Erosion behaviour of rotary kiln refractory and its effects on ringing during steel-rolling oily sludge incineration

Rotary kiln incineration is a desirable disposal option for steel-rolling oily sludge. However, ringing remains a key challenge in the highly efficient operation of rotary kilns. This study investigates the erosion behaviour of refractory bricks in a rotary kiln during steel-rolling oily sludge incineration and its effects on ringing. The degree of refractory brick erosion (i.e. iron permeation-depth and quantity) depends on the roasting temperature and time. The iron permeation-depth (3.1 mm) after 36 h of roasting at 1350 °C is greater than that (0.7 mm) after 12 h of roasting at 1200 °C. In the same zones of the refractory bricks, iron permeation increases with the roasting temperature and time. This is because the molten substances generated from the steel-rolling oily sludge erode the refractory bricks, whereas the loosened surface of the eroded refractory bricks is conducive to the continual permeation of molten substances in the refractory bricks. Steel-rolling oily sludge is mixed with refractory brick powder to produce briquettes, which are then used to simulate the permeation and erosion processes. Adding 20% refractory bricks to the briquettes decreases the cohesion strength of the briquettes from 9.07 to 11.71 kN to 2.97-4.44 kN when roasting is performed at 1250 °C for 5-30 min. Although haematite contributes to the high cohesive strength of the rings, the primary components of the refractory brick are transformed into eutectic substances, which decreases the cohesive strength of the rings. These findings provide a useful reference for developing ringing mitigation methods for rotary kilns.