On-line local thermal pulse analysis sensor to monitor fouling and cleaning: Application to dairy product pasteurisation with an ohmic cell jet heater

International audienceIn the process industry, fouling is considered as a complex (sometimes partially known and identified) phenomenon. In this paper, a fouling sensor (FS) based on local differential thermal analysis is scrutinized and we report the comparison of two operating modes, steady (STR) and periodic (PTR) thermal regimes. Moreover, the development of alternating technologies like direct joule effect (ohmic) heating to pasteurise and sterilise liquid food products in a continuous process is of great scientific and industrial interest. Heat treatment by direct Joule effect exhibits numerous advantages because rapid heating kinetics or homogeneous heat treatment is required. However, fouling of electrode surfaces in this kind of apparatus is much more problematic than in conventional heat exchangers. In the present study, a new continuous ohmic heating apparatus (Emmepiemme (R), Piacenza, Italy) in which an alternating electrical current is applied directly to a jet falling between two stainless steel electrodes is investigated during pasteurisation of a dairy product. Conventional fouling measurements (pressure drop, heat transfer or electrical parameters) cannot be used in such a heater. Fouling and cleaning phases are monitored with fouling sensor and fouling quantified

Metrological performances of fouling sensors based on steady thermal excitation applied to bioprocess

International audienceFood and industrial bioprocesses are impacted by (biolfouling which generates failures from reduction of process efficiency (ex: reduction of heat transfer coefficient) up to health risk issue (e.g. biofilm formation). In present work, 3 fouling sensors based on a thermal excitation (steady thermal regime) were developed and described. These sensors were designed with different technologies (macro structure and Micro-Electro-Mechanical-Syste ms MEMS), geometries (intrusive cylindrical, flush plan) and packaging (presence or absence of cover panel) and compared. Laboratory setups were designed to characterize sensor responses under controlled operating conditions in batch and continuous process including clean condition and using layers of adhesive tape to simulate fouled conditions. Thermal responses from excitation under steady thermal regime at different heat flux were linearized then discussed as function of technology, geometry and packaging impacts. Packaging heat resistance, response times, efficient heat flux, and quantification of fouling were investigated. Finally, metrological limits were identified

Contrôle d'un encrassement laitier en procédé continu : comparaison de trois méthodes

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Soft-Sensors for Monitoring B. Thuringiensis Bioproduction

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