Flow rate measurement at gas scrubbers

Measuring flow rate in polluted and aggressive exhaust gases at gas scrubbers or in moisture-saturated air after the gas scrubbers

Process data

Measuring task:
Flow velocity for the gas scrubber’s process control

Measuring point:
Polluted exhaust air before gas scrubbing; humid and condensing air

Measuring range:
Usually up to 20 m/s

Process pressure:

Process environment:
Usually ambient temperature up to 100 °C

Recommended products

Vortex insertion probe


For the use in aggressive media:

Vortex Probe VA40 ZG10 ProductProduct data sheet

Vortex Probe VA40 ZG4productproduct data sheet

For the use in humid air:

Vortex Probe VA40 ZG7
Productproduct data sheet


Many production processes result in exhaust air with hazardous components such as chloride or sulphur. It has to be cleaned before it’s released into the environment. One way to clean it is with the help of a gas scrubber, where the exhaust air is „scrubbed“ from the pollution. Before it gets to the gas scrubber the polluted air and afterwards the clean but moisture saturated air must be measured.


Your advantage

The process is controlled and secured through the measurement; around the clock!

Our sensors are perfectly suited for the use in aggressive gas mixtures or humid and condensing gases

Reliable flow measurement in aggressive gases and polluted exhaust air

Gas scrubbers are based on the princible of absorption. Pollution of air is absorbed by the liquid. Gas scrubbers come in a variety of different designs. To ensure efficient cleaning the flow rate needs to be monitored.
Höntzsch vortex sensors are perfectly suited for this. Given their robustness and the many available material combinations we’re able to master measuring tasks others fail to deliver. We developed the Vortex ZG10 made out of PVDF especially for aggressive media to be even more resistant to acidic media.

For example when producing iron(III) chloride

Iron(III) chloride is a chemical compound of iron and chlorides. Iron chloride is produced by dissolving iron in hydrochloric acid and then introducing chlorine, whereby the resulting iron(II) chloride FeCI2 is converted into in iron(III) chlorid that is obtained by evaporating the solution. For technical production, chlorine is passed over ferrous scrap at about 650 °C. The process produces exhaust air laden with hydrochloric acid, which is highly caustic. It’s neutralised in gas scrubbing by drizzling of water. Before gas scrubbing, actual flow velocity of the contaminated air is measured with our sensors to regulate the gas scubber. Höntzsch sensors made out of plastic (PVDF) as an alternative to metallic designs are able to measure gases that produce acids in humid states.


Use of iron(III) chloride

Iron(III) chloride is for example used in biological wastewater treatment in sewage treatment plants as a flocculating agent. This binds harmful substances in the water and filters them out. Since iron chloride can dissolve copper it is used to etch printed circuit boards and pressure plates. It is also used in medicine for deficiency syndromes.


Further applications for flow rate measurement at gas scrubbers

Scrubbers are also successfully used for cleaning flue gas, when desulphurising biogas or when cleaning exhaust gas in electroplating plants. Measuring exhaust flow behind the scrubber is no easy task. The moisture-saturated often condensating air is often a criterion for exclusion for many measuring methods. Not for our robust vortex sensors! The special design in combination with ultrasonic detection of the vortexes allows use even in gases with 100 % humidity and potential condensate.