Biphasic CO₂ Absorption Process (BiCAP)

To help the U.S. meet its new carbon capture goals, ISTC is working in collaboration with the Illinois State Geological Survey (ISGS) and the Applied Research Institute on the campus of the University of Illinois at Urbana-Champaign and external partner Trimeric Corporation of Buda, Texas, to develop an innovative, low-cost approach for CO₂ capture from burning coal during electrical generation.

Lab-Scale Project

With funding from the U.S. Dept. of Energy in October 2015, ISTC is assisting ISGS to develop a novel biphasic solvent process at a lab-scale (10KWe) for CO₂ capture. The objectives of this lab-scale research project are to:

Demonstrate a novel biphasic CO₂ absorption process (BiCAP). Generate engineering and scale-up data to leverage the technology to the bench- or small pilot-scale demonstration level.

New Technology vs. Conventional Carbon Capture

The conventional CO₂ absorption process (e.g., Monoethanolamine [MEA]; Figure 1) starts with carbon dioxide-rich flue gas entering the absorber where the CO₂ is absorbed and mixed with a solvent (in this case MEA); the clean gas leaves the top of the absorber. Then the CO₂ rich solvent passes through a heat exchanger and a stripper where the solvent is stripped of the CO₂ and returned to the absorber. The concentrated CO₂ is then pressurized. While conventional carbon capture methods are effective in removing CO₂, they are very energy intensive and nearly double the cost generating energy.

The introduction of a biphasic solvent method after the absorber (Figure 2) helps increase the stripping capacity due to the increased concentration of CO₂ in the second solvent phase. In addition, there is less energy and compression work required to compress the CO₂. However, the equipment needed is still the same size as the conventional carbon capture technology making this method only slightly less cost intensive.

In Period I of this project, ISGS developed an advanced biphasic CO₂ absorption process, dubbed BiCAP (Figure 3), which has multi-liquid-liquid phase separation (LLPS) that allows low CO₂ loading throughout absorption (Figure 4), resulting in faster kinetics. In addition, BiCAP solvents have larger solvent capacities both for absorption and stripping which in turn further reduces the heat needed, compression work requirements, and CO₂ stripper size. ISTC researchers evaluated the thermal and oxidation stabilities of biphasic solvents to help find the best one for this study.

In Period II of this project, ISTC and ISGS are studying the corrosive properties of solvents on carbon and stainless steel, which are materials used in power plants. Those results will provide important information for future scale-up of this BiCAP process.

Related publications

• Modeling, Design, and Testing of a Novel Biphasic Solvent-Enabled Absorption System for Post-Combustion Carbon Capture (15th International Conference on Greenhouse Gas Control Technologies GHGT-15; 5-8 Oct 2020, Abu Dhabi, UAE)
• Phase Change Solvents for Post-combustion CO2 Capture: Principle, Advances, and Challenges (Applied Energy 239(1), 876-897 (2019)).
• Experimental Investigation and Thermodynamic Modeling of Phase Transition and Equilibria in a Biphasic Solvent System for CO2 Capture (Industrial & Engineering Chemistry Research 57(29), 9627-9640 (2018)).

Bench-Scale Project

In spring 2018, additional U.S. Dept. of Energy funding was received by ISGS and ISTC for a three-year bench-scale (40kWe) project to further evaluate and test their biphasic extraction method of CO₂ extraction (BiCAP).

The primary goal of this new project is to leverage the BiCAP process and validate its technical advantages through a fully-integrated bench-scale testing in a relevant flue gas environment. The proposed technology is aimed at achieving a CO₂ capture cost of $30/tonne and >95% CO₂ purity to meet DOE’s Transformational CO₂ Capture goals. 

Results tested with the 40kWe bench-scale unit fabricated and installed at Abbott power plant showed that:

• Monoethanolamine (MEA) or biphasic solvent was stable during operation of the bench-scale unit.
• MEA had a lower gas treatment capacity than BiCAP solvent for the same unit.
• Amine vapor emissions from BiCAP1 solvent was less than that from MEA, consistent with previous laboratory measurements.
• Initial tests for BiCAP1 revealed a heat duty of ~2,200-2,800 kJ/kg of CO₂ captured vs. optimal 4,000-4,500 kJ/kg for MEA solvent.
• Bench-scale tests are in progress and will verify if BiCAP2 has better performance than BiCAP1 observed in previous lab-scale tests.

Results are exptect in summer 2023.

40kWe unit at Abbott Power Plant on the campus of the University of Illinois at Urbana-Champaign. 

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