System and method for cryogenic air separation using a booster loaded liquid turbine for expansion of a liquid air stream

Abstract

A system and method for cryogenic air separation arrangement having a booster loaded liquid turbine for expansion of a liquid air stream or other fluid having liquid-like densities is provided. The disclosed booster loaded liquid turbines are relatively small to provide an aerodynamic and speed match between the turbine and the coupled gas compressor. The coupled gas compressor is a supplemental booster compressor and may be a dedicated warm booster compressor or alternatively a cold booster compressor.

What is claimed is: 
     
         1 . An air separation unit having a booster loaded liquid turbine arrangement configured to produce one or more oxygen enriched streams and one or more nitrogen enriched streams, the air separation unit comprising:
 a main air compression system configured to receive an incoming air stream and produce a compressed air stream at a pressure of between about 5 bar(a) and 15 bar(a);   a pre-purification unit configured to pre-purify the compressed air stream to produce a compressed, pre-purified air stream;   a primary booster compressor configured to receive a portion of the compressed, pre-purified air stream and produce a further compressed, pre-purified air stream at a pressure of between about 25 bar(a) and 90 bar(a);   a supplemental booster compressor configured to further compress the further compressed, pre-purified air stream and produce a still further compressed, pre-purified air stream at a pressure of between about 30 bar(a) and 95 bar(a);   a main heat exchanger configured to cool the still further compressed, pre-purified air stream to produce a liquid air stream;   a liquid turbine operatively coupled to the supplemental booster compressor and configured to expand the liquid air stream and produce an expanded air stream at a pressure between 7 bar(a) and 12 bar(a) and wherein the work of expansion is used to drive the supplemental booster compressor; and   a distillation column system comprising a higher pressure column and a lower pressure column linked in a heat transfer relationship via a condenser reboiler, the distillation column system configured to receive all or a portion of the expanded air stream in the higher pressure column for distillation of the expanded air stream into the one or more oxygen enriched streams and the one or more nitrogen enriched streams.   
     
     
         2 . The air separation unit of  claim 1  wherein the supplemental booster compressor is a cold booster compressor configured to receive further compress the further compressed, pre-purified air stream at a pressure of between about 40 bar(a) and 50 bar(a) that has been partially cooled in the main heat exchanger and produce a still further compressed, pre-purified air stream at a pressure of between about 50 bar(a) and 60 bar(a). 
     
     
         3 . The air separation unit of  claim 1  wherein the supplemental booster compressor is a warm booster compressor configured to further compress the further compressed, pre-purified air stream at a pressure of between about 70 bar(a) and 90 bar(a) before any cooling in the main heat exchanger and produce a still further compressed, pre-purified air stream at a pressure of between about 75 bar(a) and 95 bar(a). 
     
     
         4 . The air separation unit of  claim 1  wherein the portion of the compressed, pre-purified air stream received by the primary booster compressor is a boiler air stream comprising between about 25% to 45% by volume of the compressed, pre-purified air stream. 
     
     
         5 . The air separation unit of  claim 1  further configured such that all of the expanded air stream is directed to the higher pressure column of the distillation column system. 
     
     
         6 . The air separation unit of  claim 1  further configured such that a first portion of the expanded air stream is directed to the higher pressure column of the distillation column system and a second portion of the expanded air stream is further reduced in pressure and directed to the lower pressure column of the distillation column system. 
     
     
         7 . A method of air separation comprising the steps of:
 compressing an incoming air stream in a main air compression system configured to a pressure of between about 5 bar(a) and 15 bar(a);   pre-purifying the compressed air stream to produce a compressed, pre-purified air stream;   further compressing all or a portion of the compressed, pre-purified air stream in a primary booster compressor to produce a further compressed, pre-purified air stream at a pressure of between about 25 bar(a) and 90 bar(a);   still further compressing the further compressed, pre-purified air stream in a supplemental booster compressor to produce a still further compressed, pre-purified air stream at a pressure of between about 30 bar(a) and 95 bar(a);   cooling the still further compressed, pre-purified air stream in a main heat exchanger to produce a liquid air stream;   expanding the liquid air stream in a liquid turbine operatively coupled to the supplemental booster compressor to produce an expanded air stream at a pressure between 7 bar(a) and 12 bar(a) and wherein the work of expansion drives the supplemental booster compressor;   separating the expanded air stream into one or more oxygen enriched streams and the one or more nitrogen enriched streams in a distillation column system comprising a higher pressure column and a lower pressure column linked in a heat transfer relationship via a condenser reboiler, the distillation column system configured to receive all or a portion of the expanded air stream in the higher pressure column.   
     
     
         8 . The method of  claim 7  further comprising the step of partially cooling the further compressed, pre-purified air stream in the main heat exchanger and wherein the supplemental booster compressor is a cold booster compressor configured to further compress the cooled, further compressed, pre-purified air stream at a pressure of between about 40 bar(a) and 50 bar(a) to produce a still further compressed, pre-purified air stream at a pressure of between about 50 bar(a) and 60 bar(a). 
     
     
         9 . The method of  claim 7  wherein the supplemental booster compressor is a warm booster compressor configured to further compress the further compressed, pre-purified air stream at a pressure of between about 70 bar(a) and 90 bar(a) to produce a still further compressed, pre-purified air stream at a pressure of between about 75 bar(a) and 95 bar(a). 
     
     
         10 . The method of  claim 7  wherein the portion of the compressed, pre-purified air stream received by the primary booster compressor is a boiler air stream comprising between about 25% to 45% by volume of the compressed, pre-purified air stream. 
     
     
         11 . The method of  claim 7  wherein all of the expanded air stream is directed to the higher pressure column of the distillation column system. 
     
     
         12 . The method of  claim 7  wherein a first portion of the expanded air stream is directed to the higher pressure column of the distillation column system and a second portion of the expanded air stream is further reduced in pressure and directed to the lower pressure column of the distillation column system.