JP3423265B2 - Chemical injection and treatment method in pre-coated bag filter device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-coat system for filtering, neutralizing and adsorbing soot, acidic harmful gases and dioxins in exhaust gas generated from a refuse incinerator. The present invention relates to a method of ejecting and treating a medicine in a bag filter device. [0002] Exhaust gas discharged from a refuse incinerator contains dioxins, which are toxic substances, in addition to dust and acidic harmful gases. An adsorption method using a carbon-based substance such as activated carbon using a filter is generally used. FIG. 7 is a schematic diagram showing a configuration of a conventional refuse incineration facility disclosed in Japanese Patent Application Laid-Open No. 5-23539. In FIG. 7, reference numeral a denotes a combustion furnace, and a boiler c is connected via a gas mixing chamber b provided at the outlet side of the combustion furnace a, and the temperature of the exhaust gas drops to 600 to 700 ° C. A high-temperature dust collector d is installed in the middle part. A reaction tower f having a sprayer e at the head and a bag filter h having a screw conveyor g at the bottom are connected on the exhaust side of the boiler c. And is released into the atmosphere from the chimney j. On the other hand, on the discharge side of the screw conveyor g, a collecting ash transferring means comprising a chute pipe k, a conveying conveyor m, a bucket elevator n and the like is connected, and the collected ash removed from the bag filter h is removed. The ash is transferred to a chute p provided above the combustion furnace a via the collecting ash transferring means. [0007] The fly ash composed of incombustibles and unburned matter generated from the combustion furnace a and the exhaust gas at about 800 ° C containing acidic toxic gas and dioxins were reburned in the gas mixing chamber b. After that, it is introduced into the boiler c and cools down.
The fly ash contained by the high-temperature dust collector d in the high-temperature zone of 0 ° C. or higher is filtered and removed, and a small amount of an organic chlorine compound attached to the fly ash also generates dioxins.
Most are designed to be pyrolyzed. Next, the exhaust gas subjected to the primary treatment is introduced into the reaction tower f, and the contained acidic harmful gas is neutralized by an alkaline agent such as slaked lime slurry sprayed from the sprayer e. In the bag filter h in the next step, the fly ash, the organochlorine compound and the neutralization reaction compound which cannot be removed by the high-temperature dust collector d are filtered and removed, and the exhaust gas is attracted as a clean gas. The air is sucked by the ventilator i and discharged from the chimney j into the atmosphere. [0010] The above collected ash collected by the bag filter h is appropriately removed, and then is introduced into the combustion furnace a from the chute p through the collected ash transferring means connected to the screw conveyor g. Organic chlorine compounds, neutralization reaction products and unreacted chemicals are thermally decomposed in a gas mixing chamber b at 800 ° C.
The remaining collected ash is discharged outside through recovery ports q and r provided at the bottom of the combustion furnace a and the boiler c. In the above-mentioned conventional refuse incineration facility, calcium chloride, which is a reaction product sprayed by the reaction tower f, collected by the bag filter h, and returned to the gas mixing chamber b, is used. Slaked lime, which is an unreacted chemical, is changed to quick lime by being thermally decomposed in the high tropics of 800 ° C. or higher in the gas mixing chamber. However, this thermal decomposition is a short-time solid-gas contact, and the residual quicklime that cannot be completely combined with the chlorine in the exhaust gas is directly discharged from the recovery ports q and r to the outside of the facility. It is dangerous because it reacts with the moisture inside and generates high heat. Further, not only can the amount of lime used not be saved, but also the amount of collected ash (discharged ash), which is a specially controlled waste, does not decrease, so that it is impossible to reduce post-treatment costs. The organic chlorine compound which has been substantially completely thermally decomposed in the gas mixing chamber b is then resynthesized from the reaction tower f between the bag filters h to form dioxins.
There is a limit to taking dioxin countermeasures using only a neutralizing agent such as slaked lime. For this reason, taking out the collected ash into a separate device and heating it requires not only increased equipment and heating costs, but also unstable temperature. Because it is difficult to heat all collected ash in
There is a drawback that the dioxin removal rate is rather low. Further, as indicated by a two-dot chain line, an adsorbent t such as activated carbon is supplied to the upstream side of the bag filter h to adsorb the dioxins, and then the total amount of ash collected by the bag filter h is transferred to the gas mixing chamber. b, the unburned matter is reburned and the pyrolysis of dioxins is also carried out, as in the case described above. The disadvantage is that the device becomes complicated if the problem is addressed. FIG. 8 shows "method and apparatus for spraying slaked lime and an adsorbent" disclosed in Japanese Patent Application Laid-Open No. 10-21649. . In FIG. 8, the exhaust gas from an incinerator (not shown) introduced into a boiler c is cooled to an appropriate temperature of a bag filter h by a cooling tower u, and is filtered by slaked lime and adsorbent on the surface of the bag filter h described later. -The gas is neutralized and adsorbed and becomes a clean gas, which is released into the atmosphere from the chimney j. Here, the slaked lime cut out from the slaked lime silo v and the adsorbent cut out from the adsorbent silo w are cut out respectively in predetermined amounts, and are fed by air to the powder mixing apparatus x by the blower y. To become a mixed powder mixed at a predetermined ratio,
It is attached to the filter cloth in the bag filter h together with the blown exhaust gas. The ash discharged from the bag filter h, which is composed of the collected dust and reacted and unreacted powder, is usually used as it is, together with expensive activated carbon not adsorbing dioxins. Because it is discharged outside,
In addition to the problem of soaring chemical costs and increasing the amount of ash emitted, the cost of post-processing is further increased.In addition to the increase in burn loss, the color of the ash becomes black, resulting in incomplete combustion. There was even a risk of getting confused. Further, in the operation state of the exhaust gas entrainment type precoat system described later, even if the concentration of the acidic harmful gas at the outlet of the bag filter is much lower than the regulation value, if the differential pressure of the bag filter becomes the prescribed value, the removal is performed. For this reason, unreacted or unadsorbed drugs are often discharged, which not only wastes the cost of drugs but also increases the amount of ash discharged due to excessive supply of each drug. Furthermore, since the specific gravities of the activated carbon and the slaked lime are different, the distribution of the drug in the precoat layer on the filter cloth is not uniform, and the drug efficiency is reduced. According to a first aspect of the present invention, there is provided a method for injecting and treating a chemical in a pre-coated bag filter device according to the first aspect of the present invention, wherein a plurality of exhaust gas treatment facilities for treating exhaust gas generated from a waste incinerator are provided. A pre-coating type bag filter device having a unit dust collecting mechanism, in which a required amount of a carbon-based adsorbent is previously adhered to the surface of the filter cloth in an operation after being washed off, and then the adsorbent formed by the adsorbent is used. Initially spraying a smaller amount of neutralizing agent than anticipated amount onto the surface of the agent layer to form a two-stage pre-coat layer in a short period of time, and the acidity at the outlet of the bag filter device which rises with continued operation Depending on the concentration of the harmful gas, at least one of the chemicals produced by pyrolyzing the neutralizing chemical or a part of the collected ash collected in the reburning facility installed above the refuse incinerator. The additional supply of chemicals is repeated intermittently until the differential pressure of the bag filter device, which increases due to the accumulation of the additional supply chemicals and soot and soot, reaches the specified value. Reduce gas concentration,
When the differential pressure specified value is reached, each unit dust collecting mechanism is sequentially removed, and then a part of the collected ash is returned to the reburning facility. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of a refuse incineration facility. In FIG. 1, reference numeral 1 denotes a refuse incinerator, which includes a combustion chamber 12 including an inclined ceiling portion 11 made of refractory and steel, a dry grate, a combustion grate, a post-combustion grate, and a combustion completion device. And a water spray device 14 installed above the combustion chamber 12. Reference numeral 2 denotes a reburning facility installed above the refuse incinerator 1. A reburning burner 21 is provided at the lower end, and a reburning chamber main body 22 made of refractory and steel is mounted on the reburning facility. High-temperature air preheater 23 and push-in blower 2
4, a combustion air passage 25 connected to the upper and lower portions of the grate group 13 from the air preheater 23, and a high-temperature flue 26 connecting the air preheater 23 and an air heater 31 for preventing white smoke described below. It is composed of Numeral 31 denotes a high-temperature air heater for preventing white smoke in the exhaust gas. The air sucked by the white air blower 32 and heated by the air heater 31 is supplied to a mixed flue 38 described later. (See FIG. 2) to heat the exhaust gas discharged from the chimney. Reference numeral 33 denotes a gas cooling device provided downstream of the air heater 31. The gas cooling device 33 includes a plurality of water injection type cooling means 3.
4, and the outlet of the gas cooling device 33 is connected to the bag filter device 4 via a medium temperature flue 35. The above-mentioned air preheater 23 and air heater 31, hot water generating means (not shown), and other auxiliary equipment constitute a residual heat utilization facility. Reference numeral 4 denotes a precoat type bag filter device comprising a plurality (only one unit is shown in the figure) of a unit dust collecting mechanism, and a filtration chamber 42 in which a plurality of filter cloths 41 are suspended.
And a clean gas chamber 44 provided at the upper part of the filter chamber 42 and provided with a removing means 43; a clean gas duct 45 for discharging clean gas; and a branch flue 36 attached to the lower part of the filter chamber 42. The hopper section 46 and the collected ash discharging means 47 are constituted. A medicine blower 52, an adsorbent storage tank 54 having an adsorbent feeder 53, and a medicine storage tank 56 having a medicine feeder 55 are provided in the middle of a blower pipe 51 branched from the clean gas duct 45. The medicine blower 52, the adsorbent feeder 53, the adsorbent storage tank 54, the medicine feeder 55, and the medicine storage tank 56 supply the medicine supply device 5.
Is configured. The end of the blower pipe 51 is connected to the middle temperature flue 35. The bag filter device 4 and the medicine supply device 5 configured as described above constitute an exhaust gas treatment facility. Further, below the collected ash discharging means 47,
Classification means 6 for separating the reacted neutralizing agent and adsorbent constituting the discharged ash from non-combustible substances such as dust by a method such as centrifugation.
1 and a switching conveyor 62 which can be transported in both directions. One of the switching conveyors 62 is connected to a collecting ash processing unit 63 and the other is connected to a medicine hopper 65 at one end via a collecting ash transferring unit 64. The classification means 61, the switching conveyor 6
2. The collected ash processing device 6 is constituted by the collected ash processing means 63, the collected ash transfer means 64, the chemical hopper 65, and the reburning feeder 66. Next, the operating state of the refuse incineration facility configured as described above will be described mainly with reference to FIGS. 2 to 4 and, if necessary, referring to FIG. FIG. 2 is a schematic flow chart showing the flow of the main substances in the refuse incineration plant. The solid line shows the exhaust gas and clean gas system, the dotted line shows the air and water system, and the dashed line shows the chemical and ash collection system. I have. In FIG. 2, a combustion gas 71 containing dust and unburned matter and dioxins discharged by combustion in the refuse incinerator 1 enters the reburning chamber main body 22 after being stirred by the inclined ceiling 11. After the reburning by the reburning burner 21 (see FIG. 1), the dioxins are pyrolyzed into high-temperature reburning gas 72, enter the air preheater 23, and exchange heat with the combustion air 73 from the push-in blower 24. The gas is introduced into the heater 31 and exchanges heat with the white air 74 from the white air blower 32 to form an exhaust gas 75 at 650 to 800 ° C., and enters the gas cooling device 33. Exhaust gas 75 entering the gas cooling device 33
Is cooled at once by a cooling means 34 such as a water injection device to become a medium temperature gas 76 of about 170 to 200 ° C., and is introduced into the bag filter device 4 through a medium temperature flue 35. On the other hand, the clean gas duct 45 and the medium temperature flue 35
A blower pipe 51 is connected between them, and a medicine blower 52 is provided.
A part of the clean gas 77 described later sucked by
A carbon-based adsorbent 81 such as powdered activated carbon and an adsorption aid supplied from an adsorbent storage tank 54 via an adsorbent feeder 53 is
Subsequently, a neutralizing agent 82 such as slaked lime or calcium carbonate supplied from the drug storage tank 56 via the drug feeder 55 is supplied into the medium temperature gas 76 (FIG. 1).
reference). As described above, the mixed gas 78 in which the carbon-based adsorbent 81 and the neutralizing agent 82 are supplied to the medium temperature gas 76.
Are mixed in the bag filter device 4.
The dioxins remaining therein are adsorbed by the carbon-based adsorbent 81, and the acidic harmful gas is also neutralized by the neutralizing agent 82 to become the clean gas 77, and the clean gas duct 4
5. The air reaches the mixed flue 38 via the induction ventilator 37, is heated by the white air 74 sent from the air heater 31, and is discharged into the atmosphere from the chimney. The carbon-based adsorbent 81 adsorbing the soot and dioxins in the mixed gas 78 and the carbon-based adsorbent 81 adsorbed on the filter cloth 41 collected by the bag filter device 4 and the neutralized acidic harmful gas. The Japanese chemicals 82 are removed from the surface of the filter cloth 41 by the removing means 43 in the clean gas chamber 44 to become the collected ash 83, and become the chemicals 84 from which the incombustible substances have been removed by the classification means 61, and become the switching conveyor 62. The incombustibles 85 discharged and classified above are collected by the ash collecting means 63.
(See FIG. 1). The medicine 84 is transported to the collecting ash transfer means 64 via the switching conveyor 62 and is temporarily stored in the medicine hopper 65. The stored drug 84 is fed into the reburning chamber main body 22 through the reburning feeder 66 at the time of additional supply described later, and is reburned together with the combustion gas 71, so that carbon dioxide adsorbing dioxins in the drug 84 is removed. The system adsorbent 81 burns to generate carbon dioxide gas, and the adsorbed dioxins are thermally decomposed. On the other hand, one of the reacted calcium chlorides constituting the drug 84 is converted into quick lime by thermal decomposition and sent to the bag filter device 4 through the high-temperature flue 26, the medium-temperature flue 35 and the like to be described later. However, since there is a sufficient neutralization reaction time in the reburn chamber main body 22 and the remaining heat utilization equipment in addition to the blowing up effect of the inclined ceiling portion 11, there is no danger of an exothermic reaction with moisture due to quick lime, The use amount of the neutralizing agent can be reduced by the above-mentioned reuse. Thereafter, the exhaust gas 75 cooled from the reburn gas 72 is cooled at once from the high temperature state by the gas cooling device 33 as described above, so that the resynthesis of dioxins does not occur. Further, when the neutralizing agent is excessive in the system due to the reuse of lime or when the reaction efficiency is reduced, the above collected ash 83 is directly switched without performing the classification by the classification means 61. The conveyer 62 discharges the collected ash to the collecting ash processing means 63 and performs processing including dioxins. Next, referring to FIGS. 3 to 6, the operation of the pre-coated bag filter device will be described by comparing the present invention system and the conventional system. FIG. 3 is a diagram showing the removal of the bag filter and the change in the differential pressure and the concentration of harmful gas in each drug supply state in the case of the method according to the present invention. FIG. FIG. 5 is a diagram showing changes in differential pressure and harmful gas concentration in dropping and each drug supply situation, and FIG.
FIG. 6 is a cross-sectional view showing the state of attachment of each substance to the surface of the filter cloth in the case of the method of the present application, and FIG. 6 is a cross-sectional view showing the state of adhesion of each substance to the surface of the filter cloth in the case of the conventional method. First, in the conventional method shown in FIG. 4, when the differential pressure of the bag filter approaches a specified value, the adherence on the filter cloth surface is sequentially removed for each unit dust collecting mechanism to return the differential pressure to the origin. A mixture of a neutralizing agent such as slaked lime or calcium carbonate and an adsorbent such as powdered activated carbon and an auxiliary additive added together with the exhaust gas are supplied at once to the dropped filter cloth. After forming a precoat layer (see FIG. 6), the supply of the drug is stopped, and the process proceeds to a normal filtration operation including a neutralization / adsorption reaction. If the differential pressure gradually rises and reaches a specified value due to the accumulation of soot and dust that continues to fly along with the continuation of the filtering operation, the operation returns to the above-mentioned removing operation. However, there is a tendency for excessive supply of the neutralizing agent to place too much emphasis on the reduction with respect to the maximum value. In addition to the activated carbon that has reacted with acidic harmful gases and the activated carbon that has adsorbed dioxins, unreacted slaked lime and activated carbon that has residual adsorption capacity are also removed along with the dust layer that has grown on the surface. Dropping and expelling expensive drugs unused. In order to solve the problem, in the method of the present invention shown in FIG. 3, after the removal, first, a necessary amount of the carbon-based adsorbent 81 determined based on the past performance and experience of the factory is used.
Is supplied to the filter cloth together with the exhaust gas, and then about half of the neutralizing agent 82 taking into account the concentration of harmful gas at the outlet of the bag filter device 4 is also entrained in the exhaust gas. A pre-coat layer is formed by being primarily adhered to the top. Here, the carbon-based adsorbent 81 has a low specific gravity,
Since the specific gravity of the neutralizing agent 82 is relatively heavy, each layer can be made to adhere more evenly than in the case of the mixed injection as in the conventional method. Subsequently, the operation proceeds to the filtration operation for passing through the precoat layer. However, as described above, the amount of the neutralizing agent 82 attached is small and the thickness of the precoat layer is thin, so that the load on the ventilation facility is light and the rate of rise of the differential pressure is low. Although it has the advantage of being slow,
Hazardous gas concentrations rise relatively quickly. Therefore, by grasping the degree of increase in the concentration of the harmful gas, the medicine 84 stored in an amount corresponding to the increase is intermittently supplied to the reburn chamber main body 22 at appropriate intervals until the pressure difference limit is reached.
The quicklime obtained by converting the reacted calcium chloride in the drug 84 is fed into the bag filter device 4 through the high-temperature flue 26, the medium-temperature flue 35 and the like to form the drug 84 layer, thereby achieving a neutralization performance. Maintain (see FIG. 5). If the differential pressure rises to the specified value by repeating this additional supply, the flow returns to the initial drop-off. This series of operations is necessary because the concentration of harmful gas can be obtained continuously with a simple device.
By supplying an appropriate amount of the neutralizing agent 82 and the agent 84 based on the concentrations, it is possible to prevent the discharge of unreacted slaked lime, but the dioxin concentration requires a long time for the analysis and is a factor to be controlled. Because it is unsuitable, the supply amount of the carbon-based adsorbent 81 is set in advance based on the past performance and experience of the factory, and the entire supplied amount is used up as effectively as possible. Fine adjustment such as additional supply of the combustion air 73 and cooling in the furnace by the water spray device 14 (see FIG. 2) can also be performed by the CO concentration as the reference value. It has been described that the neutralizing agent 82 is supplied only when the initial precoat layer is formed, and the agent 84 is additionally supplied. However, even if the order is changed, the simultaneous injection of the neutralizing agent 82 and the agent 84 is performed. But you can. As described above, according to the method for ejecting and treating a medicine in the pre-coated bag filter device of the present invention, when the bag filter device is operated after being dropped off, the necessary amount of the bag filter device is first determined in advance. A carbon-based adsorbent is deposited on the surface of the filter cloth, and then a smaller amount of a neutralizing agent than expected is sprayed on the adsorbent layer in the initial stage to form a pre-coated layer of both in a short time. Depending on the concentration of the acidic harmful gas at the outlet of the bag filter device which rises with the continuation of the operation thereafter, until the differential pressure of the bag filter device reaches a specified value, the neutralizing agent or pyrolysis is generated. The chemical is repeatedly supplied repeatedly to reduce the concentration of the acidic harmful gas, and when the differential pressure reaches a specified value, each unit dust removal mechanism is sequentially washed off, and then a part of the collected ash that has been shaken off Is returned to the reburning facility and reburned, the carbon-based adsorbent burns and becomes carbon dioxide, the adsorbed dioxins are decomposed by thermal decomposition, and the chemical is pyrolyzed and reused It has been made like that. Therefore, wasteful discharge can be prevented by effectively using up expensive carbon-based adsorbents such as activated carbon, and neutralizing agents such as slaked lime supplied in a required amount can be reused. It becomes possible. Further, the carbon-based adsorbent is burned in a reburning facility and discharged as carbon dioxide, and the neutralizing agent is circulated for use, so that the amount of ash discharged to the outside is minimized, and post-treatment costs are reduced. We can save. Further, in order to preliminarily deposit a carbon-based adsorbent having a low specific gravity, the thickness of the precoat layer is averaged, and the efficiency of filtration, neutralization and adsorption is increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the overall configuration of a waste incineration facility. FIG. 2 is a schematic flow chart showing the flow of main substances in a waste incineration facility. FIG. 3 is a diagram showing changes in differential pressure and harmful gas concentration in the case where a bag filter is removed and each medicine is supplied according to the method of the present invention. FIG. 4 is a diagram showing changes in the differential pressure and the concentration of harmful gas in the case of the conventional method in which the bag filter is removed and each medicine is supplied. FIG. 5 is a cross-sectional view showing the state of attachment of each substance to the surface of the filter cloth in the case of the method of the present invention. FIG. 6 is a cross-sectional view showing the state of attachment of each substance to the surface of a filter cloth in the case of a conventional method. FIG. 7 is a schematic diagram showing a configuration of a conventional refuse incineration facility. FIG. 8 is a schematic diagram showing a configuration of still another conventional incineration facility. [Description of Signs] 1 Waste incinerator 2 Reburning facility 4 Bag filter device 41 Filter cloth 81 Carbon-based adsorbent 82 Neutralizing agent 84 Chemical

Claims (1)

(57) [Claims 1] A pre-coat type bag filter device having a plurality of unit dust collection mechanisms provided in an exhaust gas treatment facility for treating exhaust gas generated from a refuse incinerator, wherein Upon operation, it allowed with adhesive beforehand necessary amount of carbonaceous adsorbent filter cloth surface, followed by of forming the adsorbent
The adsorbent layer on the surface, and initial inject fewer neutralizing agent than expected required amount, short precoat layer two stages by both
Formed with time, depending on the acid harmful gas concentration of the bag filter instrumentation 置出 opening increases with subsequent continuous operation, a portion of the neutralizing agent or払落been collected ash above the waste incinerator by intermittently additional supply at least one of the drugs that are generated by thermal decomposition at afterburning equipment provided, the
Increased due to additional supply of chemicals and the accumulation of soot and dust
Until the differential pressure of the applied bag filter device reaches the specified value
Will repeat the additional supply of drugs to reduce the concentration of acidic harmful gases.
Reduce, at the time when the differential pressure specified value is reached, after sequentially removing each unit dust collecting mechanism, a part of the collected collected ash is returned to the reburning facility. And treatment method in a pre-coated bag filter device.