Tests of the protective coatings of the refractory lining of copper-smelting converters

Conclusions The authors investigate the mechanism and kinetics of formation of the protective coating of the refractory lining of copper-smelting converters. The use of alumina-containing materials to create the protective coating permits an increase in the campaign time of the converter between repairs by a factor of 1.5–2 (in comparison with a magnetite coating), a decrease in the coating deposition time from 5.5–6 to 2–2.5 h, and a decrease in the rate of wear of the coating from 14.5–16.2 to 5.5–6.6 mm/day.Translated from Ogneupory, No. 5, pp. 29–33, May, 1981.     

Physicochemical properties of the deposits from the circulating water at the Zaporozhe Refractory Plant

Conclusions The deposits in the study are multicomponent polydispersed suspensions characterized by a solid-phase concentration of 3.79–17.7% density 1–1.09 g/cm³, and a pH of 8.2–11.9. When the deposits are left to stand for 10 days they become compacted up to 40–70% of the original volume. The size of the aggregates of the dispersed phase change from 5 to 50 m with a predominant particle size of 5 to 20 m (64–79%). The electrokinetic potential of the phase is from –1.5 to –12.8 mV for various batches of deposits.The dispersion medium of the deposits is characterized by a pH of 8–11.5; a density of 1 g/cm³; viscosity of 0.001 Pa·sec; an electrical resistivity of 7.8·10^–4 to 44·10^–4–1·cm^–1; and a concentration of dry residue up to 1490 mg/liter.The dispersed phase of the deposits has a density of 2.16–2.52 g/cm³ and consists mainly of oxides of silicon, aluminum, calcium and a very small amount of oxides of titanium, iron, magnesium, and manganese.The addition of polyacrylamide to the original deposits in amounts of 25 to 400 mg/liter leads to a reduction in the electrokinetic potential of the particles, to their aggregation, and to spatial structure-formation.With the addition of polyacrylamide in amounts of 100–250 mg/liter to the deposits, the size of the aggregates decreases 15–30-fold by comparison with the untreated. The addition of PAA does not significantly affect the chemical composition of the dispersed phase.The data in this paper have been used to plan the cleansing equipment at the Zaporozhe Refractory Plant.Translated from Ogneupory, No. 5, pp. 30–33, May, 1984.     

Effect of aluminum sulfate content of the precipitation bath on fibre physico-mechanical properties

Conclusions A high-strength fibre is obtained on spinning into precipitation baths containing 30–45 g/liter aluminum sulfate and 65–70 g/liter sulfuric acid, and having a bath density of 1.30–1.31 kg/m³. The relative breaking load of the fibre is 28 cN/tex, its elastic modulus in the wet state is 1380 MPa, and its elongation at break is 16%.At an aluminum sulfate content of 15–17 g/liter in the precipitation bath, an increase in sulfuric acid concentration from 90 to 129 g/liter leads to an increase in relative breaking load and the relative strength of fibre in a loop.Translated from Khimicheskie Volokna, No. 3, pp. 40–41, May–June, 1987.     

Gas-flame guniting of the lining of intermediate continuous steel-casting ladles

Conclusions As a result of laboratory investigations and rig testing of the flame guniting of intermediate ladles for continuous steel-casting plant we recommend the following bodies: 90% corundum, 10% sodium tripolyphosphate; 80–90% corundum, 20–10% chamotte; 80–90% high-alumina chamotte, 20–10% chamotte. The particle size of the corundum body is <0.088 mm, high-alumina <0.25 mm.The optimum guniting cycle is: consumption of natural gas 60 m³/h, oxygen 100 m³/h, gunite body 150–200 kg/h, guniting distance 450–550 mm, rate of moving the burner 1.0 m/min.In the case of chamotte, the coefficient of gunite body utilization equals 0.75, for high-alumina 0.70, and for corundum 0.40, with an open porosity in the gunite coating of 10–15, 8–10,and 4–6%, respectively.Using the experimental equipment the body made from 90% corundum and 10% sodium tripolyphosphate was used to gunite the side surface of the lining of an intermediate ladle. The wear of the gunite section of the lining was 1.3–2.5 mm per heat.Translated from Ogneupory, No. 4, pp. 37–42, April, 1973.     

Changes in the magnetic properties of chromite ore heated with scale

Conclusions Chrome spinel and gangue of Kimpersarski chromite ores has a low and scarcely distinguishable magnetic susceptibility which does not alter after heating at temperatures from 400° to 1300°C. The magnetic susceptibility of the ores fired with additions of iron oxide or scale at 1000–1300°C increases from (20–120)×10^–6 to (1650–3400)×10^–6 cm³/g. The increase in the magnetic properties of chromite ores after firing occurs on account of the increase in the magnetic susceptibility of the gangue from (50–120)×10^–6 to (6000–8000)×10^–6 cm³/g. Thus after firing of chromite ores with iron-containing additives the gangue acquires ferromagnetic properties. The magnetic susceptibility of the gangue is 50–115 times greater than chrome-spinel which permits us to use highly productive magnetic separators with low and medium magnetic field forces for their treatment.     

Calculated rates of soil acidification of intensively used grassland in the Netherlands

The major processes involved in acidification of soils under intensively managed grassland are the transformation and subsequent leaching of applied nitrogen (N), assimilation of excess cations in herbage and acidic atmospheric deposition. Carbonates from fertilizers and excess cations in purchased concentrates are the most important proton (H⁺) neutralizing agents applied to grassland. In this study, the effects of grazing, cutting and N application on the net proton loading from each of the main processes were calculated, using a simple model.On mown swards, simulated excess cation uptake by the sward released 4.5–9.3 kmol_c H⁺ ha^–1 yr^–1. The total proton loading on mown grassland decreased from about 8.0 to 5.3 kmol_c ha^–1 yr^–1 when fertilizer N input as CAN-27 increased from 0 to about 400 kg ha^–1 yr^–1. Contributions from atmospheric deposition ranged from 2.2 kmol_c ha^–1 yr^–1 when herbage yield exceeded 10 Mg ha^–1 yr^–1 to 3.0 kmol_c ha^–1 yr^–1 when herbage production was only 5.5 Mg ha^–1 yr^–1.On grazed swards, transformation of organically bound N from urine and dung to nitrate (NO ₃ ^- ) and the subsequent leaching of excess NO ₃ ^- was the main source of protons. Application of 400 kg N ha^–1 yr^–1 to grazed swards increased the proton loading from transformed N from 3.9 to 16.9 kmol_c ha^–1 yr^–1. The total proton loading on grazed swards exceeded that of mown swards when the input of fertilizer N exceeded 150 kg ha^–1 yr^–1.Underestimation of the amount of N immobilized in the soil biomass and lost by denitrification may have resulted in a slight overestimation of the amount of N lost by leaching and thereby also the simulated total proton loading.     

Rheological and technological properties of cassiterite suspensions and of the casts made from them

Conclusions The rheological and technological properties of cassiterite suspensions, as of the casts made from them, have been studied as a function of their pH. It is established that the optimum intervals correspond to pH 1–3 and 11–12.4. At these values of pH, cassiterite products were obtained with an open porosity of 1.5–4.0%, apparent density of 5.97–6.27 g/cm³, and an ultimate bend strength of 750–900 kgf/cm². The alkali slips for the casting of thick-walled articles cannot reasonably be used because of their slow setting rate.Translated from Ogneupory, No. 2, pp. 45–49, February, 1979.     

Thermal conductivity of insulating refractories measured by the standard method and by the cylinder method

Conclusions The coefficients of thermal conductivity of insulating refractories measured by the method prescribed in GOST 12170-66, using the recommended thermometers with a scale division of 0.1°C and thermal insulation made from firebrick with an apparent density of 1.0 g/cm³, are appreciably higher than data obtained by the cylinder method. At average temperatures of 200–500°C (400–1000°C on the hot face) the discrepancy comes within the range 50–200%; when T_mean=600–700°C (1200–1300°C on the hot face) the discrepancies diminish to 0–30%.The maximum apparatus error in determining the thermal conductivity according to GOST 12170-66 with the use of Beckmann thermometers and low thermal-conducting linings is 10–30% for – 0.2–1.0 kcal/(m·h·deg), which greatly exceeds that indicated in the standard, ±10%. The maximum proportion in the error comes from the measurement of the drop in water temperature as it passes through the calorimeter. Consequently, the use of the standard recommended thermometers with scale divisions of 0.1°C is unacceptable for measurements on materials with a low thermal conductivity, since it may lead to errors of about 100%.Detailed comparison of the results of measuring this factor on standard equipment using the Beckmann thermometers, and on the improved instrument designed by the Ukrainian Institute (the cylinder method), showed that the mean square deviation of the experimental values for thermal conductivity for identical specimens with respect to the interpolation curves in the case of standard determinations is 2–3 times greater than the corresponding deviation for the cylinder method.In most experiments the interpolation curves =f(T) for the standard method is different by ±15–25% from the curves obtained with the cylinder method. This displacement apparently is due to certain constant errors connected with the unaccounted-for sources of error in the standard methods.The proposed method of determining the coefficient of thermal conductivity is of interest for scientific-research work. The use of the cylinder method is industry is associated with difficulties in preparing the specimens — Editors.Translated from Ogneupory, No. 8, pp. 45–52, August, 1971.     

Study of the service of high-alumina and kaolin refractories in the checkers and structure of blast-furnace stoves

Conclusions The structure of kaolin brick in the high-temperature zone of the stove after 6.7–7.2 years service at subcupola temperatures of 1300°C underwent substantive external and structural changes.In the structure of the stove made from high-alumina brick VGO-62 after six years service we detected substantially less change.In the kaolin brick of the upper rows of the checker three clearly defined zones are formed: working (slag), impregnated with alkalis, the transition zone (porcelain-type), and the least-changed zone. During the service of high-alumina refractories mullite crystallizes, which confirms the results of work carried out previously.Owing to the creep of kaolin and high-alumina refractories 4–5% shrinkage of the brick occurs in the upper rows of the checker, and at a depth of 2.5–6.0 m — 1.5–2.0%. The height of the checker diminishes under these conditions by 0.8–1.0 m.The densification of the structure of the upper rows of the checker corresponds to a reduction in porosity and an increase in the density of the brick.The temperature of initial deformation under load of 2 kg/cm² of the slagged kaolin refractories taken from the upper rows of the checker diminishes by 150–200°C, and in the lower layers of the checker it does not alter. This factor for high-alumina refractories in service increases by 160–190°C. In the high-temperature zone of the stoves it is desirable to test dense, high-alumina refractories containing 72–75% Al₂O₃.Translated from Ogneupory, No. 5, pp.14–19, May, 1972.     

A device for the take-up of pneumatically tangled acetate yarns onto a spinning package

Conclusions Three variants of take-up and winding devices have been developed; these permit one to take up yarn from the spinning machine onto a commercial package by a frictionless method and ensure a constant linear velocity of yarn winding.The device operates under the following regimes: linear winding rate, 400–600 m/min; yarn tension up to regulating roll, 4.5–5.0; tension after it, 8–9 cN; weight of package, 3 kg.The devices ensure obtaining acetate pneumatically tangled yarns with 15–35 pneumatically tangled sections per m of yarn with a uniform distribution over the yarn length; the density of the yarn in the package is 850–950 kg/m³.Translated from Khimicheskie Volokna, No. 1, pp. 46–48, January–February, 1985.     

A spectroelectrochemical investigation of the influence of sodium diisobutyldithiophosphinate on silver dissolution in aqueous cyanide

Polarization studies have been carried out to determine the influence of diisobutyldithiophosphinate (DIBDTPI) on the dissolution of silver in cyanide solutions at pH 11. DIBDTPI was found to inhibit dissolution at concentrations similar to those used when this compound is applied as a flotation collector. The inhibition efficiency in 10^–2 mol dm^–3 CN^– was found to increase with increase in DIBDTPI concentration in the range 10^–6–10^–4 mol dm^–3, and with increase in time of exposure of the silver to the DIBDTPI solution. The inhibition efficiency found for 10^–4 mol dm^–3 DIBDTPI in quiescent 10^–2 mol dm^–3 CN^– solution at 23 °C was 64.6% and 95.0% for exposure times of 10 min and 2 h, respectively. These values are significantly less than those found previously for 2-mercaptobenzothiazole under the same conditions. Surface enhanced Raman spectroscopy showed that inhibition was associated with adsorption of DIBDTPI displacing cyanide from the silver surface. Voltammetry at 0.5 mV s^–1 indicated that adsorption of DIBDTPI involves charge transfer.     

Effect of the steel substrate on the composition of gases in enameling

Gases emitted from the bulk of a steel substrate and desorbed from its surface in heating in the process of enameling are identified. It is shown that the effect of the steel substrate on the composition of gas bubbles in the glass-enamel coating consists in generation of carbon monoxide, hydrogen, and steam.Translated from Steklo i Keramika, Nos. 1 – 2, pp. 44 – 45, January – February, 1996.     

Using dinas in the top zone of checkers for blast furnace stoves

Conclusions Experience with the use of dinas in the upper zone of blast furnace stove checkers showed that, at a hot blast temperature of 900–1000°C and with a temperature of up to 1200°C in the gases under the cupola, the dinas practically preserved its refractoriness and strength in four years operation; cracking was slight and the checker channels were completely preserved.When these cupola conditions prevailed, the structure of the top 60–65 rows of checker (9–9.5 m), made from dinas is quite adequate, and the underlying rows of firebrick were in an excellent state.Fluxing oxides falling into the stoves from the blast gas and air used for combustion, and also from moist blast gas, reduce the refractoriness of the changed zones of the dinas, but only by 30–40°C.It is necessary to study carefully the behavior of dinas in these conditions at higher subcupola gas temperatures, say at up to 1400–1500°C.Translated from Ogneupory, No. 4, pp. 31–35, 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.     

Study of the thermal stability of a poremit emulsion

Results are presented from a study of the thermal stability of a poremit emulsion. Safe storage and processing times and temperatures are indicated along with the effect of the emulsion on the thermal stability of other materials. Satisfactory thermal stability is attained with an emulsion of poremit in lubricating oils and fuel oils containing up to 3.5% sulfur and from 10 to 17% water. No heat is released for several days at temperatures of 90–110°C. The emulsion begins to break down at 205–210°C, this process intensifying at 240–250°C. The self-ignition temperature of the emulsion is within the range 310–370°C.State Scientific Research Institute Kristall, 606007, Dzerzhinsk. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 6, pp. 89–96, November–December, 1994.     

Effect of γ-radiation in the quality of high-molecular sulfite cellulose

Conclusions The effect of ionizing radiation on the molecular weight characteristics and ability to be dissolved of high-molecular, high-viscosity sulfite cellulose has been investigated.A radiation dose range of 5–10 kGy has been established, on absorption of which by high-molecular, high-viscosity sulfite cellulose, the degree of polymerization is reduced to 840. The reactivity is increased to 80/11 (% CS₂/% NaOH) and the share of the main fraction, having a DP of 200–800, rises to 52–60%. Irradiation of cellulose is suitable for use in the manufacture of viscose fibre.Translated from Khimicheskie Volokna, No. 1, pp. 30–31, January–February, 1988.     

Role of sintering additives in the production of lime refractories

Conclusions A production technology is proposed for lime refractories covering the preparation of high-density lime clinker, followed by crushing, batching, adding waterproof bond, pressing the goods, and firing at 2020 K.The technology for obtaining high-density lime clinker resistant to atmospheric hydrolysis, includes milling CaCO₃ to a particle size of 100–150 m with simultaneous incorporation of sintering additives (2–6% TiO₂ or 2–4% titanium ferrites), and the use of water solutions of sulfite lye as bond; pelletizing and firing at 2020 K. The lime clinker has an apparent density of 2.75–3.03 g/cm³, and an open pelletizing and firing at 2020 K. The lime clinker has an apparent density of 2.75–3.03 g/cm³, and an open porosity of 3.4–9.8%.The lime products have an apparent density of 2.65–2.97 g/cm³, open porosity 4.4–16.4%, compressive strength 60–140 N/mm², and refractoriness under load 1610–1700°C and above.Translated from Ogneupory, No. 2, pp. 13–16, February, 1992.     

Choosing the sizes of longitudinal gaps between product settings in tunnel kilns

Conclusions A method is proposed for selecting the heat-engineering rational longitudinal geometric characteristics of the setting of products for tunnel kilns.A reduction in the longitudinal gaps between the settings in a high-temperature tunnel kiln to 300–350 mm leads to a 12–13% increase in the heat transfer and introducing internal gaps between the semi-settings to a 7–10% increase.Translated from Ogneupory, No.4, pp. 13–16, April, 1967.     

Anodic behaviour of alkaline solutions containing copper cyanide and sulfite on the graphite anode

Sulfite may be added to copper cyanide solutions to reduce cyanide oxidation at the anode during copper electrowinning. Anodic sulfite oxidation is enhanced in the presence of copper cyanide. Sulfite also suppresses the oxidation of copper cyanide. The effect of sulfite on the oxidation of copper cyanide decreases with increasing mole ratio of cyanide to copper. This is related to the shift in the discharged species from Cu(CN)₃ ^2– to Cu(CN)₄ ^3– with increasing mole ratio of cyanide to copper. Sulfite is oxidized to sulfate. At [Cu⁺] = around 1 M, CN:Cu = 3.0–3.2, [OH^–] = 0.05–0.25 M, [SO₃ ^2–] = 0.4–0.6 M and the temperature = 50–60 °C, the anodic current efficiency of sulfite reached 80–90%. With further increase in sulfite concentration beyond 0.6 M, the current efficiency of sulfite oxidation will not be increased significantly. Further increase in CN:Cu mole ratio will result in decrease in the anodic current efficiency.     

Potential impact of agroforestry on soil nutrient balances at the farm scale in the East African Highlands

There is much current interest in the potential role of agroforestry in the mitigation of nutrient depletion in Sub-Saharan Africa. Using data from farm surveys and trials, a static model of N and P flows was constructed for a standard farm system, representative of typical subsistence farms in humid parts of the East African Highlands. The model was used to explore the possible impact of improved agroforestry systems on nutrient budgets, to identify priorities for research.Soil nutrient balances in the standard farm system were - 107 kg N and - 8 kg P ha^–1 yr^–1. Agroforestry systems did not significantly reduce the N deficits except when a high proportion of the total biomass was returned to the soil, rather than removed from the farm. Agroforestry increased N input through biological N fixation and deep N uptake, but this was offset by a larger nutrient removal from the farm in harvested products, which increased from 38 kg N in the standard system to 169 kg N ha^–1 yr^–1 in an intensive dairy-agroforestry system. Agroforestry did not increase P inputs, and harvested P increased from 6 kg P in the standard farm system to 29 kg P ha^–1 yr^–1 in the dairy-agroforestry system. Thus, moderate P inputs, of 20 kg P ha^–1 yr^–1 were required to maintain soil P stocks.N leaching from the field was the most significant nutrient loss from the farm system, with a range of 68 to 139 kg N ha^–1 yr^–1. The capture of subsoil N by deep-rooted trees in agroforestry systems substantially increased N-use efficiency, providing 60 kg N ha^–1 yr^–1 in the dairy-agroforestry system. The budgets were sensitive to N mineralization rates in subsoils, N losses from soils and manures, and effectiveness of deep-rooted plants in subsoil N capture, for which there is little data from the region. Therefore, high priority should be given to research in these areas.The current model can not account for important feedback mechanisms that would allow analysis of the long-term effects of nutrient budgets on nutrient availability and plant productivity. Dynamic models of farm nutrient budgets that include such interactions are needed to further assess the sustainability of farming systems.