اثر اصلاح تركيب منيزيت ايراني بر ريزساختار و خواص آجرهاي ديرگداز منيزيت-كرومي مصرفي كوره دوار سيمان

The influence of the composition modification in the microstrure an‎d properties of magnesite-chrome rotary kiln refractory bricks prepared from the Iranian magnesite

نانو فناوري

Refractories are materials that tolerate the influences of the external parameters on the furnace bodies through a high resistance against high temperatures, abrasion, mechanical effects, an‎d thermal shocks. In the alkaline an‎d alumina-based refractories, the major oxide constituents an‎d their amounts such as Al2O3 an‎d MgO determine the thermal behavior of the refractories an‎d the minor constituents such as chromium oxide, iron oxide, etc. lead to special physical an‎d chemical properties in the refractory. A comparison of the refractories of a rotary kiln shows that the alkaline refractories, i.e. the ones installed in the firing region, experience the highest erosion. Consequently, according to the requirements of refractories, local mineral mines, an‎d also the necessity of the inorganic waste applications to reduce the detrimental effects on the environment, in this research focuses on the compositional modification of Iranian magnesia, producted via leaching of serpentine ore, for application in rotary cement kilns. The specific surface area, thermal analysis, chemical composition, an‎d the constitutional phases of the Iranian an‎d foreign magnesia (dead burned) were investigated. Also, the effects of sintering temperature an‎d compositional modification using iron an‎d alumina additives on the thermal shock resistance, an‎d physical, an‎d mechanical properties of the magnesia-chromium an‎d magnesia-spinel brick bodies were clarified. Also, the effect of clinker corrosion on the magnesia-chromium body was investigated using the crucible corrosion test. Characterization methods of Brunauer-Emmett- Teller (BET), thermal gravimetry (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray fluorescence (XRF), optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-rat spectroscopy, as well as measurements of density, porosity, cold compressive strength (CCS), thermal shock resistance, an‎d hot flexural strength were applied to determine the above factors. The characterization results of the Iranian magnesia showed a specific surface area of 114m2/g with a 98% purity. Increasing the sintering temperature from 1550℃ to 1700℃, in the case of foreign magnesia bodies, increased the density an‎d decreased the porosity, from 2.5 to 2.8 g/cm3 an‎d from 20.6% to 18.3% for the magnesia-chromium; from 2.4 to 2.8 g/cm3 an‎d 18.9% to 16% for the magnesia-chromium, respectively. In the case of Iranian magnesia bodies, this temperature enhancement raised the density from 2.4 to 2.7 an‎d from 2.3 to 2.6 g/cm3 for the magnesia-chromium an‎d the magnesia-spinel, respectively. But it decreased the porosity from 18.2% to 17.4% an‎d from 20.6% to 17.3% for the Iranian magnesia-chromium an‎d magnesia-spinel bodies. The cold compressive strength increased from 398 to 568 kgf/cm3 an‎d from 395 to 576 kgf/cm3 for the foreign magnesia-chromium an‎d magnesia-spinel bodies, respectively. While it raised from 428 to 689 kgf/cm3 an‎d from 513 to 686 kgf/cm3, for the Iranian magnesia-chromium an‎d magnesia-spinel bodies, indicating the advantages of the temperature enhancement an‎d application of the Iranian magnesia. An investigation of the thermal shock resistances for these two bodies showed that the Iranian magnesia-containing sample sintered at 1700℃ had the highest thermal shock resistance among all samples. Microscopic observations also indicated better sintering at elevated temperatures, confirming the better physio-chemical properties. Up to 8% iron oxide addition to the Iranian magnesia-chromium body increased the density from 2.8 to 3.1 g/cm3 an‎d decreased the porosity from 18% to 17.1%. However, the results of hot

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