AIR POLLUTION CONTROL L 18

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AIR POLLUTION CONTROL course material by Prof S S JAHAGIRDAR,NKOCET,SOLAPUR for BE (CIVIL ) students of Solapur university. Content will be also useful for SHIVAJI and PUNE university students

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AIR POLLUTION CONTROL L 18

  1. 1. L-17 Plume Rise Formulae Air Pollution and Control (Elective -I)
  2. 2. • Gases that are emitted from stacks are often pushed out by fans. As the turbulent exhaust gases exit the stack they mix with ambient air. This mixing of ambient air into the plume is called entrainment. As the plume entrains air into it, the plume diameter grows as it travels downwind. These gases have momentum as they enter the atmosphere. Often these gases are heated and are warmer than the outdoor air. In these cases the emitted gases are less dense than the outside air and are therefore buoyant. Prof S S Jahagirdar, NKOCET 2
  3. 3. • A combination of the gases' momentum and buoyancy causes the gases to rise. This is referred to as plume rise and allows air pollutants emitted in this gas stream to be lofted higher in the atmosphere. Since the plume is higher in the atmosphere and at a further distance from the ground, the plume will disperse more before it reaches ground level. Prof S S Jahagirdar, NKOCET 3
  4. 4. Plume Rise > hs= Physical Stack height H= Effective stack height Prof S S Jahagirdar, NKOCET 4
  5. 5. Buoyancy =Plume rise < 5 Prof S S Jahagirdar, NKOCET
  6. 6. 1. IS formula Prof S S Jahagirdar, NKOCET 6
  7. 7. 2. Modified Carson and Moses formula 0.5 h  a.[(Vs .d ) / u ]  b.[(Qh ) / u ] Stability Condition a b Unstable 3.47 0.35 -1.04 5.15 2.64 2.24 Neutral Stable Prof S S Jahagirdar, NKOCET 7
  8. 8. Prof S S Jahagirdar, NKOCET 8
  9. 9. 3. Holland’s Formula Ts= Stack gas temperature in 0 K Ta =Ambient air temperature in 0 K Prof S S Jahagirdar, NKOCET 9
  10. 10. 4. Concave formula 1/ 2 h h  2.71[Q 3/ 4 /u ] It is modified by Thomas h  4.71[Q 0.444 Prof S S Jahagirdar, NKOCET /u 0.694 ] 10
  11. 11. 5. Brigg’s formula 1/3 h  114.C.( F ) /u 2 g .Vs .d .(Ts  Ta ) F 4.Ta    C  1.58  41.4    z  Prof S S Jahagirdar, NKOCET 11
  12. 12. • F= Flux (m4/Sec3) • G= gravitational acceleration. •    = potential temperature gradient  z    (Similar to dT/dZ) Prof S S Jahagirdar, NKOCET 12
  13. 13. 6. Davidson and Bryant formula Vs  h  d .   u  1 .4  T  . 1   Ts   Where, Ts-Ta= T Prof S S Jahagirdar, NKOCET 13
  14. 14. Objective Questions 1. Plume rise is measures from top of the stack and is measured up to ____________________________. 2. Stack gas temperature is ___________ than the surrounding air. 3. IS: _______ suggested plume rise formula based on Brigg’s equation. 4. Values of coefficients a and b in case of modified Carson and Moses equation for unstable stability class are ____ and ____ respectively. (Similar questions for other Stwo stability categories.) 14 Prof S Jahagirdar, NKOCET
  15. 15. 5. Plume rise is due to _________________ and _______________. 6. Effective stack height = ________________+____________________. 7. True or False? Plume rise (Δh) is the height that pollutants rise above a stack and is measured from the top of the stack to the upper edge of the plume. Prof S S Jahagirdar, NKOCET 15
  16. 16. Theory Questions Q1. Explain what is ‘Plume rise’. Give any three formulae for the same. Q2. Give IS formula for plume rise. Prof S S Jahagirdar, NKOCET 16
  17. 17. Go to Problems Prof S S Jahagirdar, NKOCET 17

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