Marine Engineering

Exhaust emissions from marine diesel engines largely comprise nitrogen, oxygen, carbon dioxide and water vapour, with smaller quantities of carbon monoxide, oxides of sulphur and nitrogen, partially reacted and non-combusted hydrocarbons and particulate material. SOx and NOx emissions, together with carbon dioxide, are of special concern as threats to human health and the environment.

Dominating influences in the formation of NOx in the combustion chamber are temperature and the longer the residence time in the high temperature, the more thermal NOx will be created.

Fuel oil is a hydrocarbon consisting of hydrogen and carbon, together with other elements most of which are unwanted.

Hydrogen has a higher calorific value than carbon, therefore, more heat may be obtained from fuels containing higher Hydrogen/Carbon ratios.

The lower specific gravity of hydrogen than carbon allows a rough rule of thumb to be; the higher the Specific Gravity, the lower the Calorific Value (and quality) of the fuel. The presence of impurities clouds the issue slightly

For efficient combustion an ignition source and sufficient oxygen need be present to completely oxidise the Hydrogen to water vapour and the carbon to carbon-dioxide.

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