Liquid ammonia (chemical formula: NH₃) is a colorless gas with a pungent odor that can be liquefied into a liquid state under low temperature and high pressure. As an important industrial chemical, liquid ammonia plays a key role in many industrial fields. This article will introduce in detail the main industrial applications of liquid ammonia, including its use in chemical industry, refrigeration, agriculture, metal processing and environmental protection.
(i) Synthetic ammonia and fertilizer production: Liquid ammonia is one of the main products of the synthetic ammonia industry, and synthetic ammonia is a key raw material for the production of fertilizers. In the Haber process, nitrogen and hydrogen react under high temperature and high pressure and catalyst to produce ammonia, which is then liquefied into liquid ammonia. Liquid ammonia can be further processed to produce urea, ammonium nitrate, ammonium phosphate and other fertilizers, which are widely used in agricultural production, providing crops with essential nitrogen elements and significantly improving the yield and quality of crops.
(ii) Synthetic organic chemicals: Liquid ammonia also plays an important role in organic chemical synthesis. Ammonia can be used as a nitrogen source to participate in a variety of organic reactions. For example, ammonia is one of the important raw materials in the synthesis of amine compounds, nitrile compounds and amide compounds. In addition, liquid ammonia can also be used to produce organic chemicals such as methanol and ethanolamine, which are widely used in chemical industry, pharmaceuticals and materials science.
(iii) Production of inorganic chemicals: Liquid ammonia can also be used to produce a variety of inorganic chemicals. For example, ammonia reacts with carbon dioxide to produce ammonium bicarbonate, which is a commonly used fertilizer. In addition, liquid ammonia can also be used to produce ammonium hydroxide (ammonia water), which has important applications in water treatment, textile printing and dyeing, and metal processing.
(I) Refrigerant: Liquid ammonia is one of the most widely used refrigerants. Its refrigeration principle is based on the evaporation heat absorption characteristics of liquid ammonia. In the refrigeration system, liquid ammonia evaporates through the evaporator and absorbs heat from the surrounding environment, thereby reducing the ambient temperature. Liquid ammonia has a large latent heat of evaporation, high refrigeration efficiency, and can achieve a lower refrigeration temperature (usually below -30°C). Therefore, it is widely used in cold storage, food processing, chemical cooling, and low-temperature laboratories.
(II) Advantages of refrigeration system: Liquid ammonia refrigeration system has multiple advantages. First, liquid ammonia has high refrigeration efficiency and can achieve effective refrigeration effect at lower temperatures. Second, the chemical properties of liquid ammonia are relatively stable, not easy to decompose, and have a long service life. In addition, the design and operation costs of liquid ammonia refrigeration systems are relatively low, which is suitable for large-scale industrial applications.
However, the use of liquid ammonia also has certain safety risks. Liquid ammonia has a strong pungent odor, is harmful to the human body at high concentrations, and is prone to fire and explosion when leaking. Therefore, the safe design and operating procedures of liquid ammonia refrigeration systems are crucial.
(i) Directly as a fertilizer: Liquid ammonia itself can be directly applied to farmland as a fertilizer. Liquid ammonia will gradually convert into ammonium ions (NH₄⁺) in the soil and be absorbed and utilized by plants. Liquid ammonia fertilizer has a high nitrogen content (about 82%), which can provide rich nitrogen elements for crops and promote plant growth. However, due to the volatility and corrosiveness of liquid ammonia, its direct application requires strict control of the application amount and application method to avoid negative impacts on the environment and crops.
(ii) Production of other fertilizers: Liquid ammonia is a key raw material for the production of a variety of fertilizers. For example, urea (CO(NH₂)₂) is produced by the reaction of liquid ammonia and carbon dioxide under high temperature and pressure. Urea is an effective nitrogen fertilizer widely used in agricultural production. In addition, liquid ammonia can also be used to produce ammonium nitrate (NH₄NO₃) and ammonium phosphate ((NH₄)₃PO₄), which can provide a variety of nutrients such as nitrogen and phosphorus to meet the needs of different crops.
(i) Metal heat treatment: Liquid ammonia has important applications in metal heat treatment. For example, in the nitriding process, liquid ammonia is used as a nitrogen source, and the active nitrogen atoms generated by decomposition penetrate into the metal surface to form a nitride layer, thereby improving the hardness and wear resistance of the metal. The nitriding process is widely used in the manufacture of high-precision mechanical parts, such as gears, bearings and molds.
(ii) Metal cleaning and degreasing: Liquid ammonia can also be used for cleaning and degreasing of metal surfaces. Ammonia water (aqueous solution of liquid ammonia) has good solubility and alkalinity, and can effectively remove oil, scale and other impurities on the metal surface. In the metal processing process, cleaning and degreasing are important steps to ensure the quality of subsequent processing. The use of liquid ammonia can significantly improve the cleanliness of the metal surface and processing efficiency.
V. Application in the field of environmental protection
(i) Waste gas treatment: Liquid ammonia plays an important role in waste gas treatment. For example, in the selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) technologies, liquid ammonia is used as a reducing agent to remove nitrogen oxides (NOₓ) from flue gas. By spraying ammonia into high-temperature flue gas, ammonia reacts with nitrogen oxides to produce nitrogen and water, thereby effectively reducing nitrogen oxide emissions and reducing air pollution.
(II) Wastewater treatment: Liquid ammonia can also be used for wastewater treatment. Ammonia water (aqueous solution of liquid ammonia) is alkaline and can neutralize acidic substances in wastewater and adjust the pH value of wastewater. In addition, ammonia water can also be used as a flocculant to promote the aggregation and precipitation of suspended particles in wastewater, thereby improving the treatment efficiency and water quality of wastewater.
(I) Energy field: Liquid ammonia is receiving more and more attention as a potential energy carrier. Liquid ammonia can store a large amount of hydrogen and exists in liquid form at room temperature, which is convenient for transportation and storage. In the future, liquid ammonia is expected to play an important role in the hydrogen economy and become a clean and effective energy carrier.
(II) Materials Science: Liquid ammonia also has important applications in materials science. For example, in semiconductor manufacturing, liquid ammonia can be used in cleaning and etching processes to remove impurities and oxide layers on the surface of silicon wafers. In addition, liquid ammonia can also be used to prepare some special materials, such as nitride ceramics and carbide ceramics.
The above is the application of liquid ammonia in industry. As an important industrial chemical, it has a wide range of applications in many fields such as chemical industry, refrigeration, agriculture, metal processing and environmental protection. Its unique physical and chemical properties, such as low boiling point, high volatility and good solubility, make it irreplaceable in industrial production. However, the use of liquid ammonia also has certain safety risks, and it is necessary to strictly abide by operating procedures and safety measures to ensure its safe and effective application. If you have any other questions, please leave us a message!
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