Gas Pollution Control

Question 1

define stationary sources of pollutants

Answer 1

fixed emitter of pollutants

Question 2

define mobile sources of pollutants

Answer 2

moving emitter of pollutants

Question 3

define natural sources of pollution

Answer 3

emitter from a natural source

Question 4

what pollutants are released in traffic related air pollution

Answer 4

PMx, VOC, NOX and CO

Question 5

define primary pollutants

Answer 5

pollutants directly into atmosphere

Question 6

define secondary pollutants

Answer 6

pollutants created through chemical reactions in the atmosphere

Question 7

what is photochemical smog and how is it formed?

Answer 7

smoky fog formed from sunlight reactions between VOC and NOx

Question 8

define acid rain

Answer 8

any form of precipitation with acidic components that fall to the ground in wet or dry forms

Question 9

draw a diagram representing acid rain formation and deposition

Question 10

what is a plume?

Question 11

name the 5 factors that have an impact on atmospheric stability and explain why?

Question 12

what is the working principle of gravitational separator?

Answer 12

carrier gas passes through settling chamber at a low velocity. The solid particles then settle to the bottom of chamber, due to their higher density.

Question 13

name two advantages of a gravitational separator

Answer 13

removes larger particles >45
high maximum operating temperature (550)

Question 14

name two disadvantages of a gravitational separator

Answer 14

not a standalone separator
cannot remove small particles

Question 15

working principle of a cyclone

Answer 15

dirty gas passes in through the inlet and inside the chamber, a spiral vortex is formed which can remove medium sized particles through inertia. The larger particles will hit the wall and fall to the bottom to be collected.

Question 16

advantages of cyclone

Answer 16

removes medium particles >5

Question 17

disadvantages of cyclones

Answer 17

cannot remove smaller particles
cannot remove sticky or fluffy particles

Question 18

working principle of gravity spray tower

Answer 18

solid particles collect onto liquid stream particles through impaction or interception

Question 19

working principle of packed bed/tower

Answer 19

solid particles attach onto particles which have a liquid film around them

Question 20

disadvantage of packed/bed tower

Answer 20

prone to high pressure loss and clogging

Question 21

working principle of a venturi (draw a diagram)

Answer 21

liquid particles accelerate through low pressure venturi throat and capture particles by impaction.

Question 22

disadvantage of absorption techniques for seperation

Answer 22

not suitable where there is wide variations in gas flow
not suitable for large gas flow
produces a sludge

Question 23

advantages of a venturi

Answer 23

separates small particles <5
very high efficiency

Question 24

advantages of absorption techniques

Answer 24

can treat hot, combustible, acidic streams

Question 25

working principle for fabric filters

Answer 25

dirty gas stream passes through woven or felted fabric that filters out particulate matter

Question 26

advantages of fabric filters

Answer 26

can separate very small particles

Question 27

working principle of ESP

Answer 27

electron avalances move out of corona regions and attach to gas molecules with attach to incoming particles

Question 28

State 3 advantages of ESP

Answer 28

works for continuous steady flow works best for consistent particle properties works best for liquid particles works well for a wide range of particle sizes

Question 29

disadvantages of ESP

Answer 29

cannot collect control solids or sticky particles

Question 30

define corona generation

Answer 30

electrical discharge generated by ionization of a fluid

Question 31

define field charging

Answer 31

collision of particles with gas ions which travel along field lines (impaction)

Question 31

define diffusion charging

Answer 31

collision of particles with gas ions due to diffusion

Question 32

write an expression for scrubbing of SO2

Question 33

State the four mechanisms that can work for removing gaseous pollutants from air?

Answer 33

absorption adsorption combustion condensation

Question 34

write an expression for oxidising catalytic systems in catalytic converter?

Answer 34

CO + O2 -> 2CO2

Question 35

write an expression for reducing catalytic systems in catalytic converter?

Answer 35

NOx-> N + O2

Question 36

write 2 expressions for three way catalytic converter?

Answer 36

2NO + CO -> N2 + CO2

Question 37

what is the working principle for fibrous gas filtration?

Question 38

where are prefilters and panel filters used?

Answer 38

building ventilation systems

Question 39

where are pocket filters mainly used?

Answer 39

heating, ventilation and air conditioning (HVAC) applications

Question 40

what is the working principle of a coalescer?

Answer 40

prefilter and then 2 stages of coalescence

Question 41

define interception

Answer 41

where a particle follows a flow stream until it colldies with a collector or filter medium

Question 42

define impaction

Answer 42

where a particle because of its inertia goes off stream and that way collides with a collector for filter medium