Free Gas Phase Research Articles

Characterization and modelling of aerosol droplet in absorption columns

Formation of aerosols can cause serious complications in industrial exhaust gas cleaning processes. Small mist droplets and fog formed can normally not be removed in conventional demisting equipment because their submicron size allows the particles or droplets to follow the gas flow (Schaber et al., 2002). As a consequence of this aerosol based emissions in the order of grams per Nm3 have been identified from PCCC plants (Khakharia et al., 2015).In absorption processes aerosols can be created by spontaneous condensation or desublimation processes in supersaturated gas phases or as a result of droplets or particles entering with the exhaust gas. Undesired aerosol formation may lead to amine emissions many times larger than what would be encountered in a mist free gas phase in PCCC development. It is thus of crucial importance to understand the formation and build-up of these aerosols in order to mitigate the problem.This paper presents a rigorous model of aerosol dynamics leading to a system of partial differential equations. In order to understand the changes taking place with a particle entering an absorber an implementation of the model is created in Matlab. The model predicts the development in droplet size, droplet internal variable profiles and the mass transfer fluxes as function of position in the absorber, and thus also at the outlet. The Matlab model is based on a subclass method of weighted residuals for boundary value problems named, the orthogonal collocation method.The model comprises a set of mass transfer equations for transferring components and the necessary diffusion reaction equations to describe the droplet internal profiles for all relevant constituents. Also included is heat transfer across the interface and inside the droplet.This paper presents results describing the basic simulation tool for the characterization of aerosols formed in CO2 absorption columns and gives examples as to how various entering droplets grow or shrink through an absorber and how their composition changes with respect to position.

Prediction of Mass Spectral Response Factors from Predicted Chemometric Data for Druglike Molecules.

A method is developed for the prediction of mass spectral ion counts of drug-like molecules using in silico calculated chemometric data. Various chemometric data, including polar and molecular surface areas, aqueous solvation free energies, and gas-phase and aqueous proton affinities were computed, and a statistically significant relationship between measured mass spectral ion counts and the combination of aqueous proton affinity and total molecular surface area was identified. In particular, through multilinear regression of ion counts on predicted chemometric data, we find that log10(MS ion counts) = -4.824 + c 1•PA + c 2•SA, where PA is the aqueous proton affinity of the molecule computed at the SMD(aq)/M06-L/MIDI!//M06-L/MIDI! level of electronic structure theory, SA is the total surface area of the molecule in its conjugate base form, and c 1 and c 2 have values of -3.912 × 10-2 mol kcal-1 and 3.682 × 10-3 Å-2. On a 66-molecule training set, this regression exhibits a multiple R value of 0.791 with p values for the intercept, c 1, and c 2 of 1.4 × 10-3, 4.3 × 10-10, and 2.5 × 10-6, respectively. Application of this regression to an 11-molecule test set provides a good correlation of prediction with experiment (R = 0.905) albeit with a systematic underestimation of about 0.2 log units. This method may prove useful for semiquantitative analysis of drug metabolites for which MS response factors or authentic standards are not readily available. Graphical Abstract ᅟ.

Raman spectroscopy and quantum-mechanical analysis of tautomeric forms in cytosine and 5-methylcytosine on gold surfaces

Spectral differences between cytosine (Cyt) and 5-methylcytosine (5MC) were investigated by means of Raman spectroscopy with a combination of density functional theory (DFT) calculations. Surface-enhanced Raman scattering (SERS) revealed discriminating peaks of 5MC from those of Cyt upon adsorption on gold nanoparticles (AuNPs). Among the notable features, the multiple bands between 850 and 700cm−1 for the ring-breathing modes of 5MC and Cyt could be correlated well with the simulated spectra based on the DFT calculations of the adsorbates on the gold cluster atoms. The relative energetic stabilities of the enol/keto and the amino/imino tautomeric forms of Cyt and 5MC have been estimated using DFT calculations, before and after binding six atom gold clusters. Among the six tautomeric forms, the 7H keto amino and the 4H imino trans forms are expected to be predominant in binding gold atoms, whereas the enol trans/cis conformers would coexist in the free gas phase. Our approach may provide useful theoretical guidelines for identifying 5MC from Cyt by analyzing Raman spectra on gold surfaces on the basis of quantum-mechanical calculations.

Effect of Water Salinity on Coal Wettability During CO2Sequestration in Coal Seams

One of the most effective ways to reduce carbon dioxide (CO2) emissions is sequestration in geological reservoirs. CO2 sequestration in coal formations enhances the methane production from coalbeds (ECBM) in addition to storing CO2. CO2 can be stored in coalbeds in three ways: free gas phase in the pore space or the cleat network system, adsorbed molecules onto the organic surface of the coal, and dissolved in the groundwater within the coal. The performance of this process is dependent on the wettability behavior of the coal–water–CO2 system. This paper presents an investigation of the effect of the formation water salinity on the wettability behavior of highly volatile bitumen coal. The captive bubble method was used to measure the contact angle in coal–water–CO2 systems at pressures up to 2000 psi. The contact angle (CA) was measured at different NaCl concentrations (0–20 g/L). The CO2 adsorption isotherm on the coal surface was examined at different water salinities (0–20 g/L NaCl). Zeta-potential mea...

A thermodynamic model to predict the aqueous solubility of hydrocarbon mixtures at two-phase hydrate-liquid water equilibrium

Understanding the fate and transport of hydrocarbons and hydrocarbon mixtures in the deep sea and underlying sediments requires accurate determination of the two-phase hydrate (H)-liquid water (Lw) thermodynamic equilibrium in the absence of a free gas phase. In addition to controlling hydrate formation directly from the aqueous phase, the H-Lw equilibrium provides the aqueous solubility of dissolving hydrate. The aqueous solubility of hydrocarbon mixture at H-Lw equilibrium was calculated based on the van der Waals and Platteeuw statistical thermodynamic model and the Holder model. Langmuir constants were calculated from cell potential parameters obtained from ab initio intermolecular potentials and thus the model contains no fitting parameters. The model accurately predicts pure methane, ethane, and propane experimental H-Lw equilibrium solubility data, including new data provided here for methane. We present hydrocarbon solubilities in water and seawater at H-Lw equilibrium at deep sea conditions for both methane and a thermogenic mixture based on the methane–ethane–propane ratio from the 2010 Macondo oil spill. We also present model predictions of the proportion of occupied large and small cages at H-Lw equilibrium for both systems, as well as hydrocarbon ratios in the hydrate phase for the thermogenic mixture.

Helium and carbon isotope signatures of gas exhalations in the westernmost part of the Pannonian Basin (SE Austria/NE Slovenia): Evidence for active lithospheric mantle degassing

We present new isotope (C, He, Ne, Ar, partly N) and compositional data from the free gas phase of fourteen degassing sites in the westernmost part of the Pannonian Basin near the Austria/Slovenia borderline. Based on these data, the origin of the gases and the degree of modification of the gas signatures due to interaction processes during migration are evaluated. The isotope signatures indicate an origin of helium and CO2 predominantly in the subcontinental mantle. Measured 3He/4He ratios from 4.95 to 6.32 Ra include the highest ones recorded in the whole Pannonian Basin system. Only at three locations in the periphery of the degassing center, a substantial admixture of crustal helium was found. The CO2 in the mofette gases and at the sites with the highest 3He/4He ratios (~6.3 Ra) is characterized by δ13C values of −3.5‰. In comparison with MORB (Mid-ocean Ridge Basalt), it is thus slightly enriched in 13C. The 3He/4He isotope ratios within the range typical for the subcontinental lithospheric mantle (SCLM) point to a fast, localized fluid transport from the magmatic reservoir to the surface.There are only few sites in European non-active volcanic regions where free gases with unmodified SCLM helium isotope signature escape at the surface. A comparison of the elemental and isotopic geochemical characteristics of gases with SCLM-helium signature from four different regions (Massif Central/France, Eifel/Germany, Eger Rift/Czech Republic and the westernmost part of the Pannonian Basin system) indicates that the European SCLM in general is characterized by a reservoir more enriched in 13C compared to MORB.

Resistivity and induced polarization monitoring of biogas combined with microbial ecology at a brownfield site

The accumulation of biogenic greenhouse gases (methane, carbon dioxide) in organic sediments is an important factor in the redevelopment and risk management of many brownfield sites. Good practice with brownfield site characterization requires the identification of free-gas phases and pathways that allow its migration and release at the ground surface. Gas pockets trapped in the subsurface have contrasting properties with the surrounding porous media that favor their detection using geophysical methods. We have developed a case study in which pockets of gas were intercepted with multilevel monitoring wells, and their lateral continuity was monitored over time using resistivity. We have developed a novel interpretation procedure based on Archie’s law to evaluate changes in water and gas content with respect to a mean background medium. We have used induced polarization data to account for errors in applying Archie’s law due to the contribution of surface conductivity effects. Mosaics defined by changes in water saturation allowed the recognition of gas migration and groundwater infiltration routes and the association of gas and groundwater fluxes. The inference on flux patterns was analyzed by taking into account pressure measurements in trapped gas reservoirs and by metagenomic analysis of the microbiological content, which was retrieved from suspended sediments in groundwater sampled in multilevel monitoring wells. A conceptual model combining physical and microbiological subsurface processes suggested that biogas trapped at depth may have the ability to quickly travel to the surface.

Carboxylic acid catalyzed hydration of acetaldehyde.

Electronic structure calculations of the pertinent stationary points on the potential energy surface show that carboxylic acids can act effectively as catalysts in the hydration of acetaldehyde. Barriers to this catalyzed process correlate strongly with the pKa of the acid, providing the potential to provide the predictive capacity of the effectiveness of carboxylic acid catalysts. Transition states for the acid-catalyzed systems take the form of pseudo-six-membered rings through the linear nature of their hydrogen bonds, which accounts for their relative stability compared to the more strained direct and water-catalyzed systems. When considered as a stepwise reaction of a dimerization followed by reaction/complexation, it is likely that collisional stabilization of the prereactive complex is more likely than reaction in the free gas phase, although the catalyzed hydration does retain the potential to proceed on water surfaces or in droplets. Lastly, it is observed that postreactive diol-acid complexes are significantly stable (∼12-17 kcal/mol) relative to isolated products, suggesting the possibility of long-lived hygroscopic species that could act as a seed molecule for condensation of secondary organic aerosols.

Direct ion imaging approach for investigation of ion dynamics in multipole ion guides.

A key requirement of electrospray ionization (ESI) and other techniques facilitating ionization at elevated pressures is the efficient transport of free gas-phase ions into the high vacuum region of the mass spectrometer. Radio frequency (RF) multipole ion guides that allow for collisional cooling are one of the most popular means of achieving this. However, their performance is highly dependent on several experimental factors, including pressure and various electrode potentials along the ion path. To experimentally visualize these effects, we have employed a position-sensitive detector at the exit of a quadrupole mass spectrometer (QMS) instrument operated in RF only mode that employs an RF only octopole as a collisional cooling ion guide. This allows the spatial distribution of the ions, and its dependence on experimentally determined conditions, to be directly visualized at the exit of the quadrupole. This investigation provides a detailed insight into the ion dynamics occurring inside multipole ion guides. This knowledge can directly be applied to instrument development and to improve the ion transmission efficiency and, thus, sensitivity. Numerical simulations using custom-developed trajectory simulation software are compared and contrasted with the experimental observations.

Ammonia synthesis by hydrogenolysis of titanium-nitrogen bonds using proton coupled electron transfer.

The catalytic hydrogenolysis of the titanium-amide bond in (η(5)-C5Me4SiMe3)2Ti(Cl)NH2 to yield free ammonia is described. The rhodium hydride, (η(5)-C5Me5)(py-Ph)RhH (py-Ph = 2-phenylpyridine), serves as the catalyst and promotes N-H bond formation via hydrogen atom transfer. The N-H bond dissociation free energies of ammonia ligands have also been determined for titanocene and zirconocene complexes and reveal a stark dependence on metal identity and oxidation state. In all cases, the N-H BDFEs of coordinated NH3 decreases by >40 kcal/mol from the value in the free gas phase molecule.

Sorption behaviour of targeted volatile organic compounds on airborne particulate matter using selected ion flow tube mass spectrometry

Intensive agriculture emits air pollutants such as inorganic gases, volatile organic compounds (VOC) and airborne particulate matter. The public can suffer from severe odour nuisance caused by these emissions, particularly in areas with high population densities. Odorous compounds are not only present in the free gas phase but undergo a partitioning between the gas phase and particulate matter making particles possible odour carriers. In order to investigate this partitioning behaviour, an advanced analytical method was developed using selected ion flow tube mass spectrometry (SIFT-MS). This method was used to determine the particle-to-air partitioning coefficients of 4 important organic odorants (acetic acid, butanoic acid, phenol and dimethyl disulphide). An air stream with constant VOC concentration was generated in a home-made system and was injected as a step function onto a chromatographic column packed with particles (PM 10 ) collected from a pig stable using high volume sampling. From the registered breakthrough curves, dimensionless particle-to-air partitioning coefficients were calculated. They ranged from 13 × 10 3 ± 3.1 × 10 3 for dimethyl disulphide to 16 × 10 5 ± 1.7 × 10 5 for phenol. Partitioning coefficients can be estimated using octanol–air partitioning coefficients available from the literature (r 2 = 0.94). The results show that particles were enriched in VOC but the fraction of sorbed volatiles was low ( 10 concentration of 1 mg m −3 .

Gas-driven radionuclide transport in undisturbed and disturbed Boom Clay

Abstract In deep geological repositories for the disposal of radioactive waste, gas can be generated by different mechanisms including anaerobic corrosion, radiolysis and microbial degradation. If the gas generation rate is larger than the capacity for the diffusive transport of the dissolved gas, a free gas phase will be formed, eventually leading to gas-breakthrough events. Depending on the timing of gas breakthrough, dissolved radionuclides (RN) and contaminants could be driven out of the clay faster than the normally expected diffusive transport. A column experiment was designed in which a water-saturated clay core is placed directly on top of a thin Boom Clay core that has been previously saturated with a tracer solution (0.01 mol l −1 NaI). A helium gas pressure is applied and stepwise increased. Upon gas breakthrough, the water on top of the column is expelled and analysed for its iodide content. The measured concentration iodide is linked to the amount of NaI-saturated pore water that was displaced. Based on the results, it can be concluded that the transport of radionuclides and contaminants because of a gas-breakthrough event is possible but appears to be very limited. The volume of water displaced is very low (three orders of magnitude) compared to the volume of gas transported upon breakthrough.

Numerical modelling and performance studies of the original and advanced TEMKIN reactor in laboratory scale testing of industrial egg shell catalysts for the selective hydrogenation of acetylene

Strong interactions between reaction kinetics and transport phenomena force the use of specialised reactors for catalysis experiments. Our working group developed an advanced version of the so called TEMKIN reactor by Temkin and Kulkova (1969), intended for the direct testing of industrial catalysts, e.g. egg shell catalysts used for the selective hydrogenation of acetylene. This work is dealing with modelling of the complex mass and heat transport to investigate and evaluate the influence on the reaction kinetics. Modelling was done using the commercial modelling software COMSOL Multiphysics® and was successfully validated by pulse tagging as well as catalysis experiments. Due to the flexible coupling possibilities in COMSOL, modelling distinguishes between the free gas phase, catalytically active porous shell and inert porous core of the catalyst pellets, ab initio depicting inner as well as outer mass transport limitations. Simulations confirmed good isothermal conditions in both reactor versions, but point out significant transport limitations in the original TEMKIN reactor due to dead zones near the catalyst pellets. Although direct numerical modelling is still challenging due to high computational demands, this work was able to show up its potential in studying laboratory scale reactor designs and catalytic systems.

Microwave plasmas applied for the synthesis of free standing graphene sheets

Self-standing graphene sheets were synthesized using microwave plasmas driven by surface waves at 2.45 GHz stimulating frequency and atmospheric pressure. The method is based on injecting ethanol molecules through a microwave argon plasma environment, where decomposition of ethanol molecules takes place. The evolution of the ethanol decomposition was studied in situ by plasma emission spectroscopy. Free gas-phase carbon atoms created in the plasma diffuse into colder zones, both in radial and axial directions, and aggregate into solid carbon nuclei. The main part of the solid carbon is gradually withdrawn from the hot region of the plasma in the outlet plasma stream where nanostructures assemble and grow. Externally forced heating in the assembly zone of the plasma reactor has been applied to engineer the structural qualities of the assembled nanostructures. The synthesized graphene sheets have been analysed by Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy and x-ray photoelectron spectroscopy. The presence of sp3 carbons is reduced by increasing the gas temperature in the assembly zone of the plasma reactor. As a general trend, the number of mono-layers decreases when the wall temperature increases from 60 to 100 °C. The synthesized graphene sheets are stable and highly ordered.

Grain-scale imaging and compositional characterization of cryo-preserved India NGHP 01 gas-hydrate-bearing cores

We report on grain-scale characteristics and gas analyses of gas-hydrate-bearing samples retrieved by NGHP Expedition 01 as part of a large-scale effort to study gas hydrate occurrences off the eastern-Indian Peninsula and along the Andaman convergent margin. Using cryogenic scanning electron microscopy, X-ray spectroscopy, and gas chromatography, we investigated gas hydrate grain morphology and distribution within sediments, gas hydrate composition, and methane isotopic composition of samples from Krishna–Godavari (KG) basin and Andaman back-arc basin borehole sites from depths ranging 26 to 525 mbsf. Gas hydrate in KG-basin samples commonly occurs as nodules or coarse veins with typical hydrate grain size of 30–80 μm, as small pods or thin veins 50 to several hundred microns in width, or disseminated in sediment. Nodules contain abundant and commonly isolated macropores, in some places suggesting the original presence of a free gas phase. Gas hydrate also occurs as faceted crystals lining the interiors of cavities. While these vug-like structures constitute a relatively minor mode of gas hydrate occurrence, they were observed in near-seafloor KG-basin samples as well as in those of deeper origin (>100 mbsf) and may be original formation features. Other samples exhibit gas hydrate grains rimmed by NaCl-bearing material, presumably produced by salt exclusion during original hydrate formation. Well-preserved microfossil and other biogenic detritus are also found within several samples, most abundantly in Andaman core material where gas hydrate fills microfossil crevices. The range of gas hydrate modes of occurrence observed in the full suite of samples suggests a range of formation processes were involved, as influenced by local in situ conditions. The hydrate-forming gas is predominantly methane with trace quantities of higher molecular weight hydrocarbons of primarily microbial origin. The composition indicates the gas hydrate is Structure I.

CO2 Injection in a Coal Seam – Insights from the European Carbolab Project with Focus on Water Geochemical Monitoring

Abstract The CARBOLAB project is funded by the European program RFCS (Research Fund for Coal and Steel). It gathers six partners from Spain, France and Poland. One of the main tasks of this project is to perform in-situ CO 2 injection in a coal seam located at 464 m depth in the Montsacro pit, Asturias, Spain. Injection of CO 2 in coal seams is one of the options for climate change mitigation but it presents lots of uncertainties and technical difficulties. Therefore work is needed to better constraint the processes especially the adsorption of CO 2 and the subsequent desorption of CH4. This work consists in experimental laboratory work, modelling aspects and real tests. This paper is focused on this last topic and more specifically on the water monitoring aspects. Complementary investigations on the gas phase can be found in other works presented by Lafortune et al. in this conference. In-situ injection of CO 2 has been performed in July 2013 in one selected coal seam. The CO 2 is injected directly in the vein and monitoring boreholes are located at the wall and in the surrounding sedimentary formations. The aim is to get a detailed and representative overview of the consequences of the CO 2 injection. Here the focus is on the geochemical monitoring. Baseline acquisitions have been performed in 2012 and early 2013. This allowed to define a strategy mainly focused on the monitoring of the saturated zone albeit the site was initially thought to be drier. Acquisitions in the unsaturated zone (free gas phase) have also been done but in a less extent. Chemical logging of water saturated boreholes (GC1S and GC3N, parallel to the seam) revealed, even at short distance, the existence of different water masses from one side of the coal vein to the other. This is mainly linked to a difference in the amount of dissolved solids in water. During the injection experiment, no noticeable deviations from the baseline values were found for GC1S borehole. At the opposite, the bottom of GC3N experienced strong changes: decrease of more than 2.5 pH units, rise of the electrical conductivity (+29%) and of the alkalinity (+23%).

Coupling of TOUGHREACT-Geochemist Workbench (GWB) for Modeling Changes in the Isotopic Composition of CO2 Leaking from a CCS Storage Reservoir

Abstract A novel coupled TOUGHREACT-Geochemist Workbench (GWB) model has been developed to predict changes of the isotopic composition of CO2 resulting from reactive transport during leakage of CO2 from a storage reservoir. In the TOUGHREACT environment, we created a simplified 2D radial multi-aquifer model with 50 vertical cells for the Shell Quest project site and simulated reactive transport processes that may occur during a hypothetical CO2 leakage event. Perl scripts were developed to take input and output data from TOUGHREACT and create input files for GWB for subsequent modeling of the isotopic composition of leaking CO2. Using this approach, we simulated the extent of changes of the isotopic composition of leaking CO2 at 1000 T/y and 100 Darcy permeability for the first 10 cells extending from the Basal Cambrian Sandstone to just above the overlying Winnipegosis. Initial results indicate that the leaking free gas phase had δ13C values of CO2 within 1 ‰ of that of the injected CO2. δ18O values of leaking CO2 showed more pronounced changes since they are controlled by oxygen isotope ratios of formation water and significant equilibrium isotope fractionation between CO2 and H2O. This suggests that ™13C values, but not ™18O values, of injected CO2 are a suitable tracer if they are sufficiently distinct from those of baseline carbon compounds.

Viscoelasticity of Ells River bitumen sand and 4D monitoring of thermal enhanced oil recovery processes

Samples of Ells River bitumen sand from Alberta, Canada were measured at low frequencies (0.2–205 Hz) to determine the temperature and frequency dependence of velocities and attenuations. The samples were first measured “as received” where the pore space is mostly filled with bitumen but also contains small amounts of air and water. With residual air in the pores, at 5°C, there is strong dispersion in the P-wave modulus and a peak in attenuation at seismic frequencies. The frequency-dependent moduli and attenuations shift by three orders of magnitude in frequency as temperature is increased from 5°C to 48°C, consistent with the bitumen viscosity. Samples were then saturated so any empty pore space is filled with water. After saturation, at 1 Hz, increasing temperature from 5°C to 49°C causes a 30% reduction in the saturated P-wave modulus, a 34% reduction in the saturated bulk modulus, and a 6% reduction in the shear modulus. This behavior can only be explained by the temperature-dependent bulk modulus of bitumen. The results enable predictions regarding the P-velocities that can be expected during seismic monitoring of thermal enhanced oil recovery processes. Velocities for cold bitumen sand are near [Formula: see text] at reservoir pressure and temperature. Following steam injection, velocities should be very low (near [Formula: see text]) in heated zones more than 50°C with a free gas phase, which could be steam or gas. There will be a progressive reduction in velocities, i.e., [Formula: see text] at 25°C and [Formula: see text] at 49°C, in areas of formation heating, but without steam or gas in the pores. Albeit smaller than the effect of steam, the effect of formation heating alone is large enough to be easily detected by today’s 4D surveys. With local rock physics calibration, it should be possible to map the areal extent of formation heating using 4D seismic data.

A cylindrical electrical resistivity tomography array for three-dimensional monitoring of hydrate formation and dissociation

The LArge Reservoir Simulator (LARS) was developed to investigate various processes during gas hydrate formation and dissociation under simulated in situ conditions of relatively high pressure and low temperature (close to natural conditions). To monitor the spatial hydrate distribution during hydrate formation and the mobility of the free gas phase generated during hydrate dissociation, a cylindrical Electrical Resistivity Tomography (ERT) array was implemented into LARS. The ERT contains 375 electrodes, arranged in 25 circular rings featuring 15 electrodes each. The electrodes were attached to a neoprene jacket surrounding the sediment sample. Circular (2D) dipole-dipole measurements are performed which can be extended with additional 3D cross measurements to provide supplemental data. The data quality is satisfactory, with the mean standard deviation due to permanent background noise and data scattering found to be in the order of 2.12%. The measured data are processed using the inversion software tool Boundless Electrical Resistivity Tomography to solve the inverse problem. Here, we use data recorded in LARS to demonstrate the data quality, sensitivity, and spatial resolution that can be obtained with this ERT array.

Determination of gas diffusion coefficients in saturated porous media: He and CH4 diffusion in Boom Clay

Boom Clay is presently studied as the reference host formation for the disposal of high-level and long-lived radioactive waste in Belgium. In a geological repository, the production of gas is unavoidable. Gas is produced by different mechanisms: anaerobic corrosion of metals in waste and packaging, radiolysis of water and organic materials in the packages and microbial degradation of various organic wastes. Corrosion and radiolysis yield mainly hydrogen while microbial degradation leads to methane and carbon dioxide. The generated gas will dissolve in the ground water. As transport in Boom Clay is dominated by diffusion, the dissolved gas is transported away from the repository by diffusion as dissolved species. If the rate of gas generation is larger than the diffusive flux into Boom Clay, the pore water within the disposal gallery will become oversaturated and a free gas phase might form. If the gas pressure keeps increasing, free gas ingress into Boom Clay will occur, most likely through creation of new pathways. In order to make a good evaluation of the balance between gas generation and gas dissipation through engineered barriers and host formation, good estimates for the gas diffusion coefficients of the gases are needed. The currently available gas diffusion parameters for hydrogen in Boom Clay suffer from a large uncertainty, and by application of conservative values for both the source term and the gas migration term the formation of a free gas phase can presently not be excluded for some waste types.In this study a versatile method was developed to determine more precisely the gas diffusion coefficient for dissolved gases in Boom Clay. For the development of the technique, He and CH4 were used.The proposed method is based on a through diffusion methodology and allows for two dissolved gases to diffuse through a clay sample at the same time. From the evolution of the diffusant concentration in both compartments, the apparent diffusion coefficients of dissolved He and CH4 were obtained: 12.2×10−10 and 2.42×10−10m2/s, with uncertainties of 10%, respectively.