Micro Motion Manuals & Guides: Flue Gas Desulfurization-FDM Installation Best Practices | Micro Motion Manuals & Guides

FLUE GAS DESULFURIZATION

Best Practices

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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 Sulte.

Controlling the usage of lime/limestone is critical to
both the plant’s operating cost and effectiveness in
meeting environmental regulatory requirements.

Calcium Sulte is often converted to gypsum. Density

measurement of the gypsum slurry on the output side

of the scrubber veries the ultimate efciency 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 specically 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).

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