Wet scrubber
The most critical sized particles are those in the 0.1 to 0.5 micrometres range because they are the most difficult for wet scrubbers to collect.
Inlet gas characteristics and dust properties (if particles are present) are of primary importance.
The versatility of wet scrubbers allow them to be built in numerous configurations, all designed to provide good contact between the liquid and polluted gas stream.
Also, the resultant scrubbing liquid must be treated prior to any ultimate discharge or being reused in the plant.
Additionally, a properly designed and operated entrainment separator or mist eliminator is important to achieve high removal efficiencies.
The greater the number of liquid droplets that are not captured by the mist eliminator, the higher the potential emission levels.
Good gas-to-liquid contact is essential to obtain high removal efficiencies in absorbers.
In general, obtaining high simultaneous gas and particulate removal efficiencies requires that one of them be easily collected (i.e., that the gases are very soluble in the liquid or that the particles are large and readily captured), or by the use of a scrubbing reagent such as lime or sodium hydroxide.
The "cleaned" gases are normally passed through a mist eliminator (demister pads) to remove water droplets from the gas stream.
A drag chain conveyor system removes the sludge and deposits in into a dumpster or stockpile.
In a wet scrubbing system, dust particles will tend to follow the streamlines of the exhaust stream.
Impaction is the predominant collection mechanism for scrubbers having gas stream velocities greater than 0.3 m/s (1 ft/s) (Perry 1973).
Very small particles (less than 0.1 μm in diameter) experience random movement in an exhaust stream.
Because of this, diffusion is the primary collection mechanism in wet scrubbers for particles smaller than 0.1 μm.
In the particle size range of approximately 0.1 to 1.0 μm, neither of these two collection mechanisms (impaction or diffusion) dominates.
Other mechanisms such as gravity, centrifugal force, and direct interception slightly affect particle collection.
Since wet scrubbers vary greatly in complexity and method of operation, devising categories into which all of them neatly fit is extremely difficult.
water gauge (¼ to ½ kPa) and are approximately 70% efficient on 10 μm particles.
Three types of packed-bed scrubbers are: Efficiency can be greatly increased by minimizing target size, i.e., using 0.003 in.
These high-gas velocities immediately atomize the coarse water spray, which is injected radially into the venturi throat, into fine droplets.
High energy and extreme turbulence promote collision between water droplets and dust particulates in the throat.
