Production of unfired tarred -dolomite brick and its service in 100-TON oxygen converters

Conclusions The use, in the production of unfired articles, of highly sintered granular dolomite without additional grinding and coal-tar pitch with a high content of pitch, ensures, after pressing of the hot bodies, the production of dense and strong articles capable of being stored in air in winter for 10–12 days.To further improve the resistance of the unfired lining, it is necessary to continue the investigation of the effect of metallurgical factors on the resistance of the unfired refractories during service in converters, and to establish the optimum parameters for the oxygen-converter melting cycle.Translated from Ogneupory, No. 2, pp. 15–19, February, 1966.     

Properties of fired dolomite refractories with tar bond

Conclusions The laboratory specimens made of tar-bonded fired dolomite showed an apparent porosity of 8 to 18%; slightly better porosity was shown by specimens made with more fully sintered dolomite.The tar barely permeates the dolomite grains.When they are stored, the porosity is increased and the bulk density and strength of the specimens are reduced. This is less obvious after coke firing.Bricks made of all the tested dolomites with the addition of 8 and 6% tar at a pressure of 500 kg/cm² showed a bulk density of 2.6 g/cm² or more. Similar results are obtained when making the bricks by pneumatic tamping.For tests in the lining of converters we recommend blocks made of freshly fired dolomite with an apparent porosity of 5–10 and 15–20 and a grain composition lower than 15–10 mm. As a bond, 6 to 8% tar containing 65–70% medium coaltar pitch and 35–30% anthracite oil should be added. The blocks have to be pressed at at least 500 kg/cm².     

A study of the enrichability of Shchelkovo deposit dolomite by a photometric method

Conclusions A study of the optical and physical properties of Shchelkovo deposit dolomite ore shows that its petrographic varieties possess a significant contrast in color. The coefficient of reflection of dolomite (65–75%) differs significantly from that of silica concretions (20–25%), which are harmful impurities. Such a difference is the basis for application of photometric separation of dolomite ores.As a result of photometric sorting of the 15–20-, 10–15-, and 5–10-mm fractions of the dolomite ore, the harmful impurities were removed from it in the form of silica concretions, and the silicon dioxide content in the beneficiated concentrate was reduced to 1.1–1.2% from the 2.2–2.3% in the original. In chemical composition the concentrate meets the requirements for raw material used for the production of high-quality refractories.Despite the simplicity of beneficiation of dolomite ore by the photometric method with the large color contrast between the dolomite and the silica concretions, its separation is complicated by the fact that silicon is present in the dolomite itself (silicon dioxide content more than 1%). Therefore the production of material with a content of not more than 1.3% SiO₂ is difficult and requires careful observation of the sorting method and the use of equipment with a high resolving capacity.The introduction of the proposed flow plan for beneficiation, including photometric separation, will make it possible to supply the iron and steel plants of the European portion of the Russian Soviet Federative Socialist Republic with raw material for the production of high-quality refractories as the result of further use of Shchelkovo dolomite deposit.Translated from Ogneupory, No. 2, pp. 29–33, February, 1984.     

Increasing the thermal efficiency of a rotary kiln for firing dolomites from various deposits

Conclusions More uniform firing of dolomite of various fractions can be achieved by reducing the upper limits of the dolomite particle size to 10–12 mm and excluding fractions < 5mm. Considering the low resistance of chrome-magnesite brick in the firing zone it is necessary to use periclase-spinel brick.The use of GVM burners for burning natural gas in rotary kilns increases the output of the kiln and reduces the consumption of fuel when burning dolomite. These burners can be recommended for installation in rotary kilns for firing magnesite, chamotte, lime, etc.Translated from Ogneupory, No. 4, pp. 23–26, April, 1973.     

Use of multiple regression analysis for development of a mathematical model of the resistance of converter linings

Conclusions To construct mathematical models of the process of the failure of converter linings, use can be made of the method of regression and correlation analysis.The content of silicon in the pig iron has a considerably greater effect on the stability of periclase-spinellide products than on the resistance of uncalcined refractories in a resin binder.In comparison with a lining made of resin-dolomite-magnesite products based on Novotroitsk dolomite (basic variant), products based on Zakarpatsk dolomite have the highest resistance (increased by 11.9–13.8%), and those based on ordinary metallurgical dolomite have the lowest resistance (a decrease of 9.9–10.3%).A further improvement of the mathematical model may be achieved by a fuller use of the methods of mathematical statistics.N. A. Aleksandrova participated in the work.Translated from Ogneupory, No.3, pp.44–51, March, 1968.     

Effect of some technological parameters of oxygen converter melting on the resistance of tarred dolomite — Magnesite linings

Conclusions Of the investigated factors the most important as regards wear of tarred dolomite — magnesite refractories are the concentrations of ferric oxides in the slags and the process temperatures. With a reduction in the blow time there is an increase in the lining life.An increased concentration of CaO in the slag, and consequently an increased basicity, reduces the wear of the lining. The rate of solution of the lime during the blow is not constant. In order to obtain a higher rate of increase in the CaO concentration in the slag it is desirable to make a second addition of lime before its rapid solution starts, that is, 4–6 min after the commencement of blowing.Less and more uniform wear in the lining is noted during blowing of the bath through multinozzle tuyeres.Translated from Ogneupory, No.2, pp. 35–39, February, 1970.     

Suitability of Zavadov deposit dolomites for use as raw material

Conclusions Investigations of raw Zavadov deposit dolomite showed that in strength it belongs to the dense varieties of dolomite with a fine crystalline structure. The weight % of the basic component (dolomite) is 88–98%. The impurities are calcite, quartz, clay particles, and iron oxides.By firing the dolomite in the form of the previously separated 5–25-mm fraction at 1700–1750°C it is possible to provide sintering of practically all of the samples. The use of preliminary grinding and briquetting improves sintering but does not provide significant advantages in comparison with firing in granular form. The addition of scale causes an improvement in sintering and an increase in the resistance to hydration.The resistance of hydration after firing at 1750°C in storage in air of samples Nos. 4–17 was satisfactory while the dolomite of samples Nos. 1–3 hydrated significantly more rapidly. With the addition of 1% scale and firing at 1700°C in storage in air the resistance is significantly greater.As the result of the investigation it was established that the dolomite, with the exception of individual samples, meets the requirements of Industry Standard 14-84-82 for raw metallurgical dolomite for patching and filling the sills of hearth furnaces and also for firing for metallurgical dolomite. A further improvement in dolomite quality is pssible with selective mining and benefication of it.Translated from Ogneupory, No. 2, pp. 36–40, February, 1987.     

Strength of magnesia refractories in combined thermal cyclic and mechanical loading of them

Conclusions As the result of laboratory tests of periclase-chromite refractories produced by different methods (MKhS, MKhV, and MKhVP) under the combined action of thermocyclic and mechanical loads possibilities were revealed of the most effective use of them in relation to the service conditions of plasma and electric arc furnace linings. The results of production tests of MKhS, MKhV, and MKhVP refractories at various furnace lining operating temperatures agree with the laboratory data and make it possible to draw the following conclusions:MKhS parts, as the most heat resistant, may be used successfully in heating the furnace lining working surface to 1700–1750°C, which corresponds to a temperature on the boundary of spalling of the refractory of 1400–1500°C.An increase in the lining operating temperature to 1800–1900°C (1550–1650°C on the boundary of spalling) requires the use of refractories with a combination of such properties as heat resistance and high-temperature strength. These requirements are met to the greatest degree by MKhV parts.In the future for large tonnage plasma and electric arc furnaces with high mechanical loads MKhVP high-strength parts may be recommended for the lining. However, for successful use of these parts it is necessary to aim to increase their heat resistance.Translated from Ogneupory, No. 5, pp. 43–47, May, 1985.     

The service of periglase-chromite refractories in the bottom of a converter with combined blowing

Conclusions Without the use of guniting and effective buildup of a crust the life of a converter bottom lining under the conditions of Nizhnii Tagil Metallurgical Combine does not exceed 400–450 heats.Unstable life (150–300 heats) of the upper layer of the bottom lining is an indication of irrational heating up of the converter before service.As follows from the experimental heats, to increase the life of the area near the tuyeres and the joint of the converter bottom and wall linings it is necessary to use BPGK-72-12 periclase-carbon blocks.Translated from Ogneupory, No. 4, pp. 48–50, April, 1990.     

Firing Lis'Egorsk dolomite in rotary furnace

Conclusions By calcining Lis'egorsk dolomite in a rotary furnace by the dry method (0–25 mm fraction) with 3–3.5%clinker we obtained high-grade dolomite powder with an apparent density of 3.3 g/cm³.Industrial tests of the burned dolomite showed that it is suitable as a fettling material for open-hearth furnaces.     

Powdered materials for restoring open hearth linings

Conclusions The production level of powdered materials should be determined mainly in terms of their consumption per ton of production, and with regard to the materials originally laid in the lining and requiring restoration during the operation of the furnaces. Due to the development of high-temperature oxygen steel melting it will be necessary to improve the quality of burnt dolomite.The variety of, magnesite powders being prepared should be altered so as to sharply increase the production of grade MPP powders.In open hearth shops it will be necessary to arrange separate storage of the various grades of magnesite powders.Translated from Ogneupory, No. 3, pp. 39–42, March, 1971.     

Making and testing refractories from high-density,high-purity magnesite powder

Conclusions Test results for the trial batch of refractories made of dense magnesite powder in the converter lining in the trunnion zone showed that they are promising for application compared with ordinary dolomite goods with a pitch bond. The average wear of the test refractory is not more than 1.0 mm/heat, while dolomite-pitch shows a wear of 1.5 mm/heat. The resistance of blocks of dense magnesite powder in the lining of steel discharge apertures of a converter also proved to be higher than periclase (83 heats against 69).Translated from Ogneupory, No. 6, pp. 7–10, June, 1980.     

Guniting of the lining of furnaces for heating of steel billets

Conclusions A method of guniting of the rolling mill heating furnaces during shutdown for cold repairs and with a lining surface temperature of 900–1200°C was developed with the use of guniting powders produced by industry of aluminosilicate and basic compositions with hydraulic and silicate binders. The introduction of composite guniting of the lining in the cold and hot conditions makes it possible to reduce the volume of lining repair work by 10–15 m³ per furnace and the consumption of brick refractories by 0.1 kg per ton of steel rolled and to increase the life of the lining by 1.5–2.0 times.Translated from Ogneupory, No. 4, pp. 48–51, April, 1988.     

Improving the quality of grog and increasing rotary kiln output

Conclusions During the firing of raw lump kaolin in rotary kilns a dusty layer develops. Removal of the dust with the flue gases reaches 28–29%. The grog is obtained with a high water absorption (8–10%), and a predominance of fine fractions (30% fraction finer than 0.54 mm). The work of the furnace is characterized by frequent stoppages for preheating of the fired layer, premature wear of the lining, and extra repairs.It is necessary to develop a rational method for preparing kaolin in all its varieties and briquetting it with the introduction of peptizers, in order to reduce the temperature of sintering and reduce the amount of dust carried away, which will make it possible to speed up the work of the rotary furnaces at high temperatures.Translated from Ogneupory, No. 8, pp. 4–7, August, 1966.     

Rational firing cycle for converter lining

Conclusions The firing of linings in converters made from tar-bonded refractories should be done with portion loading of coke in amounts of 200 kg, with careful control of the oxygen consumption. The temperature relationship with the rate of discharge of volatiles from the tar should be taken into account.The rational temperature cycle for firing tarred dolomite linings in converters is: raising the temperature to 300–350°C at a rate of 30–40 deg/min, from 300–350 to 700–800°C at a rate of 1.5–2.0 deg/min, and from 700–800° to 1000°C at a rate of 15–20 deg/min. The total firing time is 4.5 h, the coke consumption 2.8 ton, and the oxygen consumption about 4500 m³. The use of this cycle allows excellent preparation of the lining for service, practically excluding loss of brick due to spalling, and increasing the resistance of the lining.Translated from Ogneupory, No. 6, pp. 21–27, June, 1971.     

Testing porous periclase — Spinel products in the lining of a rotary kiln burning magnesite

Conclusions The life of porous periclase-spinel products in the most badly worn section of the sintering zones of rotary kilns used for firing caustic dust is 50–100% greater than the average life of the lining in this zone made from chrome-magnesite and magnesite-chromite products.The increased wear resistance of the experimental periclase-spinel products is probably explained by the reduction in the rates of zone formation owing to the features of the phase composition and the structure of the refractories, and also the appreciable strength and comparatively low thermal conductivity.It is desirable to use perous periclase-spinel products for lining the sintering zones of rotary kilns used for firing magnesite, mainly in the most badly worn sections having a temporary fused area (skin).Translated from Ogneupory, No. 1, pp. 30–35, January, 1973.     

Firing Shchelkov and Dankov dolomites in rotary kilns with oxygen-enriched air

Conclusions As a result of enriching the air with oxygen to 23.5–24.9% during the firing of dolomite in a rotary kiln, the flame temperature is increased to 1900–1980°C, that is, by 150–185°C; the burnt dolomite, if the raw materials meet the requirements of ChMTU 8-22-67, satisfy the requirements of ChMTU 8-21-67 in terms of chemical composition and apparent density; the specific consumption of raw materials is 16–20% less, the specific yield is 40–50% greater, and the specific consumption of standard fuel is 10–14% less. The consumption of additional oxygen is 150–175 m³/ton of burnt dolomite.Translated from Ogneupory, No. 8, pp. 18–21, August, 1972.     

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.     

The effect of composition of tar bond on the properties of tarred magnesite refractories

Conclusions The most effective agents for the production of tarred magnesite articles are the bonds prepared from 70% medium-temperature coal-tar pitch and 30% anthracene oil (permissible limits, 20–40%).The anthracene fraction as a solvent pitch in the preparation of the bond can replace anthracene oil.The pitch distillates as a component of the bond give inferior results compared with anthracene oil and fraction. However, considering the high cost and scarcity of the latter, in some cases, pitch distillates can be recommended for preparing bonds for the production of tarred magnesite goods.With the use of carbon oil pitch (20% coal and 80% pitch distillates) as the bond we obtain tarred magnesite specimens of satisfactory quality. From tests of petroleum bitumen we obtained unsatisfactory results. Introduction into the refractory batch of finely milled coal and coke can be of interest in the production of slag-resistant tarred magnesite articles for lining slag zones of converters.To solve the problem of the use of bonds of the recommended composition in the production of tarred magnesite refractories for lining oxygen converters, it will be necessary to carry out industrial tests.The rules obtained in this paper for the effect of composition of bonds on the properties of tarred magnesite refractories can be used for developing the technology for tarred magnesite-dolomite and tarred dolomite refractories.Translated from Ogneupory, No. 1, pp. 39–44, January, 1966.     

Increasing the wear resistance of linings of ore furnaces for melting normal electrocorundum

The use of air-cooled linings on ore furnaces for melting normal electrocorundum has made it possible to increase their wear resistance by an order of magnitude. This is explained by the formation of a steady solid-phase skull due to a higher temperature gradient with a total decrease in the thermodynamic levels of the ambient and the refractory lining.Translated from Ogneupory, No. 10, pp. 29 – 30, October, 1995.