Prodip Kumar Sen

Analyzing Leaching Data for Low-Grade Manganese Ore Using Neural Nets and Multiobjective Genetic Algorithms

Existing acid leaching data for low-grade manganese ores are modeled using an evolving neural net. Three distinct cases of leaching in the presence of glucose, sucrose and lactose have been considered and the results compared with an existing analytical model. The neural models are then subjected to bi-objective optimization, using a predator–prey genetic algorithm, maximizing recovery in tandem with a minimization of the acid concentration. The resulting Pareto frontiers are analyzed and discussed.

Multiobjective Optimization of Manganese Recovery from Sea Nodules Using Genetic Algorithms

Treatment of low grade manganese ores is receiving widespread attention due to major use of manganese (85–90%) as ferromanganese alloy in the rapidly growing iron and steel sector and also in other important industrial products like electrolytic manganese dioxide (EMD) used in the energy sector. Manganese bearing polymetallic sea nodules containing less than 40% Mn fall in the category of lean grade ores and besides manganese these nodules are the reserve for other metals like copper, nickel, and cobalt. In this present work, treatment of these polymetallic sea nodules in an acid-based hydrometallurgical route has been proposed using two different schemes, batch and parallel in nature. Both processes have been optimized using multiobjective genetic algorithms.

Data-Driven Multiobjective Analysis of Manganese Leaching from Low Grade Sources Using Genetic Algorithms, Genetic Programming, and Other Allied Strategies

Data-driven models are constructed for leaching processes of various low grade manganese resources using various nature inspired strategies based upon genetic algorithms, neural networks, and genetic programming and subjected to a bi-objective Pareto optimization, once again using several evolutionary approaches. Both commercially available software and in-house codes were used for this purpose and were pitted against each other. The results led to an optimum trade-off between maximizing the recovery, which is a profit oriented requirement, along with a minimization of the acid consumption, which addresses the environmental concerns. The results led to a very complex scenario, often with different trends shown by the different methods, which were systematically analyzed.

A GENETIC ALGORITHMS BASED MULTI-OBJECTIVE OPTIMIZATION APPROACH APPLIED TO A HYDROMETALLURGICAL CIRCUIT FOR OCEAN NODULES

Several hydrometallurgical processes have been studied for the extraction of metals from lean ores utilizing various flow sheet options. Of particular significance is the grade of the ore being treated, the energy consumed and associated costs, options for byproduct recovery, and the relative price of the products. A process scheme needs to be optimized for simultaneously maximizing metal throughput and minimizing the direct operating costs incurred within constraints set for the operating variables. This leads to a multi-objective optimization problem. The range of input grades for raw material, which a flowsheet can handle, needs to be worked out based on an optimization exercise. A lean manganese-bearing resource such as polymetallic sea nodules has been chosen in this article for the development of an optimization approach based on which the input raw nodules grades are to be treated by a particular flowsheet. Only the chemical consumption costs have been adopted in this article as a measure of direct operating costs. A linear simulation model for the flowsheet has been developed, keeping a set of design parameters constant. The solutions generated by using a sequential modular approach become inputs to an optimization procedure based on a multi-objective genetic algorithm belonging to the differential evolution family. The variables considered in the optimization task are the grade of nodules and reactivity of different species inside the reactor. A nickel equivalent (t/h function) has been suggested as a measure of productivity, as it indirectly enhances the input manganese ore grade through a price ratio effect. This productivity function was maximized with the simultaneous minimization of direct chemical costs. Pareto optimal solutions were generated with grades of nodules and reactivity in the leach reactor as decision variables. The effect of the price ratio on the Pareto optimal solutions was also investigated. The various cases investigated clarifies the methodology for choosing an appropriate ore grade range for a given process flowsheet. Appropriate decisions regarding the nature of raw material to be used for a given flowsheet are then found on the basis of the Pareto optimal solutions.

Metals and materials from deep sea nodules: an outlook for the future

Abstract The global data on manganese reserves apparently indicate that there is no resource crunch. However, a large part of the terrestrial deposits (80%) do not meet the grade requirement for efficient production of high quality ferroalloys required for steel making. The marine mineral deposits, which have attracted the greatest interest as alternative exploitable source for this element, are the deep-sea manganese nodules. If efficient schemes for manganese recovery values are put in place, the marine deposits would rather be classified as manganese ores which would have remarkable advantages over terrestrial low grade deposits because of by product recovery of copper, nickel and cobalt. Specific processing schemes for production of manganese alloys and compounds are critically discussed in this overview. The production of high purity Cu, Ni and Co using solvent extraction has also been reviewed. Optimisation approaches for sea nodules processing schemes have been analysed. Various other potential applications of sea nodules have been brought out. The possibility of integration of the processing schemes with land based production processes are likely to render sea nodules as useful alternative sources for metals and other value added materials of the future.

Approach for Minimizing Operating Blast Furnace Carbon Rate Using Carbon-Direct Reduction (C-DRR) Diagram

An approach for reducing input carbon rate of a blast furnace using carbon-direct reduction (C-DRR) diagram has been developed. The role of shaft efficiency, blast input conditions, and heat loss rate in reducing the carbon rate has been brought out. A two-zone thermochemical model has been used to develop C-DRR diagrams for analyzing operating data of a furnace as well as predicting conditions for reducing its carbon rate. The model can be integrated with the control system of a blast furnace for driving an operating furnace to reduce carbon rates.

Study of reduction behaviour of prefabricated iron ore–graphite/coal composite pellets in rotary hearth furnace

Abstract In the present study, the reduction kinetics of prefabricated iron ore–graphite/coal composite pellets of different shapes has been studied in a rotary hearth furnace (RHF). Commercial processes involving the RHF such as ITmk3/FASTMET have major problems of low productivity owing to significant heat and mass transfer resistance through the multilayer bed and consequently limited pellet layers over the hearth. In the present investigation, an attempt has been made to improve the heat and mass transfer in such system by increasing the specific surface area of individual pellets. Both the iron ore–graphite and iron ore–coal composite pellets have been reduced in an RHF at a maximum temperature of 1200°C. The ore–coal composite showed much higher degree of reduction (81%) over ore–graphite composite pellets (61%). The tablet shaped pellet with the highest specific surface area displayed a higher degree of reduction than the cylinder or sphere shaped pellets. Although no physical slag metal separation was visible, X-ray diffraction and SEM/EDX of reduced particles indicated separation at the microlevel. Higher amount of reduction and liquid silicate formation for tablet shaped pellets, in comparison with spherical and cylindrical shaped pellets, lay the foundation of a novel process flow scheme involving the use of prefabricated pellets in the RHF.

Reduction kinetics of porous zinc oxide pellet with CO–N2 gas mixture

Abstract Effect of purity on reduction kinetics of porous zinc oxide bearing pellets in a 2 : 1 nitrogen–carbon monoxide gas mixture has been studied at 1273 K, and the experimental results have been compared with the data available in literature. Two types of materials have been selected for experimentation: laboratory grade 99% pure zinc oxide and industrial grade zinc calcine containing 78% zinc oxide. In each experiment, a single pellet with an average porosity of 60% has been subjected to reduction inside a vertical reactor under a constant flow rate of N2–CO gas mixture. Subsequently, the reduced pellets have been studied under a scanning electron microscope and an image analyser for determination of the extent of reaction at different depths of the pellet. The topmost surface layer of the reacted pellet has been found to be friable indicating the presence of loosely bound particles. Image analysis study has established that the individual zinc oxide particle of any single pellet at different depths from top surface of the pellet has not undergone any appreciable size change during the course of reaction. Such evidence suggests that no appreciable reduction has taken place below the top surface of the pellets. Assuming the process to be topochemical and irreversible with reaction rate as the rate controlling step, the rate constants have been estimated and found to be the same for both the materials, agreeing well with those reported in literature for a non-porous pure zinc oxide pellet.

Sustainable Processing of Deep-Sea Polymetallic Nodules

The possibility of commercialization of processing technology for sea nodules has been linked with comparisons with similar terrestrial process operations. In addition to techno-economic viability, an added focus to commercialization is the sustainability of the process route. The general context of sustainability is discussed. The importance of material flow analysis, recycle rates of the metals produced as well as the possibility of a flow sheet being developed to supply short supply critical metals are brought out in this context. Environmental management for flow sheets under development is important for sustainable operations. Cradle-to-gate environmental burdens such as greenhouse gas emissions and solid waste burden both for common metals as well as for several other metals are provided as a basis of comparison. Polymetallic nodules (PMN) have been likened to low-grade manganese ores where three approaches have been reported for processing. Two of these approaches involve initial processing similar to laterite ore processing for recovery of Ni, Cu, and Co followed by manganese recovery similar to terrestrial ferroalloy production/manganese compound precipitation. The third approach attempts manganese recovery as ferroalloy followed by recovery of Cu, Ni, and Co as practiced for terrestrial sulfide ores. The relatively high values of gross energy requirements and emissions for terrestrial Ni and Co as compared to common metals point out that flow sheet development effort needs to focus on controlling these parameters for a nodules processing operation. On the other hand, these parameters have relatively low values for manganese ferroalloys produced from terrestrial resources. Production of ferroalloys from sea nodules needs to be comparable to their production from land resources. An approach for impact analysis is evolved where a system expansion strategy is followed for Cu, Ni, and Co with a subprocess of recovering manganese bearing ferroalloy. Regarding the later process step, both the Gross Energy Requirement (GER) and Emission (150 MJ and 10 t CO2/t ferroalloy produced) far exceed the terrestrial processing values. For recovery of Ni, Cu, and Co, the results are process specific. For a roast reduction ammoniacal leach process, an energy input of 525 MJ and 40 kg CO2/kg of Ni equivalent is estimated as compared to 200 MJ and 12 kg CO2/kg of nickel equivalent for a complete hydrometallurgical process. Thus, the roast reduction ammoniacal leaching process is not sustainable for sea nodules processing for recovery of Ni, Cu, and Co because of high GER values and high specific CO2 emissions. The high pressure acid leaching route has comparable values to similar laterite processing operations. For flow sheet concepts involving manganese dissolution, recovery of manganese as electrolytic manganese dioxide is less energy intensive compared to residue smelting operation with high gross energy requirements and emissions. For nodule processing flow sheets involving use of energy chemicals (NH3, HCl, H2),appropriate reagent recycle schemes for reagents need to be conceived; else process integration with external flow sheets needs to be contemplated for enhancing sustainability. Considering resource crunch of rare earth elements with respect to terrestrial resources, the recovery of rare earth from sea nodules will enhance the sustainability of the sea bed deposits.

International Smelting Technology Symposium (Incorporating the 6th Advances in Sulfide Smelting Symposium), edited by J. P. Downey, T. P. Battle, and J. F. White, John Wiley and Sons, Inc.

The book comprises of selected papers from the International Smelting Technology Symposium (Incorporating 6th Advances in Sulfide Smelting Symposium), held in conjunction with the 2012 TMS Annual M...