Moisture Measurement in aggressive and heavily polluted flue gas

Moisture Measurement in aggressive and heavily polluted flue gas

The Task
Exhaust gas, such as flue gas of big combustors or the circulating air of drying systems, can contain a high dust content and also aggressive medias. Adhesion or plugging in fabric and cloth filters or sooting and dew point corrosion in pipe and chimney systems can happen after condensate formation. Against this too dry flue gas causes in electric filters and flue gas desulphurization a worse filtration performance. In order to control efficient and energy-saving the heat recovery respective to control the steaming it is necessary to measure the dew point temperature or the absolute humidity under extreme condition.

The solution
HYGROPHIL H 4230 is a process hygrometer designed to meet the highest industrial demands in respect of corrosion resistance, continuous duty and protection from contamination. Permanent self-cleaning means that the instrument is very well suited to cope with measurement air contaminated with acids, oils, dusts, solvents and other aggressive substances and that it displays a convincing level of precision. It is used in the partly unclean raw gas flows of power stations, dryers and combustion system mainly for the following purposes:

  • dew point monitoring in pipe and filter Systems
  • equipment and process control depending on the humidity
  • flue gas Analysis


The measurement principle
HYGROPHIL H 4230 works by the principle of psychometric gas Humidity Measurement, which is notable for its high accuracy and good reproducibility. All further variables can be calculated from the temperature differential of the wet and dry temperature sensor. This corresponds to the secondary standard method according to DIN 50012 and requires no calibration. A dosed jet of measurement gas flows past the dry sensor and strikes the wet sensor embedded in a water cylinder. The wet sensor is supplied continually with tenside-charged fresh water. This and the impact pressure of the gas means that the dirty surface is continually renewed, thus ruling all cross effects during measurement.