why charcoal burns so hot even though it’s already been burned
In: Physics
So when you make charcoal your actually burning the impurities out of it. Whats left is pure carbon,much like coal, which oxidizes at a much higher temp than impure carbon. The impurities take up oxygen that could otherwise fuel the carbon combustion.
When you make charcoal you aren’t burning wood, you’re basically cooking it. You’re cooking the wood. You have to prevent it from getting any oxygen so it won’t burn and you cook it until the moisture leaves it. Im not an expert on it and I’m not familiar with the exact chemical reaction that takes place but I do know you aren’t burning it. If the fire reaches the wood and it gets oxygen then it will burn just like normal.
All fire is, is what’s called an exothermic reaction. Basically a material reacts with another material and produces and excess of heat. In wood the thing that reacts is the cellulose which give the wood it’s structure. Cellulose actually will react in 2 different ways when heat is applied. In relatively low heat, high oxygen environments like the one use to make charcoal the cellulose will simply form the black char by bonding with oxygen (which releases heat).
However in the presence of higher heat and lower oxygen that char will react again. This time producing hydrogen, nitrogen, and other gas which themselves burn at a high temperature, as well as producing that white ash you see when charcoal is burned. Some people refer to this as “gassification”. We create this high heat low oxygen environment with starter fluid, but then the reactions sustains itself until all the cellulose is consumed.
after reading the answers, im left wondering how people figured this stuff out before the advent of modern science
Wood is a bunch of stuff all mixed together. Some of it burns at high temperature and some at lower temperature.
When you make charcoal, you’re burning off almost all the stuff that burns at lower temperatures. You’re left with a lump of almost pure carbon that burns at a very high temperature. It burns really hot because turning it into charcoal gets rid of the stuff that doesn’t burn really hot.
This is similar to milk vs cheese.
Cheese is the awesome substance left over when you remove all the boring bits from milk. There’s a whole process that looks a little like cooking to make the cheese.
With Charcoal, it is burnt in a special way to make sure we just burn out the dud bits of the wood and are just left with the pure carbon fuel part.
When you normally burn wood, the pure carbon part burns really well but the rest of the wood gets in the way. Burning just the charcoal means you’re only burning the bits that “want” to get burned.
Because it’s already been burned. It just hasn’t been burned all the way. When you ignite charcoal, you’re finishing the job after all the hard work has been done
Wood is mostly made up of long complex hydrocarbons molecules. This is pretty good for a tree since it’s what makes wood so tough, but long complex hydrocarbons don’t burn very efficiently. In order for them to act as fuel, they need to break down into shorter hydrocarbons, which is a process that happens as the molecules heat up from the fire.
As well wood, even dry wood, as a lot of moisture in it. Sap etc. Light it on fire and that moisture also needs to heat up and boil off, which take heat away from the fire.
This is OK and wood isn’t that bad fuel source, but both those facts limit the amount of heat that can be produced. The reaction can only break down those long molecules into nice burnable short ones so quickly and you can only boil off the moisture so fast.
If you want to make wood into a hotter burning fuel you need to drive off as much of that moisture as possible, and ideally break down those hydrocarbons into shorter ones. You can do both by heating the wood up, but not letting all of it burn away. Very conveniently fire is good at heating things up and wood is pretty flammable. When you burn wood in a charcoal kiln, you burn much of it as fuel to convert the remainder into charcoal. If you don’t manage the temperature inside the kiln well, it either wont turn into charcoal (to cold), or it’ll all just burn away on you (to hot).
After letting it burn, you smother the fire and once it’s cooled down whats left is a bunch of wood that’s gone partway through the process of burning. All those long hydrocarbons that make wood so tough have broken down leaving a much more brittle material, and all the moisture boiled away making it both bone dry, much lighter, very porous and unable to rot.
All the stuff that slows down the reaction has been done so when you reignite the remaining charcoal it can burn much more quickly, and thus produce much more heat.
Also while the charcoal burns much hotter, producing charcoal is not very efficient. Even in a really good kiln with good dry wood to start with, more than half the possible energy you could have gotten out of the wood is spent in producing the charcoal. A poor kiln with bad material will lose north of 80%.
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