Sulfur oxides mitigation

Increased use of biofuels and peat, which can be facilitated by efficient drying methods, means in itself a mitigation of the greenhouse effect. A further advantage is that no emission of sulfur oxides takes place. The emission of is strongly dependent on the combustion tanperature. A dried fuel would hence mean increased emissions of NO. This may be partly counterbalanced by the decreased amount of excess air and better possibilities for control of the combustion process achievable with a dried fuel. The low temperature at the combustion of very moist fuels might lead to increased amounts of unbumed hydrocarbons in the flue gases. 

Since the time when English kings recognized that the burning of coal could produce noxious fumes (Chapters 14 and 15), there has been a series of attempts (not always continuous) to mitigate the amounts of noxious gases entering the atmosphere, the least of which have been attempts to reduce the amount of sulfur oxide(s) (particularly sulfur dioxide) released to the environment. 

Even though these drawbacks can typically be mitigated by appropriate system design, many consider that better anodes will be needed. To improve the sulfur tolerance and reduction oxidation tolerance of the anodes, several groups are working on oxide-based anodes. 

Anodic protection is a powerful technique used to mitigate corrosion of liquor tankage. However, the electrochemistry of Kraft hquors is complex due to the multiple oxidation states of sulfur compounds, the number of possible Fe-S-H20 reactions, and the existence of active-passive behavior. The electrochemical behavior may be further complicated because some Fe-S compounds are semiconductors. The major sulfur species in Kraft liquors are listed in Table 12.10. 

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