FLUE GAS DESULFURIZATION
Best Practices
www.Emerson.com
Flue Gas Desulfurization – Installation
Absorber
Tower
Bottom
Fraction
Gypsum
Recirculation
Water
Limestone
Slurry
Oxidizing Gas
Clean Flue Gas
Flue
Gas
FDM
FDM
FDM
Gypsum
Gypsum
Tank
Underground
Best Practices
What is Flue Gas Desulfurization (FGD)?
FGD is a set of technologies used to remove Sulfur Dioxide
(SO2) from exhaust ue gases in coal, oil-red, and wasteto-energy power stations. SO2 is a pollutant/irritant in air and
a major contributor in the creation of acid rain. SO2 emissions
are subject to strict environmental protection regulations.
How does a FGD system work?
Exhaust ue gas is drawn from the boiler and forced
into an absorber tower by a booster fan. Once inside the
absorber tower, the gas ows upwards through a dense
shower of lime or limestone slurry. The slurry absorbs
the Sulfur Dioxide (SO2) in the ue gas. The absorption
process converts the lime/limestone into Calcium Sulte.
Controlling the usage of lime/limestone is critical to
both the plant’s operating cost and effectiveness in
meeting environmental regulatory requirements.
Calcium Sulte is often converted to gypsum. Density
measurement of the gypsum slurry on the output side
of the scrubber veries the ultimate efciency of the
scrubbing process and is also used to prevent blocking
of the spray nozzles in the slurry re-circulation process.
How should the FDM be installed
for optimum performance?
The correct installation of the FDM in this application
is critical. So the following topics/guidelines need to be
considered for each installation. MC-001976 ‘Slurry
Installation Best Practices’ provides general guidelines
for the installation of the FDM in slurry measurement
applications, but these guidelines provide additional
information specically related to the installation of the
FDM in a Flue Gas Desulfurization process.
Flow Rate / Velocity
It is critical to ensure that the ow velocity be kept high
enough to keep the solids in solution, but not too high
as this may cause erosion of the FDM wetted parts.
For larger diameter pipes, a T-Piece installation
can be used. The FDM insertion depth can be
selected to suit the ow velocity (see gure 1).
For small diameter pipes, a Free-Stream installation
can be used. This option may require the diameter of
the pipe to be increased using reducers/expanders
to lower the velocity to the desired rate (see gure 2).
If this technique is used, there must be 20” (500mm)
of upstream straight run to avoid any jetting effect of
the slurry. Any jetting effect would result in the FDM
measuring a non-representative sample of the slurry.
An ideal solution for measurement of limestone slurry concentration
and gypsum slurry density is the Fork Density Meter (FDM).
Page 2
Best Practices
STATUS
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Figure 1
T-Piece Installation
Flue Gas Desulfurization – Installation
Velocity ≤ 10 ft/sec
(3 m/s)
10 < Velocity ≤ 13ft/sec
(4 m/s)
13 < Velocity ≤ 16ft/sec
(5 m/s)
Figure 2
Free-Stream Installation
Vertical Pipe with
Concentric Reducers
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Flow Velocity Free-Stream
Min 0.3m/sec (1ft/sec)
Max 0.6m/sec (2ft/sec)
FDM Fork Tine Orientation
Gap between the FDM fork tines must always be vertical:
• Solids drop down
• Entrained gas will go up
Fork Density Meter
Direct Insertion
Density Meter
Page 3
Flue Gas Desulfurization – Installation
Best Practices
Main Process Pipe Diameter
3” (DN80) and above – Vertical and Horizontal
Pipeline
We recommend that for ≥ 3” (DN80) pipelines, the
FDM should be mounted in a T-Piece installation.
The T-Piece should be 3” (DN80) and must be
mounted at an angle to ensure that it will self-drain.
Flow velocity as low as 1.0m/s is acceptable, and
preferred velocity is 3m/sec. Care should be taken
at ow velocities of 5m/sec as there is an increased
risk of the T-Piece clogging. Additional cleaning
may be required.
Viscosity of the slurry should not exceed a
maximum of 500cP to ensure proper product
refreshment in the T-Piece.
It is recommended that a purge/drain connection
located on the upper part of the T-Piece
(horizontal installation) or on the side of the of
the T-Piece (vertical pipe). The use of a purge
connection will allow for easy ushing if and when
required.
2” (DN50) 2.5” (DN65) – Vertical and Horizontal
Pipeline
T-Piece Installation
Horizontal Pipeline
In some applications, the main pipe diameter may
only
be 2” (DN50) or 2.5” (DN65). In this instance
we recommend that the FDM be mounted in a
Free-Stream installation. Minimum ow velocity
is 0.3m/sec. The maximum ow velocity should
be no greater than 0.6 m/s, so the pipe may have
to be expanded. For a horizontal pipe, eccentric
reducers should be used, while for vertical
pipes, concentric reducers should be used.
If the main pipe has to be expanded to DN80
(3”), the T-Piece cannot be used as there will be
inadequate turbulence to ensure a good mixing in
the T-Piece. The Free-Stream installation should
still be used. Although this installation has the
advantage of being self-cleaning, once installed,
the FDM will require a simple eld calibration.
Vertical Pipeline
Page 4
Flue Gas Desulfurization – Installation
Best Practices
Free-Stream Installation
Vertical Pipe
Installation Summary
Free-Stream Horizontal Pipe
dimensions are identical, but FDM
is rotated through 90° so that
vibrating tines are vertical
About Micro Motion
For over 35 years, Emerson’s Micro Motion has been a technology leader delivering
the most precise ow, density and concentration measurement devices for scal applications,
process control and process monitoring. Our passion for solving ow and density measurement
challenges is proven through the highly accurate and unbeatable performance of our devices.
The contents of this publication are presented for informational purposes only, and while every effort has been made to ensure their accuracy, they are not to
be construed as warrantees or guarantees, express or implied, regarding the products or services described herein or their use or applicability. All sales are
governed by our terms and conditions, which are available on request. We reserve the right to modify or improve the design or specification of such products
at any time without notice.
Emerson Automation Solutions
Micro Motion Inc.
7070 Winchester Circle
Boulder, Colorado USA 80301
T: +1 800 522 6277
T: +1 (303) 527 5200
www.Emerson.com
GI-002104 Rev C 12/2017
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