PERFORMANCE CHARACTERISTICS OF THE EMEW® CELL
P.A. Treasure
Electrometals Technologies Ltd, 28 Commercial Drive, Ashmore,
Queensland, Australia
婷婷玉立
ABSTRACT
Electrometals Technologies Limited has brought from concept to
commercial availability a new electrowinning technology, which
overcomes many of the process and cost limitations that plague
conventional EW plants. Progress in its development over the period
between 1996 and 2002 has been characterid by continual improvements性价比最好的手机
in engineering of the technology, growing acceptance of its capabilities,
and an expanding ba of installed facilities in a variety of process
ttings. Extensive work has been carried out on application of the
patented EMEW® cell to electrowinning of a number of metals in a
variety of mining and industrial ttings. Established usages for the
technology range from extraction of low grade metals from mine and
industrial waste solutions, through treatment of metal refinery bleed
streams, to primary metal production at large mining operations. The
technology is patented in most countries around the world, and has been
commercially implemented at a number of locations. Key operating
characteristics of the cell are discusd.
INTRODUCTION
The high performance of the EMEW® cell technology is achieved through a hydraulic mechanism which achieves higher rates of metal ion transport to a cathode than in a conventional electrowinning reactor. The esntial difference is that the EMEW® cell is constructed from a pair of concentric tubular, rather than planar, electrodes. The ends of the asmbly are fitted with plastic end caps, thus forming a clod chamber through which target solution can be pumped at high rate. The resulting high flow and efficient mixing result in ‘forced’ and continual supply of metal ions to the surface of the cathode. The cell is capable of producing metal powder or plate and, in the former ca, harvesting is carried out on a fully automated basis.
Since the introduction of the EMEW cell to the industry a number of years ago, there have been significant advances in both the cell engineering and its application. Its usage now covers a wide range of metals - including copper, silver, gold, tin, nickel, cobalt, lead and zinc. The metals are electro-won from a wide range of solution chemistries, including acid and alkaline, either directly or in conjunction with solvent extraction (SX) or ion exchange (IX) systems.
The EMEW® cell achieves marked improvement in cell hydrodynamics in a very simple and cost effective manner. Across most applications that have been examined and tested, capital and operating costs are lower than in an equivalent conventional tankhou.
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Table 1: Tested EMEW® Technology Applications
SECTOR APPLICATION Primary Metals Direct electrowinning of Cu from dump and heap leach projects
Direct electrowinning of Au and Ag from mine leach solutions
Direct electrowinning of Co from leach solutions
Production of Ni cathode and powder from leach solutions
High current density electrowinning of Zn from mine leach solns.
Acid Mine
Drainage Removal of Cu from acid mine drainage streams
Recovery/stripping of Ni from tailings ponds
Metal Refineries Leaching and electrowinning of Cu from refinery tank hou sludges
Production of high grade Ni from Cu refinery waste materials
Ag electrorefining过敏性荨麻疹的症状和治疗
Recovery of Cd from primary Zn and refinery waste solutions
Recovery of Cu and precious metals from Au refinery waste streams
Treatment of Cu electrorefinery bleed streams
Recovery of Cu from zinc refinery waste
Hydrometallurgy Purification of primary Ni leach solutions. through direct EW of Cu
Purification of primary Co leach solutions through direct EW of Cu
High current electrowinning of Cu from SX-EW tank hou bleeds
Purification of primary Zn leach solutions through direct EW of Cu
Recovery of residual metals from various plant waste streams Industrial waste Removal of Cu from general industrial waste streams
Treatment of photographic waste solutions
Recovery of Cu from computer chip manufacturing etchant solutions
Recovery of Ni from electroplating waste solutions
Treatment of platinum catalysts
Recovery of Sn from various industrial waste solutions
Leaching and electrowinning of Zn from industrial waste materials
Table 2: Commercially Applied EMEW® Applications
牛奶中毒1 Direct electrowinning of cathode copper from dump and heap leach projects
2 Leaching and electrowinning of copper from copper refinery tank hou sludges
3 Recovery of copper from pickling solution - copper parts manufacturers
4 Recovery of copper from pickling solutions - copper rod and wire manufacturers
5 Replacement of cementation of copper from waste streams
6 Removal of copper from general industrial waste streams
7 Production of nickel from copper refinery waste materials and solutions
8 Recovery of nickel from industrial waste solutions
Furthermore, improvement in operating efficiency and the versatility of the technology has expanded the breadth of applications over which electrowinning (EW) in general can be contemplated.
Some of the specific advantages that the EMEW® technology displays include: •It is extremely simple to operate and has no moving parts.
•The cell is modular and portable, facilitating relocation and expansion.
•Cell cost is lower than for a conventional unit.
•The technology’s capability of processing low grade streams is well proven. •Its efficiency permits significantly higher current density than conventional units. •The technology operates over an extremely wide range of metal concentration. •The cell is more tolerant of contaminants in solution (e.g. iron and chlorides) •Without major change to the hardware, capable of extracting a variety of m
etals. •It is capable of lective electrowinning of metals from complex solutions. •The clod nature of the cell prevents acid mist in the plant.
•It allows complete control of the gaous products from electrowinning.
•The cell can be ud to produce a metal powder or plate.
Electrolyte is pumped through the cell from the
bottom.
Power is
Applied
(-)
Figure 1 – Schematic EMEW Plaitng Cell
The technology has been tested in numerous process ttings over the past ten years. Many of the
此外的近义词applications examined have been in areas where conventional electrowinning is considered to be either impossible or not viable. As well as demonstrating higher efficiencies in applications where electrowinning is conventionally applied, the EMEW® technology has therefore opened up the window of applications over which the basic process can be applied. Although the design and concept of the EMEW® cell has been generally standardid there are a number of engineering and process modifications that can be made to suit particular usage. Different chemistries and operating necessities may dictate differing requirements with respect to overall size of the cells, electrode materials, distance between the electrodes and flow regime that is ud.
Table 1 details process ttings in which the EMEW® technology has been comprehensively tested over the years, while Table 2 prents details on where the EMEW® technology has been implemented commercially on a number of the applications.
The following paper prents operating performance and general cost data from four applications for EMEW® which have yet to be commercially implemented – but are being considered on the basis of recent pilot work.
COPPER SX-EW TANK HOUSE BLEED STREAMS Approximately 25% of world copper production i
s generated directly at mine sites through the process of heap leaching of oxide copper ores, followed by solvent extraction (SX) and electrowinning (EW) of a high quality cathode. As in refineries, all copper electrowinning tank hous need to continuously bleed a proportion of the tankhou solution inventory, in order to prevent excess build up of contaminants transferred from the primary leach solution. The contaminants of particular importance in copper SX-EW are iron (which can lead to reduced production rate) and chlorides (which can lead to degradation of the electrodes in the tankhou). The higher the concentration of the contaminants in the leach solution, the higher the volume of bleed stream necessary to maintain the required low levels. The bleed stream in established operations is generally ‘dispod of’ in one of two ways. It is added to the primary feed to the SX circuit – where copper is recovered again and nt round again to the tankhou, or the stream is taken directly back to the leach circuit – and cycles back through an even longer path.
Comprehensive piloting, carried out recently at a large operation in South America, has tested the u of the EMEW® technology for direct recovery of in excess of 90% of the contained copper. The targets of the programme were to asss the level to which current density could be pushed, whilst still maintaining high efficiency, and at asssing the quality of the copper produced – all through a b
road range in copper concentration. The overall aim of the programme was the establishment of an alternative treatment route for the bleed streams. The test programme, which comprid 22 individual runs, provided clear confirmation that the EMEW® technology is capable of application at significantly higher current densities than applied in conventional tanks. The result is a substantial increa in production rate per square meter of cathode, when compared with a conventional tank hou. Also, the operating windows under which the technology maintains high current efficiency and product quality are extremely broad – with one of its demonstrated features being the capability to electrowin metals efficiently down to very low concentrations.
The solution tested was a relatively typical SX-EW tankhou bleed, with the following composition: Cu, 36 – 42 g/l; H2SO4, 175 - 210 g/l, HNO3, 4 – 60 ppm; Cl, 13 – 36 ppm; Co, 120 – 250 ppm; Al, 40 – 60 ppm; Fe, 1 – 1.2 g/l; Fe2+, 10 – 160 ppm; Mn, 3 - 10 ppm. Figure 1 shows current efficiency measurements through the ries of test runs, against copper concentration at varying current density. Product from all of the test runs was a den cathode, easily harvested from the cells. Competency of the cathode was maintained down to below 1 g/l copper, and contamination by a few elements (primarily O and S) only became apparent when copper in solution was stripped to below 2 g/l.
Figure 2. Current Efficiency vs. Copper Concentration The recorded average contaminant levels in the cathode, from electrowinning down to below 10 g/l Cu, are prented in Table 3 and are compared with the site’s normal tankhou limits for certain elements.
Table 3. Bleed Electrolyte Cathode Purity
Fe Ni Element Ag As Bi C Cd
Max (ppm) 12 2 1 5
五花肉
Avg
(ppm) 0.2 0.2 0.1 44.4 0.1 2.8 0.2
Te
Zn
Sn
Pb S Sb
Element O
Max (ppm) 100 3 9 1 1
(ppm) 69.5 0.4 4.5 0.1 0.4 0.3 0.4
Avg
As would be expected, there is a slight power consumption penalty in electrowinning at higher than n
ormal current density. There is, however, a capacity in the EMEW® cell to tailor the electrode gap to the application being developed. Cathode morphology in all of the tests at this site was good, therefore allowing potential for narrowing the electrode gap in the cell and thereby lowering voltage.
离职表模板The DC power consumption recorded at varying current densities during this pilot programme were 3.04, 2.58, and 2.44 kWh/kg of copper at current densities of 900, 600, and 500 A/m2, respectively.
The data collected from tests with two different cell models (6 inch and 8 inch diameter) indicate that a power cost saving of up to 15% can be achieved, through narrowing the electrode gap in the cell by 10 mm.
The bleed electrolyte programme was performed using 6 inch diameter EMEW® plating cells, with an active cathode area of approximately 0.5 m2. This model of the cell has been widely accepted in small to medium sized projects, as the resulting cathodes (25 kg) are easily handled by site labour. In a larger operation it is more likely that a larger EMEW® unit would be ud (8 inch diameter, with 1 m2 cathode area). The equivalent
