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Matrix CFD saves $0.5 million in equipment upgrades
The Chlor-Alkali Plant operated by Oji Fibre Solutions Tasman mill produces hydrogen, which is explosive at concentrations greater than 4% by volume. To mitigate the risk of an explosion, in New Zealand the standard AS/NZS 60079.10.1 ("Classification of areas – Explosive gas atmospheres") is mandated to be used to determine areas where specialist explosion protected (Ex) equipment must be installed to control any potential ignition sources. This equipment is expensive and the existing hazardous area classification was thought to be overly conservative. If the true size and extent of the explosive atmosphere could be determined more accurately, this would help Oji Fibre Solutions make better decisions on where to install this specialist equipment.
Beca AMEC’s process and electrical engineers approached Matrix to develop a computational model of a chlor-alkali plant to consider how hydrogen would build up inside the plant under a range of different gas release scenarios. Matrix used a numerical technique called computational fluid dynamics (CFD) to simulate the dispersion of hydrogen inside the plant. This allowed Beca AMEC to visualise hydrogen concentrations within the plant, more accurately define the hazardous areas and make better decisions about where to install specialist Ex equipment.
The simulation work clearly showed that hydrogen concentrations (depicted below) from any potential gas releases drop quickly below the explosive limit. Even under a catastrophic failure of the hydrogen cell the traditional approach to hazardous areas classification would have provided an overly conservative hazardous area classification. The revised classification enabled Oji Fibre Solutions to save an estimated $350,000 to $550,000 in electrical equipment upgrades.