COMPLETE COMBUSTION

No Author. (2015). Combustion Reaction. Available: http://pixshark.com/combustion-reaction-examples-in-real-life.htm. Last accessed 30/04/2015.

Combustion is the chemical process of burning stuff. What happens is that oxygen from the air reacts with the fuel (in this case cellulose in the wood C6H12O5) (No Author (2015)) turning it into carbon-dioxide and water, this also releases lots of heat. This can be expressed by the chemical equation below:

A constant oxygen supply is required for this reaction to occur properly. If a constant supply of oxygen is not present, incomplete combustion will occur (Slattery.P 2015). See equation below:

The main difference between complete combustion (where enough oxygen is supplied) and incomplete combustion is that incomplete combustion releases toxic pollutants (seen as smoke) and releases nowhere near as much heat (Slattery.P 2015).

When you burn wood though, it will never be entirely complete or incomplete combustion but rather a mixture of both. In order to get more heat from less fuel, you want to have a greater percentage (or rate) of complete combustion than incomplete combustion.

Therefore the more air you can get in the fire, the hotter the fire will burn and ultimately the quicker and less wood you'll need to preheat your oven. (Slattery.P 2015)

Rocket stoves are simply an L or J shaped piece of pipe. How a rocket stove works is that fuel is fed into the lower part of the J (or L) and set alight. This causes the air inside the stove to heat up and therefore be drawn upwards. This upward draw causes fresh air from outside to be sucked in through the lower part and therefore straight through the fire. This results in an extremely high rate of complete combustion to the point where there is no noticeable smoke and it burns hotter than a regular fire with the same wood (Halford.L (2015), Stephenson.M (2008)). See short clip below of a simple rock stove on action.

Pizza ovens on the other hand can be very smoky especially when initially lit. This is due to the lack of circulating air in the oven and through the fire itself (Stephenson.M (2008)).

See the current of air within a pizza oven in the diagram below

It can be seen that within a standard pizza oven a convection current occurs similar to that in a rocket stove, but as the air doesn’t actually travel through the fire and the flow of hot air escaping competes with the flow of cool air entering, not as much fresh air is supplied to the burning fuel (Jeavons.R (2009), Field.H & Denzer.K (2007), Eli.R (2015)). This results in a higher rate of incomplete combustion than in a rocket stove (Slattery.P (2015)). This clearly shows that a rocket stove is much more efficient with fuel and time than a pizza oven.

2015.