Corrosion of the wash solvent column at the Fort Lewis, Washington, solvent-refined-coal pilot plant

Solvent Refined Coal (SRC) liquefaction pilot plants have demonstrated the feasibility of converting high-sulfur, high-ash coals into clean-burning fuels. Scaleup to commercial levels of production demands component reliability, which depends on materials performance. Corrosion has been troublesome in the fractionation area of the SRC pilot plants, particularly in the wash solvent column at the Fort Lewis, Washington, plant. To investigate the corrosion problem, activities at ORNL have included on-site metallographic examination, analyses of failed components and surveillance coupons, and laboratory experiments. The mechanism of corrosion is speculated to be the oxidation of iron and nickel to form a soluble iron compound leaving an insoluble nickel sulfide scale. A strong correlation is observed between temperature, corrosion rate, and the nickel content of the alloy. The exact cause of the corrosion is still under investigation but is suspected to include a combination of organic compounds and chlorine.