Rema Tip Top ' ' '

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Rema Tip Top . . .
. . . around the FGD system
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Rema Tip Top . . .
. . . around the FGD system
Wet FGDs

• Fossil fuel combustion generates a number of
  gaseous pollutants including sulfur dioxide -
  that can be effectively controlled by air
  pollution control processes.
• Three main technologies are used to control
  sulfur dioxide emissions
• limestone based wet FGD
• lime based dry FGD
• seawater FGD
• Flue gas desulphurization (FGD) involves the
  removal of sulfur dioxide (SO2) contained in
  gases produced by the combustion of fossil fuels
  such a coal, oil, municipal solid waste,
  automobile tires and many industrial processes
  such as gasoline refining, cement, paper, glass,
  steel, iron, and copper production. Sulfur
  dioxide emissions are believed to be a primary
  contributor to acid rain and have been regulated
  by every industrialized nation in the world.
• The most common of the FGD options is the wet
  system and it is the focus of this presentation.

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Rema Tip Top . . .
. . . around the FGD system
Wet FGDs

• In reality the basic concept and application of
  the FGD system is not too terribly complicated.
  And if all the system had to was vent the high
  temperatures of SO2 gas, and other gas mixtures,
  that are generated as a result of the coal
  burning process the application would be fairly
  simple. It is likely mild carbon steel is all
  that would be required to handle these
  conditions.
• What makes this whole application so complicated
  are the components required to scrub the gas to
  greatly reduce the SO2 emissions. The sum of the
  whole process takes the gas and at different
  points it can transition from gas to a vapor or a
  liquid state. The drop in temperature can cause
  the gas to cross its dew point which creates the
  corrosive condensate that can attack unprotected
  steel.
• The gas mixtures in an individual plant can vary
  somewhat and each gas mixture has its own dew
  point. Therefore it is important to gather all
  data points about the proposed or existing system
  in order to make the best corrosion protection
  option.

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Wet FGD System(click on an area name to see more
information)
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Rema Tip Top . . .
. . . around the FGD system
Raw Gas Ducts
The raw gas ducts take the untreated gas from the
boilers and introduce it into the FGD system
circuit. The temperature of this gas is generally
the hottest you will find, somewhere between 275
F to 375 F, in the FGD system circuit. These
gases are not yet scrubbed and so they are highly
acidic and may contain flyash or some other
particulate.
Possible Recommendations Coroflake 28 (vinyl
ester) - 1.2 mm thickness Coroflake 48 (vinyl
ester) - .9 mm thickness Alternate Coroflake 23
(vinyl ester) - 1 - 1.5 mm thickness Chemoline 4B
(rubber) - 4, 5 or 6 mm thickness Chemoline 4CN
(rubber) - 4, 5, or 6mm thickness
Ducting
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Rema Tip Top . . .
. . . around the FGD system
Bypass Ducts
Frank, Please provide a general description of
this area. The bypass duct is used when if
becomes necessary to circumvent the FGD system
circuit??

• Possible Recommendations
• Coroflake 23 (vinyl ester) - 1 - 1.5 mm thickness
• Coroflake 28 (vinyl ester) - 1.2 mm thickness
• Coroflake 48 (vinyl ester) - .9 mm thickness

Inside ducting view
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Rema Tip Top . . .
. . . around the FGD system
Gas Gas Heater
In the wet limestone FGD process untreated gas is
cooled through the gas gas heater prior to
entering the absorber. Conversely, the cleaned
gas is heated in the gas gas heater prior to
entering the stack. The temperature changes are
accomplished by allowing the two flue gas flows
to exchange heat from the hot flow to the
cold. This process creates a highly corrosive
environment since you have untreated gas entering
at approximately 250- 320 F and then is cooled
down to approximately 170- 230 F. This change
causes the gas to pass through its acid dew point
level. The result is that the gas gas heater is
subject to fly ash particulate and acid
condensate on the untreated side and a
combination of water droplets, generally with a
high chlorine count, unreacted limestone and the
remaining of SO2 on the clean gas side.
Possible Recommendations Coroflake 18 (vinyl
ester) - 2.0 mm thickness Coroflake 23 (vinyl
ester) - 1 - 1.5 mm thickness Coroflake 28 (vinyl
ester) - 1.2 mm thickness Coroflake 48 (vinyl
ester) - .9 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Slurry Processing Tanks

• There can be several different tanks that make up
  the processing area for the slurry. The whole
  processing area insures that the absorber has a
  continual flow or supply of the limestone slurry
  to spray. The tanks that are usually involved in
  this process would include
• Thickener tanks
• Filtrate tanks
• Gypsum slurry tanks
• Limestone tanks
• Holding tanks
• Impellers

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Rema Tip Top . . .
. . . around the FGD system
Slurry Processing Tanks
Thickener tanks - these tanks receive the spent
slurry overflow created inside the absorber.
Calcium sulfite slurries normally require a
thickener to increase their concentration to 25 -
40 wt. solids prior to vacuum filtration. The
solid content entering into these tanks is about
10-15 solids. Inside these tanks the solids
settle to the bottom and are then raked off and
moved to the filtration process. Because of the
high of solids this application is susceptible
to high abrasion wear and some corrosion wear.
Possible Recommendations Chemoline 4B (rubber) -
4, 5 or 6 mm thickness Chemoline 4CN (rubber) -
4, 5, or 6 mm thickness Topline W (vinyl ester)
-3.2 mm thickness Topline 68 (epoxy) - 2.5 mm
thickness
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Rema Tip Top . . .
. . . around the FGD system
Slurry Processing Tanks
Filtrate tanks - are fed wastewater produced in
the process. Here the water is filtered for
remaining solids before being reused in the flow
process.
Frank, Not exactly clear on this tank.
Possible Recommendations Topline 68 (epoxy) -
2.5 mm thickness Coroflake 60 (epoxy) - 3.2 mm
thickness Alternates Chemoline 4B (rubber) - 4, 5
or 6 mm thickness Chemoline 4CN (rubber) - 4, 5,
or 6 mm thickness Topline W (vinyl ester) -3.2 mm
thickness
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Rema Tip Top . . .
. . . around the FGD system
Slurry Processing Tanks
Gypsum slurry tanks - inside these tanks is the
gypsum slurry that was created inside the
absorber towers recirculation tank. From here the
slurry has to be washed and dewatered to create
the saleable finished byproduct - gypsum. The
gypsum purity is normally around 95 but this is
dependent on the initial limestone quality and
any residual fly ash content remaining in the
flue gas. The gypsum tends to have an abrasive
effect and therefore rubber lining is a good
choice for protection.
Possible Recommendations Chemoline 4B (rubber) -
4, 5 or 6 mm thickness Chemoline 4CN (rubber) -
4, 5, or 6 mm thickness Topline W (vinyl ester)
-3.2 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Slurry Processing Tanks
Limestone tanks - containment area for the
storage of the unused crushed an finely milled
limestone. AT this point the limestone has gone
through a ball mill and been reduce to a fine
particle size.
Possible Recommendations Chemoline 4B (rubber) -
4, 5 or 6 mm thickness Chemoline 4CN (rubber) -
4, 5, or 6 mm thickness Topline W (vinyl ester)
-3.2 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Slurry Processing Tanks
Holding tanks - these tanks store the process
water and crushed limestone slurry mixture. This
mixture is pumped into the absorber spray zone
area and is used to scrub the raw gas.
Possible Recommendations Chemoline 4B (rubber) -
4, 5 or 6 mm thickness Chemoline 4CN (rubber) -
4, 5, or 6 mm thickness Coroflake 28 (vinyl
ester) - 1.2 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Slurry Processing Tanks
Impellers - used to agitate the slurry and keep
it in suspension. The very nature of this
requirement makes the impellers subject to high
abrasion wear.
Possible Recommendations Chemoline 4A (rubber) -
4, 5, or 6 mm thickness Alternate Chemoline 4B
(rubber) - 4, 5 or 6 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Absorbers/Scrubbers
The raw gas is introduced into the scrubber
through the inlet and rises through the scrubber.
It passes through a limestone spray mist zone
where the limestone spray combines with most of
the SO2 to form calcium sulphite. The byproduct
of calcium sulphite falls into a storage tank in
the lower portion of the scrubber. Air is blown
into the storage tank. The oxygen in the air
turns the calcium sulphite into calcium sulphate
or gypsum. The gypsum is dewatered with the
extracted water being recirculated and reused to
make more limestone slurry in the slurry
tanks. The cleaned gas continues to rise and
exits via the outlet at the top of the absorber
vessel.
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Rema Tip Top . . .
. . . around the FGD system
Absorbers/Scrubbers

• Within the absorber there are several different
  components. All of these different areas are
  candidates for some corrosion protection option.
• Components of a Wet Absorber
• Absorber inlet
• Absorber recirculation tank
• Absorber spray zone
• Absorber moisture separators
• Absorber outlet
• Absorber internal supports
• Headers
• Absorber tray/gas distribution devices

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Rema Tip Top . . .
. . . around the FGD system
Absorbers/Scrubbers
Absorber inlet - this is the point at which the
dry gas interfaces with the wet environment
inside the scrubber. At this interface it is not
uncommon to see some spray back from the absorber
back into the inlet duct. Often the
coating/lining that is used on the inside of the
absorber extends back into the inlet ducting to
guard against this corrosive environment.
Possible Recommendations Coroflake 28 (vinyl
ester) - 1.2 mm thickness Coroflake 48 (vinyl
ester) - .9 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Absorbers/Scrubbers
Absorber recirculation tank - this tank is
typically integrated into the absorber structure
and is located in the lower portion of the unit.
Its function is to contain the slurry that is
created as a result of the raw gas passing
through the spray zone. The tank floor is
susceptible to high abrasion wear due to the high
amount of solids that are agitated to keep them
in suspension. Rubber or flake linings are
advantageous when slurry chloride concentrations
are gt 20,000 ppm. It is not uncommon to see
rubber lining on floor and part way up the walls
and a flake lining up the remaining wall.
Possible Recommendations Chemoline 4B (rubber) -
4, 5 or 6 mm thickness Topline W (vinyl ester)
-3.2 mm thickness Alternate Chemoline 4CN
(rubber) - 4, 5, or 6 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Absorbers/Scrubbers
Absorber spray zone - this is the region within
the scrubber where the raw gas is sprayed with a
limestone slurry mist. Spray impingement against
the tower wall does occur and since the reagent
slurry is 15-20 solids it therefore causes
abrasion wear. Due to its high abrasion
resistance and low permeability rubber is a good
option here. Resin linings require thicknesses
1.5 to 2 times the norm to overcome their
inherent high permeability.
Possible Recommendations Chemoline 4B (rubber) -
4, 5 or 6 mm thickness Alternate Chemoline 4CN
(rubber) - 4, 5, or 6mm thickness Topline W
(vinyl ester) -3.2 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Absorbers/Scrubbers
Absorber mist eliminator area - Frank, not
exactly sure of what happens here. This area is a
final wash down of the clean gas so to reduce the
amount of remaining solids in the clean gas as
well as reduce the amount of water in the clean
gas headed to the stack. The gas moves past the
spray zone area and moves through a series of
trays designed to elminate the solids. After the
trays a fine mist is used to remove the water in
the clean gas stream. The mist also serves to
clean the scale deposits that can build up on the
tray system.
Possible Recommendations Coroflake 23 (vinyl
ester) - 1 - 1.5 mm thickness Coroflake 24 (vinyl
ester) - 1 - 1.5 mm thickness Coroflake 28 (vinyl
ester) - 1.2 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Absorbers/Scrubbers
Absorber outlet - this is the point where the
cleaned gas exits the scrubber area. The concern
here is no longer the abrasive actions of the
high solids slurry but rather sulfuric acid. This
develops as a result of the combination of water
and the residual SO2 left in the clean gas.
Consideration needs to be given to that interface
from the absorber outlet to the clean air duct.

• Possible Recommendations
• Coroflake 23 (vinyl ester) - 1 - 1.5 mm thickness
• Coroflake 24 (vinyl ester) - 1 - 1.5 mm thickness
• Coroflake 28 (vinyl ester) - 1.2 mm thickness
• Chemoline 4B (rubber) - 4, 5 or 6 mm thickness
• Alternate
• Chemoline 4CN (rubber) - 4, 5, or 6mm thickness

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Rema Tip Top . . .
. . . around the FGD system
Absorbers/Scrubbers
Absorber internal supports - support beams are
required for the overall structural integrity of
the absorber tower. These beams are usually a box
beam type design to make lining easier.
Frank, Check these recommendations out.
Possible Recommendations Coroflake 23 (vinyl
ester) - 1 - 1.5 mm thickness Coroflake 24 (vinyl
ester) - 1 - 1.5 mm thickness Coroflake 28 (vinyl
ester) - 1.2 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Absorbers/Scrubbers
Headers - Frank, not exactly sure of what happens
here.
Possible Recommendations Chemoline 4A (rubber) -
4, 5 or 6 mm thickness Alternate Chemoline 4B
(rubber) - 4, 5 or 6 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Absorbers/Scrubbers
Circulation pipes - Frank, not exactly sure of
what happens here.
Possible Recommendations Chemoline 4A (rubber) -
4, 5 or 6 mm thickness Alternate Chemoline 4B
(rubber) - 4, 5 or 6 mm thickness
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Rema Tip Top . . .
. . . around the FGD system
Clean Gas Ducts
After the raw gas has passed through the absorber
unit it exits via the absorber outlet and is now
cleaned or scrubbed. It travels through ducting
to either the gas gas heater or to the stacks.
Possible Recommendations Coroflake 23 (vinyl
ester) - 1 - 1.5 mm thickness Coroflake 24 (vinyl
ester) - 1 - 1.5 mm thickness Coroflake 28 (vinyl
ester) - 1.2 mm thickness Chemoline 4B (rubber) -
4, 5 or 6 mm thickness
Clean gas ducting
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Rema Tip Top . . .
. . . around the FGD system
Stacks/Chimneys
The last component in the FGD system circuit is
the stacks. By far, the largest quantity of SO2
emissions come from the exhaust stacks of
coal-fired power generation stations. However
after the gas has been processed through the FGD
the SO2 emissions have been greatly reduced. It
is possible to reduce these emissions by as much
as 98. The main considerations within the
stacks is related to the relatively cool
temperatures (lt 230º F), wet and acidic
conditions. These conditions create a very
strong corrosive environment. Historically, the
lining within the stacks has been brick, steel
alloy (solid or wallpaper) or ceramic tile. Flake
coatings have been successful on a somewhat
limited basis. Flake coatings represent a lower
initial investment cost but some would say that
future maintenance costs will eat of the initial
savings.
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Rema Tip Top . . .
. . . around the FGD system
Stacks/Chimneys
Possible Recommendations Coroflake 23 (vinyl
ester) - 1 - 1.5 mm thickness Coroflake 28 (vinyl
ester) - 1.2 mm thickness Coroflake 48 (vinyl
ester) - .9 mm thickness
Looking up inside of stack
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