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Transcript of University of Texas at AustinMichigan Technological University 1 Module 6: Flowsheet Environmental...
University of Texas at Austin Michigan Technological University1
Module 6: Flowsheet Environmental Impact
AssessmentChapter 11
David R. Shonnard
Hui Chen
Department of Chemical Engineering
Michigan Technological University
University of Texas at Austin Michigan Technological University2
Module 6: Outline
Educational goals and topics covered in the module
Potential uses of the module in chemical engineering courses
Review of environmental impact assessment methods
Application of Tier 3 environmental impact assessment to a detailed flowsheet - Chapter 11
After the flowsheet input output structure, unit operation designations, and mass/heat integration have been completed, the last step in the
process to improve the environmental performance of a chemical process design is to perform a detailed environmental impact assessment
University of Texas at Austin Michigan Technological University3
Module 6: Educational goals and topics covered in the module
Students will: learn to apply a systematic risk assessment methodology to the
evaluation of chemical process designs
integrate emission estimation, environmental fate and transport calculation, and relative risk assessment to rank process design alternatives
University of Texas at Austin Michigan Technological University4
Module 6: Potential uses of the module in chemical engineering courses
Process Design course:• develop and use environmental objective functions to rank process
design alternatives
• rank process designs quantitatively based on environmental criteria
Transport phenomena course:• Module on interphase mass transfer in the environment
University of Texas at Austin Michigan Technological University5
Module 6: Essential features of environmental impact assessment for
chemical process design
Computationally efficient
Environmental performance metrics quickly calculated using output from commercial process simulators
Link waste generation and release to environmental impacts
Environmental metrics linked to process parameters
Impacts based on a systematic risk assessment methodology
Release estimates fate and transport exposure risk
University of Texas at Austin Michigan Technological University6
Module 6: Systematic risk assessment methodology
National Academy of Sciences, 1983
1. Hazard Identification (which chemicals are important?)
2. Exposure assessment (release estimation, fate and transport, dose assessment)
3. Toxicity assessment (chemical dose - response relationships)
4. Risk Characterization (magnitude and uncertainty of risk)
Result: Quantitative risk assessment (e.g. excess cancers)
Atmospheric dispersion Model, Ca
Thibodeaux, L.J. 1996, Environmental Chemodynamics, John Wiley & Sons
University of Texas at Austin Michigan Technological University7
Carcinogenic Risk Example (inhalation route)
Module 6: Quantitative risk calculation
Risk i = (Ca CR EF ED)
(BW AT )SF
i
Exposure Dose
Dose - Response Relationship,Slope Factor
Result: # excess cancers per 106 cases in the population; 10-4 to 10-6 acceptable
Disadvantage: Only a single compartment is modeled / Computationally inefficient Highly uncertain prediction of risk
University of Texas at Austin Michigan Technological University8
Carcinogenic Risk Example (inhalation route)
Module 6: Relative risk calculation
Relative Risk =
(Ca CR EF ED)
(BW AT )SF
i
(Ca CREF ED)(BW AT )
SF
Benchmark
= Ca SF i
Ca SF Benchmark
Result: Risk of a chemical relative to a well-studied benchmark compound
Advantage: If C is calculated for all compartments using a multimedia compartment model, computationally efficient
University of Texas at Austin Michigan Technological University9
Module 6: Tier 3 Relative risk index formulation
Exposure Potential Inherent Impact Parameter
Chemical “i”Benchmark Compound
Dimensionless Risk Index ( Ii*) =
[(EP)(IIP)]i
[(EP)(IIP)]B
Process Index (I) (Ii* )
i1
N
(mi)EmissionRate ofChemical, i
Chemical Specific
Process
University of Texas at Austin Michigan Technological University10
Module 6: Airborne emissions estimation
Unit Specific EPA Emission Factors Distillation/stripping column vents Reactor vents Fugitive sources
Correlation (AP- 42, EPA) Storage tanks, wastewater treatment Fugitive sources (pumps, valves, fittings)
Criteria Pollutants from Utility Consumption Factors for CO2, CO, SO2, NOx, AP- 42 (EPA) factors
Process Simulators (e.g. HYSYS)
University of Texas at Austin Michigan Technological University11
Waste stream summaries based on past experience
1. Hedley, W.H. et al. 1975, “Potential Pollutants from Petrochemical
Processes”, Technomics, Westport, CT
2. AP-42 Document, Chapters 5 and 6 on petroleum and chemical industries,
Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm
3. Other sources
i. Kirk-Othmer Encyclopedia of Chemical Technology, 1991-
ii. Hydrocarbon Processing, “Petrochemical Processes ‘99”, March 1999.
Module 6: Release estimates based on surrogate processes
University of Texas at Austin Michigan Technological University12
Model Domain Parameters• surface area - 104 -105 km2
• 90% land area, 10% water• height of atmosphere - 1 km• soil depth - 10 cm• depth of sediment layer - 1 cm• multiphase compartments
Multimedia compartment model Processes modeled• emission inputs, E• advection in and out, DA
• intercompartment mass transfer, Di,j
• reaction loss, DR
Module 6: Multimedia compartment model formulation
Mackay, D. 1991, ”Multimedia Environmental Models", 1st edition,, Lewis Publishers, Chelsea, MI
University of Texas at Austin Michigan Technological University13
Module 6: Multimedia compartment model input data
Environmental Property UnitSpreadsheet
Location Benzene Ethanol PCPMolecular Weight g/mole C6 78.11 46.07 266.34
Melting Point ° C C7 5.53 115 174
Dissociation Constant log pKa C8 4.74
Solubility in Water g/m3 C11 1.78E+2 6.78E+5 14
Vapor Pressure Pa C12 1.27E+4 7.80E+3 4.15E-3
Octanol-Water Coefficient log Kow C13 2.13 -0.31 5.05
Half-life in air hr C33 1.7E+1 5.5E+1 5.50E+2
Half-life in water hr C34 1.7E+2 5.5E+1 5.50E+2
Half-life in soil hr C35 5.5E+2 5.5E+1 1.7E+3
Half-life in sediment hr C36 1.7E+3 1.7E+2 5.50E+3
University of Texas at Austin Michigan Technological University14
Module 6: Multimedia compartment model typical results
Chemical Percentage (%)
(emission scenario) Total mass(kg)
Air Water Soil Sediment
Benzene (a) 1.98x104 99.59 0.29 0.12 1.0x10-3
Benzene (b) 1.41x105 4.48 95.17 5.5x10-3 0.35
Benzene (c) 6.86x104 20.61 1.61 77.78 5.8x10-3
Ethanol (a) 4.56x104 92.87 3.85 3.28 2.9x10-3
Ethanol (b) 7.35x104 0.22 99.7 7.8x10-3 0.08
Ethanol (c) 7.84x104 0.92 5.64 93.42 0.02
Pentachlorophenol (a) 2.07x106 0.26 2.56 97.07 0.11
Pentachlorophenol (b) 4.59x105 7.2x10-5 96.19 0.03 3.78
Pentachlorophenol (c) 2.39x106 2.9x10-4 0.54 99.44 0.02
(a) 1000 kg/hr emitted into the air compartment(b) 1000 kg/hr emitted into the water compartment(c) 1000 kg/hr emitted into the soil compartment
University of Texas at Austin Michigan Technological University15
1. The percentages in each environmental compartment depend upon the emission scenario
a) the highest air concentrations result from emission into the air
b) the highest water concentrations are from emission into water
c) the highest soil concentrations are from emission into soil
d) highest sediment concentrations are from emission into water
2. Chemical properties dictate percentages and amounts
a) high KH results in high air concentrations
b) high KOW results in high soil concentrations
c) high reactions half lives results in highest pollutant amounts
Module 6: Multimedia compartment model typical results - interpretations
University of Texas at Austin Michigan Technological University16
Module 6: Nine Environmental Impact /Health Indexes
R ela t iv e R isk In d e x E q u a tio n
IG W , i* GWP i
G lo b a l W a r m in g
IG W , i* N C
MW C O2
MW i
O zo n e D ep le t io nIO D, i
* ODP i
S m o g F o rm a tio nI S F, i
* MIR i
MIR R O G
A cid R a inIA R, i
* ARP i
ARP S O2
GW P = g lo b a l w a rm in g p o ten tia l, N C = n u m b er o f c a rb o n s a to m s, O D P = o zo n ed e p le tio n p o te n ta l, M IR = m a x im u m in c re m e n ta l rea c tiv ity , A R P = a c id ra in p o ten tia l .
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R e l a t i v e R i s k I n d e x E q u a t i o n
H u m a n T o x i c i t yI n g e s t i o n R o u t e I *
IN G C W , i LD 5 0, To lu en e
C W , To lu en e LD 5 0, i
H u m a n T o x i c i t yI n h a l a t i o n R o u t e I *
IN H C A , i LC 5 0 , To lu en e
C A , To lu en e LC 5 0, i
H u m a nC a r c i n o g e n i c i t yI n g e s t i o n R o u t e
I *C IN G
C W , i HV i
C W , B en zen e HV B en zen e
H u m a nC a r c i n o g e n i c i t yI n h a l a t i o n R o u t e
I *C IN H
C A , i HV i
C A , B en zen e HV B en zen e
F i s h T o x i c i t yI *
F T C W , i LC 5 0 f , P C P
C W , P C P LC 5 0 f , i
L D 5 0 = l e t h a l d o s e 5 0 % m o r t a l i t y , L C 5 0 = l e t h a l c o n c e n t r a t i o n 5 0 % m o r t a l i t y ,a n d H V = h a z a r d v a l u e f o r c a r c i n o g e n i c h e a l t h e f f e c t s .
Module 6: Nine Environmental Impact /Health Indexes
University of Texas at Austin Michigan Technological University18
Multi-Criteria Decision Analysis Multi-Criteria Decision Analysis
. . . . . . . . . . Chemical I1 InI2
EmissionRate
AABBCC
nn . . . . . . . . . .
ReportReport
Process Simulator OutputProcess Simulator Outputor Conceptual Designor Conceptual Design
EFRATEFRAT
. . . . . . . . . .
. . . . . . . . . . MS ExcelMS Excel®®
List of Chemicals, Equipment specifications, Utility consumption, Annual throughput
Chemicals,Equipment specifications, annual throughput
Chemicals, KH, KOW
Chemicals,, LC50, HV, MIR…
Physical Properties, Toxicology, Physical Properties, Toxicology, Weather, Geographical,Weather, Geographical,
and Emission Factors Databasesand Emission Factors Databases
Air Emission Air Emission CalculatorCalculator
Chemical Partition Chemical Partition CalculatorCalculator
Relative Risk IndexRelative Risk IndexCalculatorCalculator
University of Texas at Austin Michigan Technological University19
Environmental Fate and Risk Assessment Tool (EFRAT)• links with HYSYS for automated assessments
WAste Reduction Algorithm (WAR)• reported to be linked with ChemCAD
• US EPA National Risk Management Research Laboratory
Cincinnati, OH
Dr. Heriberto Cabezas and Dr. Douglas Young
US Environmental Protection Agency
National Risk Management Research Laboratory
26 W. Martin Luther King Dr.
Cincinnati, OH 45268
Module 6: Software tools for environmental impact assessment of
process designs
University of Texas at Austin Michigan Technological University20
Gaseous Waste StreamToluene & Ethyl Acetate193.5 kg/h each; 12,000scfm, balance N2
Vent
Vent ; 21 - 99.8 % recoveryof Toluene and Ethyl Acetate
Make-up oilAbsorption oil (C-14)10 – 800 kgmole/h
50/50 MassMixed Product
AbsorptionColumn
DistillationColumn
Module 6: Absorption - distillation process:analysis of an existing separation
sequence
HYSYS Flowsheet
University of Texas at Austin Michigan Technological University21
Module 6: Unit-specific emission summary
100 kgmole/hr Oil Flow Rate;
Oil Temperature = 82˚F; T=180˚FWhere are the centers for energy consumption and emissions?
UNIT OPERATION Mass
Flow Toluene Ethyl C-14 SOx NOx CO2 CO TOC
"METHOD" (kg/hr) Acetate
Absorption
Column "HYSIS" 19,840 0.002 128 4.23
Distillation "emission
Column factor" 259.1 0.019 0.007
Fugitive "emission
Sources factor" 259.1 0.062 0.062
Storage
Tank "correlation" 259.1 0.0014 0.0014
Reboiler
Energy (10 6 Btu/hr) 6.16 3.93 0.52 499 0.129 0.007
Total Emissions (kg/hr) 0.088 128.07 4.23 3.93 0.52 499 0.129 0.007
Emission rate (kg/hr)
University of Texas at Austin Michigan Technological University22
Module 6: Risk index summary
Which chemicals have the highest impact indexes?
Compound I* GW I* OD I* SF I* AR I* ING I* INGC I* INH I* INHC I* FT
Toluene 3.34 0 0.9 0.0 1 0 1.0 0 0.02
Ethyl Acetate 2 0 0.3 0.0 9.7 0 3.3 0 0.04
SOx 0 0 0.0 1.0 0 0 0.0 0 0.00
NOx 40 0 0.0 0.7 0 0 0.0 0 0.00
CO2 1 0 0.0 0.0 0 0 0.0 0 0.00
CO 0 0 0.0 0.0 0 0 141.2 0 0.00
C-14 3.1 0 0.0 0.0 0 0 0.0 0 0.00
TOC 3.1 0 1.0 0.0 0 0 0.0 0 0.00
Relative Risk Index (I*)
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Module 6: Process environmental summary
All units in kg/yrEmission from IFT IING IINH IGW ISF IAR
utility 0.00E+00 0.00E+00 1.44E+05 5.21E+06 1.70E+02 1.27E+04
absorber 4.67E+04 1.08E+07 3.73E+06 2.36E+06 3.74E+05 0.00E+00
tank 3.36E+00 6.43E+02 2.55E+02 2.95E+02 1.09E+02 0.00E+00
distillation column 5.06E+00 6.43E+02 3.60E+02 6.82E+02 3.12E+02 0.00E+00
fugitive 3.12E+01 5.30E+03 2.35E+03 2.90E+03 1.12E+03 0.00E+00
Emission of IFT IING IINH IGW ISF IAR
Ethyl Acetate 4.68E+04 1.09E+07 3.73E+06 2.24E+06 3.72E+05 0.00E+00
Toluene 1.92E+01 1.22E+03 1.22E+03 4.07E+03 2.11E+03 0.00E+00
Tetradecane 0.00E+00 0.00E+00 0.00E+00 1.15E+05 1.14E+03 0.00E+00
Carbon dioxide 0.00E+00 0.00E+00 0.00E+00 4.87E+06 0.00E+00 0.00E+00
Carbon monoxide 0.00E+00 0.00E+00 1.44E+05 0.00E+00 0.00E+00 0.00E+00
Nitrogen dioxide 0.00E+00 0.00E+00 0.00E+00 3.40E+05 0.00E+00 6.39E+03
Sulfur dioxide 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 6.36E+03
TOC 0.00E+00 0.00E+00 0.00E+00 6.51E+02 1.35E+02 0.00E+00
Process Index (I) (Ii*) i1
N
(mi )100 kgmole/hr Oil Flow Rate;
Oil Temperature = 82˚F; T=180˚F
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Module 6: VOC recovery by absorption into tetradecane (C14)
0
20
40
60
80
100
120
0 100 200 300 400 500 600
Absorber Oil Flow Rate (kgmole/hr)
% R
eco
very
of
VO
Cs
Toluene Ethyl Acetate
University of Texas at Austin Michigan Technological University25
Module 6: Environmental index profiles
0 10 2050
100200
300400
500
IGW
100 IAR
10 IINH0
500
1000
1500
2000
2500
3000
Absorber Oil Flow Rate (kgmoles/hr)
Indexes(kg/hr)
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Module 6: Interpretation of environmental assessment results
Risk reductions at 50 kgmole/hr flow rate Global Warming Index - 41% reduction Smog Formation Index - 86 % reduction Acid Rain Index - small increase Inhalation Route Toxicity Index - 78 % reduction Ingestion Route Toxicity Index - 18 % reduction Ecotoxicity (Fish) Index - 19 % reduction
Absorber oil choice is not an optimum Oil selectively absorbs toluene, but ethyl acetate has a higher value
Multiple indexes complicate the decision
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Use of EFRAT : evaluate the MA process
Basecase (Dibutyl phthalate absorber oil) with and without heat integration
Simulate 3 case studies using heat integrated flowsheet» Dibutyl phthalate absorber oil» Dibenzyl ether absorber oil» Diethylene glycol butyl ether acetate absorber oil
Module 6: Maleic anhydride from n-butane process flowsheet evaluation
University of Texas at Austin Michigan Technological University28
Follow the tutorial instructions given in the notebook!
The SCENE file has been linked to a HYSYS case file
Add three additional emission sources
Complete the relative risk assessment calculations
Module 6: Maleic anhydride from n-butane:
Use of EFRAT on basecase flowsheet
University of Texas at Austin Michigan Technological University29
Module 5: Heat integration of the MA flowsheet
Without Heat Integration
9.70x107 Btu/hr-9.23x107 Btu/hr
2.40x107 Btu/hr
-4.08x107 Btu/hr
Reactor streams generate steam
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Module 5: Maleic anhydride flowsheet with heat integration
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Module 6: Maleic anhydride from n-butane:
effect of heat integration on risk indexes
IGW ISF IAR IINGIINH
IFT
No Heat Integration
Heat Integration1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
1.E+10
Relative Risk Indexes
(kg/yr)
30.4%reduction
72.2%reduction
RemainingIndexes areunchanged
University of Texas at Austin Michigan Technological University32
IGWISF IAR
IINGIINH
IFT
Dibutyl Phthalate
Dibenzyl Ether
DGBEA1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
1.E+10
Relative Risk Index
(kg/yr)
Module 6: Maleic anhydride from n-butane:
effects of absorber oil choice
16.3%reduction
85.1%reduction
81.7%reduction
42.1%reduction
University of Texas at Austin Michigan Technological University33
Module 6: Summary / Conclusions
Educational goals and topics covered in the module
Potential uses of the module in chemical engineering courses
Review of environmental impact assessment methods
Application of Tier 3 environmental impact assessment to a detailed flowsheet - Chapter 11 » Heat integration of the Maleic Anhydride flowsheet
» Effects of absorber oil choice for the MA flowsheet