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In This Issue:

• Ask an Expert: Stopping separation
• Feature: Roller mill safety
• Read It Here First: Heat exchanger cools sugar
• Industry News

Q: We are a manufacturer of dietary supplements. We use a slant-cone blender and a V-blender to blend our raw materials for direct compression. We discharge the finished blend into several rigid containers. We find more fines in the last container, especially on the top, when we discharge the finished blend. We’ve tried to minimize the fines on the top by discharging, closing the blender’s lid, operating the blender for two turns, then discharging again, but this hasn’t solved our problem. What can we do to avoid these fines?
-- B. Tran, San Fernando, Calif.

David Dickey, senior consultant, MixTech, says:
Usually when handling free-flowing powders with a wide particle size distribution, vibration and transfer will bring the large particles to the top of the container. The wider the particle size distribution, the more likely it is that separation will occur. Typically, particles that are about three times the size of the other particles may separate. The number of particles with those differences needs to be a significant quantity for segregation to be an issue.

About the only reason that small particles would be on the top is if air passing through the powder bed is carrying the small particles upward. This effect can be present in tumble blenders, but usually only when extremely small, dust-like particles are in the blend.

The most likely explanation from your description of the problem is that as the powder is discharged from the blender, air is flowing up through the discharge nozzle and blowing the small particles to the top in a process called elutriation. If this is the case, check the top of your blender and make sure that it’s vented. If it isn’t, try venting. That way, as the powder flows out the bottom, air flows in the top.
      Continued >>

David Dickey is a senior consultant for MixTech in Dayton, Ohio.

Editor’s note: To send your comments or questions about this or other issues related to handling and processing dry bulk solids, send an e-mail to holly@cscpub.com.

A roller mill is a powerful asset for crushing dry bulk materials, but that power can be hazardous if you don’t operate and service the mill safely. Here are some ground rules for operating your roller mill safely.

Your first line of defense is simple caution. Most industrial accidents happen when people get careless, so always follow general machine safety procedures when you’re near the roller mill. Make sure you read your mill’s operations and maintenance manual and that you understand the information. The mill manufacturer has gone to great lengths to make sure operators know the specifics of safely conducting both operation and maintenance, and it makes sense to take advantage of that expertise.

Your second line of defense is vigilance. Machines with rotating parts are particularly dangerous, so make sure the guards around the mill’s belt drives, inlet, and outlet are properly installed and maintained. Make sure the mill also has the appropriate safety interlocks, which stop the mill when an access door or cover is opened during operation. Never try to defeat these guards, interlocks, or other safety mechanisms for the sake of convenience; they’re there for your protection.
      Continued >>

Raffinerie Tirlemontoise SA (Group RT), a member of the SÜDZUCKER AG Group, operates a sugar processing factory in Brugelette, Belgium. For 3 months each fall, the Brugelette factory operates 24 hours a day, 7 days a week, extracting and refining sugar from regionally grown sugar beets to produce ready-to-use crystalline sugar.

The factory’s cooling system was a combination rotary drum dryer and cooler -- the dryer used a heated countercurrent airflow to dry the sugar, and the cooler used an ambient countercurrent airflow to cool the sugar from 45°C (113°F) to 30°C (86°F). But when the company installed new equipment in the crystallization workshop’s processing line, the new equipment discharged the sugar at 50°C (122°F). The dryer continued to perform well, but the cooler couldn’t handle the sugar’s increased discharge temperature and was unable to cool it to 30°C.

The factory can’t sell agglomerated sugar to its European Market clients, so any agglomerates that formed had to be sent back through the process and melted down and crystallized again, which meant higher energy costs and inefficiencies. The company needed to find a better way to cool the sugar.

To find out how the company solved its hot-sugar problem, you can read “Case history: Factory is sweet on new heat exchanger” in the October issue of Powder and Bulk Engineering. To read it today, click here.

CSC launches new digital magazine
Inhalation, a new magazine focusing on the delivery of inhaled pharmaceuticals, will launch as an online-only publication. The magazine’s publisher, CSC Publishing, St. Paul, Minn., is also the publisher of Powder and Bulk Engineering. The new magazine will feature technical and application articles as well as product news and reviews. The first issue will be available in late October.

Visit www.inhalationmag.com to sign up for a free subscription.


IEST seeks help on crucial industry guidelines
The Institute of Environmental Sciences and Technology (IEST) Working Groups, which develop the standards and recommended practices for controlled environments and cleanroom industries, will hold working group sessions at the IEST Fall Conference, November 11-14, 2007 at the Hilton Garden Inn in Hoffman Estates (Northwest Suburban Chicago), Illinois.

The sessions will discuss best practices across industries and distill the experiences of leaders in these fields. Approximately twenty-two working group sessions will be held at the conference. Learn about the latest research from leading industry experts in your field.

Registration is open at www.iest.org/fallconference/fallconference.htm.


Got tips?
Powder and Bulk Engineering is looking for readers willing to share their tips for solving a dry bulk material processing or handling problem or an equipment problem. Share your better way for keeping material flowing, optimizing the drying process, preventing unwanted agglomeration, keeping your batch-weighing operation accurate, or maintaining your process equipment. Contact editor (Ms.) Terry O’Neill at toneill@cscpub.com.

30th Biennial IBA Technical Conference, October 21-24 at the Hilton Savannah DeSoto Hotel in Savannah, Ga. Sponsored by the Institute of Briquetting and Agglomeration (IBA). Contact Tom"Feldkamp, 715-543-2750, fax 715-543-2751 (tnfeldkamp@centurytel.net; www.agglomeration.org).

Troubleshooting Your Dust Collector, Webinar, November 13, 12:00 Eastern Daylight Time. Sponsored by Powder and Bulk Engineering. Presenter Gary Johnson will describe efficient methods of troubleshooting and common symptoms of dust control problems at hoods, ducts, collectors, and fans. To register, click here.

Measuring Powder Flowability and Its Applications: A Hands-On Design-Oriented Workshop, October 15-16, in Nashville, Tenn. Sponsored by E&G Associates. Covers powder flow and solids handling issues, including segregation, material handling, feeding filling operations and other topics. Contact E&G at 615-269-3740, fax 615-269-3740 (courses@powdernotes.com; www.powdernotes.com).