Applications of Process Engineering Principles in Materials Processing, Energy and Environmental Technologies: An EPD Symposium in Honor of Professor Ramana G. Reddy: Pyrometallurgy II
Sponsored by: TMS Extraction and Processing Division, TMS Light Metals Division, TMS: Energy Committee, TMS: Hydrometallurgy and Electrometallurgy Committee
Program Organizers: Shijie Wang, Rio Tinto Kennecott Utah Copper; Michael Free, University of Utah; Shafiq Alam, University of Saskatchewan; Mingming Zhang, Arcelor Mittal; Patrick Taylor, Colorado School of Mines

Wednesday 8:30 AM
March 1, 2017
Room: 15B
Location: San Diego Convention Ctr

Session Chair: Neale Neelameggham, Ind LLC; Bradford Wesstrom, Freeport-McMoRan Copper & Gold

8:30 AM  
Chloridizing Roasting of Bismuthinite with Sodium Chloride-oxygen: Rafael Padilla1; Luis Salinas1; Maria Ruiz1; 1University of Concepcion
    Chloridizing roasting of bismuthinite (Bi2S3) with NaCl-O2 has been studied to remove Bi by volatilization from copper concentrates that contain bismuthinite. The study was conducted using mixtures of Bi2S3 and NaCl in a horizontal furnace and TGA apparatus. The variables were temperature, oxygen partial pressure, and NaCl concentration. The chlorination was analyzed by weight loss measurement method. XRD results of calcines reacted for short times in 21% O2, and 850-1000 C showed the presence of Bi, BiOCl, and Na2SO4, while at longer times Bi2O3 was identified. Thus, the Bi2S3 chlorination-volatilization proceeds through intermediates compounds Bi and BiOCl. Temperature affected significantly the weight loss of samples. At 600 and 900 C in 10.3% oxygen, the maximum weight loss was 4% and 20%, respectively. An increment in the partial pressure of oxygen in the range 1 to 21% affected negatively the Bi2S3 conversion. Bismuth volatilization by NaCl roasting would be marginal.

8:50 AM  
Natural Gas Utilization in Blast Furnace Ironmaking: Tuyre Injection, Shaft Injection and Prereduction: P. Chris Pistorius1; Jorge Gibson1; Megha Jampani1; 1Carnegie Mellon University
    Increased utilization of natural gas in blast furnace ironmaking can decrease both the cost and the carbon intensity of ironmaking, given current US natural gas prices. In this paper, three ways to utilize natural gas are compared: tuyre injection, prereduction of iron ore, and shaft injection. The basis for comparison includes coke replacement ratios, carbon intensity, furnace productivity and approximate costs. These were calculated using relevant mass and energy balances, a blast furnace productivity correlation based on the bosh gas flow rate, and measured and modeled prereduction kinetics. Of the natural gas utilization methods, prereduction has the highest effective coke replacement ratio (and hence the largest advantage in raw material cost), but also the highest capital requirement.

9:10 AM  
Selective Sulfation Roasting of Rare Earths from NdFeB Magnet Scrap: Brett Carlson1; Patrick Taylor1; 1Colorado School of Mines
    Rare earth magnets play an increasingly important role in high end technology, and the manufacture of rare earth magnets, such as the NdFeB type, consume a large amount of the rare earths produced. Recycling of this material could provide an important domestic source for these materials. A selective sulfation roast has been developed; the central principle of which is to take advantage of the differing stabilities of the rare earth sulfates as compared to those of iron under a reactive atmosphere. To determine the kinetics of this reaction, a thermal gravimetric apparatus is constructed and the sulfation of iron oxide and neodymium oxide are studied under different experimental conditions. This data is used to determine parameters in modeling the system. This process is shown to effectively separate the high value rare earth components from iron, the major component of this waste stream.

9:30 AM  
Gold Solubility in Smelting Slags for the Recycling of Industrial and Mining Wastes: Jun-Gil Yang1; Hyun-Sik Park2; Joohyun Park1; 1Hanyang University; 2Korea Institute of Geoscience and Mineral Resources (KIGAM)
    Gold is one of the most valuable and precious metals. But, the extraction efficiency of gold from natural resources is very low and labor-intensive due to very low concentration of gold, i.e. 1-5 ppm, which means that gold extraction processes produce extensive amounts of tailings. The gold content in PCB of mobile phone is about 100 to 400 ppm, which is enormously greater than that found in natural ores. Consequently, a requirement for recycling waste PCB and gold mine tailings becomes increasing for maintaining sustainable society. Because the pyrometallurgical processes are issued due to economic reasons, it is needed to understand the thermodynamic behavior of gold in smelting slag under oxidizing and reducing atmosphere at high temperatures. In this study, the effect of slag chemistry, oxygen potential and temperature on gold solubility in smelting slag will be discussed.

9:50 AM Break

10:10 AM  
Solid State Reduction of Iron, Manganese and Chromium Oxide Ores with Methane: Rauf Eric1; Petteri Halli2; Pekka Taskinen2; Amit Bhalla1; 1University of the Witwatersrand; 2Aalto University
    Sustainable development requires less energy consumption with lower carbon footprint. In this review the solid state reduction behavior of three oxide ores using methane gas are briefly summarized based on experimental work conducted in our laboratories. The discussion concentrates mainly on mechanisms of the reduction studied through SEM-EDAX and X-ray diffraction techniques. Limited preliminary kinetic input is also mentioned. Iron ore containing titanium and vanadium could be reduced significantly in the solid state with methane-hydrogen mixture up to 400C lower than is needed in ordinary solid state carbothermic process. The reduction of chromite and manganese ores were possible similarly at lower temperatures with potential energy savings lower carbon footprint.

10:30 AM  
Stibnite Chloridizing with Calcium Chloride-oxygen at Roasting Temperatures: Rafael Padilla1; Ilitch Moscoso1; Maria Ruiz1; 1University of Concepcion
     Antimony and arsenic are impurities in copper concentrates found normally as stibnite (Sb2S3), tetrahedrite (Cu12Sb4S13) and enargite (Cu3AsS4). When copper concentrates contain appreciable amounts of As and Sb, they must be removed before smelting to avoid environmental pollution. Oxidizing volatilization roasting at 500-700 C has been used to eliminate these impurities. However, only a fraction of Sb volatilizes in those conditions; therefore, Sb eliminations from concentrates remains unresolved. In this study, the chloridizing roasting of Sb2S3 using CaCl2-O2 was investigated to remove the antimony from concentrates. XRD analysis of calcines indicated that the overall reaction could be written as: Sb2S3 + CaCl2 +O2 = 2SbCl3 + CaSO4 Temperature and oxygen partial pressure have a significant effect on the rate of reaction. About 90 % conversion was obtained at 750 C, 5.4 % oxygen in 20 min. High oxygen concentrations arrest the advance of the reaction forming various antimony oxides.

10:50 AM  
Investigations on Rotary Tool Near-dry Electric Discharge Machining: Vineet Yadav1; Pradeep Kumar1; Akshay Dvivedi1; 1Indian Institute of Technology, Roorkee
    Near-dry electric discharge machining (EDM) is a process variant of EDM, which uses two-phase flow of liquid and gas as dielectric medium. This article reports the results of an investigation pertaining to the drilling of holes on high speed steel (T2 grade) by a rotary tool near-dry EDM. The One-Factor-At-a-Time (OFAT) approach was used for experimentation. The effects of process parameters, viz. peak current, pulse duration, gas pressure, liquid flow rate, and tool rotation speed on material removal rate (MRR) and overcut were investigated. The dielectric medium used was a mixture of glycerin-air. The experimental results reveal that rotation of the tool electrode along with high pressure of two-phase dielectric medium contribute in effective flushing of inter electrode gap. The MRR measured with rotary tool near-dry EDM was three to four times higher in comparison with conventional EDM. Additionally, appreciable surface quality was achieved.