Process to compress air and its use in an air separation process and systems using said processes

Abstract

The invention is directed to a process and a system to compress air. The process involves the following steps, (i) compressing air in a compressor, (ii) cooling the compressed air as obtained in step (i) (iii) further compressing the air of step (ii) in a second compressor, (iv) further compressing at least part of the compressed air as obtained in step (iii) in a booster compressor, wherein the compressor in step (i) is an axial compressor, the compressor of step (i) and (iii) are driven by a common first driver and the booster compressor is driven by a separate second driver and wherein the compressors of steps (i) and (iii) are split into two individual casings.

1 . A process to compress air comprising the following steps,
 (i) compressing air in a compressor,   (ii) cooling the compressed air as obtained in step (i)   (iii) further compressing the air of step (ii) in a second compressor,   (iv) further compressing at least part of the compressed air as obtained in step (iii) in a booster compressor, wherein the compressor in step (i) is an axial compressor, the compressors of steps (i) and (iii) are driven by a common first driver and the booster compressor is driven by a separate second driver and wherein the compressors of steps (i) and (iii) are split into two individual casings.   
   
   
       2 . A process according to  claim 1 , wherein the first driver is a steam turbine. 
   
   
       3 . A process according to  claim 2 , wherein the steam turbine operates on steam having a pressure of between 1.8 and 11 Mpa inlet pressure. 
   
   
       4 . A process according to  claim 1 , wherein the compressor in step (iii) is a radial or isothermal compressor and wherein a gear box is present between the first driver and the second compressor. 
   
   
       5 . A process according to  claim 1 , wherein the second driver is a steam turbine or electric motor. 
   
   
       6 . A process according to  claim 5 , wherein the second driver is an electric motor driver and wherein a gear box is present between the electric motor driver and the booster compressor. 
   
   
       7 . A process according to  claim 1 , wherein the capacity of the axial compressor in step (i) is between 25000 and 40000 t/d air. 
   
   
       8 . A process according to  claim 1 , wherein the pressure is increased in step (i) from ambient to between 0.3 and 1.2 MPa. 
   
   
       9 . A process according to  claim 1 , wherein the pressure is increased in step (iii) to between 1 and 2 MPa. 
   
   
       10 . A process according to  claim 1 , wherein the pressure is increased in step (iv) to between 8 and 11 MPa. 
   
   
       11 . A process for separating oxygen from air by cryogenic air separation, wherein compressed air as obtained in step (iii) of the process according to  claim 1  is cooled against expanded air as obtained in step (iv) of said process and wherein oxygen is separated by means of distillation from the cooled and compressed air. 
   
   
       12 . A system for compressing air comprising
 (a) an axial compressor,   (b) cooling means to cool, in use, compressed air obtained in the axial compressor,   (c) a radial or isothermal compressor to further compress, in use, the compressed and cooled air, and   (d) a booster compressor to further compress, in use, at least part of the compressed air, wherein the axial compressor and the radial or isothermal compressor have a common first driver and wherein the axial compressor and the radial or isothermal compressor are split into two individual casings and wherein the booster compressor is provided with a second driver separate from the first driver.   
   
   
       13 . A system according to  claim 12 , wherein the first driver is a steam turbine. 
   
   
       14 . A system according to  claim 12 , wherein the second driver is a steam turbine or electric motor. 
   
   
       15 . A system according to  claim 14 , wherein the second driver is a motor driver and wherein a gear box is present between the motor driver and the booster compressor. 
   
   
       16 . A system according to  claim 12 , wherein the axial compressor (a) is a modified axial compressor as derived from an existing axial compressor of a large industrial or aeroderivative gas turbine, and wherein the number of stages of the large industrial or aeroderivative gas turbine compressor part is reduced.