Going Ballistic Main ImageOur technology expert gives readers a complete look at a separation method that is growing in usage at MRFs around North America. BY ROGER GUTTENTAG

Rutger Zweers, director of sales for equipment manufacturer Stadler America, the ballistic separation idea was first developed by Germany-based Stadler as a sorting solution in Europe for recyclable and waste materials. Within the last five years, the ballistic approach has started to be adopted in North America as part of new MRFs or system upgrades. Figure 1 on page 15 provides an example of a typical ballistic unit with some of its key components identified.

One end of the unit is elevated to create a slope that averages about 15 degrees. Material is typically metered at the lower end with the infeed positioning dictated by available spacing and manufacturer recommendations with respect to the mass flow being processed. Crankshafts then power a series of perforated vertical paddles to move in an elliptical motion so that each paddle is moving both vertically and horizontally.

Figure 2 shows what happens to a material stream after it is metered onto the deck of the machine. Flat materials move forward to the top end while 3-D products fall backwards to the lower end of the deck. At the same time, the paddle perforations allow the screening out of smaller materials. Some manufacturers also provide an option to stack one to three units in order to accommodate a higher throughput or to achieve multiple screenings based on different paddle perforations in each deck.

The technology is commonly described as one that separates separating “rounds” from “flats.” But according to Chris Hawn, North American sales manager for Machinex, a better way to understand ballistic separation is imagining materials reacting differently to the process of being bounced around. A similar perspective is provided by Richard Howard, vice president of MetalTech Systems. “One type of material (2-D) absorbs energy and the other is repelled by it,” he explains. The result is that flat and flexible 2-D materials cling to the paddles, which move those items forward. At the same time, 3-D rigids will generally bounce backwards in response to the paddles’ upward strokes.”

Read the rest here: Going Ballistic by Roger Guttentag