Effects of Burning Different Fuels
There are many varieties of coal being used in combustion processes around the world; the most widely used are anthracite, bituminous, sub-bituminous, and lignite. When burning coal a considerable amount of carbon dioxide is generated given the extremely high levels of carbon in coal; since carbon requires more oxygen to burn, more combustion air is needed to burn coal that other fossil fuels.
In addition to the carbon dioxide emissions, coal burning creates some other pollutants including NOx, sulfur dioxide (SO2), sulfur trioxide (SO3), and particle emissions. Sulfur dioxide chemically combines with water vapor in the air to produce a weak form of sulfuric acid, one of the main causes of acid rain.
Oil fuels are mostly a mixture of very heavy hydrocarbons, which have higher levels of hydrogen than those found in coal. At the same time, oil contains less carbon than coal and therefore requires less combustion air to achieve complete combustion. Therefore, burning oil releases less carbon dioxide than burning coal, but more carbon dioxide than burning natural gas. Most of the pollutants produced when burning coal are also a byproduct of burning oil.
Natural gas requires much less air in combustion because of its relatively low amounts of carbon and high amounts of hydrogen. The burning of natural gas is cleaner than the burning of oil and coal. When gas is burned with insufficient combustion air some volatile hydrocarbons can be created, which could become a safety hazard; care should be taken to avoid dangerous conditions.
The burning of natural gas produces less greenhouse gases, which are believed to be one of the main sources for global warming. In equivalent amounts, burning natural gas produces about 30% less carbon dioxide than burning oil and 45% less carbon dioxide than burning coal.
In addition to the carbon dioxide emissions, gas burning creates NOx emissions, while the emissions of sulfur dioxide (SO2) and Particles are negligible.
Other fuels including wood, diesel, gasoline, propane, butane, bio fuels such as ethanol, etc. have there own combustion properties that will affect the combustion efficiency and emissions of the process.