Adsorption of Benzene Onto 10X and 13X Molecular Sieve

Authors: 
Arredondo, J. H. - Presenter, Rice University
Metcalf, A., Rice University
Hsu, B. Y., Worstell and Worstell, Consultants
Worstell, J. H., Worstell and Worstell, Consultants
The heat recovery equipment in Ammonia processes downstream the secondary reformer typically consists of a process gas cooler operating as steam generator and a steam super-heater. Those heat exchangers are major contributors for the overall process efficiency and are crucial for the production reliability.

Depending on the licensor the super-heated steam temperature is in a range of 330°C to 470°C at a pressure range 100bar to 130bar. Since high steam parameters are valuable, a further steam-super heating is performed in the primary section or by fired heaters.

For the typical application the so called U-type steam super heater was developed and established by SCHMIDTSCHE SCHACK as well as by a limited number of other heat transfer equipment suppliers approx. 15 years ago. The U-type has special features, which enable a robust mechanical design and good temperature control capability for the process gas as well as for the super-heated steam.

However, based on the process flow schema, the U-type is close to the mechanical threshold when gas and steam temperatures in the upper range will be applied. Since the steam super-heater is a valuable but critical part in the process chain of Ammonia production, SCHMIDTSCHE SCHACK has designed and manufactured a steam super-heater, which enables for higher steam parameters up to 540°C / 130bar. The design is a combination of proven features and this apparatus is currently applied at a Methanation process, but can also be installed in Ammonia production lines. This new steam super-heater therefore provides the licensor and the customer a further reliable potential for improving the overall process efficiency.

The contribution starts with a discussion on different super heater arrangements and concepts to realize such high steam parameters with reliable equipment. This is followed by a further comparison of both steam super-heater designs mentioned above. Detailed insight into the process flow is given and intelligent measures to protect the equipment against metal dusting attack are discussed. The mechanical limitations of a reliable application and operation are shown and the contribution concludes with a commercial outlook comparing the investment cost of the equipment with the additional value when increasing the super-heated steam temperature for the process.