The in-line scrubbers are multi-inlet installations, where the main engine and auxiliary engines are connected to the same scrubber tower.
In addition, the MAN Diesel & Turbo two-stroke main engines of the newbuildings are equipped with EGR (exhaust gas recirculation) systems to reduce NOx emissions to meet Tier III requirements.
In the EGR process approximately one third of the exhaust gas is washed with a scrubbing unit to remove particles from the exhaust gas before it is recycled back into the engine.
The process water used in the exhaust gas washing is continuously cleaned during EGR operation, which is where Langh Tech's water treatment technology is applied.
After being cleaned, the purified process water is fed back to the process circulation or sent overboard. Similar water treatment is also used for the process water of the SOx scrubber system. Langh Tech is the first company to combine water treatment technology for both SOx scrubber process water and EGR process water.
The Langh Tech water treatment technology is based on membrane filtration, reducing operational costs. The amount of waste is compressed into only small amounts of dry sludge. Additionally, membrane filtration cleans the overboard discharge water far beyond MARPOL requirements.
EGR process water treatment has required long and thorough testing by MAN Diesel & Turbo, and at the end of 2016, Langh Tech received approval for its system from MAN Diesel & Turbo.
The combined water treatment for EGR and SOx scrubber requires very good purified water quality to be fed back to the EGR. The combined water treatment system saves space onboard, and further, only one chemical compound, caustic soda (NaOH), is needed to tackle both NOx and SOx emissions.
Using EGR for NOx removal eliminates the use of the urea required by SCR (selective catalytic reduction) solutions.