Thermochemical Processing Flashcards
What are the methods of thermochemical reduction mentioned?
- Reduction with H2
- Reduction with CO
- Reduction with CH4
- Extraction with F2
- Sabatier process
These processes are candidates for oxygen production as referenced by Li et al. (2012).
What is ilmenite’s chemical formula?
FeTiO3
Ilmenite is a significant mineral resource found in lunar Mare.
What does the mnemonic ‘OIL – RIG’ represent?
- Oxidation Is Loss (of electrons)
- Reduction Is Gain (of electrons)
This mnemonic helps to remember the definitions of oxidation and reduction.
What are the main challenges for solid-gas interaction?
- Homogeneous heat distribution
- Solid-gas exposure
- Energy requirements
These challenges need to be addressed for effective solid-gas reactions.
What is a blast furnace used for?
Steel production by reducing Fe2O3 with carbon
It is a longstanding process where iron ore and coke react with ascending hot gases.
What is the equilibrium reaction for ilmenite reduction with hydrogen?
FeTiO3 + H2 ⟺ Fe + TiO2 + H2O
This reaction is mildly endothermic at high temperatures.
What is the rate-controlling step in the ilmenite reduction process?
H2 diffusion in the reduced layer
This step is critical across all experimental conditions for temperature and hydrogen content.
What is the yield of ilmenite reduction at 1000 °C according to Taylor et al. (1993)?
10 wt%
This yield was achieved in proof of concept experimental studies.
What are the pros of using ilmenite for hydrogen reduction?
- Single reaction step already yields water
- Mild reaction temperatures
- Abundant resource in Mare regions
These advantages make ilmenite a promising candidate for oxygen production.
What are the cons of using ilmenite for hydrogen reduction?
- Beneficiation of ilmenite is recommended
- Only low oxygen yield possible (typically <5 wt%)
These limitations affect the efficiency of the process.
What is the chemical reaction for glass reduction with hydrogen?
FeO(glass) + H2 ⟺ Fe + H2O
Glass contains up to 20 wt% FeO and offers faster reaction kinetics compared to silicates.
What is a significant factor in the reduction process of glass?
Impact liberates solar-wind implanted H (and possibly C)
This process forms spherical Fe droplets as a result of the reduction.
What are the pros of glass reduction with H2?
- Single reaction step already yields water
- Mild reaction temperatures
- Glass is an abundant resource across the lunar surface
This is higher compared to the 22.3 kcal/mol required for reduction using H2.
What is the effect of temperature on the reaction rate for ilmenite reduction?
Comparison of reactants H2 and CO
Zhao and Shadman, 1993
What is a fluidised bed reactor concept used for?
Ilmenite reduction with CO
Lewis et al. 1993
What are the pros of ilmenite reduction with CO?
- Mild reaction temperatures
- Ilmenite is an abundant resource in Mare regions
What are the cons of ilmenite reduction with CO?
- Beneficiation of ilmenite is recommended and greatly affects process efficiency
- Cracking of CO2 requires much energy
- Reduction rate is slower compared to using hydrogen
What is the feedstock for ilmenite reduction with CH4?
Ilmenite (FeTiO3) from high-Ti mare basalts (10–20 vol% of rocks, less in soils)
What is the reaction for ilmenite reduction with CH4?
FeTiO3 + CH4 ⟺ Fe + TiO2 + CO + 2 H2
What is the temperature range for ilmenite reduction with CH4?
Around 1000 °C
What are the pros of ilmenite reduction with CH4?
- Medium reaction temperatures
- Ilmenite is an abundant resource in Mare regions
What are the cons of ilmenite reduction with CH4?
- Beneficiation of ilmenite is recommended and greatly affects process efficiency
- Hydrogenation as additional process step
- Additional reactant needed (hydrogen)
What is carbothermal reduction?
Includes all processes involving molten reactant and carbon in some form
What is the reaction for carbothermal reduction variant 1?
Mg2SiO4 + 2 CH4 ⟺ 2 MgO + Si + 4 H2 + 2 CO
What is the reaction for carbothermal reduction variant 2?
FeTiO3 + C ⟺ Fe + TiO2 + CO
What is the required temperature for highest efficiency in carbothermal reduction?
1600–2000 °C
What are the pros of carbothermal reduction?
- Higher oxygen yield possible (~10 wt% in tests with tephra)
- No beneficiation required and applicable to various minerals
What are the cons of carbothermal reduction?
- High reaction temperature (melt)
- Added system complexity and material handling challenges
- Considerable reactant makeup (5–20%) requires resupply or compensation from SWIP
What is the general reduction reaction when using fluorine?
MxyOy + y F2 ⟶ xy MF2/x + y/2 O2
What is the reaction for extracting aluminum oxide with fluorine?
Al2O3 + 3 F2 ⟶ 2 AlF3 + 3/2 O2
What are the pros of using fluorine for extraction?
- About 80% of the total oxygen can be released
- Moderate temperatures required (350–650 °C)
What are the cons of using fluorine for extraction?
- Experiments have only been done with small sample quantities
- Fluorine needs to be recycled to a high degree
- Fluorine is toxic to humans
What is the temperature range for ilmenite reduction with H2?
700–1000 °C
What is the reaction for the Sabatier process?
CO2 + 4 H2 ⟺ CH4 + 2 H2O
What temperature range is required for the Sabatier process?
300–400 °C
What are the pros of the Sabatier process?
- Well known process, part of the LSS on the ISS
- Exothermic reaction, excess heat can be used to drive reactor
What are the cons of the Sabatier process?
- Hydrogen needs to be imported from Earth
- Excess heat might require radiators or heat sinks
What is the candidate process for O2 production that involves reduction with H2?
Ilmenite and glass
What are the cons of glass reduction with H2?
- Beneficiation of glass is required if not taken from a pyroclastic deposit
- Process has not yet been demonstrated on a plant scale
What is the reduction formula for Ilmenite reduction with CO?
FeTiO3 + CO <–> Fe + TiO2 + CO2
