Mitsubishi Heavy Industries (MHI) has collaborated with Mitsubishi Hitachi Power Systems (MHPS) to develop a large-scale Rectangular Marine Scrubber, which is designed to remove sulphur oxides (SOx) from the exhaust gases emitted by marine diesel engines.

The solution combines MHPS’ comprehensive flue-gas treatment technologies cultivated through desulphurisation systems for thermal power plants with MHI's expertise in marine engineering.

It also features a rectangular box-shape configuration, which allows for the easy installation of the solution in small spaces and provides improved emissions treatment for high-output engines, such as those used on large-scale container ships.

The solution is capable of purifying exhaust gas emitted from inexpensive heavy fuel oil to a level comparable to more expensive low-sulphur fuels. It can also be retrofitted onto existing ships.

MHI states that the scrubber was developed in response to the International Maritime Organisation’s (IMO) SOx emissions regulations, which are set to be enforced worldwide from 2020.

The SOx scrubber uses seawater as its cleaning agent via an ‘open-loop’ system, where seawater intake is sprayed directly onto the exhaust gas.

"The solution is capable of purifying exhaust gas emitted from inexpensive heavy fuel oil to a level comparable to more expensive low-sulphur fuels."

The horizontal and vertical dimensions of the rectangular scrubber tower have enabled users to customise the solution, which provides higher volume efficiency than cylindrical scrubbers.

MHI further noted that the new SOx scrubber system’s main unit can be set into the upper deck's engine casing, freeing up room in the ship's load space. The system is ideal for large-scale container ships that use a ‘twin island’ design.

MHI and MHPS are planning to test the scrubber on various ships in preparation for its certification.

Deliveries of the scrubber are currently scheduled from 2020.

Image: Conceptual outline for ultra large container ship. Photo: courtesy of MITSUBISHI HEAVY INDUSTRIES, LTD.