Chemistry of Oil Flashcards
what is crude oil?
raw material (decomposed vegetation + animal life compressed - high pressure, millions of years)
examples of products from crude oil:
motor + activation; - gassoline - kerosene - diesel - gass oil - fuel oil (all refined)
what is crude oil made up from?
hydrogen + carbon (+ range of components e.g. sulphur to water)
what is the generic name for any petroleum (crude + by-products)?
hydrocarbons
what is the simplest form of a hydrocarbon molecule?
methane (gas) - CH4
what determines the physical characteristics of the petroleum?
- length of chain - manner in which they are joined
what is the second smallest petroleum hydrocarbon?
ethane (C2H6)
what state are hydrocarbons in if they have less than 5 carbon atoms at normal ambient temp + pressure?
gases
what state are hydrocarbons in if they have between 6 and 19 carbon atoms at normal ambient temp + pressure?
liquids
what state are hydrocarbons in if they have 20 or more carbon atoms at normal ambient temp + pressure?
solids
what is an octane rating?
a measure of flammability
what are aromatics?
ring-type arrangements of hydrocarbons
why are aromatics more reactive?
they are hydrogen deficient
what process do all different ways of refining crude oil start with?
the distillation process (fractionating)
what process comes after distillation in refining crude oil?
cracking
how and why can different components of crude oil be distilled (into fractions)?
- heating - different boiling points
what is the diagram associated with atmospheric distillation of crude oil
what is the main difference between atmospheric distillation and vacuum distillation?
vacuum distillation can be done at higher temperatures
what are the main hazards of petroleum?
- flammability
- toxicity
what 2 things have to be considered when discissing flammability?
- vapour pressure
- volatility
what are the main considereations of crude oil based cargo in relation to vapour pressure?
- water evapourates slowly - gasoline evapourates quickly
- petroleum = various components of hydrocarbon family- some more volitile than others
- some exist as gases - may have evapourated off before reaching ship
- within cargo tank - oil = different from chemical make up of vapour in ullage space above cargo
- in vapour = more lighter components - evapourate 1st
what temperature is absolute zero?
-273 *C
how are molecules bound together?
inter-molecular attraction
what is evapouration?
changing from liquid to a vapour
what is condensation?
changing from vapour to liquid
what does S.V.P stand for?
saturated vapour pressure
when does S.V.P (saturated vapour pressure) stop?
when there are an equal number of molecules leaving the liquid as there are re-entering it
what does S.V.P mean?
no more vapour can be produced at that temperature
what happens to the S.V.P reading if the temperature is increased?
S.V.P reading increases with temperature
what does T.V.P stand for?
true vapour pressure
what does R.V.P stand for?
Reid Vapour Pressure
what is the T.V.P?
the highest vapour pressure possible
when does the T.V.P occur?
when the gas to liquid ratio is effectively zero
what makes the T.V.P difficult to measure?
you need to have detailed knowledge of the molecular makeup of the liquid in question
where can you find the R.V.P test results on a ship?
on load port documentation
what is the diagram of the R.V.P testing equipment?
what does the amount of evapouration depend on for any given liquid?
- surface area
- vapour to liquid ratio
- turbulence
why does the surface area rather than the volume of a liquid effect the evapouration rate?
evapouration occurs only at the surface of a liquid (not in the body)
what is the ullage space?
space above the liquid in a cargo tank
why is the density of a vapour a concern on a ship?
- most hydrocarbon are denser than air
- tend to linger at bottom of tanks, pumprooms etc.
- causing problems in removing the vapour
why is flammability a concern in relation to vapour of a liquid?
- liquids cannot burn unless vapour is produced
- flammability is a function of the ability to give off vapour
what is the Flashpoint?
the lowest temperature at which a liquid gives off enough vapour to form a flammable mixture in air when an external ignition source is applied
what 3 things need to be present at the same time for fire to occur?
- fuel
- oxygen
- source of ignition (generates heat)
what is the Flammable Range?
the region between the Lower and Upper Flammable Limits
what happens to the Flammable Range if the oxygen content is reduced?
Flammable Range decreases until at about 11% oxygen by volume - insufficient air to sustain combustion
how is the atmosphere described if the space above the Upper Flammable Limits (U.F.L)?
Too Rich
how is the atmosphere described if it is below the Lower Flammable Limits (L.F.L)?
Too Lean
Where should all safe tanker opperations aim to opperate in relation to the Flammable Zone?
Aim to opperate outside of the Flammable Zone at all times!
What is the main source of reference for tanker safety?
the Internation Safety Guide for Oil Tankers and Terminals
how does the International Safety Guide for Oil Tankers and Terminals classify petroleiums’?
into 2 groups:
- Volatile
- Non-Volatile
What is threshold for classifying petroleums as volatile or non-volatile?
- those with a flashpoint below 60*C = volatile
- flashpoint of 60*C or above = no-volatile
what significance has temperature of 60*C in relation to volatility of petroleums’?
an arbitary temperature of classification of petroleum - above ambient temperatures found anywhere in the world
why is liquid being sprayed out of a small hole in a pipe particularly dangerous in relation to the flashpoint of that liquid?
the flashpoint falls - specific surface area involved
what is the Fire Point of a substance?
Temperature at which the substance gives off enough vapour to ignite + stay alight (when exposed to external source of ignition)
what is the Auto Ignition Temperature?
if a flammable liquid is heated sufficiently high - vapour will ignite without external source of ignition being applied
what does A.I.T stand for?
Auto Ignition Temperature
What does Toxic mean?
Poison
what are the main routes of entry into the body for a toxic substance?
- ingestion
- inhalation
- intra dermal (through the skin)
Name 2 examples of acute poisons:
- cyanide
- hydrogen sulphide
name 3 chronic poisons:
- lead
- mercury
- benzene
what are Time Weighted Averages?
Standards established for concentrations of airbourne substances based on what humans can tolerate safely with no ill effects for an 8 hour working day, every day
what does O.E.L stand for?
Occupational Exposure Limit
What are the 2 types of O.E.L?
- Long term - 8 hour T.W.A
- Short term - 15 minute one off exposure at a higher level
what does O.E.L mean?
set level that, based on current scientific knowledge - won’t damage a worker through inhalation day after day
what does M.E.L stand for?
Maximum Exposure Limit
what does P.E.L stand for?
Permissible Exposure Limit
why were M.E.L and P.E.L limits introduced?
for substances that cause most harm to health - ‘safe’ levels of exposure cannot be ascertained or are unachievable
