SULFREE

With the growing number of vehicles, the disposal of used tires is an increasing problem. They are also often disposed of illegally or dumped in landfills, which poses a serious environmental problem. But the technology to recover high-quality materials from used tires is evolving. As part of the EU-funded SULFREE project (Tyre recycling pyrolysis for producing oil with less than 0.2% sulphur content, low cost sulphur impregnated carbon for reducing mercury air emissions, with simultaneous elemental), researchers developed a complete process to turn waste rubber into valuable materials.‍The process begins with microwave pyrolysis. Since no waste tire recycling microwave pyrolysis plants were previously in operation, this was a great success. Fricke und Mallah supplied 5 microwave generators, each with 3 kW / 2450 Mhz, for this process. Using the innovative internal mixing system with disks and bars, the used rubber is intensively mixed to achieve complete pyrolysis.

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‍Industrial carbon black and hot gas, the products of the pyrolysis process, each have a high sulphur content. The carbon black is activated using steam to increase its market value. The hot steam is cooled, compressed and injected under pressure into a fixed bed reactor to produce ultra-low sulphur oil and gas as well as sulphur.‍A condenser system, which produces condensed high-sulphur oil instead of steam, significantly reduces the cost of the process. The condenser's shell-and-tube heat exchanger facilitates heat and vapor recovery to meet the system's energy requirements and to activate the carbon black.‍Scientists demonstrated the cost-effectiveness of the system. The recovery rates were comparable to those of existing programs (more than 90 %). The important difference, however, is the resulting high-quality products: Pyrolysis oil, sulphur-impregnated activated carbon, elemental sulphur as well as combustion gases.

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SULFREE is of great economic and ecological benefit, as the promotion of tire recycling minimizes the illegal disposal of used tires.