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Wet and Dry Scrubbing 273

Packing height = 24 in.
Gas loading = 500 lb/h-ft 2
Liquid temperature = 75°F
3. The chemical reactions involved in scrubbing carbon dioxide are dependent on the
actual scrubbing solution chosen. In this example using a scrubbing liquor of 25 %
sodium carbonate and 4 % caustic, the chemical reactions are

CO + NaOH → NaHCO
2 3
CO + H O + Na CO → 2 NaHCO
2 2 2 3 3
Example 21
Because the greenhouse effect of carbon dioxide gas is well established and human activi-
ties are the largest source of CO entering the atmosphere, the burden rests upon humanity
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to solve the economic conundrum currently limiting efforts to bring CO emission under
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control. The wet scrubber system introduced in Example 20 or a similar wet scrubber system
is quite capable of removal of CO from an air emission stream. However, the economic and
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political considerations currently are such that even in developed nations, such as the United
States and the European Union, governments are not willing to force their domestic indus-
tries to institute such well-proven methods of CO emission control. Discuss the following:
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1. Technical limitations to removal of carbon dioxide from an air emission stream.
2. The economic and political solutions and driving forces for carbon dioxide control.
3. The possible combined technical and economic solutions to carbon dioxide emission
reduction.

Solution
1. The technical limitations for removal of carbon dioxide from an air emission stream
are presented in the following discussion. From a strictly engineering viewpoint, CO
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could be easily removed from the air emission of any industrial facility (such as a
coal-fired power plant or other single-source site of CO ) using an alkali (such as
2
sodium carbonate/caustic) and a wet scrubber packed with highly efficient mass
transfer media (such as Q-PAC or similar).
There is no technical limitation to removing CO from an air emission stream. The
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only limitation to such a scrubber would be that absorption of CO beyond 360 ppmv,
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the ambient level of CO in the atmosphere, would obviously not be an effective use
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of resources.
2. Following is a discussion on the economic and political solutions and driving
forces for carbon dioxide control: Economic solutions for CO emission reduction
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and control are very difficult to find. The wet scrubbing technology for CO emis-
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sion control (shown in Example 20) is widely rejected as being too costly for
industry and society, in general, to accept. Although the societal benefits of CO
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emission reduction and control are no longer widely debated, the realities of the
marketplace, global competition, and the parochial individual interests of various
nations have all combined to prevent forward movement and application of proven
methods of keeping CO from entering the atmosphere. When products are sold in
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the world marketplace that are of equal or similar quality, the lowest-cost product
will eventually dominate the marketplace. Higher-cost competition will be driven
to extinction as a result.