Agnieszka Surowiak

Optimization of reagent dosages with the use of response surface methodology and evaluation of test results with upgrading curves in graphite flotation

ABSTRACT The aim of this study is to reduce reagent consumptions in graphite flotation with the addition of Aero 3477 promoter to the flotation stage. A three-level Box–Behnken design is used for optimization and modeling of flotation stages. For this purpose, the flotation experiments are performed in two steps. The maximum weight recovery and the minimum ash content values of the rougher concentrate are calculated as 21.41 and 32.49% using diesel oil dosage (714.24 g/t), methyl isobutyl carbinol (MIBC) dosage (212.81 g/t), and sodium silicate (Na2SiO3) dosage (1451.189 g/t), respectively, in the preliminary experiment tests. Subsequently, keeping the Na2SiO3 dosage constant, Aero 3477 promoter is added to the flotation stage to provide reduction at reagent consumptions. As a result, the reagent consumptions of diesel oil dosage (162.10 g/t), MIBC dosage (129.58 g/t), and Aero 3477 promoter dosage (168.96 g/t) are supplied to reach the approximate weight recovery and the ash content as in primary experimental results. Considerable dosage decreases in both diesel oil and MIBC are achieved using promoter. Moreover, experimental studies are also evaluated using upgrading curves.

Determination of the Important Operating Variables On Cleaning Fine Coal by Knelson Concentrator and Evaluation Of The Performance Through Upgrading Curves

ABSTRACT This study presents the beneficiation of coal fines in a Knelson concentrator. With a view to achieving this aim, the bowl speed (250–1250 rpm), fluidization water flow rate (2–4 l/min), solids ratio (10–30%) and feed flow rate (1.5–2.5 l/min) were determined as independent variables. The effects of these variables on the yield of concentrate, the ash content and the combustible matter recovery in concentrate were examined using a central composite design. Quadratic regression models with estimated coefficients were developed to evaluate the responses and three-dimensional plots were presented to evaluate the interactions of independent variables versus responses. It is possible to obtain clean coal with approximately 12% ash content from the coal feed having approximately 24% ash content. Additionally, the optimal results were evaluated by using upgrading curves. The comparison of upgrading curves proved that the Knelson concentrator is quite efficient in cleaning fine coals and it allowed the evaluation which parameters would occur with certain expected quality of concentration.

Statistical analysis of sedimentation process of mineral suspension with application of bioflocculation

On the basis of empirical data the approximation of settling curve h=f(t) for various initial concentrations of the coal sludge flotation concentrate and coal tailings suspension was done in the paper, where t – time of settling, h –way passed by the suspension. The experiment was conducted for both cases with use of bioflocculant and without it. The bioflocculants were, in various doses, activated sludges originating from municipal sewage treatment plant. Such functions as exponential, logarithmic or rational ones were used to conduct the approximation. The evaluation of fitting was done by means of mean squared standard error. On the basis of obtained functions describing settling curve the settling velocity was determined as \( v\left( t \right) = f^{\prime} \left( t \right) \) and velocity was calculated as \( v = \frac{1}{\Delta }\int_{0}^{\Delta } {v(t)} \,dt, \) where Δ is maximum time of settling. The determined settling curves were the basis to investigate relation between settling velocity and initial concentration as well influence of applied bioflocculants on settling velocity. The evaluation of influence of bioflocculants sort on efficiency of mineral suspensions settling was done.