The exhaust gas cleaning process for sulphur dioxide reduction starts when the exhaust gas enters the precooling
unit. Through water injection from the booster system and some evaporation, the exhaust gas is
cooled down and ready to enter the scrubber tower. The decreasing temperature of the exhaust gas
reduces the gas velocity causing a small turbulence that distributes the exhaust gas at the bottom of the scrubber tower.
From the bottom of the scrubber the exhaust gas rises up, and during this process SOx will condense. With
the help of gravity, the condensed SOx in combination with the sodium in the water will be carried
downward to the bottom of the scrubber with the water that enters in the middle section of the scrubber tower.
The water that enters the middle section of the scrubber through a specially designed nozzle shower
system ensures that all sulphur dioxide is washed out and is led back to the process tank.
The exhaust gas continues upwards through a demister which is placed at the top of the scrubber tower
preventing water droplets to be carried away with the outlet gas flow. A nozzle system near the demister
washes out particles that manage to patch through the scrubber tower and prevents fouling.
The water in the process tank is recirculated in the scrubber system and as the sulphur content in the
scrubber water will increase it is necessary to add more sodium in the form of NaOH, sodium hydroxide.
During this process not only sulphur is washed out but also soot and ash particles as well as unburned oil.
The particles and the unburned oil are led with the process water into the water treatment unit where it is
separated into sludge content and wastewater. The process water which is now salt water is led back to the
process tank if it can be used again. If there is no more sodium hydroxide in the process water, it is up to
the individual vessel whether the clean process water is to be discharged or sent to a holding tank for later