pinecone/core-2020-05-10-deduplication huggingface dataset:
Numerical study of the coupling between reaction and mass transfer for liquid-liquid slug flow in square microchannels

While the benefits of miniaturisation on processes have been widely demonstrated, its impact on microfluidics and local mechanisms such as mass transfer is still little understood. The aim of this work is to simulate coupling between reaction and mass transfer in microchannels for liquid-liquid slug flow. First, the extrapolation to confined flow of the classical model used to calculate interfacial mass fluxes in reactive infinite media was studied. This model consists in estimating transferred fluxes between two phases as a function of the enhancement factor E. Its expression depends on the model used to represent interfacial mass transfer. In infinite media, Lewis and Whitman’s stagnant film theory is generally preferred for its simplicity and its reliability. In the case of confined slug flow, the limitation of such a model to predict interfacial fluxes is highlighted. Secondly, the case of liquid-liquid competitive consecutive reactions in microchannels is considered. This work emphasizes the unfavourable impact of the length between droplets on selectivity. This is a direct consequence of mass transport mechanisms in microchannels
Integration of a Ca looping system for CO2 capture in existing power plants

[EN] This work analyses a Ca looping system that uses CaO as regenerable sorbent to capture CO2 from the flue gases generated in power plants. The CO2 is captured by CaO in a CFB carbonator while coal oxycombustion provides the energy required to regenerate the sorbent. Part of the energy introduced into the calciner can be transferred to a new supercritical steam cycle to generate additional power. Several case studies have been integrated with this steam cycle. Efficiency penalties, mainly associated with the energy consumption of the ASU, CO2 compressor and auxiliaries, can be as low as 7.5 percentage points of net efficiency when working with low CaCO3 make-up flows and integrating the Ca looping with a cement plant that makes use of the spent sorbent. The penalties increase to 8.3 percentage points when this possibility is not available. Operation conditions aiming at minimum calciner size result in slightly higher efficiency penalties.This work is partially supported by the European Commission under the 7th Framework Programme (CaOling project). I. Martínez thanks Diputación General de Aragón for the F.P.I. fellowship and MICINN for the FPU fellowship.Peer reviewe
Simulation of liquid water beakthrough in a nano-tomography reconstruction of a carbon paper gas diffusion layer

This is a preprint of an article published in the AIChe Journal [© American Institute of Chemical Engineers]. The published version can be found at:  http://dx.doi.org/10.1002/aic.12581This study reports the feasibility of newly simulating liquid water intrusion into the porous gas diffusion\ud
layer (GDL) of a polymer electrolyte fuel cell (PEFC) using X-ray nano-tomography and two-phase\ud
lattice Boltzmann (LB) simulation. A digital 3D model of the GDL is reconstructed using X-ray nanotomography\ud
while two-phase porous flow is simulated at two different levels of surface wettability by\ud
applying a newly-developed numerical LB model. The results show liquid infiltration in a hydrophobic\ud
GDL is comparatively lower (pore saturation of 0.11 to 0.90) than that for a hydrophilic GDL (pore\ud
saturation of 0.36 to 0.96) over the liquid intrusion range of 1 kPa . 100 kPa. Visualisation of simulated\ud
results in three dimensions reveal dissimilar liquid infiltration characteristics for the two levels of\ud
wettability considered, yet also reveal a general breakthrough of liquid water at a pressure of 10 kPa\ud
due to specific structural features of the GDL
Dynamic effects on capillary pressure-saturation relationships for two-phase porous flow: implications of temperature

This\ud
is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and\ud
reproduction in any medium, provided the original work is properly cited.Work carried out in the last decade or so suggests that the simulators for multiphase flow in porous media should include an\ud
additional term, namely a dynamic coefficient, as a measure of the dynamic effect associated with capillary pressure. In this work,\ud
we examine the dependence of the dynamic coefficient on temperature by carrying out quasi-static and dynamic flow simulations for\ud
an immiscible perchloroethylene–water system. Simulations have been carried out using a two-phase porous media flow simulator\ud
for a range of temperatures between 20 and 80\ud
C. Simulation domains represent 3-D cylindrical setups used by the authors for\ud
laboratory-scale investigations of dynamic effects in two-phase flow. Results are presented for two different porous domains, namely\ud
the coarse and fine sands, which are then interpreted by examining the correlations between dynamic coefficient(s) and\ud
temperature, time period(s) required for attaining irreducible water saturation, and the dynamic aqueous/nonaqueous phase\ud
saturation and capillary pressure plots. The simulations presented here maintain continuity from our previous work and address the\ud
uncertainties associated with the dependency of dynamic coefficient(s) on temperature, thereby complementing the existing\ud
database for the characterization of dynamic coefficients and subsequently enabling the users to carry out computationally\ud
economical and reliable modeling studies
Sulfation rates of cycled CaO particles in the carbonator of a Ca-looping cycle for postcombustion CO2 capture

[EN] Calcium looping is an energy-efficient CO2 capture technology that uses CaO as a regenerable\ud
sorbent. One of the advantages of Ca looping compared with other post-combustion technologies\ud
is the possibility of operating with flue gases that have a high SO2 content. However,\ud
experimental information on sulfation reaction rates of cycled particles in the conditions typical\ud
of a carbonator reactor is scarce. This works aims to define a semi-empirical sulfation reaction\ud
model at particle level suitable for such reaction conditions. The pore blocking mechanism\ud
typically observed during the sulfation reaction of fresh calcined limestones is not observed in\ud
the case of highly cycled sorbents (N>20) and the low values of sulfation conversion\ud
characteristic of the sorbent in the Ca-looping system. The random pore model is able to predict\ud
reasonably well the CaO conversion to CaSO4 taking into account the evolution of the pore\ud
structure during the calcination/carbonation cycles. The intrinsic reaction parameters derived for\ud
chemical and diffusion controlled regimes are in agreement with those found in the literature for\ud
sulfation in other systemsThis work is partially funded by the European Commission (FP7-CaOling project).Peer reviewe
On the use of process analytical technologies and population balance equations for the estimation of crystallization kinetics. A case study.

International audienceThe batch cooling solution crystallization of ammonium oxalate was performed in water at various constant cooling rates. Measurements of the solute concentration were obtained using in situ attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy, and final estimates of the crystal size distribution (CSD) were computed; thanks to in situ image acquisition and off-line image analysis. The crystallization process was then simulated using population balance equations (PBEs). Estimates of the nucleation and the growth parameters were computed through model/experiments fitting. According to the cooling rate, the PBE model allowed distinguishing between two distinct crystallization regimes, separated by an "intermediate regime." The respective contributions and shortcomings of solute concentration measurements and granulometric data to the identification of nucleation and growth kinetic parameters are analyzed and discussed. It is shown in particular that no real separate estimation of nucleation and growth parameters can be obtained in the absence of CSD data
State and specific growth estimation in heterologous protein production by Pichia pastoris

The productivity of an industrial fermentation
process involving a filamentous microbe is heavily dependent
on the morphological form adopted by the organism.
The development of systems capable of rapidly and accurately
characterizing morphology within a given process
represents a significant challenge, as the complex phenotypes
that are manifested are not easily quantified. Conventional
parameters employed in these analyses are often of limited
value, as they reveal little about the branching behavior of
the organism; an important consideration given the demonstrated
link between branching frequency and metabolite
production. In this study, the influence of branching behavior
on the spatial distribution of mycelia grown in silico is
examined through fractal analysis. It is demonstrated that
fractal dimension, quantified based on the frequency distribution
of parameterized boundary curves, and lacunarity act
as robust estimators of branching behavior. The analysis can,
in theory, be applied to any morphological form, providing
universally applicable process parameters for more complete
data acquisition.This work was supported by a grant from the Spanish programme of Chemical Processes Technologies (CTQ2007-60347; CTQ2010-15131), HP2007-0045 from Science and Innovation Ministry, 2009-SGR-00281 and the Reference Network in Biotechnology (XRB) from the DURSI (Generalitat de Catalunya). Support from "Luso-Spanish Integrated Actions" (Action 100/08) are also acknowledged. JMB would like to thank the Spanish Education Ministry for his predoctoral fellowship
Dynamic effects in capillary pressure relationships for two-phase flow in porous media: Experiments and numerical analyses

This is an open access article under the terms of the Creative Commons\ud
Attribution License, which permits use, distribution and reproduction in\ud
any medium, provided the original work is properly cited.Well defined experiments and numerical analyses are conducted to determine the importance of dynamic effect in capillary pressure relationships for two-phase flow in porous media. Dynamic and quasi-static capillary pressure-saturation (P -S ) and, ∂S /∂t-t curves are determined. These are then used to determine the dynamic effects, indicated by a dynamic coefficient (τ) in the porous domains which establishes the speed at which flow equilibrium (∂S /∂t = 0) is reached. τ is found to be a nonlinear function of saturation which also depends on the medium permeability. Locally determined τ seems to increase as the distance of the measurement point from the fluid inlet into the domain increases. However, the functional dependence τ-S follows similar trends at different locations within the domain. We argue that saturation weighted average of local τ-S curves can be defined as an effective τ-S curve for the whole domain which follows an exponential trend too
Experimental measurement of dynamic effect in capillary pressure relationship for two-phase flow in weakly layered porous media

This is an open access article under the terms of the Creative Commons\ud
Attribution License, which permits use, distribution and reproduction in\ud
any medium, provided the original work is properly cited.Well-defined laboratory experiments have been conducted to determine the significance of dynamic effect in capillary pressure relationships for two-phase flow in weakly heterogeneous (layered) porous media. The heterogeneous layers are composed of a fine sand layer sandwiched between two coarse sand layers. Dynamic and quasi-static capillary pressure-saturation (P-S) and ∂S/∂t-t relationships are determined, which are then used to determine the dynamic effect, indicated by a dynamic coefficient (τ). As well known, τ establishes the speed at which flow equilibrium (∂S/∂t = 0) is reached. In consistent with previous studies, τ is found to be a nonlinear function of saturation that depends on the medium permeability and the intensity of heterogeneity. τ values increase in the regions of less permeability (fine sand) in the domain. However, the τ-S functional dependence follows similar trends at different locations within the domain including regions of different permeability. We argue that saturation weighted average of local τ-S curves can be used as an effective τ-S curve for the whole domain which, when done, follows an exponential trend too. The effective τ-S curves suggest that the effective τ values for the porous layers lie between the τ values of coarse and fine sands at the same water saturation, and it is dominated by the τ values of coarse sand as it occupied the maximum volume of the domain. © 2012 American Institute of Chemical Engineers
Bubble columns for condensation at high concentrations of noncondensable gas: Heat-transfer model and experiments

Carrier gas based thermodynamic cycles are common in water desalination applications. These cycles often require condensation of water vapor out of the carrier gas stream. As the carrier gas is most likely a noncondensable gas present in very high concentrations (60–95%), a large additional resistance to heat transfer is present. It is proposed to reduce the aforementioned thermal resistance by condensing the vapor–gas mixture in a column of cold liquid rather than on a cold surface using a bubble column heat exchanger. A theoretical predictive model for estimating the heat-transfer rates and new experimental data to validate this model are described. The model is purely physics based without the need for any adjustable parameters, and it is shown to predict heat rates within 0 to −20% of the experimental values. The experiments demonstrate that heat-transfer rates in the proposed device are up to an order magnitude higher than those achieved in existing state-of-the-art dehumidifiers.Center for Clean Water and Clean Energy at MIT and KFUP
Multifluid modeling of the desulfurization process within a bubbling fluidized bed coal gasifier

The desulfurization process to a two-dimensional (2-D) and three-dimensional (3-D) Eulerian-Eulerian computational fluid dynamic (CFD) model of a coal bubbling fluidized gasifier is introduced. The desulfurization process is important for the reduction of harmful SOx emissions; therefore, the development of a CFD model capable of predicting chemical reactions involving desulfurization is key to the optimization of reactor designs and operating conditions. To model the process, one gaseous phase and five particulate phases are included. Devolatilization, heterogeneous, and homogeneous chemical reactions as well as calcination and desulfurization reactions are incorporated. A calcination-only model and a calcination plus desulfurization model are simulated in 2-D and 3-D and the concentrations of SO2 leaving the reactors are compared. The simulated results are assessed against available published experimental data. The influence of the fluidized bed on the desulfurization is also considered
Prediction of particle charging in a dilute pneumatic conveying system

When particles are transported in pipelines, they acquire electrostatic charges as they come into contact with the pipe wall. Charged particles can cause problems such as particle agglomeration, blockage, and explosion. Understanding the particle charge can help to prevent these issues. This study investigates a technique for predicting the particle charge in a straight pipe of any given length, as well as the pipe length at which electrostatic equilibrium occurs, through experimentation in a short 1-m pipe section. Experimentation with five different types of particles and four pipe wall materials at longer pipe lengths were used to validate the technique. This predictive technique is applicable to a range of particle shapes and sizes under the restriction that charge transfer is due to impact charging
Mathematical modeling and design of layer crystallization in a concentric annulus with and without recirculation

This article has been accepted for publication and undergone full peer review but has not been\ud
through the copyediting, typesetting, pagination and proofreading process which may lead to\ud
differences between this version and the Version of Record. Please cite the published version at: http://dx.doi.org/10.1002/aic.14049A solution layer crystallization process in a concentric annulus is presented that removes the need for filtration. A dynamic model for layer crystallization with and without a recirculation loop is developed in the form of coupled partial differential equations describing the effects of mass transfer, heat transfer, and crystallization kinetics. The model predicts the variation of the temperature, concentration, and dynamic crystal thickness along the pipe length, and the concentration and temperature along the pipe radius. The model predictions are shown to closely track experimental data that were not used in the model's construction, and also compared to an analytical solution that can be used for quickly obtaining rough estimates when there is no recirculation loop. The model can be used to optimize product yield and crystal layer thickness uniformity, with constraints on the supersaturation to avoid bulk nucleation by adjusting cooling temperatures in the core and jacket. © 2013 American Institute of Chemical Engineers
Model-based design of a plant-wide control strategy for a continuous pharmaceutical plant

This is the pre-peer reviewed version of the article which has been published in final form at http://dx.doi.org/10.1002/aic.14107The design of an effective plant-wide control strategy is a key challenge for the development of future continuous pharmaceutical processes. This article presents a case study for the design of a plant-wide control structure for a system inspired by an end-to-end continuous pharmaceutical pilot plant. A hierarchical decomposition strategy is used to classify control objectives. A plant-wide dynamic model of the process is used to generate parametric sensitivities, which provide a basis for the synthesis of control loops. Simulations for selected disturbances illustrate that the critical quality attributes (CQAs) of the final product can be kept close to specification in the presence of significant and persistent disturbances. Furthermore, it is illustrated how selected CQAs of the final product can be brought simultaneously to a new setpoint while maintaining the remaining CQAs at a constant value during this transition. The latter result shows flexibility to control CQAs independently of each other
Experimental investigation of hysteretic dynamic effect in capillary pressure-saturation relationship for two-phase flow in porous media

This article was published in the serial AIChE Journal [Wiley / © American Institute of Chemical Engineers]. The definitive version is available at:  http://dx.doi.org/10.1002/aic.14121Well-defined laboratory experiments have been carried out to investigate hysteretic dynamic effect in capillary pressure–saturation relationships for two-phase flow in homogeneous and heterogeneous (layered) porous media. Conceptually, the dependence of the capillary pressure curves on the rate of change of saturation (dSw/dt) is defined as the dynamic effect in capillary pressure relationship, which is indicated by a dynamic coefficient, τ (Pa s) and it determines the rate at which two-phase flow equilibrium is reached, i.e., dSw/dt = 0 where Sw and t are the water saturation and time, respectively. The dependences of τ on various fluid and porous materials properties have been studied in the context of drainage; but, there is limited study for imbibition and the hysteresis of τ−Sw relationships. As such, the emphasis in this article is on reporting τ−Sw curves for imbibition while also demonstrating the hysteresis in the τ−Sw relationships by comparing τ−Sw curves for drainage (previously reported) and imbibition (this study) in carefully designed laboratory experiments. Homogeneous sand samples composed of either fine (small particle size and lower permeability) or coarse (larger particle size and higher permeability) sand have been used for these experiments. Furthermore, a layered domain made of a find sand layer sandwiched between two coarse sand layers is used as a model of heterogeneous domain. The results of the study confirm that the τ−Sw relationships are hysteretic in nature and, as such, the speed to flow equilibrium should vary depending on whether drainage or imbibition takes place. At a particular water saturation, the magnitudes of the dynamic coefficient (τ) are found to be generally higher for imbibition, which imply that the speed to flow equilibrium at the same saturation will be slower for imbibition
A new technique for recovering energy in thermally coupled distillation using vapor recompression cycles

Even though it has been proved that a fully thermally coupled distillation (TCD) system minimizes the energy used by a sequence of columns, it is well-known that vapor/liquid transfers between different sections produce an unavoidable excess of vapor (liquid) in some of them, increasing both the investment and operating costs. It is proposed here to take advantage of this situation by extracting the extra vapor/liquid and subjecting it to a direct/reverse vapor compression cycle. This new arrangement restores the optimal operating conditions of some of the affected sections with energy savings of around 20–30% compared with conventional TCD columns. Various examples, including the direct and reverse vapor recompression cycles, are presented. Furthermore, in each example, all possible modes of distillation (direct, indirect and Petlyuk distillation) with and without vapor recompression cycles (VRC) are compared to ensure that this approach delivers the best results.The authors would like to acknowledge financial support from the Spanish Ministerio de Ciencias e Innovación (PPQ, CTQ2009–14420-C02-02 and CTQ2012–37039-C02-02)
Precipitation of hydroxyapatite at 37 °C in a meso oscillatory flow reactor operated in batch at constant power density

A meso oscillatory flow reactor (OFR) was successfully applied for the precipitation of hydroxyapatite (HAp) nanoparticles. Mixing efficiency of the mesoreactor operated batchwise in a vertical tube was evaluated at constant power density, by monitoring variation of hue values upon mixing both spatially and temporally. The best operating conditions for fast mixing and a more homogeneous reaction medium were verified for f = 0.83 Hz and x0 = 4.5 mm. HAp precipitation was then carried out under these conditions at 37 °C for different mixing Ca/P molar ratios. HAp nanoparticles with a mean size (d50) of about 67 nm and a narrow size distribution were obtained. Furthermore, the obtained results show the advantages of the meso-OFR over a stirred tank batch reactor due to the production, about four times faster, of smaller and more uniform HAp nanoparticles. © 2013 American Institute of Chemical Engineers AIChE J, 2013This work was supported by the Portuguese Foundation for Science and Technology (SFRH/BD/42992/2008) through the MIT-Portugal Program, Bioengineering Systems Focus Area. The authors are thankful to Dr Jorge Ferreira from LNEG (Laboratorio Nacional de Energia e Geologia, Portugal) for carrying out the X-ray measurements and his help with the interpretation of results