Abstract:
A process for producing methanol, where a hydrocarbon feedstock ( 1 ) is reformed and a make-up syngas is reacted in a synthesis loop, obtaining crude methanol which is further treated to obtain high-grade methanol, and where the carbon dioxide dissolved in the crude methanol is recycled to the reforming section in order to adjust the stoichiometric number of the make-up syngas. In a preferred embodiment, a flash gas ( 9 ) separated from the crude methanol ( 8 ) and light ends ( 10 ) coming from distillation are recycled to a compressor ( 106 ) and fed to a primary reformer ( 100 ); further carbon dioxide can be recycled from the flue gas ( 11 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/201,556, filed Aug. 15, 2011, which is a national phase of PCT/EP2010/052893, filed Mar. 8, 2010, which claims priority to European Patent Application No. 09155137.4 filed Mar. 13, 2009, the disclosures of which are hereby incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to synthesis of methanol from reforming of a hydrocarbon feedstock. 
       PRIOR ART 
       [0003]    A large number of methanol (MeOH) plants in the world operate with a synthesis gas produced by steam reforming of a hydrocarbon feedstock, usually a light hydrocarbon such as natural gas. The steam reforming yields a make-up synthesis gas mainly comprising carbon oxides (CO, CO 2 ) and hydrogen (H 2 ), which is reacted in a high-pressure synthesis loop to produce methanol. The source of hydrocarbon can be any hydrocarbon or mixture thereof; a common example is natural gas. 
         [0004]    A prior art process is based on the following steps: the feed gas, for example natural gas, is de-sulphurized and steam-reformed, producing a hot syngas usually at a pressure of around 20-40 bar; the syngas is cooled to recover heat, and fed to a main syngas compressor to raise the pressure at the operating value of the synthesis loop (usually 100 bar or more); the syngas is then reacted in said loop, obtaining a so-called crude methanol; the crude methanol is then treated in a distillation section in order to reach the required purity. 
         [0005]    The steam-reforming can be performed with different configurations: non-limitative examples are: a stand-alone primary reformer; a primary reformer followed by a secondary reformer, possibly an auto-thermal reformer; a stand-alone auto-thermal reformer. 
         [0006]    The reactions in the synthesis loop can be summarized as: 
         [0000]      CO+2H 2→ CH 3 OH  (I)
 
         [0000]      CO 2 +3H 2→ CH 3 OH+H 2 O  (II)
 
         [0007]    The reactants CO, CO 2  and H 2  are supplied by the make-up syngas. It can be understood from the above reactions that the concentration of carbon oxides (CO and CO 2 ) and hydrogen of the make-up syngas is crucial. The molar hydrogen-to-carbon ratio of the syngas produced in the reforming process is usually defined by the stoichiometric number R: 
         [0000]    
       
         
           
             R 
             = 
             
               
                 
                   [ 
                   
                     H 
                     2 
                   
                   ] 
                 
                 - 
                 
                   [ 
                   
                     CO 
                     2 
                   
                   ] 
                 
               
               
                 
                   [ 
                   CO 
                   ] 
                 
                 + 
                 
                   [ 
                   
                     CO 
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
         [0008]    The thermodynamic correct value of R is 2; it is known however that the kinetic of the reactions in the high-pressure (HP) synthesis loop asks for an optimum R slightly greater than 2, preferably in the range 2.05 to 2.3, depending on the CO/CO 2  ratio. A higher or lower R of the syngas means that the HP loop operates under its capability. 
         [0009]    The syngas delivered by the reformer(s) can significantly deviate from said optimum value of R, so there is the need to adjust the stoichiometric number to the optimum value close to 2. 
         [0010]    Known measures to adjust the value of R are: the recycling of hydrogen from the synthesis loop purge gas, based on membranes or on pressure swing adsorption (PSA) devices, and the recycling of carbon dioxide contained in the flue gas from the steam reforming process. Recycling a H 2 - or CO 2 -containing stream helps respectively to increase, or to lower, the value of R. 
         [0011]    For example, a process based on auto-thermal reforming typically produces a syngas with carbon oxides in excess (R&lt;2); in this case recovering hydrogen from the HP loop purge gas and adding recovered hydrogen to the make-up syngas helps to adjust (i.e. increase) the value of R. On the contrary, a primary reformer produces a hydrogen-rich syngas and, in this case, the stoichiometric number R is balanced by recovering carbon dioxide from the flue gas of the reformer itself. 
         [0012]    Recovering the carbon dioxide contained in the flue gas is however expensive. A conventional CO 2 -recovery section for this purpose is made basically with an absorber tower where the flue gas are counter-currently washed with a suitable solution, e.g. an amine-based solution; a CO 2 -rich solution is separated at the bottom of the tower and is purified in a regenerator, where reboilers supply heat to the solution in order to break the bound between the solution and the carbon dioxide; a CO 2 -rich gaseus stream is separated at the top of the regenerator, compressed in a suitable compressor and recycled back to the primary reformer. 
         [0013]    This recovery section is normally very expensive and consumes a lot of energy. A substantial amount of energy, in fact, is required to separate the carbon dioxide from the rest of the flue gas components. The economical impact of this technique of CO 2  recovery on the whole process is not negligible. 
         [0014]    The majority of the existing MeOH plants, and many of the new plants, are based on steam reforming of the feed gas charge with a primary reformer and, then, suffer the problem of hydrogen excess in the make-up syngas. The reforming process of these plants usually delivers a make-up syngas with R&gt;3. As above, the recover of the carbon dioxide contained in the flue gas can help to solve this problem but is quite expensive, both in terms of capital cost and energy consumption. Hence, there is the need to find a less expensive way to balance the reactants of the make-up syngas close to the optimum value for the downstream synthesis loop. 
         [0015]      FIG. 3  is a simplified layout of a prior-art methanol plant, comprising a reformer  100 , a synthesis loop  103 , a CO 2  recovery section  105  and a hydrogen recovery section  107 . Crude methanol produced in the loop  103  is de-gassed in a flash gas separator  104 . Carbon dioxide is recovered from the flue gas of the reformer  100  and recycled to the same reformer, via a CO 2  compressor  106 . 
         [0016]    The flash gas  9  from said separator  104  and light ends  10  released from distillation of crude methanol are recycled as fuel to the primary reformer  100 , together with a portion  13  of the feed  1 , and a stream  18  from the hydrogen recovery section  107 . 
       SUMMARY OF INVENTION 
       [0017]    In a process for synthesis of methanol, the technical problem faced by the invention is to provide a simple and inexpensive method for adjusting the content of carbon oxides and hydrogen in the make-up syngas, in particular in a hydrogen-rich make up syngas. 
         [0018]    The basic idea underlying the invention is to recover the carbon dioxide dissolved in the crude methanol. It has been found that this carbon dioxide can be recovered with relatively inexpensive equipments, compared to the recovery from the flue gas of a reformer. Hence, the invention makes available a cost-effective CO 2  rich stream that can be used to balance, at least partially, the stoichiometric number R of the make-up syngas. 
         [0019]    In accordance with the invention, the above technical problem is solved with a process for producing methanol, comprising the steps of:
       a. reforming a hydrocarbon feedstock in a reforming process step, obtaining a make-up syngas comprising carbon oxides and hydrogen;   b. reacting said make-up syngas in a methanol synthesis loop, obtaining crude methanol;   c. processing said crude methanol to obtain methanol of a required purity;   characterized by the steps of:   d. recovering at least one CO 2 -containing stream from the processing of said crude methanol, and   e. recycling said at least one CO 2 -containing stream as an input stream for said reforming process step.       
 
         [0026]    The term “CO 2 -containing stream” is used in this specification to mean a stream containing carbon oxides, mainly carbon dioxide CO 2 . The term CO 2  stream will also be used with the same meaning. 
         [0027]    In preferred aspects of the invention, the step of recovering a CO 2 -containing stream from crude methanol is performed with at least one of the following techniques, and preferably with both the following techniques:
       recovering a flash gas stream released by de-pressurization of the crude methanol produced in the synthesis loop;   recovering a gas stream containing carbon dioxide released by distillation of the crude methanol.       
 
         [0030]    The flash gas stream released by de-pressurization of the crude methanol has a relevant content of CO 2 , due to high solubility of the CO 2  in the methanol. The gas stream released in the distillation process is usually referred to as “light ends”. The light ends are commonly released from the top of the first column (topping column) of a distillation section, and they are also rich of carbon dioxide. 
         [0031]    Said flash gas stream and said light-ends stream, in one embodiment of the invention, are mixed together forming a single CO 2 -containing flow, which is recycled to the reforming section, being the input stream of the process step e) as listed above. 
         [0032]    The invention is also applicable to a process including the conventional carbon-dioxide recovery from the flue gas of a reformer. In some embodiments of the invention, the disclosed recovery of carbon dioxide from crude methanol is used in combination with the recovery from the flue gas of the reformer(s); in other embodiments, the recover from crude methanol can be the only recover of carbon dioxide 
         [0033]    The recovered CO 2 -containing stream can be fed directly or indirectly to the reforming process. In a preferred embodiment, said CO 2 -containing stream is compressed in a suitable CO 2  compressor and mixed with the hydrocarbon feedstock, at the inlet of a reformer of the reforming section. Said reformer can be an autothermal reformer or a primary reformer, such as a catalytic tube reformer, possibly followed by a secondary reformer. 
         [0034]    The invention is applicable preferably, but not exclusively, to process and plants with a stand-alone primary reformer producing a syngas with a significant hydrogen excess, e.g. with the stoichiometric number R around 3, or even greater; the recover of carbon dioxide dissolved in the crude methanol, and its recycle to the reformer, helps to adjust the stoichiometric number at the correct value close to 2. 
         [0035]    The main advantage of the inventive process is that at least part of the carbon dioxide is recovered in a much less expensive way, if compared to the known separation from the flue gas of the reformer. It should be noted that the flash gas and light ends are used as fuels or discharged in the prior art, while the invention provides their more effective use as process streams. The recycle of said streams allows gives a better low heating value (LHV) of the fuel gas used in the plant, achieving a better efficiency of the primary reformer. This better efficiency of the primary reformer can be explained with a higher pre-heating temperature achievable in the reformer coils, and with a lower temperature and flue gas flow rate at reformer stack. A higher efficiency of the primary reformer means also lower pollutant emissions in the atmosphere. 
         [0036]    Referring now to embodiments featuring the carbon dioxide recovery from the reformer flue gas, the further CO 2 -containing stream recovered from crude methanol, e.g. from flash gas and/or light ends, is fed to a carbon dioxide compressor, downstream a recovery section operating on said reformer flue gas. The gas recycle at the suction of the CO 2  compressor reduces the overall carbon dioxide required from the energy-intensive process of CO 2  recovery from the flue gas, thus resulting in significant energy savings for the whole process. 
         [0037]    In summary, the recycle of carbon oxides (mainly CO 2 ) at the suction of the CO 2  compressor allows to achieve the following benefits/advantages: the reduction of the cost and energy consumption of the conventional CO 2  recovery section (when provided); improved energy efficiency of the plant and specifically of the primary reformer; reduced pollutant emissions. 
         [0038]    It should be noted that carbon dioxide is a reactant in the synthesis loop, hence the recycle of the carbon dioxide dissolved in the crude methanol is also positive for the synthesis loop. 
         [0039]    f appropriate, the process may also include hydrogen recovery from synthesis loop purge gas. The H 2 -rich stream so obtained is preferably injected upstream the main syngas compressor. 
         [0040]    The invention also relates to a plant for carrying out the above process. In particular, the invention relates to a plant for producing methanol comprising: a reforming section receiving a hydrocarbon feedstock, and producing a reformed make-up syngas comprising carbon oxides and hydrogen; a methanol synthesis loop, fed with the make-up syngas and producing crude methanol; a section where said crude methanol is processed to obtain methanol of a required purity; the plant being characterized by:
       means for recovering at least one CO 2 -containing stream separated from the processing of said crude methanol, and   means feeding said at least one CO 2 -containing stream to said reforming section.       
 
         [0043]    Preferably, the plant comprises a flash gas separator where a flash gas containing CO 2  is obtained from de-pressurization of crude methanol. The means for recovering said flash gas and feeding it to reforming section comprise a piping feeding the flash to the inlet of a CO 2  compressor, and feeding the delivery of said compressor at the inlet of the reforming section. Said means can also comprise a piping adapted to recover the light-ends gas stream released in a distillation section of crude methanol. 
         [0044]    Another object of the invention is a method for revamping of an existing plant. Hence, one aspect of the invention is a method for revamping a methanol plant, said plant comprising at least a reforming section receiving a hydrocarbon feedstock, and producing a make-up syngas comprising carbon oxides and hydrogen, a methanol synthesis loop fed with the make-up syngas and producing crude methanol, and a section where said crude methanol is treated to obtain substantially pure methanol, the method being characterized by the provision of at least:
       means for recovering at least one CO 2 -containing stream separated from said crude methanol, and   means feeding said CO 2 -containing stream to said reforming section.       
 
         [0047]    A first application of the inventive method involves that, in a plant for producing methanol with a conventional CO 2 -recovery section, the flash gas and/or the light ends are recovered and fed to the inlet of said existing CO 2  compressor. In this case, the energy consumed by the flue gas CO 2 -recovery section is decreased, as a less expensive CO 2  feed is available from the flash gas and light ends stream. A second application involves that, in a plant with no CO 2  recovery, a new compressor for the carbon dioxide is installed. As apparent for a skilled person, the revamping will also involve the provision of necessary equipment and auxiliaries such as piping, valves, etc. . . . . 
         [0048]    The advantages of the invention will be more evident with the following detailed description of a preferred embodiment, presented as a non-limitative example. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0049]      FIG. 1  is a simplified block diagram of a methanol plant according to one embodiment of the invention, and including the recovery of carbon dioxide from the flue gas of a primary reformer. 
           [0050]      FIG. 2  is a simplified block diagram of a plant according to another embodiment of the invention. 
           [0051]      FIG. 3  is a simplified layout of a prior art methanol plant. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0052]    The plant of  FIG. 1  comprises basically a primary reformer  100 , a gas cooler  101 , a syngas compressor  102 , a methanol synthesis loop  103 . The primary reformer  100  is part of a reforming section  110 , comprising also a CO 2  recovery section  105  and a CO 2  compressor  106 . 
         [0053]    The primary reformer  100  is for example a catalytic tube reactor, according to well known art. All the above equipments are known in the art and therefore they are not described in detail. The reforming section  110 , in other embodiments of the invention, may comprise an autothermal reformer or a primary reformer followed by a secondary reformer. 
         [0054]    The reforming section  110  is fed with a hydrocarbon-containing feedstock  1 , such as natural gas. In the example, the natural gas enters the reformer  100  as a stream  3 , after mixing with a stream  12  containing recycled carbon dioxide. The reformed hot syngas  4  produced in the primary reformer  100  is cooled in the gas cooler  101 , e.g. from around 800° C. to 100° C. or less, and fed to the loop  103  through the compressor  102 . Stream  5  indicates the output of cooler  101 , the stream  6  is the inlet of compressor  102 , and the stream  7  is the hi-pressure compressed make-up syngas fed to the loop  103 . 
         [0055]    The loop  103  operates usually around 100 bar, producing crude methanol  8 . Said crude methanol  8  is a mixture of methanol and water, plus some CO 2  (typically around 1.5%) and is sent to a distillation section (not shown) to obtain methanol of a given purity or grade. 
         [0056]    A low-pressure flash gas separator  104  separates the crude methanol stream  8  into a flash gas  9  and de-gassed crude methanol  19 . The crude methanol  8  is de-pressurized through a valve (not shown), down to the working pressure of the separator  104 , for example at around 5-10 bar, preferably 6 bar. The methanol stream  19  is sent to the downstream distillation section. 
         [0057]    The flash gas  9 , containing the carbon dioxide formerly dissolved in the crude methanol  8 , is recycled to the reforming section  110 . A stream  10  of light ends produced in the distillation section, in the example, is also recycled to said reforming section  110 . 
         [0058]    Referring with greater detail to the layout of  FIG. 1 , the reforming section  110  is equipped with a conventional CO 2 -recovery section  105  and related compressor  106 , recycling the carbon dioxide contained in the flue gas  11  of the reformer  100 . The recovery section  105  delivers a CO 2 -rich stream  14 , obtained from said flue gas  11 , to inlet of the compressor  106 . Said compressor  106  delivers a stream  12 , which is mixed with the feedstock  1 , or with a portion  2  thereof as in  FIG. 1 , thus enriching of carbon dioxide the feed  3  of the reformer  100 . 
         [0059]    The flash gas  9  and light ends  10  are mixed to form a single stream  15 , which is fed to the suction side of the compressor  106  and, hence, recycled to the primary reformer  100  in the same way as said CO 2 -rich stream  14 . In alternative embodiments, the streams  9  and  10  may be recycled to the reforming section  110  with separate flow lines. 
         [0060]    Both the streams  9  and  10  contain a relevant amount of carbon oxides, mainly carbon dioxide. As an example, a typical composition of the flash gas  9  is around 60% CO 2 , around 25% CH 4  and 10% hydrogen, with small percentages of nitrogen (2%), steam (2%), carbon oxide (&lt;1%), plus small amounts (&lt;0.01%) of He, Ar, methanol. The light ends  10  may contain for example 75% CO 2 , 20% steam, some methanol and methane, plus inerts and impurities. 
         [0061]    In the shown embodiment, the plant also comprises a hydrogen recovery section  107  for recovering H 2  from a purge gas stream  16  taken from the loop  103 . Said section  107  outputs a hydrogen-rich stream  17  which is mixed with the output  5  of the gas cooler  101 , to form the inlet flow  6  of the gas compressor  102 . It should be noted that hydrogen is a reactant for the synthesis of methanol as seen in reactions (I) and (II) above, hence the recycle of the stream  17  is useful for the whole efficiency of the plant. A preferred injection point, as shown, is between the gas cooler  101  and the syngas compressor  102 , at the suction side of said compressor. 
         [0062]    The section  107  also produces a fuel stream  18  containing carbon oxides, which is recycled to the reformer  100 , possibly mixed with a portion  13  of the feedstock  1 . The remaining portion  2  of said feedstock  1 , in this example, is mixed with the CO 2 -containing stream  12  delivered by the compressor  106 , to form the feed  3  of the reformer  100 . The entity of the mixing portion  13  depends on specific needs, and may be for example around 30% of total feed  1 . 
         [0063]    A simplified layout is shown in  FIG. 2 , where the reforming section  110  has no CO 2 -recovery section, and the flue gas  11  is discharged. The input of the compressor  106  is then the stream  15  formed by the flash gas  9  and/or the light-ends  10 . The other equipments are as in  FIG. 1 . 
         [0064]    The invention, as stated above, is applicable also to the revamping of existing plants. In this case, the invention is best applicable to a methanol plant featuring the CO 2  recovery from the reformer flue gas, as in  FIG. 1 . Assuming that the methanol plant already comprises the section  105  and compressor  106 , the revamping is carried out basically by re-routing the piping of the flash gas  9  and/or light ends  10  to the suction side of the compressor  106 . Usually, the compressor does not need substantial modification to receive this additional input. 
         [0065]    For example, the prior-art layout of  FIG. 3  can be revamped to the inventive layout of  FIG. 1 , substantially by re-routing the piping of flash gas  9  and light ends  10  to the inlet side of the compressor  106 . Hence, a preferred revamping in accordance with the invention comprises the step of re-routing the piping of a flash gas separated by de-pressurization of crude methanol from the synthesis loop, and re-routing the piping of a further CO 2 -containing stream recovered from distillation of crude methanol, said re-routing being directed to a CO 2  compressor feeding the reforming section. 
         [0066]    Nevertheless, the invention is also applicable to revamping of methanol plants with no CO 2  recover from the flue gas, as in  FIG. 2 . In this case, the revamping involves the installation of a new compressor  106 . 
         [0067]    The invention achieves the aims and purposes as stated above. As an example, it has been found that by recycling the flash gas  9  and light ends  10 , up to 20% less CO 2  is required from the recovery section  105 , for a given output of make-up syngas to the loop  103 . Accordingly, a new plant according to  FIG. 1  can be realized with savings around 20% in the cost of said section  105 . 
       Example 
       [0068]    The following is a comparison between a conventional methanol plant with CO 2  recovery from flue gas  11 , as in  FIG. 3 , and the inventive plant according to the layout of  FIG. 1 , Tables 1a to 1c relate to the conventional plant ( FIG. 3 ) and Tables 2a to 2c relate to the plant of the invention. The comparison has been done considering to keep approximately the same final production. 
         [0069]    The energy consumption of the plant can be calculated as the heat value of the feed  1  (on LHV basis) per metric ton (mt) of methanol produced. In this example, the energy consumption is decreased from 7.33 GCal/mt of the existing plant to 7.29 GCal/mt; moreover the tables 1 and 2 show that the flue gas temperature and flow rate at the stack are decreased, improving the plant efficiency and reducing the environmental impact. It can be calculated that the better efficiency of the primary reformer reduces the carbon dioxide emissions of more than 6500 tons/year. 
         [0070]    In case the radiant box and/or the CO 2  recovery section are close to their maximum capability, the invention can be applied to increase the plant production up to 0.4/0.6% of the final methanol production. 
         [0071]    The following tables 1a to 1c contain data of the base plant of  FIG. 3 . 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1a 
               
             
             
               
                   
               
               
                 (base plant) 
               
             
          
           
               
                 Stream 
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
               
               
                   
               
             
          
           
               
                 Vapour 
                   
                 1.00 
                 1.00 
                 1.00 
                 1.00 
                 0.85 
                 0.86 
                 1.00 
               
               
                 Fraction (mole) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Temperature 
                 ° C. 
                 15.0 
                 192.5 
                 198.1 
                 870.0 
                 82.0 
                 81.3 
                 147.9 
               
               
                 Pressure 
                 bar 
                 16.01 
                 23.71 
                 23.71 
                 19.71 
                 16.51 
                 16.51 
                 96.47 
               
               
                 Molar Flow 
                 kmole/hr 
                 4115.5 
                 6816.1 
                 7797.3 
                 17243.0 
                 14072.5 
                 14434.6 
                 12004.7 
               
               
                 Mass Flow 
                 kg/hr 
                 68057.1 
                 118261.6 
                 160969.2  
                 240367.3 
                 183237.7 
                 186369.1 
                 142557.9 
               
               
                 Composition 
                 % mol wet 
                   
                   
                   
                   
                   
                   
                   
               
               
                 CO 
                   
                 — 
                 0.027% 
                 0.024% 
                 13.311%  
                 16.309%  
                 15.916%  
                 19.138%  
               
               
                 CO 2   
                   
                 1.030% 
                 0.579% 
                 12.845%  
                 7.118% 
                 8.718% 
                 8.814% 
                 10.586%  
               
               
                 H 2   
                   
                 0.010% 
                 0.632% 
                 0.553% 
                 45.248%  
                 55.440%  
                 56.030%  
                 67.371%  
               
               
                 H 2 O 
                   
                 — 
                 57.874%  
                 50.823%  
                 32.621%  
                 17.449%  
                 17.017%  
                 0.233% 
               
               
                 CH 4   
                   
                 97.560%  
                 40.275%  
                 35.207%  
                 1.559% 
                 1.911% 
                 2.035% 
                 2.447% 
               
               
                 Ethane 
                   
                 0.520% 
                 0.212% 
                 0.186% 
                 — 
                 — 
                 — 
                 — 
               
               
                 Propane 
                   
                 0.080% 
                 0.033% 
                 0.029% 
                 — 
                 — 
                 — 
                 — 
               
               
                 nButane 
                   
                 0.040% 
                 0.016% 
                 0.014% 
                 — 
                 — 
                 — 
                 — 
               
               
                 nPentane 
                   
                 0.020% 
                 0.008% 
                 0.007% 
                 — 
                 — 
                 — 
                 — 
               
               
                 N 2   
                   
                 0.720% 
                 0.331% 
                 0.292% 
                 0.132% 
                 0.162% 
                 0.174% 
                 0.209% 
               
               
                 O 2   
                   
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 He 
                   
                 0.020% 
                 0.009% 
                 0.008% 
                 0.004% 
                 0.004% 
                 0.005% 
                 0.006% 
               
               
                 CH 3 OH 
                   
                 — 
                 0.001% 
                 0.001% 
                 — 
                 — 
                 — 
                 — 
               
               
                 Ar 
                   
                 — 
                 0,002% 
                 0.013% 
                 0.006% 
                 0.007% 
                 0.009% 
                 0.010% 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1b 
               
             
             
               
                   
               
               
                 (base plant) 
               
             
          
           
               
                 Stream 
                   
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
                 14 
               
               
                   
               
             
          
           
               
                 Vapour 
                   
                 0.03 
                 1.00 
                 0.81 
                 1.00 
                 1.00 
                 1.00 
                 1.00 
               
               
                 Fraction (mole) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Temperature 
                 ° C. 
                 42.1 
                 49.5 
                 63.3 
                 136.6 
                 233.0 
                 15.0 
                 40.0 
               
               
                 Pressure 
                 bar 
                 6.00 
                 4.41 
                 5.41 
                 0.97 
                 26,51 
                 16.01 
                 1.26 
               
               
                 Molar Flow 
                 kmole/hr 
                 4719.8 
                 148.5 
                 84.9 
                 19349.2 
                 981.2 
                 1331.5 
                 1024.0 
               
               
                 Mass Flow 
                 kg/hr 
                 135319.7 
                 4646.8 
                 3215.0 
                 534540.7 
                 42707.6 
                 22018.7 
                 43480.3 
               
               
                 Composition  
                 % mol wet 
                   
                   
                   
                   
                   
                   
                   
               
               
                 CO 
                   
                 0.021% 
                 0.641% 
                 0.023% 
                 — 
                 — 
                 — 
                 — 
               
               
                 CO 2   
                   
                 3.214% 
                 58.728%  
                 74.215%  
                 9.284% 
                 98.049%  
                 1.030% 
                 93.959%  
               
               
                 H 2   
                   
                 0.358% 
                 11.242%  
                 0.242% 
                 — 
                 — 
                 0.010% 
                 — 
               
               
                 H 2 O 
                   
                 25.048%  
                 2.275% 
                 18.882%  
                 20.339%  
                 1.835% 
                 — 
                 5.930% 
               
               
                 CH 4   
                   
                 0.817% 
                 24.781%  
                 2.087% 
                 — 
                 — 
                 97.560%  
                 — 
               
               
                 Ethane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
                 0.520% 
                 — 
               
               
                 Propane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
                 0.080% 
                 — 
               
               
                 nButane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
                 0.040% 
                 — 
               
               
                 nPentane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
                 0.020% 
                 — 
               
               
                 N 2   
                   
                 0.072% 
                 2.176% 
                 0.188% 
                 67.913%  
                 0.021% 
                 0.720% 
                 0.020% 
               
               
                 O 2   
                   
                 — 
                 0.001% 
                 — 
                 1.653% 
                 0.001% 
                 — 
                 0.001% 
               
               
                 He 
                   
                 0.002% 
                 0.068% 
                 — 
                 0.004% 
                 — 
                 0.020% 
                 — 
               
               
                 CH 3 OH 
                   
                 70.466%  
                 0.002% 
                 4.362% 
                 — 
                 — 
                 — 
                 — 
               
               
                 Ar 
                   
                 0.003% 
                 0.085% 
                 — 
                 0.807% 
                 0.094% 
                 — 
                 0.090% 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1c 
               
             
             
               
                   
               
               
                 (base plant) 
               
             
          
           
               
                 Stream 
                   
                 15 
                 16 
                 17 
                 18 
                 19 
               
               
                   
               
             
          
           
               
                 V.F. (mole) 
                   
                 0.93 
                 1.00 
                 1.00 
                 1.00 
                 0.00 
               
               
                 Temperature 
                 ° C. 
                 51.9 
                 43.5 
                 50.0 
                 50.0 
                 44.0 
               
               
                 Pressure 
                 bar 
                 4.41 
                 93.57 
                 35.01 
                 35.01 
                 6.00 
               
               
                 Molar Flow  
                 kmole/hr 
                 233.5 
                 659.1 
                 362.1 
                 297.0 
                 4848.8 
               
               
                 Mass Flow 
                 kg/hr 
                 7861.8 
                 8293.0 
                 3131.3 
                 5161.7 
                 135672.9 
               
               
                 Compo- 
                 % mol  
                   
                   
                   
                   
                   
               
               
                 sition 
                 wet 
                   
                   
                   
                   
                   
               
               
                 CO 
                   
                  0.416% 
                  2.071% 
                  0.641% 
                  3.815% 
                 — 
               
               
                 CO 2   
                   
                 64.361%  
                 10.390% 
                 12.557% 
                  7.748% 
                  1.329% 
               
               
                 H 2   
                   
                  7.242%  
                 49.858% 
                 78.951%  
                 14.385% 
                  0.004% 
               
               
                 H 2 O 
                   
                  8.316% 
                  0.157% 
                  0.251% 
                  0.042%  
                 30.035% 
               
               
                 CH 4   
                   
                 16.526% 
                 34.359% 
                  6.879%  
                 67.866% 
                  0.036% 
               
               
                 Ethane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 Propane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 nButane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 nPentane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 N 2   
                   
                  1.453% 
                  2.929% 
                  0.640% 
                  5.720% 
                  0.003% 
               
               
                 O 2   
                   
                  0.001% 
                  0.001% 
                 — 
                  0.003% 
                 — 
               
               
                 He 
                   
                  0.043% 
                  0.085% 
                  0.029% 
                  0.153% 
                 — 
               
               
                 CH 3 OH 
                   
                  1.588% 
                 — 
                 — 
                 — 
                 68.592% 
               
               
                 Ar 
                   
                  0.054% 
                  0.150% 
                  0.052% 
                  0.269% 
                 — 
               
               
                   
               
             
          
         
       
     
         [0072]    The following table 2a to 2c contain data of the revamped plant. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2a 
               
             
             
               
                   
               
               
                 (revamped plant) 
               
             
          
           
               
                 Stream 
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
               
               
                   
               
             
          
           
               
                 Vapour 
                   
                 1.00 
                 1.00 
                 1.00 
                 1.00 
                 0.85 
                 0.86 
                 1.00 
               
               
                 Fraction (mole) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Temperature 
                 ° C. 
                 15.0 
                 193.0 
                 198.9 
                 870.0 
                 82.0 
                 81.3 
                 147.9 
               
               
                 Pressure 
                 bar 
                 16.01 
                 23.71 
                 23.71 
                 19.71 
                 16.51 
                 16.51 
                 96.47 
               
               
                 Molar Flow 
                 kmole/hr 
                 4098.4 
                 6812.4 
                 7853.1 
                 17243.2 
                 14076.2 
                 14458.7  
                 12028.2 
               
               
                 Mass Flow 
                 kg/hr 
                 67774.3 
                 118236.4 
                 161706.0 
                 240250.6 
                 183185.0 
                 186372.8 
                 142550.8 
               
               
                 Composition 
                 % mol wet 
                   
                   
                   
                   
                   
                   
                   
               
               
                 CO 
                   
                 — 
                 0.027% 
                 0.035% 
                 13.295%  
                 16.286%  
                 15.871%   
                 19.079%  
               
               
                 CO 2   
                   
                 1.030% 
                 0.566% 
                 12.726%  
                 7.103% 
                 8.696% 
                 8.779%  
                 10.542%  
               
               
                 H 2   
                   
                 0.010% 
                 0.644% 
                 0.776%  
                 45.271%  
                 55.453%  
                 56.098%  
                 67.433%  
               
               
                 H 2 O 
                   
                 — 
                 58.468%  
                 50.950%   
                 32.604%  
                 17.449%  
                 16.994%  
                 0.233% 
               
               
                 CH 4   
                   
                 97.560%   
                 39.686%  
                 34.898%  
                 1.561% 
                 1.912% 
                 2.038% 
                 2.449% 
               
               
                 Ethane 
                   
                 0.520% 
                 0.209% 
                 0.182% 
                 — 
                 — 
                 — 
                 — 
               
               
                 Propane 
                   
                 0.080% 
                 0.032% 
                 0.028% 
                 — 
                 — 
                 — 
                 — 
               
               
                 nButane 
                   
                 0.040% 
                 0.016% 
                 0.014% 
                 — 
                 — 
                 — 
                 — 
               
               
                 nPentane 
                   
                 0.020% 
                 0.008% 
                 0.007% 
                 — 
                 — 
                 — 
                 — 
               
               
                 N 2   
                   
                 0.720% 
                 0.332% 
                 0.343% 
                 0.156% 
                 0.191% 
                 0.206% 
                 0.247% 
               
               
                 O 2   
                   
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 He 
                   
                 0.020% 
                 0.009% 
                 0.010% 
                 0.004% 
                 0.005% 
                 0.006% 
                 0.007% 
               
               
                 CH 3 OH 
                   
                 — 
                 0.001% 
                 0.019% 
                 — 
                 — 
                 — 
                 — 
               
               
                 Ar 
                   
                 — 
                 0.002% 
                 0.013% 
                 0.006% 
                 0.007% 
                 0.008% 
                 0.010% 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2b 
               
             
             
               
                   
               
               
                 (revamped plant) 
               
             
          
           
               
                 Stream 
                   
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
                 14 
               
               
                   
               
             
          
           
               
                 Vapour 
                   
                 0.03 
                 1.00 
                 0.81 
                 1.00 
                 1.00 
                 1.00 
                 1.00 
               
               
                 Fraction (mole) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Temperature  
                 ° C. 
                 42.2 
                 49.5 
                 63.3 
                 133.7 
                 234.3 
                 15.0 
                 40.0 
               
               
                 Pressure 
                 bar 
                 6.00 
                 4.41 
                 5.41 
                 0,97 
                 26.51 
                 16.01 
                 1.26 
               
               
                 Molar Flow  
                 kmole/hr 
                 4718.7 
                 141.8 
                 84.9 
                 18986.7 
                 1040.7 
                 1356.4 
                 870.0 
               
               
                 Mass Flow 
                 kg/hr 
                 135138.2 
                 4373.9 
                 3215.0 
                 522389.0 
                 43469.6 
                 22430.5 
                 36941.3 
               
               
                 Composition 
                 % mol wet 
                   
                   
                   
                   
                   
                   
                   
               
               
                 CO 
                   
                 0.020% 
                 0.643% 
                 0.023% 
                 — 
                 0.089% 
                 — 
                 — 
               
               
                 CO 2   
                   
                 3.051% 
                 57.301%   
                 74.215%  
                 8.598% 
                 92.321%  
                 1.030%  
                 93.959%  
               
               
                 H 2   
                   
                 0.362% 
                 11.886%  
                 0.242% 
                 — 
                 1.639% 
                 0.010% 
                 — 
               
               
                 H 2 O 
                   
                 25.155%  
                 2.262%  
                 18.882%  
                 20.380%  
                 1.743% 
                 — 
                 5.930% 
               
               
                 CH 4   
                   
                 0.792% 
                 25.109%  
                 2.087% 
                 — 
                 3.558% 
                 97.560%  
                 — 
               
               
                 Ethane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
                 0.520% 
                 — 
               
               
                 Propane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
                 0.080% 
                 — 
               
               
                 nButane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
                 0.040% 
                 — 
               
               
                 nPentane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
                 0.020% 
                 — 
               
               
                 N 2   
                   
                 0.083% 
                 2.628% 
                 0.188%  
                 68.535%  
                 0.412% 
                 0.720% 
                 0.020% 
               
               
                 O 2   
                   
                 — 
                 0.001% 
                 — 
                 1.668% 
                 0.001% 
                 — 
                 0.001% 
               
               
                 He 
                   
                 0.003% 
                 0.083% 
                 — 
                 0.004% 
                 0.012% 
                 0.020% 
                 — 
               
               
                 CH 3 OH 
                   
                 70.532%  
                 0.002% 
                 4.362% 
                 — 
                 0.136% 
                 — 
                 — 
               
               
                 Ar 
                   
                 0.003% 
                 0.085% 
                 — 
                 0.814% 
                 0.088% 
                 — 
                 0.090% 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2c 
               
             
             
               
                   
               
               
                 (revamped plant) 
               
             
          
           
               
                 Stream 
                   
                 15 
                 16 
                 17 
                 18 
                 19 
               
               
                   
               
             
          
           
               
                 V.F. (mole) 
                   
                 0.93 
                 1.00 
                 1.00 
                 1.00 
                 0.00 
               
               
                 Temperature 
                 ° C. 
                 52.0 
                 43.5 
                 50.0 
                 50.0 
                 44.2 
               
               
                 Pressure 
                 bar 
                 4.41 
                 93.57 
                 35.01 
                 35.01 
                 6.00 
               
               
                 Molar Flow 
                 kmole/hr 
                 226.7 
                 691.0 
                 382.5 
                 308.5 
                 4854.5 
               
               
                 Mass Flow 
                 kg/hr 
                 7588.9 
                 8536.5 
                 3187.8 
                 5348.7 
                 135764.3 
               
               
                 Compo- 
                 % mol  
                   
                   
                   
                   
                   
               
               
                 sition 
                 wet 
                   
                   
                   
                   
                   
               
               
                 CO 
                   
                  0.411% 
                  1.999% 
                  0.614% 
                  3.716% 
                 — 
               
               
                 CO 2   
                   
                 63.636% 
                  9.871% 
                 11.842% 
                  7.428% 
                  1.292% 
               
               
                 H 2   
                   
                  7.525% 
                 50.772% 
                 79.805% 
                 14.782% 
                  0.005% 
               
               
                 H 2 O 
                   
                  8.487% 
                  0.156% 
                  0.249% 
                  0.042% 
                 30.102% 
               
               
                 CH 4   
                   
                 16.485% 
                 33.552% 
                  6.668% 
                 66.877% 
                  0.036% 
               
               
                 Ethane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 Propane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 nButane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 nPentane 
                   
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 N 2   
                   
                  1.714% 
                  3.402% 
                  0.738% 
                  6.705% 
                  0.004% 
               
               
                 O 2   
                   
                  0.001% 
                  0.001% 
                 — 
                  0.003% 
                 — 
               
               
                 He 
                   
                  0.052% 
                  0.101% 
                  0.035% 
                  0.184% 
                 — 
               
               
                 CH 3 OH 
                   
                  1.635% 
                 — 
                 — 
                 — 
                 68.560% 
               
               
                 Ar 
                   
                  0.053% 
                  0.145% 
                  0.050% 
                  0.263% 
                 —