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

7

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

10

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

19

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??