Category Archives: Chemical engineering

What to do with Carbon Dioxide

In my 17 December 2016 post, “Climate Change and Nuclear Power,” there is a chart that shows the results of a comparative life cycle greenhouse gas (GHG) analysis for 10 electric power-generating technologies. In that chart, it is clear how carbon dioxide capture and storage technologies can greatly reduce the GHG emissions from gas and coal generators.

An overview of carbon dioxide capture and storage technology is presented in a December 2010 briefing paper issued by the London Imperial College. This paper includes the following process flow diagram showing the capture of CO2 from major sources, use or storage of CO2 underground, and use of CO2 as a feedstock in other industrial processes. Click on the graphic to enlarge.

Carbon capture and storage process

You can download the London Imperial College briefing paper at the following link:

https://www.imperial.ac.uk/media/imperial-college/grantham-institute/public/publications/briefing-papers/Carbon-dioxide-storage—-Grantham-BP-4.pdf

Here is a brief look at selected technologies being developed for underground storage (sequestration) and industrial utilization of CO2.

Store in basalt formations by making carbonate rock

Iceland generates about 85% of its electric power from renewable resources, primarily hydro and geothermal. Nonetheless, Reykjavik Energy initiated a project called CarbFix at their 303 MWe Hellisheidi geothermal power plant to control its rather modest CO2 emissions along with hydrogen sulfide and other gases found in geothermal steam.

Hellisheidi geothermal power plantHellisheidi geothermal power plant. Source: Power Technology

The process system collects the CO2 and other gases, dissolves the gas in large volumes of water, and injects the water into porous, basaltic rock 400 – 800 meters (1,312 – 2,624 feet) below the surface. In the deep rock strata, the CO2 undergoes chemical reactions with the naturally occurring calcium, magnesium and iron in the basalt, permanently immobilizing the CO2 as environmentally benign carbonates. There typically are large quantities of calcium, magnesium and iron in basalt, giving a basalt formation a large CO2 storage capacity.

The surprising aspect of this process is that the injected CO2 was turned into hard rock very rapidly. Researchers found that in two years, more that 95% of the CO2 injected into the basaltic formation had been turned into carbonate.

For more information, see the 9 June 2016 Washington Post article by Chris Mooney, “This Iceland plant just turned carbon dioxide into solid rock — and they did it super fast,” at the following link:

https://www.washingtonpost.com/news/energy-environment/wp/2016/06/09/scientists-in-iceland-have-a-solution-to-our-carbon-dioxide-problem-turn-it-into-stone/?utm_term=.886f1ca92c56

The author notes,

“The researchers are enthusiastic about their possible solution, although they caution that they are still in the process of scaling up to be able to handle anything approaching the enormous amounts of carbon dioxide that are being emitted around the globe — and that transporting carbon dioxide to locations featuring basalt, and injecting it in large volumes along with even bigger amounts of water, would be a complex affair.”

Basalt formations are common worldwide, making up about 10% of continental rock and most of the ocean floor. Iceland is about 90% basalt.

Detailed results of this Reykjavik Energy project are reported in a May 2016 paper by J.M. Matter, M. Stute, et al., Rapid carbon mineralization for permanent disposal of anthropogenic carbon dioxide emissions,” which is available on the Research Gate website at the following link:

https://www.researchgate.net/publication/303450549_Rapid_carbon_mineralization_for_permanent_disposal_of_anthropogenic_carbon_dioxide_emissions

Similar findings were made in a separate pilot project in the U.S. conducted by Pacific Northwest National Laboratory and the Big Sky Carbon Sequestration Partnership. In this project, 1,000 tons of pressurized liquid CO2 were injected into a basalt formation in eastern Washington state in 2013. Samples taken two years later confirmed that the CO2 had been converted to carbonate minerals.

These results were published in a November 2016 paper by B. P McGrail, et al., “Field Validation of Supercritical CO2 Reactivity with Basalts.” The abstract and the paper are available at the following link:

http://pubs.acs.org/doi/pdf/10.1021/acs.estlett.6b00387

Store in fractures in deep crystalline rock

Lawrence Berkeley National Laboratory has established an initiative dubbed SubTER (Subsurface Technology and Engineering Research, Development and Demonstration Crosscut) to study how rocks fracture and to develop a predictive understanding of fracture control. A key facility is an observatory set up 1,478 meters (4,850 feet) below the surface in the former Homestake mine near Lead, South Dakota (note: Berkeley shares this mine with the neutrino and dark matter detectors of the Sanford Underground Research Facility). The results of the Berkeley effort are expected to be applicable both to energy production and waste storage strategies, including carbon capture and sequestration.

You can read more about this Berkeley project in the article, “Underground Science: Berkeley Lab Digs Deep For Clean Energy Solutions,” on the Global Energy World website at the following link:

http://www.newswise.com/articles/view/663141/?sc=rssn&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+NewswiseScinews+%28Newswise%3A+SciNews%29

Make ethanol

Researchers at the Department of Energy’s Oak Ridge National Laboratory (ORNL) have defined an efficient electrochemical process for converting CO2 into ethanol. While direct electrochemical conversion of CO2 to useful products has been studied for several decades, the yields of most reactions have been very low (single-digit percentages) and some required expensive catalysts.

Key points about the new process developed by ORNL are:

  • The electro-reduction process occurs in CO2 saturated water at ambient temperature and pressure with modest electrical requirements
  • The nanotechnology catalyst is made from inexpensive materials: carbon nanospike (CNS) electrode with electro-nucleated copper nanoparticles (Cu/CNS). The Cu/CNS catalyst is unusual because it primarily produces ethanol.
  • Process yield (conversion efficiency from CO2 to ethanol) is high: about 63%
  • The process can be scaled up.
  • A process like this could be used in an energy storage / conversion system that consumes extra electricity when it’s available and produces / stores ethanol for later use.

You can read more on this process in the 19 October 2016 article, “Scientists just accidentally discovered a process that turns CO2 directly into ethanol,” on the Science Alert website at the following link

http://www.sciencealert.com/scientists-just-accidentally-discovered-a-process-that-turns-co2-directly-into-ethanol

The full paper is available on the Chemistry Select website at the following link:

http://onlinelibrary.wiley.com/doi/10.1002/slct.201601169/full

 

 

 

 

New Catalyst Could Greatly Reduce the Cost of Splitting Water

Splitting water (H2O) is the process of splitting the water molecule into its constituent parts: hydrogen (H2) and oxygen (O2). A catalyst is a substance that speeds up a chemical reaction or lowers the energy required to get a reaction started, without being consumed itself in a chemical reaction.

Water moleculeWater molecule.  Source: Laguna Design, Getty Images

A new catalyst, created as a thin film crystal comprised of one layer of iridium oxide (IrOx) and one layer of strontium iridium oxide (SrIrO3), is described in a September 2016 article by Umair Irfan entitled, “How Catalyst Could Split Water Cheaply.” This article is available on the Scientific American website at the following link:

http://www.scientificamerican.com/article/new-catalyst-could-split-water-cheaply/?utm_source=howtogeek&utm_medium=email&utm_campaign=newsletter

The new catalyst, which is the only known catalyst to work in acid, applies to the oxygen evolution reaction; the slower half of the water-splitting process.

Author Irfan notes that, “Many of the artificial methods of making hydrogen and oxygen from water require materials that are too expensive, require too much energy or break down too quickly in real-world conditions…” The availability of a stable catalyst that can significantly improve the speed and economics of water splitting could help promote the shift toward more widespread use of clean, renewable fuels. The potential benefits include:

  • May significantly improve hydrogen fuel economics
  • May allow water splitting to compete with other technologies (i.e., batteries and pumped storage) for energy storage. See my 4 March 2016 posting on the growing need for grid energy storage.
  • May improve fuel cells

At this point, it is not clear exactly how the IrOx / SrIrO3 catalyst works, so more research is needed before the practicality of its use in industrial processes can be determined.

The complete paper, “A highly active and stable IrOx/SrIrO3 catalyst for the oxygen evolution reaction,” by Seitz, L. et al., is available to subscribers on the Science magazine website at the following link:

http://science.sciencemag.org/content/353/6303/1011.full

 

A Brief History of Fireworks

There is a good history of fireworks by Joe Carmichael posted on the INVERSE website at the following link:

https://www.inverse.com/article/9731-fireworks-a-brief-history-of-things-exploding-attractively

Here, you can scroll through an illustrated timeline (see screenshot, below) from the advent of bamboo firecrackers in 200 BCE to modern day fireworks.

Tiimeline of fireworks  Source: INVERSE

Of local interest, the timeline includes the July 4th 2012 San Diego Big Bay Boom (aka Big Bay Bust), when a technical malfunction caused all fireworks on multiple barges in the bay to be fired prematurely in a spectacular 30 second pyrotechnic display.

San Diego 2012 Big Bay Bust  Source: YouTube

In case you missed the actual event, you can see a (short) video at the following link:

http://www.nydailynews.com/news/national/san-diego-fireworks-big-bay-boom-ruined-video-article-1.1108259

My personal favorite is the Sydney, Australia New Year’s fireworks display, which begins with what looks like an explosive demolition of the Harbor Bridge and then continues with the spectacular main event seen in the photos below.

2016 New-Years-Eve-Sydney-Fireworks2016 sydney-fireworks-ceremonySource: http://www.inewyearsevequotes.com/happy-new-years-eve-sydney-fireworks-2016/

You can see a short video of the start of Sydney’s 2016 New Year’s fireworks at the following link:

http://www.theguardian.com/world/video/2015/dec/31/sydney-harbour-new-year-fireworks-2016-video

 

 

Radioisotope Thermoelectric Generators (RTG) for Spacecraft: History and Current U.S. Pu-238 Production Status

Radioisotope Thermoelectric Generators (RTG), also called Radioisotope Power Systems (RTS), commonly use non-weapons grade Plutonium 238 (Pu-238) to generate electric power and heat for National Aeronautics and Space Administration (NASA) spacecraft when solar energy and batteries are not adequate for the intended mission.

Approximately 300 kg (661 lb) of Pu-238 was produced by the Department of Energy (DOE) at the Savannah River Site between 1959 – 1988. After U.S production stopped, the U.S. purchased Pu-238 from Russia until that source of supply ended in 2010.

Limited production of new Pu-238 in the U.S re-started in 2013 using the process shown below. This effort is partially funded by NASA.  Eventually, production capacity will be about 1.5 kg (3.3 lb) Pu-238 per year. The roles of the DOE national laboratories involved in this production process are as follows:

  • Idaho National Engineering Lab (INEL):
    • Store the Neptunium dioxide (NpO2) feed stock
    • Deliver feed stock as needed to ORNL
    • Irradiate targets provided by ORNL in the Advanced Test Reactor (ATR)
    • Return irradiated targets to ORNL for processing
  • Oak Ridge National Lab (ORNL):
    • Manufacture targets
    • Ship some targets to INEL for irradiation
    • Irradiate the remaining targets in the High Flux Isotope Reactor (HFIR)
    • Process all irradiated targets to recover and purify Pu-238
    • Convert Pu-238 to oxide and deliver as needed to LANL
  • Los Alamos National Lab (LANL):
    • Manufacture the Pu-238 fuel pellets for use in RTGs

Pu-238 production process

Diagram source: Ralph L McNutt, Jr, Johns Hopkins University APL, 2014

The U.S. has an existing inventory of  about 35 kg (77 lb) of Pu-238 of various ages.  About half is young enough to meet the power specifications of planned NASA spacecraft. The remaining stock is more than 20 years old, has decayed significantly since it was produced, and does not meet specifications.   The existing inventory will be blended with newly produced Pu-238 to extend the usable inventory. To get the energy density needed for space missions while extending the supply of Pu-238, DOE and NASA plan to blend “old” Pu-238 with newly produced Pu-238 in 2:1 proportions.

NASA slowly has been developing an Advanced Stirling Radioisotope Generator (ASRG), which should be capable of producing about four times the power of older RTGs per unit of Pu-238. However, the ASRG produces less waste heat, which can be used productively to warm electronics in the interior of a spacecraft, such as the Mars rover Curiosity. The ASRG may not be available in time for the next space mission requiring an RTG power source, in which case an existing RTG design will be used.

Read a history of RTGs and more information on current U.S. Pu-238 production status in a 2014 presentation by Ralph L McNutt, Jr, at the following link:

http://www.lpi.usra.edu/sbag/meetings/jan2014/presentations/08_1545_McNutt_Pu238_SBAG.pdf

9 February 2016 Update

On 22 December 2015, DOE reported production of 50 grams of new Pu-238.

DOE reported that it plans to set an initial production target of 300 – 400 grams (about 12 ounces) of Pu-238 per year. After implementing greater automation and scaling up the process, ORNL expects to reach the the production target of 1.5 kg (3.3 lb) Pu-238 per year.

The next NASA mission that will use an RTG is the Mars 2020 rover, which will use the same Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) as used on NASA’s Mars rover Curiosity. MMRTG can provide about 110 watts of electrical power to a spacecraft and its science instruments at the beginning of a mission.

You can read the ORNL announcement of initial Pu-238 production at the following link:

https://www.ornl.gov/news/ornl-achieves-milestone-plutonium-238-sample