ASCOMP provides consulting services in chemical and process engineering, with design-oriented activities in various sub-branches, including: bubble column reactors, CVD reactors, fluidized bed processes, three-phase flow separation, chemical reaction in automotive catalysts, Nanoparticles precipitation in CIJ reactors, etc. Our services are packaged in the form of a tractable workflow modeling concept for chemically-reacting, multiphase flow processes, consisting in systematically comparing and interpreting the results of different modeling frameworks. The core-strength of this workflow is based on TransAT’s extended modelling capabilities for flows involving both single-phase and multiphase systems, with simple or complex rheology, involving fast or infinite chemical reactions. The selected examples below highlight the modelling capabilities of TransAT and potential practical impact in this sector.
Bubble Column Reactors
Multiphase flow reactors are used in chemical reaction engineering for a variety of processes. e g in petrochemical industry, metallurgy and other energy systems. The most recurrent example is multiphase flow in Bubble Column Reactors (BCR), where flow transients and multiple spatial and temporal scales dictate the reactor performance. TransAT Suite offers a pallet of predictive models helping obtaining better and economically viable technologies for process intensification and optimization of these types of reactors. The overall workflow built around TransAT Suite offers a technical valuable terms of design or operating parameters, working precisely to replace empiricism-based replace trial-and-error by detailed flow hydrodynamics towards improving existing processes and scale-up of new processes.
Surface Reaction in Automotive Catalytic Pollutant Converters (CPC)
The design of efficient CPC’s in automotive applications is of vital importance in this industry. Briefly, a good CPC combines efficient pollutant conversion with a low pressure drop. Due to the high Damkohler numbers at typical operating conditions the pollutant conversion is mainly limited by efficient mass-transfer from the bulk fluid to the catalytically coated surface. Recently ceramic foams have been proposed as an alternative to honeycomb, where pore scale simulations have been used to characterize pressure drop heat and mass transfer in foams. In numerical as well as in experimental studies it is apparent that the geometrical modelling of the porous structure is the biggest uncertainty. Combining the strength of IST meshing with advanced models in TransAT Multiphysics, we were recently capable of conducting pore scale simulations of catalytic reactors with micro-kinetic modelling considering coupled heat and mass transfer. Further, since pore-scale simulations are computationally expensive, we have upgraded the model with a volume averaged reduced-order (1D instead of 3D) approach involving a number of assumptions. The resulting volume-averaged description is compared to a pore scale simulation that takes into account the heat released by the reactions, variable fluid properties and conjugate heat transfer.
Separation of Dispersed Fluid Systems in Hydrocyclones
Hydrocyclone systems provide an efficient way for removing solid particles in the 4 to 100+ micron range from various slurries (sands out of water). Hydrocyclones typically make finer separations than are practical with screening separators and at significantly higher capacities. In many applications cyclones can be used in place of decanter centrifuges, providing the desired result at lower cost. The systems are supplied in either an open-manifold (radial or linear orientation) or a Packed-Vessel configuration. Both configurations can process high feed rates per minute, depending on the size and number of systems installed. Hydrocyclone separators can also be used to separate dispersed liquid-liquid systems, e.g. oil-water in the petrochemical industry, and as such they involve droplet-droplet interaction mechanisms. Separation is due to phase density difference combined to gravity effects. The relative motion of particles/droplets with respect to the mean flow induced by centrifugal forces results in droplet separation at the cyclone walls and at the underflow or upper flow. Development of new method for coupled solution of population balances with flow field including droplet breakup and coalescence, describing the impact of droplet interactions on separation processes. TransAT Multiphase deals with this class of flows, accounting with the physics of particle-particle-wall-flow interactions, under transient turbulent motions.
Nanoparticles precipitation in a Confined Impinging Jets Reactor (CJIR)
Micro-mixer devices, such as the CIJR are currently under study, in particular for precipitation processes of micro- and nano-particles, in a variety of applications that include pharmaceuticals, cosmetics, dyes and pesticides. For example the process of solvent displacement can be employed to produce polymeric nano-particles carrying an active principle to be used in targeted drug delivery. In solvent displacement the pharmaceutical active principle and the polymer are dissolved in an organic solvent and then rapidly mixed with an anti-solvent. The faster the overall mixing process occurs, the smaller and the more monodisperse the particles will be. The detailed simulations performed by TransAT HPC were ound to be essential in understanding and explaining the flow behavior and the development of turbulence, in particular with respect to the important effects of the inlet boundary conditions. Oscillations present in the inlet flow of the device are in fact primarily responsible for the chaotic and turbulent effects in the reactor. These results provide insights that are important in the development of appropriate computational models for this type of micro-reactor or mixers.