Showing papers on "Magnesite published in 1985"

High-temperature structure refinements of calcite and magnesite

Abstract: Crystal structure parameters have been determined from X-ray intensity data collected for single crystals of calcite at24,200,400,600,750, and 800'c, and magnesite at24,2N,3(f|., 400, and 500"C. Refinements utilizing a rigid-body model and an anisotropic thermal model show good agreement in thermal parameters and R values, suggesting that the rigid-body model is valid over the temperature range studied. Comparison between the two minerals' response to temperature shows markedly different behaviors of the CO3 group. The negative thermal expansion along a for calcite is explained in terms of the large libration parameters and thermal expansion coeffrcients. Mean thermal expansion coeflicients are calculated for selected interatomic distances. A libration correction was applied to bonds within the carbonate group, and the corrected C-O interatomic distance increased more rapidly in calcite than in magnesite. Mean thermal expansion coeflicients for the Ca-O interatomic distance fc""_o : 15.9 x 10-6.C-1) in calcite and the Mg-O distance in magnesite fa"r_o:15.g x 10-6"C-l) are comparable to those found in other CaOu and MgOu octahedra. At 800"C the I : odd reflections of calcite are unobserved preferentially (I < 2o), possibly indicating the onset of orientational disorder. However, no phase transitions were found, and the decrease in intensity may be a result of increased thermal motion of the oxygen atoms.

Periclase-chromite refractories from fused materials

Abstract: Experiments were carried out to obtain high-grade fused chromite-periclase. It is shown that during the melting of batch consisting of raw magnesite and chromite ore we eliminate the process of reducing the chromite ore to metallic ferrochromium, which adversely affects both the content of Cr2O3 in the fused material, and also the commerical appearance of the resulting refractories. We developed a technology for preparing periclase-chromite refractories with chromite-periclase constituents. The goods obtained possess good physicoceramic properties and a low content of silicates. The articles thus prepared were used to make the linings of the most critical parts of converters, Kivset unit in PZhV furnaces, which allowed an increase to be made in the duration of campaigns for these units of 1.5–2 times.

Reclaiming chrome-magnesite or magnesite-chrome brick fragments

Abstract: Magnesite-chrome and chrome-magnesite brick fragments are sorted, stored, opt. moistened, and then crushed to a particle size of less than 50 mm. in the moist condition or while spraying with water and opt. simultaneously magnetically separating the iron content. The crushed material is stored for 3-5 weeks with periodic moistening with water and washed until liq. flows out from the material.

Studies on the Sinterability of Pure and Al2O3 Containing Forsterite Prepared from Rice Husk Ash

Abstract: Forsterite (2MgO.SiO2), a well-known non-feldspathic high frequency insulator (5 MHzs), was prepared by using magnesite/MgCO3and rice husk ash obtained after controlled burning as a source of MgO and SiO2 respectively and sintered at 1200°, 1250° and 1300°C for 1, 2, 3 and 4 hrs at each temperature. Effect of minor additive like A12O3 (added up to 5 wt %) on sintering was studied. Data were analysed using the empirical equation D = K log t + C and Arrhenius equation. Addition of 5 wt % Al2O3 has shown higher density (2.5 gm.cm−3) than that of pure forsterite (2.06 gm.cm−3) fired at 1300°C for 4 hours.

Experience and prospects for beneficiating magnesite ores from the satkinsk deposits (Review)

Abstract: At the Magnezit Combine for the first time in our country magnesite has been dressed in heavy suspensions. Experience accumulated during the operation of heavy-medium equipment facilitated a significant improvement in the production scheme and equipment formulation for separation of the ores in heavy suspension. The introduction of heavy-medium separation permitted the retreatment of depleted ores and dumped material. The yield of concentrate increased by 11.5% with a simultaneous increase in the yield of tailings by a factor of 3.76 and a reduction in the cost of the handling of 1 ton of concentrate by 71.9 kopecks. Work is being done to find the optimum version of reprocessing the screenings from heavy-medium fractions 8-0 mm. The most promising methods of beneficiating magnesite are deemed to be flotation beneficiation, photoseparation, and gravitational dressing, using heavy-medium turbocyclones. Work is also being done to study further the prospective method of chemical beneficiation of magnesite raw materials.

Method of reprocessing rubble from magnesite chromium bricks or chromium magnesite bricks, rubble reprocessed by the method and the use thereof

Abstract: The invention relates to a method of reprocessing rubble from magnesite chromium bricks and chromium magnesite bricks, the rubble material being stored after sorting and, if appropriate, being moistened daily with water over a period of 1 to 3 weeks and being comminuted in the moist state or with spraying of water to grain sizes below 50 mm, and this comminuted material being stored for a period of 3 to 5 weeks with a periodical moistening with water and being washed out until liquid emerges from the material. The comminuted and washed-out material is comminuted to grain sizes of 0 to 6 mm and used for producing refractory bricks and especially rotary kiln bricks for rotary cement kilns.

Flotation Studies on Low Grade Magnesite Deposits from Sujikonda near Daroji Bellary district, Karnataka State

Abstract: Magnesite, an important basic refractory raw material, has been in short supply in recent years. To find an alte-rnative to high costlow boron containing sea water magne-site, users have been looking more towards sources of a natural magnesite. Magnesite ( MgCO3 ) is commonly found in granular, compact earthy masses occurring as amorphous or crystalline deposits. The amorphous type of deposits are the most common variety found as veins in serpentine rocks. The low grade ores produced do not meet the chemical purity required by the consuming industries (Table-1). The low grade ores have to be upgraded by physical benefi-ciation methods to render them usable, besides, conserving high grade reserves of magnesite. in view of the proposed Vijayanagara steel plant in Toranagallu, the occurrence of Sujikonda magnesite deposit close to the steel plant attains greater significance. The magnesite deposit of Sujikonda area is of low grade with MgO = 29:60 wt.% ; Ca0 = 5.61 wt. %; Si02 = 3.84 wt. %; and R2 03 = 31.04 wt. %. In the present investigation the authors carried out experiments to understand the flotation behaviour of low grade magnesite.

Use in open-hearth roofs of periclase-chromite parts made from electrofused periclase-chromite

Abstract: A production test was made in the roof of a 180-ton open hearth of periclase-chromite parts produced by the Magnesite Combine from electrofused periclase-chromite.