高炉炉缸炭砖环裂机制初探

Discussion on Mechanism of Ring Crack in BF Hearth

热力学计算表明,高炉炉缸仅存在纯的碱金属蒸气,不存在碱金属的氧化物和碳酸盐,并且碱金属蒸气压很低,不是对炉缸炭砖进行侵蚀的直接原因,而当前大多文献认为环裂是碱蒸气侵蚀的结果。炭砖传热性能较差时炭砖内部热应力较大,诱发炭砖产生微裂纹,纯的碱金属蒸气通过炭砖的微裂纹不断向炭砖低温区流动和扩散,微裂纹是环裂产生的诱因。在炉缸的高压环境下,800~900℃时钾蒸气在微裂纹中液化,然后与炭砖的硅铝质灰分反应,造成灰分体积膨胀30%~50%,加剧炭砖微裂纹扩展,形成裂纹,是环裂产生的必要条件。计算表明,只有碱蒸气富集液化后才能与一氧化碳共同作用,在裂纹里形成活性炭沉积,这种反应持续不断地进行,对炭砖裂纹进行持续的膨胀挤压,炭砖裂纹不断扩展,最终割裂炭砖形成环裂。提高炭砖传热效果和阻止炉缸CO窜气是避免炭砖产生环裂的根本措施。

In the BF hearth,alkali oxides and alkali carbonates were transformed into purified alkali metal vapor,and the pressure of alkali vapor was very low.Alkali vapor was not the direct cause for the erosion of carbon brick in BF hearth.The erosion of carbon bricks was due to the alkali vapor,and it′s obviously wrong.Thermal stress was very high when the temperature gradient was high in carbon brick,and then it caused microcracks in carbon bricks,and alkali vapor can flows and spread through these microcracks into the low temperature field in bricks,so thermal stress was the precondition for erosion of carbon bricks in BF hearth.At high pressure in BF hearth,the alkali vapor liquidized between 800-900 ℃ in those microcracks,gradually,it enriched in these micrcracks.The volume of ash in the carbon brick′s microcracks expanded by 30%-50% after it reacted with liquid alkali,and then the microcracks expanded because of the expansion of ash′s volume,and this was the necessary condition for the ring crack of carbon bricks in BF hearth.Calculation proves that,in the microcracks,only liquid alkali can be react with carbon monoxide and then depositcarbon forms,so the microcracks could constantly expand as long as this reaction happens,and then cut off carbon bricks and ring crack forms.It was of great importance to improve the heat transfer performance of carbon bricks and prevent carbon monoxide penetrating inside of carbon bricks for the avoidance of ring crack.