St. Lawrence Starch Co., Ltd. selected Ferralium® 255 to rebuild a distillation column that had failed by stress corrosion cracking at its Mississauga, Ontario plant.
The plant operates four distillation columns. A converted starch slurry from the fermenters is fed into the top of the towers; it contains about 10 volume-percent alcohol and 300-350 ppm of chlorides - the source of the stress corrosion cracking. Temperatures range from 150 to 230 degF, and the four columns have a capacity of 5 million imperial gallons of 193-proof vodka per year.
After the oldest column failed, corrosion engineers supplied St. Lawrence with a test rack of possible upgraded substitutes, and Ferralium® 255 was selected for the new column. Because it is more than twice as strong as Alloy 316L stainless steel, thinner sections could be used in the construction - an added incentive.
About 4T (9,000 lbs) of Ferralium® 255 were used by Dominion Welding and Fabricating, Ltd. in Agincourt, Ontario to make the new column, which stands nearly 60 ft high. The 54" diameter shell was rolled from 0.141" thick sheet, 48" x 170". Tray support rings were supplied as 1/4" to 1 1/2" abrasive-cut plate rolled to the 54" diameter. The handhole flanges were machined from 9" diameter bar stock, and the 2:1 semi-elliptical heads were spun. No problems were experienced in either fabrication or welding.
