Ammonia Braun process

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

Purifier An ammonia synthesis process, developed and sold by C. F. Braun, CA. 

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). 

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. 

It is well known that the conversion of hydrogen and nitrogen per pass is only 20%-30% for the present catalytic ammonia synthesis technology (Table 1.4). Most synthesis gases need to be returned to the reaction system, which increases power consumption. In order to increase conversion per pass, it must increase the outlet ammonia concentration of reactor. Accordingly, it can be seen from Table 1.4 that it is necessary to increase reaction pressure for small and medimn scale aimnonia plants and Topspe process, or to reduce the content of inert gas in sjmthesis gas for Topspe and Braun processes, or to reduce ammonia concentration in the inlet of converter for small and medium scale ammonia plants and Kellogg process. But all of these operations will add the power consumption or unit gas consumption. 

Multistage ammonia synthesis process which uses feed and high-pressure steam generation to cool the products of intermediate stages. B. J. Grotz (C. F. Braun Co.). AU 8321381 (1984) GB 2144724 (1985) US 4501123 (1985). 

In the C. F. Braun process for ammonia manufacture, excess air is added in the second reformer. The excess nitrogen thus introduced must be removed prior to the synthesis step to avoid excessive loss of hydrogen and excessive compression costs. At the same time that the excess nitrogen is condensed and removed, the remaining traces of carbon monoxide, the methane, and most of the argon are removed, leaving a gas comparable to that produced by the nitrogen wash operation. 

In some ammonia plants, the residual methane (ca. 1% by volume) and some of the residual argon (ca. 0.3% by volume) are completely removed by low temperature conden.sation, as is surplus nitrogen from the. secondary reforming process (Braun purifier concept). 

Processes Small and medium scale ammonia plants Kellogg Topsoe Braun ICl AMV... 

Fig. 9.4 Process flow of Braun synthesis ioop 1-Synthesis gas compressor 2-4-Converter 5,9-Heat exchangers 6-8-Waste heat boilers 10-Ammonia cooler 11-Separator 12-Liquid ammonia tank 13-Set of recovery ammonia from vent gas.

The ammonia converter in the purifier process is the Braun 2-stage adiabatic synthesis converter. In process engineering terms this is a two-bed, axial-flow converter with heat exchange between the beds. However, the mechanical design differs from the majority of modem converters in that each catalyst bed is enclosed in its own separate pressure shell (see Fig. 7.9). 

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