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Combustion

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Fire is one of the most common types of combustion

Combustion is a chemical reaction that occurs when a fuel reacts with oxygen. A simple definition would be, when anything burns it is a combustion reaction. There are many different types of combustion. Different types of combustion have different uses in out everyday lives, and some forms are just down right dangerous. Complete and incomplete combustion are two of the biggest categories for combustion which I will go into more below. Combustion is very useful to our world today. We use it in our vehicles, to cook food, and even types of respiration are used in our bodies. Scientists are continually learning more and more about combustion and how it can further science and be useful to the average persons everyday life. The Phlogiston Theory was one of the first theories about combustion, and although the base principals are incorrect, it got scientists minds turning in the right direction when thinking about combustion. Combustion still has many instabilities and things that make it hard to control. While combustion can be dangerous it can also be very useful in the lives that we lead today.

Types

This is an image of what happens when wood goes through combustion

There are many different kinds of combustion. Complete, incomplete, rapid, slow, and spontaneous combustion are just a few kinds [1]

Complete combustion uses all of the fuel reactant. There is no fuel left over in complete combustion. An example of a complete combustion would be burning wood outside. In the outdoors there is enough oxygen to completely burn the fuel reactant. Most of the time when talking about complete combustion it is in reference to the burning of hydrocarbons. In complete combustion the only two products that result are water vapor (H2O) and carbon dioxide (CO2). There are no bi-products when dealing with complete combustion.

Incomplete combustion does not use all of the fuel reactant. An example of this would be wood burning in a small gas fire place. Here, there is not enough oxygen to completely burn the fuel, which in this case is the wood. Again incomplete combustion is typically referring to hydrocarbons. There are many different bi-products that occur when talking about incomplete combustion. Most often it tends to be water (H2O), carbon dioxide (CO2), and carbon monoxide (CO) [2]

Rapid combustion happens quickly, as the name would suggest. Oxidation occurs too fast to be controlled resulting in large amounts of heat and light energy, which produces an explosion or a flame. Some examples of rapid combustion would be petrol, diesel, or hydrogen gas.

Slow combustion, again as the name might suggest, takes place slowly. Another name for this sort of combustion is smoldering combustion. It tends to not have a flame and take place at low temperatures. Coal, wood and cotton are just a few examples of substances that can complete slow combustion. Respiration is another example of a slow combustion. There is no heat or light that is produced in this form of combustion.

Spontaneous combustion can cause a lot of harm because it starts without a flame. Just heat in itself speeds up the reaction rates. If heat from oxidation can not escape like it needs to, it builds up and this causes an increase in temperature. In order to prevent this from occurring, you have to control the rates of chemical reactions. These things can occur in many different places. They can occur in factories, where oil accumulates on scrap material. Farms, where hay can oxidize in confined spaces is another example. This spontaneous combustion can even occur in homes if you have an oily paint on a rag, as the paint dries it creates heat and can catch on fire. Combustible material needs to be stored in ventilated areas where heat has the ability to be released [3]

Uses

Combustion is used for many different purposes in society today, as discussed previously. Just a few examples of its use is gas ovens, cars, and fossil fuel power plants. These are just a few different ways that combustion reactions are used in our everyday lives. Combustion reactions are mostly used as a source for heat and light.

Fire is a big use of combustion. People use fire everyday to cook, keep warm, and have light. These are just a few very common uses of fire as a form of combustion. While these are just the basic uses of combustion, throughout the years more and more discoveries are being made. Some of the most recent discoveries are the steam engine and gas vehicles. Steam engines involve the combustion of a base substance, most typically coal that is used to boil water. The steam from this boiled water is used as energy for whatever movement needs to be completed. This is the same process that is used for fossil fuel power plants today. Many vehicles today use combustion. The burning of fuel is what makes vehicles run and fun. [4]

Fuels

Methane going through combustion and producing carbon dioxide and water.

Fuels are the materials that undergo combustion. The most common examples of these are wood, gasoline, and coal. Fuels are the biggest part of combustion, without them it could not occur. Liquid fuels tend to go through combustion in the gas phase. There are three main phases of combustion. The fuel begins to warm up, it turns into a gas, where it can be used for energy, and then the solid phase, when the combustion begins to die down and turn into ash. These are the main ways that fuels go through combustion.

Fossil Fuel combustion has become a big deal in the past few years. Many people complain about the effect that the burning of the fossil fuels has on the environment [5].

Natural gases tend to be less hazardous, but the more useful gases, such as coal and gasoline can let off harmful pollutants into the environment. The combustion of methane is one of the cleaner gases that go through combustion, since most natural gases are made up of mostly methane. Methane, when combusted, produces carbon dioxide, water and energy. Below is the chemical reaction for the combustion of methane CH4[g] + 2 O2[g] -> CO2[g] + 2 H2O[g] + energy [6]

Phlogiston Theory

People have studied fire for as long as it has existed. There are many different people and many different claims throughout history of different people claiming different discoveries. The Phlogiston theory is one the first major attempts at trying to explain combustion. It was made in 1667 by Johann Joachim Becher [7] Phlogiston is said to be a substance that exists in all combustible elements and is only released during combustion. When Becher was studying fire he claimed that there was a "wild spirit" that crept out of the fire during what we now call combustion. He called this substance phlogiston. His idea was that all combustible elements contain phlogiston and when it is burned, the phlogiston is burned out, and any substance that did not contain this phlogiston was noncombustible [8]

The Phlogiston theory no longer holds any relevance in the scientific culture today. Many aspects were disproved in the late seventeen to early eighteen hundreds. It tried to explain the process of combustion which we can now contribute to oxidation. This theory was made before the discovery of oxygen. While the Phlogiston theory is discredited today, it was an amazing theory made in a time with much less information on the science of combustion [9]

References

  1. Combustion-Reactions About.com-Chemistry. Web. April 1, 2014 (date accessed).
  2. ScienceDaily. Combustion ScienceDaily. Web. April 1, 2014 (date accessed).
  3. Andrews, Natalie. Types-of-Combustion eHow. Web. June 27, 2011 (date published).
  4. Combustion. ScienceClarified. Web. 15 April 2014 (Date-Accessed).
  5. Fossil-Fuel-Combustion-Waste Environmental-Protection-Agency. Web. May 5, 2013 (last updated).
  6. Ophardt, Charles. Combustion-of-Fossil-Fuels Virtual-Chembook. Web. April 15, 2014 (date accessed).
  7. Kondratiev, Victor History-of-the-study-of-combustion Encyclopedia-Britannica. Web. April 1, 2014 (date accessed).
  8. Phlogiston-Theory Princeton. Web. April 1, 2014 (date accessed).
  9. What-is-phlogiston? Fun-Trivia. Web. April 1, 2014 (date accessed).