Mercury Porosimetry Data Research Articles

Characterization of Porous β-Type Tricalcium Phosphate Ceramics Formed via Physical Foaming with Freeze-Drying.

Porous β-tricalcium phosphate (Ca3(PO4)2; β-TCP) was prepared via freeze-drying and the effects of this process on pore shapes and sizes were investigated. Various samples were prepared by freezing β-TCP slurries above a liquid nitrogen surface at -180 °C with subsequent immersion in liquid nitrogen at -196 °C. These materials were then dried under reduced pressure in a freeze-dryer, after which they were sintered with heating. Compared with conventional heat-based drying, the resulting pores were more spherical, which increased both the mechanical strength and porosity of the β-TCP. These materials had a wide range of pore sizes from 50 to 200 µm, with the mean and median values both approximately 100 µm regardless of the freeze-drying conditions. Mercury porosimetry data showed that the samples contained small, interconnected pores with sizes of 1.24 ± 0.25 µm and macroscopic, interconnected pores of 25.8 ± 4.7 µm in size. The effects of nonionic surfactants having different hydrophilic/lipophilic balance (HLB) values on foaming and pore size were also investigated. Materials made with surfactants having lower HLB values exhibited smaller pores and lower porosity, whereas higher HLB surfactants gave higher porosity and slightly larger macropores. Even so, the pore diameter could not be readily controlled solely by adjusting the HLB value. The findings of this work indicated that high porosity (>75%) and good compressive strength (>2 MPa) can both be obtained in the same porous material and that foaming agents with HLB values between 12.0 and 13.5 were optimal.

Tortuosity of pore channels in tight rocks as a key parameter in fluid flow ability

Tortuosity is a significant parameter in porous materials analysis. Not only, when it comes to rocks or soils but also cellular materials, alloys or cells, the multiple definitions exist for tortuosity and several purposes. Geometrical tortuosity describes the pore network paths; on the other hand thermal, diffusional, electrical and hydraulic tortuosity refers to the transport processes in the pore network. Computed X-ray tomography (CT) is the best solution in tortuosity estimation, thanks to the 3D images. In particular, computed X-ray tomography, together with mercury porosimetry (MICP), pulse- and pressure-decay permeability methods (PDP), as well as electrical parameter measurements (EPM), links and expands the information about the tortuosity into the greater meaning. The geological material was composed of tight, low-porosity and low-permeability gas-saturated rocks cored from the present depth of deposition below 3000 m, containing different lithologies, as sandstones, mudstones, limestones, and dolomites. The research presents the novel approach in the identification and analysis of the main pore channels based on 3D CT images. Algorithm of the central axis identifies and analyzes the whole main flow path and calculates tortuosity. High correlation was observed between the tortuosity and Swanson parameter from mercury porosimetry data. Moreover, the high correlation was detected between the tortuosity and saturation exponent from electrical parameter measurement in analyzed tight low-porosity and low-permeability deposits. Multilinear regression (MLR) allows estimating absolute permeability taking CT, MICP and EPM parameters into consideration. Combination of these parameters in one equation with high determination coefficient gives credence in estimating preliminary absolute permeability (PDP) based on the data which is executed as standard core analysis (MICP and EPM) and data from the non-invasive method (CT).

Densification of A3-3 matrix graphite to inhibit the infiltration of liquid FLiBe salt in molten salt reactors

In this study, a novel graphite was prepared by adding MCMBs (mesocarbon microbeads) to densify matrix graphite A3−3, a typical fuel element and moderator material in high-temperature gas-cooled reactors. The densified graphite was evaluated as a potential fuel element material for molten salt reactors (MSRs). In particular, the effects of MCMB loading on physical properties and the corresponding effects on the infiltration of liquid fluoride salt in MSRs were studied, as molten salt infiltration can impact safe reactor operation. MCMBs with a mean particle size of approximately 3 μm were added to matrix graphite A3−3 at loading levels of 1 wt%, 5 wt%, 10 wt%, and 15 wt%, and samples were prepared by a quasi-isostatic pressing process at 250 MPa. Mercury porosimetry data showed that MCMB-densified graphite (MDGs) had lower porosity (approximately 15 vol%) and median pore diameters (ranging from 105 to 306 nm) compared to A3−3 itself (22.9 vol% porosity and 573 nm median pore diameter). Importantly, the MDGs exhibited greatly reduced infiltration by FLiBe molten salt compared to unmodified A3−3. For instance, A3−3 modified with 1 wt% MCMB exhibited a 2.1 % weight increase after treatment at 1 MPa for 20 h, while unmodified A3−3 exhibited a weight increase of 11.6 %. This study revealed that MDGs could be promising candidate materials for the graphite matrix of fuel elements as well as a neutron moderator and reflector in MSRs.

Deposition, Diagenesis, and Sequence Stratigraphy of the Pennsylvanian Morrowan and Atokan Intervals at Farnsworth Unit

Farnsworth Field Unit (FWU), a mature oilfield currently undergoing CO2-enhanced oil recovery (EOR) in the northeastern Texas panhandle, is the study area for an extensive project undertaken by the Southwest Regional Partnership on Carbon Sequestration (SWP). SWP is characterizing the field and monitoring and modeling injection and fluid flow processes with the intent of verifying storage of CO2 in a timeframe of 100–1000 years. Collection of a large set of data including logs, core, and 3D geophysical data has allowed us to build a detailed reservoir model that is well-grounded in observations from the field. This paper presents a geological description of the rocks comprising the reservoir that is a target for both oil production and CO2 storage, as well as the overlying units that make up the primary and secondary seals. Core descriptions and petrographic analyses were used to determine depositional setting, general lithofacies, and a diagenetic sequence for reservoir and caprock at FWU. The reservoir is in the Pennsylvanian-aged Morrow B sandstone, an incised valley fluvial deposit that is encased within marine shales. The Morrow B exhibits several lithofacies with distinct appearance as well as petrophysical characteristics. The lithofacies are typical of incised valley fluvial sequences and vary from a relatively coarse conglomerate base to an upper fine sandstone that grades into the overlying marine-dominated shales and mudstone/limestone cyclical sequences of the Thirteen Finger limestone. Observations ranging from field scale (seismic surveys, well logs) to microscopic (mercury porosimetry, petrographic microscopy, microprobe and isotope data) provide a rich set of data on which we have built our geological and reservoir models.

Dual Compressibility Characteristics of Lignite, Subbituminous, and High-Volatile Bituminous Coals: A New Insight into Permeability

Pore compressibility is an important physical property of coal, which controls geomechanical behavior and hydrocarbon reserve evaluation of coal seams. However, the representation of pore compressibility is usually oversimplified in coalbed methane (CBM) reservoir analysis. This study proposes the adoption of the dual compressibility concept, where both accessible porosity (connected pore) and the inaccessible portion of the coal compressibility contribute to the storage and transport capacities of coal reservoirs, provided the availability of mercury porosimetry data. We characterize dual compressibility as a function of confining pressure and identified the effect of factors, such as coal rank, moisture content, and porosity. It was found that pore compressibility reduces decreased one order of magnitude, from 10−3–10−2 to 10−4–10−3 MPa−1, with confining pressure increasing up to 413.3 MPa. The calculated compressibility of accessible pores is one-to-two orders of magnitude higher than the inaccessible portion of the coal. Using a compressibility correction on pore volume connectivity and permeability estimates showed a 23% reduction in those estimates. Results suggest that high pore compressibility affects storage and transport capacity more significantly than previously regarded. We propose a new model to estimate coal permeability as a function of confining pressure and accessible pore compressibility. The model uses integrated intrusion correction and pore compressibility values from the Katz–Thompson method. Pore volume and permeability response with pressure were evaluated according to coal rank, macro-lithotype, and seam. This work provides an improved methodology to estimate hydrocarbon reserves and CBM reservoir performance through more accurate pore volume and permeability evaluations from mercury porosimetry data.

ASP flooding in tight carbonate rocks

Alkaline-Surfactant-Polymer (ASP) floods can mobilize oil left behind by waterfloods by lowering the interfacial tension. However, conducting such floods in tight carbonate rocks presents several challenges, e.g., polymer transport in low permeability carbonates, presence of divalent ions, geochemical interactions with chemicals and rock surface, pore-scale heterogeneity, and oil-/mixed-wettability. This paper addresses the first three challenges. A systematic study of polymer transport in low permeability carbonate cores was performed. Shearing of high molecular weight polymers and successive filtration treatment were performed to improve polymer size distribution. Single phase polymer transport experiments were performed in low permeability carbonate rocks, and optimum pretreatment method was developed. Surfactant phase behavior and aqueous stability experiments were performed to develop ultralow tension ASP and SP formulations with a reservoir crude oil. ASP and SP corefloods were performed in oil-wet low permeability limestone rocks. The oil recovery, pressure drop, effluent ionic composition, effluent viscosity and effluent surfactant concentrations were measured. PHREEQC simulations were performed to understand geochemical reactions during ASP floods. The polymer treatment procedure was able to successfully transport polymer through low permeability Edwards Yellow limestone cores, but not through Texas Cream limestone due to differences in their pore structures. It was found that polymer hydrodynamic radius must be smaller than the pore throat radii of the rock for successful polymer transport. Therefore, mercury porosimetry data of the porous medium is critical for polymer selection, especially in case of low permeability rocks. Tertiary ASP floods resulted in improving the cumulative oil recovery to 77–87% OOIP, whereas SP flood improved the cumulative oil recovery to 85% in an outcrop core. Surfactant retentions during ASP and SP corefloods were found to be 0.4 mg/g-rock and 0.3 mg/g-rock, respectively, in outcrop cores.

An Ising-Based Simulator for Capillary Action in Porous Media

Multiphase flows in porous media are encountered in several contexts—e.g., hydrocarbon recovery operations, battery electrodes, microfluidic devices, etc. Capillary-dominated flows are interesting due to the complex interplay of interfacial properties and pore geometries. Conventional hydrodynamic flow solvers are computationally inefficient in the capillary-dominated regime, particularly in complex pore structures. The algorithm developed here specifically targets this regime to reduce simulation times. We minimise the fluid–fluid and fluid–solid interaction energies through an approach inspired by the ferromagnetic Ising model. We validate the algorithm on (1) model pore geometries with analytical solutions for capillary action, and (2) rocks with available mercury porosimetry data. We validate its predictions for model geometries and sandstones using (1) curvatures calculated from theories developed by Mayer–Stowe–Princen, Ma and Morrow, and Mason and Morrow; (2) predictions from GeoDict, a commercial software package, which also includes a state-of-the-art drainage simulator; (3) mercury porosimetry data. Drainage capillary pressure curves predicted for Bentheimer and Fontainebleau rocks reasonably match porosimetry data.

Textural characterization of chars using fractal analysis of N2 and CO2 adsorption

The application of fractal analysis to nitrogen and carbon dioxide adsorption isotherms is used together with other textural analysis techniques with the aim of obtaining a better knowledge of the phenomena leading to char formation. This is an important point since chars are key intermediate materials during the manufacturing process of active carbons. The materials under study were series of chars obtained from a high-volatile A bituminous coal oxidized in air at 543 and 473K for different periods of time extending up to 42days. The fractal characteristics of the chars were obtained from the nitrogen and carbon dioxide adsorption isotherms by using the methods proposed by Neimark, Wang and Li, and the fractal version of the Frenkel-Halsey-Hill method. The latter approach was found suitable for the high pressure interval of N2 isotherms. Evolution of the fractal properties in the series of chars is compared with that corresponding to the series of precursor coals. Changes in pore network during carbonization depend on the severity of the air preoxidation of the coal. This happens since preoxidation conditions other properties and processes such as the texture of the precursor coals, the release of the volatile matter as well as the plastic behaviour of coals. These three points were found to be the key factors that determine the fractal characteristics of char. The role of the pore characteristics of the coal on the textural features of the obtained chars is boosted if coal preoxidation is carried out at the more elevated temperature, 543K. The role that the phenomena occurring throughout the carbonization of oxidized coals have on the textural characteristics of the chars obtained is explained considering fractal features together with other textural properties. The results of this work are compared with previous fractal studies based on mercury porosimetry data and conventional textural techniques.

Effects of air flow rate on the oxidation of NBG-18 and NBG-25 nuclear graphite

The effects of air flow rate (FR) (FR range: 1–10 L/min) on the oxidation of NBG-18 and NBG-25 nuclear graphite grades at temperatures between 600 and 1100 °C were studied, in reference to the standard test procedure for measuring oxidation rates of nuclear graphite in air (ASTM D 7542-09). The results showed that the FR effects on oxidation rate (OR) increase with increasing temperature with negligible FR effects at 600 °C for both materials. At high temperatures (>800 °C) there appears to be a two-stage relationship between FR and OR, which corresponds to the transition between reaction rates dominated by chemical kinetics and those dominated by diffusion. The material-specific microstructure appeared strongly influences this transition. The overall OR-FR behaviours of NBG-18 were higher than NBG-25 at 600–800 °C while negligible differences in the OR-FR behaviours between the two grades were observed at 900–1100 °C. The mercury porosimetry data showed that the higher OR-FR behaviours observed in NBG-18 may partly be attributed to the differences in the pore size distribution (open porosity and cumulative pore area) between the grades, especially for the large size pores (diameter ≫ 5 × 103 nm).

Weathering of metapelites from the Quadrilátero Ferrífero mineral province, southeastern Brazil

Low-grade metamorphic rocks are known for their low mechanical strength and high weatherability. In the Quadrilatero Ferrifero, an important mineral province located in southeastern Brazil, this set of features results in frequent issues with mining and road slope instability, mainly associated with phyllites. Despite the significant iron ore production that occurs in this province, little is known about the geotechnical properties of the materials constituting the weathering front. Here, we report work aimed at investigating the changes in the basic properties of phyllites at four weathering grades. The methodology used included the field classification and mapping of four weathering grades in order to assess their spatial distribution on a road slope, as well as sampling for geological characterization by petrography and X-ray diffraction (XRD). In addition, the authors performed a physical characterization of all weathering grades, including index properties, mercury porosimetry, and strength data obtained with a Schmidt hammer both in the field and in the laboratory as well as using the point load test (PLT). Results showed the relevance of structural features such as discontinuities and metamorphic foliation observed in the weathering morphology in situ, with different weathering intensities occurring along the slope. Changes in the porosity and pore size distribution in the weathering front were nonlinear, as were resistance variations. The difficulty involved in performing the macroscopic identification of weathering grades due to the very fine texture of the rock as well as microstructural heterogeneities are likely causes of the observed variability in phyllite properties. This fundamental knowledge may aid the prediction of short-term and long-term scenarios for slope stability based on rock weatherability.

On the characterization of pore size distribution of building materials

Moisture affects significantly the energy performance of air conditioning systems, the durability of materials, and the health of occupants. One way of reducing those effects, without increasing the energy costs, is by means of using porous material ability of absorbing and releasing moisture from/to the adjacent environment, which attenuates the indoor relative humidity variation. This natural ability is intrinsically related to the porous microstructure. Therefore, the characterization of the pore space is an important research theme in the building physics area. This article aims to present a method for obtaining the pore size distribution based on adsorption isotherms and mercury porosimetry data. First, the theoretical formulation based on the Gibbs free energy for a two-phase (liquid–vapor) system, using the De Boer and Zwikker model, is presented, allowing the calculation of the critical adsorbed thickness for pore filling, critical radius, adsorbed moisture content, capillary condensation content, available surface for adsorption, and the distribution of micropores for a wide range of radius. The adsorption isotherm curve is estimated for high relative humidity values through mercury porosimetry, along with the adsorption curve obtained from the experiment. The pore volume distribution calculated by this method can be used to estimate transport coefficients for liquid and vapor phases.

Determination of the Hydraulic Radius of the Porous Structure of Ceramic Materials

The existing relations describing capillary inhibition in porous materials based on an ideal model and mercury porosimetry data are analyzed. It is shown that in transitioning from the hydraulic radius of an ideal model to the hydraulic radius of a capillary-porous material the tortuosity and narrowing (widening) of capillaries, the increase in temperature associated with sorption of water vapor, and the variation of the water viscosity as a function of the hydraulic radius of the capillary must be taken into account. The experimental data are used to make a quantitative evaluation of these effects. On this basis a relation is proposed for determining the hydraulic radius of the porous structure of the ceramic materials used for construction articles.

Induced polarization and pore radius — A discussion

Permeability estimation from induced polarization (IP) measurements is based on a fundamental premise that the characteristic relaxation time [Formula: see text] is related to the effective hydraulic radius [Formula: see text] controlling fluid flow. The approach requires a reliable estimate of the diffusion coefficient of the ions in the electrical double layer. Others have assumed a value for the diffusion coefficient, or postulated different values for clay versus clay-free rocks. We have examined the link between a widely used single estimate of [Formula: see text] and [Formula: see text] for an extensive database of sandstone samples, in which mercury porosimetry data confirm that [Formula: see text] is reliably determined from a modification of the Hagen-Poiseuille equation assuming that the electrical tortuosity is equal to the hydraulic tortuosity. Our database does not support the existence of one or two distinct representative diffusion coefficients but instead demonstrates strong evidence for six orders of magnitude of variation in an apparent diffusion coefficient that is well-correlated with [Formula: see text] and the specific surface area per unit pore volume [Formula: see text]. Two scenarios can explain our findings: (1) the length scale defined by [Formula: see text] is not equal to [Formula: see text] and is likely much longer due to the control of pore-surface roughness or (2) the range of diffusion coefficients is large and likely determined by the relative proportions of the different minerals (e.g., silica and clays) making up the rock. In either case, the estimation of [Formula: see text] (and hence permeability) is inherently uncertain from a single characteristic IP relaxation time as considered in this study.

An improvement of the fractal theory and its application in pore structure evaluation and permeability estimation

AbstractWe present an improved fractal model for pore structure evaluation and permeability estimation based on the high pressure mercury porosimetry data. An accumulative fractal equation is introduced to characterize the piecewise nature of the capillary pressure and the mercury saturation. The iterative truncated singular value decomposition algorithm is developed to solve the accumulative fractal equation and obtain the fractal dimension distributions. Furthermore, the fractal dimension distributions and relevant parameters are used to characterize the pore structure and permeability. The results demonstrate that the proposed model provides better characterization of the mercury injection capillary pressure than conventional monofractal theory. In addition, there is a direct relationship between the pore structure types and the fractal dimension spectrums. What is more, the permeability is strongly correlated with the geometric and the arithmetic mean values of fractal dimensions, and the permeability estimated using these new fractal dimension parameters achieve excellent result. The improved model and solution give a fresh perspective of the conventional monofractal theory, which may be applied in many geological and geophysical fields.

Investigation of microstructure and mechanical properties of novolac/silica and C/SiO2/SiC aerogels using mercury porosimetry method

Novolac/silica nanocomposite aerogels are prepared through the sol–gel polymerization process under a solvent saturated vapor atmosphere. The silica phase is extracted from rice husk ash in the form of silica xerogel powder. Nanocomposite aerogels are then fabricated through sol–gel polymerization of novolac resin in the presence of silica xerogel powder. These nanocomposite aerogels are then converted to carbon/silica and carbon/silica/silicon carbide nanocomposite aerogels using pyrolysis and carbothermal reduction processes at 800 and 1500°C, respectively. Mercury porosimetry method is used for the evaluation of microstructure and mechanical properties of fabricated hybrid nanocomposite aerogels. Mercury porosimetry analysis and scanning electron microscopy results confirmed that the Pirard and Washburn theories are valid for the evaluation of aerogels' pore size distribution. The buckling intrusion mechanism is studied for all polymeric and carbon nanocomposite aerogels below transition pressure. The effect of heat treatment on the microstructural properties is also investigated by mercury porosimetry analysis. The Young's modulus values are determined using mercury porosimetry data and compression results. Based on our results, the Young's modulus of hybrid nanocomposite aerogels is not necessarily related to the density of aerogels.

Investigation of pore structure and fractal characteristics of the Lower Silurian Longmaxi shales in western Hunan and Hubei Provinces in China

The pore structure characteristics of the Lower Silurian Longmaxi Formation shales collected from western Hunan and Hubei were investigated using high-pressure mercury injection and low-temperature N2 adsorption/desorption experiments. Total organic carbon values, thermal maturity values and mineralogical compositions were also obtained by relevant experimental methods. The TOC value varies from 0.71% to 4.75%, with a mean value of 2.58%, and their thermal maturities have reached the over-mature stage and dry gas generation window. Quartz and clay minerals are the major mineral compositions in the samples. In contrast to previous studies of other shales (Chalmers and Bustin, 2008; Han et al., 2013; Wang et al., 2013), there are no carbonates in the shale samples of this area. Due to their biogenic source, quartz content is positively correlated with TOC values. Pore size distributions obtained from mercury injection experiments were divided into three groups. Samples with higher TOC content always have smaller dominant pore sizes, and the pore sizes of samples with higher clay mineral content and lower TOC values may be larger, with a major peak between 30 nm and 1 μm. Through analyzing the N2 adsorption and desorption isotherms, we found that the morphology of pores in the shales rich in organic matter is narrow neck and wide body, and that of those rich in clay minerals is flat-shaped. BJH and DFT models were used to derive pore size distributions using N2 adsorption data, and both are representative. The differential distribution curves of pore volumes and surface areas show that all shale samples' dominant pore sizes are within the range of micropores and mesopores, and they are the major contributors to pore surface areas, while mesopores and macropores make more significant contributions to pore volumes. The specific surface area calculated by the BET method ranges from 6.12 to 28.42 m2/g, with an average value of 16.14 m2/g, and the total pore volume varies from 0.0105 to 0.0338 cm3/g, with a mean value of 0.0213 cm3/g. The correlational analysis between pore structure parameters and TOC value, quartz and clay mineral content indicates that organic matter and quartz are positively associated with the micropores and fine mesopores, though larger pores can also exist in organic matter, and clay minerals play an important role in mesopores and macropores generation. Due to the infeasibility of using mercury porosimetry data to obtain fractal dimensions, Dn calculated from N2 adsorption data are used, its value ranges from 2.6353 to 2.7694, with an average value of 2.7284. As we know, the more micropores contained in the shale, the more complex the pore structure will be, and as a result, the fractal dimension will be larger. Therefore, organic matter and quartz positively influence fractal dimension, and there is a negative relationship between clay mineral content and fractal dimension.

Improving the accuracy of catalyst pore size distributions from mercury porosimetry using mercury thermoporometry

Mercury porosimetry is still frequently used to obtain the pore size distributions (PSDs) for porous heterogeneous catalyst pellets. However, unless the contact angle in the Washburn equation is correctly calibrated, porosimetry strictly remains only a relative technique. There is a particular potential issue for catalyst samples containing heavy metals, which may present (relatively) wetting surfaces to mercury, when the standard analysis is based upon the presumption of consistent non-wetting behaviour. Data in the literature on the impact of heavy metals on mercury intrusion is conflicting with some studies suggesting they do impact intrusion and some suggesting they do not. This study uses complementary gas sorption and mercury thermoporometry experiments that were fully serially-integrated with porosimetry to provide additional information to improve the interpretation of the basic mercury porosimetry data and validate the pore sizes obtained from it. These complementary data have been used to show that the wetting effect from heavy metals on intrusion may be confined to the smallest nanopores in the sample where the pore wall potentials begin to overlap. It has also been shown that confined mercury shows a significant advanced melting effect during thermoporometry. The thermoporometry studies revealed that the common interpretation of sharp intrusion curves and high entrapment levels in porosimetry data as implying ink-bottle pore geometries is flawed.

Determining hydraulic radii of construction wall materials in capillary moisture transfer

The present paper provides an analysis of the existing dependencies describing the kinetics of fluid capillary rise in porous materials on the basis of the ideal model and on the basis of mercury porosimetry data; it also determines and describes the factors related to the deviation from the approximated experimental data (the discrepancy between the predicted values and the experimental data). A dependence for determining the pore hydraulic radius in the ideal model was obtained from the condition of the identical kinetics of capillary water rise in both the actual material and in its model. A method was developed of assessing the hydraulic radius required for determining capillary moisture transfer in shielding structures which takes into account the effect of narrowing and widening of capillaries, the effect of the temperature rise related to water vapour sorption and the effect of changes in water viscosity.

Consolidation and dewatering of a microfibrillated cellulose fiber composite paper in wet pressing

The emerging research field of bio-based nanomaterials has gained a lot of interest recently. One of the most promising new range of materials are the micro and nanofibrillated celluloses, or nanocelluloses that are based on wood or other natural cellulose sources. While the strength increasing potential of nanocelluloses is evident in light of the current knowledge, the related challenges in dewatering are inevitable due to the hydrophilic nature and the large relative surface area of the material. The target of this work was to characterize the dewatering and structural changes of a high filler content (70wt% precipitated calcium carbonate) biocomposite containing microfibrillated cellulose in a wet pressing process. Softwood bleached kraft pulp fibers were used as a reinforcement in the composite. Press dewatering performance together with dynamic density measurements were made with a press simulator, and scanning electron microscopy and mercury intrusion porosimetry were used in the structural analysis of the samples. The dewatering of a new type of MFC based composite was shown to be better than traditional softwood based fibers. The high amount of filler in the structure does not contribute to the binding of water and helps to provide channels for water removal. Mercury porosimetry data was able to partially explain the good press dewatering of the composite paper compared to a SBKP reference paper. Based on the results, it can be concluded that the dewatering of the MFC composite is not limited by the wet pressing operation commonly used in the paper manufacturing industry. Excellent optical properties together with potential cost savings supports the use of this type of novel composite in future applications.

Fractal analysis in pore structure of coal under conditions of CO2 sequestration process

A high pressure supercritical CO2 (HP-ScCO2) geochemical reactor was used to simulate CO2 sequestration into deep coal seam under around 40°C and 9.8MPa for 72h and fractal analysis were employed to study the mercury intrusion data of 4 different coal rank samples before and after the ScCO2–H2O treatment, focusing on the pore structure. It is revealed from the mercury porosimetry data that after exposure to the ScCO2–H2O fluid, the true density of coal samples are changed as well as total pore volume and porosity most importantly in the increase of micro-pore range. Fractal analysis is introduced to distinguish inter- and intraparticle pores at lower mercury intrusion pressure and to identify the initial pressure associated with the coal compressibility. Three values of fractal dimension (D1, D2 and D3) are obtained under different pressure ranges, which can be classified corresponding to three different mercury intrusion processes. Varied D1 values are mainly due to the accumulation mode of samples in the penetrometer and can be used to distinguish the interpore and intrapore intrusion process at lower pressure range of mercury intrusion. D2 values represents the mercury intrusion into intrapores. D3 value is decreasing as coal rank increased and can be used to describe the initial pressure when coal samples begin to be compressed or deformed at higher pressure of mercury intrusion. The experiments revealed that CO2 sequestration process changed the physical properties of coal samples, especially in compression resistance. Coal rank and ash content in coal are very important factors which will affect the variation of coal structure during CO2 sequestration.