Thermo Fuel

Current situation of recycling of plastics Pyrolysis Structure of the System Operations

ThermoFuel is a process whereby scrap and waste plastics are converted into synthetic fuel.

The system uses liquefaction, pyrolysis and the catalytic breakdown of plastics. The system can handle almost all the plastic that is currently being sent to landfills.

A major advantage of the process is its ability to handle unsorted, unwashed plastic and its extremely high efficiency. A ThermoFuel plant can produce up to 19k litres of fuel from 20 tonnes of waste 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.

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Current situation of recycling of plastics

Various methodologies have been tried and tested to process waste plastics for many years, with recycling becoming the most common method reflecting the needs of the time. Plastics that cannot be processed are handled by waste management companies by normal landfilling or gasification.

In recent years, the building or expanding of gasifiers has become difficult due to opposition from governments and community groups with environmental concerns, most notably the levels of emissions.

Liquefaction of plastic is a superior method of reusing this resource. The distillate product is an excellent fuel and makes ThermoFuel one of the best, economically feasible and environmentally
sensitive recycling systems in the world today.

ThermoFuel synthetic fuels can be used in any standard synthetic engine, trucks, buses, trains, boats,
heavy equipment and generators.

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Pyrolysis

Pyrolysis is a process of thermal 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 plastic is pyrolised at 370ºC-420ºC and the pyrolysis gases are condensed in a 2-stage condenser to give a low sulphur content distillate.

The essential steps in the pyrolysis of plastics involves:

1. evenly heating the plastic to a narrow temperature range without excessive temperature variations
2. purging oxygen from pyrolysis chamber,
3. managing the carbonaceous char by-product before it acts as a thermal insulator and lowers the heat transfer to the plastic
4. careful condensation and fractionation of the pyrolysis vapours to produce distillate of good quality and consistency

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Structure of the System

The system consists of stock infeed system, pyrolysis gasification chamber, catalytic converter, condensers, centrifuge, oil recovery line, off-gas cleaning, and adulterant removal.

Waste plastics are loaded via a hot-melt infeed system directly into main pyrolysis chamber.

When the chamber temperature is raised, agitation commences to even the temperature and homogenise the feedstocks. Pyrolysis then commences to the point of product gasification. Non-plastic materials fall to the bottom of the chamber.

The gas goes through the (patented) catalytic converter and is converted into the distillate fractions by the catalytic cracking process. The distillate then passes into the recovery tank after cooling in the condensers.

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, then to the storage tanks.

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Operations

The heart of the pyrolysis system is the prime chamber, which performs the essential functions of homogenisation, controlled decomposition and outgassing in a single process. The process requires minimal maintenance apart from carbon residue removal, and produces consistent quality distillate
from mixed and low-grade plastic waste.

The key to an efficient pyrolysis process is to ensure the plastic is heated uniformly and rapidly. If temperature gradients develop in the molten plastic mass then different degrees of cracking will occur and products with a wide distribution of chain lengths will be formed.

Another important aspect of pyrolysis is to use a negative pressure (or a partial vacuum) environment. This ensures that oxidation reactions are minimised and that gaseous pyrolysis vapours are quickly removed from the process chamber thereby reducing the incidence of secondary reactions and the formation of undesirable by-products.

The polymer is gently 'cracked' at relatively low temperatures to give predominantly straight chain aliphatic hydrocarbons with little formation of by-products. These hydrocarbons are then selectively condensed and cleaved further catalytically to produce the average carbon chain length required
for distillate fuel.

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