A year ago, the first PWR BLOK from the Swedish clean tech company Swedish Stirling was commissioned at the site of ferro-chrome producer Afarak Mogale. PWR BLOK, which is based on the Stirling technology used in Swedish submarines, is a unique new solution for energy recovery of industrial residual gases. The technology has the potential for large cost savings for South Africa’s metal industry and at the same time significantly reduce carbon dioxide emissions. Swedish Stirling are now ready to launch in South Africa in a larger commercial scale, and has raised capital from new, knowledgeable investors to begin volume production in the coming year.
Metal production is extremely electricity-intensive. The energy bill accounts for approximately one-third of the industry’s total cost, and half of all that energy is then lost in form of residual gases that are only flared away. This is a well-known fact, and for decades the industry has tried to come up with solutions to recover parts of this energy to reduce costs. Attempts with internal combustion engines, gas and steam turbines have been tried, but all solutions have failed. The reason is usually that the gas is of such uneven quality that most engines with internal combustion doesn’t work, or the technical solutions are simply too expensive.
PWR BLOK is able to handle residual gas with uneven quality thanks to the Stirling engine and the fact that the heat is applied externally. The solution is simple. The PWR BLOK is placed adjacent to the smelter and the residual gas is fed to, and combusted in the PCU (Power Conversion Unit). The heat is then converted by the Stirling engines into electricity that is returned to the smelter. The recycling reduces the producer’s need for purchased electricity by up to 15%, and thus also carbon dioxide emissions. A single PWR BLOK reduces emissions in South Africa by approximately 3500 t pa.
Extensive operation at Afarak Mogale
The collaboration with Afarak has enable Swedish Stirling to run extensive operation and test of the PWR BLOK at the plant in Mogale. The company’s South African team has been able to show that PWR BLOK is capable of producing electricity of grid quality, even at extremely varied gas qualities with high hydrogen content. PWR BLOK are also able to manages the particles that are always present in residual gases, which was an element of uncertainty for Swedish Stirling’s technicians in the beginning of the project.
“Thanks to the collaboration with Afarak Mogale, we have gained valuable test results and experience that we now have used to further develop the technology. With the amount of operation hours, we feel confident to proceed on a larger commercial scale,” says Heije Westberg, Swedish Stirling’s chief technology officer.
“Swedish Stirling’s standard of performance during the project was highly commendable and it was a privilege for Afarak Mogale to be associated with this ground-breaking energy conversion project,” says Afarak Mogale’s general manager, Wayne Pickering.
Second generation PWR BLOK to TC Smelter
Swedish Stirling is now preparing the installation of an upgraded version of PWR BLOK (generation 2) – which was shipped from Sweden in February this year. The new unit has a new control system that will make it far easier to integrate new features and to optimise operation in the future. It will shortly be commissioned into full commercial operation at Samancor Chrome’s TC Smelter plant.
Swedish Stirling RD-team is also currently working with PWR BLOK generation 3. This is the version of PWR BLOK that Swedish Stirling will start to produce on a larger scale. Glencore SA is one of many companies that have expressed interested, and in February Swedish Stirling and Glencore signed an energy conversion agreement for a plant with up to 25 PWR BLOK at the Lydenburg smelter.
To be able to finalise the full-scale launch in South Africa, Swedish Stirling raised additional capital from several new investors, both institutional and private. Investors include Spotify’s well-known CEO and founder Daniel Ek.