System and apparatus for compressing and cooling an incoming feed air stream in a cryogenic air separation plant

Abstract

A system and apparatus for compression of an incoming feed air stream using at least two variable speed compressor drive assemblies controlled in tandem is provided. The first variable speed driver assembly drives at least one compression stage in the lower pressure compressor driven while the second variable speed driver assembly drives higher pressure compression stage disposed either in the common air compression train or the split functional compression train of the air separation plant. The first and second variable speed driver assemblies are preferably high speed, variable speed electric motor assemblies each having a motor body, a motor housing, and a motor shaft with one or more impellers directly and rigidly coupled to the motor shaft via a sacrificial rigid shaft coupling.

What is claimed is: 
     
         1 . A system for compressing and cooling a feed air stream to a cryogenic air separation plant comprising:
 (i) a common air compression train comprising:   a lower pressure single stage or multi-stage compressor of a common air compression train configured to compress at least a portion of the incoming feed air stream;   a first variable speed driver assembly directly and rigidly coupled to the lower pressure single stage or multi-stage compressor and configured to drive at least one compression stage in the lower pressure single stage or multi-stage compressor;   a higher pressure single stage or multi-stage compressor of the common air compression train fluidically coupled to the lower pressure single stage or multi-stage compressor and configured for further compressing the compressed feed air stream from the lower pressure single stage or multi-stage compressor;   a second variable speed driver assembly directly and rigidly coupled to the higher pressure single stage or multi-stage compressor and configured to drive at least one compression stage in the higher pressure single stage or multi-stage compressor; and   a pre-purification unit disposed downstream of the lower pressure single stage or multi-stage compressor and configured to remove impurities from the compressed feed air stream exiting the lower pressure single stage or multi-stage compressor or from the compressed feed air stream exiting one or more stages of the higher pressure single stage or multi-stage compressor;   (ii) a split functional air compression train fluidically coupled to the common air compression train configured for handling one or more portions of the compressed, purified air from the common air compression train, the split functional air compression train further comprising one or more compression stages configured for further compressing some or all of the one or more portions of the compressed, purified air handled in the split functional air compression train;   (iii) a primary heat exchanger configured to cool the one or more portions of compressed, purified air to temperatures suitable for rectification in a distillation column system of the cryogenic air separation plant; and   (iv) one or more controllers operatively coupled to the variable speed driver assemblies wherein a speed of the second variable speed driver assembly is adjusted in response to changes in the operating conditions of the cryogenic air separation plant and a speed of the first variable speed driver assembly and wherein a ratio of the speed of the variable speed driver assemblies prior to such adjustment is different than the ratio of the speed of the variable speed driver assemblies after adjustment.   
     
     
         2 . The system of  claim 1  wherein the first variable speed driver assembly and the second variable speed driver assembly are high speed electric motor assemblies each having a motor body, a motor housing, and a motor shaft with one or more impellers directly and rigidly coupled to the motor shaft. 
     
     
         3 . The system of  claim 1  wherein the lower pressure single stage or multi-stage compressor further comprises two compression stages arranged in parallel and driven directly by a double ended variable speed driver assembly, wherein the two compression stages are configured to receive and compress ambient pressure air to produce a first compressed air stream. 
     
     
         4 . The system of  claim 3  wherein each of the two compression stages are configured to receive and compress different volumetric flows of ambient pressure air. 
     
     
         5 . The system of  claim 3  wherein the one or more higher pressure single stage or multi-stage compressors of the common air compression train further comprises a third compression stage and a fourth compression stage arranged in series and driven by a double ended second variable speed driver assembly, wherein the third compression stage is configured to receive and compress the first compressed air stream to produce a second compressed air stream and the fourth compression stage is configured to receive and compress the second compressed air stream to produce a third compressed air stream. 
     
     
         6 . The system of  claim 1  wherein the lower pressure single stage or multi-stage compressor further comprises a first compression stage and a second compression stage arranged in series and driven directly by a double ended first variable speed driver assembly, wherein the first compression stage is configured to receive and compress ambient pressure air and produce a first compressed air stream and the second compression stage is configured to receive and compress the first compressed air stream to produce a second compressed air stream. 
     
     
         7 . The system of  claim 6  wherein the one or more higher pressure single stage or multi-stage compressors of the common air compression train further comprises a third compression stage and a fourth compression stage arranged in series and driven by a double ended second variable speed motor assembly, wherein the third compression stage is configured to receive and compress the second compressed air stream to produce a third compressed air stream and the fourth compression stage is configured to receive and compress the third compressed air stream to produce a fourth compressed air stream. 
     
     
         8 . The system of  claim 1  wherein the lower pressure single stage or multi-stage compressor further comprises a single stage compressor driven directly by a single ended first variable speed driver assembly, wherein the single compression stage is configured to receive and compress ambient pressure air and produce a first compressed air stream. 
     
     
         9 . The system of  claim 8  wherein the one or more higher pressure single stage or multi-stage compressors of the common air compression train further comprises a second compression stage and a third compression stage arranged in series and driven by a double ended second variable speed driver assembly, wherein the second compression stage is configured to receive and compress the first compressed air stream to produce a second compressed air stream and the third compression stage is configured to receive and compress the second compressed air stream to produce a third compressed air stream. 
     
     
         10 . The system of  claim 1  wherein the lower pressure single stage or multi-stage compressor further comprises a first compression stage and a second compression stage arranged in series and driven directly a double ended first variable speed driver assembly, wherein the first compression stage is configured to receive and compress ambient pressure air and produce a first compressed air stream and the second compression stage is configured to receive and compress the first compressed air stream to produce a second compressed air stream. 
     
     
         11 . The system of  claim 10  wherein the one or more higher pressure single stage or multi-stage compressors of the common air compression train is a single stage compressor that includes a third compression stage driven by a single ended second variable speed driver assembly, wherein the third compression stage is configured to receive and compress the second compressed air stream to produce a third compressed air stream. 
     
     
         12 . The system of  claim 1  further comprising one or more further compression stages of the common air compression train and such one or more further compression stages are configured as an integrally geared compressor. 
     
     
         13 . The system of  claim 1  wherein one or more compression stages in the split functional air compression train are configured as an integrally geared compressor. 
     
     
         14 . The system of  claim 1  wherein the one or more portions of the purified, compressed air stream in the split functional air compression train further comprise a first portion of a boiler air stream and a second portion of an upper column turbine air stream. 
     
     
         15 . The system of  claim 1  wherein the one or more portions of the purified, compressed air stream in the split functional air compression train further comprise a first portion of a boiler air stream and a second portion of a lower column turbine air stream. 
     
     
         16 . The system of  claim 1  wherein the one or more portions of the purified, compressed air stream in the split functional air compression train further comprise a first portion of a boiler air stream, a second portion of an upper column turbine air stream, and a third portion of a warm recycle turbine air stream. 
     
     
         17 . The system of  claim 1  wherein the portions of the purified, compressed air stream in the split functional air compression train further comprise a first portion of a boiler air stream, a second portion of a lower column turbine air stream, and a third portion of a warm recycle turbine air stream. 
     
     
         18 . The system of  claim 1  further comprising one or more intercoolers disposed between consecutive compression stages in the common air compression train wherein each intercooler is configured to cool the compressed air stream. 
     
     
         19 . The system of  claim 1  further an aftercooler disposed between a compression stage in the common air compression train and a pre-purification unit wherein the aftercooler is configured to cool the compressed air stream exiting the compression stage prior to purification of the compressed feed air stream. 
     
     
         20 . The system of  claim 1  wherein the pre-purification unit is an adsorptive pre-purification unit. 
     
     
         21 . The system of  claim 1  further comprising a compressed air diversion circuit and wherein a portion of the compressed feed air stream from the common air compression train is diverted to repressurize the adsorptive pre-purification unit. 
     
     
         22 . The system of  claim 1  further comprising a compressed air diversion circuit disposed upstream of the pre-purification unit and wherein a portion of the compressed feed air stream from the common air compression train is diverted to heat the air entering an air suction filter house to prevent ice build-up. 
     
     
         23 . The system of  claim 1  further comprising a compressed air diversion circuit disposed downstream of the pre-purification unit and wherein a portion of the compressed, purified air stream from the common air compression train is diverted to supply clean, dry air to selected applications in the cryogenic air separation plant. 
     
     
         24 . The system of  claim 1  further comprising a vent circuit and wherein a portion of the compressed feed air stream from the common air compression train is vented. 
     
     
         25 . The system of  claim 1  wherein at least one stage of compression in the common air compression train comprises a centrifugal compressor having inlet guide vanes wherein the inlet guide vanes are adjusted to control the flow rate of the feed air stream to the centrifugal compressor. 
     
     
         26 . A system for compression of a feed air stream to a cryogenic air separation plant comprising:
 (i) a common air compression train comprising:
 a lower pressure single stage or multi-stage compressor of a common air compression train configured to compress at least a portion of the incoming feed air stream; 
 a first variable speed driver assembly directly and rigidly coupled to the lower pressure single stage or multi-stage compressor and configured to drive at least one compression stage in the lower pressure single stage or multi-stage compressor; 
 one or more further compression stages of the common air compression train wherein such one or more further compression stages are configured as an integrally geared compressor; and 
 a pre-purification unit disposed downstream of the lower pressure single stage or multi-stage compressor and configured to remove impurities from the compressed feed air stream exiting the lower pressure single stage or multi-stage compressor or from the compressed feed air stream exiting one or more stages of the higher pressure single stage or multi-stage compressor; 
   (ii) a split functional air compression train fluidically coupled to the common air compression train, configured for handling one or more portions of the compressed, purified air from the common air compression train, the split functional air compression train further comprising:
 a higher pressure single stage or multi-stage compressor configured for further compressing some or all of the one or more portions of the compressed, purified air handled in the split functional air compression train; and 
 a second variable speed driver assembly directly and rigidly coupled to the higher pressure single stage or multi-stage compressor and configured to drive at least one compression stage in the higher pressure single stage or multi-stage compressor; 
   (iii) a primary heat exchanger configured to cool the one or more portions of compressed, purified air to temperatures suitable for rectification in a distillation column system of the cryogenic air separation plant; and   (iv) one or more controllers operatively coupled to the variable speed driver assemblies wherein a speed of the second variable speed driver assembly is adjusted in response to changes in the operating conditions of the cryogenic air separation plant and a speed of the first variable speed driver assembly and wherein a ratio of the speed of the variable speed driver assemblies prior to such adjustment is different than the ratio of the speed of the variable speed driver assemblies after adjustment.   
     
     
         27 . A system for compression of a feed air stream to a cryogenic air separation plant comprising:
 (i) a common air compression train comprising:
 a lower pressure single stage or multi-stage compressor of a common air compression train configured to compress at least a portion of the incoming feed air stream; 
 a first variable speed driver assembly directly and rigidly coupled to the lower pressure single stage or multi-stage compressor and configured to drive at least one compression stage in the lower pressure single stage or multi-stage compressor; 
 an intermediate pressure compressor of the common air compression train wherein such an intermediate pressure compressor is configured as an integrally geared compressor; 
 a higher pressure single stage or multi-stage compressor of the common air compression train fluidically coupled to the lower pressure single stage or multi-stage compressor and configured for further compressing the compressed feed air stream from the lower pressure single stage or multi-stage compressor; 
 a second variable speed driver assembly directly and rigidly coupled to the higher pressure single stage or multi-stage compressor and configured to drive at least one compression stage in the higher pressure single stage or multi-stage compressor; and 
 a pre-purification unit disposed downstream of the lower pressure single stage or multi-stage compressor and configured to remove impurities from the compressed feed air stream exiting the lower pressure single stage or multi-stage compressor or from the compressed feed air stream exiting one or more stages of the higher pressure single stage or multi-stage compressor; 
   (ii) a split functional air compression train fluidically coupled to the common air compression train configured for handling one or more portions of the compressed, purified air from the common air compression train, the split functional air compression train further comprising one or more compression stages configured for further compressing some or all of the one or more portions of the compressed, purified air handled in the split functional air compression train;   (iii) a primary heat exchanger configured to cool the one or more portions of compressed, purified air to temperatures suitable for rectification in a distillation column system of the cryogenic air separation plant; and   (iv) one or more controllers operatively coupled to the variable speed driver assemblies wherein a speed of the second variable speed driver assembly is adjusted in response to changes in the operating conditions of the cryogenic air separation plant and a speed of the first variable speed driver assembly and wherein a ratio of the speed of the variable speed driver assemblies prior to such adjustment is different than the ratio of the speed of the variable speed driver assemblies after adjustment.