Gas concentraition : sampling and measurement

1. GAS CONCENTRATION:
SAMPLING
AND
MEASUREMENT

2. Common Combustion products are:
Oxides of Carbon – CO and CO2
Oxides of Nitrogen – NO,N2O NO2 etc.
Oxides of Sulphur – S0x
Un burnt Fuel (HC)
Particulate matter – Soot / smoke

3. • The concentration of a candidate gas in a mixture of gases
may either be specified on volume basis or on mass basis
• On volume basis the units are either PPMv (parts per million)
or PPBv (parts per billion)
UNITS
6
Volume of candidate gas 1
1
Total volume of gas mixture 10
PPMv  
9
Volume of candidate gas 1
1
Total volume of gas mixture 10
PPBv  

4. Methods
of
measurement:
Gas
Concentration
Non
separation
methods:
Non Dispersive
Infrared Analyzer
(NDIR)
Differential
Absorption
LIDAR (DIAL)
Chemiluminesce
nce NOx
detection
Separation
methods
Gas
Chromatography
Orsat gas
analyzer

5. ORSAT
GAS
ANALYZER
Source : research paper on gas analysis

6. MEASURING INSTRUMENTATION
1. Methods in which we requiring laboratory analysis of
collected sample
2. Direct reading instrumentation
capable of sampling a volume of gas ,performing
immediate analysis internally and displaying result
visually
like : an ALCOHOL BREATHER

7. 1. Grab / Instantaneous / a short term samples
- evacuated flask or metal canister/cylinder
- syringes
- plastic bags
- gas & liquid displacement collector ( eudiometer )
2. The integrated / average / long term samples
- collected by passing a gas through absorptive,
adsorptive and condensing medium
METHODS REQUIRING LABORATORY ANALYSIS OF
COLLECTED SAMPLE

8. GRAB / INSTANTANEOUS / A SHORT TERM SAMPLES
Evacuated Metal Sampler
Volume range : 200 to 1000 CC
Application :
• Alcohol Breath Tester
• Sampling of variety of organic vapors
like benzene , methyl ethyl ketone ,
styrine etc.
Pic : research notes , michel j pitch

9. GRAB / INSTANTANEOUS / A SHORT TERM SAMPLES
Sampling bags
Material :
1. P V C
2. Teflon
3. Fluoro carbons
Source : flue gas analysis report , singvaldeson(elsevier)

10. GRAB / INSTANTANEOUS / A SHORT TERM SAMPLES
Gas / Liquid Displacement Collector
Source : flue gas analysis report , singvaldeson (elsevier)

11. GRAB / INSTANTANEOUS / A SHORT TERM SAMPLES
A general scheme
of an “Eudiometer”
Source : internet
A perforated tube sampler ,
which is used to take sample of gases
From a stack

12. • Employed principles :- “ absorption ”, “ Adsorption ”,
“Condensation ”.
• These are proposed for to qauntify ..
– concentration of contaminant to which worker is exposed very
significantly over a work shift period.
i.e. Like in a coal mine
– When ambient concentrations of contaminant is low ,
i.e. than the time extension must be requires to collect.
THE INTEGRATED / AVERAGE / LONG TERM SAMPLES

13. THE INTEGRATED / AVERAGE / LONG TERM SAMPLES
Source : webnar heath solutions

14. THE INTEGRATED / AVERAGE / LONG TERM SAMPLES
By Absorption :
• Simple gas wash bottles
-Greenberg smith &
midget impinger
• Spiral/helical absorbers
• Fritted bubblers
• Glass beaded columns
source: https://us.vwr.com/store/search/searchResult

15. THE INTEGRATED / AVERAGE / LONG TERM SAMPLES
1. Spiral/helical absorbers
2. Fritted bubbler (Glass beaded columns)
Source : flue gas analysis report , singvaldeson (elsevier)

16. DIRECT READING INSTRUMENTS
The direct reading instruments are of two types :-
1. The one which produces colour changes(colorometric indicator)
like .. [ Liquid reagents, Chemically treated papers, Detector tubes]
2. The second comparised of thoes which have electronic circuitary
- capable of taking samples ,
performing qualitative/quantitative analysis internally
and displaying the results immediately on
a dial / digital display panel / graphical tape print out.
like : voltmeter , speedometer, oil , fuel & battery
indicator of vehicle ,

17. • This is an important concept , before collection and weighing the
perticulates we need to do what is called “isokinatic sampling”.
• We simply can take this as precautions , or may one can summerise it
in just two sentences…
1. There should be no directly hitting of gas stream on the wall of the
probe tube.
2. The velocity of gas with which we drowing a sample by means of a
sempler into perticulate, needs to same as source velosity.
i.e. our driving force selection
ISOKINATIC SAMPLING

18. ORSAT APPRATUS
Source : mechanical instrumentation , DS KUMAR

19. Contd..
1. Flask 1 : contains KOH (one part KOH + 2 parts water by
weight) and this absorbs CO2
2. Flask 2 : contains alkaline solution of pyragallic acid (5 gm
pyragallic acid mixed in 15 gm water with 120gm KOH
mixed with 80 gm of water) to absorb O2.
3. Flask 3 : contains cuprous chloride (CuO dissolved in 20
timesits weight of concentrated HCL acid till it becomes
colourless) to absorb CO

20. • Contd…
Source : american journal of measurement

21. • Contd..
Source : American journal of measurements

22. • Contd…
Schematic of three way valve

23. • Contd…
Source: american journal of measurements