Report of Plastic Recycling Technology

Sophea BOEUT

Mining and Mineral Processing Engineer

Institute of Technology of Cambodia

Chulalongkorn University

Hokkaido University

2014

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Table of Contents

List of Figure................................................................................................................................................. ii

List of Table .................................................................................................................................................. ii

Previous research .............................................................................................................................. 1

I. Introduction .............................................................................................................................. 2

II. Types of Plastic and the Application ............................................................................ 2

III. Life Cycle of Plastics—Water Bottle ......................................................................... 4

IV. Plastics Recycling ................................................................................................................. 6

IV.1 Recycling Process .............................................................................................................. 7

IV.2 Plastic recycling techniques .................................................................................... 9

a). Process Separation of ABS, PS and PP ......................................................................... 9

b). Separation PVC from PET/PVC Mixture .................................................................... 12

IV.3 Plastic recycling and saving term ...................................................................... 13

V. Conclusion ................................................................................................................................. 14

REFERENCES ............................................................................................................................................. 15

APPENDIX ................................................................................................................................................. 17

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List of Figure

Figure 1-Different types of plastics with different needs .............................................................................. 4

Figure 2-Life Cycle of Plastic Process .......................................................................................................... 5

Figure 3-Plastic Recycling Plant (www.biophysics.sbg.ac, 2014) ............................................................... 8

Figure 4-Extruder (www.biophysics.sbg.ac, 2014) ...................................................................................... 9

Figure 5-Flowchart of each stage in separation processes .......................................................................... 10

Figure 6-(a) Flotation process of PVC from PET; (b) Simplified mechanism for separation of PET and

PVC. ............................................................................................................................................. 12

List of Table

Table 1-Plastic types ..................................................................................................................................... 3

Table 2-Properties of main types of plastics ............................................................................................... 11

Table 3-Result of flotation separation PVC from PET (Somsak, 2014) ..................................................... 13

Table 4-Comparison the energy use and resources price of virgin and recycled materials ........................ 14

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I. Introduction

Plastic is the general common term for a wide range of synthetic or semi-synthetic

materials used in a huge, and growing, range of applications, (plasticseurope.org). It is making

the lives changing and more convenient: cleaner, easier, safer and more enjoyable. Plastics are

widely use in packing, building and construction, electrical and electronic, automobile and other

use of it. Anyway, the most common plastic materials encountered are those for packaging and

wrapping. The demand of plastic is increase every year according to the worldwide average

growth rate 5-6% (Somsak, 2014). Plastic-The Fact, has researched the amount of plastic

production every year; and the data researched from 2009 until 2012 have been shown. 45

million tonnes of plastics had been produced in 2009, 46.4 million tonnes in 2010, 47 million

tonnes in 2011 and in 2012, the amount of plastics production increase dramatically to 241

million tonnes. It was the huge incensement. Then one estimation about Global consumption of

plastics will be increase to 297.5 million tonnes in 2015, (Global Industry Analysts, Inc., 2014)

and from one article The Next Century of a conference topic Plastic Industry Forecasts and

Trends, announced that the amount of plastic will be 400 million tonnes in 2020, (Paddos,

1999). The average production since 2009 to 2012 resulting that 39.475% of total plastic is for

packing, 20.45% for building and construction, other 5.525% is for electrical and electronic

while the rest 26.8% for the other consumption. China is the leading producer of plastics with

23.9%, and the rest of Asia is Japan about 20.7%, European production accounts for 20.4% of

the world’s total production, (Plastic-The Fact 2013).

II. Types of Plastic and the Application

Plastic can be found both in nature and synthetic, however, the common plastic use

nowadays are from synthetic, the man-made, in which the source are from crude oil, coal and

natural gas. There are several types of plastics. In an attempt to bring order to plastics

classification for recycling purposes, the Society of the Plastics Industry (SPI) devised some

voluntary codes in 1988. Table 1 below shows the difference types of plastics and some

information about them. According to Plastic-The Facts, 2013, the amount of plastic types are

not the same based on the market need of each type of plastic. In 2012, there were 6.5% of PET,

12% of HDPE, 10.7% were PVC, 17.5% were PELD, 18.8% PP, 7.4% were PS, and the rest

27% were for the other products as shown in details in Figure 1 below

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Table 1-Plastic types

Plastic

ID code

Name Color Density

(g/ml) Application Recycled product

PET-

Polyethylene

Terphthalate

Green

1.35

Fizzy drink bottles, frozen meal

packages, water bottle, bear bottle,

mouthwash bottle.

Fiberfill in coats, Carpet,

Camera film, Lumber

HDPE-

High-Density

Polyethelene

Red

1.00-0.93

Milk, washing-up liquid bottles,

detergent bottles, oil bottles, toys,

plastic bags.

Trash cans, Floor tile,

Flower pots, Garden

furniture

PVC-

Polyvinyl

Chloride

---

1.40

Food trays, cling film, bottles for

squash, mineral water, shampoo,

vegetable oil bottles, blister

packaging.

Floor mats, Flexible

hoses, Playground

equipment

LDPE

Low-Density

Polyethylene

White

Bead

0.93-0.86

Carrier bags, bin liners, bread bags,

clothing, carpet, furniture, garment

bags, shrink-wrap.

Floor tile, Furniture,

Garbage can liners

PP-

Polypropylene

Purple

0.90

Microwaveable meal trays.

Videocassette cases,

Lawn mower wheels,

battery cable, Landscape

boarders

PS-

Polystyrene

Translu-

cent

white

1.05

Yoghurt pots, foam meat or fish

trays, hamburger boxes, egg

cartons, vending cups, plastic

cutlery, protective packaging for

electronic goods and toys.

Flower pots, Trash cans,

Thermometers, Rulers

Others

---

--- The plastics that don’t fall into any

of above categories, such as

Melamine,

---

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Figure1. Different types of plastics with different needs

III. Life Cycle of Plastics—Water Bottle

For life cycle of plastics contain many stages since extraction, production process until

end of use of plastics. In this case, the plastic bottles are details description. The vast majority of

bottles are manufactured from petroleum, some of which comes from deposits as much as three

billion years old. Some manufacturers use bioplastics made from plant materials to create their

bottles, out of concern for the environment.

In the case of a bottle made from petroleum, the oil must be extracted before being

shipped to a processing facility and then distilled to separate out the various hydrocarbons it

contains. When oil has been extracted, it is typically moved into container tankers for shipping to

refinery facilities. At a refinery, the oil can be submitted to a variety of distillation processes,

such as fractional distillation, where the crude oil is heated, causing its various components to

separate so that the refinery can make gas, fuel oil, plastics, and a variety of other products. The

plastic is made by mixing hydrocarbons extracted from crude oil with chemical catalysts,

triggering polymerization.

Next, manufacturers produce plastic pellets, which are melted down into preforms, which

look like small test tubes; the preforms, in turn, can be heated, causing them to expand and turn

into conventional water bottles. The ready uses bottles are typically bottling companies order

preforms, expanding the water bottles at their own facilities as needed. The bottles are transfer to

use in different types of needs and different places according to the market needs. The bottles

Figure 1-Different types of plastics with different needs

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must be sterilized so that they are safe for beverages, and then they are filled, capped, labeled,

packed into cases, and prepared for shipping. At this stage in the life cycle, the bottle could end

up in any number of places, from a relief camp for refugees to the shelf at a high-end

supermarket. Once a PET plastic bottle ends up in the hands of an end-consumer, it has three

possible fates after its contents have been consumed: it may be reused, recycled, or thrown

away as the discarded. The Fact 2013 has shown the data of plastics waste in Europe in 2012

that there were 26.3% of plastics has been recycled, 35.6% for energy recovery and 38.1% as

landfill disposal. The same as the website of wisegeek.org that there are 15-35% of plastics make

their way into recycling facilities depending on the region. The Figure 2 is showing clearly about

Life Cycle of plastics.

Figure 2-Life Cycle of Plastic Process

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The recycle should be after bottles are used many times. However, when plastics enter a

landfill, it can take hundreds of years to decay, and it can have a profound environmental impact.

The route to the landfill is often so long, as bottles are the common form of litter around the

world, requiring volunteers or government agencies to collect such bottles and bring them to a

facility for recycling or other forms of disposal. As plastic bottles decay, they take up precious

landfill space, and some leach harmful chemicals into the ground, potentially polluting the soil

and water.

IV. Plastics Recycling

The plastic can be reused or recycled many times. The recycling process can be

considered as the environmental friendly and energy saving and more sustainable comparing to

extraction the virgin resources to produce. To help identify the different plastics, a Plastics

identification Code is stamped on the final product to indicate what type of resin it contains as

shown clearly in Table 1. Some types of plastics can be recycled while some cannot recycle. The

recycle of plastic can be stage from the easiest to the most difficult ones.

Easy Plastic to Recycle

- Number 1-PET, Polyethylene Terephthalate: The easiest and most common plastics

to recycle. For example soda and water bottles, medicine containers and many other

common consumer products containers. The product recycled becomes fiberfill for

winter coats, sleeping bags and life jackets.

- Number 2- HDPE, High-density Polyethylene: These include heavier containers that

hold laundry detergents and bleaches as well as milk, shampoo and motor oil. This

kind of plastic can recycle into toys, piping, plastic lumber and rope. Number 1 and 2

are widely accepted at recycling center.

Plastic less Commonly Recycled

- Number 3-PVC, Polyvinyl Chloride: commonly used in plastic pipes, shower

curtains, medical tubing, vinyl dashboards, and even some baby bottle nipples, gets

number 3.

- Numbers 4-LDPE, Low-Density Polyethylene: such as wrapping films, grocery and

sandwich bags, and other containers made of low-density polyethylene.

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- Number 5-PP, Polypropylene: containers used in Tupperware, among other products,

few municipal recycling centers will accept it due to its very low rate of recyclability.

Useful Plastic to recycle

- Number 6 goes on polystyrene (Styrofoam) items such as coffee cups, disposable

cutlery, meat trays, packing “peanuts” and insulation. It is widely accepted because it

can be reprocessed into many items, including cassette tapes and rigid foam

insulation.

Hardest Plastics to Recycle

- Last, but far from least, are items crafted from various combinations of the

aforementioned plastics or from unique plastic formulations not commonly used.

Usually imprinted with a number 7 or nothing at all, these plastics are the most

difficult to recycle and, as such, are seldom collected or recycled. More ambitious

consumers can feel free to return such items to the product manufacturers to avoid

contributing to the local waste stream, and instead put the burden on the makers to

recycle or dispose of the items properly.

IV.1 Recycling Process

There are several steps in recycling process:

- Selection/Collection: The recyclers or preprocessors have to select the waste or scrap

which are suitable for recycling or reprocessing. . The collection area should be in the

cities, crowded towns and other available regions. Once the (dominating) packaging

industry has completed the shift towards biodegradable and recyclable materials, only

then it is feasible to provide every major block with a recycle bin for plastic

collection.

- Separation: The plastics mostly mix together with different types of plastic and

sometimes with the other household waste such as plastic, cans, organic materials, so

that why the separation process must be involved to separate them into independently.

- Processing of reusable plastics: The reusable and more homogenous material is

finally packed and piled before being forwarded to appropriate processing plants. The

production line involves shredding the plastics into tiny pellets and automatically

separated by its colour. The two essential prerequisites for high-quality recycling or

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plastics are — 1). The material has to be sorted properly and 2). It has to be free of

contaminants. Figure 3 is showing the processing plant of recycled plastic.

Figure 3-Plastic Recycling Plant (www.biophysics.sbg.ac, 2014)

First of all, plastics have been transported from different sources of waste, then plastics

are conveyed by conveyor belts feeding into first shredderwww.biophysics.sbg.ac, 2014, as the

course size, and continuously feed to cleaner sprinkler. The fine shredder is used to crush smaller

size of pellets. The types of plastic are then identified on the basic of a programmed pattern

match with emission lines in the optical spectrum. According to the slide-spectrometric results,

plastic materials are sorted, pulverized and cleaned if necessary. Finally, they are melted in an

extruder and processed into granulates or prefabricated compounds, which are then handle in

subsequent production steps (www.biophysics.sbg.ac, 2014). The melting system in extruder is

called thermal shear heat, the heat occurring between friction of the screw and channels. This

shear heat will melt the plastics and then melting plastics are forced to leave by plunger into cold

moulds as shown in Figure 4.

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Figure 4: Extruder (www.biophysics.sbg.ac, 2014)

- Processing of Non-Reusable Plastics components: Like scanned plastic materials

are not reusable. These kind of plastics are usually shredded then discard into landfill

or other approved dumping site.

IV.2 Plastic recycling techniques

Recently, because of the plastic recycling activities are more interesting, the development

of different separation methods is notable. The separation process is done to separate different

plastic from each other with high purity, for example PVC from PET, ABS, PS and PP, etc.;

sometimes, it helps to separate those plastic from other waste such as aluminum cans, paper, iron

materials and other organic materials. Several methods like flotation and sink-float separation

technique, electrostatic separation, a dry separation technique that utilizes the electrical charging

of particles, has been mainly developed for the mineral beneficiation (Gjergj Dodbiba et al.,

2003).

a). Process Separation of ABS, PS and PP

The process of separation is contain few big separation processes as air tabling, triboelectric

separation as well as combination of sink-float separation and froth flotation can be of great help.

In order to effectively separate a plastic mixture, the separating method should be chosen after

carefully analyzing the composition and the properties of the plastics to be separated. (Gjergj

Dodbiba, et al., 2006).

Figure 4-Extruder (www.biophysics.sbg.ac, 2014)

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The raw materials were the mixture of the plastic types for 50%/50% of PVC/PP,

ABS/PS and PET/PE. The size shape of raw materials was the output from shredder with the

irregular shape varying from 2.38 – 3.36 mm. Figure 5 shows clearly about the flowchart of

separation process of ABS, PS and PP.

Figure 5-Flowchart of each stage in separation processes

The initial process started from air Table by removing the PVC from mixed PVC/PP. The

process aimed to separate the high-density particle from low-density ones. The high density is

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settled on the bed while the low one is float on the top of bed. PVC’s density is μ=1.4 g/ml and

PP’s density is 0.9 g/ml which is lower than water’s density. The velocity of airflow was 1.6 m/s;

vibrating frequency of deck, f = 11.95/s; end slope α=4.4°; side slope β=2.5°, height of riffles,

h1= 7 mm, (Appendix A). The percent recovery was 97.1% and grade was 99.3% of PP and

PVC’s recovery was 99.5% and 99.3% of grade.

The second steps was to separate ABS (Acrylonitrile—butadiene—styrene) from mixture

of ABS/PS by using Triboelectric cyclone separator. The main supplier is DC power. A basis for

the triboelectric separation of a binary mixture can be created if constituents of the mixture

acquire charges of opposite polarities. The measure of polarity is the triboelectric series in Table

2 which arranges between ABS and PS. At the end, ABS flakes were charge positively, whereas

the PS flakes were charges negatively and collected in the opposite side bins next to the positive

electrode, (Appendix B). PS was collected from b1 and b2 (negative charge collected) while b4

and b5 were ABS (positive charge collected). The percent recovery was 100% and 74%

respectively.

Table 2-Properties of main types of plastics

Polymer type Density

(kg/m3)

Contact angle with

water (°)

Triboelectrostatic

series

Acrylonitrile−butadiene−styrene, ABS 1060 87.3 End positive (+)

End negative (-)

Polyethylene terephthalate, PET 1350 76.5

Polystyrene, PS 1050 86.3

Polyethylene, PE 960 96.8

Polypropylene, PP 900 95.0

Polyvinyl chloride, PVC 140 86.4

Finally, the separation of PET from mixing PET/PE was done by Combination of Sink-

Float Separation and Froth Flotation. PET is a useful plastic that can easily be reused as raw

material to produce other PET products. PE’s density is 0.96 g/ml which is lower than water

(1g/ml) that makes PE float in water. However, the reagent DAA, Dodecylamine acetate, was

used with the concentration of 0.02kg/m3, in order increase the floatability of PE by rendering it

hydrophilic. The result was shown that the thin-flat PET did attach to the air bubbles, developing

their floatability, (APPENDIX C). PET’s density is higher than water’s (1.35 g/ml and water is 1

g/ml); that the nature of hydrophobic state and sink in water. The experimental result was seen

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the grade and the recovery rate of PET decrease with increasing capacity of the device. The

grade of PET was 99.7% and recovery was 90.3%.

The conclusion of these separation techniques could be concluded on the acceptable

methods in separation PVC, ABS and PET from mixture of PVC/PP, ABS/PS and PET/PE. The

results from each stage showed the good efficiency of grades and recovery.

b). Separation PVC from PET/PVC Mixture

The mixture of PVC and PET flakes were shredded into the size shape 5x5 and thickness of 0.3

mm by a cutter of plastic. Three mixtures were represented, 75:25, 50:50 and 25:75 of PVC/PET,

representative different colors, red for PVC and green for PET. The environment was base with

the pH in between 11-12 at temperature 60 °C. Different densities are 1.24 g/ml and 1.33 g/ml of

PVC and PET. NaOH was used to wash the organic contamination in 20 minutes. The reagent

was Calcium Lignosulfonate (commercial grade CaLS) as wetting agent, then pipe oil as the

frother (Terpineol, commercial grade). Adjusting pH by NaOH solution and tap water was really

used throughout the experiment. Figure 6 illustrates the process of experiment and how it works

in the reality.

(a) (b)

Figure 6-(a) Flotation process of PVC from PET; (b) Simplified mechanism for

separation of PET and PVC.

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The experiment was done in different kinds of condition like 75:25, 50:50, and 25:75 of PET and

PVC; anyways, the aim was to explore the best result. After the experiment process, the each

result was not purity a hundred percent, however, the rougher float/cleaning were be able

involving in order to reach the completed flotation stage between these two types of plastics. The

detail result is shown in Table 3 below. Flotation method is efficiency in separation PVC from

PET effectively. It is usable technique for plastics waste separation.

Table 3-Result of flotation separation PVC from PET (Somsak, 2014)

Ratio of PET/PVC

%weight PET

CaLS (mg/l)

Recovery

PVC PET

75:25 74 7.5 100 100 (after 4th of Rougher)

50:50 48 7.5 100 100 (after 2th of Rougher)

25:75 24 7.5 100 100 (after 3th of Rougher)

IV.3 Plastic recycling and saving term

Recycling plastic is making the balance of environmental, energy, economic and

disparities saving. Fossil fuels such as natural gas (methane gases)/non-renewable resources, oil

and coal are used in production process of plastic, emitting dangerous greenhouse gases and

toxic chemicals. The methane is 20 times stronger than carbon dioxide and up to 4% of

emissions from landfill, (Plastic Recycling Fact Sheet, 2009). Most plastic is not biodegradable

and will be surviving in the environment for hundreds of years if it is discarded in landfill. Since

the raw materials of plastic are petroleum/natural gas and plastic consume 4% of the world’s oil

which is estimated of using 2 million barrels of oil every day (The ImpEE, 2005; Recycling Fact,

2012), while the world’s oil supplies are becoming depleted. As petroleum prices increase it is

becoming more financially viable to recycle polymers rather than produce them from raw

materials. The term of recycling plastic should be saving both virgin sources in using with other

purpose and energy saving; it takes only 10% as the average of the energy to recycle the plastics

as would be used in preparing the plastic from its raw materials, (Recycling Fact, 2012). Table 4

is illustrating the comparison between virgin sources and recycles plastic energy consumption.

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Table 4-Comparison the energy use and resources price of virgin and recycled materials

V. Conclusion

Plastic is widely used all around the world for everyday life, construction,

automobile, electronic and other things. Because it shows the modernity and more facility of life,

the demand of plastics is increased year by year. In the same time of that convention, the impact

from using plastic cause mainly to the greenhouse gases, global warming since the origin of

plastic is made from fossil fuel or non-renewable gases like methane gas; thus, the virgin sources

of plastic seems to be so limited that make the recycling and converting plastic waste to energy

are very interesting to the world nowadays. The recycling plastic is not only saving the

petrochemical sources but also saving the energy for production which is adaptable to the green

environment policy. The recycling technique are involving air separation, density, electrical,

sink-float and flotation method. According to the previous researches of these problems, the

recovery efficiency is high enough to use those techniques. Anyways, please think that:

Plastics are too valuable to through away!

Each piece of plastics waste is money!

Landfill plastic must be eliminated since it takes hundreds of years to discompose and

causes contamination to the surrounding communities.

Commodity plastic

Energy, virgin

materials (MJ/kg)

Price, virgin

materials ($/kg)

Energy, recycled

materials (MJ/kg)

Price, recycled

materials ($/kg)

HDPE 77-85 1.9-2.0 ≈35-45 0.84-0.97

PP 75-83 1.8-1.85 ≈35-45 0.99-1.1

PET 79-88 2.0-2.1 ≈60-64 1.1-1.2

PS 96-105 1.5-1.6 ≈40-50 0.75-0.86

PVC 63-70 1.4-1.5 ≈35-40 0.77-0.99

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REFERENCES

Dodbiba, G. Shibayama, A. Miyazaki, T. and Fujita, T. (2003), “Triboelectrostatic Separation of

ABS, PS and PP Plastic Mixture”, The Mining and Materials Processing Institute of

Japan, 44(1), 161-166.

Dodbiba, G. Shibayama, A. Miyazaki, T. and Fujita, T. (2006),”Sorting Techniques for Plastics

Recycling” The Chinese Journal of Process Engineering, 6(2), 186-191.

Jean-Pierre, H, (2004), “Waste Plastics Recycling A Good Practices Guide By And For Local & Regional

Authorities”.

Plastic Waste Management Institute, (2009), “An Introduction to Plastic Recycling”.

Plastic-The Fact, (2010), “An analysis of European latest plastics production, demand and waste

data”, report.

Plastic-The Fact, (2011), “An analysis of European latest plastics production, demand and waste

data”, report.

Plastic-The Fact, (2012), “An analysis of European latest plastics production, demand and waste

data”, report.

Plastic-The Fact, (2013), “An analysis of European latest plastics production, demand and waste

data”, report.

R. Gent, M. Menéndez, M. Toraño, J. and Torno, S. “Enhanced Plastics Recycling Cyclone

Media Separation”, University of Oviedo, Oviedo, Spain, (E-

mail:gentmalcolm@uniovi.es).

Saisinchai. S, (2014), “Separation of PVC from PET/PVC Mixture using flotation by Calcium

Lignosulfonate Depressant”, Engineering journal, 18, ISSN 0125-8281,

(http://www.engj.org/).

The ImpEE Project, (2005), “Recycling of Plastic”, University of Cambridge.

Websites:

Jose, S.(2012), “Global Plastics Consumption in 2015 report”, Global Industry Analysts, Inc.,

PRWeb,(http://www.prweb.com/releases/plastics_bioplastics/engineered_plastics/prweb9

194821.htm).

Plastic recycling, 2014, (online), (www.biophysics.sbg.ac.at/waste/plastic).

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Recycling facts, (2012), “Recycling, Energy Savings”, (http://www.facts-on-

recycling.com/recycling-energy-savings/)

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APPENDIX

A: Air Table B: Triboelectric cyclone separator

C: Sink-float and Flotation D: Media separation flow paths in conocylindrical

(A) Cylindrical, (B) type DMS cyclone