JP2014140824A - Sulfuric acid ammonium salt elimination method in exhaust gas treatment equipment and exhaust gas treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce energy cost and reduce equipment cost.SOLUTION: Exhaust gas treatment equipment includes: a bypass exhaust line 30; and a gas circulation line 31 that includes a circulation blower 32, a circulation gas heater 33, a catalytic reaction tower 20, and a heat exchanger 17, and decomposes ammonium salt of sulfuric acid deposited in the catalytic reaction tower 20 and the heat exchanger 17 by heated circulation heated gas. A circulation gas exhaust channel portion 31c for discharging a part of the circulation heated gas from the gas circulation line 31 and introducing the part of the circulation heated gas to an inlet of a bag filter 16, and a supplementation outdoor air introduction channel portion 31d for introducing outdoor air into the gas circulation line 31 when the part of the circulation heated gas is discharged are provided in this gas circulation line 31. Heat decomposition components of the circulation heated gas discharged from the circulation gas exhaust channel portion 31c are captured by the bag filter 16 and then discharged from the bypass exhaust line 30 into atmosphere.

Description

  The present invention relates to a method for removing ammonium salt of sulfuric acid in an exhaust gas treatment facility and an exhaust gas treatment facility.

In the exhaust gas treatment line, there is a catalyst denitration system in which ammonia reaction gas is blown into exhaust gas and brought into contact with a denitration catalyst to install a catalytic reaction tower for denitration. In this case, ammonium sulfate [ammonium sulfate, (NH ₄ ) ₂ SO ₄ ] or hydrogen sulfate is added to the catalyst in the catalytic reaction tower or the heat transfer tube of the heat exchanger installed downstream of the catalytic reaction tower. It is known that ammonium [acid ammonium sulfate, NH ₄ HSO ₄ ] precipitates and accumulates, thereby reducing the denitration efficiency and the heat transfer efficiency.

  In a general exhaust gas treatment line, after exhaust gas is cooled by a cooling tower, neutralizing and / or adsorption chemicals are blown into the bag filter, and adsorbed materials such as dust, salts, dioxins and heavy metals are removed by the bag filter. Collect and remove. Further, a reducing agent such as ammonia gas is blown into the exhaust gas, introduced into the catalytic reaction tower, nitrogen oxides are removed from the exhaust gas, and then discharged from the chimney.

  By the way, Patent Document 1 discloses an example of removing the ammonium salt of sulfuric acid deposited and deposited on the catalyst of the catalytic reaction tower during the operation of the furnace. In the exhaust gas treatment line of Patent Document 1, the catalytic reaction tower is divided into a plurality of reaction parts, and when ammonium salt of sulfuric acid is deposited and deposited to reduce the reaction efficiency, the exhaust gas is introduced into a part of the reaction part. The exhaust gas heated to the thermal decomposition temperature is introduced only into the reaction section to thermally decompose the ammonium salt of sulfuric acid. And the exhaust gas containing a thermal decomposition component joins exhaust gas at the inlet of a cooling tower, and sends it out to a bag filter.

JP-A-10-192657

  However, the exhaust gas temperature introduced into the bag filter is around 160 ° C., and the thermal decomposition temperature of the ammonium salt of sulfuric acid is around 300 ° C., so that the heat energy heated from 160 ° C. to 300 ° C. is large, and the catalyst is deposited on the catalyst. Problems such as the time required for the thermal decomposition of the deposited ammonium salt of sulfuric acid, and the fact that the catalytic reaction tower is divided into a plurality of reaction parts makes the structure and piping complicated and the equipment costs high. was there.

  An object of the present invention is to solve the above problems and to provide a method for removing ammonium salt of sulfuric acid in an exhaust gas treatment facility and an exhaust gas treatment facility that can reduce energy costs and equipment costs.

The invention described in claim 1
A method for removing ammonium salts of sulfuric acid in an exhaust gas treatment line equipped with a bag filter, a heat exchanger and a catalytic reaction tower from an upstream side to an exhaust gas treatment line of exhaust gas discharged from a furnace,
During the operation of the furnace, exhaust gas discharged from the bag filter is discharged to the atmosphere side,
A circulating heating gas is circulated through a gas circulation line provided with at least one of the catalytic reaction tower and the heat exchanger, a circulation fan, and a circulation gas heater, and the circulation gas is circulated by the circulation gas heater. Thermally decomposing ammonium salt of sulfuric acid deposited in the catalytic reaction tower or / and in the heat exchanger by heating,
A part of the circulating heating gas is discharged into the exhaust gas and introduced into the bag filter. After the pyrolysis component accompanying the circulating heating gas is collected, it is discharged into the atmosphere.

The invention according to claim 2 is the method according to claim 1,
The furnace was operated at reduced NO _X in the exhaust gas,
A part of the circulating heating gas is led out to the bag filter and the outside air is introduced into the gas circulation line.

The invention described in claim 3
From the upstream side of the exhaust gas treatment line of exhaust gas discharged from the furnace, a method for removing ammonium salt of sulfuric acid in an exhaust gas treatment facility equipped with a bag filter, a heat exchanger and a catalytic reaction tower,
While the furnace is stopped, circulating heating gas is circulated through a gas circulation line provided with at least one of the catalytic reaction tower and the heat exchanger, a circulation fan, and a circulation gas heater, and the circulation gas heater By heating the circulating heating gas to thermally decompose the ammonium salt of sulfuric acid deposited in the catalytic reaction tower or / and in the heat exchanger,
Furthermore, after mixing and cooling the outside air to a part of the circulating heating gas discharged from the gas circulation line, introducing it into the bag filter, and collecting the pyrolysis components accompanying the circulating heating gas, To be discharged.

According to a fourth aspect of the present invention, in the method of the third aspect, a predetermined amount of neutralizing and / or adsorbing chemical is blown into the bag filter before the furnace is stopped.
The invention according to claim 5
From the upstream side of the exhaust gas treatment line of exhaust gas discharged from the furnace, a bag filter that collects salts, adsorbate and soot, a heat exchanger that heats the exhaust gas, and a catalytic reaction tower that removes nitrogen oxides from the exhaust gas An exhaust gas treatment facility comprising:
Provide a bypass exhaust line for exhausting the exhaust gas discharged from the bag filter to the atmosphere side,
A circulating blower, a circulating gas heater, and at least one of the catalytic reaction tower and the heat exchanger, and the catalytic reaction tower and / or the heat exchange with the circulating heating gas heated by the circulating gas heater A gas circulation line to decompose the ammonium salt of sulfuric acid accumulated in the vessel,
Providing a circulating gas exhaust passage section for leading a part of the circulating heating gas of the gas circulation line to an inlet of the bag filter;
When exhausting a part of the circulating heating gas, a replenishment outside air introduction flow path section for introducing outside air into the gas circulation line is provided,
The pyrolysis component of the circulating heating gas discharged from the circulating gas exhaust passage is collected by the bag filter and discharged from the bypass exhaust line.

The invention according to claim 6 is the configuration according to claim 5,
In the circulating gas exhaust flow path section, a cooling external air introduction flow path section for mixing and cooling the outside air with the circulating heating gas is provided,
The circulating heated gas discharged from the circulating gas exhaust flow path while the furnace is stopped is mixed with the external air from the cooling external air introducing flow path, cooled, and introduced into the bag filter.

The invention according to claim 7 is the configuration according to claim 5 or 6,
A circulating gas temperature detector for detecting the temperature of the circulating heating gas in the gas circulation line;
An exhaust gas temperature detector for detecting the exhaust gas temperature at the bag filter outlet;
An exhaust gas component detector for detecting the concentration of ammonia gas and / or sulfur oxide in the exhaust gas discharged from the bypass exhaust line;
A circulation gas discharge valve provided in the circulation gas exhaust passage,
A replenishment outside air introduction valve provided in the replenishment outside air introduction flow path section;
A thermal decomposition controller for controlling the opening degree of the circulating gas discharge valve and the outside air introduction valve,
The pyrolysis controller controls the temperature of the circulating heating gas based on the detected value of the circulating gas temperature detector during operation of the furnace, and the detected values of the exhaust gas temperature detector and the exhaust gas component detector. Based on the above, the opening degree of the circulating gas discharge valve and the supplementary outside air introduction valve is controlled.

The invention according to claim 8 is the configuration according to claim 6 or 7,
A cooling outside air introduction valve provided in the cooling outside air introduction flow path section;
The thermal decomposition controller
While the furnace is stopped, the temperature of the circulating heating gas is maintained within a proper temperature range in which the ammonium salt of sulfuric acid can be decomposed for a predetermined time, and the ammonium salt of sulfuric acid deposited in the catalytic reaction tower and / or the heat exchanger After opening the circulating gas discharge valve, a part of the circulating heating gas is led out to the circulating gas exhaust passage part, and the outside air introduction valve for cooling is opened, and the outside air is supplied to the circulating gas exhaust passage part. It introduces and cools circulating heating gas, and controls the temperature of the mixed gas of circulating heating gas and external air to the range suitable for a bag filter.

The invention according to claim 9 is the configuration according to claim 5 or 6,
The bag filter preheater and the bag filter preheat blower installed for preheating the bag filter are installed in the gas circulation line so that they can be used as a circulation blower and a circulation gas heater.

  According to the first aspect of the present invention, the exhaust gas remaining in the gas circulation line system is circulated as a circulation heating gas, and the circulation heating gas is heated to a temperature equal to or higher than the thermal decomposition temperature of the ammonium salt of sulfuric acid. The heat energy cost can be reduced, the ammonium salt of sulfuric acid deposited in the catalytic reaction tower and heat exchanger can be effectively pyrolyzed, the piping structure and equipment can be simplified, and the equipment Cost can be reduced.

According to the second aspect of the present invention, the gas circulation line is operated while exhausting the furnace into the atmosphere without passing through the catalytic reaction tower by operating the furnace at low NO _X and reducing the amount of NO _X in the exhaust gas in advance. In addition, the ammonium salt of sulfuric acid deposited in the catalytic reaction tower and the heat exchanger can be effectively pyrolyzed by the circulating heating gas. In addition, since the outside air is introduced into the gas circulation line when the circulating heating gas is discharged, the components of the pyrolysis gas accompanying the circulating heating gas can be almost completely discharged from the gas circulation line, and the cracked gas becomes a gas. It can be prevented from remaining in the circulation line and causing corrosion.

According to the invention described in claim 3, while the furnace is stopped, the circulating heating gas is heated and circulated using the gas circulation line, so that the heat energy cost can be reduced and the catalytic reaction tower, the heat exchange can be reduced. Since the ammonium salt of sulfuric acid deposited in the vessel is pyrolyzed, the piping structure and equipment can be simplified, and the equipment cost can be reduced. In addition, after cooling and mixing the outside air with the circulating heating gas after pyrolysis, it is introduced into the bag filter to solidify the ammonia gas and SO _X contained in the circulating heating gas without damaging the bag filter. Can be collected.

According to the fourth aspect of the present invention, even when the furnace is stopped, the ammonia and SO _X contained in the circulating heating gas are reacted and adsorbed by the neutralizing and adsorbing agents blown in advance. It can be collected effectively.

  According to the invention described in claim 5, the bypass exhaust line for discharging the exhaust gas discharged from the bag filter, and the catalytic reaction tower and the heat exchanger by heating the circulating heating gas to a temperature capable of thermally decomposing ammonium salt of sulfuric acid. Since the gas circulation line is provided, the ammonium salt of sulfuric acid deposited in the catalytic reaction tower and the heat exchanger during the operation of the furnace can be pyrolyzed. Therefore, since the circulating heating gas can be heated and circulated along the gas circulation line and used repeatedly, the heat energy cost can be reduced and the ammonium salt of sulfuric acid deposited in the catalytic reaction tower and heat exchanger is good. Therefore, the piping structure and the structure of the catalytic reaction tower can be simplified, and the equipment cost can be reduced.

  According to the invention described in claim 6, even when the furnace is stopped, the circulating heating gas is circulated in the gas circulation line to thermally decompose the ammonium salt of sulfuric acid deposited in the catalytic reaction tower or the heat exchanger. it can. And since the outside air can be mixed and cooled with the circulating heating gas led out to the bag filter from the gas circulation line through the cooling outside air introduction flow path section, it is possible to introduce a mixed gas at an appropriate temperature into the bag filter. It is possible to prevent the bug filter from being burned out.

  According to the seventh aspect of the present invention, the temperature of the circulating heating gas and the temperature of the mixed gas of the circulating heating gas and the exhaust gas derived from the gas circulation line are controlled by the pyrolysis controller, whereby the ammonium salt of sulfuric acid. Can be effectively thermally decomposed, the components of the exhaust gas can be kept good, and thermal damage of the bag filter can be prevented.

  According to the invention described in claim 8, even when the furnace is stopped, the ammonium salt of sulfuric acid can be effectively pyrolyzed by controlling the temperature of the circulating heating gas by the thermal decomposition controller. In addition, by mixing the outside air with the circulating heating gas derived from the gas circulation line and cooling the mixed gas, the pyrolysis component contained in the circulating heating gas is solidified and further neutralized or adsorbed on the bag filter. The chemicals for neutralization can be neutralized or adsorbed and collected by the bag filter, and the bag filter can be prevented from burning.

  According to the ninth aspect of the present invention, by using a circulating gas blower and a circulating gas heater that are installed in advance, it can be easily applied to existing exhaust gas treatment equipment, and equipment costs can be reduced. .

FIG. 1 is a configuration diagram illustrating a first embodiment of an exhaust gas treatment facility according to the present invention during normal operation. It is explanatory drawing which thermally decomposes the ammonium salt of a sulfuric acid at the time of a driving | operation of an incinerator. It is explanatory drawing which thermally decomposes the ammonium salt of a sulfuric acid at the time of a rest of an incinerator. Example 2 of the exhaust gas treatment facility according to the present invention is shown and is a configuration diagram during normal operation. It is explanatory drawing which thermally decomposes the ammonium salt of a sulfuric acid at the time of a driving | operation of an incinerator. It is explanatory drawing which thermally decomposes the ammonium salt of a sulfuric acid at the time of a rest of an incinerator.

[Example 1]
Embodiment 1 of the present invention will be described below with reference to FIGS.
(Basic structure)
As shown in FIG. 1, in this exhaust gas treatment facility, for example, a boiler 12 for heat recovery of exhaust gas and a cooling tower 13 for cooling the exhaust gas are installed downstream from an incinerator (furnace) 11 for waste. Yes. A bag filter 16, a heat exchanger (heated side) 17, a gas reheater 18, a catalytic reaction tower 20, a heat exchanger (heating side) 17, an induced draft are sent to the exhaust gas treatment line 10 downstream from the cooling tower 13. The machine 21 and the chimney 22 are installed in order, and the exhaust gas is sequentially introduced and processed.

The bag filter 16 collects hydrogen chloride, SO _x , heavy metals, dust, dioxins, etc. contained in the exhaust gas, and activated carbon for adsorbing harmful substances such as heavy metals and dioxins on the upstream side of the bag filter 16. Activated carbon supply device 14 that blows gas into the exhaust gas, and a drug supply device that blows neutralizing alkaline chemicals such as slaked lime into the exhaust gas in order to react with hydrogen chloride (HCl), sulfur oxide (SO _X ), etc. in the exhaust gas 15 is provided.

The heat exchanger 17 for reheating and the gas reheater 18 are for heating the exhaust gas supplied to the catalytic reaction tower 20 installed on the downstream side to an optimum temperature. In the catalytic reaction tower 20, a reducing agent such as ammonia gas is injected into the exhaust gas from the ammonia supply device 23, and NO _X (nitrogen oxide) or the like is removed by bringing the exhaust gas into contact with the denitration catalyst.

In the above configuration, ammonium sulfate [ammonium sulfate, (NH ₄ ) ₂ SO ₄ ] and ammonium hydrogen sulfate [acidic ammonium sulfate, NH ₄ HSO ₄ ], which are ammonium salts of sulfuric acid, are deposited in the catalytic reaction tower 20 and the heat exchanger 17. When deposited, the denitration efficiency and the heat transfer efficiency are lowered, and therefore, equipment and piping for performing an operation of thermally decomposing and removing the ammonium salt of sulfuric acid are provided.

(Bypass exhaust line)
A bypass exhaust line 30 is branched from the exhaust gas treatment line 10 between the bag filter 16 and the heat exchanger 17, and an outlet of the bypass exhaust line 30 is connected to an inlet side of the induction blower 21. And by this bypass exhaust line 30, exhaust gas can be discharged | emitted in the atmosphere via the chimney 22 from the induction blower 21, without passing the heat exchanger 17, the gas reheater 18, and the catalytic reaction tower 20. FIG.

(Gas circulation line)
As clearly shown in FIG. 2, in the gas circulation line 31, a catalytic reaction tower 20, a heat exchanger (heating side) 17, a circulation fan 32, and a circulation gas heater 33 are installed in this order from the upstream side. The gas circulation line 31 includes a shared flow path portion 31a using a part of the exhaust gas treatment line 10 and a heating flow path portion 31b provided separately. The common flow path portion 31 a is a pipe shared with the exhaust gas treatment line 10 from the catalytic reaction tower 20 to the outlet side of the heat exchanger (heating side) 17.

  The heating flow path portion 31b is a pipe connected from the outlet side of the common flow path portion 31a to the inlet side of the catalytic reaction tower 20 via the circulation blower 32 and the circulation gas heater 33. In addition, the heating channel 31 b is connected to the inlet of the bag filter 16 and connected to the circulation gas exhaust channel 31 c that leads out part of the circulating heating gas of the gas circulation line 31 and the inlet side of the circulation fan 32. The replenishment outside air introduction flow path portion 31d for introducing replenishment outside air into the gas circulation line 31 and the cooling which is connected to the outlet side of the circulation gas exhaust flow passage portion 31c and introduces the cooling outside air to the circulating heating gas An outdoor air introduction flow path portion 31g is provided.

  The circulating blower 32 circulates the circulating heating gas along the gas circulation line 31. The circulating gas heater 33 heats the circulating heating gas to 320 ° C. to 450 ° C., which is an appropriate range, above the decomposition temperature of the ammonium salt of sulfuric acid.

  A first bypass passage 31e is branched from the gas circulation line 31 between the circulation gas heater 33 and the catalytic reaction tower 20 to the heating passage 31b, and an outlet of the first bypass passage 31e is connected to the catalytic reaction tower 20. And the heat exchanger (heating side) 17 is connected to a common flow path portion 31a. By this first bypass flow path portion 31e, the circulating heating gas heated by the circulating gas heater 33 can be directly introduced into the heat exchanger 17 without passing through the catalytic reaction tower 20.

  In addition, the second bypass channel portion 31f is branched from the first bypass channel portion 31e, and the outlet of the second bypass channel portion 31f is connected to the heating channel portion 31b on the upstream side of the circulating gas exhaust channel portion 31c. ing. By this second bypass flow path portion 31f, the circulating heated gas discharged from the catalytic reaction tower 20 can be circulated to the heating flow path portion 31b without passing through the heat exchanger (heating side) 17.

A circulating gas temperature detector T <b> 1 that detects the temperature of the circulating heating gas is installed at the outlet of the circulating gas heater 33. An exhaust gas temperature detector T2 for detecting the temperature of the exhaust gas is provided at the outlet of the bag filter 16. Further, an exhaust gas component detector M for detecting the concentration of ammonia gas (NH ₃ ) and / or sulfur oxide (SO _X ) contained in the exhaust gas is provided at the outlet of the induction fan 21.

  Furthermore, in order to switch the exhaust gas passing through the plurality of lines 10, 30, 31 and the flow path portions 31a to 31f and the flow path of the circulating heating gas, dampers (hereinafter referred to as a plurality of switches that can be opened and closed and the flow rate of which can be adjusted). A switching valve).

  First, the first to seventh switching valves V1 to V7 are provided in the exhaust gas treatment line 10 (including the common flow path portion 31a). That is, in the exhaust gas treatment line 10, the first switching valve V <b> 1 provided on the upstream side at the connection part of the circulating gas exhaust flow path part 31 c, the second provided between the branch part of the bag filter 16 and the bypass exhaust line 30. Between the switching valve V2, the branch portion of the bypass exhaust line 30 and the third switching valve V3 provided between the heat exchanger (heated side) 17 and the connection portion between the gas reheater 18 and the heating flow path portion 31b. Heat exchange with the fourth switching valve V4 provided in the second switching valve V5, the fifth switching valve V5 provided between the catalytic reaction tower 20 and the connection portion of the first bypass flow passage portion 31e, and the connection portion of the first bypass flow passage portion 31e. The sixth switching valve V6 provided between the heaters (heating side) 17 and the seventh switching valve provided between the branching portion of the exhaust gas treatment line 10 and the heating flow path portion 31b and the connection portion of the bypass exhaust line 30. Valve V7.

  Further, the bypass exhaust line 30 is provided with an eighth switching valve V8 in the vicinity of a branch portion with the exhaust gas treatment line 10, and a ninth portion near the connection portion with the exhaust gas treatment line 10 on the downstream side of the eighth switching valve V8. A switching valve V9 is provided.

  An eleventh switching valve V11 and a twelfth switching valve V12 are provided in the gas circulation line 31 excluding the common flow path portion 31a. That is, in the heating flow path part 31b, the 11th switching valve V11 provided between the branch part from the exhaust gas treatment line 10 and the connection part of the second bypass flow path part 31f and the first bypass flow path part 31e branch. And a twelfth switching valve V12 provided between the connecting portion of the exhaust gas treatment line 10 connected to the catalytic reaction tower 20.

  In addition, a thirteenth switching valve (circulation gas discharge valve) V13 is provided in the circulation gas exhaust passage portion 31c between the branch portion of the heating passage portion 31b and the connection portion of the cooling outside air introduction portion 31g. Further, a fourteenth switching valve (cooling outside air introduction valve) V14 is provided in the cooling outside air introduction portion 31g. Furthermore, a fifteenth switching valve (replenishment outside air introduction valve) V15 is provided in the supplementary outside air introduction section 31d. In the first bypass channel 31e, a sixteenth switching valve V16 is provided between the branch of the heating channel 31b and the branch of the second bypass channel 31f. Furthermore, the 17th switching valve V17 is provided in the 2nd bypass flow-path part 31f in the branch part vicinity of the 1st bypass flow-path part 31e.

  41 operates the first to ninth switching valves V1 to V9 and the first to seventeenth switching valves V11 to V17 based on the circulating gas temperature detector T1, the exhaust gas temperature detector T2, and the exhaust gas component detector M. It is a controller for thermal decomposition.

(Furnace operating state)
A normal operation state of the incinerator 11 will be described with reference to FIG.
In a normal operation state, the first to seventh switching valves V1 to V7 are opened, and the remaining eighth and ninth switching valves V8 and V9 and the first to seventeenth switching valves V11 to V17 are closed.

  1) Activated carbon is blown into the exhaust gas discharged from the cooling tower 13 from the activated carbon supply device 14, and adsorbs harmful substances such as heavy metals and dioxin in the exhaust gas to the activated carbon. Further, a neutralizing alkaline chemical such as slaked lime is blown into the exhaust gas from the chemical supply device 15, and this alkaline chemical is reacted with hydrogen chloride, sulfur oxide, etc. in the exhaust gas. And exhaust gas is introduce | transduced into the bag filter 16, and these reaction products and activated carbon adsorbate are collected with soot dust.

  2) The exhaust gas is sequentially introduced into a reheat heat exchanger (heated side) 17 and a gas reheater 18 and heated to a temperature suitable for the catalyst denitration system, and then sent to the catalyst reaction tower 20. In the catalytic reaction tower 20, nitrogen oxides are reduced and removed by injecting a reducing agent such as ammonia gas into the exhaust gas from the ammonia supply device 23 and bringing the exhaust gas into contact with the catalyst.

  3) After exhaust gas is introduced into the heat exchanger (heating side) 17 and heat is recovered by heating the exhaust gas introduced from the bag filter 16 to the catalytic reaction tower 20, the atmosphere is passed through the chimney 22 by the induction fan 21. Drain inside.

(Furnace operation-pyrolysis work)
With reference to FIG. 2, a method for thermally decomposing ammonium salt of sulfuric acid deposited on the catalytic reaction tower 20 and the heat exchanger (heating side) 17 during the operation of the incinerator 11 will be described.

11) aqueous ammonia or urea solution into the incinerator 11, such as by spraying water, performing low NO _X operation with reduced NO _X in the exhaust gas.
12) From the normal operation state, the third switching valve V3, the fourth switching valve V4, and the seventh switching valve V7 are closed, the eighth switching valve V8 and the ninth switching valve V9 are opened, and the exhaust gas discharged from the bag filter 16 Is introduced into the bypass exhaust line 30 and discharged from the induction blower 21 via the chimney 22. At the same time, the eleventh switching valve V11 and the twelfth switching valve V12 are opened (the fifth and sixth switching valves V5 and V6 are opened, and the thirteenth to seventeenth switching valves V13 to V17 are closed), and the circulation blower 32 is activated. The exhaust gas remaining in the system is circulated as a circulating heating gas, and the circulating gas heater 33 is activated to heat the circulating heating gas.

  13) In the thermal decomposition controller 41, the temperature of the circulating heating gas is monitored by the circulating gas temperature detector T1, and when the decomposition temperature of the ammonium salt of sulfuric acid (ammonium sulfate is 280 ° C) or higher, for example, around 320 ° C, By controlling the heating by the circulating gas heater 33 and holding the circulating heated gas at a temperature within a predetermined range (for example, 320 ° C. or higher and 450 ° C. or lower) for a predetermined time, the inside of the catalytic reaction tower 20 and the heat exchanger (heating) Side) Ammonium salt of sulfuric acid deposited in 17 is thermally decomposed. The thermally decomposed ammonia gas and sulfur oxide are accompanied by the circulating heating gas.

  Here, the reason why the temperature of the decomposition heating gas is set to 320 ° C. or more is that if it is less than 320 ° C., there is a possibility that the thermal decomposition of the ammonium salt of sulfuric acid may not be performed sufficiently. This is because there is a possibility of adversely affecting components such as the catalyst of the tower 20 and the heat transfer tubes of the heat exchanger 17.

14) When a predetermined period of time during which the ammonium salt of sulfuric acid in the catalytic reaction tower 20 and the heat exchanger (to-be-heated) 17 is sufficiently pyrolyzed has elapsed based on previously experimental data, the operation of the controller 41 for pyrolysis In response to the command, the thirteenth switching valve V13 is slowly opened, and a part of the circulating heated gas is merged with the exhaust gas of the exhaust gas treatment line 10 and introduced into the bag filter 16. At this time, the pyrolysis controller 41 monitors the temperature of the exhaust gas by the exhaust gas temperature detector T2, and the thirteenth switching valve V13 is used so that the temperature of the exhaust gas is excessively raised by the circulating heating gas and does not adversely affect the bag filter 16. To control the discharge amount of the circulating heating gas. Further, the concentration of ammonia gas (NH ₃ ) and / or sulfur oxide (SO _X ) discharged from the chimney 22 by the exhaust gas component detector M is monitored, and ammonia gas and sulfur oxide in the exhaust gas discharged into the atmosphere. The discharge amount of the circulating heated gas is controlled by operating the thirteenth switching valve V13 so that the concentration of the gas does not increase excessively.

  Further, since the circulating heating gas in the gas circulation line 31 decreases, the 15th switching valve V15 is opened to introduce the outside air into the gas circulation line 31 from the refilling outside air introduction flow path portion 31d, and the circulating gas heater 33 circulates the heating gas. Heat.

  15) Ammonia gas and sulfur oxide entrained in the discharged circulating heating gas are cooled by the combined exhaust gas to form solid ammonium sulfate (ammonium sulfate) or ammonium hydrogen sulfate (acidic ammonium sulfate). It is collected and further reacted with an alkaline agent such as slaked lime in the exhaust gas or adsorbed on activated carbon, and the reaction product and activated carbon adsorbate are collected by the bag filter 16.

  16) In the above method, the case where the ammonium salt of sulfuric acid deposited on the catalyst reaction tower 20 and the heat exchanger 17 is simultaneously pyrolyzed has been described. However, the catalyst reaction tower 20 and the heat exchanger 17 are each pyrolyzed independently. It can also be made.

  For example, when only the ammonium salt of sulfuric acid deposited in the catalytic reaction tower 20 is thermally decomposed, the sixth switching valve V6 and the eleventh switching valve V11 are closed and the seventeenth switching valve V17 is opened (the sixteenth switching valve V16 is closed). Thus, the circulating heating gas discharged from the catalytic reaction tower 20 may be circulated to the heating channel portion 31b via the first bypass channel portion 31e and the second bypass channel portion 31f.

  When only the ammonium salt of sulfuric acid deposited on the heat exchanger 17 is thermally decomposed, the twelfth switching valve V12, the fifth switching valve V5, and the seventeenth switching valve V17 are closed, and the sixth switching valve V6 and the sixteenth switching valve V16. The circulation heating gas discharged from the circulation gas heater 33 may be introduced into the heat exchanger (heating side) 17 from the first bypass channel 31e and the common channel 31a.

(Furnace shutdown-pyrolysis work)
With reference to FIG. 3, a method for thermally decomposing ammonium salt of sulfuric acid deposited on the catalytic reaction tower 20 and the heat exchanger (heating side) 17 while the incinerator 11 is stopped will be described.

21) Before stopping the incinerator 11, activated carbon or an alkaline chemical is blown into the bag filter 16 from the activated carbon supply device 14 and the chemical supply device 15 for about several tens of minutes to several hours.
22) The first switching valve V1, the third switching valve V3, and the fourth switching valve V4 are closed, and the eleventh switching valve V11, the twelfth switching valve V12, the fifth switching valve V5, and the sixth switching valve V6 are opened (seventh). To ninth switch valve V7 to V9 and thirteenth to seventeenth switch valves V13 to V17 are closed). Then, the circulation blower 32 is activated to circulate the exhaust gas remaining in the system of the gas circulation line 31 as the circulation heating gas, and the circulation gas heater 33 is activated to heat the circulation heating gas.

  23) In the thermal decomposition controller 41, the temperature of the circulating heating gas is monitored by the circulating gas temperature detector T1, as in the previous step 13), and the decomposition temperature of the ammonium salt of sulfuric acid (ammonium sulfate is 280 ° C.) or higher. Thus, for example, when the temperature is around 320 ° C., the heating of the circulating gas heater 33 is controlled to maintain the circulating heating gas at a temperature within a predetermined range (for example, 320 ° C. or higher and 450 ° C. or lower) for a predetermined time. Then, the ammonium salt of sulfuric acid deposited in the catalytic reaction tower 20 and the heat exchanger (heating side) 17 is thermally decomposed by the circulating heating gas. The thermally decomposed ammonia gas and sulfur oxide are accompanied by the circulating heating gas.

  24) As in the previous step 14), when a predetermined time for the ammonium salt of sulfuric acid in the catalytic reaction tower 20 and the heat exchanger (heating side) 17 to be thermally decomposed has elapsed based on previously experimented data, In response to an operation command from the decomposition controller 41, the induction fan 21 is activated simultaneously with opening the thirteenth switching valve V13, the fourteenth switching valve V14, the eighth switching valve V8, and the ninth switching valve V9. That is, the thirteenth switching valve V13 is opened and a part of the circulating heating gas is sent to the circulating gas discharge path portion 31c. At the same time, the fourteenth switching valve V14 is opened and the circulating gas discharge path portion from the cooling outside air introduction flow path portion 31g is opened. The outside air is introduced into 31c, and the circulating heated gas discharged by the outside air is cooled. Then, the mixed gas of the circulating heating gas and the outside air is introduced into the bag filter 16 through the exhaust gas treatment line 10. At this time, the ammonia gas and sulfur oxide entrained in the circulating heating gas are cooled by mixing with the combined outside air, and become solid ammonium sulfate (ammonium sulfate) or ammonium hydrogen sulfate (acidic ammonium sulfate) by the bag filter 16. It is collected or further reacted with an alkaline agent such as slaked lime remaining on the bag filter 16 or adsorbed on the activated carbon and collected by the bag filter 16. The mixed gas is discharged from the bypass exhaust line 30 via the induction blower 21 and the chimney 22.

25) In the pyrolysis controller 41, the temperature of the exhaust gas at the bag filter 16 outlet is monitored by the exhaust gas temperature detector T2, and ammonia gas (NH ₄ ) and / or sulfur oxidation discharged from the chimney 22 by the exhaust gas component detector monitors the concentration of the object (sO _X), so as not to adversely affect the temperature of the exhaust gas is too high the bag filter 16, also the concentration of ammonia gas and sulfur oxides in the exhaust gas released into the atmosphere The exhaust amount of the circulating heating gas is controlled by adjusting the opening degrees of the thirteenth switching valve V13 and the fourteenth switching valve V14 so as not to increase too much. Further, since the circulating heating gas in the gas circulation line 31 decreases, the 15th switching valve V15 is opened to introduce the outside air into the gas circulation line 31 from the refilling outside air introduction flow path portion 31d, and the circulating gas heater 33 circulates the heating gas Heat.

  26) In the above method, the case where the ammonium salt of sulfuric acid deposited on the catalytic reaction tower 20 and the heat exchanger 17 is pyrolyzed at the same time has been described. However, as in the step 16), the catalytic reaction tower 20 or the heat exchanger. The 17 sulfuric acid ammonium salts can also be thermally decomposed independently.

(Effect of Example 1)
According to Example 1,
A) The exhaust gas discharged from the bag filter 16 is discharged from the induction blower 21 through the chimney 22, and the circulation heating gas is supplied from the circulation blower 32 via the circulation gas heater 33 to the ammonium salt of sulfuric acid. Since the gas circulation line 31 is provided to heat the gas to a temperature at which it can be pyrolyzed and circulates to the catalyst reaction tower 20 and the heat exchanger 17, the gas is deposited on the catalyst reaction tower 20 and the heat exchanger 17 during operation of the incinerator 11. Ammonium sulfates such as ammonium sulfate [ammonium sulfate, (NH ₄ ) ₂ SO ₄ ] and ammonium hydrogen sulfate [acid ammonium sulfate, NH ₄ HSO ₄ ] can be effectively thermally decomposed. Thus, since the circulating heating gas can be heated and circulated along the gas circulation line 31 and repeatedly used, the thermal energy cost can be reduced. And the piping structure and the structure of the catalyst denitrator can be simplified, and the equipment cost can be reduced.

  B) The pyrolysis gas (ammonia gas and sulfur oxide) entrained in the circulating cracked gas is cooled by the exhaust gas joined at the inlet of the bag filter 16, and is solid ammonium sulfate (ammonium sulfate) or ammonium hydrogen sulfate (acid ammonium sulfate). ), Reacts with an alkaline agent such as slaked lime in exhaust gas, or is adsorbed by activated carbon and collected by the bag filter 16. Accordingly, it is possible to effectively prevent the pyrolysis gas component from being included in the exhaust gas discharged into the atmosphere.

  C) Even when the incinerator 11 is stopped, the circulating heating gas can be circulated through the gas circulation line 31 to thermally decompose the ammonium salt of sulfuric acid deposited on the catalytic reaction tower 20 or the heat exchanger 17. In addition, since a part of the circulating heating gas leading out can be cooled by mixing outside air from the cooling outside air introduction flow path portion 31g, a mixed gas at an appropriate temperature can be introduced into the bag filter 16, and the bag filter 16 burnout can be prevented.

D) By controlling the temperature of the circulating heating gas to be equal to or higher than the thermal decomposition temperature of the sulfuric acid ammonium salt by the thermal decomposition controller 41, the sulfuric acid ammonium salt can be effectively thermally decomposed. Further, when the circulating heating gas is discharged, the circulating heating gas derived from the gas circulation line 31 and the exhaust gas are mixed to control the temperature of the exhaust gas, thereby preventing the bag filter 16 from being burned out.
E) Even when the incinerator 11 is stopped, the temperature of the circulating heating gas is controlled by the thermal decomposition controller 41 to be equal to or higher than the thermal decomposition temperature of the ammonium salt of sulfuric acid, so that the catalytic reaction tower 20 and the heat exchanger 17 Ammonium salt of sulfuric acid can be effectively thermally decomposed. Further, the circulating heating gas derived from the gas circulation line 31 is cooled by mixing the outside air for cooling, so that the pyrolysis component contained in the circulating heating gas is solidified and further left for neutralization and adsorption. It can be collected by the bag filter 16 after being reacted and adsorbed with a chemical for use. Further, it is possible to prevent the bag filter 16 from being burned out.

[Example 2]
Next, a second embodiment of the present invention will be described with reference to FIGS.
(Basic structure)
This exhaust gas treatment facility is equipped with a preheating gas heating line for preheating by sending warm air to the bag filter at the start-up to prevent dew point corrosion due to condensation on the bag filter and deliquescence of slaked lime. A preheating heater and a preheating blower are provided. As shown in FIG. 5, in the second embodiment, in the exhaust gas treatment facility provided with the preheating gas heating line 50, the gas circulation line 31 is provided similarly to the first embodiment, and the preheating heater is used as the circulation gas heater 33 </ b> A. And a preheating blower is used as the circulation blower 32A. Hereinafter, the same members as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

(Preheating gas heating line)
The preheating gas heating line 50 is branched from the exhaust gas treatment line 10 on the outlet side of the bag filter 16 and is connected to the inlet of the circulation fan 32A, and the bag filter 16 is connected to the outlet of the circulation gas heater 33A. The discharge flow path part 50b connected to the exhaust gas treatment line 10 on the outlet side of the gas is provided, and the outlet of the circulating fan 32A and the inlet of the circulating gas heater 33A are connected.

  And the discharge flow path part 50b is used as the circulation gas exhaust flow path part 31c. The heating channel 31b is connected to the outlet of the common channel 31a and reaches the inlet of the circulating gas heater 33A. The upstream heating channel 31b1 reaches the inlet of the catalytic reaction tower 20 from the outlet of the circulating gas heater 33A. It is comprised with the downstream heating flow-path part 31b2 connected to the waste gas processing line 10 of this.

  Further, the exhaust bypass flow path portion 31h is branched to the suction flow path portion 50a between the branch port of the exhaust gas treatment line 10 and the connection portion of the upstream heating flow path portion 31b1, and the outlet of the exhaust bypass flow path portion 31h is the circulating gas. It is connected to the exhaust flow path part 31c (discharge flow path part 50b). A cooling outside air introduction flow path 31g is connected to the circulation gas exhaust flow path 31c (discharge flow path 50b).

Furthermore, the replenishment outside air introduction flow path portion 31d is connected to the suction flow path portion 50a between the connection portion of the upstream heating flow path portion 31b1 and the inlet of the circulation fan 32A.
The preheating gas line 50 is provided with a twenty-second switching valve V22 between the inlet of the suction flow passage 50a and the branch of the discharge bypass flow passage 31h, and the discharge flow passage 50b is connected to the circulating gas heater 33A. A 23rd switching valve V23 is provided between the outlet and the connection portion of the discharge bypass flow passage 31h, and the 23rd switching valve V23 is not opened during the decomposition process. Further, a 21st switching valve V21 is provided between the connection part and the outlet of the cooling outside air introduction flow path part 31g in the discharge flow path part 50b. Furthermore, a thirteenth switching valve V13 is provided in the discharge bypass flow path portion 31h.

Furthermore, a circulating gas temperature detector T1 is installed in the vicinity of the outlet of the circulating gas heater 33A.
(Furnace operating state)
Since the operation state of the incinerator 11 is the same as that of Example 1 as shown in FIG. 4, description is abbreviate | omitted.

(Furnace operation-pyrolysis work)
With reference to FIG. 5, a method for thermally decomposing ammonium salt of sulfuric acid deposited on the catalytic reaction tower 20 and the heat exchanger (heating side) 17 during the operation of the incinerator 11 will be described. Since this thermal decomposition method is the same as in Example 1, only the outline will be described.

31) The incinerator 11 is operated at low NO _X.
32) The exhaust gas exhaust route discharged from the bag filter 16 is switched from the exhaust gas treatment line 10 to the bypass exhaust line 30. The circulation blower 32A is activated to circulate the exhaust gas remaining in the system of the gas circulation line 31 as a circulation heating gas, and the circulation heating gas is heated by the circulation gas heater 33A.

  33) When the temperature of the circulating heating gas reaches about 320 ° C. above the decomposition temperature of the ammonium salt of sulfuric acid by the thermal decomposition controller 41, the circulating gas heater 33A is controlled to make the circulating heating gas at 320 ° C. or higher and 450 ° C. The following is held for a predetermined time. Thereby, the ammonium salt of sulfuric acid deposited in the catalytic reaction tower 20 and the heat exchanger (heating side) 17 is thermally decomposed.

34) When the time required for the thermal decomposition of the ammonium salt of sulfuric acid has elapsed, after the 21st switching valve V21 is opened, the 13th switching valve V13 is slowly opened, and a part of the circulating heating gas is exhausted from the exhaust gas treatment line 10. And is introduced into the bug filter 16. At this time, the amount of circulating heated gas discharged is controlled by the thermal decomposition controller 40 so as not to adversely affect the bag filter 16. Further, the exhaust gas component detector M controls the thirteenth switching valve V13 so that the concentration of ammonia gas (NH ₃ ) and sulfur oxide (SO _X ) discharged from the chimney 22 does not rise too much, thereby discharging the circulation heating gas. Control the amount.

Further, outside air is introduced into the gas circulation line 31 from the replenishment outside air introduction flow path portion 31 d and mixed with the circulating heating gas in the gas circulation line 31.
35) Ammonia gas and sulfur oxide entrained in the circulating heating gas discharged are cooled by the combined exhaust gas to form solid ammonium sulfate (ammonium sulfate) or ammonium hydrogen sulfate (acid ammonium sulfate), or slaked lime in the exhaust gas The reaction product and the activated carbon adsorbate are collected by the bag filter 16 by reacting with an alkaline agent such as, or adsorbed on the activated carbon.

  In the above method, the case where the ammonium salt of sulfuric acid deposited on the catalytic reaction tower 20 and the heat exchanger 17 is simultaneously pyrolyzed has been described. However, the catalytic reaction tower 20 and the heat exchanger 17 are each pyrolyzed independently. You can also.

(Furnace shutdown-pyrolysis work)
With reference to FIG. 6, a method for thermally decomposing ammonium salt of sulfuric acid deposited on the catalytic reaction tower 20 and the heat exchanger (heating side) 17 while the incinerator 11 is stopped will be described. Since this thermal decomposition method is the same as in Example 1, only the outline will be described.

  41) Before stopping the operation of the incinerator 11, activated carbon or an alkaline chemical is blown into the bag filter 16 from the activated carbon supply device 14 and the chemical supply device 15 for about several tens of minutes to several hours.

  42) The exhaust gas exhaust path exhausted from the bag filter 16 is switched from the exhaust gas treatment line 10 to the bypass exhaust line 30. After the gas circulation line 31 is closed, the circulation blower 32A is activated to circulate the exhaust gas remaining in the system of the gas circulation line 31 as a circulation heating gas, and the circulation gas heater 33A is activated to circulate. Heat the heated gas.

  43) When the temperature of the circulating heating gas reaches about 320 ° C. above the decomposition temperature of the ammonium salt of sulfuric acid by the thermal decomposition controller 41, the circulating gas heater 33A is controlled to make the circulating heating gas at 320 ° C. or higher and 450 ° C. The following is held for a predetermined time. Thereby, the ammonium salt of sulfuric acid deposited in the catalytic reaction tower 20 and the heat exchanger (heating side) 17 is thermally decomposed.

  44) When the time required for the thermal decomposition of the ammonium salt of sulfuric acid has elapsed, after the 21st switching valve V21 is opened, the 13th switching valve V13 is slowly opened, and a part of the circulating heating gas is supplied to the discharge flow path section 50b. Simultaneously with the discharge, the fourteenth switching valve V14 is opened, the outside air is introduced from the cooling outside air introduction passage portion 31g to the discharge passage portion 50b, and the circulating heating gas is cooled to a temperature suitable for the bag filter 16 by the outside air. Then, a mixed gas of the circulating heating gas and the outside air is introduced into the bag filter 16. Ammonia gas and sulfur oxide, which are thermal decomposition components entrained by the circulating heating gas, are cooled by mixing with the outside air that has been combined into solid ammonium sulfate (ammonium sulfate) or ammonium hydrogensulfate (acidic ammonium sulfate). , And collected by the bug filter 16. Further, the pyrolysis component accompanying the circulating heating gas reacts with an alkaline agent such as slaked lime remaining in the bag filter 16 or is adsorbed by the activated carbon and collected by the bag filter 16. Then, the mixed gas is discharged from the bypass exhaust line 30 through the induction blower 21 and the chimney 22.

45) At this time, the discharge amount of the circulating heating gas and the introduction amount of the outside air are controlled by the thermal decomposition controller 41 so as not to adversely affect the bag filter 16. Further, the thirteenth switching valve V13 is operated to discharge the circulating heating gas so that the concentrations of ammonia gas (NH ₃ ) and sulfur oxide (SO _X ) discharged from the chimney 22 by the exhaust gas component detector M do not increase excessively. The amount is controlled. Further, outside air is introduced into the gas circulation line 31 from the supplementary outside air introduction flow path portion 31d in response to the decrease in the circulating heating gas.

  46) The above method is a case where the ammonium salt of sulfuric acid deposited on the catalyst reaction tower 20 and the heat exchanger 17 is simultaneously pyrolyzed, but each of the ammonium salts of sulfuric acid in the catalyst reaction tower 20 or the heat exchanger 17 is independently used. It can also be pyrolyzed.

  According to the said Example 2, there can exist an effect similar to Example 1. FIG. Moreover, it can be used as the circulating gas heater 33A and the circulating blower 32A by using the preheating heater and the preheating blower of the existing preheating gas heating line 50, and the existing equipment is effectively used to reduce the equipment cost. Can be reduced.

DESCRIPTION OF SYMBOLS 10 Exhaust gas treatment line 11 Incinerator 14 Activated carbon supply apparatus 15 Chemical supply apparatus 16 Bag filter 17 Heat exchanger 20 Catalytic reaction tower 21 Induction fan 22 Chimney 23 Ammonia supply apparatus 30 Bypass exhaust line 31 Gas circulation line 31a Common flow path part 31b Heating Channel portion 31b1 Upstream heating channel portion 31b2 Downstream heating channel portion 31c Circulating gas exhaust channel portion 31d Replenishment outside air introduction channel portion 31e First bypass channel portion 31f Second bypass channel portion 31g Cooling outside air Introduction flow passage 31h Discharge bypass flow passage 32 Circulation fan 32A Circulation fan 33 Circulation gas heater 33A Circulation gas heater 41 Pyrolysis controller T1 Circulation gas temperature detector T2 Exhaust gas temperature detector M Exhaust gas component detector V13 13th Switching valve (circulation gas discharge valve)
V14 14th switching valve (cooling outside air introduction valve)
V15 Fifteenth switching valve (replenishment outside air introduction valve)
50 Preheating gas heating lines V21 to V23 21st to 23rd switching valves

Claims (9)

A method for removing ammonium salts of sulfuric acid in an exhaust gas treatment line equipped with a bag filter, a heat exchanger and a catalytic reaction tower from an upstream side to an exhaust gas treatment line of exhaust gas discharged from a furnace,
During the operation of the furnace, exhaust gas discharged from the bag filter is discharged to the atmosphere side,
A circulating heating gas is circulated through a gas circulation line provided with at least one of the catalytic reaction tower and the heat exchanger, a circulation fan, and a circulation gas heater, and the circulation gas is circulated by the circulation gas heater. Thermally decomposing ammonium salt of sulfuric acid deposited in the catalytic reaction tower or / and in the heat exchanger by heating,
In an exhaust gas treatment facility characterized in that a part of the circulating heating gas is discharged into the exhaust gas and introduced into the bag filter, and the pyrolysis components accompanying the circulating heating gas are collected and then discharged into the atmosphere. Method for removing ammonium salt of sulfuric acid. The furnace was operated at reduced NO _X in the exhaust gas,
The method for removing ammonium salt of sulfuric acid in an exhaust gas treatment facility according to claim 1, wherein a part of the circulating heating gas is led out to the bag filter and simultaneously outside air is introduced into the gas circulation line. From the upstream side of the exhaust gas treatment line of exhaust gas discharged from the furnace, a method for removing ammonium salt of sulfuric acid in an exhaust gas treatment facility equipped with a bag filter, a heat exchanger and a catalytic reaction tower,
While the furnace is stopped, circulating heating gas is circulated through a gas circulation line provided with at least one of the catalytic reaction tower and the heat exchanger, a circulation fan, and a circulation gas heater, and the circulation gas heater By heating the circulating heating gas to thermally decompose the ammonium salt of sulfuric acid deposited in the catalytic reaction tower or / and in the heat exchanger,
Furthermore, after mixing and cooling the outside air to a part of the circulating heating gas discharged from the gas circulation line, introducing it into the bag filter, and collecting the pyrolysis components accompanying the circulating heating gas, A method for removing ammonium salt of sulfuric acid in an exhaust gas treatment facility, characterized by The method for removing ammonium salt of sulfuric acid in an exhaust gas treatment facility according to claim 3, wherein a predetermined amount of neutralizing and / or adsorbing chemical is blown into the bag filter before the furnace is stopped. From the upstream side of the exhaust gas treatment line of exhaust gas discharged from the furnace, a bag filter that collects salts, adsorbate and soot, a heat exchanger that heats the exhaust gas, and a catalytic reaction tower that removes nitrogen oxides from the exhaust gas An exhaust gas treatment facility comprising:
Provide a bypass exhaust line for exhausting the exhaust gas discharged from the bag filter to the atmosphere side,
A circulating blower, a circulating gas heater, and at least one of the catalytic reaction tower and the heat exchanger, and the catalytic reaction tower and / or the heat exchange with the circulating heating gas heated by the circulating gas heater A gas circulation line to decompose the ammonium salt of sulfuric acid accumulated in the vessel,
Providing a circulating gas exhaust passage section for leading a part of the circulating heating gas of the gas circulation line to an inlet of the bag filter;
When exhausting a part of the circulating heating gas, a replenishment outside air introduction flow path section for introducing outside air into the gas circulation line is provided,
An exhaust gas treatment facility characterized in that a pyrolysis component of a circulating heating gas discharged from the circulating gas exhaust flow path is collected by the bag filter and discharged from the bypass exhaust line. In the circulating gas exhaust flow path section, a cooling external air introduction flow path section for mixing and cooling the outside air with the circulating heating gas is provided,
6. The circulating heating gas discharged from the circulating gas exhaust flow path during shutdown of the furnace is mixed with the external air from the cooling external air introduction flow path, cooled, and introduced into the bag filter. Exhaust gas treatment equipment. A circulating gas temperature detector for detecting the temperature of the circulating heating gas in the gas circulation line;
An exhaust gas temperature detector for detecting the exhaust gas temperature at the bag filter outlet;
An exhaust gas component detector for detecting the concentration of ammonia gas and / or sulfur oxide in the exhaust gas discharged from the bypass exhaust line;
A circulation gas discharge valve provided in the circulation gas exhaust passage,
A replenishment outside air introduction valve provided in the replenishment outside air introduction flow path section;
A thermal decomposition controller for controlling the opening degree of the circulating gas discharge valve and the outside air introduction valve,
The pyrolysis controller controls the temperature of the circulating heating gas based on the detected value of the circulating gas temperature detector during operation of the furnace, and the detected values of the exhaust gas temperature detector and the exhaust gas component detector. The exhaust gas treatment facility according to claim 5, wherein the opening degree of the circulating gas discharge valve and the supplementary outside air introduction valve is controlled based on A cooling outside air introduction valve provided in the cooling outside air introduction flow path section;
The thermal decomposition controller
While the furnace is stopped, the temperature of the circulating heating gas is maintained within a proper temperature range in which the ammonium salt of sulfuric acid can be decomposed for a predetermined time, and the ammonium salt of sulfuric acid deposited in the catalytic reaction tower and / or the heat exchanger After opening the circulating gas discharge valve, a part of the circulating heating gas is led out to the circulating gas exhaust passage part, and the outside air introduction valve for cooling is opened, and the outside air is supplied to the circulating gas exhaust passage part. The exhaust gas treatment facility according to claim 6, wherein the exhaust gas treatment facility is introduced to cool the circulating heating gas and control the temperature of the mixed gas of the circulating heating gas and the outside air to a range suitable for the bag filter. The bag filter preheater and the bag filter preheat blower installed for preheating the bag filter are installed in a gas circulation line so that they can be used as a circulation blower and a circulation gas heater. The exhaust gas treatment facility described.

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