Operational fluid for a vapour circuit processing device and a method for operating same

Abstract

The invention relates to an operating fluid for a steam cycle process apparatus comprising a steam generator, an expander, a condenser and a reservoir for the operating fluid, comprising a working medium that evaporates by supplying heat in the steam generator, performs mechanical work in the vapour phase by expanding in the expander and condenses in the condenser and an ionic liquid which forms a mixture with the working medium, wherein the melting point of the mixture lies below −5° C.

1 - 23 . (canceled) 
     
     
         24 . Operating fluid for a steam cycle process apparatus comprising:
 an evaporable working medium that is assigned a freezing point; and   an ionic liquid having at least one organic compound as a cation, wherein the ionic liquid in pure form at a given reference pressure has a melting point which is lower than 100° C. and lies at a higher temperature than the freezing point of the working medium; and   wherein the ionic liquid forms a mixture with the working medium without complex bonds and the melting point of the mixture lies below −5° C.; and   the ionic liquid has a decomposition temperature which lies above the evaporation temperature of the working medium.   
     
     
         25 . The operating fluid according to  claim 24 , characterised in that the working medium comprises water. 
     
     
         26 . The operating fluid according to  claim 24 , characterised in that the decomposition temperature of the ionic liquid is higher than 200° C. and preferably higher than 300° C., and in particular higher than 350° C. 
     
     
         27 . The operating fluid according to  claim 26 , characterised in that the melting point of the ionic liquid in pure form lies in the range of 0-100° C. 
     
     
         28 . The operating fluid according to  claim 24 , characterised in that the melting point of the mixture of working medium and ionic liquid lies below −10° C. and in particular preferably below −30° C. 
     
     
         29 . The operating fluid according to  claim 24 , characterised in that the working medium and the ionic liquid have a weight fraction of at least 0.01 gw. % (percent by weight) in the mixture. 
     
     
         30 . The operating fluid according to  claim 24 , characterised in that the weight ratio of ionic liquid to working medium in the mixture is 90:10-10:90, preferably 80:20-20:80, and particularly preferably 60:40-40:60. 
     
     
         31 . The operating fluid according to  claim 24 , characterised in that the anion of the ionic liquid is a C1 to C4 alkyl sulphonate, preferably methyl sulphonate or a completely or partially fluorinated C1 to C4 alkyl sulphonate, preferably trifluoromethyl sulphonate. 
     
     
         32 . The operating fluid according  claim 24 , characterised in that the cation of the ionic liquid is pyridinium or imidazolium or phosphonium or morpholinium and the anion of the ionic liquid is a C1 to C4 alkyl sulphonate, preferably methyl sulphonate or a completely or partially fluorinated C1 to C4 alkyl sulphonate, preferably trifluoromethyl sulphonate. 
     
     
         33 . The operating fluid according to  claim 24 , characterised in that the ionic liquid comprises as cations 1-ethyl-3-methyl imidazolium (EMIM) and the anion is selected from the group formed by HSO 4   − , MeSO 3   −  and CF 3 SO 3   − . 
     
     
         34 . The operating fluid according to  claim 24 , characterised in that the operating fluid additionally is a lubricant or an addition to a lubricant. 
     
     
         35 . A method for operating a steam cycle process which is executed in an apparatus comprising a steam generator, an expander, a condenser and a reservoir for an operating fluid, wherein the method comprises the following process steps:
 when cold starting the steam cycle process, an operating fluid is supplied to the steam generator, which comprises a mixture of a working medium and an ionic liquid, wherein the ionic liquid serves as a frost protection agent and in the mixture with the working medium has a melting point which lies below −5° C., and wherein the decomposition temperature of the ionic liquid lies above the evaporation temperature of the working medium in the steam generator;   in the steam generator the working medium is evaporated from the mixture and supplied in vapour form to the expander for expansion whilst performing mechanical work and then condensed in the condenser;   above a predetermined operating temperature the mixture of ionic liquid and working medium is separated so that the weight fraction of the ionic liquid to the operating fluid supplied to the steam generator is reduced by at least 50% and preferably 80%, and particularly preferably 95%.   
     
     
         36 . The method according to  claim 35 , characterised in that above a predetermined operating temperature the condensate of the working medium produced in the condenser is guided into a tank for the working medium which is separate from the reservoir for the operating fluid. 
     
     
         37 . The method according to  claim 36 , characterised in that above a certain level in the separate tank for the working medium, the inflow of the operating fluid from the reservoir to the steam generator is interrupted and exclusively working medium is supplied from the separate tank for the working medium to the steam generator. 
     
     
         38 . The method according to  claim 36 , characterised in that the operating fluid not evaporated in the steam generator is supplied to a tank for the ionic liquid, which is formed separately from the reservoir for the operating fluid. 
     
     
         39 . The method according to  claim 38 , characterised in that a lubricant circuit is supplied from the tank for the ionic liquid. 
     
     
         40 . The method according to  claim 39 , characterised in that the lubricant circuit is used for lubrication of the expander. 
     
     
         41 . The method according to  claim 39 , characterised in that the steam cycle process in a vehicle is operated with an internal combustion engine and the lubricant circuit is used for the lubrication of at least one moving component of the internal combustion engine. 
     
     
         42 . The method according to  claim 35 , characterised in that the operating temperature is determined by a measurement of the temperature of the operating fluid in the reservoir. 
     
     
         43 . The method according to  claim 35 , characterised in that when the steam cycle process is at a standstill, after a predetermined time and/or below a predetermined ambient temperature the ionic liquid and the working medium are combined.