Radial flow ammonia synthesis converte

Figure 1.12 Radial flow ammonia synthesis converter by Haldor-Topsoe. (Source Couper et al. [12]. Reproduced with permission of Elsevier.)...

S-200 Radial Flow Ammonia Synthesis Converter without Lower Heat Exchanger... 

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.)...

Anonymous. Radial flow ammonia converter—New ammonia synthesis design. Nitrogen 31 12 (1962). 

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).

Due to the high activity (ammonia neat value) used at above 15 MPa and the heat transfer problem of converter needs to be solved. One of the ways is to use multibeds, intercooled, radial-flow ammonia converter and to use ruthenium catalyst combined with iron catalyst. If the ruthenium catalyst was put after iron catalyst in converter, it can not only solve the heat transfer problem, but also reduce the quantity of the ruthenium catalyst. Therefore, the ruthenium catalyst can be applied in the present ammonia synthesis process. After further renovation of the process, the effect of save energy can be obtained. 

Ammonia synthesis converters with radial flow in tubular cooled catalyst beds have been suggested by Toyo Engineering Corp. [520] and in [502]. The Toyo concept has, so far, not been used industrially, while the concept described in [502] has, as mentioned above, been demonstrated in revamps of converters originally designed by SBA. It is claimed that the cross flow makes it possible -through proper design of the cooling tube bundles - to optimize the temperature profile so that it follows very closely the maximum reaction rate curve. It is furthermore reported that the heat transfer coefficients obtained in practice in... 

Haldor Topspe s ammonia synthesis technology is based on the S-200 ammonia converter. This is a two-bed radial flow converter with indirect cooling between the beds. Features of the S-200 include efficient use of converter volume and low pressure drop (factors related to the use of small catalyst particles 1.5 to 3.0 mm), and high conversion per pass due to indirect cooling85. 

Synthesis gas is compressed to the synthesis pressure, typically ranging from 140 to 220 kg/cm2g and converted into ammonia in a synthesis loop using radial flow synthesis converters, either the two-bed S-200, the three-bed S-300, or the S-250 concept using an S-200 converter followed by a boiler or steam superheater, and a one-bed S-50 converter. Ammonia product is condensed and separated by refrigeration. This process layout is flexible, and each ammonia plant will be optimized for the local conditions by adjustment of various process parameters. Topsoe supplies all catalysts used in the catalytic process steps for ammonia production. 

The ammonia synthesis loop uses two ammonia converters with three catalyst beds. Waste heat is used for steam generation downstream the second and third bed. Waste-heat steam generators with integrated boiler feedwater preheater are supplied with a special cooled tubesheet to minimize skin temperatures and material stresses. The converters themselves have radial catalyst beds with standard small grain iron catalyst. The radial flow concept minimizes pressure drop in the... 

Kellogg has developed for its ruthenium catalyst based KAAP ammonia process [404], [478] a special converter design. Four radial flow beds are accommodated in a single pressure shell with intermediate heat exchangers after the first, second and third bed. The first bed is loaded with conventional iron catalyst, the following ones with the new ruthenium catalyst. Figure 95 is a simplified sketch of the converter and the synthesis loop of the KAAP for a new plant. For revamps Kellogg has also proposed a two-bed version completely loaded with ruthenium catalyst to be placed downstream of a conventional converter [398]. 

In the early days the synthesis gas was produced at atmospheric pressure, and the synthesis gas was compressed in reciprocating compressors to pressures as high as 100 MPa in some cases. Capacities were limited to around 300 - 400 MTPD due to limitations in reciprocating compressors. However, with the development of steam reformer based front-ends and the introduction of centrifugal compressors, the ammonia plant capacities suddenly increased to 1000 MTPD with ammonia synthesis loop pressures typically around 15 MPa. Since the 1960 s new developments have been in the ammonia converter designs, such as introduction of radial flow converters and introduction of converters with multiple catalyst beds to increase ammonia conversion. 

As mentioned above, Haldor Topsoe A/S, KBR, and Uhde GmbH share the major part of the market for new ammonia synthesis technology. For plant retrofits also others are active and especially for ammonia converter revamps, Ammonia Casale offer their ammonia synthesis technology. The main feature of the Casale technology is the so-called axial-radial flow synthesis converter (55, 56), and (57). 

In Haldor Tops0e s ammonia and methanol synthesis processes a series of adiabatic beds with indirect cooling between the beds is normally used, at least in large plants. In smaller plants internally cooled reactors are considered. In ammonia synthesis, the Tops0e solution is today the so-called S-200 converter (Fig. 7) and L6j. This converter type, which is a further development of the S-100 quench-type converter, was developed in the mid seventies the first industrial unit was started up in 1978, and today about 20 are in operation or on order. Both the S-100 and the S-200 reactors are radial flow reactors. The radial flow principle offers some very specific advantages compared to the more normal axial flow. It does, however, also require special catalyst properties. The advantages of the radial flow principle and the special requirements to the catalyst are summarized in Table 5. 

In methanol synthesis, the case for radial flow converters is less obvious. Tops0e has earlier proposed, the use of one-bed radial flow converters in large methanol plants. Later analyses, partly based on a change of catalyst type, have, however, led to the conclusion that axial flow should be preferred even in very large methanol synthesis converters. The reasons for this difference in reactor concept between ammonia synthesis and methanol synthesis are in the differences between the properties of the catalysts. As mentioned above, the ammonia synthesis catalyst is ideally suited for the radial flow principle. This is not true for the methanol synthesis catalyst. The reasons for not using the radial flow principle in methanol synthesis are the following ... 

V. Vek and P. Kyril, Second Generation of Radial Flow Converters in Ammonia Synthesis, Fertiliser Industry Annual Review XI, p. 89 (1988). 

Radial flow converter for ammonia synthesis processes. (Haldor Topsoe). ZA 645279 (1964). 

Ammonia synthesis process. The converter includes a primary reaction vessel with more than two radial-flow catalytic beds, a secondary reaction vessel with more than one catalytic bed, and a separate high-temperature heat exchanger between reaction vessels. R. G. Byington and R. M. Osman (Exxon Research Engineering Co.). CA 1200673 (1986). 

In converters with radial flow the above mentioned disadvantages do not exist. Radial flow converters can be designed for very large capacities without excessive reactor diameter, and a low pressure drop can be maintained even with very small catalyst particles. The advantages of radial flow reactors for ammonia synthesis is discussed in [459, 502, 541, 542]. The pressure drop as function of catalyst particle size is discussed in [488]. Radial flow has been used in converters with cooling tubes [520], in quench cooled converters (see below) and in converters with indirect cooling (see Sect. 6.4.3.3.2). 

Ammonia synthesis at 140 bar with a two-bed radial flow converter with indirect cooling. Make-up gas addition after the separator. 

Synthesis of ammonia in a low pressure loop (at 60-70 kg/cm g). Drying of the mixture of make-up gas and recycle gas by molecular sieves. Synthesis in a proprietary three-bed radial flow converter with indirect cooling between the beds. 

The new rathenium catalyst has been used in the Pacific Ammonia Inc plant at Kitimat in British Columbia since 1992. Ammonia had been made there, from the methanol plant purge gas, since 1986 using a conventional iron synthesis catalyst. The new rathenium catalyst converter was in series with the old converter. Although in 1992 there was no additional synthesis gas to increase production capacity, the ruthenium catalyst operated well in a radial flow reactor and reduced both the steam and electricity used by 30-40% and 5-10% respectively. The new catalyst was said to be twenty times as active as the iron catalyst, and the effluent gas contained about 20% ammonia. 

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