Critically important heterogeneous catalytic reactions for energy conversion and chemicals production have been run for decades in fixed bed reactors packed with catalyst pellets, whose operation is intrinsically limited by slow heat removal/supply. There is urgent need for a...
Critically important heterogeneous catalytic reactions for energy conversion and chemicals production have been run for decades in fixed bed reactors packed with catalyst pellets, whose operation is intrinsically limited by slow heat removal/supply. There is urgent need for a new generation of chemical reactors to address the current quest for process intensification.
In the INTENT project we propose that a game-changing alternative is provided by structured reactors wherein the catalyst is washcoated onto or packed into structured substrates, like open-cell foams or 3D printed periodic open cellular structures (POCS), fabricated with highly conductive metals (Al, Cu).
The goal of INTENT is to elucidate fundamental and engineering properties of such novel conductive structured catalysts, investigate new concepts for their design, manufacturing, catalytic activation and operation and demonstrate their potential for a quantum leap in the intensification of crucial catalytic processes for the production of sustainable energy vectors:
i) distributed Hydrogen generation via efficient small-size methane reformers
ii) conversion of syngas to clean synthetic fuels in compact Fischer-Tropsch Synthesis reactors
iii) production of solar Hydrogen.
To this purpose we combine CFD modelling with lab-scale experimentation in order to identify the optimal structure-performance relation of existing and novel substrates, use such new knowledge to design optimized prototypes, apply additive manufacturing technologies for their production, and construct a semi-pilot tubular reactor to test them at a representative scale.
The project results will enable novel reactor designs based on tuning geometry, materials and configurations of the conductive internals to match the activity â€“ selectivity demands of specific process applications, while impacting also other research areas.
The new reactor technology will have significant influence on both the Energy and on the Environment scenarios. Just as an example, it will enable compact Gas-to-Liquids process technologies with potential to drastically reduce flaring of associated and remote Natural Gas.
Task 1 - The fundamental investigation of the transport properties of open-cell foams as enhanced catalyst substrates has produced an original procedure for the digital reconstruction of foams from two easily accessible pieces of information, i.e. porosity and pore size. It generates faithful replicas of real foams, as well as virtual foams with variable geometric features suitable for numerical parametric analysis and optimization.
Pressure drops, heat and mass transfer in open-cell foams have been extensively investigated by combining experiments with CFD simulations. This has enabled to generate a dimensionless correlation for fluid/solid mass transfer coefficients covering an unprecedented range of geometrical and flow variables, and an optimal design that maximizes the effective thermal conductivity of the foam matrix.
Fundamental research is proceeding to characterize: i) the heat transfer properties of washcoated foams under reactive conditions; ii) the heat transfer properties of foams packed with catalyst microparticles; iii) the transport properties of 3D printed POCS.
Task 2 â€“The catalytic activation of metallic foams by washcoating was first addressed. The innovative spin coating method has been systematically compared to the conventional dip coating, revealing improved uniformity of the deposited catalytic layers and superior control of the coating characteristics. The alternative method for catalytic activation of cellular substrates investigated in INTENT relies on packing open-cell foams and POCS with catalyst micro-particles. All the factors influencing the loading of the catalyst particles, and therefore the catalyst inventory, have been elucidated.
Additive manufacturing (3D printing) of Al POCS started early in the project thanks to a collaboration with Prof. Stefano Beretta, Department of Mechanical Engineering of Politecnico di Milano. Regular cellular materials offer additional degrees of freedom for the design of optimized catalyst substrates and look therefore very promising for process intensification. Samples with different geometrical and structural features have been produced and characterized by pressure drop, heat and mass transfer measurements, in combination with CFD simulations.
Task 3 - A semi-pilot jacketed tubular reactor is under construction, in view of demonstrating the INTENT concepts at a representative scale.
Lab-scale methane steam reforming experiments over Rh-based catalyst particles in the presence and in the absence of Cu foams have pointed out significant mitigation of the radial temperature gradients in the reactor due to the enhanced effective thermal conductivity. This improved the performances of the heat-transfer limited endothermic process. The study is being extended to other cellular conductive reactor internals.
Along similar lines, Fischer-Tropsch (FTS) runs over Co-based catalyst particles in a lab-scale reactor in the presence and in the absence of Al foams and POCS demonstrated a substantially improved temperature control when the reactor was loaded with the packed conductive internals, enabling unprecedented CO conversions (up to 80% with heat duties over 1.7 MW/m3). The work proceeds in the following directions: i) testing of improved structured internals (POCS with skin); ii) mathematical modeling; iii) scale-up in the pilot unit.
An experimental facility with generation of simulated solar light is under construction to study cellular substrates for the solar methane steam reforming.
\"Significant progress beyond the state of the art at the beginning of the INTENT project has been achieved so far in the following areas:
- Geometrical and digital characterization of open-cell foams and other cellular substrates. We use the methodology developed in INTENT to generate \"\"virtual digital foams\"\": these provide a computational domain for CFD simulations but can be also 3D printed and tested under reactive flow conditions, thus removing any geometrical uncertainty from the comparison between simulations and experiments.
- Analysis of the transport properties of cellular substrates: the combination of experiments and CFD simulations is a methodological approach first successfully demonstrated in INTENT to analyze gas/solid heat and mass transfer and pressure drop in open-cell foams. It has enabled unprecedented engineering correlations for transport properties in foams.
- Activation of cellular substrates by packing with catalyst microparticles: packed foams and packed POCS are a new concept; we are now reporting data on the related transport properties and the first applications under reactive conditions.
- Application of Al foams and POCS packed with catalyst particles to the strongly exothermic and temperature-sensitive Fischer-Tropsch synthesis (FTS). This new concept enabled to run the reaction almost isothermally in a lab-scale tubular reactor up to very high CO conversions, corresponding to extreme heat duties not accessible to conventional packed-bed reactors.
- Application of washcoated/packed Cu foams to the strongly endothermic Methane Steam Reforming for syngas and hydrogen production, leading to improved syngas productivities.
The above results seem very promising for the intensification of key catalytic processes for energy conversion.\"
More info: http://www.intent.polimi.it.