A Conversation for Metals, their Properties and Reactivity - a Beginners' Guide

Case Study: Tantalum (Woops!)

Post 1

Steve K.

As a young chemical engineer, I was assigned to investigate an alternate process for making a chemical. My employer, a major chemical manufacturer, was under fire for the current process, which had environmental problems. The new process also made a waste stream that was undesirable, but could be made acceptable by heating to high temperatures (and pressures to keep it liquid), destroying the objectionable chemical. The problem was that acid was produced in the destruction, so the combination of high temperature and acid would destroy most materials, even glass-lined metal, which my company had a LOT of.

After some research, I learned that tantalum, a very expensive metal, would handle the conditions. A supplier of tantalum, who had sold my company a boatload of the metal at another plant, gave me some tantalum tubing to conduct some tests, which I did. Avoiding the details, the process worked great, but after a while I made a mistake and plugged the 10' long, 1/8" diameter coiled tubing with salt, another byproduct. I could not get anything through the small tubing, including wire to ream it out, so I checked the melting points of the salt and the tantalum tubing, the former being much lower than the latter.

Plan: Run the plugged tube through a small, very high temperature furnace, at a temperature between the melting point of the salt and the metal, blow some nitrogen through and push the molten salt out.

The plan was pretty good, and I did it. But I missed one detail. Anybody?

Case Study: Tantalum (Woops!)

Post 2


What DOES happen when Tantalum reacts with nitrogen?

Or did our old friend Charles' Law (volume of a gas is proportional to temperature) blow up in your face? smiley - run

Case Study: Tantalum (Woops!)

Post 3

Mu Beta

Yeah. My money's on tantalum nitride. Which won't remain in a tubular shape for long. smiley - biggrin

Once in a while it'd be nice to hear of a chemical engineer who doesn't blow things up on a regular basis. smiley - winkeye


Case Study: Tantalum (Woops!)

Post 4

Steve K.

I don't think it was the nitrogen, but the oxygen (air) outside the tubing. In any case, all that was left inside the furnace was powder. Maybe if I had blanketed the furnace with nitrogen ...

Fortunately, I had enough data before the powdering to sell the process, but the whole project got cancelled for reasons related to raw material supply. In retrospect, I think it was an effort to get the EPA off the back of the old plant, which would have shut down with everybody getting laid off.

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