Efficient modeling of the nonlinear dynamics of tubular heterogeneous reactors.

Highlights • The global-nonlinear dynamics of heterogeneous tubular reactors is modeled. • An adjustable-order ODE model is built by PDE spatial discretization. • Multiplicity is assessed with bifurcation analysis through continuation with respect to order. • The methodology is applied to a 13-profile gasification reactor with experimental data. • The gasification reactor is robuslty bistable and is modeled with order 30. Abstract The problem of efficiently describing the nonlinear dynamics of spatially distributed tubular heterogeneous reactors is addressed, including multiplicity, stability, and transient behavior. An adjustable-order model is generated with a convergent partial differential equation (PDE)-to-ordinary differential equation (ODE) discretization. Efficiency means the ability to describe the PDE dynamics quantitatively, up to kinetics-transport (KT) parameter error propagation and with the smallest possible order. The problem is solved by combining notions and tools from nonlinear dynamics (bifurcation analysis and structural stability), numerical methods (error propagation analysis and continuation), and chemical reactor engineering. Solvability requires the existence of an order below the critical one for the onset of excessive error propagation. The approach is applied to a 13-profile gasification reactor with experimental data, unknown multiplicity, and finite difference (FD) discretization. It is found that the reactor is robustly bistable, and can be described by a 30th-order model with considerably less equations than in previous related studies. [ABSTRACT FROM AUTHOR]