Antônio Cezar Faria Vilela

Concrete Performance With Admixtures of Electrical Steel Slag and Copper Copper Concerning Mechanical Properties

The generation of solid residues and an adequate final destiny for them is a subject that has attracted more and more research. The recycling of solid by-products as construction materials can be an alternative to reduce costs of the latter and it can also reduce the impact on the environment. Nevertheless, it is fundamental that the characteristics of these new materials be equivalent to the traditional ones or even better, if possible. In this context, the use of electric steel slag and copper slag can be a potential alternative to the admixtures used in concrete and mortars. Results of physical, chemical and physical-chemical characterizations of electric steel slags from Rio Grande do Sul and copper slags from Bahia, both in Brazil, are presented in this work. Also presented are results of compressive tests, flexural tests and Brazilian tests in concrete specimens with these admixtures, indicating the viability of their use.

Characterization study of electric arc furnace dust phases

Electric arc furnace dust (EAFD) is a solid waste generated in the collection of particulate material during steelmaking process in electric arc furnace. The aim of this work is to carry out a chemical and structural characterization of two EAFD samples with different Zn contents. Optical emission spectroscopy via inductively coupled plasma (ICP), X ray diffractometry (XRD) and Mossbauer spectroscopy analysis were carried out in such EAFD samples. From XRD measurements, the samples exhibits the following phases: ZnFe2O4, Fe3O4, MgFe2O4, FeCr2O4, Ca0.15Fe2.85O4, MgO, Mn3O4, SiO2 and ZnO. The phases detected by Mossbauer spectroscopy were: ZnFe2O4, Fe3O4, Ca0.15Fe2.85O4 and FeCr2O4. Magnesium ferrite (MgFe2O4), observed in the XRD patterns as overlapped peaks, was not identified in the Mossbauer spectroscopy analysis.

Evaluation of environmental compatibility of EAFD using different leaching standards.

A study on laboratory scale to evaluate the environmental compatibility of electric arc furnace dust (EAFD) is reported in this article. EAFD, a waste by-product of the steel-making process, was generated on a steel plant located in Brazil. Different leaching tests, NBR10005 (Brazilian), AFNORX31-210 (French), JST-13 (Japanese), DIN38414-S4 (German), TCLP (American), and NEN 7343 (Netherland) were conducted. These leaching procedures are batch tests and are columns conducted in a way that an equilibrium condition should be achieved. The pH of the medium showed a crucial parameter governing the release of metals from the solid phase into solution. As the pH of the medium varies with the leachant used, this determines the dissolution of the elements. Zn, Pb, Mn, Cd, and Cu presented high leachability at NBR10005 procedures (acid pH). Except Pb and Cr, the leachability of all others metals in leaching tests with alkaline pH decreases with the increase of the pH. NBR10005 classifies the EAFD as a hazardous waste due to high concentration of Pb and Cd in leachate. The column tests are presented in the following order of leaching: Pb>Cr>Zn>Mn>Cu>Cd.

Reactivity of Brazilian Coal, Charcoal, Imported Coal and Blends Aiming to Their Injection into Blast Furnaces

For about 10 years the steel industry in Brazil has used pulverized coal injection (PCI) technology in the blast furnaces based on imported coals. In order to decrease the dependence on imported coals, Brazilian coal, which has limited use due to high ash content, was suggested to be mixed with imported coal and charcoal. The aim was to examine the reactivity of the samples. The charcoal use in the steel industry contributes to the CO 2 emission reduction, since it represents a renewable source of energy. The reactivity of the coals, charcoal and mixtures was evaluated through simultaneous thermal analyses. Results of this study are presented and discussed.

Thermal Analysis Evaluation of the Reactivity of Coal Mixtures for Injection in the Blast Furnace

Pulverized Coal Injection (PCI) is an important standard technology replacing coke partially by pulverized coal into the blast furnace that allows a significant reduction of hot metal costs and environmental impact, contributing to a decrease of coke requirements for ironmaking. Coals typically used in this process in Brazil are, at current time, exclusively imported from many countries, although economic important coal-measures occur in the southern part of the country. The Brazilian coals have a low rank, higher contents of inert components, proportioning nocoking properties and an expected high reactivity. Due to these caractheristics, these coals could be used for injection in the blast furnaces in order to decrease the dependency on high cost imported coals. The efficiency in the combustion and the coal reactivity are considered important parameters in the blast furnace, since a larger amount of char (unburned coal) causes severe problems to the furnace operation. The aim of the present work is to compare the reactivity of a south Brazilian coal, obtained from Faxinal mine, with two imported coals and the blends of the Brazilian coal with the imported ones. The reactivity of these coals and their blends were evaluated in a thermogravimetric analyzer. In the experiments, various mass ratios of Faxinal coal and the imported coals were used to compose the blends. The gasification reaction with pure CO2 was conducted under isothermal conditions at 1050 °C and atmospheric pressure. The experimental results show the greater reactivity of the Faxinal coal. The additive behavior was confirmed. The blends with a composition of up to 50% Faxinal coal have parameters according to the usual limits used for PCI.

Evaluation of Secondary Steelmaking Slags and Their Relation with Steel Cleanliness

Based on data provided from an industrial plant and FactSage commercial software use, a study of secondary refining slags and inclusion cleanliness was performed. Six heats of two slag series, namely, A and B, with average chemical composition (wt pct) of 43.00CaO-25.90SiO2-12.96Al2O3-18.13MgO for series A and 49.98CaO-23.88SiO2-10.11Al2O3-11.99MgO-4.03CaF2 for series B, were used for the study. Both series used DIN 38MnS6 modified steel. The effective viscosity, solid fraction, composition of the liquid fraction, and slag saturation degree in MgO (calculated through thermodynamic software) were related to the experimental results obtained for the inclusion cleanliness. The B slags showed lower effective viscosity than the A slags, due to their high liquid fraction. Regarding the capacity of slags in the inclusion removal, slag B5 resulted in the lowest inclusion density and was considered as the best choice among the slags studied. The inclusion species formed using B slags are constituted especially of CaO-Al2O3-SiO2 and MgO-Al2O3 and are Al2O3 rich. The presence of sulfide-type inclusions (AlMnS and CaS) were more pronounced among A slags.

Reciclaje de escoria granulada de fundición (EGF) como sustitución de parte del cemento en hormigón

The recycling of industrial solid wastes has become an indispensable practice to the natural resource preservation, in the cost and environmental impact reduction. The utilization of alternative materials in the civil construction industry is attractive and correct way in terms of economy and environment. As result of that, the slag recycling as raw material in pavement, concrete and cement are already common practices, where the noblest use of this material depends on the existence of adequate characteristics to the proposed use. The foundry granulated slag is a waste generated in the process of cast iron production via cupola furnace. Previous studies have shown that this slag, with lower particle size, presents good pozzolanic properties. Also, its amorphous structure resulting from fast cooling linked to an adequate chemical composition may permit a noblest application of this solid waste, such as cement substitute. This work has the aim of studying the performance of concrete using foundry granulated slag as a partial substitute of cement, evaluating its mechanical properties. Concrete samples were molded with different combinations of slag amounts (10%, 30% and 50%) to partially substitute cement, and water/agglomerate (0,40; 0,55 0,70) rates. Such combinations were compared with the reference concrete (without slag). For each concrete age (7, 28 and 91 days) mechanical tests were carried out as uniaxial compressive strength, splitting tensile strength and flexural strength. The results have shown that the granulated slag present an adequate performance (mechanical properties) to the proposed application.

Behaviour of coal ashes for pulverised coal injection at high temperatures in relation to their chemical and mineralogical composition - experimental and computational analysis

Abstract The selection of coals for pulverised coal injection usually consists of evaluating the carbonaceous matter. However, the reduction of permeability in the lower section of the blast furnace with high rates of pulverised coal injection can be associated with remaining ashes from the coal combustion process. The aim of this work is to evaluate the behaviour of coal ashes at high temperatures in relation to their chemical and mineralogical composition. These ashes were submitted to the following analysis: chemical (X-ray fluorescence), mineralogical (X-ray diffraction), fusibility (heating microscopy) and viscosity (rotational viscometer). The software FactSage was also used to evaluate the behaviour of coal ashes. It was observed that samples present different chemical and mineralogical compositions, reflecting in the fusibility and viscosity of ashes. Their proportions and relevant phases were determined by computational thermodynamics and also related to the experimental work.

Assessment of viscosity calculation for calcium-silicate based slags using computational thermodynamics

This study focuses on the viscosity calculation of molten slags using computational thermodynamics. Different slag systems and their measured viscosities from different references were used and compared with those obtained through FactSage software. To calculate the viscosity of each slag the Viscosity module available in FactSage 6.4 was used. In order to perform the evaluation of computational thermodynamics in viscosity calculation, six different slag systems were presented, all of which were formed of calcium-silicate melts. In total, 162 slags, in temperatures ranges from 1423 K (1150 oC) to 2089 K (1816 °C) were presented for all slag systems. The software showed a tendency to produce viscosity values lower than those found in the literature measured by an experimental method. The relative deviation between the measured and calculated viscosity values is in the range of 13.31 to 37.53% for evaluated systems. Considering all references and systems, the average deviation between measured and calculated viscosities is 23.61%, which, according to literature, is an acceptable value. The CaO-SiO2-Al2O3 and CaO-SiO2-FeO systems showed the best agreement between the experimental method and the method calculated through FactSage 6.4 with a very good fitting between viscosity values.

Combustibility and reactivity of coal blends and charcoal fines aiming use in ironmaking

Charcoal is a very important reducing agent in Brazil, the world’s largest steel industry based on charcoal blast furnace. Charcoal generates large amounts of charcoal fines during its production and processing. A good alternative for harnessing this fuel is the injection into coke-based blast furnaces via PCI process (Pulverized Coal Injection), a key technology for reducing use of coke in ironmaking. This study aimed to evaluate the combustibility and reactivity to CO2 of binary blends of charcoal fines and coals with purpose to PCI. Moreover, it was also attempted to identify the reasons for the different behavior of coals. The work was carried out by thermogravimetric analysis (TGA). The proportions of charcoal used were 10, 20 and 50% in mass. Charcoal showed the highest combustibility and reactivity among tested fuels and the blends formulated had higher combustibility and reactivity than single coals.