Method and apparatus for compressing a gas

Abstract

In a method for compressing a gas, the gas is compressed in a compressor having an intermediate stage and a final stage, an intermediate cooler for cooling the gas downstream of the intermediate stage and a final cooler for cooling the gas downstream of the final compression stage, a refrigerant coming from a source is divided into a first flow and a second flow, the first flow is sent to cool the intermediate cooler and the second flow is sent to cool the final cooler, the first and second heated flows being at different temperatures, the first heated flow is sent to provide heat to an element, producing a first cooled flow, and the second heated flow is mixed with the first cooled flow and the mixture is sent to the source.

1 . A method for compressing a gas, the method comprising the steps of:
 compressing the gas in a compressor having at least two stages, the at least two stages comprising a first compression stage and a final compression stage configured to compress the gas downstream of the first compression stage;   cooling the gas downstream of the first compression stage in an intermediate cooler;   cooling the gas downstream of the final compression stage in a final cooler;   dividing a refrigerant into a first flow and a second flow, wherein the refrigerant is sourced a refrigerant source or a refrigerant cooling system;   sending the first flow to cool the intermediate cooler only;   sending the second flow to cool the final cooler only;   removing the first heated flow from the intermediate cooler, and removing the second heated flow from the final cooler, wherein the first and second heated flows being at temperatures that differ by at least 30° C., wherein the first heated flow is hotter than the second heated flow;   sending the first heated flow at least periodically to provide heat to a heat consuming element thereby producing a first flow cooled to a third temperature;   mixing the second heated flow, which has not been sent to provide heat to the heat consuming element and has not been cooled, with the first at least periodically cooled flow; and   sending the mixture to the refrigerant source or to the refrigerant cooling system.   
     
     
         2 . The method according to  claim 1 , wherein the first heated flow has undergone a temperature increase of between 30° C. and 80° C., in the intermediate cooler. 
     
     
         3 . The method according to  claim 1 , wherein the second heated flow has undergone a temperature increase of between 5° C. and 15° C. in the final cooler. 
     
     
         4 . The method according to  claim 1 , wherein the first and second flows arrive at the intermediate cooler and at the final cooler respectively at the same temperature, for example between 15° C. and 25° C. 
     
     
         5 . The method according to  claim 1 , wherein the first heated flow is sent to the heat consuming element where at least periodically it is not cooled or at least periodically it is not sent to the heat consuming element. 
     
     
         6 . The method according to  claim 1 , wherein at least periodically, the second heated flow is mixed with the first flow cooled to the third temperature. 
     
     
         7 . The method according to  claim 5 , wherein at least periodically, the second heated flow is mixed with the first flow that has not been cooled. 
     
     
         8 . The method according to  claim 1 , wherein the second heated flow is mixed with the first heated flow, whether or not it has been cooled by the heat consuming element. 
     
     
         9 . The method according to  claim 1 , wherein the first flow is smaller than the second flow. 
     
     
         10 . The method according to  claim 1 , wherein all of the refrigerants of the compressor are flows of refrigerant, for example water, coming from the refrigerant source or a refrigerant cooling system. 
     
     
         11 . The method according to  claim 1 , wherein the first flow is 5 to 15 times smaller than the second flow. 
     
     
         12 . The method according to  claim 1 , wherein the first flow is periodically sent to the heat consuming element. 
     
     
         13 . The method according to  claim 1 , wherein the first flow is continuously sent to the heat consuming element. 
     
     
         14 . A method for separating air by cryogenic distillation, the method comprising the steps of:
 compressing air, and   cooling the compressed air;   purifying the compressed air in a purification unit by pressure and/or temperature swing adsorption; and   separating the compressed air by distillation, thereby forming an oxygen- and/or nitrogen-enriched fluid,   wherein at least one portion of the air is compressed according to the method as claimed in  claim 1 ,   wherein the purification unit is regenerated by a regeneration gas.   
     
     
         15 . The method as claimed in  claim 14 , wherein all of the air is compressed according to the method as claimed in  claim 1 . 
     
     
         16 . The method as claimed in  claim 14 , wherein the heat consuming element is a heater configured to heat at least one portion of the regeneration gas upstream of the purification unit and the first heated flow supplies all of the heat necessary for taking the regeneration gas to a temperature suitable for regenerating the purification unit. 
     
     
         17 . The method as claimed in  claim 14 , wherein the heat consuming element is a heater configured to heat at least one portion of the regeneration gas upstream of the purification unit and the first heated flow supplies only some of the heat necessary for taking the regeneration gas to a temperature suitable for regenerating the purification unit, the rest of the heat needed being provided by an additional heater. 
     
     
         18 . An apparatus for compressing a gas, associated with a heat consuming element, the apparatus comprising:
 a compressor having at least two stages, including a first compression stage and a final compression stage configured to compress a gas downstream of the first compression stage;   an intermediate cooler configured to cool the gas downstream of the intermediate or first compression stage;   a final cooler configured to cool the gas downstream of the final compression stage;   means for dividing a refrigerant coming from a refrigerant source or a refrigerant cooling system, into a first flow and a second flow;   a first duct configured to send the first flow to cool the intermediate cooler only;   a second duct configured to send the second flow to cool the final cooler only;   a first removal duct configured to remove the first heated flow from the intermediate cooler;   a second removal duct configured to remove the second heated flow from the final cooler, wherein the first and second heated flows are at temperatures that differ by at least 30° C., the first heated flow being hotter than the second heated flow;   means for at least periodically sending the first heated flow to provide heat to the heat consuming element thereby producing a first at least periodically cooled flow;   means for sending the second heated flow to mix with the first at least periodically cooled flow, directly without passing through the heat consuming element or a cooling apparatus; and   means for sending the mixture formed to the refrigerant source or to a refrigerant cooling system.