Papers by Keyword: Pressure Filtration

Abstract: Magnesium-aluminium spinel (MgAl₂O₄) in the form of transparent ceramics is applied in shields of infrared detectors or emitters, high-temperature widows and elements of military aircrafts and vehicles. Apart from high transparency for specific wave lengths, such materials should have good mechanical properties, especially hardness. It is the reason for production of the fine-grained materials. It seems that they can be produced from submicron powders consolidated by one of colloidal techniques. The work presents preliminary results of investigations on colloidal consolidation of two fine spinel powders with different particle size by pressure filtration and slip casting. The aim of the studies was consolidation of the fine powders leading to green samples with narrow pore size distribution. The samples were then sintered in isothermal conditions. Microstructure, Vickers hardness and transmission in infrared spectrum of the dense materials were examined.

Abstract: Construction wastes have attracted more and more public attention with the development of the city construction. On the basis of summarizing the existing slurry treatment technologies in relevant area, a new slurry treatment process is proposed according to the characteristics of waste bored pile slurry. Three steps included in this process: slurry purification, flocculation and pressure filtration. A practical application is used to demonstrate the feasibility of this process. The results show that the slurry is disposed without pollution, achieving zero discharge of pollutants.

Abstract: With enhanced awareness of energy conservation and environmental protection, more attention has been paid to the high moisture content of the filtration products used in the flotation process as commonly employed in coal preparation plants. In this paper, we choose fine coal (–0.5mm) samples obtained from the Xiqu Coal Preparation Plant in China as our research objective. Tests were performed under three different experimental conditions: direct pressure filtration, electrolysis pressure filtration, and electricity decompression filtration with different electrodes. Thus our aim was the evaluation of the impact of electrodes on the electrolysis-pressure-filtration effect on fine coal dewatering. The results of this study indicate that when the coal slurry concentration is 400g/L, and when the electrode is aluminum-aluminum (90V, 14min), we can achieve the best effect and the lowest moisture content of the filter cake, which is 10%. The electrolysis pressure filter has a high dewatering efficiency, an advanced technical index, requires little power consumption (obviously energy-saving), needs only a small amount of maintenance, and is stable and reliable in operation, Thus the electrolysis pressure filter is the most effective and economical processing equipment for fine coal dewatering and has prospects for broad application.

Abstract: The stability of dispersed and flocculated colloidal particles under 1 atm and applied pressure was discussed thermodynamically with the activity and chemical potential defined by Henry’s law and Raoult’s law. The calculated result under 1 atm is represented by a colloidal phase diagram as functions of surface potential and solid content of particles. Application of pressure accelerates the phase transition from dispersed to flocculated suspension. The phase transition pressure, which is observed in the applied pressure-suspension height relation during pressure filtration at a constant crosshead speed of piston, is affected by (1) particle concentration, (2) particle size, (3) surface potential, (4) degree of dissociation of polyelectrolyte dispersant and (5) applied electric field (DC and AC). The influence of above factors was discussed theoretically and experimentally.

Abstract: There has been an increasing tendency to determine liquid metal quality using pressure filtration methods such as Prefil Footprinter tests. The scientific understanding of this method, however, is emerging only recently with the introduction of derivative methods. Based on the investigation of flow behavior over the pressure filtration test, classic filtration theory has been successfully applied to understand the filtrate weight versus filtration time curve. The “clean” and “effective” resistance of filter medium, overall filtration resistance, cake resistance, pressure loss and distribution can be quantitatively calculated now. In the present work, a typical weight versus time curve from the Prefil Footprinter test of a cast Al-Si alloy is analyzed and discussed in details. The method developed in the work can provide new insights into the filtration behavior.

Abstract: The applied pressure and suspension height during consolidation of a 15 vol% Al2O3 suspension (0.15 μm α-Al2O3 particles, isoelectric point pH 7.8) at pH 3 - 10 in a closed cylinder were continuously recorded using a pressure filtration apparatus. The apparent viscosity decreased with decreasing suspension pH. The final packing density of the dispersed acidic suspensions at pH 3.2 and 5.6 reached 62 – 63% at 19 MPa of applied pressure. The viscous basic suspensions at pH 7.8 and 9.6 were consolidated to 52 – 54 % density. Because of the release of the stored elastic strain energy, the height of the consolidated Al2O3 compact increased after releasing the pressure. The energy required to consolidate 1 cm3 of Al2O3 particles was in the range from 3.0 to 15.9 J, and became larger for the dispersed acidic suspensions. The energy applied between two colloidal particles during consolidation (W) was compared to the interaction energy (Ei) between two particles in a suspension.

Abstract: The activation of silicon carbide by boron and carbon is required to obtain dense monophase sintered body from SiC powder. The presence of carbon renders casting from aqueous suspension impossible. The SiC powders with boron and extra carbon were prepared by combustion method (SHS), where carbon was bound to SiC particles in a stable way. The experiments showed that this powder could be used for processing by casting of aqueous suspension. Finally nearly dense polycrystals were obtained by pressureless sintering.