Optimal operation of a membrane reactor network

Abstract

In this contribution, the operation of a membrane reactor network (MRN) for the oxidative coupling of methane is optimized. Therefore, three reactors, a fixed bed reactor (FBR) and two packed bed-membrane reactors, are modeled. For the (CPBMR), a two-dimensional (2-D) model is presented. This model incorporates radial diffusion and thermal conduction. In addition, two 10 cm long cooling segments for the CPBMR are implemented based on the idea of a fixed cooling temperature positioned outside the reactor shell. The model is discretized using a newly developed 2-D orthogonal collocation on finite elements with a combination of Hermite for the radial and Lagrangian polynomials for the axial coordinate. Membrane thickness, feed compositions, temperatures at the inlet and for the cooling, diameters, and the amount of inert packing in the reactors are considered as decision variables. The optimization results in C 2 yields of up to 40% with a selectivity in C 2 products of more than 60%. The MRN consisting of an additional packed-bed membrane reactor with an alternative feeding policy and a FBR shows a lower yield than the individual CPBMR.In case, second-order derivatives appear in a differential equation, the continuity of first-order derivatives across finite elements needs to be ensured. For this application, Hermite cubic polynomials are of advantage. Their usage guarantees the continuity of the function itself and its first derivative Figure 2. Sketch for the heated or cooled model of the CPBMR.

Spatial Concentration and Temperature Profiles in Dual‐Packed‐Bed Catalytic Reactors: Oxidative Coupling of Methane

“…Herein, we report for the first time spatially resolved species concentration and temperature profiles in a dual fixed‐bed OCM reactor with interstage O 2 injection by using microprobe sampling8 and demonstrate that the yields of C 2+ products in the OCM can significantly be increased by distributed O 2 feed, as noted earlier 5–7. The information‐rich spatial profiles also provide new quantitative insight into the close coupling of the formation of C 2+ products and O 2 levels in OCM reactors and, as such, should be valuable for the improvement and validation of predictive models.…”

“…Early reactor simulations that used global OCM reaction kinetics were particularly encouraging, as they suggested the feasibility for attaining yields for C 2+ products as high as +50 % if the O 2 feed was distributed along the reactor, that is, by using membrane‐type reactors 5–7. Although these predictions may not be realistic, as the global reaction models used are well recognized to be of limited predictive value, they nevertheless create optimism regarding the future of the OCM process.…”

MOSAIC – Enabling Large‐Scale Equation‐Based Flow Sheet Optimization

“…The latter uses 2D orthogonal collocation on finite elements based on Lagrangian and Hermite polynomials. Details hereon can be found in . Afterwards, the fully discretized parts are joined together using connectors to form a single large‐scale algebraic equation system describing the entire PTSA section.…”

Mosaic

“…The reactor is 20 cm long and each 10 cm a different heating segment exists to heat or cool the system. The reactor is part of a larger network of reactors discussed in (Esche et al, 2013). Let it suffice to say, that the shell-and tube-side feeds of the reactor, i.e.…”