The town of Deva in Romania is located south of the Transylvanian Ore Mountains. Located on the outskirts of the city is the Xella plant, now one of the largest plants in the Xella Group, where autoclaved aerated concrete (AAC) products are produced. Around 400,000 cubic meters are produced here annually and in a round-the-clock operation.

As part of the routine energy assessments of the plants, the Energy team, together with the team on-site, found a way to save a significant amount of CO2 emissions: optimizations to the process heat recovery system here will soon contribute to our climate targets.

How AAC is produced

AAC is made from the mineral raw materials sand, quicklime, cement and water. The building materials are created by hardening them in so-called autoclaves, i.e. sealable pressure vessels, for between eight and twelve hours at around 190 degrees Celsius. The process heat is carried away with the product and has so far been partially lost to the environment.

Some of this unavoidable heat energy loss can be recovered: a heat recovery system ensures this. The heat is thus returned to the boiler, reducing fuel consumption and CO2 emissions. 

Saving 1,000 tons of CO2 a year with optimized heat recovery

With the help of an optimized heat recovery system, as little energy as possible is now to be lost. In addition, the generation of the steam required in the production process should also be as energy-efficient as possible. These tasks are performed by the new heat recovery system, because it returns the heat generated in the production process to it as efficiently as possible.

Optimal cooperation

Currently, the rebuilds in Deva are running at full speed. The project is also a showcase example in that the period between identification of the optimization to the current implementation was only a few months. This was mainly due to the great know-how of the colleagues on site in Deva and the great willingness to cooperate and the good collaboration within the Group. "We really work hand in hand with our colleagues at the Deva plant. That's why it's possible that the new system will be up and running by spring at the latest," explains Thomas Nowakowski, Head of Energy Management.