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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The global heat transfer fluid (HTF) market is hot. By 2017 its value will reach $2.56 billion, a rise of almost $1 billion from 2011. So says market researcher MarketsandMarkets, Dallas,  in a new report.

Published on November 24, 2012, "Global Heat Transfer Fluid (Thermic Fluid/High Temperature/Synthetic Heat Transfer Fluids) Market — by Product Type (Mineral Oils, Silicone & Aromatics, PAG & Glycol Based Products & Others), Application & Geography — Forecasts to 2017" notes that Dow, ExxonMobil, Shell and Solutia (now part of Eastman Chemical) accounted for 76% of the market in 2011. It goes on to say that demand in the chemical industry for HTFs with greater thermal and oxidation stability will increase significantly over the next six years.

One such demand is coming from reaction cooling, a trend noted by Air Products, Allentown, Pa. "We are using liquid nitrogen (LIN) to cool HTFs as low as -90°C. There is even a trend now to go colder, even down to -120°C. This represents a challenge because it's difficult to get many HTFs to operate at this temperature," notes John Tremblay, technical manager, cryogenic applications, Basingstoke, U.K.

Such low temperatures cause viscosity problems with many traditional HTFs and thus require vendors to adjust their formulations accordingly. However, vendors often can't easily get down to the required temperatures in their own laboratories. In response, Air Products has built a test rig that evaluates the performance of different HTFs in a pilot-scale heat exchanger.

"It's rated at 10 kW at -90°C. We've tested five or six different fluids on it. There is a definite move away from methanol and other solvents to silicone fluids and other lower-flammability-risk fluids," says Tim Boland, research associate, cryogenics, Allentown.

"Companies that produce HTFs often want us to do testing for them. Also, it's important for us when we get a new enquiry from a manufacturer to be able to show that we can cool their HTFs without freezing them and causing all the associated process problems," adds Tremblay.

Although originally constructed in Allentown, the rig currently is operating at Air Products' technology center in Shanghai, China (Figure 1).

Users wanting a single HTF that can handle many different, often multi-step processes is another trend Air Products notices. "So, the pressure is on us to deliver LIN cooling that will achieve this and we have done a lot of testing on it," says Tremblay.

Customers scaling up from bench to pilot to full-scale production also are turning to Air Products. "Along the way they typically change cooling technology from flammable-solvent-type solutions, such as acetone/dry ice, to more production-friendly HTFs. They often need our expertise when it comes to choosing the best HTF for these scaleups," explains Boland.

A good example of this, he says, is when custom fine chemical houses want to extend their product lines but don't have the knowledge or experience to operate below their typical -20°C lowest temperature. Here, Air Products can offer support such as showing how to run reactors at much colder temperatures.

LIN itself offers a very attractive pricing strategy for many customers because it's a variable cost, for example when used by toll manufacturers, Tremblay contends. "LIN can also get to lower temperatures than many much more expensive mechanical refrigeration processes," he notes. LIN has further appeal, too. First, its associated plant is simple to operate and easy to maintain. Second, costs can be further offset by recycling and using it for other applications, such as inerting and blanketing.

In terms of the market, Air Products is seeing more companies who traditionally use refrigerants moving to HTFs and particularly to the more robust silicone oils.

"The market is moving from flammable HTFs to combustible HTFs to non-combustible HTFs. Concerns over health and safety and the environment are driving this, along with lower temperature processes," says Boland.

Tremblay believes future developments will involve smaller, more efficient plants capable of leaner processing: "The reaction kinetics here could get more volatile, generate more heat and therefore need more cooling."

For Boland, growing environmental awareness in Asia is important. "We are already seeing a much greater use of low temperature condensation technology in China, for example."

Meanwhile, in response to demand for HTFs suitable for higher temperatures, Paratherm, West Conshohocken, Pa., has added to its portfolio two new aromatic-based HTFs for closed-loop liquid-phase heating: Paratherm GLT for use up to 288°C and Paratherm HR, which is good to 343°C in fired heaters and 357°C in waste-heat-recovery and full convection heaters.

Increasing demand from the biomass fuel industry, which uses even higher temperatures in its processes, is prompting the company to work on other new HTF formulations.

At the other end of the temperature scale, Paratherm also is keeping busy. When Bedoukian Research, Danbury, Conn., a maker of aroma and flavor ingredients, needed to expand its product line, lower temperature processing became even more of a critical issue. "We were looking for a long time to find a thermal fluid that would do what we need it to do," says general manager Greg Pignone.

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