METHOD FOR RECYCLING COMBUSTION GASES FOR THERMOCHEMICAL REGENERATION

Abstract

Thermochemical regeneration is enhanced by injecting fuel gas to draw in recycled combustion gas from one regenerator to form a mixture that is pumped to the other regenerator.

Description

METHOD FOR RECYCLING COMBUSTION GASES FOR THERMOCHEMICAL REGENERATION Field of Invention The present invention relates to combustion in furnaces such as glass melting furnaces, where the material is fed into the furnace and heated and / or melted by the heat of combustion produced inside the furnace. Background of the Invention The technology that uses pairs of regenerators in repeated cycles to utilize the heat contained in the hot gaseous combustion products (also called flue gases) from a furnace (such as a glass-melting furnace) is generally known. In one cycle, the flue gas is passed through a first regenerator where the hot flue gas heats the structure inside the first regenerator, while another gas stream, such as gaseous oxidant, is passed through a second regenerator that has already been heated, to heat the gas stream that is then passed to the furnace and thus cool the second regenerator. Then, in the second cycle, the flue gas is passed through the second regenerator to heat it, and the gas stream is in turn passed through the first regenerator that had been heated. Ref. 316634 heated in the previous cycle. The two cycles alternate. U.S. Patent No. 6,113,874 describes an improved technology that can be implemented using paired regenerators, which outlines useful heat recovery methods for furnaces employing regenerators. More specifically, a stream of combustion products formed in the furnace is passed through a first regenerator to heat the regenerator and cool the combustion products. A portion of the cooled combustion products is then combined with fuel to form a mixture that is passed through a second heated regenerator, where the mixture undergoes an endothermic reaction to form synthesis gas. This synthesis gas is then fed back into the furnace and burned. The present invention provides the ability to practice these technologies with improved efficiency and economy. Brief Description of the Invention One aspect of the present invention is a method for carrying out combustion in a furnace, comprising: (A) burning fuel in a furnace to produce gaseous combustion products, and (B) alternatively (1) passing the gaseous combustion products from the furnace to and through a first cooled regenerator to heat the first regenerator and cool the gaseous combustion products, and injecting a gaseous fuel stream into a recycle stream comprising the cooled gaseous combustion products in the first regenerator, to entrain the recycle stream into the injected gaseous fuel stream thereby forming a mixture of the gaseous fuel with the entrained gaseous combustion products and to propel the mixture into a second heated regenerator, and, in the second regenerator, reacting the gaseous combustion products and the fuel in the mixture in an endothermic reaction to form synthesis gas comprising hydrogen and CO,and passing the synthesis gas from the second regenerator to the furnace and burning it in the furnace, and (2) passing the gaseous combustion products from the furnace to and through a second cooled regenerator to heat the second regenerator and cool the gaseous combustion products, and injecting a gaseous fuel stream into a recycle stream comprising the cooled gaseous combustion products in the second regenerator, to entrain the recycle stream into the injected gaseous fuel stream thereby forming a mixture of the gaseous fuel with the entrained gaseous combustion products and to propel the mixture to a heated first regenerator, and, in the first regenerator, reacting the gaseous combustion products and the fuel in the mixture in an endothermic reaction to form synthesis gas comprising hydrogen and CO,and pass the synthesis gas from the first regenerator to the furnace and burn it in the furnace. The recycled combustion gas stream into which the gaseous fuel stream is injected is typically split from the entire stream of cooled gaseous combustion products that in turn comes out of each cooled regenerator, in which case the remaining cooled gaseous combustion products are passed to the extractor. In a preferred embodiment of this invention, after each gaseous fuel mixture is formed with entrained gaseous combustion products, additional gaseous fuel is added to the mixtures before the mixtures are alternately propelled into the first and second heated regenerators. Another embodiment of the invention uses a device having first and second chambers connected by a passage, and in step (B)(1) a stream of gaseous fuel is injected into the gaseous combustion products in a first chamber of the device, and the resulting mixture of gaseous fuel and gaseous combustion products is passed from the first chamber through the passage and through the second chamber into the second heated regenerator; and in step (B)(2) a stream of gaseous fuel is injected into the gaseous combustion products in the second chamber of the device and the resulting mixture of gaseous fuel and gaseous combustion products is passed from the second chamber through the passage and through the first chamber into the first heated regenerator. In a preferred embodiment of this invention, the first chamber is inside the first regenerator and the second chamber is inside the second regenerator. The first and second regenerators are separated by a wall that is in contact with both, and the passage between the first and second chambers is through this wall. In this embodiment, no external conduits are required for the regenerators. In this invention, a purging stage is preferably incorporated, wherein at the end of stage (B)(1) before stage (B)(2) begins, the passage of gaseous fuel to the second regenerator is discontinued, and mobile gas is passed to and through the second regenerator to purge gaseous fuel from the second regenerator; and wherein at the end of stage (B)(2) before stage (B)(1) begins, the passage of gaseous fuel to the first regenerator is discontinued, and mobile gas is passed to and through the first regenerator to purge gaseous fuel from the first regenerator. Preferably, the mobile gas is injected into, and carries, a stream of recycled combustion gas to form a mixture that is propelled toward the regenerator being purged. Brief Description of the Figures Figure 1 is a flowchart of one modality of the present invention. Figure 2 is a schematic cross-sectional view of a portion of the modality in Figure 1. Figure 3 is a schematic cross-sectional view of another part of the modality in Figure 1. Figure 4 is a flowchart of another modality of the present invention. Figure 5 is a cross-sectional view of a device useful in the practice of the present invention. Figure 6 is a flowchart of another modality of the present invention. Figure 7 is a cross-sectional view of a device useful in the practice of the present invention. Figure 8 is a cross-sectional view of the regenerator equipment that incorporates yet another modality of the invention. Detailed Description of the Invention The present invention uses a heat recovery process that recaptures usable heat from high-temperature combustion gas exhaust streams. Preferred examples of combustion processes with which the method of this invention can be practiced include glass melting furnaces, in which the glass-forming ingredients are melted together to form molten glass. This heat recovery process occurs in two cycles, which are referred to herein as the flue gas cycle and the reforming cycle. These two cycles are carried out alternately in two or more regenerators filled with heat recovery units. The heat recovery process is preferably performed in conjunction with furnaces and other combustion devices that use oxyfuel combustion processes, i.e., combustion of fuel with a gaseous oxidizer comprising an oxygen content of at least 50% by volume, and preferably at least 80% by volume, more preferably at least 90% by volume, and even at least 99% by volume, because the flue gases produced by oxyfuel combustion have higher concentrations of H₂O and CO₂, both of which promote the endothermic reforming reactions used in the method of this invention.During the flue gas cycle, heat recovery units in a first regenerator extract and store heat from a high-temperature flue gas, which is fed from the furnace into and through this regenerator. Then, in the reforming cycle, a portion of the cooled flue gas exiting the first regenerator (referred to herein as recycled flue gas or RFG) is fed into another (second) regenerator and mixed with a fuel stream (referred herein as reforming fuel or RF). In the following description, pure methane (CH4) is described as the reforming fuel for illustrative purposes. Other satisfactory fuels include any combustible gas, gas mixture, or vaporized liquid fuels, including, but not limited to, natural gas, propane, and LPG (liquefied petroleum gas). In the reforming cycle, the mixture of reforming fuel oil (RFO) and reforming fuel enters the second regenerator, in which the heat recovery unit has already been heated, as described herein, and flows through it into the furnace. The temperature of the RFO mixture passing through the second regenerator continues to rise due to heat extraction from the preheated heat recovery unit. As the RFO mixture passes through the second regenerator, it reaches a temperature at which the reforming reactions begin and continue, producing hydrogen (H2) and carbon dioxide (CO2). The reforming reactions are endothermic, and the heat required to promote these reactions is absorbed from the heated heat recovery unit.The gaseous composition produced by the reforming reactions typically comprises one or more components such as H2, CO, unreacted gases including H2O, CO2, CH4, nitrogen, any residual NOx, and soot. The gaseous composition thus produced may also be referred to as synthesis gas in this description. The synthesis gas exits the second regenerator to the furnace and is burned in the furnace with the oxidant to provide thermal energy for heating and / or melting the material in the furnace. After a certain time interval, the operation of the two regenerators is reversed; that is, the regenerator used in the flue gas cycle is switched to the reforming cycle, and vice versa. After another period, the operation of the two regenerators is reversed again. The timing of the reversals can be determined by elapsed time or by other criteria, such as the temperature of the flue gas exiting the first regenerator in the flue gas cycle. The reversal process is carried out according to a predetermined mechanism and plan, where the valves are sequenced to open and close, and the flow of the moving gases is activated and deactivated at specific times. The operation and control of the present invention are described in further detail below, together with Figures 1 to 8. With reference, first, to Figure 1, an end-port combustion glass furnace (5) equipped with two regenerators (100) and (200) in the end wall (3) of the furnace (5) is used as an example. However, the operation described herein of a pair of regenerators can be carried out in the same manner whether the pairs of regenerators are side by side on one side of the furnace (5) or are located on opposite sides of the furnace (5). As shown in Figure 1, the end-port combustion glass furnace (5) has a feeding station, represented as (31), where the feed material (30), comprising solid materials for glassmaking (known as charge and / or waste glass), is charged into the furnace to be heated and melted. The flow of molten glass exiting the furnace (5) is represented as (90). The furnace (5) is equipped with the first regenerator (100) on the left side of the furnace and the second regenerator (200) on the right side. Vertical cross-sectional views of the two regenerators are shown in greater detail in Figures 2 and 3. As shown in Figures 1 and 2, the interior of the furnace (5) is connected to the upper space (530) of the regenerator (200) by the port neck (205). Within the regenerator (200) refractory materials (represented as (520)) are provided, arranged with passages between the refractory materials through which gas can flow to and from the lower chamber space (500) via gas passages (515) supported by the arch (510), which also supports the weight of the refractory bed in the regenerator (200). As also shown in Figures 1 and 2, the conduit (260) is connected to the lower space (500) and to the device (210), which is described in more detail below. The supplemental gaseous fuel supply line (21) is connected to the conduit (260) through valve (230). The reforming fuel line (20) is connected to the device (210) through valve (220) to allow reforming fuel to flow into the device (210) as described herein. The mobile gas line (22) is connected to the device (210) through valve (240) to allow purge gas to flow into the device (210) as described herein. The combustion gas line (250) is connected to the device (210) so that it can pass gas to the device (210) or receive gas from the device (210) as described herein.The combustion gas line (250) extends from the device (210) to line (350) and line (150), which are described below. Line (350) passes through valve (300), which adjusts the ratio of gas flowing through lines (250) and (150) to the gas flow through line (350) to the mobile device (310), which is any device capable of drawing gas towards itself through line (350), such as a fan, blower, or eductor. Line (315) is connected to the mobile device (310) and to the discharge represented by (400), meaning that it does not re-enter the furnace but is discharged to the atmosphere and / or conveyed to one or more other stations for storage and / or further treatment, or any combination thereof. As shown in Figures 1 and 3, the interior of the furnace (5) is connected to the upper space (430) of the regenerator (100) by the port neck (105). Within the regenerator (100) refractory materials (represented as (420)) are provided, arranged with passages between the refractory materials through which gas can flow to and from the lower chamber space (405) through gas passages (415) supported in the arch (410) which also supports the weight of the refractory bed in the regenerator (100). As also shown in Figures 1 and 3, the conduit (160) is connected to the lower space (405) and to the device (110), which is described in more detail below. The auxiliary gaseous fuel supply line (11) is connected to the conduit (160) through valve (130). The reforming fuel line (10) is connected to the device (110) through valve (120) so that it can deliver reforming fuel to the device (110) as described herein. The mobile gas line (12) is connected to the device (110) through valve (140) so that it can deliver purge gas to the device (210) as described herein. The combustion gas line (150) is connected to the device (110) so that it can pass the qas to the device (110) or receive the qas from the device (110) as described herein.The combustion gas line (150) extends from the device (110) to line (150) and line (350) and discharge (400) described above. In the configuration shown in Figure 4, the elements bearing reference numbers that appear in Figure 1 are the same as those described herein with respect to Figure 1. In addition to these elements, line (150A) is connected to conduit (160) and to line (250) and to line (350B). Line (250A) is connected to conduit (260) and to line (150) and to line (350A). Line (350A) passes through valve (300A) to the mobile device (310), and line (350B) passes through valve (300B) to the mobile device (310). The gas flows to zr Lrnn / Lznz / E / YiAi through these lines, and the proportions of flows that pass through, and do not pass through, the devices (110) and (210), can be controlled by the size of the lines and by the settings of the valve (300) and the movable device (310), and optionally by providing control valves on the lines (150A) and (250A).This mode may be preferable in some operations, compared to the mode in Figure 1, in that the mode in Figure 1 requires that all gaseous combustion products leaving the regenerator (200) in the duct (260) to the device (110) or to the line (350) pass through the device (210), and requires that all gaseous combustion products leaving the regenerator (100) in the duct (160) to the device (210) or to the line (350) pass through the device (110), whereas the mode in Figure 4 does not require such gas flows to pass through devices (210) and (110) respectively, which provides operational flexibility that may be useful to operators. Figure 5 represents a useful embodiment (550) of a device that can be used as device (110) and / or device (210) described herein. The device (550) has a solid exterior (560) provided with an inlet opening (551), a second opening (552), and an outlet (558), all of which communicate with a hollow interior (557). The hollow interior (557) includes the chamber (554) and the passage (555) that communicates with the chamber (554). The opening (551) terminates in the nozzle opening (553) opposite the chamber (554). The passage (555) can be essentially cylindrical, but preferably includes a convergent / divergent configuration shown as (556) in Figure 5.That is, the diameter of the passage (555) decreases with distance from the chamber (554), from where it makes contact with the chamber (554) to a point (or segment) where the diameter is at a minimum, and then from that point it increases with increasing distance from the chamber (554). This convergent / divergent shape improves the entrainment of gaseous combustion products in the convergent section and helps to recover static pressure in the divergent section. Devices of the type described herein that are useful as devices (110) and (210) include devices known as eductors, which use the kinetic energy of a moving fluid (such as the stream emerging from the nozzle (553)) to entrain another fluid.During operation, when a device (550) is to be used as device (210) as described herein, the conduit (260) is connected to the opening (552), the line (20) is connected to the opening (551), and the line (250) is connected to the opening (558). Similarly, when a device (550) is to be used as device (110) as described herein, the conduit (160) is connected to the opening (552), the line (10) is connected to the opening (551), and the line (150) is connected to the opening (558). When two different mobile gases such as fuel gas and mobile gas to produce the purge gas stream are connected to an eductor, a single nozzle is used, such as nozzle (553), or two separate nozzles (not shown) with two connecting lines and separate openings (not shown).A preferred two-nozzle configuration is that of concentric nozzles consisting of a central nozzle connected to the first mobile gas and an annular nozzle around the central nozzle connected to the second mobile gas. Figures 6 and 7 depict another alternative embodiment of equipment useful in the present invention. In the embodiment shown in Figure 6, the reference-numbered elements appearing in Figure 1 are the same as those described herein with respect to Figure 1. In addition to these elements, device (610) is provided in place of device (110), device (210), and lines (150) and (250). Valve (300) provides control of the proportion of gas flowing in conduits (160) and (260) that passes to the discharge (400) instead of to device (610), in the same manner that valve (300) controls the flows to line (350) as described above with respect to Figure 1. zr Lrnn / Lznz / E / YiAi With reference now to Figure 7, the device (610) is in effect a pair of devices of the type described herein as (550) with respect to Figure 5, connected end-to-end at their respective openings (558). That is, the device (610) has a solid exterior (620) provided with two inlet openings (611) and two secondary openings (612), all of which communicate with a hollow interior. The hollow interior includes two chambers (614) and a passage (615) that connects to both chambers (614). The openings (611) terminate in nozzle openings (613), each of which opens into one of the chambers (614). The passage (615) may be essentially cylindrical, but preferably includes a convergent / divergent configuration, which appears as (616) in Figure 7.That is, the diameter of the passage (615) decreases with distance from a chamber (614), where the passage (615) makes contact with the chamber (614) at a point (or segment) where the diameter is at its minimum, and then increases with decreasing distance from the other chamber (614). This convergent / divergent configuration improves the entrainment of gaseous combustion products in the convergent section and helps to recover static pressure in the divergent section. Preferably, the passage in this configuration is geometrically symmetric, meaning that the distances from each chamber to the point or segment of minimum diameter are the same, and the rate of change of the diameter with respect to the distance from each chamber is the same for each passage between a chamber (614) and the point or segment of minimum diameter.During operation, the conduit (260) is connected to one of the openings (612) and the line (20) is connected to one of the openings (611); and the conduit (160) is connected to the other of the openings (612) and the line (10) is connected to the other of the openings (611). Figure 8 represents another alternative equipment arrangement with which the present invention can be implemented. This embodiment is advantageously used when the regenerators (100) and (200) are separated by a common wall (800) that is in contact with both regenerators (100) and (200). Such a common wall may be a single solid structure constructed of refractory bricks or other heat-resistant material, or it may consist of two such solid structures enclosing a space between them. One surface (801) of the wall (800) is in contact with the space containing refractory materials (420), and another surface (802) of the wall (800) is in contact with the space containing refractory materials (520).In the embodiment shown in Figure 8, the device (610) is located in the opening (805) that extends through the wall (800), such that one of the aforementioned openings (612) is inside the regenerator (100) and another opening (612) is inside the regenerator (200). More specifically, one opening (612) is in the lower space (500) and another opening (612) is inside the lower space (405). Preferably, the opening (612) in the device (610) faces downwards towards the lower floor of the regenerators to prevent dust and debris from the refractory materials above from falling into the opening. There is also an opening (611) of the device (610) inside the regenerator (100) and an opening (611) inside the regenerator (200).In this mode, a network of ducts between the openings (612) and the inside of the regenerators is not needed, since the devices (610) are already inside the regenerators. The method of the present invention can be carried out in the following manner. With reference, first, to Figures 1, 2, and 3, in one operating cycle the regenerator (200) is in the combustion cycle, where the gaseous combustion products (flue gas) from inside the furnace (5) enter the port neck (205) and then flow into the upper space (530) of the regenerator (200). As it flows through the passages between the refractory materials inside the regenerator (200), this flue gas stream heats the refractory materials (520) and enters the lower chamber space (500) through the gas passages (515) in the refractory bed. As shown in Figures 1 and 2, the cooled combustion gas stream zr Lrnn / Lznz / E / YiAi exits the regenerator (200) in the duct (260). In this cycle, valves (230), (220), and (240) are closed. In this embodiment of the invention, the cooled combustion gas passes through the device (210) into the line (250). Most of the combustion gas in the line (250) passes through the valve (300) to the discharge (400) as defined herein. A portion of the combustion gas from the line (250), preferably between 5 and 30%, passes into the line (150) and then enters the device (110) through the opening (552) (Figure 5). This is recycled combustion gas (RFG). The remaining combustion gas is preferentially passed towards the discharge. The reforming fuel (RF) is supplied via line (10) through the open valve (120) to the device (110) through the opening (551) and nozzle (553). During this portion of the cycle, the valve (140) must be closed. The reforming fuel feed through the nozzle (553) draws the combustion gas that has entered the device (110) into the combustion gas stream. This entrainment forms a combustion gas and reforming fuel mixture in the chamber (554). The entrainment is preferably carried out by injecting the fuel gas at high pressure and velocity, and preferably in a direction that allows the injected combustion gas stream to intersect the combustion gas inlet stream. Preferably, the mass flow ratio of the entrained recycled combustion gas to the injected gaseous fuel is 0.5:1 to 30:1, and more preferably 0.5:1 to 20:1.The injected fuel gas should exit the nozzle (553) at high speed created by a high gas supply pressure, preferably from 5 psig to 200 psig, more preferably from 5 psig to 100 psig, to engulf the combustion gas into the injected fuel gas, to create a mixture of the injected fuel gas with the combustion gas, and to propel the created mixture towards the regenerator (100). As shown in Figures 1 and 3, the reforming fuel and flue gas mixture exits the device (110) through the duct (160) and enters the lower space (405) of the regenerator (100). If desired, additional reforming fuel is fed into the reforming fuel and flue gas mixture exiting the device (110). This additional reforming fuel can be supplied through line (11) by means of the open valve (130). Preferably, the mass flow rate of this additional reforming fuel is greater than the mass flow rate of gaseous fuel injected into the regenerator and carrying the recycled flue gas.The addition of this additional gaseous reforming fuel can help establish that the fuel gas and flue gas mixture entering a regenerator meets a desired recycled flue gas to reforming fuel (RFG / RF) ratio within a desired range, which is typically 0.5:1 to 3:1, by volume. The reforming fuel and flue gas mixture (with or without additional fuel fed via line (11) into the mixture exiting device (110)) enters the preheated refractory packing (420) of the regenerator (100) through the gas passages (415). The regenerator (100) has already been heated in a previous cycle by the passage of flue gas from the furnace into and through the regenerator (100). The temperature of the reforming fuel / flue gas mixture increases as it flows through the heat recovery unit of the regenerator (100). When the reforming fuel / flue gas temperature reaches the reforming temperature, endothermic reforming reactions occur in which the reforming fuel (e.g., CH4) reacts with the CO2 and H2O in the reforming fuel to form CO, H2, and some soot. The heat required for the endothermic reforming reactions is taken from the hot heat recuperators.The reforming reaction continues as the RFG and RF mixture continues its movement into the upper zr Lrnn / Lznz / E / YiAi space (430). The gas stream (425) (referred to herein as the reformed or synthesis gas stream) exits the top of the heat recovery unit (420). The stream (425) is at a high temperature and includes species such as CO, H2, soot, unreacted CH4, unreacted CO2, and H2O. The synthesis gas stream (425) passes through the port neck (105) and enters the furnace (5). The synthesis gas stream exits the refractory packing compartment (420) at temperatures ranging, for example, from 1800 to 2500 °F. This synthesis gas is burned in the furnace (5) represented as the flame (40) to generate additional combustion heat useful for heating and / or melting material in the furnace, such as glassmaking materials.The oxidant required for the combustion of the synthesis gas is supplied through a conduit (135) via an open valve (115). This oxidant may be air, or it may have an oxygen content greater than that of air, i.e., at least 21% by volume and, preferably, greater than or equal to 80% by volume, more preferably greater than or equal to 90% by volume or even at least 99% by volume. Typically, the method of the present invention takes place with one regenerator in the combustion cycle and one regenerator in the reforming cycle, for approximately 20 to 40 minutes or until the refractory materials in the reforming regenerator are too cold to provide sufficient heat to promote the desired endothermic chemical reactions. At that point, and continuing now with the description herein, where the regenerator (200) was in the combustion gas cycle and the regenerator (100) was in the reforming cycle, the furnace (5) undergoes a reversal in which the regenerator (200) is switched to the reforming cycle for heat recovery and the regenerator (100) is switched to the combustion gas cycle for heat accumulation. Before reversal, the remaining synthesis gas in the regenerator (100) must be purged to the furnace (5). In this case, the reforming fuel flow supplied to the regenerator is first stopped by closing valves (120) and (130) while allowing the reforming fuel gas (RFG) flow from device (110) to continue. During purging, the RFG flow rate can be increased to reduce the time required for the purging to be completed. The remaining synthesis gas in the regenerator (100) is purged by the RFG over a specified time interval, so that almost all of the synthesis gas in the regenerator is expelled to the furnace and burned completely. Purging can be carried out by supplying mobile gas from line (12) by opening valve (140). The mobile gas must not contain combustion fuel.Suitable blowdown gas may include any combustion gas (preferably clean compressed combustion gas from one of the regenerators), steam, air, carbon dioxide, and / or other gases or mixtures thereof, provided that the oxygen content of the blowdown gas is less than 25% by volume, more preferably less than 15% by volume, and even more preferably less than 2% by volume. The oxygen concentration of the mobile gas mixture and entrained gaseous combustion products formed during the blowdown stage must be less than 10%, preferably less than 6%, more preferably less than 4%, and even more preferably less than 2%, by volume on a wet basis. The blowdown gas is preferably fed at a pressure of 1 psig to 1000 psig, preferably 5 psig to 150 psig.The mobile gas drag ratio (i.e., the ratio of the dragged combustion gas flow rate to the mobile gas flow rate) should be 1 to 30 or 1 to 20, preferably 5 to 30 or 5 to 20, and most preferably 10 to 30. After the reversal, the combustion gas from the furnace passes through the regenerator (100) instead of the regenerator (200), and a portion of the combustion gas passes to the discharge (as defined herein), while a portion or the remainder is drawn into the device (210) with gaseous fuel to form a combustion gas and reforming fuel mixture that is pumped to the regenerator (200) (with or without additional reforming fuel, which, if desired, is fed through line (21) via valve (230). To carry out this cycle, valve (240), which was closed, is opened, and valves (120) and (130), which were open, are closed.The reforming fuel mixture and recycled combustion gas undergoes in the regenerator (200) the endothermic reactions that had been produced in the regenerator (100) in the previous cycle as described in the present description, to produce synthesis gas (425), which passes to the furnace (5) where it is burned with oxidant (235) that is fed through the valve (225). To carry out the method of the present invention with the arrangement shown in Figure 4, the operation is performed as described above with reference to Figures 1, 2, and 3, with the additional feature that the valves (300A) and (300B) can be fully or partially opened or closed, as desired, to adjust the amount of gas passing through the devices (110) and (210) during each cycle of operation. As mentioned above, the gas flows can also be controlled by appropriate adjustments of the valve (300) and the movable device (310). To perform the method of the present invention with the arrangements shown in Figures 6 or 8, the operation is as described above with reference to Figures zr Lrnn / Lznz / E / YiAi 1, 2 and 3. The device (610) is advantageous because all the gas that comes out of one chamber (614) goes into the other chamber (614), thereby simplifying operation and requiring fewer lines and valves. It is hereby stated that, as of this date, the best method known to the applicant for putting the aforementioned invention into practice is the one that is clear from the present description of the invention.

Claims

Having described the invention as above, the following claims are claimed as property:

1. A method for carrying out combustion in a furnace, characterized in that it comprises (A) burning fuel in a furnace to produce gaseous combustion products, and (B) alternatively (1) passing the gaseous combustion products from the furnace to and through a first cooled regenerator to heat the first regenerator and cool the gaseous combustion products, and injecting a stream of gaseous fuel into a recycle stream comprising the cooled gaseous combustion products in the first regenerator, to draw the recycle stream into the injected stream of gaseous fuel thereby forming a mixture of the gaseous fuel with the drawn-in gaseous combustion products and to propel the mixture into a second heated regenerator, and, in the second regenerator,reacting the gaseous combustion products and the fuel in the mixture in an endothermic reaction to form synthesis gas comprising hydrogen and CO, and passing the synthesis gas from the second regenerator to the furnace and burning it in the furnace, and (2) passing the gaseous combustion products from the furnace to and through a second cooled regenerator to heat the second regenerator and cool the gaseous combustion products, and injecting a gaseous fuel stream into a recycle stream comprising the cooled gaseous combustion products in the second regenerator, to entrain the recycle stream towards the injected gaseous fuel stream thereby forming a mixture of the gaseous fuel with the entrained gaseous combustion products and to propel the mixture towards a first heated regenerator, and, in the first regenerator,to react the gaseous combustion products and the fuel in the mixture in an endothermic reaction to form synthesis gas comprising hydrogen and CO, and to pass the synthesis gas from the first regenerator to the furnace and burn it in the furnace.

2. A method according to claim 1, characterized in that it further comprises, in step (B)(1), feeding additional gaseous fuel into the gaseous fuel mixture with entrained gaseous combustion products before the mixture is pumped into the second heated regenerator, and, in step (B)(2), feeding additional gaseous fuel into the gaseous fuel mixture with entrained gaseous combustion products before the mixture is pumped into the first heated regenerator.

3. A method according to claim 1, characterized in that in step (B)(1) the gaseous fuel stream is injected into the gaseous combustion products in a first chamber of a device having first and second chambers that are connected by a passage, and the mixture of gaseous fuel and gaseous combustion products is passed from the first chamber through the passage and through the second chamber to the second heated regenerator; and wherein in step (B)(2) the gaseous fuel stream is injected into the gaseous combustion products in the second chamber of the device and the mixture of gaseous fuel and gaseous combustion products is passed from the second chamber through the passage and through the first chamber to the first heated regenerator.

4. A method according to claim 3, characterized in that the first chamber is inside the first regenerator and the second chamber is inside the second regenerator, the first and second regenerators are separated by a wall that is in contact with the regenerators, and the passage between the first and second chambers passes through the wall.

5. A method according to claim 1, characterized in that at the end of step (B)(1) before step (B)(2) has commenced, the passage of gaseous fuel to the second regenerator is discontinued, and thereafter a mobile gas stream containing no gaseous fuel is injected into a recycle stream comprising the cooled gaseous combustion products in the first regenerator, to engulf the recycle stream in the injected mobile gas stream thereby forming a mixture of mobile gas with the engulfed gaseous combustion products and to propel the mixture towards a heated second regenerator, to purge gaseous fuel from the second regenerator;and wherein at the end of stage (B)(2) before stage (B)(1) has begun, the passage of gaseous fuel to the first regenerator is discontinued, and then a mobile gas stream containing no gaseous fuel is injected into a recycle stream comprising the cooled gaseous combustion products in the second regenerator, to engulf the recycle stream in the injected mobile gas stream, thereby forming a mixture of mobile gas with engulfed gaseous combustion products, and to propel the mixture to a heated first regenerator, to purge gaseous fuel from the first regenerator.

6. A method according to claim 5, characterized in that the mobile qas is selected from the group consisting of steam, air, recycled cooled combustion gas, and mixtures thereof.

7. A method according to claim 1, characterized in that the mass flow ratio of the entrained recycle stream to the gaseous fuel is between 0.5 and 30.

8. A method according to claim 2, characterized in that the mass flow rate of the additional fuel is greater than the mass flow rate of the gaseous fuel according to claim 1.

9. A method according to claim 5, characterized in that the ratio of the mass flow rate of the entrained recycle stream to the mass flow rate of the mobile gas stream is between 1 and 30.

10. A method according to claim 5, characterized in that the oxygen concentration in the mixture of the mobile gas with the entrained gaseous combustion products is less than 10% by volume on a wet basis.

11. A method according to claim 3, characterized in that the passage has a convergent-divergent section in the passage.