Sea Water Magnesia Research Articles

Effect of limestone composition on milk-of-lime quality in seawater magnesia production

We determined the possibility of using various grades of limestones in the production of seawater magnesia. The quality and yield of the purified milk of lime are determined primarily by the mineral and chemical compositions of the limestones used and the degree of burning. The quality of the milk of lime using contaminated limestones can be improved by double-stage enrichment of the milk in hydro cyclones.

Transporting slurry for the production of seawater magnesia

Hydrated magnesium oxide slurry produced from vacuum filters is unsatisfactorily handled by transportation with belt conveyers and augers.

Investigating the sintering of seawater magnesium hydroxide

To obtain densely sintered seawater magnesia powders it is necessary to ensure a molar ratio of CaO/SiO2 of not more than 1 in the slurry. Incorporating B2O3 in amounts of not less than 0.5% on the calcined weight improves the sintering of the seawater magnesium hydroxide: the porosity of the fired (rotary furnace) powder varies from 8 to 12%. Preliminary drying or heating of the slurry, followed by briquetting of the material, produces a seawater magnesia with a porosity of 7–11% and a content of 95–97% MgO, and 2.3-0.5% CaO. Preference should be given to predrying of the slurry, since in this case no fuel is needed for removing the chemically bonded water.

Sintering of Magnesia Brick an Influence of Various Factors on its Contraction Rate

Magnesia bricks were fired at 1600° to 1700°C and changes in their properties, especially the volume contraction due to sintering and the grain growth of periclase, were examined. Effects of temperature and firing time on the rate of sintering contraction were investigated.The volume change of refractories in reheating has been examined usually by the repeat contraction measurements. In this investigation, the reheat linear change of magnesia bricks was considered as a kind of rate process including sintering reaction.The reheat linear changes for two kinds of burnt magnesia bricks from sea-water magnesia were measured at 1600° to 1700°C, and the correlation among reheat change, temperature and reheating time was analysed. It was found that the repeat contraction (S) will be approximately expressed by the following equation including reheating temperature (T), time (t) and activation energy for sintering contraction (Es);S=ks√texp(-Es/RT)This correlation may be applied to the estimation of brick contraction in furnace linings during service and also to adjust the firing condition for making bricks.Reheating promotes the grain growth of periclase in magnesia bricks approximately proportionally to reheating temperatures, where silicates will retard the grain growth of periclase.The standardized methods for reheat change measurements prevailing at present will not be always fit to bricks of these grades. The authors propose an example of optimum condition for reheat change test: 10hrs reheating at 1700°C.

Effect of Kaolin Addition on Properties of Forsterite Porcelain

The stability of the forsterite porcelian in hydrogen at high temperatures, which is required in the application of the forsterite porcelain to a high frequency insulator, is governed by additives used to promote sintering. Among several additives examined kaolin has the effect to make the porcelain stable in hydrogen at high temperatures, so giving it favorable properties for Mo-Mn metallizing processed under such conditions.In this paper 0-10% of kaolin was added to forsterite porcelains which were prepared from Fukushima siliceous stone and sea-water magnesia in the molar ratio of MgO: SiO2=2:1.By the addition of kaolin the temperature range for sintering was remarkably extended and the firing shrinkage was almost constant within this range. The coefficient of linear thermal expansion decreased with the increase of added kaolin, and no considerable change was found by repeated heat treatments. With the increase of kaolin content from 0 to 10%, the softening temperature under load lowered to 1160°C from 1280°C. The electric resistance at elevated temperatures lowered gradually, but was still sufficiently high for practical use. The flexural strength decreased and the modulus of elasticity lowered gradually in the temperature range from room temperature to 300°C with the increase of kaolin content. The modulus of elasticity, however, became larger with the rise of temperature in this temperature range.Within 5% of kaolin added, the dielectric constant and dielectric loss were unvaried and these values were excellent for the high frequency insulator.The result of X-ray diffraction gave only the pattern of the forsterite. By microscopic observation, forsterite crystal grain changed from allotriomorphic into idiomorphic and glass matrix increased with the kaolin content.It is concluded that the addition of 2.5-5.0% of kaolin was most suitable for preparing the forsterite porcelain for this purpose.

Refractory Properties of Indian Sea-water Magnesia

Chemical and physical properties of a sample of dead-burnt sea-water magnesia supplied by Messrs. Tata Chemicals, Mithapur, were studied with a view to utilise it for refractory purposes. Though th...

Influence of Excess Magnesia on the Properties of Forsterite Porcelain

It was reported already that the forsterite porcelain containing excess silica has the narrow range of sintering temperatur and the low softening temperature under load, and the present paper concerns with the influence of excess magnesia on the properties.A mixture of Mg(OH)2 and SiO2 (α-quartz) corresponding to the molar ratio of 2.2 MgO: 1.0 SiO2 was prepared from the materials of high purity.It was heated with the velocity of 200°C/hr., to various temperatures, kept constant for 15 min., and cooled rapidly.X-ray analysis was used to identify the minerals in the fired specimens. It was confirmed that the formation of forsterite began at about 1000°C and was completed at 1460°C. The amount of quartz and periclase decreased with temperature; the former disappeared at about 1400°C, while the latter remained even at the highest temperature of the heat treatment. The inversion of quartz occured at 1240°C, but it disappeared at 1460°C.The specimen clacined previously at 1460°C and mixed with 5% kaolin could be sintered between 1380°-1500°C.By X-ray method only the existence of forsterite was detected from the sintered body. The dielectric loss of this specimen was very small.Forsterite porcelains made from sea water magnesia and silicious stone were also studied; six batches having the compositions, MgO 57-70, SiO2 42-30% were calcined until the X-ray proved the termination of the forsterite forming reaction. They were ground and mixed with 5% of kaolin. The sintering temperatures were 1340°-1520°C, increasing with the increase of MgO.The coefficient of thermal expansion, the thermal conductivity, and the thermal shock resistance have increased with the increase of MgO- content. The trend of the softening temperature was reflected the relations in the phase diagram. The bending strength became lower with increasing MgO, which presumably came from the effect of the aggregation of forsterite crystals.Although X-ray failed to detect the periclase clystals in the specimens containing 58-62% MgO, it is highly probable that the mineral composition are the same with the forsterite porcelain which does not contain excess of MgO.These two, however, showed some difference in the properties; especially, the softening temperature under load of the former was considerably higher than that of the latter. Microscopic observation showed that the excess MgO was disolved in the glass matrix, and made the refractive index higher. Moreover, such a texture may be considered as being responsible for the higher softening temperature under load.The electrical properties of the specimens made from pure chemical as well as natural raw materials were excellent.It was concluded that the forsterite porcelain having the base composition of 58-62% MgO are the best for using as the vacuum tube.

The Relation Between the Microstructure and the Thermal Expansion of Forsterite Porcelain

The thermal expansion of forsterite porcelain, which is one of the most important properties for use in electron tube, and the effect of different firing temperature, and of repeated heating were investigated. Based on the experimental results the relation between the microstructure and the thermal properties were discussed.The coefficients of linear expansion along each axis of synthesized forsterite were measured by X-ray with a result; a-axis 10.47, b-axis 12.50, c-axis 11.05×10-6, in the temperatures 20°-800°C. These values correspond to that of the forsterite porcelain containing much forsterite.Referring to the data of Navias (J. Am. Ceram. Soc., 37 [8] 329 (1954)) it was pointed out that the elevation of the firing temperature of 25°C would accompany with the increase of the coefficient by 1.0×10-6, and this is the figure being intorelably large for the vacuum sealing with metal.To study this phenomenon many batches of forsterite porcelain were prepared, and fired at different temperatures. The specimen made from talc, sea-water magnesia and BaCO3 showed the marked decrease of the coefficient (about 1×10-6) with the elevation of firing temperature from 1400° to 1500°C. Under microscope was observed the increase of glassy phase with increasing firing temperature, which probably leads to the reduction of the expansion coefficient.The coefficient of the specimens containing MgO and SiO2 in various ratios have also beem measured. Forsterite porcelain having excess of SiO2 (SiO2 47%) showed the increase of the coefficient of about 1.2×10-6 by the elevation of firing temperature from 1400° to 1500°C, which, however, decreased with increasing MgO. The specimens containing excess MgO showed only a very small variation.By microscopic observation of the specimens containing excess SiO2, the forsterite crystal showed a marked aggregation by the elevation of firing temperature, causing the decrease of the coefficient, while in the forsterite containg excess of MgO the aggregation was scarecely recognized, and consequently gave the constant coefficient.Moreover, for many kinds of forsterite porcelain, the variations of the coefficients of linear thermal expansion by the repeated heating were measured. They could be classified into two groups, i.e., one coefficients increased, and the other coefficient did not nearly or entirely increased with repeated heating. The former has more glassy substance than the latter, and it was concluded that such a glassy substance decreased the coefficient by the repeated heating.The authors have confirmed that the composition of forsterite porcelain for use in electron tube should be in excess of MgO and the glassy substance should be reduced as far as possible.

On the Influence of Additions on the Sintering and Dead-burning of Sea-water Magnesia. Studies on the Dead-burned Sea-water Magnesia, I

The purpose of this investigation is to study the effects of various impurities which might be present in sea-water magnesia on the sintering and dead-burning properties.The influence of CaO, SiO2, Al2O3, Fe2O3 etc. additions on the sintering and dead-burning of magnesia has been investigated. The results obtained are shown as follows;(1) The sintering of dead-burned magnesia is influenced greatly by molar ratio of CaO/SiO2 and CaO/Fe2O3, (2) and the suggestion is made that the effect of additions in promoting the sintering of sea-water magnesia may be related to the chemical composition of the original sea-water magnesia.(3) The relation between the sintering characteristics of magnesia and molar ratio CaO/SiO2, CaO/Fe2O3, and CaO/Al2O3 was made clear.(4) There is no obvious relationship between the densification of dead-burned magnesia and the promoting growth of periclase crystals.(5) An optimum addition of additives beyond which sintering is inhibited was determined from the study of mineral composition of products.

Studies on the Microstructure of Dead-burned Magnesia Studies on Dead-burned Sea Water Magnesia, II

The microstructure of magnesium oxide calcined at temperature of 1400°C to 1750°C and the effect of various oxide additions to magnesia on the microstructure of products were investigated by electron and petrographic microscopy. The results obtained are as follows:Growth of hexagonal periclase crystal is observed for magnesium oxides of relatively high purity obtained at calcining temperatures of 1650° to 1750°C. Fig. 1 (2), (3) show the well formed crystals in the specimens having high load-bearing capacity at temperature of 1680°C.Additions such as CaO, SiO2 and Fe2O3 to magnesia promote the sintering by increasing the amount of vitreous phase. However, degree of crystal growth and microstructure of the products depend on the kind of oxide additions and the relative amounts of the additives. For example, additions of CaO and SiO2 in amounts of 1.0 or 2.0molal ratio CaO/SiO2 improve the load-bearing capacity at high temperature. The matrix in the products tends to include compounds indicating high melting point which have high refractoriness under load. Additions of Fe2O3 and CaO produce samples containing fine MgO⋅Fe2O3 together with liquid phase and also promote the growth of periclase crystal. Additives such as CaO, SiO2 and Fe2O3 improve the resistance to hydration of MgO. The hydration rate may be reduced by coating the crystallities with the protective layer of matrix.

Progress Report on our new SEAWATER MAG NESIA PLANT

RETURN TO ISSUEPREVAdvertisementNEXTProgress Report on our new SEAWATER MAG NESIA PLANTCite this: Chem. Eng. News 1959, 37, 19, 90Publication Date (Print):May 11, 1959Publication History Published online6 November 2010Published inissue 11 May 1959https://doi.org/10.1021/cen-v037n019.p090Copyright © 1959 AMERICAN CHEMICAL SOCIETYArticle Views54Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (139 KB) SUBJECTS:Seawater Get e-Alerts

Properties of Forsterite Porcelain Containing Excess Silica

The forsterite porcelains were prepared from mixtures of Mg(OH)2 and SiO2 (α-quartz), both of high purity, in the molar ratio of 2:1.2 with and without the admixtures of Kaolin and BaCO3. The mixtures were heated at the velocity of 200°C/hr, kept at various temperatures for 15min., and cooled rapidly in air.X-ray diffraction analysis and the microscopic observation were made for the identification of minerals formed in the fired specimens. For the specimen without the admixtures the formation of forsterite, which was exothermic, was found to set in at about 1100°C and complete at about 1400°C. The formation of protoenstatite began from 1280°C by the secondary reaction of 2MgO⋅SiO2 and SiO2. In the specimen with the addition of 5% Kaolin (PSF-O) which sintered at 1460-1500°C were found forserite, protoenstatite, clinoenstatite, α-quartz, and periclase. In the specimen with the addition of 5% Kaolin and 10% BaCO3 (PSF-B) which sintered at 1300-1420°C were found forsterite, BaO⋅2SiO2, 2BaO⋅3SiO2, and BaO glass. The dielectric losses at 1Mc/s of both specimens, PSF-O and PSF-B, were alike and very small, whereas the value at 10, 000Mc/s of PSF-O was smaller than that of PSF-B.For the practical purpose, the forserite porcelains were also made from sea water magnesia and silicious stone instead of from pure Mg(OH)2 and α-quartz. The base composition was the same as above, but in this case the admixtures were BaCO3, ZnO, and CaO⋅2B2O3 glass. They were added respectively to the base batch by 5 and 10% by weight. The batches without the admixtures were also prepared. The seven kinds of batches thus prepared were calcined respectively until the forsterite forming reaction was completed. They were ground and mixed with 5% Kaolin, and again fired at various temperatures. These fired specimens were examined for their thermal, mechanical, and electrical properties. It was found that the admixtures such as BaCO3, ZnO, and CaO⋅2B2O3 glass had a favorable effect of reducing the dielectric loss of the fired specimen; especially the addition of BaCO3 was most effective. The results of the test of refiring in H2 atmosphere at 1300°C showed, however, that these admixtures in the fired specimens were easy to be reduced and evaporate. Therefore, as the vacum tube the forsterite porcelain without the admixture was recommended.

マグネシア質過リン酸石灰の研究

マグネシア質過リン酸石灰の研究

Thermal production of metallic magnesium from sea water magnesia

Raw materials used in this experiment are the magnesia obtained from sea water, and calcium silicide as reducing agent. The process is as follows. The magnesia and calcium silicide are ground and mixed, and the mixture is briquetted. When the briquetts are reduced in vacuo for several hours at high temperature, magnesium is distilled from the charge briquestts and condensed on a removable sleeve of the retort.The authors have investigated the following items:(1) Effect of reaction time.(2) Effect of reaction tempetature.(3) Effect of mol ratio.(4) Effect of fluorspar.(5) Effects of magnesia and calcium silicide particle sizes.

Studies on Magnesian Superphosphate by Using Sea-Water Magnesia

Studies on Magnesian Superphosphate by Using Sea-Water Magnesia

Manufacture of the Special Dolomite Refractories (Dolomitic, Magnesia-rich Refractories) by Utilizing Waste Lime from Acetylene Generator to Sea Water

Slmiy waste lime was utilized as precipitating agent for sea water magnesia having the CaO: MgO mol ratio of about 0.2. The precipitate was burned at 1500°C for 3 hrs. On the obtained samples of refractories, chemical analysis, tests on physical properties, slaking test, corrosion test against basic steel furnace slag as well as against fused phosphate fertilizer and Portland cement clinker were made. The results show possible use of these low cost refractories to the steel, fertilizer and cement industries.

Studies on Manufacturing Processes and Compositions of Sea Water Magnesia, (IV)

In continuing previous studies (Reports Part I-III by one of the present authors Shoichiro NAGAI and his collaborators, this Journal, 59, 456 (1951), 60, 540 (1952), 62, 248 (1954), the present authors reported the results of further continued studies on the preparation and chemical compositions of magnesium hydroxide by reacting diluted bittern solution to lime containing solution obtained from slaked lime, quick lime or calcined dolomite. Various kinds of reacting conditions between these two kinds of solutions were fully experimented and discussed by comparing the results of analyses of lime content and other impurities in the precipitated magnesium hydroxide, and its calcined magnesia or magnesia clinker, precipitating velocity, and volume or density of the precipitate Mg(OH)2.The products of these experiments, magnesium hydroxide, calcined magnesia or magnesia clinker, are already in some parts studied and are also being now further studied on their utilization methods to make (a) magnesia-chromite basic refractories, (b) magnesia cement (magnesium oxychloride cement), (c) magnesia gypsum or magnesia-dolomite plasters, etc., which results are already reported in some parts in the separate studies (Studies on Magnesia Cement from Sea Water Magnesia (Report I and II): Bulletin of the Society of Salt Science, Japan, 5, 251 (1951), 6, 6 (1952); Studies on Chrome-Magnesia Refractories by using Sea Water Magnesia (Report I-III): this Journal, 60, 60 and 422 (1952) 61, 152 (1953); Studies on Special Magnesia Cement by using Sea Water Magnesia (Report I): this Journal, 61, 266 (1953), etc., and will be further reported in the near future as continued reports of the above cited papers.

Experimental Manufacture of Spinel Refractories from Bauxite and Sea-Water Magnesia

Experimental Manufacture of Spinel Refractories from Bauxite and Sea-Water Magnesia

Studies on Manufacturing Processes and Compositions of Sea Water Magnesia, (III)

Studies on Manufacturing Processes and Compositions of Sea Water Magnesia, (III)

Studies on Chromite-Magnesia Refractories by using Sea-Water Magnesia, (IV)

In continuing the previous studies (This Journal, 60 No. 668, p. 60-65 and No. 676, p. 422-425 (1952); 61 No. 682, p. 152-154 (1953)), the present authors reported in the present paper, the results of further studies on the chromite-magnesia refractories by using chromite ore and special sea-water magnesia clinker obtained by dead burning special magnesium hydroxide contained a few percents of ferric oxide, which was specially obtained from dilute bittern solution by settling with slaked dolomite slurry from calcined dolomite with 3-5% limonite powder.Among many comparative testings, the best result was obtained as one of the example, having, the following phisical properties and chemical compositions: True density: 3.86, Aparent density: 3.83, Volume density: 2.90, Perosity: 24.1%, Water absorption: 8.3%, Compressive strength: 420kg/cm2, SiO2: about 8%, Al2O3: about 12%, Fe2O3: about 15%, CaO: about 3%, MgO: about 32% and Cr2O3: about 32%. But these contents of SiO2, Al2O3 and Fe2O3 are a little too large owing to the low grade of chromite ore, and the content of CaO is a little too large owing to the high lime content of sea-water magnesia clinker.