Testo 350 Field Guide - Actoolsupply.com

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3.3.4 Flue gas purification/Cleaning
The amount of air pollutants carried in flue gases and their emission into the
atmosphere can be reduced by installation of dedicated purification units in the
flue gas path between boiler and stack:
• Emission of particulate matter
is reduced or almost eliminated by installation of dust precipitators of numereous
designs and operating principles
• Emission of gaseous pollutants
can be reduced to a certain extent by using low-emission fuels; a more effective
reduction is achieved by combustion optimization (fluidized bed combustion,
staged air supply) and even more by flue gas purification processes such
as adsorption, thermal treatment, etc.
Gas analysis is an important tool to monitor and control such processes.
Particulate matter control
• Centrifugal separators (cyclones)
Cyclones are devices in which particles are caused by means of centrifugal
forces to be propelled to locations outside the gas stream from where they
may be removed and discharged. Reverse flow cyclones are the most common
ones with tangential inlet and axial gas and particle outlet.
• Electrostatic precipitators
Electrostatic precipitators are devices in which an electrical field is maintained
to cause particles to acquire an electrical charge. The charged particles are
forced to travel to a collector electrode where from they are removed and
discharged from the process. Electrostatic precipitators are preferably used to
filter high volume gas streams in power stations, cement plants, metallurgical
plants etc.
Electrostatic filters may be damaged in case of an explosive gas mixture enters
the filter chamber and passes through the electric field. Effective protection
from that may be realized by measuring the CO content of the flue gas upstream
the filter.
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