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Greetings!
 Welcome to the Fall 2010 issue of Jenike & Johanson's Mining E-Newsletter. As you know, while the short-term market outlook for many sectors of mining industry is not the best, market conditions are expected to improve in the next couple of years due to higher consumption of metals and minerals in the developing nations. The present slowdown offers a great opportunity to think about improvements to your material handling systems, and be ready when the market improves.
Jenike & Johanson is prepared to assist you with material storage and handling projects at your mines. In this issue, we focus on typical flow problems that occur as a result of freezing conditions and look at how to address them. |
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Freezing Conditions & Ore Handling
 Handling of moist ore when temperature falls below 32°F (0°C) is of particular concern to operations. Freezing related flow problems occur primarily due to temperature differences between the bulk solid and contact surfaces. Mainly, four different scenarios can occur:
- Ore and surfaces in contact with the ore are below 23°F (-5°C)
- Ore and surfaces in contact with the ore are between 23°F and 32°F (-5°C and 0°C)
- Ore above 32°F (0°C) and surfaces in contact with the ore below 32°F (0°C)
- Ore below 32°F (0°C) and surfaces in contact with the ore above 32°F (0°C)
Depending on the scenario, the problems manifested will differ and will require different solution approaches.
Below, we discuss in general the flow problems caused as a result of freezing conditions and the approaches to solve them. For more information, please visit our website or contact us.
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Does Freezing of Stagnant Zones Minimize Live Capacity of Your Stockpile?
 Stockpiles are one of the most economical means of storing large quantities of ore. However, if the reclaim system has not been designed to take into account the effect of freezing conditions on material flow, arching and ratholing problems may get worse. The stagnant material in the stockpile may freeze and can further reduce live capacity, which means more downtime and lack of surge capacity.
Typically, several gravity reclaim hoppers, with either apron or belt feeders, are used under stockpiles to discharge the ore onto a common collection belt conveyor. To achieve reliable discharge during freezing conditions, the arrangement and configuration of the gravity reclaim hoppers must take into account the effect of freezing on the flow properties of the ore. We have worked on numerous projects providing reclaim system designs for new installations as well as retrofits, using our typical project approach. With our proven design methodologies and 3D CAD program, we can assist you in designing or improving your stockpile reclaim system to provide reliable operation even in adverse weather conditions.
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Does Freezing Complicate Your Crusher Feed?
 In open pit mines, freezing complicates the primary crusher feed. Damp fines can freeze and adhere to the dump hopper and grizzly, limiting throughput of the crusher. Large, frozen lumps can form that block crusher feed chutes. These problems result in costly downtime and necessitate manual intervention. These problems can be minimized by designing the crusher feed system to take into account the effects of freezing on the flow properties of the ore.
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Does Freezing Increase Build-Up On Your Chutes & Hopper Walls?
 Typically, the fines present in the ore are the primary cause of buildup problems. Damp fines can adhere and build up on the uninsulated, cold surfaces of chutes and hopper walls. This could lead to plugging problems in transfer chutes. Poorly designed transfer points plug frequently, are prone to high wear, create spillage and dusting problems, and cause high belt wear. Build-up on hopper walls can change the flow pattern in hoppers to funnel flow. This can result in loss of live capacity, and flow stoppages due to arching and ratholing problems.
For chute design, free fall height and abrupt changes in the direction of material flow should be minimized in order to control material impact pressures that can cause build-up and can also lead to high chute wear. For hoppers, the hopper wall surface should be steep and smooth enough to promote flow. Outlet size of the hopper should be designed so as to prevent arching and ratholing. If you have transfer points and hoppers that need improvement, we can assist you.
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Upcoming Courses
 Jenike & Johanson engineers will be presenting their popular powder and bulk solids handling courses for ASME/AIChE (American Society of Mechanical Engineers and American Institute of Chemical Engineers) in Orlando, Florida on November 30, December 1 and December 2, 2010.
This course is highly recommended for personnel in the mining industry involved in selection, operation and maintenance of ore and concentrate handling equipments. It will arm them with the knowledge required to reliably handle these materials.
Obtain registration details
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J&J Publications Related to Mining
For more information on the following publications, please contact Jenike & Johanson's librarian directly via email or telephone at 978-649-3300.
- "Design of Stockpiles in Mining Operations" by Francisco J. Cabrejos
- "Ore Pass Design For Reliable Flow" by David J. Goodwill and Francisco J. Cabrejos
- "Chutes as the Ultimate Dust Controls" by Greg Petro, Thomas J. Baxter and Francisco J. Cabrejos
- "Interfacing Belt Feeders and Hoppers to Achieve Reliable Operations" by John W. Carson, Francisco J. Cabrejos and Michael Rulff
- "Improving Storage and Handling of Ores in Mining and Processing Applications" by Jayant Khambekar, Michael Rulff and Francisco Cabrejos
Contact Jenike & Johanson about these publications
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Background of Jenike & Johanson
Jenike & Johanson is a consulting engineering firm specializing in the science and technology of bulk solids handling. In our four laboratories in the United States, Canada, and Chile, we have tested more than 10,000 bulk solids and used the results to design accurate, cost-effective solutions to flow-related problems for more than 3,000 companies around the world in such industries as cement, chemicals, pharmaceuticals, energy, mining, consumer goods, solid waste, and more.
We have over forty years experience applying practical, science-based technologies to implement robust processes, and a history of solving difficult challenges others cannot resolve.
Learn more about Jenike & Johanson's role in the mining industry
We look forward to providing you with practical, cost-effective solutions to your bulk solids handling problems.
Sincerely,
Jayant Khambekar, Ph.D.
Jenike & Johanson, Inc.
Tel: 978-640-3300
jkhambekar10@jenike.com
www.jenike.com
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