ISSN 2594-357X
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Abstract
Over the past 10 years, as a consequence and to counter constraints of availability and price, voestalpine Stahl has implemented several projects to use injected reducing agents more flexibly. The use of waste plastics in the steel industry is an appropriate way to recycle industrial and municipal wastes and therefore contributes to the environmental protection. Furthermore the amount of coke replaced by injected reducing agents has a direct influence on the CO2 balance in the blast furnace. In the BF A in Linz, up to 110,000 tons of plastics per year are now used as a reducing agent; this corresponds to an injection rate up to 40 kg/tHM. Despite the available experience in waste plastics injection, systematic investigation of its reaction kinetics is still missing. Four waste plastics types of different origin and treatment processes have been tested at RWTH Aachen University using an injection rig that simulates conditions in the tuyère, injection lance and in the oxygen area of the raceway. Conversion behaviour has been examined for various plastics concentrations characterised by the oxygen / carbon atomic ratio. Waste plastics of two grain sizes have been injected: 2-3 mm and the original size used at voestalpine Stahl. The change in the microstructure and the surface of injected substances were determined as well. The conversion degree depends on two mechanisms: the change in the particle-specific surface that is affected by its mass and shape factor and the change in the particle dimension or volume; respectively diffusion or reaction kinetics can be limiting factors depending on the balance between both mechanisms. Industrial experience including material preparation, replacement ratios and the analysis of trace elements and heavy metals such as Pb, Zn, Cd and Hg is discussed as well.
Over the past 10 years, as a consequence and to counter constraints of availability and price, voestalpine Stahl has implemented several projects to use injected reducing agents more flexibly. The use of waste plastics in the steel industry is an appropriate way to recycle industrial and municipal wastes and therefore contributes to the environmental protection. Furthermore the amount of coke replaced by injected reducing agents has a direct influence on the CO2 balance in the blast furnace. In the BF A in Linz, up to 110,000 tons of plastics per year are now used as a reducing agent; this corresponds to an injection rate up to 40 kg/tHM. Despite the available experience in waste plastics injection, systematic investigation of its reaction kinetics is still missing. Four waste plastics types of different origin and treatment processes have been tested at RWTH Aachen University using an injection rig that simulates conditions in the tuyère, injection lance and in the oxygen area of the raceway. Conversion behaviour has been examined for various plastics concentrations characterised by the oxygen / carbon atomic ratio. Waste plastics of two grain sizes have been injected: 2-3 mm and the original size used at voestalpine Stahl. The change in the microstructure and the surface of injected substances were determined as well. The conversion degree depends on two mechanisms: the change in the particle-specific surface that is affected by its mass and shape factor and the change in the particle dimension or volume; respectively diffusion or reaction kinetics can be limiting factors depending on the balance between both mechanisms. Industrial experience including material preparation, replacement ratios and the analysis of trace elements and heavy metals such as Pb, Zn, Cd and Hg is discussed as well.
Keywords
Waste plastics injection; Raceway; Reaction kinetics; Conversion degree; Trace elements.
Waste plastics injection; Raceway; Reaction kinetics; Conversion degree; Trace elements.
How to refer
Knepper, Marco;
Babich, Alexander;
Senk, Dieter;
Buergler, Thomas;
Feilmayr, Christoph;
Kieberger., Nina.
WASTE PLASTICS INJECTION: REACTION KINETICS AND
EFFECT ON THE BLAST FURNACE PROCESS
,
p. 798-810.
In: 42º Seminário de Redução de Minério de Ferro e Matérias-primas / 13º Seminário Brasileiro de Minério de Ferro / 6th International Congress on the Science and Technology of Ironmaking,
Rio de Jabeiro,
2012.
ISSN: 2594-357X
, DOI 10.5151/2594-357X-22161
