Solid plasma reactor and method of operating a fixed bed reactor

Abstract

The invention relates to a solid plasma reactor and to methods for operating a fixed bed reactor. According to the invention, they enable the pyrolysis of a wide variety of plastic fractions and organic solids. In addition, lime, for example, can be burned very effectively and without fossil fuels.

Description

[0001] Title: Solid plasma reactor and process for

[0002] Operating a fixed-bed reactor

[0003] Description

[0004] The invention relates to a solid-state plasma reactor and selected applications of the reactor according to the invention. The solid-state plasma reactor according to the invention provides a technology that is not limited to the applications claimed by way of example, but can contribute to solving the global challenges of our time. It can contribute to the defossilization of the economy and the closing of material cycles. The term "defossilization" refers to the economy increasingly using fewer fossil fuels and raw materials in production in order to ultimately reduce carbon dioxide emissions.

[0005] In connection with the invention, the term "gas discharge" is used; it includes both glow discharges and arcs.

[0006] DE 36 31 015 A1 discloses a process for producing a clean gas containing carbon monoxide and hydrogen. This process involves producing a raw gas in a gasifier by injecting a gaseous oxidizing agent at a temperature of around 1000°C into the gasifier. In the gasifier, wood or coal, for example, is converted together with the oxidizing agent into a raw gas at a temperature of around 440°C. A plasma generator is then used to add further energy to the raw gas in an additional reaction chamber, and the gas is then further processed in several cleaning steps. This process and system are technically complex and require a lot of both thermal and electrical energy.The invention is therefore based on the object of providing a reactor which enables the efficient and economical conversion of solids into a product gas, whereby in some applications a solid, non-gaseous product, such as quicklime, is produced in addition to the product gas.

[0007] This object is achieved according to the invention by a reactor comprising a reactor chamber, at least one plasma generator with two electrodes, at least one gas inlet, at least one gas outlet for the product stream and at least one recirculation line, wherein the electrodes of the at least one plasma generator are arranged between the gas inlet and the reactor chamber so that they are flowed through or around by the gas flowing through the gas inlet into the reactor chamber.

[0008] The reactor according to the invention enables a very effective implementation of processes in which one or more gas phase reactions and one or more solid phase reactions take place simultaneously.

[0009] The energy required for this is supplied to the gas or gas mixture flowing into the reactor chamber by means of a glow discharge or a non-thermal arc which is present between the electrodes of the plasma generator. The inventive arrangement of the gas inlet and the electrodes of the plasma generator ensures that the gas flowing through the gas inlet into the reactor chamber flows into a space between the electrodes of the plasma generator. As a result, the gas comes into contact with a gas discharge taking place between the electrodes. This gas discharge brings at least part of the gas into the plasma-like state.

[0010] At least part of the gas leaves the plasma generator as non-thermal plasma with very high temperatures (the electrons have temperatures greater than 10,000 K, the ions have temperatures greater than 1,000 K) and flows directly into the reactor chamber.

[0011] Due to the very high temperatures of the non-thermal plasma, the reactions and conversion processes in the reactor chamber proceed very reliably and rapidly. Immediately after the gas flowing into the reactor chamber through the gas inlet has passed through the reaction zone of the plasma generator (also referred to as plasma), the desired product gas is present. A portion of this product gas can be withdrawn via the gas outlet for the product stream.

[0012] The portion of the product gas remaining in the reactor chamber flows toward the solid present in the reactor chamber or through it if it is present as a bed. In doing so, it transfers heat to the solid. The heat input decomposes the solid, producing gaseous molecules that are returned to the gas inlet through the recirculation line along with the product gas.

[0013] The heat transfer from the very hot non-thermal plasma to the solid in the reactor vessel (via thermal radiation and conduction) occurs at high power, reliably and quickly bringing the solid to high temperatures. The portion of the product gas withdrawn via the gas outlet for the product stream also transfers energy to the solid in the reactor chamber via thermal radiation. Due to the high energy input at high temperatures, a wide variety of solids can be reliably decomposed into gaseous molecules in the reactor according to the invention.

[0014] The specific energy input into the working gas can be controlled by the electrical power of the plasma or the volume flow of supplied gas. The recirculation rate is adjusted to maintain the desired concentration of the product gas. In some applications, very high temperatures are required for the desired conversion, such as the conversion of limestone to quicklime. In some cases, the high temperatures ensure that pollutants are reliably converted into harmless / non-toxic compounds. In any case, the reactions are intensified and accelerated. This, among other things, leads to the wide range of possible applications of the reactor according to the invention.

[0015] In other words: The electrical energy required to operate the plasma generator is transferred directly to the gas with virtually no loss. If the solid-state plasma reactor according to the invention is powered by renewable electricity, the operation of the reactor does not cause any CO2 emissions.

[0016] A further advantage of the reactor according to the invention is that its power can be controlled very quickly and within a wide range (e.g., between 20% and 100% of the rated power) without negatively impacting the quality of the product gas or the solid products (e.g., quicklime). This makes it possible to purchase surplus renewable electricity very cheaply whenever there is a surplus in the power grid, thereby improving the economic efficiency of the reactor according to the invention. Furthermore, the shutdown of renewable electricity generation systems (photovoltaics, wind energy converters) can be avoided.

[0017] The thermal energy of the hot gases / plasma in the

[0018] The heat from the reactor chamber is then transferred very efficiently and quickly to the solids contained therein. Heat transfer occurs not only through conduction, but primarily through thermal radiation. As a result, the solid is decomposed into its components at very high temperatures (greater than 1,000 °C), leaving virtually no residue, or converted into a product (e.g., quicklime), depending on the application.

[0019] Due to the high decomposition temperatures, even problematic compounds in the solids, such as toxins, are decomposed very reliably. Contamination of the solids, for example, with halogens, such as those found in PVC, also poses no problem, since no catalyst is used in the reactor according to the invention, and catalysts are also not required in the subsequent process steps that further process the product gas.

[0020] Even contaminated solids are reliably decomposed in the reactor. Due to the high decomposition temperatures, toxic / harmful compounds contained in the solids are converted into harmless ones. The compounds that make up the solids are broken down into very small molecules or even atoms and then form new compounds with the gases in the reactor chamber.

[0021] This means that, in addition to its high energy efficiency, the operation of the solid-state reactor according to the invention is also inherently safe, as it does not produce any toxic organic by-products, regardless of the solids fed in. In a further advantageous embodiment of the invention, the recirculation line connects the reactor chamber to the gas inlet. This means that a portion of the gas stream flowing into the reactor through the gas inlet was previously located in the reactor chamber. The reactions taking place inside the reactor chamber can be controlled via the ratio between the recirculated gas from the reactor chamber and the additional gas fed into the reactor.

[0022] The proportion of newly introduced gas relative to recirculated gas can range from 0% to 50%, depending on the application. The recirculated gas can be moved by a blower or compressor in the recirculation line or in the gas inlet.

[0023] To improve the quality of the product gas, the invention provides for the installation of a separator in the recirculation line and / or in the product gas line. This allows, for example, volatile metals or other disruptive gaseous components to be separated. This not only further improves the quality of the product gas, but also prevents damage to downstream equipment.

[0024] Furthermore, it is possible, and in many cases advantageous, to provide a heat exchanger in the recirculation line so that part of the thermal energy of the gas in the recirculation line can be transferred to a liquid or gaseous heat transfer medium. This waste heat can be used elsewhere, e.g., in a process downstream of the reactor according to the invention. This increases the efficiency of the overall process.

[0025] This is possible because the waste heat generated in plasma processes occurs at a high temperature. For example, an absorption system for recovering CO2 from the product gas can be regenerated using the resulting waste heat.

[0026] In some applications of the reactor according to the invention, the demand for high-energy electrons to reform the gases in the plasma is so high that more heat is generated than is needed in the reactor. In these cases, the waste heat can be removed through the heat exchanger and used elsewhere.

[0027] It is also possible to provide an actuator, such as a slide valve or a flow control valve, in the recirculation line, preferably after the heat exchanger, in order to be able to actively control the flow rate of the gas through the recirculation line.

[0028] In the gas inlet and / or the recirculation line there is generally a blower or a jet pump which sucks in the new gas to be introduced into the process as well as the gas flowing through the recirculation line and conveys it into the reactor.

[0029] In order to be able to control the operation of the reactor even better, a controllable flap or a controllable flow control valve can be provided in the gas inlet and / or the recirculation line in addition to or as an alternative to the blower or the jet pump. In order to ensure that the heat transfer and the resulting decomposition or conversion of the solid takes place as quickly and efficiently as possible, a grate or a rotary tube is provided in the reactor chamber in a preferred embodiment of the invention. The solid lies on the grate or the rotary tube and can therefore be very easily flowed through or onto by the hot gas / plasma in the reactor chamber. This intensifies the decomposition and makes it more effective.

[0030] According to the invention it is further provided that the gas outlet for the product flow is arranged between the plasma generator and the grate.

[0031] The recirculation line, in turn, is arranged so that the gas flowing through the reactor chamber into the recirculation line first flows past the solid in the reactor chamber and / or at least partially through the solid. This intensifies and accelerates the heat transfer from the hot gas to the solid and consequently accelerates the decomposition of the solid into atoms or small / short molecules. These are recirculated and returned to the reaction zone of the plasma reactor. The recirculating gas is therefore enriched with pyrolysis products. In the reaction zone, the pyrolysis products are converted into the desired product gas.

[0032] If the solid is stored on a grate or a rotary tube in the reactor chamber, it is particularly advantageous if the outlet of the recirculation line and the gas inlet or the plasma generator are arranged on different sides of the grate or the rotary tube, so that the gas must flow through the solid before it reaches the recirculation line. It is particularly preferred if the plasma generator comprises a pin electrode and a ring electrode arranged concentrically thereto. A non-thermal gas discharge occurs between the pin electrode and the ring electrode.

[0033] The geometry of the electrodes and their arrangement ensures that the entire gas mixture flowing through the gas inlet into the reactor chamber is guided through the reaction zone of the plasma reactor.

[0034] A direct current glow discharge or a non-thermal arc using direct current is preferred. The very high direct voltage required for this can be achieved with the aid of an electrical circuit for providing a direct voltage for the plasma generator. A corresponding patent application was filed by the same applicant with the EPO on the same day (Official File Number PCT / EP2022 / 053608). The disclosure of that application is hereby incorporated by reference into the content of this patent application.

[0035] However, an alternating voltage can also be applied between the electrodes of the plasma generator.

[0036] Regardless of the type of power supply to the electrodes, a thin, rod-shaped, non-thermal gas discharge is created between the electrodes. In order to optimize the energy transfer from the rod-shaped gas discharge to the gas flowing into the reactor chamber across the entire cross-section of the ring electrode, the invention provides for magnets (electromagnets or permanent magnets) to set the arc or glow discharge in motion so that it moves in a circular motion around the pin electrode. Together with the flow of the gas flowing through the ring, this results in very good energy transfer to the gas flowing through the ring electrode. The uniform energy input means that a high conversion of the chemical processes in the plasma can be achieved with each flow.

[0037] Alternatively, or in addition to this solution using magnets, it is also possible to provide a guide element for the incoming gas upstream of the electrodes. This guide element can, for example, be designed as a honeycomb structure that serves as a flow straightener and flame screen. Alternatively, it is also possible to align the channels of this guide element in such a way that a swirl is imparted to the gas flowing into the reactor chamber. This can also set the gas discharge in motion.

[0038] To ensure that the processes taking place in the reactor chamber can run continuously, a further advantageous embodiment provides for a lock for introducing solids into the reactor chamber. This lock is preferably a gas-tight lock, so that no gas can escape into the environment through the lock during the introduction of solids into the reactor chamber.

[0039] Process claims 10 ff. are directed to particularly advantageous and exemplary applications of the reactor according to the invention. Application I: Plasma-based plastic pyrolysis

[0040] The process according to the invention for producing synthesis gas in a solid plasma reactor comprises the process steps: gasification and / or pyrolysis of an organic solid and reforming the resulting gas with carbon dioxide and / or water vapor.

[0041] Polyethylene, polypropylene, polystyrene, phenolic plastic, polyamide, polycarbonate, polyurethane, polyethylene terephthalate, polyacrylate, polyester, polyvinyl chloride, cellulose, wood, biogenic residues or a mixture of these components can be used as organic solids.

[0042] In a preferred embodiment, a partial stream of the synthesis gas (carbon dioxide (CO2) and carbon monoxide (CO)) is withdrawn from the reactor as product gas.

[0043] In the reactor according to the invention, organic residues, such as plastic waste, are first gasified using the heat of the non-thermal plasma. This pyrolysis gas is then reformed with steam or CO2 in the same reactor to produce a synthesis gas.

[0044] The plasma is non-thermal and is generated by direct current or alternating current between the ring and pin electrodes of the plasma generator.

[0045] The following reactions take place: The fixed bed / solid 15 made up of organic components is gasified or reacts with other gas components due to the heat.

[0046] Possible reactions for polyethylene (repeating unit CH2) as a solid are e.g.

[0047] 2 CH2- C + CH4C + CO2^2CO

[0048] The resulting gases are mixed with CO2 and / or water vapor. The gas mixture is passed through the plasma. Possible reactions include:

[0049] CH4+ 3CO2~^2H2O + 4CO CH4+ H2O -► CO + 3 H2

[0050] A small portion of the resulting gas is removed from the reactor vessel after the plasma (via gas outlet 6) as product gas. The larger portion of the resulting gas is circulated within the reactor vessel to transfer the heat to the fixed bed / solid 15. This is preferably done using recirculation line 7.

[0051] Two reactions take place simultaneously in the reactor vessel: pyrolysis of the solid and reforming. Both processes are endothermic. The energy required for this is supplied to the gas by the plasma generator at a very high temperature level and without significant transfer losses, making the pyrolysis of even very stable compounds readily possible.

[0052] In this application, the advantages of the plasma reactor according to the invention come into play: High temperatures occur in the plasma, so that organic molecules (e.g., toxins) can be decomposed very reliably. This allows many and various carbon-containing starting materials to be pyrolyzed with virtually no residue.

[0053] Impurities such as halogens (e.g. from PVC) are not a problem, as no catalysts are used. They only affect the composition of the produced gas or the gas treatment.

[0054] The implementation of two processes in one reactor vessel enables an internal energy exchange between the processes, so that only the reaction enthalpy required for the overall balance of both processes needs to be supplied by the plasma generator. This saves the additional heat energy otherwise required for pyrolysis, gasification, or thermal decomposition.

[0055] Application 2 : Production of quicklime and carbon monoxide

[0056] In a process according to the invention for producing quicklime in a solid-state plasma reactor, lime (CaCO3) is used as the solid. It comprises the following process steps: decomposition of the lime (CaCO3) into calcium oxide (CaO) and carbon dioxide (CO2) by the high temperatures of the plasma, and decomposition of the carbon dioxide (CO2) into carbon monoxide (CO) and oxygen (O2) by the plasma. In a further advantageous embodiment, an oxygen absorber can be used and / or a partial stream of the resulting carbon monoxide (CO) can be removed from the reactor as product gas.

[0057] This application produces quicklime while simultaneously avoiding carbon dioxide emissions into the environment. This latter aspect is of utmost importance because conventional quicklime production is responsible for a significant portion of global CO2 emissions. Today, quicklime is produced from lime. This requires burning lime (CaCO3) at high temperatures (over 900°C). This process generates CO2 emissions in two ways: a fossil fuel is burned to generate the necessary high temperatures. Furthermore, CO2 is released during the burning of the lime.

[0058] During the production of quicklime according to the invention, no CO2 is released, but only the desired quicklime, carbon monoxide, and oxygen; at least for the carbon monoxide, there is a demand, so that significant revenues can be generated from its sale.

[0059] Lime (CaCO3) is used as a solid reactant. The heat released by the plasma causes it to decompose into calcium oxide (quicklime or cement) and carbon dioxide (CO2). After circulation, the carbon dioxide (CO2) is separated into carbon monoxide (CO) and oxygen (O2).

[0060] The reaction equations are as follows:

[0061] Thermal decomposition of lime: 1000 °C CaCO3- > CaO + CO2T \ H = +181 kJmol 1

[0062] Splitting of CO2:

[0063] 1 CO2-+ CO + -O2I AH = +283 kJ mo 1

[0064] A large part of the gas is circulated as a recirculating stream to transport heat.

[0065] To increase efficiency, an oxygen absorber is used. Oxygen can be extracted through various processes, such as diffusion-driven membranes, electrochemically, by adsorption, or through solid ion conductors.

[0066] Depending on the technology, this can be located inside the reactor chamber of the reactor according to the invention or outside. A ceramic membrane capable of selectively conducting oxygen ions at high temperatures is preferably used for this purpose.

[0067] No fossil raw materials are required to burn lime in the plasma reactor according to the invention. The thermal energy is provided electrically by the plasma. The resulting CO2 is split directly in the reactor, producing carbon monoxide (CO) as a second product in addition to quicklime. Carbon monoxide represents a valuable carbon source for the chemical industry of the future. The sale of the carbon monoxide generates revenue that helps cover energy costs. During this process, no carbon dioxide (CO2) is released into the environment. This is an important contribution to combating climate change.

[0068] Similarly, the firing of various metal carbonates is possible using the same process. The metal oxide is formed along with carbon monoxide and oxygen.

[0069] Oxygen can be extracted from the gas in the same reactor or outside the reactor in the recirculating gas stream.

[0070] Oxygen can be extracted at high temperatures or after cooling the gas as previously described.

[0071] In a particularly preferred variant, the plasma is generated directly in the reactor chamber (the reactor) and not in a separate cavity. This improves heat transfer from the gas to the solid. As a result, the efficiency and conversion rate increase.

[0072] Further advantages and advantageous embodiments of the invention can be found in the following drawings, their description, and the patent claims. All features disclosed in the drawings, their description, and the claims can be essential to the invention both individually and in any combination.

[0073] drawing

[0074] Figure 1 shows a simplified and schematic representation of the reactor according to the invention;

[0075] Figure 2 shows a detail of the ring electrode and the pin electrode and the conducting element from Figure 1;

[0076] Figures 3, 4 and 5 show different configurations of reactors according to the invention;

[0077] Figure 6 shows the integration of a reactor according to the invention into a process for producing CO and CO2; and

[0078] Figure 7 shows the efficiency and conversion in the splitting of CO2.

[0079] Description of the implementation examples

[0080] Figure 1 shows a highly simplified representation of the plasma reactor 1 according to the invention. It comprises a reactor vessel 3 with a gas inlet 5, a gas outlet 6 for the product stream, and a recirculation line 7.

[0081] Located inside the reactor vessel 3, the reactor chamber 12, is a part of the plasma generator, namely a pin electrode 9 and a ring electrode 11. The pin electrode 9 is generally the cathode in a gas discharge, while the ring electrode 11 is preferably designed as an anode.

[0082] The electrical circuit required for this purpose is housed in an external housing, which is shown in Figures 3 to 5. The gas inlet 5 is guided in such a way that the inflowing gas flows through a (cylindrical) cavity 17 above the ring electrode 11 and past the central pin electrode 9 to the ring electrode 11.

[0083] A guide element 21 for the inflowing gas mixture is provided in the cavity 17. It can be designed, for example, as an open-pore ceramic foam. It serves as a flow straightener and prevents heat from entering the reactor chamber 12 into the cavity 17 and the gas inlet 5. However, the guide element 21 can also be designed as a honeycomb structure that imparts a swirl to the gas.

[0084] An arc or glow discharge, hereinafter referred to as gas discharge 13, is created between the tip of the pin electrode 9 and the actual ring electrode 11. The inflowing gas is at least partially converted into a non-thermal plasma by the gas discharge, thereby reaching very high temperatures (the electrons have temperatures greater than 10,000 K, the ions have temperatures greater than 1,000 K).

[0085] This plasma then enters the actual reactor chamber 12. There, it transfers heat by radiation and conduction to the other gaseous components in the reactor chamber 12 and also to the solid 15 located in the lower part of the reactor chamber 12, which is usually in the form of a bed.

[0086] The extremely high temperature of the electrons results in a very good, rapid, and complete pyrolysis of the solid 15 present in the reactor chamber. It also ensures a very good heat transfer (mainly through gas radiation) to the solid.

[0087] The solid material can, for example, be granules or shredded material from plastic waste, such as polypropylene, polystyrene, phenolic plastic, polyamide, polycarbonate, polyurethane, polyethylene terephthalate, polyacrylate, polyester, polyvinyl chloride, cellulose, or wood.

[0088] The solid, along with any associated contaminants or pollutants, is reliably broken down into its chemical components at very high temperatures. The high temperatures result in the toxic or pollutant substances being broken down into usable compounds. Typically, the solid molecules are split into volatile molecules. The gaseous starting products obtained from the solid in this way combine with the gaseous components flowing in through the gas inlet in the reaction zone of the plasma reactor to form the desired new compounds, the product gas.

[0089] By transporting part of the gas in the reactor chamber via the recirculation line 7 into the gas inlet 5, the residence time of the gas in the reactor chamber 12 and the energy supplied to the gas by the plasma 13 can be controlled.

[0090] Magnets 39 are arranged at the edge of the cavity 17. They can be permanent magnets or electromagnets. The resulting magnetic field lines are indicated by dotted lines. Due to the magnetic field lines, the glow discharge 13 makes a circular movement around the pin electrode 9 and in this way sweeps over the entire annular area between the ring electrode 11 and the pin electrode 9. This intensifies the excitation of the gas flowing through the annular area. The plasma created in the reaction zone has, to a first approximation, the shape of a disk due to the rapid rotation of a discharge channel between the pin electrode 9 and the ring electrode 11 at 50 Hz up to several kHz and takes up a large volume.

[0091] Figure 2 shows a detail of the reactor according to the invention in a slightly enlarged manner.

[0092] The guide element 21 can also have a honeycomb structure (not shown), similar to a catalyst. The gas flows from 17 into the reactor chamber 12 through these channels, which run parallel to one another and parallel to the longitudinal axis of the pin electrode 9. This embodiment of a guide element 21 also prevents heat from being introduced into the cavity 17 and acts as a rectifier.

[0093] However, it is also possible to arrange and shape the channels (not shown) of a guide element 21 in such a way that they impart a swirl to the gas. Then, after flowing through the guide element 21 and the glow discharge 13, the gas enters the reactor chamber 3 with a swirl. This further improves the distribution of the plasma or the highly heated gas in the reactor chamber. In some cases, the magnets 39 can be omitted.

[0094] Figures 3, 4 and 5 show simplified

[0095] Sectional views of differently configured reactors 1 according to the invention are shown. Most

[0096] Components of these sectional views are already known.

[0097] Therefore they will not be explained again .

[0098] The electrical circuit of the plasma generator 23, which supplies the electrodes 9, 11 with high voltage (DC or AC) to start and maintain the glow discharge, is schematically represented by a block 41. Details of this circuit can, as already mentioned, be found in a patent application filed by the applicant with the German Patent and Trademark Office (DPMA) on the same day.

[0099] In Figures 3 to 5, the reactor chamber 12 is arranged laterally of the plasma generator 23. Between the plasma generator 23 and the reactor vessel 3, an intermediate piece 43 is provided, to which the gas inlet 5 and the outlet 6 for the product gas are connected.

[0100] In the embodiments according to Figures 3 and 5, a grate 25 is provided in the reactor chamber 12. The solid 15 is located on this grate 25. The embodiments of Figures 3 and 5 differ primarily with regard to the arrangement of the grate 25 relative to the intermediate piece 43. A solid 15 is layered on the grate 15. The recirculation line 7 branches off at the upper end of the reactor vessel 3.

[0101] Figure 4 shows a configuration with an inclined grate. The solid material 15 is located at the bottom of the reactor vessel 3, and the recirculation line 7 is located at the right-hand end of the reactor vessel 3 in Figure 4. The embodiment shown in Figure 5 largely corresponds to the embodiment shown in Figure 3. The positions of the grates 15 differ substantially.

[0102] Figure 6 shows a further exemplary embodiment of the reactor 1 according to the invention. It is integrated into a plant for producing carbon monoxide CO or synthesis gas based on CO2 as the gaseous starting material and polyethylene, polypropylene, polystyrene, phenolic plastic, polyamide, polycarbonate, polyurethane, polyethylene terephthalate, polyacrylate, polyester, polyvinyl chloride, cellulose, wood or a mixture containing one or more of these substances as the solid 15.

[0103] A lock 27 is provided on the reactor vessel 3 to convey the solid 15 into the reactor vessel 3. This lock 27 is preferably gas-tight and allows solids to be conveyed continuously or intermittently from a storage vessel 31 into the reactor vessel 3 with the aid of a conveying device 29.

[0104] For reasons of clarity, the lock 27 and the conveyor device 29 are not shown in the other figures.

[0105] In this exemplary embodiment, the reactor 1 comprises two plasma generators 23. The two plasma reactors 23 are installed in the ceiling of the reactor chamber 12. The gas inlet 5 supplies the plasma generators 23 with gas. A fan 33 is arranged in the gas inlet 5 and determines the volume flow flowing through the gas inlet 5 into the reactor chamber 12.

[0106] The recirculation line 7 opens into the gas inlet 5 upstream of the blower 33. The blower 33 therefore also sucks in the gas flowing through the recirculation line 7 and conveys it, together with the gas (here CO2) located in the gas inlet 5, into the reactor chamber 12.

[0107] It is also possible for a blower or a suction jet pump (not shown) to be arranged in the recirculation line 7. It is also possible for a flow control valve (not shown) to be arranged in the gas inlet 5 and / or the recirculation line 7. Both serve to control the volume flow in the gas inlet 5 and the recirculation line 7 and thus enable better process control.

[0108] A first separator 35 and a heat exchanger 37 are arranged in the recirculation line 7. With the first separator 35, for example, volatile metals, halogens, or other undesirable substances can be separated from the gas. With the help of the heat exchanger 37, the gas is cooled in the recirculation line 7, and the heat thus obtained is then used with the help of the heat exchanger 37 in one of the subsequent process steps, for example, in the regeneration of a gas absorber or the drying of solid reactants.

[0109] The gas outlet 6 for the product stream flows into a further separator 45, in which, for example, halogen acids and water are separated from the product gas, so that in this application it only contains CO2 and CO. The product gas is then separated into its gas components CO2 and CO.

[0110] Part of the CO2 can be pumped into gas inlet 5. Another part of the CO2 can be used in other processes or stored in deep underground layers; this process is also known as carbon capture and storage (CCS).

[0111] The energetic efficiency and conversion of a glow discharge plasma generator according to the invention during the splitting of CO2 is shown in Figure 7. An electrode arrangement as indicated in Figure 2 is used. The inside diameter of the ring electrode 11 was 22 millimeters. The tip of the pin electrode 9 ended (unlike shown in Figure 2) approximately three millimeters above the upper edge of the ring electrode 11. Given this configuration, the results shown in Figure 7 could be achieved.

[0112] It can be seen that the electrode arrangement and discharge characteristics allow for a high efficiency of over 40% and a high conversion of 28%. This is possible due to the uniform energy input into the plasma and the electrode arrangement used. The advantages of the reactor according to the invention are explained below using two selected applications: plastics pyrolysis and the production of quicklime.

[0113] List of reference symbols Plasma reactor Reactor vessel Gas inlet Outlet for the product gas Recirculation line Pin electrode Ring electrode Reactor chamber Gas discharge Solid cavity Cylindrical section of the ring electrode 11 Guide element Plasma generator Grate Lock Conveyor screw Storage container Fan First separator Heat exchanger Magnet Housing Intermediate piece Second separator

Claims

Claims: Reactor comprising a reactor chamber (12), at least one plasma generator (23) with two electrodes (9, 11), at least one gas inlet (5), a gas outlet (6) for the product stream, and a recirculation line (7), wherein the at least one plasma generator (23) is arranged between the gas inlet (5) and the reactor chamber (12) so that it is permeated by the gas or gas mixture flowing into the reactor chamber (12) through the gas inlet (5). Reactor according to claim 1, characterized in that the gas or gas mixture flowing into the reactor chamber (12) through the at least one gas inlet (5) is directed through the reaction zone of the plasma and then directly onto a solid located in the reactor chamber (12). Reactor according to claim 1 or 2, characterized in that the recirculation line (7) flows through a separator (35) and / or a heat exchanger (37).Reactor according to any one of the preceding claims, characterized in that a grate (25) or a rotary tube is provided in the reactor chamber (12). Reactor according to any one of the preceding claims, characterized in that the gas outlet (6) for the product flow is arranged between the plasma generator and the grate or solids. A reactor according to any one of the preceding claims, characterized in that the recirculation line (7) is arranged such that the gas flowing from the reactor chamber (12) into the recirculation line (7) (previously) flows past and / or through a solid (15) located in the reactor chamber (12). A reactor according to any one of the preceding claims, characterized in that the plasma generator (23) comprises a pin electrode (9) and a ring electrode (11). A reactor according to any one of the preceding claims, characterized in that the plasma generator (23) generates a non-thermal gas discharge (13) by means of a direct current voltage. A reactor according to any one of the preceding claims, characterized in that the plasma generator (23) comprises permanent magnets or a magnetic coil (39) which set an electric arc or a glow discharge (13) present between the pin electrode (9) and the ring electrode (11) in motion.Reactor according to any one of the preceding claims, characterized in that a guiding element (21) for the inflowing gas is provided upstream of the electrodes (9, 11), wherein the guiding element (21) aligns and / or imparts a swirl to the gas flowing through the gas inlet (5) into the plasma generator (23). Reactor according to any one of the preceding claims, characterized in that it comprises a sluice (27) for the continuous or intermittent introduction of solid material (15) into the reactor chamber (12).

12. Process for the production of synthesis gas in a solid plasma reactor (1) comprising the process steps: Gasification and / or pyrolysis of an organic solid (15) , and Reforming the resulting gas with carbon dioxide (CO2) and / or water vapor (H2O) .

13. Method according to claim 11, characterized in that the organic solid contains polyethylene, polypropylene, polystyrene, phenolic resin, polyamide, polycarbonate, polyurethane, polyethylene terephthalate, polyacrylate, polyester, polyvinyl chloride, cellulose, wood, biogenic residues or a mixture of these components.

14. Method according to claim 11 or 12, characterized in that a partial stream of the synthesis gas (carbon dioxide (CO2) and carbon monoxide (CO) ) is taken from the reactor (1) as product gas.

15. Process for the production of a metal oxide (M x O y ) in a solid-state plasma reactor (1) in which the carbonate of the same metal (M) is used as the solid x (CO3) y ) is used, encompassing the following process steps: Decomposition of the metal carbonate (M x (CO3) y ) in its oxide (M x O y ) and carbon dioxide (CO2) due to the high temperatures of the plasma, and Decomposition of carbon dioxide (CO2) into carbon monoxide (CO) and oxygen (O2) by the plasma (13) .

16. Process according to 15, in particular production of quicklime (CaO) , in a solid plasma reactor (1) in which lime (CaCOs) is used as the solid, comprising the process steps: Decomposition of limestone (CaCOs) into calcium oxide (CaO) and carbon dioxide (CO2) by the high temperatures of the plasma, and - Decomposition of carbon dioxide (CO2) into carbon monoxide (CO) and oxygen (O2) by the plasma (13) .

17. Method according to claim 14, characterized in that an oxygen absorber is used.

18. Method according to claim 14 or 15, characterized in that a partial stream of the carbon monoxide is extracted from the reactor (1) (CO) as product gas.

19. Method according to one of the preceding method claims, characterized in that it is carried out using a reactor (1) according to one of claims 1 to 10.

20. Method according to one of the preceding method claims, characterized in that the plasma is generated directly in the reactor space (12) of the reactor (1) and not in a separate cavity.

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