Process for the Separation of Gas Products from Waste Tire Pyrolysis

In recent years, pyrolysis has proven to be an effective thermochemical process for the recycling of waste tires. After pyrolysis, three fractions are obtained: carbonaceous solids, liquid hydrocarbons, and the so-called noncondensable gases. In this paper, the starting point is the pyrolysis reactor outlet that provides a gas stream with a temperature of 600 °C and a pressure of 2 bar, comprising both the condensable and the noncondensable fractions. Although the pyrolysis process is technically and environmentally feasible, its economic viability will clearly depend on the possible salability or use of the three main derived products. Focusing on liquid hydrocarbons, usually the most abundant and valuable fraction, they are a mixture of aliphatic, aromatic, and polar compounds with a boiling point ranging between approximately 70 and 400 °C. Therefore, it is difficult to find possible applications different from their direct combustion without a purification or separation step for their commercialization. In this paper, a complete process for the separation of valuable gas and liquid fractions is described by using commercial process simulation software. After a condensation step, the liquid stream is derived to a conventional crude distillation column where it is fractionated and the gas stream is conducted to an absorption column where H2S and CO2 are removed to obtain a clean gas. In addition to the complete flow sheet description, an energy balance is provided and the liquid fractions are compared to those obtained in crude distillation.