There is a Better Way to Capture CO2

Scientists right here at Penn State are ensuring a healthy Earth and a sustainable energy infrastructure by revolutionizing the way carbon dioxide is captured from power plants. Researchers from the Penn State EMS Energy Institute and the Research Triangle Institute (RTI), with funding from the U.S. Department of Energy, are making profound strides in the development of a more cost-effective and energy-efficient carbon capture technology.

The ongoing ~$3M DOE project entitled “Bench-Scale Development of an Advanced Solid Sorbent Based CO₂ Capture Process for Coal-Fired Power Plants” was awarded in 2011 involving the collaboration among RTI International, Masdar and Penn State, and co-led by the director of the EMS Energy Institute, Dr. Chunshan Song. Dr. Song, a distinguished professor of Fuel Science and Chemical Engineering in the John and Willie Leone Family Department of Energy and Mineral Engineering, has been conducting this specific type of carbon capture research for well over a decade now. Dr. Song and his project team have joined researchers at RTI, headquartered in Durham, NC, in order to help build the pilot-scale model for testing, as well as run tests and diagnose engineering problems.

With the growing problem of global climate change, along with the desire to save companies and rate payers a few dollars, the U.S. Department of Energy requires that 90% of carbon dioxide released from a coal-fired power plant must be captured to prevent the gas from being emitted into the atmosphere. The current state-of-the-art carbon capture technology is known as liquid amine scrubbing. But, Dr. Song and his team believe their technology will be able to capture more carbon dioxide for less energy output; in turn, saving companies and power plants money and time.

Known as molecular basket sorbent (MBS), Dr. Song’s team of scientists have developed a new sorbent which, in the lab, can remove 100% of the carbon dioxide released during coal-fired energy production. Dr. Xiaoxing Wang, one of Dr. Song’s closest associates on this project, gives an example of how this new technology will outpace the current liquid amine scrubbing method. Dr. Wang says that if a coal-fired power plant were to use liquid amine scrubbing, the cost of electricity would increase by 75-85% of the current rate based on DOE study. While the new technology represents > 40% reduction in cost of CO₂ capture, ~40% reduction in energy penalty and significantly lower capital cost than the state-of-the-art amines.

Testing of the sorbent has taken the next step in development: elevating to pilot-scale demonstrations. Now, in a larger-than-lab-scale setting, Dr. Song, along with the engineers at RTI, are able to more accurately test the sorbent and its effectiveness and, in turn, make modifications in order to perfect the new technology. Dr. Xiaoxing Wang described the new facility, located in Durham, NC, as having the sorption column that reaches anywhere between 12 and 15 meters high. Within the column, flue gas laden with CO₂ is injected from the bottom and propelled upwards, while the solid mass sorbent is pulled down the shaft by gravity. When the sorbent and the gas interact, the carbon dioxide is pulled out of the gas by the sorbent. When the solid MBS hits the bottom of the column, it is then looped over into what Dr. Wang called a “regenerator.” The regenerator will then pull the CO₂ from the sorbent and the cycle will begin again.

According to Dr. Wang, the project goal is to have the sorbent run continuously in the cycle for 500 hours. The group has already run tests in 10-day sequences. For the first three days, the engineers and scientists turned the cycles on and off. Following that, they allowed the cycle to run for three straight days. For the remainder of the testing period, the cycle was once again toggled on and off. By running tests in this manner, RTI and the team has demonstrated and proved the success of using the MBS technology for CO₂ capture and some of important operating parameters have been collected.  

After the 10-day period, the results have been communicated to Dr. Song and his team at the Penn State Energy Institute. The researchers are now working on modifications and what Dr. Wang called “upgrades” in order for the sorbent to operate more effectively at bench-scale.

Dr. Song, along with Dr. Wang, their team of scientists and the engineers at RTI, are laying the pathway for a new, cleaner and more efficient method for power plants to capture CO₂. If successful, the molecular basket sorbent could have a huge impact on not only the environment, but also produce large-scale savings for power companies.