Ammonia converter Casale

As discussed above, several different types of ammonia converters are available. These types include axial quench converters (e.g., standard Kellogg reactors), tube cooled converters (e.g., TVA and Synetix designs), axial-radii designs (e.g., Ammonia Casale retrofit) and Kellogg s horizontal design. Typical operating data for different types of ammonia converters are shown in Table 6.4204. 

Casale axial-radial technology for the ammonia converter... 

Ammonia Casale SA Ammonia Natural gas (NG) Process produces anhydrous ammonia from natural gas by applying Casale s high-efficiency secondary reformer design, axial-radial technology for shift conversion, ejector ammonia wash system, axial-radical technology for ammonia converter and advanced waste-heat boiler design in the synthesis loop. 5 2010... 

The Casale method of operation Is based upon thermal control of the ammonia converter. In order to effect this control a certain percentage (supposedly one-third) of the ammonia formed is left in the gases returning to the catalyst, thus retarding the rate of conversion and In turn holding down the generation of heat. Operation is carried on at a... 

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). 

As far as ammonia converter design is concerned. Ammonia Casale s technology has already been introduced in Section 7.2.3. Ammonia Casale converter designs using the axial-radial flow concept have achieved considerable success in recent years, particularly for modification of existing axial-flow converters. These converter retrofits can be achieved by in situ changes to the converter internals in the case of converters where the catalyst basket cannot be removed from the pressure shell. 

Fig. 17. (a) Kellogg vertical quench converter (b) Ammonia Casale converter basket modification. 

The ammonia loop is based on the Ammonia Casale axial-radial three-bed converter with internal heat exchangers. Heat from the ammonia synthesis is used to 1) generate high-pressure steam and 2) preheat feed gas. The gas is then cooled and refrigerated to separate ammonia product. Unconverted gas is recycled to the syngas compressor208 214... 

For revamps of ammonia synthesis converters, Ammonia Casale offers 1) an in-situ modification of bottle-shaped converters of the Kellogg type, and 2) a three-bed intercooled configuration. The intercooled design is similar in some ways to the Uhde design discussed below213. 

Axial-radial flow pattern was introduced by Ammonia Casale. Converters with strictly radial gas flow require mechanical sealing of the top of each catalyst bed... 

An axial-radial flow converter has been introduced by Ammonia Casale [490,492, 551-553]. The special feature of this design is that gas can enter each catalyst bed both from the top (in axial direction) and from the side through perforations (in radial direction), see Fig. 6.11 (from [492]). The gas leaves the catalyst bed through perforations in the inner wall. There are no perforations in an upper part of the inner wall, and the gas entering at the top of the bed is therefore forced to flow through part of the catalyst in partially axial flow before it can leave the catalyst bed. This flow principle can be used in quench cooled... 

Fig. 6.11. Principle of axial-radial flow converter. Ammonia Casale design (from [492])...

Fig. 6.19. Four bed Kellogg quench cooled converter after modification to Ammonia Casale s four bed quench cooled axial-radical flow concept (from [591])...

Ammonia Casale Axial-radial flow through three catalyst beds with inter-bed heat exchange or quench cooling. A second converter holding the third bed has been used. 

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