The photographs on the cover are an example of an aluminum furnace featured 

on the Harbison Walker web page (top), cathodoluminescence of a fusion-cast 

spinel refractory (center), and cathodoluminescence of a fusion-cast alumina 

refractory (bottom). 

1 

Refractories for Industrial Processing: 

Opportunities for Improved Energy 

Efficiency 

James G. Hemrick,* H. Wayne Hayden,† Peter Angelini,* 

Robert E. Moore,§ and William L. Headrick§

*Oak Ridge National Laboratory

†

Metals Manufacture, Process, and Controls Technology, Inc. 

§

R. E. Moore and Associates 

January 2005 

Prepared for the DOE-EERE Industrial Technologies Program 

Table of Contents 

List of Figures and Tables ............................................................................................................... v

Executive Summary ...................................................................................................................... vii

Abbreviations and Acronyms......................................................................................................... ix

1. Introduction............................................................................................................................. 1

2. Current Refractory Status ....................................................................................................... 1

2.1 Usage in Industry......................................................................................................... 4

2.2 Current R&D Status..................................................................................................... 4

3. Estimated Metrics for Overall Energy Savings Opportunities ............................................... 5

4. Process Technology and Performance Barriers ...................................................................... 7

4.1 Kilns and Calciners...................................................................................................... 7

4.2 Reverberatory Furnaces ............................................................................................... 8

4.3 Boilers and Reactor Systems ..................................................................................... 10

4.4 Gasifiers..................................................................................................................... 13

5. Overall R&D Barriers and Pathways for Refractories.......................................................... 15

6. Specific R&D Areas with Barriers and Pathways ................................................................ 17

6.1 Improved Castable and Monolithic Refractory.......................................................... 17

6.2 Modified Fiber Materials ........................................................................................... 17

6.3 Surface Modification (Coatings, Physical or Thermal Alteration) ............................ 17

6.4 Synthetic Aggregates and Powders............................................................................ 18

6.5 High-Temperature Properties of Refractories............................................................ 18

6.6 In Situ and Graded Refractories................................................................................. 19

6.7 Sensors for Materials Performance............................................................................ 19

7. References............................................................................................................................. 22

Appendix A: Discussion of Refractory Usage by Process Industries........................................... 26

A.1 Aluminum .................................................................................................................. 26

A.2 Cement and Lime....................................................................................................... 30

A.3 Chemical and Petrochemical...................................................................................... 33

A.4 Forest Products .......................................................................................................... 35

A.5 Glass .......................................................................................................................... 37

A.6 Heat-Treating and Annealing..................................................................................... 40

A.7 Iron and Steel............................................................................................................. 41

A.8 Metal Casting............................................................................................................. 44

A.9 References for Appendix A ....................................................................................... 48

Appendix B: Rotary Kiln Analysis Schematic, Conditions, and Results..................................... 50

Appendix C: Reverberatory Furnace Schematics......................................................................... 56

Appendix D: Reverberatory Furnace Analysis Conditions and Results........................................ 58

Appendix E: Boiler Schematic ...................................................................................................... 62

iii 

List of Figures and Tables 

Figures 

ES.1. Temperature regimes for industrial applications of refractories ..................................... vii

1. Long-term energy benefit opportunities estimated for the four analyzed 

furnace types ...................................................................................................................... 6

2. Improving refractory materials for improved energy efficiency ..................................... 16

B.1. Longitudinal section of a typical rotary kiln .. ................................................................. 50

C.1. Reverberatory furnace schematic ..................................................................................... 56

C.2. Typical reverberatory aluminum-melting furnace ........................................................... 57

E.1. Boiler furnace sections .................................................................................................... 62

Tables 

1. Types of furnaces utilized in American industry ............................................................... 2

2. Refractory barriers for furnaces utilized in American industry.......................................... 3

3. Energy analysis by industry with estimated short-term and long-term

energy savings opportunities from improved refractories.................................................. 5

4. Total effect of improved refractories on rotary kilns ......................................................... 8

5. Total effect of improved refractories on reverberatory furnaces...................................... 10

6. Steam system assessment tool single header analysis results for improved 

insulation for improved boiler efficiency ......................................................................... 11

7. Steam system assessment tool single header analysis results for improved 

pipework insulation for improved steam transfer systems ............................................... 11

8. Potential energy savings from improved boiler efficiency due to improved 

refractories and improved transfer pipe-work insulation ................................................. 12

9. Renewable energy generation potential (billion kWh/year) from black liquor 

in the pulp and paper industry in the southeastern United States..................................... 15

10. Recommended R&D pathways for advanced refractories ............................................... 20

A.1. Feedstock for energy use in the cement industry, 1993-2001 .......................................... 32

A.2. Estimated energy use in melting and refining .................................................................. 38

A.3. Conversion of North American glass melters to oxy-fuel firing as 

of 1998 and as of 2004 ..................................................................................................... 39

A.4. Process and energy data for U.S. metals casting industry ................................................ 45

v 

Executive Summary 

Refractory materials with properties suitable for high-temperature applications are used 

throughout U.S. industry as insulation and/or containment vessel linings in high-temperature and 

corrosive environments. Indeed, it would be difficult to identify an industrial process that does 

not use refractory materials in one aspect or another. These materials must not only be capable of 

performing these tasks at elevated temperatures, but may also be called upon to bear mechanical 

loads and transfer heat. Refractories are characterized by two aspects that qualify them as 

strategic materials in support of American industry: (1) their ability to contain heat, chemicals, 

and melts; and (2) the crosscutting nature of their utility. 

Figure ES.1 shows the ranges of usage temperatures for numerous industrial applications of 

refractories. This report and the attached appendices describe the current furnace technologies 

used by U.S. industries with specific highlighted analysis focused on four furnace types—kilns/ 

calciners, reverberatory furnaces, boilers and reactor systems, and gasifiers—which are common 

to multiple industries and are representative of areas where significant energy improvement could 

be made through future refractory improvement. Analyses of these four types of furnaces alone 

suggest potential energy savings of over 400 trillion Btu/year. In addition to identifying areas of 

opportunity, this report describes possible crosscutting research and development (R&D) 

pathways for overcoming refractory-related performance barriers which could lead to improved 

energy efficiency through both the alteration of current materials and practices and the 

development of new materials, furnace designs, or redesigned processes of varying sizes. 

Fig. ES.1. Temperature regimes for industrial applications of refractories. 

vii 

Abbreviations and Acronyms 

BLS black liquor solids 

BOF basic oxygen furnace 

Btu British thermal unit 

DOE U.S. Department of Energy 

EAF electric arc furnace 

EERE Energy Efficiency and Renewable Energy (DOE) 

FCCU fluidized catalyst cracking unit 

ITP Industrial Technologies Program (DOE) 

MECS Manufacturing Energy Consumption Survey 

ORNL Oak Ridge National Laboratory 

R&D research and development 

TBtu trillion Btu 

ix 

Refractories for Industrial Processing 

1. Introduction 

The Industrial Technologies Program (ITP), part of the Department of Energy’s Office of Energy 

Efficiency and Renewable Energy (DOE-EERE), seeks to improve the energy intensity of the 

U.S. industrial sector through a coordinated program of research and development (R&D), 

validation, and dissemination of energy efficiency technologies and operating practices. To 

achieve its mission, ITP partners with industry, equipment manufacturers, and other stakeholders 

to develop technologies that enable industry to use less energy per unit of output. Refractories are 

a class of materials of critical importance to manufacturing industries with high-temperature unit 

processes. This study describes industrial refractory applications and identifies refractory 

performance barriers to energy efficiency for processing. The report provides recommendations 

for R&D pathways leading to improved refractories for energy-efficient manufacturing and 

processing. 

2. Current Refractory Status 

There are many different types of furnaces used in industries in the United States, each with 

different refractory needs and challenges. A discussion of the refractory issues for several energyintensive processing industries can be found in Appendix A. Fifteen classifications of furnaces 

with several common issues can be identified. Typical industrial applications of these fifteen 

furnace types are shown in Table 1. Refractory challenges and problems related to these furnace 

types, as reported by industry personnel and discussed in detail in Appendix A, are shown in 

Table 2. 

Of these fifteen furnace types, four are highlighted in this document: kilns/calciners, 

reverberatory furnaces, boilers and reaction systems, and gasifiers. These were selected because 

they are common to multiple industries and representative of areas where significant energy 

savings [on the order of trillions of Btu (TBtu)/year] could be realized through future refractory 

improvement. Although emphasis was placed on blast furnaces, basic oxygen furnaces (BOFs), 

and other furnace types found in the steel industry, we have chosen not to focus on these furnaces 

because of their design practice of intentionally leaking energy so as to induce a steep thermal 

gradient through the lining. Additionally, BOF refractories are known to last thousands of heats, 

and little improvement is expected in improving refractories for these applications. 

Analysis and discussion will address refractory improvements leading to higher energy efficiency 

and improved product yield for each of these four furnace types. Discussion will focus on the 

energy-intensive industries of the United States including aluminum, cement and lime, chemicals 

and petrochemicals, forest products, glass, heat treatment and annealing, iron and steel, and metal 

casting. 

1 
2 

Table 1. Types of furnaces utilized in American industry 

Furnace type 

Industrial furnace applications 

Aluminum Cement & lime Chemical/ petro­ chemical Forest products Glass Heat treat Iron & steel M

cas

Blast furnace X Basic oxygen furnace X Reverberatory furnace X 

X 

X X 

Multiple hearth Ladle/tundishe/trough X 

X 

X X 

Electrolytic smelting X Kilns X X X X X X Electric arc furnace (EAF) X Cupola X Heat treat X X X X X Still X Reactor/reformer X Boiler X X X X X Gasifier X X Heat exchanger X X X X X X X X a Key to “Other”: 

1. Lead 6. Mining 2. Copper 7. Oxide melting 3. Molten metal handling 8. Various metal products 4. Magnesium 9. Organic and inorganic products 5. Ceramics 10. Virtually all industries 
Table 2. Refractory barriers for furnaces utilized in American industry 

Furnace type 

Refractory challenges 

Abrasion 

Caking/ 

agglomeration 

Contamination/ 

fouling 

Corrosion/ 

wear Erosion 

Mechanical 

degradation 

Thermal 

insulation 

m

de

Blast furnace X 

X 

X X 

Basic oxygen furnace X X X X X Reverberatory furnace X X X X Multiple hearth X 

X 

X 

Ladle/tundishe/trough X X X X X Electrolytic smelting X X X X Kilns X X X X X X X Electric arc furnace (EAF) X X X Cupola Heat treat Still X 

X 

X 

Reactor/reformer X 

X 

X 

Boiler X X X X X X Gasifier X 

X 

X X X 

Heat exchanger X 

X 

X 

3 
Refractories for Industrial Processing 

2.1 Usage in Industry 

Although refractories are used in most, if not all, of U.S. industries, the iron and steel industry 

consumes 70% of the refractories produced globally, while the cement and lime industry 

consumes 7%, the ceramics industry 6%, the glass industry 3–4%, and the oil industry about 4%.1 

In 1998, a survey was conducted by the U.S. Advanced Ceramics Association and Oak Ridge 

National Laboratory (ORNL) to determine opportunities for advanced ceramics to meet the needs 

of manufacturing industries.2

 These industries included aluminum, chemicals and petrochemicals, 

forest products, glass, metals casting, and steel. Additionally, the supporting industry of heat 

treating and annealing was considered. From this survey, a number of critical areas were 

identified in each of these industries where improvements could lead to substantial economic and 

energy savings. 

Additionally, the general practice of most industries is to choose fuel types and sources based 

primarily on cost and availability. This, in many cases, leads to variations in fuel quality and 

purity which will directly impact the performance of the refractory materials used in the 

respective furnaces. This must be considered when choosing furnace materials and when 

evaluating energy efficiency. 

2.2 Current R&D Status 

Substantial changes that have occurred in refractories technology over the past 25 years have 

resulted in crosscutting impacts on a number of manufacturing industries,2

 including the use of 

fibrous and high-strength porous insulation to reduce energy consumption in heat-treating 

furnaces. In the steel industry, the use of resin-bonded MgO-C-metal linings in basic oxygen 

furnaces significantly increases the number of heats between needed relinings, and SiC-based 

refractories have led to increased furnace life for steel blast furnaces. In the glass industry, the 

advent of oxy-fuel melting has led to renewed interest in alternative refractory materials that will 

allow for processing at higher temperatures and greater corrosion resistance to high alkali and 

water-rich environments. Additionally, many more recent ceramic compositions have received 

limited evaluation but have not reached maturity or production status. All of these events are 

representative of industrial process improvements that can be accomplished through advances in 

refractory materials, yet additional improvements could lead to even greater energy savings 

throughout the various industries. 

The choice of refractory materials for a certain application is often dictated by the trade off 

between cost and performance. In the past economic considerations have led to the selection of 

lower cost/poorer performing refractories over higher performance/higher cost materials. Yet, 

with rising energy costs, environmental regulations, and economies of scale; higher priced 

premium refractory materials are receiving renewed interest and may prove cost effective in 

many applications for which they were previously deemed unsuitable. 

4 
Refractories for Industrial Processing 

3. Estimated Metrics for Overall Energy Savings 

Opportunities 

Energy usage in several of the industries and estimates of potential energy savings through 

improvements in refractories are shown in Table 3. The values shown in this table are based 

primarily on DOE Manufacturing Energy Consumption Survey (MECS) data describing 

manufacturing energy consumption in the year 1998.3 The estimates of energy usage affected by 

refractories are based on evaluation of industry roadmap documents and discussions with industry 

leaders. Energy savings goals are based on the needs of the industries and estimates for the four 

typical furnace types (Table 1) used throughout many of the industries, which are presented in 

detail in Appendices B, C, and D. These analyses are based on heat balance studies where the 

energy supplied to the system through combustion is equal to the sum of (1) latent heat in the 

furnace exhaust gases, (2) heat lost through the furnace walls and roofs, and (3) heat required for 

heating reactants to the process temperature and phase transformations at that temperature. The 

achievement of theoretical efficiency would require that items 2 and 3 be equal to zero. From a 

practical point of view, perfect efficiency is not probable, but improvements in furnace 

refractories could help facilitate improvements of furnace efficiency beyond the levels of present 

technology. The projected saving opportunities in the range of 166 TBtu/Yr to 830 TBtu/Yr are 

equivalent to the yearly residential electrical usage of New York state and the yearly residential 

air conditioning usage of the US, respectively. 

Table 3. Energy analysis by industry with estimated short-term and long-term energy savings 

opportunities from improved refractories 

Energy savings goals for 

Industry NAICS 

codes 

Total 

TBtu/yeara 

Usage affected by 

refractories 

Percent TBtu/Yr 

improved refractories 

(TBtu/Yr) 

Near-term 

2% 

Long-term 

10% 

Aluminum 3313XX1 441 90% 397 7.9 39.7 

Chemical 325XXX 3,704 50% 1,852 37.0 185.2 

Fabricated metalsb 33281 445 90% 401 8.0 40.1 

Forest products 321XXX, 3,248 40% 1,299 26.0 129.9 

322XXX 

Foundries 3315XX 233 90% 210 4.2 21.0 

Glass 3272XX 203 70% 142 2.8 14.2 

Iron & steel 33111 1,672 85% 1,421 28.4 142.1 

Petroleum & coal 324XXX 3,622 50% 1,811 36.2 181.1 

products 

Stone, clay products

c 327XXXd 766 100% 766 15.3 76.6 

All 14,334 — 8,299 165.8 829.9 

a TBtu = trillion Btu/year. Source: U.S. Department of Energy, Energy Information Administration, 1998 MECS 

Consumption, Table N3.2, Fuel Consumption, 1998. 

b Includes heat treatment. c Primarily cement and lime. d Excludes category for glass, 3727XX. 

Additionally, one must consider that declines in certain properties may have a direct influence on 

other related properties. This is evident for example in a furnace wall where lack of corrosion 

5 
Refractories for Industrial Processing 

resistance may result in a reduction in thermal efficiency as decreases in wall thickness due to 

corrosion will lead to decreased insulating ability of the furnace wall. The furnace efficiency will 

now not only be impacted, but thinning of the refractory wall may also lead to shut-down of the 

furnace for maintenance causing loss of production and the need for additional energy to reheat 

the furnace. Energy considerations from all these areas are considered in Table 3. 

Figure 1 shows the potential energy benefit opportunities represented by the four furnace types 

analyzed. 

Fig. 1. Long-term energy benefit opportunities estimated for the four analyzed 

furnace types. 

6 
Refractories for Industrial Processing 

4. Process Technology and Performance Barriers 

4.1 Kilns and Calciners 

Kilns and calciners, or the products produced by them, are used in many industries (aluminum, 

cement, chemical, forest products, glass, iron and steel, and mining) and therefore have 

crosscutting interests. Analyses were performed to evaluate cases for both alumina and lime 

calcinations, based on use of rotary-type kilns for various flame temperatures, exhaust 

temperatures, and wall/roof losses (Appendix B). For all the heat supplied by combustion, the 

gross available heat is calculated from the heat content of the flame less the heat content of the 

exhaust gases, and a part of the heat supports wall loses while the remainder is available for the 

work of the kiln/calcinations of feed to product. 

4.1.1 Industrial Applications of Process Technology 

Aluminum — alumina, carbon, lime Glass - lime 

Cement and lime — lime, cement Iron and steel - lime 

Chemical and petrochemical — lime Mining — raw materials 

Forest products — lime 

4.1.2 Current Technology 

Two types of kilns typically found in the industries listed were selected for review. In the case of 

alumina calcination, we considered a kiln measuring 3.5 m in diameter by 80 m long with an 

output of approximately 250,000 tons/year; for lime calcinations, we chose a kiln measuring 5 m 

in diameter by 50 m long with an output of approximately 365,000 tons/year. In the lime 

calcination process, product is often lost through dust loss as loose powder is blown out of the 

kiln along with the exhaust gases. Therefore, in the lime analysis, both the case of no dust and the 

more realistic condition of up to 20% of the calcined product being lost as dust were considered. 

Calculated heat of reactions (at 77°F) of 634 Btu/lb and 1364 Btu/lb were used for the alumina 

and lime calcination processes, respectively, leading to a calculated total heat requirement of 

1728 Btu/lb for the alumina calcination process and 2196 Btu/lb for the lime calcination process. 

4.1.3 Energy Impact 

Energy benefits resulting from refractories in kilns are related to the following operational 

improvements: 

1. An increase in the adiabatic flame temperature of 200°F (as with modified oxy-fuel firing at 

about 20% enrichment) can lead to substantial fuel savings due to thermal efficiency. 

2. A decrease in the exhaust temperature of 200°F (resulting in greater heat retained for the 

actual process) also leads to a substantial fuel savings. 

3. A decrease in wall/roof losses of 200,000 Btu/ton of product can result in substantial energy 

savings (considering half the supplied energy goes up the stack, with the remainder available 

to support work and wall losses). 

4. Process yield improvements will result in substantial energy benefits. 

For the energy analyses, it was assumed that a little over half of the total calcined alumina 

produced in the United States (4.4 million metric tons in 2001) was produced using a rotary kiln. 

Similarly, it was assumed that of the 20 million short tons of lime produced in the United States 

7 
Refractories for Industrial Processing 

in 2002, about 80% of the production was performed using rotary kiln calciners. It was also 

assumed that 80% of the 103 million metric tons of cement produced in the United States in 2002 

was produced using rotary kilns operating in the temperature range of 2600 to 3000°F. Results of 

the analysis are shown in Table 4. 

Table 4. Total effect of improved refractories on rotary kilns 

Energy-intensive 

process industries Product Fuel decrease 

(Btu/ton) 

Wall loss 

decrease 

(Btu/ton) 

Tons affected 

per year 

Energy benefits 

per year 

(TBtu) 

Aluminum Al2O3 413,000 200,000 2,500,000 1.5 

Cement and lime Cement 800,000 200,000 82,400,000 82.4 

Cement and lime, 

chemical and 

petrochemical, 

forest products, 

glass, iron and 

steel 

Lime: 

 No dust 

 20% dust 

413,000 

885,000 

200,000 

250,000 

16,000,000 

16,000,000 

9.8 

18.3 

All 112a 

a

 Without carbon and sulfur contributions. 

Source: Portland Cement Association, Economic Industry Overview, 2003.

4.1.4 Barriers Related to Refractory Materials for Kilns and Calciners 

The central conclusion from the analyses for concerning kilns and calciners is that as flame 

temperatures increase and exhaust temperatures approach process temperatures, greater thermal 

efficiency is realized. Hence, improvements in reducing the thermal conductivity of the 

refractories, and improving the chemical and mechanical properties of the refractories, will have a 

significant payoff in overall fuel consumption. Addressing the following barriers associated with 

the performance of refractory materials used in kilns and calciners would improve energy 

efficiencies. 

1. Unavailability of refractories with sufficient high-temperature strength, erosion/corrosion 

resistance, creep resistance, resistance to large temperature gradients, and stability at higher 

temperatures for use with elevated furnace flame temperatures. 

2. Lack of sufficient high-temperature durability and corrosion/erosion resistance in current 

refractories for improved heat transfer through increased levels of stirring and agitation of the 

material being processed. 

3. Unavailability of refractories with lower thermal conductivity and greater high-temperature 

stability needed to achieve substantial reductions in wall and roof heat losses. 

4. Lack of knowledge concerning operations needed to increase refractory life, reduce product 

sticking, and increase levels of product recovery for the reduction of unscheduled outages, 

improvement of product yield, and the increase of furnace campaign lives. 

4.2 Reverberatory Furnaces 

Analyses of reverberatory furnaces were performed to evaluate cases of aluminum, copper, and 

glass-melting furnaces for various assumed values of flame temperatures, exhaust temperatures, 

and wall/roof losses. For all the heat supplied by combustion, the gross available heat is the heat 

8 
Refractories for Industrial Processing 

content of the flame less the heat content of the exhaust gases. Additionally, part of the gross 

available heat supports wall losses and the remainder supports melting, the real job of the furnace. 

Reverberatory furnace schematics are provided in Appendix C. 

4.2.1 Industrial Applications of Process Technology 

Aluminum — metal melting Metal casting — metal melting 

Glass — glass melting Copper — metal melting 

Iron and steel — metal melting 

4.2.2 Current Technology 

Analyses of reverberatory furnaces were based on a nominal furnace having a capacity for 

melting 20,000 lb of material per hour. This is a typical size used in the aluminum industry and is 

used for the other industrial analyses for comparison purposes. For the fixed melting capacity of 

20,000 lb/h, the energy needed for melting is the same in all aluminum melting cases, 504 Btu/lb. 

In the analysis, wall and roof losses from 0 (really impossible) to 10 million Btu/h, or 0 to 

500 Btu/lb of material, have been assumed. This range is expected to span the full spectrum of 

industrial practice. The gross available heat to do these jobs is the difference in flame and exhaust 

heat contents. It has been assumed that natural gas fuel with an adiabatic flame temperature of 

~3600°F has been used as a base, with increasing flame temperatures that may be achieved 

through regenerators/recuperators or oxygen enrichment. 

Exhaust temperatures ranging from 1400 to 2000°F have been assumed. Increasing exhaust 

temperatures at fixed flame temperatures results in total heat consumptions ranging from 

777 Btu/lb (61% thermal efficiency) to 2261 Btu/lb (22.3% thermal efficiency). Furnaces in the 

aluminum industry generally fall in this range, as summarized below: 

Furnace type Thermal efficiency 

Normal furnace (poor to good practices) 2500–1350 Btu/lb 

State-of-the-art new furnace 1350–1200 Btu/lb 

Furnace builders’ lower limit for reverb. 1200–1000 Btu/lb 

New/radical technology 1000–504 Btu/lb 

Similar efficiencies are expected in the other two industries studied. 

4.2.3 Energy Impact 

Energy benefits that could result from improved refractories in reverberatory furnaces are related 

to the following operational improvements: 

1. An increase in the adiabatic flame temperature of 200°F (e.g., oxy-fuel firing with 20% 

oxygen) leads to substantial fuel savings due to thermal efficiency. 

2. A decrease in the exhaust temperature of 200°F (resulting in greater heat retained for the 

actual process) also leads to a substantial fuel savings. 

3. A decrease in the wall/roof losses of 2.5 million Btu/h also results in substantial energy 

savings (considering half the supplied energy goes up the stack, with the remainder available 

to support melting and wall losses). 

For the calculations, it was assumed that annually in the United States, 9.3 billion lb of aluminum 

(half of all the ingot and mill products in the aluminum industry in 1998) are melted in 

reverberatory furnaces, 0.36 billion lb of refined copper from scrap is processed in reverberatory 

9 
Refractories for Industrial Processing 

furnaces, and an average of the 40 billion lb of glass is produced using reverberatory furnaces 

(based on 1999 numbers). In addition, 20% oxygen enrichment was assumed for the metal 

melting cases, while 100% oxygen enrichment was assumed for the glass melting case. The 

details of the calculations are presented in Appendix D. Results of the analysis are shown in 

Table 5. 

Table 5. Total effect of improved refractories on reverberatory furnaces 

Energy-intensive 

process industries Product 

Fuel 

decrease 

(Btu/lb) 

Wall loss 

decrease 

(Btu/lb) 

Pounds 

affected per 

year 

(× 109

) 

Energy benefits 

per year 

(TBtu) 

Aluminum, copper

a

Glass 

All 

 Metal melting 

Glass melting 

452 

476 

200 

100 

10 

40 

2 

(20% enrichment) 

76 

(100% enrichment) 

78 a Without iron and steel and metal casting contributions 

Sources: American Metal Market, Metal Statistics 1998, 90th ed., 1998; DOE Office of Industrial Technologies, 

Energy and Environmental Profile of the U.S. Glass Industry, 2002. 

4.2.4 Barriers Related to Refractory Materials for Reverberatory Furnaces 

The central conclusion from these analyses is that as flame temperatures increase and exhaust 

temperatures approach process temperatures, greater thermal efficiency is realized. As shown in 

Appendices B, D, and E, the impact of reducing wall losses by 2.5 million Btu/h leads to 

corresponding savings of 4.5 million Btu/h for aluminum (232 Btu/lb), 7.5 million Btu/h for 

copper (333 Btu/lb), and 11.9 Btu/h for glass (595 Btu/lb). Hence, improvements in reducing the 

thermal conductivity of the refractories, and improving the chemical and mechanical properties of 

the refractories, will have a significant payoff in overall fuel consumption. Addressing the 

following barriers associated with the performance of refractory materials used in reverberatory 

furnaces would improve energy efficiencies. 

1. Unavailability of refractories with sufficient high-temperature strength, erosion/corrosion 

resistance, creep resistance, resistance to large temperature gradients, and stability at higher 

temperatures for use with elevated furnace flame temperatures. 

2. Lack of sufficient high-temperature durability and corrosion/erosion resistance in current 

refractories and materials for improved heat transfer through increased levels of stirring and 

agitation of the material being processed. 

3. Unavailability of refractories with lower thermal conductivity and greater high-temperature 

stability. 

4. Lack of knowledge concerning the interactions between refractories and process 

environment/operations which leads to reduced refractory life, product sticking unscheduled 

outages, low product yield, and limited furnace campaign lives. 

4.3 Boilers and Reactor Systems 

Boilers and reactor systems are found in most industrial settings and therefore are of key interest 

as a crosscutting unit process. For the following analysis, boilers for the production of steam are 

considered for the aluminum, cement and lime, chemical and petrochemical, forest products, and 

10 
Refractories for Industrial Processing 

heat treatment industries. (See Appendix E for a schematic illustration of boiler furnace sections.) 

Additional areas for energy efficiency improvements also exist in chemical reactors utilizing 

catalysts and other reactions. 

4.3.1 Industrial Applications of Process Technology 

Aluminum — steam production Forest products — steam production 

Cement and lime — steam production Heat treatment — steam production 

Chemical and petrochemical — steam production 

4.3.2 Current Technology 

For the purpose of the performance analyses of boilers, a standard unit using a single header 

boiler system has been assumed. 

4.3.3 Energy Impact 

Improved refractory practice in boilers will result in energy benefits either from improving the 

boiler efficiency through improved vessel insulation and/or by reduced heat losses during steam 

transfer through improved transfer pipework insulation. 

The DOE Best Practices Steam System Assessment Tool was used to analyze the effects of 

improving boiler efficiency from 85 to 87% through use of the following: 

• Improved insulation for improved boiler efficiency 

• Improved pipework insulation for improved steam transfer systems 

The effects of increasing boiler efficiency by 2% and reducing heat losses during steam transfer 

by 10% are shown in Tables 6 and 7. 

Table 6. Steam system assessment tool single header analysis results for improved insulation 

for improved boiler efficiency 

85% efficient 87% efficient 

Variable boiler case boiler case Improvement 

Fuel cost, $1000/year 4,000 3,908 92 (2.30%) 

Fuel consumption, std ft3/h 71,421 69,799 1,622 (2.27%) 

CO2 emissions, 1000 lb/year 66,403 64,876 1,527 (2.30%) 

NOx emissions, 1000 lb/year 131 128 3 (2.29%) 

Table 7. Steam system assessment tool single header analysis results for improved pipework 

insulation for improved steam transfer systems 

Current 10% 

Variable operation improvement Improvement 

Fuel cost, $1000/year 4,000 3,924 76 (1.90%) 

Fuel consumption, std ft3/h 71,421 70,065 1,356 (1.90%) 

CO2 emissions, 1000 lb/year 66,403 65,142 1,261 (1.90%) 

NOx emissions, 1000 lb/year 131 129 2 (1.53%) 

11 
Refractories for Industrial Processing 

As shown in Table 6, a 2% improvement in boiler efficiency leads to a 2.3% improvement in fuel 

cost and consumption, while the 10% improvement in the efficiency of the transfer pipework 

insulation leads to a 1.9% improvement in fuel cost and consumption. As shown in the tables, 

there are also decreases in emissions associated with improvements in boiler efficiency and 

pipework insulation. If these fuel savings are then applied to the chemical, petroleum refining, 

and pulp and paper industries, estimates can be made concerning the possible energy savings 

resulting from implementation of these improvements in each industry. Table 8 shows the results 

of such an analysis. 

Table 8. Potential energy savings from improved boiler efficiency due to improved refractories 

and improved transfer pipe-work insulation 

Capture Projected 

IOF industry segment TBtu % basis fuel savings 

(%) (TBtu) 

Chemical industry steam opportunities 

Present usage of fuel for generating steam 1,540 

Opportunity for improving boiler efficiency 2.3 

from 85 to 87%

 Fuel saved 35 

Opportunity for reduced line heat losses by 10% 1.9 

 Fuel saved 30 

Chemical industry fuel reduction 65 40 26 

Pulp and paper steam opportunities 

Present usage of fuel for generating steam 2,596 

Opportunity for improving boiler efficiency 2.3

from 85 to 87%

 Fuel saved 60 

Opportunity for reduced line heat losses by 10% 1.9

 Fuel saved 49 

Pulp and paper industry fuel reduction 109 40 44 

Petrochemical steam opportunities 

Present usage of fuel for generating steam 1,675 

Opportunity for improving boiler efficiency 2.3 

from 85 to 87%

 Fuel saved 39 

Opportunity for reduced line heat losses by 10% 1.9 

 Fuel saved 31 

Petrochemical industry fuel reduction 70 40 28 

Total steam opportunity 244 40 98 

According to the DOE-EERE Best Practices report concerning steam usage in the chemical 

manufacturing, pulp and paper, and petroleum industries,4

 1540, 2596, and 1675 TBtu of fuel, 

respectively, is used to generate steam per year by each industry (see Table 8). As can be seen, on 

a 40% capture basis (i.e., 40% of the existing plants will use the improved refractory and 

insulation systems), the levels of projected fuel savings are 26, 44, and 28 TBtu, respectively, for 

the chemical, pulp and paper, and petroleum refining industries. This results in a total projected 

fuel savings of 98 TBtu across the three industries. 

12 
Refractories for Industrial Processing 

4.3.4 Barriers Related to Refractory and Insulating Materials for Boilers and Reactors 

The central conclusion from these analyses is that decreased fuel consumption resulting from 

improved boiler efficiency can be achieved through better insulation practices. As shown, the 

impact of increasing boiler efficiency by 2% and reducing heat losses during steam transfer by 

10% will result in a total fuel savings of 98 TBtu for the industries studied. Addressing the 

following barriers associated with the performance of refractory and insulating materials used in 

boilers and reactors would reduce energy requirements: 

1. Unavailability of insulating refractories with sufficiently low thermal conductivities to lead to 

increases in energy efficiency levels for boiler operations. 

2. Unavailability of improved insulating materials for transfer pipework that could help reduce 

heat losses during steam transfer operations. 

4.4 Gasifiers 

Gasifiers are currently being used in the chemical and petrochemical industry for coal and 

biomass gasification and in the forest products industry specifically for black liquor gasification. 

This technology has the potential for biomass solid fuels to be converted into fuel gas “syngas” 

consisting largely of hydrogen (H2) and carbon monoxide (CO). This gas can then be burned 

cleanly and efficiently in a gas turbine to generate electricity and/or used to synthesize clean 

transportation fuels or chemicals. 

Gasification is currently used in the chemical industry as a means to produce clean energy, highvalue energy products, and various petrochemicals from coal (including the possibility of 

producing hydrogen fuel, high-grade transportation fuels, and industrial-grade methanol). 

Experimental gasifiers are being applied in a few chemical and pulp and paper plants for coal or 

black liquor conversion, while gasification is also being used as a means of using biomass as an 

energy source rather than a waste product. In the future, the forest products industry may use 

gasification to replace Tomlinson boilers. 

A limitation on the use of these experimental gasifiers is the lack of reliable refractories for 

containment. If the refractory requirement could be met, coal, black liquor, and biomass 

gasification could lead to greater reductions in purchased energy and even change these industries 

from net energy importers to net energy exporters.5

 Gasification holds the promise of generating 

175% more electrical power than do current technologies, but the gasification technology 

currently in use requires frequent refractory relines of the vessels, hence reducing the economic 

and energy benefits.5

 Additionally, although chemical or pulp and paper manufacturing facilities 

are not currently used to produce transportation fuels from biomass, they may become a valuable 

asset for establishing an infrastructure for such technology. Future gasification-based 

“biorefineries” might produce a variety of renewable fuels, electricity, and chemicals in 

conjunction with pulp and paper products. 

4.4.1 Industrial Applications of Process Technology 

Chemical and petrochemical — coal and biomass gasification 

Forest products — black liquor gasification 

4.4.2 Current Technology 

A coal gasifier generally consists of a metallic shell protected by a lining made up of two to six 

concentric layers of refractory protecting the interior of the vessel. Coal gasifers are expected to 

13 
Refractories for Industrial Processing 

operate at high temperatures and moderate pressures, and with gas and particle flows containing 

H2, CO, H2O, C, H2S, HCl, hydrocarbons, metallic impurities, and salts. These linings have 

average lifetimes on the order of 7000 run hours and generally fail because of excessive 

mechanical wear (erosion), chemical penetration of slag into the structure of the innermost brick 

(corrosion), or some combination of these two mechanisms. Erosive wear occurs as the feedstock 

itself causes physical decay of refractory hot-face surfaces when injected at high velocities. 

Corrosive attack occurs when the coal slag residues penetrate the refractory hot face surface, thus 

weakening the refractory by forming solid-solution phases. 

The nominal scale of an average pulp and paper mill is 6 million lb/d of black liquor solids 

(BLS)—the equivalent of 1.5 million Btu/h or 438 MW fuel—corresponding to 1900 machine dry 

short tons per day of paper production (1725 metric tons).5

 Pulp mills processing more than 

6 million lb/day BLS account for about one-third of all U.S. capacity today, and this fraction will 

grow over time as mill consolidations continue. A standard sized gasifier for this size mill is 

considered. This unit was assumed to have a BLS concentration of 80% and a steam pressure of 

1870 psia. 

4.4.3 Energy Impact 

For the following analysis, we considered a combined-cycle gasifier typical of those used for coal 

or black liquor gasification with the requirements above. Combined-cycle black liquor 

gasification has the potential of producing more than twice the current output of electricity per 

ton.5

 In many cases, power in excess of a chemical or pulp mill’s needs could be produced and 

exported. Further, if gasified coal or black liquor were converted to a high-quality synthetic gas 

similar to syngas produced from fossil residual oil, the energy and economic benefits would be 

even greater. Conventional processes could then be used to convert the gas to liquid fuels or 

hydrogen. 

According to the economic and energy analysis performed by Larson et al.,5

 full implementation 

of the black liquor gasification initiative could achieve the following energy benefits by 2020: 

1. Production of up to 8 GW of electricity from sustainable, renewable raw materials by 2020 

through black liquor gasification alone. 

2. Production of 16 GW or more of electric power for the application of black liquor 

gasification in conjunction with wood residual gasification by 2020. 

3. Alternatively, displacement of more than 282 million barrels of oil per year if these 

technologies were applied to syngas production to be used for liquid fuels. 

The total of these biomass energy sources consumed at pulp mills in 2002 was estimated at 

1.6 quads (one quad is 1015 Btu).6

 The potential renewable energy generation potential from black 

liquor in the pulp and paper industry in the southeastern United States is shown in Table 9. 

Refractories and insulation materials play key roles in many of the unit operations involved in 

both of these industries. It is estimated that processes affected by refractories account for about 

40% of the industries’ direct energy consumption. Based on subsequent analyses of typical 

furnaces and unit processes, improvement of refractory systems for these two industries could 

lead to energy savings opportunities up to 129 TBtu/year. 

14 
Refractories for Industrial Processing 

Table 9. Renewable energy generation potential (billion kWh/year) from black 

liquor in the pulp and paper industry in the southeastern United States 

Technology 

Potential by 2020 

(billion kWh/year) 

Equivalent energy 

(TBtu/year) 

Conventional coal combustion 726 

(33–35% efficient) (energy needed) 

Combined cycle gasification 660 

(45–50% efficient) (energy needed) 

 Total improvement 66 

Chemical 440 

Forest products 

Tomlinson recovery boiler 4.4 15 

High-efficiency Tomlinson 16.7 57 

recovery boiler 

Combined cycle gasification 36.2 124 

 Total improvement 67 

4.4.4 Barriers Related to Refractory Materials for Gasifiers 

Addressing the following barriers associated with the performance of refractory materials used in 

gasifiers would reduce energy requirements: 

1. Unavailability of advanced refractory materials with improved corrosion/erosion resistance, 

improved reliability, and reduced maintenance costs. 

2. Lack of refractories with resistance to high alkali atmospheres and high levels of stress, 

which lead to gasifier containment issues. 

3. Lack of alternate refractory designs which would provide refractory surfaces (using coatings, 

chemical alteration of refractory surfaces, physical alteration of refractory surfaces, etc.) that 

are more impervious to wear and corrosive attack. 

4. Unavailability of refractory materials with greater thermal compatibility with metallic 

materials used in gasifiers. 

5. Overall R&D Barriers and Pathways for Refractories 

Evaluation of refractory usage, barriers, and needs of these several energy-intensive process 

industries shows that several common themes arise in the pursuit of improving refractory 

materials for greater energy efficiency. These themes relate to improving energy efficiency by 

reducing energy loss and increasing productivity through the development of higher-strength 

refractories capable of operating at higher temperatures, the development of refractories with 

lower thermal conductivity to reduce wall losses at higher service temperatures, the tailoring of 

thermal expansion capabilities of current refractories, and the development of refractories with 

greater resistance to chemical and mechanical wear (corrosion, erosion, abrasion, etc.). This 

concept is shown in Fig. 2. 

15 
Refractories for Industrial Processing 

Fig. 2. Improving refractory materials for improved energy efficiency. 

Through analysis of current refractory use, current barriers, possible improvements in process 

energy efficiency, and R&D refractory needs for several process industries, many issues common 

to multiple industries become apparent. The research focus areas and technical R&D topics below 

have been identified as issues common to many applications of refractories. 

1. Understand the degradation mechanisms of refractories in different environments 

Determine the mechanisms responsible for the chemical and mechanical degradation of 

refractories in the various environments in which they operate. 

2. Achieve improvements in thermal control 

Determine the thermomechanical properties of refractory materials and develop materials that 

will allow furnaces to operate with longer campaigns and with higher levels of insulation to 

reduce heat losses. This may also involve the implementation of new furnace designs, the 

formulation of newly redesigned processes, or the re-engineering of existing industrial 

practices. 

3. Evaluate thermomechanical properties at elevated temperature 

Determine the key properties of refractories at elevated temperatures, including hot modulus 

of rupture, hot crushing strength, creep behavior, refractoriness under load, physical and 

thermal spall resistance, dimensional changes (elastic modulus, thermal expansion, and 

growth from chemical alteration), and thermal conductivity. 

4. Form an expert advisory committee 

Assemble a committee composed of current and retired industry experts to serve in an 

advisory role for industry-focused refractory R&D projects. Additionally, inventory and 

preserve existing industrial equipment and facility resources through systematic surveys of 

refractory experts (especially retirees) so that industrial furnaces and existing laboratories can 

be utilized, when possible, to augment new experimental system requirements. 

16 
Refractories for Industrial Processing 

6. Specific R&D Areas with Barriers and Pathways 

The following text summarizes pathways for overcoming barriers for the six specific R&D areas 

that can yield the greatest returns in refractories. 

6.1 Improved Castable and Monolithic Refractory 

Barrier 

Inadequate resistance to corrosive and mechanical wear, which limits the use of castable and 

monolithic refractories. 

Pathways 

• Fabricate fusion-cast refractories (such as alumina zirconia refractories) that do not include 

silica or other glass formers. These refractories should possess greater corrosion resistance 

and thermoelastic properties. The refractories would be of use to industries such as glass, 

pulp and paper, and many others. 

• Fabricate components for continuous measurement of parameters such as temperature, bath 

chemistry, etc., that will have long-term stability in high-temperature industrial solvents, such 

as cryolite for the electrolytic production of aluminum. Candidate materials such as HfB2, 

HfC, ZrB2, ZrC, and TaC should be considered. 

• Develop oxide/nitride grain boundary additives leading to closure of open porosity in silica, 

mullite, and magnesium aluminates as used by the glass and other industries. 

6.2 Modified Fiber Materials 

Barrier 

Lack of fiber insulation materials with lower thermal conductivity, greater chemical 

resistance, and higher temperature stability limits. 

Pathways 

• Produce frothed latex/fiber mixes for gunning to reduce airborne fibers during installation. 

Enhance adhesion of materials to steel and other metals for application in heat treatment 

furnaces. Develop new inorganic binder systems. 

• Fabricate fibrous materials with greater strength and lower friability for use in heat treatment 

and chemical and petrochemical industries. 

6.3 Surface Modification (Coatings, Physical or Thermal Alteration) 

Barrier 

Lack of techniques and materials for applying surface coatings or inducing physical alteration 

of refractory surfaces through either mechanical or thermal means. 

17 
Refractories for Industrial Processing 

Pathways 

• Modify surfaces or near-surfaces of sintered alumina and mullite refractories by applying 

corrosion/erosion-resistant coatings such as spinel phases (or additional corrosion-resistant 

materials) for use by industries such as glass, pulp, and paper. 

• Determine the effects of “preexisting” refractory heating conditions that, when applied 

concurrently with high-intensity infrared heating, modifies the surface of bonded refractories 

and results in the residual compression of a modified surface at service temperatures. One 

advantage of this could be an increase in the “strain-free” temperature of refractories used in 

process industries. 

• Determine the applicability of radiation-heating attenuation/mitigation, and if applicable, 

simulate refractory structures that would maximize its effect to optimize radiant heat transfer 

(e.g., improve oxy-fuel fired systems for the aluminum, glass, metal casting, and iron and 

steel industries). 

• Investigate the effects of radiative heating and transmittance in refractories on thermal 

conduction for minimizing thermal losses from various types of furnaces used throughout the 

selected industrial areas. 

6.4 Synthetic Aggregates and Powders 

Barrier 

Lack of higher-performance aggregates that would increase the life and durability of 

refractory products used across the various industries and lack of higher-quality matrix 

materials that would increase the durability of refractories. 

Pathways 

• Measure and model strength as a function of aggregate size distribution. Tailor microstructure 

so that flexure and compression strengths are increased. 

• Explore candidate aggregate coatings as “additives” that control or binder grain boundary 

effects (e.g., diffusion, heat transfer, corrosion-resistance, etc.) for improved refractory 

processing. 

6.5 High-Temperature Properties of Refractories 

Barrier 

Lack of information on the high-temperature thermomechanical and corrosion properties of 

current and newly developed refractory materials. 

Pathways 

• Develop realistic test methods and environmental tests systems in order to evaluate elevated 

temperature properties. Evaluate corrosion behavior of refractories for various effects of 

water/CO/CO2/alkali content on the corrosion and phase stability of refractories used in 

gasifiers and in the glass, aluminum, steel, and metal casting industries. Develop lab-scale 

systems to evaluate the degradation of refractories up to 2000°C. 

• Systematically characterize and model reheat-generated permanent expansion effects in 

fusion-cast and bonded refractories, a phenomenon known to occur in many refractory 

systems used throughout the various process industries, but not currently understood. 

18 
Refractories for Industrial Processing 

• Perform postmortem analysis on failed refractory components from several industries and 

identify service-limiting flaw types. Use component samples for measurement of strength 

distribution and compare to strength distribution of virgin materials. Perform probabilistic 

strength-size-scaling analysis using both distributions as input and predict failure time of 

components. 

• Measure the corrosion resistance of bonded refractories as a function of refractory sintering 

temperature and interpret the performance in reference to service temperature. 

• Investigate the effect of specimen size in refractories by measuring strength (modulus of 

rupture) as a function of specimen size in bonded or fusion-cast refractories. Determine if 

variations in strength can be represented by a Weibull distribution and if strength is sizescaled. 

6.6 In Situ and Graded Refractories 

In situ refractories are defined as brick or unshaped products that react internally or with 

furnace atmospheres and/or slag components to enhance their performance. Natural in situ 

formation of Fe-Mg-O spinels in steel-making furnaces permits improved life and durability 

of these furnaces. 

Barrier 

Lack of R&D to improve existing in situ refractory systems and for development of new 

in situ systems for additional industrial applications 

Pathways 

• Model crack initiation and growth as a function of material, depth, and service properties 

using microstructure-based finite element analysis (e.g., μ-FEA, OOF). Simulate and 

optimize hypothetical microstructures that hinder crack growth. 

• Develop high-intensity infrared heating techniques to fabricate optimized graded refractory 

structures, and measure thermomechanical stability and corrosion resistance. 

• Model, simulate, and design refractory microstructures that promote maximum creep and 

erosion resistances. 

• Determine the effect of crystallography of base and in situ phases on the development of 

thermal stresses and the stability of in situ layers. 

• Determine and optimize “substrate” surface geometries (e.g., dimples, corrugated, saw-tooth) 

that will minimize shear stresses in thermo-environmental barrier refractory coatings that are 

subjected to a thermal gradient. 

6.7 Sensors for Materials Performance 

Barrier 

Lack of sensors to monitor refractory-related issues including wall thickness regression, gas 

phases, and other environmental conditions. 

Pathways 

• Develop sensors and methods for the measurement of spectral emissivity for application in 

glass tanks and metal melting furnaces. 

• Develop sensors and methods for the monitoring of wall regression due to corrosion, erosion, 

and wear in glass tanks and metal melting furnaces. 

19 
Refractories for Industrial Processing 

• Develop continuous real-time measurement techniques for parameters such as temperature, 

pressure, melt analysis, flue gas analysis, and environmental gas phases. 

The tasks and the industries which will benefit from the projects described above are shown in 

Table 10. As is evident from the table, these suggested R&D pathways are crosscutting. Although 

there is a current trend for many of these industries moving overseas, it is believed that the R&D 

pathways proposed will directly benefit U.S. industry. Even as processes such as aluminum 

smelting and glass production move off shore, there will still be a need for remelting and other 

production domestically. 

Table 10. Recommended R&D pathways for advanced refractories 

Technical R&D 

potential pathways Aluminum 

Cement 

& lime 

Chem. / 

petrochemical 

Industry segment 

Forest 

products Glass Heat treatment 

Iron 

& 

steel 

Metal 

casting 

Improved castable 

and monolithic 

refractories 

X X X X X X X X 

Modified fiber 

materials 

X X X 

Surface modifications 

(coatings, 

alterations) 

X X X X X X 

Synthetic aggregates 

and powders 

X X X X X X X 

Elevated temperature 

refractory 

properties 

X X X X X X X 

In situ and gradient 

refractories 

X X X X X X X 

Sensors for materials 

performance 

X X X X X X X X 

20 
21 
Refractories for Industrial Processing 

7. References 

1. J. Mosser and G. Karhut, “Refractories at the Turn of the Millennium,” Paper presented at 

UNITECR ’99, Berlin, Germany, pp. xxv–xxx, Sept. 1999. 

2. D. W. Freitag and D. W. Richerson, Opportunities for Advanced Ceramics to Meet the Needs 

of the Industries of the Future, DOE/ORO 2076, U.S. Department of Energy, Office of 

Industrial Technologies, December 1998. 

3. U.S. Department of Energy, Energy Information Administration, 1998 MECS Consumption, 

Table N3.2, Fuel Consumption, 1998. 

4. U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Steam 

System Opportunity Assessment for the Pulp and Paper, Chemical Manufacturing, and 

Petroleum Refining Industries: Main Report, available online at http://www.oit.doe.gov/ 

bestpractices/technical_publications.shtml under “Market Assessments.” 

5. E. D. Larson, S. Consonni, and R. E. Katofsky, A Cost-Benefit Assessment of Biomass 

Gasification Power Generation in the Pulp and Paper Industry, Princeton University, 

October 2003. Available online at http://www.princeton.edu/~energy/publications/pdf/2003/ 

BLGCC_FINAL_REPORT_8_OCT_2003.pdf. 

6. DOE/EIA Renewable Energy Annual 2001, DOE/EIA-0603, 2001 

22 
23 
APPENDICES 

24 
25 
Appendix A — Chemical and Petrochemical 

Appendix A: 

Discussion of Refractory Usage by Process Industries 

A.1 Aluminum 

Current Industry Operations and Refractory Use 

Aluminum production is energy-intensive, consuming about 0.4 quads of electrical energy per 

year in the United States.1 Additionally, the industry faces many of the same competitive 

pressures as the steel industry, including global competition, energy consumption issues, and 

pollution abatement. Therefore, a technology road map has been created to address these issues 

by targeting areas such as energy consumption, productivity, emissions, recycling, quality, 

alternate technologies, and by-products.2 

Many systems are used in the production of aluminum and its alloys, all of which depend on the 

proper selection and management to ensure the cost effectiveness of the metallurgical and 

refractory practices. These systems include steam boilers for Bayer plants, calciners, and carbon 

baking furnaces used for the production of the anodes which are consumed in the Hall-Heroult 

reduction process. In Hall-Heroult electrolytic reduction cells, the key refractories are those used 

to support the cathode hearth and to minimize the penetration of bath constituents into the carbon 

cathode and underlying refractories. Melting furnaces for alloy production by the primary and 

secondary producers include large fossil-fuel-fired reverberatory furnaces as well as a variety of 

induction furnace designs dominated by the coreless and the channel induction types. 

Temperatures and corrodant chemistries, as well as furnace atmospheres, determine the lining 

used for each of these processes. The refractories used for each will be briefly reviewed. 

Primary Aluminum Production 

The production of primary aluminum metal is based on three major steps. The first involves the 

mining of bauxite ore. There are no high-grade deposits in the United States; therefore, 

refractories play little role in this process. 

The second process involves the conversion of bauxite to metallurgical grade alumina. The Bayer 

process is based on digestion of bauxite in caustic solution heated with superheated steam to form 

sodium aluminate. Impurities are removed from the pregnant caustic by chemical reactions with 

dissolved species (primarily SiO2) and filtration of insoluble impurities (primarily iron oxide). 

The saturated solution is then cooled in precipitator tanks in which aluminum trihydrate is 

precipitated and then recovered by filtration. The aluminum trihydrate is converted to alumina by 

calcination. Two methods of calcination are employed in the industry: use of fluid bed calciners 

and use of rotary kilns. 

The third process involves conversion of alumina to aluminum by electrolytic reduction using the 

Hall-Heroult process. In the reduction process alumina is dissolved in a molten bath (cryolite, 

Na3AlF6, with additions of AlF3, CaF2, and sometimes LiF and MgF2). The cell for this process 

utilizes a containment system consisting of a steel shell lined with a castable refractory, a porous 

insulating refractory, a less porous semi-insulating refractory, and finally firebrick. A carbon 

cathode acts as the bottom of the cell for molten aluminum containment. The side-wall 

refractories are generally phosphate-bonded alumina brick or alumina castable materials. Because 

the sides of cell have less insulation, more heat is lost through the walls than the floor. The lower 

26 
Appendix A — Chemical and Petrochemical 

wall temperature is actually beneficial, causing electrolytes in contact with the wall to solidify 

and form a “frozen ledge” which protects the walls of the cell from penetration by molten 

cryolite. This practice is successful, but involves a trade-off between energy efficiency and 

electrolytic cell stability and lifetimes in terms of energy consumption. 

Reduction cells currently employ various refractories just below the carbon cathode which during 

service degrade in various ways, permitting bath constituents to move into the cathode carbon and 

refractories. The systems in place today include fireclay bricks, castable refractories, semiinsulating refractories, and insulating bricks. Systems for primary aluminum production involve 

several different designs depending on the level of amperage and the numbers and array of anode 

blocks. The current intensity for operating reduction cells throughout the world ranges from 

60,000 to 500,000 A. Yet, they all still involve a carbon cathode hearth and consumed carbon 

anodes in which the bauxite ore charge and the systems of alkali fluoride fluxes are placed and 

held while the reduction process is carried out continuously. Typically the reduction process is 

carried out at a temperature in the range of 960 to 970°C. The refractories are key components in 

reduction cells. The atmosphere inside the cavity of a reduction cell is very reactive, containing a 

mixture of CO2, CO, HF, SO2, and particulate fluoride salts. 

In all cases it seems that the formation of a feldspathic composition at the interface between the 

cathode and the barrier is highly desirable but that other bath species can still penetrate the barrier 

and lead to highly shortened cell life. Further, downward movement of alkalis and bath 

constituents through the hearth toward the subhearth insulation eventually results in the failure of 

the furnace, an event which is still quite unpredictable. Because of this, furnace lives vary from 

hundreds to thousands of days. 

Taberaux3

 has reviewed the failure mechanisms of aluminum reduction cell systems. Fireclay 

brick in one reported case lasted over 3000 days, showing that the material itself can meet the 

challenge, all other factors being optimal in their selection and control. Castables have 

disadvantages in cast-in-place systems, and currently the preference is for precast monolithic 

systems, which have had good success. Two types of dry barrier refractories are currently being 

used. Their advantages rest on ease and rapidity of installation and lack of joints. They include 

aluminosilicates on the one hand and anorthite feldspar on other, chosen because it undergoes 

beneficial in situ reactions and is, in fact, patented. 

Carbon anode baking furnaces have historically been constructed of aluminosilicate bricks. 

These bricks have sufficient refractoriness that efforts to replace them with alumina-reinforced 

versions have not been cost-effective. The challenge to the brick comes from its coking and from 

the alkalis present in the electrode feedstock. Most recently, fireclays with very low alkali content 

have been used for the production of bricks increasingly designed with surface locking systems 

that reduce the bowing of walls, which is the principal reason for the replacement of the 

refractories. Because such large numbers of bricks are used in carbon baking furnaces, attempts 

have been made to recycle them, but past efforts have not resulted in the formulation of a costeffective protocol. 

Schubert4

 recently addressed the basic issues of movement of the flue walls, and points to the 

findings in postmortems that the insulation may be inadequate for the support role that it plays. 

The many challenges to the flue walls include (1) alkali infiltration and attack from bath 

carryover, via recycled anode butts in the recipe; (2) fluoride salt attack from bath carryover, via 

recycled anode butts in the recipe; (3) minor “squatting” from elevated temperatures and load; 

(4) mechanical damage from impact of the anode and/or the crane during loading and unloading; 

(5) thermal shock, especially during the cooling cycle; (6) construction details that aggravate 

27 
Appendix A — Chemical and Petrochemical 

normal wear and tear; (7) various problems due to improper expansion allowances; and (8) coke 

sticking to refractory, aggravated by alkali content. 

Semifabricated and Secondary Aluminum Production 

Secondary aluminum production involves recycling of aluminum metal scrap. This is carried out 

in a variety of furnace designs. When large volumes of alloy are required, reverberatory furnaces 

are traditionally used. These furnaces have seen a constantly evolving refractory practice. 

Monolithics replaced bricks in the distant past, and currently monolithics in the form of precast 

“big blocks” are receiving renewed interest. A recent paper by Canon5

 reports that the real 

advantage of precast furnace components rests in the time savings rather than in the extension of 

service life. 

As in the case of the subhearth refractories used in pot furnaces, it is essential to develop a freeze 

zone in the walls of all the furnaces. This is done by selection of refractories and appropriate 

thicknesses. It is also essential to restrict the penetration of the aluminum alloy into the refractory, 

which is achieved by incorporation of additives, some of which are proprietary. As it is 

impossible to keep oxygen from reacting with the aluminum metal, a so-called bellyband 

develops in all types of melters. Because of the fluctuating level of the metal in some furnaces, 

the bellyband can be quite wide and eventually extend into the furnace to such an extent that it 

must be removed. In the case of the largest reverberatory types of furnaces the removal is 

sometimes carried out using large robotic devices. In many instances the furnace has to be shut 

down to effect adequate removal. In the hearth region of the melter, linings of silicon nitride– 

bonded silicon carbide are used for molten aluminum contact areas. 

After melting, the molten aluminum flows through refractory-lined troughs between the various 

process steps. These troughs are typically lined with oxide ceramics such as fused silica or mullite 

with 10–15% porosity and special additives to resist wetting. These materials are installed in 

board or castable form and are used due to their low thermal expansion and good thermal shock 

resistance. Still, erosion and abrasion issues are of concern. SiC-based materials have been 

considered for this application but are more expensive than oxide refractories. 

Bellyband buildup is the overriding issue in melting furnaces. Quesnel et al. 6 have reviewed the 

problem for aluminum holding furnaces and melters. There is a lack of understanding concerning 

the mechanisms of bellyband formation. The two types of tests typically used in the study of 

candidate refractories are a bellyband corrosion test (which is a simple cup test) and an 

immersion test (which really looks at the penetrability of the refractory by the metal). Long use of 

these tests has produced inconclusive answers about the mechanism of attachment, and it is 

apparent that new approaches are needed. 

Barriers 

Refractories play key roles in most of the unit operations involved in the production of primary 

and secondary aluminum. It is estimated that about 90% of the direct energy use by the industry is 

in processes affected by refractories. Recommended improvements for refractories include 

applications for refining, reduction, carbon anode baking, and melting operations. Based on 

subsequent analyses of typical furnaces and unit processes, improvement of refractory systems 

for the aluminum industry could lead to energy savings opportunities up to 29.2 TBtu/year. The 

specific barriers are as follows: 

28 
Appendix A — Chemical and Petrochemical 

• Aluminum Refining 

Unavailability of improved refractories for superheated steam generation, as well as 

improved refractories for calcining operations, particularly rotary kilns for alumina and lime, 

which could lead to improved energy efficiency for refining operations. 

• Aluminum Reduction 

Lack of understanding concerning the mechanisms and degradation scenarios leading to the 

failure of reduction cell refractories and, ultimately, the reduction cell. Further, there is a lack 

of improved linings and refractories with improved resistance to bath penetration that would 

permit extended lives for reduction cells. 

• Carbon Anode Baking Furnaces 

Unavailability of stronger insulating shapes for components of carbon baking furnaces. 

• Aluminum Melting Furnaces 

Lack of understanding regarding the mechanisms of bellyband buildup formation. This is 

complicated by the inability of current tests to provide conclusive answers regarding the 

mechanism of attachment and to provide sufficient performance projections. 

R&D Pathways 

• Refining 

o Develop improved refractory and insulation systems for high-temperature steam 

generation. 

o Improve refractory materials for calcining operations, particularly for rotary kilns. 

• Reduction 

o Develop a fuller understanding of cell refractory failure through chemical and 

physical modeling of the reactions and transport mechanisms. Develop knowledge 

and control of all aspects of the chemical and physical properties of the refractories, 

and optimized refractory design approaches for reduction cells carrying increasing 

current intensities. 

o Develop a sidewall refractory design that would allow direct contact with the molten 

cryolite bath, permitting elimination of the “frozen ledge.” 

o Develop refractories with improved toughness, impact resistance, and abrasion 

resistance for the hearth region of reduction cells. 

• Carbon Baking 

o Develop understanding of the manner in which insulation components are being 

affected chemically and mechanically by the loads from the overlying charge and 

wall refractories. Perform studies of the mechanical properties of such used 

refractories to provide answers to these and related questions tied to assuring 

thermomechanical stability. 

o Develop improved refractories and furnace designs for reducing energy consumption 

in carbon melting furnaces though modeling of design, process control, quality 

control, and selection of hot-face refractories, not only in the flue walls but in other 

components of the furnaces. 

29 
Appendix A — Chemical and Petrochemical 

• Melting Furnaces 

o Develop more accurate simulations of the melting process. 

o Develop a materials approach that involves the development of graded monolithic 

linings, cast in place or precast, which have much denser surface regions and might 

also contain additives to dissuade penetrants. Determine the key factors which affect 

penetration and attachment such as the permeability of the surface region to the metal 

or altered metal. 

o Develop improved refractories for aluminum melting and casting operations, 

including advanced refractories for reverberatory melting furnaces and prefired 

refractory riser tubes for low-pressure aluminum die casting applications that are 

economical, strong, thermal-shock-resistant, and nonwetting to molten aluminum, 

and that have low gas permeability. 

o Develop efficient, long-life degassing components for aluminum alloy production. 

A.2 Cement and Lime 

Current Industry Operations and Refractory Use 

The United States is the third largest cement-producing country in the world (after China and 

India). The production of cement and its intermediate product, cement clinker, has risen steadily 

over the last decade, with consumption increasing 40% while production has only increased 27%. 

This has led to increased imports in the short term, mainly from Canada and Mexico, but could 

lead to further expansion of the domestic industry in the long term. Currently, there are 115 

cement manufacturing plants in the United States, with about 75% of the total plants owned by 

only 10 large companies: Lafarge North America, Inc.; Holcim (US), Inc.; CEMEX, SA de CV; 

Lehigh Cement Company; Ash Grove Cement Company; Essroc Cement Corporation; Lone Star 

Industries, Inc.; RC Cement Company; Texas Industries, Inc. (TXI); and California Portland 

Cement Company. 

The 1997 Economic Census report (sampling 279 establishments) shows that refractories (clay or 

non-clay) account for 2.5% of the total cost for the cement industry, or approximately $61.5 

million of the total $2.5 billion spent. 

A typical modern cement plant may include the following refractory lined units: (1) a preheater 

equipped with several cyclones as a heat exchanger, (2) a precalciner with a burner for the 

decarbonization process, (3) a kiln, and (4) a kiln cooler. The preheater, cyclones, and heat 

exchangers heat the cement raw meal or slurry before it is passed to the rotary kiln. This aids fuel 

economy by decreasing the amount of heat that the kiln must supply. The precalciner uses 

preheated combustion air from the clinker cooler and/or kiln exit gases with separate burners to 

calcinate up to 95% of the raw material. A precalciner kiln system consisting of a rotary kiln with 

an external furnace may also be used for heating cement raw meal to calcination temperatures. 

This system also often has a multistage cyclonic preheater attached to it for further heating 

efficiency. 

The kiln is where cement raw mix is dried, calcined, and burned into clinker at temperatures of 

2600–3000°F. Kilns can be rotary (rotating at one to three revolutions per minute) or shaft type 

and use coal, oil, gas, or other fuel for heating. A rotary kiln will generally be divided into zones 

30 
Appendix A — Chemical and Petrochemical 

for drying, preheating, calcining, burning, and cooling. Kilns having a preheater and/or 

precalciner do not usually contain the first three zones. The molten batch emerges from the lower 

end of the kiln in the form of very hot, marble-sized chunks known as “clinker.” Once out of the 

kiln, the clinker goes through a cooling process in the kiln cooler. When cool, the clinker is ready 

to pass through a series of grinding and milling processes that result in the gray powder we know 

as cement. 

The kiln is the heart of the plant and is generally lined with fired bricks. Monolithic refractories 

are used only in tapered parts of the inlet chamber, the manhole of the calciner, and the charging 

inlet of the kiln. These monolithics are required to posses high resistance to reaction with cement 

raw materials, high resistance to penetration/infiltration of alkalis, as well as high resistance to 

mechanical stress. Generally, dense low-cement, high alumina castable with service temperatures 

of 1700–1800°C (3092–3272°F) is used here. 

A typical long kiln will include a drying zone, a preheating zone, a calcining zone, a burning 

zone, a transition zone, and a cooling zone to create a temperature profile in the kiln. Generally, 

fireclay bricks or high-alumina bricks are used in the drying and calcining zones. Lightweight 

insulating bricks are used to reduce the heat loss from the kiln. In these zones, refractories are 

subjected to abrasion and structural spalling caused by reactions with alkali from the cement raw 

materials. The temperature is relatively low in these zones, but because of the use of various 

wastes as fuel and constant temperature fluctuations, the refractory wear can become severe. Fuel 

types vary among petroleum coke, tires, solid wastes, etc., resulting in increased concentrations of 

alkalis (Na, K), sulfur (S), and chlorine (Cl) as well as other environmentally detrimental metals 

(Pb, Zn). As a results, the refractories are subjected to harsher alkaline sulfate [(K3Na(SO4)2, 

K2SO4] and alkaline chloride (KCl, NaCl) condensation at cooler zones. Sulfur additionally 

combines with the cement component (CaO) to form CaSO4 cotectic liquid. These liquid and 

vapor phases infiltrate into bricks, resulting in refractory densification, increased thermal 

conductivity, and thermal expansion which ultimately reduces the structural flexibility of kiln 

linings. Additionally, the increase in thermal conductivity often damages the steel shell. 

Monolithic refractories are also used in sections of cement kilns, typically at the outlet where 

wear rates are very high. At these zones, dense silicon carbide–based castables are often used. 

The cyclones in the preheater section of cement plants are also lined with dense castables, due to 

the complexity of their shapes and the wear resistance required. The shell of the exhaust gas duct 

is made from both dense and insulating castable material. In the cooler section of the plant, 

monolithic refractories are used to line the ceiling. The upper and middle cyclones of the calciner 

are generally lined with fireclay castable or equivalent gunning materials possessing a service 

temperature of 1400–1500°C (2552–2732°F). One common problem with this arrangement arises 

when cement raw materials reach the inlet chamber and riser because they adhere (stick) to the 

refractory lining and thus cause clogging. This clog is either mechanically removed or removed 

with high-pressure water. 

In the United States, as in most industrialized countries, two types of manufacturing processes 

have become prevalent in the cement industry; these are known as the “wet process” and the “dry 

process.” Although in many respects these processes are the same, or very similar, in the older 

wet process, ground raw materials are mixed with water to form a thick liquid slurry, while in the 

dry process crushed limestone is used and raw materials are mixed together without the addition 

of water, leading to higher energy efficiency, since drying is not needed. Currently there is a 

general trend in the United States to convert wet kiln technology to dry kiln technology; as a 

result, in 2000 there were 32 wet and 77 dry kilns. 

31 
Appendix A — Chemical and Petrochemical 

The major fuels used in U.S. cement plants are coal and coke, or coal and petroleum, and are used 

for the clinkering process. After 1980, however, other fuels—including tires, solid and liquid 

hazardous wastes, and nonhazardous wastes such as oils and solvents—began to be gradually 

used. The use of these alternative fuel types has significantly increased in recent years, as shown 

in Table A.1. Overall, this suggests that there have been no major changes in energy-efficient fuel 

use in cement kilns since 1990, although more modern plants have been built. The survey, by the 

Portland Cement Association (PCA), suggests slightly lower average energy uses of 4.73 GJ per 

million metric ton of clinker and 4.91 GJ per million metric ton of Portland cement for 2000. 

Further, the 1997 Economic Census report (sampling 279 establishments) showed that energy 

costs (fuel costs and purchased electricity costs) account for 40% of the total cost for the cement 

industry, with approximately $485 million spent on fuel and a similar amount spent on 

electricity.

7 

Table A.1. Feedstock for energy use in the cement industry, 1993-2001 (thousand metric tons) 

1993 1994 1995 1996 1997 1998 1999 2000 2001 % 

change 

Coal 10,034 10,484 8,241 8,764 9.035 9,066 9,206 10,095 10,240 2.05 

Coke 

from coal 

NA NA 455 458 351 432 343 442 420 –7.69 

Petroleum 

coke 

NA NA 1,475 1,295 1,288 1,197 1,622 1,351 1,370 –7.11 

Fuel oilsa 46 49 42 64 86 73 82 124 93 102.2 

Natural 

gasb 

668 650 1,069 710 672 720 653 338 397 –40.5 

Tires 70 120 158 191 277 269 685 374 300 328.6 

Solid 

wastes 

90 74 68 72 68 74 816 1,016 320 255.6 

Liquid 

wastesa 

744 600 885 910 835 1,268 906 929 829 11.4 

a

 Millions of liters. b

 Millions of cubic liters. 

Barriers 

Refractories play key roles in calcining operations, the core production method for the cement 

and lime industries. It is estimated that almost all of the energy consumption is affected by 

refractories. Recommended improvements for refractories include applications for all of the 

thermal zones of typical rotary calciners. Based on subsequent analyses of typical furnaces and 

unit processes, improvements to refractory systems for the cement and lime industries could lead 

to opportunities for energy savings of up to 42.3 TBtu/year. The specific barriers are shown 

below. 

• Unavailability of chrome-free refractories for use in the transition zones of lime kilns, where 

refractories are subjected to large temperature fluctuations by the repeated detachment and 

adhesion of the cement coating. 

• Unavailability of refractories with adequate corrosion resistance and adhesion (coating) 

ability for use in the burning zone of lime kilns, where temperatures reach to above 1450°C 

(2642°F). 

32 
Appendix A — Chemical and Petrochemical 

• Unavailability of refractory monolithics with high abrasion resistance as well as high 

resistance to mechanical and thermal spalling for the inlet chamber and riser of kilns to 

replace less adherent silicon carbide castables and precast shapes. 

• Unavailability of monolithic refractory materials with resistance to alkali reaction for use as 

clinkers in the cooling zone of the kiln to replace low-cement, high-alumina castables used in 

the area. 

R&D Pathways 

• Develop monolithics with better abrasion resistance and low or no adherence properties. 

• Develop methods to modify the surfaces of clinker zone brick, so as to encourage the 

formation of protective coatings by physically altering the refractory surface or through 

chemical alteration of the surface. Develop and improve magnesia-spinel brick and 

demonstrate the effect of zirconia additions. 

• Identify non-chrome-containing refractories which possess increased corrosion resistance to 

the environment present in cement manufacturing. 

• Develop nondestructive techniques for monitoring wear of refractories. 

• Develop and improve silicon carbide castables to produce products with improved thermal 

properties and even less adherence to cement raw materials. 

A.3 Chemical and Petrochemical 

Current Industry Operations and Refractory Use 

The chemical industries have processing equipment that spans a broad range of types, with 

associated processing temperatures ranging from as low as 370–425°C (700–800°F) to as high as 

1870°C (3400°F). The refractory-lined units in a typical full-spectrum refinery can include 

fluidized catalyst cracking units (FCCUs), catalytic reformers, fired heaters, boilers, hydrogen 

reformers, ethylene furnaces, incinerators, and carbon furnaces. Some of these units are designed 

to have substantial insulating capability in their linings, while others are low-temperature-process 

units, like FCCUs that contain only a single layer of refractory designed to withstand the 

extremely severe abrasion caused by the catalyst. 

The estimated cost of refractory lining installation and maintenance work for the chemical and 

petroleum industries is relatively low (as low as 1% of the total operating cost) compared to other 

equipment construction and maintenance costs; yet, refractory lining degradation and failure are 

leading factors for frequency and duration of shutdowns. Due to lower operating temperature, as 

compared to other industries, refractory is not normally affected by high temperatures, yet 

refractory degradation may be caused by erosion, corrosion, and mechanical stresses caused by 

thermal cycling, depending on location of the refractory within the unit. Another problem that can 

affect refractory reliability is the manner in which the refractory is installed (i.e., pneumatically 

gunned, shotcreted, vibration cast, pump cast, and/or hand packed). Additionally, with operating 

time, minor imperfections can become locations of exacerbated lining degradation. Lining design 

(i.e., anchoring, lining thicknesses, and design of construction/expansion joints) can also add to 

lining degradation. 

33 
Appendix A — Chemical and Petrochemical 

Also, the total tonnage of refractories in an average-sized full-spectrum refinery can be as high as 

1000 tons of refractory for a single lining that is intended to last for at least a decade: a typical 

refinery requires approximately 2500 tons of refractory. Some of the more critical units are put on 

maintenance, with annual turnaround, and the replacement and repair of refractories for a single 

unit can amount to 250 tons, or a fourth of the lining. 

Virtually all of the refractories used by chemical plants are monolithics. These include castables, 

cast vibration mixes, gunning mixes, low- and no-cement castables, plastics, and a variety of 

insulating refractories. Because many of the temperatures of refinery processes are too low to 

promote a ceramic bond to replace the hydraulic bond of calcium aluminate–bonded castables, 

the refractory practice has been based largely on phosphate-bonded plastics, which develop the 

needed properties at or below the process temperatures. Refractory practice varies widely from 

one company to another. Some companies have incorporated castables, especially vibratables, 

into their practice, and today companies are evaluating shotcretable refractories in locations 

where a ceramic bond can be developed at the process temperature. 

However, the place where advances in refractories may have the greatest impact on efficiency in 

the chemical industry is in the boilers used to produce steam for power generation. Improvements 

in the thermal efficiency of boilers themselves, through improved insulation, and in the insulation 

used on transfer pipework could lead to reduction in heat loss and lower fuel consumption. 

In the petrochemical and synthesized gas industries in particular, new designs in the catalyst 

support media and the installation of refractory insulation have increased operation life and 

efficiencies of reactors of various types. New refractory designs for support media have allowed 

increased flow rate and longer productive life for expensive catalyst materials. More attention 

being paid to the use of sprayable refractory ceramic fiber lining materials as well as new 

microporous silica backup materials. More attention is also being paid to the use of precast parts 

for component of the various unit processes, and wider use of precast technology is anticipated. 

Because it is so important to maintain shell temperatures of vessels and reactors above a threshold 

temperature to avoid condensation onto the shell, designers are trying to refine the models for 

predicting temperature gradients and cold face temperatures. Lack of data on the thermal 

conductivity of many commercial monolithic refractories is holding back progress in this area. 

Barriers 

Refractories and insulation materials play key roles in most of the varied unit operations involved 

in the production of chemical and petrochemical products; it is estimated that about 50% of the 

industries’ direct energy consumption is in processes affected by refractories. Based on 

subsequent analyses of typical furnaces and unit processes, improvement of refractory systems 

for the chemical and petrochemical industries could lead to energy savings opportunities of up to 

266.4 TBtu/year. The specific barriers are shown below. 

• Lack of understanding of high-temperature properties such as creep rupture, short-time 

strength, thermal conductivity, thermal expansion, ductility, and stability for the monolithic 

refractories used in this industry. 

• Lack of understanding of the corrosion properties of refractories used in the chemical and 

petrochemical industries, which subject materials to conditions ranging from hot-oxidizing 

environments to environments that contain hot halogen gases or gases with entrained 

particles. 

34 
Appendix A — Chemical and Petrochemical 

• Lack of understanding regarding turnaround times and maintenance costs, which have 

become increasingly more important cost elements. Lack of understanding regarding the 

reduction of energy consumption and air pollution. 

• Lack of understanding regarding high-temperature and corrosive environments which limit 

refractory life and increase maintenance costs in numerous chemical and petrochemical 

reactors. 

R&D Pathways 

• Develop improved refractories for minimizing mechanical damage to refractory-lined 

refining vessels through reduction of the amount of mechanical stresses on the lining. 

• Perform work to optimize the physical properties of refractories (i.e., thermal insulation, 

erosion resistance, corrosion resistance, thermal shock resistance, strength, porosity, and 

permeability) under known required operating conditions for specific unit types. Develop 

realistic and reproducible product development and quality control testing that can be used to 

relate step improvements in needed physical properties of the current refractory lining 

materials in service. 

• Develop improved methods of analysis for high-temperature equipment through techniques 

for online refractory inspection. 

• Develop longer-life refractories that are field-repairable, less brittle, and more shockresistant. 

• Acquire thermophysical, kinetic and mechanical data on refractories. 

• Develop ceramic-metal-matrix composites with improved stability and explore surface 

modification and/or coatings for use in corrosive environments. 

• Develop materials to withstand high temperatures (1000–3000°F) while retaining superior 

strength, ductility, corrosion and wear resistance to resist damage due to corrosion and high 

temperatures present in the chemical process industry. 

• Develop materials with enhanced resistance to organic acid environments and improved 

materials for chlorine-based processes, to improve plant operations and maintenance 

requirements and reduce costs. 

• Develop refractories and refractory coatings for high-temperature furnaces to reduce energy 

and maintenance costs. Develop high-temperature nonstick surfaces that do not degrade or 

become volatile at high temperatures to help reduce needed maintenance of chemical process 

equipment. 

A.4 Forest Products 

Current Industry Operations and Refractory Use 

Although the pulp and paper industry is not a substantial user of refractories, the forest products 

industry is the third largest consumer of energy in the United States, at approximately 3.3 quads 

per year.8

 To its credit, the industry generates 63% of its own energy using recycled woody waste 

products and other renewable sources for fuel (bark, wood, and pulping liquor). Since 1972, the 

industry has reduced its use of fossil fuels and purchased energy by about 2% while increasing 

total production by nearly 64%. In the future, black liquor and biomass gasification will lead to 

35 
Appendix A — Forest Products 

greater reductions in purchased energy and could even change the pulp and paper industry from a 

net energy importer to a net energy exporter. Gasification holds the promise of generating 175% 

more power than do current Tomlinson furnaces, but the gasification technology currently in 

place requires yearly refractory relines of the vessels.9 

Lime recovery kilns are used in most forest products industries as an integral component of the 

Kraft pulping process, with lime recovery kilns operating at a level of 7 million Btu/ton of lime 

recovered. Yet, these kilns have the disadvantages of cyclic production rates, poor product 

quality, dust cycles, rings, material buildups, and blockages. Most of these deficiencies can be 

related to premature brickwork failure and buildups, with loss in production of up to 35 days per 

year being attributed to ringing. 

Barriers 

It is estimated that about 40% of direct energy consumption by the forest products industry is in 

processes affected by refractories. Based on subsequent analyses of typical furnaces and unit 

processes, improvement of refractory systems could lead to energy savings opportunities of up to 

129 TBtu/year. Specific barriers are shown below. 

• Lack of understanding regarding problems associated with sticking of reactants and products 

to the refractory linings of lime kilns, limiting their operating lives. 

• Unavailability of materials with corrosion resistance to the harsh, high-alkali black smelt 

environment (consisting of steam, sulfur, hydrogen, and CO) and abrasion/erosion resistance, 

spall resistance, and thermal compatibility with metallic materials used in the gasifiers. 

• Unavailability of improved materials for containment which do not react with the high-alkali 

atmosphere present in the gasifier. Such reactions result in slabbing, which limits the lining 

life. 

• Lack of a database on the properties of the castable materials used in this industry, 

information which is not provided by the refractory producers. 

• Unavailability of improved refractories for Tomlinson recovery boilers to replace fireclay, 

alumina brick, or similar monolithic compositions used in the floor. Improved refractories 

could decrease the amount of furnace downtime needed for repairs and would decrease 

energy usage due to shutdown and restart cycles. 

• Lack of refractory systems with sufficient alkali corrosion resistance for storage container 

linings used for hot pulping chemicals. 

R&D Pathways 

• Develop improved refractories for lime kilns to reduce downtime due to ringing and buildups, 

thus leading to increases in energy efficiency due to better thermal management and increases 

in lime kiln lining lifetimes. 

• Develop advanced refractories to provide suitable materials for use in black liquor and 

biomass gasifiers. Advanced refractories could lead to substantial improvements in energy 

efficiency for the forest products industry, which currently requires yearly refractory relines 

of the vessels. 

• Develop materials with greater resistance to the corrosion in molten salt environments, 

greater abrasion/erosion resistance, and greater spall resistance. In addition, develop alternate 

refractory schemes to provide refractory surfaces which are more impervious to wear and 

36 
Appendix A — Forest Products 

corrosive attack through coatings, chemical alteration of refractory surfaces, physical 

alteration of refractory surfaces, etc. 

• Develop refractory materials which are more thermally compatible with metallic materials 

used in gasifiers. 

A.5 Glass 

Current Industry Operations and Refractory Use 

The glass industry produces a wide variety of products using different process technologies. 

Perceived differences across the segments of the glass industry remain a barrier to broad-based 

industry collaboration. These differences have led individual segments to select different melting 

technologies, prefer different refractories, and operate furnaces that differ in size and scale. 

Capital and operating costs for the individual segments reflect these product and process 

differences. Further, differences in glass types and industry segments and the needs of large 

versus small furnaces limit the ability to define common interests. There are also concerns with 

project definition and management for cooperative efforts: costs, timing, and sharing of technical 

and financial risks and the intellectual property generated. 

Melting of the batch is accomplished using different types and sizes of furnaces, with refining 

occurring in the melting chamber. Furnaces may be discontinuous (<5 ton/day) or continuous 

(large operations, estimated to last up to 10–12 years today). Continuous furnaces may be directfired (units fired with natural gas and producing 20–150 ton/day), recuperative furnaces (directfired furnaces fitted with recuperators to recover heat from exhaust gases), regenerative furnaces 

[the most commonly used furnaces, with capacities of 100–1000 ton/day, and with the furnace 

heat collected in a regenerator that is used to preheat combustion air as high as 1260°C (2300°F) 

and achieve higher energy efficiency] or all-electric melters. 

Commonly, alumina-zirconia-silica refractories are used as sidewalls, with zirconia content 

ranging from 33 to 41%. Chrome-containing refractories are also used in the fiberglass industry 

because of their additional corrosion and erosion resistance, but their use is decreasing because of 

environmental concerns about chrome. Refractories containing chrome are not used in the flat, 

container, or pressed/blown glass industries because chrome impurities can discolor the glass. 

Silica is commonly used for the crown of the furnace, or sometimes mullite if oxy-fuel firing is 

employed. Due to chemical incompatibilities, a layer of alumina-zirconia-silica is often used as a 

buffer between the crown and sidewall.1 

Significant progress has been made in reducing energy intensity in areas of the glass industry 

over the last ten years. This increase in efficiency has been accomplished mostly through 

improved process control systems, the development and use of advanced refractory materials, and 

technologies such as oxy-fuel firing and electric boost, which increase production capacity. 

Advanced technology has reduced the fuel consumed per ton of glass melted by 25% since the 

early 1980s, and energy use has declined in the fiberglass sector by 30% since 1978.10 

Still, energy efficiency depends on the size of the operation and the production rate. For example, 

a large (120 ton/day) all-electric furnace uses electricity at 66% overall efficiency, while a small 

all-electric furnace (4 ton/day) has about 34% overall efficiency.

11 Electric glass-melting furnaces 

are more thermally efficient than oxy-fuel because there is less mass (melt basin only) and less 

surface area for heat losses. Average oxy-fuel melters consume 3–5 MMBtu from fossil fuel per 

37 
Appendix A — Glass 

ton of glass melted. This is in comparison with the average electric consumption of all-electric 

direct resistance glass melters of about 2.7 MMBtu/ton. 

Yet, modern glass melting still requires a high-temperature device that consumes a significant 

quantity of energy, with melting energy representing about 15% of the manufacturing costs. 

Although there are some proven energy-reduction technologies for melting that are not currently 

being implemented and some concepts which have been identified to further reduce energy 

consumption (improvements in corrosion-resistant refractories, insulation, combustion, process 

control), the economic incentive for adopting these proven technologies and developing these 

new concepts may not currently be sufficient to justify the cost and the effort. This may be 

because the industry views minimizing the energy cost per ton of glass produced as more 

important than reducing the energy content as measured in thermal units and because the value of 

the energy saved at the current cost of energy, with an assumed low rate of cost escalation, is not 

sufficient to justify many energy-saving technologies. In particular, technologies that require any 

significant capital investment are usually discarded by the glass industry or looked upon 

unfavorably, with many glass manufacturers expecting a one- to two-year payback for capital 

investments.12 Specific energy usage by sector is shown in Table A.2. 

Table A.2. Estimated energy use in melting and refining 

Av. specific Annual 

Glass sector energy use energy use 

(106

 Btu/ton) (10 TBtu) 

Flat 8.6 42.9 

Container 5.5 53.1 

Pressed/blown 7.3 18.1 

Fiber 8.4 25.6 

Source: DOE, Energy and Environmental Profile of the US Glass Industry, 

DOE/GO -102002-1590, Office of Industrial Technologies, April 2002. 

Oxy-fuel firing is also still a viable technology and could improve efficiency in the glass industry. 

The trend towards using oxy-fuel firing is steadily increasing because an oxy-fuel furnace can 

produce the same amount of glass as with gas and/or air, but at a lower fuel input.13 Additionally, 

when regenerative furnaces are converted to oxy-fuel firing, the regenerator refractory structure is 

not needed, eliminating the exhaust volume by as much as 75%.

14 As of 1998, only 20% of the 

glass furnaces in the United States had been converted from air-fuel to oxy-fuel technology, with 

the greatest conversion rate found in the fibers sector.15 To date, it is estimated that the number of 

conversions has increased only to around 25% of the total industry.15 A breakdown of the number 

of conversions to oxy-fuel technology completed by 1998 in each sector of the glass industry is 

shown in Table A.3, along with estimates of the number of conversions made to date. Therefore, 

there is still a great opportunity for further improvements in the energy efficiency of the glass 

industry through further utilization of oxy-fuel fired furnaces. Further improvements in refractory 

technology are needed to fully utilize the benefits of oxy-fuel technology. 

Boosting with oxygen firing will result in increased production but will also increase the melting 

cost per ton of glass. This trade-off is accepted by the industry because the additional capacity 

gained is at a much lower capital cost than that associated with building new furnaces. Sampling 

of the industry indicates that to date, 125–150 of 500–550 total glass furnaces have been 

38 
Appendix A — Glass 

Table A.3. Conversion of North American glass melters to oxy-fuel firing as 

of 1998 and as of 2004 

Glass sector No. of oxy-fuel 

conversions 

Total no. of 

glass tanks 

% converted 

Containers 23 210 10 

Fibers 41 110 37 

 Textiles 

 Insulation 

(30) 

(11) 

(70) 

(40) 

(42) 

(27) 

Flat 2 45 5 

Specialty 54 235 23 

 All sectors 120 600 20 

Containers 27 180 15 

Fibers 46 100 46 

 Textiles 

 Insulation 

(35) 

(11) 

(62) 

(38) 

(56) 

(29) 

Flat 3 45 7 

Specialty 60 225 27 

 All sectors 136 550 25 

As of 1998 

As of 2004 (estimated) 

converted to oxy-fuel firing. This is only 25% of all the furnaces in the industry, leaving a large 

number of furnaces that could be converted to the more efficient technology, leading to pollution 

abatement and higher energy efficiency, if improved alternate refractories with sufficient 

corrosion resistance and thermal efficiency could be found. Of the various segments making up 

the glass industry, the fiber area has made the most use of oxy-fuel firing, with nearly 50% of 

these furnaces having been converted; in second place is the specialty area, with over 25% of the 

furnaces converted. Great opportunities exist in the flat and container glass segments, which have 

conversion rates on the order of 5 to 15%. 

Barriers 

Refractories and insulation materials play key roles in many of the unit operations involved in the 

glass production; it is estimated that about 70% of the direct energy consumption is in processes 

affected by refractories. Based on subsequent analyses of typical furnaces and unit processes, 

improvement of refractory systems for the glass industry could lead to energy savings 

opportunities of up to 13.9 TBtu/year. Specific barriers are shown below. 

• Unavailability of durable and inexpensive materials for use for refractories in constant 

contact with molten glass, combustion gases, and hot glass products in glass furnaces which 

operate continuously at temperatures exceeding 1400°C in the molten bath and 1600°C in the 

combustion atmosphere for operating lives of 8–10 years. 

• Unavailability of parts and installation equipment to replace parts and materials that fail 

during production campaigns, without major furnace shut-downs and loss production. 

• Limitations on energy efficiency and degrading glass quality, particularly in oxy-fuel 

environments, due to limitations of refractory performance. 

• Lack of knowledge that would improve the performance and quality of existing refractories 

and lead to increased production life and lower installation costs. 

39 
Appendix A — Glass 

• Lack of modeling of corrosion mechanisms that would help determine solutions for reducing 

corrosion in refractories and for providing adequate on-line sensors that would optimize 

operation control, leading to longer-life, corrosion-resistant refractories, thereby reducing 

capital costs for glass melting and forming applications. 

• Lack of knowledge in the form of a materials property database, identification of new melting 

techniques and their associated refractories, and better methods for the evaluation and repair 

of refractories in service. 

R&D Pathways 

• Develop integrated furnace models for the prediction of methods for improving thermal 

efficiency, for developing new glassmaking technologies, and for projecting performance of 

alternate refractory materials. 

• Develop refractories (particularly for furnace crowns) having sufficient strength and 

corrosion resistance at higher operating temperatures when using oxygen enrichment. 

• Develop monolithic and/or coated refractories that will be more resistant to penetration of 

corrosive liquid and gaseous species. 

A.6 Heat-Treating and Annealing 

Current Industry Operations and Refractory Use 

Heat-treating is a $20 billion industry in the United States and represents $75 billion or more in 

value-added manufacturing globally.

16 It is also crosscutting, enabling technology that affects 

most of the industries found in the United States, including aluminum, glass, iron and steel, and 

metal casting. The goal of the Heat Treating Industry Vision 2020 is to reduce energy usage in the 

heat-treating industry by 80%. To achieve this goal, cooperation is needed between all the related 

industrial groups, including the heat treating community, metal producers, foundry and forging 

groups, fabricators, government, and academia. 

One of the most important research needs for this industry is the development of integrated 

process models. Heat treating today is viewed as an experience-based art. However, in the future 

it must function in a scientific, predictive environment, where processes are truly understood and 

capable of being simulated. For example, it has been demonstrated that the solutionizing time for 

a cast aluminum alloy could be reduced from 12 to 2 h with no loss of quality or properties. This 

magnitude of heat treatment cycle time reduction could result in increased productivity and/or 

reduced energy consumption of greater than 50%. Validated databases for multicomponent alloys 

and predictive models will enable comparable results to be achieved for a wide range of alloys 

and applications.17 

Barriers 

Refractories and insulation materials play key roles in various furnace systems used in the heattreating and annealing industries; approximately 90% of direct energy consumption is in 

processes affected by refractories. Based on subsequent analyses of typical furnaces and unit 

processes, improvement of refractory systems for the heat treatment and annealing industries 

could lead to energy savings opportunities up to 45 TBtu/year. Specific barriers are shown below. 

40 
Appendix A — Heat Treating and Annealing 

• Unavailability of high-performance refractories for the improvement of thermal efficiency in 

furnace systems that would lead to reduced cycle times, lower required energy input, and 

lower processing costs. 

• Unavailability of gradient refractory systems with lower thermal conductivity and hightemperature strength and corrosion/erosion resistance for reducing heat losses and improving 

chemical compatibility. 

• Unavailability of refractory materials with longer lifetimes due to improved corrosion 

resistance, extended temperature resistance, and mechanical thermal stability, while also 

possessing reduced costs. 

R&D Pathways 

• Develop improved insulation materials to achieve higher operating temperatures, reduce heat 

losses, and eliminate reheating while also reducing process time and production costs. 

• Develop higher-efficiency insulation materials to increase the thermal efficiency of current 

processes and simultaneously lower heat-treatment times, leading to significant reduction of 

energy consumption levels. This could then lead to the development and application of 

accelerated heating technologies, which will require alternative insulation materials with 

greater thermal shock resistance and high-temperature stability. 

A.7 Iron and Steel 

Current Industry Operations and Refractory Use 

In the steel industry, competitive pressures such as worldwide overcapacity, the high cost of 

energy, environmental and safety regulations, competing materials, customer demand for high 

quality, and the high cost of capital have led to a need for sweeping changes across the industry. 

Therefore, four critical areas for improvement or targets of opportunity were identified: 

(1) process efficiency through improved throughput, quality, and energy efficiency, (2) increased 

recycling, (3) new processes to avoid or reduce air and water pollution, and (4) product 

development.18 

As part of the approach to address these areas, refractories currently used throughout the steel 

making process were analyzed. Oxide-based ceramics of aluminum, calcium, zirconium, 

chromium, magnesium, and carbon are primarily used in steel contact in an effort to reduce 

contamination and interaction with the highly alkaline slags. Nonoxide ceramics consisting of 

combinations of silicon, titanium, tungsten, and aluminum are used for hot handling applications 

where thermal shock resistance, creep resistance, wear resistance, and resistance to acidic species 

is desired. These materials may be in the brick or castable form. In many areas of steel furnaces 

refractory life is extended by splashing slag against the refractory walls. This slag solidifies on 

the wall, forming a protective layer. This process, though highly successful, is very inefficient 

thermally. 

Today, steelmaking from pig iron commences in the transfer ladle ahead of the basic oxygen 

furnace (BOF) and continues after the BOF to the ladle stations and on to the tundish, which 

distributes the steel into the continuous casting or stationary molds. Refractories for all these unit 

processes are selected on the basis of their longevity and the cleanliness of the steel that passes 

through them. The cost per pound of refractories for all the various components, with few 

41 
Appendix A — Iron and Steel 

exceptions, has increased markedly with the awareness that advanced refractories can meet the 

goals of greatly extended service and contribute to the quality of the steels. 

In steel ladles, maintenance costs are high and heat efficiency is poor. Currently, high-alumina 

and magnesia-based castable refractories are preferred for ladle linings at and below the slag line 

due to the high process temperatures, erosion from the stirred bath, and the high corrosiveness of 

the slag. Life is short for these refractories; they typically last for only 30 to 50 heats. Highertemperature-capable oxide/carbon mixtures have been evaluated for use to provide a balance 

between purity, thermal shock resistance, and erosion resistance, along with other alternative 

refractories with longer life, lower cost, and safer disposal. Yet, no material of choice has been 

identified. 

Monolithics (refractory concretes and gunning mixes) comprise at least 60% of all refractories 

used in iron and steelmaking in the United States today (over 70% in Japan), and there is a strong 

trend to increased use of precast versions of monolithics. Installation practice has undergone 

some major advances which translate to much more rapid original construction, replacement of 

working linings, and repair. The adaptation of shotcreteing methods from construction concrete 

technology has resulted in significant reductions in downtime and in some cases longer service 

life as well. In the ladle lining practice, it has been possible to successively repair the original 

lining such that complete relining is no longer necessary. 

Improved materials for runners (used to flow the molten steel from a BOF or an electric arc 

furnace to the refining ladles) are needed. These components are generally constructed from 

fireclay brick, alumina castable, or chromia castable. They experience corrosion, wear, and 

thermal stresses that limit their lives to one to two weeks. Similar improvements are needed for 

water-cooled pipes and stirrers enclosed in refractory. They also experience corrosion, wear, and 

thermal stresses that limit their life and require weekly repair. 

Energy consumption in the various unit processes found in the iron and steel industry has 

changed substantially due to advances in refractory practice, but it is difficult to identify the role 

of refractories in energy savings because many changes are being made in designs and 

combustion practices as well as in metallurgical and slag practices. Some unit processes like blast 

furnaces and BOF melters are designed to leak energy to induce a steep thermal gradient through 

the lining. In an extreme example of this process design concept, the walls and roofs of electric 

arc furnaces are water-cooled to cause the steepest possible thermal gradient. Consequently, it is 

in the other unit processes where refractory practice contributes to energy savings in several ways 

(e.g., more efficient insulation, extension of the time between maintenance shutdowns, reduction 

in the amount of refractory scrap and reduction in metal scrap through improved cleanliness of 

the final steel products). 

As mentioned, blast furnaces and BOF melters are designed to leak energy, and even in the case 

of most ladles, insulation is minimized in the walls and bottoms in an effort to induce a thermal 

gradient in the interest of reducing the refractory wear. Ladle covers, on the other hand, are 

absolutely necessary to conserve the temperature of the contained metals and are made from 

increasingly advanced materials. There are many opportunities for direct energy savings in all of 

the unit processes and components in iron and steel plants that are not designed to incorporate 

steep thermal gradients. There are also opportunities to extend refractory life through the use of 

lining thickness monitors and other sensors and instruments which improve the combustion 

efficiency and reduce stack losses as well as release of undesirable products of the processing of 

the iron and steel. 

42 
Appendix A — Iron and Steel 

Significant improvements are needed for meeting operating challenges for monolithic 

refractories. Monolithic linings possess many inherent problems. Ideally, steelmakers would like 

to have monolithic linings for all of the ladles and even for the basic oxygen furnace. The socalled basic lining has received considerable research attention, but no reports of success in a 

BOF have been reported to date. Problems exist with the hydratability of the basic components of 

the products, which are based on MgO, magnesite, doloma (calcined dolomite, CaCO3·MgCO3), 

and spinel. Further, monolithics for BOF linings need to incorporate substantial amounts of 

carbon in the form of graphite, and research is ongoing to resolve the problem that derives from 

the interference of the high volumes of graphite with the binder systems of the monolithics. 

Barriers 

Refractories and insulation materials play key roles in the smelting, refining, and melting 

operations used in the iron and steel industries; it is estimated that 85% of the industries’ direct 

energy consumption is in processes affected by refractories. Based on subsequent analyses of 

typical furnaces and unit processes, improvement of refractory systems for the iron and steel 

industries could lead to energy savings opportunities up to 148.5 TBtu/year. Specific barriers are 

shown below. 

• Lack of adequate corrosion resistance for refractories in contact with molten metal, which 

leads to undesirable equipment lifetimes. This is especially important for refractories used in 

parts of furnaces, ladles, and tundishes. 

• Unavailability of improved materials for runners (used to flow the molten steel from a BOF 

or an electric arc furnace to the refining ladles), water-cooled pipes, and stirrers enclosed in 

refractory. 

• Lack of utilization of advanced monolithics in ladles due to problems with their explosive 

tendencies and lack of data on some of the key input properties and parameters for most of 

the monolithic products that meet the requirement for steel ladle practice. 

• Unavailability of improved impact pads at the bottom of ladles, which experience high wear, 

thermal shock, and abrasion. 

• Unavailability of thin-walled alumina refractory ladle shrouds that are used to reduce oxygen 

pick-up during pouring with lifetimes of greater than ten heats in the extreme conditions of 

this application. 

R&D Pathways 

• Develop methods for suppressing the hydration of magnesites. 

• Develop refractory linings with improved life and reduced maintenance requirements, to 

reduce the yearly or even monthly maintenance shutdowns generally necessary to repair 

refractory problems. Reducing the frequency of or eliminating these shutdowns would 

provide significant cost reduction, not to mention associated energy savings. 

• Develop advanced materials (such as refractories with in situ coatings or externally applied 

coatings) for resisting corrosion/erosion damage. 

• Develop new materials along with improved materials databases for members of the industry 

to adapt to new materials in their operations. 

• Develop improved refractories for use in various parts of furnaces, heat processing 

equipment, ladles, and tundishes. 

43 
Appendix A — Iron and Steel 

o Develop improvements in runners, water-cooled pipes and stirrers, which all 

experience corrosion, wear, and thermal issues that can limit their life and require 

weekly repair. 

o Develop improvements in materials and installation methods for ladle bottoms and 

impact pads by using ceramic coatings or alternate localized materials. 

o Develop long-lived, economically feasible, prefired refractory crucible linings for 

induction melting of stainless steel in air-melt operations. 

o Develop improved ceramic/refractory materials for net shape steel casting, 

eliminating rolling mill operations. 

A.8 Metal Casting 

Current Industry Operations and Refractory Use 

Energy consumption for the metals casting industry is on the order of 0.2 quads per year.20 This 

resulted in an estimated energy cost for the foundries industry in the United States of $1.2 billion 

in 19977

 and $1.5 billion in 1998,20 or about 10% of the total material cost put into production 

and 4–5% of the value of total shipment.21 Therefore, the industry wishes to optimize melting, 

holding, and heat-treating furnaces to conserve energy (i.e., to reduce energy usage by 20%) and 

minimize pollutant emissions. Further, the industry wishes to increase the life of refractories and 

other ceramic components that are exposed to molten metals and/or furnace environments and 

develop in-line sensors that are stable in the molten metal environment.10 

The unit processes utilized in the metal casting industry are lined with a wide range of refractory 

compositions (including silica, alumino-silicate, high alumina, zircon, magnesia, spinel, chrome, 

and magnesia-carbon) and forms (monolithics, precast shapes, and bricks). Most metals casting 

industry melting and holding furnaces are lined with ceramic refractories which are selected to 

minimize reaction with the specific metal being processed. Major refractory lined units include 

reverberatory furnaces, crucible (pot) furnaces, channel induction furnaces, coreless induction 

furnaces, electric arc furnaces, and pouring ladles. These furnaces are lined with wide ranges of 

refractory compositions, including silica, alumino-silicate, high alumina, zircon, magnesia, spinel, 

chrome, and magnesia-carbon. 

Substantial problems do still exist with molten material containment and handling. For example, 

cupola linings for ferrous alloy melting usually require weekly repairs because of corrosion and 

mechanical damage. An alternative to refractory linings is “skull melting” (in titanium melting, 

for example) where in a mechanism similar to the slag splashing in the steel industry or the 

formation of a “frozen ledge” in the aluminum industry, a protective layer of metal is solidified 

on the containment vessel surface, creating a corrosion-resistant layer but lowering the thermal 

efficiency of the system. 

Iron foundries are the major energy consumer for this sector, representing about 12% of the 

industry, followed by steel foundries at about 10%. Within each process, approximately 55% of 

the total energy cost is used for the melting of the metal, with other processes (core making, mold 

making, heat treatment, and post-casting processes) accounting for the other 45%. Although the 

total energy cost (fuel + electricity) accounts for only about 10% of the total material cost, it can 

44 
Appendix A – Metal Casting 

be as high as 20% or more for many foundries depending on efficiency and the materials 

processed. Specific energy usage by the metals casting industry is given in Table A.4. 

Table A.4. Process and energy data for U.S. metals casting industry 

Process Energy consumption 

Cupola melting Total: 8.6 × 106 Btu/ton 

Coke: 5.8 × 106 

Electricity: 1.1 × 106 

Natural Gas: 1.6 × 106 

Oxygen: 0.1 × 106 

Core making and mold making 7–20% energy, 1–3 × 106 Btu/ton 

Electric melting Induction furnace: 4.3–7.6 × 106 Btu/ton 

Electric arc furnace: 4.3–5.2 × 106 Btu/ton 

Electric-resistance heated reverberatory 

furnace: 5.2–7.9 × 106 Btu/ton 

Gas-fired melting furnace Crucible: 1.8-6.8 × 106 Btu/ton 

Reverb.: 2.5-5.0 × 106

 Btu/ton 

Refining and pouring processes Electricity: 0.4 × 106 Btu/ton 

Natural gas: 0.2 × 106 Btu/ton 

Cleaning and finishing processes 1.0 × 106 Btu/ton 

Investment casting Electricity: 3.0 × 106 Btu/ton 

Natural gas: 4.0 × 106 Btu/ton 

Lost foam casting 2.5 × 106 Btu/ton 

Die casting Electricity: 4.0 × 106 Btu/ton 

Natural gas: 5.0 × 106 Btu/ton 

Other casting processes Permanent: 2.5 × 106 Btu/ton 

Shell mold: 2.5 × 106 Btu/ton 

Plaster mold: 3.0 × 106

 Btu/ton 

Source: Energy and Environmental Profile of the U.S. Metal Casting Industry. 

Although the service life of refractory linings for all foundry practices has been extended greatly 

in the last decade, many of the problems identified above still persist. For example, most channel 

and coreless induction furnaces in iron and steel foundries use spinel-forming dry-vibratable 

castable, a shift from the wet ramming practiced in the past. This extended the service campaign 

of the foundries, but metal penetration and chemical corrosion by slag still persists. Also, there 

are few case studies that show good refractory maintenance management, new refractory 

development, or proper selection methods resulting in great energy savings and reduced melting 

cost. With the ever-increasing demand for quality cast metal, alloy composition, and innovative 

melting technologies, refractories sections have been pushed to more challenging positions. 

Research programs in refractories science and technology in the United States have never been as 

large and as comprehensive as R&D programs for other industry and technology sectors. 

Nonetheless, the metal casting industry is still one of the largest industry sectors in the United 

States, and the refractories industry is essential to it. 

For steel casting, wear of refractories and reaction of the refractories with highly basic (calciacontaining) slag can generate defect-forming inclusions. High-alumina refractories are generally 

used throughout this area of the process, with application of zirconia-based materials in areas of 

high wear and thermal shock and magnesia-based materials in areas of high slag corrosion. 

45 
Appendix A – Metal Casting 

Carbon materials cannot be used for this application, as they react with oxide-based refractories 

to form CO and with aluminum in steel to form alumina. Similarly, silica-based refractories 

cannot be used because of contamination issues. 

There is a serious lack of data on the mechanical, thermal, and chemical properties of monolithic 

refractories; and much of the data that exists is lacking in detail or is obsolete. There is only one 

reference source for such key data as strength, modulus of elasticity, thermal conductivity, heat 

content, permeability, thermal shock and creep behavior; and this source was first available 15 

years ago. Hundreds of new and updated versions of monolithics are on the market today, but 

there is very little design and other technical data available aside from the product data sheets, 

which do not list much beyond bulk properties and some typical values (not to be used in design 

but only as guide for selection). 

Barriers 

Refractories are used throughout the various unit processes found in the metal casting industry; 

approximately 90% of the direct energy consumption is in processes affected by refractories. 

Based on subsequent analysis of typical furnaces and unit processes, improvement of refractory 

systems for the metal casting industry could lead to energy savings opportunities up to 

8.5 TBtu/year. Specific barriers are shown below. 

• Lack of methods and materials to reduce or eliminate refractory failure due to physical 

erosion and chemical corrosion by molten metal and slags in nearly all stages of metal 

melting, refining, and pouring processes where refractories make contact with molten metal. 

• Lack of methods and materials to reduce or eliminate refractory failure related to fusion of 

refractories and chemical corrosion by MnO and FeO in steel foundries where the molten 

steel is generally tapped at high temperatures [up to 2150°C (3900°F)], and the common 

practice is to use low-cost silica, zircon, or alumino-silicate ramming mixes and plastics, 

especially in those foundries that apply acid melting practices in smaller furnaces. 

• Lack of methods and materials to reduce or eliminate clogging or build-up formation in 

channels and throats is problematic for most metal casting operations. 

• Lack of methods and materials to reduce or eliminate refractory wear in electric arc furnaces 

for the melting of steel, where reduced refractory wear and energy savings would be 

especially beneficial. 

• Lack of methods and materials to reduce or eliminate wear and reaction of refractories with 

highly basic (calcia-containing) slags for steel casting. 

• Lack of data on the mechanical, thermal, and chemical properties of monolithic refractories, 

with much of the data that exists lacking in detail or being obsolete. 

R&D Pathways 

• Develop improved refractories that will resist physical erosion and chemical corrosion by 

molten metal and slags. Specifically, develop material systems for steel containment that are 

chemically stable with the molten metal and that provide mechanical integrity against wear 

and abrasion. 

• Develop improved refractories which are resistant to corrosion by MnO and FeO to prevent 

fusion of refractories in steel casting. 

46 
Appendix A – Metal Casting 

• Develop refractories which will resist the adhesion of molten metal that results in clogging or 

build-up formation in channels and throats. 

• Develop improved refractories for use in electric arc furnaces for the melting of steel that will 

resist wear and provide energy savings though improved insulation. 

• Determine the mechanical, thermal, and chemical properties of monolithic refractories used 

in the metal casting industry. 

• Develop novel low-cost and high-performance monolithics (in particular for iron, steel, and 

aluminum foundries), basic gunning mixes, and MgO-graphite castable for rapid repair of 

electric arc furnaces. 

• Develop and model slag chemistry compatible with refractory linings and maximize the slag 

foaming properties, along with efforts to reduce or eliminate repair and patching of electric 

arc furnaces due to refractory wear. 

47 
Appendix A – References 

A.9 References for Appendix A 

1. D. W. Freitag and D. W. Richerson, Opportunities for Advanced Ceramics to Meet the 

Needs of the Industries of the Future, DOE/ORO 2076, U.S. Department of Energy, Office 

of Industrial Technologies, December 1998. 

2. Aluminum Industry Technology Roadmap, The Aluminum Association, February 2003. 

3. A. T. Taberaux, “Recent Development in Refractories for Aluminum Cells,” pp. 271–81 in 

Proceedings of the International Symposium: Advances in Refractories for the 

Metallurgical Industries II, ed. M. Rigaud and C. Allaire, Montreal, Quebec, August 4–9, 

1996. 

4. D. Schubert, “Refractories for Primary Aluminum Production,” pp. 74–80 in Proceedings of 

the Thirty-Seventh Symposium on Refractories, St. Louis, Missouri, March 23, 2001. 

5. J. Canon, “Aluminum Furnace Design: Reduction of Metal into Metal Out Time,” pp. 237– 

53 in 39th Symposium on Refractories, STL Section of the ACerS, April 9–10, 2003. 

6. S. Quesnel, C. Allaire, and S. Afshar, “Corrosion of Refractories at the Bellyband of 

Aluminum Holding and Melting Furnaces,” pp. 321–27 in Proceedings of the International 

Symposium: Advances in Refractories for the Metallurgical Industries II, ed. M. Rigaud 

and C. Allaire, Montreal, Quebec, August 4–9, 1996. 

7. Economic Census 1997 

9. U.S. Environmental Protection Agency, Profile of the Pulp and Paper Industry, 2nd ed., 

EPA/310-R-95-015, 2002. Available online at http://www.epa.gov/compliance/resources/ 

publications/assistance/sectors/notebooks/pulp.html. 

9. E. D. Larson, S. Consonni, and R. E. Katofsky, A Cost-Benefit Assessment of Biomass 

Gasification Power Generation in the Pulp and Paper Industry, Princeton University, 

October 2003. Available online at http://www.princeton.edu/~energy/publications/ 

pdf/2003/BLGCC_FINAL_REPORT_8_OCT_2003.pdf. 

10. Glass: A Clear Vision for a Bright Future, U.S. Department of Energy, Office of Industrial 

Technologies, 1996. Available online at http://www.eere.energy.gov/industry/ 

glass/pdfs/glass_vision.pdf. 

11. All-Electric vs. Oxyfuel Glass Melting, EPRI Technical Report TR-112788, Electric Power 

Research Institute, April 1999. 

12. GMIC Advancing Glass Melting Technologies: A Technical and Economic Assessment. 

13. Energy and Environmental Profile of the US Glass Industry, DOE/GO -102002-1590, U.S. 

Department of Energy, Office of Industrial Technologies, April 2002. 

14. M. J. Damsell, M. L. Joshi, J. R. Latter, and D. B. Wishnick, Glass Technology 37, 114 

(1996). 

15. Personal correspondence with refractory and glass industry representatives. 

16. ASM Heat Treating Society, An R&D Plan for the Heat Treating Community, 2001. 

Available online at http://www.asm-intl.org/pdf/RD_Plan_Heat_treat_Community.pdf. 

17. WPI Integrated Heat Treatment Model for Aluminum Castings, available online at 

http://www.wpi.edu/Academics/Research/MPI/News/twoawards.html. 

48 
Appendix A – References 

18. Steel Technology Roadmap, American Iron and Steel Institute, December 2001. Available 

online at http://www.steel.org/mt/roadmap/roadmap.htm. 

19. Metal Casting Industry Profile, 2004. Available online at http://www.eere.energy.gov/ 

industry/metalcasting/profile.html. 

20. Metal Casting: Annual Report, 2000. Available online at http://www.eere.energy.gov/ 

industry/metalcasting/annualreport.html (2004 report). 

49 
Appendix B 

Appendix B: 

Rotary Kiln Analysis Schematic, Conditions, and Results 

Fig. B.1. Longitudinal section of a typical rotary kiln. Reprinted from Modern Refractory 

Practice, 3rd ed., Harbison Walker Refractories, Pittsburgh, 1950. 

Assumptions for alumina calcination, rotary kiln 

Plant production 500,000 tons Al2O3/year 

 Assume two kilns 

Output per kiln, no downtime 277,778 tons Al2O3/year 

With 90% uptime 250,000 tons Al2O3/year 

Output per day 685 tons Al2O3/d 

Output per hour 29 tons Al2O3/h 

Kiln diameter 3.5 m (11 ft) 

Kiln length 80 m (262 ft) 

Kiln exterior surface 880 m2 (9468 ft2) 

Reaction 2 Al(OH)3 → Al2O3 + 3 H2O 

Heat of reaction at 77°F 634 Btu/lb Al2O3

Assume reaction temperature of 1100°C 

2012°F 

 say 2000°F 

Heating products to 2000°F 

Al2O3 562 Btu/lb Al2O3

 3 H2O 532 Btu/lb Al2O3 

Total heat requirement 1728 Btu/lb Al2O3 

3,456,824 Btu/ton Al2O3 

Heat of reaction 

35.91 cal/mol Reaction 634 

64,638 Btu/#mol Heating 562 Al2O3 

634 Btu/lb Heating 532 H2O 

Total 1,728 Btu/lb Al2O3 

50 
Appendix B 

Results of alumina rotary kiln analysis 

(Temperatures in °F) 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 2000 

Reaction Energy 3,456,824 39.84% 

Wall Loss Energy 400,000 4.61% 

Exhaust Energy 4,821,030 55.56% 

Total Energy 8,677,853 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 2000 

Reaction Energy 3,456,824 42.46% 

Wall Loss Energy 400,000 4.91% 

Exhaust Energy 4,285,360 52.63% 

Total Energy 8,142,183 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 2000 

Reaction Energy 3,456,824 37.87% 

Wall Loss Energy 600,000 6.57% 

Exhaust Energy 5,071,030 55.56% 

Total Energy 9,127,853 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 2000 

Reaction Energy 3,456,824 40.36% 

Wall Loss Energy 600,000 7.01% 

Exhaust Energy 4,507,582 52.63% 

Total Energy 8,564,406 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 1800 

Reaction Energy 3,456,824 44.81% 

Wall Loss Energy 400,000 5.19% 

Exhaust Energy 3,856,824 50.00% 

Total Energy 7,713,647 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 1800 

Reaction Energy 3,456,824 47.17% 

Wall Loss Energy 400,000 5.46% 

Exhaust Energy 3,471,141 47.37% 

Total Energy 7,327,965 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 1800 

Reaction Energy 3,456,824 42.61% 

Wall Loss Energy 600,000 7.39% 

Exhaust Energy 4,056,824 50.00% 

Total Energy 8,113,647 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 1800 

Reaction Energy 3,456,824 44.85% 

Wall Loss Energy 600,000 7.78% 

Exhaust Energy 3,651,141 47.37% 

Total Energy 7,707,965 100.00% 

Savings for alumina 

Btu/ton Nature of saving saved 

Effect of 200°F increase in flame temperature 472,621 

Effect of 200°F decrease in exhaust temperature 912,268 

Effect of reducing wall loss energy from 600,000 to 

400,000 Btu/ton 413,056 

51 
Appendix B 

Assumptions for lime calcination, rotary kiln 

Plant production 730,000 tons CaO/year

 Assume two kilns 

Output per kiln, no downtime 405,556 tons CaO /year 

With 90% uptime 365,000 tons CaO /year 

Output per day 1,000 tons CaO /d 

Output per hour 42 tons CaO /h 

Kiln diameter 5 m (16 ft) 

Kiln length 50 m (164 ft) 

Kiln exterior surface 785 m2 (8,454 ft2) 

Reaction CaCO3 → CaO + CO2

Heat of reaction at 77°F 1364 Btu/lb CaO 

Assume reaction temperature of 1000°C 

1832°F 

 say 1800°F 

Heating products to 1800°F 

CaO 371 Btu/lb CaO 

CO2 391 

Total heat requirement 2126 Btu/lb CaO 

4,252,259 Btu/ton CaO 

Heat of reaction 

57.29 cal/mol Reaction 1364 

103,122 Btu/#mol Heating 417 CaO 

1,839 Btu/lb Heating 415 CO2 

Total 2,196 Btu/lb CaO 

52 
Appendix B 

Results of lime rotary kiln analysis (neglecting dust loss) 

(Temperatures in °F) 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 2000 

Reaction Energy 4,252,259 40.62% 

Wall Loss Energy 400,000 3.82% 

Exhaust Energy 5,815,323 55.56% 

Total Energy 10,467,582 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 2000 

Reaction Energy 4,252,259 43.30% 

Wall Loss Energy 400,000 4.07% 

Exhaust Energy 5,169,176 52.63% 

Total Energy 9,821,435 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 2000 

Reaction Energy 4,252,259 38.95% 

Wall Loss Energy 600,000 5.50% 

Exhaust Energy 6,065,323 55.56% 

Total Energy 10,917,582 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 2000 

Reaction Energy 4,252,259 41.51% 

Wall Loss Energy 600,000 5.86% 

Exhaust Energy 5,391,399 52.63% 

Total Energy 10,243,657 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 1800 

Reaction Energy 4,252,259 45.70% 

Wall Loss Energy 400,000 4.30% 

Exhaust Energy 4,652,259 50.00% 

Total Energy 9,304,517 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 1800 

Reaction Energy 4,252,259 48.11% 

Wall Loss Energy 400,000 4.53% 

Exhaust Energy 4,187,033 47.37% 

Total Energy 8,839,291 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 1800 

Reaction Energy 4,252,259 43.82% 

Wall Loss Energy 600,000 6.18% 

Exhaust Energy 4,852,259 50.00% 

Total Energy 9,704,517 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 1800 

Reaction Energy 4,252,259 46.12% 

Wall Loss Energy 600,000 6.51% 

Exhaust Energy 4,367,033 47.37% 

Total Energy 9,219,291 100.00% 

Savings for lime, neglecting dust loss 

Btu/ton Nature of saving saved 

Effect of 200°F increase in flame temperature 567,631 

Effect of 200°F decrease in exhaust temperature 1,095,660 

Effect of reducing wall loss energy from 600,000 to 

400,000 Btu/ton 413,056 

53 
Appendix B 

Results of lime rotary kiln analysis (assuming 20% dust loss) 

(Temperatures in °F) 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 2000 

Reaction Energy 5,102,710 39.00% 

Wall Loss Energy 400,000 3.06% 

Exhaust Energy 7,581,767 57.94% 

Total Energy 13,084,478 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 2000 

Reaction Energy 5,102,710 43.30% 

Wall Loss Energy 400,000 3.39% 

Exhaust Energy 6,283,012 53.31% 

Total Energy 11,785,722 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 2000 

Reaction Energy 5,102,710 37.39% 

Wall Loss Energy 600,000 4.40% 

Exhaust Energy 7,944,267 58.21% 

Total Energy 13,646,978 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 2000 

Reaction Energy 5,102,710 41.51% 

Wall Loss Energy 600,000 4.88% 

Exhaust Energy 6,589,678 53.61% 

Total Energy 12,292,389 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 1800 

Reaction Energy 5,102,710 43.87% 

Wall Loss Energy 400,000 3.44% 

Exhaust Energy 6,127,936 52.69% 

Total Energy 11,630,647 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 1800 

Reaction Energy 5,102,710 48.11% 

Wall Loss Energy 400,000 3.77% 

Exhaust Energy 5,104,439 48.12% 

Total Energy 10,607,150 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3600 

Exhaust Temperature 1800 

Reaction Energy 5,102,710 37.39% 

Wall Loss Energy 600,000 4.40% 

Exhaust Energy 7,944,267 58.21% 

Total Energy 13,646,978 100.00% 

Parameter Btu/ton % Usage 

Flame Temperature 3800 

Exhaust Temperature 1800 

Reaction Energy 5,102,710 46.12% 

Wall Loss Energy 600,000 5.42% 

Exhaust Energy 5,360,439 48.45% 

Total Energy 11,063,150 100.00% 

Savings for lime, assuming dust loss 

Btu/ton Nature of saving saved 

Effect of 200°F increase in flame temperature 1,565,167 

Effect of 200°F decrease in exhaust temperature 965,410 

Effect of reducing wall loss energy from 600,000 to 

400,000 Btu/ton 885,374 

54 
55 
Appendix C 

Appendix C: 

Reverberatory Furnace Schematics 

Fig. C.1. Reverberatory furnace schematic. 

56 
Appendix C 

Fig. C.2. Typical reverberatory aluminum-melting furnace. Reprinted from Modern 

Refractory Practice, 3rd ed., Harbison Walker Refractories, Pittsburgh, 1950. 

57 
Appendix D 

Appendix D: Reverberatory Furnace Analysis Conditions and 

Results 

Results of aluminum reverberatory furnace analysis 

Temperature (oF) 

Wall/roof Loss 

Case Flame Exhaust (Btu/h) 

Case 1 3600 1600 5,000,000 

Case 2 3800 1600 5,000,000 

Case 3 3600 1600 7,500,000 

Case 4 3800 1600 7,500,000 

Case 5 3600 1800 5,000,000 

Case 6 3800 1800 5,000,000 

Case 7 3800 1600 7,500,000 

Case 8 3800 1800 7,500,000 

Results of aluminum reverberatory furnace analysis 

(Temperatures in °F) 

Case 1 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 1600 

Melting Energy 10,095,271 37.2% 

Wall Loss Energy 5,000,000 18.4% 

Exhaust Energy 12,076,217 44.4% 

Total Energy 27,171,489 100.0% 

Case 3 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 1600 

Melting Energy 10,095,271 31.9% 

Wall Loss Energy 7,500,000 23.7% 

Exhaust Energy 14,076,217 44.4% 

Total Energy 31,671,489 100.0% 

Case 5 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 1800 

Melting Energy 10,095,271 33.4% 

Wall Loss Energy 5,000,000 16.6% 

Exhaust Energy 15,095,271 50.0% 

Total Energy 30,190,543 100.0% 

Case 7 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 1800 

Melting Energy 10,095,271 28.7% 

Wall Loss Energy 7,500,000 21.3% 

Exhaust Energy 17,595,271 50.0% 

Total Energy 35,190,543 100.0% 

Case 2 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 1600 

Melting Energy 10,095,271 38.7% 

Wall Loss Energy 5,000,000 19.2% 

Exhaust Energy 10,978,379 42.1% 

Total Energy 26,073,651 100.0% 

Case 4 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 1600 

Melting Energy 10,095,271 33.2% 

Wall Loss Energy 7,500,000 24.7% 

Exhaust Energy 12,796,561 42.1% 

Total Energy 30,391,833 100.0% 

Case 6 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 1800 

Melting Energy 10,095,271 35.2% 

Wall Loss Energy 5,000,000 17.4% 

Exhaust Energy 13,585,744 47.4% 

Total Energy 28,681,016 100.0% 

Case 8 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 1800 

Melting Energy 10,095,271 30.2% 

Wall Loss Energy 7,500,000 22.4% 

Exhaust Energy 15,835,744 47.4% 

Total Energy 33,431,016 100.0% 

58 
Appendix D 

Savings for aluminum reverberatory furnaces 

Furnace change 

Btu/h 

saved 

Btu/lb Al 

saved 

Effect of 200°F increase in flame temperature 1,411,637 70.58 

Effect of 200°F decrease in exhaust temperature 3,486,046 174.30 

Effect of reducing wall loss energy from 7.5 to 5 million 4,642,045 232.10 

Case 1 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 2200 

Melting Energy 6,272,301 21.6% 

Wall Loss Energy 5,000,000 17.2% 

Exhaust Energy 17,713,616 61.1% 

Total Energy 28,985,917 100.0% 

Case 3 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 2200 

Melting Energy 6,272,301 17.7% 

Wall Loss Energy 7,500,000 21.2% 

Exhaust Energy 21,642,188 61.1% 

Total Energy 35,414,489 100.0% 

Case 5 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 2400 

Melting Energy 6,272,301 18.5% 

Wall Loss Energy 5,000,000 14.8% 

Exhaust Energy 22,544,602 66.7% 

Total Energy 33,816,904 100.0% 

Case 7 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 2400 

Melting Energy 10,095,271 24.4% 

Wall Loss Energy 7,500,000 18.2% 

Exhaust Energy 23,721,632 57.4% 

Total Energy 41,316,904 100.0% 

Results of copper reverberatory furnace analysis 

(Temperatures in °F) 

Savings for copper reverberatory furnaces 

Case 2 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 2200 

Melting Energy 6,272,301 23.4% 

Wall Loss Energy 5,000,000 18.7% 

Exhaust Energy 15,499,414 57.9% 

Total Energy 26,771,715 100.0% 

Case 4 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 2200 

Melting Energy 6,272,301 19.2% 

Wall Loss Energy 7,500,000 22.9% 

Exhaust Energy 18,936,914 57.9% 

Total Energy 32,709,215 100.0% 

Case 6 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 2400 

Melting Energy 6,272,301 20.5% 

Wall Loss Energy 5,000,000 16.3% 

Exhaust Energy 19,323,945 63.2% 

Total Energy 30,596,246 100.0% 

Case 8 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 2400 

Melting Energy 6,272,301 16.8% 

Wall Loss Energy 7,500,000 20.1% 

Exhaust Energy 23,609,659 63.2% 

Total Energy 37,381,960 100.0% 

Furnace change 

Btu/h 

saved 

Btu/lb Al 

saved 

Effect of 200°F increase in flame temperature 3,018,769 150.94 

Effect of 200°F decrease in exhaust temperature 5,791,405 289.57 

Effect of reducing wall loss energy from 7.5 to 5 million 6,662,946 333.15 

59 
Appendix D 

Results of glass reverberatory furnace analysis 

(Temperatures in °F) 

Case 1 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 2800 

Melting Energy 13,771,643 16.3% 

Wall Loss Energy 5,000,000 5.9% 

Exhaust Energy 65,700,751 77.8% 

Total Energy 84,472,394 100.0% 

Case 3 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 2800 

Melting Energy 13,771,643 14.4% 

Wall Loss Energy 7,500,000 7.8% 

Exhaust Energy 74,450,751 77.8% 

Total Energy 95,722,394 100.0% 

Case 5 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 3000 

Melting Energy 13,771,643 12.2% 

Wall Loss Energy 5,000,000 4.4% 

Exhaust Energy 93,858,216 83.3% 

Total Energy 112,629,859 100.0% 

Case 7 

Parameter Btu/h % Usage 

Flame Temperature 3600 

Exhaust Temperature 3000 

Melting Energy 13,771,643 10.8% 

Wall Loss Energy 7,500,000 5.9% 

Exhaust Energy 106,358,216 83.3% 

Total Energy 127,629,859 100.0% 

Case 2 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 2800 

Melting Energy 13,771,643 19.3% 

Wall Loss Energy 5,000,000 7.0% 

Exhaust Energy 52,560,601 73.7% 

Total Energy 71,332,244 100.0% 

Case 4 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 2800 

Melting Energy 13,771,643 17.0% 

Wall Loss Energy 7,500,000 9.3% 

Exhaust Energy 59,560,601 73.7% 

Total Energy 80,832,244 100.0% 

Case 6 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 3000 

Melting Energy 13,771,643 15.4% 

Wall Loss Energy 5,000,000 5.6% 

Exhaust Energy 70,393,662 78.9% 

Total Energy 89,165,305 100.0% 

Case 8 

Parameter Btu/h % Usage 

Flame Temperature 3800 

Exhaust Temperature 3000 

Melting Energy 13,771,643 13.6% 

Wall Loss Energy 7,500,000 7.4% 

Exhaust Energy 79,768,662 78.9% 

Total Energy 101,040,305 100.0% 

Savings for glass reverberatory furnaces 

Furnace change 

Btu/h 

saved 

Btu/lb glass 

saved 

Effect of 200°F increase in flame temperature 19,521,102 976.06 

Effect of 200°F decrease in exhaust temperature 31,173,901 1,558.70 

Effect of reducing wall loss energy from 7.5 to 5 million 11,906,250 595.31 

60 
61 
Appendix E 

Appendix E: Boiler Schematic 

Fig. E.1. Boiler furnace sections. Reprinted from Modern Refractory Practice, 3rd ed., 

Harbison Walker Refractories, Pittsburgh, 1950. 

62 
63