environmental issues and hazards in the chemical research ... · laboratory. class c fires involve...
TRANSCRIPT
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Environmental issues and hazards in the chemical research laboratory
Ulf Ellervik
Accidental fires and explosions
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Accidental fires and explosions
1. Introduction2. Fires3. Explosions4. Regulations5. Examples6. Incompatible chemicals
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BrandskyddshandbokBrandfarlig och explosiv vara
LU BYGGNAD | LUNDS UNIVERSITET
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• 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
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• 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
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• What is a fire? -combustion
CH4 + 2 O2 CO2 + 2 H2O
1. Introduction
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detonation, 1500 m/sfire, 1 mm/s deflagration, 100 m/s
1. Introduction
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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
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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%
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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
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2. Fires2.1 Liquids -Relative density of vapour
air 1.0toluene 3.2gasoline 3.0hydrogen 0.1
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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
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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
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2. Fires2.3 Solid materials Dust explosions - suspensions of particles in air can explode
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2. Fires2.3 Solid materials
Metal fires - magnesium, sodium, aluminum, iron, zinc,dust Metal fires are very difficult to extinguish!
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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
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2. Fires2.4 Spontaneous ignition
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2. Fires2.5 Compounds that will form flammable
gases in contact with water
examples: sodium (hydrogen) lithium aluminum hydride (hydrogen) calcium carbide (acetylene)
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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
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2. Fires2.6 Different types of fires
An oil fire usually makes a lot of soot.
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2. Fires2.6 Different types of fires
An oil fire usually makes a lot of soot.
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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!!!!
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2. Fires2.8 Extinguishers
Foam extinguishers (usually not found in laboratories) are suitable for class A and B, but not D fires.
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2. Fires2.8 Extinguishers
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.
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2. Fires2.8 Extinguishers
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!
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2. Fires2.8 Extinguishers
Sand. Do not forget sand for flammable metals (class D).
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3. Explosions
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detonation, 1500 m/sfire, 1 mm/s deflagration, 100 m/s
3. Explosions
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3.1 Thermodynamics -How does an explosive work?
3. Explosions
energy
products
activation energy
explosionenergy
explosivecompound
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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
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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
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3.1 Thermodynamics -Explosion power = explosion energy x gas formation
3. Explosions
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3.1 Thermodynamics -Explosion power = explosion energy x gas formation
3. Explosions
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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
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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
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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
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3.3 Organic peroxides
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
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3.3 Organic peroxides
3. Explosions
OO
OOO
O
triacetoncykloperoxid, TATPWARNING! Too unstable to
be used as an explosive
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4.1 Labelling of flammable compounds
Swedish regulations:
Brandfarliga varor = Brandfarliga vätskor Brandfarliga gaser Brandreaktiva varor
4. Regulations
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4.1 Labelling of flammable compounds
Swedish regulations:
Gases:
4. Regulations
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4.1 Labelling of flammable compounds
Swedish regulations:
Gases:
4. Regulations
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4.1 Labelling of flammable compounds
Swedish regulations:
Flammable liquids
4. Regulations
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4.1 Labelling of flammable compounds
Swedish regulations:
Fire reactive compounds
orand
4. Regulations
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4.1 Labelling of flammable compounds
Swedish regulations:
Flammable compounds should not be stored with toxic compounds or corrosives!
If both flammable and toxic - store as flammable
4. Regulations
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4.1 Labelling of flammable compounds
Swedish regulations:
Flammable gases should not be stored with flammable liquids
4. Regulations
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4.1 Labelling of flammable compounds
Swedish regulations:
Flammable liquids should not be stored with fire reactive compounds
4. Regulations
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4.1 Labelling of flammable compounds
Swedish regulations:
Explosives should not be stored with any other compounds, not even other explosives
4. Regulations
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4.2 Explosive atmosphere
Swedish regulations:
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
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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
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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
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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
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6. Incompatible chemicals