ERG helps Crown Pet Foods deliver improvements in odour emissions

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Source: ERG (Air Pollution Control) Ltd

ERG (Air Pollution Control) Ltd announces the successful installation of a new odour control plant at Crown Pet Foods as part of a £1m plus investment in upgraded odour control at their Castle Cary, Somerset, factory.

Crown Pet Foods, who are owned by the global group Royal Canin, completed a new state-of-the-art pet food production facility at Castle Cary in late 2007. Although the facility incorporated sophisticated odour control, it became apparent over the first few months of operation that the odour reduction achieved was inadequate and that further enhancements were urgently needed. Crown Pet Foods’ first step was to call in Entec, one of the UK’s leading consultancies in this field. Entec rapidly carried out a full odour assessment together with complex odour modelling. The investigation’s conclusion was that the odour concentration in the outlet stack needed to be reduced to avoid odourous emissions. A new target odour level was set which was lower than at any other Royal Canin production facility. The decision was taken to carry out pilot trials to prove odour abatement technology and to give Crown confidence that the odour removal upgrade would meet their stringent new target.

Based on the recommendation of Entec, ERG, a leading and highly experienced air pollution control company was selected to carry out pilot trials at a Royal Canin production facility in France. ERG has 6 different pilot plants and by using a packed tower from one, a heat exchanger from another and a carbon filter from a third, ERG was able to quickly assemble a suitable pilot scale solution. The newly configured system was shipped to France, installed and tested, all within 4 weeks. In parallel with the pilot trials, ERG carried out an engineering design study to investigate the practicalities of installing the proposed new equipment. Space was tight but thanks to some innovative thinking by Royal Canin’s Engineering Manager, Eric Lefeuvre, and ERG’s Engineering Director, David Gladman, a solution was agreed.

As expected, the pilot trial testing was successful achieving outlet emissions within the target level across a broad range of exhausts from different production runs. ERG was immediately awarded the contract to supply and install a full scale operational system within 16 weeks.

The final installed system comprises an initial treatment of the hot humid exhaust gases from the cooking and drying process by “scrubbing” with continually cooled water. This involved passing the odorous exhaust gases up though a stainless steel tower filled with “packings” which are continually wetted with cooled re-circulation liquor. This first stage of the cleaning process reduces the temperature of the gas from over 60oC down to less than 33oC.

The cooling of the scrubbing liquor is achieved by passing the liquor through four banks of air blast coolers which use ambient air to remove the about 1 Mega Watt of energy from the liquor. The advantage of cooling in this way is that unlike cooling towers there is no visible exhaust plume.

The partially treated and cooled gas is then re-heated by a steam-heated heat exchanger to raise the gas temperature by 5oC, thus reducing the relative humidity to less than 70%. This is important as the next stage in the process is to pass the dry but odorous gas through two activated carbon filters working in parallel. This final stage of the cleaning process cleans the gas to achieve an outlet level well within the acceptable target limit. The carbon filters are designed to operate for more than twelve months before the carbon needs to be changed, and an extensive network of sampling ports enables the operators to monitor how the carbon’s activity is being depleted over its life cycle.

Andy Brock, the ERG Project Manager said “ERG was uniquely suited to giving Crown Pet Foods the support they needed. The combination of our 30 years of experience in dealing with this type of project, together with our pilot plants, has enabled us to contribute to what we are confident is an excellent and innovative solution. This project was particularly challenging as the scrubber and filters had to be installed into a completed building via a small lift at 16m and 30m above ground respectively.”

Commenting on the installation, Glenn Jefferson, Factory Director at Crown Pet Foods said: “The results from the new ERG odour control plant are excellent. We are all delighted to have eliminated any odour emissions and to be a good neighbour within the local community”.

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