REFRACTORIES REVIEW: Thermal Management Advances
June 1, 2007
Every day, refractories serve the very important functions of controlling and confining high temperatures and chemical reactions in industrial processes worldwide. The theme of the 43rd Symposium on Refractories, held March 28-29, was Thermal Management. The meeting, which was co-sponsored by the St. Louis Section and Refractory Ceramics Division of the American Ceramic Society, was attended by 110 people. In addition to the technical program summarized below, an exposition showcased 19 exhibitors.
Invited LectureV. Pandolfelli of the Federal University of Sao Carlos, Brazil, discussed the function of organic fibers in the dryout of castables. He shared several of his conclusions, including:
- The length of organic fibers can be significantly reduced in the mixing process. The best fiber length after mixing is 3 mm, while the best fiber diameter is 15 µ.
- The permeability of castables increases faster with more fiber content.
- There is no effect of fibers on the drying rate of a castable before melting, but as soon as they melt (polypropylene's melting point is 165°C), the drying rate increases because the permeability increases.
- A polyethylene fiber was developed with a lower melting point (100°C), which lowered the temperature at which the permeability increased.
Energy Control and Cost SavingsF. McMann of North American Mfg. Co. discussed the management of energy usage in rotary and tunnel kilns, starting with a review of the variables that can be monitored and controlled. It is a common priority to reduce operating costs while not decreasing product quality, which can be achieved by retrofitting existing kilns.
K. Moody from Thermal Ceramics reviewed various new insulation lining options to cut energy consumption in refinery and petrochemical plant heaters, as related to possible energy shortages and the desire to reduce operating costs. Lining designs, such as those made for floors and upper/lower walls that can reduce heat loss by 25-40%, were discussed and illustrated.
Unifrax Corp.'s A. Cadin presented information and examples of insulation options for thermal management that are increasingly important because energy prices are rising, and industry in general needs to reduce the energy requirement per unit of production. A wide variety of insulation designs are available, including full thickness linings, surface veneers and thermally efficient backup.
R. Chambers from Fosbel discussed the cost and energy savings associated with in-situ (hot) furnace repairs in glass furnaces, and presented data for several actual cases.
To optimize the energy conservation of industrial furnaces, heaters, etc., it is important to use valid thermal conductivity data to design linings and select repair/retrofit materials. J. Hemrick (Oak Ridge National Lab) discussed progress in developing the equipment and procedure for measuring the thermal conductivity of large refractory samples (e.g., 200 x 250 x 50 mm) using an infrared lamp. In addition, C. Kistler (Orton Ceramic Foundation) reviewed an update of the ASTM C-201 water calorimeter units for measuring thermal conductivity. The changes have resulted in thermal conductivity results that are roughly 10% higher than the 1993-era ASTM procedure, and have the potential to come within 10% of the hot-wire test method.
H. Shulman of Ceralink, Inc. reviewed the procedure and benefits of microwave-assist technology (MAT) for manufacturing refractories, wherein radiant heat (electric or gas) is combined with microwave energy. MAT was found to provide a heating rate two times faster than gas alone for a high-alumina refractory.
Castables, Anchors and MulliteR. McConnell from Almatis discussed the aging behavior of alphabond binder in four self-flow castables. Alphabond is more hygroscopic than CA cement and requires special packaging. Initial results for aging at 35°C and 85% RH showed that alphabond-bonded castables have reasonable shelf life without special packaging. More testing will be done to clarify the aging effects and shelf life.
N. Longshaw (CERAM Research, UK) reported initial findings for a new test in development to measure the corrosion of metal anchors. Such a test is needed because metal anchors are implicated in the failure of an estimated 500,000 tons of castable linings each year.
Kyanite Mining Corp.'s D. Jain presented results of a controlled study with several sources of alumina, silica, mullite and kyanite to see how much mullite forms and at what temperature (1000 to 1650°C). It was found that, for pure alumina and silica, no mullite forms until 1500°C. Additionally, kyanite converts to mullite in the range 1250 to 1450°C, and silica fume and alumina can be replaced by micronized kyanite to enhance mullite formation at lower temperatures.
Awards PresentedThe 40th T.J. Planje-St. Louis Refractories Award was presented to Leonard Krietz, vice president of R&D for the Refractory Materials Division of Plibrico Co., LLC. A graduate of Rutgers Univ., he has worked in the refractories industry for more than 30 years.
The Al Allen Award for the best published refractory paper in 2005-2006 was presented by the Refractory Ceramics Division to V. Pandolfelli for "Setting Additive Influence on the Thermomechanical Properties of Wet Shotcrete Refractory Castable Matrices," which appeared in the American Ceramic Society Bulletin, August 2005.
The 2007 St. Louis Symposium Proceedings can be obtained by contacting Patty Smith of the University of Missouri-Rolla at (573) 341-6265 or e-mail email@example.com .