WtOil

Introduction

WtOil is an optional stage of the Entech-Tru-RES™ for plastics.  Whereas the WtGas system is based upon immediate firing of the gas produced, this alternative is for the plastic portion of the waste to be converted into fuel oil for storage and use elsewhere (as a replacement to fossil fuel oil).  It's based upon a pyrolysis process that converts the plastics from its solid to condensable vapour form, so that it can be fired to power vehicles or generate energy; with emissions that are superior to firing of conventional fossil fuel oil. The WtOil solution is as described below.

Technology

The WtOil system has solved traditional problems associated with pyrolysis technology.  The process employs patented highly-energetic far infra-red (FIR) heating rods that promote efficient cracking and minimise coking problems.  Far infra-red radiation is highly energetic and close to the microwave region of the electromagnetic spectrum.

Most common hydrocarbon plastics are suitable for pyrolysis.  Generally the larger the subsistent in the side chain then the easier the plastic can be degraded.  The order of increasing side chain size is high-density polyethylene < low-density polyethylene polypropylene < polystyrene. The WtOil system can be used to convert all kinds of PP, PE, PS waste plastics into oil by pyrolysis.

PP, PE and PS waste plastics

Process Description

The WtOil process of pyrolysis thermally degrades plastic, breaking the bonds of the polymer to produce lower molecular weight oligomers and monomers.  The vapours resulting from the process are condensed to produce an oil/wax hydrocarbon product which has a high degree of purity, which are further refined in the process by selective fractionation to give predominantly diesel fuel oil.  Pyrolysis typically takes place at relatively low temperatures in the range 350-450 deg. C.

WtOil P-Fuel Process

It's necessary to find the optimal pyrolysis conditions and upgrading process to obtain marketable products (e.g. diesel fuel or gasoline) from plastic wastes.  Controlled thermal degradation using internal far infra-red heating, as used by the WtOil system produces a much narrower product distribution of carbon atom number and reduces the reaction temperature as compared with other processes.

Temperature and heating rates have considerable influence in the pyrolysis process and can be controlled to produce desired solid, gas and liquid products.  The WtOil system is capable of faster heating rates than conventional pyrolysis processes (because it utilises internal far infra-red heating) and this reduces the yield of char resulting in increased efficiency.  Far infra-red radiation is highly energetic since it is close to the microwave region of the electromagnetic spectrum.

In addition to temperature, the type of pyrolysis reactor is also important in determining fuel oil product yield.  The WtOil system fast heating rates with short hot zone residence times and rapid quenching of the products are proven to favour formation of diesel products.  Also, the removal of pyrolysis products from the hot zone reduces the extent of secondary reactions which is proven to increase liquid fuel oil fraction formation at the expense of char formation.

The WtOil system through the use of low-temperature pyrolysis and efficient cracking achieves liquid fuel yields of up to 80-85%, with the resultant product resembling diesel fuel oil, kerosene, gasoline or other useful hydrocarbon liquids.  An added advantage of pyrolysis is that the light gases by-product produced (additional to the fuel oil produced) can be used to provide the energy requirements for the process.