Hydrogen Production From Coal Gasification

The continuously increasing demand for hydrogen worldwide calls for a variety of reliable production methods. In addition to natural gas reforming, hydrogen can be produced through coal gasification, accounting for approximately 18% of the world’s hydrogen. Read more about this process below.

What Is Coal Gasification?

Coal gasification is the process of producing synthesis gas or syngas. Syngas is a mixture of hydrogen, methane, carbon monoxide, carbon dioxide and water vapor. Originally developed to produce coal gas for heating, cooking and lighting, present-day coal gasification focuses on electricity generation and the production of chemical feedstocks.

Hydrogen from coal gasification can be used for various purposes, such as upgrading fossil fuels, making ammonia and powering a hydrogen economy.

How Does Coal Gasification Work?

Known as the second-largest and most effective hydrogen production method worldwide, coal gasification is a reliable alternative to natural gas reforming.

1. Gasification: The process begins by turning coal into synthesis gas (syngas) at 1800 degrees Celsius (3272 degrees Fahrenheit). It combines pulverized coal with an oxidant like air, steam or oxygen.
2. Cooling and cleaning: The syngas undergoes a cooling and cleaning process to remove other gases and particles. Some components removed during syngas cleaning are mercury, sulfur, particulate matter and trace contaminants. This leaves hydrogen, carbon monoxide and carbon dioxide.
3. Shifting: The syngas goes to the “shift reactor,” which mixes carbon monoxide with steam and converts it into more hydrogen and carbon dioxide. At this point, the syngas is only mainly composed of carbon dioxide and hydrogen.
4. Purification: After the shifting process, the syngas are separated into hydrogen and carbon dioxide streams. Upon purification, hydrogen is ready for use, while carbon dioxide is captured.
5. Usage: Pure hydrogen is now ready for various applications, such as electricity generation, fuel cell conversion and chemical manufacturing.

Carbon Dioxide Sequestration

Although coal gasification for hydrogen is reliable and cost-effective, it also has the biggest climate impact among commercially available hydrogen production methods.

Coal gasification produces 18 to 20 kilograms of carbon dioxide emissions for every kilogram of hydrogen. This is roughly twice the amount of emissions produced by steam methane reforming at 8 to 12 kilograms per the same amount of hydrogen.

To mitigate the environmental impact of coal gasification, carbon dioxide undergoes sequestration after purification. Carbon capture and storage is the method of capturing and storing carbon from the atmosphere to minimize emissions. It’s a way to reduce the environmental impact of hydrogen production and make the process more sustainable.

Benefits of Coal Gasification for Hydrogen Production

While it does significantly impact the environment, hydrogen production from coal gasification still presents many benefits, including:

• Cleaner emissions: The syngas produced through gasification has lower sulfur and nitrogen oxide emissions than coal.
• Resource utilization: Gasification allows the utilization of coal’s other chemical properties. In addition to hydrogen production, the gasification process also produces synthetic natural gas, petrochemicals and ammonia.
• Higher efficiency: Syngas facilitates efficient combustion, which translates to energy efficiency and low operation costs for refineries.

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