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Fast firing of brick is not a new idea. Every brick manufacturer is aware that one or two brick placed in a lab kiln can be successfully fired in anywhere from four to 12 hours. Over the past 30 years, various methods have been applied to try to make this concept a reality in a manufacturing environment; however, none has been commercially viable for the production rates required.
Recently, a new fast firing system has been developed* that offers both high production rates and a favorable return on investment. Imagine layers of brick floating through the kiln in a way that allows the kiln gases to pass around each brick. The brick are treated individually and uniformly-similar to what happens in the lab kiln, only in much greater quantities. With this new system, brick manufacturers can gain a competitive advantage through increased productivity, lower fuel consumption, higher quality and reduced scrap rates.
*This patent-pending system was developed at EISENMANN Corp., Crystal Lake, Ill.
A Unique Loading ArrangementThe new system is based on a loading arrangement that places two-high pairs of brick in multiple layers on the kiln car. The keys to the system are the support structure for the ware and the load/unload machine.
The ware support structure is a matrix of siliconized silicon carbide posts and beams. The use of siliconized silicon carbide carries a number of benefits, including:
- A temperature use limit of 2460°F
- Superior strength at peak firing temperature (a modulus of rupture [MOR] of 37,000 psi)
- Long life due to zero porosity (it is completely impervious due to the matrix of silicon within the structure, as well as the protective coating of silica glass that forms on all surfaces)
- Light weight relative to traditional cordierite-based kiln car furniture
The posts are securely anchored into the kiln car frame. Proper positioning of the posts and beams is crucial to an automatic system-any variation can cause problems in loading or unloading. The beams are arranged at the desired levels for two-high layers of brick and support multiple pairs of round alumina-mullite stringers upon which the brick are loaded. (Alumina-mullite is a proven support material in the brick industry and has the added advantage of low cost in the most consumable area of the system.) The kiln car tops are made of ceramic fiber for reduced heat storage and low maintenance.
The load/unload machine has been used successfully in the dinnerware industry for the past 10 years. Recently, similar technology has been successfully applied to the heavy loads that are required for handling structural clay brick. The completely automatic machine first finds each level on the car. A series of forks traverses through the car, and the two-high layer of brick and stringers are lifted onto or off of the kiln car structure. The machine is capable of loading or unloading 13,000 modular brick per hour and is designed to operate 24 hours per day, seven days per week, with as few as three operators per shift.
The kiln employs a suspended flat roof and high-velocity burners firing over and under the load, which helps ensure uniform firing. The kiln design includes state-of-the-art automatic process control; automated kiln car handling; kiln car tracking via bar coding of each car; and overall system data collection, which facilitates the collection of information such as the thermal process history of each car of brick and total inventory control.
Benefits of the SystemThe new system provides a number of benefits compared to conventional firing technologies. Faster firing cycles equate to a smaller kiln and dryer and an overall smaller building footprint. This, in turn, reduces the capital cost for the system. For example, a 90 million modular-brick-per-year system can be installed in less than 50,000 square feet of production area. As a result, the industry benchmark of capital cost per 1000 brick can be reduced by as much as one-third.
Additionally, the optimal heat exchange for the ware results in lower fuel consumption, improved temperature uniformity, and greater control of size and other physical properties. The open ware-loading configuration greatly enhances the ease and speed of drying due to greater recirculation of hot gases around each brick. And since each layer is only two brick high, the firing cycle can be achieved with less breakage, no kiln marking and minimal defective product.
Another benefit is that the fast cycles minimize lead time for sales and provide faster product quality feedback. It has also been proven in lab tests that faster firing cycles reduce fluoride emissions. In a commercial-scale plant, this can eliminate the costly addition of a scrubber.
A prototype kiln car has been designed and constructed for use at the National Brick Research Center at Clemson University. Fast firing tests are currently under way with leading brick manufacturers, and the results so far have been extremely positive. With this new system, brick manufacturers can revolutionize their firing process and enhance their bottom line.
For more information about the new brick firing system, contact EISENMANN Corp., 150 E. Dartmoor Dr., Crystal Lake, IL 60014; (815) 455-4100; fax (815) 455-1018; e-mail firstname.lastname@example.org ; or visit http://www.eisenmann.com .