外电场作用下熔渣对MgO-C耐火材料的侵蚀行为

以高温炉渣为电解质,工业MgO-C砖为阴极,钼丝为阳极,研究外电场作用下耐火材料在炉渣中的腐蚀行为。研究结果表明,在CaO-SiO_2-Al_2O_3渣系中,单质硅的析出电位约为-6.1V;在CaO-SiO_2-Fe_2O_3渣系中,单质铁的析出电位约为-1.25V,硅的析出电位为-5.85V。当外加电压小于炉渣分解压时,电压趋使炉渣中离子(Fe~(2+),SiO_4~(2-))定向移动,阴极附近熔渣粘度不断增加,熔渣在耐火材料中扩散速度下降,导致炉渣渗透深度减小。当外加电压高于炉渣分解压时,电压加速炉渣的电化学分解,单质Si和Fe的析出是诱发熔渣组成发生偏移的驱动力,加速高熔点沉积层的形成,而高熔点沉积层有效阻断炉渣与耐火材料直接接触,导致渗透深度显著下降。高熔点沉积层组成与熔渣组成密切相关,在CaO-SiO_2-Al_2O_3渣系中主要由Ca_2SiO_4组成,在CaO-SiO_2-Al_2O_3-MgO渣系中主要由MgAl_2O_4组成。

Corrosion Behavior of MgO-C Refractory in Slag Under the Applied Voltage

The corrosion behavior of MgO-C refractories in molten slag was investigated under the applied voltage using MgO-C brick and molybdenum as the cathode and anode,respectively.The results show that the deposition potential of Si is about-6.1 V in the slag of CaO-SiO2-Al2O3 system and-1.25 V of Fe,-5.85 V of Si in the CaO-SiO2-Fe2O3 system,respectively.When the voltage is applied between the cathode and anode,ions,such as SiO42-and Fe2+,move to the cathode and aggregate around the cathode.When the voltage applied is lower than the decomposition voltage of slag,the aggregated ions lead to an increase of viscosity of slag around the cathode,which decays the diffusion of slag toward the MgO-C refractories and then leads to a decrease of penetration depth.When the applied voltage is larger than the decomposition voltage of slag,liquid Si or Fe is produced in the role of applied voltage,which causes the shift of slag composition toward the high melting products (Ca2SiO4,MgAl2O4).The formation of high melting product layer is supposed to be a good physical and chemical protection for the refractory because they hinder the direct contact between the slag and the refractory.The type of electrodeposit products is closely related to slag compositions,for example,Ca2SiO4 formed in CaO-SiO2-Al2O3 system and MgAl2O4 formed in CaO-SiO2-Al2O3-MgO system.