GOALI:Catalyst Deactivation and Heat Transfer Modelling for Fixed Bed Reactors Using Computational Fluid Dynamics

Worcester Polytechnic Institute, Worcester MA

Investigators

Abstract

ABSTRACT PI: Anthony G. Dixon and Hugh Stitt Institution: Worcester Polytechnic Institute Proposal Number: 0625693 Title: GOALI: Catalyst Deactivation and Heat Transfer Modelling for Fixed Bed Reactors Using Computational Fluid Dynamics Today's increasing environmental and economic pressures on the chemical industry have resulted in a continuing push towards more efficient processing in chemical reactors, by increasing conversion and selectivity, and by managing the energy requirements of the process effectively. The key to accomplishing these goals is improving understanding of the physical and chemical processes taking place within chemical reactors, upon which correct design and operation are based. Catalytic tubular fixed bed reactors are widely used for large-scale, heterogeneously-catalyzed gas-phase reactions, such as steam reforming. These reactors have large heat effects, especially near the tube wall, where strong temperature gradients exist. For analysis and scale-up, modeling and simulation are essential tools. Existing models, however, have been found to be inadequate, and do not allow reliable priori design. The main reason that the current models are not good enough is that they are based on intuitive simplifications, with the model parameters being fitted to specific conditions. The intellectual merit of this project is that a systematic approach to fixed bed reactor modeling is will be undertaken using first principles to understand the effects of tube wall heat transfer and of catalyst particle design on reactor performance. Building on previous work by the Principal Investigators, a methodology will be developed to improve one's ability to predict radial temperature profiles in catalyst tubes, and to assess the impact of heat transfer on catalyst performance. Computational fluid dynamics (CFD) will be used to simulate fluid flow patterns and temperature fields around the catalyst, to capture the effects of changes in the catalyst particle shapes and features. This will be coupled with transport and reaction inside the solid catalyst particles, with emphasis on the effects on catalyst deactivation through coking. The result of this coupled approach will be that deactivation rates inside the reactor tubes will be evaluated under the correct conditions, especially in the near-wall region, giving much improved predictive capability. A feature of the work will be the collaborative effort between industry and academia, allowing extensive validation of the computer simulations by comparison to data taken directly from industrial pilot plants, and ensuring that the practical, industrial perspective informs the work at all stages. The broader impact of this work lies in the benefits to society of improved methods for carrying out catalytic reactions, and in education and infrastructure development. Johnson Matthey is a major supplier and innovator in catalyst development. The improved understanding of the interaction between heat transfer and catalyst deactivation that will result from this collaborative work will increase catalyst and reactor tube life, thus having positive consequences for sustainable engineering. Of particular importance for the future is hydrogen production, and efficient use must be made of the abundant reserves of natural gas, using conversion technologies such as steam reforming, the focus of this project. It is also important that the students who are educated in reaction engineering are exposed to modern computational tools. Both undergraduate and graduate students will be involved in this research. The project results will be disseminated broadly, through industrial use and interdisciplinary conferences.