PNNL-developed solvent breaks barriers, captures carbon for less than industrial counterparts
DOE/PACIFIC NORTHWEST NATIONAL LABORATORY
RICHLAND, Wash.–As part of a marathon research effort to lower the cost of carbon capture, chemists have now demonstrated a method to seize carbon dioxide (CO2) that reduces costs by 19 percent compared to current commercial technology. The new technology requires 17 percent less energy to accomplish the same task as its commercial counterparts, surpassing barriers that have kept other forms of carbon capture from widespread industrial use. And it can be easily applied in existing capture systems.
In a study published in the March 2021 edition of International Journal of Greenhouse Gas Control, researchers from the U.S. Department of Energy’s Pacific Northwest National Laboratory–along with collaborators from Fluor Corp. and the Electric Power Research Institute–describe properties of the solvent, known as EEMPA, that allow it to sidestep the energetically expensive demands incurred by traditional solvents.
“EEMPA has some promising qualities,” said chemical engineer Yuan Jiang, lead author of the study. “It can capture carbon dioxide without high water content, so it’s water-lean, and it’s much less viscous than other water-lean solvents.”
Carbon capture methods are diverse. They range from aqueous amines–the water-rich solvents that run through today’s commercially available capture units, which Jiang used as an industrial comparison–to energy-efficient membranes that filter CO2 from flue gas emitted by power plants.
Current atmospheric CO2 levels have soared higher in recent years than at any point within the last 800,000 years, as a new record high of 409.8 parts per million was struck in 2019. CO2 is primarily released through human activities like fossil fuel combustion, and today’s atmospheric concentrations exceed pre-industrial levels by 47 percent.
At a cost of $400-$500 million per unit, commercial technology can capture carbon at roughly $58.30 per metric ton of CO2, according to a DOE analysis. EEMPA, according to Jiang’s study, can absorb CO2 from power plant flue gas and later release it as pure CO2 for as little as $47.10 per metric ton, offering an additional technology option for power plant operators to capture their CO2.
Jiang’s study described seven processes that power plants can adopt when using EEMPA, ranging from simple setups similar to those described in 1930s technology, to multi-stage configurations of greater complexity. Jiang modeled the energy and material costs to run such processes in a 550-megawatt coal power plant, finding that each method coalesces near the $47.10 per metric ton mark.
Solving a solvent’s problems
One of the first known patents for solvent-based carbon capture technology cropped up in 1930, filed by Robert Bottoms.
“I kid you not,” said green chemist David Heldebrant, coauthor of the new study. “Ninety-one years ago, Bottoms used almost the same process design and chemistry to address what we now know as a 21st century problem.”
The chemical process for extracting CO2 from post-combustion gas remains largely unchanged: water-rich amines mix with flue gas, absorb CO2 and are later stripped of the gas, which is then compressed and stored. But aqueous amines have limitations. Because they’re water-rich, they must be boiled at high temperatures to remove CO2 and then cooled before they can be reused, driving costs upward.
“We wanted to hit it from the other side and ask, why are we not using 21st century chemistry for this?” Heldebrant said. So, in 2009, he and his colleagues began designing water-lean solvents as an alternative. The first few solvents were too viscous to be usable.
“‘Look,'” he recalled industry partners saying, “‘your solvent is freezing and turning into glass. We can’t work with this.’ So, we said, OK. Challenge accepted.”
Over the next decade, the PNNL team refined the solvent’s chemistry with the explicit aim to overcome the “viscosity barrier.” The key, it turned out, was to use molecules that aligned in a way that promoted internal hydrogen bonding, leaving fewer hydrogen atoms to interact with neighboring molecules.
Heldebrant draws a comparison to children running through a ball pit: if two kids hold each other’s hands while passing through, they move slowly. But if they hold their own hands instead, they pass as two smaller, faster-moving objects. Internal hydrogen bonding also leaves fewer hydrogen atoms to interact with overall, akin to removing balls from the pit.
Pivoting to plastic
Where the team’s solvent was once viscous like honey, it now flowed like water from the kettle. EEMPA is 99 percent less viscous than PNNL’s previous water-lean formulations, now nearly on par with commercial solvents, allowing them to be utilized in existing infrastructure, which is largely built from steel. Pivoting to plastic in place of steel, the team found, can further reduce equipment costs.
Steel is expensive to produce, costly to ship and tends to corrode over time in contact with solvents. At one tenth the weight, substituting plastic for steel can drive the overall cost down another $5 per metric ton, according to a study led by Jiang in 2019.
Pairing with plastic offers another advantage to EEMPA, whose reactive surface area is boosted in plastic systems. Because traditional aqueous amines can’t “wet” plastic as well (think of water beading on Teflon), this advantage is unique to the new solvent.
The PNNL team plans to produce 4,000 gallons of EEMPA in 2022 to analyze at a 0.5-megawatt scale inside testing facilities at the National Carbon Capture Center in Shelby County, Alabama, in a project led by the Electric Power Research Institute in partnership with Research Triangle Institute International. They will continue testing at increasing scales and further refine the solvent’s chemistry, with the aim to reach the U.S. Department of Energy’s goal of deploying commercially available technology that can capture CO2 at a cost of $30 per metric ton by 2035.
###
This study, “Techno-economic comparison of various process configurations for post-combustion carbon capture using a single-component water-lean solvent,” was funded by the U.S. Department of Energy Office of Fossil Energy.
Pacific Northwest National Laboratory draws on its distinguishing strengths in chemistry, Earth sciences, biology and data science to advance scientific knowledge and address challenges in sustainable energy and national security. Founded in 1965, PNNL is operated by Battelle for the U.S. Department of Energy’s Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States. DOE’s Office of Science is working to address some of the most pressing challenges of our time. For more information, visit PNNL’s News Center. Follow us on Twitter, Facebook, LinkedIn and Instagram.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Paragraph 5, concerning amount of CO2 in the atmosphere: “CO2 is primarily released through human activities like fossil fuel combustion,”
Is this true? No, most of the CO2 emitted to the atmosphere is due to natural processes.
Natural processes are at least 95% of the release.
The chemical formula for EEMPA is pretty complex. Nobody seems to discuss its toxicity or a potential environmental harm.
Even if it were free, it still wouldn’t be worth it.
Here’s what the molecule “EEMPA” looks like. The full name is N-(2-ethoxyethyl)-3-morpholinopropan-1-amine.
It’s just a tweak on conventional amine-capture technology. Fun stuff for chemists, and another way to increase the cost of electric power for everyone else.
Unless another technical use can be found for the chemistry, or unless the work provides an avenue to advance chemical theory or practice, the research is an utter waste of time.
Just as is pretty much all of AGW-directed effort.
Entirely agree, Pat, see my comment on Willis’ thread above. Apart from the lack of understanding of the cost aspects of such scrubbing, they seem without any thought on the costs of engineering a plant to make EEMPA. Someone presumably has been roped in to pay for the 4000 gallon pilot plant, suitable as they say for a 0.5MW energy plant. There aren’t many that small!
I was standing in this open field one day when all these wind turbines started rising out of the ground. Yes I know what he is talking about that it takes no energy.
In Northern areas where natural gas IS available, greenhouse operation during the winter benefits from the heating and increased CO2 required to warm greenhouses. But with increased restrictions on natural gas, many will welcome the advances being shown in LENR. (spam alert!-do not read replies)
That being said, we still need CO2 to raise greenhouse atmospheres to 1,000 ppm CO2 or thereabout.
Vertical gardening is another area that is likely to more important with lower electrical/heat costs.
Don’t throw your CO2 away!
[QUOTE FROM ARTICLE]”The chemical process for extracting CO2 from post-combustion gas remains largely unchanged: water-rich amines mix with flue gas, absorb CO2 and are later stripped of the gas, which is then compressed and stored. But aqueous amines have limitations. Because they’re water-rich, they must be boiled at high temperatures to remove CO2 and then cooled before they can be reused, driving costs upward.”[ENDQUOTE]
The main problem with the classical amine solutions is not that they need to be “boiled at high temperatures”, but that they need to be stripped at low pressure, so that the concentrated CO2 needs to be compressed to supercritical pressure (about 1,100 psi) to be safely stored.
Ethanolamines have been routinely used in petroleum refineries, mainly to capture hydrogen sulfide (H2S) from off-gases from hydrotreaters used to desulfurize kerosene and diesel fuel. They also absorb CO2, but most hydrotreater gas does not contain much CO2.
In a typical configuration, high-pressure hydrotreater gas (containing mostly hydrogen, methane, ethane, and traces of H2S) is contacted with lean (low-H2S) cold amine solution (normally methyl diethanolamine) in water. The amine solution reacts with H2S) and exits the bottom of the absorber, from which it is heated by exchange with warm lean amine, then flashed into a low-pressure stripping tower, reboiled using steam. Sweetened (H2S free) gas from the top of the absorber can be used as fuel.
The reaction of H2S with amine, which is favored at low temperature and high pressure, is reversed at high temperature and low pressure, so the H2S is released from the amine, and leaves the top of the tower. The overhead condenser is used to condense any boiled water, which is refluxed to the stripper, while concentrated H2S remains in the gas phase, where it can be reacted to either elemental sulfur (Claus plant) or sulfuric acid.
Hot, lean amine from the bottom of the stripper is then cooled by heat exchange with rich amine, and further cooled by cooling water, and pumped back to the absorber tower. This system works well for absorbing hydrogen sulfide, because high pressures are not needed at the inlet of Claus plants or sulfuric acid plants.
The use of amine solutions for CO2 capture is much more difficult, due to the sheer volume of CO2 to be recovered (about 15 to 20% in flue gas) compared to the traces (<1%) of H2S in hydrotreater gas. This requires huge absorption and stripping columns, and large pumps to circulate the amine.
The main advantage of this new amine solution seems to be that some of the CO2 is recovered at high pressure (probably by heating, in order to reverse the reaction), which means that some of the compression energy can be saved. Still, the “semi-rich solution” has to be flashed at low pressure to remove the remainder of the CO2. Also, does recovering some of the CO2 at high pressure require more heat input to reverse the reaction, since the higher partial pressure of CO2 would tend to favor the absorption reaction, and disfavor the stripping reaction (Le Chatelier’s Principle)?
Reducing the cost of carbon capture and sequestration from $58.30 to $47.10 per metric ton (about 19%) may be helpful, but is it really necessary? An extra metric ton of CO2 in the atmosphere raises the average concentration by 0.000000000012 ppm (about 0.12 parts per quadrillion)–can anyone demonstrate that it would cause $47.10 worth of damage to the environment? A plant can convert a metric ton of CO2 into 682 kg of glucose by photosynthesis–what about the value of the glucose?
On of the most disturbing/ridiculous things I got from this article is that there is an “International Journal of Greenhouse Gas Control”.
$47 per metric tonne, times 36.7 GT CO2 emitted per year, = $1.7 TRILLION just to stay even …
Math. Don’t’cha love it?
w.
Fifty three years ago I built and operated two conventional absorbtion plants to operate this very process. Both used conventional water-base amine solvents. The plants captured a relatively high proportion of the CO2 when run with a high amine concentrations but the steel components (virtually everything) dissolved almost as you watched. Reducing the amine concentration made the corrosion problem tolerable but CO2 capture fell dismally. I can see the virtue of running an almost anhydrous process in corrosion resitant plastic equipment. Potentially this will considerably increase the efficiency of the carbon capture. However there is no mention of the elephant in the room. CO2 is absorbed by the solvent at low temperature and stripped by raising the temperature of the saturated solvent. Heat is required to run the process. Heat can be recovered from the hot stripped solvent but this will be difficult and expensive unless the viscosity of the solvent can be reduced to a level comparable with that of water. I will follow this program with interest but I don’t think that it will be a commercial goer for the purpose of ‘saving the earth’.
For every CO2 molecule used by plants, a molecule of O2 is produced. I don’t see a problem.
I have a better idea. Nuclear Energy.
EEMPA is N-(2-ethoxyethyl)-3-morpholinopropan1-amine. Your homework assignment is to draw the molecule from this name. I think it looks like this:
CCOCC-NH-CCC-M where M is morpholine (six member ring with nitrogen in the #1 location and oxygen in the #4 location). The linkage between the main part of the molecule and morpholine appears to be between the third carbon atom in the propane backbone and the nitrogen in the morpholine group. Hydrogens are omitted on the carbon chains.
There is already a tested technology out there which allows you to burn fossil fuels to generate electricity, and capture all of its CO2 for resale. It is already economically competitive with natural gas plants. However, it uses fossil fuels, and the CO2 is frequently used to inject into oil reservoirs for better recovery. https://www.forbes.com/sites/jeffmcmahon/2021/01/08/net-power-ceo-announces-four-new-zero-emission-gas-plants-underway/?sh=1be65955175b
Net Power’s pilot project was very successful. The Allam Cycle captures and separates pretty well all of the exhaust gases. They currently have four commercial power plants under construction.