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Greetings!
Greetings! Welcome to Jenike & Johanson's Fall 2010 Chemical E-Newsletter. The focus of this issue is on bulk handling challenges and approaches that are relevant to the chemical industry.
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How to Prevent Caking
 In many chemical plants, the product is a powder that appears to be free of agglomerates when packaged in bags or other containers. Because moisture often results in caking, the powder is thoroughly dried, and often, a vapor barrier is included in the packaging. Nevertheless, customers may report receiving excessive caked material. Even when a powder is packaged dry, unwanted agglomeration can still occur over time due to moisture migration, a consequence of temperature gradients that occur when the powder is packaged at elevated temperatures but then stored or transported under ambient temperatures.
Once moisture migration takes place, three mechanisms cause caking:
- Water can act as a plasticizer and soften the material.
- When exposed to high relative humidity air, some powders can adsorb enough water to form liquid bridges.
- Solid bridges between particles may form if soluble matter in liquid bridges precipitates during cooling or drying.
To analyze this problem and find a remedy, the root cause must be uncovered. Shear cell tests that measure the powder's gain in cohesive strength during storage can be conducted under controlled conditions in a laboratory. Such an analysis will reveal the target powder moisture content that will eliminate caking.
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Moving Bed Reactors
 Chemical reactions that involve bulk solids can often best be carried out in moving bed reactors. Moving bed reactors are especially useful in the case of equilibrium-limited reactions, since conversions can be increased beyond equilibrium if the gaseous products are removed from the bulk solid reactant. Moving bed reactors are also practical if spent catalyst must be removed to maintain desired reactivity.
Having a uniform solids velocity profile within the moving bed reactor is critical to ensure a uniform residence time. This is accomplished by ensuring that the solids flow pattern within the reactor is mass flow, which occurs when the walls of the hopper section of the reactor are steep enough and have sufficiently low wall friction to allow the solids to move along the walls. In addition, the outlet of the reactor must be properly sized to prevent obstructions to flow from developing. Flow property testing is required to determine the critical outlet dimensions and hopper angles. |
Jenike & Johanson Presents at ChemInnovations
 Greg Mehos, project engineer, presented a paper titled "Critical Aspects of Moving Bed Dryer and Operation" at the 1st Annual ChemInnovations Conference and Exposition. The paper describes how hoppers or silos that have been modified to allow injection of a gas can be used to remove moisture or other volatile compounds from bulk solids.
To obtain a copy of this paper, contact Jenike & Johanson.
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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 will include topics such as:
- Equipment types and the solutions to flow problems commonly associated with each of them
- How friction, cohesion, compressibility, and other properties affect the flow of solids through various types of feeders, chutes, reactors, bins and hoppers
- How to specify and select hardware best suited to avoid various bulk solid flow problems and objectives, including how to retrofit existing equipment to correct flow problems
- Solving problems associated with solids handling, such as lost production, downtime, extra labor, poor quality control, degraded material, and unreliable equipment
Obtain registration details
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Jenike & Johanson Publications Related to Chemicals
For more information on the following publications, please contact Jenike & Johanson's librarian directly via email or telephone at 978-649-3300.
- "Critical Aspects of Moving Bed Dryer Design and Operation"
- "Efficient Drying of Bulk Solids in Silos"
- "Handle Bulk Solids Safely and Effectively"
- "Design and Operation of Gravity Dryers"
- "Successfully Scale-Up Solids Handling"
- "Modifying Your Storage Vessel for Trouble-Free Continuous Purging or Conditioning - Part 1 and Part 2"
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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 chemical industry
We look forward to providing you with practical, cost-effective solutions to your bulk solids handling problems.
Sincerely,
Greg Mehos
Jenike & Johanson, Inc.
Tel: 978-649-3300
www.jenike.com
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