Seawater and Industrial Outlook for Titanium “Promising” According to TITANIUM EUROPE 2013 Experts
Industrial use of titanium products has been on the increase since that market became a significant consumer of the metal some 40 years ago. This is due, fundamentally, to titanium’s unique set of metallurgical attributes, including high strength, low density and, most important, resistance to corrosion in multiple process environments including mineral acids, organic acids and seawater at temperatures up to 130⁰ Celsius for CP alloys.
Titanium plate heat exchangers, welded and seamless tubes, welded and seamless pipe, autoclaves, pressure vessels and other components are now standard in power generation, desalination, chemical processing, and many other industries. Rob Henson, Manager of Business Development for Uniti Titanium™, outlined this state of titanium in industrial applications, focusing on seawater service, as host of the Industrial Panel at Titanium Europe 2013. The recent event was sponsored by the International Titanium Association. Uniti, a joint venture of VSMPO of Russia and Allegheny Technologies Incorporated (ATI) of the US, manufactures titanium mill products for industrial, automotive and consumer markets. Prior to the forum, Henson explains the competitive advantages titanium has gained in the past two years over copper-nickel, which has been the historical workhorse material in seawater.
“We’ve crossed the point where titanium is more economical that copper-nickel when strength and density are considered. Copper-nickel prices are continuing to rise, due to demand, a declining mine grade and the increasing cost of energy to produce those minerals.” Titanium, in contrast, “is very abundant in nature, and is seeing expanded global production and enhanced availability.” Titanium offers other advantages. Henson says that installed cost can be less than with copper-nickel.
“Copper-nickel is half the strength of titanium and twice the density. With titanium, you can buy a much thinner wall tube because of the strength and also buy a lot less pounds because of the low density. Engineers have to make sure they design for the attributes of titanium and when they do the installed cost will be less.” In addition, because titanium is resistant to erosion corrosion, microbial influenced corrosion and crevice corrosion in seawater, “we have a demonstrated life expectancy in the power generation industry that’s proven to be 40-plus years.” Power generation is one of the largest industrial markets for titanium, followed by desalination plants, “that have been operating for more than 30 years without corrosion problems.” In fact, applications for seawater are the fastest growing industrial segment for titanium, states Henson. “It’s fair to say any process environment that uses seawater, or brackish or wastewater is an opportunity for titanium.”
A potential new seawater application for the metal, in a process that can convert the temperature differential between surface and deep water into electricity, was discussed at the conference by Thierry Millot, Senior Expert Material, DCNS. The company is a French naval defense firm with a 20-year history using titanium tubes in seawater loops and heat exchangers on submarines. Millot explains that the heart of this OTEC (Ocean Thermal Energy Conversion) technology relies on a high capacity seawater/ammonia tube heat exchanger with very long tubes.
“Titanium grade 2 appears as one of the best candidate materials for welded tubes considering its lower maintenance cost and longer life expectancy in a corrosive environment,” he says. Millot also outlined a longer-term DCNS project, FLEXBLUE, a civil nuclear power plant that lies on the sea bed and could supply electricity to large cities close to shore. It capitalizes on the company’s experience designing nuclear submarine heaters. He says “titanium is being considered for heat exchangers, secondary loop condensers and piping systems due to its excellent and wellknown behavior in sea water.” The use of titanium for tubes, tube sheets, castings and forgings may also be potentially significant. Stephane Pauly, Business Development Manager, Nobleclad, points out similar maintenance and lifecycle cost advantages for titanium clad steel, in which explosive welding joins a corrosion-resistant titanium alloy to lower-cost steel for pressure containment.
Nobelclad, a business segment of Dynamic Materials Corporation, started as an explosion metal forming business in the late 1960s and explosion welding remains its core business today. For the mineral industry, titanium clad is used in autoclaves for pressure acid leaching of nickel and cobalt ore, as it is a more durable and reliable choice than non-metallic linings. “If you look from a long-term operating view at such equipment, because titanium clad requires no maintenance, it is a cost-effective solution,” according to Pauly. It also has proven performance records in heavy, high-pressure reactors and columns used in PTA manufacture. The third largest application for titanium clad is in heat exchangers. “Using explosives to weld, we are able to make very specialized and precise components like the tube sheets used with highly corrosive fluids,” he states. “This precision and reliability also apply to nuclear components. The nuclear industry is healthy in Europe, so that is a market where we are on the positive slope in terms of revenue.”
Explosive welding can also be used to weld titanium to other metal. Where titanium is conventionally welded using TIG or MIG processes, Pauly explains, “if you want to join, say aluminum and titanium for structural applications, there are not many technologies to do that. Explosive welding is one those.” As an expert in cladding technology, Nobelclad also offers the flexibility to explosion weld metal from the size of a book to 30 square meters. For the future, Pauly says Nobelclad is “working hard on new products, new developments in the processing industry. We’re working on R&D of new, lower cost titanium grades that have not been used in the past.” Overall, the message of the industrial experts at Titanium Europe 2013 was bullish for the metal over the next decade. Economic growth, population growth and infrastructure development should drive expanded use of titanium in seawater and other industrial applications.