Category: Liquid Ammonia
Liquid Ammonia Storage Tanks
Liquid ammonia, also known as anhydrous ammonia, is a colorless liquid with a strong irritating odor. As an important chemical raw material, ammonia is usually obtained as liquid ammonia by pressurizing or cooling the gaseous ammonia gas for convenient transportation and storage. Liquid ammonia is easily soluble in water, and when dissolved in water, it forms ammonium ions NH4+ and hydroxide ions OH-, which are alkaline solution. Liquid ammonia is stored in pressure-resistant cylinders or steel tanks, and cannot coexist with acetaldehyde, acrolein, boron and other substances. Liquid ammonia is widely used in industry and is corrosive and volatile, so it has a high incidence of chemical accidents.
2013-2017 Liquid Ammonia Industry Research and Investment Prospects Assessment ReportLiquid ammonia is mainly used to produce nitric acid, urea and other chemical fertilizers, and can also be used as a raw material for medicine and pesticides.
In the defense industry, it is used to make rocket and missile propellants. It can be used as an ammonia raw material for organic chemical products. Because liquid ammonia is converted into gaseous ammonia after gasification, it can absorb a large amount of heat and is known as a "refrigerant". At the same time, liquid ammonia has a certain bactericidal effect, so it is used for sterilization and cooling in the poultry farming industry. Liquid ammonia can also be used for mercerization finishing of textiles. The lone electron pairs in the NH3 molecule tend to form coordination bonds with other molecules or ions to form various forms of ammine compounds.
Liquid ammonia is a good solvent. Due to the molecular nature and the presence of hydrogen bonds, liquid ammonia is very similar to water in many physical properties. Some active metals can replace hydrogen from water and form hydroxides, but it is not so easy to replace hydrogen in liquid ammonia. But liquid ammonia can dissolve metals to form a blue solution. This metal liquid ammonia solution can conduct electricity and slowly decompose to release hydrogen, and has strong reducing properties.
For example, when metallic sodium is dissolved in liquid ammonia, it loses its valence electrons to generate positive ions: liquid ammonia is heated to 800-850°C, and under the action of a nickel-based catalyst, ammonia is decomposed to obtain a hydrogen-nitrogen mixed gas containing 75% H2 and 25% N2. The gas produced by this method is a good protective gas and can be widely used in the semiconductor industry, metallurgical industry, and other industries and scientific research that require a protective atmosphere.
Ammonia and acetic acid gas are heated to 420°C and synthesized under the action of a catalyst to synthesize acetonitrile.
Ammonia synthesis is the process of ammonia production, whose task is to synthesize the refined hydrogen-nitrogen mixture into ammonia in a fast and economical way under the action of a catalyst. For the synthesis system, liquid ammonia is its product.
Industrial ammonia synthesis of various processes are generally categorized by the level of pressure.
1. High pressure method:
Operating pressure of 70 ~ 100MPa, temperature of 550 ~ 650 ℃. The main advantage of this method is that the ammonia synthesis rate is high, the ammonia in the mixture is easy to be separated. Therefore, the process, equipment are more compact. However, because of the high synthesis rate, more heat is released, the catalyst temperature is high, easy to overheat and lose activity, so the service life of the catalyst is shorter. And because of the high temperature and high pressure operation, the equipment manufacturing, material requirements are higher, the investment cost is large. This method is seldom used in industry.
2. Medium pressure method:
Operating pressure of 20 ~ 60MPa, temperature 450 ~ 550 ℃, its advantages and disadvantages between the high-pressure method and the low-pressure method, this method is more mature technology, the economy is better. Because the determination of the synthesis pressure, no more than from the equipment investment and compression power consumption of these two aspects to consider. From the point of view of power consumption, the power consumption of the synthesis system accounts for the proportion of the total power consumption of the plant. Power consumption not only depends on the pressure term, but also depends on other process indicators and the arrangement of the process. In general, in the range of 15 ~ 30Pa, the difference in power consumption is not big, so the world uses this method a lot.
3. Low-pressure method:
The operating pressure is about 10MPa and the temperature is 400～450℃. Because the operating pressure and temperature are relatively low, so the equipment requirements are low, easy to manage, and the catalyst activity is higher, which is the advantage of this method. However, the catalyst used in this method is very sensitive to poisons, easy to be poisoned, and the service life is short, so the purity of the raw gas refining requirements are strict. And because of the low operating pressure, the ammonia synthesis rate is low, the separation is more difficult, and the process is complicated. The actual industrial production of this method has not been used. Ammonia synthesis process can be roughly divided into: the preparation of raw gas; raw gas purification; gas compression and ammonia synthesis of four major parts.
4. Other methods:Aniline industrialized continuous production of diphenylamine (under the action of the catalyst) in the process of by-products of ammonia generation, the ammonia compressed and cooled down into liquid ammonia. In this process to carry out sewage, and bring impurities, so the liquid ammonia purity is lower, the use is limited.
