Method for refining iron-containing materials

Abstract

Various embodiments include processes for purifying and / or preparing iron-bearing materials. Various embodiments include the purification and / or preparation of iron ore, iron, and intermediates thereof. Various embodiments include a method of purifying an iron-bearing material comprising leaching one or more soluble species of impurities from the iron-bearing material using a leach solution comprising fluorine.

Description

[Technical field]

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 307,462, entitled "PROCESSES FOR PURIFYING IRON-BEARING MATERIALS," filed February 7, 2022, and U.S. Provisional Patent Application No. 63 / 365,297, entitled "PROCESSES FOR PURIFYING IRON-BEARING MATERIALS," filed May 25, 2022. The contents of both applications are incorporated herein by reference in their entirety for all purposes. [Background technology]

[0002] Energy storage technologies are playing an increasingly important role in the power grid. At the most basic level, these energy storage assets provide smoothing to better match generation and demand on the grid. The services performed by energy storage devices benefit the power grid over multiple timescales, from milliseconds to years. Today, energy storage technologies exist that can support timescales from milliseconds to hours, but long-term and ultra-long-term (collectively, >8 hours) energy storage systems are needed.

[0003] Iron-based negative electrode electrochemical systems (or the alternative iron-based anode electrochemical systems described above) are an attractive option for electrochemical energy storage. However, achieving high performance with iron-based negative electrodes can be challenging, especially at low discharge rates, e.g., discharge rates where the full discharge time is greater than about 8 hours, e.g., 8 hours, >8 hours, 8-16 hours, 16 hours, >16 hours, 16-24 hours, 24 hours, >24 hours, 24-30 hours, 30 hours, >30 hours, etc. Sponge iron is an excellent candidate for an iron-based negative electrode because of the cost of sponge iron, but electrodes made from sponge iron may face challenges in achieving improved performance despite the promising material properties of sponge iron.

[0004] Iron-based alkaline electrochemical systems are an attractive option for long-term energy storage at grid scale due to the low rights costs of iron and alkaline electrolyte components. Grid-scale energy storage requires lower cost than traditional iron electrode materials, which in turn require the use of raw materials that may be of lower purity. Impurities can be detrimental to the performance of iron electrodes. It is difficult to remove some of these impurities from iron-containing materials in a low-cost, manufacturing-scalable manner to obtain high-performance, low-cost iron materials.

[0005] Therefore, there is a need to remove impurities from iron-bearing materials in a low-cost, manufacturing-scalable manner to obtain high performance, low-cost iron materials. Some of the specific impurities that are important to remove are silica (SiO2) (also called silicon dioxide), alumina (Al2O3) (also called aluminum oxide), magnesia (MgO) (also called magnesium oxide), calcia (CaO) (also called calcium oxide), and manganese oxide.

[0006] This "Background" section is intended to introduce various aspects of the art that may be related to embodiments of the present invention. As such, the discussion above in this section is intended to provide a framework for better understanding the present invention, and should not be construed as admissions of prior art. Summary of the Invention

[0007] Various embodiments include processes for purifying and / or preparing iron-bearing materials. Various embodiments include the purification and / or preparation of iron ore, iron, and intermediates thereof. Various embodiments include methods for purifying iron-bearing materials that include leaching one or more soluble species of impurities from the iron-bearing material using a leach solution that includes fluorine.

[0008] Various embodiments include processes for removing impurities such as silica, alumina, magnesia, manganese oxide, and / or calcia from iron-containing materials. Various embodiments may include one or more materials and / or processes for leaching soluble species from the iron-based material.

[0009] Various embodiments may include alkaline leaching techniques to dissolve impurities from iron-containing materials.

[0010] Various embodiments may include acid leaching techniques to dissolve impurities from iron-bearing materials.

[0011] Various embodiments for refining iron-containing materials may include the use of fluxes such as NaBO2, LiBO2, Li2B2O7, and the like.

[0012] Various embodiments may include an ammonium bifluoride (NH4HF2) silica dissolution technique to dissolve impurities from iron-containing materials.

[0013] Ammonium fluoride (NH4F) or ammonium bifluoride (NH4HF2) or ammonium bifluoride (3NH4·HF2), or mixtures, solutions, and derivatives thereof, hereafter collectively referred to as AF, can be used to selectively dissolve silicates from iron-bearing ores and minerals, iron, and partially processed intermediates thereof. Without being bound to a particular scientific interpretation, the inventors believe that AF can dissolve or partially dissolve solid siliceous compounds. Compared to other chemical reagents that can dissolve silicates in targeted iron-bearing materials, such as hydrofluoric acid (HF), alkali metal hydroxides (NaOH, KOH, etc.), and high-temperature melts (e.g., molten chlorides or fluorides or oxides), AF has the advantages of being less toxic and safer than HF, and more reactive at lower temperatures and concentrations than alkali metal hydroxides or high-temperature melts.

[0014] Various embodiments may include modifying impurity species in iron-containing materials to make them benign compounds.

[0015] Various embodiments may include processes for refining and / or preparing iron-containing materials carried out in one or more stages in processing iron ore for one or more purposes, such as for processing the iron ore into sponge iron-based battery components. In various embodiments, the one or more stages in processing the iron ore may include milling, blending, binder addition, fluxing, filtering, pelletizing, induration, iron ore pellet (IOP) formation, reduction, crushing, pulverizing, heating, hot pressing, and / or forming battery components such as electrodes.

[0016] Various embodiments may include methods for preventing or limiting stannate precipitation, such as for preventing or limiting stannate precipitation for long-life, high performance iron electrodes. Various embodiments may provide methods for removing CaO and / or MgO from iron electrode materials.

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the claims and, together with the general description set forth above and the detailed description set forth below, serve to explain the features of the claims. [Brief description of the drawings]

[0018] [Figure 1A] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure.

[0019] [Figure 1B] 1 illustrates example steps in an example battery component manufacturing process according to various embodiments.

[0020] [Figure 2A] 1 is a graph showing the corrosion rate and corrosion strength of iron in the presence of stirred aqueous solutions.

[0021] [Figure 2B] 1 shows a graph of the results of silica dissolution experiments at different pH.

[0022] [Diagram 3] 1 is a graph of the pH dependence of silica dissolution experiments.

[0023] [Figure 4] FIG. 1 is a block diagram illustrating iron ore processing operations and devices for processing iron ore into battery components such as electrodes, and opportunities for impurity removal, such as silica removal, along with iron ore processing, according to various embodiments.

[0024] [Diagram 5] According to various embodiments, an example process for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from an iron-containing material is provided. [Figure 6] According to various embodiments, an example process for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from an iron-containing material is provided. [Figure 7] According to various embodiments, an example process for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from an iron-containing material is provided. [Figure 8] According to various embodiments, an example process for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from an iron-containing material is provided. [Figure 9] According to various embodiments, an example process for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from an iron-containing material is provided. [Figure 10] According to various embodiments, an example process for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from an iron-containing material is provided. [Figure 11]According to various embodiments, an example process for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from an iron-containing material is provided.

[0025] [Figure 12A] This is a Pourbaix diagram showing the pH range where Ca and Mg begin to become highly soluble in Ca- and Mg-based aqueous solutions, compared to Fe. [Figure 12B] This is a Pourbaix diagram showing the pH range where Ca and Mg begin to become highly soluble in Ca- and Mg-based aqueous solutions, compared to Fe. [Figure 12C] This is a Pourbaix diagram showing the pH range where Ca and Mg begin to become highly soluble in Ca- and Mg-based aqueous solutions, compared to Fe.

[0026] [Figure 13] 1A-1D illustrate various exemplary systems in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 14] 1A-1D illustrate various exemplary systems in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 15] 1A-1D illustrate various exemplary systems in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 16] 1A-1D illustrate various exemplary systems in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 17] 1A-1D illustrate various exemplary systems in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 18] 1A-1D illustrate various exemplary systems in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 19] 1A-1D illustrate various exemplary systems in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 20] 1A-1D illustrate various exemplary systems in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 21] 1A-1D illustrate various exemplary systems in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The following examples are provided to illustrate various embodiments of the present systems and methods of the present invention. Such examples are intended to be illustrative and may be prophetic, and should not be considered limiting or in any way limit the scope of the present invention.

[0028] Various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or similar parts. References to specific examples and implementations are for illustrative purposes only and are not intended to limit the scope of the claims. The following description of embodiments of the invention is not intended to limit the invention to such embodiments, but rather to enable one of ordinary skill in the art to make and use the invention. Unless otherwise noted, the accompanying drawings are not drawn to scale.

[0029] As used herein, unless otherwise specified, room temperature is 25° C. and standard temperature and pressure are 25° C. and 1 atmosphere. Unless expressly stated otherwise, all tests, test results, physical properties, and values ​​that are temperature dependent, pressure dependent, or both, are provided at standard ambient temperature and pressure.

[0030] In general, the term "about," as used herein, unless otherwise specified, is meant to encompass a variation or range of ±10%, the experimental or instrumental error associated with obtaining a stated value, preferably whichever is greater.

[0031] As used herein, unless otherwise stated, recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise stated herein, each individual value within a range is incorporated herein as if it were individually recited herein.

[0032] It should be noted that it is not necessary to provide or express the theory underlying the novel and innovative process, material, performance, or other beneficial features and characteristics that are the subject of or associated with embodiments of the present invention. Nevertheless, various theories are provided herein to further advance the art in the field. The theories presented herein are not intended to limit, restrict, or narrow in any way the scope of protection afforded to the claimed invention unless expressly stated otherwise. Such theories may not be necessary or practiced to utilize the present invention. Furthermore, it is understood that the present invention may be coupled with new and previously unknown theories to explain the function-characteristics of embodiments of the methods, articles, materials, devices, and systems of the present invention. Such subsequently developed theories shall not limit the scope of protection afforded to the present invention.

[0033] The various embodiments of the systems, equipment, techniques, methods, activities, and operations illustrated herein can be used in various other activities and other fields in addition to those illustrated herein. In addition, such embodiments can be used, for example, with other equipment or activities that may be developed in the future and with existing equipment or activities that may be modified in part based on the teachings herein. Furthermore, the various embodiments and examples illustrated herein can be used with each other, in whole or in part, and in various different combinations. Thus, the configurations provided in the various embodiments herein can be used with each other. For example, elements of an embodiment having A, A', and B, and elements of an embodiment having A", C, and D can be used with each other in various combinations, for example, A, C, D, and A, A", C, D, etc., in accordance with the teachings herein. Thus, the scope of protection given to the present invention should not be limited to the specific embodiments, configurations, or arrangements shown in the specific embodiments, examples, or embodiments of the specific figures.

[0034] Electrochemical cells, such as batteries, store electrochemical energy by using the difference in electrochemical potential to create a voltage difference between the positive and negative electrodes. When the electrodes are connected by a conductive element, this voltage difference produces an electric current. In a battery, the negative and positive electrodes are connected in series by an external and internal resistive element. In general, the external element conducts electrons and the internal element (the electrolyte) conducts ions. Since a charge imbalance cannot be maintained between the negative and positive electrodes, the two must supply ions and electrons at the same rate. During operation, the flow of electrons can be used to power an external device. Rechargeable batteries can be charged by applying an opposing voltage difference, which results in an electric current and ion flow that flows in the opposite direction to the battery discharging during operation.

[0035] Embodiments of the present invention include devices, systems, and methods for long-term and ultra-long-term low-cost energy storage. As used herein, "long-term" and / or "ultra-long-term" may refer to energy storage periods of 8 hours or more, such as an 8-hour energy storage period, an energy storage period ranging from 8 hours to 20 hours, an energy storage period ranging from 20 hours to 24 hours, an energy storage period ranging from 24 hours to 1 week, an energy storage period ranging from 1 week to 1 year (e.g., from days to weeks to months). In other words, "long-term" and / or "ultra-long-term" energy storage cells refer to electrochemical cells that may be configured to store energy for days, weeks, or seasons. For example, an electrochemical cell may be configured to store energy generated by a solar cell during summer months when sunlight is abundant and solar power generation exceeds power grid needs, and discharge the stored energy during winter months when sunlight may be insufficient to meet power grid needs.

[0036] Generally, in an embodiment, the long-term energy storage cell may be a long-term electrochemical cell. Generally, this long-term electrochemical cell can store electricity generated by the power generation system when: (i) the power source or fuel for the generation is available, abundant, cheap, and combinations and variations thereof; (ii) the power needs or demands of the grid, customer, or other users are less than the amount of electricity generated by the power generation system, the price paid to provide such electricity to the grid, customer, or other users is below the economically efficient point for generating such electricity (e.g., the generation cost exceeds the market price of electricity), and combinations and variations thereof; and (iii) combinations and variations of (i) and (ii), and other reasons. This electricity stored in the long-term electrochemical cell can then be distributed to the grid, customer, or other users when it is economical or otherwise needed. For example, the electrochemical cell may be configured to store energy generated by solar cells during summer months when sunlight is abundant and solar power generation exceeds power grid needs, and to discharge the stored energy during winter months when sunlight may be insufficient to meet power grid needs.

[0037] According to other embodiments, the invention includes devices, systems, and methods for storing energy for short durations of less than about 8 hours. For example, the electrochemical cells may be configured to store energy generated by the solar cells during a diurnal cycle when solar generation exceeds grid needs during the day, and release the stored energy later in the evening when solar light may be insufficient to meet grid needs. As another example, the invention may include energy storage for use as a backup power source when electricity provided by the grid is insufficient in facilities such as homes, commercial buildings, factories, hospitals, or data centers where required discharge times vary from a few minutes to a few days.

[0038] In some embodiments, an electrochemical cell includes a negative electrode, a positive electrode, an electrolyte, and a separator disposed between the positive and negative electrodes (e.g., as shown in FIG. 1A). FIG. 1A shows an example of an electrochemical cell 100, such as a battery, including a negative electrode and an electrolyte 102 separated from a positive electrode and an electrolyte 103 by a separator 104. The separator 104 may be supported by a polypropylene mesh 105 and a polyethylene frame 108 of the cell 100. Current collectors 107 may be attached to each of the negative electrode 102 and positive electrode 103 and supported by a polyethylene backing plate 106. In some embodiments, the temperature of the electrochemical cell 100 may be controlled, such as by insulation around the cell 100 and / or a heater 150. For example, the heater 150 may increase the temperature of the cell 100 and / or certain elements of the cell, such as the electrolytes 102, 103. The configuration of the electrochemical cell 100 in FIG. 1A is merely an example of one electrochemical cell configuration according to various embodiments and is not intended to be limiting. Other configurations, such as electrochemical cells with different types of meshes and / or without polypropylene mesh 105, electrochemical cells with different types of frames and / or without polyethylene frame 108, electrochemical cells with different types of current collectors and / or without current collectors, electrochemical cells with different types of backing plates and / or without polyethylene backing plates 106, electrochemical cells with different types of insulators and / or without insulators, electrochemical cells with different types of heaters and / or without heater 150, may be substituted for the example configuration of electrochemical cell 100 shown in FIG. 1A, and other configurations are in accordance with various embodiments.

[0039] In some embodiments, multiple electrochemical cells 100 of Figure 1A may be electrically connected in series to form a stack. In certain other embodiments, multiple electrochemical cells 100 may be electrically connected in parallel. In certain other embodiments, multiple electrochemical cells 100 are connected in a mixed series-parallel electrical configuration to provide a preferred combination of current and voltage.

[0040] According to various embodiments, the anode is comprised of a pelletized, briquette, pressed, or sintered iron-containing compound. Such iron-containing compounds may include one or more forms of iron ranging from highly reduced (more metallic) to highly oxidized (more ionic) iron. In various embodiments, the iron-containing compounds may include various iron phases, such as iron oxide, iron hydroxide, iron sulfide, iron carbide, or combinations thereof. In various embodiments, the anode may be a sintered iron agglomerate having various shapes. In some embodiments, atomized iron powder or sponge iron powder may be used as a feed material to form the sintered iron electrode. In some embodiments, the green body may further include a binder, such as a polymer or an inorganic clay-like material. In various embodiments, the sintered iron agglomerate may be formed in a furnace, such as a continuous feed calcining furnace, a batch feed calcining furnace, a shaft furnace, a rotary calcining furnace, or a rotary hearth. In other embodiments, iron ore may be fed directly to a reduction furnace without heat treatment (e.g., as in various sponge iron manufacturing processes or fluidized bed reactors). In various embodiments, the iron active material feedstock may include forms of reduced and / or sintered iron-containing precursors, known to those skilled in the art as direct reduced iron (DRI), and / or by-product materials thereof. Various embodiments may include processing the iron active material feedstock, such as DRI pellets, using electrical, electrochemical, mechanical, chemical, and / or thermal processes prior to introducing the iron active material feedstock into the electrochemical cell.

[0041] Various embodiments are discussed regarding the use of iron active material feedstocks such as direct reduced iron (DRI) (also called sponge iron) as battery (or cell) materials, battery (or cell) components, and combinations and variations thereof. In various embodiments, the iron active material feedstock (e.g., DRI) may be produced from or may be material resulting from the reduction of natural or processed iron ore without reaching the melting temperature of iron. In various embodiments, the iron ore may be taconite or magnetite or hematite or goethite, etc. In various embodiments, the iron active material feedstock (e.g., DRI) may be in the form of pellets, which may be spherical or substantially spherical. In various embodiments, the iron active material feedstock (e.g., DRI) may be in a form other than pellets, such as particulates, granules, briquettes, chips, discs, chunks, powders, dust, etc., and may be other than spherical. In various embodiments, the iron active material feedstock (e.g., DRI) may be porous and may contain open and / or closed internal pores. In various embodiments, the iron active material feedstock (e.g., DRI) may include material that has been further processed by hot or cold briquetting. In various embodiments, the iron active material feedstock (e.g., DRI) may be produced by reducing iron ore form factors (e.g., iron ore pellets, briquettes, etc.) to form more metallic (more reduced, less oxidized) materials, such as iron metal (FeO), wustite (FeO), or composite forms (e.g., composite pellets, composite briquettes, etc.) that include iron metal and residual oxide phases. In various non-limiting embodiments, the iron active material feedstock (e.g., DRI) may be reduced iron ore taconite, direct reduced ("DR") taconite, reduced "blast furnace (BF) grade" pellets, reduced "electric arc furnace (EAF) grade" pellets, "cold direct reduced iron (CDRI)" pellets, direct reduced iron ("DRI") pellets, hot briquetted iron (HBI), or any combination thereof. In the iron and steel industry, DRI is sometimes called "sponge iron" and its use is common, particularly in India, or in the pressed and sintered powder metallurgy industry.

[0042] According to various embodiments, an electrochemical cell, such as cell 100 of FIG. 1A, includes a negative electrode (also called an anode), a positive electrode (also called a cathode), and an electrolyte. The negative electrode may be a ferrous material. The electrolyte may be an aqueous solution. In certain embodiments, the electrolyte may be an alkaline solution (pH>10). In certain embodiments, the electrolyte may be a near-neutral solution (10>pH>4).

[0043] Various embodiments include processes for purifying iron-containing materials. Various embodiments include the purification of iron ore, iron, and intermediates thereof. Various embodiments include processes for preparing iron-containing materials. Various embodiments include the preparation of iron ore, iron, and intermediates thereof. Various embodiments may include processes for purifying and / or preparing iron-containing materials for various purposes, such as battery applications, or any other purpose.

[0044] Various embodiments include a process for removing impurities, such as silica, alumina, calcia, magnesia, and / or manganese oxide, from iron-containing materials.

[0045] Various embodiments may include processes for purifying iron-containing materials, such as by removing impurities such as silica, alumina, CaO, and / or MgOa, which may occur at one or more steps in a process for forming any type of iron-containing material, such as one or more steps in the manufacture of DRI pellets, one or more steps in the manufacture of DRI fines, one or more steps in an electrolytic iron manufacturing process, etc. Various embodiments may include processes for purifying iron-containing materials, such as by removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, which may occur at one or more steps in a process for forming any type of iron-containing material for use in batteries, such as one or more steps in a process for using pelletized DRI in the manufacture of electrodes or other battery components, a process for using DRI fines in the manufacture of electrodes or other battery components, a process for using electrolytic iron in the manufacture of electrodes or other battery components, etc. By way of example, FIG. 1B illustrates example steps of a battery component manufacturing process 152 using pelletized DRI, an example step of a battery component manufacturing process 154 using fines-based DRI, and an example step of a battery component manufacturing process 156 using electrolytic iron. The steps in processes 152-156 are merely examples and various embodiments may include other processes and / or other steps.

[0046] As an example, processes 152-156 may begin with a mining step in which iron is mined and materials such as rock associated with the iron deposit are extracted. In various embodiments, embodiment methods of purifying the iron-bearing materials described herein, such as by removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed during and / or after mining in processes 152-156. In processes 152-156, a crushing step may follow mining, in which the mined rock may be crushed and / or ground into smaller pieces. Crushing may reduce the mined rock into smaller pieces than the original mined rock and begin to separate the desired iron ore from the gangue in the mined rock. In various embodiments, the methods of purifying iron-bearing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after the crushing and grinding steps in processes 152-156. In processes 152-156, beneficiation may follow crushing and grinding and may include chemical and / or physical separation of gangue from the iron ore. In various embodiments, the methods of purifying iron-bearing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after the concentrating steps in processes 152-156. The crushing and / or concentrating steps may result in an ore concentrate. In processes 152 and 154, an optional silica removal step may be performed after the concentrating step. For example, the silica removal step may remove silica and / or other materials from the ore concentrate. In various embodiments, embodiment methods of purifying iron-bearing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after the optional silica removal steps in processes 152 and 154. In process 152, a pelletizing step may be performed after beneficiation and / or the optional silica removal step.In various embodiments, the methods of purifying iron-bearing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after the pelletizing step in process 152. In process 152, a consolidation (or sintering) step may follow pelletizing. In various embodiments, the methods of purifying iron-bearing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after the consolidation step in process 152. In processes 152 and 154, a direct reduction step may be performed (e.g., after consolidation in process 152 or after optional silica removal in process 154), in which iron ore may be reduced by heating without reaching the melting temperature of iron. In various embodiments, the methods of purifying iron-bearing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after the direct reduction step in processes 152 and 154. In process 152, the resulting DRI pellets may be pulverized to reduce their size and / or produce DRI fines. In various embodiments, the methods of purifying iron-bearing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after the pulverization step in process 152. After beneficiation, digestion and purification of the iron ore may be performed at 156, followed by electrodeposition and drying. In various embodiments, embodiment methods of purifying iron-bearing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after the digestion and purification steps in process 156.In various embodiments, the methods of purifying iron-containing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after electrodeposition in process 156. In various embodiments, the methods of purifying iron-containing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after drying in process 156. The iron material obtained from pulverization in process 152, direct reduction in process 154, and / or drying in process 156 may be placed in a die and heated in processes 152-156. In various embodiments, the methods of purifying iron-containing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after die filling in processes 152-156. In various embodiments, the methods of purifying iron-containing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after reheating in processes 152-156. In processes 152 and 154, an optional decarburization step may be performed after reheating the filled die. In various embodiments, the methods of purifying iron-containing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after decarburization in processes 152 and 154. In processes 152-156, the iron material in the die may be hot consolidated and then cooled to form a battery component, such as an iron electrode. In various embodiments, embodiment methods of purifying iron-bearing materials described herein, for example, by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after hot consolidation in processes 152-156.In various embodiments, embodiment methods of purifying iron-bearing materials described herein, such as by removal of impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide, may be performed before, during, and / or after cooling in processes 152-156.

[0047] Various embodiments may provide methods of refining iron-bearing materials at one or more different processes, for example, when iron is in an ore concentrate process (e.g., after iron ore acquisition (e.g., mining) and after iron ore crushing and beneficiation), when iron is in an iron ore pellet process, when iron is in a high purity iron ore fines or iron ore pellet fragment (e.g., less than 6 mm) process, when iron is in a direct reduced iron process, when iron is part of a finished anode, before and / or after addition of a binder, etc. Table 1 provides various examples of processes / iron-bearing materials and a discussion of each. [Table 1]

[0048] Various embodiments may provide a method of refining iron-bearing materials that may produce an ore concentrate with a selected soluble silica content range. Soluble silica content may be defined as the silica content that is soluble in an alkaline environment after the material is incorporated into an alkaline battery. The soluble silica specification is essentially the same for iron ore pellets and iron ore concentrates, since the silica specification is based on wt%-Fe and given in terms of the amount of silica. Soluble silica content may be measured by subjecting the material to an extended leaching treatment (≧2 weeks) at a temperature close to the boiling point of the alkaline leach solution (≧90° C.). After the leaching treatment, soluble silica may be measured by one of two measurement techniques: 1) by a technique known in the art for quantifying the mass fraction of silica, e.g., inductively coupled plasma in combination with appropriate spectroscopy, followed by analysis of the amount of Si left in the material. When defining silicon content relative to the amount of Fe left in the material, the material may be evaluated from techniques known in the art to quantify total iron content, such as ISO2597, and comparing the Si and Fe content of the material before and after the leaching operation; or 2) direct measurement of silicon leached into the alkaline leach solution in the form of silicate. The mass fraction of dissolved silicate may be measured by any of the techniques known in the art for detecting silicate in alkaline solutions, including but not limited to ICP-OES. The alkaline leach solution may be a solution of 7M KOH. If the solubility of silica in the electrolyte used in the electrochemical cell using the Fe active material is significantly different, the soluble silica leaching method may instead be performed in the electrolyte used in the electrochemical cell. Through experimentation, the inventors have found that ≥2 weeks at 90°C is sufficient in many cases to measure the soluble silica content of the Fe active material. However, in some cases, silica may dissolve very slowly from the Fe active material, and a longer time or a different dissolution temperature may be required to achieve complete dissolution of the silica. In some cases, it may be necessary to electrochemically cycle the Fe active material to release all of the silica, in which case the soluble silica content may be measured by sampling the electrolyte and / or the Fe active material recovered from the cycled electrochemical cell.Various embodiments may provide a method of refining iron-bearing material that may produce an ore concentrate having a selected soluble silica content range, where the specified range of soluble silica content is SiO2 wt% relative to Fe weight percent (wt%), e.g., 0<0.01x<0.85, 0<0.01x<0.65, 0<0.01x<0.33, 0<0.01x<0.16, 0<0.01x<0.11, etc.

[0049] The amount of soluble silica tolerated in the cell may alternatively or additionally be defined based on the amount of silica that enters the electrolyte. Dissolved silica can be measured by sampling the electrolyte from the cell or by performing a leaching experiment from the cell as described above and converting the silica content measured in the cell to an equivalent silica concentration by appropriately adjusting the ratio of leached Fe active material (e.g., mL leachate / g Fe active material) to the ratio of electrolyte to Fe active material (e.g., mL electrolyte / g Fe active material). It is desirable for the soluble silica content to be <400 mM silicate, <200 mM silicate, <100 mM silicate, <50 mM silicate, <25 mM silicate, <10 mM silicate, and most preferably <5 mM silicate.

[0050] Various embodiments may provide a method of refining iron bearing materials that may produce iron ore pellets (IOP) with a selected soluble silica content range. Numerous other measurements may be collected in connection with the processing, transportation, and reduction of iron oxide pellets in various reduction techniques. The IOP material properties shown here are merely examples of properties that may be important to the performance of a secondary storage system. The IOP may also be designed to allow proper processing (e.g., reduction) of the IOP in downstream processes. Strength, other impurity levels, etc. are all related to the success of the process, but are also specific to the details of the process performed. The open porosity within the pellet is specifically the open porosity. The open porosity may be measured by measuring the envelope density of the pellet and the skeletal density of the pellet, thereby deriving the porosity within the pellet. This may be measured by various techniques known in the art, such as helium pycnometry to measure the porosity of a porous body, or mercury porosimetry to measure true and immersed density, or helium pycnometry to measure the envelope density. Various embodiments may provide a method of refining iron bearing material that may produce iron ore pellets (IOP) having a selected soluble silica content range, where the specified range of soluble silica content is SiO2 wt% relative to Fe weight percent (wt%), e.g., 0<0.01x<0.85, 0<0.01x<0.65, 0<0.01x<0.33, 0<0.01x<0.16, 0<0.01x<0.11, etc. Various embodiments may provide a method of refining iron bearing material that may produce iron ore pellets (IOP) having a selected intrapellet open porosity range, e.g., 20-50 volume percent (vol%), 25-45 vol%, 29-42 vol%, less than 50 vol%, greater than 20 vol%, etc. Various embodiments may provide a method of refining iron-containing material that may produce iron ore pellets (IOPs) having a selected total iron content, such as greater than 62%, greater than 65%, greater than 67%, etc.

[0051] Various embodiments may provide methods for purifying iron-bearing materials that may produce DRI (or similar sponge iron) with a selected range of soluble silica content. Numerous other measurements may be collected in connection with the processing, transportation, and reduction of DRI in various reduction techniques. The DRI material properties shown here are merely examples of properties that may be important to the performance of secondary storage systems. DRI may also be designed to allow for proper downstream processing or incorporation into batteries. Strength, other impurity levels, etc. may all be relevant to successful processing and incorporation into batteries, but are also specific to the details of the processing performed. Open porosity within DRI pellets is specifically open porosity. Open porosity may be measured by measuring the envelope density of the DRI pellets and the skeletal density of the DRI pellets, and then deriving the porosity within the pellets from the DRI. This may be measured by various techniques known in the art, such as helium pycnometry to measure porosity of porous bodies, or mercury porosimetry to measure true and immersed density, or helium pycnometry to measure envelope density. Various embodiments may provide a method of purifying iron-containing material that may produce DRI (or similar sponge iron), e.g., DRI pellets, having a selected soluble silica content range, where the specified range of soluble silica content is SiO2 wt% relative to Fe weight percent (wt%), e.g., 0<0.01x<0.85, 0<0.01x<0.65, 0<0.01x<0.33, 0<0.01x<0.16, 0<0.01x<0.11, etc. Various embodiments may provide methods of refining iron-containing materials that may produce DRI (or similar sponge iron), e.g., DRI pellets, having a selected intra-pellet open porosity range, e.g., 50-75 volume percent (vol%), 55-72 vol%, 57-67 vol%, less than 75 vol%, greater than 50 vol%, etc. Various embodiments may provide methods of refining iron-containing materials that may produce DRI (or similar sponge iron), e.g., DRI pellets, having a selected total iron content, e.g., greater than 85%, greater than 90%, greater than 92%, etc.

[0052] Various embodiments may provide a method of refining iron-bearing materials that may produce high purity iron ore fines or iron ore pellet (IOP) fragments (e.g., less than 6 mm) with a selected soluble silica content range. For some iron ores, the intra-ore porosity does not need to be high or specified. Due to the mineralogy of the ore, the ore can be reduced to a highly metallized state and has a large amount of measurable porosity before the reduction process. The intra-pellet open porosity of the IOP fragment is specifically open porosity. The open porosity may be measured by measuring the envelope density of the IOP fragment and the skeletal density of the IOP fragment, thereby deriving the porosity within the IOP fragment. This may be measured by various techniques known in the art, such as helium pycnometry to measure the porosity of a porous body, or mercury porosimetry to measure true and immersed density, or helium pycnometry to measure envelope density. Various embodiments may provide a method of purifying iron-bearing material that may produce high purity iron ore fines or iron ore pellet (IOP) fractions (e.g., less than 6 mm) having a selected soluble silica content range, where the specified range of soluble silica content is SiO2 wt% relative to Fe weight percent (wt%), e.g., 0<0.01x<0.85, 0<0.01x<0.65, 0<0.01x<0.33, 0<0.01x<0.16, 0<0.01x<0.11, etc. Various embodiments may provide a method of purifying iron-bearing material that may produce high purity iron ore fines or iron ore pellet (IOP) fractions (e.g., less than 6 mm) having a selected intrapellet open porosity range, e.g., 20-50 volume percent (vol%), 24-45 vol%, 29-42 vol%, less than 50 vol%, greater than 20 vol%, etc. Various embodiments may provide a method of refining iron-containing material that may produce high purity iron ore fines or iron ore pellet (IOP) fractions (e.g., less than 6 mm) having a selected total iron content, such as greater than 62%, greater than 65%, greater than 67%, etc.

[0053] Various embodiments may provide a method of purifying an iron-containing material that may produce a material processed into an electrode for use in an electrochemical system having a selected soluble silica content range. The geometric density of the active material-containing region of the electrode may be defined as the mass of the electrode active material relative to the volume occupied by the electrode active material, including the porosity within and between the active material particles. The geometric density of the electrode does not include the weight and volume of the current collector or other parts of the electrode design that do not contain active material. Various embodiments may provide a method of purifying an iron-containing material that may produce a material processed into an electrode for use in an electrochemical system having a selected soluble silica content range, where the specified range of soluble silica content is SiO2 wt% relative to Fe weight percent (wt%), e.g., 0<0.01x<0.85, 0<0.01x<0.65, 0<0.01x<0.33, 0<0.01x<0.16, 0<0.01x<0.11, etc. Various embodiments may provide methods of purifying iron-containing materials that may produce materials that are processed into electrodes for use in electrochemical systems, where the active area of ​​the electrode region has a selected geometric density, e.g., 1.2-4 grams per cubic centimeter (g / cc), 1.5-4 g / cc, 1.8-2.6 g / cc, 1.9-2.5 g / cc, less than 4 g / cc, greater than 1.2 g / cc, etc. Various embodiments may provide methods of purifying iron-containing materials that may produce materials that are processed into electrodes for use in electrochemical systems, where the active area of ​​the electrode region has a selected geometric density, e.g., greater than 85%, greater than 90%, greater than 92%, etc., of the iron-based active material.

[0054] Various embodiments for purifying iron-bearing materials may include a leaching process. A leaching process may be considered any process in which 1) a material is exposed to a leaching solution, and 2) a component of the material exposed to the leaching solution is partially or completely dissolved in the leaching solution. In the context of this disclosure, etching and leaching may be considered synonymous. In other words, instances in this disclosure of the terms "etching" or "etching" in relation to a process may be considered synonymous with the terms "leaching" or "leaching" in relation to that process, and such processes should be understood as "leaching processes" as defined in this paragraph.

[0055] Various embodiments for purifying iron-bearing materials may include an alkaline leaching process. Various embodiments include a method of purifying an iron-bearing material that includes leaching one or more soluble species of impurities from the iron-bearing material using a leach solution that includes fluorine.

[0056] Various embodiments may include one or more processes for leaching soluble species from the iron-based material. Various embodiments may include alkaline leaching techniques for dissolving impurities from the iron-containing material. Dissolution-based processes are attractive because they can purify the iron-containing material to very low levels of impurities.

[0057] In some alkaline leaching processes, concentrated base (e.g., NaOH and / or KOH) may be used to leach base-soluble species from the iron-containing material. Higher base concentrations are known to accelerate the leaching rate of silica and alumina. Concentrations of 0.1 to 10 M may be industrially relevant leach solutions. In various embodiments, the fluorine-containing components of the leach solution may have a molar concentration of about 100 parts per million (ppm) or greater than 100 ppm, such as about 100 ppm, 100 to 10,000 ppm, about 100 to 500 ppm, about 500 ppm, 100 ppm to 5,000 ppm, about 500 ppm to 5,000 ppm, greater than 500 ppm, 500 to 5,000 ppm, about 5,000 ppm, greater than 5,000 ppm, about 5,000 ppm to 10,000 ppm, about 10,000 ppm, etc. In various embodiments, the fluorine-containing component of the leach solution has a molar concentration of 500-5000 ppm.

[0058] In some processes, the leach solution is washed and re-concentrated to recover the expensive leaching chemicals in the leach solution. In such processes, the concentration of the leach solution may be selected so that the concentration of the re-concentrated leach solution is close to or identical to that of the leach tank, so that leaching proceeds in a closed loop with little to no need to refresh the solution composition.

[0059] In general, the leach solution can be more effectively utilized in the leaching process if primary leach impurities are removed from the leach solution so that the leach solution is not saturated with dissolved impurities. In some leaching processes, impurity removal chemicals may be added to the leach solution to prevent the solution from becoming saturated. Two of the primary impurities targeted for removal from iron-bearing materials are silica and alumina. Dissolved silica and alumina can be effectively removed from the alkaline solution by related chemicals such as calcium hydroxide or calcium oxide (which can convert to calcium oxide on hydration). Thus, in some leaching processes, the leach solution may come into contact with calcium hydroxide-containing materials, and the silica and alumina do not saturate the solution. In some leaching processes, calcium hydroxide-containing materials (or related precursors) can be continuously added and removed to carry out a continuous leaching process without saturating the bath.

[0060] In some leaching processes, the bath may be heated to accelerate the dissolution of silica and alumina so that the material leaches in a time scale that is practically reasonable and cost-effective. The required bath temperature is related to the microscopic structure of the ore and the phases of the silica- and alumina-bearing impurities, but generally temperatures between 30°C and the boiling point of the leach solution are preferred.

[0061] In some leaching processes, removal of dissolved impurities may be more efficient at a temperature different from the temperature optimal for leaching the impurities from the iron-bearing material. In these circumstances, different processes may occur at separate temperatures. For example, silicate-based species may dissolve in alkaline solution at high temperatures and precipitate out of solution via calcium hydroxide or magnesium hydroxide materials at low temperatures.

[0062] The solubility and dissolution rate of silica-based species in alkali is strongly related to the silica phase. In some leaching processes, the iron-containing material may be selected such that the silica-based species is the fast dissolving species. In some embodiments, iron ores or other sources containing fast dissolving species may be used to facilitate processing and reduce costs. For example, fast dissolving species such as amorphous silica and / or tridymite / cristobalite may be preferred over the slowest dissolving quartz phase.

[0063] When metallized iron-containing materials are used in the purification process, there is a possibility that the metallic iron will be oxidized during the etching process. This is generally undesirable, so corrosion inhibitors may be introduced into the feed material and / or leach solution to retard the oxidation of the iron while impurity removal is taking place. In one aspect, sulfides or silicates may be introduced into the solution to retard the corrosion of metal ions. In some embodiments, corrosion inhibitors used in the ferrous metallurgy field to inhibit water corrosion may be used to retard the corrosion of metallic iron. Examples of corrosion inhibitors that may be introduced into the feed material and / or leach solution in various embodiments may be selected from the following non-limiting set: sodium thiosulfate, sodium thiocyanate, polyethylene glycol (PEG) 1000, trimethylsulfoxonium iodide, zincate (by dissolving ZnO in NaOH), hexanethiol, decanethiol, sodium chloride, sodium permanganate, lead (IV) oxide, lead (II) oxide, magnesium oxide, sodium chlorate, sodium nitrate, sodium acetate, iron phosphate, phosphoric acid, sodium phosphate, ammonium sulfate, sodium phosphate, sodium sulfate ... ammonium, ammonium thiosulfate, lithopone, magnesium sulfate, iron(III) acetylacetonate, hydroquinone monomethyl ether, sodium metavanadate, sodium chromate, glutaric acid, dimethyl phthalate, methyl methacrylate, methylpentynol, adipic acid, allyl urea, citric acid, thiomalic acid, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, propylene glycol, trimethoxysilylpropyl diethylene, aminopropyl trimethoxysilane, dimethyl acetylene dicarboxylate (DMAD), 1,3-diethylthiourea, N,N'-Diethylthiourea, Aminomethylpropanol, Methylbutynol, Amino-modified organosilanes, Succinic acid, Isopropanolamine, Phenoxyethanol, Dipropylene glycol, Benzoic acid, N-(2-aminoethyl)-3-aminopropyl, Behenamide, 2-phosphonobutanetricarboxylic acid), MIPA borate, 3-methacryloxypropyltrimethoxysilane, 2-ethylhexanoic acid, Isobutyl alcohol, t-butylaminoethyl methacrylate, Diisopropanolamine, Propylene glycol n-propyl ether, Sodium benzotriazole, Aminotrimethylene Pentasodium phosphonate, sodium cocoyl sarcosinate, pyridinium lauryl chloride, steartrimonium chloride, stearalkonium chloride, calcium montanate, quaternium-18 chloride, sodium hexametaphosphate, dicyclohexylamine nitrite, lead stearate, calcium dinonylnaphthalene sulfonate, iron(II) sulfide, sodium hydrogen sulfide, iron pyrite, sodium nitrite, complex alkyl phosphate esters (e.g., RHODAFAC® RA600 emulsifier), 4-mercaptobenzoic acid, ethylenediaminetetraacetic acid, ethylenediaminetetraacetate (EDTA), 1,3-Propylenediaminetetraacetate (PDTA), nitrilotriacetate (NTA), ethylenediamine disuccinate (EDDS), diethylenetriaminepentaacetate (DTPA), and other aminopolycarboxylates (APC), diethylenetriaminepentaacetic acid, 2-methylbenzenethiol, 1-octanethiol, manganese dioxide, manganese(III) oxide, manganese(II) oxide, manganese oxyhydroxide, manganese(II) hydroxide, manganese(III) hydroxide, bismuth sulfide, bismuth oxide, antimony sulfide (III), antimony(III) oxide, antimony(V) oxide, bismuth selenide, antimony selenide, selenium sulfide, selenium(IV) oxide, propargyl alcohol, 5-hexyn-1-ol, 1-hexyn-3-ol, N-allylthiourea, thiourea, 4-methylcatechol, trans-cinnamaldehyde, iron(III) sulfide, calcium nitrate, hydroxylamine, benzotriazole, furfurylamine, quinoline, tin(II) chloride, ascorbic acid, 8-hydroxyquinoline, pyrogallol, tetraethyl aluminate, ammonium, calcium carbonate, magnesium carbonate, antimony dialkyldithiophosphate, potassium stannate, sodium stannate, tannic acid, gelatin, saponin, agar, 8-hydroxyquinoline, bismuth stannate, potassium gluconate, lithium molybdenum oxide, potassium molybdenum oxide, hydrogenated light oils, heavy naphthenic petroleum fractions (e.g., sold as Rustlick® 631), antimony sulfate, antimony acetate, bismuth acetate, hydrotreated heavy naphtha (e.g., sold as WD-40®). , tetramethylammonium hydroxide, NaSb tartrate, urea, D-glucose, C6Na2O6, potassium antimony tartrate, hydrazine sulfate, silica gel, triethylamine, potassium antimonate trihydrate, sodium hydroxide, 1,3-di-o-tolyl-2-thiourea, 1,2-diethyl-2-thiourea, 1,2-diisopropyl-2-thiourea, N-phenylthiourea, N,N'-diphenylthiourea, sodium antimony L-tartrate, rhodizonic acid disodium salt, sodium selenide, potassium sulfide, and combinations thereof.

[0064] In various embodiments, concentrates of different origins, such as fluxes, can be added to the iron-bearing material to modify the phases of impurities, such as silica, alumina, and silica and alumina, to make the impurities (e.g., silica, alumina, calcia, magnesia, and / or manganese oxide) soluble, insoluble, or easily mechanically separable. As an example, during the blending stage of the pelletizing process, concentrates of different origins, such as fluxes, can be added to modify the phases of silica, alumina, calcia, magnesia, and / or manganese oxide to make the silica, alumina, calcia, magnesia, and / or manganese oxide soluble, insoluble, or easily mechanically separable. As a specific example, dolomitic lime (MgO-CaO) can be added to the concentrate during consolidation, and silica can be combined with dolomitic lime to form a SiO2-MgO-CaO phase, which can be amorphous. In another example, alumina (e.g., bauxite or other mineral forms of alumina) may be added in combination with CaO or MgO to produce a low melting amorphous SiO2-Al2O3-(CaO or MgO) phase.

[0065] Various embodiments for refining iron-containing materials may include an acid leaching process.

[0066] Various embodiments may include one or more materials and / or processes for leaching soluble species from iron-based materials. Various embodiments may include acid leaching techniques for dissolving impurities from iron-containing materials.

[0067] Silica can be dissolved in acids, such as hydrofluoric acid (HF). However, the first problem is that it may be difficult to reproduce the silica dissolution rate using HF. The second problem is that iron oxide is unstable in acidic environments and may dissolve in acidic solutions to form soluble Fe-containing ionic species such as Fe2+.

[0068] In a first embodiment, a first etch rate of iron oxide is adjusted to be much slower than a second etch rate of an impurity (silica) that is desired to be dissolved or otherwise removed from the iron-containing material. In a further example of the first embodiment, in an etchant comprising HF, the first etch rate of iron oxide is very slow and the second etch rate of silica is fast.

[0069] In a second embodiment, the iron-containing material is immersed in a buffered hydrofluoric acid solution. A first example of the buffered hydrofluoric acid solution includes ammonium bifluoride (NH4HF2). A second example of the buffered hydrofluoric acid solution includes potassium bifluoride (KHF2).

[0070] In a third embodiment, the iron-containing material is immersed in an acid mixture, which may include HF, hydrochloric acid, sulfuric acid, and nitric acid.

[0071] Various embodiments for purifying iron-containing materials may include leaching soluble species from iron-based materials, for example, by silica dissolution with ammonium bifluoride (NH4HF2). For example, ammonium bifluoride (NH4HF2) may be used to dissolve silica-based impurities in iron-containing materials, and more specifically, silica may be exposed to ammonium fluoride or a mixture of ammonium fluoride and ammonium bifluoride in an aqueous medium to produce ammonium silicofluoride. The ammonium silicofluoride may then be precipitated to produce precipitated silica, potentially allowing recycling of the ammonium bifluoride etchant, thereby allowing for a closed-loop etching process by dissolving and precipitating silica. In addition to ammonium bifluoride and hydrogen fluoride, other etchants may be used to remove silica from iron-containing materials in various embodiments. For example, such etchants contain fluorine F. Some such etchants are described in Konstantinos D. Demadis et al. 2012, Additive-Driven Dissolution Enhancement of Colloidal Silica. 3. Fluorine-Containing Additives (referred to herein as Demadis et al.), and Ehrlich et al. 2010 Modern Views on Desilicification: Biosilica and Abiotic Silica Dissolution in Natural and Artificial Environments, both of which are incorporated herein in their entirety as part of this disclosure for all purposes, and which describe various etchants that may be exemplary of etchants used in various embodiments to dissolve silica-based impurities in iron-containing materials. Of particular interest are etchants that provide solubility and high etch rates with minimal safety risks, and have high selectivity for etching silica, alumina, calcia, magnesia, and / or manganese oxides relative to iron. One such etchant is sodium fluorophosphate Na2PO3F.

[0072] Various embodiments for purifying iron-containing materials may include methods for controlling the reaction of the iron-containing material with the etching solution by controlling the pH to reduce or minimize corrosion. In some embodiments, the pH of the etching solution may be usefully manipulated so that the iron-containing material is stable or corrodes very slowly in the solution. This applies when the etching solution can achieve a high etching rate in a pH range where corrosion of the iron-containing material is minimal. In general, iron corrosion may be minimized in a mild to moderate alkaline environment with a pH of 8 to 13. (See, e.g., FIG. 2A, which reproduces a figure from Marcel Pourbaix's Atlas of Electrochemical Equilibria.) One example of an etching solution that exhibits high etching activity at the above pH is Na2PO3F. FIG. 2B reproduces data from Demadis et al., showing high dissolution of silica in aqueous solutions at pH 7 and 9. In general, there are many such buffered etching solutions containing fluorine, any of which may be used in various embodiments, and the pH of the solution may be adjusted to co-optimize iron reactivity and silica dissolution rate.

[0073] Various embodiments for purifying iron-containing materials may include methods to control the reaction of the iron-containing material with the etching solution by controlling the chemistry of the etching solution to suppress or eliminate corrosion. In some embodiments, the solubility of silica (and associated etch rate) is strongly related to pH. In many cases, etching solutions have higher solubility for silica and faster etching rates at pHs farther away from neutral. In the case of HF and ammonium bifluoride etches, for example, the silica etchant is most effective at a more acidic pH. This is illustrated in the data shown in FIG. 3, which reproduces data from Demadis et al. Normally, etching in acid is at odds with keeping the iron-containing material in the solid state, since iron and many of the iron compounds are known to dissolve in acid solutions. To suppress or eliminate this risk, soluble iron ions may be added to the etching solution. The presence of such ions will reduce the driving force for dissolving iron into solution. In some embodiments, it may be useful to dissolve iron to its solubility limit in the etching solution, so that the driving force for iron dissolution is completely eliminated.

[0074] In some embodiments, the dissolved iron ions may be provided by dissolution of a portion of the iron-containing material. Recycling the etching solution in a closed loop may maximize the amount of iron-containing material that is retained throughout the etching process.

[0075] In some embodiments, dissolved iron ions may be provided by adding a suitable soluble iron salt to the etching solution, such as FeSO4: ferrous sulfate; iron(II) sulfate, FeCl2: ferrous chloride; iron(II) chloride, Fe(NO3)3: ferric nitrate; iron(III) nitrate, Fe(SO4)3: ferric sulfate; iron(III) sulfate, FeCl3: ferric chloride; and / or iron(III) chloride.

[0076] Various embodiments for purifying iron-containing materials may include ammonium bifluoride (NH4HF2) etching.

[0077] Various embodiments may include one or more materials and / or processes for leaching soluble species from iron-based materials. Various embodiments may include ammonium bifluoride (NH4HF2) silica dissolution techniques for dissolving impurities from iron-containing materials.

[0078] Ammonium bifluoride may be used to dissolve silica-based impurities in iron-bearing materials, and more specifically, silica may be exposed to ammonium fluoride or a mixture of ammonium fluoride and ammonium bifluoride in an aqueous medium to produce ammonium silicofluoride, which may then be precipitated to produce precipitated silica, potentially allowing recycling of the ammonium bifluoride etchant, thereby enabling a closed-loop etching process by dissolving and precipitating silica.

[0079] Ammonium fluoride (NH4F) or ammonium bifluoride (NH4HF2) or ammonium bifluoride (3NH4·HF2), or mixtures, solutions, and derivatives thereof, hereafter collectively referred to as AF, can be used to selectively dissolve silicates from iron-bearing ores and minerals, iron, and partially processed intermediates thereof. Without being bound to a particular scientific interpretation, the inventors believe that AF can dissolve or partially dissolve solid siliceous compounds. Compared to other chemical reagents that can dissolve silicates in targeted iron-bearing materials, such as hydrofluoric acid (HF), alkali metal hydroxides (NaOH, KOH, etc.), and high-temperature melts (e.g., molten chlorides or fluorides or oxides), AF has the advantages of being less toxic and safer than HF, and more reactive at lower temperatures and concentrations than alkali metal hydroxides or high-temperature melts.

[0080] As referred to herein, AF may include a solid compound or a mixture of solid compounds, a molten or partially molten form of said solid compound, or AF dissolved in a liquid, said liquid including water, a polar solvent, a non-polar solvent, or a mixture of said solvents. The dissolved concentration of AF in the liquid solvent may range from a lower limit of 0.001M to an upper limit of 20M, preferably in the range of 0.01M to 10M, and even more preferably in the range of 0.01M to 5M.

[0081] In some embodiments, the AF used to process the iron-containing material is used once and discarded, or refurbished or recycled after use. However, in preferred embodiments, a closed-loop process is used in which the AF is regenerated and reused, reducing or eliminating the need to supply additional AF to process new materials. An example of such a closed-loop process is provided here. The process may be carried out in a batch mode or as a continuous process.

[0082] Considering the use of NHF as AF, a multi-stage reactor may have a first stage in which silica is dissolved. Without being bound to a particular scientific interpretation, the dissolution reaction is, for example, a reaction that produces ammonia according to the following reaction: SiO2+6NH4F→(NH4)2SiF6+2H2O+4NH3 (1)

[0083] Such reactions may be carried out at temperatures ranging from about 25° C. to about 110° C. In order to facilitate the forward reaction, it is necessary to reduce the activity of the ammonia reaction product. This may be accomplished by separating the ammonia from the water by known methods, for example by distillation taking advantage of the high vapor pressure of ammonia.

[0084] In the second stage of the reactor, reaction (1) is reversed by increasing the activity of ammonia. A stoichiometric ratio of ammonia to ammonium silicofluoride greater than 4:1 is desirable. This results in reprecipitation of SiO2 and the production of NHF. The solid precipitated SiO2 is then separated from the liquid, for example by filtration or centrifugation, and can be discarded or beneficially used in another application.

[0085] Another possible reaction in which a similar reaction scheme can be used is SiO2+6NH4F→H2SiF6+2H2O+6NH3 (2) It is.

[0086] As another example, consider the use of ammonium bifluoride NH4HF2 in a similar scheme. Ammonium bifluoride can dissolve silica via the following reaction: SiO2+4NH4HF2→(NH4)2SiF6+2NH4F+2H2O (3) or SiO2+4NH4HF2→SiF4+4NH4F+2H2O (4) or SiO2+3NH4HF2→H2SiF6+3NH3+2H2O (5)

[0087] In reaction 5, SiO2 can be dissolved and then precipitated, and thereby removed, from iron-bearing materials, using a reaction scheme similar to that described above with ammonium fluoride.

[0088] The embodiments of the present invention include the above-mentioned method for dissolving and reprecipitating silicates from the iron-bearing material. The present invention also includes a multi-stage reactor for carrying out the dissolution reaction and removing and capturing the product of the dissolution reaction to feed it to a subsequent stage precipitation reactor. The present invention also includes a system for carrying out such a process, which includes a source of iron-bearing material and a source of AF, a reactor or reactors for carrying out the dissolution and reprecipitation process, and a subsystem for separating the treated solid siliceous material from the liquid and optionally drying the solid, and optionally delivering the treated iron to a manufacturing operation of various products using the iron-bearing material, including but not limited to iron, steel, and electrochemical batteries. Such a system may be run in whole or in part using renewable energy, such as a power source with low embodied carbon.

[0089] The siliceous material present in the iron-bearing material (also called "gangue") may not be pure silica, but may contain other components soluble in acid or base, along with silica, which is soluble when reacted with AF. One example is calcium silicate, where the calcium component is soluble in acid (e.g., HCl or HNO3 or H2SO4), and silica is soluble in AF. In general, leaching or dissolving one phase promotes the leaching or dissolution of the other phase. Thus, an acidic solution, also containing AF, may be used to leach or react said calcium silicate at the same time. Optionally, if there is a phase that is preferentially leached by one of the reactants, a sequential process may be used. For example, in the calcium silicate example, the iron is first reacted with acid to dissolve or partially dissolve the calcium component, and then reacted with AF to dissolve or partially dissolve the silica component. Alternatively, the order of operations may be reversed.

[0090] According to some embodiments, any of the chemical dissolution reactions described herein may be supplemented with mechanical energy, for example, by grinding or milling. As an example, iron ore material undergoing leaching with an AF solution or acid may be simultaneously ground using, for example, ball milling or attritor milling to increase the efficiency or rate of the chemical reactions.

[0091] Various embodiments may include one or more materials and / or processes for leaching soluble species from iron-based materials. Various embodiments may include removal of silica dissolution and / or other impurities from iron-bearing materials using chemical reagent techniques other than AF to dissolve impurities from the iron-bearing material, for example, silica dissolution using hydrofluoric acid (HF), alkali metal hydroxides (including NaOH and KOH), and / or high temperature melts (e.g., molten chlorides or fluorides or oxides).

[0092] Various embodiments for refining iron-containing materials may include the use of fluxes such as NABO2, LiBO2, Li2B2O7, and the like.

[0093] Various embodiments may include one or more materials and / or processes for leaching soluble species from the iron-based material. Various embodiments may include silica dissolution by addition of a fluxing agent (e.g., a glass fluxing agent). One example of a fluxing agent is a metabolic salt.

[0094] In a first embodiment, a flux is added to an iron material, the iron material including silica. The silica in the iron material forms a fluxed silica material. In the first embodiment, the fused silica material is heated to the melting point (liquid phase) of the fused silica material, which is lower than the melting point of iron. The fused silica material can then be separated from the iron material.

[0095] In one embodiment, the fused silica is separated from the iron-rich containing material by preferentially wicking the silica into a porous substrate where the contact angle of the fused silica phase is lower than the iron-containing material. The porous substrate thus acts as a high temperature sponge to absorb the fused silica material. The porous substrate may be a high melting phase of silica.

[0096] In some embodiments, the iron-based ore concentrate may be refined by any of the methods described herein to achieve lower impurity content, focusing on the reduction of silica, calcia, and alumina-containing impurities. The iron-based ore concentrate may then be used directly as an active material in the creation of an electrode, rather than processing the iron ore to form reduced iron species. In this manner, the ore material may be used to manufacture an electrode using methods common in the art for forming electrodes from non-conductive or semi-conductive active materials. In some embodiments, the iron-based ore concentrate may be a magnetite ore concentrate, which may usefully take advantage of the semiconductive properties of magnetite to facilitate electron transport through the battery electrode. In some embodiments, the iron-based ore concentrate may be combined with either a binder and a conductive additive. The binder may be any binder system useful in the manufacture of iron electrodes for use in alkaline environments, such as carboxymethyl cellulose (CMC), polyacrylic acid, and / or Teflon. The conductive additive may be any conductive additive known in the art to enhance electron transport to alkaline battery electrodes, including, but not limited to, carbon black or graphite. The formulation may be comprised of 94% by weight iron ore based concentrate, 3% conductive additive, and 3% binder.

[0097] FIG. 4 is a block diagram illustrating processing operations and devices for processing iron ore into battery components such as electrodes, along with the possibility of silica removal, in accordance with various embodiments of iron ore processing. For example, FIG. 4 may illustrate an example of the example operations discussed with reference to FIG. 1B. FIG. 4 illustrates that iron ore, such as in the form of chunks and / or fines, may be milled, crushed, and / or pulverized, for example, by a ball mill 401. By way of example, water may be added to the ball mill 401 such that a milled iron slurry exits the ball mill 401. The milled iron ore passes through a mixing vessel 402 where various additives, such as binders, clays, and / or water, may be added to the milled iron ore slurry. The milled iron ore and additives combined in the mixing vessel 402 may produce a blended iron concentrate, which may be filtered in one or more filtration units 403. Filtration may remove unwanted materials and / or liquids from the blended iron concentrate. Filtration may produce a cake material. The blended iron concentrate cake material goes through a pelletizing process 404 to produce green pellets, which go through an induration process 405 to form iron ore pellets (IOPs). The IOPs may go through a reduction process 406 and be formed into DRI pellets, which may be crushed and / or pulverized in a crushing / pulverization process 407. The crushed / pulverized DRI may go to a furnace 408 for heating and may go through a hot pressing process 409 to form battery components, such as one or more electrodes.

[0098] In various embodiments, chemical refining processes, such as chemical removal processes of silica, alumina, calcia, magnesia, and / or manganese oxide, may occur during processing of iron ore into DRI and into battery components such as electrodes at process points 421, 422, 423, 424, 425, and / or 426. For example, process point 421 may be chemical silica removal after wet milling of iron ore. For example, process point 422 may be chemical silica removal after blending and addition of binders and / or fluxes to the iron concentrate. For example, process point 423 may be chemical silica removal from IOP. For example, process point 424 may be chemical silica removal from DRI pellets. For example, process point 425 may be chemical silica removal from crushed / pulverized DRI. For example, process point 426 may be chemical silica removal from battery component form factors after assembly of the battery components, such as chemical silica removal from electrodes after assembly of the electrodes.

[0099] Figures 5-11 show examples of processes for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from iron-containing materials according to various embodiments. As an example, the processes shown in Figures 5-11 may be implemented as part of processing operations and devices for processing iron ore into battery components such as the electrodes shown in Figure 4.

[0100] 5 shows an example of an operation according to various embodiments in which one or more etching / leaching agents 501 for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from the iron-bearing material may be introduced into the concentrate mixing vessel 402. For example, an acid may be introduced into the vessel 402. The introduction of one or more etching / leaching agents 501 into the mixing vessel 402 may represent the simplest process modification for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from the iron-bearing material.

[0101] Figure 6 shows an example of an operation similar to Figure 5 where a second filtration step 601 is used to rinse the filter cake with a neutralizing agent 602. The second filtration step 601, which includes rinsing with a neutralizing agent 602, may avoid dilution of the recycle stream. The filtration step 601 may produce a rinse recycle stream 604 and an etchant / leachant recycle stream 603.

[0102] In various embodiments, heat may be added to the system to aid in the chemical etching and / or leaching process. For example, heat may be added to the mixing vessel 402, after the mixing vessel 402 (e.g., in a flow reactor), and / or during the filtration process.

[0103] FIG. 7A shows an example of another configuration similar to that of FIG. 6. Specifically, FIG. 7A shows an example of an operation according to various embodiments in which one or more etching / leaching agents 501 for removing impurities such as silica, alumina, calcia, magnesia, and / or manganese oxide from the iron-bearing material may be introduced into the concentrate mixing tank 402, and heat may be added to assist the etching / leaching chemical operation to remove SiO2 without dissolving the Fe species. For example, FIG. 7A shows heat being added upstream of the mixing tank 402 (sometimes referred to as a reaction vessel) by a plug flow reactor 702. The concentrate stream exiting the mixing tank 402 may be heated by a heater 701, and reaction of the etching and / or leaching agent 501 to target SiO2 may occur in the plug flow reactor 702. Heat may be added by the heater 701 into the mixing tank 402, upstream of the plug flow reactor 702 after the mixing tank 402, and / or directly into the plug flow reactor 702. In some embodiments, a dual tube heat exchanger configuration may be used for the plug flow reactor 702, where the concentrate stream exiting the mixing vessel 402 passes through the inner tube and the heating medium passes through the annular section. This configuration may be preferred when the etching and / or leaching agent reactions require short, precise times. The annular section may be divided into various heating and cooling zones. Temperature sensors 703 may be included in the system to monitor the temperature of the concentrate stream in the mixing vessel 402, before entering the plug flow reactor 702, and / or after exiting the plug flow reactor 702.

[0104] FIG. 7B shows an example of another configuration similar to FIG. 7A. In this configuration, the plug flow reactor 702 is replaced with a pseudo-plug flow reactor 750 formed from a series of stirred vessels 751, such as one or more stirred vessels 751, three stirred vessels 751, more than three stirred vessels 751, etc. Each stirred vessel may include an individual heating coil to controllably provide heat to the concentrate stream as it passes through the vessel 751. Although the pseudo-plug flow reactor 750 may have less heating accuracy than the true plug flow reactor 702, the pseudo-plug flow reactor 750 may still allow heat to be added to the concentrate stream to assist in the etching / leaching chemistry that removes the SiO2 without dissolving the Fe species.

[0105] 8 illustrates a rotating drum filter and rinse process 802 that may be incorporated into a filtration operation such as filtration operations 403 and / or 601 described above. The rotating drum filter and rinse device 802 may dilute the etching / leach solution but may not reduce the recycle potential.

[0106] FIG. 9 illustrates a two-stage filtration process 902 that may be incorporated into a filtration operation such as filtration operation 403 and / or 601 described above. As shown in FIG. 9, a neutralizing agent may be added to the rinse step. In this embodiment, a two-stage filtration process is employed. The first filtration 903 removes most of the etching / leaching solution for recycling. The filter cake is then mixed with the neutralized rinse in a mixing tank 905. The second filtration 904 removes the rinse and prepares the concentrate for pelletization. A ceramic disc filter may be one example of a filter that may be used in the first filtration 903 and / or the second filtration 904. A ceramic disc filter may be preferred for this embodiment due to its increased throughput capacity. However, other filter media and / or filter processes may be substituted for the ceramic disc filter in various embodiments.

[0107] In embodiments where the iron is refined into larger formats, the etching and / or leaching solutions may be applied to the iron material using full or partial immersion processes, such as single or multi-stage baths, fixed bed silos, spiral conveyors, and / or other types of processes, at any stage of the production line: IOP, DRI pellets, crushed DRI, or electrode slabs. For example, a bath with an immersion conveyor may be used to expose the iron material to the etching solution. A bath with an immersion conveyor moving at a controllable speed may allow for excellent time precision. As another example, a spiral conveyor through which the iron material passes in the liquid etching solution may be used to expose the iron material to the etching solution. As another example, a fixed bed silo may be used to expose the iron material to the etching solution. In various embodiments, a water rinse may be incorporated into the process to rinse the iron material after the etching solution is removed. In various embodiments, the etching solution, such as the etching solution bath, spiral conveyor liquid, fixed bed silo, etc., may or may not be heated. In various embodiments, the etching and / or leaching solution may be applied to the ferrous material using a full or partial immersion process, such as single or multi-bath, fixed bed silo, spiral conveyor, and / or other type of process, during or after any of the processes 404-409 described with reference to Figure 5. In various embodiments, the etching solution / leach solution may be circulated continuously or intermittently through a full or partial immersion process, such as single or multi-bath, fixed bed silo, spiral conveyor, and / or other type of process, through a regeneration process that may cause etched or leached materials, such as silica, alumina, calcia, magnesia, and / or manganese oxide, to precipitate from the etching solution / leach solution, thereby recharging the etching solution / leach solution.

[0108] 10 shows an example of an etchant batch process, where IOP pellets on a conveyor, for example IOP pellets ranging in size from about 5 mm to about 15 mm, are immersed in the etchant bath by passing through the conveyor and are rinsed with water after exiting the etchant bath. The belt speed of the conveyor can be controlled to ensure precise time of exposure of the IOP pellets to the etchant bath.

[0109] FIG. 11 shows an example of an etchant batch process, where crushed and / or pulverized DRI pellets on a conveyor, for example DRI pellets ranging in size from about 2 mm to about 5 mm, are immersed in the etchant bath by conveyor passage and are rinsed with water after exiting the etchant bath. The DRI pellets may pass through a second neutralizing rinse step separate from the etchant bath. The belt speed of the conveyor may be controlled to ensure precise time of exposure of the DRI pellets to the etchant bath. The etchant bath solution may be continuously cycled out of the bath through a regeneration process that may precipitate silica from the etchant bath solution.

[0110] Stannate can be a performance enhancing additive for iron anodes. In some circumstances, the performance enhancing effect of stannate requires that the stannate be soluble. Stannate concentrations of 1-300 mM are often desirable to enhance the performance of iron anodes in alkaline media.

[0111] Some impurities in the iron electrode active material or other parts of the cell may precipitate stannate, resulting in the stannate reaching a lower solubility than necessary to realize enhanced electrochemical performance. Additionally, or alternatively, precipitation of stannate from a soluble to an insoluble state may result in increased costs for the stannate-containing additive to achieve the same level of performance in the absence of stannate precipitation.

[0112] Various embodiments include several methods for limiting or eliminating precipitation of stannate from the electrolyte.

[0113] In addition to the stannate-specific incentives, these methods have a more generalizable problem to solve. The more general problem is that whenever an impurity is present in an electrochemical cell, the impurity can react with the electrolyte or electrodes, causing deviations in electrochemical performance. Thus, it is generally desirable to control the composition of all components in the cell and ensure that the impurities do not react with the rest of the cell.

[0114] Various embodiments include methods and systems for removing impurities from materials entering an electrochemical cell. Various embodiments include methods and systems for passivating or reacting the impurities so that they cannot interact with the remainder of the cell.

[0115] Stannate may precipitate on materials that form stable compounds in the presence of tin in alkaline solutions. As outlined below, such stable compounds may be used to effectively inhibit stannate loss in some cases. However, other elements may form compounds with tin in the presence of alkaline solutions, permanently reducing the amount of tin in solution. Calcium, magnesium, aluminum, and manganese may all form stable compounds, especially in the presence of stannate. More specifically, CaO, MgO, Al2O3, and Mn-based oxides all react with stannate to produce metal-stannate compounds that have low solubility in alkaline solutions compared to the concentrations required to enhance iron electrode performance.

[0116] In general, it is often useful to remove impurities from the electrode material to prevent detrimental interactions with the electrochemical behavior of the cell. As an example, in some cases it is useful to remove impurities that cause stannate precipitation when iron negative electrodes are used in alkaline solutions.

[0117] In the case of electrode active materials having such impurities, removal of such impurities can be accomplished by dissolving the impurities or treating other materials prior to placing the electrode active material in contact with a stannate-containing solution.

[0118] Various embodiments may include removal of impurities by dissolution.

[0119] Ca and Mg are commonly found as impurities in low-cost ferrous materials, usually in the form of CaO / MgO and / or their hydroxides (Ca(OH)2 and Mg(OH)2). Since CaO and MgO as oxides convert to their hydroxides in aqueous solution, it is the inventor's experience that the oxides (CaO, MgO) may be treated similarly to the hydroxides with regard to dissolution / reaction behavior in aqueous solution.

[0120] CaO and MgO are basic oxides and can be readily dissolved in acid. Thus, the above materials can be removed from solution using acid. When using acid to dissolve these oxides from the iron-containing active material, it may be necessary to buffer the acid solution appropriately so that the CaO and MgO are selectively leached with acid while retaining the majority of the iron-containing active material. Ca(OH)2 also begins to dissolve at highly basic pH (needing about 13 for low solubility and pH 11.5 for high solubility), but requires an acidic component of the etchant to drive dissolution. Similarly, Mg(OH)2 is soluble at pHs below about 11 and highly soluble at pHs below about 8.

[0121] Similar considerations apply to the removal of other impurities that can be dissolved in acid, such as Al2O3 and Mn-based oxides. Thus, the various acid-based embodiments described below for the removal of CaO and MgO and / or their hydroxides (Ca(OH)2 and Mg(OH)2 may apply to the removal of other impurities, such as Al2O3 and Mn-based oxides. Thus, in the various embodiments described below for the removal of impurities CaO and MgO and / or their hydroxides (Ca(OH)2 and Mg(OH)2, other impurities, such as Al2O3 and Mn-based oxides, may be substituted for CaO and MgO and / or their hydroxides (Ca(OH)2 and Mg(OH)2, and the various embodiments may be used to remove such other impurities.

[0122] 12A to 12C are Pourbaix diagrams showing the pH ranges in Ca- and Mg-based aqueous solutions where the solubility of Ca and Mg begins to increase, in comparison with that of iron.

[0123] Various embodiments may include an etching solution to remove impurities such as one or more of CaO and MgO, and / or one or more of its hydroxides (Ca(OH)2 and Mg(OH)2.

[0124] Ideally, a solution for treating iron active materials would have limited reaction with the iron active material being treated, rapid reaction with the impurities being removed, and high solubility of the impurities. Numerous solution configurations are possible depending on the iron active material being treated. As shown in the Pourbaix diagrams of Figures 12A-12C, iron dissolves in low pH solutions (< about 5), and these are generally not preferred solutions for treating iron active materials. However, there are pH ranges where Mg and Ca have high solubility, specifically pH ranges that overlap with about 5-10, where iron is passivated and / or exhibits very low corrosion rates. Those skilled in the art will recognize that the above pH ranges are approximate and are subject to many considerations of other experimental factors.

[0125] While many different acids can be used to remove CaO and MgO from iron electrode materials, there are preferred acid chemistries for carrying out such dissolution processes. Specifically, weak or buffered acid chemistries that result in a pH in the preferred range of 5-10 are desirable. The anions used in the acid should be selected to minimize corrosion of the iron and to be compatible with the electrochemical cell if any minor contamination occurs. For example, if the etch is performed on iron ore concentrate, an acid that can be volatilized in a furnace in subsequent processing (such as nitric acid) is preferred. Hydrochloric acid is generally undesirable since contamination with chloride ions can be detrimental to iron electrode performance, and more generally to electrochemical cell performance. Sulfate ions are often not detrimental to iron electrode performance in small amounts, so sulfuric acid etches may be used on active materials that are etched prior to entering the electrochemical cell. In all cases, after the etching process, the material should be rinsed or otherwise purified to ensure that no other impurities enter the cell. The buffer selected for etching will be related to the target pH range, but a few examples include carbonate / bicarbonate acetic acid, C6H13NO4S, and any of a number of other buffers common in the art.

[0126] Various embodiments may include controlling the amount of molten iron to expand the stability region of the iron.

[0127] The pH range over which the rate of iron etching / corrosion is low is a function of the amount of dissolved iron in solution; the higher the concentration of dissolved iron, the wider the pH range of passivation and the lower the rate of iron corrosion. Therefore, iron ions may be intentionally added to expand the pH range over which iron does not significantly etch, thereby manipulating the dissolution process at low pH to increase the rate of etching of Mg- and Ca-based compounds. The dissolved Fe concentration required for enhanced passivation increases exponentially with a linear decrease in pH.

[0128] Various embodiments may include adding a corrosion inhibitor to reduce the corrosion rate of the iron.

[0129] In many practical situations, impurities may be removed, albeit slowly, from iron in a solution that is nominally iron corrosive. In such situations, corrosion inhibitors may be added to the etching bath to stabilize the iron from corrosion. Additionally or alternatively, the iron material to be treated may be treated with a corrosion inhibitor before it contacts the etching solution. Depending on the solution chemistry, a number of corrosion inhibitors can be used, such as thioureas, sulfides (e.g., sodium sulfide), silicates, or other thiolated organics (e.g., hexanethiol, heptanethiol, octanethiol, etc.).

[0130] Various embodiments may include recycling of the etching solution. In some circumstances, the etching solution may be purified and continuously reused. For example, the etching solution may be exposed to a substance that precipitates the impurities being removed. In some cases, Mg and Ca may be precipitated by bubbling CO2 through the etching solution and exposing them to the carbonate ions formed to form calcium carbonate and magnesium carbonate. In other cases, impurities may be precipitated by exposure to other counterions, such as fluoride or phosphate ions, that render the dissolved impurities less soluble. In other cases, the solution may be passed through any other process known in the art for selective removal of ions, such as reverse osmosis and ion-selective membranes.

[0131] Various embodiments may include passivation of impurities.

[0132] In some cases, impurities may be passivated or reacted so that they cannot further react with the electrolyte, thereby limiting the ability of the impurities to adversely affect the electrochemical properties. In one example, the impurities may be treated with low solubility passivating ions. In the case of calcium and magnesium, fluoride and phosphate ion treatments may be used to form slightly soluble to insoluble, highly stable, low Ksp (solubility product) compounds, thereby preventing these materials from reacting with other components of the electrochemical cell. In some cases, the treatment process may occur before the impurities enter the cell. In other examples, treatment may be performed when the material enters the cell, by having the treatment material in the electrolyte or otherwise incorporating it within the cell.

[0133] In some cases, passivation of the surface of impurity particles can occur through adsorption of species that do not form low Ksp compounds. For example, aluminates or silicates can be added to the solution to form a surface layer of calcium silicate hydrate, magnesium silicate hydrate, forming a passivating film on Ca and Mg. Importantly, not all of the CaO or MgO particles need to react to be effectively passivated.

[0134] Various embodiments may include reacting the impurities, which may result in precipitation with a compound that preferentially reacts with the impurity, such that the stannate is maintained in solution.

[0135] In some circumstances, stannate precipitation may be prevented by having another reaction take place instead of stannate precipitation. This can be accomplished by adding a co-additive along with the stannate so that calcium or magnesium will preferentially react with the co-additive instead of the stannate. Fluoride, phosphate, and carbonate ions can all be used to form stable compounds with Mg and Ca in solution. The material added to preferentially react with Ca may be added at the beginning of the battery cell's life, or may be dosed or otherwise introduced slowly during operation to allow the reaction to occur without the instantaneous concentration of co-additive in the electrolyte being too high.

[0136] Various embodiments may include a method of purifying an iron-bearing material, comprising leaching one or more soluble species of impurities from the iron-bearing material, wherein the leaching comprises leaching using a leach solution comprising fluorine. In various embodiments, the leach solution comprises ammonium fluoride (NH4F) or ammonium bifluoride (3NH4·HF2), or a mixture thereof. In various embodiments, the leach solution comprises ammonium bifluoride (NH4HF2). In various embodiments, the leaching comprises dissolving the impurities using hydrofluoric acid (HF), alkali metal hydroxides (e.g., NaOH and KOH), and / or high temperature melts (e.g., molten chlorides or fluorides or oxides). In various embodiments, the leach solution comprises sodium fluorophosphate (Na2PO3F). In various embodiments, the fluorine-containing component of the leach solution has a molar concentration of 100-10,000 ppm. In various embodiments, the fluorine-containing component of the leach solution has a molar concentration of 500-5,000 ppm. In various embodiments, the iron-containing material is iron ore, iron, and / or intermediates thereof. Various embodiments may further include controlling the pH of the leach solution. In various embodiments, the pH is controlled in the range of 8-13. In various embodiments, the pH is controlled in the range of 7-9. In various embodiments, the pH is controlled in the range of 5-10. Various embodiments may further include adding a soluble iron salt to the leach solution. In various embodiments, the iron salt comprises one or more of ferrous sulfate; ferrous sulfate, ferrous chloride, ferric nitrate, ferric sulfate, and / or ferric chloride. Various embodiments may further include adding iron ions to the leach solution. Various embodiments may further include adding one or more corrosion inhibitors to the leach solution. Various embodiments may further include recycling the leach solution. Various embodiments may include a method of purifying an iron-bearing material, the method comprising leaching one or more soluble species of impurities from the iron-bearing material, the leaching comprising dissolution by addition of a flux. Various embodiments may further include forming an electrode of a battery using the purified iron-bearing material. Various embodiments may further include providing the battery in a bulk energy storage system.In various embodiments, the bulk energy storage system is a long term energy storage (LODES) system. Various embodiments may include a battery and / or bulk energy storage system comprising at least one electrode formed at least in part in accordance with the operations of the methods of this paragraph.

[0137] Various embodiments may include a method of ameliorating the adverse effects of impurities in an iron electrode, comprising passivating impurities in an iron-containing material such that the passivated impurities do not react with the electrolyte of a battery in which the iron-containing material is used. Various embodiments may include a method of ameliorating the adverse effects of impurities in an iron electrode, comprising adding a co-additive to the iron-containing material that preferentially reacts with the impurities in the iron-containing material in place of the stannate added to the iron-containing material. In various embodiments, the impurities include calcium or magnesium. In various embodiments, the co-additive includes fluoride ions, phosphate ions, and / or carbonate ions. In various embodiments, the methods discussed in this paragraph may be practiced in combination with one or more of the methods discussed in the previous paragraph. In various embodiments, the purification of the iron-containing material is carried out at one or more stages in the processing of iron ore to form battery components. In various embodiments, one or more of the above steps may be included before, during, and / or after milling, blending, binder addition, fluxing, filtering, pelletizing, induration, iron ore pellet (IOP) formation, reduction, direct reduced iron (DRI) pellet formation, crushing, pulverizing, heating, hot pressing, and / or forming a battery component. In various embodiments, the battery component is an electrode. In various embodiments, refining includes adding an etching and / or leaching agent to the concentrate mix tank, rinsing the filter cake with a neutralizing agent, heating the concentrate stream with the added etching and / or leaching agent, rotary drum filtering, two-stage filtering, partially immersing the iron material in the etching and / or leaching solution, fully immersing the iron material in the etching and / or leaching solution, and / or regenerating the etching and / or leaching solution. Various embodiments may include using the refined iron-containing material to form a battery electrode. Various embodiments may further include using the refined iron-containing material to form a battery electrode. Various embodiments may further include providing the battery in a bulk energy storage system. In various embodiments, the bulk energy storage system is a long term energy storage (LODES) system.Various embodiments may include a battery and / or bulk energy storage system comprising at least one electrode formed at least in part according to the operations of the methods of this paragraph.

[0138] Various embodiments may include a method of purifying an iron-bearing material, comprising etching and / or leaching one or more soluble species of impurities from the iron-bearing material, the impurities comprising silica, alumina, magnesia, manganese oxide, and / or calcia. In various embodiments, the leaching comprises alkaline leaching. In various embodiments, the leaching comprises acidic leaching. In various embodiments, the leaching comprises dissolution by addition of a fluxing agent. In various embodiments, the leaching comprises dissolving the impurities using ammonium fluoride (NH4F) or ammonium bifluoride (NH4HF2) or ammonium bifluoride (3NH4·HF2), or mixtures, solutions, and derivatives thereof (hereinafter collectively referred to as AF). In various embodiments, the leaching comprises dissolving the impurities using hydrofluoric acid (HF), alkali metal hydroxides (e.g., NaOH and KOH), and / or high temperature melts (e.g., molten chlorides or fluorides or oxides). In various embodiments, the iron-containing material is iron ore, iron, and / or intermediates thereof. In various embodiments, the etching includes an ammonium bifluoride (NH4HF2) etch. In various embodiments, the etching includes an etch with an etchant containing fluorine. In various embodiments, the etching includes an etch with sodium fluorophosphate (Na2PO3F). Various embodiments may further include controlling the pH of the etching solution. In various embodiments, the pH is controlled in the range of 8-13. In various embodiments, the pH is controlled in the range of 7-9. In various embodiments, the pH is controlled in the range of 5-10. Various embodiments may further include adding a soluble iron salt to the etching solution. In various embodiments, the iron salt includes one or more of ferrous sulfate; ferrous sulfate, ferrous chloride, ferric nitrate, ferric sulfate, and / or ferric chloride. Various embodiments may further include adding iron ions to the etching solution. Various embodiments may further include adding one or more corrosion inhibitors to the etching solution.Various embodiments may further include recycling the etching solution.Various embodiments may include a method of purifying an iron-containing material, the method including modifying impurity species in the iron-containing material to benign compounds. In various embodiments, the impurity is silica and the modification includes adding an additive to convert the silica to a silicon compound. In various embodiments, the additive is dolomitic lime. Various embodiments may include a method of purifying an iron-containing material, the method including passivating an impurity in the iron-containing material such that the passivated impurity does not react with the electrolyte of the battery in which the iron-containing material is used. Various embodiments may include a method of purifying an iron-containing material, the method including adding a co-additive to the iron-containing material that preferentially reacts with the impurities in the iron-containing material in place of the stannate added to the iron-containing material. In various embodiments, the impurity includes calcium or magnesium. In various embodiments, the co-additive includes fluoride ions, phosphate ions, and / or carbonate ions. In various embodiments, the purification of the iron-containing material is performed at one or more stages in the processing of iron ore to form a battery component. In various embodiments, one or more of the above steps may be included before, during, and / or after milling, blending, binder addition, fluxing, filtering, pelletizing, induration, iron ore pellet (IOP) formation, reduction, direct reduced iron (DRI) pellet formation, crushing, pulverizing, heating, hot pressing, and / or battery component formation. Various embodiments may further include forming an electrode of a battery using the refined iron-containing material. Various embodiments may further include providing the battery in a bulk energy storage system. In various embodiments, the bulk energy storage system is a long term energy storage (LODES) system. Various embodiments may include a battery and / or bulk energy storage system comprising at least one electrode formed at least in part according to the operations of the method of this paragraph.

[0139] Various embodiments described and illustrated herein may provide devices and / or methods for use in bulk energy storage systems, such as long-term energy storage (LODES) systems, short-term energy storage (SDES) systems, etc. As an example, various embodiments may provide batteries (e.g., battery 200) for bulk energy storage systems, such as batteries for LODES systems. Renewable energy sources are becoming increasingly prevalent and cost-effective. However, many renewable energy sources face intermittency issues that hinder the adoption of renewable energy sources. The impact of the intermittent tendency of renewable energy sources may be mitigated by pairing them with bulk energy storage systems, such as LODES systems, SDES systems, etc. To support the adoption of combined generation, transmission, and storage systems (e.g., renewable generation sources paired with bulk energy storage systems, and power plants with transmission facilities in either the power plant and / or the bulk energy storage system), devices and methods are needed to support the design and operation of such combined generation, transmission, and storage systems, such as the various embodiment devices and methods described herein.

[0140] A combined generation, transmission, and storage system may be a power plant that includes one or more generation sources (e.g., one or more renewable generation sources, one or more non-renewable generation sources, a combination of renewable and non-renewable generation sources, etc.), one or more transmission facilities, and one or more bulk energy storage systems. The transmission facilities in either the power plant and / or the bulk energy storage systems may be co-optimized with the generation and storage systems or may impose constraints on the design and operation of the generation and storage systems. The combined generation, transmission, and storage system may be configured to meet various output targets under various design and operational constraints.

[0141] 13-21 illustrate various exemplary systems in which one or more aspects of various embodiments can be used as part of a bulk energy storage system, such as a LODES system, an SDES system, etc. For example, various embodiments described herein with reference to FIGS. 1A-12C can be used as batteries for a bulk energy storage system, such as a LODES system, an SDES system, etc., and / or various electrodes described herein can be used as components of a bulk energy storage system. As used herein, the term "LODES system" refers to a bulk energy storage system configured to have a rated duration (energy / power ratio) of 24 hours (h) or longer, such as a duration of 24 hours, a duration of 24 hours to 50 hours, a duration of more than 50 hours, a duration of 24 hours to 150 hours, a duration of more than 150 hours, a duration of 24 hours to 200 hours, a duration of more than 200 hours, a duration of 24 hours to 500 hours, a duration of more than 500 hours, etc.

[0142] FIG. 13 illustrates an exemplary system in which one or more aspects of the various embodiments may be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include the batteries of the various embodiments described herein, the various electrodes described herein, and the like. The LODES system 2404 may be electrically connected to a wind farm 2402 and one or more transmission facilities 2406. The wind farm 2402 may be electrically connected to the transmission facility 2406. The transmission facility 2406 may be electrically connected to a power grid 2408. The wind farm 2402 may generate power, and the wind farm 2402 may output the generated power to the LODES system 2404 and / or the transmission facility 2406. The LODES system 2404 may store the power received from the wind farm 2402 and / or the transmission facility 2406. The LODES system 2404 can output the stored power to a transmission facility 2406. The transmission facility 2406 can output power received from one or both of the wind farm 2402 and the LODES system 2404 to a grid 2408 and / or can receive power from the grid 2408 and output the power to the LODES system 2404. The wind farm 2402, the LODES system 2404, and the transmission facility 2406 can together comprise a power plant 2400, which may be a combined power, transmission, and storage system. Power generated by the wind farm 2402 may be fed directly to the grid 2408 via the transmission facility 2406 or may first be stored in the LODES system 2404. In certain cases, the power supplied to the power grid 2408 may be provided entirely from the wind farm 2402, entirely from the LODES system 2404, or from a combination of the wind farm 2402 and the LODES system 2404.The distribution of power from the combined wind farm 2402 and LODES system 2404 power plant 2400 may be controlled according to a predetermined long-term (multi-day or even multi-year) schedule, or may be controlled according to a day-ahead (24-hour notice) market, or may be controlled according to an hour-ahead market, or may be controlled in response to real-time pricing signals.

[0143] As one example of the operation of the power plant 2400, the LODES system 2404 can be used to reshape and "stabilize" the power produced by the wind farm 2402. In one such example, the wind farm 2402 may have a peak power output (capacity) of 260 megawatts (MW) and a capacity factor (CF) of 41%. The LODES system 2404 may have a power rating (capacity) of 106 MW, a rated duration (energy / power ratio) of 150 hours (h), and a rated energy of 15,900 megawatt hours (MWh). In another such example, the wind farm 2402 may have a peak power output (capacity) of 300 MW and a capacity factor (CF) of 41%. The LODES system 2404 may have a power rating (capacity) of 106 MW, a rated duration (energy / power ratio) of 200 hours, and a rated energy of 21,200 MWh. In another such example, the wind farm 2402 may have a peak power output (capacity) of 176 MW and a capacity factor (CF) of 53%. The LODES system 2404 may have a power rating (capacity) of 88 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 13,200 MWh. In another such example, the wind farm 2402 may have a peak power output (capacity) of 277 MW and a capacity factor (CF) of 41%. The LODES system 2404 may have a power rating (capacity) of 97 MW, a rated duration (energy / power ratio) of 50 hours, and a rated energy of 4,850 MWh. In another such example, the wind farm 2402 may have a peak power output (capacity) of 315 MW and a capacity factor (CF) of 41%. The LODES system 2404 may have a power rating (capacity) of 110 MW, a rated duration (energy / power ratio) of 25 hours, and a rated energy of 2,750 MWh.

[0144] FIG. 14 illustrates an exemplary system in which one or more aspects of the various embodiments may be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include the batteries of the various embodiments described herein, the various electrodes described herein, and the like. The system of FIG. 24 may be similar to the system of FIG. 13, except that a photovoltaic (PV) station 2502 may be used instead of the wind power station 2402. The LODES system 2404 may be electrically connected to the PV station 2502 and one or more transmission facilities 2406. The PV station 2502 may be electrically connected to the transmission facility 2406. The transmission facility 2406 may be electrically connected to the power grid 2408. The PV station 2502 may generate power, and the PV station 2502 may output the generated power to the LODES system 2404 and / or the transmission facility 2406. The LODES system 2404 can store power received from the PV station 2502 and / or the transmission facility 2406. The LODES system 2404 can output the stored power to the transmission facility 2406. The transmission facility 2406 can output power received from one or both of the PV station 2502 and the LODES system 2404 to the grid 2408 and / or can receive power from the grid 2408 and output the power to the LODES system 2404. The PV station 2502, the LODES system 2404, and the transmission facility 2406 together can comprise a power plant 2500, which may be a combined power, transmission, and storage system. Power generated by the PV station 2502 may be fed directly to the grid 2408 via the transmission facility 2406 or may first be stored in the LODES system 2404. In certain cases, the power supplied to the power grid 2408 may be provided entirely from the PV stations 2502, entirely from the LODES systems 2404, or from a combination of the PV stations 2502 and the LODES systems 2404.The distribution of power from the combined PV base 2502 and LODES system 2404 power plant 2500 may be controlled according to a predetermined long-term (multi-day or even multi-year) schedule, or according to a day-ahead (24-hour notice) market, or according to an hour-ahead market, or in response to real-time pricing signals.

[0145] As one example of the operation of the power plant 2500, the LODES system 2404 can be used to reshape and "balance" the power produced by the PV station 2502. In one such example, the PV station 2502 may have a peak power output (capacity) of 490 MW and a capacity factor (CF) of 24%. The LODES system 2404 may have a power rating (capacity) of 340 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 51,000 MWh. In another such example, the PV station 2502 may have a peak power output (capacity) of 680 MW and a capacity factor (CF) of 24%. The LODES system 2404 may have a power rating (capacity) of 410 MW, a rated duration (energy / power ratio) of 200 hours, and a rated energy of 82,000 MWh. In another such example, the PV station 2502 may have a peak power output (capacity) of 330 MW and a capacity factor (CF) of 31%. The LODES system 2404 may have a power rating (capacity) of 215 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 32,250 MWh. In another such example, the PV station 2502 may have a peak power output (capacity) of 510 MW and a capacity factor (CF) of 24%. The LODES system 2404 may have a power rating (capacity) of 380 MW, a rated duration (energy / power ratio) of 50 hours, and a rated energy of 19,000 MWh. In another such example, the PV station 2502 may have a peak power output (capacity) of 630 MW and a capacity factor (CF) of 24%. The LODES system 2404 may have a power rating (capacity) of 380 MW, a rated duration (energy / power ratio) of 25 hours, and a rated energy of 9,500 MWh.

[0146] FIG. 15 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include the batteries of the various embodiments described herein, the various electrodes described herein, and the like. The system of FIG. 15 may be similar to the systems of FIG. 13 and FIG. 14, except that the wind farm 2402 and the photovoltaic (PV) farm 2502 may both be power generating devices operating together in a power plant 2600. The PV farm 2502, the wind farm 2402, the LODES system 2404, and the transmission facility 2406 together may comprise a power plant 2600, which may be a combined power generation, transmission, and storage system. Electricity generated by the PV sites 2502 and / or wind farms 2402 may be delivered directly to the grid 2408 via the transmission facility 2406 or may first be stored in the LODES system 2404. In certain cases, the electricity provided to the grid 2408 may be delivered entirely from the PV sites 2502, entirely from the wind farms 2402, entirely from the LODES system 2404, or from a combination of the PV sites 2502, the wind farms 2402, and the LODES system 2404. The delivery of electricity from the combined wind farms 2402, the PV sites 2502, and the LODES system 2404 power plant 2600 may be controlled according to a predetermined long-term (multi-day or even multi-year) schedule, or according to a day-ahead (24-hour notice) market, or according to an hour-ahead market, or in response to real-time pricing signals.

[0147] As one example of the operation of the power plant 2600, the LODES system 2404 may be used to reshape and "stabilize" the power produced by the wind farm 2402 and the PV farm 2502. In one such example, the wind farm 2402 may have a peak power output (capacity) of 126 MW and a capacity factor (CF) of 41%, and the PV farm 2502 may have a peak power output (capacity) of 126 MW and a capacity factor (CF) of 24%. The LODES system 2404 may have a power rating (capacity) of 63 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 9,450 MWh. In another such example, the wind farm 2402 may have a peak power output (capacity) of 170 MW and a capacity factor (CF) of 41%, and the PV farm 2502 may have a peak power output (capacity) of 110 MW and a capacity factor (CF) of 24%. The LODES system 2404 may have a power rating (capacity) of 57 MW, a rated duration (energy / power ratio) of 200 hours, and a rated energy of 11,400 MWh. In another such example, the wind farm 2402 may have a peak power output (capacity) of 105 MW and a capacity factor (CF) of 51%, and the PV farm 2502 may have a peak power output (capacity) of 70 MW and a capacity factor (CF) of 31%. The LODES system 2404 may have a power rating (capacity) of 61 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 9,150 MWh. In another such example, the wind farm 2402 may have a peak power output (capacity) of 135 MW and a capacity factor (CF) of 41%, and the PV farm 2502 may have a peak power output (capacity) of 90 MW and a capacity factor (CF) of 24%. The LODES system 2404 may have a power rating (capacity) of 68 MW, a rated duration (energy / power ratio) of 50 hours, and a rated energy of 3,400 MWh. In another such example, the wind farm 2402 may have a peak power output (capacity) of 144 MW and a capacity factor (CF) of 41%, and the PV farm 2502 may have a peak power output (capacity) of 96 MW and a capacity factor (CF) of 24%.The LODES system 2404 may have a power rating (capacity) of 72 MW, a rated duration (energy / power ratio) of 25 hours, and a rated energy of 1,800 MWh.

[0148] FIG. 16 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include the batteries of the various embodiments described herein, the various electrodes described herein, and the like. The LODES system 2404 may be electrically connected to one or more transmission facilities 2406. In this manner, the LODES system 2404 may operate in a "standalone" manner to arbitrate energy near market prices and / or avoid transmission constraints. The LODES system 2404 may be electrically connected to one or more transmission facilities 2406. The transmission facilities 2406 may be electrically connected to a distribution grid 2408. The LODES system 2404 may store power received from the transmission facilities 2406. The LODES system 2404 may output the stored power to the transmission facilities 2406. The power transmission facility 2406 may output power received from the LODES system 2404 to the power distribution grid 2408 and / or may receive power from the power distribution grid 2408 and output the power to the LODES system 2404.

[0149] The LODES system 2404 and the transmission facility 2406 together can constitute a power generation plant 900. As an example, the power generation plant 900 may be located downstream of the transmission constraints, close to the power consumption. In such an exemplary downstream power generation plant 2700, the LODES system 2404 may have a duration of 24 to 500 hours and may perform full discharges once or multiple times per year to support peak power consumption at times when the transmission capacity is not sufficient to serve customers. In addition, in such an exemplary downstream power generation plant 2700, the LODES system 2404 may perform several shallow discharges (daily or more frequently) to arbitrage the difference between nighttime and daytime electricity prices and reduce the overall cost of electricity service to customers. As a further example, the power generation plant 2700 may be located upstream of the transmission constraints, close to the power generation. In such an exemplary upstream power plant 2700, the LODES system 2404 may have a duration of 24 hours to 500 hours and may fully charge once or multiple times per year to absorb excess generation at times when transmission capacity is insufficient to distribute electricity to customers. In addition, in such an exemplary upstream power plant 2700, the LODES system 2404 may shallowly charge and discharge several times (daily or more frequently) to arbitrage the difference between nighttime and daytime electricity prices and maximize the value of the power generation facility's output.

[0150] FIG. 17 illustrates an exemplary system in which one or more aspects of the various embodiments may be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include the batteries of the various embodiments described herein, the various electrodes described herein, and the like. The LODES system 2404 may be electrically connected to commercial and industrial (C&I) customers 2802, such as data centers, factories, and the like. The LODES system 2404 may be electrically connected to one or more transmission facilities 2406. The transmission facilities 2406 may be electrically connected to a distribution grid 2408. The transmission facilities 2406 may receive power from the distribution grid 2408 and output the power to the LODES system 2404. The LODES system 2404 may store the power received from the transmission facilities 2406. The LODES system 2404 may output the stored power to the C&I customers 2802. In this manner, the LODES system 2404 can operate to reshape the power purchased from the grid 2408 to match the consumption patterns of the C&I customers 2802 .

[0151] The LODES system 2404 and the transmission facility 2406 together may comprise a power generation plant 2800. As an example, the power generation plant 2800 may be located near the power consumption, i.e., near the C&I customers 2802, such as between the power distribution grid 2408 and the C&I customers 2802. In such an example, the LODES system 2404 may have a duration of 24 hours to 500 hours and may purchase power from the market at a time when power is cheaper, thereby charging the LODES system 2404. The LODES system 2404 may then discharge and provide power to the C&I customers 2802 at a time when the market price is higher, thus offsetting the market purchases of the C&I customers 2802. As an alternative configuration, the power generation plant 2800 may be located not between the power distribution grid 2408 and the C&I customers 2802, but between a renewable resource, such as a PV site, a wind farm, etc., and the transmission facility 2406, which may be connected to the renewable resource. In such an alternative example, the LODES system 2404 may have a duration between 24 hours and 500 hours, and the LODES system 2404 may be charged at a time when renewable output may be available. The LODES system 2404 may then discharge to cover some or all of the C&I customers 2802's power needs and provide the C&I customers 2802 with renewable generated electricity.

[0152] FIG. 18 illustrates an exemplary system in which one or more aspects of the various embodiments may be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include the batteries of the various embodiments described herein, the various electrodes described herein, and the like. The LODES system 2404 may be electrically connected to a wind farm 2402 and one or more transmission facilities 2406. The wind farm 2402 may be electrically connected to the transmission facility 2406. The transmission facility 2406 may be electrically connected to a C&I customer 2802. The wind farm 2402 may generate power, and the wind farm 2402 may output the generated power to the LODES system 2404 and / or the transmission facility 2406. The LODES system 2404 may store the power received from the wind farm 2402.

[0153] The LODES system 2404 can output the stored power to the transmission facility 2406. The transmission facility 2406 can output the power received from one or both of the wind farm 2402 and the LODES system 2404 to the C&I customers 2802. The wind farm 2402, the LODES system 2404, and the transmission facility 2406 together can comprise a power plant 2900, which can be a combined generation, transmission, and storage system. The power generated by the wind farm 2402 can be delivered directly to the C&I customers 2802 via the transmission facility 2406, or can be stored in the LODES system 2404 first. In certain cases, the power provided to the C&I customers 2802 can be delivered entirely from the wind farm 2402, entirely from the LODES system 2404, or from a combination of the wind farm 2402 and the LODES system 2404. The LODES system 2404 may be used to reshape electricity generated by the wind farm 2402 to match the consumption patterns of the C&I customers 2802. In one such example, the LODES system 2404 may have a duration of 24 hours to 500 hours and may charge when renewable generation by the wind farm 2402 exceeds the C&I customers 2802 loads. The LODES system 2404 may then discharge when renewable generation by the wind farm 2402 falls below the C&I customers 2802 loads to provide the C&I customers 2802 with a stable renewable profile that offsets some or all of the C&I customers 2802 electricity consumption.

[0154] FIG. 19 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include the batteries of the various embodiments described herein, the various electrodes described herein, and the like. The LODES system 2404 may be part of a power plant 3000 that integrates a large amount of renewable generation into a microgrid, for example, blending the output of renewable generation by the PV site 2502 and the wind power plant 2402 with existing thermal generation by, for example, a thermal power plant 3002 (e.g., a gas plant, a coal plant, a diesel generator set, etc., or a combination of thermal generation methods), where the renewable generation and thermal generation serve the C&I customer 2802 loads when availability is high. A microgrid such as the microgrid composed of the power plant 3000 and the thermal power plant 3002 can provide an availability of 90% or higher. Electricity generated by the PV site 2502 and / or wind farm 2402 may be delivered directly to C&I customers 2802 or may first be stored in the LODES system 2404 .

[0155] In a particular case, the power provided to the C&I customers 2802 may be entirely from the PV sites 2502, entirely from the wind farms 2402, entirely from the LODES systems 2404, entirely from the thermal power plants 3002, or any combination of the PV sites 2502, the wind farms 2402, the LODES systems 2404, and / or the thermal power plants 3002. As an example, the LODES systems 2404 of the power plant 3000 may have a duration of 24 hours to 500 hours. As a specific example, the C&I customers 2802 load may be 100 MW peak, the LODES systems 2404 may have a power rating of 14 MW and a duration of 150 hours, the cost of natural gas may be $6 / million British thermal units (MMBTU), and the renewable occupancy may be 58%. As another specific example, the C&I customer 2802 load may be 100 MW peak, the LODES system 2404 may have a power rating of 25 MW and a duration of 150 hours, the cost of natural gas may be $8 / million British thermal units (MMBTU), and the renewable occupancy may be 65%.

[0156] FIG. 20 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include the batteries of the various embodiments described herein, the various electrodes described herein, and the like. The LODES system 2404 can be used to enhance the nuclear power plant 3102 (or other inflexible power generation facilities such as thermal, biomass, and / or any other type of power plant with a ramp rate of less than 50% of rated power in one hour and a capacity factor of 80% or higher) to add flexibility to the combined output of the power plant 3100 composed of the combined LODES system 2404 and the nuclear power plant 3102. The nuclear power plant 3102 can be operated at a high capacity factor and at its highest efficiency point, and the LODES system 2404 can be charged and discharged to effectively reshape the output of the nuclear power plant 3102 to match customer power consumption and / or market price of electricity. As an example, the LODES system 2404 of the power plant 3100 may have a duration of 24 hours to 500 hours. In one specific example, the nuclear power plant 3102 may have a rated power output of 1,000 MW, and the nuclear power plant 3102 may be forced to operate at minimum stable power generation or even shut down for long periods of time due to a drop in the market price of electricity. The LODES system 2404 can avoid shutting down the facility during market price drops and charge, and then the LODES system 2404 can discharge during market price increases to increase the total power generation.

[0157] FIG. 21 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include the batteries of the various embodiments described herein, the various electrodes described herein, and the like. The LODES system 2404 may operate in conjunction with an SDES system 3202. The LODES system 2404 and the SDES system 3202 together may comprise a power plant 3200. As an example, the LODES system 2404 and the SDES system 3202 may be co-optimized, such that the LODES system 2404 can provide various services including long-term backup and / or bridging over multi-day variations (e.g., multi-day variations in market prices, renewable generation, power consumption, and the like). The SDES system 3202 can provide various services including rapid support services (e.g., voltage control, frequency regulation, etc.) and / or bridging across diurnal variations (e.g., diurnal variations in market prices, renewable generation, power consumption, etc.). The SDES system 3202 may have a duration of less than 10 hours and a round trip efficiency of greater than 80%. The LODES system 2404 may have a duration of 24 hours to 500 hours and a round trip efficiency of greater than 40%. In one such example, the LODES system 2404 may have a duration of 150 hours and can support customer power consumption for up to one week of renewable generation shortage. The LODES system 2404 can also support customer power consumption during a diurnal generation shortage event to enhance the capacity of the SDES system 3202. Additionally, the SDES system 3202 can power customers during a diurnal generation shortage event and provide quality services such as power conditioning and voltage control and frequency regulation.

[0158] The above method descriptions are provided only as illustrative examples and are not intended to require or imply that the steps of the various embodiments must be performed in the order presented. As one skilled in the art would understand, the order of steps in the above embodiments may be performed in any order. Words such as "then," "then," and "next" are not necessarily intended to limit the order of steps, and such words may be used to guide the reader through the method description. Additionally, any reference to a claim element in the singular, for example, using "a," "an," or "said," (the article "a," "an," or "the"), should not be construed as limiting the element to the singular.

[0159] Furthermore, any step of any embodiment described herein can be used in any other embodiment. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the basic principles defined herein can be applied to other embodiments without departing from the scope of the present disclosure. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.

Claims

1. 1. A method for purifying an iron-containing material, comprising: leaching one or more soluble species of impurities from the iron-bearing material; the leaching step comprises leaching with a leach solution comprising fluorine; method.

2. 2. The method of claim 1, wherein the leach solution comprises ammonium fluoride (NH4F) or ammonium bifluoride (3NH4.HF2), or a mixture thereof.

3. The method of claim 1 , wherein the leach solution comprises ammonium bifluoride (NH 4 HF 2).

4. 10. The method of claim 1, wherein the leaching step comprises dissolving impurities using hydrofluoric acid (HF), alkali metal hydroxides (e.g., NaOH and KOH), and / or high temperature melts (e.g., molten chlorides or fluorides or oxides).

5. The method according to any one of claims 1 to 4, wherein the leaching solution comprises sodium fluorophosphate (Na 2 PO 3 F).

6. 10. The method of claim 1, wherein the fluorine-containing component of the leach solution has a molar concentration of 100 to 10,000 ppm.

7. 7. The method of claim 6, wherein the fluorine-containing component of the leach solution has a molar concentration of 500 to 5000 ppm.

8. 10. The method of claim 1, wherein the iron-containing material is iron ore, iron, and / or intermediates thereof.

9. The method of claim 1 further comprising controlling the pH of the leaching solution.

10. 10. The method of claim 9, wherein the pH is controlled in the range of 8 to 13.

11. The method of claim 10, wherein the pH is controlled in the range of 7 to 9.

12. The method of claim 11, wherein the pH is controlled in the range of 5 to 10.

13. 10. The method of claim 1, further comprising adding a soluble iron salt to the leach solution.

14. 14. The method of claim 13, wherein the iron salt comprises one or more of ferrous sulfate, iron (II) sulfate, ferrous chloride, ferric nitrate, ferric sulfate, and / or ferric chloride.

15. 10. The method of claim 1, further comprising adding iron ions to the leach solution.

16. 10. The method of claim 1, further comprising adding one or more corrosion inhibitors to the leach solution.

17. The method of claim 1 further comprising recycling the leach solution.

18. 1. A method for purifying an iron-containing material, comprising: leaching one or more soluble species of impurities from the iron-bearing material; The step of leaching includes dissolution by addition of a flux; method.

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