Principle, Construction, Working, Uses, Merits and Demerits of Perforated and Non-perforated Basket Centrifuge : Pharmaguideline

Perforated Basket Centrifuge

The centrifuge is used for filtration. The perforated wall separates solids from liquids based on the difference in densities.
In the bowl, there are perforations along the sides.
The perforated wall allows liquid to pass, while solids are caught in the bowl during the liquid phase.
The solid sediment is removed from the centrifuge sediment after the machine stops.

In most cases, the filter cloth is lined with a perforated stainless-steel basket (typically 1-2 m in diameter)
A typical basket rotates at 25 rpm, and speeds above this may result in excessive strain on the basket
Upon entering, the filter cloth holds the product against centrifugal force by throwing it outwards
As the filtrate passes through the cloth, it is drained through the liquid outlet. On the cloth, the solid material remains.
Alternatively, the centrifuge can be sprayed with water to wash the cake

When a basket is stationary, material is placed on the basket
During centrifugation, the amount of material should be optimal, otherwise, the basket is greatly stressed. Even distribution of material should be ensured.
To rotate the basket, power must be applied so that maximum speed is reached as quickly as possible
There are 1000 revolutions per minute in the basket.
The power required to run the machine is relatively small compared to that required to start it and bring it up to full speed.
In centrifugation, the perforated wall keeps liquids out, while solid particles stay in the basket.
At the outlet, the liquid is collected from the basket
The cake is spun until it is as dry as possible
A high speed is sometimes used to ensure the cake is completely dried
Power is cut off after a specific amount of time. Centrifugal force is applied to stop the centrifuge.
Bringing the basket to rest
A blade is used to cut the solid cake, which is then manually unloaded

It is extensively used to separate crystalline drugs from mother liquor (such as aspirin) using perforated basket centrifuges
Solids may also be removed from a liquid using it. Precipitated proteins, for instance, are removed from insulin
A perforated basket centrifuge is used to separate sugar crystals

Compact and occupying very little floor space, the centrifuge is very space efficient
The system is capable of handling solid-rich slurries as well as paste-like slurries
There is very little moisture in the final product
To separate the dissolved solids from the cake, this method is used
The process moves quickly

Due to the complexity of the entire process, labour costs are high
Batch processing is involved
It is inevitable that machines used for extended periods of time will undergo considerable wear and tear. The centrifuge may cause the solids to clump together over an extended period of time, making it difficult to remove together.

There is no perforated or porous medium present in this sedimentation centrifuge, so separation takes place according to differences in densities between the samples.
Solids settle at the side of the basket during centrifugation, while liquids settle at the top of the basket where they are collected by a skimming tube.

Stainless steel is used for the basket. A vertical shaft is connected to the basket.
A tube for inlet and a tube for skimming are contained in the basket.

Continuously fed suspension enters the basket. While centrifugation is occurring, solids remain stuck to the walls, and liquids remain on the top.
Solids are scraped off with a scraper from the basket after liquid is collected in a skimming tube.

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