RU2030432C1 - Working substance for absorption refrigerate machine - Google Patents

Abstract

FIELD: refrigeration engineering. SUBSTANCE: working substance has, wt. -% : difluorochloromethane 2.4-44.2; 1,1,1-trifluoroethane or 1,1-difluoroethane or 1,1,1,2-tetrafluoroethane 3.6-46.3; strong-based anionite in hydroxyl form 1.4-4.1, and methylpropylketone - the rest. EFFECT: enhanced quality of substance. 3 cl, 1 tbl

Description

 The invention relates to refrigeration, and in particular to working substances - absorbers of organic substances that produce cold when two liquids are mixed without changing their state of aggregation, and can be used in absorption refrigeration machines operating mainly on freons.

 Known refrigerant containing Freon-22 40-95 wt.% And 1,1,1-trifluoroethane (Freon-143) the rest [1].

 However, the known refrigerant contains hydrofluorochlorocarbon - Freon-22 in significant quantities, which is ozone-depleting (activity coefficient - 0.05) with an average residence time of 20 years (relative greenhouse effect - 0.07), which makes it an environmentally polluting substance. In addition, Freon-22 has increased chemical and thermal instability and causes corrosion of the material of the adsorption refrigeration machine under the influence of products of the destruction of the refrigerant - hydrogen halide and water. A known refrigerant requires prior dehydration and removal of hydrohalic acids.

 The closest in technical essence is the working substance of adsorption refrigeration machines containing methylpropyl ketone and Freon-22 [2].

 However, the known working substance contains hydrofluorochlorocarbon - Freon-22 (difluorochloromethane), which is ozone-depleting (ozone activity coefficient - 0.05) with an average residence time of 20 years (relative greenhouse potential - 0.07), which makes it an environmentally polluting substance. In addition, difluorochloromethane has chemical and thermal instability, causing corrosion of the material of the adsorption refrigeration machine under the influence of degradation products of the working substance - hydrogen halide and water. It is required when using preliminary dehydration of the working substance.

 Achievable technical result of the invention is to reduce the corrosive activity of the working substance while increasing its environmental cleanliness.

The technical result is achieved by the fact that the known working substance of an adsorption refrigeration machine containing methylpropyl ketone and difluorochloromethane additionally contains 1,1,1-trifluoroethane or 1,1-difluoroethane, or 1,1,1,2-tetrafluoroethane and strongly basic anion exchange resin in hydroxyl form in the following ratio of components, wt.%: Difluorochloromethane 2.4-44.2
1,1,1-trifluoroethane
or 1,1-difluoroethane,
or 1,1,1,2-tetra-fluoroethane 3.6-46.3
Strongly basic
hydroxyl anion exchanger 1.4-4.1 Methyl propyl ketone
As a strongly basic anion exchange resin in hydroxyl form, AB 17x8 (specific volume 3.0 cm ³ / g) is predominantly used.

Increased ecological cleanliness of the working substance is achieved by the use of refrigerant - difluorochloromethane (CFC-22) as a mixture with 1,1,1-trifluoroethane (freon-143B, t _refluxing = _-. 47.6 ° ^C) or 1,1-difluoroethane (freon 152a, t _heated. = -24.7 ^{° C,} the relative greenhouse effect <0.1) or 1,1,1,2-tetrafluoroethane (CFC-134a, t _heated. = -26.8 ^C. , relative greenhouse effect <0.2). This allows to reduce the percentage of difluorochloromethane (Freon-22) in the refrigerant and, as a consequence, to reduce its environmental hazard, since all newly introduced freons - 134a, -143v and -152a have an ozone activity coefficient of 0. As a result, the overall azo activity of the refrigerant is approximately an order of magnitude.

Freons - 134a, -143b and -152a have a slightly lower cooling capacity compared with Freon-22, which may cause a slight decrease in the specific heat capacity of the mixture of each of these freons with Freon-22. However, methyl propyl belongs to the working substance, boils within the operating temperature refrigerant boiling (-45) - (- 25) ^{° C} in the evaporator of the refrigeration unit, as itself a high boiling point substance having a normal boiling point of 101.7 ^{° C,} whereas the freons used in the working substance change their state of aggregation (boil) in the working range of the boiling temperature of the adsorption refrigeration unit.

In the composition of the proposed methyl propyl working substance (6-09-52-88 MRTU mark "h") boils in the temperature range 65-100 ^{° C,} thereby increasing the specific heat of the working medium and, as a result, partially compensates for the magnitude of the specific heat capacity of the refrigerant losses due introduction of freons - 134a, -143b, -152a to freon-22. In addition, due to the low vapor pressure due to the relatively high boiling point, methylpropyl ketone has a high adsorption ability to freons contained in the working substance compared to freons. And freons (-22, 134a, -143v, -152a) methylpropyl when mixed with a liquid, which is the melting point of - 77.8 ^{° C,} resulting in formation of hydrogen bonds to form a mixture with a negative deviation from Raoult's law. The consequence of this is the absorption of heat during the formation of such a solution. All of the above, in aggregate, makes it possible to compensate for the decrease in specific heat when introducing Freon-22 freons -134a, -143b, -152a into the refrigerant and to increase the cooling capacity of an adsorption refrigeration machine while increasing the environmental cleanliness of the working substance.

CO₂+2HCl+2HF
Причем, как известно, гидросодержащие углероды растворяют значительное количество воды и растворимость ее значительно выше, чем в галогензамещенных углеродах, не содержащих водород. Поэтому для обязательного предварительного удаления воды из гидросодержащих углеродов с целью их стабилизации, что очень важно для надежного эксплуатационного процесса в холодильной машине, требуются значительные экономические и временные затраты на специальном оборудовании.As noted above, all freons contained in the working substance are chemically and thermally (upon boiling) unstable and undergo partial decomposition during operation of the adsorption refrigeration unit with the formation of hydrohalic acids and other compounds that cause increased corrosion of the material of the adsorption refrigeration machine during operation and causes premature machine failure. Moreover, the water present in the working substance is a catalyst for the decay of freons according to an exemplary scheme:
CCl ₂ F ₂ + 2H ₂ O

CO ₂ + 2HCl + 2HF
Moreover, as you know, hydrocontaining carbons dissolve a significant amount of water and its solubility is much higher than in halogenated carbons that do not contain hydrogen. Therefore, for the obligatory preliminary removal of water from hydro carbon-containing carbon in order to stabilize them, which is very important for a reliable operational process in the refrigeration machine, significant economic and time costs for special equipment are required.

R+H₂O а по схеме R-OH+2HCl

RHCl₂+H₂O где R-ОН - схематическое изображение анионита.The introduction into the working substance of the adsorption refrigeration machine of strongly basic anion exchange resin in the hydroxyl form of GOST 20301-74 allows not only to remove the hydrohalic acids formed during the thermal and chemical decomposition of the working substance, but does not require preliminary mandatory dehydration of hydrofluorocarbons. This is due to the discovered effect of superequivalent absorption of hydrohalic acids by anion exchange resin in the presence of water, which is 2-3 times higher than its exchange capacity and increases with increasing humidity of the anion exchange resin. An increase in sorption ability occurs for two reasons. Firstly, as a result of the extraction distribution of hydrogen chloride (fluoride) between an organic solvent (methylpropyl ketone) and water in the anionite phase, and secondly, since a very concentrated acid solution is obtained in the anionite phase (up to 8M for wet anionite), and for of concentrated solutions of hydrohalic acids, association processes are strongly developed, then the exchange does not proceed according to the scheme:
HCl + R-OH

R + H ₂ O a according to the scheme R-OH + 2HCl

RHCl ₂ + H ₂ O where R-OH is a schematic representation of anion exchange resin.

 Moreover, the water released as a result of ion exchange remains in the anion exchange resin and increases its exchange capacity. To ensure the high absorption capacity of the anion exchange resin until enough water is formed in it as a result of ion exchange, the AB-178 anion exchange resin is either prepared immediately wet, or it absorbs water from the working substance, including hydrofluorocarbons, which are present in them at a level solubility.

 Thus, the introduction of a strongly basic anion exchanger in hydroxyl form allows one to reduce the corrosive activity of the working substance with respect to the material of the equipment of the adsorption refrigeration unit and to stabilize the working substance, especially freons, for the entire period of its operation due to the constant removal of hydrohalic acids from the reaction zone and the catalytic chemical and thermal decomposition of freon water.

 Strongly basic anion exchange resin is a high molecular weight polymer compound of a three-dimensional helium or macroporous structure containing basic functional groups. As a strongly basic anion exchange resin in the proposed working substance, anion exchangers AB-17x8 and AB-17x8 h C (helium structure with a quaternary trimethylammonium functional group) are used; AB-17P and AV-17-10P / 08 (macroporous structure with a quaternary trimethylammonium functional group); AB-29-12P (macroporous structure with a quaternary dimethyl-ethanolammonium functional group).

 The proposed working substance adsorption refrigeration machines are prepared as follows. The strongly basic anion exchange resin is converted to the hydroxyl form by passing a NaOH solution through a column filled with a commercial strongly basic anion exchange resin in chlorine form. The regeneration of a strongly basic anion exchange resin with a NaOH solution is carried out until a negative reaction to chlorine ions in the filtrate is carried out. After this, the anion exchange resin is washed from alkali with water. Then the anion exchange resin is dried to constant weight in a vacuum oven. Dry anion exchange resin is dispersed and a fraction of 0.63-0.80 mm is taken. To obtain a wet anion exchange resin, it is kept in an isolated vessel until equilibrium is established with water vapor over a solution of sulfuric acid.

 After preparation of the strongly basic anion exchange resin in hydroxyl form, it is weighed in an amount of 1.4-4.1 wt.%, For example 14-41 g of anion exchange resin, and placed in methylpropyl ketone, previously purified from dissolved gases, taken in an amount of 5.4-93.2 wt. %, for example 54-932 g of methylpropyl ketone.

 After that, Freon-22 is pre-cleaned and mixed with Freon-134a, -143b or -152a in a ratio of 2.4-44.2 wt.% To 3.6-46.3 wt.%, For example 24-442 g to 30 -463 g, respectively. Thermostat in individual cylinders until the same temperatures are reached methylpropyl ketone with strongly basic anion exchange resin and a mixture of Freon-22 with Freon -134a, -143b or -152a. When the temperatures are compared, the valves open and through the connecting channel the mixture of Freon-22 with Freon -134a, -143b or -152a under pressure enters the cylinder with methylpropylketone with strongly basic anion exchange resin, supplementing the second cylinder to 100 wt.%, Up to 1000 g.

 The obtained working substance allows to prevent corrosion of the material of the adsorption refrigeration machine under the action of products of chemical and thermal decomposition of the components of the working substance while increasing its environmental purity (reducing ozone activity) and maintaining or some increase in cooling capacity.

 The table presents experimental data on the degree of protection of carbon steel, tin-plated with tin, and aluminum alloy grade AMG-6 at various ratios of components in the working fluid.

Corrosion tests were carried out in conditions of evaporation - condensation at ¹⁰⁰ ° C for 96 hours on plates 30h30h50 mm clearance from St3, tinned tin, and alloy AMG-6 aluminum. The corrosion rate was determined by the gravimetric method.

 The test results presented in the table, after a month of operation in a working substance with boiling refrigerant, showed that the optimal concentrations of the components are in the range presented in examples 2-6, 8-11. At the same time, the maximum protective effect is achieved for tin-plated steel and AMG-6 aluminum alloy not less than an order of magnitude greater in comparison with the prototype (example No. 12).

 In the event that the concentration of the strongly basic anion exchange resin AB-17x8 is lower than the boundary value of 1.4 wt. % (example N 1) there is a sharp deterioration in the corrosion protection of tin-plated steel and AMG-6 aluminum alloy, which is due to the insufficient content of anion exchange resin in the volume of the working substance and, as a result, the inability to completely withdraw from the contact zone with tin-plated steel, and AMG-6 aluminum alloy formed during the chemical and thermal decomposition of freons of hydrogen halide acids and water.

 The excess concentration of strongly basic anion exchange resin above the boundary value of 4.1 wt. % (example 7) is impractical due to the fact that increasing the consumption of anion exchange resin does not increase the degree of protection of tin-plated steel and AMG-6 aluminum alloy, and excessive spraying of anion exchange resin can lead to a decrease in the cooling capacity of the working substance. The use of the brands AB-17x8chS, AV-17P, AV-17-10P / 08 and AV-29-12P as a strongly basic anion exchange resin led to approximately the same results (examples 8-11).

 When the content of freons from methylpropyl ketone goes beyond the boundary values: less than 2.4 wt.% For freon-22, less than 3.0 wt.% For freons -143v, 134a, or -152a, less than 5.4 wt.% For methylpropylketone, as well as over 44.2 wt.% for Freon-22, over 46.3 wt.% for Freon -143B, -134a, or -152a and over 93.2 wt.% for methylpropyl ketone, the adsorption refrigeration machine does not produce cold for external consumer, and only works on losses to the environment.

 The optimal strongly basic anion exchange resin is AB-17x8hC with an optimal concentration of 3.9-4.1 wt.%.

=

где R =

ΔН - интегральная теплота смешения при определенной концентрации компонентов, кДж/кг;
Δ Т - разность температур кипения компонентов, ^оС;
r_пар - теплота парообразования компонента, температура кипения которого минимальна.The optimal hydrofluorocarbon is Freon-152a with an optimal concentration of 15-35 wt.%, Which provides, as noted above, with the integrated heat of mixing when dissolved in methylpropyl ketone, the refrigerating capacity is slightly higher than the refrigerating capacity of the working substance according to the prototype with a thermal coefficient of the mixture of 0.099 and 0.092, respectively. The thermal coefficient of the mixture was estimated by the ratio:
Ψ =

=

where R =

ΔН is the integral heat of mixing at a certain concentration of components, kJ / kg;
Δ T is the difference in boiling temperature of the components, ^о С;
r _steam is the heat of vaporization of the component, the boiling point of which is minimal.

=

где С_см - теплоемкость смеси кДж/(кг˙град);
m_см - масса смеси, кг;
Δt - падение температуры в результате смешения компонентов;
С_к - теплоемкость калориметра кДж/(кг˙град).The integral heat of mixing N is determined by the formula
H

=

where C _cm is the heat capacity of the mixture kJ / (kg˙ grad);
m _cm is the mass of the mixture, kg;
Δt is the temperature drop as a result of mixing of the components;
With _to - the heat capacity of the calorimeter kJ / (kg˙ grad).

 When Freon was introduced into the working substance, 143B, or -134a, the thermal mixing coefficient was obtained at 0.096 and 0.094, respectively. However, within the experimental error, they are all approximately equal.

Based on the foregoing achievable technical result of the invention is:
The decrease in the corrosive activity of the working substance is no less than an order of magnitude relative to the material of the adsorption refrigeration machine due to the introduction of a strongly basic anion exchange resin in hydroxyl form, which removes the products of chemical and thermal decomposition of freons - hydrogen halide and water from the working substance.

 It allows to increase the ecological purity of the working substance by 50-90% by reducing the content of ozone-active freon-22 in the working substance and using it as a refrigerant in a mixture with ozone-inactive freons - 134a, -143b and 152a, as well as due to the absorption of hydrogen halide by the anionite while maintaining or some increase in cooling capacity and thermal mixing coefficient.

 It allows you to use the components of the working substance and, first of all, freon without preliminary dehydration to increase their chemical stability due to the introduction of strongly basic anion exchange resin.

 It makes it possible to increase the chemical and thermal stability of the working substance by at least an order of magnitude due to the absorption of strongly basic anion exchange resin from it, catalyzing the process of its destruction, and hydrogen halide acids, which lead to the destruction of the material of the adsorption refrigeration machine and the products of such destruction of the material entering the working substance.

The proposed working substance can be used in absorption refrigeration machines to obtain a temperature in the evaporator from -30 to 30 ^about C.

Claims (1)

1. WORKING MATERIAL OF AN ABSORPTION REFRIGERATING MACHINE, containing methylpropyl ketone and difluorochloromethane, characterized in that it further comprises 1,1,1-trifluoroethane or 1,1-difluoroethane, or 1,1,1,2-tetrafluoroethane and a strongly basic anion exchange resin in hydroxyl form in the following ratio of components, wt.%
Difluorochloromethane - 2.4 - 44.2
1,1,1-trifluoroethane, or 1,1-difluoroethane, or 1,1,1,2-tetrafluoro - 3.6 - 46.3
Strongly basic anion exchange resin in hydroxyl form - 1.4 - 4.1
Methyl Propyl Ketone - Else
2. The working substance according to claim 1, characterized in that it contains a strongly basic anion exchange resin brand AB - 17x8 in hydroxyl form.

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