The most Advanced Technologies for ... - CASALE GROUP

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Axial-Radial Shift Converter Axial-radial shift converter The new design developed by Ammonia Casale for shift converters is based on the used of the axial-radial catalyst bed and can be applied both to revamping and to new converters. The shift conversion section is often one of the main bottlenecks in an ammonia plant, particularly as the catalyst ages and loses activity. The new axial-radial confi guration has an inherently low pressure drop over the catalyst bed, and this makes it possible to use a smallersized catalyst, which is more active and more resistant to poisons. If the plant capacity needs to be increased, the transformation of the existing shift converters into axial-radial shift converters can de-bottleneck the shift section. The lower pressure drop will, in fact, eliminate the hydraulic constraints allowing the system to operate with a higher gas fl ow, and, at the same time, reduce the specifi c energy consumption. Moreover, the higher effi ciency of the small size catalyst will allow increasing the conversion even if the residence time and the steam to carbon ratio are decreased as a consequence respectively of the capacity increase and other modifi cations as part of the plant revamping. The higher conversion will give also a lower average CO concentration at the outlet, correspondingly increasing the ammonia production obtained from a given amount of process gas. Furthermore, the axial-radial shift converter, due to its small catalyst size, is more resistant to poisons, granting a longer catalyst life with smaller loaded volumes. An existing shift converter can easily be transformed to the axialradial design by introducing new vertical cylindrical perforated inlet and outlet walls in prefabricated sections, which are assembled inside the existing converter vessel. The new design has also the following additional features: • the catalyst is protected from water droplets carried over from any upstream locations; • different volumes of catalyst can be loaded with no need for mechanical modifi cations; • it is easy to operate. Axial-radial synthesis converter The ammonia converter is one of the most critical items when planning a revamp to save energy or increase capacity, and Ammonia Casale has developed various synthesis converter designs to be able to offer to the industry always the most effi cient and advanced solution for its needs. All Casale ammonia converter designs are based on the axial-radial bed design that guarantees highest effi ciency, with the use of 1.5-3 mm size catalyst, and lowest pressure drop. One fundamental innovation introduced by Casale in synthesis converter design, which also contributes to reaching higher effi ciency, is the three-bed confi guration, normally with inter-bed heat exchangers. This confi guration, introduced by Casale in the late 80’s, gives maximum thermodynamic effi ciency and the highest catalyst utilization. Another fundamental innovation introduced by Casale is the “insitu” modifi cation of bottle-shaped converters of the type found in many Kellogg plants. This concept allows the revamping of existing converters without having to replace the converter itself, with a considerable reduction of the investment cost. The Casale axial-radial ammonia converter design also enables the recovery of the reaction heat at the highest temperature level, generating high-pressure steam. 3 Three bed indirectly-cooled ammonia converter projects in terms of capacity increase and reduction in energy consumption. Casale now has more than 140 converters onstream, out of which about 50 are “insitu” modifi cations and about 40 are three-bed inter-cooled full bore opening converters. For optimal and safest operating conditions, the Casale axial-radial ammonia converter design also allows fully independent control of the inlet temperature of each catalyst bed. Pseudo-isothermal synthesis converter In order to cope with demands for very large increases in plant capacity, requiring the highest possible increase in converter effi ciency in order to maintain the feasibility of the revamping approach, Ammonia Casale has developed the pseudo-isothermal ammonia synthesis converter, which is able to push the effi ciency of the Casale converter even The continuous development and improvement of Casale ammonia converters has enabled us to tackle more and more challenging revamping Pseudo-isothermal ammonia synthesis converter
further then the three beds intercooler design. This converter, based on direct heat removal from the catalyst bed with plate elements, reaches the ultimate converter effi ciency. The catalyst beds, design according to the axial-radial bed concept, are always operating along the maximum reaction rate curve. Two pseudo-isothermal ammonia converters are in operation. A more detailed description of this type of technology is given in the section covering methanol technologies. Secondary reformer burner Ammonia Casale has developed, through its sister company Casale Chemicals, a new secondary reformer burner design utilizing advanced fl uid dynamic simulation techniques. The Casale advanced secondary reformer burner achieves the following goals: • low pressure losses in both the air and primary reformer streams (
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