Designing of the dryer section of nutritional yeast production plant – Industrial sector review – Part 8

Designing of the dryer section of nutritional yeast production plant – Industrial sector review – Part 8

Nozzle Atomizers

Nozzle atomizers are best suited to less viscous fluids. These are also called pressure nozzles and are well known of their simplicity of design. The feed is fed to the nozzle under pressure and pressure energy is utilized from the nozzle orifice to disperse
the liquid in the form of spray. The nozzle produces a high speed film of liquid that readily disintegrates into a spray as the film is unstable.

The nozzle atomizers produce coarse particle product with a mean size of 120 to 250µm (Maters, 1971). The advantage of pressure nozzles lie in their low cost, ease of replacement and simple maintenance.  Depending on the nozzle capacity, the pressure nozzles
can also be used to atomize the viscous fluid of kinematic viscosity of up to 0.01 m²/s or dynamic viscosity of 16. 9 cp (Coulson, 1991)

Another type of atomizer, called gas atomizer which uses gaseous energy is also available to be considered, although it has not yet found widespread application. It is knows that it produces dusty product containing proportion of very small particles (Coulson,
1991), so the use of it is not recommended.

Although the viscosity of the cream suggests that both the atomizers can be used, the selection of the atomizer was based on the advantages of using each of the atomizers. There are many advantages of using the rotary atomizer over the nozzle one, which
are explained here:

Advantages of using the Rotary Atomizer over Nozzle atomizer

The advantages of using the rotary atomizer are that these are reliable, easy to operate and can handle fluctuating feed flow rates.  Furthermore these have the ability to handle high feed flow rates without atomizer duplication and to handle abrasive feed
stock. Rotary atomizer has the negligible clogging tendencies due to large flow ports.  These gives the dryer the flexibility to work at higher capacity requirement (incase it is required) and it can also operate under variable cream inlet conditions.

The rotary atomizer gives fine particle product, which match the size distribution of the required nutritional yeast produced. The fine particle size is required because the product is a form of protein supplements which is to be used directly (by pressing)
into vitamin tablets and as an ingredient in cheese substitute. It can also consumed as protein supplement powder to prevent vitamin deficiency or increase strength. The finely divided powder easily dissolves in water and hence is easy to consume. The product
has to be of superior quality as for direct human consumption with most particles of equal size and optimum density, moisture etc. For this reason, the rotary atomizer was selected.

Continued in part 9

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Posted by Ahmed Tariq on Feb 28 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