My best information at this time indicates this massive building was completed in 1955 at a cost of $19,000,000 and features a 637-foot stack. The plant was the first of its kind, utilizing a process invented and developed by the company to separate iron from the waste ore produced by mining nickel. The high grade iron that resulted from this proceass gave the company a new revenue stream and boosted the efficiency of their operation overall.
Three years later, CIL began an acid plant adjacent and the company purchased the plant from CIL in 1981.
The company began construction of a new, cleaner acid plant and closed this facility down on May 30, 1991.
Currently, while the building itself is doing precious little, the stack behind it has been connected to the still-operating plant a distance behind it.
Update March 15, 2018: Demolition has begun and is slated to be complete by the end of the year. See attached news article from CBC.