Abstract The large amount of dust generated in electric arc furnace aligned with its chemical composition makes this dust a potential source of iron in the direct reduction iron process. Thus, the aim of this research is to investigate the reduction of pellets produced with electric arc furnace dust using hydrogen as the reducing agent. The kinetic investigation was examined applying the differential method. In addition, the influence of reducing gas stream and temperature in the reduction process were investigated applying the Forced Stepwise Isothermal Analysis technique. The temperature studied varied from 500 to 1000°C with isothermals in each 50°C. The reducing gas was a mixture of 10% of hydrogen and 90% of argon. Then, the product characterization was carried out via scanning electron microscope and X-ray analysis. A thermogravimetric test showed a mass loss of 42 wt% due to the reduction of iron and zinc oxides. Besides this, the reduction occurred in three steps: 550-650°C, 700-800°C, 850-950°C. Between 550-650°C, the reduction was controlled by a nucleation mechanism with an Ea of 41.1 kJ/mol. In the second step (700-800°C), a mixed control between nucleation and diffusion was obtained with an Ea of 89.1 kJ/mol. Furthermore, a crust of iron was formed around the pellet, which hindered the reducing gas diffusion into the pellet. In the third stage (850-950°C), the formation of a sintered structure was noted, which decreased pore volume. The internal diffusion of reducing gases was determined as the controlling mechanism, with an Ea of 130.9 kJ/mol.

Abstract The study aimed to characterize the mineral wools obtained from wastes of the cutting step of marble and granite, in order to evaluate the possibility of their use on an industrial scale. Mixtures of marble and/or granite wastes were prepared in order to reach the chemical composition of rock and glass wools. The batches were melted in an electric arc furnace in laboratory scale at 1450ºC and casted with water, in order to obtain a higher cooling rate. Characterization work was performed in batches that formed vitreous material, and with superior incorporation of the residues: 11.7% and 14.6% of marble waste with glass wool and rock wool, respectively; 78.3% and 91.6% of an association of marble and granite wastes with glass wool and rock wool, respectively. Computational thermodynamics was used in order to obtain the main phases at 800ºC and determine the liquid and solid content at 1400, 1450 and 1500ºC. In addition, the materials obtained were characterized via chemical analysis using X-ray fluorescence, DTA, X-ray diffraction and SEM. The results indicate that the marble and granite waste are composed mainly of CaO (34.7 wt.%) and SiO2 (66.3 wt.%), respectively. An amorphous crystalline structure was obtained in all tests, indicating that this material can be used as an insulation material. The crystallization temperatures were determined around 800ºC.

Steelmaking slag and residues from granite cuttings are industrial wastes with considerable production, however limited applications. This work studied an inertization and recovery process of such wastes as raw materials into production of rock wool (i.e. a thermo-acoustic insulator with growing market). Several batches were produced aiming the chemical proprieties of a currently marketed rock wool. Mixtures were casted at temperatures of 1400-1500 °C, then quenched in water and also poured into a Herty Viscosimeter. Produced materials with thickness smaller than 500µm were characterized by chemical analyses, XRD, SEM, EDS and DTA. ThermoCalc software was used to simulate the cooling curves of rock wools. Results showed that incorporation of wastes does not affect the main qualities of rock wool, the thermal insulation and prevention of fire spread. Raw material batches of rock wools may assimilate up to 66% of granite waste, or 53% steelmaking slag, or 70% combining both materials.

A tradicional produção de açúcar, associada à crescente produção de etanol, faz da indústria sucroalcooleira um dos principais segmentos da economia brasileira. As indústrias brasileiras de açúcar e álcool processaram cerca de 630 milhões de toneladas de cana em 2009, gerando, aproximadamente, 142 milhões de toneladas de bagaço. Este trabalho apresenta uma possibilidade de destinação para o bagaço da cana através da queima controlada associada à síntese de nanotubos de carbono (CNTs), materiais que possuem inúmeras possibilidades de aplicações tecnológicas devido as suas excepcionais propriedades. Foi utilizado o processo de pirólise a 1000ºC associado a um sistema catalisador, visando à recuperação dos gases gerados como matéria-prima para a síntese dos CNTs. As emissões gasosas foram analisadas por cromatografia e os materiais produzidos foram caracterizados com o emprego de MEV, MET, TGA e espectroscopia Raman. Os resultados mostraram que o uso do catalisador resultou na diminuição das emissões gasosas. Nanotubos de carbono com comprimentos de 10 a 40 µm e diâmetros entre 20 e 50 nm foram produzidos.

The traditional sugar production associated with the growing ethanol production makes the sugarcane industry one of the main segments of the Brazilian economy; together the Brazilian industries of sugar and ethanol processed about 630 million tons of sugarcane in 2009, which generated approximately 142 million tons of bagasse. This work presents an economically and environmentally viable solution for the bagasse disposal through the controlled burn associated with the synthesis of carbon nanotubes (CNTs), materials that have a wide range of potential technological applications due to its exceptional properties. The pyrolysis process at 1000°C associated with a catalyst system were used to recover the generated gases as raw material for the synthesis of CNTs. Gaseous emissions were analyzed by chromatography and the produced materials were characterized with the use of SEM, TEM, TGA and Raman spectroscopy. Results showed that the catalyst application resulted in the reduction of gaseous emissions. Carbon nanotubes with lengths of 10-40 µm and diameters in the range of 20-50 nm were produced.

The world's largest ethanol producer (USA) uses corn as feedstock. DDGS (distillers dried grains with solubles) is the main waste generated from this process (around 32 million t/year). DDGS samples were pyrolyzed at 1000 ºC in a furnace with controlled atmosphere. The effluent was channeled to a second furnace, in which catalyst substrates were placed. Chromatographic analysis was used to evaluate the gaseous effluents, showing that the catalyst reduced hydrocarbon emissions. The solid products formed were analyzed by SEM and TEM. Graphitic structures and carbon nanofibers, 50 µm in length and with diameters of 80-200 nm, were formed.

Styrene-Butadiene-Rubber (SBR) is a synthetic rubber copolymer used to fabricate several products. This study aims to demonstrate the use of SBR as feedstock for carbon nanomaterials (nanofibers and nanotubes) growth, and therefore to establish a novel process for destination of waste products containing SBR. A three stage electrically heated flow reactor was used. Small pellets of rubber were pyrolyzed at a temperature of 1000 ºC. The pyrolyzates were mixed with oxygen-containing gases and were burned. The products of combustion were used to synthesize the carbon nanomaterials (CNMs) at the presence of a catalyst. CNMs have a wide range of potential applications due to their extraordinary mechanical, thermal and electrical properties. Produced materials were characterized by SEM and TEM, whereas combustion products were assessed using GC. Results showed that CNMs with outer diameters of 30-100 nm and lengths of about 30 µm were formed. Therefore, it was demonstrated that waste products containing SBR can be used to generate CNMs which are value-added products of intense technological interest.