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summary:

 

     Each kilogram of liquid ammonia cracking can produce 2.64Nm3 mixed gas, which contains 75% hydrogen and 25% nitrogen. After ammonia is cracked, the obtained gas contains less impurities (water vapor in impurities is about 2 g/m3, residual ammonia is about 0.01%), and then through molecular sieve adsorption purifier, the dew point of the gas can be reduced to -600C ~ -700C, Residual ammonia can be reduced to below 3PPM.

 

     Ammonia cracking hydrogen production furnace can be used for bright annealing of non-ferrous metals, silicon steel, chromium steel, tungsten-molybdenum alloy and stainless steel and other metal materials and parts, decarburization treatment of silicon steel sheet, copper-based, iron-based powder metallurgy sintering, metal of electric vacuum devices Hydrogen burning treatment of parts, protective sintering and sealing of semiconductor devices, raw material gas for palladium alloy membrane diffusion and purification of hydrogen, etc.

 

     The raw material ammonia is easy to obtain, the price is low, and the raw material consumption is less. Ammonia cracking to produce protective gas has the advantages of low investment, small volume and high efficiency.

 

The principle of hydrogen production

 

     Ammonia (gaseous) is cracked into 75% hydrogen and 25% nitrogen under the action of a catalyst at a certain temperature and pressure, and absorbs 21.9 kcal of heat. The main reactions are:

 

                                              2NH3—3H2+N2-21.9 kcal

 

     Because the whole process is an endothermic reaction, increasing the temperature is conducive to ammonia cracking, and at the same time it is a volume expansion reaction, reducing the pressure is conducive to the decomposition of ammonia, generally controlled at about one atmospheric pressure, and the temperature is more suitable between 800-850 ° C .

 

     The purity of cracked hydrogen is very high, and the volatile impurities in the total are only traces of residual ammonia and water. It can be seen that high-purity gas can be obtained only by removing traces of residual ammonia and water. Gas purification adopts temperature swing adsorption technology.

 

     Temperature swing adsorption (TSA) technology is a gas separation and purification process based on the adsorption performance of gas molecules on the inner surface of the adsorbent (porous solid substance) at different temperatures. Impurity gas is adsorbed at room temperature, and impurity gas is desorbed when heated. .

 

Attachment: Ammonia Decomposition Process

 

     The surface of the molecular sieve is full of micropores, which can absorb 20% of its own weight at normal temperature and pressure (water and impurities during static adsorption, and can be completely regenerated at a temperature of about 350 °C. The purification device is controlled by the valve, each time Automatically switch once every 24 hours to obtain product gas with qualified purity and impurity content.

 

Attachment: purification process flow

 

Equipment level and structural characteristics

 

     Structural features of Gaopu ammonia cracking hydrogen production furnace:

 

     Cracking tube: W-type cracking tube is made of high-quality 0Cr25Ni20 stainless steel, TIG welded, and equipped with a special catalyst of sintered nickel. A cracking rate of 99.99% was produced at a temperature of 800°C-850°C.

 

     Heating chamber: The heating chamber is heated by alloy elements with low watt density to ensure a long service life. The heating chamber adopts vacuum suction filter forming light aluminum silicate fiberboard for thermal insulation.

 

     Heating wire installation method: It is installed by hot-plugging, and the heating wire can be replaced without stopping the gas.

 

     Gas Cooler: Equipped with gas heat exchanger and airfoil water cooling pipes with riser.

 

     Temperature control: Microcomputer controller adjusts K-type thermocouple, set point temperature or control adjustment, digital display;

 

     High-efficiency vaporizer: The vaporization of liquid ammonia adopts electric heating (optional) to vaporize liquid ammonia.

 

     Structural features of hydrogen purifier:

 

     Switching control: The activation and regeneration of molecular sieve is realized after heating by built-in heater. One adsorber is in use and the other is prepared; one is in adsorption operation, and the other is in desorption regeneration; the process is controlled by valve switching and regeneration temperature.

 

     Adsorbent: Zeolite 5A type molecular sieve is used, which has strong adsorption performance. It can adsorb water vapor and impurity gas equivalent to 20% of its own weight under normal temperature and pressure. Remove trace ammonia and trace water to produce high-quality pure gas.

 

     Adsorber: The adsorber adopts the built-in rod heater of the Austrian EBNER process. The heating rod is designed with low surface load, and the heating rod does not contact the molecular sieve during heating, and the molecular sieve is heated by the heated gas, which ensures the high efficiency and reliability of the adsorber. .