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AQ Quiz 4
Modules 15 and 16
| Question | Answer |
|---|---|
| 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
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