JP6854663B2 - Exhaust gas treatment method and exhaust gas treatment equipment - Google Patents

Description

The present invention relates to an exhaust gas treatment method and an exhaust gas treatment device.

Glass products such as glass bottles are manufactured by melting raw materials such as silica sand, soda ash, and lime and cullet made by crushing empty bottles in a melting furnace with a burner (about 1500 ° C) and molding the melted glass. Will be done. From the melting furnace that melts the glass, the combustion exhaust gas containing the combustion exhaust gas from the burner and the components generated from the melted glass is discharged. The combustion exhaust gas discharged from the melting furnace contains air pollutants NOx and SOx, and it is necessary to remove these pollutants from the combustion exhaust gas before releasing the combustion exhaust gas into the atmosphere. Further, since the combustion exhaust gas contains catalyst poisoning components such as SOx and adhesive components derived from the glass raw material, it is difficult to use the "selective catalyst reduction method" which is a conventional NOx treatment technique.

An exhaust gas treatment method is known in which _{NO is converted to NO 2} by ozone using a local cooling region of mist formed by spraying cooling water on the exhaust gas, and then _{NO 2} is removed by a reducing agent (for example). See Patent Document 1). _{In this method, Na 2} SO ₄ fine particles are generated from the reducing agent, and it is necessary to remove these fine particles from the exhaust gas with a dust collector.

Japanese Unexamined Patent Publication No. 2015-16434

In the conventional exhaust gas treatment method using the local cooling area of the mist, the dust collector may be corroded or the filter of the dust collector may be blocked. Further, in the conventional exhaust gas treatment method, ozone may be thermally decomposed before being used for oxidation of NO, and the efficiency of removing NOx is not sufficient.
The present invention has been made in view of such circumstances, and can efficiently remove NOx in the exhaust gas, and suppresses corrosion of the dust collector and clogging of the filter of the dust collector. Provide an exhaust gas treatment method that can be used.

According to the present invention, ozone is supplied to a local cooling region of 150 ° C. or lower of the first mist formed by spraying the first cooling water into the exhaust gas containing NOx and SOx, and the exhaust gas on the downstream side of the first mist is supplied. An exhaust gas treatment method in which a second mist is formed by spraying an aqueous NaOH solution therein, and dust in the exhaust gas is removed by a dust collector provided on the downstream side of the second mist. The first mist is an exhaust gas treatment method. It is formed by spraying the first cooling water into the exhaust gas from the spray holes provided around the ozone ejection port that supplies ozone gas to the local cooling area, and the amount of the first cooling water sprayed or the amount of the NaOH aqueous solution sprayed is determined. Provided is an exhaust gas treatment method characterized in that the temperature of the exhaust gas flowing into the dust collector is adjusted to be higher than 150 ° C. and 350 ° C. or lower.

In the exhaust gas treatment method of the present invention, since ozone is supplied to the local cooling region of 150 ° C. or lower of the first mist formed by spraying the first cooling water into the exhaust gas containing NOx, the NO contained in the exhaust gas is ozone. Can be oxidized and converted to NO _2. Further, since ozone is supplied to the local cooling region of 150 ° C. or lower, it is possible to suppress the thermal decomposition of ozone, and it is possible to efficiently convert _{NO contained in the exhaust gas into NO 2. Further, since NO is converted to NO 2} in the local cooling region of the first mist, it is possible to prevent the exhaust gas temperature on the downstream side of the first mist from becoming too low.
In the exhaust gas treatment method of the present invention, the first mist is formed by spraying the first cooling water into the exhaust gas from a spray hole provided around an ozone ejection port that supplies ozone gas to the local cooling area. Therefore, ozone gas can be supplied from the ozone ejection port to the central portion of the first mist formed by spraying the first cooling water from the spray holes, and the ozone gas is supplied into the exhaust gas outside the first mist. Can be suppressed. Therefore, it is possible to suppress the thermal decomposition of ozone gas, and the ozone gas can be efficiently used for the NO oxidation reaction.

In the exhaust gas treatment method of the present invention, a second mist is formed by spraying an aqueous NaOH solution into the exhaust gas containing _{SOx and NO 2 on the downstream side of the first mist, so that the second mist is reduced from SO 2} and NaOH. The agent Na ₂ SO ₃ can be produced, and NO ₂ can be reduced to N _{2 by Na 2} SO _3. Therefore, NOx contained in the exhaust gas can be efficiently removed in the second mist. Further, since NO ₂ is reduced to N ₂ in the second mist, it is possible to prevent the exhaust gas temperature on the downstream side of the second mist from becoming too low. Incidentally, Na ₂ SO ₄ is produced by the Na ₂ SO ₃ and NO ₂ as a reducing agent to react, dust Na ₂ SO ₄ is produced in the exhaust gas.

In the exhaust gas treatment method of the present invention, dust in the exhaust gas is removed by a dust collector provided on the downstream side of the second mist, so that Na ₂ SO ₄ dust in the exhaust gas can be removed by the dust collector. ..
In the exhaust gas treatment method of the present invention, the amount of the first cooling water sprayed or the amount of the NaOH aqueous solution sprayed is adjusted so that the temperature of the exhaust gas flowing into the dust collector is higher than 150 ° C. It is possible to prevent the temperature from falling below the acid dew point (for example, the sulfuric acid dew point), and it is possible to prevent the acidic solution from adhering to the dust collector. Therefore, it is possible to prevent the metal member contained in the dust collector from being corroded by the acidic solution. Further, it is possible to prevent dust from adhering to the inside of the dust collector by using an acidic solution as a binder, and it is possible to prevent the filter contained in the dust collector from being blocked.
In the exhaust gas treatment method of the present invention, the amount of the first cooling water sprayed or the amount of the NaOH aqueous solution sprayed is adjusted so that the temperature of the exhaust gas flowing into the dust collector is 350 ° C. or lower, so that the dust collector is thermally deteriorated. Can be suppressed.

It is a schematic block diagram of the exhaust gas treatment apparatus of one Embodiment of this invention. It is the schematic sectional drawing of the spray nozzle included in the 1st spray part and the ozone supply part.

In the exhaust gas treatment method of the present invention, ozone is supplied to a local cooling region of 150 ° C. or lower of the first mist formed by spraying the first cooling water into the exhaust gas containing NOx and SOx, and the exhaust gas is more than the first mist. This is an exhaust gas treatment method in which a second mist is formed by spraying a NaOH aqueous solution into the exhaust gas on the downstream side, and dust in the exhaust gas is removed by a dust collector provided on the downstream side of the second mist. The 1 mist is formed by spraying the first cooling water into the exhaust gas from the spray holes provided around the ozone ejection port that supplies ozone gas to the local cooling area, and the spray amount of the first cooling water or the NaOH aqueous solution. The spray amount is adjusted so that the temperature of the exhaust gas flowing into the dust collector is higher than 150 ° C. and 350 ° C. or lower.

According to the present invention, ozone is supplied to a local cooling region of 150 ° C. or lower of the first mist formed by spraying the first cooling water into the exhaust gas containing NOx and SOx, and the exhaust gas on the downstream side of the first mist is supplied. A second mist is formed by spraying an aqueous NaOH solution into the exhaust gas, a third mist is formed by spraying a second cooling water into the exhaust gas, and a collection provided on the downstream side of the second and third mists. This is an exhaust gas treatment method for removing dust in exhaust gas with a dust collector. The first, second and third mists are formed in the exhaust gas flowing through a reaction tower having a water sealing tank at the bottom, and the second cooling water is The water is stored in the water sealing tank, and the amount of spray of the second cooling water is adjusted so that the temperature of the exhaust gas flowing into the dust collector is higher than 150 ° C and lower than 350 ° C. Exhaust gas treatment methods are also provided. By adjusting the temperature of the exhaust gas flowing into the dust collector by the amount of the second cooling water sprayed, the amount of the first cooling water sprayed and the amount of the NaOH aqueous solution sprayed can be reduced. As a result, it is possible to suppress the overlap of the first mist and the second mist, and it is possible to suppress the reaction between the ozone gas in the first mist and the reducing agent in the second mist. In addition, the NaOH aqueous solution can be efficiently used for exhaust gas treatment. Further, by forming the third mist with the water (second cooling water) stored in the water sealing tank, the water stored in the water sealing tank can be consumed. Therefore, it is possible to suppress an increase in the solute concentration of the water stored in the water-sealed tank, and it is possible to omit the drainage treatment of the water stored in the water-sealed tank.

In the exhaust gas treatment method of the present invention, it is preferable to adjust the spray amount of the first cooling water so that the exhaust gas flows in the local cooling region of the first mist at 150 ° C. or lower for 1 second or longer. As a result, it is possible to suppress the thermal decomposition of the ozone gas in the local cooling region, and it is possible to efficiently _{convert the NO gas in the exhaust gas into the NO 2} gas.
In the exhaust gas treatment method of the present invention, it is preferable to adjust the spray amount of the NaOH aqueous solution so that the exhaust gas flows through the second mist over 2 seconds or longer. As a result, the duration of the minute water droplets contained in the second mist can be set to 2 seconds or more, and the chemical reaction in which the reducing agent Na ₂ SO _{3 is generated from SO 2 and NaOH in the second mist,} It is possible to secure time for the chemical reaction of reducing NO ₂ to N ₂ by Na ₂ SO _3. Therefore, NOx in the exhaust gas can be efficiently removed.

_{In the exhaust gas treatment method of the present invention, the measured value of the SO 2} concentration of the exhaust gas downstream from the second mist or upstream from the first mist, the measurement result of the pH measurement of the dust collected by the dust collector, and the second mist. It is preferable to adjust the spray amount of the NaOH aqueous solution or the NaOH concentration of the NaOH aqueous solution to be sprayed based on at least one of the measured values of the NOx concentration of the exhaust gas downstream. As a result, SOx and NOx in the exhaust gas can be efficiently removed.
In the exhaust gas treatment method of the present invention, the first and second mists are preferably formed in the exhaust gas flowing through the reaction tower having the water-sealed tank at the bottom, and the oxidation-reduction potential or pH of the water stored in the water-sealed tank. It is preferable to adjust the spray amount of the NaOH aqueous solution or the NaOH concentration of the NaOH aqueous solution to be sprayed based on the above. As a result, when the amount of NaOH or the reducing agent of the second mist is insufficient, the amount of NaOH or the reducing agent can be increased immediately, and the generation of acidic dust can be suppressed.

In the exhaust gas treatment method of the present invention, the second mist is preferably formed by spraying a mixed aqueous solution of NaOH and a reducing agent. As a result, _{NO 2} can be reduced to N _{2 by both Na 2} SO ₃ generated from _{SO 2} and NaOH and the reducing agent contained in the mixed aqueous solution, and NO x in the exhaust gas can be efficiently removed. Can be done.
In the exhaust gas treatment method of the present invention, it is preferable to adjust the spray amount of the mixed aqueous solution or the reducing agent concentration of the mixed aqueous solution to be sprayed based on the measured value of the NOx concentration of the exhaust gas downstream from the second mist. As a result, NOx in the exhaust gas can be efficiently removed.

The present invention comprises a reaction tower provided so that exhaust gas containing NOx and SOx at 200 ° C. or higher flows in, a dust collector provided so that exhaust gas discharged from the reaction tower flows in, and the reaction tower. A first spray portion provided so as to spray the first cooling water into the exhaust gas flowing through the exhaust gas to form a first mist having a local cooling region of 150 ° C. or lower, and to supply ozone to the local cooling region. An ozone supply unit provided, a second spray unit provided so as to spray a NaOH aqueous solution on the downstream side of the first mist of the exhaust gas flowing through the reaction tower to form a second mist, and a first or first spray unit. 2 The first or first adjustment unit is provided with an adjustment unit provided to adjust the spray amount of the spray unit so that the temperature of the exhaust gas flowing into the dust collector is higher than 150 ° C. and 350 ° C. or lower. Also provided is an exhaust gas treatment apparatus characterized in that it is provided so as to adjust the spray amount of the second spray unit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configurations shown in the drawings and the following description are examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

FIG. 1 is a schematic configuration diagram of the exhaust gas treatment device of the present embodiment. FIG. 2 is a schematic cross-sectional view of a spray nozzle included in the first spray unit and the ozone supply unit.
In the exhaust gas treatment method of the present embodiment, ozone is supplied to a local cooling region of 150 ° C. or lower of the first mist 6 formed by spraying the first cooling water 41 into the exhaust gas containing NOx and SOx, and the first The second mist 7 is formed by spraying the NaOH aqueous solution 42 into the exhaust gas on the downstream side of the mist 6, and the dust 32 in the exhaust gas is removed by the dust collector 3 provided on the downstream side of the second mist 7. The first mist 6 is formed by spraying the first cooling water into the exhaust gas from a spray hole 51 provided around the ozone ejection port 37 that supplies ozone gas to the local cooling area. The amount of the first cooling water 41 sprayed or the amount of the NaOH aqueous solution 42 sprayed is adjusted so that the temperature of the exhaust gas flowing into the dust collector 3 is higher than 150 ° C. and 350 ° C. or lower.

Further, in the exhaust gas treatment method of the present embodiment, ozone is supplied to a local cooling region of 150 ° C. or lower of the first mist 6 formed by spraying the first cooling water 41 into the exhaust gas containing NOx and SOx. The second mist 7 is formed by spraying the NaOH aqueous solution 42 into the exhaust gas on the downstream side of the first mist 6, and the third mist 8 is formed by spraying the second cooling water 34 into the exhaust gas. This is an exhaust gas treatment method for removing the dust 32 in the exhaust gas by a dust collector 3 provided on the downstream side of the 2 mist 7 and the 3rd mist 8. The second cooling water 34 is formed in the exhaust gas flowing through the reaction tower 2 having the sealed tank 9, and the second cooling water 34 is the water stored in the water sealed tank 9, and the spray amount of the second cooling water 34 flows into the dust collector 3. It is characterized in that the temperature of the exhaust gas to be exhausted is adjusted to be higher than 150 ° C. and 350 ° C. or lower.

The exhaust gas treatment device 50 of the present embodiment has a reaction tower 2 provided so that exhaust gas of 200 ° C. or higher including NOx and SOx flows in, and a collection provided so that exhaust gas discharged from the reaction tower 2 flows in. The dust collector 3 and the first spraying portion 15 provided so as to spray the first cooling water 41 into the exhaust gas flowing through the reaction tower 2 to form the first mist 6 having a local cooling region of 150 ° C. or lower. The ozone supply unit 18 provided to supply ozone to the local cooling region and the NaOH aqueous solution 42 are sprayed on the downstream side of the first mist 6 of the exhaust gas flowing through the reaction tower 2 to form the second mist 7. The second spraying unit 16 provided in the dust collector 3 and the adjusting unit 20 provided to adjust the spray amount of the first spraying unit 15 or the second spraying unit 16 are provided. It is characterized in that the spray amount of the first spray unit 15 or the second spray unit 16 is adjusted so that the temperature of the inflowing exhaust gas is higher than 150 ° C. and 350 ° C. or lower.
Hereinafter, the exhaust gas treatment method and the exhaust gas treatment device of the present embodiment will be described.

The exhaust gas to be treated by the exhaust gas treatment method and the exhaust gas treatment device 50 of the present embodiment is not particularly limited as long as it is an exhaust gas containing NOx and SOx, but for example, the exhaust gas of the glass melting furnace 1, the exhaust gas of the boiler, and the waste incinerator. Exhaust gas etc.
The reaction tower 2 can be provided so that the exhaust gas to be treated flows into the reaction tower 2, flows inside the reaction tower 2, and is discharged from the reaction tower 2. Further, the reaction tower 2 can be provided so that the exhaust gas flows from the bottom to the top of the reaction tower. The temperature of the exhaust gas flowing into the reaction tower 2 may be 200 ° C. or higher and 600 ° C. or lower, or 250 ° C. or higher and 550 ° C. or lower. The first mist 6, the second mist 7, and the third mist 8 formed in the exhaust gas flowing through the reaction tower 2 will be described later.

The reaction tower 2 can have a water sealing tank 9 at the bottom. The dust 32 coarsened inside the reaction tower 2 falls inside the reaction tower and dissolves in the sealing water 34 of the water sealing tank 9.
Further, an ORP meter for measuring the redox potential of the sealing water 34 stored in the water sealing tank 9 can be provided. Further, a pH meter for measuring the pH of the sealed water 34 stored in the water sealing tank 9 can be provided. The ORP meter or pH meter can be connected to the control unit 10 by the signal line 11 or wirelessly.

The dust collector 3 and the chimney 4 can be provided so that the exhaust gas discharged from the reaction tower 2 flows through the dust collector 3 and is discharged into the atmosphere from the chimney 4. The dust collector 3 is, for example, an electric dust collector, a bug filter, or the like.
A pH measuring device 29 can be provided so as to measure the acidity of the dust 32 collected by the dust collector 3. The pH measuring device 29 can be provided so as to measure the pH of the aqueous solution obtained by dissolving the dust 32 in water. The pH measuring device 29 can be connected to the control unit 10 by a signal line 11 or wirelessly. Further, an oxidation-reduction potential measuring device may be provided so as to measure the redox potential of the dust 32 collected by the dust collector 3.

An exhaust gas thermometer 25 for measuring the temperature of the exhaust gas flowing through the exhaust gas path of the exhaust gas treatment device 50 can be provided. For example, a thermometer 25a can be provided to measure the temperature of the exhaust gas flowing into the reaction tower 2, and the thermometer 25b and the thermometer 25c can measure the temperature of the first mist 6 formed in the reaction tower 2. 25d can be provided so as to measure the temperature of the exhaust gas flowing into the dust collector 3. These thermometers 25 can be connected to the control unit 10 by a signal line 11 or wirelessly. Therefore, the exhaust gas temperature can be monitored by the control unit 10. Further, the exhaust gas treatment device 50 can be controlled based on the measured value of the thermometer 25.

A gas concentration measuring device 26 for measuring the component gas concentration of the exhaust gas flowing through the exhaust gas path of the exhaust gas treatment device 50 can be provided. The gas concentration measuring device 26 can be provided so as to measure the NO concentration, NOx concentration, SO ₂ concentration or O _{2 concentration of the exhaust gas. For example, a gas concentration measuring device 26a can be provided so as to measure the NO concentration, NOx concentration, SO 2} concentration and O ₂ concentration of the exhaust gas flowing into the reaction tower 2, and the NO concentration of the exhaust gas flowing into the dust collector 3 can be provided. , NOx concentration, SO ₂ concentration and O ₂ concentration can be measured by providing a gas concentration measuring device 26b, and NO concentration, NOx concentration, SO ₂ concentration and O ₂ concentration of the exhaust gas discharged from the dust collector 3 can be provided. The gas concentration measuring device 26c can be provided so as to measure. These gas concentration measuring devices 26 can be connected to the control unit 10 by a signal line 11 or wirelessly.

The first spraying unit 15 is provided so as to spray the cooling water 41 into the exhaust gas flowing through the reaction tower 2 to form the first mist 6. The first spraying unit 15 is provided, for example, so as to send the cooling water 41 to the spray nozzle 23a by the pump 22a and spray the cooling water 41 into the exhaust gas flowing through the reaction tower 2 from the spray nozzle 23a. The spray nozzle 23 can be, for example, a two-fluid spray nozzle that mixes and ejects cooling water 41 and compressed air. Further, the spray nozzle 23 can be provided so that the cooling water 41 and the compressed air are mixed and sprayed from the plurality of spray holes 51. Further, the spray hole 51 can be provided around the ozone ejection port 37. For example, like the spray nozzle 23a shown in FIG. 2, the spray nozzle 23a can have a plurality of spray holes 51, and the cooling water 41 can be sprayed from each spray hole 51 in a two-fluid system. Further, air inflow holes 52 can be provided around the plurality of spray holes 51 of the spray nozzle 23a. The spray nozzle 23a can be cooled by the air flowing into the reaction tower 2 from the air inflow hole 51, and the ozone gas can be suppressed from being thermally decomposed.
Further, the spray amount of the first spray unit 15 can be adjusted by adjusting the liquid feed amount of the pump 22a. Further, the cooling water 41 can be water or a non-reducing aqueous solution. The cooling water 41 may be ozone water.
In the present embodiment, the mist means that a large number of minute water droplets are suspended in the exhaust gas and a large number of minute water droplets are flowing along with the flow of the exhaust gas. Further, 80% or more of the water droplets contained in the mist may have a size of 500 μm or less.

When the cooling water 41 is sprayed into the exhaust gas, many minute water droplets are formed in the exhaust gas, and the first mist 6 is formed in the exhaust gas. The minute water droplets contained in the first mist 6 gradually evaporate and disappear due to the heat of the exhaust gas. Due to the heat of vaporization when the minute water droplets evaporate, a local cooling region in which the temperature of the exhaust gas is locally lowered is formed in the first mist 6. The exhaust gas temperature in this local cooling region is lower than the exhaust gas temperature immediately upstream of the first mist, and is lower than the exhaust gas temperature immediately after the first mist 6 disappears.

The first spray unit 15 is provided so that a local cooling region of 150 ° C. or lower is formed in the first mist 6. For example, the spray amount of the first spray unit 15 can be adjusted so that a local cooling region of 150 ° C. or lower is formed in the first mist 6.
The first spraying unit 15 can be provided with a local cooling region of the first mist 6 at 150 ° C. or lower so that the exhaust gas flows over 1 second or more and 5 seconds or less. This makes it possible to suppress the thermal decomposition of ozone in the local cooling region. In addition, it is possible to secure a reaction time in which the NO gas contained in the exhaust gas is oxidized by the ozone gas.
For example, the pump 22a is fed based on the amount of exhaust gas flowing through the reaction tower 2 and the measured values of the exhaust gas thermometer 25b and the exhaust gas thermometer 25c provided to measure the temperature of the local cooling region of the first mist 6. By adjusting the amount of liquid and the amount of spray, the first mist can be formed so that the exhaust gas flows in the local cooling region of the first mist at 150 ° C. or lower for 1 second or more and 5 seconds or less. The amount of exhaust gas can be calculated from, for example, the amount of exhaust gas from the exhaust fan.
Further, the spray amount of the first spray unit 15 can be adjusted so that the temperature of the exhaust gas flowing into the dust collector 3 is higher than 150 ° C and lower than 350 ° C.

Such adjustment of the spray amount of the first spray unit 15 can be performed by the control unit 10 (adjustment unit 20). For example, the control unit 10 inputs the measured values of the thermometers 25a, 25b, 25c, and 25d and the exhaust amount of the exhaust fan, calculates the spray amount of the first spray unit 15 and the liquid feed amount of the pump 22a, and causes the pump 22a. The amount of liquid to be sent can be output. Then, the spray amount of the first spray unit 15 can be adjusted by adjusting the liquid feed amount of the pump 22a to the input value.

The ozone supply unit 18 is provided so as to supply ozone to the local cooling region of the first mist 6 at 150 ° C. or lower. By supplying ozone to a local cooling region of 150 ° C. or lower, NO contained in the exhaust gas can be oxidized by ozone and converted _{to NO 2.} Therefore, it is possible to convert a NO gas having a property of being difficult to dissolve in water in a local cooling region into a NO _{2 gas having a property of being easily dissolved in water.}
Since ozone is supplied to a local cooling region of 150 ° C. or lower, it is possible to suppress thermal decomposition of ozone. Therefore, the NO gas in the exhaust gas can be efficiently converted into the _{NO 2 gas.}

The ozone supply unit 18 may be provided so as to supply ozone to the local cooling region by providing the ozone gas ejection port 37 in the spray nozzle 23a included in the first spray unit 15. Further, the ozone supply unit 18 can be provided so as to supply ozone gas to the local cooling region from a portion of the spray nozzle 23a surrounded by a plurality of spray holes 51. As a result, ozone gas can be supplied to the central portion of the first mist 6 formed by spraying the cooling water 41 from the plurality of spray holes 51, and the ozone gas is supplied into the exhaust gas outside the first mist 6. It can be suppressed from being done. Therefore, it is possible to suppress the thermal decomposition of ozone gas, and the ozone gas can be efficiently used for the NO oxidation reaction. For example, as in the spray nozzle 23a shown in FIG. 2, the ozone ejection port 37 can be provided in a portion surrounded by a plurality of spray holes 51. By spraying the cooling water 41 from the plurality of spray holes 51 to form the first mist 6 and ejecting the ozone gas from the ozone ejection port 37, the ozone gas can be supplied to the central portion of the first mist 6.
Further, the ozone supply unit 18 may have an ozone ejection port that directly supplies ozone gas to the local cooling region of the first mist 6. Further, the ozone supply unit 18 may be provided so as to supply ozone gas to the local cooling region of the first mist 6 by spraying ozone water (including water having fine ozone bubbles) with the spray nozzle 23a. Further, the ozone supply unit 18 may be provided so that the ozone-containing compressed air and the cooling water 41 are mixed and ejected by the two-fluid spray nozzle 23a.
The ozone supply unit 18 can be provided so as to supply the ozone gas generated by the ozone generator 36 (ozonizer) to the local cooling region of the first mist 6.

The second spraying unit 16 can be provided so as to spray the NaOH aqueous solution 42 on the downstream side of the first mist 6 of the exhaust gas flowing through the reaction tower 2 to form the second mist 7. The second mist can be formed by spraying the NaOH aqueous solution into the exhaust gas containing _{SOx and NO 2} on the downstream side of the first mist 6 using the second spraying unit 16. The second spraying unit 16 can be provided so as to form the second mist 7 by spraying the NaOH aqueous solution 42 into the exhaust gas after the first mist 6 has disappeared. As a result, the first mist 6 and the second mist 7 can be separated and formed, and the reaction between the reducing agent in the second mist 7 and the ozone gas in the first mist 6 can be suppressed. Can be done.

The second spray unit 16 is provided, for example, so as to send the NaOH aqueous solution 42 to the spray nozzle 23b by the pump 22b and spray the NaOH aqueous solution 42 into the exhaust gas flowing through the reaction tower 2 from the spray nozzle 23b. The spray nozzle 23b can be, for example, a two-fluid spray nozzle that mixes and ejects an aqueous NaOH solution 42 and compressed air. Further, the spray amount of the second spray unit 16 can be adjusted by adjusting the liquid feed amount of the pump 22b.

When the NaOH aqueous solution 42 is sprayed into the exhaust gas, many minute water droplets are formed in the exhaust gas, and the second mist 7 is formed in the exhaust gas. The minute water droplets contained in the second mist 7 gradually evaporate and disappear due to the heat of the exhaust gas. Therefore, the exhaust gas from the reaction tower 2 flows through the second mist 7 in the region until the second mist 7 is formed and disappears.

Since the exhaust gas flowing through the reaction tower 2 _{contains SO 2} and the minute water droplets containing the second mist 7 contain NaOH, the chemical reaction as shown in the following formula (1) can proceed in the second mist 7. _{Therefore, SO 2} contained in the exhaust gas can be removed (the exhaust gas can be desulfurized), and Na ₂ SO ₃ which is a reducing agent can be generated in the fine droplets of the second mist 7.
SO ₂ + 2 NaOH → Na ₂ SO ₃ + H ₂ O ... (1)
Further, since the exhaust gas flowing through the reaction tower 2 _{contains NO 2} produced by oxidizing NO with ozone, a gas-liquid reaction as shown in the following formula (2) can proceed.
2NO ₂ + 4Na ₂ SO ₃ → N ₂ + 4Na ₂ SO ₄ ... (2)
_{Therefore, NO 2} can be reduced to N ₂ in the second mist 7, and NO x in the exhaust gas can be removed. Since it is considered that the chemical reactions of the formulas (1) and (2) proceed in the fine water droplets of the second mist 7 or at the gas-liquid interface between the fine water droplets and the exhaust gas, these chemical reactions determine the duration of the fine water droplets. It should be longer than the time required to proceed (which is considered to be required for about 1 second).
When the chemical reaction of the formula (2) proceeds, Na ₂ SO _{4 is generated from the reducing agent Na 2} SO ₃ , and Na ₂ SO ₄ dust is generated in the exhaust gas.
Further, since NO ₂ is reduced to N ₂ in the second mist 7, it is possible to prevent the exhaust gas temperature on the downstream side of the second mist 7 from becoming too low.

_{The second spraying unit 16 sprays a mixed aqueous solution 42 of Na 2} SO ₃ and NaOH, which is a reducing agent, on the downstream side of the first mist 6 of the exhaust gas flowing through the reaction tower 2 to form the second mist 7. Can be provided in. As a result, _{NO 2} can be reduced to N ₂ by both _{Na 2} SO _{3 generated from SO 2} and NaOH and Na ₂ SO ₃ contained in the mixed aqueous solution 42, and NOx in the exhaust gas can be efficiently reduced. Can be removed.

The spray amount of the second spray unit 16 can be adjusted so that the exhaust gas flows through the second mist 7 over 2 seconds or more and 6 seconds or less. As a result, the duration of the minute water droplets contained in the second mist 7 can be set to 2 seconds or more, and the time for advancing the chemical reaction as described in the above formulas (1) and (2) can be secured. it can. Therefore, NOx in the exhaust gas can be efficiently removed. Further, it is possible to prevent the exhaust gas temperature on the downstream side of the second mist 7 from becoming too low.
For example, by adjusting the amount of liquid sent from the pump 22b and the amount of spray based on the amount of exhaust gas flowing through the reaction tower 2 and the measured value of the exhaust gas thermometer 25, the exhaust gas is discharged in the second mist 7 for 2 seconds. The second mist 7 can be formed so as to flow over 6 seconds or less. The amount of exhaust gas can be calculated from, for example, the amount of exhaust gas from the exhaust fan.
Further, the spray amount of the second spray unit 16 can be adjusted so that the temperature of the exhaust gas flowing into the dust collector 3 is higher than 150 ° C and lower than 350 ° C.

Such adjustment of the spray amount of the second spray unit 16 can be performed by the control unit 10 (adjustment unit 20). For example, the control unit 10 inputs the measured value of the thermometer 25 and the exhaust amount of the exhaust fan, calculates the spray amount of the second spray unit 16 and the liquid feed amount of the pump 22b, and outputs the liquid feed amount to the pump 22b. be able to. Then, the spray amount of the second spray unit 16 can be adjusted by adjusting the liquid feed amount of the pump 22b to the input value.
The spray amount of the second spray unit 16 can be 80 to 120 when the spray amount of the first spray unit 15 is 100. Since the second mist 7 is formed on the downstream side of the first mist 6, the exhaust gas temperature immediately before the second mist 7 is lower than the exhaust gas temperature immediately before the first mist 6. Therefore, even if the amount of spray is the same, the duration of the minute water droplets of the second mist 7 is longer than the duration of the minute water droplets of the first mist 6.

The second spraying unit 16 can be provided so that the NaOH concentration or the reducing agent concentration of the aqueous NaOH solution to be sprayed or the mixed aqueous solution of NaOH and the reducing agent can be adjusted. As a result, the amount of NaOH to be sprayed or the amount of the reducing agent can be changed according to the state of the exhaust gas, and the NaOH or the reducing agent can be efficiently used. For example, the second spray so that the high-concentration NaOH aqueous solution 43 or _{the high-concentration mixed aqueous solution 43 of NaOH and Na 2} SO ₃ can be added to the NaOH aqueous solution 42 or the mixed aqueous solution 42 sprayed by the second spray unit 16 by the pump 22c. The portion 16 can be formed. By adjusting the liquid feed amount of the pump 22c, the NaOH concentration or the reducing agent concentration of the aqueous solution sprayed by the second spraying unit 16 can be adjusted.

The second spraying unit 16 sprays the amount of the NaOH aqueous solution 42 sprayed, the amount of the mixed aqueous solution 42 sprayed, or sprayed based on the measured value of _{the SO 2} concentration of the exhaust gas downstream of the second mist 7 or upstream of the first mist 6. It can be provided so as to adjust the NaOH concentration or the reducing agent concentration of the aqueous solution. Such adjustment can be performed by the gas concentration measuring device 26, the control unit 10, and the pump 22. As a result, it is possible to suppress a decrease in the SOx removal efficiency of the exhaust gas and a decrease in the _{amount of Na 2} SO _{3 produced.}

The second spray unit 16 determines the spray amount of the NaOH aqueous solution 42, the spray amount of the mixed aqueous solution 42, or the NaOH concentration or the reducing agent concentration of the sprayed aqueous solution based on the measured value of the NOx concentration of the exhaust gas downstream from the second mist 7. It can be provided to adjust. Such adjustment can be performed by the gas concentration measuring device 26, the control unit 10, and the pump 22. As a result, it is possible to suppress a decrease in the NOx removal efficiency of the exhaust gas.

The third spraying unit 17 can be provided so as to spray the cooling water 34 (sealing water 34) into the exhaust gas flowing through the reaction tower 2 to form the third mist 8. By providing the third spray unit 17, the exhaust gas can be cooled by the first to third mists, and even if the exhaust gas has a high temperature (for example, the temperature at the inlet of the reaction tower 2 is 450 ° C. or higher), it can be collected. The temperature of the exhaust gas flowing into the dust collector 3 can be 350 ° C. or lower or 230 ° C. or lower. Further, the third spray portion 17 may be provided so as to form the third mist 8 on the upstream side of the first mist 6, and the third mist 8 may be provided between the first mist 6 and the second mist 7. It may be provided so as to form the third mist 8 on the downstream side of the second mist 7. Further, the third spray unit 17 can be provided so as to form a third mist 8 separated from the first mist 6 or the second mist 7.
When the exhaust gas can be cooled to 350 ° C. or lower or 230 ° C. or lower by the first and second mists, the third spray unit 17 can be omitted.
The third spraying unit 17 can be provided so as to pump up and spray the sealing water 34 stored in the water sealing tank 9. In this case, water is newly supplied to the water sealing tank 9 by the amount of the pumped water. Therefore, it is possible to prevent the sealing water 34 stored in the water sealing tank 9 from concentrating due to the dissolution of the fallen dust. Further, since it is possible to prevent the solute concentration of the sealing water 34 from increasing, the wastewater treatment of the sealing water 34 can be omitted.

The spray amount of the third spray unit 17 can be adjusted so that the temperature of the exhaust gas flowing into the dust collector 3 is higher than 150 ° C and lower than 350 ° C. The spray amount of the third spray unit 17 can be adjusted by the control unit 10 (adjustment unit 20). For example, the control unit 10 can input the measured value of the thermometer 25, calculate the spray amount of the third spray unit 17 and the liquid feed amount of the pump 22d, and output the liquid feed amount to the pump 22d. Then, the spray amount of the third spray unit 17 can be adjusted by adjusting the liquid feed amount of the pump 22d to the input value.

_{Since Na 2} SO ₄ dust is generated in the exhaust gas by the chemical reactions of the above formulas (1) and (2), the dust 32 is contained in the exhaust gas downstream of the second mist 7 or downstream of the third mist 8. Is done. Of the dust 32, the large dust falls to the water sealing tank 9 at the lower part of the reaction tower 2 due to gravity and dissolves in the sealing water 34. Therefore, the redox potential and pH of the sealing water 34 change depending on the components contained in the dust 32.
If the amount of the amount or reducing agent NaOH second mist 7 is insufficient, it may produce acidic dust such as NaHSO _4. If a _{large amount of acidic dust such as NaHSO 4} enters the dust collector 3, the metal member of the dust collector 3 may be corroded.
When acidic dust is generated, this acidic dust also dissolves in the sealing water 34, so that the redox potential of the sealing water 34 changes to the positive side and the pH changes to the acidic side.

The second spraying unit 16 adjusts the spray amount of the second spraying unit 16 or the NaOH concentration or the reducing agent concentration of the aqueous solution to be sprayed based on the oxidation-reduction potential or pH of the sealing water 34 stored in the water sealing tank 9. Can be provided. By providing the second spraying unit 16 in this way, when the amount of NaOH or the reducing agent of the second mist 7 is insufficient, the amount of NaOH or the reducing agent can be increased immediately, and acidic dust is generated. It can be suppressed.
For example, an ORP meter for measuring the oxidation-reduction potential of the sealing water 34 or a pH meter for measuring the pH of the sealing water 34 is provided, the measured value is input by the control unit 10, and the control unit 10 sends the liquid to the pump 22b or 22c. A signal that increases the amount can be output.

The dust collector 3 can be provided so that the exhaust gas discharged from the reaction tower 2 flows in. The dust collector 3 can be provided immediately after the reaction tower 2 via the flow path pipe. By providing the dust collector 3, _{the dust of Na 2} SO ₄ generated in the reaction tower 2 can be removed from the exhaust gas. The dust collector 3 may be an electric dust collector or a bug filter. The heat resistant temperature of the electrostatic precipitator is about 350 ° C., and the heat resistant temperature of the bag filter is about 230 ° C.

When the third spray unit 17 is provided, the spray amount of the third spray unit 17 is adjusted so that the temperature of the exhaust gas flowing into the dust collector 3 is higher than 150 ° C. Further, the spray amount of the third spray unit 17 can be adjusted so that the temperature of the exhaust gas flowing into the dust collector 3 is 180 ° C., 200 ° C., 220 ° C. or 250 ° C. or higher. When the third spray unit 17 is not provided, the spray amount of the first spray unit 15 or the spray amount of the second spray unit 16 is adjusted so that the temperature of the exhaust gas flowing into the dust collector 3 is higher than 150 ° C. .. Further, the spray amount of the first spray unit 15 or the second spray unit 16 can be adjusted so that the temperature of the exhaust gas flowing into the dust collector 3 is 180 ° C., 200 ° C., 220 ° C. or 250 ° C. or higher. ..
By adjusting the amount of spray in this way, it is possible to prevent the temperature of the exhaust gas flowing through the dust collector 3 from falling below the acid dew point (for example, the sulfuric acid dew point), and the acidic solution adheres to the dust collector 3. Can be suppressed. Therefore, it is possible to prevent the metal member contained in the dust collector 3 from being corroded by the acidic solution. Further, it is possible to prevent dust from adhering to the inside of the dust collector 3 by using an acidic solution as a binder, and it is possible to prevent the filter included in the dust collector 3 from being blocked.

When the dust collector 3 is an electric dust collector, the spray amount of the first spray unit 15, the second spray unit 16 or the third spray unit 17 is set so that the temperature of the exhaust gas flowing into the dust collector 3 is 350 ° C. or less. Adjust so that When the dust collector 3 is a bug filter, the spray amount of the first spray unit 15, the second spray unit 16 or the third spray unit 17 is set so that the temperature of the exhaust gas flowing into the dust collector 3 is 230 ° C. or less. Adjust so that As a result, it is possible to prevent the dust collector 3 from being thermally deteriorated.

_{When an acidic component such as NaHSO 4} is generated in the reaction column 2, the dust collected by the dust collector 3 also contains acidic dust. Further, when desulfurization by the second mist 7 is insufficient, the dust collected by the dust collector 3 contains acidic dust. Therefore, when _{an acidic component such as NaHSO 4} is generated or desulfurization is insufficient, the redox potential of the aqueous solution of the dust collected by the dust collector 3 changes to the positive side, and the pH changes to the acidic side. When the dust collected by the dust collector 3 becomes acidic in this way, the dust collection efficiency of the dust collector 3 may decrease. Further, the acidic dust causes the metal member of the dust collector 3 to be acidicly corroded.

The second spraying unit 16 adjusts the spray amount of the second spraying unit 16 or the NaOH concentration or the reducing agent concentration of the aqueous solution to be sprayed based on the oxidation-reduction potential or pH of the aqueous solution of dust collected by the dust collector 3. Can be provided. By providing the second spraying unit 16 in this way, when the amount of NaOH or the reducing agent of the second mist 7 is insufficient, the amount of NaOH or the reducing agent can be increased immediately, and acidic dust is generated. It can be suppressed. Further, the dust in the dust collector 3 can be neutralized, and the dust collector 3 can be prevented from being acidicly corroded.
For example, a pH measuring device 29 for measuring the pH of an aqueous solution of dust collected by the dust collector 3 or an ORP measuring device for measuring the oxidation-reduction potential of the aqueous solution is provided, and the control unit 10 inputs the measured value to control the control unit. 10 can output a signal to the pump 22b or 22c to increase the liquid feed amount. For example, the NaOH concentration of the aqueous solution sprayed by the second spraying unit 16 can be adjusted so that the pH of the aqueous solution of the dust collected by the dust collector 3 is 7 or more.

Exhaust gas treatment experiment The exhaust gas discharged from the glass melting furnace was treated by the exhaust gas treatment device as shown in FIG. Further, as the spray nozzle 23a, a spray nozzle as shown in FIG. 2 was used. The duct diameter of the reaction tower is 3.5 m. Water was sprayed into the exhaust gas flowing through the reaction tower by the first spraying unit to form the first mist, and ozone gas was supplied into the first mist by the ozone supply unit. Further, a second mist was formed by spraying an aqueous NaOH solution (which does not contain a reducing agent) into the exhaust gas flowing through the reaction tower by the second spraying unit. Moreover, the spraying by the third spraying part is not performed. An electric dust collector was used as the dust collector. Table 1 shows the amount of exhaust gas, the amount of spray, and the like. Table 2 shows the measured values of the exhaust gas temperature and the gas concentration measurement results at the reaction tower inlet and the reaction tower outlet. In addition, the measured value of the exhaust gas temperature at the height where the first spray part of the reaction tower is installed, the measured value of the exhaust gas temperature at a height 1.5 m higher than the first spray part of the reaction tower, and the first spray part of the reaction tower. Table 3 shows the measured values of the exhaust gas temperature at a height 3.0 m higher than that. The measured values shown in Table 3 are the average values of the measured values at a plurality of points in the reaction column.

By spraying with the first and second spraying parts under the conditions shown in Table 1 and supplying ozone from the ozone supply part, the temperature of the exhaust gas flowing into the electrostatic precipitator could be set to 244 ° C. This prevented the electrostatic precipitator from being corroded. Further, the exhaust gas temperature at a height 1.5 m higher than that of the first spray portion could be set to 94 ° C. Since the flow velocity of the exhaust gas in the reaction tower is about 0.7 m / sec, the exhaust gas should flow in the local cooling area of 150 ° C. or less of the first mist formed by the first spraying part over 2.1 seconds. A local cooling zone could be formed. It is considered that this prevented the thermal decomposition of ozone in the local cooling region and secured the reaction time for the NO gas contained in the exhaust gas to be oxidized by the ozone gas.
By treating the exhaust gas in this way, a desulfurization efficiency of 57.3% and a desulfurization efficiency of 19% could be achieved. Moreover, the oxidation efficiency of NO by ozone gas (ΔNO / O ₃ ) could be set to 85%.

1: Glass melting furnace 2: Reaction tower 3: Dust collector 4: Chimney 6: 1st mist 7: 2nd mist 8: 3rd mist 9: Water seal tank 10: Control unit 11: Signal line 15: 1st spray Part 16: 2nd spray part 17: 3rd spray part 18: Ozone supply part 20: Adjustment part 22, 22a, 22b, 22c, 22d: Pump 23, 23a, 23b, 23c: Spray nozzle 25, 25a, 25b, 25c , 25d: Exhaust gas thermometer 26, 26a, 26b, 26c: Gas concentration measuring device 28: ORP meter 29: pH measuring device 31: Water droplet 32: Dust 34: Sealed water (cooling water) 36: Ozone generator 37: Ozone jet Outlet 41: Cooling water 42: NaOH aqueous solution ( _{mixed aqueous solution of NaOH and Na 2} SO ₃ ) 43: High-concentration NaOH aqueous solution ( _{high-concentration mixed aqueous solution of NaOH and Na 2} SO ₃ ) 50: Exhaust gas treatment device 51: Spray hole 52: Air inflow hole

Claims (9)

Ozone is supplied to the local cooling region of 150 ° C. or lower of the first mist formed by spraying the first cooling water into the exhaust gas containing NOx and SOx, and the NaOH aqueous solution is contained in the exhaust gas downstream of the first mist. Is an exhaust gas treatment method in which a second mist is formed by spraying, and dust in the exhaust gas is removed by a dust collector provided on the downstream side of the second mist.
The first mist is formed by spraying the first cooling water into the exhaust gas from a spray hole provided around the ozone ejection port that supplies ozone gas to the local cooling area.
The ozone outlet and the spray hole are openings provided in the same spray nozzle.
The spray holes are provided so as to mix the first cooling water and compressed air and spray them in a two-fluid system.
A method for treating an exhaust gas, characterized in that the amount of sprayed first cooling water or the amount of sprayed NaOH aqueous solution is adjusted so that the temperature of the exhaust gas flowing into the dust collector is higher than 220 ° C. and 350 ° C. or lower. Ozone is supplied to the local cooling region of 150 ° C. or lower of the first mist formed by spraying the first cooling water into the exhaust gas containing NOx and SOx, and the NaOH aqueous solution is contained in the exhaust gas on the downstream side of the first mist. A second mist is formed by spraying the exhaust gas, a third mist is formed by spraying the second cooling water into the exhaust gas, and the exhaust gas is exhausted by a dust collector provided on the downstream side of the second and third mists. It is an exhaust gas treatment method that removes the dust inside.
The first mist is formed by spraying the first cooling water into the exhaust gas from a spray hole provided around the ozone ejection port that supplies ozone gas to the local cooling area.
The ozone outlet and the spray hole are openings provided in the same spray nozzle.
The spray holes are provided so as to mix the first cooling water and compressed air and spray them in a two-fluid system.
The first, second and third mists are formed in the exhaust gas flowing through the reaction tower having a water sealing tank at the bottom.
The second cooling water is the water stored in the water sealing tank.
A method for treating an exhaust gas, characterized in that the amount of spray of the second cooling water is adjusted so that the temperature of the exhaust gas flowing into the dust collector is higher than 220 ° C. and 350 ° C. or lower. The exhaust gas treatment method according to claim 1 or 2, wherein the amount of spray of the first cooling water is adjusted so that the exhaust gas flows in the local cooling region of the first mist at 150 ° C. or lower for 1 second or longer. The exhaust gas treatment method according to any one of claims 1 to 3, wherein the spray amount of the NaOH aqueous solution is adjusted so that the exhaust gas flows through the second mist over 2 seconds or longer. _{The measured value of the SO 2} concentration of the exhaust gas downstream of the second mist or upstream of the first mist, the measurement result of the pH measurement of the dust collected by the dust collector, and the NOx concentration of the exhaust gas downstream of the second mist. The exhaust gas treatment method according to any one of claims 1 to 4, wherein the spray amount of the aqueous NaOH solution or the concentration of the NaOH of the aqueous NaOH solution to be sprayed is adjusted based on at least one of the measured values. The first and second mists are formed in the exhaust gas flowing through the reaction tower having a water sealing tank at the bottom.
The exhaust gas treatment method according to any one of claims 1 to 5, wherein the spray amount of the NaOH aqueous solution or the NaOH concentration of the NaOH aqueous solution to be sprayed is adjusted based on the oxidation-reduction potential or pH of the water stored in the water-sealed tank. The exhaust gas treatment method according to any one of claims 1 to 6, wherein the second mist is formed by spraying a mixed aqueous solution of NaOH and a reducing agent. The exhaust gas treatment method according to claim 7, wherein the spray amount of the mixed aqueous solution or the reducing agent concentration of the mixed aqueous solution to be sprayed is adjusted based on the measured value of the NOx concentration of the exhaust gas downstream from the second mist. In the reaction tower provided so that the exhaust gas containing NOx and SOx at 200 ° C. or higher flows in, the dust collector provided so that the exhaust gas discharged from the reaction tower flows in, and the exhaust gas flowing through the reaction tower. A first spray unit provided to spray the first cooling water to form a first mist having a local cooling region of 150 ° C. or lower, and ozone provided to supply ozone to the local cooling region. A supply unit, a second spray unit provided so as to form a second mist by spraying an ozone aqueous solution on the downstream side of the first mist of the exhaust gas flowing through the reaction tower, and a first or second spray unit. It is equipped with an adjustment unit provided to adjust the amount of spray.
The ozone supply unit has an ozone ejection port provided in the spray nozzle.
The first spray unit has a spray hole provided in the spray nozzle and has a spray hole.
The spray holes are provided around the ozone ejection port, and are provided so as to mix the first cooling water and compressed air and spray them in a two-fluid system.
The adjusting unit is provided so as to adjust the spray amount of the first or second spraying unit so that the temperature of the exhaust gas flowing into the dust collector is higher than 220 ° C. and 350 ° C. or lower. Exhaust gas treatment equipment.

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