Issue link: http://www.e-digitaleditions.com/i/858601
powderbulk.com PBE August 2017 7 Words worth noting from PBE articles in 2017 January — Mixing and Blending "Normally, the more cohesive your material, the more shear required to mix it. Low-shear and mid-shear mix- ers are suitable for more free-flowing materials, while mid-shear, high-shear, impact, and particle-design mix- ers are suitable for more cohesive materials." — from "Choosing a mixer for low-shear batch mixing," Chris Paulsworth "Solvent-based cleaners might be necessary if your material isn't water soluble. Depending on your mater- ial's chemical characteristics and solubility and the severity of any material caking on the mixer's interior surfaces, further cleaning may be needed." — from "Suppliers' tips" February — Screening and Classifying "The airstream carries the milled material from the grinding chamber to the mill's air classifier wheel, which is designed to allow particles small and light enough to be carried in the airstream through the clas- sifier wheel and exit the mill while rejecting oversized particles back to the grinding chamber." — from "Case history: Milling and classifying for a more efficient sor- bent" "Check the screen channel gaskets to ensure that they're mounted correctly on the screen ring. Occasion- ally clean the solids buildup from the gaskets. Inspect the gaskets periodically for evidence of cracking, break- age, or crimps. If you see damage, replace gaskets as needed." — from "Suppliers' tips" March — Pneumatic Conveying "An ideal pneumatic conveying system has few or no bends because each bend requires more conveying en- ergy and can become a point for conveying line wear, particle degradation, and plug formation. However, many systems are installed almost as an afterthought and seem to be designed to go around every obstacle in the plant." — from "Pneumatic points to ponder…," Jack D. Hilbert "A true sign that a rotary valve is starting to wear is when you notice an increase in air leakage (also called blow-by) through the rotor vanes. This affects the amount of material that can enter the rotary valve, re- ducing the pocket-filling efficacy and decreasing the amount of material feeding into the conveying system." — from "Suppliers' tips" April — Drying "Some dryer types, such as drum dryers, may damage fragile pellets. The circular fluid-bed dryer, however, is more suitable for handling fragile pellets, as it agitates, moves, and dries the pellets with only vibration and air- flow." — from "Case history: Circular fluid-bed dryer improves pelletizing process" "When moisture is removed from a wet powder, re- gardless of hygroscopicity, generally the powder be- comes less cohesive and more free-flowing. The material's angle of repose will typically decrease, and, depending on the initial wetness and amount of mois- ture removed, the dried material may become dustier than it was before the drying process." — from "Suppli- ers' tips" May — Bagging and Packaging "Pallet load instability has been a problem for years, but due to the complexity of the process chain, no defined levels of responsibility exist for when an unstable pallet causes product damage during transport. Because most stretch film is sold through distributors, film man- ufacturers often have little contact with end users and receive little to no feedback when a stretch-wrapped pallet fails." — from "Stretch wrap film and pallet load stability," David Finnemore "Automation can be used at various points in the bag- ging process, from placing empty bags into the equip- ment at the beginning of the line to having a robot automatically palletize the bags and wrap the pallets at the end of the packaging line. A common request from customers is to create a packaging line with one worker loading empty bags and watching over the line and an- other driving a forklift bringing supplies and taking the loaded and wrapped pallets to the shipping ware- house." — from "Suppliers' tips" June — Size Reduction "Even if you think you understand your material, you may still benefit from a complete material analysis. A mill is a big investment and fine grinding is an inher- ently expensive process, but a thorough understanding of your material will help you optimize the mill's operat- ing parameters to minimize energy and maintenance costs while producing a consistently high-quality prod- uct." — from "Using particle analysis to optimize agita- tor bead mill performance," Kevin Kirkwood "Over time, as plant capacities increase and different raw materials or ingredients are introduced, consider going back to the equipment supplier to explore new features that may be available or finding a company with a broad product range, size reduction expertise, and process design expertise along with testing facili- ties to help you get more out of your size reduction equipment." — from "Suppliers' tips" July — Mechanical Conveying "The aeromechanical conveyor avoids many of the problems associated with conveying difficult materials because the high-speed airstream fluidizes and carries the material through the conveying tube. The material "rides" through the conveying tube quickly, making lit- tle contact with the tube wall and discharging com- p l e t e l y d u r i n g o p e r a t i o n . " — f r o m " U s i n g aeromechanical conveyors for difficult-to-handle mate- rials," Nick Webber "Knowing the rate at which upstream equipment intro- duces material into a conveyor is important for deter- mining whether accumulation or transport buffers or infeed controls will be needed to control the material feedrate. Overlooking the maximum capacities of in- feed and discharge equipment can cause the conveyor to be either starved or overfilled with material." — from "Suppliers' tips"