2 Review the Theory and Operation of Electrostatic Classifiers

Electrostatic Separation

Electrostatic separation is a beneficiation technique that exploits the differences in conductivity between different minerals to accomplish separation (Higashiyama and Asano, 2007; Kelly and Spottiswood, 1989a,b,c).

From: Minerals Technology , 2013

Mineral Processing

Swapan Kumar Haldar , in Mineral Exploration (Second Edition), 2018

13.5.5 Electrostatic Separation

Electrostatic separation works on the natural conductivity properties between minerals in feed. Separation is between economical ore constituents, noneconomic contaminants, and gangue. The common units are loftier-tension plate and screen electrostatic separator. The electrostatic plate separators piece of work past passing a stream of particles over a charged anode. The electrostatic minerals lose electrons to the plate and are pulled away from other particles due to induced attraction to the anode. The dry stream of moving particles is preferred between 75 and 250  μm, with close size distribution and uniformity of shape for efficient separation. Information technology is used for separating monazite, spinel, sillimanite, tourmaline, garnet, zircon, rutile, and ilmenite from heavy beach/stream placer sand. The electrostatic technique with local modification is extensively used in Australia, Indonesia, Malaysia, and India adjoining Indian Sea for separation of mineral sands.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128140222000137

Mineral Processing

Errol G. Kelly , in Encyclopedia of Physical Science and Technology (Third Edition), 2003

3.G.2 Theory of Electrostatic Separation

There are three singled-out stages in electrostatic separation processes: particle charging, separation at the grounded surface, and separation caused by the trajectory of the particles. Particle charging tin occur by iii possible mechanisms: contacting of different materials, ion bombardment, and consecration.

Contacting, followed past separation, of dissimilar materials results in ane existence positively charged and the other negatively charged. Bulk movement with repeated contacts is necessary for sufficient charging.

Charging by ion battery occurs as the air between the particle and electrode conducts by a corona discharge. If the particle is a nonconductor, it does not lose charge while in contact with the grounded rotor and is held to the surface by its own "epitome" force F _i . This force represents the attraction between the charged nonconducting particle and the grounded surface, the latter being equivalent to a similar accuse of reverse sign in a mirror image position behind the surface. The force is given by

(34) ${\text{F}}_{\text{i}}=\frac{\mathrm{one}}{{\text{G}}_{\epsilon }}\frac{{\text{e}}^{+}{\text{east}}^{-}}{{\text{d}}^2}$

where east ⁺, e ⁻  =   particle and image charges, respectively; K _ϵ  =   dielectric abiding.

Consecration charging of a particle occurs on a grounded surface in the presence of an electric field. Both the conducting and nonconducting particles initially develop opposite charges on opposing faces, but because the conducting particle loses one of these charges to the grounded rotor, it develops an equipotential surface and experiences an electrical force F _e away from the rotor given by

(35) ${\text{F}}_{\text{east}}={\text{due east}}^{\pm }\mathcal{Eastward}$

where E  =   electric field strength.

The separation that occurs at a grounded surface so results from the differing forces on the particles. With high tension separators, the of import forces are the image force F _i and the centrifugal force. Equating these forces yields the pinning factor

(36) $\frac{{\text{F}}_{\text{i}}}{{\text{F}}_{\text{c}}}=\frac{6{\left({\text{east}}^{\pm }\right)}^2}{\pi {\rho }_{\text{south}}{\text{K}}_{\epsilon }{\text{d}}^5{\omega }^{\mathrm{ii}}\text{R}}$

where R  =   rotor radius; ω   =   rotor angular velocity. The pinning factor is a measure of the trend of the particle to be pinned to the rotor.

The trend of a particle to be lifted from the rotor of an electrostatic separator is given by the lifting factor obtained past equating the two significant forces, electric and centrifugal:

(37) $\frac{{\text{F}}_{\text{due east}}}{{\text{F}}_{\text{c}}}=\frac{\mathrm{vi}\mathcal{Eastward}{\text{e}}^{\pm }}{\pi {\rho }_{\text{due south}}{\text{d}}^{\mathrm{iii}}{\omega }^2{\text{R}}^2}$

Similarly, for a plate-type electrostatic separator, balancing the electrical and gravitation forces gives

(38) $\frac{{\text{F}}_{\text{eastward}}}{{\text{F}}_{\text{c}}}=\frac{6\mathcal{E}{\text{e}}^{\pm }}{\pi {\rho }_{\text{s}}\text{one thousand}{\text{d}}^3}$

When the particles get out the grounded conductor, they follow a trajectory determined by electrical, gravitational, and drag forces. The resulting equations require numerical integration.

Because all electrostatic separators give incomplete separations, multiple stages are used. The probability of collection of whatever component at each stage tends to remain abiding, so that the process tin exist modeled by a probability relationship such equally Eq. (24). The probability p will have some relationship to the parameters described earlier.

Read full chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B012227410500870X

Oil Refining and Products

Abdullah K. Aitani , in Encyclopedia of Free energy, 2004

2.2 Crude Oil Processing

Equally a starting time step in the refining process, water, inorganic salts, suspended solids, and water-soluble trace metal contaminants are removed by desalting using chemic or electrostatic separation. This procedure is unremarkably considered a part of the crude distillation unit. The desalted crude is continuously drawn from the top of the settling tanks and sent to the crude fractionation unit of measurement. Distillation of crude oil into straight-run cuts occurs in atmospheric and vacuum towers. The main fractions obtained accept specific boiling-betoken ranges and can be classified in society of decreasing volatility into gases, light distillates, center distillates, gas oils, and remainder. The composition of the products is straight related to the characteristics of the crude candy. Desalted crude is processed in a vertical distillation column at pressures slightly above atmospheric and at temperatures ranging from 345 to 370°C (heating above these temperatures may cause undesirable thermal dandy). In order to further distill the residue from atmospheric distillation at higher temperatures, reduced pressure is required to forestall thermal cracking. Vacuum distillation resembles atmospheric distillation except that larger diameter columns are used to maintain comparable vapor velocities at the reduced pressures.

Read total chapter

URL:

https://world wide web.sciencedirect.com/science/commodity/pii/B012176480X00259X

Urban mining of E-waste matter: treasure hunting for precious nanometals

Sammani Ramanayaka , ... Meththika Vithanage , in Handbook of Electronic Waste product Management, 2020

2.2.1.three Sieving and separation

Sieving is carried out in the physical recycling process to classify the different sized particles based on the various sizes of sieve apertures to the desired particulate size for separation. Sieving is not only been utilized to prepare a uniformly sized feed but likewise to upgrade metal contents (Kaya, 2016). The screening is essential as the particle size and shape of metals are different from that of plastics and ceramics. Rotating screen is used mainly for metal recovery in WEEE recycling process.

Based on the variation in shape, density, and electric conductivity of metallic and nonmetallic materials in WEEE electrostatic separation are considered as a promising way to recover metals from pulverized WPCBs. Recycling industry basically used shape separation by tilted plate and sieves. Copper recovery is promising by an inclined conveyor with a vibrating plate from electric cable waste matter, printed circuit board scrap, and waste matter television and personal computers in Japan (Cui and Forssberg, 2003).

Magnetic, electrostatic, and density separation are mechanical separation techniques that have been widely used in urban mining of WEEE. Low-intensity drum separators are the standard method of magnetic separation for the recovery of ferromagnetic metals from nonferrous metals and other nonmagnetic wastes (Hsu et al., 2019). Magnetic separation is in general performed outset, followed by shredding or grinding to fine particle size, and after that electrostatic separation is practical. High-intensity separators are used for possible separation of copper alloys from the waste matrix (Veit et al., 2005). Through an intense magnetic field, copper alloys with relatively high mass susceptibility (Al multicompound bronze), copper alloys with medium mass susceptibility (Mn multicompound statuary, special brass) and copper alloys with low mass susceptibility and/or diamagnetic material beliefs (Sn and Sn multicompound bronze, Lead and Lead multicompound bronze, and brass with low Fe content) can be separated (Cui and Forssberg, 2003).

Electrostatic separation is considered every bit advantageous compared to the other physical techniques every bit it is smoothen operation, less hazardous, and requires less energy (Lu and Xu, 2016). Electrostatic separation is based upon electrical electrical conductivity and separates the nonconductive materials from the conductive ones. Although the electrostatic separators were initially recovered nonferrous metals from automobile fleck or municipal solid waste product, at present widely used for WEEE utilized explicitly for the recovery of copper or aluminum from chopped electric wires and cables and recovery of copper and precious metals from printed circuit board chip (Lu and Xu, 2016). Information technology has been observed that the multistage process is needed to separate conductors from nonconductors (Hsu et al., 2019). Both corona discharging and eddy current-based electrostatic separation have received meaning attention in the separation of ferrous and nonferrous metals and the separation of plastics from the plastic and metal mixture. Particle size has become a limiting factor, along with the sticking result of larger particles in terms of corona separation, whereas eddy current-based electrostatic separation depends on the menstruation of the particles (Cui and Forssberg, 2003).

Gravity separation is considered as the best concrete separation choice for nonmetals from the metals past dissimilar specific gravities. Density separation is dependent on the density and the size of the components. Gummy liquids such every bit tetrabromoethane can serve equally the separation medium where the metals tin can exist separated from the plastics or ceramics. Conventional gravity separators that are used in Due east-waste product recycling are h2o or airflow tables, dense media separation, and sifting. Density separation techniques that take extensively been used in the mineral processing industry are now practical into Due east-waste product recycling as WEEE consists of many plastics, with a density less than two.0   g/cm³; light metal, primarily Al and glass, with a density of 2.7   g/cm³; and heavy metals, predominantly Cu and ferromagnetic, with a density more than 7   g/cm³ (Kaya, 2016). The enriched fractions are treated by chemical techniques: pyrometallurgical and hydrometallurgical processes later mechanical/physical treatments in society to excerpt precious metals.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128170304000231

Microbe-assisted management and recovery of heavy metals from electronic wastes

R.One thousand. Murugappan , Thousand. Karthikeyan , in Ecology Direction of Waste Electrical and Electronic Equipment, 2021

6.iii Electrometallurgical processes

Electrometallurgical processes serve as an culling to pyrometallurgical and hydrometallurgical methods, which releases dioxins and furans or high volumes of effluents, respectively. Electrometallurgy intends to recycle printed circuit boards without consuming a keen amount of energy (pyrometallurgical methods) and also without generating a great amount of effluents (hydrometallurgical methods). The printed excursion boards scrap used in the magnetic and electrostatic separation were previously comminuted and separated by size in different fractions. The fractions were dissolved with aqua regia or sulfuric acid and and then placed in an electrochemistry prison cell to recover the metals separately. Electrowinning (EW) is as well ane of the efficient technologies that help to recover metals from the metallic-containing solutions or leachates. Selective recovery of the target metal is one of the principal advantages of electrowinning. Moreover, in EW less or no secondary waste matter is generated, no hazardous chemicals are used and comparatively require lesser cost investment. EW engineering is adopted for the selective recovery of base metals such as Cu and Pb from electronic scraps (Mecucci and Scott, 2002; Madenoglu, 2005).

Read full chapter

URL:

https://world wide web.sciencedirect.com/science/commodity/pii/B9780128224748000040

Coal

Deepak Pudasainee , ... Rajender Gupta , in Future Energy (3rd Edition), 2020

two.iv.1.4 Preparation of ultra clean coal

The idea of UCC is that the ash-free coal (AFC) tin be used more efficiently to provide electricity either via direct firing into the gas turbine followed by a steam cycle or via catalytic gasification followed by fuel cell. Chemical cleaning of coal to obtain more or less AFC tin can be broadly classified into 2: concrete and chemical. Fig. 2.9 shows the physical and chemical coal cleaning pathways and the characteristics of the cleaned coal [31] . In physical cleaning, there is no involvement of chemicals and the coal construction does not change. Concrete cleaning involves the removal of minerals by methods such equally gravity separation, barm flotation, electrostatic separation, magnetic separation, oil agglomeration, and air dense medium fluidization [32]. In the air dense medium–fluidized bed process, the lighter coal particles containing fewer minerals floats on the surface of the bed and the particles with the higher mineral content sink.

Figure ii.ix. Physical and chemical coal-cleaning pathways and the characteristics of the cleaned coal [31]. AFC, ash-complimentary coal; UCC, ultraclean coal.

Reprinted with permission from Copyright Elsevier 2017.

Fifty-fifty though physical coal cleaning is easy and depression cost, it does take the problem that only impurities in the larger sized particles tin can be cleaned (e.g., gravity separation requires particle size >0.5   mm). Physical cleaning cannot remove finely distributed minerals and chemically divisional species inside a coal matrix.

Chemical cleaning methods are meliorate than concrete methods because chemical processes can remove finely distributed minerals and organically bounded chemic species. The chemical cleaning methods tin exist divided into two categories: apply of chemicals that dissolve minerals, usually called equally UCC, and solvents for dissolving the coal-similar matter, unremarkably chosen AFC. In UCC, there is no change in the coal structure of the product, whereas in AFC, the coal structure is changed. In UCC, the ash content ranges between 0.1% and 5%, whereas in AFC, ash content is less than 0.1%. The details of the product process, yield advantages, and disadvantages of these processes accept been presented in our recent review [31]. Extraction of organic matters using NMP (N-methyl-ii-pyrrolidone) to produce AFC likewise reduces sulfur; in particular, inorganic sulfur is completely removed [33].

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780081028865000025

Recycling of Postindustrial and Postconsumer Plastics Containing Flame Retardants

Yard. Schlummer , in Polymer Green Flame Retardants, 2014

4.two Dry sorting processes

Sorting processes are most oftentimes required in social club to provide blazon sorted fractions for recompounding processes. Dry sorting processes apply mechanical (sieves) or electrostatic forces or they sort by means of spectroscopic detection systems. Sieves or air classifiers are applied to reduce the amount of fine particles in waste material plastic fractions, since the fines incorporate minor metal particles from grinding processes and dust collected on plastic surfaces in the use or reclamation stage. These foreign materials may worsen the mechanical properties of recycled plastics. However, sieving or air classification take no bear upon on the FR organisation.

Electrostatic separators are applied to separate mixtures of two or three different polymers by ways of electrostatic forces [24] . If one of the three plastics in the input stream contains (B)FR, this process may separate FR equipped from other plastics. Even so, such defined input streams are most likely found in postindustrial waste material and are generally not present in existent postconsumer eastward-waste. Therefore, electrostatic separation of postconsumer plastics in e-waste is merely applied to fractions obtained by preceding processes (e.chiliad. sink and float fractions).

Manual spectroscopic detection devices take been applied in recycling operations of dismantling plants, whereas these techniques are practical to comparably large plastic parts (unground casings, etc.). NIR and midinfrared MIR can be applied to sort plastic parts co-ordinate to their polymer types unless their color is too nighttime to produce analyzable spectra. ABS and ABS equipped with TBBPA can exist differentiated by NIR, whereas ABS and ABS equipped with other BFR cannot exist distinguished by this technique. Therefore, NIR is not a powerful tool to sort FR and FR-gratis polymers.

In contrast, bromine or phosphorous tin be detected past sliding spark spectroscopy (SSS), which can be performed past low cost manual devices. Thus, the combination of SSS and NIR provides information suitable for an effective sorting of FR-free polymers. As both instrument browse plastics within seconds, their application in dismantling plants appears to be a reasonable and low toll recycling approach for light plastics.

Withal, from an economical indicate of view, automated sensor-based sorting is considered to be more effective than manual approaches. These techniques are applied to coarsely basis plastic waste and bailiwick particles with 5–50   mm to the sensor system e.grand. on a band conveyer. An NIR camera or an alternative sensor organisation analyzes the particles coming across and controls a bravado device that may and so blow a particle out of a waste product stream, if the sensor results indicate the presence (or absence) of a given polymer. These sorting techniques are rather effective; however, they piece of work best with highly full-bodied target polymers (>80%). Equally long as a complex mixture is to be segregated, the sorting will take to exist done in several sequent sorting steps in society to produce reasonably pure polymer fractions. This is necessary since the mechanical sorting by blowing off particles always leads to a small-scale amount of falsely sorted particles. This is exemplified in Table 5, which provides experimental data on the automated NIR separation of footing gray monitor casings. Whereas the separation of ABS and PS has not been completely optimized in this example, PC/ABS tin can well be segregated from ABS and PS. However, there is a small percentage of half dozen% ABS and PS particles, which have been sorted falsely into the PC/ABS fraction.

Table five. Experimental Data on the Quality of Online NIR Sorting of a Heterogeneous Mixtures (Scrap of Greyness Monitor Casings)

Trial	Separated Fraction	Plastics Identified in Separated Fractions
		ABS	PS	PC/ABS	Others
Monitor casings batch 1	ABS	87%	7%	0%	7%
	PS	26%	51%	9%	14%
	PC/ABS	3%	3%	94%	0%
Monitor casings batch two	ABS	90%	0%	3%	7%
	PS	16%	77%	3%	3%
	PC/ABS	3%	3%	94%	0%

An innovative approach applies light amplification by stimulated emission of radiation spectroscopy to sort plastics automatically by a sensor technique that produces analyzable spectra even for black polymers [43]. Thus, NIR and light amplification by stimulated emission of radiation spectroscopy provide 2 powerful sorting tools with respect to polymer type. XRT is also used every bit detector in automated sorting systems and can differentiate polymers of dissimilar specific atomic densities. As the optical density is significantly increased past BFR, e.g. it has been shown that XRT may separate BFR-free polymers from BFR polymers. As for the manual approach, a combination of two automatic sensor-based technologies appears to be capable of sorting pure and BFR-gratis polymer fractions from WEEE.

Read total chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780444538086000251

Recycling of waste material printed circuit boards: A review of current technologies and treatment status in People's republic of china

Kui Huang , ... Zhenming Xu , in Journal of Hazardous Materials, 2009

Corona electrostatic separation (CES) was an environmental-friendly (no wastewater or gas during the process) and efficient way for the recovery of metals from waste material PCBs and widely studied by Xu [19–29]. CES (Fig. 11) is based on the farthermost differences in density and electrical conductivity of metallic and nonmetallic materials from pulverized PCBs. Co-ordinate to a report from the Shanghai team, effects of operating parameters of CES and backdrop of metallic metals (such equally particle shapes and particle sizes) on the efficiency of CES were widely studied by Xu [19–22]. The results indicated that CES was an important technology suitable for separating metals from nonmetals and particle sizes between 0.6 and 1.ii   mm were most feasible for separation in industrial awarding [xix].

Fig. 11. Diagram of CES [19].

Read full article

URL:

https://world wide web.sciencedirect.com/science/article/pii/S0304389408012570

A review of the beneficiation of rare earth element bearing minerals

Adam Jordens , ... Kristian E. Waters , in Minerals Engineering, 2013

3.four Electrostatic separation

Electrostatic separation is a beneficiation technique that exploits the differences in electrical conductivity between different minerals to achieve separation ( Higashiyama and Asano, 2007; Kelly and Spottiswood, 1989a,b,c). Electrostatic separation techniques are typically only used when alternative processing techniques volition non suffice, equally the comminution steps in mineral processing flowsheets are generally wet processes and the energy requirements to drive off all moisture prior to electrostatic separation can be significant (Kelly and Spottiswood, 1989a). In the context of rare earth mineral processing, the typical use of electrostatic separation is in the separation of monazite and xenotime from gangue minerals with similar specific gravity and magnetic properties (Ferron et al., 1991; Zhang and Edwards, 2012). A specific example of this is when xenotime, which is more than strongly paramagnetic than monazite, is full-bodied with ilmenite afterward magnetic separation of heavy mineral sands (Gupta and Krishnamurthy, 1992). In this case the only means past which xenotime may be removed from the ilmenite is via electrostatic separation, equally ilmenite is conductive but xenotime is non (Gupta and Krishnamurthy, 1992).

Electrostatic separation is a valuable technique for heavy mineral sand beneficiation, and the successful awarding of this procedure to separate ultrafine (<37   μm) coal particles may nowadays an opportunity to treat the fines produced in many currently operating mineral processing circuits that account for significant rare earth losses (Higashiyama and Asano, 2007). Unfortunately, all electrostatic separation techniques (drum-type, belt-type, plate-blazon etc.) suffer from the requirement that the feed material must be completely dry (Higashiyama and Asano, 2007). Bated from the heavy mineral sand deposits, near all other discovered rare world deposits (aside from the ion-adsorbed clays in southern China) require some class of comminution prior to separation and these grinding operations are heavily reliant on slurried feed cloth. The energy costs associated with completely drying a ground ore prior to an electrostatic separation footstep are likely to be far too cost-prohibitive for such a process to be applied on an industrial scale.

Read full article

URL:

https://world wide web.sciencedirect.com/science/article/pii/S0892687512003597

A review of mineral processing of ilmenite past flotation

Jihua Zhai , ... Si Wan , in Minerals Engineering, 2020

3.one.1.3 Electrostatic separation

Electrostatic separation tin can exist applied in ilmenite upgrading because of the conductivity difference between ilmenite and its co-existing minerals such as titanaugite and zircon. High-tension (electrical) and electrostatic plate separators are commonly employed for this purpose ( Australia, 2019). The successful industrial awarding is reported in Australia for the selective separation of ilmenite, rutile, zircon and monazite by means of electrostatic separation, together with magnetite separation in view of their different magnetic and electrical backdrop at various elevated temperatures (Australia, 2019; Farjana et al., 2018; Jones, 2009). As a combined processing technology, rare globe drum magnets are first used to remove ilmenite from mined heavy mineral concentrate feed, from which virtually of the ilmenite tin be recovered. And so non-magnetic minerals are processed by electrostatic separation to obtain conductor minerals (rutile and leucoxene) and non-conductors (consisting of zircon, kyanite, quartz, monazite and staurolite). After, the non-conductors are treated by gravity separation to remove the lower specific gravity material (quartz, kyanite, garnet, and staurolite) from the college specific gravity zircon. After gravity separation, electrostatic separation is used again to remove remainder conductors from the zircon and induced whorl magnets are used to separate traces of monazite and staurolite from zircon.

As far as the authors' knowledge, no report on the electric current awarding of electrostatic separation in ilmenite industry tin can exist found in China. Electrostatic separation has been used to set loftier purity ilmenite and titanaugite in labs, and besides used for theoretical studies on separating ilmenite from its associated gangue minerals such as quartz and zircon. Ziemski and Holtham (2005) used electrostatic separation to separate titanium minerals (ilmenite and zircon) using a new theory of particle discharge in high tension gyre (HTR) separation, and the influence of particle bed and size was considered. Triboelectric separation of ilmenite from quartz is besides successful in lab experiments, provided optimum airflow rate, feed rate and voltage (Yang et al., 2018). Overall, in that location are some limitations impeding the popularization and industrial use of electrostatic separation in ilmenite dressing, such as high requirement for feedstock quality in terms of moisture content (completely dry) and uniform granularity, safe operation for workers (dust problem) and limited handling chapters (<5 t/h).

Read full article

URL:

https://www.sciencedirect.com/science/commodity/pii/S0892687520303782

michiegreak1974.blogspot.com

Source: https://www.sciencedirect.com/topics/earth-and-planetary-sciences/electrostatic-separation

Share :