Hydrogen Production through Coal Gasification

Coal to Hydrogen
Source: https://www.nsenergybusiness.com/features/coal-gas-conversion-us-canada/

Presently, coal gasification provides around 18% of the total hydrogen in the world, and is the second-largest and most cost-effective way of producing hydrogen. In China, the scenario is quite different.  There coal gasification is the main production method where 62% of its hydrogen comes through the process. Hydrogen production through coal gasification is considered to have the most climate impact since the process results in 18-20 kg of CO2 emissions per 1 kg of H2 while steam methane reforming emits 8-12 kg per the same. Coal gasification is a thermo-chemical process where coal breaks down into a few gases and particulate matter during the process. Anyway, after 4 major steps, hydrogen and carbon dioxide can be separated out as the final products.    

Technology Behind Coal Gasification

Block Diagram for Coal Gasification
Block Diagram for Coal Gasification Source: https://www.ieabioenergy.com/

1st step:
Through gasification, coal gets to turn into a very hot synthesis gas (Syngas) at a temperature of around 1800 celsius which is a mixture of carbon monoxide, hydrogen and carbon dioxide along with other trace gases such as Sulfur Dioxide and particulate matter.

2nd step:
In the next stage, syngas is cooled and cleaned to remove trace gases and particles. In this process sulfur, mercury, particulate matter and other contaminations are removed.

3rd step:
Then cleaned syngas is transferred to the shift reactor. Through shift reaction, CO is converted to CO2 and afterwords the product stream is mostly H2 and CO2.

Final Step:
Finally, CO2 and H2 are separated into two streams. If the plant is equipped with CCSU (Carbon Capturing Storage and Utilize) technology, CO2 is captured, stored and utilized.

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