干熄焦炉用氮化硅结合碳化硅过梁砖的破损机制

Degradation mechanism of Si3N4 bonded SiC lintel bricks for dry quenching coke oven

比较了干熄焦炉斜道区用后2年和6年的氮化硅结合碳化硅过梁砖及其原砖的体积密度、显气孔率、常温抗折强度及化学组成变化,分析了不同使用年限和不同使用部位(分别为风道侧、炉腔侧、中心部位)过梁砖的物相组成、显微结构和孔径分布,以了解其侵蚀劣化过程。结果表明:N2为主以及CO、CO2、H2、O2和CH4共存的弱氧化、还原交替的混合气氛中,当氧化气氛占主导时,过梁砖不断遭受CO2、O2等氧化介质的氧化侵蚀,氧化产物SiO2发生多晶转变产生膨胀以及裂纹破坏;而当含CO、H2等的还原气氛占主导时,氧化产物SiO2又会被分解,使结构进一步疏松破坏。因此,氧化和还原反应的交替侵蚀是氮化硅结合碳化硅过梁砖劣化的重要原因之一。

The Si 3N 4 bonded SiC lintel bricks used in inclined channel area of dry quenching coke oven for 2 years and 6 years as well as the original bricks were compared in terms of the bulk density,apparent porosity,cold modulus of rupture and chemical composition.The phase composition,microstructure and pore size distribution of the lintel bricks with different service periods and different service positions (flue side,chamber side and core) were analyzed in order to understand their erosion degradation process.The results show that N 2 is the majority and CO,CO2,H2,O2 and CH 4 coexist,so the mixed atmosphere alternates between weak oxidation and reduction;when the oxidation atmosphere is dominant,the lintel bricks are corroded by oxidizing media such as CO2 and O2,and the crystal transformation of the reaction products SiO2 leads to expansion and cracks;while when the reduction atmosphere containing CO and H2 is dominant,the oxidation product SiO 2 will be decomposed,loosening the structure further.Therefore,the alternating corrosion of oxidation and reduction reactions is one of the important reasons for the deterioration of silicon nitride bonded silicon carbide lintel bricks.