Self-sustained smouldering treatment technology for high-moisture sludge: Pilot-scaled tests with continuous operation.

ABSTRACT

Smouldering is a novel, low-energy, low-cost technology for disposing of sludge with high moisture. Currently, related researches focus on the lab-scale with batch disposal, but more reports about the pilot-scale with continuous process need to be done. Based on our previous research, this study further enlarged the pilot-scale smouldering reactor height from 1.2 m to 2.0 m and provides insight into the smouldering performance under long-term continuous operation and the influence of the discharging residue interval and Darcy velocity. The temperate evolution shows that the discharging residue interval significantly affects the reaction location stability due to the difference between the smouldering upward velocity and the feed-stock descent velocity. Furthermore, the unburnout content, heavy metal in the smouldering-derived residue, the non-condensable flue gas concentrations (O2, CO, NOx, VOCs, dioxin), and the components of the condensable liquid are deeply investigated. The pilot-scale measurements show that 30 s and 40 s for the discharging residue interval under the studied operating condition may be reasonable for the high (3.5 cm/s and 5.0 cm/s) and low (2.5 cm/s) Darcy velocity, respectively. Comprehensively, the condition with 30 s for the discharging residue interval and 3.5 cm/s for the Darcy velocity is suggested in the future actual application.