Blast furnaces, plastics waste used

As indicated, pig iron production requires input of a reducing agent. Stahlwerke Bremen uses plastic waste as a substitute for fuel oil. Plastics are injected into the blast furnace in a similar way to coal powder or fuel oil. In order to remove fibres and metal particles a separation takes place. Large particles are separated via a screen of > 18 mm. The smaller plastic waste particles (< 18 mm) go to the injection vessel. There, an injection pressure of about 0.5 MPa is built up. Via a pneumatic process the plastics can be dosed and discharged into the blast furnace. The bulk density of the plastics has to be 0.3 tonnes/m. ... 

Separation of plastics such as from household waste and use as reducing agent in blast furnaces or for feedstock recycling... 

Use of soiled, commingled plastics waste in blast furnace as carbon donors. 

The pyrolysis is complicated by the fact that plastics show poor thermal conductivity, while the degradation of macromolecules requires considerable amounts of energy. The pyrolysis of mixed plastic wastes and used tires has been studied in melting vessels, blast furnaces, autoclaves, tube reactors, rotary kilns, cooking chambers, and fluidized bed reactors [17,18]. 

Under ecological aspects utilization of plastics waste in blast furnace represents a meaningful process variant. 60 % of the plastics waste are re-used materially as... 

Bauermeister et al. [6] have tried to summarize the aspects discussed above in an effectivity ranking for the re-using processes of plastics waste valid for german relations without considering re-using plastics waste in blast furnace. The results of Bauermeister et al. [6] were completed and are presented in table 6. The effectivity ranking corresponds to a cost hierarchy of the processes. 

Re-using of plastics waste in blast furnace process and rotary sintering kiln in the cement production process were not considered by [6]. As reported in [11,12] the use of plastics waste in the blast furnace process is very effective and enables to utilize large amounts of waste. 

Fractions of plastics waste which are not possible or not meaningful to recycle in material (mechanical) recycling processes are used in blast furnace or recycled in feedstock (chemical) recycling. Here hydrogenation has the priority followed by gasification and pyrolysis. Pyrolysis of type clean plastics waste will be suited only in exceptional cases. 

Additionally, the industry recently is at the heart of the recycling-based society by utilizing many types of wastes such as used tires, plastics and sewage sludge, and also by-products such as blast furnace slag, as alternative fuels and raw materials. In 2012 total consumption of those wastes and by-products reached 30 million tonnes which is equivalent to 6% of the total wastes disposed in Japan and, as a consequence, the remaining capacity of existing landfill sites is estimated to have been extended by 7.7 years. 

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