Covestro investing €200m in Spanish expansion, new chlorine technology

Leverkusen, Germany – German materials supplier Covestro AG is planning to build its own chlorine production plant in Tarragona, Spain, using a homegrown sustainable process: oxygen-depolarised cathode technology.

In a 19 June statement, the company said the industrial-scale plant will be based at its current production facility in Spain and will consume around a quarter less energy than the conventional method.

Covestro said it is currently investing around €200 million at Tarragona to increase the site’s competitiveness, the new chlorine production plant being a key part of the investment.

Construction of the new plant in Tarragona is scheduled to begin in the first half of 2019.

Chlorine is mainly needed at Tarragona to make MDI, a precursor for rigid foam.

“About one-third of the production costs for chlorine are usually spent on energy. Thus, the selected technology makes an important economic contribution,” Covestro explained.

According to chief technology officer Klaus Schäfer, the main reasons for choosing the process were sustainability and energy efficiency.

“This is a special success story for us since the development of this technology began at our company over two decades ago,” added Schäfer.

Chlorine is needed to make around two-thirds of all polymers, yet it does not occur naturally in its pure form.

Instead, it is only found in chemical compounds – such as in rock salt, from which chlorine can be obtained using electrolysis, which is very energy-intensive.

However, Covestro, in partnership with ThyssenKrupp Uhde Chlorine Engineers, have developed a technology, which they claim consumes around 25% less energy than conventional electrolysis through the use of an oxygen-depolarized cathode (ODC).

ODC technology is based on the conventional membrane process, in which chlorine, caustic soda and hydrogen are usually produced from rock salt and water.

The crucial difference, Covestro explained, is that the hydrogen-generating electrode normally used is replaced by an oxygen-depolarised cathode.

“Only chlorine and caustic soda are produced. As a result, a voltage of just around two instead of three volts is required,” added the company.

“The change in this process sounds simple, but was a ground-breaking development for chlorine manufacturing,” commented Hanno Brümmer, head of production at the polyurethanes segment which includes the company’s global chlorine activities.

Initial invention and development work on the process began in 1992, with the first demonstration plant on an industrial scale built in Krefeld-Uerdingen in 2011.