JP5612886B2 - Exhaust gas treatment apparatus and exhaust gas treatment method using the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an exhaust gas treatment apparatus and an exhaust gas treatment method using the same, and in particular, an exhaust gas treatment that removes soot and acid gas components from combustion exhaust gas discharged from a waste incinerator or the like to make them harmless. The present invention relates to an apparatus and an exhaust gas treatment method using the same.

  In a process that discharges combustion exhaust gas containing soot and acid gases (HCL, SOx, etc.) such as waste incinerators such as waste treatment facilities, dust is removed with a bag filter and powdered slaked lime is sprayed into the exhaust gas. In general, the acid gas and slaked lime particles are contacted and removed with high efficiency by attaching and holding the slaked lime on the filter cloth of the bag filter.

  However, the surface of slaked lime particles only reacts sufficiently with acid gas, and there is a part called unreacted slaked lime near the center of the slaked lime particle, which exceeds the chemical requirement expected from the neutralization reaction of acid gases. The slaked lime (for example, equivalent ratio of about 1.5 to 3) is introduced to remove the acidic gas component and satisfy the exhaust gas regulation value. In addition, a system has also been proposed in which fly ash collected in the bag filter is sprayed again into the exhaust gas before the bag filter and recycled to effectively use unreacted slaked lime in the fly ash.

  For example, there can be mentioned an exhaust gas treatment method and a treatment apparatus that can efficiently remove dust and harmful gas components in combustion exhaust gas by using slaked lime as exemplified in FIG. Specifically, the recovered reacted slaked lime is pulverized, and the obtained pulverized slaked lime is again circulated and supplied into the combustion exhaust gas. In the exhaust gas treatment apparatus in which the slaked lime supply device 104 for supplying slaked lime is provided in the communication path 103 between the dust collector 102 and the dust collector 102, the slaked lime collector 106 is connected to the dust collector 102 by connecting the slaked lime collector 106 that collects the reacted slaked lime. A pulverizer 107 for pulverizing the recovered slaked lime is connected, and an exhaust gas treatment apparatus is configured in which the pulverizer 107 and the communication passage 103 are connected by a circulation passage 108 (see, for example, Patent Document 1). Here, 105 indicates a blower and 109 indicates a waste pit.

  Moreover, the processing method of the combustion exhaust gas which can save the usage-amount of the slaked lime which neutralizes the acidic gas in exhaust gas which is illustrated in FIG. 7 can be mentioned. Specifically, slaked lime is introduced into the exhaust gas flue of the waste incinerator 1 to neutralize HCl gas in the exhaust gas, and the neutralized product and unreacted slaked lime are removed as powder by the bag filter 210 and purified. In the exhaust gas treatment method in which the exhaust gas is discharged from the chimney 212 and the removed powder is introduced into the ash melting furnace 218 and solidified, the exhaust gas at the point B upstream of the slaked lime introduction point A and the point C downstream of the baghouse 209 The HCl concentration is continuously measured (231, 234). When the HCl gas concentration at point B increases, the amount of slaked lime introduced is temporarily increased, and at the end of the temporary increase in supply, HCl at point C is temporarily increased. The powder removed by the bag filter 210 is circulated to the slaked lime introduction point A until the concentration falls below the regulation value, and the unreacted slaked lime is reused (for example, see Patent Document 2). Here, 201 is a waste incinerator, 207 is a slaked lime hopper, and 236 is a circulation line.

  Further, a method for treating exhaust gas is described in which slaked lime is supplied into the combustion exhaust gas generated from the waste incinerator, and the exhaust gas is guided to a dust collector while absorbing and reacting harmful gas components in the exhaust gas with slaked lime. be able to. Specifically, as illustrated in FIG. 8, the incinerator 301 incinerates waste to obtain main ash, and the generated exhaust gas is guided to the flue 304 where slaked lime is supplied from the slaked lime feeder 303. Then, the harmful gas component contained in the exhaust gas is absorbed and reacted with slaked lime. The absorption reaction is continued up to the filter 302a of the dust collector 302, and fly ash, reacted slaked lime and unreacted slaked lime are collected as dust collection dust. The dust collection dust is applied to a fine powder classifier 308 to separate unreacted slaked lime. The separated unreacted slaked lime is circulated and supplied again into the combustion exhaust gas. Therefore, most of the slaked lime supplied in excess in anticipation of safety is collected by the dust collector 302, separated from the collected dust, and circulated again into the combustion exhaust gas, so that the amount of slaked lime supplied is reduced. In addition, even if the exhaust gas fluctuates, harmful gases can be removed safely and reliably (see, for example, Patent Document 3). Here, 305 is an ash melting furnace, 306 is an induction fan, and 307 is a chimney.

Japanese Patent Laid-Open No. 06-007631 JP-A-11-248141 JP 2001-2119030 A

However, in the exhaust gas treatment method and exhaust gas treatment apparatus as described above, the following problems and problems may occur.
(I) The exhaust gas treatment method and treatment apparatus as illustrated in FIG. 6 is adapted to react with acid gas by renewing the surface covered with the reaction product by applying the dust collected in the bag filter to a pulverizer. It is a way to proceed. However, the pulverized slaked lime with a small particle size adheres to the filter cloth, leading to an increase in pressure loss and deterioration in handling properties. was there. Moreover, in this processing apparatus, the reacted slaked lime is put into a pulverizer, and the particle size is reduced to be put into an exhaust gas processing system. At this time, it was applied to the pulverizer together with the collected fly ash of the bag filter mixed with the dust from the incinerator, and there was a problem that the efficiency of the pulverization process and the energy efficiency deteriorated.

  (Ii) In addition, the exhaust gas treatment method illustrated in FIG. 7 is a method for controlling the amount of slaked lime used by controlling the amount of slaked lime and dust collected in the bag filter in circulation based on the measured HCL concentration in the exhaust gas. Although it is possible to reduce the reaction efficiency, the reaction efficiency is reduced by the reaction product generated on the surface of the slaked lime even if the slaked lime that has already been reacted is recycled. It was.

  (Iii) Further, as illustrated in FIG. 8, in the exhaust gas treatment method aiming to obtain a high reaction rate by circulating only the fly ash having a small particle diameter to the front stage of the bag filter, the circulation portion was included. The small particle size of slaked lime causes an increase in the pressure loss of the bag filter and a deterioration in handling properties. Moreover, when the particle size of the slaked lime actually obtained varies greatly, there is a problem that an appropriate response cannot be made. For example, when a large number of slaked stones with a larger particle size than the initially set fine powder classifier accounted for, most of them are excluded and discharged out of the system, and the desired reaction rate cannot be secured. Will occur. In addition, the measurement data of the applicant of this processing method show that the small particle size slaked lime has a large amount of unreacted components and the large particle size has a small amount.

  (Iv) In general, the neutralization reaction between the acidic gas component in the exhaust gas and the neutralizing agent is formed by the progress from the surface of the neutralizing agent to the pore surface or the inner layer, and the neutralizing agent per unit weight. However, the smaller the particle size, the higher the reaction efficiency than the larger particle size. On the other hand, the neutralizing agent having a small particle size enters the pores of the filter element of the bag filter and the inside of the fiber material, and is not easily removed even during backwashing, leading to an increase in pressure loss of the filter element. In dry neutralization treatment of acidic components in exhaust gas, how to solve such contradictory conditions by a simple method is a big problem.

  (V) Furthermore, slaked lime used for exhaust gas treatment is generally a standard product called “JIS special name”, and the particle size is “28 mesh (approximately 600 μm) overall, 100 mesh (150 μm or less) fineness residue. It is only specified as “less than 5.0%”. It is generally known that the reaction efficiency varies with the particle size, but in actual operation, it can be handled by increasing the spray amount of slaked lime, and the concentration of acid gas in the exhaust gas varies depending on the facility. The difference in the slaked lime particle size has not been regarded as a serious problem because the concentration is not clear. However, in recent years, there is an urgent need to reduce the amount of chemicals used, such as slaked lime, from the viewpoint of saving resources and tightening the final disposal site. In addition, when a neutralizing agent having a large average particle size dispersion range such as “JIS special slaked lime” is introduced into the bag filter, the particle size of the region contributing to the actual reaction efficiency is different from the JIS standard. Therefore, it is difficult to perform sufficient quality control in terms of reaction efficiency. Therefore, commercialization of “high-reaction slaked lime”, which has been adjusted in particle size at the time of production and increased in specific surface area for the purpose of improving reaction efficiency, is proceeding with commercialization, but it is more expensive than “JIS special slaked lime” and practical. The current situation is lacking in nature.

  Therefore, an object of the present invention is to use a dry exhaust gas treatment apparatus that sprays a neutralizing agent such as slaked lime and removes soot and acid gas components using a bag filter without using a special auxiliary agent as described later. The amount of neutralizing agent used by preventing the increase of pressure loss and handling property of bag filters due to the small particle size neutralizing agent and improving the reaction efficiency of acid gas and neutralizing agent by simple means. It is an object to provide an exhaust gas treatment apparatus capable of reducing the amount of exhaust gas and an exhaust gas treatment method using the same.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by an exhaust gas treatment apparatus and an exhaust gas treatment method using the same, and have completed the present invention.

  The present invention includes an exhaust gas introduction part to which exhaust gas is introduced, a neutralizer supply part to which a neutralizing agent is supplied, a soot and dust in the exhaust gas, and an acid gas component in the exhaust gas that has reacted with the neutralizing agent. A bag filter for collecting a neutralizing agent, a classification unit for classifying a solid component discharged from the bag filter, a pulverizing unit for pulverizing at least a part of the classified solid component, the pulverizing unit or the pulverizing unit; An exhaust gas treatment having a neutralizing agent circulation passage for returning a part of the solid component discharged from the classification section to the bag filter, and a discharge passage for discharging the remaining amount, and for removing dust and acid gas components In the apparatus, the supplied neutralizing agent and the refluxed solid component introduced into the bag filter are 3 to 10% of a large particle size component having an average particle size of 20 to 150 μm and a residual particle size of 20 μm in average particle size. The following small particle size It is characterized by including an ingredient.

  In the exhaust gas treatment, it is an important issue to prevent an increase in the pressure loss of the bag filter while ensuring the reaction efficiency of the neutralization treatment with the acidic component in the exhaust gas. In the verification process, the present invention forms a circulation system using classification means and crushing means in order to reduce clogging of the filter element of the bag filter (hereinafter sometimes simply referred to as “filter cloth”), By using part of the fly ash containing newly supplied neutralizer, soot in exhaust gas and used neutralizer as a reaction aid, the optimum conditions that can solve the above problems are secured. The knowledge that it can do is obtained. In addition, by pulverizing and refluxing only the neutralizing agent having a large particle size classified by the classification unit, rapid filtration due to the pulverization and refinement of particles accompanying the repeated refluxing of the neutralizing agent having a small particle size. It is possible to prevent an increase in pressure loss of the fabric and a deterioration in handling properties. With such a configuration, in the dry exhaust gas treatment device that removes soot and acid gas components in the exhaust gas, by a simple means to prevent an increase in the pressure loss of the bag filter due to a small particle size neutralizer and deterioration of handling properties, It has become possible to reduce the amount of neutralizing agent used by increasing the reaction efficiency of the acid gas and the neutralizing agent. Hereinafter, the term “average particle diameter” refers to the median diameter (D50) in principle.

The present invention is the above exhaust gas treatment apparatus, wherein the neutralizing agent supply unit is provided in the neutralizing agent circulation flow path, and the neutralizing agent from the neutralizing agent supply unit is the pulverizing unit and / or the It is introduced into the bag filter in a state of being mixed with the neutralizing agent discharged from the classification unit.
In an exhaust gas treatment apparatus that targets exhaust gas containing harmful gas or dust, it is not preferable to provide a staying part or a connection part that may be corroded or leaked in the flow path through which the gas to be treated flows. This corresponds to the exhaust gas flow path from the exhaust gas introduction part to the bag filter in the exhaust gas treatment device. In the present invention, the recirculated fly ash (having the ability as a neutralizing agent and a reaction aid) has a new medium. By mixing the mixture with the bag filter and introducing it into the bag filter, it becomes possible to prevent the possibility of corrosion and leakage of the exhaust gas passage.

The present invention is the above-described exhaust gas treatment apparatus, wherein the neutralizing agent introduced from the neutralizing agent supply unit is slaked lime corresponding to “JIS special name”, and a chemical whose particle size distribution is measured in advance. It is characterized by being.
If the “JIS special name” slaked lime that is generally used is used as it is as a neutralizing agent, various problems as described above may occur. However, in the present invention in which the large particle size component is effectively used, a drug containing a large amount of such components can be obtained under optimal conditions by controlling the ratio of the large particle size component and the small particle size component to be refluxed. It is possible to adjust the large particle size component and the small particle size component in the solid component introduced into the. In other words, it is possible to control the supply amount of the neutralizing agent and the reaction aid appropriate for fluctuations in the properties of the exhaust gas (for example, the content of acid gas components and dust).

The present invention is the exhaust gas treatment apparatus , wherein a dust separation unit for separating the dust in the solid component discharged from the bag filter is provided between the bag filter and the classification unit, and in the classification unit, Soot and dust are separated, and a solid component mainly composed of a reacted neutralizer is classified.
As described above, in the exhaust gas treatment apparatus according to the present invention, the dust contained in the exhaust gas can be the target of the reaction aid by performing the classification treatment, while the dust covers several mm or more. Since there is also an order of particle size components, there is a concern that this device may lead to a reduction in efficiency of the apparatus. Therefore, these particle size components in the refluxed fly ash are separated by providing a coarse material removal decoration before classification. As a result, the efficiency of the classifier can be improved.

The present invention provides the exhaust gas treatment apparatus, wherein a flow rate adjusting device is provided in a flow path from the pulverization section to the bag filter and a flow path from the classification section to the bag filter, and a flow from the neutralizer supply section to the bag filter. It is characterized by having a particle size distribution measuring section in the channel and / or the neutralizing agent circulation flow path and a control section for controlling the flow rate adjusting device by the output of the particle size distribution measuring section.
Substances to be introduced into the bag filter are exhaust gas containing soot and acid gas components, etc., a neutralizer consisting of new large particle size components and small particle size components, and used large particle size components and small particles to be refluxed It becomes a reflux gas containing a neutralizer composed of a diameter component and a large particle size component and a small particle size component composed of dust and reaction products. At this time, the activity (hereinafter sometimes referred to as “reaction activity”) of each component and the function as a reaction aid (hereinafter also referred to as “auxiliary function”) are the dust and acid gas in the exhaust gas. It depends greatly on the ingredients. The present invention simulates the amount of substance introduced into the basic bag filter, that is, the flow rate of each flow path so that the reaction activity and the auxiliary function become the optimum conditions, for example, using these as indices, By measuring the particle size distribution in the channel and controlling the flow rate of the predetermined channel, it is possible to accurately manage and control the reaction activity and auxiliary agent function, and reduce the amount of new neutralizing agent introduced it can.

The present invention is an exhaust gas treatment method using any one of the above exhaust gas treatment apparatuses, wherein a solid component mainly composed of a reacted neutralizer collected in a bag filter is classified, and a small amount of the reacted neutralizer is obtained. A part of the particle size component is discharged from the discharge passage, and a neutralizing agent equivalent to the amount of the small particle size component introduced into the bag filter in the steady operation state is introduced from the neutralizing agent supply unit. It is characterized by.
As will be described later, according to the inventor's verification, even when the small particle size component of the neutralizing agent reacts efficiently in the bag filter in a steady operation state and is refluxed as it is, [reaction efficiency] / [during reflux] It is difficult to improve the total amount of neutralizing agent]. That is, in order to ensure high reaction efficiency in the bag filter, it is necessary to secure a predetermined amount of the small particle size component introduced into the bag filter. At this time, the neutralizing agent to be refluxed is mainly composed of a small particle size component obtained by pulverizing the large particle size component, and a new neutralizing agent equivalent to the amount of the small particle size component introduced into the bag filter. As a result, the total of the small particle size components introduced into the bag filter becomes substantially constant, and the large particle size component that functions as a neutralization reaction and reaction aid is substantially reduced by the new neutralizer. A fixed amount will be introduced, and a steady operation state in which a small particle size component and a large particle size component are balanced can be formed, and a high reaction efficiency and an increase in bag filter pressure loss can be prevented. Become.

Further, the present invention is the above exhaust gas treatment method, wherein before the exhaust gas treatment is started, a neutralizer having a large particle size is introduced into the bag filter in advance, and a large particle size is formed on the filter element surface of the bag filter. The neutralizing agent is retained.
The large particle diameter component of the neutralizer has a function as a reaction aid. At this time, it is preferable that a predetermined amount of the reaction aid is present in the vicinity of the filter cloth surface in order to prevent the small particle size component from adhering to the inside of the filter cloth. The present invention is intended to form an initial coating layer by spraying a large particle size component on a filter cloth in advance before a small particle size component containing fine particles is actually introduced into the bag filter. Such a coating layer can make the function of preventing an increase in pressure loss due to a large particle diameter component introduced later more effective. Further, it is effective to form a porous aeration part by spraying corresponding to several percent of the total fly ash amount during normal operation to promote the reaction and prevent clogging.

1 is an overall configuration diagram illustrating a basic configuration of an exhaust gas treatment apparatus according to the present invention. The enlarged view which illustrates the state of the neutralizing agent etc. in the filter cloth vicinity of a bag filter. Explanatory drawing which illustrates the simulation of the function of the 1st structural example of the waste gas processing apparatus which concerns on this invention. The block diagram which shows the 2nd structural example of the waste gas processing apparatus which concerns on this invention. The block diagram which shows the 3rd structural example of the waste gas processing apparatus which concerns on this invention. The whole block diagram which illustrates the outline of the processing apparatus of the waste gas concerning a prior art. The figure which shows the structure of the apparatus which embodies the processing method of the combustion exhaust gas which concerns on a prior art. The whole block diagram which illustrates the outline of the processing method of the waste gas concerning a prior art.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. An exhaust gas treatment apparatus according to the present invention (hereinafter referred to as “the present apparatus”) has an exhaust gas introduction part, a neutralizing agent supply part, a bag filter, a classification part, a pulverizing part, a neutralizing agent circulation flow path and a discharge path, and is pulverized. Alternatively, a part of the pulverized solid component (fly ash) is returned to the bag filter, and the solid component introduced into the bag filter including the newly supplied neutralizer has an average particle diameter of 3 to 10%. It contains a large particle size component of 20 to 150 μm and a small particle size component having an average particle size of 20 μm or less as the remaining amount. Specifically, the following configuration prevents an increase in the pressure loss of the bag filter and deterioration of handling properties, and reduces the amount of neutralizing agent used by increasing the reaction efficiency between the acid gas and the neutralizing agent. It became possible.

<Configuration example of this device>
As one embodiment of this apparatus, a basic schematic overall configuration is shown in FIG. 1 (first configuration example). In the present apparatus 10, exhaust gas containing dust and acid gas components is introduced from the exhaust gas introduction unit 1. A neutralizing agent having a predetermined particle size distribution, that is, a new neutralizing agent containing a small particle size component and a large particle size component in a predetermined ratio is supplied from the neutralizing agent supply unit 2. The bag filter 3 is introduced with exhaust gas, a new neutralizing agent, and a solid component to be refluxed from the introduction port 3a. The filter cloth 30 provided in the bag filter 3 separates the dust in the exhaust gas, and the neutralizing agent causes the soot to be acidic. A gas component removal process is performed. There are also provided an exhaust port 3b through which the treated gas component is exhausted, and an exhaust port 3c through which a solid component containing the used neutralizing agent, dust and reaction products (also referred to as “fly ash”) is exhausted. . The classification unit 4 has a classification function (for example, a function for controlling the number of revolutions in a wind classifier) corresponding to a reference particle diameter (for example, an average particle diameter of 20 μm when slaked lime is used as a neutralizing agent). The fly ash discharged from the discharge port 3c is classified into a large particle size component having a particle size equal to or larger than the standard and a small particle size component having a particle size equal to or smaller than the standard. The pulverization unit 5 performs pulverization so that the large particle size component classified by the classification unit 4 becomes a small particle size component. Although the apparatus 10 shows an example in which all of the classified large particle diameter components are introduced into the pulverizing section, as described later (provided with a broken line channel La in the figure), the large particle diameter from the classification section 4 A configuration in which a part of the fly ash is refluxed and only a part thereof is pulverized is also possible. The neutralizing agent circulation flow path (hereinafter referred to as “flow path Lr”) constitutes a flow path for returning a part of the fly ash discharged from the pulverization unit 5 or the pulverization unit 5 and the classification unit 4 to the bag filter 3. To do. This apparatus 10 shows a configuration example in which classified small particle size components, large particle size components, and pulverized small particle size components can be returned to the flow path Lr. The discharge path Lo constitutes a flow path for discharging the small particle size component in the fly ash discharged from the classification unit 4 out of the system of the apparatus 10. In this apparatus 10, the small particle size component discharged | emitted from the grinding | pulverization part 5 which was not recirculated may also be discharged | emitted.

  Here, a bag filter device such as a backwash type can be used as the bag filter 3. In addition to such a filtration dust collector, an electric dust collector having a neutralization reaction function or the like can be used. The classifying unit 4 may be a wind classifier, a cyclonic classifier, an air separate type or other dry classifier, or a sieve classifier. As the pulverization unit 5, various commercially available pulverizers (stirring type, roller type, vibration type, etc.) that can be pulverized to a small particle size component of 20 μm or less can be used. A pulverizer (for example, trade name “ACM Pulverizer A type” manufactured by Hosokawa Micron Co., Ltd.) or a dispersion type pulverizer (for example, trade name “Drymeister” manufactured by Hosokawa Micron Co., Ltd.) can be suitably used. The particle size of the drug can be measured by, for example, LDV (Laser Doppler flow rate type).

This apparatus has a flow control device (not shown) in the flow path from the pulverization section 5 to the bag filter 3 and the flow path from the classification section 4 to the bag filter, and the flow from the neutralizer supply section 2 to the bag filter 3. It is preferable to provide a particle size distribution measuring unit (not shown) in the channel and / or flow path Lr, and to provide a control unit that controls the flow rate adjusting device by the output of the particle size distribution measuring unit. Exhaust gas treatment flow rate, acid gas component concentration, dust amount or particle size distribution in exhaust gas, large and small particle size components of new neutralizer, large and small particle size components in recirculated fly ash As an index, the amount of substance introduced into the basic bag filter, that is, the flow rate of each flow path, is simulated so that the reaction activity and auxiliary agent function of each component become the optimum conditions, and the concentration of acidic gas components in the exhaust gas By measuring the particle size distribution in a predetermined flow path according to the amount of dust and the like, and controlling the flow rate of the predetermined flow path, it is possible to manage and control the reaction activity and the auxiliary agent function with high accuracy.

[Function of neutralizer]
As the neutralizing agent, slaked lime, potassium hydroxide, sodium hydroxide, sodium hydrogen carbonate and the like are preferable. This is because the reactivity with the acid gas component is high and the handling of the reaction product is easy. The neutralizing agent is newly introduced from the neutralizing agent supply unit 2, and the small particle size component mainly contributes to the reaction efficiency of the neutralization reaction with the acidic gas component in the exhaust gas, and the large particle size component mainly assists the reaction. Contributes to the function as an agent. In order to ensure such a function, the particle size of the neutralizing agent is, as shown in the experimental results to be described later, based on an average particle size of 20 μm and a smaller particle size component of 20 μm to 150 μm. It is preferable to do. In addition, when slaked lime is used as a neutralizing agent, it is preferable to introduce a new slaked lime equivalent to “JIS special name” whose particle size distribution has been measured in advance. Since the main component is a small particle size component and a large amount of a large particle size component is contained, it is possible to ensure both the reaction efficiency and the function of the reaction aid, which are problems of the present apparatus.

  By introducing the neutralizing agent having a small particle size of 20 μm or less as a main component into the bag filter 3, high reaction efficiency between the acidic gas component and the neutralizing agent can be ensured. In other words, most of the neutralization reactions are dominated by the surface reaction of the granular neutralizing agent, and the neutralizing agent having a small particle size has a small surface area, but a large amount of neutralizing agent is introduced into the bag filter. As a whole, the introduced neutralizing agent can be expected to have very high reaction efficiency. As will be described later, the neutralizing agent having an average particle size of more than 20 μm has a lower reaction efficiency than the neutralizing agent having a small particle size, and the average particle size of 20 μm has its critical significance in the neutralization treatment. And gained knowledge. In addition, when a neutralizing agent with a large average particle size dispersion range such as “JIS special slaked lime” is introduced into the bag filter, the particle size of the region contributing to the actual reaction efficiency is different from the JIS standard. Therefore, it is difficult to perform sufficient quality control in terms of reaction efficiency, but it is possible to eliminate such problems by maintaining a small amount of a small particle size component including a used neutralizer to be refluxed. it can. According to the inventor's verification, “JIS special slaked lime” actually manufactured and sold has an average particle diameter of about 4 to 40 μm, and has a wide dispersion value of the average particle diameter.

  Similarly, fly ash consisting of a neutralizing agent having a large particle diameter of 20 to 150 μm and a soot and dust is introduced into the bag filter, thereby functioning as a reaction aid and reaction without using a special reaction aid. And an increase in pressure loss due to clogging of the filter cloth can be prevented. Further, the reaction product produced by the neutralization reaction also functions as a reaction aid because the small particle size components aggregate together to form a non-reactive large particle size component like slaked lime. The presence of a large number of neutralizing agents having a large particle size is not preferable from the viewpoint of reaction efficiency. However, in this apparatus, when it is thrown into the system for the first time, it plays the role of a reaction aid, prevents clogging of the bag filter, and constitutes a porous ventilation portion. Then, after being discharged at the time of backwashing the bag filter, it is sent to a pulverizer by a classifier and atomized, so that the reaction surface area is increased, and it can contribute to the reaction when it is introduced into the bag filter next time.

[Function of reaction aid]
The function of the reaction aid will be described in detail based on the state of the neutralizing agent in the vicinity of the filter cloth 30 of the bag filter illustrated in FIG. When the reaction aid 31 is present in the vicinity of the surface of the filter cloth 30, the function of preventing clogging due to the adhesion of the small particle size component 32 to the inside of the filter cloth 30 can be ensured. The small particle size component 32 referred to here includes a dust component constituting a part of the dust, in addition to the small particle size component of the neutralizing agent. In this apparatus, the function of the reaction aid is secured not only by the large particle size component of the neutralizing agent but also by some large particle size components of the dust, aggregates of the reaction product 33 or mixed condensates thereof. be able to. The function of the reaction aid can be made more effective by introducing a neutralizer with a large particle size into the bag filter before starting the exhaust gas treatment. Since the neutralizing agent having a large particle size is held on the filter cloth 30 surface of the bag filter and an initial coating layer is formed, even if a small particle size component including fine particles is introduced into the bag filter during the exhaust gas treatment, It is possible to reduce the penetration and adhesion of small particle size components to the deep part of the cloth 30 and to more effectively maintain the function of preventing the increase in pressure loss due to the large particle size components introduced later by such a coating layer. Can do. In addition, by introducing a large particle size component equivalent to several percent of the total amount of fly ash even during normal operation, a porous aeration part can be formed in the coating layer to promote reaction and prevent clogging. it can.

[Reflux of fly ash]
Fly ash from the bag filter is classified into a large particle size component and a small particle size component based on an average particle size of 20 μm. As a basic example, the small particle size component is discharged outside the system, and the large particle size component Is pulverized and refluxed as a small particle size component and introduced into the bag filter 3. By pulverizing and refluxing only the neutralizing agent having a large particle size classified by the classifying unit, the filter cloth can be abruptly crushed and refined by repeatedly refluxing the neutralizing agent having a small particle size. Increase in pressure loss and deterioration in handling properties can be prevented. Moreover, it leads to preventing unnecessary wear of the pulverized portion. However, in this equipment, when the reaction efficiency between the neutralizing agent and the acid gas component is low or the reaction rate is slow, a part of the classified small particle size component is refluxed to increase the reaction efficiency, The amount of neutralizing agent introduced can be reduced. Further, the entire amount of the large particle size component of the fly ash is not pulverized, but a part thereof can be refluxed and introduced into the bag filter 3 as it is. Furthermore, a part of the classified small particle size component and a part of the large particle size component can be refluxed simultaneously. A part of the large particle size component is pulverized into small particle size components, each predetermined amount is refluxed, and introduced into the bag filter together with a new neutralizing agent whose particle size distribution is known, thereby further increasing the reaction efficiency, The amount of new neutralizing agent introduced can be reduced.

  In this apparatus, soot and dust contained in the exhaust gas can be introduced into the bag filter as a reaction aid by performing classification and pulverization treatment. Since soot contains a large particle size inorganic component mainly composed of a silicon compound, it can be used as a reaction aid by performing classification and pulverization treatment so as to have the above average particle size. Therefore, since the large particle size component in the novel neutralizing agent can be pulverized to a smaller particle size after use, the introduction amount of the novel neutralizing agent can be reduced.

The function of this apparatus is simulated using the configuration of the first configuration example. As shown in FIG. 3, the introduction amount G of the base gas in the exhaust gas, the introduction amount A of the acidic gas component, the introduction amount Ds of the small particle size component (20 μm or less) of the dust, the large particle size component of the dust (20 to 150 μm) ) Introduction amount D _L , introduction amount Du of super-large particle size (150 μm or more) of dust, introduction amount Ns of small particle size component (reaction rate α) of neutralizer, large particle size component (reaction rate) of neutralizer β) introduction amount N _L , reaction product small particle size component Rs, reaction product large particle size component introduction amount R _L , refluxing solid component introduction amount R, and acid gas component introduction amount A is If all the neutralizing agents introduced react, the amount of substance Bi introduced into the bag filter, the small particle size component / large particle size component ratio Br at that time, and the control conditions for each amount introduced are as follows: It becomes.

(1) When the entire amount of the large particle size component in the fly ash is pulverized and the solid component R to be refluxed is only the pulverized component (the reflux ratio of the large particle size component is a: when the total amount is refluxed a = 1)
R = a × (N _L + D _L + Du + R _L )
Bi = (A + Ds + D _L + Du) + (Ns + N _L ) + R
Br = (Ds + Ns + R) / (N _L + D _L + Du)
A ≦ α × Ns + β × N _L + a × α × (1-β) × N _L
Specifically, assuming that the reaction rate is 100% for the supply unit of the small particle size component of the new neutralizing agent and the reaction rate is 50% for the large particle size component, the supply rate A of the acidic gas component is equivalent to 1 When the above supply amounts are Ns = 90 and N _L = 10, the reaction rate can be ensured to be Ns (= 90) + N _L (= 10 × 0.5) = 95%. When the entire amount of the large particle size component is refluxed, it contributes to the reaction as a small particle size component by pulverization. Therefore, the introduction amount R (N) of the neutralizing agent to be refluxed is the same as _NL ′ = 10, The remaining reaction rate can be assumed to be 50%. That is, assuming that the supply amount of the neutralizing agent introduced into the bag filter during steady operation is ideally an equivalent ratio of 1, the reaction rate is
[Ns (= 90) + N _L (= 10 × 0.5) + N _L ′ (= 10 × 0.5)] / (90 + 10 + 10) = 91%.
At this time, considering the change in the concentration of the acid gas component, the risk of fluctuations in the reaction rate of the neutralizing agent, etc., the acid gas component is neutralized almost entirely by setting the equivalent ratio to the acid gas component to 2-3. It becomes possible.

(2) When a part of the large particle size component in the fly ash is refluxed without being crushed (the reflux ratio of the large particle size component is b), and the remaining amount is crushed and refluxed (of the large particle size component) Let the reflux ratio be c: c = 1−b when the entire remaining amount is refluxed)
R = b × (N _L + D _L + Du + R _L ) + c × (N _L + D _L + Du + R _L )
Bi = (A + Ds + D _L + Du) + (Ns + N _L ) + R
Br = [(Ds + Ns) + c × (N _L + D _L + Du + R _L )] / [(N _L + D _L + Du) + b × (N _L + D _L + Du + R _L )]
A ≦ α × Ns + β × N _L + c × α × (1−β) × N _L + b × β × (1−β) × N _L
Specifically, under the same conditions as in (1) above, the reaction rate with the novel neutralizing agent can be ensured to be 95%. The introduction amount R (N _L ) of the large particle size component of the neutralizing agent to be refluxed is the same as the maximum N _L ′ = 10, and the remaining reaction rate is almost 0%. That is, assuming that the supply amount of the neutralizing agent introduced into the bag filter during steady operation is ideally an equivalent ratio of 1, the reaction rate is
[Ns (= 90) + N _L (= 10 × 0.5)] / (90 + 10 + 10) = 86%.
On the other hand, when the introduction amount R (N _L ) of the large particle component of the neutralizing agent to be refluxed is the minimum value, it corresponds to the case of (1) above, and the reaction rate at the reflux ratio c is
[Ns (= 90) + N _L (= 10 × 0.5) + N _L ′ (= c × 10 × 0.5)] / (90 + 10 + c × 10) <91%.
At this time, considering the change in the concentration of the acid gas component, the risk of fluctuations in the reaction rate of the neutralizing agent, etc., the acid gas component is neutralized almost entirely by setting the equivalent ratio to the acid gas component to 2-3. It becomes possible.

[Other configuration examples of this device]
A second configuration example of this apparatus is illustrated in FIG. It is not preferable to provide a staying part or a connection part that may be corroded or leaked in the flow path through which the gas to be treated flows. In the second configuration example, the neutralizing agent supply unit 2 is provided in the flow path Lr, and the new neutralizing agent introduced from the neutralizing agent supply unit 2 is discharged from the pulverization unit 5 and / or the classification unit 4. It is introduced into the bag filter 3 in a state of being mixed with the neutralizing agent. At this time, the exhaust gas does not come into contact with the new neutralizing agent and the solid component to be recirculated to the bag filter 3 at all. However, in the neutralization reaction having a high reaction rate, the exhaust gas flow does not affect the reaction efficiency. The possibility of road corrosion and leakage can be prevented. This is particularly effective when the reaction product is a hygroscopic and highly soluble substance.

[Third configuration example of the apparatus]
A third configuration example of this apparatus is illustrated in FIG. Between the bag filter 3 and the classifying unit 4, a dust separating unit 6 for separating the dust in the fly ash discharged from the bag filter 3 is provided. In the classifying unit 4, the dust is separated, and the reacted neutralizing agent. It classifies the fly ash which has as a main component. The dust in the exhaust gas also has a particle size component on the order of several mm or more, which inhibits the neutralization reaction and has a low function of the reaction aid, which may cause a decrease in efficiency of the apparatus. Therefore, the efficiency of the classifying unit 4 can be improved by separating the ultra-large particle size components in the fly ash that has been refluxed by providing a coarse substance removal decoration (dust separation unit 6) before classification. In addition, the function as a reaction aid of the large particle size component in the neutralizer can be improved, and the reaction efficiency of the neutralization reaction can be improved.

<Exhaust gas treatment method using this device>
Next, the exhaust gas treatment method using this apparatus will be described in detail based on the first configuration example. In this apparatus, the acidic gas component in the introduced exhaust gas reacts with the neutralizing agent introduced into the bag filter 3 and is discharged as a reaction product, and the collected dust is extracted as fly ash. . That is, the treatment of exhaust gas in this apparatus is roughly divided into treatment of acid gas components and dust in the exhaust gas.

[Treatment of exhaust gas]
The exhaust gas is introduced into the bag filter 3 from the exhaust gas introduction unit 1 through the introduction port 3a. Here, the acidic gas component in the exhaust gas reacts with the neutralizing agent introduced in the bag filter 3 (including the newly introduced portion and the used portion that has been refluxed) to generate a reaction product on the surface of the neutralizing agent. And collected on the filter cloth 30. As acidic gas components, strong acidic components such as HCL, SOx, and NOx are targeted, and weakly acidic components such as CO ₂ are excluded. Further, the reaction product is separated from the neutralizing agent to form an agglomerate or an agglomerate mixed with a neutralizing agent having a very small particle diameter, and is similarly collected on the filter cloth 30. For example, when slaked lime (Ca (OH) ₂ ) is used as a neutralizing agent, the reaction product referred to here corresponds to CaCl ₂ produced by the reaction of HC1 in the exhaust gas with slaked lime. Since it has hygroscopicity, it absorbs moisture in the exhaust gas and forms aggregates and condensates with large particle sizes. The collected acidic gas component is discharged from the bag filter 3 through the discharge port 3c as a part of the fly ash together with the neutralizing agent and the aggregate during the cleaning process such as back washing of the bag filter 3. Most of the discharged acidic gas components are discharged out of the system from the discharge path Lo, and are reused or discarded after being subjected to a predetermined detoxification process. Part of the discharged acidic gas component (mainly the reaction product on the surface of the neutralizing agent having a large particle size) is introduced into the flow path Lr through the classification unit 4 (partially through the pulverization unit 5). , Is returned to the bag filter 3.

  The dust in the exhaust gas is collected on the filter cloth 30 in the bag filter 3 and, during the cleaning process such as backwashing of the bag filter 3, as a part of the fly ash together with the neutralizing agent and the aggregates through the discharge port 3c. It is discharged from the bag filter 3. Soot includes various solid components including silicon compounds and aluminum compounds. Most of the discharged dust is discharged out of the system through the discharge path Lo, and is reused or discarded after a predetermined detoxification process. However, a part of the large particle size component of the discharged dust is introduced into the flow path Lr together with the neutralizing agent of the large particle size component through the classifying unit 4 and refluxed to the bag filter 3 as a reaction aid. The exhaust gas from which the acid gas component and the dust are separated is discharged out of the system through the exhaust port 3b.

  Here, in the steady operation state of the present apparatus, it is preferable that a neutralizing agent in an amount substantially equal to the amount of the small particle size component introduced into the bag filter 3 is introduced from the neutralizing agent supply unit 2. That is, in order to ensure high reaction efficiency in the bag filter 3, it is necessary to secure a predetermined amount of a small particle size component mainly including a neutralizing agent introduced into the bag filter 3. At this time, as shown in the simulation (1), the small particle size component obtained by pulverizing the large particle size component of the used neutralizing agent is used as the main component of the neutralizing agent to be refluxed, and this is supplied to the bag filter. By adding a new neutralizing agent in an amount approximately equal to the amount of small particle size components introduced, the total amount of small particle size components introduced into the bag filter becomes substantially constant, and the neutralization reaction and reaction A large amount of the large particle size component that functions as an auxiliary agent is introduced by a new neutralizing agent, and a steady operation state in which the small particle size component and the large particle size component are balanced can be formed. It is possible to prevent high reaction efficiency and increase in bag filter pressure loss.

  Further, as described above, before starting the exhaust gas treatment, a large particle size neutralizing agent is introduced into the bag filter 3 in advance, and the large particle size neutralizing agent is held on the filter cloth 30 surface of the bag filter 3. It is preferable. By spraying a large particle diameter component on the filter cloth 30 in advance, an initial coating layer is formed on the surface of the filter cloth 30, and the function of preventing an increase in pressure loss due to the large particle diameter component introduced later is made more effective. Can do. At the same time, even during normal operation, spraying corresponding to several percent of the total amount of fly ash makes it possible to form a porous aeration part and promote the reaction and prevent clogging.

[Example 1]
The particle size of the neutralizing agent in the exhaust gas treatment apparatus has a great influence on the reaction efficiency of the neutralization reaction (corresponding to the removal rate of acid gas components). Here, the relationship between the particle size of slaked lime used as a neutralizing agent and the SOx removal rate was verified, and the technical effect was verified.
(1) Experimental conditions About the exhaust gas processing apparatus which concerns on a 1st structural example, the SOx removal rate of the small particle size component and large particle size component of slaked lime was demonstrated. The “JIS special slaked lime” actually manufactured and sold has an average particle size of 4 to 40 μm, but slaked lime having an average particle size as exemplified in Table 1 below is under the condition of an equivalent ratio of about 3. The reaction efficiency was verified.

(2) Verification Results As shown in Table 1 below, it has been found in actual machine tests that the acid gas removal function (especially SOx) decreases when the particle size is large. In particular, since the SOx removal function changes at an average particle size of about 20 μm, the knowledge that the average particle size of about 20 μm has a critical significance was obtained.

[Example 2]
The particle size distribution of the neutralizing agent in the exhaust gas treatment apparatus has a great influence on the pressure loss of the bag filter. That is, the small particle size component gives pressure loss, while the large particle size component plays a role as a reaction aid. Here, the relationship between the particle size of slaked lime used as a neutralizing agent and the pressure loss of the bag filter was verified, and the technical effect was verified.

(1) Experimental conditions About the exhaust gas processing apparatus which concerns on a 1st structural example, the pressure loss of the small particle size component and large particle size component of slaked lime was demonstrated. The pressure loss of slaked lime having an average particle size as shown in Table 2 below was measured under the same conditions as in actual operation for about several tens of minutes to several hours.

(2) Experimental results As shown in Table 2 below, it has been found in actual machine tests that the change in pressure loss is large when the particle diameter is about 7 μm or less. That is, it was found that the function as a reaction aid can be expected to have a great effect at a particle size of about 7 μm or more. As described above, the knowledge that “JIS special slaked lime” actually manufactured and sold has an average particle diameter range of about 4 to 40 μm has been obtained. Considering such knowledge in connection with the results of this experiment, by using “JIS special slaked lime” as a neutralizing agent as it is, it is possible to ensure a function as a reaction aid together with a function of removing acid gas. found.

DESCRIPTION OF SYMBOLS 1 Exhaust gas introduction part 2 Neutralizing agent supply part 3 Bag filter 3a Introduction port 3b Exhaust port 3c Exhaust port 4 Classification part 5 Grinding part 10 Exhaust gas processing apparatus (this apparatus)
30 Filter cloth Lo discharge channel Lr channel (neutralizing agent circulation channel)

Claims (7)

An exhaust gas introduction part to which exhaust gas is introduced, a neutralizer supply part to which a neutralizing agent is supplied, dust in exhaust gas, and a neutralized agent produced by reacting an acid gas component in exhaust gas with the neutralizing agent. Bag filter to be collected, classification part for classifying the solid component discharged from the bag filter, pulverizing part for pulverizing at least a part of the classified solid component, the pulverizing part or the pulverizing part and the classification part In the exhaust gas treatment apparatus that has a neutralizing agent circulation flow path for recirculating a part of the discharged solid component to the bag filter, a discharge path for discharging the remaining amount thereof, and performs a removal process of dust and acid gas components,
A flow control device for the flow path from the pulverization section to the bag filter and the flow path from the classification section to the bag filter, the flow path from the neutralizing agent supply section to the bag filter, and / or the neutralizing agent circulation flow path. An exhaust gas treatment apparatus comprising: a particle size distribution measuring unit; and a control unit that controls the flow rate adjusting device according to an output of the particle size distribution measuring unit . The supplied neutralizer and the refluxed solid component introduced into the bag filter are 3 to 10% of a large particle size component having an average particle size of 20 to 150 μm and a small amount having an average particle size of 20 μm or less as the remaining amount. The exhaust gas treatment apparatus according to claim 1, further comprising a particle size component. The neutralizing agent supply unit is provided in the neutralizing agent circulation channel, and the neutralizing agent from the neutralizing agent supply unit is mixed with the neutralizing agent discharged from the pulverization unit and / or the classification unit. in the state, the exhaust gas processing apparatus according to claim 1 or 2, wherein the introduced into the bag filter. The neutralizing agent introduced from the neutralizing agent supply section is slaked lime corresponding to "JIS special name", and is a chemical whose particle size distribution is measured in advance . The exhaust gas treatment apparatus according to any one of the above. Between the bag filter and the classifying unit, a dust separating unit for separating the dust in the solid component discharged from the bag filter is provided. In the classifying unit, the dust is separated and the reacted neutralizing agent is mainly used. The exhaust gas treatment apparatus according to any one of claims 1 to 4, wherein a solid component as a component is classified. An exhaust gas treatment method using the exhaust gas treatment apparatus according to any one of claims 1 to 5, wherein a solid component mainly composed of a reacted neutralizer collected in a bag filter is classified, and the reacted neutralizer A part of the small particle size component is discharged from the discharge passage, and a neutralizing agent equivalent to the amount of the small particle size component introduced into the bag filter in the steady operation state is introduced from the neutralizer supply portion. An exhaust gas treatment method characterized by that. The neutralizing agent having a large particle diameter is introduced into the bag filter in advance before the exhaust gas treatment is started, and the neutralizing agent having a large particle diameter is held on the filter element surface of the bag filter. 6. The exhaust gas treatment method according to 6.

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