Nikkam Suresh

COAL-FINE BENEFICIATION STUDIES OF A BENCH-SCALE WATER-ONLY CYCLONE USING ARTIFICIAL NEURAL NETWORK

Coal fines generated in Indian coal preparation plants account for 25%–30% of run-of-mine (ROM) coal. Coal cleaning is receiving increasingly greater attention of process engineers in view of the increase in amounts to be handled as well as the difficult washability characteristics of high-ash-content Indian coals. Froth flotation is usually practiced in Indian coal washeries for washing the coals to bring down their ash content to acceptable limits. Because of the supply of feed coal from multiple sources, their different characteristics and composition, viz., varying mineralogy and ash content, presence of microfines, and their varying oxidation levels, the fine coal circuits, more often than not, fail to deliver consistent product quality and desired yields. Water-only cyclones have been used in most of the western countries for treating coal and mineral fines below 3 mm. However, the industrial use of these cyclones in India has not yet been put to practice in the coal-washing industry; the primary reason for this being that their design is unsuitable for high-ash content coals and therefore needs to be suitably modified according to the feed material characteristics. Highlighted in the present paper are the results of a case study of beneficiation of high-ash fine coal, using a water-only cyclone. The influence of two of the critical design variables, viz., cyclone length and solid concentration, on which the cyclone performance and the process yield (%) depend to a great extent, is described. Further, based on the experimental data of a water-only cyclone of varying lengths used for below a 3 mm coal beneficiation study, an attempt has also been made to develop a three-layer feed-forward artificial neural network (ANN) model, which is inherently trained using an error-back propagation algorithm. The results evince that the predictions from the ANN model are in good qualitative and quantitative agreement with the experimental observations, thereby validating the applicability and accuracy of the developed ANN model.

A performance model for water-only gravity separators treating coal

The conventional method for predicting the performance of coal cleaning units is by plotting a generalized distribution curve, which is cumbersome. This paper outlines attempts to describe the Tromp curve using a Rosin-Rammler type of equation for estimating performance. Experiments were carried out on a laboratory (76 mm) water-only cyclone to produce Tromp curves of widely varying nature. The results were used for model development. Performance data for different coal washing units such as jigs, tables, spiral concentrators and industrial water-only cyclones were also selected from the literature to check the validity of the model.

Effect of desliming on the magnetic separation of low-grade ferruginous manganese ore

In the present investigation, magnetic separation studies using an induced roll magnetic separator were conducted to beneficiate low-grade ferruginous manganese ore. The feed ore was assayed to contain 22.4% Mn and 35.9% SiO2, with a manganese-to-iron mass ratio (Mn:Fe ratio) of 1.6. This ore was characterized in detail using different techniques, including quantitative evaluation of minerals by scanning electron microscopy, which revealed that the ore is extremely siliceous in nature and that the associated gangue minerals are more or less evenly distributed in almost all of the size fractions in major proportion. Magnetic separation studies were conducted on both the as-received ore fines and the classified fines to enrich their manganese content and Mn:Fe ratio. The results indicated that the efficiency of separation for deslimed fines was better than that for the treated unclassified bulk sample. On the basis of these results, we proposed a process flow sheet for the beneficiation of low-grade manganese ore fines using a Floatex density separator as a pre-concentrator followed by two-stage magnetic separation. The overall recovery of manganese in the final product from the proposed flow sheet is 44.7% with an assay value of 45.8% and the Mn:Fe ratio of 3.1.

Statistical Optimization of Coal–Oil Agglomeration Using Response Surface Methodology

ABSTRACT In this study, a three-level and five-variable Box-Behnken design combined with response surface methodology (RSM) was used to develop an approach to analyze the behavior of different variables of oil agglomeration where pulp density, oil dosage, agglomeration time, particle size, and oil type were varied. The response of coal–oil agglomeration to this variation was investigated using the Box-Behnken design. The efficiency of this process was evaluated by calculating percent ash rejection (%AR) and percent organic-matter recovery (%OMR). The optimal conditions established were pulp density (3%), oil dosage (15%), agglomeration time (15 min), and particle size (0.15 µm) using linseed oil with a predicted %AR and %OMR as 66.02% and 95.93%, respectively, with a desirability of 94.20%. The optimal condition was experimentally validated as 64.60% for ash rejection and 93.94% for organic-matter recovery. The coefficient of determination (R2) was found to be .870 and .926 for %AR and %OMR, respectively.

Magnetic separation studies on ferruginous chromite fine to enhance Cr:Fe ratio

The Cr:Fe ratio (chromium-to-iron mass ratio) of chromite affects the production of chrome-based ferroalloys. Although the literature contains numerous reports related to the magnetic separation of different minerals, limited work concerning the application of magnetic separation to fine chromite from the Sukinda region of India to enhance its Cr:Fe ratio has been reported. In the present investigation, magnetic separation and mineralogical characterization studies of chromite fines were conducted to enhance the Cr:Fe ratio. Characterization studies included particle size and chemical analyses, X-ray diffraction analysis, automated mineral analysis, sink-and-float studies, and magnetic susceptibility measurements, whereas magnetic separation was investigated using a rare earth drum magnetic separator, a rare earth roll magnetic separator, an induced roll magnetic separator, and a wet high-intensity magnetic separator. The fine chromite was observed to be upgraded to a Cr:Fe ratio of 2.2 with a yield of 55.7% through the use of an induced roll magnetic separator and a feed material with a Cr:Fe ratio of 1.6.

Water distribution in water-only cyclones

Abstract Experiments conducted on water-only cyclones both at the laboratory (76 mm) and plant scale level (350 mm) treating Coal and Magnetite slurries have revealed that there exists a linear relationship between the flowrates of water in the feed and in the overflow streams. Further, a “Generalised Water Distribution Plot” which is independent of all the design and operating variables has been proposed to predict the water distribution in water-only cyclones. This plot has been represented by an equation of the form: ( Wof / Spig ) = −0.0144 + 0.9932 ( Wf / Spig ) This relationship has been found to be unique for both laboratory and industrial cyclones.

Kinetic Studies on Petrographic Components of Coal in Batch Flotation Operation

ABSTRACT In the present paper, an attempt was made to study the kinetic behavior of different types of maceral during flotation of a washery grade-IV type of coking coal. Three important operational variables, viz. collector dose (kg/ton), frother dose (kg/ton), and feed solid concentrations (%), were varied, and their effects on the response parameters like recoveries of ash and petrographic components, viz. vitrinite (V), liptinite (L), and inertinite (I), were evaluated. A first-order flotation kinetic equation was fitted for the batch test data for evaluating the rate of flotation (k) of coal components. Use of a three-level Box-Behnken factorial design was adopted to minimize the number of experiments and modeling of response parameters in batch coal flotation. The obtained results were evaluated with quadratic programming to develop second-order regression equations. For understanding of the influence of interactional effects, response surface methodology (RSM) approach was adopted. Taking advantages of the quadratic programming, it was observed that recovery of 100% vitrinite was obtained without collector, however, with frother dosage and feed solid concentration of 0.75kg/ton and 5%, respectively. Similarly, minimum ultimate recovery of ash and inertinite component was achieved at intermediate range of reagent dosages and pulp density (collector ≡ 0.40–0.45kg/ton, frother ≡ 0.40–0.45kg/ton, and feed solid concentration of 9–10%). The influence of these process variables of the batch coal flotation on ultimate recovery (R∞) and rate constant (k) values of maceral components are discussed critically in this paper.

Evaluation of the Characteristics of As-received and Washed Low Grade Indian Coals for Their Industrial Applications

Coal is the most widely used source of global energy. With the fast depletion of coal quality in India, utilizing the abundantly available low grade coals through appropriate technologies for meeting the energy demands is the need of time. During the various industrial application of coal, its characteristics are crucial. Five as-received low grade coals from Rajapur, Rajrappa, Kargali, Kedla, and Kathara coal mines of Jharkhand (India) and corresponding washed coals/clean fractions were characterized. These are low moisture-low volatile-low sulphur non-coking coals, except Rajapur coal, which is medium volatile poor coking. Rajapur and Rajrappa coals have medium ash, whereas other coals have high ash. Rajapur coal has the highest C and calorific value followed by Rajrappa, Kedla, Kargali, and Kathara coals; the variation of H and N content is insignificant. After washing, Rajrappa and Kargali are poor coking and Rajapur, Kedla, and Kathara are medium coking. For power generation, as-received coals of Rajrappa and Kedla, and washed coals of Kargali and Kathara can be used; for directly reduced iron purpose, Rajrappa as-received coal can be used. For coke making, washed coals of Rajapur and Kathara coals and stamp charging; Kedla and Rajrappa washed coal with the blend of low ash medium volatile coal and good coking coal, respectively, in conjunction with stamp charging, may be significant. Also, Kargali and Rajrappa washed coals can be used to make formed coke. The rejects from coal washing comprising a substantial amount of coaly matter together with higher ash can be used for power generation using fluidized bed combustion.

Dry High-Intensity Magnetic Separation in Mineral Industry – A Review of Present Status and Future Prospects

ABSTRACT High intensity dry magnetic separators are in use for various applications in the mineral as well as coal processing industries. Evaluation of the performance of these separators treating different minerals has become an active research topic. Several attempts have been made by different researchers and technologists to understand the separation behavior of particles in each of these separators treating different types of para-magnetic minerals. Despite all these efforts, these separators are yet to find widespread applications to treat different para-magnetic minerals. Therefore, the present status of these separators with a brief description of their operating principles, applications, and modeling are reviewed in this article. Also, the research work needs to focus on each separator has been highlighted.

Performance Evaluation of Basic Flotation Kinetic Models Using Advanced Statistical Techniques

ABSTRACT It is well evident that mathematical models play a key role in any time-dependent kinetic process; Froth flotation is a process resulting from the interaction of air bubbles, mineral surface, and chemical reagents. Flotation is a kinetic phenomenon where residence time is usually studied to reckon the flotation performance in terms of grade and recovery. The use of mathematical models is not only limited to performance assessment but they also find their application in designing and optimization of flotation circuits. Hence, it is justifying why froth flotation is being studied so intensively in mathematical terms. Literature review reveals that many models co-relating recovery (y), time (t), rate constant (a), and ultimate recovery of component (R) have been developed in the past; however, the practical applicability and correct methodology to select these models still needs to be studied. In the present investigation seven models were evaluated by comparing the model output with experimental data obtained from coal flotation experiments at different conditions of chemical reagents (collector and frother dosage) and pulp density. The paper also describes the application of classical statistical tools, such as least square method, sum of square error test, standard error test, F-test, test for Jarquebera, test statistic for skewness and kurtosis, and AIC value test, to assess the deviation of model output from experimental data. Results indicate that most of the studied models, if properly calibrated, work well for coal flotation data set. No single model was found to be uniformly the best for all the data set studies. The models were ranked according to their scores obtained on performing statistical tests on them.