Case Study:- Measuring Hydrogen Fluoride ( HF )
Hydrogen fluoride can exist as a colorless gas and when dissolved in water it forms form hydrofluoric acid.
Hydrogen fluoride is produced by the action of sulfuric acid on pure grades of the mineral fluorite: CaF2 + H2SO4 → 2 HF + CaSO4
Inhalation of hydrofluoric acid vapours may cause severe throat irritation, cough, dyspnoea, cyanosis, lung injury and pulmonary enema resulting in death.
Hydrogen fluoride typically is used in the production of refrigerants, high-octane gasoline, aluminium, plastics, electrical components, and incandescent light bulbs
Since HF is very important from industrial point of view but at same time must be operated with utmost safety because of its harmful effect. Hence selection of right type of HF analyser with correct sample handling system becomes essential.
Measuring Principle Types:
Fourier Transformed Infra-Red (FTIR)
Fourier transform infrared spectroscopy (FTIR) is a technique which is used to obtain infrared spectrum of absorption, emission, and photoconductivity of solid, liquid, and gas in waste incinerators, power and cement plant. It is costly but when used for multi gas measurement becomes cost effective. Being based on IR principle it inherently suffers from interference due to other gas absorption in nearby spectrum. This type of principle is for measuring low concentration of HF. Sample lines to be heated enough to prevent condensation.
This technique uses sample extraction for measurement.
Tunable Diode Laser Technique
Tunable Diode Laser (or TDL) measurements are based on absorption spectroscopy. The system operates by measuring the amount of laser light that is absorbed (lost) as it travels through the gas being measured. Laser technique is very expensive for single gas measurement. This principle also requires H2O measurement for moisture correction.
Limitations is high dusty sample and small stack diameter due to lack of required optical length
It is available in both in situ and extractive type of sample measurement.
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