Papers by Keyword: Sedimentation

Abstract: Cleaner melt transfer is critical to the broader use of recycled aluminium alloys in high-end structural casting applications, where oxide bifilms and intermetallic inclusions, such as Fe-containing intermetallics, can significantly affect the casting's mechanical properties. In counter-gravity low- and high-pressure casting, the launder system must not only promote the sedimentation of inclusions but also deliver a stable, cleaner melt to the crucible. Prior research showed that 15° double baffles in the mid-section of the sedimentation launder at a flow rate of 100 kg·h^-1 provide high efficiency. The present work investigates the influence of baffle design at the launder-crucible interface, where the melt enters the crucible before casting. Fluid dynamic simulations were carried out at a 100 kg·h^-1 flow rate for three inlet configurations: (i) full baffle; (ii) lifted baffle; and (iii) split baffle. Inclusions of various densities and diameters were tracked. Results indicate that the full baffle, while beneficial as a benchmark and efficient, is impractical because it generates fresh oxide surfaces. The lifted baffle provided the most effective reduction in inclusions, like the full baffle setup, enhancing sedimentation and suppressing entrainment, while the split baffle showed intermediate behaviour. Moreover, the lifted configuration promoted centrifugal flow (at lower velocities, it still made a partial contribution) within the crucible, directing inclusions towards the crucible wall and the stagnation-velocity zone, and enabling the crucible itself to act as a final sedimentation stage before the counter-gravity pump extracts the melt. These results demonstrate that combining mid-launder optimisation with crucible inlet baffle design enables cleaner, more automated melt delivery, thereby strengthening the use of recycled aluminium alloys in structural casting applications.

Abstract: The article deals with the peculiarities of the process of clay particle aggregation when coagulant and flocculant are introduced, as well as the regularity of formation and deposition of the formed flocs. The studies were carried out on a model suspension of bentonite clay with a concentration of 1-10 g/l. In the course of the study, the regularities of aggregate formation in the process of coagulation; the combined action of coagulants and flocculants, as well as the destruction of flocs under the influence of mechanical action were determined, and theoretical ideas were formed regarding the models of the process and the structure of the formed aggregates. It was found that the aggregation of fine particles has optimal ratios of both the concentration of the solid phase and the ratio of flocculant to the solid phase, at which the maximum rate of particle settling is observed. The optimum concentration for this type of clay, at which the maximum flocculation rate is observed, was 4-6 g/l. At other optimum concentrations, a slowdown in floc settling is observed due to the lack of formation of a spherical structure at low concentrations and compressed settling at higher concentrations. To intensify the sedimentation of loose flocs, it was proposed to introduce additional mineral lime particles with a particle size of 20-40 μm, which increase the weight of flocs and accelerate their sedimentation.

Abstract: River-carried solids, especially during floods, lead to dam sedimentation. Dredging extends dam life, but excess unusable sediment storage threatens the environment. The aim of this work is to investigate the influence of the recovery of calcined mud from Chorfa dam on the physico-mechanical and chemical characteristics of mortars fiber bundles. The sludge is used as a partial substitute for cement by volume at rates of 10%, 15%, 20% and 25%. All test specimens had water / binder (W/B) ratio and steel fibers ratio. Testing programme included measuring the fluidity, ultrasonic pulse velocity test, dynamic modulus of elasticity, flexural and compressive strengths. Compared to the control mortar, the fluidity represented by the diameter of M0, M15 and M25 mixtures decreased by approximately 11%, 14% and 22%, respectively. The compressive strength of M15 increased by 17.4% at 28 days, compared with the control specimen. At 7 days, the ultrasonic speed of the M25 mixture decreases by 1.7% compared to that of M15. The dynamic modulus of elasticity of M20 and M25 increases by 13% and 12% as the age ranges from 2 to 28 days. At 28 days, the flexural strength of the M20 blends increased by approximately 64%.

Abstract: Kuala Ceurape Beach is located in the Jangka District of Bireun Regency, on the Malacca Strait. This beach is renowned for its powerful waves and tides, but it is also susceptible to changes in coastal morphology, which can result in erosion and sedimentation. From 2006 to 2019, the estuary of the Kuala Ceurape coastline experienced sedimentation, leading to its closure. This issue could potentially disrupt the activities of local fishermen who rely on the estuary. To address this problem, the Aceh government proposed a plan to open the estuary channel while optimizing coastal morphology. A numerical modeling study using Delft3d application and spatial analysis study is being conducted to determine the impact of the jetty development plan on the estuary. Two scenarios are being considered: the first involves opening the estuary without building a jetty, while the second involves building a jetty. The numerical modeling considers four cardinal directions and uses input data such as bathymetry, tides, and waves. Spatial analysis is carried out using ArcGIS. Simulation results show that without the jetty building plan, sediment accumulation near the mouth of the estuary leads to its closure and a coastline progress of around ±127.583 m. However, with the jetty building plan, sediment accumulation is relatively smaller at the mouth of the estuary, and shipping is not hindered. Sediments are dominant to the right of the jetty in both scenarios, and there is still some erosion. Nevertheless, the plan to open the estuary channel with the jetty building will benefit local fishermen and increase the river's ability to drain water into the sea.

Abstract: The article deals with the use of granite filer as a concrete admixture. It examines the filter in detail not only as a whole (one component in concrete) but separates it into fractions. Since it is a filter produced during cutting, grinding and polishing of granite elements, it is granite slurry. For these reasons, the simplest method of separation - sedimentation in a flowing liquid - was applied to separate the individual fractions. After drying, the individual fractions were examined for their suitability for use in concrete. The most important physical and chemical parameters - bulk density, specific surface area, grain shape and size, chemical composition - were determined. Based on the measured values and in relation to previous in-house investigations, granite filer can be considered as a suitable admixture for cement composites.

Abstract: A mathematical model of the process of gas propagation in the atmosphere and its sorption by fine flow has been developed. The use of the finite difference method in modeling allows to obtain numerical solutions of the spatial distribution of gas concentration during its deposition by a jet of arbitrary intensity and shape. The proposed method of mathematical description of the process of sorption of hazardous gases allows you to choose an arbitrary number and spatial location of nodal points that satisfy the Courant-Friedrichs-Levy condition. The developed model allows to predict the intensity of gas sorption in technological processes and in the elimination of the consequences of emergencies. The use of the developed model will increase the efficiency of emergency management and choose effective methods of sorption of hazardous gases in the atmosphere. The results of numerical calculations confirmed the efficiency of the developed model and theoretically demonstrated the effectiveness of using water curtains for the sorption of ammonia from the atmosphere. According to the simulation results, it is established that the use of fine spray jets can significantly reduce the distance of distribution of hazardous gas.

Abstract: The effect of mixing suspended nanoparticles into a bi-disperse magneto-rheological fluid on sedimentation phenomena is explored. A reference bi-disperse MRF has been modified using a ferrofluid containing magnetite nanoparticles of two shapes (spheres or hexagonal platelets) suspended in paraffin-oil as carrier fluid. The reference MRF was prepared with a mixture of two diameter sizes for the micrometric particles. The reference MRF was also prepared using two different grades of carbonyl-iron micrometric particles (herein these will be referred to as HARD and SOFT), which differ each other for their mechanical properties. The experiment monitored the evolution with time of the sediment-supernatant interface. This experiment showed that the presence of nanoparticles (particularly the spherical ones) slows down the sedimentation effects in terms of ratio and rate, independently of the other characteristics of the fluid. This study also showed that fluids based on SOFT carbonyl iron powders, in presence of nanospheres, are more stable than HARD carbonyl iron powder based fluids, since their sedimentation rate slows down in the long term. At the same time, HARD particle-based magnetorheological fluids show smaller sedimentation ratios than SOFT based fluids.

Abstract: This research aims to study the impact of continuous pulsed electric field (PEF) on glycerin separation from Transesterification process. Transesterification process of biodiesel production using 100 ml vegetable oils with alcohol of 1:5 molar ratio together with potassium hydroxide (KOH) as catalyst 1 wt.% for the reaction. The designed glass tube reaction chamber is 250 ml contained with coaxial cylindrical electrodes. The applied voltage to an electrode was at 1 kV and frequency of 1 kHz with pulse duration of 500 μs and also 4 kHz with pulse duration of 125 μs. The results showed that the glycerin volume from transesterification process has rapidly sedimented with pulsed electric field method. It is much faster than using conventional gravity method. The sedimentation rate increases rapidly with an increasing in frequency of the applied voltage. The highest volume of glycerin sedimentation of 10.2 ml is by using pulsed electric field at 1 kV and 4 kHz.

Abstract: Cement compositions prepared by mixing cement with a stabilized finely dispersed slag suspension, which allow improving the structural, physical and mechanical characteristics of the cement stone are considered. On the first day of hardening, the strength of modified specimens increased by 54%, at the grade age - by 43%, and the porosity decreased by 13.8 and 17.3%, respectively. The possibility of obtaining an injection solution for soil consolidation on the basis of Portland cement and a stabilized slag suspension with the concentration of a finely dispersed slag of 50 g/l is considered. Studies have shown that the injection solution under study has reduced viscosity and sedimentation, increased compressive strength. After 28 days of hardening, the strength was 14.2 MPa, which is higher than the recommended values ​​for consolidation of soil under the foundations (4-6 MPa), and at a concentrated load, for the base under the foundations of the columns (9-10 MPa). The data obtained allows considering an injection solution based on Portland cement and slag suspension for the use in the injection technology of soil consolidation.

Abstract: The tritium breeder materials used in solid tritium breeding blanket of fusion reactor are lithium-based ceramics, like lithium titanate (Li₂TiO₃), lithium orthosilicate (Li₄SiO₄), lithium aluminate（LiA1O₂) and lithium zirconate (Li₈ZrO₆). Among them, Li₂TiO₃ has the advantages of stable chemical property, high mechanical strength and high lithium content, so it has become one of the preferred materials. Based on the design of solid blanket and tritium extraction process, breeder materials need to be made into a certain shape of pebbles. B Spherical breeder is widely used in the design of fusion reactor for the larger specific surface area, more channels between the pebbles to diffuse and release tritium, and easier loading or unloading. However, due to the high requirements of the breeder pebbles, the production control are not complete. In this paper, a new preparation method of ceramic pellets with high sphericity, polymer assisted sedimentation method, was used to prepare ceramic pebbles. The slurry consists of micro-scaled ceramic powder and organic monomers. Spherical droplets of ceramic slurry were obtained by sedimentation method in viscous liquids. The organic monomer contained in the droplets was heated to polymerize into small pellet preforms during the sedimentation process. By optimizing the sintering process, the fabricated pebbles could perform high compressive load (>18 N), spherical shape (0.95~1.02), uniform particle size (0.8~1.2mm) and porosity (15~20 %). The main advantages of this method is the mild preparation conditions (50~110 °C), the simplified transfer and purification process and convenient industrialization.. The obtained product has high spherical shape, uniform particle size, high compactness and mechanical strength.