There are two bowl configurations available for disc-stack centrifuges. With the help of the machine stoppage, a “self-cleaning” (also known as auto ejecting) bowl can automatically eject the separated sludge at regular intervals. The separated sludge is kept in a “manual-cleaning” (also known as “solids retaining”) bowl, which requires manual cleaning on a regular basis. In order to open and remove the sludge from the bowl, the operator must stop the centrifuge.
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Centrifuge Bowl Self-Cleaning Operation
Through the feed tube, the process fluid is introduced into the bowl. The incoming liquid is given the rotating velocity by the disc stack. Centrifugal force causes the heavy phase, or water, to move outward.
The lighter oil (light phase) is moved inward and toward the center of the bowl by it. The paring disc pump allows the clean oil to leave the bowl after rising to the top.
Water, which is the heavy phase, passes over the top disc and emerges through the water-paring disc from the bowl.
Solids, the heaviest phase, gather at the edge of the bowl. Periodically, the “self-cleaning” bowl opens to release the separated solids. This is how the mechanism works.
At predefined intervals, the hydraulic operating system opens and closes the bowl. Sludge-ejection ports in the bowl body open when the sliding piston is pushed down. The separated sludge is immediately ejected from the bowl by the extremely high centrifugal g-force inside.
The solids content of “self-cleaning” disc centrifuges is limited to approximately 8% (%v/v) because of their intermittent sludge ejection feature. An increased solids content increases the likelihood of clogged bowls and repeated cycles of sludge ejection. From the standpoint of the centrifuge, neither of these circumstances is ideal.
Operation of a Manual Centrifuge Bowl
The process fluid enters the “manual-clean” bowl through the top. Before the fluid reaches the disc stack, the distributor gives it rotation. The separation takes place in the space between the stack’s discs.
The heavier fluid (heavy phase) and solids are pushed toward the bowl’s edge (wall) by the strong g-force. The water (heavy-phase) travels through the passage over the top disc to the heavy-phase outlet while the solids gather on the bowl watt.
The oil’s (light phase) displacement is in the direction of the bowl’s inner center. It ascends to the paring disc pump via the distributor channels. The centrifuge bowl’s clean light oil is pumped out by means of this pump.
The centrifuge must be stopped periodically by the operator in order to manually remove the collected solids from the bowl.
Compared to the previously mentioned “self-cleaning” bowls, these solid-bowl centrifuges are substantially simpler. The hydraulic sludge ejection system is not integrated into the bowl.
Because of its streamlined design, the hydraulic operations beneath the bowl can be performed without the need for an operating water system, unlike “self-cleaning” centrifuges. This facilitates the installation, upkeep, and operation of these “manual-clean” centrifuges.
The application of these centrifuges is limited to processing fluids with minimal or no solids due to their “solids-retaining” design. To put it another way, these centrifuges are perfect for applications involving the separation of liquids.
FAQ
Disc stack centrifugation: How does it operate?
The revolving bowl of a disc stack centrifuge contains conical discs that are closely spaced. These discs immediately impart the bowl’s rotation to the process fluid by dividing the incoming fluid into thin layers. High centrifugal forces produced by the fluid’s rotation cause the heavier solids to separate from the fluid, resulting in separation.
What do the conical discs in a disc stack centrifuge serve as?
The fluid column is divided into layers by the conical discs. Between these discs, the process fluid travels in a radial pattern. These discs’ close proximity shortens the sediment’s settling distance, which improves settlement efficiency and speed.
How is a disc stack centrifuge designed?
A disc stack centrifuge’s design consists of a rotating bowl that contains a series of thin, closely spaced conical discs. As the fluid to be separated travels through the interdisc space, it rotates as well. Higher density solids settle on the disc surface due to the centrifugal force created by the rotation, and the separated fluid exits the bowl. The main purpose of the disc stack centrifuge is to separate the solids from the fluid.
What is a disc stack centrifuge’s disc stack exactly?
The disc stack in a disc stack centrifuge is a collection of conical plates, or discs, stacked vertically. This stack of thin plates is stored inside the centrifuge bowl. Thin metal strips are affixed to each disc, and these strips function as vertical spacers to create a gap between the discs.
What is a disc stack centrifuge’s particle size efficiency?
Particle size efficiency of a disc stack centrifuge is 0.5 microns for metal particles and 1 micron for non-metal particles.
Dimensions and Absorbency
The flow rate of each centrifuge for a given fluid is the basis for disc centrifuge sizing. An OEM-published flow rate chart, for instance, is included with every Alfa Laval centrifuge and indicates the expected capacity for various fluids, such as hydraulic oil, diesel, and fuel oil.
These centrifuges have a capacity that goes from two gallons per minute to more than 500 gallons per minute.
Another important detail regarding disc centrifuges should be taken into account by the user. In real-world centrifuge applications, a centrifuge’s “rated” capacity is largely irrelevant. The hydraulic swallowing capacity of a centrifuge to prevent overflow is known as its rated capacity.
The “rated” capacity is higher than the actual processing capacity. According to the previous discussion, the properties of the process liquid and contaminants determine the actual processing capacity.
Put differently, different liquids require different capacities from the same model of centrifuge. This discrepancy stems from Stokes’ law, which states that the viscosity of the fluid is one of several factors affecting the centrifuge’s efficiency.