CENTER FOR CHEMICAL PROCESS SAFETY -...
Transcript of CENTER FOR CHEMICAL PROCESS SAFETY -...
GUIDELINES FOR
Use of Vapor Cloud
Dispersion Models
SECOND EDITION
CENTER FOR CHEMICAL PROCESS SAFETY
of the
American Institute of Chemical Engineers345 East 47th Street, New York, NY 10017
Copyright © 1996American Institute of Chemical Engineers345 East 47th StreetNew York, New York 10017
All rights reserved. No part of this publication may be reproduced,stored in a retrieval system, or transmitted in any form or by anymeans, electronic, mechanical, photocopying, recording, or otherwisewithout the prior permission of the copyright owner.
Library of Congress Cataloging-in Publication DataGuidelines for use of vapor cloud dispersion models / Center for
Chemical Process Safety of the American Institute of ChemicalEngineers.
p. cm.Includes bibliographical references and index.ISBN 0-8169-0702-11. Atmospheric diffusion—Mathematical models. 2. Hazardous
substances—Environmental aspects—Mathematical models.3. Vapor clouds—Mathematical models. I. American Institute ofChemical Engineers. Center for Chemical Process Safety.QC880.4.D44G85 1996628.5T0113—<ic20 96-26950
This book is available at a special discount when ordered in bulk quantities.For information, contact the Center for Chemical Process Safety of theAmerican Institute of Chemical Engineers at the address shown above.
It is sincerely hoped that the information presented in this document will lead to an even moreimpressive safety record for the entire industry: however, the American Institute of ChemicalEngineers, its consultants. CCPS subcommittee members, their employers, their employers'officers and directors and EARTH TECH disclaim making or giving any warranties orrepresentations, express or implied, including with respect to fitness, intended purpose, use ormerchantability and/or correctness or accuracy of the content of the information presented inthis document. As between (1 ) the American Institute of Chemical Engineers, its consultants.CCPS subcommittee members, their employers, their employers' officers and directors andEARTH TECH and (2) the user of this document, the user accepts any legal liability orresponsibility whatsoever for the consequence of its use or misuse.
Preface
For 40 years the American Institute of Chemical Engineers (AIChE) hasbeen involved with process safety and loss control issues in the chemical,petrochemical, hydrocarbon process, and related industries and facilities.AIChE publications and symposia are information resources for the chemi-cal engineering and other professions on the causes of process incidents andthe means of preventing their occurrences and mitigating their consequences.
The Center for Chemical Process Safety (CCPS), a directorate ofAIChE, was established in 1985 to develop and disseminate technicalinformation for use in the prevention of major chemical process incidents.With the support and direction of the CCPS Advisory and Managing Boards,a multifaceted program was established to address the need for processsafety management systems to reduce potential exposures to the public,facilities, personnel, and the environment. This program involves thedevelopment and publication of guidelines related to specific areas ofprocess safety management; organizing convening, and conducting semi-nars, symposia, training programs, and meetings on process safety-relatedmatters; and cooperation with other organizations, both internationally anddomestically, to promote process safety. CCPS's activities are supported byfunding and expertise from over 90 entities.
In 1987 CCPS published Guidelines for Use of Vapor Cloud DispersionModels, and in 1989, Workbook of Test Cases for Vapor Cloud SourceDispersion Models. These books have served well but are now outdated.At nearly a decade old, they refer to an earlier generation of vapor cloudmodels.
The present book has been expanded to include both source term modelsand vapor cloud dispersion models, and it incorporates worked exampleswith the model descriptions.
Acknowledgments
The American Institute of Chemical Engineers and the Center for ChemicalProcess Safety (CCPS) express their gratitude to all the members of theVapor Cloud Modeling Subcommittee for their unstinting efforts andtechnical contributions in the preparation of this Guidelines. The membersof this distinguished group are:
Ronald J. Lantzy, Chair
Gib R. Jersey, Vice ChairWilliam J. Hague, Past ChairDouglas N. BlewittSanford G. BloomDonald J. ConnolleyGeorge E. DeVaullSeshu DharmavaramEbrahim EsmailiDavid J. Fontaine
Gene K. LeeJohn T. MarshallDavid McCreadyRobert MoserRonald D. MyersMalcolm L. PrestonJerry M. SchroyKenneth W. SteinbergJawad Touma
Rohm and Haas Company
Mobil Technology CompanyAlliedSignal, Inc.Amoco CorporationLockheed Martin Energy SystemsAKZO Nobel Chemicals, Inc.
Shell Oil CompanyDuPont CompanyExxon Research and Engineering Co.Chevron Research and Technology Co.
Air Products and Chemicals, Inc.Dow USA, Texas Operations
Union Carbide CorporationCigna Property and CasualtyRohm and Haas CompanyICI Engineering TechnologyMonsanto CompanyExxon Research and Engineering Co.U.S. Environmental Protection Agency
CCPS guidance and counsel were appropriately provided by its recentdirector, Bob G. Perry, and its current director, Jack Weaver. Liaisonbetween the Subcommittee and CCPS was provided by William J. Minges,CCPS Staff.
The contract for preparing the Guidelines was awarded to EARTH TECH(formerly Sigma Research Corp.), Concord, MA. The following people arethe authors of this book:
Steven R. Hanna, EARTH TECH.Peter J. Drivas, Gradient Corp.Joseph J. Chang, EARTH TECH.
We acknowledge the dozens of scientists and engineers who prepareduseful discussions of their models, who took the time to complete question-naires, and who sent copies of relevant manuscripts to EARTH TECH.
CCPS also expresses its appreciation to members of the TechnicalSteering Committee for their valuable advice and support.
The group to whom the Subcommittee is especially indebted consistsof those who volunteered to provide peer review:
J. Steven Arendt JBF Associates, Inc.Daniel A. Crowl Michigan Technological UniversityThomas O. Gibson Dow Chemical CompanyKenneth Harrington BattelleMichael J. Hitchler Westinghouse Savannah River CompanyJohn A. Hoffmeister Lockheed Martin Energy SystemsJohn Hudson PC/?, Inc.Dimitrios Karydas Factory Mutual Research Corporation
Steven Kent Raytheon Engineers and Constructors, Inc.Georges A. Melham Arthur D. Little, Inc.Kenneth Mosig AIU Energy/Starr Technical Risks Agency, Inc.John A Noronha Eastman Kodak CompanyFrank P. Ragonese Mobil Oil Corporation
Nomenclature
First mention
SECT. EQ. NO.
al9a2 Entrainment constants 5.2.2 (5-7)
A (m2) Effective cross-sectional building area 5.7.2 (5-66)
A1 ? A2 Constants in cloud depth formulas 5.3.2 (5-34)
Ah(m2) Puncture area 4.2.1 (4-2)f\
A (m) Area of pipe or pool 4.2.1 (4-6)
Bc (m s~ ) Buoyancy flux for continuous plume 5.1 (5-3a)
B{ (m4s~2) Buoyancy flux for instantaneous cloud 5.1
SjOnV1) Continuous liquid spill rate 4.2.4 (4-19)
с (ms"1) Speed of sound in gas 4.2.2 (4-10)
c2(10"12m2(im~2) Conversion factor 5.9.1 (5-67)
снт (J s^m'2^1) Heat transfer coefficient 4.2.5 (4-23)
c0 Discharge coefficient 4.2.1 (4-2)
cp (J kg^Kr1) Gas specific heat at constant pressure 4.2.1
cpa (J kg^K'1) Specific heat of air 5.6 (5-54)
cpl (J kg^K'1) Liquid heat capacity 4.2.3.2 (4-15)
cpm (J kg^K"1) Specific heat of hazardous gas 5.6 (5-54)
cps (J kg^KT1) Specific heat of underlying surface 5.3.3 (5-37)
cv (J kg^KT1) Gas specific heat at constant volume 4.2.1
C(kgm~3) Concentration 2.1 (2-1)
С Dimensionless concentration 5.7.2 (5-63)
C* (kg m"3) Concentration threshold 6.5
C(kgnT3)
C0'(kgm-3)
Cp'(kgm-3)
C^kgkg-1)
C/'Ckgkg-1)Ccl(kgnf3)
c,Cm(kgnf3)QCkgrn-3)C0(kgm-3)Cp(kgm-3)C^Ckgm-3)
4(m)
D (mV1)
DB (mV1)
Dc(m)
Я;(т)
D0(m)
£p(m)/>р(цт)
ERPG
/
/area
F^CkgnrV1)Fwet (kg m~2s~1)FAC2FB
g (ms~2)
£0(ms-2)GCkgs-V2)
hc (Wm"2 K"1)
Mm>
Mean or average concentration
Observed concentration random variability
Predicted concentration random variability
Concentration of gas in plume
Concentration of liquid in plumeConcentration on plume centerlineCloudiness indexMean concentrationInitial concentrationObserved concentrationPredicted concentrationPeak concentration
Tank diameterMolecular diffusivity of pollutant gasBrownian diffusivity for particlesSource dimension for continuous releaseSource dimension for instantaneous releaseInitial cloud widthPipe diameter
Particle diameter
Emergency Response Planning Guidelines
Pipe friction factorArea view factorParticle deposition fluxWet deposition fluxFraction within a factor of twoFractional bias
<2Acceleration of gravity (9.8 ms )
Reduced gravity = g(p0 - pa)/pa
Mass emission rate per unit area
Heat transfer constantInitial cloud depth
6.3
6.6 (6-18)
6.6 (6-19)
5.6 (5-51)
5.6 (5-53)6.34.2.5 (4-25)5.55.2.2 (5-13)6.6 (6-18)6.6 (6-18)6.3
4.2.2 (4-11)5.9.2 (5-75b)5.9.2 (5-76)5.55.55.1 (5-1)4.2.1 (4-6)
5.9.1 (5-67)
3.4
4.2.1 (4-6)4.2.5 (4-24)5.9.1 (5-69)5.9.2 (5-80)8.2 (8-4)8.2 (8-5)
3.3 (3-1)
5.54.2.3.2(4-15)
5.3.3 (5-38)5.3.2
Лр(т)Ag(m)Яв(т)Hf(mKs~l)Я, (т)tfs(WnT2)
#vap(Jkg~')
#wc (m>
/fcgCms-1)
Plume centerline height above ground
Stack height
Building height
Sensible heat flux
Height of liquid above puncture
Convective heat flux
Heat of vaporization of liquid
Plume depth, worst case
Intermittency of concentration record
Mass transfer coefficient
fcs (J s"1 m~1K~1)Thermal conductivity of soil
KF, K^, Kg
К (т2 s'1)
L(m)
Mm)
Mm)Mm)LAI
т (kg)
ntj (kg)mt (kg)
Dimensionless factors
Eddy diffusivity vector
Monin-Obukhov length
Length of building wake or cavity
Length of pipe
Length of tank
Leaf Area Index
Liquid mass in pool
Mass of gas component j
Total mass in pipeline
M (kg kg-mole"1 ) Molecular weight
Mi (kg kg-mole~ ) Molecular weight of gas component у
M0(mV2)
MG
«To
^Re
^Sc
^Sh
"st
P
p (N m"2)
Initial plume momentum flux
Geometric mean
Total moles of liquid
Reynolds number
Schmidt number
Sherwood number
Stokes number
Probability density function
Tank pressure
5.4 (5-40)
5.1 (5-4a)
5.7.1 (5-62)
3.3 (3-1)
4.2.2 (4-10)
5.3.3 (5-38)
4.2.3.1 (4-14)
2.1 (2-1)
6.4 (6-13)
4.2.5.2 (4-29)
4.2.5.1 (4-28)
4.2.1 (4-6)
5.6 (5-49)
3.3 (3-1)
5.7.4
4.2.1 (4-6)
4.2.2 (4-13)
5.9.2 (5-78b)
4.2.5 (4-22)
5.3.2 (5-17)
4.2.1 (4-5)
4.2.1
5.3.2 (5-17)
5.2.1 (5-17)
8.2 (8-1)
4.2.6 (4-34)
4.2.5.2 (4-30)
4.2.5.2 (4-30)
4.2.5.2 (4-30)
5.9.2 (5-77)
6.3 (6-6)
4.25.1 (4-1)
pa(Nm-2)
P,s(Nm-2)
/>0(NnT2)
Pv(NnT2)
P (mm ЬГ1)
P
^(kgs-'nT2)
«condCJs'1)
<?conv (J s ')
^evapCJs"1)
^(JS4)
««mCJs'1)eckgs-1)Gangs'1)GfCkgs-1)
6i(kg)e.ckgs-1)GoCkgs-1)
r(m)
r.Csm-1)
rcut (s nf1)
r^sm"1)
rgtsnT1)
r,(m)
rs (s m-1)rt (s m'1)
R
R(m)
R (J КГ1 kg'1)
R*
Ri*
».
'̂o
Ambient pressure
Saturation vapor pressure of component i
Stagnation pressure
Vapor pressure
Precipitation rate
Cumulative density function
Evaporation rate per unit area
Conduction heat transfer from ground
Convection heat transfer from air
Heat loss due to evaporation
Radiative heat transfer from air
Incident solar radiation
Source mass emission rate
Evaporation rate of liquid pool
Mass emission rate of liquid that flashes
Mass in instantaneous cloud release
Liquid mass flow rate
Initial source mass emission rate
Distance on building from source to receptor
Aerodynamic resistance
Cuticle resistance
Stomate resistance
Resistance to transfer across surface
Liquid pool radius
Surface resistance
Transfer resistance
Correlation coefficient
Plume radius
Gas constant for specific gas
4.2.1 (4-1)
4.2.6 (4-34)
4.2.3.2(4-15)
4.2.3.2(4-15)
5.9.2 (5-81)
6.3 (6-7)
4.2.6 (4-34)
4.2.5 (4-22)
4.2.5 (4-22)
4.2.5 (4-22)
4.2.5 (4-22)
4.2.5 (4-22)
2.1 (2-1)
4.2.5 (4-26)
4.2.3.1 (4-14)
5.4 (5-4)
4.2.2 (4-10)
4.2.1 (4-4)
5.7.2 (5-64)
5.9.2 (5-70)
5.9.2 (5-78b)
5.9.2 (5-78b)
5.9.2 (5-78b)
4.2.4 (4-18)
5.9.2 (5-70)
5.9.2 (5-70)
8.2 (8-3)
5.2.2 (5-7)
5.3.2 (5-17)
Universal gas constant (83 10 J K~l kg-mole"1) 4.2. 1
Local cloud Richardson number
Ambient Richardson number
Critical Richardson number
5.3.2 (5-30)
5.6 (5-60)
5.1 (5-1)
s(m)
•̂ CF
t(s)
fe(s)Г(К)
Г* (К)ГЬ(К)rd(s)r,(s)
. Г0(К)
ГР(К)
Г,(8)
^soil(K)
w (m s"1)
и (m s'1)
u (m s"1)
M! (m s~ )
w* (m s~l)
wa (m s"1)
we (m s-1)
мн (m s"1)
ws (m s"1)
wst (m s'1)
wwc (m s'1)
v (m s"1)
vd (m s'1)vedge (m S"1)
v^kg-1)
vs (m s'1)vtop (m s'1)VctmV1)
^(mV1)
Distance along plume axis
Slip correction factor
Time
Exposure time
Temperature turbulent fluctuation
Temperature, air
Normal boiling point of liquid
Time duration of release
Integral time scale
Temperature, tank
Pool temperature
Sampling time
Soil temperature
Wind speed
Wind speed turbulent fluctuation
Wind vector
Wind speed at height of 1 m
Friction velocity
Advection velocity of cloud
Entrainment rate
Wind speed at height of building
Plume speed along axis
Wind speed at stack height
Wind speed, worst case
Gross entrainment velocity
Dry deposition velocity
Edge entrainment velocity
Difference in specific volume between
liquid and gas
Gravitational settling speed
Top entrainment velocity
Volume flow rate
Initial volume flow rate
5.2.2 (5-7)
5.9.1 (5-68)
4.2.1 (4-4)
6.5
3.3 (3-3)
3.1
4.2.3.1 (4-14)
5.5
6.3 (6-9)
4.2.1
4.2.5 (4-22)
6.3
4.2.5.1 (4-28)
3.3 (3-4)
3.3 (3-2)
5.6 (5-49)
9.1
3.3 (3-1)
5.3.2 (5-20)
5.2.1
5.7.2 (5-63)
5.2.2 (5-7)
E (E-9)
2.1 (2-1)
5.3.2 (5-26)
5.9.2 (5-70)
5.3.2 (5-28a)
4.2.3.2(4-15)
5.9.1 (5-67)
5.3.2 (5-28a)
5.3.2 (5-28a)
5.1 (5-1)
V j (m3)Vio(m3)
V, (m3)
Mm3)VG
w(ms-1)
w' (m s"1)
w0 (m s"1)
W(m)
WB(m)
Wc(m)
Wwc (m)
*(m)
*g(m)о
xix0(m)
xv(m)
y(m)
?o(m)
z(m)
Zd(m)
«„(т)zp(m)
a
as (m2 s-1)
P(s)
Y=Vc v
8
AC0(kgnT3)
ACp(kgm-3)
Volume of instantaneous cloud
Initial volume of instantaneous cloud
Volume of liquid in tankVolume of instantaneous spill
Geometric variance
Local jet vertical speed
Vertical wind speed fluctuation
Initial jet velocity
Plume widthWidth of building
Width of canyon between buildings
Plume width, worst case
Distance from cloud to receptor
Distance where plume touches ground
Initial liquid mole fraction of component i
Alongwind position of cloud center
Virtual source distance
Lateral position
Lateral centerline position of plume
Height above ground
Reference height (usually 10 m)
Roughness length
Plume height above source
Mass conservation factor
Thermal diffusivity of soil
Time constant for release from pipe
Gas specific heat ratio
Dirac delta function
Data error in observed concentration
Error in predicted concentrationdue to data errors
5.3.2 (5-18)
5.1 (5-2)
4.2.2 (4-11)4.2.4 (4-18)
8.2 (8-2)
5.2.1
3.3 (3-3)
5.2.1
8.4
5.7.2
5.7.1 (5-61)
2.1 (2-1)
5.1 (5-2)
5.2.2 (5-12)
4.2.6 (4-34)
5.4 (5-41)
5.4
5.4 (5-40)
5.4 (5-40)
3.3 (3-4)
5.9.2 (5-71)
3.2
5.2.1 (5-5)
4.2.1 (4-4)
4.2.5.1 (4-28)
4.2.1 (4-4)
4.2.1 (4-1)
6.4 (6-13)
6.6 (6-18)
6.6 (6-19)
Ah (т)
^upwind (m>
Ay(m)
^initial (m)
V
8
ed (m2 s-3)
A(s-!)
fiCkgnfV 1)
v(m2 s"1)
Ф.П
Фpa(kgnT3)
Paer (kg m"3)
p! (kg пГ 3)
p0(kgnT3)
Ppo (kg m""3)Ps(kgm-3)
psp (kg пГ3)
pw(kgnT3)
ac (kg m-3)
Maximum rise of dense plume
Distance dense cloud travels upwind
Crosswind distance traveled by plume
Distance cloud spreads laterally at source
Del operator
Liquid emissivity
Eddy dissipation rate
Wet removal inverse time scale
Air viscosity
Molecular viscosity of air
Solar angle above horizon
Dimensionless function of Ri
Ambient air density
Mass of aerosol per unit cloud volume
Liquid density
Gas density in tank
Initial plume density
Density of underlying surface
Solid particle density
Density of water
Standard deviation of concentrationfluctuations
OSB = 5.67 x 10~8 J s'V^K"4 Stefan-Boltzmann constant
cx(m)
Sy(m)
Gyi (m)az(m)
ene^0)
Alongwind dispersion parameter
Lateral dispersion parameter
Lateral dispersion of instantaneous puff
Vertical dispersion parameter
Angle of plume axis with horizontal
Angle of liquid surface in tank
5.2.2 (5-11)
5.3.2 (5-22)
5.2.1 (5-6)
5.3.2 (5-23)
5.6 (5-49)
4.2.5 (4-24)
5.2.2 (5-15)
5.9.2 (5-79)
5.9.1 (5-67)
5.9.2 (5-75a)
4.2.5 (4-25)
5.6 (5-57)
5.1 (5-1)
5.3.2 (5-16)
4.2.2 (4-11)
4.2.1 (4-2)
5.1 (5-1)
5.3.3 (5-37)
5.9.1 (5-67)
4.2.4 (4-20)
6.4 (6-15)
4.2.5 (4-24)
5.4 (5-41)
5.3.1
6.3 (6-3)
5.3.1
5.2.2 (5-7)
4.2.2 (4-13)