Electra is a green iron company that produces clean iron with zero carbon emissions. It has raised $113M funding to commercialize the low-temperature aqueous metallurgical process for producing pure metallic iron for green steel production using iron ore waste and intermittent renewable energy. Its green steel pilot plant is already under construction at Electra’s headquarters in Boulder, Colorado.
Challenges: carbon emission of steel industry
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The steel production industry is one of the largest industrial sectors in the world, making a significant contribution to the global economy. However, it is also responsible for a substantial amount of carbon dioxide (CO₂) emissions, a major contributor to climate change. The International Energy Agency (IEA) estimates that the steel industry is responsible for approximately 7% of global carbon dioxide emissions.
The main source of carbon dioxide emissions in the steel production industry comes from the use of fossil fuels, particularly coal, to generate the high temperatures required to melt and refine iron ore. The process of producing steel also requires large amounts of electricity, which is primarily generated from fossil fuel sources.
To address the problem of carbon dioxide emissions in the steel industry, there is a growing need to transition towards more sustainable and renewable energy sources such as solar and wind power. This would enable the production of green steel, which has a significantly lower carbon footprint than traditional steel. As the cost of renewable energy decreases, the transition away from fossil fuels and towards clean electricity for steel production becomes increasingly attractive.
However, electrically-driven iron production presents its own set of challenges, such as the intermittent nature of renewable energy sources and the difficulty of dissolving and reducing iron ores while removing impurities. One major challenge is that high-temperature processes are difficult to interrupt or shut down without a substantial amount of backup energy storage to maintain the high temperature.
Thereby, there is a need for a low-temperature electrical process compatible with intermittent renewable energy sources for producing pure iron from iron ore for green steel production.
Electra develops an ore dissolution and iron conversion system that uses renewable energy sources such as solar and wind to enable efficient, low-temperature aqueous metallurgical processes for producing relatively pure metallic iron from various iron source materials, including relatively low-purity iron feedstock materials.
The diagram below depicts the ore dissolution and iron conversion system.
The system comprises two decoupled subsystems: dissolution and plating.
The dissolution subsystem has an acid regeneration cell that generates acid solution by electrolyzing water at anode. The acid is used to dissolve ore feedstock in a dissolution tank that is fluidically connected to the cathode of the acid regeneration cell. The cathode reduces ferric ions (Fe³⁺) dissociated from the ore to ferrous ions (Fe²⁺). The ferrous enriched dissolution solution is purified and separated into anolyte and catholyte streams for the plating subsystem. The cathode of the plating system electrically plates iron metal by reducing ferrous ion (Fe²⁺) in the catholyte. The produced iron metal can be used for green steel production.
The diagram below depicts the dissolution subsystem.
The ore feedstock, such as hematite (Fe₂O₃), contains iron in the iron (III) state. When dissolved in acid, hematite dissociates into ferric ions (Fe³⁺). In order to electrolytically plate metallic iron, any Fe³⁺ needs to be first reduced to ferrous ion (Fe²⁺).
The dissolution subsystem uses an acid regeneration cell to produce acid solution for the dissolution of ore feedstock and convert ferric ions (Fe³⁺) to ferrous ions (Fe²⁺) to obtain ferrous enriched dissolution solution that is further purified for the iron plating in the plating subsystem.
- Acid regeneration cell
The acid regeneration cell comprises a cathode, a cathode chamber, an anode, an anode chamber, and a separator membrane of proton exchange membrane (PEM) between the two electrodes. The cathode is made of carbon or graphite felt. The anode is made of precious metal, such as Ir, Ru, Pt, Rh, and Pd.
The acid regeneration cell operates at around 60 ºC. The current density applied to an acid regeneration cell is between 0.1 and 2 A/cm².
When an electrical current is applied to the cell, water from a water tank is oxidized at the anode, resulting in the production of oxygen gas (O₂) and protons (H⁺), according to the reaction:
H₂O → 2H⁺ + ½O₂↑ + 2e⁻
The solution exiting the anode chamber is fed through a gas-liquid separation device (not shown) that removes oxygen from the solution before returning it to the water tank and then the anode chamber of the acid regeneration cell.
The protons generated by water electrolysis migrate from the anode chamber to the cathode chamber through the porous PEM. The protons combine with anions such as SO₄²⁻ to form acid.
At the cathode, ferric ion (Fe³⁺) is reduced to ferrous ion (Fe²⁺) according to the reaction:
Fe³⁺ + e⁻ → Fe²⁺
Due to the acid attack, the iron metal formation at the cathode is prevented in this step, resulting in no efficiency loss. The solution leaving the cathode chamber is enriched with ferrous (Fe²⁺) salt and acid.
The solution is then returned to the dissolution tank, where the newly generated acid is used to dissolve more iron feedstock, and convert it to ferric salt, and the process continues. The dissolution tank is maintained at about 50 to 90 ºC to facilitate dissolution. The complete dissolution of hematite ores is within acceptable time frames of 24 to 30 hours.
In conclusion, the acid regeneration cell has two functions.
One function is to regenerate the acid that is consumed by the dissolution of iron feedstock in the dissolution tank. Without the acid regeneration cell, acid is consumed in the dissolution reaction and acid concentration would gradually decrease as the dissolution progresses.
A second function is to convert ferric ion (Fe³⁺) to ferrous ion (Fe²⁺). The removal of ferric ions greatly increases the dissolution rate of the ore. During the dissolution process with continuous liquid recirculation, the acid regeneration cell maintains a relatively low ferric concentration while increasing the ferrous concentration, thereby generating double benefits for iron feedstock dissolution.
Dissolution of ore feedstock causes a quantity of insoluble impurities such as silica and soluble impurities such as aluminum, silicon, titanium and phosphorus.
Before returning the dissolution solution to the acid regeneration cell, it is desirable to separate any solid or colloidal impurities from the solution. Any suitable solid-liquid separation device or technique, such as filtration, can remove solid impurities. Colloidal impurities can be removed by flocculation with a flocculant such as polyethylene glycol, or polyethylene oxide.
Before the ferrous enriched dissolution solution enters the cathode chamber of the iron plating cell, it is necessary to remove soluble impurities, such as aluminum cations (Al³⁺), phosphate (PO₄³⁻), silicon, and titanium, which can cause problem for iron plating processes.
Aluminum hydroxide (Al(OH)₃), titanium hydroxide, and phosphates can be precipitated without substantial precipitation of iron ions by raising the pH above 3 until about 5. Increasing the solution’s pH can also be used to remove colloidal silica.
It is generally desirable to raise the pH without introducing new impurities. Therefore, metallic “accessory iron” can be used to raise the solution’s pH sufficiently to precipitate these impurities.
Iron metal displaces the aluminum cation in the solution to precipitate aluminum hydroxide, according to the reaction:
Al₂(SO₄)₃ + 3Fe + 6H₂O → 2Al(OH)₃↓ + 3FeSO₄ + 3H₂↑
In addition, iron metal converts any dissolved ferric iron (Fe³⁺) to ferrous iron (Fe²⁺) via the following reaction:
Fe₂(SO₄)₃ + Fe → 3FeSO₄
Iron metal can also consume remaining acid in the treated solution according to reaction, which is beneficial to the following iron plating process:
H₂SO₄ + Fe → FeSO₄ + H₂↑
The diagram below depicts the plating subsystem.
The plating subsystem uses an electrical plating cell to produce iron metal from the ferrous enriched solution generated by the dissolution subsystem.
The plating cell comprises a cathode, a cathode chamber, an anode, an anode chamber, and a membrane separating the two electrodes. The anode is made of carbon or graphite. The cathode is made of carbon, graphite, steel, stainless steel, copper, zinc, or titanium. The membrane is PEM or anion exchange membrane (AME).
The plating subsystem has catholyte and anolyte tanks to receive catholyte and anolyte streams that are separated from the ferrous enriched solution stream produced by the dissolution subsystem. The catholyte and anolyte circulate through the cathode and anode chambers of an electrochemical plating cell, respectively.
When an electrical current is applied across the plating cell, iron metal is electroplated on the cathode by reducing ferrous ions (Fe²⁺) via the following reaction:
Fe²⁺ + 2e⁻ → Fe↓
Simultaneously, in the anolyte, the ferrous ion (Fe²⁺) is oxidized to ferric ion (Fe³⁺) on the anode of the plating cell, according to the reaction:
2Fe²⁺ → 2Fe³⁺ + 2e⁻
The plating electrolytes are recycled to the dissolution tank in the dissolution subsystem for reuse in subsequent dissolution and acid regeneration operations. Once the desired quantity of iron has been electroplated in batch, the plating process is complete. Plated iron metal is removed from the cathode chamber of the plating cell.
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Electra is developing the ore dissolution and iron conversion system to enable efficient, low-temperature aqueous metallurgical processes for producing relatively pure metallic iron from various iron source materials. Its green steel pilot plant is already under construction at Electra’s headquarters in Boulder, Colorado. The images below show that Electra can plate large areas of iron metal for use in the production of green steel.
Electra has raised a total of $113.5M in funding over 4 rounds, including a Grant round, two Venture-Series Unknown rounds, and a Corporate round. Their latest funding was raised on Dec 8, 2022 from a Corporate Round round.
Electra is funded by 11 investors, including National Science Foundation, Temasek Holdings, Valor Equity Partners, S2G Ventures, Breakthrough Energy Ventures, Amazon, Capricorn Investment Group, Lowercarbon Capital, Baruch Future Ventures, BHP Ventures, and Nucor Corporation. Nucor Corporation and Lowercarbon Capital are the most recent investors.
Sandeep Nijhawan is Founder.
Sandeep Nijhawan is CEO.