In-situ improved corrosion resistance of corundum-mullite refractory for the incineration of hazardous spent high-salt organic liquor by Cr2O3: Interfacial anti-erosion mechanism

Existing refractory-life-extending technologies had concentrated on the preparation of homogeneous high-performance refractory materials in advance. In this paper, an in situ anti-erosion approach of conventional corundum-mullite refractory material was proposed for the incineration of hazardous spent high-salt organic liquor, in which the powdery additives were directly added into the spent liquor. The phase transformation, interfacial morphology evolution, and pore distribution of the corundum-mullite refractory with and without Cr 2 O 3 /ZrO 2 addition were compared, and the in situ anti-erosion mechanism was determined via the XRD , SEM, XPS , mercury intrusion porosimetry , and thermodynamic analyses. In conventional corrosion, molten Na 2 SO 4 , the primary phase of incinerating slag, directly entered the interior of the corundum-mullite refractory through pores on the interface. The Na 2 SO 4 strongly reacted with alumina and silica at 1000–1300 °C to produce liquid albite and nepheline. Upon the addition of Cr 2 O 3 into the spent liquor, the Cr 2 O 3 powder was suspended in the spent liquor and deposited at the refractory interface to form a protective (Al,Cr) 2 O 3 solid solution layer with Al 2 O 3 . The dense corrosion-resistant layer of (Al,Cr) 2 O 3 with a depth of 0–3 mm on the surface of the firebricks seldom reacted with molten Na 2 SO 4 . This protective layer can effectively slow down the penetration and erosion of incinerating slag. The environmental risks of Cr(VI) contamination associated with the Cr 2 O 3 addition in the incineration process were also evaluated in this work. Eventually, preliminary trial operation results showed that the service life of the corundum-mullite firebrick was prolonged after 5% Cr 2 O 3 addition into the spent liquor.