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Shahkarami, P., Neretnieks, I., Moreno, L. & Liu, L. (2019). Channel network concept: an integrated approach to visualize solute transport in fractured rocks. Hydrogeology Journal, 27(1), 101-119
Open this publication in new window or tab >>Channel network concept: an integrated approach to visualize solute transport in fractured rocks
2019 (English)In: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157, Vol. 27, no 1, p. 101-119Article in journal (Refereed) Published
Abstract [en]

The advection-dispersion equation, ADE, has commonly been used to describe solute transport in fractured rock. However, there is one key question that must be addressed before the mathematical form of the so-called Fickian dispersion that underlies the ADE takes on physical meaning in fractures. What is the required travel distance, or travel time, before the Fickian condition is met and the ADE becomes physically reasonable? A simple theory is presented to address this question in tapered channels. It is shown that spreading of solute under forced-gradient flow conditions is mostly dominated by advective mechanisms. Nevertheless, the ADE might be valid under natural flow conditions. Furthermore, several concerns are raised in this paper with regard to using the concept of a field-scale matrix diffusion coefficient in fractured rocks. The concerns are mainly directed toward uncertainties and potential bias involved in finding the continuum model parameters. It is illustrated that good curve fitting does not ensure the physical reasonability of the model parameters. It is suggested that it is feasible and adequate to describe flow and transport in fractured rocks as taking place in three-dimensional networks of channels, as embodied in the channel network concept. It is argued that this conceptualization provides a convenient framework to capture the impacts of spatial heterogeneities in fractured rocks and can accommodate the physical mechanisms underlying the behavior of solute transport in fractures. All these issues are discussed in relation to analyzing and predicting actual tracer tests in fractured crystalline rocks.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Solute transport, Channel network concept, Non-Fickian behavior, Advection-dispersion equation, Matrix diffusion
National Category
Geophysical Engineering
Identifiers
urn:nbn:se:kth:diva-245940 (URN)10.1007/s10040-018-1855-6 (DOI)000458520300007 ()2-s2.0-85053217977 (Scopus ID)
Note

QC 20190308

Available from: 2019-03-08 Created: 2019-03-08 Last updated: 2019-03-18Bibliographically approved
Lara, G. A., Moreno, L., Ramírez, Y. & Cisternas, L. A. (2018). Modeling an airlift reactor for the growing of microalgae. Open Chemical Engineering Journal, 12(1), 80-94
Open this publication in new window or tab >>Modeling an airlift reactor for the growing of microalgae
2018 (English)In: Open Chemical Engineering Journal, ISSN 1874-1231, Vol. 12, no 1, p. 80-94Article in journal (Refereed) Published
Abstract [en]

Objective: The flow dynamics of an airlift reactor for the growing of microalgae is modeled using Computational Fluid Dynamics (CFD). The model is applied to the operation and optimization of the reactor, giving a valuable picture of the liquid movement and carbon dioxide trajectory at different air injection flow rates. Methods: A novel aspect of the model is that air and carbon dioxide are injected at separated locations. Air is injected at the bottom of the reactor and CO 2 injection takes place in the downcomer region of the reactor to obtain longer CO 2 paths, improving its transference. Results: The results show modeling is a useful tool in the control of the reactor operation; for example, in avoiding the sedimentation of microalgae or for detecting the existence of zones with extremely low CO 2 concentrations.

Place, publisher, year, edition, pages
Bentham Science Publishers B.V., 2018
Keywords
Biofuel, Bubble column reactor, CFD, Fluent, Microalgae, Modeling, Photo-bioreactor
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-246504 (URN)10.2174/1874123101812010080 (DOI)2-s2.0-85061527047 (Scopus ID)
Note

QC 20190329

Available from: 2019-03-29 Created: 2019-03-29 Last updated: 2019-03-29Bibliographically approved
Meng, S., Liu, L., Mahmoudzadeh, B., Neretnieks, I. & Moreno, L. (2018). Solute transport along a single fracture with a finite extent of matrix: A new simple solution and temporal moment analysis. Journal of Hydrology, 562, 290-304
Open this publication in new window or tab >>Solute transport along a single fracture with a finite extent of matrix: A new simple solution and temporal moment analysis
Show others...
2018 (English)In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 562, p. 290-304Article in journal (Refereed) Published
Abstract [en]

A new simple and robust solution, based on uniform steady-state flow velocity, is developed for the problem of solute transport in a fracture-matrix system with a finite penetration depth of a radioactive contaminant into the rock matrix. The solution is an extension of Liu et al. (2017) to finite penetration depth and an alternative solution strategy to the problem solved by Sudicky et al. (1982). The solution takes the form of a convolution of two functions. The first function describes the probability density function of the residence time distribution of a conservative solute resulting merely from advection and Fickian dispersion. The second function is actually the impulse response of the fracture-matrix system in the case of a plug flow without any hydrodynamic dispersion. As a result, the effects of Fickian dispersion and matrix diffusion on solute transport are decoupled, and thus the resulting breakthrough curve can be analyzed in terms of those two functions. In addition to this, the derived Péclet numbers of those two functions, based on temporal moments, are also found to be associated with the derived Péclet number of the resulting breakthrough curve. By comparing the Péclet numbers of those two functions, the contribution of Fickian dispersion and matrix diffusion to solute spreading is determined in a straightforward way. This can aid to find out the dominating mechanism on solute transport, and therefore the performance of breakthrough curve.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Dispersion, Fractured rocks, Matrix diffusion, Péclet number, Solute transport model, Temporal moment analysis
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:kth:diva-228725 (URN)10.1016/j.jhydrol.2018.05.016 (DOI)000438003000022 ()2-s2.0-85047099016 (Scopus ID)
Funder
Swedish Nuclear Fuel and Waste Management Company, SKB
Note

QC 20180529

Available from: 2018-05-29 Created: 2018-05-29 Last updated: 2018-07-27Bibliographically approved
Moreno, L., Ordonez, J. I. & Cisternas, L. A. (2017). Dissolution Model of Multiple Species: Leaching of Highly Soluble Minerals. Metallurgical and materials transactions. B, process metallurgy and materials processing science, 48(3), 1817-1826
Open this publication in new window or tab >>Dissolution Model of Multiple Species: Leaching of Highly Soluble Minerals
2017 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, no 3, p. 1817-1826Article in journal (Refereed) Published
Abstract [en]

Dissolution of multi-species from a solid matrix is widely extended in different processes such as leaching of minerals; however, its modeling is often focused on a single species. A model for the simultaneous dissolution of soluble species was developed, which considers different solubilities and dissolution rates and considers that particle collapses when the rapidly soluble species is depleted. The collapsed matter is formed by inert material and a fraction of the soluble species with lower dissolution rate that has not dissolved yet. The model is applied to the leaching of a water-soluble mineral (caliche) with two soluble species dissolving simultaneously with different rates. Measured outlet concentrations of nitrate and magnesium were used to validate the model. Results showed that the model reproduced adequately the leaching of species with rapid and intermediate dissolution rate. Effect of the operating and kinetic parameters on the leaching process is also shown using the actual conditions of heap leaching for caliche mineral.

Place, publisher, year, edition, pages
Springer, 2017
National Category
Geochemistry
Identifiers
urn:nbn:se:kth:diva-207876 (URN)10.1007/s11663-017-0936-6 (DOI)000400385900037 ()2-s2.0-85015653079 (Scopus ID)
Note

QC 20170530

Available from: 2017-05-30 Created: 2017-05-30 Last updated: 2017-11-09Bibliographically approved
Yang, G., Neretnieks, I., Moreno, L. & Wold, S. (2016). Density functional theory of electrolyte solutions in slit-like nanopores II. Applications to forces and ion exchange. Applied Clay Science, 132, 561-570
Open this publication in new window or tab >>Density functional theory of electrolyte solutions in slit-like nanopores II. Applications to forces and ion exchange
2016 (English)In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 132, p. 561-570Article in journal (Refereed) Published
Abstract [en]

An extended reference fluid density approach/weighted correlation approximation (RFD/WCA) of density functional theory (DFT) for size-asymmetric electrolytes presented in part I is applied to calculate the forces and the ion exchange for Ca- and Na-montmorillonite systems in equilibrium with salt solutions. Our modeling shows that the DFT calculations are in excellent agreement with Monte Carlo simulations and experimental results. The results indicate that the ion size plays an important role in force-distance relation. Due to the excluded volume effect, the osmotic pressure curve predicted by DFT is shifted towards larger separation distances with increasing the diameter of counterions. Additionally, the interaction can be switched from attraction to repulsion with increasing diameter of counterions from standard to hydrated ionic size. Furthermore, the quantitative characterization of the exchange of calcium for sodium at room temperature on Wyoming bentonite is investigated with the DFT modeling in aqueous solutions at pH 7.0. It is found that a significant variation of the selectivity coefficient could be observed with the surface charge density, ionic diameter and interlayer separations. This implies that ion selectivity in compacted bentonite differs from that in dilute smectite dispersions.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Density functional theory, Montmorillonite, Ion exchange, Osmotic pressure, Swelling pressure
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-196377 (URN)10.1016/j.clay.2016.08.006 (DOI)000385600600065 ()2-s2.0-84991585055 (Scopus ID)
Note

QC 20161129

Available from: 2016-11-29 Created: 2016-11-14 Last updated: 2017-06-28Bibliographically approved
Mahmoudzadeh, B., Liu, L., Moreno, L. & Neretnieks, I. (2016). Solute transport through fractured rock: Radial diffusion into the rock matrix with several geological layers for an arbitrary length decay chain. Journal of Hydrology, 536, 133-146
Open this publication in new window or tab >>Solute transport through fractured rock: Radial diffusion into the rock matrix with several geological layers for an arbitrary length decay chain
2016 (English)In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 536, p. 133-146Article in journal (Refereed) Published
Abstract [sv]

The paper presents a model development to derive a semi-analytical solution to describe reactive solute transport through a single channel in a fracture with cylindrical geometry. The model accounts for advection through the channel, radial diffusion into the adjacent heterogeneous rock matrix comprising different geological layers, adsorption on both the channel surface, and the geological layers of the rock matrix and radioactive decay chain. Not only an arbitrary-length decay chain, but also as many number of the rock matrix layers with different properties as observed in the field can be handled. The solution, which is analytical in the Laplace domain, is transformed back to the time domain numerically e.g. by use of de Hoog algorithm. The solution is verified against experimental data and analytical solutions of limiting cases of solute transport through porous media. More importantly, the relative importance and contribution of different processes on solute transport retardation in fractured rocks are investigated by simulating several cases of varying complexity. The simulation results are compared with those obtained from rectangular model with linear matrix diffusion. It is found that the impact of channel geometry on breakthrough curves increases markedly as the transport distance along the flow channel and away into the rock matrix increase. The effect of geometry is more pronounced for transport of a decay chain when the rock matrix consists of a porous altered layer.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Analytical solution, Radial matrix diffusion, Geological rock layers, Fractured rock, Radionuclide decay chain
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-183591 (URN)10.1016/j.jhydrol.2016.02.046 (DOI)000374811200011 ()2-s2.0-84959564763 (Scopus ID)
Note

QC 20160318

Available from: 2016-03-17 Created: 2016-03-17 Last updated: 2017-11-30Bibliographically approved
Shahkarami, P., Liu, L., Moreno, L. & Neretnieks, I. (2016). The effect of stagnant water zones on retarding radionuclide transport in fractured rocks: An extension to the Channel Network Model. Journal of Hydrology, 540, 1122-1135
Open this publication in new window or tab >>The effect of stagnant water zones on retarding radionuclide transport in fractured rocks: An extension to the Channel Network Model
2016 (English)In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 540, p. 1122-1135Article in journal (Refereed) Published
Abstract [en]

An essential task of performance assessment of radioactive waste repositories is to predict radionuclide release into the environment. For such a quantitative assessment, the Channel Network Model and the corresponding computer program, CHAN3D, have been used to simulate radionuclide transport in crystalline bedrocks. Recent studies suggest, however, that the model may tend to underestimate the rock retarding capability, because it ignores the presence of stagnant water zones, STWZs, situated in the fracture plane. Once considered, the STWZ can provide additional surface area over which radionuclides diffuse into the rock matrix and thereby contribute to their retardation.

The main objective of this paper is to extend the Channel Network Model and its computer implementation to account for diffusion into STWZs and their adjacent rock matrices.

In the first part of the paper, the overall impact of STWZs in retarding radionuclide transport is investigated through a deterministic calculation of far-field releases at Forsmark, Sweden. Over the time-scale of the repository safety assessments, radionuclide breakthrough curves are calculated for increasing STWZ width. It is shown that the presence of STWZs enhances the retardation of most long-lived radionuclides except for 36Cl and 129I.

The rest of the paper is devoted to the probabilistic calculation of radionuclide transport in fractured rocks. The model that is developed for transport through a single channel is embedded into the Channel Network Model and new computer codes are provided for the CHAN3D. The program is used to (I) simulate the tracer test experiment performed at Äspö HRL, STT-1 and (II) investigate the short- and long-term effect of diffusion into STWZs. The required data for the model are obtained from detailed hydraulic tests in boreholes intersecting the rock mass where the tracer tests were made.

The simulation results fairly well predict the release of the sorbing tracer 137Cs. It is found that over the short time-scale of the tracer experiment, the effect of diffusion into STWZs is not as pronounced as that of matrix diffusion directly from the flow channel, and the latter remains the main retarding mechanism. Predictions for longer time-scale, tens of years and more, show that the effect of STWZs becomes strong and tends to increase with transport time. It is shown that over the long times of interest for safety assessment of radioactive waste repositories, STWZs can substantially contribute to radionuclide retardation, though for the short time-scales the impact is not very strong and is not expected to affect the results of short-term field experiments.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Channel Network Model, Stagnant water zones, Matrix diffusion, Radionuclide transport, CHAN3D program, Fractured rocks
National Category
Chemical Process Engineering Other Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-213978 (URN)10.1016/j.jhydrol.2016.07.031 (DOI)000382269500088 ()2-s2.0-84979030705 (Scopus ID)
Note

QC 20170926

Available from: 2017-09-07 Created: 2017-09-07 Last updated: 2019-09-04Bibliographically approved
Mahmoudzadeh, B., Liu, L., Moreno, L. & Neretnieks, I. (2015). Rock fracture closing moderated by pressure solution. In: Future Communication Technology and Engineering - Proceedings of the 2014 International Conference on Future Communication Technology and Engineering, FCTE 2014: . Paper presented at International Conference on Future Communication Technology and Engineering, FCTE 2014, 16 November 2014 through 17 November 2014 (pp. 269-275). CRC Press/Balkema
Open this publication in new window or tab >>Rock fracture closing moderated by pressure solution
2015 (English)In: Future Communication Technology and Engineering - Proceedings of the 2014 International Conference on Future Communication Technology and Engineering, FCTE 2014, CRC Press/Balkema , 2015, p. 269-275Conference paper, Published paper (Refereed)
Abstract [en]

Fracture apertures may decrease or increase by different mechanical and chemical mechanisms when the fractures are subject to stress. A model is presented to describe fracture closure/opening that accommodates pressure dissolution at contacting asperities as well as free-face dissolution/precipitation at free faces of the fracture and of the rock matrix. The derived analytical model accounts for the fact that dissolved minerals carried by flowing water along the fracture can not only diffuse into and out of the adjacent rock matrix but also at first diffuse into the stagnant water zone existing in part of the fracture plane and then from there into and out of the rock matrix adjacent to it. The analytical solution is used to study fracture closure/opening rate in a pseudo steady state, PSS, procedure. This simple model allows us to gain some insights into which processes and mechanisms have the larger impact on the fracture aperture under different circumstances.

Place, publisher, year, edition, pages
CRC Press/Balkema, 2015
Keywords
Dissolution, Rocks, Stresses, Chemical mechanism, Contacting asperities, Fracture apertures, Fracture closure, Free-face dissolution/precipitation, Pressure dissolution, Pressure solution, Pseudo steady state, Fracture
National Category
Geochemistry
Identifiers
urn:nbn:se:kth:diva-181595 (URN)2-s2.0-84951836365 (Scopus ID)9781138027770 (ISBN)
Conference
International Conference on Future Communication Technology and Engineering, FCTE 2014, 16 November 2014 through 17 November 2014
Note

QC 20160318

Available from: 2016-03-18 Created: 2016-02-02 Last updated: 2016-03-18Bibliographically approved
Ordóñez, J. I., Moreno, L., González, J. F. & Cisternas, L. A. (2015). Use of discharged brine from reverse osmosis plant in heap leaching: Opportunity for caliche mining industry. Hydrometallurgy, 155, 61-68
Open this publication in new window or tab >>Use of discharged brine from reverse osmosis plant in heap leaching: Opportunity for caliche mining industry
2015 (English)In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 155, p. 61-68Article in journal (Refereed) Published
Abstract [en]

Caliche is a highly water-soluble mineral that is exploited in northern Chile for its valuable content of iodine and nitrate, which are used in technological, medical, agriculture, dietary, and industrial applications. The processing of this mineral is through vat or heap leaching, where the species are dissolved using mainly fresh water and intermediate solutions. Since the deposits are located in zones with scarce water availability, one of the challenges for this industry is the search for new sustainable sources of water to face the process requirements. The use of groundwater sources by the mining industry has affected the domestic water supply for the nearest populations, increasing the need for new water alternatives as desalination of seawater by reverse osmosis (RO). A disadvantage of this method is the generation and discharge of highly concentrated brines to sea. In this work, the feasibility to use RO brine for caliche leaching was empirically proved through column-leaching experiments, which showed high recoveries of iodine and nitrate. Therefore, the use of RO brines may be an interesting option, on one side, for covering the increasing demand of processing water and, on the other side, to diminish the negative impact of brine disposal to the sea.

Keywords
Brine, Caliche, Leaching, Reverse osmosis, Seawater, Desalination, Groundwater, Iodine, Nitrates, Water supply, Column leaching experiments, Concentrated brines, Domestic water supply, Groundwater sources, Process requirements, Reverse osmosis plants, Water availability, Brines
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-167733 (URN)10.1016/j.hydromet.2015.04.008 (DOI)000356192200009 ()2-s2.0-84928136163 (Scopus ID)
Note

QC 20150601

Available from: 2015-06-01 Created: 2015-05-22 Last updated: 2019-02-07Bibliographically approved
Rodriguez-Gomez, R., Renman, G., Moreno, L. & Liu, L. (2014). A model to describe the performance of the UASB reactor. Biodegradation, 25(2), 239-251
Open this publication in new window or tab >>A model to describe the performance of the UASB reactor
2014 (English)In: Biodegradation, ISSN 0923-9820, E-ISSN 1572-9729, Vol. 25, no 2, p. 239-251Article in journal (Refereed) Published
Abstract [en]

A dynamic model to describe the performance of the Upflow Anaerobic Sludge Blanket (UASB) reactor was developed. It includes dispersion, advection, and reaction terms, as well as the resistances through which the substrate passes before its biotransformation. The UASB reactor is viewed as several continuous stirred tank reactors connected in series. The good agreement between experimental and simulated results shows that the model is able to predict the performance of the UASB reactor (i.e. substrate concentration, biomass concentration, granule size, and height of the sludge bed).

Keywords
CSTR, Kinetic, Model, UASB, Wastewater
National Category
Microbiology
Identifiers
urn:nbn:se:kth:diva-144112 (URN)10.1007/s10532-013-9656-z (DOI)000332797600007 ()2-s2.0-84895786597 (Scopus ID)
Note

QC 20140414

Available from: 2014-04-14 Created: 2014-04-10 Last updated: 2017-12-05Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8241-2225

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