Capturing CO2 from ambient air - David Keith

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List of Tables 2.1 Chemistry of example air capture system. . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2 Chemistry of autocaustization process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.3 Chemistry of caustic recovery with titanates. . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4 Energy requirements of the air capture system by component. . . . . . . . . . . . . . . . . 15 3.1 Energy requirements of contactor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2 Capital cost of cooling towers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.3 Cost estimates for the contactor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.1 Input parameters for system cost estimate . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.2 Cost of example system and improved system by component . . . . . . . . . . . . . . . . . 55 4.3 Sensitivity of cost estimates to changes in assumptions. . . . . . . . . . . . . . . . . . . . . 55 x
Chapter 1 Introduction The climate is changing. For decades it was a matter of debate, a point of uncertainty, whether humans could fundamentally alter the earth’s climate system. Now it is an observable fact: we can, we have, and we will continue to do so. Last year, 2005, was the hottest on record, continuing an accelerating warming trend that has brought the global mean temperature up 0.8 ◦ C over the past century (Hansen et al., 2006). But the changes we see are not only in temperature. Severe damage to ecosystems and harm to humans can now be attributed to climate change, including extensive bleaching of coral reefs (Sugden, 2005), massive loss of forests due to pine beetle infestation (Carroll et al., 2003; Gan, 2004), increased forest fire activity (Westerling et al., 2006), and increased intensity of hurricanes (Webster et al., 2005; Emanuel, 2005). The principle cause of this climate change is the emission of carbon dioxide (CO2) to the atmosphere when humans burn fossil fuel. The combustion of coal, oil, and natural gas has fueled two centuries of economic development across the world. Today, 80% of global energy use relies on fossil fuel (IPCC, 2005). Fossil fuel use is integral to the functioning of society at every level: the manufacturing of every manner of consumer good, the movement of people and products, the maintenance of shelter from the elements, the production of food, and the provision of water. And yet, with every ton of carbon burned, the earth is altered in ways both predictable and unpredictable. The changes in climate to come will likely threaten many people’s access to those basic services: shelter, food, and water. Additionally, the irreversible damage to the world’s ecosystems, including the extinction of a large fraction of the earth’s species, will be the most extensive civilized humans have ever experienced (Thomas et al., 2004). This leaves us in a difficult position; industrial society is built around fossil fuels, and yet their use poses a grave and mounting threat. Fossil fuel use and the associated carbon emissions continue to grow exponentially (see Figure 1.1). Many nations have begun programs to limit CO2 emissions, though current measures are not sufficient to achieve dramatic reductions. Notably, the two largest emitters, China and the United States, have no national regulation on CO2. Nonetheless, there is a general expectation that further international agreements will be reached to limit CO2 emissions, and that a global market for carbon emissions reduction will be developed. Such a market already exists in the European Union, and has the effect of putting a value on CO2 emissions reduction. There are various options available to meet regulatory demands. Energy conservation and efficiency improvements are the lowest-cost near-term measures. Improvements in average vehicle fuel efficiency 1
Page 1 and 2: Capturing CO2 from ambient air: a f
Page 3 and 4: For my family, friends, and everyon
Page 5 and 6: etween the National Science Foundat
Page 7 and 8: Contents Acknowledgments iv Abstrac
Page 9: List of Figures 1.1 Global CO2 emis
Page 13 and 14: egeneration at a high enough concen
Page 15 and 16: 1.4 Routes to air capture 1.4.1 Org
Page 17 and 18: The NaOH approach is the primary su
Page 19 and 20: there is no compelling reason to ca
Page 21 and 22: 7Na2CO3(l)+5Na2Ti3O7(s) ⇋ 4Na8Ti5
Page 23 and 24: changing the process design to acco
Page 25 and 26: Component / source GJ/t-CO2 electri
Page 27 and 28: Chapter 3 Contactor In this chapter
Page 29 and 30: the CO2 capture rate in a spray sys
Page 31 and 32: CO 2 absorption per pass [mol/l] 10
Page 33 and 34: CO 2 absorption [mmol/pass] 16 14 1
Page 35 and 36: Figure 3.5: Water loss measured in
Page 37 and 38: 3.3.1 CO2 depletion in air With lon
Page 39 and 40: where vt,1 and vt,2 are the termina
Page 41 and 42: surface area [m 2 -surface / m 3 -r
Page 43 and 44: spray mass density [kg / ln(μm)] 1
Page 45 and 46: average surface area [m 2 -spray /
Page 47 and 48: As a bound on the effects of coales
Page 49 and 50: Draft type Height [m] Crosssectiona
Page 51 and 52: 2. Median assumptions, no coalescen
Page 53 and 54: capture system. We can also see tha
Page 55 and 56: Multistage spray One possible solut
Page 57 and 58: Although, the cost of water loss ma
Page 59 and 60: 3.5.6 Solids formation - scaling an
Page 61 and 62:
Chapter 4 Cost of air capture Altho
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Capital Capacity Electric a Thermal
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Component Capital + O&M Energy cost
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Chapter 5 Discussion Overview In th
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5.2 Lessons for assessing of future
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Bibliography Adams, P. J. and Seinf
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IPCC (2001). Climate Change 2001: M
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Tzivion, S., Feingold, G., and Levi
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F Liquid flow rate in the contactor
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Appendix B Experimental details and
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Figure B.2: Photograph of completed
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Figure B.4: Two cranes lift the rea
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fastened together and lined, the re
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The prototype has three particle fi
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Figure B.7: Sampling points of CO2
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In order to calculate CO2 absorbed,
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Absorbed CO 2 [mol/l] 0.3 0.25 0.2
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periodic switching of the spray on
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Capturing CO2 from ambient air - David Keith

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