Against strong international competition, NUTEC Bickley has won the contract to supply a four-car shuttle kiln to one of the world’s foremost energy technology companies. This kiln will be installed at the customer’s investment casting facility and will be used to sinter the ceramic cores. Depending on the exact nature of the cores, the firing cycle will be anything from 20 up to 80 hours.
“Our expertise is widely respected by this customer, with our having previously worked with another of its subsidiaries, a major transformer manufacturer, supplying 15 furnaces and ovens in the last 10 years,” NUTEC Bickley’s VP of Ceramics Alberto Cantú said. “Advanced technologies and cutting-edge manufacturing are at the heart of this global corporation’s strategy, and we are proud to have been selected to assist in expanding and improving ceramic core production.”
The gas-fired shuttle kiln will typically operate up to 2010°F (1100°C) and employs a twin-deck kiln car setting.
Setting dimensions for each car are 47-inch long x 63-inch wide x 34-inch high (1.19 x 1.59 x 0.87 meters) and the kiln’s effective load volume across the four cars is 230 cubic feet (6.55 cubic meters) – with an average total product weight of 970 pounds (440 kilograms).
Sintering is achieved via 12 high-velocity nozzle-mix burners, each individually controlled with its own automatic ignition and safety system, firing above and below the load in a staggered sequence. These high-performance burners, and the way they are configured, provide optimum levels of turbulence and heat transfer, which in turn promotes excellent temperature distribution and uniformity throughout the load.
This kiln will benefit from integration of NUTEC Bickley’s proprietary IMPS combustion control system, configured to deliver pulse control across eight multi-temperature zones, alternating between high and low fire with variable excess air. In practice, this means adjustable and programmable levels of excess air throughout the sintering cycle. The system introduces excess air only when it is required, thereby enhancing both process control and fuel efficiency.
Once the sintering cycle is complete, the IMPS cooling mode is initiated and is available for multi-zone temperature control. Cooling air is supplied to the kiln through the burners, as well as through automatic air-cooling nozzles for shorter cycle times. The cooling nozzles pulse together with the burners’ control zones according to the input required by the cycle and load.
Considering all kiln zones and sintering modes, IMPS offers a number of important benefits to the customer, including:
- Energy savings
- Improved process control
- Utilization of the maximum kinetic energy available from the burners
- Improved temperature uniformity, without the need for excess air
- High turndown ratio
- Easy re-zoning of the kiln via the software program
- High gas recirculation volumes
- Better energy transfer from the gases to the product
- Reduced NOx generation
Sintering of ceramic cores is further optimized by the integration of NUTEC Bickley’s chamber pressure control system that guarantees process stability by using a linear flow-controlled exhaust damper. This is fabricated with a cordierite multi-louver with silicon carbide shafts. The system provides precise control of the exhaust gases and chamber pressure.
All kilns for advanced manufacturing rely on the very highest quality insulation, and this is no exception. The kiln walls are fully lined using NUTEC’s US patented high thermal efficiency Jointless ceramic fiber system for excellent insulation and long life coupled with low maintenance.
The fiber lining is rated at 2600°F (1425°C). The kiln side wall to kiln car seals are constructed using a combination of refractory and insulation brick with a double-labyrinth seal to prevent heat loss and radiation leakage from the kiln chamber, as well as preventing the infiltration of cold air. A sand seal is incorporated to aid in this system.
In operation, the kiln door is opened at the end of the sintering cycle to permit the four kiln cars to be removed. A second set of cars with unfired product is then moved into the kiln so that a new firing cycle can begin. NUTEC Bickley will supply eight cars as part of this contract.
Kiln car movement is via a semi-automatic transfer car system that will move the cars from the kiln and to two different stations, each of which includes sensors to position the cars in loading/unloading positions.