Carbon capture

US energy provider NRG Energy plans to show that it can capture CO₂ from conventional coal-fuelled, electric power plants on a commercial scale.

To do so, it has teamed up with Portsmouth, New Hampshire-based Powerspan, developers of a post-combustion, regenerative process that uses an ammonia-based solution to capture CO₂ from the flue gas of a power plant and then release it in a form that is ready for safe transportation and permanent geological storage.

To date, CO₂ capture demonstrations on coal-fuelled power plants have been conducted only at pilot scale. The new demonstration system will be conducted at NRG's WA Parish plant near Sugar Land, Texas, one of the largest coal power stations in the US.

Once operational in 2012, it is expected to capture and sequester about one million tons of CO₂ annually - ranking it among the world's largest carbon capture projects and potentially the first to achieve commercial scale capture and sequestration from an existing coal-fuelled power plant.

Powerspan’s CO₂ capture process, called "ECO2"  is a scrubbing process that uses an ammonia-based solution to capture CO₂ from a flue gas. The CO₂ capture takes place after the nitrogen oxides (NOx), sulphur dioxide (SO₂), mercury and fine particulate matter have already been captured - either using Powerspan’s technology or any other air pollution control system.

Once the CO₂ is captured, the resulting solution is regenerated to release the CO₂ and ammonia. The ammonia is then recovered and returned to the scrubbing process and the CO₂ is processed into a form that is ready for sequestration. Ammonia is not consumed in the scrubbing process, and no separate by-product is created.

The CO₂ captured from the WA Parish plant is expected to be used in enhanced oilfield recovery operations in the Houston, Texas area.