Enriching Flour, Enriching Lives: The Flour Fortification Initiative

22.1. Powder Feeders
Powder feeders are the first and foremost critical step in the process of fortification technology. There are many types of feeders that are available from a number of firms including ingredient suppliers and milling equipment manufacturers. Different types of feeders include volumetric, gravimetric and loss-inweight feeders. Volumetric feeders are the most popular type of feeder used in North America.
Fig. 103: Power feeder (with kind permission from AIC Canada)

One such feeder is described above (Fig. 103). As can be seen from the diagram, the float, indicating the level of the additive in the hopper, can be removed along with a lid that covers the top of the feeder. Additives are added from the top into the hopper. The sides of the hopper, along with built-in guide vanes, flex with an oscillating motion to provide a constant agitation. The powder flows to the feed rolls from the hopper. Stainless steel feed rolls are driven in opposite directions, facilitating discharge of the powder in a thin uniform layer over the width of the rolls. This width of stream can be adjusted externally by means of a slide that can be moved along a graduated scale. The feeder may also be provided with a variable speed motor, in which case the powder feed control is accomplished by varying the rpm. When equipped with a variable speed drive using a DC motor, it provides a 4 to 20 milliamps signal that can be communicated through a controller for controlling the rate of addition from a remote point. The powder feeder is interlocked to prevent any discharge when there is no flour or when the flour conveyor is not running.

22.2. Screw Feeders
These feeders are simple in design (Fig. 104). It consists of a large hopper that is filled with a micronutrient premix. A rotating screw is located at the bottom of the hopper. The rotation of the screw moves the micronutrient premix to an outlet where it is discharged into a flour conveying line. The feed rate is controlled by a variable speed DC motor drive connected to the screw. A large conditioning screw or flexible pulsating plates near the bottom of the hopper maintain the premix in a free-flowing condition, thus avoiding bridging problems.
Fig. 104: Screw feeder (with kind permission from DSM Nutritional Products)

Advantages of this type of feeder are that it sustains a constant addition rate, has a wider range of delivery rates and hopper capacity, uses fewer mechanical parts and is less expensive to build. It may be more sanitary and easier to maintain than the other types of feeders. It is the main type of feeder available as new equipment.


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