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Content archived on 2024-06-18

Multiscale Analysis and Design for Process Intensification and Innovation

Final Report Summary - MADPII (Multiscale Analysis and Design for Process Intensification and Innovation)

Chemical processes, which require an intensive exchange of energy and/or interaction between two phases are typically carried out in fluidized bed reactors. In these reactors, the mobile phase (normally a gas) enters from the bottom, passes through and interacts with the bed forming stationary phase (often a solid) and leaves through the top. The relative velocity between both phases (slip velocity) tends to drag the stationary phase out of the bed. This drag force needs to be balanced by the gravitational force to keep the bed stable and the particles in place. Since the gravitational force is fixed, it limits the applicable slip velocity and thus the productivity of the process. By replacing the gravitational force with a larger centrifugal force, higher slip velocities can be realized leading to process intensification. This is the basic idea and topic of the MADPII (multiscale-analysis-and-design-process-intensification-and-innovation) project. The centrifugal force is created in a vortex reactor. A video introducing this technology can be found at
The objectives of the project were (1) to design, characterize and operate a special type of vortex reactor and (2) to explore chemical processes that may benefit from this reactor concept.
The reactor of interest is a gas-solid vortex reactor (GSVR) in static configuration with no moving parts. The rotating bed is created by a large gas flow entering the cylindrical reactor through narrow slots in tangential direction. Because the bed is rotating, this reactor type is also called rotating bed reactor (RBR). The gas not only accelerates the solids but also provides or removes heat and participates possibly in chemical reactions. A RBR has never been used for two-phase chemical reactions, in part because RBRs are not well understood in detail. The MADPII project has focused on providing an improved understanding of this reactor type by constructing and operating prototype reactors. A cold-flow reactor has extensively been used to measure bed characteristics and flow fields, which have been further analyzed with CFD calculations. A second smaller reactor was built to measure heat and mass transfer, to gain experience with continuous reactor loading and to tackle scale-down issues. Building upon results from these ‘non-reactive’ reactors, a third scaled-down compact reactive reactor has been constructed for biomass pyrolysis. Initial tests show: a stable bed of biomass is easily maintained, char segregates from the bed and leaves with the gas flow, and very short space times between pyrolysis and char/oil separation are achievable. Besides this reactive RBR, an innovative reactor design idea subject to IP protection has been investigated as a follow-up project (ERC-2014-PoC #664876 GSVRotor [1/6/2015-1/12/2016]).
A suitable test case for the GSVR technology is the conversion of biomass via fast pyrolysis, because the quality of the pyrolysis product depends strongly on the heating rate and on the fast separation between solid and gaseous pyrolysis products. Thus, various aspects of fast pyrolysis of lignocellulosic biomass has been studied, including (1) characterization of the complex mixtures of pyrolysis products using improved GCxGC analytics, (2) correlation of product yields with biomass composition, (3) construction and operation of a micro-pyrolyser setup for biomass fast pyrolysis studies at well-controlled conditions, (4) detailed pyrolysis studies of model compounds and derived products, (5) development of elementary step kinetic models, (6) reactor simulations to validate the model and to predict pyrolysis yields, and (7) first principle calculations to further improve the kinetic models. The results confirm the great potential for converting biomass via fast pyrolysis in a GSVR to valuable products.
A second candidate reaction to be tried out in a GSVR is the catalytic oxidation of methane. A comprehensive microkinetic model, including catalyst descriptors, that accounts for gas phase and catalytic reaction steps in the short contact time catalytic partial oxidation of methane has been developed, which was implemented in a one-dimensional reactor model accounting explicitly for the irreducible mass transfer limitations. A new packed-bed reactor model with focus on accurate description of transport phenomena has been developed and applied to catalytic partial oxidation of methane. It shows that diffusion limitations play a significant role. The results suggest that a GSVR could be a beneficial reactor for this process.