Pyrolysis Discussion Board
Comité de Discusión sobre Pirólisis
** Background information from the EPA's Scrap Tire Website **
Pyrolysis is a method to break down tires into potentially usable end products. Called by a variety of names, such as thermal distillation and destructive distillation, pyrolysis is the heating of organic compounds in a low oxygen environment.
Pyrolysis of waste tires generates combustible gases, oil, and char products. The quantity and quality of each product depends on variables including temperature, pressure, and residence time. Outputs for a typical pryolysis process are:
Oil: Usually varies in quality from saleable fuel oil that may need processing to lower-value oil blend stock.
Char: Contains a mixture of carbon black, titanium dioxide, zinc, steel and other trace inorganic compounds present in tires.
Gas: May be used to fuel the pyrolysis process or be combusted in a flare.
Although many attempts have been made over the past several decades, EPA is not aware of any commercial pyrolysis systems operating continuously in the U.S. According to the U.S. Rubber Manufacturer’s Association’s 2007 Edition, Scrap Tire Markets in the United States, tire pyrolysis did not play a role in the management of scrap tires in the United States as of late 2007. One reason for this is that the value of the pyrolysis-derived oil, char, and gas has thus far has been lower than the overall cost of the pyrolysis process that produced them. The technology continues to be explored for commercial feasibility, and there are a limited number of pilot operations that have been built.
When investigating the pyrolysis process, some of the practical considerations include:
- Challenges of operating in an oxygen-limited, high temperature environment with complex equipment and an abrasive feedstock (scrap tires);
- Environmental considerations such as the need for air emission control systems and disposal of products or byproducts that may be unmarketable. In addition, zinc and sulfur, both found in tires, are not destroyed or decomposed thermally and may remain in one or more of the pyrolysis products;
- It is difficult to optimize quality and yields of the pyrolysis-derived gas, oil, and char since conditions that favor one often have a negative impact on another. Refining end products may add costs if it is necessary to meet customer needs and may require additional pollution controls;
- Markets of sufficient size and price that support the pyrolysis operation must be developed for pyrolysis-derived oil, char and gas. The quality and thus value of these end products may be different from the commercially available materials against which they are competing;
- Products may have regulatory requirements that need to be met in order to be sold (i.e., Toxic Substance Control Act (TSCA) (Contact Jim Alwood for further information (email@example.com); and
- The need to ensure availability of a steady and adequate supply of tires within an affordable haul distance.
4.24 Pyrolysis, Ex Situ Soil Remediation Technology, Remediation Technologies Screening Matrix and Reference Guide, Version 4.0 (FRTR)
2007 Edition, Scrap Tire Markets in the United States (U.S. Rubber Manufacturers Association, May 2009)
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