EPA-600/2-76-032d
December 1976
Environmental Protection Technology Series
SOURCE ASSESSMENT:
PHTHALIC ANHYDRIDE
(AIR EMISSIONS)
Industrial Environmenta! Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
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.
EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental
Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the
views and policy of the Agency, nor does mention of trade
names or commercial products constitute endorsement or
recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-76-032d
December 1976
SOURCE ASSESSMENT:
PHTHALIC ANHYDRIDE
(AIR EMISSIONS)
by
R. W. Serth and T. W. Hughes
Monsanto Research Corporation
1515 Nicholas Road
Dayton, Ohio 45407
Contract No. 68-02-1874
ROAP No. 21AXM-071
Program Element No. 1AB015
EPA Project Officer: Dale A. Denny
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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PREFACE
The Industrial Environmental Research Laboratory (IERL) of
EPA has the responsibility for insuring that pollution con-
trol technology is available for stationary sources to meet
the requirements of the Clean Air Act, the Water Act and
the Solid Waste legislation. If control technology is un-
available, inadequate, uneconomical or socially unacceptable,
then financial support is provided for the development of
the needed control techniques for industrial and extractive
process industries. Approaches considered include: process
modifications, feedstock modifications, add-on control de-
vices, and complete process substitution. The scale of the
control technology programs ranges from bench to full scale
demonstration plants.
The Chemical Processes Branch of the Industrial Processes
Division of IERL has the responsibility for investing tax
dollars in programs to develop control technology for a
large number (>500) of operations in the chemical industries.
As in any technical program, the first question to answer
is, "Where are the unsolved problems?" This is a determina-
tion which should not be made on superficial information;
consequently, each of the industries is being evaluated in
detail to determine if there is, in EPA's judgment, suffi-
cient environmental risk associated with the process to
invest in the development of control technology. This report
contains the data necessary to make that decision for the
air emissions from phthalic anhydride manufacture.
iii
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Monsanto Research Corporation has contracted with EPA to
investigate the environmental impact of various industries
which represent sources of pollution in accordance with EPA's
responsibility as outlined above. Dr. Robert C. Binning
serves as Program Manager in this overall program entitled,
"Source Assessment," which includes the investigation of
sources in each of four categories: combustion, organic
materials, inorganic materials and open sources. In this
study of phthalic anhydride manufacture, Mr. Kenneth L. Baker
and Mr. Edward J. Wooldridge served as EPA Project Leaders.
IV
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CONTENTS
Section Page
I Introduction 1
II Summary 3
III Source Description 14
A. Process Description I4
1. o-Xylene Based Process 16
2. Naphthalene Based Process 33
B. Materials Flow 53
1. o-Xylene Based Process 53
2. Naphthalene Based Process 59
C. Geographical Distribution 59
IV Emissions 66
A. Selected Pollutants 66
1. o-Xylene Based Process 66
2. Naphthalene Based Process 70
B. Location and Description 71
1. Scrubber Vent 71
2. Incinerator Stack 72
3. Storage Tank Vents 78
4. Flaker and Bagger Vent 82
5. Transport Loading Facility Vent 83
6. Catalyst Storage Hopper Vents 84
7. Fugitive Emissions 85
8. Dual Thermal Incineration 87
C. Environmental Effects 89
1. Definition of a Representative 89
Source
2. Emission Factors 90
3. Source Severity 92
4. Industry Contribution to Total 100
Atmospheric Emissions
5. Affected Population 100
6. Growth Factor 105
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CONTENTS (continued)
Section Page
V Control Technology 106
A. State of the Art 106
B. Process Modifications 109
1. The Rhone-Progil "Chauney '71" 110
Process
2. Maleic Anhydride Recovery HO
3. Direct Production of Phthalates H3
4. Alternate Feedstocks
VI Growth and Nature of the Industry
A. Present Technology
B. Emerging Technology
C. Marketing Strengths and Weaknesses
VII Appendixes 125
A. Storage Tank Calculations 126
B. Rationale for Not Considering All 133
Species Listed in Table 21
VIII Glossary of Terms I37
IX Conversion Factors and Metric Prefixes
X References
VI
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LIST OF FIGURES
Figure
1 Breakdown of Phthalic Anhydride Pro-
duction in the Continental United States
2 BASF Process for Manufacture of Phthalic 17
Anhydride from o-Xylene
3 Organic Liquid Heat-Transfer System 27
4 Reaction Mechanism for the Catalytic 30
Oxidation of o-Xylene
5 Badger-Sherwin-Williams Process for Manu- 35
facture of Phthalic Anhydride from
Naphthalene
6 Schematic Diagram of Scrubber for Phthalic 44
Anhydride Plant
7 Schematic Diagram of Thermal Incinerator 47
for Phthalic Anhydride Plant
8 Phthalic Anhydride Plant Locations 65
9 Maleic Anhydride Recovery Process 112
10 Flow Diagram for Direct Production of 114
Phthalates
11 Uses of Phthalic Anhydride 118
Vll
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LIST OF TABLES
Table
1 Summary of Emission Data for a Represen-
tative o-xylene Based Phthalic Anhydride
Plant
2 Summary of Emission Data for a Represen- 7
tative Naphthalene Based Phthalic Anhydride
Plant
3 Source Severity Factors and Industry Contri- 8
bution to Total Emissions for o-xylene Based
Phthalic Anhydride Production (Controlled
Emissions)
4 Source Severity Factors and Industry Contri- 10
bution to Total Emissions for Naphthalene
Based Phthalic Anhydride Production (Controlled
Emissions)
5 Affected Population Summary 13
6 Stream Code for BASF Process Illustrated in 18
Figure 2
7 Summary of Tankage Requirements for a 25
5.9 x 104 Metric Tons/Yr o-xylene Based
Phthalic Anhydride Plant
8 Heats of Reaction for the Oxidation of 32
o-xylene
9 Reactor System Heat Balance for Production 33
of Phthalic Anhydride from o-xylene
10 Stream Code for Badger-Sherwin-Williams 36
Process Illustrated in Figure 5
11 Typical Scrubber Material Balance for a 45
Naphthalene Based Phthalic Anhydride Plant
12 Heating Values of Organic Compounds in 46
Scrubber Purge Stream
13 Incinerator Material Balance for a Naph- 48
thalene Based Phthalic Anhydride Plant
14 Summary of Tankage Requirements for a 49
5.9 x 10U Metric Tons/Yr Naphthalene Based
Phthalic Anhydride Plant
15 Typical Properties of Davison Grade 902 51
Catalyst
16 Heats of Reaction for the Oxidation of 52
Naphthalene
viii
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LIST OF TABLES (continued)
Table Page
17 Reactor System Heat Balance for Pro- 53
duction of Phthalic Anhydride from
Naphthalene
18 Material Balance for a 5.9 x 104 Metric 54
Tons/Yr o-xylene Based Phthalic Anhydride
Plant
19 Material Balance for a 5.9 x 104 Metric 60
Tons/Yr Naphthalene Based Phthalic Anhy-
dride Plant
20 Phthalic Anhydride Plants 64
21 Possible Reaction Products from the 67
Oxidation of Xylene
22 Concentrations of Contaminatns in Switch- 73
Condenser Off-Gas
23 Typical Scrubber Vent Gas Composition for 74
o-xylene Based Process
24 Typical Scrubber Vent Gas Composition for 75
Naphthalene Based Process
25 Typical Incinerator Flue Gas Composition 76
for o-xylene Based Process with Scrubber-
Incinerator Combination
26 Typical Incinerator Flue Gas Composition 77
for Naphthalene Based Process with Scrubber-
Incinerator Combination
27 Typical Incinerator Flue Gas Composition 79
for o-xylene Based Process Using Direct
Thermal Incineration
28 Typical Incinerator Flue Gas Composition 80
for Naphthalene Based Process Using Direct
Thermal Incineration
29 Storage Tank Working and Breathing Losses 81
for a 5.9 x 10^ Metric Tons/Yr Phthalic
Anhydride Plant
30 Frequently Used Heat-Transfer Fluids 86
31 Fugitive Emissions from Phthalic Anhydride 87
Plants
32 Typical Flue Gas Composition for Dual 88
Incinerator
IX
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LIST OF TABLES (continued)
Table
33 Emission Factors for o-xylene Based
Phthalic Anhydride Plants
34 Emission Factors for Naphthalene Based 93
Phthalic Anhydride Plants
35 Source Severity Equations 97
36 Emission Heights for Representative Source ^7
37 Source Severity Factors for a Representative 98
o-xylene Based Phthalic Anhydride Plant
38 Source Severity Factors for a Representative 99
Naphthalene Based Phthalic Anhydride Plant
39 Nationwide Emissions of Criteria Pollutants 1°1
from Phthalic Anhydride Industry (Controlled
Emissions)
40 Emissions of Criteria Pollutants from 102
Phthalic Anhydride Industry by State
(Controlled Emissions)
41 Affected Population 104
A-l Storage Tank Input Data for o-xylene 129
Based Plant
A-2 Storage Tank Input Data for Naphthalene 130
Based Plant
A-3 Storage Tank Calculation Summary for
o-xylene Based Plant
A-4 Storage Tank Calculation Summary for 132
Naphthalene Based Plant
B-l Compounds Not Included in Study 134
x
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LIST OF SYMBOLS
Symbol Definition
A Area
C Diameter factor
Cap Production capacity
C. Production capacity of plant i
D Tank diameter
Dp Mean population density
D County population density for plant i
e 2.72
E Emission factor, g/kg
E1 Emission factor, Ib/ton
F Hazard factor
F Equivalent gasoline working loss
F Paint factor
P
H Effective emission height
H' Tank outage
K Turnover factor
L Total petrochemical loss, barrels
L, Total petrochemical loss, pounds
L Total equivalent gasoline loss
L Equivalent gasoline breathing loss
M Molecular weight
N Number of turnovers per year
P Vapor pressure
Q Mass emission rate
S Source severity
t, t0 Averaging times
u Average wind speed
V Tank capacity
W Liquid density
XI
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LIST OF SYMBOLS (continued)
Symbol
x
AT
xmax
xmax
x"(x)
Definition
Distance downwind from source
Average daily ambient temperature
change
Vertical dispersion coefficient
Maximum mean ground level concen-
tration (short term average)
Maximum mean ground level concen-
tration (long-term average)
Annual mean ground level concen-
tration
XII
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SECTION I
INTRODUCTION
Phthalic anhydride (PAN) is an important industrial chemical
which is principally used in the manufacture of plasticizers,
polyester resins, and alkyd resins. Present production capa-
city in the United States is nearly 5 x 105 metric tons/yr.
Phthalic anhydride is manufactured by the catalytic vapor-
phase oxidation of either ortho-xylene. (designated herein
as o-xylene) or naphthalene. The o-xylene based plants
employ fixed-bed reactors, while the naphthalene based plants
use the fluid-bed process. This document presents a detailed
study of the phthalic anhydride industry from the standpoint
of atmospheric emissions and their potential environmental
impact.
The major results of this study, summarized in Section II,
include emission factors for each species emitted to the
atmosphere from each emission point within a representative
phthalic anhydride plant. Also tabulated are several factors
designed to measure the environmental hazard potential of
phthalic anhydride operations. These include source severity
factors, the industry contribution to total atmospheric
emissions of criteria pollutants, and the population affected
by a representative plant.
1 metric ton = 106 grams = 2205 pounds =1.1 short tons
(short tons are designated "tons" in this document); other
conversion factors and metric system prefixes are presented
in Section IX.
1
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Detailed descriptions of phthalic anhydride manufacturing
processes are given in Section III. Discussion is limited
to the BASF (Badische Anilin und Soda-Fabrik) process for the
oxidation of o-xylene, and the Badger-Sherwin-Williams process
for the oxidation of naphthalene, since these two processes
dominate the industry. Included are descriptions of each
major processing step, flow diagrams, process chemistry, and
material and energy balances.
Atmospheric emissions from phthalic anhydride plants are
discussed in Section IV. The species known to be emitted
and/or produced by the processes are detailed, and each
emission point within the plant is described. Compositions
and flow rates of streams emitted to the atmosphere are
provided. A representative phthalic anhydride plant is
defined, and emission factors for such a plant employing
the best available control technology are given. These
emission factors are then used to generate source severity
factors, the industry contribution to total emissions of
criteria pollutants, and the affected population.
Present and future aspects of pollution control technology
in the phthalic anhydride industry are considered in Section
V. Several process modifications are described which are
likely to have an impact upon the industry in the near
future.
Economic and production trends in the phthalic anhydride
industry are addressed in Section VI. The trends in each of
the industries that are major consumers of phthalic anhydride
are also analyzed. Finally, estimates of phthalic anhydride
production through the remainder of the present decade are
discussed.
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SECTION II
SUMMARY
Phthalic anhydride is manufactured by the catalytic vapor-
phase oxidation of either o-xylene or naphthalene. There
are currently 10 phthalic anhydride plants operating in the
continental United States, plus one in Puerto Rico, having
a total capacity of 4.95 x 105 metric tons/yr (5.44 x 105
tons/yr). Of the plants in the continental U.S., seven uti-
lize o-xylene as a feedstock and the remaining three use
naphthalene. All of the o-xylene based plants employ fixed-
bed reactors, while the three naphthalene based plants use
fluid-bed processes. The population densities of the
counties in which the plants are located range from 30 to
4,905 persons per square kilometer.
Sources of atmospheric emissions within phthalic anhydride
plants include the scrubber vent(s) and/or incinerator
stack(s), storage tanks, the flaker and bagger vents, the
transport loading facility vent, and fugitive emissions.
The catalyst storage hopper vents are additional sources of
emissions in naphthalene based plants.
The main process waste gas from the phthalic anhydride switch
condensers is controlled either by a scrubber-incinerator
combination or by direct incineration. The latter method
has the advantage of providing control of carbon monoxide
as well as the organic species in the waste gas. Either
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the scrubber or the incinerator, or both, may also be used
to control the waste streams from the product purification
section of the plant. Alternatively, a separate scrubber or
incinerator may be used to control these streams.
Storage tanks contain o-xylene or naphthalene, crude phthalic
anhydride, and refined phthalic anhydride. Available control
devices include conservation vents on o-xylene and naphthalene
tanks, and condensers or sublimation traps on phthalic
anhydride tanks. The latter tanks may also be vented to
the incinerator for control.
In the flaking and bagging operations, liquid phthalic anhydride
is solidified in the form of flakes and packaged in bags for
shipment. The vents from these operations are ducted to a
cyclone and/or a baghouse for control. Phthalic anhydride
is also shipped in the liquid form. At the transport loading
facility, liquid phthalic anhydride is pumped into tank
trucks or railway tank cars for shipment.
Fugitive emissions include heat-transfer oil (e.g., Dow-
therm A®, a diphenyl-diphenyl oxide eutectic mixture) which
escapes from the heat-transfer circuits during process
upsets. In the case of naphthalene based plants, vanadium
oxide catalyst dust is also emitted during catalyst transfer
operations in which the fluid-bed catalyst is pneumatically
conveyed between the storage hoppers and the reactor. Vents
on the catalyst storage hoppers are additional sources of
emissions during these operations. The vents are equipped
with cyclone separators for emissions control.
Emissions data for o-xylene based plants are summarized in
Table 1. The data correspond to a plant with a dual incin-
eration control system, which represents the best available
control technology. The main process incinerator controls
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Table 1. SUMMARY OF EMISSION DATA FOR A REPRESENTATIVE
o-XYLENE BASED PHTHALIC ANHYDRIDE PLANT
Species emitted
Particulate
Main process incinerator
Secondary incinerator
Flaker and bagger
Sulfur oxides
Main process incinerator
Nitrogen oxides
Main process incinerator
Secondary incinerator
Carbon monoxide
Main process incinerator
Secondary incinerator
Maleic anhydride
Main process incinerator
Secondary incinerator
Phthalic anhydride
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
Benzoic acid
Main process incinerator
Secondary incinerator
Diphenyl oxide6
Fugitive emissions
o-Xylene
Storage tanks
Formaldehyde
Main process incinerator
Secondary incinerator
Total hydrocarbonsS
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
Emission factor, g/kg
Uncontrolled
b
~b
0.10
5.0 ± 25%
_c
~c
125.0 ± 20%
52.0 ± 20%
3.75 ± 83%
15.6 ± 20%
10.6 ± 53%
0.29 ± 10%
0.10
0.45 ± 10%
_b
3.12 ± 20%
1.25 ± 50%
0.016
0.20 ± 10%
2a\
72.8 ± 30%
18.8 ± 60%
0.49 ± 10%
0.1
0.45 ± 10%
0.116
Controlled
0.25 ± 50%
0.125 ± 50%
0.001
5.0 ± 25%
1.25 ± 50%
0.125 ± 25%
0.125 ± 50%
1.25 ± 50%
1.82 ± 25%
0.038 ± 90%
0.545 ± 25%
0.106 ± 60%
0.003 + 20%
0.001
0.005 ± 20%
_d
0.109 ± 25%
0.0125 ± 55%
_d
0.002 ± 20%
0.074f
2.6 ± 30%
0.16 ± 60%
0.005 ± 20%
0.001
0.005 + 20%
_d
Control
efficiency.
99
0
99.9
96.5
99
96.5
99
99
99
99
96.5
99
99
96.5
96.5
99
99
99
99
Emission factor is defined as weight of emission per unit
weight of phthalic anhydride product.
Emission data not available.
No emissions generated in uncontrolled process.
Fugitive emissions are not controlled.
Heat-transfer fluid, assumed to be Dowtherm A.
Total aldehydes reported as formaldehyde.
^Includes all non-methane organic species.
-------
the main process waste gas and the secondary incinerator
handles the waste streams from the product purification sec-
tion of the plant. Error bounds on the emission factors
were estimated wherever possible.
Emissions data for a naphthalene based plant with a dual
incineration control system are presented in Table 2. In
arriving at these values it was assumed that this control
system, which is currently in operation on an o-xylene based
plant, could be applied to a naphthalene based plant without
altering the control efficiency of the system. The accuracy
of the emission factors in Table 2 is believed to be gener-
ally poorer than that of the values listed in Table 1, as
reflected in the estimated error bounds.
i
In order to quantify the hazard potential of phthalic an-
hydride operations, a severity factor was defined which
represents the ratio of the mean maximum ground level ex-
posure to the hazard level of exposure for a given pollutant
from a given source. Using Gaussian plume dispersion theory
together with the controlled emission factors in Tables 1
and 2, severity factors were calculated for o-xylene and
naphthalene based plants having production capacities of 5.9
x 101* metric tons/ yr (6.5 x 10H tons/yr) . The results are
summarized in Tables 3 and 4. Also listed are the annual
mass emissidns from a single plant and from the phthalic
anhydride industry, and the percentage contribution of the
industry to the total mass emissions of criteria pollutants
(particulate, NO , SO , CO, and hydrocarbons). These values
X X
are all based on the controlled emission factors listed in
Tables 1 and 2, and, hence, represent hypothetical emissions
which would occur if all plants employed the best available
control technology.
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Table 2. SUMMARY OF EMISSION DATA FOR A REPRESENTATIVE
NAPHTHALENE BASED PHTHALIC ANHYDRIDE PLANT
Species emitted
Particulate
Main process incinerator
Secondary incinerator
Flaker and bagger
Nitrogen oxides
Main process incinerator
Secondary incinerator
Carbon monoxide
Main process incinerator
Secondary incinerator
Phthalic anhydride
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport and loading
Fugitive emissions
Maleic anhydride
Main process incinerator
Secondary incinerator
Benzoic acid
Main process incinerator
Secondary incinerator
Naphthoquinone
Main process incinerator
Secondary incinerator
Naphthalene
Storage tanks
Vanadium oxide catalyst
Catalyst storage
Fugitive emissions
Diphenyl oxide
Fugitive emissions
Formaldehyde
Main process incinerator
Secondary incinerator
Total hydrocarbons^
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
Emission factor,3 g/kg
Uncontrolled
b
~b
0.10
_ c
_ c
50.5_c
20.4
9.8
0.37
0.10
0.45b
7.0
4.9
1.56_b
0.69
6.6
0.60
0.41L
_D
0.016
*A
31.8
26.5
0.97
0.1
0.45
0.116
+ 50%
± 40%
± 70%
± 10%
+ 200%
± 80%
± 40%
± 40%
± 70%
± 10%
+ 79%
- 35%
± 70%
± 10%
± 10%
Controlled
0.25 ± 70%
0.125 ± 70%
0.001
1.25 ± 70%
0.125 t 40%
0.05 ± 70%
1.25 ± 70%
0.71 i 50%
0.10 ± 80%
0.004 ± 20%
0.001
0.005 .
d
0.24 + 200%
0.05 ± 90%
0.05 + 50%
_D
0.02 ± 50%
0.07 ± 80%
0.006 + 20%
0.01 _,
d
_d
0.074^
D
1.09 + 85%
40%
0.27 ± 80%
0.01 t 20%
0.001
0.005 + 20%
Control
efficiency,
99
99.9
96.5
99
99
99
99
96.5
99
96.5
96.5
99
99
97.5
96.5
96.5
99
99
99
99
Emission factor is defined as weight of emission per
unit weight of phthalic anhydride product.
Emission data not available.
No emissions generated in uncontrolled process.
Fugitive emissions are not controlled.
Heat-transfer fluid, assumed to be Dowtherm A.
Total aldehydes reported as formaldehyde.
"includes all non-methane organic species.
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Table 3. SOURCE SEVERITY FACTORS AND INDUSTRY CONTRIBUTION TO TOTAL EMISSIONS FOR O-XYLENE BASED
PHTHALIC ANHYDRIDE PRODUCTION (CONTROLLED EMISSIONS)
00
Species emitted
Particulate (total)
Main process incinerator
Secondary incinerator
Flaker and bagger
Sulfur oxides (total)
Main process incinerator
Nitrogen oxides (total)
Main process incinerator
Secondary incinerator
Total hydrocarbons (total)
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
Carbon monoxide (total)
Main process incinerator
Secondary incinerator
Phthalic anhydride (total)
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
Maleic anhydride (total)
Main process incinerator
Secondary incinerator
Emissions
- from all -
plants,3
metric
tons/yr
113
1,500
413
865
413
198
557
Emissions
from represent-
ative plant, "
metric tons/yr
22.2
14.8
7.4
0.06
295.0
295.0
81.2
73.8
7.4
170.3
153.4
9.4
0.30
0.06
0.30
6.8
81.2
7.4
73.8
39.0
32.2
6.3
0.18
0.06
0.30
109.6
107.4
2.2
Severity
factor,
0.0095
0.019
0.0038
0.14
0.14
0.061
0.23
0.056
0.0071
0.0088
0.044
4.0
0.000053
0.0021
0.28
0.20
0.024
0.050
0.24
5.4
0.45
Industry contribution to total emissions, c %
Nationwide
0.00063
0.0050
0.0018
0.0034
0.00042
California
0.0014
0.0492
0.0032
0.0051
0.0006
Illinois
0.0033
0.0249
0.0144
0.0161
0.0022
Louisiana
0.0039
0.1200
0.0133
0.0061
0.0010
New
Jersey
0.0148
0.0641
0.0166
0.0208
0.0028
Texas
0.0040
0.0393
0.0062
0.0077
0.0012
Emissions not calculated for individual emission points.
bA representative plant is defined to be one having a production capacity of 5.9 x lO1* metric tons/yr (6.5 x 101* tons/yr)
CIndustry contribution calculated only for criteria pollutants.
Includes all non-methane organic species.
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Table 3 (continued).
SOURCE SEVERITY FACTORS AND INDUSTRY CONTRIBUTION TO TOTAL EMISSIONS FOR O-XYLENE BASED
PHTHALIC ANHYDRIDE PRODUCTION (CONTROLLED EMISSIONS)
Species emitted
Benzoic acid (total)
Main process incinerator
Secondary incinerator
Diphenyl oxide6 (total)
Fugitive emissions
o-Xylene (total)
Storage tanks
Formaldehyde (total)
Main process incinerator
Secondary incinerator
Emissions
from all
, . a
plants,"
metric
tons/yr
36
4.8
0.6
22
Emissions
from represent-
ative plant,
metric tons/yr
7.1
6.4
0.74
0.94
0.94
0.12
0.12
4.4ff
4.4f
-9
Severity
factor,
0.0065
0.0030
18.5
0.00022
f
0.074
-9
Industry contribution to total emissions, %
Nationwide
California
Illinois
Louisiana
New
Jersey
Texas
Emissions not calculated for individual emission points.
A representative plant is defined to be one having a production capacity
of 5.9 x 10" metric tons/yr (6.5 x lO1* tons/yr)
Industry contribution calculated only for criteria pollutants.
Heat-transfer fluid, assumed to be Dowtherm A.
Total aldehydes reported as formaldehyde.
"Data not available.
-------
Table 4. SOURCE SEVERITY FACTORS AND INDUSTRY CONTRIBUTION TO TOTAL EMISSIONS FOR
NAPHTHALENE BASED PHTHALIC ANHYDRIDE PRODUCTION (CONTROLLED EMISSIONS)
Species emitted
Particulate (total)
Main process incinerator
Secondary incinerator
Flaker and bagger
Nitrogen oxides (total)
Main process incinerator
Secondary incinerator
Total hydrocarbons (total)
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
Carbon monoxide (total)
Main process incinerator
Secondary incinerator
Phthalic anhydride (total)
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Maleic anhydride (total)
Main process incinerator
Secondary incinerator
Benzoic acid (total)
Main process incinerator
Secondary incinerator
Naphthoquinone (total)
Main process incinerator
Secondary incinerator
Emissions
from
all plants, a
metric tons/yr
56
206
224
195
123
44
7.6
13
Emissions
from represent-
ative plant, "
metric tons/yr
22.2
14.8
7.4
0.06
81.2
73.8
7.4
88.1
64.4
15.9
0.59
0.06
0.30
6.8
76.8
3.0
73.8
48.4
41.9
5.9
0.24
0.06
0.30
17.2
14.2
3.0
3.0
3.0
_e
5.3
1.2
4.1
Severity
factor
0.0095
0.019
0.0038
0.14
0.061
0.10
0.095
0.014
0.0088
0.044
4.0
0.000021
0.0021
0.36
0.20
0.032
0.050
0.24
0.72
0.60
0.0030
_ G
0.15
2.1
Industry contribution to total
emissions, c %
Nationwide
0.00031
0.0009
0.0009
n. 00020
New
Jersey
0.0102
0.0114
0.0074
0.0018
Pennsylvania
0.0023
0.0049
0.0182
0.0038
aEmissions not calculated for individual emission points.
''Representative plant is defined to be one having a production capacity
of 5.9 x 10" metric tons/yr (6.5 x 101* tons/yr)
clndustry contribution calculated only for criteria pollutants.
dIncludes all non-methane organic species.
eData not available.
-------
Table 4 (continued). SOURCE SEVERITY FACTORS AND INDUSTRY CONTRIBUTION TO TOTAL EMISSIONS FOR
NAPHTHALENE BASED PHTHALIC ANHYDRIDE PRODUCTION (CONTROLLED EMISSIONS)
Species emitted
Naphthalene (total)
Storage tanks
Vanadium oxide catalyst (tota
Catalyst storage
Fugitive emissions
Diphenyl oxide (total)
Fugitive emissions
Formaldehyde (total)
Incinerator I
Incinerator II
Emissions
from
all plants,
metric tons/yr
0.9
.) 1.5
2.4
II9
Emissions
from represent-
ative plant, b
metric tons/yr
0.35
0.35
0.59
0.59
0.94
0.94
4.4JJ
4.49
Severity
factor
0.0058
1.4
18.5
v.u,-,
Industry contribution to total
emissions , %
Nationwide
New
Jersey
Pennsylvania
Emissions not calculated for individual emission points.
Representative plant is defined to be one having a production capacity
of 5.9 x 10" metric tons/yr (6.5 x 101* tons/yr)
Industry contribution calculated only for criteria pollutants.
Heat-transfer fluid, assumed to be Dowtherm A.
9Total aldehydes reported as formaldehyde.
-------
Phthalic anhydride production in 1973 totaled 4.658 x 105
metric tons (5.12 x 105 tons) in the United States. Pro-
duction in 1978 is expected to total 4.99 x 105 metric tons
(5.49 x 105 tons). Thus, assuming that the same level of
control exists in 1978 as existed in 1973, emissions from
the phthalic anhydride industry will increase by 7% over
that period; i.e.:
Emissions in 1978 _ 4.99 x 105
Emissions in 1973 4.658 x 1(P ~
The average number of persons exposed to high contaminant
levels from phthalic anhydride operations was estimated and
designated as the "affected population." The calculation
was made for each species emitted and for each emission point
within a representative plant for which the severity factor
exceeds 0.1 or 1.0. The results are presented in Table 5.
The largest values of affected population are 525,000 persons
for o-xylene based production and 9,200 persons for naphtha-
lene based production.
12
-------
Table 5. AFFECTED POPULATION
(number of persons)
Compound
Sulfur oxides
Main process incinerator
Nitrogen oxides
Main process incinerator
Total hydrocarbons
Main process incinerator
Fugitive emissions
Phthalic anhydride
Main process incinerator
Secondary incinerator
Transport loading
Maleic anhydride
Main process incinerator
Secondary incinerator
Diphenyl oxide
Fugitive emissions
Formaldehyde
Main process incinerator
Naphthoquinone
Main process incinerator
Secondary incinerator
Vanadium oxide catalyst
Catalyst storage
g-Xylene based plant
No. of persons
where
X/F > 1.0
0
0
0
40
0
0
0
44,000
0
300
0
a
a
_a
No. of persons
where
X/F > 0.1
6,700
5,600
9,600
500
19,000
3,100
140
525,000
8,800
3,400
15,000
a
_a
_a
Naphthalene based plant
No. of persons
where
X/F > 1.0
_a
0
0
6
0
0
0
0
0
50
0
0
500
40
No. of persons
where
X/F > 0.1
_a
870
0
77
4,100
460
22
9,200
1,800
540
2,300
1,300
7,000
650
U)
No emissions.
-------
SECTION III
SOURCE DESCRIPTION
A. PROCESS DESCRIPTION
The first commercial phthalic anhydride process was patented
by Badische Anilin und Soda-Fabrik (BASF) in Germany in 1896.
The process utilized the liquid-phase oxidation of naphtha-
lene in concentrated sulfuric acid in the presence of mercury
sulfate.1 In 1917, a catalytic vapor-phase process for the
oxidation of naphthalene was developed in both the United
States and Germany. Phthalic anhydride was first produced
by the vapor-phase oxidation of xylene in 1946 in the United
States.2 o-Xylene has now become the preferred raw material
due to its lower cost and somewhat better yield ratio compared
with naphthalene. At present, all units in the world, with
the exception of Progil in France, use vapor-phase processes.
In 1975, 67% of the phthalic anhydride produced in the
continental United States was obtained from o-xylene and
33% from naphthalene as shown in Figure 1 (and in Table 20)-3'1
1Ockerbloom, N. E. Xylenes and Higher Aromatics, Part 3:
Phthalic Anhydride. Hydrocarbon Processing. 22:162-166,
September 1971.
2Landau, R., and H. Harper. Phthalic Anhydride. Chemistry
and Industry (London). July 29, 1961, p. 1143-1152.
3Phthalic Anhydride. Chemical Marketing Reporter. 205:9,
March 4, 1974.
4Anderson, E. V. Phthalic Anhydride Makers Foresee Shortage
Chemical and Engineering News. 53:10-11, June 30, 1975.
14
-------
PHTHALIC ANHYDRIDE PLANTS
10 PLANTS
o-XYLENE BASED
7 PLANTS
67% OF CAPACITY
NAPTHALENE BASED
3 PLANTS
33% OF CAPACITY
tn
BASF PROCESS
4 PLANTS
53% OF CAPACITY
VON HEYDEN PROCESS
3 PLANTS
OF CAPACITY
BADGER-SHERWIN-WILLIAMS
PROCESS 2 PLANTS
24% OF CAPACITY
OTHER PROCESS
1 PLANT
9% OF CAPACITY
Figure 1. Breakdown of phthalic anhydride production in the continental United States
-------
1. o-Xylene Based Process
Phthalic anhydride is presently produced in the United States
from o-xylene by the von Heyden process, which is licensed
in somewhat different forms by Chemiebau and Lurgi, and by
the BASF process, developed in the late 1960's. In 1975,
79% of the o-xylene based production in the continental
United States involved use of the BASF process and 21%
utilized the von Heyden process. 3'H Figure 2 is a schematic
flow diagram for the BASF process, which is described in
the following subsections. The numbered streams in Figure
2 are identified in Table 6. Since the gross features of
the von Heyden process differ only in minor ways from the
BASF process, the former will not be described per se.
a. Chemistry - The vapor-phase oxidation of o-xylene to
phthalic anhydride on a vanadium oxide catalyst can be
represented by the following equation:
catalyst r „ Q + ^^
0
o-xylene oxygen phthalic water
anhydride
The principal side reactions are the result of the further
oxidation of phthalic anhydride to maleic anhydride, carbon
oxides, and water. Based on the work of Bernardini and
Ramacci,5 the main sequence of reactions in the oxidation
of o-xylene is as follows:
5Bernardini, F., and M. Ramacci. Oxidation Mechanism of
o-Xylene to Phthalic Anhydride. Chimica e 1'Industria
(Milan). 481:9-17, January 1966.
16
-------
ATMOSPHERIC EMISSIONS
STEAM
i-i O^. <" *
JS _*•© ' 1 " (§)^j®
"l 1
A B G I j»
1 STEAM \_J
r&£ ' ©
PROCESS <£fcs^ ^rjLJ—
— ^->- O-XYLENE STORAGE TANK VENT GAS
tt K • )>
-t^STEAM *
-*=rWATER
H ^ ,
® ( T^o"
V /^ •
1
±=
®
J\ — ^
L
®
1 0|L. TO SECONDARY
t 4 SCRUBBER OR-
'~*-f~_~M~~W — | INCINERATOR
TO s^uTaTRT ^ ®fVACUUM
TO SECONDARY 5 _ /-^rt?}
trannnro -<---) W STFAM -^ — ^f
OR INCINERATOR --^-"-^ (|) WATER — »•
©„ P
N !3L
'
r 1
fi r~^i
Q OIL R
LJ U« , „
1 ^TITV- *
IT
'OIL'
BASF PROCESS FOR THE MANUFACTURE OF
PHTHALIC ANHYDRIDE FROM o-XYLENE
A. O-XYLENE STORAGE L. INCINERATOR
B. 502 STORAGE M. HEATER
C. O-XYLENE PREHEATER N. CRUDE PRETREATMENT TANK
D. COMPRESSOR 0. PRECOOLER
E. AIR PREHEATER P. STRIPPER
F. REACTOR IFIXED BEOI Q, EVAPORATOR
G. '.IOLHVS ALT HEAT EXCHANGER R. EVAPORATOR
H. WASTE HEAT BOILER S. RECTIFIER
1 SWITCH ,0'!CF\s[R5 T. PHTHALIC Ar.h '• JRIG'C STORAGE
J. CRUDE PRODUCT STORAGE I. FLAKER
K, SCRUBBER V. BAGGING MACHINE
STEAM
WATER
®.
®
•*- WATER
K *^}
^^r « ,, ®^ CRUDE PHTHALIC ANHYDRIDE
r STORAGE TANK VENT GAS
f ® n
'• -®,-J S ®
IVACUUM ^ AIR
'ff\| ^. L _
^1L ^ -*^ Fua
TO SECONDARY
INCINERATOR
, . W. REFINED PHTHALIC ANHYDRIDE
STORAGE TANK VENT GAS
A® (3)
T^ ^^ ^ o A*CO inn D»rriro i/tur p«c
-*1 1
i .A
© B
j
PHTHALIC ANHYORIOt
*" IKANSFOKI
LOADING FACILITY
— ^- TO WAREHOUSE
^" TO TANK CARS
Figure 2. BASF process for manufacture of phthalic anhydride from o-xylene
-------
Table 6. STREAM CODE FOR BASF PROCESS ILLUSTRATED IN FIGURE 2
Stream
Identification
00
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
o-Xylene feed
Sulfur dioxide
Filtered air
Reactor feed
Reactor product
Boiler effluent
Crude product
Condenser off-gas
Scrubber vent
Scrubber liquid purge
Crude PAN product
Pretreatment exhaust
Pretreated crude
Stripping column exhaust
Stripping column overhead
Rectifying column feed
Rectifying column vacuum exhaust
Rectifying column bottom product
Distillation light ends
Stream
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
Identification
Refined PAN
Water to steam generator
Generated steam
Water to waste-heat boiler
Steam from waste-heat boiler
Scrubber makeup
Incinerator stack gas
Water to cooling coil
Steam from cooling coil
Water to cooling coil
Steam from cooling coil
Incinerator fuel
Combustion air
Flaker and bagger vent
o-Xylene storage vent
Crude product storage vent
Refined PAN storage vent
Loading facility vent
Fugitive emissions
-------
o-xylene
o-methyl-
benzyl
alcohol
o-tolual-
dehyde
o-toluic
acid
0
O
C02, CO, H2O
HC-
phthalide
phthalic
anhydride
-Cx
II
0
maleic
anhydride
Direct oxidation of o-xylene or any of the intermediates
to carbon oxides and water can also occur. A certain
amount of bypassing of intermediates in the sequence is
also possible. In addition, many other reactions are
possible. For example, Bernardini and Ramacci presented a
scheme containing 21 compounds and 31 reaction arrows.5
b. Feed Materials - Feed materials used in the BASF
process consist of o-xylene, air, and sulfur dioxide. The
xylene feed (stream 1 in Figure 2) contains 95% by weight
o-xylene, the remainder consisting of meta- and para-
xylenes (designated as m- and p-xylenes). Only the o-
xylene can form phthalic anhydride. The m- and p_-xylenes
are reportedly converted to carbon oxides and water under
commercial reactor conditions.6 However, Bhattacharyya
6Friedrichsen, W., et al. Production of Phthalic
Anhydride. British Patent No. 1,082,326 (to BASF),
September 6, 1967.
19
-------
and Gulati7 state that the products of p_-xylene oxidation
include maleic anhydride, p_-tolualdehyde, p_-toluic acid,
terephthalic acid, and p-benzoquinone, while m-xylene oxi-
dation yields maleic anhydride, m-tolualdehyde, isophthalic
acid, and p_-benzoquinone.
Filtered air (stream 3) is compressed to a gage pressure
of 48.2 kPa to 55.2 kPa and preheated to 149°C using steam.
The liquid xylene feed is also preheated and vaporized by
injection into the hot air stream. A small amount (0.5-2.5%
by weight6) of sulfur dioxide (stream 2) is added to the
feed stream in order to maintain catalyst activity.
c- Reactor - In the BASF process, the weight ratio of air
to xylene in the feed stream (stream 4) to the reactor (unit
F) is 25, which is equivalent to 1 mole percent xylene (weight
ratios as low as 20 and as high as 34 have been reported in
the literature)-8 Excess air is employed to ensure that the
mixture is below the lower explosive limit of 1.5 mole
percent o-xylene.9 After removal of unvaporized feed, the
reactants are fed to the fixed-bed reactor, which operates
at about 380°C within a range of 300-390°C.6'9
The active form of the catalyst contains a mixture of V+5
and V+k. The role of the S02 is to adjust the redox con-
ditions so as to maintain the v+Vv+5 ratio within an
optimum range of from one to nine.6
7Bhattacharyya/ S. K., and I. B. Gulati. Catalytic Vapor-
Phase Oxidation of Xylenes. Industrial and Engineering
Chemistry. 5£: 1719-1726, December 1958.
8Spitz, P. H. Phthalic Anhydride Revisited. Hydrocarbon
Processing. £7:162-168, November 1968.
9Schwab, R. F., and W. H. Doyle. Hazards in Phthalic
Anhydride Plants. Chemical Engineering Progress. 66:49-
53, September 1970. —
20
-------
The BASF reactor has a capacity of approximately 1.44 x 101*
metric tons/yr and a diameter of 4.2 m.8 The reactor con-
tains 9,948 catalyst-filled tubes which are 25.4 mm in dia-
meter and 3 m long.8 (A larger version of this reactor con-
taining approximately 13,000 tubes is also used in some plants.)
A typical BASF plant consists of four reactors which can be
split to operate on two production trains.10 A molten salt
(sodium-potassium nitrate-nitrite eutectic)9 is circulated on
the shell side of the reactor to remove the heat produced in
the exothermic reaction. The molten salt passes through an
external heat exchanger (unit G) where high pressure steam is
produced. The gases leave the reactor at 375°C (stream 5)
and pass through a waste heat boiler (unit H) for additional
steam generation.
The conversion of the xylene in the reactor is 100%, with
a maximum yield of 1.03 kg phthalic anhydride per kilogram
of 95% o-xylene feed.11 (The theoretical yield is 1.39 kg
per kilogram of 100% o-xylene.1)
d. Switch Condensers - Due to the excess (567%) of air
employed in the reactor, the partial pressure of the
phthalic anhydride in the effluent gas stream is such that
the dew point is below the melting point (130.8°C) of
phthalic anhydride. Hence, the product condenses as a solid.
This operation is carried out in a parallel bank of tubular
condensers (unit I) which are alternately heated and cooled
by separate heat-transfer oil streams on an automatically con-
trolled cycle. During the cooling portion of the cycle,
phthalic anhydride crystallizes on the outer surfaces of
the finned tubes. During the heating portion of the cycle,
the solid phthalic anhydride is melted and then transferred
to the crude product storage tank (unit J). A typical
10Phthalic Anhydride: Return to Overcapacity. Chemical and
Engineering News. 4j3:18-19, March 15, 1971.
Phthalic Anhydride by Vapor-Phase Oxidation. The Oil and
Gas Journal. 7JL:92, March 12, 1973.
21
-------
operation1.2 employs a sequence of nine individual condensers,
with six condensing and two melting at any given time. The
ninth unit is on standby to allow for periodic cleaning and
maintenance without disruption of service. Residual gases
from the condensers (stream 8) at a temperature of 66°C and
gage pressure of 26 kPa are sent to a water scrubber (unit K)
or, in some plants, directly to an incinerator (unit L).
e. Product Purification - The crude product, which contains
99% to 99.5% phthalic anhydride as phthalic acid,11 is stored
at 149°C under atmospheric pressure. The refining operation
consists of two steps: a heat treatment step followed by a
vacuum distillation. The crude product (stream 11) passes
through a preheater (unit M) and then to the pretreatment
tank (unit N), where it is held at an elevated temperature
under vacuum for 8 to 12 hours. The purpose of the heat
treatment is to decompose color-forming compounds and to
convert them to higher molecular weight materials that can
be separated from the main product by distillation. At the
same time, dissolved phthalic acid is dehydrated to the
anhydride, and the associated water and other low-boiling
materials, such as maleic anhydride and benzoic acid, are
partially evaporated and removed through the vacuum jet
ejector exhaust stream (stream 12). This exhaust stream is
sent to either the scrubber (unit K) or a separate control
device (which may be another scrubber or another incinerator).
The pretreatment tank is discharged to a continuous distil-
lation system consisting of a stripping column (unit P) and
a rectifying column (unit S), both of which operate in the
range of 2.67 kPa to 26.7 kPa absolute pressure. The discharge
i2Riley, H. L. How to Design and Operate Fluidized-Catalyst
PA Plants. Hydrocarbon Processing and Petroleum Refiner.
42:167-172, June 1963.
22
-------
stream passes through a precooler (unit O) and enters the
stripping column at about 186°C. Maleic anhydride and benzoic
acid are separated in the overhead stream (stream 15) which
is sent to the main incinerator (unit L) or to a secondary
control device (via stream 19) for disposal. The bottom
stream from the stripping column passes to the evaporators
(reboilers, units Q and R). Part of the stream is recycled
to the stripping column, and the remainder (stream 16) enters
the rectifying column (unit S).
The bottom stream (stream 18) from the rectifying column
(the residue) is sent to the main incinerator or a secondary
incinerator for disposal. Phthalic anhydride (99.99%) is
taken overhead, condensed, and sent to the product storage
tank (unit T) where it is stored at atmospheric pressure
and 149°C.
The phthalic anhydride in the storage tanks can be pumped
to tank cars for shipment as a liquid, or it can be sent to
a flaking machine (unit U) for solidification. The flaked
product is weighed and packaged in 36-kg bags by a bagging
machine (unit V).
f. Incinerators - The switch-condenser off-gas may be
treated either by a scrubber-incinerator combination or by
direct incineration. These operations are common to both
the o-xylene and naphthalene based plants. The scrubber-
incinerator combination is discussed in Section III.A.2.g,
"Naphthalene Based Process," since the available data are
for a naphthalene based plant. A dual incineration system,
which is currently in operation on a 5.9 x 10H metric
tons/yr o-xylene based plant, is described below. Either
system should be equally applicable to o-xylene and naphtha-
lene based operations.
23
-------
The dual incineration system employs two thermal incinerators,
one of which treats the switch-condenser off-gas while the
other treats all of the waste streams from the product puri-
fication section of the plant. However, in the plant
currently using the system, the switch-condenser off-gas is
handled by two parallel incinerators, one on each of the two
production trains. The total phthalic anhydride design
capacity of this system is 8.84 x 101* metric tons/yr.
The two parallel incinerators incorporate waste-heat boilers
which produce steam at 400°C and a gage pressure of 4,480
kPa.13 The incinerators operate at 700°C to 760°C and the
combusted gases exit from the stacks at 250°C. The reported
control efficiency of this unit is 99.9% for carbon monoxide
and 96.5% for combined organics when operating at 760°C.13
The secondary incinerator used to treat the waste streams
•
from the product purification section of the plant is designed
to handle overheads and residues, and burns natural gas to
maintain an operating temperature of 650°C. The reported
control efficiency achieved by the unit is 99% for combined
organics.13
g. Storage Tanks - The feedstock, crude product, and re-
fined product storage tank requirements for a typical 5.9 x 104
metric tons/yr o-xylene based phthalic anhydride plant are
summarized in Table 7.13
Conservation vents can be used on o-xylene storage tanks to
minimize breathing losses. The breather valves are set to
open between 1.0 kPa and 1.47 kPa pressure.1H o-Xylene is
13Personal communication, H. M. Lacy, Monsanto Company.
April 7, 1975.
1£tFawcett, R. L. Air Pollution Potential of Phthalic Anhy-
dride Manufacture. Journal of the Air Pollution Control
Association. 2£: 461-465, July 1970.
24
-------
Table 7. SUMMARY OF TANKAGE REQUIREMENTS FOR A
5.9 x 104 METRIC TONS/YR o-XYLENE BASED
PHTHALIC ANHYDRIDE PLANT
Tank
no.
1
2
3
4
5
6
7
8
Material stored
o-Xylene
o-Xylene
Crude product
Crude product
Phthalic anhydride
Phthalic anhydride
Phthalic anhydride
Phthalic anhydride
Capacity,
m3
329
3,331
360
360
341
341
379
757
Turnovers
per year
230
23
65
65
72
72
44
44
aDetailed storage tank calculations are shown in
Appendix A.
stored at ambient temperature and has a vapor pressure of
from 0.13 kPa to 1.47 kPa under these conditions. The tanks
may also be blanketed with nitrogen to prevent the formation
of an explosive mixture in the vapor space above the liquid
xylene.
Crude and refined phthalic anhydride storage tanks are
maintained at 149°C to 160°C, at which temperatures the
vapor pressure is 2.27 kPa to 3.33 kPa. The tanks are
blanketed with dry nitrogen to prevent the entry of oxygen
and water vapor. The former creates a fire hazard while
the latter results in the hydrolysis of phthalic anhydride
to phthalic acid. Conservation vents are not used on these
25
-------
tanks because the phthalic anhydride vapors tend to solidify
and plug the vents. Control can be maintained by venting
the tanks to the incinerator or by the use of condensers
or sublimation boxes in which the phthalic anhydride is
removed from the vent stream by condensation and solidifi-
cation.
h. Heat-Transfer Circuits - The BASF process employs three
heat-transfer fluid systems: (1) a molten salt system which
removes heat from the reactor (units F and G in Figure 2);
(2) an organic fluid (e.g., Dowtherm A, a diphenyl-diphenyl
oxide eutectic) system that heats and cools the switch con-
densers (units I); and (3) an organic fluid system which
services the product purification section (units M, N, O, Q,
R). Molten salt heat exchange systems and organic systems
are described in the literature.15'16"22
15Uhl, V. W., and H. P. Voznick. Molten Salt as a Heat
Transfer Medium. Chemical Engineering Progress. 59:33-
35, May 1963.
16Fried, J. R. Heat-Transfer Agents for High-Temperature
Systems. Chemical Engineering. 8jO: 89-98, May 28, 1973.
17Seifert, W. F., L. L. Jackson, and C. E. Sech. Organic
Fluids for High-Temperature Heat-Transfer Systems.
Chemical Engineering. 79^:96-104, October 30, 1972.
18Purdy, R. B., et al. Indirect Heating with Aromatic Oils.
Chemical Engineering Progress. _5_9_: 43-46, May 1963.
19Conant, A. R., and W. F. Seifert. Dowtherm Heat Transfer
Medium. Chemical Engineering Progress. 5J^:46-49, May 1963
20Petersen, D. E., and R. K. Bedell. UCON Heat Transfer
Fluid. Chemical Engineering Progress. 59^36-39, May 1963.
21Davis, W. J., and P. G. Benignus. Therminol FR-2 Heat
Transfer Systems. Chemical Engineering Progrsss.
59^:39-42, May 1963.
22Frikken, D. R., K. S. Rosenberg, and D. E. Steinmeyer.
Understanding Vapor-Phase Heat-Transfer Media. Chemical
Engineering. 82^86-90, June 9, 1975.
26
-------
Details of the heat-transfer circuits employed in phthalic
anhydride plants are not available. However, the essential
features of the organic fluid systems are illustrated in
the basic liquid-phase heat-transfer system shown in Figure 3
Heat-transfer fluid is pumped from the direct-fired heater
to the user system. A surge tank is located on the suction
side of the pump in order to accommodate thermal expansion
of the liquid during startup and surging due to the venting
of line-trapped steam.
VENT TO
ATMOSPHERE
SURGE
TANK
NATURAL GAS
OR
FUEL OIL
VALVE
HEATER
RELIEF
VALVE
USER SYSTEM
VALVE
Figure 3. Organic liquid heat-transfer system
Surge tanks are normally designed for maximum temperatures
of 50°C to 60°C in order to provide a cold-fluid seal to
the atmosphere, thereby minimizing fluid oxidation. In
order to achieve these temperatures, tanks are not insula-
ted, and may be water jacketed. The surge tank is vented
to the atmosphere when the vapor pressure of the fluid is
sufficiently low to permit an unpressurized system and the
fluid is sufficiently stable to air oxidation. Higher
27
-------
vapor pressure fluids require system pressurization, which
can be accomplished by blanketing the surge tank with an
inert gas.
i. Waste Water Streams - One source of waste water in
phthalic anhydride plants is the steam boiler blowdown, which
amounts to 0.52 kg per kilogram of phthalic anhydride.13
Another source of waste water in some plants is the secondary
scrubber used to control the waste streams from the product
purification section of the plant. The liquid purge from
this scrubber must either be incinerated or sent to a waste
water treatment facility.
j. Plant Shutdown, Turnaround, and Start-up - Data on
o-xylene based phthalic anhydride plant shutdowns, turn-
arounds, and start-ups were obtained from industry.13
Phthalic anhydride plants are shut down on an average of
once per year. During start-up, the reactor is brought to
operating temperature by heating the process air in a natural
gas heater. The mixture of hot air and combustion gases is
passed through the reactor and then vented directly to the
atmosphere.
Start-up or other operating upsets can result in emissions
of heat-transfer fluid (designated "oil" in Figure 2) from
surge tank vents in the heat-transfer circuits associated
with the switch condensers and with the product purification
section of the plant. The emissions are in the form of an
aerosol mist, which reportedly settles in the immediate
vicinity of the emission point due to the low vapor pressure
of the heat-transfer fluid. These emissions are estimated
to be 0.016 g/kg phthalic anhydride, of which 95% is estimated
to originate from the switch-condenser circuit.13
28
-------
k. Catalyst - Many variations of the vanadium oxide
catalyst are possible.6 In one example,6 the catalyst
consists of 3.75 wt % vanadium oxide (as V2O5) and 21.25
wt % potassium pyrosulfate on a titanium dioxide carrier
(75 wt %). To activate the catalyst, about 65% of the
vanadium is converted to the tetravalent state by heating
in air containing SO2. Under the reaction conditions, the
vanadium oxide-potassium pyrosulfate mixture is present as
a melt in the pores of the Ti02 carrier which has a grain
size of 0.2 mm to 0.5 mm.
In a study of vanadium oxide catalyzed oxidation reactions,
Simard, et al.23 concluded that the organic oxidations
take place at the surface of the catalyst through ionic
reactions. Based on this observation, one possible mechanism
for the reaction is indicated in Figure 4. Simard, et al.
postulated that the surface layer of the catalyst is
composed of oxygen ions and pentavalent vanadium ions in
the geometrical arrangement shown. In Step 1, an o-xylene
molecule is adsorbed on the catalyst surface. In Step 2,
a hydrogen ion is removed from the hydrocarbon by a surface
oxygen ion, and an electron from the hydrocarbon is trans-
ferred to a vanadium ion. In Step 3, a covalent bond is
formed between the available carbon atom and the hydroxide
group and an electron is transferred from the organic
molecule to a vanadium ion. In the fourth step, the
organic molecule (o-methylbenzyl alcohol) is desorbed from
the surface leaving a vacant site on the surface. Following
this, an oxygen atom from an oxygen molecule in the gas
phase would fill the vacant site and be reduced to a minus
23Simard, G. L., et al. Vanadium Oxides as Oxidation
Catalysts. Industrial and Engineering Chemistry.
47_:1424-1430, July 1955.
29
-------
0.367 nm
0.367 nm
OO
O O O
0.367 nm
STEP 1
STEP 2
STEP 3
OJ
O
0.367 nm
O O O
O© O O o O
O o O o O
O © O O o O
O O O
(IN THE GAS PHASE)
STEP 4
Figure 4. Reaction mechanism for the catalytic oxidation of o-xylene
-------
2 valence while the two adjacent V+Lt ions would be oxidized
to V+5. Further oxygen atoms would then be added to the
organic molecule in a similar fashion.
Alternatively, the reaction could proceed via oxygen ions
adsorbed on the catalyst surface rather than incorporated
in the lattice. In either case, electrons must be trans-
ferred from donor sites in the catalyst to oxygen atoms in
order to form oxygen ions. The catalytic activity of the
vanadium oxide is due in part to the fact that it is a
semiconductor (n-type) which facilitates these electron
transfer processes.24
The following three-stage mechanism for the oxidation of
sulfur dioxide on a vanadium oxide catalyst has been pro-
posed by Glueck and Kenney:25
V205-S03 + S02 -
(vosOiJ2 - ^V2o4*so3 + so3
V2O4-SO3 + 1/2 02 - ^V2O5
In the above equations, V2O5-SO3 represents vanadium pentoxide
in the melt associated with sulfur trioxide formed from the
decomposition of the pyrosulfate anion. The result of the
first two steps is the reduction of vanadium from the
pentavalent to the tetravalent state. This provides an
explanation of the role of the sulfur dioxide in maintaining
the v+Vv+5 balance in the catalyst.
24Cullis, C. F. Heterogeneous Catalytic Oxidation of
Hydrocarbons. Industrial and Engineering Chemistry.
5_9:18-27, December 1967.
25Glueck, A. R., and C. N. Kenney. The Kinetics of the
Oxidation of Sulphur Dioxide Over Molten Salts.
Chemical Engineering Science. 2^:1257-1265, 1968.
31
-------
1. Reactor System Heat Balance - The oxidation of o-xylene
is an exothermic chemical reaction. The standard heats of
reaction for the main reaction and principal side reactions
were calculated on the basis that all of the compounds
involved are in the vapor state, and the results are listed
in Table 8. The heat released in a commercial reactor has
been estimated to be 17.1 MJ/kga phthalic anhydride formed,26
and this value agrees well with an estimate based on the
data in Table 8.
Table 8. HEATS OF REACTION FOR THE OXIDATION OF o-XYLENE
Reaction
Heat of reaction
MJ/kg
MJ/kg mol
o-Xylene + 302 •*• phthalic anhydride
+ 3H20
o-Xylene + 7. 5O2 •*• maleic anhydride
+ 4C02 + 4H20
o-Xylene + 10.502 -> 8C02 + 5H2O
12.5
28.2
41.2
1,286
2,983
4,387
The heat of reaction is used to generate steam in the molten-
salt heat exchanger and in the waste-heat boiler. Part of
this steam is used to satisfy process requirements and the
remainder is available for export. A representative energy
balance for a phthalic anhydride plant is given in Table 9.
;1 MJ = 1 x 106 joules = 948 Btu (see Section IX).
26Schwartz, W. A., et al. Engineering and Cost Study of Air
Pollution Control for the Petrochemical Industry, Volume 7:
Phthalic Anhydride Manufacture from Ortho-xylene. Air
Products and Chemicals, Inc., Houdry Division. U.S.
Environmental Protection Agency. Research Triangle Park.
Publication EPA-450/3-73-006-g, July 1975. 108 p.
32
-------
Table 9. REACTOR SYSTEM HEAT BALANCE FOR PRODUCTION OF
PHTHALIC ANHYDRIDE FROM o-XYLENEa
Heat in
MJ/kg PAN
Exothermic heat of reaction
Feed preheat
TOTAL
17.1
3.8
20.9
Heat out
MJ/kg PAN
Steam generation
Reactor internal cooling
Waste heat boiler
Reactor heat losses
Switch condensers
Incremental effluent heat content
TOTAL
10.6
6.0
0.1
3.3
0.9
20.9
Basis:
Table 18 Material Balance.
Xylene feed at 26.7°C, air at 26.7°C.
Feed preheated to 149°C.
Reactor outlet temperature, 375°C.
Condenser effluent gas at 65.6°C.
Effluent from waste heat boiler at 163°C.
Difference in heat content between condenser effluent
streams and reactor feed streams.
2. Naphthalene Based Process
All of the phthalic anhydride currently produced from
naphthalene in the United States is made via the fluid-bed
process. Two of the three plants now in operation, which
account for 73% of the naphthalene based production, use
the Badger-Sherwin-Williams process, first commercialized
in the early 1960's. The Koppers Company plant in Bridge-
ville, Pennsylvania, uses a fluid-bed process developed by
33
-------
American Cyanamid, which built and operated the plant in the
1950's. This process was never licensed, and the plant was
eventually taken over by Koppers when they acquired all of
Cyanamid's facilities at the Bridgeville location.8 Figure
5 is a schematic flow diagram for the Badger-Sherwin-Williams
process, which is described below. Process streams numbered
in Figure 5 are identified in Table 10.
a. Chemistry - The vapor-phase oxidation of naphthalene to
phthalic anhydride on a vanadium oxide catalyst can be
represented by the following equation:
O + 2C02 + 2H2O
1+4 1/2 02
naphthalene oxygen phthalic carbon water
anhydride dioxide
The side reactions are the consequence of the further
oxidation of phthalic anhydride to maleic anhydride, carbon
oxides, and water. Based on the work of loffe, et al.,27
the main sequence of reactions in the oxidation of naphthalene
is as follows:
27loffe, I. I., et al. Kinetics and Vapor Phase Oxidation
Mechanism of Aromatic Hydrocarbons. VI. Zhurnal
Fizicheskoi Khimii (Journal of Physical Chemistry).
29^692-698, 1955.
34
-------
ATMOSPHERIC EMISSIONS
U>
• NAPTHALENE STORAGE TANK VENT GAS
PROCESS
AIR
PROCES .
STEAM -
WATER -
1
STEAM
?
1®
TmFRESH^G
^"* r*UJ4TCD(^
WATER
VACUUM TO
SCRUBBER OR 1,
INCINERATOR.-1-1
OIL
VACUUM TO
SCRUBBER OR
INCINERATOR
(1?
A. NAPTHALENE STORAGE
B. COMPRESSOR
C. AIR PREHEATER
D. REACTOR (FLUID BED)
E. CATALYST FILTER
F. STEAM GENERATOR
G. PARTIAL CONDENSER
H. SWITCH CONDENSERS
I CRUDE STORAGE
*- SCRUBBER VENT GAS
INCINERATOR STACK GAS
>-FUGITIVE EMISSIONS
CATALYST STORAGE HOPPER VENTS
CRUDE PHTHALIC ANHYDRIDE
STORAGE TANK VENT GAS
REFINED PHTHALIC ANHYDRIDE
STORAGE TANK VENT GAS
*-TRANSPORT LOADING FACILITY VENT
PHTHALIC ANHYDRIDE
TRANSPORT LOADING
FACILITY
-»- TO TANK CARS
-+- aAKER AND BAGGER VENT
J. SCRUBBER
K. INCINERATOR
L, HEATER
M. CRUDE PRETREATMENT TANK
N. PRECOOLER
0. DISTILLATION COLUMN
P. PHTHALIC ANHYDRIDE STORAGE
Q. FLAKER
R. BAGGING MACHINE
TO WAREHOUSE
BADGER-SHERWIN-WILLIAMS PROCESS FOR MANUFACTURE OF
PHTHALIC ANHYDRIDE FROM NAPTHALENE
Figure 5. Badger-Sherwin-Williams process for manufacture of
phthalic anhydride from naphthalene
-------
Table 10. STREAM CODE FOR BADGER-SHERWIN-WILLIAMS
PROCESS ILLUSTRATED IN FIGURE 5
Stream
Identification
Stream
Identification
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Naphthalene
Air
Reactor product
Crude from partial
condenser
Partial condenser
off-gas
Crude from switch
condenser
Crude product
Switch-condenser
off-gas
Scrubber vent
Scrubber makeup
Scrubber liquid
purge
Crude PAN
Pretreatment vacuum
exhaust
Distillation column
feed
Distillation column
vacuum exhaust
Distillation column
light ends
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Distillation column
bottom product
Refined PAN
Incinerator stack gas
Incinerator fuel
Combustion air
Water to steam
generator
Generated steam
Cooling water
Steam
Flaker and bagger
vent
Naphthalene storage
vent
Crude product
storage vent
PAN storage vent
Catalyst storage
hopper vents
Loading facility
vent
Fugitive emissions
36
-------
o
II
H
0
II
c>
C\
O
•cx
naphthalene 1,4-dihydroxy- 1,4-naphtho- phthalic
naphthalene quinone anhydride
~CO2, CO, H2O
HC Cx
II
O
maleic anhydride
Direct oxidation of naphthalene or any of the intermediates
to carbon oxides and water can also occur. A certain amount
of bypassing of intermediates in the sequence is also
possible. In addition, a reaction path involving
1,2-naphthoquinone as an intermediate has been reported in
the literature.28
b. Feed Materials - Feed materials used in the Badger-
Sherwin-Williams process consist of naphthalene and air.
Two of the naphthalene based plants use petroleum naphtha-
lene while the other two use desulfurized coal-tar
28Shelstad, K. A., J. Downie, and W. F. Graydon. Kinetics
of the Vapor-Phase Oxidation of Naphthalene Over a
Vanadium Catalyst. Canadian Journal of Chemical Engin-
eering. 3£:102-107, August 1960.
37
-------
naphthalene. Typical compositions of petroleum and coal-
tar naphthalene are:29'30
Wt %
Naphthalene
Coal-tar naphthalene 92 - 96
Petroleum naphthalene 99.0 - 99.7
Sulfur
0.5 - 1.0
0.001
Tetralin
2
0
Present-day catalysts are capable of handling naphthalene
feedstocks with sulfur content as high as 1%.12'31 However,
the sulfur in coal-tar naphthalene is principally in the
form of thionaphthene, which is converted to maleic anhydride
and sulfur oxides rather than phthalic anhydride.12'32'33
The resultant loss in yield of phthalic anhydride (1% sulfur
is equivalent to 4.2% thionaphthene) is apparently the pri-
mary reason for the use of desulfurized naphthalene.
The reaction products of the tetralin (1,2,3, 4-tetrahydro-
naphthalene) present in coal-tar naphthalene are not known.
The most likely products, however, are maleic anhydride,
carbon oxides, and water. Some tetralin may also be
29Graham, J. J., and P. F. Way. Phthalic Anhydride by
Fluid Bed Process. Chemical Engineering Progress.
5£: 96-100, January 1962.
30Personal communication, L. B. Evans, U.S. Environmental
Protection Agency (Data originally supplied by U.S.
Steel Corp.). June 12, 1975.
31Chopey, N. P. Fluid-Bed Phthalic Anhydride. Chemical
Engineering. 6J9:104-106, January 22, 1962.
32Riley, H. L. Design of Fluidized Reactors for Naphtha-
lene Oxidation: A Review of Patent Literature. Trans-
actions of the Institution of Chemical Engineers (London)
3J7:305-313, 1959.
33Improvements Relating to the Oxidation of Aromatic
Hydrocarbons. American Cyanamid Company. British
Patent No. 850,817, January 2, 1957.
38
-------
converted to phthalic anhydride via a mechanism such as
the following:
H 0-OH
tetralin 1-hydroperoxy- <*-tetralone 1,4-naphtho-
tetralin quinone
O
II
x?-VC\
£)C /°
•
-------
particles in the fluidized bed reactor.29' 34 Within the
fluid bed, a uniform temperature is maintained (to ± 5°C)
in the range of 340°C to 380°C.3k Reactor pressure is set
by the backpressure of equipment downstream.
The reaction vessel itself is simply a large container of
sufficient size to hold the required amount of catalyst.
Single reactors having capacities of more than 4.5 x 104
metric tons/yr are feasible with the fluid-bed process.8
The catalyst bed is supported on a gird plate having holes
through which the fluidizing air is blown. Naphthalene feed
is introduced into the fluid bed through nozzles. Adequate
space above the normal bed level is provided to allow for
catalyst settling before the gases leave the reactor. The
ratio of bed depth to diameter is about 3:1 and the contact
time during reaction is 10 to 20 seconds.29
Removal of the heat produced by the exothermic reaction is
accomplished by means of cooling tubes located directly in
the catalyst bed. Water is circulated in these tubes and
steam is thereby generated directly without the need of a
secondary heat-transfer fluid.
The conversion of naphthalene in the reactor is 100% with
a yield of 0.97 kg phthalic anhydride per kilogram of
naphthalene feed.35 (The theoretical yield is 1.16 kg per
kilogram of 100% naphthalene.1)
34Graham, J. J. The Fluidized Bed Phthalic Anhydride
Process. Chemical Engineering Progress. 66:54-58,
September 1970.
35Phthalic Anhydride (Sherwin-Williams/Badger). The Badger
Company, Inc. Hydrocarbon Processing. 4_6:215, November
1967.
40
-------
d. Catalyst Filter - Effluent gases leaving the reactor
are cooled to about 260°C before entering the catalyst filter
unit (unit E) in order to prevent secondary reactions taking
place on the filters.3 The entrained catalyst particles are
separated from the gas stream by specially designed porous
ceramic filter elements. Process air is used to periodically
blow back the filters, and the catalyst particles are returned
directly to the reactor bed. Fiber glass filters, used in
some processes, are described in detail in Reference 12.
e. Condensers - Due to the low air to naphthalene ratio
employed in the fluid-bed process, the crude phthalic
anhydride is recovered both as a liquid and a solid. Between
40% and 60%29 of the product is obtained directly as a
liquid in the partial condenser (unit G) and the remainder
is condensed as a solid in the switch condensers (units H).
The latter operate in the same manner as those described
for the BASF process. However, the partial condensation of
product plus the reduced air rate greatly reduces the load
on the switch condensers with a concomitant reduction in
size and cost.
The tail gases (stream 8) leave the switch condensers at
66°C and are sent either to a water scrubber (unit J) or
directly to the incinerator (unit K). The low air rate
The cooling may be accomplished in a quenching section
within the reactor itself, rather than in an external heat
exchanger as shown in Figure 5. The quenching section is
simply a second fluidized bed located above the main bed
and separated from it by a grid plate. Further details of
this reactor scheme may be found in Reference 36.
Rousseau, W. P. C. Production of Phthalic Anhydride.
U.S. Patent No. 3,080,382 (to the Badger Co.), March
5, 1963.
41
-------
makes direct incineration more economical than in the fixed-
bed process.
The crude product is stored as a liquid at 149°C and atmos-
pheric pressure (unit I).
f. Product Purification - Crude phthalic anhydride (stream
12) from the crude product storage tank passes through a
preheater (unit L) and then to the pretreatment tank (unit
M) in much the same manner as in the BASF process. Treating
chemicals consisting of maleic anhydride (1 g per kilogram
PAN) and sodium hydroxide (0.05 g per kilogram PAN) are
added to promote the pretreatment process.37' In the
Badger-Sherwin-Williams process the final product is obtained
by means of a batch distillation column which operates at
an absolute pressure of 2.66 kPa. The light ends (stream 16)
are taken off at a reflux ratio of 40 and sent to the
incinerator for disposal. The main cut is then taken at a
reflux ratio of 1, condensed, and sent to the phthalic
anhydride storage tank (unit P), where it is held at 149°C
and atmospheric pressure. The residue, or bottoms product,
is sent to the incinerator.
The refined phthalic anhydride (99.7% minimum) can be
pumped to tank cars for shipment in liquid form, or it can
be sent to flaking and bagging machines (units Q and R) for
shipment as a solid.
37Personal communication, L. B. Evans, U.S. Environmental
Protection Agency (Data originally supplied by Union
Carbide Corporation). June 12, 1975.
42
-------
g. Scrubber and Incinerator -
(1) Scrubber - The characteristics of the effluent gas from
the switch condensers impose a number of constraints on the
design of a scrubber for phthalic anhydride plants:
• The efficient removal of aldehydes and maleic
anhydride requires a multistage rather than a
single-stage unit.14'38
• Since the liquid effluent from the scrubber must
be incinerated to avoid a water pollution problem,
a recycle system is necessary to minimize the
volume of the effluent stream.
• The organic compounds present in the condenser
tail gas are highly corrosive, thus requiring
the use of corrosion resistant materials of
construction.
A scrubber designed to meet the above requirements is
illustrated in Figure 6.38 (The process streams in Figure 6
are numbered for later reference to the material balance
given in Table 11.) The unit consists of two stages, each
of which contains a conventional fluid-bed packing on a
supporting grid. The two stages are separated by a conical
shaped deflector plate and collection tray. The unit is
designed to operate between 35°C and 40°C with an organic
removal efficiency of 98% to 99%. This high efficiency is
possible because most of the organics are solids at the
scrubber operating conditions. The material of construc-
tion is 316 stainless steel.
38Ferrari, D. C., and C. G. Bertram. Method and Apparatus
for the Removal of Organics from Chemical Waste Gases.
U.S. Patent No. 3,624,984 (to the Badger Co.), December
7, 1971.
43
-------
VENT GAS
MIST ELIMINATOR
\
CONDENSER
TAIL GAS
RECYCLE _
2"d STAGE
PURGE ,
^ t
k-
Xto*.
M
•*•-*• TT^f
2nd
STAGE
/ \
*?F "^^
1st
STAGE
v/
.i^^—' rnrni ifl
^ FREsH V\
ist STAGE
^ RECYCLE
1st STAGE PURGE
TO INCINERATOR
Figure 6. Schematic diagram of scrubber for
phthalic anhydride plant38
The condenser tail gas enters the first stage at approxi-
mately 66°C. The scrubbing liquor for this stage consists
of the purge from the second stage and the first stage
recycle stream. The liquor is slurry containing 10% to 12%
by weight of organic solids. The concentration of organic
compounds, both dissolved and in the form of slurry solids,
ranges from 10% to 50% by weight depending on the composi-
tion of the gas being treated. A portion of the recycle
stream is continuously purged and sent to the incinerator
for disposal.
In the second stage, the gas is scrubbed with a dilute
solution (0.5% to 3% by weight) of organic pollutants
(chiefly maleic acid). Fresh water is added to the second
44
-------
stage at a rate sufficient to replace the water removed
from the scrubber in the two exit streams. The makeup
water combines with the second stage recycle stream to form
the second stage scrubbing liquor. The scrubbed gas stream
passes through a mist eliminator and is then vented to the
atmosphere at 38°C.
Table 11 gives a typical scrubber material balance, obtained
from the Badger patent,38 for a naphthalene based phthalic
anhydride operation. In this example, only the condenser
effluent stream is fed to the scrubber. In practice, the
Table 11. TYPICAL SCRUBBER MATERIAL BALANCE FOR A
NAPHTHALENE BASED PHTHALIC ANHYDRIDE PLANTa
Stream No. :
Description:
Temperature, °C:
Component
Air
H20
Maleic anhydride
Phthalic anhydride
Benzoic acid
Naphthoquinone
Maleic acid
Phthalic acid
TOTALS
1
Condenser
tail gas
66
2
Makeup
water
16
3
Vent gas
38
4
1st stage
purge
38
Flow rates, kg/hr
222,273
4,545
291
141
11
11
227,272
6,272
6,272
222,273
9,545
4.6
2.3
0.5
0.9
231,826
1,202
11
11
339
155
1,718
Blanks indicate no mass flow of component
exhaust gases from the steam ejectors in the purification
section of the phthalic anhydride plant may also be fed to
the scrubber. In addition, it will be noted that sulfur
45
-------
and carbon oxides are included with the air, since they
behave as inert gases in the scrubbing operation. The flow
rates in this example correspond to a production rate of
approximately 5.68 x 104 metric tons/yr.
(2) Incinerator - Incinerators used in phthalic anhydride
plants are of two types: direct flame (thermal) units and
catalytic units. Catalytic incinerators are auto-thermal
and operate at temperatures of 427°C to 482°C. The catalyst
is platinum, platinum family or platinum activated alumina
on a metal ribbon mesh or ceramic base.14 Thermal incinerators
operate at temperatures of 700°C to 982°C and consume fuel
equivalent to 279 kJ per kilogram of phthalic anhydride
produced.38
A thermal incinerator38 is shown schematically in Figure 7-
(The process streams in Figure 7 are numbered for later
reference to the material balance given in Table 13.) The
primary feed stream to the incinerator is the liquid purge
from the first stage of the scrubber. Other feed streams
may include the residue (liquid), light ends (gas), and
ejector exhaust (gas) streams from the product purification
section of the plant. Heating values of the main organic
components in the scrubber purge stream are listed in
Table 12. The heating value of the liquid residue stream
is estimated to be 23.3 MJ/kg.38
Table 12. HEATING VALUES OF ORGANIC COMPOUNDS IN
SCRUBBER PURGE STREAM
Compound
Maleic acict
Phthalic acid
Benzoic acid
Naphthoquinone
Gross heat of
combustion, MJ/kg
13.8
21.6
26.5
29.1
46
-------
TO
ATMOSPHERE
RESIDUE
PITCH
LIGHT ENDS
AND EJECTOR
EXHAUST
LIQUID PURGE
FROM SCRUBBER
V | ® COMBUSTION
AIR
FUEL GAS
ATOMIZING STEAM
OR AIR
Figure 7. Schematic diagram of thermal incinerator
for phthalic anhydride plant38
The liquid purge stream is atomized immediately before
entering- the combustion area of the incinerator by either
a steam or an air stream. Fuel gas (e.g., methane) and
combustion air (25% in excess of the stoichiometric amount)
are introduced into the incinerator in a conventional manner
to provide an operating temperature of 760°C to 870°C. Heat
recovery is achieved by means of a coil which can be used
either to preheat the combustion air (as shown in Figure 6)
or to generate steam.
The incinerator reportedly attains an efficiency of 99.9%
conversion of organic materials. A material balance on the
incinerator38 is shown in Table 13. The feed stream in this
example is the scrubber purge stream of Table 11.
47
-------
Table 13.
INCINERATOR MATERIAL BALANCE FOR A NAPHTHALENE BASED PHTHALIC
ANHYDRIDE PLANT3
Stream No. :
Description:
Temperature, °C:
Component
Maleic acid
Phthalic acid
Benzoic acid
Naphthoqu inone
H2O
Oxygen
Nitrogen
Methane
C02
Organic s
TOTAL
1
Scrubber
purge
38
2
Atomizing
steam
186
3
Fuel
gas
16
4
Combustion
air
16
Flow rates, kg/hr
339
155
11
11
1,202
1,718
572
572
30
30
823
2,717
3,540
5
Stack gas
760
2,006
155
2,717
982
0.0059
5,860
00
Blanks indicate no mass flow of component.
-------
h. Storage Tanks - Table 14 summarizes the feedstock, crude
product, and refined product storage tank requirements for a
5.9 x lO4 metric tons/yr naphthalene based phthalic anhydride
plant.30 The crude and refined phthalic anhydride is stored
under the same conditions as described previously for o-xylene
based plants. Naphthalene storage tanks are maintained at
85°C to 100°C, at which temperatures the vapor pressure is
1.33 kPa to 2.67 kPa. Emission of naphthalene vapor can be
controlled by means of conservation vents.
Table 14. SUMMARY OF TANKAGE REQUIREMENTS FOR A
5.9 x 104 METRIC TONS/YR NAPHTHALENE BASED
PHTHALIC ANHYDRIDE PLANT
Tank
no.
1
2
3
4
5
6
7
8
9
Material stored
Naphthalene
Naphthalene
Naphthalene
Crude product
Crude product
Phthalic anhydride
Phthalic anhydride
Phthalic anhydride
Phthalic anhydride
Capacity,
m3
3,785
3,785
1,893
333
1,514
182
182
568
568
Turnovers
per year
1
13
26
148
2
130
130
2
40
i. Catalyst Storage Facilities - The fluid-bed process
involves two catalyst storage facilities which are not
shown in Figure 5. During the blow-back cycle of the
catalyst filter (unit E), the fines fraction of the fluid-
bed catalyst is separated and removed from the system as
"spent" catalyst. The fines fraction consists primarily of
catalyst particles less than 40 ym in diameter. The spent
catalyst stream is sent to a tangential cyclonic separator
where the catalyst particles are removed from the entraining
air stream with a removal efficiency of 98.5%.37 The
49
-------
recovered catalyst flows by gravity to a drum, approximately
0.2 m3 in volume, which is designated the spent catalyst
storage facility. The exhaust gas stream from the cyclone
is vented to the atmosphere. This operation is intermittent
and totals approximately 50 hr/yr.37
During periods of reactor shutdown for routine or emergency
maintenance, the catalyst is removed from the reactor and
transferred pneumatically to a catalyst storage hopper.
This operation is performed an average of four to eight
times per year, and has a duration of about 12 hours.37
The hopper vent is equipped with a cyclone separator that
recovers entrained catalyst with an efficiency of 90%.37
The recovered catalyst is returned to the storage hopper,
while the exhaust gas stream from the cyclone vents to the
atmosphere.
j. Heat Transfer Circuits - The Badger-Sherwin-Williams
process employs two organic fluid heat-transfer systems:
(1) the circuit that heats and cools the switch condensers
(units H); and (2) the circuit which services the product
purification train (units L, M, N, O). The fluid-bed
reactor is water cooled (units D and F). The organic fluid
systems are similar to those discussed previously for the
BASF process (Section III.A.l.h.).
k. Plant Shutdown, Turnaround, and Start-up - Naphthalene
based phthalic anhydride plants are shut down for emergency
or routine maintenance an average of four to eight times
per year.37 During these periods, the fluid-bed catalyst
is transferred pneumatically from the reactor to the catalyst
50
-------
storage hopper as described above. These transfer operations
result in emissions of catalyst particles from the storage
hopper vent and from fugitive sources. No data are available
on emissions of heat-transfer fluid (designated "oil" in
Figure 5) from the heating and cooling circuits during start-up
and other process upset conditions. However, these emissions
are presumably similar to those experienced by o-xylene based
plants, which have been described previously.
1. Catalyst - Davison Grade 902 Catalyst3 is a finely
divided vanadium oxide catalyst on a silica gel base used
for the direct air oxidation of naphthalene to phthalic
anhydride in fluid-bed reactors. Typical chemical and
physical specifications are given in Table 15.
Table 15. TYPICAL PROPERTIES OF DAVISON GRADE 902 CATALYST
Chemical analysis
Volatile at 374 °C
V205
K2SOk
S03
SiO2
Physical analysis
Bulk density
Surface area
Average pore diameter
Particle size distribution
£20 ym
>20 ym but <40 ym
>40 ym but ^80 ym
>80 ym
Wt %
1
9
29
12
50
Value
195 kg/m3
40 m2/g
3 mm
Wt %
12
11
28
49
W. R. Grace & Company, Davison Chemical Division. A newer
version of this catalyst, Davison Grade 906, is reported in
Reference 37. Grade 906 contains 3.5% V205 by weight.
51
-------
The primary purpose of the K2SO4 modifier is to slow down
the reaction rate and prevent over-oxidation of the naph-
thalene.29 The Badger-Sherwin-Williams reactor uses
0.6 gram of catalyst per kilogram of phthalic anhydride
produced.37
m. Reactor System Heat Balance - The oxidation of naph-
thalene is an exothermic chemical reaction. The standard
heats of reaction for the main reaction and principal side
reactions were calculated on the basis that all of the
compounds involved are in the vapor state, and the results
are listed in Table 16. Published figures for the heat
released in a commercial reactor are 16.3 to 20.9 MJ/kg
phthalic anhydride.9 A value of 17 MJ/kg phthalic anhydride
was estimated in Reference 26, and is in good agreement with
an estimate based on the data in Table 16.
Table 16.
HEATS OF REACTION FOR THE OXIDATION
OF NAPHTHALENE
Reaction
Naphthalene + 4.5O2 -»• phthalic anhydride
+ 2C02 + 2H2O
Naphthalene + 9O2 -»• maleic anhydride
+ 6CO2 + 3H2O
Naphthalene + 1.5O2 -> naphthoquinone + H2O
Naphthalene + 1202 •*• 10CO2 + 4H2O
Heat of reaction
MJ/kg
MJ/kg mol
14.0
28.4
3.7
39.6
2,732
395
51
547
Steam is generated by circulating water through the reactor
cooling coils, and also in the partial condenser. Part of
this steam is used to satisfy process requirements and the
remainder is available for export. A representative energy
balance for a naphthalene based phthalic anhydride plant is
presented in Table 17.
52
-------
Table 17. REACTOR SYSTEM HEAT BALANCE FOR PRODUCTION OF
PHTHALIC ANHYDRIDE FROM NAPHTHALENES
Heat in
Exothermic heat of reaction
Air preheat
Total
Heat out
Steam generation
Reactor internal cooling
Partial condenser
Reactor heat loss
Reactor effluent cooler
Switch condensers
Incremental effluent heat content
Total
MJ/kg PAN
17.0
1.5
18.5
MJ/kg PAN
13.2
2.0
0.1
1.6
1.2
0.4
18.5
Basis:
Material balance given in Table 19.
Naphthalene feed at 93°C/ air at 26.7°C.
Air preheated to 149°C.
Reactor outlet temperature, 371°C.
Condenser effluent gas at 66°C.
Difference in heat content between condenser
effluent streams and reactor feed streams.
B.
MATERIALS FLOW
1. o-Xylene Based Process
The flow diagram for the BASF process was given in Figure 2.
Table 18 is a material balance for a typical 5.9 x 104 metric
tons/yr plant, based on data obtained from Reference 26.
53
-------
Table 18. MATERIAL BALANCE FOR A 5.9 x 101* METRIC TONS/YR
O-XYLENE BASED PHTHALIC ANHYDRIDE PLANT
Stream No. :
Description:
Temperature, °C:
Gage pressure, kPa:
Component
Sulfur dioxide
Carbon monoxide
Carbon dioxide
Nitrogen
Oxygen
Phthalic anhydride
Maleic anhydride
Benzoic acid
o-Xylene
m- and p_-Xylene
Misc. organics
Particulate
Water
Total
1
Xylene
27
0
2
Sulfur
dioxide
27
3
Air
27
0
4
Reactor
feed
149
50
5
Reactor
product
375
6
Boiler
effluent
163
7
Crude
product
149
0
8
Condenser
off-gas
66
26
Plow rates, kg/hr
7,098.6
334.6
7,433.2
34.1
34.1
140,897.3
42,804.1
1,996.8
185,698.2
34.1
140,897.3
42,804.1
7,098.6
334.6
1,996.8
193,165.5
34.1
1,095.9
3,784.6
140,897.3
32,819.1
7,517.7
591.8
51.8
34.1
6,339.1
193,165.5
34.1
1,095.9
3,784.6
140,897.3
32,819.1
7,517.7
591.8
51.8
34.1
6,339.1
193,165.5
34.5
7,350.4
276.4
31.4
34.1
7,726.8
34.1
1,095.9
3,784.6
140,862.8
32,819.1
167.3
315.4
20.4
6,339.1
185,438.7
Ul
a
Blanks indicate data not available.
Blanks indicate no mass flow of exponent.
^Listed in Table 21.
-------
Table 18 (continued). MATERIAL BALANCE FOR A 5.9 x 10U METRIC TONS/YR
O-XYLENE BASED PHTHALIC ANHYDRIDE PLANT
Stream No. :
Description:
Temperature, °C:a
Gage pressure, kPa:'
Component
Sulfur dioxide
Carbon monoxide
Carbon dioxide
Nitrogen
Oxygen
Phthalic anhydride
Maleic anhydride
Benzoic acid
o-Xylene
m- and p_-Xylene
Misc. organics
Particulate
Water
Total
9
Scrubber
vent
38
0
10
Scrubber
liq. purge
38
11
Crude
PAN
149
0
12
Pretreatment
exhaust
-98.6
13
Pretreated
crude
14
Stripping
col. exhaust
-98.6
15
Stripping col.
overhead
-98.6
16
Rectifying
col. feed
186
Flow rates, kg/hr
34.1
1,095.9
3,784.6
140,897.3
32,819.1
3.2
8.2
6.8
4.6C
7,680.9
186,334.7
193.6
321.8
13.6
3,866.8
4,395.8
34.5
7,350.4
276.4
31.4
34.1
7,726.8
34.5
31.8
14.6
2,181.8e
2,262.7
7,318.6
261.8
31.4
34.1
7,645.9
7,280.0
14.5
34.1
7,328.6
U1
01
Blanks indicate data not available.
Blanks indicate no mass flow of component.
Primarily solids from make-up water.
B2181.8 kg/hr H20 condensate from steam ejector.
-------
Table 18 (continued). MATERIAL BALANCE FOR A 5.9 x 10U METRIC TONS/YR
O-XYLENE BASED PHTHALIC ANHYDRIDE PLANT
Stream No. :
Description:
Temperature, °C:
Gage pressure, kPa:
Component
Sulfur dioxide
Carbon monoxide
Carbon dioxide
Nitrogen
Oxygen
Phthalic anhydride
Maleic anhydride
Benzoic acid
o-Xylene
m- and p_-Xylene
Misc. organics0
Particulate
Water
Total
17
Rectifying
column vac.
exhaust
-98.6
18
Rectifying
col . bottom
product
19
Distillation
light Ends
20
Refined
PAN
149
0
21
Water to
steam gen.
16
22
Generated
steam
213
1,910
Flow rates, kg/hr
7.3
34.1
41.4
38.6
247.3
31.4
•
317.3
7,272.7
14.6
7,287.3
28,527.3
28,527.3
28,527.3
28,527.3
23
Water
to waste-
ht. boiler
16
16,263.6
16,263.6
24
Steam
from waste-
ht. boiler
157
476
16,263.6
16,263.6
(Jl
Blanks indicate data not available.
Blanks indicate no mass flow of component.
CListed in Table 21.
-------
Table 18
(continued). MATERIAL BALANCE FOR A 5.9 x 104 METRIC TONS/YR
O-XYLENE BASED PHTHALIC ANHYDRIDE PLANT
Stream No. :
Description:
Temperature, °C:
Gage pressure, kPa:
Component
Sulfur dioxide
Carbon monoxide
Carbon dioxide
Nitrogen
Oxygen
Phthalic anhydride
Maleic anhydride
Benzoic acid
o-Xylene
m- and p_-Xylene
Misc. organics
Particulate
Water
Ethane
Methane
Nitrogen oxides
Total
25
Scrubber
makeup
16
26
Incinerator
stack gas
927
0
27
Water to
cooling coil
16
28
Steam from
cooling coil
129
160
29
Water to
cooling coil
16
30
Steam from
cooling coil
129
160
31
Incinerator
fuel
16
32
Combustion
Air
27
0
Flow rates, kg/hr
3,026.8
3,026.8
18.2
2,759.1
9,660.9
395.4
3.6
3.2f
4,992.3
1.4
17,834.1
"*•
30.5
65.9
299.1
395.5
9,630.9
2,916.8
136.4
12,684.1
Blanks indicate data not available.
^Blanks indicate no mass flow of component.
Primarily solids from make-up water.
-------
Table 18 (continued). MATERIAL BALANCE FOR A 5.9 x 104 METRIC TONS/YR
O-XYLENE BASED PHTHALIC ANHYDRIDE PLANT
Stream No . :
Description:
Temperature, °C:
Gage pressure, kpa
Component
Sulfur dioxide
Carbon monoxide
Carbon dioxide
Nitrogen
Oxygen
Phthalic anhydride
Maleic anhydride
Benzoic acid
o-Xylene
m- and p_-Xylene
Misc. organics
Particulate
Water
Total
33
Flaker
and bagger vent
27
0
34
o-Xylene
stg. vent
27
0
35
Crude product
stg. vent
149
0
36
PAN
stg. vent
149
0
37
Loading
facility vent
27
0
38
Fugitive
emissions
27
0
Flow rates, b kg/hr
0.007
0.007
0.014
0.014
0.008
0.008
0.02
0.02
0.03
0.03
1/1
00
Blanks indicate no mass flow of component.
-------
Sources of atmospheric emissions from the BASF.process are:
the scrubber vent (stream 9) and/or the incinerator flue
gas (stream 26), xylene storage (stream 34), crude product
storage (stream 35), refined product storage (stream 36),
flaker and bagger vent (stream 33), transport loading
facility vent (stream 37), and fugitive emissions (stream 38)
In addition, plants which employ a secondary scrubber or
incinerator to control waste streams from the product puri-
fication section of the plant will have emissions from
these devices.
2. Naphthalene Based Process
The flow diagram for the Badger-Sherwin-Williams process was
given in Figure 5. Table 19 is a material balance for a
5.9 x 104 metric tons/yr plant, based on data obtained from
Reference 26.
Sources of atmospheric emissions from the Badger-Sherwin-
Williams process are: the scrubber vent (stream 9), and/or
the incinerator flue gas (stream 19), naphthalene storage
(stream 27), crude product storage (stream 28), refined
product storage (stream 29), flaker and bagger vent (stream
26), transport loading facility vent (stream 31), catalyst
storage hopper vents (stream 30), and fugitive emissions
(stream 32).
C. GEOGRAPHICAL DISTRIBUTION
There are currently eight companies manufacturing phthalic
anhydride at ten locations in the continental United States,
plus one in Puerto Rico. Table 20 lists the manufacturers
and plant capacities, and the plant locations are shown in
Figure 8. The population densities of the counties in which
the plants are located range from 30 to 4,905 persons/km2-
59
-------
Table 19. MATERIAL BALANCE FOR A 5.9 x 104 METRIC TONS/YR
NAPHTHALENE BASED PHTHALIC ANHYDRIDE PLANT
Stream No. :
Description:
Temperature, °C: a
Gage pressure, kPa:
Component
Naphthalene
Phthalic anhydride
Maleic anhydride
Naphthoquinone
Misc. organics
Oxygen
Nitrogen
Carbon dioxide
Carbon monoxide
Water
Total
1
Naphthalene
93
0
2
Air
27
0
3
Reactor
product
260
7,497.3
37.7
7,535.0
22,130.0
68,197.3
90,327.3
7,492.3
101.4
53.2
37.7
12,225.4
68,197.3
7,030.4
366.4
2,356.4
97,860.5
4
Crude from
partial
condenser
149
Flow rates
5
Part. cond.
off-gas
, b kg/hr
6
Crude from
switch cond.
149
7
Crude
product
149
0
7,344.1
50.4
48.2
37.7
17.3
20.0
65.5
7,583.2
8
Switch-cond.
off-gas
66
148.2
50.9
5.0
12,208.2
68,177.3
7,030.4
366.4
2,290.9
90,277.3
Blanks indicate data not available.
3Blanks indicate no mass flow of component.
-------
Table 19 (continued). MATERIAL BALANCE FOR A 5.9 x 10" METRIC TONS/YR
NAPHTHALENE BASED PHTHALIC ANHYDRIDE PLANT
Stream No. :
Description:
Temperature, °C:
Gage pressure, kPa:
Component
Naphthalene
Phthalic anhydride
Maleic anhydride
Naphthoguinone
Misc. organics
Oxygen
Nitrogen
Carbon dioxide
Carbon monoxide
Water
Total
9
Scrubber
vent
38
0
10
Scrubber
makeup
16
11
Scrubber
liq. purge
38
12
Crude
PAN
149
0
13
Pretreatment
vac. exhaust
-98.6
14
Dist. col.
feed
186
15
Dist. col.
vac. exhaust
-98.6
16
Dist. col.
light ends
-98.6
Flow rates, kg/hr
12,208.2
68,177.3
7,030.4
366.4
7,344.1
50.4
48.2
37.7
17.3
20.0
65.5
7,583.2
18.2
17.3
20.0
65.5
121.0
5.0
35.9
40.9
Blanks indicate data not available.
Blanks indicate no mass flow of component.
-------
Table 19 (continued). MATERIAL BALANCE FOR A 5.9 x 1014 METRIC TONS/YR
NAPHTHALENE BASED PHTHALIC ANHYDRIDE PLANT
Stream No. :
Description:
Temperature , °C :
Gage pressure, kPa:
Component
Naphthalene
Phthalic anhydride
Maleic anhydride
Naphthoquinone
Misc. organics
Oxygen
Nitrogen
Carbon dioxide
Carbon monoxide
Water
Methane
Ethane
Particulate
Nitrogen oxides
Total
17
Dist. col.
bottom prod.
18
Refined
PAN
149
0
19
Incinerator
stack gas
927
0
20
Incinerator
fuel
16
21
Combustion
air
27
0
22
Water to
steam gen.
16
23
Steam from
steam gen.
213
1,910
24
Cooling
water
16
Flow rates, kg/hr
48.2
48.2
37.7
134.1
7,272.7
14.6
7,287.3
35,154.6
35,154.6
35,154.6
35,154.6
5,340.9
5,340.9
to
Blanks indicate data not available.
Blanks indicate no mass flow of component.
-------
Table 19 (continued). MATERIAL BALANCE FOR A 5.9 x 104 METRIC TONS/YR
NAPHTHALENE BASED PHTHALIC ANHYDRIDE PLANT
Stream No. :
Description:
Temperature, °C:
Gage pressure, kPa:
Component
Naphthalene
Phthalic anhydride
Maleic anhydride
Naphthoquinone
Misc. organics
Oxygen
Nitrogen
Carbon dioxide
Carbon monoxide
Water
Total
25
Steam
135
207
26
Flaker
and bagger
vent
27
0
27
Naphthalene
stg. vent
90
0
28
Crude prod.
stg. vent
149
0
29
PAN
stg. vent
149
0
30
Catalyst storage
hopper vents
27
0
31
Loading facility
vent
27
0
32
Fugitive
emissions
27
0
Flow rates, kg/hr
5,340.9
5,340.9
0.007
0.007
0.044
0.044
0.012
0.012
0.014
0.014
0.03
0.03
u»
Blanks indicate no mass flow of component.
-------
Table 20. PHTHALIC ANHYDRIDE PLANTS3'
Number
1
2
3
4
5
6
7
8
9
10
—
Company
Allied Chemical
BASF Wyandotte
Exxon Corp .
Koppers Co.
Koppers Co.
Monsanto Co.
Monsanto Co.
Std. Oil Calif.
Stepon Chem. Co.
U.S. Steel
Occidental Petroleum
Nominal
capacity,
10* metric
tons/yr
15.9
59.0
40.8
40.8
79.4
40.8
59.0
22.7
22.7
68.0
45.4
Location
El Segundo, Calif.
S. Kearny, N.J.
Baton Rouge, La.
Bridgeville, Pa.
Cicero, 111.
Bridgeport, N.J.
Texas City, Texas
Richmond, Calif.
Millsdale, 111.
Neville Island, Pa.
Arecibo, P.R.
County
population
density,
persons/km2
662
4,905
233
842
2,197
64
160
152
112
30
39
Raw
material
o-Xylene
o-Xylene
o-Xylene
Desulf. naphthalene
o-Xylene
Petro naphthalene
o-Xylene
o-Xylene
o-Xylene
Desulf. naphthalene
o-Xylene
Process
Chemiebau (von Heyden)
BASF
BASF
Own (fluid bed)
BASF
Badger-Sherwin-Williams
BASF
Lurgi (von Heyden)
Chemiebau (von Heyden)
Badger-Sherwin-Williams
Chemiebau (von Heyden)
The following plants are not in operation:
—
—
—
—
—
—
—
Union Carbide Co.
Allied Chemical
Allied Chemical
W. R. Grace
Reichhold Chemicals
Reichhold Chemicals
Sherwin-Williams
45.4
45.4
15.0
34.0
13.6
45.4
9.1
Institute and South
Charleston, W. Va.
Frankford, Pa.
Ironton, Ohio
Fords, N.J.
Elizabeth, N.J.
Morris, 111.
Chicago, 111.
95
5,861
47
714
2,020
22
2,197
Petro naphthalene
Naphthalene
Naphthalene
Naphthalene
Naphthalene
o-Xylene
Naphthalene
Badger-Sherwin-Williams
Badger
Own (fixed bed)
Badger-Sherwin-Williams
Badger-Sherwin-Williams
Unknown
Badger-Sherwin-Williams
Numbers refer to code shown in Figure 8.
-------
Figure 8. Phthalic anhydride plant locations
The total U.S. capacity in 1975 was 4.95 x 10s metric tons/yr
In addition to this, a 2.27 x 10*4 metric tons/yr expansion of
the U.S. Steel Plant at Neville Island, Pennsylvania is
scheduled for completion in 1975.u
65
-------
SECTION IV
EMISSIONS
A. SELECTED POLLUTANTS
1. o-Xylene Based Process
A complete list of the possible reaction products from the
oxidation of xylene, according to the work of Bernardini and
Ramacci,5 and Bhattacharyya and Gulati,7 is given in Table 21,
In these experimental laboratory studies, gas chromatography
and various other quantitative analytical techniques were
employed to identify the reaction products. In addition to
the compounds shown in Table 21, emissions from o-xylene
based phthalic anhydride plants contain sulfur oxides,
nitrogen oxides, particulates, and diphenyl oxide (from
Dowtherm® heat-transfer fluid). Of the above mentioned
compounds, the following are either known or suspected of
being emitted on the basis of previously published data:llf»26
o-xylene, phthalic anhydride, maleic anhydride, benzoic
acid, o-tolualdehyde, formaldehyde, acetaldehyde, phthalalde-
hyde, acrolein, carbon monoxide, sulfur oxides, nitrogen
oxides, particulates, and diphenyl oxide. Hence, these
compounds were selected for study in this program. The
rationale for not considering the remaining materials listed
in Table 21 is presented in Appendix B.
66
-------
Table 21. POSSIBLE REACTION PRODUCTS FROM THE
OXIDATION OF XYLENE
Compound
Formula
o-Methylbenzyl alcohol
o-Tolualdehyde
o-Toluic acid
Toluene
o-Hydroxymethylbenzoic acid
Citraconic anhydride
Phthalaldehyde
COOH
CH2OH
O
II
•c"c\
II 0
O
CHO
CHO
67
-------
Table 21 (continued). POSSIBLE REACTION PRODUCTS FROM
THE OXIDATION OF XYLENE
Compound
Formula
Maleic anhydride
O
II 0
Phthalide
CH2
Phthalaldehydic acid
COOH
CHO
Benzoic acid
COOH
Phthalic anhydride
Phthalic acid
COOH
OOH
Carbon oxides and water
CO, CO2, H2O
o'-Carboxylphenyl-o-
methylphenyl acetate
CHo COO
CH3 HOOC
68
-------
Table 21 (continued). POSSIBLE REACTION PRODUCTS FROM
THE OXIDATION OF XYLENE
Compound
Formula
o'-Methylphenyl-o-
~ methylphenyl acetate
bis(o-Methylphenyl) methyl
ether
)-CH2
H3C
,2-bis(o-Methylphenyl) ethane
CH2 CH2
'CH3 H3C
Formaldehyde
HCHO
Acetaldehyde
CH3CHO
Acrolein
H
p_-Tolualdehyde
p_-Toluic acid
CHO
CH3
COOH
CH-
69
-------
Table 21 (continued). POSSIBLE REACTION PRODUCTS FROM
THE OXIDATION OF XYLENE
Compound
Formula
Terephthalic acid
COOH
COOH
p_-Benzoguinone
m-Tolualdehyde
CHO
Isophthalic acid
COOH
'COOH
2. Naphthalene Based Process
A reaction scheme for the oxidation of naphthalene, similar
to that for the oxidation of o-xylene, has not been published.
In addition to the reaction sequence given in Section III.A.2.b.
involving 1,4-naphthoquinone, Shelstad, et al.,28 have reported
70
-------
a path involving 1,2-napththoquinone as an intermediate.
Thus, 1,2-dihydroxynaphthalene and 1,2-naphthoquinone are
expected reaction products. In addition, the compounds
listed in Table 21 may also be formed by the oxidation of
naphthalene. Furthermore, transfer operations involving
the fluid-bed catalyst result in emissions of vanadium
oxide catalyst dust. Hence, the species selected for
detailed study in this program include those selected for
the o-xylene based process, with the addition of naphthalene,
the naphthoquinones, the dihydroxynaphthalenes, and vanadium
oxide catalyst dust.
B. LOCATION AND DESCRIPTION
The sources of atmospheric emissions within phthalic anhydride
plants are: the main process scrubber vent and/or the
incinerator stack, storage tank vents (feedstock, crude
product, and refined product), the flaker and bagger vent,
the liquid product loading facility vent, and fugitive
emissions. The catalyst storage hopper vents are an addi-
tional source of emissions in naphthalene based plants.
Those plants which employ a secondary scrubber or incinerator
to treat the waste streams from the product purification
section of the plant also have emissions from these units.
Each of the above sources is discussed below.
1. Scrubber Vent
The scrubber vent gas (stream 9 in Figures 2 and 5) is a
continuous source of emissions consisting of scrubbed
process off-gas from the switch condensers. Typical
concentration ranges for the major contaminants in the
condenser off-gas, as given by Fawcett,14 are shown in
71
-------
Table 22. The corresponding flow rates for a 5.9 x 101*
metric tons/yr plant are in agreement with the material
balances given in Tables 18 and 19 (which are based on the
Houdry data26) with one exception: that is, the flow rate
of maleic anhydride for a naphthalene based plant, which is
51 kg/hr in Table 19.
The organic compounds are removed from the condenser off-gas
stream with a maximum efficiency of 98% to 99% in the
scrubber,38 while the carbon and sulfur oxides are vented to
the atmosphere. Typical compositions for the scrubber vent
gas stream are presented in Tables 23 and 24 for o-xylene
and naphthalene based plants, respectively. These values
are based on the material balance data of Tables 18 and 19
and, in the case of naphthalene based plants, the assumption
of a scrubber efficiency of 98% for organics.
2. Incinerator Stack
The incinerator flue gas (stream 26 in Figure 2 and stream 19
in Figure 5) is another continuous source of emissions. The
incinerator is used to burn the liquid purge from the scrubber
or, in the case of plants employing direct incineration, the
switch-condenser off-gas. The waste streams from the product
purification section of the plant and the phthalic anhydride
storage tank vents may also be fed to the incinerator.
Typical compositions of the stack gas are presented in Tables
25 and 26 for o-xylene and naphthalene based plants employing
a scrubber-incinerator combination. These values are based
on the material balances given in Tables 18 and 19 and, in
the case of naphthalene based plants, on the assumption of
organic removal efficiencies of 98% and 99% in the scrubber
and incinerator, respectively. The results for plants
72
-------
Table 22. CONCENTRATIONS OF CONTAMINANTS IN SWITCH-CONDENSER OFF-GAS14
Material
Phthalic anhydride
Maleic anhydride
Benzoic acid
Aldehydes (as CH20)
Carbon monoxide
Carbon dioxide
Sulfur dioxide
Naphthoquinone
Concentration ,
ppm by vol.
40-200
100-600
5-40
10-100
1,000-10,000
6,000-50,000
50-200
10-30
Flow rate,3
kg/hr
39-193
64-383
4-32
2-20
180-1,800
1,740-14,500
21-84
5.1-15
Uncontrolled
emission factor,
g/kg
5.4-26.5
8.8-52.6
0.55-4.4
0.28-2.8
24.8-248
239-2,000
2.9-11.5
0.7-2.1
U)
For a production rate of 5.9 x 104 metric tons/yr.
Only present when naphthalene is the feedstock.
-------
Table 23.
TYPICAL SCRUBBER VENT GAS COMPOSITION
FOR O-XYLENE BASED PROCESS
Production rate = 5.9 x 104 metric tons/yr
Temperature = 38°C
Gage pressure = 0 kPa
Component
Phthalic anhydride
Maleic anhydride
Benzoic acid
o-Tolualdehyde
Phthalaldehyde
Formaldehyde
Acetaldehyde
Acrolein
Carbon monoxide
Carbon dioxide
Sulfur oxides
Nitrogen
Oxygen
Water
Particulate
Others
Total
Concentration ,
wt %
0.0017
0.0044
0.0036
a
_a
a
a
_a
0.59
2.03
0.018
75.62
17.61
4.12
0.0025
a
100.0
Average
flow
rate,
kg/hr
3.2
8.2
6.8
a
a
a
a
a
1,095.9
3,784.6
34.1
140,897.3
32,819.1
7,680.9
4.6
a
186,334.7
Emission
factor,
g/kg
0.44
1.13
0.94
a
_a
a
a
_a
150.7
520.4
4.69
19,373.
4,513.
1,056.
0.63
_a
25,631
Not reported in data source.
74
-------
Table 24. TYPICAL SCRUBBER VENT GAS COMPOSITION
FOR NAPHTHALENE BASED PROCESS
Production rate = 5.9 x 10H metric tons/yr
Temperature = 38°C
Gage pressure = 0 kPa
Component
Phthalic anhydride
Maleic anhydride
Benzoic acid
Naphthoquinone
o-Tolualdehyde
Phthalaldehyde
Formaldehyde
Ace t a Idehyde
Acrolein
Carbon monoxide
Carbon dioxide
Sulfur oxides
Nitrogen
Oxygen
Water
Particulate
Others
Concentration ,
wt %
_a
_a
a
_a
a
a
_a
a
a
a
_a
a
a
_a
a
_a
a
Average
flow
rate,
kg/hr
3.0
1.0
0.2
0.15
b
b
b
_b
_b
366.
7,030.
0.0
68,177.
12,208.
_b
4.6
_b
Emission
factor,
g/kg
0.41
0.14
0.03
0.02
b
b
b
_b
_b
50.4
967-
0.0
9,378.
1,679.
_b
0.63
_b
Not calculated because data lacking for one or more
major components.
Not reported in data source.
75
-------
Table 25.
TYPICAL INCINERATOR FLUE GAS COMPOSITION FOR
O-XYLENE BASED PROCESS WITH
SCRUBBER-INCINERATOR COMBINATION
Production rate = 5.9 x 104 metric tons/yr
Temperature = 927°C
Gage pressure = 0 kPa
Component
Phthalic anhydride
Maleic anhydride
Benzoic acid
o-Tolualdehyde
Phthalaldehyde
Formaldehyde
Acetaldehyde
Acrolein
Carbon monoxide
Carbon dioxide
Sulfur oxides
Nitrogen oxides
Nitrogen
Oxygen
Water
Methane
Ethane
Particulate
Others
Total
Concentration ,
wt %
_a
a
0.020
_a
_a
_a
_a
_a
0.10
15.47
_a
0.0079
54.17
2.22
27.99
_a
_a
0.018
_a
100.0
Average
flow
rate,
kg/hr
_a
_a
3.6
_a
_a
_a
_a
_a
18.2
2,759.
_a
1.4
9,661.
395.4
4,992.
a
_a
3.2
_a
17,834
Emission
factor,
g/kg
_a
_a
0.50
_a
_a
_a
_a
_a
2.50
379.
_a
0.19
1,328.
54.4
686.
_a
_a
0.44
_a
2,451
Not reported in data source,
76
-------
Table 26.
TYPICAL INCINERATOR FLUE GAS COMPOSITION FOR
NAPHTHALENE BASED PROCESS WITH
SCRUBBER-INCINERATOR COMBINATION
Production rate = 5.9 x ID4 metric tons/yr
Temperature = 927°C
Gage pressure = 0 kPa
Component
Phthalic anhydride
Maleic anhydride
Benzoic acid
Naphthoquinone
o-Tolualdehyde
Phthalaldehyde
Formaldehyde
Acetaldehyde
Acrolein
Carbon monoxide
Carbon dioxide
Sulfur oxides
Nitrogen oxides
Nitrogen
Oxygen
Water
Methane
Ethane
Particulate
Others
Concentration ,
wt %
_a
_a
a
a
a
_a
a
a
_a
_a
_a
_a
a
_a
a
_a
_a
_a
_a
a
Average
flow
rate,
kg/hr
1.75
0.87
0.15
0.07
_b
_b
_b
_b
_b
18.2
_b
_b
1.4
_b
_b
_b
_b
_b
3.2
_b
Emission
factor,
g/kg
0.24
0.12
0.02
0.01
_b
_b
_b
_b
_b
2.50
_b
_b
0.19
_b
_b
_b
_b
_b
0.44
_b
Not calculated because data lacking for one or more
major components.
Not reported in data source.
77
-------
employing direct incineration are presented in Tables 2713
and 28.26
The composition of the incinerator flue gas depends upon
incineration temperature, combustion efficiency, type of
incinerator (thermal or catalytic), and feed material
composition. Incinerator temperature determines the nitrogen
oxides content of the stream due to oxygen fixation of
nitrogen, while combustion efficiency governs the quantities
of feed materials burned. Feed material composition deter-
mines the overall composition of the stack gas.
Removal efficiencies of up to 99% of organic materials are
reported for a thermal incinerator in series with a water
scrubber.38 In the case of direct thermal incineration of
the switch-condenser off-gas, efficiencies of 96.5% for
organic material and 99.9% for carbon monoxide have been
attained.13 One difficulty with the latter method of control
is that the entire contaminant load exhausts to the atmos-
phere during periods of incinerator flame-out, which occur
an average of six times per year.13 Nevertheless, the
available data indicate that direct thermal incineration
is the best overall method of control at the present time
(see Section V.A).
3. Storage Tank Vents
The emissions from feedstock, crude product, and refined pro-
duct storage tank vents (stream 34, 35, and 35 in Figure 2;
streams 27, 28, and 29 in Figure 5) for a 5.9 x 10** metric
tons/yr production rate have been estimated and are presented
in Table 29. These estimates were obtained using the data
in Tables 7 and 14 together with the empirical correlations
78
-------
Table 27.
TYPICAL INCINERATOR FLUE GAS COMPOSITION FOR
o-XYLENE BASED PROCESS USING
DIRECT THERMAL INCINERATIONl3
Production rate = 5.9 x 104 metric tons/yr
Temperature = 250 °C
Gage pressure = 0 kPa
Component
Phthalic anhydride
Maleic anhydride
Benzoic acid
o-Tolualdehyde
Phthalaldehyde
Forma Idehyde
Acetaldehyde
Acrolein
Carbon monoxide
Carbon dioxide
Sulfur oxides
Nitrogen oxides
Nitrogen
Oxygen
Water
Methane
Ethane
Particulate
Others
Concentration ,
wt %
_a
_a
_a
a
_a
a
a
_a
a
a
a
_a
_a
a
a
_a
_a
a
a
Average
flow
rate,
kg/hr
4.0
13.2
0.8
_b
_b
_b
_b
_b
0.9
_b
36.4
9.1
_b
_b
_b
_b
_b
1.8
_b
Emission
factor,
g/kg
0.55
1.82
0.11
_b
_b
_b
_b
_b
0.125
_b
5.0
1.25
_b
_b
_b
_b
_b
0.25
_b
Not calculated because data lacking for one or more
major components.
Not reported in data source.
79
-------
Table 28.
TYPICAL INCINERATOR FLUE GAS COMPOSITION FOR
NAPHTHALENE BASED PROCESS USING
DIRECT THERMAL INCINERATION26
Production rate = 5.9 x 104 metric tons/yr
Temperature = 250°C
Gage pressure = 0 kPa
Component
Phthalic anhydride
Maleic anhydride
Benzoic acid
Naphthoquinone
o-Tolualdehyde
Phthalaldehyde
Formaldehyde
Acetaldehyde
Acrolein
Carbon monoxide
Carbon dioxide
Sulfur oxides
Nitrogen oxides
Nitrogen
Oxygen
Water
Methane
Ethane
Particulate
Others
Concentration /
wt %
_a
_a
_a
_a
_a
_a
_a
_a
_a
a
_a
_a
a
_a
_a
a
_a
a
_a
_a
Average
flow
rate,
kg/hr
5.2
1.8
0.4
0.15
_b
_b
_b
_b
_b
0.4
_b
_b
9.1
_b
_b
_b
_b
_b
1.8
_b
Emission
factor/
g/kg
0.71
0.24
0.05
0.02
_b
_b
b
b
_b
0.05
_b
_b
1.25
_b
_b
_b
_b
_b
0.25
_b
Not calculated because data lacking for one or more major
components.
3
Not reported in data source.
80
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Table 29. STORAGE TANK WORKING AND BREATHING LOSSES FOR A 5.9 x 104 METRIC TONS/YR
PHTHALIC ANHYDRIDE PLANT
Process
raw material
o-Xylene
Naphthalene
Species
o-Xylene
Phthalic anhydride
(crude)
Phthalic anhydride
(refined)
Naphthalene
Phthalic anhydride
(crude)
Phthalic anhydride
(refined)
Uncontrolled
emission
rate,
kg/hr
1.38
0.80
2.04
4.36
1.16
1.40
Uncontrolled
emission
factor,
gAg
0.19
0.11
0.28
0.60
0.16
0.19
Controlled
emission
rate,
kg/hr
0.014
0.008
0.020
0.044
0.012
0.014
Controlled
emission
factor ,
g/kg
0.002
0.001
0.003
0.006
0.002
0.002
Control
efficiency,
%
99
99
99
99
99
99
00
-------
for petrochemical losses from storage tanks which have been
formulated by the American Petroleum Institute.39"43 The
correlations give uncontrolled emission rates; the controlled
emission rates listed in Table 29 are based on a control
efficiency of 99%.44 The estimated accuracy of the empirical
correlations is ±10%.39~43 Calculations are presented in
the Appendix.
Emission control devices presently in use comprise conser-
vation vents on o-xylene and naphthalene tanks, and condensers
or sublimation boxes on crude and refined phthalic anhydride
tanks. Phthalic anhydride tanks may, alternatively, be vented
to the incinerator for control. However, it is common practice
to vent some or all of the storage tanks directly to the
atmosphere.
4. Flaker and Bagger Vent
The vent from the flaking and bagging operations (stream 33
in Figure 2; stream 26 in Figure 5) is a continuous source
"Evaporation Loss from Fixed Roof Tanks. American Petro-
leum Institute. New York. API Bulletin No. 2518. 1962.
38 p.
40Use of Variable Vapor Space Systems to Reduce Evaporation
Loss. American Petroleum Institute. New York. API
Bulletin No. 2520. 1964. 14 p.
H1Petrochemical Evaporation Loss from Storage Tanks.
American Petroleum Insittute. New York. API Bulletin
No. 2523. 1969. 14 p.
42Evaporation Loss from Floating Roof Tanks. American
Petroleum Institute. New York. API Bulletin No. 2517.
1962. 13 p.
4 Evaporation Loss in the Petroleum Industry - Causes and
Control. American Petroleum Institute. New York. API
Bulletin No. 2513. 1959. 57 p.
44Personal communication, R. G. Lunche and A. B. Netzley,
Los Angeles County Air Pollution Control District.
March 28, 1975.
82
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of particulate emissions. This stream, which contains
phthalic anhydride as the only contaminant, is ducted to a
cyclone separator or baghouse for recovery of the solid
product. For a 5.9 x 104 metric tons/yr plant, the uncon-
trolled emission rate for this stream is estimated to be
0.7 kg/hr of phthalic anhydride, with a corresponding emis-
sion factor of 0.1 g/kg.26 The controlled emission rate is
0.007 kg/hr, with a corresponding emission factor of 0.001
g/kg, assuming that a control efficiency of 99% is achieved
with a bag filter.44
5. Transport Loading Facility Vent
The liquid product transport loading facility vent (stream
37 in Figure 2; stream 31 in Figure 5) is a continuous source
of atmospheric emissions. The only contaminant in this
stream is phthalic anhydride. Using the emission factor
data listed in Reference 45, the uncontrolled emission rate
for this stream is estimated to be 3.3 kg/hr of phthalic
anhydride, based on an emission factor of 0.45 g/kg loaded,
a production rate of 5.9 x 10H metric tons/yr, and 100% of
product shipped in liquid form. A control efficiency of 99%
was assumed, based on the data in Reference 45. This yields
a controlled emission rate of 0.03 kg/hr and a controlled
emission factor of 0.005 g/kg phthalic anhydride produced.
The accuracy of these values is considered to be equivalent
to that for storage tanks, i.e., ±10% for uncontrolled
emissions.46
45Air Pollution Engineering Manual, 2nd Edition. Danielson,
J. A. (ed.). Environmental Protection Agency. Research
Triangle Park. Publication No. AP-40. May 1973. 987 p.
^Personal communication. W. Fitzgibbons, Standard Oil of
Ohio (SOHIO). June 23, 1975.
83
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6. Catalyst Storage Hopper Vents
The vents on the storage facilities for active and spent
catalyst are intermittent sources of emissions from
naphthalene based plants. The emissions consist of the fines
fraction (primarily particles <40 ym in diameter) of the
vanadium oxide catalyst, which is described in Table 15.
Both vanadium oxide and silica dusts are respiratory irri-
tants, and vanadium oxide can be toxic if taken internally.34
Emissions occur during catalyst transfer operations in which
the catalyst is conveyed pneumatically from the reactor
system to the storage hoppers. Cyclone separators are
employed on the hopper vents to recover the entrained catalyst
particles from the air stream.
The uncontrolled emission rate from the spent catalyst
storage vent in a 4.08 x lO4 metric tons/yr plant is 295 kg/
hr.37 The operation is intermittent with a total duration of
approximately 50 hr/yr. The uncontrolled emission factor is
therefore 0.36 g/kg. The controlled emission rate is 4.6
kg/hr, and the corresponding emission factor is approximately
0.005 g/kg. Thus, the control efficiency is 98.5%.
The uncontrolled emission rate from the active catalyst
storage vent in a 4.08 x 104 metric tons/yr plant is 22.7
kg/hr.37 The emissions occur an average of four to eight
times per year and have a duration of approximately 12 hours
per occurrence. Thus, the uncontrolled emission factor is
approximately 0.05 g/kg. The controlled emission rate is
2.3 kg/hr, and the corresponding emission factor is 0.005
g/kg. The control efficiency is therefore 90%.
The uncontrolled and controlled emission factors for the
combined catalyst storage vents are 0.41 g/kg and 0.01 g/kg,
respectively, resulting in a combined control efficiency of
97.5%.
84
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7. Fugitive Emissions
Fugitive emissions from phthalic anhydride manufacture
originate from a number of sources: pump seals, flanges,
valves, and compressor seals. In addition to these losses
that occur under normal operating conditions, operating
upsets can result in emissions of fluid from the heat-
transfer circuits associated with the switch condensers and
the product purification section of the plant. A typical
heat-transfer fluid used in phthalic anhydride plants is
Dowtherm A, a eutectic mixture of diphenyl oxide (73.5%) and
diphenyl (26.5%). This material has a very noticeable odor
which has been described as that of rose-geranium.14 Diphenyl
oxide has an odor threshold of between 0.01 ppm and 0.001 ppm
by volume.l4
The most frequently used organic heat-transfer fluids are
listed in Table 30 together with their compositions and
usable temperature ranges.16'17 Also listed are the thres-
hold limit values (TLV's).47 Of the fluids listed, Mobil-
therm Light® and Therminol 66® are known to be used in
phthalic anhydride plants.13 Emissions of these fluids
are in the form of aerosol mists, which reportedly settle
in the immediate vicinity of the source.13 It is estimated
that 95% of these emissions originate from the switch-
condenser heat-transfer circuit.13
47Threshold Limit Values for Chemical Substances and
Physical Agents in the Workroom Environment with Intended
Changes for 1975. American Conference of Governmental
Industrial Hygienists. Cincinnati. 1975. 97 p.
85
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Table 30. FREQUENTLY USED HEAT-TRANSFER FLUIDS
Name
Dowtherm A
Dowtherm E
Dowtherm G
Dowtherm H
Dowtherm J
Humbletherm 500
Mobiltherm Light
Mobiltherm 600
Mobiltherm 603
Therminol 44
Therminol 55
Therminol 60
Therminol 66
Therminol 77
Therminol 88
Therminol FR-1
Ucon 50-HB-280X
Composition
Diphenyl-diphenyl oxide
eutectic
o-Dichlorobenzene
Di- and tri-aryl ethers
Aromatic oil
Alkylated aromatic
Aliphatic oil
Aromatic oil
Alkylated aromatic
Paraffinic oil
Modified ester
Alkylated aromatic
Aromatic hydrocarbon
Modified terphenyl
Polyphenyl ether
Mixed terphenyl
Polychlorinated biphenyl
Ether of polyalkylene
oxide
Usable
temperature
range,
16 to 400
-18 to 260
-10 to 345
-10 to 290
-75 to 300
-20 to 315
-30 to 205
-20 to 315
-18 to 315
-50 to 220
-18 to 315
-50 to 315
-7 to 345
16 to 370
145 to 425
-4 to 315
-18 to 260
TLV,
g/m3
0.001
0.300
0.009
0.007
0.009
0.005
Composition and usable temperature data for most of the heat-transfer
fluids are reprinted with permission from Chemical Engineering, May 28,
1973, Copyright (c), McGraw-Hill, Inc., New York, N.Y. 10020
Other trade names include Thermex, Therm-S, Diphyl, and Therminol VP-1.
In the Badger-Sherwin-Williams process, product purification
is a batch operation. Hence, fugitive emissions can arise
from the batch filling and dumping of process vessels. In
addition, emissions of vanadium oxide catalyst dust may occur
during catalyst loading and unloading operations. Estimates
of fugitive emissions are summarized in Table 31.13'26 It
has been assumed that the heat-transfer fluid is Dowtherm A,
which is listed as diphenyl oxide, its major component.
86
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Table 31. FUGITIVE EMISSIONS FROM PHTHALIC ANHYDRIDE PLANTS
Compound
Phthalic anhydride
Maleic anhydride
Benzoic acid
Naphthoquinone
Diphenyl oxide
Vanadium oxide catalyst
r
o-Xylene
Naphthalene
Formaldehyde
Acetaldehyde
Phthalaldehyde
o-Tolualdehyde
Acrolein
Dihydroxynaphthalene
Combined hydrocarbons
Average
emission
rate,
kg/hr*
0.12
0.73
Emission
factor,
g/kg
0.016
0.10
For a 5.9 x 104 metric tons/yr plant.
Naphthalene based plants only.
Co-Xylene based plants only.
Does not include diphenyl oxide.
Note: Blanks indicate data not available,
8. Dual Thermal Incineration
Available data13'26 indicate that the best presently feasible
method of control utilizes direct thermal incineration of the
switch-condenser off-gas together with a secondary thermal
incinerator to treat the waste streams from the product puri-
fication section of the plant (see Section V.A). Typical compo-
sitions and emission rates for the latter unit are presented
in Table 32 for an o-xylene based plant.13 This unit treats
87
-------
Table 32. TYPICAL FLUE GAS COMPOSITION
FOR DUAL INCINERATOR
Production rate = 5.9 x 104 metric tons/yr
Temperature = 760°C
Gage pressure = 0 kPa
Component
Phthalic anhydride
Maleic anhydride
Benzoic acid
o-Tolualdehyde
Phthalaldehyde
Formaldehyde
Acetaldehyde
Acrolein
Carbon monoxide
Carbon dioxide
Sulfur oxides
Nitrogen oxides
Nitrogen
Oxygen
Water
Methane
Ethane
Particulate
Others
Total
Concentration ,
wt %
0.010
0.0037
0.0012
0.11
5.55
0.011
55.47
8.32
30.51
0.011
100.0
Average
flow
rate,
kg/hr
0.8
0.3
0.1
9.1
455.
0.9
4,545.
682.
2,500.
0.9
8,194.
Emission
factor,
g/kg
0.11
0.04
0.0125
1.25
62.6
0.125
625.
93.8
344.
0.125
1,127.
Note: Blanks indicate data not reported.
88
-------
all of the waste streams from the product purification section
of the plant, and reportedly achieves a control efficiency
of 99% for combined organics. The applicability of such a
unit to naphthalene based plants is uncertain since product
purification is a batch operation in these plants. However,
no fundamental barrier to its use in naphthalene based plants
is apparent.
C. ENVIRONMENTAL EFFECTS
1. Definition of a Representative Source
For the purpose of assessing the source severity, a repre-
sentative o-xylene based phthalic anhydride plant is defined
to be one using the BASF process and having a production
capacity of 5.9 x 10k metric tons/yr. The BASF process is
specified because it is the newest and most widely used
technology, accounting for 79% of the o-xylene based pro-
duction in 1974.3'4 The standard size BASF plant has two
production trains of two reactors each, and has a capacity
of 5.9 x 104 metric tons/yr. The seven o-xylene based
plants operating in the United States range in capacity
from 1.59 x lO4 to 7.94 x 104 metric tons/yr with a mean
value of 4.28 x 104 metric tons/yr.
A representative naphthalane based phthalic anhydride plant
is defined to be one using the Badger-Sherwin-Williams pro-
cess and having a production capacity of 5.9 x 104 metric
tons/yr. The Badger-Sherwin-Williams process is the dominant
fluid-bed technology and accounted for 73% of the naphthalene
based production in 1974.3/4 There is no standard size for
the Badger-Sherwin-Williams fluid-bed reactors. Hence, the
representative source capacity was chosen so as to place
the source severity calculations on the same basis as that
used for o-xylene based production. The three naphthalene
89
-------
based plants range in size from 4.08 x 101* to 6.8 x 101* metric
tons/yr with a mean production capacity of 4.99 x 104 metric
tons/yr.
The source severity is assessed on the basis that the best
available control technology is applied to the representative
source. This implies that the switch-condenser off-gas is
controlled by direct thermal incineration and that a secondary
thermal incinerator is employed to treat all of the waste
streams from the product purification section of the plant.
(See Section V.A.) The dual thermal incineration system is
currently used in two of the four plants employing the BASF
process, and will probably be installed in other plants in
the future. It is also assumed that all storage tank vents,
as well as the transport loading facility vent, are fully con-
trolled. In addition, the flaker and bagger vent is assumed
to be equpped with a suitable bag filter.
2. Emission Factors
Emission factors for an o-xylene based plant equipped with a
dual incineration control systemare given in Table 33. The
data were obtained from References 13 and 26, except as noted.
The control efficiencies of the two incinerators were measured
only for total organic material. In order to obtain controlled
emission factors of individual organic species it was assumed
that they were controlled with this same efficiency. Error
bounds on the emission factors were estimated wherever possi-
ble. The bounds on uncontrolled emission factors for the two
incinerators were taken directly from Reference 13. Those
for storage tanks and transport loading were obtained from
References 39-43, and Reference 46, respectively. The bounds
on controlled emission factors were taken to be somewhat
higher in order to reflect the uncertainty in the control
efficiencies of individual species. The threshold limit
values (TLV's of the individual species, as given in Refer-
ence 47, are also listed in Table 33.
90
-------
Table 33. EMISSION FACTORS FOK o-XYLENE BASED PHTHALIC ANHYDRIDE PLANTS
Species
Partioulate
Main process incinerator
Secondary incinerator
Flaker and bagger
Sultur oxides
Main process incinerator
Nitrogen oxides
Main process incinerator
Secondary incinerator
Carbon monoxide
Main process incinerator
Secondary incinerator
Maleic anhydride
Main process incinerator
Secondary incinerator
Phthalic anhydride
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
Benzoic acid
Main process incinerator
Secondary incinerator
Diphenyl oxide
Fugitive emissions
o-Xylene
Storage tanks
Formaldehyde
Main process incinerator
Secondary incinerator
Acetaldehyde
Main process incinerator
Secondary incinerator
Phthalaldehyde
Main process incinerator
Secondary incinerator
o-Tolualdehyde
Main process incinerator
Secondary incinerator
Acrolein
Main process incinerator
Secondary incinerator
Total hydrocarbons
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
TLV,
g/n>3
0.010
0.813
0.009
0.055
0.001
0.006
0.050
0.001
0.435
0.003
0.180
J
J
0.00025
0.067
T
Emission factor, g/kg
Uncontrolled
_ a
^
0.10
5.0 ± 25%
_
— C
125.0 ± 20%
_ c
52.0 ± 20%
3.75 ± 83%
15.6 ± 20%
10.6 ± 53%
0.28 ± 10%e>1
0.10
0.45 ± 10%g
3
3.12 ± 20%
1.25 ± 50%
0.016
p
0.19 ± 10%
h i
n ^ U J 1
" a
a
"* a
a
a
a
-
72.8 ± 30% ,
18.8 ± 60% '
0.47 ± 10%
0.1 g
C.459
0.116
Controlled
0.25 ± 50%
0.125 ± 50%
0.001
5.0 + 25%
1.25 ± 50%
0.125 + 25%
0.125 ± 50%
1.25 ± 50%
1.82 ± 25%
0.038 ± 90%
0.545 ± 25%
0.106 ± 60%
0.003 ± 20%
0.001
0.005 ±h20%9
n
0.109 ± 25%
0.0125 t 55%
.
-
0.002 ± 20%
i
Confrol
efficiency. %
- .
99D
0
99.9
-
A
96.5°
99d
,
96. ,5
99b
99b
99b
9q9
o
96ti5
99
b
99
A
0.0741 a 96.^"
-
a
a
"a
a
a
a
"a
2.6 ± 30%
0.16 ± 60%
0.005 ± 20%
0.001 q
0.005y h
96.5
99 b
99 D
992
99
Data not available.
Estimate based on data from
Reference 44.
CNo emissions generated in uncontrolled
process.
Assumed equal to va!ue measured for
total organics in Reference 13.
Calculated using empirical correlations
given in References 39-43.
Value is for refined product storage
cnly; crude product storage tanks are
vented to the main process incinerator.
"value for loading racks given in
Reference 45.
Fugitive emissions are lot controlled.
1Total aldehydes reported as formaldehyde
in Reference 44.
JTLV not defined.
klncludes all non-methane organic species.
Includes 3.2 g/kg unspecified organic-
residues.
91
-------
Emission factors for a naphthalene based plant equipped with
a dual incineration control system are presented in Table 34.
The data were obtained from Reference 26, except as noted.
It was assumed that this control system could be applied to
a naphthalene based plant without having its control efficiency
altered. It was also assumed that the particulate and nitro-
gen oxides emissions from the two incinerators would be the
same as the corresponding values for an o-xylene based plant.
Error bounds for emission factors from the two incinerators
were assigned on the basis of (1) the corresponding values
for an o-xylene based plant; (2) the fact that the accuracv
of the data for naphthalene based production is believed to
be generally poorer than that for o-xylene based production;
and (3) the ranges for uncontrolled emission factors given
in Table 22. Error bounds on emission factors for storage
tanks and transport loading are the same as those for o-xylene
based production.
3. Source Severity
In order to obtain a quantitative measure of the hazard po-
tential of phthalic anhydride production, the source severity,
S, is defined as:
S = (1)
where x is the maximum time-averaged ground level concen-
max
tration of each pollutant emitted from a representative plant,
and F is defined as a primary ambient air quality standard
for criteria pollutants (particulate, SO , NO , CO and hydro-
X X
carbons) , while for non-criteria pollutants,
F = TLV- 8/24 -0.01, g/m3
The factor 8/24 adjusts the TLV for continuous rather than
workday exposure, and the factor of 0.01 accounts for the
fact that the general population is a higher risk group than
healthy workers.
92
-------
Table 34.
EMISSION FACTORS FOR NAPHTHALENE BASED
PHTHALIC ANHYDRIDE PLANTS26
Species
Particulate
Main process incinerator
Secondary incinerator
Flaker and bagger
Nitrogen oxides
Main process incinerator
Secondary incinerator
Carbon monoxide
Main process incinerator
Secondary incinerator
Phthalic anhydride
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
Maleic acid
Main process incinerator
Secondary incinerator
Benzoic acid
Main process incinerator
Secondary incinerator
Naphthoquinone
Main process incinerator
Secondary incinerator
Naphthalene
Storage tanks
TLV,
g/m3
0.010
0.009
0.055
0.006
0.001
0.050 J
0.0004k
0.050
Emission factor, g/kg
Uncontrolled
a
-
0.10
-
50.5 ±C50%
-
20.4 ± 40%
9.8 ± 70% ,
0.35 ± 10%e'T
0.10
0.45 ±a!0%9
-
7.0 + 200% 1
4.9 ± 80%
1.56 ±a40%
-
0.69 ± 40%
6.6 ± 70%
p
0.60 ± 10%
Controlled
0.25 ± 70%
0.125 ± 70%
0.001
1.25 ± 70%
0.125 ± 40%
0.05 ± 70%
1.25 ± 70%
0.71 ± 50%
0.10 ± 80%
0.0004 ± 20%
0.001
0.005 ±h20%9
-
0.24 + 200% 1
0.05 ± 90%
0.05 ±,50%
d
0.02 ± 50%
0.07 ± 80%
0.006 ± 20%
Control
efficiency, %
- .
99
99.9
-
A
96 5 d
"h
"b
99b
99 9
•
96y5d
99°
A
96.5°
96^,5
99
h
99°
Data not available.
Estimate based on data from Reference 44.
No emissions generated in uncontrolled process.
Assumed equal to value measured for total organics in Reference 13.
Calculated using empirical correlations given in References 39-43.
Includes both refined and crude product storage tanks.
Value for loading racks given in Reference 45.
Fugitive emissions are not controlled.
Uncontrolled emission factor of 7.0 g/kg, obtained from Reference 26, is believed to
be low; compare Table 22.
Estimate based on the value of 0.080 for benzene.
k
TLV for naphthoquinone assumed equal to the value for quinone.
93
-------
Table 34 (continued). EMISSION FACTORS FOR NAPHTHALENE
BASED PHTHALIC ANHYDRIDE PLANT26
Species
Vanadium oxide catalyst
Catalyst storage
Fugitive emissions
Diphenyl oxide
Fugitive emissions
Forma Idehyde
Main process incinerator
Secondary incinerator
Ace ta Idehyde
Main process incinerator
Secondary incinerator
Phthalaldehyde
Main process incinerator
Secondary incinerator
o-Tolualdehyde
Main process incinerator
Secondary incinerator
Acrolein
Main process incinerator
Secondary incinerator
Dihydroxynaphthalene
Main process incinerator
Secondary incinerator
Total hydrocarbons
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
TLV,
0.00056
0.001
0.003
0.180
-h
_n
0.00025
n
0.067
Emission factor, g/kg
Uncontrolled
0.41
a
0.016
2 -i b , in
a
a
a
-
a
a
"a
"
a
~a
a
"a
3.18 + 79%
- 35%
26.5 ± 70%P
0.95 ± 10%
0'.459
0.116
Controlled
0.01
_a
_
0.0741"
a
a
"a
-
a
a
~a
a
"a
~
a
"a
1.09 + 85%
- 40%
0.27 ± 80%
0.01 ± 20%
0.001
0.0059 h
_»
Control
efficiency, %
97.5
j
96. 5d
96.5
99b
nn b
99 g
99y
Data not available.
Estimate based on data from Reference 44.
Assumed equal to value measured for total organics in Reference 13.
Fugitive emissions are not controlled.
Calculated using the rule for mixtures given in Reference 47, the catalyst composition
given in Table 15, and the following individual TLV's: V205, 0.00089 g/m3; Sib2, 0.0003
g/m3 for total dust, respirable and nonrespirable; S03, 0.013 g/m3. The TLV for V205
was obtained by multiplying the listed value of 0.0005 g/m3 V205 as V by the factor
(182 g V205)/(102 g V) = 1.78 In lieu of other information, the TLV of K2S01( was
assumed to be large compared with those of the other components. Thus,
TLV
catalyst 0.09 0.5 0.12
0.00089 0.0003 0.013
0.00056 g/m3
n
Total aldehydes reported as formaldehyde in Reference 44.
TLV not defined.
Includes all organic species.
Includes 5.2 g/kg unspecified organic residues.
Thus, the source severity represents the ratio of the maxi-
mum mean ground level exposure to the hazard level of ex-
posure for a given pollutant.
94
-------
The maximum ground level concentration, x / is calculated
in 3.x
according to Gaussian plume dispersion theory:
v
x
max 2 -
TTH eu
where Q = mass emission rate, g/sec
u = average wind speed, m/sec
H = effective emission height, m
e = 2.72
Equation (2) yields a value for a short-term averaging time
during which the Gaussian plume dispersion equation is valid.
The short-term averaging time was found to be 3 minutes in a
study of published data on lateral and vertical diffusion.^8
For a continuously emitting source, the maximum mean ground
level concentration for time intervals between 3 minutes and
24 hours can be estimated from the relation:49
'to
0. 17
xmax xmax t
where t = the averaging time
tQ = the short-term averaging time (3 min.)
For non-criteria pollutants, the averaging time, t, is 24
hours. For criteria pollutants, the averaging times are
those used in the definition of the primary ambient air
quality standards. The only exception is NO , for which the
X
48Nonhebel, G. Recommendations on Heights for New Industrial
Chimneys. Journal of the Institute of Fuel. 33:479-511,
July 1960.
49 Turner, D. B. Workbook of Atmospheric Dispersion Estimates,
U.S. Department of Health, Education, and Welfare, Public
Health Service. Cincinnati. Publication No. 999-AP-26.
1969. 64 p.
95
-------
primary standard averaging time is one year. Since Equation
(3) is not valid for averaging times of this magnitude, the
calculation of x for NO is based on Equation (5.13) of
max x
Reference 49, which estimates the annual average ground level
concentration .
Insertion of the national average wind speed of 4.5 m/sec into
the above equations leads to the severity factor equations
listed in Table 35. The emission heights which were used in
the calculations are given in Table 36. The heights for the
two incinerators were obtained from Reference 13, that for the
f laker and bagger from Reference 50, and the others were
estimated. The emission rates, Q, were obtained from the
controlled emission factors in Tables 33 and 34. The resulting
severity factors are tabulated in Tables 37 and 38 for o-xylene
and naphthalene based plants, respectively. In these calcula-
tions, it was assumed that Gaussian plume dispersion theory is
equally valid for all emissions, irrespective of their chemical,
physical, or topological characteristics.
The largest value of the severity factor in Tables 37 and 38
is 18.5 for diphenyl oxide. This value is based on the
assumption that Dowtherm A heat-transfer fluid is used in the
plant. However, it is clear from the TLV's listed in
Table 30 that the severity factor for this emission is highly
dependent on the particular fluid used. Thus, assuming the
same emission rate, the severity factor would be 37.0 for
Therminol FR-1® and 0.06 for Dowtherm E.
The above severity factors for diphenyl oxide emissions and
vanadium oxide catalyst emissions from catalyst storage
50Personal communication, L. B. Evans, U.S. Environmental
Protection Agency (Data originally supplied by Stepan
Chemical Company). June 12, 1975.
96
-------
Table 35. SOURCE SEVERITY EQUATIONS
Pollutant
Particulate
SO
x
NO
x
Hydrocarbons
CO
All others
S (dimensionless)
70 QH~2
50 QH-2
315 OH'2-1
162.5 QH~2
0.78 QH~2
5.5 QH~2 (TLV)
Q = emission rate, g/sec
H = emission height, m
TLV = threshold limit value, g/m3
Table 36. EMISSION HEIGHTS FOR REPRESENTATIVE SOURCE
Source of emissions
Main process incinerator
Secondary incinerator
Storage tanks
Flaker and bagger
Transport loading
Fugitive emissions
Catalyst storage
Emission
height,
m
61.0
30.5
15.2
6.1
6.1
3.1
12.2
facilities were calculated by treating these intermittent
sources as continuous sources with their respective annual
emission rates. Severities calculated with emission rates
based on the average duration of these emissions would be
considerably higher. For instance, S = 216 for vanadium
oxide catalyst emissions. Although the duration of the
diphenyl oxide emissions is not known, the severity calcula-
ted on this basis would be correspondingly higher.
97
-------
Table 37. SOURCE SEVERITY FACTORS FOR A REPRESENTATIVE O-XYLENE BASED PHTHALIC ANHYDRIDE PLANT
Compound
Particulate
Sulfur oxides
Nitrogen oxides
Carbon monoxide
b
Total hydrocarbons
Phthalic anhydride
Maleic anhydride
Benzoic acid
Diphenyl oxide
o-Xylene
Formaldehyde
Acetaldehyde
Phthaldehyde
o-Tolualdehyde
Acrolein
Source severity
Main process
incinerator
0.0095
0.14
0.14
0.000053
0.23
0.28
5.4
0.0065
a
a
d
0.074
c
c
c
c
Secondary
incinerator
0.019
a
\A
0.061
0.0021
0.056
0.20
0.45
0.0030
a
a
c
c
c
c
c
Storage
tanks
a
a
u
a
a
0.0071
0.024
a
a
a
0.00022
a
a
a
a
a
Flaker and
bagger
0.0038
a
vl
a
a
0.0088
0.050
a
a
a
a
a
a
a
a
a
Transport
loading
a
a
u
a
a
0.044
0.24
a
a
a
a
a
a
a
a
a
Fugitive
emissions
a
a
u
a
a
4.0
c
c
c
18.5
C
C
C
C
C
C
10
00
No emissions.
Includes all non-methane organic species.
"Data not available.
Total aldehydes reported as formaldehyde.
-------
Table 38. SOURCE SEVERITY FACTORS FOR A REPRESENTATIVE NAPHTHALENE BASED
PHTHALIC ANHYDRIDE PLANT
VD
Compound
Particulate
Nitrogen oxides
Carbon monoxide
b
Total hydrocarbons
Phthalic anhydride
Maleic anhydride
Benzoic acid
Naphthoquinone
Diphenyl oxide
Vanadium oxide
catalyst
Naphthalene
Formaldehyde
Acetaldehyde
Phthalaldehyde
o-Tolualdehyde
Acrolein
Dihydroxynaphthalene
Source Severity
Main
process
incinerator
0.0095
0.14
0.000021
0.10
0.36
0.72
0.0030
0.15
a-
a
a
d
0.074
c
c
\*
c
r
\*
c
\*
Secondary
incinerator
0.019
0.061
0.0021
0.095
0.20
0.60
a
2.1
a
a
c
c
r
Vrf
c
r
\*
r'
\*
Storage
tanks
a
a
a
0.014
0.032
a
a
u
a
0.0058
a
a
a
a
a
Flaker
and
bagger
0.0038
a
0.0088
0.050
a
a
a
a
a
a
a
a
Transport
loading
a
a
0.044
0.24
a
a
a
a
u
a
a
a
a
a
a
a
a
Catalyst
storage
a
a
a
a
a
a
a
a
1.4
a
a
a
a
a
a
a
Fugitive
emissions
a
a
w
a
4.0
c
c
c
c
18.5
c
c
c
c
c
c
c
c
No emissions.
tancludes all non-methane organic species.
"Data not available
Total aldehydes reported as formaldehyde.
-------
4 . Industry Contribution to Total Atmospheric Emissions
The mass emissions of criteria pollutants (particulate, SO ,
X
NO , CO, and hydrocarbons) resulting from phthalic anhydride
X
production were calculated using the controlled emission
factors from Tables 33 and 34 together with the production
capacity data from Table 20. The appropriate emission fac-
tor was multiplied by the production capacity nationwide and
for each state in which phthalic anhydride plants are located
The total mass emissions from all sources nationwide and for
each state were obtained from Reference 51. The percent
contributions to the total emissions resulting from phthalic
anhydride production were computed using these values. The
results are presented in Table 39 for nationwide emissions,
and Table 40 for individual state emissions.
5. Affected Population
A measure of the population which is exposed to a high
contaminant concentration due to a representative phthalic
anhydride plant can be obtained as follows . The values of
x for which
= 0.1 or 1.0 (4)
r
are determined by iteration. The value of x(x)f tne annual
mean ground level concentration, is computed from the
equation : 4 9
X(x) =
a ux
z
A /_5\2
2 I a.
(5)
511972 National Emissions Report. U.S. Environmental
Protection Agency. Research Triangle Park. Publication
No. EPA-450/2-74-012. June 1974.
100
-------
Table 39.
NATIONWIDE EMISSIONS OF CRITERIA POLUTANTS FROM PHTHALIC
ANHYDRIDE INDUSTRY (CONTROLLED EMISSIONS)
Material
emitted
Carbon monoxide
Sulfur oxides
Particulates
Nitrogen oxides
Hydrocarbons
Source
All sources
Phthalic anhydride production
o-Xylene based
Naphthalene based
All sources
Phthalic anhydride production
o-Xylene based
Naphthalene based
All sources
Phthalic anhydride production
o-Xylene based
Naphthalene based
All sources
Phthalic anhydride production
o-Xylene based
Naphthalene based
All sources
Phthalic anhydride production
o-Xylene based
Naphthalene based
Emissions,
metric tons/yr
97.6 x 106a
608
413
195
30.2 x 106a
1,500
1,500
0
18.0 x 106a
169
113
56
22.4 x lO63
619
413
206
25.3 x 106a
1,089
865
224
% Contribution
100.
0.00062
0.00042
0.00020
100.
0.0050
0.0050
0
100.
0.00094
0.00063
0.00031
100.
0.0028
0.0018
0.0009
100.
0.0043
0.0034
0.0009
o
aData obtained from Reference 51.
^Includes all non-methane organic species.
-------
Table 40.
EMISSIONS OF CRITERIA POLLUTANTS FROM PHTHALIC ANHYDRIDE INDUSTRY
BY STATE (CONTROLLED EMISSIONS)
Material
emitted
Carbon monoxide
Sulfur oxides
Particulate
Nitrogen oxides
Hydrocarbons
State
California
Illinois
Louisiana
New Jersey
Pennsylvania
Texas
California
Illinois
Louisiana
New Jersey
Pennsylvania
Texas
California
Illinois
Louisiana
New Jersey
Pennsylvania
Texas
California
Illinois
Louisiana
New Jersey
Pennsylvania
Texas
California
Illinois
Louisiana
New Jersey
Pennsylvania
Texas
Total g
emissions,
106 metric
tons/yr
8.25
6.43
5.65
2.88
3.74
6.91
0.39
2.05
0.17
0.46
2.94
0.75
1.01
1.15
0.38
0.15
1.81
0.55
1.67
0.98
0.42
0.49
3.02
1.31
2.17
1.83
1.92
0.82
0.89
2.22
Emissions from
phthalic anhydride
plants,
metric tons/yr
53
141
56
134
142
81
192
510
204
295
0
295
14
38
15
38
41
22
53
141
56
137
149
81
111
295
118
231
162
170
Phthalic
anhydride
contribution, %
0.0006
0.0022
0.0010
0.0047
0.0038
0.0012
0.0492
0.0249
0.1200
0.0641
0.0
0.0393
0.0014
0.0033
0.0039
0.0250
0.0023
0.0040
0.0032
0.0144
0.0133
0.0280
0.0049
0.0062
0.0051
0.0161
0.0061
0.0282
0.0182
0.0077
Data obtained from Reference 51.
^Includes all non-methane organic species.
-------
where Q = emission rate, g/sec
H = effective emission height, m
x = downwind distance from source, m
u = average wind speed (4.5 m/sec)
a = vertical dispersion coefficient, m
z
For atmospheric stability class C (neutral conditions) ,
a is given by:52
a = 0.113 x°-911 (6)
z
The affected area is then computed as
A = Tr(x22 - xL2) , km2 (7)
where xj and x2 are the two roots of Equation (4).
The (capacity weighted) mean population density, D , is
calculated for each plant type (o-xylene and naphthalene)
as follows:
E CIDP.
Dt> = —^=Tn ' persons/km2 (8)
where C. = production capacity of plant i
Dp = county population density for plant i
The product A-D is designated the "affected population."
52Eimutis, E. C., and M. G. Konicek. Derivations of
Continuous Functions for the Lateral and Vertical Atmo-
pheric Dispersion Coefficients. Atmospheric Environment,
£:859-863, 1972.
103
-------
Table 41. AFFECTED POPULATION
(number of persons)
Compound
Sulfur oxides
Main process incinerator
Nitrogen oxides
Main process incinerator
Total hydrocarbons
Main process incinerator
Fugitive emissions
Phthalic anhydride
Main process incinerator
Secondary incinerator
Transport loading
Maleic anhydride
Main process incinerator
Secondary incinerator
Diphenyl oxide
Fugitive emissions
Formaldehyde
Main process incinerator
Naphthoquinone
Main process incinerator
Secondary incinerator
Vanadium oxide catalyst
Catalyst storage
o-Xylene based plant
No. of persons
where
X/F > 1.0
0
0
0
40
0
0
0
44,000
0
300
0
a
a
_a
No. of persons
where
X/F > 0.1
6,700
5,600
9,600
500
19,000
3,100
140
525,000
8,800
3,400
15,000
_a
_a
_a
Naphthalene based plant
No. of persons
where
X/F > 1.0
_a
0
0
6
0
0
0
0
0
50
0
0
500
40
No. of persons
where
X/F > 0.1
_a
870
0
77
4,100
460
22
9,200
1,800
540
2,300
1,300
7,000
650
No emissions.
-------
The affected population was computed for each compound and
each source for which the severity factor, S, exceeds 0.1.
The results are presented in Table 41. The mean population
density for O-xylene based plants is 1,667 persons per
square kilometer, and for naphthalene based plants it is
261 persons per square kilometer. For x/F - 0.1, the total
number of persons affected by a representative o-xylene
based plant is 525,000 persons, while the total number
affected by a representative naphthalene based plant is
9,200 persons. For 7/F - 1-0, the values are 44,000 persons
for an o-xylene based plant and 500 persons for a naphthalene
based plant.
6. Growth Factor
In 1973, 4.658 x 105 metric tons of phthalic anhydride was
produced in the United States.53 As discussed in Section VI,
production is expected to total 4.99 x 105 metric tons in
1978. Thus, assuming that the same level of control technology
exists in 1978 as existed in 1973, the emissions from the
phthalic anhydride industry will increase by 7% over that
period; i.e.:
Emissions in 1978 _ 4.99 x 105
Emissions in 1973 ~ 4.658 x 105 ~
3Naphthalene Feedstock Outlook Mixed. Chemical and
Engineering News. _52:14-17, July 8, 1974.
105
-------
SECTION V
CONTROL TECHNOLOGY
A. STATE OF THE ART
At the present time, all phthalic anhydride plants employ
pollution control devices to treat the switch-condenser
off-gas/ which constitutes the greatest potential source of
air pollution from phthalic anhydride manufacture. The
control devices in use are water scrubbers and/or inciner-
ators, either thermal or catalytic. The large air to feed
ratio, particularly in o-xylene based plants, makes the
scrubber-incinerator combination more economical than
incineration alone due to the large volume of gas that must
be handled.
Organic removal efficiencies of up to 98% to 99% in the
scrubber and 99.9% in the incinerator are achieved.38
However, carbon monoxide and sulfur oxides are not controlled
and are emitted to the atmosphere via the scrubber vent.
Further treatment of the scrubber vent gas (e.g., by a CO
boiler or gas adsorption) would be expensive due to the
low concentration (approximately 0.6% by weight) of pollu-
tants in this stream. The principal advantage of direct
incineration of the switch-condenser off-gas is that it
allows the carbon monoxide to be controlled. Control
efficiencies of 99.9% can be achieved for this contaminant
106
-------
with an organic conversion efficiency of 96.5%.13 The
sulfur oxides are again vented to the atmosphere, however.
The scrubber and/or incinerator can also be used to control
the waste streams from the product purification section of
the phthalic anhydride plant. Alternatively, a separate
control device may be employed for this purpose. The best
control system presently in use employs direct thermal
incineration of the switch-condenser off-gas together with
a second thermal incinerator that handles the waste streams
from the product purification section. Water scrubbers are
also used in some plants to treat some of the latter streams.
The dual incineration system provides better overall emissions
control than the scrubber-incinerator system or other systems
being used for the following reasons:
(1) The removal efficiency for total organics is 96.5%
for the dual incineration system being used at two
phthalic anhydride plants. The scrubber-incinerator
system is capable of achieving 97% removal of total
organics in existing commercial plants, but the dual
incineration system has a better potential for
increased organics removal through increased incin-
eration temperatures in the existing plants.
Theoretical calculations indicate that the organics
removal efficiency will be 99% when operating at a
temperature of approximately 860°C instead of
760°C.5lf The scrubber-incinerator system does not
demonstrate this flexibility in existing plants.
54Chi, C. T., and T. W. Hughes. Technical and Economic
Evaluation of Phthalic Anhydride Plant Air Pollution Con-
trol. Monsanto Research Corporation. Dayton. Prelimi-
nary Draft Report. U.S. Environmental Protection Agency,
Contract 68-02-1320, Task 25. August 1976.
107
-------
However, increasing the flame temperature in the
dual incineration system by 100°C will increase
the NO emissions by about 15%. The NO source
x x
severity at 760°C is 0.14; at 860°C it will be
0.16 (0.14 x 1.15).
(2) Direct thermal incineration of the switch-condenser
off-gas removes 99% of the carbon monoxide. The
scrubber incinerator system cannot control carbon
monoxide emissions since the incineration is per-
formed on the scrubber purge liquid (blowdown)
and not on the scrubber vent gas. The carbon
monoxide source severities for the dual incinera-
tion system and the scrubber-incineration system
on an o-xylene based plant are 0.000053 and 0.21,
respectively. For a naphthalene based plant, the
severities are 0.000021 for dual incineration and
0.084 for the scrubber-incineration combination.
The percent contribution to nationwide carbon
monoxide emissions is 0.002% for dual incineration
versus 0.047% for the scrubber-incinerator system.
The contributions to total carbon monoxide emissions
in New Jersey (the largest of the statewide contri-
butions) are 0.0047% for the dual incineration
system and 0.43% for the scrubber-incinerator
combination.
(3) The use of a secondary (dual) incinerator for
control of waste streams from the product puri-
fication section of the plant is preferable to use
of a secondary scrubber to control these streams.
The dual incinerator has a high (99%) control
efficiency for organics and does not generate an
additional liquid waste stream requiring disposal
as does scrubbing.
108
-------
(4) The use of a secondary incinerator for the product
purification waste streams is also superior, from
an operating standpoint, to using the main process
incinerator for control of these streams. The
product purification waste streams vary in flow
rate, physical properties, and composition from
the switch-condenser off-gas. The secondary in-
cinerator is designed for optimal control of
product purification wastes while the main process
incinerator is designed for optimal control of the
switch-condenser off-gas.
Emissions from p_-xylene storage tanks are controlled by the
use of conservation vents. Phthalic anhydride storage tanks
are controlled by means of condensers or sublimation traps,
or by venting to the incinerator. Naphthalene storage tanks
can also be controlled by means of conservation vents. In
most plants, however, either some or all of the storage tanks
are vented directly to the atmosphere.
Cyclones and baghouses are used to control the emission of
phthalic anhydride dust from the flaking and bagging oper-
ations. In the case of naphthalene based plants, cyclones
are also used on the new and spent catalyst storage hopper
vents to control the emission of vanadium oxide catalyst
dust during catalyst transfer operations.
B. PROCESS MODIFICATIONS
A number of modifications to the basic phthalic anhydride
process have been proposed in the recent literature. Since
these modifications will potentially have an effect on
pollution control methodology with respect to phthalic
anhydride production, they are discussed in this section.
109
-------
1. The Rhone-Progil "Chauney '71" Process
A new process for the production of phthalic anhydride from
o-xylene has been developed by Rhone-Progil in France. 55 A
1.5 x 104 metric tons/yr plant has been in operation since
1971 in Aisne, France, and the process has been licensed to
Resins/ Inc. (Philippines) and to Reposa (Spain). The flow
diagram for the new process is very similar to that for the
BASF process (Figure 2), with the following differences:
• No sulfur or sulfur dioxide is required in the
reactor feed to maintain catalyst activity. Hence,
this source of pollution is eliminated.
• The switch-condenser off-gas is controlled by
means of a catalytic incinerator without an inter-
mediate scrubber. This control method is econo-
mically more attractive here than with the BASF
process due to a lower air to o_-xylene feed
ratio. (Specific figures have not been published.)
• The liquid waste stream from the distillation
section is further processed to produce solid
pellets, which are disposed of by burning.
It is claimed55 that the exhaust gases from this process
"meet all existing and forecasted regulations."
2. Maleic Anhydride Recovery
The UCB (Brussels, Belgium) process for the recovery of
maleic anhydride from the scrubber liquid waste stream is
55Zimmer, J. C. New Phthalic Anhydride Process. Hydro-
carbon Processing. 5_3_: 132-134, November 1974.
110
-------
described in Reference 56. A similar process has been
developed by BASF.57 Instead of being sent to the inciner-
ator for disposal, the scrubber liquid purge stream is sent
to the continuous maleic anhydride recovery system shown
schematically in Figure 9. The recovery process can be
divided into three steps: concentration, dehydration, and
distillation. The first step removes the organic compounds
from the scrubber purge stream in two stages. In the first
stage, part of the water is evaporated at a closely controlled
temperature to avoid any crystallization of organics. In
the second stage, the remaining water is flashed off in an
evaporator, leaving a bottom stream of liquid organics.
The water removed in both stages, which contains some residual
organic material, is condensed and recycled to the scrubber.
In the second step, the liquid organic stream is sent to a
dehydration unit where the organic acids are thermally
dehydrated to the anhydrides. The maleic anhydride and
dehydration water are distilled off and separated by a
selective condensation process. The water is recycled to
the scrubber, while the crude maleic anhydride is sent to
the vacuum distillation column for purification (Step 3).
The refined maleic anhydride (97.7%) is taken overhead and
the bottom stream from the distillation column is recycled
to the dehydrator. If maleic anhydride of greater purity
is required, a further purification step can be added.
The recovery of the water is also important because sodium
ion-free water must be used in the process. Sodium ions
catalyze the polymerization of maleic anhydride, and this
reaction can result in an explosion.
56Weyens, E. Recover Maleic Anhydride. Hydrocarbon
Processing. S3:132-134, November 1974.
57Wirth, F. Recover MA from PA Scrubber Water. Hydro-
carbon Processing. 5_4_: 107-108, August 1975.
Ill
-------
-CONCENTRATION *f« DEHYDRATION *|« Dl STILLATION
FROM PAN SCRUBBER
If
3
E
5
P
I
J
^
RESIDUES TO BURNER
UJ
o
k 1
L-,-
= 3
o _
< t-
TO PAN SCRUBBER
MALEIC ANHYRIDE TO STORAGE
Figure 9. Maleic anhydride recovery process56
-------
The major components in the liquid waste stream from the
dehydrator are phthalic anhydride, benzoic acid, citraconic
anhydride, and maleic anhydride. This stream can be disposed
of in a conventional burner. Hence, a phthalic anhydride
plant incorporating this modification does not require an
incinerator for waste disposal.
3. Direct Production of Phthalates
The single largest use of phthalic anhydride is in the
production of ortho-phthalates, which are used as plasti-
cizers. Phthalates are manufactured by reacting phthalic
anhydride with the desired alcohol in the presence of
sulfuric acid, which catalyzes the reaction. Wu and Maa58
have suggested a modification of the phthalic anhydride
process, by which the phthalate, rather than phthalic
anhydride, is produced. A schematic flow diagram of the
proposed process is shown in Figure 10. The reactor gases
(stream 5), instead of being sent to switch-condensers, are
fed to an absorption tower where they are contacted with
an alcohol-sulfuric acid mixture (stream 6). The phthalic
anhydride is absorbed in the alcohol and reacts to form the
monoester. Thus, separation of phthalic anhydride from the
gas mixture and esterification to monoester are carried out
in a single step. The monoester-alcohol-sulfuric acid
mixture (stream 8) is sent to a fractionation tower where
the reaction proceeds further to form the diester. The
phthalate is taken off as the bottom stream (stream 9) from
the fractionation tower, while the overhead stream (stream
10) is condensed and sent to a separator where the water
formed in the esterification reaction is removed. The
58Wu, W. H., and J. R. Maa. Make Phthalates Direct,
^Hydrocarbon Processing. 5^:117-118, April 1974.
113
-------
PROCESS (1
A o XYLENE STORAGE
B S02 STORAGE
C. O-XYLENE PREHEATER
D. COMPRESSOR
E. AIR PREHEATER
F. REACTOR
G. ABSORPTION TOWER
H. FRACTIONATION TOWER
I SEPARATOR
ALCOHOL
H2S04 "
WASTE
GAS
H
PHTHALATES
WATER RICH
PHASE
Figure 10. Flow diagram for direct production of phthalates
58
-------
organic-rich phase (stream 11) from the separator is recycled
to the absorption and fractionation towers.
The waste gas stream from the absorption tower (stream 7) is
expected to have a composition similar to the switch-condenser
off-gas in the standard phthalic anhydride process. Hence,
scrubbing and/or incineration would be required as control
measures for this stream. The principal advantage of the
modified process, from the standpoint of air pollution control,
is that the emissions from the product purification section
of the standard phthalic anhydride plant would be eliminated.
Emissions of heat-transfer fluid from the switch-condenser
heat-transfer circuits would also be eliminated, as well as
phthalic anhydride emissions from the flaking and bagging
operations. Phthalic anhydride emissions from storage tanks
and the transport loading facility vent would be replaced by
phthalate emissions. The other waste stream from the modified
process is the water-rich phase (stream 12) from the separa-
tor. This stream is expected to contain, as contaminants,
alcohol, sulfuric acid, phthalic acid, maleic acid, benzoic
acid, phthalate and other organics. Hence, this stream pre-
sents a serious water pollution control problem.
4. Alternate Feedstocks
Phthalic anhydride processes based on feed materials other
than o-xylene and naphthalene are possible and may become
important in the future should supplies of the latter
materials become scarce. Two alternate raw materials that
have been used are methyl naphthalene, which must be de-
methylated prior to use, and acenaphthlene.59 Both of these
compounds are obtained from coal tar. In fact, coal tar con-
tains more methyl naphthalenes than naphthalene.
59Austin, G. T. Industrially Significant Organic Chemicals,
Part 8. Chemical Engineering, 24^107, July 22, 1974.
\
115
-------
SECTION VI
GROWTH AND NATURE OF THE INDUSTRY
A. PRESENT TECHNOLOGY
Phthalic anhydride is currently produced in the United States
from o-xylene via the fixed-bed process and from naphthalene
via the fluid-bed process. The BASF process is the most
recent and most widely used fixed-bed process, while the
Badger-Sherwin-Williams process is the dominant fluid-bed
process. In recent years, o-xylene has become the preferred
feedstock due to its lower unit product cost, and all new
plants built since 1968 use o-xylene. This trend is further
reflected in the fact that since 1968, 10 naphthalene based
plants in the U.S. have been shut down and naphthalene based
capacity has declined from 2.39 x 105 metric tons/yr in 1968
to 1.5 x 105 metric tons/yr in 1975.1'3'4 (However, a
2.27 x 104 metric tons/yr expansion of the U.S. Steel naph-
thalene based plant is scheduled for start up in 1975.4)
This trend could be reversed in the future if rising petro-
leum prices should result in a more favorable price for
coal-tar naphthalene than for o-xylene. Since the fixed-bed
plants are capable of operating with either o-xylene or
naphthalene, a change of feedstock could be made both quickly
and easily.
116
-------
B. EMERGING TECHNOLOGY
Two significant improvements in the fixed-bed o-xylene
based process have been made by Rhone-Progil.55 First, in
the Rhone-Progil process sulfur dioxide is not required in
the reactor feed stream to maintain catalyst activity.
Hence, this source of air pollution is eliminated. Second,
a lower air to xylene feed ratio has been achieved (although
a specific figure has not been published), thus reducing the
volume of waste gas that must be treated. This reduction in
the volume of waste gas improves the economics of treatment
by direct incineration, as opposed to treatment by a scrubber-
incinerator combination. Direct incineration has the advan-
tage of controlling the emission of the carbon monoxide
that is present in the waste gas stream.
Other recent innovations in phthalic anhydride production
involve the recovery of maleic anhydride55 and benzoic
acid55 as by-products from the waste gas stream. The pro-
duction cost of maleic anhydride by the UCB recovery
process56 is less than the raw material cost alone for the
conventional process using benzene. In addition, the cost
of process equipment is less than for a benzene based plant
of the same capacity. With increasing costs for petro-
chemicals, it is expected that by-product recovery from
phthalic anhydride production will become even more
economically attractive in the future.
C. MARKETING STRENGTHS AND WEAKNESSES
Figure 11 shows schematically the usage of phthalic anhydride
in the United States. 60 Each of the major product categories
is discussed below.
60 chemical Origins and Markets, 4th Edition. Menlo Park,
Stanford Research Institute, Chemical Information Services,
1967. 99 p.
\
117
-------
oo
PHTHALIC a.
ANHYDRIDE
nniiALAtt PU-TICIZCR- » [PLASTICIZERS FOR POLYVINU CHLORIDE
'Tli^ElHYLHEXYLrPHTHALATE 1 AND COPOLYMER RESINS
OmSOOECYL) PHTHAL4TE
SlJJm^HTHmu"" » pLASTICIZER FOR POLYVINYL ACETAH
BiETHYL PHTHiLATEn . " 1 *«» CELLULOSICS
|_ DIMETHYL PHTHALATEj V. *—
^\^ ^PPLASTICIZERS FOR POLYVIHYL ICETATE
[AND CELLULOSICS: INSECT REPELLANTS
^ IIHS1TIJR4TFD ^
""I POLYESTER RESINS \
rTcTRArHinon AHH TFTRiRB(wn~! Rl<*C RET*ROAHTS IN POLYeSTER RESIHS,
1 TETRACHLORO- AND TETRABRCMO- POLYURETt1AMrFOAH3 5URFACE ^A*TIHQ^
^i PHTHALIC ANHYDRIDES AND ACIDSl 1 r-Tm" i.
1 —
// '1
MOLDED PLASTICS
POLYESTER RESINS
_. „,„,„, rilTI,.LrlN pHEOICIHALS
«. PIIEHOLPHTIIALriN » j^H m[um
^ nillHI?ArHHf! '1-niHYnBnvYAHTHRAOIIIHnHFl »— OYFS
ODKSTWKTIOK APPLICATIONS
DAT HULLS
UH3PORTATIOJ4 APPLICATIONS
•-CASTIHG RESIHS, AUTOMOTIVE PUTTIES
DYES
PLASTICIZERS
•-pHTHALOCYANIHE DYES
JAZO AHD INDIGO ID DYES
«IHYL ANTHRANIUTE —
•*- PERFUME
Figure 11. Uses of phthalic anhydride
60
-------
The largest single use of phthalic anhydride is in the
manufacture of plasticizers, which accounts for 50% of the
phthalic anhydride produced in the U.S.3 Plasticizers are
diphthalates produced by the esterification reaction of two
moles of alcohol with one mole of phthalic anhydride in the
presence of sulfuric acid, which catalyzes the reaction.
O
II
H2SO4 /^C
0 + ROH + R'OH [ |T + H2O
The major phthalic anhydride plasticizers, with their per-
centages of total phthalic plasticizer production, are:1
di(2-ethylhexyl)phthalate (40%)
di(isodecyl)phthalate (15%)
di(iso-octyl)phthalate (9%)
n-octyl-n-decyl phthalate (6%)
About 87% of these products are used to impart low-temperature
flexibility, resilience, high impact strength, and good
electrical properties to polyvinyl chloride polymers and
copolymers (with vinyl acetate). Hence, their future growth
is tied directly to that of non-rigid PVC.
Raw material shortages, the slump in the automobile industry,
and concern over the health hazards of vinyl chloride monomer
could seriously affect the growth of non-rigid PVC. For
example, new legislation restricting worker exposure to
vinyl chloride monomer may curtail output and force much
119
-------
higher resin prices.61 In fact, production for the first
quarter of 1975 was down nearly 40% compared to the same
period in 1974. 4 In spite of these concerns, however, the
industry is planning at least a one-third increase in PVC
resin capacity by the end of 1976.62
The above caveats notwithstanding, overall plasticizer pro=
duction is expected to increase at an average annual rate of
5% in the period 1975 to 1980. Phthalate ester plasticizers
will ikely increase at a slightly lower level due to an
increasing demand for more flame-retardant vinyls, which will
result in a greater use of phosphate plasticizers. In
addition, some competition is expected from specialty plasti-
cizers such as the trimellitates, the adipates, and the
sebacates, in applications where improved properties are im-
portant. Historically, phthalate ester plasticizers ex-
perienced an average growth rate of 9% in the period 1963 to
1973.63
The second largest use of phthalic anhydride is in the manu-
facture of unsaturated polyester resins, which accounts for
24% of domestic phthalic anhydride production.3 Unsaturated
polyesters are made from unsaturated organic acids (as their
anhydrides) and glycols, and are crosslinked with mono-
mers such as styrene, vinyltoluene, and diallyl phthalate.
A typical reaction involving maleic and phthalic anhydrides
is:
6 Edwards, P. Chemicals '75/Aliphatics. Chemical Marketing
Reporter. 207:40-42, January 6, 1975.
62Burke, D. P. Forecast '75 Riding it Out. Chemical Week.
116_: 17-24, January 8, 1975.
53Synthetic Organic Chemicals, U.S. Production and Sales.
U.S. International Trade Commission (formerly U.S. Tariff
Commission). Washington. 1963-1974.
120
-------
?
TJfV r* s-*
(N) || N0 + (2N) HOROH + (N) ^^ X~ Heat
HC—C-7
O
Maleic anhydride Glycol
Phthalic anhydride
H-
O O 0 0
|| II II II
5RO-C-CH=CH-C-ORO-C C-
Prepolymer
-OH
N
Heat
Catalyst
Styrene
O O 0
II II II
OT?O C* f"*H I^*H~ f^— ^P/^— ^*
wr\w ^. v^n L.n L. wi\^ v-
CH2 £
0 00
ii II II
-ORO-C-CH-CH-C-ORO-C
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II
/-»
"A
0
II
A J
Unsaturated polyester resin
In 1973, 78% of unsaturated polyester resins were used for
the production of glass fiber reinforced plastics (FRP) and
the remainder for non-reinforced applications.64
The average annual growth of unsaturated polyester resin
production from 1963 to 1973 was 15%.65 After a slight
decline in 1970, growth in the 1971-1973 period averaged
22%.65/6S These large increases in polyester resin consump-
tion were the result of a large increase in the pleasure
boat business, the large-scale use of synthetic marble and
FRP tub/shower units in construction, and the first large-
scale applications of low profile, low shrink resins in the
transportation and equipment markets.
6£f1972 Annual Statistical Report. The Society of the Plastics
Industry. New York. November 16, 1973.
65Anderson, E. V. Growth Slows in Top 50 Chemicals' Output.
Chemical and Engineering News. 52i10-13, May 6, 1974.
121
-------
The years 1973 and 1974, especially the latter, were charac-
terized by widespread shortages of raw materials, including
styrene, maleic anhydride, and most glycols. As of late
1974, raw material availability was generally adequate,
although some glycols were still in short supply. As a
result of the severe raw material shortages in the first nine
months of 1974, reported unsaturated polyester resin produc-
tion for this period was down by 10% compared to the same
period in 1973.66 Production for the first quarter of 1975
was down 24% compared to the first quarter of 1974.4 How-
ever, growth is expected to resume after the first half of
1975.
The average annual growth rate for unsaturated polyester
resins is expected to be 11% to 13% in the period 1974 to
1979. This rate of growth will result in an increase in
production from an estimated 3.85 x 105 to 4.4 x 105 metric
tons in 1974 to 6.6 x 105 to 8.21 x 105 metric tons in 1979.
The demand for phthalic anhydride in this area is expected
to grow at a level somewhat below that of total unsaturated
polyester resin production. This is due to the substitution
(some of which is believed to be permanent) of isophthalic
resins for some phthalic-based resins caused by the recent
raw materials shortage.
The third major outlet for phthalic anhydride is the produc-
tion of alkyd resins, which accounts for 19% of domestic
phthalic anhydride production.3 Alkyd resins are a type of
polyester resin, being the reaction product of a polybasic
acid and a polyol. Alkyds, however, contain an unsaturated
monocarboxylic acid, such as those from the drying oils, as
66Anderson, E. V. Recession Stifles Output of Top 50
Chemicals. Chemical and Engineering News. 53:30-33,
May 5, 1975.
122
-------
a modifying agent. Thus, after coating on a surface, the
alkyd resin can undergo further oxidative polymerization
like a drying oil to yield a very tough, elastic, weather-
resistant film. These synthetic enamels have been used
extensively for the finishing of automobiles and household
appliances.
Until 1961, alkyd resin manufacture was the largest single
user of phthalic anhydride. The rapid rise in plasticizer
demand and, later, in unsaturated polyester resins, combined
with the slow growth of alkyd resins (due primarily to
competition from other surface coating resins), resulted in
alkyds dropping to third on the list of phthalic anhydride
consumers. Phthalic anhydride consumption for alkyd resin
manufacture has remained nearly static in the period 1967
to 1974 (9.34 x 101* metric tons in 1967 versus 8.89 x 104
metric tons in 1974).63
Total alkyd surface coatings consumption is expected to
decline at an average annual rate of -5% to -1% in the
period 1975-1978, mostly as the result of increased compe-
tition from other coating systems and stricter anti-pollution
laws governing the use of solvent-based paints.
Exports and various miscellaneous products account for 7%
of the phthalic anhydride produced in the U.S.3 Included
in this category are anthraquinone and its derivatives
(intermediates for the synthesis of anthraquinone dyes), lead
phthalate (a PVC stabilizer), tetrachloro- and tetrabromo-
phthalic anhydride (fire retardants in polyester resins),
diallyl phthalate (a crosslinking agent for polyesters),
dibutyl phthalate and phthalonitrile (insecticides), phenol-
phthalein (a pH indicator and laxative), phthalein and
xanthene dyes, phthalimide (used in various organic syntheses
and in the manufacture of perfume and indigo dye), and eosin
(tetrabromofluorescein) inks and dyes.
123
-------
Exports have exhibited a sharp increase during the past
four years, as is shown below:4'63
Phthalic anhydride
Year exports/ 103 metric tons
1971 3.48
1972 6.26
1973 10.08
1974 15.42
During the first quarter of 1975, however, exports ran at
an annual rate of only 1.1 x 103 metric tons. The reason
is that foreign phthalic prices had dropped below the domes-
tic price.4
Domestic phthalic anhydride production increased at an
average annual rate of 8.4% during the period 1963 to 1973.3
In 1974, production totaled 4.692 x 105 metric tons. During
the first quarter of 1975, however, production totaled only
5.62 x 104 metric tons.4 This corresponds to an annual rate
of 2.248 x 105 metric tons, which is less than half the
nominal plant capacity in the U.S. The sharp drop in
phthalic production reflects the declines in phthalic's
major markets, polyvinyl chloride and unsaturated polyester
resins.
Phthalic production is expected to recover in the second
half of 1975 to reach a total output of approximately
3.18 x 105 metric tons for the year. Annual production is
projected to reach 4.99 x 105 metric tons in 1978 and
6.35 x 105 metric tons in 1980.4
124
-------
SECTION VII
APPENDIXES
A. Storage Tank Calculations
B. Rationale for Not Considering All Species Listed in
Table 21
125
-------
APPENDIX A
STORAGE TANK CALCULATIONS
The procedure for calculating the emissions from storage
tanks is outlined in this section. The equations given
below were derived in References 39-43.
Step 1. Calculate the equivalent gasoline breathing loss;
24 / p \0.68
--_
1000 i4.7-p
rjl.73/tiM0.51 ( Am\ 0 . 50 p p (A
D (H } (AT) c (A
where L = equivalent gasoline breathing loss, bbl/yr
P = vapor pressure of material stored at bulk
temperature, psia
D = tank diameter, ft
H1 = average tank outage, ft
AT = average daily ambient temperature change, °F
F = paint factor
C = diameter factor
The bulk temperatures of the material stored were taken to
be 200°F for naphthalene tanks, 300°F for phthalic anhydride
tanks, and 74°F for o-xylene tanks. The latter temperature
was obtained by adding 5°F to the ambient temperature, as
recommended in References 39-43 for tanks held at ambient
temperature. The ambient temperature was assumed to be 69°F,
the national mean ambient temperature.
126
-------
Tank diameters were computed by assuming a height of 50 ft
for all tanks. The average tank outage, i.e., freeboard,
was taken as one-half the tank height, or 25 ft.
The average daily ambient temperature change, AT, was taken
as 20°F, which is the national average value. The paint
factor, Fp, was assumed equal to unity, the value for white
paint in good condition. This factor can be as high as
14.6 for gray surfaces. The diameter factor, C, is equal
to unity for tanks 30 ft or larger in diameter. For smaller
tanks, the value is obtained from a graph given in Reference 41,
and is between 0.25 and 1.0.
Step 2. Calculate the equivalent gasoline working loss:
where F =
V =
N =
Pg= 157000 PVNKT
equivalent gasoline working loss, bbl/yr
tank capacity, bbl
number of turnovers per year
turnover factor =1.0 for N £ 36
180 + N
(A-2)
6N
for N > 36
Step 3. Compute total equivalent gasoline loss, L :
L = L + F
9 Y
Step 4. Compute petrochemical losses:
L = o.os (|)LC
(A-3)
(A-4)
where L = total petrochemical loss, bbl/yr
M = molecular weight of chemical stored
W = liquid density of chemical stored, Ib/gal
127
-------
Step 5. Calculate emission factor:
Lj = L (42) (W) (A-5)
E1 = •=—- (A-6)
E = f- (A-7)
where Lj = petrochemical loss, Ib/yr
Cap = production capacity, ton/yr
E1 = emission factor, Ib/ton
E = emission factor, g/kg
The necessary input data for the above calculations are
tabulated in Tables A-l and A-2, while the results are
summarized in Tables A-3 and A-4. The tank numbers in
these tables correspond to those in Tables 7 and 14 for o-
xylene and naphthalene based plants, respectively.
128
-------
Table A-l. STORAGE TANK INPUT DATA FOR o-XYLENE BASED PLANT
Tank number
1
2
3 & 4
5 & 6
7
8
Input data
Average ambient temp. , °F
Average ambient temp, change, °F
Material molecular weight
Liquid density, Ib/gal
Vapor pressure at bulk temp., psia
Bulk temp. , °F
Tank diameter, ft
Tank outage, ft
Paint factor
Diameter factor
Turnover factor
No. turnovers per year
Tank capacity, bbl
69
20
106
7.37
0.194
74
17.3
25
1.0
0.81
0.297
230
2,070
69
20
106
7.37
0.194
74
54.8
25
1.0
1.0
1.0
23
21,000
69
20
148
8.35
0.33
300
17.9
25
1.0
0.83
0.63
65
2,260
69
20
148
8.35
0.33
300
17.5
25
1.0
0.82
0.58
72
2,140
69
20
148
8.35
0.33
300
18.5
25
1.0
0.84
0.85
44
2,380
69
20
148
8.35
0.33
300
26.1
25
1.0
0.98
0.85
44
4,760
to
ID
-------
Table A-2. STORAGE TANK INPUT DATA FOR NAPHTHALENE BASED PLANT
Tank number
1
2
3
4
5
6 & 7
8
9
Input data
Average ambient temp. ,
Average ambient temp.
change, °F
Material molecular
weight
Liquid density, Ib/gal
Vapor pressure at bulk
temp. , psia
Bulk temp. , °F
Tank diameter, ft
Tank outage, ft
Paint factor
Diameter factor
Turnover factor
No. turnovers per year
Tank capacity, bbl
69
20
128
8.0
0.31
200
58.4
25
1.0
1.0
1.0
1
23,810
69
20
128
8.0
0.31
200
58.4
25
1.0
1.0
1.0
13
23,180
69
20
128
8.0
0.31
200
41.3
25
1.0
1.0
1.0
26
11,905
69
20
148
8.35
0.33
300
17.3
25
1.0
0.81
0.37
148
2,095
69
20
148
8.35
0.33
300
37.0
25
1.0
1.0
1.0
2
9,524
69
20
148
8.35
0.33
300
12.8
25
1.0
0.65
0.40
130
1,143
69
20
148
8.35
0.33
300
22.6
25
1.0
0.93
1.0
2
3,571
69
20
148
8.35
0.33
300
22.6
25
1.0
0.93
0.92
40
3,571
U)
o
-------
Table A-3. STORAGE TANK CALCULATION SUMMARY FOR o-XYLENE BASED PLANT
Tank
No.
1
2
3
4
5
6
7
8
Material stored
o-Xylene
o-Xylene
Crude product
Crude product
Phthalic anhydride
Phthalic anhydride
Phthalic anhydride
Phthalic anhydride
Capacity,
gal
87,000
880,000
95,000
95,000
90,000
90,000
100,000
200,000
Losses
gal/yr
546
2,770
858
858
836
836
872
1,747
Ib/yr
4,027
20,417
7,165
7,165
6,977
6,977
7,282
14,584
Emission
factor, g/kg
0.031
0.157
0.055
0.055
0.054
0.054
0.056
0.112
U)
-------
Table A-4. STORAGE TANK CALCULATION SUMMARY FOR NAPHTHALENE BASED PLANT
Tank
No.
1
2
3
4
5
6
7
8
9
Material stored
Naphthalene
Naphthalene
Naphthalene
Crude product
Crude product
Phthalic anhydride
Phthalic anhydride
Phthalic anhydride
Phthalic anhydride
Capacity,
gal
1,000,000
1,000,000
500,000
88,000
400,000
48,000
48,000
150,000
150,000
Losses
gal/yr
2,582
3,970
2,899
953
1,422
490
490
577
1,310
Ib/yr
20,658
31,759
23,194
7,954
11,872
4,090
4,090
4,819
10,937
Emission
factor, g/kg
0.165
0.254
0.186
0.064
0.095
0.033
0.033
0.039
0.088
U)
ro
-------
APPENDIX B
RATIONALE FOR NOT CONSIDERING ALL SPECIES LISTED IN TABLE 21
A number of the possible reaction products listed in Table 21
were not studied explicitly in this work since they are emitted
in, at most, trace amounts. The compounds are not emitted in
greater than trace amounts for the following reasons:
They are not formed in greater than trace amounts, due
either to unfavorable conditions in a commercial reactor,
or to the fact that they are reaction products of
feedstock impurities which are themselves present in
sma11 amounts.
They are too reactive to be stable under the process
conditions.
An exception is citraconic anhydride, which may be emitted
in greater than trace amounts. However, it is undoubtedly
included in the reported data as maleic anhydride, since the
two are chemically very similar. This is not considered to
be a drawback because it is reasonable to assign citraconic
anhydride the same TLV as that of maleic anhydride (in lieu
of other information) and to treat the two together for the
purpose of pollution control.
Each of the compounds listed in Table 21 but not explicitly
included in the study is listed in Table B-l, together with
the reason for its exclusion.
133
-------
Table B-l. COMPOUNDS NOT INCLUDED IN STUDY
Compound
Reason for exclusion
CO
o-Methylbenzyl alcohol
o-Toluic acid
p_-Toluic acid
Toluene
o-Hydroxymethylbenzoic acid
Citraconic anhydride
Phthalide
Phthalaldehydic acid
Phthalic acid
Terephthalic acid
p_-Benzoquinone
Isophthalic acid
o'-Carboxylphenyl-o-methylphenyl acetate
o_' -Methylphenyl-o-methylphenyl acetate
bis(o-Methylphenyl)methyl ether
1,2-bis(o-Methylphenyl)ethane
Reactive intermediate
Reactive intermediate
Precursor is feed impurity
Reactive; formation not favored under com-
mercial reactor conditions
Reactive intermediate
Reported as maleic anhydride
Reactive intermediate
Reactive intermediate
Emitted as phthalic anhydride
Precursor is feed impurity
Precursor is feed impurity
Precursor is feed impurity
Formation not favored under commercial reactor
conditions; would be decomposed by incinera-
tion
-------
As a further justification for not considering the above
compounds, upper limits were estimated for the source severity
due to these compounds. All of the above compounds are in-
cluded in the category "miscellaneous organics" listed in
Tables 18 and 19. (See also Table 33, footnote 1, and
Table 34, footnote p.) For the purpose of this calculation,
it is assumed that the miscellaneous organics in the reactor
product stream are partitioned between the crude product and
switch-condenser off-gas in the same ratio as phthalic anhy-
dride. Using the data in Table 18 for o-xylene based plants,
this procedure yields 33.3 kg/hr miscellaneous organics in
the crude product stream, and 0.8 kg/hr in the switch-con-
denser off-gas. The former amount is assumed to be removed
during product purification and sent to the secondary in-
cinerator. The latter amount is sent to the main process
incinerator. Removal efficiencies of 96.5% in the main
process incinerator and 99% in the secondary incinerator are
assumed. These are the values for total organics obtained
from Reference 13. The resulting emission rates are
0.028 kg/hr from the main process incinerator and 0.333 kg/hr
from the secondary incinerator. The corresponding source
severities are:
1.15 x 10~5 f .
S = ==-rr for main process incinerator
1 J_iV
5 5 x lO"1*
S = — =jrr= for secondary incinerator
IJjV
Assuming an average TLV for the miscellaneous organics of
0.001 g/m3 (equivalent to maleic anhydride), the source
severities are 0.01 for the main process incinerator and
0.55 for the secondary incinerator.
135
-------
A TLV of 0.001 g/m3 represents a very stringent assumption,
since maleic anhydride has the lowest TLV of the major species
which are emitted. If the TLV for phthalic anhydride
(0.006 g/m3) is used in the calculation, the severity for the
secondary incinerator is less than 0.1. In addition, the
estimated severities are for the total of all species included
in the miscellaneous organics category. The severity for any
individual compound should be much smaller.
A similar calculation based on the data in Table 19 for a
naphthalene based plant results in the following source
severities for miscellaneous organics:
S = 1 03 x
— ' — ==-r= - for main process incinerator
C QQ y 10""1*
S = ——==rr= for secondary incinerator
Assuming a TLV of 0.001 g/m3 yields source severities of 0.01
for the main process incinerator and 0.61 for the secondary
incinerator.
136
-------
SECTION VIII
GLOSSARY OF TERMS
ATMOSPHERIC STABILITY CLASS - Class used to designate
degree of turbulent mixing in the atmosphere.
BADGER-SHERWIN-WILLIAMS PROCESS - Fluid-bed process developed
by Sherwin-Williams Co. and the Badger Company for the oxi-
dation of naphthalene to phthalic anhydride.
BASF PROCESS - Fixed-bed process developed by Badische Anilin
and Soda Fabrik for the oxidation of o-xylene to phthalic
anhydride.
CRITERIA POLLUTANT - Emission species for which an ambient
air quality standard has been established.
EMISSION FACTOR - Weight of material emitted to the atmos-
phere per unit weight of phthalic anhydride produced.
FLAKER - Device which solidifies liquid phthalic anhydride
in the form of flakes.
MAIN PROCESS INCINERATOR - Incinerator which burns the
off-gas from the switch condenser.
NON-CRITERIA POLLUTANT - Emission species for which no
ambient air quality standard has been established.
PARTIAL CONDENSER - Condenser used to condense phthalic
anhydride as a liquid in the fluid-bed process.
SECONDARY INCINERATOR - Incinerator which burns the
waste streams from the product purification section of
the phthalic anhydride plant.
SWITCH CONDENSER - Condenser used to condense phthalic
anhydride as a solid.
TANK OUTAGE - Distance from liquid surface to top of
storage tank.
137
-------
SECTION IX
CONVERSION FACTORS AND METRIC PREFIXES67
To convert from
degree Celsius
joule (J)
kelvin
kilogram (kg)
CONVERSION FACTORS
to
degree Fahrenheit
British thermal unit
degree Celsius
pound-mass (Ib mass
Multiply by
t« = 1.8 t£ + 32
9.479 x lO'4
t£ = tj - 273.15
2.204
kilogram (kg)
meter (m)
meter (m)
meter (m)
meter (m)
meter3 (m3)
meter3 (m3)
pascal (Pa)
Prefix Symbol
mega M
kilo k
milli m
micro y
nano n
avoirdupois)
ton (short, 2,000 Ib
mass)
angstrom
foot
micron
mile
barrels (42 gal)
gallon (U.S. liquid)
pound- force/inch2
(psi)
PREFIXES
Multiplication
factor
106 5
103 5
10~3 5
10~6 5
10~9 5
1.
1.
3.
1.
6.
6.
2.
1.
102
000
281
000
215
293
642
450
X
X
X
X
X
X
io-3
1010
IO6
io-*
IO2
10-"
Example
MJ
kg
mm
ym
nm
= 5
= 5
= 5
= 5
= 5
X
X
X
X
X
IO6
IO3
io-3
10~6
io-9
joules
grams
meter
meter
meter
67Metric Practice Guide. American Society for Testing and
Materials. Philadelphia. ASTM Designation: E 380-74.
November 1974. 34 p.
138
-------
SECTION X
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-76-032d
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Source Assessment: Phthalic Anhydride (Air Emissions)
5. REPORT DATE
December 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
R. W. Serth and T.W. Hughes
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Monsanto Research Corporation
1515 Nicholas Road
Dayton, Ohio 45407
10. PROGRAM ELEMENT NO.
1AB015; ROAP 21AXM-071
11. CONTRACT/GRANT NO.
68-02-1874
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT ANC
Final; 1/75-4/76
NO PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA-ORD
15.SUPPLEMENTARY NOTES Project officer for this report is Dale A. Denny, Mail Drop 62,
919/549-8411 Ext. 2547.
16. ABSTRACT .
The report gives results of an analysis of atmospheric (air) emissions from
ortho-xylene- and naphthalene-based phthalic anhydride manufacturing plants. Uncon-
trolled and controlled emission factors are given for each species emitted to the
atmosphere from each source within a typical plant, based on the latest data available.
Emissions data are used to calculate three factors designed to quantify the hazard
potential of the emissions: (1) source severity (the ratio of maximum mean ground-
level concentration of a pollutant to the concentration which constitutes an incipient
health hazard), (2) the industry contribution to total atmospheric emissions of cri-
teria pollutants, and (3) the population exposed to high contaminant levels from a
representative plant. Detailed process descriptions and flow sheets are presented
for the BASF fixed-bed ortho-xylene process and the Badger-Sherwin-Williams fluid-
bed naphthalene process. Present and future aspects of pollution control technology
in the industry are discussed, including a number of possible process modifications.
Economic and production trends in the phthalic anhydride industry and in each of the
industries that are major consumers of phthalic anhydride are analyzed. Water-
related emissions are to be discussed in a future, separate report.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Phthalic Anhydride
Industrial Processes
Xylenes
Naphthalene
Air Pollution Control
Stationary Sources
Source Assessment
Ortho-xylene
13B
07C
13H
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisRepon)
Unclassified
21. NO. OF PAGES
154
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
145
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