The use of FRP in FGD applications

06 January 2007

Don Kelley

Record amounts of wet flue gas desulphurisation (FGD) equipment made from fibre reinforced plastic 

(FRP) are currently being installed in coal-fired power plants in North America. While regulations are 

driving the current demand for wet FGD equipment, a significant increase in the price of high nickel alloy 

is driving the use of less costly FRP in wet FGD systems. Don Kelley of Ashland Performance Materials 

compares the cost and reliability of FRP with other materials in wet FGD applications.

In 2005, the Environmental Protection Agency (EPA) issued the Clean Air Interstate Rule (CAIR) that 

requires a significant reduction in sulphur dioxide (SO2) emissions across 28 US eastern states by 2015. 

This has created a great demand for the installation of wet FGD equipment in a number of coal-fired 

power plants. Wet FGD is the preferred method for SO2 removal from flue gas in coal-fired power plants. 

It has a global experience base, it is cost effective, and removes up to 99% of the SO2. However, 

depending on chloride levels and operating pH, wet FGD processes can be highly corrosive to metals.

In the 1990s, high nickel alloy-clad steel was the preferred material of construction for absorber vessels, 

ductwork and stack liners in wet FGD processes. It had good corrosion resistance and did not cost much 

more than field-fabricated FRP. Since then, a six-fold increase in nickel price and short supply has made 

high nickel alloy-clad steel very expensive compared to FRP. Companies such as AEP, Dayton Power & 

Light, Duke Energy, Santee Cooper, the Southern Company, TVA and WE Energies have chosen FRP for 

its cost-effectiveness and reliability in wet FGD service. FGD equipment made from FRP is about half the 

cost of nickel alloy-clad steel, and it has more than 25 years of case histories to back up its use in FGD 

systems. FRP has been used successfully in stack liners, ductwork, absorber vessels and limestone slurry 

piping.

Other materials such as rubber-lined carbon steel, acid brick-lined carbon steel and resin-coated carbon 

steel have been used in wet FGD systems. These materials do not all have the same service life qualities, 

nor do they have the same cost.

In this article, FRP will be used as a reference material and will be compared to the other materials for 

service life and cost in wet FGD service.

Cost

With the rising cost of nickel, FRP has become a very competitive material of construction. The total 

installed cost for FRP ranges from about $125 to $150 per ft2 in North America (prices may vary in other 

countries). It is very competitive with acid brick or rubber-lined carbon steel (Table 1) and much less 

expensive than alloy-clad carbon steel. It is generally more expensive than resin-coated carbon steel but 

has a longer service life in most applications. Because FRP does not require insulation, FRP ductwork is 

actually less expensive than resin-coated carbon steel (Table 2).
Table 1: Cost comparison of absorber construction 

materials. (Cost obtained from a major power 

engineering firm in 2003.)

Construction material

Installed cost 

($)

Cost 

ratio

Epoxy vinyl ester resin-coated 

carbon steel

1 735 000 0.70

FRP made with epoxy vinyl ester 

resin

2 475 000 1.00

Acid brick or rubber-lined 

carbon steel

3 025 000 1.22

C-276 clad carbon steel 4 500 000 1.82

Table 2: Ductwork cost comparison.

Construction material

Installed cost 

($)

Cost 

ratio

FRP made with epoxy vinyl ester 

resin

1 100 000 1.00

Resin-coated carbon steel 1 265 000 1.15

C-276 clad carbon steel 2 000 000 1.80

Chemical resistance

Chemical resistance is a key predictor of service life in FGD applications. Compared to metals (Table 3), 

FRP made from a bis A epoxy vinyl ester resin has as good or better chemical resistance than Alloy C-276 

and is superior to 317L stainless steel. FRP has unusual resistance to chlorides and is superior to alloys in 

high chloride environments. Based on more than 25 years of experience and testing in FGD systems, FRP 

based on epoxy vinyl ester resin has the chemical resistance necessary for long-term service life.

Table 3: Epoxy vinyl ester resin chemical resistance 

compared to metal.

Materials Sulphuric

acid

Hydrochloric 

acid

Acid 

chloride 
salts

317L stainless 

steel

25°C 

below 5%

NR NR

FRP made with 

bis A epoxy vinyl 

ester resin

100°C to 

30%

80°C to 15%

100°C all 

conc.

Alloy C-276

100°C to 

30%

80°C to 15%

65°C to 20M 

ppm at low 

pH

FRP

The use of FRP in coal-fired power plant FGD systems dates back to the 1970s. FRP has been used 

extensively in limestone slurry piping systems and to a lesser degree in stack liners. In the 1990s several 

large scrubbing vessels were made from FRP. The power industry was slow to accept the use of FRP in 

large scrubber vessels due to concerns for high upset temperatures. Improvements in FRP technology 

have eased temperature concerns by demonstrating the ability of epoxy vinyl ester resin based FRP to 

withstand upset temperatures of 315°C (600°F).

Because not all resins are suitable for processes that have thermal cycling or high temperature 

excursions, it is important to consult the resin manufacturer when choosing a resin for these types of 

applications.

Case histories

FRP case histories include absorber towers, slurry piping, ductwork and stack liners. The use of FRP in 

stack liners and slurry piping began in the 1970s. Several ducts were installed in the 1980s, and a few 

large absorber towers were built in the 1990s.

The most common material of construction for slurry piping (Figure 2) in wet FGD systems is FRP based 

on epoxy vinyl ester resin. With an abrasion-resistant liner, FRP pipe based on epoxy vinyl ester resin has 

been successful in more than 150 plant sites dating back to 1977. Brominated epoxy vinyl ester resins 

are used on projects that require fire protection.

The second largest use of FRP in wet FGD is stack liners. Since 1977, a number of FRP stack liners have 

been installed and are still in service today as shown in Table 4. Two were removed due to faulty 

construction and replaced with acid brick linings. Fabrication errors were the root cause for having to 

reline five liners. These have been very successfully relined with brominated novolac epoxy vinyl resin. 

The rest are in good to excellent condition and require minimum maintenance.
One factor that inhibited the use of FRP in absorbers and stack liners in the power industry was the 

1980s experience with stack liners. Although many were successful, a few notable exceptions caused 

concern about FRP in the minds of many engineers and owners in the 1980s. Since that time it has 

become obvious that fabrication errors were the root cause. By the early 1990s standards such as ASTM 

D5364 and ASME RTP-1 for material selection, design, fabrication, erection and quality control were 

developed to help avoid fabrication errors. Owners became more aware of the importance of inspection 

and workmanship and were willing to take ownership of these important factors to avoid the mistakes 

of the past. These important developments led to the successful construction and operation of stack 

liners, ductwork and absorber vessels in the 1990s.

FRP stacks and stack liners made from epoxy vinyl ester resin are shown in Figure 3, Figure 4 and Figure 

5. These are located in New York, Germany and Austria respectively and have been in service with startup dates ranging from 1994 to 2000.

Some of the first large FRP absorber vessels for FGD are shown in Figure 8 and Figure 9. The vessel in 

Figure 8 was made from brominated epoxy vinyl ester resin. The vessel, known as a jet bubbling reactor 

(JBR), the ductwork and stack were fabricated on site in Yates, Georgia, USA. The JBR is part of a 

limestone slurry FGD process that has all the chemical reactions taking place in one vessel to produce 

high quality gypsum.

The most massive operational FRP absorber vessel in the world (Figure 10) was fabricated on site in 

Alberta, Canada, in 1996. This vessel was also a JBR and was made with DERAKANE 411-350 epoxy vinyl 

ester resin. The FRP shell alone weighed 89.4 tonnes (197 000 lbs). It is 20.7 m (68 ft) in diameter and 

19.8 m (65 ft) tall.

Some of the largest FRP absorbers in Europe (Figure 11) were made from DERAKANE epoxy vinyl ester 

resin. They are both 9 m (29.5 ft) in diameter and 49 m (160.8 ft) tall and have been in service since 

1998.

New construction

Since the EPA issued the CAIR in 2005, there has been an unprecedented demand for FRP as a material 

of construction in wet FGD applications. Table 6 is a summary of 49 locations in the USA that are using 

FRP for stack liner construction. With over 3 million ft2 of laminate, this is the largest use of FRP for stack 

liners in the history of the power industry.

Proven performance

FRP made with DERAKANETM or HETRON® epoxy vinyl ester resin is an ideal material of construction for 

FGD stack liners, ductwork, absorber towers, limestone slurry piping and spray headers with the 

following advantages:

o proven performance over 30 years; 
o much lower cost than Alloy C-276 clad carbon steel; and 

o less maintenance than other materials.

Figure 4: Ingolstadt power station stack liners in Ingolstadt, Germany, made with Novolac epoxy vinyl 

ester resin and operating with minimum maintenance since 1994.

Figure 1: Stack liner section made from HETRON® FR992 epoxy vinyl ester resin exposed to 315°C 

(600°F) for one hour.

Figure 2: Lime slurry spray headers made with DERAKANE® 411 epoxy vinyl ester resin. These have been 

in operation since 1987 at the RWE lignite fired power station at Weisweiler, Germany.

Figure 3: Milliken power station stack liners in Western New York, made with DERAKANE 510N epoxy 

vinyl ester resin and operating with minimum maintenance since 1994. 
Figure 5: Simmering power station with FRP lined stack in Wienstrom, Vienna, Austria, made with high 

temperature Novolac epoxy vinyl ester resin and in excellent condition since 2000 start-up. 

Figure 6: Intermountain Power ductwork (28'ID) and transitions in Delta, Utah, USA. 

Figure 7: Florina Power Station flue gas ducts in Greece made with DERAKANE 411 epoxy vinyl ester 

resin and operating with minimum maintenance since 2000. 

Figure 8: Yates scrubber, mist eliminator, and stack operating since 1992 and made with HETRON FR992 

epoxy vinyl ester resin.
Figure 9: 24' ID by 120' tall FRP scrubber in Fernandina, Florida.

Figure 10: The world's largest (20.7 m x 19.8 m) operational FRP flue gas scrubber, fabricated on site for 

Suncor Inc in Alberta, Canada, and operating since 1996. 

Figure 11: Among the world's tallest (49 m) FRP scrubbers, for the PCK refinery in Schwedt, Germany, 

operating since 1998 and made with epoxy vinyl ester resin.

Figure 12: The world's largest (88 ft x 77 ft) FRP flue gas scrubber, under construction on site for Dayton 

Power and Light Stewart Plant in Aberdeen, Ohio, USA.

Table 4: 2005 status of FRP stack liners in FGD service. 
Table 5: 2005 status of FRP ducts in FGD service. 

Table 6: FRP stack liners with kickoff dates from 2004 to 2008. 

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