Newton's Efficiency Research Articles

Effect of inlet speed on gravitational air separator for cenospheres accumulation from fly ash: modeling using computational fluid dynamics (CFD)

Dry gravity separation is widely used in industries due to its low operational cost. Furthermore, it does not require water to perform its separation process. Commonly used gravity separator is cyclone separator. Unfortunately, this type of separator is unable to yield various purities for its products. A modified gravity separator as an alternative relies on terminal velocity difference for different diameter and density is evaluated in this paper. The separated particles are coal fly ash and cenosphere which are the results of coal combustion where the content of cenosphere is generally 0.1% of total mass. Separated cenospehere can be used for various applications in the field of materials. In this simulation we use a particle model with a ratio of fly-ash to cenosphere mass of 1:1. Particles behavior in this gravity separator is affected by terminal velocity, linear speed, as well as rheology. Modeling with CFD (Computational Fluid Dynamics) using the Discrete Phase Model can take into account the behavior of particles that are affected by these factors. This model assumes that the simulated particles are perfectly round in shape. It uses the Euler-Lagrange framework in which the perfectly rounded particles (discrete phases, Lagrange frames) interact with air (continuous phase, Euler framework) and performed with ANSYS Fluent software. This study evaluates the effect of speed variation on Newton efficiency (NE) on a given geometry. Simulations were performed with variations of inlet velocity: 0.1 m/s; 0.25 m/s; 0.5 m/s; 1 m/s; 2 m/s; and 3 m/s. It was found that the lower the speed, the higher the NE and the optimum NE of 0.41 is obtained with 0.25 m/s inlet velocity.

Copper and metals concentration from printed circuit boards using a zig-zag classifier

The consumption of electronic products has grown considerably in the last decades. These products become obsolete in a short period of time, generating electronic waste, which presents loads of materials harmful to health and metals of great value to industries. In this work, an innovative metal concentration technique for PCBs was applied aiming at the valuable metals recovery from ground printed circuit boards (PCBs) of computers that would be discarded. The PCBs were comminuted, classified by sieving and the metallic materials were processed in a zig-zag classifier type. The Schytil's phase diagram was developed to estimate the air flow rate to be used in the classifier. The product of each step was characterized. The copper content rose from 13.8% (w/w) to 48.8% (w/w) after the passage of the PCBs powder through the classifier. Its recovery and Newton's efficiency were above 89.4% and 0.91, respectively. The total content of metals was increased from 39.5% (w/w) to 89% (w/w) with a recovery of more than 82% and Newton's efficiency of 0.67 for the particle size in the range from 0.2 to 0.1mm. The gold content has increased from 200ppm to more than 8000ppm after segregation by a simple manual concentration. Results shown that the use of zig-zag classifier to separate and concentrate metals was fairly effective, do not generate liquid and gaseous effluents and eliminates a number of pyrometallurgical or hydrometallurgical steps for metals obtaining.

Performance of dry-separation processes in the recovery of cenospheres from fly ash and their implementation in a recovery unit

Cenospheres recovery is one of the coal fly ash beneficiations, providing economic as well as environmental benefits. Current techniques, such as lagoon or other wet-separation processes, consume large amounts of water and add to water pollution due to leaching of toxic materials from fly ash. The other possible disadvantage is the need for a wide operational area, which is unsuitable for densely populated countries. As wet-separation processes have some disadvantages, an improved and/or sustainable alternative recovery technique is required. An air classifier is one of the alternative techniques. In this study, two types of air classifiers, namely a closed-type pneumatic separator and a micron separator, have been investigated. In terms of separation efficiency, it was found that the micron separator has the potential to be applied in cenospheres recovery from coal fly ash, giving a Newton's efficiency of 0.44, as compared to a value of about 0.26 for the closed-type pneumatic separator. The cenospheres recoveries of both pieces of equipment at their optimum Newton's efficiencies were similar at over 60wt.%. The separation performance was further assessed from the particle distributions of the overflow and underflow products obtained from both pieces of equipment, as well as from SEM images. It was found that the lower Newton's efficiency of the closed-type pneumatic separator was due to the re-concentration of fine particles in the underflow product at air-flow rates higher than 2.2m/s (the underflow product yield was about 55wt.%).In order to further confirm the applicability of this technique, the micron separator, which had provided higher separation efficiency and cenospheres recovery, was deployed in a cenospheres recovery unit prior to the use of a wet-separation process (float and sink tank). About 80% of the cenospheres was recovered, with an 87.8% reduction in the total mass of fly ash to be separated in the float and sink tank. Consequently, much less water was needed for the process of cenospheres recovery. Moreover, it was also confirmed that the micron separator could yield higher quality fly ashes, that is, fly ash types I and II, from lower feed quality of fly ash type IV, which is the lowest category in commercial classification of fly ash according to JIS A6201.

Recovery of cenospheres from coal fly ash using a dry separation process: Separation estimation and potential application

The degree of separation in the recovery of cenospheres from coal fly ash has been estimated for both wet and dry separation processes by applying the terminal velocity concept of particles. Particle diameter and density were determined by sieving industrial cenospheres and coal fly ash type IV, the model particles. This information was then utilized to calculate the terminal velocity needed to estimate the separation performances of both the wet and dry separation processes. Based on this estimation, the dry separation process performed similarly to the wet separation process, with an optimum Newton's efficiency of 0.54, only slightly lower than that of the wet separation process of 0.6. Moreover, it was observed that the cenospheres were concentrated in the underflow product, whereas for the wet separation process the reverse was true. The findings of this assessment were verified using a micron separator. Similar tendencies in the concentration of cenospheres in the underflow products were obtained. An optimum Newton's efficiency as high as 0.44 was achieved, with 66% recovery of the cenospheres. The recovery of the cenospheres was only 4% lower than the estimated value (70%), from which we conclude that dry separation processes are interesting technologies to apply to the recovery of cenospheres from coal fly ash because of their high efficiencies.

Adhesion of Escherichia coli onto quartz, hematite and corundum: Extended DLVO theory and flotation behavior

The adhesion of Escherichia coli onto quartz, hematite and corundum was experimentally investigated. A strain of E. coli was used that had the genes for expressing protein for silica precipitation. The maximum cell adhesion was observed at pH <4.3 for quartz and at pH 4.5–8.5 for corundum. For hematite, cell adhesion remained low at all pH values. The microbe–mineral adhesion was assessed by the extended DLVO theory approach. The essential parameters for calculation of microbe–mineral interaction energy (Hamaker constants and acid–base components) were experimentally determined. The extended DLVO approach could be used to explain the results of the adhesion experiments. The effect of E. coli on the floatability of three oxide minerals was determined and the results showed that E. coli can act as a selective collector for quartz at acidic pH values, with 90% of the quartz floated at 1.5 × 10 9 cells/ml. However, only 9% hematite and 30% corundum could be floated under similar conditions. By using E. coli and no reagents, it was possible to separate quartz from a hematite–quartz mixture with Newton's efficiency of 0.70. Removal of quartz from the corundum mixture was achieved by E. coli with Newton's efficiency of 0.62.

Floatability of rare earth phosphors from waste fluorescent lamps

Zeta-potential measurements were made to determine the electric state of phosphor materials on the basis of which a feasibility study could be performed for the use of flotation in the recovery of fine ( d 50 < 13 μm) rare earth phosphors from waste fluorescent lamps. Tests were carried out with pure specimens of white (calcium halo-phosphate), red, green and blue (rare earth) phosphors, with a 17 : 1 : 1 : 1 ratio of their mixture, and with actual waste phosphor materials. The effects of a cationic (dodecyl ammonium acetate, DAA) and two anionic (sodium dodecyl sulfate (SDS) and sodium oleate (NaOl)) collectors on the floatability of materials, as well as that of Na 2SiO 3 dispersant on the separation characteristics, were investigated at different pH ranges. The process, applied to actual discarded waste phosphors gave, in a two-stage separation scheme, sink products assaying 17.7–23.8% and 21.5–25.9% rare earth phosphors for DAA and SDS flotation, respectively. The recovery and Newton's efficiency were about 70–90% and 0.26–0.37, 66–82% and 0.18–0.20, respectively for DAA and SDS flotation.

Feasibility of an efficient recovery of rare earth-activated phosphors from waste fluorescent lamps through dense-medium centrifugation

Experiments were carried out with waste phosphors collected during the recycling of end-of-life fluorescent lamps to obtain a highly enriched phosphors product as starting material for the better extraction of rare earth elements. The aim of this work was therefore to separate low-density calcium halo-phosphate phosphors from high-density rare earth-activated phosphors through dense-medium centrifugation (with di-iodomethane as organic dense-medium). The feasibility of the process and the conditions for a good separation (higher Newton's efficiency) appear to be a function of the rotation speed of the centrifugal separator, the pulp concentration and the adsorption of a surfactant (sodium oleate, NaOl) during the pre-treatment stage. The effect of the centrifugation time was less pronounced. Through this study, a sink product assaying 48.61% of rare earth-activated phosphors could be recovered from waste phosphor materials pre-treated with 5 × 10 −5 mol/dm 3 of sodium oleate (NaOl) surfactant. The Newton's efficiency and recovery of the separation were 0.84 and 97.34%, respectively. The process feasibility was reinforced by the possibility to recover, through laboratory batch tests, more than 99.8% of the di-iodomethane (CH 2I 2).

Jig separation of plastics from scrapped copy machines

A TACUB jig was applied to separate waste plastics [polystyrene (PS), acrylonitrile butadiene styrene (ABS), and polyethylene terephthalate (PET)] used in copy machine. The effect of water pulsation including amplitude and frequency on the separation performance was investigated for the feeds containing three plastics. Good results were obtained under suitable conditions. Grades of 99.8% PS, 99.3% ABS, and 98.6% PET were recovered as the products in the top, middle and bottom layers, respectively. Based on these results, a processing pilot plant for recycling of plastics from scrapped copy machines was constructed. Two cells of a TACUB jig were used in the plant to separate the plastics containing PS, ABS and PET, where PET was recovered from the first cell as bottom layer product, and ABS and PS from the second cell as bottom and top layer products, respectively. A monitor and control system of the jig operation was developed. High recoveries of PET, ABS, and PS with high grades were achieved, and the Newton's efficiency of the first cell was 0.99.

畑作における麦類の自生作物化と作付体系に関する研究 ＶＩ 揺動選別機による自生コムギ粒混入オオムギの選別特性

We investigated the separating characteristics of rough rice separaters to contaminated barley grains by mixing of volunteer wheat grains.A principal factor in separation by rough rice separater was the difference ratio of grain length. So the difference ratio of grain length for barley and volunteer wheat grain were 1:0.78.The performance of a rough rice separater for removing volunteer wheat grain from barley grain was poor, when separating the rice from the chuff. When the pan oscilation was 160rpm and pan slope, 16°, the rough rice separater efficiently removed volunteer wheat grain. So barley grain had met the standerd requirements at inspecting.Then Newton's efficiency was 0.7. But thirty percent of the barley grain were discharged with wheat grain.This operation was an emergency measure of prevention against the contamination of barley grain by mixing of volunteer wheat grain. Because barley grain loss on separating by rough rice separater resulted from falling in shipment of barley.