MXPA98004444A - Process for enriched combustion using electrolyte ionic conductor sol systems - Google Patents

Abstract

A process for separating a feed gas stream in an oxygen enriched gas stream which is used in a burner and an oxygen depleted gas stream. The feed gas stream is compressed, and the oxygen is separated from the feed gas compressed stream by using an ion transport module that includes an ion transport membrane having a retentate side and a permeate side. The permeate side of the ion transport membrane is purged with at least a portion of the gas stream of combustion products obtained from combustion in the burner of the gas stream leaving the permeate side of the ion transport module.

Description

PROCESS FOR ENRICHED COMBUSTION USING SOLID ELECTROLYTE ION CONDUCTOR SYSTEMS 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 the economic efficiency and the problems related to the contamination of combustion processes. RIGHTS OF THE GOVERNMENT OF IOS E.U. This invention was made with the support of the Government of the United States under Cooperation Agreement No. 70NANB5H1065 granted by the National Institute of Standards and Technology. The Government of the United States has certain rights in the invention. BACKGROUND OF THE INVENTION Many different oxygen separation systems, for example organic polymer membrane systems, have been used to separate selected gases from air and other gas mixtures. The 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 traces of other gases. However, an entirely different type of membrane can be made from certain inorganic oxides. These solid electrolyte membranes are made of inorganic oxides, typified by zirconium oxides stabilized with calcium or yttrium and analogous oxides having a fluorite or perovskite structure. 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 ionic or electrically driven conductors only. Recent research has led to the development of solid oxides that have the ability to conduct oxygen ions at elevated temperatures if a chemical potential is applied. These ion conductors or pressure driven mixed conductors can be used as membranes for the extraction of oxygen from oxygen-containing gas streams if a partial pressure ratio of oxygen sufficient to provide the chemical potential is applied. Since the selectivity of these materials for oxygen is infinite and oxygen flows generally of several levels of magnitude higher than with conventional membranes can be obtained, attractive opportunities for oxygen production are created using these ion transport membranes. Although the potential of these oxide ceramics as separation membranes is great, there are certain problems in their use. The most obvious difficulty is that all known oxide ceramic materials exhibit appreciable oxygen ion conductivity only at elevated temperatures. They should be operated usually above 500 ° C, generally in the range of 600 ° C-900 ° C. This limitation subsists despite much research to find materials that work well at lower temperatures. The solid electrolyte ion conductor technology is described in more detail in the U.S. Patent. , Do not. ,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. However, the combustion processes usually operate at high temperature and therefore there is the potential to efficiently integrate the ion transport systems with the improved oxygen combustion processes and the present invention involves novel schemes for the integration of transport systems. of ions with improved oxygen combustion processes. 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 andOn the contrary, it can create many problems. For example, nitrogen reacts with oxygen at combustion temperatures to form nitrogen oxides (N0?), 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 exhaust gases which in turn increases the heat loss in the exhaust gas and decreases the thermal efficiency of the combustion process. To minimize these problems, oxygen-enriched combustion has been practiced commercially for many years. There are several benefits of oxygen-enriched combustion (CEO) that include reduced emissions (particularly of nitrogen oxides), increased energy efficiency, reduced volume of exhaust gas, cleaner and more stable combustion and the potential for increased thermodynamic efficiency in downstream cycles. These benefits of the CEO, however, must be weighed against the cost of oxygen that has to be obtained for this application. As a consequence, the market for the CEO depends to a large extent on the cost of production of oxygen enriched gas. It has been estimated that up to 100,000 tons would be required. per day of oxygen for new CEO markets 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 this goal. The CEO is discussed in detail in "Study of Performance of Oxygen-Enriched Combustion Systems" by H. Kobayashi, Vol. 1: Technical and Economic Analysis (Report # DOE / ID / 12597), 1986 and Vol. 2: Evaluation of Market (Report # DOE / ID / 12597-3), 1987, Union Carbide Company-Linde Division, Reports for the Dept. of Energy of the U.S. , Washington, D.C. The literature relating to the technology of ion transporting conductors for use in oxygen separation of a gas stream includes: Hegarty, U.S. Patent. No. 4,545,787 entitled "Process for Producing Oxygen as Sub-Product of Turbine Energy Generation", refers to a method to generate 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 residue with another portion of the resulting air stream, and expanding the final combustion product through a turbine to generate power. Hegarty mentions the use of silver compound membranes and solid electrolyte membranes of metal oxide compounds 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 nonpermeated product is heated after and passed through a turbine for power generation. Mazanec et al., US Patent No. 5,160,713 entitled "Process for Separating Oxygen from Gas Containing Oxygen Through the Use of a Bi-Containing Mixed Metal Oxides Membrane", describes bismuth-containing materials that can be used as conductors of oxygen ions. Tas publications related to enhanced or oxygen-enriched combustion (CEO) include reports from the US Department of Energy. mentioned above written by H. Kobayashi and H. Kobayashi, J.G. Boyle, J.G. Keller, J.B. Patton and R.C. Jain, "Technical and Economic Evaluation of Oxygen Enriched Combustion Systems for Applications in Industrial Furnaces", in Meetings of the Symposium of 1986 on Industrial Combustion Technologies, Chicago, IL, April 29-30, 1986 ed. M.A. Lukasiewics, American Society for Metals, Metals Park, OH, which discusses the various technical and economic aspects of combustion systems enhanced with oxygen.

Oxygen enriched combustion has been practiced commercially using obtained oxygen or by cryogenic distillation or by non-cryogenic processes such as pressure swing absorption (AOP). All these processes operate at or below 100 C and therefore are difficult to integrate with combustion processes. Research on ionic conductors of solid electrolyte has been carried out for many years. Solid electrolytes have been used primarily in sensors and fuel cells, and to experimentally produce small amounts of pure oxygen from air, taking advantage of the infinite selectivity for oxygen transport. Electrically driven solid electrolyte membranes have also been used to remove traces of oxygen from inert gas streams, where the application of a sufficient voltage to the membrane can reduce the oxygen activity of the gas stream retained to a very low value . Many of these materials, however, do not have appreciable oxygen ion conductivity. Only lately have materials been synthesized that have sufficiently high oxygen ion conductivities to make the gas separation process economically viable. The commercial processes of separation, purification or enrichment of gases based on these materials have yet to be developed. The methods for integrating oxygen separation with oxygen enriched combustion have also not been discussed in the prior art. The inventors are not aware of the above description of a process configuration for the integration of an oxygen production system based on ion transport with CEO. OBJECTIVES OF THE INVENTION Therefore, it is an object of the invention to eliminate the need for an independent oxygen generating system or oxygen supply and to provide an efficient integrated process for improved combustion with oxygen by thermally and operationally integrating the various process operations. . Another object of the invention is to minimize or eliminate the formation of N0? in the burner processes and the thermal losses due to the heating of the nitrogen gas. Still another object of the invention is to recover a nitrogen-rich gas stream from the ion transport module to be used as a by-product. Another object of the invention is to control the concentration of oxygen in the exhaust gas stream used in the combustion process. SUMMARY OF THE INVENTION The invention comprises a process for separating a feed gas stream containing elemental oxygen into an oxygen enriched gas stream and an oxygen depleted gas stream wherein the oxygen enriched gas stream is used in an oxygen gas stream. burner, said process comprising the steps of (a) compressing the feed gas stream; (b) separating the oxygen from the compressed stream of feed gas using an ion transport module that includes an ion transport membrane having a retentate side and a permeate side to separate a purified stream of oxygen gas in the permeate side and correspondingly exhausting the oxygen on the retentate side to produce the gas stream depleted in oxygen, the purified stream of oxygen gas is mixed with other gaseous components on the permeate side to form the gas stream enriched in oxygen; and (c) purging the permeate side of the ion transport membrane with at least a portion of a combustion product gas stream obtained from combustion in the burner of the gas stream leaving the permeate side of the transport module. of ions. In a preferred embodiment of the invention, the feed gas stream is air. In another preferred embodiment of the invention, the gas stream resulting from combustion used to purge the permeate side of the ion transport membrane includes a reactive gas which reacts with the flow of purified oxygen gas penetrating through the membrane of ion transport. In another preferred embodiment of the invention, the gas stream produced by combustion is cooled before being used to purge the permeate side of the ion transport membrane. In another preferred embodiment of the invention, the gas stream leaving the permeate side of the ion transport module has an oxygen concentration of about 10% to about 90%. In another preferred embodiment of the invention, the feed gas stream is compressed before being fed to the ion transport module. In another preferred embodiment of the invention, the burner is integrated with the ion transport module on the permeate side of the ion transport membrane. In another preferred embodiment of the invention, at least a portion of the gas stream resulting from combustion is used in a downstream process and at least a portion of a gas stream product downstream of the downstream process can be used to purge the permeate side of the ion transport membrane. In another embodiment of the invention, a gas stream containing oxygen is added to at least a portion of a product gas stream downstream of the downstream process and the resulting gas stream is passed through a post-burner to burn any remaining fuel in the downstream product gas stream. In yet another preferred embodiment of the invention, the burner and the downstream process are integrated with the ion transport module on the permeate side of the ion transport membrane. In other preferred embodiments of the invention, the downstream process involves the oxidation of metals, the purification of metals by the oxidation of impurities in metals, or a blast furnace. BRIEF DESCRIPTION OF THE DRAWINGS Other objectives, aspects and advantages will occur to those skilled in the art of the following description of preferred embodiments and accompanying drawings, in which: Fig. 1 is a schematic diagram showing the integration of the production of oxygen by ion transport with oxygen enriched combustion and a downstream process; Fig. 2 is a schematic diagram showing the integration of oxygen production by ion transport with oxygen enriched combustion and a downstream process similar to Fig. 1; Fig. 3 is a schematic diagram similar to Fig. 2 where the burner is integrated with the ion transport module; and Fig. 4 is a schematic diagram showing how the ion transport process, the burner and the downstream process are integrated into a single module. DETAILED DESCRIPTION OF THE INVENTION The invention will now be described in detail with reference to the Figures in which like reference numerals are used to indicate similar elements. The present invention reveals process configurations that allow the economically attractive integration of oxygen production by ion transport with oxygen enriched combustion (CEO). Although pressure driven processes are preferred because of the simplicity of their design, the concepts described herein are applicable to systems that use either an ion-conductive membrane only "having electrodes and an external circuit for electron return or a mixed conductive membrane. Commercial processes currently for oxygen production typically operate at temperatures below 100 ° C. Due to this low temperature, they do not gain significant efficiencies through integration with a CEO process.The high operating temperatures (usually higher than 600 ° C) make The ion transport process is intrinsically well suited for integration with high temperature processes, such as combustion, that use oxygen, and it will be shown that the combustion gases from the outlet can be used beneficially to improve the performance of the membrane. Ion transport The traditional oxygen production processes Eno (for example, PSA, TSA or membrane-based processes) can not easily take advantage of exhaust gases due to their high temperature when they leave the combustion chamber. The essence of the current process configuration is an ion transport membrane that employs a solid oxygen-conductive or mixed-conductive membrane to separate oxygen from an oxygen-containing gas, typically, but not necessarily, air, and 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 improves the driving force through the ion transport membrane and effects a high flow of oxygen and a lower requirement of membrane area. These benefits accumulate even when the feed gas stream is at a relatively low pressure, thus reducing the system's energy requirements to a practical level of interest. The recirculation of combustion exhaust gases is also beneficial because it provides a discharge current that is important to control the temperature in the burner and minimize the formation of NO? (for example, from the nitrogen that infiltrates). The efficiency of this process could also be improved by adding fuel to the exhaust gas that enters the oxygen separator. This also reduces the partial pressure of oxygen on the permeate side, resulting in even higher oxygen fluxes in the ion transport separator. In some embodiments of the invention, the ion transport module can also function as the burner, thus eliminating the need for a separate burner, unless the application requires a gas stream leaving the burner at a temperature above 1100. ° C, the maximum operating temperature of many of the 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, the heat generated in a post-burner and hot gases recirculated combustion products, among others. In most mixed conductors, the electronic conductivity greatly exceeds the oxygen ion conductivity 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 the crystalline structures of fluorite and perovskite. 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.

Fig. 1 is a schematic diagram showing the integration of oxygen production by ion transport with oxygen enriched combustion. During operation, the feed gas stream 1 containing elemental oxygen, usually air, is compressed at a relatively low pressure in the fan or compressor 2 to produce the compressed feed gas stream 3 which is heated in the exchanger heat 33 against the waste gas stream 31 and the product stream of nitrogen gas 37 to produce the warmed stream of feed gas 4. The gas stream 28 can be divided from the lukewarm stream of feed gas 4 and used in the optional post-burner 26 to let the feed gas stream 5, which is optionally heated in the heater 34, produce the hot stream of feed gas 6. The hot stream of feed gas 6 then enters the side of feed of the ion transport module 35 employing an ion transport membrane 7 having a retentate side 7a and a permeate side 7 b. A portion of the oxygen in the hot stream of feed gas 6 is removed in the ion transport module 35 and the gas stream 8 flowing out becomes enriched-in-nitrogen relative to the feed gas stream 1. The 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 10 contains oxygen and this gas stream 10 is later mixed with the fuel gas stream 11. The air stream 12 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 the fuel gas stream 11, the fuel gas stream 15 can be fed directly to the burner 14. By operating the burner 14 under a condition close to stoichiometric or slightly rich in fuel, the concentration of oxygen in the off-gas stream 16 can be maintained at low levels. In this embodiment the outlet 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 used in a downstream process 19 which requires heat input and the relatively cooler outlet gas stream 20 of the downstream process 19 can also be divided into two portions, the outlet gas stream 21 and the outlet gas stream 22. The fuel gas stream 25 can be added to the output gas stream 21 to produce the gas stream 38. The gas stream 38 can be added to the gas stream 17 to produce the gas stream 9 entering the 5.8 transport module 35 and is used for purging the permeate side 17b of the ion transport membrane 7. Although not shown here, the gas stream 17 can be used to heat the lukewarm feed gas stream 5 by heat exchange to produce the gas stream. hot gas feed 6 instead of using the optional heater 34. Output gas stream 22 optionally fed to optional burner 26 where air stream 27 or gas stream 28 are optionally added to produce the hot stream of waste gas 29. The waste gas hot stream 29 can be converted to gas stream 30 or gas stream 31. As stated above, gas stream 31 is used in heat exchanger 33 to heat the compressed stream of feed gas 3 to produce the waste gas stream 32. The gas stream 30 can be mixed with the retentate gas stream 8 rich in nitrogen if the nitrogen does not go to be used as a by-product and if the temperature of the outlet gas stream 30 is suitably high. The retained gas stream 8 is likely to be at a higher pressure than the outlet gas stream 30 and it may be necessary to release the excessive pressure from the retained gas stream 8 using the expansion valve 23 to produce the gas stream. retained 34 before it is mixed with the gas stream 30. If the retained gas stream 24 is desired as a product gas stream rich in nitrogen, the gas streams 36 and 30 are not mixed. The use of a purge gas stream 9 depleted in oxygen in the ion transport module 35 will greatly lower the partial pressure of oxygen on the permeate side 7b of the ion transport membrane 7 and allow the rapid transport of oxygen to the through the membrane 7. The fuel gas streams 11, 15 and 25 can be introduced to the process configuration at any or all points shown in Fig. 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 partial pressure of oxygen 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, thus reducing some of the heating requirements of the oxygen transport process. In this case, the nitrogen-rich gas stream 8 leaving the ion transport module 35 could be made hotter. This could make the heat transfer in the heat exchanger 33 more efficient, thus reducing the area required for heat exchange and potentially eliminating the need for the heater 34 upstream of the ion transport module 35. If sufficient fuel can be burned in the ion transport module 35 in the purge or the permeate side 7b of the ion transport membrane 7, the need for a separate burner 14 can be completely eliminated, ie, the ion transport module 35 would also serve as the burner (as described in Fig.3). In such a situation, a simplification of the system and reduction of significant costs may result. The arrangements of the reactive purge are described in "Reactive Purge for Gas Separation by Solid Electrolyte Membrane", E.U. Series No. 08 / 567,699, filed December 5, 1995 and incorporated herein by reference. The preferred configuration for ion transport modules using a reactive purge are described in "Solid Electrolyte Ionic Conductor Reactor Design", E.U. Series No- (Attoney Docket No. D-20352), filed on April 29, 1997 and also incorporated herein by reference. Both requests are common property with the present application. It could be advantageous to operate the burner 14 with a fuel-rich mixture slightly because this will lead to the partial oxidation of the added fuel to the permeated stream of gas 10, resulting in an off-gas stream 16 containing hydrogen gas and carbon monoxide. As stated above, the gas stream 17 is optionally used to purge the permeate side 7b of the ion transport membrane 7. 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 purge side 7b of the ion transport membrane 7 and this will allow an even faster transport of oxygen through the carrier membrane of the ion transport membrane. ions 7. Of course, similar results could be achieved by introducing hydrogen gas as a fuel gas stream 25, however, it will not be effective-encased as the fuel-rich fed to burner 14, since hydrogen gas is a relatively expensive fuel . The use of a rich-in-fuel feed for the burner 14 as described above makes the need for using a pre-produced hydrogen gas obvious, 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 gas streams 18 and 22 to contain carbon monoxide and hydrogen gas, which can be simply vented to the atmosphere if the concentration is low. As stated above, it may be possible, however, to install post-burner 26 (perhaps catalytic) to which excess air is added 27 to burn carbon monoxide and hydrogen gas if their concentrations are sufficiently high. The gas stream 28 of the lukewarm stream of feed gas 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 the combustion products as purge gas stream 9 and due to the infinite selectivity of the ion transport membrane 7 for oxygen, it is possible to limit the increase in temperature of the flow of gas 13 in the burner 14 without the need for excess air and thus exclude the nitrogen from the combustion process, which eliminates the formation of N0 ?. 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 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 in The purge side will typically be in the range of 1 to 3 atm. The pressure on the supply side will be from 1 to 3 atm. if nitrogen is not a by-product, and from 1 to 20 atm. if nitrogen is a by-product. Oxygen ion conductivity (u¡-) of the ion transport membrane: Typically in the range of 0.01-100 S / cm (1 S = l / 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 5000 microns; preferably less than 1000 microns and more preferably less than 100 microns. Configuration: The elements of the ion transport membrane can be tubular or planar. As previously stated, asymmetric or composite ion transport membranes (ie, pressurized 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. Effective membrane thickness: 20 microns Ionic conductivity, j: 0.5 S / cm Operating temperature: 800 ° C Substrate porosity: 40% Standard mathematical models have been used to determine the operating conditions for the process shown in Fig. 1 , that is, the membrane area requirement and the contributions of electrical and thermal energy required in several points. This example, modeling a process using a configuration of Fig. 1, is for illustrative purposes only and no attempt has been made to optimize the process configuration. The main reason why optimization has not been attempted is that optimization is generally based on economic considerations and the commercial production of ion transport membrane systems is still far from being mature, and no estimates are currently available of reliable costs on such systems. For the present example, looking at Fig. 1, the fuel is added to the process only as the fuel gas stream 11. Furthermore, the optional gas stream 17 is not considered, that is, the gas streams 16 and 18 are identical . Furthermore, nitrogen is not seen as a by-product and the retained gas stream 36, obtained from the retained gas stream 8 after reducing the excess pressure of the retentate using the relief valve 23, it 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 of gas. retained gas 8 upstream of the heat exchanger 33. Since the exhaust gas stream 22 does not contain carbon monoxide and hydrogen gas, the afterburner 26 is not installed. Basis for the example: A downstream process that requires a heat input of 1.26 million Kcal / hr.

* Cubic Meters per Hour at Sea Level Fig. 2 is a schematic diagram similar to Fig. 1 that shows a more efficient alternative that uses the installation of a catalytic afterburner. During operation, the feed gas stream 41 containing elemental oxygen, usually air, is compressed at a relatively low pressure by the fan or compressor 42 to produce the compressed feed gas stream 43 which is heated in the exchanger heat 73 against the waste gas hot stream 40 and the product stream of nitrogen gas 64 to produce the lukewarm feed gas stream 44. The gas stream 70 can be divided from the supply hot gas stream 44 and used in the optional post-heater 69 for letting the feed gas stream 74 which is optionally heated in the heater 75 produce the hot feed gas stream 45. The hot feed gas stream 45 then enters the feed side of the feed gas 45. 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 feed gas hot stream 45 is removed in the ion transport module 46 and the outgoing gas stream 48 becomes rich in nitrogen relative to the feed gas stream 41. The permeate 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 air stream 52 can be optionally added. Fig. 2 is a schematic diagram similar to Fig. 1 which shows a more efficient alternative that uses the installation of a catalytic afterburner. During operation, the feed gas stream 41 containing elemental oxygen, usually air, is compressed at a relatively low pressure by the fan or compressor 42 to produce the compressed feed gas stream 43 which is heated in the exchanger of heat 73 against the waste gas hot stream 40 and the product stream of nitrogen gas 64 to produce the lukewarm feed gas stream 44. The gas stream 70 can be divided from the hot feed gas stream 44 and used in the optional post-burner 69 to let the feed gas stream 74 which is optionally heated in the heater 75 produce the hot feed gas stream 45. The feed hot gas stream 45 then enters the feed side of the ion transport module 46 employing an ion transport membrane 47 having a retentate side 47a and a permeate side 47b. A portion of the oxygen in the feed gas hot stream 45 is removed in the ion transport module 46 and the outgoing gas stream 48 becomes rich in nitrogen relative to the feed gas stream 41. The permeate 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 air stream 52 can optionally be added to the gas stream 50. The fuel gas stream 53, then to pass through an optional fan (not shown), then enters the burner 54. Optionally or in addition to the fuel gas stream 51, the fuel gas stream 55 can be fed directly to the burner 54. Operating the burner 54 near the stoichiometric condition or slightly rich in fuel, the concentration of oxygen in the exhaust gas stream 56 can be maintained at low levels. 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 a downstream process 59 which requires heat input and the relatively colder exhaust gas stream 60 of the downstream process 59 may also be divided into two portions, the exhaust gas stream 61 and the exhaust gas stream 62. 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. Ta Exhaust 62 can optionally be divided into two portions, the hot waste gas stream 40 and the gas stream 77. As stated above, the hot waste gas stream 40 is used in the heat exchanger 73 to heat the compressed gas feed stream 43 to produce the waste gas stream 74. The gas stream 77 can be mixed with the stream of retained gas 48 rich in nitrogen 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 from the exhaust gas stream 62 by burning it in the post-burner 69 and also to generate heat energy to improve the efficiency of the heat exchanger 73. The retained gas stream 48 is likely which 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 retained gas stream 76 before being mixed with the gas stream 77 to produce the gas stream 80. The gas stream 80 is fed to the optional after-burner 69 where the gas stream 70 is optionally added to produce the hot waste gas stream 39. In this case, one would need to ensure that the stream 80 contains sufficient oxygen for combustion to continue to completion. Cone said before, the gas stream 70 taken from the warm gas feed stream 44 can optionally be added to the post-burner 69 to ensure this. It should be noted that the flow rate 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 ratio of the heat exchanger 73 and increases the heat transfer to the compressed gas supply stream 43. The product gas stream 64 will contain oxygen (used in excess to ensure complete combustion) and products of combustion yes. the post-burner 69 is used and the product gas stream 64 is generally discarded as a waste stream. As in the embodiment of the invention shown in Fig. 1, the use of a purge gas stream 79 depleted in oxygen in the ion transport module 46 will considerably lower the partial pressure of oxygen on the permeate side 47b of the membrane ion carrier 47 and allows the rapid transport of oxygen through the membrane 47. The combustible gas streams 51, 55 and 65 can be introduced into the process configuration at any or all points shown in Fig. 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 considerably reduce the partial pressure of oxygen on the permeate side 47b of the ion transport membrane 47. This would also result in some generation of heat in the ion transport module 46 due to combustion of the fuel, thus reducing some of the heating requirements of the oxygen transport process. In this case, the gas stream 48 rich in nitrogen leaving the ion transport module 46 could become hotter and this would make the heat transfer in the heat exchanger 73 more efficient, thus reducing the area required for the exchange of heat. heat and potentially eliminating 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 permeate or purge side 47b of the ion transport membrane 47, it is it can completely eliminate the need for a separate burner 54, that is, the ion transport module 46 would also serve as the burner (as described in Fig. 3). In such a situation, a simplification of the system and a reduction of significant costs may result. As in the embodiment of the invention shown in Fig. 1, it may be advantageous to operate the burner 54 with a mixture slightly rich in fuel because this will lead to a partial oxidation of the fuel added to the permeate gas stream 50, resulting in a exhaust gas stream 56 containing hydrogen gas and carbon monoxide. Coto said 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 oxygen carrier membrane 47. The use of a fuel rich feed for the burner 54 produces hydrogen gas as part of the process cycle. As stated before, it may be possible to install the afterburner 69 (perhaps catalytic) to burn carbon monoxide and hydrogen gas if their concentrations are high enough. Fig. 3 is a schematic diagram showing another embodiment of the invention where the burner is integrated with the ion transport module, that is, where the ion transport module itself serves as a burner. During operation, the gas stream 81 containing elemental oxygen, usually air, is compressed at a relatively low pressure in the fan or compressor 82 to produce the compressed gas feed stream 83 which is heated in the heat exchanger 113. against the hot waste gas stream 116 and the nitrogen gas product stream 93 to produce the warm gas feed stream 95. The gas stream 110 can be divided from the warm gas feed stream 95 and used in the post optional burner 109 for letting the feed gas stream 84, which is optionally heated in the heater 114, produce the hot feed gas stream 85. The feed hot gas stream 85 then enters the feed side of the ion transport module-burner 86 employing the ion transport membrane 87 having a retention side 87a and a permeate side or 87b. A portion of the oxygen in the hot feed gas stream 85 is removed in the ion transport module-burner 86 and the outgoing gas stream 88 becomes enriched in nitrogen relative to the feed gas stream 81. The side permeate 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 90 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 transport burner 86 near the stoichiometric or slightly rich condition in fuel, the concentration of oxygen in the exhaust gas stream 90 can be maintained at low levels. The gas stream 98 is used in a downstream process 99 that requires heat input and the relatively cooler 100 exhaust gas stream from the downstream process 99 is also divided into two portions, the exhaust gas stream 101 and the stream. of exhaust gas 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 module-burner 86 and is used to purge the permeate side. 87b of the ion transport membrane 87. The exhaust gas stream 102 can optionally be divided into two portions, the hot waste gas stream 116 and the gas stream 115. As stated above, the hot gas stream of waste 116 is used in the heat exchanger 113 to heat the compressed gas supply stream 83 to produce the waste gas stream 117. The gas stream 115 can be clada with the retentate gas stream 88 rich in nitrogen if the nitrogen is not to be used as a by-product and if the temperature of the exhaust gas stream 115 is suitably high. The reason for this step is to remove any unreacted fuel in the exhaust gas stream 102 by combustion in the afterburner 109 and also generate heat energy to improve the efficiency of the heat exchanger 113. The retained gas stream 88 is likely to which is at a higher pressure than the exhaust gas stream 115 and it may be necessary to release the excess pressure from the retained gas stream 88 using the expansion valve 103 to produce the retained gas stream 118 before being mixed with the gas stream 115 to produce the gas stream 119.

The gas stream 119 is fed to the optional after-burner 109 where the gas stream 110 is optionally added to produce the hot waste gas stream 93. In this case one would need to make sure that the stream 119 contains sufficient oxygen for the combustion continued until its completion. As stated before, the gas stream 110 taken from the warm feed gas stream 95 can optionally be added to the post burner 109 to ensure this. It should be noted that the flow rate of the combined current is increased by mixing the exhaust gases from the ion transport module-burner 86 and the process 99 downstream. This improves the capacity ratio in the heat exchanger 113 and increases the heat transfer to the compressed gas supply stream 83. The gas stream 94 will contain oxygen (used in excess to ensure complete combustion) and combustion products if the post-burner 109 is used and the gas stream 94 is generally discarded as a waste stream. In the embodiment of FIG. 3, the heat of reaction generated in the ion transport module-burner 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 purge reagent gas stream 89 flowing into the tubes. Due to the heat generated on the purge side 87b of the tube-shaped ion transport membrane 87, the tubes will be at high temperature and act as heating elements. The tubes of the ion transport membrane 87 will radiate to the retentate side 87a or to the permeate side 87b where a process such as glass melting or metal quenching can be carried out. Also, a part of the value generated in the ion transport module 86 can be used to preheat the compressed gas feed stream 85 and the purge gas stream 89, possibly obviating the need for the heat exchanger 113 and the heater 114. 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 outlet gas (oven). If the furnace and the ion-burner transport module operate at approximately the same temperature (for example, between 800-1200 ° C), then the ion-burner transport module can be placed directly inside the furnace provided the atmosphere of the furnace is clean, that is, it does not contain any harmful species to the ion transport membrane. One way to implement this idea is shown in Fig. 4 in which the ion transport process, burner and the downstream process are all integrated into a single unit. The feed stream 132 such as heated air is directed against the cathode side 120a of the membrane 120 to produce the hot retentate depleted in oxygen 134 such as nitrogen. The downstream process 130 (eg, a furnace charge) is shown on the permeate side or the anode 120b of the ion transport membrane 120. In this configuration, the fuel gas stream 121 is fed near the side surface. permeate 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 recirculated in the furnace against the anode side 120b by natural or forced convection; for the construction shown in Fig. 4, the stream of combustion products 146, preferably obtained from furnace 130 as shown in dotted lines by stream 146a, and fuel gas stream 121 are optionally fed through the porous layer fuel distributor 122 adjacent to the permeate side 120b of the ion transport membrane 120. Preferably, the distributing layer 122 defines at least one passage or chamber for more evenly distributing the fuel 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 the 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 either of the external or integrated constructions, a two-stage ion transport system may be established in which the side The anode of the first stage is purged by the retentate stream from the first stage to produce a diluted oxygen permeate stream while the anode side of the second stage is reactive purged to produce a fuel rich permeate stream. The two permeate streams are used in a combustion furnace with or without the use of hot nitrogen holding streams in the atmosphere of the furnace. 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, preheating section of a continuous furnace of reheat), or a special chamber with appropriate heat falls to control the temperature that can be created. 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 an optimum temperature for the ion transport module. A large amount of exhaust gas is circulated through this zone to continuously purge oxygen and keep the oxygen concentration low. Low oxygen concentration and high furnace gas circulation provide synergy with the diluted oxygen combustion method. There are many advantages with the integrated processes of the invention. For example, oxygen for the CEO can be extracted from a low pressure feed gas stream using the exhaust gas stream for purging and this will result in a lower power requirement for the oxygen separation process. Because only oxygen passes 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, the optional gas stream 12) or by leaks, the fraction of nitrogen in the combustion mixture will be small. Will this minimize or eliminate the formation of N0? 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 transport of ions. 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 unit of the burner can be eliminated. This would give a simplification of the system and significant cost savings. In addition, if sufficient oxygen is withdrawn from the feed gas stream in the ion transport module, then the nitrogen-rich stream retained in the ion transport module can be used as a by-product. This may be more attractive if some fuel is added, for example, the fuel gas stream 11. If nitrogen is desired as a by-product, it may be advantageous to compress the feed gas stream to the pressure required to supply nitrogen as a product However, in this case, the gas stream retained from the ion transport module may not be mixed with the exhaust gas stream of the downstream process. In this case, either a separate heat exchanger can be installed to recover the heat from the exhaust gas stream, or heat recovery can not be attempted since the exhaust gas stream will generally be much smaller and colder than the gas stream retained.

In addition, the use of the purge gas stream decreases the oxygen concentration on the permeate side of the ion transport membrane. The decreased oxygen concentration makes the design of the ion transport module and the downstream components (eg, the burner) on the purge side considerably easier from a material point of view. In the absence of a purge stream, pure oxygen would be produced essentially on the permeate side of the ion transport membrane. The safe handling of such a high purity oxygen stream poses a significant challenge, especially at elevated temperature. In addition, the oxygen concentration at the outlet of the purge 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), changing the operating temperature of the ion transport module, or varying the membrane area of the ion transport stage. These techniques are also effective in controlling the total amount of separated oxygen and could be used for load tracking purposes. Finally, the use of an ion transport separator would eliminate the need for an independent oxygen generator (e.g., AOP) or an oxygen delivery system (e.g., tank and liquid vaporizer). This is expected to contribute to a substantial reduction in capital cost and in the cost of oxygen produced. It should be noted that a number of 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 pressurized mixed conductor ion transport membranes, it is that the inventive concept is also applicable to primary ionic conductors that are operated in the pressurized or electrically driven mode with an external return of current. Finally, although a process of oxygen separation against countercurrent is described in Fig. 1, the process can also be carried out in a concurrent or cross-flow manner. As stated before, the terms "solid electrolyte ion conductor", "solid electrolyte", "ion conductor" and "ion transport membrane" are used herein to designate either an ionic type system (electrically driven) or a mixed conductor type system (pressure driven) unless otherwise specified. The term "nitrogen" as used herein will usually mean gas depleted in oxygen, that is, exhausted in oxygen in relation to the feed gas. As discussed above, the ion transport membrane allows only the penetration of oxygen. Therefore, 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 the skilled artisan in the context of the use of the term in light of the invention flake is disclosed in the present. As used herein the term "elemental oxygen" means any oxygen without combining with any other element of the Periodic Table. Although elemental oxygen is typically found in diatomic form, it includes simple atoms of oxygen, triatomic ozone, and other forms without combining with other elements. The term "high purity" refers to a product stream that contains less than five percent by volume of unwanted gases. Preferably, the product is at least 98.0% pure, more preferably 99.9% pure, and most preferably at least 99.99% pure, wherein pure indicates an absence of unwanted gases. "Pressure oscillation absorption" or "AOP" systems refer to systems that use absorption materials that are selective for a gas, typically nitrogen, to separate that gas from other gases. Such materials include selective regime AOP materials, which usually contain carbon and provide high pressure nitrogen and low pressure oxygen, and selective AOP-equilibrium materials, which usually contain lithium and provide low pressure nitrogen and high oxygen. Pressure. Specific aspects of the invention are shown in one 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 absorption beds by pressure swing and thermal oscillation or other mass 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 attempts are made to include them within the scope of the claims.

Claims (5)

1. CLAIMS 1. A process for separating a stream of feed gas containing elemental oxygen into an oxygen-enriched gas stream and an oxygen-depleted gas stream where the gas stream enriched in oxygen is used in a burner, said process comprising: (a) compressing the feed gas stream; (b) separating the oxygen from the compressed gas feed stream using an ion transport module that includes an ion transport membrane having a retentate side and a permeate side to separate a purified stream of oxygen gas on the side permeate and correspondingly depleting the oxygen on the retentate side to produce the gas stream depleted in oxygen, mixing the purified stream of oxygen gas with other gaseous components on the permeate side to form the oxygen enriched gas stream; Y (c) purging the permeate side of the ion transport membrane with at least a portion of a gas stream of combustion products obtained from combustion in the burner of the gas stream exiting the permeate side of the module ion transport.
2. 2. The process according to claim 1, wherein the feed gas stream is air.
3. The process according to claim 1, wherein the gas stream of combustion products used to purge the permeate side of the ion transport membrane includes a reactive gas that reacts with the purified stream of oxygen gas penetrating through of the ion transport membrane.
4. The process according to claim 1, further comprising: cooling the gas stream of combustion products before being used to purge the permeate side of the ion transport membrane.
5. 5. The process according to claim 1, wherein the gas stream leaving the permeate side of the ion transport module has an oxygen concentration of about 10% to about 90%. The process according to claim 1, further comprising: heating the compressed stream of feed gas before being fed to the ion transport module. The process according to claim 1, wherein the gemer is integrated with the ion transport module on the permeate side of the ion transport membrane. The process according to claim 1, wherein at least a portion of the gas stream of combustion products is used in a downstream process. The process according to claim 8, wherein both the burner and the downstream process are integrated with the ion transport module on the permeate side of the ion transport membrane. The process according to claim 8, wherein at least a portion of the product gas stream downstream of the downstream process is used to purge the permeate side of the ion transport membrane.