The growing need to reduce environmental pollutants is steadily increasing awareness on all fronts says Marietha Strydom – Product Manager, Special Products & Chemicals - Scientific . It has become very important to control the levels of potentially harmful components in the air we breathe. With issues regarding the environment and carbon dioxide (CO²) so prolific in both the public and political eye, in addition to concerns regarding the more ‘conventional’ pollutants of nitrogen oxides (NOx) and sulphur oxides (SOx), reducing emissions is the topic of the day. Fossil fuel combustion transforms nitrogen in coal and combustion air into NOx. These gases are harmful because they contribute to the formation of acid rain and particulate matter, which reduces visibility. Multiple studies have linked particulate matter to a wide range of adverse health effects. Other potential emissions in the petrochemical industry are the wide variety of hydrocarbon compounds, many considered carcinogenic or toxic. Air emissions can include alkenes (such as propylene and ethylene), benzene, butadiene, 1,2-dichloroethylene, vinyl chloride, and carbon monoxide, to name but a few. To be able to control emissions, the levels of harmful components have to be measured and monitored.
Emission monitoring involves taking a representative sample from an industrial stream or the general environment and applying the correct analytical technique to identify and measure the level of this constituent. Environmental analysis calculates the amount of pollution being emitted into the environment, by multiplying the concentration of pollutants emitted from any given industrial process stream by the flowrate of that stream.
Petrochemical facilities must comply with legislative requirements for environmental emission monitoring and reporting. Incorrect measurement can lead to non-compliance fines as well as potential plant shutdown. Continuous emission monitoring systems are widely used to quantify the amounts of released material. As a member of The Linde Group, Afrox offers a wide range of accredited environmental calibration gas standards, including our industry-leading SPECTRA-SEAL® calibration gas mixtures, to ensure compliance on a daily basis. These standards are also the legal basis for measurements used in carbon trading.
Our goal at Afrox is to help companies to measure the concentration of these pollutants by harnessing high purity (up to 99.999% purity available locally) and precision gas mixtures from Linde. Accuracy and reliability in measurement calibration is critical. The demand for stable, accurate measurement is the cornerstone of emissions analysis. The latest techniques and equipment require high quality specialty gases for instrument operation and calibration, in addition to high purity gas distribution systems.
Today’s analytical instruments principally require a ‘gas standard’, which is the gas mixture needed to calibrate the instrument, a ‘zero gas’ to set the zero reading and a range of purge, carrier and fuel gases:
The gas standard is made up of extremely high purity gases, to a high degree of accuracy, and traceable to international standards. HiQ® calibration gas mixtures are manufactured to meet the most stringent calibration requirements – from binary to multi-component blends, with concentration levels from percent to parts per billion.
The zero gas must also be of high purity to ensure accuracy of the starting point. Once the instrument has been set up, high purity gases are also needed to conduct measurements. These gases are used either as purge, fuel or carrier gases to help separate components to be analysed and drive some of the detectors used. High purity gases provide a smooth baseline for noise-free accurate measurements. Any impurities in these gases would skew the instruments’ reading.
Analytical results have to be comparable globally, and this requirement is addressed by a large number of international directives and standards such as DIN, EN ISO/IEC 17025 and ISO Guide 34. Calibration mixtures certified to conform to these standards provide the highest level of quality assurance and allow manufacturers to confidently state that the methods used to certify their standards are accurate, consistent, documented and validated. All the regulations mentioned require the metrological traceability of measuring results using certified reference materials as the basis of comparability. Traceability is the ability to verify measurements through calibration with measuring instruments of a known accuracy that are linked to acknowledgement standards. Traceability represents a path back to one single unique internationally accepted standard – ’an unbroken chain of comparison‘. In producing calibration gas mixtures, Linde traces back to the most reliable reference materials from international entities such as NIST (National Institute of Standards and Technology) in the USA, the VSL (Van Swinden Laboratorium, formarly NMi) in the Netherlands and the NPL (National Physical Laboratory) in the UK.
The Central Analytical Department has been accredited by DAP (Deutsches Akkreditierungssystem für Prüfwesen GmbH) according to DIN EN ISO / IEC 17025:2005 for a wide range of components and mixtures. That means that a huge variety of air calibration mixtures are available from Afrox, with an ISO 17025 certificate on request. A large number of these mixtures are ‘standard’ and readily available, which means they can be imported at a fraction of the cost of a specially manufactured (made-to-order) mixture, and with a much shorter lead time.