Coal-fired power station in China. Annual investment in FGD systems will be at least 50% more in China than in the US in coming years. (Picture © Bill Perry. Used under license from
Coal-fired power station in China. Annual investment in FGD systems will be at least 50% more in China than in the US in coming years. (Picture © Bill Perry. Used under license from
Figure 1: Power plant FGD: FRP uses in yellow.
Figure 1: Power plant FGD: FRP uses in yellow.
Figure 2: FGD capacity US and China, 2007-2020.
Figure 2: FGD capacity US and China, 2007-2020.
Figure 4: Worldwide market for FRP in FGD systems, US$ millions, 2008.
Figure 4: Worldwide market for FRP in FGD systems, US$ millions, 2008.

FRP is a laminate of glass fibres and thermoset resins. The structural layers of the laminate are made up of glass fibres for strength and stiffness. Specially formulated resins are used to enhance corrosion resistance. These characteristics make fibre reinforced plastic (FRP) products ideal for many applications at power plants, particularly with respect to the corrosive environment in flue gas desulphurisation (FGD) processes.

Power plants burn fossil fuels such as coal to heat water in boilers and generate steam. A steam turbine then converts the heat energy of the fuel into mechanical energy, and then into electricity. Since coal contains sulphur, the exhaust or flue gas from the combustion of coal contains sulphur compounds. FGD processes remove the sulphur compounds so they are not discharged into the air as pollutants.

The vast majority of FGD installations worldwide are 'wet scrubber' systems. In a wet scrubber, the flue gas initially goes through a particulate removal device, such as an electrostatic precipitator or fabric filter. Then the gas stream enters a large vessel (spray tower or absorber) where it is sprayed with a slurry made of lime or limestone and water (see Figure 1). 

The calcium in the slurry reacts with the sulphur oxides to form calcium sulphite or calcium sulphate. A portion of the slurry from the reaction tank is pumped to a thickener prior to final dewatering. The remaining slurry is recirculated back into the absorber. Mist eliminators are installed in the spray tower outlet to remove moisture from the flue gas prior to discharge through the stack.

Specific FGD uses

Because of the physical strength and corrosion resistance of FRP products, the material is ideal for many applications in FGD systems, as seen in Figure 1.

Slurry recirculating piping 

Lime or limestone slurry is abrasive and often contains small amounts of chlorides and fluorides which can cause severe corrosion in metal piping. FRP is the overwhelming choice for this application since it is resistant to abrasion and corrosion.

Slurry piping inside absorbers

Spray headers and piping in the absorber must be abrasion and corrosion resistant to the slurry inside the piping, but also to the slurry cascading down through the tower. Therefore, FRP piping inside absorbers must have an additional layer of protection on the outside. About 70% of FGD installations use FRP materials inside the absorber; the other 30% opt for lined carbon steel or nickel alloys.

Absorber vessels 

Scrubbers have used FRP materials for internal components, such as piping, weirs, baffles, troughs and mist eliminators, for many years. However, FRP can also be an ideal material for construction of the large absorber vessels themselves, with diameters of 40 ft or more and heights of up to 100 ft. 

A particular type of absorber called a sump scrubber or jet bubbling reactor tends to be smaller than the spray tower type. Flue gas is introduced below the liquid level in the reactor or recirculation tank. It 'bubbles' up through the slurry, eliminating the need for spray nozzles, headers and recirculation piping. FRP is a particularly cost effective material choice for these somewhat smaller vessels. 

Outlet duct 

FRP is an ideal material for connecting FGD absorbers to stacks and chimney liners. FRP ducts can be made with a special brominated resin for fire retardancy. 

Stacks and chimney liners

FRP stacks and chimney liners are common and have been used in the power industry since the 1970s. 

Replacing nickel alloys

Sulphur oxides create a highly corrosive environment in FGD systems.A number of corrosion resistant materials have been used for these systems, including rubber-lined, acid brick-lined and resin-coated carbon steel. However, due to cost and maintenance considerations, the two most common FGD materials are nickel alloys and FRP.

Prior to 2006, nickel alloys were typically the material of choice for wet process FGD systems. However, the demand for FRP products has risen dramatically since then. The primary reason? The cost of nickel. Nickel prices hovered around $3-$4/lb in the 1990s. In 2006, nickel prices soared to $15/lb, hitting a high of $24/lb in 2007. Even though nickel prices are now in the $10/lb range, the price of commodity metals such as nickel has become very volatile in today’s economy. With a 30-year reputation for relatively stable costs, FRP has provided process engineers with a very attractive, cost effective alternative. 

Don Kelley of Ashland Performance Materials suggests that stack liner projects can be used as a indicator of overall growth in the FRP market. According to Kelley, eight FRP stack liner projects were kicked off in the US in the two year period 2004-2005. In 2007, there were 49 FRP stack liner projects and 39 projects so far in 2008. His conclusion is that FRP is rapidly replacing nickel alloys as a material of choice in FGD applications. 

Huge growth in FGD construction

According to the federal Energy Information Administration, worldwide demand for electricity will double by 2030. Coal-fired power plant capacity is expected to increase even more during that time period. According to McIlvaine Company’s World Coal-Fired Power Generation Analysis and Forecast, coal-fired plant capacity is expected to increase from 1.3 million megawatts (MW) in 2006 to 2.7 million MW in 2030. Taking plant retirements into account, construction of more than 1.7 million MW of new coal-fired power plant capacity will be initiated over the next two decades.

The disproportionate growth in coal as opposed to other fuels is due to several factors. First, oil prices are now around $115/barrel, down from a high of $147 earlier this year. Natural gas and liquefied natural gas are becoming less attractive from a cost standpoint, and coal more attractive.

Second, growth in coal-fired capacity varies by region based on the availability of the fuel. China has roughly a third of the world’s power plant capacity, and is adding to that capacity at a rapid rate. Coincidentally, coal reserves in China are among the largest in the world and it relies on coal to generate 50-80% of its electricity. As a result, the soaring demand for power in China will be a significant contributor to the growth in global coal-fired power plant capacity and a corresponding growth in FGD capacity  (see Figure 2).

In the US, power plant construction has leveled off, but FGD construction will continue at a high level because of air pollution control concerns. Ambient air quality standards for particulate matter will result in stricter sulphur dioxide emission control requirements. Stricter limits on the emission of hazardous air pollutants, such as mercury and hydrogen chloride, will also drive FGD construction since scrubbers remove such pollutants as a 'co-benefit', along with removal of sulphur compounds. 

In China, the economy has grown an average of 10%/year since 1990. China will build an unprecedented number of coal-fired plants in 2005-2011, bringing capacity from just under the the US capacity in 2005 to over twice the US capacity in 2011. Government policy in China requires new coal-fired plants to install sulphur dioxide scrubbers and requires larger existing plants to be retrofitted with scrubbers.Consequently, annual investments in FGD systems will be at least 50% more in China than in the US in coming years.
Even so, the market for FGD components and materials in China is still in its infancy. In particular, few companies can offer high quality, reliable FRP products for power plant applications. Ershigs Inc, a leading provider of FRP products for FGD systems in the US, recently announced a joint venture with Hanwei Energy Services Corp of Beijing. Hanwei manufactures FRP pipe for oil and gas production facilities. Ershigs had been looking for an opportunity to enter the Chinese market and will bring its FGD expertise to the joint venture.  Ershigs representatives estimate the market for FRP products in FGD systems in China to be at least US$1.5 billion over the next three years.

Market forecast

Sales of FRP products for new FGD system installations are projected to be approximately $500 million worldwide in 2008, broken down as shown in Figure 3.

Figure 3: Worldwide sales of FRP for new coal-fired power plant; FGD installations 2008.


US$ million

Spray headers 118.4
Recirculating piping 118.4
Vessels 52.6
Tanks/piping 52.6
Chimney liners 158.0



However, FRP does not last forever. Spray headers are subjected to abrasion and corrosion of internal and external surfaces and need to be replaced after about 15 years. Other FRP components should last 20 years.  Plants may replace just the damaged sections, or may opt to replace a complete system. In some cases, for example, rubber-lined components or stainless steel piping systems are being replaced by FRP components and piping.

As seen in Figure 3, FRP sales for new coal-fired power plant applications are expected to reach US$500 million worldwide in 2008. FRP sales for the replacement market are expected to be an additional $150 million worldwide, for a total market of US$650 million  (see Figure 4).

Market opportunity

Coal-fired power plant and FGD capacity are expected to increase significantly over the next two decades. As a result, there will be a growing demand for corrosion resistant materials such as FRP. Materials such as nickel alloy have become expensive, creating a market opportunity for FRP. The growth in FGD capacity in China, in particular, creates a market opportunity for FRP materials, due to their lower cost and proven performance in FGD processes.