Specific Particle Size Distribution Research Articles

A novel large-scale direct shear apparatus considering size effects on strength of frozen coarse-grained soils

As engineering activities in cold regions expand and the application of artificial ground freezing technology in constructions grows, understanding the strength of frozen coarse-grained soils has become imminently crucial. While existing research and testing methods have provided valuable opinions into the behavior of coarse-grained materials in frozen states, there is a recognized need to enhance and expand these methods to gain a more comprehensive understanding of how size effects influence the strength of these materials. To further investigate this issue, a novel large-scale direct shear apparatus was employed to determine the shear strength of frozen coarse-grained soil materials. The apparatus features a unique design capable of accommodating square specimens with five different section lengths: 100 mm, 150 mm, 200 mm, 250 mm, and 300 mm. Depending on the maximum load requirements and budget constraints of the experiment, the equipment can provide a maximum normal stress of 5.5–50 MPa and a maximum shear stress of 3.5–30 MPa for different sample sizes, along with precise temperature control down to −30 °C. The efficacy of the device is validated through experiments conducted on frozen coarse-grained soil samples with specific particle size distributions. This study presents the technological details involved in the development of the apparatus and offers preliminary insights into the strength characteristics of frozen coarse-grained soils, highlighting the influence of size effects. The innovative features of the apparatus help the geotechnical community to comprehensively understand the strength characteristics of this complex material, thereby improving the reliability of engineering practices that involve it.

O-PTIR spectroscopy for characterizing active pharmaceutical ingredient specific particle size distributions of nasal spray suspension products

Evaluation of the particle size distribution (PSD) of active pharmaceutical ingredients (APIs) in nasal suspension products is challenging due to the presence of both API and excipients. To characterize these intricate formulations, it is essential to have sophisticated analytical methods that offer high spatial resolution and the ability to chemically pinpoint and map out the presence of API particles. However, such advanced techniques have not been documented for nasal formulations yet.In this proof-of-concept study, we investigated the utility of optical photothermal infrared spectroscopy (O-PTIR) to analyze the PSD of commercially available Nasonex® and its generic Azonaire® nasal mometasone furoate (MM) suspensions. Simultaneous O-PTIR and Raman spectra, as well as IR chemical maps, were collected from the particles in both formulations. Spatially resolved spectra from the particles confirmed the presence of peaks related to MM (1727 cm−1, 1661 cm−1, and 1122 cm−1) and excipient microcrystalline cellulose (MCC) (1061 cm−1). The PSD of MM particles was characterized using chemical maps specific to MM (1661 cm−1) and automated imaging. Results confirmed that the PSD of both formulations were comparable. Spectral analysis also revealed the presence of free MM, free MCC, and particles containing co-localized MM and MCC.For suspension-based nasal products, O-PTIR enables the measurement of API PSD, which is critical for formulators in developing nasal suspension products. This approach holds potential as an innovative complimentary analytical tool that could diminish the need for extensive clinical endpoint bioequivalence studies when evaluating the comparability of generic and brand-name nasal suspension products.

Effect of multiple-compaction on laterite soil: geotechnical and geo-statistical analysis

Multiple-compaction demonstrates cyclic loading on laterite soils used in highway construction and its effects on engineering properties. The method determines the mechanical stability of derived soils from porphyritic granite, granite gneiss, and charnockite. Fifty-one soil samples were obtained from the horizons of the laterite soil profiles. Four sets of dynamic compactions were carried out on each sample. Index engineering properties such as specific gravity, Atterberg limits, and particle size distribution were investigated before and after multiple-compaction. The changes in engineering properties and moisture-density characteristics were investigated using the granulometric modulus and hardness index. Through multiple-compaction, larger grains in soils derived from granite gneiss and porphyritic granite disintegrated into smaller particles. The fine grains break down more easily than the large grains of quartz bound by clayey materials in charnockite-derived soils. Interestingly, the maximum dry density and optimum moisture content remain consistent in porphyritic and granite gneiss-derived soils after multiple compactions. Based on the densification and behaviour of the derived soils under multiple compaction in highway construction, porphyritic granite and granite gneiss-derived soils are more suitable as engineering materials than charnockite-derived soils.

The influence of sodium alginate on the structural and adsorption properties of resorcinol-formaldehyde resins and their porous carbon derivatives.

A series of carbon composites were synthesised by carbonisation of resorcinol-formaldehyde resin mixtures with the addition of different amounts of sodium alginate (SA) and compared with a composite prepared using Na2 CO3 as a catalyst for the polymerisation reaction. The effect of operating parameters such as SA concentration and polycondensation time on the structural and morphological properties of resorcinol-formaldehyde resins (RFR) and carbon-derived composites was investigated for further use as adsorbents. The synthesised composites were characterised by FTIR, SEM, Raman spectroscopy and N2 adsorption/desorption techniques. It was found that the morphology, specific surface area (SBET ~347-559 m2 /g), volume and particle size distribution (~0.5-4 μm) and porosity (Vpor =0.178-0.348 cm3 /g) of the composites were influenced by the concentration of SA and the synthesis technique and determined the adsorption properties of the materials. It was found that the surface of the filled chars was found to have an affinity for heavy metals and has the ability to form chemical bonds with cadmium ions. The maximum sorption capacities for Cd(II), i. e. 13.28 mg/g, were observed for the sample synthesised with the highest SA content. This confirms the statement that as-synthesised materials are promising adsorbents for environmental applications.

Influence of elevated temperature on waste concrete powder and its application in alkali activated materials

Concrete has been a common building material widely used for decades to build the infrastructure. As a results, considerable amount of waste concrete is produced which is hazardous to the environment. At present, recycling waste concrete is limited to the aggregates for non-structural applications. The low reactivity of waste concrete powder (WCP) limits its use as a binder. Therefore, this study is conducted to enhance the reactivity of WCP to increase its viability as an alkali activated binder. The study was conducted in two phases. In Phase I, the WCP was thermally treated at temperatures ranging between 600 °C and 800 °C and the impact of this calcination on the physiochemical characteristics of thermally treated waste concrete powder (TWCP) was studied. The phase transformation after calcination was analyzed by observing the properties of WCP and TWCP using scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier transformed infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) techniques. The physical changes were also studied by comparing the density, specific surface area and particle size distribution in WCP and TWCP. It was found that the thermal treatment of WCP resulted in the decomposition of several phases along with a change in quartz structure. Also with temperature increase, the increase in density and particles fineness was observed, which was significant when thermal treatment was performed at 800 °C. The alkali activated WCP and TWCP was prepared to explore the microstructure and strength. The reactivity and strength of TWCP was superior to that of WCP. However, the highest strength obtained after alkali activation of TWCP was less than 10 MPa which is not optimal for a primary binder. Therefore, in Phase II of this study, the performance of TWCP in a binary cement-based mortar was explored by blending it with 0–50 wt% ground granulated blast furnace slag (GGBS) and the series of experiments including compressive strength, flexural strength and drying shrinkage was carried out to characterize the properties of composites. The superior strength and improved drying shrinkage obtained by mortars comprising TWCP-800 were due to the combination of filler effects and increased reactivity. No significant change in the properties of mortar containing 10 wt% TWCP-800 was observed. Study reveals that the thermal treatment of WCP at 800 °C is optimal and a sustainable approach to producing a supplementary binder for alkali activated materials.

Mesoscopic discrete modeling of compression and fracture behavior of concrete: Effects of aggregate size distribution and interface transition zone

This paper presents a mesoscopic discrete modeling approach for studying compression and fracture behavior of concrete. A modified piecewise linear sieve curve was proposed to generate irregularly shaped aggregates following specific particle size distributions, and then a random particle model and the parallel bond model were implemented within a 3D framework of discrete element model (DEM). To characterize the interface transition zone (ITZ) which is generally the weak region in concrete, a reduction factor was employed to adjust the strength and consider the effect of ITZ on the mechanical response of concrete. The numerical modeling was calibrated and validated by comparing simulation results with experimental data from compression, splitting tensile, and dog-bone tests. The results demonstrate that the random aggregate model provides accurate representations of the concrete mesostructure, and the discrete model can effectively capture the effects of aggregate size distribution and ITZ on mechanical properties and crack propagation of concrete.

Novel composition of Nd-Fe-B gas atomized powder to produce compression bonded magnets

New compositions of Nd-Fe-B powders were produced via gas atomization. Helium and argon were used as atomizing gases. For the same process parameters, helium resulted in a powder that is 6 times finer than the powder produced with argon. In both cases, the atomization conditions were set to achieve fine powders and, therefore, fine microstructures, since this is critical to obtain a suitable coercivity. The powders were sieved to separate the fraction below 20 μm (∼90 % of powder atomized with He). The microstructure is formed by a mix of elongated and equiaxial grains with random crystallographic orientation and an average grain size of ∼ 1 μm, which was measured by Electron Backscattered Diffraction. This kind of measurements and images were taken for the first time for fine helium atomized Nd-Fe-B powders. The embedding of the powder in copper was found to be useful, as the conventional mounting in metallographic conductive resin produced charging of the sample. Annealing up to 1000 °C did not cause any significant grain growth that could deteriorate the magnetic properties. Annealing at 700 °C for 15 min improved the magnetic properties due to the crystallization of residual amorphous phase. Warm compaction was used to produce magnets with a high volume fraction of magnetic powder (>70 %) and low real porosity (∼5 %). These magnets exhibit a high remanence (∼0.5 T) and maximum energy product (∼35 kJ/m3), combined with a suitable intrinsic coercivity (>500 kA/m). The new compositions and processing route could cover a market niche. The thoroughly analyzed powders could be also suitable for some additive manufacturing technologies that require spherical powders with very specific particle size distributions.

Preparation and 3D printability study of bio-based PBAT powder for selective laser sintering additive manufacturing

Additive Manufacturing (AM) has been recognized as a highly versatile manufacturing method with high potentiality. Polymers are materials of central importance for AM specifically for fabrication of original and customized parts. However, most of the polymers currently in use derive from fossil sources, which extensive use represents a critical issue for the environment. This scenario encourages the use of sustainable and biodegradable biopolymers. The present paper focuses on the study of the printability of a bio-based powder, starting from an aromatic‐aliphatic biodegradable polyester, poly (butylene adipate-co-terephthalate) (PBAT), as sustainable alternative for Selective Laser Sintering (SLS) conventional materials. Bio-based polymers represent environmentally friendly materials that can be suitable for AM, although several problems still need to be solved for SLS applications. In fact, it is challenging to produce polymeric powders with specific particle size and size distribution, spherical shape, good flowability and processability. From this point of view, PBAT powder was prepared by means of an emulsion solvent evaporation method, characterized from morphological and thermal points of view, and then successfully used for SLS process, with the aim to obtain novel 3D printed objects using for the first time this biodegradable polymer.

Accelerated reactive dissolution model of drug release from long-acting injectable formulations

Long-acting injectable formulations represent a rapidly emerging category of drug delivery systems that offer several advantages compared to orally administered medicines. Rather than having to frequently swallow tablets, the medication is administered to the patient by intramuscular or subcutaneous injection of a nanoparticle suspension that forms a local depot from which the drug is steadily released over a period of several weeks or months. The benefits of this approach include improved medication compliance, reduced fluctuations of drug plasma level, or the suppression of gastrointestinal tract irritation. The mechanism of drug release from injectable depot systems is complex, and there is a lack of models that would enable quantitative parametrisation of the process. In this work, an experimental and computational study of drug release from a long-acting injectable depot system is reported. A population balance model of prodrug dissolution from asuspension with specific particle size distribution has been coupled with the kinetics of prodrug hydrolysis to its parent drug and validated using in vitro experimental data obtained from an accelerated reactive dissolution test. Using the developed model, it is possible to predict the sensitivity of drug release profiles to the initial concentration and particle size distribution of the prodrug suspension, and subsequently simulate various drug dosing scenarios. Parametric analysis of the system has identified the boundaries of reaction- and dissolution-limited drug release regimes, and the conditions for the existence of a quasi-steady state. This knowledge is crucial for the rational design of drug formulations in terms of particle size distribution, concentration and intended duration of drug release.

Improving the processability of pharmaceutical powders using atomic layer coating

Functional coatings on Active Pharmaceutical Ingredients (API) are used in the pharmaceutical industry to enhance mechanical strength, enable controlled release, taste masking, reduce formulation complexity and/or to improve drug product stability. Current API coating technologies have many challenges related to coating uniformity and defects, leading to variations in drug performance. This paper discusses using an ultra-thin API coating technology adapted from the semiconductor industry that can address many of the shortcomings of current coating technologies commonly used in the pharmaceutical industry. We show that this technique can achieve uniform and conformal nano-coating on multiple APIs without impacting their specific surface area and particle size distribution. We demonstrate the processability enhancements achieved using these coatings. The improvement in the processability of coated API was compared against uncoated API in commercially relevant unit operations used in the pharmaceutical industry, such as a loss in weight screw feeder and rotary tablet press.

Optimization of concrete mix design based on three-level separation distance of particles

This study proposed a modified mix design approach for producing concrete with reduced cement content and CO2 emissions. Three key design parameters: BSD (binder separation distance), FSD (fine aggregate separation distance) and CSD (coarse aggregate separation distance), from paste, mortar and concrete level are suggested based on the particle packing theory. The potential synergistic effects of BSD, FSD and CSD on fresh behavior, compressive strength and binder efficiency of designed concrete are evaluated. The results show that by considering the effect of particle specific area and particle size distribution, three proposed parameters exhibit better eco-efficiency and high correlations with concrete properties. The experiments together with numerical analysis show that the correlations coefficient of BSD, FSD and CSD together on slump, flow rate and compressive strength are 0.979, 0.923 and 0.913, respectively, indicating that these three values can be used together to tailor the properties of concrete. It is found that BSD is the most important parameter in determining the mechanical property, with a high correlation of 0.97. While FSD and CSD together are more sensitive on fresh behaviors. In addition, a prediction model based on machine learning was established, the errors between the measured and predicted values are within 10% and the binder efficiency in mixtures designed with three scale separation distances were increased by 7% in general, which validates the feasibility of using particle separation distances as key design parameters, and the applicability of this prediction method.

Effects of Vinyl Functionalized Silica Particles on Thermal and Mechanical Properties of Liquid Silicone Rubber Nanocomposites

It is very important to develop a new method of preparing high-performance liquid silicone rubber-reinforcing filler. Herein, the hydrophilic surface of silica (SiO2) particles was modified by a vinyl silazane coupling agent to prepare a new type of hydrophobic reinforcing filler. The structures and properties of modified SiO2 particles were confirmed using Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectrometer (XPS), specific surface area and particle size distribution and thermogravimetric analysis (TGA), the results of which demonstrated that the aggregation of hydrophobic particles is greatly reduced. Additionally, the effects of the vinyl-modified SiO2 particle (f-SiO2) content on the dispersibility, rheology, and thermal and mechanical properties of liquid silicone rubber (SR) composites were studied for application toward high-performance SR matrix. The results showed that the f-SiO2/SR composites possessed low viscosity and higher thermal stability, conductivity, and mechanical strength than of SiO2/SR composites. We believe that this study will provide ideas for the preparation of high-performance liquid silicone rubber with low viscosity.

Characterization of <i>Amuda-Isuochi</i> Nigerian Clay Deposit for Potential Industrial Applications

The aim of the work was to characterize the clay from Amuda-Isuochi, Abia state Nigeria. Preliminary research works on the area is scanty. The characterization involved chemical and elemental analyses, X-ray diffraction, specific surface area analysis, thermal analyses (TGA, DTA) and particle size distribution. The results showed that the clay is kaolin. Specific surface area of 251m2/g was observed, with average particle size of 84.67d.nm and polydispersity index of 0.203. The sample will find applications in oil and gas industry as lost circulation control material and for manufacture of proppants for hydraulic fracturing activities. Similarly, it can be used as an adsorbent and has potential applications for ceramic tile, paper, paints, fibre glass and starting material for alum. The kaolin clay will also be suitable as a nano-material. The output indicates an addition to local contents for Nigeria’s industrial development.

Mechanical and microstructural properties of high-performance concrete made with rice husk ash internally cured with superabsorbent polymers

An experimental study was carried out to determine the properties of rice husk ash (RHA) and its effect on high-performance concrete's (HPC) mechanical and microstructural properties. RHA content was placed at 0–30% at 5% step intervals and a constant water-binder ratio (W/B) of 0.3. A slump flow test was carried out to measure the workability property of the fresh HPC. In contrast, the influence of RHA contents on compressive, splitting tensile, flexural strengths and microstructural properties were examined for the hardened HPC specimens. The X-ray fluorescence (XRF), scanning electron microscopy-energy dispersive x-ray (SEM-EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy-Attenuate total reflectance (FTIR-ATR), Thermogravimetry analysis (TGA), Brunauer, Emmett and Teller (BET) specific surface area and laser diffraction particle size distribution (PSD) were used to access the feasibility of RHA in HPC. XRD and SEM/EDX techniques were conducted to investigate the hydration products and microstructure in hardened HPCs. The post-test examination showed increased compressive, splitting tensile and flexural strengths of HPC samples for a 10% RHA content mix, recording the highest compressive strength in all curing ages. As the curing ages increase, the microstructure of the samples with RHA becomes denser than the control due to the refinement of the microstructure by the RHA incorporated. The XRD and SEM/EDX confirmed the lower calcium hydroxides from pozzolanic reactivity and later formation of C–S–H. The results suggest that RHA can be used as a cement replacement for up to 10% in HPC to produce sustainable concrete.

Mechanochemical Synthesis of Nickel Mono- and Diselenide: Characterization and Electrical and Optical Properties.

Nickel mono- (NiSe) and diselenide (NiSe2) were produced from stoichiometric mixtures of powdered Ni and Se precursors by the one-step, undemanding mechanochemical reactions. The process was carried out by high-energy milling for 30 and 120 min in a planetary ball mill. The kinetics of the reactions were documented, and the products were studied in terms of their crystal structure, morphology, electrical, and optical properties. X-ray powder diffraction confirmed that NiSe has hexagonal and NiSe2 cubic crystal structure with an average crystallite size of 10.5 nm for NiSe and 13.3 nm for NiSe2. Their physical properties were characterized by the specific surface area measurements and particle size distribution analysis. Transmission electron microscopy showed that the prepared materials contain nanoparticles of irregular shape, which are agglomerated into clusters of about 1–2 μm in diameter. The first original values of electrical conductivity, resistivity, and sheet resistance of nickel selenides synthesized by milling were measured. The obtained bandgap energy values determined using UV–Vis spectroscopy confirmed their potential use in photovoltaics. Photoluminescence spectroscopy revealed weak luminescence activity of the materials. Such synthesis of nickel selenides can easily be carried out on a large scale by milling in an industrial mill, as was verified earlier for copper selenide synthesis.

Dust collection efficiency of commercial gas collection tubes

Gas sampling tubes are essential tools for the evaluation of air quality in work environments. It adsorbs toxic gaseous matters onto the surface of various granular adsorbents, such as silica gel or activated carbon packed in a thin glass tube, for quantitative analysis by gas chromatography. Currently, most of the semi-volatile matters are evaluated via aerosol filtration or solid-phase gas adsorption depending on the main phase of the substances; however, only a few substances have a sampling protocol regarding both solid and gaseous phases. Therefore, semi-volatile components evaluated by the solid-phase adsorption may result in the underestimation of the component concentrations due to particulate components passing through and remaining in the adsorbent. To highlight issues on sampling of semi-volatile matters by the solid-phase adsorption method, the collection efficiency of aerosol particles by 17 commercial gas sampling tubes were measured via pressure drop. To measure the particle collection efficiency of the gas collection tubes, precise control and dilution of the aerosol particle monitors are essential. However, we cannot apply typical filter test methods at a lower filtration flow rate than that of the aerosol particles monitors. Therefore, we developed a new experimental method that considers flow adjustment between the aerosol monitors. By assuming two specific particle size distributions and five inlet conditions, the collection efficiencies of total mass particles are estimated. From the gas-particle partitioning ratio of 16 polycyclic aromatic hydrocarbons (PAHs) in a coal tar pitch manufacturing industry, the underestimation of the concentration of semi-volatile matters using the gas collection tubes has been discussed. The aerosol particles were collected in all kinds of layers in the gas sampling tubes, such as in the glass wool cap, gas adsorbent granular bed, and polyurethane foam. Furthermore, the collection efficiency curve of all 17 gas sampling tubes tested showed similar trends; a valley around particle sizes ranging from 0.2-0.3 μm between high collection zones below 0.1 μm and above 1 μm was observed. The observations suggested granular bed filters collection mechanisms such as inertial impaction, Brownian diffusion, gravity, and interception as same as air filters. Solid-phase collection can underestimate the concentrations of multi-phase matters. Thus, we wish to highlight the importance of solid-phase collection methods along with filtration collection methods to collect all phases of semi-volatile matters.

Mechanochemical modification of crosslinked low‐density polyethylene: Effect of solid‐state shear pulverization on crosslinks, branches, and chain lengths

AbstractCrosslinked low‐density polyethylene (XLLDPE) is widely used in several specialty plastics industries. However, the permanent chemical crosslinks cause high‐melt viscosity and poor processability, preventing the material from being reused and recycled effectively. This study investigates solid‐state shear pulverization (SSSP) as a continuous, commercially viable mechanochemical processing technique to initiate the decrosslinking of XLLDPE for mechanical recycling. Post‐industrial XLLDPE scrap material was processed using SSSP with a range of pulverization conditions, which were correlated with universal processing covariants of specific mechanical energy and particle size distribution. The physical properties of SSSP‐processed materials were compared to as‐received XLLDPE and uncrosslinked low‐density polyethylene. While gel content tests confirm a gradual decrease in crosslinking density with a more energy‐intensive SSSP process, melt rheology and dynamic mechanical analysis characterization revealed additional chain architecture modifications such as branching and chain scission. Based on differential scanning calorimetry and thermogravimetric analysis, the SSSP‐processed XLLDPE retained its thermal stability and crystallinity; tensile testing results showed improved stiffness, strength, and toughness. These results indicate that tunable SSSP can transform XLLDPE into a decrosslinked, branched, and melt‐processable recycled polyethylene.

Highly Densified Fracture‐Free Silicon‐Based Electrode for High Energy Lithium‐Ion Batteries

AbstractThere has recently been an increasing volume of research in silicon‐based anodes for high energy density lithium‐ion batteries. Micron‐sized composites with high tap density and a number of pores accommodating the massive volume expansion of silicon (Si) exhibit considerable electrochemical performance with high volumetric energy density. However, huge pressure on the particle during the calendering process brings about mechanical failure which causes the formation of additional by‐products upon lithiation and electrical contact loss. Here, we discover specific particle size distribution based on the constructive simulation including calculation of the packing density depending on the different particle size distribution and stress evolution of each particle at high pressure. A silicon/graphite hybrid anode in which the silicon nanolayer (∼15 nm) is coated on the graphite is selected to validate the simulation. This anode sustains its morphological integrity and secures its void space without crack propagation of the silicon nanolayer in the densely packed electrode. As a result, it demonstrates high initial specific capacity (>500 mAh g−1), high initial Coulombic efficiency (95.2 %), low electrode swelling ratio (35 % at first cycle), and excellent capacity retention ratio (99.1 % during 50 cycles) for high energy density lithium‐ion batteries.

A novel laboratory technique for open-hole gravel-pack design

Gravel-pack completion is implemented in the wellbores to prevent sand production and minimize formation damage due to fines migration. As higher flow velocities exist near the wellbore region, sanding and fines migration are expected to occur in the wellbore vicinity. Therefore, wellbore productivity depends on the gravel-pack performance in allowing the passage of fine particles into the wellbore while preventing the entry of sand particles into the gravel-pack. The gravel design criterion proposed in the literature has been used as a guideline for gravel design, and it has typically provided adequate sand control for field operations. This study introduces a Sand Retention Test (SRT) setup to evaluate the sand production and fines plugging in wellbores completed with open-hole gravel-pack (OHGP). The SRT testing is used to replicate the widely used experimental procedure performed for gravel-pack applications and prove the reasonable repeatability of the results with respect to differential pressure measurements and the effluent fines concentration.SRT experiments with single-phase flow were conducted on a specific formation particle size distribution (PSD), incorporating the gravel-pack and wellbore screen coupon. The application of the SRT facility for OHGP is validated against pioneering experiments in the literature. The results reasonably agree on solid production and gravel-pack impairment trends between the replication and literature test results. Besides, the repeatability test results indicate reasonable agreement between the differential pressures across the sand-pack and gravel-pack and fines production in different tests.This research validates a novel laboratory testing against a gravel sizing criterion that has been commonly used in the industry. The proposed technique can customize testing for gravel-pack design and be employed for further research on the OHGP scenarios.

Pre-baked anode structure and properties as a function of the Blaine number

Anode paste for pre-baked (PB) anodes represents a composite material based on calcined coke and coal tar pitch (used as a binder). A coke aggregate mix includes 3 to 5 fractions with a particle size of 12 mm down to 75 μm, and even less. Grain fractions larger than 0.2 mm form a sort of skeleton of the binder matrix and are prepared by crushing and screening. For filling the space between the grains, a dust fraction with particles less than 0.2 mm is used. The dust fraction constitutes up to 50% of the aggregate and can contain up to 70% of particles with a size of <75 μm. The dust fraction is prepared in a fine grinding circuit of ball mills. The dust fineness is determined based on the Blaine number (BN). The BN correlates with both Specific Surface Area (SSA) and Particle Size Distribution (PSD). High BN dust may account for up to 90% of the total aggregate surface area. If dust is too fine, it leads to a higher surface area of coke particles, which causes both higher particle reactivity and higher pitch demand. The above might result in higher carbon consumption. Therefore, it is important to keep a balance in terms of the particle size of the dust fraction. This paper discusses the PB anode structure and properties as a function of the BN. Lab anodes containing dust fractions with a BN of 2120, 2880, 3600, 3950 and 4700 were used for analysis. The paper presents obtained correlations between the BN and the physical, chemical and mechanical properties of PB anodes. An optimal BN of 3600 to 4200 was determined based on porosity tests of anode blocks with different BNs using mercury porosimetry; the above range can now be recommended for PB anode production.