Ceramics and joining technology
CERAMICS AND JOINING TECHNOLOGY // RAW MATERIALS PREPERATION // GRANULATION // SHAPING // FIRING PROCESSES // HARD MACHINING // CONTROLS // LABORATORY // CERAMIC-METAL BRAZING // CERAMIC-CERAMIC AND CERAMIC-METAL SOLDERING
The transformation of a milled ceramic material generated in aqueous suspension usually requires a drying and granulation step to achieve a material state suitable for shaping by means of pressing.
For this purpose, spray dryers are frequently used that produce a press granulate in hydrothermal conditions. For this purpose, the suspension is fed through a suitable pipeline system with the help of a pump to the dryer and sprayed out of spray lance into the interior that is heated to several 100 °C.
At the head of the spray lance is a control system for the type of spray cone, which consists essentially of a nozzle with a so-called twist screw. These components are exposed to high degree of wear from the solids in the suspension, which can lead to frequent operational faults in the system.
As wear-resistant materials for this application, for more than a decade, long-term resilient components made of oxide and non-oxide ceramics have been reliably used for more than a decade in some cases. Depending on the composition of the ceramic suspension, they usually consist of high-purity dense-sintered materials on the basis of Al2O3, doped ZrO2 or Si3N4.
In the pipeline system of spray dryer usually flowmeters are installed that are used for control and regulation purposes. The equipment components in direct contact with the suspension flowing through system require high resistance to mechanical wear.
A system proven in this application is a flowmeter that works according to a magnetic induction principle with a tubular measurement cell made of oxide ceramic with high-vacuum-tight integrated electrodes. As oxide ceramic materials, today high-purity dense-sintered Al2O3 and, to meet higher requirements for mechanical and thermomechanical strength, doped ZrO2 have proven effective in such applications and in durable maintenance-free use.