Within the total energy ecological balance of aluminium the primary production has the highest part of energy consumption. The heat potential of the process off gas is about 15% of the energy input, while 4% may be used for heat recovery due to the low temperature level of about 100°C. For Hamburger Aluminium-Werk GmbH (HAW) this is an amount of 8 MW. The partners Technical University of Hamburg Harburg, Department of Plant System Design, and the HAW have developed and tested a pilot heat recovery plant with a compact pilot heat exchanger as the main component. The pilot heat exchanger is integrated into one of the total of 270 electrolytic cells. At the moment three offices are heated during winter. This pilot plant is the predecessor of a district heating system for a nearby housing complex.
A steady state model of the pilot heat exchanger has been developed and verified experimentally. The experiments have shown that with the pilot heat exchanger 18 kW to 30 kW of heat can be recovered. During long term measurements the gas-side pressure drop increased due to gas-side fouling. To mitigate gas-side fouling and to ensure reliable operation an in situ gas-side cleaning device based on movable brushes and scrapers has been developed.