Process and plant for cryogenic separation of air

Abstract

A process for cryogenic separation of air using an air separation plant configured as a high air pressure air separation plant is provided, wherein of the air initially compressed several partial air streams are formed which are at least in part further compressed, cooled in a main heat exchanger and expanded before being introduced into the column system. The partial air streams include a first partial air stream and a second partial air stream whose air is compressed in parallel in a first warm booster and a second warm booster and thereafter expanded in a first expander and a second expander mechanically coupled to the first booster and to the second booster, respectively. A corresponding air separation plant is also part of the present invention.

1 . A process for cryogenic separation of air using an air separation plant comprising a column system with a pressure column operated at a pressure in a first pressure range and a low-pressure column operated at a pressure in a second pressure range below the first pressure range, wherein
 the column system, and thereof at least the pressure column, is supplied with compressed air, all air being supplied to the column system being compressed to a pressure in a third pressure range at least 5 bar above the first pressure range, and of the air compressed to the first pressure range, several partial air streams being formed which are at least in part further compressed, cooled in a main heat exchanger and expanded before being introduced into the column system,   the partial air streams include a first partial air stream whose air is, at least in part, in the order indicated and in a single pass, compressed to a pressure in a fourth pressure range above the third pressure range in a first booster being operated with an inlet temperature of more than 0° C., cooled in the main heat exchanger, expanded in a first expander mechanically coupled to the first booster to a pressure in the first pressure range, and introduced into the pressure column,   the partial air streams include a second partial air stream whose air is at least in part, in the order indicated and in a single pass, supplied at a pressure in a fifth pressure range being above or corresponding to the third pressure range to a second expander, expanded in the second expander to a pressure in a sixth pressure range between the first and the fifth pressure range, further expanded to a pressure in the first or second pressure range, and introduced into the column system, the air of the second partial air stream is at least in part cooled before being expanded to the pressure in the sixth pressure range in a first cooling step and at least in part cooled after having been expanded to the pressure in the sixth pressure range in a second cooling step, the first and second cooling steps being performed using the main heat exchanger, internally compressed gaseous oxygen is produced in and withdrawn from the process at an absolute pressure between 3 and 9 bar, and   the air separation plant is operated without a turbine expanding air of the first partial stream and/or air of the second partial stream into the low pressure column.   
     
     
         2 . The method according to  claim 1 , wherein the fifth pressure range is above the third pressure range, wherein at least a part of the air of the second partial air stream is, before being expanded in the second expander, compressed to the pressure in the fifth pressure range in a second booster mechanically coupled to the second expander, the second booster being coupled with an inlet temperature of more than 0° C. 
     
     
         3 . The method according to  claim 1 , wherein the partial air streams include a third partial air stream whose air is at least in part liquefied in the main heat exchanger, expanded to a pressure in the first or second pressure range and introduced into the column system. 
     
     
         4 . The method according to  claim 1 , wherein the air of the third partial air stream is, at least in a first operation mode, at least in part compressed to the pressure in the fourth pressure range in the first booster and liquefied in the main heat exchanger at the pressure in the fourth pressure range. 
     
     
         5 . The method according to  claim 4 , wherein the air of the third partial air stream is, in a second operation mode, at least in part liquefied in the main heat exchanger at the pressure in the third pressure range. 
     
     
         6 . The method according to  claim 5 , wherein, in the second operating mode at least the 1.1-fold and up to the 3.0-fold amount of internally compressed gaseous oxygen is withdrawn from the air separation plant as compared to the first operating mode and wherein, in the second operating mode, at most the 0.5-fold amount of liquid oxygen is withdrawn from the air separation plant as compared to the first operating mode. 
     
     
         7 . The process according to  claim 1 , wherein liquid products are withdrawn from the air separation plant, wherein a ratio of an equivalent value characterizing a total amount of the liquid products to a total amount of the internally compressed gaseous oxygen is in a range from 0.6 to 1.6, the equivalent value corresponding to the sum of all liquid nitrogen products, all liquid oxygen products multiplied by a factor of 1.08, and all liquid argon products multiplied by a factor of 0.8, all values being expressed in normalized cubic meters per hour. 
     
     
         8 . The process according to  claim 1 , wherein the first pressure range is from 4 to 7 bar, the second pressure range is from 1 to 2 bar, the third pressure range is from 15 to 28 bar, the fourth pressure range is from 20 to 38 bar, the fifth pressure range is from 20 to 45 bar and the sixth fifth pressure range is from 9 to 21 bar absolute pressure. 
     
     
         9 . The process according to  claim 1 , wherein, from the air compressed to the third pressure range, a relative proportion of 0.6 to 0.8 is provided as the first partial air stream and a relative proportion of 0.15 to 0.30 is provided as the second partial air stream. 
     
     
         10 . The process according to  claim 2  wherein, from the air compressed to the third pressure range, a relative proportion of 0.05 to 0.15 is provided as the third partial air stream. 
     
     
         11 . The process according to  claim 1 , wherein the air of the second partial air stream is at least in part liquefied in the main heat exchanger before being expanded to the pressure in the first pressure range or in the second pressure range and thereafter being introduced into the column system. 
     
     
         12 . The process according to  claim 1 , wherein the air of the first partial air stream is at least in part cooled in the main heat exchanger to a temperature in a temperature range between −132 and −92° C. before being expanded in the first expander and wherein the air of the second partial air stream is at least in part cooled in the first cooling step to a temperature in a temperature range between −30 and 30° C. and in the second cooling step to a temperature in a temperature range between −87 and −47° C. 
     
     
         13 . The process according to  claim 1 , wherein gaseous nitrogen withdrawn from the pressure column is heated in the main heat exchanger and thereafter compressed to a product pressure. 
     
     
         14 . An air separation plant comprising a column system with a pressure column adapted to be operated at a pressure in a first pressure range, a low-pressure column adapted to be operated at a pressure in a second pressure range below the first pressure range, a first booster adapted to be operated with an inlet temperature of more than 0° C., a first expander mechanically coupled to the first booster, a second expander, and a main heat exchanger, wherein
 the air separation plant comprises means adapted to supply to the column system, and thereof at least to the pressure column, compressed air, to compress all air being supplied to the column system to a pressure in a third pressure range at least 5 bar above the first pressure range, to form, of the air compressed to the pressure in the first pressure range, several partial air streams, and to at least in part further compress, cool in the main heat exchanger and expand before being introduced into the column system said partial air streams, 
 the partial air streams include a first partial air stream, and the air separation plant comprises means adapted to subject the air of the first partial air stream at least in part, in the order indicated and in a single pass, to a compression in the first booster to a pressure in a fourth pressure range above the third pressure range, to an expansion in the first expander to a pressure in the first pressure range, and a cooling in the main heat exchanger before said expansion to the pressure in the first pressure range, and to an introduction into the pressure column after said expansion to the pressure in the first pressure range, 
 the partial air streams include a second partial air stream, and the air separation plant comprises means adapted to subject the air of the second partial air stream at least in part in the order indicated and in a single pass, to an expansion from a pressure in a fifth pressure range being above or corresponding to the third pressure range, in the second expander to a pressure in a sixth pressure range between the first and the fifth pressure range, to a further expansion to a pressure in the first or second pressure range and to an introduction into the column system, 
 the air separation plant is adapted to cool the air of the second partial air stream at least in part before being expanded to the pressure in the sixth pressure range in a first cooling step and to cool the air of the second partial air stream at least in part after having been expanded to the pressure in the sixth pressure range in a second cooling step, and to perform the first and second cooling steps using the main heat exchanger, 
 the air separation plant comprises means which are adapted to produce in and withdraw from the air separation plant internally compressed gaseous oxygen at an absolute pressure between 3 and 9 bar, and 
 the air separation plant is adapted to be operated without a turbine expanding air of the first partial stream and/or air of the second partial stream into the low pressure column. 
 
     
     
         15 . The air separation plant according to  claim 14 , wherein a second booster is provided which is adapted to be operated with an inlet temperature of more than 0° C. and which is mechanically coupled to the second expander, wherein the second booster is adapted to compress at least a part of the air of the second partial air stream to the pressure in the fifth pressure, the fifth pressure range being above the third pressure range.