(113b) High Performance Steam Super-Heater in Ammonia Production Lines

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.