Method of producing homogeneous gas mixtures

Abstract

Homogeneous compressed gas mixtures of perfluorinated and/or partially fluorinated hydrocarbons and a gas of lesser density are produced using an optionally mobile mixing station including at least the following components: a gas pre-mixing stage in which separately provided gases are brought together; a static mixer and/or buffer tank connected to the pre-mixing stage; and a compressor connected to the static mixer or buffer tank. If a buffer tank is used, a return line may be provided from the compressor outlet to the buffer tank. Mixtures of perfluorinated and/or partially fluorinated hydrocarbons and/or ethers and inert gases such as noble gases, CO 2 or N 2 and/or SF 6 , are obtained which are suitable as insulating gases for current-carrying underground cables or gas-insulated switches. High flow rates can be processed using the method, and mass flow meters ensure accuracy and reliability.

What is claimed is:  
     
         1 . A method for producing a homogeneous compressed gas mixture, said method comprising premixing separately supplied gases to form a non-homogeneous gas mixture; passing the non-homogeneous gas mixture into a static mixer or a buffer tank; conveying the gas mixture from the mixer or buffer tank into a compressor; compressing the gas mixture in the compressor; and withdrawing a substantially homogeneous compressed gas mixture from the compressor; wherein said gas mixture comprises at least one perfluorinated or partially fluorinated hydrocarbon or ether.  
     
     
         2 . A method according to  claim 1 , wherein said gas mixture further comprises at least one gas selected from the group consisting of SF 6  and inert gases.  
     
     
         3 . A method according to  claim 2 , wherein said mixture comprises an inert gas selected from the group consisting of noble gases, CO 2  and N 2 .  
     
     
         4 . A method according to  claim 1 , wherein said mixture comprises at least one perfluorinated or partially fluorinated hydrocarbon or ether and SF 6 .  
     
     
         5 . A method according to  claim 1 , wherein said mixture comprises at least one perfluorinated or partially fluorinated hydrocarbon and N 2 .  
     
     
         6 . A method according to  claim 5 , wherein said mixture consists of at least one perfluorinated or partially fluorinated hydrocarbon and N 2 .  
     
     
         7 . A method according to  claim 1 , wherein said mixture comprises at least one perfluorinated or partially fluorinated hydrocarbon selected from the group consisting of C 3 F 8 , CHF 2 CF 3 , CF 3 CHFCF 3 , CH 2 FCF 3 , CH 3 CF 3 , CHF 3 , CF 4 , CF 3 CF 3 , CF 3 OCHF 2 .  
     
     
         8 . A method according to  claim 1 , wherein the compressed gas mixture withdrawn from the compressor has a pressure of up to 13 bar.  
     
     
         9 . A method according to  claim 1 , wherein the non-homogeneous gas mixture is passed into a buffer tank and conveyed from the buffer tank to the compressor; further comprising returning a portion of the compressed gas mixture withdrawn from the compressor through a return line to the buffer tank, and wherein a control valve is installed in the return line for adjusting the return of compressed gas mixture to a desired volume percentage of the compressed gas withdrawn from the compressor.  
     
     
         10 . A method according to  claim 1 , wherein a homogeneous compressed gas mixture is produced having a composition which deviates by at most ±0.7 volume-% from ideal homogeneity.  
     
     
         11 . A method according to  claim 1 , wherein gas streams which are to be mixed are regulated using mass flow meters.  
     
     
         12 . A method according to  claim 11 , wherein said method is carried out in a mobile mixing apparatus.  
     
     
         13 . A method according to  claim 1 , further comprising introducing the substantially homogeneous compressed gas mixture as an insulating gas into a current-carrying underground cable or a gas-insulated switch.