Energy efficiency analysis of a rotating-drum dryer using hot steel balls for converter sludge

We proposed a novel rotating-drum technology for drying converter sludge with high efficiency and low cost. This study aimed to investigate the drying energy efficiency of our technology and the effect of sludge treatment mass (ms0 = 3.0–9.0 kg), steel ball temperature (Tb0 = 300–500 °C), steel ball diameter (d = 20–40 mm), and drum rotating speed (n = 1–7 rpm). The evaluation criteria of energy efficiency included energy utilization rate (ηb), specific energy consumption (SEC), drying rate (DR), etc. Results showed that appropriately increasing ms0 and decreasing Tb0 can increase ηb and reduce SEC, but also reduced DR. Selecting appropriate d and n can not only increase ηb and DR, but also reduce SEC. Under our experimental conditions, ηb is 50–95%, SEC is 0.8–1.5 kW·h/kgw, and DR is 1.0 × 10−4–1.8 × 10−3 g/(g·s). The improved self-scaling method was used to evaluate the energy efficiency under the studied working conditions, and the comprehensive optimal combination of operating parameters was obtained in our experiments, which can be achieved ηb > 78%, SEC 9.9 × 10−4 g/(g·s). [Display omitted]