prof s. a. abbasi - proses güvenliği · control of mpfs as compared to stand-alone ... individual...
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Multiple pool fires
Prof S. A. AbbasiEmeritus Professor
Centre For Pollution Control and Environmental Engineering
Pondicherry University
Dr S. M. TauseefAssistant Professor
Department of Health, Safety and Environment
University of Petroleum and Energy Studies (UPES)
Dr Tasneem AbbasiAssistant Professor
Centre For Pollution Control and Environmental Engineering
Pondicherry University
Pondicherry University
Multiple Pool fires (MPFs)
When two or more pool fires burn in close enough proximity to influence one another, they are termed ‘Multiple Pool Fires’ (MPFs)
Pondicherry University
MPFs may burn brighter than stand-
pool fires but there is little work that
can throw light on them
● Even though MPFs have known to occur fairly often in process industries, much lesser work has been done towards simulation, modeling and control of MPFs as compared to stand-alone pool fires
● Past accident analysis reveals that MPFs have huge destructive potential and have been responsible for some of the worst process industry accidents
● Surprisingly few studies exist on the mechanism of MPF development and the factors that control it
● Of special concern is the paucity of knowledge about such interactive effects of pool fires which can make MPFs more destructive than non-interacting pool fires of identical numbers and sizes
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MPFs vs stand-alone pool fires
Different forms of interactive effects distinguish MPFs in contrast to stand alone pool fires
● Individual pool fires start to burn more intensely with higher flames as the distance between them is decreased
● The interaction of number of fires burning in close proximity has substantial effect on
– the burning rate of the fuel,
– the size of the flame, and
– the rate of heat transfer from the flame to the surroundings
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A commonly observed sequence of
events in incidents leading to MPFs
Ignition source
Vapor cloud explosion
Pool fireMultiple pool fires
Pool formation
Vapor cloud formation
Overfilling
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1975 Beek, Netherlands
Naphtha, propylene
None 14 / 107 Not reported
Not reported
22.8
1977 Umm said, Qatar
Liquid propane, butane
37,521
19,873
7 / 13 100 7 76.35
1981 Shuaiba refinery tank farm, Kuwait
Petrochemicalgrade naphtha
Not reported
1 / 1 50 6 42
1983 Milford Haven, UK.
Crude oil 47,000 0 / 20 150 3 7.3
1983 Newark, New jersey, US
Gasoline 6,677 1 / 0 50 1 10
1985 Naples, Italy Gasoline, diesel, and fuel oil
27, 000 5 / 170 Not reported
6 51
1986 Thessaloniki,Greece
Crude oil, fuel oil and gasoline
Not reported
Not reported
Not reported
Not reported
Not reported
1987 Lyon, France Domestic fuel and diesel fuel
1,900
1,200
2 / 14 200 1 26
Year Location Material/ substance
Quantity (KL)
Dead / injured
Reported maximum flame height (m)
Duration (days)
Economic losses (million US $)
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A recent example of an MPF accident
Jaipur, India, 2009
Leak from a pipeline during the transfer of
petrol
Vapour cloud explosion
11 pool fires initiated
Flames visible from a distance of 30 KmFire raged for about 2 weeks till all the fuel was burnt off
12 killed200 injured$ 32 million worth of damage caused
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Factors governing MPFs
● Separation distance
● Wind effect
● Characteristics and quantity of fuel present in the pools
● Combustion products
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Huffman et al 1969Effect of separation distance on flame interactions
Individual fires
Interacting fires
Merged fires
Fuel: n-hexane, Burners: 9, Burner dia: 4-in
Dec
reas
ing
sep
arat
ion
dis
tan
ce
S
D
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Huffman et al 1969Burning rates of interacting 4-in cyclohexane fires
Center burner
Outer burners
Dimensionless separation distance, S/D
Bu
rnin
g ra
te p
er
un
it a
rea,
lb/h
rft
2
S
D
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Observations from tests
Decreasing separation distance
Flames interact
Increases the burning rate, heat release rate, flame height
Critical separation distance
Flames merge
Burn with maximum heat release rate and flame height
Burning rate and heat release rate fall, but remain at much elevated levels compared to individual fires
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Controlled experiments on MPFs
Summary of findings
● Overall flame length as well as the mass burning rate increased with decrease in the separation distance between MPFs (Liu et al., 2009; Fukuda et al., 2004; Huang and Lee, 1967; Vincent and Gollahalli, 1995; Liu et al., 2007)
● The rate of flame propagation, depth of the burning zone and the mass burning rate increases with increasing wind velocities (Rios et al. 1967)
● Closer proximity also contributed to higher flame height and heat release rate (Weng et al., 2004; Delichatsios, 2007; Vincent and Gollahalli, 1995; Fukuda et al., 2004; Liu et al., 2007)
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Modeling of MPFs
Only a few empirical and field models have been developed to model MPFs
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Modeling of MPFs
● The empirical models for MPFs developed so far have aimed to correlate the total thermal energy radiated by the MPFs with the physical characteristics of fire, aspects of overall combustion chemistry, and variation of the thermal output from different parts of MPFs
● These models can be used to estimate
– Flame geometry
Sugawa and Takahashi, (1993); Weng et al., (2004); Delichatsios, (2007); Huang and Lee, (1967)
– Burning rate
Huffman et al., (1969); Rios et al., (1967); Liu et al., (2009)
– Radiation from an MPF
Weng et al., (2004); Fukuda et al., (2005); Delichatsios, (2007)
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Controlled experiments on MPFs
Fuels tested
• Fuels tested were mostly clean burning fuels
• Such flames give rise to optically thin flames with little soot
Diameter of individual pools
• Largest size of pool studied is 0.8 m
• All other studies are on smaller pool sizes (0.02 m to 0.15 m)
• At diameters>0.2 m, heat transfer is dominated by radiation, as in large scale pool fires
Limited applicability of the data from these tests for
extrapolating results to simulate larger
MPFs
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Comparison of the predictions for flame height, burning rate, and HRR by various
empirical models with corresponding experimental data reported by Vincent
and Gollahalli (1995) and Koseki and Yumoto (1989) for MPF involving pool fires of
diameter 25.4 cm and 80 cm respectively
Models Diameter of
the pool
fires used in
the
experiment
on which
the model is
based (m)
MPF with 25.4 cm diameter pool fires
as used in experiment by Vincent and
Gollahalli (1995)
MPF with 80 cm diameter pool fires as
used in experiment by Koseki and Yumoto
(1995)
Model
predictions
Percentage error
(deviation from the data
reported by Vincent and
Gollahalli (1995))
Model predictions Percentage error
(deviation from the
data reported by
Koseki and Yumoto
(1989))
Flame height
Sugawa and
Takahashi, 1993
0.12 0.859 20 % 6.1 22 %
Weng et al.,
2004
0.0015 0.823 23% 6.4 28 %
Delichatsios,
2007
0.15 0.921 14 % 5.8 16 %
Performance of the empirical models
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Comparison of the predictions for flame height, burning rate, and HRR by various
empirical models with corresponding experimental data reported by Vincent
and Gollahalli (1995) and Koseki and Yumoto (1989) for MPF involving pool fires of
diameter 25.4 cm and 80 cm respectively
Models Diameter of
the pool
fires used in
the
experiment
on which
the model is
based (m)
MPF with 25.4 cm diameter pool fires
as used in experiment by Vincent and
Gollahalli (1995)
MPF with 80 cm diameter pool fires as
used in experiment by Koseki and Yumoto
(1995)
Model
predictions
Percentage error
(deviation from the data
reported by Vincent and
Gollahalli (1995))
Model predictions Percentage error
(deviation from the
data reported by
Koseki and Yumoto
(1989))
Burning rate
(Huffman et al.,
1969)
0.05, 0.10
and 0.15
0.0295 44% 0.0276 49%
(Liu et al., 2009) 0.05 0.0458 13% 0.0431 19%
HRR
(Weng et al.,
2004)
0.0015 174 26% - -
(Fukuda et al.,
2005)
0.048 104 24% - -
(Delichatsios,
2007)
0.15 118 14% - -
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Work we have done
Over the last 3 years the we have:
● Carried out a close study of all previous efforts to model MPFs and elucidate their mechanism
● Carried out CFD-based simulations using experimental data reported earlier by other authors to ascertain the efficacy of CFD in pool fire modeling and simulation
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CFD studies
● Evaluated several CFD turbulence models for the simulation of pool fires
● The standard k-ε model was found to simulate the experimental results most closely
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CFD studiesSimulation of a multiple pool fire involving two different fuels
Comparison of experimental results and CFD results of MPF using iso octane and kerosene
T (K) Radiation
(W/m2)
Average burning rate
(kg/m2s)
Experimental MPF with iso
octane as fuel
- 3100 0.0527 (central pool)
0.0410 (outer pools)
CFD MPF with iso octane
as fuel
1789 3806 0.03754 (central pool)
0.02915 (outer pools)
Experimental MPF with jet
A as fuel
1490 2000 0.0270 (central pool)
0.0216 (outer pools)
CFD MPF with jet A /
kerosene as fuel
1315 2572 0.0217 (central pool)
0.0175 (outer pools)
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Comparison of temperature profile
(diagonal plane) of MPF using
octane as fuel
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Comparison of temperature profile
(diagonal plane) of MPF using
kerosene as fuel
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CFD-based simulation of multiple pool
fires occurring at differing elevationsComparison of temperature profiles
SPF diameter = 48 mm MPFs at x = 60 mm, y = 20 mm MPFs at x = 60 mm, y = 0 mm
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Prevention/control of MPFs
● As of now no accident prevention/control strategies and codes of practice exist that are specific to MPFs
● The following aspects are particularly relevant to MPFs, in addition to all other measures associated with the prevention and control of stand-alone pool fires:
– Keeping adequate provision to ensure safe and quick drain-off of the fuel in case a fire starts
– Positioning of the storage tanks in a manner that ensures safe distance between the tanks based on the considerations of local meteorology, especially wind directions and speeds
– Extra precautions against overfilling/spillage – Pumping stations should be provided with drainage systems capable of
quickly and safely draining away the flammable liquid