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Focus On |
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| Solids Handling |
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4/12/2018 |
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engineering how-to
Mechanical Centrifugal Air Classifiers
By Joseph Muscolino, Sturtevant Inc.
Mechanical centrifugal air classifiers are used extensively to process aggregates, ceramics, chemicals, foods, minerals, metals, plastics, flyash and other materials. They are normally employed when the particle size that you need to separate is too fine to screen. The air-classified product can be either the granular coarse discharge with very little fines and dust, or it can be the fines discharge with very little coarse material. Air classifiers eliminate the blinding and breakage issues associated with screens. They work by balancing the physical principles of centrifugal force, drag force, collision and gravity to generate a high-precision method of classifying particles according to size and density. For dry materials of 100-mesh and smaller, air classification provides the most effective and efficient means for separating a product from the feed stream, for dedusting, or, when used in conjunction with grinding equipment, for increasing productivity. Air classifiers can only be used for dry processing. In order to effectively remove fine powders, the surface moisture of the feed must be very low. Mechanical centrifugal air classifiers are masters of accuracy. They are a good choice when the separation curve or cutpoint is too fine for screens (200–400 mesh or finer), when the capacity is too large for screens (up to 800 ton/h) and when easy adjustability is required to meet various product specifications. »
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Consider Wet Agglomeration To Improve Powder Flow
By Greg Mehos, Jenike & Johanson and Chris Kozicki, Feeco International
Agglomeration is the process of converting fine powder particles into larger particles by the introduction of external forces. Agglomeration is often desirable because the process yields a product that has a higher bulk density, contains less dust, and has improved flowability. Fine powders often exhibit flow problems in a hopper, bin or silo, such as flow stoppages, erratic flow, flooding and limited discharge rates. Flow stoppages occur when attractive forces between particles, such as Van der Waals forces, valence forces and hydrogen bridges, cause a cohesive arch to develop at the vessel outlet. In some cases, powder may only flow in a narrow channel when a feeder or gate is operated. If the material has enough cohesive strength to become stable as the flow channel empties, flow stoppages will occur when powder along the walls remains stagnant. Erratic flow results when ratholes collapse, causing the powder to arch as it impacts the outlet. The manner in which a powder flows in a hopper, bin, or silo has a great effect on the likelihood of these solids flow problems occurring. There are two primary flow patterns that can occur in a bin or silo: mass flow and funnel flow. »
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Facts at Your Fingertips
| Facts at your Fingertips: Filter Aids |
| Cake filtration is a common operation across many sectors of the chemical process industries (CPI). In cake filtration, the solid being filtered acts as a screen so that particles of the suspension are retained by the medium, resulting in the formation of filter cakes. In some cases, filtration can be difficult if the material being filtered is highly viscous. |
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what's new
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April's Technology Profile focuses on a high-pressure polymerization process for the production of low-density polyethylene (LDPE), using tubular reactors.
This new web-exclusive article examines the ways digital technologies are driving an evolution in maintenance and reliability. Included is a discussion about the mechanics of machine learning and some guidelines to foster initial discussions about asset management across organizations. |
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from our bookstore
| Engineering Economics and Economic Design for Process Engineers |
| Engineers often find themselves tasked with the difficult challenge of developing a design that is both technically and economically feasible. A sharply focused, how-to book, Engineering Economics and Economic Design for Process Engineers provides the tools and methods to resolve design and economic issues. It helps you integrate technical and economic decision making, creating more profit and growth for your organization. The book puts methods that are simple, fast, and inexpensive within easy reach. |
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