Process and plant for the liquefaction of air and for the storage and recovery of electrical energy

Abstract

A process and plant for the liquefaction of air in which a stream of pressurized air is provided at a first pressure level and is compressed by means of a compressor to a second pressure level, a first partial stream, a second partial stream and a third partial stream are formed from air of the stream of pressurized air after the compression to the second pressure level, air of the first partial stream is cooled down using cold that is produced by means of an expansion of air of the second partial stream and the third partial stream and is at least partially liquefied, and feed air that is compressed to the first pressure level and air of the second partial stream and the third partial stream that is provided at the first pressure level are used for providing the stream of pressurized air at the first pressure level.

What I claim is: 
     
         1 . A process for the liquefaction of air in which a stream of pressurized air is provided at a first pressure level and is compressed using a compressor to a second pressure level, a first partial stream, a second partial stream and a third partial stream are formed from air of the stream of pressurized air after the compression to the second pressure level, air of the first partial stream is cooled down using cold that is produced by means of an expansion of air of the second partial stream and the third partial stream and is at least partially liquefied, and both feed air that is compressed to the first pressure level and air of the second partial stream and the third partial stream that is provided at the first pressure level are used for providing the stream of pressurized air at the first pressure level, the air of the second partial stream being successively cooled down to a first temperature level, allowed to expand from the second pressure level to the first pressure level and heated with respect to the first partial stream, and the air of the third partial stream being successively cooled down to a second temperature level below the first temperature level, allowed to expand to a third pressure level below the first pressure level, heated with respect to the first partial stream and recompressed to the first pressure level, characterized in that a first booster and a second booster are used for recompressing the third partial stream, the first booster being driven by and mechanically coupled to an expansion machine that is used for the expansion of the third partial stream, the second booster being driven by and mechanically coupled to an expansion machine that is used for the expansion of the second partial stream, and the first booster and the second booster being mechanically uncoupled from one another and from the compressor. 
     
     
         2 . The process according to  claim 1 , in which a common shaft is used in each case for the mechanical coupling of the first booster to the expansion machine that is used for the expansion of the third partial stream and the second booster to the expansion machine that is used for the expansion of the second partial stream. 
     
     
         3 . The process according to  claim 1 , in which air of the third partial stream, which remains gaseous at the third pressure level and a third temperature level produced by the expansion to the third pressure level, is used as the air of the third partial stream, which after the cooling down to the second temperature level and the expansion to the third pressure level is heated with respect to the first partial stream and is recompressed to the first pressure level. 
     
     
         4 . The process according to  claim 3 , in which air of the third partial stream, which has been cooled down to the second temperature level and allowed to expand to the third pressure level and is in liquid form at the third temperature level and the third pressure level, is combined with liquefied air of the first partial stream. 
     
     
         5 . The process according to  claim 1 , in which, after cooling down and at least partially liquefying, the air of the first partial stream is allowed to expand to a fourth pressure level below the third pressure level. 
     
     
         6 . The process according to  claim 5 , in which, before being allowed to expand to the fourth pressure level, the air of the first partial stream is allowed to expand to the third pressure level. 
     
     
         7 . The process according to  claim 6 , in which the air of the third partial stream, which after cooling down to the second temperature level and expansion to the third pressure level is heated with respect to the first partial stream and recompressed to the first pressure level, after expansion to the third pressure level is combined with air of the first partial stream that has been allowed to expand to the third pressure level and remains gaseous. 
     
     
         8 . The process according to  claim 1 , in which the first pressure level lies at 5 to 25 bar and/or in which the second pressure level lies at 50 to 100 bar. 
     
     
         9 . The process according to  claim 1 , in which the third pressure level lies at least 1 bar below the second pressure level and/or the fourth pressure level lies at least 1 bar below the third pressure level. 
     
     
         10 . The process according to  claim 1 , in which the first temperature level lies at 230 to 330 K and/or in which the second temperature level lies at 140 to 180 K. 
     
     
         11 . The process according to  claim 8 , in which the first pressure level lies at 10 to 20 bar and/or the second pressure level lies at 60 to 80 bar. 
     
     
         12 . The process according to  claim 9 , in which the third pressure level lies at least 5 bar below the second pressure level and/or the fourth pressure level lies at least 5 bar below the third pressure level. 
     
     
         13 . The process according to  claim 9 , in which the third pressure level lies at least 10 bar below the second pressure level and/or the fourth pressure level lies at least 10 bar below the third pressure level. 
     
     
         14 . The process according to  claim 9 , in which the third pressure level is at most 20 bar below the second pressure level and/or the fourth pressure level lies at most 20 bar below the third pressure level. 
     
     
         15 . The process according to  claim 9 , in which the fourth pressure level lies at atmospheric pressure. 
     
     
         16 . The process according to  claim 1 , in which a first operating mode, in which air is liquefied by means of electrical energy, and a second operating mode, in which electrical energy is obtained by using the air liquefied in the first operating mode, characterized in that the process is carried out in the first operating mode. 
     
     
         17 . A plant for the liquefaction of air, with means which are designed for providing a stream of pressurized air at a first pressure level and compressing it by means of a compressor to a second pressure level, forming a first partial stream, a second partial stream and a third partial stream from air of the stream of pressurized air after the compression to the second pressure level, cooling down air of the first partial stream using cold that is produced by means of an expansion of air of the second partial stream and the third partial stream and at least partially liquefying it, and using both feed air that is compressed to the first pressure level and air of the second partial stream and the third partial stream that is provided at the first pressure level for providing the stream of pressurized air at the first pressure level, means being provided that are designed to successively cool down the air of the second partial stream to a first temperature level, allow it to expand from the second pressure level to the first pressure level and heat it with respect to the first partial stream, and are designed furthermore to successively cool down the air of the third partial stream to a second temperature level below the first temperature level, allow it to expand to a third pressure level below the first pressure level, heat it with respect to the first partial stream and recompress it to the first pressure level characterized in that a first booster and a second booster are provided for recompressing the third partial stream, the first booster being able to be driven by and being mechanically coupled to an expansion machine that is used for the expansion of the third partial stream, the second booster being able to be driven by and being mechanically coupled to an expansion machine that is used for the expansion of the second partial stream, and the first booster and the second booster being mechanically uncoupled from one another and from the compressor. 
     
     
         18 . The plant according to  claim 17 , in which the first booster is coupled to the expansion machine that is used for the expansion of the third partial stream and the second booster is coupled to the expansion machine that is used for the expansion of the second partial stream by means of a common shaft respectively.