A Changing Environment: Reflections on 50 Years of Hydrometallurgy
by
Emeritus Professor John Monhemius
Royal School of Mines
Imperial College London
ABSTRACT
Looking back over the past half century, it can be seen that the growth in the importance of hydrometallurgy for the production of non-ferrous and precious metals almost exactly parallels the rise of the environmental movement and its principal NGOs, such as Greenpeace and Friends of the Earth. The paper will review important landmarks in the development of the science and technology of hydrometallurgy and show how many of these have been influenced by pressures on the industry brought about by environmentalists. Successful innovations as well as commercial failures will be considered and lessons drawn to guide future developments.
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2014 is a landmark year for me, because it is the 50th anniversary of the start of my career in hydrometallurgy, which began in September 1964 when I arrived at the University of British Columbia to start an MSc degree in Metallurgical Engineering. Following a six day crossing of the Atlantic by ship from Southampton to Montreal, where I was astounded to learn I was less than half way to Vancouver, and then an eight hour flight over endless Canadian forests, I finally arrived at UBC’s beautiful campus overlooking the Strait of Georgia. I had chosen to study at UBC because at that time it was the leading university in North America and probably the world for teaching and research in hydrometallurgy. The main attraction was Professor Frank Forward, who was a world expert in pressure hydrometallurgy and who had been one of the main driving forces behind the development of Sherritt Gordon’s revolutionary pressure leaching and hydrogen reduction process for nickel sulphide ores. Forward was ably assisted at UBC by two lieuetenants, Ernie Peters and Ian Warren, who both went on to make their own successful careers in academic hydrometallurgy, although Ian Warren’s was cut short by his untimely early death. The current heir to this great tradition is of course our conference chairman, David Dreisinger, who is very successfully continuing to ensure that UBC remains to this day a world-class centre for teaching and research in hydrometallurgy.
One of the major driving forces for the changes in technology that have taken place in the mineral industry over the past half century has been “the environment”. The period in question, i.e. the last 5 decades, coincides almost exactly with the birth and growth of today’s worldwide environmental movement, and the NGOs with which we are all now very familiar – names such as Greenpeace, FoE, Sierra Club, etc.
As a matter of fact, while I was a student at UBC in the mid-60s, there was a fierce local controversy about a proposed copper mine on Vancouver Island. The copper ore body was situated on the edge of a deep fjiord at the north end of the island and the mining company proposed to dispose of the tailings in the bottom of the fjiord. There was much local opposition to this proposal, as people were very concerned about pollution and its effects on the Pacific salmon, which spawn in the fjiord. The opposition was strong enough to persuade the Provincial government to set up the first ever public enquiry into a mining project held in British Columbia, at which all the issues, particularly the environmental issues, were thoroughly examined.
One of the main opponents of this project was a PhD student at UBC, named Patrick Moore (no relation to the late TV astronomer), who argued the scientific case against the Island project at the public enquiry. Following this experience, Patrick Moore went on to be a founder member of Greenpeace and to become its first executive director. Thus it appears that the mineral industry was inadvertently responsible for the birth of the environmental protest movement. Another first for the industry!
In spite of the opposition, the Island Copper mine was eventually built and it operated successfully for 25 years, under a strict environmental monitoring regime, which showed that there was no significant detrimental impact on the ecology of the fjiord. The mine eventually ran out of ore and it was closed down about 16 years ago in a very innovative and unique manner, which involved blasting a channel through to the fiord and filling the mine with sea water.
Figure 1 The Island Copper Mine, Vancouver Island, BC.
Thus the mineral industry has been under the scrutiny of the environmental activists for at least 50 years and the pressures brought to bear by these well- organized groups has had profound effects on the development of technology in the industry. Back in the 1960s, in the early days of the environmental movement, nobody was worried about CO2 and global warming. Instead it was SO2 and acid rain that was making the headlines in those days. Dying forests and acidified lakes in countries like Canada and Scandinavia were blamed on the large quantities of SO2 that were pouring into the atmosphere from the industries of the USA and Western Europe.
One of the most easily identified sources of SO2 pollution were the metallurgical plants where sulphide minerals were smelted to produce metals such as copper, lead and zinc. In these processes, the sulphur was oxidized to form SO2 gas, which in many smelters in those days was disposed of directly into the atmosphere through tall chimnies.
The responses of the smelting companies to the political and regulatory pressures brought upon them varied around the world. Some bit the bullet and made the large capital investments necessary to install acid plants to convert the SO2 to sulphuric acid. The fortunate smelters, who were sited close to industrial areas, were able to sell their sulphuric acid to the chemical industry and thus to make some sort of return on their investments. More remotely sited smelters, however, had essentially to give away their acid, or even pay to have it transported away from their sites.
Other companies had more half-hearted responses and exhibited a type of corporate denial. One of the most notorious of these was INCO in Canada. INCO’s nickel smelting activities in the Sudbury district in Ontario since the early years of the 20th century had been largely responsible for the devastation of the ecology over a radius of many miles around the town of Sudbury. The company’s grudging response to pressures brought upon it to improve its environmental performance was to build one of the world’s highest smoke stacks, the INCO Super Stack, which rose some 400 metres above the town. This was an extreme example of the “dilute and disperse” solution to environmental pollution. In other words, the philosophy was to “spread it thinly over a large area in the hope that nobody notices”.
Figure 2. The INCO Super Stack, Sudbury, Ontario.
Other responses by the smelting industry to the Clean Air Acts introduced in various countries ranged from the extremes of shutting down old-fashioned smelters, to completely rebuilding them using modern, clean, smelting technologies. Both of these responses occurred in the United States. Many of the old US copper smelters are now consigned to history, but on the other hand, one of the most modern copper smelter in the world was built 1995 by Rio Tinto on the shores of the Great Salt Lake in Utah on the site of the old Garfield smelter, which smelted ore from the near-by, massive Bingham Canyon mine. When it opened, the new smelter was claimed to be the cleanest in the world, capturing at least 99.9% of the sulphur that enters in the feed. Such environmental performance, however, does not come cheaply – the smelter cost Rio Tinto close to one billion dollars nearly 20 years ago.
Figure 3. Rio Tinto’s Utah Smelter
Another response of the copper industry to the environmental pressures brought upon its smelters was to consider radically different technologies for the production of its copper. The Holy Grail was a technology that did not involve the production of SO2 gas as a co-product with the copper. This objective can be achieved in two ways:- (i) use copper oxide minerals instead of copper sulphide minerals, or (ii) turn the sulphur into water soluble sulphate instead of gaseous SO2. Both of these routes involve the use of hydrometallurgy instead of the traditional pyrometallurgical smelting process and I want briefly to look at each of these options in turn.
Prior to the 1960s, copper oxide minerals were spurned as ore minerals basically because they are not suitable for smelting, as they lack the sulphur content that acts as the fuel to generate the high temperatures needed for the smelting process. However, it is precisely the lack of sulphur that makes these minerals attractive from an environmental point of view. If there is no sulphur in the mineral, there is no sulphur disposal problem when they are processed. What was missing at that time was an enabling technology, which would allow these minerals to be economically processed for their copper content.
The key to this conundrum was solvent extraction, a process that had been born in the midst of the second world war, in the race to produce nuclear grade uranium for the atomic bomb project. For twenty years after the war, solvent extraction remained exclusively in the hands of the nuclear industry, where it was used in the production of a range of exotic metals that were needed for the construction of nuclear reactors. When I was an undergraduate, the conventional wisdom was that solvent extraction was a process that could only be contemplated for high value metals and it was not economically possible to use it for common base metals like copper. Happily, not everybody believed this conventional wisdom and there were certain individuals who were prepared to “think out of the box”, to use a modern cliché.
One of these individuals was a young and wealthy American called Maxie Anderson. Maxie was an entrepreneur out of the Richard Branson mold, a risk-taker, whose passion was ballooning. In fact, Maxie is best known for being the first person to cross the Atlantic Ocean in a balloon. He undertook this epic journey, together with two other American companions, in 1978 and later he and his team were awarded a Congressional Medal of Honour by the US Congress to mark their achievement. Tragically only a few years later, Maxie was killed in a ballooning accident in the Alps in 1983, when he was aged only 49.
Figure 4. Maxie Anderson’s Memorial Plaque
Before these ballooning adventures, Maxie Anderson had already played a key role in a development that has transformed the copper industry over the last half century. In the 1960s, Maxie owned a small copper mine in Arizona, called the Bluebird Mine. This became the site of the first application of solvent extraction outside the nuclear industry. For this to happen, however, required other individuals to also be working against conventional wisdom. One of these individuals important to this story was another American from the deep South, a Texan called Joe House. I never had the opportunity to meet Maxie Anderson, but I met Joe House on many occasions – he was a delightful character, full of American charm and with a wry sense of humour.
Joe worked for General Mills, the American food giant, in a division of the company that supplied solvent extraction reagents to the nuclear industry. (The reason for this apparently strange combination was that the organic chemicals from which the solvent extraction reagents were made were themselves by-products from the processing of certain foodstuffs). Joe realized, ahead of anybody else, that there was a good market opportunity in the copper industry for a solvent extraction reagent that was selective for copper, and so he set the research chemists at General Mills the task of designing a reagent which could extract copper from a solution while leaving behind any other metals dissolved in that solution.
After a number of false starts, the General Mills chemists came up with a reagent that would do exactly what Joe wanted and it was given the code name LIX 64N. L/I/X stood for Liquid/Ion /Exchange and 64 for the year in which it was invented – 1964. The reason for the “N” is not so obvious – perhaps it was the Nth compound that they had tried!
Joe House’s big problem was now to get his new invention tested. The metallurgical industry is notorious for its desire to be second to install new processes. This is where Maxie Anderson came into the story: he owned a copper mine, he was young and wealthy, and he enjoyed a challenge. Not having shareholders and a board of directors to worry about, Maxie was willing to put up his own money to fund the very risky step of introducing a radically different technology into an industry where the basic methods of making copper had not changed significantly since the Bronze Age. This technology, which is now known the world over as SX-EW (Solvent Extraction-Electrowinning) was installed in Maxie’s Bluebird Mine in Miami, Arizona and the new plant began operations in 1968, in the heady days of flower power, student protests and the anti-Vietnam war movement.
This plant was quite small, not much more than a large pilot plant, producing about 6000T of copper per year, less than a month’s production from a conventional, medium-sized copper smelter. However its influence on the copper industry has been profound. From those small beginnings has grown a technology that now accounts for about one fifth of primary copper production world-wide and this proportion continues to increase steadily.
Figure 5. Bluebird Mine, Miami, Arizona.
Only six years after the start-up of the Bluebird plant, two very large SX-EW copper plants were opened, one in Zambia on the Copper Belt and the other in Arizona, not very far from the Bluebird mine. The Zambian plant at Nchanga was the biggest in the world when it began operations in 1974 and it remains the biggest, even today, with a rated capacity of 120,000 T/a of copper metal, although it is many years since it produced at that capacity. Both these large plants were designed in the UK by Davy-Power Gas in Stockton-on-Tees. The Anamax plant was half the capacity of the Zambian plant, although the equipment, particularly the mixer-settlers, was the same size in both plants. The difference was that the Zambian plant had twice as many mixer-settlers as the American plant.