Autothermal reactors with internal heat exchang—I Numerical and experimental studies in the multiple steady-state region

Abstract

Detailed numerical and experimental studies in the multiple steady-state region of an autothermal reactor with internal countercurrent heat exchange were conducted. The mildly exothermic water-gas shift reaction was used in the studies. In this distributed-parameter system multiple steady states were found experimentally. Although significant radial and longitudinal temperature gradients exist, one-dimensional (radially-lumped) simulations predict mean behavior quite well. For two-dimensional simulations, Legendre polynomial trial functions give faster convergence than Jacobi polynomials when using orthogonal collocation methods. Inflections in the radial temperature gradients were measured near the hot spot although not predicted by the simulations. Significant temperature jumps at the inner wall upstream of the hot spot were also measured. Production of hydrogen could be conducted at surprisingly mild conditions if the reactor could be controlled in a stable mode essentially identical to the middle unstable steady state.