To meet the stringent requirements of distributed hydrogen production, combined reaction-separation approaches to the endothermic steam methane reforming process have been investigated widely as a potential means to reduce the required reaction temperature, ratio of steam to methane in the fuel (or steam to carbon ratio), and number of sequential unit operation steps. The CHAMP-SORB is a new reactor technology for distributed hydrogen production from methane that incorporates both a hydrogen-selective membrane and CO 2 adsorption into a variable volume batch operation using a four stroke cycle. Active control of the reactor volume, and hence pressure, in combination with continuous removal of both reaction products allows CHAMP-SORB to circumnavigate the equilibrium limitations of the steam-methane reforming (SMR) reaction, which otherwise limit fuel conversion, especially at temperatures below 500°C with a stoichiometric fuel mixture. In this work, we present the first demonstration of an operating CHAMP-SORB reactor, achieving SMR at temperatures as low as 400°C and at a steam to carbon ratio of 2:1. A kinetic model of the CHAMP-SORB process is developed, verified for agreement with detailed experimental measurements, and used to investigate the interactions between the reaction, permeation, and adsorption processes. Timescale analysis is introduced to explore the relationship between reactor component design dcharacteristics and the ratelimiting steps of the CHAMP-SORB. Supported by the results of kinetic simulations, the scaling analysis provides a powerful tool for rapid exploration of the operating space, including operating temperatures and hydrogen collection/utilization pressures.

A new concept of a dynamically controlled reactor, which combines the variable volume operation of CHAMP (CO2/H2 Active Membrane Piston) with direct injection of liquid fuel of DDIR (Direct Droplet Impingement Reactor), is introduced and analyzed with the primary goal of identifying conditions for the highest volumetric power (hydrogen yield) density. In the proposed CHAMP-DDIR, a liquid fuel mixture is pulsed-injected onto the heated catalyst surface for rapid flash volatilization and on-the-spot reaction, and a hydrogen selective membrane is collocated with the catalyst to reduce the diffusion distance for hydrogen transport from the reaction zone to the separation site. Uniquely, CHAMP-DDIR allows dynamic variation of the reactor volume to optimally control the residence time and reactor conditions (pressure and temperature), thus improving both the reaction and separation processes. Idealized CHAMP-DDIR simulations, without heat and mass transfer limitations in the reactor volume, are used to determine the theoretical limits on power density for various operational conditions. An enhanced CHAMP-DDIR model, which accounts for the effects of mass transport limitations and bulk temperature changes in time, is employed to evaluate possible performance improvement through combining time-modulated fuel introduction and the active change of reactor volume. Analysis reveals that significant improvement in the volumetric power density can be achieved primarily as a result of two factors: time-modulated fuel injections enable higher reaction/permeation rates by preventing the large temperature drop that accompanies a single batch liquid fuel injection and volume modulation during a batch cycle allows for reduction in required reactor volume under a constraint of maximum operating pressure.

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We present results of modeling for the design of microgaps for the removal of high heat fluxes via a strategy of high mass flux, high quality, and two-phase forced convection. Modeling includes (1) thermodynamic analysis to obtain performance trends across a wide range of candidate coolants, (2) evaluation of worst-case pressure drop due to contraction and expansion in inlet/outlet manifolds, and (3) 1D reduced-order simulations to obtain realistic estimates of different contributions to the pressure drops. The main result is the identification of a general trend of improved heat transfer performance at higher system pressure.

The use of combined reaction-separation processes in steam methane reforming (SMR) has recently received significant attention as an enticing route to meet the challenging requirements of distributed hydrogen production for fuel cell vehicles. While many of the investigations in recent literature focus solely on either CO 2 adsorption or selective H 2 membrane permeation to reduce the reactor footprint and the temperature required to drive the endothermic reaction in continuous flow reactors, the CHAMP-SORB is a new variable volume, transient batch reactor technology that utilizes both strategies simultaneously. Building upon our prior study in which we experimentally demonstrated the viability of CHAMP-SORB reactor concept on bench scale, this work focuses on understanding the heat/mass transfer and reaction/separation interactions to develop guidelines for the reactor scale-up. A combined transport-kinetic model is developed, including spatial variations of SMR reaction and CO 2 adsorption rates within the mixed catalyst/sorbent bed along with hydrogen removal via membrane separation. Insights gained by application of the model are used to improve the large scale reactor performance by concentrating the catalyst near the H 2 permeable membrane, as compared to the baseline reactor configuration with spatially uniform catalyst/ sorbent. Additionally, the modeling methodology and an approach to numerical solution of governing equations are comprehensive, including Maxwell-Stefan formalism for treating multicomponent species transport, and are generally applicable to any reactors with homogeneous and heterogeneous chemical reactions, membrane separation, and time-dependent volume change for a wide variety of chemical processes.