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.
The Project
NUTEC Bickley has just completed its latest project in the European sanitaryware sector, having designed, manufactured, and installed a large shuttle kiln in a completely new factory.
This formed part of a technical collaboration with other well-known innovators for ceramic sanitaryware, companies that took on the turnkey project, body preparation, casting, drying, and finishing aspects.
The recently commissioned plant should enable the customer to roughly double its annual capacity.
The items being fired are specialist pieces handcrafted by a producer with a history in the industry going back over 130 years. One of the principal attractions of the NUTEC Bickley design is that this kiln is extremely flexible.
It can handle a range of products, from weights of 20kg up to 80kg per piece. It can also be used for both first fire and refire. The company is also actively quoting elsewhere for shuttle kilns capable of first and refire, facilitating highly adaptable production flows.
Fig. 1 100m³ kiln with 24 burners and 12 control zones
Units and Installation
This particular kiln has an operating temperature of 2160°F (1180°C), with a maximum temperature of 2250°F (1230°C). NUTEC Bickley supplied 12 kiln cars, with six cars used inside the kiln for each cycle and the other six being loaded for the subsequent firing. Each car has two control zones (meaning there are 12 control zones across the kiln).
The setting volume of 16m³ per car is achieved via a four-deck design, delivering high density per cubic metre loading. This optimum ware setting density, allied to the latest combustion and control system and very careful control of air/gas ratios, is a major contributory factor to the kiln’s first-rate thermal performance and fuel efficiency ratings.
Reduced energy input is also guaranteed by the incorporation of NUTEC’s proprietary Jointless® low-density kiln insulation system. This consists of monolithic ceramic fiber modules engineered to cover a complete kiln wall, door, or roof. It’s a one-piece construction continuously shaped with a ceramic fibre blanket folded and anchored.
Jointless modules eliminate the joints between smaller modules (as commonly found in ceramic fibre linings) and eliminate the gaps typically located around the flues, which require higher maintenance. The insulation is rated to 2600°F (1426°C) above the kiln’s maximum temperature.
Fig. 2 5.4m wide kiln with vertical door and automatic transfer car
The gas-fired shuttle kiln employs 24 high-velocity nozzle mixing burners in a staggered pattern, firing over and under the load; this provides excellent turbulence and heat transfer – promoting great temperature distribution and uniformity throughout the load.
Again, the staggered burner pattern is designed to maximize heat transfer and temperature uniformity. Burner control units with push button spark units have been fitted on all burners.
The kiln’s chamber pressure control system provides process stability by using a linear flow-controlled exhaust damper fabricated with a cordierite multi-louver fitted with silicon carbide shafts.
In this setup, a digital pressure transmitter senses the pressure inside the kiln and provides feedback to the control system; this, in turn, modulates the linear flow-controlled exhaust damper to provide precise control of the exhaust gases and chamber pressure.
For loading/unloading, it was important to make the four-deck configuration work to maximum advantage. To address this, NUTEC Bickley designed an ergonomic deck loading system that operates via a hydraulic elevator that lowers and raises the kiln cars to the ideal height for ware loading.
Fig. 3 4-deck kiln cars
