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An efficient and safe process technology to convert plastic waste products into diesel fuel
 

Plastics are very widely used in a variety of applications. However, more than 38% of the plastic products have a very short life time since they are predominantly used for packaging application. Plastics are also used for other consumer non durable products. These plastics also have a short life time. It is expected that almost 40% of plastics are found as waste after their utilization is completed. Since about 170 million tpa of plastics are consumed globally, about 70 million tons of plastics are found in the waste stream every year. Since plastics continue to have a healthy growth of about 5% globally their presence in the waste will increase continuously.

Earlier, when consumption was low these plastic products were predominantly put in "Landfills". However, the consumption of plastics over the last two decades has increased dramatically due to tquantum jump in plastics consumption in China and India. In fact, the Asian region with 40% of the world's population presently accounts for 35% of the global plastics consumption. With limited availability of landfills, disposal of plastic products at the end of their service life has become a major issue. Recycling is being pursued by many countries all over the World, but there is a limit since the recycled products do not have performance of the virgin products. Bio degradable plastics have been developed in the last two decades but their commercialization so far has been limited. Whether these two approaches can at all resolve the problems of disposal of plastic products remains to be seen.

Plastic is derived from petrochemical resources. In fact these plastics are essentially solidified oil. They therefore have inherently high calorific value. Most of the commonly used plastics can produce 0.90 % of oil if they are properly incinerated and pyrolized. Liquefaction of plastic waste is a superior method of reusing this "useless" resource. The distillate product is an excellent fuel thus making this alternate as one of the best possible options. Liquefaction fuels can be used as fuel for diesel burners, trucks and generators, as well as co-generators.

Liquification and recovery of fuel from plastic however, is quite expensive and is prone to the environmental hazards. Ozmo Energy Ltd, an Australian company has developed a safe process technology which is known as "Thermofuel" to convert plastic wastes into green fuel. It is called green because it is environmentally friendly and does not produce any hazard.
Thermofuel process system uses liquefaction, pyrolysis and the catalytic breakdown of plastics, a process whereby scrap and waste plastic are converted into liquid hydrocarbons that can be used as fuels. It can handle almost all the plastic that is currently being sent to landfills.

Pyrolysis is a process of degradation in the absence of oxygen. Plastic waste is continuously treated in a cylindrical chamber and the pyrolytic gases condensed in a specially-designed condenser system to yield a hydrocarbon distillate comprising straight and branched chain aliphatics, cyclic aliphatics and aromatic hydrocarbons. The resulting mixture is essentially equivalent to petroleum distillate. The density of "green" distilled fuels is close to that of regular diesel, as well as its other characteristics. Green Fuel contains the same energy content as conventional diesels, but with significantly reduced emissions levels for environmentally sound operation. Existing diesel engines can run fully effectively on these fuels with no engine modification.

This system can handle almost all the plastic that is currently sent to landfills, including co-mingled municipal and manufacturing wastes, chemical and oil drum/bottles, MSW plastics including wraps, packaging, bottles and toys as well as milk crates, silage wraps, irrigation tubing and pipes. There is no need to identify plastics by type for it to be used in the process. It is only necessary to separate the commingled plastic stream away from the general waste stream. This is a major advantage of this process and eliminates a costly process of segregating the type of plastic.

This means that heavily contaminated plastics such as mulch film can be processed without difficulty. The same applies to silage wrap, trickle tape and other agricultural plastics. Other normally hard to recycle plastics such as laminates of incompatible polymers, multilayer films or polymer mixtures can also be processed with ease unlike in conventional plastic recycling techniques. In fact, most plastics can be processed directly even if contaminated with dirt, Aluminium laminates, printing inks, oil residues, etc. During the pyrolysis process, non-plastic materials fall to the bottom of the chamber and could be eliminated later.
The char residue produced is about 5% of the output for relatively clean polyolefin feedstocks and up to 8-10% for PET-rich feedstocks. Since the char passes acid leaching tests it can simply be landfilled.

This patented technology distributed with exclusive rights by "Ozmo Energy Ltd" in several markets will be introduced in various European countries in the next period of time, as a series of new plants will be put into operation. The technology is being offered in India by deTox, Surat. The applied process is a truly sustainable waste recycling solution, diverting plastic waste from landfills, utilizing the embodied energy content of plastics and producing a highly usable commodity that, due to its cleaner burning characteristics, is in itself more environmentally friendly than conventional distillate.

As a result of an intensive R&D undertaking started in 1983 by Ozmo Energy Ltd., several waste recycling plants have been working throughout the World for the last years .The first one was set up in Japan and is in use for more than 8 years. This process is therefore well proven and successful. It is economically viable and has ability for virtually uninterrupted operation.There are several sizes of these plants designed based on the availability of quantity of plastic waste per day. Typically the plastic waste required per day can be as low as 10 MT/day to as high as 40 MT/day.

Process
Waste plastics are first loaded into pyrolysis chamber. The chamber can generally be filled within 30 minutes. When the chamber temperature is raised, the plastics begin to melt and agitation commences to even the temperature. Pyrolysis then commences.
The gas goes through the patented catalytic converter and is converted into the distillate fraction by the catalytic cracking process. The distillate then passes into the recovery tank after cooling in the condenser. From the recovery tank, the product is sent to a centrifuge to remove contaminants such as water or carbon. The cleaned distillate is then pumped to the reserve tank where a small quantity is drawn off as fuel for the system itself. The remaining product is pumped to the storage tanks. Plastics are separated into oil, gas and char residue by pyrolysis. Recovery ratio and characteristics of the product distillate differs depending on the types of plastics or decomposing temperature.
Approximately 950 ml of oil can be recovered from 1kg plastics such as Olefins including Polyethylene (PE) and polypropylene (PP), or polystyrene (PS). Generally, input feedstock plastics do not require washing or sorting.
A comparison of the distillate produced from a commingled plastic mix compared with regular diesel has been conducted by gas chromatography, and shows good similarity between fuels, however, the distillate shows cleaner burning characteristics and contains no chemical elements other than those which can be found in the plastic waste.

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