Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 75-77). Also available via the Internet.

The objective of this investigation was to determine the sensitivity of three selected input parameters in the operational control of continuous bottan-fed thickeners used for the treatment of coal refuse slurries. The three variable paramenters were "Feed Flow Rate," "Feed pH," and "Feed Solids Concentration." These three input parameters were studied under three polymeric conditions. The X-ray analysis of underflow refuse samples from two coal preparation plants showed that the samples contained clays of various types. Kaolinite type clay was chosen as the feed material in this investigation. The static settling tests on the kaolinite-water suspensions using polymers showed that slurries with 5.0% or less feed solids concentration could be separated by all the polymeric conditions (cationic, anionic, and cationic-anionic). The continous solid-liquid separation in the laboratory thickener showed that a 3.0% feed solids was the maximum feed solids concentration that could be used in the continuous thickener operation with the same polymeric conditions. The minimum feed solids concentration was 1.0% solids. The feed pH ranged from 5.0 to 10.0, and the feed flow rate ranged from 915 to 2275 ml/min. The collective determination of the most and least sensitive variables was based on an experimental design procedure, employing Response Surface Methodology (RSM), to develop mathematical models for the thickener control. The three polymeric conditions used were, cationic polymer, anionic polymer, and a combination of cationic-anionic polymer. For each polymeric condition, two mathematical models were developed: one for overflow response, the other for underflow response. The formation of small flocs by the cationic polymer produced a sludge bed which prevented the particles from escaping into the overflow. The movement of the sludge bed was rapid. To prevent the bed from passing a pre-determined height, the underflow pump was "on" during most of the experimental time. This situation brought a low solids underflow, but the desired quality of the overflow was reasonably good. The anionic polymer did not produce a good overflow, because neutralization of the surface charges did not occur and a sludge bed never formed. This condition left the underflow pump "off" at all times, except when samples were to be withdrawn for the analysis. Overflow was the worst quality compared to the other polymeric conditions. The underflow quality was better than the underflow of the cationic tests, and almost as good as the underflow with the combination polymer. The use of the combination cationic-anionic polymer produced large floes immediately, because of the surface charge neutralization and bridging action that occurred. The time allowed for this action was longer for low to medium flow rates, producing larger flocs which settled and prevented the formation of a sludge bed. However, the desired quality of overflow and underflow remained good. For the majority of the runs with combination polymer, the underflow pump was "off" at all times, except when samples were withdrawn for the analysis. The overflow and underflow quality was the best desired quality for the combination polymer when compared to the results obtained utilizing the cationic and the anionic polymers separately. The input variables were used to develop six mathematical models. With the aid of the models, contour plots of the main responses were generated; that is, the "suspended solids in the overflow" and the "percent solids in the underflow." The plots gave regions of the best thickener performance within the wide variations of the three mentioned input variables. The plots would allow an operator to control and/or adjust any of the three variables to achieve optimum conditions. The combination polymers produced the best desired quality of overflow and underflow. For this polymeric condition, changes in the feed solids concentration was the most sensitive factor in the maintenance of the overflow quality, and the feed pH was the most sensitive factor for the maintenance of the underflow quality. The role of the feed flow rate for the maintenance of both overflow and underflow quality was proved to be moderate. / Ph. D.

The mining of coal in arid regions has led to calls for research in to the field of dry beneficiation, / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

Este estudo foi feito a partir de uma amostra de carvão extraído na mina da Vale- Moçambique, localizada no distrito de Moatize, Província de Tete. O trabalho visa analisar o sistema de reagentes na flotação de finos de carvão mineral pertencente à camada UCB. Dentre os métodos de beneficiamento de carvão, a flotação se destaca como um dos mais importantes para a concentração deste material, em particular no tratamento de partículas finas. A alimentação total da planta de processamento da Vale- Moçambique é de 8000 tph de carvão, onde 10% dessa alimentação corresponde a fração fina que alimenta o circuito de flotação. O material utilizado nesse estudo apresentou uma granulometria 96% menor do que 0,25 mm. Os reagentes utilizados nos ensaios de flotação foram betacol e óleo diesel como agentes hidrofobizantes e MIBC como espumante. O intervalo de concentrações de betacol na primeira fase de ensaios foi de 200 g/t a 500 g/t, e na segunda fase foi de 200 g/t a 500g/t de óleo diesel e manteve-se constante o MIBC em 300 g/t. Os resultados mostraram que é possível, a partir de uma alimentação com o teor de cinzas em torno de 22,84%, obter produtos com teores abaixo de 10% de cinzas, com uma recuperação mássica em torno de 50%. A recuperação de matéria carbonosa também foi avaliada e apresentou resultados positivos. Complementando esse estudo, foi avaliado o efeito da recuperação de H2O e foi observado que para as concentrações de betacol as recuperações variaram de 6 a 9%, e para óleo diesel mais MIBC foram de 4 a7%. / This study was done from a sample of coal mined at the Vale-Mozambique mine, located in Moatize district, Tete Province. The aim of this work is to analyze the reagent system in the flotation of coal fines belonging to the UCB layer. Among coal processing methods, flotation stands out as one of the most important for the concentration of this material, in particular in the treatment of fine particles. The total feed of the Vale-Mozambique processing plant is 8000 tph of coal, where 10% of this feed corresponds to the fine fraction that feeds the flotation circuit. The material used in this study had a particle size of 96% smaller than 0.25 mm. The reagents used in the flotation tests were betacol and diesel oil as hydrophobizing agents and MIBC as frother. The range of betacol concentrations in the first test phase was 200 g / t at 500 g / t, and in the second phase 200 g / t at 500 g / t of diesel oil and MIBC were kept constant at 300 g / t. The results showed that it is possible, from a feed with the ash content around 22.84%, to obtain products with levels below of 10% ash, with a mass recovery around 50%. The recovery of carbonaceous matter was also evaluated and presented positive results. Complementing this study, the effect of H2O recovery was evaluated and it was observed that for the concentrations of betacol the recoveries ranged from 6 to 9%, and for diesel oil plus MIBC were 4 to 7%.

Thesis (M.Sc.(Earth Science Practice & Management))--University of Pretoria, [2008]. / Abstract in English. Includes bibliographical references (leaves 85-88).

Thesis (MSc.(Metallurgical Engineering)--University of Pretoria, 2007. / Includes bibliographical references.

Este estudo foi feito a partir de uma amostra de carvão extraído na mina da Vale- Moçambique, localizada no distrito de Moatize, Província de Tete. O trabalho visa analisar o sistema de reagentes na flotação de finos de carvão mineral pertencente à camada UCB. Dentre os métodos de beneficiamento de carvão, a flotação se destaca como um dos mais importantes para a concentração deste material, em particular no tratamento de partículas finas. A alimentação total da planta de processamento da Vale- Moçambique é de 8000 tph de carvão, onde 10% dessa alimentação corresponde a fração fina que alimenta o circuito de flotação. O material utilizado nesse estudo apresentou uma granulometria 96% menor do que 0,25 mm. Os reagentes utilizados nos ensaios de flotação foram betacol e óleo diesel como agentes hidrofobizantes e MIBC como espumante. O intervalo de concentrações de betacol na primeira fase de ensaios foi de 200 g/t a 500 g/t, e na segunda fase foi de 200 g/t a 500g/t de óleo diesel e manteve-se constante o MIBC em 300 g/t. Os resultados mostraram que é possível, a partir de uma alimentação com o teor de cinzas em torno de 22,84%, obter produtos com teores abaixo de 10% de cinzas, com uma recuperação mássica em torno de 50%. A recuperação de matéria carbonosa também foi avaliada e apresentou resultados positivos. Complementando esse estudo, foi avaliado o efeito da recuperação de H2O e foi observado que para as concentrações de betacol as recuperações variaram de 6 a 9%, e para óleo diesel mais MIBC foram de 4 a7%. / This study was done from a sample of coal mined at the Vale-Mozambique mine, located in Moatize district, Tete Province. The aim of this work is to analyze the reagent system in the flotation of coal fines belonging to the UCB layer. Among coal processing methods, flotation stands out as one of the most important for the concentration of this material, in particular in the treatment of fine particles. The total feed of the Vale-Mozambique processing plant is 8000 tph of coal, where 10% of this feed corresponds to the fine fraction that feeds the flotation circuit. The material used in this study had a particle size of 96% smaller than 0.25 mm. The reagents used in the flotation tests were betacol and diesel oil as hydrophobizing agents and MIBC as frother. The range of betacol concentrations in the first test phase was 200 g / t at 500 g / t, and in the second phase 200 g / t at 500 g / t of diesel oil and MIBC were kept constant at 300 g / t. The results showed that it is possible, from a feed with the ash content around 22.84%, to obtain products with levels below of 10% ash, with a mass recovery around 50%. The recovery of carbonaceous matter was also evaluated and presented positive results. Complementing this study, the effect of H2O recovery was evaluated and it was observed that for the concentrations of betacol the recoveries ranged from 6 to 9%, and for diesel oil plus MIBC were 4 to 7%.

Este estudo foi feito a partir de uma amostra de carvão extraído na mina da Vale- Moçambique, localizada no distrito de Moatize, Província de Tete. O trabalho visa analisar o sistema de reagentes na flotação de finos de carvão mineral pertencente à camada UCB. Dentre os métodos de beneficiamento de carvão, a flotação se destaca como um dos mais importantes para a concentração deste material, em particular no tratamento de partículas finas. A alimentação total da planta de processamento da Vale- Moçambique é de 8000 tph de carvão, onde 10% dessa alimentação corresponde a fração fina que alimenta o circuito de flotação. O material utilizado nesse estudo apresentou uma granulometria 96% menor do que 0,25 mm. Os reagentes utilizados nos ensaios de flotação foram betacol e óleo diesel como agentes hidrofobizantes e MIBC como espumante. O intervalo de concentrações de betacol na primeira fase de ensaios foi de 200 g/t a 500 g/t, e na segunda fase foi de 200 g/t a 500g/t de óleo diesel e manteve-se constante o MIBC em 300 g/t. Os resultados mostraram que é possível, a partir de uma alimentação com o teor de cinzas em torno de 22,84%, obter produtos com teores abaixo de 10% de cinzas, com uma recuperação mássica em torno de 50%. A recuperação de matéria carbonosa também foi avaliada e apresentou resultados positivos. Complementando esse estudo, foi avaliado o efeito da recuperação de H2O e foi observado que para as concentrações de betacol as recuperações variaram de 6 a 9%, e para óleo diesel mais MIBC foram de 4 a7%. / This study was done from a sample of coal mined at the Vale-Mozambique mine, located in Moatize district, Tete Province. The aim of this work is to analyze the reagent system in the flotation of coal fines belonging to the UCB layer. Among coal processing methods, flotation stands out as one of the most important for the concentration of this material, in particular in the treatment of fine particles. The total feed of the Vale-Mozambique processing plant is 8000 tph of coal, where 10% of this feed corresponds to the fine fraction that feeds the flotation circuit. The material used in this study had a particle size of 96% smaller than 0.25 mm. The reagents used in the flotation tests were betacol and diesel oil as hydrophobizing agents and MIBC as frother. The range of betacol concentrations in the first test phase was 200 g / t at 500 g / t, and in the second phase 200 g / t at 500 g / t of diesel oil and MIBC were kept constant at 300 g / t. The results showed that it is possible, from a feed with the ash content around 22.84%, to obtain products with levels below of 10% ash, with a mass recovery around 50%. The recovery of carbonaceous matter was also evaluated and presented positive results. Complementing this study, the effect of H2O recovery was evaluated and it was observed that for the concentrations of betacol the recoveries ranged from 6 to 9%, and for diesel oil plus MIBC were 4 to 7%.

M.Ing. / Eskom's power stations receive their main supply of coal from mines next to the power stations. The coal supply contracts only specify maximum allowable variations of some coal quality parameters. The quality of the supplied coal can, however, vary greatly within a few hours. The boilers in the power plant are optimized for a certain quality of coal, while the supplied coal is burnt as it is received from the mine. The variations in the coal quality can, therefore, have a negative impact on both the life expectancy and maintenance costs of the power plant as well as the controllability of the boiler. The effects of short term variations in the coal qualities can be reduced by segregating the supplied coal into separate stockpiles according to coal quality parameters such as ash content and volatile matter, and then blending different portions from these stockpiles to a preferred coal quality before the coal goes to the boilers. A self organising feature map neural network was proposed in this research, to determine how to separate the supply coal, according to measured coal quality data. Furthermore, linear programming was proposed to determine the proportions to be taken from each stockpile in order to achieve a more consistent blended coal again. The segregating and blending systems are described in this thesis; and they were tested by means of a simulation based on measured coal quality data from a power station. It was shown that it is possible to successfully segregate coal from a single supply and then blend the different stockpiles to render coal with less short term variations in its quality parameters. The blending process uses stockpile size as its main driver to optimize the selection of the proportions, such that the most coal is taken from the largest stockpile, while the resultant coal quality remains within the specified constraints.

Dense medium cyclones (DMCs) have become the workhorse of the coal preparation industry due to their high efficiency, large capacity, small footprint and low maintenance requirements. Although the advantages of DMCs make them highly desirable, size-by-size partitioning data collected from industrial operations suggest that DMC performance can suffer in response to fluctuations in feed coal quality. In light of this problem, a multi-stream monitoring system that simultaneously measures the densities of the feed, overflow and underflow medium around a DMC circuit was designed, installed and evaluated at an industrial plant site. The data obtained from this real-time data acquisition system indicated that serious shortcomings exist in the methods commonly used by industry to monitor and control DMC circuits. This insight, together with size-by-size partition data obtained from in-plant sampling campaigns, was used to develop an improved control algorithm that optimizes DMC performance over a wide range of feed coal types and operating conditions. This document describes the key features of the multi-stream monitoring system and demonstrates how this approach may be used to potentially improve DMC performance. / Master of Science