(147d) Dynamic Data Reconciliation, Parameter Estimation, and Plant-Wide Modeling of a Microwave (MW)-Assisted Direct Non-Oxidative Methane Dehydroaromatization (DHA) Process

The microwave (MW) technology has been commercially used for many years with applications in wood drying, pharmaceuticals, and food industry for cooking, thawing, pasteurization and preservation of food materials. Over the past several years, it is being increasingly investigated for assisting chemical reactions both for the homogenous and heterogeneous reactive systems [1]. Enhancement of reaction rate and improvement of product yields in MW-assisted reactors have been the two main reasons for the increased interest in application of MW for reaction engineering.

Modeling of MW-assisted catalytic fixed bed reactors and theoretical analysis of MW-assisted endothermic reactions has been pursued by a few authors. Gerasev [2] has developed a 1-D heterogeneous model of a packed bed catalytic reactor for an irreversible endothermic reaction. The gas in the reactor is assumed to absorb the MW energy changing its composition. Their study used Lambert’s law for MW power propagation. A study comparing the conventional and microwave heating efficiency of a packed column with dielectric catalyst has been performed by Cherbanski [3]. They used Lambert’s law for microwave power propagation inside the reactor. Bhattacharya et al. [4] performed a comprehensive theoretical analysis of the effect of MW heating for a first order endothermic reaction in reactor packed with dielectric material. The current literature lacks kinetic and reactor models for a MW-assisted methane dehydroaromatization (DHA) process. In this process deactivation due to coke formation takes place making it difficult to develop an accurate kinetic model and estimate its parameters due to the transient operation and complex interaction between the MW and changing reactant composition and coke formation in the reactor.

A kinetic model including a model of coke formation is proposed for an in-house catalyst for the direct non-oxidative methane DHA reactor. Formation of coke is a dynamic process affecting also the dynamics of conversion and yield from the reactor. However with the current measurement technology, it is not feasible to measure the changing mass and composition of coke inside the reactor. To satisfy the carbon and hydrogen balance in the experimental data of the product flowrates from the reactor, a dynamic data reconciliation problem is solved. Subsequently a dynamic parameter estimation problem is solved using the reconciled data. This rate model is then used to develop a multi-scale reactor model where mass transfer, heat transfer, reaction kinetics and MW propagation in the catalyst particles are modeled and integrated with the bulk reactor model where MW propagation is modeled based on the configuration and design of the MW generator and the wave guide. The MW reactor model is then used to develop and optimize a plant-wide model. Economics of the MW-assisted process are compared with a commercial process for conversion of natural gas to aromatics via methanol synthesis.

References

[1] Lidström P, Tierney J, Wathey B, Westman J. Microwave assisted organic synthesis - A review. Tetrahedron 2001. https://doi.org/10.1016/S0040-4020(01)00906-1.

[2] Gerasev AP. Emergence of traveling wave endothermic reaction in a catalytic fixed bed under microwave heating. Energy 2017. https://doi.org/10.1016/j.energy.2016.11.042.

[3] Cherbański R. Numerical simulations of heat transfer in a packed column: comparison of microwave and convective heating. Heat Mass Transf Und Stoffuebertragung 2015. https://doi.org/10.1007/s00231-014-1447-5.

[4] Bhattacharya M, Basak T, Senagala R. A comprehensive theoretical analysis for the effect of microwave heating on the progress of a first order endothermic reaction. Chem Eng Sci 2011. https://doi.org/10.1016/j.ces.2011.08.003.