Air Pollution Control Engineering

1. Air Pollution Control Engineering Prof. Jiakuan Yang Huazhong University of Science and Technology

2. Lecture 6 Air Pollutant Concentration Models Ⅰ What is Air pollutant Concentration Model? Ⅱ Fixed-box model Ⅲ Gaussian Diffusion Model Ⅳ Other topics about Air pollutants transporting Ⅴ Summary

3. (4) Gaussian plume , two-dimensional spreading equation ②

4. (4) Gaussian plume , two-dimensional spreading equation ③ three terms of Gussian plume equation • First term, when y = 0 , ( z – H) = 0, so exp 0 = 1 The first term is the concentration on the centerline of the plume . With the increase of downwind distance(x), c on centerline is decreasing.

5. (4) Gaussian plume , two-dimensional spreading equation Diffusion in y direction. Second term < 1 c The second term shows how the concentration decreases as we move in the horizontal.

6. Z 7 8 y 10 7 6 (4) Gaussian plume , two-dimensional spreading equation Diffusion in z direction. Third term The same as the second term. Z x y

7. 沿着Z方向的正态分布

8. Page 136, Figure 6.8 Page 135, Figure 6.7 , would depend on wind speed, and on the degree of atmospheric turbulence, degree of solar heating. downwind distance (4) Gaussian plume , two-dimensional spreading equation

9. Page 135, Figure 6.7 Page 136, Figure 6.8

11. -H (5) Gaussian plume equation considering reflection effect of the ground H

13. (5) Gaussian plume equation considering reflection effect of the ground

14. (6 ) ground-level concentration when z = 0

15. Ⅳ Other topics about Air pollutants transporting (1) Building wakes(建筑物尾迹) A plume may get sucked into the low pressure wake behind a building , leading to a high local concentration . The simple rule of thumb for avoiding .This problem is to make the stack height at least 2.5 times the height of the tallest nearby building .

16. Ⅳ Other topics about Air pollutants transporting (2) Aerodynamic down wash（空气下洗区） When the stack is located near a mountain, the simple Graussian plume equations will not be applied . The ground-level concentrations from stack where certainly many times what would be calculated with the simple ( flat world ) Graussian plume equations .

17. Ⅴ Summary (1) Fixed-box models – qualitatively Gaussian plume models – point sources , quantitatively

18. Ⅴ Summary • 2) Gaussian plume models are applied in • Flat terrain • The instantaneous meteorology is simple • Not work in • Mountainous country • Nor for long distance • Nor at times when the meteorology is complex

19. Ⅴ Summary (3) Building wakes, local mountains, and other sources of air flow perturbations complicate air pollution models.

20. Ⅴ Summary The Gaussian plume diffusion model there are three important equations for Gaussian plume , two-dimensional spreading . (1) Basic Gaussian plume equation

21. Ⅴ Summary (2) Basic Gaussian plume equation modified by effect of the ground (3) Ground-level concentration equation

22. Example 6.4 A factory emits 20g/s of SO2 at height H . Wind speed is 3m/s . At a distance of 1km downwind , the values of σy andσz are 30m and 20m ,respectively . What are the SO2 concentrations at the centerline of plume ,and at a point 60 meters to the side of the centerline and 20 meters below the centerline . At centerline , x = 1000m , y =0 , z = H σy =30m , σz= 20m u =3m/s , Q = 20 g/s

23. Example 6.4 = 1770μg/m3

24. Example 6.4 At the point away from centerline = 145μg/m3

25. This Lecture and the Next Lecture • This Lecture: • Chapter 6 Page 119~143 Page 149~154 • The Next Lecture: • Chapter 7 Page 160~203

26. Homework Page 134, Example 6.4 What is the SO2 ground-level concentration at the downwind distance 1km? (H=50m) Page 152, 6.2 Page 153, 6.3 Page 153, 6.6

27. DISCUSSIONS • Topics about Air pollution: • Introducing yourself • Interesting news or information about air pollution your having read or heard • Your opinions on this Air Pollution course • Your suggestions for Chinese Air Pollution • Other familiar issues about Air Pollution