Flue Gas Analysis Apparatus

1. ORSAT Apparatus for Flue gas
Analysis
Prepared By : -
Umar Farooq
Senior Chemist / Shift Supervisor
MSC ( Chemistry ) MBA ( Marketing )
umar7325@outlook.com
107301@se.com.sa
SEC Shoaiba Makkah
Saudi Arabia

2. Introduction about Orsat Apparatus
An Orsat gas apparatus is a piece of Laboratory Equipment used to analyze a gas sample
(Typically fossil fuel flue gas) for its oxygen, carbon monoxide and carbon di
oxide content. Although largely replaced by instrumental techniques, the Orsat remains a
reliable method of measurement and is relatively simple to use.
It was patented before 1873 by Mr. H Orsat.
The apparatus consists essentially of a calibrated water-jacketed
gas burette connected by glass capillary tubing to two or three absorption pipettes
containing chemical solutions that absorb the gasses it is required to measure. For safety
and portability, the apparatus is usually encased in a wooden box.
Other types
 Orsat-Aimer Products Orsat apparatus
 Orsat-Fischer apparatus
 Orsat-Lunge apparatus
 Orsat-Friedrichs apparatus

3. Flue Gas Analysis
Flue gases are the outlet gases obtained when a fuel is burned with air in combustion
equipment's like engines and boilers. Based on the fuel composition flue gases are formed,
a fuel having carbon and hydrogen compounds generates flue gas containing oxides of
carbon and hydrogen because the oxygen in air burns with components that release heat
energy and resulting the combusted materials.
In construction of fire heater, boilers, combustion engines and combustor
the outlet is given out with a cylinder shape chimney so that the hot flue gases are ejected
into the atmosphere. In design and calculating the performance of the above equipment's
the flue gas is used for analysis which help to determine the composition of the carbon
dioxide, oxygen, nitrogen and carbon monoxide.
Based on this analysis results the fuel inlet flow
rate, air flow rate and burner are controlled to get the efficiency of the fired heaters. By the
following presentation the flue gas analysis can be demonstrated by using Orsat apparatus,
of course this is a standard piece of equipment. Many high accurate digital and portable
devices are available to determine the composition of flue gas.
Flue gas analysis
carried out at
stage-1

4. working principle
The apparatus used for flue gas ( O2, CO2 & CO ) analysis is called Orsat Apparatus
It consists of a water burette of 100ml.capacity and is graduated in 0.2ml divisions, it
is connected to a stop cock at top with an absorption pipette connected at each
position .
The absorption pipette contain 30% KOH Which is used to remove CO2 from
flue gas. The second absorption pipette from flue gas contain 30% alkaline pyragallol
solution which absorb O2 gas from flue gas . Some time a third absorption pipette is
provided to measure CO ( in case of incomplete combustion ). It contain ammonia Cal
cuprous chloride solution .
The bottom of the burette is connected to a movable reservoir
( levelling bottle ) containing 25% NaCl solution acidified with HCl and colored with
methyl orange .
By adjusting the height of levelling bottle gases in burette may be
vented to atmosphere . The were five stop cock valve in ORSAT apparatus as shown
in figure . There are four steps to operate this apparatus .

5. Chemical absorption phenomena
Typical flue gas analyzers measure the quantity of carbon dioxide, carbon monoxide
and oxygen by a chemical absorption principle. Based on the absorption factor of these
three components their respective absorbing solutions are selected in three different
bulb compartments. When the gas is passed into these bulbs consecutively, where
each component is separated in sequence that helps to know the volume drop from
initial flue gas volume.
Water vapor in flue gas removed by adsorption on solid calcium
chloride and then passed into three pipettes. The sequence of absorption should
always be started from CO2, O2 and CO if the absorption solutions are ammoniacal
cuprous chloride; alkaline pyrogalic acid and KOH were selected as reagent in the
Orsat apparatus analyzer
Trouble shooting
during Flue gas
analysis

6. Operation of Orsat apparatus by
volumetric procedure
Step No.1
Open the stop cock valve No .1 and raise the levelling g bottle to such a height ,
So that colored water level is “0” position in the burette. Close valve no connect
the rubber tubing to sample line and open the
Valve on sampling line . Also open the valve No.1 allow the gas sample to
bubble through colored solution and let it to scape in the atmosphere through
neck of levelling bottle to inshore that all air has been expelled from the
apparatus .
Step No.2
Collect about 110-120ml gas in the burette by the lowering leveling bottle . Close
the valve No.1 and open No.5 . The water level in the burette will slightly raise as
Pressure of the gas sample release to the atmosphere slowly raise the levelling
bottle to the position , So that water level at the burette is 100 close valve No.5.
in this way exactly 100ml of gas at atmosphere pressure has been collected .

7. Operation of Orsat apparatus
Step No.3
Now open valve No.4 and raise the levelling bottle to a suitable height. By this
operation pressure builds p in the burette due to in coming colored water. The
gas in the burette is forced into absorption pipette containing 30% KOH Solution
.the KOH Solution is forced to move into the solution reservation attached to the
pipette . Now lower the leveling bottle , as level of water lower in the raising and
lowering of levelling bottle . The gas coms in contact with absorption solution
several time .close valve No.4.
Now bring the level bottle to a position so that its
water level and water level in the burette same. Read the level of water in the
burette suppose it is “ X” Then % of
CO2=100-X

8. Operation and Reaction
Step No.4
Now open valve No.3 and proceed as step No.3.Absorption pipette contains alkaline pyraglallol solution which
absorbs O2. Close valve and burette in the same position . Note the reading on burette suppose it is “Y” the O2
content can be calculated is % of
O2=( 100-X)-Y.
If O2 is not detected in gas sample then pass it through the third pipette by operating valve No.2. This
pipette contain ammonium cuprous chloride which absorbed CO gas absorption in pipette is due to the presence of
CO,CO2 can also be absorbed in cuprous solution . The reaction that take place during operation of or set
apparatus are.
2KOH + CO2 K2CO3 + H2O( Potassium Carbonate )
C6H6O3+3O2 C2H2O4+CH3COOH+CO2+CO
2CuCl2+2CO ( in NH3 Solution ) CuCl CO
2
Cu ++ + CO CuO + C

9. Chemical Reaction Further statistics
Under alkaline
condition
pyrogallol
(1,2,3-trihydroxy-
benzene) is
oxidized by
oxygen
CO2 disappears
from the gaseous
phase

10. General use’s of these Chemical
 Potassium Hydroxide KOH
Potassium Bi Carbonate KHCO3
Oxalic Acid C2H2O4
Acetic Acid ( Vinegar ) CH3COOH
Honeybee coated
with oxalate
crystals
Potassium
Bicarbonate Also
Good for Bones
o Vinegar use as
a preservative.
o Apple Cider
vinegar relives
digestive
problem

11. Calculation Table
Average molecular weight of the flue gas can be calculated using the volume or mole percentage composition
determined by the Orsat analysis. Let’s take for example the following composition,CO2 30%, CO 0.2%, SO2
2.2%, N2 63.0%, O2 4.6%.
Components Mole percentage, %, MP
Mole fraction, MF=
MP/100 Molecular weights, MW MF * MW
CO2 30 0.3 44 13.2
CO 0.2 0.002 28 0.056
SO2 2.2 0.022 64 1.408
N2 63 0.63 28 17.64
O2 4.6 0.046 32 1.472
TOTAL (sum) 100 1 33.776
Average molecular
weight 33.776

12. Modern analyzers derived from
Orsat apparatus
Based on the Orsat analyzing technique not only flue gases but process gas like methane,
propane ,natural gas & Hydrogen Sulphite can be analyzed continuously in a process flow
streams. Many new Orsat apparatus models are re engineered and modified by electronic and
automation technology so that they do multitask in a process industry. They measure, control
and disengage the process systems. The demand for composition measurement in continuous
flow pipeline even at high temperature and pressures fulfilled by latest engineered models that
are nitrogen analyzer, oxygen analyzer, carbon dioxide analyzer, methane analyzer.
These modules contain a measuring probe, a signal transmitter and receiver, instrument air
sockets, display and controls box. Measuring probes are developed based on the membrane
technology, a thin film membrane allow specific molecules to pass through it and these
molecules will affect the conductivity of the thermocouple type system which give out signal
proportional to the chemical molecules.

13. Automatic Orsat apparatus
How would be a Orsat apparatus that can operate
automatically rather than manual operations. Let see what are
devices required for building the apparatus.
 Suction blower
 Orifice for pressure and flow rate measurement to know the volume
of the flue gas entering the apparatus
 Conductive meter to know the concentrations of the components
 Pressure and temperature indicator to know the operation conditions
 Tubes with packing to ensure the high gas liquid contact
 Automatic control valve with timer and solenoid set up operated by
the program of PLC
Alternate of Orsat
Apparatus