Pore Structure, Permeability, and Alkali Attack Resistance of Al 2 O 3 -C Refractories
- PDF / 1,899,899 Bytes
- 9 Pages / 593.972 x 792 pts Page_size
- 59 Downloads / 195 Views
ODUCTION
REFRACTORIES in the transition zone of a cement kiln, BF stack, hot blast stove, total oxygen combustion glass tank, gasifier, etc. are usually attacked by alkali vapor in service.[1–5] However, alkali corrosion mechanisms of refractories are far from sufficient owing to the relatively long service life of the refractories, as well as the difficulty in understanding the complete exposure history.[6,7] Generally, it is recognized that a gaseous alkali substance enters a refractory through open pores, reacts with certain components in the refractory at high temperature, or condenses, concentrating at cool areas. Then cracks gradually form in these areas under longterm thermal shock, eventually causing the destruction of the refractories. So the apparent porosity of refractories is used to evaluate the capacity of gaseous attack resistance. In a cement kiln, for example, the gaseous corrosion of magnesia-spinel bricks can be effectively retarded by lowering the apparent porosity.[7,8] Actually, in carbon blocks for the BF, the pore size and
YIBIAO XU, Postdoctoral Student, SHAOBAI SANG and SHUJING LI, Associate Professors, YAWEI LI, LEI ZHAO, and YUANBING LI, Professors, and BO REN, Postgraduate Student, are with The Key State Laboratory Breeding Base of Refractories and Ceramics, Wuhan University of Science and Technology, Wuhan 430081, People’s Republic of China. Contact e-mail: sangshaobai@ 126.com Manuscript submitted August 9, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS A
permeability are more important evaluation indexes than the apparent porosity, because hot metal can hardly infiltrate into the carbon blocks with microporous structure and low permeability.[9–13] Therefore, it can be deduced that the pore structure and permeability of refractories also have great influence on the refractories’ alkali attack resistance, because a gaseous alkali substance penetrates into refractories through open pores just like the hot metal does into carbon block. However, few specific reports can be found about the relationship between pore structure, permeability, and the alkali resistance of refractories. Like carbon blocks, Al2O3-C refractories have been widely used in blast furnaces (BFs) due to their relatively high strength, high thermal conductivity, low permeability, good alkali resistance, and low fabrication cost.[14,15] To further understand the mechanism of vapor corrosion on refractories, alkali attack on Al2O3C refractories with different pore structures and permeabilities will be carried out in the present work. To adjust the pore size of the Al2O3-C refractories, several approaches are adopted in the preparation process. (1) Ultrafine Al2O3 powders and microsilica are used based on the dense packing theory.[9,16,17] (2) Silicon powder is introduced to form new phases such as SiC/mullite at high temperatures to optimize the pore structure in the matrix, as reported in previous works.[17–20] Then the microstructure, pore size distribution, and permeability of the prepared Al2O3-C refractories and their corrosio
Data Loading...
