Mehod for gradual sealing of a gas

Abstract

A method is proposed for compressing a gas in stages in a compressor arrangement ( 100, 200, 300, 400 ) having a plurality of compression stages (I-VI) which are connected together sequentially by a main line ( 1 ) and in which the gas, guided through the main line ( 1 ), is respectively compressed from a suction-side pressure level to a pressure-side pressure level and is heated by this compression from a suction-side temperature level to a pressure-side temperature level, wherein a feedback amount of the gas, guided through the main line ( 1 ), is at least temporarily removed from the main line ( 1 ) downstream of one of the compression stages (V), is fed to an expansion process, and is fed back into the main line ( 1 ) upstream of the same compression stage (V). It is provided that the pressure-side pressure level of the compression stage (V) downstream of which the feedback amount is removed from the main line ( 1 ) is a supercritical pressure level, that the feedback amount is expanded to a subcritical pressure level, that the feedback amount is fed to the expansion process at the pressure-side temperature level of the compression stage (V) downstream of which it is removed from the main line ( 1 ), and that the feedback amount is cooled only after being expanded and before and/or after being fed back into the main line ( 1 ). The invention also relates to a compressor arrangement ( 100, 200, 300, 400 ).

1 . A method for compressing a gas in stages in a compressor arrangement having compression stages (I-VI) which are connected together sequentially by a main line and in which the gas, guided through the main line, is respectively compressed from a suction-side pressure level to a pressure-side pressure level and is heated by this compression from a suction-side temperature level to a pressure-side temperature level, a feedback amount of the gas, guided through the main line, being at least temporarily removed from the main line downstream of one of the compression stages (V), being fed to an expansion process, and being fed back into the main line upstream of the same compression stage (V), characterised in that the pressure-side pressure level of the compression stage (V) downstream of which the feedback amount is removed from the main line is a supercritical pressure level, in that the feedback amount is expanded to a subcritical pressure level, in that the feedback amount is fed to the expansion process at the pressure-side temperature level of the compression stage (V) downstream of which it is removed from the main line, and in that the feedback amount is cooled only after being expanded and before and/or after being fed back into the main line. 
     
     
         2 . The method according to  claim 1 , wherein a further feedback amount of the gas, guided through the main line, is at least temporarily removed from the main line downstream of a further compression stage (VI), is fed to an expansion process, and is fed back into the main line upstream of the same further compression stage (VI), wherein the pressure-side pressure level of the further compression stage (VI) downstream of which the further feedback amount is removed from the main line is a supercritical pressure level, wherein this further feedback amount is expanded to a supercritical pressure level, and wherein the feedback amount is cooled only after being expanded and before and/or after being fed back into the main line. 
     
     
         3 . The method according to  claim 1 , wherein an additional feedback amount of the gas, guided through the main line, is at least temporarily removed from the main line downstream of an additional compression stage (III, IV), is fed to an expansion process, and is fed back into the main line upstream of the same additional compression stage (III, IV), wherein the pressure-side pressure level of the additional compression stage (III, IV) downstream of which the further feedback amount is removed from the main line is a subcritical pressure level, wherein this additional feedback amount is expanded to a subcritical pressure level, and wherein the feedback amount is cooled only after being expanded and before and/or after being fed back into the main line. 
     
     
         4 . The method according to  claim 1 , wherein a further heat exchanger is used in a return line used to return the feedback amount and/or in the main line. 
     
     
         5 . The method according to  claim 1 , wherein the feedback amount is fed back into the main line upstream of one or more compression stages (I- 1 V) which are arranged upstream of the compression stage (V) downstream of which the feedback amount is removed from the main line. 
     
     
         6 . The method according to  claim 1 , wherein the feedback amount is controlled based on an attainable or attained suction-side or pressure-side pressure level of one of the compression stages (I-VI). 
     
     
         7 . The method according to  claim 1 , wherein the gas is cooled between the compression stages (I-VI) using cooling water which is maintained within a predetermined temperature range. 
     
     
         8 . The method according to  claim 1 , wherein the gas is ethylene or an ethylene-rich gas, which is provided in particular using a steam cracking method, or wherein the gas is ethane or an ethane-rich gas, or wherein the gas is carbon dioxide or a carbon dioxide-rich gas. 
     
     
         9 . The method according to  claim 1 , wherein a plurality of the compression stages ( 1 -VI) are driven by one or more common shafts, by which the respective compression stages (I-VI) are mechanically coupled. 
     
     
         10 . The method according to  claim 9 , wherein a plurality of the compression stages (I-VI) are respectively driven by a plurality of common shafts. 
     
     
         11 . The method according to  claim 10 , wherein the plurality of common shafts are mechanically coupled by a transmission. 
     
     
         12 . A plant which is configured to compress a gas in stages and which comprises a compressor arrangement with compression stages (I-VI) which are connected together sequentially by a main line and in which the gas, guided through the main line, can be respectively compressed from a suction-side pressure level to a pressure-side pressure level and can be heated by this compression from a suction-side temperature level to a pressure-side temperature level, means being provided which are configured to at least temporarily remove a feedback amount of the gas, guided through the main line, from the main line downstream of one of the compression stages (V), to feed it to an expansion process and to feed it back into the main line upstream of the same compression stage (V), characterised in that the plant is configured to be operated such that the pressure-side pressure level of the compression stage (V) downstream of which the feedback amount is removed from the main line is a supercritical pressure level and in that the feedback amount is expanded to a subcritical pressure level, in that means are provided which are configured to feed the feedback amount to the expansion process at the pressure-side temperature level of the compression stage (V) downstream of which the feedback amount is removed from the main line, and in that means are provided which are configured to cool the feedback amount only after it has been expanded and before and/or after it is fed back into the main line. 
     
     
         13 . The plant according to  claim 12  which is configured to implement a method for compressing a gas in stages in a compressor arrangement having compression stages (I-VI) which are connected together sequentially by a main line and in which the gas, guided through the main line, is respectively compressed from a suction-side pressure level to a pressure-side pressure level and is heated by this compression from a suction-side temperature level to a pressure-side temperature level, a feedback amount of the gas, guided through the main line, being at least temporarily removed from the main line downstream of one of the compression stages (V), being fed to an expansion process, and being fed back into the main line upstream of the same compression stage (V), characterised in that the pressure-side pressure level of the compression stage (V) downstream of which the feedback amount is removed from the main line is a supercritical pressure level, in that the feedback amount is expanded to a subcritical pressure level, in that the feedback amount is fed to the expansion process at the pressure-side temperature level of the compression stage (V) downstream of which it is removed from the main line, and in that the feedback amount is cooled only after being expanded and before and/or after being fed back into the main line.