The second-largest steelmaker in Japan is joining the growing ranks of steel companies using waste plastics to fuel their blast furnaces. NKK Corp., based in Kawasaki City, near Tokyo, plans to use about 66 million pounds of mixed plastic waste as feedstock in its pig iron furnaces this fall.
According to the company's test data, 440 pounds of waste plastics can replace 904 pounds of coke and 198 pounds of pulverized coal in the production of one ton of pig iron.
In the NKK system the mixed plastic waste is first treated to remove PVC, and then crushed and agglomerated before it is blown into the furnaces.
NKK claims its proprietary system reduces carbon dioxide emissions 30 percent, and achieves 80 percent blast furnace efficiency.
In the NKK process, scrap and a small amount of coke are charged from the top of the furnace, while oxygen, pulverized coal and coarse plastics are injected as heat sources, requiring less energy and achieving almost twice the productivity of current processes.
NKK uses the same technology to incinerate plastic waste in municipal waste plants, and is one of the leading waste incinerator contractors in Japan.
Similar techniques are surfacing elsewhere in the world as countries deal with the waste plastic recycling issue.
In Germany, for instance, Wirtschafts-vereinigung Stahl, a steel industry association based in Dusseldorf, estimates that the German steel industry could use all 1.4 billion pounds of the plastic waste collected by Duales System Deutschland, the government agency set up to handle wastes collected under Germany's restrictive plastic recycling law, as well as 1 billion pounds of light shredded plastic waste.
A series of experiments in German steel factories has shown that waste plastics can replace heavy oil in blast furnaces, without seriously increasing harmful emissions, and that the savings in fuel costs could offset higher processing costs and result in economic benefits to the industry.
Other German firms also have devised ways to use unsorted plastic wastes to make kunstoffe - or plastic - oil, which can be used as a feedstock in the petrochemical cracking process to create more chemicals and plastic building blocks.
While problems still exist, particularly in production costs, more recyclers are concluding that traditional mechanical ``product-to-product recycling'' has limitations in how much plastic it can actually recycle, while feedstock and fuel recycling methods offer potential for the future, according to Wirtschaftsvereinigung Stahl.
