Carbon Capture

From Flue to Blue Hydrogen

Global warming and climate change concerns are intensifying global efforts to reduce the concentration of greenhouse gases such as carbon dioxide (CO₂) in our atmosphere. Increasingly, attention is focusing on the need to remove CO₂ from the flue gases released by several processes in countless industries including power, chemicals and steel. Carbon capture is a key strategy in meeting today’s CO₂ emission reduction targets.

Carbon Capture Strategies

There are three different carbon capture strategies to choose from, depending on the source of the gas:

1. Pre-combustion technologies separate CO₂ before the combustion process. Reforming and gasification processes react fossil fuels with air or pure oxygen to create a synthesis gas comprised of hydrogen (H₂), carbon monoxide (CO), and carbon dioxide (CO₂). The CO₂ molecules are separated out of the syngas stream before combustion or further downstream chemical use of the syngas takes place.
2. Oxy-fuel combustion technologies burn fuel in an almost purely oxygenated environment. Oxygen is separated from air and then combusted with a fossil fuel to produce CO₂ and water vapor. This combustion, for example, drives turbines and generates electricity, then the water vapor is cooled, condensed, and removed while the CO₂ is captured, purified and piped away.
3. Post-combustion technologies separate CO₂ from the exhaust after the combustion process. This is the most widely used CCS technology for retrofitting industrial and power generating facilities. During the post-combustion process, flue gas resulting from burning fossil fuels passes through an absorber column with circulating liquid solvent, which absorbs the CO₂ molecules. A heating medium like steam enables the adjacent regeneration column releases the CO₂ from the solvent, and the CO₂ is captured and piped away before it reaches the atmosphere.

Many chemical applications rely on CO₂ scrubbing. Oxyfuel technology is an ideal way to increase the efficiency of combustion processes in new power plants. And post-combustion capture (PCC) is targeted specifically at flue gas in existing power plants, typically using a solvent to chemically absorb the CO₂ from the flue gases after the combustion process.

The captured gas can be further purified and liquefied for commercial use - for example, as food-grade CO₂ for the production of food and beverages, as a feedstock for the production of commodities like methanol or urea or in greenhouses. Alternatively, it can be stored underground (sequestered) as a carbon abatement measure.