Abstract:
A method for the coproduction of oxygen, hydrogen and nitrogen using an ion transport membrane is provided. This method includes separating a compressed, hot air stream in an ion transport membrane, thereby producing a product oxygen stream and a hot nitrogen rich stream; utilizing at least a portion of the hot nitrogen rich stream as a heat source for reforming a hydrocarbons stream, thereby producing a syngas stream and a warm product nitrogen stream; and separating the syngas stream into a product hydrogen stream and a carbon dioxide rich stream.

Description:
BACKGROUND 
     Ion transport membranes (ITMs) consist of ionic and mixed-conducting ceramic oxides that conduct oxygen ions at elevated temperatures of 1475-1650 F. Air is compressed to about 230 psia, heated to 1650 F, and fed to ITM. Hot oxygen permeates through the membranes. The permeate pressure has to be kept low to provide oxygen partial pressure driving force across the membrane. Typically, 50% to 80% oxygen recovery seems possible. 
     SUMMARY 
     A method for the coproduction of oxygen, hydrogen and nitrogen using an ion transport membrane is provided. This method includes separating a compressed, hot air stream in an ion transport membrane, thereby producing a product oxygen stream and a hot nitrogen rich stream; utilizing at least a portion of the hot nitrogen rich stream as a heat source for reforming a hydrocarbons stream, thereby producing a syngas stream and a warm product nitrogen stream; and separating the syngas stream into a product hydrogen stream and a carbon dioxide rich stream. 
     In another embodiment, the method includes separating a compressed, hot air stream in an ion transport membrane, thereby producing a hot product oxygen stream and a nitrogen rich product stream; utilizing at least a portion of the hot oxygen product stream as a heat source for reforming a hydrocarbons stream, thereby producing a syngas stream; and separating the syngas stream into a product hydrogen stream and a carbon dioxide rich stream. 
     In another embodiment, the method includes separating at least a portion of a compressed, hot air stream in a first ion transport membrane, thereby producing a product oxygen stream and a first hot nitrogen rich stream; introducing at least a portion of the compressed, hot air stream and a first hydrocarbon stream into a second ion transport membrane reactor, thereby producing a first syngas stream and a second hot nitrogen rich stream, combining the first hot nitrogen stream and the second hot nitrogen stream into a product nitrogen stream; introducing the first syngas stream and a second hydrocarbon stream into a syngas reformer, thereby producing a second syngas stream; and separating the second syngas stream into a product hydrogen stream and a carbon dioxide rich stream. 
     In another embodiment, the method includes introducing a first hydrocarbon stream and a first steam stream into an exchange reformer, thereby producing a first syngas stream, separating at least a portion of a compressed, hot air stream in a first ion transport membrane, thereby producing a product oxygen stream and a first hot nitrogen rich stream; introducing at least a portion of the compressed, hot air stream and the first syngas stream into a second ion transport membrane reactor, thereby producing a second syngas stream and a second hot nitrogen rich stream, combining the first hot nitrogen stream and the second hot nitrogen stream into a product nitrogen stream; and separating the second syngas stream into a product hydrogen stream and a carbon dioxide rich stream. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic representation of one embodiment of the present invention. 
         FIG. 2  is a schematic representation of one embodiment of the present invention. 
         FIG. 3  is a schematic representation of one embodiment of the present invention. 
         FIG. 4  is a schematic representation of one embodiment of the present invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Illustrative embodiments of the invention are described below. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     To reduce the compression requirements for oxygen, a multi-stage membrane system is provided. The oxygen is withdrawn at successively reduced pressure. 
     Turning to  FIG. 1 , air stream  101  is compressed in compressor  102 , thereby producing compressed stream  103 . Compressed stream  103  is then heated by indirect heat exchange with purified nitrogen stream  115  in heat exchanger  104 , thereby producing compressed, heated air stream  105 . Heated air stream  105  may have a temperature of between 800-1000 C. Heated air stream  105  is introduced into ion transport membrane (ITM)  106 , wherein oxygen product stream  107  and hot nitrogen rich stream  108  are formed. Oxygen product stream  107  may be at a pressure of between about 0.5 and 2.0 barA. Oxygen product stream  107  may then be cooled, compressed and used further downstream (not shown). Hot nitrogen rich stream  108  may have a temperature of between about 800 and 1000 C, and, depending on the amount of oxygen recovered in ion transport membrane  106 , may also have oxygen present. 
     Hot nitrogen rich stream  108  may be mixed with hydrogen stream  125  and introduced into combustion chamber  109 , in order to achieve the desired level of residual oxygen in stream  127 , as well as increasing the temperature of this stream. Bypass stream  130  and/or heated stream  127 , are combined into nitrogen stream  110 , which is then introduced into exchanger reformer  111 . Additionally, hydrocarbon stream  112  and steam stream  113  are introduced into exchanger reformer  111 , wherein, utilizing the heat of stream  110 , syngas stream  114  is produced. Combusted nitrogen rich residue stream  115  is high purity nitrogen stream, which after having at least a portion of its heat being utilized in exchanger reformer  111 , is sent to air heater  104 , to provide additional heat. After indirectly exchanging heat with compressed stream  103 , cooled nitrogen stream  126  may be used downstream or other processes (not shown). 
     Syngas stream  114  is then introduced into water gas shift reactor  116 , wherein shifted stream  117  is produced. Carbon dioxide rich stream  119  may then removed from shifted syngas stream  117  in carbon dioxide removal unit  118 , solvent, such as amines. CO2 removal is optional. Purified shifted syngas stream  120  is produced by carbon dioxide removal unit  118 . 
     Purified shifted syngas stream  120  is introduced into PSA  121 , wherein tail gas stream  122  and hydrogen rich stream  123  are produced. A portion  125  of hydrogen rich stream  123  may be used in combustion chamber  109  as fuel, with the balance  124  being exported for use elsewhere. Tail gas stream  122  may contain unconverted CH4, and CO, and unrecovered H2 and may be made available for use as fuel. 
     Heat recovery from various streams such as syngas exit reformer, and shift reactor is not shown. The heat could be used for steam generation or heating of process streams. Water produced by the combustion of hydrogen and oxygen is recovered as purified N2 is cooled. Such condensate can be used to generate steam required for steam reforming. 
     Turning to  FIG. 2 , air stream  201  is compressed in compressor  202 , thereby producing compressed stream  203 . Compressed stream  203  is then heated by indirect heat exchange with purified nitrogen stream  215  in heat exchanger  204 , thereby producing compressed, heated air stream  205 . Heated air stream  205  may have a temperature of between 800-1000 C. Heated air stream  205  is introduced into ion transport membrane (ITM)  206 , wherein oxygen product stream  207  and hot nitrogen rich stream  208  are formed. Oxygen product stream  207  may be at a pressure of between about 0.5 and 2.0 barA. Oxygen product stream  207  may then be cooled, compressed and used further downstream (not shown). Hot nitrogen rich stream  208  may have a temperature of between about 800 and 1000 C, and, depending on the amount of oxygen recovered in ion transport membrane  206 , may also have oxygen present. 
     Hot nitrogen rich stream  208  is then mixed with hydrogen stream  225  and introduced into combustion chamber  209 , in order to achieve the desired level of residual oxygen in stream  215 , as well as increasing the temperature of this stream. Combusted nitrogen rich residue stream  215  is high purity nitrogen stream, which is sent to air heater  204 , to provide additional heat. After indirectly exchanging heat with compressed stream  203 , cooled nitrogen stream  226  may be used downstream or other processes (not shown). 
     A portion  210  of oxygen product stream  207  is combined with hydrocarbon stream  212  and steam stream  213  are introduced into autothermal reformer  211 , wherein, at least partially utilizing the heat of stream  210 , syngas stream  214  is produced. 
     Syngas stream  214  is cooled (not shown) then introduced into water gas shift reactor  216 , wherein shifted stream  217  is produced. Carbon dioxide rich stream  219  may then removed from shifted syngas stream  217  in carbon dioxide removal unit  218  with solvents, such as amines. CO2 removal is optional. Purified shifted syngas stream  220  is produced by carbon dioxide removal unit  218 . 
     Purified shifted syngas stream  220  is introduced into PSA  221 , wherein tail gas stream  222  and hydrogen rich stream  223  are produced. A portion  225  of hydrogen rich stream  223  may be used in combustion chamber  209  as fuel, with the balance  224  being exported for use. Tail gas stream  222  may contain unconverted CH4, and CO, and unrecovered H2 and may be made available for use as fuel. 
     Heat recovery from various streams such as syngas exit reformer, and shift reactor is not shown. The heat could be used for steam generation or heating of process streams. Water produced by the combustion of hydrogen and oxygen is recovered as purified N2 is cooled. Such condensate can be used to generate steam required for steam reforming. 
     Turning to  FIG. 3 , air stream  301  is compressed in compressor  302 , thereby producing compressed stream  303 . Compressed stream  303  is then heated by indirect heat exchange with purified nitrogen stream  315  in heat exchanger  304 , thereby producing compressed, heated air stream  305 . Heated air stream  305  may have a temperature of between 800-1000 C. Heated air stream  305  is introduced into first ion transport membrane (ITM)  306 , wherein oxygen product stream  307  and first nitrogen rich stream  308  are formed. Oxygen product stream  307  may be at a pressure of between about 0.5 and 2.0 barA. Oxygen product stream  307  may then be cooled, compressed and used further downstream (not shown). First nitrogen rich stream  308  may have a temperature of between about 800 and 1000 C, and, depending on the amount of oxygen recovered in first ion transport membrane  306 , may also have oxygen present. 
     First nitrogen rich stream  308  is then mixed with hydrogen stream  325 , and second nitrogen rich stream  310 , and introduced into combustion chamber  309 , in order to achieve the desired level of residual oxygen in stream  315 , as well as increasing the temperature of this stream. Combusted nitrogen rich residue stream  315  is high purity nitrogen stream, which is sent to air heater  304 , to provide additional heat. After indirectly exchanging heat with compressed stream  303 , cooled nitrogen stream  326  may be used downstream or other processes (not shown). 
     A portion  327  of heated air stream  305  is introduced to an ion transfer membrane reactor  328 . At least a portion of methane  312  and steam  313  mixture stream  330  is introduced into the permeate side of the ion transport membrane reactor  328 . The ion transport reactor  328  produces first syngas stream  331  and a second nitrogen rich stream  310 . Second nitrogen rich stream  310  is combined with first nitrogen rich stream  308 , to form combined nitrogen rich stream  229 , which is then introduced combustion chamber  309 . Stream  330  reacts with O2 permeating in second ion transport membrane reactor  328 , generating first syngas stream  331 , which may contain H2, CO, and CO2. 
     First syngas stream  332  is further combined with second part of steam stream  312  and second hydrocarbon stream  313  and is introduced into syngas reactor  311 , wherein second syngas stream  314  is produced. Second syngas stream  314  is then introduced into water gas shift reactor  316 , wherein shifted stream  317  is produced. Carbon dioxide rich stream  319  may then removed from shifted syngas stream  317  in carbon dioxide removal unit  318  with a solvent, such as amines. CO2 removal is optional. 
     Purified syngas stream  320  is introduced into PSA  321 , wherein tail gas stream  322  and hydrogen rich stream  323  are produced. A portion  325  of hydrogen rich stream  323  may be used in combustion chamber  309  as fuel, with the balance  324  being exported for use. Tail gas stream  322  may contain unconverted CH4, and CO, and unrecovered H2 and may be made available for use as fuel. 
     Heat recovery from various streams such as syngas exit reformer, and shift reactor is not shown. The heat could be used for steam generation or heating of process streams. Water produced by the combustion of hydrogen and oxygen is recovered as purified N2 is cooled. Such condensate can be used to generate steam required for steam reforming. 
     The syngas reactor and ITM-2 can be integrated in various ways. The syngas reactor can be a separate vessel as shown in  FIG. 3 . Or the syngas reactor may have ITM tubes, with air on inside and natural gas and steam on the outside. The outside of the tubes have catalyst coating for reforming reaction. 
     Turning to  FIG. 4 , air stream  401  is compressed in compressor  402 , thereby producing compressed stream  403 . Compressed stream  403  is then heated by indirect heat exchange with purified nitrogen stream  415  in heat exchanger  404 , thereby producing compressed, heated air stream  405 . Heated air stream  405  may have a temperature of between 800-1000 C. Heated air stream  405  is introduced into ion transport membrane (ITM)  406 , wherein oxygen product stream  407  and hot nitrogen rich stream  408  are formed. Oxygen product stream  407  may be at a pressure of between about 0.5 and 2.0 barA. Oxygen product stream  407  may then be cooled, compressed and used further downstream (not shown). Hot nitrogen rich stream  408  may have a temperature of between about 800 and 1000 C, and, depending on the amount of oxygen recovered in ion transport membrane  406 , may also have oxygen present. 
     A portion  427  of heated air stream  405  is introduced to an ion transfer membrane reactor  428 . At least a portion of methane  412  and steam  413  is introduced into the exchange reformer  411 , thereby producing first syngas stream  430 . First syngas stream  430  is introduced into ion transport membrane reactor  428 . The ion transport reactor  428  produces second syngas stream  431  and a second nitrogen rich stream  410 . Second nitrogen rich stream  410  is combined with first nitrogen rich stream  408 , to form combined nitrogen rich stream  429 , which is then introduced combustion chamber  409 . Stream  430  reacts with O2 permeating in second ion transport membrane reactor  428 , generating second syngas stream  431 , which may contain H2, CO, and CO2. 
     Second syngas stream  431  is introduced into exchange reformer  411 , wherein it provides at least a portion of the heat required for syngas production. Cooled second syngas stream  432  is then introduced into water gas shift reactor  416 , wherein shifted stream  417  is produced. Carbon dioxide rich stream  419  may then removed from shifted syngas stream  417  in carbon dioxide removal unit  418  with a solvent, such as amines. CO2 removal is optional. 
     Purified syngas stream  420  is introduced into PSA  421 , wherein tail gas stream  422  and hydrogen rich stream  423  are produced. A portion  425  of hydrogen rich stream  423  may be used in combustion chamber  409  as fuel, with the balance  424  being exported for use. Tail gas stream  422  may contain unconverted CH4, and CO, and unrecovered H2 and may be made available for use as fuel.