JP3711490B2 - Method and apparatus for oxidizing SO2 in exhaust gas using HO2 radical as OH generating reactive species in radical chain reaction of SO2 oxidation - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention performs the processing method of the processing method and the exhaust gas in the exhaust gas containing SO ₂ that can generate the HO ₂ radical controlled stably maintain the OH generation reaction in the radical chain reaction of oxidation of SO ₂ Related to installation.
[0002]
[Prior art]
SO _X discharged into the atmosphere, especially SO _2, has been a problem as a cause of acid rain. In Europe and North America, SO _X and NO _X discharged from large-scale thermal power plants are acid rain. And the impact on forest and lake ecosystems is even more severe. In addition, the problem becomes a cross-border problem that cannot be solved by a single country. Furthermore, along with the globalization of the economy, this problem becomes a source of these exhaust gases not only in developed countries but also in developing countries. Are also causing complex problems in connection with economic growth.
[0003]
The resolution of the exhaust gas generation problems, such as SO _2, chemical and methods, such as SO ₂ from combustion exhaust gas carried out by suppression win be the cause of SO ₂ of the fuel itself as low-sulfur process of the fuel There are methods for removal by processes, etc., and studies have been made in the respective technical fields. In particular the development of the latter technical means is difficult to advance remove SO _X generating compound is important when using coal as fuel. A solution to such a problem, particularly a dry method is effective for the treatment of SO _{2 in a} combustion facility with a poor water source, and the following technologies 1, 2 and the like have been proposed for such technology. Yes. 1, a method using a lime-gypsum reaction, that is, a method in which an alkaline earth desulfurization agent is blown into a combustion furnace or a flue, and is a method that does not use water and has an advantage of easy management of equipment. is there. 2. Further, as a dry method, there is an activated carbon adsorption method. The principle of this method is SO ₂ adsorption by activated carbon, oxidation to SO ₃ and H ₂ SO ₄ by reaction with H ₂ O in exhaust gas. Although it is a method of collecting, there is a problem that costs are high. The electron beam method is used to dissociate part of O ₂ and H ₂ O in the exhaust gas to generate O, OH, HO ₂ radicals and ions, and to oxidize SO ₂ and NO ₂ to produce sulfuric acid and nitric acid miss. Then, NH ₃ is blown into the reactor to form an ammonium salt aerosol, which is collected by an electric dust collector (EP) such as Cottrell. The dry method called pulse corona induced plasma chemical process (PPCP method) is also a similar technique in which radical ion generation means is changed from the electron beam method to the above means in that radical ions are generated and an electric dust collector is used. .
[0004]
However, this method has disadvantages such as the use of many chemical materials and the cost of equipment and management, and it is difficult to put it to practical use as an SO ₂ treatment technique in developing countries. However, the method using the radical ions mentioned in the latter half of the above 2 is attractive in that there is a possibility that the amount of drugs to be used is extremely small.
[0005]
[Problems to be solved by the invention]
Object of the present invention reduces the use of an agent, and to provide a reaction efficient SO ₂ processing methods and apparatus. Under such circumstances, the present inventors can form a radical chain oxidation reaction system of SO ₂ that can supply radicals involved in the oxidation of SO _{2 in} a stable and controlled manner, focusing on the reactivity of radicals. in the intensive study of the method and apparatus, it found that a system can be constructed capable of generating the radical Le O H involved in the oxidation of SO ₂ with high efficiency, it was possible to solve the problem of the present invention.
[0006]
[Means for Solving the Problems]
The first invention (1) and more formed flow tube or at least the surface of at least the inner surface inner surface temperature was maintained at 327 ± 50 ° C. in a borosilicate glass is more formed on a borosilicate glass Exhaust gas containing SO ₂ or SO ₂ and NO in a flow tube provided with a member whose glass surface temperature is maintained at 327 ± 50 ° C., and OH radicals that trigger a radical oxidation chain reaction of SO ₂ a H ₂ O ₂ or the exhaust gas treatment method comprising SO _2, characterized in that with the HNO ₃ and type electrically oxidizing the SO ₂ by chain reaction comprising the reaction of forming HO ₂ radicals generate. Preferably, (2) the introduction of the _H 2 _{O 2} or HNO ₃ to produce OH radicals to the flow tube, _H 2 _{O 2} or HNO ₃ to a catalyst or ultraviolet light irradiation means and further main component a precious metal is disposed The exhaust gas treatment method comprising SO _{2 according} to claim 1, more preferably (3) the exhaust gas is generated by coal combustion. The exhaust gas treatment method containing SO _{2 according} to (1) or (2), more preferably (4) generation of HO ₂ radicals in the oxidation chain reaction in an exhaust gas treatment flow pipe containing SO _2. is an exhaust gas processing method comprising the respective SO _2, characterized in that monitor and control that means is provided, and further, preferably, Nd in (5) HO ₂ radical monitoring means generating a: Y Characterized in that said using double harmonic of the G laser is an exhaust gas processing method comprising the SO _2.
[0007]
The second of the present invention is more formed a flow pipe in which at least the inner surface of the flow tube or at least the surface of borosilicate glass is more formed on borosilicate glass the inner surface temperature with a heating means for maintaining the 327 ± 50 ° C. of And a flow pipe provided with a member provided with means for maintaining the temperature of the glass surface at 327 ± 50 ° C., and a preheating device for the gas for introducing exhaust gas containing SO ₂ into the flow pipe. The OH radical generator or N ₂ provided with means for introducing H ₂ O ₂ or HNO ₃ that generates OH radicals that trigger the SO ₂ oxidation chain reaction into the flow pipe Treatment installation of exhaust gas containing SO ₂ comprising at least means for introducing the diluted OH radical generator and means for monitoring and controlling the production of HO ₂ radicals in the flow tube .
[0008]
[Embodiments of the present invention]
The present invention will be described in more detail. A. In the method and apparatus of the present invention, the oxidation reaction of SO ₂ is presumed to comprise the following reaction steps. 1, OH + SO ₂ + M → HOSO ₂ + M (R1) 2, HOSO ₂ + O ₂ → SO ₃ + HO ₂ (R ₂ ) 3, NO + HO ₂ → NO ₂ + OH (R ₃ ) where M is the other For example, N ₂ or the like. As a reaction for inhibiting the chain reaction, 4, OH + HO ₂ → H ₂ O + O ₂ (R ₄ ), that is, in order to suppress this inhibition reaction, it is necessary to keep the concentration of OH or HO ₂ at 10 ppm or less. B. The outline of the process of the present invention will be described with reference to the drawings. Fu is a combustion furnace, for example, a coal combustion boiler. The exhaust gas from Fu is blown to the flow reactor FR by the blower B, for example. Although the FR is not shown, the inner surface of the reactor is maintained at, for example, 327 ° C. by appropriate heating means H and an electric heater (ribbon heater). On the upstream side of the Fu it is introduced into the FR of _H 2 _{O 2} or HNO ₃ to initiate the oxidation reaction of SO ₂ by radical chain through GR radical former catalysts (Pt networks) Cat. In the FR , a GR radical is generated, and SO ₂ in the exhaust gas is oxidized to SO ₃ by the radical chain oxidation reaction of the reactions (1) to (3), and further reacts with water in the exhaust gas to become sulfuric acid mist. The mist is collected by a collecting device S, for example, an electric dust collector. The said device, hand stage you measured by observing the generation of indirectly OH radical generation of HO _2, for example, Nd: by measuring the detected emission wavelength with twice the harmonic of a YAG laser I was able to observe.
[0009]
【Example】
Example 1
Borosilicate glass glass (SiO ₂ ; 81%, B ₂ O ₇ : 12.7%, Al ₂ O ₃ ; 2,3%, Na ₂ O; 4.0%, K ₂ O; 0.04%, In a flow reaction tube in which the inner surface temperature of Fe ₂ O ₇ ; 0.03) is maintained at 327 ± 5 ° C., SO ₂ (more NO may be contained at a concentration of 1000 ppm. A small amount of H ₂ O is present. .) Is introduced at a linear velocity of 10 to 150 cm / sec. A gas containing H ₂ O ₂ is supplied to the flow reaction tube through a tube whose surface is heated to the above temperature in an amount of 1 to 10% with respect to the gas. In the flow tube, SO ₂ is oxidized by radical chain reaction consisting of the elementary reaction to produce SO ₃ , and further, a small amount of water present in VEX becomes sulfuric acid mist, and an electric precipitator (EP) provided downstream. Is recovered as sulfuric acid.
[0010]
In order to indirectly detect HO ₂ , the flow tube is provided with a detection device (not shown) using harmonics twice that of the Nd: YAG laser, and the reaction temperature and the amount of HO ₂ generated Was observed. The result is shown in FIG. In the vicinity of 327 ° C., it is shown that the radical chain reaction proceeds. Incidentally, the solid line in FIG. 2a shows the correlation between the amount of HO ₂ generated by the Pt catalyst and the reaction temperature.
[0011]
【The invention's effect】
As described above, the present invention makes it possible to use HO ₂ , a radical that is stably supplied by the heated glass surface catalytic function, in the radical chain oxidation reaction of SO ₂ , thereby reducing the use of chemical agents, In addition, the present invention has an excellent effect that an efficient oxidation process of SO ₂ can be realized.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the apparatus for SO ₂ oxidation treatment by radical chain reaction of the present invention. FIG. 2 shows the reaction with the actual measurement value and the predicted value (solid line) of the amount of HO ₂ radical produced by the catalytic activity of the borosilicate glass surface. Correlation between temperature correlation (b), predicted amount of HO ₂ radical production by Pt catalyst and reaction temperature (a)
[Explanation of symbols]
Fu Combustion furnace (combustion boiler) B Blower H Flow reactor heater GR radical generator FR flow reactor EP Electric dust collector GT Treated gas St Exhaust gas stack

Claims (6)

At least the inner surface is more formed flow tube or at least the surface of borosilicate glass is more formed on a borosilicate glass and the temperature of the glass surface 327 ± 50 ° C. inner surface temperature was maintained at 327 ± 50 ° C. H ₂ O ₂ or HNO ₃ for generating an exhaust gas to be treated containing SO ₂ or SO ₂ and NO and OH radicals that trigger a radical oxidation chain reaction of SO ₂ exhaust gas treatment method comprising SO _2, characterized in that introduced to oxidizing the SO ₂ by chain reaction comprising the reaction of forming HO ₂ radicals. In the introduction of _H 2 _{O 2} or HNO ₃ to produce OH radicals to the flow tube, provided further means for introducing _H 2 _{O 2} or HNO ₃ to a catalyst or ultraviolet light irradiation means is arranged as a main component a precious metal The method for treating exhaust gas containing SO _{2 according} to claim 1. The exhaust gas treatment method containing SO _{2 according} to claim 1 or 2, wherein the exhaust gas is generated by coal combustion. The SO _{2 according} to any one of claims 1 to 3, wherein means for monitoring and controlling generation of HO ₂ radicals in the oxidation chain reaction is installed in the exhaust gas treatment flow pipe containing the SO _2. An exhaust gas treatment method comprising: 5. The exhaust gas treatment method including SO _{2 according} to claim 4, wherein the HO ₂ radical production monitoring means uses a harmonic twice as high as that of an Nd: YAG laser. Temperature of at least the inner surface is more formed flow tube or at least the surface of borosilicate glass is more formed on a borosilicate glass and the glass surface with a heating means for maintaining the inner surface temperature of the flow tube 327 ± 50 ° C. A flow pipe provided with a member provided with a means for maintaining the temperature at 327 ± 50 ° C., and an exhaust gas introduction section that may be provided with a preheating device for introducing the exhaust gas containing SO ₂ into the flow pipe, The OH radical generator or the OH radical generator diluted with N ₂ provided with means for introducing H ₂ O ₂ or HNO ₃ that generates OH radicals that trigger the SO ₂ oxidation chain reaction into the flow tube processing installation of the introduction means and an exhaust gas containing at least containing SO ₂ with means for monitoring and controlling the production of HO ₂ radical in the flow tube.

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