medium that is easy to settle, the higher the speed, the greater the shaft power, which is easy to cause the mechanical or solid material to be pushed out, causing the material to block. Therefore, the appropriate speed should be selected according to the factors such as the power of the Decanter Centrifuge, the feed, the dehydration effect and other factors. For the “three muds” that are not easy to settle, when the rotation speed is high to a certain value, there will be a phenomenon that the separation effect decreases, the sludge production decreases, and the solid content in the filtered liquid increases. When the rotation speed is reduced, the mud production fork will increase. This is because the material slips in the drum and cannot be pushed out. At the same time, as the speed increases, the absolute differential increases, and the stirring effect of the spiral drum is enhanced.

It is very important to consider the factor for the selection of Decanter centrifuge, here’s some important factors for the users:

1.1 Differential ratio

The settling velocity of solids in different media is different, and the degree of aggregation is different, so different differential speed ratios should be used. When the other parameters remain unchanged, the differential speed is large, the solid material is pushed out faster, the amount increases, and the liquid content increases, the shaft power generally decreases, but the separation effect will decrease, that is, the solid content in the filtered liquid Will increase. As the differential speed increases, it actually acts as a stirrer in the drum. Choosing the right differential ratio is the first factor to consider when choosing a model.

1.2 Length-to-diameter ratio

The aspect ratio is the ratio of the axial length of the Decanter centrifuge drum to its diameter. The working area of the Decanter Centrifuge is divided into several areas such as feeding, sedimentation, drying, and unloading. The length of the settlement area is the main parameter that determines the separation effect. The longer the settlement area, the greater the aspect ratio, the better the separation effect, but the greater the shaft power. Different length-to-diameter ratios should be selected according to different media properties (mainly settlement performance), and should be considered in combination with differential speed ratios.

1.3 Power

The use of larger power can improve the processing capacity, especially when the settlement performance of the medium is very good. The user has certain difficulty in choosing the model. In the face of new media or media without successful use experience, relevant tests should be conducted.

2 Determination of operating parameters

2.1 Adjustment of overflow diameter

There are four options for the overflow diameter of the general Decanter centrifuge. The larger the diameter of the overflow, the longer the drying zone, and the lower the water content of the filter cake, but the higher the solid content of the filtered liquid, so the appropriate overflow diameter should be adjusted. For the “three mud” that is not easy to settle, it should be smaller, and for the medium that is easy to settle, such as TA residue, it should be larger.

2.2 Speed

According to the working principle of the Decanter Centrifuge, the higher the speed, the better the separation effect, the dryer the filter cake, the clearer the filtered liquid, and the greater the shaft power. This is an important parameter in actual operation, but it is not that the higher the speed, the better the effect. Generally speaking, for the medium that is easy to settle, the higher the speed, the greater the shaft power, which is easy to cause the mechanical or solid material to be pushed out, causing the material to block. Therefore, the appropriate speed should be selected according to the factors such as the power of the Decanter Centrifuge, the feed, the dehydration effect and other factors. For the “three muds” that are not easy to settle, when the rotation speed is high to a certain value, there will be a phenomenon that the separation effect decreases, the sludge production decreases, and the solid content in the filtered liquid increases. When the rotation speed is reduced, the mud production fork will increase. This is because the material slips in the drum and cannot be pushed out. At the same time, as the speed increases, the absolute differential increases, and the stirring effect of the spiral drum is enhanced.

The decanter centrifuge operators often encounters problems like material blocking material during their daily use. Here are some normal solutions about the blocking issue to share with our users:

When the decanter centrifuge cannot be turned on normally and the auxiliary inverter alarms overload, we can remove the protective cover of the auxiliary motor and move the input shaft pulley of the differential with the hand wheel. The phenomenon proved to be that too much material between the spiral and the drum caused the spiral to jam. The solution is as follows:

1. Catch the differential pulley with something, and manually rotate the steering wheel to rotate the drum, until the resistance obviously disappears. Then adjust the main and auxiliary machines to a lower frequency, start at low speed, and rinse with water.

2. Some decanter centrifuges are equipped with foreign frequency converters, such as ABB, Siemens, etc. Some frequency converters have a special low-speed protection starting method.

If the low-speed and high-torque starting function can be realized, just adjust the main and auxiliary machines to the low-speed section and rinse with water.

Another method is to hold the drum in place, remove the end water blocking adjustment plate of the drum, adjust the auxiliary machine to reverse, turn on, and let the material be discharged from the drain outlet of the drum. Then adjust the auxiliary machine to forward rotation and discharge. Repeat the operation. This method is suitable for large length-diameter ratio decanter centrifuges where the material blocking is particularly serious and the artificial rotation cannot move at all.

GN can not only provide users with Dewatering Decanter Centrifuges, rely on GN rich production line of separation and conveying equipment. GN can also provide users with turnkey solutions for the material dewatering process, including solutions for material transportation, classification and dewatering.

GN is a professional manufacturer in Decanter centrifuge field. 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.

The screw conveyor is a main component of decanter centrifuge, its structure, materials and parameters are directly related to the separation effect, production capacity and service life of the decanter centrifuge. The screw conveyor is mainly composed of a spiral blade, a spiral cylinder and a feed chamber.

    ①Spiral blade: The spiral blade of the recovery device is a continuous integral spiral blade, the spiral winding direction is right-handed, the blade is perpendicular to the generatrix of the drum, and arranged at equal pitch. Since the spiral blade directly contacts the solid-phase sediment, the solid-phase sediment and the blade move relatively. The blades will wear out in daily use, and the ability to transport sediment after the wear is reduced, so that the moisture content of the sediment increases. In daily inspection work, attention should be paid to the inspection of spiral blades. Maintenance personnel sometimes only pay attention to the inspection of rotating parts and ignore spiral blades. If the spiral of the centrifuge has open welding, cracks or severe wear, it should be repaired in time. The repaired welding place on the screw pushing surface should be polished and smooth, and the spiral should be corrected. The stress relief heat treatment is more difficult to operate, so it is more important to focus on strengthening the protection of the spiral during daily use.

    ②Spiral cylinder body: The spiral cylinder body is also a cone-pillar combination type. The inner cavity of the cylinder is the feed cavity, and there are four feed distribution holes in the feed cavity.

     ③Feeding position: In production, the closer the feeding point is to the liquid phase outlet, the smaller the particles have no chance to deposit and will be discharged together with the centrifugal liquid. The manufacturer takes this into consideration when producing the centrifuge. The precision of the feeding point set at the small end of the spiral is set at the middle and rear of the spiral cylinder, which is equivalent to extending the drying zone and solid phase material. The time for centrifugal separation of the liquid is correspondingly extended to ensure the dryness of the solid phase discharge.

By the way, if you are interested in our products, please check the following items of our company on Alibaba:

Decanter centrifuge

3–Phase Disc centrifuge

Sludge dewatering Screw press

Oil water separator

Centrifugal pump

Vacuum Pump

Submersible pump