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                    274                                                    Lawrence K. Wang et al.

                          As an example, the US government will not force CO emission limitations on its
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                          coal-burning electrical generating facilities because this would force its industries,
                          such as steel, automotives, and chemicals, to accept much higher electrical power
                          costs. Such costs would need to be recovered by the various industries affected
                          through higher pricing, and as just mentioned, this will not be allowed by the global
                          forces driving the current world economy. Only if all industries in all nations are
                          required to implement CO reduction technologies will the competitive disadvantage
                                                2
                          of single nations or groups of nations placing CO emission requirements on their
                                                                    2
                          respective industries be negated.
                          At present the international community is attempting to educate world leaders in the
                          hope that a political solution, even if temporary, may be found for this problem (63).
                          Also, as awareness of the harmful effects of CO emissions grows, governments will
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                          become more likely to commit resources to development of alternative technologies
                          to limit CO emission.
                                    2
                       3.  The possible combined technical and economic solutions to carbon dioxide emission
                          reduction are presented as follows. A plausible alternative technology is collection of
                          CO emission streams for reuse. Research for utilization and reduction of CO emis-
                             2                                                           2
                          sions has been conducted by Wang and colleagues (48,49). Wang and Lee (49) have
                          reported that collection of carbon dioxide emissions at tanneries, dairies, water-
                          treatment plants, and municipal wastewater-treatment plants for in-plant reuse as
                          chemicals will be technically and economically feasible.
                          About 20% of organic pollutants in a tannery’s wastewater are dissolved proteins,
                          which can be recovered using the tannery’s own stack gas (containing mainly carbon
                          dioxide). Similarly, 78% of dissolved proteins in a dairy factory can be recovered by
                          bubbling its stack gas (containing mainly carbon dioxide) through its waste stream
                          using a new type of wet scrubber (see Example 25). The recovered proteins from
                          both tanneries and dairies can be reused as animal feeds. In water-softening plants
                          for treating hard-water removal using a chemical precipitation process, the stack
                          gas can be reused as a precipitation agent for hardness removal. In municipal
                          wastewater-treatment plants, the stack gas containing carbon dioxide can be reused
                          as both a neutralization agent and a warming agent. Because a large volume of car-
                          bon dioxide gases can be immediately reused as chemicals in various in-plant
                          applications, the plants producing carbon dioxide gas actually may save chemical
                          costs, produce valuable byproducts, conserve heat energy, and reduce the global
                          warming problem (48,49).


                    Example 22
                       Discuss the following:
                       1.  The similarities and dissimilarities between wet scrubbing process and gas stripping
                          process.
                       2.  The possibility of a combined wet scrubbing and gas stripping process.
                       Solution
                       1.  The following presents a discussion on the similarities and dissimilarities between the
                          wet scrubbing process and the gas stripping process. Wet scrubbing and gas stripping
                          are both mass transfer unit operations. Only the direction of the movement of a given
                          pollutant species is different. In a wet scrubber, such as in the previous example of
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