With the PSA 10.525 Sir Galahad and the PSA 10.515 Liquid Sampling Mercury Preconcentrator System

Hydrocarbon Monitoring

Mercury and its organic and inorganic compounds are often present in natural gas and petrochemical products, feedstocks for many industrial reactions. Generally aluminium rotors and/or condensers are used. The low levels of mercury attack the aluminium components and cause stress fractures. Mercury induced corrosion on aluminium heat exchangers has resulted in several shut-downs which require costly replacement and loss of production.

P S Analytical has a reputation for providing reliable instrumentation to determine the mercury levels in natural gas using the PSA 10.525 Sir Galahad. The PSA 10.525 Sir Galahad uses a purge and trap approach to collect mercury and its derivatives from the gas prior to re-vaporisation into a stream of argon and measurement by atomic fluorescence spectroscopy. The measurement of mercury in natural gas condensates has, however, presented more difficult problems, due to the nature of the product and the low levels of mercury involved.

Following a joint research programme with a British University and a Malaysian Petrochemical Company, PSA developed a simple and effective method to analyse natural gas condensates reliably at levels below 1ppb of mercury. The team developed a means of analysing mercury in liquid hydrocarbons. Samples are vaporised at 400°C and mercury is collected on a trap held at 200°C in a simple but effective procedure.

The procedure has been verified both by measurement of the recovery of known levels of organomercury standards and by the analysis of various condensates, spike recoveries of the order of 100% being the norm.

The PSA 10.515 Liquid Sampling Mercury Pre-Concentration System with the PSA 10.525 Sir Galahad

PSA has further developed this as a specific accessory for the PSA 10.525 Sir Galahad instrument; the PSA 10.515 Pre-concentration System. This system vaporises the condensate sample into an argon stream over a heated Amasil® trap. The mercury and mercury compounds are retained in the trap and the hydrocarbons vented to waste. The mercury levels are quantified by transferring them via a clean argon stream to the PSA 10.525 Sir Galahad for analysis.

Validation that the condensate contains less than 1ppb of mercury is provided in a simple and effective manner, quickly repaying the investment in the instrumentation. The quality of this work was rewarded by the presentation of a Royal Society of Chemistry Industrial Affairs Division Team Award, please visit our Awards page for more details.

Further development of this product has resulted in a reliable online method of measuring mercury in volatile hydrocarbons and condensates. The PSA 10.690 Online Mercury Preconcentration System is used in conjunction with the PSA 10.670 Online Mercury Analyser controlled by PSA Online Software to provide safe, reliable online monitoring of multiple liquid phase volatile hydrocarbon samples.

Hydrocarbon Monitoring

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