MXPA00003019A - Process for enriched combustion using solid electrolyte ionic conductor systems - Google Patents

Abstract

A combustion or partial oxidation process for using an oxidant with a low nitrogen concentration. An oxygen-containing gas is introduced into an ion transport module including an ion transport membrane having a retentate side with a first pressure and a permeate side with a second pressure to separate a purified oxygen gas stream on the permeate side and correspondingly depleting the oxygen on the retentate side to produce the oxygen-depleted gas stream. A purge gas stream containing a low concentration of nitrogen is passed to the permeate side to form an oxidant stream containing less than about 40%oxygen. The oxidant stream and a fuel are then introduced into a combustion or reaction chamber to produce heat and products of combustion or partial oxidation.

Description

PROCESS FOR COMBUSTION ENRIQU ECI DA USAN DO ELECTROLITO SOLI DO ION CONDUCTOR SYSTEMS CROSS REFERENCE WITH RELATIVE APPLICATIONS This is a continuing part of the patent application of E. U. , Serial No. 08 / 868,962, filed on June 5, 1997.

FIELD OF THE INVENTION The invention relates to the integration of improved combustion with oxygen with oxygen separation processes employing solid electrolyte ion conductor membranes, and more particularly, to the integration of these processes to improve economy, efficiency and problems. related to contamination of combustion processes that use a diluted oxygen stream as the oxidant.

BACKGROUND OF THE INVENTION Many different oxygen separation systems have been used, for example, organic polymer membrane systems, to separate gases selected from air and other gas mixtures. Air is a mixture of gases that can contain varying amounts of water vapor and, at sea level, has the following approximate composition in volume: oxygen (20.9%), nitrogen (78%), argon (0.94%), with the rest consisting of other gases in traces. However, an entirely different type of membrane can be made from certain inorganic oxides. These electrolyte membranes solid are made of inorganic oxides, typified by zirconium oxides stabilized with calcium or yttrium and analogs having a structure of fluorite or perote. Some of these solid oxides have the ability to conduct oxygen ions at elevated temperatures if an electrical potential is applied across the membrane, that is, they are driven electrically or only ionic conductors. Recent research has led to the development of solid oxides that have the ability to conduct oxygen ions at elevated temperatures if a chemical driving potential is applied. These pressure-driven ion conductors or mixed conductors can be used as membranes for the extraction of oxygen from streams of oxygen-containing gases if a sufficient ratio of partial pressures of oxygen is applied to provide a chemical driving potential. Since the selectivity of these materials for oxygen is infinite and oxygen flows of generally several times greater magnitude than for conventional membranes can be obtained, attractive opportunities for oxygen production are created using these ion transport membranes. Although the potential of these oxide ceramic materials as gas separation membranes is great, there are certain problems in their use. The most obvious difficulty is that all known materials of oxide ceramics exhibit appreciable oxygen ion conductivity at elevated temperatures only. They usually must be operated well above 500 ° C, generally in the range of 600 ° C to 900 ° C. This limitation remains despite the great research to find materials that work well at lower temperatures. The solid electrolyte ion conductor technology is described in more detail in U.S. Patent No. 5,547,494 to Prasad et al. , entitled "Staged Electrolyte Membrane", which is incorporated herein by reference to more fully describe the state of the art. The combustion processes, however, usually operate at high temperature and therefore there is the potential to efficiently integrate ion transport systems with oxygen enhanced combustion processes and the present invention involves novel schemes for the integration of transport systems of ions with improved combustion processes with oxygen. Most conventional combustion processes use the most convenient and abundant source of oxygen, that is, air. The presence of nitrogen in the air does not benefit the combustion process and, on the contrary, it can create many problems. For example, nitrogen reacts with oxygen at combustion temperatures, forming nitrogen oxides (NOx), an undesirable contaminant. In many cases, combustion products must be treated to reduce nitrogen oxide emissions below environmentally acceptable limits. In addition, the presence of nitrogen increases the volume of the flue gas which in turn increases the heat losses in the flue gas and decreases the thermal efficiency of the combustion process. To minimize these problems, Oxygen enriched combustion (OEC) has been commercially practiced for many years. There are several benefits of oxygen-enriched combustion including reduced emissions (particularly nitrogen oxides), increased energy efficiency, reduced flue gas volume, cleaner and more stable combustion, and the potential for increased thermodynamic efficiency in current cycles down. These benefits of the OEC should be weighted, however, against the cost of oxygen that must be manufactured for this application. As a consequence, the market for OEC depends greatly on the production cost of oxygen enriched gas. It has been estimated that as much as 100,000 tons would be required. per day of oxygen for new markets in the OEC if the cost of oxygen enriched gas could be reduced to approximately $ 15 / ton. It seems that gas separation processes that use ion transport membranes have the promise of reaching that goal. The OEC is discussed in detail in Oxigen Enriched Combustion System Performance Studv. by H. Kobayashi, Vol. 1: Technical and Economic Analvsis (Report # DOE / ID / 12597). 1986, and Vol 2: Market Assessment (Report # DOE / I D / 12597-3). 1 987, Union Carbide Company-Linde Division, reports for the Department of Energy of the U. , Washington, D. C). The literature related to ion transport conductor technology for use in oxygen separation from gas streams includes: m-tWtíSSÉm.l £ - Hegarty, U.S. Patent No. 4,545,787, entitled Process for Producing Oxygen Sub-Product of Turbine Energy Generation, refers to a method for generating energy from a stream of compressed air and heated, by removing oxygen from the air stream, burning a portion of the resulting air stream with a fuel stream, combining the combustion effluent with another portion of the resulting air stream, and expanding the product from Final combustion through a turbine to generate energy. Hegarty mentions the use of composite silver membranes and 10 solid electrolyte membranes of metal oxides to remove oxygen from the air stream. Kang et al., Patent of E. U. , No. 5,516,359, entitled Integrated High Temperature Method for Oxygen Production, refers to a process for separating oxygen from heated and compressed air using a solid electrolyte ion conductor membrane where the non-permeated product is further heated and passes through a turbine for power generation. Mazanec et al., Patent of E. U. , No. 5, 160,713, entitled Process for Separating Oxygen from a Gas Containing Oxygen Using a Membrane Containing Two Mixed Metal Oxides, describes bismuth-containing materials that can be used as oxygen ion conductors. Publications related to enhanced or oxygen enhanced combustion (OEC) include reports from the Dept. Energy the U. , previously mentioned by H. Kobayashi and Technical and .m ^ ^ ^ £ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ , JG Keller, J. B. Patton, and R. C. Jain, in Proceedings of the 1986 Symposium on Industrial Combustion Technologies, Chicago, I L, April 29-30, 1986. ed. M. A. Lukasiewics, American Society for Metals, Metals Park, OH, which discusses the different technical and economic aspects of oxygen-enhanced combustion systems. Oxygen enriched combustion has been practiced commercially using oxygen manufactured either by cryogenic or non-cryogenic distillation processes such as Oscillating Pressure Adsorption (PSA). All these processes operate at or below 100 ° C and therefore are difficult to thermally integrate with combustion processes. When the boiler of a steam power plant works with oxygen and fuel, the energy required to separate air in the cryogenic plant of the current technique is very significant and consumes approximately 16% of the total energy generated from the boiler power plant single cycle steam. The compression of air required for air separation is the main source of this energy requirement. Oxygen is very expensive to use in most boiler applications. In a typical operation of a boiler heated with air-fuel, the air is fed at a pressure of several centimeters of H2O to the combustion chamber ¿$? M. .M - «? ¡¡¡? K £ fefc8l ¡fc > . . ,. ,,,. ^. ^., ^, -. ^ ¿5 ^ which operates at approximately atmospheric pressure. Compress the air at a low pressure of a few kg / cm2 man. it is considered very expensive due to the increased energy requirement for compression and a consequent loss of efficiency in power generation. A practical problem with using ceramic membranes is the lack of control resulting from leakage in ceramic joints and through cracks in ceramic membrane tubes. Ceramic materials are susceptible to developing stress cracks when used at elevated temperatures, and especially under changing temperature conditions. Therefore, it is highly desirable to develop a robust ceramic membrane system that can continue to operate efficiently and effectively despite cracks in the ceramic membrane tube due to thermal and mechanical stresses.

OBJECTIVES OF THE INVENTION It is therefore an object of the invention to provide a combustion process enriched with oxygen or partial oxidation in which air is fed to the ceramic membrane module at near atmospheric pressure and which requires substantially less electrical energy than the current conventional practice. It is another object of the invention to minimize the formation of NOx and thermal losses due to heating of the nitrogen gas in the combustion process.

It is still another object of the invention to recover a nitrogen-rich gas stream from the ion transport membrane module to be used as a by-product. It is another object of the invention to produce a flue gas stream rich in carbon dioxide for recovery.

BRIEF DESCRIPTION OF THE INVENTION The invention comprises a process of combustion or partial oxidation to use an oxidant with a low concentration of nitrogen. A gas containing oxygen is introduced to an ion transport module that includes an ion transport membrane having a retentate side with a first pressure and a permeate side with a second pressure to separate a stream of purified oxygen gas in the permeate side and correspondingly depleting the oxygen on the retentate side to produce the gas stream exhausted in oxygen. A stream of purge gas containing a low concentration of nitrogen is passed to the permeate side to form an oxidant stream containing less than about 80% oxygen. The oxidant stream and a fuel are then introduced into a reaction or combustion chamber to produce heat and products of combustion or partial oxidation. In a preferred embodiment, air is used as the oxygen-containing gas. The ratio of the first pressure to the second pressure is less than 4.78, preferably between 0.5 and 4.0, more preferably between 0.8 and 2.0, and most preferably between 0.9 and 1.5. The oxidant stream comprises between 1% to 40% oxygen, more preferably between 2% to 15%, and most preferably between 3% to 10% oxygen. The purge gas comprises less than 10% nitrogen, preferably less than 5% nitrogen. The temperature of the oxidant stream is preferably above 500 ° C and the oxidant stream is introduced into the combustion or reaction chamber without substantial cooling.

BRIEF DESCRIPTION OF THE DIAMETERS Other objects, aspects and advantages of the invention will occur to those skilled in the art from the following description of preferred embodiments and the accompanying drawings, in which: Figure 1 is a schematic diagram which shows the integration of oxygen production by ion transport with combustion enriched with oxygen and a downstream process; Figure 2 is a schematic diagram showing the integration of oxygen production by ion transport with oxygen enriched combustion and a downstream process similar to Figure 1; Figure 3 is a schematic diagram similar to Figure 2 where the burner is integrated with the ion transport module; Figure 4 is a schematic diagram showing how the ion transport process, the burner, and the downstream process are integrated in a single module; Figure 5 is a schematic diagram showing one mode of the ion transport process, the burner, and the downstream process integrated in a single module; and Figure 6 is a schematic diagram showing one embodiment of two separate ion transport membrane processes in which no recirculation of flue gas is used in one of the processes.

DETAILED DESCRIPTION OF THE INVENTION The invention will now be described in detail with reference to the figures in which similar reference numerals are used to indicate similar elements. The present invention describes process configurations that allow the economically attractive integration of oxygen production by ion transport with oxygen enriched combustion (OEC). Although pressure-driven processes for ion transport membranes are preferred due to the simplicity of their design, the concepts described herein are applicable to membrane systems that use either an ionic conductor membrane only having electrodes and an external circuit for electron return or a mixed conductor membrane. Current commercial oxygen production processes typically operate at temperatures below 100 ° C. Due to this low temperature, significant efficiencies are not gained through integration with an OEC process. The elevated temperatures of . # :. t * l3ISm.m- & (operation (usually higher arj $? o C) make the ion transport process intrinsically well suited for integration with high temperature processes, such as combustion, that use oxygen. In addition, it will be shown that exhaust flue combustion gases can be beneficially used to increase the performance of the ion transport membrane. Traditional oxygen production processes (eg, PSA, TSA, or membrane-based processes) can not easily take advantage of exhaust flue gases due to their high temperature when leaving the combustion chamber. The essence of the current process configuration is an ion transport membrane that uses a solid oxygen-conductive or mixed-conductive membrane to separate oxygen from an oxygen-containing gas, typically, but not necessarily, air, and to use the separated oxygen in a downstream process that includes, but is not limited to, oxygen enriched combustion. To reduce the partial pressure of oxygen on the permeate side of the ion transport membrane, an oxygen-depleted gas (for example, waste gases from the combustion process or any downstream process) is used as a purge gas stream . Such purging greatly increases the driving force through the ion transport membrane and effects a high oxygen flow and a lower membrane area requirement. These benefits accumulate even when the feed gas stream is at relatively low pressure, thus reducing the system's energy requirements to those of practical interest. The recirculation of gas from j £ S £ uS > B &, * b &? Mli * * exhaust combustion is also beneficial because it provides a stream of diluent that is important to control the temperature in the burner and minimize the formation of NOx (eg, from the nitrogen contained in the environmental air that infiltrates). The efficiency of this process could also be increased by adding fuel to the flue gas entering the oxygen separator. This further reduces the partial pressure of oxygen on the permeate side, resulting in even greater oxygen fluxes in the ion transport separator. In some embodiments of the invention, the ion transport module can also function as the burner, unless the application requires a gas stream leaving the burner at a temperature above 1.100 ° C, the maximum temperature of operation of many current ion transport membranes. It should be noted that the heat necessary to maintain the temperature of the ion transport module within the range of operation can come from a variety of sources known to those skilled in the art, including, for example, heat generated in a post-burner and gases hot recirculated combustion products, among others. In most mixed conductors, the electronic conductivity greatly exceeds the conductivity of oxygen ions at the operating temperatures of interest, and the overall oxygen transport from one side to the other is controlled by the conductivity of oxygen ions. A number of potential mixed conductors have been identified in both fluorite and perovskite crystal structures. The behavior of ion transport membranes has been studied extensively (for example, for fuel cells) and can be precisely modeled. Table 1 is a partial list of mixed conductors of interest for oxygen separation. Table I Figure 1 is a schematic diagram showing the integration of oxygen production by ion transport with combustion enriched with oxygen. During operation, stream 1 of feed gas containing elemental oxygen, usually air, is compressed at a relatively low pressure in the fan or compressor 2 to produce the stream 3 of compressed feed gas which is heated in the heat exchanger 33 against the waste gas stream 31 and the product gas stream 37 to produce the gas stream 4 heated feed. The gas stream 28 can be divided from the hot feed gas stream 4 and used in the optional afterburner 26 to leave the feed gas stream 5 which is optionally heated in the heater 34 to produce the stream 6. hot gas feed. The hot stream 6 of feed gas then enters the feed side of the ion transport module 35 which employs an ion transport membrane 7 having a retentate side 7a and a permeate side 7b. A portion of the oxygen in the hot stream 6 of feed gas is removed in * ^ & the ion transport module 35 and the outgoing gas stream 8 becomes enriched with nitrogen with respect to the feed gas stream 1. The permeate side 7b of the ion transport membrane 7 is purged using the purge gas stream 9 containing combustion products. The permeate gas stream 1 0 contains oxygen and this gas stream 10 is later mixed with the fuel gas stream 1 1. The stream 12 of air, oxygen or air enriched with oxygen can optionally be added to the gas stream 10. The fuel gas stream 13, after passing through an optional fan (not shown), then enters the burner 14. Optionally or in addition to or in place of the fuel gas stream 1 1, a fuel gas stream 15 may feeding directly to the burner or furnace 14 to generate heat and transfer heat to a furnace charge or to heat the transfer surfaces. By operating the burner 14 near a stoichiometric or slightly fuel-rich condition, the concentration of oxygen in the exhaust gas stream 16 can be maintained at low levels. In this mode the exhaust gas stream 16 of the burner 14 is divided into two portions, the gas stream 17 and the gas stream 18. The gas stream 18 is optionally used in the downstream process 19 which requires heat input and the relatively cooler exhaust gas stream 20 from the downstream process 19 can also be divided into two portions, the exhaust gas stream 21 and the exhaust gas stream 22. The fuel gas stream 25 can be added to the stream 21 of the exhaust to produce the gas stream 38. The gas stream 38 can be added to the gas stream 17 to produce the gas stream 9 which enters the ion transport module 35 and is used to purge the permeate side 17b of the ion transport membrane 7. Although not shown herein, the gas stream 17 or burner 14 can be used to heat the feed air 3 and / or the heated feed gas stream 5 by heat exchange to produce the hot stream 6 of feed gas. instead the heat exchanger 33 and / or the optional heater 34 is used. The exhaust gas stream 22 optionally fed to an optional afterburner 26 where the air stream 27 or the gas stream 28 is optionally added to produce the hot stream 29 of waste gas. The hot stream 29 of waste gas can be converted into the gas stream 30 or the gas stream 31. As mentioned above, the gas stream 31 is used in the heat exchanger 33 to heat the compressed feed gas stream 3 to produce the waste gas stream 32. The gas stream 30 may be mixed with the stream 8 of nitrogen-retained gas if the nitrogen is not to be used as a by-product and if the temperature of the exhaust gas stream 30 is suitably high. When the retained gas stream 8 is at a higher pressure than the exhaust gas stream 30 and it may be necessary to release the excess pressure from the retained gas stream 8 using the expansion valve 23 to produce the retained gas stream 34 before it is mixed with the gas stream 30. When the pressure of the current 8 exceeds 2 atm, it is advantageous to replace the expansion valve 23 with an expansion turbine to extract work from the arrow or to generate power. If the retained gas stream 24 is desired as a product gas stream rich in nitrogen, the gas streams 36 and 30 do not mix. The use of an oxygen-depleted purge gas stream 9 in the ion transport module 35 will greatly decrease the oxygen partial pressure on the permeate side 7b of the ion transport membrane 7 and allow for the rapid transport of oxygen through the membrane 7. The fuel gas streams 1, 15 and 25 can be introduced to the process configuration at any or all of the points shown in Figure 1 to obtain the benefits of the invention; the use of at least one fuel gas stream is essential to the invention. For example, it may be desirable to add the fuel gas stream 25 upstream of the ion transport module 35 to greatly reduce the oxygen partial pressure on the permeate side 7b of the ion transport membrane 7. This would also result in some heat generation in the ion transport module 35 due to combustion of the fuel, thereby deviating somewhat from the heating requirements of the oxygen transport process. In this case, the stream 8 of nitrogen-rich gas leaving the ion transport module 35 could become hotter. This would make heat transfer in the heat exchanger 33 more efficient, thereby reducing the area required for heat exchange and potentially eliminating the need for heater 34 upstream of the ion transport module 35. If enough fuel can be burned in the ion transport module 35 on the purge or permeate side 7b of the ion transport membrane 7, the need for a separate burner 14, i.e. Ion transport would also serve as the burner (as described in Figure 3). In such a situation, a simplification of the system and a reduction of significant costs may result. The reactive purge arrangements are described in "Reactive Purge for Separation of Gases by Solid Electrolyte Membrane", E. U. , Serial No. 08 / 567,699, filed December 5, 1995 and incorporated herein by reference. The preferred configuration for ion transport modules using a reactive purge is described in "Solid Electrolyte Ionic Conductor Reactor Design", EU, Serial No. 08 / 848,204, filed on April 29, 1997 and incorporated as well. to the present by reference. Both requests are of common ownership with the present application. It may be advantageous to operate the burner 14 with a slightly rich fuel mixture because this will lead to the partial oxidation of the fuel added to the permeate gas stream 10, resulting in an exhaust gas stream 16 containing hydrogen gas and carbon monoxide. As mentioned before, the gas stream 17 is optionally used to purge the permeate side 7b of me ^ ??? Yes the membrane 7 transporter of ions. It should be noted that the hydrogen gas is a highly reducing gas with a higher reactivity than many other gaseous fuels, and its presence in the ion transport module 35 will result in an extremely low partial pressure of oxygen on the 7b side of the membrane purge 7 ion transporter and this will allow an even faster oxygen transport through the ion transporter membrane 7. Of course, similar results could be achieved by introducing hydrogen gas as the fuel gas stream 25, however, it will not be cost effective as the fuel rich feed to the burner 14, since hydrogen gas is a relatively expensive fuel. The use of a fuel rich feed for burner 14 as described obviates the need for a use of a previously produced hydrogen gas, since hydrogen gas is produced as a part of the process cycle. Operating the burner 14 in a fuel rich condition, however, could cause the exhaust gas streams 18 and 22 to contain carbon monoxide and hydrogen gas, both of which can be simply vented to the atmosphere if the concentration is low. As mentioned before, it may be possible, however, to install a post-burner 26 (perhaps catalytic) to which excess air 27 is added to burn carbon monoxide and hydrogen gas if its concentration is sufficiently high. The gas stream 28 of the hot feed gas stream 4 could also be added to the post-burner 26 to provide the post-burner requirements.

It is interesting to note that by virtue of the recirculation of combustion products as stream 9 of purge gas, and due to the infinite selectivity of the ion transport membrane 7 for oxygen, it is possible to limit the temperature increase of stream 13 of gas in the burner 14 without the need for excess air and thereby exclude the nitrogen from the combustion process, which substantially eliminates NOx formation. This synergistic effect is a general principle of the invention and is an aspect of many of the embodiments of the invention. Typical ranges for the operating parameters of the ion transport module used in the invention are as follows: Temperature: typically in the range of 400-1000 ° C, and preferably in the range of 400-800 ° C. Pressure: the pressure on the purge side will typically be in the range of 1 -3 atm. The pressure on the feed side will be 0.8-3 atm if nitrogen is not by-product, and 1 -20 atm if nitrogen is a by-product. Oxygen Ion Conductivity (μ,) of the Ion Transport Membrane: typically in the range of 0.01 - 100 S / cm (1 S = 1 / ohm). Thickness of the Ion Transport Membrane: the ion transport membrane can be used in the form of a dense film, or a thin film supported on a porous substrate. The thickness (t) of the membrane / ion transport layer will typically be less than 5,000 microns; preferably less than 1,000 microns, and most preferably less than 100 microns. Configuration: the elements of the ion transport membrane can be tubular or flat. As mentioned before, asymmetric or composite ion transport membranes (ie, pressure driven membranes) are used in the examples discussed herein. The following properties are based on typical values reported in the literature for such membranes as could be used in the present invention. 10 Effective membrane thickness: 20 microns Ion conductivity, μ (: 0.5 S / cm Operating temperature: 800 ° C Substrate porosity: 40% 15 Standard mathematical models have been used to determine the operating conditions for the process shown in Figure 1, that is, the membrane area requirement and the power and thermal energy inputs required at several points.

A process using a configuration of Figure 1 is for illustrative purposes only and no attempt has been made to optimize the configuration of the process. The main reason why an optimization has not been attempted is that optimization is generally based on economic considerations and production commercial ion-carrier membrane systems is still far from being mature, and there are currently no estimates of reliable costs in such systems. For the present example, observing Figure 1, the fuel is added to the process only as a 1 1 stream of fuel gas. In addition, the optional gas stream 17 is not considered, that is, the gas streams 16 and 18 are identical. In addition, nitrogen is not seen as a by-product and the stream 36 of retained gas, obtained from the stream 8 of gas retained after reducing the excess pressure of the retentate using the relief valve 23, is mixed with the gas stream 30, taken from the exhaust gas stream 29. In general, however, it is not effective to lower the pressure of the retained gas stream 8 or to add the gas stream 30 to the stream 8 of gas retained upstream of the heat exchanger 33. Since the gas stream 22 Exhaust does not contain carbon monoxide and hydrogen gas, post-burner 26 is not installed. Bases for the Example: a downstream process that requires a heat input of 5 million BTU / hr.

Figure 2 is a schematic diagram similar to Figure 1 showing a more efficient alternative using the catalytic afterburner installation. During operation, the feed gas stream 41 containing elemental oxygen, usually air, is compressed at a relatively low pressure in the fan or compressor 42 to produce the stream 43 of compressed feed gas which is heated in the exchanger heat 73 against hot stream 40 of waste gas and stream 64 of nitrogen gas product to produce stream 44 of heated feed gas. The gas stream 70 can be divided from the hot feed gas stream 44 and used in the optional afterburner 69 for & amp; & amp; ", leave the feed gas stream 74 the one optionally heated in the heater 75 to produce the hot stream of feed gas. The hot feed gas stream 45 then enters the feed side of the ion transport module 46 which employs an ion transport membrane 47 having a retentate side 47a and a permeate side 47b. A portion of the oxygen in the hot feed gas stream 45 is removed in the ion transport module 46 and the outgoing gas stream 48 becomes enriched with nitrogen with respect to the feed gas stream 41. The permeate side 47b of the ion transport membrane 47 is purged using the purge gas stream 79 which contains combustion products. The permeate gas stream 50 contains oxygen and this gas stream 50 is later mixed with the fuel gas stream 51. The stream 52 of air, oxygen or air enriched with oxygen can optionally be added to the gas stream 50. The fuel gas stream 53, after passing through an optional fan (not shown), then enters the burner or furnace 54. Optionally or in addition to, or in place of the fuel gas stream 51, a gas stream 55 Fuel can be fed directly to the burner 54. In the burner or furnace 54 the heat is transferred to a load or heat transfer surfaces. By operating the burner 54 near a stoichiometric or slightly fuel-rich condition, the concentration of oxygen in the exhaust gas stream 56 can be maintained at low levels. * "^ Ék & The exhaust gas stream 56 from the burner 54 can be divided into two portions, the gas stream 57 and the gas stream 58. The gas stream 58 is used in the downstream process 59 which requires heat input and the relatively cooler exhaust stream 60 of the downstream process 59 can also be divided into two portions, the exhaust gas stream 61 and the 62 exhaust gas stream. The fuel gas stream 65 can be added to the exhaust gas stream 61 to produce the gas stream 78. The gas stream 78 can be added to the gas stream 57 to produce the gas stream 79 which enters the ion transport module 46 and is used to purge the permeate side 47b of the ion transport membrane 47. The exhaust gas stream 62 can optionally be divided into two portions, the hot stream 40 of waste gas and the stream 77 of gas. As mentioned above, the waste gas hot stream 40 is used in the heat exchanger 73 to heat the compressed feed gas stream 43 to produce the waste gas stream 74. The gas stream 77 can be mixed with the stream 48 of nitrogen-retained gas if the nitrogen is not to be used as a by-product and if the temperature of the exhaust gas stream 77 is suitably high. The reason for this step is to remove any unreacted fuel in the exhaust gas stream 62 by combustion in a post-burner 69 and to also generate heat energy to improve the efficiency of the heat exchanger 73. The gas stream 48 retained it is quite possibly that it is at a higher pressure than the exhaust gas stream 77 and it may be necessary to release the excess pressure from the retained gas stream 48 using the expansion valve 63 to produce the gas stream 76 retained before it is mixed with the gas stream 77 to produce the gas stream 80. The gas stream 80 feeds to the optional afterburner 69 where the gas stream 70 optionally adds to produce the hot stream 39 of waste gas. In this case one would need to make sure that the stream 80 contains enough oxygen for combustion to proceed to completion. As mentioned before, the gas stream 70 taken from the heated feed gas stream 44 can optionally be added to the post-burner 69 to ensure this. It should be noted that the flow ratio of the combined current is increased by mixing the exhaust gases from the ion transport module 46 and the downstream process 59. This improves the capacity regime in the heat exchanger 73 and increases the heat transfer to the compressed gas feed stream 43. The product gas stream 64 will contain oxygen (used in excess to ensure complete combustion) and combustion products if the afterburner 69 is used and the product gas stream 64 is generally disposed of as a waste stream. As with the embodiment of the invention shown in Figure 1, the use of an oxygen depleted purge gas stream 79 in the ion transport module 46 will greatly decrease the oxygen partial pressure on the permeate side 47b of the ion transport membrane 47 will allow the rapid transport of oxygen through the membrane 47. Xas streams 51, 55 and 65 of combustible gases can be introduced to the process configuration at any or all of the points shown in Figure 2 to obtain the benefits of the invention and the use of at least one fuel gas stream is essential to the invention. As before, it may be desirable to add the fuel gas stream 65 upstream of the ion transport module 46 to greatly reduce the oxygen partial pressure on the permeate side 47b of the ion transport membrane 47. This would also result in some heat generation in the ion transport module 46 due to combustion of the fuel, which deviates somewhat from the heating requirements of the oxygen transport process. In this case, the stream 48 of nitrogen-rich gas leaving the ion transport module 46 could become hotter and this could make heat transfer in the heat exchanger 73 more efficient, thereby reducing the area required for heat exchange and would potentially eliminate the need for heater 75 upstream of the ion transport module 46. If enough fuel can be burned in the ion transport module 46 on the purge or permeate side 47b of the ion transport membrane 47, the need for a separate burner 54, i.e. Ion transport would also serve as the burner (as described in Figure 3). In such a situation, a simplification of the system and a reduction of significant costs may result.

As with the embodiment of the invention, it shows < # áfe © & "Figure 1, it may be advantageous to operate the burner 54 with a mixture slightly rich in fuel because this will lead to the partial oxidation of the *. fuel added to the permeate gas stream, resulting in an exhaust gas stream 56 containing hydrogen gas and carbon monoxide. As mentioned before, the gas stream 57 is optionally used to purge the permeate side 47b of the ion transport membrane 47 and the presence of hydrogen gas in the ion transport module 46 will result in an extremely low partial pressure of oxygen on the purge side 47b of the ion transport membrane 47 and this will allow an even faster oxygen transport through the ion transport membrane 47. The use of a fuel rich feed for the burner 54 produces hydrogen gas as a part of the process cycle. As mentioned before, it may be possible to install a post-burner 69 (perhaps catalytic) to burn carbon monoxide and hydrogen gas if its concentration is high enough. Figure 3 is a schematic diagram showing another embodiment of the invention where the burner is integrated with the ion transport module, ie, where the ion transport module serves the same as the burner. During operation, the feed gas stream 81 containing elemental oxygen, usually air, is compressed at a relatively low pressure in the fan or compressor 82 to produce the feed gas stream 83 which is heated in the heat exchanger. heat 1 13 against hot stream 136 of waste gas and current 93 of nitrogen gas product to produce stream 95 of heated feed gas. The gas stream 1 10 can be divided from the hot feed gas stream 95 and used in the optional afterburner 109 to leave the feed gas stream 84 which is optionally heated in the heater 14 to produce the hot 85 stream of feed gas. The hot feed gas stream 85 then enters the feed side of the ion-burner transport module 86 which employs an ion transport membrane 87 having a retentate side 87a and a permeate side 87b. A portion of the oxygen in the hot stream 85 of feed gas is removed in the ion transport-burner module 86 and the outgoing gas stream 88 becomes enriched with nitrogen with respect to the feed gas stream 81. The permeate side 87b of the ion transport membrane 87 is purged using the purge gas stream 89 which contains combustion and fuel products. The permeate gas stream 50 contains oxygen and the air stream 92 can optionally be added to the gas stream 90 to produce the gas stream 98. By operating the ion-burner transport module 86 near a stoichiometric or slightly fuel-rich condition, the concentration of oxygen in the exhaust gas stream 90 can be maintained at low levels. The gas stream 98 is used in the downstream process 99 which requires heat input and the relatively cooler exhaust stream 100 of the downstream process 99 can also be divided into two portions, the 101 dre exhaust gas stream and the exhaust gas stream 102. The fuel gas stream 105 is preferably added to the exhaust gas stream 101 to produce the gas stream 89 which enters the ion transport-burner module 86 and is used to purge the permeate side 87b of the membrane 87 ion transporter. The exhaust gas stream 102 can optionally be divided into two portions, the hot stream 16 of waste gas and the stream 1 of gas. As mentioned before, the current 1 16 hot waste gas is used in the heat exchanger 1 13 to heat the compressed gas feed stream 83 to produce the waste gas stream 17. The gas stream 1 15 can be mixed with the stream 88 of nitrogen-retained gas if the nitrogen is not to be used as a by-product and if the temperature of the exhaust gas stream 15 is suitably high. The reason for this step is to remove any unreacted fuel in the exhaust gas stream 102 by combustion in a post-burner 109 and to also generate heat energy to improve the efficiency of the heat exchanger 1 13. The retentate gas stream 88 it is quite possibly that it is at a higher pressure than the exhaust gas flow 15 and it may be necessary to release the excess pressure from the retained gas stream 88 using the expansion valve 103 to produce the stream 18 of gas retained before to mix with the gas stream 1 15 to produce the gas stream 19.

The current 1 1 9 deyjas df «? Fnenta to the optional post-burner 10F where the current 1 10 of? J | it optionally adds to it to produce the hot stream 93 of waste gas. In this case one would need to make sure that the 119J lh current has enough oxygen for combustion to proceed to completion. As mentioned before, the gas stream 1 10 taken from the heated feed gas stream 95 can optionally be added to the afterburner 109 to secure it. It should be noted that the flow ratio of the combined current is increased by mixing the exhaust gases from the ion transport-burner module 86 and the process 99 downstream. This improves the capacity regime in the heat exchanger 1 13 and increases the heat transfer to the compressed gas feed stream 83. The gas stream 94 will contain oxygen (used in excess to ensure complete combustion) and combustion products if the afterburner 1 09 is used and the gas stream 94 is generally disposed of as a waste stream. In the embodiment of Figure 3, the heat of reaction generated in the ion transport-burner module 86 is removed from or consumed in the burner in a heat transfer process by convection and / or radiation. For example, the ion transport membrane 87 can be formed as tubes with the reactant purge gas stream 89 flowing into the tubes. Due to the heat generated on the purge side 87b of the ion transport membrane 87 formed as tubes, the tubes will be at an elevated temperature and will act as heating elements. Tubes of a membrane 87 - - ^ ¿aa ^ T.-i, ^ - ^ .., ^.

Ion transporter will radiate f retentate side 87a or to permeate side 87b where a process such as glass melting or metal quenching could be carried out. Also as part of the heat generated in the ion transport module 86 could be used to preheat the compressed gas feed stream 85 and purge gas stream 89, possibly obviating the need for the heat exchanger 1 13 and heater 1 14. Note that the furnace charge will be placed on the permeate side 87b of the ion transport membrane 87 (ie, the side with the oxidizing gas) in this case. It is also possible to integrate the ion-burner transport module with an internal circulation of the flue gas (furnace). If the furnace and the ion-burner transport module operate at approximately the same temperature (for example, between 800 ° -1, 200 ° C), then the ion-burner transport module can be placed directly inside the furnace provided that the furnace atmosphere is "clean", that is, it does not contain any species to the detriment of the ion transport membrane. One way of implementing this idea is shown in Figure 4 in which the ion transport process, the burner and the downstream process are all integrated into a single unit. The feed stream 1 32 such as heated air is directed against the cathode side 120a of the membrane 120 to produce the hot retentate 134 depleted in oxygen such as nitrogen. The downstream process 130 (e.g., a furnace charge) is shown on the permeate or anode side 120b of the ion transport membrane 120. In this configuration, the fuel gas stream 121 is * feeds near the surface of the permeate side 120b, thereby sweeping and / or efficiently consuming the oxygen transported through the ion transport membrane 120. The combustion products in the hot zone 138 could be sealed in the furnace against the anode side 120b by natural or forced convection; for the construction shown in Figure 4, combustion product stream 146, preferably obtained from furnace 130 as shown in dashed lines by stream 146a, and fuel gas stream 121 are optionally fed through layer 122 porous fuel distributor adjacent to the permeate side 120b of the ion transport membrane 120. Preferably, the distributor layer 122 defines at least one passage or chamber for distributing fuel more evenly through the membrane 120. The reacted permeate 136 containing oxygen and combustion products is directed to the furnace 130 through the hot zone 138. Preferably, a portion of hot nitrogen 140 is directed through the valve 142 to provide an inert atmosphere over the furnace 130. Additional fuel 144 may be added to the furnace 130 as desired. In another construction, the ion transport membrane 120 is part of a separate module that is external to the furnace 130. In any of the external or integrated constructions, a two-stage ion transport system may be established in which the anode side of the first stage is purged by the retentate stream of the first stage to produce a dilute oxygen permeate stream while the \ amp; ß of the anode of the second stage is reactive purged to produce a permeate stream rich in fuel. The two streams shown are used in a combustion furnace with or without the use of hot nitrogen retention streams in the furnace atmosphere. When the peak temperature of the furnace is much higher than the operating temperature of the ion transport, a zone of the furnace with the "correct" temperature can be selected for the operation of the ion transport (for example, pre-heated section of an overheated furnace). continuous), or a special chamber with appropriate heat wells can be created to control the temperature. For example, in boiler applications or oil heaters, it would be feasible to use the furnace heat loads (ie, water or oil pipes) to create an area of optimum temperature for the ion transport module. A large amount of flue gas is circulated through this zone to purge oxygen continuously and keep the oxygen concentration low. The low oxygen concentration and the high furnace gas circulation provide synergy with the diluted oxygen combustion method. There are many advantages of the integrated processes of the invention. For example, oxygen for OEC can be extracted from a low pressure feed gas stream using the exhaust gas stream to purge and this should result in low energy requirement for the oxygen separation process.

Because only oxygen flows through the ion transport membrane, no nitrogen is added to the purge gas stream leaving the ion transport module. Even if air is introduced into the combustion mixture, either intentionally (for example, optional gas stream 12) or leakage, the fraction of nitrogen in the combustion mixture will be small. This should minimize or eliminate NOx formation in the burner. In addition, by properly mixing the exhaust gases taken before and after the downstream process, it is possible to control the inlet temperature of the purge to the desired one in the ion transport process. This can eliminate the need to pre-heat the purge gas independently. Also, if the combustion of all the fuel can be carried out in the ion transport module, the separate burner unit can be eliminated. This would give the system significant simplification and cost savings. In addition, if sufficient oxygen is removed from the feed gas stream in the ion transport module, then the nitrogen-rich stream retained from the ion transport module can be used as a product. This can be most attractive if you add some fuel, for example, the 1 1 stream of fuel gas. If nitrogen is desired as a by-product, it may be advantageous to compress the feed gas stream to the pressure required for supply of product nitrogen. However, in this case, the gas stream retained from the ion transport module may not mix with the exhaust gas stream from the downstream process. In this case, either a separate heat exchanger to recover heat from the exhaust gas stream may be installed, or heat recovery may not be attempted since generally the gas flow to the iscape will be much smaller and colder. compared to the retained gas stream. In addition, the use of the purge gas stream decreases the oxygen concentration on the permeate side of the ion transport membrane. The reduced concentration of oxygen makes the design of the ion transport module and downstream components (eg, a burner) on the purge side considerably easier from a material point of view. In the absence of a purge stream, essentially pure oxygen would be produced on the permeate side of the ion transport membrane. The safe handling of such high purity oxygen stream has a significant challenge, especially at elevated temperature. In addition, the oxygen concentration in the purge exhaust can be easily controlled by a number of techniques: for example, by varying the flow rate of the feed gas stream, varying the flow rate of the purge gas stream ( increased recycling of the combustion products), by changing the operating temperature of the ion transport module, or by varying the membrane area of the ion transport stage. These techniques are also effective for controlling the total amount of separated oxygen and could be used for load tracking purposes.

Finally, the use def e | Ion transport would eliminate the need for an oxygen generator alone (eg, PSA) or an oxygen supply system (eg tank and liquid vaporizer) This is expected to be a substantial reduction in capital cost and in the cost of the oxygen produced a mode directed particularly to this invention is shown in Figure 5. The feed or air stream 232 is pre-heated to a suitable temperature from about 500 ° C to 1 000 000 ° C. feed or air preferably contains a relatively high oxygen concentration of typically more than 15% oxygen. This feed or air stream 232 is then introduced to the retentate side 220aa of the ion transport membrane 220 through the permeate side 120b to the permeate chamber 238., which is connected to the main combustion chamber or furnace 230. The temperature of the main chamber is determined by the requirement of the heating process and may be higher or lower than the temperature of the permeate chamber 238. A significant portion of the flue gas generated in the furnace 230 is recirculated as the stream 246 to the permeate chamber 238. The stream 246 causes the oxygen concentration on the permeate side 220b of the ion transport membrane 220 to decrease and increase the oxygen flow through the oxygen transport membrane 220. As an option, the fuel stream 221 can be introduced into the permeate chamber 238 to reduce the oxygen concentration of the recirculated stream 246 and / or to reactive purge the permeate side 220b and also to provide heat to raise the temperature of the permeate. I hit the retention side. The pumped chamber 238 is optionally segmented into a two-stage ion transport membrane system using a reactive purge at the stage and a second stage chimney gas purge (not shown). The fuel stream 221 is preferably injected at high velocity to induce proper circulation of the hot stream 246 of flue gas from the furnace 230 by the high velocity jet aspiration effect. Other means of recirculating hot flue gas include, but are not limited to, a circulating fan and an eductor using compressed flue gas or steam can be used. In addition to or in place of the internal recirculation stream 246, the external recirculation stream 248 can be used. In a preferred embodiment the stack gas stream 247 of the furnace 230 is cooled in the heat exchanger 260 and the cooled side stream 248 is compressed and injected into the first chamber 238 to induce proper circulation of the hot gas stream 246 of chimney. The process can be used for many industrial furnaces, such as furnaces for heat treatment of metals, steel reheating, glass melting and aluminum melting, but is particularly suitable for boilers for generating steam and for furnaces for heating process fluids such as oil heaters, fractionation furnaces and steam-methane reformer furnaces. In the following description of the invention, a process for generating steam is described. However, it is not intended to be limiting for the application of this invention. He It is preferable that the purge gas contains a low concentration of nitrogen, which, through transport to the permeate side of the ion transport membrane, forms the stream 236 of oxidant containing between 1% to 40% oxygen ^, preferably between 2% to 15% oxygen, and most preferably between 3% to 10% oxygen. The ion transport membrane 220 effectively forms two sides of the reactive area having the same or different pressure, the retentate side 220a having a first pressure and a permeate side 220b having a second pressure. The ratio of the first pressure to the second pressure is less than 4.78, preferably between 0.5 and 4.0, more preferably between 0.8 and 2.0, and most preferably between 0.9 and 1.5. In the conventional process of oxygen separation from air using a mixed conductor ion carrier membrane system, the feed air has to be compressed at a minimum pressure of 4.78 atm in order to achieve a partial pressure of oxygen from the air. 1 atm on the retention side. Thus, a theoretical minimum pressure ratio of 4.78 is required to produce pure oxygen at 1 atm on the permeate side. In order to produce a high oxygen flow through the membrane, a practical system requires pressure ratios of 10 to 30 to produce partial oxygen pressure ratios of about 2 to 6. To compress feed air to 10-20 A large amount of electrical energy is required. Low pressure ratios are advantageous for reducing the energy required to compress the feed air. In an idealized system both the first and second pressures are equal and ? e = & atmospheric »which minimizes the energy recovery and potential gas leak between the 220a side of permeate. In such a process, the only pressure requirement for the supply air streams and purge gas is to overcome the normal pressure drops associated with gas flows through the membrane module and the furnace. It should be noted that this invention allows the penetration of oxygen through the ion transport membrane even when the pressure ratio is less than 1, that is, the pressure on the retentate side is less than that on the permeate side. It is because the oxygen penetration is driven by the ratio of the oxygen partial pressure of the retentate side to that of the permeate side. By keeping the partial pressure of oxygen on the permeate side low, it is possible to reach a partial oxygen pressure ratio of more than two while maintaining the total pressure ratio near or below 1. Under such condition, gas leaks caused by imperfect seals of the ceramic membrane tubes or by cracks in the ceramic membrane tubes flow from the permeate side to the retentate side and prevent the infiltration of nitrogen into the kiln 230. In order of reducing NOx formation and maintaining a high concentration of CO2 in the flue gas, it is preferable to keep the nitrogen concentration in the furnace 230 below 10%. In the permeate chamber 238, fuel jets are optionally used to recirculate the hot flue gas from furnace 230 to the permeate chamber 238. Steam jets or other gas jets, such as compressed chilled flue gas stream 248, they can be used to provide additional purge gas and to facilitate the circulation of the flue gas through the jet pump effect. The fuel jet reacts with the oxygen contained in the recirculated flue gas and permeate oxygen from the ion transport membrane tubes, reducing the concentration of oxygen in the permeate chamber 238 and generating heat. Boiler tubes, steam superheater tubes and / or steam reheat tubes can optionally be placed in the permeate chamber 238 as heat wells to control the temperature of the chamber. The temperature of the membrane tube in the permeate chamber 238 is preferably maintained at an optimum membrane temperature, typically between 600 ° C and 1, 000 ° C, controlling the rate of flow of the feed air 232, the flow rate of the fuel 221 injected into this permeate chamber 238 and the amount of hot gas 246 of recirculated chimney. The average oxygen concentration in the oxidant mixture 236, consisting of fuel combustion products 221, oxygen transported through the ion transport membrane 220, and recirculated chimney gas 246, at the outlet of the permeate chamber 238 can be controlled from 1% to 40% oxygen, preferably from 2% to 10%, and most preferably between 3 and 10% oxygen. This mixture is circulated to the combustion chamber 230, preferably without cooling. The air flow through the retained side of the ion carrier membrane tubes and the fuel gas / flue gas flow on the permeate side can be arranged in a countercurrent mode to maximize the oxygen flow through the vessels. trans membrane tubes parta c? A smaller concentration of oxygen is usually preferred on the permeate side 220b to increase the rate of oxygen penetration of the ion transport membrane. However, a large volume of flue gas has to be recirculated to keep the oxygen concentration low. Thus, the aforementioned range is preferred. In furnace 230, fuel 244 is injected and mixed with hot stream 236 of diluted oxygen from combustion permeate chamber 238 to generate steam in the conventional manner for the radiant section of a steam boiler. The process of combustion of diluted oxygen as described in Development of the Dilute Oxygen Combustion Burner for High Temperature Furnace Applications, by H. M Ryan, et al., Proceedings of the Fourth International Conference on Technologies and Combustion or Clean Enviroment, July 7- 10, 1997 and the Patent of E. U. No. 5,076,779 describes the preferred combustion process to achieve low NOx emissions and high thermal efficiency. Preferably 50% to 98% of the flue gas generated in the furnace 230 is recirculated to the permeate chamber 238 and the remainder to the convection heat transfer unit 260 to generate, overheat and reheat the steam and to heat the feeding water . The flue gas stream 249 is optionally passed through a condensate heat exchanger 264 to recover the latent heat of the steam in the flue gas. The total recovery of the latent heat of the flue gas in the flue gas provides a theoretical energy improvement of approximately 10% for natural gas combustion, in addition to the improvement in efficiency as a result of the reduced sensible heat in the gas stream 263 of. ^ Chilled emenea. The combustion of oxygen provides a unique advantage over the combustion of air for the recovery of latent heat due to the high concentration of water vapor in the flue gas. For example, the concentration of water vapor in the flue gas from natural gas-oxygen combustion is approximately 65% and the dew point is approximately 88 ° C. By cooling the flue gas to approximately 49 ° C the concentration of Water vapor is reduced to 13% by volume. Approximately 93% of water vapor can be condensed. In comparison, the concentration of water vapor in the flue gas from natural gas-air combustion is approximately 18% and the dew point is approximately 58 ° C. By cooling the flue gas to approximately 49 ° C, it can condense approximately 41% of the water vapor. Further cooling to 32 ° C is required to condense approximately 77% water vapor in the combustion of natural gas-air. As a result, an unexpectedly large fraction of water vapor contained in the flue gas can condense at a relatively high temperature when it burns. natural gas or a fuel with a high ratio of hydrogen to atomic carbon with oxygen. By condensing the water vapor the volume of flue gas is further reduced and the carbon dioxide rich stream is produced for recovery and potential production of carbon dioxide. The nitrogen-rich hot stream 234 of the retentate chamber is passed through a convection heat transfer unit 261 to heat the feed water and optionally provide heat for steam generation, overheat or reheat. Alternatively, this hot stream 234 can be used to preheat feed air, as shown in Figures 1 to 3. A high purity nitrogen stream can be produced using a two-stage ion transporter system with a reactive purge in the first stage and a chimney gas purge in the second stage. The heating of the feed air stream 232 can also be done indirectly in a heat exchanger (not shown) with the hot flue gas stream 247 and / or by placing air heating tubes in the furnace 230 and / or in the 238 permeate chamber. In addition, an in-line burner (not shown) can be used to heat air at a higher temperature. Although in-line heating results in a reduction in the oxygen concentration of feed air stream 232 and therefore reduces the driving force for oxygen flow, the simplicity of the on-line direct heating system offers a significant reduction in cost of capital on the indirect heating system. > s ^ ^ -: ^^^ nfTlW ?? rte1ÉÉ '? ai an integrated ion transport-combustion membrane process depicted in Figure 5.

Table V Specifications for Key Modules in the Integrated Process Feed fan (not shown) (efficiency = 75%) (kW) 930 Total amount of fuel supply 221 plus 244 (million joules / hr) 611668 In the previous example, a large amount of hot stack gas is recirculated to maintain the oxygen concentration on the permeate side of the membrane at 7.43%, which helps to increase the oxygen flow through the membrane without compressing the membrane. high pressure air feed stream Producing high purity nitrogen with a reactive purge passage in the conveyor 220 membrane of ions, substantially all the oxygen contained in the feed air stream 232 penetrates through the ion transport membrane 220 and is used for combustion with the fuel streams 221 and 244. The flow rate of the air feed is 1, 256.62 MCN H compared to 4,692.82 MCN H in the previous example shown in Table II. The large reduction in the air feed rate reduces the amount of heat required to heat feed air and the energy required in the feed air fan. The fan power required in this example is 9.3 kw and 333.09 MCN H of oxygen are separated by the ion transport membrane, which correspond to 0.079 kw of power per 2.83 MCN H of oxygen. In comparison, the previous example consumes 58 kw of energy to produce 329.12 MCN H of oxygen, corresponding to 0.5 kw of energy per 2.83 MCN H. It should be noted that the current state of the art of air separation technologies consume approximately 0.8 kw of energy to produce 2.83 MCN H of industrial grade oxygen at a purity of 90% to 95% oxygen and 1 atmosphere. Thus, the integrated ion-combustion membrane process of this invention reduces energy consumption to separate air for oxygen combustion as much as 90%. Another embodiment of this invention provides a process whereby recirculation of flue gas is not used in an ion-transport membrane chamber purged relatively from a two-membrane chamber combustion process depicted in Figure 6.

• Certain common aspects in both Figures 5 and 6 are not repeated in the present, and common aspects can be alluded to in the description of the embodiment of Figure 5. In Figure 6, a hot stream 334 rich in nitrogen is introduced. from the first retaining chamber to the second retaining side 372a of the ion transport membrane 372 in the second retention chamber 370. Oxygen penetrates through the second permeate side 372b of the ion transport membrane 372 into the second permeate chamber 350, in which a high flow of relatively purged oxygen is reached even though the nitrogen feed stream 334 contains a low oxygen concentration. The fuel stream 355 is injected into the second permeate chamber 350 to react with the oxygen flow of the second permeate side 372b of the ion transport membrane 370, whereby the hot stream 373 of synthetic gas (syngas) is formed. , a gas stream containing combustible gases such as hydrogen and carbon monoxide. Optionally, recycled flue gas or steam 356 can be injected into the second permeate chamber 350 to modulate the temperature. The hot stream 373 of synthetic gas is introduced into the furnace 330 and mixed with the hot oxidant stream 336 of the first permeate chamber 338, which provides the oxygen for combustion. Optionally, additional air or oxygen stream 357 is injected into the furnace 330 to burn the hot stream 373 of synthetic gas and provide heat to the process. ^ gj ^^^ a | § j ^ Current 334 rich in nitrogen is enriched as it passes through the second side 372a of retentate, where oxygen is removed as it passes through the second ion transport membrane 372 into the second permeate chamber 350, and a high purity nitrogen stream 365 is formed. The high purity nitrogen stream 365 then passes through the convection heat transfer unit 361 to recover the cold nitrogen stream 362 for further use or processing. It should be noted that a number of process modifications are possible within the spirit of the process configuration discussed above. For example, it may be advantageous to use the exhaust gas from the downstream process to heat the feed gas stream. It is also possible to add some air to the purge gas stream leaving the ion transport module. This may be particularly desirable for start-up operations or for load tracking purposes. Furthermore, although the processes described herein are for mixed-conductor pressure-driven ion transport membranes, it is obvious that the inventive concept is also applicable to ionic conductors mainly that are operated in the pressurized or electrically powered mode with an external current return. . Finally, although Figure 1 shows a process of oxygen separation against the current, the same process can be carried out also in a concurrent or cross current mode. As mentioned before, the terms "solid electrolyte ion conductor", "solid electrolyte", "ion conductor", and "membrane" "Ion carrier" are generally used herein to designate either an ionic type (electrically driven) system or a mixed conductor type (pressure driven) system unless otherwise specified. "Nitrogen" as used herein will usually mean oxygen depleted gas, ie, depleted in oxygen relative to the feed gas As discussed above, the ion transport membrane allows only oxygen penetration. the composition of the retentate will depend on the composition of the feed gas.The feed gas will be depleted in oxygen but will retain nitrogen and any other gases (eg argon) present in the feed gas.The meaning of the term will be clear to an expert in the art in the context of the use of the term in light of the invention as described herein As tea is used herein The term "elemental oxygen" means any oxygen that is not combined with any other element in the Periodic Table. Although typically found in diatomic form, elemental oxygen includes simple atoms of oxygen, triatomic ozone, and other forms without combining with other elements. The term "high purity" refers to a product stream which contains less than five percent by volume of undesirable gases. Preferably the product is at least 98.0% pure, more preferably 99.9% pure, and most preferably at least 99.99% pure, where "pure" indicates an absence of undesirable gases.

"Oscillating pressure adsorption" or "PSA" systems refer to systems that use adsorption materials that are selective for a gas, typically nitrogen, to separate that gas from other gases. Such materials include selective rate PSA materials, which usually contain carbon and provide high pressure nitrogen and low pressure oxygen, and selective equilibrium PSA materials, which usually contain lithium and provide nitrogen at low pressure and high oxygen. Pressure. Specific aspects of the invention are shown in 1 or more of the drawings for convenience only, since each aspect can be combined with other aspects according to the invention. In addition, various changes and modifications may be made to the given examples without departing from the spirit of the invention. Such modifications may include the use of oscillating oscillating pressure and thermal adsorption beds or other bulk oxygen separation methods to provide the function of the polymer membranes discussed above. Alternative modalities will be recognized by those skilled in the art and are intended to be included within the scope of the claims.

Claims (10)

1. R EIVINDICATION EN 1 A combustion process using an oxidant with a low concentration of nitrogen comprising: (a) introducing an oxygen-containing gas to an ion transport module that includes an ion transport membrane having one side of retained with a first pressure and a permeate side with a second pressure forming a permeate chamber to separate a stream of purified oxygen gas on the permeate side and correspondingly depleting the oxygen on the retained side to produce a stream of gas exhausted in oxygen; (b) passing a stream of purge gas containing a low concentration of nitrogen to the permeate side to form an oxidant stream containing less than about 40% oxygen; 15 (c) introducing said oxidant stream and a fuel into a combustion chamber to produce heat and combustion products
2. 2. The combustion process of claim 1 wherein said oxygen-containing gas is air.
3. 3. The combustion process of claim 1 wherein the ratio of said first pressure to said second pressure is less than 4.78.
4. 4. The combustion process of claim 1 wherein said oxidant stream comprises between 1% and 40% oxygen.
5. 5. The combustion process of claim 1 wherein said purge gas comprises less than 10% nitrogen 4¡3ú ?? i fr-aSfJsM
6. 6. The combustion process of claim 1 wherein the ratio of partial pressures of oxygen from said retentate side to said permeate side is greater than 2 and the total pressure ratio on said retentate side to said permeate side is less than 1 .
7. 7. A combustion process using an oxidant with a low concentration of nitrogen comprising: (a) introducing an oxygen-containing gas to an ion transport module including first and second ion transport membranes, said first carrier membrane of ions having a first retentate side with a first retentate pressure and a first permeate side with a first permeate pressure forming a first permeate chamber for separating a first stream of purified oxygen gas in the first permeate side and which exhaustively depletes the oxygen in the first retentate side to produce a first gas stream exhausted in oxygen; (b) introducing said first gas stream depleted in oxygen to said second ion transport membrane having a second retentate side with a second retentate pressure and a second permeate side with a second permeate pressure forming a second retentate chamber. permeate to separate a second stream of purified oxygen gas on the second permeate side and correspondingly depleting the oxygen on the second retentate side to produce a second stream of oxygen depleted gas; Mj ^ fejg ^ j ^^^ (c) passing a first stream of purge gas containing a low concentration of nitrogen to said first permeate side to form an oxidant stream containing less than about 40% oxygen; (d) passing a second stream of purge gas containing a fuel and a low concentration of nitrogen to said second permeate side to form a stream of synthetic gas; (e) introducing said oxidant stream, said synthetic gas stream into a combustion chamber to produce heat and combustion products.
8. 8. The combustion process of claim 7 further comprising recovering nitrogen gas.
9. 9. The combustion process of claim 7 wherein said oxygen-containing gas is air.
10. 10. The combustion process of claim 7 wherein the ratio of said first retentate pressure to said first permeate pressure is less than 4.78.