Abstract Cornstarch is one of the most used depressants in mineral flotation operations. However, corn is a costly input for the Brazilian mineral industry, since its main destination is to serve the animal and human food market and exports. In this study, sorghum and millet, two cheaper starch sources, were tested in order to reduce the mining dependence on corn. A simplex lattice design mixture {3,4} was used to evaluate the best proportion of corn, millet, and sorghum flours to be used as a pyrochlore depressant in relation to the industrially adopted cornstarch (Stargill 6172 supplied by Cargill). Flotation tests were carried out on a bench scale Denver flotation cell. All tests were performed in triplicate in a single rougher stage. The results found suggest that sorghum flour was a stronger pyrochlore depressant compared to corn and millet flours, with an average Nb2O5 content of 1.72 ± 0.05% and recovery of 80.75 ± 4.10%. These values were close to the ones found with Stargill 6172 (1.32 ± 0.02 and 80.95 ± 1.13%, Nb2O5 content and recovery, respectively), the industrially adopted depressant. The marked price and the easiness in the production of the flour in relation to the extraction of starches makes the sorghum flour a potential pyrochlore depressant, replacing the industrially used cornstarch.

RESUMO Ações para tratamento, reutilização e destinação adequada de resíduos perigosos (RP), a exemplo dos gerados em serviços de saúde, atividades agrossilvopastoris e oficinas mecânicas ganham importância, observando que o descarte inadequado pode ocasionar problemas ambientais. Algumas pesquisas têm apontado uso das cinzas oriundas de RP, em substituição parcial do cimento Portland ou como agregado miúdo em matrizes cimentícias, conforme as propriedades dos materiais. O objetivo desta pesquisa foi identificar as características físicas, químicas e mineralógicas das cinzas geradas em uma incineradora de RP situada no estado da Bahia/Brasil, sendo essas submetidas aos ensaios de caracterização, tanto in natura quanto após etapa de calcinação à 1000 °C, denominadas de cinza pesada (CP) e cinza calcinada (CC), respectivamente. Determinou-se a distribuição granulométrica, perda ao fogo, propriedades térmicas, composição química, morfologia, carbono orgânico total e reatividade, sendo as amostras classificadas pela norma da ABNT NBR 12653/2014. Os resultados obtidos indicam significativas diferenças entre os materiais analisados, nos aspectos físicos, químicos e mineralógicos. O uso das técnicas e métodos possibilitou classificar as amostras estudadas de forma que não atendem os requisitos mínimos normativos, entretanto, não é possível descartar a utilização das CC em matrizes cimentícias.

ABSTRACT Actions for the treatment, reuse and proper disposal of hazardous waste (WH), such as those generated in health services, agroforestry activities and mechanical workshops gain importance, noting that improper disposal can cause environmental problems. Some researches have pointed to the use of ash from WH, in partial replacement of Portland cement or as a fine aggregate in cementitious matrices, according to the properties of the materials. The objective of this research was to identify the physical, chemical and mineralogical characteristics of the ash generated in a RP incinerator located in the state of Bahia/Brazil, which were subjected to characterization tests, both in natura and after the calcination step at 1000 °C, called heavy ash (AH) and calcined ash (AC), respectively. The granulometric distribution, loss on fire, thermal properties, chemical composition, morphology, total organic carbon and reactivity were determined, and the samples were classified according to the ABNT NBR 12653/2014 standard. The results obtained indicate significant differences between the analyzed materials, in the physical, chemical and mineralogical aspects. The use of techniques and methods made it possible to classify the studied samples in a way that they do not meet the minimum normative requirements, however, it is not possible to rule out the use of AC in cementitious matrices.

Abstract Brazil is among the world's largest iron ore producers. The standard concentration method is reverse cationic flotation using amines, and their derivatives, such as quartz collector and corn (as either grits, flour, or starch) as the hematite depressant. Corn is considered cheap, abundant, and available all around the country. However, its demand has been abruptly increasing over the last few years, mainly due to the emerging of new attractive markets, such as ethanol production. In order to propose a feasible replacement for corn, hematite and quartz samples from the Brazilian Iron Quadrangle were tested in a modified Hallimond tube using millet starch as depressant for the first time (corn and sorghum starch were used as benchmark). Tests were carried out with four different depressant dosages and four different pHs, all in triplicate. It was possible to reach quartz floatability above 98% and hematite depressability above 93% for millet and sorghum starches. This fundamental study shows that replacing corn with millet poses a real opportunity to reduce operational costs.

Abstract Starches are widely used as depressant in froth flotation operations in Brazil due to their efficiency, increasing the selectivity in the inverse flotation of quartz, depressing iron ore. The starch market has been growing and improving in recent years, leading to better products attending the requirements of the mineral industry. The major source of starch used for iron ore is the cornstarch, which needs to be gelatinized, by heat or sodium hydroxide (NaOH) addition (also known as caustisized starch), prior its use. This stage has a direct impact on industrials costs, since the lower consumption of NaOH in gelatinization provides better control of the pH in the froth flotation and reduces the amount of electrolytes present in the pulp. In order to evaluate the influence of temperature on the NaOH consumption, gelatinization tests were carried out with temperatures ranging from 25 to 65 ºC, measuring the volume of NaOH. All tests were performed in triplicate. A linear model correlating the temperature and the NaOH need for the cornstarch gelatinization has been stablished. This model can allow mineral industries to optimize the NaOH amount used to prepare the depressant used in froth flotation. For example, the reduction in NaOH could easily reach 480 L per ton of cornstarch when performing gelatinization with the cornstarch solution at 35 ºC instead of 25 ºC (reduction of approximately 34% in the NaOH consumed).

O desaguamento é uma das operações unitárias industriais mais importantes e é amplamente adotada em diferentes indústrias. Atualmente, a disposição dos rejeitos do processamento mineral é um grande problema, devido ao impacto ambiental gerado. O processamento da rocha fosfática na Anglo American Fosfato Brasil, situada em Catalão/GO, gera, aproximadamente, 180 t/h de rejeitos de 480 t/h alimentadas na usina (aproximadamente 37,5% da alimentação da usina), com 5 a 10% de sólidos e, aproximadamente, 14% de P2O5. Atualmente os rejeitos são encaminhados diretamente para a barragem de rejeitos. O presente trabalho propõe a geração de pasta produzida a partir do rejeito gerado na usina. O líquido clarificado, obtido através de ensaios de sedimentação, foi drenado e a polpa remanescente foi encaminhada para o segundo estágio, consistindo de filtragem a vácuo. A adição de floculante permitiu uma taxa de sedimentação mais rápida e uma performance mais alta no estágio de desaguamento, sendo o último devido ao fato de o material floculado ter sido retido pelo meio filtrante e não passar pelo mesmo, fato que ocorria sem a adição do floculante. Os resultados obtidos foram satisfatórios para a produção de pasta usando rejeito com, aproximadamente, 65% de porcentagem de sólidos

The dewatering stage is among the most important industrial unit operations, and is widely adopted in many different industries. Nowadays, mineral processing tailings disposal is a big problem due to the environmental degradation it causes. The phosphate rock processing in Anglo American Phosphate Brazil, situated in Catalão/ Go/Brazil, generates around 180 t/h of tailings for a plant feed of 480 t/h (approximately 37.5% of the processing plant feed), with 5 to 10% of solids and approximately 14% of P2O5. Nowadays, the tailings are sent directly to the tailings dam. The present work proposes paste production using the tailings from the phosphate rock processing plant. Through decantation of a tailings sample, a clarified liquid was obtained and drained. The decanted pulp then went through a second stage consisting of vacuum filtration. Flocculant addition in this stage generated a faster sedimentation rate and a higher dewatering performance in next stage of dewatering, because the flocculated material was retained by the filter medium instead of passing through it. The results were satisfactory for paste tailings production with a solid percentage of around 65%.

Um problema para a resolução de balanços de massa, em usinas de processamento mineral, é o cálculo da carga circulante presente em circuitos fechados. Uma família de métodos possíveis de aplicação, para a resolução desse cálculo, diz respeito aos métodos iterativos, que consistem em um loop finito, no qual a cada iteração a solução inicial do sistema é refinada de modo a se aproximar da solução real. O presente trabalho apresenta um algoritmo iterativo de baixa complexidade, para o cálculo de carga circulante em circuitos fechados, possibilitando, assim, a construção de balanços de massa, metalúrgico e de água que seja confiável. As equações propostas, no algoritmo, foram obtidas através da análise de diversos sistemas industriais, levando-se em conta os parâmetros operacionais do processo. A validação do método foi realizada com dados industriais reais, visando a assegurar uma maior confiabilidade dos resultados obtidos. Dois diferentes tipos de circuitos fechados, com diferentes níveis de complexidade, são apresentados de modo a elucidar o algoritmo proposto, permitindo-se afirmar que tal algoritmo pode ser aplicado a qualquer circuito fechado, no processamento de minerais. Os resultados obtidos foram satisfatórios, no que tange à velocidade de processamento, à convergência da solução e ao número de iterações necessárias para o cálculo da carga circulante.

A problem for solving mass balances in mineral processing plants is the calculation of circulating load in closed circuits. A family of possible methods for the resolution of these calculations is the iterative method, consisting of a finite loop where in each iteration the initial solution is refined in order to approach the exact solution. The present work presents a low-complexity iterative algorithm for circulating load calculation in mineral processing closed circuits, thus enabling the construction of reliable mass, metallurgical and water balances. The proposed equations on the algorithm were obtained through the analysis of many industrial systems, taking into account the process operational parameters. A validation was performed with real industrial data, in order to ensure a greater reliability of the obtained results. Two different types of closed circuits are presented, each one with different levels of complexity, to clarify the proposed algorithm. With the results, it is possible to affirm that the proposed iterative algorithm can be successfully applied to any kind of closed circuit in mineral processing. The results were satisfactory with respect to processing speed, convergence of the solution and the number of iterations required for the circulating load calculation.