A Cleaner, Cheaper Route to Titanium
Posted by commendatori on August 2, 2008
Titanium is as strong as steel, but weighs only about 60 percent as much. It’s also highly resistant to corrosion, and handles temperature extremes well. So, not surprisingly, the aerospace industry wants to use much more of it in the next generation of planes, making them lighter and reducing fuel costs.
But there’s a hitch: at around $40 per pound today, titanium is expensive — and the price keeps going up.
Now a startup, Avanti Metal, using technology developed at MIT, hopes to commercialize a process that drastically reduces the cost of producing titanium, making more of it available for large, lighter-weight airplanes. The process, developed by MIT chemist Donald Sadoway, applies an environmentally benign, direct electrolysis method to make the metal.
Titanium is naturally abundant. But processing titanium oxide found in the ground to make a usable metal is slow and produces toxic waste. “The price of titanium has gone through the roof,” says Corby Anderson, director of the Center for Advanced Mineral and Metallurgical Processing at the University of Montana. “It’s double what it was this time last year — and last year it was pretty high.”
Jeffrey Sabados, president of the four-person Avanti, estimates that, based on production plans published by Boeing and Airbus, there’ll be a 30,000-ton shortage of titanium by 2010. He claims that Avanti’s process for refining titanium could slash costs to about $3 per pound. Then, if the metal then sells for even $25 per pound, an estimate he calls conservative, it’s a huge potential profit.
Since the early 1950s, titanium has been produced through the Kroll process. Manufacturers first make titanium chloride, which gets processed into titanium tetrachloride, and then mixed with magnesium, which draws out the titanium and produces chlorine gas. The result is a porous material, contaminated with magnesium salts, which requires further processing to remove the salts and make it usable for manufacturing. The process is so toxic that it’s difficult to get the permits needed to build a new plant in order to expand production.
Sadoway says their process is much greener. They mix titanium oxide with other oxides, such as magnesium oxide or calcium oxide; then they heat the mixture to about 1,700 degrees Celsius. This produces a bath of molten oxides, through which an electric current can be run. The electricity produces electrolysis, breaking the bond between the titanium and oxygen atoms, and the heavier titanium sinks. The result is a pool of liquid titanium at the bottom and oxygen bubbling out the top. The other molten oxides remain in place, acting as the electrolyte when more titanium oxide is added. “You just keep making more and more and more metal,” Sadoway says.
So far, though, Sadoway and colleagues have made only a few grams with an experimental reactor cell. It’s hard for the small, ceramic device to sustain the high temperature needed. Avanti is hoping to raise enough money from investors to build a larger prototype to actually produce a pool of liquid titanium. Sadoway hopes to begin putting together a team of scientists by August and to build working titanium smelters by August 2008.
Nabil Elkouh, president of Erigo Technologies, a consulting firm that puts together deals between researchers and investors, and who’s an advisor to Avanti, cautions that their projection of producing titanium at one-tenth of the current cost, may be optimistic at this point. “They may have something great, but it may take four years,” he says. “It may not ever be one-tenth the cost — but what if it were half the cost? That’d still be great.”
Anderson says plenty of people, from university researchers to companies like DuPont, are working on better ways to produce titanium. He hopes to visit MIT this summer to look at Sadoway’s process and see how well it works.