1 Synthetic thermal oil can be divided into the following types:
1) benzene ring type heat transfer oil
This type of heat-conducting oil is a compound containing a benzene molecular ring with a paraffinic branch chain, and is a substance that combines a short-branched alkane group with a benzene ring. Its boiling point is 170 ~ 180 ℃, and its freezing point is below -80 ℃, so it can be used as an antifreeze. The characteristics of this kind of material are that it will not easily precipitate within the applicable range, and the isopropyl-linked compounds are even more.
2) Alkyl naphthalene type heat transfer oil
The structure of this type of heat transfer oil is a compound linked to an alkane branch on the benzene ring molecule. The side chains to which it is attached are generally methyl, dimethyl, isopropyl, etc. The type and number of the side chains attached to it determine the properties of the compound. Alkyl naphthalenes whose side chain is mono-linked to methyl can be applied to gas-phase heating systems in the range of 240 ~ 280 ° C.
3) Alkyl biphenyl heat transfer oil
This type of heat transfer oil is a type of compound with an alkyl branch attached to a biphenyl ring. It is composed of a short-chain alkyl group and a biphenyl ring. The type and number of the alkyl group determine its properties. The larger the number of alkane groups, the worse the thermal stability. In this kind of product, Xiaoyang heat-conducting oil synthesized from iso-iso, iso-, iso-isomer and biphenyl has the best quality, its boiling point is less than 330 ° C, and its thermal stability is also the best. Is a reasonable product for use in the range of 300 ~ 340 ℃.
4) Diphenyl and diphenyl ether low melting mixture type heat transfer oil
This product has the best heat resistance among organic heat carriers because it does not have an alkane-based side chain on the benzene ring. The low-melting mixture of such products with a freezing point (12.3 ° C), at normal temperature, has a boiling temperature in the range of 256 ~ 258 ° C, which is more economical to use. This is because the melting points of both substances are higher (biphenyl is <71 ° C, diphenyl ether <28 ° C). In the process of evaporation of the low-melting mixture, no concentration of any component occurs, and the liquid properties are not changed. Due to the combination of ether substances in diphenyl ether, long-term use at high temperature (350 ° C) will produce phenolic substances. This substance has low corrosivity and has a certain corrosive effect on carbon steel, etc., with moisture.
2 Mineral-type thermal oil
Mineral heat-conducting oil is a product of a certain distillation range in petroleum refining process, and the important components vary with the composition of the base oil. Most are a mixture of long-chain alkanes and naphthenes.