China-2006

MOLTEN METAL FLUXING/TREATMENT: HOW BEST TO ACHIEVE THE DESIRED QUALITY REQUIREMENTS

Martin B. Taylor, M.Sc., STAS Inc. 1846 Outarde, Chicoutimi (Quebec)

Canada G7K 1H1

ABSTRACT

Metal quality is continually improving for a wider and wider range of alloys and products. Fluxing is a common term used to describe a variety of cleansing operations including degassing, alkaline removal and inclusion removal. STAS being a leader in fluxing technologies is able to provide options for treating molten metal at various stages in the production process. A brief overview of available equipment together with their application will be followed by supporting data illustrating the metallurgical improvements which can be achieved under a wide range of conditions for each of these equipments. They include the Treatment of Aluminium in a Crucible (TAC); Furnace Fluxing including the Rotary Flux/Gas Injectors (RFI/RGI); Degassers including the Alcan Compact in-line Degasser (ACD); Filters including CFFs and Deep Bed Filters (ABFs).

INTRODUCTION

Molten metal fluxing (or treatment) has been discussed in numerous papers (1,2,3) at various conferences over the last few years; yet for some, the requirements and benefits are not always clearly understood. The purpose of this paper is to simply highlight the more common technologies and indicate where they are applied in the manufacturing process: "Is molten metal best treated in the potroom or in the casthouse or even in a separate building?" Consideration is also given to briefly describe their effect on the environment and the undesired but necessary increases in costs, which add value to the product.

Reference is made to both primary and secondary plants whose requirements for metal treatment vary considerably in order to meet customers' needs.

This paper draws extensively on a paper presented at the TMS 2002 (4), which adequately describes the challenges facing the aluminium industry in the development and optimisation of metal treatment technologies and practices.

CLASSIFICATION OF PLANTS

Aluminium plants can be classified in several ways, but the most practical is to separate them into three categories: either primary, secondary or even tertiary. Why is this? Because the integrated or primary plant has a range of choices in deciding at what stage in the process to treat the metal, which is different from that of the recycler or remelter or even the foundry.

a) Primary (Smelter)

A primary plant is defined as the production of aluminium from alumina, which in turn is obtained from bauxite; impurities need to be removed from the molten metal produced in the electrolytic cells. A primary or smelter plant is often, though not always, fully integrated to the downstream product. For example, the smelter may be fully integrated to produce strips using continuous casting or billets. Or it may be integrated downstream at a company's sister plant, perhaps located at a distance whereby

China-2006

road transport is used to transport the molten metal to a finishing plant, where there is a rolling mill or a foil plant, etc.

Considerations for metal treatment are quite different for the smelter, where treatment in a crucible can be carried out. For example, impurities are carried over in the form of bath material from the potroom crucible and into the holding furnace. Skimming and siphoning may be a simple form of metal treatment to minimise the carry-over. Removal of hydrogen, alkalines and inclusions are requirements for the finished product from the melter/holder furnaces.

Table 1 provides typical impurity levels in metal from both the smelter and the remelt/recycle plants.

b) Secondary (Remelter and Foundry)

The charge material usually consists of ingots and in-house generated scrap. In the remelter and/or foundry, hydrogen and sodium removal is essential if porosity in the finished product and cracks developed during service are to be avoided. Similarly, alkalines need to be removed; for example, the presence of sodium can lead to edge cracking whilst rolling to final thickness. Inclusions need to be reduced.

c) Tertiary (Recycler)

The charge material consists usually of products such as used beverage cans or car components, scrap as well as drosses. In this paper, the "tertiary" and "secondary" are grouped together for simplicity. Impurities present in drosses as well as a pick-up of alkalines such as calcium are frequently encountered; hydrogen too will need to be reduced as there is a pick-up during reprocessing.

SOME DEFINITIONS

a) Fluxing/Treatment

And what is meant about the term "fluxing"? (5) Is it really different from metal treatment?

At the 1997 Annual Meeting of the TMS, one of the sessions was titled "Cast Shop Technology: Metal Treatment-Fluxing", thus using the term synonymously; in this paper, the term "metal treatment" will be mostly used.

Fluxing can take the form of gas fluxing or solid fluxing. The purpose of fluxing in the sense of treatment is to remove impurities in liquid aluminium. Under some circumstances, a so-called impurity might be an alloying agent and therefore considered a desirable addition. Examples would be sodium additions as a modifier, or magnesium to produce higher strength aluminium alloys. Yet, sodium is removed also to avoid edge cracking during rolling and "demagging" when magnesium is in the scrap but not required in finished products.

b) Impurities

It is important to qualify and quantify the impurities present in the aluminium (6,7,8). They include hydrogen, alkalines and inclusions (both metallic & non-metallic, including oxides, borides, nitrides,

Table 1

Characteristic Smelter Remelt

Composition ≥ 99.7% Al Alloyed or close to final composition

Hydrogen 0.1 – 0.3 ppm 0.2 – 0.6 ppm Alkali Na

Ca Li

30 – 150 ppm 2 – 5 ppm

0 – 20 ppm

≤ 10 ppm 5 – 40 ppm

< 1 ppm

Inclusions (PoDFA scale)

> 1 mm2/kg Al4C3

0.5 < mm2/kg < 5.0 Al2O3, MgO, MgAl2O4,

Al4C3, TiB2

China-2006

carbides and chlorides). Instruments, which need to be calibrated properly, are now available to accurately measure the presence of each of these impurities. They need to be specified and properly operated if comparisons are to be made for quality considerations for a plant. For example, there are several techniques to measure hydrogen levels both in the solid and liquid state. They include the Alscan method, now recognised as the standard. For inclusions, they might include the PoDFA or the LiMCA (9) methods, the former providing quality in the sense of defining the kind of inclusions present, and the latter providing quantities in the sense of the number of inclusion counts of different sizes per volume of liquid metal.

c) Chlorine

Chlorine gas has been used frequently in the past for fluxing, but due to environmental and cost considerations, there is now a strong movement to discontinue its use in several countries. For this reason, the technologies are divided into two groups: the first can be called the "chlorine route", and the second group would be the "non-chlorine" route.

TECHNOLOGIES – THE EQUIPMENT

Treatment of Aluminium in Crucibles (TAC)

Main purpose is to remove alkalines in the smelter; secondary purpose is to remove inclusions (10).

What can the TAC do? Lithium and sodium levels can be reduced to a few ppm, within total stirring and cycle times of less than 10 and 30 minutes respectively (see Figure 1). There have been more than 20 installations in 15 plants on three continents.

Environment and cost considerations include: adds another step in the process, with both capital and operating/maintenance costs; need to skim before processing, and decision needed whether or not to skim afterwards; where to locate: in the potroom or in a separate building or in the casthouse; emission control required.

Sketch 1

Photo 1: TAC

Capital cost in US$ is approx. 250 to 500 K, depending on design. Operating/maintenance costs in US$ are approx. 0.60-0.70¢/tonne.

LITHIUM AND SODIUMCONCENTRATION VS REACTION TIM E

REACTION TIM E (M IN .)

% R

EMO

VA

L

-InC C

O

Figure 1

China-2006

Rotary Flux/Gas Injector (RFI/RGI)

Main purpose is to remove alkalines and inclusions either with a solid potassium/magnesium chloride flux (RFI) or with chlorine gas (RGI) using nitrogen as a carrier gas in the melter/holder furnace (11); secondary purpose is to stir the liquid melt for homogenising in the furnace.

Photo 2: Typical RFI – Mobile

Photo 3 – Fixed RGI

If TAC is not an option and chlorine gas is not available, then the RFI can remove the sodium. Typically, 75% removal can be obtained (see Table 2 for an example of a 6XXX series and Table 3 for a 3XXX series) (12).

Table 2: Alloy Grade 6XXX – Smelter Table 3: Alloy Grade 3XXX – Remelter

Na (ppm) Na (ppm) (%) K (min-1) Average

30 8 73 -0.05 Ca Na

Furnace before RFI treatment 10.7 3.1

Furnace after RFI fluxing 4.2 0.8

Efficiency(%) 60% 75%

Removal rate, Kinetic, K (min-1) 0.037 0.054

Assuming the alkalines have been reduced in the TAC, then an RFI is also used as an effective stirrer for the molten metal to bring it to uniform chemistry and temperature levels (homogenising) (see Figure 2). Electromagnetic stirring is an option for the melter/holder furnace.

Should high magnesium alloy remelt be added to the furnace, then sodium pick-up can occur which needs to be removed with the RFI. On the other hand, by skimming the potroom metal to remove bath material and using siphoning into the furnace, then sodium pick-up can be avoided.

With the RFI/RGI, inclusions are also removed by as much as 95% (see Table 4).

Some claims are made that it is possible to remove hydrogen gas from the furnace; this is true, but due to high surface/volume ratio and operating temperatures, there is a rapid pick-up in the hydrogen content to equilibrium levels,

thus rendering the removal of hydrogen a marginal value at best (see Figure 3).

EVALUATION OF STIRRING EFFICIENCY FOR THE ROTARY INJECTOR

740

750

760

770

780

790

1 2 3 4 5 6

Time (min.)

Tem

pera

ture

(deg

. C)

BottomSurface

Figure 2

China-2006

Table 4: Typical Metal Cleanliness at Holder Spout

1XXX 3XXX 5XXX 6XXX

RFI RGI RFI RGI RFI RGI RFI RGI

Total PoDFA (mm2/kg) 0.01 – 0.4 --- 0.01 – 0.5 0.01 – 0.5 0.01 – 0.5 0.05 – 0.6 0.01 – 0.4 0.05 – 0.5

LiMCA- N20 (K/kg) 5 – 25 --- 15 – 25 10 – 30 15 – 35 20 – 40 15 – 20 20 – 40

Environment and cost considerations include: choice of chlorine gas as a flux or a solid flux; furnace time required to achieve targeted removal levels; decision required to select type of injector, either mobile or fixed to floor and/or furnace. Emissions of HCl and dust are reduced by up to 90% compared with chlorine lancing.

Both argon and nitrogen gases can be used as carrier gases; in either case, nitrides are not detected.

Alternate technologies are available including porous plugs, which inject argon. There have been some attempts to inject chlorine gas together with argon – limitations of this technology are that they are poor stirrers and blockages readily occur, whilst wear around the plugs can lead to premature furnace lining replacement.

Lancing using both nitrogen and chlorine gas has been a method used for quite some time. Limitations are that this technique does not provide effective stirring, noxious emissions are high, and the furnace time is very long.

Finally, manual additions of solid flux is still in use in many casthouses., but this technique is far from being efficient.

Capital cost in US$ is approx. 125 to 200 K, depending on model. Operating/maintenance costs in US$ are approx. 2-4$/tonne.

In-Line Degassing

Main purpose is to remove hydrogen gas from the liquid melt after the holding furnace and before the filter and/or casting pit (13) .

Secondary purpose is inclusion and alkaline removal, which can be effectively achieved only if the chlorine option is used. Some recent advances with sealed degassers claim to be able to reduce inclusions.

With the ACD and only using argon gas, hydrogen is effectively reduced to equilibrium levels. Until recently, degasser suppliers claimed reductions in terms of percentage reductions and not absolute reductions. It has been shown (14) that the target to measure and to compare is the value which can be achieved under the ambient conditions and the casting temperature (equilibrium levels), which can vary wildly from plant to plant and from season to season. For example, a degasser can degas to levels below 0.09 ppm (Alscan readings) in winter in Quebec whereas the same degasser under

Figure 3: Degassing in Furnace

China-2006

identical operating conditions for the same alloy can only reduce to 0.20 ppm or even higher in summer in hot and humid climates.

Photo 4: 6-Rotor ACD

Photo 5: 4-Rotor ACD

Alkaline removal is not really an option in the degasser without the use of chlorine; although due to the reactivity of sodium, in reality there is a slight reduction.

It is unclear as to the removal efficiency of inclusions without the use of chlorine. There is definitely an increase in dross generation, which is known to hinder inclusion removal; and in fact there may be an inclusion generation. However, the introduction of sealed degassers may lead to efficient inclusion removal. The removal efficiency of any degasser, with or without the use of chlorine, is known to depend upon the level of impurities entering the degasser. The dirtier the metal entering the degasser, the higher the inclusion removal.

Environment and cost considerations in choosing a suitable degasser: there is a hold-up of molten aluminium which needs to be flushed for each alloy change, and there is a need to maintain suitable operating temperatures. The recently introduced Alcan Compact Trough Degasser (ACD) effectively overcomes these problems. Space limitations need to be addressed for all types of degassers.

The use of chlorine gas is becoming more and more of a problem as it is being increasingly banned from the plants. However, small quantities of chlorine gas assist in inclusion removal and still meet MACT emission standards.

Capital cost in US$ is approx. 150 to 300 K, depending on flow rate. Operating/maintenance costs in US$ are approx. 0.75¢-1.5$/tonne for an ACD.

Filters

Main purpose is to remove inclusions (15,16,17). There are three (3) main types of filters: the Ceramic Foam Filter (CFF), the Porous Tube Filter (PDF) and the Deep Bed Filter (DBF). In general, the DBF and the PDF are able to more consistently remove inclusions to very low levels as measured by LiMCA or PoDFA. On the other hand, short production runs of different alloys can justify the use of a CFF. Conversely, long runs of the same alloy can justify the use of a DBF or PDF.

Capital cost in US$ is approx. 150 to 500 K for DBF and + 50 K for CFF, depending on flow rate. Operating/maintenance costs in US$ are approx. 1-2$/tonne for DBF and 2-4$/tonne for CFF.

China-2006

Some casthouses install a CFF before the DBF to prolong life of the latter.

Filtering of inclusions is usually required after the degassing. Although degassers can be very effective inclusion removers, this is only the case when chlorine gas is used in the degasser. For the non-chlorine route, this is not an option.

Several factors will determine which type of filter to use. The CFF is the most common filtering method used. The DBF or PDF is used where there are few alloy changes and efficient filtering is required, such as for can stock or foil.

Inclusions removed include oxides, carbides and, to a lesser extent, borides.

CHOOSING THE RIGHT TECHNOLOGY – DISCUSSION

1 – SMELTER (INTEGRATED) 2 – REMELTER (NON-INTEGRATED)/ RECYCLER / FOUNDRY

A – The Non-Chlorine Route TAC and/or RFI ACD or other degasser (sealed units) DBF or PDF or CFF

A – The Non-Chlorine Route RFI ACD or other degasser (sealed units) DBF or PDF or CFF

B – The Chlorine Route RGI ACD or other degasser with argon &

chlorine DBF or PDF or CFF

B – The Chlorine Route RGI with nitrogen & chlorine ACD or other degasser DBF or PDF or CFF

Photo 6: Deep Bed Filter (DBF)

China-2006

Figure 4: Smelter (1) – Non-Chlorine Route (A)

FILTER TAC RFI ACD

CFF DBF Main Purpose Removes alkalines Removes alkalines

& inclusions Removes hydrogen Removes inclusions Removes

inclusions Secondary Purpose

Removes inclusions Stirs Removes inclusions Not Applicable Not Applicable

Placement Either potroom, separate building or in casthouse

before melter/holder

In the holding furnace Between holder & filter

Between degasser & casting pit

Between degasser & casting pit

Entry: ≤ 150 Na / ≤ 20 Li Entry: 20-30 Na / 4 Ca OR (if TAC used) Na < 5

Entry: 0.20-0.30 H2 Entry: 0.5 < 5 mm2/kg

Entry: 0.5 < 5 mm2/kg

Typical Levels (ppm): Alkalines + H2 Exit: < 5 Na / < 2 Li Exit: Na < 1 / 1 Ca Exit: 0.10-0.20

(at equilibrium) Exit: < 0.1 mm2/kg

PoDFA Exit: < 0.1 mm2/kg

PoDFA Inclusion Removal

Not Available Exit: 0.01-0.6 mm2/kg PoDFA, depending on alloy

NONE, except for sealed

Variable: 40-90% Consistent 90% removal

Dross Generation

Very little; excess AlF3 returned to pot

Reduction of 25-30% compared with lancing

Generates more when no Cl2 used

N/A N/A

Figure 5: Smelter (1) – Chlorine Route (B)

FILTER TAC RGI ACD

CFF DBF Main Purpose N/A Removes alkalines

& inclusions Removes hydrogen Removes inclusions

Secondary Purpose

N/A Stirs Removes alkalines & inclusions

N/A N/A

Placement N/A In the holding furnace Between holder & filter Between degasser & casting pit

Between degasser & casting pit

N/A Entry: 20-30 Na / 4 Ca Entry: 0.20-0.30 H2 Entry: 0.5 < 5 mm2/kg Entry: 0.5 < 5 mm2/kg Typical Levels (ppm) N/A Exit: 1-2 Na / 1 Ca Exit: 0.10-0.20

(at equilibrium) Exit: < 0.1 mm2/kg

PoDFA Exit: < 0.1 mm2/kg

PoDFA Inclusion Removal

N/A PoDFA: 0.01-0.6 mm2/kg depending on alloy

+ 70% Variable 40-90% Consistent 90% removal

Dross Generation

N/A Reduction of 25-30% compared with lancing

Few kilograms per drop Not Applicable Not Applicable

China-2006

Figure 6: Remelter/Recycler/Foundry (2) – Non-Chlorine Route (A)

FILTER TAC RFI ACD

CFF DBF Main Purpose N/A Removes alkalines

& inclusions Removes hydrogen Removes inclusions Removes inclusions

Secondary Purpose

N/A Stirs Removes inclusions N/A N/A

Placement N/A In the holding furnace Between holder & filter Between degasser & casting pit

Between degasser & casting pit

N/A Entry: 3 Na / 11 Ca Entry: 0.20-0.30 H2 Entry: 0.5 < 5 mm2/kg Entry: 0.5 < 5 mm2/kg Typical Levels (ppm) N/A Exit: Na < 1 / 4 Ca Exit: 0.10-0.20

(at equilibrium) Exit: < 0.1 mm2/kg

PoDFA Exit: < 0.1 mm2/kg

PoDFA Inclusion Removal

N/A Exit: 0.01-0.6 mm2/kg PoDFA, depending on alloy

NONE, except for sealed Variable: 40-90% Consistent 90% removal

Dross Generation

N/A Reduction of 25-30% compared with lancing

Generates more when no Cl2 used

N/A N/A

Figure 7: Remelter/Recycler/Foundry (2) – Chlorine Route (B)

FILTER TAC RGI ACD

CFF DBF Main Purpose N/A Removes alkalines

& inclusions Removes hydrogen Removes inclusions

Secondary Purpose

N/A Stirs Removes alkalines & inclusions

N/A N/A

Placement N/A In the holding furnace Between holder & filter Between degasser & casting pit

Between degasser & casting pit

N/A Entry: 31 Na / 12 Ca Entry: 0.20-0.30 H2 Entry: 0.5 < 5 mm2/kg Entry: 0.5 < 5 mm2/kg Typical Levels (ppm) N/A Exit: < 1 Na / 4 Ca Exit: 0.10-0.20

(at equilibrium) Exit: < 0.1 mm2/kg

PoDFA Exit: < 0.1 mm2/kg

PoDFA Inclusion Removal

N/A PoFDA: 0.01-0.6 mm2/kg depending on alloy

+ 70% Variable 40-90% Consistent 90% removal

Dross Generation

N/A Reduction of 25-30% compared with lancing

Few kilograms per drop N/A N/A

China-2006

SUMMARY

Clients' Needs

Strategically, there are two main approaches which can be used to meet clients' needs. The first is to be PRO-ACTIVE, the second to be REACTIVE. What is meant by this is that in order to be pro-active, then a company (or plant) needs to invest and optimise its quality levels and then offer its product into the market place as a superior value to the customer.

The reactive approach is quite simply one in which complaints are made to the producer who then scrambles to learn and understand the technologies which are available for him in order to meet the customers' requirements.

Figure 8 provides typical specification levels for the various products.

Unf

ilter

edA

lloy

Ext

r usi

on

Pur

eF o

ilFi

ltere

d

Com

pute

rD

isksFi

ltere

dA

lloy

Inclusions

Alk

a lis

1

100

10

1

100

10

1000

1000

3

millionParts per

billionParts per

trillionParts per

Figure 8: Typical Impurity Concentrations in Some Aluminium Products

Producers' Choice

1 – SMELTER (1)

The Non-Chlorine Route (A) [see Fig. 4]

This route requires a TAC ( ) and/or RFI ( ), a degasser ( ) and a filter ( ) in order to meet specifications consistently.

A TAC must be used to remove alkalines; this is the best option for reducing sodium. There is also a revival of interest in the use of lithium carbonate to improve current efficiencies in cells due to a reduction in price of this product. A TAC will be necessary to remove lithium contamination which can lead to surface defects and to avoid pouring nozzle blockages at the casting pit.

To install a TAC requires a high capital cost investment. Is capital available?

Where to locate a TAC is crucial. Is it the responsibility of the potroom to provide a cleaner product, or is it best done in the casthouse? … Clearly an important operational decision.

China-2006

If alkalines are reduced in a TAC, then the metal is transferred to the melter/holder for stirring and/or alloying where an RFI can be used for inclusion removal.

Reduction of hydrogen is then carried out with an in-line degasser, followed by removal of inclusions to specification in either a CFF and/or DBF.

The Chlorine Route (B) [see Fig. 5]

Assuming a TAC is not available, this route requires an RGI ( ) – in which chlorine gas is used for alkaline and inclusion removal – a degasser ( ) and a filter ( ) in order to meet specifications consistently. When chlorine is used, even small amounts of less than 0.5% chlorine plus argon gas will lead to a drier dross in the degasser. The dry dross is less wearing on rotors and also ensures high inclusion removal.

Stoichiometric additions of chlorine can ensure high alkaline removal of plus 90%, though typically 70% for sodium removal and 50% for calcium removal (see Table 5).

Table 5

Average, A356 alloy

Li Na Ca

Before crucible transfer (pot room) 0.0011 0.0036 0.0004 After transfer (cast house) 0.0010 0.0027 0.0002 Furnace after fluxing 0.0003 0.0001 0.0001

* Pick-up was due to alloy additions in the furnace.

Although chlorine gas is cheaper than the solid fluxes (see RFI), the total operating/maintenance costs need to take into account the high cost of the effects of corrosion on buildings and equipment plus the expensive measures needed to ensure the good health of workers in the safety issue. Dross generation is reduced by 25-30%.

2 – REMELTER/FOUNDRY/RECYCLER (2)

The Non-Chlorine Route (A) [see Fig. 6]

Charge material consists of scrap and remelt alloys from the smelters.This route requires an RFI ( ), a degasser ( ) and a filter ( ) in order to meet specifications consistently. Usually there is far less sodium present in the charge, but calcium can be a problem due to scrap contamination.

No pretreatment in the pot crucible is possible (TAC). The RFI can be used in either the melter or the holder furnace for the purpose of alkaline removal. However, to optimise homogenisation before casting, then clearly the holder furnace is preferred, in which the RFI is a good stirrer.

Calcium requires longer treatment times to reduce than sodium.

The Chlorine Route (B) [see Fig. 7]

This route requires an RGI ( ), a degasser ( ) and a filter ( ) in order to meet specifications consistently.

China-2006

ACKNOWLEDGEMENTS

Thanks to Alcan, and in particular to Mr. Peter Waite, for their assistance in preparing this document.

REFERENCES

1. "Principles of Aluminum Metal Treatment", Continuing Education Committee Short Course, Presented at the 122nd TMS Annual Meeting, Denver, Colorado, 21-22 February 1993.

2. B. Gariépy et al., "Aluminum Ladle Metallurgy (ALM): A New Process for More Efficient Alloy Preparation", Light Metals, 1988, 457-462.

3. C. Celik and D. Doutre, "Theoretical and Experimental Investigation of Furnace Chlorine Fluxing", Light Metals, 1989, 793-800.

4. Peter Waite, "A Technical Perspective onMolten Aluminum Processing", Presented at the TMS Annual Meeting, Seattle, Washington, February 2002.

5. "Aluminium Project Fact Sheet", Office of Industrial Technologies, Energy of Efficiency and Renewable Energy, U.S. Department of Energy.

6. R. I. Guthrie, and D. A. Doutre, "On-Line Measurements of Inclusions in Liquid Metals", International Seminar on Refining and Alloying of Liquid Aluminum and Ferro-Alloys, Trondheim, Norway, August 1985, 145-163.

7. D. Doutre et al., "Aluminium Cleanliness Monitoring: Methods and Applications in Process Development and Quality Control", Light Metals 1985, TMS-AIME, 1179-1195.

8. J.-P. Martin, F. Tremblay, and G. Dubé, "Alscan: A New and Simple Technique for In-line Analysis of Hydrogen in Aluminum Alloys", Light Metals, 1989, 903-912.

9. H. P. Krug, and W. Schneider, "A Contribution to Inclusion Measurement After In-line Degassers with PoDFA and LiMCA", Light Metals, 1998, 863-870.

10. G. Dubé, and V. J. Newberry, "TAC – A Novel Process for the Removal of Lithium and Other Alkalis in Primary Aluminum", Light Metals, 1983, 991-1003.

11. G. Béland et al., "Rotary Flux Injection: Chlorine-Free Technique for Furnace Preparation", Light Metals, 1998, 843-847. 12. M.B. Taylor, "Which Method to Choose for Alkaline Reduction? Either in the Pot Room Crucible or in the Casthouse?",

Presented at the TMS Annual Meeting, Seattle, Washington, February 2002.

13. P. Waite, and R. Thiffault, " The Alcan Compact Degasser: A Trough-Based Aluminum Treatment Process Part 1: Metallurgical Principles and Performance", Light Metals, 1996, 1001-1005.

14. P. D. Waite, "Improved Metallurgical Understanding of the Alcan Compact Degasser After Two Years of Industrial Implementation in Aluminum Casting Plants", Light Metals, 1998, 791-796.

15. D. Kocaefe, R.T. Bui, and P. Waite, "2D Transient Mathematical Model of Aluminum Filtration", Light Metals, 2000, 817-823.

16. D. Kocaefe, R. T. Bui and A. Chapdelaine, "1D Mathematical Model of Deep Bed Filtration", Light Metals 1999, Canadian Institute of Mining, Metallurgy and Petroleum, 1999, 203-217.

17. C. Dupuis, G. Béland, and J.-P. Martin, "Filtration Efficiency of Ceramic Foam Filters for Production of High Quality Molten Metal Alloys", Light Metals Processing and Applications, Canadian Institute of Mining, Metallurgy and Petroleum, 1993, 349-358.