Issue link: http://www.e-digitaleditions.com/i/558599
7 PBE August 2015 Words worth noting from PBE articles in 2015 January — Mixing and Blending "Every time you transfer a blend from one vessel to another, it has the potential to segregate. You can't assume that because the blend is adequate in the blender it'll remain that way after it's discharged." — from "Five fundamentals for effective blend sampling," Eric Maynard "Through automation, you can reduce the amount of labor required to run your operation and the number of times the finished blend needs to be moved or handled, and you can engineer your process to accurately and consistently control the blend ratios to ensure that the finished blend is correct every time." — from "Suppliers' tips" February — Screening and Classifying "The long-stroke screener is also ideal for screening fertilizers, which are typically free flowing but are also highly abrasive. The low-frequency motion limits wear on the screener components even while providing sharp separation and high throughput." — from "A short introduction to long-stroke screeners," Manfred Bruckner "The very best way to determine how long a screen will last on any given application is by keeping good records and having a good preventative maintenance program. For example, if you find that your screens last for approximately 12 weeks, change them in 10." — from "Suppliers' tips" March — Pneumatic Conveying "In a pneumatic conveying system, the conveying gas (such as air or nitrogen) is really a compressible fluid whose volume changes depending on the gas's pressure and temperature. As the gas's volume changes, its velocity in the conveying line changes as well." — from "Pneumatic points to ponder…," Jack D. Hilbert "When a mill's production throughput is less than its design capacity, a poorly selected pneumatic conveying system is usually at fault, even when the system was supplied as part of the mill package. In some cases, an ineffective conveying system can reduce the mill's grinding capacity by as much as 50 percent." — from "How to get better grinding performance with pneumatic conveying," Gary Liu "Maintaining airflow is essential to successful pneumatic conveying of sticky, chunky material. A higher system differential will keep the material moving." — from "Suppliers' tips" April — Drying "The law of conservation of mass tells us that the mass of the moist material entering the dryer should equal the mass of the dry material exiting the dryer plus the mass of the water vapor driven off. If the masses are unequal, it's likely that the material's been thermally damaged during drying and VOCs have been driven off." — from "Preventing thermal particle damage in your continuous convection dryer," Becky Long "If you're drying solvents instead of water from your material, or if there's a significant fire risk, the dryer can be designed to operate without oxygen. This can be done using nitrogen under a closed circuit or by self- inerting, using a specially designed burner that consumes most of the oxygen (approximately 97 percent) in the combustion air." — from "Suppliers' tips" May — Bagging and Packaging "The bulk bag filler has a dual-concentric filling nozzle that includes a combination bag inflator and venting system. This system inflates the bag before filling and then vents the displaced air as the bag fills." — from "Case history: Farmer reaps big rewards from automated bulk bag filling system" "Every material has an optimal feeding method. You have to start with a feeding method (gravity, vibratory, screw, or air) that works with your material and then you can start working on upsizing the machine or decreasing the filling rate." — from "Suppliers' tips" June — Size Reduction "The theoretical amount of energy required to reduce a material's particle size is often less than 1 percent of the energy it actually takes a mill to do it. Most of the energy used to operate the mill is absorbed by elastic or inelastic particle deformation or lost to friction, noise, heat, and vibration in the equipment." — from "Energy consumption in common fine grinding mills," Gary Liu "While past experience is a factor in selecting a mill for your application, testing in the manufacturer's equipment will give you confidence that you've selected the appropriate machine. Many suppliers don't charge for testing in their equipment, so it's to your benefit to take advantage of this opportunity." — from "Suppliers' tips" July — Mechanical Conveying "A bucket elevator is often very tall, and an ignition near its boot can create a chimney effect, resulting in increased turbulence as the heated air rises through the shaft and flows around the buckets. This turbulence can re-entrain the dust clinging to the housing walls, adding fuel to the fire." — from "How to prevent or mitigate a dust explosion in your bucket elevator," Bill Stevenson "The most economical conveyor design is typically a narrow conveyor running at high speed. However, when handling a fragile material, you need a wider belt running at a slower speed to achieve the same capacity while protecting the material." — from "Suppliers' tips"