Fernando Vernilli

Wear mechanism for blast furnace hearth refractory lining

Abstract Over recent years, owing to the need to increase productivity, it has been necessary among other things to increase the hot metal temperature in the blast furnace hearth. As a result, refractory lining wear becomes more intense. While publications present a host of comparative tests for hearth refractories and their performance, hardly any information is available in such publications regarding reaction mechanisms and further deterioration of these materials. Based upon comparative laboratory test results using two carbon materials of different concepts, the various reaction mechanisms and enhanced refractory lining deterioration for the blast furnace hearth have been identified. From an understanding of these wear mechanisms acting upon the hearth lining, it has been decided to introduce some practical operating measures, with a view to extending the blast furnace campaign.

Recycling of Steel Sludge into Red Ceramic

The present paper has for objective to evaluate the effect of fine steel sludge waste incorporation on the properties and microstructure of a kaolinitic clayey body used to the fabrication of bricks and roofing tiles. Compositions were prepared with additions of waste of 0, 5 and 10 wt.% in a kaolinitic clay from the county of Campos dos Goytacazes, State of Rio de Janeiro, Brazil. To determine the technological properties such as bulk density, linear shrinkage, water absorption and flexural strength, specimens were prepared by uniaxial pressure at 20 MPa and then fired in a laboratory furnace at 700°C, 900°C and 1100°C. The microstructure of the fired specimen was evaluated by SEM. The results showed that the incorporation up to 10 wt. % of fine steel sludge does not change the ceramic properties, specially, at low temperatures. Hence, the recycling of steel sludge into red ceramic fabrication can be considered as an environmentally correct solution for the final disposal of this type of waste.

Behaviour of biofuel addition on metallurgical properties of sinter

Abstract Blast furnace gas yield is essentially controlled by a gas-solid reaction phenomenon, which strongly influences hot metal manufacturing costs. As a result of rising prices for reducing agents on the international market, Companhia Siderúrgica Nacional decided to inject natural gas into its blast furnaces. With more gas inside the furnace, the burden permeability became even more critical. To improve blast furnace gas yield, a new technological approach was adopted; raising the metallic burden reaction surface. To that end, a special sinter was developed with permeability being controlled by adding micropore nucleus forming agents, cellulignin coal, without, however, degrading its mechanical properties. This paper shows the main process parameters and the results from physicochemical characterisation of a sinter with controlled permeability, on a pilot scale, compared to those of conventional sinter. Gas flow laboratory simulations have conclusively corroborated the positive effects of micropore nucleus forming agents on enhancing sinter permeability.

Recycling of steelworks refractories: processing and properties

The maintenance of several steel-making equipment of the Companhia Siderúrgica Nacional (CSN/Brazil) builds up about 11 000 tons of refractory waste per year. Most of that refractory waste is disposed off in landfill sites without any application. That action permanently excludes an important alternative source of raw material from the productive cycle. In this context, in the particular case in CSN, all critical points of the generation cycle and recycling of refractory waste were investigated, aiming to use these residues as reprocessed raw material in the Refractory Industry – reverse logistics. The project implementation, through an integrated solution, was technically and financially feasible with an economic return of about US

Production and Characterization of Ti-Nb Alloys, Using Powders Obtained by HDH Process Aiming the Development of Biomaterials

1 million per year in terms of net present value. The reuse of this refractory waste also minimises the environmental impact generated by the production, consumption and disposal of refractory materials from steel production.

Influence of Firing Temperature on the Behavior of Clay Ceramics Incorporated with Elephant Grass Ash.

Titanium is a metal that has high melting point 1668 ° C, the boiling point of 3287° C, low density (4.54 g/cm3) and modulus of elasticity around 12.7 MPa x104. However, one of the most important properties is the biocompatibility, which makes this metal to be the most widely used in biomedical. Several alloys were developed using titanium such as the alloy Ti-6Al-4V, however Al and V show toxic characteristics to the organism. The alloy TiNb has been studied to replace the alloy Ti-6Al-4V, because it presents high biocompatibility, low modulus of elasticity, high corrosion resistance and low toxicity. The alloy TiNb can be obtained by conventional melting route or powder metallurgy, where the powders can be obtained by spray drying, chemical reactions and the process of hydrogenation and dehydrogenation (HDH).The hydrogenation is carried out by inserting hydrogen in the structure of Ti and Nb in vacuum at high temperatures, forming a phase extremely fragile called hydride of Ti and Nb, thus enabling the reduction of particle size by milling. Upon heating under vacuum, the hydrogen is extracted to yield the metals Ti and Nb since the hydrogen forms a reversible phase with metals. This work aims the production and characterization of the alloy TiNb where the powders are obtained through the HDH process, varying the concentration of Nb by weight from 10 to 50%.To analyze the morphology and pore size, formation and composition of phases, we used the techniques of microstructural characterization and mechanical by scanning electron microscopy, BET, X-ray diffraction and compression test. The results showed a heterogeneous distribution of Nb in the matrix Ti as well as a decrease in the modulus of elasticity with increase in percentage of Nb.

Recycling of Benefited Blast Furnace Sludge into Red Clay Ceramic

The microstructural and technological properties of clay ceramic incorporated with 10 and 20 wt% of elephant grass ashes were investigated at different firing temperatures of 650, 850 and 1050oC. X-ray diffraction were used to obtain the minerals and phase compositions. The microstructure was analyzed by scanning electron microscopy. The technical properties related to water absorption, linear shrinkage and flexural rupture strength were obtained by standard test. The results showed significant changes in the microstructure and phasic composition with increasing firing temperature. A marked improvement in the water absorption, decreasing to 18% as well as increase in strength, above 5 MPa, was found at 1050°C. However, only a slight contribution might be attributed to the incorporation of elephant grass ash. Nevertheless, its use as a by-product and the associated saving in clay are relevant environmental and economical advantages.

Incorporation of Global Blast Furnace Sludge into Clayey Ceramic

The blast furnace sludge is a waste generated after the washing step of the blast furnace gas. The reuse of this waste in the steelmaking process itself is quite problematic. This study aims to analyze the possibility of the incorporation of a type of blast furnace sludge, benefited by a process that uses helical separators, into red ceramic. Specimens were prepared by uniaxial pressing at 20 MPa and then fired at 750°C and 950°C. The evaluated technological properties were linear shrinkage, water absorption and flexural rupture strength. The results showed that the benefited blast furnace sludge significantly influences the evaluated properties, by impairing the linear shrinkage and the water absorption but improving the mechanical strength.

Characterization of a Water Clearing Treatment Residue and Its Application as Clay Ceramic Addition

The blast furnace is one the main systems used in steelmaking plants operating with iron ores. In addition to the production of pig iron and slag, the blast furnace operation also generates a considerable amount of wastes such as dust usually collected in the upwards flowing gas. The dust collecting stage, without separation procedures, produces a sludge, which cannot be recycled inside the plant due to the concentration of undesirable earth alkaline metals as well as zinc. A possible solution for this so-called global blast furnace sludge (GFS) is its incorporation, outside the plant, into clayey ceramic products processed at high temperatures. Therefore, the objective of the present work was to investigate the effect of GFS incorporation, in amounts of 5 and 10 wt%, into kaolinitic clay ceramics fired at 750, 950 and 1050oC. Initially, the GFS was characterized and, after processing, incorporated into ceramics that were then tested for the water absorption, linear shrinkage and flexural strength. It was found significant improvements in the properties for GFS incorporated ceramics fired at 1050oC.

Niobium Sintering Process Using Design of Experiment: Taguchi`s Method

The addition of industrial residues into common red clay ceramic has been, from many decades, an alternative of using other low cost raw materials and, more recently, as an environmentally correct destination for polluting substances. An important residue, known as yellow sludge, is that generated at the water clearing stage (WCS) of a treatment plant by some heavy industries such as an integrated steel making. Since this yellow sludge residue is normally disposed in ways that pollutes water bodies, the objective of the present work was to characterize a WCS yellow sludge and investigate its addition into clay ceramics. The residue was characterized by X-ray fluorescence, particle size distribution and scanning electron microscopy. The addition was carried out up to 7.5 wt% followed by firing at 800oC. The added ceramics were evaluated in terms of water absorption, linear shrinkage, dry apparent density and flexural rupture strength. It was found that the residue addition does not practically alter the ceramic technical properties.