Approaches To Improve Separation Efficiency of Eddy Current

Article pubs.acs.org/est

Approaches To Improve Separation Efficiency of Eddy Current Separation for Recovering Aluminum from Waste Toner Cartridges Jujun Ruan and Zhenming Xu* School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People’s Republic of China S Supporting Information *

ABSTRACT: Separation efficiency of eddy current separation (ECS) is low (about 85%) in industrial application for recovering aluminum from crushed waste toner cartridges. Influencing factors of ECS were studied to improve the separation efficiency. Operation factors were researched by orthogonal experiment of ECS on investigating the separation distance between aluminum and plastic flakes. The results indicated the difference (ωR-v) between feeding speed (v) and rotation speed (ω) of magnetic drum (radius: R) was critical factor of influencing the separation efficiency, feeding speed (v) was general factor, and collecting position (H) was subordinate factor. Separation efficiency decreased as the increasing of v, and increased as the increasing of (ωR-v). 0.9 m was the optimal value of H in the orthogonal experiment. Influencing factors of particle characteristics and machine structure were studied by newly established models for computing the separation distance between aluminum and plastic flake in ECS. The results indicated changing of particle size would influence the separation efficiency greater than ω and particle shape. Separation efficiency will increase as the increasing of particle size and ω. Shape of circle is beneficial to improve separation efficiency. Finally, approaches to improve separation efficiency of ECS were presented.

1. INTRODUCTION In recent years, the global production of e-waste is estimated to be 20−25 million tons per year, while China produced about 2.5 million tons.1−3 Furthermore, China has been one of the greatest received regions of e-waste imported from the developed countries.4,5 E-waste has been a problem that is exigent to be solved because of the fast growing and containing both toxic and valuable materials. However, for lack of advance recovery technology, serious environmental contaminations have been caused in the activities of recovering e-waste by exposed manual dismantling, open incineration, and acid washing.6 Thus, efficient and environment-friendly technology has been the urgent need for disposing e-waste. The published recovery technologies of e-waste mainly include manual dismantling, pyrometallurgy, hydrometallurgy, and mechanical method.7,8 Therein, mechanical method had been the preferred technology because of its efficiency and little secondary pollution.9−12 Large numbers of waste toner cartridges have been produced.13 The comprised materials of waste toner cartridges were given in Supporting Information (SI) Figure S2a. A production line for recovering waste toner cartridges had been developed in previous work.14 Appearance of the line was given in (SI) Figure S2b. The main shortage of the line was that separation efficiency of eddy current separation (ECS) was low in production, although ECS has been reported as a preferred © 2012 American Chemical Society

technology in recycling light metals from end-of-life vehicles,15,16 waste household appliances,17 and discarded PC.18 Separation efficiency of ECS can be computed by ξ=

Mlm + M nm Mlm + M mid + M nm

(1)

Where Mlm is the mass of light metal; Mnm is the mass of nonmetal; Mmid is the mass of middling fraction (not be separated) in ECS. Separation efficiency of ECS for recovering aluminum from crushed waste toner cartridges was only about 85%. Manual sorting was required to separate aluminum from the middling fraction. However, manual sorting decreased the work efficiency of the production line. Thus, how to improve separation efficiency of ECS has been the pressing problem in the recovery of waste toner cartridges. Additionally, improvement of separation efficiency of ECS also can reduce the secondary-pollution (dioxin and furan) brought from plastic in later smelting process for purifying the recovered aluminum. For improving separation efficiency, models of ECS had been established to research the influencing factor.19,20 The influencing factors of ECS included operation (feeding speed, Received: Revised: Accepted: Published: 6214

March 1, 2012 April 12, 2012 May 9, 2012 May 9, 2012 dx.doi.org/10.1021/es3008358 | Environ. Sci. Technol. 2012, 46, 6214−6221

Environmental Science & Technology

Article

Figure 1. (a) Employed eddy current separator, (b) employed materials, (c) process of ECS.

rotation speed of magnetic field), particle characteristics (shape, conductivity, size, volume, and cross sectional area perpendicular to magnetic flux, intensity of induced eddy current in particle), and machine structure (pair of magnetic poles, magnetic intensity, and radial distance from axes of magnetic drum to particle). However, some of the above influencing factors, such as intensity of induced eddy current and radial distance from axes of magnetic drum to particle, were hard to control in production. These influencing factors should be replaced by other controllable factors. Meanwhile, there was a lack of particular investigation of the movement behavior of particle in the magnetic field.21,22 Some interesting influencing factors (such as collection position of particle) were unconsidered. Thus, the published models of ECS need to be optimized. With the purpose of obtaining the approaches to improve separation efficiency of ECS, influencing factors of ECS were researched based on investigating the separation distance between particles. Separation distance was considered as the representation of separation efficiency because separation efficiency increased as the increasing of separation distance. Definition of separation distance between aluminum and plastic was given in SI Figure S3. Operation factors were studied by orthogonal experiment of ECS on investigating separation distance between aluminum and plastic flakes. Influencing factors of particle characteristic and machine structure were discussed based on the newly established models for computing the separation distance between aluminum and plastic flakes in ECS. Finally, approaches to improve the separation efficiency of ECS were given. This study can guide the industrial application of ECS in e-waste recovering.

2. MATERIALS AND METHODS 2.1. Materials. Employed eddy current separator was horizontal magnetic drum separator (see Figure 1a). The magnetic drum was comprised of nine pair of NdFeB magnets with N−S−N orientation. The introduction of the running process of eddy current separator was presented in SI Figure S1. Employed aluminum and plastic materials were collected from crushed waste toner cartridges. Aluminum and plastic, contained in waste toner cartridges, had large two-dimension size and would be crushed into flakes, with various shapes of circle, rectangle, and triangle, by shearing machine. The min-size and max-size aluminum flakes, selected from crushed waste toner cartridges, which had the representative shapes of circle, rectangle, and triangle, were marked as C1, C2, R1, R2, T1, T2 (see Figure 1(b)). Physical properties of the flakes and eddy current separator were measured and given in SI Table s1. The process of ECS was given in Figure 1 (c). Aluminum and plastic were fed into ECS with different feeding speeds, rotation speeds of magnetic field, and collection positions. The separation distances between aluminum and plastic flakes were measured. 2.2. Orthogonal Experiment of ECS for Studying Operating Factors. Orthogonal experimental design is an efficient experimental method for studying the influence of different factors in different levels.23,24 We used this method to study operation factors of ECS. The operation factors of ECS included feeding speed (v), difference between feeding speed and rotation speed of magnetic field (ωR-v), and collecting position of materials (H). In order to investigate the variation trend of separation distance caused by different levels of these three factors, four levels of the factors were chosen. Table L16(43) was employed in the orthogonal experiments of ECS. Levels of the factors were given in Table 1. These four levels were chosen based on equally dividing the limits of feeding 6215

dx.doi.org/10.1021/es3008358 | Environ. Sci. Technol. 2012, 46, 6214−6221


Article

Table 1. Levels of the Factors in Orthogonal Experiment of ECS

Fr R =

factors levels

v(m/s)

(ωR-v) (m/s)

H (m)

1 2 3 4

0.2 0.4 0.8 1.6

0 0.5 1 2

0.3 0.6 0.9 1.2

=

T

Fr =

Br k(ωmR − v)γVSp2Bm δ R 2 3

16π R

1 (sec α0 − 1)2

δR

L 2(L + W )

(3)

Br k(ωmR − v)γVSp2Bm δT 2 3

16π R

1

δ 2 T

(sec α0 − 1)

=

W C (4)

Where Br is the magnetic flux intensity of the field (T); k is the number of pairs of magnets; ωm is the rotation speed of magnetic drum (rad/s); R is the radius of magnetic drum (m); v is feeding speed (m/s); γ is the conductivity of paritcle (S/ m); V is the volume of particle (m3); Sp max cross area of particle in horizontal (m2); Bm magnetic flux intensity of the magnetic drum surface (T); δ is the oriental (shape) factor of particle; α0 is the detachment angle of particle from conveyor belt; L is the longest side of particle; W is the width of particle. C is the circumference of the particle. 2.3.2. Investigation of the Coacted Forces and Movement Behaviors of Particles in ECS. Movement behavior of aluminum in ECS was divided into three stages: (1) entering magnetic field, (2) detaching from conveyor belt surface, (3) exiting from magnetic field (see Figure. 3). At the beginning of stage (1), eddy current force increased as the particle moving close to magnetic drum, and the force was divided into vertical component and horizontal component. Horizontal component was counteracted by the friction force of conveyor belt and no relative motion will happen between aluminum and belt. As the increasing eddy current force, vertical component would be greater than the gravity force (G) of the flake, and aluminum will have a vertical-upward acceleration and move upward. Meanwhile, eddy current force will decrease along with the upward movement of aluminum due to the decline of magnetic flux of magnetic 19

speed, rotation speed of magnetic field, and height of the eddy current separator in lab. ECS experiments were performed according to design of table L16(43). 2.3. Construction of the Models for Computing Separation Distance. Operation factors were researched by orthogonal experiment of ECS. However, this method was not suitable to investigate the influencing factors of particle characteristics and machine structure. The reason is that structure parameters of designed separator and particle characteristics were inconvenient to change optionally. Thus, models for computing separation distance between aluminum and plastic flakes were established to study the influencing factors of particle characteristics and machine structure. The models were established based on the previous models of eddy current force and detailed investigation of coacting forces on particles as well as their movement behavior in ECS. 2.3.1. Models of Eddy Current force. The models of eddy current force acting on circle, rectangle, and triangle aluminum flakes were expressed as25 Fr C =

Br k(ωmR − v)γVSp2Bm 3 3

16π R

1 (sec α0 − 1)2

(2)

Figure 2. Analysis of the coacting force and movement behavior of aluminum flake in ECS. 6216



Article

drum. When the vertical component was equal to gravity force, aluminum flake will be suspended and keep constant radial distance to the axis (O) of separator. The position of the flake was called point (x0, y0). Point (x0, y0) can be considered as the detachment point of aluminum flake from separator surface. Meanwhile, point (x1, y1) is supposed as the symmetry point of (x0, y0) at the right of y-axis (Figure. 3). The movement of aluminum flake from point (x0, y0) to point (x1, y1) can be considered as rectilinear motion. At this rectilinear movement, magnetic fluxes of aluminum flake and magnetic drum was considered to be parallel, horizontal component of eddy current force can be neglected, and repulsive force can be supposed as equal to its gravity force. Once aluminum flake passes over point (x1, y1), vertical component of eddy current force will be less than gravity force. Horizontal component of repulsive force can no longer be neglected since the directions of the two magnetic fluxes will no longer been parallel. Horizontal component will accelerate aluminum in horizontal direction until it passes through the boundary of the magnetic field. Furthermore, the movement of aluminum flake in vertical direction is controlled by gravity force and vertical component of ECS. We suppose point (x2, y2) as the exiting position of aluminum from the magnetic field. As passing through point (x2, y2), aluminum flake only subjects to gravity force and the movement can be considered as horizontal projectile motion. Due to no response to magnetic field, movement behavior of plastic flake in ECS was considered as horizontal projectile motion (see Figure 2).

Table 2. Range Analysis of the Results of ECS That Followed the Design of L16(43)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 sum of ds level 1 sum of ds level 2 sum of ds level 3 sum of ds level 4 range

3. RESULTS AND DISCUSSION 3.1. Results of ECS Orthogonal Experiment. Ruler was used to measure the separation distance (d) between aluminum and plastic flakes in ECS. Results of orthogonal experiments were presented in Table 2. Meanwhile, ranges between different sums of separation distances (ds) influenced by different levels of every factor were also given in Table 2. Higher value of range indicated the factor was more important to influence the separation efficiency. Therefore, (ωR-v) was the critical factor, v was general factor, and H was subordinate factor. The influencing sequence of the factors was (ωR-v) > v > H. Furthermore, we defined the levels of every factor as abscissa; set the sum of separation distances caused by every operation factor in different levels as ordinate; and then tendency charts of the levels of every operation factor were painted and given in Figure 2. Seen from Figure 3a, separation distance decreased as the increasing of v. Figure 3b indicated that separation distance would increase as the increasing of (ωR-v). Seen from Figure 3c, as the increasing of H, separation distance increased at first and then decreased when the value of H was greater than 0.9 m. Thus, the optimal value of H was 0.9 m in the orthogonal experiments of ECS. 3.2. Construction of Models for Computing Separation Distance. In the construction of models, air resistance was neglected, feeding speed was supposed as 0.4 m/s. Rotation speeds of the magnetic field were 400 rpm (ω1) and 800 rpm (ω2) respectively. 3.2.1. Models for Computing Detachment Point of Aluminum Flake. Eddy current force impels aluminum to detach from magnetic drum. At the beginning of the detachment, horizontal component of eddy current force is neglected and Fr(x0 , y ) ≈ F⊥ 0

v(m/s)

(ωR-v) (m/s)

H (m)

d (m)

influenced by

0.2 0.8 0.4 1.6 0.2 0.8 0.4 1.6 0.2 0.8 0.4 1.6 0.2 0.8 0.4 1.6 0.945

0.5 2 2 0.5 1 0 0 1 0 1 1 0 2 0.5 0.5 2 −0.022

0.9 0.3 0.9 0.3 0.3 0.9 0.3 0.9 1.2 0.6 1.2 0.6 0.6 1.2 0.6 1.2 0.727

0.283 0.283 0.35 0.15 0.299 −0.006 −0.005 0.234 −0.003 0.25 0.317 −0.008 0.366 0.234 0.233 0.301 Total 3.278

influenced by

0.895

0.9

0.841

influenced by

0.761

1.1

0.861

influenced by

0.677

1.3

0.849

0.268

1.322

0.122

experiments

Where Fr(x0,y0) is the repulsive force when aluminum arrives at point (x0, y0), F⊥ is vertical component of the repulsive force. Aluminum detached from conveyor belt when: Fr(x0 , y ) ≥ mg 0

(6)

Where m is mass of aluminum, g is acceleration of gravity (m/ s2). Detachment angle (α0) of aluminum from the conveyor belt can be calculated by the intersection points of the curves of eddy current force and gravity.25 Detachment angles (α0) of aluminum flakes (C1, C2, R1, R2, T1, and T2) in different operation parameters were given in Table 3. Then, coordinate of detachment point (x0, y0) of aluminum flake can be calculated by

x0 = Rtgα0

(7)

R cos α0

(8)

y0 =

Point (x1, y1) is the symmetry point of (x0, y0) relative to Y-axis. The coordinates of point (x1, y1) of aluminum flakes (C1, C2, R1, R2, T1, and T2) are presented in Table 3. 3.2.3. Models for Computing Exiting Point of Aluminum Flake from Magnetic Field. See Figure 2, as passing through point (x1, y1), eddy current force offers two accelerations in horizontal and vertical direction to aluminum flake. The horizontal and vertical accelerations keep changing in direction and magnitude. It is difficult to express the horizontal and vertical accelerations accurately. Thus, average acceleration was employed to express the horizontal and vertical accelerations. At point (x1, y1), horizontal acceleration can be expressed as a x1 = gsin α1 (9)

(5) 6217



Article

ax =

gsin α1 2

(11)

ay =

gcos α1 2

(12)

Thus, trajectory model of aluminum from point (x1, y1) to (x2, y2) can be expressed as ⎡ ⎤2 2 ⎛ ⎞ 2( x − x ) 1 v v 1 y = − (g − ay)⎢⎢ + ⎜ ⎟ − ⎥⎥ + y1 2 ax ax ⎝ ax ⎠ ⎣ ⎦ (13)

Meanwhile, equation of the boundary of magnetic field is xb 2 + yb 2 = (R + η)2

(14)

Where η is the radial distance between magnet surface and field boundary (m). The intersection point of the curves of trajectory equation and field boundary equations is the exiting points of aluminum. Curves of movement trajectory of aluminum flakes (C1, C2, R1, R2, T1, and T2), moving from point (x1, y1) to (x2, y2), and the boundary of the magnetic field were plotted in SI Figure S4. Then, the coordinates of every exiting point were calculated and presented in Table 3. 3.2.4. Models for Computing Horizontal Throw of Aluminum Flake. Horizontal throw (D) of aluminum flake is comprised of two parts: one is the horizontal distance from Yaxis to existing point (x2, y2); the other is the horizontal distance from point (x2, y2) to the collection position (see Figure 2). Abscissa of point (x2, y2) had been obtained in the above calculation. Horizontal distance from point (x2, y2) to collection position is determined by the horizontal muzzle velocity (vx) of aluminum after leaving magnetic field and the vertical height (H) from collection position to conveyor (see Figure 2). Horizontal and vertical muzzle velocities (vx and vy) of aluminum when leaving magnetic field can be presented as vx = v +

g sin α1 2

4|y2 − y1| g (2 − sin α1)

4|y2 − y1| ⎛ 2 − cos α1 ⎞ ⎟ vy = g ⎜ ⎝ ⎠ 2 g (2 − sin α1)

(15)

(16)

vx and vy of aluminum flakes (C1, C2, R1, R2, T1, and T2) were presented in Table 3. Movement of aluminum flake from point (x2, y2) to the collection position can be considered as horizontal projectile motion. Thus, horizontal throw (D) of aluminum flakes in ECS can be computed by Figure 3. Tendency charts of the levels of every operation factor in orthogonal experiments of ECS.

D = vx

Where α1 is the symmetry angle of α0. Vertical acceleration can be expressed as a y = gcos α1 (10)

2(H − |y2 |) g

⎛ vy ⎞2 vy +⎜ ⎟ − + x2 g ⎝g⎠

(17)

Horizontal throws (D) of aluminum flakes (C1, C2, R1, R2, T1, and T2) were given in Table 3. 3.2.5. Model for Computing Horizontal Throw of Plastic Flake. Movement behavior of plastic in ECS is considered as horizontal projectile motion (see Figure 2). The horizontal throw (D′) of plastic is only determined by feeding speed and the vertical height (H) from the collection position to conveyor. Trajectory equation of plastic in ECS can be expressed as

1

Eddy current force will disappear as the aluminum flake passes through point (x2 , y2 ). So, average horizontal acceleration (ax) and vertical acceleration (ay) of aluminum in the movement from point (x1, y1) to point (x2, y2) can be expressed as 6218



Article

Table 3. Results of Each Step for Calculating Separation Distance between Aluminum and Plastic Flakes with the Feeding Speed 0.4 m/s calculation results materials

ω(rpm)

α0 (deg)

(x1, y1)

(x2, y2)

vx (m/s)

vy (m/s)

D (m)

d (m)

C1

400 800 400 800 400 800 400 800 400 800 400 800

12.6 14.9 7.5 9.2 8.6 10.2 8.3 9.7 9.6 11.2 8.6 9.7

(0.021, 0.1023) (0.026, 0.1033) (0.013, 0.1008) (0.016, 0.1013) (0.015, 0.1011) (0.017, 0.1016) (0.014, 0.1010) (0.016, 0.1014) (0.016, 0.1014) (0.019, 0.1019) (0.015, 0.1011) (0.016, 0.1014)

(0.146, −0.033) (0.148, −0.024) (0.136, −0.064) (0.141, −0.052) (0.137, −0.059) (0.14, −0.05) (0.138, −0.057) (0.139, −0.054) (0.141, −0.052) (0.147, −0.044) (0.137, −0.06) (0.139, −0.054)

0.606 0.643 0.527 0.552 0.546 0.569 0.538 0.561 0.560 0.585 0.545 0.562

0.968 0.978 0.980 0.963 0.981 0.971 0.966 0.969 0.969 0.974 0.976 0.979

0.351 0.368 0.308 0.325 0.317 0.330 0.317 0.326 0.327 0.338 0.318 0.326

0.189 0.206 0.146 0.163 0.155 0.168 0.155 0.164 0.165 0.176 0.156 0.164

C2 R1 R2 T1 T2

Figure 4. Results of testing experiments.

D′ = v

2H g

flake were performed three times in order to investigate experimental error. Separation distances between aluminum and plastic were measured and the results were presented in Figure 4. Meanwhile, separation distances computed by the models were also presented in Figure 4. It can be seen that calculation results of separation distances were in the variation range of experiment results. Calculation results were agreed with experiment results. 3.2.8. Comparison of the New Models with Other Models. In this section, the newly established models were compared with the published models on their contained parameters.20,23,25 Detailed comparison procedure was given in SI Table S2. The comparison results indicated that the new models complemented the uncontained influencing factors in published models to the literature of ECS models. The added factors (detailed shape factor, intensity of magnetic field on surface of magnetic drum, radius of magnetic drum, boundary of magnetic drum, and collection position) in new models provided new approaches to improve the separation efficiency of ECS. 3.3. Analysis of Influencing Factors of Particle Characteristic and Machine Structure. Analysis of influencing factors of particle characteristic and machine structure were based on the calculation results of separation distance between aluminum and plastic in ECS. The analysis

(18)

Thus, under the condition of feeding speed (v) 0.4 m/s, and H 0.8 m, the horizontal throw of plastic flake in ECS was 0.162 m. 3.2.6. Model for Computing Separation Distance. Based on the calculation of D and D′, separation distance can be obtained from the following equation d = D − D′ = vx

2(H − |y2 |) g

⎛ vy ⎞2 vy 2H +⎜ ⎟ − + x2 − v g g ⎝g⎠ (19)

The separation distances between aluminum flakes (C1, C2, R1, R2, T1, and T2) and plastic flake in ECS were presented in Table 3. Separation distance increased as the increasing of rotation speed of magnetic field. 3.2.7. Testing Experiment. In order to test the accuracy of the models for calculating separation distance, ECS experiments were performed in lab. Aluminum flakes (C1, C2, R1, R2, T1, T2), employed in calculation, were fed into ECS together with plastic flake. Experiments were performed with feeding speed 0.4 m/s, rotation speed of the magnetic field 400 and 800 rpm respectively. ECS experiments for every aluminum 6219



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Table 4. Analysis of the Calculation Results of Separation Distances Influenced by Different Influencing Factors of Particle Characteristic and Machine Structure influencing factors flake shape sum of separation distances (m)

circle (C1+C2) rectangle (R1+R2) triangle (T1+T2)

range

Rotation speed of magnetic field

flake size 0.704 0.642 0.661 0.062

large (C1+R1+T1) small (C2+R2+T2)

1.059 0.948 0.111

400 rpm 800 rpm

0.966 1.041 0.075

Figure 5. Approaches to improve separation efficiency of ECS.

results were given in Table 4. The range of sum of separation distances caused by different particle size was 0.111, which was larger than the ranges caused by particle shape and rotation speed of magnetic field. It meant that changing of particle size brought greater impact on separation efficiency than rotation speed of field and particle shape. The influencing sequence was size > rotation speed of field > shape. Separation efficiency increased as the increasing of particle size and rotation speed of magnetic field. Meanwhile, shape of circle brought positive impact on separation efficiency of ECS. 3.4. Approaches to Improve Separation Efficiency of ECS. According to the results of orthogonal experiment of ECS and the established models for calculating the separation distance, the approaches to improve separation efficiency of ECS were suggested in Figure 5. Approaches from Particle Characteristic. Shearing process should be controlled to keep the aluminum particle in greater size (volume) and two-dimension area as long as the toner cartridges can be completely liberated. The shape of sieve mesh should be manufactured in a circle. Approaches from Machine Structure. On the premise of saving production cost, eddy current separator should employ high intensity magnets, more pairs of magnetic poles as well as decrease the radius of magnetic drum. Approaches from Operating Factors. on the premise of saving energy, the rotation speed of magnetic field should be increased as far as possible. Meanwhile, on the condition that

keeping enough work efficiency, feeding speed should be as low as possible. Collection position of particle can be set according to experiment. Approaches to improve separation efficiency of ECS were proposed, based on researching the influences of operation factors, particle characteristic factors, and machine structure factors on separation efficiency. These approaches can guide the structure design of separator, shearing methods of materials, and operation of ECS. These approaches could contribute to the industrial application of ECS in e-waste recycling.

■

ASSOCIATED CONTENT

S Supporting Information *

Contents present the running process of eddy current separator, tables show the physical properties of aluminum flakes and eddy current separator, the comparison results of the new models to others, figures show the comprised materials of waste toner cartridges, sketch of the production line for recovering waste toner cartridges, definition of separation distance between aluminum and plastic flakes, calculation results of the exiting positions of aluminum flakes (C1, C2, R1, R2, T1, and T2) in ECS. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Phone:+86 21 54747495; fax:+86 21 54747495; e-mail: [email protected]. 6220



Article

Notes

(22) Köhnlechner, R.; Schlett, Z.; Lungu, M.; Caizer, C. A new wet Eddy-current separator. Resour., Conserv. Recycl. 2002, 37, 55−60. (23) Wu, J.; Li, J.; Xu, Z. Optimization of key factors of the electrostatic separation for crushed PCB wastes using roll-type separator. J. Hazard. Mater 2008, 154, 161−167. (24) Ilgin, M.; Gupta, S. Evaluating the Impact of Sensor Embedded Products on the Performance of an Air Conditioner Disassembly Line. Int. J. Adv. Manuf. Technol. 2011, 53, 1199−1216. (25) Ruan, J.; Xu, Z. A new model of repulsive force in eddy current separation for recovering waste toner cartridges. J. Hazard. Mater. 2011, 192, 307−313.

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by Shanghai Tongji Gao TingYao Environmental Science & Technology Development Foundation.

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REFERENCES

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Approaches To Improve Separation Efficiency of Eddy Current

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