Papers by Keyword: Fine Particles

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: Critical raw materials (CRMs) are of primary importance for energy storage systems as needed for electromobility. Many mineral deposits which contain CRMs are low-grade ores. To liberate the CRMs, a grinding of the mineral ores to very fine sizes below 20 µm particle size is necessary. However, the present class of industrial flotation plants fail to extract such fine and ultrafine particles. To improve the recovery in fine particle flotation, techniques have been developed which attempt to agglomerate the fine valuable particles into larger aggregates which subsequently can be separated by established technologies such as froth flotation. Carrier flotation is one of these techniques. The present work reviews the state of the art of this technique for the recovery of fines and ultrafines.

Abstract: Biological effects and ecotoxicity of NPs CeO₂ with particle size Δ₅₀ =16 nm and hydrobionts tolerance was measured in simulation based on test-reactions of a group of organisms representing major trophic levels of aquatic ecosystem. Biological activity of NPs CeO₂ was noted against bacterial biosensor Ekolum, Сhlorella v. B., Paramecium c., Daphnia m. S. and Danio r. Toxicity and hazard level of NPs CeO₂ were measured using biotesting and hydrobionts. Toxicity of NPs CeO₂ against luminescent bacteria Ekolum and Paramecium c. and Danio r. was not established (L(E)С₅₀ > 100 mg/l). In accordance with SGS and EC 93/67/EEC, NPs CeO₂ is considered highly toxic (acute toxicity Level 1). Biomarkers and NPs CeO₂ tolerant hydrobionts were determined. Range of tolerance of hydrobionts to NPs was established. The upper limit of tolerance was determined for certain hydrobionts by values of L(E)С₅₀: 0.009 mg/l (by volume of Chl a) for Сhlorella v. B. and 46.15 mg/l (by mobility) for Daphnia m. S.

Abstract: This article reviewed some of the measures taken to control particulate matters by combining the latest fine particles dominating technologies both at home and abroad. The coagulation technological principles and research achievements of fine particles were suggested. The research highlightly analyzed the technical principles and characteristics of electric coagulation technology, acoustic coagulation technology, vapor condensation technology, thermal coagulation technology,chemical coagulation technology, magnetic coagulation technology, turbulent coagulation technology and light coagulation technology.On the basis of comprehensive analysis of these technologies, it pointed out the development trend of fine particle control technology.

Abstract: The removals of PM_2.5 from coal combustion by electrostatic precipitator (ESP) and wet flue gas desulfurization (WFGD) system with adding chemical agglomeration solution were investigated experimentally based on coal-fired thermal system. The experimental results show that the average diameter of particles could grow more than four times with the effect of wetting, liquid bridge force and adsorption bridging, and the PM_2.5 concentration of ESP outlet can decrease 40% under typical flue gas conditions. The removal efficiency of fine PM_2.5 is improved about 30% when adding chemical agglomeration solution before desulfurization tower.

Abstract: The objective of this study is employing acoustic coagulation to induce agglomeration of fine and ultrafine particles after wet flue gas desulfurization (WFGD) and analyzing its effectiveness and characteristic based on numerical simulation. Matters such as calcium sulfate and calcium sulfite in WFGD can form very fine particles. Smoluchoski’s equation is employed as the simulating model. Orthokinetic coagulation, hydrodynamic coagulation and Brownian coagulation are taken into account to form the agglomeration kernel. An improved sectional arithmetic is introduced to achieve sectional size adjusting automatically according to the mass concentration of particles, so that section size is fine where the mass concentration is large to guarantee computational accuracy, but coarse where the mass concentration is small to save computation time. Besides, mass conservation rate is introduced to estimate the calculation error in the compute of mass concentration. Simulation results show that the overall number concentration decreased more than 40% after acoustic wave acting on the flue gas for 2 second; Increasing sound intensity level (SIL) is more effective to coagulation than increasing frequency; There exists an optimal acoustic wave frequency within 1500~2000Hz; Coarse particles are more sensitive to acoustic wave frequency than fine particles.

Abstract: The purpose of this study is to construct a turbulent aggregation device which has specific performance for fine particle aggregation in flue gas. The device consists of two cylindrical pipes and an array of vanes. The pipes extending fully and normal to the gas stream induce large scale turbulence in the form of vortices, while the vanes downstream a certain distance from the pipes induce small one. The process of turbulent aggregation was numerically simulated by coupling the Eulerian multiphase model and population balance model together with a proposed aggregation kernel function taking the size and inertia of particles into account, and based on data of particles’ size distribution measured from the flue of one power plant. The results show that the large scale turbulence generated by pipes favours the aggregation of smaller particles (smaller than 1μm) notably, while the small scale turbulence benefits the aggregation of bigger particles (larger than 1μm) notably and enhances the uniformity of particle size distribution among different particle groups.

Abstract: The activated carbon fine particles, as damping agents, are filled into the impact damper. With experimental method, the performance of the fine particles impact damper to the main system is compared with the multi-unit impact damper. The results indicate that the damping effect of the impact damper with activated carbon fine particles is not better than that of the multi-unit impact damper, but it has a much better effect to restrain the strong nonlinear of response than the multi-unit impact damper. In a certain resonance region, there is an optimum particle filled rate to the fine impact damper.

Abstract: Study on the fine particle dispersion in the room is very important for creating and maintaining a healthy indoor environment. The paper presented a new dispersion model of fine non-spherical particles formulated in a Lagrangian way based on its dynamic characteristics. In this model, the effects of gravity, resistance, particles shape and random force were taken into account. The influences of gravity and non-spherical particles shape on its dispersion process were analyzed in theory. Simulation result and theory analysis showed the models established in the paper performed better than the random walk model.

Abstract: Study on the fine particle dispersion in the room is very important for creating and maintaining a healthy indoor environment. An experiment of a carbon nanofiber material blown in smoke box was taken and the mass concentrations of the aerosol formed by this material were measured. Dispersion process of this material in the smoke box was simulated by random walk model, spherical particles aerosol dispersion model and non-spherical particles aerosol dispersion model, respectively. The setting velocities of the aerosol in the smoke box were calculated according to the mass concentrations at different times and the influences of gravity and non-spherical particles’ shape on its dispersion process were analyzed in theory.