JP2013543059A - Method and system for reducing solid feedstock by electrolysis - Google Patents

Abstract

In a method of electrolytically reducing a solid feedstock, such as a solid metal oxide feedstock, an electrode module (10) is positioned at a first position where the feedstock will be loaded. The loaded module is then transferred from the first position and engaged with an electrolysis chamber (220) containing molten salt. A voltage is applied to the electrode module to reduce the solid feedstock. The loaded module may be transferred into the transfer module.
[Selection] Figure 7

Description

  The present invention relates to a method for reducing a solid feed comprising one or more metal compounds such as metal oxides to produce a reduced product. As is known from the prior art, the electrolysis process can, for example, reduce a metal compound or metalloid compound to a metal, metalloid, or partially reduced compound, or reduce a mixture of metal compounds to form an alloy. It may be used to To avoid repetition, the term metal is used in this document to encompass all such products, such as metals, metalloids, alloys, intermetallics, and partially reduced products. become.

  The present invention relates to a method for reducing a solid feed comprising one or more metal compounds such as metal oxides to produce a reduced product. As is known from the prior art, the electrolysis process can, for example, reduce a metal compound or metalloid compound to a metal, metalloid, or partially reduced compound, or reduce a mixture of metal compounds to form an alloy. It may be used to To avoid repetition, the term metal is used in this document to encompass all such products, such as metals, metalloids, alloys, intermetallics, and partially reduced products. become.

  In recent years, there has been great interest in the direct production of metals by reduction of solid feedstocks, such as solid metal oxide feedstocks. One such direct reduction process is a Cambridge FFC electrolysis process (described in WO 99/64638). In the FFC process, a solid compound, such as a solid metal oxide, is placed in contact with the cathode in an electrolysis cell containing a molten salt. A potential is applied between the cathode and anode of the cell so that the compound is reduced. In the FFC process, the potential resulting in a solid compound is lower than the deposition potential for cations from the molten salt. For example, when the molten salt is calcium chloride, the cathode potential at which the solid compound is reduced is lower than the deposition potential for the deposition of metallic calcium from the salt.

  Other reduction processes have been proposed to reduce the feedstock in the form of a solid metal compound connected to the cathode, such as the polar process described in WO 03/076690 and the process described in WO 03/048399 Has been.

  Conventional implementations of the FFC process and other electroreduction processes typically involve the production of a feedstock in the form of a preform or precursor made from a solid compound powder to be reduced. This preform is then carefully coupled to the cathode to allow reduction to occur. When multiple preforms are coupled to the cathode, the cathode can be lowered into the molten salt and the preform can be reduced. Producing preforms and attaching them to the cathode can be very labor intensive. This system works well on a laboratory scale but is not suitable for mass production of metals on an industrial scale.

International Publication No. 99/64638 International Publication No. 03/076690 International Publication No. 03/048399

  The object of the present invention is to provide an electrolysis process more suitable for the reduction of solid feedstock on an industrial scale.

  The present invention provides a method for the electrolytic reduction of a solid feedstock as defined in the appended independent claims to which reference should now be made. Preferred or advantageous features of the invention are set out in the various dependent dependent claims.

  Accordingly, a method for reducing a solid feedstock by electrolysis includes positioning an electrode module comprising at least one electrode in a first position for loading the feedstock, and loading the solid feedstock onto the electrode module. Moving the electrode module from the first position to engage the electrode module with the electrolysis chamber such that the feedstock contacts the molten salt in the electrolysis chamber; and the electrode module such that the solid feedstock is reduced Applying a voltage to.

  Preferably, the electrode module comprises at least a cathode and an anode that can be coupled to a power source so that a potential can be generated between the anode and the cathode. The electrode module may comprise one or more bipolar electrodes.

  Preferably, the solid feed is loaded in contact with the cathode or the cathode surface of the bipolar electrode.

  It may be advantageous for the electrode module to be transferred from the first position in the transfer module. The transfer module may take the form of a housing that defines a chamber in which the electrode module may be raised. Preferably, the transfer module is sealable so that the electrode module may be transferred in a controlled manner, for example under an inert atmosphere.

  It may be particularly preferred that the electrode module is heated to a predetermined temperature before engaging the electrolysis chamber. In a preferred embodiment, the electrolysis chamber contains the molten salt when the electrode module is engaged. If the electrode module is not at the proper temperature, thermal distortion or thermal shock of the electrode module components may occur, resulting in failure of the electrode module components. Therefore, the electrode module is preferably heated to a temperature close to the temperature of the molten salt. The predetermined temperature may therefore be in the range of about 500 ° C. to 1200 ° C. depending on the temperature of the molten salt. Particularly preferably, the temperature is in the range of 700 ° C to 1000 ° C, for example about 800 ° C or 850 ° C.

  Advantageously, the electrode module may be heated under an inert atmosphere in the transfer module. The transfer module may comprise a heating element that raises the temperature in the module to a predetermined temperature in order to heat the electrode module. Alternatively, the transfer module may comprise means for allowing heated gas to be introduced into the transfer module to heat the electrode module.

  It may be preferred that the electrode module is transferred from the transfer module to a heating station for heating to a predetermined temperature. For example, the transfer module may engage the heating station and transfer the electrode module into a separate heating station to allow the electrode module to be heated. In this embodiment, the transfer module does not have to comprise the heating element itself.

  Thus, the electrode module is transferred from the loading station within the transfer module, lowered into the heating station, heated to a predetermined temperature, raised back into the transfer module and transferred to the electrolysis chamber. May be preferred.

  The electrode module is preferably sealed in the transfer chamber of the transfer module by closing the closure. Preferably, the closure is a gate valve and the gate is slidable to seal the transfer chamber within the transfer module.

  The opening of the electrolysis chamber, ie the opening through which the electrode module may be delivered for engaging the electrolysis chamber, is preferably closed by an openable closure. Particularly preferably, the closure is a gate valve that can be opened to allow the electrode module to be delivered to the electrolysis chamber.

  It may be desirable to remove the electrode module from the electrolysis chamber after electrolysis to recover the reduced feedstock. Preferably, the electrode module is removed at or near the operating temperature of the electrolysis chamber and under conditions where the molten salt contained in the electrolysis chamber is still in a molten state.

  Preferably, the electrode module is lifted from the electrolysis chamber into the transfer module.

  It may be advantageous for the electrode module to be cooled under an inert atmosphere in the transfer module after removal from the electrolysis chamber. If the electrode module is hot, for example at 800 ° C., the temperature drops enough to avoid auto-ignition of any carbon parts of the electrode module or rapid oxidation of any reduced feed located on the electrode module Until then, it is important that the module is not in contact with oxygen or air.

  The electrode module may be cooled under an inert atmosphere in the transfer module after being removed from the electrolysis chamber. Thus, the transfer module may be provided with cooling means, such as a water cooling tube, to reduce the temperature of the electrode module, or with means for flowing a cooling gas through the transfer module.

  Alternatively, the electrode module may be transferred to a separate cooling station within the transfer module and cooled to a predetermined temperature under an inert atmosphere.

  The cooling station preferably comprises a cooling chamber in which an electrode module may be engaged to provide cooling. The method thus transfers the electrode module in the transfer module to the cooling station, lowers the electrode module into the cooling station, cools the electrode module to a predetermined temperature, and transfers the electrode module to the transfer module. And moving it back away from the cooling station.

  The molten salt remaining on the electrode module will solidify when the electrode module is cooled. Therefore, when the electrode module is cooled, it is coated with a solidified salt film. Thus, it may be advantageous to transfer the electrode module from a reduced feed to a washing station for washing salt. The cleaning station may comprise a cleaning device suitable for directing a jet of water towards the electrode module to clean the salt from the feedstock. The cleaning station may further comprise means for collecting spent water from the cleaning process.

  It may be advantageous to transfer the electrode module to a separate extraction station to facilitate access to the electrode module for removing reduced feedstock. It is particularly preferred that the electrode module has a removable tray that can be uncoupled from the electrode module. Thus, it may be preferred that the solid feed is loaded on a removable tray that is separate from the electrode module, and the removable tray is coupled to the electrode module for loading the feed on the electrode module. It may also be advantageous that the tray may be removed from the electrode module in order to facilitate removal of the reduced feedstock.

  Preferably, the feed is loaded in contact with the cathode structure of the electrode module, eg, the surface of the cathode surface of the cathode or bipolar electrode. This is essential when the reaction to reduce the feedstock is initiated using the FFC process. However, other reduction processes may be used.

  It is particularly preferred that the electrolytic reaction in this process proceeds by electrolytic deoxidation of the solid feedstock, for example by electrolytic deoxidation by the FFC process.

  This method may be applicable for use with any electrode module that can be loaded with feedstock and engaged in an electrolysis chamber for electrolysis of the feedstock. There may be numerous specific embodiments of electrode modules that may be preferred to be used in this manner.

  In a preferred embodiment of the invention, the electrode module is a removable electrode module for engaging the electrolysis chamber, the removable electrode module being one of the first electrode, the second electrode, and preferably the rod. A suspension structure comprising a suspension rod coupled to the first electrode at the end of the first electrode, wherein the second electrode is suspended or supported by the suspension structure, and the suspension structure removes the second electrode from the first electrode. It may be advantageous to provide at least one electrically insulating spacer element for holding in a spatially separated state.

  In a further preferred embodiment of the present invention, the electrode module is a removable electrode module for engaging the electrolysis chamber, the removable electrode module being solid for reduction by electrolysis in the anode and the molten salt electrolyte. It may be advantageous to provide a cathode for supporting a portion of the feedstock and to keep the feedstock in contact with the cathode.

  In a further preferred embodiment of the invention, the electrode module is a removable electrode module for engaging the electrolysis chamber, the removable electrode module comprising a first electrode and a cover, wherein the removable electrode is When engaged with the electrolyzer, the first electrode may be advantageously located in the electrolysis chamber so that it may be used for electrolysis and the cover spans the opening of the electrolysis chamber.

  In a further preferred embodiment of the invention, the electrode module is a removable electrode module for engaging the electrolysis chamber, the removable electrode module having a lifting element to allow the module to be lifted. It may be advantageous that the first electrode is coupled to the lower end of the suspension rod and that elastic means is arranged between the lifting element and the upper end of the suspension rod.

  The various aspects and embodiments of the invention described herein may be particularly well suited for the reduction of large batches of solid feedstock on a commercial scale. In particular, embodiments of removable electrode modules that include a vertical arrangement of bipolar electrodes allow multiple bipolar elements to be placed within a small plant footprint and reduced production that can be obtained per unit area of the processing plant. It can effectively increase the amount of objects.

  The various aspects and embodiments of the invention described herein are particularly suitable for the production of metals by reduction of a solid feedstock comprising solid metal oxides. Reduction of pure metal oxide can produce pure metal, and reduction of feedstock containing mixed metal oxide or a mixture of pure metal oxides produces alloys and intermetallic compounds. There is a possibility.

  Some reduction processes may only work when the molten salt or electrolyte used in the process contains a metal species (reactive metal) that forms a more stable oxide than the metal oxide or compound being reduced. There is. Such information is readily available in the form of thermodynamic data, particularly Gibbs free energy data, and may be conveniently obtained from a standard Ellingham diagram or predominance diagram or Gibbs free energy diagram. Thermodynamic data and Ellingham diagrams for oxide stability are available and understood by electrochemists and smelters (in this case, those skilled in the art will be familiar with such data and information) .

  Accordingly, preferred electrolytes for the reduction process may include calcium salts. Calcium forms an oxide that is more stable than most other metals, and therefore may act to facilitate the reduction of any metal oxide that is less stable than calcium oxide. In other cases, salts containing other reactive metals may be used. For example, the reduction process according to any aspect of the invention described herein may be performed using a salt comprising lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, or yttrium. . Chloride or other salts may be used, including chlorides or mixtures of other salts.

  By selecting the appropriate electrolyte, almost any metal oxide may be able to be reduced using the methods and apparatus described herein. In particular, beryllium, boron, magnesium, aluminum, silicon, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, germanium, yttrium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, and lanthanum Lanthanides, including cerium, praseodymium, neodymium, samarium, and oxides of actinides, including actinium, thorium, protoactinium, uranium, neptunium, and plutonium, may be reduced using molten salts, preferably containing calcium chloride There is.

  One skilled in the art can select an appropriate electrolyte to reduce a particular metal oxide therein, and in many cases, an electrolyte containing calcium chloride will be suitable.

  Specific embodiments of the invention will now be described with reference to the drawings.

1 is a perspective view of a removable electrode module embodying one or more aspects of the present invention. FIG. It is a side view of the removable electrode module of FIG. It is a top view of the removable electrode module of FIG. FIG. 2 is a side cross-sectional view of the removable electrode module of FIG. 1 illustrating the structure of various electrodes and support components of the removable electrode module. FIG. 2 is a schematic cross-sectional view of an electrolyzer having an electrolysis chamber suitable for receiving the embodiment of the removable electrode module illustrated in FIG. 1. FIG. 6 is a schematic cross-sectional view of the removable electrode module of FIG. 1 engaged with the electrolyzer illustrated in FIG. FIG. 6 is a schematic cross-sectional view of the removable electrode module of FIG. 1 housed in a transfer module installed on the electrolyzer of FIG. 5 in a ready state for engaging the electrode module with the electrolysis chamber of the electrolyzer. . FIG. 6 is a schematic cross-sectional view of the removable electrode module of FIG. 1 after being delivered from the transfer module and engaged with the electrolyzer of FIG. 2 is a perspective view of a removable cathode tray structure suitable for use as a cathode tray in the removable electrode module of FIG. 1. FIG. FIG. 10 is a plan view of the cathode tray structure of FIG. 9. FIG. 10 is a side view of the cathode tray structure of FIG. 9. FIG. 6 is a cross-sectional view of a second embodiment of a removable electrode module according to one or more aspects of the present invention. FIG. 6 is a cross-sectional view of a third embodiment of a removable electrode module according to one or more aspects of the present invention. FIG. 6 is a schematic cross-sectional view of an alternative method of coupling a removable electrode module to a lifting means according to an embodiment of the present invention. 2 is a schematic illustration of an electrode module installed at a loading station with a transfer module positioned over the electrode module. 1 is a schematic illustration of an electrode module held in a transfer module above a heating station. 1 is a schematic diagram illustrating a transfer module engaged with a heating station. 1 is a schematic illustration of an electrode module held in a transfer module above a cooling station. 1 is a schematic diagram illustrating a transfer module engaged with a cooling station. 1 is a schematic illustration of an electrode module experiencing cleaning at a cleaning station.

  A removable electrode module according to a first embodiment of the present invention will now be described with reference to FIGS. The electrode module 10 includes a terminal anode 20, a terminal cathode 30, and seven bipolar electrodes 40, 41, 42 distributed spatially separated from each other above the terminal cathode 30 and below the terminal cathode 20. , 43, 44, 45, 46. Each of the end cathode 30, end anode 20, and intermediate bipolar electrodes 40, 41, 42, 43, 44, 45, 46 is substantially circular in shape and has a diameter of about 550 mm.

  The terminal cathode 30 has a composite structure including a lower part and an upper part. The lower portion is substantially a cathode base element 30a formed from a grade 310 stainless steel disk having a diameter of 550 mm and a thickness of 60 mm. The upper portion is provided by a removable tray assembly 30b installed on the top surface of the base element 30a. The removable tray assembly 30b is illustrated in FIGS. 9, 10, and 11 and is described in more detail below. A central hole having a diameter of about 130 mm is defined through the central portion of the assembled tray assembly 30b.

  Each of the seven bipolar electrodes 40, 41, 42, 43, 44, 45, 46 includes a lower portion 40a, 41a, 42a, 43a, 44a, 45a, 46a and an upper or tray assembly portion 40b, 41b, 42b, 43b, 44b, 45b, 46b. The portion of the tray assembly above each of the bipolar electrodes is identical to the portion 30b of the tray assembly above the end cathode 30.

  Each lower portion 40a, 41a, 42a, 43a, 44a, 45a, 46a of the bipolar electrode is formed from a carbon, eg, graphite, disk having a diameter of 550 mm and a thickness of 60 mm. A hole having a diameter of about 130 mm is defined through the central portion of each of the bipolar electrodes 40, 41, 42, 43, 44, 45, 46.

  To help guide the gas generated on the lower surface of each bipolar electrode to the outer periphery of each bipolar electrode, a plurality of channels 50 approximately 10 mm wide are defined on the lower surface of each bipolar electrode.

  The first bipolar electrode 40 is supported directly above the terminal cathode 30 by a first electrically insulating spacer element 60. The first electrically insulating spacer element 60 is a tubular spacer formed from alumina. The first electrically insulating spacer element may alternatively be formed from other electrically insulating ceramic materials such as yttria or boron nitride.

  In some embodiments, the first electrically insulating spacer element 60 is placed directly above the cathode base element 30a. In other embodiments, a ceramic insert 70 formed from a ceramic material that will not reduce under cell operating conditions is disposed between the terminal cathode base element 30a and the first electrically insulating spacer element 60. .

  The lower surface of the lower portion 40a of the first bipolar electrode 40 is a first electrically insulating spacer such that the first bipolar electrode 40 is supported through the first electrically insulating spacer element 60 by the terminal cathode base element 30a. Installed on element 60.

  The second bipolar electrode 41 is supported directly above the first bipolar electrode 40 via the second electrically insulating spacer element 61. The second electrically insulating spacer element 61 is a tubular alumina element that is substantially identical to the first electrically insulating spacer element 60. The second electrically insulating spacer element is placed on the upper surface of the lower portion 40 a of the first bipolar electrode 40. The lower surface of the lower portion 41a of the second bipolar electrode is then in a second position so that the second bipolar electrode 41 is supported by the first bipolar electrode via the second electrically insulating spacer element 61. Installed on the electrically insulating spacer element.

  This support structure is repeated for each of the bipolar electrodes. Accordingly, the third bipolar electrode 42 is supported by the second bipolar electrode 41 via the third electrically insulating spacer element 62. The fourth bipolar electrode 43 is supported by the third bipolar electrode 42 via the fourth electrically insulating spacer element 63. The fifth bipolar electrode 44 is supported by the fourth bipolar electrode 43 via the fifth electrically insulating spacer element 64. The sixth bipolar electrode 45 is supported by the fifth bipolar electrode 44 via a sixth electrically insulating spacer element 65. The seventh bipolar electrode 46 is supported by the sixth bipolar electrode 45 via the seventh electrically insulating spacer element 46.

  The terminal anode 20 is formed from a graphite disk having a diameter of 550 mm and a thickness of 60 mm. A channel is defined on the lower surface of the anode in the same manner as defined above in connection with the bipolar electrode. One purpose of these channels is to assist in the removal of gas generated at the lower surface of the terminal anode 20. A hole having a diameter of about 130 mm is defined through the central portion of the terminal anode 20. The terminal anode is supported directly above the seventh bipolar electrode 46 via an eighth electrically insulating spacer element 67.

  The removable electrode module 10 further comprises a heat insulating ceramic cover 100 disposed just above the terminal anode 20. The cover 100 is formed from alumina, but any insulating ceramic material could potentially be used and is designed to cover the electrolysis chamber of the electrolyzer during the electrolysis reaction. The cover 100 is supported by the upper surface of the terminal anode 20 via a ninth electrically insulating support element 68. The ninth electrically insulating support element 68 is similar to the previously described electrically insulating support element, but has a greater length.

  A central hole is defined through the cover 100. Thus, a hole or cavity extending downwardly through the removable electrode module is defined from the top surface 101 of the cover 100 through each of the tubular electrically insulating spacer 68, the center of the anode, and the bipolar electrodes and their associated spacer elements. . A suspension rod 110 extends through this hole or cavity and is coupled to the cathode base element 30a of the end cathode 30 by a thread that engages a threaded hole defined in the cathode base element 30a. The suspension rod 110 does not contact any other electrode or spacing element. A seal is formed by a graphite gland packing, such as a braided graphite rope or other similar gland packing material 120, at a point where the suspension rod 110 passes through a central hole defined through the cover 100.

  At its upper portion, the suspension rod 110 is coupled to the j-slot connector 130. The j-slot connector is a bayonet connector that is well known for joining pipe cut surfaces in the petroleum industry. The connection between the suspension rod and the j-slot connector is achieved by a washer and nut 111.

  The suspension rod 110 may be used to lift the entire removable electrode module 10 when, for example, raising or lowering the electrode module. In use, the suspension rod may need to function at high temperatures. Accordingly, the rod 110 and the associated nut and washer 111 that couple the rod 110 to the j-slot connector 130 are formed from a high nickel alloy suitable for operation at high temperatures.

  The anode 20 is coupled to two graphite risers 21, 22 to allow an electrical connection to be made between a power source (not shown) and the terminal anode 20. The graphite risers 21, 22 are coupled to the terminal anode 20 by graphite studs 23, 24. The graphite risers 21, 22 pass through holes defined in the cover 100 so that the removable electrode module can be in electrical connection with the top of the riser when it is in engagement with the electrolysis chamber of the electrolyzer. It extends vertically above the terminal anode 20. The gap between the risers 21, 22 and the associated holes defined through the cover 100 for passing the risers is sealed by a braided graphite rope or other similar gland packing material 25.

  The removable electrode module 10 is designed to have three loading states or support states.

  In the first of these three states, the removable electrode module is placed on the lower surface of the cathode base element 30a. In this state, the weight of the bipolar element, anode, and cover are all transmitted through the cathode base element 30a, and the suspension rod 110 is not tensioned.

  In the second loaded state, the j-slot connector 130 is coupled to the lifting mechanism and the entire weight of the module is supported through the suspension rod 110 that is coupled to the cathode base element 30a.

  In the third loaded state, the removable electrode module 10 may be supported at a plurality of points on the lower surface 102 of the cover 100. In this state, the weight of the module is transmitted through the suspension rod 110 supported by the cover 100 and coupled to the cathode base element 30a.

  Thus, the module may be free-standing on its cathode base element 30a, suspended by the j-slot coupler 130 at the upper end 110 of the suspension rod, or suspended by the lower side 102 of the cover 100. .

  The suspension rod 110 is coated with an electrically insulating material 115 throughout its length from the point of attachment to the cathode base element 30a to the sealing point with the braided graphite rope 120 as the suspension rod 110 passes through the cover 100 or Cladded. This electrically insulating material is the alumina coating 115, but any high temperature electrically insulating material may be used. For example, the coating 115 may be boron nitride. The coating may be applied by any known method, such as dip coating or spray coating.

  A removable tray assembly forming part of each of the terminal cathode 30 and the seven bipolar electrodes 40, 41, 42, 43, 44, 45, 46 is illustrated in FIGS. 9, 10, and 11. The tray assemblies 30b, 40b, 41b, 42b, 43b, 44b, 45b, 46b are formed by two connectable portions 151, 152. When joined together, the entire tray assembly is substantially circular and has a diameter of about 542 mm at room temperature. The tray assembly is made of metal, so the diameter is due to thermal expansion at the operating temperature of the removable electrode module (usually between about 500 ° C. and 1200 ° C. when used in an electrolytic reaction in molten salt). May increase to about 550 mm.

  The respective bases 153, 156 of the tray assembly portions 151, 152 are formed from a mesh suitable for supporting a solid feedstock. Around the periphery of the assembled tray assembly, a circumferential lip extends up about 30 mm above the height of the mesh 153,156. A plurality of downwardly extending legs 155 extend downwardly from the circumferential lip 154 by a distance of about 10 mm below the height of the meshes 153, 156.

  The entire tray assembly may be placed on the top surface of the associated electrode portion to form the electrodes of the electrode module. For example, the tray assembly 30b may be placed on the upper surface of the end cathode base plate 30a to form the end cathode 30, or the tray assemblies 40b, 41b, 42b, 43b, 44b, 45b, 46b may be bipolar. It may be placed on the upper surface of the lower portion of the bipolar electrodes 40a, 41a, 42a, 43a, 44a, 45a, or 46a to form the electrodes. Electrical contact is made between the tray assembly and its associated electrode portion through downwardly extending legs 155.

  When the removable electrode module comprising the removable tray assemblies 30b, 40b, 41b, 42b, 43b, 44b, 45b, 46b is placed in an electrolysis chamber containing the molten salt, the molten salt is on top of it. Can flow into a gap formed between the upper surface of the electrode portion where the tray assembly is installed and the mesh bases 153 and 156. The molten salt can therefore flow upward through the mesh base 153, 156 of the tray assembly and thus across any solid feedstock supported on the bases 153, 156.

  The tray assembly is formed with a central hole for surrounding an electrically insulating spacer element, for example, an electrically insulating spacer element 60 that supports the first bipolar electrode 40.

  The tray assembly is formed of two connectable parts, a first part 151 and a second part 152, each part being substantially semicircular. The two parts 151, 152 can be joined by a stud and slot configuration. The stud 160 extends from the mating surface or mating edge 162 of the second portion and defines a slot 161 for receiving the stud 160 in the corresponding mating surface 163 of the first portion 151.

  In use, each half or portion 151, 152 of the tray assembly may be separately removed from the removable electrode module 10 to load the feed or to remove the reduced product.

  A removable tray assembly forms the top of each of the terminal cathode and bipolar electrodes. These parts of each electrode become the cathode when the removable electrode module is used for electrolysis.

  The removable tray assemblies 30b, 40b, 41b, 42b, 43b, 44b, 45b, 46b are manufactured from 310 grade stainless steel. The removable tray assembly may be made from many other materials, and the choice of material may depend on the nature of the feed to be reduced. For example, it may be desirable to use a tray assembly formed from a metal that will not contaminate the reduced product. For example, it may be desirable to form a cathode tray assembly from tantalum or a tantalum-coated metal, in which case a removable electrode module will be used to reduce tantalum oxide to metallic tantalum.

  The removable electrode module according to the first specific embodiment described above may be particularly advantageous when used for the reduction of a solid feedstock in a molten salt electrolyte. The removable tray assembly is conveniently loaded with solid feedstock on each separate removable tray assembly portion 151, 152, and the loaded portion of the tray assembly in place in the electrode module. Installation allows it to be loaded into a removable electrode module.

  At room temperature, the removable electrode module 10 has a total height of 1645 mm from the lower surface of the cathode base plate 30 a to the lower surface of the cover 100. The height from the lower surface of the cathode base plate 30a to the top of the j-slot connector 130 is 2097 mm. As described above, the electrodes 30 and 40 to 46 have a diameter of 550 mm. The maximum diameter of the cover 100 is 830 mm. Some of these dimensions may change as the temperature changes. In particular, the height value may increase by 5-10 mm at the operating temperature of the electrode module.

  The removable electrode module 10 according to the first embodiment of the invention described above can be advantageously used with any electrolyzer having an electrolysis chamber suitable for receiving the module 10 in an engaged state. There is. A schematic diagram of such an electrolyzer 200 is provided by FIG.

  The electrolyzer 200 includes a housing 210 that houses an electrolysis chamber 220 defined within a graphite crucible 230, and an upper rim 231 of the graphite crucible 230 defines an opening to the electrolysis chamber 220. The upper surface of the rim 231 is coated with an area of 15 mm thick elastic graphite material to seal the rim 231 against the underside of the cover 100 of the removable electrode module 10. The sealing material installed on the upper rim 231 is a braided graphite gland packing material that may be deformed and recover its shape.

  The housing 210 further contains a furnace heating element 240 for maintaining the temperature of the graphite crucible 230, a molten salt inlet 250 and a molten salt outlet 260 for allowing molten salt to flow through the electrolysis chamber 220. A gas vent line 270 is provided toward the upper portion of the electrolysis chamber 220 to allow gas generated during any electrolysis reaction occurring in the electrolysis chamber to escape. A DC supply cathode bus bar 280 is coupled to the graphite crucible 230, allowing the entire graphite crucible 230 to couple the graphite crucible directly to the power source.

  The graphite crucible 230 is lined with an alumina liner 290. The alumina liner 290 provides electrical insulation between the sidewalls of the graphite crucible 230 and any removable electrode module 10 that is engaged within the electrolysis chamber 220. The liner is made from alumina, but may be made from any suitable electrically insulating ceramic material that is substantially inert under the processing conditions within the electrolysis chamber 220.

  The upper part of the electrolyzer comprises a gate valve type closure 300 that allows external access to the electrolysis chamber 220 to be provided. The gate valve closure 300 includes a gate 310 formed from a thermal barrier material, such as a ceramic material. Actuation device 320 allows gate 310 to slide back and forth to open and close gate valve 300, thereby allowing access to electrolysis chamber 220 within electrolyzer 200.

  FIG. 6 illustrates a removable electrode module according to the first embodiment described above in connection with FIGS. 1-4, engaged with an electrolyzer of the type illustrated in FIG.

  The lower inner surface of the graphite crucible 230 is raised to form a pedestal 232. When engaged with the electrolysis chamber 220, the removable electrode module 10 is placed on this raised pedestal 232 in the graphite crucible 230. Thus, the lower surface of the terminal cathode 30 of the removable electrode module is in physical and electrical contact with the inner surface of the graphite crucible 230.

  The bipolar electrodes 40-46 and the anode 20 of the removable electrode module 10 are located in a portion of the electrolysis chamber that is electrically insulated from the side wall of the crucible 230 by the ceramic liner 290. The lower surface 102 of the cover 100 of the removable electrode module 10 makes contact with the upper rim 231 of the graphite crucible 230. When the cover contacts the rim 231, the flexible graphite sealing material placed on the upper rim can be deformed to provide a seal. It is noted that the graphite sealing material could alternatively or additionally be placed on the lower surface 102 of the cover 100.

  In use, the temperature in the electrolysis chamber can vary considerably. Accordingly, the dimensions of some components of the removable electrode module, such as the suspension rod 110, can vary by a few millimeters. The elastic material placed on the upper rim of the graphite crucible 230 is preferably elastic and deformable enough to accommodate any such thermal strain and maintain a viable seal with the lower side 102 of the cover 100. Have

  The removable electrode module anode risers 21, 22 extend upward through the cover 100. Electrical contact with these risers may be made by an operable DC anode busbar 250 that is actuated to contact the anode risers and thus may provide an electrical connection between the anode and the power source.

  In use, a removable electrode module loaded with molten salt in the electrolysis chamber 220 and loaded with a reducible feedstock engages the electrolysis chamber. The anode bus bar is actuated to contact the anode risers 21, 22, via the anode 20 (through the anode riser and activatable anode bus bar 250) and the terminal cathode 30 (through the graphite crucible 230 and the cathode DC bus bar 280. A potential is applied between them. The applied potential is sufficient to reduce the feedstock. The required potential can vary depending on the type of feedstock and the composition of the molten salt.

  In many situations, particularly with regard to the reduction of the solid feedstock in the molten salt electrolyte, it may be advantageous that a removable electrode module at or near its operating temperature can engage the electrolysis chamber of the electrolyzer. For many molten salt electrolytes, this means that the electrolysis chamber contains the molten salt at a temperature between 500 ° C and 1200 ° C. When a room temperature removable electrode module is inserted into an electrolysis chamber containing molten salt, for example at a temperature of 1000 ° C., the components of the removable electrode module experience severe and rapid thermal strain. there is a possibility. In particular, the ceramic components of the removable electrode module can experience severe thermal shock and can therefore fail. As a complication, if the removable electrode module as described above in connection with the first embodiment of the removable electrode module is preheated to a temperature of 1000 ° C. in air, the removable electrode The graphite part of the module can burn.

  It may be particularly desirable to be able to remove the removable electrode module from the electrolysis chamber of the electrolyzer immediately after electrolysis occurs and without waiting for the electrolysis chamber to cool. Care will need to be taken to ensure that an oxygen-containing atmosphere, such as air, has not contacted the hot removable electrode module. As a result of the failure of the safety device against this, the graphite parts of the electrode module burn, the reduced metal product placed in the removable electrode module burns or oxidizes, due to the rapid cooling of the module Severe thermal deformation and failure can occur.

  In order to allow the removable electrode module to engage the electrolysis chamber of the electrolyzer at a temperature close to the operating temperature, and the removable electrode module is disengaged from the electrolysis chamber at a temperature close to the operating temperature. In order to make this possible, it is desirable that the removable electrode module can be retracted into the transfer module before being transferred or transported to the electrolyzer. The transfer module may include a heating element and / or a cooling element. The transfer module may simply be a shroud that can maintain an inert atmosphere within it, which insulates or is controlled by the preheated electrode module prior to loading into the electrolysis chamber. Insulate the now disengaged electrode module from the electrolysis chamber before being transported to a separate location for cooling.

  FIG. 7 illustrates a removable electrode module as described above in connection with FIGS. 1-4 disposed within an embodiment of the removable transfer module 400. The removable transfer module 400 includes a housing 410 formed from 310 grade stainless steel and is lined with a refractory lining. The refractory lining may be any other suitable material such as a ceramic brick lining or fiberboard that insulates the interior of the transfer module. The interior of the transfer module comprises a transfer cavity 420 in which the removable electrode module 10 may be placed.

  The transfer module may comprise means for coupling to the j-slot connector at the top of the removable transfer module and means for retracting the removable transfer module into the transfer chamber 420. For example, the transfer module 400 may include a winch for lifting a removable electrode module.

  The upper portion of the transfer module 400 comprises means for lifting the transfer module, such as one or more hooks 430. Such lifting means allow the entire transfer module to be lifted and moved between the electrolyzer 200.

  The lower part of the transfer module 400 is closed by a gate valve 440. The gate valve includes a heat resistant gate 450 operable to open and close an opening to the transfer module chamber 420. A transfer module that includes a gate valve may be conveniently installed over the gate valve of the electrolyzer 200 as described above in connection with FIG. Opening the gate valve 440 associated with both the transfer module and the electrolyzer 200 may provide access to the electrolysis chamber opening 220. The removable electrode module 10 is then transferred through the opening of both the gate valve associated with the transfer module and the gate valve associated with the electrolyzer to allow the electrode module to be placed in the electrolysis chamber 220. Can be lowered from chamber 420. Each gate valve can then be closed as illustrated in FIG. 8, and then the transfer module 400 may be removed.

  The first embodiment of the removable transfer module, as described above and illustrated in FIGS. 1-4, has eight working electrodes (ie, end terminals) on which the solid feedstock may be reduced. The upper part of the cathode 30 and the upper part of each of the bipolar electrodes 40 to 46). For some reactions, it may be desirable to reduce a lower volume of solid feedstock. For these purposes, it may be desirable for a removable electrode module to have a lower cathode electrode surface area. A second embodiment of a removable electrode module according to one or more aspects of the present invention is illustrated by FIG.

  The full size of the removable electrode module as illustrated in FIG. 12 is the same as the removable electrode module illustrated in FIGS. 1-4, and thus this second implementation of the removable electrode module. The form may be used in combination with the same electrolysis apparatus as in the first embodiment. However, the removable electrode module 1200 of the second embodiment of the present invention comprises a terminal cathode 1230 and a terminal anode 1220, with only one bipolar electrode 1240 being disposed between the terminal anode 1220 and the terminal cathode 1230. . The terminal anode, terminal cathode, and bipolar electrode are identical in structure and configuration equivalent to that described above in connection with the first embodiment of the present invention. Because there are fewer bipolar electrodes disposed between the terminal anode 1220 and the terminal cathode 1230, the graphite electrode risers 1221 and 1222 are more than those described above in connection with the first aspect of the present invention. Is also substantially long. If necessary, several cross sections of the graphite riser may be joined by a female threaded stud 1226. The cover 1201 is supported directly above the upper surface of the anode 1220 via a plurality of electrically insulating ceramic spacers 1268.

  Except for these specific adaptations required to ensure that the outer dimensions of this removable electrode module are the same as the dimensions of the module of the first embodiment of the present invention, the second of the present invention. All other elements of the removable electrode module according to this embodiment are the same as those described above.

  In accordance with certain aspects of the invention, it is not essential that the removable electrode module comprises a bipolar electrode. FIG. 13 illustrates a third specific embodiment of a removable electrode module according to one or more aspects of the present invention. This third embodiment includes a terminal anode 1320 and a terminal cathode 1330 but does not include a bipolar electrode. Terminal cathode 1330 and terminal anode 1320 are constructed in the same manner as terminal anode 20 and terminal cathode 30 described above in connection with the first embodiment of the present invention. The outer dimensions of the removable electrode module 1300 of the third embodiment are the same as the dimensions of the first and second embodiments of the removable electrode module. All other details of the third embodiment of the removable electrode module as illustrated in FIG. 13 are described above in connection with the first or second embodiment of the removable electrode module. Similar to that described.

  In the embodiment described above, the suspension rod 110 is coupled to the j-slot connector 130 by fastening the ends of the rod 110 to the connector 130 with washers and bolts 111. Any tolerances necessary to form a seal between the underside of the cover 100 and the rim 231 of the crucible 230 that forms an opening to the electrolysis chamber 220 are achieved by using an elastic sealing material on the rim. The FIG. 14 illustrates an alternative coupler that may be used in one embodiment of a removable electrode module. For ease of reference, the same reference numbers are given to the same components as those present in the first embodiment described above.

  In the alternative embodiment illustrated in FIG. 14, the suspension rod 110 of the electrode module is coupled to the j-slot connector 130 by a flange 1410 that transmits a load onto the j-slot connector through a set of disc springs 1400. Flange 1410 is secured to spring 1400 by nut 1420.

  As the module is lifted, the weight of the module is transmitted through the suspension rod 110 and compresses the spring 1400. The spring biases upward against the lower surface of the flange 1410. Spring 1400 may be any suitable spring means. For example, the spring may include a helical spring.

  Coupling the electrode module to a lifting means such as a j-slot connector with an elastic spring in between may provide advantages in use. For example, when the electrode module is lowered into the electrolysis chamber as described above, contact is made between the rim surrounding the chamber opening and the lower surface 102 of the cover 100 to form a seal. In the embodiment described above, the module base plate 30a must be placed in physical contact with the inner wall of the crucible to provide a cathode connection. The use of resilient means such as a disc spring 1400 disposed between the lifting means and the suspension rod may allow additional movement of the electrode module after the seal is formed by the cover 100. Furthermore, such elastic means may advantageously accommodate dimensional changes in the suspension rod caused by thermal fluctuations.

  One embodiment of a removable electrode module comprising elastic means and lifting means disposed between one or more suspension rods supporting the electrode uses an elastic sealing material surrounding the opening of the electrolysis chamber It may be adopted as an alternative to or in addition to the above.

  The following description of the method for electrolytically reducing a solid feedstock according to a specific embodiment of the present invention uses a removable electrode module 10 as described above. The processing method can be broken down into a number of steps.

  Step 1—Removable electrode module 10 comprises eight layers of cathode electrodes (ie, one cathode and seven bipolar electrodes that act as both anode and cathode) and an anode. Each upper surface of the working electrode comprises a removable tray assembly itself formed by two connectable portions 151,152. As a first step in the process, a feedstock consisting of a plurality of solid oxide preforms is loaded onto the respective surfaces of removable tray assembly elements 151, 152.

  Step 2—Loaded tray assembly is transferred to a removable electrode module located at the electrode module loading station. The loaded tray assembly is placed on a removable electrode module 10 and each pair of tray assembly portions 151, 152 is connected to a cathode electrode (eg, 30, 40, 41, 42, 43, 44, 45). , 46) is formed.

  Step 3—The loaded removable electrode module 10 is raised into the transfer chamber 420 of the transfer module 400. To raise the removable electrode module 10 into the transfer chamber 420, the transfer module 400 is positioned vertically above the working station. The gate valve 440 of the transfer module 400 is actuated to slide the gate 450 open, allowing access to the transfer chamber 420. A bayonet coupler (not shown) is lowered by a winch 465 located on the transfer module 400. The bayonet fitting couples to the j-slot connector 130 on the removable electrode module 10, thereby allowing the removable electrode module 10 to be raised into the transfer module chamber 420.

  Step 4-The entire transfer module 400 containing the removable electrode module 10 may be lifted and moved by a plurality of hooks 430. In step 4, the entire transfer module containing the electrode module is moved to a position vertically above the heating station. This is illustrated in FIG. The transfer module 400 is coupled to the heating station 500 with the removable electrode module 10 positioned directly above the heating chamber 510. The heating station includes a housing 501 that houses a heating chamber 510 surrounded by a plurality of heating elements 520.

  Step 6—The electrode module is lowered by the winch 465 until the lower surface 102 of the cover 100 is installed on the rim 502 of the heating chamber 510. The bayonet coupler is removed from the j-slot connector 130 and the gate 450 is closed. The removable electrode module 10 now engages the heating station and supports the full weight of the module through the underside of the cover 100. This configuration is illustrated in FIG.

  Step 7—The electrode module 10 is heated to a predetermined temperature in the heating chamber 510 of the heating station 500. For electrolysis in molten salt, this predetermined temperature is probably somewhere between 500 ° C and 1200 ° C. For example, the temperature may be raised to 700 ° C or 800 ° C. The heating rate of the module is controlled so that the ceramic parts of the electrode module do not experience thermal shock. Thus, heating may be performed at a rate between 1 ° C. per minute and 10 ° C. or 20 ° C. per minute. For example, heating may occur at a rate of about 5 ° C. per minute. Heating is performed under an inert atmosphere, such as an argon atmosphere or a nitrogen atmosphere.

  Step 8—When the electrode module is heated to a predetermined temperature, the electrode module 10 is once again raised into the transfer chamber 420 of the transfer module 400.

  Step 9—The gate valve is closed, thereby sealing the transfer chamber 420. An inert atmosphere, such as an argon or nitrogen atmosphere, is maintained in the transfer module.

  The heat loss rate is low because the walls of the transfer module are insulated. Therefore, when the electrode module 10 is heated to a predetermined temperature and sealed in the transfer module 400, the temperature of the module 10 slowly decreases.

  Step 10-The transfer module 400 containing the electrode module 10 at a predetermined temperature is moved to a position directly above the electrolysis chamber. Access to the electrolysis chamber 220 is restricted by the presence of the gate valve 300 installed above the electrolysis chamber. This is illustrated in FIG.

  Step 11-The transfer module 400 is coupled to the electrolyzer 200 that houses the electrolysis chamber 220. The gate valve 440 associated with the transfer module is aligned with the gate valve 300 associated with the electrolyzer so that the electrode module 10 can achieve access to the electrolysis chamber 220 when both gate valves are opened. The

  Step 12-The gate valve 440 on the transfer module is opened.

  Step 13-The gate valve on the electrolyzer 200 is opened.

  Step 14-The electrode module 10 is lowered into engagement with the electrolysis chamber. The electrolysis chamber contains molten salt at or near its desired operating temperature. The preheated electrode module 10 is also at or near the operating temperature. This operating temperature may be, for example, about 800 ° C. The electrode module is placed in the electrolysis chamber 220 such that the lower surface of the cathode end 30 of the electrolysis module 10 is in physical contact with the graphite crucible 230 that defines the electrolysis chamber 220. This has been described above and is illustrated in FIG.

  Step 15-The anode bus bar 250 is moved into contact with the anode risers 21, 22 of the removable electrode module 10.

  A potential is applied between the anode 20 and the cathode 30 of the electrode module 10. This potential is sufficient to reduce the feedstock in contact with the cathode surfaces of the cathode and bipolar electrodes, respectively. The potential required to reduce the feedstock will depend on the nature of the system. Thus, for the reduction of the titanium oxide feedstock in molten salt based calcium chloride, the potential voltage at each cathode face of the electrode module 10 may be between 2 and 3 volts.

  The potential is applied for a time sufficient to reduce the solid feedstock.

  There may be a number of further processing steps to recover the reduced product from the electrode module 10 after electrolysis to reduce the feedstock. Accordingly, the following additional steps are used in specific embodiments of the present invention to recover the feedstock reduced after electrolysis.

  Step 17-The electrolysis cell current is switched off, thus removing the voltage at the surface of each electrode.

  Step 18-The anode busbar is pulled away from contact with the graphite anode risers 21,22.

  Step 19-The electrode module is raised out of the molten salt and into the transfer module 400. In order to allow time for the molten salt to drip freely from the electrode module 10, the electrode module is slowly raised.

  Step 20-The gate valve 300 on the electrolyzer 200 is closed.

  Step 21-The gate valve 440 on the transfer module is closed.

  Step 22-The transfer module containing the electrode module 10 is then disengaged from the electrolyzer 200 and moved to a position just above the cooling station 600. This is illustrated in FIG.

  Step 23-The transfer module 400 is coupled to the cooling station 600.

  Step 24-The gate valve 440 is opened to allow the removable electrode module 10 to access the cooling chamber 610.

  Step 25-The electrode module 10 is lowered into the cooling chamber until the lower surface 102 of the cover 100 rests on the upper rim of the cooling chamber 610. Cover 100 effectively forms a seal to cooling chamber 610. This is illustrated in FIG.

  Step 26-The cooling chamber comprises a wall 620 of a highly thermally conductive material, for example a metallic material such as stainless steel. The wall houses a water jacket 625 through which a constant supply of cold water is provided by an inlet 630 and an outlet 631. The water jacket allows heat to be efficiently removed from the thermal module 10. The cooling rate may be controlled by changing the rate at which water passes through the cooling jacket 625.

  Step 27-When the electrode module 10 is cooled to a predetermined temperature, it is raised into the transfer module 400.

  Step 28-The cooled electrode module 10 in the transfer module 400 is moved to a position just above the cleaning station.

  Step 29-The cooled electrode module is lowered into the cleaning station and placed on its cathode base plate 30a.

  Step 30-A jet of water 700 is discharged from a nozzle 705 connected to the pipe 710. The water jet 700 is directed to the electrode module 10 and in particular to the tray assembly containing the reduced feedstock. The water jets are preferably induced to wash away any residual salt and reduced feedstock that they cover the electrode module.

  Step 31-After cleaning, the electrode module 10 is raised into the transfer module 400.

  Step 32-The cleaned electrode module and transfer module are moved to a position above the pick-up station.

  Step 33-The cleaned electrode module is lowered to the position of the removal station.

  Step 34-The electrode tray assembly containing the reduced product is removed from the electrode module 10.

  Step 35-Reduced product is removed from the tray assembly and packaged for further processing.

  The specific embodiments of the method described above may not be used in all cases. For example, different steps may be used, or some steps may be omitted.

  The reduction of the solid feedstock preferably proceeds by an electrolytic deoxidation reaction such as an FFC process.

Claims (22)

A method of reducing solid feedstock by electrolysis, comprising:
Positioning an electrode module comprising at least one electrode in a first position for loading a feedstock;
Loading a solid feedstock onto the electrode module;
Moving the electrode module from the first position and engaging the electrode module with the electrolysis chamber such that the feedstock contacts molten salt in the electrolysis chamber;
Applying a voltage to the electrode module such that the solid feedstock is reduced;
Including methods.   The method of claim 1, wherein the electrode module is transferred from the first location within a transfer module.   The method of claim 1 or claim 2, wherein the electrode module is heated to a predetermined temperature before engaging the electrolysis chamber.   The method of claim 3, wherein the electrode module is heated under an inert atmosphere in the transfer module.   The method of claim 3, wherein the electrode module is transferred from the transfer module to a heating station and heated to a predetermined temperature.   The electrode module is transferred from the loading station in the transfer module, lowered into the heating station, heated to a predetermined temperature, raised back into the transfer module and transferred to the electrolysis chamber. The method according to claim 5.   7. A method according to any of claims 2 to 6, wherein the electrode module is sealed in the transfer chamber by closing a closure, preferably the closure is a gate valve.   The opening of the electrolysis chamber is closed by an openable closure, preferably the openable closure is an openable gate valve to allow the electrode module to be fed into the electrolysis chamber A method according to any of the preceding claims.   A method according to any preceding claim, further comprising the step of removing the electrode module from the electrolysis chamber after electrolysis to recover the reduced feedstock.   The method of claim 9, wherein the electrode module is lifted from the electrolysis chamber into the transfer module.   The method of claim 10, wherein the electrode module is cooled under an inert atmosphere in the transfer module after being removed from the electrolysis chamber.   The method of claim 10, wherein the electrode module is transferred to a cooling station and cooled to a predetermined temperature.   The electrode module is transferred to the cooling station in a transfer module, lowered into the cooling station, cooled to a predetermined temperature, and raised back into the transfer module to leave the cooling station. 13. The method of claim 12, wherein the method is transferred.   14. A method according to any one of claims 9 to 13, wherein the electrode module is further transferred to a washing station for washing salt from the reduced feedstock.   15. A method according to any of claims 9 to 14, wherein the electrode module is further transferred to a removal station for removing the reduced feedstock.   The solid feed is loaded onto a removable tray that is separate from the electrode module, and the removable tray is then coupled to the electrode module for loading the feed onto the electrode module. A method according to any of the preceding claims.   A method according to any preceding claim, wherein the feedstock is loaded in contact with the cathode structure of the electrode module.   A method according to any preceding claim, wherein the electrode module comprises one or more bipolar electrodes and the feedstock is loaded in contact with the cathode face of each bipolar electrode.   A process according to any preceding claim, proceeding by electrolytic deoxidation of the solid feedstock.   A method of reducing a solid feedstock substantially as herein described with reference to the drawings.   An electrolysis system comprising an electrode module, a transfer module, a heating station, an electrolysis chamber, and a cooling station.   An electrode module, a transfer module, a heating station, and a cooling station substantially as herein described with reference to the drawings.

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