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Table of Contents
                            CONTENTS
PREFACE
ABOUT THE AUTHORS
ACKNOWLEDGMENTS
PART I: A CHEMICAL ENGINEER'S GUIDE TO ENVIRONMENTAL ISSUES AND REGULATIONS
	1 AN INTRODUCTION TO ENVIRONMENTAL ISSUES
		1.1 Introduction
		1.2 The Role of Chemical Processes and Chemical Products
		1.3 An Overview of Major Environmental Issues
		1.4 Global Environmental Issues
		1.5 Air Quality Issues
		1.6 Water Quality Issues
		1.7 Ecology
		1.8 Natural Resources
		1.9 Waste Flows in the United States
		Summary
		References
		Problems
	2 RISK CONCEPTS
		2.1 Introduction
		2.2 Description of Risk
		2.3 Value of Risk Assessment in the Engineering Profession
		2.4 Risk-Based Environmental Law
		2.5 General Overview of Risk Assessment Concepts
		2.6 Hazard Assessment
		2.7 Dose-Response
		2.8 Exposure Assessment
		2.9 Risk Characterization
		Summary
		References
		Problems
	3 ENVIRONMENTAL LAW AND REGULATIONS: FROM END-OF-PIPE TO POLLUTION PREVENTION
		3.1 Introduction
		3.2 Nine Prominent Federal Environmental Statutes
		3.3 Evolution of Regulatory and Voluntary Programs: From End-of-Pipe to Pollution Prevention
		3.4 Pollution Prevention Concepts and Terminology
		References
		Problems
	4 THE ROLES AND RESPONSIBILITIES OF CHEMICAL ENGINEERS
		4.1 Introduction
		4.2 Responsibilities for Chemical Process Safety
		4.3 Responsibilities for Environmental Protection
		4.4 Further Reading in Engineering Ethics
		References
		Problems
PART II: EVALUATING AND IMPROVING ENVIRONMENTAL PERFORMANCE OF CHEMICAL PROCESSES
	5 EVALUATING ENVIRONMENTAL FATE: APPROACHES BASED ON CHEMICAL STRUCTURE
		5.1 Introduction
		5.2 Chemical and Physical Property Estimation
		5.3 Estimating Environmental Persistence
		5.4 Estimating Ecosystem Risks
		5.5 Using Property Estimates to Estimate Environmental Fate and Exposure
		5.6 Classifying Environmental Risks Based on Chemical Structure
		References
		Problems
	6 EVALUATING EXPOSURES
		6.1 Introduction
		6.2 Occupational Exposures: Recognition, Evaluation, and Control
		6.3 Exposure Assessment for Chemicals in the Ambient Environment
		6.4 Designing Safer Chemicals
		References
		Problems
	7 GREEN CHEMISTRY
		7.1 Green Chemistry
		7.2 Green Chemistry Methodologies
		7.3 Quantitative/Optimization-Based Frameworks for the Design of Green Chemical Synthesis Pathways
		7.4 Green Chemistry Expert System Case Studies
		Questions for Discussion
		References
		Problems
	8 EVALUATING ENVIRONMENTAL PERFORMANCE DURING PROCESS SYNTHESIS
		8.1 Introduction
		8.2 Tier 1 Environmental Performance Tools
		8.3 Tier 2 Environmental Performance Tools
		8.4 Tier 3 Environmental Performance Tools
		References
		Problems
	9 UNIT OPERATIONS AND POLLUTION PREVENTION
		9.1 Introduction
		9.2 Pollution Prevention in Material Selection for Unit Operations
		9.3 Pollution Prevention for Chemical Reactors
		9.4 Pollution Prevention for Separation Devices
		9.5 Pollution Prevention Applications for Separative Reactors
		9.6 Pollution Prevention in Storage Tanks and Fugitive Sources
		9.7 Pollution Prevention Assessment Integrated with HAZ-OP Analysis
		9.8 Integrating Risk Assessment with Process Design—A Case Study
		Questions for Discussion
		References
		Problems
	10 FLOWSHEET ANALYSIS FOR POLLUTION PREVENTION
		10.1 Introduction
		10.2 Process Energy Integration
		10.3 Process Mass Integration
		10.4 Case Study of a Process Flowsheet
		Summary
		References
		Problems
	11 EVALUATING THE ENVIRONMENTAL PERFORMANCE OF A FLOWSHEET
		11.1 Introduction
		11.2 Estimation of Environmental Fates of Emissions and Wastes
		11.3 Tier 3 Metrics for Environmental Risk Evaluation of Process Designs
		Summary
		References
		Problems
	12 ENVIRONMENTAL COST ACCOUNTING
		12.1 Introduction
		12.2 Definitions
		12.3 Magnitudes of Environmental Costs
		12.4 A Framework for Evaluating Environmental Costs
		12.5 Hidden Environmental Costs
		12.6 Liability Costs
		12.7 Internal Intangible Costs
		12.8 External Intangible Costs
		References
		Problems
PART III: MOVING BEYOND THE PLANT BOUNDARY
	13 LIFE-CYCLE CONCEPTS, PRODUCT STEWARDSHIP, AND GREEN ENGINEERING
		13.1 Introduction to Product Life Cycle Concepts
		13.2 Life-Cycle Assessment
		13.3 Life-Cycle Impact Assessments
		13.4 Streamlined Life-Cycle Assessments
		13.5 Uses of Life-Cycle Studies
		Summary
		Questions for Discussion
		References
		Problems
	14 INDUSTRIAL ECOLOGY
		14.1 Introduction
		14.2 Material Flows in Chemical Manufacturing
		14.3 Eco-Industrial Parks
		14.4 Assessing Opportunities for Waste Exchanges and Byproduct Synergies
		Summary
		References
		Problems
APPENDICES
	A: DETAILS OF THE NINE PROMINENT FEDERAL ENVIRONMENTAL STATUTES
	B: MOLECULAR CONNECTIVITY
	C: ESTIMATING EMISSIONS FROM STORAGE TANKS
	D: TABLES OF ENVIRONMENTAL IMPACT POTENTIALS—TABLES D-1 TO D-4
	E: PROCEDURES FOR ESTIMATING HIDDEN (TIER II) COSTS—TABLES E-1 TO E-5
	F: ADDITIONAL RESOURCES—WEB RESOURCES/ONLINE DATABASES/SOFTWARE
INDEX
	A
	B
	C
	D
	E
	F
	G
	H
	I
	K
	L
	M
	N
	O
	P
	R
	S
	T
	U
	V
	W
                        
Document Text Contents
Page 2

GREEN ENGINEERING
Environmentally Conscious Design

of Chemical Processes

DAVID T. ALLEN
AND

DAVID R. SHONNARD

Prentice Hall PTR
Upper Saddle River, NJ 07458
www.phptr.com

www.phptr.com

Page 286

Both reactions are reversible and at equilibrium. When CO2 is recovered and
recycled back to the reactor, it decomposes in the reactor as fast as it forms, and no
net conversion of methane to CO2 occurs. This requires additional operating costs,
but there is no selectivity loss of reactant, the process is cleaner, and it may be the
lowest cost option overall (Mulholland and Dyer, 1999).

Figure 9.3-5 shows a process flow diagram for a reactor combined with a sep-
arator that recycles reactants and byproducts back to the reactor. This configura-
tion can be operated such that all reactants fed to the reactor are converted to
product with no net waste generation from the process. Selectivity improvements
for reversible reactions can also be realized by employing separative reactors, as
discussed later.

More complicated chemical reactions, compared to the few simplistic first-
order reactions mentioned above, are common in the chemical industry, and their
pollution-generating potential must be evaluated on a case-by-case basis. How-
ever, the general trends discussed are expected to hold for more complex reaction
networks.

CO � H2O4 CO2 � H2

CH4 � H2O4 CO � 3H2

9.3 Pollution Prevention for Chemical Reactors 265

τ = kp t

kp/kw = 100

kp/kw = 10

kp/kw = 2

kp/kw = 1

kp/kw = 1 kp/kw = 2

kp/kw = 10

kp/kw = 100

D
im

e
n
si

o
n
le

ss
C

o
n

ce
n

tr
a

tio
n

[R]/[R]o

[P]/[R]o

[W]/[R]o

10 2 3 4 5

0.2

0.0

0.4

0.6

0.8

1.0

Figure 9.3-2 Effect of product and waste reaction rate constants on product and waste concentra-
tions in a first-order irreversible series reaction. The reactor residence time has been made dimen-
sionless using the product reaction rate constant.

Page 287

The choice of chemical reactor type within which the reaction is carried
out is also an important issue for process design and pollution prevention. A
continuous-flow stirred-tank reactor (CSTR) is not always the best choice. A plug
flow reactor has several advantages in that it can be staged and each stage can be
operated at different conditions to minimize waste formation (Nelson, 1992). In
a novel application of a plug flow reactor, DuPont developed a catalytic route
for the in-situ manufacture of methyl isocyanate (MIC) using a pipeline reactor,
resulting in only a few pounds of MIC being inventoried in the process at any
one time. This strategy minimizes the chance of a catastrophic release of MIC,
such as happened at Bophal, India, in 1984 (Menzer, 1994; Mulholland, 2000).

When hot spots are a problem for highly exothermic reactions carried out in a
fixed-bed catalytic reactor, a fluidized-bed catalytic reactor will likely avoid the un-
wanted temperature excursions. Good temperature control is critical for reducing
byproduct formation reactions that are highly temperature-sensitive. An example
where a fluidized-bed reactor succeeded in reducing waste formation is in the
production of ethylene dichloride, an intermediate in the production of polyvinyl
chloride (PVC) (Randall, 1994). The prior fixed-bed design operated with a
temperature range of 230–300�C while the newer fluidized-bed design was able to
run at between 220–235�C.

266 Unit Operations and Pollution Prevention Chap. 9

τ = kp t

kp/kw = 1

kp/kw = 100

kp/kw = 10

kp/kw = 2D
im

e
n
si

o
n
le

ss
C

o
n

ce
n

tr
a

tio
n

[P]/[R]o

[P]/([P]+[W])

20 4 6 8 10

0.2

0.0

0.4

0.6

0.8

1.0

Figure 9.3-3 Effect of product and waste reaction rate constants on product yield ([P]/[R]o) and
product modified selectivity ([P]/([P]�[W])) for a first-order irreversible series reaction. The reactor res-
idence time has been made dimensionless using the product reaction rate constant.

Page 572

Storage tanks, 494–496
estimating emissions, 493–508
fixed-roof storage tanks:

paint solar absorbance for, 501
total losses from, 494–496

floating roof tanks, 239
rim-seal loss factors for, 502

Stratospheric ozone layer, 12
Streamlined life-cycle assessments:

advantages, 447
data gathering for inventories/characteri-

zation, 441–442
guidance, 447
pitfalls, 447
qualitative techniques for inventories/

characterization, 442–447
Structural analog, 50
Structure activity relationships (SARs), 50,

97
Subchronic effects studies, 45
Submerged loading, 232
Substituton reactions, 185–186
Sulfur dioxide/nitrogen oxides, and acid

deposition, 20–21
Superfund Amendments and Reauthoriza-

tion Act (SARA), 24
Surface contamination, origin of, 22
Synthesis pathways, 185–189
Synthetic Organic Chemical Manufacturing

Industry (SOCMI) emission factors,
224, 289

System boundaries, 422–424
Systems Analysis Branch (SAB) website,

526

T

Tables of environmental impact potentials,
509–513

TANKS program, 536
Tetraethyl lead, 19
Third trophic producers, 23
Threshold limit values (TLVs), 52, 143,

204–207

Index 551

Tier 1 environmental performance tools,
200–215

alternatives synthetic pathways, evaluat-
ing, 209–215

economic criteria, 201–202
environmental criteria, 202–204
permissible exposure limits (PELs),

204–207
recommended exposure limits (RELs),

204–207
threshold limit values (TLVs), 204–207
toxicity weighting, 207–209

Tier 2 costs, estimating, 515–521
Tier 2 environmental performance tools,

215–246
environmental performance, assessing,

244–246
environmental release assessment,

216–219
modeled release estimates, 231–239
release characterization and documenta-

tion, 239–243
release quantification methods, 220–231

Tier 3 environmental performance tools, 246
Tier 3 metrics for environmental risk evalu-

ation of process designs, 375–390
acid rain, 379
global warming, 376–378
ozone depletion, 378–379
smog formation, 379–386
andtoxicity, 386–390

Toluene, 99, 103, 287
Total cost assessment, 399
Toxic agents, interaction of, 39
Toxic air pollutants, exposure to, 156–160
Toxic Release Inventory (TRI), 26, 67, 181,

208, 244, 448, 526
Toxic Substances Control Act (TSCA), 66,

68, 93–94, 126, 132, 211, 475–477
existing chemicals testing, 476
information gathering, 475
new chemical review, 476
regulatory controls and enforcement,

476–477

Page 573

Toxicity, 131, 212, 386–390
carcinogenic toxicity, 387–390
developmental, 45
non-carcinogenic toxicity, 386–387

Toxicity weighting, 207–209
Toxicology, the Basic Science of Poisons

(Casarett/Doull), 52
Toxnet, 51
TOXNET, 532
Tracking material flows, 426
TRIAGE Chemical Studies Database, 532
Trichlorofluoromethane, 12
Tropospheric ozone, 10–12

U

UCSS (Use Clusters Scoring System), 536
Ultimate aerobic biodegradation index,

group contributions to, 125
Underground injection releases, 218
United States Code (U.S.C.), 63
US Environmental Protection Agency

(EPA), See Environmental Protec-
tion Agency (EPA)

U.S. Geological Survey, 163
U.S. safety/health/environmental statutes

implying risk assessment, 43
Utility sources, secondary emissions from,

228–231

V

Vapor balance service, 234–235
Vapor pressure, 100–103, 129
Variable-vapor-space tanks, 239, 288

552 Index

Vinyl sulfones, 190
VOC emissions, 17–18
Volatile organic compounds (VOCs), 15,

70, 182, 289
Voluntary risk, 36

W

WAR (WAste Reduction Algorithm),
536–37

Waste flows in the U.S., 24–28
Waste treatment, 71
Waste treatment costs, estimating, 405
Wastes, estimation of environmental fates

of, 362–374
Water pollution:

and leaking underground storage tanks,
22

and transportation sources, 23
Water quality issues, 22–23

Exxon Valdez oil spill, 23
Water releases, 218
Water-sediment transport, 369–370
Water solubility, 110–112, 129
Water vapor, 10
Web resources, 523–529
Wind/wind speed, 17
Wipe samples, 151–152
Worker exposure, monitoring, 145–146
Working losses, 238–239, 287
Workplace Environmental Exposure Level

(WEEL), 143
Workplace exposure, techniques for mod-

eling, 56

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