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AQ Quiz 4

Modules 15 and 16

QuestionAnswer
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%
Cascade impactor 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
Gravitational settling Slow velocity, long device. Good for >50 AED micrometersparticles
Inertial compaction The gas is able to turn corners quickly but the particulate does not- baffle collectors, cyclones, and centrifugal collectors.
Cyclones Air comes in at top and spirals downwards- the particulate drops out due to the inertia of impact with side of cylinder
Centrifugal collector basically a giant fan that spits out particulate that gets collected on the blades
Wet scrubbers 1. Direct interception, inertia, brownian movement 2. Droplet sweep - make sure interaction happens
Types of wet scrubbers Spray tower and venturi
Electrostatic precipitators Charge the particles then collect with an oppositely charged plate
Filtration systems 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
Condensation May be indirect or direct. Indirect most common- tube and shell (gas inside tube, has a cool shell- like an ice bath)
Condensation issues Tube fouling, tube corrosion, specific loading
Incineration of gases Destruction removal efficiency- 99.999% Produces radicals which destroy more pollutant
Combustion issues Incomplete combustion leads to carbon monoxide, byproducts, efficiency slips, Halogens and sulfurs
Incinerator types 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
Biological methods Biofilters for example. Efficient but requires lots of management
Created by: swilson67