Pneumatic conveyors can move fine, dry material using pressure or vacuum. The material is totally enclosed within tubes or pipes that are best suited for small, dry, low bulk density products such as wheat, sugar, cement powder, sands, and other aggregates. They are a flexible option to move products around existing equipment and are relatively small. They can convey material fast and without any product loss.
The three main pneumatic conveyor types are dilute phase, dense phase, and semi-dense phase conveyors.
Dilute phase pneumatic conveyors are used for nonfragile materials and implement low pressure, high-velocity air streams which fluidize fine particles. They are used for conveying light, non-abrasive materials that are not easily breakable such as flour, carbon, and powder chemicals. They come either as pressure or vacuum conveyors. Pressure conveyors work best with powders with bulk densities less than ~62 lb./ft3 and can move granules long distances. Vacuum conveyors are best suited for materials that pack under pressure (woodchips, fibers, etc.) and are reserved for short distances.
Dense phase pneumatic conveyors utilize high pressure and low velocity to move products prone to breakage. The product is “pulsed” thought the system, sometimes with the help of air injectors. Dense phase conveyors are slower but are easier on the material. Common applications of dense phase pneumatic conveyors are for moving heavy bulk density products, abrasives (sugar, salt, etc.), blended products, plastic pellets, and other fragile materials. Dense phase pressure conveyors gently convey particles smaller than 0.75 in over long distances (250+ ft), while dense phase vacuum conveyors can do the same but at much shorter distances (<200 ft.).
Semi-dense phase pneumatic conveyors are both pressurized and have an air mover, allowing them to convey non-fragile materials smaller than 0.25 in at medium velocity. Semi-dense pneumatic conveyors are used when dense or dilute conveyors do not work, as they provide some increased speed yet still protect the material through the system. They work well with aeratable, abrasive materials like cement and fly ash and can convey them at rates around 1,500-3,500 ft./min.
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