A DUAL-CATALYST BED CONCEPT FOR INDUSTRIAL METHANOL SYNTHESIS

Abstract

The present work investigates a dual-catalyst bed concept for industrial methanol synthesis. A system with two catalyst beds instead of a single catalyst bed is developed for methanol synthesis. In the first catalyst bed, the synthesis gas is partly converted to methanol in a conventional water-cooled Lurgi type reactor. This bed functions at a higher than normal operating temperature and at high yield. In the second bed, the reaction heat is used to preheat the feed gas to the first bed. The continuously reduced temperature in this bed provides increasing thermodynamic equilibrium potential. In this bed, the reaction rate is much lower and, consequently, so is the amount of reaction heat. This feature results in milder temperature profiles in the second bed because less heat is liberated than in the first bed. In this way the catalysts are exposed to less extreme temperatures and catalyst deactivation via sintering is circumvented. This system results in outstanding technical features due to the extremely favorable temperature profiles over the catalyst beds. In this work, a one-dimensional quasi-steady plug flow model is used to analyze and compare the performance of dual-bed and conventional single-bed reactors. The results of this work show that the dual-catalyst bed system can be operated with higher conversion and longer catalyst life time.

Keywords:

• Dual-catalyst bed
• Exothermic reversible reactions
• Heat exchanger reactor
• Long-term deactivation
• Methanol reactor