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By Arthur E. Morris

Process modeling software is used extensively in process engineering, but there is a notable lack of affordable software for educational uses. This paper describes two educationally oriented software programs for thermochemical modeling of processes involving metals, minerals, and ceramic materials. Both programs run as Excel@ spreadsheet files. The first is FREED, a thermodynamic database program containing datafiles for 2500 species. It contains the entire U. S. Bureau of Mines and most of the U. S. Geological Survey database, plus data for scores of other species drawn from various sources. Several modules are available for manipulating and viewing the data. The second program is THERBAL, for making thermodynamic calculations using FREED data. Equilibrium calculations can be made for systems with non-ideal solutions, for a specified set of pressure, temperature, and input amounts of reactants. An optional heat balance is also calculated. The results are displayed as tables or charts in Excel worksheets. Examples of the use of THERBAL will be given for the reforming of natural gas for DRI production, DRI production, and EAF steelmaking. Some observations will be made on its use in the classroom. The development of FREED and THERBAL was initially carried out at the Department of Metallurgical Engineering, University of Missouri - Rolla as part of a project to preserve and enhance the Bureau of Mines database. The current versions were developed privately by the authors.

Jan 1, 2002

By P. A. Botha

Most sinter producers prefer to use a range of iron ores with the aim to optimize their sinter blends. ISCOR is however limited to the use of ore from two deposits, namely Sishen and Thabazimbi. Only sinter produced from Sishen ore is described in this report. The Sishen iron ore deposit provides high-grade hematite ore with a mean iron content of 65 per cent. Three major ore types are developed: massive, laminated and conglomeratic. The main ore mineral is hematite with minor to trace amounts of quartz, mica, phosphates and, in places, carbonates. A sinter product is characterized by its mineralogical composition and metallurgical properties. The production rate also plays an important role in the economic evaluation of sinter quality. Sinter-pot tests were conducted with varying basicities, given as the ratio of CaO to SiO:< and coke content. The results of these tests were characterized by mineralogical and metallurgical methods. Basicity of a sinter mix directly influences the mineralogical composition and metallurgical properties. The content of calcium ferrite and calcium silicate increases with increasing basicity, thereby increasing the reducibility and cold strength of the sinter product. Experiments performed during this study provided a model for the optimization of the sinter mix with respect to its mineralogical and metallurgical parameters.

Jan 1, 1991

By Jonkion M. Font, Ramana G. Reddy

A thermodynamic model for a priori predictions of arsenic and antimony impurity capacity in Ni-Cu mattes and slags was developed based on the Reddy-Blander (RB) capacity model. The As and Sb capacities were calculated a-priori considering the RB capacity model in Ni-Cu mattes and FeO-FeO1.5-MgO-CuO0.5-NiO-SiO2 slag at 1573 K and 0.1 to 1 atm partial pressure of SO2. The results showed an excellent agreement between the model calculated and experimental data of arsenic and antimony capacities between the mattes and slag. The impurity capacity model developed here, can be extended for prediction of impurity capacities in multi-component base metal slags and base metal mattes. Such a priori predictions of impurity capacities can lead to develop or improve the efficiency of impurity removal from the base metal smelting, converting and refining processes.

Jan 1, 2014

By Mototsugu Matsuno

A new process has been developed to treat fly ash generated from municipal incinerators, which contains not only toxic metals such as lead and cadmium, but also dioxins. The process includes the following steps; fly ash is formed into green pellets with some additives and the pellets are then roasted to eliminate or stabilize the toxic metals and to decompose dioxins. A pilot plant with a capacity of approximately 100 kg/hr was used to test the process, The tests verified that heavy metals were either volatilized or stabilized and dioxins were decomposed by high-temperature roasting. The pelletized ash was found to be non-toxic, so that it can be recycled as artificial lightweight aggregate. It was also found that volatilized metals collected as secondary ash can be recycled as smelting resources.

Jan 1, 2003

By Wenbo Luo, Kang Liu, Jilai Xue

"Coal fly-ash(CFA) from thermal power plants is rich in Al2O3, which has great potential as an alternative resource for alumina production. In this work, Alz03 contained in the coal fly-ash was extracted using an acid sintering-leaching process. This process was enhanced by aid of power ultrasound during the leaching. The recovery rate of Al2O3 was increased with ultrasound, compared with the similar process without ultrasound under the identical operation conditions. Leaching temperature can be lowered by about 10-l5°C and the processing time reduced by about 50%. The process kinetics were investigated in details for a better understanding of the fundamentals on the effects of power ultrasound. The obtained results demonstrate the potential application in reducing processing energy and increasing production rate.Introduction Coal fly ash is a typical solid waste generated from coal combustion in thermal power station. Vast amount of CF A accumulation lead to serious environmental problems such as air and water pollution, cropland occupation, radioactive contamination, etc. However, CFA is rich in Al2O3 and SiO2 content, so that it has a potential use as recourses for alumina and silica production [1]. Aluminum industry, especially in China, has made a rapid expansion in recent years accompanying with a large amount of bauxite consumption, resulting a urgent demand to develop secondary alumina resources like CF A to maintain a sustainable development of aluminum industry that faces grim challenge [2].Acid leaching is an efficient technology to use in alumina extraction from CF A. Since the particle of CF A is not naturally existed mineral but was formed in molten state at high temperature, the internal Al-O-Si bonds are so strong to separate alumina from the ash particle. Because of this reason, the direct acid leaching [3-6] operated at ambient temperature has low extraction efficiency, approximate 30% to 40%, which is attributed to self inhibition effect from CaS04 generated by reaction between CaO and H2S04 [7-8]. High pressure leaching can efficiently decompose mullite to release A12O 3 content in the fly ash particles, but this requires autoclave material having strong acid corrosion resistance, high temperature (100°C-300°C) and pressure (1.0MPa-2.SMPa) resistance while its operating security is low and its acid consumption is large [9]. Concentrated acid boil process is conducted at near acid boiling point (200 °C - 300 °C) in 4 mouth flask wrapped by electric heating jacket with high mass ratio of acid and ash to achieve high Al203 recovery rate from CFA. Its disadvantages are similar to the high pressure leaching technology except no-pressure, and also the operating solution at nearly boiling point acid may easily spill and splash with additional acid loss and potential safety hazard [10]."

Jan 1, 2014

By cheng Peng-fei, TANG Hai-yan, guo Xiao-chen, LI Jing-she, Liang Yong-cang, Zhao Baojun

In the process of oxygen blast furnace, the lower coke ratio and the higher coke load make the skeleton coke more important. To understand the dissolution of coke in melting and dropping zone, the influence of FeO content, temperature and reaction time on the dissolution of coke with slag were studied by single-factor experiment. Meanwhile, the three factors and three levels orthogonal were conducted. The dissolution degrees were characterized by the weight loss ratio and diameter variation. The results showed that the weight loss ratio increased and the diameter decreased with the increase of FeO content, temperature and time. The three factors and three levels orthogonal test showed that time was the most significant factor on coke dissolution, FeO content of the second, and finally the temperature. The microstructure of coke after reaction indicated that the dissolution occurred on coke surface.

Jan 1, 2016

By Yongqi Sun, Zuotai Zhang

Our study investigated the influence of P2O5 and B2O3 on the viscosity and crystallization behavior of Ti-bearing blast furnace (Ti-BF) slags for the purpose of Ti extraction. The investigation of the crystallization behaviors were carried out using a single hot thermocouple technique (SHTT) and the viscosity was obtained by rotating cylinder method. For the viscosity, the results showed that P2O5 substantially increased the slag viscosity. P2O5 is a network-forming oxide, which increased the degree of polymerization of slags and accordingly increased the slag viscosity. However, both of slag viscosity and apparent activation energy for viscous flow remarkably decreased with B2O3 addition. As a typical network forming oxide, B2O3 was introduced into the network and existed dominantly as 2-D structure, BO3 triangular, which caused a simpler structure and a decreasing slag viscosity. As for the crystallization behaviors of Ti-BF slags, both P2O5 and B2O3 enhanced the crystallization trend of rod-shape rutile and suppressed the crystallization trend of dendrite CaTiO3. Therefore the added P2O5 and B2O3 caused the primary phase change from CaTiO3 to rutile. Additionally, it was found that the rod-shape rutile showed a 1-D growth, whereas the dendrite CaTiO3 showed a 3-D growth style.

Jan 1, 2015

By Wenxian Zhu, Xuema Li, Patrick R. Taylor

"Experiments were performed in a non-transferred arc, thermal plasma flow reactor to investigate the synthesis of ultra fine boron nitride (BN) powder from the reaction system of boron oxide (Bz03), methane (CH4), ammonia (NH3) and hydrogen (H2). Argon (Ar) and nitrogen (N2) were used as plasma gases. The thermodynamics and kinetics of the synthesis reactions were examined and a chemical reaction mechanism was proposed. The powders produced under certain operating conditions had high purity and good conversions. All the products were extremely fine powders (< 30nm) and were uniform in size distribution. The powder products were analyzed by chemical and physical characterization. The effects of the reaction variables on the conversions from B203 to BN and the purity of the products were investigated.IntroductionIn the past few decades, boron nitride (BN) has attracted a great deal of interest because of its excellent thermal, chemical and electrical properties (1-4) It has a high thermal stability and thermal conductivity. Chemically, it is very stable and is not wetted by most molten metals and slag. It is also an excellent low loss insulator. Since hexagonal boron nitride (h-BN) is light in weight, strong and easily fabricated, it has applications in a variety of specialized high temperature areas, such as a high temperature lubricant, crucibles for molten metals, thermocouple protection tubes, break rings for horizontal continuous casting of steel, and friction reducing coatings. In cubic form, boron nitride is one of the hardest materials known, second only to diamond, and it is an excellent material for tools in which the use of carbon based materials is limited by oxidation or reaction with metals."

Jan 1, 1998

By Mansoor Barati

The present paper is based on a term project for final year undergraduate students, requiring them to evaluate a process for producing silicon from rice husk. The traditional method for production of silicon involves carbothermal reduction of quartz in electric arc furnaces at temperatures exceeding 2000 °C. The technology consumes a considerable amount of electrical energy as well as fossil fuels, resulting in significant CO2 emissions. A flowsheet for production of silicon metal from rice husk is laid out in this paper. The technology will consist of combustors, which will generate steam using the rice husk biomass, power generator, and electric furnace for reduction of the rice husk. Materials and energy balance calculations presented here indicate that such process can be operated independent of external electricity.

Jan 1, 2014

By Liu Wei-feng

In this paper, the practice of separating precious metals from base metals in gold-antimony alloy by selective chlorination leaching under controlling potential in China has been introduced in detail. The precious metals and the base metals can be separated completely when the complex gold-antimony alloy is treated by this process. The impurity metals were removed effectively since the leaching efficiencies of copper, nickel and antimony are over 99%, with direct recovery of gold being 99.83% that is about 20% higher than that of the original process and silver, antimony, copper and nickel are also recovered effectively. The gold grade of the resulting crude gold powder can reach to 94%.The new process has been applied in the treatment of gold-antimony alloy for two years, and many former procedures have been cancelled, such as electrolysis, Anode slime leaching by nitric acid, smelting in crucible and blowing in muffle. The new process is more shorten, lower cost and friendly to the circumstance comparing to the original process.

Jan 1, 2008

By Rak-lun Choi

Plasma-induced damage of InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) has been studied in terms of forward turn-on and reverse breakdown voltages, together with etch rate and surface morphology. The physical degradation of sidewall along with rough surface morphology of n-GaN caused by increased ion scattering induced the deterioration of the forward and reverse voltages. It was found that the turn-on voltage is sensitive to the surface roughness of the etched n-GaN and the breakdown voltage is strongly affected by the sidewall contamination. Annealing under nitrogen after the mesa etching improved the electrical properties of the InGaN/GaN MQW LEDs. Efficient blue light-emitting diodes (LEDs) were fabricated using InGaN/GaN triangular MQWs. The LEDs with triangular QWs showed a lower operation voltage and 2.4 times higher light output power than those with the rectangular MQW LEDs at 20 mA and 20 °C. The intensity of electroluminescence (EL) at 20 mA was almost independent of ambient temperature in the triangular QW LED, but decreased substantially in the rectangular one.

Jan 1, 2003

By Shengli Wu, Mingyin Kou, Laixin Wang, Xinliang Liu, Zhennan Qi, Yujue Wang

Softening and melting experiments were conducted on four kinds of imported lump ores named A-D, under different temperature intervals within the self-developed visualization high temperature furnace. By calculating the reduction and shrinking degree under different intervals, softening and melting indexes were determined. These ores all expanded firstly followed by shrinkage with the temperature increasing. The difference of lump ore’s own characteristic led to different softening and melting behavior. The results showed that the looser the structure was, the better the reducibility will be. The compact structure and good reducibility led to high expansion rate. The beginning softening temperature declined and the ending softening temperature increased because of high porosity, which resulted in wide softening temperature interval. The charging ratio of lump ore A should be improved. Lump ore B should be distributed in the center of the blast furnace. Lump ores C and D should be used less.

Jan 1, 2016

By B. C. Jena

Activities of carbon, cobalt and nickel were evaluated in the ternary systems iron-carbon-cobalt and iron-carbon-nickel for the temperature range 1300-1600°C for cobalt and 1300-1700°C for nickel. The carbon activities were determined from the knowledge of activities (1) in the binary system iron-carbon, (2) in the dilute ternary systems and (3) from the knowledge of carbon saturation data. The activities were mathematically expressed with the Taylor series expansion of Wagner&apos;s interaction parameter formalism modified to suit concentrated solutions. The cobalt and nickel activities were determined from the knowledge of carbon activities by applying the Gibbs-Schuhmann integration and from cobalt and nickel activities in the binary systems iron-cobalt and iron-nickel. Partial molar enthalpies of mixing were determined based on the temperature behaviour of the activity coefficients.

Jan 1, 1992

By L. M. Abrantes, A. P. Paiva

"A brief review of some innovative methods for the direct recovery of metals from loaded organic phases is presented; emphasis is given to electroreductive stripping and cementation, which are described and illustrated by examples: of current research. The recovery of silver using a two-phase electrolysis - by direct application of an electrical potential to a mixture of a metal loaded organic phase· containing Cyanex 471X, obtained by solvent extraction, and a stabilized sodium thiosulfate solution - is more extensively discussed. The overall efficiencies are analyzed and compared with data obtained by conventional stripping procedures. Some preliminary results achieved for the recovery of the precious metal using galvanic stripping, applied directly to similar organic solutions and involving zinc and iron powders as reducing agents, are also evaluated.Introductory ReviewThe application of hydrometallurgical methods to the recovery of metal values from ores and concentrates has been receiving a growing interest, either from researchers or from the mining industry [1].For the concentration / purification of the relatively low concentrated metallic solutions resulting from the leaching of those raw materials, solvent extraction (SX) is a well established technique [2]; the loaded organic solvent is then conventionally contacted with a suitable aqueous solution, the metal in its final form being usually recovered from this solution by electrowinning.As an efficient and / or selective stripping is sometimes difficult to achieve, depending on the specific characteristics of the system under consideration, some alternative procedures have been analyzed in order to overcome this problem. One of the chosen routes, mainly developed by Hirai and Komasawa, is to promote the reduction of the desired metal species in the organic phase, in such a way that the stripping stage becomes feasible; for the selective stripping of vanadium from a solvent containing a mixture of vanadium and molybdenum, the authors successfully used reductive [3], electro-reductive [4,5] and photo-reductive [6] techniques. The two latter methodologies have also been applied to the recovery of europium from a solvent containing europium, samarium and gadolinium [7,8].However, further processing is necessary to recover the metal in its solid state; therefore, methods causing the direct reduction of the metal species in the organic phase to their fmal metallic form would be of interest, as an intermediate step would be avoided"

Jan 1, 1997

By C. Flores

A novel process using solid metals for the direct reduction of more noble metal ions from solvent extraction organics has been developed. Base metals recovery has been the principal focus of investigations to date but feasibility tests have now also been made on galvanically stripping selected precious metals. In this study gold (III) was loaded from an aqueous HAuCI4 .3H20 solution into a mixed organic 40 vol.% TBP, 10 vol. % D2EHPA in kerosene. The direct precipitation of metallic gold from the loaded organic phase using zinc powder and iron, aluminum and copper slabs at 70 °C was successfully demonstrated. The gold reduction rates were relatively fast even though the conductivity of the organic solutions is very low. The reaction rates were studied as a function of the variables zinc particulate size, oxygen and nitrogen atmosphere, water content in the organic phase, organic ratios and temperature. The gold morphology was usually powdery or dendritic in nature but continuous films were obtained in some instances. Activation energies were calculated and possible reaction mechanisms are discussed. In general, the results obtained were very promising and showed that gold can be successfully cemented from selected organic solvents by galvanic stripping using less noble solid metal reductants.

Jan 1, 1995

By L. W. Beckstead

In a conventional zinc refinery plant, zinc concentrates were roasted at 950°C. The calcine was ground and leached in a series of leaching vessels using sulfuric acid. The pH in the first leaching vessel was maintained at 2.5, while the pH of the solution exiting the last vessel was about 5.4. The leached residue typically contained (in percent) 0.1 Ag, 0.2 As, 0.7 Cd, 2 Cu, 15 Fe, 10 Pb, and 15 Zn, and it was classified as hazardous material according to the EP-toxicity test. In order to make the residue non-hazardous, and to recover most of the metal values from the residue, a brine leach process was developed. The process consisted of leaching the zinc leach residue in CaCI, brine solution at pH 2 for 1 hour at 90°C. Silver extraction was about 95 percent, while lead, copper, cadmium, zinc, and iron extractions were about 80, 50, 50, 30, and less than 0.5 percent, respectively. More extreme conditions of acidity could have been used in the leaching stage to increase zinc dissolution, but iron dissolution would have significantly increased which would have complicated subsequent recovery steps. The leached and washed residue passed the EP-toxicity leach test and could be disposed as non-hazardous. Silver, copper, and lead in the leach solution were recovered by zinc cementation, while zinc and cadmium were recovered by sulfide precipitation. The resulting solution can be recycled in the process after magnesium precipitation.

Jan 1, 1993

By Jana Dobrovska

Solidification and cooling of a continuously cast slab and simultaneous heating of a mould is a very complicated problem of transient heat and mass transfer. Nowadays, the solving of such a problem is impossible without numerical models of the temperature field not only of the slab itself, while it is being processed through the whole concasting machine (Caster), but of the mould as well. Two original numerical models have been developed and used in the investigation of a continuously cast steel slab. The first (one of two) 3D model of the temperature field of a concasting is capable of simulating the temperature field of a caster. Experimental research and data acquisition have to be conducted simultaneously with the numerical computation-not only to confront it with the actual numerical model, but also to make it more accurate throughout the process. After computation, it is possible to obtain the temperatures al each node of the network, and at each time of the process. The utilization of the numerical model of solidification and cooling of a concasting plays an indispensable role in practice. The potential change of technology-on the basis of computation-is constantly guided by the effort to optimize, i.e. to maximize the quality of the process. The user can therefore choose any appropriate longitudinal or cross-section of a slab and display or print the temperature field in a 3D or 20 graph whenever necessary. The second numerical model of dendritic segregation of elements assesses critical points of slabs from the viewpoint of their increased susceptibility to crack and fissure. In order to apply this model, it is necessary to analyze the heterogeneity of samples of the constituent elements (Mn, Si and others) and impurities (P, S and others) in characteristic places of the solidifying slab. The numerical model, based on measurement results obtained by an electron micro-probe, generates distribution curves showing the dendritic segregation of the analyzed element, together with the distribution coefficients of the elements between the liquid and solid states. The combination of both models enables the prediction of cracks and fissures in critical points of the continuously cast carbon-steel slab. Both models had been applied in the industrial investigation of a cast low-carbon-steel slab.

Jan 1, 2003

By G. Coryell, S. Blaskovich

"A computer model has been developed to simulate the flash furnace and converter operations at the ASARCO Hayden Copper Smelter. The focus of the modeling was to optimize the converter operation to eliminate high matte level episodes in the flash furnace. These episodes (reducing feed to the furnace) resulted from the lack of converter operation scheduling. The model provided ""what if?"" scheduling scenarios that led to increased efficiency of the converter and flash furnace operations.This paper discusses alternatives studied to optimize the converter operation and the development of the computer modeling program, including implementation of the project. The discussion details the results of the project including the conversion from batch to a real time converter scheduling process. IntroductionASARCO's Hayden Smelter consists of a fluid bed drying system, an Inco oxygen flash smelting furnace, Peirce Smith converters, two anode furnaces and two casting wheels, gas cleaning plant, 2800 stpd sulfuric acid plant, 650 stpd oxygen plant and 200 gpm water treatment plant. The process flow sheet of the plant is shown in Figure 1.Over the past several years, the Hayden smelter has been involved in productivity improvement and cost reduction programs. This has been necessary to become a low cost copper producer in today's market. Part of the productivity improvement program was the use of process control to streamline the flash furnace and converter operations. Process control, through the use of computers and electronic controllers, has played an increasingly important role in optimizing processes in the Hayden Plant since the startup of the Inco flash furnace in 1983."

Jan 1, 1989

By I. M. Richardson, M. Janssen, I. J. Bennett, V. A. Popovich

The most critical processing step during the manufacture of screen-printed crystalline solar cells is firing aluminium and silver contacts, which generates residual stresses and solar cell bowing. In this paper, an alternative Ag contact formation mechanism is proposed and aspects related to electrical contact properties, residual stresses and layer delamination are investigated. It is found that there are two main processing parameters affecting the uniformity and delamination of the Ag/Si interface, namely the peak firing temperature and the silicon surface roughness. Silicon surface polishing gives a better wetting of the silicon surface by the glass layer, resulting in a good contact and lower incidence of large voids, compared to the case of highly textured surfaces. The non-uniformity in the glass layer and large voids at the Ag/Si interface (in the case of a textured surface) are expected to have a negative effect on the mechanical strength of the solar cell.

Jan 1, 2015

By K. Narayan Prabhu, W. D. Griffiths

"Heat transfer during the unidirectional solidification of a cast iron alloy against cast iron chills was investigated using an inverse modelling approach. Chills of thickness 100 mm and 10 mm were used, to simulate gravity die cruiting conditions and the use of chills in sand moulds. In both cases transient heat transfer, measured by the interfacial heat flux and heat transfer coeffieient; declined from initially high values in the first few seconds of solidification, to values about an order of magnitude lower which persisted for the remainder of the experiments. In the case of the thin chill it became saturated with heat until it was no longer in a position to extract further heat from ·the casting. These results were interpreted by studying the resistance to heat transfer from the casting offered by the ·casting-chill interface and the chill itself for example, the thermal resistance of the casting-chill interface can be influenced by the deformation of their respective surfaces and their subsequent relationship.IntroductionDie casting cast iron offers several advantages such as energy savings, higher mould yield, and better surface quality over the sand casting process1 • The process is· environmentally' friendly because of the elimination of the sand. However the design and construction of metallic moulds is expensive and a faulty die design may result in a defective casting: A simulation based process design of die castings would enable die designers and solidification modellings to try better designs of dies on the computer and arrive at a cost effective solution more quickly. This has numerous benefits for the die caster, as he would be able to produce sound castings with very short lead times.The success of a solidification model to predict accurately the thermal history and the location of hot, spots inside a solidifying casting depends to a large extent on the heat transfer data prescribed at the metal/mould interface. Many measurements of the heat transfer coeffident (or the heat flux) between a solidifying aluminum alloy and a chill have shown that the heat transfer coefficient is a function of most of the variables of the casting process2 - 8. However heat transfer studies during the solidification of ferrous alloys are rather limited. The high temperatures involved suggest that the contribution due to radiation heat transfer cannot be neglected."

Jan 1, 2000