The LANXESS Mfg Diphyl Range of Heat Transfer Fluids are synthetic based which are designed for use in high temperature range. These products which are based on very stable aromatic molecules allow for a wide range of application, from liquid at temperatures from –30to 330°C to pressurized liquid/vapour up to 400°C. The unique products can be used in an almost unlimited number of applications in the wood, metal, oil refinery, chemical, polymer and many other industries.
● Diphyl® Heat Transfer Fluid (Diphyl® HTF)– Diphyl® Heat Transfer Fluid for very high temperatures, pressure(less) application in liquid/vapour phase
● Diphyl® DT Heat Transfer Fluid (Diphyl® DT HTF)– Diphyl® DT Heat Transfer Fluid for low to medium temperatures, pressure(less) application in liquid phase
● Diphyl® THT Heat Transfer Fluid (Diphyl® THT HTF)– Diphyl® THT Heat Transfer Fluid for high temperatures, application in liquid phase
Selection Criteria for Heat Transfer Fluid:
An essential factor in the selection of a heat transfer medium is its thermal stability at the working temperature required for the process. The thermal stability determines the service life of the Heat Transfer Fluid and also influences the design of the heater and the heat users. Diphyl® provides the highest level of thermal stability of any of the HTFs currently on the market, having a maximum operating temperature of 400 °C. Diphyl® has the particular advantage that it can also be used in the vapour phase. This means that simple systems can be used to heat large and also complex plants, while maintaining an equal temperature at all points where heat transfer occurs.
Thermal Stability of Heat Transfer Fluid:
The thermal stability is an expression of the durability of an organic Heat Transfer Fluid when exposed to high temperatures. The determination of the thermal stability of fresh HTF is described in DIN 51528.
Every organic Heat Transfer Fluid undergoes thermal decomposition to a small degree above a certain temperature, i.e. is partially transformed into low-boiling, high-boiling and non-evaporable components. The decomposition rate increases exponentially in the upper temperature range. In this range, a temperature increase of 10K can be expected to double the rate of decomposition. The decomposition of a HTF is influenced by its chemical structure, purity and temperature, and also by plant specific conditions, such as the temperature profile and contamination. In practice, thermal decomposition becomes noticeable starting at roughly 50 K below the permissible feed temperature.
Aromatics such as the Diphyl® products have shown superior thermal stability compared to mineral HTF. The low-boiling components dissolved in the HTF reduce the flash point and increase the vapour pressure, which can lead to evaporation in the event of local pressure drops. Resultant products which have a higher boiling point or are non-evaporable can lead to an increase in the viscosity of the HTF and thus to deteriorating heat transfer and a growing pressure loss. As a result, the boundary layer temperature may increase due to a drop in the flow velocity.
Chemical Stability of Heat Transfer Fluid:
Above 100°C, organic Heat Transfer Fluid reacts exothermically with atmospheric oxygen to form decomposition products containing oxygen (including organic acids) and high-molecular condensation products.
These reaction products are thermally less stable than the non-oxidised and can lead to acceleration of the decomposition rate, as well as to an increase in viscosity. A rule of thumb states that the aging process accelerates exponentially at temperatures above 60°C and doubles for every 10 K increase in temperature. Certain materials (non-ferrous metals and their alloys) and contaminants (rust, water) act as catalysts and speed up the aging process even further. Oxygen and other gases are dissolved to a greater degree by cold Heat Transfer Medium than by warm ones.
Health and Safety
To date, no harmful effects resulting from the use of Diphyl® as a Heat Transfer Medium have been detected in the human organism. Food and drink must be protected against contamination with Diphyl®. Splashes of hot Diphyl® (>60°C) on the skin should be immediately and thoroughly cooled with cold water, in order to minimise the damage caused by scalding. Diphyl® vapour smells extremely unpleasant even in very low concentrations, so that it is unlikely that anyone would inhale it in excessive quantities. A protective mask with a filter (type A) should be worn when entering a room filled with Diphyl® vapour.
These are the minimum requirements to be observed by anyone working with organic liquids in the chemical industry. More detailed guidelines and information are included in the
corresponding safety data sheets.
These data sheets include detailed information on:
● the chemical properties of the Diphyl® HTF, toxicological and ecological aspects
● physical and safety-related properties, e.g. flash point and autoignition temperature
● transport
● technical and personal protective measures
● storage and handling
● procedures in the case of accidents
