TDL in-situ analysers use selective spectroscopy to provide highly specific measurements free from interference from other IR absorbing gases. The ability to operate in high dust and high temperature conditions makes them the ideal choice for modern process control where fast measurement feedback is required to optimise dynamic plant functions
Formaldehyde (HCHO) occurs in organic substances (fruit and wood) and can diffuse to the outside. It is present in nearly all incomplete combustions and other oxidation processes of long-chain organic substances.
Formaldehyde is a colorless, pungent smelling substance which occurs as gas at room temperature. As a gas, its odor is still perceptible in very small concentrations. In combination with air, formaldehyde forms explosive compounds in a wide range of concentrations. The explosion range lies between 7 vol% (87 g/m³) as lower explosion limit (LEL) and 73 vol% (910 g/m³) as upper explosion limit (UEL).
Since April 1, 2015 formaldehyde has been classified as “probably carcinogenic to humans” in a legally binding form. In 2004, the World Health Organization (WHO) changed the classification, which had existed since 1995, to “carcinogenic to humans”.
Limit values for the permissible formaldehyde concentrations are specified in various ordinances and guidelines. The Committee for Indoor Standard Values defined a standard value of 0.1 mg/m³ in 2016. The current TA-Luft (Technical Instructions on Air Quality Control, the “Clean Air Regulation”) specifies a limit value of 5 mg/m³ for emission monitoring and the limit values should be monitored continuously.
Various measuring methods are used to determine formaldehyde. For industrial applications, the laser measuring system by Airoptic, a TDSL laser in the mid-infrared range, has established itself. For this purpose, the formaldehyde concentrations are determined by means of tunable laser diodes. The laser measuring system is suitable for emission monitoring and process control and is designed for 24/7 continuous operation. The measurement is carried out during the process and does not require any sample conditioning. Upon delivery, the measuring system is factory-calibrated and re-calibration is not necessary during operation. This means that the user will only have low operating and maintenance costs.
Typical industries in which increased formaldehyde concentrations may occur are listed below:
• Chipboard production
• Systems for coating and varnishing components
• Coffee-roasting plants
• Carpet manufacturing & storage
• Automotive emissions
• Asphalt mixing facilities
The laser spectrometer has the following features:
• Very small measuring ranges can be realized – HCHO ranges from 0 to 10 ppm/0 to 1 ppm
• Process temperature from 0 to 200 °C (650 °C) [32 to 392 °F (1202 °F)]
• Real-time measuring – typical response time < 0.1 second
• High selectivity – no impairment by other components in the sample gas
• High sensitivity – limit of detection below 10 ppb per meter
• In-situ monitoring – reliable and representative formaldehyde measuring over large measuring sections (e.g. chipboard production)
• For indoor measurements, a measuring system with open measuring section is available
• Maintenance-free – equipped with a self-calibration function, no field calibration required
• IP65 housing, suitable for outdoor and indoor installations as well as harsh environments
• Resistant to dust and smoke in the measuring process (up to 50 g/m³)
• ATEX version available