Recovered carbon black

Holley, C.A., Method for recovering carbon black from composites, US patent, 5,728,361, 1998. 

Table III shows a sample of the properties of carbon black, in which the recovered carbon black is compared with the commercial carbon black ( 2, h 9 5 9 6). The reinforcing properties of the recovered carbon black are higher than those of GPF grade.

The recovered carbon black contains a high percentage of ash and a high level of PH (6 7.). The properties of the carbon black depend upon the kind of the scrap tires and condition of the pyrolysis, especially the pyrolysis temperature. 

There could be numerous uses for the recovered carbon black for rubber goods such as vehicle tires, footwear, rubber sheets, conveyer belts, dockfenders, etc. Some samples of rubber goods such as bicycle tires and safety shoes have been made with the recovered carbon black and their durability has been tested in comparison with commercial ones. At least in short term tests, for example, three months, the safety shoes made with the recovered carbon black showed higher abrasion resistance than the commercial shoes in which HAF-LS carbon black was used. The test results are shown in Table IV (6). 

Flaps for truck tires have also been made with recovered carbon black using 10 to b0% of the total carbon black. These have been tested by JATMA (Japan Automotive Tire Manufacturers Association). The flaps with the recovered carbon black have shown sufficient durability in laboratory tests and actual road tests. 

The disposal cost for a T5000 tons per year capacity plant is estimated in Fig.10 to be 2 yen per kg., therefore, it costs 12 yen for an average Japanese PC tire (6 kg). This disposal cost is low in comparison with usual disposal charges presently collected in various districts in Japan, which vary from 50 to 100 yen per scrap PC tire. Three fourths of the income from the sale of the recovered products depends upon the sale of the recovered carbon black, therefore, it is most important that salable carbon black is recovered from the pyrolysis process. In... 

Carbon black Recovered carbon black (PP test)... 

A pyrolysis system has been developed to recover useful material from scrap tires. An actual plant was constructed in 1979 The plant will be on a trial for a year to demonstrate that the equipment of the plant satisfies the test specifications and that the recovered carbon black has the quality demanded by the rubber industry. After passing one year tests, it will be put into commercial operation. This project is a full scale recycling for scrap tires supported by public agencies which also supported the pulverizing plant in Osaka. It is expected that the completion of the project will open a new course for recycling and disposal of waste. 

Pyrolysis of scrap tires gives as major products, gas, oil, and residue. The gas is the result of thermal cracking and dehydrogenation. The oil derives from extender oils used in the compounding of the vulcanizates as well as from the depolymerization fragments from the rubber. The residue represents recovered carbon black as well as any inorganic material used in the fabrication of the original rubber. 

Carrying out secondary processing steps on these three fractions enables them to be converted into value-added products. For example, once purified, the pyro-gas fraction can be used as an energy source to help run the pyrolysis operation. The oil fraction can be turned into carbon black by a furnace process, or into fuel oil, or chemical feedstock by distillation. The char fraction can be treated to yield products such as activated carbon, recovered carbon black and recovered inorganic compounds. 

When a completely non-oxidising atmosphere is used (i.e., vacuum pyrolysis), it is also possible to recover carbon black from the tyre rubber. This is called pyrolytic carbon black (PCB) and it has the potential to be used in new rubber products (Section 8.2.3). 

An important marketable product that can be obtained from the char fraction is recovered carbon black (also called PCB). The carbon black recovered from the pyrolysis of waste tyres accounts for around 30-35% of the total material generated by the process, with the exact figure depending on the types of tyres being pyrolysed. 

In the same presentation. Yon explained that a large number of companies (>50) had investigated the possibility of reclaiming carbon black from tyres, but that very few had continuously produced any commercial product for the market place. Also, the fact that recovered carbon black (or alternative carbon black as Carbon Clean Tech AG refer to it) is not like conventional carbon black was underlined due to the fact that it is derived from a mixture of rubber tyres, containing a mixture of carbon blacks, the structures of which will have been altered in service, and that the tyres contain a large number of other chemicals that influence the surface properties of the recovered black. 

Testing methods and quality protocols essential to ensuring rubber recycling can take Its place In today s quality conscious world are described. Also Included Is using waste rubber to generate energy and manufacture new materials such as fuel oils and recovered carbon black. 

The lamp black process is likely the oldest industrial process and has consequently been the object of numerous engineering variants. Figure 4.2 describes the principle of a typical modem plant. The partial combustion of a feedstock (oil generally) in an atmosphere purposely poor in oxygen produces smoke, which is cooled down and filtered to recover carbon black particles that are subsequently flocculated. The control of the pyrolytic process is loose and results in a large distribution of elementary particle sizes (from 60 to 200 nm). This fabrication process tends to be abandoned today in favor of the much cleaner and more versatile furnace one. 

Starting aaterial for their preparation and subsequent activation. Graphitized carbon blacks have low surface areas, usually less than 100 K /g and typically 5-30 u /g. They have a low capacity for low molecular weight analytes but have been used successfully for the isolation of heavier nonpolar analytes that might be difficult to recover from more active forms of carbon [169,170]. The most common form of carbon used for trace enrichment is granular activated carbon, generally prepared by tbe low temperature... 

Di Corcia [368] used subcritical water (phosphate-buffered) extraction with a graphitised carbon black cartridge to recover terbuthylazine herbicide and its metabolites from soil. 

The U.S. Environmental Protection Agency s Control Technology Center recognizes the need for data describing the air quality impacts of two of these disposal options the controlled burning of tires to recover its fuel value and pyrolysis for fuel and carbon black. The purpose of this report is to summarize available air emissions and control data and information on tire pyrolysis and burning tires for fuel. 

Each of the radicals is then degraded by the repeated elimination of monomeric units. The activation energy of the depolymerization was fonnd to be 105 J/mol at 400° C. The excellent heat transfer in a linidized bed, the low residence time of the monomers, and the low temperatnre gradient in the bed explain why so few side prodncts and so little carbon black is formed. After distillation the recovered liqnid can be polymerized to new PMMA withont any other pnrification. 

The reinforcing action of these small spherical particles of carbon arises from reactions of unsaturations in the main chain with free radicals present on the surface of the particles. Other particles also interact weakly by means of a process in which segments of polymer are absorbed on the porous surface of the carbon black. Figure 3.21 shows how the particles of carbon black act as extra cross-links connecting chains of the elastomer. It can be seen in the scheme that the deformation results from the sliding of the chains located between two spherical particles. Once the deforming force is removed, the chains between particles more or less recover their initial length. 

The bound chloride in plastics containing PVC is recovered as hydrogen chloride gas from pyrolysis. Considerable amounts of carbon soot are produced in this reaction. By adding superheated steam and hydrogen, the amount of carbon black produced can be reduced from 8.8 to 2.1 wt-% (13). 

Several pyrolysis processes using reactors such as a fluidized bed (3 ), a shaft furnace, an extruder and a rotary kiln have also been studied in Japan. Pyrolysis using a rotary kiln has been studied since 1973 (U ). A pilot plant test was finished in 1976, and an actual plant with a capacity of 7,000 ton per year has been constructed at Sumitomo Cement Co., Ltd. in AK0 City, Hyogo Prefecture, in 1979 (l) The plant will recover fuel oil and carbon black from the scrap tires. 

---