Metal substrate provides alternative catalytic converter technology

Citation

(1999), "Metal substrate provides alternative catalytic converter technology", Anti-Corrosion Methods and Materials, Vol. 46 No. 5. https://doi.org/10.1108/acmm.1999.12846ead.004

Metal substrate provides alternative catalytic converter technology

Keywords Sandvik, Emission

A new design of metal substrate for catalytic converters, developed and manufactured by EcoCat AB, is thought to be set to compete with existing metal and ceramic substrate technology in the emissions control market (Plate 3).

Plate 3 The new design of metal substrate for catalytic converters from EcoCat AB

EcoCat is a recently established company owned by Sweden's Sandvik Group.

Based on well established heat-wheel recovery technology, the new EcoCat metal substrate produces turbulence in the exhaust gas which is the key to its new design concept. It reportedly represents a new approach for monoliths used in controlling emissions.

The new substrate has a channel design incorporating a 60° triangular shape manufactured from flat and corrugated foils and, mechanically locked together by a "tongue and groove" system, the self-locking construction prevents telescoping during operation.

The design is said to result in high utilisation of steel strip, a low substrate weight and an efficient and high open frontal area of between 85 and 95 per cent for any given area and gas flow. In a ceramic substrate the open frontal area is about 55-60 per cent and in a conventional metal substrate, the corresponding value is about 70-80 per cent.

The "tongue and groove" system, combined with raised sections or "bumps" on the channel walls, creates controlled turbulence in the exhaust gases. The "bumps" are strategically placed at predetermined intervals so that when turbulence reduces, it is automatically regenerated. The purpose is to produce effective mass transfer of gas towards the channel wall and to avoid too high a pressure drop over the substrate. The relationship between the mass transfer and the pressure drop is very favourable in EcoCat substrates compared with conventional catalyst laminar flow designs.

EcoCat believes that in subsequent canning and coating operations to produce the finished monolith, the new design comes into its own. A very thin mantle (0.25mm or 0.01in.) applied around the substrate, with grooves that fit into corresponding grooves in the substrate, means that there is no risk of telescoping when the mantle is welded to the canning.

During coating, the wide channel design is said to virtually eliminate the possibility of coating build-up or clogging.

An independent study by the Department of Chemical Reaction Engineering, Chalmers University of Technology in Gothenberg, Sweden has reported:

Bumps on the channel walls of metallic monoliths were found to significantly increase the mass transfer rate. The increase is largest at the highest flow rates. The bumps also increase the pressure drop, but the increase in mass transfer is greater than the increase in pressure drop. Thus, the new catalyst presents a promising alternative to today's metallic and ceramic monolith catalysts.

Details available from EcoCat AB. Tel: +45 26 26 52 00; Fax: +46 26 26 52 52.