Navegando por Assunto "Bauxite waste"

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Acesso aberto (Open Access)
Absorção do dióxido de carbono por resíduo de bauxita em torres de absorção
(Universidade Federal do Pará, 2013-03-04) BOTELHO, Fernando Aracati; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968
One of the most discussed environmental problems on the world scene today is global warming and its implications. Although the greenhouse effect is a natural phenomenon, the increase in emissions of gases such as CO2 from the combustion process may favor its aggravation. Following this line, there is interest in conducting research to minimize the release of this gas in the atmosphere. This work aims to study the process of absorption of carbon dioxide by aqueous phase of bauxite residue (soda and dissolved ions in solution) in spray tower and tower saddles random (both pilot scale), as well as check the pH change in this absorption process to both towers. Evaluate pH change and CO2 absorption capacity by considering the following variables: the type of absorption tower, using the supernatant as the absorbent means and the use of the suspension heated by resistances. The results showed that the suspension of bauxite residue absorbed significant amount of CO2, both the spray tower as the tower saddles. The average absorption rate was around 8.42% for the spray tower and 9.34% for the tower saddles. The ability carbonating the suspension of 27%-p was about 33.3 kg CO2 per tonne of waste and there was a substantial reduction of the alkalinity of the residue by reaction with gaseous effluents with a mean decrease of 4.0 and 3.5 pH units for the tower saddles and sprinkler respectively.
Acesso aberto (Open Access)
Influência da granulometria e de aditivos no comportamento reológico do rejeito de lavagem da bauxita
(Universidade Federal do Pará, 2014-03-13) GONÇALVES, Silvane Gonçalves e; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968; FELIPE, Augusta Maria Paulain Ferreira; http://lattes.cnpq.br/8871741271063047
In the bauxite mining in Parogominas-PA city, tailings are discarded in the processing with 33,5% of solids content and small granulometry with D50 below 5 μm. These factors contribute to this suspension basically formed by sílico aluminates, with high concentrations of kaolinite clay, have high viscosity and high initial tension flow. It was performed granulometric analysis and determined the chemical and mineralogical composition of the material. The granulometric analysis was made by wet sieving and the small particles were determined by laser diffraction. The determination of the chemical composition was made by Fluorescence Spectrometry X-ray, identifying considerable amounts of alumina available, 21,28%. The mineralogical composition was determined by X-ray diffraction (XRD), obtaining gibbsite, hematite, quartz and kaolinite. It was performed the determination of the friction factors pulp, using equation to fluids that have Herschel-Bulkley behavior and using the Dodge and Metzner correlations. It was used VT550 viscosimeter, with coaxial cylinder sensorSV1, to make defloculation and flocculation test using different rheological additives. The additives used were: sodium hexametaphosphate, hydroxamate, aluminum sulphate, sodium polyacrylate and 25% anionic polyacrylamide. The trials were realized in shear rate of 100 s-1, time 20s and temperature of 32ºC.It was performed also, analysis of viscosity of pulps with different pH and in samples less 38μm (400# Tyler), with the objective of evaluate how the particle size and pH influenced in the behavior of additives. The study showed that particle size and pH influence on the behavior of additives, because if the particle size is very small better is the behavior of the additive. The behaviors of the additives as flocculation or defloculation depend of the pH.
Acesso aberto (Open Access)
Resíduo da bauxita na produção de agregados graúdos sintéticos para concreto estrutural: análise de durabilidade
(Universidade Federal do Pará, 2022-12-15) MACHADO, Vinícius Costa; PICANÇO, Marcelo de Souza; http://lattes.cnpq.br/4535052395600357
In the midst of environmental policies, civil construction began to seek alternative materials, such as those arising from industrial waste; and with each passing day this has become more common. This fact is related to issues involving: the high demand for construction materials; the depletion of raw material reserves; the high cost and space of waste storage; and possible risks to public health arising. In the case of industrial waste, mining waste should be highlighted, in particular the bauxite residue (BR) resulting from the Bayer ore refining process, which has already become a promising alternative raw material in several countries, including Brazil for a number of applications. The BR has been studied and used somewhat recently in the production of coarse aggregates for concrete, with success in several studies. However, the information available regarding the use of coarse synthetic aggregates in concrete is mostly linked to its physical-mechanical properties, with a certain lack of data regarding their influence on the durability of structural concrete. The study initially addressed the physical mechanical characteristics and reactive potential by alkali-aggregate reaction (AAR) of 3 coarse synthetic aggregates (AGS 70, AGS 80 and AGS 90), obtained from BR together with silica and clay, based on in the normative requirements required for use in concrete. Soon after, the concrete produced with these aggregates, in total replacement of pebbles, were evaluated regarding their physical-mechanical properties (resistance to axial compression, traction due to diametric compression, modulus of elasticity, water absorption by capillarity) and durability (accelerated carbonation and penetration of chlorides). The results showed that the synthetic BR aggregates were consistent with the technical specifications for use in structural concrete and did not trigger AAR, thus remaining inoculum. The axial compression strength (28 days) reached values between 36-24 MPa; traction and modulus of elasticity showed little variability; capillary absorption was proportional to the increasing linear trend of water absorption by coarse aggregates; highlighting the concretes with AGS 70 and AGS 80 that obtained better performance in the physical-mechanical characteristics analyzed. The carbonation resistance of concretes containing AGS 70 and AGS 80, based on normative references, were classified as low and exceptional respectively. Regarding the penetration of chlorides, they were classified as moderate resistance (with AGS 70 and AGS 80) and low (with AGS 90) according to the methodology used.