Environmental issues and hazards in the chemical research ... · laboratory. Class C fires involve flammable gases Class D fires involve combustible metals, such as magnesium, titanium,

Environmental issues and hazards in the chemical research laboratory

Ulf Ellervik

Accidental fires and explosions

Accidental fires and explosions

1. Introduction2. Fires3. Explosions4. Regulations5. Examples6. Incompatible chemicals

BrandskyddshandbokBrandfarlig och explosiv vara

LU BYGGNAD | LUNDS UNIVERSITET

• Flammable compounds are probably the most common hazardous material in the laboratory

• The hazard is dependent on the ability to vaporize, ignite and burn or explode

1. Introduction

• What are the dangers?

Solid flammable compounds -BH3•NEt3

Flammable liquids -ether

Flammable gases -acetylene

Self-igniting compounds -BuLi

Compounds that will form flammable -KHgases in contact with water

Oxidizing compound -KMnO4

Organic peroxides -benzoyl peroxide

Explosives -picric acid

1. Introduction

• What is a fire? -combustion

CH4 + 2 O2 CO2 + 2 H2O

1. Introduction

detonation, 1500 m/sfire, 1 mm/s deflagration, 100 m/s

1. Introduction

2. Fires2.1 Liquids

Flash point - the lowest temperature at which a liquid gives off vapor in sufficient concentration to be ignited by a flameIgnition temperature - the lowest temperature required to initiate combustion without a flameFlammability limits- the concentration of vapor in air where the mixture is flammable

2.1 Liquids

2. Fires

Liquid Flash point Ignition temp. Flam. limit

diethylether -45 °C 170 °C 1,7 - 36%

gasoline -40 °C 400 °C 1 - 8%CS2 -30 °C 80 °C 0,6 - 60%acetone -18 °C 465 °C 2,5 - 13%methanol 10 °C 455 °C 5,5 - 36%ethanol 12 °C 365 °C 3,3 - 19%kerosene 38–72 °C 220 °C 1,2 - 7,8%diesel 60°C 220 °C 0,6 - 6,5%

2.1 Liquids -Swedish regulations

Klass 1 tfp < 21°C Extremely flammable R12 F+ Highly flammable R11 F examples: acetone, ether, gasoline, pyridineKlass 2a 21°C < tfp < 30°C R10

examples: xylene, 1-butanol,

Klass 2b 30°C < tfp <55°C

examples: kerosene (fotogen), acetic acid

Klass 3 55°C < tfp < 100°C

examples: DMF, DMSO, nitrobenzene

2. Fires

2. Fires2.1 Liquids -Relative density of vapour

air 1.0toluene 3.2gasoline 3.0hydrogen 0.1

2. Fires2.1 Liquids -Statical electricity

Problem: -statical electricity in solvents can give a spark

Solution: -ground the container -do not pour from more than 10 cm

2.2 Gases -Flammable gas - gas that is combustible in air at 20°C -Flammability limits (% in air)

2. Fires

Gas Flammability limit Ignition temp.Methane 4,4 - 17% 537°CButane 1,7 - 10,9% 470°CHydrogen 4 - 77% 560°CAcetylene 2,3 - 100% 305°C

2. Fires2.3 Solid materials Dust explosions - suspensions of particles in air can explode

2. Fires2.3 Solid materials

Metal fires - magnesium, sodium, aluminum, iron, zinc,dust Metal fires are very difficult to extinguish!

2. Fires2.4 Spontaneous ignition

A substance reaches its ignition temperature without an external heat source examples: oily rags, dust, organic material mixed with oxidizers, alkali metals, finely divided pyrophoric metals, white phosphorous

2. Fires2.4 Spontaneous ignition

2. Fires2.5 Compounds that will form flammable

gases in contact with water

examples: sodium (hydrogen) lithium aluminum hydride (hydrogen) calcium carbide (acetylene)

2. Fires2.6 Different types of fires

Class A fires are ordinary materials like burning paper, lumber, cardboard, plastics etc. Class B fires involve flammable or combustible liquids such as gasoline, kerosene, and common organic solvents used in the laboratory. Class C fires involve flammable gases Class D fires involve combustible metals, such as magnesium, titanium, potassium and sodium as well as pyrophoric organometallic reagents such as alkyllithiums, Grignards and diethylzinc. These materials burn at high temperatures and will react violently with water, air, and/or other chemicals. Class E (US: C) fires involve energized electrical equipment, such as appliances, switches, panel boxes, power tools, hot plates and stirrers. Water is usually a dangerous extinguishing medium for class C fires because of the risk of electrical shock unless a specialized water mist extinguisher is used. Class F (US: K) Cooking oil


An oil fire usually makes a lot of soot.


An oil fire usually makes a lot of soot.

2. Fires2.7 Extinguishers

Water extinguishers (usually not found in laboratories) are suitable for class A (paper, wood etc.) fires, but not for class B, C and D fires such as burning liquids, electrical fires or reactive metal fires. In these cases, the flames will be spread or the hazard made greater!Rather unusual!

Never ever use water on an oil fire!!!!


Foam extinguishers (usually not found in laboratories) are suitable for class A and B, but not D fires.


Dry chemical extinguishers are useful for class ABC and E fires and are your best all around choice. They have an advantage over CO2 extinguishers in that they leave a blanket of non-flammable material on the extinguished material which reduces the likelihood of reignition. They also make a terrible mess - but if the choice is a fire or a mess, take the mess! Note that there are two kinds of dry chemical extinguishers! Usually contain sodium bicarbonate or potassium bicarbonate or ammonium phosphate, which also works on A fires.


CO2 (carbon dioxide) extinguishers are for class B fires. They don't work very well on class A fires because the material usually reignites. CO2 extinguishers have an advantage over dry chemical in that they leave behind no harmful residue. That makes carbon dioxide a good choice for an electrical fire involving a computer or other delicate instrument. CO2 extinguishers are not approved for class D fires!


Sand. Do not forget sand for flammable metals (class D).

3. Explosions

detonation, 1500 m/sfire, 1 mm/s deflagration, 100 m/s

3. Explosions

3.1 Thermodynamics -How does an explosive work?

3. Explosions

energy

products

activation energy

explosionenergy

explosivecompound

3.1 Thermodynamics -How much energy?

3. Explosions

Combustion with lot of air

3 CO2 + 2.5 H2O + 1.5 N2 + 0.5 O

7 CO2 + 2.5 H2O + 1.5 N2 – 10.5 O

O2NO ONO2

ONO2

NO2O2N

NO2

3.1 Thermodynamics -How much energy?

3. Explosions

The Kistiakowsky Wilson rules- hydrogen is converted to water-if there is oxygen left carbon is converted to CO-if there is oxygen left CO is converted to CO2-nitrogen is converted to N2

3.5 CO + 3.5 C + 2.5 H2O + 1.5 N2

NO2O2N

NO2

3.1 Thermodynamics -Explosion power = explosion energy x gas formation

3. Explosions

3.1 Thermodynamics -Explosion power = explosion energy x gas formation

3. Explosions

3.2 Common explosives A compound is may be explosive if it contains a lot of oxygen and some of the following groups

3. Explosions

peroxides and ozonides

chlorates and perchlorates

nitrocompounds and nitrates

diazocompounds and azides

acetylenides

fulminates

organometallics

–OClO2 –OClO3

–NO2 –ONO2

–N –N3

–O–O– –O–O–O–

–C C–

N–

–ONC

M–C

3.2 Common explosives

3. Explosions

PbN6Hg(ONC)2O2NO ONO2

ONO2

NO2O2N

NO2

OHNO2O2N

NO2

NN

NNO2

NO2O2N

Explosive explosion

energy (kJ/mol)

gas formation (dm3/g)

explosion power (%)

aktivation energi (kJ/mol)

mercury fulminat

–500 0.21 14 105

lead azid –469 0.22 13 160 nitroglycerin –1406 0.74 171 176 pikric acid –744 0.83 100 242 TNT –1016 0.74 115 222 RDX –1118 0.91 169 199

3.3 Organic peroxides

3. Explosions

Some compounds can form organic peroxides due to air oxidation

List A - (Three Months) - Peroxide Hazard on Storage Divinyl acetylene Isopropyl ether Potassium metal Sodium amide Vinylidene chloride


3. Explosions

List B - (Twelve Months) - Peroxide Hazard on Concentration Acetal Cumene Cyclohexene Diacetylene Dicyclopentadiene t-butylalcohol Dioxane Ethylene glycol dimethyl ether (glyme) Ethyl ether Methyl acetylene Methylcyclopentane Methyl i-butyl ketone Tetrahydrofuran Tetrahydronophthalene Vinyl ethers


3. Explosions

OO

OOO

O

triacetoncykloperoxid, TATPWARNING! Too unstable to

be used as an explosive

4.1 Labelling of flammable compounds

Swedish regulations:

Brandfarliga varor = Brandfarliga vätskor Brandfarliga gaser Brandreaktiva varor

4. Regulations



Gases:

4. Regulations



Gases:

4. Regulations



Flammable liquids

4. Regulations



Fire reactive compounds

orand

4. Regulations



Flammable compounds should not be stored with toxic compounds or corrosives!

If both flammable and toxic - store as flammable

4. Regulations



Flammable gases should not be stored with flammable liquids

4. Regulations



Flammable liquids should not be stored with fire reactive compounds

4. Regulations



Explosives should not be stored with any other compounds, not even other explosives

4. Regulations

4.2 Explosive atmosphere


Classification of zones for explosive atmospheres Zone 0 - always risk for explosion, inside containers Zone 1 - Sometimes risk for explsion, 0.5 m from an open bottle Zone 2 - seldom risk for explosion, 1 m from an open bottle

4. Regulations

5. Examples

Acetylene - explosive in 2.5-80% in air, dangerous under pressure AlCl3 -forms large amount of HCl if subjected to water Ammonia -reacts with iodine to give explosive nitrogen triiodide Benzoyl peroxide - decomposes spontaneously above 50°C Carbon disulfide - toxic and can be ignited on a glowing light bulb Diazomethane - extreme explosion hazard DMSO - decomposes violently on contact with active chlorine compounds

5. Examples

Dry ice - do not keep in closed container Ethers - peroxide hazard Ethylene oxide - can explode if heated Halogenated compounds - do not mix with sodium Hydrogen peroxide - can decompose if in contact with iron or other metals Litium aluminum hydride - can take fire with tetrahydrofuran

5. Examples

Ozone - give highly explosive ozonides Palladium - can get on fire when dry Perchlorates - the use should be avoided. Permanganates - explosive if mixed with sulfuric acid Phosphorus - should be stored under water Phosphorus trichloride - reacts with water to give phosphorus acid which decomposes and form phosphine which may ignite Potassium - more reactive than sodium

6. Incompatible chemicals

Documents

Environmental issues and hazards in the chemical research ... · laboratory. Class C fires involve flammable gases Class D fires involve combustible metals, such as magnesium, titanium,