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

Abstract

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 Cr2O3/ZrO2 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 Na2SO4, the primary phase of incinerating slag, directly entered the interior of the corundum-mullite refractory through pores on the interface. The Na2SO4 strongly reacted with alumina and silica at 1000–1300 °C to produce liquid albite and nepheline. Upon the addition of Cr2O3 into the spent liquor, the Cr2O3 powder was suspended in the spent liquor and deposited at the refractory interface to form a protective (Al,Cr)2O3 solid solution layer with Al2O3. The dense corrosion-resistant layer of (Al,Cr)2O3 with a depth of 0–3 mm on the surface of the firebricks seldom reacted with molten Na2SO4. This protective layer can effectively slow down the penetration and erosion of incinerating slag. The environmental risks of Cr(VI) contamination associated with the Cr2O3 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% Cr2O3 addition into the spent liquor.