On the mixing in confined impinging jet mixers – Time scale analysis and scale-up using CFD coarse-graining methods

Metzger, Lukas; Kind, Matthias

doi:10.1016/j.cherd.2016.02.019

Cited by 23 publications

(9 citation statements)

References 26 publications

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“…They concluded that the longest and most intense ultrasound irradiation during co-precipitation improves the morphology, particle size, surface area and particle distribution of CZA catalysts compared to non-sonicated samples [47]. However, it is important to stress that a transient mode of operation causes each particle to go through an individual history of solid formation which can further increase the inhomogeneity of the precipitate [48][49][50][51]. Therefore, it is essential to prove whether a continuously operated co-precipitation, where mixing limitations should be minimal, gives access to catalysts with an increased degree of homogeneity due to a quasi steady-state, and therefore more homogeneous precipitation conditions [40,[52][53][54].…”

Section: Introductionmentioning

confidence: 99%

Enhanced Direct Dimethyl Ether Synthesis from CO2-Rich Syngas with Cu/ZnO/ZrO2 Catalysts Prepared by Continuous Co-Precipitation

et al. 2020

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The manufacturing of technical catalysts generally involves a sequence of different process steps, of which co-precipitation is one of the most important. In this study, we investigate how continuous co-precipitation influences the properties of Cu/ZnO/ZrO2 (CZZ) catalysts and their application in the direct synthesis of dimethyl ether (DME) from CO2/CO/H2 feeds. We compare material characteristics investigated by means of XRF, XRD, N2 physisorption, H2-TPR, N2O-RFC, TEM and EDXS as well as the catalytic properties to those of CZZ catalysts prepared by a semi-batch co-precipitation method. Ultra-fast mixing in continuous co-precipitation results in high BET and copper surface areas as well as in improved metal dispersion. DME synthesis performed in combination with a ferrierite-type co-catalyst shows correspondingly improved productivity for CZZ catalysts prepared by the continuous co-precipitation method, using CO2-rich as well as CO-rich syngas feeds. Our continuous co-precipitation approach allows for improved material homogeneity due to faster and more homogeneous solid formation. The so-called “chemical memory” stamped during initial co-precipitation is kept through all process steps and is reflected in the final catalytic properties. Furthermore, our continuous co-precipitation approach may be easily scaled-up to industrial production rates by numbering-up. Hence, we believe that our approach represents a promising contribution to improve catalysts for direct DME synthesis.

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Section: Introductionmentioning

confidence: 99%

Enhanced Direct Dimethyl Ether Synthesis from CO2-Rich Syngas with Cu/ZnO/ZrO2 Catalysts Prepared by Continuous Co-Precipitation

et al. 2020

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“…Metzger and Kind conducted many numerical studies on the fast precipitation crystallization processes using CFD-PBE (population balance equation) [18]. Metzger et al used spatially and temporally averaged reduced numeric measurement and CFD methods to investigate the precipitation crystallization in a confined impinging jet mixer [19]. Therefore, the CFD tool has become a very popular and credible computational tool for investigating and measuring needed information about the flow field in an impinging stream reactor.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Studies on Flow and Turbulence Characteristics of Impinging Stream Reactors with Dynamic Inlet Velocity Variation

Liu

Yue²,

et al. 2018

Energies

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Impinging stream technique has been widely used in engineering industries. Insufficient data are available on the effects of dynamic inflow conditions on the flow and turbulence characteristics of an impinging stream reactor. In this study, we investigate and discuss the flow and turbulence characteristics of an impinging stream reactor with dynamic inlet velocity variation, e.g., sinusoidal, parabolic, step or triangular variation. The effects of period, amplitude, phase difference, mean inlet velocity and type of dynamic inlet velocity variation on the motional behaviors of the impinging surface and the mean turbulence kinetic energy (k) of the impingement region are investigated and discussed using particle image velocimetry (PIV) and computational fluid dynamics (CFD) at various values of L/D (the ratio of impinging spacing to nozzle diameter). The results show that the impinging surface makes back-and-forth motions in impinging stream reactors with dynamic inlet velocity variation. The mean k of the impingement region during one period is dominated by both the inlet velocity conditions and the geometric configuration. Dynamic inflow conditions bring more turbulence energy and pulsating characteristics to impinging zones over constant inlet velocity for an instantaneously moving impinging surface. Impinging stream reactors with dynamic inlet velocity variation provides more intense turbulence properties over conventional impinging stream reactors at the same mean inlet velocity. This work shows that the impinging streams with dynamic inlet velocity variation has strong potential for future relevant reactors and processes for engineering applications.

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“…The drag force F D can be calculated according to the Ergun and Wen and Yu drag model [38], shown in Equations (8)- (11). β represents interphase momentum exchange coefficient, based on the soft-sphere model:…”

Section: Particle Motion Equationsmentioning

confidence: 99%

“…The impinging stream technique was first proposed by the Soviet scientist Elperin in 1961, and then investigated and discussed by many scholars and scientists [1][2][3][4]. The impinging stream reactor can effectively strengthen interphase heat and mass transfer, and thus is widely used in drying [5,6], absorption [7,8], micromixing [9][10][11], combustion [12], crystallization [13], extraction [14,15], nanoparticles preparation [16,17], and so on, which has created great potential for engineering applications.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulations of a Gas–Solid Two-Phase Impinging Stream Reactor with Dynamic Inlet Flow

Liu

Yue²,

et al. 2018

Energies

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Fluid flow characteristics and particle motion behavior of an impinging stream reactor with dynamic inlet flow (both inlet velocity patterns exhibit step variation) are investigated and discussed with the computational fluid dynamics–discrete element method (CFD–DEM). The effect of T (variation period of the dynamic inlet flow) and ∆u (inlet velocity difference) on the motion characteristics of single and multiple particles, as well as the mean particle residence time, are studied and discussed. The research results indicate that, compared with the traditional impinging stream reactor (both inlet velocities are equal and constant) with equal mean inlet velocity (um) within one period, the impinging surface is instantaneously moving and the flow regime is varied with time in the impinging stream reactor with dynamic inlet flow. The impinging stream reactor with dynamic inlet flow provides higher cost performance over the traditional impinging stream reactor, under equal um, in terms of single-particle residence time. Moreover, three new particle motion modes exist in multi-particle motions of the impinging stream reactor with dynamic inlet flow; particles are accelerated by the original or reverse fluid and perform oscillatory motion at least once after an interparticle collision. Whether it is a single particle or multi-particles, the mean particle residence time reaches a maximum value when T/2 is approximately equal to the first particle acceleration time, since the maximum axial kinetic energy increases in every oscillatory motion compared with traditional impinging stream, and the number of oscillatory motions is increasing. The mean residence time of a particle in the impinging stream reactor with a dynamic inlet flow increases with increasing ∆u, since the dynamic inlet conditions and increasing ∆u can continuously supply more energy to particles and thus cause more particles to enter one of the three new modes of particle motion.

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On the mixing in confined impinging jet mixers – Time scale analysis and scale-up using CFD coarse-graining methods

Cited by 23 publications

References 26 publications

Enhanced Direct Dimethyl Ether Synthesis from CO2-Rich Syngas with Cu/ZnO/ZrO2 Catalysts Prepared by Continuous Co-Precipitation

Enhanced Direct Dimethyl Ether Synthesis from CO2-Rich Syngas with Cu/ZnO/ZrO2 Catalysts Prepared by Continuous Co-Precipitation

Experimental and Numerical Studies on Flow and Turbulence Characteristics of Impinging Stream Reactors with Dynamic Inlet Velocity Variation

Numerical Simulations of a Gas–Solid Two-Phase Impinging Stream Reactor with Dynamic Inlet Flow

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