The Processing Challenges of Powders and Bulk Solids
Powders and bulk solids are among the most challenging materials to handle in a food or beverage processing plant, for various reasons.
They require specialized equipment for unloading as well as conveying. They’re not discrete units, like products or packages – but they usually don’t flow freely like liquids, either. They’re liable to all kinds of flow interruptions. And in the worst-case scenario, they can cause electrostatic explosions with potentially tragic consequences.
“In a food or beverage plant, it’s not enough for a conveyor system to transfer ingredients from one point to another,” says David Nichols, vice president of sales and marketing for Volkmann USA. “The ingredients need to be protected from contamination and degradation along the way. And when transferring powders, the conveyor system needs to prevent dust from escaping into the workplace and prevent the potential for an explosion.”
The flow issue is arguably the most important and pervasive. Depending on their makeup, products in powder or bulk form are prone to cling to surfaces, especially if they’re high in fat or moisture. This can lead to problems like buildup on the interior of tubes or vessels, or “ratholing” or “bridging” of product in hoppers, preventing them from dropping down to the bottom. Examples of such problem products include almond flour, pancake mix and brown sugar.
Conveyance options Handling powers and bulk solids is largely a question of matching them to the right kind of conveying system. The major alternatives are pneumatic, flexible screw, tubular cable and vibratory bed.
Pneumatic conveyors use compressed air to blow product through a tube. Flexible screw conveyors use an auger, usually stainless steel, inside a polymer or stainless-steel tube. They can be routed at any angle (though not, obviously, as curves or bends). Tubular conveyors use disks, usually polymer, strung on a cable through the interior of a pipe, that drag the product along. Vibratory conveyors use a vibrating or reciprocating motion to move product along a bed or trough without any use of belts or other propulsion.