含TiC熔渣对MgO-C砖的侵蚀机制

Corrosion mechanism of TiC-containing slag to MgO-C bricks

为了有效回收钛资源和满足高温碳化—低温氯化工艺对耐火材料的要求,采用热力学计算、XRD和SEM等研究手段分析了高温碳化过程中含TiC熔渣对MgO-C砖的侵蚀机制。热力学计算结果表明:1)温度越高,熔渣的侵蚀能力越强,当温度低于1560℃时,熔渣与MgO-C砖反应生成MgAl_(2)O_(4)、Mg_(2)SiO_(4)和MgTi_(2)O_(4)等高熔点物相,对MgO-C砖侵蚀较慢,但当温度高于1560℃时,前期生成的高熔点物相逐渐溶解,从而对MgO-C砖侵蚀加剧;2)随着碳化反应的进行,熔渣中TiO_(2)含量降低,TiC含量逐渐增加,熔渣对MgO-C砖的侵蚀逐渐减弱。用后MgO-C砖的显微结构分析发现:镁碳砖的侵蚀机制是气氛中氧气与碳反应,形成气孔,熔渣中TiO_(2)和SiO_(2)等再与基质MgO反应先形成高温中间相,随着反应进行再形成低熔点相,导致MgO-C砖逐渐被侵蚀。

To effectively recover titanium resources and meet the requirements of the high temperature carbonization-low temperature chlorination process to refractories,the corrosion mechanism of TiC-containing slag to MgO-C bricks during high-temperature carbonization process was analyzed through thermodynamic calculations,XRD and SEM.The thermodynamic calculation results show that:(1)the higher the temperature,the stronger the corrosion ability of the slag;below 1560℃,the slag reacts with MgO-C bricks to generate high melting point phases such as MgAl_(2)O_(4),Mg_(2)SiO_(4),and MgTi_(2)O_(4),which slow down the corrosion rate of MgO-C bricks;however,at above 1560℃,the high melting point phases generated in the early stage gradually dissolve,thereby intensifying the corrosion to MgO-C bricks;(2)as the carbonization reaction progresses,the TiO_(2) content in the slag decreases,while the TiC content gradually increases,and the corrosion of the slag to MgO-C bricks gradually weakens.According to the microstructure analysis of the used MgO-C bricks,the corrosion mechanism of MgO-C bricks is that O_(2) in air reacts with graphite forming pores;TiO_(2) and SiO_(2) in the slag react with MgO and the matrix of the brick to form high-temperature intermediate phases first,and as the reaction progresses,low melting point phases form,leading to the gradual corrosion of MgO-C bricks.