|By: Richard Mowat||POSTED: 06/14/12 10:56 PM
FILED AS: Magnesium
COMMENTS FEED: RSS 2.0;
Magnesium Production With Gossan’s Zuliani Process
With the acquisition of a large, high purity dolomite deposit and a breakthrough high efficiency magnesium production process, Gossan Resources Ltd. is poised to begin producing magnesium in Manitoba on a commercial scale. The company has the rights to the proprietary Zuliani process and proposes to couple the new technology with hydroelectric energy sources for cheaper, more efficient, and greener production of magnesium metal.
What Is Magnesium?
Magnesium is an alkaline earth metal that is critical to life on Earth. It is the fourth most abundant element in the Earth’s composition and accounts for 13% of the planet’s total mass. Magnesiumions are highly water-soluble, and magnesium is the fifth most common element in seawater. Only oxygen, hydrogen, chlorine and sodium account for higher percentages. A tremendous amount of magnesium is locked away in the Earth’s mantle, however, and it is only the eighth most abundant element in the planet’s crust.
Magnesiumis the eleventh most abundant element in the human body and plays essential roles in biochemistry. Hundreds of human enzymes are based on magnesium complexes. Without this crucial element, intracellular energy transfer could not occur through the ATP cycle, nor could the replication of DNA occur. Magnesiumis a cofactor for human DNA polymerases.
Humans obtain biologically available magnesium by drinking water or other liquids that contain dissolved magnesium, by eating red meats, and by consuming green vegetables. Just as iron is the metallic ion around which the hemoglobin complex in red blood is constructed, magnesium is the metallic ion around which green chlorophyll complexes are formed in plants. This is why magnesium salts are important components of mineral fertilizers.
What Are The Commercial Uses For Magnesium?
In addition to biological needs and agricultural usage, magnesium is also an important industrial chemical. It can be used as a substitute for aluminum in most applications. The principal limitation is production cost. Magnesium is currently 20% more expensive than aluminum to produce, and import tariffs on Chinese-produced magnesium increase costs in the U.S. to nearly double the costs of aluminum production.
According to the 2012 Mineral Commodity Summaries, which is published by the United States Geological Survey, use in aluminum alloys accounts for 43% of all magnesium consumption. Aluminum-based magnesium alloys are widely used in the packaging and transportation industries. The addition of small amounts of magnesium to aluminum imparts strength, lightness, corrosion resistance, and resistance to sparking.
Marine aluminum alloys contain up to 5.5% of magnesium. Aerospace applications, where high strength and resistance to corrosion are critical requirements, use aluminum alloys that contain up to 3.5% magnesium .
Aluminum beverage containers are generally constructed of an aluminum alloy with 1.1% magnesium in the body of the can and 4.5% magnesium in the stronger lid. The beverage container industry uses a relatively small amount of magnesium in aluminum alloys, but the production volume of aluminum cans is such that beverage containers account for the largest commercial use of magnesium.
Die Cast And Wrought Structural Metals
Structural uses of magnesium through castings and wrought products account for 40% of primary metal consumption. Magnesium alloys are light, strong, weld easily, have excellent impact resistance, and are resistant to corrosion. There are many structural magnesium alloys in use today. The most common formulations contain 9% or less aluminum, 2% or less zinc, and small amounts of manganese. Alloys with aluminum in the higher percentages are used in die castings. Lower aluminum content alloys are used to produce magnesium extrusions, magnesium forgings, sheet magnesium, plate magnesium, and other wrought forms.
Die cast magnesium alloys are the fastest growing structural market for magnesium alloys. The materials are widely used in the automotive industry to produce wheels, cylinder head covers, valve covers, clutch and transmission housings, and steering columns. Outside of the automotive industry, die cast magnesium alloys are commonly used where light weight and strength are crucial concerns. They are used to produce lawnmower decks, chainsaw housings, bicycle frames, metal baseball bats and fishing reels.
Low-density magnesium alloys are critically important for sand cast aerospace applications. Specially formulated alloys containing small amounts of zirconium, yttrium, silver and rare earths are cast into high-temperature components that operate at temperatures of up to 575 degrees Fahrenheit. These components are found in engine frames, air intake manifolds, canopy frames, speed brakes, and helicopter gear boxes.
Wrought magnesium alloy products include hand trucks, loading ramps, nuclear fuel containment vessels, and even baking racks. Because they are easy to machine and exhibit high dimensional stability, magnesium alloy plate products are widely used for the construction of cutting jigs.
Magnesium alloys are also processed by thixomolding. Thixomolding injects semisolid alloy material into a heated mold to produce thin components in complex shapes.
Iron And Steel Processing
The USGS reports that desulfurization of iron and steel currently accounts for 11% of U.S. magnesium consumption. Sulfur is soluble in liquid iron in any concentration, but the solubility in solid iron is limited to about 0.01%. When liquid steel solidifies, an iron-iron sulfide eutectic is formed along the iron grain boundaries. The eutectic weakens the bonding between the iron grains and causes brittleness in the steel at temperatures where the metal is normally rolled and forged.
Iron typically contains 0.025 to 0.050% sulfur when it is received from blast furnaces. The sulfur must be reduced to levels of 0.002% or lower for the production of high-quality structural steels, and one of the most advanced hot metal desulfurization methods relies on magnesium reagent.
Powdered or granulated magnesium compounds are injected into the ladle of liquid steel where they react with sulfur to form the ladle slag top. The slag is removed from the top of the ladle and leaves behind sulfur-free liquid steel. Other compounds can also be used for desulfurization, but the magnesium reagent is fast, efficient, and results in higher yields.
In addition to desulfurization, ferrosilicon magnesium additives are also used to produce ductile iron and spheroidal graphite iron. The graphite impurities within iron usually nucleate as flakes. When magnesium is present, the graphite nucleates as spherical particles and gives the finished iron much greater ductility. Ductile iron is commonly used to produce pipe.
Other Industrial Uses
Magnesium anodes are used to suppress galvanic corrosion in steel storage tanks and underground pipelines. Magnesium is used as a reducing agent in the production of uranium, in Grignard alkylations of aldehydes and ketones, and in military dry cell batteries. Magnesium powders are widely used in pyrotechnics displays, and wrought magnesium alloys are used to create the printing plates used in photoengraving.
The History Of Magnesium
Magnesium is a highly reactive element, and pure magnesium is not known to occur naturally. It was first produced as an elemental metal in 1831 when the French chemist Antoine Alexandre Brutus Bussy heated dehydrated magnesium chloride and elemental potassium in a glass tube. The reaction produced potassium chloride and small accumulations of elemental magnesium.
Magnesium was first produced commercially in Germany in 1886. Commercial production in other countries did not occur until 30 years later when military demand led to magnesium production in the United States, Canada, Great Britain, France, and Russia. The magnesium was required for the production of flares and tracer bullets.
Germany’s production continued to increase in support of that country’s military expansion leading up to World War II, and by 1938 Germany was producing 60% of the world’s commercial magnesium supply. Global production at this point was only about 34,000 tons per year.
Military usage increased global magnesium needs dramatically. Germany constructed a 10,000 ton per year facility in Norway in 1940, but the plant operated for only a few years before it was destroyed by Allied bombs. Facilities were constructed in France at Jarrie and St. Auban that had a capacity of 3,000 tons per year, but the facilities were under-utilized during the German occupation of that country and produced only about 400 tons per year.
Japan operated multiple magnesium production facilities during World War II. Midway through the war, Japan had nine facilities in operation. Six of the facilities were located in Japan, two were in Korea, and one was located in Taiwan. By the end of the war in 1945, Japan had 16 plants producing magnesium to meet military needs. The magnesium was used in aluminum alloys for the production of Zero fighter planes and for various incendiary requirements. The Japanese facilities all used magnesite and brines as starting materials.
To support the U.S. war effort, the United States undertook a huge expansion in magnesium production between 1940 and 1943. Fifteen magnesium production facilities were constructed during that time period. Dow Chemicals doubled the size of a production facility in Michigan in 1940 and began construction of a facility in Texas in that same year. The Michigan plant used brine as a magnesium chloride source, and the Texas facility used seawater. The remaining 13 magnesium production facilities were built by the U.S. government. Eight facilities extracted magnesium through electrolytic processes, six used silicothermic thermal reduction processes, and one facility used a carbothermic thermal reduction process. By the end of 1943, the U.S. had the capacity for more than 290,000 tons of magnesium production.
Military demand for magnesium dropped after World War II, and worldwide magnesium production declined in favor of cheaper aluminum production. The United States continued to meet 45% of the world’s magnesium demands until the late 1990s. In 1995, China accounted for only 4 to 7% of global magnesium production, but by 2005 it had captured 60% of the global market share. By 2010, the United States Geological Survey estimated Chinese production to be 654,000 tons per year, approximately 85% of all global production, while U.S. production had dropped to approximately 7% of global demand.
In 2011, U.S. magnesium production was limited to a single facility in Utah. That plant uses Great Salt Lake brines as feed for an electrolytic process.
Commercial Production Techniques
Geologically, more than 80 minerals have a composition of 20% magnesium or greater. Of these minerals, only brucite, bishofite, carnalite, dolomite, magnesite, and olivine are used as raw material for magnesium production. Brines, fly ash, and asbestos tailings are also sources of commercial production.
Dolomite and magnesite are the most commonly used raw materials for magnesium production. Magnesite is the naturally occurring mineral composed of magnesium carbonate, and dolomite is a naturally occurring mineral composed of calcium magnesium carbonate. Magnesite contains more magnesium than dolomite, but large deposits of magnesite are geographically restricted. Dolomite deposits are widely available, and it is the mineral used in the largest commercial magnesium extraction process.
Because magnesium-bearing minerals are so common, commercial extraction has occurred in many locations through a wide variety of production methods. Two production processes, the electrolysis of molten magnesium chloride and the thermal reduction of magnesium oxide, have become the most widely used commercial production methods. The raw material reserves for either process are so plentiful that they are considered to be inexhaustible.
Production Through Electrolytic Extraction
The electrolytic method accounts for the majority of global magnesium production. The magnesium chloride used in this process is obtained from ocean water, from brines that are rich in magnesium chloride, from the residual bitterns that result from commercial potash production, and from dolomite and magnesium oxide ores. magnesium production in Israel occurs exclusively through the electrolysis of salt water through Dead Sea Magnesium Ltd. That company is a joint venture between Israel Chemicals Ltd. and Volkswagen AG. U.S. Magnesium, the only company currently producing magnesium in the United States, uses the electrolysis process on brines from the Great Salt Lake in Utah.
When magnesium is produced from salt brines, the material must first be dried to produce anhydrous magnesium chloride. The magnesium is then extracted from the molten salt through an electrolytic process.
When magnesium is produced from dolomite or magnesite, the minerals are first crushed, roasted, and mixed with seawater. Magnesium hydroxide settles to the bottom of this mixture. It is collected, mixed with a solid carbon source used to melt and reduce metal ores, and then reacted with chlorine. This reaction produces molten magnesium chloride that is then electrolyzed to produce elemental magnesium. The magnesium floats to the surface of the melt and is collected.
Production Through Thermal Reduction
Thermal reduction uses dolomite, brucite, or magnesite as the magnesium furnace feedstock. Of these minerals, dolomite is the most widely available material. Thermal reduction is very inefficient, very labor-intensive, and requires approximately 35-40 megawatts per ton of magnesium produced. It is, however, the magnesium production process used by China, the world’s top magnesium supplier.
There are multiple variations of the thermal reduction process for magnesium production, but only three have seen any commercial success. They are the Pidgeon process, the Bolzano process, and the Magnetherm process. All three techniques react calcined dolomite with ferrosilicon reductant in a vacuum furnace. They primarily differ only in the means of supplying heat to the reaction.
- The Pidgeon Process
The thermal reduction of dolomite was first developed in Italy in 1938. Two years later, Dr. Lloyd Montgomery Pidgeon, a Canadian chemist, refined the technique by introducing ferrosilicon into close-ended, nickel-chromium-steel alloy vacuum retorts. The silicon acts as a reducing agent at high temperatures. The process is now known as the Pidgeon silicothermic reduction process or, in many cases, the Pidgeon process. The Canadian company Dominion Magnesium was the first facility in the world to use this process in 1941.
The Pidgeon process is the oldest, simplest, least energy-efficient, and most labor-intensive production technique. It has remained unchanged since the 1940s and requires the lowest initial capital investment of any thermal reduction production process for magnesium. It has become dominant in world magnesium production simply because it is the method used by China. China has coal-rich provinces and cheap labor, so energy efficiency is not a consideration, and that country relies almost exclusively on the Pidgeon process. China is currently the world’s largest supplier of elemental magnesium.
In the Pidgeon process, mixtures of finely powdered calcined dolomite and ferrosilicon are briquetted and charged into sealed 11-inch nickel-chromium-steel alloy vacuum retorts. The dolomite is calcined to remove water and carbon dioxide. These materials would both be gaseous at reaction temperatures and would otherwise continuously cause a back-reaction with magnesium vapor.
The retorts are inserted horizontally into a furnace for external heating of the reaction zone. In China, the furnace is usually coal-fired. The vessels are heated over a period of 11 hours, and magnesium vapors are continuously removed through a water-cooled condenser with removable baffles. This process is essentially a distillation of magnesium metal, and it produces high purity magnesium crowns. The magnesium crowns are manually removed to be melted again and cast into ingots while the retorts are charged for another production batch. Each ton of magnesium production requires approximately 11 tons of raw materials. Access to a large dolomite deposit is a requirement for this process.
The Pidgeon process is a thermodynamically unfavorable reaction and only proceeds when heat is continuously supplied and magnesium vapor is continuously removed. The boiling point of magnesium metal at atmospheric pressure is 1,994 degrees Fahrenheit. Conducting the reaction in vacuum retorts allows the use of lower temperatures, but the reaction still requires a great deal of energy. The energy efficiency for the Chinese process is only about 12%. It would not be economically feasible without China’s large supply of cheap coal. The environmental impact of the Pidgeon process and its effect on global warming, especially when carried out on the scale realized by China, is significant.
The Bolzano Process
In the Bolzano process, dolomite-ferrosilicon briquettes are stacked into the retorts and heated by internal electric heating. The reaction time is longer than the Pidgeon process at 20 to 24 hours.
The use of internal heating in the retorts allows the use of larger reaction vessels and the production of larger batches than the Pidgeon process. The Bolzano process is used in Italy and Brazil.
The Magnetherm Process
The dicalcium silicate slag formed in both the Pidgeon and Bolzano processes has a melting point of approximately 3,600 degrees Fahrenheit and is a solid at production temperatures in both processes. The Magnetherm process, which was developed by Pechiney Electrometallurgie in 1963, reduces the melting point of the slag to less than 2,900 degrees Fahrenheit through the addition of aluminum oxide to the initial charge. The slag is maintained in a liquid state through resistive heating with a water-cooled copper electrode. As magnesium vapor is collected in a condenser system, molten slag and ferrosilicon are periodically removed.
World Market Issues
In 2005, the United States imposed antidumping tariffs on Chinese and Russian magnesium alloy imports. Magnesium die casters subsequently complained that production volumes were being reduced by these tariffs. In 2010, after a five-year review period, the U.S. International Trade Commission voted to retain antidumping duties on Chinese imports and to revoke the tariffs on magnesium alloy imported from Russia.
In March of 2010, the Commission gave public notice of the results of the five-year review. U.S. Magnesium, which is the only magnesium producer in the United States, and the United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union, Local 8319, appealed the Commission’s decision. The labor union represents the workers at the magnesium facility. The appeal argued that the potential effects of relaxing antidumping duties should have been evaluated as a whole and not assessed for individual countries.
U.S. Magnesium also appealed an EPA decision to classify the company’s production facility in Rowley, Utah as a superfund site. That appeal was denied in January of 2011. The decision gives the EPA the authority to conduct additional site inspections and impose clean-up requirements on the company.
A New Production Process And New Market Opportunities
Gossan Resources Ltd. is currently investigating commercialization of a refinement to the Magnetherm process that has been proposed by Dr. Douglas J. Zuliani. The process is highly efficient and operates at a cost 25 to 30% lower than Chinese production costs using the Pidgeon process.
Although the specifics of the Zuliani process are proprietary and have not been released, it has been demonstrated to operate at atmospheric pressures and to provide calcined dolomite and silicon yield efficiencies of greater than 92%. Use of this technology would result in a 20% reduction in the required charges of calcined dolomite and a 30% reduction in the required charges of ferrosilicon when compared to Chinese Pidgeon plant operations.
The process further proposes the use of hydroelectric energy to heat production batches. More efficient use of raw materials with a greener, sustainable energy source would substantially lower the overall environmental impact of magnesium production. The resulting reduction in greenhouse gas emissions makes the Zuliani process extremely attractive to investors as cap-and-trade legislation looms over all North American manufacturing facilities.
In addition to world-wide rights to the high efficiency Zuliani process, Gossan Resources also owns a very large deposit of high purity dolomite and a large silica sand deposit that could serve as a source of ferrosilicon.
Gossan Resources intends to produce magnesium metal in Manitoba, Canada from the large dolomite deposit using this new process.