Wednesday, June 20, 2007
Nitrogen purging is common in Oil & Gas, refinery, Petrochemical & Chemical plant. Some factors you may need to consider...
Generally Nitrogen purging is conducted to evacaute oxygen content to a level low enough so that it has no effect to process fluid. If you need to reduce to a VERY low oxygen level e.g. light water reactor, you may need to consider other methods.
You may need to assess you N2 quality. Plant N2 may contain 3% - 5% Oxygen, if your system need to go below 3%, obviously no way you can use plant nitrogen. You may need to use Liquified Nitrogen which may have >99.5% purity.
Criticallity of purging section
If you are purging reactor section, please always consider high purity N2.
Continuous versus Pressurise/depressurise
Large volume system better to apply pressurise/depresurise method. Plant Nitrogen supply pressure probably in the range of 8-10 barg. It may not be sufficient. You may take long time to purge your system. You may consider the Liquified Nitrogen.
Minimise N2 usage
If your system can take water after purging e.g. amine system, you may consider to fill the system with water and follow by N2 purging (replacing the water content). This significantly reduce N2 consumption.
"Nitrogen is a notorious and stealth killer!". Try to limit the volume of purging section filled with N2. The discharge section should be directed to minimum manning area.
Normally pressurise / depressurise method will create high pitch and high SPL noise. You may need to comply to authority requirements during purging.
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