Chemical makers increasingly are turning to mechanical conveying, often to overcome the cost and limitations associated with pneumatic systems.
For example, Nynas Bitumen, Ellesmere Port, U.K., a bitumen, bitumen emulsion and polymer modified binders manufacturer, recently made the switch. The company, faced with the need for a major upgrade, decided that opting for mechanical conveying would obviate two major problems of its pneumatic conveying system: the wear and tear that dry additives were having and the sizeable filtration system required.
Nynas installed four aero-mechanical conveyors and associated equipment from Spiroflow Systems, Monroe, N.C. Ranging in length from 23 to 72 ft, the conveyors operate in vertical, inclined and horizontal directions and can handle 1.5 ton/hr of polymer additives. Because there's no net displacement of air, the plant doesn't need any venting or filtration equipment. The new system reportedly provides a substantial increase in output and much improved process cleanliness over the previous pneumatic system.
The quest for better energy efficiency increasingly is driving the choice. "A typical pneumatic conveying solution can use as much as ten times the energy consumption of one of our mechanical solutions. In the past this wasn't an issue because a solution was proposed by engineering and procurement went out and bought it. Now procurement has a much closer understanding of plant operating costs. This effect is even more profound in Europe, where operating costs are that much higher than in the U.S.," notes Jeff Dudas, Spiroflow's CEO.
Spiroflow offers flexible screw conveyors and aero-mechanical units (Figure 1), both with capacities up to 40,000 lb/hr. Its 2010 acquisition of Dynamet added both cable and disk and chain drag conveying to that portfolio. The latter suits very heavy duty, 24/7, 365-day/yr applications where servicing is difficult and materials need to be moved up to 450 ft. "Heavy duty drag conveying is a real problemsolver especially for materials that are very heavy, very adhesive, or easily fluidized. It makes them 100% conveyable," notes president Michel Podevyn.
Testing of solids often is crucial to coming up with the optimum conveying solution. "You can test two samples of the same material from different plants and each could need a different method of conveying; so we never set out with the intent to sell a particular solution," says Dudas. He cites the case of two carbon black samples from different manufacturers tested last year. They had been processed in different ways, resulting in different particle sizes and shapes. "Both companies wanted to transport, bag and densify their carbon black, but each needed a different solution." Spiroflow's labs in Monroe and Clitheroe, U.K., so far have tested over 8,000 material samples from customers.
"I wouldn't like to guess how many samples of calcium carbonate we have tested over the years and many are totally different. But it is very important for our customers that the solution we offer gives them product consistency," adds Podevyn.
Spiroflow also cites the importance of its systems group. "This was set up to overcome a big change we have seen in customers over the last few years — engineering outsourcing. So we have to be able to offer systems integration," says Dudas. The group also heavily focuses on improving the automation of conveying technologies. "We fine-tune all of the equipment here, replicating, for example, path runs, throughput rates, drive speeds and angles. None of our competitors offer the same service," boasts Podevyn.