What are the production processes for synthetic ammonia?

The production process includes the following steps: 1. Raw gas preparation – the task here is to produce the nitrogen and hydrogen gases required for synthesizing ammonia. These gases can be obtained by mixing hydrogen and nitrogen that have been produced separately, or by generating a mixture of hydrogen and nitrogen at the same time. Hydrogen is derived from water vapor and various fuels containing hydrocarbons, while nitrogen comes from air. 2. Desulfurization – desulfurizing agents are used to remove sulfides from the raw gas. 3. Shift reaction – carbon monoxide reacts with steam to produce hydrogen and carbon dioxide, thereby removing most of the carbon monoxide present in the raw gas. 4. Desulfurization again – after the shift reaction, the raw gas contains a significant amount of carbon dioxide, which comes both from the raw gas preparation process and from the shift reaction itself. The task is to remove most of the carbon dioxide from the feed gas using a decarburization solution. 5. Process for removing small amounts of carbon monoxide and carbon dioxide: The purpose of this process is to eliminate the remaining carbon monoxide and carbon dioxide in the feed gas, thereby obtaining a pure hydrogen-nitrogen mixture. 6. Compression process: First, the feed gas is compressed to the pressure required for purification; the gases are then purified to yield a pure hydrogen-nitrogen mixture. This mixture is subsequently compressed to the pressure necessary for the ammonia synthesis reaction. 7. Ammonia synthesis process: Ammonia is synthesized from hydrogen and nitrogen under conditions of high temperature, high pressure, and in the presence of a catalyst. 8. The main raw materials include fuels such as coke, coal, natural gas, heavy oil, and light oil, as well as water vapor and air. Last edited by *aoye613 on 2009-3-16 at 14:54

The ammonia synthesis process involves the following steps: coal crushing and screening, coal gasification, gas pre-treatment, gas shift reaction, removal of residual sulfur or CO₂ through low-temperature methanol washing, methanation, and then compression of the syngas to produce ammonia. Most of the gas, after pretreatment, goes into the ammonia synthesis process, while a small portion is used as fuel for gas turbines to drive the gas compressors. The waste heat from the exhaust gases of gas turbines and the waste heat generated during the process is utilized to produce superheated steam at 2.5–6.5 MPa. This steam is first used in steam turbines to generate power, and then as process steam. Its lower-grade waste heat is exploited by circulating hot water to supply steam to the gas conversion process, thereby avoiding the use of medium-pressure steam.

Introduction to natural gas processing: 1. Natural gas cleaning -- compression -- hydrogen sulfide removal -- first-stage and second-stage conversion -- shift reaction -- carbon dioxide removal -- methanation -- compression -- synthesis of liquid ammonia -- cryogenic recovery. Introduction to coal processing: 1. Coal gasification -- desulfurization -- shift reaction -- carbon dioxide removal -- methanation -- compression -- synthesis of liquid ammonia -- cryogenic recovery

(1) Kellogg process. The first set of large-scale ammonia synthesis plants with low energy consumption, designed by the American company Kellogg, was put into operation in 1983, with an energy consumption of 29.31 GJ per ton of ammonia produced. After the 1990s, the company, in collaboration with BP, developed more advanced ammonia synthesis processes – the KAAP and KRES combined technologies – which reduced the energy consumption per ton of ammonia to 25.96–27.21 GJ, representing a significant breakthrough in ammonia synthesis technology. The KAAP technology uses Fe-based catalysts for ammonia synthesis with high activity at low temperature and pressure. The KRES technology is a self-heating conversion technique; the equipment consists of a heat-exchanging first-stage conversion furnace and an adiabatic second-stage conversion furnace. The hot converted gas coming out of the second-stage furnace provides all the necessary heat to the first-stage furnace through heat exchange, thereby significantly reducing energy consumption. (2) Braun process. The energy-saving measures adopted by Brown Company in the United States mainly involve reducing the consumption of natural gas as fuel – that is, reducing the load on the first-stage converter (raising the CH4 content at the outlet from 10% to around 30%) and increasing the load on the second-stage converter while adding excess air there (which generates a large amount of reaction heat to supply the heat needed for the conversion of residual CH4). This results in a lower temperature in the first-stage converter and thus less consumption of natural gas as fuel. At the same time, deep cryogenic purification is used to remove excess nitrogen, and a gas turbine drives the air compressor, resulting in an energy consumption of 28.4 GJ per ton of ammonia. In China, energy-saving technologies with a low water-to-carbon ratio have been applied to a section of the converter used in the imported Brown unit, while the ammonia synthesis process employs a three-tower and three-waste-heat boiler system to generate high-pressure steam from waste heat, thereby further reducing energy consumption. (3) ICI process. The AM-V process of the British company ICI, in addition to adopting some energy-saving measures from the Brown process, is primarily characterized by the development and use of Fe-Co catalysts for ammonia synthesis that exhibit good activity at low temperatures and pressures. In 1988, ICI developed a simplified and scaled-down LCA process, constructing two plants with a daily ammonia production capacity of 450 tons each; the energy consumption per ton of ammonia was 29.31 GJ, demonstrating that medium-sized ammonia synthesis plants can also achieve energy-saving levels comparable to those of large-scale plants. (4) KPK process. The KPK process is an abbreviation for KRES/PURIFIER/KAAP; it incorporates advanced technologies from Kellogg and Braun. It features the use of heat-exchange converters in place of traditional single-stage conversion furnaces, as well as ruthenium-based catalysts and cryogenic purification techniques, making it a new type of energy-efficient ammonia synthesis process.