Optical measurements of SO2, SO3 and other gases

Paul Boughton

High-resolution optical technologies – such as ultraviolet differential optical absorption spectroscopy (DOAS) and Fourier transform infrared (FTIR) spectroscopy – can make gas measurements right in the process stream, without extracting any sample or using any test probe. A focused beam of light shoots across the stream and the spectral traces that process gases leave are analysed. The strength of the absorption spectrum yielded in the light corresponds to a concentration of the gas along the light path.

Many gases can be picked up this way. Sulphur dioxide (SO2) and Sulphur trioxide (SO3) are monitored in dynamic ranges (from milligrams to grams per cubic metre). Sulphuric acid plants, as well as metal smelters that produce off-gases high in SO2 and SO3, benefit from using this type of gas monitoring system. Near real-time measurement is provided in process gases that are hot (up to 1,000°C) and that may contain high levels of dust (several grams per cubic metre).

Other gases that the system can be programmed to read include combustion related gases, nitrogen oxides (NOx), carbon monoxide (CO) and carbon dioxide (CO2). Reactive compounds, such as hydrogen chloride (HCl), hydrogen fluoride (HF), and ammonia (NH3), are monitored with ease since this system doesn’t employ any sampling or condition equipment that these gases may react with.

This is a non-extractive gas monitoring solution that provides continuous unattended operation over extended periods of time.

For more information, www.engineerlive.com/epe

Opsis is based in Sweden. 


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