Tiago Ramos Ribeiro

An analysis of Brazilian sugarcane bagasse ash behavior under thermal gasification

BackgroundAshes from sugarcane were analyzed by X-ray fluorescence, ash content, X-ray diffraction, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). FactSage 6.4 database software was used to estimate viscosity at high temperatures (900 - 1550°C) of them.ResultsThe results showed that although ashes from sugarcane bagasse contain silica, most of its SiO2 is from soil contamination. Higher and lower silica samples treated at 1350°C for 20 minutes showed that the fine portion of fraction of the ashes melted at this temperature.ConclusionsThe melting phase could act as sticking flux for the coarse silica particles on the gasifier bottom wall, which could compromise the gasification process.Graphical Abstract(a) Nanoparticles of SiO2 absorbed by sugarcane bagasse, (b) microparticle of SiO2 in the fibers of bagasse after processed in the mill, and (c) particles of SiO2 from the soil not melted, and glass phase formed by the reaction of nano SiO2 and other nutrients elements of the plant such as K, Na, Ca, P, and Fe at 1350 oC/20 min.

Silicon refining by a metallurgical processing route

Directional solidification experiments were carried out in a Bridgman furnace to remove carbon and metallic impurities from silicon. For carbon removal, solidification was achieved by extracting the mold from the hot into the cold zone of the furnace, while for the removal of metallic impurities, solidification occurred by cooling the furnace with a motionless mold. In the experiments of carbon removal, a mold extraction rate of 5 µm/s results in an ingot with columnar grain structure aligned in the ingot axial direction and a macrosegregation of carbon and SiC particles to the ingot top regions. However, at a mold extraction rate of 80 µm/s, the grain structure consisted of columnar grains aligned in the radial direction and SiC particles were observed throughout the ingot, showing lower macrosegregation with a carbon concentration still larger at the ingot top. In the metallic impurities removal experiment, an ingot with a columnar grain structure aligned in the ingot axial direction was obtained and the concentration profiles showed significant metallic impurities macrosegregation to the ingot top.

Brazilian iron ore and production of pellets

ABSTRACT Brazil is the second-largest producer of iron ore in the world. Brazilian richer superficial deposits are composed of brittle material with fine texture and significant amounts of fines are generated during mining and transport. Another type of ore found in this country is the itabirites that have lower iron contents. Beneficiation and concentration steps are required to prepare these materials for the pelletizing process. A general view of Brazilian types of iron ores, mines, and mining companies is given in this work. Special attention is given to pelletizing and the influence of mineralogical characteristics of different ores on the production and final properties of iron ore pellets.

Modification of BOF Slag for Cement Manufacturing

The use of metallurgical slags in cement manufacturing depends on the phases that compose such slags, which are affected by changes in slag chemical composition as well as by cooling rates adopted during solidification. Two different slags were produced in a pilot scale metallurgical reactor by mixing additives into 300 kg of re-melted BOF slag followed by natural cooling or by adding of steel balls to it. Quantitative XRD, SEM and Raman analysis of slag samples revealed the relationship among cooling conditions and crystalline phases.

Treatment of Molten Steel Slag for Cement Application

Steel slag can be an alternative in cement mineral admixture, partially as a substitute for blast furnace slag. A pyrometallugical process has been investigated to promote the chemical composition modification of molten steelmaking slag in a metallurgical reactor. Experiments were conducted by remelting 300 kg of steel slag followed by chemical modification of liquid slag. The modified slags were naturally cooled in the metallurgical reactor or cooled by steel balls. XRD and SEM analysis of slag samples revealed the relationship among chemical composition, cooling conditions and amorphous and crystalline phases. Cement samples were produced by mixing 25% of treated steelmaking slag with 75% of Portland cement, resulting in more than 280 J/g of accumulated hydration heat in 72 h, expansion lower than 0,1% in the autoclave tests and compressive strength higher than 42 MPa after 28 days. The process indicates potential to be applied as a steelmaking slag treatment.