IsaKidd refining technology
[1] Originally, the copper starter sheets were separated from the mother plate manually, but over time the process was automated.
[2][5] MIM Holdings began marketing the Isa Process technology in 1980, as a result of demand from other refinery operators.
Falconbridge subsequently independently developed a similar process to improve operations at its Kidd Creek copper refinery, near Timmins, Ontario.
The current efficiency of the refining process depends, in part, on how close the anodes and cathodes can be placed in the electrolytic cell.
Bumps and bends in either can lead to short-circuiting or otherwise affect the current distribution and also the quality of the cathode copper.
[3] Prior to the development of the Isa Process technology, the standard approach was to use a starter sheet of high-purity copper as the initial cathode.
Because of the manufacturing cost of the starter sheets, refineries using them tend to keep them in the cells as long as possible, usually 12–14 days.
[2] Wax was used rather than an edge strip to avoid having a ledge that would collect falling anode slimes and contaminate the cathode copper.
[2] The original cathode stripping machine was based on that used at the Hikoshima plant of the Mitsui Mining and Smelting Company of Japan.
[2] This shorter cycle time improves current efficiency as less short circuits occur and there is less nodulation of the cathode surface.
[1] However, following the success of early installations in Townsville, Timmins, and many other places, the permanent stainless steel cathode technology has had widespread introduction.
BHAS commissioned in 1985 a solvent extraction and electrowinning (“SX–EW”) to recover copper from copper–lead matte produced as a by-product of the lead smelting operations.
[19] The chloride in the leach solution at Port Pirie proved to be a problem for the stainless steel cathodes of the Isa Process.
Falconbridge Limited in mid-1981 commissioned a copper smelter and refinery near Timmins, Ontario, to treat concentrate from its Kidd Mine.
[7] Kidd cathode copper was not able to meet its customers’ specifications and obtaining product certification for the London Metal Exchange (“LME”) became a key focus.
[7] After several process improvements were instigated, it was ultimately realised that the use of copper starter sheets was preventing the Kidd refinery meeting its cathode quality targets.
[7] The company’s board of directors gave approval for the conversion of the refinery to the Kidd technology in April 1985.
[7] The conversion was completed in 1986[7] and the Kidd refinery became the third[8] to install permanent cathode and automated stripping technology.
[15] The Kidd Process technology did not use wax, as it was thought that it could exacerbate the impurity problems with which the plant had been struggling.
[22] A discontinuity in the structure is formed at the intersection that results in a weak zone, along which the copper splits during stripping.
[22] However, this cost is offset by greater reliability and predictability in the increase in resistance over time, allowing for maintenance planning.
[16] The solid-copper hanger bars, on the other hand, lose electrical performance over a shorter period of time due to corrosive attack on the joint and sudden failure is possible.
[16] The new cathode plate design was tested in the CRL refinery in Townsville and at Compania Minera Zaldivar in Chile.
LDX 2101 has superior mechanical strength to the 316L stainless steel, allowing thinner sheets to be used for the cathode plates.
[22] Xstrata Technology worked with a manufacturer to produce sheets that did meet the required flatness tolerance.
[13] The design of the plate features a stainless-steel jacket that surrounds a solid-copper hanger bar, protecting it from corrosion.
[13] A corrosion-resistant resin inside the stainless steel jacket protects the conductive interior weld between the header bar and the plate.
[13] The hanger bar is then finished with high-quality sealing to prevent ingress of electrolytes into the conductive interior weld.
This had been a problem area for the carousel stripping machines, in which copper released from the cathode plate fell into an envelope and was then transferred to a material handling device.
[15] Similarly, sticky copper deposits (generally related to poor surface condition on the cathode plate, such as corroded surfaces or improper mechanical treatment), heavily nodulated cathode and laminated copper caused problems for stripping.
