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Subcontract Report 

NREL/SR-550-39819 

May 2006 

Investigation of Opportunities for 

High-Temperature Solar Energy in 

the Aluminum Industry 

August 1995 

J. Murray 

Portland State University 

Portland, Oregon 
National Renewable Energy Laboratory

1617 Cole Boulevard, Golden, Colorado 80401-3393 

303-275-3000 • www.nrel.gov 

Operated for the U.S. Department of Energy 

Office of Energy Efficiency and Renewable Energy 

by Midwest Research Institute • Battelle 

Contract No. DE-AC36-99-GO10337

Subcontract Report 

NREL/SR-550-39819 

May 2006 

Investigation of Opportunities for 

High-Temperature Solar Energy in 

the Aluminum Industry 

August 1995 

J. Murray 

Portland State University 

Portland, Oregon 

NREL Technical Monitor: A. Lewandowski 

Prepared under Subcontract No. XCK-5-15114-00 
This publication was reproduced from the best available copy 

Submitted by the subcontractor and received no editorial review at NREL

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Abstract 

This report gives the conclusions drawn hrn a study of the wtential application of hightemperature solar process heat for production of al-um. I have reviewed the most important 

thermal aspects of alternative alllminum process technologies as they have been published either 

in technical literature or in patents. This work is not, therefore, a true feasibility study of a new, 

solar- based alllminum process. Rather, it is a preliminary technical emmination and summary of 

the the- portions of the enormous number of processes studied ovp the last 120 years for the 

manufacture of aluminum, coupled with an examination of the natum and position of the 

aluminum industry in the US. today to detgmine whether a process based on the use of hightemperature solar process heat might be received with interest at this we. 

Many processes would be feasible with solar process heat. I basexi my recommendations 

for funher study on three criteria: 

the proposed process should have been substantially re-hed by one 

of the major American-based aluminum companies 

The use of solar process heat might solve technical or pr-ss problems 

previously encountered 

The use of high-temperature solar energy could be a critics component 

in the economic or technical success of the process. 

In addition, I looked for processes that might adapt easily to the use of high-temperature solar 

energy. In particular, in my experience, this meant: 

The process did not require tight temperature control for k success 

The process could be conducted at atmospheric pressure 

The process could be operated without a windowed receiver, that is it 

did not require extremely tight atmospheric control qither for the 

process itself or for the likely materials of construction 

High-temperature heat storage would not be necessary for process 

success. 24-hour operation would either not be absolutqly critical, or 

the process could be performed with two or more distinct steps, one of 

which could nm continuously if desired 

these criteria. I have recommended thrce processes as pasticularlv suitable for the use 

of high-temperam sol-rn energy as process heat. ~br one of thck, a cafb~bermic reduction 

process as described in Kibby's Reynolds Metals Company patents, *e thermal energy provided 

by highly-concentrated sunlight is the only process energy required. lior the other two processes, 

a reduction to an aluminum-silicon alloy as described in AlC08/DOE research publications and 

reduction to an AN intermediate compound, the product of the theadd portion of the process 

still requires some electric process energy for the production of alm$num metal. 
Table of Contents 

Abstract ....................................................................................................................................................... I 

lnucxiuction ........................................................................................................................................... 1 

Bac kgmund ............... u.. .......*................................................................................................................. 1 

The smcm of the three components of aluminum productionBauxite mining ....................................................................................... " ............................. ..... 1 

Bayer Process ..........*.......................... .................... ................. .. .............*.............*..*............. 1 

Hall-Hhult Pmess .................................................................... .,, ............................................ 1 

Energy Requirements for Primary Aluminum Production ........................................ .................................. 4 

SolKces of Power .......................................................................................................................... 4 

Aluminum Production: Background ................................ ,,. ..........*.....*............................,.*....*.........*....... 8 

Theory ........................................................................................................................................... 8 

Dit Reduction Aocesses ................... .. .... .. ...........,...... ........................................................ 8 

Practice ....................................................................................................................................... 1 

Why should the DOE and Aluminum Companies be Intemmd in an Alternative hcess? ...................... 13 

1) Capital costs related to volumetric productivity ............................ ... ............................... 13 

2) International competitiveness of aluminum industry determined by costs of production 

3) Hall-H&roult/Bayer processes rn mature technologies ......................................................... 14 

4) Development of a more environmentally friendly process .............................. .. ................. 17 

Unique Opportunities for Solar Energy ........................................... ....... ................................................ 17 

1) Solar Energy is a Unique Source of Process Heat .................. ....................................... 17 

2) The Solar Advantage: fixed cats ..... , ...........,...................*..........,...................................... 17 

3) Drastic Reduction of C02 Emissions . ., ......*.................., ........ , ............................... ........ 18 

Review of 

ReductiorJReaction 

the known ptocesses 

Dry 

for 

Processes 

duminum 

that 

production 

primarily ........... replace 

,. 

the 

.... 

Bayer ........ Fbccs to give A1203 

..... 2 

..... 20 

Alternative Ore -.End product A1203 ........................ ..-. .... ....... .............. ................... 20 

Chemical (wet) pr~cesses to replace the Bayez ~IOCXSS to give A1203 .......*................. ............ 22 

Alternative Processes-End product Aluminum or Aluminum AUoy , ......................................... 24 

Thermal proccss to form an intamediate. followed by elecmlysis ............................................ 27 

identifying Processes with the Best Potential for Solar Arocess Heat .......... , .......................................... 28 

Desirable feam for solar-thermochemid process ................................. .., ......................................... 30 

Conclusion ..,..........,..... .. ...... ... ........................................... .................. ......................................... 30 

Processes with wrcellent potential for high-temperature soh process heat ......*......., .............................. 30 

Aocess #1: Alcoa Al-Si alloy reduction process ., .............. , ....... ........... 30 

Process #2: Reynolds Carbothennal Reduction ................... ,. .............. .................................. 30 

Process #3: Carbothennal production of AN Intrrmedke ...... ........................ ....................... 31 

Appendix A: haviews with Process Managers and -has at Alcoa, IQbx and Reynolds .......... 32 

Alcoa .. , ............................. ........................... ~.......n~.........~.v..-.................................... 32 

Reynolds ......................... ..... ....., .. ..... .. ...n............ ............... " ..... ..... .............. ........... ................ 32 

H+ m-.H.....n .....-. ..n........mmH~..n.......nn....*.n.....no....n-*.n-..~.....nn.nnn........n.....*.... .*.*35 

Alunite Aocesses .,. n.~n-..-~~.n~~~n~n~~~n~-nu-n..un~.~~~~.n**..~.~en7.....r~~~....o.....u.....rr....... 35 

Melt-Quench process for Anoahosite ................................... ............................... ............. 36 

Acid hlOceSSeS ...... ..,.n,..m.....................-..- ~~..Hnn.U..W~~.~~C. ...r....w.o.o........ ..................... 36 

Processes that Replace the Hall-HQoult Process to malre Aluminum 

Direct Thd Processes for Aluminum Production .......................................................... 36 

Production of Al-Si AUoy ..., .......................................................................... 37 

Production of Intcnncdiatt Al-compound ......... ..,... .. ...... , ..................................... ............... 37 

4-CL PrOceSSeS .. .C.nm..HH ........... n...-....*n....*....****....n"..........* ~=~...........38 

Aluminum -cation Processes ., ................................. .. ......... ......... ........................................ 38 

Economic/Market factoIs ., ........................ .. .... .. ......,..... .. ........ , ...... ..1.1..1.q13-1 ................................ 38 

Patents ...................................................................... ............................................................................ 39 
ALN PrOceSS.. ............................................................................................................................... 39 

Carbotherrnic hxtxses .............................................................................................................. 40 

Reynolds Carbothermic Process .................................................................................. ..... ... ........ .40 

Alma Carbothermic Pmcess .... ......... " ...................... ........................ ............................................ 41 

Alma Electrolytic Refining Process ............................................................................. ........ 1 

Other Prcsws~ ............................... ., ............................................................................................ 41 

List of Figures and Tables 

Fig. 1 . Distribution of currently known reserves of bauxite worldwide ................., ....... ...................... 2 

Fig . 2 . Distribution of primary aluminum capacity for the big 3 producers in US ................................. 3 

Fig . 3 . Total final consumption of energy. elec&ity by industry in OECD nation$ ........................... -5 

Fig . 4 . The relative enerjgy contents for aluminum and other competing materials ................................ 6 

Fig 

Fig 

. 

. 5 

6 

. 

. Lacation Source of 

of 

electricity 

US . primary 

consumed 

aluminum 

by primary 

smelters 

aluminum 

.........

industry in OECD n+tim ...................... 7 

Fig . 7 . Theoreticat energy required to produce aluminum from alumina for Hall. ASP processes ......... 8 

Fig . 8a . Total energy to make metal hm sevd oxides ............................... .... ...... ., ............................... 9 

.Fig . 8b . Total energy to make intermediate compound Erom alumina; energy req- to electrolyze 

compound to form aluminum ......................... .. ............................... .. ......... .- ............,..*.*.......................... 9 

Fig . 9 . Theoretical energies for carbothermal reduction of Si02 and A1203 ....... ..., ............................... 10 

Fig . 10 . Themetical energies in kWg A1 to produce AI via three processes.. Hall. ASP and AIN ........ 11 

Fig . 11 . Flow of energy and matem for Bayer & Hall process ., ..,........,.... ... ..., .................... 12 

Fig . 12 . MarLct price for metals showing effect of its abundance and method for mction ................. 13 

Fig . 13 . Price of aluminum ingot in US market 1954-1991 ..... ..., .....,.......... .... .. ................................ 15 

Fig 14 . Alte~fonasofahuninmarcsuperimposedonsolar~uxmapofUS -.,, ..................... 16 

Fig 15 Processes that primarily replace the Bayer Process ,, ., u........,..~......... A.".......~,,............... 19 

Fig 16 Processes that result in production of aluminum or alloy .,.,., .............................................. 23 

Fig . 17 . System concept for solar process .. u~~~~~~~~~~~~~~~~~~~.larlar~"W~

Table 1 . Primary aluminum producers in the United States for 1993 ...*................. ,, .............. .,.......... 3 

Table 2 . Composition of aluminum ores .. ............................................................ + .............................. 15 

Table 3 . Summary of iargesde experiments and commacia1 carbothd pr* plants ............... 3 
Introduction 

The scope of this study was to review altemative aluminusl p-ss technologies and 

recommend those most suitable for the use of high-temperam solar energy as process heat. 

This work is not, therefore, a me feasibility study of a new alum@upl process. Rather, it is a 

preIiminary technical examination and summary of the thermal ti#ti~ns of the enonnous number 

of processes studied over the last 120 years for the manufacture of aluminum, coupled with an 

examination of the nature and position of the aluminum industry iq the U.S. today to determine 

whether a process based on the use of high-temperature solar prooess heat might be received with 

interest at this time. I expected that a positive finding would resul! in a short list of suitable 

candidate processes, and I included exploratory contacts with the *or aluminum companies to 

assess their interest in alternative processes. Finally, where the net& for further research to 

adapt a process to concenbrated solar energy process heat were clw to me, I provide a 

recommended course of action for further technical research. 

To achieve these goals, there were thne questions that neded to be answered: 

1) Why should the aluminum industry be interested in an 

why might they also consider an alternative 

2) Why should the Department of Energy (and 

aluminum process based on high-temperature solar ene 

makers) be interested in supporting the development of ah alternative 

3) What is the nahue of highly concentrated for process heat 

and what makes a process a candidate for solar process heat? 

Background 

The structure of the three components of aluminum productio -Bauxite mining; Bauxite 

to alumina (Bayer Process) and Alumina to aluminum (Hall-H R ult Process) 

aluminum is the most common m 

today relies bauxite, a form of its 

world's reserves are located in the four 

serves were 
major aluminum consuming nations dominate with about 70% of primary aluminum production 

located in the U.S., Canada, Europe and Japan. Although the various production stages are 

technologically and geographically distinct, they are often linked by vertical integration, as all of 

the major aluminum companies, for example, own bauxite mines, alurmina processing and 

aluminum smelting facilities (Peck, 1988). Joint ventures have been the next most favored 

alternative to within-firm ownership, and long-term contracts the last altemativ (Barham, 1994). 

Percent World Bauxite Production 

Fig. 1. Currently known world reserves of bauxite. The four major banxite nations, Guinea, Ausealia, Brazil. 

and Jamaica hold 68% of the bauxite resems. 

The aluminum industry is highly concentrated and vertically integrated. As of 1960, six 

fms accounted for most of the world's aluminum @uction (althqugh there were 20 other 

producers). The big six were Alcoa(U.S.), Alcan(Canada), Kaiser qlltminum and Chemical 

Company (U.S.), Pechiney(France), Reynolds Metals Company (U.S .), Schweizerische 

Aluminium AG (Alusuisse; Switzerland). These six companies owped or controlled 45% of the 

western world's bauxite, 625% of its alumina production and 52.5% qf the primary album 

production. The tendency from the 1960s through the 80's has been away from the 

concentration of the first stage (mining/alnmina/aluxninurn) with incheased involvement by the 

companies in later phases of aluminum transformations. 

As new producers have entenxi the market, the number of alpmhum producers has 

increased from 26 in 1960 to 71 in 1981. Siace then, paRidy as the enormous production 

capacity of the emerging nations of the fonm Soviet Union have b@n felt in the aluminum 

market, the market share for the big six has declined furtherThere are 10 primary aluminum producers in the US.; Al Jleynolds, Kaiser, Alumax, 

Noranda, Ormet, International Light Metals Canporation, TST Inc. % CO. Alcan and National 

South&, table 1. The three largest, historically Alcoa, Reynolds vfi Kaiser, have always held 

an oligopolistic position in the aluminum industry. In 1960 the big were responsib1e for 

around 87% of total U.S. capacity; cmntly this market share is do- to about 60%, as shown in 

fig. Z.(Kennedy, 1985) All three are vertically integrated from the €bauxite mining stage through 

to the final fabricated product. All have major foreign holdings. 
Energy Requirements for Primary Aluminum Production 

The primary aluminum industry is one of the most energy-intensive industrial sectors 

worldwide, fig. 3. Most of the energy consumed by the aluminum industry is required for the 

smelting stage, and is used in the form of electricity for the electrolysis of alumina. The energy 

required to make aluminum is compared to that requhd for other competing materials in fig. 4. 

Production of aluminum accounts for around 4% of total electricity production for the 

Organization for Economic Cooperation and Development (OECD) countries,~ and is higher for 

some countries. In Norway, for example, aluminum production consumes 16%, and in Iceland it 

consumes 44% of the national electricity produced (OECD, 1983). 

Sources of Power 

Aluminum smelting facilities in the US are located near relatively cheap and abundant 

sources of electric power, fig. 5. About 35% of US capacity is located in the Pacific Northwest, 

in the Bomede Power Administration's (BPA) senrice area and 14% in the Tennessee Valley 

Authority's (TVA) area because of Federal hydropower. The remaining half of US capacity is 

supplied by about 20 different power organizations. The two largest are the New York-State 

Power Authority and the Big Rivers Electric Corporation in Kentucky. Smelters are found in the 

Ohio Valley because of cheap coal resources, and mund the Gulf coast because of access to 

cheap natural gas and proximity to the Southern b%UXite regions. Both areas afford access to 

cheap transportation. The other area of concentration, New York state, offers cheap hydropower 

from Niagara Falls. 

Historically, the aluminum companies have controlled the profitability of aluminum by 

shifting their production to nations and smelters with the cheapest, most seem power or other 

favorable arrangements. In the U.S., Alcan recently acquired a smelur; Pechiney and Alusuisse 

sold its interests in U.S. smelting facilities. In Western Europe, all six own smelters. In 

Australia the big six account for most of the smel~g capacity through joint ownership with local 

interests. In Brazil both Alcoa and Alcan own smelters. Alcan was dominant in Canada until 

1980, owning all but one of the smelters, but since 1980 all of the big six have plans to build 

smelting capacity in Canada. 

Hydropower is thc most important source of cheap electricity for the aluminum industry. 

Figure 6 shows that in 198 1, about 52.6% of the power consumed by the primary aluminum 

industry in the Western world came hm hydropower. Coal-generated elecaicity contributed 

another 27.5%. nuclear-generated power about 6%. and oil and gas represented about 6.8 and 7.2 

percents, respectively. When OECD and non-OECD nations are considered separately, however, 

the energy sources an quite different. Non-OECD nations relied much more heavily on 

hydropower with nearly 73% of the elecfricity consumed coming from this resome. Canada has 

been extremely successful in attracting new smelter construction, and as seen in fig. 6, the entire 

industry in Canada relies on hydropower. In In98 1, coal supplied about 30.5% of the electricity 

to OECD smelters, a result mainly of the U.S. situation. 



Aluminum Production: Background 

Theory 

The direct production of metals by reduction of their oxides an high-temperature, 

energy-intensive processes. The total amount of energy required is the enthalpy change for the 

reaction & Of this total, as shown in fig. 7, an amount equal to the Gibbs fiee energy change of 

the reaction AG may have to be supplied as high-quality enagy, for example, in the form of 

electrical work or by introducing a reducing agent. Thc remainder, &-&, may be supplied t relatively inexpensively as process heat Where electrical work is required, it must typically be 

obtained from a high-temperam thermal reservoir created by the combustion of fuels, however 

the efficiency of such conversion is restricted by Camot law. It is, therefore, thermodynamically 

wasteful to use electrical energy, or the equivalent Gibbs free energy of a reducing agent, in 

excess of what is required by AG of the reaction in order to compensate for the additional process 

heat needed. Frequently that is the case in many commercial electrolytic processes and reducing 

furnaces with the result that the energy cost is a substantial portion of the value of the final 

product. 

Research efforts to find a direct thermal method for making aluminum from its ore or 

from alumina are as old as the industry itself. Though some technical success has been achieved, 

- generally processes have failed economically because they required very high temperature 

process heat that could only be supplied electrically. 

Total Process Energ Aluminum vaporizes 1 o.sA&-AI + 1.4 \ 

Chloride Electrolysis Cell 

4 

I I I Reduction wlh C to CO, 

Temperature ("C) 

Fig. 7. Theoretical energy required to produce aluminum fhm alumina The typs of energy required over the 

temperature range at which the Hall-&ult cell apaa~es are. fmm cheapest to most expensive: 

Energy form Hall-H&oult Cost 

thamalcnergy = 259boftotal 1 

Chemical reduction energy (C) = 35% of total 4 

Izleamlysis~ = 409boftotal 16 

Direct Reduction Processes 

Several difficulties arc encoun& in the attempt to design a single thermal process to 

make aluminum along the lines of a arbthermal blast-fumact pmxss used for other metals. 

Compared to other metal oxides A1203 is vay stable. The temperature required for its reduction 

with carbon would be in the range 2000-2200 OC. The energy requid for any process to make 

one g-mole of metal hxn its oxide is shown in fig. 8a. The energy required to make aluminum 

is nearly the highest shown at around 200 kcaVgmole. This fact alone does not prevent the 

development of a successful process% dmthexmal process to make silicon exists, requiring - more energy than aluminum. There is no way to decxease this amount of energy; the only option 
the process designer has is to attempt to find a series of steps that might apportion the energy economically among the available sources: thermal, chemical or electrical. 

There arc three main problems that must be addressed beforc a direct reduction process 

will be commercially viable. The first is that the temperature at which appreciable reduction of 

A1203 occurs is also very near the temperature at which the metal is a vapor, and significant 

losses of A1 would be expected in the vapor phase as the suboxide A120(g), or as Al(g). This is 

not an insurmountable problem, as shown by the success of the Imperial Smelting Roccss, where 

zinc is recovered as a vapor. The problem of metal loss in the form of a volatile intermediate has 

been solved in the co~~ally successful carbothennal process to make Si from its oxide. 

Even higher losses of Si metal appearing as SiO are predicted, but Si metal is commercially 

produced in a submerged-arc carbotherma1 process. The main obstacle to developing a viable 

thermal reduction process for aluminum seems to be that the Al-C-0 system at high temperatures 

forms a partly liquid-partly solid oxide- and carbide-containing mlt with little or no aluminum 

recovered. This presents a major technical challenge in the design of a reactor/fumace to 

augment the production of Al, and creative attempts to solve these dficulties appear in, for 

example, the patents awarded to Kibby et al. The third problem that must be solved is that A4C3 

is soluble in the metal at the temperatures at which the reduction occurs in amounts roughly 

equal to 20-37% A4C3 by weight, producing a liquid product that is to pour. Since one 

of the main goals of any successful direct reduction process is to recover duminum in a 

substantially pure state, this level of contamination with the carbide represents aeajor 

diseconomy for the process. 

Fig. 8, The left-hand graph shows thc total energy each of the metals Al, Fe, Mg, Pb, Si, Ti and Zn require to 

win one g-atom of metal hn the respective oxides. The right-hand graph shows tfic strategy that might 

be used in cunsideting a process design to form an intermediate compound from the oxide Al203. The 

distance from the candidate intermediate to is a measme of the total amount of en- that must 

be expended to fonn that intermediate. 'Zht dhncc fmm the intumanintr. to A1 is a measure of the 

energy that must be expended to win the metal bin the intmmdhte. One can aee that it would take a 

good deal of themd energy to fbrm AlN from &%, but comparatively little electrical energy to 

eftctrolyzt the AlN to A1 and N2. (A.h adapted hm Cochmu, 1987, data from JANAF tables) 

A combustion-heated coke-fired process would produce about 18 tons of CO per ton Al 

produced. This causes sevd difficulties. Alma found, in an experimental program to make an 

Al-Si alloy by direct reduction of AbO3-Si@ containing ores, that this large flow of reducing 

gas effectively prevented the formation of metal in the combustion-heated blast furnace. Volatile 

SiO and A120 species carried off the A1 and Si at the elevated temperatures fiom the rcaction 

zone, then caused severe reactor problems by condensing and "bridging" the reactor outlet. 
Because of the large mounts of CO produced by this process, to be economic it would have to 

be considcnd as a CO or H2 cogenmating process. Furthermore, any impurities present in the Csource appear in the metal or alloy metals produced. In some processes, this dictates the use of 

petroleum coke for a pure C source, and further hum the economy of 'the process. These rn all 

problem that a solar heated process might solve, since the process could be conducted with the 

stoichiomeaic required mounts of C, or with as the reducing agent. Bureau of Mines 

researchers found that wood waste was catalytic in some csses as a carbon source for A-Si alloy 

production; a solar heated process would require far less wood waste than a combustion heated 

process, so this may be a feasible alternative to pure coke. 

Fig9 shows the energy required to make A1 from A1203 via the theoretical equation 4 CI a 

1 

'Z A1203 +; C -> A1 + CO; AM @ -200O0C.; and compares it to the same process for the 

production of Si. The Al-producing reaction does not proceed in this way; most likely carbides 

and oxycarbides are formed which then are reduced to the metal, but even if this were an 

accurate picture of how the Al might be produced, it is clear from fig. 9 that the reaction will not 

proceed using thermal energy alone until temperatures well above 20OO0C. These art the process 

temperatures used in the experimental, wke-fired blast furnace research in Japan, and proposed 

in Kibby's patents. 

are 

for 

1 atm 

0 500 1000 1500 U)OO 2500 3000 

Temperature (OC) 

Fig. 9. Thdcal energies in kwh per kg metal produced that are quired to convert A1203 to A1 and Si@ to 

Si far a carbothenaal process with CO as the product gas. The figure illusttatcS two points. First, that 

thae is no relationship between the temperatun required for a process and the energy. Si may be 

produced at about 17509C. whae A1 requires process temperatures of about 2000°C. The &tion of 

Si02 requires mart energy than the ~~ of At203 to Al metal. kamd, Si wporkm at a very high 

temperatme while A1 is vay Wy to be preseilt as a vapar at the tmpmbm re~uiFed fa the thermal 

duction 'Ihere is a succegsful commercial carbothermic process for Si productioq as yet. none 

has been implunented for A1 though it is ttrecretically possible. 

One strategy might be to form an in- compound using thermal energy, then 

electrolyze or chemically reduce that intermediate. This is the appmach that most of the 

alternative processes use. Figure 8b shows how one might choose among possible compounds. 

The distance hm A1203 to the intEnncdiate compound is thc total energy that must be supplied 

to form the compound, and the closer the wmpound is to Al the less energy that must be 

expended to electrolyze the wmpound to produce the metal. The Hall-HWt process uses a 

combination of e1ectrical and chemical to reduce A1203 to Al. If an intemediate such as ALN 

could be formed thermally, then far less e1ectrical energy would be required to win the metal 
than currently used in the Hall-Hhult process. Figure 10, taken from Cochran's paper, shows 

how thne processes, the Alma chloride process, the Hall-Hhult, and a potential AlN 

electrolysis process apportion the energy. 

Another strategy is to use thermal energy to produce an alloy of aluminum, then remove 

the aluminum from the alloy using a thed process, chemical process or electrolytic process. 

Examples of all three of these approaches are discussed in the technology review section. 

Exothermic 

CPrbo- 3.1, 

Alcoa 

Smelting 

Process 

Preparation 

J-JalCHeroult and 

Process Electrolysis 

of AIN 

During 

Cerbonitridation of 

Alumina 

Fig. 10. Theoretical energies in kWh/kg Al required to convert A1203 to Al fm three pmcases: the Alcoa 

chloride process, The Hall-HWt proctss and a new process that might preqare AN ClLfbOthennaUy for 

eleclrolysis to Al and N2. (Cochran. 1987) 

Practice 

The production of aluminum from its ore at present relies on two processes developed in 

the late 1 800's.: the Bayer process which produces pure alumina from bauxite ore, and the HallHeroult process which produces aluminum hm alumina. The Bayer process uses about a 

quarter of the total energy requirement. Most of this energy is thennal. The cost of the Bayer 

process represents about 27% of the cost of aluminum production. T'he Hall-Hhult process 

uses about three quarters of the total energy. Most of this energy is electrical energy. The cost 

of the Hall-Hhult process represents between 20 and 40% of the cost of aluminum production 

for US. manufacturers (Cochran, 1987). 

The Hall-Hhult process dominates the technology of producing aluminum. It is 

primarily an electrolytic process in which pure alumina (Alfl3) dissolved in cryolite, a double 

fluoride of aluminum and sodium Na3AlF6, is reduced electrically and chemically at about 

960°C. The electric power is supplied through carbon elecaodes which extend into the molten 

salts bath, and the carbon in the e1ectzlOdes also scrves to reduce the wj. Electric power is 

thus saved at the expense of carbon consumption, with the disadvantage that any impurities in 

the electrode carbon will show up in the final d. This adds expense since the consumable 

electrodes must be made of vay pure carbon. 

Figuns 7 and 9 illustrate the theoretical energy required to produce aluminum from 

alumina as a function of temperature. The amount of energy represented at the vertical line 

labeled Hall-Hhult at 960°C has three segments. The energy supplied from the carbon 

reducing electrodes that form C02 at the temperature at which the cell is operated, is shown at 

around 3.1 kWh/kg Al. Theoretically, around 3.5 kwg A1 should be supplied electrically, and 
the nmainder, about 2.1 kWh/kg A1 could then come from thermal sources. Unfortunately, 

modem Hall-Hhult cells are still so inefficient (about 40-45% based on the theoretical) that all 

of this energy is added from the electxic sounx. The thermal energy generated through this 

inefficiency must be removed from the cell, and this need to remove energy actually limits the 

ability to gain an economy of scale since it limits the size of the cell that may be used 

(conversation with Cochran). 

Fig. 11. Now of energy and materials required for the Bayex and Hall-Mt processes. 'he amount of 

elec&al energy required can be as high as 17,400 kWh/hct& ton fm an older plant.. The approximate 

amounts of energy for each stage are given in figure. The energy remaining is used in casting the 

aluminum ingots; the final stage of aluminum production. 

The Hall-Hhult process also relies on a starting feed of pure alumina, the majority of 

which is produced hm bauxite by the Bayer process. Typical energy requirements per metric 

ton of aluminum are shown in fig. 11 (OECD, 1976). It is important to distinguish between 

thermal and electric forms of energy since the costs of c1ectrical energy are about sixteen times 

greater than the costs for a combustion-heated thermal process (Aggarwal and Sinek). 
Why should the DOE and Aluminum Companies be Interested in an Alternative 

Process? 

1) Capital costs are related to volumetric productivity: Hdl-H&odt is very low 

According to Cochran, metals produced by thermal processes have the lowest market 

price. The market for aluminum in the past has expanded by replacing the use of other metals 

(and materials) when the cost of alllminum has decreased due to technoIogicaI improvements to 

the process. The volume productivity of a process has the strongest effcct on capital and labor 

requirements, the two leading cost sectors for the primary alllminum indusby. Because the HallHtroult cell only produces aluminum on the planar surface of the cathode its productivity is 

about 0.0014 volume aluminum per hour per unit cell volume. This is only about 10% of the 

productivity of a blast furnace, where the metal is produced in a three-dimensional zone of the 

reactor. The 14-bipolar chloride cell of the Alma Smelting Process (ASP), at 0.004 volume 

aluminum per hour per unit cell volume, was an improvement, but it introduced other cost factors 

that finally made it uneconomic. The process complexity and process stream volume are two 

other strong influences on capital costs. Roccsses like the ASP that require gas-phase streams or 

liquid solutions entail large increases in the process stream volume.(Cochran, 

2) International competitiveness of aluminum industry determined by costs of production: Hall-H&ouIt based industry is dependent on availability of cheap, plentiful electricityElectrolytic processes are inherently more expensive than thermal 

Next to a metal's abundance in the earth's crust, the most important factor in determining 

price is the method of production used Metals that are produced thcfmaily have the lowest 

price, and this inmascs by a factor of between 4 and 23 for metals that must be electrolytically 

produced, as seen in fig. 12 taken hm Cochran's paper(Cochran, 1987). 

Fig. 12. Market price for metals showing tht tffccts on price of the average abundance of the metal in the earth's 

crust and the methods used for produci it. 

The main motivation for continued interest in an altcmative process is that the 

international competitiveness of thc US. altlminum indus6y is determined by the costs of 

production; for the Hall-Hhlt proctss these are dominated by the costs of energy. Advantage 

in the aluminum industry is ovuwhclmingly determined by access to cheap power. It is not only 

the present cost that is hpr&ht, however, but the assessment of future variability in the cost of 

electric power. The U.S., with i diverse and dexxntralized policy and regulation of electric 

price, and varied ownemhip of tItctric genaathg capacity is pcrccived as entailing a higher risk 

than countries with public ownership. 

The U.S. after the oil price shocks of the 70's has lost competitiveness in the international 

arena for construction of new smeltas, with such activity moving to Aus- Brad and 
Canada. The last new smelter in the US was constructed in the 1960's (Peck, 1988). Merton 

Peck, economist at Yale University, in his book "The World Aluminum Industry in a Changing 

Energy Era" suggests that the U.S. industry is most likely also in the process of losing 

competitiveness for the operation of existing smelters due to high energy costs. In the case of 

hydropower in the Pacific Northwest, this is dependent both on natural availability, demand from 

other customers, and public policy decisions that fix the price aluminum smelters pay for power. 

Peck notes: 

"Aluminum smelting is a capital-intensive production process. Consequently, 

there is a significant difference between two definitions of costs: unit operating 

costs and total unit costs. Unit operating costs are the costs that can be avoided by 

not operating the smelter. In order of general importance, the principal 

components of aluminum smelter operating costs are alumina, electricity, labor, 

and other raw materials. Total unit wsts include capital wsts, as well as items 

like property taxes and insurance, which apply whether the smelter owes or 

not. 

Operating costs are the costs Primary producers consider when deciding 

whether or not to operate a smelter. A simple statement of a producer's decision 

criterion is that a smelter is operated if its unit operating costs are equal to or less 

than the current price for aluminum, Unless that condition is met the firm can 

reduce its losses by closing the smelter. It is often profitable for a firm to operate 

a smelter even though the price of alluninum is less than the total unit cost (the 

smelter in that instance operates at a loss by conventional accounting standards). 

This situation arises because, as noted above, the total unit cost includes costs that 

are incd whether the smelter operates or not. Hence the loss would be even 

greater if the smelter were not operated. Because aluminum smelting is a capitalintensive process, the gap between unit opaating and total unit costs is 

substantial ...... 

Smelters with very high unit operating costs are called swing capacity smeltem 

and are usually operated only when prices are high. 

3) Hall-H6roultlBayer pt'ocesses are mature technologies; opportunity for cost savings are 

incremental only 

The wsts and energy usage figures for the present processes, taken with the fact that the 

Bayer/Hall-HQoult process is a mature technology that is most likely approaching a real lower 

limit in costs and process improvements, provide much of the motivation in the starch for an 

alternate smelting process. Further motivation comes from the intense competition both within 

the worldwide aluminum industry and new competition with emerging, lower-cost materials. 

(Cochran, 1987). Figure 13 gives the pi= per pound for .aluminum sold in the US markett 

This plot illustrates sevd points. The cost of aluminum ingot on the world market has 

fluctuated by a factor of two cven when cumsidered in terms of constant dollars ova the period 

1954-1991. This fluctuation has forced the closing of many aluminum smelters, cven in the 

Pacific Northwest where the costs of electricity are especially low. A steady decrease in the rcal 

cost of duminum is also appmnt during the *war years as the process was made ever more 

efficient. 

Figure 13 also shows one of the challenges that any new aluminum process must meetnot only must it compete with the Hall-Hhult process, but it must be emnomic enough through 

the lows in the aluminum market to pay off investment costs in new facilities. Cochran 

estimates this would mean that the costs for any new prwess would have to be almost half of the 

t 1 have adjusted the prices to 1991 values using tht Msrshpn and Swift iada. published monthly in Chemical 

Engineering. Ovtr the years this index has worked better than other more ged indices such as the 81 or CEs 

index to adjust dollar values for the Chemical and Process Indusiry. 
average Bayer-Hall-Hhdt process to allow profitable operation through the lows in the price 

cycle for altltninum (Cochran, 1987). Cochran points out that there is no single cost factor in the 

cumnt process that amounts to the required reduction, so any new process will have to 

significantly nduce several cost fa~torsimultaneously. For this reason, and also because the 

energy costs in the Hall-HQoult process are equal to the Baytr production costs, I have widened 

- - the scope of my study to include dternative processes that (perhaps preferentially) begin with the 

aluminum ore and end with the metal The added advantage, should such a process be feasible, 

is that the U.S. is relatively poor in bauxite and quite rich in other duminum-containhg ores 

such as kaolin clays, anorthosite, laterites and others. The chemical composition and mass .? percentage of W3 contaioed in some of the prospective alumina sources are shown in table 2. 

Fip 14 shows the known deposits in the U.S. of these forms of aluminum orc superimposed 

on a map giving the yearly average kt solar insolation. 

Fig. 13. Price of aluminum ingot in the US market fm the years 1954-1991 cJrpcssed as 1991s. Data horn 

Metals Week and Chemical Engineering. lhe values br 1954-1990 bavc been adjusted m 19915 using 

the Msrshall and Swift index far these years (Chanical Fmginecring, various -4 issues). 

Bauxite 

*I.% I 

Boehmite 

Oisspore 

I GWte 

Ksolin day 

Anorthosle 

Albite 

Anorthite 

Coal fly ash 

Coal Waste/Sha&s 

~lunite 

Table 2. Composition of oPha aluminumataining ares on a mass perpent basis. 

4) Development of a more environmentally friendly process 

Among environmental ngulations watched closely by the aluminum industry, the . growing concern about global warming involves the industry on two of its emissions; C02 and 

plyfluorinated carbon compounds. a is released Wtly from the electrolysis process, and 

from the fossil-fuel electricity generating stations supplying electricity fos the Hall-Hhult 

process. When the oombustion of the consumable anodes alone is cons&md, the manufacture - of aluminum releases 22 kg of C!@ per kg aluminum. The residence times of the CF4 and C2F6 

emitted are estimated to be of the order of 10 rnillenia, resulting in an eqMvalent global warming 

equivalent to 15-20 kg C@ per kg aluminum. T The possibility of a gend carbon tax on C@ emissions could have the most serious 

impact, increasing the cost of aluminum production by about $100 per metric tm(Morton, 1992) 

Regulation of emissions of fluoride compounds hm the Hall-Hhoult proctss are incorporated 

in the new provisions of the Clem Air Act, and the possibility of elimina~g them is one strong 

motivation behind the search for inert electrode materials. This is a goal strongly supported by 

DOE restarch at all three major aluminum co~npanies. The development of viable inert cathodes 

would represent only a partial reduction in CR emissions over what might be possible with a - non-HaU-H6rou1t-based process. 

Although the aluminum indusw worldwide relies on hydropowerI for most of its process 

electricity, there is evidence that this pattem may be changing. As the costs and availability of 

hydropower have fluctuated, mare smelters in the Pacific Nonhwest arc Wg toward naturalgas generated electricity supplied by pipelines from Canada. New Smelm have been 

constructed in the Middle East, a location that offers cheap and abundant patural gas. Policy 

experts within the Northern Power Planning Council with whom I have *ken pointed out that 

all of the good hydropower sites in the Pacific Northwest have been used, and thcn exists a d 

possibility that some older dams may not be relicensed 

Unique Opportunities for Solar Energy 

1) Solar Energy is a Unique Source of Process Heat 

Highly concentrated sunlight is capable of supplying proccss heat dor chemical reactions 

at vesy high temperam. On an industxial Scale, thermal energy at tern- up to about 

1500 K have been generated for direct use in gas turbines. A p~liminary/sct of calculations 

indicates that the size of a solar facility for aluminum processing would & within tbe range of 

- sizes already built or analyzed far electric genating facilities. Pitman d Vant-Hull, for 

example, analyzed the performance of a two-aperture receiver receivin&crgy fmm a field of 

heliostats. Temperatures predicted in their dl are in the range ncededlfor aluminum 

- reduction. Higher temperatllns (and less amgy) are routinely produced fa expaimtntal work, 

and we feel 

2) The Soh Advantage: fixed ax&; steady supply 

As mentioned in the section on why industry should be interested in an alternative 

process, it is not only the high cost of electricity that is making the its international 

competitiveness. Risk is imposed by fluctuating costs and fear of 

use of solar energy as process heat may well have an advantage. 

concentrating facility for electricity generation is fiquently not competitipe with other fucl 

sources of energy because it entails such a large initial capital wst. This may be thought of by 
considering the costs for a coal generating plant if it was forced to buy; all of the coal it would 

consume in its lifetime. This capital cost may not be as important a fagor when considered 

alongside the advantage an aluminum company would derive from kn wing that the energy for 

its process would be constant, basically covered in the amortization of, e plant capital costs. 

3) Drastic Reduction of COz Emissions 

L 

Use of high-temperature solar process heat will drastically redqcc C0.L emissions from 

the aluminum industry, with the release tied only to tht stoichiomeaic pount of carbon naeded 

for the process rather than being tied to either the fuel usad to genaattielectricity (*as in the case 

of natural-gas or coal generated electricity) or to the C02 reld in @e Hall-Hhult process. 

The gas product frmn the process will be CO rather than a; if desire& a water-gas shift reactor 

could recover H2 from the process. I 

Review of the known processes for aluminum p~oduction 

Many of the processes proposed to replace the Baycr process ha(vc been implemented to 

the pilot-scale level. During WWII, the Bureau of Mines supported a ~bmber of nscarch 

projects around the country in a national defense effort to find and devglop domestic, nonbauxite sources for alllminum ore. A mini-plant was operated through the 50's at least in 

Laramie Wyoming to gain operating experience with the most promisqg of these processes. The 

research literature extends will back into the mid- l8O0's, when the maiq challenge seemed to be 

the difficult problem of removing the silica without losing alumina in tlic various ons. Key infomation on the thermal portions of these processes has been sumr&kd in fig. 15. 

Alternative Ore Processes-End product Alto3 

In many processes, an initial step in ore preparation is a relatively high-temperature 

(900°C) roasting of the ore to change its handling pmpgties. This is edpecidy important in 

processes that use clays, but an initial thd step may also be used to iincrease the solubility of 

the alumina and perhaps decrease that of the impurities for acid proces es, or to pre-reduce some 

of the impurities, especially the silica. Most processes end with a cala&tion step C8tZied out at 

1000-1200°C to drive off the water bound to the alumina and form of 

afumina One other very interesting 

soluble fonn was to melt the ore at temperatures near 

into water, onto steel plates or blowing it into fibers 

1967). These steps appear a be 

high-temperature solar process heat. Other 

require lower-temperature process heat easily supplied from a solar-heqted standard transfa fluid 

such as high-pressure steam. I have not covered the details of the chen+istry of the wet portions 

of these processes, nor have I given a complete description of the high-pmperature portions of 

most of them. Excellent chemical reviews appear in Edwards (Edw-, 1930). Pearson 

(Pearson, 1955), and any handbook on Inorganic Chemistry. This fi* is mostly useful as a 

tool in organizing and presenting the processes I discuss, but is no 

chemical process flowsheet. The temperatures I have given are 

guessing on my part, since chemistry reviews don't seem to be 

infomation, and some of it comes from patents that are so old 

temperatures are approximate at best. I have noted important 

might add value where they are known to me; conversely, I 

that are negative products. 

In the summary presented here I have separated the alumina ex 

types. The strategy of the "chemical methods" attempt to extract the 

solution, aiming to form a pure aluminum salt solution whilc leaving 

insoluble. Their thermal requirements are typically Ae 

high-temperature ore pre-treatment step, and end with 

step, but the main challenges are in the cos 

chemical steps involved. The "dry processes" 

reduce the impurities to a metallic state, 

are typically carried out almost entiFcly at 

have been developed for many, an electric 

ReductionllReaction Dry hocesses that primarily replace the Bay Recess to give AN3 T 

Sinter-leaching processes 

Alumina may be extracted from morthosite, clays and coal w tes via lime and lime-soda 

sintcr processes These are high-tempcram dry processes that rely o the reaction of the 

alumina with lime and or sods to produce soluble sodium or calcium dates. Cement is a 

co-product, and is important in rnaldng these processes competitive. S veral alllminum 

companies expedmented with and abandoned versions of this process !IL ly in the century; Alcoa 

ran a commercial pht in Badin, N.C. from 1925-1928, later opening 4 plant in Mda, Canada. 
The U.S. Burcau of Mines researched sinter processes to extract alumina from non-bauxitic ores 

starting from WWII and continuing at least into the 80's in a national prom to find domestic 7 sou- for aluminum manufacturc(Cservenyak, 1947; hdquist, 1963; Hem, 1969; Peters, 

1967; Eisele, 1979). Pdel efforts appeared in Canada(Archiba1d. 1944). Articles on he 

processes have appcarad moFc recently as interest in using coal waste and fly ash for alumina 

- manufacture has grown(padilla, 19828t1983; Goodboy, 1976). The eon between alumina 

and soda occurs at about 900°C, but the process is operated at higher te~~pcratures, up to about 

1300°C, to give a more easily handled product. The impmities in the ore also combine with the 

soda to form silicates, ferrates and titanates. Lime is generally added to minimhe soda loss to 7 these compounds. The process has generally been conducted in an electric furnace. 

Pedersen Process 

The Pedersen process has been in operation since 1928 at the Hflyanger plant of the 

Norsk Alllminium Co. Its original purpose was to produce a low-sulfur pig iron, but later the 

process was adapted to use the high-ironfiow-silica bauxite that came to Norway hm Greece 

and France. A mixtu~~ of bauxite, limestone with a low MgO content, coke and iron ore is 

smelted in an electric furnace at temperatures around 1300-140O0C. Alwa, in cooperation with - 

the US Bureau of Mines, developed a blast furnace for the process (Edwards, 1930). Pig iron 

and a calcium aluminate-calcium silicate slag are recovered, and the slag is leached in hot 

sodium carbonate-caustic solution to form soluble sodium aluminate and insoluble calcium 

carbonate. 

Alcoa "Dry Process" 

'Ilk process was originally investigated by IU, but he could not pdy the alumina well 

enough to use it in the electrolysis cells. Alcoa solved these problems, and optrated a 

commercial process for some years. A mixture of Fe and Si-containing bauxites, with a proper 

mixture of Si, Fe and Ti is dehydrated at probably around 1O0O0C. It is then smt1ted in an 

electric furnace with carbon to reduce all of the impurities and some of the alumina A layer of 

pure molten alumina forms which floats above a layer of molten Fe-Si-&Ti alloy. The top layer 

is poured off at about 25WC, and the alloy is tapped out on the side of the furnace. As the 

alumina is pod off it can be blown into small hollow spheres with a j t of supexheated steam 

or air. This step also helps oxidize any remaining k, remaiaing C aad k 'smlved carbides. To 

improve the purity of the alumina, an acid leach step may be added..(Edwads, 1930) 

Haglund Process 

The Haglund process is a modification of the Alma dry process. It has been in operation 

at Maghera, Italy fkom 1929-1936, and at the Vereinigte Aluminium w&e (VAW) plant in 

Lauta, Germany. The key modikation this process introduces is the 10$ming of the melting 

point of the ore by at least MO°C through the presence of sulfur. In this pnx:ess, iron sulfide 

(pyrite) is included with the bauxite and coke furnace charge. The rcsdg aluruina appears as 

corundum. The process could also be used a produce Al2S3 for a subs+pent dispmportionation 

reaction producing Al. 

Serpek A W Process 

One of the more interesting dry pcesses was patented and 

century primarily as a mute to atrnmonia With the developmnt of 

process became less economical and wd sccm~ to have ceased on 

an interesting process for a solar cycle if ammonia is also a desired 

is highly endothermic, is the production of aluminum nitride. This 

1600°C via a reaction between C, flowing N2 and the &03(Sohn, 

The leach step in NaOH produces NH3, which can also be produd by 

steam or water at about 60O0C. The final step is the calcination scp at 

A1203 (Pearson, 1955; Edwards, 1930; Scrpek patents; 1907-1917). 
Chemical (wet) processes to replace the Bayer process to give A1203 

- Kalunite process and ammonium sdfore process 

The Kalunite process, which relies on the c0-production of f- and sulfuric acid to 

make it economical, was commercialized in Marysville, Utah in the early 40's (?) and in the 70's 

in southwestern Utah (Walker, 1974; Fleischer, 1944). The process would be applicable to any - aluminous raw material that could be converted to potassium alum. Temms required in the 

process are moderate, ranging from about 60O0C for the initial dehydration to 1000°C for the 

final calcination. 1 The ammonium sulfate process is similar thermally to the Kalunite process, with a ht 

step at 45M50°C and a final calcination step at 1000-12OO0C(St.CIair, 1944). 

Acid Processes and the H+ process 7 - The main thamal dkd for each of these processes appears a in the fmal 

calcination step, canied out at temperatures around 1000°C The H+ commercial in 

France by the Pechiney company(Michelct, 1979). Investigations 

country were performed under the Bmu of Mines, beginning 

fmd domestic sources for 

details and variants of such processes; I have 

have also been published(Nunn, 1979; Pew, 1967; 

12oO0C. 

-- feedstock for the process, a pre treatment step 

that occur with the 

carried out at temperatures from 

r f 

Alternative Processes-End product Aluminum or Aluminum Alloy 

-+ Key thermal aspects of alternative processes that begin either wi* alumina or a form of 

ore and end with pure aluminum or an aluminum alloy arc summarized in fig. 16. 

Direct Thermal Processes to produce Alm'luult 

- From my literature survey and talks with researchers at Alcoa, Reynolds and Kaiser, it 

seems that the major aluminum companies that were working on research into direct reduction 

thennd processes to make aluminum in a conventional electric smelting a combustion-heated 

furnace have gradually abandoned the idea. More details arc given in Appendix A. Their work 

- l has turned now to investigations of a process that might take place in a molten carbideoxycarbide mixture, or to the production of an intermediate compound, or to the production of an 

aluminum alloy that could be further refined to the needed purity. The best reviews of early r--. carbothermal processes were written by P.T. Stroup (1964), Pearson (1955) and Edwards (1930). 

At the end of the 1950's and beginning of the 1960's there was renewed research into 

carbothennal routes to aluminum. The reactors and processes proposed were electrothermal, 

though Alcoa has a patent that shows a conceptual process heated by a nuclear reactor (Cochran, 3 1976). Four aluminum companies (Alcoa, Alcan, Pechiney-Ugine and Reynolds) and Japan did 

large-scale testing. 

- Alcoa, direct reduction to duminzun 

In the SO'S, Alma was awded a patent for a direct method of pmducing dlminum in an 

electric furnace (Miller, 1958; Moafeldt, 1989). Details of the proccss, such as the wnfguration 

of the rcactor, are not given, but the temperatures appear to have been in the range 1900- 

-- 210°C. A carbon-containing molten aluminum phase floated above a molten oxycarbide layer, 

but on cooling the carbon deposited as &C3. This could be separated + the molten 

aluminum with a fluxing agent (chlorine or aluminum chloride), and tk metal was equal in 

1 

quality to electrolytically produced alrlminwn DBiculties would be expected in separating the 

fluxing agent for ncycle 

Reynolds, & Alcan: multi-stage reduction to aluminum 

- 

- 

T--T 

-- 

--- 

t 

patents spacify a pulsed or moving arc to limit the v 

Direct Rcmcaion of Ore to produce an AM-Fc-Ti-Mn dby 

It is possible to carbothumically rtduce the arc to product an dbum aUoy. The 

strategy of the pnxxsses that produce an alloy of aluminum is to d- the amount of 

aluminum lost as a vapor by alloying it with another met& then to sepdate it later by a refining 
step. Thae are a number of thermal processes that were used on a co-ercial scale early in the 

history of the aluminum industry. Table 3 surmnarizes the direct ndu n processes that result 

in an alloy of aluminum that had been researched up to about 1961 a 

and amended by Motzfeldt (1989). Some of these may have merit now, specially if many of the 

technical difficulties that made them uneconomical have been solved. I ve not had time to 

evaluate them in the detail required. My review section here focuses rnp on the processes 

researched in the later years (40's-80's). I am also very intrigued by wesses that wexe 

implemented by Gennany during WW& many were technologically innpvative though not 

comxtitive with the conventional tmcesses. Maw were develd to 8 commercial scale in 

 post'^^ and WWII Germany bkause the econolhics weren't t6e dacibg factor. 

Cowany Locat ion Starting A~Y I Maximum 

Year produdion 

Cowles Lockport, NY 1886 15 AI-85 Cu 150 kg AVday 

Cowles Mltton, England 1886 15 Al-85 Cu 100 kg AUday 

ALCOA Badin, NC 1924 35 AI-65 Cu 500 towyear 

ALCOA Badin, NC 1928 30 AI-70 Si 1000 ton total 

Metallgesellschaft Honem, Germany 1 926 60 AI-40 Si 

VAW Lauta, Germany 1936 Converted to Si 

VAW Pocking, Germany 1942 60 AI-40 Si 

Bureau of Mines Albany, OR 1951 40 AI-60 Si 

Natl. Met. Corp Springfield, OR 1954 Converted to Si 

TVA Wllson Dam& 1947 50 A150 Si 

USSR-St ate Dnepr, USSR 1937 30 Af-70 Si 

10,000 towear 

2000 towear 

16,000 towyear 

Experimental 

3600 towear 

Experimental 

1000 towear 

Pechiney Nogueres, France 1961 AI-AI& 4000 towear 

ALCAN Arvida, Canada 1961 Al-Fe-Si 7000 towear 

I 

Carbon Reduction 

10-2046 A1 that was used as copper 

ul trapme aluminum 

Table 3. From Stroup (1964) and Moafeldt (1989): A summary of the largescale cdperhnents and commercial 

processes used for the production of aluminum alloys by a direa thermal (cllrbosbamal) process. 
percent A1 in their rcactor. Material losses were large; 40-7096 of the qluminum fkom the bauxite 

was lost as dust or evaporated@okiya, 1983 & 1986; Yokokawa, 1985; Motzfeldt, 1989). 

Akan Monochloride processing of Carbothem0calIj,-produced Alloy 

Alcan developed and commercialized a process in Arvida, Canada, based on reversible 

reactions in the Q-AI system that extracted A1 hm the impure alloy whose main component 

was aluminum and allowed recovery of the metal through back nxctioq and condensation. 

Patented by Gross in 1949, it was based on the nversibk reaction 2Al+ A1Q3 <-> 3M, and 

was referred to as the monochloride process. The reaction to form Alcl is endothdc at 1000- 

140O0C, and is reversible at a lower temperature, 700-800°C. Crushed alurninurn-containing alloy was heated to l2OO0C with AlCl3 in an endothermic reaction andthe resulting mixture 

cooled and condensed to recover aluminum. The alllminum was racovw in the liquid state, 

and the AICl3 rccirculated. The process was complex; a technical sucqss, but an economic 

failure according to a company chemist(McGeer, 1986). The main diijiculties were the 

production of environmentally unacceptable, stable chloride compounc$ that required treatment, 

and the problem of finding materials to withstand the corrosive chlorid~s. - AlcodDOElBureau ofMines 

The Bureau of Mines supported considerable research from the 40's through the 50's into 

processes that would use nonbauxite ores to produce aluminum. Sever@ successful projects weE 

scaled up to large experimentaVsmal1 pilot plant she. Alma and DOE cohhted to investigate 

the feasibility of a blast-funrace process to prcxiuce ALSi alloys that w~dd berefined in a 

membrane-separated electrolysis cell Alma had under development '@e investigation began in 

the late 1970's, and ended in 1983 with the publication of several exte ive final reparts@runo, 1983; Troup, 1983) and more condensed presentations at the AIME 19 9$ 3 Annual 

Mee~g@resented 1983; papers published 1984; Bruno, 1984, Troup, 1984; Stevenson, 1984). 

simulating a combustion-heated electric 

furnace swept with an 

this process because 

formation of Al, 

extremely difficult, and the 

combustion heated 

decreasing the electricity use 

lowering the combustion CO 

is a problem that would not be cncoun 

would be only that evolved from the reduction 

Previous studies had indicated that the 

occurred in three s 
since the results from the blast-furnace research were so poor that the ject was ended in 1983 

(Bruno, 1983). The cell quires substantial thermal energy to keep it t its operating 

Thermal process to form an intermediate, followed by electrolysis 

Y 

temperature; another straighdorward application for solar process heati 

I believe some of these 

The temperatures rcqvired to 

with the direct reduction 

may be familiar to the reader and numerous 

patents wen issued, but the unanimous that 

the process was flawed to the point (see, c.g., McGM, 1986 

and Motzfeldt, 1989). 

odd be less. A 

3 N(S) ->Al2S3 (s) + A1 Q. 
The process to form AW requires higher tcmpemtures than the sulfidization process. 

Various temperatures are cited in the literature. My experience was that AlN could be formed in 

a carbothermal process at atmospheric pressure at temperatures of 1400-1550°C; this agrees with 

the earlier work by Sohn and Muck (Sohn, 1986; Murray, 1994). It is desirable to minimize 

the temperature used: higher temperatures result in very stable forms of AlN that arc difficult to 

dissolve. Some research appears to have been done to find appropriate &ctrolytes for an AlN 

elecmlysis process (Bonomi, 1982), with more work cited hm researchers in the former USSR 

on the problem. There is some hope that a bipolar cell with inat electrodes could be developed 

for this proccss. I don't know how one would separate the Si3N4 and popsibly Sic produced 

from the Al203-SiO~ containing ore. so Als3 may be the most apppaiate starring point for an 

AlN electroIysis process. 

Electrolysis aAl~mi~u)u Orein Hall Cell; production of Al-Si alloy 

Hall also worked to develop a process that might use an unrefined ore in an electrolysis 

cell. In theory, it should be possible through a multi-staged elecmlysis to separate the metal 

components of an ore in sequence Fe. Si, Ti, Al, Mg through Ca Unfbqumtely, the depositions 

of these metals overlap because they form alloys and other compounds. The Si content in the 

cell causes a loss in cumnt efficiency proportional to its concentration in the melt. Thc AI-Si 

metal produced can be refined through electfolytic or thermal pesses, as discussed earlier. 

Identifying Processes with the Best Potential for Solar Process Heat 

It is not entirely the goal of this project to identify the most therqmdynamically elegant 

aluminum extraction process fm fimha study as a candidate for solar-thm process heat 

We the distribution of energy usage in a process is of interest (ie. the ~hernical 

thermodynamics), an equally important consideration is to identify a process that has been 

substantially researched but that failed economically because of the necmity to add hightemperature process heat fiom electric sources, or has failed technically flue to the nature of the 

process heat added. This is an area in 

available at temperatures far above 

might be viewed as 

is constructed, other 

heat. Much of 

applications I looked for. 

1) well-researched processes 

for which 

2) the use of solar process heat might solve problem previouslyt encountered, 

and thus 

3) the use of high-temperature solar energy wuld be the critical Pomic and technical 

factor in their success or failure. 

The first criterium meant that I did not consider in much depth alperging techn010gies 

such as plasma production of aluminum, or other processes that seem to/ have received mostly 

academic interest such as the sulfur routes to aluminum. I 

The second eliminated other processes that might well adapt solar process heatexample might be the one genaally known as the Aicoa Smelting has been 

implemented to the pilot stage and ded out co befolc failing for 

other -om that the implementation of solar zf%:?~T 

The third criterium required some subjective input-I looked in pecular for processes 

that had to be conducted at such high temperatures that electric furnaces(or nuclear reactors) 

were the only option for implementation. 

Desirable features for solar-thermochemical process 

Other desirable process fams come dhctly from my experience designing chemical reactors 

for solar process heat: 

1) Process does not require tight temperature control for successr SO to 100°C 

2) mess can be condusted at atmospheric pressure 

3) Control of reaction atmosphere not critical so that receiverhactor may operate 

without a window. 

4) Intenuptible process is desirable-the consequmcts of nnsche&ded shutdown are not 

dire 

5) 24-hour operation not critical, or process has two or more sqs, some of which might 

be perfarmed at night. 

Using these criteria for choosing among the many alternative alqum extraction 

processes reviewed here, I believe three types of processes have the greapst potential for 

immediate success. The at is a reduction process to an Mi alloy do g the lines of work that 

was done by Alcoa under a joint project with DOE in the late 70's and c$ ly '80's@runo, 1983). 

The second would be a direct carbothenrial reduction process to aluminqn along the lines 

described in Reynolds patents (Kibby, l973,1976,1977,198O, 1982,1983). Of future interest, a 

carbothermal process to make an AlN intermediate that could be elech~olyzed more easily than 

A1203 using nonconsumable electrodes should be researched mon My. 

Conclusion 

Pmesses with excellent potential for high-temperature solar process heat 

Process #1: Alcoa AI-Si alloy reduction process 

Alma researched the production of an aluminum-silicon alloy fa futther refining 

to pure aluminum or use directly as an alloy. Two of the most 

encountered could be solved through the use of solar process heat 

studies could be easily adapted for solar p~axss heat 

heating. The process control requirements were modest, and the 

Problem #I: Tom1 r@ia of products 

The flow rate of CO would be much lower through a solarexweme problems with bridging and reflux of the product would be 

Furthermore, the report from ha mentions the potential technical 

operating with a closed reactm, this should be more easily achieved 

with an arc-type furnace design. 1 

Other process dficulties aided by the avaikMlity of solm process 

The eltctrolytic -on of the A1 and Si would also extend heating of 

the electrolysis cell. This step of the process could be carried likely, over the 

entire 24-ho~ period) so that %-hour operation could be 
The main process question that would need to be addressed would be the effect of 

running a reactor only during daylight hours, or the possible benefits of nqming 24 hours with 

supplemental extemal heating from an electric source. I 

Process #2: Reynolds Car bothermal Reduction 

Kibby's patents describe several process and reactor concepts for wrbothermal 

production of a lowcarbide aluminum. I have included this as a caudidaw process despite its 

complexity and apparmt need for fairly tight oontml. 

Problem #I: Control of heat rate critical 

In my conversations with Kbby, he indicated the critical need to iqnoduce process heat 

at exactly the correct heat rate to achieve a successful recovery of aluminqm metal. Kibby felt 

that this might be an area for which solar heating could improve the proce~s because it was 

nearly impossible to conaol the heat me with an electric arc furnace. 

Problem 472: high temperawes required for process ustainuble only with qlectricfurMce 

The use of solar process heat is also dictated by the temperatures quired+n the range 2050- 

2150°C. 

As with the Alcoa process. it will be necessary to investigate whew the pnxxss can be 

successfully interrupted or whether amihy heating will be required Th main advantage of 

this process is that it, if it can be made to w& it xesdts in substantially pb aluminum metal. 

No further electricity is required for the process. The main difficulty to bq overcome are that the 

reactors described in Kibby's patents are complex, two-stage and two-te 

that would pose quite an engineering challenge to adapt for solar 

zone or reactor also would appear to reqh fairly tight 

potential for producing lowcarbide metal. 

Process #3: CPrbothemal production of AlN Intermediate 

It is possible to produce AIN arbothermally either from an imp- ore or hm pure 

alumina. For a process based on the former, two thermal steps would be qscded to fom the pure 

AlN required for electrolysis to aluminum metal, but both of these steps ccpuld be identical 

carbothennal reductions in a niaogcn atmosphere. 

Problem #2: high temperatures required for process a 

The temperatures required to produce AlN from 

are lower than those requirtxi in the two direct reduction 

desirable. The process temperature appears to affect 

of the AN produced. so the lowest temperature wnsi 

desirable. The comparatively low temperam reduces and po 

volatile aluminum containing compounds. The 

and oxycarbide foxmation is inhibited. The 

from the formation of complex 

tubular reactors or other 

maintenance of an inert protective atmusphere unnecessary. 

The main drawback for this process is that it would no replace 

completely. The theuretical electrolysis 

A1 produced, so the potential exists fa 

to find suitable cle~tf~lytes for an 

further. 
Appendix A 

Interviews with Process Managers and Researchers at Alcoa, Kaiser and Reynolds 

I had long-term and fairly substantial, cooperative contact with senior research managers 

at both Alcoa and Reynolds. At Alcoa, my fmt point of contact was with R. Lee Troup, author 

of the section of Alma's final =port on the failure of the direct-combustion heated reduction 

project. He indicated that then was no &roundswell of interest currently in direct reduction 

- processes that he was aware of, but that the pattern for technologies there was that they tended to 

remain dormant for long periods, then reemerge when problems had been solved. He 

recommended I speak with C. Norm Cochran, who continues to maintain his interest in 

- carbotherma1 and direct reduction processes. His name is on many of the Alcoa carbotherma1 

process patents. He retired from Alma about 7 years ago, after serving as their technology 

planner, but continues to consult actively on projects. He confirmed Troup's impressions that 

research into alternative processes was unfortunately a "dead issue" at Alcoa, with research into 

-- Hall process impmvements dominating. He indicated that he had been working on the 

theoretical background for an alternative thermal process for which he could not divulge details, 

but which would have a vay good potential for solar pnxxss heat. Some of its potential -. advantages included a good productivity per unit reactor volume, indicating the potential for 

achieving excellent economies of scale; no production of intermediates; no loss of alnminum to 

volatiles; complete rrxycle of alumina and the ability to operate as a batch and interruptible 

process if required. I then spoke with Marshall Bruno, the manager rtspo&ble fa the AhaDOE research to mske Al-Si via carbtherrnal reduction of ore. He also indid that although 

there was not cumntly "a tremendous interest in almnative pmcesses, it was not true that there 

was no interest". He mentioned that she new director (at the Technical Center? of Alma itself? I 

- failed to record the details) had shown keen intatst in direct reduction messes, though no 

action had come of it as yet Marshall put the group from NREL in touch with sevd people 

within Alma, and also gave us the names of interested DOE anministra~. I sent him a copy of 

- the interim repon from April. 

Reynolds 

At Reynolds, my first point of contact was with the Power Manager for Pacific Northwesst; 

Dan Ten Eyck. He immediately referred me to Alton Tabemux, managm of theExtractive 

Metallurgical Technology department in the Manufacturing Technology Laboratory at Reynolds 

Metals Company in Alabama He told me that although there had been intense interest and work - to develop a viable direct carbothcnnal process in the 70's and 80's. that the company had already 

spent a great deal of money on this line of xesearch and that the feeling wy they were convinced 

that it wasn't possible. He indicated that carbothemal "has a bad name" at the lab; that his 

- impression was that the chemistry was the main problem. He referred me however, to Bob 

Kibby, a now-retired researcher whose name is on most of the Reynolds 

patents of the last 30 years. Though he retired 14 years ago, he contin c$bom-pmccss 

the feasibility of a carbothd mute to the manufbcture of alumhum. 7 

length several times; he persuaded me to include the Reynolds 

researched in the list of candidates for sok thermal processc~. 

solved two of the thnc main chemical-process complex problems - that the use of solar energy as process heat might solve the final rIifficulty of controlling the heat 

rate to control vaporization which could only be awkwardly solved when #n dcceric arc was used 

as the heat source. He further recommended that I speak with Tony Saav who continues in 

a msauch and managerial position at Reynolds, and who had worked cl ," ly with him on 

carbothermal reduction research. I did not have a chance to contact him. 
Kaiser 

Pacific Northwest, 

Specialist Here, 

either from the 

such work would bt too large a - into alternative processes in the 

underway. They are researching process refinements and improvements, pome of it DOE 

sponsored and probably similar to the other companies. Steve indimted the plants the 

- company owns in the Pacific Northwest are "old and paid-fw'*-50 years 

Kaiser is vertically integrated there was no interest in processes to replace 

steps. This confirmed my impression of activity at Kaiser4 had not seen 

semh for example, a fact which could either be symptom of extreme 

the Bayer-bauxite Kaiser patents in my 

cor~onuc sccrocy or 

inactivity in the field. 
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Metallurgy Lecture, The Metallurgical Society of AIME, MetalZwgicd Transactions B, 12B, 

June 1981, pp203-215. 

EL. Singleton, D.E. Kirby and TA. Sullivan, "Electrowinning A1-m hm Aluminum 

Chloride: Operation of a Two-Compartment Cell", RL 7212, U.S. Bu$au of Mines, 1968. 

EL. Singleton, D.E. Kirby and T.A. Sullivan, "Electrowinning from Alumhum 

Chloride: Operation of a Single-Compartment Cell", R.I. 7353, of Mines, 1968 

Aluminum Purification Processes 

W.C. Aitkenhead, Review of Recent Gaman DeveIopments in Allminp Refining", FIAT Final 

Report 907,s March 1947, 

E. Bonnier, l~lectrulysc des Aluminatest', Con* IntQaational de L'Quminium", Paris 1954. 

ItW. St Clair and DD. Blue, "Rccovq of Aluminum hm Cnde Al@humSilicon Alloy by 

Extraction with Molem Zinc", Bureau of Mines ILI. 4535,1949. 

F.C. Frary, The Electrolytic Refining of Aluminum', Trmacfions ofqk American 

Elenrochemical Society, v XLW, 1925, pp275-286. 

WJ. Howell, CA Eckcrt, and RN. Anderson, "Carbothennic Reductipn Using muid Metal 

Solvents", Jod of Mernls, V40, no 7.. 1988, pp21-23. 
Economic/Market factors 

R.G. Adams, 'U.S. and World Energy Outlook-Implications foir the Aluminum Industry", 

Jouml of Metals, v33 n0.6 (198 I), pl4l- 144. 

B. Barham, S.G. Bunker and D. O'Heran, States. Firms and Ra w Maws the Wo rld Ecologv of 

Aluminum, University of Wisconsin Press, Madison, Wisconsin, 1994. ' 

S.C. Manahala, 'The Runary Aluminum Industq in the Commonweal@ of Independent StatesPart I", Joml of Metals, v44 no1 1 (1992). pp38-40. 

D. Morton, ''Today's Aluminum Industry: Facing the Economic and Endironmental Challengest', 

Journal of Metals, v44 no. 11 (1992), p6. 

OECD, Jndustrial Adaptation in the Primq Aluminum Industry, Paris, 1976. 

OECD, ,Aluminum industry: enery aspects of structural chanee, Paris, 1983. 

M. Peck, ed. The World Aluminum Industry in a Chanein~ Energv ~esources for the 

Future, Washington D.C., 1988. 

S.R. Spector, "Rice and Availability of Energy in the Alllminum Indus*", Journal of Metals, 

v33 n0.6 (198 I), p138-139. 

J.A. Stuckey, Vertical Intwtion and Joint Ventures in the Aluminum I$dustry, Harvard 

University Ress, Cambridge, Massachusetts, 1983. 

ustnal Outlook 1994.35th Annual Edition, U.S. Department of Commerce/International 

Trade Administration. 

ALN frocess 

1,030,929 (19 12) 

Process of Manufacturing Aluminium Nitrid 

0.Sexpek (SociCtt generale des Nitmes) 

1,060,509 (19 13) 

mess for the Manufacture of Aluminium Nitrid 

0.Serpek (Soci6tC generale des Nims) 

1,155,840 (1915) 

Process of Fixing Nitrogen 

0.Seqek (SociCd generale des Nitmes) 

1,180,840 (1916) 

Rocess of Producing Aluminium Nitrid 

G Guilini 

1,196,639 (19 16) 

Process of Fixation of Nitrogen 

A. Badin (Soci6t6 genaalt des Nitrures) 

1,198,965 (1916) 

t'~hislistdoesn~caachammpl~&wof theps~tlircnrmc. ?hipisap 

aquind because they seemd to be em tccbnicrlly intaesting a might contain dia 

adaptcdfasolarpmcess. TMgocdboobcaUahdkusshsofmanyofthepatcll~ 

"Carbothdc Production of Aluminum" cows cabhmk methods patented fbm 

Edwards, Fmy, and Jcffries book "The Aluminum Indusay" lists .ad discusses mary 

1930). 

;onal"~listnofpaentsI 

:hesof~thatcouldbe 

W ke-Motzfeldt's 

1968 though 1987. 

~f the early patents (though 
Mess for Fixing Nitrogen by Means of F~Ko-Aluminium or other fm alloys 

0.Serpek (Soci6d generak des Nitrum) 

1,305,414 (19 19) 

Rocess and Apparatus for the Production of Metallic Nihds 

F.T. Snyder 

1,311,568 (1919) 

Process and Apparatus for Ptoducing Nitrogen Compounds, Especially Nitrids 

A.R. Lindblad 

1,350,149 (1920) 

Process of Producing Nitrid of Aluminium from materiuals containing quminic oxid 

V. Gerber 

1,366,720 (192 1) 

M.C.J. Elis& de Loisy 

Process and Plant for Industrially Carrying out Chemical Reactions in aa Artificial Atmosphere 

3,032,398 (1962) 

Process and Furnace for the Continuous Production of Aluminum Nitride 

J. Clair (Pechiney) 

Carbothermic Processes 

2,843,475 (1958) 

Method of Producing Aluminum 

P. Weiss (VAW) 

4,099,959 (1978) 

Process for the Production of Alllminum 

E.W. Dcwing, JP. Huni, R.R. Sood and F.W.Southm(Alcan) 

4,213,599 (1978) 

Apparatus for the Production of Aluminum 

E*W. Dewhg, J.P. Huni, RR Sad and F.W.Southam(Alcan) 

4,314,846 (1982) 

Method for Carbotherrnic Production of Aluminum 

K. Motzfeldt 

4.394,167 (1983) 

Method of Carbothermicall y Mucing AluminumU .S . Patent 

K. Kuwahara, (Mitsui Alllminum) 

Reynolds Carbothertdc Process 

3,257,199 (1966) 

Thexmal Reduction 

W. Schmidt (Reynolds) 

3,254,988 (1966) 

Thermal Reduction 

W. Schmidt and G-P. Koch(Reyno1ds) 

3,758,290 (1973) 

Carbothermic Production of Aluminum 

EM. Kibby (Reynolds) 
Treatment of Carbothdcally Produced Aluminum 

R.M. Kibby (Reynolds) 

4,033,757 (1977) 

Carbothennic Reduction Process 

R.M. Kibby (Reynolds) 

4,216,010 (1980) 

Aluminum Purification System 

R.M. Kibby (Reynolds) 

4,334,917 (1982) 

Carbothermic Reduction Furnace 

R.M. Kibby (Reynolds) 

4,419,126 (1983) 

Aluminum Purification System 

R.M. Kibby (Reynolds) 

Alcoa Carbothermic Process 

2,829,961 (1958) 

Roducing Aluminum 

MA. Miller, L.M. Foster, and CD. Baker (Alma) 

3,971,653 (1976) 

Carbothefmic Production of Aluminum 

C.N. Cochran (Alcoa) 

4,046,558 (1977) 

Method for the Production of Aluminum-Silicon Alloys 

S.K. Das and R.A. Milito (Alcoa) 

4,053,303 (1977) 

Method of Carbothermically Producing Aluminum-Silicon Alloys 

C.N. Cochran, SK Das, and RA Milit0 (Alcoa) 

Alma Electrolytic Refining Process 

1 ,S34,O3 1 (1 925) 

Electrolytic Roduction of Aluminum 

F.C. Frary (Alcoa) 

1,5343 16 (1925) 

Roduction of Metallic Aluminum frmn Impure Maw. Hwpes, F.C. Frary and J.D. Edwards (Alcoa) 

1,534,3 17 (1925) 

Electro1ytic Aoduction of Aluminum 

W. Hoopcs, F.C. Frary and J.D. Edwards (Alcoa) 

1,534,318 (1925) 

E1ectr01ytic Refining of Aluminum 

W. Hoopts, EC. Frary and JD. Edwd (Alcoa) 

1.5343 19 (1925) 

Refining Aluminum Electrolytically with Fused Electrolytcs 

W. Hoopes, F.C. Frarv (Alma) 
Other Masses 

1,569,483 (1926) RE 17,001 (1928) 

Process of Treating Ores Containing a Refixtory Oxide 

T.R Haglund 

1,618,105 (1927) 

Process of Manufacturing Amllminum Hydroxide 

H. Pedersen (Alcoa) 

2,09O,4S 1 (1 937) 

Manufacture of Aluminium 

0. Knrh 

2,474305 (1949) 

Process for the Production and Refining of Aluminium 

P. Gross 

2,470,306 (1949) -. 

Process for the Production and Refining of Metals 

P. Gross 

3.615359 (197 1) 

Process for Producing Al-um 

C Toth (Applicd Aluminum Research Corporation) 

3,615,360 (197 1) 

Process for the Continuous Production of Aluminum 

RG. Hanis, RV. Bailey, C. Toth (Applied Aluminum Research Cappmtion) 

3,681,561 (1972) 

Method of Making Aluminum-Silicon Alloys 

F.W. Frey. D.O. Hutchinson, KK. Seth (Ethyl Corporation) 

3.66 1562 (1972) 

Reactor and Method of Makkg Alllminum-Silicon Alloys 

KK. Seth, C.W. Lanier (Ethyl Corporation) 

3,853,541 (1974) 

Method for Producing Aluminum Metal Directly hm Ore 

D.F. Othmer 
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4. TITLE AND SUBTITLE

Investigation of Opportunities for High-Temperature Solar Energy in 

the Aluminum Industry 

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NREL/SR-550-39819 

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WW1F.1000 

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J. Murray 

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Department of Mechanical Engineering 

Portland State University 

Portland, Oregon 

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14. ABSTRACT (Maximum 200 Words)

This report gives the conclusions drawn from a study of the potential application of high-temperature solar process 

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aluminum process technologies; solar process heat; concentrated solar energy 

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