Vládia Cristina Gonçalves de Souza

Estimativa de qualidade de carvão por meio de perfilagem geofísica de gama natural e resistividade

This study investigates geophysical logging as a tool to predict coal quality. Some of the coals chemical parameters were determined by laboratory analysis and were compared against values derived from geophysical logging correlation (natural gamma radiation and resistivity versus ash content, specifically). The results showed a strong correlation between the coals natural gamma emissions and their ash content. From this correlation, a simple linear model was obtained and used to estimate ash grades, directly from geophysical logging records. The error of these predictions is less than ± 5%. Additionally, results showed no correlation between the sulphur grade, or volatile matter, and the geophysical records. Ash grades derived from natural gamma ray values can be usedas secondary information to evaluate coal quality during resource estimation, when combined with lab analysis and appropriate geostatiscal methods. The methodology is illustrated by means of a case study at a coal deposit located in southern Brazil.

Methodology for determining rom size distribution

A methodology to determine the size distribution curve of the ROM was developed in a Brazilian iron ore mine. The size of the larger fragments was determined taking photographs and setting the scale of the images to analyze their dimensions (length of their edges and areas). This was implemented according to a specific protocol of sampling that involves split and homogenization stages in situ of a considerable quantity of ore (about 259 metric tonnes). During the sampling process, larger fragments were separated and smaller size material was screened. The methodology was developed initially in order to preview the performance of a primary gyratory crusher that is fed directly from trucks. Operational conditions of the equipment such as closed and open-side settings could be adjusted previously, obtaining different product size distributions. Variability of size of the fragments affects subsequent stages of crushing and can increase circulating load in the circuit. This leads to a decrease of productivity or recovery of the ore dressing. The results showed insignificant errors of accuracy and reproducibility of the sampling protocol when applied to friable itabirite rocks.

Efeito dos elementos estranhos (foreign íons) sobre a Microdureza Vickers das fases cristalinas em clínqueres co-processados

This study determines the average value of Vickers micro-hardness of the clinker crystalline compounds and evaluates the effect of foreign ions and mineralogical composition on the micro-hardness results. A signifi cant number of samples were collected from the feed-conveyor belt of the clinker ball mill at eleven co-processing kilns in Brazil. The results show that the micro-hardness varies according to the type of impurities and their distribution. Also, the mineralogical content and alumina/iron ratio play an important role.

Efeito das impurezas dos clínqueres coprocessados sobre sua quebra em Drop Weigth Tester (DWT)

In this study, the possible correlation between impurities presented in the crystalline compounds of the coprocessed clinkers and their breakage strength (determined by Drop Weigth Tester-DWT) is verified. This latter is used to predict the grindability of these materials by providing the impact parameter (A.b). The higher the impact parameter is, the lower the breakage strength is. For the tested clinkers, the average content (wt. %) of impurities in the crystallized phases, including alkalies, barium, strontium, manganese and titanium was determined. For this, microanalysis with an EDX (Energy Dispersive X-Ray) system coupled to the SEM (Scanning Electron Microscopy) was used. The statiscal analysis of the chemical results suggests a strong correlation between the impurities and impact parameter.

Estudo por microscopia óptica e lupa das características mineralógicas e microestruturais do clínquer aplicado ao processo de moagem e qualidade do cimento

Have been widely studied influence clinkers micro structural and mineralogical characteristics on its grinding behaviour, due to high cost of this stage at the end of the fabrication process and the requirements of market quality. In this work, one used the optical microscope and the magnifying glass to describe and analyze the samples of particles of various sizes of clinker, deriving from a factory at south of Brazil. Through this study, it was evidenced, in the samples collected, the occurrence of a high degree of corrosion the minerals of alite and belite. It was even observed that the size of particles do not influence the quantity of microcracks, because that is of physical-chemical origin and it do not mechanical. Therefore, it was concluded that corrosion lead to formation of a large quantity of pores and many channels, make easy the formation of microcracks, that increase, in turn, the grinding behaviour of cement clinker, but at expenses of a considerable reduction in the cement quality.

Estudo da influência da microestrutura do clínquer sobre a moagem na fabricação de cimento: microscopia eletrônica de varredura

As continuation of a study previously realized with optical microscope and magnifying glass, on samples of clinker collected from a factory at south of Brazil, it was realized analysis on electron microscopic. The objective was search more information that could or not corroborate the high degree of corrosion of the crystals result, pointing by first instruments, due the presence of a high content of metals. The analysis on electron microscope have show the existence of a model of microcracks and of corrosion of the crystals, as much alite as belite. The use of the energy dispersive X-ray help to fortify the hypothesis of a situation with high content of Fe2O3, liquid phase and metals, included titanium.