Tantalizing tale

It takes its name from Greek mythology and its ability to withstand corrosive media is itself legendary. Now Alfa Laval is using the exotic metal tantalum in a new and cutting-edge range of heat exchangers.

DATE 2017-07-13 AUTHOR Ulf Wiman

I put the heat exchanger on the table and said, ‘Let’s sign a confidentiality agreement right now.’” Mats Nilsson, R&D Manager at Alfa Laval’s product centre compact heat exchangers, is recalling his first meeting with the external partner that Alfa Laval has cooperated with to develop its new and unique tantalum heat exchanger range.

Responsible for technology scouting, Nilsson had come across a small Danish company that used the metal tantalum to treat various products. “I immediately thought of our compact heat exchangers,” he says. “They had done some tests with other heat exchangers, but lacked the product knowledge to succeed. We could
provide that.”

Tantalum may be a well-kept secret, but it is probably right in front of you – in your mobile phone. It is mainly used for electronic components, but given its properties, it is finding increased use in other industries. “It is perfectly suited to fine and speciality chemicals companies that heat exchange hot, corrosive media, for example in recovery and dilution of sulphuric acid, agrochemical and flow battery applications,” says Market Manager Anna Ljungqvist.

Storing electricity is a great challenge. Flow batteries may play an important part in the future, using wind and sun energy to load chemical batteries. These chemicals are often aggressive acids, which makes tantalum heat exchangers a perfect fit.

Tantalum is a rare, very costly metal, whose melting point is exceeded only by that of tungsten, rhenium, osmium and carbon. The new heat exchangers only use a 50μm thin layer (the thickness of hair), which is metallurgically bonded to all steel surfaces that come in contact with corrosive media. Ljungqvist says: “It is enough to give the heat exchanger its characteristics, and makes it a cost-effective solution.” 

The thin layer says a lot about the properties of tantalum. Still, post-production testing is crucial: an uncovered spot of just one square millimetre would lead to a heat exchanger corroding in a matter of hours. Alfa Laval’s new tantalum range offers end users robust and compact high-performance heat exchangers that provide long lifetime, minimal maintenance and low installation costs for applications using hot strong acids. There are currently some 20 Alfa Laval tantalum heat exchangers installed in assorted processes around the world.

One is at an American speciality chemicals manufacturer that previously used a three-metre-long graphite block heat exchanger to handle hot sulphuric acid. Once a year the heat exchanger had to be hoisted down from its fourth-floor position, opened and repaired – a costly and timeconsuming process. “When they received our 30cm-high tantalum heat exchanger they thought that we must have miscalculated,” smiles Ljungqvist. “How could it possibly be up to the task? But now all the maintenance required is a weekly hot water flushing, which is performed in place.”

It's not only customers’ jaws that have dropped. “I have been in the business for 30 years, but that this worked out so well surprised even me,” says Nilsson, who stresses that Alfa Laval R&D is constantly on the lookout for new technologies and continually visits customers to learn more about their business challenges. There are some 25 development projects on-going at any given time.

He concludes: “It is key that we understand new technologies and how they can lead to innovative solutions that benefit our customers.”

 

Tantalum in brief

  • Symbol: Ta
  • Atomic number: 73
  • Element category: transition metal
  • Melting point: 2,996 °C
  • Boiling point: 5,425 °C
  • Density: 16,654 kg/m³
  • Properties: blue-grey, dense, ductile, very hard, and at temperatures below 150°C almost completely immune to attack by aggressive acids
  • Application areas: electronic components and in demanding applications such as jet engine components, chemical process equipment, nuclear reactors and implants