3.2.1 The purpose of the scrubber is to cool the
flue gas and remove most of the sulphur dioxide and particulate soot.
All three actions are achieved by direct contact between the flue
gas and large quantities of seawater.
3.2.2 Before entering the bottom of the scrubbing
tower the gas is cooled by being passed either through a water spray,
or bubbled through a water seal. Such a seal may also serve as the
additional safety device to prevent any leakage of gas from the boiler
uptake when the scrubber is opened up for inspection or maintenance.
3.2.3 In the scrubbing tower itself the gas moves
upwards through downward flowing water. For maximum contact between
gas and water, several layers made up of one or more of the following
arrangements may be fitted:
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.1 spray nozzles;
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.2 trays of “packed” stones or plastic
chippings;
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.3 perforated “impingement” plates;
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.4 venturi nozzles and slots.
3.2.4 At the top of or downstream of the scrubbing
tower, water droplets are removed by one or more demisters which may
be polypropylene mattresses or cyclone dryers.
Designs of individual manufacturers vary considerably.
A typical arrangement for an inert gas system