Experimental Study On High-quality Of Silica Brick For Coke Oven

In this paper, physicochemical and thermodynamic properties of 4 main kinds of silicas in Hunan province, influence of mineralizer and techical condition on silica brick for coke oven were anlysised by means of chemical analysis, XRD, IR and OM. This study can help refractories enterprises in south China resolve their problem such as low content tridymite and properties of silica brick for coke oven. The main conclusions are summarized as follows:The main 4 kinds silicas of Hunan province on physicochemical and thermodynamic properties were analysised. The results showed that: major chemical composition of silicas was SiJO₂, its content of 1^#,2^#,3^#,4^# silicas respectly was 98.24%, 99.22%, 99.10%, 97.77%, main chemical composition and physical properties of them meet requirements of high quality silica brick. Impurities ingredients were Al₂O₃,Fe₂O₃ and CaO, the main harmful impurity was Al₂O₃, and the content of it as follows: 0.69%,0.33%,0.33%,1.04% . The results analysised by XRD and OM showed that: because of big grains,low density and loose structure, high content of Al₂O₃, 4^# silicas inhibit to transformation sequence of polymorphs of quartz. Because of small grains and tight structure, low content of Al₂O₃; 2^#,3^# silicas can improve transformation sequence of polymorphs of quartz.To understand the effects of the mineralizer on poperties of silica bricks of coke oven. Specimens were added FeO+ CaO,Fe₂O₃+CaO,MnO+CaO as mineralizer. The results showed that FeO+CaO was the best mineralizer for transfomation of quartz to tridymite. Proper addition of FeO+CaO can improve the sintering and strength of the castable. However, excessive addition will reduce the properties of silica brick. Under the testing condition, the optimum addition of mineralizer was 1.0%FeO+ 2.0%CaO.To understand the effects of technical condition on properties and transformation sequence of polymorphs of SiO₂ silica bricks. Different grain size distribution, firing temperature, soaking time and shaping pressure on preparation of silica brick of coke oven were studied. The results showed that suitable grain size distribution,firing temerature,soaking time and shaping pressure really can reduce the density,swelling and residual quartz; improve the content of tridymite. Under the condition of this test, the best technical condition followed as : with 15:20:15:50 from coarse to medium, small and powder grain size distribution; The critical size of no more than 3mm and less than 2mm; shaping pressure at 50MPa, the rate of firing during 1100-1250℃, 1250-1350℃, 1350-1430℃respectly follow as:10℃/h,5℃/h,1.5℃/h, firing at 1430℃and more than 40 hours of soaking time.