At Afarak SA’s Mogale Alloys plant in Krugersdorp, a cleantech company from Sweden is transforming toxic gases created by ferrochrome production into electricity — and at a cost that undercuts Eskom.

In January 2018, the project was just a sketch on a serviette, but now, having successfully demonstrated its feasibility, Ripasso Energy has seven power-generating units en route from Sweden to SA, with the first expected to arrive in February. Together, the 45ft royal-blue containers will generate a total 2.8MW for the energy-intensive Mogale Alloys operations from its very own waste gas.

SA business has been struggling to cope with growing electricity prices and Eskom has now applied for an annual tariff hike of 15% for the next three years.

The ferro alloys industry, represented by the Ferro Alloy Producers’ Association, is a major energy user and has warned it will be particularly hard-hit should a double-digit tariff increase transpire.

Ripasso’s offering, a container-based solution that harnesses energy from gas and is known as the PWR BLOK 400-F, would be beneficial to SA’s mining and processing industry, says Ripasso Energy SA GM David de Mattos. “Every single metals production company in the world has furnace off-gas. The potential for this technology in our mining and processing industry in SA is enormous.”

He says the key to the business model is simple: waste gas must be burnt, so why not burn it with Ripasso Energy and receive electricity in return?

Ripasso Energy, a Sweden-listed company, started as a solar technology company before moving into furnace off-gas, waste gas produced by an industrial process.

De Mattos says the PWR BLOK 400-F has the edge because it uses Stirling engines — an external combustion as opposed to the more common internal combustion engine.

The gas from a ferro alloy furnace is volatile, says Jandri van der Vyver, Ripasso’s site manager at Mogale alloys.

“At some stages you have maybe 65% CO [carbon monoxide] and 18% hydrogen, and the next moment it switches around and you can have a 50-50 ratio.” For internal combustion engines this is a problem as a phenomenon known as “knocking” can occur, which damages the engine.

Stirling engines

The Stirling engines remove the risk of dealing with volatile gas because they burn it in a combustion chamber under very low pressure and with no compression, just heat.

The commercial licence for this particular Stirling engine was held by Kockums, a company formerly owned by the Swedish state and renowned for the manufacture of war ships and submarines. It was bought by Ripasso and developed into the highly efficient engine it is today.

The price of the electricity the PWR BLOK 400-F produces depends on each set-up. Ripasso offers a variety of business models. “The first option is that we are purely a service provider. The company buys the equipment, we operate and maintain the equipment and the company derives all of the profit and the benefits from self-generation,” De Mattos says. “Ripasso can also rent units or take full responsibility for generating the power, which means we would still beat the Eskom tariff, but it would be a smaller profit margin.”

The 2.8MW generated by the project at Mogale alloys, though enough to power about 560 households, will only account for 5% of the operation’s massive power consumption, says Afrak SA CEO Bertus van der Merwe.

But he believes it a good start, with the potential for more — possibly 10MW.

“If you have the ideal set-up — if there is gas available — they can replicate one-third of your power. Those extra megawatts make a real difference in our industry where we utilise extensive power,” Van der Merwe says.

“The industry needs to look at alternative options, otherwise the way the price increases are going, there won’t be an industry.”