S. Komar Kawatra - Academia.edu (original) (raw)

Papers by S. Komar Kawatra

Mining, metallurgy & exploration, May 1, 2015

Fine-grained hematite ore can be concentrated by the process of selective flocculation and disper... more Fine-grained hematite ore can be concentrated by the process of selective flocculation and dispersion, which relies on proper reagent selection and control of water chemistry. While many previous studies have been performed analyzing the effects of different reagents on this process in a laboratory environment, this paper focuses on investigating the water chemistry within the process in a pilot-scale continuous deslime thickener. The pH, sodium concentration, calcium concentration and magnesium concentration were varied to determine their effects on the iron concentrate grade and recovery, and the phosphorus concentrate grade and rejection in the pilotscale selective deslime thickener. The ideal pH for the iron grade and recovery of the process using a starch selective flocculant was found to be 10.5. Phosphorus rejection, however, was increased at lower pH values. Minimization of sodium concentration was shown to improve iron grade, iron recovery and phosphorus rejection. Calcium acted as a nonselective flocculant showing higher iron recovery, lower iron grade and lower phosphorus rejection with increasing concentration. Conclusions could not be drawn from the experiments that varied magnesium concentration. The zeta potential of the solid-liquid interface of particles in each sample taken was also analyzed to show relationships between zeta potential and process performance. In all cases, a maximization of the magnitude of zeta potential correlated with increased iron grade and recovery. This supports the hypothesis that a higher level of dispersion enhances the selective flocculation and separation process.

Mining, metallurgy & exploration, Nov 1, 2015

In many mineral processing applications it is necessary to know the isoelectric points of the var... more In many mineral processing applications it is necessary to know the isoelectric points of the various minerals in the

Mineral Processing and Extractive Metallurgy Review, Jan 25, 2022

International Journal of Mineral Processing, Sep 1, 2012

Filtration of hematite ore slurries can be a bottleneck in some hematite processing plants due to... more Filtration of hematite ore slurries can be a bottleneck in some hematite processing plants due to inadequate filtration rates caused by the dispersion of fine particles. Flocculation of fine particles in the slurry decreases the specific cake resistance of the filter cake allowing for increased filtration rates. CO 2 sparging of hematite slurry was shown to increase the filtration rate by altering the pH and the surface chemistry of the particles. It was shown that an increase in filtration rate of 278% can be accomplished by lowering the pH from 11 to 6.5 using CO 2 at a lab scale. This was attributed to increased flocculation of hematite and silica particles in the ore.

Journal of Environmental Sciences-china, Mar 1, 2022

CO2 utilizations are essential to curbing the greenhouse gas effect and managing the environmenta... more CO2 utilizations are essential to curbing the greenhouse gas effect and managing the environmental pollutant in an energy-efficient and economically-sound manner. This paper seeks to critically analyze these technologies in the context of each other and highlight the most important utilization avenues available thus far. This review will introduce and analyze each major pathway, and discuss the overall applicability, potential extent, and major limitations of each of these pathways to utilizing CO2. This will include the analysis of some previously underreported utilization avenues, including CO2 utilization in industrial filtration and the processing of raw industrial materials such as iron and alumina. The core theme of this paper is to seek to treat CO2 as a commodity instead of a liability.

Mining, Metallurgy & Exploration, 1998

The generation of airborne dust is a significant problem for the mineral industry. Previous studi... more The generation of airborne dust is a significant problem for the mineral industry. Previous studies in the literature concluded that surfactants were the most effective dust suppressant agents since they enhance the wetting characteristics of the material. However, personnel in the iron ore industry have reported that these agents were not effective. Why is it that surfactants are effective for materials like coal but not iron ore? If surfactants can not control dust levels, what other reagents should be considered? A fundamental problem in addressing these questions is that there was no standard method for evaluating the effectiveness of dust suppressants. Although it was possible to conduct experiments at an industrial site, it was difficult to have consistent, controlled conditions. There are various factors such as throughput, wind conditions, temperature, humidity, and access limitations which make it very difficult to conduct controlled experiments. To get around these difficulties, a novel dust tower method was developed The method exposed the treated material to the types of conditions which were expected to occur at a processing facility, namely multiple impacts and sufficient drop height. Using these systematic studies, the suppressants were evaluated based upon reductions in measured dust levels. Even though surfactants improved the wetting rate of the iron ore as much as 96%, surfactants were no more effective than water in suppressing dust levels in the dust tower. Hygroscopic agents were 79% more effective than water, even though these reagents actually reduced the wetting rate by approximately 99%. This means that effective wetting was not the concern with iron ore dust. This is why surfactants were ineffective for the iron ore industry. Reagents which reduced moisture loss were the most effective in suppressing iron ore dust.

Effects of Baffle Open Area 7.3.3 Effects of Baffle Position 7.4 EXPERIMENTAL RESULTS 86 7.4.1 Ba... more Effects of Baffle Open Area 7.3.3 Effects of Baffle Position 7.4 EXPERIMENTAL RESULTS 86 7.4.1 Baffle Open Area 86 7.4.2 Baffle Position and Tracer Results 89 7.5 DISCUSSION 93 7.5.1 Effects of Baffling 93 7.5.2 Comparison of the Baffled Column and Conventional Cells 98 7.6 CONCLUSIONS 104 8 PLANT STUDIES AT EMPIRE COAL 106 8.1 INTRODUCTION 106 8.2 COLUMN DESIGN 106 8.3 PLANT CONDITIONS 108 8.4 OPERATING CONSIDERATIONS 111 8.5 REAGENT DETERMINATION FOR ON-LINE TESTS 114 8.6 CONTINUOUS ON-LINE EXPERIMENTS 118 8.6.1 Pyrite Recovery 8.6.2 Capacity Effects 8.7 OFF-LINE CONTINUOUS TESTS 8.7.1 Off-Line Continuous Test Procedure 8.7.2 Off-line Continuous Test Results 8.7.3 Particle Size Effects 8.8 COARSE-COAL BATCH EXPERIMENTS 8.8.1 Procedure 8.8.2 Results-Baffle Effects 8.8.3 Results-Frother Effects 8.9 CONCLUSIONS 9 MARKETING AND COMMERCIALIZATION 150 9.1 APPLICATIONS 9.2 PROCESS WASTES 9.3 IMPLICATIONS FOR THE EMPIRE COAL PLANT 150 9.4 PROCESS IMPLEMENTATION 150 9.5 COST ESTIMATES

Mining, Metallurgy & Exploration, 1989

Experimental Work o 5 10 20 30 40 50 60 SIZE, micrometers Fig. 1-Observed seasonal variations in ... more Experimental Work o 5 10 20 30 40 50 60 SIZE, micrometers Fig. 1-Observed seasonal variations in cyclone performance in an iron ore processing plant. Laboratory Studies • SUMMER, 20 0 e d 50 = 20 micrometers o WINTER, 3°e d 50 =25 microme.ters 9100 u,

Carbon dioxide sequestration by conversion to carbonates has become a promising option for CO2 st... more Carbon dioxide sequestration by conversion to carbonates has become a promising option for CO2 storage. Experiments were conducted to determine the feasibility of CO2 sequestration at ambient conditions using a Ca-rich industrial waste in a carbonate solution. The Ca-rich industrial waste used in this study was lignite fly ash. Fly ash was chosen because it is cheap, available near large CO2 point sources, already in powder form, and reactive due to amorphous properties. In the experimental setup , CO2 absorption was inferred by monitoring feed and exhaust gas CO2 concentrations. The addition of an alkali to a fly ash-distilled water solution provided a 50% increase in CO2 absorption of the solution. Absorption time also increased by 50% compared to a fly ash-distilled water solution. TGA analysis was used to determine the extent of CO2 sequestration in the carbonate form. At a liquid to solid ratio of 20:1, the conversion of " free " calcium to carbonates was 75%. A CO2 b...

Mining, Metallurgy & Exploration, 2011

Considerable effort has been directed towards understanding the carbothermic reduction mechanisms... more Considerable effort has been directed towards understanding the carbothermic reduction mechanisms of selfreducing, fluxing dried green balls to produce pig iron nuggets. Given the geometry of the situation, some investigators believed that the shrinking core model was applicable. Hence, this study involved investigation of the applicability of the shrinking core model to pig iron nugget production. The experiments involved heat treatment of dried green balls utilizing either a laboratory-scale resistance box furnace or a gas-fired muffle furnace at various furnace temperatures and residence times. The products were analyzed for the following: (i) preferred reaction pattern, (ii) distribution of the metallized areas, (iii) % iron content variation in the pig iron nuggets from surface to center, (iv) carburization pattern and (v) physical and chemical properties of the pig iron nuggets. It was determined that the reduction of iron oxide occurred simultaneously throughout the sample and not beginning at the surface and propagating inward; thus the shrinking-core model was not applicable. Heat transfer and gas diffusion from surface to center were not the rate-limiting steps for reduction and carburization reactions.

Mining, Metallurgy & Exploration, 2013

To meet the growing need for CO 2 capture and storage technology, Michigan Technological Universi... more To meet the growing need for CO 2 capture and storage technology, Michigan Technological University is researching CO 2 capture and storage using carbonate solutions. The objective of the present study was to increase the absorption rate of CO 2 into the carbonate solution without reducing the absorption capacity of the solution. This approach used a polypropylene glycol methyl ether (PPGME) as a surfactant to chemically alter the gas bubble size. Experiments were conducted to study the absorption rate of CO 2 at varying surfactant concentrations of 0, 0.12, 0.24, 0.36 and 0.48 g/L. Results showed that as the concentration of surfactant increased in solution, the absorption rate also increased. The CO 2 absorption rate increased from 3.45 mmol/min CO 2 at 0 g/L PPGME to 3.92 mmol/min CO 2 at 0.48 g/L PPGME. This amounted to a 14% increase in the CO 2 absorption rate with no decrease in absorption capacity of the solution.

Mining, Metallurgy & Exploration, 2006

The iron nugget process is an economical, environmentally friendly, cokeless, single-step pig iro... more The iron nugget process is an economical, environmentally friendly, cokeless, single-step pig iron making process. Residence-time dependent process requirements for the production of pig iron nuggets at a fixed furnace temperature (1,425°C) were investigated. Depending on the residence time in the furnace, three chemically and physically different products were produced. These products were direct reduced iron (DRI), transition direct reduced iron (TDRI) and pig iron nuggets (PIN). The increase in the carbon content of the structure as a function of residence time was detected by optical microscopy and microhardness measurements. Sufficient carbon dissolution for the production of pig iron nuggets was obtained after a residence time of 40 minutes. The pig iron nuggets produced had chemical and physical properties similar to blast furnace pig iron. They were liquid-state products, and the slag was completely separated from the metal.

I Fly-ash is produced by all coal-fired utilities, and it must be removed from the plant exhaust ... more I Fly-ash is produced by all coal-fired utilities, and it must be removed from the plant exhaust gases, collected, and disposed of. While much work has been done in the past to utilize fly-ash rather than disposing of it, we nevertheless do not find widespread examples of successful industrial utilization. This is because past work has tended to find uses only for high-quality, easily-utilized fly-ashes, which account for less than 25% of the fly-ash that is produced. The main factor which makes fly-ashes unusable is a high unburned carbon content. In this project, physical separation technologies are being used to remove this carbon, and to convert these unusable fly-ashes into usable products. The main application being studied for the processed fly-ash is as a binder for inorganic materials, such as iron-ore pellets. Work in the first quarter concentrated on obtaining samples of materials to be used (fly-ash, and magnetite ore), training of personnel on pelletization procedures, obtaining and setting up pelletization apparatus in the MTU laboratories, and running pelletization experiments with bentonite binder to establish a baseline for comparison with the fly-ash binders to be made. In the second quarter, additional fly-ash samples were collected from the E. D. Edwards station (Bartonville, IL). Experimentation was begun to study the removal of carbon from these fly-ashes by froth flotation, and to make and test pellets that use fly-ash as binder.

Encyclopedia of Chemical Processing (Print Version), 2005

The Coal Handbook: Towards Cleaner Production, 2013

Current blast furnace technology is a two-stage ironmaking process that requires that iron ore co... more Current blast furnace technology is a two-stage ironmaking process that requires that iron ore concentrate first be formed into pellets, fired at 1260°C, cooled, transported to the blast furnace, and then reheated to approximately 1500°C to produce pig iron. This heating, cooling, and then reheating wastes a great deal of energy, which would be saved if the ironmaking process had only a single heating step. Kobe Steel's ITmk3 process is intended as a replacement for blast furnace processing that produces "pig iron nuggets" directly from cold-pelletized iron ore concentrate in a single stage of heating. It is therefore more energy-efficient than the current technology. Iron nuggets are produced by combining iron ore concentrate with a reducing agent (finely ground low-sulfur coal), a binder, and a flux to form pellets. These pellets are then heated to approximately 1400-1500°C in a rotary-hearth furnace. Upon heating, the pellets self-reduce to molten iron and molten slag, which separate from each other to form a metallic pig iron nugget and a slag drop. Upon cooling, the slag separates cleanly from the metal nugget. The objective of this project was to determine how the transformation from powdered iron oxide to metal+slag occurs, to examine how the transformation is affected by temperature and processing time, and to determine the optimum conditions for producing iron nuggets as a function of temperature. This project determined that, contrary to what had been believed by the developers of the ITmk3 process, the iron oxides did not directly react with the coal to produce pig iron in a single step. Instead, the transition consisted of the following stages: 1. Coal volatiles reacted with the iron oxides to produce "Direct Reduced Iron" (DRI) 2. Silicate gangue, coal ash, flux, and FeO melted to produce a slag, while the direct reduced iron began to melt due to dissolving excess carbon from the coal. This produced a mixed slag/metal product, "Transition Direct Reduced Iron" (TDRI) 3. The TDRI then fully separated into a liquid pig iron drop and a liquid slag drop. Upon cooling, this produced a pig iron nugget and a cleanly-separated slag nodule. The time needed for this transformation was a strong function of temperature, with times ranging from over 40 minutes at 1400°C, to approximately 10 minutes at 1500°C. It was determined that industrialscale rotary-hearth furnaces were producing nuggets with highly variable quality due to some pellets being heated more than others, with the cooler pellets having insufficient time to complete the transformation to iron nuggets. Uniform heating in the furnace is therefore key to maintaining satisfactory nugget quality.

The reduction of sulfur oxides from high sulfur coal burning utility companies has resulted in th... more The reduction of sulfur oxides from high sulfur coal burning utility companies has resulted in the production of huge quantities of wet flue-gas desulfurization scrubber sludge. A typical 400 MW power station burning a coal containing 3.5% sulfur by weight and using a limestone absorbent would produce approximately 177,000 tons (dry weight) of scrubber sludge per year. This brownish colored, finely divided material contains calcium sulfite (CaS03"l/2H20), calcium sulfate (CaS04"2H20), unreacted limestone (CaC03), and various other impurities such as fly-ash and iron oxide particles. The physical separation of the components of scrubber sludge would result in the re-use of this material. The primary use would be conversion to a highly pure synthetic gypsum. This technical report concentrates on the effect of baffle configuration on the separation of calcium sulfite/sulfate from limestone. The position of the baffles as they related to the feed inlet, and the quantity of the baffles were examined. A clean calcium sulfite/sulfate (less than 2.0~0 limestone by weight) was achieved with the combination of water-only cyclone and horizontally baffled column.

Minerals Engineering, 1996

On-line measurement of slurry viscosity was carried out to study the effect of viscosity on the c... more On-line measurement of slurry viscosity was carried out to study the effect of viscosity on the cut (d50) size of hydrocyclone classifiers. As slurry viscosity increases, the settling rate of particle decreases, causing the d50 size to become coarser. The viscometer set-up used a vibrating sphere viscometer and a specially designed slurry presentation device to avoid settling of solids during