BRICK & CLAY RECORD: Solving a Sticky Screening Problem

November 1, 2004
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A new screen design is helping General Shale efficiently handle even extremely wet raw materials.

Above: The 5 x 10 MEV screens, supplied by Midwestern Industries.

General Shale Brick, Inc. is always looking for a better way to make brick. When the company built its new face brick plant in Rome, Ga., it used only top-of-the-line equipment-from highly uniform Ceric kilns to robotic loaders and unloaders, and state-of-the-art packaging systems. The plant was built in two phases. Phase 1, completed in November 2003, featured one kiln and the capacity to produce 65 million standard brick equivalents (SBEs) per year. Phase 2, completed in September 2004, brought a second kiln online, along with the capacity to produce another 65 million SBEs.

The grinding room, which was completed along with Phase 1, services both plants and also features state-of-the-art systems. Designed to handle 150 tons per hour of raw material, the room contains a 4260 Grand SlamTM rotary impact crusher supplied by Stedman, one 5 x 10 MEV scalping screen and three 5 x 10 MEV finish screens supplied by Midwestern Industries, and a 3624 hammer mill supplied by J.C. Steele. All of the equipment was chosen specifically to handle the Rome plant's raw materials-a schist from Atlanta, a shale mined onsite and a shale from a mine shared with Florida Tile on Berry College's campus in nearby Mount Berry, Ga.

As with all experienced brick manufacturers, General Shale knew it would have to deal with some wet materials from time to time, depending on the weather. But it didn't realize just how wet its materials would be in the first year of the plant's operation.

"We had a lot of rain and flooding in this area late last year, and the ground under our stockpiles was saturated. A lot of that moisture migrated up into our raw materials," explains Terry Beverly, General Shale's director of engineering.

A Sticky Problem

Such wet materials created a sticky problem in the grinding room. The materials are brought into the plant through three feed hoppers and are blended on a single variable-speed feeder belt. From there, the material is sent through the rotary impact crusher and then across the primary scalping screen. Oversized material is sent first to the hammer mill and then to the three finish screens. Any material that doesn't go through the finish screens at that point is sent back to the hammer mill, and continues in that tailings loop until the particles are small enough to go through the screens.

All of the equipment in the Rome grinding room-including the screening systems, which feature high-frequency screens and electric screen heating-is designed to efficiently handle wet clay. However, there was one sticking point.

"The material is fed through a round opening and hits a half-moon diverter plate in the material distributor, which spreads the material out evenly over the screens and enhances screening efficiency. It's an innovative design and it worked fairly well, but we had some problems with our wet material sticking to the diverter plate," explains Beverly.

A close-up of the new material distributor design, which features a heated diverter plate to keep wet materials moving efficiently through the process.

A Heated Solution

General Shale approached Midwestern Industries with the problem, and Midwestern immediately put its engineers to work devising a solution. The resulting technology is relatively simple. The diverter plate is heated to around 150§F, which breaks the surface tension and keeps the material from adhering to the plate. When used in conjunction with high-frequency screens and electric screen heating, the new technology fully optimizes screening efficiency.

After installing the screens with the heated diverter plates, General Shale saw an instant improvement in the throughput of its Rome grinding operation. "The screens are doing a good job," Beverly says. "Like any other plant, we get a little less material through the screens as the moisture content goes up, but that's normal. We certainly don't get the sticking that we would without the heated diverter plate, so that helps us increase our throughput even when our materials are damp.

"It's nice to have technology that enables us to efficiently deal with extremely wet material when we have to," he adds.

For more information about screening solutions, contact Midwestern

Industries, Inc. at P.O. Box 810, Massillon, OH 44648-0810; (330) 837-4203; fax (330) 837-4210; or P.O. Box 10157, Macon, GA 31297-0157; (478) 781-8725; fax (478) 781-8746; e-mail ; .

General Shale is a subsidiary of the Wienerberger Group, headquartered in Vienna, Austria. For more information about General Shale, contact the company at P.O. Box 3547, Johnson City, TN 37602; (800) 414-4661; . More information about the Wienerberger Group can be found at .

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