JP5835940B2 - Exhaust gas treatment method and exhaust gas treatment apparatus - Google Patents

Description

The present invention relates to an exhaust gas treatment method and an exhaust gas treatment apparatus for removing SO _{3 in} combustion exhaust gas.

Combustion exhaust gas containing sulfur oxides such as SO ₂ and SO ₃ is discharged from a combustion furnace that burns fuel containing 0.5 wt% or more of sulfur such as heavy fuel or coal fuel.
SO ₃ is generated when a part of SO ₂ is oxidized in a high temperature environment. Therefore, the abundance of SO ₃ is about several percent with respect to SO ₂ . However, SO ₃ causes clogging and corrosion of the air heater and corrosion of the flue, and when it is cooled and discharged from the chimney, it causes purple smoke (blueish smoke). It is desirable.

As a method for removing SO ₃ , an ammonia injection method in which ammonia gas is blown into combustion exhaust gas is known. Patent Document 1 discloses a method of spraying desulfurization effluent containing dissolved salts such as Na ₂ SO ₄ into combustion exhaust gas as a method for removing SO ₃ more easily and cheaply than the ammonia injection method. Patent Document 2 discloses a method of spraying desulfurization waste water from a wet desulfurization apparatus using a lime gypsum method into combustion exhaust gas.

JP 2006-326575 A (Claims 1, 9, paragraphs [0009] and [0025]) JP 2008-246406 A (Claim 1, Claim 14, paragraphs [0007], [0041], [0046])

In the exhaust gas treatment apparatus disclosed in Patent Literature 1 and Patent Literature 2, a two-fluid nozzle is adopted as a spraying means for spraying desulfurized waste water. The two-fluid nozzle sprays the liquid as fine droplets by mixing the pressurized air and the liquid to be sprayed inside the nozzle.
When an aqueous solution containing a dissolved salt is sprayed into high-temperature combustion exhaust gas, the dissolved salt is dried in the vicinity of the gas-liquid contact surface inside the two-fluid nozzle and a precipitate is generated. This precipitate grows toward the pressurized air flow path side. For this reason, the flow path area of pressurized air becomes small and the spraying pressure of pressurized air increases. On the other hand, the flow path of the liquid side tends to flow because the flow rate of the pressurized air decreases, and the spray pressure of the aqueous solution decreases. That is, there is a problem that the dissolved salt cannot be finely sprayed and the SO ₃ removal performance is lowered.

In the case where the precipitate is water-soluble, it is possible to dissolve and remove the precipitate by periodically supplying water to the liquid side flow path and carrying out displacement cleaning. However, if frequent washing is performed to remove the precipitates, the spraying of the desulfurization waste water is stopped during the washing, so that the SO ₃ removal performance is deteriorated.

In addition, when spraying an aqueous solution containing CaSO ₄ that is sparingly soluble in water, such as desulfurization effluent of a wet desulfurization apparatus using a lime gypsum method, the above cleaning is performed when precipitates grow and accumulate in the pressurized air flow path. Then, since the precipitate cannot be removed sufficiently, the nozzle is blocked.

  An object of the present invention is to provide an exhaust gas treatment method and an exhaust gas treatment apparatus that can spray a dissolved salt stably from a two-fluid nozzle for a long period of time.

In order to solve the above-mentioned problems, the present invention is an exhaust gas treatment method for removing SO ₃ contained in combustion exhaust gas, which is a chloride, hydroxide, sulfate of any of Ca, Mg, Na, and K. Alternatively, an aqueous solution containing a dissolved salt, which is at least one of carbonates, and compressed air are merged inside each of a plurality of two-fluid nozzles, and the merged aqueous solution and the pressurized air are combined with each other. Sprayed from the fluid nozzle into the flue located upstream of the wet desulfurization apparatus, and the precipitation of the dissolved salt is suppressed by the pressurized air at the junction of the aqueous solution and the pressurized air inside the two-fluid nozzle. Provided is an exhaust gas treatment method in which an amount of water or water vapor is added to humidify the pressurized air.
In the said invention, it is preferable that the said aqueous solution is made into the desulfurization waste_water | drain of the said wet desulfurization apparatus by the lime gypsum method.

The present invention also relates to an exhaust gas treatment device for removing SO ₃ contained in combustion exhaust gas, wherein any one of chlorides, hydroxides of Ca, Mg, Na, K is provided in the flue upstream of the wet desulfurization device. A plurality of spray means comprising a two-fluid nozzle for spraying an aqueous solution containing a dissolved salt, which is at least one of sulfate or carbonate, together with pressurized air, and a humidifying unit for supplying water or water vapor to the pressurized air , A pressurized air spray pressure measuring unit that measures the spray pressure of the pressurized air, an aqueous solution spray pressure measuring unit that measures the spray pressure of the aqueous solution, and water or steam supplied from the humidifier to the pressurized air The exhaust gas processing apparatus is provided with a control unit that adjusts the amount to the amount that can suppress the precipitation of the dissolved salt at the junction of the aqueous solution inside the two-fluid nozzle and the pressurized air.

  By adding a predetermined amount of water or water vapor to the pressurized air and humidifying it, the rate at which the dissolved salt precipitates and grows at the junction of the pressurized air and the aqueous solution inside the two-fluid nozzle can be reduced. As a result, the exhaust gas treatment device can be operated without closing the two-fluid nozzle for a long period of time.

In the above invention, the humidification amount of the pressurized air, by a 0.03 kg / Nm ³ or more, since a reliably suppress spray pressure of the pressurized air and an aqueous solution the precipitation of dissolved salts can be stabilized preferable.

  In the said invention, it is preferable that the spray pressure of the said pressurized air is 0.04 Mpa or more higher than the spray pressure of the said aqueous solution.

When the spray pressure of the pressurized air is lower than the spray pressure of the aqueous solution, the aqueous solution scatters toward the passage through which the pressurized air flows from the junction of the pressurized air and the aqueous solution in the two-fluid nozzle. The scattered aqueous solution adheres to the flow path of the pressurized air and the dissolved salt is deposited, and the flow area of the pressurized air is reduced. As a result, the dissolved salt cannot be finely sprayed, and the SO ₃ removal ability decreases.
Therefore, in the present invention, the spray pressure of the pressurized air is set to 0.04 MPa or more higher than the spray pressure of the aqueous solution, thereby suppressing the scattering of the aqueous solution and reliably preventing the nozzle from being clogged. It can be stabilized.

In the above exhaust gas treatment method, when the spray pressure of the pressurized air reaches a predetermined pressure, the supply of the pressurized air and the aqueous solution is stopped, the flow path of the pressurized air in the two-fluid nozzle, and The flow path of the aqueous solution is preferably washed with water.
In the above exhaust gas treatment apparatus, the exhaust gas treatment apparatus includes: first water circulation means for circulating water through the flow path of the pressurized air; and second water circulation means for circulating water through the flow path of the aqueous solution of the dissolved salt, The control unit further stops the supply of the pressurized air and the aqueous solution to the spraying means when the spraying pressure of the pressurized air reaches a predetermined pressure, and in the two-fluid nozzle of the spraying means water is circulated by the first water circulation unit to the flow path of the pressurized air, water by the second water circulation unit to the flow path of the aqueous solution of the dissolved salts in the two-fluid nozzle of the spraying means It is preferable to circulate.

As described above, the amount of dissolved salt deposited has a correlation with the spray pressure of pressurized air. Therefore, in the present invention, when the spray pressure of the pressurized air reaches a preset pressure, the supply of the pressurized air and the aqueous solution is stopped, and not only the aqueous solution flow path but also the pressurized air flow path. Supply water to clean the inside of the flow path. By doing so, it is possible to periodically remove the dissolved salt deposited in the flow passage in the two-fluid nozzle, so that it is possible to prevent a decrease in the spray amount of the aqueous solution containing the dissolved salt and to stop spraying due to the nozzle clogging. Can be prevented. As a result, SO ₃ can be stably removed over a long period of time. CaSO ₄ is hardly soluble in water. However, if the amount of precipitation is small, it can be dissolved in water for cleaning and removed from the two-fluid nozzle.

In the exhaust gas treatment apparatus and the exhaust gas treatment method of the present invention, the pressurized air is humidified to suppress the deposition and deposition of dissolved salt at the junction of the pressurized air and the aqueous solution inside the two-fluid nozzle. For this reason, spraying of the aqueous solution containing dissolved salt is stabilized for a long period of time. Further, when the spray pressure of the pressurized air reaches a predetermined pressure, the supply of the pressurized air and the aqueous solution is stopped, and not only the aqueous solution flow passage but also the pressurized air flow passage is washed. Thereby, the supply_amount | feed_rate fall of the aqueous solution containing dissolved salt and the spray stop by the obstruction | occlusion of a nozzle can be prevented. That is, the exhaust gas treatment method and the exhaust gas treatment device of the present invention can maintain high SO ₃ removal efficiency over a long period of time.

1 is a schematic view of an exhaust gas treatment apparatus according to an embodiment of the present invention. 1 is a schematic view of an exhaust gas treatment apparatus according to an embodiment of the present invention. It is a section schematic diagram of a two fluid nozzle. It is a graph showing the time-dependent change of pressurized air spray pressure and aqueous solution spray pressure when the humidification amount of pressurized air is 0.02 kg / Nm ³ . It is a graph showing the time-dependent change of pressurized air spray pressure and aqueous solution spray pressure when the humidification amount of pressurized air is 0.03 kg / Nm ³ . It is a graph showing the time-dependent change of the pressurized air spray pressure and aqueous solution spray pressure when making the spray pressure of pressurized air 0.02 Mpa higher than the spray pressure of aqueous solution. It is a graph showing the time-dependent change of the pressurized air spray pressure and aqueous solution spray pressure when making the spray pressure of pressurized air 0.04 Mpa higher than the spray pressure of aqueous solution.

FIG. 1 is a schematic view of an exhaust gas treatment apparatus according to an embodiment of the present invention. The exhaust gas treatment apparatus 100 is provided in a flue downstream of a boiler (combustion furnace) 110. The exhaust gas treatment apparatus 100 includes a denitration apparatus 111, an air heater 112, a dry electrostatic precipitator 113, a wet desulfurization apparatus 114, a wet electrostatic precipitator 116, and a chimney 115.
The boiler 110 is, for example, a boiler that burns heavy oil or coal containing a relatively large amount of sulfur.
The denitration device 111 removes nitrogen oxides (NOx) contained in the combustion exhaust gas flowing from the boiler 110.
The air heater 112 exchanges heat between combustion exhaust gas and combustion air required by a pushing fan (not shown). Thus, the combustion air is heated by the sensible heat of the combustion exhaust gas and supplied to the boiler 110.
The dry electrostatic precipitator 113 collects dust in the combustion exhaust gas by electrostatic force.

The wet desulfurization apparatus 114 employs a gypsum lime method, a sodium method, and a water mug method. The wet desulfurization device 114 includes an absorbent spray 120 for spraying an aqueous solution containing an SO ₂ absorbent, a packed bed 121 disposed below the absorbent spray 120, and a storage provided below the packed bed 121. Part 122.
The filling layer 121 is configured to be provided with a resin filler, for example.
The reservoir 122 stores an aqueous solution of the absorbent. An absorbent of SO ₂ is supplied from the absorbent supply means 123 to the storage unit 122. The absorbent is CaO (lime) for the gypsum lime method, NaOH for the sodium method, and Mg (OH) ₂ for the water mug method. Air is supplied to the reservoir 122 from an air supply means (not shown).

An absorbent supply pump 124 is provided between the absorbent spray 120 and the reservoir 122. The absorbent supply pump 124 pumps the aqueous solution containing the absorbent in the reservoir 122 into the absorbent spray 120. The pumped aqueous solution containing the absorbent is sprayed from the absorbent spray 120 into the wet desulfurization apparatus 114. Thus, the absorbent and SO ₂ reacts, sulfites and sulfates are produced. In the case of the lime gypsum method, CaSO ₄ · 2H ₂ O (gypsum) is generated. Note that, for example, CaSO ₃ is also dissolved in the reservoir 122, but is actively oxidized by the air supplied by the air supply means. Since CaSO ₄ is sparingly soluble in water, most of the CaSO ₄ exists as a solid in the reservoir 122 and only a small part dissolves in the aqueous solution in the reservoir 122. On the other hand, MgSO ₄ is produced from MgO contained in the lime. Therefore, the aqueous solution stored in the storage unit 122 includes CaSO ₄ and MgSO ₄ . In the case of the sodium method, Na ₂ SO ₄ is formed. In the case of the water mug method, MgSO ₄ is formed. The aqueous solution containing the reaction product is stored in the storage unit 122. Accordingly, the reaction product is circulated in the wet desulfurization apparatus 114.

A wet electrostatic precipitator 116 may be provided in the flue downstream of the wet desulfurizer 114. The wet electrostatic precipitator 116 always sprays cleaning water on the collecting part, and removes dust and SO ₃ that could not be collected by electrostatic force. The wet electrostatic precipitator 116 is supplied with an alkaline solution such as a NaOH aqueous solution or a Mg (OH) ₂ aqueous solution for neutralization.

A plurality of spraying means 140 are provided in the flue 130 between the dry electrostatic precipitator 113 and the wet desulfurizer 114. A plurality of spraying means 140 are installed in the flue 130.
FIG. 2 is an enlarged schematic view of the cross section of the flue 130. The spray means 140 includes a protective tube 141 inserted into the flue 130, a pipe (aqueous solution pipe) 150 through which an aqueous solution containing a dissolved salt stored in the protective pipe 141 flows, and a pipe through which pressurized air flows ( And a plurality of two-fluid nozzles 142 connected to the aqueous solution pipe 150 and the pressurized air pipe 160.

The dissolved salt in the present invention is at least one of chloride, hydroxide, sulfate, or carbonate of any of Ca, Mg, Na, and K. Among the dissolved salts, the sulfate is included in the desulfurization effluent of the wet desulfurization apparatus 114. For this reason, desulfurization waste_water | drain can also be used for the said aqueous solution. In this case, the aqueous solution pipe 150 is connected to the absorbent supply pump 124 as shown in FIG. Alternatively, an extraction pump different from the absorbent supply pump 124 may be provided in the storage unit 122, and the extraction pump and the aqueous solution pipe 150 may be connected.
Alternatively, the aqueous solution pipe 150 is not connected to the wet desulfurization apparatus 114 through a pump as shown in FIG. 1, but may be connected to a tank or the like for storing an aqueous solution containing the dissolved salt.
A valve 151 is provided in the aqueous solution pipe 150 outside the flue 130. A pipe 152 for supplying water (industrial water) is connected to the valve 151 as shown in FIG.
A pressure gauge (aqueous solution spray pressure measuring unit) 153 for measuring the spray pressure of the aqueous solution is connected to the aqueous solution pipe 150. The pressure gauge 153 may be connected to the aqueous solution pipe 150 outside the flue 130 or may be provided to be connected to the aqueous solution pipe 150 inside the protective tube 141.

A valve 161 is provided in the pressurized air pipe 160 outside the flue 130. A pipe 162 for supplying industrial water is connected to the valve 161 as shown in FIG.
A humidification pipe 163 (humidification unit) through which water or water vapor for humidifying the pressurized air flows is separately connected to the pressurized air pipe 160. A valve 164 is connected to the humidifying pipe 163. When water vapor circulates, a steam pipe is connected.

  In addition, a pressure gauge (a pressurized air spray pressure measuring unit) 165 for measuring the spray pressure of the pressurized air is installed in the pressurized air pipe 160. The pressure gauge 165 may be connected to the pressurized air pipe 160 outside the flue 130, or may be provided to be connected to the pressurized air pipe 160 inside the protective pipe 141.

  The pressure gauges 153 and 165 are connected to the control unit 170. The valves 151, 161, 164 are connected to the control unit 170. The control unit is, for example, a computer.

  FIG. 3 is a schematic cross-sectional view of a two-fluid nozzle. The liquid and gas flow paths inside the two-fluid nozzle 142 are an aqueous solution flow path 143 connected to the aqueous solution pipe, a pressurized air flow path 144 connected to the pressurized air pipe, and a pressurized air flow path 144. And a mixed flow passage 146 connected to the nozzle tip 147 from the junction 145 of the aqueous solution flow passage 143.

Hereinafter, a method for treating exhaust gas according to an embodiment of the present invention will be described.
Outside the flue 130, water or water vapor is supplied from the humidification pipe 163 to the pressurized air flowing through the pressurized air pipe 160, and the pressurized air is humidified. When water is supplied from the humidification pipe 163 to the pressurized air pipe 160, the water is heated to become water vapor when it reaches the spraying means 140, and the pressurized air is humidified.
The humidified pressurized air is supplied from the pressurized air pipe 160 to the pressurized air flow passage 144 of the two-fluid nozzle 142.

  An aqueous solution containing a dissolved salt is supplied from the aqueous solution pipe 150 to the aqueous solution flow passage 143 of the two-fluid nozzle 142. In the case of FIG. 1, the desulfurization waste water of the wet desulfurization apparatus 114 is supplied as an aqueous solution containing a dissolved salt.

The aqueous solution containing pressurized air and dissolved salt supplied to the two-fluid nozzle 142 is mixed with the pressurized air at the junction 145 between the pressurized air flow passage 144 and the aqueous solution flow passage 143, and passes through the mixed flow passage 146. Sprayed into the flue 130 from the nozzle tip 147.
The two-fluid nozzle 142 sprays the aqueous solution into the flue 130 as droplets having a diameter of 10 to 100 μm, preferably 20 to 50 μm, more preferably 25 to 35 μm. Hot flue gas flows through the flue 130. As a result, the water is evaporated from the sprayed droplets, and refined and dried dissolved salt particles are generated. SO ₃ contained in the combustion exhaust gas is adsorbed and fixed to the dissolved salt particles, and SO ₃ is removed from the combustion exhaust gas. Further, a portion with SO ₃ in sulfuric acid salt contained in the dried particles of the dissolved salt reacts, SO ₃ is removed.
The environment in which the aqueous solution is sprayed is set to a temperature equal to or higher than the evaporation temperature of water because the water needs to evaporate while the sprayed droplets are scattered. Furthermore, to react with SO _3, it is equal to or higher than the dew point temperature of the SO _3, 130 ° C. or higher, and preferably from 140 ° C. or higher. Specifically, the combustion exhaust gas flowing through the flue 30 is about 150 ° C to 200 ° C.

  At this time, the pressure gauge 153 measures the spray pressure of the aqueous solution, and the pressure gauge 165 measures the spray pressure of the pressurized air. The measured values of the spray pressures are transmitted to the control unit 170.

Here, the controller 170 controls the opening degree of the valve 164 to adjust the amount of water or water vapor supplied to the pressurized air pipe 160. The supply amount of water or water vapor is set so that precipitation of the dissolved salt contained in the aqueous solution does not occur at the junction 145 of the aqueous solution and pressurized air inside the two-fluid nozzle 142. As the humidification amount, a value obtained by conducting a preliminary test is adopted. Specifically, the supply amount of water or water vapor is determined so that the humidification amount of the pressurized air is 0.03 kg / Nm ³ or more inside the two-fluid nozzle.

  The control unit 170 controls the opening degree of the valves 151 and 161 installed in the aqueous solution pipe 150 and the pressurized air pipe 160 so that the spray pressure of the pressurized air becomes higher than the spray pressure of the aqueous solution. At this time, the difference between the spray pressure of the pressurized air and the spray pressure of the aqueous solution is preferably 0.04 MPa or more.

FIG. 4 is a graph showing changes over time in the pressurized air spray pressure and the aqueous solution spray pressure when the humidification amount of the pressurized air is 0.02 kg / Nm ³ . FIG. 5 is a graph showing changes over time in the pressurized air spray pressure and the aqueous solution spray pressure when the humidification amount of the pressurized air is 0.03 kg / Nm ³ . 4 and 5, the vertical axis represents the spray pressure and the horizontal axis represents time, and in both figures, the scale is the same time interval. In the experiments of FIG. 4 and FIG. 5, desulfurization effluent of the lime gypsum method was used as an aqueous solution.

In FIG. 4, the spray pressure of pressurized air increases with time. This is because CaSO ₄ is dried and deposited at the confluence portion 145 of the two-fluid nozzle 142 and grows toward the pressurized air flow passage 144, and the flow passage area of the pressurized air flow passage 144 is reduced. On the other hand, since the flow path area of the aqueous solution flow passage 143 does not change, it is easier to circulate compared to pressurized air. For this reason, as shown in FIG. 4, the spray pressure of the aqueous solution decreases.

In FIG. 5 where the humidification amount of the pressurized air at the temperature reached by the two-fluid nozzle is 0.03 kg / Nm ³ , the spray pressure of the pressurized air and the spray pressure of the aqueous solution are almost constant. That is, spraying stable for a long time is performed under the conditions of FIG. In the humidification amount of FIG. 5, the rate at which CaSO ₄ precipitates and grows at the junction 145 of the two-fluid nozzle 142 is greatly reduced.

From the above results, it can be said that by setting the humidification amount of the pressurized air to 0.03 kg / Nm ³ or more, the precipitation of the dissolved salt can be suppressed and the spraying of the aqueous solution can be stabilized at the joining portion of the two-fluid nozzle. . That is, the exhaust gas treatment device can be operated for a long period of time.

  FIG. 6 is a graph showing changes over time in the pressurized air spray pressure and the aqueous solution spray pressure when spraying is started by setting the spray pressure of the pressurized air 0.02 MPa higher than the spray pressure of the aqueous solution. FIG. 7 is a graph showing changes over time in the pressurized air spray pressure and aqueous solution spray pressure when the spray pressure of pressurized air is 0.04 MPa higher than the spray pressure of the aqueous solution. 6 and 7, the vertical axis represents the spray pressure and the horizontal axis represents time, and in both figures, the scale is the same time interval. In the experiments of FIGS. 6 and 7, lime gypsum method desulfurization effluent was used as an aqueous solution.

As shown in FIG. 6, when the difference in the initial spray pressure is 0.02 MPa, the spray pressure of the pressurized air gradually increases. On the other hand, when the difference in the initial spray pressure was 0.04 MPa as shown in FIG. 7, the increase in the spray pressure of the pressurized air was significantly gentler than when the difference was 0.02 MPa. As for the spray pressure of the aqueous solution, the spray pressure of the aqueous solution decreases in a shorter time in FIG. 6 than in FIG.
A part of the aqueous solution that has passed through the aqueous solution flow passage 143 is scattered from the joining portion 145 toward the pressurized air flow passage 144 and adheres to the wall surface of the pressurized air flow passage 144, thereby reducing the flow area of the pressurized air. Let When the difference between the spray pressure of the pressurized air and the aqueous solution is small, scattering cannot be sufficiently suppressed. For this reason, when the spray pressure difference was 0.02 MPa, the deposition / deposition rate of the dissolved salt was faster than when 0.04 MPa, and an increase in the pressurized air spray pressure and a decrease in the aqueous solution spray pressure occurred.
From the above results, it was shown that if the spray pressure of the pressurized air is set to 0.04 MPa or more higher than the spray pressure of the aqueous solution, it is effective for preventing the two-fluid nozzle from being blocked.

In the exhaust gas treatment method of this embodiment, the two-fluid nozzle 142 is cleaned when the spray pressure of the pressurized air measured by the pressure gauge 165 reaches a predetermined set value. The cleaning is performed one by one among the plurality of spraying means 140 provided in the flue 130 so as not to stop the SO ₃ removal.

Specifically, when the spray pressure of the pressurized air measured by the pressure gauge 165 reaches a predetermined set value, the control unit 170 stops the supply of the aqueous solution by the valve 151, and the pressurized air by the valve 161. Stop supplying. The controller 170 closes the valve 164 and stops the supply of humidifying water and water vapor.
Next, the controller 170 supplies water from the valves 151 and 161 to each of the aqueous solution pipe 150 and the pressurized air pipe 160. The supplied water flows through the aqueous solution flow passage 143 and the pressurized air flow passage 144 of the two-fluid nozzle 142, passes through the mixed flow passage 146, and is discharged from the nozzle tip 147 into the flue 130.
After a predetermined time has elapsed, the controller 170 stops supplying water at the valves 151 and 161 and supplies the aqueous solution pipe 150 and the pressurized air pipe 160 with the CaSO ₄ -containing aqueous solution and pressurized air, respectively. Thereby, a washing process is completed about one of a plurality of spraying means provided in a flue.
After the cleaning process for one spraying unit 140 is completed, the above-described cleaning process may be sequentially performed for another spraying unit.

  The set value of the spray pressure for starting the cleaning and the time required for the cleaning process may be appropriately set based on the blockage of the flow passage in the nozzle, the degree of recovery of the spray pressure of the pressurized air and the aqueous solution, and the like. For example, the cleaning step is set to be performed when the spray pressure of the pressurized air is increased by 0.02 MPa from the predetermined spray pressure or when the variation from the set value exceeds 10%.

In the experiment shown in FIG. 4, the above-described washing process was performed at the time indicated by the arrow in the figure. When the cleaning of the present embodiment is performed, the spray pressure of the pressurized air and the spray pressure of the aqueous solution are changed to values almost equal to the set values at the start of operation (values on the left axis in FIG. 4). That is, even if it is a deposit of CaSO ₄ that is sparingly soluble in water, regular cleaning is performed not only on the aqueous solution flow path but also on the pressurized air flow path. Removed.
By performing the above-described cleaning process, an aqueous solution containing CaSO ₄ can be stably sprayed into the flue 130 over a long period of time.

DESCRIPTION OF SYMBOLS 100 Exhaust gas treatment apparatus 113 Dry type electrostatic precipitator 114 Wet desulfurization apparatus 130 Flue 140 Spray means 141 Protective pipe 142 Two-fluid nozzle 150 Aqueous solution pipe 151,161,164 Valve 153,165 Pressure gauge 160 Pressurized air pipe 163 Humidification Piping 170 Controller

Claims (7)

An exhaust gas treatment method for removing SO ₃ contained in combustion exhaust gas,
An aqueous solution containing a dissolved salt that is at least one of chlorides, hydroxides, sulfates, or carbonates of Ca, Mg, Na, and K and pressurized air are provided in each of the plurality of two-fluid nozzles. The combined aqueous solution and the pressurized air are sprayed from the two-fluid nozzle into a flue located upstream of the wet desulfurization device,
An amount of water or water vapor that can suppress precipitation of the dissolved salt is added to the pressurized air at a junction of the aqueous solution and the pressurized air inside the two-fluid nozzle, and the pressurized air An exhaust gas treatment method to be humidified.   The exhaust gas treatment method according to claim 1, wherein the aqueous solution is desulfurization effluent of the wet desulfurization apparatus by a lime gypsum method. The exhaust gas treatment method according to claim 1, wherein a humidification amount of the pressurized air is set to 0.03 kg / Nm ³ or more.   The exhaust gas treatment method according to claim 1, wherein a spray pressure of the pressurized air is 0.04 MPa or more higher than a spray pressure of the aqueous solution. When the spray pressure of the pressurized air reaches a predetermined pressure, the supply of the pressurized air and the aqueous solution is stopped,
The exhaust gas treatment method according to any one of claims 1 to 4, wherein the pressurized air flow passage and the aqueous solution flow passage in the two-fluid nozzle are washed with water. An exhaust gas treatment apparatus for removing SO ₃ contained in combustion exhaust gas,
An aqueous solution containing at least one of a chloride, hydroxide, sulfate, or carbonate of Ca, Mg, Na, or K in a flue upstream of the wet desulfurization apparatus together with pressurized air A plurality of spray means comprising a two-fluid nozzle for spraying;
A humidifying unit for supplying water or water vapor to the pressurized air;
A pressurized air spray pressure measuring unit that measures the spray pressure of the pressurized air;
An aqueous solution spray pressure measuring unit for measuring the spray pressure of the aqueous solution;
The amount of water or water vapor supplied from the humidification unit to the pressurized air is set to an amount capable of suppressing the precipitation of the dissolved salt at the junction of the aqueous solution and the pressurized air inside the two-fluid nozzle. An exhaust gas treatment apparatus comprising a control unit for adjustment. First water circulation means for circulating water through the flow path of the pressurized air;
Second water circulation means for circulating water through a flow path of the aqueous solution of the dissolved salt,
The controller further stops the supply of the pressurized air and the aqueous solution to the spraying means when the spraying pressure of the pressurized air reaches a predetermined pressure, and the two-fluid nozzle of the spraying means wherein the pressurized air of the flow passage in the first water distribution means to distribute water, water by the second water circulation unit to the flow path of the aqueous solution of the dissolved salts in the two-fluid nozzle of the spray means in The exhaust gas treatment apparatus according to claim 6 which distributes.

Images