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B1 Retrofit
of SCR-Systems - Formation mechanisms of SO3-aerosols and
implications on the Flue Gas Cleaning System
Michael
J. Frank and Prof. Dr. Heinz Gutberlet
Abstract
The retrofit of DeNOx-systems has been
accomplished in nearly all German power plants during the
nineteen-eighties as an implementation of the respective
prescriptions of the environmental legislation (13. BImSchV). Since
then, many years of experience have been accumulated at
E.ON Engineering regarding the operation, the efficiency and the
impact on the total flue gas cleaning system. Especially the
often-reported opacity problems occurring after the retrofit of DeNOx-systems
still remain to be an issue of key-interest.
This
paper shall contribute to the general understanding of formation
mechanisms of SO3 in its different states, its
concentration profiles along the flue gas path and the specific
effects related to SO3 or sulphuric acid observed in the
individual components of the boiler and flue gas cleaning system.
Results obtained in several measuring campaigns in power stations in
Germany as well as in the United States are shown and discussed. The
dependencies on specific process conditions such as sulphur content
of coal, the catalyst type, air heater setpoint temperatures and the general configuration of the
plant are discussed.
As sulphuric acid as a conditioning agent has
an important effect also on the efficiency of electrostatic
precipitators, the relevant test results are specifically reviewed
in this respect.
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B2
Experiences
of Wet Type Electrostatic Precipitator Successfully Applied for
SO3
Mist Removal in Boilers Using High Sulfur
Hidekatsu
Fujishima
and
Chikayuki Nagata
Mitsubishi
Heavy Industries, Ltd.
Abstract
In
thermal power plants, especially using high sulfur content fuel,
much attention is recently paid to SO3 emission, because gaseous SO3 in flue gas is condensed to sulfuric acid mist (SO3 mist) in the wet type FGD, which is installed to
meet SO2 emission regulation. SO3 mist is very fine under-sub-micron sized particulate matter (PM),
which is very visible even if the concentration is relatively low,
and causes air pollution. SO3 is often recognized as a part of the total SOx. However, recently, discussion comes out, especially in the United
States, that the condensed SO3 mist should be included in the total dust instead of SOx and regulated together with solid dust. In order to
remove SO3 mist from flue gas, wet type electrostatic precipitator (WESP)
installed in the horizontal gas flow at downstream of FGD (Flue Gas Desulfurization System) is one of the best
solutions and the most proven technology at this moment. This paper
describes the experiences of WESP successfully applied in Japan and
Europe, and also shows the advantages of the technology. Measuring
method of solid dust and SO3 concentration is a very
important issue for WESP application, which is discussed in this
paper as well.
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