Process Technology Training Series
Ammonia
Module from the Process Technology Training Series curriculum.
Ammonia (NH3) as Fuel & Hydrogen Carrier · Comparative Properties
| Property | Ammonia (NH3) | Hydrogen (H2) | Diesel (DF) | Units | Rationale |
|---|---|---|---|---|---|
| Molecular weight | 17 | 2 | ~200 | g/mol | NH3 denser than H2, easier storage |
| Energy density (volumetric) | 14.4 | 10.5 | 35 | MJ/liter | H2 lower, ammonia competitive vs. H2 |
| Energy density (gravimetric) | 18.6 | 120 | 45 | MJ/kg | H2 superior; ammonia 2x diesel |
| Boiling point | –33 | –253 | ~180–360 | °C | Ammonia liquid at moderate pressure (8–10 bar) |
| Vapor pressure (at 20°C) | 8.5–9.2 | — | minimal | bar | Requires pressure vessel or cryogenic |
| Storage method | Pressurized (8–10 bar) or cryogenic | High-pressure (300–700 bar) or cryo | Ambient tank | — | NH3 easiest; H2 requires extreme pressure |
| Boil-off rate (cryogenic 72h) | 0.8–1.5% | 3–5% | negligible | % | NH3 better than H2 for long-term marine |
| Toxicity (TLV-TWA) | 25 | — | — | ppm | Harmful via inhalation; requires safety systems |
| Odor threshold | 1–5 | none | — | ppm | Pungent, used as odorant in H2 blends |
| Flammability range | 15–28% | 4–75% | 0.6–5.2% | % in air | Narrower window; safer than H2 or diesel |
| Flame temperature | 2100 | 2100 | 2500 | °C | Similar combustion temp (slight NOx advantage) |
| NOx formation (combustion) | Higher (0.1–0.5% N as NOx) | Very low | ~0.01% | % of N/fuel | Major drawback: N source; SCR needed |
| Storage stability | Excellent (indefinite) | Good if sealed | Good | — | NH3 most stable long-term |
| Cold start capability | Moderate (–33°C boil-off) | Poor (cryo only) | Excellent | — | Blend (ammonia + diesel) viable |
| Production cost (green, 2024) | ~$0.50–1.50 | ~$2.50–6.00 | ~$0.50–1.00 (crude oil dependent) | $/kg | Ammonia cheaper if electrolyzer cost drops |
| Key Conversion Technologies | |||||
| Process | Efficiency (%) | Product | Cost | Maturity & Notes | |
| Ammonia Decomposition (NH3 cracking) | 60–80% | H2 (3 mol) + N2 | Exothermic (22 MJ/kg NH3) | Ru/Ni catalyst @ 400–600°C; mature for fuel cells | |
| Haber-Bosch (N2 + H2 → NH3) | 40–60% (per-pass, ~95% overall with recycle) | Ammonia | 3000–5000 bar, 400–500°C | Mature industrial; cost-limited by green H2 | |
| Green Haber-Bosch (with PEM H2) | 40–60% (same, but green H2 input) | Green Ammonia | 45–50% efficiency overall | 2024+: scaling with renewable H2; new plants | |
| ITM (Ion Transport Membrane) + Haber | 50–65% | Ammonia (+ O2 co-product) | Emerging | Synth. air (N2 + O2 sep.) + H2 one-step; TRL 7–8 | |
| Plasma-assisted NH3 synthesis | 35–50% | Ammonia (from N2 + H2) | Emerging (high electrochemistry) | Electrochemical route, lower pressure; TRL 5–6 | |
| Ammonia as H2 carrier for fuel cells | Via cracking (above) | H2 for PEM/SOFC | Cracking cost-dependent | Promising marine/truck applications; integration key | |
| Applications & Scale-Up Potential | |||||
| Application | Status (2024) | Key Requirement | Challenges & Drivers | ||
| Maritime Fuel (large ships) | Early demo (MAN, WinGD) | Easy bunkering (8–10 bar), onboard cracking | High-efficiency marine engines; SOx/NOx limits → ammonia attractive | ||
| Power Generation (co-fired) | Pilot (5–15% NH3 blend in coal/gas) | NOx scrubbing (SCR/SCR catalysts) | Decarbonization pathway; infrastructure adaptable | ||
| Internal Combustion Engines (ICE vehicles) | Lab-scale demonstrations | Dual-fuel (NH3 + ignition fuel) or pure + piloting | Cold-start, NOx emissions, knock resistance limit | ||
| Fuel Cells (indirect via H2) | Research stage | Cracking reactor + PEM/SOFC fuel cell stack | Refueling convenience & H2 density advantage vs. liquid H2 | ||
| Long-haul shipping (2030+) | Target (regulatory drivers, IMO 2050) | Ship-mounted cracking or shore-based supply | Sulfur/carbon caps, energy density trade-off vs. H2 | ||
| Long-duration energy storage | Emerging concept | Green ammonia + cracking as seasonal buffer | Compete with batteries/FCEV grids; cost parity 2035+ | ||
| NOx & Safety Considerations | |||||
| Ammonia combustion produces NOx (0.1–0.5% by mass of fuel); Selective Catalytic Reduction (SCR) with urea/ammonia required for compliance with MARPOL Annex VI / EPA Tier 4 (Tier 5 pending). Safety: ammonia toxic in air at 25+ ppm (TLV-TWA); monitoring & venting required. Cold-start challenging; dual-fuel (ammonia + diesel/methanol pilot) emerging as practical compromise for vehicles. |
Source: Process_Technology_Training_Series_v1.xlsx · Sheet: Ammonia
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