WO2005118738A1

WO2005118738A1 - Refrigerant mixture of dimethyl ether and carbon dioxide

Info

Publication number: WO2005118738A1
Application number: PCT/JP2005/010035
Authority: WO
Inventors: Seijyuro Maiya; Osamu Nakagome; Hideyuki Suzuki; Yasuhisa Kotani; Toshifumi Hatanaka; Toshihiro Wada
Original assignee: Japan Petroleum Exploration Co., Ltd.; Showa Tansan Co., Ltd.; Nkk Co., Ltd.
Priority date: 2004-06-04
Filing date: 2005-06-01
Publication date: 2005-12-15
Also published as: JP2005344057A

Abstract

Disclosed is a safe, non-toxic refrigerant exhibiting excellent performance which is obtained by mixing dimethyl ether and carbon dioxide as refrigerants. This refrigerant does not deplete the ozone layer, and has an extremely low global warming potential. Specifically disclosed is a refrigerant composition for freezers which is characterized by containing 90-40 mol% of dimethyl ether and 10-60 mol% of carbon dioxide based on the total mole number of the dimethyl ether and carbon dioxide.

Description

Specification

Mixture refrigerant of dimethyl ether and carbon dioxide

Technical field

The present invention relates to a refrigerant composition containing dimethyl ether and carbon dioxide used for a car air conditioner, a commercial “home air conditioner and a gas heat pump (GHP)”, and an electric heat pump (EHP). You.

Background art

[0002] Freon (CFC fluorocarbon, HCFC hydrated fluorocarbon) has been used widely as a refrigerant for refrigerators and air conditioners worldwide because of its excellent refrigerant capacity. However, at present, CFC production has been abolished in Japan and developed countries in Europe and the United States in 1996 due to the fact that CFCs contain chlorine and destroy the ozone layer. Production of HCFC (noid-fluorofluorocarbon), which is the same specified fluorocarbons, will be gradually regulated after 2004, and will be completely abolished by 2010 in Europe and by 2020 in other developed countries.

[0003] Also, the alternative chlorofluorocarbon (HFC hydrate mouth fluorocarbon, PFC, SP6) that replaces the above specified fluorocarbon has zero ozone depletion potential, low toxicity, non-combustibility, satisfactory properties and performance, but is not compatible with mineral oil. There is a problem of deterioration of compatibility and lubricity. In particular, although this alternative fluorocarbon does not destroy the ozone layer but has a very high global warming potential, it is left to the voluntary action of the industry, which is currently subject to specific regulations, but its use will be abolished in the near future. Will be stopped or heavily regulated.

[0004] Recently developed natural refrigerants such as hydrocarbons (propane, isobutane), carbon dioxide, ammonia, water, and air also have characteristics of zero ozone depletion potential and almost zero global warming potential. However, there are drawbacks in safety, performance, convenience, etc. In other words, propane is comparable to HFC in performance, but is highly flammable. Carbon dioxide is nonflammable. • Low toxicity but low efficiency. • High pressure (12MPa). Ammonia has the same efficiency as HFC but has toxicity, pungent odor and incompatibility with copper. Water and air are non-flammable and non-toxic, but have very low efficiency. [0005] Furthermore, since carbon dioxide has a large sensible heat effect, it has recently been used in EHP refrigerants such as eco-ecules for heating and hot water supply. However, diacid carbon has a low latent heat effect of 1 ヽ, and is extremely inefficient for use in cooling.

[0006] On the other hand, dimethyl ether (DME) is known to be convenient for use in cooling, which has a very high latent heat effect, but is practically used from the viewpoint of safety because it is flammable. Not.

[0007] Carbon dioxide has a critical temperature of 31.1 ° C and a boiling point of 56.6 ° C, whereas dimethyl ether has a critical temperature of 126.85 ° C and a boiling point of 25 ° C. However, the physical properties of the two are very different. For this reason, carbon dioxide is used as a refrigerant in a very high pressure region of low pressure of about 3 MPa to high pressure of about lOMPa, whereas dimethyl ether is used as a solvent at a relatively low pressure of low pressure of about 0.7 MPa to high pressure of about 2 MPa. It is known to be used and exhibit the best performance as a refrigerant under such pressure conditions. Therefore, even though carbon dioxide and dimethyl ether may be used alone as refrigerants, the idea of mixing carbon dioxide and dimethyl ether with completely different properties and using them as refrigerants has not been proposed. Was.

Patent Document 1: JP-A-2000-204361

Patent Document 2: Japanese Patent Application Laid-Open No. 2000-96071

Disclosure of the invention

Problems to be solved by the invention

[0008] The present invention provides a non-flammable non-flammable and / or non-flammable non-flammable, non-flammable non-flammable non-toxic refrigerant with a low risk of ozone depletion. The purpose is to provide.

Means for solving the problem

[0009] The present inventors have found that dioxygenated carbon dissolves well in DME, and have extremely high thermal efficiency by mixing dioxygenated carbon with high sensible heat effect and DME with high latent heat effect. As a result of various investigations on the assumption that a refrigerant could be obtained, the present invention was reached.

That is, the present invention provides a refrigerant comprising dimethyl ether and carbon dioxide. Related to the composition.

The invention's effect

[0011] As described above, the refrigerant composition of the present invention provides a safe, non-toxic, excellent cooling and heating system that does not destroy the ozone layer and has a global warming potential (GWP) of almost zero. Refrigerant with hot water supply capacity.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail.

[0013] Dimethyl ether used in the refrigerant composition of the present invention includes, for example, coal gasification gas, BOG (Boil of Gas) of LNG tank, natural gas, by-product gas of steelworks, petroleum residue, waste, and biomass. Using gas as a raw material, dimethyl ether can be directly synthesized from hydrogen and sodium hydroxide or can be obtained indirectly from methanol and hydrogen via methanol synthesis.

[0014] The carbon dioxide used in the refrigerant composition of the present invention is obtained by, for example, purifying by compression "liquefaction" using a by-product gas generated by power such as an ammonia synthesis gas or a hydrogen production plant for heavy oil desulfurization.

[0015] The mixing ratio of dimethyl ether and diacid carbon in the refrigerant composition of the present invention is appropriately determined according to the type of a refrigerator such as a car air conditioner or a commercial / home air conditioner in which the refrigerant is used, refrigerant compositions of the present invention, based on the total moles of dimethyl ether and diacid I匕炭element, preferably, dimethyl ether 90 mole% to 40 mole ^_0/0, the carbon dioxide 10 to 60 mole ^_0/0, further preferably, dimethyl ether 85 mole% to 60 mole ^_0/0, the carbon dioxide 15 to 40 mole ^_0/0, particularly preferably dimethyl ether 85 mole% to 70 mole%, containing carbon dioxide 15 to 30 mole% . If the content of dimethyl ether is less than 40 mol%, a sufficient coefficient of performance as described below cannot be obtained, and the properties as a refrigerant are extremely poor. On the other hand, if dimethyl ether is more than 90 mol%, the refrigerant composition is flammable, which is not preferable for safety.

[0016] The refrigerant composition of the present invention is prepared by, for example, filling a container with a fixed amount of liquid dimethyl ether from a tank filled with liquid dimethyl ether, and then filling the liquid liquefied carbon dioxide filled tank with a predetermined amount of liquid dimethyl ether. The refrigerant composition having the mixing ratio described above can be obtained by filling the carbon dioxide. In addition, the refrigerant composition of the present invention is prepared by filling a container with a predetermined amount of liquid dimethyl ether. After filling, the gas phase of the container may be filled with a gas of carbon dioxide, dissolved in dimethyl ether under pressure, and mixed to prepare.

[0017] To the refrigerant composition of the present invention, for example, water can be added as another additive. Water has the characteristics of strong solubility of about 7 mol% in dimethyl ether under the condition of 1 atm and temperature of 18 ° C, high evaporation (condensation) latent heat, and high critical point! Since the rate of change of latent heat with respect to temperature is small, large latent heat can be obtained even in a high-temperature region. Therefore, it is expected that even higher thermal efficiency can be obtained by mixing three types of sensible heat effect, high carbon dioxide, high latent heat effect, and dimethyl ether and water. In this case, the mixing ratio of water should not exceed 7 mol% in consideration of solubility in dimethyl ether.

[0018] Method for evaluating refrigerant characteristics

Cooling / Return / Hot water supply system

The principle of the cooling system is based on the continuous heat exchange between the latent medium and the surrounding medium, which takes away heat energy from the surrounding medium when the substance (refrigerant) evaporates. Further, since the evaporation temperature of the refrigerant depends on the pressure, the lower the pressure, the lower the evaporation temperature, so that a lower temperature can be obtained.

[0019] On the other hand, the principle of the heating Z hot water supply system is achieved by continuous heat exchange with water, air, or the like, since the surrounding heat is taken away by the evaporation of the refrigerant, and the hot gas is further compressed. .

[0020] The cooling and heating Z hot water supply system based on the principle of such a cooling and Z heating system is a system that can perform a continuous process of refrigerant evaporation and compression, and includes a compressor, a condenser, an expansion valve, and an evaporator. And a cycle (cooling / heating reference cycle) system composed of pipes through which refrigerant circulates through these devices. Figure 1 shows a non-limiting example of this cycle system. The roles of these devices are described below.

• EQ 1 compressor: ヽ Absorbs the cold ヽ refrigerant gasified by the evaporator and compresses it into high-temperature, high-pressure gas.

• EQ2 condenser: A high-temperature, high-pressure gaseous medium discharged from the compressor is cooled by water or air (outside air) and condensed into a liquid (for heating Z hot water supply). • EQ3 expansion valve: Expands high-temperature, high-pressure liquid refrigerant to low-temperature, low-pressure refrigerant. • EQ4 evaporator: The low-temperature, low-pressure refrigerant is brought into contact with the surrounding gas at the outlet of the expansion valve to remove the heat and evaporate to evaporate into a gas (for cooling).

[0021] Cold cold — 暧 Hot water supply capacity

In order to actually evaluate the refrigerant cooling Z heating Z hot water supply capacity, the above-mentioned reference cycle is numerically modeled, and a general-purpose numerical chemical process simulator is used. Effect of Heat Exchange Characteristics of Heat Exchange on the Performance of Mixed Refrigerant Heat Pump Cycles ", Journal of the Japan Refrigeration Society, Vol. 7, No. 1, pp. 65-73, 1990, etc.) be able to. The general-purpose numerical chemical process simulator has a built-in database of thermodynamic properties of various components, and performs equilibrium thermodynamic calculations between the components of the iridani components corresponding to the mechanical engineering functions of various systems.

[0022] In the numerical simulation, the system comprising the compressor, the circulator, the expansion valve, and the evaporator through which the refrigerant circulates is digitized, and the compressor output pressure (P1), condenser output temperature (T2), evaporator Cooling Ζ heating with temperature (Τ3) and dimethyl ether ZCO molar concentration as parameters

2

評価 Evaluate the hot water supply capacity as a coefficient of performance (COP).

[0023] Cooling coefficient of performance = total absorbed heat in cooling evaporator ÷ compressor power

Heating Z Hot water supply coefficient of performance = Total amount of heat discharged from the refrigerant in the condenser ÷ Compressor power In the present invention, preferably, a regular melting model for melting is used as an equation for estimating thermodynamic physical property values of the refrigerant. For the equation of state, it is possible to evaluate with higher accuracy by applying the equations of SPK (Soave-Redlich-Kwon g).

[0024] Refrigerators that can suitably use the refrigerant composition of the present invention include, but are not limited to, car air conditioners, commercial and household air conditioners, gas heat pumps (GHP), and electric heat pumps (EHP). In addition, the refrigerant composition of the present invention can be used for car air conditioners, commercial / home air conditioners, GHPs / EHPs, etc. in principle using existing refrigerants such as R22. However, in consideration of the physical properties of the refrigerant composition of the present invention, it is further desirable to design the mechanical aspects such as the condenser and the piston so as to be adapted to the refrigerant composition of the present invention.

[Example] Hereinafter, the content of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[0026] DME CO solubility test

2

To determine the degree of dissolution of the DME / CO mixed system, and to

2

To determine the coefficient of performance in the system, a solubility test of DMEZCO was performed. Trial

2

The test method is as follows.

(1) Enclose 300 g of DME in a pressure vessel (500 mL), and measure the weight after encapsulation using an electronic balance.

(2) Put the pressure vessel in the thermostat and bring it to a constant temperature.

(3) Inject carbon dioxide to a certain pressure with the booster pump.

(4) The charged carbon dioxide is calculated from the weight before and after the filling (d = 0.lg).

During filling, shake the pressure vessel up and down so that DME / CO is sufficiently mixed.

2

The test was performed by standing vertically.

Table 1 shows the obtained results. As shown in Table 1, K volume of CO and DME

2

The values were 0.66 <KDME <0.80 and 2.59 <KCO <3 under the measurement conditions, respectively.

Two

42, which indicates that the carbon dioxide dissolves well in DME.

[Table 1]

Table 1 DME / CO remelting test results

_{_{• ZC0 2 = V * YC0 2}} + L * XC0 2

_{• Z C0 2 + ZDME = V} + L

• KC0 ₂ = YC0 ₂ / X C0 ₂

• KDME = YDME / XDME

(First Example)

The coefficient of performance (COP) in the mixed refrigerant cycle system of dimethyl ether and carbon dioxide shown in Fig. 1 is determined. The simulation was performed by the following procedure using a numerical chemical process simulator.

[0030] Simulation procedure

The state quantities (volume, enthalpy, entropy, etc.) of streams (1) to (4) in the mixed refrigerant cycle of dimethyl ether and carbon dioxide in FIG. 1 are determined by simulation, and the coefficient of performance COP of the following equation is obtained. .

[0031] COP = Hl / H2

HI: Total amount of heat discharged from the refrigerant condenser

H2: Compressor power from (4) to (1)

At this time, the following conditions were set.

[0032] The compressor is of a centrifugal type, with mechanical efficiency = 1.0 and multiplex efficiency = 0.6.

[0033] Condenser outlet temperature: 35 ° C

Expansion valve outlet pressure: 0.1 to 0.8MPa

Compressor pressure: 2.0, 4.0, 8.0, 12. OMPa [0034] Estimation of vapor-liquid equilibrium physical properties of DME + CO mixed system

2

In the simulation 'study, the accuracy of the physical property estimation model to be used is an important factor, and the study was conducted as follows.

Generally, the gas-liquid equilibrium relationship is represented by the following equation.

[0036] [Number 1]

0 i: Gas phase Fugacity Coeff.

P: System Pressure

yi: gas phase mole fraction

f, ^m : liquid phase S quasi-Fugacity

r, ⁽⁰⁾ : liquid phase fi factor

JC,: Liquid phase mole fraction

eX 丄 Vi I RTdp; Poynting Facter The following three points should be considered.

(1) γ. ⁽⁰⁾ model for DME

(2) Degree of relative volatility of DME and CO

2

(3) Enthalpy and entropy models

[0037] DME is an oxygen-containing low molecular weight compound. A typical example is that boiling point of ethanol is 78 ° C, whereas boiling point of DME is 25 ° C. It has no strong polarity. Therefore, a regular dissolution model can be applied to γ ^{(ω) of} DME.

[0038] From the solubility test data of DMEZCO obtained above (Fig. 2), the K v

twenty two

The olume values are in the range of 0.68 <KDME <0.80 and 2.54 <KCO <3.42, respectively, under the measurement conditions, and there is no significant difference between the volatility of DME and CO.

twenty two

I understand. Thus, the vapor pressure model can be applied to f.

[0039] In addition, with respect to enthalpy and entropy, the highest possible

2

Since the working pressure is about 1 OMPa, it is appropriate to use the SPK (Soave-Redlich-Kwong) equation of state. [Equation 2] p ₌ R. | l + (0.48 tens 1.574w- 0.176w ² ) (1 Ττ) 'J

v-bv ² + bv r ^a) : Regular Solution Model

_ / ϊ (.)-Vaper Pressure Model

<ί i, H, S: SRK equation of State

Poynting Facter; Consideration Since the Poynting Factor cannot be neglected when the system pressure reaches a certain high pressure (several MPa), this point was also taken into consideration.

[0041] Program

The following A and B types of programs were used.

(l) DME CO A

2

Flash calculation for a given composition, T (temperature), P (pressure).

[0042] A Bubble Point was calculated under the given composition and P1 (compressor pressure).

Thus, it is possible to confirm the accuracy of the model for estimating the gas-liquid equilibrium property value and to determine whether or not the total condensation in the condenser is possible.

[0044] (2) DME CO B

2

Using the simulator described above, COPs were obtained as follows for the refrigerant composition containing dimethyl ether and carbon dioxide, for comparison, R22, dimethyl ether alone, and carbon dioxide alone.

Example 1

[0045] In the system of Fig. 1, 80 mol% of dimethyl ether and 20 mol% of carbon dioxide at a compressor pressure of 2.0 MPa, a condenser outlet temperature of 35 ° C, and an expansion valve outlet pressure of 0.3 to 0.4. The COP of the refrigerant composition containing was 1.7 to 2.1. When the outlet pressure of the expansion valve was 0.4, the expansion valve outlet temperature was 6 ° C and the evaporator outlet temperature was 6 ° C.

Example 2

[0046] In the same system, the compressor pressure was 2.0MPa, the condenser outlet temperature was 35 ° C, and the expansion valve was The COP of the refrigerant composition containing 70 mol% of dimethyl ether and 30 mol% of carbon dioxide at an outlet pressure of 0.3 to 0.4 MPa was 1.2 to 1.5. When the expansion valve outlet pressure was 0.4, the expansion valve outlet temperature was 8 ° C and the evaporator outlet temperature was 2.8 ° C.

Example 3

[0047] In the same system, a refrigerant composition containing 60 mol% of dimethyl ether and 40 mol% of carbon dioxide at a compressor pressure of 2.0 MPa, a condenser outlet temperature of 35 ° C, and an expansion valve outlet pressure of 0.6 MPa. Its COP was 1.4. In this case, the expansion valve outlet temperature was 1.2 ° C and the evaporator outlet temperature was 10.5 ° C.

Example 4

[0048] In the same system, a refrigerant composition containing 50 mol% of dimethyl ether and 50 mol% of carbon dioxide at a compressor pressure of 4.0 MPa, a condenser outlet temperature of 35 ° C, and an expansion valve outlet pressure of 0.5 MPa. The COP was 1.1. In this case, the expansion valve outlet temperature was −21 ° C., and the evaporator outlet temperature was −0.2 ° C.

[Comparative Example 1]

In the same system, the R22 COP was 2.3 at compressor pressure = 1.61 MPa, condenser outlet temperature = 42 ° C, and expansion valve outlet pressure = 0.4 MPa. In this case, the outlet temperature of the expansion valve was -6.3 ° C, and the outlet temperature of the evaporator was 6.3 ° C.

[Comparative Example 2]

In the same system, the maximum COP of dimethyl ether alone was 1.6 at compressor pressure = 2.0 MPa, condenser outlet temperature = 35 ° C, and expansion valve outlet pressure = 0.2 MPa. In this case, the expansion valve outlet temperature was -6 ° C, and the evaporator outlet temperature was 6 ° C.

[Comparative Example 3]

In the same system, the maximum COP of the dioxygenated carbon alone refrigerant at the compressor pressure = 12 MPa, the condenser outlet temperature = 35 ° C, and the expansion valve outlet pressure = 3 MPa was 1.1. In this case, the expansion valve outlet temperature was 1 ° C and the evaporator outlet temperature was 1 ° C.

Table 2 shows the COP, expansion valve outlet temperature, evaporator outlet temperature, and compressor discharge temperature obtained in each example. As is clear from Table 2, in Examples 1 and 2, a refrigerant composition having a COP close to R22 and having a good cooling effect (evaporator outlet temperature of 10 ° C or less) was obtained. ことが

[Table 2] Table 2 Comparison table of R22, carbon dioxide alone, and dimethyl ether alone under the same conditions using the same system

From the above results, the refrigerant composition of the present invention can be used as an industrial 'industrial air conditioner (heat pump)' refrigerant for refrigerators and can reduce the heat island phenomenon in systems that operate at a condensation outlet temperature of 35 ° C or lower. Is expected to be used as a cogeneration refrigerant that utilizes geothermal heat.

(Second embodiment)

Flammability evaluation test

The flammability of the refrigerant composition of the present invention was evaluated according to the flame length test of the Japan Aerosol Association. The test method is as follows.

Sample temperature: 24 ° C to 26 ° C. Place the injection port of the sample blower 15 cm from the ignition burner.

Adjust the burner flame length to 4.5 cm to 5.5 cm.

Press the injection button and inject in the best condition. After 3 seconds, lower the tip and end of the flame vertically and measure the horizontal distance of the flame as the flame length.

[0055] The evaluation criteria are as follows.

X: Flame length 20cm or more (combustible)

〇: Flame length is less than 20cm (slightly burning)

◎: No flame is recognized (non-combustible)

Blow early: Inject contents up to 20%

Medium blow: Inject contents up to 50%

End of blow: Inject contents up to 80%

A flammability evaluation test was performed on Sample Nos. 1 to 7 in Table 3 and the results are shown in Table 4.

[Table 3] Samples for 3 sex evaluation

[Table 4] Table 4 Flammability evaluation test results

As is clear from the above results, dimethyl ether itself can be made nonflammable or nonflammable by mixing 10% by mole or more of flammable carbon dioxide. (Third Embodiment)

Other physical properties of refrigerant composition

Table 5 shows other refrigerant physical properties measured for the refrigerant composition of the present invention, dimethyl ether alone, carbon dioxide alone, and R22. Here, the saturated liquid density, latent heat of vaporization, gas thermal conductivity, liquid viscosity, and gas viscosity are physical property values during operation of the refrigerator.

[0060] As is clear from Table 5, the refrigerant composition of the present invention did not greatly differ from R22 in latent heat of vaporization, gas thermal conductivity, gas viscosity, and the like.

[Table 5]

[6200 Table 5 Comparison of refrigerant properties

For C 0 ₂ concentration of 100%, a supercritical state in operation compression pressure 11 MP a.

C0 ₂ concentration of 20% and the D ME concentration of 80%, at a supercritical state by operating compression pressure 2. 0 MP a.

C0 ₂ concentration of 50% and the DME concentration of 50%, a supercritical state in operation compression pressure 3. 0 MP a.

JIS C9612 test conditions comply (air conditioning refrigerant temperature) based Dzugu R22, propane, ammonia §, carbon dioxide, dimethyl ether alone, a mixture of 20% dimethyl ether 80 mole ^_0/0 and Nisani匕炭containing and dimethyl ether 90 mole% Figure 3 compares the cooling capacity and heating capacity of a 10 mol% mixture of carbon dioxide.

[0063] In comparison with these refrigerants under the JIS standard, the refrigerant mixture of dimethyl ether and carbon dioxide was low in COP except for carbon dioxide, but it was nonflammable, Since the dani coefficient is almost zero and it is a safe substance without toxicity, it is expected to be used as a refrigerant for car air conditioners and household air conditioners.

Brief Description of Drawings

[FIG. 1] A dimethyl ether and diacid carbon mixed refrigerant cycle system.

[Figure 2] DME CO B program flow.

2

[Figure 3 Refrigerant capacity comparison based on ISC 9612 test conditions.

Claims

The scope of the claims

[1] A refrigerant composition for a refrigerator, comprising 90 mol% to 40 mol% of dimethyl ether and 10 to 60 mol% of carbon dioxide, based on the total number of moles of dimethyl ether and carbon dioxide. .

[2] ether 85 mole% to 70 mole ^_0/0, the refrigerant composition according to claim 1, characterized in that it contains 15 to 30 mole ^_0/0 of carbon dioxide.

[3] A method of using a refrigerant composition containing 90 mol% to 40 mol% of dimethyl ether and 10 to 60 mol% of carbon dioxide in a refrigerator, based on the total number of moles of dimethyl ether and carbon dioxide. .