US20160047054A1

US20160047054A1 - Iron powder production via flow electrolysis

Info

Publication number: US20160047054A1
Application number: US14/826,403
Authority: US
Inventors: Yan Wang; Qiang Wang
Original assignee: Worcester Polytechnic Institute
Current assignee: Worcester Polytechnic Institute
Priority date: 2014-08-15
Filing date: 2015-08-14
Publication date: 2016-02-18
Also published as: WO2016025793A1

Abstract

The iron and steel industry has a history of environmental consciousness, and efforts are continually made to reduce energy consumption and CO₂emissions. However, the carbothermic process has approached limits on the further reduction of greenhouse gas emissions, and only marginal improvements can be expected. Low temperature electrolysis using a dispersion medium to efficiently distribute charge throughout a colloid mixture including iron oxide provides an environmentally friendly method for performing an electrochemical reduction of Fe₂O₃to produce granular Fe. An electrical-ionic conductive colloidal electrode containing the electrochemically active species (Fe₂O₃particles), the liquid electrolyte (NaOH solution), and a percolating electrical conductor (carbon network) is utilized to produce Fe. The resulting simultaneous percolation of electrons and ions effectively increases the area of the current collector, and enables the process to function at higher currents and rate of charge transfer than static electrolysis.

Description

RELATED APPLICATIONS

This patent application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent App. No. 62/037,723, filed Aug. 15, 2014, entitled “ELECTROLYSIS BASED STEEL FABRICATION,” incorporated by reference in entirety.

BACKGROUND

Iron (Fe) is the most widely used metal, and currently nearly all crude Fe is produced by reducing Fe ores with coke in a blast furnace at a temperature of 2000 degrees Celsius. This carbothermic reduction process directly produces liquid metal, however it generates two metric tons of CO2 per metric ton of crude Fe produced. In addition to carbon emissions from the blast furnace, the iron and steel industry contributes greenhouse gas (GHG) in several ways, including coke production emissions, the use of carbonate flux during calcination, and emissions from the carbon electrodes in electric arc furnaces.

SUMMARY

Configurations herein are based, in part, on the observation that iron production produced by conventional carbothermic processes (Fe₂O₃+C=Fe+CO₂) using high temperature blast furnaces for heating required to generate the desired reaction. Unfortunately, conventional approaches suffer from the shortcoming that the carbothermic approach generates large quantities of carbon dioxide and other so-called “greenhouse gases” that are environmentally detrimental. Accordingly, configurations herein substantially overcome the above described shortcomings by providing a low temperature electrolysis (LTE) approach that generates iron powder from an electrochemical reaction in a fluidic substance, and avoids the high temperature reaction and resulting volume of carbon dioxide.
Conventional attempts to generate low temperature electrolysis based iron have encountered difficulty with volume and throughput because the electrical current, or electrons, are limited to the contact point of the electrode, and further that the iron particles have the tendency to adhere to the electrode once the reaction is complete.
These major challenges have prevent the LTE process from being adopted in commercial plants. Conventional electroextraction of metal is normally achieved from dissolved species, which are transported by electromigration and diffusion. The solubility of reactant and liquid-to-surface mass-transfer control can be the main limitation for productivity. In the current alkaline LTE process, one way is Fe₂O₃particles suspend in alkaline solution and Fe₂O₃particles also need to diffuse to the electrode surface for the electrochemical reaction to occur, which lowers the reaction rate. Kinetically, the diffusion of solid Fe₂O₃particles to the electrode surface can be the limiting step, and the point, or single, electrode area limits the reaction rate. Fe is deposited on the electrode surface, and therefore the electrode must be removed in order to collect Fe, which could interrupt the production process. The other way is Fe₂O₃particles are pressed to a pellet under very high pressure. The pellet is treated as cathode in alkaline electrolyte. Due to the very poor electronic conductivity of Fe₂O₃, the reaction rate is also very slow.
In order to overcome above challenges associated with the LTE process, configurations herein introduce a process where the electrons and ions can percolate into the liquid mixture, referred to as a colloid, and this mixture contains the iron oxide or other target substance that can be extracted easily from the electrolysis, which significantly increases the reaction rate and allow the production continuously. The fluidic substance defining a conductive Fe₂O₃colloidal electrode flows into an electrochemical cell, for continuous electrolysis, from an input reservoir. Fe is collected in an extraction reservoir, which facilitates the collection of the reduced Fe. An electronic-ionic conductive colloidal electrode, which contains the electrochemically active species (Fe₂O₃particles), the liquid electrolyte (NaOH solution), SDBS and a percolating electronic conductor (carbon network) is utilized to overcome the diffusion limitation of Fe₂O₃electrolysis associated with 2-dimensional reaction area and the poor electronic conductivity of Fe₂O₃. A formed 3-dimensional network with mixed conductivity significantly increases the reaction area and electrolysis current. Fe₂O₃particles then do not need to diffuse to the electrode surface for the effective electrochemical reaction to occur and percolated carbon network increases electronic conductivity effectively.
In further detail, the method for low temperature electrolysis (LTE), as disclosed herein includes circulating a fluidic substance between opposed electrodes, in which the fluidic substance is defined by a colloid including a reactant, an electrolyte, and a disbursement medium, the colloid responsive to an electric charge for producing a target reaction. A flow pump or other flow process agitates the fluidic substance for disposing the fluidic substance between the opposed electrodes, and an electrical source applies an electric charge to the opposed electrodes for electrolytically causing the target reaction. Outflow from the pumped fluidic substance is directed to a reservoir for receiving the circulated fluidic substance, which now includes a precipitate or result of the target reaction for separating a desired substance from the fluidic substance.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

FIG. 1 a shows the dispersement medium in the fluidic substance including the reactant;

FIG. 1 b shows a graphing of an increase in electrical charge resulting from the dispersement medium of FIG. 1 a;

FIG. 2 shows a flow electrolysis design for agitating the fluidic substance between the opposed electrodes for facilitating electrolysis using the dispersement medium of FIG. 1 b; and

FIGS. 3 a-3 c show promoting or shifting the electrochemical reaction rate away from undesired substances such as hydrogen gas.

DETAILED DESCRIPTION

Configurations discussed below depict an example arrangement of the disclosed approach. The fluidic substance defining the colloid circulates through a flow vessel or other containment for agitating the fluidic substance in communication with electrodes.
The fluidic substance flows between a source and collection reservoir. The source reservoir contains a mixture defining the colloid including the iron oxide or other reactant, the electrolyte, typically an alkaline substance, and the dispersement medium for facilitating charge conductivity through the fluidic substance, such as a carbon network resulting from carbon powder. The colloid mixture including the disbursement medium (carbon) therefore defines a colloid electrode because the liquid substance itself conducts the electrical charge to the Fe₂O₃particles. Following electrolysis in the flow vessel, the fluidic substance flows to the collection reservoir where iron particles (Fe) or other result of the electrolysis are gathered and extracted by a magnetic, filtration or other separation approach.
FIG. 1 a shows the dispersement medium in the fluidic substance including the Fe₂O₃reactant. Referring to FIG. 1 a, in a fluidic substance 100, a dispersement medium 110 such as carbon powder percolates throughout the fluidic substance 100 to form a carbon network 112. An electron flow 114 from an electrode 116 transports electrons to a reactant 120 such as iron oxide (Fe₂O₃). A resulting electrolysis (electrochemical reaction) generates iron particles (Fe) as the desired substance 130, which is then physically extracted or filtered out as the fluidic substance 100 is pumped into a containment reservoir. In the example approach, the electrolysis reaction is given by:
Cathode: Fe₂O₃(s)+3H₂O+6e⁻→2Fe(s)+60H⁻
Anode: 60H⁻→3/2O₂(g)+3H₂O+6e⁻
FIG. 1 b shows a graphing of an increase in electrical charge resulting from the dispersement medium of FIG. 1 a. Referring to FIGS. 1 a and 1 b, the electrode 116 provides voltage resulting in a current to an opposed electrode through the fluidic substance 100. In a suspension without the dispersement medium 110, electrical flow is limited as current encounters resistance, as shown by line 140. In a colloid defined by the reactant mixed with the dispersement medium 110, current flow is facilitated as electrons may pass between particles of the particles (i.e. carbon atoms) of the dispersement medium 110, as shown by line 142. The disclosed colloids may include gels, sols, and emulsions, such that the particles do not settle and are difficult to separate out by ordinary filtering or centrifuging as in a suspension. In the example configuration, the fluidic substance 100 is defined by a colloid mixture defining a colloidal electrode, which contains the electrochemically active species (Fe₂O₃particles), the liquid electrolyte (NaOH solution), and a 3D percolating electrical conductor (C network). The simultaneous percolation of electrons and ions effectively increases the area of the current collector, and enables the process to function at high currents rates such as those in FIG. 1 b.
In the example configuration, the iron oxide defines a reactant responsive to electrolysis for generating iron particles and oxygen as a by-product, rather than CO₂as in conventional approaches. Alternate configurations may employ other reactants, in which the reactant is form of the desired substance in a molecular form responsive to the electric charge to result in a desired substance as a result of the target reaction. A fluidic substance 100 including the reactant generates the desired substance from electrolysis of the reactant resulting in an alternate molecular form of the reactant, such as the disclosed Fe₂O₃to Fe as in the reaction above.
Other forms of the reactant may also benefit from the approach herein in addition to iron oxide. For example, the reactant may include forms of other metals such as Fe, Ag, Ni, Cu, and rare earth elements for extraction as the desired substance.
FIG. 2 shows a flow electrolysis design for agitating the fluidic substance 100 between the opposed electrodes for facilitating electrolysis using the dispersement medium of FIG. 1 b. Referring to FIGS. 1 a, 1 b and 2, a flow vessel 150 may include an electrochemical cell fluidically coupled between a colloid reservoir 152, or source, and an output reservoir 154. A pump 156 drives and agitates the fluidic substance 100 from the reservoir 152 through the flow vessel 150 where the fluidic substance 150 is in communication with opposed electrodes, including a titanium plate cathode 160 and a platinum foil anode 162 connected to a voltage source 164 such as a potentiostat. The electrodes are not limited to titanium and platinum. Other metals/alloys and materials can also be utilized as the electrodes. A series of parallel opposed plates 160-N and 162-N define the electrodes and enhance the surface area of the electrodes for transfer of electrons to the fluidic substance 100, and the resulting iron particles contained in an outflow liquid 100′ in the output reservoir 154.
The pump 156 operation and a resulting flow rate of the fluidic substance 100 across the electrodes may be altered to conform to a desired reaction rate in the flow vessel. The reaction rate may depend on such factors as the electrical plate size, the fluid vessel size, the capacity of the pump, and other factors which affect the speed with which electrolysis occurs in the flow vessel. Flow may be altered according to static and continuous modes, and circulating the fluidic substance based on intervals of static containment of the fluidic substance and resuming a fluidic flow of the fluidic substance across the opposed electrodes following the interval. A continuous mode may also be employed for circulating the fluidic substance in a continuous flow across the electrodes and collecting the continuous flow in a reservoir for extracting the desired substance.
The dispersement medium 110 percolates throughout the fluidic substance 100 permits electrolysis even when the Fe₂O₃particles are not in contact with an electrode 160, 162 as the electrons 114 are dispersed throughout the fluidic substance 100 by the carbon particles in the dispersement medium 110 which conducts charge. The electrode 160, 162 plates disperse an electric charge throughout the fluidic substance from conductivity of the dispersement medium for transporting electrons from at least one of the opposed electrodes 160, 162 to the reactant via the dispersement medium 110. Thus, the dispersement medium 110 defines a percolating electrical conductor dispersed in the fluidic substance 100 and conducive to conducting electrical charges throughout the fluidic substance 100 for providing electrons to the target reaction.
In operation, the pump 156 draws the fluidic substance from the colloid reservoir 152 to propel the fluidic substance 110 through the flow vessel 150 for agitating the fluidic substance 100 to disposing the fluidic substance between the opposed electrodes. Movement of the fluidic substance, in combination with the dispersement medium, allows electrical communication between the reactant particles as electrons flow to the reactant for generating the desired substance through electrolysis. In this manner, the flow vessel 150 circulates the fluidic substance between the opposed electrodes 160, 162, such that the fluidic substance 100 is defined by a colloid including a reactant, an electrolyte, and a disbursement medium, in which the colloid includes the reactant responsive to an electric charge for producing a target reaction. The reactant flowing through the flow vessel 150 generates an electrolytic reaction from a colloidal electrode, in which the colloidal electrode is defined by the combination of the dispersement medium 110 and the reactant for transporting electrons to reactant molecules distant from a charge surface, and the electrolytic reaction results in the desired substance through electrolysis of the reactant, Fe₂O₃in the example shown. While the disclosed examples exhibit an example reactant as iron oxide (Fe₂O₃) and the dispersement medium as carbon for resulting in iron particles (Fe) as the desired substance, other reactants responsive to electrolysis may also be employed in the colloidal electrode.
In the example arrangement, the opposed electrodes include a colloid electrode 160 defined by a titanium plate, and a counter electrode 162 defined by a platinum foil, and the flow vessel 150 employs a plurality of titanium plates 160-N and opposed planar platinum foil 162-N electrodes arranged in a series of parallel planes, typically opposed pairs, in the flow vessel 150 for transporting the fluidic substance 100 between the opposed electrodes for collection in the reservoir 154.
Since the disclosed fluid substance 100 depicts a colloidal electrode that possesses both electrically and ionically conductive properties, hematite particles don't need to diffuse from bulk solution to the surface of the electrode for electrolyzing, and the conversion rate from Fe₂O₃to Fe is not limited by the residence time of the particle adsorbing on electrode surface. The carbon network can conduct the electrons, which forms a 3D reaction network, significantly increasing reaction area and reaction rate. The disclosed approach demonstrates the use of electrolysis in a colloidal electrode for LTE to avoid generation of greenhouse gases resulting from high temperature reactions. A further consideration includes ensuring that the electrochemical reaction does not generate undesirable by-products, such as hydrogen gas. FIGS. 3 a-3 c show promoting or shifting the electrochemical reaction (rate) potential away from undesired substances such as hydrogen gas. Selection of a particular electrolyte provides an alkaline substance that shifts the reaction to avoid generation of undesirable or harmful precipitants. In FIG. 3 a, the potential 170 at which iron electrolysis occurs is very close to the potential at which hydrogen is produced (2H⁺→H₂), and the current peak of reducing Fe²⁺ to Fe is merged with the current of H2 evolution. Selection of the proper type and percentage of electrolyte mitigates such an undesirable result. As shown in FIG. 3 b, addition of sodium sulfide shifts the potential of the iron reaction 170′ well above that of hydrogen production. FIG. 3 c shows the reduction charge 180 and the potential 182 for the electrochemical reaction with sodium sulfide 184 and without 186.
The colloid therefore benefits by defining the fluid substance 100 based on selecting the electrolyte based on an electrochemical reaction rate for shifting electrolysis towards reactions resulting in the generation of the desired substance and away from reactions resulting in hydrogen gas (H₂). In the example arrangement, the electrolyte may be an alkaline substance selected from the group consisting of sodium hydroxide (NaOH) and sodium sulfide (Na₂S).
In the examples discussed above, the dispersement medium demonstrates how carbon affects the electronic conductivity and viscosity of the colloidal electrodes under static condition. Alternate configurations systematically determine the electronic conductivity, viscosity and stability of the colloidal electrodes, by changing the content of the disbursement medium and electrolyte before and after flow. It is desirable to have a high concentration of carbon, to increase electronic conductivity, and a high concentration of Fe₂O₃to get a high current density, although at a certain point the colloidal electrodes may become excessively viscous and unusable in flow electrolysis. The electronic conductivity and viscosity will be measured with different compositions of the colloidal electrodes. Correlations may then link the viscosity with the electronic conductivity to determine the effects of the rheology on the conductivity. For example, it may be revealed that colloidal electrodes with the same amount of C and different viscosity possibly possess different electronic conductivity and electrolysis currents.
While the system and methods defined herein have been particularly shown and described with references to embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

What is claimed is:

1. A method for low temperature electrolysis (LTE), comprising:

circulating a fluidic substance between opposed electrodes, the fluidic substance defined by a colloid including a reactant, an electrolyte, and a disbursement medium, the colloid responsive to an electric charge for producing a target reaction;

agitating the fluidic substance for disposing the fluidic substance between the opposed electrodes;

applying an electric charge to the opposed electrodes for electrolytically causing the target reaction; and

receiving the circulated fluidic substance including a precipitate of the target reaction for separating a desired substance from the fluidic substance.

2. The method of claim 1 wherein a reactant form of the desired substance is a molecular form responsive to the electric charge to result in a desired substance as a result of the target reaction.

3. The method of claim 2 further comprising generating the desired substance from electrolysis of the reactant resulting in an alternate molecular form of the reactant.

4. The method of claim 1 further comprising dispersing an electric charge throughout the fluidic substance from conductivity of the dispersement medium for transporting electrons from at least one of the opposed electrodes to the reactant via the dispersement medium.

5. The method of claim 4 wherein the dispersement medium is a percolating electrical conductor dispersed throughout the fluidic substance and conducive to conducting electrical charges throughout the fluidic substance for providing electrons to the target reaction.

6. The method of claim 1 further comprising generating an electrolytic reaction from a colloidal electrode, the colloidal electrode defined by the combination of the dispersement medium and the reactant for transporting electrons to reactant molecules distant from a charge surface, the electrolytic reaction resulting in the desired substance through electrolysis of the reactant.

7. The method of claim 1 further comprising selecting the electrolyte based on an electrochemical reaction rate for shifting electrolysis towards reactions resulting in the generation of the desired substance and away from reactions resulting in hydrogen gas (H₂).

8. The method of claim 7 wherein the electrolyte is an alkaline substance selected from the group consisting of sodium hydroxide (NaOH) and sodium sulfide (Na₂S).

9. The method of claim 5 wherein the reactant is iron oxide (Fe₂O₃) and the dispersement medium is carbon for electrolyzing iron particles (Fe) as the desired substance.

10. The method of claim 9 wherein the opposed electrodes include a colloid electrode defined by a titanium plate, and a counter electrode defined by a platinum foil, wherein a plurality of titanium plates and opposed planar platinum foil electrodes are arranged in a series of parallel planes in a flow vessel for transporting the fluidic substance from between the opposed electrodes for collection in a reservoir.

11. An electrolysis apparatus, comprising:

a fluidic substance defined by a colloid including a reactant, an electrolyte, and a disbursement medium, the colloid responsive to an electric charge for producing a target reaction;

a flow vessel having opposed electrodes for circulating the fluidic substance from a colloid reservoir to an output reservoir after circulating the fluidic substance between the opposed electrodes;

a pump for circulating and agitating the fluidic substance for disposing the fluidic substance between the opposed electrodes; and

a power source for applying an electric charge to the opposed electrodes for electrolytically causing the target reaction, the output reservoir for receiving the circulated fluidic substance including a precipitate of the target reaction for separating a desired substance from the fluidic substance.

12. The apparatus of claim 11 wherein the reactant is form of the desired substance in a molecular form responsive to the electric charge to result in a desired substance as a result of the target reaction.

13. The apparatus of claim 12 wherein the flow vessel generates the desired substance from electrolysis of the reactant resulting in an alternate molecular form of the reactant.

14. The apparatus of claim 11 wherein the disbursement medium is configured to disperse an electric charge throughout the fluidic substance from conductivity of the dispersement medium for transporting electrons from at least one of the opposed electrodes to the reactant via the dispersement medium.

15. The apparatus of claim 14 wherein the dispersement medium is a percolating electrical conductor dispersed throughout the fluidic substance and conducive to conducting electrical charges throughout the fluidic substance for providing electrons to the target reaction.

16. The apparatus of claim 15 further comprising generating an electrolytic reaction from a colloidal electrode, the colloidal electrode defined by the combination of the dispersement medium and the reactant for transporting electrons to reactant molecules distant from a charge surface, the electrolytic reaction resulting in the desired substance through electrolysis of the reactant.

17. The apparatus of claim 11 wherein:

the reactant is iron oxide (Fe₂O₃),

the dispersement medium is carbon powder;

the electrolyte is an alkaline substance selected from the group consisting of sodium hydroxide (NaOH) and sodium sulfide (Na₂S).

18. The apparatus of claim 17 wherein the flow vessel has a plurality of opposed electrodes include a colloid electrode defined by a titanium plate, and a counter electrode defined by a platinum foil, wherein a plurality of titanium plates and opposed planar platinum foil electrodes are arranged in a series of parallel planes in a flow vessel for transporting the fluidic substance from between the opposed electrodes for collection in a reservoir.

19. A method for electrochemical iron production comprising:

providing a electrolysis containment system having an anodic (anode) and cathodic (cathode) side, and a cell responsive to an electric charge;

circulating, adjacent to the cathodic side, a hematite conductive colloid including Fe₂O₃, conductive carbon and sodium hydroxide solution, the cathodic side in fluid communication with an cathodic portion of the cell;

circulating, adjacent to the anodic side, an alkaline solution, the anodic side in fluid communication with an anodic portion of the cell; and

harvesting, from the cell, iron particles.

20. The method of claim 1 further comprising harvesting oxygen from the anode side of the electrolysis containment system.

21. The method of claim 1 wherein the reactant includes forms of at least one of Fe, Ag, Ni, Cu, and rare earth elements.

22. The method of claim 4 further comprising circulating the fluidic substance based on intervals of static containment of the fluidic substance and resuming a fluidic flow of the fluidic substance across the opposed electrodes following the interval.

23. The method of claim 4 further comprising circulating the fluidic substance in a continuous flow across the electrodes and collecting the continuous flow in a reservoir for extracting the desired substance.