Normal Size Small Size show me how
AQ Quiz 4
Modules 15 and 16
|Features of particles
|Wide size range Small particles don't settle out easily Wet particles easier to capture Particles can gain a charge
|Emissions reduction efficiency
|(Enter-exit)/exit * 100%
|Seven plates that collect different size particles all at once
|Before you pick your PCD, you should know what about the particle?
|Size, stack gas temperature, stack gas moisture
|Slow velocity, long device. Good for >50 AED micrometersparticles
|The gas is able to turn corners quickly but the particulate does not- baffle collectors, cyclones, and centrifugal collectors.
|Air comes in at top and spirals downwards- the particulate drops out due to the inertia of impact with side of cylinder
|basically a giant fan that spits out particulate that gets collected on the blades
|1. Direct interception, inertia, brownian movement 2. Droplet sweep - make sure interaction happens
|Types of wet scrubbers
|Spray tower and venturi
|Charge the particles then collect with an oppositely charged plate
|Basically a bag vacuum (Baghouse) May be shaken or reverse air cleaned. Shaken has a dirty and clean side
|Which removal systems have highest efficiency?
|Baghouse filter and venturi scrubber
|Why is size unimportant when choosing a PCD for gases/vapors?
|The molecules are the same size
|Factors affecting rate of absorption
|Temperature, SA, Glow of absorbant and gas
|Bubble cap absorption scrubber
|Pollutant gas bubbles up through trays causing pollutants to get trapped in liquid
|Counter current packed absorbtion scrubber
|Liquid filtered down onto packing creating a film. Gas goes up and gets stuck
|Absorption scrubber efficiency
|95% - gets better with more height and diameter
|Types of adsorbants
|GAC, activated alumina, molecular sieves
|Packed GAC beds
|The offline bed is steam heated to release VoC which can be recovered. Once dry, bed is reused.
|How can you condense gases?
|Decrease temperature, increase pressure, or both
|May be indirect or direct. Indirect most common- tube and shell (gas inside tube, has a cool shell- like an ice bath)
|Tube fouling, tube corrosion, specific loading
|Incineration of gases
|Destruction removal efficiency- 99.999% Produces radicals which destroy more pollutant
|Incomplete combustion leads to carbon monoxide, byproducts, efficiency slips, Halogens and sulfurs
|Thermal oxidation (TOX) Thermal oxidation w/heat recovery (THROX) Catalytic oxidation
|Are flares a PCD?
|No- their efficiency is too low. This is a back up measure
|Biofilters for example. Efficient but requires lots of management