Coatings Save Power Plant Scrubber

By: Jennifer Kramer

When a major Midwest coal-fired power plant began to have areas of corrosion in their Flue Gas Desulphurization (FGD) system equipment they knew that they faced a difficult problem: rebuild or repair.

The FGD unit is perhaps the most abused in the power plant. Simply put, it is the structure in which the fly ash and the sulfur dioxide are removed from the exhaust flue gases as coal (or oil) is burned to produce steam that runs the turbines which power the plant’s electricity generators. Thus, the unit interior is constantly exposed to harsh conditions. Realizing that simply patching the low carbon steel substrate would lead to future corrosion, the power plant management turned to Joe Vandiver and his crew at Universal Blastco for a coatings solution.



Vandiver explains, “coatings are uncommon in FGD systems due to failures in the past. But recent failures in low carbon steel substrates have the power companies looking for new solutions.” After a proposal process, during which Vandiver convinced the owners that the coatings “are installed on low carbon steel in lieu of much more expensive stainless steel or other alternate materials, saving the customer a great deal of money on items that are required by law for air quality environmental compliance,” Universal won the bid to install “vinyl ester-based laminate lining systems manufactured by ITW Futura Coatings in approximately 200,000 sq.ft. of interior FGD system equipment surfaces, including process tanks, wastewater tanks, absorber modules, and smoke stacks over a period of approximately nine months.”

It’s A Blast

Not only would the working conditions be difficult, the project was scheduled to begin in the midst of winter in St. Louis and would continue into the humid summer months. Project manager Sean Skey describes the unique challenges. “First we set up containment. If the tanks didn’t have closed tops, we used scaffolding and chain link fencing with tarps on top to contain dust. Then we used plastic tarps to cover the breech at the bottom, the absorber outlets, inlets…any open areas. Temperature and humidity control is 100% at all times since the coating must be kept at a constant 55°F to 65°F and humidity must be below 80%. We ran Munters 4500 cfm DH units 24/7.”

The crew then ran Black Beauty abrasives through six ton blast pots powered by IR915HP compressors. Clean-up followed with 1600 cfm dryers, 500E Hurricane Vacuums, Munters 4500 cfm DH units and 20,000 cfm dust collectors.

Next came the coatings installation. Vandiver says, “The systems installed are built up of multiple layers of spray- and trowel-applied materials with mat reinforcements and of varying compositions depending on the specific area of the vessel interiors. The performance of these systems relies upon, among other things, the surface preparation to NACE No.1/ SSPC-SP-5 as well as surface contaminant control of chlorides and other contaminants.” The installation was augmented with the use of Flake Glass catalyst injection pumps modified to internal specifications.

The crew, as well as a third party, NACE-certified inspector “verified the integrity of the preparation and installed lining systems at multiple stages utilizing direct contact surface profile measurement tools, SSPC Visual Standards, NACE surface finish weld replica standards, SCAT contamination test kits, wet and dry film thickness gauges, surface thermometers, psychrometers / psychrometric tables, and high voltage spark testing equipment,” Skey states.

Safety First

Safety played a big role during the project. According to Universal Blastco’s Safety Director, Chris Sicker, the safe execution of the project was the direct result of constant attention paid in the areas of fall protection, confined space access and control, respiratory protection, hazard communication, and abrasive blasting.

Vinyl ester resins contain styrene which, if not properly managed, poses a fire and respiratory danger. Standard PPE included steel toe boots, hard hats and safety glasses, fall protection protocols for work over 6 feet, and full- and half-face respiratory protection, including Survivair-supplied respirators and cartridges. The crew wore abrasive blasting hoods and Kevlar sleeves during surface prep. “CO2 monitors and Q-RAE and Q-RAE Plus brand four/five gas detection systems were used in a highly stressed and regimented air monitoring program conducted continuously during the project to insure both levels of respiration safety as well as flammability were properly dealt with,” says Sicker. A third-party rescue crew was hired for standby high-angle rescue requirements (over 500 foot elevations).

The project went smoothly and according to schedule thanks to the skilled and dedicated crew. And the implications are farther reaching than those of the average coatings project. Vandiver sums up the job, “The successful management of the exacting requirements for the successful performance of these systems is allowing the world’s largest engineering and construction firms to consider coatings as a real option for use on stainless steels in power plant systems exposed to high levels of abrasion and corrosion.” 

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