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Life cycle Analysis of Aluminum Foil Packaging Material Olfat El-Sebaie, Manal Ahmed, Ahmed Hussin, Fahmay EL-Sharkawy, Manal Samy Environmental Health Department, High Institute of Public Health, Alexandria University ABSTRACT A fundamental tent of life cycle analysis (LCA) is that every material product must become a waste. To choose the greener products, it is necessary to take into account their environmental impacts from cradle to grave. LCA is the tool used to measure environmental improvements. Aluminum (Al) is the third most common element found in the earth’s crust, after oxygen and silicon. Al packaging foil was chosen as the material for the study with its life cycle perspective at Alexandria. The Al packaging produced from virgin and recycled Al was investigated through life cycle stages in these two production processes; primary and secondary. The aim of this study is to evaluate the environmental impact of aluminum packaging process by using life cycle analysis of its product from two different starting raw materials (virgin and recycled aluminum). The input and output materials, energy, water, natural gas consumptions, and solid waste uses in the foil industry had been analyzed in order to identify those with significant contribution to the total environmental impacts. From the survey done on the two life cycles, it was found that in environmental terms, the most important emissions from the primary process are the emission of CO2 and perfluorocarbon (PFC) gases, which produce the greenhouse effect, and SO2 as well as the emission of fluorides and polyaromatic hydrocarbons (PAH compounds), which are toxic to humans and the environment. On over all material balance, it was found that the ingot shares by 45% of the feed to the casthouse furnaces at Egyptian Copper Work (ECW), net production of the casthouse is 43.76%, Correspondence to: Dr. Manal A. Mohamed Environmental Health Department, High Institute of Public Health Alexandria University E-mail: [email protected]

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and the yield of rotary dross furnace (RDF) is 28.8%. The net production of the foil unit represents 35% of the total input to the unit. By comparing the two life cycles, it is obvious that, for water consumption, 93.5% is used in the primary cycle, while 6.5% is used in the secondary cycle. For electricity consumption, 99.3% is used in the primary cycle; while 0.63% is used in the secondary cycle. For the natural gas consumption, 46.66% is used in the primary cycle excluding Nag' Hammady as it uses fuel oil, while 53.34% is used in the secondary cycle. Using a matrix approach, the primary cycle scored 6 heavy loaded factors out of 9, while the secondary cycle scored 3 heavy loaded factors out of 9. It can be concluded that Al recycling (secondary cycle) in Al industry decreases the use of virgin material, energy use, and environmental loadings, while increasing the economic life of products, and reducing overall material demands. So, the secondary cycle is to be recommended and is the most favorable option in most of the factors influencing the two cycles. Monitoring of the furnaces, automatic control of the metal, proper dross cooling, better refining of molten Al, rate of solidification of molten Al, and proper annealing process will lead to reduction of the overall fuel, water, and electricity consumption and metal losses will be minimum.

INTRODUCTION In our daily lives, we acquire and discard the products of industry, most often giving little or no thought to where they come from or where they will go once we have finished with them. Life cycle analysis (LCA) is defined as looking holistically at the environmental consequences associated with the cradle-to-grave life cycle of a product or process. It encompasses extracting and processing of raw materials, manufacturing, transportation, distribution, use, reuse, maintenance, recycling, and waste management.(1) The importance of LCA is likely to increase in the future as companies are eager to develop sustainable products. The motivating factors for using LCA are legislation, customer demand, Eco-labeling programmes, and ISO 14000. In addition, LCA can serve as decision making tool for industry, e.g., a product manufacturer compares the

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current product to modifications to the same product, evaluates opportunities to reduce environmental impacts, and it is useful for identifying opportunities for pollution prevention decisions.(2) Nowadays, aluminum’s low density coupled with its unique properties which include durability and ease of recycling let aluminum becomes more a core material across a spectrum of products. The range includes ingots, flat-rolled products, different types of pipe, rod, wire, and a variety of consumer goods which include packaging.(3) In Eastern and third world countries, up to 50% of food is wasted because of nonavailability or inadequate packaging and transportation. It is creating problems of refuse disposal and for wasting energy and natural resources.(3) The most immediate environmental issue facing the packaging industry is solid waste management. As a result, the packaging industry has been the target of a disproportionate number of LCA’s.(4) Aluminum is a sustainable material. At the current primary aluminum production level, known bauxite reserves will last for hundreds of years. More than 55 per cent of the world's aluminum production is powered by renewable hydro-electric power. Products made from aluminum can be recycled repeatedly to produce new products. The increasing use of recycled metal saves both energy and mineral resources needed for primary production.(5) Aluminum packaging materials consist of Al foil from primary Al manufacture. The foil is a very thin sheet of rolled Al supplied in its pure form or in a variety of alloys. The largest single use of Al foil is for the household foil. Al packaging offers a wide range of advantages as it protects, preserves, and makes food safe. It is not combustible and chemically resistant in contact with substances in the range of pH 4-9. In packaging, aluminum is used either plain or converted. But, the majority of aluminum packaging is used in converted form, i.e., the packaged

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goods don’t get in contact with the aluminum itself, there is an intermediate layer of lacquer, plastic, paper, or cardboard lining the aluminum. These coatings serve as protective layers.(5) The production of metallic aluminum on a commercial scale has four essential steps: preparation

of

high

purity

alumina,

preparation

of

cryolite,

manufacture of electrodes, and manufacture of metallic aluminum from alumina.(6) In Egypt, Al metal is produced by the Egyptalum Company of Nag' Hammady in Upper Egypt from the virgin alumina (Al2O3). In this process, alumina is reduced by electrolysis, in the presence of cryolite and fluorspar, into Al metal in the form of slabs, sheets, billets,..,etc. On the other hand, Al can be manufactured from Al scrap.(7) In this respect, the most important manufacturer is the Egyptian Copper Works of Alexandria. The two processes of producing Al differ in their requirements for raw materials and energy, and waste emissions. Therefore, their environmental impacts are likely to differ.(7) The aim of this study is compare between the two life cycles of aluminum packaging industry in Alexandria starting either from its virgin raw material or from recycled aluminum manufacturing step to the final product and using a matrix approach as a tool for evaluating these cycles as regard to the resources used, energy consumed, and air; water; and solid emissions generated during the production cycle.

MATERIAL AND METHODS Two factories were selected in this study. The first one was Egyptalum of Nag' Hammady at Upper Egypt and the second was Egypt Copper Works (ECW) at Hagar El-Nawatia in Alexandria. The study started at Nag' Hammady and continued at ECW to compare between primary and secondary life cycles.

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Background on the Al industry: Aluminum ore, most commonly bauxite, is plentiful and occurs mainly in tropical and sub-tropical areas: Africa, West Indies, South America, and Australia. Bauxite is refined into aluminum oxide tri-hydrate (alumina) and then electrolytically reduced into metallic aluminum.(8) Four tonnes of bauxite are required to produce two tonnes of alumina and two tonnes of alumina are required to produce one tonne of aluminum metal. Bauxite is washed, ground and dissolved in caustic soda (sodium hydroxide) at high pressure and temperature. The resulting liquor contains a solution of sodium aluminate and undissolved bauxite residues containing iron, silicon, and titanium. These residues sink gradually to the bottom of the tank and are removed. They are known colloquially as "red mud". The clear sodium aluminates solution is pumped into a huge tank called a precipitator. The result is a white powder, pure alumina. The caustic soda is recycled to the start of the process and used again. Then Alumina is dissolved in an electrolytic bath of molten cryolite (sodium aluminum fluoride Na3AlF6) within a large carbon lined steel container known as a "pot". The electric current flows between a carbon anodes (positive), made of petroleum coke and pitch, and a cathode (negative), formed by the thick carbon lining of the pot. Molten aluminum is deposited at the bottom of the pot and is siphoned off periodically, taken to a holding furnace, refined and then generally cast.(8)

Sampling sites and samples collection: •

Ten dross samples were taken from the continuous casthouse unit (primary cycle). Five samples of dross were taken from melting and holding furnaces (F11, F13). Other five samples were collected from the black dross delivered from the waste of the rotary dross furnace (RDF).

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Ten samples were taken from the semi-continuous furnaces (secondary cycle). Five samples were taken from the skimmed dross of the furnace F22, where the dross was directly thrown onto an area in front of it. Five mixed samples were collected from the dross resulting from the two furnaces F21 and F23 which were charged with any aluminum scrap from any aluminum unit and pressed foil.

•

Seven samples of aluminum scrap were taken from the reception area of the scrap (electric wires, plates, cooking utensils, pieces of different assorted items, and pieces of aluminum window frames).

•

Analysis of samples: - Estimation of bulk density (ζ) of dross. ζ = (M/V). - Estimation of the percentage of Al samples; dross and external scrap.

•

The representative samples were analyzed for Al by Atomic Absorption Spectrophotometer, Perkin Elmer Analyst 300. The flame was nitrous oxide-acetylene. The wave length was 309 nm and the slit was 0.7 nm.

•

Material balance was prepared to calculate the recycling streams from each operation unit in the casthouse to determine the percentage of the dross and the yield from each unit.

•

Life cycles analysis: The two life cycles (primary and secondary) were surveyed in details as regards to all raw materials input and product outputs and were followed up related to the flow of materials and energy demands, water, natural gas, and emissions.

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Comparison between the two life cycles and recommendation for optimization and maximize recycling of aluminum mechanism.

RESULTS AND DISCUSSION The study comprised three phases: a pre-assessment phase, a data collection phase to derive a material balance, and a synthesis phase which included a waste reduction plan and cleaner production strategies.

Life cycles analysis of Al production at Nag' Hammady. It utilizes the Hall-Heroult process to reduce alumina by electrolysis into aluminum metal. The company has two types of electrolytic cells (pre-backed cells (dry) and Soderberg cells (wet)), pot rooms, casthouses, and rolling (hot and cold) department. The unit processes consist of Al cells production unit, anode paste plants, sintering coke factory, two casthouses, cryolite manufacturing unit, and rolling section (hot-rolled products amount to 120000 tons/y and coldrolled products amount to 60000 tons/y). Its products include slabs, ingots, wire rods with various diameters, strips, and T-bars. Product purity ranges between 99.7% and 99.8% Al. Nag' Hammady factory consumes 2/3 of the High Dam electricity and table (1) illustrates the annual production of primary Al, total water, and electricity consumption at Nag' Factory.(9) It is clear that it consumes 17704 KW/ton of primary Al produced and consumes 34677.5 m3 water/ton of Al produced. Aluminum smelting is energy-intensive. On average around the world, it takes some 15700 kWh of electricity to produce one tonne of aluminum from alumina, that is why the smelters are located in areas supplied with hydro-electric power.(10)

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Table 1:

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The Annual Production of Primary Al, Total Water, and Electricity Consumption at Nag' Hammady Factory.

Primary Al production (tonnes) 189427

Total water consumption (m3*1000) 65688.64

Electricity consumption (KW*1000) 3353657

Emissions at Nag' Hammady Air emission: It is observed that the emission from the cells are predominantly CO2, O2, fluoride, fine particulate Al2O3 dust, and emulsified coal dust. On average, the smelting process itself, per ton of aluminum, is now responsible for the production of 1.75 tonnes of CO2 (from the consumption of the carbon anodes) and the equivalent of an additional 2 tonnes of CO2 from perfluorocarbon (PFC) emissions.(11) The main environmental problem associated with aluminum smelters is fluoride emissions as they have had adverse effects on the wildlife around the plant.(11) There are two main types of fluoride emissions; a mixture of the inorganic fluorides (NaF, ALF3, and HF) and organic perflurocarbons (CF4 and C2F6). Hydrogen fluoride (HF) is originating from the electrolyte, formed by the reaction of electrolyte components with hydrogen from the anodes. Zahran(12) reported that most of the hydrogen fluoride (HF) cell emissions occurred during anode changing and metal tapping. He recommended using wet scrubbing system which uses aqueous spry to remove fluorides. On the other hand, Al industry is the major source of perflurorocarbons gases mainly CF4 such that the effect of 1 ton CF4 (g) is the same as 6500 tonnes of CO2 (g).(11) Polycyclic aromatic hydrocarbons (PAHs) are produced during the manufacture of pre-baked anodes (0.05 kg per ton) and during the electrolytic process in the Soderberg cell (0.25 kg per ton). The main technological approaches to minimize harmful gaseous and particulate emissions are improved cell design, operation, and process control;

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replacing Soderberg cells with modern pre-backed cells, which have lower anode effect frequencies and much lower polycyclic aromatic hydrocarbon (PHA) emissions, and the use of inert anode will reduce the CO2 emission.(13) From the public health point of view, both particulate and gaseous hydrogen fluoride is the reason for asthma. In addition, PAH cause greater incidence of cancer in the urinary bladder and lung. Also, the operators are exposed to heat radiation which results in heat stress.(11) So, personal protective measures, like dust and gas masks, must be used to reduce the exposure to fluoride emissions in the smelters. Solid waste resulting from primary Al industry: The quantity of red mud to be disposed off might be 2-3 times the quantity of Al2O3 produced. Thus its disposal is a problem to Bayer processing plants.(14) Spent potlining (SPL) is an unavoidable by-product of the aluminum smelting process and the material that lines the electrolytic cells known as pots. The SPL has significant energy content from the carbon lining and other beneficial characteristics for utilization, for example, in cement production, but it includes both fluorine and a small amount of cyanide absorbed over the operational life of the pot. The aluminum industry recognizes that SPL has properties that make it a valuable material for use in other processes and will therefore strive to convert all SPL into feed stocks for other industries, which include cement, steel, and construction aggregate companies, or to re-use and/or process all SPL in its own facilities. On the other hand, the smelting process is continuous. If production is interrupted by a power supply failure of more than four hours, the metal in the pots will solidify and convert to solid waste, often requiring an expensive rebuilding process.(10)

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Life cycle analysis of Al production in Egyptian Copper Works (ECW) It is the largest producer of semi-fabricated items like Al sheet, foil, and extrusions. This company consists of five aluminum units as shown in figure 1:

Figure (1): Flow sheet of AL strips factory.

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1. Continuous casthouse unit where 5% of the annual production at Nag' Hammady is delivered to it with a purity of 99.7 to 99.8% in addition to home scrap. This unit includes melting and holding furnaces (F11, F12, and F13), casting machines, a cold rolling mill, and processing facilities which include slitters; cut to width; cut to length machines; and circular saws, three annealing furnaces, and a rotary dross furnace. 2. The Foil unit: cold-rolled annealed aluminum coils from the continuous casthouse are the input to the foil unit. Products of this unit are aluminum foil plates, industrial coil for Miraco Air Conditioning Co., export, and local foil for domestic usage. The product of this unit is coils which go to the foil unit and/or to consumer, aluminum sheets, and aluminum disc for the utensils industry. 3. Semi-continuous casting unit (Recycling units for secondary cycle): This unit contains three furnaces F21, F22, and F23. For F21 and F23, the input is pure scrape (domestic household, packaging sector, old cable wires, and home scraps, in addition to any scrap from the aluminum units in the factory (foil unit and Pural utensils unit). The output is semi-balls used for reduction in iron industry. For F22, the input is ingots, scrap of the non-ferrous slab rolling mill unit, and any defective products in the stores. The output is aluminum blocks which are transported to the non-ferrous slab rolling mill unit to produce discs or sheets for aluminum utensil industry in rural areas. 4. Non-ferrous slab rolling mill unit. Blocks from the semi-continuous casting unit with a thickness of 12 cm are preheated in a furnace then hot-rolled to reduce thickness from 12 cm to 6 mm, followed by cold rolling into sheets with the customer desired dimensions. 5. Utensils manufacturing unit (Pural). The input is sheets from the continuous casthouse, while the output is utensils for cooking.

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Estimation of bulk density and Al% in selected samples It was found that average density (M/V) of white dross from casthouse (ζ1) was 1.2798 g/cm3, black dross from RDF (ζ3) was 1.358 g/cm3, and dross from semi-continuous of recycling unit (ζ2) was 1.293 g/cm3. This means that white dross which almost contains aluminum in it possesses the lowest specific gravity, dross from semi-contiuous casting which includes inclusions, so it has higher density, while black dross which includes more inclusions (as the white dross and treated in RDF) specific gravity is higher than that of both. Table (2) illustrates the average of chemical analysis of Al resulting from primary cycle (Nag' Hammady) and secondary cycle (ECW). It is clear that Nag' Hammady sample (primary) product has nearly equal percentage of Al % with recycling unit product from F22 and higher than Al% from F23 which is also clear from increase in density of sample taken from this recycling unit. Table (3) estimates the Al% in dross of casthouse, black dross in RDF, recycling unit, and Al scrap (27 samples). It is clear that the average Al% in the recycling unit dross is 56.4% which is lower than that existing in the furnaces of the casthouse (82.84%). This is due to that the input charge to the casthouse furnaces is ingot (99.7-99.8%), in addition to the home scrap, while the input charge for F22 is ingot and non-ferrous slab scrap and F21& F23 is completely external scrap of different Al% content. Table (2): Average of Chemical Analysis of Al in Alloy from Nag' Hammady and Product of F22 and F23 in the Recycling Unit, ECW. Elements% Sample Nag' Hammady F22 Product F23 Product

Si

Fe

Cu

Mn

Mg

Ni

Zn

Ti

Al

0.05 0.09 3.0

0.15 0.22 2.5

0.0025 0.008 0.9

0.0017 0.004 0.08

0.009 0.002 0.065

0.03 0.002 0.1

0.0025 0.03 2.5

0.0046 0.009 0.015

99.75 99.65 91

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Table (3): The Al % in Dross of Casthouse, Black Dross in RDF, Recycling Unit, and Al Scrap (27 Samples). Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Aver.

Al % in dross of casthouse

Al % in dross of RDF

Al % in dross of recycling unit

Al % in scrap of recycling unit

70.74 54.07 78.55 89.32 21.64 79.43 37.67 72.3 62.3 79.73 53.2 89.0 81.3 66.69 82.28 29.48 43.27 69.16 57.1 40.85

82.84

55.92

56.4

90.6 90.91 89.87 87.6 94.0 91.1 90.67 90.68

Sample No. 1,10,17: Dross from F23 in the recycling unit. 3: black dross existing RDF in the casthouse. 5,6,7,9: black dross RDF in the caste house. 11: Dross from F11 in recycling unit. 14,18,19: Dross from F22 in recycling unit. 22: Returnable product. 25: Metal scrap. 27: rejected from F23 to be recycled.

2,16: Dross from F21. 4: Dross from F11+F13 (HF). 8: Dross from F13 in the castehouse. 12,13: Dross from F11+F13. 15: Dross from F13 (MF). 23,24: Rural scrap. 26: Al scrap of window frame.

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Material balance on continuous casthouse including all recycling streams Figure (2) shows a material balance calculation on continuous casthouse including recycling streams and Table (4) illustrates the average annual input and output tonnes within the casthouse. By applying an overall mass balance on the casthouse process, it is clear that ingot % fed to the casthouse furnaces is 45% which is lower than the % of the primary metal of Alcoa,s Davenport Plant (Texas) that ranges between 60-64% of the casthouse feed, with the remainding being scrap from the fabrication operations in the plant.(15) The total dross of the casthouse is 1005.7 tonnes/y and its % is 5.32% which is in agreement with Patterson(16) who stated that the dross from a reverbratory furnace is 5-6%. From Fig. (2) and Table (4), the actual Al recovered by RDF (289.72 tonnes/yr) is much greater than the theoretical calculated value (35.85 tonnes/year), i.e., the factory’s figure is 8 times greater than the Al recovered that should be obtained by RDF. This can be due to the addition of some ingots, home scrap, and rejected parts of coils from the caster to the dross entering RDF. In spite of that addition, the yield of RDF is 28.8%. This low recovery rate of RDF was due to the uncontrolled RDF temperature, no classification for the Al balls in the dross by using mesh size, no rotation of the furnace during the process, and the irregular analysis of Al % in white and black dross to determine the yield % of RDF and to determine the effects of variations in melt chemistry on dross formation and composition. Table (4): The Average Annual Input and Output Tonnes within the Casthouse. Ingot 8503.482

Input Home scrap 10401.7

Al recovered from RDF to recycling unit 289.720

Foils coils, 94 cm width 1930.940

Output Disks coils 13814.98

Sheets coils 1115.910

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Figure (2): Flow chart for the continuous casthouse processes.

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On the other hand, the efficiency of rolling the coil produced by Nag' Hammady is less than that of rolling the ECW coils as shown in Table (5). This is due to the more width of the strip of the Nag' Hammady coils. Table (5): The Efficiency of Rolling Mill and Rewinding Machine in the Casthouse, and their Scraps due to Slitting Both Sides while Producing Foil Coils. Casting machine input for foil (1461.92)* (397.95)** 1841.87

Rolling Mill Output

Efficiency %

Rewinding Machine output

Efficiency %

(1267.06)* (1574.092)** 1574.092

87 82

(1229.177)* (297.82)** 1526.997

97 97

Final product foil coils unit (1325.067)* 1325.067

Scrap of Rolling Mill

Scrap of rewinding machine

(194.86)* (72.898)** 267.758

(38.012)* (47.224)** 47.224

* Coil weight produced by casthouse of ECW. **Coils weight produced by Nag' Hammady.

From Fig. (2) and Table (5), it was found that R1= 1332 tonnes/yr, R2= 469.56 tonnes/yr, R3= 47.22 tonnes/yr, R4+R5= 7958 tonnes/yr, R6= 397.9 tonnes/yr, and R7= 330.9 tonnes/yr. The percentage recycled from C2 (cut to length) and C3 (cut to width), pressers, and shears= 48.59%.

Material balance on recycling unit It is clear from Table (6) that F22 has the highest yield % (output/input). This was due to the fact that the charge to F22 is ingots, in addition to non-ferrous slab rolling unit scrap of known composition, while F21 and F23 are charged with edge trimmings that are contaminated with rolling and hydraulic lubricants as well as external scrap that contains other contaminants as paints and ferrous metals. As regarding to dross % (dross/input), it is clear that dross percentage from F21 and F23 is greater than that from F22, which indicates that pure scrap produces more (nearly doubled) dross than a mixture of ingot and scrap.

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Table (6): Average Annual Total Input, Output, Dross of the Furnaces, and Percentage of their Yields and Dross in the Recycling Unit. Input (tonnes) Output (tonnes) F21 F22 F23 F21 F22 F23 Furnace Total 1145.61 1790.213 2111.519 1038.37 1684.4 1901.63 Yield % 90.6 94.1 90

Dross (tonnes) F22 F23 105 210 Dross % 9.4 5.9 10

F21 107

Water and electricity consumed per tonne of Al produced by ECW Table (7) illustrates the average annual water and electricity consumption for the production of casthouse unit, foil unit, and recycling unit during the study year. Water is used for cooling the cylinders of the casting process. If cooling water has hardness, scales will be deposited in the shell and core. Therefore, the cooling rate efficiency will decrease leading to non-uniformity in the cooling rate which causes defects in the strip products. Also, corrosion of the shell occurs. So, the quality of water used for cooling is very important. It is essential for cooling the annealing furnaces, but for economic reasons during the study period, no cooling occurs which led to furnaces stresses and decreasing in their efficiency, decreasing in their capacity from 56 tones to 10-12 tonnes, and higher annealing temperature. Table 7:

The Average Annual Consumption of Water, Electricity, and Natural Gas per Ton within the Casthouse, Foil Unit, Recycling Unit, and Non-Ferrous Slab Rolling Mill.

Production Unit

Product (tonnes)

Water consumption (m3)

M3/ton

Casthouse

8885.847

56090

6.312

Foil unit 463.77 Recycling 4726.516 unit Non-ferrous slab rolling 1091.810 mill

155.5

0.34

Electricity consumption (KW) 1325.067+7560.78 Foil+ (disks + sheets) 2070.18

556854

117.8149

6250

5.72

KW/ton

Natural M3 natural gas/ton gas (m3)

1400.09

1400.09

233.66

4.46

--------

--------

88830

18.7939

1261577

267.5

2627.985

2.498

206.53

0.189

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On the other hand, the natural gas consumption (m3) for one ton of Al produced by the RDF was 0.526 (152.265/289.72). The amount of natural gas consumed by melting and holding furnaces of F11, F12, and F13 of the caster section in the continuous casthouse for the production of caster lines was 233.66 m3/ton.

Emissions at ECW Total fuel consumption is 4228 t/y fuel oil and 4000 t/y gas oil. The annual average emitted air pollutants load (t/y) are 9.6 *102 CO, 1.3*107 CO2, 1.4 *104 NOx, and 8*104 SOx. In addition, the ECW generates high fluoride emissions which are responsible for damage to vegetation in the area close to the plant.(12) On the other hand, total water consumption is 156000 m3/y and wastewater generated is 135000 m3/y. The average characteristics of the final wastewater is 80 *103 g/m3 COD, 62*103 g/m3 BOD, 25 *103 g/m3 oil & grease , pH 7, with heavy metals > 1.0 g/m3. Solid waste is ~ 600000 Kg of aluminum slag/y.

Comparison between the two life cycles (Primary and Secondary) Table (8) compares between the primary and secondary Al life cycles according to the results of their consumption of electricity, water, and natural gas at each stage during the field study. It is obvious that, for water consumption, 93.5% is used in the primary cycle, while 6.5% is used in the secondary cycle. For electricity consumption, 99.3% is used in the primary cycle; while 0.63% is used in the secondary cycle. For the natural gas consumption, 46.66% is used in a part in the primary cycle excluding Nag' Hammady as it uses fuel oil, while 53.34% is used in the secondary cycle. In the primary cycle, 92.65% of the electricity is used at Nag' Hammady, while 7.33% and 0.02% are used in the casthouse and foil units at ECW, respectively. For water consumption 98.12% of the water is consumed in the primary cycle at Nag' Hammady, while 1.79%

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and 0.1% are used in the casthouse and foil units in ECW, respectively. In the secondary cycle, 98% of the electricity, 76.66% of water, and 99.9% of natural gas are used in the recycling unit. So, it is very important to focus on Nag' Hammady emissions and solid waste, then on the casthouse in the ECW. Table (8): Comparison between the Two Life Cycles of Al Production. Cycle type Place Consumption Electricity (KW/tonne) Total electricity Cost (L.E/ton) Water (m3/ton) Total m3/ton Cost (L.E/ton) Natural gas m3/ton M3/tonne Cost (L.E/ton)

Primary cycle ECW Nag' Hammady Casthouse Foil 17704.218

346.775 ----------

1400.09 19108.76 1910.876 6.312 353.427 88.356 233.66 233.66 116.83

4.46

0.34 -------

Secondary cycle Non-ferrous Recycling slab rolling units mill 117.81

18.79 266.9

2.407 120.217 12.020 24.51 6.13

5.72 0.189

267.615 133.800

N.B: Nag' Hammady uses Mazot. Consumption of RDF from natural gas was 0.526 m3/ton. Cost of electricity P.T.10/kw, for water P.T. 25/m3, for natural gas P.T. 50/m3

Recycling one kilogram of aluminum can save up to 8 kilograms of bauxite, four kilograms of chemical products, and 14 kilowatt hours of electricity.(17) The recycling of aluminum requires only 5% of the energy to produce secondary metal as compared to primary metal and generates only 5% of the greenhouse gas emissions. That is; recycling of aluminum can save 95 percent of the energy required to make the same amount of aluminum from virgin materials.(18) Also, Recycling of postconsumer aluminum saves an estimated 84 million tonnes of greenhouse gas emissions per year, equivalent to the annual emissions from 15 million cars.(19,20) One third of the aluminum used world-wide

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however is produced from recycled aluminum scrap, a process which only produces a total of 0.18 tonnes of CO2 per tonne of aluminum.(21) Recycling of one ton of aluminum is equivalent to not releasing 13 tons of carbon dioxide (a greenhouse gas) into the air. So, aluminum companies have invested in dedicated state of the art secondary metal processing plants to recycle aluminum which saves energy, conserves natural resources, reduces the use of city landfills, and provides added revenue for recyclers and local town government.(22,23) Matrix approach for comparison: Table (9) illustrates comparison between the primary and secondary life cycles using a matrix approach. It is clear that the natural gas consumption in Nag' Hammady is not taken into consideration as Nag' uses mazot. As regards to maintenance and labours, the primary cycle is almost controllable at Nag' Hammady and partially controlled at ECW (casthouse and foil unit). The secondary cycle depends on labour and continuous maintenance, so, these two factors are higher in this cycle than the primary cycle. On the other hand, the numbers in the factors column represent the importance of load of each factor in relation to the other factors. The scores of 0.8167 and 0.1833 show the load of magnitude of the primary and secondary cycles, respectively. As the score of the primary cycle is high, this indicates that this cycle is unacceptable and optimization should be taken into consideration to reduce the environmental effects of these factors. Eco-design uses a tool known as environmental product development strategy wheel (life cycle strategy wheel). The aim of this wheel is to create a win situation to both the environment and the company.(24,25) So, numerical values derived from Table (9) are used to draw life cycle design strategy wheel (Fig. 3). It is noticed that the primary cycle scored 6 heavy loaded factors out of 9 which are cost, electricity, water, material, emissions, and solid waste. While the secondary cycle recorded 3 heavy loaded factors out of 9 which are

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labour, natural gas, and maintenance. So the secondary cycle is to be recommended and is the most favorable option in most of the factors influencing the two cycles. Table 9:

Comparison between the Primary and Secondary Life Cycles Using a Matrix Approach. Factors

Capital cost: Land 9/62 Water 3/62 Electricity 8/62 Natural gas 1/62 Net result Consumptions and others Electricity 8/62 Water 4/62 Natural gas 5/62 Materials 5/62 Labour 3/62 Maintenance 2/62 Emissions 8/62 Solid waste 6/62 Net result

Primary

Secondary

944/1000 935/1000 993/1000 47/100 0.96

6/1000 65/1000 7/1000 53/100 0.04

994/1000 94/100 47/100 9/11 3/11 3/10 8/10 9/12 0.8167

6/1000 6/100 53/100 2/11 8/11 7/10 2/10 3/12 0.1833

N.B: - The numbers in the factors column represent the importance of load of each factor in relation to the other factors. - The higher the score, the higher its impact within the factor, i.e., its stress on the environment and natural resources. Primary cycle

Secondary cycle

Cost 1000

Maintenanace

Electricity 100

10

Solid waste

Water 1

Emissions

Natural gas

Labour

Materials

Figure (3): LiDS wheel illustrating a comparison between primary and secondary life cycles.

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It can be concluded that Al recycling (secondary) in Al industry decreases the use of virgin material, energy use, environmental loadings, and labour, while increasing the economic life of products, and reducing overall material demands. Thus recycling is critical to a sustainable future for metal products. Life cycle and other quantitative assessments have determined that aluminum recycling is significantly less intense (energy, electricity, emissions, water, minerals, …,etc.) than primary aluminum production. RECOMMENDATIONS It is recommended to: •

Control furnaces temperature.

•

Replace the mazot with natural gas in Nag' factory to avoid its emissions. Use of wet scrubbing system to remove fluoride. Use spent-pot-lining in electric furnaces and for production of cryolite.

•

Mix the molten Al inside the furnaces and the use of inert gas for mixing to avoid defects.

•

Perform regularly chemical analysis for molten Al, dross, black dross, and scrap samples.

•

Avoid leakage of hydraulic oils from mixing with rolling oils.

•

Save million tonnes of black dross and spent potlining from going to landfill by good recycling.

•

Ensure presence of cooling cycle in the annealing furnaces to save heat.

•

Apply continuous emission monitoring system to reduce the emissions.

•

Minimum metal loss, maximum energy efficiency, and low pollution levels must be a priority.

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Finally, the secondary cycle is to be recommended and is the most favorable option in most of the factors influencing the two cycles. Increasing use of recycled aluminum will save both energy and mineral resources needed for primary production. Also, there is no difference between primary and recycled aluminum in terms of quality and properties.

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