Patent Publication Number: US-8991209-B2

Title: Process and installation for producing high-pressure nitrogen

Description:
BACKGROUND 
     In installations for producing nitrogen under pressure, the nitrogen is usually produced directly at the pressure of use, for example between 5 and 10 bars. Purified air, compressed slightly above this pressure, is distilled so as to produce the nitrogen at the top of the column and the reflux is achieved by expansion of the “oxygen enriched liquid” (liquid at the base of the column formed by air enriched with oxygen) and cooling of the condenser at the top of the column by means of this expanded liquid. The oxygen enriched liquid is thus vaporized at a pressure of between about 3 and 6 bars. 
     If the size of the installation justifies this, the vaporized oxygen enriched liquid is passed through an expander so as to maintain the installation in the cold state but, often, this refrigerating production is excessive, which corresponds to a loss of energy. In the opposite hypothesis, the cold state is maintained by an addition of liquid nitrogen coming from an exterior source, and the vaporized oxygen enriched liquid is simply expanded in a valve and then travels through the thermal heat exchanger serving to cool the initial air. Consequently, here again, a part of the energy of the vaporized oxygen enriched liquid is lost. 
     While the invention disclosed in U.S. Pat. No. 4,717,410 (hereinafter referred to as “the Grenier cycle”) is very effective for producing high pressure nitrogen, in order to meet the customer demand for the high-pressure nitrogen product in recent years, even if the Grenier cycle is utilized, boosting product nitrogen by the addition of a nitrogen compressor is often necessary. One alternative is that high pressure nitrogen can be supplied by increasing the top condenser pressure. However this method deteriorates the recovery ratio, as well as the specific power. 
     In FIG. 2 of the Grenier patent, gas is withdrawn from the lower part of the column and sent to the expander. Because the gas composition is similar to air composition, this means this method deteriorates the nitrogen recovery ratio. 
     An object of the invention is to provide a process and apparatus to permit the production of high pressure nitrogen with high recovery ratio without an additional nitrogen compressor. 
     SUMMARY 
     A method and apparatus for producing high pressure nitrogen is provided. This system includes a first compressor for compressing air and cooling air to substantially the dew-point, a high pressure column, a medium pressure column, a conduit for introducing at least a portion of the compressed air at a base of the high pressure column; a conduit for removing a oxygen enriched liquid from the base of the high pressure column; a first valve for reducing the pressure of the oxygen enriched liquid to a medium pressure, where the medium pressure is between the high pressure and atmospheric pressure, a conduit for introducing the oxygen enriched liquid at an intermediate place of the medium pressure column; a second valve for reducing the pressure of at least a part of the liquid removed from the base of the medium pressure distillation column, to a low pressure to cool a top condenser of the medium pressure column and to form a waste vapor stream; a cold compressor for compressing a vapor stream removed from the medium pressure column, cooling the compressed vapor stream, and introducing it into the base of the high pressure column; a heat exchanger for heating the waste vapor stream, a first expander for expanding the heated stream to produce power; a conduit for withdrawing liquid from the top of the medium pressure column, pump for pumping the withdrawn liquid to high pressure and injecting it at the top of the high pressure column; and conduit for withdrawing product nitrogen from the top of the high pressure column. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  illustrates a single expander embodiment, in accordance with one embodiment of the present invention. 
         FIG. 2  illustrates a double expander embodiment, in accordance with one embodiment of the present invention 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Illustrative embodiments of the invention are described below. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     The current invention provides a process and apparatus to solve aforementioned drawbacks. As explained above, higher pressure nitrogen can be supplied by increasing top condenser pressure. However, higher system pressure also results in reduced recovery of nitrogen because the distillation columns are less efficient at higher pressure. Referring to  FIG. 1 , waste gas is withdrawn from the top of column by a conduit  101 , heated through the exchanger  102  to a suitable temperature level then expanded in expander  103  and again introduced into exchanger  102 , after which it leaves the system as waste  120 . At higher waste gas pressure, less waste gas is needed to achieve the thermal equilibrium since the waste gas expander  103  operates at higher pressure ratio. Therefore, for the system to achieve the improved performance, the product nitrogen recovery ratio must be improved at higher pressure when compared to the Grenier cycle. This increase in recovery ratio reduces the waste gas flow allowing the system to reach an optimum thermal equilibrium. Therefore, by providing an improved nitrogen recovery at higher pressure, the present system is suitable for producing high pressure nitrogen efficiently without using an additional nitrogen product compressor. 
     Also, in the present invention, oxygen rich gas (waste gas) is withdrawn from the top condenser by a conduit  101  and sent to expander  103  in order to achieve thermal equilibrium or refrigeration balance of the process. Because oxygen rich gas is used for thermal equilibrium, it does not alter the product nitrogen recovery ratio. Preferably, by adopting expander  103 , at least a portion of the work output from expander  103  may be used to operate the cold nitrogen compressor  105 . A gas whose composition is close to air is withdrawn from the medium pressure distillation column  106 . The gas is sent to the aforementioned cold nitrogen compressor  105  and pressurized to approximately the same pressure as the high pressure column  107 . Pressurized gas is then introduced into the bottom of the high pressure distillation column  107  in order to improve product nitrogen recovery ratio. By improving product nitrogen recovery ratio, a reduction in manufacturing cost may be achieved 
     One embodiment of the present invention pertains to an installation with a expander  103 , a heat exchanger  102  and a double distillation column  106 ,  107 . The distillation column is formed by a lower main column  107  operating at high pressure, i.e. at the production pressure, about 10 bars, and an upper auxiliary column  106  operating at a medium pressure, about 5 bars. Each of these columns has a top condenser  108 ,  109  respectively. 
     In  FIG. 1 , compressed air  111 , free of moisture and carbon dioxide is cooled to about its dewpoint through the heat exchanger  102  and introduced at the base of the column  107 . The oxygen enriched liquid  112 , in equilibrium with the inlet air received at the base of the column  107 , is reduced in pressure to the medium pressure in an expansion valve  113  and introduced at an intermediate point of column  106 . In the medium pressure column  106 , the descending liquid is enriched in oxygen and cools the main condenser  108  at the base of the column  106 , to ensure the reflux in the column  107 . The bottom liquid  140  of column  106  is reduced in pressure in an expansion valve  114  and then serves to cool the top condenser  109  and ensure the reflux in the column  106 . 
     The liquid  140 , is vaporized in condenser  109  at a pressure of about 1.7 barg, to form stream  101 , which is then warmed in heat exchanger  102  and then expanded in expander  103  to provide the refrigeration balance needed for achieving the thermal equilibrium. After the expansion, the gas is then warmed in exchanger line  102  so as to constitute the residual gas  120  of the installation. 
     A fraction of the condensed flow of condenser  109  is withdrawn from column  106  by a conduit  116  and brought back by a pump  117  to the high pressure and re-injected at the top of column  107 . 
     A gaseous stream with a composition close to air is withdrawn from the column  106  and sent by a conduit  118  to cold compressor  105  and pressurized to slightly above the pressure of the high pressure column  107 . As used herein, the term “cold compression” means the method of mechanically raising the pressure of a gas stream that is lower in temperature than the ambient level feeds to the cryogenic separation system and returned to the system at a sub ambient temperature. The gaseous stream withdrawn from column  106  and sent to cold compressor  105  may be withdrawn at an intermediate point at the same level as oxygen enriched liquid  112  was introduced. The mechanical energy of cold compression must be balanced by refrigeration The gas is then cooled by the heat exchanger  102 , and introduced to bottom of distillation column  107  in order to improve product nitrogen recovery.
         The gaseous nitrogen stream  119  is withdrawn from the top of column  107 , warmed in heat exchanger  102  and recovered as nitrogen product.       

     In one embodiment of the present invention, this apparatus comprises a heat exchanger  102  for cooling feed air to substantially the dew-point thereof, a high pressure distillation column  107 , a medium pressure distillation column  106 . This invention also includes a conduit  130  for introducing at least a portion of said cooled compressed air at a base of said high pressure distillation column  107 , a conduit  112  for removing a oxygen enriched liquid from the base of said high pressure distillation column, a first valve  113  for reducing the pressure of said oxygen enriched liquid to a medium pressure, wherein said medium pressure is between said high pressure and atmospheric pressure. The apparatus also comprises a conduit  132  for introducing said oxygen enriched liquid at an intermediate place of said medium pressure distillation column  106 ; a second valve  114  for reducing the pressure of at least a part of a liquid removed from the base of said medium pressure distillation column  106 , to a low pressure to cool a top condenser of said medium pressure distillation column and to form a waste vapor stream  101 . A THC purge stream  141  also is removed from the top condenser of said medium pressure distillation column. This invention includes a cold compressor  105  for compressing a vapor stream  118  removed from the medium pressure distillation column  106 , a heat exchanger  102  for cooling said compressed vapor stream, and a conduit  131  for introducing it into the base of said high pressure distillation column. The apparatus also comprises a heat exchanger  102  for heating said waste vapor stream, a first expander  103  for expanding said heated stream to produce power; a conduit  116  for withdrawing liquid from the top of said medium pressure distillation column  106 , a pump  117  for pumping said withdrawn liquid to said high pressure and injecting it at the top of the high pressure distillation column  107 ; and a conduit  119  for withdrawing product nitrogen from the top of the high pressure distillation column. 
     A non-limiting example of one embodiment of the above invention follows: 
     First Embodiment with a Nominal 0.82 MPaG Air Inlet Pressure 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                   
               
             
            
               
                 Stream: 
                 111 
                 130 
                 112 
                 119 
                 115 
                 118 
                 134 
                 131 
               
               
                   
               
               
                 Flow rate (Nm3/hr) 
                 1000 
                 1000 
                 621 
                 607 
                 607 
                 58 
                 58 
                 58 
               
               
                 Pressure (MPaG) 
                 0.85 
                 0.84 
                 0.84 
                 0.83 
                 0.82 
                 0.432 
                 0.84 
                 0.83 
               
               
                 Temperature (C.) 
                 55 
                 −166 
                 −166 
                 −171 
                 53 
                 −175 
                 −153 
                 −166 
               
               
                 Nitrogen (%) 
                 78.1 
                 78.1 
                 63.1 
                 100.0 
                 100 
                 82.3 
                 82.3 
                 82.3 
               
               
                 Argon (%) 
                 0.9 
                 0.9 
                 1.6 
                 0.0 
                 0.0 
                 1.1 
                 1.1 
                 1.0 
               
               
                 Oxygen (%) 
                 21.0 
                 21.0 
                 35.3 
                 0.0 
                 0.0 
                 16.6 
                 16.6 
                 16.6 
               
               
                   
               
               
                 Stream: 
                 116 
                 136 
                 114 
                 101 
                 122 
                 121 
                 120 
                 141 
               
               
                   
               
               
                 Flow rate (Nm3/hr) 
                 169 
                 169 
                 393 
                 391 
                 391 
                 391 
                 391 
                 2 
               
               
                 Pressure (MPaG) 
                 0.42 
                 0.83 
                 0.43 
                 0.10 
                 0.10 
                 0.03 
                 0.01 
                 0.10 
               
               
                 Temperature (C.) 
                 −179 
                 −178 
                 −172 
                 −180 
                 −145 
                 −158 
                 53 
                 −180 
               
               
                 Nitrogen (%) 
                 100.0 
                 100.0 
                 44.3 
                 44.6 
                 44.6 
                 44.6 
                 44.6 
                 19.0 
               
               
                 Argon (%) 
                 0.0 
                 0.0 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
               
               
                 Oxygen (%) 
                 0.0 
                 0.0 
                 53.3 
                 53.2 
                 53.2 
                 53.2 
                 53.2 
                 78.6 
               
               
                   
               
            
           
         
       
     
     First Embodiment with a Nominal 1.00 MPaG Air Inlet Pressure 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                   
               
             
            
               
                 Stream: 
                 111 
                 130 
                 112 
                 119 
                 115 
                 118 
                 134 
                 131 
               
               
                   
               
               
                 Flow rate (Nm3/hr) 
                 1000 
                 1000 
                 735 
                 614 
                 614 
                 197 
                 197 
                 197 
               
               
                 Pressure (MPaG) 
                 1.04 
                 1.03 
                 1.03 
                 1.02 
                 1.01 
                 0.54 
                 1.03 
                 1.02 
               
               
                 Temperature (C.) 
                 55 
                 −163 
                 −163 
                 −168 
                 53 
                 −172 
                 −151 
                 −163 
               
               
                 Nitrogen (%) 
                 78.1 
                 78.1 
                 64.6 
                 100.0 
                 100 
                 82.7 
                 82.7 
                 82.7 
               
               
                 Argon (%) 
                 0.9 
                 0.9 
                 1.5 
                 0.0 
                 0.0 
                 1.0 
                 1.0 
                 1.0 
               
               
                 Oxygen (%) 
                 21.0 
                 21.0 
                 32.9 
                 0.0 
                 0.0 
                 16.3 
                 16.3 
                 16.3 
               
               
                   
               
               
                 Stream: 
                 116 
                 136 
                 114 
                 101 
                 122 
                 121 
                 120 
                 141 
               
               
                   
               
               
                 Flow rate (Nm3/hr) 
                 152 
                 152 
                 386 
                 384 
                 384 
                 384 
                 384 
                 2 
               
               
                 Pressure (MPaG) 
                 0.54 
                 1.02 
                 0.54 
                 0.15 
                 0.15 
                 0.03 
                 0.01 
                 0.15 
               
               
                 Temperature (C.) 
                 −176 
                 −176 
                 −169 
                 −178 
                 −140 
                 −159 
                 53 
                 −178 
               
               
                 Nitrogen (%) 
                 100.0 
                 100.0 
                 43.3 
                 43.4 
                 43.4 
                 43.4 
                 43.4 
                 19.2 
               
               
                 Argon (%) 
                 0.0 
                 0.0 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.5 
               
               
                 Oxygen (%) 
                 0.0 
                 0.0 
                 54.3 
                 54.2 
                 54.2 
                 54.2 
                 54.2 
                 78.3 
               
               
                   
               
            
           
         
       
     
     One embodiment of the present invention pertains to an installation with a first expander  204 , a second expander  203 , a thermal heat exchanger  202  and a double distillation column  206 ,  207 . The distillation column is formed by a lower main column  207  operating at high pressure, i.e. at the production pressure, about 10 bars, and an upper auxiliary column  206  operating at a medium pressure, about 5 bars. Each of these columns has a top condenser  208 ,  209  respectively. 
     In  FIG. 2 , compressed air  211 , free of moisture and carbon dioxide is cooled to about its dew point through the heat exchanger  202  and introduced at the base of the column  207 . The oxygen enriched liquid  212 , in equilibrium with the inlet air received at the base of the column  207 , is reduced in pressure to the medium pressure in an expansion valve  213  and introduced at an intermediate point of column  206 . In the medium pressure column  206 , the descending liquid is enriched in oxygen and cools the main condenser  208  at the base of the column  206 , to ensure the reflux in the column  207 . The bottom liquid  240  of column  206  is reduced in pressure in an expansion valve  214  and then serves to cool the top condenser  209  and ensure the reflux in the column  206 . 
     A gaseous stream with a composition close to air is withdrawn from the column  206  and sent by a conduit  218  to cold compressor  205  and pressurized to slightly above the pressure of the high pressure column  207 . The gas is then cooled by the heat exchanger  202 , and introduced to bottom of distillation column  207  in order to improve product nitrogen recovery. By improving product nitrogen recovery ratio, a reduction in manufacturing cost may be achieved 
     Waste gas is withdrawn from the top condenser  209  by a conduit  201 , heated in heat exchanger  202  to a suitable temperature level, a first portion of the waste gas  221  is expanded in a first expander  204 , thereby producing a first expanded stream  223 . A THC purge stream  241  also is removed from the top condenser of said medium pressure distillation column. And a second portion of the hot waste gas  222  is expanded in a second expander  203 , thereby producing a second expanded stream  224 . The temperature of the first portion  221  and the second portion  222  are not the same. In one embodiment, the temperature of the second portion  222  is greater than that of the first portion  221 . 
     The first expanded line  223  and the second expanded line  224  can be recombined and again introduced into heat exchanger  202 , after which it leaves the system as waste  220 . At least a portion of the work output from second expander  203  (or first expander  204 ) may be used to operate the cold nitrogen compressor  205 . 
     The liquid  240 , is vaporized in condenser  209  at a pressure of about 1.7 barg, to form stream  201 , which is then warmed in heat exchanger  202  and then expanded in expander  203  to provide the refrigeration balance needed for achieving the thermal equilibrium. After the expansion, the gas is then warmed in exchanger line  202  so as to constitute the residual gas  220  of the installation. 
     A fraction of the condensed flow of condenser  209  is withdrawn from column  206  by a conduit  216  and brought back by a pump  217  to the high pressure and re-injected at the top of column  207 . The gaseous nitrogen stream  219  is withdrawn from the top of column  207 , warmed in heat exchanger  202  and recovered as nitrogen product. 
     The skilled artisan will recognize that there are additional expander arrangements possible, and should not be limited to the scheme indicated in  FIGS. 1 and 2 . In addition to an improvement in the temperature level in the heat exchanger  202 , the double expander arrangement also provides the advantage of higher inlet temperature to the second expander  203 , which is beneficial from the aspect of its work output. Higher work output means more flow can be recycled and higher product recovery. It is also useful to note that in the scheme of  FIG. 1 , the excess refrigeration generated by the expander  103  and utilized to balance out the refrigeration required for the process can be dissipated, for example, in an integrated oil brake or generator brake (not shown). 
     In one embodiment of the present invention, this apparatus comprises a heat exchanger  202  for cooling feed air to substantially the dew-point thereof, a high pressure distillation column  207 , and a medium pressure distillation column  206 . This invention also includes a conduit  230  for introducing at least a portion of said compressed air at a base of said high pressure distillation column; a conduit  212  for removing a oxygen enriched liquid from the base of said high pressure distillation column  207 ; and a first valve  213  for reducing the pressure of said oxygen enriched liquid to a medium pressure, wherein said medium pressure is between said high pressure and atmospheric pressure. The invention also includes a conduit  232  for introducing said oxygen enriched liquid at an intermediate place of said medium pressure distillation column  206 ; a second valve  214  for reducing the pressure of at least a part of a liquid removed from the base of said medium pressure distillation column, to a low pressure to cool a top condenser of said medium pressure distillation column  206  and to form a waste vapor stream. This invention also includes a cold compressor  205  for compressing a vapor stream removed form the medium pressure distillation column  206 , cooling said compressed vapor stream, and introducing it into the base of said high pressure distillation column  207 . This invention also includes a heat exchanger  202  for heating said waste vapor stream, a first expander  203  for expanding a portion of said heated stream to produce power; and a second expander  204  for expanding another portion of said heated stream to produce power. This invention also includes a conduit  216  for withdrawing liquid from the top of said medium pressure distillation column  206 , a pump  217  for pumping said withdrawn liquid to said high pressure and injecting it at the top of the high pressure distillation column  207 ; and a conduit  219  for withdrawing product nitrogen from the top of the high pressure distillation column. 
     Second Embodiment with a Nominal 0.82 MPaG Air Inlet Pressure 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
             
               
                   
               
             
            
               
                 Stream: 
                 211 
                 230 
                 212 
                 219 
                 215 
                 218 
                 234 
                 231 
                 216 
               
               
                   
               
               
                 Flow rate (Nm3/hr) 
                 1000 
                 1000 
                 630 
                 612 
                 612 
                 74 
                 74 
                 74 
                 167 
               
               
                 Pressure (MPaG) 
                 0.85 
                 0.84 
                 0.84 
                 0.83 
                 0.82 
                 0.42 
                 0.84 
                 0.83 
                 0.423 
               
               
                 Temperature (C.) 
                 55 
                 −166 
                 −166 
                 −171 
                 53 
                 −175 
                 −153 
                 −166 
                 −179 
               
               
                 Nitrogen (%) 
                 78.1 
                 78.1 
                 63.2 
                 100.0 
                 100 
                 82.3 
                 82.3 
                 82.3 
                 100 
               
               
                 Argon (%) 
                 0.9 
                 0.9 
                 1.6 
                 0.0 
                 0.0 
                 1.1 
                 1.1 
                 1.0 
                 0.0 
               
               
                 Oxygen (%) 
                 21.0 
                 21.0 
                 35.2 
                 0.0 
                 0.0 
                 16.6 
                 16.6 
                 16.6 
                 0.0 
               
               
                   
               
               
                 Stream: 
                 236 
                 214 
                 201 
                 222 
                 224 
                 220 
                 221 
                 223 
                 241 
               
               
                   
               
               
                 Flow rate (Nm3/hr) 
                 167 
                 388 
                 386 
                 75 
                 75 
                 386 
                 311 
                 311 
                 2 
               
               
                 Pressure (MPaG) 
                 0.83 
                 0.42 
                 0.10 
                 0.09 
                 0.02 
                 0.01 
                 0.09 
                 0.03 
                 0.10 
               
               
                 Temperature (C.) 
                 −178 
                 −172 
                 −180 
                 −63 
                 −83 
                 53 
                 −148 
                 −160 
                 −180 
               
               
                 Nitrogen (%) 
                 100.0 
                 43.6 
                 43.8 
                 43.8 
                 43.8 
                 43.8 
                 43.8 
                 43.8 
                 18.5 
               
               
                 Argon (%) 
                 0.0 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
               
               
                 Oxygen (%) 
                 0.0 
                 54.0 
                 53.8 
                 53.8 
                 53.8 
                 53.8 
                 53.8 
                 53.8 
                 79.1 
               
               
                   
               
            
           
         
       
     
     Second Embodiment with a Nominal 1.00 MPaG Air Inlet Pressure 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
             
               
                   
               
             
            
               
                 Stream: 
                 211 
                 230 
                 212 
                 219 
                 215 
                 218 
                 234 
                 231 
                 216 
               
               
                   
               
               
                 Flow rate (Nm3/hr) 
                 1000 
                 1000 
                 630 
                 617 
                 617 
                 207 
                 207 
                 207 
                 151 
               
               
                 Pressure (MPaG) 
                 1.04 
                 1.03 
                 1.03 
                 1.02 
                 1.01 
                 0.54 
                 1.03 
                 1.02 
                 0.53 
               
               
                 Temperature (C.) 
                 55 
                 −163 
                 −163 
                 −168 
                 53 
                 −172 
                 −150 
                 −163 
                 −176 
               
               
                 Nitrogen (%) 
                 78.1 
                 78.1 
                 64.6 
                 100.0 
                 100 
                 82.7 
                 82.7 
                 82.7 
                 100 
               
               
                 Argon (%) 
                 0.9 
                 0.9 
                 1.5 
                 0.0 
                 0.0 
                 1.0 
                 1.0 
                 1.0 
                 0.0 
               
               
                 Oxygen (%) 
                 21.0 
                 21.0 
                 32.8 
                 0.0 
                 0.0 
                 16.3 
                 16.3 
                 16.3 
                 0.0 
               
               
                   
               
               
                 Stream: 
                 236 
                 214 
                 201 
                 222 
                 224 
                 220 
                 221 
                 223 
                 241 
               
               
                   
               
               
                 Flow rate (Nm3/hr) 
                 151 
                 383 
                 381 
                 188 
                 188 
                 381 
                 193 
                 193 
                 2 
               
               
                 Pressure (MPaG) 
                 1.02 
                 0.54 
                 0.15 
                 0.149 
                 0.02 
                 0.01 
                 0.15 
                 0.03 
                 0.15 
               
               
                 Temperature (C.) 
                 −176.8 
                 −169.2 
                 −178 
                 −120 
                 −143 
                 53 
                 −148 
                 −166 
                 −178 
               
               
                 Nitrogen (%) 
                 100.0 
                 42.9 
                 43.0 
                 43.0 
                 43.0 
                 43.0 
                 43.0 
                 43.0 
                 18.9 
               
               
                 Argon (%) 
                 0.0 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.4 
                 2.5 
               
               
                 Oxygen (%) 
                 0.0 
                 54.7 
                 54.6 
                 54.6 
                 54.6 
                 54.6 
                 54.6 
                 54.6 
                 78.6