Overview

Producing protective mixed gas via ammonia cracking is an easily implemented industrial gas preparation method, for the following three core reasons:

1.High ammonia cracking efficiency: Ammonia can be fully decomposed under low pressure with nickel catalyst at a constant temperature of 780~800℃, with a decomposition rate up to 99.9%.

2.Simple gas purification process: Liquid ammonia raw material features ultra-high purity. Its volatile impurities only consist of tiny amounts of inert gas and dissolved water, with nearly zero oxygen content. Besides, ammonia cracking is an irreversible chemical reaction under working conditions. Only a dehumidification process is required to remove trace moisture from cracked gas to obtain refined hydrogen-nitrogen mixed gas. This eliminates harmful non-metallic elements such as chlorine and oxygen that cause defects in semiconductor manufacturing.

3.Sufficient & cost-effective raw material supply in China: Liquid ammonia is widely available at low market prices, with low unit consumption. 1 kg of liquid ammonia can produce 2.67 Nm³ hydrogen-nitrogen mixed protective gas.

Working Principle

Under specified pressure, temperature and the catalysis of nickel catalyst, 1 mole of gaseous ammonia decomposes into 1.5 moles hydrogen and 0.5 moles nitrogen with heat absorption. The chemical reaction formula is shown below:

2NH₃ —Catalyst→ 3H₂ + N₂ – Q

National Standard GB536-86 for Liquid Ammonia Raw Materia

Index Item	Premium Grade	First Grade	Second Grade
NH₃ Content (%)	99.9	99.8	99.6
Moisture & Oil Content (%)	0.1	0.2	0.4

Note: Liquid ammonia for ammonia cracker hydrogen generators must reach First Grade or higher per GB536-86 standard.

Saturation Temp (°C)：-30,-25,-20,-15,-10,30,-5,0,5,10,15,20,25,30

Saturation Pressure (kgf/cm²): 1.21,1.54,1.94,2.41,2.96,3.61,4.37,5.25,6.27,7.4,8.74,10.22,11.89

The hydrogen-nitrogen mixed gas generated by ammonia cracking is premium reducing protective atmosphere, widely adopted in semiconductor manufacturing, metallurgy, mechanical processing, heat treatment and other gas-dependent production & research laboratories.

Technological Process Flow

Gaseous ammonia from ammonia cylinder or storage tank passes through ammonia pressure reducing valve for pressure regulation. The treated gaseous ammonia enters gas jacket and heat exchanger to exchange heat with high-temperature cracked gas, then flows into cracking furnace filled with activated nickel catalyst. At 800℃, ammonia is fully decomposed into hydrogen and nitrogen mixture.

High-temperature cracked mixed gas flows back into heat exchanger and gas jacket to conduct heat exchange with incoming raw ammonia. It cools down cracked gas while preheating gaseous ammonia to recover waste heat for energy saving. After heat exchange, cracked gas is further cooled via radiator and cooler, then sent to purifier to remove residual water and trace unreacted ammonia, finally delivered to production terminals for use.

Important Notes:

1.Only gaseous ammonia can be fed into ammonia cracking hydrogen equipment. If liquid ammonia is output from tank or cylinder, it must be fully vaporized via vaporizer first, then depressurized before entering the cracking unit.

2.When ambient temperature is low or ammonia consumption surges, the supply of gaseous ammonia from cylinder/tank may fail to match equipment demand. Forced ammonia vaporization is required to solve insufficient gas supply; water shower vaporizer is the most common auxiliary vaporization solution.

Main Technical Specifications (Model: AQ/FC-80)

AQ/FC-80 Energy-saving Ammonia Cracking Furnace with Automatic Purification Unit

Item	Specification
Rated Gas Output	≥80 Nm³/h
Dew Point of Purified Gas	≤ -60℃ (moisture index)
Residual Ammonia Content in Purified Gas	≤ 5 ppm
Working Pressure	≤ 0.05 MPa
Power Supply	380V, 50Hz
Total Power	Cracking Furnace: 81 KW,Purification Device: 12.0 KW
Liquid Ammonia Consumption (under rated output)	20.0 kg/h
Operating Temperature of Cracking Furnace	800 ~ 850℃
Dryer Working Temperature	Ambient Temperature
Dryer Regeneration Temperature	200 ~ 250℃
Overall External Dimension	2100 × 2400 × 2500 mm (subject to actual equipment)

Technical Advantages

1.Easy maintenance & convenient overhaul.

2.Thick thermal insulation: 350mm insulation layer for furnace body, 300mm insulation layer for furnace cover.

3.Continuous gas supply protection: The unit keeps supplying protective gas automatically in case of power failure or compressed air cut-off.

4.Lower ammonia consumption during molecular sieve regeneration to save raw material cost.

Main Equipment Components

1.Furnace Liner / Cracking Vessel

2.Electric Heating Elements (Resistance Wire)

3.Heat Exchanger

4.Radiator Cooler

5.Molecular Sieve Adsorbent

6.Pneumatic Control Valves

7.Touch Screen HMI

8.Flow Detection & Electrical Control Cabinet

Function of Each Component

1.Furnace Liner: Complete catalytic cracking of ammonia into 75% hydrogen and 25% nitrogen mixed protective gas.

2.Electric Heating Element: Provide stable thermal energy to maintain optimal cracking temperature inside furnace liner.

3.Heat Exchanger: Preheat raw gaseous ammonia and recover waste heat to cool high-temperature cracked gas for energy saving.

4.Radiator Cooler: Secondary cooling of cracked gas discharged from heat exchanger.

5.Molecular Sieve: Adsorb residual moisture and trace unreacted ammonia to purify outlet protective gas.

6.Pneumatic Valves: Realize automatic switching, heating and regeneration cycle of dual molecular sieve dryers.

7.Touch Screen HMI: Set temperature parameters of cracking furnace & dryer, adjust dryer adsorption working time and regeneration cycle time.

8.Flow Detection Module: Real-time display of output ammonia cracking mixed gas flow rate.