NO318619B1 - Device for combustion of a carbonaceous fuel, a method for operating said device, and use of said device. - Google Patents

Description

The present invention relates to a device for burning a carbon

containing fuel in a nitrogen-free atmosphere, a method for operating said device and use of said device.

The device can be integrated with a power plant (i.e. gas turbine(s)) to achieve an energy-efficient process for power production with reduced emissions of carbon dioxide and NOx into the atmosphere. In addition, the device can be integrated with a chemical plant that performs endothermic reactions.

Conventional combustion processes used for carbonaceous fuels will i

in addition to the production of the most important end products carbon dioxide and water (steam) also produce a good deal of heat (heat of combustion). A conventional combustion reaction between e.g. methane and oxygen will give approximately 804 kJ per moles of methane:

When this combustion process is integrated with e.g. a power plant (ie gas turbines) or a chemical plant that carries out endothermic reactions, it is crucial that the total energy loss in the combustion process is as low as possible.

Furthermore, due to the environmental aspects of CO2 and NOx, it is crucial that the emission of these components into the atmosphere is reduced significantly together

similar to conventional processes. Conventional combustion processes produce an exhaust gas with a C02 concentration of between 3 and 15% depending on the fuel and which combustion and heat recovery process is used.

The reason the concentration is so low is that the air contains approximately 78% nitrogen by volume. During combustion processes at high temperature in air, nitrogen will react with oxygen and form the environmentally harmful polluting gas NOx.

A reduction in the emission of carbon dioxide into the atmosphere makes it necessary either to separate the carbon dioxide from the exhaust gas or to raise the concentration in the exhaust gas to such a level that it is suitable for various chemical processes or for injection, e.g. in a geological formation for long-term disposal or to improve the recovery of oil from an oil reservoir.

From cold exhaust gas that is normally discharged at close to atmospheric pressure, C02 can be removed using several different separation processes, e.g. chemically active separation processes, physical absorption processes, absorption with molecular sieves, membrane separation and cryogenic techniques. Chemical absorption, for example with alkanolamines. is considered the most practical and economical method of separating C02 from the exhaust gas. These separation processes consume energy and require heavy and bulky equipment. In a power generation process, these separation processes will reduce the power yield by 10% or more.

It is possible to increase the concentration of the C02i exhaust gas from a combustion reaction to a level suitable for use in various chemical processes or for injection e.g. in a geological formation for long-term disposal or to improve the recovery of oil from an oil reservoir by burning the carbonaceous fuel with pure oxygen instead of air.

Commercial air separation methods (eg cryogenic separation or PSA (Pressure Swing Absorption)) for the production of pure oxygen require 250 to 300 kWh/tonne of oxygen produced. If one uses these methods to supply a combustion process with oxygen in a gas turbine cycle, they will reduce the net yield of energy from the gas turbine cycle by at least 20%. The cost of producing oxygen in a cryogenic unit will significantly increase the price of the electrical power produced and can be as much as 50% of the price of the electrical power.

However, a method that requires less energy than these separation methods is known from European Patent Application 658 367-A2. The patent application describes the use of a mixed conducting membrane (a Mixed Conducting Membrane (MCM)) integrated with a gas turbine system where the membrane separates oxygen from a heated air stream.

EP 170244 describes a method for generating net power in a combustion turbine as well as the production of an oxygen-enriched by-product.

EP 916386 describes a method for producing oxygen, nitrogen and/or carbon dioxide in combination with power generation.

EP 882486 deals with a combustion process where a compact electrolyte ion conducting membrane is used to achieve a more economical and less polluting process.

EP 213548 describes a method for producing oxygen and nitrogen in combination with heat recovery from a combustion process.

However, none of these publications deals with a device for an energy-efficient combustion of a carbon-containing fuel.

A mixed conductor membrane (MCM) is defined as a membrane made of materials with both ionic and electronic conductivity. The membrane transports oxygen selectively. The driving force through the membrane is proportional to the logarithmic ratio of the partial pressures of oxygen; log(p02(l)/p02(N)), where (I) is the side of the membrane where oxygen is delivered (from air), and (II) is the side of the membrane where oxygen is received. To keep the transport rate (flux) of oxygen high, it is important to keep a low partial pressure on the oxygen receiving side. Therefore, to further improve the efficiency of this membrane process, a carrier gas is used to reduce the partial pressure of oxygen on the oxygen receiving side of the membrane and thus increase the flux of oxygen through the membrane, e.g. as described in US 5562754 and NO-A-972632.

In order to achieve the practical use of mixed conductor membranes (MCM) when they are used as an oxygen supplier in a combustion process, the following criteria are essential: a) The driving force for the oxygen transport through the membrane, expressed as the logarithmic ratio between the oxygen pressures; log(p02(l)/p02(ll)), must

is kept high.

b) The membrane must operate at a high temperature (>600 °C) to achieve a sufficient oxygen flux through the membrane. Therefore, air or others must

gases that come into contact with the membrane have a high temperature.

To ensure that the driving force through the membrane is kept high, the oxygen on the receiving side of the membrane must: i) be transported away from the membrane surface by means of a carrier gas, or ii) be consumed by a chemical reaction (e.g. a combustion process) directly on

the oxygen receiving side.

This means that the device which is to carry out an energy-efficient combustion in a nitrogen-free atmosphere must be made to function under such process conditions as those mentioned above. Thus, there is a need for such a device which is not known before and a method which is not known before to operate such a device.

The main aim of the present invention was to provide a device which is effective for achieving the combustion of a carbonaceous fuel in a nitrogen-free atmosphere. Another object of the invention was to provide a device which is effective in achieving a combustion process which results in an exhaust gas with a high concentration of C02 and a low concentration of NCy

Furthermore, it was an aim of the invention to provide a method for operating said device.

A further aim of the invention was to provide a plant and a method for an energy-efficient power production.

Another aim of the invention was to provide a plant and a method for power production with reduced emissions of carbon dioxide and NOx into the atmosphere.

The inventors found that the described objectives were met by using a device where one or more mixing conductor membrane modules, one or more heat exchanger modules and one or more combustion chambers are enclosed in a hollow shell (a pressure chamber) defining a casing. The device can also be integrated with one or more gas turbines in a plant for power production. It can also be integrated with a chemical plant that performs an endothermic reaction to supply the reaction with the necessary heat.

The mixing conductor membrane(s) used in the device according to the present invention will, under such conditions as described above (in points a) and b)) transport oxygen from a gas that supplies oxygen (e.g. air) to a gas that receives oxygen. The gas receiving oxygen has a lower partial pressure of oxygen than the gas delivering oxygen. The gas receiving oxygen is added to a carbon-rich fuel (eg natural gas) and between the oxygen and the added fuel a combustion reaction takes place which produces heat.

Combustion of natural gas with pure oxygen produces an exhaust gas containing the two main products carbon dioxide and water (steam). According to the present invention, it is the exhaust gas that is used to receive oxygen. The oxygen-rich gas stream (ie the oxygen-enriched exhaust gas) is fed to the combustion chamber and used as an oxidizing agent in the combustion reaction. This avoids producing the environmentally harmful NCv gas.

The heat energy produced in the combustion reaction is used by means of one or more heat exchangers to heat the air supplied to the MCM module(s) as well as to heat deoxygenated air from the MCM module(s) before it can enter a power generation turbine or a chemical plant that performs an endothermic reaction.

In other words, the air flow that is fed to the membrane is heated without the production of C02 or NOxi flow. In the combustion reaction, almost all the oxygen is consumed, and thus the exhaust gas, which now has a very low partial pressure of oxygen, can be recycled to the MCM as a carrier gas that takes oxygen with it before it is led to the combustion chamber again. This means that we have a continuous combustion. From the exhaust, a drawdown stream must be taken to balance the added fuel and the received oxygen to prevent mass build-up. This drain flow, which is taken out of the device at high pressure and temperature, can also be fed to a power production system (turbine). In the turbine, the pressure in the discharge flow is lowered and it is cooled so that almost all the steam is condensed into water. This means that the gas flow will mainly consist of carbon dioxide. This carbon dioxide stream must be compressed to a pressure that makes it possible to inject it into an underground reservoir, a reservoir that can be an aquifer or a gas or oil reservoir. These reservoirs should be qualified to ensure long-term disposal.

As mentioned above, the exhaust gas is used as carrier gas to take up oxygen in the membrane module(s) and transport the oxygen to one or more combustion chambers where fuel is added. The heat produced in the exhaust gas must be transported to the air stream in an efficient manner, and in such a way that leakage between carrier gas and air is prevented or reduced to an acceptable level.

Furthermore, the inventors found that if they used a structure with many plates or channels as an MCM module, and/or as a heat exchanger module, it led to the device becoming very efficient. Structures with many channels have been found to be the most advantageous because they can be extruded in one piece (ie a monolith) and thus a large surface area is obtained on this one piece. Preferably, both the heat exchanger module(s) and the MCM modules are made of a ceramic material that can withstand the present process conditions (atmosphere, temperature and pressure).

Such structures, especially with channel diameters below 10 mm, provide a very high surface area/volume unit. If every other row of channels is made with inlet openings as described in US Patent 4271110, a simplified branching system is obtained to every other row of channels and thus a low probability of leakage between the air side and the oxygen receiving side.

In order to obtain the largest possible surface area for heat exchange and/or oxygen transport (when used as an MCM module) the channels should be very small and each of the air channels should be surrounded by (i.e. share walls with) the other gas (i.e. carrier gas /exhaust gas). Such a configuration needs a very complicated system to distribute the two gases (manifolding) to each neighboring channel.

According to the present invention, such monolithic structures with many channels are connected together in such a way that the MCM module is mounted between two heat exchanger modules. Furthermore, these modules are assembled in a pressure chamber which is hereafter defined as the reactor. Such a system will ensure that the MCM can operate at a defined temperature that is higher than the temperature of the air stream supplied to the system and below the combustion temperature (ie the temperature of the exhaust gas from the combustion chamber).

Another important feature of the present invention is the flow pattern for the two gas streams. The first gas flow (air flow) has a flow from inlet to outlet of the reactor that follows the direction of the channels in the monolithic structures (ie heat exchangers and MCM). This means that the gas enters and exits the open channels on the small end surfaces and flows through an open space or closed structure that binds these ends together. The second gas stream flows in and out of the side openings in the monolith, through bypass spaces or connections to the side hatch of the nearest monolithic structures. These bypass spaces surround the inner open space for the first gas.

Such a flow pattern for the gases will make it possible for one of the gases, here the other gas, to leak and fill all available space or "voids" in the reactor. The requirement for a gas-tight seal is then reduced for the first gas to only apply to sealing against the second gas (not against the "void" in the reactor) which is located in the internal connections between the monolithic structures.

This move is very important because a controlled leakage of . gas to build up and equalize the pressure inside the reactor vessel, and to avoid mixing, only one of the gases is allowed to leak. This controlled and necessary leakage makes it possible to use a flexible seal with a defined leakage rate for the diverting couplings for the other gas. Flexibility is very important to avoid heat stress in the connecting parts/monolithic structures and thus fatal cracks.

By filling the reactor with gas of almost the same pressure as the gas inside the monolithic channels, only the outer pressure shell of the reactor must withstand the absolute or total pressure of the process. The pressure against the monolithic walls is reduced to resist the pressure difference between the two gases (gas 1 and gas 2 on

Figure 3).

The scope of the invention and its special features are as defined in the accompanying patent claims.

The invention is further explained and illustrated with the following figures.

Figure 1 shows a sketch of an embodiment of the device according to the present invention including the functional parts such as heat exchanger module, MCM module and combustion chamber. Also included is a pressure booster, shown here as a jet ejector powered by high-pressure steam. In this version, all the modules are mounted inside the reactor. Figure 2 shows another embodiment of the device according to the present invention including the same functional parts such as heat exchanger module, MCM module as well as a combustion chamber and a pressure booster, but in this embodiment the combustion takes place in a separate vessel which is connected to the reactor. The pressure booster is mounted in the connecting pipes, preferably in front of the combustion chamber where the carrier gas has its lowest temperature. Figure 3 shows a sketch of a monolith structure with many channels used

as an MCM module and/or as a heat exchanger module.

Figure 4 shows an embodiment of the reactor with the various modules as well as the

other functional components of the reactor.

Figure 5 shows different forms of the connections between the MCM and heat exchanger modules and different methods used to seal the connections between the modules. Figure 6 shows an embodiment of the device according to the present invention where the combustion chamber is mounted outside the reactor as well as some of the internal components which have been removed from the reactor to better illustrate these individual components. Figure 7 shows a more detailed illustration of the entire device according to the present invention and the individual components of the reactor. Figure 8.1 shows an embodiment of a power plant where the device according to

present invention is integrated with gas turbines.

Figure 8.2 shows another embodiment of a power plant where the device according to the present invention is integrated with gas turbines and where more than one reactor has a common combustion chamber. Figure 9.1 shows an embodiment of the device according to the present invention where each process stream is provided with a number in accordance with Table 1.

Figure 9.2 illustrates which way the air flows through the reactor.

Figure 1 shows a schematic diagram of the device according to the present invention showing the process flows and the important process units (H-01), (X-01), (H-02), (F-01) and (1-01). The units are all mounted inside the reactor's pressure shell (casing, (RT)) which in this example is identical to the shell of the device. The figure shows that an oxygen-containing gas stream (here air) is passed through a compressor. The compressed air stream (AN-030) is passed on to the heat exchanger module (H-01) where it is heated (AN-050) before it is passed to the MCM module (X-01) where oxygen is separated from the air stream which thus becomes an oxygen-poor air stream (AL-010). The oxygen-poor air stream (AL-010) is fed to the heat exchanger (H-02) to be heated further before being fed out of the device (AL-020). The oxygen-poor air stream (AL-020) can be fed to a turbine for power generation or to a chemical plant that performs endothermic reactions. A carrier gas (EG-020) is fed to the MCM module (X-01), takes up oxygen at the oxygen receiving side of the membrane and is transported further through the heat exchanger module (H-01). The oxygen-enriched gas stream (EGO-030) is then compressed in a pressure intensifier (1-01) before being fed to the combustion chamber (F-01). The combustion chamber (F-01) where the fuel (NG-010) is added and burned is in this example mounted inside the reactor's pressure shell. The exhaust gas (EG-010) is now almost oxygen-free due to the combustion in (F-01).

Part of the hot combustion product or off-gas (EG-010) is taken out as a drain stream (EG-040) to prevent the accumulation of mass in the reactor, while the rest of the product gas is fed to the heat exchanger module (H-02) and heated to the operational the temperature of the membrane. In the membrane module, electricity (EG-020) acts as a carrier gas. The hot and oxygen-enriched carrier gas stream (EGO-020) is fed to the heat exchanger module (H-01) to heat the incoming gas stream (AN-030). The heated air stream (AN-050) is introduced into the MCM module (X-01) at the operating temperature of the MCM modules (X-01). A pressure intensifier (1-01) must be installed to improve circulation in the carrier gas loop and ensure continuous combustion. In Figure 1, this is a jet ejector which is operated by injecting steam under high pressure. Jet ejector has the advantage that it has no moving parts and can be built in a material (ie ceramic material) that can withstand very high temperatures. The oxygen-poor gas stream (AL-020) and the tapping stream (EG-040) can be fed to gas turbines for power generation.

Figure 2 shows another embodiment of the device according to the present invention where the pressure booster (1-01) and the combustion chamber (F-01) are mounted outside the reactor's pressure shell (RT), but inside the shell of the device. This feature helps to simplify the construction of the device. The advantage of mounting (1-01) and (F-01) outside the reactor is that maintenance work is simplified and that it becomes possible to use cooling equipment. Thus, a rotary pressure increasing machine can be used as a pressure intensifier (1-01) as shown in this figure. The flow pattern in this design is the same as in the design shown in Figure 1. The only difference is that high pressure (HP) steam is not injected (because no jet ejector is used), but this will not change the principle flow pattern. Injection of high pressure steam (HP) as shown in Figure 1 will reduce the net efficiency of power production in the process, and therefore a rotary machine as shown in Figure 2 is more beneficial for efficiency.

An external combustion chamber will also simplify the fuel injection system (NG-010) and make it easier to scale up the device as shown in Figure 8.

Figure 3 shows a monolithic structure with many channels which, according to the present invention, can advantageously be used both as a heat exchanger module and a membrane module. As mentioned above, such structures are advantageous mainly because of the ease with which they can be manufactured. But the present invention is not limited to the use of only such structures, and other configurations (e.g. plates) may be an alternative.

According to Figure 3, with the same names of the flows as in Figures 1 and 9, gas 1 represents the gas flows (AN-030) and (AN-050) if the monolith structure is module (H-01), the gas flows (AN-050 ) and (AL-010) if the monolith structure is module (X-01). If the monolith structure is module (H-02), gas 1 is the gas streams (AI-010) and (AI-020).

Gas 2 represents the gas streams (EGO-020) and. (EGO-030) if the module is (H-01), the gas flows (EG-030) and (EGO-010/020) if the module is (X-01) and the gas flows (EG-020) and (EG-030) if the module is (H-02).

Gas 1 follows the straight path through the channels and is therefore always led in and out through the open rows of channels at the ends of the monolith. Gas 2, normally the carrier gas, is always fed in and taken out through the openings in the side wall of the monolith structures. Since these monolithic structures are preferably made by extrusion, all the channels will have the same length. The inlet and outlet openings for gas 2 must be made after the extrusion by machining every second column of channels as visualized in the figure. After processing down to the preferred depth, the open rows of channels (created during processing) must be closed with a seal in such a way that a sufficient opening area for the side hatch (inlet and outlet for gas 2) is retained.

The problem of preventing leakage in the distribution system for two different gases fed into and out of the monoliths with many channels is reduced to a minimum by making these inlet and outlet openings as described below and as shown in

Figure 3.

According to the present invention, the channels have a diameter of less than 10 mm. A diameter of between 1 and 8 mm is preferred. Figure 4 shows an embodiment of the reactor as described under Figure 2, where the combustion chamber and the pressure booster are mounted outside the reactor casing. The figure shows the connection flanges on the inlet (EG) and outlet (EGO) for the carrier gas flow as well as the inlet (AN) for the air flow and the outlet (AL) for the oxygen-poor air flow. Inside the reactor, the direction of these currents is visualized with dashed lines. The heat exchanger (H-01), the MCM module (X-01) and the heat exchanger (H-02) are fixed together with the connections between (H-01), (X-01) and (H-02). These connections are preferably glass-sealed before they are mounted in the reactor, to ensure against leakage, and will thus be in one piece (ie tightly joined). During heating, this entire part must be able to expand. This is described in more detail under Figure 7. Figure 5 shows alternative shapes for the connections between (X-01) and (H-01/H-02). (H-01) and (X-01) as well as (X-01) and (H-02) can therefore be closely connected to each other with different components as shown in the figure. The most important factor is to have a good seal without leakage between the inner gas (i.e. gas 1 as described under Figure 3, preferably air) and the outer gas (i.e. gas 2 as described under

Figure 3, preferably carrier gas).

Figure 6 shows an embodiment of the device according to the illustration in Figure 2, where both the combustion chamber (F-01) and the pressure booster (1-01) are mounted outside the reactor. Fuel (NG) is injected into the low-temperature zone in front of the intake of (1-01) to ensure good mixing with the oxygen-enriched carrier gas (EGO) before it is introduced into the combustion chamber (F-01). Due to too low a temperature, the combustion can be improved, at least partially, with a catalyst. The carrier gas stream (EGO) from (H-01) is cooled by the air stream (AN) and has its lowest temperature before (1-01). The pressure in the flow (EGO) is increased by means of (1-01) before it is fed into the combustion chamber (F-01) outside the reactor. In (F-01), the oxygen in the stream (EGO) reacts with the added fuel, and combustion occurs. In combustion, almost all oxygen is consumed. Thus, the exhaust gas (EG), which mainly contains the reaction products C02 and H20, will have a low content of oxygen. (EG) is fed into the second heat exchanger (H-02), where it heats up the oxygen-poor air stream (AL) from the reactor.

(EG) will thus be cooled slightly by (AL) in (H-02) before it is fed into the membrane module(s) (X-01). In (X-01), (EG) acts as a carrier gas and takes up oxygen that is transported through the membrane wall from the air side. The oxygen-enriched carrier gas leaving (X-01), now labeled (EGO), is then fed into the first heat exchanger (H-01) where the air stream (AN) is heated and the stream (EGO) is cooled. In other words, a cooled oxygen-containing carrier gas (EGO) now returns via (1-01) to (F-01) and you thus get a combustion/carrier gas loop that is favorable for continuous combustion.

Either from the oxygen-enriched carrier gas (EGO) or from the exhaust gas (EG), a bleed-off gas must be taken out to prevent the accumulation of mass in the carrier gas loop due to the transport of oxygen from the air and the addition of fuel. An example of an outlet for the tapping gas is shown in Figures 8.1 and 9.1.

Some of the individual components of the reactor are also shown in Figure 6.

Figure 7 shows a more detailed embodiment of the device according to the present invention.

The reactor's pressure chamber 1 contains the low-temperature heat exchanger 9, the high-temperature heat exchanger 19 and the MCM modules 15. Thus, all other parts are built around these units 9, 15 and 19, which ensures good heat transport (from carrier gas/exhaust gas to air) and oxygen transport (from air to carrier gas). Parts 8, 14 and 18 are used to create a round shape at the outer wall of the heat exchangers and MCM modules to ensure a less complicated seal. These parts can also be made with channels in such a way that they can be used as heat exchangers 8 and 18 or as MCM modules 14. The individual parts 10, 11, 12 and 13 will fit together and form the link between the low temperature heat exchanger 9 and the MCM modules 15 as shown in Figure 5.3. In the same way, the individual parts 16, 17, 20 and 21 form the connection between the MCM modules 15 and the high-temperature heat exchanger 19. The connection part 11 will preferably be glass-sealed to 9 and 15 at both ends, and part 21 in turn will be glass-sealed to 15 and 19. So the thermal expansion for the material in 11 must match both 9 and 15, and correspondingly the thermal expansion for the material in 21 must match 15 and 19. An alternative is to extrude these connecting parts 11 and 21 with a gradual change in composition of the material so that the material at the end of 11 which is connected to 9 fits together with this mhp. thermal expansion, while the other end of 11 fits together with 14. Similarly, 21 could also be made in such a way that the thermal expansion fits together with the material in both 15 and 19 to avoid cracks. Also, the plenum air intake chamber, unit 7, could be glass sealed to the low temperature heat exchanger 9 to ensure minimal leakage. So the thermal expansion for the material in 7 must also match 9. In the same way, outlet plenum 23 for oxygen-poor tufted glass can be sealed to 18 and 19, and thus 23 must be made of a material that matches 18 and 19 mhp. thermal expansion. Part 7 is made at the inlet end (incoming air) of a round shape (pipe) so that it can more easily fit into a flexible seal 5. The same is also done for the outlet plenum 23 (for the oxygen-poor warm air). Here too, in the same way as with the inlet, a ring seal 24 is shown. For a vertical orientation as shown in Figure 7, a lower flexible seal may be unnecessary. This end could be fixed and the thermal expansion could occur at the upper end due to the flexibility of the seal 5. Thus, a seal must be used in at least one end which allows expansion in the longitudinal direction. In the present invention, this is solved by designing the inlet and/or outlet connections 4 and 25 in a round shape (pipe end). This makes it easier to achieve a flexible seal. The flexible sealing rings 5 and 24 must be made of a temperature-resistant material (ceramic or metal). Other flexible "pipe" sealing systems can also be used.

The inlet and outlet pipes 4 and 25 can have the same shape to simplify fabrication. The inlet pipe 4 leads the air flow to the plenum inlet which is formed by 7 and is made so that flexible seals 5 can be fitted. The inlet pipe 4 is preferably made of a material which also functions as a heat barrier or lining between the hot inlet air and the outer metal pipe which is connected to the pressure chamber casing. This is particularly important for the outlet pipe 25 at the hot end. The figure also shows parts 6 and 22, which act as a heat barrier or liner between the combustion/carrier gas and the pressure chamber's metallic inlet/outlet pipes with connecting flanges.

The figure also shows the heat barrier and insulation 3 between the hot internal parts and the outer metal wall or casing of the pressure chamber. By keeping the temperature low (<500 °C) in the outer pressure jacket, heat loss can be reduced and make it possible to make the pressure jacket from a common material (ie carbon steel). By lowering the temperature, the thickness of the wall is also reduced and thus also the total weight of the device. This is important for offshore installations.

The parts 3 are also made in such a shape and in such a material that they can function as support for the inner parts. 2 is a layer of flexible material between the inner wall (pressure jacket) and 3 allows some movement caused by thermal expansion. Figure 8.1 shows an embodiment of the device according to the present invention where the device is integrated with gas turbines. Figure 8.2 shows another design that integrates the reactor with gas turbines where more than one reactor has a common combustion chamber.

According to the present invention, one or more reactor units can be connected together and share a common combustion chamber as shown in Figure 8.1. This will make it possible to produce a high number of reactors of standard size and provides a cost-effective production by increasing the total power yield (scaling up) by integrating or connecting reactors of standard size as shown in Figure 8.2. If, for example, the individual device in the plant shown in Figure 8.1 produces 10 MW of power and the plant shown in Figure 8.2 has 6 reactors of the same size as a standard single reactor, the plant will produce approximately 60 MW.

Figure 8.1 shows two different options for extracting the tapping current. One alternative (alt. 1) is to take a drain stream from the cold part of the carrier gas loop. The drain stream will have a temperature that makes it possible to send it directly to a steam turbine. The tapping stream which is withdrawn as shown under alternative 1 contains oxygen, and this process stream can thus be used for further heat production in a nitrogen-free atmosphere and also as a heat source in an endothermic process. In alternative two (alt. 2), a drain stream is taken out after combustion, and this is therefore almost oxygen-free and has a high temperature. If a steam turbine is used to improve power production from this flow, the temperature must be lowered, e.g. by injecting water. The draining stream can be withdrawn anywhere in the carrier gas loop. Figure 8.1 also shows that the inlet pipe for air (from compressor to reactor) is longer than the outlet pipe for oxygen-poor air (from reactor to turbine). This has been found to be advantageous due to the higher temperature in the oxygen-poor outlet air stream compared to the inlet stream.

Figure 9.1 shows the device according to the present invention with the direction of flow drawn for the different gas streams. The figure shows that an oxygen-containing gas stream (AN-030), preferably a compressed air stream, is fed to the heat exchanger module (H-01) where it is heated before being fed on to the MCM module (X-01). Oxygen is transported through the membrane wall and taken up by the carrier gas stream (EG-030). An oxygen-enriched carrier gas stream exits the module (X-01), and is now called (EGO-010).

Part of the fuel, (NG-030), is mixed with the stream (EGO-010) in an additional combustion chamber (F-02) located between (X-01) and (H-01), where the heat produced in this the combustion is fed to the heat exchanger (H-01) to heat the incoming air. It must be emphasized that the present invention will work without this combustion chamber (F-02) as explained under Figure 6. In this embodiment, the carrier gas flow (EGO-020) when it enters the heat exchanger (H-01) will have a slightly higher temperature than the flow ( EGO-010) and slightly less oxygen content. The carrier gas stream (EGO-020) is then fed to the heat exchanger (H-01) to heat the incoming air to the MCM module (X-01). The carrier gas stream (EGO-030) from (H-01) is now at its lowest temperature and is led to the main combustion chamber (F-01) outside the reactor where most of the fuel (NG-.020) is burned. A pressure intensifier (1-01) is mounted near the inlet to the main combustion chamber (F-01). The pressure difference between EGO-030 to EGO-040, which is increased by the pressure booster (1-01), is used to ensure circulation in the carrier gas/exhaust gas loop.

Part of the hot exhaust gas (EG-040) is withdrawn as a drain stream to prevent the accumulation of mass in the combustion/carrier gas loop. In principle, the drain current (EG-040) can be withdrawn anywhere in the carrier gas loop. For example, it can be taken out at the cold end, from (EGO-030), and sent directly to a steam turbine. The exhaust gas (EG-020) is passed through the high temperature heat exchanger (H-02) to the membrane module (X-01). (EG-030) acts as carrier gas and takes up oxygen that is transported through the membrane from the air side and transports it further to the combustion chamber. So you get a closed loop with continuous combustion of a carbon-rich fuel with 02 in a C02- and H20-rich atmosphere.

Figure 9.2 shows how the plenum inlet and outlet 7 and 23 and the heat exchangers (H-01) and (H-02) and the MCM module (X-01) can be built in a sealed unit. This serves to illustrate an important feature of the present invention, namely the direction or paths of the two main flows of air and carrier gas which help to reduce the leakage between the air and carrier gas flow to a minimum. The air flow flows in a straight line and goes directly through the internal closed spaces between the heat exchanger (H-01) and (H-02) and the MCM module (X-01), while the carrier gas flow goes in and out of the open side hatches in (H- 01), (X-01) and (H-02). To ensure that the pressure builds up inside the reactor, the carrier gas should be allowed to fill the void in the reactor. This will ensure that only the outer reactor casings need to be designed to withstand the total pressure of the process.

Another advantage would be to have a low pressure difference (<5 bar) between the air side and the carrier gas side, preferably with somewhat higher pressure on the carrier gas side. This will ensure,

in the event of a leak between the air stream and the carrier gas stream, that the leakage path will be from the carrier gas side (C02 and H20) to the air side. This will be less harmful than if the air leaks into the combustion loop (the carrier gas), especially from an environmental point of view. If nitrogen (air) leaks into the combustion (carrier gas loop) it can lead to the production of NOx gas.

In addition, a smaller pressure difference between the air and carrier gas side will make it possible to construct the device with thinner walls in the monoliths, which provides better heat transport and oxygen transport (X-01 only). This will also lead to lower weight.

Table 1 below gives examples of data for the process streams with ta.lt designations in accordance with Figure 9.1. Characteristics of the air flow at intake: 20 bar, 450 °C and 79 kg/s. The oxygen transport through the membrane is 6.12 kg/s (the installed membrane area corresponds to this). Fuel is added in quantities that are adapted to the stoichiometry of the combustion reaction.

Claims (15)

1. A device for burning a carbonaceous fuel in a nitrogen-free atmosphere, characterized by said device comprises a hollow shell (RT) with an inlet for transporting said fuel (NG-010), an inlet for transporting a compressed oxygen-containing gas stream (AN-030), an outlet for withdrawing an oxygen-poor gas stream (AL-020 ) and an outlet for discharge of a drain current (EG-040); and said shell encloses one or more heat exchanger modules (H-01, H-02) arranged to heat the incoming compressed oxygen-containing gas stream; one or more mixing conductor membranes (X-01) arranged to separate oxygen from said oxygen-containing gas stream, resulting in an oxygen-rich gas stream and said oxygen-poor gas stream; a first and optionally a second combustion chamber (F-01, F-02) for burning said fuel with an inlet connected to said fuel inlet (NG-010) to convey fuel to said chamber, an inlet (EGO-040) connected to said heat exchanger module(s) to convey hot, oxygen-rich gas (EGO-030) to said chamber and an outlet (EG-010) connected to said membrane module(s) to convey exhaust gas (EG-020) from the combustion chamber to the membrane module ; a pressure booster (1-01) installed in front of the first combustion chamber; means (11, 21) for connecting said heat exchanger module(s) and membrane module(s); means (7, 23) for connecting said heat exchanger module(s) and said membrane module(s) to the inlet for the compressed oxygen-containing gas stream and the outlet for the oxygen-poor gas stream as well as means for conveying part of said exhaust gas stream (EG-020) directly to said heat exchanger module(s) and back to said inlet from the combustion chamber. 2. A device according to claim 1, characterized by said heat exchanger module(s) (H-01, H-02), said membrane module(s) (X-01), said means (7, 11, 21, 23), an outlet for said hot oxygen-rich gas stream (EGO-030) , said outlet for the withdrawn oxygen-poor gas stream (AL-020), an inlet for said exhaust gas and said inlet for compressed oxygen-containing gas stream (AN-030) are all installed in a pressure vessel (reactor). 3. Device according to claim 1, characterized by said heat exchanger module(s) (H-01, H-02), said membrane module(s) (X-01), said second combustion chamber (F-02), said means (7, 11, 21, 23), an outlet for said warm oxygen-rich gas stream (EGO-030), said outlet for withdrawn oxygen-poor gas stream (AL-020), an inlet for said exhaust gas and said inlet for compressed oxygen-containing gas stream (AN-030) are all installed in a pressure vessel. 4. Device according to claim 1, characterized by said modules and said second combustion chamber are interconnected vertically, one above the other. 5. Device according to claim 1, characterized by said modules are interconnected vertically, one above the other. 6. Device according to claim 1, characterized by said membrane module is installed between two heat exchanger modules. 7. Device according to claim 1, characterized by said second combustion chamber is installed between one of the heat exchanger modules and a membrane module. 8. Device according to claims 2 and 3, characterized by said outlet for said hot oxygen-rich gas stream (EGO-030) is connected to the inlet of the first combustion chamber (EGO-040) and said inlet for said exhaust gas is connected to the outlet from the first combustion chamber. 9. A device according to claim 1, characterized by . said pressure booster (1-01) is a fan or a compressor. 10. Device according to claim 1, characterized by said heat exchanger module(s) (H-01, H-02) and said membrane module(s) (X-01) comprise a monolithic structure with many channels. 11. Procedure for operating a device as specified in claims 1 to 10, characterized in that said method includes the following steps: a compressed oxygen-containing gas stream is fed to a first heat exchanger module where it is heated by means of heat generated by burning a fuel in a combustion chamber; said heated gas stream is fed to a mixing conductor membrane(s) where most of the oxygen is separated from said gas stream and an oxygen-poor gas stream is obtained; a carrier gas is fed into said membrane module to absorb the oxygen, and the oxygen-enriched carrier gas is further fed to a pressure booster; the compressed carrier gas stream is fed into the combustion chamber where it is mixed with a fuel for combustion; and said oxygen-poor gas stream is fed to another heat exchanger module for further heating before it is discharged from said device. 12. Procedure according to claim 11, characterized by said combustion product (the exhaust gas) is used as carrier gas. 13. Procedure according to claim 11, characterized by part of the exhaust gas is taken out as a drain stream to prevent the accumulation of mass in the device. 14. Use of a device and a method according to claims 1-13 in a plant for power generation. 15. Use of a device and a method according to claims 1-13 in a chemical plant that performs an endothermic reaction