The theoretical study and the worldwide research were completed with a feasibility study based upon a number of tests.
Speed of operation
A tyre of about 2 meters in diameter can be handled and cut, with the side walls and tread removed and debeaded, in about 5 minutes. Size reduction of all parts depends on type and size of the tyre.
The crumbling time with separated NR and SBR powder (e.g. 100µm in one step) depends on type and size of the tyre.
Some details of the process
The NR and the SBR / butyl powder is 99.999% pure with an average size of about 800µm to 100 µm (or less) depending on processing speed without further grinding.
The steel is 100% clean and can be sold or re-used, all textile is recovered.
All water is specially treated and recycled.
UHP water jetting requires pumps at 6,200 bar, with 15 µm openings in diamond nozzle devices rotating at various speeds.
Mechanical tests have been done on a mixture of NR and UHP powder to check the relative physical properties of the mixture.
The TS (tensile strength), the M 300% ( Modulus at 300% elongation) and the EaB (Elasticity at breaking point) even with 30% UHP powder gave excellent results. (reports available)
Based upon the analysis of UHP water jetting stripping process we concluded that devulcanization takes place just in the course of the stripping process.
The UHP high-energy water jet breaks the sulphur bonds of polymer matrix, while it preserves polymer chains. This happens at the edge of the crumb-powder and therefore is much more effective the smaller the powder grain is e.g. 200µm.
Safety of operation is required because of the dangerous cutting properties of the jet stream at mach 2.5 speed (about 800m/sec) launching a piercing water jet.
The danger is not only the high pressure pump with all the piping, valves etc but also the UHP jet stream itself.
The danger of the Legionella disease, which only can contaminate in a sprayed warm water jet, is realistic because the water outlet at the nozzle is about 40°C, the perfect temperature for the Legionella breading.
The potential danger for Legionella infection has been overcome by state of the art process.
The noise level of the operation is high, about 105 decibel at 1meter of the nozzles. This has a direct and indirect relation with the design of the crumbling housing and the overall workshop design and dimensions. Generally spoken the noise level can be reduced easily.
The operation persons do require special safety training and all technicians of the pumps and UHP water jet should of need to have a special certificate for working with UHP piping systems.