The specific surface area of the dispersed phase in suspensions, emulsions, bubble columns and aerosols plays a decisive role in the increasement of heat and mass transfer processes. This has a direct effect on the space-time yield in large-scale chemical/process engineering production plants. Initial investigations show that an easy-to-install optical backscatter sensor outputs the dispersed surface area as a direct primary signal under certain boundary conditions. The article describes the construction, the mode of operation and first investigations applying of this new sensor. The sensor works even in high concentrated suspensions and emulsions, where conventional nephelometry already fails. Trends and limitations found so far for the sensor, which can be used in-line in batch and continuously operated crystallizers, even in harsh production environments and in potentially explosive zones, are shown.

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