NOAH N COPPER ASSIGNMENT Final Vers

 

The Reduction of Environmental Impacts caused by Copper Extraction:

From the Case of the Ashio Mining Pollution

How has the copper refining process been improved so that the environment is better protected in the last century as well as into the future and what alternatives or solutions have emerged?

Noah Nishihara Home Group E05

 

Key Concept to Investigate: Scientific knowledge, understanding, and inquiry can enable scientists to develop solutions, make discoveries, design action for sustainability, evaluate economic, social, cultural, and environmental impacts, offer valid explanations, and make reliable predictions.

 

 

 

 

 

 

 

 

 

 

 

Table of Contents

 

Table of Contents. 2

Introduction. 3

The Conventional Process of Producing Copper. 4

The Case of the Ashio Mining Pollution in Reducing Sulphur Dioxide Emissions. 8

Solutions to the Problem.. 8

Improvements in Production of Copper. 9

Other Improvements. 10

Bibliography. 11

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Introduction

Copper has been used since the Sumerians of Mesopotamia created tools, sculptures and sleds 6,000 years ago (CDA Inc. 2017b). Copper supported the transition from Stone Age to metal agesand the Industrial Revolution. The demand is currently increasing due to our relianceupon electricity (OTA 1988, p.iii). However, all stages of production can devastate environments(Massachusetts Institute of Technology 2016). While the leaching of solid waste is harmful, the degree of the problem varies.Besides, the waste and tailings are reclaimed (OTA 1988, p.175-177).

Environmental Impacts of Copper Production

 

Figure 1

U.S.  Congress, Office of Technology Assessment 1988 p.161

In Figure 1 there are many other pollutants besides toxic gases and waste, however, the primary focus is on sulphide ores, which account for 80% of all sourced ore, and how the sulphur dioxide producedfrom iscaptured during pyrometallurgical processes instead of dispersing into the atmosphere.The extracted ores contain only 2 to 3 percent copper and mustbe processedpyrometallurgically (Asian Metal Inc.).

Figure 2: Escondida in Chile is the biggest copper producer in the world (CDA Inc. 2017).

The Conventional Process of Producing Copper

Pyrometallurgical recovery of copper is known for itselevated temperature reactions in roasting, smelting, converting and (fire) refining (OTA 1988, p.133).Firstly, ores with concentrations varying from copper, metallic pyrites, and gangue are mined. It is sent to a crushing plant (CDA Inc. 2017a).The pulverisedore is then ground;this stage is referred to as comminution which creates a large surface area.It is further concentrated through froth floatation (beneficiation)in which copper rises to the surface with air bubbles as a froth. This happens because water and hydrophobic-causingchemicals are mixed with the ore particles and air is blown through the solution. Gangue stays below.

Figure 3: Concentration of copper ore by froth flotation; University of York 2013.

The resultingconcentrate is then roasted in a furnace with oxygen to increase purity (CDA Inc. 1997a, 2017a).

(CDA Inc. 2017a,2017b).

The two equations in brackets are contaminants in the ore; here they also become oxides and are removed. According to CDA Inc. (2017a)roasting removes some sulphur and produces ‘calcine’, a solid shown as Oxidation of metal sulphides provides heat (OTA 1988, p.756). Temperature differences can result in varying products. Equation A and B are examples of the reaction giving copper monosulfide.

This thenundergoes smelting; producing copper matte . Smelting heats calcine with fluxes to remove the iron oxide. Thisleaves the‘matte’ or copper and iron sulphides (CDA Inc. 2017a). Lower density slag covers pure mattewhile sulphur dioxide is collected.CDA Inc. (1997)reports ‘the heated dry gas produced through smelting and converting is cooled, cleaned, dried, and treated with a catalytic converter in an acid plant to produce sulphur trioxide.’ This is shown: occurring at above 435 degrees. Adding water to it produces sulphuric acid. Also, for safety, water may be substituted with sulfuric acid to form oleum, whereupon water is added to regenerate sulfuric acid (Burrows, A et al. 2013).

In the Peirce-Smithconverter, moltenmatte is blown with air through tuyeres so that the iron sulphide oxidizes into iron oxide and SO₂ is captured. Iron oxide then reacts with the added flux of mainly silica.

The two equations focus upon the formation of slag (CDA Inc. 2017a).

The resulting fayalite slag is poured out and reused as a flux for smelting (OTA 1988, p.756). New matte is addedto repeat the process untilenough copper sulphidehas accumulated. It then becomes blister copper after oxygen is blown in, sulphur is oxidised, and copper is reduced.Copper (I) sulphidebecomesblister copper and sulphur dioxide in this way:

Blister refers to the effect of dissolved gases on solidified copper and its purity is 95 to 98%(CDA Inc. 2017a).

The ‘fire-refining’stage produces purer anode copper by introducing gases as a reducing agent that removes oxygen from blister copper.The copper mayrequire casting.

Then a lengthy electrolysis reaction produces 99.99% pure copper:

The blister copper is eluted from the anode as ions and electrodeposited on the cathode as copper. The cathode copper contains lessthan 0.004% impurities (OTA 1988, p.105). The electrolyte is copper sulphateand sulfuric acid with additives. Impurities accumulate in the electrolyte or sludge.The usage of electricity is lowerthan electrowinningfor oxide ores (Sako Y. 2006).

Copper is melted and casted for distribution (OTA 1988, p.145).

Flow diagram summarising the sulphide ore processing stages

Figure 5: A flow diagram summarising the processes used to manufacture copper from its ore; University of York 2013.

Figure 4 (CDA Inc. 2017).

The Case of the Ashio Mining Pollution in Reducing Sulphur Dioxide Emissions

Ashio is well-known as the first pollution case in Japan. Causes of the Ashio mine pollution includeleaching of waste material. With greater awareness, wastes are no longer disposed of incorrectly. However, the gas emissions created the greatest damage. Records show that trees were cut for the operation and newly grown saplings were unable to develop properly. Finally, a bushfire created bare patches of groundrock which then directly infiltrated the river. The ecosystem of the WataraseRiverwas destroyed(商兆琦 2013). Current sulfuric acid production methods were impossible to implement due to low SO₂ concentration and lack of proper cleaning and collection systems(酒匂幸男(Sako Y.) 2011).

Solutions to the Problem

Local politician Shozo Tanaka took the matter even to the emperor, and managed to force some solutions. This set an example for future Japanese social action and contributed attention to the issue, however, when the government allowed the installation of tall chimneys and a system based on the use oflimewater ( ) trickling down in it, the ‘mist’ failed to neutralise pollutants(酒匂幸男(Sako Y.) 2011).

An effective solution came as late as1956, when flash furnaces raised gas concentrations by eliminating excessive air from mixing into the reaction.American acid production technology was implemented with the newer flash furnaces, thus restricting pollution(酒匂幸男(Sako Y.) 2011). However, different processes resulted in varied emission concentrations(小峰新平2011). Outokumpu furnaces were chosen for its superiority over electric furnaces, ability to solve the SO₂ problem, and because reverberatory furnaces were in disrepair after the war. Trials began in 1956, and use ended in 1989. The current widespread use of flash furnaces and SO₂ capturing technology is mainly due to a century of pollution reduction research completed in Ashio (酒匂幸男(Sako Y.) 2011). Businessmen place profit over environment; scientists develop efficient solutions to suit.

Citizens of Ashiohope to enlist the area as heritage, while visitors are still finding slow recovery of the ecosystem a concern. 

 

Improvements in Production of Copper

Figure 4: The manufacture of copper using the ISASMELT process; University of York 2013.

The widely used reverberatory furnace emits dilute sulphur dioxide gas which is unconvertible to sulphuric acid. Its replacement with efficient flash furnaces that utilise the heat produced from oxidation has been slow. This is disappointing, as development of the Flash Smelting process has reduced the pollution arising from copper extraction (OTA 1988, p.107). Anotherprocess known as ‘continuous converting’ combines roasting, smelting, and converting but this has limitations.Electric furnaces have low gas emission but high energy consumption and low adoption rates (小峰新平2011).

The newest process is ISASMELT. This involves the mixing and pressing into pellets of copper concentrates, fluxes, and fuel which is then put into the furnace with oil, oxygen, and methane. Matte is quickly produced in an efficient reaction (University of York 2013). ISASMELT furnaces are slim, energy efficient, and captures sulphur dioxide well.

(Alvearet al. 2010).

The process involves oxidation of the slag (FeO) and regenerative reactions involving magnetite, concentrate and fluxes to form copper matte, slag and concentrated sulphur dioxide gas.

ISASMELT furnaces smelt and Rotary Holding Furnaces then separate matte and slag. Furthermore, a third furnace (converter) is required. With concentrated copper, ‘direct’ smelting or ISACONVERT® TSL where roasting or converting is combined with smelting may be used (CSIRO 2015).Copper is concentrated before processing for sustainability and lower costs. Thus, pyrometallurgical processes are flexible.

This furnace would not have seen widespread use without the contributions made by Mount Isa Mines Ltd and CSIRO. ISASMELT technologybegan taking shape in the 1970s, with the invention of a lance tip protected with a slag coating (part of SiroSmelt) by Dr John Floyd and others to improve a tin-smelting process. The Mount Isa Smelter site demonstrated practical use in 1987, and in 1989, MIM and CSIRO agreed to incorporate SiroSmelt components within ISASMELT technology. Licensing began in 1990 and reduction in energy use was observed in each project. Over ten plants are in use.However, bath smelters require durable lances; it isinadequatefor replacing flash smelters (CSIRO 2015).

Other Improvements

Modern techniques substantially reduce the degree of devastation caused on the surroundings of a copper mine. New processing facilities are unlikely, so improvements in smelting and adoption of efficient processes is necessary. This involves developing hydrometallurgy to extract copper from sulphide ores (Liew F. 2008). While the process only works with oxide ores or wastes, its efficiency rivals others (OTA 1988, p.141). Biohydrometallurgy is another field but involves bacterial oxidation (University of York 2013).Due to a limitation of resources, raw copper production is expected to falter within this century. One third of the demand is currently covered with recycled copper (CDA Inc. 2017a).  It follows that scrap copper recycling is expected to increase as mining production decreases.

Figure 5 Recycling & the Future of Mining 2012, The Business of Mining

Conclusion

Copper extraction from sulphide ores has been improved to reduce the emission of sulphur dioxide. While collection of gas has been a swift solution, extraction processes vary and several types introduce other issues. Effects suffered in Ashio led to more smelters becoming less environmentally destructive. Further research into impacts of copper recyclingare planned for future studies.

Word count: 1194

(From 1578 total minus 212 words of in-text references and 172 words for captions/equations)

 

 

 

 

 

 

 

 

Bibliography

Books

Burrows, A, Parsons, A, Pilling, G, Price, G & Holman, J 2013, Chemistry³: introducing inorganic, organic and physical chemistry, Oxford University Press, Oxford and New York

Websites

1.      Asian Metal Inc. n.d., 铜的冶炼及分类Copper smelting and classification accessed 15 April 2017, <http://baike.asianmetal.cn/metal/cu/extraction.shtml>.

2.      Commonwealth Scientific and Industrial Research Organisation, 2015-2017, SiroSmelt, accessed 9 May 2017, <https://csiropedia.csiro.au/sirosmelt/>.

3.      Copper Development Association Inc. 1997a, How Copper is Made, accessed 18 April 2017, <https://www.copper.org/publications/newsletters/innovations/1997/11/howdo3.html>.

4.      Copper Development Association Inc. 1997b, Wringing Sulfuric Acid out of Sulfur Dioxide Emissions, accessed 18 April 2017, <https://www.copper.org/publications/newsletters/innovations/1997/11/howdo4.html>.

 

5.      Copper Development Association, 2017a, Copper Mining and Extraction: Sulfide Ores, accessed 12 April 2017, <http://copperalliance.org.uk/education-and-careers/education-resources/copper-mining-and-extraction-sulfide-ores>.

6.      Copper Development Association Inc. 2017b, The Sumerians and Chaldeans, accessed 18 April 2017, <https://www.copper.org/education/history/60centuries/ancient/thesumerians.html>.

7.      Dudgeon S, 2009, Copper Mining: From the Ground Up, accessed 7 April 2017, <http://faculty.virginia.edu/metals/cases/dudgeon3.html>.

8.      Gerardo R. F. Alvear F., Arthur P. &Partington P. 2010, Feasibility to Profitability with Copper ISASMELT™ accessed 18 April 2017, <http://www.isasmelt.com/EN/Publications/Technical%20Papers/Alvear.pdf>.

9.      Liew F. 2008, Pyrometallurgy Versus Hydrometallurgy, accessed 4 April 2017, <http://tes-amm.com.au/downloads/TES-AMM_analysis_pyrometallurgy_vs_hydrometallurgy_April_2008.pdf>.

10.  Massachusetts Institute of Technology 2016, Environmental Damage,accessed 4 April 2017, <http://web.mit.edu/12.000/www/m2016/finalwebsite/problems/environment.html>.

11.  Sako Y. 2006, Development of Copper Smelting and Refining Technologyaccessed 15 April 2017, <http://sts.kahaku.go.jp/diversity/document/system/pdf/020.pdf>.

12.  University of York 2013, Copper., accessed 12 April 2017, <http://www.essentialchemicalindustry.org/metals/copper.html>.

13.  U.S.  Congress, Office of Technology Assessment 1988, Copper: Technology and  Competitiveness,  U.S.  Government Printing Office, Washington,  DC<https://www.princeton.edu/~ota/disk2/1988/8808/880808.PDF>.

14.  商兆琦 2013, 足尾鉱毒事件をめぐる明治知識人 ,新潟大学, accessed 5 April 2017, <http://dspace.lib.niigata-u.ac.jp/dspace/bitstream/10191/21630/1/20_151-175.pdf>.

15.  環境政策-足尾鉱毒事件と明治時代の鉱害-足尾、別子、日立鉱山の比較、公害反対運動の神様・田中正造2014 , accessed 5 April 2017, <http://env.ssociety.net/20140423_3.pdf>.

16.  足尾鉱毒事件と渡良瀬川 ,東日本建設業保証, accessed 5 April 2017, <http://www.ejcs.co.jp/library/kenkyukai/85_kouen.pdf>. p.4

17.  第ー章足尾銅山鉱毒事件一公害の原点一(n.d), accessed 5 April 2017,<http://d-arch.ide.go.jp/je_archive/pdf/book/unu_jpe5_d02.pdf>. p. 23

18.  小峰新平2011,足尾銅山での銅製錬の変遷と排ガス処理の歴史,accessed 5 April 2017, <http://www.nikko-ashio.jp/images/ashio/report3.pdf>.

19.  酒匂幸男(Sako Y.) 2011, 足尾における自溶炉製錬技術の先駆性及び国内外に与えた影accessed 15 April 2017, <http://www.nikko-ashio.jp/images/ashio/ashio_report1_3.pdf>. p.22

Images

1.    Copper Development Association, 2017, Copper Mining and Extraction: Sulfide Ores (Escondida in Chile is the biggest copper producer in the world), accessed 12 April 2017, <http://copperalliance.org.uk/images/librariesprovider5/education-images/escondida-mine-(bhp-billiton).jpg?sfvrsn=3>.

2.      Copper Development Association, 2017, Copper Mining and Extraction: Sulfide Ores (flow diagram summarises the sulfide ore processing stages), accessed 12 April 2017, <http://copperalliance.org.uk/images/librariesprovider5/education-images/sulfide-ore-treatment-1-560x356.jpg?sfvrsn=0>.

3.      Masato Fukuoka 2016, 選鉱／製錬とは, Various Diagrams, accessed 12 April 2017, <http://home.hiroshima-u.ac.jp/mfukuok/er/Rmin_SS.html>.

4.      Mitsubishi Materials Corporation 2015, 製錬工程,accessed 12 April 2017, <http://www.mmc.co.jp/naoshima/process/>.

5.      Recycling & the Future of Mining 2012, The Business of Mining, chart, accessed 12 April 2017,<https://businessmining.files.wordpress.com/2012/04/copper-global-mining-demand-to-2080.png>.

6.      University of York 2013, A flow diagram summarising the processes used to manufacture copper from its ore., accessed 12 April 2017, <http://www.essentialchemicalindustry.org/images/stories/700_Copper/Copper_16.JPG>.

7.      University of York 2013, Concentration of copper ore by froth flotation., accessed 12 April 2017, <http://www.essentialchemicalindustry.org/images/stories/700_Copper/Copper_05.JPG>.

8.      University of York 2013, The manufacture of copper using the Isasmelt process., accessed 12 April 2017, <http://www.essentialchemicalindustry.org/images/stories/700_Copper/Copper_07.JPG>.

9.      U.S.  Congress,  Office  of  Technology  Assessment 1988, ‘Environmental Impacts of Copper Production’, Diagram, Copper:  Technology  and  Competitiveness,  U.S.  Government  Printing  Office, Washington,  DC <https://www.princeton.edu/~ota/disk2/1988/8808/880810.PDF>.