198

Flue gas analysis for industry

Goals

The following goals apply when measuring industrial flue gases:

Emissions monitoring

Adherence to legally specified limit values (e.g. TA Luft); meetingISO 14000 requirements.Important parameters: NOx (NO +NO2), SO2, CO, H2S, O2 and insome cases CO2.

Adjustment and optimisationof systems

This often goes together withadherence to emission limit values.Otherwise the aim here is to reduceoperation costs by saving energy.Important parameters: O2, CO, CO2,excess air value and efficiency.

Process monitoring in thermal manufacturing procedures

What is important here isatmosphere monitoring anddocumentation for qualityassurance purposes (ISO 9000), reduction of rejectnumbers and costs by savingenergy and cutting down on stopperiods. Important parameters: O2,CO, CO2, SO2.

O2 measuring cell

Anode

Cathode

Outer electric circuit

Temperature sensor

Aqueous electrolyte

Gas Gas

Infrareddetector

Infraredprojector(lamp)

Interference filterI= 4.27 µm

Absorption CO2

CO2 infrared sensor

Portable flue gas analysersfrom Testo

For over 16 years Testo has beenmanufacturing portable flue gasanalysers for special industrialapplications.

These instruments fulfill the highrequirements of industry e.g.:- High accuracy (comparable with

infrared or chemiluminescencetechnology from stationaryapplications)

- Long-term measurements(practically stationary) lastingfrom several hours to severalweeks

- Flexible range of sampling probesfor the different sampling points

- High to extreme measuringranges for use in crude gas orspecial burner atmospheres

- Service by the user to save oncosts and reduce down times

- Not affected by dusty or moist flue gas or “tough” ambientconditions (high temperature,vibrations...)

The measurement principles

Testo uses electrochemicalmeasuring cells for the O2, CO, NO,NO2, H2S and SO2 parameters.These sensors have majoradvantages for portableapplications:- Not affected by vibrations and

changes in temperature- Small dimensions and low weight

Measuring cell e.g. for toxic gases

Flue gas (e.g. CO)

Gas permeable membrane

Gas permeable membrane

Operational electrode

Reference electrode

Backplate electrode

Aqueous electrolyte Fresh air

- Easy to change without cal gas- Wide measuring ranges and low

zero point drift for lowconcentrations

- Extreme linearity over the wholemeasuring range

An NDIR sensor is used for CO2.

CO2

CO2

H+

OH-

OH-

OH-

OH- OH

-

OH-

OH-

Gas permeable membrane

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Oil/gas burner CO: + + + +

Coal furnace CO: +; SO2: + + + +

Wood combustion CO: + o + +

Block-type thermal power station NO: o o + +

Steel and nonferrous CO: + o + +

Cement production - - o +

Glass industry CO: +; SO2: + + + +

Terotechnology o + + +

Universities/Technical colleges o + + +

Burner/Boiler manufacturers o + + o

Chemical industry + + + +

Garbage incineration - - o +

Therm. post-combustion - + + +

199

Flue gas analysis for industry

Typical applications

+ = recommendedo = recommended in some cases- = not recommended

Overview and operation (example: testo 360)

- Condensate collection to protectthe instrument

- Accurate NO2, SO2 measurement- Unsupervised long-term meas-

urement

Operation

Two physical principles:a) Peltier cooling unitb) Permeation dryer

Testo uses the Peltier cooling unitwith the following advantages:- Not affected by dirt and dust- No service costs- Lowest absorption of NO2 and

SO2 level for exactmeasurements

Why gas preparation?

Application testo 325-I testo 300 M-I testo 350 M testo 360testo 300 XL-I testo 350 XL

Flue gas probe

p/Velocity measurement Alarm output

Additional probeinputs

Instrument controlpower unit etc.

Temperature measurement

Flue gasmoisture

meas.

Gas dehumidification

Instrument heating

Heatedhose

Cal gas inlet

Cal gas Condensate outlet

NotebookOperation

ProgrammingAnalysis

Saving

PrintoutFilesAnalog recorder

Alarm

Probes

Gas outlet

Power

O2 CO NO NO2 SO2CO2

HC

∆

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