Process-water residues in fireclay and magnesia refractory production

Conclusions Particle size analyses of process water residues from fireclay and magnesia refractory production enable settlement rates to be established within water cleaning plant.From wet volume tests on residues it is possible to work out sludge volumes and cleaning cycle times for settlement plantl.Residues consisting of grog, magnesite, chromite, magnesite-chromite mixtures, and grog-clay mixtures with seven-tenths grog or over, should be removed mechanically from a horizontal settling tank after 1 day or longer, e.g., with a bucket crane or similar mechanism. A clay residue should be pumped out, but if it stands for 2 days or more it may be dug out.A coagulated residue of clay or a clay-grog mixture with seven tenths clay or more should be pumped out, but a 73 clay-grog mixture can be removed mechanically after settling for 3 days.Coagulated grog, magnesite, or chromite residues can be moved hydraulically for the first day, but if they stand longer they must be moved mechanically. If sludge is to be moved mechanically from a settling tank the clean water over it must be removed first, and appropriate equipment must be allowed for. If a sludge is to be removed hydraulically it must first be stirred up in some way.Translated from Ogneupory, No. 2, pp. 11–16, February, 1969.     

Plugs and nozzles for intermediate ladles in continuous steel casting with automatic jet control

Conclusions We prepared and tested in service refractories satisfying the requirements of automatic casting from the intermediate ladle in continuous steel-casting plants. The high-alumina conical plugs and unfired magnesite inserts fixed to fireclay nozzles can be recommended for further use.Translated from Ogneupory, No. 1, pp. 32–35, January, 1970.     

Magnesite beneficiation in heavy suspensions

Conclusions A department for magnesite beneficiation in heavy suspensions with an output capacity of 1 million tons/ yr has come on stream at the Magnezit Combine.The flow sheet of the magnesite beneficiation includes beneficiation of the small and large ore fractions in separate sections in two stages using conical and cylindrical separators. The beneficiation of magnesite containing up to 5% impurities in place of the 15% envisaged in the design project should be carried out in a single stage.It was established that the process efficiency of magnesite separation depends on the lump size of the original magnesite, the type and productivity of the separators, and the structuromechanical properties of the suspension.The beneficiation of the magnesite in heavy suspensions gave concentrate of grades 1 and 2 containing 45–46% MgO, 0.5–0.8% SiO₂, and 0.8–1.2% CaO. The concentrate yield was 85–95%.The wear of MKhS and PShS bricks produced from the powder of the beneficiated magnesite is 10–15% less than that of bricks produced from the powder of ordinary magnesite.Translated from Ogneupory, No. 1, pp. 31–37, January, 1978.     

Investigating and testing phosphate bonded firebrick

Conclusions An addition of orthophosphoric acid to fireclay body contributes to strengthening and sintering of the body, and also improves its crystallization, which means that the body can be used as an unfired material for making ramming bodies and products.The optimum addition is 2–3% (on 100%) of 85%-orthophosphoric acid, for the grain-size composition of grog and clay content which were used in the above experiments.The strength of the body increases with an increase in the amount of clay constituent; and with the use of finer fractions of clay, with an increase of up to 600°C in the heat process temperature.To obtain air stable products it is necessary to heat process them at temperatures not below 400°C.The use of ramming fireclay bodies will increase the life of bottoms of steel casting ladles and give big saving effects.Translated from Ogneupory, No.6, pp. 4–10, June, 1967.     

Increasing the spalling resistance of fireclay refractories by adding combustible organic liquids and m ineral a dditives

Summary The combined addition of hydrophobic organic liquids and mineral (refractory) additions improves the structure and physico-mechanical properties of fireclay refractories. The spalling resistance is greatly increased.The spalling resistance of fireclay specimens assessed by the number of heat cycles before destruction with the combined action of mazut and mineral additives is 2.0–2.8 times greater than with the manufacture of the articles without these additives.The increase in spalling resistance occurs owing to the development of microcracks in the structure around the grains of grog, with a simultaneous reduction in the modulus of elasticity and coefficient of thermal expansion and also an increase in deformation before failure (/E) of the material.The addition to the hydrophobic organic liquid (mazut) of fine powders (magnesite, alumina) permits not only a considerable increase in spalling resistance, but also a certain reduction in the porosity and an increase in the strength of the products.Separate introduction of the additives (mazut on the grog, magnesite and kaolin to the bond) gives worse results compared with the above method (lower spalling resistance, increased expansion).Thus it was shown that the main factor determining the resistance of fireclay refractories against thermal strains is the nature of the contacts of the surfaces of the grains of grog and the bond.Semiplant testing of the method showed that the addition of 5% mazut and 5% calcined kaolin (or magnesite) doubled the life of fireclay saggers.     

Industrial production of dense powder from Satkinsk magnesite beneficiated by flotation

Conclusions The beneficiation by flotation of Satkinsk magnesites of the fourth grade with fine mutual growth of minerals allows us to obtain from them a product containing (calculated on the calcined substance) 94.0–96.5% MgO, 0.3–0.4% SiO₂, and 1.40–2.87% CaO.A technology was developed for producing dense powder from the magnesite beneficiated by flotation, specifying combined fine grinding of it with caustic magnesite in a tube mill, briqueting on smooth roller presses, and burning the briquet in a rotary kiln.In industrial conditions using the beneficiated (flotation) and briqueted Satkinsk magnesite, firing in a rotary kiln, we obtained high-quality powder with an apparent density of 3.13–3.32 g/cm³, with a developed direct bond in the periclase crystals. The powder of all fractions is homogeneous in chemical composition, does not contain free calcium oxide, and may be used completely without aging for producing magnesite refractories for critical locations in furnaces.Translated from Ogneupory, No. 2, pp. 5–11, February, 1972.     

Physicochemical processes during the contact of steel with casting nozzles

Conclusions The results of physicochemical processes taking place in casting nozzles depend on the content of the steel of chemically active components and the composition of the refractory. An examination of the phase diagram of the systems forming contact zones in the nozzles enabled us to obtain a nomogram for determining the degree of erosion or tightening up of the nozzles in the intermediate ladles as a function of the composition of the refractory material and the content of aluminum in the steel being cast.In order to explain the stable feed of metal from the intermediate ladels in continuous steel casting plant in the crystallizer we recommend the casting of rimmed steel through magnesite nozzles, killed steel with a content of less than 0.01% aluminum through zircon nozzles, and containing more than 0.01% aluminum through fireclay (35–40% Al₂O₃).Translated from Ogneupory, No. 6, pp. 33–38, June, 1973.     

Magnesite from Safonikha deposit

Conclusions Provided the Safonikha magnesite is blended, it can be used to make high-quality magnesite brick with a forsterite bond with apparent porosity 12–16%, bulk density 2.94–3.04 g/cm, compressive strength 1500 kg/cm and refractoriness-under-load of 2 kg/cm, 1670–1720°.The magnesite represented by the laboratory samples Nos. 1, 6, 8, 11, 13 and 14, and the second technological sample come up to the requirements for raw material for magnesite metallurgical powders. The magnesite in the remaining samples can also be used for making metallurgical powders, provided it is first enriched.     

The sintering of flotation-concentrated magnesite

Conclusions An investigation was carried out of the sintering of flotation-concentrated magnesite containing (in terms of the calcined substance) 95.3% MgO, 0.52% SiO₂, and 2.0% CaO.The process parameters for the production of a high-density (open porosity less than 11%) sintered powder from concentrated magnesite proved to be as follows: 15% caustic magnesite added as binder to the concentrated magnesite, grinding the mix of concentrated and caustic magnesites in tube mills to a powder of a specific surface greater than 6000 cm²/g (i.e., containing 98% particles smaller than 60), wetting with water to a moisture content of 6–8%, forming 10–12-mm-thick briquets on a smooth-roller press at a pressure of 1000–1200 kgf/cm², and firing the briquets in a rotary kiln at a flame cone temperature of 1760°C.This technology for the mass production of a high-density, good-quality powder from concentrated magnesite precludes the use of a sintering additive and thermal activation both of which lower the refractoriness and increase the net cost of the finished product.Translated from Ogneupory, No. 2, pp. 3–7, February, 1977.     

Cordierite ceramics—Spalling-resistant high-melting refractories

Conclusions The production technology of cordierite refractories from fireclay and magnesite differs from other processes in that the components have to be finely ground.The components must be accurately apportioned and the mass thoroughly mixed preferably in batch mixers. Otherwise, the production process of cordierite refractories does not differ from that of chamotte brick.The use of fireclays with a high Al₂O₃ content (38%) and magnesite eliminates the need for commercial alumina.     

Circulating water in systems for the wet purification of air from dust

Conclusions In Systems for the wet purification of air from calcined magnesite and chamotte dusts the clarified waste waters can be used repeatedly without coagulation. If the water is contaminated with clay coagulation with lime is necessary.Translated from Ogneupory, No.4, pp. 45–48, April, 1968.     

The influence of technological factors on the densification of forsterite green ware

Conclusions The grading of bodies made of dunite containing 20% additions of metallurgical magnesite ensuring a reduction in green porosity lies in the range 50–80% fraction 3–0.5 mm, 0–30% 0.5–0.088 mm and 20–50% finer than 0.088 mm.With an increase in fabricating pressure the relationship between the porosity of the green ware and grading diminishes.With a reduction in the grain sizes of the top and lower fractions the green porosity increases. An increase in moisture content from 4 to 6% in most cases increases the green porosity.An addition of 2–4% sulfite lye reduces the porosity (without a correction for pore filling by lye).The porosity of the green brick is greatly increased during firing. With the presence in the body of finely ground metallurgical magnesite the region of minimum porosity of fired specimens compared with the corresponding region for green brick moves to the side with the large content of fines.Dunite bodies with 20% fine magnesite giving the minimum porosity and shrinkage in firing should be used with the following grading: 10–40% fraction 3-0.5 mm, 10–40% 0.5–0.088 mm, and 50–70% finer than 0.088mm.An increase in the fines in the body leads to high shrinkage and deformation of the specimens in firing.     

Determining the maximum possible rates of single sided heating of refractories

Conclusions Tests on refractories on a special rig showed that the permitted heating rates on the hot face, without producing important changes in the engineering properties, are as follows: for dinas refractories 3 deg/min, magnesite 7.5 deg/min, and chrome — magnesite and magnesite — chromite up to 20 deg/min. These rates are greater than the calculated rates which may be due to the effect of structural heterogeneities in the product. However, the use of such heating rates for the refractories in the structure of heating units is possible after careful practical checking in industrial conditions.Translated from Ogneupory, No. 4, pp. 51–55, April, 1971.     

Beneficiation technology for natural and caustic magnesite using the hydrochloric acid method

Conclusions A study was made of the solution kinetics in hydrochloric acid of natural magnesite and caustic magnesite dust extracted from the waste gases of rotary kilns. It is shown that the solution rate of caustic dust in cold acid (cold solution method) is 10–12 times higher than the rate for natural magnesite at 80–100°C (hot solution method) and hence the use of dust for obtaining a high purity product would substantially increase the output of the chemical beneficiation plant.In dissolving caustic dust, heating of the solvent (acid) and milling of the material to be dissolved are excluded. Working with cold acid facilitates the choice of chemically resistant equipment and improves working conditions.Chemical beneficiation of the dispersed caustic magnesite dust, including its solution in cold 12.5% HCl, precipitation of sesquioxides, filtration, hydrolysis, and washing of the calcium oxide will improve the highpurity finished product (98.2–99.1% MgO).Translated from Ogneupory, No. 7, pp. 14–18, July, 1980.     

Sintering of MgO made from MgCl2

Conclusions The production parameters for a densely sintered magnesite powders made from MgO obtained from the thermal decomposition of MgCl₂ have been established. It is shown that the mechanical activation of MgO can be carried out in a vibromill for 10–20 min with an addition of a surface-active material (distillery waste or C₇-C₉ (fatty acids).Under pilot-plant conditions, using the process which has been developed, we obtained an MgO briquette of apparent density 3.20–3.33 g/cm³, an open porosity of 1.6–4.6%, and a MgO concentration of 97.9%. The magnesite and magnesite-chrome articles based on this briquette have excellent properties.Deceased.Translated from Ogneupory, No. 7, pp. 41–45, July, 1979.     

Melting refractory materials in the OKB-514 electric furnace and making parts for them

Conclusions The optimum conditions for melting magnesite into blocks using the OKB-514 electric furnace can be considered a voltage of 97 volts on the low side and a mean hourly charge of 50 kilograms. Of the methods of feeding powders to the furnace that were tried out, the continuous method is the most efficient.Parts with high properties can be machined from blocks of fused basic refractories.Parts made by the ceramic method from fused materials, including from a mixture of fused and sintered powders, are marked by high density (porosity 13–19%), refractoriness-under-load of 2 kg/cm higher than 1800°, and spalling-resistance of 5–15 heating-cooling cycles when cooled in water from 1300°.Using the OKB-514 furnace, with reduced periodic feeding, it is possible to produce fused magnesite containing up to 98% MgO when the initial raw material contains 90% MgO. The part of the block (10–15%) with the high MgO content can be separated during the finishing operation.     

Unfired magnesite refractories in resin phosphate bonding

Conclusions A process has been developed for producing unfired, dense, thermal-shock and slag-resistant magnesite refractories with a resin-phosphate binding.One feature of this process is the molding of the articles with an addition of orthophosphoric acid but without heating from a mass containing coarse (> 0.5 mm) magnesite grains and also fine magnesite grains (< 0.5 mm) coated with resin.Translated from Ogneupory, No. 7, pp. 56–58, July, 1979.     

Properties of refractories produced from synthetic magnesia

Conclusions The sinterability, open porosity, and cold-crushing strength of magnesite and magnesite-chromite specimens processed from magnesia powders (96–97% MgO) are improved with a decrease in the size of the periclase grains in the powder and with an increase in the firing temperature and do not depend on the percent and composition of the silicates and on the B₂O₃ content of the magnesia powder.The high-temperature bending strength of both types of refractories increases with a decrease in the B₂O₃ content of the magnesia powder. The creep resistance of the magnesite specimens increases with the ratio CaO/SiO₂ in the magnesia powder while the creep resistance of the magnesite — chromite specimens does not depend on this index.The indices of the open porosity and strength of the magnesite and magnesite — chromite specimens were optimal when they were produced with magnesia obtained by the bicarbonate method from dolomite.To produce dense and strong magnesite refractories from magnesia, they should be fired at a temperature not below 1700°C. The firing temperature of magnesite — chromite refractories should not be below 1750°C.Translated from Ogneupory, No. 6, pp. 53–57, June, 1978.     

Production and service-testing of refractories based on flotation-concentrated magnesite

Conclusions Flotation-concentrated magnesite and pure and concentrated chromite were used for producing high-temperature fired magnesite, magnesite-chromite, and periclase-spinel refractories which, compared with ordinary types, contained less silicates and, more direct bonds between the high-refractoriness minerals so that their refractoriness under a load and their thermal strength were higher.In the lining of 100-ton converters for steel, the durability of the experimental magnesite refractory produced from concentrated magnesite and tar-impregnated was 19% better than that of ordinary tarbonded magnesite brick.In the lining of the tuyere zone and of the zone above it in 20-ton and 30-ton converters for copper and nickel, the durability of the experimental magnesite-chromite and periclase-spinel refractories produced from concentrated magnesite and concentrated and pure chromite was 30–35% better than that of ordinary MKhS and PShS type refractories.Translated from Ogneupory, No. 1, pp. 11–15, January, 1976.     

Experimental enrichment of Satkinsk magnesites in heavy suspensions

Conclusions The tests confirmed that it is possible to enrich magnesites from the zone of contact with dolomites in heavy suspensions with the production of first-grade concentrate with a magnesite yield of not less than 82–84% of the starting product. Crushing of magnesite with a control screening reduces the output of unenriched class 5-0 mm.Enrichment in a heavy suspension of dolomitic magnesite permits also the separation of pure dolomite. The quality of the concentrate will depend on the content of dolomitic magnesite which in the main passes into the heavy fraction. In some cases it will be possible to separate an intermediate dolomitic fraction.Translated from Ogneupory, No. 1, pp. 26–30, January, 1966.