14 Pyrolysis of Scrap Tires Using the Tosco II Process—a Progress Report B. L. SCHULMAN and P. A. WHITE
1
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Tosco Corporation, 18200 West Highway 72, Golden, CO 80401
During the course of developing the TOSCO II process for pyrolyzing oil shale, Tosco examined the application of this process to other organic materials such as coal, tar sands, municipal waste and scrap tires. Initially, the processing of scrap tires became of interest because of the high oil yield obtained from the decomposition of the rubber — about 150 gallons per ton, compared to 30-35 gallons per ton for oil shale. At that time, carbon black had approximately the same value as oil and, although it was known that the carbon black was recovered in good quality, its contribution to the potential economics was modest. In 1974, both carbon black and oil prices rose sharply, and later operations focused more closely on the carbon black product. After a series of pilot plant investigations, The Goodyear Tire & Rubber Company and Tosco entered into a program to define the commercial potential of the tire program. A major part of this effort was to construct and operate a 15 ton a day pilot plant specifically designed for pyrolyzing scrap tires and develop the appropriate techniques to recover the valuable liquid and carbon black materials in a suitable commercial form. Generally, the goals of the program were to define the methods for improving the process efficiency in three areas: 1. Optimize process conditions for maximum plant capacity and process yields. 2. Demonstrate best techniques for recovery of the carbon black with an acceptable commercial quality. 3. Demonstrate new mechanical hardware which could improve product recovery or lower total plant investment. 'Current address: Tosco Corporation, 10100 Santa Monica Blvd., Los Angeles, CA 90067
0-8412-0434-9/78/47-076-274$05.00/0 © 1978 American Chemical Society Jones and Radding; Solid Wastes and Residues ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
14.
SCHULMAN
A N D WHITE
Pyrolysis of Scrap Tires
275
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Pyrolyzing Scrap Rubber Showed Surprising Yield — Polymer Cracks Easily With No Coke Formation The pyrolysis of rubber tires was found to be surprisingly different from processing other organic materials in that the materials making up the tires decomposed in a "cleaner" manner than other organic materials . Scrap tires consist of many elements which can roughly be categorized into four elements: 1. Synthetic rubber (butadiene-styrene copolymer) 2 . Extender oils 3. Organic cord and inorganic belting 4. Carbon black and fillers Analysis of the pyrolysis products which form at 900 to 1000°F showed that the organic polymers simply decomposed into liquid and gas with no coke deposition on the residue. The carbon black, fillers and inorganic belting remain behind as a solid residue. The form of the residue is essentially the same as the original materials used in the tire. For example, fiberglass cord may unravel into single strands; steel (as belting or bead wire) will show up as single or tangled strands; and the carbon black, together with the fillers, will appear as individual particles or loose agglomerates less than one micron in diameter. The major technical advantage of this controlled pyrolysis is that the carbon black is recovered in a "virgin form" — its reinforcing properties are the same as those of the mixture of the various grades of the carbon black which is used in the initial formulation of the tire. The inorganic additives are indicated by the ash content — the typical tire char will show an ash content in the range of 13-16%, as illustrated in Table I. The ash consists mostly of zinc, silica and titanium, with varying amounts of other elements as shown in Table II. Standard rubber formulation tests, together with the use in making tires has shown that the carbon black can be re-used in portions of the tire according to the char's grade. The Key To A Successful Process Is To Maximize Capacity And Maintain Carbon Black Quality The general TOSCO II process description has been well documented. (i) A simplified flow diagram of the process is illustrated in Figure 1. The shredded scrap tires are dried and fed to the rotary pyrolysis drum. Hot ceramic balls from a ball heater flow to the drum, also, where the mixing action raises the reaction temperature to 9 0 0 - 1 0 0 0 ° F . The organic materials decompose
Jones and Radding; Solid Wastes and Residues ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
Jones and Radding; Solid Wastes and Residues ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
2.33
0.24 2.1*6
0.25
2.3^
Chlorine, #
Sulfur, $
13-71 100.00
15» 36
100.00
100.01
0.18
Ο.13
0.17
$
Nitrogen,
Ash, $
0.27
0.75
Ô.7U
Hydrogen, Ο.85
81Λ9
82.66
Fiberglass-Belted
81.15
$
Steel-Belted
Carbon, $
Moisture,
Non-Belted
Table I . U l t i m a t e A n a l y s i s o f a T y p i c a l T i r e Char
Downloaded by RUTGERS UNIV on December 31, 2017 | http://pubs.acs.org Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0076.ch014
0.25 0.60 2.5Ο ΙΛΟ Ο.36
0.l8 0.25 I.50 0.80 0.32 19.09
0.l6
0.27
2.3Ο
1.60
Ο.38
19.62
Lead
Barium
Magnesium
Phosphorus
Potassium
5.Ο6 2.77
6.0k
2.67
CaO
Sulfur
2
1^.27
Ti0
11.99
ZnO
Jones and Radding; Solid Wastes and Residues ACS Symposium Series; American Chemical Society: Washington, DC, 1978.
1.27
6.08
10.28
to
CO
crap
21.31
8-
Pyro\
52.33
2.00
1.10
2.00
Iron
> HITE
S1O2
0.l6
0.13
0.15
Chromium
2Λ0
I.5O
2Λ0
^0.03
Fiberglass-Belted (Ash 13.7 v t 1o)
Aluminum
i)
