Electrochemical Processing Flashcards
What are the three types of Extractive Metallurgy?
- Pyrometallurgy: based on temperature
- Hydrometallurgy: using solvents
- Electrometallurgy: using electricity
What does the Nernst equation relate?
It relates the Gibbs free energy deltaG to the decomposition potential E
What is Hall-Heroult process
- Major industrial process for aluminum extraction
- Molten salt electrolysis process
What is FFC process?
Process for oxygen production, demonstrated yield of 40-45 wt.%
What are the types of electrolysis extraction?
Molten salt electrolysis
Molten regolith electrolysis
Ionic Liquid Electrolysis
What do the (lighter) Highlands on the moon consist of?
- Ca-rich Plagioclase
- Pyroxene
- Olivine
What do the darker spots on the lunar regolith consist of?
- Plagioclase
- Orthopyroxene
- Clinopyroxene
- Olivine
- Ilmenite
What are some Pyrometallurgy processes?
- Hydrogen Reduction
- Carbothermal Reduction
What are some Hydrometallurgy Processes?
- Leaching
- Aqueous Solving
What are Electrometallurgy Processes?
- Molten salt electrolysis
- Molten oxide/regolith electrolysis
- Steel Ionic Liquids Electrolysis
What does an Ellingham show?
- It shows the temperature dependence of the stability of compounds
- A negative Gibbs energy indicates a reaction is spontaneous, more negative is more spontaneous
What are positive properties of molten salts as electrolytes?
- Reasonable Melting Points
- High Electrical Conductivity
- Large Electrochemical Window
- High Regolith/Oxide Solubility
- Appropriate Sat. Vapor Pressure
- Low Viscosity and Density
- Low Cost
What are some Inert Anode Requirements for the FFC process?
- Sufficient Electrical Conductivity
- Thermal Stability at opt. temp.
- Corrosion Resistance to Molten Salt
- Resistance to Gases
- Facilitates O2 Formation
- Machinability
- Cost
What are the pros and cons of molten salt electrolysis
Pros:
- Landing site agnostic, more components can be reduced
- High oxygen yield
- Direct alloy production possible
Cons:
- Energy Intensive
- Non-indigenous Electrolytes
- Complex multiphase behavior
What is Molten Regolith Electrolysis (MRE)?
- Able to process any planetary regolith to produce oxygen and metals
- No beneficiation required
- Landing-site agnostic
What are the pros and cons of Molten Regolith Electrolysis?
Pros:
- Molten site agnostic
- Direct alloy production
- No reagents required
Cons:
- Energy Intensive
- Complex Multiphase Behavior
- Hard to start up
What is Ionic Liquid Electrolysis?
- Three step process
- Dissolving regolith with acid
- Electrolysis of solution
- Regeneration of the IL
What are desirable properties of ionic liquids for IL?
- Liquid at room temperature
- Large electrochemical window and thermochemical stability
- Very low volatility
What are the pros and cons of IL electrolysis?
Pros:
- Low temperature process
- Well known process in industrial metal
Cons:
- Low oxygen yield
- Restricted solubility of Regolith in IL
- Non-indigenous IL
What are the requirements of the Hall-Heroult process?
- Sufficient electrical conductivity
- Thermal stability at op. temp. (1000°C)
- Corrosion resistance to molten salt
- Resistance to gases
- Facilitates O2 formation
- Machinability
- Cost
What happens with too much / too little CaO in the FFC process?
Too much: Localized concentration limits can be hit
Too little: Ca2+ is sources from CaCl2 instead
Which 3 distinct alloy groups dominate the product of an FFC process?
- Al/Fe alloy
- Fe/Si alloy
- Ca/Si/Al alloy
What are the key challenges of MSE?
- Identification of suitable oxygenevolving inert anode
- Salt recycling and purification
- Regolith handling and
continuous processing - Material selection to withstand
extreme corrosive environment - Regolith management in the salt
- Impact of low-gravity
environments on the system
What are the requirements for the inert anode in MRE?
- Sufficient electrical conductivity
- Thermal stability at op. temp. (>1600°C)
- Corrosion resistance to molten regolith
- Resistance to gases
- Facilitates O2 formation
- Machinability
- Cost
What is the impact of low gravity on an MRE reactor?
- Oxygen is removed from the system as gas
- Lower gravity inhibits the removal of bubbles, lower process efficiency
- Bubble removal techniques challenging in high-temperature process
