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 Industry Explosions in Food Industry Diana Castellanos Mary Kay O’ Connor PROCESS SAFETY CENTER Oct-27-2009
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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)
[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]
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