Fouling Monitoring: Local Thermal Analysis

In the process industry including agro and bioprocess, fouling is considered to be a complex andmisunderstood phenomenon. Heating, holding, and cooling operations are carried out in continuous orbatch processes and fouling occurs in equipment with a wide range of kinetics (from minutes up to years)and dimensions (from micrometers up to centimeters). Control and understanding of the foulingphenomenon is of industrial interest as it leads to reduction in process performances, higher energyconsumption, and issues with water management. In industrial processes (agri-food, pulp and paper,petrochemistry, etc.), the detection of the fouling level in production lines is a major consideration foroptimizing cleaning sequences and their frequency. It is important to have real-time and continuousinformation about the fouling status of equipment. In heat exchangers, this information is necessary tomonitor impaired heat transfers due to deposits (safety and quality of the final product), to preventbiofilm (Legionellarisks mitigation) in cooling towers, to reduce costs associated with production, andto optimize chemical discharges which have significant environmental consequences. Various methods,including rheological, chemical, mechanical, optical, ultrasonic, and thermal, have been reported. In thisentry, we discuss a fouling sensor that is based on local differential thermal analysis and was developedto study fouling phenomena in batch and continuous processes. First, a bibliographic overview presentssimilar experimental devices, and theoretical considerations are described. Second, materials andmethods are described before presenting our experimental results and a discussion dealing with operat-ing mode, sensor sensitivity to fouling (deposit elimination and formation), and potential applications.The comparison of two operating modes for the sensor—steady (STR) and periodic (PTR) thermalregimes—is also given. Finally, the temperature profile and sensitivity are modeled for the existingsensor geometry