Aurolzmunster, Austria – It is well known that, depending on its design, a clinker cooler generates approximately 1.4 – 2.0 Am3 of exhaust air per kilogram of clinker. During normal operation, the air has a temperature of approx. 220 – 300 °C and a dust load of some 10 mg/Am3. During upset operation, these values can increase to 450 °C and 30 g of dust per Am3 for short periods of time.

In order to ensure that economically available filter media can be used, exhaust gases are cooled to adjust their temperature (filter intake temperature). The amounts of energy released by this process are considerable: the cooling of 200 000 Am3/h of dry air by 100 °C corresponds to a thermal output of approximately 3.5 megawatts [MW]. Scheuch’s new approach to regenerative waste heat utilization addresses precisely these energy losses.

The heat transferred to the cooling air in the air/air heat exchanger is transferred to a heat cycle. Also the additionally installed air/oil heat exchanger is driven by heated cooling air and not with process exhaust gas, enhancing the heat exchangers operating safety and reliability because contamination and deposits are excluded. Compared to the process gas integrated variant, it is also substantially less expensive with respect to investment costs. Depending on the energy utilization (drying of raw materials, pre-heating of fuels, space heating), the air/oil heat exchanger pays for itself within a few months. Due to the favorable costing such retrofit is recommended for existing air/air heat exchangers.

One of the first projects to utilize this technology will cool exhaust gases to a maximum temperature of 130 °C and recover 1.3 MW of otherwise spoiled energy for the pre-heating of heavy oil. In another project equipped with a new EMC 8M filtration plant, Scheuch is integrating a two-stage air/air heat exchanger for further utilization of the heat energy.