Abstract:
The invention provides a method and system for the separation of a mixture containing H2, hydrocarbon, and C02. The generated mixture ( 3 ) is introduced into a distillation column ( 2 ) having a side stream to generate a top stream comprising H2 ( 21 ), a middle (volatility) stream comprising hydrocarbon ( 30 ); and a bottom stream comprising C02 ( 32 ). In a preferred embodiment, the mixture further comprises N2 which is obtained in the top stream ( 21 ). In a most preferred embodiment, the H2 and the N2 are present in a molar ratio of 3H2:1N2. The generated H2 and N2 may be used for the synthesis of ammonia. Thus, the invention also proves a method and system for the generation of ammonia.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to methods and systems for the separation of mixtures containing carbon dioxide, hydrocarbon, and hydrogen. The invention may be used, for example, for the separation of a syngas to produce hydrogen and nitrogen which may be used in the synthesis of ammonia. 
       BACKGROUND OF THE INVENTION 
       [0002]    The term “synthesis gas”, also known as “syngas” refers to a gas mixture containing carbon dioxide and/or monoxide and molecular hydrogen generated by the gasification of a carbon-containing fuel to a gaseous product with a heating value. Syngas is produced, for example, by steam reforming of natural gas or liquid hydrocarbons to produce hydrogen, the gasification of coal and in some types of waste-to-energy gasification facilities. Syngas is used, for example, as intermediates in creating synthetic natural gas, and for producing ammonia or methanol. Syngas is also used as an intermediate in producing synthetic petroleum for use as a fuel or lubricant. 
         [0003]    In the synthesis of ammonia from stoichiometric air (as a source of nitrogen) and hydrocarbons (as a source of hydrogen), the hydrocarbon, such as methane, is made to react with steam at elevated temperatures to generate H 2 , CO, CO 2 H 2 O. This produces a raw syngas containing, in addition to these compounds, residual unreacted hydrocarbon, as well as N 2 , and other air constituents. The N 2  and H 2  must then be separated from the other components of the syngas for the generation of ammonia. 
         [0004]    There are two main problems in the production of ammonia. One problem relates to the fact that excessive amounts of hydrocarbon, typically methane, remain unreacted in the conversion of the hydrocarbon to H 2  and CO, so that the ammonia yield is far from optimal. This so-called hydrocarbon slip can be reduced by using high reforming temperatures. Secondly, CO 2  must be removed from syngas to prevent poisoning of the catalyst used in the ammonia conversion, and this CO 2  removal requires high capital costs and is also costly in terms of energy consumption. 
         [0005]    Significant work has been applied to the development of methods for the removal of carbon dioxide from a syngas. The processes can be separated into four general classes; absorption by physical solvents, absorption by chemical solvents, adsorption by solids, and distillation. 
         [0006]    The high relative volatility of methane with respect to carbon dioxide makes cryogenic distillation theoretically very attractive. However, the methane/carbon dioxide distillative separation has a significant disadvantage in that solid carbon dioxide exists in equilibrium with vapor-liquid mixtures of carbon dioxide and methane at particular conditions of temperature, pressure, and composition. Obviously, the formation of solids in a distillation tower has the potential for plugging the tower and its associated equipment. Increasing the operating pressure of the tower will result in warmer operating temperatures and a consequent increase in the solubility of carbon dioxide, thus narrowing the range of conditions at which solid carbon dioxide forms. However, additional increases in pressure will cause the carbon dioxide-methane mixture to reach and surpass its critical conditions. Upon reaching criticality, the vapor and liquid phases of the mixture are indistinguishable from each other and therefore cannot be separated. A single-tower equilibrium separation operating in the vapor-liquid equilibrium region bounded between carbon dioxide freezeout conditions and the carbon dioxide-methane critical pressure line may produce a product methane stream containing 10% or more carbon dioxide. 
         [0007]    Various methods have been devised to avoid the conditions at which carbon dioxide freezes and yet obtain an acceptable separation. Two processes which utilize additives to aid in the separation are disclosed in U.S. Pat. No. 4,149,864 to Eakman et al, and U.S. Pat. No. 4,318,723 to Holmes et al. 
         [0008]    Eakman et al discloses a process for separating carbon diokide from methane in a single distillation column. If insufficient hydrogen is present in the column feedstream, hydrogen is added to provide a concentration from about 6 to 34 mole percent, preferably from about 20 to about 30 mole percent. The separation is said to take place without the formation of solid carbon dioxide. The tower pressure is preferably held between 1025 and 1070 psia. 
         [0009]    Holmes et al adds alkanes having a molecular weight higher than methane, preferably butane, to the tower feed to increase the solubility of carbon dioxide and decrease its freezing temperature line. The additive n-butane is added at an amount from about 5 moles to 30 moles per 100 moles of feed. 
         [0010]    U.S. Pat. No. 4,511,382 to Valencia et al discloses separating acid gases, particularly carbon dioxide, from methane by cryogenic distillation in which an effective amount of a light gas, preferably helium, is added to a stream containing methane and carbon dioxide and cryogenically distilling the mixed stream to produce a liquid carbon dioxide stream and an enriched methane stream. The distillation tower or at least a portion thereof may then be operated at a pressure higher than the critical pressure of methane. 
         [0011]    A process for the separation of carbon dioxide from a predominantly methane stream is described in U.S. Pat. No. 2,888,807 to Bocquet. The separation requires the use of two distillation columns arranged in series. When the carbon dioxide is present at a concentration below 8 mole percent, the feed is introduced into the first column of the series, and where the carbon dioxide is present at concentration above 8 mole percent, the feed is introduced directly into the second column of the series. The first column is operated at or below the critical temperature of methane such that feed to each column provides a carbon dioxide concentration below which, on cooling at the operating pressure of the column, would produce a solid carbon dioxide phase. Effluents from the top of the second column contain substantially the same concentration of carbon dioxide as the feeds to the first columns. The operating pressure applied to the second column is maintained above a critical pressure defined as that at which the carbon dioxide phase will exist, and above which pressure a solid carbon dioxide phase will not coexist with a vapor. 
         [0012]    U.S. Pat. No. 7,090,816 to Malhotra et al discloses a method for the purification of syngas, such as occurs in the manufacture of ammonia, using cryogenic distillation. Refrigeration for the distillation is obtained from waste fluid expansion using a liquid expander to recover mechanical work from the waste fluid. This method reduces pressure loss in the syngas stream and reduces compression and power relative to similar ammonia generating processes. 
       SUMMARY OF THE INVENTION 
       [0013]    In one of its aspects, the invention provides a method for the separation of a mixture containing H 2 , hydrocarbon, and CO 2 . In accordance with this aspect of the invention, the mixture is introduced into a distillation column having a side stream. Distillation of the mixture using a column having a side stream generates three streams, as follows:
       (i) a top stream comprising H 2 ;   (ii) a middle stream comprising hydrocarbon; and   (iii) a bottom stream comprising CO 2 .       
 
         [0017]    In a preferred embodiment of the method and system of the invention, the mixture further comprises N 2 . In a most preferred embodiment, the H 2  and N 2  are present in a molar ratio of 3:1. This may be achieved by mixing the hydrocarbon with a stoichiometric amount of air, as is known in the art. Embodiments in which the H 2  and N 2  are present in this molar ratio are useful for generating H 2  and N 2  for use in the manufacture of ammonia. Thus, in another of its aspects, the invention provides a method and system for the production of ammonia. In accordance with this aspect of the invention, a mixture containing H 2 , N 2 , hydrocarbon, and CO 2  is introduced into a distillation column to produce the three streams described above. The top stream comprising H 2  and N 2  is then used to generate ammonia by any method known in the art. 
         [0018]    The process has several degrees of freedom allowing flexibility in determining the operating parameters of the system, such as methane slip and side stream composition, and can improve the efficiency of the raw syngas generating process. 
         [0019]    Thus, in one of its aspects, the present invention provides a method for the separation of a mixture containing H 2 , hydrocarbon, and CO 2 , the method comprising introducing the mixture into a distillation column having a side stream to generate:
       (i) a top stream comprising H 2 ;   (ii) a middle (volatility) stream comprising hydrocarbon; and   (iii) a bottom stream comprising CO 2 .       
 
         [0023]    The hydrocarbon is preferably, although not necessarily, methane. In a preferred embodiment of the method of the invention, the mixture further comprises N 2  which is obtained by the method in the top stream. In a most preferred embodiment, the H 2  and the N 2  are present in the mixture in a molar ratio of 3H 2 :1N 2 . Thus, in another of its aspects, the invention provides a method for generating ammonia. 
         [0024]    In another of its aspects, the invention provides a system for generating and separating a mixture containing H 2 , hydrocarbon, and CO 2 , the system comprising:
       (a) means for generating a mixture containing H 2 , hydrocarbon, and CO 2 ; and   (b) a distillation column having a side stream configured to receive the mixture and to generate from the mixture:
           (i) a top stream comprising H 2 ;   (ii) a middle stream comprising hydrocarbon; and   (iii) a bottom stream comprising CO 2 .   
               
 
         [0030]    The means for generating a mixture containing H 2 , hydrocarbon and CO 2 , may be any such system known in the art. 
         [0031]    The hydrocarbon of the system is preferably, although not necessarily, methane. In a preferred embodiment of the system of the invention, the mixture further comprises N 2  which is obtained by the method in the top stream. In a most preferred embodiment, the H 2  and the N 2  are present in the mixture in a molar ratio of 3H 2 :1N 2 . Thus, in yet another of its aspects, the invention provides a system for generating ammonia. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawing, in which: 
           [0033]      FIG. 1  shows a system for separating a mixture containing H 2 , hydrocarbon, and CO 2 , in accordance with one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0034]      FIG. 1  shows a system  1  for separating a feed mixture  3  containing H 2 , N 2 , hydrocarbon and CO 2 , in accordance with one embodiment of the invention. The system  1  comprises a distillation column  2 , a reboiler  4  and a condenser  18 . The distillation column  2  comprises one or more trays  8 , as is known in the art for distillation columns. The feed mixture  3  may be a gas, or liquid/gas mixture. The feed mixture  3  is introduced into the distillation column  2  at an inlet  10  and is deposited into a feed tray  12  of the column  2 . After the mixture reaches equilibrium in the feed tray  12 , the H 2  and N 2 , flow up the column while the CO 2  is liquefied and flows to the bottom by gravity. The working pressure inside the column should be above about 5 bar in order to assure that the CO 2  can exist in the liquid phase in the column. Part of the hydrocarbon entering the column is liquefied, mixed with the CO 2 , and then flows down towards the bottom of the column. Gaseous hydrocarbon first rises in the column and liquefies by the liquid nitrogen, and then flows down and re-evaporates. In every tray there is a liquid/vapor equilibrium whose composition is determined by the tray&#39;s temperature. 
         [0035]    The distillation column  2  generates a condenser feed stream  14  containing primarily the H 2  and N 2  in gaseous form. The output stream  14  is introduced into a condenser  18  that generates a liquid reflux  20  that returns to the column  2 , preferably to the top tray  22  of the column. The reflux of the top stream to the column is preferably performed using a reflux ratio between 0.001 and 10, and more preferably between 0.5 and 2. It is possible to alter the temperature gradient in the column by varying the reflux rate. 
         [0036]    The reflux  20  serves as a cooling source inside the column for the trays  8  above the feed tray  12 . In the lower part of the column, where the temperature is higher, only small amounts of liquid nitrogen are present, and most of the cooling for the trays  8  below the feed tray  12  is provided by liquid hydrocarbon and liquid CO 2 . An overhead product stream  21  containing primarily gaseous H 2  and N 2  is drawn off from the condenser  18 . As explained above, the overhead product stream  21  can be used in the synthesis of ammonia. The distillation column  2  also generates a reboiler feed stream  24  containing primarily hydrocarbon and CO 2 . The reboiler feed stream  24  is introduced into the reboiler  4 . In the reboiler  4 , hydrocarbon boils, and may be withdrawn as a vapor side stream  30 , while liquid CO 2  is withdrawn as a bottom stream  32 . The liquid CO 2  in the bottom stream is easier to dispose of than gaseous CO 2 . The reboiler generates a boilup  26  that is returned to the column  2  preferably to the bottom tray  28  of the column  2 . The vapor side stream  30  can be recycled and reformed and used to generate new feed stream  3 . Recycling of the hydrocarbon increases the utilization of the hydrocarbon, thus increasing the ammonia yield. 
         [0037]    The column preferably has a pressure between 5 bar to a critical pressure of the mixture, and more preferably between 7 bar to 55 bar. 
         [0038]    In an alternative embodiment, (not shown), a side stream is withdrawn from a tray  8  in the column  2 , instead of withdrawing the side stream  30  from the reboiler  4 . In another embodiment, the feed stream  3  is introduced directly into the reboiler which is set to conditions under which CO 2  is a liquid at its bubble point and is withdrawn. 
       EXAMPLES 
       [0039]    The method and system of the invention was implemented on the process simulator UniSim Design Version R370Build 13058 of Honeywell. 
       Example 1 
       [0040]    In this example, the operating parameter values shown in Table 1 were used in the simulation. The thermodynamic package used was the Peng Robinson Sour Vapor package. 
         [0000]    
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 Syn loop pressure 
                 15 bar 
               
               
                 primary reforming temperature 
                 700° C. 
               
               
                 Number of trays 
                 12 plus condenser and reboiler 
               
               
                 inlet temperature 
                 −55° C. (feed stream in gaseous state) 
               
               
                 Location of feed inlet 
                 Tray 7 from the bottom 
               
               
                 Reflux ratio 
                 1.9 
               
               
                 Side stream draw stage 
                 Reboiler 
               
               
                 Side stream flow rate 
                 300 kgmole/hour 
               
               
                   
               
             
          
         
       
     
         [0041]    Table 2 shows in Column (a) the feed stream  3  to the column  2  that was generated by the simulation using the parameters of Table 1. The flow rate (col (b)), molar fraction (col (c)), and the partial pressure (col (d)) of the feed stream are also shown in Table 2. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                 Feed Stream 
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 (a) 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 654 
                 0.164 
                 2.455 
               
               
                 H 2   
                 2206 
                 0.552 
                 8.280 
               
               
                 CH 4   
                 368 
                 0.092 
                 1.381 
               
               
                 N 2   
                 751 
                 0.188 
                 2.819 
               
               
                 Ar 
                 17.59 
                 0.004 
                 0.066 
               
               
                 Total 
                 3996.59 
                 1.000 
                 15 
               
               
                   
               
             
          
         
       
     
         [0042]    Table 3 shows the composition of the processed syngas, or overhead stream  14 , as well as its flow rate and the pressure of the stream  14 , as determined by the simulation. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Syngas (overhead 
                 Flow rate 
                   
                 partial pressure 
               
               
                 stream): 
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 Species 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 0 
                 0 
                 0 
               
               
                 H 2   
                 2207 
                 0.748 
                 11.22 
               
               
                 CH 4   
                 0.0033 
                 1 × 10 −6   
                 1.5 × 10 −5   
               
               
                 N 2   
                 735.6 
                 0.249 
                 3.735 
               
               
                 Ar 
                 6.131 
                 0.004 
                 0.06 
               
               
                 Total 
                 2948.75 
                 1 
                 15 
               
               
                   
               
             
          
         
       
     
         [0043]    Table 4 shows the composition of the side stream  30  that was generated. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                   
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 Side Stream: 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 5.4 
                 0.018 
                 0.27 
               
               
                 H 2   
                 0 
                 0 
                 0 
               
               
                 CH 4   
                 270.59 
                 0.905 
                 13.575 
               
               
                 N 2   
                 14.03 
                 0.046 
                 0.69 
               
               
                 Ar 
                 8.77 
                 0.029 
                 0.435 
               
               
                 Total 
                 298.8 
                 1.000 
                 15 
               
               
                   
               
             
          
         
       
     
         [0044]    Table 5 shows the composition of the bottom stream  32  that was generated. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 5 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                 Bottom stream 
                 [kgmol/hr] 
                 molar fraction - x 
                 [atm] 
               
               
                 (a) 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 648.6 
                 0.865 
                 12.975 
               
               
                 H 2   
                 0 
                 0 
                 0 
               
               
                 CH 4   
                 97.41 
                 0.13 
                 1.95 
               
               
                 N 2   
                 1.372 
                 0.00183 
                 0.0275 
               
               
                 Ar 
                 2.682 
                 0.035 
                 0.525 
               
               
                 Total 
                 750.064 
                 1.000 
                 15 
               
               
                   
               
             
          
         
       
     
         [0045]    Table 6 shows the ammonia product yield, the purity of the ammonia yield, the condenser duty, and the reboiler duty. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 6 
               
               
                   
                   
               
             
             
               
                   
                 ammonia product yield 
                 593.6 
                 ton/day 
               
             
          
           
               
                   
                 purity of the ammonia yield 
                 0.997 
               
             
          
           
               
                   
                 Ammonia temperature 
                 −28° 
                 C. 
               
               
                   
                 Ammonia pressure 
                 15 
                 bar 
               
               
                   
                   
               
             
          
         
       
     
         [0046]    Table 7 shows the energy consumption. Energy costs were calculated assuming a use of a nitrogen refrigerant utility at a cost of 1 million dollar/million kcal/hr/yr. The energy demand and cost were determined by the reflux ratio. When running the column at 15 bar the reflux composition was primarily liquid nitrogen. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 7 
               
               
                   
                   
               
             
             
               
                   
                 Condenser duty 
                 7.08 × 10 6   
                 Energy cost of 
                 $7.08 
               
               
                   
                   
                 kcal/hr 
                 Condenser 
                 million/year 
               
               
                   
                 Reboiler duty 
                 1.06610× 6   
                 Energy cost of 
                 $1.0661 
               
               
                   
                   
                 kcal/hr 
                 Reboiler 
                 million/year 
               
               
                   
                   
               
             
          
         
       
     
         [0047]    Table 8 shows the steady state tray composition profile of the column (molar flows, kgmole/hr). 
         [0000]    
       
         
               
               
               
               
               
               
               
             
           
               
                 TABLE 8 
               
               
                   
               
             
             
               
                   
                 CO 2   
                   
                 CH 4   
                   
                   
                   
               
               
                 Stage 
                 (Vap) 
                 H 2  (Vap) 
                 (Vap) 
                 N 2  (Vap) 
                 Ar (Vap) 
                 Temperature 
               
               
                   
               
               
                 Condenser 
                 1.01 × 10 −26   
                 2208 
                 1.55 × 10 −4   
                 735.8 
                 5.526 
                 −185.5 
               
               
                 12  
                 6.21 × 10 −22   
                 2484 
                 1.17 × 10 −2   
                 5984 
                 84.91 
                 −169.9 
               
               
                 11  
                 3.58 × 10 −19   
                 2368 
                  6.8 × 10 −2   
                 7123 
                 154.7 
                 −168.6 
               
               
                 10  
                 1.45 × 10 −16   
                 2347 
                 0.3185 
                 7146 
                 232 
                 −168.4 
               
               
                 9 
                 5.76 × 10 −14   
                 2343 
                 1.461 
                 7016 
                 337.8 
                 −168.2 
               
               
                 8 
                  2.3 × 10 −11   
                 2339 
                 6.671 
                 6809 
                 484.5 
                 −167.8 
               
               
                 7 
                     9.3 × 10 −9   
                 2333 
                 30.32 
                 6486 
                 681.7 
                 −167.2 
               
               
                 6 
                     3.7 × 10 −6   
                 2321 
                 135.6 
                 5896 
                 918.2 
                 −165.3 
               
               
                 5 
                     1.3 × 10 −3   
                 2290 
                 568.8 
                 4577 
                 1066 
                 −158.5 
               
               
                 4 
                 0.2306 
                 2241 
                 1796 
                 2274 
                 747.8 
                 −143.4 
               
               
                 3 
                 8.181 
                 2229 
                 2965 
                 1125 
                 281.8 
                 −138.1 
               
               
                 2 
                 0.3702 
                 1.156 
                 40.59 
                 13.89 
                 4.67 
                 −123.7 
               
               
                 1 
                 2.649 
                 0.1531 
                 206.2 
                 26.98 
                 17.31 
                 −117.5 
               
               
                 Reboiler 
                 6.481 
                 3.18 × 10 −3   
                 287.4 
                 8.145 
                 11.93 
                 −108.3 
               
               
                   
               
               
                   
                   
                   
                 CH 4   
               
               
                 Stage 
                 CO 2  (Liq) 
                 H 2  (Liq) 
                 (Liq) 
                 N 2  (Liq) 
                 Ar (Liq) 
                 Temperature 
               
               
                   
               
               
                 Condenser 
                  6.2 × 10 −22   
                 276.4 
                 1.15 × 10 −2   
                 5248 
                 79.38 
                 −185.5 
               
               
                 12  
                  3.6 × 10 −19   
                 160 
                 6.78 × 10 −2   
                 6387 
                 149.2 
                 −169.9 
               
               
                 11  
                 1.45 × 10 −16   
                 139.2 
                 0.318 
                 6411 
                 226.4 
                 −168.6 
               
               
                 10  
                 5.75 × 10 −14   
                 134.8 
                 1.46 
                 6280 
                 332.2 
                 −168.4 
               
               
                 9 
                  2.3 × 10 −11   
                 131.1 
                 6.67 
                 6073 
                 479 
                 −168.2 
               
               
                 8 
                 9.27 × 10 −9    
                 125.3 
                 30.32 
                 5750 
                 676.2 
                 −167.8 
               
               
                 7 
                 3.72 × 10 −6    
                 113.1 
                 135.6 
                 5160 
                 912.7 
                 −167.2 
               
               
                 6 
                 1.33 × 10 −3    
                 82.19 
                 568.8 
                 3841 
                 1061 
                 −165.3 
               
               
                 5 
                 0.2306 
                 33.09 
                 1796 
                 1539 
                 742.3 
                 −158.5 
               
               
                 4 
                 8.181 
                 21.44 
                 2965 
                 388.9 
                 276.2 
                 −143.4 
               
               
                 3 
                 655.3 
                 1.59 
                 412.3 
                 22.42 
                 19.54 
                 −138.1 
               
               
                 2 
                 657.6 
                 0.1562 
                 578 
                 35.5 
                 32.19 
                 −123.7 
               
               
                 1 
                 661.4 
                 6.25 × 10 −3   
                 659.1 
                 16.67 
                 26.8 
                 −117.5 
               
               
                 Reboiler 
                 648.7 
                 1.99 × 10 −5   
                 97 
                 0.7374 
                 3.48 
                 −108.3 
               
               
                   
               
             
          
         
       
     
         [0048]    In this example, the energy consumption of the overall process, 7.15 Gcal/mton ammonia) similar to the energy consumption of existing processes. is the lowest of all the simulations that were performed. 
       Example 2 
       [0049]    In this example, the operating parameter values shown in Table 9 were used in the simulation. The thermodynamic package used was the Peng Robinson package. 
         [0000]    
       
         
               
               
             
           
               
                 TABLE 9 
               
               
                   
               
             
             
               
                 Syn loop pressure 
                 45 bar 
               
               
                 primary reforming temperature 
                 800° C. 
               
               
                 Number of trays 
                 10 plus condenser and reboiler 
               
               
                 Location of feed inlet 
                 Tray 6 from the bottom 
               
               
                 inlet temperature 
                 −55° C. (feed stream in gaseous state) 
               
               
                 Reflux ratio 
                 1.3 
               
               
                 Side stream draw stage 
                 Tray 4 from the bottom 
               
               
                 Side stream flow rate 
                 290 kgmole/hour 
               
               
                   
               
             
          
         
       
     
         [0050]    Table 10 shows in Column (a) the feed stream  3  to the column  2  that was generated by the simulation using the parameters of Table 1. The flow rate (col (b)), molar fraction (col (c)), and the partial pressure (col (d)) of the feed stream are also shown in Table 2. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 10 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                 Feed Stream 
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 (a) 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 716 
                 0.176 
                 7.92 
               
               
                 H 2   
                 2266 
                 0.556 
                 25 
               
               
                 CH 4   
                 317 
                 0.078 
                 3.51 
               
               
                 N 2   
                 763 
                 0.187 
                 8.415 
               
               
                 Ar 
                 9.5 
                 0.0023 
                 0.103 
               
               
                 Total 
                 4071.5 
                 1 
                 45 
               
               
                   
               
             
          
         
       
     
         [0051]    Table 11 shows the composition of the processed syngas, or overhead stream  14 , as well as its flow rate and the pressure of the stream  14 , as determined by the simulation. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 11 
               
               
                   
               
               
                 Syngas (overhead 
                 Flow rate 
                   
                 partial pressure 
               
               
                 stream): 
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 Species 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                 CO 2   
                 9.683 × 10 −5   
                 3.11 × 10 −8   
                 1.39 × 10 −6   
               
               
                 H 2   
                 2266 
                 0.729 
                 32.805 
               
               
                 CH 4   
                 77 
                 0.025 
                 1.125 
               
               
                 N 2   
                 755.2 
                 0.243 
                 10.935 
               
               
                 Ar 
                 9.088 
                 0.0029 
                 0.1305 
               
               
                 Total 
                 3107 
                 1 
                 45 
               
               
                   
               
             
          
         
       
     
         [0052]    Table 12 shows the composition of the side stream  30  that was generated. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 12 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                   
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 Side Stream: 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 53.727 
                 0.185 
                 8.325 
               
               
                 H 2   
                 0 
                 0 
                 0 
               
               
                 CH 4   
                 236.94 
                 0.815 
                 36.675 
               
               
                 N 2   
                 8 
                 0.0275 
                 1.2375 
               
               
                 Ar 
                 0 
                 0 
                 0 
               
               
                 Total 
                 290.667 
                 1 
                 45 
               
               
                   
               
             
          
         
       
     
         [0053]    Table 13 shows the composition of the bottom stream  32  that was generated. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 13 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                 Bottom stream 
                 [kgmol/hr] 
                 molar fraction - x 
                 [atm] 
               
               
                 (a) 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 662.7 
                 0.995 
                 44.775 
               
               
                 H 2   
                 0 
                 0 
                 0 
               
               
                 CH 4   
                 3.077 
                 4.62 × 10 −3   
                 0.2 
               
               
                 N 2   
                 0.0065 
                 9.76 × 10 −6   
                  4.4 × 10 −4   
               
               
                 Ar 
                 0.003 
                  4.5 × 10 −5   
                 2.02 × 10 −4   
               
               
                 Total 
                 665.75 
                 1 
                 45 
               
               
                   
               
             
          
         
       
     
         [0054]    Table 14 shows the ammonia product yield, the purity of the ammonia yield, the condenser duty, and the reboiler duty. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 14 
               
               
                   
                   
               
             
             
               
                   
                 ammonia product yield 
                 617.8 
                 ton/day 
               
             
          
           
               
                   
                 purity of the ammonia yield 
                 0.977 
               
             
          
           
               
                   
                 Ammonia temperature 
                 −28° 
                 C. 
               
               
                   
                 Ammonia Pressure 
                 15 
                 bar 
               
               
                   
                   
               
             
          
         
       
     
         [0055]    Table 15 shows the energy consumption. Energy costs were calculated assuming a use of a nitrogen refrigerant utility at a cost of 1 million dollar/million kcal/hr/yr. For the reboiler, refrigerated brine was used as a utility at a cost of $4×10 4 /million kcal/hr/yr. The energy demand and cost were determined by the reflux ratio. When running the column at 45 bar the reflux composition was primarily liquid nitrogen and methane. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 15 
               
               
                   
               
             
             
               
                 Condenser duty 
                 6.582 × 10 6   
                 Energy cost of 
                 $6.58 
               
               
                   
                 kcal/hr 
                 Condenser 
                 million/year 
               
               
                 Reboiler duty 
                 2.872 × 10 6   
                 Energy cost of 
                 $0.13 
               
               
                   
                 kcal/hr 
                 Reboiler r 
                 million/year 
               
               
                   
               
             
          
         
       
     
         [0056]    Table 16 shows the steady state tray composition profile of the column molar flows (kgmole/hr). 
         [0000]    
       
         
               
               
               
               
               
               
               
             
           
               
                 TABLE 16 
               
               
                   
               
             
             
               
                   
                 CO 2   
                   
                 CH 4   
                   
                   
                   
               
               
                 Stage 
                 (Vap) 
                 H 2  (Vap) 
                 (Vap) 
                 N 2  (Vap) 
                 Ar (Vap) 
                 Temperature 
               
               
                   
               
               
                 Condenser 
                 2.48 × 10 −5   
                 1938 
                 43.7 
                 646.3 
                 7.661 
                 −166.1 
               
               
                 10  
                 5.17 × 10 −2   
                 2196 
                 1390 
                 2685 
                 57.69 
                 −126.2 
               
               
                 9 
                 0.7223 
                 2083 
                 2645 
                 1772 
                 47.57 
                 −114.5 
               
               
                 8 
                 4.416 
                 2071 
                 3256 
                 1203 
                 31.33 
                 −110.3 
               
               
                 7 
                 20.66 
                 2072 
                 3464 
                 995.6 
                 21.79 
                 −108.2 
               
               
                 6 
                 88.52 
                 2062 
                 3311 
                 910.9 
                 16.67 
                 −104 
               
               
                 5 
                 2.862 
                 4.929 
                 41.23 
                 8.343 
                 0.2172 
                 −76.69 
               
               
                 4 
                 37.77 
                 4.351 
                 388.4 
                 33.9 
                 1.481 
                 −55.54 
               
               
                 3 
                 100.2 
                 1.562 
                 962.4 
                 40.67 
                 2.652 
                 −16.26 
               
               
                 2 
                 113.7 
                 0.2723 
                 1048 
                 21.95 
                 2.071 
                 0.9492 
               
               
                 1 
                 122.2 
                 4.15 × 10 −2   
                 986.6 
                 10.2 
                 1.385 
                 6.963 
               
               
                 Reboiler 
                 166.3 
                  2.7 × 10 −3   
                 433.5 
                 2.231 
                 0.4723 
                 9.122 
               
               
                   
               
               
                   
                   
                   
                 CH 4   
               
               
                 Stage 
                 CO 2  (Liq) 
                 H 2  (Liq) 
                 (Liq) 
                 N 2  (Liq) 
                 Ar (Liq) 
                 Temperature 
               
               
                   
               
               
                 Condenser 
                 5.17 × 10 −2   
                 257.4 
                 1346 
                 2038 
                 50.03 
                 −166.1 
               
               
                 10  
                 0.722 
                 145.1 
                 2601 
                 1126 
                 39.91 
                 −126.2 
               
               
                 9 
                 4.416 
                 132.5 
                 3212 
                 556.6 
                 23.67 
                 −114.5 
               
               
                 8 
                 20.66 
                 134 
                 3420 
                 349.3 
                 14.13 
                 −110.3 
               
               
                 7 
                 88.52 
                 123.9 
                 3267 
                 264.6 
                 9 
                 −108.2 
               
               
                 6 
                 596.1 
                 8.019 
                 450.2 
                 32.75 
                 1.392 
                 −104 
               
               
                 5 
                 631 
                 7.441 
                 797.4 
                 58.31 
                 2.656 
                 −76.69 
               
               
                 4 
                 666.6 
                 1.562 
                 1096 
                 41 
                 2.775 
                 −55.54 
               
               
                 3 
                 680.1 
                 0.2724 
                 1181 
                 22.3 
                 2.194 
                 −16.26 
               
               
                 2 
                 688.6 
                 4.16 × 10 −2   
                 1120 
                 10.54 
                 1.508 
                 0.9492 
               
               
                 1 
                 732.8 
                 2.83 × 10 −3   
                 566.6 
                 2.564 
                 0.5954 
                 6.963 
               
               
                 Reboiler 
                 566.4 
                 1.23 × 10 −4   
                 133.1 
                 0.3323 
                 0.1231 
                 9.122 
               
               
                   
               
             
          
         
       
     
         [0057]    A phase diagram for the five component mixture of this invention is unavailable in the literature. However, from an analysis of the phase diagram of the corresponding binary system (CO 2 /CH 4 ), and the fact that a high concentration of H 2  leads to an increase of the critical pressure and also to a decrease in the freezing pressure of the CO 2 , it can be concluded that under the conditions (pressure and temperature) of this example the working conditions of the system of the present invention in which CO 2  freezing is prevented are broader than those of the binary system. 
         [0058]    It is worth noting that for this multi-component mixture, the vapor pressure line of pure CH 4  will not limit the separation boundary at low temperatures. Each of the gasses in the column of the multi-component mixture, other than the methane, has a lower critical temperature than methane. 
       Example 3 
       [0059]    In this example, the input stream was first cooled to a temperature of −100° C. which condenses most of the CO 2  in the feed stream. The cooled feed stream was then passed though a flush allowing most of the CO 2  to be removed from the other components of the feed stream, before being introduced into the column. The operating parameter values shown in Table 17 were used in the simulation. The thermodynamic package used was the Peng Robinson package. 
         [0000]    
       
         
               
               
             
           
               
                 TABLE 17 
               
               
                   
               
             
             
               
                 Syn loop pressure 
                 15 bar 
               
               
                 primary reforming temperature 
                 700° C. 
               
               
                 Number of trays 
                 12 plus condenser and reboiler 
               
               
                 Location of feed inlet 
                 Tray 7 from the bottom 
               
               
                 inlet temperature 
                 −100° C. (feed stream in gaseous state) 
               
               
                 Reflux ratio 
                 0.5 
               
               
                 Side stream draw stage 
                 reboiler 
               
               
                 Side stream flow rate 
                 410 kgmole/hour 
               
               
                   
               
             
          
         
       
     
         [0060]    Table 18 shows in Column (a) the feed stream  3  to the column  2 , before passing through the flush, that was generated by the simulation using the parameters of Table 1. The flow rate (col (b)), molar fraction (col (c)), and the partial pressure (col (d)) of the feed stream are also shown in Table 18. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 18 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                 Feed Stream 
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 (a) 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 711.2 
                 0.169 
                 2.535 
               
               
                 H 2   
                 2285 
                 0.542 
                 8.13 
               
               
                 CH 4   
                 447.7 
                 0.106 
                 1.59 
               
               
                 N 2   
                 761 
                 0.18 
                 2.7 
               
               
                 Ar 
                 9 
                 0.002 
                 0.003 
               
               
                 Total 
                 4213 
                 1 
                 15 
               
               
                   
               
             
          
         
       
     
         [0061]    Table 19 shows in Column (a) the feed stream  3  to the column  2 , after having passed through the flush, that was generated by the simulation using the parameters of Table 1. The flow rate (col (b)), molar fraction (col (c)), and the partial pressure (col (d)) of the feed stream are also shown in Table 19. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 19 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                 Feed Stream 
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 (a) 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 121.3 
                 0.033 
                 0.495 
               
               
                 H 2   
                 2285 
                 0.63 
                 9.45 
               
               
                 CH 4   
                 447.7 
                 0.1235 
                 1.8525 
               
               
                 N 2   
                 761 
                 0.21 
                 3.15 
               
               
                 Ar 
                 9 
                 2.48 × 10 −3   
                 0.0372 
               
               
                 Total 
                 3624 
                 1 
                 15 
               
               
                   
               
             
          
         
       
     
         [0062]    Table 20 shows the composition of the processed syngas, or overhead stream  14 , as well as its flow rate and the pressure of the stream  14 , as determined by the simulation. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 20 
               
               
                   
               
               
                 Syngas (overhead 
                 Flow rate 
                   
                 partial pressure 
               
               
                 stream): 
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 Species 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 0 
                 0 
                 0 
               
               
                 H 2   
                 2286 
                 0.735 
                 11.025 
               
               
                 CH 4   
                 57.9 
                 0.0186 
                 0.28 
               
               
                 N 2   
                 761.9 
                 0.245 
                 3.675 
               
               
                 Ar 
                 9 
                 2.89 × 10 −6   
                 4.3 × 10 −5   
               
               
                 Total 
                 3107 
                 1 
                 15 
               
               
                   
               
             
          
         
       
     
         [0063]    Table 21 shows the composition of the side stream  30  that was generated. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 21 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                   
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 Side Stream: 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 30 
                 0.0731 
                 1.1 
               
               
                 H 2   
                 0 
                 0 
                 0 
               
               
                 CH 4   
                 380 
                 0.926 
                 13.89 
               
               
                 N 2   
                 0 
                 0 
                 0 
               
               
                 Ar 
                 0 
                 0 
                 0 
               
               
                 Total 
                 410 
                 1 
                 15 
               
               
                   
               
             
          
         
       
     
         [0064]    Table 22 shows the composition of the bottom stream  32  that was generated. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 22 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                 Bottom stream 
                 [kgmol/hr] 
                 molar fraction - x 
                 [atm] 
               
               
                 (a) 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 92.21 
                 0.9 
                 13.5 
               
               
                 H 2   
                 0 
                 0 
                 0 
               
               
                 CH 4   
                 9.764 
                 0.095 
                 1.43 
               
               
                 N 2   
                 0 
                 0 
                 0 
               
               
                 Ar 
                 0 
                 0 
                 0 
               
               
                 Total from bottom 
                 101.947 
                 1 
                 15 
               
               
                 stream 
               
               
                 CO 2  from flush 
                 589.9 
                 1 
                 15 
               
               
                 Total (Flush + Column) 
                 691.874 
                 0.986 
                 15 
               
               
                   
               
             
          
         
       
     
         [0065]    Table 23 shows the ammonia product yield, the purity of the ammonia yield, the condenser duty, and the reboiler duty. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 23 
               
               
                   
                   
               
             
             
               
                   
                 Ammonia product yield 
                 619 
                 ton/day 
               
             
          
           
               
                   
                 purity of the ammonia yield 
                 0.988 
               
             
          
           
               
                   
                 Ammonia temperature 
                 −28° 
                 C. 
               
               
                   
                 Ammonia pressure 
                 15 
                 bar 
               
               
                   
                   
               
             
          
         
       
     
         [0066]    Table 24 shows the energy consumption. Energy costs were calculated assuming a use of a nitrogen refrigerant utility at a cost of 1 million dollar/million kcal/hr/yr. The energy demand and cost were determined by the reflux ratio. When running the column at 15 bar the reflux composition was primarily liquid nitrogen. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 24 
               
               
                   
               
             
             
               
                 Condenser duty 
                 3.466 × 10 6   
                 Energy cost of 
                 $3.466 
               
               
                   
                 kcal/hr 
                 Condenser 
                 million/year 
               
               
                 Reboiler duty 
                 1.466 × 10 6   
                 Energy cost of 
                 $1.466 
               
               
                   
                 kcal/hr 
                 Reboiler r 
                 million/year 
               
               
                   
               
             
          
         
       
     
         [0067]    Since the concentration of CO 2  in the column is low due the flushing of the CO2, freezing of any CO 2  in the column will not occur under the pressure 15 bar. This simulation also corresponds to a system in which the cooled feed stream is fed directly into the reboiler. 
       Example 4 
       [0068]    In this example, the operating parameter values shown in Table 1 were used in the simulation. The thermodynamic package used was the SRK package. 
         [0000]    
       
         
               
               
             
           
               
                 TABLE 25 
               
               
                   
               
             
             
               
                 Syn loop pressure 
                 15 bar 
               
               
                 primary reforming temperature 
                 750° C. 
               
               
                 Number of trays 
                 10 plus condenser and reboiler 
               
               
                 Location of feed inlet 
                 Tray 6 from the bottom 
               
               
                 inlet temperature 
                 −55° C. (feed stream in gaseous state) 
               
               
                 Reflux ratio 
                 1.2 
               
               
                 Side stream draw stage 
                 reboiler 
               
               
                 Side stream flow rate 
                 199 kgmole/hour 
               
               
                   
               
             
          
         
       
     
         [0069]    Table 26 shows in Column (a) the feed stream  3  to the column  2  that was generated by the simulation using the parameters of Table 1. The flow rate (col (b)), molar fraction (col (c)), and the partial pressure (col (d)) of the feed stream are also shown in Table 26. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 26 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                 Feed Stream 
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 (a) 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 769 
                 0.189 
                 2.835 
               
               
                 H 2   
                 2330 
                 0.573 
                 8.595 
               
               
                 CH 4   
                 177 
                 0.0435 
                 0.65 
               
               
                 N 2   
                 776 
                 0.191 
                 2.865 
               
               
                 Ar 
                 9.36 
                 0.0023 
                 0.0345 
               
               
                 Total 
                 4061 
                 1 
                 15 
               
               
                   
               
             
          
         
       
     
         [0070]    Table 27 shows the composition of the processed syngas, or overhead stream  14 , as well as its flow rate and the pressure of the stream  14 , as determined by the simulation. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 27 
               
               
                   
               
               
                 Syngas (overhead 
                 Flow rate 
                   
                 partial pressure 
               
               
                 stream): 
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 Species 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 1.9 × 10 −9   
                      6 × 10 −13   
                 ~0 
               
               
                 H 2   
                 2330 
                 0.74 
                 11.1 
               
               
                 CH 4   
                 29.84 
                 9.48 × 10 −3   
                 0.142 
               
               
                 N 2   
                 776 
                 0.246 
                 3.69 
               
               
                 Ar 
                 9.3 
                 2.95 × 10 −3   
                 0.04425 
               
               
                 Total 
                 3146 
                 1 
                 15 
               
               
                   
               
             
          
         
       
     
         [0071]    Table 28 shows the composition of the side stream  30  that was generated. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 28 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                   
                 [kgmol/hr] 
                 molar fraction - y 
                 [atm] 
               
               
                 Side Stream: 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 83 
                 0.417 
                 6.25 
               
               
                 H 2   
                 0 
                 0 
                 0 
               
               
                 CH 4   
                 116 
                 0.583 
                 8.75 
               
               
                 N 2   
                 0 
                 0 
                 0 
               
               
                 Ar 
                 0 
                 0 
                 0 
               
               
                 Total 
                 199 
                 1 
                 15 
               
               
                   
               
             
          
         
       
     
         [0072]    Table 29 shows the composition of the bottom stream  32  that was generated. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 29 
               
               
                   
               
               
                   
                 Flow rate 
                   
                 partial pressure 
               
               
                 Bottom stream 
                 [kgmol/hr] 
                 molar fraction - x 
                 [atm] 
               
               
                 (a) 
                 (b) 
                 (c) 
                 (d) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 CO 2   
                 685.4 
                 0.956 
                 14.35 
               
               
                 H 2   
                 0 
                 0 
                 0 
               
               
                 CH 4   
                 31.33 
                 0.044 
                 0.65 
               
               
                 N 2   
                 0 
                 0 
                 0 
               
               
                 Ar 
                 0 
                 0 
                 0 
               
               
                 Total 
                 716.7 
                 1 
                 15 
               
               
                   
               
             
          
         
       
     
         [0073]    Table 30 shows the ammonia product yield, the purity of the ammonia yield, the condenser duty, and the reboiler duty. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 30 
               
               
                   
                   
               
             
             
               
                   
                 Ammonia product yield 
                 628.4 
                 ton/day 
               
             
          
           
               
                   
                 purity of the ammonia yield 
                 0.992 
               
             
          
           
               
                   
                 Ammonia temperature 
                 −28° 
                 C. 
               
               
                   
                 Ammonia pressure 
                 15 
                 bar 
               
               
                   
                   
               
             
          
         
       
     
         [0074]    Table 31 shows the energy consumption. Energy costs were calculated assuming a use of a nitrogen refrigerant utility at a cost of 1 million dollar/million kcal/hr/yr. The energy demand and cost were determined by the reflux ratio. When running the column at 15 bar the reflux composition was primarily liquid nitrogen. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 31 
               
               
                   
               
             
             
               
                 Condenser duty 
                 7.718 × 10 6   
                 Energy cost of 
                 $7.718 
               
               
                   
                 kcal/hr 
                 Condenser 
                 million/year 
               
               
                 Reboiler duty 
                 1.883 × 10 6   
                 Energy cost of 
                 $1.883 
               
               
                   
                 kcal/hr 
                 Reboiler r 
                 million/year 
               
               
                   
               
             
          
         
       
     
         [0075]    The ammonia yield of this example (628.4 ton/day) is the greatest of the presented examples. The bottom product of this example (utilizing the SRK package) contains only CO 2  and CH 4  as opposed to Examples 1 and 2. Thus, in Example 1 where, in addition, there were also small amounts of liquid N 2  and liquid Ar, there was a relatively low bottom stream temperature (−108° C.), in comparison to the relatively high bottom stream temperature of Example 4 (−53.44° C.).