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Benfield Process Scrubber

In the purification of the gas stream, the focus is to prevent an under- or overdosing of the scrubbing liquid. Inline analyzer are used to prevent insufficient gas cleaning and in case of overdosage the higher material usage and associated costs. By a continuous measurement directly in the process, an optimum concentration management can be assured.

Sonic velocity measurement with the LiquiSonic® controller 40


A hot potassium carbonate (K2CO3) solution is used in the Benfield process as a scrubbing liquid. The gas to be cleaned is passed under high pressure in a coun-terflow through the K2CO3 solution in the absorber. The scrubbing solution K2CO3 is enriched with CO2 and reacts partially to potassium bicarbonate KHCO3. The purified gas leaves the absorber at the upper end. The temperature range in the absorption process is between 100 °C and 110 °C. 

The desorption is carried out by steam and under pressure loss, whereby the captured CO2 is emitted into the scrubbing liquid. The regenerated K2COis then fed back to the absorption cycle. The LiquiSonic® 40 analyzer allows the optimal response to concentration fluctuations in the scrubbing liquid. Too high KHCO3 concentration results in foam formation and lesser CO2 absorption performance. At too low K2COconcentration, sufficient absorption is not ensured.


The LiquiSonic® sensors are easily installed in the pipeline (typically DN 80) from the absorber to the desorber and the recirculation. The robust sensor construction and the optional special materials, like HC2000, promote long process life. The LiquiSonic® controller 40 is connected to the LiquiSonic® immersion sensor and the device for the second physical value. The controller displays the K2CO3 concentration and KHCO3 - salt content.

Typical measuring range:
concentration range K2CO3: 0 to 25 wt%
concentration range KHCO3: 0 to 25 wt%
temperature range: 80 to 110 °C

Customer value

LiquiSonic® 40 provides a precise inline concentration measurement of 3-component mixtures with real-time monitoring.  This allows an automatic control of the K2CO3 concentration in the range of the maximum absorption or the maximum efficiency of the scrubber. LiquiSonic® enables a reduction of labor cost through the elimination of manual process steps:

  • time saving: 1 h per day

Through prevention of under- or overdosing, the operational costs related to their consumption at absorber (K2CO3) and desorber (steam) are saved.