CS258284B1 - Heat-carrying liquid - Google Patents

Abstract

Heat transfer fluids are used for indirect heating, i.e. for transferring heat from a heat source to a consumer. They must be sufficiently thermally stable, must not decompose at higher temperatures or form compounds with higher molecular weight through polycondensation reactions, and must have a minimum vapor pressure in the temperature range used. The preparation of heat transfer fluids known to date is disproportionately demanding in terms of raw material and energy costs. The heat transfer fluid according to the invention consists of up to 26 parts by weight of 1,1-diphenylethane, 5 to 26 parts by weight of 3-ethyl-1,1-diphenylethane, 5 to 10 parts by weight of 4-ethyl-1,1-diphenylethane, 10 to 35 parts by weight of diethyl-1,1-diphenylethane isomers, up to 1.8 parts by weight of ethylbiphenyl isomers, up to 0.5 parts by weight of pentaethylbenzene, up to 1.5 parts by weight of tetraethylbenzene isomers, 5 to 30 parts by weight of other alkyl homologues of 1,1-diphenylethane with a distillation range of 270 to 395 °C, 15 to 25 parts by weight of ethylene and propylene oligomers, this component being characterized by a boiling point range of 320 to 365 °C, a kinematic viscosity at +20 °C 9.5 to .12.7 mm^.s"·!, specific gravity 977 to 985 kg/nH and a freezing point below -40 °C. Another component is up to 1 part by weight of an additive with anti-corrosion and antioxidant effect.

Description

The invention relates to a heat transfer fluid based on 1,1-diphenylethane and its mono-, di-, or polyethyl homologues.

A heat transfer fluid is a fluid used for indirect heating, i.e. for transferring heat from a heat source to a consumer. The fluid must meet significant quality requirements. It must be sufficiently thermally stable, must not decompose at higher temperatures and at the same time form compounds with higher molecular weight through polycondensation reactions, which can significantly increase the viscosity of the heat transfer fluid during use. Suitable viscosity is another quality parameter, as it is important that heat transfer takes place with minimal consumption of mechanical energy, necessary to transport the heated fluid from the heat source to the consumer.

In order to avoid heat transfer at higher temperatures being carried out under pressure, which subsequently places increased demands on the design of the heat transfer system, it is necessary for the heat transfer fluid to have a minimum vapor pressure in the temperature range used. A low freezing point is also desirable, which brings advantages when starting up the heat transfer system and when using the fluid for both heating and cooling. An important factor in evaluating the complex properties of these fluids is their effect on the corrosion of metal materials, which affects the possibility and scope of their use in the design of heat transfer systems.

Heat transfer fluids must also be oxidation and hydrolysis stable and have a service life of at least 10,000 operating hours. Last but not least, other requirements are placed on this type of fluid: economy, guaranteeing maximum safety, reliable heat transfer throughout the system, easy regulation within a narrow range, minimal toxicity and easy biodegradability in the environment. So far, the most commonly used eutectic mixture of biphenyl with diphenyl oxide, solidifying at a temperature of around 32 °C, has been used for heat transfer.

Another group of heat transfer fluids used are Delotherms with the following designations:

AP /mixture of isomeric mono- and diisopropylbiphenyls usable up to a maximum temperature of 220 °C/,

AH /mixture of chlorine derivatives and isopropyl homologues of biphenyl/, DH /average composition corresponds to trichloro derivative of biphenyl, usable up to a maximum temperature of 300 °C/ and DK /tetrachloro derivative of biphenyl usable up to a maximum temperature of 320 °C/.

The use of Delotherms based on polychlorinated biphenyls is particularly suitable in cases where the heat transfer fluid must be non-flammable. However, their disadvantage is their considerable toxicity. Delotherms based on a mixture of mono- and diisopropyl biphenyls, produced according to Czechoslovak AO 140 977 and 173 158, are characterized by a high boiling point /approx. 300 °C at 98.06 kPa/, a low freezing point /approx. -45 °C/ and high thermal stability. However, they do not have the required resistance to oxidation that polychlorinated biphenyls have.

The liquid is also flammable and therefore unsuitable for use in operations with a risk of fire. A common disadvantage of the above-mentioned biphenyl-based heat transfer fluids is the thermal dimerization of benzene. Heat transfer fluids based on distillation fractions from petroleum, especially aromatic-naphthenic fractions, and synthetic products Dubotherm /based on isomeric didodecylbenzenes/ and Slovtherm, which are chemically similar to them, are also known.

The disadvantages of these fluids lie mainly in their low resistance to elevated temperatures and oxidation. Other heat transfer fluids used mainly abroad are Santotherm FR series (polychlorinated biphenyls), Santotherm 77 (aromatic ether), Santotherm 130 and 190 (based on moisture-sensitive organosilicates), manufactured by Monsanto, Gilothermy TH (partially hydrogenated polyphenyls), ALD (mixture of alkylated biphenyls) DO, D 12, Pa RD,

ON, OMP and OD manufactured by Rhone Poulene, Marlotherm S /mixture of isomeric dibenzylbenzenes usable up to a temperature of approximately 350 °C/ and Marlotherm L /based on diphenylmethane/, manufactured by Httls.

All of the aforementioned heat transfer fluids meet most of the quality parameters, the common disadvantage of which is the high production requirements - both in terms of raw materials and energy.

The heat transfer fluid according to the invention eliminates the aforementioned disadvantages. This heat transfer fluid consists of up to 26 parts by weight of 1,1-diphenylethane, 5 to 26 parts by weight of 3-ethyl-1,1-diphenylethane, 5 to 10 parts by weight of 4-ethyl-1,1-diphenylethane, 10 to 35 parts by weight of diethyl-1,1-diphenylethane isomers, up to 1.8 parts by weight of ethylbiphenyl isomers, up to 0.5 parts by weight of pentaethylbenzene, up to 1.5 parts by weight of tetraethylbenzene isomers, up to 30 parts by weight of other alkyl homologues of 1,1-diphenylethane with distillation ranges of 270 to 395 °C, 15 to 25 parts by weight of ethylene and propylene oligomers, this component being characterized by a boiling point range of 320 to 365 °C, a kinematic viscosity at +20 °C of 9.5 to 12.7 mm ³ .with a specific gravity of 977 to 985 kg/m ³ and a freezing point below -40 °C.

Another component is up to 1 part by weight of an additive with anti-corrosion and antioxidant effects.

The liquid according to the invention has a sufficiently low freezing point below -50 °C, so that it can be used for both cooling and heating. Its advantage is also low viscosity, e.g. at -20 °C 2 -1 does not exceed 96 mm .s , which predetermines its use in devices operating outside operational buildings in the winter. This property also determines the good startability of the device during prolonged shutdown in winter and summer. Its thermal and oxidative stability is comparable and in some cases even higher than that of previously known heat transfer fluids with the exception of polychlorinated biphenyls. Its main advantage, however, is the fact that, unlike the energy- and technologically demanding production of biphenyl-based liquids, it is obtained by a simple distillation process during the processing of higher-boiling residues from the production of ethylbenzene by the alkylation method.

The practical composition of the heat transfer fluid according to the invention and its properties are shown in the following examples.

Example 1

A mixture of aromatic hydrocarbons with a boiling point range at atmospheric pressure of 265 to 320 °C and the composition: 26.0 parts by weight of 1,1-diphenylethane,

25.6 parts by weight of 3-ethyl-1,1-diphenylethane, 11.1 parts by weight of 4-ethyl-1,1-diphenylethane, 0.7 parts by weight of 2-ethylbiphenyl, 0.4 parts by weight of 3-ethylbiphenyl, 0.5 parts by weight of 4-ethylbiphenyl, 13.3 parts by weight of isomers of diethyl-1,1-diphenylethane, 0.2 parts by weight of oligomers of ethylene and propylene. The liquid is further defined by the following physical properties: refractive index at 20 °C 1.551 7, specific gravity $72 kg.m ³ , flash point 139 °C, kinematic viscosity at 20 °C 6.579 mm ³ .s ³ , pour point below -50 °C, sediment in n-hexane 4.10 % and distillation curve given in Table I. Other properties of this substance, by which the quality of the heat transfer fluid is usually assessed, are given in Table II.

To improve some physical and chemical properties, a liquid is described with commercial antioxidants, anti-corrosion or detergent-dispersant additives in an amount of 1 part by weight, which does not affect the numerical values of the parameters mentioned above. The influence of these

additives on properties is also given in Table II. Table I Distillation curve heat transfer fluids extracted vol. % start 10 ‘ 20 30 40 50 60 70 80 90 95 temperature °C 276 285 286 288 289 291 294 298 301 309 319

Example 2

A mixture of aromatic hydrocarbons with a boiling point range of 295 to 320 °C is used as the heat transfer fluid, with the following composition: 4.3 parts by weight of 1,1-diphenylethane, 0.2 parts by weight of pentaethylbenzene, 0.4 parts by weight of 3-ethylbiphenyl, 0.4 parts by weight of 4-ethylbiphenyl,

22.7 parts by weight of 3-ethyl-1,1-diphenylethane, 14.2 parts by weight of 4-ethyl-1,1-diphenylethane, 34 parts by weight of isomers of diethyl-1,1-diphenylethane, 9.7 parts by weight of

AND

Table II

Oxidation stability tests of heat transfer fluid Acid number Kinematic viscosity

Additive quantity (wt. part) Cu plate loss appearance (mg) (mg :KOH/ή) change /mm 2. 0 h . with ¹ ) at 50 °C Evaporation rate % Settlements deposition 0 h 182.5 h 182.5 h change none 0.6 intact . 0.03 0.61 0.58 4.12 5.30 28.6 2.51 no Multadie 1 54.1 red- brown 0.45 0.87 0.42 4.24 6.17 45.5 3.75 yes Antioxidant K4 1 0.4 intact 0.05 0.55 0.50 4.27 5.15 20.6 3.20 no Hitec E-542 1. 0.4 intact 0.08 0.86 0.78 4.43 5.23 18.1 2.98 no Santolube BX 0.3 intact 0.11 0.82 0.71 4.40 5.30 20.4 3.14 no

parts of other alkyl homologues of 1,1-diphenylethane with a boiling point range of 277 to 333 °C and 14.1 parts by weight of oligomers of ethylene and propylene with a distillation curve shown in Table I. The liquid is further defined as follows: refractive index at 20 °C 1.550 9, flash point 158 °C, kinematic viscosity at 20 °C 8.80 mm ² .s ^-1 , specific gravity 973 kg.m ³ , freezing point below -50 °C, sediments in n-hexane 6.9.10 % by weight distillation curve - see Table III.

Table III

Distillation curve of heat transfer fluid vol ^GS % ^start - ^{10 20 30 40 50 60 70 80 90 95} tgplota 277 296 299 300 301 303' 305 308 311 319 333

The results of the oxidation stability tests of this heat transfer fluid alone and added with 1 part by weight of the substances listed in Table II are identical to the results in this table with the exception of the kinematic viscosity at 50 °C, which is 3.8 mm ² .s ^-1 before and 4.6 mm ² .s ^-1 after the oxidation stability test.

Example 3 — 3

The heat transfer fluid is defined by the following properties: specific gravity 990 kg.m, refractive index at 20 °C 1.574 1, kinematic viscosity at 20 °C 29.65 mm ² .s ³ , flash point 162 °C, freezing point -40 °C. Its composition is as follows: 4.9 parts by weight of 3-ethyl-1,1-diphenylethane, 4.7 parts by weight of 4-ethyl-1,1-diphenylethane, 35 parts by weight of the isomers diethyl-1,1-diphenylethane, isopropyl-1,1-diphenylethane and isopropylethyl-1,1-diphenylethane, 3.6 parts by weight of 3- and 4-(1-phenylethyl)-1,1-diphenylethane, 26.8 parts by weight of other alkyl homologues of 1,1-diphenylethane with a boiling range of 300 to 385 °C and 25 parts by weight of ethylene and propylene oligomers with a distillation curve shown in Table IV.

Table IV

Distillation curve of heat transfer fluid

extracted vol. % start 10 20 30 40 50 60 70 80 90 95 geplot 300 317 324 330 335 341 347 355 368 379 385 Results exams oxidative stability with this liquid are listed in Table V

Example 4

The heat transfer fluid is defined by the following properties: specific gravity 974 kg.m, refractive index at 20 °C 1.553 2, kinematic viscosity at 20 °C 10.88 mm ² .s ^-1 , flash point 159 °C, freezing point -48 °C. Its composition is as follows: 3.9 parts by weight of 1,1-diphenylethane, 0.2 parts by weight of pentaethylbenzene, 0.4 parts by weight of 3-ethylbiphenyl, 0.4 parts by weight of 4-ethylbiphenyl, 21 parts by weight of 3-ethyl-1,1-diphenylethane, 13.3 parts by weight of 4-ethyl-1,1-diphenylethane, 34.9 parts by weight of isomers of diethyl-1,1-diphenylethane, isopropyl-1,1-diphenylethane and isopropylethyl-1,1-diphenylethane, 0.4 parts by weight of 3- and 4-(1-phenylethyl)1,1-diphenylethane, 10.4 parts by weight of other alkyl homologues of 1,1-diphenylethane with a boiling point range of 277 to 322 °C and 15.1 parts by weight of oligomers of ethylene and propylene with by the distillation curve shown in Table VI.

Table VI

Distillation curve of heat transfer fluid volume ⁶³ »' ^za6 · ^{10 20 30 40 50 60} temperature

C 277 286 287 289 290 291 295

80 90 95

299 303 312 322

Table

Oxidation stability tests of heat transfer fluid

Additive quantity (wt. part)

Acid number Kinematic viscosity

Plate Cu__(mg KOH/q)_/mm ² .s~l) at 50 °C Evaporation- Deposits % deposition loss appearance 0 182.5 change 0 182.5 change (mg) hhhh

none 0.8 intact 0.02 0.59 0.57 5.95 7.89 32.6 1.25 no Muldatic, 1 37.6 red- brown 0.31 0.39 0.08 4.24 5.41 27.6 1.30 no Hitec E-542 1 0.6 intact 0.13 0.81 0.68 6.17 7.95 28.8 1.92 no Santolube BX 1 0.5 • intact 0.07 0.71 0.64 5.92 8.09 36.7 1.81 no Antioxidant K4 1 0.8 intact 0.17 0.55 0.32 6.14 7.72 25.7 1.77 no Lubrisol 1 0.5 intact 0.16 0.84 0.68 6.31 8.18 29.6 1.45 no barium thiophosphonate 1 -1.6 gray-black _t 0.15 1.13 0.98 6.17 8.34 35.2 2.25 no Paramo 52 1 -0.7 brownish-gray 0.15 0.55 0.40 6.18 8.52 37.9 1.79 no

The results of the oxidation stability tests of this liquid alone and with the addition of 0.5 part by weight of the substances listed in Table-II are identical to the results in this table with the exception of the kinematic viscosity at 50 °C, which is 3.9 mm ² .s ^-1 before and 4.6 mm ² .s ^_1 after the oxidation stability test.

Example 5

The heat transfer fluid is defined as follows: specific gravity 988 kg.m, refractive index at 20 °C 1.571 8, kinematic viscosity at 20 °C 27.56 mm ² .s, flash point 161 °C, freezing point -42 °C. Its composition is as follows: 0.4 parts by weight of 1,1-diphenylethane,

6.7 parts by weight of 3-ethyl-1,1-diphenylethane, 5.6 parts by weight of 4-ethyl-1,1-diphenylethane, 34.8 parts by weight of the isomers of diethyl-1,1-diphenylethane, isopropyl-1,1-diphenylethane and isopropylethyl-1,1-diphenylethane, 3.2 parts by weight of 3- and 4-(1-phenylethyl)-1,1-diphenylethane, 25.3 parts by weight of other alkyl homologues of 1,1-diphenylethane with a boiling range of 298 to 393 °C and 25 parts by weight of oligomers of ethylene and propylene with a distillation curve shown in Table VII.

)'-'u 1 k a VII Distillation curve of heat transfer fluid liquids discarded item start 10 20 30 40 50 60 70 80 90 95 temperature °C 298 316 322 329 333 340 345 354 367 378 393 Results oxidation stability tests this liquids alone and additive 0.5 mass-

The results of the substances listed in Table II are consistent with the results in this table except for the kinematic viscosity at 50 °C, which is 8.0 mm ² .s ^-3 before and 9.6 mm ² .s ^-3 after the oxidation stability test.

Claims (1)

object of the invention Heat transfer fluid based on 1,1-diphenylethane and its mono-, di- or polyethylene homologues, characterized in that it consists of up to 26 parts by weight of 1,1-diphenylethane, 5 to 26 parts by weight of 3-ethyl-1,1-diphenylethane, 5 to 10 parts by weight of 4-ethyl-1,1-diphenylethane, 10 to 35 parts by weight of diethyl 1,1-diphenylethane isomers, up to 1.8 parts by weight ethylbiphenyl isomers, up to 0.5 parts by weight of pentaethylbenzene, up to 1.5 parts by weight of isomers of tetraethylbenzene, 5 to 30 parts by weight of other 1,1-diphenyl ethane alkylhomologues having a distillation range of 270 to 395 ° C, 15 to 25 parts by weight of oligomers This component is characterized by a boiling range of 320 to 365 ° C, a kinematic viscosity at +20 ° C of 9.5 to 12.7 mm ² s ^-1 , a specific gravity of 977 to 985 kg / m ³ and a pour point. below -40 ° C, and is additive with up to 1 part by weight of an additive with anticorrosive and antioxidant effect.