How is ammonia gas liquefied?

2023-07-28

1. How is ammonia gas liquefied?

High pressure: the critical temperature of ammonia gas is 132.4C, beyond this temperature ammonia gas is not easy to liquefy. But under high pressure conditions, ammonia can be liquefied even at temperatures below the critical temperature. Under normal circumstances, as long as the ammonia pressure is above 5.6MPa, it can be liquefied into ammonia water.
Low temperature: Compared with other gases, ammonia is easier to be liquefied. One of the main reasons is that the critical temperature of ammonia is relatively low. Therefore, ammonia gas is more easily liquefied at low temperature. At standard atmospheric pressure, the boiling point of ammonia is about 33.34°C, and at this temperature, ammonia is already in a liquid state.
In the air at high temperature, ammonia molecules are easily combined with water molecules to form ammonia water, which is a liquid ammonia gas solution.
Volatility: The molecular structure of ammonia gas is simple, the force between molecules is relatively weak, and ammonia gas is extremely volatile. Therefore, as long as the temperature and pressure of the gas are sufficiently lowered, ammonia gas can be easily liquefied.

2. Why is ammonia lighter than air?

Ammonia is less dense than air. If the relative molecular mass of a certain gas is known, according to its relative molecular mass, you can judge its density compared with that of air. The average relative molecular mass of air is 29. Calculate its relative molecular mass. If it is greater than 29, the density is greater than air, and if it is less than 29, the density is smaller than air.

3. What happens when ammonia is left in the air?

explosion occurs. Ammonia water is a colorless gas with a strong irritating odor and is easily soluble in water. It may explode when the air contains 20%-25% ammonia. Ammonia water is an aqueous solution of ammonia. The industrial product is a colorless and transparent liquid with a strong and spicy suffocating smell.

4. How much ammonia is toxic in the air?

When the concentration of ammonia in the air is 67.2mg/m³, the nasopharynx feels irritated; when the concentration is 175~300mg/m³, the nose and eyes are obviously irritated, and the breathing heart rate is accelerated; when the concentration reaches 350~700mg/m³, workers cannot work; When the concentration reaches 1750~4000mg/m³, it can be life-threatening.

5. What are the uses of ammonia gas?

1. Promote plant growth: Ammonia is an important source of nitrogen needed for plant growth, which can improve soil fertility and promote plant growth and development.

2. Manufacture of chemical fertilizers: Ammonia is an important raw material for the manufacture of nitrogen fertilizers. After chemical reactions, it can be made into ammonia water, urea, ammonium nitrate and other fertilizers.

3. Refrigerant: Ammonia has good refrigeration performance and is widely used in the manufacture of refrigerants, refrigeration equipment and other fields.

4. Detergent: Ammonia gas can be used to clean glass, metal surfaces, kitchens, etc., and has the functions of decontamination, deodorization, and sterilization.

6. How does an ammonia manufacturing plant produce ammonia?

1. Ammonia production by the Haber method:
N2(g)+3H2(g)⇌2NH3(g) △rHθ=-92.4kJ/mol (reaction conditions are high temperature, high pressure, catalyst)
2. Ammonia production from natural gas: natural gas is desulfurized first, then undergoes secondary transformation, and then undergoes processes such as carbon monoxide conversion and carbon dioxide removal, to obtain a nitrogen-hydrogen mixture, which still contains about 0.1% to 0.3% of carbon monoxide and carbon dioxide (volume ), after being removed by methanation, a pure gas with a hydrogen-to-nitrogen molar ratio of 3 is obtained, which is compressed by a compressor and enters the ammonia synthesis circuit to obtain the product ammonia. The synthetic ammonia production process using naphtha as raw material is similar to this process.
3. Ammonia production from heavy oil: Heavy oil includes residual oil obtained from various advanced processes, and partial oxidation method can be used to produce synthetic ammonia raw material gas. The production process is simpler than natural gas steam reforming method, but an air separation device is required. The oxygen produced by the air separation unit is used for the gasification of heavy oil, and the nitrogen is used as raw material for ammonia synthesis.
4. Ammonia production from coal (coke): coal direct gasification (see coal gasification) has various methods such as atmospheric pressure fixed bed intermittent gasification, pressurized oxygen-steam continuous gasification, etc. For example, in the early Haber-Bosch process for ammonia synthesis, air and steam were used as gasification agents to react with coke at normal pressure and high temperature to produce gas with a molar ratio of (CO+H2)/N2 of 3.1 to 3.2, called For semi-water gas. After the semi-water gas is washed and dedusted, it goes to the gas cabinet, and after being transformed by carbon monoxide, and compressed to a certain pressure, it is washed with pressurized water to remove carbon dioxide, and then compressed with a compressor and then washed with cuproammonia to remove a small amount of carbon monoxide and carbon dioxide. , and then sent to ammonia synthesis.

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