Autorizo a reprodução e divulgação total ou parcial deste trabalho, por qualquer meio convencional ou eletrônico, para fins de estudo e pesquisa, desde que citada a fonte. À minha família. AGRADECIMENTOS À Basf, pelo apoio incondicional.Ao amigo Antônio Henrique Pereira, pelo apoio desde o início.Aos colegas da Alcoa, Railson Maciel, Diomedes, André Ricardo, Clodoaldo, Lucivaldo, Diana, Paulão, Robson e Montoro, que tanto contribuíram para o trabalho.

No abstract

The applications of Gy's formula are appropriate for calculating variances of the fundamental sampling error (FSE) at any stage of the sampling protocol and before samples are collected as well. However, the formula can be inaccurate because general factors are used to estimate the ore characteristic. In order to allow the calculation of fundamental sampling error and the minimum representative sample masses without using Gy's factors, there are experiments to calibrate the sampling parameters, namely: the heterogeneity test (HT); the sampling tree experiment (STE) and the segregation free analysis (SFA). The present work describes the experimental procedure for the three calibration methods using bauxite and shows the correlation between them.

Reconciliation plays a key role in controlling and analysing mine operations. It consists in comparing model estimates with actual results produced by the plant, being used as an indicator, a monitoring tool. Discrepancies between these values are common in the mining industry and they highlight problems during processing steps. However, these discrepancies do not necessarily need to be brought to zero, as long as their order of magnitude is understood. Prognostication, a new concept that seeks to replace reactive reconciliation, aims to raise and correct the real causes of these variations. A common cause of this type of problem is sampling, which in most cases is not performed correctly, providing biased samples and compromising reconciliation analyses. The present study reports, evaluates and improves reconciliation in a bauxite mine located in the city of Poços de Caldas/MG, in Brazil and reports on a study of the heterogeneity of the ore. A common practice of the bauxite mines in Poços de Caldas is to carry out the last stage of sampling manually from the trucks before the ore goes to the treatment plant. The data evidenced that this sampling is biased and systematically overestimates the planned ore grades. In addition, it has been confirmed that the best alternative for the company is to implement a conveyor belt sampler collecting increments every 15 minutes. This method shows the best adherence to the plan, that is 100.7% for available alumina and 83% for reactive silica.

A amostragem pode ser definida como o conjunto de operações destinadas à obtenção de uma amostra representativa de uma dada população ou lote de material. A redução da massa deve ser feita de forma criteriosa a fim de assegurar a confiabilidade dos processos envolvidos, não alterando as propriedades físico-químicas, tais como, teor e constituintes mineralógicos, do lote inicial. Mesmo que todos os procedimentos de amostragem sejam corretamente realizados, ainda haverá um erro associado à heterogeneidade constitucional do minério que não pode ser eliminado; o erro fundamental de amostragem (FSE). Neste contexto, os testes de heterogeneidade foram desenvolvidos com o objetivo de estimar o erro fundamental de amostragem. O presente trabalho estuda o desvio padrão gerado pela heterogeneidade constitucional do minério de alumínio da região oeste do Pará, a partir dos resultados obtidos no teste de heterogeneidade, visando otimizar protocolos de amostragem.

No abstract

A produção de alumina através do processo Bayer gera grande quantidade de resíduo conhecido como "lama vermelha". O resíduo é separado do denominado licor verde que contém íons aluminato solubilizados, e direcionado para etapas de separação sólido/líquido realizadas em tanques (lavadores), onde ocorre a dosagem de polímeros solúveis em água que induzem a sedimentação. Utiliza--se sistema de decantação contracorrente com o objetivo de espessar a lama, recuperando o máximo possível de soda cáustica fornecendo um "overflow" contendo baixa concentração de resíduos. O uso de polímeros floculantes em pó, com alto peso molecular e carga iônica adequada, apresenta ganhos significativos relacionados à redução de dosagem, velocidade de sedimentação e compactação do "underflow" resultando em redução significativa de custos no processo produtivo. Entretanto, apesar dos benefícios relatados, muitas refinarias no Brasil ainda fazem uso de polímeros floculantes em emulsão. Nesse trabalho avaliou--se a performance do floculante em pó da Basf (linha Alclar®) com diferente peso molecular e carga iônica. Avaliou--se também de forma comparativa, a associação de poliacrilamida em pó e na forma de emulsão, ao hidroxamato para avaliar a redução do consumo de hidroxamato nas refinarias, quando se utiliza o floculante em pó da linha Alclar® associado. PALAVRAS--CHAVE:resíduo Bayer, sedimentação, floculante em pó POWDER FLOCCULANT APPLICATION FOR BAYER RESIDUE SEDIMENTATION IN THE ALUMINIUM INDUSTRY ABSTRACTThe alumina production through Bayer process generates a large amount of residue known as red mud. Once separated from green liquor (GLQ), red mud is direct to washing steps where synthetic flocculant dosage promotes solid liquid separation. The goal is thickening the slurry to recover caustic sodium as much as possible. The use of powder polyacrylamide with high molecular weight and suitable ionic charge results in significant gains in terms of dosage, settling rate, underflow compaction and overflow turbidity. However, the alumina industry in Brazil still using emulsion flocculants despite the reported benefits. In this paper was evaluated the performance of different powder flocculants from BASF (Alclar® line). In addition, was performed a comparison between powder polyacrylamide and emulsion flocculants associated or not with hydroxamates.

The presence of copper in distilled sugar cane spirits, especially cachaça produced in alembics, has impeded the marketing of this product. Red mud (RM) is a residue obtained from alumina production. It contains a high concentration of metal oxides and is very alkaline. The RM was dried at 100 oC and sifted through a 150-micron sieve. The sample was characterized by B.E.T. nitrogen adsorption, scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) and Atomic Absorption Spectrometry (A.A.S.). The textural parameters indicate that the total surface area (S.T.) was 21.9 m2g-1, and the total volume pore (V.T.) was 0.09 cm3g-1. The RM (1 g) was stirred for two hours with a 1.0 L cachaça sample containing 9.39 mg of copper L-1 and filtered under atmospheric pressure. The concentration of copper ions detected in the filtrate was 0.00 mg L-1. No copper ions were retained when the cachaça was filtered through the RM under high pressure without stirring prior to filtration.