Combustion is a chemical process which involves the burning or rapid oxidation of a fuel.
Complete combustion reaction means when a hydrocarbon reacts with sufficient amount of oxygen forming carbon dioxide and water.
Incomplete combustion reaction means when a hydrocarbon reacts with insufficient amount of oxygen forming carbon monoxide and water.
Incomplete combustion cause environmental pollution.
Complete combustion results in more energy than incomplete combustion.
Combustion is the process of burning or oxidation, which may be accompanied by light and heat. Oxygen itself does not burn, but it supports combustion. The rate of combustion is influenced by both oxygen concentration and its partial pressure.
Incomplete combustion means a reaction or course of action which entails only partial burning of a fuel. This may be due to a lack of oxygen or low temperature, preventing the complete chemical reaction. Carbon monoxide is produced as a byproduct from incomplete combustion of carbon.
Complete combustion takes place when there is a constant and enough oxygen supply. Incomplete combustion takes place when there isn’t enough oxygen supply.
In complete combustion, limited number of products is produced in contrast to incomplete combustion.
Complete combustion will be:
Alkenes + Oxygen -> Water + Carbon Dioxide
For example:
C5H12+ 8(O2) -> 6(H2O) + 5(CO2)
Incomplete combustion is when there is not enough O2 to react fully. So its products may include C, or CO, which both require less oxygen. So it is more like:
[Alkenes] + [Oxygen] -> [Water] + [Carbon Dioxide] + [Carbon Monoxide] + [Carbon}
Though some of the products may not be produced at all.
For example:
C5H12 + 5(O2) -> 6(H2O) + 4(CO) + C
Example of burning natural gas,
Complete combustion;
CH4 + 2O2 --> CO2 + 2H2O
Incomplete combustion
CH4 + O2 --> C + 2H2O
Complete combustions need the most oxygen. Insufficient oxygen produces incomplete combustion.
Incomplete combustion can arise from a shortage of air or surplus of fuel or poor distribution of fuel. It is usually obvious from the color or smoke, and must be corrected immediately. In the case of oil and gas fired systems, CO or smoke (for oil fired systems only) with normal or high excess air indicates burner system problems. A more frequent cause of incomplete combustion is the poor mixing of fuel and air at the burner. Poor oil fires can result from improper viscosity, worn tips, carbonization on tips and deterioration of diffusers or spinner plates.
The ideal combustion ratio ("complete combustion") for propane is 1 part propane (4%) to 24 parts of air (96%). Even at this ideal ratio, combustion products, known as flue gases, still occur. However, under this scenario, those products are harmless carbon dioxide and water.
Incomplete combustion (due to either rich or lean burns) may produce harmful combustion by-products such as carbon monoxide and aldehydes.
Combustion is the burning of fuel (carbon) to produce carbon dioxide.
Incomplete combustion produces carbon monoxide which is harmful to the environment!
Commonly used fuels like natural gas and propane generally consist of carbon and hydrogen. When a fuel has a large ratio of hydrogen, more excess air must be provided. Water vapor is a by-product of burning hydrogen. To maintain its vaporous state, it robs heat from the flue gases, which would otherwise be available for more heat transfer.
Natural gas contains more hydrogen and less carbon per BTU than fuel oils and as such produces more water vapor. Consequently, natural gas is generally slightly less efficient than fuel oil.
Too much, or too little fuel with the available combustion air may potentially result in unburned fuel and carbon monoxide generation. A very specific amount of O2 is needed for perfect combustion and additional (excess) air is required for good combustion. Too much additional air can contribute to CO generation, lower efficiencies and perhaps unsafe conditions with heating equipment not out living its full service life.
With coal firing, unburned carbon can comprise a big loss. It occurs as grit carry-over or carbon-in-ash and may amount to more than 2% of the heat supplied to the boiler. Non-uniform fuel size could be one of the reasons for incomplete combustion. In chain grate stokers, large lumps will not burn out completely, while small pieces and fines may block the air passage, thus causing poor air distribution. In sprinkler stokers, stoker grate condition, fuel distributors, wind box air regulation and over-fire systems can affect carbon loss. Increase in the fines in pulverized coal also increases carbon loss.
Combustion or burning is a complex sequence of exothermic (releasing energy) chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames.
In incomplete combustion, there is not enough oxygen to react completely with the fuel. The products of incomplete combustion are Carbon, Carbon Monoxide, Carbon Dioxide and Water vapor. Whereas the products of complete combustion are only carbon dioxide and water vapor.
Incomplete combustion occurs when there isn't enough oxygen to allow the fuel (usually a hydrocarbon) to react completely with the oxygen to produce carbon dioxide and water, also when the combustion is quenched by a heat sink such as a solid surface or flame trap. When a hydrocarbon burns in air, the reaction will yield carbon dioxide, water, carbon monoxide, pure carbon (soot or ash) and various other compounds such as nitrogen oxides. Incomplete combustion is much more common and will produce large amounts of byproducts, and in the case of burning fuel in automobiles, these byproducts can be quite unhealthy and damaging to the environment.
If a hydrocarbon undergoes complete combustion, only carbon dioxide and water is produced. If it undergoes incomplete combustion, carbon monoxide and carbon particles may also be produced.
Quality of combustion can be improved by design of combustion devices, such as burners and internal combustion engines.