Ammonia production takes place worldwide, mostly in large-scale manufacturing plants that produce 183 million metric tonnes [1] of ammonia (2021) annually. [2] [3] Leading producers are China (31.9%), Russia (8.7%), India (7.5%), and the United States (7.1%). 80% or more of ammonia is used as fertilizer. Ammonia is also used for the production of plastics, fibres, explosives, nitric acid (via the Ostwald process), and intermediates for dyes and pharmaceuticals. The industry contributes 1% to 2% of global CO
2. [4] Between 18–20 Mt of the gas is transported globally each year. [5]
Before the start of World War I, most ammonia was obtained by the dry distillation of nitrogenous vegetable and animal products; by the reduction of nitrous acid and nitrites with hydrogen; and also by the decomposition of ammonium salts by alkaline hydroxides or by quicklime, the salt most generally used being the chloride (sal-ammoniac).
Adolph Frank and Nikodem Caro found that Nitrogen could be fixed by using the same calcium carbide produced to make acetylene to form calcium-cyanamide, which could then be divided with water to form ammonia. The method was developed between 1895 and 1899.
While not strictly speaking a method of producing ammonia, nitrogen can be fixed by passing it (with oxygen) through an electric spark.
Heating metals such as magnesium in an atmosphere of pure nitrogen produces the nitride, which when combined with water produce the metal hydroxide and ammonia.
The Haber process, [7] also called the Haber–Bosch process, is the main industrial procedure for the production of ammonia. [8] [9] The German chemists Fritz Haber and Carl Bosch developed it in the first decade of the 20th century. The process converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using an iron metal catalyst under high temperatures and pressures. This reaction is slightly exothermic (i.e. it releases energy), meaning that the reaction is favoured at lower temperatures [10] and higher pressures. [11] It decreases entropy, complicating the process. Hydrogen is produced via steam reforming, followed by an iterative closed cycle to react hydrogen with nitrogen to produce ammonia.
The primary reaction is:
Because ammonia production depends on a reliable supply of energy, fossil fuels are often used, contributing to climate change when they are combusted and create greenhouse gasses. [15] Ammonia production also introduces nitrogen into the Earth's nitrogen cycle, causing imbalances that contribute to environmental issues such as algae blooms. [16] [17] [18] Certain production methods prove to have less of an environmental impact, such as those powered by renewable or nuclear energy. [18]
Sustainable production is possible by using non-polluting methane pyrolysis or generating hydrogen by water electrolysis with renewable energy sources. [19] Thyssenkrupp Uhde Chlorine Engineers expanded its annual production capacity for alkaline water electrolysis to 1 gigawatt of electrolyzer capacity for this purpose. [20]
In a hydrogen economy some hydrogen production could be diverted to feedstock use. For example, in 2002, Iceland produced 2,000 tons of hydrogen gas by electrolysis, using excess power from its hydroelectric plants, primarily for fertilizer. [21] The Vemork hydroelectric plant in Norway used its surplus electricity output to generate renewable nitric acid from 1911 to 1971, [22] requiring 15 mWh/ton of nitric acid. The same reaction is carried out by lightning, providing a natural source of soluble nitrates. [23] Natural gas remains the lowest cost method.
Wastewater is often high in ammonia. Because discharging ammonia-laden water into the environment damages marine life, nitrification is often necessary to remove the ammonia. [24] This may become a potentially sustainable source of ammonia given its abundance. [25] Alternatively, ammonia from wastewater can be sent into an ammonia electrolyzer (ammonia electrolysis) operating with renewable energy sources to produce hydrogen and clean water. [26] Ammonia electrolysis may require much less thermodynamic energy than water electrolysis (only 0.06 V in alkaline media). [27]
Another option for recovering ammonia from wastewater is to use the mechanics of the ammonia-water thermal absorption cycle. [28] [29] Ammonia can thus be recovered either as a liquid or as ammonium hydroxide. The advantage of the former is that it is much easier to handle and transport, whereas the latter has commercial value at concentrations of 30 percent in solution.
Making ammonia from coal is mainly practised in China, where it is the main source. [6] Oxygen from the air separation module is fed to the gasifier to convert coal into synthesis gas (H2, CO, CO2) and CH4. Most gasifiers are based on fluidized beds that operate above atmospheric pressure and have the ability to utilize different coal feeds.
The American Oil Co in the mid-1960s positioned a single-converter ammonia plant engineered by M. W. Kellogg at Texas City, Texas, with a capacity of 544 m.t./day. It used a single-train design that received the “Kirkpatrick Chemical Engineering Achievement Award” in 1967. The plant used a four-case centrifugal compressor to compress the syngas to a pressure of 152 bar Final compression to an operating pressure of 324 bar occurred in a reciprocating compressor. Centrifugal compressors for the synthesis loop and refrigeration services provided significant cost reductions.
Almost every plant built between 1964 and 1992 had large single-train designs with syngas manufacturing at 25–35 bar and ammonia synthesis at 150–200 bar. Braun Purifier process plants utilized a primary or tubular reformer with a low outlet temperature and high methane leakage to reduce the size and cost of the reformer. Air was added to the secondary reformer to reduce the methane content of the primary reformer exit stream to 1–2%. Excess nitrogen and other impurities were erased downstream of the methanator. Because the syngas was essentially free of impurities, two axial-flow ammonia converters were used. In early 2000 Uhde developed a process that enabled plant capacities of 3300 mtpd and more. The key innovation was a single-flow synthesis loop at medium pressure in series with a conventional high-pressure synthesis loop. [30]
In April 2017, Japanese company Tsubame BHB implemened a method of ammonia synthesis that could allow economic production at scales 1-2 orders of magnitude below than ordinary plants with utilizing electrochemical catalyst. [31] [32]
In 2024, the BBC announced numerous companies were attempting to reduce the 2% of global carbon emissions caused by the use/production of ammonia by producing the product in labs. The industry has become known as "green ammonia." [33]
One of the main industrial byproducts of ammonia production is CO2. In 2018, high oil prices resulted in an extended summer shutdown of European ammonia factories causing a commercial CO2 shortage, thus limiting production of CO2-based products such as beer and soft drinks. [34] This situation repeated in September 2021 due to a 250-400% increase in the wholesale price of natural gas over the course of the year. [35] [36]
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula NH3. A stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pungent smell. Biologically, it is a common nitrogenous waste, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to fertilisers. Around 70% of ammonia produced industrially is used to make fertilisers in various forms and composition, such as urea and diammonium phosphate. Ammonia in pure form is also applied directly into the soil.
The Haber process, also called the Haber–Bosch process, is the main industrial procedure for the production of ammonia. The German chemists Fritz Haber and Carl Bosch developed it in the first decade of the 20th century. The process converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using an iron metal catalyst under high temperatures and pressures. This reaction is slightly exothermic (i.e. it releases energy), meaning that the reaction is favoured at lower temperatures and higher pressures. It decreases entropy, complicating the process. Hydrogen is produced via steam reforming, followed by an iterative closed cycle to react hydrogen with nitrogen to produce ammonia.
Urea, also called carbamide, is an organic compound with chemical formula CO(NH2)2. This amide has two amino groups joined by a carbonyl functional group. It is thus the simplest amide of carbamic acid.
Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide, in various ratios. The gas often contains some carbon dioxide and methane. It is principally used for producing ammonia or methanol. Syngas is combustible and can be used as a fuel. Historically, it has been used as a replacement for gasoline, when gasoline supply has been limited; for example, wood gas was used to power cars in Europe during WWII.
Industrial processes are procedures involving chemical, physical, electrical, or mechanical steps to aid in the manufacturing of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy industry.
Steam reforming or steam methane reforming (SMR) is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water. Commonly natural gas is the feedstock. The main purpose of this technology is hydrogen production. The reaction is represented by this equilibrium:
The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures and pressures in the presence of a nickel catalyst. It was discovered by the French chemists Paul Sabatier and Jean-Baptiste Senderens in 1897. Optionally, ruthenium on alumina makes a more efficient catalyst. It is described by the following exothermic reaction:
Gas mixtures can be effectively separated by synthetic membranes made from polymers such as polyamide or cellulose acetate, or from ceramic materials.
The water–gas shift reaction (WGSR) describes the reaction of carbon monoxide and water vapor to form carbon dioxide and hydrogen:
Coal liquefaction is a process of converting coal into liquid hydrocarbons: liquid fuels and petrochemicals. This process is often known as "Coal to X" or "Carbon to X", where X can be many different hydrocarbon-based products. However, the most common process chain is "Coal to Liquid Fuels" (CTL).
Calcium cyanamide, also known as Calcium carbondiamide, Calcium cyan-2°-amide or Calcium cyanonitride is the inorganic compound with the formula CaCN2. It is the calcium salt of the cyanamide (CN2−
2) anion. This chemical is used as fertilizer and is commercially known as nitrolime. It also has herbicidal activity and in the 1950s was marketed as cyanamid. It was first synthesized in 1898 by Adolph Frank and Nikodem Caro (Frank–Caro process).
Pressure swing adsorption (PSA) is a technique used to separate some gas species from a mixture of gases under pressure according to the species' molecular characteristics and affinity for an adsorbent material. It operates at near-ambient temperature and significantly differs from the cryogenic distillation commonly used to separate gases. Selective adsorbent materials are used as trapping material, preferentially adsorbing the target gas species at high pressure. The process then swings to low pressure to desorb the adsorbed gas.
Industrial gases are the gaseous materials that are manufactured for use in industry. The principal gases provided are nitrogen, oxygen, carbon dioxide, argon, hydrogen, helium and acetylene, although many other gases and mixtures are also available in gas cylinders. The industry producing these gases is also known as industrial gas, which is seen as also encompassing the supply of equipment and technology to produce and use the gases. Their production is a part of the wider chemical Industry.
Water gas is a kind of fuel gas, a mixture of carbon monoxide and hydrogen. It is produced by "alternately hot blowing a fuel layer [coke] with air and gasifying it with steam". The caloric yield of this is about 10% of a modern syngas plant. Further making this technology unattractive, its precursor coke is expensive, whereas syngas uses cheaper precursor, mainly methane from natural gas.
Hydrogen gas is produced by several industrial methods. In 2022 less than 1% of hydrogen production was low-carbon. Fossil fuels are the dominant source of hydrogen, for example by steam reforming of natural gas. Other methods of hydrogen production include biomass gasification and methane pyrolysis. Methane pyrolysis and water electrolysis can use any source of electricity including renewable energy. Underground hydrogen is extracted.
The Frank–Caro process, also called cyanamide process, is the nitrogen fixation reaction of calcium carbide with nitrogen gas in a reactor vessel at about 1,000 °C. The reaction is exothermic and self-sustaining once the reaction temperature is reached. Originally the reaction took place in large steel cylinders with an electrical resistance element providing initial heat to start the reaction. Modern production uses rotating ovens. The synthesis produces a solid mixture of calcium cyanamide (CaCN2), also known as nitrolime, and carbon.
Sable Chemical Industries Limited is the sole manufacturer of ammonium nitrate (NH4NO3) in Zimbabwe.
A solar fuel is a synthetic chemical fuel produced from solar energy. Solar fuels can be produced through photochemical, photobiological, and electrochemical reactions.
Power-to-gas is a technology that uses electric power to produce a gaseous fuel. When using surplus power from wind generation, the concept is sometimes called windgas.
A reversible solid oxide cell (rSOC) is a solid-state electrochemical device that is operated alternatively as a solid oxide fuel cell (SOFC) and a solid oxide electrolysis cell (SOEC). Similarly to SOFCs, rSOCs are made of a dense electrolyte sandwiched between two porous electrodes. Their operating temperature ranges from 600°C to 900°C, hence they benefit from enhanced kinetics of the reactions and increased efficiency with respect to low-temperature electrochemical technologies.