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Waste Heat Used to Capture Emitted Carbon Dioxide


Coal-power-station-001An economical way to capture CO2 from the atmosphere using  waste heat, was established by researchers at Rice University. This method is a break-through in CO2 capturing, because most conventional techniques are energy intensive and use up high-pressure steam, valuable for electricity production.

The research published in the latest issue of the International Journal of Greenhouse Gas Control had the aim to develop an innovative technique, which can reduce greenhouse gas emissions from power plants. The project was funded by the US Department of Energy (DoE).

The use of low-grade steam not suitable for electricity production, also known as waste heat, is one of the many techniques that the team at Rice university, led by George Hirasaki, Professor of Chemical and Biomolecular Engineering, is trying to improve.

The technique is a two-phase process. First, the CO2 from the ground is piped up a column, while the ammonia-like liquid, amine, flows down the same column. The amine is the substance, which captures and removes CO2, while the pure natural gas is pushed out of the column. In the second stage, the CO2-laden amine is recycled with heat, driving the CO2 off.

Applying the process in power plants has been quite a challenge to the team, because the recycling of the amine requires great amount of heat, which could increase the cost of electricity.

Current technology used for CO2 capturing could increase electricity cost by 70 to 100 %, according to one of the co-authors and a graduate student at Rice, Sumedh Warudkar. This was the reason why the team looked at using waste heat as a cheap alternative.

Warudkar tested various ways to improve the technique, including tailoring of the chemical formulation of amine, adjusting the size and pressure of the reactors, as well as experimenting with different types of steam.

The next step for the team will be to provide a comparison between already existing techniques on the market.  This would be possible after establishing the most optimal amine formula, reactor size and type of steam.

The team is convinced that their optimized formula and the use of waste heat, will reduce the need to use steam that could produce electricity.

Further work is now focused on testing new materials in order to make the process of CO2 capturing much more economical.




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