Methanol. An overview on production, uses, characteristics, handling and future.
Report 2003.LT.6697, Transport Technology, Logistic Engineering.
Methanol, or Methyl Alcohol, is a colourless liquid at ambient
temperatures with a mild, characteristic alcohol odour. It is the simplest
of a long series of organic compounds called alcohols. The molecular
formula is CH3OH. Methanol is a violent and potent nerve poison
and exposure to methanol can cause blindness or death. Methanol is generally
considered non-corrosive and is highly miscible with water. It is a clean
burning fuel with non-luminous, pale blue flame and forms explosive
mixtures with air.
Methanol can be produced from a wide variety of fossil feedstocks,
including natural gas, coal, and petroleum but also renewable sources as
biomass and municipal waste. Originally methanol was obtained from the
destructive distillation of wood but nowadays natural gas is the main
feedstock since the combination of gas prices and the process involved
with making methanol out of natural gas is the most cost-efficient way. In
the future however coal might also be an attractive feedstock since
worldwide coal reserves exceed natural gas reserves by far and new more
efficient production technologies for making methanol out of coal are on
the way. Methanol from biomass would also be a good alternative to natural
gas since it is a very environmental-friendly fuel but is comparatively
still too expensive.
Methanol is currently produced and used worldwide in a variety of
industrial applications, including formaldehyde (37% of the total demand),
methyl tert-butyl-ether or in short MTBE (28% of world demand) and acetic
acid (8% of world demand). Formaldehyde is mainly used in making plywood
and MDF, MTBE as an octane enhancer in automotive fuel and acetic acid
mainly as a solvent in chemical reactions.
Methanol is one of the most promising alternative automobile fuels from a
non-petroleum source. It can be used directly as a gasoline but an even
cleaner use would be in fuel cells. This fuel cell might also be used as a
power generator on industrial or domestic scale.
Worldwide, over 90 methanol plants have the capacity to produce about 40
million tonnes of methanol annually. This capacity is not fully utilized
since the market for methanol stagnated while new plants were already
being built. The reason for this growth decrease is the ban on MTBE in
many states in the US. Demand for methanol however will keep on growing
and might face an enormous boost when the methanol fuel cell becomes a
success in the near future.
Methanol is not carcinogenic but can be highly toxic when ingested. A small
doses might already result in irritation to the mucous membranes, headache,
sleepiness, nausea, confusion, loss of consciousness, digestive and visual
disturbances. Larger amounts can cause narcosis, acidosis (formation of acid
throughout the whole body) and even death.
Since methanol is hydrophilic and infinitely soluble in water it dissolves
rapidly into the surface in case of a spill. Biodegradation is the primary
process for methanol removal from the environment. Aerobic microorganisms
play a prominent role in this process. They oxidize organic contaminants
by consuming oxygen, leading to the mineralization of methanol. This way
methanol spill is turned to formaldehyde and subsequently assimilated into
cell material. Relative to gasoline, methanol is safer and milder to the
environment. Hazards incurred by gasoline releases are greater than those
of methanol releases, and will persist much longer in the environment.
Methanol is stable under normal storage conditions and is not subject to
hazardous polymerization reactions, but can react violently with strong
oxidizing agents. The greatest hazard involved in handling methanol is the
danger of fire or explosion. Therefore precautions such as diking and fire
fighting provisions must be taken. For small fires, water or chemical
extinguishing agents are adequate. Larger fires may require
alcohol-resistant foams for control [M. Howe-Grant, J.I. Kroschwitz, R.E. Kirk,
D.F. Othmer Kirk-Othmer Encyclopedia of Chemical Technology vol.16,
Wiley, New York (1995)]. Chemical protection may be provided with hermetic
clothing, gloves and footwear and a full-face, positive pressure, self-contained
breathing apparatus or an air line. Suitable protective materials for equipment
include polyvinyl plastic, neoprene or rubber.
Personnel involved in the storage and handling of methanol require eye and
skin protection from the irritating properties of methanol in the event of
a spill. Contact lenses should not be worn, since plastic lens materials
may absorb and concentrate methanol against the eye. Additional
respiratory protection is not required with adequate local explosion-proof
ventilation [Kirk & Othmer ibid.].
In shipping, methanol is classified by the IMO as a noxious liquid of
classification C, requiring a vessel of type III to be shipped in. Though
methanol is often shipped across world seas by parcel carriers the amount
of dedicated methanol vessels is increasing. One of those ships is the
Millenium Explorer, a 100.000 dwt methanol carrier with at least twice the
capacity of any other vessel of its type. This tanker is capable of
carrying 120.000 tonnes of methanol distributed over 12 cargo tanks with
zinc silicate coatings and carries it's own nitrogen generator on board to
blanket the methanol in these tanks with inert gas. Common pumping systems
to transfer the methanol are electrically or hydraulically driven
centrifugal pumps and deepwell pumps and hydraulically driven submerged
pumps. Stripping of the cargo is an important feature onboard these
Completely enclosed equipment is necessary when storing methanol. This
avoids ignition and human contact. Furthermore the storage tanks must be
vented and, preferably, be equipped with vapour emission controls. In
storage areas smoking and open fires are prohibited. Furthermore explosion
proof electrical equipment should be used and proper electrical grounding
is necessary to protect against lightning strikes and the release of
accumulated static electricity [Methanex ibid.]. With methanol an inert
gas blanket might be used to prevent oxidation and the build up of explosive
vapour. Storage of methanol with incompatible matter should be avoided. Storage
tanks of welded construction are normally satisfactory. Copper, zinc,
aluminium or plastics are unsuitable for storage. They are attacked slowly
and will contaminate the methanol. For long term storage mild steel is the
recommended construction material. In shipping, tanks with a zinc-silicate
coating are preferred.
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