kth.sePublications
Change search
Refine search result
12 51 - 77 of 77
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 51.
    Moreno, Luis
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Ordonez, Javier I.
    Cisternas, Luis A.
    Dissolution Model of Multiple Species: Leaching of Highly Soluble Minerals2017In: 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)
    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.

  • 52.
    Neretnieks, Ivars
    et al.
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Moreno, Luis
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Prediction of some in situ tracer tests with sorbing tracers using independent data2003In: Journal of Contaminant Hydrology, ISSN 0169-7722, E-ISSN 1873-6009, Vol. 61, no 04-jan, p. 351-360Article in journal (Refereed)
    Abstract [en]

    Some recent converging tracer tests with sorbing tracers at the Aspo Hard Rock Laboratory in Sweden, the TRUE tests, have been predicted using only laboratory data and hydraulic data from borehole measurements. No model parameters were adjusted to obtain a better fit with the experiments. The independent data were fracture frequency and transmissivity data obtained in the field and laboratory data on sorption and matrix diffusion. Transmissivity measurements in five boreholes in the rock volume containing the region surrounding the injection and collection points show that there is a high frequency of water conducting fractures. Of 162 packed off sections with 0.5 m packer distances, 112 were found to have a transmissivity above the detection limit. The specific flow-wetted surface (FWS) of the rock mass could be estimated from these data. The transmissivities were found to be reasonably well described by a lognormal distribution. Laboratory data on diffusion and sorption properties together with the hydraulic data were used to predict the residence time distribution (RTD) of the sorbing tracers. The results were compared with the experimental breakthrough curves. In these experiments, the water residence time is very small compared to the residence time of the sorbing tracers due to their diffusion and sorption within the rock matrix. We thus could neglect the influence of the water residence time in our predictions. Therefore, no information on water residence times or on dispersion was needed. The dispersion of the sorbing tracers is caused by the different sorbing tracer residence times in different pathways. The sorbing tracer residence time is determined by the ratio of flowrate to the flow-wetted surface in the different pathways and not by the water residence time. Assuming a three-dimensional flow pattern and using the observed fracture frequency and flowrate distribution, breakthrough curves for three strongly sorbing tracers were predicted. Only the laboratory data, the transmissivity measurements and the pumping flowrate were used in the predictions. No information on the water residence time as obtained by the nonsorbing tracers was used. The predictions were surprisingly accurate.

  • 53. Ordonez, Javier I.
    et al.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Mellado, Mario E.
    Cisternas, Luis A.
    Modeling validation of caliche ore leaching using seawater2014In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 126, p. 10-17Article in journal (Refereed)
    Abstract [en]

    Leaching column experiments of caliche were performed using seawater as the leaching agent because the caliche deposits are located in Northern Chile where water resources are scarce. The use of seawater without desalination is an attractive alternative for mining operations. The experimental recoveries of different ions were modeled using a hybrid model, which uses empirical information and fundamental principles. The following ions were considered: nitrate, iodine, sulfate, chloride, sodium, potassium and magnesium. The model explicitly considers different column heights, irrigation rates, and leaching agents. A sensitivity analysis showed that parameters associated with the particle level predominantly determined the calculated recoveries. The predictive capability was also tested, and the results were generally good, except for the sulfate ion, the dissolution of which was controlled by the presence of other ions.

  • 54. Ordóñez, J. I.
    et al.
    Condori, A.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Cisternas, L. A.
    Heap leaching of caliche ore. Modeling of a multicomponent system with particle size distribution2017In: Minerals, E-ISSN 2075-163X, Vol. 7, no 10, article id 180Article in journal (Refereed)
    Abstract [en]

    Caliche is a mineral exploited in northern Chile, from which iodine and Nitrate salts (saltpeter) are obtained. This ore is the most important source of iodine in the world and is processed mainly by heap leaching using water as a leaching agent. Heap leaching of caliche ore is carried out by the stacking of ROM (Run-Of-Mine) material, where the particle size distribution covers a wide range, from a few millimeters up to several decimeters, even diameters about 1 m. During the leaching, the multiple soluble species of caliche, which can reach total fractions larger than 40%, are dissolved at different rates, mainly controlled by their solubilities. When it occurs and unlike most other leachable ores, the particle size diminishes. The leaching modeling of several soluble species of caliche has been recently addressed; however, one of the main assumptions is the idealization that the heap is composed of particles of the same size. The present work aims to complement the previously formulated phenomenological models for caliche ore leaching, through a model that considers the simultaneous dissolution of two species from caliche with three different particle sizes. These two water-soluble species have different solubilities and dissolution rates and the conceptual model considers that both species are dissolved at the particle surface. When the most soluble species is being depleted, the particle collapses, leaving a remaining fraction of the less soluble species together with insoluble material. The less soluble species is now being dissolved from the collapsed material. This article also includes the experimental verification of the conceptual model using data obtained from column leaching tests conducted for this purpose, focusing on the dissolution of two soluble species: Nitrate and Magnesium.

  • 55. Ordóñez, J. I.
    et al.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    González, J. F.
    Cisternas, L. A.
    Use of discharged brine from reverse osmosis plant in heap leaching: Opportunity for caliche mining industry2015In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 155, p. 61-68Article in journal (Refereed)
    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.

  • 56. Ordóñez, J. I.
    et al.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Gálvez, E. D.
    Cisternas, L. A.
    Seawater leaching of caliche mineral in column experiments2013In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 139, p. 79-87Article in journal (Refereed)
    Abstract [en]

    Caliche is a mineral that contains a high fraction of soluble minerals and that is exploited in Northern Chile through vat or heap leaching for the production of iodine and nitrate. In this zone, the water availability is scarce, being a critical issue for the mining industries and whereby the use of other leaching agents as seawater may be a viable alternative. For this reason in the present study, column-leaching experiments using seawater were performed, including different irrigation rates and column heights. It is found that the highly soluble minerals such as nitrate and iodate are rapidly leached, while for other minerals like sulphate and chloride, the outlet concentration increased once that part of the sodium has been removed. Crystals of sodium sulphate were found at the column bottom, when this was dismantled. An existing phenomenological model (Gálvez et al., 2012) was used to analyse the changes of concentration of nitrate and iodine (as iodate) with a good agreement between the experiments and the simulations. On the other hand, for sulphate and chloride a new model was developed, which takes into account the dissolution and precipitation phenomena of these ions. The model was able to capture the trends observed in the experiments for the outlet concentrations of the modelled ions.

  • 57. Reyes, O.
    et al.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Parada, F.
    Sánchez, M.
    Modelling of bacterial leaching in heap with forced aeration2007In: Automation in Mining, Mineral and Metal Processing, 2007, no PART 1, p. 81-86Conference paper (Refereed)
    Abstract [en]

    A transient model for bioleaching of copper sulphide minerals in heaps/dumps with forced aeration was developed for a bed formed by particles of different particle sizes. Equations for the transport of oxygen, mass balance for copper and ferric ions, and heat transport were considered. The reaction in the particles was described by the shrinking core model. The present work considers two principal objectives. First, the possibility to find some "average radius" that represents the performance of a heap with a distribution of particle size was studied. Two possible average radii were tested. The first one is the "weight average radius" where the weight fraction for each size is used as weighting factor. The second one is the "surface average radius" where the weighting factor is the specific surface fraction for each size. The simulations show that it is not possible find such average radius. This means that the performance of the heap can not be determined using an "average radius", therefore a distribution of particle sizes has to be used. And the second objective, heap bioleaching with forced aeration was studied identifying the zones where the aeration is not appropriate in order to optimise the aeration configuration. The criterion used for the optimisation is to obtain almost the same reaction rate at a same height. The simulations indicate that this may be obtained by increasing the gas flow or by decreasing the distance between the aeration channels.

  • 58.
    Rodriguez, Raul
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Modeling of substrate degradation and microorganism growth in an UASB reactor2010In: CBEE 2009: Proceedings of the 2009 International Conference on Chemical, Biological and Environmental Engineering, Singapore: World Scientific Publ Co Ptd Ltd , 2010, p. 76-80Conference paper (Other academic)
    Abstract [en]

    A model for substrate degradation and microorganism growth in an UASB reactor was developed. The model is transient and takes into account advection, dispersion and degradation of the substrate. For the micro-organisms, the growth is described by a Monod type equation including a death constant. The model also assumes that a fraction of the microorganisms in the reactor may be carried out by the water flow. The UASB reactor is described as formed by many well-stirred reactors in series. Parameters for the model were taken from literature and MATLAB was used to solve the model. The sensibility of the process to the model parameters was also addressed.

  • 59.
    Rodriguez, Raul
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, LuisKTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Modelling of an Upflow Anaerobic Sludge Blanket reactor2010Collection (editor) (Other academic)
    Abstract [en]

    A model describing both physical and biological processes in Upflow Anaerobic Sludge Blanket (UASB) reactors was developed The main objective of the modelling was to take into account the transient growth of the microorganisms from the start-up of the reactor until a steady state is reached In addition, the model considers the degradation of the substrate and its reaction with the biomass, which is present in the form of spherical granules of different sizes For the degradation of the substrate within the granule, the mass transport through the stagnant film around the granule and the intra-particle diffusion are accounted for, together with the specific reaction rate In the model, the growth of the biomass follows the Contois kinetics The amount of biomass reaches a steady state after weeks or months Biomass is generated when substrate is degraded and a given fraction of biomass disappears per unit of time, which is determined by the decay constant The value of this constant is taken from the literature The model also considers that a fraction of the biomass may be carried out by the water flow The model was solved by using COMSOL Multiphysics Data from the literature was used in order to illustrate the processes occurring in the UASB reactor Modelling can be a useful tool for the design and optimization of UASB reactors

  • 60.
    Rodriguez, Raul
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Simulation of a UASB reactor2011Article in journal (Other academic)
    Abstract [en]

    A model has been developed to describe the behaviour of a UASB reactor with respect to substrate degradation, microorganism growth and granule size. The model is transient and includes advection, dispersion, and reaction terms. It also considers microorganism decay and the fraction of the biomass that can be dragged by the effluent. A mass balance was established in order to obtain an expression for the rate of the reaction occurring in the granule. It takes into account the resistance due to the mass transport through the stagnant film around the granule, the intra-particle diffusion, and the degradation rate within the granule.

     The model was solved using COMSOL Multiphysics software and data from the literature were used to study the performance of the model. The agreement between the model and the experimental results was satisfactory. The majority of the substrate is degraded at the bottom of the reactor due to the high density of granules present in that region. This kind of simulation may be a very helpful tool in the development and improvement of UASB reactors by predicting the reactor performance under different operating conditions.

  • 61.
    Rodriguez-Gomez, Raúl
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Liu, Longcheng
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    A model to describe the performance of the UASB reactor2014In: Biodegradation, ISSN 0923-9820, E-ISSN 1572-9729, Vol. 25, no 2, p. 239-251Article in journal (Refereed)
    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).

    Download full text (pdf)
    fulltext
  • 62.
    Rodríguez-Gómez, Raúl
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Liu, Longcheng
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    A model to predict the behavior of UASB reactors2013In: International Journal of Environmental Research, ISSN 1735-6865, E-ISSN 2008-2304, Vol. 7, no 3, p. 705-714Article in journal (Refereed)
    Abstract [en]

    A model describing the main processes occurring in the UASB reactor was developed; in order to maintain simplicity and applicability of the model, only the fundamental aspects were considered. In the model, the reactor is divided in several well-stirred reactors coupled in series and it comprises substrate degradation, biomass growth and the reactions that take place within the granules. The important contribution of the paper is the development of a model taking into account the mass transfer through the film around the granules, the intra-particle diffusion, and the degradation reaction. The model enables the determination of the removal efficiency of the substrate and the increase of both the height of the sludge bed and the granule size with time. The simulated results of an experimental UASB reactor treating sugar-cane mill wastewater were found to be in good agreement with the performance of the reactor. The sensitivity analysis shows that the performance of the reactor is determined by several parameters. The most important parameters are: the bioconversion rate, the mass transfer coefficient in the film, the intra-particle diffusivity, the volumetric fraction of biomass in the reactor, and the number of CSTR considered. These parameters should therefore be carefully determined. The model could be a useful tool in the optimization and development of UASB reactors.

    Download full text (pdf)
    fulltext
  • 63.
    Shahkarami, Pirouz
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Liu, Longcheng
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Analytical solution for N-member decay chain transport in fracture in rock2013In: Rock Characterisation, Modelling and Engineering Design Methods - Proceedings of the 3rd ISRM SINOROCK 2013 Symposium, Taylor & Francis Group, 2013, p. 323-328Conference paper (Refereed)
    Abstract [en]

    A model is developed to describe the transport of an N-member radionuclide decay chain along a discrete fracture situated in a porous matrix. An analytical solution is presented and a series of simulations are performed to study the relative significance of diffusion process into rock matrix, stagnant water, chain decay and hydrodynamic dispersion. The results show that a simplified model that ignores the effect of stagnant water zone can lead to significant error in the estimated time of arrival and peak value of the nuclides. The results demonstrate that for a two-member decay chain, neglecting the parent and modeling its daughter as a single species can result in significant overestimation of peak value of the nuclide. Moreover, it is found that as the dispersion increases, the arrival time and peak time of daughter decrease, while the peak value increases.

  • 64.
    Shahkarami, Pirouz
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Liu, Longcheng
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Radionuclide migration through fractured rock for arbitrary-length decay chain: Analytical solution and global sensitivity analysis: new2015In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 520, p. 448-460Article in journal (Refereed)
    Abstract [en]

    This study presents an analytical approach to simulate nuclide migration through a channel in a fracture accounting for an arbitrary-length decay chain. The nuclides are retarded as they diffuse in the porous rock matrix and stagnant zones in the fracture. The Laplace transform and similarity transform techniques are applied to solve the model. The analytical solution to the nuclide concentrations at the fracture outlet is governed by nine parameters representing different mechanisms acting on nuclide transport through a fracture, including diffusion into the rock matrices, diffusion into the stagnant water zone, chain decay and hydrodynamic dispersion. Furthermore, to assess how sensitive the results are to parameter uncertainties, the Sobol method is applied in variance-based global sensitivity analyses of the model output. The Sobol indices show how uncertainty in the model output is apportioned to the uncertainty in the model input. This method takes into account both direct effects and interaction effects between input parameters. The simulation results suggest that in the case of pulse injections, ignoring the effect of a stagnant water zone can lead to significant errors in the time of first arrival and the peak value of the nuclides. Likewise, neglecting the parent and modeling its daughter as a single stable species can result in a significant overestimation of the peak value of the daughter nuclide. It is also found that as the dispersion increases, the early arrival time and the peak time of the daughter decrease while the peak value increases. More importantly, the global sensitivity analysis reveals that for time periods greater than a few thousand years, the uncertainty of the model output is more sensitive to the values of the individual parameters than to the interaction between them. Moreover, if one tries to evaluate the true values of the input parameters at the same cost and effort, the determination of priorities should follow a certain sequence.

  • 65.
    Shahkarami, Pirouz
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Liu, Longcheng
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    The effect of stagnant water zones on retarding radionuclide transport in fractured rocks: An extension to the Channel Network Model2016In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 540, p. 1122-1135Article in journal (Refereed)
    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.

  • 66.
    Shahkarami, Pirouz
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Moreno, Luis
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Liu, Longcheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Channel network concept: an integrated approach to visualize solute transport in fractured rocks2019In: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157, Vol. 27, no 1, p. 101-119Article in journal (Refereed)
    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.

  • 67.
    Sidborn, Magnus
    et al.
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Casas, Jesus
    Martínez, Joaquín
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Moreno, Luis
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Two-dimensional Dynamic Model of a Copper Sulphide Ore Bed2003In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 71, p. 67-74Article in journal (Refereed)
    Abstract [en]

    A two-dimensional dynamic model for bioleaching of secondary copper minerals from a pile has been developed. In the model. aeration of the pile is considered to be due to natural convection caused by the density gradient in the air within the bed. The rate of sulphide mineral dissolution is modelled according to the unreacted core model. The transport of ferric ions from the particle surface to the reaction zone is calculated considering film diffusion, diffusion within the particle and reaction kinetics. The rate of oxidation of the ferrous ion by bacteria attached to the ore surface is modelled using the Michaelis-Menten relationship. The influences of temperature, dissolved ferric iron and dissolved oxygen in the leaching solution are considered in the kinetic formulation. The set of partial differential equations is solved using the FEMLAB(R) software. The model was used to study the influence of process variables on copper recovery in the bed with time. This model is a useful tool to aid the design and optimisation of industrial operations.

  • 68. Soler, J. M.
    et al.
    Neretnieks, Ivars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Moreno, Luis
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Liu, Longcheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Meng, Shuo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Svensson, U.
    Iraola, A.
    Ebrahimi, H.
    Trinchero, P.
    Molinero, J.
    Vidstrand, P.
    Deissmann, G.
    Říha, J.
    Hokr, M.
    Vetešník, A.
    Vopálka, D.
    Gvoždík, L.
    Polák, M.
    Trpkošová, D.
    Havlová, V.
    Park, D. -K
    Ji, S. -H
    Tachi, Y.
    Ito, T.
    Gylling, B.
    Lanyon, G. W.
    Predictive Modeling of a Simple Field Matrix Diffusion Experiment Addressing Radionuclide Transport in Fractured Rock. Is It So Straightforward?2022In: Nuclear Technology, ISSN 0029-5450, E-ISSN 1943-7471, Vol. 208, no 6, p. 1059-1073Article in journal (Refereed)
    Abstract [en]

    The SKB GroundWater Flow and Transport of Solutes Task Force is an international forum in the area of conceptual and numerical modeling of groundwater flow and solute transport in fractured rocks relevant for the deep geological disposal of radioactive waste. Two in situ matrix diffusion experiments in crystalline rock (gneiss) were performed at POSIVA’s ONKALO underground facility in Finland. Synthetic groundwater containing several conservative and sorbing radiotracers was injected at one end of a borehole interval and flowed along a thin annulus toward the opposite end. Several teams performed predictive modeling of the tracer breakthrough curves using “conventional” modeling approaches (constant diffusion and sorption in the rock, no or minimum rock heterogeneity). Supporting information, derived from small-scale laboratory experiments, was provided. The teams were free to implement different concepts, use different codes, and apply the transport and retention parameters that they considered to be most suited (i.e., not a benchmark exercise). The main goal was the comparison of the different sets of results and the analysis of the possible differences for this relatively simple experimental setup with a well-defined geometry. Even though the experiment was designed to study matrix diffusion, the calculated peaks of the breakthrough curves were very sensitive to the assumed magnitude of dispersion in the borehole annulus. However, given the very different timescales for advection and matrix diffusion, the tails of the curves provided information concerning diffusion and retention in the rock matrix regardless of the magnitude of dispersion. In addition, although the task was designed to be a blind modeling exercise, the model results have also been compared to the measured experimental breakthroughs. Experimental results tend to show relatively small activities, wide breakthroughs, and early first arrivals, which are somewhat similar to model results using large dispersivity values. 

  • 69.
    Soler, Josep M.
    et al.
    IDAEA-CSIC, 08034, Barcelona, Spain.
    Kekäläinen, Pekka
    University of Helsinki, FI-00014, Helsinki, Finland.
    Pulkkanen, Veli Matti
    VTT Technical Research Centre of Finland Ltd, FI-02044, VTT, Finland, VTT.
    Moreno, Luis
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Iraola, Aitor
    Amphos 21, 08019, Barcelona, Spain.
    Trinchero, Paolo
    Amphos 21, 08019, Barcelona, Spain.
    Hokr, Milan
    Technical University of Liberec, 461 17, Liberec 1, Czech Republic.
    Říha, Jakub
    Technical University of Liberec, 461 17, Liberec 1, Czech Republic.
    Havlová, Václava
    ÚJV Řež, a.s, 250 68, Husinec, Czech Republic.
    Trpkošová, Dagmar
    ÚJV Řež, a.s, 250 68, Husinec, Czech Republic.
    Vetešník, Aleš
    Czech Technical University in Prague, 160 00, Prague 6, Czech Republic.
    Vopálka, Dušan
    Czech Technical University in Prague, 160 00, Prague 6, Czech Republic.
    Gvoždík, Libor
    Progeo, 252 63, Roztoky, Czech Republic.
    Milický, Martin
    Progeo, 252 63, Roztoky, Czech Republic.
    Polák, Michal
    Progeo, 252 63, Roztoky, Czech Republic.
    Fukatsu, Yuta
    Japan Atomic Energy Agency (JAEA), Tokai-mura, Naka-gun, Ibaraki, 319-1184, Japan, Tokai-mura, Naka-gun.
    Ito, Tsuyoshi
    Japan Atomic Energy Agency (JAEA), Tokai-mura, Naka-gun, Ibaraki, 319-1184, Japan, Tokai-mura, Naka-gun.
    Tachi, Yukio
    Japan Atomic Energy Agency (JAEA), Tokai-mura, Naka-gun, Ibaraki, 319-1184, Japan, Tokai-mura, Naka-gun.
    Svensson, Urban
    Computer-aided Fluid Engineering AB, 371 65, Lyckeby, Sweden.
    Park, Dong Kyu
    Korea Atomic Energy Research Institute (KAERI), Daejeon, 3405, Republic of Korea.
    Ji, Sung Hoon
    Korea Atomic Energy Research Institute (KAERI), Daejeon, 3405, Republic of Korea.
    Gylling, Björn
    Gylling GeoSolutions, Evanston, Illinois, 60203.
    Lanyon, G. William
    Fracture Systems Ltd, St Ives, Cornwall, TR26 1EQ, United Kingdom.
    Predictive and Inverse Modeling of a Radionuclide Diffusion Experiment in Crystalline Rock at ONKALO (Finland)2023In: Nuclear Technology, ISSN 0029-5450, E-ISSN 1943-7471, Vol. 209, no 11, p. 1765-1784Article in journal (Refereed)
    Abstract [en]

    The REPRO-TDE test was performed at a depth of about 400 m in the ONKALO underground research facility in Finland. Synthetic groundwater containing radionuclide tracers [tritiated water tracer (HTO), 36Cl, 22Na, 133Ba, and 134Cs] was circulated for about 4 years in a packed-off interval of the injection borehole. Tracer activities were additionally monitored in two observation boreholes. The test was the subject of a modeling exercise by the SKB GroundWater Flow and Transport of Solutes Task Force. Eleven teams participated in the exercise, using different model concepts and approaches. Predictive model calculations were based on laboratory-based information concerning porosities, diffusion coefficients, and sorption partition coefficients. After the experimental results were made available, the teams were able to revise their models to reproduce the observations. General conclusions from these back-analysis calculations include the need for reduced effective diffusion coefficients for 36Cl compared to those applicable to HTO (anion exclusion), the need to implement weaker sorption for 22Na compared to results from laboratory batch sorption experiments, and the observation of large differences between the theoretical initial concentrations for the strongly sorbing 133Ba and 134Cs, and the first measured values a few hours after tracer injection. Different teams applied different concepts, concerning mainly the implementation of isotropic versus anisotropic diffusion, or the possible existence of borehole disturbed zones around the different boreholes. The role of microstructure was also addressed in two of the models.

  • 70.
    Soler, Josep
    et al.
    CSIC, Inst Environm Assessment & Water Res, IDAEA, Jordi Girona 18-26, Barcelona 08034, Catalonia, Spain..
    Meng, Shuo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Moreno, Luis
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Liu, Longcheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Kekalainen, Pekka
    Univ Helsinki, FIN-00014 Helsinki, Finland..
    Hokr, Milan
    Tech Univ Liberec, Liberec 46117 1, Czech Republic..
    Vetesnik, Ales
    Tech Univ Liberec, Liberec 46117 1, Czech Republic..
    Reimitz, Dan
    Czech Tech Univ, Prague 16000 6, Czech Republic..
    Visnak, Jakub
    Czech Tech Univ, Prague 16000 6, Czech Republic..
    Vopalka, Dusan
    Czech Tech Univ, Prague 16000 6, Czech Republic..
    Krohn, Klaus-Peter
    Gesell Anlagen & Reaktorsicherheit, GRS, D-38122 Braunschweig, Germany..
    Tachi, Yukio
    JAEA, Japan Atom Energy Agcy, Tokai, Ibaraki 3191184, Japan..
    Ito, Tsuyoshi
    JAEA, Japan Atom Energy Agcy, Tokai, Ibaraki 3191184, Japan..
    Svensson, Urban
    Comp Aided Fluid Engn AB, S-37165 Lyckeby, Sweden..
    Iraola, Aitor
    Amphos 21, Barcelona 08019, Catalonia, Spain..
    Trinchero, Paolo
    Amphos 21, Barcelona 08019, Catalonia, Spain..
    Voutilainen, Mikko
    Univ Helsinki, FIN-00014 Helsinki, Finland..
    Deissmann, Guido
    Forschungszentrum Julich, D-52425 Julich, Germany.;JARA CSD, D-52425 Julich, Germany..
    Bosbach, Dirk
    Forschungszentrum Julich, D-52425 Julich, Germany.;JARA CSD, D-52425 Julich, Germany..
    Park, Dong Kyu
    Korea Atom Energy Res Inst, Daejeon 34057, South Korea..
    Ji, Sung-Hoon
    Korea Atom Energy Res Inst, Daejeon 34057, South Korea..
    Gvozdik, Libor
    PROGEO, Rortoky 25263, Czech Republic..
    Milicky, Martin
    PROGEO, Rortoky 25263, Czech Republic..
    Polak, Michal
    PROGEO, Rortoky 25263, Czech Republic..
    Gylling, Björn
    Gylling GeoSolut, Evanston, IL 60203 USA..
    Lanyon, Bill
    Fracture Syst Ltd, St Ives TR26 1EQ, Cornwall, England..
    Modelling of the LTDE-SD radionuclide diffusion experiment in crystalline rock at the Aspo Hard Rock Laboratory (Sweden)2022In: Geologica Acta, ISSN 1695-6133, E-ISSN 1696-5728, Vol. 20, p. 1-32Article in journal (Refereed)
    Abstract [en]

    This study shows a comparison and analysis of results from a modelling exercise concerning a field experiment involving the transport and retention of different radionuclide tracers in crystalline rock. This exercise was performed within the Swedish Nuclear Fuel and Waste Management Company (SKB) Task Force on Modelling of Groundwater Flow and Transport of Solutes (Task Force GWFTS). Task 9B of the Task Force GWFTS was the second subtask within Task 9 and focused on the modelling of experimental results from the Long Term Sorption Diffusion Experiment in situ tracer test. The test had been performed at a depth of about 410m in the Aspo Hard Rock Laboratory. Synthetic groundwater containing a cocktail of radionuclide tracers was circulated for 198 days on the natural surface of a fracture and in a narrow slim hole drilled in unaltered rock matrix. Overcoring of the rock after the end of the test allowed for the measurement of tracer distribution profiles in the rock from the fracture surface (A cores) and also from the slim hole (D cores). The measured tracer activities in the rock samples showed long profiles (several cm) for non-or weakly-sorbing tracers (Cl-36, Na-22), but also for many of the more strongly-sorbing radionuclides. The understanding of this unexpected feature was one of the main motivations for this modelling exercise. However, re-evaluation and revision of the data during the course of Task 9B provided evidence that the anomalous long tails at low activities for strongly sorbing tracers were artefacts due to cross-contamination during rock sample preparation. A few data points remained for Cs-137, Ba-133, Ni-63 and Cd-109, but most measurements at long distances from the tracer source (>10mm) were now below the reported detection limits. Ten different modelling teams provided results for this exercise, using different concepts and codes. The tracers that were finally considered were Na-22, Cl-36, Co-57, Ni-63, Ba-133, Cs-137, Cd-109, Ra-226 and Np-237. Three main types of models were used: i) analytical solutions to the transport-retention equations, ii) continuum -porous-medium numerical models, and iii) microstructure-based models accounting for small-scale heterogeneity (i.e. mineral grains, porosities and/or microfracture distributions) and potential centimetre-scale fractures. The modelling by the different teams led to some important conclusions, concerning for instance the presence of a disturbed zone (a few mm in thickness) next to the fracture surface and to the wall of the slim hole and the role of micro-fractures and cm-scale fractures in the transport of weakly sorbing tracers. These conclusions could be reached after the re-evaluation and revision of the experimental data (tracer profiles in the rock) and the analysis of the different sets of model results provided by the different teams.

  • 71. Valdez, S.
    et al.
    Ordonez, J. I.
    Cisternas, L. A.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Leaching of coarse caliche ore. Experiment and modelling2016In: Brazilian journal of chemical engineering, ISSN 0104-6632, E-ISSN 1678-4383, Vol. 33, no 1, p. 105-114Article in journal (Refereed)
    Abstract [en]

    Heap leaching of caliche ores is frequently performed with run-of-mine (ROM) material, which includes rocks of very different sizes; however, most of the experimental data are obtained using small particles. To contribute to the understanding of caliche leaching, an experiment using coarse particles was carried out. The recoveries obtained from this experiment were compared with those observed in the leaching of fine particles and, as expected, a larger volume of leachant was required for leaching coarse particles to reach the same recovery. For the highly soluble species nitrate, the recovery was modelled using a previously developed model, obtaining good agreement without any fitting by using only the mass transfer coefficient obtained, by fitting, from fine particle leaching data in previous works. Physical properties such as permeability and capillarity were determined, showing that capillary forces are large, but that the permeability is very small, implying that flow through caliche particles should be very small.

  • 72. Yan, J. Y.
    et al.
    Moreno, Luis
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Neretnieks, Ivars
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    The long-term acid neutralizing capacity of steel slag2000In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 20, no 03-feb, p. 217-223Article in journal (Refereed)
    Abstract [en]

    The long-term acid neutralizing capacity (ANC) of the electric are furnace slag investigated by batch pH titration, and the neutralizing processes of the slag were evaluated by reaction path modeling. Reaction time plays an important role for the determination of the ANC for the steel slag. The relatively slow reactions may give large contributions to the ANC for a long-term leaching process, pH-dependent reactivities of the steel slag were found in the high pH range. The neutralizing rates at high pH were much slower than that at relatively low pH. Below pH 9, the reaction rates became less pH-dependent and usually fast. The features of neutralizing reactions of the slag may be explained by its mineralogical composition and dissolution kinetics in the neutralizing processes.

  • 73.
    Yang, Guomin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Density functional theory of electrolyte solutions in slit-like nanopores I. The RFD/WCA approach extended to non-restricted primitive model2017In: APPLIED CLAY SCIENCE, ISSN 0169-1317, Vol. 135, p. 526-531Article in journal (Refereed)
    Abstract [en]

    An extended reference fluid density approach/weighted correlation approximation (RFD/WCA) of density functional theory (DFT) is tested for the description of the non-restricted primitive model of electrolyte solutions in slit-like nanopores. The RFD/WCA approach of modeling size-asymmetric ions is validated by reproducing the density and electrostatic potential profiles of planar electrical double layer systems in the presence of mixtures of mono- and multivalent ions. The results from the DFT agree quite well with Monte Carlo simulations and satisfy the contact density sum rules of ionic fluid under a wide range of conditions. These findings suggest that a generic RFD/WCA approach can be formulated within the framework of the restricted and non-restricted primitive model to further investigate the swelling and ion exchange of clay minerals.

  • 74.
    Yang, Guomin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Wold, Susanna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Density functional theory of electrolyte solutions in slit-like nanopores II. Applications to forces and ion exchange2016In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 132, p. 561-570Article in journal (Refereed)
    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.

  • 75.
    Zhao, Zhihong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    A new numerical method of considering local longitudinal dispersion in single fractures2014In: International Journal for Numerical and Analytical Methods in Geomechanics, ISSN 0363-9061, E-ISSN 1096-9853, Vol. 38, no 1, p. 20-36Article in journal (Refereed)
    Abstract [en]

    The solutions of advection-dispersion equation in single fractures were carefully reviewed, and their relationships were addressed. The classic solution, which represents the resident or flux concentration within the semi-infinite fractures under constant concentration or flux boundary conditions, respectively, describes the effluent concentration for a finite fracture. In addition, it also predicts the cumulative distribution of solute particle residence time passing through a single fracture under pulse injection condition, based on which a particle tracking approach was developed to simulate the local advection-dispersion in single fractures. We applied the proposed method to investigate the influence of local dispersion in single fractures on the macrodispersion in different fracture systems with relatively high fracture density. The results show that the effects of local dispersion on macrodispersion are dependent on the heterogeneity of fracture system, but generally the local dispersion plays limited roles on marodispersion at least in dense fracture network. This trend was in agreement with the macrodispersion in heterogeneous porous media.

  • 76.
    Zhao, Zhihong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Analytical solution of coupled stress-flow-transport processes in a single rock fracture2011In: Computers & Geosciences, ISSN 0098-3004, E-ISSN 1873-7803, Vol. 37, no 9, p. 1437-1449Article in journal (Refereed)
    Abstract [en]

    A closed-form solution is presented for modeling the coupled stress-flow-transport processes along a single fracture embedded in a porous rock matrix. Necessary assumptions were made to simplify the subject into a two-dimensional (2D) problem, considering the changes of fracture aperture and matrix porosity under various stress conditions. The cubic law was assumed to be valid for the fluid flow in the fracture, with an impermeable rock matrix. For transport mechanisms, advective transport along the fracture, longitudinal hydrodynamic dispersion in the flow direction, and the matrix diffusion were considered in three different transport models under constant concentration or constant flux (Danck- werts’) inlet boundary conditions. This analytical solution can be used as a constitutive model, or as an example for validation of similar constitutive models, for modeling the coupled hydro-mechanical- chemical (HMC) processes in fracture networks of crystalline rocks. The influences of stress/deformation processes on different transport mechanisms in a single fracture under different inlet boundary conditions were studied for the first time. The results show that changes of fracture, as controlled by a combination of normal closure and shear dilatancy, have a significant influence on the solute concentration distribution both along the fracture and in the rock matrix, as well as on the solute residence/breakthrough time, especially when shear-induced dilatancy occurs. Under compressions, the decreasing matrix porosity slightly increases the solute concentration along the fracture and in the rock matrix.

  • 77.
    Zhao, Zhihong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Numerical modeling of stress effects on solute transport in fractured rocks2011In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 38, no 2, p. 113-126Article in journal (Refereed)
    Abstract [en]

    The effects of stress/deformation on fluid flow and contaminant transport in fractured rocks is one of the major concerns for performance and safety assessments of many subsurface engineering problems, especially radioactive waste disposal and oil/gas reservoir fields. However, very little progress has been made to study this issue due to difficulties in both experiments and numerical modeling. The objective of this study is to systematically investigate the influence of stress on solute transport in fractured rocks for the first time, considering different stress and hydraulic pressure conditions. A hybrid approach combining discrete element method (DEM) for stress-flow simulations and a particle tracking algorithm is developed. The impact of matrix diffusion (diffusion of molecular size solutes in and out of the rock matrix, and sorption onto the surface of micropores in rock matrix) is also included. The numerical results show that stress not only significantly changes the solute residence time through the fracture networks, but also changes the solute travel paths. Matrix diffusion plays a dominant role in solute transport when the hydraulic gradient is small, which is often encountered in practice.

12 51 - 77 of 77
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf