Strategies for Reducing Carbon Emissions

One way to reduce carbon emissions is to use fuels of lower carbon intensity. The carbon intensity of some fuels of interest is shown in Table 6.5. 

The first group of fuels, natural gas, LPG, naphtha and fuel oil, are those which are typically used in furnace operations in the petrochemical industry. This illustrates that moving from fuel oil to natural gas can achieve significant reductions in the carbon emission of a site. However, it must be remembered that on a global (cradle to grave) basis this may overestimate the benefit as these figures ignore the carbon emission in production of the fuel. This can be quite substantial for natural gas when the raw gas in the field is contaminated with carbon dioxide many fields contain 30% (mass basis) or more carbon dioxide which is stripped from the raw gas in gas plant operations in order to produce gas of a quality that can be piped (typically 2% vol.) carbon dioxide. 

A second group is coal which is seen to have much higher carbon intensity than the liquid or gaseous fuels. Coal is often used by power generation operations associated with petrochemical operations. This power is often purchased from a third party and on a global basis should be counted if power is imported. However, at the present time this type of carbon counting is not demanded by many jurisdictions leaving the 

To this list should be added renewable ethanol (i.e. from crops) and biodiesel which are more easily substituted for liquid fuels. These can be used to displace fossil fuels used in the furnace and hence lower the carbon emission. Unfortunately, in the opinion of the author, these fuels often involve major ecological impacts elsewhere such as displacement of food producing agricultural land (ethanol) or destruction of native forests (biodiesel) for the production of a favoured feedstock -palm oil. 

One way to improve carbon emissions and overall efficiency is to ensure that all furnace operations employ efficient heat recovery from the flue gas. Ideally the flue gas should be cooled in order to recover the heat of condensation of the water produced in the combustion process. 

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