Method and apparatus for cracking hydrocarbon gases

Abstract

A method for cracking hydrocarbon gas, wherein the hydrocarbon gas is passed through the flow path of an absorptive receiver reactor (1, 30, 40), characterized in that cracking occurs during passage through the receiver reactor (1, 30, 40), wherein the hydrocarbon gas is heated to its cracking temperature in a first region (21) of the flow path (2), heated to above the cracking temperature in an adjacent second downstream flow region (22), and further heated in a third further downstream region (23) of the flow path and in physical contact with a reaction accelerator across the cross section of said region, after which a product stream is discharged from the receiver reactor (1, 30, 40) downstream of the reaction accelerator, and wherein the hydrocarbon gas is heated to above its cracking temperature by absorbing black body radiation (20) which is released to the hydrocarbon gas flowing thereto by the reaction accelerator heated by solar radiation (7) incident thereon, so that the hydrocarbon gas extending in the flow path (2) to the reaction accelerator forms disk-shaped temperature zones (60 to 67) each having increasing temperatures arranged one after the other and extending transversely to the flow path (2).

Description

[0001] The invention relates to a method for cracking hydrocarbon gases, in particular methane, according to the generic concept of claim 1 and a receiver reactor for carrying out this method according to the generic concepts of claims 18, 21 and 23, and the use of a solid-state heat storage according to claim 34.

[0002] The cracking of hydrocarbon gases such as methane, ethane, propane or even butane is usually carried out on an industrial scale, with the cracking of methane in particular being considered as a possible technology for the future, since the reaction CH4->C + 2 H2 takes place in the absence of oxygen and therefore does not release CO2 emissions. The generated hydrogen serves as an energy carrier, while the carbon is used industrially to manufacture products such as industrial carbon black, graphite, diamond, carbon fibers, conductive plastics or tires.

[0003] To date, there are no known industrially available and economically viable methods for cracking methane using solar energy. The difficulty in this regard is the high temperatures required, from about 500°C to about 1200°C at ambient pressure. At 500°C (hereinafter referred to as the cracking temperature), less than 50% of the methane is dissociated at equilibrium, and at 1200°C the dissociation is complete, but only after a long (theoretically infinite) time. At increased operating pressures, higher temperatures are required to achieve the same equilibrium state, i.e., to convert a similar percentage of methane. In general, the reaction is energy-intensive, slow and difficult to manage; in addition, carbon is released in the form of free nanoparticles, i.e., soot.

[0004] WO 2018 / 205043 discloses a solar receiver, in which a fluid for transporting heat so that the heat can be used in a downstream industrial process passes through an absorption chamber of the receiver and can be heated therein by the blackbody radiation of an absorber in the receiver, i.e., by infrared radiation absorption to the required process heat, wherein in addition to CO2, water vapor, SO2, SO3, NO, NO2 and HCl, methane is also considered to be a suitable heat carrier for transporting heat to consumers due to its properties as an infrared absorbing gas.

[0005] In US Pat. No. 7,140,181, the use of solar reactors for endothermic reactions such as gas cracking is proposed, wherein the production of CO as a synthesis gas component from CO2 is described with the aid of a specially designed receiver reactor. In such a receiver reactor, ceramic rods for generating the required high temperatures are arranged in a tunnel. Another variant of the receiver reactor is generally described as an ellipsoidal "cavity reactor", in which, in order to achieve a high thermal efficiency, the gas to be dissociated is preheated absorptively and then heated to the dissociation temperature by convection over the entire large area of ​​the reactor wall provided by the ellipsoid.

[0006] Accordingly, it is an object of the present invention to provide a solar method for methane cracking and a receiver reactor for methane cracking.

[0007] This object is achieved by a method having the features of claim 1 and by a receiver reactor having the features of claims 18 , 21 and 23 and also by the use of a layered solid-state heat storage according to claim 34 .

[0008] Since the hydrocarbon gas or methane forms a disk-shaped temperature zone transverse to the flow path in the receiver reactor and thus a predetermined specific temperature stratification with the same temperature level in the individual layers, the methane is continuously heated in the direction of the reaction accelerator without forming or obtaining cold zones or overheated zones that adversely affect the degree of dissociation, so that the entire methane stream is gradually heated to the desired reaction temperature. By bringing the methane into contact with the physical reaction accelerator, the reaction rate is increased so that a substantially complete reaction is achieved in the receiver reactor passing through. By heating the methane by absorption to above its cracking temperature and far above its cracking temperature, a particularly efficient thermochemical process is obtained, wherein the cracking reaction can then be initiated relatively suddenly in the reaction accelerator up to the equilibrium temperature for complete dissociation (and higher), wherein all these advantages are achieved in a receiver reactor of simple construction and with low maintenance requirements.

[0009] Since the receiver reactor can be operated alternately with a reducible gas, even when the receiver reactor is undergoing maintenance with regard to carbon deposits, synthesis gas can be produced which can likewise be used on an industrial scale for the synthetic production of fuels.

[0010] Since the receiver reactor has a device for generating seeds in the absorber region, the fixedly mounted absorber can be replaced by a seed cloud, with the advantage that a carbon deposit is formed on the seeds and carbon and hydrogen are thus discharged directly from the receiver reactor via the seeds with the product stream, so that no maintenance is required in this respect with regard to the carbon deposits and the overall maintenance requirements are correspondingly reduced.

[0011] Since the receiver reactor is equipped with replaceable absorber elements, elements whose function is impaired due to carbon deposits can be swapped out and cleaned or replaced individually even during operation, for example while operation is ongoing or at only brief stops in operation.

[0012] The use of a layered solid-state heat storage for cracking hydrocarbon gases provides another simple and cost-effective possibility of allowing the cracking to continue operating overnight, wherein the heat required for this is preferably supplied to the heat storage used as heat storage reactor during daytime operation via a receiver reactor.

[0013] Further preferred embodiments have the features of the dependent claims.

[0014] The present invention is described in more detail hereinafter with reference to the accompanying drawings.

[0015] in:

[0016] Figure 1a A schematic diagram showing a longitudinal section of a receiver reactor designed according to a first embodiment of the invention,

[0017] Figure 1b Shows the radiant intensity of solar radiation compared to the radiant intensity of a black body at 1500 K,

[0018] Figure 2 A schematic diagram showing a longitudinal section of a receiver reactor designed according to a second embodiment of the invention,

[0019] Figure 3a A schematic diagram showing a longitudinal section of a receiver reactor designed according to a third embodiment of the invention,

[0020] Figure 3b show Figure 3a Schematic diagram of a longitudinal section of a receiver reactor of , wherein the section is offset by 90 degrees,

[0021] Figure 4 Displayed together with a diagram of the temperature distribution during operation of the receiver reactor Figure 3b A schematic diagram of the longitudinal section of

[0022] Figure 5 A schematic diagram showing another embodiment of a receiver reactor having improved feed channels,

[0023] Figure 6 Display according to Figure 5 is a schematic diagram of an embodiment of a receiver reactor,

[0024] Figure 7 Display according to Figure 5 A view of an embodiment of a receiver reactor in a horizontal operating position,

[0025] Figure 8 show Figure 7 The cross section of the annular space of the receiver,

[0026] Fig. 9 Show from Figure 8 The enlarged details,

[0027] Fig.10 Display according to the simulation Figures 6 to 9 The temperature distribution in the receiver,

[0028] Fig.11 Displays the absorption rate of pure methane and CO2,

[0029] Fig.12a A schematic diagram showing one embodiment of an arrangement according to the invention for heat recovery after cracking is completed,

[0030] Figure 12b a schematic diagram showing an arrangement for continued cracking using recovered heat, and

[0031] Fig.13 Schematic diagram showing an extended arrangement for recovering heat with continued cracking.

[0032] Figure 1a A longitudinal section of an absorptive receiver reactor 1 according to a first embodiment is shown, which has a flow channel 2 - cylindrical in the embodiment shown - for the process gas indicated by arrows 3, 4 to pass therethrough, which leads from an opening 6 for solar radiation 7 closed by a window 5 to an outlet 8 of the receiver reactor 1. The solar radiation 7 falls through the opening 6 onto the absorber region 9 of the receiver reactor 1, which is therefore located in the path of the incident solar radiation (wherein any radiation reflected by the side wall 13 also reaches the absorber region 9), in which the absorber 10 is arranged in the embodiment shown. The absorber 10 is formed by individual absorber panels 11 connected to one another via struts 12 and suspended in the flow channel 2. The absorber panels 11 are arranged so that they are located opposite the opening 6, so that the entire dimension of the absorber 10 is irradiated during operation by the solar radiation 7 falling directly thereon. The panels 11 are also arranged offset relative to one another, so that process gas and process products can easily flow through between the absorber panels 11 - the process gas can flow through the absorber region 9 and the absorber 10. Another configuration of the absorber 10 is also conceivable, for example one or two perforated plates one behind the other and in this case offset relative to one another. Finally, it is conceivable that the absorber is formed by the rear wall 10' of the receiver reactor 1 itself, wherein in this case only one outlet 8 or a plurality of outlet channels are provided. A person skilled in the art can construct the absorber or the rear wall designed as absorber appropriately for the specific case.

[0033] In operation, hydrocarbon gas, such as methane, is fed as process gas via supply line 15 into the receiver reactor 1, preferably (but not necessarily) preheated in a heat exchanger 16 and conveyed via conveying line 17 to an annular pipe 18 arranged at the opening 6, from where it is discharged into the flow channel 2 via a feed channel 19, as indicated by arrow 4. The absorber 10, which has been heated by solar radiation 7, emits black body radiation in the infrared range, as indicated by arrow 20 (in this regard, see Figure 1b description).

[0034] The process gas, in this case methane, which flows in the flow channel according to the arrow 3 is extremely transparent to the solar radiation 7, but absorbs the blackbody radiation 20 and is therefore heated absorptively. It should be pointed out here that for the sake of simplicity, the invention will hereinafter be described only with regard to methane, but other hydrocarbon gases can also be cracked according to the invention and methane therefore represents only a (no doubt very important) example of these hydrocarbon gases. A person skilled in the art can now adjust the flow rate of the methane together with the dimensions of the flow channel 2 and the radiation intensity of the absorber 10 so that the methane is heated to its cracking temperature in a first region 21 of the flow channel 2 on its way to the absorber 10, to above the cracking temperature in an adjacent second downstream flow region 22 and still further heated in a third, further downstream flow region 23 of the flow channel 2, wherein the third flow region 23 corresponds to the absorber zone 9. For the definition of the cracking temperature used here, see above and Figure 4 Description.

[0035] In the third flow region 23 or absorber zone 9, the methane is in physical contact with the absorber 10 over the cross section of the flow channel 2, which, due to this physical contact, acts as a reaction accelerator for the dissociation of methane, i.e. a reaction accelerator which simultaneously has the function of an absorber in the receiver. In this case, any convective heat transfer from the reaction accelerator designed as absorber 10 is secondary to the dissociation of the methane. As a result, the methane is relatively suddenly dissociated or cracked by this physical contact, so that a product stream containing carbon nanoparticles and hydrogen, i.e. carbon black and hydrogen, is formed in the fourth region 24 after the absorber zone 9. This stream is discharged from the receiver reactor 1 via the outlet 8 after heat has been extracted from it in the heat exchanger 16.

[0036] Since the formation of carbon nanoparticles (carbon black) already begins initially in the first region and increases slowly in the second region, a certain proportion of the nanoparticles may be deposited on the absorber 10, in this case on the absorber panel 11, and adhere thereto as a soot layer. This is not critical for the continued cracking of the freshly supplied methane, since the carbon or soot has the preferred properties of the absorber material: it is black, i.e. highly absorbs the incident solar radiation 7, it emits the desired (infrared) blackbody radiation after heating, and it is heat-resistant in the range of well over 2000° C. However, as the deposits increase, the geometry of the absorber 10 also changes with respect to its flow-through properties to such an extent that the cracking is adversely affected. The deposits must then be appropriately removed by (periodic) maintenance steps.

[0037] In the case of the embodiment shown, this is achieved by introducing the second process gas into the reactor receiver 1 via the second supply line 14 via the second transfer line 25, feeding into the second annular pipe 26 and from there, as indicated by the arrow 4, discharging into the flow channel 2 via the second feed channel 27. The second process gas is preferably a reducible or oxidizing gas, such as CO2, or particularly preferably water vapor (or a mixture thereof), which is absorptively heated in the first region 21 and the second region 22 and then chemically reacts with the carbon deposited on the absorber 10 in the absorber zone 9 according to the equation H2O + C ->CO + H2. Below, water vapor is used in this description as an example of a reducible or oxidizing gas, regardless of whether CO2 or even another carbon-oxidizing gas or gas mixture can also be used in the specific case. In other words, the receiver reactor is now also produced even during maintenance, and produces synthesis gas as a starting material for synthetic fuels. In each case, the hydrogen production is not interrupted, wherein the carbon monoxide can be used, for example, by the Fischer-Tropsch synthesis to produce methanol or other liquid hydrocarbons through the unmodified use of hydrogen (different from cracking).

[0038] A receiver reactor is created for the cracking of hydrocarbon gases, in particular methane, which has an opening 6 for solar radiation 7, and a flow channel 2 for the methane to be cracked to flow through the receiver reactor 1, and an absorber zone 9 arranged in the path of the incident solar radiation 7, designed to absorb the solar radiation and to emit black body radiation upstream into the flow channel during operation, wherein the absorber zone 9 is arranged and designed so that it is located opposite the opening 6 for solar radiation 7 and is irradiated with its entire dimensions directly incident on it during operation, and through which methane can flow, wherein supply line sections (14, 15) for hydrocarbon gas and for carbon oxidation gas (preferably water vapor) are provided, which lines can be switched so that the receiver reactor (1, 30, 40) can be operated alternately with hydrocarbon gas and reducible gas. Of course, the person skilled in the art can also construct the conveyor line 17 or 25 so that the respective conveyor line 17, 25 can be operated successively with the two process gases, which thus makes the other conveyor line redundant. According to FIG. 1 , two line arrangements ( 18 , 19 and 25 , 26 ) are preferably provided which open independently of one another into the flow channel 2 .

[0039] It is further derived that the reducible gas is passed through the receiver reactor periodically instead of the hydrocarbon gas or methane, so that the soot deposited in the flow channel 2, in particular in the absorber zone 9, is removed during the oxidation cycle by chemical reaction with the reducible gas. As mentioned above, it is preferred to use, for example, CO2 and / or water vapor as the reducible gas so that the receiver reactor produces synthesis gas in the oxidation cycle and correspondingly produces carbon black and hydrogen by cracking in the hydrocarbon cycle.

[0040] Figure 1bA diagram 150 is shown, on whose horizontal axis the wavelength in μm is plotted in the range of 0 μm to 6 μm, and on whose vertical axis the electromagnetic radiation in W / m 2 Curve 151 shows the solar spectrum as it exists on the Earth's surface, i.e. the solar radiation after it has passed through the Earth's atmosphere, and curve 152 shows the spectrum of a black body at 1500°K.

[0041] In the receiver reactor according to the invention, the solar radiation 7 reaches the absorber 10 essentially with a spectrum according to curve 151, since the process gas used in the receiver reactor according to the invention, for example methane, is essentially transparent for this spectrum. As explained above, the absorber 10 therefore absorbs the solar radiation and is heated accordingly, for example to 1500° K or more. With increasing temperature, the absorber 10 itself emits radiation, but in a changed frequency range, so that the process gas used is now no longer transparent for this emitted blackbody radiation - it is absorbed by the process gas and heated accordingly. It should also be pointed out that curve 152 corresponds to the emission of an ideal blackbody, and that the real absorber 10 therefore only approximately follows the spectrum according to curve 152. Likewise, the process gas used (hydrocarbon gas) does not completely absorb the real spectrum emitted by the absorber 10, but is sufficient for the process gas to be heated by this greenhouse effect for cracking according to the invention (in this regard, also see Fig.11 ).

[0042] Figure 2 A schematic diagram of a longitudinal section of a receiver reactor 30 according to a second embodiment of the invention is shown. Unlike the receiver reactor of FIG. 1 , the absorber zone 9 does not have a fixedly mounted absorber, but rather has a device 31 for generating a cloud of seeds 32 which, when in physical contact with the methane, initiate its cracking as seed units for cracking, i.e. they fulfil the functions of absorber and reaction accelerator and act as such. These seeds preferably consist of soot particles 32 which are injected through nozzles 33 from a supply line 34 for a gas-seed mixture into the methane flowing through the flow channel 2 as indicated by the arrow 3, so that a persistent cloud of seeds or soot particles 32 is formed in the absorber zone 9 (or in the third region 23 ), which cloud is absorptively heated by the incident solar radiation 7 , thus itself emitting blackbody radiation 20 and thus heating the flowing methane in the first region 21 to its cracking temperature and above its cracking temperature in the second region 22 . The seed cloud spreads over the cross section of the flow channel 2 and acts as a reaction accelerator for cracking in the third region 23 (in this regard, see also Figure 4), wherein the carbon formed by the cracking is deposited on the seeds or soot particles 32 and discharged from the reactor receiver 30 via the outlet 8. If undesired deposits are to be removed on the section of the supply line 32 extending into the flow channel 2, the person skilled in the art can set up, for example, a water vapor cycle according to the embodiment described in FIG. 1 . In the specific case, it is also possible to orient the nozzle 33 toward the orifice 6 so as to eject the seeds or soot particles 32 against the methane flow (arrow 3). This can be advantageous in terms of carbon deposition, since the soot that has been formed is less deposited than the soot that is formed during the cracking process initiated by physical contact with the line 34.

[0043] For cracking methane, a receiver reactor 30 is created, which has an orifice 6 for solar radiation 7, and a flow channel 2 for passing the methane to be cracked through the receiver reactor 1, and an absorber zone 9 arranged in the path of the incident solar radiation 7, designed to absorb the solar radiation and emit black body radiation upstream into the flow channel 2 during operation, wherein the absorber zone 9 is arranged and designed so that it is located opposite the orifice 6 for solar radiation 7 and is irradiated with its entire dimensions during operation by the solar radiation 7 directly incident thereon, wherein the absorber zone 9 further comprises a device 31 for generating a cloud of seeds, preferably soot particles 32. For generating the seeds, the device preferably has at least one spray nozzle 33 for the seeds, preferably soot particles 32.

[0044] In addition, a method is created, whereby preferably Figure 2 The receiver reactor 30 shown in the figure injects a cloud of seeds 32 into the flowing methane in the third flow region 23 so as to induce cracking in a cross-section of the flow, and wherein the cloud is designed so as to be located in the path of incident sunlight 7 and absorb said sunlight, thereby heating and also emitting black body radiation 20 upstream into the flowing methane.

[0045] Figure 3a A schematic diagram of a longitudinal section of a receiver reactor 40 according to another embodiment is shown. In the absorber zone 9, an absorber 41 is arranged, which has a plurality of - in this case rod-shaped - absorber elements 42, which in turn can be moved via a displacement device 43, which is only indicated schematically here, in the direction of a double-headed arrow 44 into an operating position in the absorber zone 9 of the flow channel 2 or withdrawn to an unloaded position outside the absorber zone 9. A person skilled in the art can design the displacement device 43 appropriately in the specific case. Absorber elements 42, the function of which is adversely affected by deposits, can be withdrawn from the absorber zone by means of the displacement device 43 and replaced by absorber elements 42 without harmful deposits. This can be carried out while the reactor receiver 40 is in operation, by replacing individual absorber elements one after another or in response to the detection of deposits or by replacing them all at once, for example, at night.

[0046] Figure 3bShow perpendicular to Figure 3a Schematic diagram of a longitudinal section of a receiver reactor 40 oriented in the length of an absorber element 42. Two rows of absorber elements 42 arranged one behind the other can be seen, wherein of course only one row or more than two rows can also be provided.

[0047] A receiver reactor is created for the purpose of cracking hydrocarbon gases, in particular methane, which has an orifice for solar radiation, a flow channel for passing the methane to be cracked through the receiver reactor, and an absorber zone arranged in the path of the incident solar radiation, designed to absorb the solar radiation and to emit blackbody radiation upstream into the flow channel during operation, wherein the absorber zone is arranged and designed so that it is located opposite the orifice for solar radiation and during operation is irradiated over its entire dimensions by the solar radiation directly incident thereon so that it can be flowed through by hydrocarbon gas - in this case methane, wherein an absorber is further arranged in the absorber zone, which includes absorber elements that can be moved independently of each other between an operating position in the absorber zone and a replacement position outside the absorber zone, and a moving device for the absorber elements.

[0048] The displacement device is preferably designed to change the current operating conditions of the absorber element in its operating position in a predetermined manner.

[0049] The displacement device is also preferably designed to replace a used absorber element with a fresh absorber element in the idle position.

[0050] In this case, the absorber or parts of the absorber are replaced or cleaned, preferably during continued operation, after a predetermined threshold value for deposits has been reached.

[0051] In another preferred embodiment, the flow channel 2 is designed as a tube and has a straight axis, wherein the window 5 is located at one end thereof and transversely to the axis, and the absorber zone 9 is located at the other end thereof and also transversely to the axis and extends over the entire cross section of the flow channel 2 at this location. It should be pointed out here that a tubular or cylindrical design of the flow channel 2 can be provided for all embodiments according to the invention. A person skilled in the art can design the flow channel 2 - and the absorber - appropriately for the specific case.

[0052] Figure 4 The diagram 50 shows the temperature distribution in the first region 21 to the third region 23 of the flow channel 2 during operation of the receiver reactor 40. Figure 3b Schematic diagram of a longitudinal section of a receiver reactor 40 of FIG. 50 . The distance A from the window 5 to the end of the absorption zone 9 is plotted on the horizontal axis, the temperature T is plotted on the vertical axis. Arrow 3 again indicates the flow direction of methane. However, the conditions shown in diagram 50 also apply analogously to the individual embodiments of the receiver reactor according to the invention or the method according to the invention for cracking hydrocarbon gases.

[0053] Curve 51 shows the temperature distribution on the axis 52 of the flow channel 2, curve 53 shows the temperature distribution near the side wall 13, and curve 54 shows the temperature distribution of methane flowing from the window 5 through the absorber 41 (or according to Figure 2 In the periodic operation described by , there is also the average temperature distribution of oxidizing gas or water vapor).

[0054] These curves are only shown qualitatively in the figure, but they are based on a mathematical model of the applicant's absorptive receiver designed with a straight tubular flow channel 2 as shown in Figures 1 to 4. The system has been modeled using the most accurate method currently available, namely "Spectral line-by-line (LBL) photon Monte Carlo raytracing", where the absorption coefficients are taken from the FIITEMP 2010 Spectroscopic Database. A receiver is modeled whose absorption chamber (areas 21 to 23) has a diameter of 15.96 m and a height of 15.96 and whose orifice 6 has a diameter of 11.28 m. This results in a directly irradiated area of ​​200 m2 for the absorption chamber 9. 2 And the area of ​​orifice 6 is 100 m 2 Water vapor is assumed as the heat transfer medium (with no significant changes in properties in the case of methane) at a pressure of 1 bar and without a window in orifice 6. The radiation flow at orifice 6 is 1200 kW / m 2 and 600 kW / m at the absorption zone (9) 2 (Its area is twice that of the orifice 6). Depending on the temperature conditions and the mean temperature and deviation, this modeling can be applied to the center or the wall of the flow channel 2, especially in view of the relatively low input temperature of the methane for cracking when entering the flow channel 2. In particular, these curves show the continuous increase in temperature in the flow channel 2 caused by absorptive heating and the reduction of the deviation of the temperature of the flowing methane in the area close to the wall and in the axial area from the respective mean temperature, which is important for the cracking process.

[0055] Methane is discharged into the flow channel 2 through the annular pipe 18 (preferably preheated by the heat exchanger 16), and the distance A in the diagram 50 is 0. Since the side wall 13 is heated by the black body radiation 20 (or also by the solar radiation 7 incident obliquely through the window 5), the methane is already heated to the cracking temperature T in the area close to the wall. c As explained above, the term cracking temperature is used here to mean the temperature at which 50% of the methane is dissociated under equilibrium conditions, ie after an infinite time.

[0056] However, due to the continuous flow (arrow 3) and the slow reaction, the equilibrium state is not reached in the first region 21 of the flow channel 2; the percentage of dissociated methane is significantly lower than that corresponding to the average temperature (curve 54). Therefore, the average temperature reaches the cracking temperature Tc The end of the first region 22 (distance A 22 ), the cleavage does not start until 21. Here, there is a region near the wall that is significantly overheated relative to the cleavage temperature, i.e., a region in which the cleavage continues (sluggishly), and a significantly too cold region in the middle of the flow channel 2, in which the cleavage has not yet occurred. In other words, the dissociation in the region 21 starts unevenly.

[0057] At the end of the second region 22 (distance A 23 ), the average temperature (curve 54) is significantly higher than the cracking temperature T c , where the deviation between the temperature near the wall and the temperature in the middle (curves 53 and 51) becomes smaller - the cracking starts over the entire cross section of the flow channel 2. However, here too, the dissociation does not continue very deeply and is not yet uniform enough to correspond to the equilibrium state at the average temperature (curve 54). Taking into account the temperature and time course (equilibrium state), only a very small proportion of cracked methane is still present, which is insufficient for economically reasonable operation of the receiver reactor.

[0058] In the third region 23, the absorber zone 9, the methane is in physical contact with a reaction accelerator which is designed as an absorber, for example a stationary absorber 10, 42 as shown in FIG. 1 or 3a, b or according to Figure 2 The seed 32 cloud. When it passes through the absorber zone 9, the temperature absorption of methane increases greatly, the deviation between the temperature at the wall 13 and the axis of the flow channel 2 and the average temperature becomes smaller and cannot adversely affect the uniformity of the dissociation reaction in the cross section of the absorber zone 9, and is therefore no longer important for the cracking process itself.

[0059] In detail, the passage through the third region 23 or absorber zone 9 brings about two effects: Firstly, the methane molecules are heated very sharply by the strong infrared radiation shortly before the physical contact, and they dissociate or superheat very strongly (relative to the cracking temperature). Secondly, the physical contact acts as a seed unit for the dissociation, which then takes place rapidly and almost completely due to the superheating of the methane. As explained above, a certain amount of soot deposits on the stationary absorbers 10, 42 is unavoidable here, but these deposits which do not interfere with the cracking itself can be removed, for example, at night or by solar operation with an oxidizing gas. It should be noted that Figure 2 The reaction accelerator shown in FIG. 3 , which is designed as an absorbent seed cloud, is particularly advantageous with regard to deposits, since the deposits form on the seeds 32 and are then discharged from the receiver reactor 30 via the outlet 8 with the stream (now of soot particles and hydrocarbon gases).

[0060] The result is that temperature zones are formed one after another in the flow channel (these are roughly divided into three zones 21 to 23 in the description), cf. Figure 41 and 2 for the regions 60 to 67 envisaged here. Of course, these regions 60 to 67 extend through the flow channel 2, but in order to reduce unnecessary details in the figure as much as possible, the dotted lines are drawn only up to the side wall 13 of the flow channel 2.

[0061] Regardless of where exactly the zone boundaries are set, it can be determined that they extend transversely to the flow channel 2, are designed in the form of a disk, and that the temperature increases by absorption from one temperature zone to the next, respectively, although in each temperature zone there is of course no completely uniform temperature distribution, but rather a slightly non-uniform temperature distribution (each temperature zone 60 to 67 has its own respective higher temperature level), but at least starting from the second flow region 22, their temperature boundaries are increasingly close to each other (at the beginning of the first flow region, see region 60, this is not yet the case due to the nature of the process). As a result, after the second flow region 22, almost complete and uniform heating of the methane is achieved for cracking, so that the cracking can be carried out with a very high degree of dissociation that meets the industrial requirements. In addition, the receiver reactors 1, 30, 40 are suitable for continuous operation, wherein carbon deposits can be removed during operation or at night (see the description of Figures 1, 3a and 3b) or are essentially not produced (see the description of Figures 1, 3a and 3b). Figure 2 description).

[0062] In general, according to the present invention, there is provided a method for cracking a hydrocarbon gas, preferably methane, wherein the hydrocarbon gas is conveyed through a flow passage of a receiver reactor and wherein cracking occurs while passing through the receiver reactor, wherein the methane is heated to its cracking temperature in a first region of the flow passage, heated to above the cracking temperature in an adjacent second downstream flow region, and further heated in a third further downstream region of the flow passage and physically contacts a reaction accelerator in a cross section in this region, after which a product stream is discharged from the receiver reactor downstream of the reaction accelerator, and wherein the hydrocarbon gas is heated to above its cracking temperature by absorbing black body radiation which is released to the hydrocarbon gas flowing thereto by the reaction accelerator heated by solar radiation incident thereon, so that the methane in the flow passage extending to the reaction accelerator forms disk-shaped temperature zones, each having increasing temperatures, arranged one after another and extending transversely to the flow passage.

[0063] In this case, the absorber of the receiver reactor preferably acts as a reaction accelerator, through which the medium flowing through the receiver reactor flows.

[0064] The hydrocarbon gas is thus heated absorptively in the first and second regions of the flow channel (regardless of whether an absorber or a reaction accelerator is used), and the heating in the third region of the flow channel is also carried out absorptively, wherein although convective heat transfer may be achieved at the absorber acting as a reaction accelerator by physical contact, this is almost negligible compared to the heat absorbed absorptively, because the hydrocarbon gas has been absorptively heated to the temperature required for cracking and dissociated by physical contact. It should be further pointed out here that the walls of the flow channel 2, especially in the regions 21 and 22, also emit blackbody radiation, which is also absorbed by the hydrocarbon gas. Accordingly, it is provided here that in the above-mentioned feature (according to which the hydrocarbon gas is heated to above its cracking temperature by absorbing blackbody radiation, which is released to the hydrocarbon gas flowing thereto by the reaction accelerator heated by the solar radiation incident thereon), this blackbody radiation released by the wall is also included.

[0065] It should be noted that the embodiments given in this specification can be combined, so those skilled in the art can combine the embodiments according to specific circumstances. Figure 3a and 3b The replaceable absorber element is based on Figure 2 1 , or alternatively, the removal of carbon deposits is achieved with the aid of an oxidizing gas.

[0066] In solar tower power plants, a construction form is also used in which a receiver, in this case a receiver reactor according to the invention, is arranged at the top of the tower and oriented downwardly in an inclined manner in order to directly collect radiation from the heliostat array. Due to the inclined orientation, correspondingly inclined temperature zones 60 to 67 can be generated, which can generate convective flows in the heat transfer fluid, which in turn can interfere with the temperature stratification created by the temperature zones and thus also with the desired, as uniform as possible, temperature distribution in the third region 23 or in the absorber region 9.

[0067] For other configurations, such as in solar tower power plants, the receiver reactor according to the invention can be oriented vertically, wherein the radiation from the heliostat array is then deflected vertically downwards via mirrors arranged in the solar tower to the receiver 100 located close to the ground, an arrangement referred to by those skilled in the art as "beam down". (Conversely, the radiation from the heliostat array can also be deflected vertically upwards via mirrors or by the heliostats themselves, wherein the receiver 100 is then located at the top of the solar tower).

[0068] In particular in a vertically downwardly oriented receiver 100, the flow of the fluid passing through the absorber chamber 28 is designed to be fairly uniform, thereby producing a distinct temperature stratification over the height of the absorber chamber 28. In the case of a "beam down" arrangement, it may be beneficial, depending on the circumstances, to provide not only a sufficiently high flow rate of the heat-transferring or heat-absorbing fluid, such as methane, to the absorber, but also to provide a flow rate of the heat-transferring or heat-absorbing fluid, such as methane, to the absorber as described below. Figures 5 to 10 The swirling flow in the fluid is shown in FIG.

[0069] Therefore, according to another embodiment of the receiver reactor 1, it is provided that the process gas, at least the hydrocarbon gas to be cracked, or even the reducible gas such as Figure 5 The feed channels 19' and 27' shown in the figure are introduced tangentially into the flow channel 2 through corresponding modifications, so that the gas flowing in the direction of the arrow 3 also rotates around the axis 52. Here, the outlet 8 can also be slightly offset from the middle of the flow channel 2, so that it is close to the top side of the receiver 60, for example in the specific case, that is, in the case of an inclined mounted receiver 60.

[0070] For this purpose, the feed channels 19' and 27' are preferably designed so that they open tangentially into the flow channel 2 and create additional swirls in the flow of the respective process gas as indicated by arrows 61 and 62. As a result, the receiver reactor 60 is maintained according to the tilted position even when the receiver reactor 60 is in the tilted position. Figure 4 The temperature zone of the chart is 50 60 to 67.

[0071] In the case of an eccentric arrangement of the outlet 8 relative to the flow channel 2 , the process gas can rotate about an axis which is respectively parallel to the axis 52 .

[0072] As a result, the receiver reactor 60 is designed so that the feed channel is tangential to the longitudinal axis (52) of the flow channel 2 so that when the receiver reactor 60 is in operation, the process gas in the flow channel 2 has a swirling flow about the axis 52 on its way to the absorber zone (9).

[0073] It should be noted here that flow rotation or swirl can also be generated by deflection plates in the flow chamber 2 , which is preferably achieved in its first region 21 due to a specific temperature stratification, so that the outlay for the receiver reactor 60 according to the invention is only insignificantly increased.

[0074] Figure 6 A schematic diagram showing a receiver 110 arranged obliquely on the side of the orifice 3 facing the solar radiation, wherein a supply line 104 for a radiation-absorbing medium (process gas) arranged tangentially with respect to the axis 103 can be seen, which generates a medium rotation or swirl in the medium flowing to the absorber 27. In this figure, the absorber 27 can be seen through the orifice or quartz window 3, wherein in order to minimize the details in the figure, the flow path of the medium through the absorber (or through it) is not shown, but instead only the outlet pipe end 106 from which the medium leaves the receiver 110 is indicated by a dotted line. The outlet pipe end is preferably arranged slightly eccentrically offset upwards, which, in combination with the swirl in the flowing medium, helps to produce a stable temperature in the heat transfer medium at the location of the outlet pipe end 106.

[0075] As a result, the receiver reactor is preferably designed so that during operation, the process gas at least partially swirls around an axis 52 of the absorber chamber parallel to the conveying direction when passing through the flow channel 2 in the conveying direction, wherein the receiver reactor preferably has a medium inlet opening arranged on the flow chamber 2, which is oriented tangentially relative to its axis 52 in the same swirl direction.

[0076] It should be pointed out here that flow rotation or swirl can also be produced by deflection plates in the flow channel 2 , which is preferably achieved in its cold region due to the specific temperature stratification, so that the outlay for the receiver according to the invention is only not significantly increased.

[0077] Figures 7 to 10 Details of the receiver reactor 120 are shown, which is designed for high efficiency even in an inclined or horizontal position. Figure 7 An external view of the receiver reactor 120 is shown, Figure 8 and 9 shows a cross section through the reactor, and Fig.10 The layered temperature distribution in its flow channel 2 according to the applicant's simulation is shown. In order to reduce the details in the drawings, the insulation of the receiver reactor 120 and its supporting external structure, which can be easily imagined by a person skilled in the art in a specific case, are omitted.

[0078] Figure 7 The receiver reactor 120 is shown with its flow channel 2, the collecting chamber 33 and the outlet pipe end 121 (in this regard, see also the comments on FIGS. 1 and 5 ). It can also be seen that the cooling (T in ) A supply arrangement 122 for process gas. The supply arrangement 122 has an annular chamber 123 into which a supply line 124 for process gas opens as indicated by arrow 125, wherein the process gas that has passed through the annular chamber 123 and flows into the receiver 120 passes through the flow channel 2 in a main flow direction parallel to the axis 127, is heated there and finally, after cracking, is released via the collecting chamber 33 and the outlet pipe end 121 at a temperature T out The solar rays 4 pass through the opening blocked by the annular chamber 123 in the figure or through the window 3 to the flow channel 2 and reach the inside of the collecting chamber 33, the inner wall of which is designed as a solar radiation absorber in the embodiment shown. Figure 6 It is explained in the description of that in the illustrated embodiment the outlet pipe end 121 is also arranged to be offset upwards.

[0079] Figure 8 The cross section of the annular chamber 123 is shown, wherein the cross section in turn passes through the shaft 127 extending longitudinally through the flow channel 2 and the supply line 124 (see also Fig.10). Here, the annular chamber 123 is shown to scale, as are the adjacent areas of the flow channel 2 and the opening 3 or window 3 for solar radiation. However, as previously indicated, insulation and supporting structures have been omitted, in particular those for the window 3 and the annular chamber 123. Also shown is a supply line 124 for the process gas, which is arranged on the upstream or inlet side. Downstream or on the outlet side, the annular chamber 123 is divided into an outer annular channel 132 with an annular outlet slit 130 and an inner annular channel 133 with an annular outlet slit 131. The outer channel 132 extends coaxially with the axis 127 of the flow channel 2 and is adjacent to its wall 138, while the inner channel 133 has a truncated cone-shaped design and is oriented obliquely toward the interior of the absorption chamber 28. As a result, a region of reduced flow toward the absorber is formed in the vicinity of the wall 138, which is only reduced or to a no longer important extent, wherein a uniform temperature stratification is ultimately obtained in the cross section of the flow channel 2 before the absorber (in this regard, see also Fig.10 ), although the walls are slightly hotter (cf. Figure 5 50 in the diagram). Therefore, the flow component particularly preferably extends from the outer channel 132 parallel to the wall 138, and its angle with the wall 130 is preferably less than or equal to 15 degrees, particularly preferably less than or equal to 10 degrees, and most particularly preferably less than or equal to 5 degrees. At an angle of less than or equal to 10 degrees or 15 degrees, a positive effect can still be achieved.

[0080] The annular channels 132, 133 are provided with deflection plates 134, 135 (see Fig.11 b) so that orifices for the process gas are formed in the outlet slits 130, 131 and also impart a flow component tangential to the axis 127 to the process gas. The flow channel 2 is thus entered in a directed flow and has a (swirl) flow direction tangential to the axis 127 in addition to a main flow direction parallel to the axis 127. This results in spiral flow lines 136 and 137 which are shown in the figure for illustration. As a result, disturbances of temperature stratification in the receiver 120, for example due to temperature-induced convective flows, can be suppressed, in particular in an inclined or horizontal orientation.

[0081] Fig. 9 Show from Figure 8 In particular, the deflection plates 134 ′ to 134 ″′ and the components of the directional flow 136 , namely the component 141 in the main flow direction and the tangential component 142 , can be seen.

[0082] A receiver reactor is created, which has an orifice for the process gas opening into the flow channel 2, which is arranged in the immediate vicinity of the wall 138 of the flow channel 2 and produces a flow component of the process gas flowing into the flow channel 2 at an inclination of less than 15 degrees, preferably equal to or less than 5 degrees, relative to the wall 138 in the main flow direction. According to the findings of the applicant, such a small angle helps to avoid, near the wall 138, areas of reduced flow velocity towards the absorber, which are important for the efficiency of the absorber.

[0083] Furthermore, a receiver reactor is created in which the delivery device comprises openings for the heat transfer and absorption medium into the flow channel 2 , which generate a flow component of the process gas flowing into the absorption chamber 28 which is tangential to the axis 127 of the flow channel 2 .

[0084] Finally, a method for operating a receiver reactor is created, in which the process gas is caused to rotate in the flow channel 2 so that it has a swirl flow in the flow channel 2 about an axis (127) extending in the conveying direction or main flow direction.

[0085] Fig.10 The temperature distribution in the flow channel 2 of the receiver reactor 120 is shown according to a CFD simulation performed by the applicant with the following boundary conditions:

[0086] ■ Diameter of absorption chamber 0.8 m, pressure in flow channel = 1 bar

[0087] ■ T in = 800 °K, mass flow rate of process gas = 0.045 kg / s

[0088] ■ Solar radiation efficiency through transparent aperture 3 = 250 kW, aperture diameter: 0.6 m

[0089] ■ Process gas: Water vapor

[0090] ■ Spectral radiative behavior of water vapor modeled using the weighted sum of grey gases (WSGG) model and radiative behavior solved using the discrete ordinate (DO) method

[0091] ■ Black wall, ε wall = 1

[0092] ■ Gravity acting vertically downward (horizontal receiver)

[0093] ■ Angle of fluid flowing into the absorption chamber: 45 degrees

[0094] The angle of the fluid flowing into the annular channel 132 is Fig. 9The angle between the directional flow 136 in the annular channel and the main flow direction 141. As previously described, the annular channel 133 has a truncated cone-shaped configuration, i.e., its downstream end is circular. The angle of the fluid flowing out of it into the absorption chamber is similarly the angle between its flow direction and the tangent on the circle.

[0095] Here, a simplified geometry in the region between the optical aperture 3 and the wall 138 of the flow channel 2 is assumed from the simulation: the outlet slits 130 and 131 ( Figure 8 and 9 ) is replaced by a truncated cone-shaped wall area 150.

[0096] The simulation revealed an outlet temperature T of 1862 °K out And the temperature stratification shown in the figure, which is represented by temperature curves 140 to 145. Temperature curve 140 corresponds to a temperature of 1420 °K, curve 141 corresponds to a temperature of 1533 °K, curve 142 corresponds to a temperature of 1589 °K, curve 143 corresponds to a temperature of 1645 °K, curve 144 corresponds to a temperature of 1702 °K, and curve 145 corresponds to a temperature of 1870 °K.

[0097] It was found that despite the complex thermodynamic conditions (even at very high temperatures caused in particular by the hot wall 138 heated by radiation from the absorber 27) and the complex flow conditions caused in particular by convection generated by temperature differences and gravity, there is a temperature stratification in the process gas (in this case water vapor) in which the temperature increases continuously from the orifice 3 to the outlet pipe end 121, as a result of which, for example, efficiency-reducing back radiation can be minimized through the orifice 3. It should also be pointed out that the person skilled in the art can appropriately determine the inflow direction and the swirl or rotation of the fluid in the absorption chamber about an axis extending through the absorption chamber, as well as the position of the outlet pipe end (depending on the temperature) in the specific case. Figure 2 and 3 to 6 centered or according to Fig. 9 and 10 For example, if optimal swirl can be produced by other parameters (such as those simulated above), the outlet pipe end can be arranged centrally even in the case of horizontal orientation. Conversely, a combination of relatively weak or non-optimal swirl and an offset position of the outlet pipe end can produce the desired temperature stratification.

[0098] In another embodiment according to the invention, during the hydrocarbon gas cycle, i.e. during the cracking process, CO2 is fed into the flow channel 2 in addition to the hydrocarbon gas, which is mixed with the hydrocarbon gas, heated and enters the third zone 9 with it (Figures 1 to 5). Thus, according to the applicant's calculations ( Fig.11 ), particularly in combination with methane and CO2, unexpectedly an increased thermal efficiency of the receiver reactor is achieved, with the further advantage that more synthesis gas components can be produced, namely CO in addition to H2.

[0099] Fig.11 A diagram 160 is shown, in which the wavelength in μm is plotted on its horizontal axis and the electromagnetic radiation absorptivity of the absorbing gas is plotted on its vertical axis, wherein the absorptivity value of 1 is reached when the gas absorbs 100% of the radiation at the wavelength in question, ie 100% of its energy content.

[0100] Curve 161 shows the absorption rate of methane and curve 162 shows the absorption rate of CO2 - according to the applicant's calculation under the following assumptions: pressure = 1 bar, path length = 10 meters, wherein the data are based on the Reims database for methane and the HITEMP 2010 database for CO2.

[0101] If one of the curves 161, 162 has a value less than 1, it is concluded that the corresponding proportion of the radiation at the relevant frequency is not absorbed and therefore passes from the absorber 10 through the process gas to the window 5 of the receiver reactor, where it leaves the receiver reactor as back radiation. However, the back radiation indicates a reduction in the efficiency of the receiver reactor, because the heat supplied by the solar radiation 7 cannot be used to heat the process gas in the case of reflected radiation. The actual absorption gas thus leads to a reduction in the efficiency of the absorptive receiver and correspondingly to a reduction in the yield of hydrogen and carbon in the cracking process. According to the invention, CO2 is now mixed into methane in the hydrocarbon gas cycle, as a result of which the absorption in the wavelength range of at least 1.5 μm to 6 μm is substantially equal to 1, because roughly speaking, methane or CO2 is almost completely absorbed. Specifically, for example, in the wavelength range between 3.1 μm and 3.9 μm, the absorption of methane is almost 0, but the absorption of CO2 is close to 1. Accordingly, the back radiation is significantly reduced compared to methane alone as process gas, so that more heat is generated in the receiver reactor, thereby correspondingly increasing the efficiency.

[0102] As mentioned above, in addition to the higher efficiency, a dual chemical reaction now takes place, namely the cracking of methane and the reaction between methane and CO2, summarized in the reaction equation 1 CH4+ 1 / 2 CO2->1 / 2 C(s) + 2 H2(g) + 1 CO(g), where (s) refers to the solid phase and (g) refers to the gas phase. It is therefore found that compared to the cracking itself, the reaction is 1 CH4->1 C(s) + 2 H2(g), not only is the efficiency higher, but CO is also produced as a further syngas component.

[0103] A person skilled in the art can determine the ratio of hydrocarbon gas to CO2 appropriately in the specific case, wherein methane is preferably used as hydrocarbon gas and the number of moles of methane / number of moles of the mixture of methane and CO2 in the third region (23) of the flow channel (2) is 60 to 90%, preferably 60-70%, particularly preferably 66.67%. The amount ratio is determined for the third region (23) because in the specific case CO2 can only be supplied starting from the second region 22, which is preheated, for example, via the heat exchanger 16 (see, for example Figure 3a ).

[0104] Fig.12a An arrangement is shown for recovering heat from the product of the receiver reactor 1, 30, 40 discharged via the outlet 8, the temperature of the product preferably still being at the temperature level existing in the third flow region 23 or absorber zone 9. If black body radiation is also released towards the outlet 8 by the absorber 10, 32, 42 (and the side wall in front of the outlet 8) and absorbed by the product according to its absorptivity, the product is not cooled before the outlet 8. After the outlet 8, the product passes through a shut-off valve 170 into a first line arrangement having a line 171 connecting the receiver reactor 1, 30, 40 to a heat storage reactor 172. During daytime operation of the receiver reactor 1, 30, 40, i.e. when there is sufficient solar radiation 7 to enable cracking in the receiver reactor 1, 30, 40, the shut-off valve 170 is opened and the product from the receiver reactor flows into the heat storage reactor 172 and charges it with heat, i.e. cools there and leaves the heat storage reactor via line 173, wherein a carbon particle filter 174 can be arranged in line 173 to finally discharge H2 from this line.

[0105] The heat storage reactor 172 is designed as a layered solid heat storage with a bulk material filler as solid heat storage element as described in, for example, WO 2012 / 027 854, through which the heat products from the receiver reactors 1, 30, 40 pass, heating them to charge the heat storage reactor 172. Fig.12a , 12b In the embodiment of the reservoir reactor 172 shown in , the packing of bulk material has a structure of refractory material, such as ceramic blocks 177, which are located within the internal flow path 176 of the reservoir reactor 172 and arranged so that the product is flushed around them (and if they are permeable or porous, also through them) to make physical contact. The structure of the bulk material, such as ceramic blocks 177, can be determined by those skilled in the art in a specific case.

[0106] During operation, when charging of the heat storage reactor 172 begins, first the topmost ceramic blocks 177 are heated to an upper temperature T by the products from the receiver reactors 1, 30, 40 flowing through them. o, wherein the product cools itself and heats the next layer of ceramic block 177 slightly lower, and so on, until the product reaches the lower limit temperature T u flows through the subsequent layers of ceramic block 177 and finally at a temperature T u The heat is discharged through the discharge line 173. In the heat storage reactor 172, a temperature distribution is achieved as shown by the temperature curve 180 in the diagram 181, whose horizontal axis shows the temperature and whose vertical axis shows the distance in the flow direction through the flow path 176.

[0107] As charging continues, curve 182 shows the heat distribution in the heat reservoir 172. Finally, curve 183 corresponds to the temperature distribution in the fully charged heat reservoir 172. In other words, while the heat reservoir 172 is being charged, the ceramic blocks 177 are heated downward layer by layer to the upper limit temperature until, with further charging, the temperature of the product in line 173 rises to a temperature exceeding the lower limit temperature T u , because even the bottom ceramic block 177 is heated.

[0108] A method is created in which the hot product stream discharged from the receiver reactor (1, 30, 40) downstream of the reaction accelerator is preferably conveyed via a first line arrangement to a layered heat storage reactor 172 having a solid heat storage element 177 and then conveyed through it so that it is charged with heat from the product to a temperature T above the cracking temperature o Furthermore, a receiver reactor is created, the outlet 8 of which is connected via a first line arrangement to a layered reservoir reactor 172 having an internal flow path 176 for conveying the products from the receiver reactors 1, 30, 40, in which solid state reservoir elements 177 are again arranged so that the conveyed products are flushed around and through them into physical contact.

[0109] For information on lines 186 and 200 with shut-off valves 187, 201, see Figure 12b Description.

[0110] Figure 12b Shown in night operation Fig.12a 18, 19. The arrangement for heat recovery is provided when the receiver reactor 1, 30, 40 is not in operation, either at night, during maintenance or when the solar radiation is too low. This is indicated by the cover 185, which shields the receiver reactor from the sun. The shut-off valve 170 is closed accordingly. A second line arrangement with line 186 leads from a hydrocarbon gas source (e.g. methane) to the heat storage reactor 172, wherein the shut-off valve 187 is opened in line 186 so that hydrocarbon gas can flow into the heat storage reactor 172 in the direction of the arrow in line 187.

[0111] In the region of the topmost ceramic block 177, the hydrocarbon gas is heated to a temperature T o, which clearly exceeds the cracking temperature, see the description above. The ceramic block 177 cools down and the heat storage reactor 172 now unloads heat. The ceramic block 177 in contact with the hydrocarbon gas acts as a reaction accelerator, similar to the cracking in the receiver reactors 1, 30, 40, see the description of the cracking in the receiver reactor above. As a result, cracking of the hydrocarbon gas occurs in the heat storage reactor 172, wherein the cracking products continue to flow through the heat storage reactor 172 and are finally discharged to the outside via line 173. Graph 190 shows the time after the start of heat unloading (curve 191), during the heat unloading process (curve 192) and at the time when the heat storage reactor is unloaded and ready according to Fig.12a The temperature distribution in the heat storage reactor 172 after a new heat charge (curve 193) is described. It should be noted here that cracking is endothermic, so the energy required is obtained from the cooling of the ceramic block 177.

[0112] A method is created in which a charged heat reservoir reactor is preferably unloaded by cracking a hydrocarbon gas therein. A method is also created in which a hydrocarbon gas, preferably methane, is preferably fed into a heat reservoir reactor from a hydrocarbon gas source via a second line arrangement and then passes through it, wherein the hydrocarbon gas is physically contacted with solid heat reservoir elements during passage through the heat reservoir reactor to accelerate cracking. Furthermore, a receiver reactor 1, 30, 40 is preferably created in which a stratified heat reservoir reactor 172 is connected to a second line arrangement, which itself is connected to a hydrocarbon gas source and leads to an internal flow path 176 for the product of the receiver reactor 1, 30, 40. Finally, a use of a stratified heat reservoir with solid heat reservoir elements as a heat reservoir reactor for cracking of hydrocarbon gases, in particular methane, is created, said solid heat reservoir elements being arranged in their internal flow path so that during operation, a heat transfer gas is flushed around them to come into physical contact.

[0113] As mentioned above, during the cracking process, carbon may be deposited on the reaction accelerator (in the heat storage reactor 172: solid heat storage element or bulk material filler or ceramic block 177), which can be removed by oxidizing gas, such as water vapor. Accordingly, a third line arrangement with line 200 is additionally provided, which is connected to the oxidizing gas source and can provide, for example, water vapor to the heat storage reactor 172. In order to remove the carbon, the shut-off valves 170, 187 are closed accordingly, and the shut-off valve 201 in the line 200 is opened. The hydrogen produced again is discharged together with carbon monoxide via line 173.

[0114] A method is created in which an oxidizing gas, such as water vapor, is preferably fed from a source via a third circuit arrangement into a reservoir reactor 172 and then passed therethrough to remove therefrom carbon that has been deposited on solid reservoir elements 177. The stratified reservoir reactor 172 is then connected to a third circuit arrangement for water vapor, wherein this circuit arrangement opens into an internal flow path 176 for the product of the receiver reactor 1, 30, 40.

[0115] Fig.13 show Fig.12a and 12b , but to which is added a reservoir reactor 172', wherein the reservoir reactor is connected to the receiver reactors 1, 30, 40 via line 171' of the first line arrangement and to the discharge line 173 via line 173'. Line 186' with a shut-off valve 187' connects the reservoir reactor 172' to the hydrocarbon gas source, as is the case with the reservoir reactor 172 via line 186. In other words, the reservoir reactor 172' is preferably of the same construction type as the reservoir reactor 172, including all feed lines and discharge lines, wherein the water vapor line of the third line arrangement with the corresponding shut-off valve is omitted to minimize the details in the figure.

[0116] This configuration enables various loops to be implemented during operation of the receiver reactors 1, 30, 40, the reservoir reactor 172, and the reservoir reactor 172'. As an example, Fig.13 A circuit is shown in which the reservoir reactor 172 is unloaded by cracking of hydrocarbons supplied via line 186 and the reservoir reactor 172' is charged by the receiver reactor 1, 30, 40. For example, one of the reservoir reactors 172, 172' can always be charged while the other is unloaded by cracking or carbon residues from the cracking cycle are removed from it in the steam cycle. According to the invention, it is also possible to interconnect more than two reservoir reactors in the manner shown and then operate them in different circuits in day and night operation.

[0117] Preferably, a method is created in which a plurality of heat storage reactors 172, 172' are connected to a receiver reactor (1, 30, 40) via a line arrangement, and one of these heat storage reactors is alternately charged with heat, unloaded by cracking or decarbonized by cycles of an oxidizing gas such as water vapor. Preferably, one heat storage reactor 172, 172' is connected to a third line arrangement, which itself is connected to a source of an oxidizing gas such as water vapor and leads to an internal flow path for the product of the receiver reactor.

Claims

1. A method for cracking hydrocarbon gases, wherein the hydrocarbon gases are passed through a flow channel (2) of an absorptive receiver reactor (1, 30, 40), Features Cracking occurs while passing through a receiver reactor (1, 30, 40), wherein the hydrocarbon gas is heated to its cracking temperature in a first region (21) of the flow channel (2), heated to above its cracking temperature in an adjacent second downstream flow region (22), and further heated in a third further downstream region (23) of the flow channel, wherein it is in physical contact with a reaction accelerator in a cross-section of this region, after which a product stream is discharged from the receiver reactor (1, 30, 40) downstream of the reaction accelerator, and wherein the heating of the hydrocarbon gas to above its cracking temperature is achieved by absorbing black body radiation (20) which is released to the hydrocarbon gas flowing thereto by the reaction accelerator heated by solar radiation (7) incident thereon, so that the hydrocarbon gas extending in the flow channel (2) to the reaction accelerator forms disk-shaped temperature zones (60 to 67) each having increasing temperatures arranged one after another and extending transversely to the flow channel (2).

2. The method according to claim 1, wherein the absorber (10, 41) of the receiver reactor (1, 30, 40) serves as a reaction accelerator through which the medium passing through the receiver reactor (1, 30, 40) flows.

3. A method according to claim 1, wherein in a third further downstream region (23) a cloud of seeds (32) is injected into the flowing hydrocarbon gas to induce cracking in a cross-section of the flow, and wherein the cloud is formed so as to be located in the path of incident solar radiation (7), absorbing said sunlight, thereby being heated and also releasing black body radiation (20) upstream into the flowing methane.

4. The method according to claim 3, wherein soot particles are used as seeds (32).

5. A method according to claim 1, wherein the hydrocarbon gas in the hydrocarbon gas cycle is periodically replaced and a reducible gas is passed through the receiver reactor (1, 30, 40) so that the soot deposited in the flow channel (2) is dislodged by chemical reaction with the reducible gas during the oxidation cycle.

6. The method according to claim 5, wherein water vapor is used as the reducible gas.

7. A method according to claim 6, wherein the receiver reactor (1, 30, 40) produces synthesis gas in the oxidation cycle and produces carbon black and hydrogen in the hydrocarbon gas cycle.

8. The method according to claim 1, wherein the absorber (10, 41) or parts of the absorber (10, 41) are replaced or cleaned during continued operation after a predetermined threshold value for deposits has been reached.

9. The method according to claim 1, wherein the hydrocarbon gas is methane.

10. A method according to claim 1, wherein at least the hydrocarbon gas is supplied tangentially relative to the longitudinal axis (52) of the flow channel (2) so that the gas directed to a third further downstream region (23) of the flow channel (2) also rotates around an axis parallel to the longitudinal axis (52).

11. A method according to claim 5, wherein a gas, i.e. at least one of a hydrocarbon gas and a reducible gas, is caused to rotate in at least a first region (21) and a second downstream flow region (22) of a flow channel (2) so that it has a swirl flow in the flow channel (2) around a longitudinal axis (52) parallel to the conveying direction (3).

12. The method according to claim 1, wherein in the hydrocarbon gas cycle, in addition to the hydrocarbon gas, CO 2 It is fed into a receiver reactor (1, 30, 40) and passed through the receiver reactor (1, 30, 40) so that it is absorptively heated together with the hydrocarbon gas.

13. A method according to claim 12, wherein methane is used as the hydrocarbon gas and in a third further downstream region (23) of the flow channel (2), the number of moles of methane / methane and CO 2 The molar amount of the mixture is 60 to 90%.

14. The method according to claim 12, wherein methane is used as the hydrocarbon gas and in the third further downstream region (23) of the flow channel (2), the number of moles of methane / methane and CO 2 The molar amount of the mixture is 60-70%.

15. The method according to claim 12, wherein methane is used as the hydrocarbon gas and in the third further downstream region (23) of the flow channel (2), the number of moles of methane / methane and CO 2 The molar amount of the mixture is 66.67%.

16. A process according to claim 1, wherein the hot product stream discharged from the receiver reactor (1, 30, 40) downstream of the reaction accelerator is supplied via a first line arrangement to a stratified reservoir reactor (172, 172') having a solid-state reservoir element (177) and then passes through the reservoir reactor so that it is charged with heat from the product up to a temperature above the cracking temperature.

17. The method according to claim 16, wherein the charged heat reservoir reactor (172, 172') removes heat by cracking hydrocarbon gas therein.

18. A method according to claim 17, wherein hydrocarbon gas is supplied to the reservoir reactor (172, 172') from a hydrocarbon gas source via a second line arrangement and then passed through the reservoir reactor, wherein the hydrocarbon gas is brought into physical contact with the solid reservoir element (177) while passing through the reservoir reactor to accelerate cracking.

19. The method according to claim 17, wherein the oxidizing gas is fed from the oxidizing gas source via a third line arrangement into the reservoir reactor (172, 172') and then passed through the reservoir reactor so that carbon deposited on the solid reservoir element (177) is removed therefrom.

20. The method according to claim 19, wherein the oxidizing gas is water vapor, CO 2 or a mixture of these gases.

21. The method according to claim 17, wherein a plurality of heat storage reactors are connected to a receiver reactor (1, 30, 40) via a first line arrangement and to a hydrocarbon gas source via a second line arrangement, and one of these heat storage reactors (172, 172') is alternately charged with heat while another one (172', 172) is unloaded by cracking of the hydrocarbon gas.

22. A receiver reactor (1, 30, 40) for a method for cracking hydrocarbon gases according to claim 1, comprising an orifice (6) for solar radiation (7), a flow channel (2) for passing methane to be cracked through the receiver reactor (1, 30, 40), and an absorber region (9) arranged in the path of the incident solar radiation (7) and designed to absorb the solar radiation and, during operation, emit black body radiation (20) upstream into the flow channel (2), Features The absorber zone (9) is arranged and designed so that it is located opposite the orifice (6) for the solar radiation (7) and is irradiated over its entire dimensions during operation by the solar radiation (7) directly incident thereon, wherein a supply line section (14) for hydrocarbon gas and a supply line section (15) for a gas for oxidizing carbon are provided which can be switched so that the receiver reactor (1, 30, 40) can be operated alternately with hydrocarbon gas and with a reducible gas.

23. The receiver reactor of claim 22, wherein the hydrocarbon gas is methane.

24. The receiver reactor according to claim 22, wherein two line arrangements (18, 19 and 25, 26) are provided which open independently of one another into the flow channel (2).

25. The receiver reactor of claim 22, wherein the reducible gas is water vapor.

26. A receiver reactor for a method for cracking hydrocarbon gases according to claim 1, comprising an orifice (6) for solar radiation (7), a flow channel (2) for passing methane to be cracked through the receiver reactor (1, 30, 40), and an absorber region (9) arranged in the path of the incident solar radiation (7) and designed to absorb the solar radiation and, during operation, to emit black body radiation (20) upstream into the flow channel (2), Features The absorber zone (9) is arranged and designed so that it is located opposite the aperture (6) for the solar radiation (7) and during operation is illuminated over its entire dimensions by the solar radiation (7) directly incident thereon, wherein the absorber zone (9) further comprises means (31) for generating a cloud of seeds (32).

27. The receiver reactor of claim 26, wherein the hydrocarbon gas is methane.

28. The receiver reactor according to claim 26, wherein for generating the seeds (32), the device (31) has at least one spray nozzle (33) for the seeds (32).

29. A receiver reactor according to claim 28, wherein the seeds (32) are soot particles.

30. A receiver reactor for a method for cracking hydrocarbon gases according to claim 1, comprising an orifice (6) for solar radiation (7), a flow channel (2) for passing methane to be cracked through the receiver reactor (1, 30, 40), and an absorber region (9) arranged in the path of the incident solar radiation (7) and designed to absorb the solar radiation and, during operation, to emit black body radiation (20) upstream into the flow channel (2), Features The absorber zone (9) is arranged and designed so that it is located opposite the orifice (6) of the solar radiation (7) and is irradiated by the solar radiation (7) directly incident on it in its entire dimensions during operation, and is designed so that it can be passed through by the hydrocarbon gas passing through the flow channel (2), wherein an absorber (41) is further arranged in the absorber zone (9), and the absorber has an absorber element that can be moved independently of each other between an operating position in the absorber zone (9) and a replacement position outside the absorber zone (9) and a moving device (43) for the absorber element (42).

31. The receiver reactor of claim 30, wherein the hydrocarbon gas is methane.

32. Receiver reactor according to claim 30, wherein the movement device (43) is designed to change the current operating conditions of the absorber element (42) in its operating position in a predetermined manner.

33. Receiver reactor according to claim 30, wherein the moving device (43) is designed to replace a used absorber element (42) with a fresh absorber element (42) in an unloaded position.

34. A receiver reactor according to any one of claims 22, 26 or 30, wherein the feed channel (17', 27') is designed to be tangential to the longitudinal axis (52) of the flow channel (2) so that during operation of the receiver reactor (1, 30, 40), the process gas in the flow channel (2) has a swirl around the longitudinal axis (52) on its way to the absorber zone (9).

35. A receiver reactor according to any one of claims 22, 26 or 30, wherein the side walls (13) of the flow channel (2) and / or the absorber zone (9) are free of cooling means, such that the receiver reactor (1, 30, 40) operates in accordance with its intended use.

36. Receiver reactor according to claim 35, wherein the side walls (13) of the flow channel (2) and / or the absorber zone (9) are free of cooling channels.

37. A receiver reactor according to any one of claims 22, 26 or 30, wherein the delivery device has an orifice for the hydrocarbon gas leading to the absorber chamber (28, 57), which is arranged in the vicinity of the wall (138) of the absorption chamber (28, 57) and generates a flow component of the fluid flowing into the absorption chamber (28, 57) with an inclination of less than 15 degrees relative to the wall (138) in the main flow direction.

38. A receiver reactor according to any one of claims 22, 26 or 30, wherein the delivery device has an orifice for the hydrocarbon gas leading to the absorber chamber (28, 57), which is arranged in the vicinity of the wall (138) of the absorption chamber (28, 57) and generates a flow component of the fluid flowing into the absorption chamber (28, 57) with an inclination of less than or equal to 10 degrees relative to the wall (138) in the main flow direction.

39. A receiver reactor according to any one of claims 22, 26 or 30, wherein the delivery device has an orifice for the hydrocarbon gas leading to the absorber chamber (28, 57), which is arranged in the vicinity of the wall (138) of the absorption chamber (28, 57) and generates a flow component of the fluid flowing into the absorption chamber (28, 57) with an inclination of less than or equal to 5 degrees relative to the wall (138) in the main flow direction.

40. A receiver reactor according to any one of claims 22, 26 or 30, wherein the delivery device has an orifice for the hydrocarbon gas leading to the absorber chamber (28, 57), which generates a flow component of the fluid flowing into the absorption chamber (28, 57) tangentially to the axis (127) of the absorption chamber (28, 57).

41. A receiver reactor according to any one of claims 22, 26 or 30, wherein a 2 A further supply line section (14) which can be switched so that hydrocarbon gas and CO 2 The mixture is fed into the flow channel (2) of the receiver reactor (1, 30, 40).

42. A receiver reactor according to claim 41, wherein the hydrocarbon gas is methane.

43. A receiver reactor according to any one of claims 22, 26 or 30, wherein its outlet (8) is connected via a first line arrangement to a stratified heat reservoir reactor (172), which has an internal flow path (176, 176') for conveying products of the receiver reactor (1, 30, 40), wherein solid state heat reservoir elements (177) are arranged in turn to allow the conveyed products to flow around them and / or through them to come into physical contact.

44. A receiver reactor according to claim 43, wherein the stratified heat storage reactor (172, 172') is connected to a second line arrangement which is itself connected to a hydrocarbon gas source, which opens into an internal flow path (176, 176') for the product of the receiver reactor (1, 30, 40).

45. A receiver reactor according to claim 43, wherein the stratified heat storage reactor (172, 172') is connected to a third line arrangement which is itself connected to a source of oxidizing gas, which opens into an internal flow path (176, 176') for the products of the receiver reactor (1, 30, 40).

46. ​​The receiver reactor of claim 45, wherein the oxidizing gas is water vapor or CO 2 or a mixture thereof.

47. A receiver reactor according to claim 43, wherein the stratified heat reservoir (172, 172') has solid state heat reservoir elements (177) arranged in the internal flow paths (176, 176') of the stratified heat reservoir so that during operation the gas flows around them to come into physical contact.

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