About Coal:
- It is a mixture of two components: carbon-based matter (the decayed remains of prehistoric vegetation) and mineral matter (which comes from the ground from which the coal is dug). The carbon-based matter is composed of five main elements: carbon, hydrogen, oxygen, nitrogen and sulfur.
- coal’s formation process as a progression from biomass (newly dead plant matter) to charcoal (almost pure carbon). Over time, the oxygen and some hydrogen are gradually removed, leaving more and more carbon behind.
- Brown coal thus contains slightly more hydrogen than black coal, although the biggest difference between the two is in their carbon and oxygen contents.
Coal composition:
| Types of Coal | Carbon content | Hydrogen content | Nitrogen content | Sulfur content | Oxygen content |
| Black coal | 91.7 | 4.5 | 1.3 | 0.8 | 1.8 |
| Brown coal | 70.6 | 4.7 | 1.2 | 2.1 | 21.4 |
| Biomass | 50.8 | 6 | 0.6 | 0.1 | 42.5 |
Combution vs Gasification:
Combustion, or burning, is the complete oxidation of a fuel such as coal, a process that produces heat and carbon dioxide.
- Carbon dioxide itself cannot be further oxidised, and thus is the non-combustible end product of the burning process.
Gasification, however, the coal is not completely oxidised. Instead, the coal is reacted with a compound called a gasification agent.
- Gasification is endothermic, which means it doesn’t produce heat. Quite the opposite, in fact – it needs heat input to progress.
- Because the resulting gas is not fully oxidised, that means it can itself be burned as a fuel.
About Coal based Hydrogen production technology process:
Firstly, The process begins with partial oxidation, where some air is added to the coal, which generates carbon dioxide gas through traditional combustion.
- Not enough is added, though, to completely burn the coal – only enough to make some heat for the gasification reaction.
- Brown coals are generally preferred for gasification over black coals as the high oxygen content of this type of coal is less chemically stable and therefore easier to break apart during the gasification reaction. Plus there is a small boost from the hydrogen that is already present in the coal.
Then the Carbon dioxide produced, reacts with the rest of the carbon in the coal, to form carbon monoxide (this is the endothermic gasification reaction, which needs heat input).
Carbon monoxide in the gas stream is now further reacted with steam, generating hydrogen and carbon dioxide.
The hydrogen can then be run through an on-site fuel cell to generate high-efficiency electricity.
Result:
- Hydrogen produced in this way is not a zero-emission fuel as Carbon dioxide is emitted. However, When hydrogen is used as a fuel, it releases only water as a byproduct. This makes it a zero-emission clean fuel, at least at the point of use.
