In addition to looking at their own emissions, steelmakers have some opportunities to help reduce the environmental impact of other materials. The use of plastic, both as a source of carbon units and for the physical properties it can give to coke, could be one way of doing this profitably.
SBB 9 June A subsidiary of north China steel giant Shougang Group named Shouhuan Technique, based in Hebei province’s Tangshan, has begun introducing waste plastic in its coking operations aiming to supplement coking coal and help cut production costs.
Trials using a pilot plant began in May and Shouhuan Technique hopes to use about 10,000 tonnes/year of soft plastic waste such as sheeting and bags for blending with low-caking coking coal. These are then carbonised to produce coke.
A Shougang researcher tells Steel Business Briefing that its method differs from that of say, the Japanese mills, where used PET bottles are granulized first before being used in the coke ovens. Shougang directly blends soft waste plastic with low-caking coking coal before sending the result to a reaction chamber.
“The key step in the process is to perfectly control the temperature to ensure the waste plastic melts rather than burns so that it enhances the caking ability of the (weak) coking coals,” he says. Indeed, results to date show the ‘molded coal’ obtained through the process produces coke of sufficient quality for use in Shougang’s 4,000 cubic m blast furnace in Tangshan.
“However, the (pilot) plant’s scale is small and we need to wait to see how successful the process is for reducing costs,” says the researcher. “But I believe it will perform well, as the price of waste plastic is much lower than premier coking coal.”
Products of Shouhuan Technique will be fed to Qian’an Zhonghua, a jv between Shougang and Kailuan Coke Ltd that supplies coke to the steelmaker’s works. The jv’s present coke-making capacity is 3.3m t/y. For now, plastics will meet only a tiny fraction of Shougang’s carbon units.