Week 4-Emission Air Pollution (L7)

8/17/2019 Week 4-Emission Air Pollution (L7)

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CCB 4213 Air Pollution Engineering

Week 4- Lecture 7

May 2015 Semester

Em iss ion & A ir Pol lu t ion

Measurement

http://www.google.com.my/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=xXPwF6i7PQ-h0M&tbnid=IntRv9JiZoHGJM:&ved=0CAUQjRw&url=http://relax-mind.blogspot.com/2011_07_01_archive.html&ei=vTyaUZCFPIPtrAfFtICABg&bvm=bv.46751780,d.bmk&psig=AFQjCNEz2Kd9dXaGr_IAdgFZgK7_4Tjmrg&ust=1369148846436765http://www.google.com.my/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=xXPwF6i7PQ-h0M&tbnid=IntRv9JiZoHGJM:&ved=0CAUQjRw&url=http://relax-mind.blogspot.com/2011_07_01_archive.html&ei=vTyaUZCFPIPtrAfFtICABg&bvm=bv.46751780,d.bmk&psig=AFQjCNEz2Kd9dXaGr_IAdgFZgK7_4Tjmrg&ust=1369148846436765http://www.google.com.my/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=xXPwF6i7PQ-h0M&tbnid=IntRv9JiZoHGJM:&ved=0CAUQjRw&url=http://relax-mind.blogspot.com/2011_07_01_archive.html&ei=vTyaUZCFPIPtrAfFtICABg&bvm=bv.46751780,d.bmk&psig=AFQjCNEz2Kd9dXaGr_IAdgFZgK7_4Tjmrg&ust=1369148846436765http://www.google.com.my/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=xXPwF6i7PQ-h0M&tbnid=IntRv9JiZoHGJM:&ved=0CAUQjRw&url=http://relax-mind.blogspot.com/2011_07_01_archive.html&ei=vTyaUZCFPIPtrAfFtICABg&bvm=bv.46751780,d.bmk&psig=AFQjCNEz2Kd9dXaGr_IAdgFZgK7_4Tjmrg&ust=1369148846436765http://www.google.com.my/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=xXPwF6i7PQ-h0M&tbnid=IntRv9JiZoHGJM:&ved=0CAUQjRw&url=http://relax-mind.blogspot.com/2011_07_01_archive.html&ei=vTyaUZCFPIPtrAfFtICABg&bvm=bv.46751780,d.bmk&psig=AFQjCNEz2Kd9dXaGr_IAdgFZgK7_4Tjmrg&ust=1369148846436765http://www.google.com.my/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=xXPwF6i7PQ-h0M&tbnid=IntRv9JiZoHGJM:&ved=0CAUQjRw&url=http://relax-mind.blogspot.com/2011_07_01_archive.html&ei=vTyaUZCFPIPtrAfFtICABg&bvm=bv.46751780,d.bmk&psig=AFQjCNEz2Kd9dXaGr_IAdgFZgK7_4Tjmrg&ust=1369148846436765http://www.google.com.my/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=xXPwF6i7PQ-h0M&tbnid=IntRv9JiZoHGJM:&ved=0CAUQjRw&url=http://relax-mind.blogspot.com/2011_07_01_archive.html&ei=vTyaUZCFPIPtrAfFtICABg&bvm=bv.46751780,d.bmk&psig=AFQjCNEz2Kd9dXaGr_IAdgFZgK7_4Tjmrg&ust=1369148846436765


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ecture Outcome

By the end of this course, the students should

be able to understand:

• Air pollution measurements• Type of air pollution measurements

• Problems involved in air pollution

measurements

• Conduct sampling, determine flowratesand estimate emissions

• Emission Factor


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INTRODUCTION

• Two kinds of air pollution measurements: – Ambient Measurement: concentration of

pollutants in the air in which the public breathes

– Source Measurement: concentration/emissionrates from air pollution sources

• Concentrations in the ambient is important todetermine whether the air is indeed safe for breathing

• Rates of various sources must be measured (to beable to regulate time, location & amount emitted) tocontrol the concentrations


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• Ambient measurements (or simply

termed as Monitoring) and sourcemeasurement (source testing) caneither be carried out for legal purposes

or by the relevant industries’. • Both monitoring & source testing are

conducted by different people withdifferent terminologies but almost all airpollution measuring devices havesimilar set-up as shown in the nextfigure.


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Figure 4.1

The components of any ambient-monitoring or source-sampling device. If the detector

functions in real time (not cumulative), then the gas meter is not needed, but some kind of

signal integrator or recorder is not needed

Devices or

procedures

for

positioning

the sampling

probeDetector to

quantify

instantaneous or

cumulativeamount of

pollutant

Sample

gas

flow

Inlet devices

to remove

unwantedmaterials

Gas

Meter

Sampling probe,

heated if necessary

to preventcondensation

Air

mover

(pump)

Vent to

air


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Air pollution measurements involve two

problems:

• To obtain a suitable, representative sample

• To determine the concentration of pollutant

of interest

To obtain a representative ambient air sample

is hard; the problem lies entirely on thisquestion:

What is the sui table location for obtaining a

sample of ambient air?

A Representative Sample


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Example: CO measurement (EPA): Problems of

choosing a sampler site

Downtown

air-monitoringstation

Office building

Air-monitoringstation

County

courthouse

CO concentration

inside structure>NAAQS

Parkingstructure


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• Location of ambient air sampler…

- to which the public has free access

- pollutant concentration is highest

• Ambient monitor should be placed where it has

power, shelter, constant temperature

environment, easy access to monitoring

personnel, protection from vandalism, (free

rent?)• Detailed guidelines for proper placement of

intakes for air samplers


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• Variation invelocity and

concentration

• Multiple point

measurementand averaging is

needed

• Figure shows

that thedifferences in

velocities &

concentrations

are substantial.

Source Testing Problems

Horizontal

reading


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Example 1.

In a source test, the stack was divided into four sectors, each of which

had the same cross-sectional area. The following velocities and

pollutant concentrations were measured in these sectors: Sector number Velocity V, m/s Concentration c, mg/m

3

1 10 500

2 12 600

3 14 650

4 15 675

What is the average pollutant concentration in the gas flowing in this

stack? The average concentration is

areasequalfor

avg

V

Vc

AV

AcV volumeTotal

massTotalc

areavelocity

ionconcentrat areaelocityv

3

61615141210

675x15650x14600x12500x10

m

mg


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• If the sampled sectors did

not have equal areas this

calculation would be morecomplex

• If one went far enough

downstream in this duct one

would find that the flowvelocities and particle

concentrations had become

uniform, source sampling can

be done at that particularpoint

• Not practical in a real plant:

see Fig. 4.4


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Getting Representative Samples

Problems and solutions:

• Inlets sucked into particulate sampler; Bug screens

exclude all but the smallest particles

• Possibility of gases to condense or reacts with

solids; heated probes are normally used

• Acid gases like SO2 will react with alkaline solids

on a filter, increasing solids weight

• Grab samples must not react with containers


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Concentration Determination

• Concentrations may be measured by real timeinstruments, of which most is operated optically

• Interference in optical measuring instruments and

the problem is not trivial• Example: To measure SO2 in nitrogen gas, SO2 is

passed through a dilute solution of NaOH:

SO2 + 2 NaOH Na2SO3 + H2O

• Change in NaOH concentration can be easily

measured by acid-base titration


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Averaging

• If we are measuring ambient air quality with real-timeinstruments, we generally want to know the average

concentration over some period of time so that we can

compare it with the applicable ambient standards, which all

have some measuring period.

• This is calculated by

cdt

t Δ

1cavg

ionconcentratAverage

where c = the instantaneous concentration

indicated by the instrument

t = the time of measurement


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• For averaging instruments (ex: PM10 & PM2.5

samplers)

timexrateflowAir

ghtfilter weiinIncreasecionconcentratAverage avg


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Example 2

A PM2.5 sampler ran for 24 hours at an average flow

rate of 16.7 L/min. The tare weight of the fresh filterwas 0.1400 g, and the gross weight of the filter, dried

to the same humidity as the fresh filter, was 0.1405 g.

What was the average PM2.5 concentration in the air

drawn through the sampler?


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Example 2

A PM2.5 sampler ran for 24 hours at an average flow

rate of 16.7 L/min. The tare weight of the fresh filterwas 0.1400 g, and the gross weight of the filter, dried

to the same humidity as the fresh filter, was 0.1405 g.

What was the average PM2.5 concentration in the air

drawn through the sampler?

3

-5

3 m

g

20.810x2.08m

L1000

xmin60

h

x24hx16.7L/min

0.1400)g(0.1405 μ

m

g

c 3avg


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• For gaseous pollutant, sampling train would be

used in practice


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Standard Analytical Methods

• Test methods for major pollutants in ambient air:• Reference Method

• Equivalent Method: simpler, easier and cheaper

• Particulate Matter, TSP, PM10, & PM2.5

• Filter’s weight gain is divided by the measured cumulativeair flow through the filter to determine particle

concentration

• Sulphur Dioxide, SO2 • West-Gaeke method - a known volume of air is bubbled

through sodium tetrachloromercurate, which forms a

complex with SO2. Then, the solution is treated with

pararosaniline to form intensely coloured pararosaniline

methyl sulfonic acid, which concentration is determined in

a colorimeter


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• Ozone (O3)

• The air is mixed with ethylene, which reacts with

ozone in a light emitting (chemiluminescent) reaction.

The light is measured with a photomultiplier tube

• Carbon monoxide (CO)

• The concentration is measured by non-dispersive

infrared (NDIR) absorption. Here nondispersive means

that the infrared radiation is not dispersed by a prismor grating into specific wavelength; rather, filters are

used to obtain a wavelength band at which CO

strongly absorbs

• Lead (Pb)• A TSP filter is extracted with nitric and hydrochloric

acids to dissolve the lead. Atomic absorption

spectroscopy is then used to determine the amount of

lead in the extract


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• Hydrocarbons (Non-methane)• Gas is passed through a flame ionization detector (FID),

where the hydrocarbon burn in a hydrogen flame.

Hydrocarbons cause more ionization and is detectedelectronically. Part of the sample is diverted to a gas

chromatograph, where methane is separated from other

gases and then quantified. Its concentration is subtracted

from the total hydrocarbon value from the FID

• Nitrogen dioxide (NO2)• NO2 is converted to NO, which is then reacted with ozone.

The light from this chemiluminescent reaction is measured.

Because the ambient air contains NO (often more than NO2),

a parallel sample is run without conversion of the NO2 to NO,and the resulting NO reading is subtracted from the combined

NO and NO2 reading to give the NO2 value. The instrument

normally reports the NO concentration as well


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The mass flow rate of pollutant is the product of theconcentration in the gas and the molar or mass

flow rate of the gas

Determining Pollutant Flow Rates

ionconcentratmolar pollutantxgasof flowratemolarflowratemolarPollutant


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Example 3.

The train sampling shown Fig 4.5 (textbook) indicatesthat the concentration of SO2 in a stack is 600 ppm

(mole). The Pitot tube and manometer in the same

figure indicate that the flow velocity is 40 ft/s. The stack

diameter is 5ft. The stack gas temperature andpressure are 450oF and 1 atm. Determine, what is the

SO2 flow rate? Given molar density of SO2 at 20oC is

given as 0.00259 lb-mol/ft3.


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Diameter= 5ft

Concentration=600 ppm

Flow rate= 40ft/s

P=1 atm at 450oF

Density of SO2= 0.00259 1b-mol/ft3 at 20oCstack


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UNITS CONVERSIONS

THE GAS CONTANT

8.314 m3

.Pa (mol.K)0.08314 L.bar/(mol.K)

0.08206 L.atm/(mol.K)

62.36 L.mm Hg/(mol.K)

0.7302 ft3.atm/(lb-mole.oR)

10.73 ft3.psia/(lb-mole.oR)8.314 J/(mol.K)

1.987 cal/(mol.K)

1.987 Btu/(lb-mole.oR)

T(K) = T(oC) + 273.15

T(oR) = T(oF) + 459.67

T(oR) = 1.8T(K)

T(oF) = 1.8T(oC) + 32


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Solution:

Pollutant molar flow rate

= molar flow rate of gas x pollutant molar concentration in gas

The molar flow rate of the gas is = velocity x Area x density

= V A ρ

C

R F

C

o

o

o

o

oo

232

910450at

R 528F6820STPat

Given;


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The molar flow rate of SO2 is1.18 lb-mol/s x 600 x 10-6 = 7.08 x 10-4 lb-mol/s

= 0.32 mol/s

Multiplying by the molecular weight of SO27.08 x 10-4 x 64 = 4.53 x 10-2 lb/s = 163 lb/h = 20.6 g/s = 74.1 kg/h

(This calculation is suitable for a stack whose velocity

and concentration are the same at every point and

time in the stack. Otherwise, averaging is needed)

Solution:

The molar flow rate of the gas is = V A ρ

R

R

o910

528

xftstd

mol-lb

10x2.59xft54xs

ft

40

o

3

3-2

mol536mol-2.2lb

mol1000x

s

mol-lb 1.18

s

mol-lb 1.18


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• Emission testing is expensive.

- for simple & well-defined sources, it is tedious but not difficult- for poorly defined sources, reliable test results are difficult

• To overcome the problem, emission factor is introduced, develop

based on the high-quality test data.

• Given for pulverized coal and assuming after combustion 25%

ash appears as bottom and 50% form as fly ash (carried away by

gas stream)

• This emission factor is used to estimate the new and existing

materials.

Emission Factors


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Term used: A: best

E: worst

PC-pulverized coal

Reference

Pittsburgh seam coal

Analysis

C=75.8%

H=5%

O=7.4%

N=1.5%

S=1.6%

Ash=8.7


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Example 4

Table 4.2 shows part of two tables from one section of the EPA emission factors

library. It shows the estimated emissions from the combustion of bituminous

coal if no control devices are used. These are the emissions going into thecontrol devices. Comparing them to the permitted emissions coming out of the

plant (see Table 3.1), one can estimate the degree of control required.

Using this table, estimate the emissions from a 500-MW power plant at full

load, burning a typical Pittsburgh steam coal. The thermal efficiency is 35

percent. The power plant’s boiler is assumed to be of the PC, wall-fired, dry

bottom type.


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UNITS CONVERSIONS

Quantity Equivalent Values

Mass 1 kg =1000 g = 0.001 metric ton =2.20462 Ibm= 35.27392oz

1 Ibm = 16 oz = 5×10-4 ton= 453.593 g = 0.453593 kg

Length 1 m = 100 cm = 1000 mm = 106 microns (µm) = 1010 angstroms ()

= 39.37 in = 3.2808 ft = 1.0936 yd = 0.0006214 mile

1 ft = 12 in = 1/3 yd = 0.3048 m = 30.48 cm

Volume 1 m3 = 1000 L = 106 cm3 = 106 mL

= 35.3145 ft3 = 220.83 imperial gallons = 264.17 gal = 1056.68 qt

1 ft3 = 1728 in3 = 7.4805 gal = 0.028317 m3 = 28.317 L = 28,317 cm3

Force 1 N = 1 kg.m/s2 = 105 dynes = 105 g.cm/s2 = 0.22481 Ibf

1 Ibf = 32.174 Ibm.ft/s2 = 4.4482 N = 4.4482 × 105 dynes

Pressure 1 atm = 1.01325×105 N/m2 (Pa) = 101.325 kPa = 1.0325 bar

= 1.01325 × 106 dynes/cm2 = 760 mmHg at 0oC (torr) = 10.333 m H2O at 4oC

= 14.696 Ibf /in2 (psi) = 33.9 ft H2O at 4

oC = 29.921 in Hg at 0oC

Energy 1 J = 1 N.m = 107 ergs = 107 dyne.cm = 2.778 × 10-7 kW.h = 0.23901 cal

0.7376 ft.Ibf = 9.486 × 10-4 Btu

Power 1 W = 1 J/s = 0.23901 cal/s = 0.7376 ft.lbf /s = 9.486× 10-4 Btu/s = 1.341×10-3 hp


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h

ton 17910x3.585

kW1000 x

Btu3413 x

Btu/lb13,600x35.0

MW500

valueheating.coalEfficiency

outputPowerratenConsumptioCoal

5

h

lb

MW kWh

Solution


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h

tonne

hlb

tonlb

A

1.7h

ton 7.8

10x56.1h

ton179x8.7x10

rate

flowcoal

ton

lb10

rate

flowcoal

factor

emission

rateemissionParticle

israteemissione particulatThe

4


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Group Activity (CLO3,C4:PO2)

Discuss how to make the ambient and source

measurement for the following industries.

• Palm oil

• Cement


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CONCLUSION

You have understand the following:

• Air pollution measurements

• Determine air pollutionmeasurements

• Emission Factor


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End of Lecture

Thank you

Documents

Week 4-Emission Air Pollution (L7)