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AIR POLLUTION CONTROL L 16
 

AIR POLLUTION CONTROL L 16

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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

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 16 AIR POLLUTION CONTROL L 16 Presentation Transcript

    • L-19 and L-20 Dispersion of Pollutants: Gaussian Dispersion Model (GDM) Air pollution and Control (Elective -I)
    • Stability classes
    • Stability Classes • Developed for use in dispersion models • Stability classified into 6 classes (A – F) • A: strongly unstable – Large lapse rates • B: moderately unstable • C: slightly unstable • D: neutral- Less or zero lapse rate • E: slightly stable – mild inversion • F: moderately stable – moderate to severe inversion
    • Pasquill’s Stability table
    • General Structure of Air Pollution Models Air Quality Model Output: Concentration Distribution Input 1: Emissions Input 2: Meteorology Input 3: Atmospheric Chemistry Prof S S Jahagirdar, NKOCET Input 4: Surface Properties 5
    • Air Pollution modeling :Parameters in Models 1. Source Parameters (Emission Characteristics) Emission rates of pollutants (mass/time) Physical location of source Temperature of gas release Plume Rise 2. Meteorology Atmospheric temp. Atmospheric stability (needed for Dipersion coefficients) Wind velocity 3. Atmospheric Chemistry Chemical Reaction in the atm. Depositions (wet or dry) 4. Surface Parameters (Properties) Surface geometry, roughness, seas, urban or rural 6 areas etc
    • Why Use Dispersion Models? • Predict impact from proposed and/or existing development – NSR- new source review – PSD- prevention of significant deterioration • Assess air quality monitoring data – Monitor location • Assess air quality standards or guidelines – Compliance and regulatory • Evaluate AP control strategies – Look for change after implementation 7
    • Why Use Dispersion Models? • Evaluate receptor exposure • Monitoring network design – Review data – Peak locations – Spatial patterns • Model Verification 8
    • Model Assumptions • Gaussian dispersion modeling based on a number of assumptions including – Steady-state conditions (constant source emission strength) – Wind speed, direction and diffusion characteristics of the plume are constant – Mass transfer due to bulk motion in the x-direction – Conservation of mass, i.e. no chemical transformations take place – Wind speeds are >1 m/sec. – Limited to predicting concentrations > 50 m downwind 9
    • 10
    • 11
    • • Horizontal dispersion coefficient 12
    • • Vertical dispersion coefficient 13
    • Atmospheric Stability Classes 14
    • Dispersion Coefficients: Horizontal 15
    • Dispersion Coefficients: Vertical 16
    • Maximum Ground Level Concentration Under moderately stable to near neutral conditions, s y  k1s z The ground level concentration at the center line is  H2  C x,0,0  exp  2  2 k1s z u  2s z  Q ---------------- Eq - A The maximum occurs at dC / ds z  0 H  sz  2 Put in Eq - A Once sz is determined, x can be known and subsequently C. C  x, 0, 0   17 Q s ys z u exp  1  0.1171 Q s ys z u
    • How to use GDM? Need to know proper orientations of both Source and Receptor: Source at (0,0,H) and Receptor at (x,y,z) C(x,y,z;H) Pollutant Emission Rate from source: Q (mass of pollutant/time) NOT Volume flowrate of Stack gas Atmospheric Stability Category (A, B, C. etc.) 18
    • Wind velocity at stack height : u Dispersion Coefficients : σy and σz (can be determined from graphs) Effective Stack height: H = hs + Δh  Calculation of Plume rise (Δh ) by any one formula (Refer lecture on plume rise) THEN USE GDM 19  C(x,y,z;H) =….
    • Example - 1 • A stack in an urban area is emitting 80 g/s of NO. It has an effective stack height of 100 m. The wind speed is 4 m/s at 10 m. It is a clear summer day with the sun nearly overhead. Estimate the ground level concentration at a) 2 km downwind on the centerline and b) 2 km downwind, 0.1 km off the centerline. 20
    • Example 1. Determine stability class Assume wind speed is 4 km at ground surface. Description suggests strong solar radiation. Stability class B 21
    • Example 2. Estimate the wind speed at the effective stack height Note: effective stack height given – no need to calculate using Holland’s formula p  z2   u 2  u1   z   1  Prof S S Jahagirdar, NKOCET p   100  4   10  0 .2  22
    • Example 3. Determine σy and σz σy = 290 σz = 220 220 290 23
    • Example 4. Determine concentration using Eq 11-12 a. x = 2000, y = 0  1  0 2   1  100  2  80 C ( 2000,100,0)  exp     exp      ( 290)(220)(5.6)  2  290    2  220       C ( 2000,0)  6.43 10 5 g/m3  64.3 μg/m 3 Prof S S Jahagirdar, NKOCET 24
    • Example 4. Determine concentration using Eq 11-12 a. x = 2000, y = 100  1  100  2   1  100  2  80 C ( 2000,0)  exp     exp      (290)(220)(5.6)  2  220    2  220       C (2000,100,0)  Prof S S Jahagirdar, NKOCET 25
    • L-20 Problems on GDM Air Pollution and Control Elective -I Prof S S Jahagirdar, NKOCET 26
    • Example-2 • An industrial boiler is burning at 12 tons (10.9 mton) of 2.5% sulfur coal/hr with an emission rate of 151 g/s. The following exist : H = 120 m, u = 2 m/s, y = 0. It is one hour before sunrise, and the sky is clear. Determine downwind ground level concentration at 10 km. Stability class = sy = sz = C(10 km, 0, 0) = 27
    • Exercise-3 • If emissions are from a ground level source with H = 0, u = 4 m/s, Q = 100 g/s, and the stability class = B, what is downwind concentration at 200 m? At 200 m: sy = sz = C(200 m, 0, 0) = 28
    • Go to Additional problems 29
    • Objective Questions Q1. GDM is used for _____________________ ______________________________________. Q2. σy and σz values depend upon __________. Q3. In GDM ‘H’ is _________ ___________. Q4. Greater the wind speed and mixing heights _______________ will be the concentration of pollutants. Q5. Max ground level concentration is given by _________________ . 30
    • Theory Questions Q1. What are assumptions made in Gaussian dispersion model? Q2. What is Gaussian dispersion equation? Explain meaning of each and every term in it. Also give its different forms. Q3. Write about how to use GDM. Q4. What is use of Dispersion models? Q5. Discuss parameters needed for air pollution modeling. 31