Professor Christina Cogdell
09 December 2014
Copper Pipe Production
Copper pipe is an essential product for our life. Main benefits copper pipe offers include variety of applications, high conductivity, and above all, its long life-cycle. Main raw material for the production of copper pipe is copper ores. For copper pipe, both copper scrap and newly refined copper, called cathode copper or cathode, are basically used. Other raw material used for copper tube is according to each area’s economic situation; limitation of money, access to sources, the technical capabilities. In copper pipe production, a very highly pure copper is required, so copper is one of the few common metals that are refined to almost 100% purity. Extraction of pure copper is the more important part of the production than fabrication of the semi product. In addition, copper pipe is such a recyclable product that it even can be used repeatedly as a “raw material.” Thus, it can be said that copper pipe is a useful product with long life cycle.
The copper pipe production begins with mining in which it is rare to discover natural pure copper. We often find copper ores which are often combined with other chemicals. Approximately, four fifths of all copper comes from sulfide ores in which the copper is chemically combined with sulfur. The rest of 20 percent is from oxide ores, carbonate ores, or other mixed ores. Copper mining takes place globally. According to the Copper Development Association, Inc. (n.d.), Chile is the largest producer of copper in the world, followed by America. Peru, Canada, the Ural Mountains in Russia, and parts of Africa also have the major mines. Copper is mined both in open pits and underground. The common mining to mine sulfide ores is drilling and blasting open-pit mines with explosives. First step is taking materials above the ore away to discover the ore deposit underneath which may result in a huge open pit, like even a mile or more. Inside of the pit, there is a spiral road to go down and use equipment. Huge dump trucks lift up the mined ore to out of the hole. After mining, sulfide copper ores undergo a certain process to make cathode copper.
In this essay, I focused on a processing method, called pyrometallurgy, which is utilized on sulfide ores to refine concentrated copper. This is not only because it is a common method, but also it has some benefit; the advantage of processing sulfide ores for copper is that fuel or carbon is not needed as a reduction agent during the smelting process, because instead, the sulfur contained in the ore provides the energy for smelting and fire refining. It even generates extra energy for either melting copper scrap or making heat or power for other processes. It can be said that processing sulfide ores by pyrometallurgical method is more efficient method than other types of ores. As for copper pipe which can be used for electrical applications, pretty high purity is needed, so almost all unwanted materials have to be physically or chemically taken away through couple of steps in which the purity of copper extremely goes up. Here are 4 steps of processing the sulfide ores and materials used.
In the first step, called “concentrating”, impurities, such as dirt, clay, and a variety of minerals included in the copper ore are first physically removed by using water and frother. A series of cone crushers break copper ore into small pieces. After water is poured into them, several types of mills are used to grin the mixture into even smaller pieces until it becomes about 0.25mm in diameter. A liquid chemical, called a frother for which pine oil is usually used, is added. What is pine oil? Pine oil is made from needles, twigs and cones of pines, particularly Pinus sylvestris that can be found in Europe and Asia, from Western Europe to eastern Siberia. Though it is usually used for aromatherapy, in an industrial process of metal extraction, called “froth floatation,” pine oil collects metal from ores. In this case, pine oil as a frother is used to soak all copper sulfide ores. This mixture is then located in tanks, called flotation cells with injection of air from the bottom. Bubbles produced from the frother works for concentrating process, and the water is drained off. The concentration of the mixture left is about 25-35%. The concentrate copper still have sulfides of copper and iron, smaller concentrations of gold, silver, and other materials.
After the physical process, a chemical process called “smelting” comes next to remove the iron and sulfur by using one or two furnaces with a silica flux, or quartz sand which is commonly in inland, continental settings and non-tropical coastal places. Materials which can be used for this process are limestone, silica, dolomite, borax, and fluorite. Most iron and other impurities chemically binds with the flux which keeps them separated from copper, and the sulfur with oxygen to form sulfur dioxide. The matte, the material left in the furnace, is a mixture of copper sulfides and iron sulfides. The concentration of the copper is about 60%.
In a “converting” process, lime and additional silica flux are added into a converter with oxygen blowing to undergo further chemical reaction with the metal oxide. In this step, scrap copper may also be used. The resulting molten material, known as "blister copper," contains approximately 99% copper. In spite of the relatively high purity, further refining is required. To remove remaining, like sulfur, oxygen, and other impurities, the blister copper has to undergo refining process.
Next step is “fire refining” in which air is blown through the copper to get rid of remaining sulfur, oxygen, and other impurities. The blister copper is heated in a refining furnace which is fueled by natural gas. The level of unwanted materials are checked by operators with using a sample of the refined copper. The concentrated copper, whose level of purity is about 99.5%, is then poured into molds for the electrorefining process to get more than 99.95% pure copper. The valuable byproducts, such as gold, silver, selenium, and tellurium would fall to the bottom in a pile. It is collected and processed to extract these metals.
All steps of processing are not necessarily conducted at the same place; some steps are finished at the mine site, while others may be done at different places. In this process, several other chemicals are added to process and refine copper. In addition to the sulfide ores, sulfuric acid, oxygen, lime, silica, and other materials are often used. In this process, several other chemicals are added to process and refine copper.
In the fabrication of copper pipe, using both cathode which is processed in the process above and a clean scrap, copper pipes are formed through several steps. No materials are added specially. In extrusion, casting, drawing process, raw materials are not added in copper, because as I mentioned above, the most important thing in copper product is its purity. Even for the process, energy material sources only used.
What is the most important thing in copper pipe production is that not only newly refined copper is used; large amount of copper scraps are used, too. Another reason that I chose to talk about pyrometallurgical process is that it is also processing of copper scraps. As for clean scrap copper, after melting in a furnace it undergoes reducing and casting while lower purity scrap requirse electrolytic refining with sulfuric acid. Copper, as either an unprocessed state or a product, is one of the highly recyclable materials keeping its quality. According to the research by Copper Institute Association Inc. (n.d), 80% of the copper ever mined is still reused today. Processing of secondary materials follows the same steps that I talked above to extract copper but requires fewer.
The copper pipe and sometimes other copper require high purifying process. Some materials are added in pyrometallugy to keep impurities away from copper. As for raw materials, copper production begins with sulfide ores which are mined globally. In concentrating process, pine oil as a frother is used to get the concentrate copper. Silica flux is used to cause chemical reaction with impurities within the ores. Converting process requires additional silica flux and limestone for further refined copper. Two steps of refining process allow the material to be purified to almost 100%. Fabrication of copper pipe only requires only thermal or physical processes, no raw materials. Those same steps are also used for processing of secondary copper product, and thus, copper pipe can be a product and a raw material at the same time.
Chris Cavette. How copper is made. N.d
Dr. Anton Klassert, Dr. Henrike Sievers, Dr. Ladji Tikana. Life Cycle Assessment of Copper Product. N.d.
Konrad J. A. Kundig, Ph.D. “How Do They Do That? Making Copper Plumbing Tube”
Sep.1998 Tube, Pipe & Fittings - Copper Development Association Copper Association Inc.
N.a. OPUS: Material: Copper. The Mechanical Contracting Education & Research
N.a. Copper. Wikipedia. 17 Oct 2014 .
N.a. Copper Processing. n.d.
N.a. Copper Tube Handbook - Copper Development Association. Copper Development
Association Inc. 2011
N.a. Copper Tubing Wikipedia. 28 Oct 2014.
N.a. Silica Flux - Minerals Education Coalition. Asarco. N.d.
N.a. “The Environmental Profile of Copper Products.” European Copper Institute.” N.d.
Professor Christina Cogdell
Design 40A Sec. 01
9 December 2014
The Embodied Energy and Efficiency of Copper Tubing
Copper is one of several metal type elements that has uses in many applications including tubing and piping. Copper was first discovered around 9000 B.C. somewhere in the Middle East (Stanczak). Since its discovery, the use and development of this metal has continued to grow around the world. Copper tubing was first brought to and used in the United States between the late 1920’s and early 1930’ and has been the primary source for most types of plumbing tubing and various other applications including AC units and HVAC systems. Copper tubing is popular because of its high efficiency properties. Copper is one of the best conductors of heat and electricity, it has a low erosion rate, a long life, and produces low amounts of CO2 emissions in its processing (Institute). The evidence found shows that copper tubing is energy efficient throughout its life cycle, which include the following: mining, fabrication and production, transportation and distribution, and recycling and waste products.
Before Copper tubing can be made, the mining process must first be performed, which uses around 20% of the total energy requirement in the production of copper ("Energy Use in the Copper Industry")(Energy Use 151). There are two common types of mining: open pit, which is used to extract copper ore when it is near the surface, and underground mining, which is used when copper ore is not near the surface (Inc.). Both techniques of mining include the use of various machines and equipment. Some of these include shovels, bulldozers, trucks, and drills. Each one of these tools uses energy in the form of human power and or gasoline and electricity. If we measure energy used in Btu’s (British thermal units) then open-pit mining uses on average 20 million Btu of energy per every ton of copper cathode produced in the form of drilling, blasting, loading, hauling, and ancillary (Energy Use 152). Most mined copper comes from multi-metal mines, such as silver and gold that are collected and then transported to refining factories. The copper mined will usually come in the form of cathodes or ingots, also known as primary copper. These natural copper ores have concentrations around .23% (Institute). The mining process of copper contributes to a large portion of the energy consumed in producing the final product of copper tubing. However, compared to earlier decades, current methods of mining use much less energy to recover the small amounts of metal. Some of these improvements include modern machinery and tools that use less electricity and diesel gasoline. Still, many argue whether it’s still worth the money and time to continue harvesting copper ore, as our primary source of copper is from scrap, which is also known as secondary copper production ("Copper Info")(Copper Info 2014). While a large portion of energy is used in its harvesting, the majority is still used in its production from copper ores and ingots into its final form of copper tubing.
After the mining process, the copper is transported to a fabrication mill where it will undergo several steps to achieve its final form as tubing. The second part of the production process uses a lot more energy than in mining because it has to undergo 7 different steps. The first step is melting and refining, and the initial process differs with what type of copper is being used. If it is primary copper, then it will go straight to melting, but if secondary copper is being used, then it needs to be refined before it can be melted. The extra step of secondary copper does use more energy because it requires a different type of furnace to be refined and melted, however it is much cheaper and more abundant than primary copper. First the copper is heated up to temperatures between 2300 and 2400 degrees Fahrenheit. The melted metal is then fire refined by adding oxygen. This addition causes the impurities to react with the oxygen forming oxides that float to the surface and are removed. The molten metal is then checked to ensure it has reached 99.9% +Cu or greater, and is finished by adding phosphorus to remove the added oxygen. The second step is casting. The molten copper is transferred to a holding furnace, which then is poured and cast into large molds called logs in either a continuous or semi-continuous method. With continuous casting, the metal is poured horizontally and water runs over to freeze it, while semi-continuous casting is poured vertically and the process has stop briefly after the length of the copper log reaches the bottom of the mold. In both methods, after the copper logs are poured, formed, and cooled, they are cut to size depending on the certain requirements. They are now called billets. The third step is piercing. The billets are reheated to 1535 degrees Fahrenheit. Next a pointed rod is driven through the center lengthwise to form the inside wall of the soon to be copper tube. The fourth step is extrusion. The billet is reheated once again and is placed in an extrusion press. A ram pushes the billet through a hole in a premade die creating a long, hollow tube with varying lengths, which is then cooled and cleaned to remove any overlapping. The fifth step is drawing. The tube is pulled through hardened steel dies to reduce its diameter both inside and on the outside. It is kept pointed at one end so as to fit and be pulled easily through each die, where afterwards the point is cut off. Tubes sold in straight lengths get passed through a series of straightening rollers, while tubes sold in coils are passed through curved patterned rollers. The sixth step is the annealing process. For tubes that will be sold in the soft condition, they get passed through an annealing furnace at 1300 degrees Fahrenheit. This tube has the same qualities as hard-drawn tube except for its appearance as it has a matte finish. The seventh and final step before the tube can be sent out for distribution is the cleaning and testing phase. The tubes are chemically cleaned and tested to make sure all requirements are met (Konrad J. A. Kundig "How Do They Do That? Making Copper Plumbing Tube"). Throughout the seven-step process an enormous amount of energy is used. The energy used comes from the fuels heating the furnaces, the electricity powering the factory including its machines, computers, generators, etc., and its gasoline costs for the transportation and distribution of the product (National Machinery Exchange).
Another large portion of energy use and costs account for all three uses of transportation: land, air, and sea. Most distribution is national, with the United States consisting of about six major manufactures, but there is some international distribution to certain areas. In total, a large amount of energy in the production of copper tubing comes from the fabrication and transportation of the product alone. With all of the energy use and costs coming from these two areas, knowing that copper demand will only increase from year-to-year, companies have had to find ways to reduce energy and costs (Glenn Barr). Therefore, recycling copper has become very popular.
After the production and distribution process, a manufacturer needs to start the process over again. With costs in production and transportation continuously increasing, there has been a need to find ways to lower these expenses. In more recent years, manufacturers are buying more secondary copper for processing because of how easy, safe, and affordable it is to use in making new copper tubing (Konrad J. A. Kundig "Innovations: Copper Water Tube: Good for Consumers, Good for the Environment"). Extracting copper from ore takes about 100GJ/ton, and recycling copper uses about 10GJ/ton, about 10% less energy saving a lot of money, energy, and harmful gas emissions. Most of the emissions come from the mining and refining processes, mainly in the form of waste gases such as sulphur dioxide, which is captured to make sulphuric acid, and CO2 from the vehicles and machinery (Science). Every part of copper that can be recycled is recycled and is reused to make the same high quality copper tubing, or other copper products, from which it originated. Copper materials that are recycled keep their original physical properties. Keeping these properties enabling one to create the same high quality copper products from scrap means no down-recycling or having to create cheaper products(Inc.). Choosing to recycle copper for the production process means that manufactures spend less money and use less energy in the mining process. Copper has a long life span if proper maintenance is performed resulting in high efficiency and be cost-effective. Having copper tubing in your house can save you a lot of money in energy bills due to its thermal properties, and will last a very long time because of its low erosion properties (Michael A. McNeil). Due to its long life and recyclable properties, it also greatly reduces the amount of objects that would otherwise be put into landfills. This helps promote the green initiative and shows a push towards renewable energy in the form of recycling.
The evidence presented in this paper has shown that copper tubing is most efficient in its final form. This metal tubing has a long life cycle in which it is efficient in its erosion durability and thermal abilities. It is able to retain all properties even after it has been scraped and reproduced as new copper tubing. Copper tubing plays a large part in the renewable energy sector. While the mining and production process do use a substantial amount of energy, overall it proves to be energy efficient once the copper tube is completed and used in its various applications.
1. "Copper Info." HowStuffWorks. Web2014.
2. "Energy Use in the Copper Industry." Vol. Prnceton University: Princeton Review. 151-58. Web.
3. Glenn Barr, Jennifer Defreyne, David Jones, Robert Mean, CESL. "On-Site Processing Vs. Sale of Copper Concentrates." (2005): 1-15. Web.
4. Inc., Copper Development Association. "Copper - from Beginning to End." Copper Developement Association Inc. 2014. Web2014.
5. Institute, Europian Copper. "The Environmental Profile of Copper Products." (2012): 1-8. Web. December 2014.
6. Institute, Europian Copper. "Life Cycle: Life Cycle Assessment for Coper Products." (2014): Web. December 2014
7. Konrad J. A. Kundig, Ph.D. "How Do They Do That? Making Copper Plumbing Tube." Copper Develpoement Association Inc. 1998. Web2014.
8. "Innovations: Copper Water Tube: Good for Consumers, Good for the Environment." Copper Development Association Inc. 1998. Web2014.
9. Michael A. McNeil, Nicholas Bojda, Jing Ke, Stephane de la Rue du Can, Virginie E. Letschert and James E. McMahon. Business Case for Energy Efficiency in Support of Climate Change Mitigation, Economic and Societal Benefits in the United States: Ernest Orlando Lawrence Berkeley National Laboratory, 2011. Print.
10. National Machinery Exchange, INC. "Copper Tube & Tubing Production & Processing Plant." Web2014.
11. Science, School. "Copper Recycling and Sustainability: Benefits of Recycling." Web2014.
12. Stanczak, Marianne. "A Brief History of Copper." CSA 2005. Web2014.
Wastes and Emissions
December 9, 2014
Wastes and Emissions of the Copper Pipe Life Cycle
Although copper mining is considered to be one of the less harmful types of metal mining, the wastes and emissions from copper mining and production still have a great effect on the environment in terms of water pollution, air pollution, and the creation of waste byproducts. The overall impacts of copper mining and production include groundwater contamination from underground mines, disposal of waste, dust from mines, mill, and tailings, waste from tailings, sulfur dioxide emissions from the smelting process, and slimes created by the refining process (Environmental Aspects).
Both the mining and processing of copper ore create huge quantities of “liquid and solid waste” (Environmental Aspects 173). The EPA estimates that “between 1910 and 1981, all types of metallic ore mining and beneficiation in the US generated a total amount of waste of more than 40 billion tonnes” (Environmental Aspects 173). The production of copper is responsible for “roughly half” of that sum (Environmental Aspects 173). One of the main effects of mining is the “large-scale land disturbances” that have the ability to alter the “natural flow” of surface and ground waters. This may cause the lowering of the water table surrounding the copper mines. During the mining process, sulfides that are normally underground are exposed to water and air, which creates a reaction that produces sulfuric acid and iron (Environmental Aspects 174).
When mining occurs, “metals of concern” such as arsenic, cadmium, and lead are released from the Earth and in to the atmosphere (Environmental Aspects 174). These metals are toxic to humans and animals, and can build up in the environment and enter the food chain if they are exposed during the mining process (Environmental Aspects 174). Additionally, the “removal and fracturing of rock and soil” during the mining process contributes to dust and “fine solids” that can then be moved by wind or water (Environmental Aspects 174).
Tailings, a byproduct of the mining process, are different from the waste created directly by mining and leaching due to the fact that they are “very fine and retain a certain amount of water after disposal” (Environmental Aspects 177). “Continuous seepage from groundwater infiltration” is the main way that tailings can be transported throughout the environment (Environmental Aspects 177). This seepage can “flush sulfates, dissolved liquids, trace metals and organics in to ground water” (Environmental Aspects 177). The ponds that are used to hold tailings also tend to release metals such as copper, gold, silver, and zinc in addition to arsenic, cadmium and lead (Environmental Aspects 177).
Hydrometallury and Pyrometallurgy are the two main processes used to obtain copper in its purest form. Specifically, hydrometallurgy is less often used in the copper production process, although it is still an option for copper processing. Hydrometallurgy is defined as the “extraction of metal from ore by preparing an aqueous solution of a salt of the metal and recovering the metal from that solution” (“Hydrometallurgy”).
Leaching is also known as the “dissolution of the metal or metal compound in water” (Encyclopedia Brittanica). Unlike smelting, neither leaching nor solvent extraction produce sulfur dioxide gas. However, leaching and solvent extraction both pose a threat to water quality and must have their waste disposal regulated (Environmental Aspects 167). The byproducts left over from the leaching process have the potential to “release acidic effluents, toxic metals, and total dissolved solids” in to nearby areas (Environmental Aspects 177).
ii. Solvent Extraction
Solvent extraction is a process in which the “weak cuprous solution is mixed with an organic liquid” (Klassert 39). The organic liquid then becomes concentrated with the copper. These liquids then get “separated, by density separation in a settler unit’ (Klassert 39). This liquid is then “mixed with a strongly acidic solution…and copper is re-extracted due to pH-dependency into the electrolyte, which is then used in electro winning” (Klassert 39). After the copper is extracted from this solution, the leftover solution, called “raffinate,” contains all of the leftover elements. This raffinate is “recycled back in to leach dumps,” which can cause water pollution due to the addition of “uranium, radium, and radon” to the water streams (Copper Mining and Production Wastes).
iii. Electro Winning
The purpose of the electro winning process is to make the copper cathodes completely pure. In the electro winning process, an electrolyte is “pumped through a series of tanks or ‘cells’” (“Electrowinning”). These tanks are filled with “lead plates, alternating with sheets of thin copper…” and these copper sheets act as the “anode pole of an electric circuit” (“Electrowinning”). An electrical current runs through these sheets and causes the copper ions to “attach” to the “starter sheet.” This process takes about a week and at the end of it, “100-300 pound copper cathodes…99.999 percent pure” (“Electrowinning”).
Pyrometallurgy is the “extraction and purification of metals” through the use of heat. Heating the metal results in the transformation of sulfur ores into oxides, as the sulfur escapes as sulfur dioxide gas (“Pyrometallurgy”). Each step of the pyrometallurgic process creates waste and emissions.
Smelting is the main process in pyrometallurgy. It is done in order to “reduce iron ores (“Pyrometallurgy”). Smelting processes produce large amounts of “particulate matter, trace elements and sulfur oxides.” The sulfur dioxide emissions in particular are known to be connected to “visibility degradation and acid deposition” (Environmental Aspects 162). A device in the smelting process called the “reverberatory furnace” occurs during the “charging of calcine or green concentrate.” These emissions escape through small openings in the body of the furnace (Environmental Aspects 164). Another process that takes place during the smelting process is the gas cleaning process. The gases created by the smelting process go through a five-step process. This process creates wastes and emissions such as dust and sludge (Environmental Aspects 165).
ii. Fire Refining
In the process of fire refining, copper is put in the furnace and “air is blown through the molten mixture to remove residual sulfur” (“Copper Smelting” 291). This copper is then “cast into anodes” in order to go on to the next step of processing (“Copper Smelting” 291).
iii. Electrolyte Refining
The electrolyte refining process produces waste products known as “slimes.” These slimes are “rich in selenium, tellurium, arsenic, gold, silver, and platinum” (Environmental Aspects 178). Sediments created by electrolyte refining often “settle from a combined slurry composed of effluents from spent electrolyte as well as contact cooling of furnaces, spent anode and cathode rinse water, plant washdown and wet air pollution control” (Environmental Aspects 178).
V. Product Fabrication
i. Melting and Alloying
This process begins with the “melting of copper cathodes in a shaft furnace” (Friedrich 255). After the copper is initially melted, the product is “casted directly or subjected to a casting furnace” where it is kept and “heated to casting temperature” (Friedrich 255). In this process, copper is oxidized by air “through oxygen injection or top blowing” (Friedrich 256). Byproducts and wastes that are produced by this process are dissolved material byproducts and gases. These gases can be removed by “inter gas purging.” Zinc and arsenic are also waste elements created during the melting process (Friedrich 256).
ii. Continuous Casting
In the process of continuous casting, “metal is poured in to cylindrical graphite molds.” These molds are then cooled with water so that the copper freezes quickly. This forms a “solid log of pure copper” (Kundig).
iii. Extrusion/Continuous Extrusion
Copper extrusion is a process in which copper billets are put in “the chamber of an extrusion press.” For copper pipes, these billets will have a hole in them, which will then be widened, in order to create a hollow tube. Copper oxide is a waste product of this process and is typically “recycled to the refining furnace” (Kundig).
The drawing process takes the now-hollow copper tube through several machines that cause the tube’s diameter to be reduced, as well as the tube’s wall thickness (Kundig).
VI. Mould Casting
Both the melting process and the moulding process create “fugitive emissions of metal oxide fumes.” This occurs when the “molten metal” is poured in to the molds. Dusts are also created by “charcoal or other lining” that is typically used in copper molds (Background Report 7).
VII. Assumptions and Failures
While researching this process, it was very difficult to find evidence of wastes or emissions for the electrowinning process. It was suggested in several articles that spent electrolytes are recycled back in to different parts of the copper production process, so perhaps the impacts of the wastes or emissions of this step are considered to be insignificant.
N.a. “Background Report – Secondary Copper Smelting, Refining and Alloying.” U.S. Environmental Protection Agency. PDF file. http://www.epa.gov/ttnchie1/ap42/ch12/bgdocs/b12s09.pdf
“Copper Mining and Production Wastes.” Radiation Protection. U.S. Environmental Protection Agency, August 30, 2012. Web. October 28, 2014.
N.a. “Copper Smelting.” Pollution Prevention and Abatement Handbook: World Bank Group. July, 1998. Web. December 8, 2014. http://www.ifc.org/wps/wcm/connect/45bb400048865823b456f66a6515bb18/copper_PPAH.pdf?MOD=AJPERES
“Electrowinning.” Freeport-McMoran. N.d. Web. December 8, 2014. http://www.fcx.com/resources/fmi/electro.html
N.a. “Environmental Aspects of Copper Production.” Princeton.edu. PDF File. https://www.princeton.edu/~ota/disk2/1988/8808/880810.PDF
Friedrich, Bernd; Krautlein, Christoph. “Melt Treatment of Copper and Aluminium – The Complex Step Before Casting.” Association of Metallurgical Engineers of Serbia. PDF File. http://www.metalurgija.org.rs/mjom/vol12/No%204/2BERND.pdf
“Hydrometallurgy.” Encyclopedia Britannica. June 18, 2013. Web. December 8, 2014. http://www.britannica.com/EBchecked/topic/484985/pyrometallurgy
Klassert, Anton; Sievers, Henrike; Tikana, Ladji. “Life Cycle Assessment of Copper Products.” Deutsches Kupferinstitut – Life Cycle Centre. n.d. http://eplca.jrc.ec.europa.eu/ELCD3/resource/external_docs/255/ECI_LCA_of_Copper_Products_Report_5140044a-4bec-11dc-8314-0800200c9a66.pdf
Kundig, J.A. Konrad, Ph.D. “How Do They Do That? Making Copper Plumbing Tube” Sep. 1998 Tube, Pipe & Fittings - Copper Development Association
Copper Association Inc.
“Pyrometallurgy.” Encyclopedia Britannica. June 18, 2013. Web. December 8, 2014. http://www.britannica.com/EBchecked/topic/484985/pyrometallurgy