The installation of a central controller and Variable Speed Drive compressor from Atlas Copco has significantly reduced energy costs for German paper manufacturer Stora Enso. As per the utility management team (or shop floor team), the company has cut the cost of generating compressed air by 30%. Taking all necessary conversion measures into account, the entire investment has been amortized in just one year.
At its Hagen site, Stora Enso produces almost half a million tons of paper per year, which equals almost 6.250.000.000 A4 papers. Close to 170,000 m3 of compressed air has to be generated every day to operate the paper machines, calendars, winders and cutters. Five compressors supply the internal compressed air system and cover the highly fluctuating demand, which at peak times can rise rapidly by up to 5000 m3/h.
In 2010, the company decided to optimize its compressed air system and installed an ES 130 T central controller, as well as a ZR 315 VSD compressor from Atlas Copco.
The ES 130 T controls several compressor sizes and types from various manufacturers. The system tests, stores and analyzes to ensure that the most suitable compressors are activated. As a result, the output of the five connected machines is geared, in terms of overall energy, towards achieving the optimum operating point and is continuously adjusted to meet the demand. This optimized operation not only means that energy consumption, CO2 emissions and costs are drastically cut, but also has a positive impact on the service life of the compressors.
Stora Enso has also invested in a new ZR 315 VSD (Variable Speed Drive) compressor. Graduate engineer Stjepan Horvat, responsible for the compressed air supply in the Hagener plant, says: “We had the problem that our high-performance compressors were constantly toggling between full load and idling, with the controller sometimes requesting a turbo for just two minutes."
After the installation upgrade, the original turbo compressors - operating in their 70 to 100% turndown range - now provide the required compressed air base load, while the ZR315 VSD - thanks to its speed regulation - operates primarily in the partial load range to respond to the varying demand for compressed air at any time. A proven combination of compressor technologies avoiding extremely long idle times, a lot of wasted energy and high CO2 emissions.
Once the central controller and VSD compressor had been installed, Stora Ensa's energy consumption fell by 30%. As a result, the company's entire investment has been amortized within one year.
At Stora Enso, sustainability and energy saving have yet another dimension: The heat discharged by the compressors is used twice. In winter, it heats up the production hall and in summer, it pre-heats the process water required for production.