PB-241 990
ENERGY CONSUMPTION
THE PRIMARY METALS AND PETROLEUM INDUSTRIES
Dow CHEMICAL COMPANY
PREPARED FOR
NATIONAL ENVIRONMENTAL RESEARCH CENTER
APRIL 1975
DISTRIBUTED BY:
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PB-241 990
EPA-650/2-75-032-b
April 1975
Environmental Protection Technology Series
.*.'•••
.".'•*•
.•.'•*•
I
55
\,
O
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing
1 REPORT NO.
EPA-650/2-75-032-b
2.
4. TITLE AND SUBTITLE
Energy Consumption:
The Primary Metals and Petroleum Industries
5. REPORT DATE
April 1975
6. PERFORMING ORGANIZATION CODF
7. AUTHORIS)
8. PERFORMING ORGANIZATION
John T. Reding and Burchard P. Shepherd
PB 241 930
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Dow Chemical, U.S.A.
Texas Division
Freeport, Texas 77541
'O. PROGRAM ELEMENT NO.
1AB013; ROAP21ADS
11. CONTRACT/GRANT NO.
68-02-1329, Task 5
- i
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
NERC-RTP, Control Systems Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND P:' „
Final Task: 8/71-3/7
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
gives results of a study of energy consumption in the pnirr/r
metals and petroleum industries. It analyzes energy-intensive steps or operatic.is
for commonly used manufacturing processes. Results of the analyses are in the form
of energy consumption block diagrams, energy-intensive equipment schematic dia-
grams , and tables that indicate the causes of energy losses, as well as possible
conservation approaches. The most common energy-intensive operations in these
industries are; (primary metals) — furnace operation and electrolysis; and
(petroleum) — furnace operation and distillation. Energy losses in these operations
could be reduced by: design, operation, and process modification: better insulation
and maintenance; process integration; waste utilization; and research and develop-
ment.
17.
KEY WORDS AND DOCUMENT ANALYSIS
S. DESCRIPTORS
Energy
Consumption
Metal Industry
Petroleum Industry
Conservation
Furnaces
Electrolysis
18. DISTRIBUTION STATEMENT
Unlimited
Distillation
Insulation
Maintenance
Wastes
Processing
Research
Desien
b. IDENTIFIERS/OPEN ENDED TERMS
Primary Metals
Industry
19. SECURITY CLASS (This Report)
Unclassified
2O. SECURITY CLASS (This page)
Unclassified
c. COSATI Field/Group
13H
11F
13A
07D
21. NO. OF PAGES
EPA Form 2220-1 (t-73)
-------
EPA-650/2-75-032-b
ENERGY CONSUMPTION:
THE PRIMARY METALS
AND PETROLEUM INDUSTRIES
by
John T. Reding and Burchard P. Shepherd
Dow Chemical, U. S. A.
Texas Division
Freeport, Texas 77541
Contract No. 68-02-1329, Task 5
Program Element No. 1ABO13
ROAP No. 21ADE-010
EPA Project Officer: Irvin A. Jefcoat
Control Systems Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
Prepared for
U. S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
WASHINGTON, D. C. 20460
April 1975
j0 - ’
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EPA REVIEW NOTICE
This report has been reviewed by the National Environmental Research
Center - Research Triangle Park, Office of Research and Development,
EPA, and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Devel pment, U.S. Environ-
mental Protection Agency, have been grouped into series. These broad
categories were established to facilitate further development and applica-
tion of environmental technology. Elimination of traditional grouping was
consciously planned to foster technology transfer and maximum interface
in related fields. These series are:
1. ENVIRONMENTAL HEALTH EFFECTS RESEARCH
2. ENVIRONMENTAL PROTECTION TECHNOLOGY
3. ECOLOGICAL RESEARCH
4. ENVIRONMENTAL MONITORING
5. SOCIOECONOMIC ENVIRONMENTAL STUDIES
6. SCIENTiFIC AND TECHNICAL ASSESSMENT REPORTS
9. MISCELLANEOUS
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to
develop and demonstrate instrumentation, equipment and methodology
to repair or prevent environmental degradation from point and non-
point sources of pollution. This work provides the new or improved
technology required f r the control and treatment of pollution sources
to meet environmental quality standards.
This document is available to the public for sale through the National
Technical Information Service, Springfield, Virginia 22161.
Publication No. EPA-650/2-75-032-b
11
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CONTENTS
Page
EPA Review Notice ii
List of Figures iv
List of Tables vi
Sections
I Conclusions 1
II Recommendations 2
III Introduction 3
IV Energy Consumption within the Primary Metals
and Petroleum IndustrIes 5
A. Steel by the Basic Oxygen Process 5
B. Aluminum by the Bayer—Hall Process 18
C. Petroleum Refining
D. Summary of Energy Losses and
Recommended Conservation Approaches 14
V Bibliography 149
VI Glossary of Abbreviations 51
VII Appendix 52
iii
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F IGURES
No. Page
1 Steel Energy Consumption Diagram 6
2 Steel Energy Intensive Equipment Diagram
——Coke Oven io
3 Steel Energy Intensive Equipment Diagram
——Sinter Operation ii
LI Steel Energy Intensive Equipment Diagram
——Pelletlzing 12
5 Steel Energy Intensive Equipment Diagram
——Blast Furnace and Blast Stoves
6 Steel Energy Intensive Equipment Diagram
——Steelmaking (Basic Oxygen Furnace)
7 Steel Energy Intensive Equipment Diagram
--Steelmaking (Open Hearth Furnace) 16
8 Steel Energy Intensive Equipment Diagram
——Steelmaking (Electric Furnace) 1.7
9 Steel Energy Intensive Equipment Diagram
——Soaking Pit 19
10 Steel Energy Intensive Equipment Diagram
——Reheating Furnace 20
11 Steel Energy Intensive Equipment Diagram
——Annealing Ovens 21
12 Aluminum Energy Consumption Diagram 25
13 Aluminum Energy Intensive Equipment Diagram
——Steam Digestion of Bauxite and Evaporation
of Water from Caustic 27
1LI Aluminum Energy Intensive Equipment Diagram
——Rotary Kiln 28
15 Aluminum Energy Intensive Equipment Diagram
——Electrolysis Cell 30
16 Aluminum Energy Intensive Equipment Diagram
——Melting Furnace 31
iv
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FIGURES (continued)
No. Page
17 Petroleum Refining Energy Consumption Diagram 35
18 Petroleum Refining Energy Intensive Equipment
Diagram-—Crude Distillation 37
19 Petroleum Refining Energy Intensive Equipment
Diagram——Distillate Hydrodesulfurization 38
20 Petroleum Refining Energy Intensive Equipment
Diagram--Catalytic Reforming 40
21 Petroleum Refining Energy Intensive Equipment
Diagram-—Fluid Catalytic Cracking 41
22 Petroleum Refining Energy Intensive Equipment
Diagram--HF Alkylation 42
23 Petroleum Refining Energy Intensive Equipment
Diagram-—Aromatics Extraction 43
2 4 Petroleum Refining Energy Intensive Equipment
Diagram-—Coking
V
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TABLES
No. Page
1 Steel Energy Conservation Approaches 22
2 Aluniinurn Energy Conservation Approaches 32
3 Petroleum Refining Energy Conservation Approaches 46
Summary of Energy Losses and Recommended
Conservation Approaches 47
vi
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SECTION I
CONCLUSIONS
Most of the energy consumption within the primary metals in-
dustry is concentrated in a relatively few operations.
Furnace combustion is the principal operation in the steel
manufacturing process. Electrolysis is the principal
operation in the aluminum manufacturing process. Most of the
energy consumption within the petroleum industry occurs in
furnace combustion and distillation operations. Losses in
these operations can be decreased by employing conservation
approaches. These include:
• Design modifications to increase waste heat recovery
from furnaces.
• Design modifications to recover energy from high
pressure streams in parts of the petroleum refining
process.
• Design modifications to allow lower energy input into
distillation columns.
• Proper maintenance practices, especially with regard
to heat exchange surfaces and insulation.
• Operation modifications to avoid losses in electrolytic
cells and distillation columns.
• Greater use of insulation to limit heat losses.
• Research and development to develop processes with
increased yields.
• Waste utilization by more recycle of scrap steel and
aluminum.
• Waste utilization to prevent the loss of the fuel value
of waste streams.
1
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SECTION II
RECOMMENDATIONS
The energy conservation approaches suggested in this report
could be further defined arid specified in more detail.
Unanswered questions which should be considered include:
• The economic feasibility of the conservation
approaches.
• The difficulty of implementing the approaches.
2
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SECTION III
INTRODUCTION
Purpose
The purpose of the total task is to provide a breakdown of
energy consumption within the six primary industrial cate-
gories——primary metals, chemicals, petroleum, food, paper,
and stone, clay, glass, concrete. The purpose of the portion
of the total task covered by this report is to provide a
breakdown of energy consumption within the primary metals
and petroleum industries only. This breakdown can give
direction to subsequent conservation efforts.
Scope
This report analyzes high energy consumption operations with-
in the primary metals industry (SIC 33) and the petroleum
industry (SIC 29). The principal pieces of energy—intensive
equipment used in these operations are identified. Finally,
the causes of energy losses in these operations, the approxi-
mate magnitude of the losses, and possible approaches to
decrease these losses are indicated.
General Background
The National Academy of Engineering has been commissioned
by the Environmental Protection Agency to conduct a com-
prehensive assessment of the current status and future
prospects of sulfur oxides control methods and strategies.
The agreement between the Environmental Protection Agency
and the National Academy of Engineering states explicitly
that special data collection projects may be required to
provide the National Academy of Engineering panel with
the background necessary for viewing all aspects of the
problem in perspective. This report is one segment of
the data collection project associated with the National
Academy of Engineering assessment.
One method of limiting the amount of SO emissions arising
from energy conversion is simply to decrease fuel use
through energy conservation. In the year 1968, it has
been reported that 4l.2 percent of the total energy con-
sumption In the United States was in the industrial sector.
More specifically, 28 percent of the national energy con-
sumption was in the six industrial categories encompassed
by this total task. Conservation efforts directed toward
industries in these six categories should obtain the
greatest Impact.
3
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General Approach
The processes for manufacturing steel and aluminum were re-
viewed. Approximately 85 percent of the energy consumption
within the primary metals category occurs in the manufactur-
ing processes for these two metals. In addition, the process
for refining crude oil was reviewed.
Energy consumption block diagrams were drawn for each process.
These diagrams indicate the operations within the processes
where large amounts of energy are used. These energy—
intensive operations have been further analyzed. Sbhematic
diagrams show the physical and operational appearance of the
energy—consuming equipment. Causes of energy losses in the
energy—intensive operations, the approximate magnitude of
the losses, and possible conservation approaches have been
determined.
14
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SECTION TV
ENERGY CONSUMPTION WITHIN THE PRIMARY METALS
AND PETROLEUM INDUSTRIES
Several observations need to be made concerning the analyses
of energy consumption in the steel, aluminum, and petroleum
refining processes.
The type of energy used in each energy—intensive
operation is included on the process block diagrams.
Different types of energy are not equivalent. Approxi-
mately 3 Btu’s of fuel energy are required to generate
1 Btu of electrical energy. Approximately 1.1 to 1.3
Btu’s of fuel energy are required to generate 1 Btu of
steam energy.
• Energy values for the steel and aluminum processes are
always expressed in terms of energy per unit weight of
product. Energy values for the petroleum refining
process are expressed in terms of energy per unit
weight of crude oil processed.
• The tables showing energy conservation approaches give
estimates of losses in each operation of the process
and in the overall process. The losses listed in each
operation are additive. The losses listed in the
overall process often overlap with losses within
operations and are not additive.
• The values for energy input and losses are derived
from a variety of sources as listed in the bibliography.
The values are typical for published technology. New
plants may already use conservation approaches recom-
mended in this report and, thereby, use less energy
than indicated in the figures.
• Energy conservation approaches are listed in the tables.
In many cases a more specific explanation of the recom-
mended energy conservation approach is listed along
with the approach. An explanation of the conservation
approaches is included in the appendix for those
instances where the meaning of the term may be vague.
A. Steel by the Basic Oxygen Process
Figure 1 shows the primary steps in the steel manufacturing
process using the basic oxygen furnace. The major energy
consumption operations are coking of coal; agglomerating of
5
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Figure 1. Steel energy consumption diagram
[ 1972 USA shipments: 83.5 x l0 kg (1814 x io ib)]
[ 1972 energy consumption (primarily coal and natural gas):
110,000 MW (3300 x 1012 Btu)]
Energy input Reclaimed energy Heat rejection
Coal’
I— Coking 230 kJ/kg
26,200 kJ/kg _____ __________ ___________________
_____ ______ (100 Btu/lbY
(11,300 Btu/lb) Radiation,
Coal’
-
Flue convection
‘U b0r4
.o
gases 700 kJ/kg • , . _
_________________
. mc
(300 Btu/lb)
‘- m 0 0 a’ 6 1 45°K (700°F)
• 4.) 0 U
o C\J O’.O
00 ( C’J —jO
Coke oven
— 250 kJ/kg __ ___ gas 1460 kJ/kg
—
700 Btu/lb) ( 200 Btu/lb)
Coke oven gas Light oil, 925°K (1200°F)
tar, coke ammonia, tar,
breeze coke breeze
by—products
a)
— 230 kJ/kg , _
o (100 Btu/lh)
C,
By—product fuel 925°K (1230°F’
.0 a’ value 1880 kJ/kg
(815 Btu/lb)
. .-. a)
a) i
t_ )
Coke 720 kJ/kg
.-
o o a) (310 Btu/lb)
LC’. a’ I 1370°K (2000°F)
0 o
600 kJ/kg _______ _________________
ing 230 kJ/kg
— I-
(260 Btu/lb)
Radiation
Natural gas .,
4)
a)
ases 1160 kJ k
t C) ___
(500 Btu/lb)
a) 395°K (250°F)
. ‘4 0
o 00
4) 0a) 230 kJ/kg
a) ,
° ( 100 Btu/1b)
o r-4
O 535°K (500°F)
Iron ore
pellets and
sinter
(continued on next
• Coal is feed and energy source in this operation. page)
6
-------
Figure 1 (Continued).
Energy input Reclaimed energy Heat rejection
Cok ICoke Air Iron ore
oven gsj Blast oxygen pellets and
tar furnace sinter
gas
— jB1ast stoves.I
ases 230 kJ/kg
Iron
Limestor pack __________ ___________
ore Air (100 Btu/lb)
,- 4 )
last 1 420°K (300°F)
4.)
Lc Lr%
Q j5 ____ ______
r-1( 1 lron m
aking(endo
_______ ______ 1150 kJ/kg
(500 Btu/lb)
980 kJ/kg — 1 Radiation,
(1420 Btu/lb) side reac 2150 kJ/k g
Fuel oil, _______
natural gas ______ 30 Btu/Th)
convection
5100 kJ/kg 580 kJ/kg
— lolten
(2200 Btu/lb) )ig Molten (250 Btu/lb)
Blast furnace
iron slag 2030°K (3200°F)
gas
4.)
700 kJ/k:g
—. C l ) 0) — 4
.0 cs 0 C) (300 Btu/’b
535°K (500° ?)
Unrecovere
. 0 . blast
furnace gar
3000 kJ/kg
r40 r-l -ICCl
‘4’— C .) c’4- bO O .300Btu/lb) Oxygen
Scrap
Steelmaking
1460 kJ/kg
________________________ ot he rmi C
Bb
UU U/iD )
(50 Btu/lb)
Radiation,
Fuel oil,
electricity
convection
Top
.0
- a.’ _________________
gases 580 kJ/kg
- 4. )CCl (250 Btu/lb)
l920°K (3000°F)
[ Fuel plus
1C\ .0 0)
heat energy]
Molten
‘.0 C’J . -l
If’ ‘—S steel
Scrap
(continued on next page)
7
-------
Figure 1 (Continued)
32 40 kJ/kg
(l 400 Btu/lb)
Natural gas
kJ/kg •
Mixed gases
Molten
steel
Casting (Ingot)
__ ____I-
Stack
gases
Rehea .
Heat rejection
r
Scrap
1100 kJ/kg
-
703 kJ/kg
- (300 Btu/lb)
Radiation,
convection
1620 kJ/kg
r’ (700 Btu,’lb)
925°K (1200°F)
1150 kJ/kg
(500 Btu/lb)
Natural gas
230 kJ/kg
(100 Btu/lb)
580 kJ/kz
(250 Btu/lb)
870 — 1147 0 0 K
(1100 — 2200°F)
350 kJ/k -
Finished
steel ‘—
(150 Btu/lb)
980 — 15 1 40°K
(1300—2300°F)
Unaccounted for
230 kJ/kg (100 Btu/lb)
Energy input
Reclaimed energy
I
Mixed gases
I
Ingot
T
Soaking
( 480 Btu/lb) -
1920°K (-3000°F)
1460 kJ/kg -
Ingot
I- : ,
a’
C,.
.0
-4 ci
4-, t -
Q.e )
.-I .-4
N- )< ‘-I
‘-4 -4 0
(200 Stu/Ib)
Radiation,
convect ion
700 kJ/kg
Primary rolling
(300 Btu/lb)
925°K (1200°F)
kJ/kg
Rolled
steel
Scrap
—I
/ ( 430 Btu/lb) —
-l5 40°K (-2300°F)
Stack
gases
Secondary_roiiing_j.
crap
I
920 kJ/k
(A400 Btu/lb) -
-l5LtO°K (-2300°F)
Heat treating
& forging
ack
gases
Radiation, convection
8
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iron ore; ironinaking; steelmakirig; soaking of irigots; reheat-
ing of blooms, billets, and slabs; and heat—treating or
forging. These operations account for more than 80 percent
of the total energy consumption in the manufacture of steel.
Energy consumption in the steel manufacturing process is
hig ily dependent on the ratio of scrap—to—blast—furnace iron
that is fed to the steelrnaking furnace. The energy values
used in this report are based on a scrap—to—pig Iron feed
ratio of 1:2. This is approximately the average of the
overall steel industry.
Figure 2 shows the coking operation. Coal iS distilled at
approximately 1370°K (2000°F) using the combustion of coke
oven gas and blast furnace gas as the heat source. The coke
oven is a rather complicated piece of equipment. Coal is
located in narrow slots typically 40 feet long by 20 feet
high by 18 inches wide. Hot combustion gases pass between
slots containing coal, down through brick checkerwork, and
then out waste heat flues. Combustion air is preheated by
passing through previously heated brick checkerwork. Flow
of combustion gases is reversed periodically so that each
half of the brick checkerwork (regenerators) is being heated
half the time and cooled half the time. Products from the
coke oven include coke, coke oven gas, tar, light oil,
ammonia solution, and coke breeze (small pieces of coke
which pass through 1/2—inch screen). The coke oven gas,
coke breeze, and part of the tar are used as fuel in other
portions of the steel manufacturing process.
Figures 3 and J4 show two agglomerating operations that are
commonly used to Improve iron ore permeability and improve
gas—solid contact in the blast furnace. Agglomeration also
decreases the amount of fine material that is blown out of
the blast furnace. The agglomerating operations are sinter—
ing and pelletizing.
Figure 3 shows that the sintering operation occurs on a
traveling grate that conveys a bed of ore fines, limestone
fines, and coke breeze. The bed (coke breeze) is ignited
by gas burners and, as the mixture moves along the grate,
air is pulled down through the mixture to keep the breeze
burning. The heat sinters the mixture at 16L 0°K (2500°F)
into pea— to baseball—size lumps. Approximately one—third
of the Iron ore burden in a typical blast furnace is
sintered.
Figure 14 shows that the pelletizirig operation also occurs on
a traveling grate. Pellets are formed from iron ore,
bentonite, and moisture. The pellets are coated with coal
9
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Figure 2.
Steel energy intensive equipment diagram — coke oven
[ Rejected heat: Radiation — 230 kJ/kg (100 Btu/lb)
Flue gases — 700 kJ/kg (300 Btu/lb) at 6 1 15°K (700°F)
Coke oven gas — L460 kJ/kg (200 Btu/lb) at 925°K (1200°F)
Tar, light oil, ammonia water stream — 230 kJ/kg (100 Btu/lb) at
925°K (1200°F)
Coke — 720 kJ/kg (310 Btu/lb) at 1370°K (2000°F)]
Coal Coal Coal
11’
Ovens
_
.4j
- fl
I
!i TiL .
I
(4
IIII
E
-I-
—j
11
Ill
Coke Oven
4 Coke oven gas
light oil,
ammonia
solut ion
Coke, coke
breeze
J Blast furnace
gas, air
Coke
oven
gas
Li’
Waste heat
flue
Energy input
26,200 kJ/kg
(11,300 Btu/lb)
gases 2,L1 40 kJ/kg
Energy output
coke
coke oven gas
tar
light oils
coke breeze
losses
18,100 kJ/kg
5,560 kJ/kg
1,270 kJ/kg
325 kJ/kg
970 kJ/kg
2,L Ll0 kJ/kg
7,800 Btu/lb)
2,L400 Etu/ib)
550 Btu/lb)
1L40 Btu/lb)
420 Btu/lb)
1,050 Btu/lb)
Note All energy is expressed in terms of energy
finished steel.
per unit weight of
Coke
oven gas
Blast furnace
gas, air
1 1 U
0
-------
Figure 3. Steel energy intensive equipment diagram — sinter operation
tRejected heat: Radiation — 230 kJ/kg (100 Btu/lb)
Exhaust gases — 1160 kJ/kg (500 Etu/ib) at 395°K (250°F)
Hot sinter or pellets — 230 kJ/kg (100 Btu/lb) at 535°K (500 0 F)]*
* Rejected heat quantities are
operations.
Note: All energy is expressed
f finished steel
totals for sintering and pelletizing
In terms of’ energy per unit weight
Ore fines,
limestone fines
tural gas
Burner hood
,Th
to
cooling
Dust
SI TEFING MACHINE
11
-------
Figure 4.
Steel energy intensive equipment diagram — pelletizing
[ Rejected heat: Radiation — 230 kJ/kg (100 Stu/ib)
Exhaust gases — 1160 kJ/kg (500 Btu/lb) at 395°K (250°F)
Hot sinter or pellets — 230 kJ/kg (100 Btu/lb) at 535°K (500 0 F)]*
* Rejected heat quantities are totals for sintering and pelletizing
operations.
Note: All energy is expressed 1 terms of energy per unit weight of finished
steel.
Iron ore
Vibrating
Bentonite
Coal coating
drum
Pellets to
Pelletizing Machine screening & storage
12
-------
which is ignited on the traveling grate. Recuperated hot air
from the cooling hood is used to dry and preheat the pellets.
Natural gas is used to ignite the pulverized coal or coke
breeze fuel. Some heat is sometimes obtained from the oxi-
dation of magnetite to hematite. The pelletizing operation
occurs at 1370—l590°K (2000—2 1 400°F). Approximately 50 per-
cent of the iron ore burden in a typical blast furnace is
pelletized.
Figure 5 shows the ironmaking portion of the steel manufactur-
ing process. The reduction of iron ore to iron takes place in
the blast furnace. The reducing agent is coke which not only
reduces the iron ore but also provIdes heat to melt the iron.
Additional heat is also provided by the “hot blast” which Is
a mixture of air and oxygen that has been heated in the blast
stoves. The fuel for the blast stoves is blast furnace gas
plus natural gas. Some hydrocarbon fuels are also generally
injected into the blast furnace. The temperature in the lower
part of the blast furnace is l750°K (2700°F). The blast fur-
nace gas coming off the top of the furnace Is used as a fuel
throughout the steel process.
Figure 6 shows the steelmaking operation using the basic oxy—
gen furnace. Pig iron from the blast furnace generally
contains excessive amounts of carbon, silicon, manganese,
and phosphorus. These Impurities are quickly oxidized by
oxygen which is blown onto the molten metal. These oxidation
reactions liberate heat so that very little additional heat-
ing is needed to keep the metal molten.
Figure 7 shows the steelmaking operation using the open hearth
furnace. Air for combustion passes through brick checkerwork
regenerators in one direction for 15 to 20 minutes and then
Is directed in the opposite dIrection. The air provides oxy-
gen to oxidize impurities in the steel and to burn fuel for
heat. The combustion gases pass through the brick checker—
work regenerators and then to boilers. The open hearth
furnace is declining in importance because of its slowness.
It also requires more energy than the now dominant basic
oxygen furnace. The use of an oxygen lance increases the
speed of this operation and also decreases energy consumption.
The decrease in energy consumption is due primarily to a de-
crease in the amount of heat—absorbing nitrogen which passes
through the system.
Figure 8 shows the steelmaking operation using a dIrect-arc
electric furnace. Electricity is used to generate heat to
melt scrap steel. Preheating of the charge can be used to
reduce energy requirements in melting scrap. Oxygen lancing
speeds oxidation of pig iron and results In energy savings.
This method of producing steel is increasing in importance.
13
-------
Figure 5. Steel energy intensive equipment diagram — blast furnace and
blast stoves
[ Rejected heat: Radiation,other—1l50 kJ/kg (500 Btu/lb)
Sensible heat in blast furnace gas — 700 kJ/kg (300 Etu/ib) at
535°K (500°F)
Stack gas from blast stoves—230 kJ/kg (100 Btu/lb) at I20°K
(300°F)
Molten slag — 580 kJ/kg (250 Btu/lb) at 2030°K (3200°F)
Molten iron transfer—70 kJ/kg (30 Btu/lb) at 2030°K (3200°F))
[ Lost fuel: Blast furnace gas — 3000 kJ/kg (1300 Btu/lb)]
Blast furnace gas to
pits, coke oven,
Blast Furnace
Air
and
Oxygen oxygen
Note: All ener ’ Is expressed in terms of ener ’ per unit weight of finished steel.
-------
Figure 6. Steel energy intensive equipment diagram — steel making (basic
oxygen furnace)
[ Rejected heat: Radiation — 115 kJ/kg (50 Btu/lb)
Top gases (fuel value plus sensible heat)—580 kJ/kg (250 Btu/lb)
at 1920°K (3000°Ffl
Pig Iron, flux
Bat ching
hopper
Tap hole
Note: All energy is expressed
finished steel.
In terms of energy per unit weight of
Oxygen lance
Hood
Scrap steel
Ladle on transfer
car
Basic Oxygen Furnace
15
-------
Figure 7. Steel energy intensive equipment diagram — steelrnaking (open
hearth furnace with oxygen Injection)
[ Rejected heat: Radiation — 1350 kJ/kg (580 Btu/lb)
Stack gas heat — 8140 kJ/kg (360 Btu/lb) at 1 480°K (1400°F)]
[ Heat used for steam generation — 700 kJ/kg (300 Btu/lb)]
Scrap, Iron ore,
flux, pig iron
Note: All energy is expressed in terms of energy per unit weight of
finished steel produced using the open hearth furnace.
Regenerators Regenerators
Open hearth furnace
16
-------
Figure 8. Steel energy intensive equipment diagram — steelmaking
(electric furnace)
[ Rejected heat: Radiation, conduction — 700 kJ/kg (300 Btu/ib)]
Note: All energy is expressed in terms of energy per unit weight of
finished steel produced using an electric furnace.
Scrap steel, pig iron
are top charged
Electrodes
Transformer
Vault
Electric—arc furnace
17
-------
Figure 9 shows the soaking pit operation using a two—way gas—
fired soaking pit. Often coke oven gas and blast furnace gas
are used to heat solidified ingots to approximately 1600°K so
that they can be rolled into blooms, billets, and slabs.
Recuperators allow some of the heat from combustion gases to
be retained in the furnace by transferring this heat to in—
coming combustion air.
Figure 10 shows the reheating operation using a five—burner,
countercurrent fired, pusher-type, continuously reheating
furnace. Natural gas can be used as fuel in this operation
which heats slabs, blooms, and billets to approximately 151 ) K
so that they can be further rolled or milled into finished
products. Recuperators allow some of the heat from combustior
gases to be retained in the furnace by transferring this heat
to incoming combustion air.
Figure 11 shows a radiant—type annealing furnace. Approxi-
mately 25 percent of finished steel products are given an
annealing treatment at 920—1090°K (1200—1500°F) to relieve
stresses In the steel. Another 15 percent is processed at
1 1 450—1510°K (2150—2250°F) in forging furnaces. Natural gas
is often used to provide energy for these operations.
Table 1 shows the causes of energy losses In the operations of
the steel process. It also gives an estimate of the magnitude
of the losses and some possible energy conservation approaches.
B. Aluminum by the Bayer—Hall Process
Figure 12 shows the principal steps in the Bayer—Hall aluminum
manufacturing process. The major energy consumption operations
are the steam digestion of bauxite, the evaporation of water
from used caustic solution, the calcining of’ aluminum tn—
hydrate, and the remelting and heat treating of aluminum.
These operations account for over 90 percent of the total
energy consumption in the aluminum manufacturing process.
FIgure 13 shows the steam digestion of bauxite and evaporation
of water from caustic. The alumina in bauxite Is dissolved
in caustic at elevated temperature and pressure. Iron oxide,
titania, and silicates do not dissolve but form a red mud
which Is later separated from the sodium aluminate solution.
Later In the process, steam is used to boil water from a
dilute caustic solution. Aluminum trihydrate has previously
been filtered out of the caustic solution. A set of multi—
effect evaporators are used to boil water from the caustic.
Figure 1 4 shows the use of a rotary kiln to calcine a’uminum
tnlhydrate to alumina. The combustion of natural gas in
18
-------
Figure 9. Steel energy intensive equipment diagram - soaking pit
[ Rejected heat: Radiation, convection — 1460 kJ/kg (200 Btu/lb)
Stack gases — 700 kJ/kg (300 Btu/lb) at 925°K (1200°F)]
Cold
air
Two—way fired soaking pit
Cold
air
Waste gases
to stack
Note: All energy is expressed in terms of energy per unit weight
of finished steel.
Coke oven gas,
blast furnace
Coke oven gas,
glast furnace gas
19
-------
Figure 10.
Steel energy intensive equipment diagram - reheating furnace
(counter—current pusher—type continuous)
[ Rejected heat: Radiation convectlon—700 kJ/kg (300 Btu/lb)
Stack gases — 1620 kJ/kg (700 Btu/lb) at 925°K (1200°Ffl
Reheating furnace
Charging
door
Hot
waste
gases
Re cuperat or
Note: Al]. energy Is expressed in terms of energy per unit weight of
finished steel.
Natural
gas to
burners
Preheated
air to burners
Waste gases
to stack
20
-------
Figure 11.
Air into
radiant
Natural
gas
Steel energy intensive equipment diagram — annealing ovens
ERejected heat’: Radiation, conduction, other — 230 kJ/kg
(100 tu/lb)
Exhaust combustion gases: 580 kJ/kg (250 Btu/lb) at
870—l 70°K (1100—2200°F)]
Annealing furnace for coiled strip
* Includes annealing and forging oven energy.
Note: All energy Is expressed in terms of energy per unit weight of
finished steel.
Atmosphere gas
outlet
Fan drive
21
-------
Table 1. STEEL ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses approaches
1. Coke ovens
a. Radiation and 230 kJ/kg Insulation
convection (100 Btu/lb) Maintenance
b. Partial non— 700 kJ/kg Design modification
recovery of (300 Btu/lb) (waste heat recover ,,
sensible heat
of flue gases
c. Nonrecovery of 720 kJ/kg Design modification
sensible heat (310 Btu/lb) (dry quench with
of coke heat recovery)
d. Nonrecovery of 230 kJ/kg
heat in by— (100 Btu/lb)
products stream
e. Nonrecovery of 460 kJ/kg
sensible heat of (200 Btu/lb)
coke oven gas
f. Wastage of coke 100 kJ/kg Waste utilization
oven gas ( 0 Btu/lb)
2. Agglomeration
a. Radiation and 230 kJ/kg
convection (100 Btu/lb)
b. Exhausting of 1160 kJ/kg Design modification
hot gases from (500 Btu/lb) (waste heat recovery)
sintering or
pelletizing
machines and
from coolers
c. Heat in product 230 kJ/kg Design modification
sinter and (100 Btu/lb) (feed hot sinter
pellets and pellets to
blast furnace)
3. Blast furnace
a. Radiation, con— 1150 kJ/kg Insulation
vection, other (500 Btu/lb) Maintenance
22
-------
Table 1 (continued). STEEL ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses approaches
b. Partial non— 700 kJ/kg Design modification
recovery of sen— (300 Btu/lb) (waste heat recovery)
sible heat of
blast furnace
gas
c. Nonrecovery of 580 kJ/kg
sensible heat (250 Btu/lb)
of slag
d. Wastage of blast 3000 kJ/kg Waste utilization
furnace gas (1300 Btu/lb)
14• Steelmaking furnace (basic oxygen)
a. Radiation and 115 kJ/kg Insulation
convection (50 Btu/lb) Maintenance
b. Sensible heat 580 kJ/kg Design modification
in top gases (250 Btu/lb) (waste heat recovery)
5. Soaking pit
a. Partial non— 700 kJ/kg Design modification
recovery of sen— (300 Btu/lb) (waste heat recovery)
sible heat of
combustion
gases
b. Radiation and 460 kJ/kg Insulation
convection, (200 Btu/lb) Maintenance
other
6. Reheating furnace
a. Partial non— 1620 kJ/kg Design modification
recovery of (700 Etu/ib) (waste heat recovery)
sensible heat
of combustion
bases
b. Radiation and 700 kJ/kg Insulation
convection, (300 Btu/lb) Maintenance
other
23
-------
Table 1 (continued). STEEL ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses approaches
7. Annealing or forging furnace
a. Partial non— 580 kJ/kg Design modification
recovery of (250 Btu/lb) (waste heat recovery)
sensible heat
of combustion
gases
b. Radiation and 230 kJ/kg Insulation
convection (100 Btu/lb) Maintenance
8. Overall process
a. Higher energy 1160 kJ/kg Process modification
requirement (200 Btu/lb) (increase use of
for sintering pellets)
as compared to
pelletizing
b. Higher energy 700 kJ/kg Process modification
requirement for (300 Btu/lb) (replace open hearth
open hearth with basic oxygen
furnace furnace
c. Formation of 2090 kJ/kg Process modification
scrap through— (900 Btu/lb) (increase use of con—
out the process tinuous casting)
d. Loss of sensible 1700 kJ/kg Process modification
heat of ingots (730 Btu/lb) (use continuous
between casting casting)
and soaking
NOTE: All energy values in this table are expressed in terms
of energy per unit weight of finished steel.
2 4
-------
Figure 12. Aluminum energy consumption diagram
[ 1972 USA production: 3.714 x l0 kg (8.214 x lO 9 ib)]
[ 1972 energy consumption (electricity, carbon, natural gas):
15,000 MW (1450 x 1012 Btu)]*
Energy input Sodium Heat 2 eJection
Bauxite I carbonate and lime
Steam
Mixing and
steam digestion
1 Sodium alumiriate
j, solution plus
1 red mud
Steam flashing
L Steam for J
Y heating Water
recycle j
caustic J
Mud settling & filtering
_______ ______________ 700 kJ/kg
- 1 - ______ _________________________
solution 380°K (220°F)
Red mu Sodium alurninate ( (3QOB U/1br
[ Cooling and i1tering ____ 14600 kJ/kg
350°K (170°F)
29,000 kJ/kb F Caustic ( 2000 Btu/lb
Solution
_____________ __________________ ____ 700 kJ/kg
(12,500 Btu/].b) ____ _____ (30.0 Btu/lb)
Steam
austic Radiation,
1solutio ion conyection
Later vapor 20,900
A1 2 0 3 •3H 2 0 (9000 Btu/lb)
Condensate -345°K (-160°F)
to boilers
930 kJ/kg
(400 Btu/lb)
Radiation
92 LkJ/kL..._............aicio :J/kg 6 ooBtu/ gases
convection
n ic
Natural
3250 kJ/k
(1 00 Btu/lb
700°K (-800°F)
AJ,. 2 0 3 1160 kJ/kg
(500 Btu/lb)
-870°K (-1100°F)
* Electricity is counted as 3600 kJ/kWh (31413 Btu/kwh).
(continued on next page)
25
-------
Figure 12 (continued)
Energy input Heat rejection
A1 2 0 3
16 200 kJ k
(7000 Btu/lb) E lectro lysis(endothermic) 29,200 kJ/kg
(12,600 Btu/lb)
Radiation, convection,
Electricity Molten /
14 O0kJk
aluminum 1270°K (1830°F)
I Cast
50 Etu/ib)
Solid
1250°K (-1800°F)
aluminum
______________ ___________ 930 kJ/kg
8100 kJ/kg 11. reatin __1 - Radiation,
(400 Btu/lb)
(3500 Btu/lb) _____________
Natural gas ombustion convection
gases 5100 kJ/kg
(2200 Btu/lb)
1370°K (-2000°F)
LR0’h1 and __________- _________________
1050 kJ/kg
extrusion
_______________ (450 Btu/lb)
-920°K (-1200°F)
Scrap
i aluminum
IFoundry melting and/
heat in
Combus
Unaccounted for
Aluminum
3000 kJ/kg(1300 Btu/lb)
products
* Electricity is counted as 3600kJ/kWb (3413 Btu/kWh)
26
-------
Figure 13.
Aluminum energy Intensive equipment diagram — steam digestion
of bauxite and evaporation of water from caustic
[ Rejected heat: Radiation, convection — 700 kJ/kg (300 Btu/lb)
Heat in red mud — 700 kJ/kg (300 Btu/lb) at 380°K (220°F)
Heat In water vapor from evaporators — 20,900 kJ/kg (9000 8tu/lb)
at 3 1 15°K (160°F)
Heat in sodium aluminate solution — 4600 kJ/kg (2000 Btu/lb)
at 350°K (170°F)]
Strong
caustic
solution
Multi—effect evaporators
Condensate to
boilers
Condensate
Bauxite, lime
slurry
Sodium
Carbonate
Flash
drum
Steam digester
To vacuum
jet
Sodium aluminate solution
and red mud solids to
cooling
Steam
Weak caustic
solution from
aluminum trihydrate
filtration
27
-------
Figure 114.
Aluminum energy Intensive equipment diagram — rotary kiln
[ Rejected heat: Radiation — 930 kJ/kg (1400 Btu/lb)
Combustion gases — 3250 kJ/kg (11400 Btu/lb) at 700°K (800°F)
Heat In alumina — 1160 kJ/kg (500 Btu/lb) at 870°K (1100°FYI
Rotary kiln
Burner
Natural gas
Preheated air
from alumina
cooling
Aluminum
t)
Alumina
to
cooling
28
-------
preheated air provides heat to remove water of hydration at
1370°K (2000°F).
Figure 15 shows the electrolytic separation of alumina Into
aluminum and oxygen (which then reacts with carbon to form
carbon dioxide or carbon monoxide). Electricity supplies
energy to keep the molten salt bath and molten aluminum at
1250°K (1790°F). Electricity and carbon oxidation also
provide energy to dissociate the alumina.
Figure 16 shows the melting of aluminum in a crucible furnace.
Approximately one-third of aluminum castings are remelted to
obtain finished products. Natural gas is burned to provide
heat for melting and for heat treating.
Table 2 lists causes of energy losses in the aluminum
manufacturing process. It also gives estimates of energy
losses and possible conservation approaches.
C. Petroleum Refining
Figure 17 shows a petroleum refining process. Refineries vary
quite widely In complexity and in product mix. The process
shown is representative of a refinery that is producing a
high yield of gasoline from crude oil. The primary energy
consumption operations include crude oil distillation, gas
oil desulfurization, heavy naphtha desulfurization, naphtha
desulfurization, catalytic cracking, naphtha reforming, alkyla—
tion,aromatlcs extraction, and coking. Sources of energy for
these operations are primarily natural gas, refinery produced
gas, petroleum coke, and fuel oil. These operations account
for more than 80 percent of the energy consumed in the
petroleum refining process shown.
Figure 18 shows the distillation of crude oIl. The degree
of separation of the crude into components varies from one
refinery to another. The scheme shown is fairly elaborate.
The principal energy conservation practice is to preheat the
crude oil by heat exchange with components leaving the dis-
tillation columns. Natural gas or refinery produced gas is
burned to supply heat to the column feeds. Steam is also
used to provide heat to the strippers and the atmospheric
column.
Figure 19 shows the catalytic hydrogenation at high pressure
[ 1350—6800 kN/m 2 (200—1000 psi)] of gas oil or naphtha to
remove sulfur. The feed is mixed with hydrogen—rich gas,
heated to 585—730°K (600—850°F), and passed through a reacto’
containing a fixed bed of desulfurization catalyst. The feed
is heated by hot reactor effluent and by the burning of
29
-------
Figure 15. Aluminum energy intensive equipment diagram — electrolytic
cell
EReiected heat: Radiation, convection, other — 29,200 kJ/kg
(12,600 Btu/lb)
Exit gases — l ,900 kJ/kg (61400 Btu/lb) at 1270°K (1830°F)]
Alumina electrolysis cell
Insulation
Steel
pins
Alumina
Bath
Molten
aluminum
Steel
30
-------
Figure 16.
Aluminum energy intensive equipment diagram — melting
furnace
[ Rejected heat: Radiation, other—930 kJ/kg ( 00 Btu/lb)
Combustion gases—5100 kJ/kg (2200 Btu/lb) at -1370°K(--2000°F)
Heat in products —1050 kJ/kg ( 50 Btu/lb) at 920°K ( ‘1200°F)]
Aluminum
Natural gas,
air
Natural
air
* Heat quantities include melting and heat treating operations.
Crucible furnace
31
-------
Table 2. ALUMINUM ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservatirr
energy losses losses approaches
1. Digestion of
bauxite & evapo-
ration of water
from caustic
a. Radiation & 700 kJ/kg Insulation
convection (300 Btu/lb) Maintenance
b. Heat in red 700 kJ/kg
mud (300 Btu/lb)
c. Heat removed 4600 kJ/kg
in cooling of (2000 Btu/lb)
aluminat e
solution
d. Heat in vapor 20,900 kJ/kg Design modification
leaving (9000 Btu/lb) (optimize evapora—
evaporators tion scheme)
Operation modifica-
tion (close control
of wash water volume)
2. Calcining
a. Heat in exit 3250 kJ/kg Operation modiuica—
combustion (1400 Btu/l ) tion (control of
gases air/fuel ratio).
Design modification
(more complete heat
recuperation)
b. Radiation and 930 kJ/kg Insulation
convection (400 Btu/lb) Maintenance
c. Heat in 1160 kJ/kg Operation modifica—
alumina (500 Btu/lb) tion (feed hot
alumina to cells).
Design modification
(more complete heat
recuperation
3. Electrolytic
reduction
a. Anode overvolt.— 14650 kJ/kg Operation modifica--
age, resistance (2000 Btu/lb) tion (lower current
and electrical density). Research
connection and development
(catalytic additive
to anode)
32
-------
Table 2. (continued). ALUMINUM ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses approaches
b. Cathode 14650 kJ/kg Operation modifica—
resistance (2000 Btu/lb) tion (lower current
density). Research
and development
(alternative cathode
materials)
c. Electrolyte 20,1400 kJ/kg Design modification
resistance (8800 Btu/lb) (closer anode—cathode
spacing). Operation
modification (lower
current density)
d. Resistance 1850 kJ/kg Operation modifica—
between cells (800 Btu/lb) tion (lower current
density). Design
modification
e. Recombination 8100 kJ/kg Operation modifica—
of aluminum (3500 Btu/lb) tion (closer control
with oxygen of cell operation)
f. Excess carbon 5350 kJ/kg
consumption (2300 Btu/lb)
)4• Remelting and heat
treating
a. Heat in corn— 5100 kJ/kg Design modification
bustion gases (2200 Etu/ib) (waste heat recovery)
b. Radiation and 930 kJ/kg Insulation
convection (1400 Btu/lb) Maintenance
5. Overall process
losses
a. Lack of alumi— 32 000 kJ/kg Waste utilization
num recycling (11 ,000 Btu/lb) (more aluminum re-
cycling).
b. Higher energy 25,000 kJ/kg Process modification
requirement (11,000 Etu/ib) (replacement of Hall
of Hall process process with new
as compared to Alcoa process)
new Alcoa
process
33
-------
Table 2 (continued). ALUNINUM ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy loSftes losses approaches
c. Radiation 29,200 kJ/kg Insulation
convection (12,600 I3tu/lb)
electrolysis
cell
d. Heat in exit 1 4,9O0 kJ/kg Design modification
gases from (6 oo Btu/lb) (waste heat recovery)
electrolysis
cell
NOTE: Electrolytic reduction losses are electrical. Overall
process losses a. and b. are primarily electrical.
The fuel equivalent for these losses would be approxi-
mately three times the listed values.
31
-------
Figure 17. Petroleum refining energy consumption diagram
[ 1971 USA production: 610 x iü kg (1350 x i° lb)]
[ 1971 energy consumption (primarily natural gas refinery gas,
petroleum coke, fuel oil) 914,000 MW (2.8 x l0 Btu)J
Energy input Heat rejection
Crude
Radiation,
Natural
C orive Ct ion
ste am
Hea y
Asphalt stock oil naph h Wasted heat from
to asphalt existing column streams
manufacture 230 kJ/kg
( 100 Btu/lb
327 — 1 420°K
(130— 300°F)
Lubricating ,Stack
gases 230 kJ/kg
oil stocks
to lube oil By—product streams (100 Btu/lb)
manufacture 1) c 1 , C 2 gas 700° c (800°F)
2) LPG
3) Kerosine
1!) Diesel fuel
Lube oil
fraction
*4R _
Naphtha 10 kJ/kg
(70 Btu
Natural gas, ctionatiori t— r ( 5 Btu/lb)
_____ Radiation,
or refinery
gas Gas Wasted heat convection
Coke oil 1 from exiting
olumri streams 70 kJ/kg
Naphtha ____ ( 30 Btu/lb)
1420 — 530°K
(300— 500°F)
Stac
Olefin and 145 kJ/kg
paraffin gase (20
700°K (800°F)
gases — _________
350 kJ/kg _ I Hydrodesulfurizátlon 1 25 kJ/kg
(150 Btu/lb) operations ( 10 B U/lbr
Refinery gas iRadiation, convection
Desulfurize Wasted heati
Naphtha
} ...stream I fromexitin 115 kJ/kg
C 1 , C 2 I column and (50
gas,
H 2 S Gas’ reactor a 3 140_1400°K
oil (150— 250°F)
Stack gases
(continued on next page)
35
-------
Figure 17 (Continued).
Energy input Heat rejection
Desulfurized Non—aromatic Stack gases
naphtha
hydrocarbons 115 kJ/kg
Ifromaromati ( 50 Btu/1b)
Olef in and’ _ c on I
esulfurized 700°K (800°F)
as oil
gases
Pararfinj CaicI 145 kJ/kg
580 kJ/kg Irl reforming
(20 Btu/lb)
(250 Stu/ib) _______
asted heat convection
Refinery gas or fractionation _______ Radiation,
natural gas
n process
streams 115 kJ/kg
H 2 I ( 50 Btu/lb)
3140 — 1 400°K
LPG (150— 250°F)
Stack gases 210 kJ/kg
gas ( 90 Btu/1b)
Re crmate te 700°K (800°F)
j For gasol
7 blending
(5 Btu/lb)
160 kJ/kg dulf tic 10 kJ/kg
(70 Btu/lb) extraction _______ Radiation,
Steam, refinery Waste heat convection
gas in process
Aromatic streams 115 kJ/kg
hydro— I ( 50 Btu/1b)
carbons Stactc gases 340—1400°K(150—250°F)
Non—
hydrocarbom 35kJ/kg
to catalytic Desulfurized gas 1 tu b
reforming oil 700°K (800°F)
yt1ccrackingafl
1270 kJ/kg fractionation 95 kJ/kg
kJ/kg (70 Btu/lb) (140 Btu/lb)
Petroleum coke, herm c 9 Lsted Radiation,
heat In
refinery gas or
natural gas 0
_____________ streams 1460 kJ/k
_ ases
lfur remo Gaso me for ocess
_____________ tu
blending Stack 0 — 50
& fractionation Light oil gases (150-350 F)
________________ for blending __________________________
c i, c 2 ga4°’ Isobutane 700°K (800°F)
fractionation (10 Etu/lb
1460 kJ/kg Alkylation and 25 kJ/kg
200 Btu lb
heat Radiation, convection
tack streams 370°K (80—200°F)
Natural gas, LPG Alkylate as gases - 145 kJ/kg
in process 1460 kJ/kg
propane gasoline
additive 20 Btu 1b
Unaccounted for 00K ( 00 F)
36
-------
Figure 18.
Petroleum refining energy intensive equipment diagram — crude
distillation
[ Rejected heat: Radiation — 95 kJ/kg (140 Btu/lb)
Heater stack gases — 230 kJ/kg (100 Btu/lb) at 6 1 40°K (700°F)
Hot exiting column steams (wasted) — 230 kJ/kg (100 Btu/lb)
at 327 — 1420°K (130 — 300°F)]
= Steam for column and strippers
Heavy Light Medium Heavy
naphtha Kerosirie Diesel lube lube lube
Partially topped
crude
37
-------
ftgure 19.
Petroleum refining energy intensive equipment diagram —
distillate hydrodesulfuriZatiofl
[ Rejected heat: Radiat1ofl convection—25 kJ/kg (10 Btu/lb)
Heater stack gases — 115 kJ/kg (50 Btu/lb) at 700°K (800°F)
Wasted heat in process streams — 115 kJ/kg (50 Btu/lb) at
3140 400°K (150 — 250°F)i
H 2 rich gas
H 2 S plus light ends fuel gas
High pressure
separator
naphtha or
gas oil
38
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natural gas or refinery—produced gas in a heater. The product
is separated from gases in a high pressure separator, low
pressure separator, and a stripper. Heat to the stripper is
supplied by hot reactor effluent.
Figure 20 shows the catalytic reforming operation where
naphthas are converted to aromatic hydrocarbons. The dehydro—
genation reactions take place at high pressure [ 2000_L 000
kN/m 2 (300—600 psi)] and at elevated temperatures [ 720—810°K
(8 1 40_l0000F)] in a hydrogen atmosphere. Natural gas or
refinery—produced gas is burned in heaters to provide heat
for the endothermic reactions which occur. Hot reactor
effluent is used to preheat incoming feed and to provide
heat to the fractionator at the end of this operation.
Figure 21 shows a fluid catalytic cracking operation. Gas
oil is preheated in a natural gas or refinery—produced gas—
fired heater. It then carries regenerated catalyst into the
reactor—settler. The product comes out of the top of the
reactor while spent catalyst overflows a weir and falls
through a steam stripper. The steam removes entrained
hydrocarbons. Then the spent catalyst goes to the catalyst
regenerator where coke is burned off the catalyst. Regene-
rated catalyst then flows to the gas oil feed to be swept
into the reactor. The product from the reactor is fed to a
fractionator where gas, gasoline, and light oil are obtained.
The temperatures in this operation are approximately 740°K
(870°F) in the reactor and 900°K (1160°F) in the catalyst
regenerator. Coke combustion in the catalyst regenerator
supplies heat for the reactions which occur in the reactor.
The flue gas from the regenerator contains combustible carbon
monoxide fuel.
Figure 22 shows an alkylation operation where isobutane
reacts with a C 3 to C 5 olefin stream in the presence of a
catalyst. The products are branch—chained C 5 to C 0 hydro-
carbons with a high octane number. The product is called
the alkylate and is blended into gasoline. The reaction
takes place at low temperature [ 285—320°K (50—110°F)] and
is exothermic. The reactor products are separated by dis-
tillation. The fractionator is heated by burning natural
gas or refinery—produced gas In the reboiler furnace.
Figure 23 shows an aromatic extraction operation in which
reformed naphtha is separated into its aromatic and non—
aromatic components. A glycol—water mixture flows into an
extractor and dissolves the aromatic portion of the reformed
naphtha feed. The rich solvent Is then taken to a stripper
where the dissolved aromatics are separated from the solvent.
The aromatics then go to a water wash tower where traces of
39
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Figure 20.
Petroleum refining energy intensive equipment diagram —
catalytic reforming
ERejected heat: Radiation, convection — L 5 kJ/kg (20 Btu/lb)
Furnace stack gases — 210 kJ/kg (90 Btu/lb) at 700°K (800°F)
Wasted heat in process streams — 115 kJ/kg (50 Btu/lb) at
3IIO L OO°K (150—250°F)]
Fract Ion at r
H 2 recycle Retormate
‘40
-------
Figure 21.
Petroleum refining energy intensive equipment diagram — fluid
catalytic cracking
[ Rejected heat: Radiation, convection—95 kJ/kg (140 Btu/lb)
Furnace stack gases: 115 kJ/kg (50 Btu/lb) at 700°K (800°F)
Wasted heat in process streams: 1460 kJ/kg (200 Btu/lb) at
3140 — 1 450°K (150 — 350°F)
Reactor stack gases: 160 kJ/kg (70 Btu/lb) at 700°K (800°F)]
Product
Flue gas
Catalyst
regenerator
Fractionator
Clarified
oil
Pre-heater
L 1
-------
Figure 22. Petroleum refining energy intensive equipment diagram —
HF alkylation
[ Rejected heat: Radiation, convection—25 kJ/kg (10 Btu/lb)
Furnace stack gases— 45 kJ/kg (20 Btu/lb) at 700°K (800°F)
Wasted heat in process streams — l 60 kJ/kg (200 Btu/lb)
at 300—370°K (80—200°F)]
HF stripper
propane
Alkylate as
gasoline additive
42
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Figure 23.
Petroleum refining energy intensive equipment diagram —
aromatics extraction
[ Rejected heat: Radiation, convection—lO kJ/kg (5 Btu/lb)
Furnace stack gases—35 kJ/kg (15 Btu/lb) at 700°K (800°F)
Wasted heat in process streams — 115 kJ/kg (50 Btu/lb) at
3 1 40— 1 400°K (150—250°F)]
Purifica—
t ion
tower
43
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dissolved glycol are removed. The aromatics then are heated
in a natural gas or refinery gas-fired heater and fed to a
clay tower where impurities are removed. Steam is used to
provide heat to the water glycol still shown in the figure.
Figure 2 I shows a coking operation where heavy residuals are
upgraded into more valuable distillate products and coke.
The residue is fed to a distillation column where light gases
are flashed. The remaining material combines with recycle
and is pumped to a natural gas or refinery—produced gas—fired
heater where It is heated to 770°K (920°F). The liquid—vapor
mixture leaving the heater passes to a coking drum. Coke
builds up to a predetermined level in one drum, and then flow
Is diverted to the next drum. The full drum Is steamed to
strip out unconverted hydrocarbons, cooled by water, and then
Is hydraulically decoked with high pressure water jets. The
coke drum overhead vapor goes to the distillation column for
separation Into gas, gasoline, and gas oil.
Table 3 sh vs the causes of energy losses In the petroleum
refining process. It also gives estimates of the losses and
possible conservation approaches.
D. Suimnary of Energy Losses and Recommended Conservation
Approaches
Table Is a summary of energy losses and recommended con-
servation approaches for the steel, aluminum, and petroleum
industries. Combustion is the dominant operation in the
steel and petroleum refining processes while electrolysis
Is the dominant operation In the aluminum process. Oppor-
tunities are available for energy conservation in both of
these operations.
14.4
-------
Figure 2 4.
Petroleum refining energy intensive equipment diagram — coking
[ Rejected heat: Radiation, convection — 10 kJ/kg (5 Btu/lb)
Furnace stack gases _L1 5 kJ/kg (20 Btu/lb) at 700°K (800°F)
Hot exiting column streams (wasted) — 70 kJ/kg (30 Etu/ib)
at 420—530°K (300—500°F)]
Gas
Naphtha
Steam
generation
cw
Gas oil
Heavy residual
oil
45
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Table 3. PETROLEUM REFINING ENERGY CONSERVATION
APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses approaches
1. Rejected heat
a. Unrecovered 1560 kJ/kg Design modification
heat in (680 Btu/lb) (optimize heat ex—
streams exit— change system)
ing energy Maintenance (keep
intensive heat exchange
operations surfaces clean)
b. Unrecovered 955 kJ/kg Design modification
heat In stack ( 4l5 Btu/lb) (waste heat recovery)
gases
c. Radiation, 305 kJ/kg Insulation
convection (130 Btu/lb) Maintenance
d. Unaccounted 1135 kJ/kg
for (1485 Btu/lb)
2. Overall process
a. High reflux 115 kJ/kg Design modification
ratios in (50 Btu/lb) (more plates In
distillation column). Operation
columns modification (closer
control of columns)
b. Unrecovered 70 kJ/kg Design modification
potential (30 Btu/lb) (use hydraulic and
energy expander turbines)
(pressure) in
several
operations
c. Loss of fuel 115 kJ/kg Waste utilization
value of flue (50 Btu/lb) (use as fuel in
gas from boiler)
catalytic
cracking re-
generator
d. Lack of inte— 1460 kJ/kg Process integration
gration of (200 Btu/lb)
electrical
generation with
steam generation
-------
Table 4. SUMMARY OF ENERGY LOSSES AND RECOI 1MENDED CONSERVATION
APPROACHES
Level and approximate
magnitude of losses
High energy (Approximate Energy
consumption (Temperature magnitude conservation
Industry operations level) of losses) approaches
Steel Combustion, Radiation, 3115 kJ/kg 1. Design
heating and convection (1350 Btu/lb) modification
cooling 350—500°K 1390 kJ/kg 2. Insulation
(lTO— 1 O°F) (600 Btu/lb) 3. Maintenance
500—600°K 230 kJ/kg 14. Waste
(14140—620°F) (100 Btu/lb) utilization
600—700°K 11400 kJ/kg
(620—800°F) (600 Btu/lb)
TO0—1000°K 3010 kJ/kg
(800—l3 1 40°F) (1300 Btu/lb)
1000—1500°K 1650 kJ/kg
(13140—22140°F) (710 Btu/lb)
1500—2100°K 14180 kJ/kg
(22140—3320°F) (1810 Btu/lb)
Overall Process
process modification
Aluminum Electrolysis Radiation, 29,200 kJ/kg 1. Operation
convection (12,600 Btu/lb) n dification
l270°K 114,900 kJ/kg 2. Research &
(1830°F) (61400 Btu/lb) development
3. Design
modification
Digestion & Radiation, 700 kJ/kg 1. Design
evaporation convection (300 Btu/lb) modification
3 1 45°K 20,900 kJ/kg 2. Operation
(160°F) (9000 Btu/lb) modification
3. Insulation
Kiln Radiation, 930 kJ/kg 1. Design
convection (1400 Btu/lb) modification
700°K 3250 kJ/kg 2. Insulation
(800°F) (11400 Btu/lb) 3. Operation
870°K 1160 kJ/kg n dification
(1100°F) (500 Btu/lb)
Overall 1. Waste
process utilization
2. Process
dificat ion
Lt7
-------
Table 4 (continued). SUMMARY OF ENERGY LOSSES AND RECOMMENDED
CONSERVATION APPROACHES
Level and approximate
magnitude of losses
High energy (Approximate Energy
consumption (Temperature magnitude conservation
Industry operations level) of losses) approaches
Overall 3. Insulation
process 4. Design
modification
Petroleum Combustion Radiation, 305 kJ/kg 1. Design
and convection (130 Btu/lb) modification
distillation 300—550°K 1570 kJ/kg 2. Insulation
(80—530°F) (680 Btu/lb) 3. Maintenance
-700°K 960 kJ/kg
( 8OO°F) (415 Btu/lb)
Overall
process 1. Design
modification
2. Operation
modification
3. Waste
utiliation
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SECTION V
BIBLIOGRAPHY
Berg, C. A. Conservation in Industry. Science. 1814:261l 27O,
April 19, 19714.
Brantley, F. E. Iron and Steel. In: Minerals Yearbook 1972,
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Bravard, J. C., H. B. Flora, and C. Portal. Energy Expendi-
tures Associated with the Production and Recycle of Metals.
Oak Ridge National Laboratory, Oak Ridge, Tennessee. Publica-
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Gyftopoulos, E. P., Director. Study of Effectiveness of
Industrial Fuel Utilization. Thermo Electron Corporation,
Waltham, Massachusetts. Report No. TE 5357—71 714. January
19714. 120 p.
Hayden, J. E., and W. H. Levers. Design Plants to Save Energy.
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Hobson, G. D., and W. Pohi (ed.). Modern Petroleum Technology,
14th edition. New York, John Wiley & Sons, 1973. 996 p.
Hoffman, H. L. (ed.). 19714Refining Process Handbook.
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Jones, F. A. Build and Run Plants to Save Energy. Hydrocarbon
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Klinger, F. L. Iron Ore. In: Minerals Yearbook 1972,
Schreck, A. E. (ed.). Washington, U. S. Government Printing
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Kobrin, C. L. Steel’s Changing Uses of Energy. The Iron Age.
201:1145—1514 , June 6, 1968.
McGannon, H. E. (ed.). The Making, Shaping and Treating of
Steel, 9th edItion. Pittsburgh, Herbick and Held, 1971.
11420 p.
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McNanus, G. J. Electric Steelmaking Assumes New Role. Iron
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Sheridan, E. T. Coke and Coal Chemicals. In: Minerals
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50
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SECTION VI
GLOSSARY OF ABBREVIATIONS
Btu British thermal unit
cond condensate
CW cooling water
kg kilogram
kJ kiloJoule
kN kiloNewton
lb pound
m meter
psia pounds per square inch absolute
MW megawatt
stm steam
yr year
51
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SECTION VII
APPENDIX
ENERGY CONSERVATION APPROACHES
Design modification — This term includes design changes in
equipment or process.
Insulation — This term implies that a review of the economics
of additional insulation is needed.
Maintenance — This term implies that the economics of
additional maintenance effort needs review.
Process integration — This term relates to the best use
of steam by using the same steam in more than one
process or to the optimization of the steam—
electricity production ratio.
Research and development — This term relates to the improve-
ment of processes by future discoveries.
Operation modification — This term includes changes in
operating procedures or practices that do not
require a design change.
Market modification — This term relates to the substitution
of a low energy consumption product for a high
energy consumption product.
Process modification - This term relates to a change in a
process due to a change in process feedstock, raw
materials, or process route.
Waste utilization — This term relates to the use of fuel
value of waste process streams or to the recycling
of discarded materials.
52
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