Introduction to Aerosols
SATA Aerosol 101
Daniel Bonner March 18, 2015
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CONTENT
• Definition of an aerosol
• How do aerosols work
• Propellant Classifications and Physical Properties
• Blending propellants
• Regulatory and Environmental Considerations
• Safety Regulations
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WHAT IS AN AEROSOL
• An aerosol is defined as a substance enclosed under pressure
that is able to be released as a fine spray, by means of a
propellant gas.
• Propellant is a component of the aerosol package that
delivers the product.
• Typically propellants consist of liquefied or compressed
gases.
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AEROSOL PACKAGE
The aerosol package contains two
components:
1) Product
2) Propellant
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LIQUEFIED GAS
• Propane, Isobutane, Butane, DME, D152A, and D134 are all
examples of liquefied gas.
• Dispersed in the product.
• Constant pressure and spray pattern.
• Typical can product fill is 85%.
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COMPRESSED GAS
• CO2, N2, Air are examples of compressed gas
• Gas is in the head space only
• Pressure drops as product is used causing coarse spray
patterns
• Can product fill is 50-70%
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LIQUEFIED GAS
COMPRESSED GAS
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AEROSOL WITH A LIQUEFIED GAS
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AEROSOL WITH A PERMANENT GAS
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PHYSICAL PROPERTIES TO CONSIDER
Vapor Pressure influences how the product will be delivered
(Spray, foam, stream etc.).
Solubility and Miscibility
Does the propellant have the capability to mix with other
propellant and solvent?
Water Solubility >DME>Hydrocarbons>HydroFlourocarbons
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LIQUEFIED GAS PROPELLANT
Properties
Flammability
Hydrocarbons
Flammable
Dimethyl Ether
Flammable
HFCs
152A Flammable
Solvency
Density
Toxicity
Poor
Low
Low
Good
Low
Low
Poor
intermediate
Low
Environmental
Impact
VOC
VOC
Non-VOC
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LIQUEFIED PETROLEUM GAS PROPELLANTS
• Propane C3H8
• Isobutane (2-methylpropane)
• Butane C4H10
• Isopentane (2-methylbutane)
• Pentane C5H12
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HYDROCARBON PROPELLANTS
• Liquefied Petroleum Gases
(LPGs) are separated from
petrochemical mixtures via
separation from natural gas or
refinement of crude oil.
• The majority of LPG
propellants are obtained from
natural gas liquids.
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PROCESSING OF HYDROCARBON PROPELLANTS
Fractionation
• Mixtures of LPGs are separated by differences in boiling
points.
Desulphurization
•
Molecular Sieves material 13x is used to remove sulfur
species and moisture.
• Material 13x works on the idea of size exclusion.
• 13x pore size typically 10 Ângströms.
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PHYSICAL PROPERTIES OF HYDROCARBON
Propane
Isobutane
N-Butane
Isopentane
Pentane
Chemical
Formula
C3H8
C4H10
C4H10
C5H12
C5H12
Molecular
Weight
44.1
58.1
58.1
72.2
72.2
Boiling Point
-43.7 ºF
10.9 ºF
31.1 ºF
82 ºF
97 ºF
V.P. @ 70
(psig)
110
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-3
-6
Density @
70F (g/cc)
0.51
0.56
0.58
0.62
0.63
KB Value
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18
20
26
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COMMON HYDROCARBON BLENDS
A Blends
• Consist of propane/isobutane
• Pressure between 32-110 psig @70F
• Named according to the target pressure of the blend @
70F
• Common A blends A-70, A-46, A-85
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COMMON HYDROCARBON BLENDS
AB Blends
• Consist of propane and Butane
• Pressure between 18-110 psig@70F
• Common blend AB-31 and AB-46
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COMMON HYDROCARBON BLENDS
AP Blends
• Propane/Isobutane/Butane
• Pressure between 18-109 psig @ 70F
• Common blends AP-52 and AP-46
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CALCULATING BLEND PRESSURES
Raoult’s Law
The partial pressure of each component of an ideal mixture
of liquids is equal to the vapor pressure of the pure
component multiplied by its mole fraction.
Pressure of blend=(MF1 X VP1 + MF2 X VP2 +…)
• MF= mole fraction
VP = Vapor Pressure
Components of the mixture must behave like ideal gases.
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HYDROFLUROCARBONS, HYDROFLUROOLEFINS,
AND DIMETHYL ETHER PROPELLANTS
• Difluoroethane (D152A)
• 1,1,1,2-Tetrafluoroethane (D134A)
• trans-1,3,3,3 Tetrafluoropropene (1234ze)
• Dimethyl Ether (DME)
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DME PROPERTIES
•Vapor Pressure @ 70°F: 63 psig
• Vapor Pressure @ 130°F: 174 psig
• Solubility in H20: 35 wt. %
• Density: 0.66 g/cc @ 70°F
• KB Value: 60 (powerful solvent)
• Flammable Limits: 3.3 – 18.0 volume % in air
• VOC
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D152A PROPERTIES
•
•
•
•
•
•
•
Vapor Pressure @ 70°F: 63 psig
Vapor Pressure @ 130°F: 177 psig
Not soluble in H20
Density: 0.91 g/cc @70°F
KB: 11 (poor solvent)
Flammable Limits: 3.9 – 16.9 Volume% in air
Non-VOC
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HFO-1234ZE PROPERTIES
• Vapor Pressure @ 70F: 47psig
• Vapor Pressure @ 130F: 140psig
• Not soluble in water
• Density: 1.17g/cc @ 70F
• KB: <10 (poor solvent)
• Flammable Limits: None
• Low MIR
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COMPARISON OF LIQUIFIED GAS PROPERTIES
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CONSIDERING DENSITIES OF YOUR PROPELLANT
Assume 100grams of formula in which 25% is propellant.
• 25g of A70 @0.53g/cc= 47.2cc of propellant
• 25g of 152a @0.91g/cc = 27.5 cc of propellant
• 25g of 134a @1.22g/cc = 20.5cc of propellant
From a volume perspective the LPG takes up 1.7 to 2.5 times
more container space assuming equal amounts used in the
formulation.
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AZEOTROPIC BLENDS
Azeotrope is a mixture of two or more liquids whose
proportions cannot be altered by distillation.
• These mixtures deviate from Raoult’s and Dalton’s law.
• Mole fraction cannot be used to calculate blend pressure.
• D152/Isobutane.
• DME/Propane.
• D152/n-Butane.
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DETERMINING PRESSURE OF AZEOTROPIC BLENDS
• Determine the amount of each component of the blend.
• Use triangle chart provide by chemical supplier.
• DME/A45 (20/80) blend.
• Component break down.
• 11% Propane
• 69% Isobutane
• 20% DME
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COMPRESSED GASES
Carbon Dioxide (CO2)
• At 70⁰ F the pressure of
CO2 IS 830psig.
• Density 0.0018g/cc.
• CO2 requires a large
Nitrogen (N2)
• Density 0.0011g/cc.
• Not soluble in liquids.
• Produces a stream when
delivering product.
amount of head space.
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VOLATILE ORGANIC COMPOUNDS AND THE
ENVIROMENT
• The Environmental Protection Agency (EPA) defines VOCs as
photochemical reactive substance that contribute to
photochemical smog.
• Due to the increase of ozone molecules (O3) in the
troposphere regulations have been imposed by organizations
such as the EPA and California Air Resource Board (CARB).
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MAXIMUM INCREMENTAL REACTIVITY
• Maximum Incremental Reactivity (MIR) measures the tendency of a
chemical to form ozone.
• MIR scale was adopted by CARB in 2000 and adopted by the EPA
shortly after.
• Typically MIR values higher than ethane are considered VOCs.
• Compounds with MIR values lower than ethane are considered
Non-VOCs.
• MIR scale is based on the effect of VOCs on O3 for specific place.
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MIR SCALE FROM CARB’S CONSUMER PRODUCTS
REGULATION
Compounds
MIR VALUE
HFC-134a
0.00
HFC-152a
0.02
Methane
0.014
Ethane
0.28
Propane
1.15
Isobutane
1.24
Butane
1.15
Isopentane
1.45
Pentane
1.31
DME
0.93
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FLAMMBILTY OF PROPELLANTS
The Department of Transportation defines flammable
propellants as gas which has a flammable range in air
@ 20⁰ C (68⁰ F).
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FLAMMBILTY OF PROPELLANTS
Flammable Gases are categorized based on the following:
• ASTM E-681—this test method determines the upper and lower
concentration limits of flammability.
• Enclosed Space Ignition Test.
• Heat of Combustion.
• Flame Extension.
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FLAMMBILTY OF PROPELLANTS
The flame extension test is
done by holding an aerosol
can 15cm from a flame. A
flame extension of 45cm or
more indicates a flammable
product.
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FLAMMBILTY OF PROPELLANTS
• Enclosed space ignition test
is done by spraying an
aerosol can in a drum. The
drum contains a lighted
candle and has a hinged
bottom. The time to ignition
is recorded.
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HEAT OF COMBUSTION
• Level 1 Aerosols have a heat of combustion less than or equal to
8600 Btu/lbs. (20kJ/g).
• Level 2 aerosols have a total heat of combustion greater than
8600 Btu/lbs. (20kJ/g).
• Level 3 aerosols have a total heat of combustion greater than
13000Btu/lbs. (30kJ/g).
• Aerosols are classified according to National Fire Protection
Association 30B regulations.
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MEASURING OR CALCULATING THE HEAT OF
COMBUSTION
• Butane (C4H10) Heat of Combustion for one mole
ΔH= -2877.5kJ/mol found from literature.
• 1g of C4H10 x (1mol/58.1g) x (2877.5kJ/mol) = 49.5kJ
• Measuring the heat of combustion is done via bomb
calorimeter.
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BOMB CALORIMETERS
Qv=M× C ×ΔT
• Q is heat change
• M is mass
• C is specific heat
• ΔT is change in temperature
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PROPELLANT TANK FARM SAFETY
Propellant tank farms are required to meet NFPA codes.
• NFPA58: Addresses design, construction, and operation of a
LPG facility
• NFPA 30B: Addresses manufacturing and storage of aerosol
products
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PROPELLANT TANK FARM SAFETY
Electrical equipment and connections used in the tank farm
must be explosion proof.
National Electrical code or NFPA 70 Division 1 or 2
• Division I: Vapors present during long periods of time
• Division II: Vapors present under abnormal conditions
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PROPELLANT TANK FARM SAFETY
Storage tank safety requirements per NFPA 58
• Security fencing with two access points should surround
tanks
• Tanks must be fitted with safety relief valves
• Tanks must have liquid level, temperature, and pressure
gauges
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PROPELLANT TANK FARM SAFETY
Adequate fire protection must be provided for tanks
• A water supply capable of providing cooling water for 10
minutes should be on the premises
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GAS DETECTION
Catalytic Detector
• Uses the principle that
when gas oxidizes it
produces heat.
• Sensor converts
temperature change to a
signal via Wheaton bridge
circuit.
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GAS DETECTION
Open Path Gas Detector
• Emits infrared light along a
path
• If gas molecules are
present they absorb the
light and infrared beam
does not make it to the
receiver.
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Thank you!
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