Working fluid for a steam cycle process

Abstract

The present invention relates to a working fluid for a steam-turbine cycle process, said fluid comprising a working medium, a lubricant and preferably an emulsifier. The working medium is a C1 to C4 alcohol and/or a C3 to C5 ketone, optionally mixed with water. The invention also relates to a device for a steam cycle process, which device contains the working fluid, and to the use of the working fluid in an organic Rankine cycle. The lubricant is a hydrocarbon and the emulsifier is a surface-active substance.

Claims

1. A working fluid composition comprising: (a) at least one working medium (a) consisting of: (a.1) at least one C1 to C4 alcohol, or (a.2) at least one C3 to C4 ketone or mixtures of (a1) and (a2), and (a.3) optionally up to 75% by weight of water, preferably up to 50% by weight of water, based on the working medium; and (b) at least one lubricant consisting of hydrocarbons, wherein the lubricant has a kinematic viscosity of 40 to 700 mm.sup.2/s at 40 C., measured according to DIN EN ISO 3104, and wherein the proportion of the lubricant (b) on the working fluid composition is 1 to 25% by weight; and (c) at least one emulsifier (c), wherein the proportion of the at least one emulsifier is in total greater than 0.01 to 5% by weight, based on the at least one lubricant.

2. The working fluid composition according to claim 1, wherein the proportion of the working medium (a) on the working fluid is 99 to 60% by weight, preferably from 90 to 80% by weight.

3. The working fluid composition according to claim 1, wherein the lubricant (b) consisting of hydrocarbons has a kinematic viscosity of 150 to 300 mm.sup.2/s at 40 C. measured according to DIN EN ISO 3104.

4. The working fluid composition according to claim 1, wherein the lubricant (b) consisting of hydrocarbons has a boiling point, also based on a optionally present hydrocarbon mixture, of greater than 300 C. (determined by gas chromatography according to DIN51435).

5. The working fluid composition according to claim 1, wherein the lubricant is an alkylate, an alkylated naphthalene, a mineral oil, a poly-alpha-olefin (PAO) or their mixtures.

6. The working fluid composition according to claim 5, wherein the lubricant is a PAO or a mixture of PAOs, preferably combinations of low viscosity PAOs with each having a viscosity of 4 to 10 mm.sup.2/s at 100 C. and high viscosity PAOs, with each having a viscosity of 40 to 100 mm.sup.2/s at 100 C. measured in each case according to DIN EN ISO 3104.

7. The working fluid composition according to a claim 1, wherein the proportion of lubricant (b) on the working fluid composition is 5 to 25% by weight, preferably 10 to 20% by weight.

8. The working fluid composition according to claim 1, wherein the lubricant is soluble to less than 5% by weight, preferably less than 2% by weight at 25 C. within the working medium.

9. The working fluid composition according to claim 1, wherein the emulsifier (c) is selected from the group of: one or more alkenyl succinimides, preferably with molecular weight of 500 to 10000 g/mol (number average); one or more alkenyl succinamides, preferably with molecular weight of 500 to 10000 g/mol; one or more C8 to C24, preferably C10 to C18 fatty alcohol ether carboxylic acids with 2 to 10, preferably 4 to 8, alkoxylate units, particularly preferably ethylene oxide and/or propylene oxide units, and their salts, preferably ammonium salts; one or more alkoxylated C10 to C24, preferably C8 to C24 fatty alcohols with 2 to 10, preferably 4 to 8, alkoxylate units, particularly preferably ethylene oxide and/or propylene oxide units; one or more alkoxylated alkylphenols, in particular C6 to C18 alkyl, with 2 to 10, in particular 4 to 8, alkoxylate units, particularly preferably ethylene oxide and/or propylene oxide units; and mixtures thereof.

10. The working fluid composition according to claim 9, wherein the proportion of the emulsifiers is in total greater than 0.0001 to 2% by weight, based on the working fluid composition.

11. The working fluid composition according to claim 1, wherein the working fluid composition as other optional components (d) contains antiwear agents, extreme pressure additives, antioxidants, nonferrous metal inhibitors, defoamers, or their mixtures.

12. The working fluid composition according to claim 11, wherein the proportion of the optional further components (d) together is greater than 0.0001% by weight, preferably 0.0005 to 2% by weight, in each case based on the working fluid composition.

13. The working fluid composition according to claim 11, wherein the proportion of the optional further components (d) together is independently, but preferably cumulatively, greater than 0.01% by weight, particularly preferably 0.1 to 5% by weight based on the lubricant.

14. The working fluid composition according to claim 1, wherein the working composition contains 5 to 75% by weight water, particularly 10 to 50% by weight water within the working medium.

15. A device for a steam cycle process comprising at least an evaporator, an expander, a condenser and a circulation pump, and a working fluid composition comprising: (a) at least one working medium (a) consisting of: (a.1) at least one C1 to C4 alcohol, or (a.2) at least one C3 to C4 ketone or mixtures of (a1) and (a2), and (a.3) optionally up to 75% by weight of water, preferably up to 50% by weight of water, based on the working medium; and (b) at least one lubricant consisting of hydrocarbons, wherein the lubricant has a kinematic viscosity of 40 to 700 mm.sup.2/s at 40 C., measured according to DIN EN ISO 3104, and wherein the proportion of the lubricant (b) on the working fluid composition is 1 to 40% by weight; and (c) at least one emulsifier (c), wherein the proportion of the at least one emulsifier is in total greater than 0.01 to 5% by weight, based on the at least one lubricant.

16. The device according to claim 15, wherein the steam cycle process is part of a motor vehicle with an internal combustion engine, and a heat exchanger uses the waste heat of the engine and is preferably coupled to the exhaust gas system of the engine and the heat exchanger acts as an evaporator.

17. The device according to claim 15, wherein the mechanical power recovered by the expander is either coupled to the drive train of the motor vehicle, or drives a generator for generating electrical energy.

18. A method comprising: utilizing the working fluid composition according to claim 1 in an organic Rankine cycle.

Description

EXPERIMENTAL PART

(1) Emulsifying Test

(2) In order to investigate the effectiveness of emulsifiers, lubricant mixtures with a viscosity of 40 C. of 150 mm.sup.2/s from PAO 8, PAO 40 and the respective emulsifiers have been produced. 20 g of these lubricant mixtures were filled and closed respectively with 20 g working medium in a 50 ml test tube with screw cap and shaken at 20 C. for about 1 minute by hand. Afterwards, the test tube was mixed again for 1 minute on a test tube shaker at a frequency of 2200 Hz.

(3) 1 minute after turning off the test tube shaker, the phase behavior of the mixture as a measure of the emulsifying effect was evaluated qualitatively according to the following scheme: 0=no emulsifying properties 1=minimum emulsifying properties 2=good emulsifying properties 3=excellent emulsifying properties

(4) Table 1 lists the emulsifiers used, Tables 2 to 6 show the results of emulsifying tests of respective lubricant mixtures with different working media.

(5) TABLE-US-00001 TABLE 1 Product Emulsifier designation Manufacturer Chemistry Emulsifier 1 Hitec633 Afton Polyisobutene Chemicals succinimide, non-borated Emulsifier 2 C9231 lnfineum Polyisobutene succinimide, borated Emulsifier 3 Marlipal013/80 Sasol lso-tridecanol, ethoxylate Emulsifier 4 Marlipal24/60 Sasol C10/C12 alcohols, ethoxylated Emulsifier 5 Emulsogen Clariant C16 to C18 alcohol ethoxylate (5 EO)

(6) TABLE-US-00002 TABLE 2 Emulsifying properties with ethanol (=100% by weight of the working medium) Formulation By weight: %1 Emulsifying PA08 40.0 3 PA040 58.0 E Emulsifier 1 2.0 PA08 40.0 2 PA040 59.5 Emulsifier 1 0.5 PA08 40.0 3 PA040 59.0 Emulsifier 2 1.0 PA08 40.0 2 PA040 59.0 Emulsifier 3 1.0 PA08 40.0 2 PA040 59.0 Emulsifier 4 1.0

(7) TABLE-US-00003 TABLE 3 Emulsifying properties with acetone (=100% by weight of the working medium) Emulsifying Formulation % properties PA08 40.0 2 PA040 58.0 Emulsifier 1 2.0

(8) TABLE-US-00004 TABLE 4 Emulsifying properties with ethanol/water 50% by weight of ethanol and 50% by weight of water Emulsifying Formulation [%] properties PA08 40.0 3 PA040 58.0 Emulsifier 1 2.0 PA08 40.0 3 PA040 59.0 Emulsifier 2 1.0 PA08 40.0 2 PA040 59.0 Emulsifier 3 1.0 PA08 40.0 2 PA040 59.0 Emulsifier 5 1.0

(9) TABLE-US-00005 TABLE 5 Emulsifying properties with acetone/water 50% by weight of acetone and 50% by weight of water Emulsifying Formulation [%] properties PA08 40.0 3 PA040 58.0 Emulsifier 1 2.0 PA08 40.0 2 PA040 59.0 Emulsifier 2 1.0 PA08 40.0 2 PA040 59.0 Emulsifier 3 1.0 PA08 40.0 3 PA040 59.0 Emulsifier 5 1.0

(10) TABLE-US-00006 TABLE 6 Emulsifying properties with ethanol/acetone 50% by weight of ethanol and 50% by weight of acetone Emulsifying Formulation [%] properties PA08 40.0 3 PA040 58.0 Emulsifier 1 2.0 PA08 40.0 2 PA040 59.0 Emulsifier 2 1.0 PA08 40.0 2 PA040 59.0 Emulsifier 3 1.0
Autoclave test for determining thermal stability

(11) In a pressure autoclave with a capacity of 300 ml, mixtures of 60 grams (40% by weight) of lubricant and 90 grams (60% by weight) of working medium were charged respectively. As a lubricant, 2 mineral oil variants were also examined with a viscosity at 40 C. of 150 mm.sup.2/s besides lubricant mixtures on the basis of PAO. To remove the above atmosphere, in particular to remove the oxygen, the autoclave was evacuated for 30 seconds at a pressure of 500 mbar and was subsequently heated under magnetically induced stirring with an agitator at 250 C.

(12) After 28 days, the experiment was completed at 250 C. After cooling the autoclave to 20 C. the content was transferred to a separatory funnel. After a rest period of 2 hours, the re-separated phases were separated and the lubricant and working medium were tested individually for acidification. The acid numbers were determined in accordance with DIN ISO 6618. Tables 7 to 9 show the results of autoclave experiments.

(13) TABLE-US-00007 TABLE 7 Autoclave test with ethanol Neutralization number [mg KOH/g] Lubricant [%] Lubricant Working medium PA08 40.0 0.01 0.04 PA040 60.0 PA08 40.0 0.01 0.02 PA040 59.8 Emulsifier 2 0.2 PA08 40.0 0.01 0.06 PA040 58.0 Emulsifier 2 2.0 SN 900 F (H + R, 99.8 0.02 0.04 V40 - 210 mm.sup.2/s) Emulsifier 1 0.2 SN 600 (AP/E Core 76.0 0.01 0.02 600, Exxon Mobil) Brightstock (AP/E 23.8 Core 2500 ExxonMobil) Emulsifier 1 0.2

(14) TABLE-US-00008 TABLE 8 Autoclave test with ethanol/water 50% by weight of ethanol and 50% by weight of water Neutralization number [mg KOH/g] Lubricant [%] Lubricant Working medium PA08 40.0 0.01 0.04 PA040 60.0

(15) TABLE-US-00009 TABLE 9 Autoclave test with acetone Neutralization number [mg KOH/g] Lubricant [%] Lubricant Working medium PA08 40.0 0.02 0.05 PA040 58.0 Emulsifier 2 2.0

(16) The present disclosure includes that contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of the structures and the combination of the individual elements may be resorted to without departing from the spirit and scope of the invention.