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Coal is the main fuel for the direct reduced iron (DRI) plants of India, which are one of the major sources of fly ash generation. The generation of fly ash and its disposal has raised concern because of the environmental impacts. In the present study, two different fly ash samples were investigated to explore the scope of recovery of combustibles. One did not show any recovery potential. The second sample indicated that about 40% of material could be recovered, with 35% fixed carbon and 10,841 kJ kg(-1) gross calorific value. This can be used as a fuel blend in standard fluidised bed combustion boilers efficiently burning inferior coal. A process flowsheet has been suggested for the recovery purpose. It was estimated that for a small 0.2 million tonnes per year (Mtpy) capacity DRI plant, approximately 3.4 ha of land could thus annually be saved from dumping of the generated fly ash, while recovering 1.83 MW of electrical energy., (© The Author(s) 2016.)

In the present investigation, the settling performance of coal fine tailings was optimized with central composite rotatable design and response surface methodology. Pulp density, pH, and flocculant dosage were considered as theoperating parameters in the study. The maximum settling rate was observed as 230 mm/min while minimum turbidity was observed as 26.7 NTU. Coefficient of correlation (R2) between the experimental and the predicted values of the settling rate and the turbidity wereobserved to be 0.99 and 0.99, respectively. The optimum conditions of pH 7.6, flocculant dosage 16.43 gpt, and pulp density 5.4% solid, w/w, were obtained from the desirability function at the desirability of 89%. [ABSTRACT FROM AUTHOR]

The study was carried out to investigate the effect of different process parameters on the settling performance of coal fine tailings collected from a coal preparation plant in India. Response surface approach was followed to assess the effect of pulp density, pH, and flocculant dosage on settling performance. The Box–Behnken design model predicted responses were obtained with coefficient of determination R2 as 0.99 and 0.98 for settling rate and turbidity, respectively. The optimum condition established for settling rate and turbidity was found to be at pulp density – 6% w/w, pH –​ 7.84, and flocculant dosage –​ 14.58 gpt with predicted settling rate and turbidity as 194.97 mm/min and 22.56 NTU, respectively, with the desirability of 90.4%. [ABSTRACT FROM AUTHOR]

The Box–Behnken design of experiments was employed to optimize the effect of variables on the settling performance of coal fine. Variable parameters considered in the study were pulp density, pH, and flocculant dosage, and their influence was discussed using 3D surface plot. The study showed that a pulp density of 6% solid (w/w) was the most favorable condition indicated a settling rate of 221 mm/min and pH of 7.5 and flocculant dosage of 14.58 gpt were found to be the optimum condition. The empirical models developed showed a correlation coefficient (between experimental and predicted values) of 0.99 for settling rate. [ABSTRACT FROM PUBLISHER]

In the present investigation, flocculation and settling studies were carried out using a cationic flocculant. A new parameter “water recovery index” (WRI), i.e. the percentage of water recovered as the supernatant water, has been used to evaluate the performance of settling. This index was found to be a useful tool for analyzing the settling performance. The highest index value of 89.51% was obtained at 6% solid concentration, slurry pH 6.5, and at a flocculant dosage of 4.86 gpt. The empirical model developed for the settling rate indicated a coefficient of correlation (R2) of 0.99 between the experimental and predicted values. [ABSTRACT FROM PUBLISHER]