Wet-type flue gas desulfurization plant and method making use of

Details Wet-type flue gas desulfurization plant and method making use of Wet-type flue gas desulfurization plant and method making use of

1995-10-11

1997-11-11

Straub, Gary P.

Chemistry of inorganic compounds

Modifying or removing component of normally gaseous mixture

Sulfur or sulfur containing component

42324305, 42324308, 422168, B01D 5350, B01D 5378

Patent

active

056860536

DESCRIPTION:

BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATION

This application is related to commonly owned, copending application U.S. Ser. No. 08/532,758 filed Oct. 11, 1995 and having the same title.


INDUSTRIAL FIELD

This invention relates to a wet-type flue gas desulfurization plant and method making use of a solid desulfurizing agent, and more particularly, to a wet-type flue gas desulfurization plant and method making use of a solid desulfurizing agent for economically removing sulfur oxides in flue gas exhausted from combustion equipment, such as boilers, with higher desulfurization performance, decreased power for grinding solid desulfurizing agents such as limestone and for ameliorating the affect on desulfurization performance due to aluminum and fluorine components in the absorbent.


PRIOR ART

Sulfur oxides (hereinafter simply referred to as SO.sub.2) in flue gas generated as a result of combustion of fossil fuel in thermal power plants, etc., is a main cause of global environmental problems such as air pollution, acid rain and the like. Thus, studies on flue gas desulfurization methods to remove SO.sub.2 therefrom and development of flue gas desulfurization plants have become important.
Although various processes have been proposed for flue gas desulfurization, the wet-type is the major process. The wet-type processes include methods using sodium, calcium and magnesium compounds as an absorbent, respectively. The sodium method above all is excellent in reactivity between the absorbent and SO.sub.2, but the sodium compounds used are very expensive. For this reason the calcium method using relatively cheaper calcium compounds such as calcium carbonate is most widely employed as a flue gas desulfurization system for large boilers in power plants.
The desulfurization methods using such calcium compounds in the absorbent liquid are generally classified into spraying, wetted wall and bubbling systems, depending on the particular gas-liquid contacting method. While each system has outstanding characteristic features independently, the spraying system is considerably popular and reliable, and is thus the most widely used worldwide. The conventional spraying desulfurization system once comprised three towers, i.e., a cooling tower for cooling and dust-removal treatment of the exhaust gas, a desulfurization tower for spraying absorbent liquid into the exhausted gas for reaction with SO.sub.2 and a oxidation tower for oxidizing calcium sulfite formed in the desulfurization tower. Recently, a mono-tower desulfurization system (an in-tank oxidizing method) in which the desulfurization tower provides both cooling and oxidation functions has been developed and is now becoming the most popular spraying system.
FIG. 39 shows an example of a conventional spraying mono-tower desulfurization plant. In general, such a mono-tower desulfurization system comprises a tower body 1, an inlet duct 2, an outlet duct 3, a spray nozzle 4, an absorbent pump 5, a circulation tank 6, a stirrer 7, an air blower 8, a mist eliminator 9, an absorbent draining pipe 10, a gypsum draining pipe 11, a limestone supplying pipe 12, a hydroextractor 13 and the like. Several spray nozzles 4 are arranged in each of a number of horizontal arrays and several stages of these horizontal arrays are vertically spaced. The stirrer 7 and the air blower 8 are connected to the circulation tank 6 located in the bottom of the desulfurization tower where the absorbing liquid collects, while the mist eliminator 9 is arranged at an uppermost portion of the desulfurization tower or in the outlet duct 3.
Exhaust gas A exhausted from a boiler is introduced to the desulfurization tower body 1 from the inlet duct 2 and exhausted through the outlet duct 3. During such a process, the absorbing liquid is pumped from the absorbing liquid pump 5 through the absorbing liquid draining pipe 10 and is sprayed from a plurality of nozzles 4 for gas-liquid contact of the absorbing liquid with the exhaust gas A. Upon spraying, SO.sub.2 is selectively absorbed by the absorbing liquid from th

REFERENCES:
"Gas Purification" By Kohl et al, 4th. ed. Gulf Publishing Co. (1985) Houston TX, USA, pp. 316 and 319-322 (No Month).

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