WO2008059199A1

WO2008059199A1 - Non-ozone depleting refrigerant compositions for replacing hcfc22

Info

Publication number: WO2008059199A1
Application number: PCT/GB2007/004143
Authority: WO
Inventors: John Edward Poole; Richard Powell
Original assignee: Rpl Holdings Limited
Priority date: 2006-11-11
Filing date: 2007-10-30
Publication date: 2008-05-22
Also published as: GB0622562D0

Abstract

Non ozone depleting and non flammable refrigerant compositions which replace CFC22 in centrifugal chillers and are compatible with traditional lubricants (eg mineral and alkylbenzene oils) and also synthetic oxygen containing lubricants.

Description

NON-OZONE DEPLETmG REFRIGERANT COMPOSITIONS FOR

REPLACING HCFC22

This invention relates to refrigerant composition, particularly but not exclusively for replacement of HCFC22. The refrigerant compositions which are the subject of this invention are generally non flammable and have no ability to deplete the ozone layer. These compositions comprise mixtures of hydrofluorocarbons (HFCs) with small amounts of hydrocarbons. While it is well known that HFCs can replace Ozone Depleting Substances (ODS) such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), HFCs are not miscible with traditional lubricants (eg mineral and alkylbenzene oils) and must be used with synthetic oxygen containing lubricants (eg polyol ester and poly alkylbenzene oils) in order to achieve the required oil return to the compressor essential to the operation of a refrigeration unit. This invention relates to refrigerant compositions which can replace ODS with minor or in some cases no changes to the existing equipment while achieving the required level of oil circulation throughout the refrigeration system which is fundamental to its safe and satisfactory operation.

Various terms have been used in patent literature to describe refrigerant mixtures. The following definitions are taken from ASHRAE Standard 34;

Azeotrope: an azeotropic blend is one containing two or more refrigerants whose equilibrium vapour and liquid phase compositions are the same at a given pressure. Azeotropic blends exhibit some segregation of components at other conditions. The extent of the segregation depends on the particular azeotrope and the application.

Azeotropic temperature: the temperature at which the liquid and vapour phases of a blend have the same mole fractionation of each component at equilibrium for a specified pressure.

Near azeotrope: a zeotropic blend with a temperature glide sufficiently small that it may be disregarded without consequential error in analysis for a specific application. Zeotrope: blends comprising multiple components of different volatilities that, when used in refrigeration cycles, change volumetric composition and saturation temperatures as they evaporate (boil) or condense at constant pressure.

Temperature glide: the absolute value of the difference between the starting and ending temperatures of a phase-change process by a refrigerant within a component of a refrigerating system, exclusive of any subcooling or superheating. This term usually describes condensation or evaporation of a zeotrope.

According to the present invention a refrigerant composition comprises 1,1,1,2-tetrafluoroethane (HFC134a), pentafluoroethane (HFC125) and disfluoromethane (HFC32) and an additive selected from the group consisting of 2- methylpropane, 2,2-dimethylpropane, n-butane, propane, 2-methybutane, propene, n- butene, isobutene and mixtures thereof wherein HFC 134a, HFC 125 and HFC2 are in the ranges by weight:

HFC134a 45-55%

HFC125 20-30%

HFC32 35-15%

wherein the amount of HFC 134a, HFC 125 and HFC32 are selected to total 100%.

The refrigerant compositions of this invention which can be retrofitted into centrifugal chillers to replace HCFC22 without the need to change the existing lubricant or make any changes to the hardware. An important property of any replacement for HCFC22 in centrifugal chillers is its molecular weight. While HFC134a and HFC125 have higher molecular weights than HCFC22, HFC32 has a considerably lower molecular weight than HCFC22 with the result that blends of these three HFC components can be made to match the molecular weight of HCFC22.

HFC32 is mildly flammable. HFC134a is non flammable and HFC125 finds application as an industrial fire extinguishant. The combination of these three HFCs and a small amount of hydrocarbon or mixtures of hydrocarbons results in mixtures which are non flammable under all conditions of fractionation according to ASHRAE (American Society for Heating Refrigeration and Air conditioning Engineers) Standard 34. Suitable refrigerant compositions to replace HCFC22 have molecular weights in the range 75 to 95, more preferably 80 to 90 and most preferably 83 to 88. Especially preferred are blends with molecular weights within 1 unit of that of HCFC22, which is 86.47.

Suitable preferred compositions should not have vapour pressures 5% lower than that of HCFC22 over the operating range of any system in which they are used. Preferably they should not have vapour pressures lower than that of HCFC22. Suitable compositions should not have vapour pressures that are 10% greater than that of HCFC22 over the operating range of the system. Preferably they should be not be more than 5% greater.

Preferably compositions should have cooling capacities that are not less than 15% of HCFC22 and more preferably not less than 10%. Most preferably the cooling capacities should be greater than that of HCFC22.

Preferred refrigerant compositions which are the subject of this invention are also suitable for use in new equipment with synthetic oxygen containing lubricants.

A key aspect of this invention is that while the inclusion of FiFCs in the refrigerant compositions ensures low toxicity and a zero Ozone Depletion Potential (ODP), the addition of a hydrocarbon within defined ranges enables a non flammable designation of Al to be achieved as defined by ASFTRAE (American Society for Heating Refrigeration and Air conditioning Engineers) Standard 34. This invention relates to refrigerant compositions comprising hydrocarbon and hydrocarbon mixtures with HFC134a, HFC125 and HFC32 which are non flammable when fractionated under leakage tests specified under ASFERAE Standard 34 and Underwriters Laboratories UL2182.

The presence of a hydrocarbon promotes oil return to the compressor enabling traditional lubricants such as mineral and alkylbenzene oils to be used in either existing or new equipment. The appropriate selection of hydrocarbons with HFCs enables non flammability of the blend to be achieved as defined by ASHRAE Standard 34.

Although considerable care is taken to prevent leakage of refrigerant to the atmosphere, on occasions this does occur. In some territories the emission of hydrocarbons is regulated to minimise the generation of tropospheric ozone caused by the effect of sunlight on hydrocarbons mixed with oxygen. To minimise the contribution of hydrocarbon to the atmosphere by leakage of the blends which are the subject of this invention, the hydrocarbon content should be preferably less than 6% more preferably less than 3.5 %.

Percentages and other amounts referred to in the specification are by weight unless indicated otherwise and are selected from the ranges given to total 100%.

The compositions can be used in existing or new equipment to replace ODS.

Preferred weights are in the range:

HFC134a 48-53%

HFC125 22-28%

HFC32 30-19%

A more preferred range is:

HFC134a 52-53% HFC125 23-27%

HFC32 25-20% A further preferred range is:

HFC 134a 50-52%

HFC125 23-26% HFC32 ^• 27-22%

A preferred refrigerant composition comprises:

HFC 134a 51%

HFC125 24%

HFC32 22% Butane 1.5%

Isopentane 1.5% Another embodiment comprises:

Rl 34a 50%

R125 24%

HFC32 23%

Butane 1.5%

Isopentane 1.5%

Yet another embodiment comprises

Rl 34a 50%

R125 25% HFC32 22%

Butane 1.5%

Isopentane 1.5%

An especially preferred embodiment comprises:

Rl 34a 51%

R125 25%

HFC32 21%

Butane 1.5%

Isopentane 1.5%

A preferred refrigerant composition comprises

R134a 51%

R125 25%

HFC32 21%

Butane 2.4%

Isopentane 0.6% Another preferred refrigerant composition comprises

Rl 34a 52%

R125 24%

HFC32 21.5%

Butane 1.5%

Isopentane 1%

Yet another preferred refrigerant composition comprises

R134a 52%

R125 25 HFC32 20.5%

Butane 2.5%

Another embodiment comprises

Rl 34a 51.5%

R125 25%

HFC32 21%

Butane 1.9%

Isopentane 0.6%

A further composition comprises:

Rl 34a 51%

R125 25%

HFC32 21%

Butane 3%

Yet another composition comprises:

Rl 34a 51.5%

R125 25% HFC32 21%

Butane 2.5%

Preferred hydrocarbon additives are 2-methylpropane (isobutane), n-butane, propane and 2-methybutane (isopentane) and mixtures thereof from 0.6 to 4%.

The present invention confers a range of advantages over R22 and blends such as R407C including but not confined to low cost solutions to replace R22 without the need to change either the lubricant in the system or make any alterations to the hardware (R407C requires the use of synthetic lubricants) while also being non ozone depleting (R22 is an ozone depleter) and non flammable.

In another embodiment of this invention the replacement of R22 in an existing equipment is carried out progressively, not in a single step. Any HFC/hydrocarbon blend claimed in this specification can be used to top-up a centrifugal unit so that its refrigerant charge is returned to its optimum operating level. Over a period the original R22 charge will become diluted by the added HFC/hydrocarbon blend. The prolonged retention of R22 in the system has the advantage of minimising cost and ensuring that any polymer seals which rely upon swelling by R22 retain their effectiveness, thus avoiding the need to replace these components. Some combinations of R22 with the blends claimed in this patent have the further advantage that they show slightly improved refrigeration capacities over R22 itself and the blends alone.

The invention is further described by means of examples but not in a limitative sense.

Example 1

Refrigerant compositions containing Rl 34a, Rl 25, R32, R600, R601a and R600a were evaluated using NIST' s Cycle D program as replacements for R22 in a refrigerator comprising a 3 stage open compressor operating under the following conditions. System cooling capacity (kW) = 100.00

Compressor isentropic efficiency = 0.750

Compressor volumetric efficiency = 1.000

Pressure drop (in sat. temp.) (⁰C): in the suction line = 1.5 in the discharge line = 1.5

Evaporator temperature (⁰C) = -30.0

Superheat (⁰C) = 5.0

Condenser: temperature (⁰C) = 35.0

Subcooling (⁰C) = 5.0

Effectiveness of liquid line/suction line heat exchanger = 0.3

Parasitic powers (kW):

Evaporator fan = 3.000

Condenser fan = 4.000

Controls = 1.000

The results are summarised in Table 1 from which it can be seen that all the compositions provided acceptable replacements for R22.

This invention also provides a centrifugal chiller including a refrigerant as described above, wherein the lubricant is a mixture of hydrocarbon and oxygen containing lubricants.

The invention also provides a method of recharging a refrigerant in a centrifugal chiller including the step of adding a refrigerant in accordance with the first aspect of this invention to bring the combined refrigerant charge up to an optimum level. Table 1

Example 2

Refrigerant compositions containing R134a, R125, R32, R600, R601a and R600a were evaluated using NIST' s Cycle D program as replacements for R22 in a chiller/ heat pump used for air conditioning comprising a centrifugal compressor, a flooded evaporator and condenser operating under the following conditions.

System cooling capacity (kW) = 100.00 Compressor isentropic efficiency =0.750 Compressor volumetric efficiency =1.000

Evaporator temperature (⁰C) ₌ ζ

Superheat (⁰C) = 5.0

Condenser: temperature (⁰C) = 35.0

Subcooling (⁰C) = 5.0

Effectiveness of liquid line/suction line heat exchanger = 0.3

Parasitic powers (kW):

Evaporator fan = 3.000

Condenser fan = 4.000

Controls = 1.000

The results are summarised in Table 2 from which it can be seen that all the compositions provided acceptable replacements for R22.

Ta ble

2

Example 3

A refrigerant composition containing R134a, R125, R32, R600, and R22 was evaluated using NIST's Cycle D program as replacements for R22 in a chiller/heat pump used for air conditioning comprising a centrifugal compressor, a flooded evaporator and condenser operating under the following conditions.

System cooling capacity (kW) =100.00

Compressor isentropic efficiency = 0.750 Compressor volumetric efficiency = 1.000

Evaporator temperature (⁰C) = 5

Superheat (⁰C) = 5.0 Condenser: temperature (⁰C) = 35.0

Subcooling (⁰C) = 5.0

Effectiveness of liquid line/suction line heat exchanger = 0.3

Parasitic powers (kW):

Evaporator fan = 3.000 Condenser fan = 4.000

Controls = 1.000

The results are summarised in Table 3 from which it can be seen that the mixed refrigerant, containing both the HFC/hydrocarbon blend and R22, has a performance comparable to R22 alone. It is therefore concluded that the blends claimed in this specification can progressively replace R22 in a centrifugal unit. The blend evaluated has a nearly 2% greater capacity than R22 itself, both in heating and cooling modes. Table 3

Claims

1. A refrigerant composition consisting essentially of: HFC134a 45-55%

HFC125 20-30%

HFC32 35-15% by weight wherein the amount of HFC134a, HFC125 and HFC32 are selected from the amounts given to total 100% and a hydrocarbon additive selected from the group consisting of 2-methylpropane, 2,2-dimethylpropane, n-butane, propane, 2- methylbutane, propene, n-butene, isobutene and mixtures thereof.

2. A Composition as claimed in Claim 1 which meets the criteria for safety classifications Al and A2 of ASHRAE Standard 34.

3. A Composition as claimed in Claim 1 which meets the criteria for safety classification Al of ASHRAE Standard 34.

4. A refrigerant composition as claimed in any of claims 1-3 consisting essentially of the hydrocarbon additive and:

Rl 34a 45-55%

R125 20-30% HFC32 35-15%

5. A refrigerant composition as claimed in any of claim 4 consisting essentially of the hydrocarbon additive and:

Rl 34a 48-53% R125 22-28%

HFC32 30-19%

6. A refrigerant composition as claimed in any of claim 5 consisting essentially of the hydrocarbon additive and: R134a 52-53% R125 23-27%

HFC32 25-20%

7. A refrigerant composition as claimed in any of claim 6 consisting essentially of the hydrocarbon additive and: Rl 34a 50-52%

R125 23-26%

HFC32 27-22%

8. A refrigerant composition as claimed in claim 1 consisting essentially of R134a 51%

R125 24%

HFC32 22%

Butane 1.5%

Isobutane !.5%

9. A refrigerant composition as claimed in claim 1 consisting essentially of

R134a 50%

R125 24%

HFC32 23% Butane 1.5%

Isopentane 1,5%

10. . A refrigerant composition as claimed in claim 1 consisting essentially of

Rl 34a 50% R125 25%

HFC32 22%

Butane 1.5%

Isopentane !.5%

11. A refrigerant composition as claimed in claim 8 consisting essentially of Rl 34a 51%

Rl 25 25%

HFC32 21%

Butane 1.5% Isobutane 1.5%

12. A refrigerant composition as claimed in claim 1 consisting essentially of

R134a 51% R125 25%

HFC32 21%

Butane 2.4%

Isopentane 0.6%

13. A refrigerant composition as claimed in claim 1 consisting essentially of

Rl 34a 52%

R125 24%

HFC32 21.5%

Butane 1.5% Isopentane 1%

14. A refrigerant composition as claimed in claim 1 consisting essentially of

Rl 34a 52%

R125 25% HFC32 20.5%

Butane 2.5%

15. A refrigerant composition as claimed in claim 8 consisting essentially of

R134a 51.5% Rl 25 25%

HFC32 21%

Butane 1.9%

Isopentane 0.6%

16. A refrigerant composition as claimed in claim 1 consisting essentially of Rl 34a 51%

R125 25%

HFC32 21%

Butane 3%

17. A refrigerant composition as claimed in claim 1 consisting essentially of

R134a 51.5% R125 25%

HFC32 21%

Butane 2.5%

18. A refrigerant composition as claimed in claims 1-7 wherein the hydrocarbon additive is butane.

19. A refrigerant composition as claimed in claim 18 wherein the hydrocarbon additive further comprises isopentane.

20. A refrigerant composition as claimed in claims 1 to 7 wherein the hydrocarbon additive is isobutane.

21. A refrigerant composition as claimed in claim 20 wherein the hydrocarbon additive further comprises butane.

22. A refrigerant composition as claimed in claims 1-7 where the amount of hydrocarbon additive is 0.5 to 5%.

23. A refrigerant composition as claimed in claim 22 where the amount of hydrocarbon additive is 0.6 to 4%.

24. A centrifugal chiller unit including a refrigerant as claimed in claims 1 to 23 in which the lubricant is a mixture of hydrocarbon and oxygen containing lubricants.

25. A method of recharging refrigerant in a centrifugal chiller unit, including the steps of adding a refrigerant as claimed in claims 1 to 24 to the centrifugal chiller unit, without removing the R22 already present, to bring the combined refrigerant charge up to an optimum operating level.