Processes and technologies for environmentally friendly recovery and treatment of scrap (PROTECT) : final report

The low-carbon galvanized steels normally used in automotive bodies and appliances are a source of high-quality scrap feed for both BOF and EAF steel production. The aim of this project is to develop a new method to promote synergetic use of low-value energy rich waste, combined with cleaning and preheating of Zinc coated scrap. The process concept is a stand-alone concept, decoupling the preheating of scrap from the off-gas streams from the melting furnace. Within this project different aspects of the value chain have been analysed. Experimental work and tests have been carried out to derive methods of separating and refining waste streams. The separation techniques have been adopted on commercial plants and in pilot scale. Plastic fractions have been separated from the main stream dividing the waste into valuable fractions. Two different thermo-chemical conversion methods have been tested in experimental scale for utilising the plastic fractions separate, producing combustible syngas to be used as fuel in the preheating concepts. Pilot testing of scrap preheating have been carried out showing the possibility to remove organic and metallic coatings on scrap and at the same time reaching a high preheating degree. A dedicated scrubber and recovery system has been derived, to take care of the exhaust gases from the scrap preheating system. The volume gas leaving the scrap cleaning system through the stack are in the range of 80 Nm3/ton scrap which is a substantially reduced gas volume compared to the industrial gas cleaning systems from the melting furnaces. This allows for efficient and cost effective gas treatment. From theoretical calculations, different aspects of the concept have been evaluated. The evaluation shows that the concept is positive both from environmental and economic standpoint. It must however be stated that there still are some technological/metallurgical questions remaining open and more research to validate and improve before a large scale demonstration and implementation of the preheating concept can be done. Parts of the research results derived within the project can be implemented and used, into new innovations.