1 / 50

Air Pollution Control Engineering

Learn the key concepts of air pollution control engineering including sampling techniques, meteorology effects, and atmospheric motion relationships. Gain insights into the composition of the atmosphere, vertical and horizontal atmospheric stability, and pollutant transport. Dive into important meteorological elements for effective pollution control.

eleanormclaughlin
Download Presentation

Air Pollution Control Engineering

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. Questions for the Last Lecture How to get a representative polluted air sample?

  3. Answer (1) selecting a suitable sampler site (2) Excluding unwanted materials (3) Probes are normally heated to prevent condensation of gases on the walls of sampling probe

  4. Lecture 5 Meteorology for air pollution control Engineers Ⅰ Relationship between meteorology and air pollution Ⅱ Effects of horizontal atmospheric motion on atmospheric stability Ⅲ Effects of vertical atmospheric motion on atmospheric stability Ⅳ Mixing Height (混合高度) and Fumigation(薰烟扩散)

  5. Ⅰ Relationship between meteorology and air pollution (1) Air pollution process Atmosphere: Transport Dilution Modification Effects on some receptors Emission Pollutant removal by Natural mechanism

  6. 大气与空气 按照国际标准化组织（ISO）对大气和空气的定义： 大气（atmosphere）：是指环绕地球的全部空气的总和（the entire mass of air which surrounds the Earth） 环境空气（ambient air）：是指人类、植物、动物和建筑物暴露于其中的室外空气（outdoor air to which people, plants, animals and structures are exposed）

  7. 大气圈垂直结构 非均质层 • 中间层 • 平流层 • 对流层 • 散逸层（逃逸层，外层 ） • 暖层（热层，电离层） 均质层：至80-85km，主要成分氮和氧的组成比例几乎不变

  8. 对流层 • 至10km－16km • 稳定的气体组成 • 强流的对流与湍流 • 稳定降低分布6.5℃/km • 50－100m，人类活动区域及污染物 • l－2km以下，边界层或摩擦层 • lkm－2km以上，自由大气层，如雨、雪、雹形成区域

  9. 主要气象要素 • 气象要素（因子）： 表示大气状态的物理现象和物理量，气象学中统称为～。 • 与大气污染关系密切的气象要素主要有： 气温 气压 空气湿度（气湿）、 风（风向、风速） 云量云状 能见度 降水 蒸发、日照时数、太阳辐射、地面辐射、大气辐射等。

  10. 风向和风速主要气象要素 水平(horizontal)方向的空气运动称为风。 （垂直方向－升降气流） 风的来向叫风向（16个方位圆周等分） 风速：单位时间内空气在水平方向上运动距离（2或10min平均） (km/h) F－风力级（0～12级）

  11. 风速,m/s 风向和风速－风玫瑰图 某地区1988年的风玫瑰图。同心圆表示风的频率，例如，吹南风的频率约为11％，其中风速大于10.82m/s的频率约为1％，风速在3.35～5.41m/s的频率为3.5%左右。

  12. (2) Important meteorology elements on air pollution wind speed and direction atmospheric stability Because air pollution is transported in the atmosphere, the wind speed and direction, and atmospheric stability is important for air pollution transport . We hope that the air pollutants can be transported far away from the place where people often live, and dilute or remove in the atmosphere .

  13. High smokestack

  14. High smokestack

  15. (3) The atmosphere composition 78% nitrogen 21% oxygen 1% argon other trace gases : CO2, H2O, O3

  16. (3) The atmosphere motions in the atmosphere Horizontal motion wind speed and direction atmospheric stability Vertical motion Air Pollutants transport

  17. Ⅱ Effects of horizontal atmospheric motion on atmospheric stability Three elements which effect horizontal atmospheric motion. Equatorial heating, polar cooling Effects of earth’s rotation Influence of the ground and sea

  18. (1) Equatorial heating, polar cooling Schematic representation of the general circulation of the atmosphere. 600 High pressure Low pressure 300 High pressure 00 Low pressure

  19. North pole (2) Effects of earth’s rotation North pole South pole On the contrary side of clock-cycle

  20. An air parcel or polluted air parcel buoyancy weight Ⅲ Effects of vertical atmospheric motion on atmospheric stability (1) vertical motion model p.T.ρ____surrounding air

  21. density temperature (2) Factors that affect vertical motion

  22. Factors that affect vertical motion Commonly air pressure is the same at the same height.

  23. Question Vertical atmospheric motion is decided by difference between the air parcel temperature and surrounding air temperature. How do the temperatures change?

  24. (3) Dry adiabatic lapse rate (干绝热直减率) Dry adiabatic lapse rate is used to describe the temperature decrease of an air parcel when the air parcel rises. Why does the temperature of an air parcel decrease when the air parcel rises?

  25. Dry adiabatic lapse rate reversible adiabatic : negligible heat Assumption Gravity Pressure Volume Energy consumption Temperature

  26. = －10℃/km 10℃/km (3) Dry adiabatic lapse rate ( ) Rising 1 km, the temperature of air parcel decreases at 10 ℃.

  27. Dry adiabatic lapse rate ( ) Final Temperature Example Initial Temperature A parcel of air at 100m height is 5°C , when it rise at the height of 1100m , what is the temperature. T = 5°C – ( 10°C/km ) ×(1.1 –0.1)km = 5°C –10°C = – 5°C Dry adiabatic lapse rate Moving distance

  28. (4) Standard lapse rate (标准直减率) Standard lapse rate is used to describe the temperature decrease of surrounding air (or atmosphere) when the height increases. Why does the temperature of the atmosphere decrease when the height increases?

  29. Standard lapse rate (标准直减率) Sun light is transparent through the atmosphere, so the ground absorbs the largest amount of heat. Commonly the ground temperature is the highest. The farther away the ground, the lower temperature.

  30. Standard lapse rate ( )

  31. Actual lapse rate( ) (4) Standard lapse rate ( ) In the daytime, the nearer the ground, the higher temperature of the atmosphere. Z 23.4°C 1km 23.4°C T 30°C

  32. (5) Atmospheric stability Questions How do changes of the temperatures affect the atmospheric stability?

  33. Surrounding air Polluted air parcel Atmospheric stability Z(m) 0 T(℃)

  34. 10℃/km (5) Atmospheric stability Z(m) Change of the polluted air parcel is the same. However, the temperature distribution of the the surrounding air will change from time to time, and from one place to another place. 0 T(℃)

  35. ( a ) unstable Z Z1 T1’ T1 Z0 T2 T2’ When air parcel rises, T1’ > T1 T T0 air parcel will rise upper and upper. When air parcel falls, T2’ < T2 air parcel will fall lower and lower.

  36. ( b ) neutral Z a = 0 T

  37. ( c ) stable Z T1’ T1 a When air parcel rises, T2 T2’ T1’ < T1 T air parcel will fall to the stable point. When air parcel falls, T2’ > T2 air parcel will rise to the stable point.

  38. ( d ) very stable Z temperature inversion a T

  39. Temperature inversion Vertical temperature distribution model at the various time . Z Z 300m 300m 0 0 T T 10°C 21°C ( b ) Dawn + 2h ( a ) Dawn

  40. Temperature inversion Vertical temperature distribution model at the various time . Z Z 1800m 300m 0 0 T T 27°C 30°C ( d ) Midafternoon ( c ) Dawn + 4h

  41. Ⅳ Mixing Height (混合高度) Air pollutants released at ground level will be mixed almost uniformly up to the mixing height , but not above it . Thus the mixing height sets the upper limit to dispersion of atmospheric pollutants . Z T 0

  42. 平流逆温 暖空气平流到冷地面上而下部降温而形成 暖空气团 高温 低温

  43. 冷、暖气团相遇 暖气上爬，形成锋面 冷暖间逆温 锋面逆温

  44. Ⅳ Fumigation(薰烟扩散) • P113, Figure 5.15

  45. summary Stable atmosphere (low actual lapse rates or inversions ) and low wind speed lead to highest ground –level pollutant concentrations . Unstable , and high wind speed lead to lowest ground-level pollutant concentrations .

  46. This Lecture and the Next Lecture • This Lecture: • Chapter 5 Page 83~101 Page 111~115 • The Next Lecture: • Chapter 6 Page 119~146

  47. Homework 5.8 (Page 116) Which are four ways to produce a temperature inversion? (Page 111)

  48. DISCUSSION • 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

More Related