Reducing Formaldehyde in Biogas Emissions

Formaldehyde (HCHO) can be difficult to measure in hot, wet emissions, not least because it would dissolve in condensate if the sample gas is allowed to cool. Test engineers in Germany have therefore deployed portable (Gasmet DX 4000 and CX4000) FTIR analyzers to measure formaldehyde.

The complexity of formaldehyde analysis has necessitated sampling and laboratory analysis – a time-consuming and costly activity. In 2007 Wolfgang Schreier from RUK GmbH started working on the use of portable Gasmet FTIR gas analysers for formaldehyde analysis. He says: “The Gasmet units are primarily employed for measuring formaldehyde, but they can also measure other parameters such as CO, NOx and Methane..

“The DX4000 proved to be the ideal instrument for this application because it samples at high temperatures (above 180 Deg C) so formaldehyde cannot dissolve in condensate, and the instrument provides sensitive, accurate, reliable real-time formaldehyde measurements – no other portable analyser is able to achieve this."

In contrast with the portable FTIR, it is typical for the results of laboratory gas analysis to become available around 2 weeks after sampling.

While the emission limit for formaldehyde is 60 mg/m3, the plant operator receives a bonus of 1 cent per kW when formaldehyde emission levels are below 40 mg/m3, with simultaneous fulfilment of the emission limits for NO and NO2 (combined), and for CO.

Summarising Gerhard Zwick says: “The standard formaldehyde emissions monitoring package consists of a Gasmet DX4000 analyser and a heated sampling system, so no adaptations were necessary for the measurement of biogas emissions.

“We have now supplied instruments to most of the key testing organisations as well as motor and system manufacturers in Germany. Happily, the feedback has been extremely positive because, as a portable analyser, the Gasmet FTIR systems are able to test more plants, more quickly, and this lowers costs.”