Large-Scale Clarification and Filtration Process II

Question 1

Describe three types of industrial filtration equipment.

Answer 1

1. Gravity Filters: Filtration is driven solely by gravity, and it is used mainly in the laboratories.
2. Vacuum Filters: Used for large scale filtration processes. Filtration is enhanced by vacuum mechanism and continuous cake removal, and it runs for extended periods. e.g., rotary vacuum filters.
3. Pressure filters: This large scale filtration process combines the effect of gravity and pressure to facilitate the separation process. They are the most common type of filters used in the processing of pharmaceutical products. e.g., Nutsche pressure filter, Metafilter, Cartridge filters Capsule filters.
4. Centrifuge: Centrifuges use centrifugal force to separate the contents of a sample based on their density. Centrifugation can occur with either filtration or sedimentation methods.

Question 2

What are the two main types of industrial-scale centrifuges used?

Answer 2

1. Perforated basket centrifuges, which perform a filtration type operation.
2. Tubular bowl centrifuges, where particle sediment towards the wall under the influence of centrifugal force.

Question 3

Describe a perforated basket centrifuge.

Answer 3

The perforated basket centrifuge consists of a stainless-steel perforated basket lined with a filter cloth.
During centrifugation, the filtrate is forced through the cloth and removed via the liquid outlets, and the solid material is retained in the cloth.

[Learn diagram]

Question 4

Mention two applications of the perforated basket centrifuge.

Answer 4

1. It is using the separation of crystalline materials from the preparation liquid e.g. preparation of drug crystals like aspirin.
2. Removal of precipitated proteins from insulin.

Question 5

Describe the tubular-bowl centrifuge.

Answer 5

Also called centrifugal sedimenters, these consist of a rotating cylindrical bowl.

The product enters at the bottom and the centrifugal force causes the solid to be deposited on the wall as it passes up the bowl and overflows at the top.
This can be adapted to separate immiscible liquids.

Question 6

Mention 6 applications of tubular-bowl centrifuges.

Answer 6

1. Liquid-liquid separation
2. Removal of very small particles
3. Removal of solids that are compressible or slimy, and which easily block filter media
4. Separation of blood plasma from whole blood
5. Separation of different particle size fractions
6. Examination of the stability of emulsions.