Ammonia Decomposition Hydrogen Production Equipment: Revealing Its Working Principle And Operating Process

Ammonia decomposition hydrogen production units are an important type of hydrogen production equipment in modern industry. By decomposing ammonia gas under specific conditions, these units produce a mixture of nitrogen and hydrogen gases, providing hydrogen resources for a wide range of applications. This article will delve into the working principles, operational procedures, and related precautions to help readers better understand this industrial equipment.

　　The working principle of the ammonia decomposition hydrogen production unit is based on the thermal decomposition reaction of ammonia gas. Under certain temperature and pressure conditions, ammonia gas (NH3) can be decomposed into nitrogen and hydrogen gas under the action of a nickel-based catalyst. This reaction can be represented by the chemical equation 2NH3 → 3H2 + N2, meaning that every 2 moles of ammonia gas decomposition produces 3 moles of hydrogen gas and 1 mole of nitrogen gas. In the resulting hydrogen and nitrogen mixture, the volume fraction of hydrogen is approximately 75%, nitrogen is approximately 25%, and there are also trace amounts of residual ammonia and other impurities.

Liquid ammonia is the primary raw material. In the plant's operational process, liquid ammonia first passes through an inlet pressure-reducing valve to reduce pressure, then enters the ammonia vaporization tank. Inside the evaporator tank, the liquid ammonia is fully depressurized and vaporized, transforming into gaseous ammonia. Next, the gaseous ammonia passes through a heat exchanger to exchange heat with the nitrogen-hydrogen mixture, is further preheated, and then enters the ammonia decomposition furnace. Inside the ammonia decomposition furnace, the gaseous ammonia is heated to a high temperature of 800–850°C and undergoes a decomposition reaction under the action of a nickel-based catalyst, producing nitrogen and hydrogen.

　　After exiting the decomposition furnace, the decomposed nitrogen-hydrogen mixture first passes through a heat exchanger to exchange heat with the ammonia gas entering the decomposition furnace, thereby cooling down. This process not only helps recover heat but also reduces the temperature of the nitrogen-hydrogen mixture. Subsequently, the nitrogen-hydrogen mixture undergoes further cooling through a water cooler to ensure smooth subsequent processing.

The cooled nitrogen-hydrogen mixture enters the molecular sieve purification unit. Here, 5A molecular sieves utilize their large specific surface area and adsorption properties to deeply adsorb and purify residual ammonia in the mixture. After molecular sieve treatment, the ammonia content in the nitrogen-hydrogen mixture can be reduced to below 3 ppm, resulting in a pure nitrogen-hydrogen mixture.

　　During the operation of the ammonia decomposition hydrogen production unit, the following points should be noted:

　　1. The airtightness of the equipment is critical. Regular inspections must be conducted to ensure that all connections, such as nuts and bolts, are secure and free from leaks to prevent gas leakage that could compromise safety and production efficiency.

         2. Temperature control is essential for the normal operation of the equipment. The operational status of temperature gauges and thermocouples must be monitored at all times to ensure that the indicated temperature matches the actual temperature, preventing equipment damage due to overheating.

　　3. When the equipment needs to be insulated for an extended period without ammonia gas input, the automatic temperature control must be limited to no more than 500°C to prevent catalyst damage.

        4. During regeneration, the drain valve must be opened every hour for drainage, and the status of the temperature controller must be monitored to prevent uncontrolled overheating.

        5. During operation, valves must be opened or closed according to different operational conditions to prevent operational errors from affecting purification efficiency.

　　Additionally, to ensure the normal operation of the equipment and the purity of the gas, regular inspections should be conducted on gas purity, the operational status of the temperature controller, and the set values of the electric contact pressure gauge. When restarting the equipment after shutdown, nitrogen should be introduced for purging to remove any air that may have entered the system.

　　In summary, the ammonia decomposition hydrogen production unit achieves the transformation from liquid ammonia to pure nitrogen-hydrogen mixed gas through a series of complex physical and chemical reaction processes. In actual operation, strict adherence to operating procedures and precautions is essential to ensure the safe and stable operation of the equipment and the purity of the gas. This equipment not only provides an important hydrogen resource for modern industry but also drives the development and progress of related fields.