What is the production method for ammonia

The method of producing ammonia generally consists of three basic processes. Namely: separation of ammonia, ammonia synthesis, raw gas preparation, purification and compression.

(1) the preparation of raw material gas ammonia needs pure hydrogen, nitrogen gas mixture, hydrogen, nitrogen ratio of about 3 (3:1).

Coal, coke as raw material for the preparation of raw gas in two stages. The first stage is the production of semi-water gas, also known as gas production stage.

The second stage is the transformation of CO：CO + H2O ⇌ CO2 + H2 + 43KJ

The transformation is carried out with either ferrochromium or ferromagnesium as catalysts. The activity temperature of the former is low (350～520℃), but the anti-poisoning ability to H2S and so on is poor; the activity temperature of the latter is high (400～550℃), but the anti-poisoning ability to H2S and so on is stronger.

(2) purification of raw gas raw gas needs to be purified to meet the requirements of ammonia synthesis. Purification task is to remove the CO2 generated after the conversion (about 30%), residual C0 (about 2 ~ 3%) and trace O2, H2S, etc.. In addition, there are some gases, such as CH4, Ar, although non-toxic to the catalyst, but will affect the reaction rate and conversion rate of ammonia synthesis, where possible, it is best to remove.

(3) Synthesis of Ammonia The synthesis of ammonia is a reversible reaction in which heat is released and the volume of gas is reduced:

①Process conditions The selection of process conditions is aimed at achieving maximum economic efficiency. Practice has proved that, with iron based catalyst, in 3.2 × 10kPa, 450 ℃, catalyst particle size of 1.2 ~ 2.5mm, the raw gas nitrogen/hydrogen ratio of 3, circulating gas nitrogen/hydrogen ratio of 2.8, the concentration of ammonia in the export gas is larger.

The greater the pressure, the greater the reaction rate. In the past, the pressure of 3.2×10kPa was often used for production, and then the pressure was gradually reduced due to the increase in energy costs. At present, many new large-scale plant using 1.5 × 10 ~ 2.0 × 10kPa pressure, and some even with 7.1 × 10 ~ 8.1 × 10kPa pressure.

According to the activity temperature of the catalyst, the temperature of ammonia synthesis is generally controlled in the range of 400 to 500 ℃.

② catalyst ammonia synthesis using iron as the main catalyst, it has a variety of models. The A10 catalyst used in China's production, the ignition temperature of 370 ℃, heat-resistant temperature of 500 ℃, the highest activity of the temperature of about 450 ℃.

(4) When separating ammonia, the ammonia is first cooled with cold water to liquefy and separate the majority of the ammonia. Then, at a lower temperature, a small amount of ammonia is further condensed and separated with a freezer. The gas mixture after ammonia separation is used as a recycle gas and then introduced into the synthesis tower.