HDC in Pyrolysis Oil Conditioning & Refining

In the trend towards reusing resources and green energy, pyrolysis oil presents an attractive source of renewable energy. It has long been considered as a potential substitute for petroleum, or for use in a blend with petroleum, as a renewable source of energy. However, the physical characteristics

of pyrolysis oils limit their use as a fuel:

  • Pyrolysis oils experience an increase in viscosity over time due to polymerization reactions in a newly created, unstable liquid. Thermal catalytic cracking processes at the end of production of the oil can resolve this issue, but at high cost.

  • Some pyrolysis oils undergo chemical & physical changes over time which can result in the separation of the oil into multiple phases including water, wax, sludge, and tar.

  • Untreated pyrolysis oils do not follow any set a distillation curve, like crude oil does. Rather, when pyrolysis oil is heated, volatiles and water vaporize and the remaining compounds polymerize.

  • The pH of pyrolysis oils is typically very low.

Of all the waste materials available the production of useful oil from the pyrolysis of tires holds the most promise. Millions of used tires are discarded every year causing mountains at recycling facilities. Only a tiny fraction of the rubber discarded as used tires is recycled into low value products such as crumbs, mats, etc. Unfortunately, besides the technical hurdles mentioned above for biomass and plastic pyrolysis oils, tire pyrolysis oil contains very high levels of sulfur from the vulcanizing process. Typical oils may contain 1.5% to 3% by weight as sulfur. Further complicating the issue is the refractory form of these sulfur compounds. They resist most oxidation attempts such as the processes used by crude oil refineries (Hydrodesulfurization, Oxidative desulfurization, etc.). The conventional sulfur removal processes in crude oil refineries can only take the fossil crude oil down to the level of the refractory sulfur compound levels, typically around 350 ppm. In tire pyrolysis oil, most of the sulfur is tied up in refractory compounds, and therefore conventional methods are impractical for desulfurization.

Controlled Hydrodynamic Cavitation holds the promise of being able to perform multiple functions. The process is already used to break large waxy crude molecules to reduce viscosity. It can also break the sulfur compounds and oxidize them in an economically viable manner. Voltek has a patent pending process in development for desulfurizing tire pyrolysis oil. The process centers around our uniqe controlled cavitation advanced oxidation reactor which oxidizes the organic sulfur compounds to sulfones and sulfoxides. The latter are polar compounds and can dissolve in polar solvents such as water. The sulfur laden water is seprated and treated by the Voltek patent pending insitu oxidation polymers. The sulfur is reduced to elemental sulfur in the process, which can be used as a soil conditioner in agriculture.