K. V. Simonov

Powders and refractory products from flotation-concentrated magnesite

ConclusionsA detailed description was given of the flow sheet and technology of the flotation — concentration of Satkin magnesites of grades III and IV.The flotation of these two magnesite grades gave top-grade magnesite concentrates containing (in terms of the calcined substance) 94.07–96.48% MgO, 0.35–0.83% SiO2, and 1.20–2.19% CaO.A detailed analysis was made, moreover, of the technological parameters for the production of a high-density powder from flotation-concentrated magnesite ground, briquetted and fired in a rotary kiln.The magnesite powder was of good quality and contained 93.8% MgO. The apparent density of the control fraction of 3-1 mm was 3.16 g/cm3. The magnesite powder was processed into magnesite and periclase — spinel bricks the quality indices of which were higher than those of bricks produced from commercial grade magnesite powders.

Rational use of caustic magnesite dust in the production of refractories

ConclusionsAdditionally conducted investigations showed the necessity of elimination of delivery to firing of fine dust from electrostatic precipitators contaminated with low-melting compounds of sulfur and fluorine and circulating in the kiln ⇆ electrostatic precipitators closed cycle, which makes it possible to reduce the unproductive load on the dust removal equipment and discharge of dust into the atmosphere and to eliminate the crust on waste-heat boiler tube surfaces and corrosion of metal and reinforced concrete structures.The planned reconstruction of the electrostatic precipitators will make it possible to significantly increase the effectiveness of cleaning of the gases of this dust.A waste-free environmental protection method of processing of this dust into sintered clinker including removal from it and utilization of the sulfur compounds has been introduced and tested under semiproduction conditions.On the basis of the low-waste and waste-free methods developed a plan of rational composite processing of dust from cyclones into porous, dense, and fused clinkers taking into consideration solutions on preservation of the environment has been proposed. The areas of use of these clinkers for production of effective unformed and formed refractories for various purposes were determined.

Obtaining dense powder from Satkinsk magnesite beneficiated by flotation

ConclusionsEnrichment of Satkinsk magnesite by flotation yields a product containing (calculated on the calcined substance) 94.2–96.5% MgO, 0.3–0.4% SiO2 and 1.4–2.8% CaO.Enriched magnesite consists of dispersed powder with a relatively narrow particle-size range. A large quantity of particles have dimensions of 0.2–0.063 mm. The concentration of particles measuring less than 0.063 mm did not exceed 55%.In order to obtain dense powder it is necessary to carry out additional fine grinding of the enriched magnesite, ensuring a concentration of fractions less than 0.063 mm of at least 95%, reducing the average particle size by a factor of 4–6 (down to 10μ) and followed by briquetting of the milled material.

Periclase-chromite refractories from fused materials

ConclusionsExperiments 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.

Drying magnesia refractories with the flue gas of the tunnel kiln

ConclusionsExperiments at the Magnezit Plant confirmed the feasibility of drying magnesia refractories with the flue gas in the first positions of a tunnel kiln. Drying the refractories in the section where the flue gas is tapped off does not result in more rejects or in degradation of the properties of the fired products.Compounding the processes of drying and firing magnesia refractories in a single unit, viz., the tunnel kiln, makes it possible to dispense with the driers the freed floorspace of which can be used for installing equipment for mechanizing the loading of the products on the kiln trucks.

Scrap of magnesia parts, the reasons for it, and means of reducing it

ConclusionsThe most common and characteristic forms of scrap of magnesia parts differing in form, dimensions, and composition are shown. These include deviations of the dimensions from the nominal, breaking off of the corners and edges, nonuniformity, welding together, spots, voids, fire cracks, spalls, and cracks of different origin.The reasons for formation of scrap were determined. The primary of them are the reduced quality of the raw material (chromite, magnesite) with a larger quantity of impurities containing limited silicon and calcium oxides, sometimes insufficient density, grain size, and completeness of hydration of the magnesite powders, nonconformity of the bunker, proportioning, mixing, and pressing equipment to the requirements of modern production of progressive high-quality refractories, the insufficiently high binding capacity of lignosulfonates, deviations in the quality of assembly and finishing of press equipment and automatic ejectors, of the car floor lining, and in firing conditions, a high variation in density of the green parts, and nonuniform heating and cooling in the volume of the parts and of the whole charge during firing. More than 50% of the total scrap of all forms is due to firing scrap of parts.The primary means of reducing or eliminating scrap of parts and simultaneously increasing their quality based on the reasons for formation of different forms of it were noted. These above all else, are increasing the volumes and improving and introduction of new methods of concentration of magnesite and chromite, a successive increase in the share of chrome concentrates, chromium-containing broken parts, and powders by firing of magnesite and caustic dust in the production of magnesia refractory parts as the result of a decrease in the share of commercial natural chromite and magnesite, the use in the production of parts of high-quality type PMSP-93 powder produced in shaft kilns and used as the charge for production of fused materials, the use of the prospect of processes for production of dense periclase powders uniform in chemical analysis from recovered caustic dust, replacement of obsolete mixing and press equipment by more modern, increasing the strength of green parts by above all else improving the binding properties of LST and increasing pressing pressure, forming of the taper of parts by the side plates of the die, improving the quality of assembly and increasing the reliability of functioning of press equipment and automatic ejectors, improving car floor linings, introduction of new methods and increasing the volumes of production of progressive unfired refractories in place of certain forms of fired parts, observation of all production parameters, and a relationship of the wages of labor to the quantity of scrap and the quality of refractories.Introduction of the new management system and the active work of the quality groups created will open up and lead to the action of unutilized reserves for reduction of scrap.

Fusion-cast periclase-spinel materials for granular structured refractories

On etudie la fusion au four electrique et le moulage par coulee de refractaires de periclase-spinelle, ainsi que la composition chimique et mineralogique et la microstructure des produits obtenus

Microstructure and chemical composition of the phases of the fused low-silica chromite-periclase materials

In order to produce chromite (chrome)-periclase bearing refractories having a low silica content, one makes use of beneficiated concentrates of chromium ores or synthetic chromiumbearing materials [i, 2] Which require presintering or prior melting because of the fine dispersion of the products of benefieiation and synthesis. It was previously shown [3, 4] that fused materials can exhibit significant differences in the structure and that ferrochromium has a negative effect on the service properties of the products.

Obtaining fused periclase in the OKB-955N ore-thermic furnace with a triangular bath

ConclusionsWe identified the factors influencing the process of forming the nonmeltable heat-insulating layers of the block during the melting of brucite raw materials in an ore-thermic furnace designated OKB-955N.A furnaee was proposed with a bath in the form of a triangular, truncated pyramid with rounded edges, facilitating a considerable reduction in the thickness of the nonmelting heat-insulating layer, especially the skin of the block, the specific consumption of raw materials and the volume of manual and mechanical handling operations, and also giving some improvement in the quality of the periclase.The highest cost-benefit factors for operating the furnaces are obtained by combining the triangular baths with a forced melting cycle. The parameters for a high-capacity furnace with a triangular bath were worked out.

Utilization of caustic magnesite dust in the production of sintered magnesite powders

ConclusionsA method of obtaining magnesite powder and the appropriate charging equipment have been developed which make it possible to utilize effectively the caustic dust removed from the effluent gas of rotary furnaces. A feature of the new method of obtaining the powder includes the periodic alternation of the firing of dust and a mixture of it and raw magnesite in the optimal ratios.The method of obtaining powders has been achieved thanks to established and well-founded charging and firing regimes and makes it possible to reduce the incrustation by dust deposits on the heater surface of the exhaust-heat boilers, to increase the quantity and raise the quality of the fine-grain powders for the production of magnesite articles, and to improve the technical and economic characteristics of the furnace operation. Separate treatment and the deliberate use of fired powders of various qualities can be provided after the DSO-2 has been brought on line in the No. 2 magnesite powder shop at the Combine.