DUST EXPLOSIONS Experiment Setup - MKO …psc.tamu.edu/files/symposia/2009/presentations/4...Dust...
Transcript of DUST EXPLOSIONS Experiment Setup - MKO …psc.tamu.edu/files/symposia/2009/presentations/4...Dust...
Review of an Adequate Review of an Adequate Chemical Dust Suppressant Chemical Dust Suppressant Used for Prevention of Dust Used for Prevention of Dust Explosions in Food IndustryExplosions in Food Industry
Diana Castellanos
Mary Kay O’ ConnorPROCESS SAFETY CENTER
Oct-27-2009
OUTLINEOUTLINE
Introduction
Types of suppressants
Solids
Gaseous
Main characteristics that enhance suppressant effectiveness
Overview of Dust Explosion Research at the Mary Kay O’Connor Process Safety Center (MKOPSC)
Future work
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DUST EXPLOSIONS DUST EXPLOSIONS STATISTICSSTATISTICS
[1] Source: U.S. Chemical Safety and Hazard Investigation Board (CSB)
Types of Dust Involved in incidents
Metal20%
Wood24%
Food23%
Other7%
Plastic14%
Coal8%
Inorganic4%
281 incidents, 119 fatalities, and 718 injuries from 1980-2005
An average of 10 dust explosion incidents per year
An average of nearly 5 fatalities and 29 injuries per year
Injuries or fatalities occurred in 71 percent of the incidents
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DUST EXPLOSIONS DUST EXPLOSIONS STATISTICSSTATISTICS
281 incidents, 119 fatalities, and 718 injuries from 1980-2005
An average of 10 dust explosion incidents per year
An average of nearly 5 fatalities and 29 injuries per year
Injuries or fatalities occurred in 71 percent of the incidents
Types of Industries Involved in Dust Incidents
Other7%
Food Products24%
Lumber/Wood
Products15%
Chemical Manufact'g.
12%Primary Metal Industries
8%
Rubber & Plastic
Products8%
Electric Services
8%
Furniture & Fixtures
4%Equipment
Manufact'g.7%
Fabricated Metal Products
7%
4[1] Source: U.S. Chemical Safety and Hazard Investigation Board (CSB)
WHY DOES IT HAPPEN?WHY DOES IT HAPPEN?
Employers and workers are not aware of or underestimated the dust related hazards.
No effective safety measure to prevent accidents:
Interlocking systems, prevention of mechanical and electric sparks and hot surfaces, good housekeeping in the workrooms[2]
There are no adequate suppressant agents for powder explosions in the food industry
[2] Bartknecht, W. (1989). Dust Explosions. Course, Prevention, Protection. Germany, Springer Verlag Berlin Heidelberg
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DUST EXPLOSION PROCESSDUST EXPLOSION PROCESS
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Mixing Confinement
Oxidant
Ignition source
Fuel
Dust Explosion pentagon
Primary explosion send a shockwave through the plant
Dust when dispersed in air may produce a
secondary explosion
Domino effect in dust explosions
Suppression methods are based on elimination of al least one of these five
elements
OUTLINEOUTLINE
Introduction
Types of suppressants
Solids
Gaseous
Main characteristics that enhance suppressant effectiveness
Overview of Dust Explosion Research at the Mary Kay O’Connor Process Safety Center (MKOPSC)
Future work
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SUPPRESSION WITH SUPPRESSION WITH SOLID COMPOUNDSSOLID COMPOUNDS
[3] Eckhoff, R. (1997). Dust Explosions in the Process Industries. Great Britain. St Edmundsbury Press Ltd.
Keeps the combustible dust concentration below the dust flammability range.
Absorbs high quantities of heat released from explosibe reaction. [3]
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ADVANTAGESADVANTAGES DISADVANTAGESDISADVANTAGES
x Requires great quantity usage in order to be effective in the supression process.
x Introduces contamination to the product.
Suppressant effectiveness is measured by comparing MEC
SUPPRESSION WITH SUPPRESSION WITH GASEOUS COMPOUNDSGASEOUS COMPOUNDS
Reduces oxygen content in the atmosphere. Thus combustion reaction is stoped and the flame cannot propagate.
Low product contamination.
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ADVANTAGESADVANTAGES DISADVANTAGESDISADVANTAGES
x Some supressants requires great quantity usage, therefore they are not cost effective.
x Introduces asphixiation hazards.
LOC for combustion depends on the type of dust and inert gas used [4]
[4] CEP www.aiche.org/cep (Letters - August 2009)
OUTLINEOUTLINE
Introduction
Types of suppressants
Solids
Gaseous
Main characteristics that enhance suppressant effectiveness
Overview of Dust Explosion Research at the Mary Kay O’Connor Process Safety Center (MKOPSC)
Future work
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SUPPRESSANT EFFECTIVENESSSUPPRESSANT EFFECTIVENESS
[5] Eckhoff, R. (1997). Dust Explosions in the Process Industries. Great Britain St Edmundsbury Press Ltd.[6] Chatrathi, K. and J. Going (2000). Dust deflagration extinction, Amer Inst Chemical Engineers.
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High specific heat
Higher decomposition rate
Small particle size
Large surface area
Composition Compatibility with dust product. Low product contamination
System will absorb high quantities of heat released from explosive reaction [5]
Decomposition rate of inert particle higher that fuel decomposition rate would extinct the flame[6]
Smaller inert particle size dissipate faster heat radiation and heat convection [6]
High surface area available for combustion reaction enhance suppressant decomposition and heat absorption
BINARY GASEOUSBINARY GASEOUS--SOLID SUPPRESSANTSOLID SUPPRESSANT
There is a needed to identify the effectiveness of binary gas-solid suppressants which comprises
advantages and disadvantages from each compound.
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OUTLINEOUTLINE
Introduction
Types of suppressants
Solids
Gaseous
Main characteristics that enhance suppressant effectiveness
Overview of Dust Explosion Research at the Mary Kay O’Connor Process Safety Center (MKOPSC)
Future work
13
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EXPLOSION EQUIPMENT MKOPSCEXPLOSION EQUIPMENT MKOPSC
EXPLOSION EQUIPMENT MKOPSCEXPLOSION EQUIPMENT MKOPSC
Data acquisition system
Dispersion system
Ignition system
Sensor system (Piezoelectric PT)
Non-spherical stainless steel vesselCapacity: 26 L.MAWP:1000 psi.Tmax 500 0F.
Vacuum system
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16OPERATION MODE
TYPICAL DUST EXPLOSION CURVETYPICAL DUST EXPLOSION CURVE
Typical overpressure versus time during a dust explosion. Adapted from: Proust (2006)
t1: Duration of combustion
Pex: Explosion overpressure
dP/dt: Rate of pressure rise with time
Pd: Expansion pressure
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Property Definition ASTM Test
Method Application
Pmax
Maximum explosion overpressure generated in the test chamber
ASTM E 1226
Used to design enclosures and predict the severity of the consequence.
(dp/dt)
max
Maximum rate of pressure rise
ASTM E 1226
Predicts the violence of an explosion. Used to calculate KSt .
KSt Dust deflagration index ASTM E
1226 Measures the relative explosion severity compared to other dusts.
MEC Minimum explosible concentration
ASTM E 1515
Measures the minimum amount of dust, dispersed in air, required to spread an explosion.
LOC Limiting oxygen concentration
ASTM standard
under development
Determines the least amount of oxygen required for explosion propagation through the dust cloud.
PROPERTIES MEASURED BY 26L VESSELPROPERTIES MEASURED BY 26L VESSEL
Shelley, S. Update Preventing dust explosions. March 2008 CEP17
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Deflagration Index (Kst): is a volume normalized rate of pressure rise and is expressed by the cubic law: It relates the maximum rate of pressure rise to the volume of the vessel in which the explosion occurs. (ASTM E 1226)
Combustible dusts are classified by their Kst values in increasing order of explosion violence as follows:
• Kst =0 Group St0: non-explosive • 0<Kst =<200 Group St1: weak• 200<Kst=< 300 Group St2: strong• Kst > 300 Group St3: very strong
Increasing Explosibility
PROPERTIES MEASURED BY 26L VESSELPROPERTIES MEASURED BY 26L VESSEL
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Introduction
Types of suppressants
Solids
Gaseous
Main characteristics that enhance suppressant effectiveness
Overview of Dust Explosion Research at the Mary Kay O’Connor Process Safety Center (MKOPSC)
Future work
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OUTLINEOUTLINE
FUTURE WORKFUTURE WORK
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Further analysis of MEC in binary suppressant options should be performed to reveal optimum concentration ratios that reduce explosion violence. Research will also focused on dust products in food industry in order to design a systematic approach that can be used to prevent dust explosions.
- Dr. Mannan- Dr. Dedy- Victor Carreto- Dr. Passman- Dow Chemical Company- All member of MKOPSC
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AKNOWLEDGEMENTAKNOWLEDGEMENT
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THANKSTHANKS……
QUESTIONS??QUESTIONS??