Proceedings of the ASME 2013 International Mechanical Engineering Congress & ExpositionIMECE2013

November 13-21, 2013, San Diego, California, USA

IMECE2013-62396

POST-CONSUMER PLASTIC SORTATION WITH THE USE OF ELECTROMAGNETIC SEPARATION METHODS FOR RECYCLING

Connor G. Kress and Matthew FranchettiThe University of Toledo

Mechanical, Industrial, and Manufacturing Engineering DepartmentToledo, Ohio, USA

ABSTRACT

In 2010, the United States generated over 31 million tons of plastic waste, and from that total, only 8% was recycled. With demand for lower cost plastics and public attention to environmental concerns increasing, the expanding recycling industry has provided an opportunity to lower raw material costs and create sustainable jobs. Traditionally, manual or optical methods that used infrared technologies were utilized to sort plastic wastes for recycling. Once these plastic wastes were sorted, they were cleaned, shredded, and melted into raw materials. These methods are costly and can experience high nonconformance rates during the sortation processes. This paper discussed an emerging technique that utilizes a novel process that sorts shredded plastic particles by using electromagnetic (EM) waves and Ferro fluids. The process involves placing various types of shredded plastic particles of into a tank filled with Ferro fluid. The plastic particles and Ferro fluid are then subjected to an EM wave by the use of an EM coil. The EM wave alters the viscosity of the Ferro fluid and causes the shredded plastic particles to

rise and sink at different vertical levels within the Ferro fluid tank, based on their respective densities. This method allows for an efficient, accurate, and low cost method to sort plastic particles as compared to conventional technologies. This paper provides a detailed analysis of this method in terms of the equipment requirements, installation costs, operation costs, and life cycle assessment (LCA). Overviews of the model development, experimental design, and test results are provided that demonstrates proof-of-concept. Finally, a cost, efficiency, and accuracy comparison of this method to conventional methods is provided. The results of the study indicated that the EM separation method offers significant cost, efficiency, and accuracy improvements over conventional methods. EM separation method may reduce operating costs by approximately 15-20% due to reduced equipment and labor expenses versus convention methods. Initial modeling and testing indicate that accuracy rates may be increased from the 80-90% of existing methods to nearly 100%.

INTRODUCTION

Since 1960, the US Gross Domestic Product has increased from $520.5 billion to $14.6 trillion in 2010 [1]. As the United States has grown more productive, and as more goods are consumed, more waste is generated. Of this waste stream, plastic refuse is problematic for society and has experienced low recycling rates. For example, the US generated 31 million tons of plastic waste in 2010 and of that total, only 8% was recycled [2]. With increasing demand for lower cost plastics and heightened public attention to environmental concerns, the expanding recycling industry has provided an opportunity to lower raw material costs and create sustainable jobs. A cost benefit analysis of the existing plastic sortation and recycling methods is necessary to better understand and promote the increased recycling of these materials. The process of turning plastic waste into reusable material at an industrial rate has pushed recycling into the 21st century. Technological advances in the recycling field have increased the efficiency and productivity of sortation processes. By using a standardized approach, the various methods of plastic recycling technology can be quantified and compared.

Recycling rates have expanded 28% in the past 20 years (National Association for PET Container Resources, 2010). With demand for lower cost plastics increasing, and increased environmental concerns, recycling has not only become a necessity, but a profitable business. In just 2 years, recycling rates of plastics have increased by 8% alone (National Association for PET Container Resources, 2010). This is expected to be greatly influenced by the US’s Recycling Works Program which establishes a 75% solid municipal waste recycling goal for 2015 (Recycling Works Program, 2012). It also dictates that 30% of all waste in the United States will be recycled, both by the manufactures and the consumers. This sets the precedent for major growth in the recycling industry in the next several years. Along with possible subsidies from the federal government, the program is expected to generate 1.5 million new jobs in both recycling and post-manufacturing waste recovery (Recycling Works Program, 2012). The government involvement has amazing potential for

a complete redesign of the recycling market in the United States. The problem with the situation is that modern technologies are rarely used in current waste processing because the machines require large amounts of initial capital. If federal/state government subsidized capital for these operations, what technologies would they use? And how would they know that those technologies are superior to current methods?

In order to correctly analyze the current and possible future technologies presented, a control medium needed to be set. Plastic waste was chosen as a standard as its frequently recycled and very common to nearly every locality in the U.S. this makes it an ideal control variable to be used in proposed recycling plants funded by the Federal government. Landfill disposal of plastics has significantly increased (EPA,2012) and the ease of acquiring usable waste for large scale operations is a desirable feature of using plastic.

Process of the Experiment

Stage 1

The goal of this experiment is to determine the relationship between the material properties of Ferro fluid in reaction to an Electromagnetic pulse. Ideally a universal co-efficient can be found that correctly determine the wave propagation in the Ferro fluid in relation to the particle length.

Stage 2

The purpose of this stage is to produce a scale model of the machine in order to look at the processing accuracy and the overall viability of the system for an industrial basis. After completing testing, a cost-analysis of the assembly will be conducted for the purpose of implementing stage 3

Stage 3

During this stage, the construction of a full-scale model begins. It will be used for the actual industrial feasibility. After construction, the efficiency’s and costs will be compared to other market competitors.

The is a high probability that modeling can be of use to predict profitability over a time scale.

The Analysis of the Testing

During the analysis of the Experiment, two forms of testing will be used. The first stage will use theoretical math and physics to determine the mathematical relationship between the Electromagnetic Pulse and the Ferro Fluid. This relationship will further be confirmed with experimentation. Specifically, this experiment will generalize relationships and idealize the proof of concept. Whereas the analysis of the second and or third stage will be conducted largely on efficiency and cost principles.

METHODS AND MATERIALS

The idea of grinding whole plastic containers into particles prior to sorting allowed the our team to focus on developing a concept that was solely based on sorting particles (rather than both particles and containers) in such a way that was scalable.

A Ferro fluid is a fluid in which fine particles of iron, magnetite or cobalt are suspended, typically in oil, and can be manipulated with magnetic fields. The typical size of the suspended iron particles are in the nanometer range, but for this application a micrometer range will be used as larger particles tend to respond better to a magnetic field. When the fluid is subjected to an electromagnetic wave, the iron particles align and the viscosity changes.Ferro Fluid

Ferro fluid is liquid that can be manipulated with magnetic fields. For this experiment, it will act as the fluid displaying variable Viscosity’s. Ferro fluids are colloidal liquids composed of suspended ferromagnetic particles in a carrier liquid. Typically the carrier liquids are oils, water, acids, or organic solvents. In this suspension, the addition of a surfactant prevents the ferric particle from binding to each other. This results in the autonomous flow properties of the Ferro fluid when not exposed to the Magnetic Field. Yet, as a Magnetic Field is introduced into the system, the Ferro fluid will align and form temporary domains in the system. These temporary domains alter the viscosity of the Ferro fluid. Although the Ferro fluid is magnetically active

while being exposed to EM Fields, it will immediately lose those properties after the field is removed. This material feature is called colloidal liquidity, and from this characteristic the entire experiment is possible. Because Ferro fluids can change material properties when exposed to electromagnetic pulses, this allows for near complete control of the material.

Figure 1: Separation example

This is caused by the relatively small particle size of the ferromagnetic particle in the Ferro fluid. For this experiment, we examined Ferro fluid with a particle size in the range of multiple micrometers' diameter, while though technicality it is a Magnetorheological fluid. A Ferro fluid typically in in the nanometer range for diameter. It known that the larger particles respond with better results to Magnetic fields. For this experiment we will refer the liquid as a Ferro fluid.

Electromagnetic core

In order to ascertain whether Ferro fluid has any sort of measurable response to magnetic waves it is necessary to devise a method to reliably generate a magnetic field. In deciding what equipment to use to make this generation possible, a set of design criterion was laid out. These design qualifications included the ability to vary performance characteristics, the existence of experimentally tested mathematics, as well as a set of feasibility checks which included cost, manufacturability, and speed of delivery.

Upon investigation it was decided that a small, iron cored electromagnet was the best fit for our aforementioned needs. An iron core electromagnet is easily customized through changes in radius,

length and number of turns, has a well-developed set of equations for various design types and can be manufactured in house (in the MIME shop) quickly and inexpensively.

Material Properties of Box

The type of plastic chosen to contain the Ferro fluid was antistatic acrylic. It was chosen for its ability to highly resist the building of static charge. If the box was not antistatic then the acrylic would absorb charge. This charge could potentially become large enough to create voltage that could be hazardous to both equipment and/or people. If the box were to build charge on the surface then the EM waves and the Ferro fluid could be effected. Careful control of the EM waves is imperative in controlling and understanding how the Ferro fluid reacts in the given field. Also, some of the data acquisition will be done digitally; this plastic should reduce the chance of a stored charge causing a voltage change, altering the data.

This particular acrylic was also chosen because of its inherent resistance to deflection that could have been caused by a net change of pressure in the box. The acrylic is ideal for use in a pressure vessel. When this experiment was being designed, it was not yet determined whether or not a net pressure would occur, therefore causing the overall density of the Ferro fluid to fluctuate based on the relative pressure change.

After designing and building the pressure vessel, we conducted a static pressure test to determine the pressure seal of the box. Here below we plotted our results for a pressure loss resulting from the largest theoretical pressure possible based on the design of the vessel. This loss is roughly 1 psi loss over 6 minutes, or .06 psi per second. For a typical test that occurs in less than 20 seconds, and has a pressure change of less than one psi, we determined this pressure vessel is sufficiently well sealed, and deem it an acceptable standard for testing.

Graph 1: pressure loss of sealed vessel

Material Properties of Ferro Fluid

The most critical property of the Ferro fluid to be useful in plastic separation is its specific gravity. In order to control which plastic will rise to the top of the solution, the density of the fluid must be altered to values that lie between the specific gravities of differing plastics. Table 1 below shows the different types of recycled plastics and their corresponding specific gravity values.

Plastic Type

Specific Gravity (g/cm^3)

Polyolefin Polypropylene .916-.925Low-density Polyethylene .936-.955High-density Polyethylene

.956-.980

Non-olefins Bulk Polystyrene 1.050-1.220Polyvinyl Chloride 1.304-1.336Polyethylene Terephthalate

1.330-1.400

Table 1. Specific Gravity of Various Plastics

According to the MSDS sheet for the Ferro fluid, there is density range of .92-1.47 g/cc with a specific product density of 1.21 g/cc at 25 degrees Celsius. The actual density of the Ferro fluid will be confirmed experimentally using the following equation where P is the density, M is mass, and V is volume:

Using an precise digital scale and an accurate graduated cylinder, the density can effectively be calculated. For this experiment, the specific gravity

of the sample Ferro fluid was 1.15g/cc at 25 degree Celsius.

In order for any given plastic to float in the solution, the specific gravity of the Ferro fluid must be greater than that of the plastic. Based on this assumption, it was concluded that an 11% change in specific gravity is necessary in order to produce the desired effect of separating plastic waste.

Pressure Data Acquisition

Change in density of the Ferro fluid cannot be measured directly. Upon initial research, we decided to use the ideal gas law to prove that there is indeed a density change by logging a pressure change. The two variables are related by the following function:

P/ρ=RT

Assuming that the temperature is constant along with R, density will change inversely with pressure. Since the system will be closed and the box is rigid, the volume will not change by any significant amount. It is hypothesized that the excitation of the Ferro fluid by EM waves will cause the density of the fluid to increase. This will decrease the volume of the fluid causing a vacuum to be created in the air. Therefore, the team had to design a data acquisition system that would account for this negative pressure change in the air.

Two methods were proposed to measure the vacuum effect. One was the use a mechanical vacuum gauge, while the other was the idea to use a digital manometer. The mechanical vacuum gauge seemed like the likely solution because the effects from EM waves on a digital system were unknown. The team was afraid that the magnetic flux would induct a current and skew the data. However, all of the vacuum gauges that the team found used mercury to detect and scale the pressure change. Mercury is slightly magnetic and could skew the data by a large percentage since the anticipated pressure change is so small. Research done prior to the project being handed off to the team found that in the closed system contained with the aforementioned box the pressure change should be very minimal (around 1psi). The final solution

was to use a digital manometer offset from the system, making the effect from the EM waves negligible. The digital manometer is also far more accurate than the mechanical vacuum gauge.

Furthermore, a pressure transducer was placed into the Ferro fluid to examine the change in specific gravity in real time. This pressure transducer was selected on the basis of the following characteristics. Firstly, it is waterproof and highly resistant to acidic decay, as some Ferro fluids are slightly acidic. Secondly, this pressure transducer is also bidirectional; this allows a dynamic response to the Ferro fluid to be ascertained when it exposed to an Electromagnetic pulse. Thirdly, this device produces a varying signal based on voltage, not current. Combined with a calibrated data acquisition system, a detailed pressure change could be pictured accurately.

Thermal Data Acquisition

The team plans on using thermocouples to show that there will not be a significant change in temperature as the Ferro fluid is excited by an EM wave. If this is proven using experimental data taken from each thermocouple, then the method described above can be used to measure the pressure change of the system.

However, if there is a significant change in temperature, then a different method relating change in pressure and change in temperature must be used. As stated above, one of the assumptions that the team is making is that volume of the box will not change significantly. In this case Gay-Lussac’s law can be applied using the following function to derive a change in pressure:

State 1 corresponds to the system at rest before the Ferro fluid is excited by the EM coil and state 2 is real time data collected as an experiment is conducted. Pressure at state 1 will be measured without the influence of EM waves, resulting in much more accurate data. The offset digital manometer will accurately measure the pressure of the air, but there also needed to be a way to measure the initial pressure of the fluid. The team has decided to use a very accurate pressure

transducer to find this value. Change in pressure of the air will prove the concept of density change but accurate measurements of the pressure of the fluid will allow the team to quantify the change in density values. Temperature of state 1 will be measured very shortly after the EM coil is turned on so that there is a presence of a magnetic field. This may cause the data to be inaccurate. However, the goal in comparing the temperature at state 1 with a given temperature found in a predetermined state 2 is to find a ratio of the two. By subjecting both measurements to the same magnetic field, the expectation is that the error at both state 1 and 2 will be negligible, resulting in an accurate ratio that can then be plugged into the above equation to solve for pressure at state 2.

In order to account for the possible error caused by EM waves on the digital measurement system a separate experiment was designed to show the relation between the actual temperature of the system and the measured value from the thermocouples. This is imperative to determine because the effect on the measurement system from the magnetic field coupled with the Ferro fluid is unknown. Temperature will be measured right before EM waves are emitted and again right after. The system will then be heated up and the test will be conducted again until a sufficient number of data points have been collected. Then the actual temperature of the system can be plotted vs. the digital readout corresponding to the given temperature to find the relationship between the two. Using this relationship, the digital readout can be interpolated back to find the actual temperature. Having an accurate temperature will result in a more accurate derivation of the density at each state.

Magnetic Field Sensor

For this experiment two magnetic field sensors we determined to be needed in order to quantify the strength of the field propagated throughout the system. The effect on the digital measurement system is unknown so some sort of calibration is necessary. One sensor will be placed just under the coil and the other will be placed directly opposite on the other side of the box. Before testing occurred, a series of tested were conducted to find a

relationship between the magnetic field strength and the amount in which the digital measurement systems are affected in order to increase accuracy.

For this experiment we chose to use Pasport magnetic sensors. These sensors are pre-calibrated and consist of a sensor in a housing that allows for easy use and high quality data. Additionally, this system also allows multiple sensors to allow for greater data stream to confirm static conditions.as well as a comparison for calibration of instrumentation in the NI system.

Software

In this experiment, two type of software were to be used. The software for stage one will be Labview, the accompanying software with the National instruments Data acquisition system. In our experiment a Series X DAQ box was used. The data acquisition system is USB based and allows for a relative simple and inexpensive setup yet produces a high quality of accuracy. This system was also chosen on because of it closed metal frame/chassis that allows for radiant electromagnetic energy to be dissipated safely through a ground. The DAQ was used to collect data, and analyze it for material qualities.

Channel Basis Device Range Calibration

A1 Pressure Transducer 0-500spi Purchased

A2 Thermo K type TC -200&1350 F

Icebath/Boiling

A3 Thermo K type TC -200&1350 F

Icebath/Boiling

A4 Thermo K type TC -200&1350 F

Icebath/Boiling

Table 2: Thermocouple channels

Calibration of the system was conducted within 24 hours of experimentation in order to lower the likelihood of a calibration error. For the pressure transducer, the manufacturer had pre-calibrated the device. We also confirmed this basis by testing at 1 Atm. additionally; we seconded the calibration by using a different device, a Pasport Absolute pressure gauge. Both of these methods yielded near exact calibration for testing the pressure. Calibration for each k type thermocouple was achieved by recording variation from temperatures

ranging from 33! (IceBath) To 214! (Boiling water). The handheld thermometer and an infrared optical temperature measurement device seconded these results.

The second software will be ANSY Maxwell. This program will be used to model the 3D wave propagation of the electromagnetic pulse. The modeling of this experiment will likely occur in stage 2 in order to better determine the exact physic present in the exposed Ferro fluid.

Testing Method

This experiment was conducted in three major parts.

1. Ambient to EM exposure

2. EM exposure to Ambient

3. Static EM exposure

For each section we tested three voltages, and from these tests we would obtain our data samples. In the first part, an EM pulse was added in order to observe the change in Ferro fluid. Secondly, the EM pulse was removed halfway through sampling to observe the change in the density. For the third part of the experiment, we looked at the system with the ambient conditions. We also looked at a static test to confirm the test data accuracy.

DATA

Graph 2: Ambient to EM exposure, 5 Volts

Graph 3: Ambient to EM exposure, 10 Volts

Graph 4: Ambient to EM exposure, 15 Volts

Graph 5: EM exposure to Ambient, 5 Volts

Graph 6: EM exposure to Ambient, 10 Volts

Graph 6: EM exposure to Ambient, 15 Volts

Graph 7: tempurature Readings Ambient to EM exposure

Graph 8: temperture Readings EM exposure to Ambient

Magnetic Gauss Readings

For this section we chose a 10V data sample. In this sample you can see the variation in Gauss output from one side of the electromagnet to the other side

of the pressure vessel near the pressure transducer. As you can see, there is typically minimal Gauss field near the pressure transducer. This data was selected on the basis that it best represents what happened in a average test.

Graph 9: Gauss Dispersion throughout the Box

Manometer readings

During the Calibration and testing it was determined that the Net air pressure of the pressure vessel did not change. This was originally discovered by ambient readings of the manometer, while testing there appeared to be no net change in pressure. This was confirmed using a highly accurate Absolute pressure measurement device.

CONCLUSIONSAfter conducting this experiment it we believe that it is in fact possible to manipulate the internal pressures of Ferro fluid using a predetermined electromagnetic pulse. After applying a low pass filter we were able to determine the resulting net change of pressure and specific gravity.

As you can see above, when exposed to the pulse, the Ferro fluid completely reorders and causes a decrease of specific gravity. When this phenomena first appeared we assumed it to be an error in either our program or in lab setup. But after doing some research, we believe this to be a natural quality of colloidal liquids. Therefore we have concluded and proved that Ferro fluid’s specific gravity can rapidly

be changed via a magnetic pulse, while still preserving the temperature of the Ferro fluid.

Possible sources of error

This particular experiment presented some sources of error. Firstly, human error was a possible creation of error. This is largely in part to the number of different people that helped conduct the experiment. Secondly, it is possible that error appeared from our computer/DAQ system. Although these systems are highly accurate, we did not have a National Instruments Expert on hand to oversee data acquisition.

Lastly there is the possibility of the magnetic pulse affecting the measurement devices and disrupting the voltage signal. After concluding this experiment, static tests were taken to help determine whether electromagnetic waves corrupted signals. In the electromagnetic coil thermocouple, a major disruption was observed. We concluded that its extremely close proximity to the EM pulse certainly led to its corruption. This was corrected by taking the temperature before/after the coil was active. As for the other two thermocouples, very little disruption was observable, both in dynamic and static tests. Finally, after conducting static tests we were able to determine a slight level of electromagnetic disruption in the pressure transducer. This has been quantified and has been used to confirm actual pressure changes.

Te s t Ty p e V o lts P Em ( p si ) P A m ( p si ) ρ A m ( g/cm ^3) ρ Em ( g/cm ^3) De lta ρ (g/ cm ^3) % C h an geStati c 5.4 V 14.66513 14.75494 1.157 1.149957601 0.007042399 0.608677501Stati c 10.3 V 14.52481 14.76228 1.157 1.138388187 0.018611813 1.608626852Stati c 14.4 V 14.52491 14.78893 1.157 1.136344608 0.020655392 1.785254241

Dy n am ic 5.4 V 14.02982 14.35228 1.157 1.131005005 0.018952596 1.638080923Dy n am ic 10.3 V 13.77698 14.39044 1.157 1.107676931 0.030711256 2.654386884Dy n am ic 14.4 V 13.73137 14.40381 1.157 1.102985341 0.033359267 2.883255596

Table 3: % Change in Density

Further Research

From this experiment, we will progress onto stage two of this experiment. We deem this proof of concept to be valid. In the future we hope to re-examine the core design and the frequency of the voltage to maximize and refine the magnetic pulse

to produce an accurate change in the specific gravity of the Ferro Fluid.

APPENDIX A

Single Layer Iron Cored Solenoid Magnetic Flux Density Calculation

Figure 2: Solenoid coil design

Where:

Using these:

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