ASD Heat Transfer Salts

Posted on May 07, 2024

Heat is the colloquial term used to describe thermal energy. Heat transfer mediums are used in specially constructed plants to exchange energy, in other words for both heating and cooling, in various chemical processes.

Heat can be transferred in three different ways:

• Without direct contact, in other words by heat radiation (for example, the sun)
• By direct contact between materials, in other words by conduction, during which particles richer in energy release translational, rotational and vibrational energy in surges to colder particles, and
• By convection (heat flow) with liquids and gases.

Salt Radiation & Convection Applications

The high thermal capacity and thermal conductivity of molten salts make them very suitable for transferring heat in large-scale chemical plants, for example in the synthesis of Melamine, the production of aluminium oxide, and in power stations.

Due to the heavy increase in pressure at temperatures above 200°C, water and steam are very uneconomical in many cases and technically difficult to control. Organic liquids can only be used to a maximum of approx. 380°C because of their thermal instability.

If chemical reactions have to be kept at even higher temperatures, and if hundreds of tons of a substance have to be produced in very large reactors daily, other methods of transferring the heat have to be used. Therefore, the energy required is produced elsewhere in heat generators or “heaters” by burning natural gas, coal or crude oil. and transporting it into the synthesis reactor by a special heat transfer medium. Molten heat transfer salts are excellent for this purpose. Mixes of alkali nitrite and alkali nitrate, which do not require pressure, are used between temperatures of 180°C and 450°C. Special salts can even be used up to 650°C.

Heat Transfer

The advantages of heat transfer salts lie in their relatively low melting range of 138 – 142°C, in their specific heat which is especially suitable for transferring heat, heat transmission, and viscosity.

Plants operated by heat transfer salts are mainly used in process technology. Heat transfer salts cool in exothermic reactions or heat up in, for example, in lye concentration plants. Furthermore, they transfer the heat required for the fusing process in the dissociation of bauxite and they also serve to heat fluidized bed reactors. In thermal solar power stations the heat transfer salt melt transfers the heat for producing the steam. A further field of application is the drying of gases. The latest field of research is the carbonate fuel cell in which hydrogen or other gaseous fuels are oxidized in alkali carbonate melts. This process gives high performance electrical energy.

Properties of ASD Heat Transfer Salts

The finished product of prime quality is manufactured in our fully automated production plant. To avoid objectionable impurities even within ppm range, only specially selected raw materials are used, which, in particular cases, have to expel,,food grade” quality.

With our quality management system certified according to DIN ISO 9001/2008 and with extensive physical and chemical studies, at any time we ensure excellent and constant quality of our heat transfer salts at any production level.

ASD Heat Transfer Salts offer Advantages

• Excellent heat transfer properties within the working temperature range of 180-550°C. Under the prerequisite of suitable plant materials, blanketing with nitrogen and inspections of the ageing state of the melt at regular intervals, our high purity products can be even used in a temperature range around 550°C.
• Low melting point (~142°C) by using quasi-eutectic composition
• Best possible chemical stability at operating temperature
• Minimum to no foam formation during the melting-down of fresh salt
• Initial melting down with steam (6 bar/usual pressure) possible
• Regenerable with Durferrit ASD REG
• Pressureless operation of the melt despite high temperatures

Fields of Application

• Heating of chemical reactors for endothermic processes
  For instance, the commercial syntheses in packed-bed tubular reactors for heterogeneous gas phase reactions.
• Cooling of exothermal reactions for chemical syntheses processes
  The removed heat can be recovered.
• Heat Storage in CPS Solar Power Plants
  for the time-delayed generation of electricity
• Drying of Gases
• Heat Recovery
• General Heat Transfer in Process Engineering

Examples of Use

• Production of phthalic acid (PAA) and maleic acid anhydride (MAA)
• Production of acrylic acid as basic material for acrylates, coloring and super absorber materials
• Production of methylmethacrylates as basic material for flat screens (sheets), acrylic glass and adhesives
• Melamine syntheses
• Hydrogenation and dehydrogenation of hydrocarbons
• Polymerisation reactions