NUTEC Bickley is in the process of transporting all modules of a 50m-long electric tunnel kiln to the advanced manufacturing facility operated by one of North America’s leading producers of ultra-high-purity alumina and associated products. Installation is scheduled to begin shortly. The client has expanded into the production of a variety of high specification lines, and only the most technologically advanced equipment has been considered.
Alberto Cantú – VP Ceramics
Alumina calcination with advanced efficiency
“This is a significant, high-value order for one of our latest generation electric tunnel kilns,” commented Alberto Cantú, NUTEC Bickley’s Vice-President, Ceramics. “The nature of the material being processed means that tight tolerances and demanding specifications have had to be met. We are delighted that NUTEC Bickley was chosen as a key technology partner in such an important project. Moreover, it demonstrates once again how, when all necessary design parameters are in place, electric heating in continuous kilns can deliver for a wide range of manufacturing processes.”
Key features with latest proven technology
This calcination kiln, with an operatingtemperature of 1200°C (2190°F) and maximum temperature of 1350°C (2460°F), processes the material in saggars, which sit in six-high stacks that are loaded on to the 33 cars accommodated by this kiln. With a firing cycle of 23.6 hours, this means that approximately 5000kg of calcined material is processed each day. NUTEC Bickley has paid close attention to a number of bespoke design aspects, not least many special provisions to prevent equipment wear due to chemical attack that follows degassing of hydrochloric acid during the alumina heating process.
Image #1. 3D view of the electric tunnel kiln, showing its structural design and distribution of key components. The heat conduction, ventilation and conveyor systems, optimized to ensure efficient and uniform operation, are shown.
The use of electric heating, increasingly in demand by NUTEC Bickley customers old and new, is ideal for this process. Extremely tight thermal control is necessary in the kiln chamber, operating under an oxidizing atmosphere, and this particular kiln has 14 automatic control zones for heating, plus two automatic zones for cooling. To ensure maximum flexibility and management of the temperature profile, the control systems are arranged so that the exhaust, heating zones and cooling zones are all independently regulated.
The heating system comprises a combination of silicon carbide and metal alloy elements. These hang down vertically through the roof, and are sited either side of the load, with distribution configured to deliver a well-balanced temperature uniformity throughout the kiln. The electrical connection design means that elements can be replaced while the furnace is at operating temperature.
Hot gases are drawn towards the kiln entrance and are evacuated from the tunnel through exhaust ports positioned in the kiln sidewalls, via the exhaust fan. Cooling is achieved by direct air movement in the cooling zones. The temperature set points from the cooling zones are controlled automatically with cooling nozzles positioned to blow a stream of cold air above and below the load setting.
Image #2. External view of the electric tunnel kiln installed in the plant. It shows its robust structure with refractory lining, ventilation systems and conveyors, optimized to ensure thermal efficiency and operational safety.
Commitment to quality and performance
Advanced insulation systems are also key to maintaining the required performance levels. The kiln walls use lightweight insulation for rapid thermal response and fuel economy, with the lining rated for use up to 1290°C (2350ºF). The roof is lined using NUTEC Bickley’s high thermal efficiency ceramic fiber system for excellent insulation and long life coupled with low maintenance. The roof insulation combines modules of polycrystalline fiber and zirconia grade fiber.
Kiln car operation is based on a semi-continuous feed electromechanical pusher with push speed adjustment. The push speed is configurable by selecting the appropriate firing schedule at the kiln control panel. A vestibule arrangement serves to reduce exchange of air and gases between the factory and the kiln. When a car is being introduced into the kiln, the door at the entry end opens, while the door at the kiln entrance is closed.
The vestibule has two sections: the first accommodates a single car and is separated by two vertical lift doors to separate the factory’s atmosphere from the kiln atmosphere. This is managed by installing an exhaust hood which is connected to the entry exhaust fan, thus ensuring a negative pressure in the vestibule to avoid any gases from the kiln from leaving the chamber. The second section functions as a transition from the vestibule door sections to the kiln’s pusher.
In all its aspects, superior levels of design, build and performance were central to this project, particularly as the client’s production facility is certified to comply with ISO 9001, ISO 45001, and ISO 14001 standards.
For further information, please contact:
Alberto Cantú – VP Ceramics NUTEC Bickley
Carr Saltillo–Monterrey 100 (Km 62.5) 66359 Santa Catarina NL Mexico
Providing Thermal Equipment Solutions that go beyond expectations
We serve multiple industries through the design, building and installation of combustion systems, thermal insulation and highly specialized industrial furnaces, kilns and ovens. We are focused on understanding our customers’ needs and supplying the best equipment at the most competitive price.
In a major, high-value project – the second at this particular plant in Mexico – NUTEC Bickley will supply a 125m-long tunnel kiln to one of the world’s leading advanced ceramics manufacturers.
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