Powdering of sticky material

June 19, 2014 Anders Olsen

Handling sticky additive materials can be tricky and time consuming. The blocking of silos, chutes and other pieces of conveying equipment can affect operations for long periods of time, and impose the nuisance of numerous short stops and constant cleaning.

If a cold climate environment is added to the equation, the problem can escalate even further as moist, sticky material freezes in large lumps and becomes almost impossible to handle.

In a quest to overcome these challenges, the Cold Climate Group in FLSmidth has developed a new concept called, “Powdering of Sticky Material” (patent pending) at our research facility in Dania.

Extensive testing of a variety of well known conveying methods, non-stick materials, as well as new exotic surface coatings, did not lead to a durable solution. A new approach was required. Initial laboratory tests with powder-coated clay showed great potential. The concept was further developed, together with equipment modifications necessary to solve the task. At full scale, the equipment consists of two powdering stations aiding an apron feeder-type material extraction device, a powder silo and a dedusting filter.

                                               

The first station (1) pre-powders a rubber belt conveyor to prevent adhesion of the sticky material to the belt conveyor. The sticky material  
is then fed onto the belt by the extraction device by means of a special shredder, as it is critical the feed is done in small lumps (2). From here, sticky material enters a second powdering station where remaining exposed surfaces are completely encapsulated in powder by an aeration system (3). Excessive dust is removed from the rubber belt conveyor by a dedusting system before the powder-coated and easy-to-handle material continues on its path. Dedusted powder is returned to the powder silo for reuse (4).

The powdering is still effective after multiple conveyor transfers and general handling. Chutes and baffle plates are kept clean, and in long term storage powdering considerably reduces cohesion – even when the piles are frozen.

Only 2-3% of powder needs to be added to the conveyed material – a small amount when compared to the added volume required when attempting to reduce stickiness by mixing in dry material. Another process advantage is that raw meal and filter dust are ideal mediums for use as the lubricating powder. Hence, no additional additives are needed, keeping plant operating costs at a minimum. Also, from a retrofit perspective, this means existing belt conveyors can handle the added dust, and the process has a negligible impact on chemical composition.

About the Author

Anders.Olsen@FLSmidth.com

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