Page 176 - Introduction to Marine Engineering

162 Fuel oils, lubricating oils and their treatment

slime and the smell of rotten eggs (hydrogen sulphide) indicates a
contaminated system.
Water in a lubricating oil or fuel oil, oxygen and appropriate
temperature conditions will result in the growth of bacteria and
infestation of a system. The removal of water, or ensuring its presence is
at a minimum, is the best method of infestation prevention. The higher
the temperature in settling, service and drain tanks holding fuel or
lubricating oils, the better.
Test kits are available to detect the presence of bacteria, and biocides
can be used to kill all bacteria present in a system. The system must then
be thoroughly flushed out.

Exhaust emissions

Exhaust gases from engines and boilers contain atmospheric pollutants
which are principally nitrogen oxides (NO X), sulphur oxides (SO X),
carbon oxides and unburnt hydrocarbon particulates. These various
pollutants contribute to smog and acid rain, and carbon oxides
contribute to the greenhouse effect, which is increasing global
temperatures.
The IMO Marine Environment Protection Committee is considering
ways to reduce the pollutants in exhaust emissions. IMO is to add a new
Annex to MARPOL 73/78 to deal with atmospheric pollution.
The SO X content of emission may be reduced by either a reduction of
the sulphur content in fuels or an exhaust gas treatment system. New
engine technology may reduce NO X formation and thus emissions, while
carbon oxides can be reduced by good plant maintenance.
Selective Catalytic Reduction Systems are in use on some vessels, which
are said to reduce NO X emissions by 90 per cent and carbon oxides by
80 per cent. The equipment has been successfully operated on new
buildings and more recently as a retrofit on existing ships.
Major research initiatives are underway by engine builders, and
classification societies, in cooperation with shipowners, in order to obtain
data regarding achievable targets and suitable methods of measurement.
This data will enable IMO and National Authorities to develop realistic
legislation with which owners can readily comply on new and existing
vessels.
The IMO Sub-Committee on Bulk Chemicals has prepared a draft of
the new Annex to MARPOL 73/78, which will be considered at a
conference to be held in 1996. Procedures to bring the amendments into
force will be considered and the designation of special areas with specific
emission criteria.