Should Your Powder Be a Pellet?

Engineers tend to overthink things.

Consider the story of an engineering professor who observed his three-year-old building a lopsided Lego bridge. The father pointed out the structure’s fault and challenged the preschooler to shore it up. Expecting the child to add more Legos to even things out, he left the room. Upon returning, he was surprised to discover that the kid had instead removed bricks to stabilize the bridge—a much simpler solution. As an academic experiment, the professor challenged his graduate engineering students to solve the same problem. All added more Legos.

Lauren Petraglia, granulation manager at equipment supplier LCI Corp., relayed that story Tuesday in a theater session at the Powder & Bulk Solids South event in Charlotte, NC. It was a fitting lead-in to her talk about how your product could perform better as a pellet.

Some powders just don’t flow—talc, carbon black, and certain pigments were a few examples Petraglia cited. Such materials tend to bridge, rathole, or otherwise just not play nice. Often when this happens, engineers start tinkering with the equipment to fix the problem. But that can be a mistake.

“Instead of trying to overengineer this feeder, do I have the ability to think outside the box and look at my material?” Petraglia asked, rhetorically.

That’s where pelleting comes in. Using a pellet mill to mash powder into a spherical or cylindrical shape can help not only improve its flow properties but also afford benefits such as dust reduction, increased product density, more uniform packing, improved stability and shelf life, controlled release or dispersion, and more.

Petraglia offered the example of coffee chaff, the shell that’s removed from coffee beans. Chaff has the potential to be a renewable fuel source, but because it’s very low density, flows poorly, and is highly flammable, it’s often treated as waste. Turning chaff into pellets, however, makes it easier to process and ship.

“Now you’ve taken something that was a problem, solved the handling issue, created a new renewable fuel source, cut the transport cost, and improved safety,” she said.

Pelleting can also make it easier to comply with environmental laws such as those in Brazil that require plastic totes or containers used to deliver agrochemical materials be returned to the manufacturer. Those vessels must be stored by customers and ultimately shipped back. Product in pellet form, though, takes up less space, ultimately requiring fewer containers and thus reducing the cost of compliance.

Pellets can even help manufacturers proactively meet their sustainability goals. Petraglia used the example of Tide Pods, laundry detergent that’s encapsulated in dissolvable single-dose packaging. Thanks to that form factor, the manufacturer can ditch the plastic bottle and offer its product in a biodegradable sack.

So could you pellet your material? While some products—sugar, for one—prove problematic to pellet, Petraglia said the possibility is worth considering.

“Ground-up garbage, chicken manure—you name it, somebody’s tried to pellet it, she said.