Improvement of coke strength by HDPE addition

Abstract

ABSTRACT Plastic waste of different origin has been proposed and used as an additive in coal blends in metallurgical coke production for trace amounts for about two decades. Previous studies have suggested that high-density polyethylene (HDPE) can be used as an additive in coking blends for small quantities (2–3 wt% of the blend) without considerably damaging the strength properties of coke. Here, one HDPE-free and five HDPE-bearing laboratory-made cokes were produced and tested for their compressive cold strength and compressive hot strength. The temperature in the hot compressive strength tests was 1,700°C, corresponding to the temperature of the blast furnace bosh area near the tuyeres. The results showed that the trend of the cold compressive strength of coke increased as the amount of HDPE in the coking blend was increased from 0 wt% to 5 wt%. In hot compressive strength tests, cokes containing 3 wt% to 5 wt% of HDPE in the raw material blend showed non-breaking behavior, while the reference coke samples were crushed to pieces in the tests. Image analysis performed for the microscopic images of all experimental coke types revealed that the high number and area percentage of large pores impacted negatively on compressive strength of coke.