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New materials could cut parasitic energy costs for CO2 capture by up to 30-40%

A computational analysis that screened hundreds of thousands of zeolite and zeolitic imidazolate framework structures has identified many different structures that have the potential to reduce the parasitic energy loss of carbon capture technologies for powerplant flue gas by as much as 30–40% compared with amine scrubbing.

One of the main bottlenecks to deploying large-scale carbon dioxide capture and storage (CCS) in power plants is the energy required to separate the CO2 from flue gas. For example, near-term CCS technology applied to coal-fired power plants is projected to reduce the net output of the plant by some 30% and to increase the cost of electricity by 60–80%. Developing capture materials and processes that reduce the parasitic energy imposed by CCS is therefore an important area of research.

—Lin et al.

The research by scientists at Rice University; the University of California, Berkeley; Lawrence Berkeley National Laboratory (LBNL); and the Electric Power Research Institute (EPRI) was published in the journal Nature Materials.

Although no commercial power plants currently capture carbon dioxide on a large scale, a few small-scale and pilot plants do, using amine scrubbing: funneling emissions through a bath of nitrogen-based amines, which capture carbon dioxide from the flue gases. The amines are then boiled to release the CO2. Additional energy is required to compress the carbon dioxide so that it can be pumped underground.

The energy needed for this process decreases the amount that can go into making electricity. Calculations show that for a coal-fired power plant, that could amount to approximately 30% of total energy generated.

Solid materials should be inherently more energy-efficient than amine scrubbing, because the CO2 can be driven off at lower temperatures. But materials differ significantly in how tightly they grab CO2 and how easily they release it.

0601_ZEOLITE_TwoLg
One of the 50 best zeolite structures for capturing carbon dioxide. In the model, the red balls are oxygen, the tan balls are silicon. The blue-green area is where carbon dioxide prefers to nestle when it adsorbs. (Berend Smit laboratory, UC Berkeley) Click to enlarge.

Zeolites are common minerals made mostly of silicon and oxygen. About 40 of the highly porous materials exist in nature, and there are about 160 man-made types. The pore sizes and shapes vary depending upon how the silicon and oxygen atoms are arranged. The pores act like tiny reaction vessels that capture, sort and spur chemical reactions of various kinds, depending upon the size and shape of the pores. The chemical industry uses zeolites to refine gasoline and to make laundry detergent and many other products.

In 2007, Deem at Rice University and colleagues calculated millions of atomic formulations for zeolites, and they have continued to add information to the resulting catalog, which contains about 4 million zeolite structures.

In the new study, the zeolite database was examined with a new computer model designed to identify candidates for CO2 capture. The new model was created by a team led by corresponding author Berend Smit, UC Berkeley’s Chancellor’s Professor in the departments of chemical and biomolecular engineering and of chemistry and a faculty senior scientist at LBNL. Smit and his UC Berkeley group worked with study co-author Abhoyjit Bhown, a technical executive at EPRI, to establish the best criteria for a good carbon capture material. Focusing on the energy costs of capture, release and compression, they created a formula to calculate the energy consumption for any materials in the zeolite database.

What is unique about this model is that, for the first time, we are able to guide the direction for materials research and say, ‘here are the properties we want, even if we don’t know what the ultimate material will look like’. Before, people were trying to figure out what materials they should shoot for, and that question was unanswered until now.

—Abhoyjit Bhown

Running the calculations to compare the CO2-capture abilities of each zeolite would have taken approximately five years with standard central processing units (CPUs), so Smit and his colleagues at UC-Berkeley and LBNL created a new way to run the calculations on graphics processing units (GPUs). Deem said the GPU technique cut the compute time to about one month, which made the project feasible.

Our database of carbon capture materials is going to be coupled to a model of a full plant design, so if we have a new material, we can immediately see whether this material makes sense for an actual design.

—Berend Smit

Study co-authors include graduate students Li-Chiang Lin and Joseph Swisher, both of UC Berkeley; Adam Berger of the EPRI; Richard Martin, Chris Rycroft and Maciej Haranczyk, all of LBNL’s Computational Research Division; and postdoctoral fellows Jihan Kim and Kuldeep Jariwala of LBNL’s Materials Science Division. This research was supported by the Department of Energy, the Advanced Research Projects Agency–Energy and EPRI’s Office of Technology Innovation.

Resources

  • Li-Chiang Lin, Adam H. Berger, Richard L. Martin, Jihan Kim, Joseph A. Swisher, Kuldeep Jariwala, Chris H. Rycroft, Abhoyjit S. Bhown, Michael W. Deem, Maciej Haranczyk & Berend Smit (2012) In silico screening of carbon-capture materials. Nature Materials doi: 10.1038/nmat3336

Comments

kelly

'New materials could cut parasitic energy costs for CO2 capture by up to 30-40%' sounds important.

Henry Gibson

The clear answer is to burn hydrogen in all kinds of power plants, but there are few or no natural sources of hydrogen.

Hydrogen is now mostly obtained from natural gas with steam reforming, and the carbon dioxide can be separated from the hydrogen with ease.

Super-critical wet-oxygen-oxidation can produce hydrogen from water using any material that contains carbon and the CO2 can be collected and is easily formed into a liquid at the pressures required for the oxidation and collected.

The Zeolites can be used to assist in the separation of oxygen from air. If pure oxygen is used for combustion the temperatures may be too high for standard equipment, so oxygen can be diluted with CO2 that is simply recycled and a fraction of it stored. Water can also be used for separating CO2 from other gases.

The world can simply build heavy water reactors for all power plants and other heat needs on land and devote all coal and natural gas to making liquid fuels for automobiles. Water-Boxxes from GROASIS can be used to reforest large areas to capture CO2 into wood that will be stored forever in salt caverns when dead. Trees can be grown where water is available and they grew before forests were cut. ..HG>>

Henry Gibson

It should be mentioned that the cost of coal is not a major part of the cost of electricity delivered to a home. If coal were delivered free to the coal piles, the electric rates could be reduced by only one fourth or less.

Heavy water reactors could use just all of the used fuel rods from light water reactor used fuel storage units plus a small amount of thorium for the next few hundred years or more. NO more uranium would have to be mined. Spent nuclear fuel is not even five percent used up but most governments have decided to waste it to appease the unknowing bigots including themselves. It is very much identical to dumping 95 out of every 100 barrels of oil onto the ground. ..HG..

Nick Lyons

@HG: Ignorance of the fundamentals of nuclear energy is the rule, sadly. Nuclear fission is the best hope for clean, cheap energy. We should be funding research to advance the state of art far beyond the pittance we now spend. The promising molten salt reactors, research on which was dropped for political reasons during the Nixon administration, could one day provide abundant, cheap, walk-away safe energy for the world.

Engineer-Poet

The whole program of capturing CO2 from flue gases after combustion in air is backwards.  Coal should not be burned in air, period:  it should be gasified with oxygen, so the syngas can be completely scrubbed of mercury and other toxics as well as sulfur.  The resulting CO and H2 should be sent to different pathways.  SOFCs can burn CO and yield high-purity CO2 while producing electricity at upwards of 60$ efficiency; supercritical CO2 turbines fired by CO/O2 combustion are another possibility.  Hydrogen can be used for peaking generation in cheap gas turbines.

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