How can coal be converted into gas or liquid fuels?

Because coal is a hydrogen-deficient hydrocarbon, converting it into gas or liquid fuels requires the addition of hydrogen, either directly or through water.1

Coal Gasification

Coal gasification converts coal into a mixture of gases, such as carbon monoxide, hydrogen, and methane. Methods include:1
* Carbonization: Heating coal in the absence of air.2
* High-temperature processing: Pulverizing coal and mixing it with oxygen, steam, or carbon dioxide.2
* In situ gasification: Controlled, incomplete burning of underground coal beds while adding air and steam.1
* Hydrogenation: Exposing coal to hydrogen at high temperatures with a catalyst.2

Coal Liquefaction

Coal liquefaction turns coal into liquid products resembling crude oil using four primary methods:31
1. Pyrolysis and hydrocarbonization: Heating coal in the absence of air or in a hydrogen stream.1
2. Solvent extraction: Selectively dissolving coal hydrocarbons and adding hydrogen.1
3. Catalytic liquefaction: Hydrogenation performed in the presence of a catalyst.1
4. Indirect liquefaction: Combining carbon monoxide and hydrogen gases in the presence of a catalyst.1

Commercial viability for these processes remains dependent on the market prices of petroleum and natural gas.4