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

Questions for the Last Lecture 1Please give three or more Abbreviations about American environmental organizations or air pollution laws. 2 Please explain the four air pollution control philosophies.

Answer EPA : Environmental Protection Agency NAAQS : National Ambient Air Quality Standards ACGIH: American Conference of Governmental Industrial Hygienists NESHAP: National Emission Standard for Hazard and Air pollutions CAA: Clean Air Act

four air pollution control philosophies  Emission standards philosophy cleanest possible air philosophy, the best technology  Air quality standards philosophy zero-damage philosophy  Emission taxes philosophy suitable tax for emitter  Cost-benefit standards philosophy minimizing the sum of control cost and damage cost and damage cost, get maximum benefit

Lecture 4 Lecture 4 Air Pollution Measurements, Emission Estimates Ⅰ The components of monitoring or sampling device Ⅱ How to get a representative sample? Ⅲ How to determine the concentration correctly? Ⅳ How to select the sampling flow rate? Ⅴ How to select correct analytical methods? Ⅵ How to estimate emissions?

Ⅰ The components of monitoring or sampling device  Two kinds of air pollution measurements methods ambient monitoring concentrations of pollutants in the air the public breathes source testing concentration and emission rates from air pollution sources

Ⅰ The components of monitoring or sampling device Detector to quantify instantaneous or cumulative amount of pollutant Gas meter Sample Gas flow Inlet device to exclude unwanted sampling probe heated to prevent condensation Devices for positioning the sampling probe Air mover (pump) Vent to air Gas source sampling determining power Flow rate

Ⅱ How to get a representative sample? (1) selecting a suitable sampler site Generally the ambient air sampler should be located at the place to which the public has free access where the pollutants concentration is the highest.  For ambient sampling

Ⅱ How to get a representative sample?  For source testing In source testing, for most such stacks the velocity and concentration in the stack vary from point to point and from time to time, so that many separate measurements must be made and averaged.

The section near the bend, less uniform The section far away the bend, more uniform Ⅱ How to get a representative sample?  For source testing Page 66, Figure 4.3

(2) Excluding unwanted materials  a bug screen ( 昆虫网）  PM 10 ( particulate matter 10 microns or smaller )  PM 2.5 (particulate matter 2.5 microns or smaller ) Ⅱ How to get a representative sample?

(3) Probes are normally heated to prevent condensation of gases on the walls of sampling probe Ⅱ How to get a representative sample?

Ⅲ How to determine the concentration correctly? (1) Eliminating the interference effect For example Determining SO 2 concentration passes the gas through a dilute solution of NaOH. if not considering of CO 2, C determing > C true Measuring the change in NaOH concentration by simple acid-base titration. SO 2 + NaOH NaSO 3 +H 2 O CO 2 + 2NaOH Na 2 CO 3 + H 2 O

(2) Averaging the concentration Ⅲ How to determine the concentration correctly?  Real –time instruments can memorize a lot of values during a period of time. Time 0 t Concentration Average concentration =C avg = (1/t) ∫ Cdt C=area of the shadow t = the time of measurement

(2) Averaging the concentration  Averaging instruments of the concentration of particles. Average C = C avg = Total volume Total mass Example 4.2 Page 69 A PM 2. 5 sampler ran for 24 hours, average flow of 16.7 L /min, fresh filter : g, gross weight of used filter : g, what is the average PM 2.5 concentration ?

Ⅳ How to selecting the sampling flow rate? isokinetic flow sampling for particulates in stack. V n : gas velocity inside the sampling probe V s : gas velocity in the stack V n = V s nozzle stack

(1) V s < V n Density of particulate is much larger than density of air, so particulates are more inertial and keep direct. C determing < C true Mass keep constant, V n > V s C = mass flow nozzle volume

(2) V s > V n Mass keep constant, V n < V s C = mass flow nozzle volume C determing > C true

Ⅴ How to selecting correct analytical methods? P27, Table 4.1 According to standard sampling methods by EPA Test methods for major air pollutants in ambient air.

Ⅵ How to estimate emissions? Emission factors Page 74~78 Sections 4.8~4.9 are studied by yourselves.

This Lecture and the Next Lecture  This Lecture:  Chapter 4 Page 63~82  The Next Lecture:  Chapter 5 Page 83~118

Homework Page

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