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By Bora Derin, Onuralp Yucel, M. Seref Sonmez, Murat Alkan

"Latest stage in the production of boron carbide by metallothermic methods using magnesium was the leaching process. Boron carbide particles obtained by self-propagating high temperature synthesis contained several impurities such as magnesium oxide and magnesium borates after the metallothermic reactions. Removal of such contaminates by hydrometallurgical methods required to produce high purity boron carbide. Leaching by concentrated hydrochloric acid solutions resulted in the production of pure boron carbide together with high magnesium and boron containing solutions. Removal of such ions from the spent liquor was the necessity to have dischargeable solution. In this study, precipitation of magnesium and boron compounds from relevant chloride containing spent liquors and the production of saleable products was aimed. The effects of chemical reagents, pH of the solution on the precipitation efficiency of magnesium and boron compounds were investigated in the study. Chemical analysis and the characterisationof solid phases by using x-ray diffraction analysis were the latest stage.Introduction A variety of advanced ceramics, inter-metallic, organic and inorganic compounds, oxygen free single crystals, and polymers can be synthesized by using different SHS techniques [1, 2, 3]. In the SHS process, after initiation, reaction becomes self-sustaining and propagates in the reactant mixture. A high amount of heat which is generated during the process accelerates the reaction rate and thus it makes the process highly productive and economically feasible for different production scales. After the SHS process obtained powder mixture needs to reacted with acidic solutions to purify the product. In this case B2O3 was reacted together with C and Mg to synthesis fine B4C powder resulted in the production of MgO as well according to the Eq. 1 and then MgO was removed from the mixture by leaching with the concentrated HCl solution as shown in Eq. 2, respectively [4, 5]."

Jan 1, 2008

By J. Schmidl

In non-ferrous metallurgy the service life of refractory materials typically ranges from several weeks up to three years or more and is strongly dependent on operating conditions. To support our customers with the most viable refractory solution for their needs RHI Magnesita follows a structured approach of thermo-chemical calculations, experimental evaluation from lab scale up to industrial field tests and post-mortem analysis of used refractory materials. This paper will give an overview of the RHI Magnesita refractory selection process and the most recent developments of the experimental setup for the so called HF-IF test. This is a dynamic corrosion test that allows to determine fundamental properties of different refractory material types under process conditions subjected with respective customers process materials. The HF-IF experimental procedure is an excellent tool to simulate refractory wear in industrial processes, diminishing risks associated with plant trials and support decision making to choose the optimal refractory solution for the customer.

By Fuxing Yin, Akira Sato, Yoshiaki Ohsawa, Kohji Kawaharai

"INCRAMUTE alloy (nominally 45Mn-53Cu-2Al wt. %) has a specific damping capacity as high as 0.4, through a solid-solution and aging treatment. The damping behavior of the alloy is highly temperature-dependent and shows a peak near room temperature. The inadequate strength in the high damping condition restrains the practical application of the alloy, as structural components. Ferromagnetic MnB particles are dispersed in the alloy during induction remelting the matrix alloy in an argon atmosphere. Surface modification of the MnB particles by mechanical alloying (MA) and suitable control of the addition process cause a homogeneous distribution of MnB particles in the alloy. In the composite containing 2 wt. % MnB particles, temperature dependence of damping capacity is improved, and higher damping capacity is still retained in the temperatures over 60 °C. Meanwhile, the Young's modulus and tensile strength were also increased by about 20%. The roles of the MnB particles in improving both damping behavior and mechanical properties were also discussed.IntroductionMany viscoelastic materials, such as rubbers, polymers and plastics, have the superior ability to damp vibration and noise. However, in the applications as structural materials the high damping capacities of materials are pursued upon the satisfactory mechanical properties, especially those at elevated temperatures. Damping alloys are finding more and more applications in structures where noise and vibration ·should be ·eliminated. Specific damping capacity (SDC), defined as the ratio of the energy dissipated to the maximum vibration energy stored per cycle, is usually used to evaluate the damping capacity of alloys. INCRAMUTE damping alloy, developed by the International Copper Research Association, Inc., has a nominal composition of 45Mn-53Cu-2Al in weight percent. The high damping· microstructure of this alloy is obtained through the solution treatment at 820 °C followed by a water quench and aging at 400°C for 10 hours followed by cooling to room temperature [1]. With the heat treatment, a SDC peak ·vs. temperature of as high as 0.4 was observed in the alloy at the strain amplitude of about 10-3 while a tensile strength of about 500MPa was sustained."

Jan 1, 2000

By M. Omneya El-Hussaini, M. Galal Abdel Wahab, A. Mohamed Mahdy, M. Fathi El Shahat

"Um-Gheig Pb-Zn representative sample was collected from the main adite of Um-Gheig mine along Red Sea coast in Egypt. Its chemical analysis shows that, it contains 16% Zn, 2.3% Pb, 0.1% Cd and 0.1% B as elements of interest. After H2SO4 agitation leaching, the chemical composition of Um- Gheig Pb-Zn deposit ore residue assayed 2.26% Pb, 1.5% Zn, 0.085 % B and 0.01% Cd. This residue was leached with 20% HCl at S/L ratio 1/3 for 2 hours at 80o C. The chloride leach liquor was found to contain 18 g/l Pb, 13 g/l Zn, 0.1 g/l Cd and 0.75 g/l B with the corresponding leaching efficiencies 79%, 86%, 100% and 88% respectively. Lead was precipitated from the chloride leach liquor using concentrated H2SO4 to obtain PbSO4 with precipitation efficiency 96%. While boron was extracted by the selective resin Amberlite IRA743 with loading efficiency of 80%. On the other hand, Zn and Cd were precipitated using Na2S solution with 86.7% and 100% recovery efficiencies respectively.IntroductionLead-zinc ores occur in Egypt in a few localities distributed along the Red Sea coast between El Qusier and Ras Banas.. The reserve of the ore deposits has been estimated by Soviet and German Experts to be about 900,000 Ton, [1]. Onal et al., [2] recovered Pb from Pb–Zn sample containing 10.17 % Pb and 10.98 % Zn from Aladag in Turkey. El-Sherif, [3] used concentrated HCl to leach lead-zinc ore sample of Um-Sammuki area in Egypt. As had been published by Marchioretto et al. [4], the precipitation of heavy metals with lime, sulfide and caustic soda are the most commonly used economical methods for metal removal. Lead was completely removed from the anaerobically digested sludge by precipitation with NaOH and Na2S at waste water treatment plants. Mahdy et al., [5] had successfully extracted boron from the bittern solution of Qaron Lake by ion exchange resin (Amberlite IRA 743). The extraction of boron was mainly depending upon the pH value. They extracted 80% of boron at pH 5.5, while at pH 3.9 about 74% boron was extracted. Kabay et al. [6] used the column-mode to remove 1g/l of boron from geothermal waste water of the Kizildere-Geothermal Power Station by using Diaion CRB 02 Nglucamine- type chelating resins. In this regard, the removal of lead, cadmium and boron allow the residue to be reclassified as non hazardous material."

Jan 1, 2008

By Dirk Verhulst, V. I. Lakshmanan

Why Chloride Hydrometallurgy?The most available, cheapest and best known reagent for treating ores and other raw materials for the metallurgical industry is sulfuric acid. Hydrochloric acid is second in line. What often happens is that a process is developed on the basis of sulfuric acid, and that at some point the question arises: wouldn't hydrochloric acid do this better?Considering hydrochloric acid immediately opens a very interesting field of research. To summarize a few comments from another paper presented at this symposium [1]: chlorides are far more soluble than sulfates (with a few interesting exceptions); the hydrogen ion activity is greater in chloride than in comparable sulfate solutions; higher oxidative conditions are possible; regeneration is more straightforward; more diversity is possible and better conditions for the separation of species can be found for solvent extraction and ion exchange; sulfur in the ore can be separated as elemental S; higher metal concentrations in solution and more flexibility in the chosen oxidation state means significantly lower energy costs.Also, the volatility of many chlorides at higher temperature allows further separation without the need to go to a different system. Chlorides also form molten salts with a low melting point, providing another means of separation and purification in the same chloride medium.

Jan 1, 2011

By C. P. Broadbent

The process metallurgy of many nickel laterite smelting operations is controlled largely by the physical chemistry of the slag system. Consequently, accurate phase diagram information and physicochemical property data are essential to interpret and predict the behaviour and optimisation of the overall process. The system (SiO2 - MgO - FeO) first described by Bowen et al. between 1914 and 1935 and the system (SiO2 - MgO - FeO - Fe2O3) determined by Muan and Osborne in 1956 are of particular relevance to the study of nickel laterite smelting slags as these systems form a reasonable approximation of many industrial slags. This paper will review the literature for these (and other relevant) phase systems. In addition data available from the ternary and (quasi)ternary phase diagrams will be compared with data obtained from industrial slags. The physico-chemical properties under consideration will include; melting and crystallisation behaviour (solidus and liquidus temperatures), viscosity - temperature relationships, heat flux considerations, electrical conductivity, surface and interfacial tension.

Jan 1, 1993

By R. Kola

Since more than 15 years the Waelz process at "Berzelius" in Duisburg has proved suitable for reprocessing the zinc and lead containing dust and .sludge which inevitably occur in making steel in EAF-plants. The produced Waelz-oxide is agglomerated in a hot-briquetting plant and charged to an Imperial Smelting Shaft Furnace to recover the valuable elements in form of metallic zinc and lead. In view of the actual importance of the dumping problems of the EAF wastes a description of the "Berzelius" treatment route is given but also the situation in Western Europe is illustrated. Dust from stainless steel production is successfully treated in the Scan Dust Plasma Process in order to recycle Chromium and Nickel, while the resulting Zinc-Dust is treated via the Waelz-ISF-Route. For treatment of low Zinc-containing dust, sludge and fines from integrated steelworks, pilot scale tests have been carried out successfully in the Circulating Fluid Bed in order to recover metalized iron and .zinc/lead fume. A 30,000 tpy Demonstration Plant is planned?.

Jan 1, 1990

By M. Demuth, B. Holleis, M. Potesser, D. Spoljaric

"In 2005, Messer Group established a technology competence centre for metallurgy in Gumpoldskirchen (Austria), with the aim to develop oxygen burners which satisfy today's and upcoming standards of legislation as well as customer requirements. With the assistance of the Development Sponsorship Fund (FFF) of Austria, cooperation with the University of Leoben was agreed on. With the long term experience of the Gas-Warme-Institut ""GWI"" in Essen (Germany) and the University of Leoben, different new burners have been developed.The efficiency of industrial combustion processes can be increased in two ways (which can be seen in Figure 1 ), either by preheating the fuel and combustion air or by adding oxygen. Due to the high 79 % Nz ballast in air combustion, only low flame temperatures can be reached. This results in high heat loss in the exhaust gas, caused by the low combustion efficiency. Oxygen can be introduced into the combustion chamber using different techniques:• Oxygen fuel burners• Direct oxygen injection into the fuel air flame• Underlaying of the fuel air flame• Enrichment of the combustion airIn Figure 2, the theoretical flame temperature for the stoichiometrical combustion of natural gas is plotted as a function of oxygen enrichment. Therefore, it can be concluded that even low enrichment values produce higher flame temperatures and result in higher combustion efficiency."

Jan 1, 2012

By Miguel Barron

Recently, a new lance design for BOF steelmaking has been proposed in the literature. This lance, in addition to six peripheral inclined supersonic nozzles, contains a vertical centered nozzle whose oxygen flow is independent from the main oxygen supply. The above authors affirm that their lance maximizes the droplet generation without causing spitting. In this work, the performance of a lance with four peripheral nozzles and one vertical centered nozzle is numerically modeled by means of Computational Fluid Dynamics software. Transient two dimensional computer simulations were carried out considering two phases, namely molten steel and gaseous oxygen. Numerical results confirm that bath agitation and droplet generation are enhanced as a result of the vertical centered nozzle, however a proper performance of this lance, related to a conventional one, strongly depends on the Mach number of the oxygen jets and the lance height.

Jan 1, 2008

By Dean Ilievski

Mathematical modelling of the precipitation process requires that the kinetics of crystal growth, nucleation and agglomeration be known: This paper reviews the current state of knowledge on these precipitation sub-processes (ie. growth, nucleation and agglomeration) and describes a number of experimental techniques for estimating their kinetics. The experimental methods used to generate the precipitation data and the data analysis techniques used to extract the kinetics information from the data are discussed separately. There is no universal "best" technique for determining the kinetics. However, studies on multi-crystal systems are more reliable for modelling purposes than are single crystal studies. The selection of a technique will depend on which sub-processes are present. A problem with all kinetics studies is that there is generally a large uncertainty in the estimated kinetic parameters. This stems from the scatter in the experimental data being further propagated by the mathematical techniques used to extract the kinetic parameters.

Jan 1, 1996

By M. Goto, T., Matsutani, T. Igarashi

"PT. Smelting was established in February 1996 as a company to· construct the first copper Smelter and Refinery in Indonesia with US$500 million direct construction cost and operate it. The plant is located in Gresik, East Java, Indonesia and 20km northwest from Surabaya, 2nd largest city in Indonesia. The site was selected due to following .advantages.1. Adjacent PT: Petrokimia Gresik, - a fertilizer company, purchases all sulfuric acid produced through pipeline.2. Facing on the seashore of the Madura Strait, it is possible to unload copper concentrate from West Papua (3,000km from Gresik) and load granulated slag to the market.3. Close to the good harbor facilities at Surabaya for export the products.4. Gresik Industrial Area has adequate infrastructure.5. Surabaya is a quite nice city to live for people from abroad.The shareholder of PT. Smelting are Mitsubishi Materials Corporation (60.5%), PT. Freeport Indonesia (25:0%), Mitsubishi Corporation (9.5%) and Nippon Mining and Metals Co. Ltd. (4.5%).The Gresik Copper Smelter and Refinery is designed to produce 200,000 tpy of copper cathode from 660,000 tpy of copper concentrates supplied 100% by 'Grasberg Mine of PT. Freeport, Indonesia in West Papua (former Irian Jaya). Other by products are 600,000 tpy of sulfuric acid, 30,000 tpy of gypsum, 509 tpy of precious metal slime and 400,000 tpy of granulated slag. These are sold to domestic and international markets.This project adopted the Mitsubishi Continuous Copper Smelting and Converting Process in the Smelter for anode casting, Contilanod process comprising Hazelett twin belt caster and a Mannesmann's travelling shear were selected. ISA stainless steel cathode process is applied in refinery. The combination of contilanod anode and stainless steel cathode ensured good cathode quality from the very beginning of start-up SO2 gas generated from Smelter is treated by Lurgi-Mitsubishi double contact/absorption acid plant. All contact. wastewater from the plant is treated in multistage wastewater treatment plant.Electricity and oxygen are ·supplied ""over the fence"" by a company which is located in the site of the Gresik Smelter and Refinery."

Jan 1, 2000

By Eleazar Salinas R., Miguel Perez L., J. Cesar Juarez T., Martin Reyes P., Eduardo Cerecedo S., Isauro Rivera L., Francisco Patino C., Juan Hernández A.

"A complete characterization of burrows from Mining district of Pachuca - Real del Monte, in Hidalgo state Mexico, was done. These kind of residues had not been formally characterized, founding an average chemical composition of 70.43 % wt. of Si02, 7.032 % wt. of Ah03, 2.69 % wt. of Fe20 3, 0.70 % wt. of Mn, 3.98 % wt. ofK20, 3.34 % wt. of CaO, 2.50 % wt. ofNa20, 1.01 % wt. of MgO, 0.26 % wt. of Ti02, 0.04 % wt. of Zn, 0.026 % wt. of Pb, 56 g/ton of Ag and 0.6 g/ton of Au; In the same way, the residues present as majority mineralogical phases the following: Quartz, Berlinite, Orthoclase, Feldspar, Anorthoclase and Calcite. By the other hand, joint with the big volume that present these residues and the chemical and mineralogical characteristics, these materials or sub - products can be used for production of ceramics, into mixes forming some materials for architecture (bricks, blocks, and tiles), refractory bricks, in the production of cement and to get some metallic values such as gold and silver involved in these residues.IntroductionActually the mining residues in Hidalgo State, Mexico are the result of more tan 500 years of mining, leading so a great volume of deposits, which we can classify in different types, among the most communes we have: Acid Mining Waters, Waters of solid transport and elements in the form of radicals, deposits of abandoned minerals without processing, and mining wastes of processed minerals known as burrows or dumps, being these the most abundant in the Hidalgo State [1-4].Form the metallurgical point of view, it is known that a characterization study if fundamental to find the viability of reuse of these kind of residues, leading so an additional use and the opportunity of get an alternative use into several industrial processes, due to its contents of oxides of silicon, iron, aluminum, calcium, sodium and potassium, principally, besides of its mineralogy and distribution of chemical elements into its primary and secondary phases [ 1-2, 5- 6]."

Jan 1, 2011

By Manoj Kumar, Vinay Kumar, Nikhil Dhawan, Manish Wadhwa

"Electronic waste (e-waste) is a collective name given to discarded electronic devices such as Television, Cellular Phones and Personal Computers. Among the heterogeneous metals present in the e-waste are the base metals: copper, aluminium, nickel, tin, zinc, iron and precious metals: gold, silver, palladium, platinum apart from several hazardous and halogens metals. Hence there is a need to recover these metals from electronic scrap by recycling and then re-use, which can meet large amount of metals demand. Hydrometallurgical processing was employed for the recovery of metals from television printed circuit board (TV PCB). Different lixiviants such as hydrochloric acid, Sulphuric acid, and nitric acid were used to understand the dissolution behavior of copper, iron and lead present in the TV PCB. Effect of increasing concentration of nitric acid was also studied. Selective recovery of tin over 95% in the form of tin oxide was precipitated. The precipitated tin oxide was identified by X-ray diffraction technique. Tin oxide of purity more than 99.9% was obtained.IntroductionThe electrical and electronic industries comprising computers, television, mobiles, etc, which are manufactured utilizing printed circuit, boards, capacitors, resistance, soldering material etc. During production, at the end-of service life and degradation due to the advanced version with latest features generate valuable metallic and non-metallic constituents. European Union Council on waste electrical and electronic equipment (WEEE) has classified these into different categories as listed in Table 1 [Streicher-Porte et al., 2005]. Among these the information technology, telecommunications and consumer equipment constitute electronic waste (e-waste) [EC, 2002]. Almost all e-waste consists of an integrated part of printed circuit boards which is a valuable source of several metals such as copper, tin, lead, aluminium, iron, silver, gold, platinum etc. [Relay et al., 1990]."

Jan 1, 2008

By QinGuo, Shenghui Guo, Lei Li, Jinhui Peng, Linqing Dai, Libo Zhang

The ferrous removal process after carbothermic reduction of chromite fines with microwave heating combined with leaching was investigated. Under the following conditions: Reaction temperature: 1150 , Reaction time : 40min, Semi coke ratio: 12% , the iron content of the reduction product : 13.05% . Metallization achieved was 52.7%. Reduced chromite was leached with 8% of H2SO4 and FeCl3 aqueous solution. The results show that: the recovery rate of chromium can reach 88.06%, the mass ratio of chromium to iron is 3.5:1 for leaching 30 minutes with 8% of H2SO4; the recovery rate of chromium can reach 88.91%, the mass ratio of chromium and iron is 2.56:1 for leaching 4h at room temperature with FeCl3 aqueous solution (100g/L). The leaching time of latter is longer but can realize the circulation effectively and reduce the waste liquid processing problem.1

Jan 1, 2016

By Rodney Hundermark, July Ndlovu, Lloyd Nelson, Phillimon Mukumbe, Paul van Manen, Whitey Seyanund, Bart Pieterse, Bertus de Villiers, Diale Mokwena

The 2003 redoubling in power to 68MW on the Polokwane Smelter furnace represented a significant intensification in platinum group metal (PGM) smelting. Combined with onerous ‘green’ PGM concentrate smelting requirements, this yielded conditions unusually corrosive to copper coolers and refractories. This presented unexpected operational and design challenges to reliable crucible operation and maintenance. Combined with specific operational control intervention, development of protective coatings has led to the life of water-cooled copper components improving from 9 to 40 months. The furnace matte endwall was extended in 2010 to address accelerated wear of refractories and the potential risk for contact of copper components by superheated matte. An 18 month planned endwall rebuild cycle has been demonstrated (versus catastrophic failure within 9 months). Finally, benefits including lower energy consumption, improved metal recoveries and higher productivity resulting from operational and in-house design developments will be described, that justify “Celebrating the Mega-scale” in PGM smelting.

Jan 1, 2014

By J. Szekely, S. Rhee

"A mathematical formulation has been presented to describe heat and fluid flow phenomena in CVD operations. In the statement of the problem, which included consideration of plasma enhanced CVD systems, emphasis was placed on identifying the parameters which play a key role in determining the rate and the spatial uniformity of the deposition process. This was done both through the appropriate dimensionless groups and by presenting an extensive set of computed results. The main conclusions that may be drawn from this work are that the deposition rate will be inherently non-uniform for atmospheric CVD systems; this may be somewhat ameliorated by inclining the susceptor or changing the vessel contours. Operation at greatly redeced pressures and for PECVD systems will give a much more spatially uniform deposition rate.1. INTRODUCTIONIn recent years, there has been a growing interest in chemical vapor deposition techniques for the preparation of thin films for semiconductor, photovoltaic applications and for coatings in general, as evidenced by numerous journal articles and symposium proceedings devoted to this topic (1-6). An interesting variant of this technique is to perform the deposition in a plasma or glow discharge at low pressures because this technology obviates the need for the thermal decomposition of the precursor at the substrate surface and permits operation at greatly reduced temperatures (7-10).By far, the largest portion of the reported work dealing with both these aspects of the technology has been concerned with the characterization of the deposit, quite properly so. However, in more recent times it has been realized that the transport aspects of these processes are also deserving of attention because the understanding of heat flow, fluid flow and diffusional phenomena may provide the key to the solution of problems associated with obtaining uniform deposits and the proper scaling of laboratory measurements in order to design industrial CVD systems."

Jan 1, 1986

By G. H. Khoe

Neutralisation of acid uranium mill tailings with lime or other alkaline materials is usually practised to reduce the dissolved concentration of heavy metals and radio nuclides. Computer modelling of this process was carried out using the geochemical equilibrium code MINTEQA2. Computed dissolved metal and sulfate concentrations were compared with laboratory-based experimental data. It was found necessary to include the modelling of adsorption of trace metals (such as uranium and lead) by the precipitated ferric hydroxide in order to obtain acceptable concentrations in the neutralised liquors. There were limitations of the modelling exercise due to important aspects which were not addressed or properly accounted for such as chemical reaction kinetics and the effect of high ionic strength. These are discussed in the paper.

Jan 1, 1991

By Elias Rigopoulos

In the present study the reductive behavior of dust from the rotary kilns (RK), in ferronickel production from nickeliferous Greek laterites, is investigated. The study concerns dust of various origins (washing towers, electrostatic filters, polycyclones) and pellets made from the dust. Reducibility was studied in the temperature range of 700 °C to 850 °C in a laboratory tube furnace. Experimental results showed that reduction degree increases with temperature up to about 800 °C. The rate of reduction is great during the first minutes, giving a reduction degree R% equal to about 25%, in only a few minutes. After this, the rate is decreasing until it diminishes to zero after about 10-20 minutes of reaction. Maximum reduction degree achieved is 26 to 28%. Rates and reduction degrees at various temperatures are higher for the dust samples than those of the respective pellet samples. Keywords: Ferronickel, metallurgy, laterites, pellets, reduction

Jan 1, 2004

By Xuemei Zheng, Aiyuan Ma, Chao Liu, Guojiang Li, Chenyu Sun, Jinhui Peng, Libo Zhang, Yongguang Luo

In this paper, the removal of fluorides and chlorides from blast furnace dusts by water vapor enhanced microwave roasting was investigated, combined with the advantages of microwave selective heating and based on a thermodynamic analysis of zinc and lead halides. According to proposed reactions in the process, detailed experiments were systematically conducted to study the effect of roasting temperature, holding time, air flow, water vapor flow rates, and stirring speed on the efficiency of the removal of F and Cl. The results show that 97.26% of F and 64.23% of Cl could be separated when the condition of the roasting temperature of 650°C, stirring speed of 80 rpm, holding time at 60 min, air flow of 350 L/h and water vapor flow rate of 8 mL/min was optimized.

Jan 1, 2016

By John H. Schloen

Copper refineries are constantly looking for methods to upgrade their plants to reduce refining costs and to improve the purity of their electrolytic cathodes at the same time that the purity of the anodes they refine is being lowered by the rehabilitation of reverberatory furnace smelters to one of the direct smelting processes. The comments given below are based on the answers to the questionnaire returned bf the 36 copper refineries that represent 66% of the western world s refining capacity. Eleven refineries employ some form of uniform weight anade casting, e.g., Outokumpu, Contilanode, Mitsubishi, Lurgi, or Hazelett. This type of anode casting presents the best possibility for improving cathode purity. The cathode press of Phelps Dadge can improve current efficiencies and cathode quality. The press is used on first-run cathodes, after 48-60 hours, on half-cells at a time without interruption of the cell current. One refinery interrupts current for sever.al hours to allow the anode slime to settle before the, cathode pressing. The cathode press is now used at eight refineries. Apart from periodic reverse current (PRC), it is not expected that current densities will be increased. Thirty refineries, using direct current, average 231 amps/M, with a low of 178 and a high of 350. Five refineries use PRC at an average of 338 amps/M, with a low of 290 and a high of 380. Current efficiencies are good at an average of 94%, with a low of 88% and a high of 99% for the 34 refineries that reported. It must be remembered that the cycle efficiency with PRC is about 93%., so that the effective current efficiency with PRC would be only .94 X .93 or 87% However, PRC should be considered seriously for refinery expansions because it can save about 25% on capital costs.

Jan 1, 1987