Heat Transfer Fluids Aim For Extremes

Makers respond to demands to run processes at lower and higher temperatures.

By Seán Ottewell, Editor at Large

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Bedoukian uses a range of 50–200-gallon reactors to manufacture its products and needed cooling down to -60°C. The company chose Paratherm CR HTF.

"Many fluids used for cooling thicken or even freeze up below a certain point, usually at -50°C to -60°C. Paratherm CR doesn't do that. It allowed us to use colder temperatures," notes Pignone.

Since the changeover, Bedoukian has achieved higher yields and cut production time by more than 50% for batches. "We are able to run some of our cooled chemical reactions twice as fast now, and run at much lower temperatures than before with better heat transfer. This opens the door for us to produce custom syntheses that we couldn't have attempted before," he adds.

Customers are asking for more than just fluids suitable for extended temperatures, explains Paratherm's technical director Jim Oetinger. "There has been a trend for more after-sales support over the last eight or nine years and this has really accelerated over the last couple of years — mainly because maintenance has been skinned to the bone. A lot of expertise has been lost, particularly on the older equipment. Much of our support today is to do with planned maintenance; because the in-house experience has gone, the queries and requests are coming back to suppliers."

As part of its service package, Paratherm always has included an annual HTF test for customers. For many this simply involved sending in a sample of their HTFs. Today, the company is getting many more "what if?" type calls. "The audience is a lot more receptive to what we have always been saying about maintenance — that it's better to have a quarter of a day of maintenance every year than weeks of outage through breakdown. This equipment should run for years, not months," notes Oetinger.

At the same time, insurance companies are taking a tougher stance on fire issues. "We do hear about fires from time to time and there have been more of them recently. But the National Fire Protection Association (NFPA), Quincy, Mass., has put out a recommended practice for fluid heaters (NFPA 87), so clearly this problem is being recognized."

NFPA 87 covers, e.g., thermal fluid heaters and process fluid heaters in which the fluid is flowing, under pressure, and is indirectly heated.

"Up to now there have really been no national standards for fluid heaters, with people relying on information from the suppliers. Now the insurance companies are looking at the NFPA guidance and requiring users to meet the standard," he adds.

Service also plays a key role at Solutia, St. Louis, Mo., now a subsidiary of Eastman Chemical, Kingsport, Tenn. The company's Total Lifecycle Care (TLC) program long has been a cornerstone of its Therminol HTF business.

"The TLC program offers a suite of services to support the use of Therminol heat transfer fluids throughout their entire lifecycle, from design to startup to operation and maintenance," says Ravi Prakash, global business director.

To emphasize the importance of such services, Prakash points to a recent project success in Brazil at Resitol Indústria Química, Palmeira. The company is a major producer of crude sterol from tall oil extracted from byproducts of pulp and paper production.

Resitol uses a high-vacuum molecular distillation unit to extract sterol from the tall oil. The company relies on a secondary coolant fluid (SCF) rather than costlier direct cooling to achieve -70°C, a temperature necessary to maximize separation efficiency and reduce product degradation.

Following two leaks of SCF from its heat transfer system and the inability of its fluid supplier to replenish the missing material in a timely manner, Resitol contacted the local Solutia team. After discussions between the team and Resitol engineers, the existing silicone-based fluid was switched to Therminol LT, a synthetic aromatic HTF that can be used in both the liquid and vapor phase between -70°C and 315°C.

"Our local Solutia Therminol engineers provided us with comprehensive guidance for draining our old fluid, flushing the system and refilling with the new Therminol LT. They also provided on-site support as needed throughout the process until the system was started up. We have never received this level of expert support with our previous supplier. They also have local stock in case of emergencies," notes Resitol maintenance and production manager Charles Souza.

Solutia boasts a 16-strong family of synthetic fluids for indirect heating or cooling over a broad range of temperatures and applications. At one end of the temperature scale is Therminol VLT, which is aimed at single-fluid heating and cooling systems between -115°C and 175°C. At the other end is Therminol VP-1, a synthetic HTF for vapor phase systems from 257°C to 400°C, or liquid phase systems from 12°C to 400°C.

"Our flagship products, Therminol 55, Therminol 66 and Therminol VP-1, serve diverse and dynamic end markets that change from year to year. Two markets that are strong for us now are the oil and gas market and the concentrating solar power market," adds Prakash.


Seán Ottewell is Chemical Processing's Editor at Large. You can e-mail him at sottewell@putman.net.


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