Ammonia synthesis processes

Particularly in the field of heterogeneous reactions, the above-mentioned basics of reaction equilibrium and kinetics need to be supplemented by some considerations on phase equilibria and transport phenomena. In a gas-phase reaction involving a solid catalyst, for example, the convective and diffusive transport of the reactants to and from the catalyst surface as well as the adsorption and desorption on and from the catalyst surface affect the progress of the reaction, thus the reaction itself is only one step of a complex sequence. 

Pressure affects all of the above-mentioned steps. According to the Pick s law, for example, the diffusive flux is correlated to the gradient in concentration and in case of gaseous systems also to pressure. Regarding adsorption and desorption, a reaction can be accelerated by a pressure-induced higher coverage of the catalyst surface with reactants it can, however, also be slowed down due to reduced desorption of the product. As described by, for example, the Lanffnuir isotherm or the Freundlich isotherm, these steps also depend on pressure. 

A similar situation can be found in a gas-liquid system where one reactant has to be transferred from the gas phase to the liquid phase, where the reaction finally takes place. The chemical sorption of CO2 from a gas phase using an amine solution (e.g., 

ME A and MDEA) is a typical example for such a system. Again, the convective and diffusive transport has to be considered. This time, however, a gas-liquid equilibrium, which is characterized by the identity of the C02 s chemical potential in gas and liquid phases, is involved. 

Furthermore, in some cases, pressure may force two separate phases to collapse into one, causing a completely changed reaction system with respect to mass transfer resistance and composition of the reactive phase. For example, supercritical fluids are known to show distinctively increased dissolving powers. 

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Nearly all commercial nitrogen fertilizer is derived from synthetic ammonia. However, prior to the introduction of ammonia synthesis processes in the early 1900s dependence was entirely on other sources. These sources are stdl utilized, but their relative importance has diminished. 

The ammonia synthesis process consists of a series of catalytic reactions that aim to make a mixture of N2 and H2 without components that would deactivate the catalyst. Ammonia is formed only in the last reactor. 

Braun A variation on the classic ammonia synthesis process in which the synthesis gas is purified cryogenically. Widely used since the mid 1960s. 

Claude (1) Also called Claude-Casale. A high-pressure ammonia synthesis process, developed by G. Claude in the 1920s. 

LEAD An integrated ammonia synthesis process, developed by Humphreys Glasgow. 

Mont Cenis [Named after a coal mine in the Ruhr] An early ammonia synthesis process, basically similar to the Haber-Bosch process but using coke-oven gas. Operated by The Royal Dutch Group at Ymuiden, The Netherlands, since 1929. 

A second and greater opportunity came his way in the spring of 1922. Professor Fritz Haber, discoverer of the Haber ammonia synthesis process and head of the Kaiser Wilhelm Institute for Physical Chemistry (now known as the Max Planck Institute), contacted Professor Schlenk. 

We first considered applications of this approach within process engineering. Steady-state flowsheeting or simulation tools are the workhorse for most process design studies the application of simultaneous optimization strategies has allowed optimization of these designs to be performed within an order of magnitude of the effort required for the simulation problem. An application of this strategy to an ammonia synthesis process was presented. Currently, flowsheet optimization is widely available commercially and has also been installed on the FLOWTRAN simulator for academic use. 

By analyzing energy barriers for product desorption under ammonia synthesis, CO hydrogenation, and NO reduction by CO, we can refine the models further. For these three processes, the reaction conditions are very different. The ammonia synthesis process is weakly exothermic, whereas the CO hydrogenation reaction has... 

Researchers returned to the oxidation of ammonia in air, (recorded as early as 1798) in an effort to improve production economics. In 1901 Wilhelm Ostwald had first achieved the catalytic oxidation of ammonia over a platinum catalyst. The gaseous nitrogen oxides produced could be easily cooled and dissolved in water to produce a solution of nitric acid. This achievement began the search for an economic process route. By 1908 the first commercial facility for production of nitric acid, using this new catalytic oxidation process, was commissioned near Bochum in Germany. The Haber-Bosch ammonia synthesis process came into operation in 1913, leading to the continued development and assured future of the ammonia oxidation process for the production of nitric acid. 

The Braun process is a variation on the Haber-Bosch process ammonia synthesis process in which the synthesis gas is purified cryogenically1. It has been widely used since the mid-1960 s18. (Synthesis gas is a mixture of hydrogen, carbon monoxide and carbon dioxide - see Table 5.9 for more details). 

The BYAS (Bypass Ammonia Synthesis) process can be used for economical expansion of existing ammonia synthesis plants. This process introduces additional natural gas at an intermediate stage in the process. The additional nitrogen in the air, which also has to be introduced, is removed by PSA (pressure swing absorption). The process was developed and offered by Humphreys and Glasgow in the UK1. 

The high-pressure Claude-Casale ammonia synthesis process in the 1920s.1,12,20,21... 

The LCA (Leading Concept Ammonia) is essentially a simplified form of the standard ammonia synthesis process that is more suitable for smaller plants. It is described in References 1, 26, 27, and 29. 

The BYAS (Bypass Ammonia Synthesis) process can be used for economical expansion of existing ammonia synthesis plants. It is described in Reference 1. 

The KAAP (Kellogg Advanced Ammonia process) process is the first high-pressure ammonia synthesis process that makes ammonia from nitrogen and hydrogen without the aid of an iron-containing catalyst.1 It is described in References 22-25. 

The development of a practical ammonia synthesis process in the early years of the twentieth century was a profound scientific achievement of great social significance in view of the subsequent dependence of the world on fertilizer for support of its growing population. 

Application To produce ammonia from hydrocarbon feedstocks using a high-pressure heat exchange-based steam reforming process integrated with a low-pressure advanced ammonia synthesis process. 

Dual Pressure An ammonia synthesis process, based on the AMV process but providing more capacity by removing some of the product at an intermediate stage. Developed by Krupp Uhde in 2001-2002. 

LCA [Leading Concept for Ammonia, formerly Low-Cost Ammonia] A process for making ammonia from air and natural gas. Essentially a simplified form of the standard ammonia synthesis process, more suitable for smaller plants. Thermal economies are achieved in the steam reforming section. Developed by ICI from 1985 to 1988. Two units began operating at the ICI plant in Severnside, UK, in 1988. The first non-ICI installation was designed by KTI for Mississippi Chemicals, Yazoo City, MS. The name appears to be no longer used. 

Purifier An ammonia synthesis process, developed C.F. Braun and now licensed by Kellog Brown and Root. An important feature is the cryogenic removal of inert gases from the system. Seventeen plants were operating in 2005. 

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