CH715241A2 - Process for the production of syngas with the help of solar radiation and a solar reactor receiver. - Google Patents

Abstract

The invention relates to a method for producing syngas with the aid of solar radiation, in which the reactor of a receiver reactor (4) periodically for an reduction process to an upper one via an opening (13) provided therein for solar radiation through the solar radiation (13) The reduction temperature is heated and then cooled to a lower oxidation temperature for an oxidation process in the presence of an oxidation gas, the sunlight (3) being passed through an absorption chamber (15) onto an absorber (14) designed as a reactor, which is a reducible / oxidizable material and wherein a gas which absorbs the blackbody radiation (55) of the absorber (14) is passed through the absorption chamber (15) and the latter is formed such that the reflection of the absorber (14) through the opening (13) is essentially absorbed by the gas becomes. As a result, radiation losses due to retroreflection of the blackbody radiation (55) from the optical opening (13) are avoided. However, the heat of the retroreflection can be used directly in the heat-transporting fluid and is available for flexible use. The receiver reactor (4) has a simple design and is suitable as a low-cost receiver reactor.

Description

Description The present invention relates to a solar receiver reactor, i.e. a reactor that is powered directly by the energy of solar radiation.

One of the numerous applications is in the field of the production of solar fuels (solar fuels), the starting materials H2 (hydrogen) and CO (carbon monoxide) with the addition of energy - namely heat at high temperatures - from H ₂ O (water) and CO ₂ (carbon dioxide) are formed. A gas mixture that mainly contains H ₂ and CO - in addition to other gases - is called synthesis gas or simply syngas. This syngas is used to produce liquid or gaseous hydrocarbon fuels.

Syngas is preferably obtained by a redox reaction, so that the reactor must be operated alternately between an upper, the reduction _temperature T _rec i and a lower, the oxidation _temperature T _ox .

In an ETH dissertation no. 21864 "SOLAR THERMOCHEMICAL CO2 AND H2O SPLITTING VIA CERIA REDOX REACTIONS" by Philipp Furier describes an experimental, solar cerium reactor that uses concentrated sunlight (2865 suns, ie thermal radiation of up to 2865 kW / m ² ) Synthesis gas can be produced.

Sunlight in the concentration mentioned above can be generated on an industrial basis, for example with a dish concentrator according to WO 2011/072 410, so that the commercial production of synthesis gas using renewable or regenerative energy has become realistic. In addition, sunlight is now increasingly being generated in a sufficiently concentrated form in solar tower power plants, although receiver reactors are generally not provided, but rather heat is generated which is used as industrial heat by a consumer or is used, for example, to generate electricity. Correspondingly, the receiver of the belt power station heats a heat-transporting medium to a temperature T _o , which is cooled by the consumer and reaches the receiver in the circuit for renewed heating at a temperature T _in .

In solar tower power plants essentially spatially trained receivers are used, which are suitable for high temperatures, such as can be achieved for example at a concentration of 500 suns, 1000 suns or more. Such temperatures are typically above 800 K, and may reach 1500 K or more in the near future. Such receivers can also be used in dish concentrators, albeit on a smaller scale. In the present case, spatial receivers are referred to as receivers, the dimensions of which are comparatively large in all three dimensions, in contrast to tubular receivers which are used in connection with trough or channel collectors. Such tubular receivers have a dimension, the length, which is a multiple, in the range of ten or a hundred times or more of the cross-sectional dimensions, width or height. Receivers for trough collectors are not designed for the temperatures mentioned above, since the trough-shaped concentrator concentrates in two dimensions with respect to the receiver, but the field of heliostats in a tower power plant or a dish concentrator, however, in three dimensions.

Among other things, volumetric receivers are known which are also suitable for solar tower power plants, the required temperatures of more than 800 K to 1300 K being able to be achieved in such receivers. However, the high operating temperatures lead to considerable design effort.

Volumetric receivers have an extensive absorber structure, which can consist, for example, of a voluminous wire mesh or an open-pored ceramic foam. The concentrated solar radiation then penetrates into the interior of the absorber structure and is absorbed there. A heat-transporting medium such as air is passed through the open-porous absorber structure and thus absorbs heat from the open-porous absorber structure by means of forced convection. The absorber structure can also consist of a tubular structure, a lattice structure that is staggered in depth, or any structure with a large surface area that effects the convective heat transfer from the absorber structure to the heat-transporting medium when it flows through the absorber.

A volumetric receiver has become known, for example, from the REFOS project (Receiver for solar hybrid gas turbine and combined cycle systems; R. Buck, Μ. Abele, J. Kun-berger, T. Denk, P. Hellerand E. Lüpfert, in Journal de Physique IV France 9 (1999)). An outlet temperature T _out of 1100 K, with a ceramic absorber of 1300 K can be achieved by a receiver like the REFOS receiver shown.

Such receivers have the disadvantage that the absorber structure is complex to manufacture and the flow through the absorber is often unstable, in particular due to an undesirable temperature distribution during operation, and that considerable flow losses have to be accepted for the flow.

According to the ETH dissertation mentioned above, cerium is reduced to an upper temperature of 1800 K in a first, endothermic process step with the formation of oxygen; After the reduction has been completed, the cerium is then cooled to a lower temperature of 1100 K and, in a subsequent process step, the synthesis gas is produced by exothermic reoxidation; however, the endothermic heat required for the production of the syngas is much greater than the exothermic heat generated by the oxidation. This process can be repeated cyclically for a continuous production of synthesis gas; for this purpose, the cerium has to be heated periodically to 1800 K and cooled to 1100 K. For recuperation from cooling

In CH 715 241 A2, a double ring construction of a cerium carrier is proposed. Two counter-rotating, adjacent cerium rings with a common axis of rotation lie between the warm zone (1800 K) and the cold zone (1100 K) such that a section of each ring in the warm zone is at a 12 o'clock position and an opposite section in the cold zone is at a 6 o'clock position. By counterclockwise rotation of immediately adjacent cerium rings, the cold section of a first cerium ring moves clockwise in the direction of the warm zone and the warm section in the direction of the cold zone, and in the case of a second, counterclockwise rotating cerium ring, it also migrates cold section in the direction of the warm zone and the warm section in the direction of the cold zone, the two cerium rings brushing past one another and thereby continuously exchanging heat energy. Correspondingly, warm sections are cooled and cold sections are heated, which enables a recuperation of a quantity of heat. However, the efficiency of the recuperation is low due to the design and is around 25%. The demands on the design and the stability of counter-rotating, adjoining cerium rings - heat transfer, heat radiation and mechanical effort - are great.

The invention is therefore based on the object to provide a receiver reactor of simple construction with high efficiency.

[0013] This object is achieved by a method having the features of claim 1 or by a receiver reactor having the features of claim 13.

Characterized in that the absorber forms the redox reactor in a solar receiver and this is preceded by an absorption space for the blackbody radiation of the absorber in the path of solar radiation, the heat losses of the system are significantly reduced without any further design effort. If a gas that absorbs the black body radiation of the absorber is also used as the oxidizing gas, the construction is additionally simplified, since the absorption space can then also be used as a simply designed reactor space and serves as a zone shielding the retroreflection.

In addition to the task, the heat of the retroreflection can be provided for the periodic heating of the absorber to the reduction temperature and / or for external use of a receiver reactor, as is the case with conventional receivers.

Basically, the concept according to the invention, i.e. the possible and almost complete shielding of the receiver reactor by absorptive gases enables the high temperatures required for the redox reaction in the first place with the help of a simple, industrial construction of the receiver.

[0017] Further preferred embodiments have the features of the dependent claims.

The invention is described below with reference to the figures. It shows:

1a schematically shows a solar tower power plant with an embodiment of the receiver reactor according to the invention,

1b schematically shows the solar tower power plant of FIG. 1a with a further embodiment of the receiver reactor according to the invention,

2a schematically shows the structure of the receiver reactor according to the invention, the absorber space being designed as a reactor space,

2b is a diagram with the residual radiation losses of a receiver reactor according to FIG. 2a,

3a shows a diagram with operating temperatures of an exemplary syngas production of a receiver reactor according to FIG. 2a,

3b shows a diagram with the temperature of the absorber of a receiver reactor according to FIG. 2a as a function of the outlet temperature of the heat-transporting fluid,

3c shows a diagram with the temperature of the heat-transporting fluid during operation of the receiver reactor according to FIG. 3a,

4a schematically shows a longitudinal section through a receiver reactor according to the invention, the absorption space being separated from the reactor space,

4b schematically shows a cross section through the receiver reactor of FIG. 4a, the absorption space being separated from the reactor space,

5a schematically shows a modified receiver reactor for the use of partially heated heat-transporting fluid,

CH 715 241 A2

5b schematically shows yet another embodiment of the receiver reactor according to the invention with a secondary absorber,

5c schematically shows yet another embodiment of the receiver reactor according to the invention,

5d schematically shows yet another embodiment of the receiver reactor according to the invention.

Fig. 1a shows schematically a solar tower power plant 1, with a field of heliostats 2, which in a known manner direct rays 3 of the sun onto a receiver reactor 4 according to the invention, which in turn is arranged on a tower 5. The heat accumulating in the receiver reactor 4, but currently not usable or not required for the redox reaction taking place in it, is, according to the invention, transferred to a consumer 7 via a line 6 via an absorptively heated, heat-transporting fluid with a (higher) temperature T _o (which is simply referred to below as a heat exchanger), where it cools down and is then recirculated to the receiver reactor 4 via a line 8 with a (lower) temperature T _in .

Fig. 1a shows a first embodiment according to the invention, in which the absorptively heatable heat-exchanging fluid is also a gas participating in the redox reaction, which can thus contain syngas components downstream of the reactor. Correspondingly, these syngas components are also conducted as reaction products in line 6 into a separation station 9, where they are separated from the heat-transporting fluid for further use. This results in a solar reactor receiver in which the circuit line arrangement 6, 8 preferably further has a separation station 9 which is designed to separate syngas from the heat-transporting fluid and to make it available for removal from the circuit.

Fig. 1b shows a second embodiment according to the invention, wherein the absorptively heated, heat-exchanging fluid and the gas or gases participating in the redox reaction are conducted in separate line arrangements: in addition to that through lines 6 and 8 with the heat exchanger 7 formed circuit for the heat-transporting fluid further lines 10, 10 'are provided for the transport of gases participating in the redox reaction, which are prepared for operation in a process unit 11 so that the syngas can be obtained in the process unit 11.

Both embodiments (FIGS. 1 a and 1 b) have in common that heat which is not consumed is absorptively detected by the redox reaction in the receiver reactor and is fed to a consumer or heat exchanger 7. This heat can be obtained in the simplest way in terms of construction and can be used as desired. In the case of the redox process described below, in which the reactor oscillates between a lower oxidation temperature TDX and an upper reduction temperature T _rec i, this heat can also be used for the temperature rise to the reduction temperature.

2a schematically shows the structure of a receiver reactor 4 designed as a spatial receiver.

The receiver reactor 4 has a heating area 12, with an optical opening 13, for example a quartz window, and an absorber 14, wherein an absorption space 15 is provided between the quartz window 13 and the absorber 14, the medium transporting the heat the arrows shown flow from right to left, ie towards the absorber 4. For this purpose, the transport device 16 has arranged around the quartz window 13 (connected to the line 8, see FIG. 1) inlet connection 17 for heat-transporting medium with the temperature T _in , which lead into the absorption space 5, and a central one behind which Absorber 4 arranged outlet nozzle 8 for heat-transporting medium with the temperature T _o (which opens into the line 6, see Fig. 1).

The absorber 14 is designed according to the invention as a reactor element through which the arrangement shown is from a receiver to a receiver reactor, i.e. an arrangement in which concentrated solar radiation, for example from a solar tower power plant, is used to allow a redox reaction to take place under the conditions described below, here preferably the production of syngas.

To this end, the absorber 4 designed as a redox reactor has a reducible and oxidizable material for a reduction and an oxidation process, preferably CeO ₂ , which can be reduced at elevated temperature or oxidized in the presence of an oxidizing gas. The person skilled in the art can determine other materials for the specific case, for example cerium dioxide (CeO ₂ ), doped CeO ₂ , or perovskite.

Furthermore, the absorber 14 is designed according to the invention as a blackbody radiation arrangement, i.e. it has a surface 14 ', which absorbs this radiation and is arranged in the path of the incident solar radiation 3, and is designed such that the absorber 14 heats up due to the solar radiation 3 incident on its surface 14' and then corresponding black body radiation via its surface 14 ' (essentially infrared radiation) in the absorption space 15, s. see also the description below. The term blackbody radiation is used here to denote the radiation emitted by the absorber 14 on the basis of its temperature, in contrast to the sunlight 3 reflected by it. The temperature of the absorber 14 is determined by the absorption of the

CH 715 241 A2

Sunlight 3 is greatly increased and can range from, for example, 1000 K to over 2000 K, depending on the design of the receiver reactor 4 in the specific case, and depending on the materials used. In principle, however, there is no upper limit to the operating temperature range of the receiver reactor, but depends on the desired temperatures and the available materials. CeO ₂ offers the advantage that it has a high degree of absorption even in a slightly reduced state and can therefore be easily heated by the solar radiation.

Thus, the absorber 14 emits its heat output in the form of black body radiation (infrared radiation) in the absorber space 15, insofar as this is not consumed for the endothermic reaction of the reduction and the formation of syngas during the oxidation. The correspondingly required energy is supplied by solar radiation 3.

Furthermore, an infrared radiation-absorbing gas or gas mixture is used as the heat-transporting medium, which absorbs the blackbody radiation of the absorber 4 during its dwell time in the heating region 12 and heats up accordingly with regard to t _ou t. A heteropolar gas, preferably one or a mixture of the gases CO ₂ , water vapor, CH ₄ , NH ₃ , CO, SO ₂ , SO ₃ , HCl, NO, and NO ₂ , can be used as the infrared-absorbing gas.

When using such gases, there is ultimately a greenhouse effect which can be used or used by the receiver reactor according to the invention, since these gases are highly transparent to visible light, which thus essentially reaches the absorber, but little for the infrared radiation of the absorber until they are hardly transparent, so that they warm up to T _{out in} front of the absorber. It should be noted here that real gases do not absorb visible light or infrared radiation uniformly over all frequencies or are transparent to them, but above all in frequency bands specific for a particular gas. In addition, the absorption decreases with the distance from the radiation source. As a result, in terms of the absorption or transparency of radiation, one speaks of “highly transparent” or of “little to hardly transparent” above.

A determining parameter is thus the absorptivity α of the heat-transporting gas, which is measured by experiments, calculated from spectral line values from molecular spectroscopic databases (e.g. HITEMP2010), or can also be approximately determined from emissivity diagrams according to the Hottel rule.

It should be noted at this point that, of course, in addition to the visible light which has no infrared frequencies, the sunlight also has such infrared frequencies. According to the invention, these are then absorbed directly by the heat-transporting fluid in the absorption space, the energy of which is therefore used essentially without losses, since the retroreflection is in turn absorbed by the flowing fluid.

Finally, in addition to the use of an infrared absorbing gas or gas mixture, the absorption space 15 is designed in such a way and the mass flow of the heat-transporting medium is determined such that preferably essentially all of the blackbody radiation of the absorber 14 is absorbed by the heat-transporting medium, i.e. that the reflection of the absorber 14 through the opening 13 is essentially absorbed by the gas.

The retroreflection of the absorber 14 is its blackbody radiation, which lies on a path running through the opening 13 and thus - if not absorbed - is emitted into the environment and thus reduces the efficiency of the receiver reactor. According to the invention, a special zone, the absorption space 15, is now created in combination with the absorber designed as a reactor in order to eliminate these efficiency losses within the framework of the geometry that is even possible for a receiver reactor. The path running through the opening does not have to lie on a straight line, but also includes black body radiation from the absorber 14 reflected by the walls of the absorption space.

A retroreflection of the absorber 14 absorbed according to the invention requires that on the one hand the absorption space 15 is long enough, and on the other hand that the mass flow of the heat-transporting fluid is sufficient to maintain a temperature profile in the absorption space 15 such that the temperature is local the opening is only slightly above T _in , which would no longer be the case, for example, if the heat-transporting fluid stopped after a period of time.

Fig. 2b shows a diagram 16, in which on the horizontal axis the outlet temperature T _ou t of the heat-transporting gas and on the vertical axis the proportion of the black body radiation emerging from the opening 13 of the absorber 14, that is, the undesired reflection. If the opening 13 has a window made of quartz glass, for example, the reflection is indicated by curve 17, without window by curve 18. Curves 17 and 18 are the result of a simulation, see FIG. the description below for FIGS. 3a to 3c, ie they apply to an absorption space 15 with a diameter and a height of 15.95 m each, as could be suitable for a heliostat field.

Depending on the specific case, the person skilled in the art can determine the geometry of the absorber space, so that the remaining retroreflection essentially does not occur (which, however, could possibly lead to an absorption space which is disadvantageously long in other respects) or is somewhat increased if a particularly compact design is desired, in which case 80% or more, or 90% or more of the blackbody radiation of the absorber can still be absorbed.

It follows that the heat-transporting fluid is preferably composed in this way and the transport device and the absorber chamber are designed in such a way that the heat-transporting fluid is in operation of the reactor

CH 715 241 A2> 80%, preferably> 90% and very preferably> 94% of the black body radiation of the absorber, which lies on a path through the opening for the radiation of the sun.

[0039] There are three advantages to using an infrared absorbing gas:

First, according to the invention, radiation losses due to retroreflection of the blackbody radiation from the optical opening are largely or essentially completely avoided. This retroreflection noticeably reduces the efficiency of a conventional receiver (and thus a receiver reactor).

Second, the heat of the blackbody radiation from the absorber can be used directly in the heat-transporting fluid and is available for flexible use, see FIG. see also the description below.

Third, for the heating of the heat-transporting medium to T _out, neither a design effort nor corresponding flow losses have to be accepted, as is the case with conventional receivers that mainly work via convection. The related problems with volumetric receivers with spatially designed absorbers of complicated structure (construction effort, flow losses) are eliminated. This applies in particular with regard to the absorption space, since high temperatures of the absorber, but also of the side walls of the absorption space, are advantageous for the most intense blackbody radiation into the absorption space, so that coolants of all kinds are omitted, in particular cooling channels, as is the case with receivers according to the state of the art the technology is provided - either cooling channels in the walls or cooling channels in the absorber that ensure maximum convection.

The walls of the absorption space 15 and / or the absorbers 14 are therefore preferably free of any kind of coolants activated in normal operation, in particular free of cooling channels. Of course, according to the invention, emergency coolants for an extraordinary operating state can always be provided at every point of the receiver reactor in order to protect it from a prohibited operating state.

It is true that the heat-transporting medium present in the region of the optical opening 13 has the temperature T _in and thus generates its own blackbody radiation through the optical opening. However, this retroreflection is of subordinate importance compared to that of the absorber 14, since the blackbody radiation increases with the 4th power of the temperature, so the blackbody radiation of the absorber 14 would produce relevantly higher radiation losses through the optical opening, but this is not the case according to the invention.

In the embodiment shown in FIG. 2a, the heat-transporting fluid flows through the absorber 14, so that it also heats up somewhat convectively after the absorptive heating in the absorption space 15. The result is that the absorber is preferably designed for the flow through of heat-transporting fluid and the surface of the flowed-through area then further preferably consists at least partially of reducible / oxidizable material. Thus, in the embodiment shown, the absorbent gas is preferably passed through the absorber during the reduction process and during the oxidation process in such a way that it also heats up there convectively. This arrangement has the advantage that on the one hand, as mentioned, the absorber 14 does not reflect back through the opening 13 and, on the other hand, the absorber 14 can be designed for convective heat transfer to the heat-transporting medium in such a way that it easily differs from the mass flow of the heat-transporting medium the upper reduction _temperature T _rec i can be cooled to the lower oxidation _temperature T _ox (see also the description below) - but the absorber 14 can still be designed simply and with low flow losses. In an embodiment not shown in the figure, the person skilled in the art can also provide for the specific case to pass the heat-transporting fluid for the oxidation (ie in the phase of the redox cycle during the drop in the absorber temperature) with convection through the absorber and for that Reduction (ie in the phase of the redox cycle during the rise in the absorber temperature) past the absorber, for example through outlet lines 51 according to FIG. 4). Then the absorber cools down for the oxidation and heats up correspondingly relieved with regard to the reduction temperature.

Thus, the heat-transporting fluid at the inlet connection 17 has the temperature T _in , after the absorptive heating in the absorption space 15 the temperature T _out and after the outlet connection the somewhat higher temperature T _o .

In other words, in the arrangement shown in FIG. 2a, the reducing / oxidizing material is arranged on the side facing the absorption space, so that the absorption space also becomes the reactor space in which the redox reaction takes place. It is found that an at least oxidizing gas, preferably water vapor or CO ₂ , is preferably used as the infrared absorbing gas, which is passed through the absorption chamber to the absorber in such a way that it participates in the redox reaction in the absorption chamber and through the absorber is reduced in the oxidation phase. Then, as described in FIG. 1 a above, the at least oxidizing gas is preferably passed downstream of the absorber into a separation station and syngas is separated from it in this, further preferably the oxidizing gas being recirculated to the absorber chamber, and in doing so in this Circuit in the flow direction is cooled in a heat exchanger before the absorber.

Furthermore, as described above, the throughflow openings of the absorber can also be provided with the reducible / oxidizable material, and, depending on the specific case, the rear of the absorber, so that the area behind the absorber up to the outlet port becomes the reaction space.

CH 715 241 A2 The oxidation phase of the redox reactor described above necessarily precedes the reduction phase, which in turn is favored if an infrared-absorbing gas is used which has a low oxygen partial pressure, since then the reduction of the redox reactor at one each temperature occurs more, which in turn increases the efficiency of the arrangement. Preferred infrared absorbing gases used during at least the reduction phase of the redox reactor are water vapor and CO ₂ , or other gases or gas mixtures whose oxygen partial pressure is equal to or less than that of water vapor or CO ₂ at the temperatures provided for the reduction. It preferably results that a gas with an oxygen partial pressure at a temperature prevailing during the reduction phase of the redox reactor of equal or less than the higher value of the oxygen partial pressure of water vapor or CO ₂ at this temperature is used as the infrared absorbing gas, and this Gas is conducted at least during the reduction phase (through the circuit line arrangement) through the absorption chamber to the absorber, such that the absorber is reduced in the reduction phase in the presence of this gas. The reduction thus takes place more easily due to the low oxygen partial pressure, ie for a certain degree of reduction at a lower temperature than would be the case with a gas with a higher oxygen partial pressure.

These embodiments have in common that the heat-transporting fluid is a gas that can be reduced during the oxidation of the absorber, the reducible / oxidizable material of the absorber being arranged on the absorber in such a way that it lies operably in the flow path of the heat-transporting fluid so that it is is reduced in the oxidation phase of the redox reactor.

The operation of the receiver reactor according to the invention is described in more detail using the example of an embodiment according to FIG. 2, based on the diagrams formed from the applicant's simulations in FIGS. 3a to 3c.

The simulation is based on the following data:

Length and diameter of the absorption chamber 15 are each 15.96 m. This means that there is a sufficient length of the absorption chamber for the almost complete absorption of the black body radiation from the absorber. The absorber can then be designed, for example, as a simple plate, so that the receiver reactor can be easily manufactured as a constructive, low-cost solution. Then the surface of the absorber radiating into the absorption space preferably has a reducible / oxidizable material.

The diameter of the optical opening 13 is 11.28 m, which is thus suitable for receiving the radiation from the field of heliostats 2 (FIG. 1), but with an area of 100 m ^{2 is} only half the size of the absorber 14 with 200 m ² , so that the reflection of the heat-transporting fluid with the temperature T _in is reduced accordingly.

The absorber 14 consists of CeO ₂ , the weight of the receiver reactor is 1441. The radiation flow through the optical opening 13 is 1200 kW / m ² and 14 '600 kW / m ² (which is opposite the opening 13 has twice the area.

[0056] Water vapor is used as the heat-transporting and infrared-absorbing fluid, the temperature of which is T _in 1000 K. This temperature is an example of an industrial process assigned to the receiver reactor, which runs at 900 K, for example, see FIG. 1. The temperature T _ou t of the water vapor at the absorber is 1800 K with regard to the upper reduction temperature T _rec i of the absorber 14 required for the redox reaction (see also the description below for FIG. 3a).

The redox reaction at the reactor basically takes place in such a way that the absorber 14 is increasingly reduced with increasing temperature (ie it loses oxygen), the extent of the reduction depending on the temperature of the absorber 14 and the oxygen partial pressure prevailing there. The equation CeO (2-ö _ox ) -> CeO (2ö _r ed) + (5 _re d5ox) O applies to the reduction, since the absorber 14 does not release the oxygen stoichiometrically. In principle, the reduction could take place in a vacuum, but here in the presence of water vapor, which prevents the absorber 14 from reflecting back through the optical opening 13 and removes the oxygen (δ _Γ θά-δ _οχ ) Ο with it from the reactor receiver, for example the separation station 9.

With falling temperature, the absorber 14 is increasingly oxidized (ie it absorbs oxygen), the degree of oxidation in turn depending on the temperature of the absorber 14 and the oxygen partial pressure prevailing there. The heat-transporting fluid is the oxygen supplier, ie here the water vapor (the oxygen released during the reduction has been removed from the receiver reactor). For the oxidation, the equation CeO (2öred) + (ôred-Sox) H2O -> CeO (2-ö _ox ) + (δ _Γ θά-δ _0Χ ) H _{2 applies} , since the absorber 14 does not take up the oxygen stoichiometrically. As a result, H ₂ , ie hydrogen, has formed, which in turn is removed from the heat-transporting fluid to the separation station 9 (FIG. 1), separated there and made available as syngas.

The non-stoichiometric δ denotes the amount of oxygen lost by the CeO ₂ , ie the respective “reduction” or “oxidation state” which, as mentioned, depends on the oxygen partial pressure and the temperature. From the point of view of a specific redox process, there is a reduction state with a larger δ and an oxidation state with a smaller δ.

CH 715 241 A2 Fig. 3a shows a diagram 20 for the operation of the receiver reactor 1 with the data specified above. The oxygen partial pressure is plotted logarithmically on the vertical axis, and the temperature of the absorber 14 comprising a reducible / oxidizable material, which here consists of CeO _2, is plotted on the horizontal axis.

For one embodiment of the redox process in a receiver reactor according to the invention, a sufficient reduction in cerium oxide (CeO ₂ ) of Δδ = δ _Γ θά-δ _0Χ = 0.06 is assumed, where then δ _οχ = 0.04 and ö _re d = 0.1. Curve 21 shows when, depending on temperature and oxygen partial pressure, ö _rec i = 0.1. Curve 22 shows when δ _οχ = 0.04 as a function of temperature and oxygen partial _pressure . Curve 23 again shows the oxygen partial pressure of water vapor as a function of the temperature.

The intersection 24 of the curves 21 (ö _re d = 0.1) and 23 (water vapor) determines the upper absorber temperature T _re d for the reduction, the intersection 25 of the curves 22 (δ _οχ = 0.04) and 23 (Water vapor) the lower absorber temperature T _ox for the oxidation. Arrow 26 thus shows the temperature interval to be traversed at absorber 14 for the desired redox process, which generates hydrogen here. This interval is advantageously small, about 200 K, since high operating temperatures can easily be reached with the arrangement according to the invention. It should be noted here that this interval becomes increasingly smaller at even higher temperatures. Due to its design, the receiver reactor according to the invention is fundamentally suitable for being operated in such high temperature ranges as the temperature resistance of the materials selected by the person skilled in the art in the specific case allows.

3b shows a diagram 30 for increasing the temperature of the absorber 14 to the upper reduction temperature Ted. The temperature T _ou t of the heat-transporting fluid is plotted on the horizontal axis, and the temperature of the absorber 14 that can be achieved is plotted on the vertical axis . It should be noted at this point that the attainable temperature of the absorber is only slightly dependent on T _out of the heat-transport fluid, which is a flexible tuning of T _out to the external consumer (ie an adaptation of T _out to the needs of the consumer) permits , the temperature of the absorber / reactor then changing only to a much smaller extent than T _out . In this way, a desired reactor activity can be maintained, even if T _ou t fluctuates according to demand.

In the present exemplary embodiment, the inlet temperature T _{in of} the water vapor in the reactor receiver is 41000 K, see FIG. above. The starting temperature T _out can be controlled via the mass flow of the heat-transporting fluid through the absorption space 15. Curve 31 thus shows via point 31 'that the upper temperature T _re d for the reduction of the absorber 14, here 2058 K (see diagram 20, FIG. 3a), at a temperature of the water vapor of T _ou t of approx. 1750 K is reached. Since the diagram shows a state of equilibrium that has only been reached after a long time, a temperature T _ou t of approximately 1800 K is provided in order to achieve an industrially usable cycle time.

It should be noted at this point that an increase in the mass flow is sufficient for lowering the absorber temperature to T _ox , whereupon the convective cooling of the absorber by the heat-transporting fluid begins, the absorptive heating accordingly decreasing, so that the slightly enlarged one convective cooling the lower temperature T _{ox is} reached without the heat-transporting fluid having to reach the temperature of T _ou t = approx. 1800 K.

3c finally shows a diagram 40, on the horizontal axis of which the height of the receiver reactor 4 is plotted (the zero point is in the optical opening 13, the maximum height of 15.95 m for the absorber 14). The temperature of the fluid transporting heat through the absorption space 15 from the opening 13 to the absorber 14 (here water vapor) is plotted on the vertical axis. Curve 41 now shows the temperature decrease of the water vapor from 1800 K at the location of the absorber 14 backwards (against the direction of the mass flow) to the opening 13, where the temperature is 1000 K, ie at T _in . In other words, the blackbody radiation of the absorber 14 is predominantly absorbed in the case of an initial temperature of the water vapor of 1800 K (upper reduction temperature Ted), ie the corresponding heat losses are prevented, see FIG. also diagram 16 of FIG. 2b. Of course, this absorption rate also applies when the temperature at the absorber is less than 1800 K, which is the case when the absorber temperature is lowered towards the oxidation temperature.

In other words, FIGS. 3a to 3c show a proof of concept of the above-mentioned advantages of the reactor receiver according to the invention.

In summary, there is a process for the production of syngas with the aid of solar radiation, in which the reactor of a receiver reactor is periodically heated through an opening provided for solar radiation by the solar radiation for a reduction process to an upper reduction temperature and then for an oxidation process is cooled to a lower oxidation temperature in the presence of an oxidation gas, the sunlight being guided through an absorption chamber onto an absorber designed as a reactor, which has a reducible / oxidizable material, and wherein a gas absorbing the blackbody radiation of the absorber is passed through the absorption chamber conducted and this is formed such that 80% or more of the black body radiation lying on a path to the opening (the reflection of the absorber) is absorbed by the gas.

There is also a solar receiver reactor with an opening for the radiation of the sun, an absorber arranged in the path of the incident light, a reactor for a redox reaction and a transport arrangement in which a gas participating in the redox reaction operational to and from the reactor,

CH 715 241 A2 wherein the absorber is designed as a reactor, an absorber chamber is arranged between the opening for the radiation of the sun and the absorber in the path of the incident light and blackbody radiation of the absorber, and that the transport arrangement has a circuit line arrangement, in which a heat-transporting fluid circulates, the circuit being designed in such a way that the heat-transporting fluid can be loaded with heat in the absorber chamber and cooled again in the heat exchanger, the heat-transporting fluid being an IR gas which passes through a path absorbed the opening running black body radiation of the absorber.

It also results that the solar receiver reactor with an opening for the radiation from the sun, an absorber arranged in the path of the incident light and a transport arrangement for heat-transporting fluid which cools the absorber is designed such that in the path an absorption space of the light is provided in front of the absorber and the transport arrangement is further designed to guide the heat-transporting fluid through the absorption space in such a way that it is heated by the black body radiation of the absorber, the absorber being a reducible / oxidizable material for a reduction - And an oxidation process and the heat-transporting fluid has a gas that absorbs in the frequency bands of the infrared range, which gas is composed and the transport device and the absorber chamber are designed in such a way that, during operation of the reactor, the heat-transporting fluid causes the reflection of the absorber through the opening essentially absorbed, and wherein the receiver reactor is designed such that the temperature of the reducible / oxidizable material of the absorber can alternately be brought back and forth between an upper temperature T _rec i and a lower temperature T _ox .

4a schematically shows a further embodiment of the receiver reactor 100 according to the invention in a longitudinal section through a diameter of the absorption space 101, which has a cylindrical section 102 at the front in the direction of sunlight and a rear, conical section 103. An absorber 104 consists of at least one, preferably a bundle of lines 105, on the inner wall of which a reducible / oxidizable material is arranged. These lines 105 carry a gas participating in the chemical, here the redox reaction - that is, an at least oxidizing gas which loses 0 atoms during the oxidation of the absorber (or its inner coating) and is (partially) reduced to the syngas . The solar radiation heats the absorber 101, which in turn emits its blackbody radiation into the absorption space 101, the infrared absorbing gas flowing through it (arrows 106) absorbing this radiation as described above and thereby heating up.

It should be noted at this point that the at least oxidizing gas can also be used during the reduction phase, then absorbs O atoms and transported away, consequently a corresponding separation station must be provided in order to remove the O atoms from the oxidation of the absorber to remove this, otherwise no syngas would be formed in the later oxidation phase. Alternatively, it is also possible in principle to use different gases for the oxidation and for the reduction, which can be advantageous in the specific case. Furthermore, it is possible to carry out the reduction under vacuum, so that the oxygen released during the reduction is in pure form and therefore no separation from a gas stream is necessary. In addition, by reducing the oxygen partial pressure during the reduction phase at a given reduction _temperature T _rec i, the _degree of reduction ö _rec i can be increased, so that more syngas can be produced in the subsequent oxidation phase and the efficiency of the redox process can thus be increased.

It follows that the absorber is preferably designed as a section of the further line arrangement and has at least one line for the at least oxidizing gas, on the inner wall of which reducible / oxidizable material is arranged. The absorber is further preferably designed as a line bundle for at least oxidizing gas.

The end of the receiver reactor 100, in which the infrared absorbing gas enters, can be of the same design as that of the receiver reactor 4 (FIG. 2). The end of the receiver reactor 100, which has the absorber 104, on the other hand, is modified as described above, the absorber 104 being designed as a bundle of lines 105. This allows the gas participating in the redox reaction to be separated from the heat-transporting fluid, in which case it is no longer the absorption space 15 (FIG. 2) that is the reaction space for the redox reaction, but the interior of the lines 105.

The heat-transporting fluid exits laterally through openings 108 (arrows 110), arrives in a collector 109 and is finally guided in line 8 to the heat exchanger 7 (FIG. 1b), then in circulation back to the reactor receiver 100. Alternatively, the heat-transporting fluid could, for example, also be passed between the lines 105 of the absorber 104 during the oxidation, in order to additionally convectively cool the absorber to a lower oxidation _temperature T _ox , and then introduced into the line 8 via a collector (not shown here) become.

The gas participating in the redox reaction is transported back and forth between the absorber 100 and the processing station 11) according to FIG. 1b via the lines 10, 10 'shown there.

FIG. 4b schematically shows the embodiment of the receiver reactor 100 according to the invention from FIG. 4a in a view from above, corresponding to the viewing direction A-A from FIG. 4a. The rows of openings 108 for the heat-transporting fluid, which are arranged on both sides of the absorber 104 (which consists of the bundle of lines 105), can be seen, which through the only partially visible (because covered by the section 103) collector 109 into the line 8 (FIG 1b) arrives. Due to the tapered design of the lower section 103 of the absorption space 101

CH 715 241 A2

Pipes 105 in this are of approximately the same length, so that the gas flowing in them and participating in the redox reaction heats up approximately equally. Its direction of flow is indicated by arrows 111.

It follows that, after the absorption of the blackbody radiation from the absorber, the absorbing gas is preferably removed as heat-transporting fluid from the receiver reactor without participating in the redox reaction, and that an at least oxidizing gas is separated from the absorbing gas Gas is fed to the absorber for the redox reaction. Furthermore, the at least oxidizing gas is passed through the absorber, which is preferably formed by a line bundle for the oxidizing gas. The receiver reactor then also has a line arrangement for at least oxidizing gas, which leads it separately from the absorbing gas and heat-exchanging gas.

In an embodiment, not shown in the figures, the at least oxidizing gas can be supplied to the side of the absorber facing away from the absorption space, the absorber itself again being able to be designed as a plate, then being heated on its side facing the absorption space, into the absorption space radiates and on the other hand has the reducible / oxidizable material which reacts with the gas participating in the reaction. The absorber is then preferably assigned to the circuit line arrangement and also to the further line arrangement for oxidizing gas, and forms a partition between the flow path of the heat-transporting fluid and that of the oxidizing gas.

FIG. 5a schematically shows a modified receiver reactor 50 for the use of partially heated heat-transporting fluid. A cross section through a further embodiment of a receiver reactor 50 in the manner of that of FIG. 2 or of FIGS. 5a and 5b is shown schematically. The sun rays 3 fall through a window made of, for example, quartz glass 13 onto the absorber 14, the radiating surface 14 'of which heats the gas flowing through the absorption space 15, the temperature of which increases from the window 13 to the absorber 14. Correspondingly, the gas can be withdrawn via openings 51 to 51 'in the cylindrical wall of the receiver 50 at different temperatures, which are greater than Tm, as a partially heated heat-transporting medium. The arrows indicate the direction of flow of the heat-transporting gas, the arrows at openings 51 to 51 'being drawn in correspondingly longer as the temperature rises.

Alternatively - or together with the openings 51 to 51 ', a line 53 projecting into the absorption space 15 can be provided for the gas, which line then passes through openings 52 to 52 "' at the gas at the location of the openings 52 to 52" '. prevailing temperatures, which is also partially heated and has a temperature which prevails in the interior of the absorption space 15 at the location of the openings. This is particularly advantageous when a downstream process running at different temperature levels is supplied with heat by the receiver reactor 50. From this process, heat-transporting gas can then be returned to the receiver at likewise different temperatures, so that further feed lines for the heat-transporting gas into the absorber space 15 of the receiver 50 are preferably provided in the area of the openings 51 to 51 'and 52 to 52' (which are omitted here to relieve the figure).

The result is a receiver in which the transport arrangement has one or more lines 51 to 51 'and 52 to 52' for heat-transporting gas connected to an absorber space 26, which are arranged such that gas which has been partially heated is removed from the absorber space 15 and / or partially heated gas can be supplied at a location at which the temperature of the gas in the absorber space 15 essentially corresponds to the temperature of the partially heated, supplied gas.

Such supply and discharge lines for partially heated gas can be provided on an absorptive receiver reactor according to the invention without its layout, in particular the absorber 14, having to be modified - these lines can also be used or shut down without it due to the different heat transfer requires a constructive modification.

5b schematically shows a further embodiment of the receiver reactor 60 according to the invention. A section through a receiver reactor 60 is shown, which corresponds to the receiver reactor 4 from FIG. 2, but with the absorber 61 with its optical one Absorbing surface 61 'facing opening 13 has a preferably plate-shaped section 64 which projects into the absorber space 67 and which extends in the middle of the absorber space 67 against the opening 13 and which is essentially parallel to the direction of flow of the infrared absorbing, indicated by the arrows, Heat exchanging gas is aligned. The section 64 essentially absorbs black bodies emitted by the absorbing surface 61 '(infrared radiation, insofar as this has not yet been absorbed by the gas flowing along it, that is to say in particular radiation in those frequency bands for which the gas is less absorbent (see FIG Description of the frequency bands effective in real gases above). This heats up and in turn represents a blackbody radiation arrangement which radiates in the whole blackbody frequency spectrum corresponding to the temperature of section 64 and in turn heats the gas flowing past in an absorptive manner Improved use of those frequencies of radiation 55 which are only slightly absorbed by the gas, since these frequencies introduce heat into section 64, which in turn radiates in all (infrared) frequencies. Section 64 represents a secondary absorber.

Such an arrangement can be of larger dimensions, for example with a diameter of the absorber surface 61 'of 15.96 m and a length of the absorber space 67 (absorber surface 61' to optical opening 13) of 15.96 m

CH 715 241 A2. The receiver 60 is then suitable for recording the flow of a large number (or all) of heliostats in a tower power plant. It follows that the receiver 60 has an absorption space 67 and the absorber 61 projects into this space with a section or secondary absorber 64, which is preferably plate-shaped. The secondary absorber 64 can then preferably also be at least partially provided with a reducible / oxidizable material, which, however, can be at least partially different from that of the absorber 61, depending on the location on the secondary absorber, where, in principle, the same temperature conditions are not present as on the absorber 61.

In a further embodiment, not shown in the figure, a glass wall (quartz glass), for example transparent to the visible spectrum of sunlight, can be provided as the secondary absorber, which is approximately in the middle between the absorber surface 61 'and the optical opening 13 parallel to the absorber surface 61 'is arranged and has passages, for example in the manner of a perforated plate, for the heat-transporting gas. Again, the glass wall is heated by the infrared radiation of the absorber surface 61 ', or by its frequency components which have not yet been absorbed by the gas, and even in the manner of the black body radiates in both directions, namely both against the optical opening and against the absorber. According to the invention, a receiver results which has a further secondary absorber designed as a blackbody radiation arrangement with reduced convection in an absorption space located in front of the absorber, which is arranged and designed such that it can be heated by the infrared radiation of the absorber and in operation via its own Radiation in turn acts in the absorber space, it preferably being plate-shaped and particularly preferably essentially not shading the absorber.

5c shows a further reactor receiver 70 according to the invention, with an optical opening 13 and an absorber 14, the absorption space 71 tapering conically in longitudinal section and laterally opening supply lines 72 for heat-transporting fluid are provided. There are also discharge lines 73 leading away to the side for the fluid transporting heat absorptively heated. Furthermore, a slide 75 is provided, which in its open position shown in the figure is pulled out of the absorption space 71 and does not impair the flow of solar radiation onto the absorber 14 and its blackbody radiation into the absorption space 71. This configuration is particularly well suited for the reduction of the absorber 14, ie in the phase of heating it from T _ox to T _re d.

If the slide 75 is brought into the closed position, which is indicated by the dashed lines 77, the absorber 14 is shielded from the radiation of the sun, which leads to rapid cooling of the absorber 14 in the oxidation phase, ie from T _rec i to T _ox , leads. An oxidizing gas, for example CO ₂ , can then be passed through the feed lines 76 to the absorber 14, oxidize it and be guided via the outlet connection 8 to the separation station 9 (FIG. 1). This has the advantage that a larger part of the gas can be passed through the absorber for the oxidation operation, so that the absorber cools down more quickly. It is also advantageous that the concentration of the syngas (here CO) in the gas led to the separation station is high, so that the separation can be carried out efficiently. In addition, the oxidizing gas can be conducted separately from the heat-transporting fluid intended for an external consumer 7 (FIG. 1) through the transport arrangement of the receiver reactor according to the invention.

After oxidation has taken place, the slide (which here represents a radiation barrier) is brought back into the open position. It follows that a radiation barrier is provided in a further embodiment, which can alternately be brought in front of the absorber in the path of solar radiation and removed from it again.

In one embodiment, not shown in the figures, a solar power plant has at least two reactors according to the invention, which are moved against one another in the cycle of reduction and oxidation and the solar reflectors, preferably heliostats, are each directed at the reactor which is in the reduction phase is located, while the other reactor is not illuminated by the solar reflectors. As a result, a constant stream of heated heat-transporting fluid and syngas is generated in the receiver reactors, regardless of the respective redox process, even if different gases are used for the reduction and oxidation (for example, water vapor reduction and CO ₂ oxidation) become.

Of course, water vapor can be used for the reduction, which has a smaller oxygen partial pressure than the CO ₂ at the prevailing high temperatures and is therefore cheaper for the reduction than CO ₂ , while CO ₂ can be provided for the oxidation if a syngas component CO should be produced. Correspondingly, the receiver reactor according to the invention can be operated with different heat-transporting fluids, depending on how these are favorable for the reduction or oxidation process in the specific case. It follows that an oxidizing gas, preferably water vapor or CO ₂ , can also be used as the infrared-absorbing gas, or that the transport arrangement has lines for the supply of different gases into the absorber space, preferably in such a way that the absorber space (or else the Space behind the absorber) for a reduction process and a gas for an oxidation process.

5d shows a further reactor receiver 80 according to the invention, with an optical opening 13 and an absorber 81 with an annular structure consisting of segments, which is arranged in a space 82 for stepwise rotation and delimits this from the absorption space 83. In the absorption space 83 lead lines for heat-transporting gas with the temperature T _in , which flows after the absorption of the blackbody radiation of the absorber segment 84 with the temperature T _out to it and then through the segment 84 and the receiver-Re

CH 715 241 A2 leaves actuator 80 via a lead 85 arranged perpendicular to the plane of the drawing and is then led via line 6 to a consumer 7 (see FIG. 1a). The segment 84 heats up accordingly, the absorber 81 remains in this position until the segment 84 has reached the reduction temperature T _rec i.

At the same time, the segment 86 is located in an area 87 of the room 82 shielded from the solar radiation, with oxidizing gas being supplied through the feed line 88, which flows through the segment 86 cooled to the oxidation _temperature T _ox and loaded with the syngas via the Outlet line 89 is brought to the separation station 9 (FIG. 1). Reduction and oxidation thus take place simultaneously, the same gas or different gases being able to be used depending on the design of the receiver reactor 80, but of course an infrared absorbing gas, for example water vapor, is provided in the absorption space 83, while infrared absorption is not mandatory in the space section 87 is.

At the same time, a heat-transporting fluid, which flows outward through the segment 92 of the absorber 81, is also supplied in the space section 90 via the line 91, thereby cooling it, heating it up and via the overflow channel 93, which is symbolically indicated by an arrow reaches the outside of the segment 94, flows through it from the outside in, thereby heating and cooling it and finally leaving the space 90 via the line 95. The lines 91 and 93 are interconnected behind the space 82, so that a circuit of heat-transporting fluid results through the segments 92 and 94. This cycle serves to recuperate the heat from the cooling of the respective absorber segments 84, 86, 92, 94 from the reduction temperature T _re d to the oxidation _temperature T _ox . If the absorber 81 is turned clockwise (see arrow 96) by a step of 90 degrees, the segment with the reduction temperature and the segment with the oxidation temperature are in space 90, with the circuit via lines 91, 95 and the overflow duct 93 transfer heat from the segment with the reduction temperature to the segment with the oxidation temperature, so that it can be recuperated: the heat dissipated for cooling for the oxidation of one segment is transferred to the other segment to be heated for the reduction.

In this cycle, too, the heat from the blackbody radiation is continuously removed via line 85 and utilized.

The result is a method in which, according to the invention, a warmer reduction zone and a colder oxidation zone are provided on the absorber, which periodically turn to the absorption space for heating and cooling and then are turned away from it again, or a receiver reactor according to the invention, in which case preferred the absorber is divided into areas (segments) which can alternately be operatively connected to the absorber room and to an oxidation zone (room 87), an intermediate zone (room 90) preferably being provided for the recuperation of heat. There is also an embodiment of the receiver reactor according to the invention, in which the transport arrangement is preferably designed to supply an oxidizing gas to the absorber on a side facing away from the absorption space.

It should be noted at this point that, for example, in one embodiment of the receiver reactor according to FIG. 2 or 4, the cooling can be accelerated by pivoting the heliostats away from the receiver reactor. At least two receiver reactors are then preferably provided and their operation is controlled in such a way that the heliostats are cyclically pivoted from one receiver reactor to the other, one being heated for the reduction and the other being cooled for the oxidation.

In an embodiment not shown in the figures, the heat-transporting medium is in the absorption space under excess pressure, with the result that the absorption space is shortened, which in turn allows an absorption rate of over 95% to be achieved. Then the transport arrangement and the absorption space for an overpressure of the heat-transporting fluid are formed.

Claims (29)

Claims 1. A method for producing syngas with the aid of solar radiation (3), in which the reactor of a receiver reactor (4, 50, 60, 70, 80, 100) via an opening (13) provided therein for solar radiation (3) through the Solar radiation (3) is periodically heated up to an upper reduction temperature (T _o ) for a reduction process and then cooled to a lower oxidation temperature (Tu) for an oxidation process in the presence of an oxidizing gas, characterized in that the sunlight is passed through an absorption chamber (15, 67, 71, 101) is passed through to an absorber (14, 61, 105) designed as a reactor, which has a reducible / oxidizable material, and a gas absorbing the blackbody radiation (55, 56) from the absorber (14, 61, 105) in this way the absorption chamber (15, 67, 71, 101) is guided and this is designed such that 80% or more of the black body radiation (55, 56) lying on a path to the opening (13) of the absorber (14, 61, 105) is absorbed. 2. The method for producing syngas with the aid of solar radiation (3) according to claim 1, wherein 85% or more, preferably 90% or more, very particularly preferably 95% or more of the black body radiation running on the path to the opening (13) ( 55, 56) of the absorber (14, 61, 105) is absorbed, most preferably it is essentially absorbed by the gas. CH 715 241 A2 3. The method according to claim 1, wherein an at least oxidizing gas, preferably water vapor or CO _{2 is} used as infrared absorbing gas, which is passed through the absorption chamber (15, 67, 71, 101) to the absorber (14, 61, 105), such that it takes part in the redox reaction in the absorption chamber (15, 67, 71, 101) and is reduced in the oxidation phase by the absorber (14, 61, 105). 4. The method according to claim 1, wherein the infrared absorbing gas is a gas with an oxygen partial pressure at a prevailing during the reduction phase of the redox reactor (4, 50, 60, 70, 80, 100) temperature equal to or less than the higher value of Oxygen partial pressure of water vapor or CO _{2 is used} at this temperature, and this gas is passed at least during the reduction phase through the absorption chamber (15, 67, 71, 101) to the absorber (14, 61, 105) such that it is present in the presence of the latter Gases is reduced. 5. The method according to claim 3 or 4, wherein the at least oxidizing gas downstream of the absorber (14, 61, 105) in a separation station (9) and separated in this syngas from it, preferably the oxidizing gas continues in the circuit Absorption chamber (15, 67, 71, 101) returned, in this circuit in the flow direction in front of the absorber (14,61,105) is cooled in a heat exchanger (7). 6. The method according to claim 3 or 4, wherein the at least oxidizing gas is passed through the absorber (14, 61, 105) during the reduction process and / or during the oxidation process, preferably in such a way that it heats up convectively. 7. The method according to claim 1, wherein the absorbing gas after the absorption of the black body radiation of the absorber (14,61,105) as a heat-transporting fluid from the receiver reactor (4, 50, 60, 70, 80,100) is discharged without it participates in the redox reaction, and wherein at least one oxidizing gas is fed separately from the absorbent gas to the absorber (14, 61, 105) for the redox reaction. 8. The method according to claim 7, wherein the at least oxidizing gas is supplied to the side of the absorber (14, 61, 105) facing away from the absorption space. 9. The method according to claim 7, wherein the at least oxidizing gas is passed through the absorber (14, 61, 105), wherein preferably the absorber (14, 61, 105) is formed by a line bundle (105) for the oxidizing gas. 10. The method according to claim 1, wherein the infrared absorbing gas is a heteropolar gas, preferably one or a mixture of the gases CO ₂ , water vapor, CH ₄ , NH ₃ , CO, SO ₂ , SO ₃ , HCl, NO, and NO ₂ , is used. 11. The method according to claim 1, wherein gas absorbed by absorption of the blackbody radiation (55, 56) of the absorber (14, 61, 105) is removed from the absorber chamber (15, 67, 71, 101) as soon as it is partially heated and / or a partially heated gas is supplied to the absorber chamber (15, 67, 71, 101), and the supply takes place in the absorber chamber (15, 67, 71, 101) at the respective location where the temperature in the absorber chamber (15, 67, 71,101) corresponds to the temperature of the partially heated gas. 12. The method according to claim 1, wherein cerium dioxide (CeO ₂ ), doped CeO ₂ , or perovskite are used as the reducible / oxidizable material. 13. Solar reactor receiver (4, 50, 60, 70, 80, 100) with an optical opening (13) for the radiation of the sun, an absorber (14, 61, 105) arranged in the path of the incident light (3) , a redox reactor for a redox reaction and a transport arrangement in which an oxidizing gas is operatively guided to and away from the reactor, characterized in that the absorber (14, 61, 105) is designed as a redox reactor between the opening (13) for the radiation of the sun and the absorber (14, 61, 105) in the path of the incident light (3) and in the path of blackbody radiation (55, 56) of the absorber (14, 61, 105) an absorption chamber (15, 67, 71, 101), and that the transport arrangement has a circuit line arrangement (6, 8) in which a heat-transporting fluid circulates, the circuit being designed such that the heat-transporting fluid in the absorption chamber (15, 67, 71, 101) loaded with heat d can be cooled again in the heat exchanger (7), the heat-transporting fluid being an infrared-absorbing gas which emits the blackbody radiation (55, 56) from the absorber (14, 61, 105) that runs through the opening (13) on a path ) absorbed. 14. Solar reactor receiver according to claim 13, wherein the heat-transporting fluid is composed and the transport arrangement and the absorber space (15, 67, 71, 101) are designed such that the heat-transporting fluid> 80%, preferably> 90 when the reactor is in operation % and very preferably> 94% of the blackbody radiation (55, 56) of the absorber (14, 61, 105) is absorbed, which lies on a path through the opening (13) for the radiation (3) from the sun. 15. Solar reactor receiver according to claim 13, wherein the heat-transporting fluid is a gas which can be reduced during the oxidation of the absorber (14, 61, 105) and wherein the reducible / oxidizable material of the absorber (14, 61, 105) is arranged thereon that it is operable in the flow path of the heat transporting fluid so that the fluid is reduced in the oxidation phase of the redox reactor. CH 715 241 A2 16. The solar reactor receiver according to claim 13, wherein the heat-transporting fluid is an infrared-absorbing gas with an oxygen partial pressure which is equal to or less than the higher value of the oxygen partial pressure of water vapor at a temperature prevailing during the reduction phase of the redox reactor -The CO ₂ at this temperature, and wherein the circuit line arrangement (6, 8) is formed, this gas at least during the reduction phase through the absorption chamber (15, 67, 71, 101) to the absorber (14, 61, 105) conduct such that the absorber (14, 61, 105) is reduced in operation during its reduction phase in the presence of this gas. 17. Solar reactor receiver according to claim 13, wherein the circuit line arrangement (6, 8) further comprises a separation station (9) which is designed to separate syngas from the heat-transporting fluid and to provide it for removal from the circuit. 18. Solar reactor receiver according to claim 13, wherein the reducible / oxidizable material on the absorption chamber (15, 67, 71, 101) facing surface of the absorber (14, 61, 105) is arranged and preferably the absorber (14, 61, 105) is plate-shaped . 19. Solar reactor receiver according to claim 13, wherein the absorber (14, 61, 105) is designed for the flow of heat-transporting fluid and the surface of the flowed area consists at least partially of reducible / oxidizable material. 20. Solar reactor receiver according to claim 13, wherein the receiver reactor (4, 50, 60, 70, 80, 100) further comprises a line arrangement for at least oxidizing gas, which leads this separately from the absorbent gas. 21. Solar reactor receiver according to claim 20, wherein the absorber (14, 61, 105) of the circuit line arrangement (6, 8) and the further line arrangement (10, 10) for oxidizing gas is assigned and between the flow path of the heat-transporting fluid and that of the oxidizing gas forms a partition. 22. Solar reactor receiver according to claim 20, wherein the absorber (14, 61, 105) is designed as a section of the further line arrangement (10, 10 ') and has at least one line (105) for the at least oxidizing gas, on the inner wall thereof reducible / oxidizable material is arranged. 23. Solar reactor receiver according to claim 22, wherein the absorber (14, 61, 105) is designed as a line bundle (105) for at least oxidizing gas. 24. Receiver reactor according to claim 13, wherein the gas is a heteropolar gas, preferably one or a mixture of the gases CO ₂ , water vapor, CH ₄ , NH ₃ , CO, SO ₂ , SO ₃ , HCl, NO, and NO ₂ . 25. Receiver reactor according to claim 13, wherein the reducible material comprises cerium dioxide (CeO ₂ ), doped CeO ₂ , or perovskite. 26. Receiver reactor according to claim 13, wherein the transport arrangement has one or more lines (51 to 51 ', 52 to 52') for heat-transporting gas connected to an absorber space (15, 67, 71, 101), which are arranged in such a way that Partially heated gas can be removed from the absorber space (15, 67, 71, 101) and / or partially heated gas can be supplied at a location at which the temperature of the gas in the absorber space (15, 67, 71, 101) essentially corresponds to the temperature of the partially heated, supplied gas corresponds. 27. Receiver reactor according to claim 13, wherein the walls of the absorption chamber (15, 67, 71, 101) and / or the absorber (14, 61, 105) are free of coolants activated in normal operation, in particular cooling channels. 28. Receiver reactor according to claim 13, wherein the transport arrangement and the absorption chamber (15, 67, 71, 101) are designed for an overpressure of the heat-transporting fluid. 29. Receiver reactor according to claim 13, wherein a preferably reducible / oxidizable material having secondary absorber (64) is provided in the absorption space and is arranged and designed such that it can be heated by the radiation of the absorber (14, 61, 105), and during operation its own radiation in turn acts in the absorber space (15, 67, 71, 101), it preferably being plate-shaped and particularly preferably essentially not shading the absorber (14, 61, 105). CH 715 241 A2