Energy efficiency in continuous heat treatment plants: SiC/SiC components for roller kilns

Roller kilns are increasingly used for heating processes in the ceramics and metal industry because they have a very favourable energy balance. The efficiency of roller kilns could be increased considerably by wider kiln shafts. The heat losses at the feed-throughs for the transport rollers and the lateral insulation would remain constant, while the firing throughput could be increased approximately proportionally to the width. However, the present inner dimensions are already at the limit of the mechanical load capacity of the transport rollers.

A new transport roller with improved mechanical properties will be developed to widen the furnace shafts. In contrast to the monolithic ceramics used so far, this is to consist of a silicon carbide (SiC/SiC) reinforced with silicon carbide fibres.
On a demonstrator component, it is to be shown that the desired spans can be achieved. In particular, the fibre reinforcement improves the thermal shock resistance of the ceramic and achieves damage-tolerant fracture behaviour.

The technological basis for the development of ceramic rollers with high mechanical strength is the wet winding technique, which is used to produce tubular preforms. A coating of the SiC fibres is absolutely necessary to achieve a damage-tolerant behaviour of the SiC/SiC composite. The fibre coating is applied prior to forming by a newly developed wet coating process.
The process parameters for the heat treatment processes following the shaping (pressure, temperature, heating rate) are to be investigated and optimised by in-situ measurements on the thermo-optical measuring system TOM_AC.

In the sub-project: Design of roller kilns, a ceramic-compatible design for a high-strength and damage-tolerant roller is developed using FE simulation, which is then to be implemented in a demonstrator component.