Only Gases Make Heat When Burned
It
is a little known fact that only carbon monoxide and vaporised carbon actually burn, in a wood fire. I didn't mention hydrogen, but a certain poorly thought out pigment mix (basically thermite) used on a famously disastrous German Zeppelin stopped people using hydrogen gas for lift in balloons, but it is also a part of hydrocarbon combustion also, including wood, coal, oil or gas.
Hydrogen actually burns so fast that the sound you get when you burn it makes a similar sound as pulling a cork out of a test tube, from gas generated chemically like zinc or magnesium and hydrochloric acid.
But breaking down cellulose is not a heat generating business. Or more precisely, the heat generated is very small. The flames are a mix of burning carbon gas, carbon monoxide and a tiny bit of hydrogen though much of it just turns into water directly in the oxidation reaction. Oxygen and heat are required to get these exothermic end products. But they do not produce enough heat to drive a chain reaction.
Same with liquid fuels. Only boiled vapour ignites. This can be achieved with vacuum or disperser sprays, but it is only gaseous liquid fuels that burn. Again, you can oxidise them, but the reaction is not hot enough in most cases. Rocket fuel systems use a liquid or solid oxidiser for providing oxygen but the fuel has to boil first. Hydrogen is more present with hydrocarbons, and produces water vapour.
There is even methods to convert solid fuels into gas, and they all require heat and/or pressure.
In gases, pressure and heat are related. Boyles law is pressure equals the inverse of volume, when temperature is unchanged. However, heat increases pressure and so does decreasing volume. But conversely, vacuum can make a liquid boil at a lower temperature.
Combustion only occurs in the gas phase. Some liquid phase reactions produce heat and the most famous are explosives and rocket fuels and especially detonators. They increase pressure which lowers the required heat to begin a chain reaction, burning gas mixtures.
But, basically, only gases burn.
We can't stop here! This is Whale country!
Loki was born in Australia, now is wandering Amsterdam again after 9 months in Sofia, Bulgaria. IT generalist, physics theorist, futurist and cyber-agorist.
Loki's life mission is to establish a secure, distributed layer atop the internet, and enable space migration, preferably while living in a beautiful mountain house somewhere with a good woman, and lots of farm animals and gardens, where he can also go hunting and camping.
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the chemical combination of oxygen with anything else is called oxidation
two forms of which are burning and rust
after a substance is oxidized it's an oxide
For example.... iron oxide (rust) di hydrogen oxide...(H20)...carbonmonoxide (CO), carbon dioxide (Co2), carbon peroxide (CH6N2O3)...all oxides
Oxides have already combined with oxygen...they may be considered to be ash
ash doesn't burn...it's already been burned.
CO burns.
no, Co2 does not burn. carbon monoxide has a blue flame and carbon produces a broad but yellow spectrum, hydrogen is white, though not very bright. A number of metals burrn also like someone mentioned, sodium, lithium, magnesium, iron, aluminium, and nonmetallics: phosphorus, sulphur. But they sublime, because the burning temperature is above their boiling point and it takes a very hot starter, like magnesium, which ignites easily and produces ~3000°C, or yoi can use sometimes just a propane flame or so especially with fine material.
However these temperatures are too high for just making heat and the they are too rare.
I believe you can do reactions with carbon dioxide when it is supercritical, but I think they are endothermic. Carbon monoxide can be combined with hydrogen and a zinc and some other metal catalyst with it to get methanol, with a small amount of CO2.
A mix of hydrogen and carbon monoxide is called "fuel gas" and it can be used to synthesise all kinds of hydrocarbons by varying ratios and conditions and catalysts. You get it by destructive distillation of coal, heat but not enough oxygen.
Yes, CO burns 8-).
yup..because it's the product of incomplete combustion
When combustion of carbon is incomplete, i.e. there is a limited supply of air, only half as much oxygen adds to the carbon, and instead you form carbon monoxide
.....and since the carbon is not yet fully oxidized.....In the presence of oxygen, including atmospheric concentrations, carbon monoxide burns with a blue flame, producing carbon dioxide
This is how rocket stoves work. They are more efficient because they burn the gases from the wood not just the wood.
Yup. Even after the cost of gasifying the wood the net energy is higher, mainly because at the end there is little char. Normal open air burning produces a lot of carbon and other junk in aerosol form. Gasifying first burns the particles, which contain a lot of energy still.