Air separation with work expansion to high and low pressure rectification stages

Claim 2

A PROCESS FOR THE CRYOGENIC SEPARATION OF AIR INTO AT LEAST ONE LIQUID PRODUCT AND AT LEAST ONE GAS PRODUCT BY FRACTIONAL DISTILLATION AT HIGH PRESSURE AND THEN AT LOW PRESSURE WHEREIN COMPRESSED AIR IS COOLED BY HEAT EXCHANGE WITH COLD STREAMS FROM THE PROCESS COMPRISING THE STEPS OF: COMPRESSING SAID AIR TO A HEAD PRESSURE OF 120-700 SPSIG, BEING HIGHER THAN SAID HIGH PRESSURE ISTILLATION, SELECTIVELY ADSORBING CARBON DIOXIDE AND ACETYLENE ATMOSPHERIC IMPURITIES FROM SAID COMPRESSED AIR PRIOR TO CRYOGENIC COOLING SO AS TO PROVIE PRECLEANED AIR, COOLING AND WORK EXPANDING A FIRST MINOR PORTION COMPRISING 1-20% OF SAID PRECLEANED AIR TO A PRESSURE BELOW SAID HIGH PRESSURE DISTILLATION AND RECOVERING REFRIGERATION FROM THE RESULTING COLD LOW PRESSURE GAS FOR THEPROCESS, COOLING AND LIQUEFYING A SECOND MINOR PORTION COMPRISING 1-20% OF SAID PRECLEANED AIR TO FORM LIQUID AIR AND DISTILLING SAID LIQUID AIR, WITH THE REFRIGERATION FOR SAID LIQUEFYING BEING PROVIDED BY SAID COOL STRAMS FROM THE PROCESS WHICH ARE THEREBY PARTIALLY WARMED, PARTIALLY COOLING THE MAJOR PORTION OF SAID PRECLEANED AIR BY THE COLD STREAMS WHICH HAVE BEEN PARTIALLY WARMED, TO TEMPERATURE ABOVE THE TEMPERATURE OF THE COOLED AND LIQUEFIED SECOND MINOR PORTION, AND WORK EXPANDING THE PARTIALLY COOLED MAJOR PORTION TO THE PRESSURE OF SAID HIGH PRESSURE DISTILLATION SUCH THAT THE EXPANDED COLD FLUID IS SUBSTANTIALLY ENTIRELY GAS, AND FLOWING AT LEAST PART OF THE RESULTING COLD GAS TO SAID HIGH PRESSURE DISTILLATION, AND WITHDRAWING AT LEAST ONE LIQUID PRODUCT AND AT LEAST ONE GAS PRODUCT FROM THE DISTILLATION AND DISCHARGING SUCH LIQUID AND GAS PRODUCTS FROM THE PROCESS.

Claim 3

A process according to claim 1, wherein said first minor portion of said precleaned air to be work expanded is a diverted part of the work expanded major portion of said precleaned air which is reheated prior to said work expanding to pressure below said high pressure distillation.

Claim 4

A process according to claim 1 wherein said first minor portion of said precleaned air to be work expanded is cooled to an intermediate temperature, said major portion of said precleaned air to be work expanded is cooled to a lower-than intermediate temperature, and said minor and major portions are thereafter work expanded in parallel flow relation.

Claim 5

A process according to claim 1, wherein the work expanded first minor portion is thereafter heat exchanged with the precleaned air for cooling thereof as one of said cold streams.

Claim 6

A process according to claim 1, wherein said first minor portion is work expanded to the pressure of the low pressure distillation and thereafter passed to said low pressure distillation.

Claim 7

A process according to claim 1 wherein 2-15% of the precleaned air is cooled and liquefied as said second minor portion.

Claim 8

A process for the cryogenic separation of air into liquid oxygen and nitrogen products and gaseous nitrogen product by fractional distillation at high pressure and then at low pressure wherein compressed air is cooled by heat exchange with cold streams from the process comprising the steps of: compressing said air to head pressure of 120-700 psig., being higher than said high pressure distillation; selectively adsorbing carbon dioxide and acetylene atmospheric impurities from said compressed air prior to cryogenic cooling so as to provide precleaned air; cooling and work expanding a first minor portion comprising 1-20% of said precleaned air to pressure below said high pressure distillation as cold low pressure air and heat exchanging same with said precleaned air as one of said cold streams, and releasing the so-warmed low pressure air from the process as excess air; cooling and liquefying a second minor portion comprising 1-20% of said precleaned air to form liquid air and distilling said liquid air, with the refrigeration for said cooling and liquefying being provided by said cold streams from the process which are thereby partially warmed; partially cooling the major portion of said precleaned air by the cold streams which have been partially warmed, to temperature above the temperature of the cooled and liquefied second minor portion, and work expanding the Partially cooled major portion to the pressure of said high pressure distillation such that the expanded cold air is substantially entirely cold gas; introducing a larger part of said cold gas to said high pressure distillation for partial separation threin; heat exchanging a smaller part of said cold gas with said second minor portion as one of said cold streams for said cooling and liquefying thereby reheating said smaller part, and employing the reheated smaller part as said first minor portion of precleaned air to be work expanded; withdrawing liquid oxygen and liquid nitrogen products from the distillation as separate streams and discharging such liquid products from the process; discharging gaseous nitrogen product from the distillation and heat exchanging same with said precleaned air as another of said cold streams for said cooling thereof, and recovering the so-warmed gaseous nitrogen product; and discharging gaseous nitrogen waste from the distillation and heat exchanging same with said precleaned air as still another of said cold streams for said cooling thereof, and releasing the so-warmed gaseous nitrogen waste from the process.

Claim 9

A process for the cryogenic separation of air into liquid oxygen and nitrogen products and gaseous nitrogen product by fractional distillation at high pressure and then at low pressure wherein compressed air is cooled by heat exchange with cold streams from the process comprising the steps of: compressing said air to head pressure of 120-700 psig., being higher than said high pressure distillation; selectively adsorbing carbon dioxide and acetylene atmospheric impurities from said compressed air prior to cryogenic cooling so as to provide precleaned air; cooling and work expanding a first minor portion comprising 1-20% of said precleaned air to pressure below said high pressure distillation as cold low pressure air and heat exchanging same with said precleaned air as one of said cold streams, and releasing the so-warmed low pressure air from the process as excess air; cooling and liquefying a second minor portion comprising 1-20% of said precleaned air to form liquid air and distilling said liquid air, with the refrigeration for said cooling and liquefying being provided by said cold streams from the process which are thereby partially warmed; partially cooling the major portion of said precleaned air by the cold streams which have been partially warmed, to temperature above the temperature of the cooled and liquefied second minor portion, and work expanding the Partially cooled major portion to the pressure of said high pressure distillation such that the expanded cold air is substantially entirely cold gas; introducing a larger part of said cold gas to said high pressure distillation for partial separation threin; heat exchanging a smaller part of said cold gas with said second minor portion as one of said cold streams for said cooling and liquefying thereby reheating said smaller part, and employing the reheated smaller part as said first minor portion of precleaned air to be work expanded; withdrawing liquid oxygen and liquid nitrogen products from the distillation as separate streams and discharging such liquid products from the process; discharging gaseous nitrogen product from the distillation and heat exchanging same with said precleaned air as another of said cold streams for said cooling thereof, and recovering the so-warmed gaseous nitrogen product; and discharging gaseous nitrogen waste from the distillation and heat exchanging same with said precleaned air as still another of said cold streams for said cooling thereof, and releasing the so-warmed gaseous nitrogen waste from the process.

Claim 10

A process according to claim 7 wherein said excess air is heated and flowed through adsorbent beds for desorption and removal of atmospheric impurities deposited therein during the air precleaning.

Claim 11

A process for the cryogenic separation of air into liquid oxygen product and gaseous oxygen and nitrogen products by fractional distillation at high pressure and then at low pressure wherein compressed air is cooled by heat exchange with cold streams from the process, comprising the steps of: compressing said air to head pressure of 120-700 psig., being higher than said high pressure distillation; selectively adsorbing carbon dioxide and acetylene atmospheric impurities from said compressed air prior to cryogenic cooling so as to provide precleaned air; cooling and liquefying a first minor portion comprising 1-20% of said precleaned air at said head pressure by heat exchange with said cold streams to form liquir air, and distilling said liquid air for separation thereof; partially cooling a second minor portion comprising 1-20% of said precleaned air by heat exchange with said cold streams from the process, work expanding the partially cooled second minor portion to the pressure of the low pressure distillation and passing the work expanded air thereto for separation; cooling the major portion of said precleaned air by heat exchange with said cold streams from the process to lower temperature than said partially cooling, work expanding the cooled major portion to the pressure of the high pressure distillation such that the expanded cold fluid is substantially entirely gas, passing a major part of the work expanded major portion to the high pressure distillation for partial separation therein, heat exchanging a minor part of the work expanded major portion with cold gaseous oxygen product from the low pressure distillation thereby liquefying said minor part and partially warming said gaseous oxygen product, introducing the liquefied minor part to the distillation for separation therein and heat exchanging the partially warmed gaseous oxygen product with said precleaned air as one of said cold streams; withdrawing liquid oxygen from the distillation and discharging such liquid from the process as product; discharging gaseous nitrogen from the distillation, heat exchanging same with said first minor portion of precleaned air as said cold stream for liquefying thereof and heat exchanging the partially warmed gaseous nitrogen with said precleaned air as another of said cold streams, and recovering at least part of the so-warmed gaseous nitrogen as product.

Claim 12

A process for the cryogenic separation of air into liquid oxygen product and gaseous oxygen and nitrogen products by fractional distillation at high pressure and then at low pressure wherein compressed air is cooled by heat exchange with cold streams from the process, comprising the steps of: compressing said air to head pressure of 120-700 psig., being higher than said high pressure distillation; selectively adsorbing carbon dioxide and acetylene atmospheric impurities from said compressed air prior to cryogenic cooling so as to provide precleaned air; cooling and liquefying a first minor portion comprising 1-20% of said precleaned air at said head pressure by heat exchange with said cold streams to form liquir air, and distilling said liquid air for separation thereof; partially cooling a second minor portion comprising 1-20% of said precleaned air by heat exchange with said cold streams from the process, work expanding the partially cooled second minor portion to the pressure of the low pressure distillation and passing the work expanded air thereto for separation; cooling the major portion of said precleaned air by heat exchange with said cold streams from the process to lower temperature than said partially cooling, work expanding the cooled major portion to the pressure of the high pressure distillation such that the expanded cold fluid is substantially entirely gas, passing a major part of the work expanded major portion to the high pressure distillation for partial separation therein, heat exchanging a minor part of the work expanded major portion with cold gaseous oxygen product from the low pressure distillation thereby liquefying said minor part and partially warming said gaseous oxygen product, introducing the liquefied minor part to the distillation for separation therein and heat exchanging the partially warmed gaseous oxygen product with said precleaned air as one of said cold streams; withdrawing liquid oxygen from the distillation and discharging such liquid from the process as product; discharging gaseous nitrogen from the distillation, heat exchanging same with said first minor portion of precleaned air as said cold stream for liquefying thereof and heat exchanging the partially warmed gaseous nitrogen with said precleaned air as another of said cold streams, and recovering at least part of the so-warmed gaseous nitrogen as product.

Claim 13

A process according to claim 1 wherein the major portion of said precleaned air is partially cooled to temperature above the atmospheric impurity dew point prior to said work expansion.