Pneumatic Conveying Keeps Moving Ahead

Technical developments enhance performance and economics.

By Seán Ottewell, Editor at Large

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Chemical companies' demands for conveying solutions that increase throughput, shorten lead times, handle vastly differing solids, reduce costs and simplify maintenance -- all while ensuring worker and plant safety -- are spurring suppliers to develop innovative solutions.

At dense-phase pneumatic conveying specialist Air-Tec, Calderara di Reno, Italy, for example, customers' desire to handle products with vastly different levels of abrasiveness is driving developments.

The company has installed conveyors at many chemical plants. "The most common challenge that we have to face is the abrasiveness of the product," says marketing and communication manager Fulvia Lombardo.

"Abrasive materials can wear the conveying line and be damaged by high-velocity transportation; thus we find the lower conveying velocity of a dense-phase system best. This lower speed, combined with a reduced amount of compressed air or other gases, avoids pipe wear, preserves the integrity of the product and contributes greatly to reduced maintenance costs," she adds.

The company uses air boosters to introduce gas into the conveying systems to reduce friction inside the pipes, and relies on anti-wear cast iron elbows to extend downtime intervals.

Air-Tec has just completed a project at the research center of a major European-based supplier of specialty cross-linkage compounds. The challenge here was to convey one metric ton of polyvinylidene fluoride (PVDF) powder per hour over a distance of 30 meters. The conveyor also had to be usable with materials both more abrasive and fragile than PVDF, and ensure the quality of all products during handling procedures.

To achieve this, the company installed a TPA (Air-Tec Pneumatic Transport) system, its most advanced offering, which provides greater flexibility and control of transport cycles. Material is discharged into the TPA from bags and conveyed the 30 meters to two hoppers with load cells connected to gravimetric feeders. Valves allow PVDF into the hopper; they close when the target weight has been reached (Figure 1).

"This solution has also met the requirement for flexibility and can be used to convey other materials with different levels of abrasiveness and fragility that might be present in the client laboratory," says Lombardo.

In a sign of what's to come, Air-Tec's research and development department is working on combining different ratios of air and inert gases to boost conveying efficiencies and save energy. In collaboration with engineers at the University of Bologna, Italy, the company has developed a mathematical model that enables plants to "drastically" reduce energy consumption during transport of any product, says Lombardo.

FLOWABILITY
Speaking at a bulk solids conference in Guangzhou, China, on May 20th, Jaime A Gómez, global business development manager for K-Tron, Pitman, N.J., pointed out that many variables must be considered when deciding how best to implement a pneumatic conveying strategy. However, he emphasized that the first priority is to address material flowability (Figure 2).

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