The challenge of measuring sulfuric acid aerosols: Number concentration and size evaluation using a condensation particle counter (CPC) and an electrical low pressure impactor (ELPI+)

• We performed H2SO4 aerosol measurements with two measurement methods (ELPI and CPC).
• The good agreement between both methods concerning number concentration is shown.
• For the first time size information of the aerosol is obtained by measurements.
• The effect of dilution on the volatile aerosol is demonstrated.
• Measurements confirm results of simulation tool AerCoDe for homogeneous nucleation.

In this study, two different methods for the measurement of the sulfuric acid aerosol which is formed in wet flue gas cleaning processes have been investigated. The condensation particle counter (UFCPC, PALAS GmbH) provides information about the number concentration. With the electrical low pressure impactor (ELPI+, Dekati Ltd.) also the size evaluation is possible. Both measurement methods reveal number concentrations above 108 cm−3 under well controlled conditions in a pilot plant and the good conformance of the both methods is shown. With the ELPI+ the effect of dilution on the size of the volatile aerosol can be observed. The predicted trend of an existing simulation tool can be verified: the higher the sulfuric acid concentration, the larger are the droplet sizes. The number concentration, however, doesn´t change considerably when altering the sulfuric acid concentration.