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Scrubbers repurposed for CCS

“While you’re at it...”

It turns out that technology being used to remove sulfur from ship exhaust can also be used to combat the bigger threat: CO2

Scrubbers’ big moment came in 2020, when the global 0.5% sulfur cap entered force. The technology represented a straightforward way for existing vessels – generally — to continue to operate on heavy fuel oil, the cheapest ship fuel available.

But now, sulfur is not the main concern – decarbonisation is. It is generally understood that this will be impossible without the help of completely new fuel types. But Langh Tech, testing at sea on a vessel owned by its sister company, shipowner Langh Ship, this month discovered that it is in fact possible to remove a percentage of the CO2 from ship exhaust using a scrubber – some 7% at an engine load of 40%, and 3.3% at a load of 85%.

Tests use an alkali – NaOH, or HgOH2, described by Langh Tech as “readily available” — added to the scrubber washwater during closed-loop operation.

This confirms a hypothesis that Wärtsilä posited early last year, and is itself running tests to see if its own repertoire of exhaust gas treatment systems can be used for carbon capture and storage (CCS). Indeed, devising a system capable of this is something of a holy grail for an engine manufacturer, as it could have major implications in terms of getting better emissions performance out of existing vessels. Sigurd Jenssen, Director, Exhaust Treatment at Wärtsilä, said at the time: “Building on the success of existing and well-proven technologies, such as scrubbers, will be vital to succeeding on the industry’s decarbonisation goals.

“Exhaust gas abatement technologies have reached a point of maturity where it is only right that we explore their wider applications beyond sulfur compliance.”

Given the high carbon cost of building even the shiniest and most technologically advanced new eco-ships, this discovery will be more important than many in the maritime industry are willing to admit.

“Results of the tests are regarded as tentative proof of concept and additional tests with further increased alkali feed shall be conducted to verify this,” Langh Tech reported. “Langh Tech is also researching methods of extracting the captured CO2 from the process water and looking for ways to store and/or utilize the captured CO2 efficiently on board vessels and upon discharge to shore.”

As well as reading more of Engineering At Sea’s coverage of exhaust gas treatment systems (“scrubbers”), readers can also find our series of explainers on CCS here.