Cryogenic Air Separation Process

Abstract

A cryogenic process of supplying oxygen to a power generation plant including at least an air separation unit ( 9,11 ), a liquid oxygen tank ( 15 ) and an air derived component liquid tank ( 17 ), comprises: During a first period: feeding a first air stream to the air separation unit at a first flowrate, feeding liquid oxygen from the liquid oxygen tank to the air separation unit, recovering a gaseous oxygen stream with a higher flow than the liquid oxygen stream from the air separation unit, sending at least one air derived component liquid to at least one air derived component liquid tank. During a second period: feeding the at least one air derived component liquid stream from the at least one air component liquid tank to the air separation unit, extracting a liquid oxygen stream from the air separation unit to the liquid oxygen tank, recovering a gaseous oxygen stream from the air separation unit and increasing the flowrate of the first air stream, feeding the air separation unit to a value greater than the first flowrate.

1 . A cryogenic process of supplying oxygen to a power generation plant comprising at least an air separation unit, a liquid oxygen tank and an air derived component liquid tank, said process comprising:
 a. During a first period:
 i) feeding a first air stream to the air separation unit at a first flowrate; 
 ii) feeding liquid oxygen from the liquid oxygen tank to the air separation unit; 
 iii) recovering a gaseous oxygen stream with a higher flow than the liquid oxygen stream from the air separation unit; and 
 iv) sending at least one air derived component liquid to at least one air derived component liquid tank. 
   b) During a second period:
 i) feeding the at least one air derived component liquid stream from the at least one air component liquid tank to the air separation unit; 
 ii) extracting a liquid oxygen stream from the air separation unit to the liquid oxygen tank; 
 iii) recovering a gaseous oxygen stream from the air separation unit; and 
 iv) increasing the flowrate of the first air stream, feeding the air separation unit to a value greater than the first flowrate. 
   
   
   
       2 . Process according to  claim 1  wherein the air separation unit produces substantially the same flowrate of gaseous oxygen during the first and second periods. 
   
   
       3 . Process according to  claim 1  wherein the air separation unit produces a higher flowrate of gaseous oxygen during the first period than in the second period. 
   
   
       4 . Process according to  claim 1  wherein the power costs are average during the second period and below average during a third period, wherein during the third period, the process includes:
 i) feeding the at least one air derived component liquid stream from the at least one air component liquid tank to the air separation unit;   ii) extracting a liquid oxygen stream from the air separation unit to the liquid oxygen tank;   iii) recovering a gaseous oxygen stream from the air separation unit;   iv) increasing the flowrate of the first air stream feeding the air separation unit to a value greater than its flowrate in the first period; and   v) wherein the flowrates of the first air stream in the second period and the third period are substantially equal.   
   
   
       5 . Process according to  claim 1  wherein the power costs of the first period are higher than average. 
   
   
       6 . Process according to  claim 1  wherein the power costs of the second period are average or lower than average. 
   
   
       7 . Process according to  claim 1  wherein the power costs of the first period are higher than average and the power costs of the second period are average or lower than average. 
   
   
       8 . Process according to  claim 1  wherein the power demand of the first period is higher than average. 
   
   
       9 . Process according to  claim 1  wherein the power demand of the second period is average or lower than average. 
   
   
       10 . Process according to  claim 1  wherein the power demand of the first period is higher than average and the power demand of the second period is average or lower than average. 
   
   
       11 . A process according to  claim 1 , in which the power generation plant is an oxycombustion plant. 
   
   
       12 . A process according to  claim 1 , in which the power generation plant is an IGCC plant. 
   
   
       13 . A process according to  claim 17  in which at least one air derived component liquid is liquid nitrogen and wherein step iv) of period a) of  claim 1  comprises removing liquid nitrogen from a column of the air separation unit. 
   
   
       14 . A process according to  claim 1 , in which at least one air derived component liquid contains 80 mol % nitrogen or greater. 
   
   
       15 . A process according to  claim 1 , in which at least one air derived component liquid is liquid air. 
   
   
       16 . A process according to  claim 1 , in which at least one air derived component liquid contains 35 mol % oxygen or greater wherein step iv) of period a) of  claim 1  comprises removing liquid nitrogen from a column of the air separation unit. 
   
   
       17 . A process according to  claim 1  wherein in at least one of step a) ii) of  claim 1  the liquid oxygen is fed to a column of the air separation unit. 
   
   
       18 . A process according to  claim 1  wherein in step a) ii) of  claim 1  the liquid oxygen is fed to an exchanger of the air separation unit without passing via a column of the air separation unit. 
   
   
       19 . A process according to  claim 4  wherein in at least one of step i) of  claim 4  the liquid oxygen is fed to a column of the air separation unit. 
   
   
       20 . A process according to  claim 4  wherein in step i) of  claim 4  the liquid oxygen is fed to an exchanger of the air separation unit without passing via a column of the air separation unit.