r
PB-211 927
ENERGY CONSUMPTION: THE CHEMICAL INDUSTRY
ENVIRONMENTAL PROTECTION AGENCY
APRIL 1975
DISTRIBUTED BY:
National Technical Information Service
U. S. DEPARTMENT OF COMMERCE
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PB 241 927
EPA-650/2-75-032-a
April 1975
Environmental Protection Technology Series
O :$:$:^§j§i$
:::::::::::::::::::::::x:::::::^^
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TECHNICAL REPORT DATA
( P1 1 ase rccd !aWlwlwns on the reverse bc/ore completing)
REPORT NO 2
EPA-650/2-75 -032-a
3 RECIPIENT S ACCESSIOr.NO.
4 TITLE AND SU6TITLE
Energy Consumption:
The Chemical Industry
5 REPORT DATE
4pril 1975
6. PERFORMING ORGANIZATION CODE
7 AUTHORIS)
John T. Reding and Burchard P. Shepherd
8. PERFORMING ORGANIZATION REPORT NO
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Dow Chemical, U.S.A.
Texas Division
Freeport, Texas 77541
10. PROGRAM ELEMENT NO.
IABO13: ROAP 2IADE-010
11. CONTRACT/GRANT NO
68-02-1329, Task 5
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 NO PER 00 COVERED
IS SUPPLEMENTARY NOTES
lb. A8STRACTP repori gives results of a study of energy consumption in the chemical
industry. It analyzes energy-intensive steps or operations for manufacturing pro-
cesses which produce 12 of the top 50 volume chemicals in the U. S. Results of the
analyses are in the form of energy consumption block diagrams. energy-Intensive
equipment schematic diagrams, and tables that indicate the causes of energy losses,
as well as possible conservation approaches. The most common energy-intensive
operations in this industry are furnace operation, distillation, compression, refri-
geration, electrolysis, drying/calcining, and evaporation. Energy losses in these
operations could be reduced by: design, operation, market, and process modification:
better insulation and maintenance; process integration; waste utilization: and
research and development.
PRICES SUCh [ CT TO CHANCE
19 SECURITY CLASS (This Report)
Unclassified
20 SECURITY CLASS (This page)
Unclassified
17.
KEY WORDS AND DOCUMENT ANALYSIS
a
DESCRIPTORS
b IDENTIFIERS/OPEN ENDED TERMS
C COSATI
Field/Group
Energy
Compressors
13G
Consumption
Refrigerating
Chemical Industry
Electrolysis
07A, 07D
Conservation
Drying
Furnaces
Roasting
13A
Distillation
Marketing
Evaporation
Wastes
l3H
05C
18 DiSTRIBUTION STATEMENT
Unlimited
EPA Forni 2220.1 ($.73J
21. NO. OF PAGES
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EPA650/2-75-032-a
ENERGY CONSUMPTION:
THE CHEMICAL INDUSTRY
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. IABO13
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
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EPA HE VIEW 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 Development, 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 for 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-a
11
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CONTENTS
Page
ii
L18t of Figures v
List of Tables vii
Sections
Conclusions
II Recommendations 2
III Introduction 3
IV Energy Consumption within the Chemical
Industry 5
A. Chlorine by Electrolysis of Brine 7
B. Caustic Soda Concentration by
Evaporation of Water 7
C. Ethylene by Ethane Pyrolysis 13
D. Ethylbenzene by Alkylatlon of
Benzene with Ethylene 21
E. Styrene by Dehydrogenation of
Ethylbenzene 21
F. Phenol/Acetone by Oxidation of
Cumene and Cleavage of Cumene
Hydroperoxide 29
G. Cumene by Alkylation of Berizene
with Propylene 37
H. Sodium Carbonate by the Solvay
Process 37
I. Carbon Black by the Furnace Process 146
J. Oxygen/Nitrogen by Air Distillation 146
K. Operational and Design Problems of
Energy Intensive Equipment 56
iii
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CONTENTS (continued)
Page
L. Operational and Design Problems
of Heat Transfer Equipment 56
M. Chemical Industry Energy Conser-
vation Study Summary 56
V Bibliography 61
VI Glossary of Abbreviations 62
VII Appendix 63
iv
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FIGURES
No. Page
1 Chlorine Energy Consumption Diagram 8
2 Chlorine Energy Intensive Equipment
Diagram — Electrolytic Cell 9
3 Caustic Soda Energy Consumption Diagram 1].
ii Caustic Soda Energy Intensive Equipment
Diagram — Evaporators 12
5 Ethylene Energy Consumption Diagram 15
6 Ethylene Energy Intensive Equipment
Diagram — Pyrolysis Furnace and Waste
Heat Recovery Equipment 17
7 Ethylene Energy Intensive Equipment
Diagram — Compressors 18
8 Ethylene Energy Intensive Equipment
Diagram — Propylene and Ethylene Refrig-
eration Systems 19
9 Ethylene Process Refrigeration 20
10 Ethylbenzene Energy Consumption Diagram 214
11 Ethylbenzene Energy Intensive Equipment
Diagram — Distillation Columns 25
12 Styrene Energy Consumption Diagram 27
13 Styrene Energy Intensive Equipment
Diagram — Superheater, Reactor, and
Cooling Equipment 28
114 Styrene Energy Intensive Equipment
Diagram — Distillation Columns 30
15 Phenol/Acetone Energy Consumption Diagram 32
16 Phenol/Acetone Energy Intensive Equipment
Diagram — Air Compressors 33
V
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FIGURES (continued)
Page
17 Phenol/Acetone Energy Intensive Equipment
Diagram — Cumene Hydroperoxide Distilla-
tion Column 314
18 Phenol/Acetone Energy Intensive Equipment
Diagram — Acetone Distillation Columns 35
19 Phenol/Acetone Energy Intensive Equipment
Diagram — Phenol Distillation Columns 36
20 Phenol/Acetone Energy Intensive Equipment
Diagram - Cracking Furnace 38
21 Cumene Energy Consumption Diagram 140
22 Cumene Energy Intensive Equipment Diagram -
Distillation Columns 4l
23 Sodium Carbonate Energy Consumption Diagram 143
214 Sodium Carbonate Energy Intensive Equipment
Diagram - Lime Kiln 1414
25 Sodium Carbonate Energy Intensive Equipment
Diagram — Compressors 145
26 Sodium Carbonate Energy Intensive Equipment
Diagram — Calciner 147
27 Carbon Black Energy Consumption Diagram 149
28 Carbon Black Energy Intensive Equipment
Diagram - Reactor and Waste Heat Recovery
Equipment 50
29 Carbon Black Energy Intensive Equipment
Diagram - Dryer 51
30 Oxygen/Nitrogen Energy Consumption Diagram 53
31 Oxygen/NItrogen Energy Intensive Equipment
Diagram - Compressors 514
32 Oxygen/Nitrogen Energy Intensive Diagram -
Distillation Column 55
vi
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TABLES
___ Page
]. Chlorine Energy Conservation Approaches 10
2 Caustic Soda Energy Conservation Approaches i 4
3 Ethylene Energy Conservation Approaches 22
4 Ethylbenzene Energy Conservation Approaches 26
5 Styrene Energy Conservation Approaches 31
6 Phenol Energy Conservation Approaches 39
7 Cumene Energy Conservation Approaches
8 Sodium Carbonate Energy Conservation
Approaches 48
9 Carbon Black Energy Conservation Approaches 52
10 Oxygen/Nitrogen Energy Conservation
Approaches 57
11 Operational and Design Problems In Energy
Intensive Equipment 58
12 Operational Problems with Heat Transfer
Equipment 59
13 Chemical Industry Energy Conservation
Study Summary 60
vii
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SECTION I
CONCLUSIONS
Most of the energy consumption within the chemical In-
dustry is concentrated in a relatively few operations.
These Include furnace combustion, distillation, com-
pression, electrolysis, drying, and evaporation. Avoid-
able energy losses occur in all of the above operations.
Some of the losses can be eliminated by employing con-
servation techniques. These Inlcude:
• Design modifications to increase waste heat
recovery from furnaces.
• Design modifications to allow lower energy input
Into distillation columns.
• Proper maintenance practices to prevent losses
in many places.
• Process Integration to obtain maximum energy
from steam.
• Operation modifications to avoid losses in
electrolytic cells.
• Greater use of Insulation to limit heat losses.
• Research and development to develop processes
with Increased conversions or yields.
• 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 and 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
categories — 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
chemical industry only. This breakdown can give direction
to subsequent conservation efforts.
Scope
This report analyzes high energy consumption operations
in the chemical industry (SIC 28) and identifies the
principal energy intensive equipment. It points out
causes of energy losses In these operations, the approx-
imate magnitude of the losses, and possible approaches
to decrease these losses.
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 l.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 great-
est impact.
3
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General 4pproach
Ten chemical processes which result in the production of
12 of the top 50 volume chemicals were reviewed.
These processes are:
• Chlorine by electrolysis of brine
• Caustic soda concentration by evaporation of
wateD
• Ethylene by pyrolysis of ethane
• Ethylbenzene’ by alkylation of benzene with
ethylene
• Styrene by dehydrogenation of ethylbenzene
• Phenol/acetone by oxidation of cumene and
then cleavage of cumene hydroperoxide
• Cumene by alkylation of benzene with propylene
• Sodium carbonate by the Solvay process
• Carbon black by the furnace process
• Oxygen/nitrogen by distillation of air
Energy consumption block diagrams have been drawn for
each process. These diagrams indicate the operations
within the processes where large amounts of energy are
used. The energy intensive operations have been further
analyzed. Schematic diagrams which show the physical
and operational appearance of the energy consuming equip-
ment have been prepared. Causes of energy losses in the
energy intensive operations, the approximate magnitude
of the losses, and possible conservation approaches have
been determined.
‘4
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SECTION IV
ENERGY CONSUMPTION WITHIN THE CHEMICAL INDUSTRY
In order to analyze energy consumption within the chemical
industry, it was necessary to select a specific manufac-
turing process for each chemical in the study. Two
decisions had to be made:
• A production route or overall production process
had to be chosen. This is net automatic becuase
most chemicals are manufactured by more than one
process. However, the obvious choice In each
case wath to select the dominant process.
• A certain level of production technology had to
be chosen. Although energy consumption for many
chemical manufacturing processes is high, the low
cost of energy in the United States in the past
made the use of a large amount of energy conser-
vation technology uneconomical. The recent in-
creases in energy costs, however, have led to the
construction of plants that produce chemicals
using less energy than older plants. The process
technology level for this study is the best avail-
able to the general public. Much proprietary
information on more modern plants is not available.
It is therefore believed that some of the energy
conservation approaches suggested in this study
may already be in use in new plants.
Estimates of the total 1973 energy requirements to pro-
duce each chemical studied are included on the energy
consumption block diagrams. The estimates are divided
into two portions:
• Process energy consumption excluding feedstock
energy. Feedstock energy refers to first use of
fuel and petroleum products within the industrial
chemicals group.
• Feedstock or, sometimes, feedstock—plus—process energy
consumption. Any fuel generation in the process is
included in this figure as a negative number or if
fuel generation is greater than feedstock consumption,
it is so indicated.
5
-------
These estimates are approximate and are Intended only to
show the order of magnitude of energy requirements to
produce the chemicals,
The type of energy used to produce the chemicals is also
indicated on the energy diagrams. Different types of energy
are not equivalent. Approximately 3 Btu of fuel energy are
usually required to obtain 1 Btu of’ electrical energy.
Approximately 1.1 to 1.3 Btu of fuel energy are required to
obtain 1 Btu of’ steam energy.
Energy values in all figures and tables are expressed In
terms of energy per unit weight of product. In the cases
of’ the phenol/acetone process and the oxygen/nitrogen
process, phenol and oxygen are considered to be the products.
In the case of the 50 percent caustic soda process, the
energy Is expressed In terms of energy per unit weight of
100 percent caustic soda.
The tables showing energy conservation approaches give
estimates of losses or rejected heat In operations in the
process and in the overall process. The losses or rejected
heat listed In the operations are additive. The lo8ses
listed in the overall process often overlap and are not
additive.
Energy conservation approaches Include:
• insulation
• design modification
• maintenance
• process integration
• research and development
• operation modification
• market modification
• process modification
• waste utilization
6
-------
In many cases a more specific explanation of the conser-
vation 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. Chlorine by Electrolysis of Brine
Figure 3. shows the major steps In the chlorine manufac-
turing process. The process uses dlaphram type electro-
lytic cells. The major step from an energy consumption
viewpoint is the electrolytic separation of the brine
into chlorine, hydrogen, and cell liquor (dilute
caustic solution). This operation accounts for 85 to 90
percent of the total energy consumption in the process.
Figure 2 shows the general arrangement of the chlorine
electrolytic cell. Chlorine is evolved from the cell
anode while hydrogen and cell liquor come from the
cathodic compartment. The cell diaphragm separates the
anodic and cathodic compartments.
Table 1 indicates the causes of energy losses in the
electrolytic brine separation operation. It also shows
the approximate magnitude of the losses and possible
energy conservation approaches.
B. Concentration of Caustic Soda by Evaporation of
Water
FIgure 3 shows the major steps in the manufacture of
caustic soda. This process concentrates the cell
liquor from the chlorine diaphragm cell by evaporating
water from the dilute caustic solution. Approximately
80 percent of the total energy consumption occurs in the
water evaporation operation which produces 50 percent
caustic scda.
Figure shows a typical caustic soda evaporation
operation. Cell liquor enters the third effect of a
three effect evaporation system and 50 percent caustic
soda leaves the first effect. Sodium chloride In the
cell liquor is separated from the caustic soda solution
after the solution leaves the first and second effect
evaporators. Steam Is the source of heat.
7.
-------
Figure 1. Chlorine energy consumption diagram
(1973 USA production: 9.35 X i0 kg (20.6 x iO ib))
[ 1973 energy consumption (primarily electricity): 3300 MW
(100 x iO Btu)]
[ 1973 fuel generation (112): 1000 MW (30 x 1012 Btu))
Energy input
Meat rejection
Brine feed
Chemical treatments
Electrolysis cell
àHreac 6250 kJ/k
(2700 Btu/lb)
Endotherinia
2530 kJ/kg
( 1100 Btu/1b
Radiation,
convection, other
Wet chlorine
gas _____
Cooling and
I drvinz
Cell liquor to
caustic soda
process
1150 kJ/kg
(500
330°K (135°F)
230 kJ/kg
( 100 B /1br
360°K (190°F)
10.200 kJ/kg
(4L 20 Btuflb)
Electricity
11 by—product
Fuel valve
3500 kJ/kg
(1500 Btu/lb)
45 kJ/kg . -
(20 Btu/lb)
360°K (190°F)
1
Dry chlorine gas
Compressing
I
I
Liquefaction
I
Liquid
I chlorine
8
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Figure 2. Chlorine energy Intensive equipment diagram — electrolytic cell
(Rejected heat: Radiation, convection, other — 2530 kJ/kg
(1100 Btu/lb)
Hot H 2 by—product — 5 kJ/kg (20 Btu/lb) at 360°K (190°F)
Hot Cl 2 product — 230 kJ/kg (100 Btu/lb) at 360°K (190°F)
Warm cell liquor — 1150 kJ/kg (500 Btu/lb) at 330°K (135°F)]
Rectifier
Cl 2 H 2
___ 1
Brine feed — Diaphragm
Cell liauor
Electrolytic cell
9
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Table 1. CHI 1 ORINE ENERGY CONSERVATION APPROACHES
Approx imate
Causes of magnitude of Energy conservation
energy losses losses approaches
1. Electrolysis cell
a. Anode over— ‘460 kJ/kg Operation modification
voltage (200 Btu/lb) (lower current density)
Research & development
(improve anode material)
b. Cathode over— i’4oo kJ/kg Operation modification
voltage (600 Btu/lb) (lower current density)
Research & development
(Improve cathode
material)
c. Voltage drop 580 kJ/kg Design modification
across (250 Btu/lb) (thinner diaphragm)
diaphragm
d. Voltage drop in ‘460 kJ/kg
electrolyte (200 Btu/lb)
e. Voltage drop in 280 kJ/kg Design modification
anode—cathode (120 Btu/lb)
assemblies
f. Oxygen evolu— 230 kJ/kg Research & development
tion on anode (100 Btu/lb) (improve anode
material)
g. Unaccounted 580 kJ/kg
for (250 Btu/lb)
2. Overall process
a. Lack of heat 1’425 kJ/kg Design modification
recovery from (620 Btu/lb) (waste heat recovery)
H 2 , Cl 2 , and
cell liquor
streams
b. Radiatlon,con- 2530 kJ/kg Insulation
vection, other (1100 Btu/lb)
heat losses
from electro-
lysis cell
c. Failure to use 3500 kJ/kg Waste utilization
H 2 by—product (1500 Btu/lb)
as fuel
NOTE: Electrolysis cell losses are electrical. The fuel
value of these losses would be approximately three
times as large as the values listed.
10
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Figure 3.’ Caustic soda energy consumption diagram
(1973 USA production: 9.70 x iO kg (2l. 4 x
(1973 energy consumption (primarily steam):
(80 x lO Btu)]
10 ib)]
2700 MW
* Weight of products as 100% caustic soda.
Energy values are in terms of energy per unit weight of caustic soda
as 100% caustic soda.
Energy Input Heat rejection
Chlorine
cell liquor
120 kJ/kg
355°K (180°F)
(by—product)
Anhydrous NaOH (by—product)
11
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Figure 4. Caustic soda energy intensive equipment diagram — evaporators
[ Rejected heat: Radiation, convectIon, other - 120 kJ/kg
(50 Stu/Ib)
Water vapor — 5200 kJ/kg (2250 Btu/lb) at 320°K (120°F)
Hot product — ‘160 kJ/kg (200 Btu/lb) at 355°X (180°F)]
* Energy values are in terms of energy per unit weight of caustic
soda as 100% caustic soda.
Evaporators
1st effect
evaporator
To vacuum jet
12
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Table 2 shows the causes of energy losses in the evap-
oration of water from cell liquor. It also shows the
approximate magnitude of the losses and some possible
energy conservation approaches.
C. Ethylene by Ethane Pyrolysis
Figure 5 shows major steps in an ethylene manufacturing
process that uses ethane as the feedatock. Major steps
from an energy consumption viewpoint are pyrolysis of
the feed, compression of the gases from the pyrolysis
furnace, and liquefaction of the gases before distilla-
tion. Both the compression and liquefaction by refrig-
eration are necessary to allow separation by distilla-
tion of the components in the furnace exit stream. The
pyrolysis, compression, and refrigeration operations ac-
count for approximately 90 percent of the total energy
consumption in the manufacture of ethylene.
Figure 6 shows the furnace and associated waste heat
recovery equipment In a modern ethylene plant. Waste
heat is recovered from furnace stack gases and from
hot process gases leaving the furnace.
Figure 7 shows the compression of process gases from
the pyrolysis furnace. Intercooling and gas—liquid
separation are necessary between each stage of com-
pression. Acetylene hydrogenation is shown between the
third and fourth compression stages.
Figures 8 and 9 show a refrigeration system for a modern
ethylene plant. Figure 8 shows the compression of pro-
pylene arid ethylene refrigerants. Various levels of com-
pression arid expansion lead to a number of temperature
levels that are needed in the distillation columns. The
system is referred to as a cascade system because some
of the propylene refrigerant is used to cool the ethylene
refrigerant which is then used to cool several process
streams. An energy saving feature of the scheme In
Figure 8 is the use of the coldness in the bottom streams
from the demethanizer and C 2 splitter distillation columns
to cool a portion of the propylene refrigerant. Figure
9 shows the refrigeration of process gases by cold process
streams leaving distillation columns, by propylene and
ethylene refrigerants, and by the gases in the demethanizer
overhead stream. The demethanizer overhead stream is
usable as a coolant because it has been supercooled by
passing through a turbo—expander. Figure 9 also shows
13
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Table 2. CAUSTIC SODA ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses approaches
1. ReJected heat
a. Radiation, 120 kJ/kg Insulation
convection (50 Btu/lb) Maintenance
b. Water vapor 5200 kJ/kg Design modification
from last (2250 Btu/lb) (waste heat recovery)
effect
c. Hot product ‘i60 kJ/kg Design modification
(200 Btu/lb) (waste heat recovery
2. Overall process
a. Use of excess l 400 kJ/kg Design modification
steam (600 Btu/lb) (add additional effect
to evaporation
operation)
b. Low NaOH 2300 kJ/kg Research & development
concentration (1000 Btu/lb) (ionic membrane
in cell liquor diaphragm)
c. Production of 230 kJ/kg Market modification
anhydrous NaOH (100 Btu/].b) (substitute 70-74% NaOH
f or anhydrous)
Note: Energy values are in terms of energy per unit weight of
caustic soda as 100% caustic soda.
114
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Figure 5.’
Ethylene energy consumption diagram
[ 1973 USA production: 10.1 x iO kg (22.t x 1O 9 lb))
[ 1973 process energy consumption (primarily natural gas plus
H 2 , CH 1 . gases generated in the process): 9300 MW 8o x 10 12 Btu)]
[ 1973 total energy consumption (feedstock plus process
requirements) 23,000 MW (700 x 1012 Btu)]
0
U -’
‘-4
aD
.- )
0
0
C—
—s
.0I.
J - U)
. U )
•... . 4.) GJ
— ) mr-.
. 0.
0
o O {)
0 C%J 043
. .-..i U)
kJ/kg
(2100 Btu/lb)
High pressure
St earn
5..s U)
0.
O E
O. (
aD )
I 1.)
.—x
65% conversion of ethane in furnace
with an 80% yield of ethylene.
(continued on next page)
Reclaimed energy
Energy Input
20.900 kJ/kg
St earn
Meat rejection
Feedstock —
ethane
uuI Recycle ethane
(9000 Btuulb)
Natural gas or
H 2 ,CH gases
from distilla-
tion columns
t
350 kJ/kg
Pyrolvsis furnace .
(endotherTnic)
Aflreac 5150 kJ/k
(2220 Btu 1b) t
Hs1de reac = 930 kJ/kg I
(1j Btu/lb) I
67140 kJ/kg
2900 Btu/lb )
High pressure
steam
1 830 kJ/kg
(150 Btu/lb)
Radiation,
convection
Stack
•gases 2160 kJ/kg
Hot
reaction
products
(2080 Btu/lb)
Quench, water scrub,
and cooling
(930 Btu/lb)
1 48o°K (1400°F)
230 kJ/kg
.0
5 .. ’
4)
0
a’
U).
Cool
reaction
products
Compression
14870
(100 Btu/lb)
3 1 40°K (150°F)
145 kJ/kg —
Acetylene removal
I
Compress ion
F
(20 Btu/lb)
Radiation,
convection
3250
‘1
Condensate
return to
process
Compressed
reaction
products
(11400 Btu/lb)
380°K (220°F)
1750 kJ/kg
(750 Btu/lb)
380°K (220°F)
15
-------
Figure 5. (ContInued).
High pressure ____________
St earn
5H10 kJ/kg
(2330 Btu/lb)
This steam Is
used along with
additional steam
(900 kJ/kg or
390 Btu/lb) at
other points in
the process
H 2 , CH as fuel
15,300 kJ/kg
(6600 Btu/lb)
to distillation
Compressed
reaction
1’ products
Compressed, purified
reactor products
Refrigerant
$ recycle
.‘ Refrigerant
‘ compression
ndensate
ecycle
Refrigerant
Ethylene
product
25 kJ/kg
(10 Btu/lb)
Radiation,
convection
2320 kJ/kg
( 1,000 Btu/] ’ )
3 1 0°K (150°F)
580 kJ/kg
(250 Btu/lb)
Conduction,
other
Ethane recycle
Ret’rigerant recycle
Energy input
Reclaimed energy
Heat rejection
Caustic
and
water
wash.
Drying
..—
‘-3
0
0 \
C ”
‘-4
.0
-l
4)
0
C
3500 IcJ/kg
(1500 Btu/Ib)
I 380°K (220°F)
Cooling, dernethanizer,
deethanizer, and C 2 L
splitter distillation F
-_columns J
16
-------
Figure 6. EthyIrn ‘-ni rgy intensive equipment diagrarn—pyrolysis furnace
and waote heat recovery equipment
tReiected heat: Radiation, convection — 350 kJ/kg (150 Btu/lb)
Stack gases — 2160 kJ/kg (930 Btu/lb) at ll80 0 K ( 1100°F)]
Fyratysto
fu rn a c P
Furnace energy balance
Waste hrat recovery
Quench exchanger
Water ocrubhrr
(9000 Btu/lb)
Energy
input to furnace
20,900
kJ/kg
Heats
of reaction
Ethylene
Side reactions
5150
930
kJ/kg
kJ/kg
(2220
( 100
Energy
Energy
Energy
change from
transferred
loot
feed to product
to steam
5570
67 110
2510
kJ/kg
kJ/kg
kJ/kg
(21400
(2900
(1080
11830 kJ/kg
1160 kJ/kg
Btu/ lb)
Btu/lb)
Btu/lb)
Btu/lb)
Btuflb)
Condensate
Reaction
products
Low
pressure
nteam
Condensate
CH + air
20 00 kJfk
(9000 Btu/lb)
condensate
Quench Water
exchanger scrubber
(2080 Btu/lb)
( 200 Btu/1.b)
17
-------
Figure 7. Ethylene energy intensive equipment diagram — compressors
[ Rejected heat: Radiation, convection — 115 kJ/kg (20 Btu/lb)
Condensate (vapor) — 3100 kJ/kg (1350 Btu/ lb) at 380°K
C 220°F)
Hot compressed reaction products — 1850 kJ/kg (800 Btu/ lb)
at 380°K (220° ?) ]
Steam
Reaction
Condensttte
1st stage
compressor
Steam Input to earh turbine 1220 kJ/kg (525 Btu/lb)
Acetylene
hydrogenat ion
reactor
Products
Condensate
pa ia)
Steam
2nd stage 3rd stage
compressor compressor
1 1th stage
compressor
18
-------
Figure 8. Ethylene energy intensive equipment diagram — propylene and
ethylene refrigeration systems
[ Rejected heat: Radiation, convection — 25 kJ/kg (10 Btu/lb)
Condensate (vapor — 3500 kJfkg (1500 Btu/lb) at 380°K (220°F)
Hot refrigerant streams — 2320 kJ/kg (1000 Btu/lb) at -3 4O°K
( -150°F)]
Demethanizer reboiler
0
(j Dryer feed chiller
Demethanizer feed
C 2 splitter reboller
Gj Ethylene refrigeration
Deethanizer condenser
C. splitter condenser
Demethanizer condcns r
19
-------
Figure 9. Ethylelte process refrigeration
Feed #6
Feed #5
Feed #
Feed #3
Feed #2
Feed #1
* Burned in pyrolysis furnace.
Reaction
products Ethane
from feed CH 4 ., H 3
dryer recycle
Propylene
Ethylene
product
Propylene
Demethanizer
feed #2
Ethylene
Dernethanizer
feed # I
Demethanizer
feed #6
Deme t han X4e r
feed #
Demethanizer
Propylene
To
deethanizer
20
-------
the efficient practice of multi—feeding the demethanizer
column. In effect the feed stream has been partially
separated before it enters the demethanizer column.
Table 3 shows the causes of energy losses in the pyrolysis
operation, compression operation, refrigeration operation,
and overall process. It also shows the approximate mag-
nitude of the losses and some possible energy conserva-
tion approaches.
D. Ethylbenzene by Alkylatlon of Benzerie with Ethylene
Figure 10 shows the major steps In the ethylbenzene man-
ufacturing process. The process illustrated uses an
A1C1 3 catalyst to promote alkylatlon of benzene with
ethylene. The major step from an energy consumption
viewpoint is the separation of the reaction exit stream
Into components by distillation. This operation accounts
for approximately 75 percent of the total energy consump-
tion in the production of ethylbenzene.
Figure 11 shows the distillation operation. Steam pro-
vides energy for the three primary columns — the tar
removal column, the benzene column, and the ethy].benzene
C oluinn.
Table 14 shows the causes of energy losses in the distil-
lation operation and the overall process. It also shows
the approximate magnitude of the losses and possible con-
servation approaches.
E. Styrene by Dehydrogenation of Ethylbenzene
Figure 12 shows the major steps in the styrene manuf’actur—
ing process. This process uses a metal oxide catalyst to
promote the dehydrogenation of ethylbenzene at high temper-
ature. Major energy consumption operations are the heating of
reactants plus steam and the separation of the reacto
exit stream into components by distillation. These opera-
tions account for more than 90 percent of the total energy
consumption In the manufacture of styrene.
Figure 13 shows the steam superheating, reaction, heat
recovery, and desuperheating operations. Steam, natural
gas, and waste process gas are used to provide energy
for the reaction. The large amount of steam Is also
21
-------
Table 3. ETHYLENE ENERGY CONSERVATION APPROACHES
Causes of
energy ]sse
Approximate
magnitude of
losses
Energy conservation
aD roaches
1. Furnace losses
a. Hot stack
gases
b. Radiant and
convection
heat losses
2. Heat rejection in
compression operation
a. Unavailability
of latent heat
in steam to
drive the
turbine
b. Loss of heat
imparted to
compressed
gases
c. Radiation,
convection
a. Unavailability
of latent heat
in steam to
drive the
turbine
b. Loss of heat
imparted to
compressed
refrigerant
c. Radiation,
convection
2160 kJ/kg
(930 Btu/lb)
350 kJ/kg
(150 Btu/lb)
3250 kJ/kg
(l i00 Btu/lb)
1750 kJ/kg
(750 Btu/lb)
4 kJ/kg
(20 Btu/lb)
3500 kJ/kg
(1500 Btu/lb)
2320 kJ/kg
(1000 Btu/lb)
25 kJ/kg
(10 Btu/lb)
Design modification
(waste heat recovery)
Insulation
Maintenance
Process integration
(find use for the low
pressure steam exiting
the turbine)
Design modification
(waste heat recovery)
Process integration
(find use for the low
pressure steam exiting
the turbine)
Design modification
(waste heat recovery)
Insulation
4. Overall process
a. Low conversion
of etharie to
products
8100 kJ/kg
(3500 Btu/lb)
Research & development
3. Heat rejection in
refrigeration operation
Insulation
22
-------
Table 3 (continued). ETHYLENE ENERGY CONSERVATION APPROACHES
Approximate
Causes of magniti. de of Energy conservation
energy losses losses approaches
b. Low yield of 11600 kJ/kg Research & development
ethylene from (2000 Btu/lb)
ethane
c. Non—isothermal 580 kJ/kg
compression of (250 Btu/lb)
process gases
and refrigerants
d. Non—Isentroplc 700 kJ/kg Maintenance
compression of (300 Btu/lb)
process gases
and refrigerants
e. Excessive tern— 1160 kJ/kg Design modification
perature dif— (200 Btu/lb) (use more heat exchange
ferences between surface)
cold and hot Maintenance
fluids in the Insulation
refrigeration
operation
F. Non—optimiza— 460 kJ/kg Design modification
tion of (200 Btu/lb)
distillation—
refrigeration—
compression
scheme
23
-------
Figure 10. Ethylbenzene’ energy consumption diagram
[ 1973 USA production: 2.91$ x 10 kg (6.50 x iO ib)]
[ 1973 process energy consumption (primarily steam): 1130 MW
(13 x l0 2 Etu)] -
[ 1973 total energ consumption (feedatock plus process):
3150 MW (911 x 10 2 Btu)]
Energy input A1C 1 3 Heat rejection
Dried catalyst
benzene I
Ethylene
Reactor (exotherinic)
Hreac = 1280 kJ/kg
(550 Btu/lb)
Recycle diethyl— Overhead I
benzene ,vapors 1 t I 930 kJ/kg
Cooling and scrubbing
__________________________ ( i00 Btu/lbY
370°K (210°F)
Liquid
reaction
products
Aid 3 sludge g
370°K (210°F)
recycle
50%
NaOH
I decanting
I Neutralizing and 1 lus e
Water p
caustic wast
3720 kJ/kg
Heat 3720 kJ/kg
rej ected
rom
overhead (1 0 Btu lb
_______________ 355— 1 $l0°K
Steam Benzene •uI
recycle I
Tar (fuel value is (180—280°F)
Diethylbenzene I
0 kJ/kg or
100 Btu/lb)
Ethylbenzene
product
* 110% conversion of benzene to products.
95% selectivIty to ethylbenzene
99% conversion of ethylene to products
24
-------
Figure 11.
Ethylbenzene energy intensive equipment diagram — distillation
IFleiected heat: From overhead streams — 3720 kJ/kg
(1600 Btu/lb) at 355— IlO°K (180—280°F)]
React ion
products
I
1310 kJ/kg
— (560 Btu/lb)
Steam
To diethylbenzene.
column
Wet benzene to benzene
drvinz column
1180 kJ/l
lb)
team /(510 Bt
Ethyl-
berizene
product
1230
(530
Steam
kJ/kg
Btu/lb)
To gas scrubber
Tar removal
column
Benzene
column
Ethy lbenzene
column
25
-------
Table Lj• ETHYLBENZENE ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses approaches
1. Rejected heat
a. Cooling of 1280 kJ/kg Design modification
reactor exit (550 Btu/lb) (waste heat recovery)
St reams
b. Cooling of 3720 kJ/kg Design modification
overhead (1600 Btu/lb) (waste heat recovery)
streams from
distillation
columns
2. Overall process
a. Failure to 230 kJ/kg Waste utilization
use tar as (100 Btu/lb)
fuel
b. Low conversion 1850 kJ/kg Research & development
of benzene (800 Btu/lb)
c. High ref lux 700 kJ/kg Design modification
ratios in (300 Btu/lb) (more plates)
distillation
columns
26
-------
Figure 12.
Styrene 0 energy consumption diagram
[ 1973 USA production: 2.72 x 10 kg (6.01 x io lb.)]
[ 1973 energy consumption (primarily natural gas, steam):
2600 MW (78 x 1012 Btu)]
(1973 fuel generation (waste gases, residue): 730 MW
(22 x 10 1z Btu)]
5 50 kJ/kg
(2350 Btu/lb)
Natural gas,
process waste
gas
19jP0 kJ/kg
(8500 Btu/lb)
Steam
5560 kJ/kg
(2J400 Btu/lb)
St earn
J (‘40 btuf].D)
Radiation, convection
Stack
gas 835 kJ/kg
(360 Btu/l
Steam 530°K (500°F)
2300 kJ/kg
( 980 Btu/1
500°K (440°F)
20,100 kJ/kg
Residue fuel
kJ/kg (300 Btu/lb)
Styrene product
* 40% conversion of ethylbenzene to products
90% selectivity to styrene.
Energy input Reclaimed energy Heat rejection
4
Steam
I Heat exchange
and superheater
3920 kJ/kg
(1690 Btu/lb)
Ethy lbenzene
Steam 111.1
4230 kJ/kg
95 kJ/kg
(1830 Btu/lb)
bO
‘-3
0
‘L ieat exchange & reactor
1 AH .eac
herm1c
T Wet reaction
products
50 kJ/kg
( U 5 UfJ.O)
Radiation,
convection
1 Cooling I
I
I Desuperheater
I and cno11n
$Tar
Decantation and
gas separation
H 2 , other gases as fuel
3360 kJ/kg (1450 Btu/lb)
i-j
iCondensate
(8700 Btu/lb)
380°K (220°F)
I
Reaction
products
1
Distillation
luene
Benzene
r; ;ei: 5560 kJ/kg_
I ( d ’ 400btufj. 1
315-340°K
( 110—150° ?)
Ethylbenzene recycle
27
-------
Figure 13.
3tyrene energy intensive equipment diagram — superheater,
reactor, and cooling equipment
[ Rejected heat: Radiation, convection — 1 5 kJ/kg (60 Btu/lb)
Stack gases — 835 kJ/kg (360 Btu/lb) at 530°K (500°F)
Hot reaction products — 2300 kJ/kg (980 Btu/lb) at 500°K (L1110°F)
and 20,100 kJ/kg (8700 Btu/lb) at 380°K (220°F))
Steam
Desuperheater
Superheater
Natural
gas 2090 kJ/kg
(900 Btu/lb)
Air
Waste gas
oJ
3360 kJ/kg
(1 450 Btu/lb)
St earn
t Hreac
1730 kJ/kg
(750 Btu/lb)
Reactor
Reaction products
J 3920 kJ/kg and steam
U690 Btu/lb)
19100 kJ/kg
(8500 Btu/lb)
Heat exchanger
Ethylbenzene
[ ( )
)
Heat exchanger
1200 kJ/kg
(520 Btu/lb)
Heat exchanger Waste gas
30110 ser
Conden
(1310 Btu/lb) (8700 Btu/lb)
20100 kJ/kg
l————Dec
2300 kJ/kg
(980 BtU ar_ Heating value
50 kJ/kg (20 Btu/lb)
Liquid
reaction
products
Condensate
To boiler
28
-------
provided as a diluent to lower the ethylbenzene partial
pressure and thereby allow the reaction conversion to
Increase.
Figure ]. I shows the distillation operation. Steam pro-
vides energy for the primary columns - the light ends
columns, the ethylbenzene column, and the styrene column.
Table 5 shows the causes of energy losses in the super—
heating—reaction operation, the distillation operation,
and the overall process. It also shows the approximate
magnitude of the losses and possible conservation
approaches.
F. Phenol/Acetone by Oxidation of Cumene and Cleavage
of Cumene H ydroperoxide
Figure 15 shows the major steps In the phenol/acetone
manufacturing process. Cuinene Is oxidized to cumene
hydroperoxide which Is then split into phenol and acetone.
Major energy consumption operations are air compression
and separation of the reactor exit stream by distillation.
These operations account for approximately 70 percent
of the energy consumption In the manufacture of phenol!
acetone.
Figure 16 shows the compression of air which Is used to
oxidize cumene. A two stage compression scheme with
Intercooling is employed.
Figure 17 shows the separation of unreacted cumene from
cumene hydroperoxide by distillation. Steam Is used to
provide energy for this operation.
Figure 18 shows the separation of acetone from other
reactor effluent components by distillation. Steam is
the energy source for the three distillation columns —
the crude acetone column, the light ends column, and
the refined acetone column.
Figure 19 shows the separation of phenol from other
reactor effluent components by distillation. Steam Is
the energy source for the four distillation columns —
the heavy ends column, the cuznene column, the dehydro—
genation column, and the phenol column.
29
-------
Figure 111.
Styrene energy intensive equipment diagram — distUlation
(Rejected heat: From overhead streams - 5560 kJ/kg
(21100 Btu/lb) at 315—3 1 10°K (110—150°F)]
700 kJ/kg
(300 Btu/lb)
steam
cw
To waste gas
at ream
cw
Liquid reaction
products from
condenser
Ethylbenzene
column
steam
Light ends
column
cw
Styrene
column
Styrene
Residue fuel
700 kJ/kg
(300 Btu/lb)
30
-------
Table 5. STYRENE ENERGY CONSEHVATION APPROACHES
Approximate
Ca ses of magnitude of Energy conservation
energy losses losses approaches
1. Superheater,
reactor & cooling
operations
a. Heat in stack 835 kJ/kg Design modification
gases (360 Btu/lb) (waste heat recovery)
b. Radiation, ]i45 kJ/kg Insulation
convection (60 Btu/lb) Maintenance
a. Heat discarded 22, 0O kJ/kg Design modification
from process (9680 Btu/lb) (waste heat recovery)
stream
2. Rejected heat in 5560 kJ/kg Design modification
distillation (2’400 Btu/lb) (waste heat recovery)
operation
3. Overall process
a. Low ethyl— i8,500 kJ/kg Research & development
berizene (5000 Btu/lb)
conversion
b. Fuel value 50 kJ/kg Waste utilization
of tar (20 Btu/lb)
c. High reflux 930 kJ/kg Design modification
ratios in (1 00 Btu/lb) (more plates)
distillation
Columns
31
-------
Figure 15.
Phenol/acetone’ energy consumption diagram
[ 1973 USA production: phenol 1.02 x 1O 9 kg (2.25 x iO ib)
acetone 0.905 x kg (1.99 x iO ib)
(1973 energy consumption (primarily steam): 530 MW
(16 x l0’ Btu)]
[ 1973 fuel generation (tar): 60 MW (1.8 x 1012 Btu)]
I ,
700 kJ/kg
(300 Btu/lb)
Electricity
11460 kJ/kg
(630 Btu/lb)
Steam
10,600 kJ/kg
(14570 Btu/lb)
Steam I
Ac etopheno J
Cumene recycle
* 25% conversion of cumene.
92% selectivity to phenol
and acetone.
Energy values are in
terms of energy per unit
weight of phenol produced.
6140 kJ/kg
(280 Btu/lb)
Natural gas
Air
Oxidation reactor (exothermic)
AHreac 1150 kJ/kg (500 Btu/lb)
Reaction products
Ion exchange
neutralizers
] iieavies 4 phenol kcetone
product product
Stack
gas
Side
reaction products
to distillation
1390 kJ/kg
(600 Btu/lb)
355°K (175°F)
2550 kJ/kg
( 1100 B Uflbr
350°K (165°F)
10,850 kJ/kg,,
(14660 Btu/lb)
320— 1 400°K (115—260°F)
230 kJ/kg
( ..LUU Ufi0)
Blo°K (1000°F)
Energy input
Compression
Meat rejection
Cumene recycl Cumeme Hot air
- 270 kJ/k
(115 Btu/lb)
380°K (220°F)
1390 kJ/kg -
!2 , 0 I
Gas separation
(bOO Btu/lb)
385°K (230°F)
185 kJfkg
4 Concentration
distillation column
Cumene
J ( 0 Btu/lb) —
385°K (230°F)
I
recyc.Le
I
Cumene hydroperoxide
Cleavage mixer, cooler, flash drum
A}I ac: 2700 kJ/kg (1160 Btu/lb)
Exotherinic
Primarily
acetone
Primarily phenol
I
Distillation
—
4 Cracking furnace
— 145 kJ/kg
( U Utu/lb)
Radiation, convection
Tar
370 kJ/kg
j (160 Btu/lb)
535°K (500°F)
Fuel value is 1850 kJ/kg
(800 Btu/lb)
32
-------
tgurc a6. Phenol/acetone energy intensive equipment
diagram — air compression
[ Rejected heat: Hot compressed air — 270 kJ/kg
(115 Btu/lb) at 380°K (220°F)]
Air
100 kN/m 2
(1LI.7 psia) Cw
I ________ to actor
_ J 1 F650kN/m2
— ____________ psia)
Compressor Compressor
Note: Energy values are in terms of energy per
unit weight of phenol produced.
33
-------
Figure 17.
Phenol/acetone energy intensive equipment
diagram - cumene hydroperoxide concentration
distillation column
[ Rejected heat: Overhead stream — 1390 kJ/kg
(600 Btu/lb) at 355°K (175°F)]
recycle
cumene hydroperoxide
Cumene hydroperoxide
concentration column
Note: Energy values are In terms of energy per
unit weight of phenol produced.
Unreacted cumene
and cumene
ide
‘I
1, 460 kJ/kg
(630 Btu/lb)
steam
31
-------
Figure 18.
Phenol/acetone energy Intensive equipment diagram — acetone
distillation columns
(Rejected heat: Overhead streams — 1350 kJ/kg (580 Btu/lb)
at 320—335°K (115—1 1 40°F)]
Crude
acetone
column
Re fined
acetone
column
Note: Energy values are in
of phenol produced.
terms of energy per unit weight
Primarily acetone
from flash
tank
Light
ends
column
35
-------
Figure 19.
Phenol/acetone energy intensive equipment diagram — phenol
distillation column
[ Rejected heat: Overhead streams — 9500 kJ/kg (i O80 Btu/lb)
at 320-Ji00°K (115—260°F)]
Heavy ends
column
Cumene
column
Dehydration
column
Phenol
column
Note: Energy values are In terms of energy per unit weight
of phenol produced.
Phenol and
heavies from
crude acetone
column
Heavy ends
to cracking
furnace
36
-------
Figure 20 shows the cracking of the bottoms from the
heavy ends distillation column and from the acetophenone
distillation column. Natural gas is used to provide
heat for cracking of the bottoms material.
Table 6 shows the causes of energy losses ir the compres—
sj on operation, the distillation operation, the cracking
operation, and the overall process. It also shows the
approximate magnitude of the losses and possible con-
servation approaches.
Q, Cuinene by Alkylation of Benzene with Propylene
Figure 21 shows the major steps in the cumene manufac-
turing process. Phosphoric acid on alumina catalyzes
the alkylatlon of benzene with propylene. The major
energy consumption step is the separation of reactor
effluent components by distillation. This operation
accounts for approximately 90 percent of the total energy
consumption in the process.
Fj gure 22 shows the distillation scheme used to separate
the reactor exit stream components. Dowthertn is used
to provide energy for the three distillation columns —
the propane column, the benzene column, and the cumene
co 1 uxnn.
Table 7 shows the causes of energy losses In the distil-
lation operation and the overall process. It also shows
the approximate magnitude of the losses and possible
energy conservation approaches.
H. Sodium Carbonate by the Solvay Process
Figure 23 shows the major steps In the synthetic sodium
carbonate manufacturing process. The Solvay process is
used. Major steps from an energy consumption viewpoint
are the lime kiln operation, the compression of carbon
dioxide, and the calcining of sodium bicarbonate to
podium carbonate. These steps account for mere than 70
percent of the total energy consumption In the process.
Figure 2 4 shows the lime kiln operation. Coke supplies
energy to convert calcium carbonate to calcium oxide
and carbon dioxide.
Figure 25 shows the corpresslori of c rbor dioxIde
nitrogen from the lime kiln. Steam is used to provide
energy to drive the compressors.
37
-------
Figure 20.
Phenol/acetone energy intensive equipment
diagram — cracking furnace
[ Rejected heat: Radiation, conve&tlon —
115 kJ/kg (20 Btu/lb)
Hot stack gases — 230 kJ/kg (100 Btu/lb) at
810°K (1000°F)
Hot process streams — 370 kJ/kg (160 Btu/lb)
at 535°K (500°F))
Cracking furnace
plus dehydrator
Note: Energy values are in terms of energy per unit weight
of phenol produced.
Heavy ends column
and acetophenone
column bottoms
Cw
Al 2 03
To
Tar
N,
Air
Natural gas
To
C ume n e
column
38
-------
Table 6. PHENOL/ACETONE ENERGY CONSERVATION APPROACHES
Approx iniat e
Causes of magnitude of Energy conservation
energy losses losses approaches
1. Rejected heat
a. Hot compressed 270 kJ/kg Design modification
air (115 Btu/lb) (waste heat recovery)
b. Overhead 12,130 kJ/kg Design modification
streams from (5260 Btu/lb) (waste heat recovery)
distillation
columns
c. Other hot 1i500 kJ/kg Design modification
process streams (19 4O Btu/lb) (waste heat recovery)
d. Hot stack gases 230 kJ/kg Design modification
(100 Btu/lb) (waste heat recovery)
e. Radiation, 145 kJ/kg Insulation
convection (20 Btu/lb) Maintenance
2. Overall process
a. Low cumene 11460 kJ,’kg Research & development
conversion to (630 Btu/lb)
cumene hydro—
peroxide
b. Fuel value 1850 kJ/kg Waste utilization
of tar (800 Btu/lb)
c. Hig i reflux 20L 0 kJ/kg Design modification
ratios in (880 Btu/lb) (more plates)
distillation
co]. uinns
d. Non—isothermal 95 kJ/kg
compression of (140 Btu/lb)
air
e. Non—isentropic 95 kJ/kg Maintenance
compression of (1 10 Btu/lb)
air
Note: Energy values are in terms of energy per unit weight
of phenol produced. Overall process losses d and e
are electrical. The fuel value of these losses would
be approximately three times the values listed.
39
-------
Figure 21.
Cunene’ energy consumption diagram
[ 1973 USA production: 1.21 i 10 kg (2.67 x iO ib))
[ 1973 process energy consumption (primarily natural ga I):
270 74W (8.1 x 10’ Btu)]
[ 1973 total energy consumption (feedetock plus process):
1270 14W (38 x 10 Btu)]
100% propylene conversion
92% selectivity to cwnene
1 % benzerie conversion
97% selectivity to cumerie
“ Natural gas is used to heat Dowtherma.
Energy Input
Reclaimed energy
Benzene
recycle
2100 kJ/kg
Heat rejection
Bensene
propylene, and
propane
Heating
t
115 kJ,’kg
r
(900 Btu/lb)
Dowtherma
3370 kS/kg
Propane
recycle 4
6
0
‘a
0
Reactor (exothermic
Hreac 815 kS/kg
(350 Btu/lb)
.0
In
I
Reaction
Cooling 1
(1q50 Btu/lb)
Dowtherm
(50 Stu/ib)
Radiation,
convection
6170 kS/kg
I
Distillation
Propane recycle
Benzene recycle_
(2650 Btu/lb)
320—Q10°K
(120—280°F)
Diiaopropy lbenzene
Cumene
product
40
-------
Figure 22 Cumene energy intensiie equipment d agraTn — distillation
[ Rejected heat: Overhead distillation column streams —
5350 kJ/kg (2300 Btu/lb) at 320_L410°K (120—280°F)]
Propane
Benzene
Cumene
column
column
column
Benzene
recycle
2,fl50 kJ/kg
(1,050 Btu/lb)
Diisopropylbenzene
as fuel or for
‘urther processing
41
-------
Table 7. CUMENE ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses approaches
1. ReJected heat
a. Radiation, 115 kJ/kg Insulation
convection (50 Btu/lb) Maintenance
b. Overhead 6170 kJ/kg Design modification
streams from (2650 Btu/lb) (waste heat recovery)
distillation
columns
2. Overall process
a. Low benzene 3500 kJ/kg Research & development
conversion (1500 Btu/lb)
b. High reflux 700 kJ/kg Design modification
ratio In (300 Etu/ib) (more plates)
distillation
columns
Z 12
-------
Fljure 23.
Sodium carbonate energy consumption cUa ram
[ 1973 USA production: 6.80 x 10 kj (15.0 x io ib)]
[ 1973 energy consumption (primarily steam, coke): 2,000 4W
(60 x l0 Btu)]
$ Air
e
Coke
Limestone
1?
NH 3 and 1120
from calciner
NH 11 C1 solution Steam
Co 2
gPlus $ I’
Prl’ ar1lj 12 to
amm ia absorber
mmonia stills
PuriNed
brine
Mostly
N 2 from
e carbonation
towers
Ammonia absorber
(exothermic)
Carbcnation towers (exothermic)
ANreac = 17110 kJ/kg
(750 Btu/lb)
sol’n + co 2
NH and 1i 2 0 to
ammonia stills
- Filter
Tu dual Na 2 C0 product
ash (li lit ash)
plant
I 1 U StU/ID)
535°K (500°F)
iic kJJk -
700 kJ/kg
(300 Btu/lb)
380°K (220°F)
1620 kJ/kg
(700 Btu/lb
320°K (120°F)
230 kJ/k
(100 Btu/1b1
L 180°K (H00° 1)
930 I J /k.’
( 1100 Btu/1
1 175°K (110001. )
Energy input
2520 kJ/kg
(1090 Btu/lb)
Coke
Heat rejection
• Lime kiln (endothermic)
AHreac = 1,690 kJ/kg
1 (7 0
I
1 23OkJ/kg
CaO
(100 Btu/lbT
Radiation, convection
Stack gases
(primarily N 2
arid C0 2 ) 350 kJ/kg
1970 kJ/kg
(1450 Btu/lb)
SI cam
atmosphere
hCaC1 2
solution
- ess Ion
T50Btu/ lb)
1 180°K (1100°F)
25 kJ/kg
N 2
plus
Co 2
I
NH
n 1 us
CO 2
‘JH .C1, NH OH
solution
(10 Btu/Jb)
Radiation, conv€ rtLon
1300 kJ/kr
(560 BLu/ibT
Condensate 38o°K (220°F)
N 2 to
V atmosphere
$ NaHCOi + NH C1 solution
17110 kJ/kg
I ( (5U tU/LU)
320°K (l20° ’)
$ Crude NaHCO3
Calciner
211110 LJJkr’
(I t)5i1 -ii/ lb
i,Ci 2 It
carbonatiun towers
I
115 kJ/k
J (50 Btu/Lh)
— fthd ill on, conv& :I nil
43
-------
Figure 2 .
Limestone
plus coke
mixture
Sodium carbonate energy intensive equipment
diagram - lime kiln
[ Rejected heat: Radiation convection —
230 kJ/kg (100 Btu/lb)
Stack gases - Z18 5 kJ/kg (210 Btu/lb) at
535°K (500°F)
Hot lime — 115 kJ/kg (50 Btu/lb) at J 4 8O°l(
(L100°F))
Co 2 to
compressors
Recuperat ive
heater
CaO to slaker
- 4 — Air
Lime kiln
-------
Figure 25.
sodium carbonate energy intensive equipment
diagram - compressors
[ Rejected heat: Radiation, convection —
25 kJ/kg (10 Btu/lb)
Condensate (vapor) — 1300 kJ/kg (560 Btu/lb)
at 380°K (220°F)
Hot compressed CO 2 and N 2 — 700 kJ/kg
(300 Btu/lb) at 380°K (220°F)]
CO 2 and
N 2 f’rom
the lime kiln
Cw
Ste am
Cw
Condensate Condensate
To
carbonator
145
-------
Figure 26 shows the calcining of sodium bicarbonate to
sodium carbonate. Steam is the heat source.
Table 8 shows the causes of energy losses in the lime
kiln operation, the compression operation, and the cal—
cining operation. It also shows the approximate mag-
nitude of losses and possible energy conservation
approaches.
I. Carbon Black by the Furnace Process
Figure 27 shows the major steps in the carbon black man-
ufacturing process. The furnace process uses a heavy
aromatic oil as feedstock. A variety of blacks with
different properties can be obtained by altering
conditions in the reactor. The major energy consumption
steps are the reaction operation and the drying of the
carbon black. These operations account for over 80
percent of the total energy consumption In the process.
Figure 28 shows the reactor plus heat recovery equip-
ment. Natural gas is the source of energy to heat the
aromatic oil to the reaction temperature.
Figure 29 shows the drying operation. Reactor effluent
gases are used to heat the wet carbon black and remove
moisture from it.
Table 9 shows the causes of energy losses in the reaction
operation, the drying operation, and the overall process.
It also shows the approximate magnitude of the losses
and possible energy conservation approaches.
J. Q ygen/Nitrogen by Air Distillation
Figure 30 shows the major steps In the oxygen/nitrogen
manufacturing process. The compression of air accounts
for almost 100 percent of the energy consumption In this
process. However, the amount of compression required is
dependent on the heat exchange between feed and product
streams, and on the design of the distillation column.
Figure 31 shows the compression of air before it .S
cooled by product streams. Electricity is used to drive
the compressor.
Figure 32 shows the distillation column used in the
oxygen/nitrogen process to separate the components in
46
-------
Igure 26.
odium r arbonaf,e energy i.nt nsive equipment
diagram — calciner
[ Rejected heat: Radiation, convec .tion —
115 kJ/kg (50 Btu/lb)
Hot product — 230 kJ/kg (100 Stu/ib) at
( 80°X) )400°F)]
CO 3 + NH 3 + H 2 0
Rotary dryer
a)
4 )
c j
a)
0
U
Crude
NaHCO ,
Finned tubes
Steam
Na 2 CO 3
147
-------
Table 8. SODIUM CARBONATE ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses approaches
1. ReJected heat
a. Radiation, 370 kJ/kg Insulation
convection (160 Btu/lb) Maintenance
b. Stack gases 350 kJ/kg Design modification
(150 Btu/lb) (waste heat recovery)
c. Uncondensed 1300 kJ/kg Process integration
steam from (560 Btu/lb)
compressor
d. Process streams 53110 kJ/kg Design modification
(2300 Btu/lb) (waste heat recovery)
2. Overall process
a. Non—isothermal 115 kJ/kg
compression (50 Btu/lb)
b. Non—Isentropic 115 kJ/kg
compression (50 Btu/lb)
c. Gas for compres— 1150 kJ/kg Process modification
slon is only (500 Btu/lb) (use higher oxygen
0% CC 2 content combustion air)
d. Heat required 115 kJ/kg Design modification
to dry limestone (50 Btu/lb) (enclosed storage)
and coke
e. Heat lost in 230 kJ/kg
heating impuri— (100 Btu/lb)
ties in limestone
f. High water con— 3145 kJ/kg Design modification
tent In (150 Btu/lb)
calciner feed
48
-------
Figure 27.
Carbon black energy consumption diagram
[ 1973 USA production: 1.58 x l0 ’kg (3.50 x 10’ ib)]
[ 1973 process energy consumption (primarily natural gas):
800 MW (211 x lO 12 Btu)]
[ 1973 total energy consumption (feed stock oil minus generated
reactor gas plus process): 2500 MW (75 x 1012 Btu)]
Reclaimed energy
Magnetic separat
and screening
Fuel value is
32,500 kJ/kg or
14,000 Btu/lb.
Fuel value is
42,000 kJ/kg or
18,000 Btu/lb.
Ener v inout
$
Heat rejection
Aromatic*
oil
(9450
gas
115 kJ/kg
Hot,
carbon
black
I
* Aromatic oil fuel
value 18 approximately
714,500 kJ/kg
(32,000 Btu/lb)
Carbon black
product.
Reactor gas as
fuel.
49
-------
Figure 28.
Carbon black energy—intensive equipment diagram —
reactor and waste heat recovery equipment.
[ Rejected heat: Radiatiofl, convection —
700 kJ/kg (300 Btu/lb)]
Warm reactor
gas and
carbon black
Additive for
property c(
Blower
Feed
aromatic oil
-------
Figure 9.
[ Rejected heat:
Reactor gases
Carbon black energy—intensive equipment
diagram - dryer.
Radiation, convection — 115 kJ/kg
(50 Btu/lb)
Hot effluent gases — 18,500 kJ/kg
(8000 Btu/lb) at 395°K (250°F)
Hot carbon black — 115 kJ/kg
(50 Btu/lb) at 1 420°K (300°F)]
Rotary dryer
Wet carbon
black
Reactor gases
Carbon black
to magnetic
separator
51
-------
Table 9. CARBON BLACK ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses approaches
1. ReJected heat
a. Radiation and 810 kJ/kg Insulation
convection losses (350 Btu/lb)
b. Sensible heat in 2300 kJ/kg Design modification
generated reactor (1000 Btu/lb) (waste heat recovery
gases leaving when using reactor
the process gas as fuel)
c. Latent heat in 16,200 kJ/kg Design modification
generated reactor (7000 Btu/lb) (waste heat recovery
gases leaving when using reactor
the process gas as fuel)
d. Sensible heat 115 kJ/kg
from carbon black (50 Btu/lb)
product
2. Overall process
a. Energy to heat 7000 kJ/kg Process modification
inerts which are (3000 Btu/lb) (use higher oxygen
lost in quench content gas to burn
water natural gas)
b. Fuel value of 142,000 kJ/kg Waste utilization
reactor gas (18,000 Btu/lb)
52
-------
Figure 30.
Oxygen/nitrogen energy consumption diagram*
[ 1973 USA production (oxygen): 1 4.5 x i0 9 kg (31.9 x iO lb)]
[ 1973 energy consumption (electricity): 530 MW (16 x 1012 Btu)]
Reclaimed energy
Heat rejection
* Energy is expressed in terms of’ energy per unit weight of’
oxygen produced.
Energy input
Air
(250°F)
Oxygen Nitrogen
53
-------
Figure 31. Oxygen/nitrogen energy-intensive equipment
diagram — compressors
[ Rejected heat: Hot compressed air —
1150 kJ/kg (500 Btu/lb)
at 395°K (250°F)]
cw
Air
585 kN/m 2
(85 psla)
Note: Energy Is expressed in terms of’ energy per unit
weight of oxygen produced.
514
-------
Figure 32.
Oxygen/nitrogen energy—intensive equipment diagram —
distillation column.
Low pressure
[ 100 N/rn 2 (l l.5 psia))
distillation column
Liquid oxygen
Nitrogen rich liquid
High pressure
:550 N/rn 2 (80 psia))
distillation column
Oxygen rich liquid
Secondary air
previously cooled by
expansion through
turbo—expander
Main air feed
previously cooled by
exiting nitrogen and
oxygen streams
Note: Energy is expressed in terms of energy per unit weight
of oxygen produced.
Nitrogen gas
Liquid
sub—cooler
Liquid
Nitrogen
gas
55
-------
air. The design of this column along with the efficiency
of heat exchange between feed and product streams plays
a major role in determining the amount of air compression
required.
Table 10 shows the causes of energy losses in the compres-
sion operation, the distillation operation, the heat
exchange operation, and in the turbo—expander operation.
It also shows the approximate magnitude of the losses
and possible energy conservation approaches.
K. Qperational and Design Problems of Energy Intensive
Eaj4pment
The analyses of the 10 chemical processes were made under
the assumption that the plants were well designed and
operated. In actual practice several operational and
design problems commonly occur. Table 11 shows problems
associated with three large energy consumers — furnaces,
compressors, and distillation columns.
L. Qperational and Design Problems of Heat Transfer
Eguipment
In addition to energy intensive operations a common
energy wastage problem area is heat transfer equipment.
Table 12 lists equipment where problems commonly occur
along with some possible measures to overcome the problems.
M. Chemical Industry Energy Conservation Study Summary
Table 13 shows where the energy conservation approaches
suggested in this report can be applied. All processes
analyzed appear to have operations where energy losses
could be decreased. However, a more detailed analysis
of the processes and the approaches would be necessary
to determine the economic feasibility of implementing
the approaches.
56
-------
Table 10. OXYGEN/NITROGEN ENERGY CONSERVATION APPROACHES
Approximate
Causes of magnitude of Energy conservation
energy losses losses pproaches
1. Re3ected heat in 1060 kJ/kg Design modification
hot air from (460 Btu/lb) (waste heat recovery)
compressors
2. Overall process
a. Non-ideal flow 1 45 kJ/kg
volume of liquid (20 Btu/lb)
down column
b. Temperature 145 kJ/kg
differences in (20 Btu/lb)
reboiler—condens er
and liquid
sub—coolers
c. Temperature 350 kJ/kg
differences be— (150 Btu/lb)
tween fluids in
main heat ex-
change equipment
d. Non—isothermal & 350 kJ/kg Maintenance
non—isentropic (150 Btu/lb)
compression
losses
Note: Energy Is expressed in terms of energy per unit weight
of oxygen produced. All overall process losses are
electrical. The fuel value of these losses would be
approximately three times as large as the values listed.
57
-------
Table 11. OPERATIONAL AND DESIGN PROBLEMS IN ENERGY INTENSIVE
EQUIPMENT
Common operational and
design problems in high Measures to overcome
energy consumption equipment problems
1. Furnace combustion
a. Improper air/fuel ratio Provide instrumentation to
measure oxygen content in
flue gas
(automatic controls)
b. Leaks in furnace stacks Maintenance
2. Compression
a. Leaky compressor bypass Maintenance
valves
b. Overdesign of motor or Do not over design
turbine
c. Improper suction pressure Do not over design
d. Increasing clearance to Reduce compressor speed to
lower output lower output
e. Use of less expensive and Realize the value of high
less efficient turbines efficiency when selecting
and compressors equipment
3. Distillation
a. Erratic control of Automatic control
columns
b. Excessive reflux result— Produce minimum quality
i.ng in excessive component material
separation
c. Improper feed tray Any change in process
operation could result In
a change in the optimum
feed tray
d. Non—optimum distillation Consider energy saving
scheme possibilities such as
multi—feeds, side product
draw, or cascade distilla-
tion schemes
58
-------
Table 12. OPERATIONAL PROBLEMS WITH HEAT TRANSFER EQUIPMENT
Common problems with Measures to overcome
heat transfer equipment heat transfer problems
1. Steam traps
a. Faulty operation Monitoring required
b. Leaking traps Maintenance
c. Mis—design Need proper application and
sizing
2. Steam tracing
a. Leaks Maintenance
b. Unnecessarily high Substitute another fluid such
steam temperature as Dow SR—i® for steam
3. Heat exchangers
a. Fouling Maintenance
b. Higher than necessary Design for low temperature
temperature separa— differences by Increasing
tion between fluid heat transfer surface area
streams
c. Complete reliance Air cooling requires less
on water cooling power than water cooling
59
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Table 13. CHEMICAL INDUSTRY ENERGY CONSERVATION STUDY SUMMARY
Process
Energy intensive
operations
Energy conservation approaches
1
ON
2
R&D
3
DM
14
I
5
N
6
P1
—r
PM
r
MM
T
WU
Chlorine
Electrolysis
I
I
/
I
Caustic soda
Evaporation
Overall process
I
I
I
7
Ethylene
Furnace combustion
/
/
I
rompression
—
i
—
—
—
[ efrigeration
verall process
I
I
I
Ethylbenzene
Distillation
/
verall process
I
I
Styrene
Furnace combustion
I
I
I
isti1lation
I
‘erall process
I
I
—
—
—
Phenol/acetone
Compression
I
I
—
istillation
I
—
—
urnace combustion
—
t
—r
—
—
verall process
I
I
Cumene
Distillation
I
verall process
I
Sodium
carbonate
Kiln calcining
ompression
alcining (drying)
verall process
SI
/
,‘
I
I
Carbon black
Furnace combustion
I
I
‘rying
‘verah process
—
T
—
—
7
Oxygen/nitrogen
Compression
I
._
)TSti llat ion
OM — Operation modification
R&D - Research and development
DM - Design modification
I — Insulation
M - Maintenance
P1 — Process integration
PM — Process modification
MM - Market modification
WU — Waste utilization
60
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SECTION V
BIBLIOGRAPHY
Anderson, E. V. Growth Slows in Top 50 Chemicals’ Output.
Chemical and Engineering News. 52:10—13, May 6, 1971!.
Deutsch, Z. G., C. C. Brumbaug, and F. H. Rockwell. Alkali
and Chlorine Industry. In: Kirk—Othmer Encyclopedia of
Chemical Technology. 2nd Ed., Standen A. (ed.). New York,
John Wiley & Sons, Inc., 1963 i:668—75 .
Frank, S. M. Modern Ethylene Technology and Plant Design.
In: Ethylene and Its Industrial DerivatIves, Miller, S. A.
(ed.). London, Ernest Benn Limited, 1969. p. l03 l1i9.
Klenholz, P. J. Outlook for Chlorine—Caustic Production.
Chemical Engineering Progress. 70:59—63, March 1971!.
Latimer, H. E. Distillation of Air. Chemical Engineering
Progress. 63:35—59, February 1967.
Ries, H. C. Carbon Black. Stanford Research Institute,
Menlo Park, California. Process Economics Program, Report
No. 90. May 19713. 3139 p
Stokes, C. A. Carbon Black. In: Xirk—Othmer Encyclopedia
of’ Chemical Technology 2nd edition, Standen, A. (ed.). New
York, John Wiley & Sons, Inc., 1971. Supplementary Volume:
91—108.
Takaoka, S. Ethylene. Stanford Research Institute, Menlo
Park, California. Process Economics Program, Report No.
29. August 1967. 355 p.
Yen, Y. C. Chlorine, Supplement A. Stan ’ord Research
Institute, Menlo Park, California. Process Economics
Program, Report No. 6lA. May 1971!. 256 p.
Yen, Y. C. Phenol, Supplement A. Stanford Research
Institute, Menlo Park, California. Process Economics
Program, Report No. 22A. September 1972. 232 p.
Yen, Y. C. Styrene. Stanford Research Institute, Menlo
Park, California. Process Economics Program, Report No.
33. October 1967. 265 p.
Yen, Y. C. and T. H. Vanden Bosch. Styrene, Supplement A.
Stanford Research Institute, Process Economics Program,
Report No. 33A. March 1973. 223 p.
6 ].
-------
SECTION VI
GLOSSARY OF ABBREVIATIONS
Etu British thermal unit
cond condensate
CW cooling water
kg kilogram
kJ kiloJoule
kN klloNewton
kw kilowatt
lb pound
m meter
psia pounds per square inch absolute
MW megawatt
stm steam
yr year
62
-------
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 need review.
Process integration — This term relates to the best use
of steam by using the same steam in more than one
process such as to produce electricity and then heat.
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.
63
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