| The stable working with long life of blast furnace has great significance for thewhole iron making process, as the blast furnace iron craft would be predominant in along period. Although the life of the blast furnace depends on the initial design,instruments configuration and refractory application et al in some extent, the effect ofroutine maintenance on the life of blast furnace should not be ignored, after its firstrunning. Specific to the refractory materials of blast furnace in cast house, mainlyrelates to the quality, application and maintenance technology of refractory castable formain through and tap hole mixture. While, online maintenance technology at hightemperature is the main approach to increase their service time for the refractoryproducts used in main body, thus to prolong the life of the blast furnace.Colloid bonded Al2O3-SiC-C castable for blast furnace main through has beendeveloping recent years, but it has not been systemticly and theroiticly researched, andnot widely used in industrial practice yet. Al2O3-SiC-C castable with ultra low cementstill occupied the main market of the cast house refractory. With the progress of modernmetallurgy technology, the blast furnaces become more and more huge and effective,that means the increment of the iron cast frequency and its total amount, namely, therefractory castable for main through face a grim challenge for its severe serviceconditions, such as intensified erosion, corrosion and temperature fluctuations. Both theinstallation instruments and refractory materials have a remarkable progress after almost20years’ development, and almost basically meet the fundamental requirement ofonline maintenance technology at high temperature. However, the domestic refractorymaterials for online maintenance technology at high temperature still has a great gapcompared with developed countries, such as America, England and Japan, especially forthe fast drying, rapid hardening.So, in this paper, the performance of traditional Al2O3-SiC-C castable for blastfurnace main through has been improved through microstructure and compositionsoptimization. Also, a Al2O3-SiC-C pumping castable and a Al2O3-SiC-C gunningmaterial using colloid as binder have been developed, both of these two materials havebeen tested through a small scale live installation, the derived useful conclusions are as follow:Based on the design and analysis method of, the influences of Particle sizedistribution (q), PAAS, STPP and FDN on the flowability of Al2O3-SiC-C castable havebeen studied. Dataes derived by extreme difference analysis indicate that PAAS has themost obvious effect on the system’s flowability, STTP takes the second place, while theeffect of FDN seems slight. In additional, the above factors also have some effects onthe cold crushing strength, modulus of rapture, bulk density and apparent porosity.Based on the measured viscosity, zeta potential, and apparent heat released duringcuring of Al2O3-SiC-C slurry with different dispersants, the action mechanism of eachdispersant has been explored, and it is believed that their effect on the perproties ofAl2O3-SiC-C castable realized through affecting the hydration process and products ofcement component. The optimal experiment scheme suggested by the orthogonalexperiment should have a q=0.23, and include0.05%of PAAS,0.025%of STPP and0.1%of FDN.Al2O3-SiC-C castables with different particle size distribution were fabricated viathe q value vary from0.21to0.25, while the dispersants and their contents were fixed.The mechanism of temperature and particle size distribution acting on the porecharacteristics evolution has been revealed, based on the evaluation of apparent porosity,permeability, and pore size distribution of Al2O3-SiC-C castables treated at differenttemperatures. Results indicate that the temperature has greater influence on the porestructure evolution process, because of its effect on the reactions occurred duringheating, particle size distribution has a little effect despite of the pore size distributiontend to be focus and continuous with q=0.23or0.24. The slag resistance test carried outusing inductive furnace proof the better slag resistance of Al2O3-SiC-C castable withfocus and continuous pore size distribution.Thermal dynamic calculation and experimental results both suggest that the Cr2O3introduced into Al2O3-SiC-C castable would not transfer to Cr6+, in spite heat treated inthe air atmosphere, but just exists in the form of Cr3C2or original Cr2O3. Experimentsfocused on the effect of1wt%Cr2O3micro-powder indicate its addition could improvethe flowability, mechanical strength of Al2O3-SiC-C castable, but has no obvious effecton the bulk density and the apparent porosity, while it plays a prominent role inimproving the slag resistance of castable. The possibility to synthesize Ti(C,N) by in-situ reactions between TiO2andcomponents of Al2O3-SiC-C castable has been confirmed by thermal dynamicsimulation carried out by Factsage, as well as the experimental results. The directintroduction of TiO2could significantly improve the flowability of Al2O3-SiC-Ccastable, thus increase its packing density and decrease the porosity, thereby, enhancethe mechanical performance.Thermal theoretic calculations and tested thermal shock resistance results showsuitable amount of TiO2would be benefit to the thermal shock resistance improvement.In additional, the oxidation resistance has been also enhanced attributed to the carbonexistence form transformed from free carbon into chemical bonded carbon through insitu reaction. Meanwhile, in situ synthesized Ti(C,N) has made a increase of the slagviscosity in the local area between the refractory and slag, thus slow down thepenetration of slag into the deep structure of refractory, and finally, the slag resistance ofAl2O3-SiC-C castable has been improved.Selecting suitable particle size distribution, and adding12wt%~14wt%of silicacolloid as binder, excellent flowability of Al2O3-SiC-C castable has been derived,thereby, the pumping capacity has been realized. Using brown fused corundum and highgrade bauxite as aggregate, silicon powder as antioxidant and cyanite as expansionagent, and meanwhile, introducing effective quick-setting additive, the performance ofdeveloped Al2O3-SiC-C pumping castable is good.Al2O3-SiC-C gunning mixtures with different particle size distribution have beenfabricated applying Andreessen model in which the critical grain size is selected as8mm and q values vary from0.21to0.27with a interval of0.01. Evaluation of theirflowability, bulk density, apparent porosity and mechanical properties normaltemperature show that0.21might be the best q value than the others, as with q=0.21,Al2O3-SiC-C gunning mixture gains a flowability of190mm, a bigger density, lowerporosity and better mechanical strength. Based on the above results, the density ofmaterial has been improved by adjusting the aggregate type, and4wt%of siliconpowder is believed to be suitable for this system to have better oxidation resistance.Successively, an effective quick-setting additive has been selected with the assist ofPhysical MCR301reometer and zeta potential meter, which give some usefulrheological characteristics dataes of the sully of Al2O3-SiC-C gunning mixture with different dispersants and quick-setting additives. Live experiment has confirmed thedeveloped gunning mixture has a low return rate, the capacity of quick setting and to bedried fast. |
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