Designing of the dryer section of nutritional yeast production plant – Industrial sector review – Part 7

Designing of the dryer section of nutritional yeast production plant – Industrial sector review – Part 7

Choice of Pieces of Equipment

The key pieces of equipment that required careful selection were the atomizer and the separation equipment to be used in the spray dryer design. In each case there were number of variants which could be used to carry out the
specific unit operation.  Therefore each piece of equipment was researched, compared and discussed in order to determine the appropriate type of unit needed to perform the desired operation (Maters,1979).

Atomizer

Atomizers used in spray drying industry are divided into two sub division i.e. (1) Rotary atomizer and (2) Nozzle atomizer. The selection and operation of the atomizer is of supreme importance in achieving economic production
of top quality products.  The choice of atomizer to be used is strictly related to the quality and type/size of the required product.

Note:

The particle size of the yeast cell after flocculation stage is 30-70?m (i.e. in cream). The diameter of the baker’s yeast cell is 4—8 µm. The solution of the yeast particles forms small aggregates (a natural process), and therefore
raise the unflocculated yeast particle size to about 30 µm. (Jin-Sung Kim, 2001)

The viscosity of the cream is 1.8 cp (Endo, 2009)

The details of the two types of atomizers and the advantage of one over another are discussed below.

(1)  Rotary Atomizers

Rotary atomizers are most suited if fine particle product is required, the Rotary atomizer gives greater flexibility and use of operation. These employ centrifugal energy to atomize the fluid (disc or wheel rotating at speed).
The feed accelerates to the periphery and disintegrates into spray.

The rotary atomizers give fine particle product of mean size of 30 to 120µm (Msters, 1979), which match our quality product requirement. With this type of atomizers radial trajectory of droplets can be controlled and hence product
deposits on the chamber are prevented. This atomizer also called the spinning discs are very suitable for slurries and pastes with higher viscosity.

There are two different types of designs available for the rotary atomizer; Wheel atomizer and disc atomizers. The disc atomizers are used to meet coarse–spray requirement at high production rate. The advantages of using the
wheel atomizer design are described in Process Description section (Endo, 2009).

Continued in part 8

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Posted by Ahmed Tariq on Feb 25 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