Refining Corrosion Protection In Ethanol Processing Plants
In spite of a sluggish economy, U.S. ethanol production continues to grow in order to meet requirement spelled out in the Renewable Fuels Standard (RFS), which mandates that 36 billion gallons per year (bgy) of fuel to be produced by renewable resources by the year 2022.
According to Renewable Fuels Association, the U.S. fuel ethanol industry has grown to a total annual production capacity of 13.6 billion gallons and an estimated 12.8 bgy of actual production. There are 201 ethanol plants operating in 27 states and 14 new plants or plant expansions underway. "New plant construction and expansions are estimated to add 1.2 billion gallons of annual production, bringing U.S. production capacity to 14.5 bgy and requiring nearly 5.2 billion bushels of corn," Iowa State University reported.
The corn dry-grind process is the most widely used method for generating fuel ethanol by fermentation of grain, a report from the U.S. Department of Agriculture, Agricultural Research Service observed. "Increasing demand for domestically produced fuel and changes in the regulations on fuel oxygenates have led to increased production of ethanol mainly by the dry-grind process," the report explained. "Fuel ethanol plants are being commissioned and constructed at an unprecedented rate based on this demand."
A recent expansion of the Archer Daniels Midland (ADM) corn dry-grind plant in Cedar Rapids, Iowa, included the use of advanced technology coatings to protect new auxiliary and support unit infrastructure against corrosion. "The project involved two steel tanks that were 60 feet in diameter and 40 feet high," Tnemec coating consultant Keith Kennett noted. "The tanks are used to store water for the plant's fire protection system."
The exterior of the tanks was prepared in accordance with SSPC SP-6/NACE No. 3 Commercial Blast Cleaning and primed with Series 90-97 Tneme-Zinc, an advanced technology, zinc-rich urethane primer with exceptional rust-inhibitive advantages."Even if there's some sort of physical impact with the tank, the primer will sacrifice itself and not allow any corrosion to undercut the coating system," Kennett observed.
The tanks received two finish coats of Series 1074 Endura-Shield II, an aliphatic acrylic polyurethane, which were spray- and roller-applied at 2.5 mils dry film thickness (DFT). Series 1074 is highly resistant to abrasion, wet conditions, corrosive fumes and exterior weathering. "Series 1074 provides a nice, gloss finish that will retain its aesthetic appearance for many years," Kennett shared. "ADM has always taken pride in its facilities and likes to maintain an attractive appearance."
The interior of the tanks was prepared in accordance with SSPC SP-10/NACE No. 2 Near-White Blast Cleaning and coated with Series N69 Hi-Build Epoxoline II, an advanced generation a polyamidoamine epoxy with superior resistance to abrasion and chemical exposure. "N69 was specified for its proven performance in water immersion service," Kennett said.
All of the coatings were specified by Pospisil Painting, Inc., in Cedar Rapids, Iowa, based on their user-friendly application. "Their crews were familiar with the products and knew what to expect," Kennett said. "The coatings performed as expected and enabled the application crews to get in and get out on schedule."
