Ammonia Converter and Catalysts

Ammonia converter is the key equipment of the ammonia plant. In the process, the synthesis reaction must be carried out, as much as possible, close to the optimum reaction temperature of catalyst to achieve bigger productivity and higher synthesis rate. It should also strive to reduce the pressure drop of the converter, so as to reduce the power consumption of the recycle gas. In the structure, it should strive to be simple and reliable to meet the demand of high-temperature and high-pressm e. These are the basic principles for designing ammonia converter and one of the symbols for evaluating reactor quality. 

16 Schematic diagram of the direct heat exchange type of converter 

In the converter, only one of the three cooling methods mentioned above can be used, also two of them can be combined for application. For example, the cold-quench type is used between the first and the second bed, and the indirect heat exchange type is used between the second and the third bed. Some interchangers between beds are placed outside the converter such as Brown converter (Fig. 9.22). It is worth noting that because the ammonia synthesis reaction on the Fe catalyst needs high temperature (400-550°C) and high pressure (over 10 MPa), the 

1-Inlet annular gap 2-Top cap of the first bed 3-Gas distributor of the first bed inlet 4-the first bed catalyst 5-Outlet annular gap of the first bed 6-Interchanger in bed 7-Top cap of the second bed 8-Gas distributor of the second bed 9-The second bed catalyst lO-Outlet pipe of the second bed 11-Outlet pipe 12-Top interchanger. 

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In the foregoing sections the individual process steps involved in the production of ammonia from various feedstocks have been described. However, it is very important how these building blocks are combined with each other, and with the steam and power systems, to form a complete facility for the production of ammonia. The way this is accomplished has a major impact on plant efficiency and reliability, and much of the difference between the several ammonia processes and much of the development in ammonia production technology may today be found in these areas. It may be said that while Ammonia Technology was in the early days of the industry most often understood as Ammonia Synthesis Technology or even Ammonia Converter and Catalyst Technology , it is today interpreted as the complete technology involved in transformation of the primary feedstock to the final product ammonia. 

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