MechChem Africa

Precision matters in everything we do, says Hans Strydom, technical services manager for special products and chemicals at Afrox. Here he talks about Afrox’s HiQ range of innovative solutions, tailor made to suit customers’ specific speciality gas and equipment requirements.

At Afrox and all other Linde companies around the world, HiQ is the global brand for a specific range of made-for-purpose gases, gas mixtures and associated products that comply with very high purity and quality standards.

AFROX HiQ Gas Spectroscopes IndustrialAfrox HiQ speciality gases include pure ‘scientific’ gases; made-to-order scientific carrier gases and mixtures; calibration mixtures for certifying the accuracy of instruments; as well as a host of special-purpose mixtures for safety, research and development in the petrochemical, energy and mining industries, scientific laboratories and at health facilities.

At the starting point of the HiQ product range are Afrox’s high purity atmospheric gases: argon, carbon dioxide, helium, nitrogen and oxygen. For use in HiQ gas formulations, each of the source gases must be of exceptionally high purity. “We talk about gas purity levels in terms of a number of nines: a five nines (N5) purity, for example is 99.999% pure, which means it has an impurity level of less than 0.001% or 10 parts per million (ppm),” Strydom explains.

For modern HiQ gases, Afrox now offers six nines (N6) purity levels, which contain less than 1.0 ppm of contamination. This is the basis for the HiQ® 60 range, according to Strydom. These gas mixtures are designed to have a shelf life of up to 60 months, as opposed to the previous generation mixtures that could only be guaranteed for 36 months.

When it comes to the calibration of safety-critical measuring equipment, the purity level of the calibration mix represents true value. Emissions analysis of smoke stacks at refineries, power stations and processing plants is a legal requirement and, in some cases, the emission monitors used are required to detect contaminant levels below 100 ppb (parts per billion).

To calibrate these instruments, the calibration gas used must accurately mimic the polluting gas that the instrument needs to monitor – getting the measurement wrong can be costly, with potential fines. Low ppm HiQ calibration gas mixes, many of which are manufactured at Afrox’s state-of-the-art Gas Operations Centre (GOC) facility in Germiston, offer local customers legislative compliance, consistency, accuracy and cost savings, says Strydom.

Citing Afrox HiQ methane and carbon monoxide mixes, he says that these are used to calibrate the monitors for ship engine rooms, and for the explosive and toxic meters used in underground goldmines. These gases pose fire and explosion dangers, so reliably monitoring their presence is essential for the safety of people working in engine rooms or underground.

In addition to the calibration gases for environmental and safety monitors, Afrox HiQ gases are widely used as carrier gases for gas chromatography-mass spectrometry (GC-MS) instruments, which are used in laboratories and testing facilities all over the world to determine the exact constituents and contamination levels of substances.

Applications include drug detection, environmental analysis, fire and explosion investigations, and the identification of unknown substance samples. GC-MS is widely used for forensic identification of substances found at crime scenes because specific samples can be traced to the criminal with 100% certainty.

For GC-MS instruments, Afrox offers HiQ helium. The purity of the carrier gas is obviously very important to the accuracy of the result, but the instruments themselves are also very sensitive to oxygen, moisture and any hydrocarbon contaminants.

In the petrochemical industry, for example, samples of a fraction from the distillation of crude oil, such as diesel, petrol or natural gas, are analysed. The chosen fraction gets vapourised and separated on a chromatography column. It then goes into the mass spectrometer, which produces a chromatogram from which every constituent element of the sample, including all of the impurities, can be identified and quantified.

The result is automatically compared to a library of substances in a database, so all the constituents and their percentages are immediately identified. And if the instrument is calibrated for a particular substance mix – Afrox is currently working on a very toxic benzene/toluene/xylene calibration gas – then tiny quantities of the contaminant of interest can be found.

For the petrochemical industry, Strydom says that Afrox develops a vast range of calibration gases, which mimic the potentially harmful pollutants that need to be kept out of the fuels that are used by the industry.

HiQ gases are also widely used by water utilities which use GC-MS to pick up any dangerous pollutants such as volatile organics and other carcinogens in their water.

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