Obtaining magnesia and periclase refractories from bischofite from the volgograd deposits

Conclusions Experimental work was carried out to obtain from bromine liquors of bischofite of the Volgograd deposits magnesium oxide, using low capacity industrial equipment for chemical purification of magnesite, including a recuperator, a tank-collector, a spray-reactor, a cyclone, an absorption column, spray traps, a vacuum pump, and a filter press.We worked out the parameters for the processes of boiling off the liquor, thermohydrolysis of the magnesium chloride, absorption of the hydrogen chloride with the production of hydrochloric acid, washing and leaching the hydrolytic magnesium oxide, and filtration of the resulting magnesium hydroxide. During the reprocessing of the liquor containing the bischofite, using this technology, without preliminary purification to remove boron and sulfates, we obtained magnesium hydroxide with a high purity level (98.5–99.5% MgO on the calcined weight).It is shown that the magnesium hydroxide thus obtained is a high-quality raw material for the production of fused and sintered periclase with a purity of 98–99.5% MgO. The technology of sintering, including carbonization of the magnesium hydroxide, hot palletizing without bond, and firing at moderate temperatures, ensures the production of densely sintered periclase. Tiles with inserts made from fused periclase of high purity with a clear anisotropic structure facilitate the casting of two heats through the gate valves.The results obtained can serve as the starting data for the development of specifications (TLZ) and planning the production of magnesium oxide from the debrominized bischofite liquors at the Volgograd site using the thermohydrolysis method. We need to solve the problem of the use of the 20% HCl that is obtained.Translated from Ogneupory, No. 1, pp. 27–30, January, 1988.     

Effect of calcium oxide on the hydration activity of the powders of electrical-engineering periclase

Conclusions The hydration activity of the periclase powders depends to a significant extent on the hydration of free calcium oxide. The hydration resistance of the powders can be increased by fixing calcium oxide in the hydration-resistant compounds with silicon and magnesium oxides.It is also necessary to decrease the specific surface of the periclase powders for decreasing their ability to absorb moisture.Translated from Ogneupory, No. 8, pp. 9–12, August, 1988.     

水氯镁石制备金属镁的过程集成与能量分析

以无水氯化镁和氧化镁作为中间产物,电解和热还原为两个关键方法,集成各种相关过程,构建了从水氯镁石到金属镁的综合过程网络,其中涉及24个物种、20个化学过程和25个工艺路线;建立了最低能耗分析模型用于简单和复合过程的能量分析;利用物质的标准生成焓和多温等压摩尔热容,计算得出全部反应过程及工艺过程的能量消耗和热量移除。结果表明基于还原法的最优路径是水氯镁石用石灰法转为氢氧化镁,进而煅烧成氧化镁,再铝热还原成金属镁,该过程能耗360.15 kJ/mol,放出热量–315.46 kJ/mol;基于电解法的最优路径是石灰乳法生成氢氧化镁,再煅烧成氧化镁,通过在熔融电解质中电解生成金属镁,该过程能耗738.54 kJ/mol,放出热量–135.42 kJ/mol。无水氯化镁制备耗能高,不在最优路径中。     

Sintering of magnesium hydroxide obtained from magnesium chloride solutions

Conclusions We studied two batches of magnesium hydroxide obtained by precipitating out (using dolomite milk) from magnesium chloride solution formed when processing potassium ores.The effect of the compaction pressure, the firing temperature, and prior heat treatment on the sintering process of magnesium hydroxide was investigated.The experimental samples of magnesium hydroxide exhibit high sinterability and facilitate the production of periclase powders (powder bodies) having a porosity of 6.8–9.9% at a firing temperature of 1600°C. The degree of sintering of magnesium hydroxide increases with increasing compaction pressure and firing temperature. Prior heat treatment of the material at 800–1000°C intensifies the sintering process with simultaneous reduction of shrinkage.The studies conducted on the specimens prepared from a fired briquette established that the periclase (magnesite) powder obtained from magnesium hydroxide is suitable for the production of magnesia refractories.A. V. Kushchenko and G. G. Eliseeva (UkrNIIO) participated in this investigation.Translated from Ogneupory, No. 2, pp. 7–10, February, 1988.     

含铁镁白云石质合成砂的研制及其在不定形耐火材料中的应用

含铁镁白云石质合成砂生产工艺简单,它在高温下主要有方镁石固溶体（MgOss）和游离氧化钙（fCaO）两种高熔点固相,具有MgO-CaO系材料的特点,综合性能优良,在干打料、喷补料、涂抹料和隔热浇注料等耐火炉料的应用中,具有很高的耐用性。     

Hot press compaction of magnesium oxide obtained by decomposing certain compounds

Conclusions A study was made of the densification during hot pressing at 1300–1600°C of magnesium oxide activated by decomposing the hydroxide and the basic magnesium hydrocarbonate. During decomposition of these compounds at 500–700°C with a soak of 15 min, magnesium oxide forms that is actively compacted almost to the theoretical density (98.5–99.5%) at relatively low temperatures (1500–1600°C) and pressures of 150 kg/cm².We investigated the influence of the time and temperature of heat processing of the hydroxide and the basic hydrocarbonate of magnesium on the fineness of the grains and the defects of the crystalline lattices of periclase thus formed, and also on the capacity for subsequent compaction during hot pressing.The reduction in the degree of compaction during hot pressing of the materials, heat processed at temperatures below 500°C, is due to the increase in the content in them of undecomposed residue, which hinders the diffusion sintering in subsequent stages of pressing.A reduction in the degree of compaction with rise in temperature of heat processing above 500°C or with an increase in the heat-processing time with the optimum temperature, is connected not with a reduction in the defects of the crystalline lattice of the periclase formed, but with the sizes and physical state of its particles.We also studied the effect of additions of magnesium oxide obtained by heat processing the hydroxide or the basic hydrocarbonate of magnesium on the compaction during hot pressing of industrial magnesia. The introduction of 10–20% of this additive ensures a reduction in the optimum pressing temperature of 100–300°C and an increase in the density of the specimens almost to theoretical.Translated from Ogneupory, No.2, pp.46–53, February, 1967.     

Increasing the number of uses of the refractories in the slide gates of large steel-teeming ladles

Conclusions A method of enrichment of brucite by washing and sorting of it was developed. An experimental lot of composite slide gate plates for two teemings from the 300-ton steel teeming ladles of Magnitogorsk Metallurgical Combine was prepared from enriched fused brucite at Magnesite Combine. The physicochemical indices of the plates were 97.9 wt.% magnesium oxide with a nonequiaxiality of the periclase crystals of 1.94, 0.3% silica, 0.2% iron oxide, compressive strength 110 N/mm², and open porosity 12%. Under conditions of repeated openings and closings the plates made it possible to provide 100% quality teeming of the first heat and to direct 60% of the slide gates to repeated teeming, which was done with 32%. For a final experimental verification it would be desirable to prepare a larger experimental production lot of refractories using the method developed with specific repeated use.Translated from Ogneupory, No. 2, pp. 47–51, February, 1988.     

水泥熟料中方镁石定量分析

本文简要介绍了水泥熟料中氧化镁的定量分析方法,并采用化学方法和XRD内标法对水泥熟料中的方镁石进行定量分析,用回收率评价了该方法的准确性.结果表明:化学方法和XRD内标法定量水泥熟料中方镁石的含量是可行的,化学方法的回收率在99.40%以上,两种方法的测定结果一致.     

Optical method for determining impurities in periclase powders

A method for determining impurities in periclase powders by placing them in an immersion liquid with a refractive index equal to that of magnesium oxide is described. It is established that the composition of the semitransparent particles affects the color of the boundaries of the zone of transition from the immersion medium to the investigated substance. A method for determining the kind of transparent inclusions in periclase by observation in highly polarized transmitted light against light and dark fields is developed. It is shown that the transparent inclusions in particles, which are virtually indistinguishable in daylight, start to glow in polarized light against the background of a dark field.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 8, pp. 12–14, August, 1996.     

Periclase-carbon products for electric steel furnaces

Conclusions We developed a waste-free technology for the production and use of periclase-carbon concrete articles PUÉP-116 from sintered periclase powders for the walls and roofs of electric steel furnaces.The articles were made by a production scheme involving press, pallet, drying in pallets or without drying and then delivery to the user. The compressive strength of these articles is 11–18 N/mm²; they are practically gas-impermeable, have a high refractoriness under load (>1700°C), a high thermal conductivity [5–6 W/(m·K)] and magnetic susceptibility (35–38.10^–6 cm³/g). The use of these articles will increase the life of the walls in 100-ton steel furnaces compared with walls made from PKhS. In the roofs of these furnaces the periclase-carbon articles had a 25–40% lower wear. After service the articles were refused for the structure of walls and for fettling walls in admixture with periclase powder and water glass.It is desirable to organize the production of periclase-carbon articles PUÉP-116 in refractories factories and to determine the rational areas of application.Translated from Ogneupory, No. 1, pp. 23–26, January, 1988.     

Influence of the binder on the strength of a periclase green part

Conclusions The investigations showed that to provide a high quality of periclase parts from difficult-to-sinter powders (Koreisk type) it is desirable to use Solikamsk Combine lignosulfonates, which provide higher strength of the green part and increased properties of the fired parts, as the plasticizing and cementing addition.Translated from Ogneupory, No. 1, pp. 38–40, January, 1990.     

Structure and properties of fused periclase and periclase-chromite blocks produced from beneficiated starting materials

Conclusions Fused periclase and periclase-chromite blocks containing a high proportion of highmelting oxides of magnesium and chrome were produced from beneficiated starting materials.The structure and properties of the periclase and periclase-chromite were analyzed zonewise in the blocks. The thickness of the block zones with a high content of magnesium oxide and the yield of high-quality periclase and periclase-chromite depend on the degree of purity of the chemical composition of the starting materials.The content of magnesium oxide is highest and the proportion of contaminating oxides low in fused periclase produced from chemically beneficiated Satkin magnesite, and in the monocrystalline subzones of the blocks. An increase in the proportion of chromite in the mix results in a higher porosity and in a higher content of spinel and ferrochrome in the fused material. The properties are optimal in the case of a periclase-chromite material from a mix containing 15–20% chromite.Translated from Ogneupory, No. 3, pp. 37–44, March, 1978.     

Microstructural Study of Periclase Powders for Production of Periclase-Carbon Components

Results of a microstructure analysis of periclase powders (from China) of fractions 3 – 1 mm are reported. In the production of refractory materials for the lining of steel ladles, preference should be given to fused periclase powders.     

Effects of different additives on properties of magnesium aluminate Spinel–Periclase castable

Bauxite- and alumina-based spinels were employed as refractory aggregates, and sintered magnesia fine powder, calcium aluminate cement, microsilica, and activated α-Al₂O₃ were utilized as matrices. The effects of alumina powder, analytically pure zinc oxide, and analytically pure zirconia on the properties of magnesium aluminate spinel–periclase castables were studied. The results demonstrated that the addition of the three additives promoted the sintering of magnesium aluminate spinel–periclase castables. Simultaneously, the three additives significantly improved the high-temperature properties of the samples. The thermal shock resistance of the alumina powder sample increased by 200%, that of the pristine zinc oxide sample by 75%, and that of the zirconia sample by 125%. The additives effectively improved the thermal shock resistance of the magnesium aluminate spinel–periclase castable. In addition, the slag resistance depths of the samples with alumina powder and zirconia were 41% lower than that of the sample without additives, which significantly improved the slag resistance of the magnesium aluminate spinel–periclase castable.     

Role of Ti and Sn ions in spinel formation and reactive sintering of magnesia-rich ceramics

The solid solubility of magnesia in magnesium aluminate spinel and magnesium aluminate spinel in magnesia does not change with temperature thus not creating bonds or precipitation over periclase grains in a single stage sintering process. In comparison, the precipitated spinels in magnesia-chromia refractories form complex spinel due to inversion in the position of bivalent and trivalent cations within the structure, making them more stable at high temperature than either normal or inverse spinel. Additives form low-temperature compounds that diffuse into the spinel structure and create defects that change the properties of spinel solid solution. In the present study, magnesia and alumina powders along with tetravalent oxide additives were analyzed for their role in reactive densification of spinel in a single stage firing process in order to achieve a better binding system for magnesia-based refractories. These tetravalent oxides on reaction with magnesia form spinel solid solution with MgAl₂O₄ as they have similar crystal structure. The spinel solid solution formed using oxide additives is expected to have higher solubility in magnesia than magnesium aluminate spinel, resulting in improvement of the bonding during sintering through increased in solid solubility at elevated temperatures followed by precipitation of secondary spinel phases, similar to the complex spinel in magnesia-chrome refractories. The formation of spinel during firing remains as a second phase that retards the grain growth of periclase. The changes in unit cell dimensions with temperature and amount of additive were analyzed using Reitveld method and correlated with the densification behaviour at different temperatures.     

Sintering magnesium oxide obtained by the chemical beneficiation of magnesite

Conclusions A quantitative relationship was established for sintering chemically beneficiated magnesite and a method of obtaining the MgO; we also established the parameters of hydrolysis of the magnesium chloride, the quantity of residual volatiles, the temperature and rate of thermal activation of residual volatiles, the temperature and rate of thermal activation of the magnesium oxide, not washed, and washed to get rid of the calcium impurities, and also the completeness of the hydration of the magnesium oxide during leaching.A production flow line is proposed for obtaining from the enriched material sintered periclase clinkers differing in density and degree of purity.Translated from Ogneupory, No. 7, pp. 43–50, July, 1982.     

水氯镁石脱水技术的研究进展

镁化合物与金属镁及其合金具有重大工业应用价值。中国海洋和盐湖卤水中含有巨量的氯化镁,尤其是盐湖提钾后老卤经蒸发具有宏量水氯镁石(MgC l2·6H2O)产出,水氯镁石经脱水后得到的无水氯化镁是电解镁最佳的原材料。然而,水氯镁石脱水过程中存在许多技术难题一直阻碍着水氯镁石资源的广泛应用。主要介绍水氯镁石脱水技术的发展现状,内容包括气体保护法、复盐法和氨络合法等,指出了中国盐湖镁资源的巨大利用前景。     

Possibilities of beneficiation of fused periclase powders

Conclusions The method developed for chemical purification of PPÉ of calcium and silicon oxides makes it possible to decrease the content of the calcium oxide impurity limiting the quality of PPÉ at Refractory Production Union to satisfaction of the requirements for grades 1 and 2 of electrical periclase. The creation of a special area including the production of distilled water in the necessary for production introduction of the method.Translated from Ogneupory, No. 7, pp. 36–40, July, 1989.     

Manufacturing of magnesium hydroxide from natural magnesium chloride sources

Various processes for manufacturing magnesium hydroxide have been considered and tested in order to decide whether they can be employed to the full-scale production of this product from natural sources (bischofite and magnesium chloride brines). The process for the synthesis of magnesium hydroxide from magnesium chloride using sodium hydroxide has been improved.     

Effect of composition of metallurgical powder on the slopes and hearths of electric arc furnaces

Summary To reduce the sliding of fettling powders from the slopes of electric furnaces, it is desirable to use powders with not more than 10% of the fraction finer than 0.088 mm, and the SiO₂ content should be about 4.5–6%. Addition to the magnesite powder of coarse dolomite fraction 15-0.5 mm, and also 6–7% coal tar pitch, reduces the mobility of the powders.The rational composition of metallurgical powders used for fettling slopes and hearths of electric arc furnaces largely depends on the grade of steel being melted.The increase in the life of the slopes and hearths of an electric furnace in which stainless steel was being melted, fettled with MPMZ powder, was due to the increase in the content of periclase bonded with melilite and mervinite in the slopes and melilite and forsterite in the hearths.During the melting of steel of changing sorts, the increase in the life of the slopes and hearths, fettling with magnesite-dolomite powders is due to the presence of crystals of periclase bonded mainly with highly refractory dicalcium silicate.When fettling is done with MPMZ powder the structure of the slopes and hearths is identical. The use of chromemagnesite, magnesite-chromite and magnesite-dolomite powders give rise to the formation of a heterogeneous structure in the slopes and hearths which leads to their irregular wearing away.To prolong the service of the hearths and slopes of electric furnaces it is necessary to continue investigating the wear resistance of fettling materials in furnaces of different capacities, where steels of different types are being melted, typifying the life of the powders by the consumption per ton of steel melted, the burn-out profile of the lining, the interrepair periods and other factors.