Integrated liquid storage

Abstract

A system and process for liquefying a gas, comprising introducing a feed stream into a liquefier comprising at least a warm expander and a cold expander; compressing the feed stream in the liquefier to a pressure greater than its critical pressure and cooling the compressed feed stream to a temperature below its critical temperature to form a high pressure dense-phase stream; removing the high pressure dense-phase stream from the liquefier, reducing the pressure of the high pressure dense-phase stream in an expansion device to form a resultant two-phase stream and then directly introducing the resultant two-phase stream into a storage tank; and combining a flash portion of the resultant two-phase stream with a boil-off vapor from a liquid in the storage tank to form a combined vapor stream, wherein the temperature of the high pressure dense-phase stream is lower than the temperature of a discharge stream of the cold expander.

1 . A process for liquefying a gas, comprising:
 introducing a feed stream into a liquefier comprising at least a warm expander and a cold expander;   compressing the feed stream in the liquefier to a pressure greater than its critical pressure and cooling the compressed feed stream to a temperature below its critical temperature to form a high pressure dense-phase stream;   removing the high pressure dense-phase stream from the liquefier and reducing the pressure of the high pressure dense-phase stream in an expansion device to form a resultant two-phase stream and then directly introducing the resultant two-phase stream into a storage tank; and   combining a flash portion of the resultant two-phase stream with a boil-off vapor from a liquid in the storage tank to form a combined vapor stream, wherein the temperature of the high pressure dense-phase stream is lower than the temperature of a discharge stream of the cold expander.   
     
     
         2 . The process of  claim 1 , further comprising heating at least part of the combined vapor stream to ambient temperature. 
     
     
         3 . The process of  claim 2 , further comprising mixing the warmed combined vapor stream with the feed stream for recycle. 
     
     
         4 . The process of  claim 2 , further comprising venting the warmed combined vapor stream to the atmosphere to control the pressure of the storage tank. 
     
     
         5 . The process of  claim 2 , wherein the pressure of the storage tank is less than 1.5 bara. 
     
     
         6 . The process of  claim 1 , further comprising removing at least part of the combined vapor stream from the storage tank, reducing the pressure of the combined vapor stream in one or more expansion devices to form a low pressure combined vapor stream, and venting the low pressure combined vapor stream to the atmosphere to control the pressure of the storage tank. 
     
     
         7 . The process of  claim 1 , wherein the feed stream is a low pressure nitrogen feed stream from a warm end of an Air Separation Unit. 
     
     
         8 . The process of  claim 1 , further comprising mixing a low pressure nitrogen stream from a low pressure column or subcooler of an Air Separation Unit with the combined vapor stream from the storage tank prior to heating. 
     
     
         9 . The process of  claim 1 , further comprising taking a divided portion of the high pressure dense phase fluid from the liquefier, feeding the divided portion of the high pressure dense phase fluid directly to an Air Separation Unit or nitrogen generator to provide refrigeration. 
     
     
         10 . The process of  claim 9 , wherein the divided portion of the high pressure dense phase fluid is reduced in pressure and fed to a High Pressure (HP) column, a Low Pressure (LP) column, a subcooler, or a main heat exchanger of the Air Separation Unit. 
     
     
         11 . A system for liquefying an atmospheric gas, comprising:
 a first conduit for accepting a feed stream;   a liquefier fluidly connected to the first conduit for compressing and cooling the feed stream to form a high pressure dense phase fluid, wherein the liquefier comprises at least a warm expander, a cold expander, a compressor for compressing the feed stream to a pressure greater than its critical pressure, and a heat exchanger, for cooling the compressed feed stream to a temperature below its critical temperature;   a second conduit fluidly connected to the liquefier for accepting the high pressure dense-phase stream from the liquefier;   a first expansion device fluidly connected to the second conduit to reduce the pressure of the high pressure dense-phase stream to form a resultant two-phase stream;   a third conduit fluidly connected to the first expansion device for accepting the two-phase expanded stream; and   a storage tank fluidly connected to the third conduit for accepting and storing the two-phase expanded stream,   
       wherein the storage tank is designed to operate at a pressure at or below 1.5 bara, and wherein the heat exchanger is designed such that the temperature of the high pressure dense-phase stream is lower than the temperature of a discharge stream of the cold expander. 
     
     
         12 . The system of  claim 11 , wherein the storage tank is directly connected to the third conduit and wherein the first expansion device is directly connected to the second conduit. 
     
     
         13 . The system of  claim 11 , further comprising a fourth conduit fluidly connected to the storage tank for accepting a combined vapor stream comprising a flash vapor portion of the resultant two-phase stream and a boil-off vapor portion from a liquid in the storage tank. 
     
     
         14 . The system of  claim 13 , wherein the fourth conduit is fluidly connected to the heat exchanger and the first conduit. 
     
     
         15 . The system of  claim 13 , further comprising a second expansion device fluidly connected to the fourth conduit to reduce the pressure of the combined vapor stream to control the pressure of the storage tank.