Solid solar thermochemical fuel oxidation reactor

Abstract

The thermochemical oxidation reactor 11 operably extracts energy from the solid solar thermochemical fuel 13. In another aspect, the oxidation reactor comprises a main reactor chamber 15 and an extraction pipe 17 connected to the main reactor chamber for directly withdrawing hot gas from the main reactor chamber. In yet another aspect, the oxidation zone 33 of the thermochemical oxidation reactor has an internal chamber 19 having a cross-sectional area A that is larger than the internal cross-sectional areas B and C of the adjacent regeneration zone 35 and quench zone 31 of the reactor.

Description

Detailed Description of the Invention

[0001] [Cross - Reference to Related Applications] This application claims the benefit of priority to Provisional Application Serial No. 63 / 340,528, filed May 11, 2022, which is hereby incorporated by reference into this specification.

[0002] [Government Support] This invention was made with government support under Award No. DE - EE0008992 from the United States Department of Energy. The government has certain rights in this invention.

[0003] [Background and Summary] Thermochemical energy storage ("TCES") has been used experimentally with concentrating solar reactors. These typically use metal oxides to facilitate redox reactions. Conventional solar thermochemical redox reactors are generally classified as either fixed or moving. Fixed reactors use a stationary metal oxide medium that is either directly exposed to solar radiation or encounters a gas preheated by the incident solar energy. Conventional fixed reactors have the drawback of using a fixed storage device that is not suitable for high - throughput and efficient commercial use. Known reduction configurations of moving beds or rotary kilns generally suffer from particle aggregation, especially at high temperatures. Notably, in these conventional fixed and moving reactor approaches, the product before oxidation needs to be stored at high temperatures, which poses challenges for long - term storage.

[0004] Important recent solar fuel systems are disclosed in U.S. Patent Publication No. 2021 / 0325124, entitled "Scalable Thermochemical Options for Renewable Energy Storage", and PCT Patent Publication No. WO / 2002 / 035672, entitled "Solid Thermochemical Fuel Devices", both of which were invented by Klausner, Rahmatiyan, Petrash, and Landheer and are owned jointly with this application. These patent applications are hereby incorporated by reference into this specification. Nevertheless, further improvements are desired.

[0005] Summary According to the present invention, a thermochemical oxidation reactor is operable to extract energy from a solid solar thermochemical fuel. In another aspect, the oxidation reactor includes a main reactor chamber and an extraction tube connected to the main reactor chamber for directly withdrawing hot gas from the main reactor chamber. A further aspect includes a thermochemical oxidation reactor configured to extract energy from a solid solar thermochemical fuel, where the fuel entering and exiting the reactor is at room temperature, and the reactor effects chemical heat exchange between counter-flowing air and fuel therein, but no additional heat exchanger hardware is used in the reactor. In yet another aspect, a thermochemical oxidation reactor is provided where both gas and fuel enter the reactor at room temperature and a gas heated to at least 950 °C, more preferably at least 1000 °C, is obtained from the solid solar thermochemical fuel. In a further aspect, the oxidation zone of the thermochemical oxidation reactor has an internal chamber having a larger cross-sectional area compared to the internal cross-sectional areas of the adjacent regeneration and quench zones of the reactor. A method of using the thermochemical oxidation reactor is also provided.

[0006] The thermochemical oxidation reactor and method of the present invention are advantageous over conventional systems. For example, the reactor is not complex and costly to manufacture and operate. Advantageously, the reactor enables the solid solar fuel to be stored at room temperature, away from the reactor, for long periods and seasonally. Another advantage of the reactor is that it can achieve an extraction gas of at least 950 °C, more preferably at least 1000 °C, under steady-state bed conditions while showing long-term stability, energy conduction efficiency, and high throughput. Additional advantages and features of the apparatus and method will become apparent from the following description and the accompanying drawings.

[0007] Brief Description of the Drawings FIG. 1 is a schematic view showing the reactor; FIG. 2 is a schematic view showing the reactor in more detail; FIG. 3 is a perspective view showing a filter used in the reactor; and Figures 4 to 7 are graphs showing the expected experimental results of the gas extraction temperature of this reactor.

[0008] 〔Detailed Description〕 The thermochemical oxidation reactor 11 extracts energy from a solid solar thermochemical fuel ("SoFuel") 13. The fuel 13 is a packed bed of metal-based particles or pellets, preferably an Mg-Mn-O fuel, which is highly reactive at high temperatures but can be stored at room temperature for a long time. This reactor provides a novel, low-cost, and easily scalable method for obtaining high-quality heat (air below 1000°C) for use in industrial processes or electricity production.

[0009] This system has a simple and straightforward design as depicted in FIGS. 1 and 2. The oxidation reactor 11 can be divided into two main components: a main reactor chamber 15 and an extraction tube 17. The main reactor chamber 15 can range from a simple tube to a large cavity 19 depending on the performance requirements and is formed of a high-temperature material such as alumina or superalloy. Gravity transports the charged (i.e., chemically reduced) Mg-Mn-O particles 13 downward through the chamber 15 as air 21 is introduced at the lower part 23 of the chamber and flows upward.

[0010] Inside the reactor chamber 15, there are three sections of profiles from the lower part 23 to the upper part 25 of the chamber: a quenching zone 31 where cold gas is heated by the descending particles, a high-temperature oxidation zone 33, and a regeneration zone 35 characterized by preheating the particles into which the high-temperature gas flows. This design minimizes the heat loss of the system and limits the maximum temperature of the system to a single zone.

[0011] The collection areas at the upper and lower parts of the main reactor chamber enable the loading and unloading of fuel. More specifically, the hopper 41 collects and supplies the reduced fuel particles 13 at the upper part 25, while the collection tank 43 collects the used fuel particles at the lower part 23. The mobile belt conveyor 45 continuously supplies and removes the fuel particles 13 to the inlet opening of the hopper and from the outlet opening of the tank.

[0012] The resistance heating element 51 can be used to initially heat the contents of the reaction zone to the temperature (1000 °C) required to maintain a steady-state exothermic reaction. The compressor or blower 53 contains a rotating fan inside and allows such initially preheated ambient air to flow into the inlet pipe connected to one branch of the T-joint 55. The primary compressor or primary blower 57 allows ambient air at room temperature to flow into the inlet pipe 59 after the reactor has reached its nominal steady operating state, without activating the resistance heating element.

[0013] The valve 61 connected to the other branch of the T-joint 55 controls the gravity-induced downward movement of the fuel particles 13 flowing through the reactor and exiting into the collection tank 43. The particle conveyance is handled by the valve 61, which is a pulsating L-valve. The particles flow down from the reaction chamber into the T-joint 55 housed within the collection tank 43. In the case of small quantities and / or batch processing, a controlled air burst is applied horizontally to the L-valve 61, and the particles 13 are discharged from the open end. Before being discarded at the bottom of the collection tank, the discharged particles are weighed using a "catch can", which is a deformable funnel with an air pressure plug. The catch can is suspended from the roof of the collection tank by a load cell, thereby measuring the mass flow rate discharged from the system in real time. When the catch can is full, the air pressure piston extends to the lower part of the funnel. As a result, the collected particles are poured onto the bottom of the collection tank. After that, the piston retracts again, and the solid flow resumes. Due to the pulsation regime, the L-valve discharges a small amount of particles at a time and can fulfill the desired overall flow rate. This method relies on the real-time measurement of the catch can load cell to determine the required load cycle for each pulse.

[0014] In this way, the fuel 13 flows downward from the hopper 41, passes through the upper pipe or conduit 71 of the regeneration zone 35, through the reaction chamber or cavity 19 of the oxidation zone 33, and then through the lower pipe or conduit 73 of the quench zone 31. At the same time, the air 21 is pushed upward into the lower pipe 73, then through the main reaction cavity 19, then through the upper pipe 71, and then out through the air outlet port 75. As the air and fuel particles move counter to each other, the air is mixed with the fuel particles throughout the reactor.

[0015] The widest cross-sectional area and the lateral dimension "A" along the lateral plane inside the reaction cavity 19 and the oxidation zone 33 are larger than the widest cross-sectional area "B" inside the upper pipe 71 and the regeneration zone 35, and larger than the widest cross-sectional area "C" inside the lower pipe 73 and the quench zone 31. As a non-limiting example, the area and dimension "A" are at least twice, more preferably at least six times larger than each of the area and dimension "B", and the area and dimension "C". An inner wall tapered diagonally extends between the pipe of the adjacent zone and the widest part of the reaction cavity. This difference in area and dimension advantageously controls the flow rate, velocity and mixing of the fuel and air. For example, the preferred dimensional difference of these components advantageously makes the velocity of the gas less than the flow velocity of the fuel particles. The advantages of the low velocity due to the preferred dimensions of the main reaction chamber are: (a) enabling a smaller velocity of the fuel particles, which increases the residence time through the reactor; and, (b) desirably, the velocity of the air is lower than the fluidization velocity of the particle bed so as not to fluidize and lift the moving bed. As an alternative assumption, the main reaction chamber may be replaced with a pipe of constant diameter having no wider part, but the advantages of the illustrated configuration of the preferred wider size may not be achieved.

[0016] Another notable design component is the extraction tube 17 that facilitates the removal of the hot gas 81 from the system for external use. Similar to the main reaction chamber 15, this tube 17 is made of ceramic or alloy for transporting the hot gas containing oxygen-deficient air. The extraction tube 17 is attached at the longitudinal midpoint of the reaction chamber 19, preferably at the widest position, to draw the gas out from the hottest part of the reactor. To enable gas removal at this point, additional ambient air more than strictly required for thermal regeneration is introduced into the lower part of the reactor chamber. For example, about 40% - 60%, more preferably 50% of the air entering the inlet 59 is extracted as oxygen-deficient gas 81 from the tube 17. The extracted heated gas flows in a direction through the tube 17 that is offset from the primary flow direction through the reactor (i.e., along a generally vertical axis passing through zones 31, 33, and 35). In this way, a heat exchanger for removing energy from the reaction zone is not required. Instead, a high-temperature working fluid is simply introduced into the lower part of the particle bed and removed at the extraction point.

[0017] An insulating sleeve 83 surrounds the generally horizontally oriented extraction tube 17. Further, a filter 85 is disposed adjacent to the location where the extraction tube 17 connects to the main reaction cavity 19. Referring to FIGS. 2 and 3, the filter 85 is preferably a reticulated porous ceramic (RPC) material such as of the RAHP type, available from Zircar Cermanics, Inc., having a density of 0.6 g / cc - 0.8 g / cc and a composition having at least 91% Al2O3. The filter 85 permits the inflow of the hot gas 81, which is at least 950°C, more preferably at least 1000°C, from the cavity 19 into the extraction tube 17, but blocks the inflow of the fuel particles 13 into the tube 17. Further, a non-limiting and exemplary sealant for the extraction tube 17 to the main reactor chamber 15 is the Resbond 989 alumina-based adhesive or the Resbond 904 zirconia-based adhesive available from Cotronics Corp.

[0018] The extracted high-temperature gas 81 is used in a subsequent furnace 91 of the manufacturing plant. For example, such a furnace 91 may be part of a chemical distillation system, a glass manufacturing or forming system, a metal manufacturing or forming system, a cement or asphalt manufacturing kiln, a lime calcination furnace, or a natural gas or steam boiler. The combination of this oxidation reactor and the manufacturing furnace is synergistically advantageous because these manufacturing processes benefit from the use of a lower (depleted) oxygen concentration than the ambient present in the extracted gas 81, depending on the nature of the SoFuel 13 processed in the reactor 11. For example, the average oxygen concentration of the extracted gas 81 is preferably 5% to 15% lower than the ambient at room temperature (e.g., 20 °C to 22 °C).

[0019] Through the simplicity of the design of this reactor and the heat regeneration concept, this system provides a low-cost method for producing high-grade energy for industrial or energy production purposes. The countercurrent flow characteristic of the vertical gas flow in this system minimizes heat loss, thereby restricting high temperatures to the controlled zones of the reactor. As a result, high-temperature materials are used only in the innermost part of the reactor and in the extraction pipes. The remaining parts can be made of readily available and low-temperature materials and insulation. The absence of a conventional heat exchanger also contributes to the low-cost feature of this system. The absence of a heat exchanger eliminates the high machining costs associated with such components and the additional costs of the high-temperature materials themselves.

[0020] This device also helps in improving scalability. Since the oxidation reactor generates energy through the chemical reaction of the entire particle bed, the energy generation is approximately uniform in the reaction zone and does not depend on the same external heat penetration associated with a reduction design. This allows the shape of the reactor to be changed, and larger reaction cavities can be utilized for greater energy generation. The size of the reactor (and the associated sold and gas flow rates) can be designed according to the energy requirements of a specific application. Also, due to the non-binding nature of the solid fuel, the oxidation reactor can be placed anywhere where high-temperature gas is required, so the reactor can be easily introduced anywhere.

[0021] The functions and usage method of the present acidification reactor will be described below. The main chamber houses a bed of SoFuel particles that move downward. The thermochemically reduced particles are collected in a sealed funnel at the upper part of the reactor and slowly descend through the reactor tube. As the particles approach the reaction zone, they are exposed to conditions that promote oxidation, namely a temperature exceeding 1000°C and an oxygen-rich atmosphere of 20.9% O2. After releasing the energy accumulated by oxidation, the oxidized particles reach the bottom of the bed and are discharged into the storage area.

[0022] Opposite the particle bed is an upward flow of air. This flow provides an oxygen-rich environment for the oxidation of SoFuel particles. This flow minimizes sensible heat loss within the system. By flowing an appropriate amount of air opposite the moving bed of particles, the temperatures at both ends of the reactor tube are maintained at ambient temperature. This implementation forms two different functional zones: a quenching zone below the oxidation zone where hot particles are cooled by the incoming air, and a regeneration zone above the oxidation zone where hot gases supply energy to the particles approaching the oxidation zone. The additional air flow introduced at the lower part of the system enhances the upward moving regeneration flow and moves through the quenching zone into the reaction zone. This air is not further advanced upward through the particle layer but is discharged from the reactor through the extraction tube to remove the excess energy released during the oxidation process. Furthermore, the redox material preferably has a diameter between 3 mm and 6 mm, more preferably a diameter of 3.66 mm, and a molar ratio of MnO to MgO of 1:1 to mitigate sintering, bridging, and fluidization of the particles at high temperatures.

[0023] To determine the degree of chemical conversion occurring during the oxidation process, the following calculations can be employed. The degree of reduction is a useful measure to represent this quantity. The degree of reduction of SoFuel particles is at 1000°C and

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[0024] The degree of reduction is also a useful tool for estimating the average rate of chemical energy release during the oxidation process. Assuming that the mass flow rate of the solid is constant, the rate of energy released by the oxidation reaction can be approximated as

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[0025] The following calculations are used to quantify the energy released by the oxidation particles and the energy carried out of the system by the extraction flow based on the run-time measurement. From previous studies, the enthalpy of the reduction reaction of a material with a MgO to MnO ratio of 1:1 is 380 kJ / mol O2. Considering the number of moles of O2 absorbed by the particles, the rate of chemical energy release can be

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[0026] The energy extraction rate from the oxidation reactor is calculated based on the enthalpy change of the gas discharged between extraction and insertion. The gases considered in this analysis are only N2 and O2, and trace gases are omitted. The change in the specific enthalpy of an ideal gas is

Number

[0027] Figure 4 illustrates the expected performance criteria of the system in the first experiment where the reactor is filled with initially reduced particles. The rate of chemical energy release [Number] and the rate of extraction [Number] are calculated using Equations 4 and 6, respectively. The extraction temperature (T ext ) is also shown.

[0028] The beginning of the experiment is characterized by a shrinking reaction zone. Initially, the rate of heat loss exceeds the exothermic oxidation reaction. Since all the particles in the heating zone react at once, the bed releases a huge amount of energy. This spike is [Number] Since it exceeds 5000 W, it can be observed in FIG. 4. In order to maintain a stable reaction zone, various gas flow rates are mainly implemented in the regeneration flow. Furthermore, the discontinuity near the midpoint is due to the depressurization of the vessel and the addition of new particles. The steady-state behavior is observed from t = 80 minutes to t = 150 minutes, and only the regeneration flow changes. This region is the right half of the figure. Both the extraction temperature and the energy extraction rate are kept constant for more than one hour, demonstrating the steady-state operation ability of the reactor. The reaction zone generally maintains a constant size and distribution.

[0029] The results expected from the second experiment are as follows. In contrast to the first test, at t = 0 minutes, the reaction zone is filled with oxidized particles rather than reduced particles. While the particles start the reaction, external heating maintains the reaction zone temperature at 1000 °C. FIG. 5 has an additional plot of the expected time-averaged input energy. Therefore, it shows that as the reduced particles move into the reaction zone, the energy required by the coil decreases.

[0030] Next, the results expected from two additional reactor experiments starting from a bed of reduced particles are described. FIGS. 6 and 7 show a huge initial release of chemical energy before achieving steady-state operation. The mass flow rate is kept constant in both experiments, [Number] which is. It should be noted that there is no discontinuity in the data expected when loading new particles. Since it is difficult to fully reproduce the procedure, these reproducibility tests are carried out without the reload process. For ease of comparison, all corresponding scales in FIGS. 6 and 7 are set equal except for time. This discrepancy is the result of one experiment continuing for an additional 20 minutes and does not affect the comparison between the two.

[0031] [Terms] [Table 1] [Table 2] [Table 3]

[0032] Although various embodiments of the present apparatus and method have been disclosed, it should be understood that other modifications may be made. For example, in each zone of the reactor, additional parallel pipes, tubes, and piping can be employed for the inlets and outlets. Further, although some advantages may not be achieved, different particle feeding mechanisms and particle removal mechanisms can be employed instead of, or in addition to, the disclosed conveyor. The preferred temperatures, ratios, and material compositions of the fuel and the reactor apparatus may be different from the exemplary values described herein, but such alternatives may not achieve all of the advantages of the preferred configurations. Any feature of an embodiment can be mixed and adapted in a mutually replaceable manner with any of the other embodiments disclosed herein, and the dependent claims can be made multiply dependent on any of the other dependent claims in any combination. Various changes and modifications are not regarded as departing from the spirit or scope of the present invention. [Brief Description of the Drawings]

[0033]

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Claims

**Claim 1** A method of using an oxidation reactor, comprising: (a) transporting a chemically reduced solid solar fuel downward through a main reactor chamber using gravity; (b) flowing air upward through the main reactor chamber; (c) contacting the air with the fuel within the main reactor chamber; (d) oxidizing the fuel with the air and heating the air with the fuel during the contacting; (e) extracting a heated gas that is less than all of the heated air through an extraction tube connected to the main reactor chamber; and (f) flowing the extracted heated gas through the reactor in a direction offset from the flow direction of primary air. **Claim 2** The method of claim 1, wherein the extracted gas is 40% to 60% of the air entering an inlet adjacent to a quench zone of the reactor, and the gas comprises oxygen-depleted air. **Claim 3** supplying the air to the reactor at room temperature; supplying the fuel to the reactor at room temperature; outflowing a primary flow of the air from outside a regeneration zone of the reactor at room temperature; and further comprising outflowing the fuel from outside the reactor at room temperature when used. **Claim 4** storing the fuel in a pelletized form at room temperature; and further comprising continuously supplying the fuel to a hopper adjacent to an upper portion of the reactor. **Claim 5** countercurrent flowing the air and the fuel within the reactor; gravitationally moving the fuel from a regeneration zone of the reactor to an oxidation zone and then to a quench zone, wherein the main reactor chamber and the extraction tube are within the oxidation zone; moving the air upward from the quench zone, then to the oxidation zone, and then to the regeneration zone; and further comprising contacting the fuel and the air in all of the quench zone, the oxidation zone, and the regeneration zone. **Claim 6** The method of claim 1, further comprising continuously flowing the extracted heated gas from the main reactor chamber to a production furnace or kiln and preventing the fuel from exiting the extraction tube by a porous filter. **Claim 7** The method according to claim 1, further comprising thermochemically exchanging heat between the fuel and the air by the contacting and the oxidizing, without adding hardware of a heat exchanger.

8. The method according to claim 1, wherein a lateral cross-sectional area inside the main combustion chamber is larger than the maximum lateral cross-sectional area inside each of the adjacent quenching zone and regeneration zone in the reactor through which the fuel moves.

9. A method of using an oxidation reactor, comprising: (a) using gravity to carry downward chemically reduced solid solar fuel particles through a narrower upper tube in the regeneration zone, a wider main reaction cavity in the oxidation zone, and a narrower lower tube in the quenching zone; (b) pushing air upward through the quenching zone, the oxidation zone, and the regeneration zone; (c) the fuel particles first heating the air in the quenching zone that cools the fuel particles therein; (d) oxidizing the fuel particles with the air in the oxidation zone where the fuel particles heat the air to at least 950 °C; and (e) removing heat from the oxidation zone before the air moves to the regeneration zone.

10. The method according to claim 9, wherein the removing heat includes extracting less gas than all of the heated air through an extraction port directly connected to the main reaction cavity, and the extracted gas is 40% to 60% of the air entering an inlet adjacent to the quenching zone of the reactor.

11. supplying the air to the reactor at room temperature; supplying the fuel particles to the reactor at room temperature; letting a primary flow of the air flow out of the regeneration zone of the reactor at room temperature; and The method according to claim 9, further comprising letting the fuel particles flow out of the reactor at room temperature when used.

12. The method according to claim 9, further comprising continuously flowing the heat, which is the extracted and heated gas, from the side surface of the main reaction cavity to a production furnace or a kiln, and using a porous filter to prevent the heat from exiting together with the heated air from which the fuel particles are extracted.

13. The method according to claim 9, further comprising thermochemically exchanging heat between the fuel particles and the air, without adding hardware of a heat exchanger.

14. (a) Chemically reduced solar fuel particles; (b) A hopper for supplying the fuel particles through a narrower upper tube in the regeneration zone, through a wider main reaction cavity in the oxidation zone, and through a narrower lower tube in the quenching zone; (c) A compressor for flowing air in a direction opposite to the flow direction of the fuel particles through the quenching zone, the oxidation zone, and the regeneration zone; (d) The fuel particles that first heat the air in the quenching zone that cools the fuel particles inside; (e) The fuel particles that are oxidized when coming into contact with the air in the oxidation zone where the fuel particles heat the air to at least 950°C; and (f) A thermochemical oxidation reactor comprising a heating gas extraction port connected to the main reaction cavity configured to remove the heated gas from the oxidation zone before the heated air moves to the regeneration zone.

15. The reactor according to claim 14, wherein the widest region in the lateral direction of the main reaction cavity is adjacent to the longitudinal middle part thereof, and this width is wider than the widest regions in the lateral direction of the upper tube and the lower tube passing through the regeneration zone and the quenching zone, respectively.

16. The reactor according to claim 15, wherein the extraction port is connected to the side wall in the widest region in the lateral direction of the main reaction cavity, the tapered inner wall of the main reaction cavity extends between the tube of the regeneration zone and the widest region of the main reaction cavity, and the extraction port comprises a laterally elongated extraction tube extending in a direction offset from the primary flow axis of the fuel particles passing through the zone.

17. The reactor according to claim 14, further comprising a heat insulation sleeve, the extraction port comprises a laterally elongated extraction tube extending in a direction offset from the primary flow axis of the fuel particles passing through the zone, the heated gas flowing through the extraction tube is at least 950°C, the heated gas contains oxygen-deficient air, and the heat insulation sleeve surrounds the extraction tube.

18. The reactor according to claim 14, further comprising a production furnace or a kiln connected to the extraction port configured to transport the heated gas from the main reaction cavity to the furnace or the kiln, and the heated gas contains oxygen-deficient air.

19.

19. The reactor according to claim 14, further comprising a porous filter disposed adjacent to the intersection of the extraction port and the main reaction cavity.

20. The reactor according to claim 14, wherein the fuel particles are stored at room temperature before being continuously supplied to the oxidation reactor and move through the zone in the reactor by gravity, and the fuel particles include oxygen-deficient Mg—Mn—O pellets.

21. (a) Chemically reduced solar fuel; (b) A hopper for supplying fuel particles to a regeneration zone, then passing through an oxidation zone, and then passing through a quenching zone, wherein the largest lateral cross-sectional area inside the oxidation zone is larger than the largest lateral cross-sectional area inside each of the adjacent quenching zone and the regeneration zone; and (c) A thermochemical oxidation reactor comprising a compressor for flowing air in a direction opposite to the flow direction of the fuel through the quenching zone, the oxidation zone, and the regeneration zone.

22. The reactor according to claim 21, wherein the largest lateral cross-sectional area of the oxidation zone is at least six times larger than the largest lateral cross-sectional area of each of the quenching zone and the regeneration zone.

23. The reactor according to claim 21, further comprising a high-temperature gas extraction pipe disposed on a side wall adjacent to the largest lateral cross-sectional area of the oxidation zone, and the high-temperature gas flowing into the extraction pipe has a temperature of at least 950°C.

24. A supply conveyor disposed adjacent to the hopper, configured to supply the fuel from the supply conveyor to the hopper and then downward to the regeneration zone, and A removal conveyor disposed adjacent to the lower tank, further comprising a removal conveyor configured to remove the used fuel from the tank after passing through the quenching zone disposed above the tank.

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