Refractory Products Research Articles

Expansion of raw materials in the production of graphite refractories

The features of the vitrinite and fusynitic anthracites during graphitization of carbon materials based on them are analyzed. It is shown that the use of domestic fusynitic anthracite instead of scarce petroleum coke as a raw material makes it possible to obtain graphitic refractory material with increased density, resistance to abrasive wear and heat resistance. Ill. 1. Ref. 16. Tab. 2.

Production of light-weight refractories based on non-ferrous metallurgy and oil production wastes

The results of the studies showed that it is possible to obtain high-quality light-weight refractories based on industrial waste (the clay part of the gravity tailings of zircon-ilmenite ores ― non-ferrous metallurgy and drill cuttings ― oil production) without using traditional natural materials. Ill. 2. Ref. 17. Tab. 6.

Upgrading volatile fatty acids production through anaerobic co-fermentation of mushroom residue and sewage sludge: Performance evaluation and kinetic analysis

Due to complex inherent structure of lignocellulosic biomass, inefficient hydrolysis and acidification limits fermentative volatile fatty acids (VFA) production of mushroom residues. Meanwhile, the mushroom residues present insufficient nutrient with a high C/N ratio. To solve this issue, anaerobic co-fermentation of cellulose-rich Oyster champost and sewage sludge was tested to enhance the VFA production, and the effect of proportion of mixed substrate was investigated in this study. The results indicated that the sewage sludge yielded higher VFAs than the Oyster champost in single-substrate fermentative system. The maximal VFA yield of 595 mgCOD/gVSadded was achieved when the proportion of sewage sludge increased to 50% in the mixed substrate. In the co-fermentation system, the optimal C/N ratio and features of mixed substrate contributed to the enhancement in hydrolysis and acidification in terms of organic solubilization and VFA production, respectively. But the co-fermentation could not increase VFA/SCOD ratio, probably due to the existence of refractory products such as humic-like and protein-like materials. Besides, this co-fermentation system had strong buffer capacity and it was not necessary to dose chemicals to control the system pH for stable VFA production. Acetate was the dominant VFA product in co-fermentation systems. A modified-Logistic model fitted co-fermentation of sludge and Oyster champost well, and presented a faster rate and higher efficiency of VFA production.

Pulmonary ventilation and gases exchange disorders in workers engaged into refractory materials production

Introduction.Occupational exposure to dust in concentrations sometimes exceeding allowable norms, infl uence of associated hazards (irritating gases, toxic chemicals, unfavorable microclimate at workplace, heavy physical work) cause occupational and occupationally conditioned bronchopulmonary diseases and lower work capacity in workers with main occupations of refractory materials production.Objective.To study functional state of respiratory system for diagnosis of early disorders of pulmonary ventilation and gases exchange in workers of moulded refractory materials production.Materials and methods.Prospective randomized study included apparently healthy male workers (n = 61) of refractory materials plant producing chamott e-silica and spinel-periclase-carbon refractories. Clinic of Ekaterinburg medical research center in 2017–2018 provided examination of carriers (n=21) in spinel-periclase-carbon refractories production shop and pressmen (n=40) of moulding area in chamott e-silica refractories production, aged 27 to 60 years, with length of service in hazardous conditions from 4 to 37 years. Bodyplethysmography helped to assess general lung capacity (GLC), residual lung volume, ratio of residual lung volume to general lung capacity, functional residual lung capacity, bronchial resistance and diff usion lung ability by carbon oxide via single inspiration method. For nonventilated lung volume, the authors used ∆ GLC value that is a diff erence between GLC values measured via bodyplethysmography and via helium dilution in single inspiration maneuver.Results.Obstructive syndrome (6.5%) was a main type of ventilation disorders among the examinees, and equally frequent among the workers engaged into spinel-periclase-carbon refractories production (9.5%) and in those engaged into chamott esilica refractories production (5%). Th e workers engaged into spinel-periclase-carbon refractories production had obstructive syndrome associated with lung hyperinfl ation, and those engaged into chamott e-silica refractories production had also a tendency to restrictive disorders. Lung gases exchange disorders were seen in one third of the examinees, equally frequent in both workers engaged into spinel-periclase-carbon refractories production and those engaged into chamott e-silica refractories production, manifested in 2 variants: lower diff usion lung capacity (fi rst variant) and lower diff usion lung capacity with increased ∆ GLC (second variant).Conclusion.Th e study results prove necessity of bodyplethysmography and diff usion lung capacity diagnosis to reveal perfusion and ventilation disorders at early stages in workers engaged into spinel-periclase-carbon refr actories production over 8 years and in those engaged into chamott e-silica refr actories production over 12 years.

Exogenous refractory protein enhances biofilm formation by altering the quorum sensing system: A potential hazard of soluble microbial proteins from WWTP effluent

Soluble microbial refractory proteins are major components of effluent from wastewater treatment plants that utilize a biological wastewater treatment process. The remaining proteins could negatively affect downstream treatment processes by altering the bacterial quorum sensing system. In this work, we elaborated the effects of exogenous refractory protein on biofilm formation. The results showed a linear relationship between biofilm formation and experimental protein concentrations at the range typically found in effluent, 0–8.0 mg/L. Micro-observation revealed that the exogenous refractory protein stimulated extracellular polysaccharide secretion to promote biofilm maturation. Extracellular polysaccharides increased by ~200% with the addition of only 2.0 mg/L protein. In addition, exogenous refractory proteins altered the quorum sensing system gene expression and polysaccharide gene expression. This work found that exogenous protein accelerated biofilm formation by influencing the quorum sensing system, thus providing new insight into the potential harm of soluble microbial refractory products.

Synthesis and graphitization of resole resins by ferrocene

Commercial (Rs) and laboratory synthesized resoles (LSRs) containing 3–5 wt% ferrocene have been used to study the development of thermosetting resin compositions as binder materials for carbon-containing refractories (CCRs) production. The LSRs were developed based on formaldehyde to phenol 1.5 mol.% (1.5Rs) and 2.0 mol.% (2Rs). Microstructure and oxidation resistance of carbons derived from plain and modified resins have been compared. Chemical structure of the resins was studied using Fourier Transform InfraRed-Attenuated Total Reflection (FTIR-ATR) spectroscopy. X-ray Photoelectron spectroscopy was used to examine chemical changes during heat treatment of the modified products. Flow behavior of plain and formulated resins has been measured under isothermal condition. Rheology measurement results show that the selected amount of ferrocene did not affect the resin near-Newtonian fluid behavior and processability during refractory production. X-ray diffraction (XRD) analysis and transmission Electron Microscope (TEM) were used to characterize the derived carbon samples after thermal treatment of the resins. The results demonstrate that ferrocene is an excellent additive for crystallizing resoles carbon. The presence of fringes in TEM images indicates the graphitized carbon microstructure. The carbon reactivity in an oxidizing environment was also determined via thermogravimetric analyzer (TGA). Several factors, such as bond strength and atoms arrangement, have been found to control the carbonized modified-resin oxidation resistance.

Advanced boron-containing refractory castables bonded with calcium-free binders

The replacement of calcium aluminate cement (CAC) and/or the addition of specific agents (i.e., mineralizers) have been proposed as alternative routes to develop refractory products suitable for intermediate working temperatures (700–1000 °C). In this sense, the use of calcium-free binders, such as hydratable alumina or silica-based compounds, has gained some attention. Additionally, the incorporation of sintering additives to castables can speed up the expected sintering reactions, due to the generation of liquid phase in the designed microstructure during the first heating treatment of these products. Therefore, this work evaluates self-flowing high-alumina castables bonded with 4 wt.% of calcium-free binders: hydratable alumina, a novel powdered microsilica-alumina-based one or their blend. Besides that, it was also analyzed the influence of adding 0 or 1 wt.% of boron carbide to the castables, as this compound can act as a transient liquid sintering agent. The designed compositions were characterized via flowability, thermogravimetric tests, hot elastic modulus, erosion resistance, cold and hot mechanical strength and other techniques. The castable bonded with the blend of the selected binders showed shorter setting time and lower drying profile performance, as the samples’ explosion for these compositions could be detected even for small samples (50 × 50 mm) when using a heating rate of 5 °C/min. On the other hand, the refractory containing the microsilica-alumina-based binder presented enhanced thermo-mechanical behavior. Furthermore, boron addition favored faster sintering of the castables, resulting in optimized performance around 815 °C or even at 1100 °C for the mixture containing only the silica-based additive.

Hydration resistance improvement of doloma particles using different nanoparticles

Doloma (MgO.CaO) is being widely used in the manufacture of refractory products due to its favorable properties, such as the ability to refine steel melt, high refractoriness, high corrosion resistance in alkaline environments, as well as its favorable hot strength. On the other hand, hydration resistance of doloma is low due to the rapid reaction of calcium oxide (CaO) and magnesium oxide (MgO) phases with moisture in atmosphere and formation of calcium hydroxide [Ca (OH) 2] and magnesium hydroxide [Mg (OH) 2] phases. The formation of these hydroxide phases leads to the collapse of doloma containing products. Therefore, in recent years, various studies have been carried out on the use of various additives especially use of nanoparticles on the improvement of the properties of doloma refractory products. The purpose of this study is to conduct a comparative study of the impact of trivalent and tetravalent nanoparticle oxides (SiO2, ZrO2, TiO2, Fe2O3, Cr2O3, and Al2O3) on the hydration resistance of doloma particles for use in refractory products. Therefore, physical test, including resistance to hydration was performed on samples. Also, the microstructure and generated phases of the sintered specimens is evaluated using SEM/EDX and XRD analysis, respectively.

ПОВЫШЕНИЕ ЭЛЕКТРОБЕЗОПАСНОСТИ НА ПРЕССОВОМ ОБОРУДОВАНИИ ОГНЕУПОРНОГО ПРОИЗВОДСТВА

ПОВЫШЕНИЕ ЭЛЕКТРОБЕЗОПАСНОСТИ НА ПРЕССОВОМ ОБОРУДОВАНИИ ОГНЕУПОРНОГО ПРОИЗВОДСТВА

Brazilian refractory grade bauxite: a new alternative to refractories makers and users

Abstract After two centuries of the discovery, we now know that there are several types of bauxites, in which mineralogy points to the most appropriate application. In the non-metallurgical industry, bauxites with refractory grades have been applied as raw materials in the production of high-alumina refractories for both shaped and unshaped. The increase in the cost of other sources of high-alumina raw materials has encouraged the refractory producers to find a more cost-effective substitute, such as refractory-grade calcined bauxites (RGB). Nowadays, concerns rise regarding the availability of RGB due to the continuous restrictions taking place in China, which has a 95% market share. This work presents a new RGB of high-alumina content (~85%) from a Brazilian source in which process enabled a technology with high refractoriness.

Heat-Resistant Concrete Based on Alumina Cement from Substandard Raw Material

Results are provided for development of refractory concrete based on modified alumina cement using chemical industry waste. A quantitative ratio for mixed filler fractions, the effect of production factors on concrete strength, the dependence of its strength properties on form of filler, and solidification conditions are established. It is shown that with respect to physicomechanical and engineering properties the concretes developed is no worse than those existing in the market. With respect to all engineering properties this form of refractory product may be recommended as lining for high-temperature units.

Optimization of the Production Process of Vibrocasted Refractory Products

This paper deals with the optimization of the production process of vibrocasted refractory products. The main goal is to make efficient and automate the production of moulds for refractory blocks. A theoretical research was followed by an expert analysis of the current state of the manufacturing process at an industrial partner. The next step was to analyze complete portfolio of refractory vibrocasted products, which results in choosing a representative sample whose dimensions most correspond to majority of the moulds produced. Subsequently, a design was done, to make the production process more effective with respect to time, technology and construction aspects, focusing on increasing productivity, reducing human labour and increasing production modernization. In the end, the design options were evaluated in terms of time and cost, and the ideal process of the manufacturing production was recommended with respect to the latest technology. It includes a solution for material composition and optimized design of moulds for vibrocasted refractory materials to increase production efficiency moulds and cost reduction while maintaining mould accuracy and quality. These products are subject to high demands in terms of material quality and precision, and at the same time costly to produce due to manual manufacturing.

Elaboration De La Carte Géotechnique De La Ville De Lubumbashi Guide Technique De Sélection Des Sites D’implantation D’ouvrages Du Génie Civil

Geotechnical data processing that ignores the spatial aspect leads to loss of information, specification errors, non-convergent and ineffective estimation, and prediction errors. These data often present a spatial dependence (problem of spatial autocorrelation) and a heterogeneity in space (clustering problem) and sometimes temporal. The geotechnical mapping of Lubumbashi soils based on 1672 observations according to the AASHTO classification system (designation ASTM D-3282 M145), divided these soils into 11 subgroups: A-1-a (sandy gravels with clays), A-1-b (gravelly sands with clays), A-2-4 (gravelly sands with silts), A-2-5 (sandy gravels plastic silts), A-2-6 (gravelly sands with clays), A-2-7 (gravelly sands with active clays), A-4 (silts with sands), A-5 (plastic silts with sands), A-6 (clays with sand), A-7-5 (active clays), A-7-6 (active clays). Class A-3 has not been identified. Soils with an index 5 contain clays of the illite type whereas the others consist of kaolinites on plasticity Casagrande chart. Class A-1 and A-2 are good for foundation engeneering and form the potential aquifers of the city (groundwater, drainage zone, groundwater recharge zone). They also constitute favorable sites for the implantation of the cimeteries (aerated soils) because the time necessary for the destruction of bodies is brief. In this case the rotation of 5 years can be used without problem for a city with dense population like the city of Lubumbashi. Soils A-4 and A-5 are also good for subgrade-foundations, but are highly vulnerable to erosion and liquefaction. Soils A-6 and A-7 form impervious bedrock substrates. These sites can be used as the landfill site. They are also considered clay deposits in the manufacture of ceramics and refractory products. Taking into account the nature of the source rocks, the same lithology can give several types of soils depending on the parameters influencing weathering: climate (Lubumbashi's tropical climate), pH, Eh, topography, anthropization, etc. One type of soil may also come from several rock formations. The geotechnical map developed compared to the geological map of Lubumbashi, shows that soils A-1 and A2 come from conglomerates, sandstones and the lateritization process of rock formations very rich in iron such as dolomitic shale and shale. Soils A-4 and A-5 are often alteration products of silty shales and siltstones, while soils A-6 and A-7 are derived from the alteration of clay and dolomitic rocks: shales, dolomitic shales, silty shales, limestones and dolomites. The geological map is fondamental but not sufficient document for geotechnical studies. A detailed study of the soils and the state of weathering of the different parts of a rock mass is inevitable.

The method for quasiisostatic pressing of ceramic and refractory products

The method for the quasiisostatic pressing of ceramic and refractory products, frst developed in theUSSRby the PhD M. I. Timokhova is described. The stages of development of quasiisostatic pressing and its scheme are given, the range of products obtained by this method is indicated.Ill.1. Ref. 6.

The new kind of the LLC «GIR-ENGINEERING»'s refractory products

The new refractory products of the «GIR ENGINEERING» Company is presented in the article. The data on the physical and chemical properties of the manufactured articles are represented.Ill.2. Tab. 3.

The influence of the structure of refractory products on their performance properties

The influence of the structure of refractory products on such operational properties as slag resistance and heat resistance is considered. As samples, a conventional chamotte refractory (standard) and chamotte refractory made according to a new technology using non-stationary pressing pressure were used. It is shown that the porosity, slag resistance and heat resistance of products manufactured using unsteady pressure is higher than that of the standard.Ill.4. Ref. 4. Tab. 2.

The experience of the SC «Borovitch Refractory Works» production application at the SC «Oskol Electrometallurgical Works»

The results of the cooperation between SC «Borovitch Refractory Works» and the SC «Oskol Electrometallurgical Works» (SC OEW) with regard to the supplying and operational activity of the wide range of the refractory production items are given in the article. The basic development trends are pointed out which can improve and optimize the physical and chemical parameters of the supplied refractories. The main innovative refractory materials and the completed projects are regarded which have amended the technical and economic indexes of the heat vessels at the SC OEW engaged at the main metallurgical processing stages.Ill.7. Ref. 4. Tab. 5.

The recycling materials using in the refractory production

The investigating results are given for the ferrouschromium slags using as the refractory materials to prepare the refractory concretes. The temperature range of their application was defned. It was established that the magnesia oxide addition considerably reduced the Chromium VI formation during service in composition of the refractory materials manufactured on base of the ferrous-chromium slags. Ref. 5. Tab. 4.

An alternative lining of steel ladles: technical and economic aspects

Quality of steel ladles lining to a big extent determine the economic efficiency of steel-making operation. Direct costs on the refractory lining of them can reach 30–50 % of the costs of lining of a steel-making complex. Experience of utilization of refractory materials of different composition considered with the purpose of efficiency increase of refractory materials application in the steel ladles lining under conditions of steel ladle treatment. Considerable abilities shown to make the lining of steel ladle walls and bottom by both carbon-containing and carbon-free refractory materials taking into account the economic aspect. Lining base of steel-making facilities — BOFs, EAFs and steel ladles — is composed by periclase-carbon (MgO–C) refractories. However those refractories have a high heat conductivity, that effects on the heat operation of steel ladles. When using MgO–С materials, vertical fractures can appear in the ladle walls lining as its residual thickness becomes small. Under definite conditions a working lining chipping takes place, problems appear with lining destruction in the pieces angles with cavities formation at the pieces joining. To level the MgO–С drawbacks, periclase-alumo-carbon (MgO–Al2O3–С) and alumo-periclase-carbon (Al2O3–MgO–С) refractory products are used. Al2O3–MgO–C refractories are widely used in most erosion-intensive lining zone — in the combatting place of steel ladle bottom lining. In Russia monolithic lining of steel ladle bottom is successfully displacing the lining by piece products, including alumo-periclase-carbon ones. Such a replace enables to decrease specific refractory consumption and specific costs of them. At present the technology of concrete application to bottom is implemented for ladles of BOF- and steel-making shops. A technology of concrete ladle walls and bottom is intensively implemented for 120–180-ton ladles. The concrete lining of steel ladles has the following advantages: high withstandability against impregnation by metal-slag melt; absence of metal carbonization by the carbon from ladle lining; increase of running duration of safety lining layer by 2–2.5 times; absence of necessity to use nest blocks in both steel outlet unit and for bottom blow-off lance; absence of cracks in lining, wash-outs in seams, angles and edges of pieces; decrease of gaseous hydrocarbon emissions(phenol, formaldehyde, benzapilene) during lining drying, heating-up and operation (only slag belt remains, where pieces have organic binders); saving of materials, working time and manpower while making and maintain the lining; decrease of specific consumption and specific costs for lining per 1t of steel. For lining of steel ladles of big volumes (more 250 t) alumo-periclase (alumo-spinel) products are widely used in China, Europe and Japan. For such a lining the thermo-mechanical tension, arising in monolithic ladle lining, has a less importance, including at its replacing with metal by using crane. It is easier for the products to compensate the ladle geometry change, resulted in metal shall geometry change in time. A positive influence of carbon-free lining, as well as a lining with low content of magnesium oxide, on metal quality noted, first of all for low- and ultralow carbon grades, and pipe low-alloyed steels.

Magnesium Oxide: Properties, Methods of Preparation and Application (Analytical Review)

The article deals with magnesium oxide, this nutrient is widely used for the treatment and prevention of nervous and cardiovascular diseases, has an antidepressant effect of its application and further study of the properties is relevant to the applied aspects of chemical and medical Sciences. Magnesium is one of the main minerals necessary for the normal functioning of the heart, nervous system, muscles, it largely depends on the strength of bones and normal cell activity. With a balanced diet, a person usually gets enough magnesium with food. If the diet is poor in fresh vegetables, herbs, fruits, there are bad habits, then over time may develop a deficiency of this substance. In this case, magnesium oxide is prescribed by a doctor as a drug for oral administration. The main field of application of magnesium oxide is the production of refractory materials, 65 % of all magnesia is used in the production of steel, 15 % – in the cement industry, 7 % – in the production of refractories, 13 % – in other areas. For the purpose of selection of data in sources of information on properties, ways of receiving and application of the representative of mineral food – magnesium oxide the analysis of domestic and foreign literature is carried out. The analytical selection of data of some sources of information on its properties, ways of obtaining and application is presented, special attention is paid to the use of this compound in medicine. The data obtained allow the use of this chemical composition in each field of application has its own requirements for the quality of magnesium oxide.