José Antônio da Silva Souza

Application of bauxite waste from amazon region in the heavy clay industry

In this work, a method was developed for the application of red mud, an alkaline leaching waste, from a bauxite processing plant located in northern Brazil (Amazon region) as starting material for heavy clay products. Samples were prepared by pressing blends of red mud and clay, which were then fired at temperatures from 900 oC to 1190 oC. Characterization was carried out by chemical analysis, differential thermal analysis (DTA) and X-ray diffraction (XRD), and the following ceramic properties were evaluated: water absorption, linear shrinkage and flexural strength. In order to evaluate the Na+ stability in the dense ceramic, leaching tests were also carried out on the specimens after sintering process. Results indicated that samples with 50 and 70 wt% of red mud are proper for being used in the production of ceramic bodies, due to its excellent properties, mainly high mechanical resistance and low water absorption, showing thus, an option to minimizing the environmental impacts caused by the aluminum industry.

Comportamento de blocos cerâmicos estruturais produzidos a partir da mistura de lama vermelha e argila

A utilizacao de novas tecnicas de aproveitamento de residuos tem-se tornado cada vez mais importante na construcao civil, principalmente quando se trata da utilizacao de residuos de outros segmentos industriais e da reducao de consumo de materias-primas naturais. O objetivo deste estudo foi avaliar a utilizacao da lama vermelha, residuo proveniente da producao de alumina metalurgica, na producao de blocos cerâmicos vazados estruturais. A producao dos blocos foi realizada em uma industria cerâmica, a partir de uma mistura de 60% de lama vermelha (LV) e de 40% de argila. Apos a producao dos blocos, realizaram-se ensaios de acordo com as normas tecnicas, tais como absorcao de agua e compressao axial simples. A partir da analise dos resultados, observou-se que os blocos estruturais produzidos a partir da mistura de LV e argila atenderam aos parâmetros normativos quanto ao indice de absorcao de agua e de resistencia a compressao, e que as resistencias medias e caracteristicas desses blocos foram superiores as dos blocos cerâmicos de referencia.

Analyzing the Bauxite Residue Amendment Through the Addition of Ca and Mg Hydroxides Followed by Carbonation

The production of one ton of alumina using the Bayer process generates 0.7–2.0 ton of Bauxite Residue (BR) and an average of 1.0 ton of CO2. The direct use of exhaust gases to react and reduce the alkalinity of BR may allow a triple gain: improving the storage conditions, opening a range of new applications for BR and sequester from 16 to 102 kg of CO2 per ton of alumina. This paper shows a lab scale long term program to measure the effects of adding different percentages of Ca and Mg hydroxides followed by carbonation in order to enhance the precipitation of the alkalinity on stable compounds. Analysis by X-ray diffraction and scanning electron microscopy was done to monitor the appearance of carbonates. The BR pH was monitored for 600 days to evaluate the buffer effect and compared with the stabilization pH of carbonated bauxite residue without addition.

Bauxite Residue Amendment Through the Addition of Ca and or Mg Followed by Carbonation

The alumina production Bayer process generates 0.7–2.0 ton of Bauxite Residue (BR) and an average of 1.0 ton of CO2 per ton of alumina produced. The direct use of exhaust gases to react and reduce the alkalinity of BR may allow a triple gain: improving the storage conditions, opening a range of new applications for BR and sequester from 16 to 102 kg of CO2 per ton of alumina. This paper shows a lab scale long term program to measure the effects of adding different percentages of Ca and Mg salts followed by carbonation in order to precipitate the alkalinity on stable compounds. The main goal is to decrease the stabilization pH to facilitate the reuse. The processed material was analyzed periodically to monitor the appearance of carbonates. The pH of the suspension was monitored for 400 days after the reaction to evaluate the buffer effect. X-ray diffraction and scanning electron microscopy were used to analyze the reacted material.

Estudo da sinterização em reator vertical de leito fixo para produção de agregado sintético

Os agregados sinteticos vem sendo empregados na construcao civil como uma medida para reducao do extrativismo mineral. Dentro desse contexto, a reciclagem de residuos industriais configura hoje a base da maioria dos processos de reducao da exploracao dos recursos minerais. Neste trabalho estudou-se a sinterizacao em reator vertical de leito fixo para producao de agregado sintetico, a partir de 20% de pelotas e 80% de carvao vegetal. As pelotas foram confeccionadas a partir de uma mistura contendo argila, carvao vegetal e cinza volante. Realizaram-se dois experimentos variando a velocidade de succao do ar. O material produzido foi analisado por difracao de raios X, microscopia eletronica de varredura, medidas de suas propriedades cerâmicas e classificacao quanto a sua granulometria. As analises dos resultados demonstraram que as reacoes de estado solido, durante o processo de sinterizacao, foram eficientes e que o agregado produzido foi classificado como leve e graudo. O processo se mostrou interessante para a sinterizacao de agregados, podendo ser controlado pela composicao, granulometria, gradiente de temperatura e fluxo gasoso.

Alkalinity Precipitation Measurement on Carbonation of Bauxite Residue

The alumina production Bayer process generates 0.7 to 2.0 ton of Bauxite residue (BR) and an average of 1.0 ton of CO2 per ton of alumina produced. The direct use of exhaust gases to react and reduce the alkalinity of BR may allow a triple gain: improving the storage conditions, opening a range of new applications for BR and sequester from 16 to 102 kg of CO2 per ton of alumina. This paper shows the first results of a lab scale program to measure the effects of adding different percentages of CaO and MgO before carbonation in order to precipitate the alkalinity on stable compounds. . The inlet and exhaust gases were analyzed. The precipitate after carbonation was evaluated to monitor the amount of stable compounds like dawsonite. The pH of the suspension was monitored during and after the reaction to evaluate the buffer effect.

Efeito de aditivos no comportamento reológico do rejeito da bauxita

In the bauxite mining in Parogominas, PA, Brazil, tailings are discarded in the processing with 33.5% of solids content and small particle size with D50 below 5 µm. These factors contribute to this suspension basically formed by silicoaluminates, with high concentrations of kaolinite clay, increase the viscosity and the yield stress, these factors are important during the pumping. It was performed granulometric analysis and determined the chemical and mineralogical composition of the material. It was studied the use of the sodium hexametaphosphate and polyacrylamide 25% anionic to decrease the viscosity. The result show that the viscosity decrease with use of 23.8 g/ton for the polyacrylamide and 101.75 g/ton for the sodium hexametaphosphate. The particle size and the pH have influence in the behavior of the additives.

SIMULAÇÃO COMPUTACIONAL DAS PANELAS DE ACIARIA DA SIDERÚRGICA SINOBRAS S.A.

The aim of this work consists in studing the thermal behavior of ladles during steps of the operating cycle using heat transfer equations and computational simulation. From the study results sought to make improvements in order to reduce the loss of heat energy during steps of the production process. Through mathematical modeling, measurements in the plant and computational simulations were determined the temperature drops and heat losses. Therefore were proposed operational and physical changes that after practice tests and or computational simulations proved to be efficient for the reduction of heat loss and lower consumption in the ladle furnace.