Leading manufacturers of technical ceramics have become increasingly important customers for Nutec Bickley over the past 20 years. The quality and reliability of kilns for this sector are crucial factors since in many cases expensive feedstock means that rejects are unacceptable, and also firing regimes for technical ceramics tend to be more demanding than some other products. Many kilns for this sector are high or ultra-high temperature, and great experience in this area is required in order to be able to design and build the optimal system, on time, and to the customer’s complete satisfaction.
I’m pleased to say that our credentials in this area have recently been underlined with the award by a major US manufacturer in the energy field of a contract for a sixth Nutec Bickley kiln. Our association with this particular customer goes back a decade and the flawless operation of the fifth kiln that we previously supplied led this company to return to us without hesitation. The project will be executed swiftly, despite current constraints, and we aim to install and commission in September 2021.
The kiln in question is a gas-fired, downdraft elevator kiln with a maximum operating temperature of 1,650°C (3,000°F), and it has been designed to fire performance-critical high alumina components. These are complex pieces and in some cases the firing cycle can exceed 150 hours. The kiln is expected to operate 24/7, so all elements involved have to be high quality, efficient and durable.
Employing the downdraft exhaust principle enables this system to counteract the tendency for the hotter gases to accumulate at the roof of the kiln, which can cause an imbalance of temperature from top to bottom. As a result, we believe the kiln’s performance in terms of temperature uniformity is the best on the market.
We specify industry-leading high-velocity nozzle mix burners for this elevator kiln as they result in excellent turbulence and heat transfer. The way we position the burners in the kiln is equally important, and it’s done in such a way so as to promote optimum temperature distribution and uniformity throughout the product. These factors are important when it comes to the problem-free firing of specialty high alumina components.
The kiln’s multi-temperature control zones provide excellent flexibility and thermal management throughout the firing cycle. The Nutec Bickley combustion system also allows for adjustable and programmable levels of excess air throughout the firing cycle for temperature uniformity enhancement and atmosphere control. This allows the use of excess air only when required by the process, significantly improving temperature control and fuel efficiency. There is pre-programmed smooth transition between the two modes – excess air and proportional on-ratio.
In any ceramic kiln, the role of insulation is a prime consideration. This kiln uses the Nutec Bickley floating anchor refractory support system. This system anchors the refractory to the steel wall in a way that allows expansion and contraction movement of the refractory wall parallel to the steel casing, keeping the refractories from moving away from the shell. This results in a longer service life and reduced maintenance requirements. The entire hot face features high-performance bubble alumina brick rated to 1,760°C (3,200°F) with insulating firebrick backup.
Energy saving techniques play a part in all aspects of the kiln operation, one example being the use of pre-heated combustion air, recovered from kiln exhaust gases, for firing efficiency and reduced fuel consumption. Recovered warm air can also be used for diffusion air pre-heating or in other processes requiring hot air, such as in dryers or for process heating.
Nutec Bickley can design, manufacture, install and commission a range of kilns suitable for firing technical ceramics – including elevator, Carbell®, tunnel and shuttle kilns. These feature optimal efficiency and can be supplied for operating temperatures up to 1,800°C (3,270°F).
For further information on advanced kilns for firing technical ceramics, contact:
Rodrigo González, VP Ceramics
+52 81 1050 8629