What happens to the H in coal?

They combine with oxygen to form H2O. Hydrocarbons, then, form CO2 and H2O as products of combustion. A nice "clean" hydrocarbon (like alcohol), burning at a low temperature and pressure, will form little else.

The other compounds formed are byproducts, and include NOx (nitrogen and oxygen combining under heat and pressure) sulfuric acid if the coal has sulphur in it, CO, etc.

Sorry to disagree, but I believe that when you combust an alcohol both aldehydes such as formaldehyde and ketones are produced. Both of these byproducts of combustion of alcohol are more harmful than the HC and CO2 they supposedly reduce.

Aldehydes and ketones are combustible too, and will oxidise further to CO₂ and H₂O.

Ok The combustion of coal. As the coal is heated gasses are driven off they combine with atmospheric oxygen, you get heat and light (flames) these are the indication of an exothermic reaction. (Fire) the heat further converts the carbon to firstly carbon monoxide then to carbon dioxide ( I tried to lay this out as a formula but it got all messed up) The hydrogen is in the form of methane that burns to water and more carbon dioxide. The smoke is the product of incomplete combustion. Tars and particulates. The water is invisible because it is steam witch is a gas. Eventually it is all just a glow as the remaining carbon converts to heat, light, and carbon dioxide.

The volatiles having been driven off.

There is hydrogen in coal, but not in the form of methane. The hydrogen is in the form of very high molecular weight hydrocarbons. When coal is burned, the hydrogen is converted to water vapor.

If you want to see a quantitative tabulation of the the major combustion products from burning a typical natural gas, petroleum fuel oil, or coal, visit:

Flue gas emissions from fossil fuel combustion

Why does methane cause so many undergrond explosions in coal workings? China just a few days ago!

methane is natural gas I think, which is everywhere, and is probably struck sometimes when mining. They used to use birds in cagges, and when they died the miners new to get out.

Brainwave-Methane is heavier than air. It is found naturally in coal mines. It has to be forced up and out of the mines. Proper ventilation is vital for the safety of miners. James

No it's not, it's just over half the density of air. Methane has mol. wt. 16, air ~ 29. Density of gases is directly proportional to mol. wt.

Good catch!! Right on...

In addition to other posts, methane is colourless and odourless, and the main constituent of 'natural gas' supplied to many homes in the UK. To indicate its presence and alert home-owners to leaks an odourant is added to cause alarm via smell. Gas, of course, is obtained from underground reservoirs. Firedamp is worth a read, as is the Abbeystead pumping station disaster, an underground water installation affected by the unwitting presence of methane.

As well as a the presence of a flammable material, to create an explosion one also needs oxygen, present in air, and a source of ignition. Electrical equipment in coal mines, as well as numerous other locations underground, is usually type-tested, selected and constructed so as to contain the force of an internal explosion without transmitting the flame to the surrounding atmosphere, a technique commonly referred to as 'flameproofing'. There are a number of other techniques: British Standard 5345 refers to those available for assuring electrical installations do not cause explosions. Electrical designers entering this field are highly recommended to take a formal training course in the subject.

...so as to contain the force of an internal explosion without transmitting the flame to the surrounding atmosphere, a technique commonly referred to as 'flameproofing'.

In the US, motors and equipment of this sort are called "explosion proof." Many years ago, I bought a used lathe which came with an explosion proof motor. At the time, I thought, "I don't think motors routinely explode. Seems you'd have to get the speed up very very high before one would came apart." Then, I started working in the underground coal mining industry, and came to realize what the term really means. I still have the lathe and motor, and the motor gives every sign of being good for about 500 years. It was probably bought used after having been in the mines (probably powering something small that was upgraded) and probably cost (used) a tiny fraction of its new price.

Your motor was probably designed for a wood shop. Hardwood dust can rapidly ignite much like the grain elevator explosions. You will find this on space heater as well for wood shops.

Methane is a byporoduct of decomposing plant and animal material. Since coal is the remaining carbon from living material, it is only natural that methane pockets may be trapped with the coal.

Methane is actually the most easily flammable of all carbo-hydrates, where only one carbon "clamp" manages to hold four hydrogens "bombs", at least one very loosely bonded, begging for oxidation, in order to start the chain-reaction.

Please don't confuse this chemical description, with nuclear anything

Not too sure about that - according to my data ignition temp of methane is 595°C, while ethane is 515°C and ethyne (or acetylene) C₂H₂ is 305°C.

Also these compounds are hydrocarbons, not carbohydrates. As you probably know, carbohydrates are C + H + O, the H and O being in water proportion.

Cheers.....Codey

...tried to lay this out as a formula but it got all messed up...

Here is a generalised description, you may have skipped

CHOAL - I don't think there was ever a H in coal.

Methane is a big problem even in gold mines. (definitely lighter than air)

On steam trains the used to sprinkle water on the coal before burning it to improve burning. The water in the mine will most probably react with the coal.

Er, actually the water was sprayed on to reduce the dust problem. Sorry.

"...CHOAL - I don't think there was ever a H in coal..."

What about charcoal?

In underground mining, water is sprayed at the cutting site primarily to reduce dust (itself explosive when mixed with air) and to serve as a coolant for the cutting bits.

(The stuff that comes out the back of a coal mining machine is about as messy as anything in industry. The environment is cold, dark, wet, and filthy. And if explosion isn't worrisome enough, there is the every present danger of the roof caving in. In "low coal" the mining machines can work in seams only 3' high, and are designed so the the operator lies on his side while working.)

I don't think there is much reaction of water with the coal in the mines, even in high sulfur coal. (At least people don't complain of skin burns from sulfuric acid.) After combustion, on the other hand, the SO₂ formed can readily react with water to form H₂SO₄, sulfuric acid.

All constituents in coal, whether it be carbon, hydrogen, or traces of nitrogen and sulfur, go through a combustrion reaction. Since, complete combustion is an ideal case, most plants supply excess air to assure incomplete combustion does not take place, because CO is very bad compared to CO₂.

Now, since all constituents react with O₂ at combustion temperatures, you can write a reaction step for each molecule.

H + O₂ → H₂O

C + O₂ → CO₂ (complete)

2C + O₂ → 2CO (incomplete)

S + O₂ → SO₂

Therefore, H forms water vapor when combusted in the presence of oxygen. Note, that heat is also generated in each step, otherwise combustion reactions would be completely useless.

I suggest doing some searches on "methane steam reforming" to get the current state of affairs. Searches on the "Fischer-Tropes" reaction will also lead you to interesting facts.

Hydrogen burns readily and will combine with most chemicals to create acids, alcohols and bases. Most will burn depending on the temperature of the fire. The few that wont burn will end up in the smoke or ash.

The hotter you burn the coal, the cleaner is the byproducts.

Burning any organic material produces three primary products: In an excess of oxygen, the Carbon tens to produce mostly CO2 and water (H-OH). If the amount of oxygen available is limited, then mainly CO and water are the main products. The hydrogens associated with biomass, coal, petroleum products, wood, etc are primarily converted into water vapor during burning. Hold a ceramic plate or a piece of glass safely over a flame and you'll see water vapor condense on the glass, etc. It helps if the glass etc is cooled!

Ok so how much of the burn/energy output is actually do to each reaction? When pure H2 and O2 react it's alot faster and more powerful then gas. Also the reaction is slowed down by adding: an unbalanced mixture (fastest burn would be 33% O atoms, and 66% H atoms) of H and O atoms, and anything else that could get inbetween the H and O atoms, like Nitrogen. I wonder if the only, or main thing that puts out the energy could be the H and O reaction, because gasoline is a liquid, and the carbone atoms could just be there to hold the H atoms in a smaller area, and then the heat caused by the H and O reaction might fuse the other atoms together to explain their combining... What energy giving reactions don't involve the combining of H and O?

When pure H2 and O2 react it's alot faster and more powerful then gas.

Assuming by "gas" you mean gasoline (you had me scratching my head for a minute) you are right, in the sense that a kilo of H2 has about the energy of a gallon of gasoline (which is 3 kilos). Gasoline, when vaporized and mixed with O2, can give off one heck of a bang, too.

C + O2 > CO2 is also exothermic. There are many exothermic reactions (ones that give off heat) that don't involve hydrogen.

They used this in Vietnam with the fuel air bomb.

Methane gas is highly flammable. It is usually produced as a result on anerobic decomposition of organic matter, which is why it tends to form pockets underground, and of course, coal mines are always located underground. The miners, of course, require oxygen to breathe, so when the methane gas mixes with the oxygen in the air the miners are breathing, all it takes is a spark, such as from a miner's pickax striking the rockface of the coal seam, to set it off. And when that happens.....

For the hydrogen gas in coal, it all depends on how much oxygen is supplied, how hot it burns, and the burning time. With sufficient oxygen, heat energy and time to burn, all the carbon and hydrogen will burn off to form carbon dioxide and water. Insufficient oxygen, heat or burning time, or any combination of these, will result in the production of organic byproducts.