At the recent conference in Singapore dedicated to the Asian sulfur cap questions, several experts denied concerns about washwater discharged by scrubber systems, while the viability of LNG as a marine fuel was also discussed. The thing is that there is an opinion that the timetable for the implementation of IMO 2020 leads to the destruction of schedules of ship repair yards.

To be more precise, they confirm that weak coordination results in pile-ups and delays at shipyards, herewith, a successful scrubber retrofit requires appropriate cooperative agreement between the supplier and the customer. It should be noted that the average time of scrubber retrofit installation takes between 21 and 28 days.

Moreover, it is possible to reduce several days of the time but only if “all the material and equipment is already on standby when the vessel is docking in the yard”. Some experts claim that scrubber retrofits depend on the yard’s proficiency, therefore, yard time of open-loop scrubber system is generally 2-3 weeks.

Additionally, a challenge, which wet scrubber systems face, has been also discussed at the conference. The problem is corrosion within scrubber parts. Based on researchers concerning corrosion problems, the acidic washwater may lead to corrosion of wet scrubber units resulting in prolonged maintenance, repairs or even replacement.

The corrosion is caused by the sprayed sulfurous exhaust gas stream that is put into the lower portion of the wet air scrubber during air treatment, herewith, the acidic washwater flows down the walls of the scrubber system tower. While in a conventional scrubber tower the bottom part suffers from high levels of acidic corrosion, the top part may also be subjected to it but a lesser degree, because not all the SOx is taken away.

In a closed-loop wet air scrubber, the water solution is re-circulated that also leads to a risk of corrosion. According to IMO air treatment regulations, all the washwater has to be neutralized and diluted with additional seawater, so the pH level is more than 6.5 before discharge. Therefore, the proper operation of wet scrubbers plays a crucial role, taking into account concerns of corrosion damage caused by scrubber washwater.

The experts believe that manufacturers of wet air scrubbers will provide the right materials of high quality for scrubber systems, and they suppose that coatings are required only for the overboard discharge section where the washwater can affect the hull coating.

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