In order to fully understand how a decanter centrifuge operates, we must first define what a centrifuge does. In many industrial jobs, solid material often mixes with liquids, contaminating water supplies or turning mud into sludge. A decanter centrifuge is useful in that it separates solids and liquids, and has become an essential component of water waste facilities and the chemical, oil, and food processing industries. Moreover, without a centrifuge, many of these companies would become so inefficient they could not function.
There are several types of decanter centrifuges currently utilized in the industry, the most common of which are vertical, horizontal and conveyor centrifuges. The principle behind a decanter centrifuge is based on the theory of gravitational separation. For example, if you fill a glass with a mixture of mud and water, over time the weight of the mud will cause it to settle down at the base of the glass. With the mud congealed at the bottom, the water will be forced upwards, creating a clear separation between the two.
A decanter centrifuge employs the same principles of gravitational force. However, unlike the glass mixture, the process is expedited through the use of continuous rotation. In fact, rotation provides anywhere from 1000 to 4000 times the normal gravitational force, reducing the time required for separation from hours to seconds.
The concept of rotational separation is similar to rides found at amusement parks and county fairgrounds. In these rides, placing yourself at an angle allows you to overcome the gravitational forces induced by rotation. Similarly, a decanter centrifuge is essentially a bowl tube that rotates at an extremely high speed. The bowl tube is equipped with an internal conveyor which moves in the same direction but at a different velocity.
- Step 1: The slurry is inserted into the centrifuge through a connecting pipe and onto a conveyor.
- Step 2: Utilizing an internal feed compartment, the conveyor ushers the slurry through a nozzle into the bowl area.
- Step 3: The bowl rotates at high speeds to induce gravitational forces.
- Step 4: High speed rotation separates the solid material from the liquid in a matter of seconds.
- Step 5: The conveyor delivers the solid material upwards where it is discharged through a nozzle.
- Step 6: The solid material removed, the purified liquid is released from a separate output.
The ability to purify a liquid makes decanter centrifuges ideal for waste water treatment facilities. However, there are variety of industries for which such centrifuges play an important role. Similar to other decanter equipment, centrifuges are simple to install and do not require a foundation to build upon. Their efficiency saves time and materials and is an essential component for many blue collar industries..
In many industries, centrifuge equipment is utilized to separate denser elements from a mixture. Generally, this means removing a solid material from a liquid, yet it can also be used to demarcate liquids from each other. As the name implies, a centrifuge relies on centrifugal force. The faster it rotates, the more this force works to enhance gravitational pull and accelerate the separation process. The following article will focus on the application of centrifuge equipment in various industries.
As the equipment is highly efficient and effective, there has been little change in the technology regarding centrifuge equipment over the past few decades. The life span of a typical centrifuge ranges from 15 to 25 years depending on the style of the equipment and the quality of the manufacturer. Furthermore, the life of the machinery can be extended an additional 10 to 20 years with proper maintenance and care. Consequently, good centrifuge equipment can offer an extremely high return on your initial investment. This is why it is imperative that a prospective buyer consider the total cost and quality of the centrifuge as well as the estimated delivery time.
Types of Centrifuges
There are a variety of different centrifuges depending on the specific need of your business. These include decanter, tubular, basket, peeler, pusher, and disc centrifuges.
- Decanter Centrifuge – This centrifuge features an elongated cylinder with a conveyor in the center. The cylinder spins at a different velocity, which in turn pushes denser material to the exterior wall. The conveyor then distributes these solids to the opposite end of the centrifuge where it is discharged.
- Tubular Centrifuge – A tubular centrifuge consists of an extended vertical bowl that is primarily used for separating two liquids. As the bowl spins, liquid of a lesser specific density is contained within the middle, whereas liquid of a greater specific density is routed to the exterior walls. Naturally, to maintain separation each liquid is provided with its own discharge point. Any small solids contained therein must be removed through a manual process.
- Basket Centrifuge – With basket centrifuges, liquid is inserted into an internal basket. The basket then rotates at a high velocity, forcing higher density materials to the interior wall where they are trapped by a cloth filter. Materials that contain a lighter specific density, on the other hand, pass through the filter cloth and exit the bowl through a series of punctures on the wall of the basket. For example, in the case of solids and liquids, the liquid will pass through the filter and perforations while the solid material will remain inside the basket. The speed of a basket centrifuge is limited to a specific amount of revolutions per minute, or RPMs.
- Peeler Centrifuge – Peeler centrifuges are equipped with a screen designed to handle batch processes. After a slurry batch is injected into the centrifuge, the material is then passed through the screen which prevents the denser solids from seeping through. This cake of materials is then peeled off by an arm and discharged from the device.
- Pusher Centrifuge – As with a basket centrifuge, spinning the bowl of a pusher centrifuge causes the liquid inside to exit out of a side wall. However, once the basket is devoid of liquid, a pusher centrifuge has a dedicated arm that scrapes the interior and pushes the solid material from the rear of the basket, which in essence allows the basket to immediately process the next batch.
- Disc Centrifuge – A disc centrifuge operates much in the same way as a basket centrifuge with one substantial difference. The inner bowl is equipped with disc plates split in the center by an inlet. The discs are engineered to allow denser debris to settle onto the disc and placed at an angle so that the sludge will slide off into an outer discharge nozzle. The result is a smoother and faster separation process, greater capacity and higher RPMs than a traditional basket centrifuge.
The long term reliability of centrifuges induces many businesses to opt for cheaper, used equipment. It is important when evaluating a used centrifuge to consider the age of the equipment, the quality of the manufacturer, and whether its features suit the needs of your business. It is recommended that you choose a reputable brand and ask for detailed maintenance records to ensure the device was properly cared for. If your needs are more short term, there are dealers who provide centrifuge rentals for periods as short as three months.
A decanter centrifuge is an excellent tool for separating liquid and solid mixtures. Industrial work and water processing plants are often tasked with purifying substances with variable amounts of solid material, and a decanter centrifuge is engineered to remove any and all contaminates from sewage and effluent sludge. Centrifuges are also capable of separating disparate fluids such as weighted or non-weighted oil and water based liquids. For example, those in the beverage industry commonly employ decanter centrifuges to extract juices. Utilizing basic gravitational force, the centrifuge divides the denser, weightier solids from the lighter, effluviant liquid. Consequently, decanter centrifuges are utilized by a variety of industries with applications extending from water processing to the manufacturing of stainless steel.
Each decanter is equipped with a hydraulic scroll drive system that allows the user to automatically control the rate of solid material discharge. The design of the device separates solids while still maintaining their weight and consistency. For example, research has shown decanter centrifuges when used to separate mud are able to sustain the material’s viscosity and original composition. The machine provides flexibility as well, with programmable frequencies and an adjustable belt that allows for altered rotation speeds. In addition, the system offers long term reliability, with well maintained equipment lasting for up to 25 years.
The two primary types of decanter centrifuges are:
1. Solid Bowl Decanter Centrifuge
This centrifuge is encased in a shell comprised of two layers. The outer layer has a tapered aperture which allows solids to discharge as the bowl rotates. The inner layer is a hollow case molded to match the outline of the bowl. The resulting centrifuge mitigates the amount of moisture in the cake and produces material with a higher quality centrate. Solid bowl decanters are manufactured with two or three phases, and are generally inexpensive to purchase and maintain. Their environmental impact is minimal and in full compliance with CE regulations.
2. Screen Bowl Decanter Centrifuge
Ranging in 160mm to 1400mm in diameter, screen bowl decanter centrifuges are engineered to separate materials with better overall washing efficiency. Primarily used in separating polyolefins and minerals, these decanters work in multiple phases, starting with sedimentation and clarification before moving on to the water removal process.
Applications of Decanter Centrifuges
The primary application for decanter centrifuges is extracting solid materials from collected sludge. However, despite its singular purpose, the equipment can be utilized by a variety of industries. For example, oil companies employ decanters to separate debris and dirt from crude oil. Refineries also make use of the technology in conjunction with shale shakers and mud cleaners. Companies that sell processed foods and fish depend heavily on decanter centrifuges to ensure the quality of their products. Most importantly, decanter centrifuges are critical to water processing facilities and ensuring our environment is free of unnecessary toxins.