Ammonia synthesis converter details

Figure 8. Designs of ammonia synthesis converters (a) Principle of the autothermal ammonia synthesis reactor (b) Radial flow converter with capacities of 1,800 tpd (c) Horizontal three-bed converter and detail of the catalyst cartridge. (Source Walas, M. S., Chemical Process Equipment, Selection and Design, Butterworth Series in Chemical Engineering, 1988.)...

Figure 17.21. Some recent designs of ammonia synthesis converters, (a) Principle of the autothermal ammonia synthesis reactor. Flow is downwards along the wall to keep it cool, up through tubes imbedded in the catalyst, down through the catalyst, through the effluent-influent exchanger and out. (b) Radial flow converter with capacities to l tons/day Haldor Topsoe Co., Hellerup, Denmark), (c) Horizontal three-bed converter and detail of the catalyst cartridge. Without the exchanger the dimensions are 8 x 85 ft, pressure 170 atm, capacity to 2000 tons/day (Pullman Kellogg), (d) Vessel sketch, typical temperature profile and typical data of the ICI quench-type converter. The process gas follows a path like that of part (a) of this figure. Quench is supplied at two points (Imperial Chemical Industries).

More detailed reviews of the various types of ammonia synthesis converters can be found in (2, 3). 

It has been already mentioned briefly, that compared to the synthesis section itself, where of course some progress has been made in converter design and optimization of heat recovery, the more fundamental changes over the years have occurred in synthesis gas preparation and gas compression. It is therefore appropriate to discuss the various methods for the synthesis gas generation, carbon monoxide shift conversion, and gas purification in some detail. Figure 29 shows schematically the options for the process steps for ammonia production. 

The upper part of Fig. 1 shows the synthesis gas plant which is fed from the right-hand side with methane (stream l) and air (stream 2) for a combustion process to match the heat requirements of the synthesis gas process. The combustion process delivers the exhaust gas (stream 3). The synthesis gas is produced by methane, water vapor and air (streams U, 5 6) in a primary and secondary reformer and a converter (units REF1, REF2 and CON). The raw gas (stream 28) passes the gas conditioning (SEPl) which has been detailed in Fig. 3 and the synthesis gas (stream 29) enters the ammonia plant shown in the lower part of Fig. 1. The ammonia... 

The sodium form of the ZSM-5 zeolite samples with framework content 2.6 to 2.8 Alp/U.C were synthesized using TPABr and without using template in stainless steel autoclaves under autogeneous pressure at 423 K, under static conditions, with crystallization time of 72 h. Detailed description of the synthesis method has been given in our previous publication (10). The Na-ZSM-5 samples were converted to NH4-ZSM-5 by repeated ion exchange with 5N NH4NO4 solution. NH4-ZSM-5 having 4.5 AI. 7U.C has taken for hydrothermal treatment Proton form of the above mentioned catalysts were obtained from their respective ammonia forms by calcination in presence of air at 753 K for 6 h.( 10). 

PPV (62a) has been prepared by a number of different methods which were studied in detail by Horhold and Opfermann [390]. It can be synthesized by bifunctional carbonyl olefination of terephthalaldehyde according to Wittig s reaction and from />-xylylene-bis(diethyl phosphonate), as well as by dehydrochlorination of/p-xylylene dichloride with sodium hydride in A jiV-dimethylformamide and with potassium amide in liquid ammonia. The most popular route to PPV used today is the precursor route, first described by Wessling and Zimmermann [391-394] and Kanabe and Okawara [395], starting from the monomers p-xylylene-bis(di-methylsulphonium tetrafluoroborate) [395] or chloride (Scheme 11.17) [391-394]. The latter is polymerized to yield a water soluble sulphonium salt polyelectrolyte (63d) which is then purified by dialysis [396]. The precursor polymer is converted to PPV (63e) by the thermal elimination of dimethyl sulphide and HCl. The method was later developed by Horhold et al. [397], Lenz and co-workers [398,399], Murase et al. [400] and Bradley [401], One of the major improvements within the last years has been the use of tetrahydrothio-phene instead of dimethyl sulphide in the synthesis of the precursor polymer [402]. The use of the cyclic leaving group facilitates the elimination when the precursor polymers is heated at 230-300°C and leads... 

Stability problems and performance optimization of TVA-converters are discussed in [480,481,484,485]. A classical account of operating problems in a synthesis unit using TVA-converters is given in [496] which also gives mechanical details on the construction of a TVA-converter. Drawings showing mechanical details of TVA-converters may also be found in [23, 385, 497, 498]. TVA type converters have been used extensively, and may are in operation today. This converter type has been suggested quite recently for installation in new, relatively small plants (up to about 300 MTPD of ammonia) by process licensors such as Tosoe [499] and ICI [500]. 

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