BCR - Energy & Efficiency In Raw Materials Preparation
Mining ConsiderationsCompanies looking to invest in a new mine face a number of challenges. First is the price factor—how much are you willing to spend? The cost of opening a new mine has been increasing, said Bob Whittemore of General Shale Products Corp. (Johnson City, Tenn.), so you’ll want to carefully evaluate whether a new mine is actually needed. Next, you’ll need to use geological maps and aerial photography to find an appropriate mine site. Once a prospective site has been found, the next step is to take samples and submit them to the lab for testing, to determine whether the raw material is what you’re looking for.
If the tests come back positive, there are several more steps you’ll need to complete before the mine can be considered your own: 1) contact the property owner to find out if he or she is willing to sell, and then work out the details of the purchase; 2) construct a geology map containing information that relates to brick manufacture; 3) run a plant test to make sure your plant can process the material; 4) come up with a “mining scheme” (including a plan for reclamation) to use for applying for a permit; 5) pave the entrance roads; 6) put in an operations area, including settling basins; and 7) clear the property, saving the topsoil for reclamation.
During the mapping stage, three types of maps are generally used, explained Brian Besier of Acme Brick Co. (Denton, Texas). Base maps show drill locations and property features such as roads, pits and stockpiles. Isopach maps are made up of contour lines representing equal thicknesses, and cross section maps are profile drawings that show usable reserves, stripping, material description and total shrinkage. New software called Techbase™ can be used to create accurate, detailed custom maps showing details such as available reserves and a complete representation of the property surface.
Putting materials from a new mine into production often poses another set of challenges. Lab and plant tests should be done on the new materials to determine how they will perform in the finished product, but even extensive testing can’t guarantee a trouble-free operation. If cracks start to occur in production, use opportunities such as plant shutdowns to determine what’s going on in the kiln. Take samples from every car or every other car to find out where cracks are occurring. “The character of the crack is an important clue to what caused the crack and where it happened,” said John Storer-Folt (retired) of Canada Brick’s Toronto plant. A computerized “crack library”—which provides a “fingerprint” of what the crack looks like along with possible causes—can be helpful.
Regardless of whether your mine is new or old, quality control starts in the mine. That’s why Richtex Corp. in Columbia, S.C., decided to do oxide analyses on the different sections of its mine, as well as on its stockpiles. The results showed that the material hadn’t changed since the first evaluation several years ago—but it’s better to be safe than sorry. According to David McKeown of Richtex, “The lower the coefficient of variation in your raw materials, the less variance you’ll have in your brick.” To ensure easy retrieval of mine and stockpile information later on, the company compiled all available data from the oxide analyses and other lab tests in an Access™ database. This information can now be obtained at will in a variety of formats.
Equipment, Energy and DustJust knowing what’s in the raw material may not be enough to solve all of your production problems. Sometimes new equipment and changes in day-to-day operation are needed to ensure efficient manufacturing.
General Shale Products Corp. in Smyrna, Ga., recently struggled with the question of how to get enough output from its raw material. The shist and shale composing the majority of the material were being ground together but weren’t very compatible, and the company was limited to running 50-80 tons per hour of raw material.
To solve this problem, the company installed new JC Steele hammermills; made several mine modifications, including mining in only the driest, hottest weather and covering the stockpiles with plastic in the fall; made several grinding plant modifications; optimized its screens to ensure that all material would contact the screen cloth; switched from trains to trucking for material transportation; and built a covered shed to store its raw materials. As a result of these modifications, the company is currently able to run at 150 tons per hour.
According to Jochem Handle of Rieter-Werke Handle (Konstanz, Germany), raw material preparation tends to be more sophisticated in German brick plants. A machine called the Giant Hydromechanical Twin-Cradle Roller Machine is often used to achieve small particle sizes and therefore a higher quality final product. “The U.S. seems to be stuck making the same products because the quality level is not as high as it could be,” said Handle. “By adding as little as one piece of machinery—a high-speed roller—manufacturers can increase quality by as much as 45%.
“The U.S. methods work fine for the type of brick being manufactured,” Handle concluded, “but why aren’t you going further?”
Some plants are going further using other types of equipment. In 1987, General Shale’s Johnson City, Tenn., facility decided to replace its old 384 grinder. After hearing about Stedman’s Grand Slam Crusher, plant manager Terry Beverly decided to give it a try.
In July ’98, General Shale installed the first Grand Slam. It worked so well that the company decided to install a second unit less than a year later. “We were able to go from about $30,000 per year in wear parts to about $9,000 using the Grand Slam,” said Beverly. The new system also reduced large lumps in just one pass, allowing the company to combine multiple crushing stages into one and save on raw material costs.
Denny Lane of Richtex Corp. (Ninety-Six, S.C.) also touted the benefits of the Grand Slam. After just a year-and-a-half of service, the new crusher had already significantly improved the quality and efficiency of the plant’s operation. Finished material output went from 80 to 140 tons per hour, and the company was able to eliminate a second shift of three people in the grinding area. The crusher has also extended the life of other equipment in the processing area and has resulted in a reduction in energy costs.
Equipment installed in other plants centers on dust collection and control. When Acme Brick built a new plant in 1985, it designed the facility so that the slurry and mixing room was by itself, and all material conveying processes were enclosed using pipes and seals. Dust collectors were located throughout the facility, and the company thought it had a foolproof system. But when production started at the new plant, a dust problem emerged despite all these precautions.
Acme determined that the majority of the dust was being generated during cleanup by sweeping. To solve this problem, the company installed several small “sweeper vacuums.” They also relocated the fans to maximize ventilation, installed automatic doors on the mixing plant to ensure that they stayed shut, and rebalanced the dust collectors to ensure maximum efficiency. “Improvements continue to be made,” said Jim Ogg, plant manager.
The main problem with dust in the brick industry is crystalline silica exposure. According to Mary Ann Keon from Boral Bricks, Inc. (Atlanta, Ga.), a comprehensive silica standard is expected from the Occupational Safety and Health Administration (OSHA) by fall 2000. Under this standard, the permissible exposure limit (PEL) is expected to be lowered to 0.5, and reporting, medical surveillance, engineering controls and exposure monitoring will all be required. “The economic impact to manufacturing sectors will be enormous,” said Keon. “Industry needs to wake up to this issue.” Keon concluded by urging participation in a technical feasibility study being done by the National Economic Research Association. (For more information about the feasibility study, contact Mary Ann Keon at 770-645-4529.)
New Innovations and PracticesAlthough robots have been around since the late ’80s/early ’90s, they’ve hardly been used in the brick industry because no robotic arm could handle the required amount of weight at a fast enough speed. According to Christophe Aubertot from Ceric, Inc. (Golden, Colo.), all that is changing. New robots will be introduced in January 2000 that can handle 880 pounds of payload with an eight-second cycle time. Additionally, new computer control systems will allow the robots to move faster, and vision systems will help ensure accuracy in the unloading process.
Still, gantry systems will continue to have a place in the brick industry, said Don Denison of Denison Engineering (Greensboro, N.C.). Many operations that could be done by robots are better handled by gantry systems (turning tiles, etc.) to keep the weight and cost of the automated system down.
Computers continue to make a difference in numerous production processes. Several years ago, General Shale Products Corp. in Kingsport, Tenn., invested in a system that could control the amount of coating applied to the extruded column based on column speed. A “delay” in the system prevents the line feeder from starting until the column starts moving.
Mike Vickers and Jeff Young of Acme Brick Co. (Denton, Texas) used computer technology in their plant to develop a computerized lab dryer. The dryer controls air direction, velocity and temperature, as well as humidity. It also records air temperature, brick surface temperature, subsurface temperature and internal temperature, along with humidity, weight loss and shrinkage.
Fast firing is another technology still gaining ground, especially in the U.K., where fast, efficient production is imperative to remaining competitive. Fast firing systems offer computerized control, the ability to reduce labor and harmful emissions, and the ability to reduce plant size and capital costs—in some cases by as much as 50%.
Control systems can be an important part of kiln operation. According to Steve Ogonek of North American Manfacturing (Cleveland, Ohio), data obtained from the kiln should be easy to collect and manipulate. Companies considering a kiln control system should carefully evaluate the different types that are available, talking to others that have used such systems and reading magazine articles and literature. “Smart instruments,” open control systems and inexpensive “smart” sensors are available, he said, and it’s important to think “down the road” and consider future needs when selecting a control system.
Kilns, Scrubbers and SafetyGeneral Shale has made kiln safety a priority. They mandate operator safety training for their kiln operators, and emphasize safe operating procedures on the plant floor. Walkways must be kept clear, and kiln and dryer doors must be locked. Kiln safety systems are also in place. On the gas train there is a manual shutoff valve for the entire system, a low-pressure and high-pressure gas switch, regulator vents and a vent flow switch. Additionally, the kiln exhaust must be operational for the kiln to run.
“Employees are our customers—listen to their feedback,” said Neal Holladay from the company’s Johnson City, Tenn., plant. The company regularly distributes an employee questionnaire to evaluate areas of concern, and improves the safety program based on their input.
For Richtex Corp.’s Columbia, S.C., plant, emissions were a problem. The company considered using wet scrubbers, but these systems create acid water that must be neutralized with alkali. Since fluorine was the most troublesome substance being emitted in their process, Richtex decided to try using an absorber instead. The company obtained limestone from a site in South Carolina and built a storage area to ensure that the material stayed dry. So far, the system has remained trouble-free and has kept the company in compliance.
Mike Stacy of General Shale’s Mooresville, Ind., plant outlined the company’s dedication to environmental stewardship. The company has determined to recycle whatever it possibly can. Its washdown water is collected and pumped into a 100 gallon storage tank, and is later used to wet the raw materials. Engobes are collected and are fed back into the brick machine. Shale spillage is swept or shoveled, collected in a hopper, sent to a raw shale storage area and eventually reused in the brick body. Colored brick is handled like spillage but must be properly diluted to prevent contamination in the brick body. Wood waste (pallets) is given to local industries for use or burned on the kiln cars, paper waste is recycled or burned, and refractory materials are crushed and used on the mine access road. Some of the recycleable material (scrap metal, etc.) can be sold to other companies.
Old Problems and New OpportunitiesOther topics of discussion at the forum included an update on the Environmental Protection Agency’s (EPA) Maximum Achievable Control Technology (MACT) rule, cooperative research on brick freeze/thaw durability and anchor bolts, moisture expansion and color blending.
The 46th International Brick Plant Operator’s Forum will be held October 2-4, 2000, with the tentative theme, “Making a Future Through Innovation with Brick Masonry.” For more information, contact Denis Brosnan, Director, The National Brick Research Center, 100 Clemson Research Blvd., Anderson, SC 29625; (864) 656-1094; fax (864) 656-1095; e-mail firstname.lastname@example.org.
SIDEBAR: Year 2000 Short Courses On Brick Manufacturing And Ceramic TechnologySponsored by The Brick Association of the Carolinas
Brick and Heavy Clay Manufacturing
March 13-17, 2000 & July 31-August 4, 2000
For New Employees, Supervisors and Company Executives
This course was designed by Gil Robinson, long time professor of ceramic engineering, to take students on a hands-on journey from the clay pit through grinding and the mill room, with stops in drying and firing. The emphasis is on what happens and what controls each process. The characteristics of a good brick product are reviewed both from a standpoint of ASTM standards and from a standpoint of field experience. Defects and product problems are analyzed through practical examples.
The course devotes 50% of its time to hands on testing of raw materials (particle size tests) and on green, dried and fired products from the student’s own plant. Experiments are practical, low-cost and aimed at plant adaptation. The other 50% of the time is spent on lecture by the Center staff and by industry professionals. The Center offers its own “Brickmaker Certification” for those passing a recreation of Gil Robinson’s classic test at the end of the course.
Advanced Clay Technology
October 30-November 3, 2000
For Supervisors (those with an interest in an in-depth treatment of manufacturing technology), Quality Control Personnel, Lab Personnel and Research Managers
Advanced Clay Technology is a new course designed for those with an interest in a more in-depth treatment of the science and technology of manufacturing heavy clay materials. Topics include mineral constitution, particle shape and interaction, surface chemistry and fundamentals of rheology. The effects of impurities on firing characteristics are examined in-depth. Phase equilibrium diagrams are coupled to practical lab exercises with dilatometers to show the effect of impurities, firing rate and atmosphere on firing shrinkage. Color development is treated in-depth. Firing experiments are conducted to illustrate color and property development. The statistical variation in properties is described, and new thermal analysis equipment is used to demonstrate emissions on heating clay materials.
For more information about these courses, contact Denis Brosnan, Director of The National Brick Research Center, at (864) 656-1094; fax (864) 656-1095; e-mail email@example.com.