Nozzles for gas scrubbing

Engineering consideration  - Wet and dry scrubbing


Wet scrubbing


As the name would suggest wet scrubbing involves saturating the gas flow with a spray.  The fluid being sprayed will react with the gas and remove the undesirable substances.  For example, a lime slurry sprayed into an exhaust gas from a power plant will react with the sulpher dioxide in the flue and remove it.

When considering suitable nozzles fine atomisation is desirable as this increases the reactive surface area of the spray, but also reach and momentum of the spray is important especially if the gas flue is moving at a considerable velocity.  As smaller droplets have less momentum it is often the case that sprays consisting entirely of small droplets will get swept away by fast moving gas flows and fail to reach certain areas.  For this reason spiral nozzles, with their broad spectrum of droplets, are often useful.


Dry scrubbing


With dry scrubbing smaller amounts of fluid are sprayed into the gas flow but the volume of fluid is limited to that which can be evaporated from the gas flow.  So the gas remains 'dry'.  This would be necessary if contamination by the scrubbing fluid is not desirable further along the process line.

When considering suitable nozzles for dry scrubbing control is everything.  A fast moving gas flow may sweep away very fine droplets before they can react, or evaporate and thus contaminate the flow.  On the other hand, if the droplets are too large they may take too long to evaporate and contamination may still occur.  A fine balance needs to be found between the evaporation rate and the volume/consistency of the spray.


Gas Scrubbing Engineering Considerations

Gas Scrubbing Nozzle Designs