水泥熟料及碱盐对方镁石-镁铝尖晶石砖的侵蚀行为

Corrosion behavior of cement clinker and alkali salts to periclase-spinel bricks

对以电熔镁砂、电熔镁铝尖晶石为原料制备的方镁石-镁铝尖晶石砖进行了不同温度的抗侵蚀试验,研究了水泥熟料及碱盐(K2SO4、KCl)对方镁石-镁铝尖晶石砖的化学组成、矿物组成及显微结构的影响,从而研究其对方镁石-镁铝尖晶石砖的侵蚀行为。结果表明:1)水泥熟料对方镁石-镁铝尖晶石砖的侵蚀过程主要是向砖内渗透,侵蚀砖中方镁石及基质M2S生成低熔物CMS而使M2S、方镁石不断溶解,使砖形成致密的变质层,温度越高,渗透和侵蚀作用越剧烈。2)碱盐通过对砖的液相渗透和气相扩散,在砖中与杂质发生化学反应,生成新的气体并挥发,使砖的表层因碱盐的化学侵蚀而疏松,深层因残碱的沉积而致密。3)实际使用中,碱盐在高温层侵蚀砖中的方镁石及结合相而使高温层疏松,使水泥熟料大量渗透和侵蚀而形成致密的变质层;碱盐在低温层的析晶、沉积,使致密的变质层变厚。而致密且较厚的变质层在温度波动时将导致方镁石-镁铝尖晶石产生严重的结构剥落。

Fused magnesia and fused magnesium aluminate spinel （MA） were used to prepare the periclase-MA bricks for corrosion resistance tests at different temperatures. The influences of cement clinker and alkali salts （K2SO4 and KCI） on the chemical composition, mineral phase and microstructure of periclase-MA brick were researched to characterize their corrosion behavior to periclase-MA bricks. The results show that： （1）the clinker penetration into the bricks at high temperatures is the main corrosion process during which the clinker corrodes M2S in the matrix and MgO in the brick forming monticellite （CaO. MgO . SiQ2,CMS） and consequently M2S and MgO dissolve continuously, a dense deteriorative layer forms ;the higher the temperature and the more obvious the penetration and corrosion;（2）through the liquid penetration and gas diffusion ,the alkali salts react with the impurities in the brick forming new gases to emit;the brick surface becomes loose because of chemical corrosion of alkali salts,and the deeper layer of the brick becomes dense due to the sediment of residual alkalis; （3） in the actual use, alkali salts corrode periclase and binding phases in the brick resulting in the loose high temperature layer which makes much cement clinker corrodes and penetrates forming dense deteriorative layer; in low temperature layer the crystallization and sediment of alkali salts make the dense deteriorative layer thicker and this layer will result in the severe structure spalling of periclase-MA bricks when suffering temperature fluctuation.