WO2023097336A2 - Thermal purification of carbon - Google Patents

Abstract

A method of producing products includes contacting a hydrocarbon gas with a molten media, forming hydrogen and solid carbon based on the contacting, transferring the solid carbon to a heating chamber, heating the solid carbon in the heating chamber, removing at least a portion of the metal disposed on the surface of the solid carbon in the heating chamber, and recovering the solid carbon having at least the portion of the metal removed. The molten media comprises a metal in a molten state, and the carbon comprises the metal disposed on a surface of the solid carbon.

Description

THERMAL PURIFICATION OF CARBON

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63/283,947 filed on November 29, 2021, and entitled, “THERMAL PURIFICATION OF CARBON,” which is incorporated herein by reference in its entirety.

STATEMENT REGARDING GOVERNMENTALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under Grant DE-AR0001194 awarded by the Department of Energy. The government has certain rights in this invention.

SUMMARY

[0003] In some embodiments, a method for removing metals from carbon, the method comprises heating a mixture of carbon and a metal, wherein the metal is contained on a surface of the carbon; evaporating the metal from the carbon; and condensing the metal.

[0004] In some embodiments, a method of producing products comprises contacting a hydrocarbon gas with a molten media, wherein the molten media comprises a metal in a molten state; forming hydrogen and solid carbon based on the contacting, where the carbon comprises the metal disposed on a surface of the solid carbon; transferring the solid carbon to a heating chamber; heating the solid carbon in the heating chamber; removing at least a portion of the metal disposed on the surface of the solid carbon in the heating chamber; and recovering the solid carbon having at least the portion of the metal removed.

[0005] In some embodiments, a thermal purification system for producing product comprises a heater, where the heater comprises: a heating chamber configured to receive carbon, wherein the carbon comprises a metal disposed on the surface of the carbon, and a heating element configured to heat the heating chamber and vaporize at least a portion of the metal disposed on the surface of the carbon; a condenser configured to receive a carrier gas from the heater, wherein the carrier gas comprises the metal in a vapor phase, where the condenser is configured to cool the carrier gas and condense the portion of the metal.

[0006] In some embodiments, a thermal purification system for producing product comprises a heater, where the heater comprises: a heating chamber configured to receive carbon, wherein the carbon comprises a metal disposed on the surface of the carbon, and a heating element configured to heat the heating chamber; a reaction gas inlet configured to receive a reactive gas stream comprising a halide within the heating chamber and form a metal halide from the halogen contacting the metal, where the heating element is configured to vaporize at least a portion of the metal halide; and an electrolysis unit configured to receive the metal halide and form the metal and a stream comprising the halogen.

[0007] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a more complete understanding of the present disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description:

[0009] Figure 1 shows a comparison of various melt systems which include the heat input for the metal contaminant evaporation process from carbon coproduct at 1300°C and evaporative heat losses in a reactor operating at 1200°C and 10 bar, and heat input to heat the makeup media from ambient to the reactor operating temperature.

[0010] Figure 2 illustrates a schematic of a system used for thermal purification of carbon according to an embodiment.

[0011] Figure 3 illustrates a schematic of a system used for thermal purification of carbon according to another embodiment.

[0012] Figure 4 illustrates a schematic of a system using an electrowinning process to recover tin metal from tin chloride.

[0013] Figure 5 illustrates a schematic of another system using an electrowinning process to recover tin metal from tin chloride.

[0014] Figure 6 illustrates a schematic of an electrowinning cell used to separate hydrogen from any chlorine within the cell.

[0015] Figure 7 illustrates a schematic of an experimental apparatus used to produce and collect carbon in 1200°C bismuth bubble column.

[0016] Figure 8 (A) shows an experimental apparatus used to gasify bismuth metal from pelletized carbon held in alumina crucible at 1300°C under ambient pressures.

[0017] Figure 8(B) shows an image of deposited bismuth metal at outlet of quartz reactor during operation.

[0018] Figure 8(C) shows an image of deposited bismuth metal at outlet of quartz reactor after operation. [0019] Figure 9(A) shows an experimental apparatus used to remove tin from pelletized carbon held in alumina crucible.

[0020] Figure 9(B) shows an image of the carbon post removal of the tin as tin chloride.

[0021] Figure 9(C) shows an image of deposited tin chloride at outlet of quartz reactor after operation.

DETAILED DESCRIPTION

[0022] Disclosed herein are systems and methods for the separation and cleaning of carbon produced via hydrocarbon pyrolysis from molten media. The systems and methods described herein are based on transformation of hydrocarbon materials such as natural gas or other molecules or mixtures of molecules containing predominately hydrogen and carbon atoms into a solid carbon product that can be readily handled and prevented from forming carbon oxides in the atmosphere, as well as a gas phase co-product (e.g., hydrogen, unreacted hydrocarbons, other pyrolysis products, etc.). In some embodiments, the gas-phase co-product, hydrogen, can be used as a fuel or chemical. The overall process in this case can be referred to as pyrolysis, CnFhm —> mFh + nC.

[0023] A key challenge with hydrocarbon pyrolysis in molten media systems is the separation of the carbon from the molten media and the removal of residual media from the carbon once the carbon is removed from the reactor. The carbon produced can have a significant amount of residual media in the carbon product. For example, more than 50 wt.% of the solid product can comprise residual media (e.g., a metal from a molten metal, a salt from a molten salt, etc.) in the carbon as the material is initially removed. Various mechanical techniques can be used to remove a portion of the residual media, but this may not be sufficient to reduce the residual amount of media to an acceptable level. Various considerations such as the cost of replacing the media and the ability to use contaminated carbon may affect the viability of the pyrolysis process. As a result, any additional techniques or processes for removing or reducing the amount of residual media to an acceptable level would be useful in the pyrolysis process.

[0024] During methane pyrolysis, carbon is stoichiometrically produced at three times the rate of hydrogen by mass. For this reason, carbon cleanliness becomes a high priority for any process that implements expensive media or catalysts that may leave the reactor with the solid carbon during a gas-solid separation step - resulting in high media recovery and makeup costs.

[0025] Various pyrolysis reactor designs can be used in which a molten media such as a molten metal is contacted with a hydrocarbon gas in a thermally driven process. For example, potentially favorable operating conditions for commercial scale methane pyrolysis can be implemented using a thermally driven process such as a molten metal (e.g., tin, bismuth, antimony, etc.) reactor such as a bubble column. Various molten metals such as tin provide an excellent media to decompose the hydrocarbon feed due to its inability to both wet carbon and form a stable carbide, which allows the carbon to be fluidized out of the reactor and collected without media contamination. It has recently been discovered that this collected carbon is still heavily contaminated with the molten media such as tin or bismuth. Various mechanical removal techniques can be used to reduce the metal content in the carbon down from roughly 80 wt.% down to less than or equal to about 20 wt.%, or about 10 wt.%, or less than about 8 wt.%. This still leaves a significant amount of residual contamination in the carbon. The residual media in the carbon must be replaced in the reactor to continue to operate the process, which represents a materials cost that increases with residual contamination concentration in the carbon. In addition, downstream uses of the carbon may be limited based on the level of residual media contamination and its composition.

[0026] Disclosed herein is a purification process and system for the carbon that can be used to reduce the residual contamination of the carbon to less than about 2 wt.% or in some aspects less than about 1 wt.%, less than about 0.5 wt.%, or less than about 0.25 wt.%. More specifically, thermal purification of the carbon can be implemented as a possible route for media recovery. A number of factors can affect the feasibility of using a thermal purification process. There is a balance in the selection of the media between the evaporative heat loss within the reactor and the corresponding heat input required to evaporate the media material from the carbon after it is removed from the reactor. For example, if the contaminating media has a lower boiling point than the molten reaction media (e.g., tin has a boiling point of 2,602°C), then the amount of carrier gas required to transport low vapor pressure melts can be reduced. If the melt has too low of a boiling point, the increased evaporative heat losses and the sensible heating required to re-introduce this media back into the reactor can increase the heat duty required to maintain reaction temperature within the reactor. Figure 1 depicts various melt systems and the net energy requirements for their thermal purification andthe evaporative heat losses they induce in a 10 bar reactor. The following assumptions were used to provide the information in Figure 1 :

• Evaporation furnace operates at ~1300°C for each melt except for caesium, sodium, and magnesium which operate at 600°C, 800°C, and 1000°C, respectively;

• Reactor operates at 1200°C for each melt except for caesium, sodium, and magnesium which operate at 1000°C;

• Nitrogen used as carrier gas in evaporation furnace and its sensible heat is accounted for;

• Blower used for nitrogen recirculation achieves 75% efficiency;

• Carbon pellets in evaporation furnace are 1 cm in diameter, have bulk densities of 500 kg/m3, and have a bed void fraction of 45%; and • 80% methane conversion is achieved in the reactor.

[0027] Using the information in Figure 1, melt systems with a boiling point below 1500°C have high evaporative heat losses in the reactor and boiling points greater than this value require a significant amount of energy for the media evaporation process. Potential melts that balance both heat duties previously described include bismuth, calcium, lead, and antimony. Other melts that may be less efficient, but may potentially be used when taking other factors into account, can include those comprising magnesium, sodium, lithium, manganese, and indium. While not shown in Figure 1, various alloys or melts comprising mixtures of metals can also be used. The mixtures can be selected to balance both heat duties while taking the evaporative behavior of the individual components into account.

[0028] As an example of a melt system, bismuth has one of the lowest vapor pressures at operating conditions and provides a safe option due to it being both non-pyrophoric and non-toxic. In order to test the methods and systems described herein, bismuth was selected to provide a low vapor pressure melt that also reduces the heat input required for the thermal evaporation process, and the resulting system is described in the Examples herein.

[0029] In some aspects, a thermal purification system can comprise a high temperature environment configured to remove at least a portion of a contaminant from carbon through vaporization of the contaminant. The high temperature environment can rely on an inert atmosphere to avoid oxidizing the carbon and/or the contaminant while also serving to convey any of the contaminant in the gas phase out of the high temperature environment. Once removed from the high temperature environment, the contaminant can be condensed to allow for recovery of the contaminant. For example, media recovery can take place when a carrier gas transports a contaminant in the vapor phase to an adjacent and lower temperature environment where the contaminant will deposit - further driving the evaporation and transport of media from the carbon. [0030] In some aspects, vaporization of the contaminant can be aided by the introduction of one or several gas species that react with the contaminant to form a more volatile compound. Suitable reactive gases are those which do not react appreciably with pyrolytic carbon at the temperatures and pressures defined for the thermal purification process. The reactive gases may comprise a halogen. In some aspects, these reactive gases can include, but is not limited to, HF, HC1, HBr, HI, F2, Ch, Bn, and h. In some aspects, the reactive gases may also be vapor-phase halide salts of the metal reaction media. These consist of the extant monovalent, divalent, trivalent, tetravalent, and pentavalent halide salts of the metal reaction media and can include, but is not limited to, SnF4, SnCl₄, SnBn, Snl₄, BiFs, BiFs, BiCh, BiBn, Bih, PbF₂, PbF₄, PbCh, PbBn, Pbh, SbFs, SbF₅, SbCk, SbCh, SbBn, and Sbh. These gases can react with the contaminant to form a halide salt exhibiting a higher vapor pressure than its metal constituent, facilitating the evaporative purification of the pyrolysis carbon at lower temperatures. The halide salts M_kX_q, where M is a metal contaminant and X is a halogen (F, Cl, Br, I), are defined by reactions of the form:

1) where M^X- is a gas-phase metal halide salt and r > q. The metal M may constitute one or more of the elements listed in Figure 1, and is not limited to the elements listed in Figure 1. Additional metals include: Cu, Ni, Fe, Zn, and combinations thereof. The halide salt compounds resulting from the reaction between the metal contaminant and one or more of the reactive gases above may be considered “contaminants” and are amenable to removal using the thermal purification steps described herein. Additional details about the reactive purification of the carbon are provided herein.

[0031] In some aspects, the carbon can be prepared for the thermal purification by compacting and/or forming the carbon into a shape suitable for use in the thermal purification system. For example, the carbon can be machined into various shapes such as pellets, sheets, blocks, or the like to help compact the carbon into a size suitable for use in the high temperature environment. Compacting the carbon may help to reduce the overall size of the chamber being heated while also helping to reduce the entrainment of any carbon with the carrier gas for the contaminant in the vapor phase.

[0032] The carbon can then be loaded into a high temperature environment, which can comprise a chamber or vessel capable of being heated to high temperature. The high temperature environment can be heated close to or above the boiling point of the contaminant to vaporize at least a portion of the contaminant from the carbon. In some aspects, the carbon can be heated to a temperature less than the boiling point of the contaminant. At suitable temperatures, the contaminant can sublime to form a vapor that can be removed. It may be expected that the temperature used may affect the rate of removal of the contaminant, but that the final removal amount may be achieved over a range of temperatures.

[0033] The thermal purification system can also comprise an outlet of the chamber or vessel, which can receive the carrier gas comprising the contaminant in the vapor phase. The outlet can allow the carrier gas to pass to a lower temperature zone in which the contaminant may condense to a liquid or solid state for recovery. Any suitable structures can be used in the cooler zone to provide an increased surface area for the contaminant to condense on and be collected. The condensation of the contaminant may create a lower pressure to help drive the carrier gas towards the low temperature zone. In some aspects, the lower temperature zone may comprise a portion of the chamber that is cooled to a suitable temperature. Various structures can be used to collect the contaminant.

[0034] If the contaminant is the metal pyrolysis media, it may be directly recycled to the pyrolysis reactor. If the contaminant is a metal salt formed by the reaction with one or more of the reactive gases specified above, it may be transferred to another processing stream for reduction to a metallic state with the potential for regeneration of the reactive halide, hydrogen halide, or metal halide gas. This conversion of the metal salt to metal and reactive gas may be done by reaction with hydrogen gas or by electrolysis.

[0035] Using bismuth as an example, a thermal purification process can be described. While bismuth is used as an example, any of the melts or melt materials here may be present on the carbon and can be removed using the thermal purification process described herein. The working principle of thermal purification includes placing contaminated carbon in a high temperature environment where the contaminant (e.g., bismuth, etc.) will have a high vapor pressure and evaporate out of the carbon. Contaminant media recovery can then take place when a carrier gas transports this contaminant vapor to an adjacent and lower temperature environment where the lower vapor pressure bismuth allows the contaminant to be deposited, thereby further driving the evaporation and transport of media from the carbon.

[0036] The thermal purification process can be carried out at any suitable pressure. Lower pressures favor the use of a lower temperature for the removal of the contaminants. In some aspects, the thermal purification process can operate at a pressure between about 2 to about 20 psia, or in some aspects at about atmospheric pressure. The temperature of the thermal purification process can be selected based on the pressure and composition of the contaminants to allow the contaminants to be removed from the carbon. In some aspects, the process may operate at a temperature of greater than about 600°C, greater than about 800°C, greater than about 900°C, greater than about 1 ,000°C, or greater than about 1 , 100°C. In some aspects, the process may operate at a temperature of greater than about 500°C for a contaminant comprising caesium, greater than about 700°C for a contaminant comprising sodium, or greater than about 900°C for other contaminant compositions. In some aspects the process may operate at a temperature of greater than 250°C for reactively-formed metal-halide contaminants.

[0037] A carrier gas can be used to sweep the vaporized contaminants from the carbon during the heating process. Suitable carrier gases can include, but are not limited to, hydrogen, nitrogen, and/or any noble gas (e.g., helium, argon, etc.). In order to prevent possible oxidation of the carbon, an oxygen trap may be used with the carrier gas supply to capture any oxygen in the carrier gas stream. If a halide, hydrogen halide, or metal halide gas is used to convert the metal contaminant to a metal salt, it may be mixed with one or more of the above inert carrier gases to aid in vapor-phase conveyance of the contaminant.

[0038] The thermal purification process may be carried out for any suitable time period to allow a desired amount of the contaminant to be removed. In some aspects, the thermal purification process may be carried out at the high temperature (e.g., excluding the heating and cooling times) for a duration of time between about 5 minutes and about 4 hours, or between about 45 minutes, and about 1 hour. As described in more detail herein, the removal of the contaminant such as bismuth is non-linear with respect to time, and a majority of the contaminant may be removed quickly followed by a slower removal over time. The time for the purification can then be selected based on the temperature, pressure, and contaminant loading on the carbon to allow a desired removal of the contaminant.

[0039] Upon removal of the contaminant, the carbon in the chamber can be cooled prior to opening the chamber. Once cooled, the chamber can be opened and/or the carbon conveyed out of the chamber for further processing. The contaminant condensed out during the process can be collected and conveyed back into a pyrolysis process continuously, intermittently, and/or in batches. [0040] A system according the aspects noted above is shown in Figure 2. As shown, a tube type furnace can be positioned within an insulated section having an inlet insulation [E], a central furnace region that is insulated [F], and an outlet insulation [G] . The central furnace region [F] can use an external resistive heater to heat the central furnace region [F] during the thermal purification process. A temperature sensor such as a thermocouple [D] can be used to measure the temperature in the furnace region [F] during the purification process. The portion of the tube furnace outside of the outlet insulation [G] can be exposed to an airflow (e.g., induced flow by fan [H]) to create a cooled zone [L], A high surface area packing [I] can be used to allow the evaporated contaminant (e.g., a pyrolysis media) to be condensed once cooled.

[0041] The carrier gas stream [A] can be introduced through an optional oxygen scavenger or oxygen trap [B] to remove any trace oxygen in the carrier gas. Any oxygen may result in the formation of carbon oxides when the oxygen contacts the carbon, and the removal of any oxygen may prevent the reaction of the carbon. The oxygen free gas stream [C] can then pass into the tube reactor. The carbon with the contaminants therein can be placed in a crucible or other carrier to hold the carbon during the thermal purification process. As the carrier gas sweeps the carbon, the vapor phase contaminants can be carried to the cooler region [L] and condense, and the carrier gas can then leave the tube reactor as an outlet carrier gas stream [J], Once the process is complete, the carrier gas can continue to be swept through the tubular reactor to cool the carbon. When the carbon is cool, the carbon can be removed from the reactor. A new batch of carbon can then be similarly processed to continue to treat additional carbon.

[0042] Another aspect of the systems and methods disclosed herein is shown in Figure 3. The system illustrated in Figure 3 may be similar to that shown in Figure 2 and may operate on a batch or semi-continuous basis. The system of Figure 2 can allow for increased heating rates, operation with an inert carrier gas (as opposed to using vacuum), and heat recovery. The thermal purification process can operate using three phases of operation: pre-heating, evaporation, and cooling. Carbon having a contaminant such as a metal (e.g., bismuth, etc.) there can first be loaded into the batch evaporator at ambient conditions. The carbon can optionally be pre-treated using any of the techniques described herein such as pelletizing, shaping, ball milling, or the like. Once the carbon is placed into the heater 302, the heater 302 can be sealed and flushed with an inert gas (e.g., any of those described herein). The heater 302 can comprise a chamber that can be heated using any suitable heat source such as indirect resistive or combustion heaters. Once the carbon reaches the operating temperature (e.g., at or above about 1200°C, or above 1300°C for Bi), an inert carrier gas can be introduced as carrier gas 304 and pass through the heater 302.

[0043] The inert carrier gas can leave the heater 302 as stream 306 containing contaminant vapor and potentially some amount of fines from the carbon. Pre-processing the carbon may reduce the amount of fines in the carrier gas leaving the heater 302. The carrier gas can then flow through a separator such as a cyclone 308 to remove any fine particulates before entering a condenser/heat recoverysteam generator (HRSG) 310 through stream 314. While the separator is illustrated as a cyclone in Figure 3, the separator can generally comprise any separator suitable for separating particles from the carrier gas. Other suitable separators can comprise baghouses, cartridge type separators, or the like.

[0044] The fines collected in the cyclone 308 can pass to a fines outlet stream 312. The HRSG 310 can reduce the temperature of the carrier gas in stream 314 enough to pass to a baghouse 316 as stream 318. The gas leaving the baghouse 316 as stream 320 can pass to a blower 322. The blower 322 can provide a cool gas stream 324, a portion of which can pass back to be mixed with the outlet stream 314 from the cyclone 308 to cool the outlet stream 328 enough to pass to the HRSG 310. The remaining portion can form the carrier gas stream 304 passing to the heater 302. The blower 322 can therefore be used to recirculate carrier gas to the heater 302 and HRSG 310. The fines stream 326 from the baghouse 316 can be passed out of the system alone or with the fines stream 312.

[0045] Within the HRSG 310, the cooled carrier gas in stream 328 can exchange heat with water in water stream 330. The water can be heated to produce steam that can pass out in steam stream 332. The cooling of the carrier gas with the contaminants in the vapor phase in stream 328 can result in the condensing of contaminants that can be collected and pass out of the HRSG 310 as recovered contaminant stream 334. The carrier gas having the contaminant removed (or at least a portion thereol) can pass to the baghouse 316 from the HRSG 310 as carrier gas stream 318. [0046] When the evaporation phase isdone, the heat supplied to the heater 302 can be turned off. The carrier gas flow can continue to cool the carbon. Once the carbon is cooled, the carrier gas flow can be stopped and the carbon can be removed from the heater, ending the cycle. Additional batch flow processes can be carried out by introducing new carbon having the contaminants therein. Using an appropriate melt system, carbon can be produced in a suitable pyrolysis reactor. Within the reactor system, a hydrocarbon containing material such as natural gas can be passed through a molten media. The high temperature of the molten media may thermally degrade at least a portion of the hydrocarbons in the hydrocarbon feed to produce solid carbon, hydrogen, and potentially other reaction products (in addition to unreacted feed). The solid carbon may not be wetted by the molten media and/or may separate at the surface to be removed from the molten media with the outlet gas flow. The carbon can be separated and removed from the pyrolysis reactor system. As removed, the solid carbon may comprise a portion of the melt system within the solid carbon phase. The melt system can include any of those described herein including tin, bismuth, calcium, lead, antimony, magnesium, sodium, lithium, manganese, indium, zinc, iron, copper, nickel, and mixtures thereof. The resulting carbon can be processed using any of the thermal purification processes described herein.

[0047] As described above, the thermal purification methods and systems can also rely on reactive vaporization to purify the carbon and/or recover the reaction media from the carbon. Reactive vaporization can be used to reduce the residual composition of a contaminant such as a metal contaminant to a level below about 0.5 wt.%, below about 0.3 wt.%, below about 0.2 wt.% or below about 0.1 wt.%.

[0048] Within the reactive vaporization process, a reactive component can be contacted with the contaminant and form a compound having a lower boiling point and/or higher vapor pressure than the contaminant itself. Various reactants can be used, and in some aspects, the reactant can comprise a halogen. When the contaminant comprises one or more metals, the reactant can react with at least one metal to form a salt that can be removed through vaporization. For example, a reactant comprising a halogen gas, a hydrogen halide, a halide salt (e.g., a metal halide as described herein, etc.) can be contacted with the contaminant to form a compound that can be more easily and/or removed to a higher level than the contaminant alone. [0049] Using tin as an example, the reactive vaporization of tin as tin (II) chloride using chlorine (e.g., as HC1 gas) can be used reduce tin residual content in pyrolysis carbon, for example to as low as about 0.08 wt.%. The reaction between metallic tin and HC1 is carried out at temperatures above the boiling point of tin (II) chloride and is shown below in (Eq.:

Sn (s) + HCl g) SnCl₂ g) + H₂ g) T > (_{Eq 2})

623°C

The tin (II) chloride is kept at a temperature above its boiling point so that it can be separated from the solid pyrolysis carbon and conveyed elsewhere for media recovery, using any of the purification techniques as described herein.

[0050] The resulting tin (II) chloride can then be treated to recover the contaminant to allow for the media to be reused. For example, the resulting metal salt can be treated using hydrogen and/or electrochemically reduced.

[0051] For tin, the reduction of tin (II) chloride with hydrogen is thermodynamically limited and does not provide an effective route for tin recovery. It would require high partial pressures of hydrogen and the evacuation of any produced hydrogen chloride from the system to operate at temperatures lower than 1500°C; still only producing minimal amounts of metallic tin. The recovery of metallic tin will likely have to be achieved through electrowinning. Recovery of tin from tin (II) chloride through electrowinning can be achieved in either an aqueous or molten media - both providing their own advantages and disadvantages.

[0052] Aqueous electrolysis presents a number of issues, including:

• Hydrogen evolution as a competing cathodic reaction;

• Oxygen evolution which deteriorates carbon electrodes (significant cost in aluminum electrolysis), oxidation of tin chlorides leading to further chlorine generation, makes using HC1 difficult due to the presence of H2;

• Operating temperature is below boiling point of tin tetrachloride; and

• Operating temperature is below melting point of tin meaning it will deposit on cathode as dendritic solid, which leads to electrolyte entrainment and further processing is required for purification. [0053] Benefits of molten salt electrolysis can include:

• High operating temperatures is above boiling point tin tetrachloride and melting point of tin, the production liquid metal solves the morphological problem and facilitates the easy removal of the product from the cell by siphoning. Little to no entrainment of salt;

• Overpotentials due to cathodic polarization are often small in cathodic deposition, which is desirable from an energy efficiency point of view;

• High volatility of the high oxidation state metal halides (particularly chlorides), causing fuming and loss of electrolyte; and

• The much higher conductivities and diffusivities result in much lower iR losses and higher current densities can be achieved at modest voltages.

[0054] Issues with molten salt electrolysis can include issues like the fact that molten salts are powerful solvents for inorganic materials, limiting the selection of cell materials for electrodes, linings, and containers. The corrosiveness of molten salts demands the use of expensive refractories for containment.

[0055] In some aspects, molten salt electrolysis can be used based on its ability to operate at temperature above the boiling point of tin (IV) chloride (allowing it to be used in a cyclic nature to recover metallic tin) and above the melting point of tin (allowing the liquid metal to be removed from the cell easily with minimal salt entrainment. The molten salt can be maintained at a temperature above the melting point of tin and the boiling of tin (IV) chloride, but should not exceed these values too much as current efficiency decreases with increasing temperatures. Lower temperatures would also reduce the vapor pressure of the salt and reduce HC1 formation from the SnCh and H2 present in the electrowinning cell. One advantage this process has over electrolysis processes is that the metallic tin feed is practically pure and would require very minimal purification steps if any.

[0056] Ideally, only tin (IV) chloride is generated at the cathode so that it can be recirculated and used to reactively vaporize the metallic tin - creating a cyclic process that requires little to no feed streams other than pyrolysis carbon. Some amount of chlorine gas may be generated at the anode as opposed to just tin (IV) chloride.

[0057] A schematic process is outlined in Figure 4 that assumes no chlorine gas or substantially no chlorine gas is produced at the anode of the electrowinning cell. The reactive furnace 402 where the pyrolysis carbon stream 404 is introduced to the tin (IV) chloride in stream 406 can be kept at a temperature of at least about 650°C, or at least about 700°C to ensure that any tin (II) chloride produced in stream 410 is gaseous and able to be conveyed into the electro winning cell 412. The purified carbon containing a reduced amount of the contaminant can be taken out of the furnace as stream 408, which may occur on a batch or semi batch basis. The design of this reactive furnace 402 can include any suitable type of furnace include a fluidized bed to maximize heat transfer. The resulting tin (II) chloride from the reactive furnace 402 can pass to the electro winning cell 412 in gas stream 410.

[0058] The electro winning cell 412 may be similar to those seen in industrial aluminum electrolysis. It should be noted that tin (IV) chloride is very corrosive and incompatible with most materials. Non-reactive materials such as PTFE, neoprene, and polypropylene may be used in the reactor to avoid or limit corrosion. Additional equipment having corrosion resistant linings or formed from corrosion resistant materials may also be used in the system such as corrosive resistant compressors, piping, etc. The tin (IV) chloride can be removed from the electrowinning cell 412 as stream 416 and recycled to the furnace as stream 406 using a compressor or pump 418. The resulting contaminant stream 414 (e.g., tin, etc.) can be passed back to the reactor or used elsewhere in the system.

[0059] The presence of Ch gas in the recycle stream would convert any metallic tin and tin (II) chloride in the reactive furnace into tin (IV) chloride. This tin (IV) chloride would then enter the electrowinning cell at a temperature above its boiling point and bypass the electrowinning process. In order to avoid this, any chlorine gas generated at the anode must be separated from the recycle stream before re-entry into the reactive furnace. Tin (IV) chloride is only desirable to use as the reactive agent if it does not need to be replaced in the process due to its high cost and the removal of any Ch gas from the process would require additional feeds of it. Any Ch gas removed from the recycle stream can be re-introduced into the process without it interfering with tin (II) chloride production. A simplified process that accomplishes this is shown in Figure 5. In this process, the similar elements to those shown in Figure 4 can be the same or similar to those shown in Figure 4. [0060] In the configuration shown in Figure 5, any Ch gas in stream 516 generated in the electrowinning cell process 412 can be separated from the tin (IV) chloride by quenching the stream to a temperature below the boiling point of tin (IV) tetrachloride (114°C), for example using a cooler or heat exchanger 502. This liquid tin (IV) tetrachloride can then be passed (e.g., pumped, etc.) and vaporized in a heater 506 before passing as stream 510 and entering the reactive furnace 402. The separated Ch gas in stream 520 can be mixed with a Fh stream 508 in a reactor or vessel 512 to produce HC1 gas, which can be mixed in the mixer 518 with the tin (IV) tetrachloride gas in stream 510 before entering into the reactive furnace 402 as pyrolysis carbon stream 404. HC1 and tin (IV) tetrachloride will not react with each other, but will react with metallic tin to produce tin (II) tetrachloride. Tin (II) chloride and its co-product Fh gas can produce HC1 gas at elevated temperature, but will enter the el ectrowinning cell 412 at a temperature just above the melting point of tin and the boiling of tin (IV) chloride (300°C) where the production of HC1 is minimal. The H2 gas that enters the electrowinning cell 412 can be kept separate from any Ch gas that is generated at the anode in the el ectrowinning cell 412 in order to reduce or prevent the production of HC1 within the electro winning cell 412. This can be accomplished using an appropriately designed el ectrowinning cell 412.

[0061] In some aspects, the electrowinning cell can be designed to provide for an airlock to prevent any gasses entering the electro winning cell 412 from entering the el ectrowinning chamber. For example, in the design shown in Figure 6, the gases entering the cell can be present in a first chamber where tin (II) chloride can be formed and generate a liquid phase. The liquid phase can be used to form a gas lock that can prevent the processes gases from entering the chamber with the anode and cathode. The liquid can flow to the chamber to form the resulting tin (IV) chloride and potentially any chlorine gas along with the molten tin that can pass out of the system. This can allow the unreacted hydrogen to be maintained separate from the chlorine gas, if any, produced at the anode.

[0062] Thermal purification of contaminated carbon can be effective to produce carbon having a reduced contaminant concentration.

EXAMPLES

[0063] The disclosure having been generally described, the following examples are given as particular embodiments of the disclosure and to demonstrate the practice and advantages thereof. It is understood that the examples are given by way of illustration and are not intended to limit the specification or the claims in any manner.

EXAMPLE 1 : Experimental Procedure for Carbon Production

[0064] Carbon was produced in a pure bismuth bubble column operated at 1200°C and atmospheric conditions as depicted in Figure 7. The reactor used was a 1” ID x 43” quartz tube which implemented a side-fed design to mitigate the likelihood of coke deposition and blocking of the methane inlet, which is often experienced in top-fed reactors. Methane was fed into the reactor 4 inches below the hot zone and was pre-heated to 500°C using heat tape that lined the inch side arm to further mitigate the likelihood of blockage by metal freezing.

[0065] Due to the high vapor pressure of bismuth at this operating temperature, a temperature differential was established to reduce the temperature near the reactor headand prevent blockage from occurring at the outlet. This temperature differential was generated using 18 inches of insulating brick placed above the 1200°C hot zone which housed 0.25 x 1 inch quartz Raschig ring packing for its full length. The packing was supported by a quartz perforatedplate fixed in place at the furnace-insulation interface with three 0.25 inch holes to allow for gas transport.

[0066] A 0.25 inch tube was fed into the top of the reactor which introduced a 5 SLPM nitrogen sweep gas to fluidize and transport the produced carbon out of the reactor. The reactor effluent was fed into three gas-solid separation cyclones placed in series with diameters of 1.5, 1, and 0.75 inches.

[0067] A K-type thermocouple housed in a 0.125 inch diameter quartz tube was placed in the empty reactor prior to the addition of solid bismuth shot and quartz packing so that a temperature profile can be obtained on the system before the addition of any methane. After the addition of bismuth shot, the reactor was purged with argon for 3 hours to remove any oxidants before heat was added to the system. Reduction of the bismuth melt was carried out at 800°C under 200 SCCM of 1 :3 H2:Ar for 18 hours. After reduction of the melt, the furnace was set tol200°C.

[0068] Methane was introduced into the system at a flow rate of 150 SCCM for 8 hours. Carbon was continuously produced and separated from the product gas stream using a series of cyclones.

EXAMPLE 2: Melt Separation from Carbon

[0069] The working principle of thermal purification is to place contaminated carbon in a high temperature environment where the bismuth will have a high vapor pressure and evaporate outof the carbon. Media recovery can then take place when a carrier gas transports this bismuth vapor to an adjacent and lower temperature environment where the lower vapor pressure bismuth will deposit - further driving the evaporation and transport of media from the carbon. Thermal purification at atmospheric pressure using an inert carrier gas was performed using the experimental design shown in Figure 2.

[0070] As shown in Figure 8A, a 21 inch tube furnace with a 15 inch hot zone was operated at 1300°C and atmospheric pressures. Although typically operated at reduced pressures to lower the boiling point of the contamination, it was of interest to first explore a furnace operated at ambient pressures due to the possible complications of operating reduced pressure systems at commercial scale. A lower- temperature region was created near the outlet of the system by extending the quartz tubing 5 inches out of the furnace and using a fan to increase the convective heat loss. Quartz wool was placed at the outlet of the 1 inch tube to provide further surface area for bismuth condensation. [0071] Nitrogen was used as the carrier gas and a 750 mL oxygen trap was placed in-line with the feed to prevent the oxidation of any carbon. Mass spectrometry was used confirm the absence of oxygen before the furnace was operated. After the furnace was purged with nitrogen, reduction of the carbon was carried out under the hydrogen and argon at 800°C for two hours. A 6 mL AI2O3 crucible was used to house the carbon within the furnace. The carbon was first pelletized using a hydraulic press at 9 MT for 10 minutes before being loaded into the furnace due to the low density of the carbon and its ability to fluidize easily. The crucible was placed in thecenter of the furnace and an S-type thermocouple was placed adj acent to it to ensure accurate temperature measurements. [0072] Dwell time within the tube furnace was varied for three separate samples all operated at 1300°C; the XRF results are summarized in Table 1. The XRF results signify that most of the bismuth mass is evaporated within the first ten minutes of operation, which was also visually confirmed with the large metal droplets formed in Figures 8B-C being produced within the first 3 minutes. Mass transfer limitations appear to become prevalent shortly after this dwell time due to the small difference in bismuth contamination between samples 2 and 3. Carbon removed from the furnace appeared to have increased in volume and became noticeably darker. As shown in this example, thermal purification is a viable method for removing a contaminant such as bismuth from carbon.

Sample Time in Furnace Bismuth

No. [min] wt.%

1 10 0.89 ± 0.00

2 50 0.22 ± 0.00

3 116 0.21 ± 0.01

Table 1: Bismuth contamination for varying amounts of dwell time in 1300°C tube furnace quantified using XRF.

EXAMPLE 3: Reactive Separation of Media from Carbon

[0073] The working principle of reactive thermal purification is to place contaminated carbon in a high temperature environment and convert the metal contaminant into a halide compound with a sufficiently high vapor pressure such that it is evaporated out of the carbon. Media recovery can then occur when the halide compound vapor is transported to an adjacent, lower temperature environment where it condenses, further driving the evaporation and transport of the reacted media from the carbon. Reactive thermal purification of a carbon sample contaminated with metallic tin was carried out at atmospheric pressure using dry HC1 in an Ar carrier gas. The apparatus is shown in Figures 9A-9C.

[0074] The reaction apparatus consisted of a fused silica tube (1 in OD, 0.75 in ID, 18 in length) into which was placed a fused silica boat containing 0.75 g of lightly packed, tin-contaminated carbon. The silica boat was heated to 750°C using an electrical resistance heater. Dry HC1 gas was generated by slowly reacting sulfuric acid (98 % w/w) with NaCl powder. An Ar carrier gas was used to convey the HC1 to the reaction tube, where it passed over the carbon. The tin in the carbon reacted with HC1 to form SnCh vapor, which was observed to immediately condense on the unheated section of fused silica tubing downstream of the carbon (Figure 9C). The carbon was treated with HC1 gas in this manner for a period of two hours, after which the HC1 gas flow was shut off and the reaction tube was allowed to cool to room temperature. The residual tin content of the carbon post-treatment was measured by X-ray fluorescence spectroscopy to be 0.08 wt. %.

[0075] Having described various systems and methods, certain aspects can include, but are not limited to:

[0076] In a first aspect, a method for removing metals from carbon comprises: heating a mixture of carbon and a metal, wherein the metal is contained on a surface of the carbon; evaporating the metal from the carbon; and condensing the metal.

[0077] A second aspect can include the method of the first aspect, wherein the metal comprises bismuth, calcium, lead, antimony, magnesium, sodium, lithium, manganese, indium, zinc, iron, copper, nickel, or any combination thereof.

[0078] A third aspect can include the method of the first or second aspect, wherein the heating is performed under a non-oxidizing atmosphere.

[0079] A fourth aspect can include the method of any one of the first to third aspects, further comprising: passing a carrier gas over the carbon during the heating; transferring a gas phase metal vapor from the carbon using the carrier gas during the evaporating; and passing the gas phase metal vapor to a condensing section, wherein condensing the metal occurs in the condensing section.

[0080] A fifth aspect can include the method of the fourth aspect, wherein the carrier gas comprises an inert gas.

[0081] A sixth aspect can include the method of the fourth aspect, wherein the carrier gas comprises at least one of hydrogen, nitrogen, argon, helium, or any combination thereof.

[0082] A seventh aspect can include the method of any one of the first to third aspects, further comprising: passing a carrier gas comprising a halogen over the carbon during the heating; reacting the halogen with the metal to form a metal halide; evaporating the metal halide from the carbon to form a gas phase metal halide; and passing the gas phase metal halide to a condensing section, wherein condensing the metal comprises condensing the gas phase metal halide.

[0083] An eighth aspect can include the method of the seventh aspect, further comprising: reducing the metal halide to form the metal and a compound comprising the halogen; and recovering the metal.

[0084] A ninth aspect can include the method of the seventh or eighth aspect, wherein the halogen comprises at least one of fluorine, chlorine, bromine, iodine, or any mixture thereof.

[0085] A tenth aspect can include the method of any one of the first to ninth aspects, wherein the heating comprises heating the carbon to a temperature above about 800°C. [0086] An eleventh aspect can include the method of any one of the first to ninth aspects, wherein the heating comprises heating the carbon to a temperature above about 1200°C.

[0087] A twelfth aspect can include the method of any one of the first to eleventh aspects, wherein the heating comprises heating the carbon for a time between about 5 minutes and about 4 hours.

[0088] A thirteenth aspect can include the method of any one of the first to twelfth aspects, further comprising: cooling the carbon after evaporating the metal from the carbon.

[0089] A fourteenth aspect can include the method of any one of the first to thirteenth aspects, wherein the metal comprises bismuth.

[0090] In a fifteenth aspect, a method of producing products comprises: contacting a hydrocarbon gas with a molten media, wherein the molten media comprises a metal in a molten state; forming hydrogen and solid carbon based on the contacting, wherein the carbon comprises the metal disposed on a surface of the solid carbon; transferring the solid carbon to a heating chamber; heating the solid carbon in the heating chamber; removing at least a portion of the metal disposed on the surface of the solid carbon in the heating chamber; and recovering the solid carbon having at least the portion of the metal removed.

[0091] A sixteenth aspect can include the method of the fifteenth aspect, further comprising: recovering the portion of the metal removed from the carbon; and recycling the portion of the metal to the molten media.

[0092] A seventeenth aspect can include the method of the fifteenth or sixteenth aspect, wherein the metal comprises bismuth, calcium, lead, antimony, magnesium, sodium, lithium, manganese, indium, zinc, iron, copper, nickel, or any combination thereof.

[0093] An eighteenth aspect can include the method of any one of the fifteenth to seventeenth aspects, wherein heating the solid carbon is performed under a non-oxidizing atmosphere.

[0094] A nineteenth aspect can include the method of any one of the fifteenth to eighteenth aspects, further comprising: passing a carrier gas over the carbon during the heating; transferring a gas phase metal vapor from the carbon using the carrier gas during the evaporating; passing the gas phase metal vapor to a condensing section; and condensing the metal in the condensing section.

[0095] A twentieth aspect can include the method of the nineteenth aspect, wherein the carrier gas comprises an inert gas.

[0096] A twenty first aspect can include the method of the nineteenth aspect, wherein the carrier gas comprises at least one of hydrogen, nitrogen, argon, helium, or any combination thereof.

[0097] A twenty second aspect can include the method of any one of the fifteenth to twenty first aspects, wherein the heating comprises heating the carbon to a temperature above about 800°C. [0098] A twenty third aspect can include the method of any one of the fifteenth to twenty first aspects, wherein the heating comprises heating the carbon to a temperature above about 1200°C.

[0099] A twenty fourth aspect can include the method of any one of the fifteenth to twenty third aspects, wherein the heating comprises heating the carbon for a time between about 5 minutes and about 4 hours.

[00100] A twenty fifth aspect can include the method of any one of the fifteenth to twenty fourth aspects, further comprising: cooling the carbon after evaporating the metal from the carbon.

[00101] A twenty sixth aspect can include the method of any one of the fifteenth to twenty fifth aspects, wherein the metal comprises bismuth or tin.

[00102] In a twenty seventh aspect, a thermal purification system for producing product comprises: a heater, wherein the heater comprises: a heating chamber configured to receive carbon, wherein the carbon comprises a metal disposed on the surface of the carbon, and a heating element configured to heat the heating chamber and vaporize at least a portion of the metal disposed on the surface of the carbon; and a condenser configured to receive a carrier gas from the heater, wherein the carrier gas comprises the metal in a vapor phase, wherein the condenser is configured to cool the carrier gas and condense the portion of the metal.

[00103] A twenty eighth aspect can include the system of the twenty seventh aspect, further comprising: a separator configured to receive the carrier gas from the heater, separate solid particles from the carrier gas and provide the carrier gas to the condenser, wherein the separator is configured to pass the solid particles to an outlet of the separator.

[00104] A twenty ninth aspect can include the system of the twenty eighth aspect, wherein the separator comprises a cyclone or a baghouse.

[00105] A thirtieth aspect can include the system of any one of the twenty seventh to twenty ninth aspects, wherein the condenser is further configured to receive a water stream and produce a steam stream based on exchanging heat with the carrier gas.

[00106] A thirty first aspect can include the system of any one of the twenty seventh to thirtieth aspects, further comprising: a second separator configured to receive the carrier gas from the condenser, separate solid particles from the carrier gas and provide the carrier gas to a blower, wherein the second separator is configured to pass the solid particles to an outlet of the second separator.

[00107] A thirty second aspect can include the system of the thirty first aspect, wherein the blower is configured to receive the carrier gas from the second separator and transfer the carrier gas to an inlet of the heater as the carrier gas. [00108] A thirty third aspect can include the system of the thirty first or thirty second aspect, further comprising: a bypass line fluidly connecting an outlet of the blower to an inlet of the condenser, wherein the bypass line is configured to mix a portion of the cooled carrier gas from the blower with the carrier gas entering the condenser.

[00109] A thirty fourth aspect can include the system of any one of the twenty seventh to thirty third aspects, wherein the metal comprises bismuth, calcium, lead, antimony, magnesium, sodium, lithium, manganese, indium, zinc, iron, copper, nickel, or any combination thereof.

[00110] A thirty fifth aspect can include the system of any one of the twenty seventh to thirty fourth aspects, wherein the carrier gas is a non-oxidizing gas.

[00111] A thirty sixth aspect can include the system of the thirty fifth aspect, wherein the carrier gas comprises an inert gas.

[00112] A thirty seventh aspect can include the system of the thirty fifth aspect, wherein the carrier gas comprises at least one of hydrogen, nitrogen, argon, helium, or any combination thereof.

[00113] A thirty eighth aspect can include the system of any one of the twenty seventh to thirty seventh aspects, wherein the metal comprises bismuth.

[00114] In a thirty ninth aspect, a thermal purification system for producing product comprises: a heater, wherein the heater comprises: a heating chamber configured to receive carbon, wherein the carbon comprises a metal disposed on the surface of the carbon, and a heating element configured to heat the heating chamber; a reaction gas inlet configured to receive a reactive gas stream comprising a halide within the heating chamber and form a metal halide from the halogen contacting the metal, wherein the heating element is configured to vaporize at least a portion of the metal halide; and an electrolysis unit configured to receive the metal halide and form the metal and a stream comprising the halogen.

[00115] A fortieth aspect can include the system of the thirty ninth aspect, further comprising: a cooler, wherein the cooler is configured to receive the stream comprising the halogen, cool the stream comprising the halogen, and produce a liquid stream comprising a metal halide and a gaseous stream comprising a molecular halogen; a heating configured to receive the liquid stream and vaporize the liquid stream; and a reactor configured to receive a hydrogen stream and the molecular halogen, and form a hydrogen halide stream; and a mixer configured to mix the hydrogen halide stream and the vaporized liquid stream to form the reactive gas stream.

[00116] A forty first aspect can include the system of the thirty ninth or fortieth aspect, wherein the metal comprises bismuth, calcium, lead, antimony, magnesium, sodium, lithium, manganese, indium, zinc, iron, copper, nickel, or any combination thereof. [00117] A forty second aspect can include the system of any one of the thirty ninth to forty first aspects, wherein the halide comprises fluorine, chlorine, bromine, iodine, or any mixture thereof. [00118] It is to be further understood that the present description is not limited to the particular methodology, compounds, materials, manufacturing techniques, uses, and applications, described herein, as these may vary. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present systems and methods. It must be noted that as used herein and in the appended claims (in this application, or any derived applications thereol), the singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. Thus, for example, a reference to "an element" is a reference to one or more elements and includes equivalents thereof known to those skilled in the art. All conjunctions used are to be understood in the most inclusive sense possible. Thus, the word "or" should be understood as having the definition of a logical "or" rather than that of a logical "exclusive or" unless the context clearly necessitates otherwise. Structures described herein are to be understood also to refer to functional equivalents of such structures. Language that may be construed to express approximation should be so understood unless the context clearly dictates otherwise.

[00119] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this description belongs. Preferred methods, techniques, devices, and materials are described, although any methods, techniques, devices, or materials similar or equivalent to those described herein may be used in the practice or testing of the present systems and methods. Structures described herein are to be understood also to refer to functional equivalents of such structures. The present systems and methods will now be described in detail with reference to embodiments thereof as illustrated in the accompanying drawings.

[00120] From reading the present disclosure, other variations and modifications will be apparent to persons skilled in the art. Such variations and modifications may involve equivalent and other features which are already known in the art, and which may be used instead of or in addition to features already described herein.

[00121] Although Claims may be formulated in this Application or of any further Application derived therefrom, to particular combinations of features, it should be understood that the scope of the disclosure also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalization thereof, whether or not it relates to the same systems or methods as presently claimed in any Claim and whether or not it mitigates any or all of the same technical problems as do the present systems and methods. [00122] Features which are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. The Applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present Application or of any further Application derived therefrom.

Claims

CLAIMS What is claimed is:

1. A method for removing metals from carbon, the method comprising: heating a mixture of carbon and a metal, wherein the metal is contained on a surface of the carbon; evaporating the metal from the carbon; and condensing the metal.

2. The method of claim 1, wherein the metal comprises bismuth, calcium, lead, antimony, magnesium, sodium, lithium, manganese, indium, zinc, iron, copper, nickel, or any combination thereof.

3. The method of claim 1, wherein the heating is performed under a non-oxidizing atmosphere.

4. The method of claim 1, further comprising: passing a carrier gas over the carbon during the heating; transferring a gas phase metal vapor from the carbon using the carrier gas during the evaporating; and passing the gas phase metal vapor to a condensing section, wherein condensing the metal occurs in the condensing section.

5. The method of claim 4, wherein the carrier gas comprises an inert gas.

6. The method of claim 4, wherein the carrier gas comprises at least one of hydrogen, nitrogen, argon, helium, or any combination thereof.

7. The method of claim 1, further comprising: passing a carrier gas comprising a halogen over the carbon during the heating; reacting the halogen with the metal to form a metal halide; evaporating the metal halide from the carbon to form a gas phase metal halide; and passing the gas phase metal halide to a condensing section, wherein condensing the metal comprises condensing the gas phase metal halide.

23 The method of claim 7, further comprising: reducing the metal halide to form the metal and a compound comprising the halogen; and recovering the metal. The method of claim 7, wherein the halogen comprises at least one of fluorine, chlorine, bromine, iodine, or any mixture thereof. The method of any one of claims 1-9, wherein the heating comprises heating the carbon to a temperature above about 800°C. The method of claim 1, wherein the heating comprises heating the carbon for a time between about 5 minutes and about 4 hours. The method of claim 1, wherein the metal comprises bismuth. A thermal purification system for producing product, the system comprising: a heater, wherein the heater comprises: a heating chamber configured to receive carbon, wherein the carbon comprises a metal disposed on the surface of the carbon, and a heating element configured to heat the heating chamber and vaporize at least a portion of the metal disposed on the surface of the carbon; and a condenser configured to receive a carrier gas from the heater, wherein the carrier gas comprises the metal in a vapor phase, wherein the condenser is configured to cool the carrier gas and condense the portion of the metal. The system of claim 13, further comprising: a separator configured to receive the carrier gas from the heater, separate solid particles from the carrier gas and provide the carrier gas to the condenser, wherein the separator is configured to pass the solid particles to an outlet of the separator. The system of claim 14, wherein the separator comprises a cyclone or a baghouse. The system of claim 13, wherein the condenser is further configured to receive a water stream and produce a steam stream based on exchanging heat with the carrier gas. The system of claim 13, further comprising: a second separator configured to receive the carrier gas from the condenser, separate solid particles from the carrier gas and provide the carrier gas to a blower, wherein the second separator is configured to pass the solid particles to an outlet of the second separator. The system of claim 17, wherein the blower is configured to receive the carrier gas from the second separator and transfer the carrier gas to an inlet of the heater as the carrier gas. The system of claim 17, further comprising: a bypass line fluidly connecting an outlet of the blower to an inlet of the condenser, wherein the bypass line is configured to mix a portion of the cooled carrier gas from the blower with the carrier gas entering the condenser. The system of claim 13, wherein the metal comprises bismuth, calcium, lead, antimony, magnesium, sodium, lithium, manganese, indium, zinc, iron, copper, nickel, or any combination thereof. The system of claim 13, wherein the carrier gas is a non-oxidizing gas. The system of claim 21, wherein the carrier gas comprises an inert gas. The system of claim 13, wherein the metal comprises bismuth. A thermal purification system for producing product, the system comprising: a heater, wherein the heater comprises: a heating chamber configured to receive carbon, wherein the carbon comprises a metal disposed on the surface of the carbon, and a heating element configured to heat the heating chamber; a reaction gas inlet configured to receive a reactive gas stream comprising a halide within the heating chamber and form a metal halide from the halogen contacting the metal, wherein the heating element is configured to vaporize at least a portion of the metal halide; and an electrolysis unit configured to receive the metal halide and form the metal and a stream comprising the halogen. The system of claim 24, further comprising: a cooler, wherein the cooler is configured to receive the stream comprising the halogen, cool the stream comprising the halogen, and produce a liquid stream comprising a metal halide and a gaseous stream comprising a molecular halogen; a heating configured to receive the liquid stream and vaporize the liquid stream; and a reactor configured to receive a hydrogen stream and the molecular halogen, and form a hydrogen halide stream; and a mixer configured to mix the hydrogen halide stream and the vaporized liquid stream to form the reactive gas stream. The system of claim 24, wherein the metal comprises bismuth, calcium, lead, antimony, magnesium, sodium, lithium, manganese, indium, zinc, iron, copper, nickel, or any combination thereof. The system of claim 24, wherein the halide comprises fluorine, chlorine, bromine, iodine, or any mixture thereof.

26