Recycling Waste Polyethylene Materials to Useful Products via Pyrolysis
CHAPTER ONE
OBJECTIVES OF STUDY
The objectives of this work are:-
- To collect the polyethylene waste materials (discarded water sachets and plastic bottles e.tc.).
- To carry out thermal pyrolysis of the materials at a temperature of 350oC – 400oC
- To analyze each residue for toxic metals
- To use ‘fresh’ and ‘spent’ FCC catalyst within the range of 350oC – 400oC
- To monitor the quantity of fuel gases and hydrocarbon liquids evolved.
CHAPTER TWO
LITERATURE REVIEW
Due to the upward usage of polymers and plastic materials, wastage generation of these products is daily and relatively in large volume. The plastic materials often are not resolvable with microorganisms and lead to environmental pollutions, so it is necessary to recycle these materials to useful products.
Frounchi, et al. (1997) studied the mechanical recycling of PET beverage bottle. They blended recycled PET with virgin PET to increase mechanical property of it. They found that mechanical blending can be used for recycling purposes without sacrificing of the virgin PET and to reduce material cost in bottle fabrication.
Navarro, et al. (2007) studied the influence of polyethylene cap of the bottle in the mechanical recycling of PET. They found that it is not necessary to totally separate polyethylene contents, because small percentages of PE may facilitate subsequent processing of the material using injection.
(Bertolini et al, 1987). The use of low-density polyethylene for packaging treated water is on the increase in Nigeria and other West African countries. Producers of treated water prefer it, as well as the consumers because it is relatively cheap compared with that of bottled water. Polyethylene films (commonly called pure water sachets in Nigeria) are therefore seen littering the cities, schools, stadium, wedding reception venues etc. During packaging of the water, lots of waste polyethylene is generated. The producers of water sachets often burn most of the waste sachets in a pit behind their companies. These polyethylene films are non-biodegradable and can remain on the ground for years.
According to (Kiran et al, 2000), several studies have been carried out in the past and previously on pyrolysis of polyethylene and plastics using batch reactors. Pyrolysis of waste polyethylene (PE) and polystyrene (PS) showed that waste PS yielded higher liquids while waste PE yielded higher gaseous product.
Font et. al (2003) studied the evolution of semi volatile compounds and toxic by products in the pyrolysis of polyethylene from 6000oC to 9000oC. Primary decomposition of the waste leads to the production of α,ω-olefin, α-olefin and n-paraffin. At high temperatures above 7000oC – 8000oC, poly-aromatic hydrocarbons were formed.
According to Mankodi, (1986.), chemical recycling of PET waste consists of depolymerization by hydrolysis, methanolysis, glycolysis and aminolysis to obtain various monomers.
Kurokawa, (2003) studied the methanolysis of PET in the presence of aluminium tiisoproxide catalyst to form monomers. They found that using a toluene/methanol mixed solvent (20 vol. % toluene) instead of pure methanol, lead to obtain maximum yield of monomers, 88% for DMT and 87% for EG.
Genta (2006) used supercritical methanol for PET depolymerization instead of vapor methanol. They found that the rate of PET depolymerization in super critical methanol is faster than that of PET depolymerization in vapor methanol.
Yang, et al.(2002) study effect of some parameter on methanolysis of PET waste in supercritical methanol. They found that both yield of DMT and degree of PET depolymerization were seriously influenced by the temperature, weight ratio of methanol to PET and reaction time, whilst the pressure has no considerable effect, when it is above critical point of methanol.
Shukla, et al. (2006) used glycolysis method for recycling waste PET into useful auxiliaries. The advantages of this method were that chemicals used during depolymerization of PET are inexpensive and comparatively less harmful to the environment. Aminolysis is another method of chemical recycling of PET waste, which has been little explored as compared to other technique.
WHAT IS PYROLYSIS?
The thermal decomposition of carbonaceous materials in the absence of oxygen, Where the system pressure is not constrained by the vapour pressure of water, this is refereed to hydrocharring.
Pyrolysis is also referring to as a thermal treatment process where waste is subjected to heating in an atmosphere with a deficiency of oxygen below the stoichiometric combustion level.
CHAPTER THREE
MATERIALS AND METHODS
Preamble
This chapter has to do with materials that was used and tests that was carried out in the laboratory.
Materials
The material to be used carried out the research will include
- Reactor model
- Pure water sachet low density polyethylene ( LDPE)
- Constant temperature bath
- Heating mantle
- Teflon gas sampling begs
PROCEDURES
COLLECTION AND PREPARATION OF MATERIALS
Waste Pure Water Sachet
The waste pure water sachet was obtained from hostel within University of Agriculture environment. The waste pure water sachet gathering was about 100kg bags.
After gathering waste pure water sachet up-to 100kg bags, it was wash with detergent and dried for two days after which it was cut into smaller particles before taking it to the laboratory for recycling into useful products.
Reactor Model
The reactor model was made of stainless steel tube of length of 18 liters and internal diameter of 480 mm, sealed at one end and an outlet tube at the other end for the collection of the evolved gases. The reactor was lagged effectively with a fire blanket and placed in a sand bath made of iron sheets and three mega burners were used to obtain temperatures of 3000C and more. The reaction temperature of the fabricated batch reactor was controlled and monitored using a thermocouple.
CHAPTER FOUR
Procedure for GC Analysis
Fixed setting: Generally the operator must adjust gas flows to the columns, the inlets, the detectors, the split ratio. In addition, the injector and detector temperature must be set. The detector are generally held at high end of the oven temperature range to minimize the risk of analyte precipitation. All of these parameter should been set to the correct values, but double check all the instrument: Buck 530 gas chromatography equipped with an on-column , automatic injector , flam ionization detector, HP 88 Capillary column (100m x 0.25µm film thickness,) CA,USA
Detector temperature A:250C
Injector temperature 220oc
Integrator chart speed: 2cm /min
Set the oven temperature to 180oc allowed the GC to warm up.
CHAPTER FIVE
CONCLUSION AND RECOMMENDATION
Conclusion
The project research work was carried out with the aim of determining the recycling of polyethylene waste to useful product via pyroysis using low density polyethylene
REFERENCES
- ADEMILUYI, (2007) carried out a research on Preliminary evaluation of fuel oil produced from pyrolysis of waste water sachets.
- Andrew Camann et, al (2004) the widely used of plastic bags Bertolini et al, (1987). Used low density polyethylene for packaging.
- Brown et al. (2011) presented modelling and analysis for estimating profitability of two biochar Production
- Demirbas, (2004). Pyrolysis takes advantage over incineration. Energies (2012) vol 2.8.1 enhancement of char production at low temperatures
- Frounchi, et al. (1997) Studied the mechanical recycling.
- Genta (2006) used supercritical methanol for PET