An ammonia cracker (also called an ammonia dissociator) decomposes liquid ammonia (NH₃) into its constituent gases — 75% hydrogen and 25% nitrogen — through a catalytic endothermic reaction at 850–950°C over a nickel-based catalyst. The resulting cracked ammonia gas is a widely used, economical protective atmosphere for heat treatment processes in the metal industry.
Cracked ammonia atmosphere is used in: bright annealing of stainless steel, copper, brass and aluminium strips and coils; sintering of powder metallurgy components; copper brazing of automotive heat exchangers; carbonitriding and nitriding of case-hardening steel components; and continuous annealing furnaces for electrical steel (grain-oriented and non-oriented).
The primary advantages of cracked ammonia over other protective atmospheres are: lower cost — ammonia is the cheapest hydrogen source per Nm³ compared to electrolytic hydrogen or cylinder gas; safety — cracker output at near-atmospheric pressure is far safer than high-pressure hydrogen cylinders; and on-demand generation — production matches furnace consumption without storage risk.
Our ammonia crackers range from 10 Nm³/hr to 1,000 Nm³/hr of dissociated gas output and are available in electrically heated, gas-fired and waste-heat-recovery configurations. All crackers are supplied with complete safety equipment including ammonia detector, flame arrestors, check valves and pressure regulators.
Liquid ammonia is stored in bulk storage tanks or cylinders at 7–15 bar. An electrically heated or steam-traced vaporiser converts liquid NH₃ to gas phase at a controlled rate. A pressure-reducing valve delivers ammonia gas at 0.3–1.0 bar to the cracker. The vaporiser is thermostatically controlled to prevent NH₃ condensation in downstream piping, which would cause flow interruptions and cracker upset.
Ammonia gas is metered through a needle valve or mass flow controller and preheated in a recuperator tube using heat from the outgoing hot dissociated gas, raising feed temperature to 350–400°C before entering the catalyst chamber. This recuperative preheating significantly reduces the electrical energy required for cracking, typically by 25–30%.
The cracking chamber contains the nickel-based catalyst supported on an alumina substrate, packed in radial or vertical tube arrangements. At 850–950°C, the catalytic surface dissociates NH₃ with efficiency above 99.9% — less than 100 ppm residual NH₃ in the product gas. The catalyst chamber is housed in a refractory-lined furnace heated by electric elements (MoSi₂ or SiC) or gas burners, maintaining temperature uniformity within ±10°C.
Hot dissociated gas (850°C+) exits the cracking chamber and is rapidly cooled to 40–50°C in a water-cooled or air-cooled heat exchanger. Moisture — generated during cracking (NH₃ + O₂ traces) and from cooling water breakthrough — is removed by a desiccant dryer (activated alumina, regenerated by heat) to achieve a dew point of -40°C or below, preventing oxidation in sensitive annealing and sintering applications.
For applications requiring purity above standard cracked ammonia — such as copper brazing of aluminium or annealing of oxygen-free copper — a palladium diffusion purifier is added downstream. The palladium membrane at 350–400°C passes only hydrogen with 99.9999% purity, while nitrogen and residual NH₃ are rejected. Alternatively, a catalytic deoxidiser removes O₂ traces from the nitrogen carrier gas.
Cracked gas is distributed to furnace inlets at 50–200 mbar through stainless steel piping with manual or solenoid isolation valves at each furnace connection. Safety devices include flame arrestors at furnace inlets (prevents furnace back-fire propagation), check valves (prevents air ingress during shutdown), automatic purge-with-nitrogen on power failure, and catalytic bead NH₃ leak detectors in the equipment room.
| Output Capacity | 10 to 1,000 Nm³/hr DA |
| Gas Composition | 75% H₂ + 25% N₂ |
| Residual NH₃ | <100 ppm (standard) |
| Dew Point of DA | −40°C (standard drying) |
| Cracking Temperature | 850–950°C |
| Catalyst | Nickel / Alumina |
| Catalyst Life | 4–6 years (replaceable) |
| Energy Consumption | 0.5–0.9 kWh/Nm³ DA |
| Heating Type | Electric / Gas-fired |
| Standards | PESO / Factory Act / IS Codes |
Tell us your furnace type, operating temperature and gas consumption — we will recommend the right cracker size and provide an installation cost estimate.
