In April of this year, an EMC filter plant with an upstream air/air heat exchanger (including axial fans for supplying fresh air, provided by Scheuch) went into operation in the Untervaz premises of Holcim (Switzerland) AG.Creating the compact design required for the complete plant whilst ensuring that the axial fans could be accessed with ease for maintenance purposes posed a particular challenge. To meet it, a special arrangement of Scheuch axial fans was selected and the cooling air was routed through the air/air heat exchanger via return hoods.This configuration enables the heat exchanger to maintain a constant filter inlet temperature of 120°C. In turn, this means that considerably more economical filter media can be used. Another special feature of the plant is the ability to make use of the exhaust air heat from the new clinker cooler thanks to a bypass in the raw gas line. When operating in this way, the air/air heat exchanger acts as an additional cooling stage to protect the filter from excessively high temperatures in the event of a breakdown or during upset mode.A theoretical heat output of more than 5 megawatts [MW] can be achieved for this regenerative waste heat usage by means of heat extraction.