AirProtekt removes NOx and HCN contaminants at Scottish carbon fibre plant


Source: AirProtekt Limited

AirProtekt, the UK’s Air Pollution Control specialists, has installed and commissioned a combined Regenerative Thermal Oxidation (RTO) system and a Selective Catalytic Reduction (SCR) system to remove oxides of nitrogen and other gaseous contaminants, such as hydrogen cyanide (HCN), from SGL Carbon Fibers’  manufacturing facility in Muir of Ord, in the north of Scotland.


SGL Carbon Fibers is a subsidiary of German based SGL Group and the Scottish manufacturing site produces carbon fibre for use in a variety of engineering applications including items such as wind power turbine blades, computer hard disks, aircraft and car brakes which are exported to 27 countries around the world.

As part of a major multi million pound investment SGL Carbon Fibers has upgraded the production capacity of its Scottish carbon fibre manufacturing facility with the addition of two new production lines.  To assist in handling the additional emissions, including fugitives from the upgraded facility, AirProtekt was selected to supply a third Regenerative Thermal Oxidation (RTO) system at the site in combination with a new Selective Catalytic Reduction (SCR) system.  The principal purpose of the new combined system is to treat and remove pollutants such as oxides of nitrogen and hydrogen cyanide. 

The SGL carbon fibre manufacturing plant is one of a kind in the UK that uses Polyacrylonitrile (PAN) as a raw material in the form of long lengths (tows) of carbon fibre.  The tows are heated by passing through a series of electric or gas ovens and furnaces. 

The first stage of heating in ovens to 250°C in the presence of air produces oxidised Polyacrylonitrile or Panox, which is sold as an oxidised fibre product.  The Panox can be further heated within low temperature (LT) and high temperature (HT) furnaces to 1500°C, in the absence of air to produce carbon fibres for use in various engineering applications.

The chemical reactions during the heating process generate exhaust gases of oxides of nitrogen, hydrogen cyanide, ammonia, carbon dioxide, carbon monoxide and volatile organic compounds (VOCs).  The exhaust gases are extracted using Regenerative Thermal Oxidation (RTO) systems that reduce the levels of the contaminants prior to discharge through stacks, which are the main point sources of emissions from the carbon fibre manufacturing process.  The new, combined RTO and SCR system was developed, engineered and installed by AirProtekt and Lufttechnik Bayreuth (LTB) to free capacity on one of the older RTO systems, improving the capture of fugitive gases from one of the manufacturing units, and helping to address overall control of the release of odorous emissions from the Muir of Ord facility.

AirProtekt and LTB’s engineering team tailored the combined RTO and SCR system to comply with SGL Carbon Fibers’ specific emission regulation requirements.  The solution was required to allow the Muir of Ord facility to comply with the emission limit values specified in its operating permit granted by the local environmental authority, SEPA. 

AirProtekt offered the 4,500 tonnes per year Scottish carbon fibre manufacturing facility a complete package solution that involved system design, equipment supply, installation and commissioning, fully supported by an experienced after sales service team.

Trevor Lawton, AirProtekt’s managing director said: “SGL Carbon Fibers required a proven technological solution to treating its HCN gaseous emissions.  For many years AirProtekt has been the sole UK distributor of Regenerative Thermal Oxidisers for Lufttechnik Bayreuth (LTB) of Germany.  LTB has installed more than 200 RTO systems across Europe including other SGL manufacturing facilities in Europe.”

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