FEDIL Environment Award 2013 goes to Paul Wurth

Every two years the Business Federation Luxembourg FEDIL confers an Environment Award to reward companies whose innovative processes reduce the impact on the environment and conciliate productivity and preservation of natural resources. The jury of the 13rd Fedil Environment award has attributed the first prize in the category “Processes” to Paul Wurth’s Dry Slag Granulation Process with Energy Recovery. The award ceremony took place on 2 December 2013 in the premises of the Chamber of Commerce of Luxembourg.
An alternative slag treatment process
Traditionally, when tapped from the blast furnace, the liquid slag is quickly cooled down by water quenching so as to obtain granulated slag that can be valorised in the cement industry. Another process consists in dumping the slag in pits, where it cools down slowly and can later be used for road construction. In both cases, the substantial amount of energy contained in the liquid slag is lost. Today the iron and steel industry is facing crucial environmental and energy issues. Paul Wurth took up the challenge to develop an alternative slag treatment process in order to recover the energy contained in the slag while maintaining unchanged the physical properties of the granulated slag. This process is called Dry Slag Granulation with Energy Recovery.
Technical Concept
Steel spheres are injected evenly into the liquid slag providing a large contact surface for efficient heat transfer. The slag cools down rapidly from about 1 450°C to 650°C, thus ensuring vitreous solidification required for further use of the slag in the cement industry. The resulting mixture of steel spheres and solidified slag is then subject to heat recovery within a counter-current heat exchanger. The energy is recovered in form of hot air at a temperature of approximately 600°C. It can be used directly as thermal energy, or it can be converted to steam and subsequently to electrical energy.
Advantages of Dry Slag Granulation
Besides the already mentioned energy recovery, this innovative process brings about important water savings compared with wet granulation (700 litres per tonne of slag), a reduction of the sulphur and CO2 emissions, and reduced costs for transportation and further treatment (drying) due to the fact that the product is dry. Different series of trials have proven these advantages. With the financial support of the Luxembourg Ministry of Economy, the construction of an industrial pilot plant started in October 2012 on the site of Dillinger Hütte in Germany. Designed for a daily production of 80 tonnes of slag, the plant has been commissioned in November 2013. The first operating results are very promising and confirm the technical, energetic and environmental viability of this new development, which can also been applied to steelmaking, EAF or ferronickel slags.

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