Designing of the dryer section of nutritional yeast production plant – Industrial sector review – Part 3

Designing of the dryer section of nutritional yeast production plant – Industrial sector review – Part 3

Continues Dryers

Out of the many Continues Dryers available, the drum dryer and spray drier is of most interest as these are specially designed in drying of liquids or liquid suspensions. Note that our feed to the dryer only contains 18% dry solids with the remaining moisture
content.  Some other continues driers include:

Rotary dryer — best used for large scale drying of materials, mainly not heat sensitive and where product shape/quality is not as significant. Both direct heating and indirect heating can be used in this dryer.

Pneumatic or continuous fluid bed dryer – If complete dispersion of the product in a heated gas stream can be achieved and the material to be dried is too fine, than this type of dryer is preferred. Theses dryers are quite similar to the spray drier in their
operating principles (Coulson, 1991).

Drum Dryer

Drum dryers are used for liquids and dilute slurry feeds. It and can be an alternative to the spray drier if the product is required in the form of film. The product is then crushed to form powder. The drum is generally used the material is not very heat
sensitive (Stanbury, 2003).

The Drum drier consist of internally heated revolving drum on which the film of the soil mixture is deposited and dried. Drum dryers are usually steam heated and are thermally more efficient than spray drier.  The film of solid is formed by immersing part
of the drum on a trough of the cream or by spraying the feed on the surface of the drum. Double drum dryer also operate the same way as the single roller drum dryer but with increased capacity and the product is formed in the nip (space between the drums)
of the dryer.

A typical double-drum dryer with a 4 ft (1.2 m) by 10 ft (3 m) long drum can evaporate about 270 kg/h (APV dryer handbook, 2000). The Table 3.1 compares the two types of dryers with regard to the product requirements.

Continued in part 4

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Posted by Ahmed Tariq on Feb 22 2012. Filed under Sci-Tech. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry