Cyrogenic Air Separation Process and Apparatus

Abstract

A low temperature air separation process and apparatus for producing pressurized gaseous product in an air separation unit using a system of distillation columns which include cooling a compressed air stream in a heat exchange line to form a compressed cooled air stream, sending at least part of the compressed, cooled air stream to a column of the system, liquefying a process stream to form a first liquid product, storing at least part of the first liquid product in a storage tank, sending at least part of the above first liquid product from the storage tank to the air separation unit as one of the feeds, extracting at least one second liquid product stream from a column of the column system and pressurizing the at least one second liquid product stream, vaporizing the above pressurized second liquid product stream to form pressurized gaseous product in the heat exchange line and extracting a cold gas without warming it completely in the heat exchange line.

1 . A low temperature air separation process for producing pressurized gaseous product in an air separation unit using a system of distillation columns which comprises the following steps: 
 a) cooling a compressed air stream in a heat exchange line to form a compressed cooled air stream;    b) sending at least part of the compressed, cooled air stream to a column of the system;    c) in a first period of time, liquefying a process stream to form a first liquid product and storing at least part of this first liquid product;    d) in a second period of time, sending the above stored first liquid product to the air separation unit as one of the feeds;    e) pressurizing at least one second liquid product stream;    f) vaporizing the above pressurized second liquid product stream in the heat exchange line to form pressurized gaseous product; and    g) during the above second period of time, extracting a cold gas from the air separation unit at a temperature between about −195° C. and about −20° C.    
     
     
         2 . The process of  claim 1  wherein the pressurized gaseous product is oxygen product.  
     
     
         3 . The process of  claim 1  wherein the pressurized gaseous product is nitrogen product.  
     
     
         4 . The process of  claim 1  wherein the air separation unit is within a cold box and the cold gas is extracted from the air separation unit cold box at a temperature between about −195° C. and about −20° C.  
     
     
         5 . The process of  claim 1  wherein the process stream of step c) contains any proportion of oxygen, nitrogen and argon.  
     
     
         6 . The process of  claim 1  wherein the process stream of step c) is at least one of pure nitrogen, air, oxygen containing at least 37 mol. % oxygen, oxygen containing at least 65 mol. % oxygen, oxygen containing at least 85 mol. % oxygen and oxygen containing at least 99.5 mol. %.  
     
     
         7 . The process of  claim 1  wherein the cold gas of step g) is chosen from the group comprising a nitrogen rich gas, pure nitrogen gas, air, a gas having a composition similar to air, an oxygen rich gas and pure oxygen product.  
     
     
         8 . The process of  claim 1  wherein the second liquid product of step e) is the same as the stored first liquid product of step c).  
     
     
         9 . The process of  claim 1  wherein step c) is performed if the electricity rate is below a predetermined threshold.  
     
     
         10 . The process of  claim 7  wherein step c) is performed only if the electricity rate is below a predetermined threshold.  
     
     
         11 . The process of  claim 1  wherein step d) is performed if the electricity rate is above a predetermined threshold.  
     
     
         12 . The process of  claim 9  wherein step d) is performed only if the electricity rate is above a predetermined threshold.  
     
     
         13 . The process of  claim 1  wherein step g) is performed if the electricity rate is above a predetermined threshold.  
     
     
         14 . The process of  claim 11  wherein step g) is performed only if the electricity rate is above a predetermined threshold.  
     
     
         15 . The process of  claim 1  wherein at least a portion of the cold gas of step g) is heated and expanded in a hot expander to recover energy.  
     
     
         16 . The process of  claim 1  wherein at least a portion of the cold gas of step g) is injected into a gas turbine for energy recovery.  
     
     
         17 . The process of  claim 1  wherein at least a portion of the cold gas of step g) is recycled back to the air separation unit.  
     
     
         18 . The process of  claim 1  wherein the air separation unit supplies pressurized gaseous oxygen product to an IGCC facility.  
     
     
         19 . The process of  claim 18  wherein the IGCC facility comprises a gas turbine further comprising the following steps: 
 a) extracting air from the gas turbine if the rate of electricity is below a predetermined threshold; and    b) feeding above extracted air to the air separation unit    
     
     
         20 . The process of  claim 18  comprising the step of injecting pressurized cold gas to the gas turbine if the rate of electricity is higher than a predetermined threshold.  
     
     
         21 . The process of  claim 1  wherein the refrigeration of vaporizing LNG is recovered to reduce the liquefaction cost of the first liquid product.  
     
     
         22 . The process of  claim 1  comprising reducing the flow of compressed air in the heat exchanger if the rate of electricity is above a predetermined threshold as compared to the amount of air cooled in the heat exchanger if the rate of electricity is below a predetermined threshold.  
     
     
         23 . The process of  claim 1  wherein the cold gas is removed from the air separation unit without warming it in the heat exchange line.  
     
     
         24 . The process of  claim 1  wherein the cold gas is removed from the air separation unit after being warmed partially in the heat exchange line.  
     
     
         25 . A low temperature air separation process for producing pressurized gaseous product in an air separation unit using a system of distillation columns which comprises the following steps: 
 a) cooling a compressed air stream in a heat exchange line to form a compressed cooled air stream    b) sending at least part of the compressed, cooled air stream to a column of the system    c) in a first period of time, liquefying a process stream to form a first liquid product and storing at least part of the first liquid product    d) in a second period of time, sending the above stored first liquid product to the air separation unit as one of the feeds    e) pressurizing at least one second liquid product stream    f) vaporizing the above pressurized second liquid product stream to form pressurized gaseous product in the heat exchange line    g) during the above second period of time, extracting a cold gas from the air separation unit and compressing the cold gas in a compressor having an inlet temperature between about −180° C. and −50° C. and an outlet temperature of at most −20° C. to form a pressurized gas.    
     
     
         26 . The process of  claim 26  wherein the pressurized gaseous product is oxygen product.  
     
     
         27 . The process of  claim 26  wherein pressurized gaseous product is nitrogen product.  
     
     
         28 . The process of  claim 26  wherein the process stream of step c) contains any proportion of oxygen, nitrogen and argon.  
     
     
         29 . The process of  claim 26  wherein the process stream of step c) is at least one of pure nitrogen, air, oxygen containing at least 37 mol. % oxygen, oxygen containing at least 65 mol. % oxygen, oxygen containing at least 85 mol. % oxygen and oxygen containing at least 99.5 mol. %.  
     
     
         30 . The process of  claim 26  wherein the cold gas of step g) is chosen from the group comprising a nitrogen rich gas, pure nitrogen, air, a gas having a composition similar to air, an oxygen rich gas and pure oxygen product.  
     
     
         31 . The process of  claim 26  wherein step c) is performed if the electricity rate is below a predetermined threshold.  
     
     
         32 . The process of  claim 32  wherein step c) is performed only if the electricity rate is below a predetermined threshold.  
     
     
         33 . The process of  claim 26  wherein step d) is performed if the electricity rate is above a predetermined threshold.  
     
     
         34 . The process of  claim 34  wherein step d) is performed only if the electricity rate is above a predetermined threshold.  
     
     
         35 . The process of  claim 26  wherein step g) is performed if the electricity rate is above a predetermined threshold.  
     
     
         36 . The process of  claim 36  wherein step g) is performed only if the of electricity rate is above a predetermined threshold.  
     
     
         37 . The process of  claim 26  wherein the cold gas is compressed to a pressure between 35 and 80 bars abs in the compressor.  
     
     
         38 . The process of  claim 26  wherein at least a portion of the pressurized gas is heated and expanded in a hot expander to recover energy.  
     
     
         39 . The process of  claim 26  wherein at least a portion of the pressurized gas is injected into a gas turbine for energy recovery.  
     
     
         40 . The process of  claim 26  wherein at least a portion of the pressurized gas is recycled back to the column system of the air separation unit.  
     
     
         41 . The process of  claim 26  wherein the air separation unit supplies pressurized gaseous oxygen product to an IGCC facility.  
     
     
         42 . The process of  claim 41  wherein the IGCC facility comprises a gas turbine further comprising the following steps: 
 a) extracting air from the gas turbine if the rate of electricity is below a predetermined threshold    b) feeding above extracted air to the air separation unit    
     
     
         43 . The process of  claim 26  comprising the step of injecting the pressurized cold gas to the gas turbine if the rate of electricity is higher than a predetermined threshold.  
     
     
         44 . The process of  claim 26  further comprising the following steps: 
 a) warming the pressurized gas in the heat exchange line;    b) cooling additional gas in the heat exchange line to form cold additional gas; and    c) cryogenically compressing cold additional gas to higher pressure    
     
     
         45 . The process of  claim 44  wherein both gases are compressed to between about 10 and about 20 bars abs.  
     
     
         46 . The process of  claim 26  wherein the refrigeration of vaporizing LNG is recovered to reduce the liquefaction cost of the first liquid product.  
     
     
         47 . The process of  claim 26  comprising reducing the flow of compressed air in the heat exchange line if the rate of electricity is above a predetermined threshold as compared to the amount of air cooled in the heat exchange line if the rate of electricity is below a predetermined threshold.  
     
     
         48 . The process of  claim 26  wherein the cold gas is removed from the air separation unit cold box without warming it in the heat exchange line.  
     
     
         49 . The process of  claim 26  wherein the cold gas is removed from the air separation unit cold box after being warmed partially in the heat exchange line.  
     
     
         50 . The process of  claim 26  comprising the step of warming the pressurized gas in the heat exchange line.  
     
     
         51 . The process of  claim 1  wherein the air separation unit is contained within a cold box and the extracting a cold gas from the cold box at a temperature between about −195° C. and about −20° C.  
     
     
         52 . An air separation apparatus comprising: 
 a) a system of distillation columns;    b) a heat exchange line;    c) a cold box containing at least the system of distillation columns and the heat exchange line;    d) a conduit for sending feed air to the heat exchange line;    e) a conduit for sending cooled feed air from the heat exchange line to the column system;    f) means for sending a first liquid product to the column system;    g) a conduit for removing a liquid from a column of the column system;    h) a conduit for sending the liquid to the heat exchange line;    i) a conduit for removing vaporized liquid from the heat exchange line; and    j) a conduit for extracting a gas from a column of the system and for removing the gas from the air separation apparatus without warming the gas by traversing the heat exchange line in its entirety    
     
     
         53 . The apparatus of  claim 54  comprising means for storing the first liquid product outside any column of the column system.  
     
     
         54 . The apparatus of  claim 54  comprising a gas compressor connected to the conduit for extracting gas.  
     
     
         55 . The apparatus of  claim 54  comprising a conduit for removing the gas from the air separation apparatus without warming the gas in the heat exchange line.  
     
     
         56 . The apparatus of  claim 54  comprising means for liquefying a gas to form the first liquid product.