JP2004154683A - Exhaust gas treatment equipment and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of economically removing sulfuric acid mist. <P>SOLUTION: The exhaust gas treatment equipment is provided with an air pre-heating unit 3 for heating combustion air by exhaust gas discharged from a boiler; a heat recovery unit 11 for heating a heating medium by the exhaust gas; a wet type exhaust gas treatment device 6 for wet-treating the exhaust gas; a re-heating unit 13 for heating the exhaust gas by the heating medium; and a heating medium circulation line 15 for circulating the heating medium between the re-heating unit 13 and the heat recovery unit 11. The dew point of the sulfuric acid mist in the exhaust gas is between the temperature of the exhaust gas at an entrance of the heat recovery unit 11 and the temperature of the exhaust gas at a discharge port of a dust-collector 4 and is adjusted such that it becomes higher than the temperature of the exhaust gas at the discharge port of the dust-collector 4 by 30°C or more. <P>COPYRIGHT: (C)2004,JPO

Description

【００４１】
【実施例２】
図１に示した排ガス処理システムにおいて、硫酸ミスト濃度を測定し、該硫酸ミスト濃度測定値に基づき電気集塵器４出口の排ガス温度を制御する（図４参照）ことも可能である。
【００４２】
図３に、本実施例に係る熱回収器１１と再加熱器１３の熱媒循環系統の詳細図を示す。熱回収器１１と再加熱器１３のそれぞれの伝熱管１２と伝熱管１４は、熱媒循環管路１５−１、１５−２により環状に連結され、その管路の途中に設けられた循環ポンプ１０により、それらの伝熱管１２、１４内に熱媒が循環されるようになっている。伝熱管１２、１４は、熱交換の効率を向上させるために、フィンチューブ等が用いられる。熱媒循環管路１５−２には、管路の熱媒の膨張を吸収するために熱媒タンク２６が設置されている。
【００４３】
電気集塵器４出口の排ガス温度を制御する具体的な方法は下記のものが挙げられる。
熱回収器１１の出口排ガス温度を制御するために、熱媒バイパスライン１６が設けられ、電気集塵器４の出口排ガス温度を計測するミスト濃度計２２の信号により算出される電気集塵器４の出口でのミスト濃度が設定範囲となるように、熱媒バイパスライン１６に設けられた流量調整弁１８の開度を調整して熱回収量を制御している。また、熱媒循環管路１５−２には熱交換器１９が接続され、ここに蒸気または冷却水を供給管２０から流量調整弁２１の開度を調整して流すことにより熱回収器１１の出口排ガス温度を制御して、電気集塵器４の出口でのミスト濃度を制御する。
【００４４】
なお、上記実施例１では電気集塵器４の出口排ガス温度を測定しているが、電気集塵器４での排ガス温度低下が小さい場合は、熱回収器１１出口や電気集塵器４入口での排ガス温度を代わりに測定することも可能である。また、実施例２では電気集塵器４の出口でのミスト濃度の代わりに煙突８入口でのミスト濃度を測定することも可能である。
【００４５】
【発明の効果】
本発明によれば、経済的に煙突から排出される排ガス中の硫酸ミスト濃度を低減することができる。また、アルカリ性が高い石炭灰で硫酸ミストを中和して無害化するため、機器の腐食を防止することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態の排ガス処理システムの基本系統図である。
【図２】本発明の実施例１の排ガス処理システムの部分詳細構造図である。
【図３】本発明の実施例２の排ガス処理システムの部分詳細構造図である。
【図４】本発明の排ガス処理システムに関する排ガス中のＳＯ_３濃度と排ガス中の硫酸の露点温度との関係図である。
【図５】ＳＯ_３含有ガスと石炭灰の反応性を示す図である。
【符号の説明】
１：ボイラ ２：脱硝装置 ３：空気予熱器 ４：電気集塵器 ５：誘引ファン ６：湿式脱硫装置 ７：脱硫ファン ８：煙突 １０：ポンプ １１：熱回収器 １２：伝熱管 １３：再加熱器 １４：伝熱管
１５：熱媒循環管路 １６：熱媒バイパスライン １７：温度計 １８：流量調整弁 １９：熱交換器 ２０：供給管 ２１：流量調整弁 ２２：ミスト濃度計 ２５：排ガスダクト ２６：熱媒タンク[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas treatment device (also referred to as an exhaust gas treatment device) and an operation method thereof, and particularly to an exhaust gas treatment device for reducing the concentration of SO ₃ mist in exhaust gas discharged from a chimney. The present invention relates to an exhaust gas treatment apparatus in which a heat recovery device for reheating is arranged upstream of a dust collector such as a bag filter or an electric dust collector to keep the exhaust gas temperature at the outlet of the dust collector low, and an operation method thereof.
[0002]
[Prior art]
When coal is burned, sulfur (S) in the coal reacts with oxygen to generate sulfurous acid gas (SO ₂ ), and a part thereof is oxidized by a denitration catalyst or the like in a denitration device provided upstream of a combustion device exhaust gas duct. To SO ₃ . SO ₂ can be removed by a desulfurization device disposed in an exhaust gas duct on the downstream side of the denitration device, but SO ₃ reacts with moisture in the exhaust gas to form a sulfuric acid mist (H ₂ SO ₄ ) when the temperature of the exhaust gas decreases. . If the temperature of the exhaust gas falls below the dew point of sulfuric acid, liquefied sulfuric acid mist (H ₂ SO ₄ ) causes corrosion of equipment materials.
[0003]
For this reason, it is necessary to maintain the temperature of the exhaust gas at a temperature equal to or higher than the sulfuric acid dew point + α (normally 10 to 20 ° C.) up to the dust collector outlet. In consideration of sulfuric acid dew point, Ni-based high Cr high Mo called titanium alloy, tantalum alloy, Inconel 625 or Hastelloy C excellent in sulfuric acid corrosion resistance for air preheater, dry electric dust collector and GGH (gas gas heater) The use of alloys is conceivable, but these materials are 5 to 20 times more expensive than general-purpose stainless steel and are difficult to use for economic reasons.
[0004]
On the other hand, by maintaining the temperature of the exhaust gas at the sulfuric acid dew point + α (normally 10 to 20 ° C.) or more up to the outlet of the dust collector, corrosion of various devices can be prevented, but the exhaust gas temperature is kept downstream of the dust collector. The temperature drops to about 50 to 60 ° C. in the wet desulfurization device installed in the exhaust gas duct of the above, so that it becomes lower than the dew point in the wet desulfurization device and becomes sulfuric acid mist. Since the sulfuric acid mist has a small particle size, it cannot be removed very much by a wet desulfurization apparatus. The removal rate varies depending on the concentration and particle size of the sulfuric acid mist, the structure of the wet desulfurization apparatus, and the ratio (L / G) between the absorbent and the exhaust gas, but is about 10 to 50%.
[0005]
For this reason, the sulfuric acid mist is discharged from the chimney together with the dust that has not been removed by the dust collector, which causes purple smoke. Furthermore, naturally, the sulfuric acid mist discharged from the chimney has a great adverse effect on the environment, such as causing acid rain. As a method for removing the sulfuric acid mist, it is possible to install a wet dust collector in an exhaust gas duct downstream of the wet desulfurization device, but in this case, the cost of the device increases.
[0006]
As described above, in the conventional technology, it is difficult to economically remove sulfuric acid mist and prevent purple smoke, and corrosion of equipment materials of an exhaust gas treatment device is inevitable.
[0007]
The control of the exhaust gas temperature at the outlet of the heat recovery unit is described in JP-A-09-122438 and JP-A-11-347332.
[0008]
[Patent Document 1]
JP 09-122438 A
[Patent Document 2]
JP-A-11-347332
[Problems to be solved by the invention]
In the above-mentioned prior art, corrosion of equipment cannot be prevented unless expensive materials are used, and sulfuric acid mist cannot be removed unless expensive equipment is used.
[0011]
An object of the present invention is to propose an exhaust gas treatment apparatus and method for effectively removing sulfuric acid mist in exhaust gas and preventing corrosion of equipment materials of the exhaust gas treatment apparatus.
[0012]
[Means for Solving the Problems]
The above object of the present invention can be solved by the following means.
According to the first aspect of the present invention, there is provided an air preheater that preheats combustion air of a combustion device by exhaust gas discharged from the combustion device, and a heat transfer tube group that collects heat of the exhaust gas at the outlet of the air preheater into a heat medium. A collector, a dust collector for collecting dust in the exhaust gas at the outlet of the heat recovery unit, a wet desulfurization device for removing sulfur oxides in the exhaust gas at the outlet of the dust collector, and an exhaust gas at the outlet of the wet desulfurization device. And a reheater consisting of a group of heat transfer tubes for heating with a heat medium supplied from the heat recovery unit are sequentially arranged from the upstream side to the downstream side of the exhaust gas duct of the combustion device, and are provided in the heat recovery unit and the reheater, respectively. In a flue gas treatment apparatus provided with a heat medium circulation line for communicating a heat transfer tube and circulating a heat medium inside the heat transfer tube, the dew point of sulfuric acid (SO ₃ ) mist in the exhaust gas indicates the temperature of the exhaust gas at the inlet of the heat recovery unit. And the exhaust gas temperature at the outlet of the dust collector Ri, and an exhaust gas treatment apparatus provided with an outlet exhaust gas temperature control means of the dust collector to a high state 30 ° C. or higher than the temperature of the exhaust gas in the dust collector outlet.
[0013]
2. The exhaust gas treatment apparatus according to claim 1, wherein the exhaust gas temperature control means at the outlet of the dust collector comprises: (1) the dew point of sulfuric acid (SO ₃ ) mist in the exhaust gas indicates the dew point of the exhaust gas temperature at the inlet of the heat recovery device; The exhaust gas temperature at the outlet of the dust collector and (2) the exhaust gas temperature at the outlet of the dust collector may be higher than the exhaust gas temperature by 30 ° C. or more.
[0014]
Further, in the exhaust gas treatment device according to claim 1, the outlet exhaust gas temperature control means of the dust collector is a heat medium circulation flow rate adjustment means of a heat medium circulation line between the reheater and the heat recovery device or It may be configured to be at least one of a means for cooling the heat medium and a means for heating the heat medium.
[0015]
Further, in the exhaust gas treatment apparatus according to claim 1, a heat medium circulation line that branches off from a heat medium circulation line between the reheater and the heat recovery unit and passes through a heat transfer tube of the heat recovery unit is bypassed. A bypass line for circulating a heat medium only in the heat transfer tube of the reheater is provided, and the outlet exhaust gas temperature control means of the dust collector is a means for adjusting a heat medium flow rate of the bypass line. be able to.
[0016]
According to a fifth aspect of the present invention, there is provided an air preheater for preheating combustion air of a combustion device by exhaust gas discharged from the combustion device, and a heat transfer tube group for collecting heat of the exhaust gas at the outlet of the air preheater into a heat medium. A collector, a dust collector for collecting dust in the exhaust gas at the outlet of the heat recovery unit, a wet desulfurization device for removing sulfur oxides in the exhaust gas at the outlet of the dust collector, and an exhaust gas at the outlet of the wet desulfurization device. And a reheater consisting of a group of heat transfer tubes for heating with a heat medium supplied from the heat recovery unit are sequentially arranged from the upstream side to the downstream side of the exhaust gas duct of the combustion device, and are provided in the heat recovery unit and the reheater, respectively. In the exhaust gas treatment device provided with a heat medium circulation line that communicates the heat transfer tubes and circulates the heat medium therein,
The collector to the dust outlet sulfate in the exhaust gas (SO ₃₎ sulfate (SO ₃₎ to measure the mist concentration provided mist densitometer, based on the measured value of the sulfuric acid (SO ₃₎ mist densitometer, sulfuric acid in the exhaust gas ( SO ₃ ) an exhaust gas treatment apparatus provided with exhaust gas temperature control means at the outlet of the dust collector so that the dew point of the mist is between the exhaust gas temperature at the inlet of the heat recovery device and the exhaust gas temperature at the outlet of the dust collector. It is.
[0017]
In the exhaust gas treatment apparatus of claim 5, the outlet exhaust gas temperature control means of said dust collector on the basis of the measured values of sulfate (SO ₃₎ mist densitometer, the dew point of sulfuric acid (SO ₃₎ mist in the exhaust gas, wherein The exhaust gas temperature at the inlet of the heat recovery unit and the exhaust gas temperature at the outlet of the dust collector, and higher than the exhaust gas temperature at the outlet of the dust collector by 30 ° C. or more can be adopted.
[0018]
Further, in the exhaust gas treatment apparatus according to claim 5, the exhaust gas temperature control means at the outlet of the dust collector is a heat medium circulation flow rate adjusting means of a heat medium circulation line between the reheater and the heat recovery unit, or Any one or more of a means for cooling the heat medium and a means for heating the heat medium can be provided.
[0019]
Further, in the exhaust gas treatment apparatus according to claim 5, a heat medium circulation line branched from the heat medium circulation line between the reheater and the heat recovery unit and passing through a heat transfer tube of the heat recovery unit is bypassed. A bypass line that circulates a heat medium only in the heat transfer tube of the reheater is provided, and the outlet exhaust gas temperature control means of the dust collector is a means for adjusting the heat medium flow rate of the bypass line. You can also.
[0020]
According to a ninth aspect of the present invention, there is provided a heat exchanger comprising an air preheater for preheating combustion air of a combustion device by exhaust gas discharged from the combustion device, and a heat transfer tube group for recovering heat of the exhaust gas at the outlet of the air preheater to a heat medium. A collector, a dust collector for collecting dust in the exhaust gas at the outlet of the heat recovery unit, a wet desulfurization device for removing sulfur oxides in the exhaust gas at the outlet of the dust collector, and an exhaust gas at the outlet of the wet desulfurization device. And a reheater consisting of a group of heat transfer tubes for heating with a heat medium supplied from the heat recovery unit are sequentially arranged from the upstream side to the downstream side of the exhaust gas duct of the combustion device, and are provided in the heat recovery unit and the reheater, respectively. In an operation method of an exhaust gas treatment apparatus provided with a heat medium circulating line that communicates the heat transfer tubes and circulates a heat medium therein, the dew point of sulfuric acid (SO ₃ ) mist in the exhaust gas is measured at the inlet of the heat recovery unit. Exhaust gas temperature and exhaust gas at the outlet of the dust collector A management method of an exhaust gas processing device for controlling the outlet gas temperature of the dust collector so that the state is between degrees.
[0021]
The method for operating an exhaust gas treatment apparatus according to claim 9, wherein a dew point of the sulfuric acid (SO ₃ ) mist in the exhaust gas is between an exhaust gas temperature at an inlet of the heat recovery unit and an exhaust gas temperature at an outlet of the dust collector, In addition, the temperature of the exhaust gas at the outlet of the dust collector can be set to be 30 ° C. or more higher.
[0022]
Further, in the operating method according to claim 9, the exhaust gas temperature at the outlet of the dust collector is adjusted by adjusting a heat medium circulation flow rate of a heat medium circulation line between the reheater and the heat recovery unit. It can be performed by cooling or heating.
[0023]
Further, in the operation method according to claim 9, the heat medium circulating line is branched from a heat medium circulating line between a reheater and the heat recovery device, and bypasses a heat medium circulating line passing through a heat transfer tube of the heat recovery device. A bypass line that circulates the heat medium only in the heat transfer tube of the reheater is provided, and the flow rate of the heat medium in the bypass line can be adjusted as exhaust gas temperature control of the outlet of the dust collector.
According to a thirteenth aspect of the present invention, there is provided an air preheater for preheating combustion air of a combustion device with exhaust gas discharged from the combustion device, and a heat transfer tube group for recovering heat of the exhaust gas at the outlet of the air preheater to a heat medium. A collector, a dust collector for collecting dust in the exhaust gas at the outlet of the heat recovery unit, a wet desulfurization device for removing sulfur oxides in the exhaust gas at the outlet of the dust collector, and an exhaust gas at the outlet of the wet desulfurization device. And a reheater consisting of a group of heat transfer tubes for heating with a heat medium supplied from the heat recovery unit are sequentially arranged from the upstream side to the downstream side of the exhaust gas duct of the combustion device, and are provided in the heat recovery unit and the reheater, respectively. In the method for operating an exhaust gas treatment apparatus provided with a heat medium circulating line that communicates the heat transfer tubes and circulates a heat medium therein, the concentration of sulfuric acid (SO ₃ ) mist in the exhaust gas discharged from the dust collector is determined. Measure the sulfuric acid (SO ₃ ) mist concentration Of the dust collector, the dew point of the sulfuric acid (SO ₃ ) mist in the exhaust gas being between the exhaust gas temperature at the heat recovery device inlet and the exhaust gas temperature at the dust collector outlet based on the measured value of This is an operation method of the exhaust gas treatment device for adjusting the outlet exhaust gas temperature.
[0024]
The method for operating an exhaust gas treatment apparatus according to claim 13, wherein a dew point of sulfuric acid (SO ₃ ) mist in the exhaust gas is between an exhaust gas temperature at the heat recovery unit inlet and an exhaust gas temperature at the dust collector outlet, In addition, the temperature of the exhaust gas at the outlet of the dust collector can be set to be 30 ° C. or more higher.
[0025]
Further, in the operation method of the exhaust gas treatment device according to claim 13, the exhaust gas temperature at the outlet of the dust collector is adjusted by adjusting a heat medium circulation flow rate of a heat medium circulation line between the reheater and the heat recovery unit. It can be performed by cooling or heating the heat medium.
[0026]
Furthermore, in the operation method of the exhaust gas treatment apparatus according to claim 13, a heat medium circulation line that branches from a heat medium circulation line between a reheater and the heat recovery unit and passes through a heat transfer tube of the heat recovery unit is provided. A bypass line that bypasses and circulates the heat medium only in the heat transfer tube of the reheater is provided, and the exhaust gas temperature control at the outlet of the dust collector can adjust the flow rate of the heat medium in the bypass line.
[0027]
In addition, as these means for controlling the exhaust gas temperature at the outlet of the heat recovery unit, a method described in JP-A-09-122438 or JP-A-11-347332 can be used.
[0028]
[Action]
Part of sulfur dioxide (SO ₂ ) generated when burning coal reacts with oxygen in exhaust gas to form SO ₃ by a catalytic action such as a denitration catalyst. The conversion from SO ₂ to SO ₃ varies depending on the conditions, but is about 1 to 3%. Since the SO ₂ concentration discharged from a coal-fired boiler is generally about 300 to 3000 ppm, the SO ₃ concentration is about ₃ to 90 ppm. When the temperature of the exhaust gas decreases, the SO ₃ reacts with the moisture in the exhaust gas to form a sulfuric acid mist (H ₂ SO ₄ ), and sulfuric acid is condensed in a low temperature portion of the exhaust gas treatment device.
[0029]
FIG. 4 shows the influence of the SO ₃ concentration and the exhaust gas temperature on the sulfuric acid dew point temperature. The sulfuric acid dew point can be calculated by Otsuka's equation or Muller's equation as shown in the figure. When the SO ₃ concentration is ₃ to 90 ppm, the dew point is 120 to 160 ° C., though it depends on the water content.
[0030]
FIG. 5 is a test result obtained by the present inventors examining the reactivity of a gas containing 50 ppm of SO ₃ and 10% of moisture (sulfuric acid dew point: about 150 ° C.) with coal ash particles. By lowering the sulfuric acid dew point by 30 ° C., the sulfuric acid mist adhered to almost 100% ash particles. In other words, by cooling the exhaust gas in a region where the ash particle concentration in the exhaust gas is high from the inlet of the heat recovery unit to the outlet of the dust collector, and making the condition 30 ° C. lower than the sulfuric acid dew point, the sulfuric acid mist reacts with the ash particles almost 100%. I do.
[0031]
Since the ash particles show strong alkalinity, the ash particles can neutralize the sulfuric acid mist to make it harmless and prevent corrosion of equipment. Furthermore, since most (about 99.9%) of the ash particles that have reacted with the sulfuric acid mist are collected by the dust collector, the sulfuric acid mist, which is ultrafine particles, is disposed in the exhaust gas duct on the downstream side of the dust collector. Purple smoke can be prevented from being released into the atmosphere from the chimney without entering the device.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0033]
Embodiment 1
FIG. 1 shows a configuration diagram of an exhaust gas treatment system according to one embodiment of the present invention.
As shown in FIG. 1, in the exhaust gas treatment system according to the present embodiment, the exhaust gas discharged from the boiler 1 is introduced into a denitration device 2 installed in an exhaust gas duct 25, and the nitrogen oxides in the exhaust gas in the denitration device 2 Is removed and then guided to the air preheater 3. The exhaust gas guided to the air preheater 3 exchanges heat with the combustion air supplied to the boiler 1, is cooled to, for example, 120 to 170 ° C., and is introduced into the heat recovery unit 11. The heat of the exhaust gas introduced into the heat recovery device 11 is recovered by the heat medium flowing through the heat transfer tube by heat exchange, cooled to, for example, 75 to 110 ° C., and guided to the electric precipitator 4, where the waste gas in the exhaust gas is removed. Most of the dust is collected.
[0034]
The exhaust gas passing through the electrostatic precipitator 4 is pressurized by an induction fan 5 and introduced into a wet limestone-gypsum method wet desulfurization device 6 which is an example of a wet exhaust gas treatment device. Removed. The exhaust gas cooled to the saturated gas temperature in the wet desulfurization device 6 is heated by the reheater 13 and then discharged from the chimney 8 through the desulfurization fan 7 to the atmosphere. The reheater 13 is a heat exchanger provided with a heat transfer tube through which a heat medium flows like the heat recovery device 11, and the exhaust gas is heated to, for example, 90 to 110 ° C. by heat exchange with the heat medium flowing in the heat transfer tube. Raise the temperature. The heat transfer tubes of the heat recovery unit 11 and the reheater 13 communicate with each other by heat medium circulation lines 15-1 and 15-2, and the heat transfer medium is provided between the heat recovery unit 11 and the reheater 13 by the pump 10. Is circulated.
[0035]
In the exhaust gas treatment system shown in FIG. 1, by controlling the exhaust gas temperature at the outlet of the electrostatic precipitator 4, the efficiency of removing sulfuric acid mist in the exhaust gas can be increased.
[0036]
FIG. 2 shows a detailed diagram of a heat medium circulation system of the heat recovery unit 11 and the reheater 13 according to the characteristic part of the present embodiment. The heat transfer tube 12 and the heat transfer tube 14 of the heat recovery unit 11 and the reheater 13 are connected annularly by heat medium circulation lines 15-1 and 15-2, and a circulation pump provided in the middle of the lines. 10, the heat medium is circulated in the heat transfer tubes 12 and 14. Fin tubes and the like are used for the heat transfer tubes 12 and 14 in order to improve the efficiency of heat exchange. The heat medium circulation pipe 15-2 is provided with a heat medium tank 26 for absorbing the expansion of the heat medium in the pipe.
[0037]
A specific method for controlling the exhaust gas temperature at the outlet of the electrostatic precipitator 4 is as follows.
In order to control the exhaust gas temperature at the outlet of the heat recovery unit 11, a heat medium bypass line 16 is provided, which bypasses the heat recovery unit 11 and returns from the heat medium outlet of the reheater 13 to the inlet. The opening degree of the flow control valve 18 provided in the heating medium bypass line 16 is adjusted by the signal of the thermometer 17 for measuring the exhaust gas temperature so that the outlet exhaust gas temperature of the electrostatic precipitator 4 falls within a set range. The amount of heat recovered in the heat recovery unit 11 by the medium is controlled. A heat exchanger 19 is connected to the heat medium circulation line 15-2. Steam or cooling water is supplied from the supply pipe 20 to the heat recovery circuit 11 by adjusting the opening of the flow control valve 21. Control the outlet exhaust gas temperature. As a result, the temperature of the exhaust gas at the outlet of the electric precipitator 4 can be controlled.
[0038]
By adjusting the flow rate of the pump 10, the temperature of the exhaust gas at the outlet of the electric precipitator 4 can be controlled. For example, when the temperature of the exhaust gas in the exhaust gas duct 25 at the outlet of the electrostatic precipitator 4 measured by the thermometer 17 is higher than a predetermined value, the flow rate of the pump 10 is increased to increase the heat recovery device 11 and the reheater 13. During this time, the exhaust gas temperature at the outlet of the electrostatic precipitator 4 is lowered. However, conversely, when the flow rate of the pump 10 is reduced to reduce the amount of heat exchange between the heat recovery unit 11 and the reheater 13, the exhaust gas temperature at the outlet of the reheater 13 is reduced, and the surface of the heat transfer tube 14 is reduced. Care must be taken because the mist of the wet desulfurization equipment may scatter and adhere to the mist, causing corrosion.
[0039]
In the embodiment shown in FIGS. 1 and 2, the exhaust gas temperature at the outlet of the electrostatic precipitator 4 was adjusted to a predetermined value, and the sulfuric acid mist concentration in the exhaust gas at the inlet of the chimney 8 was measured. Table 1 shows the results. However, the sulfuric acid mist concentration is shown as a relative value based on the value at 150 ° C. as 100.
[0040]
[Table 1]

[0041]
Embodiment 2
In the exhaust gas treatment system shown in FIG. 1, it is also possible to measure the sulfuric acid mist concentration and control the exhaust gas temperature at the outlet of the electric precipitator 4 based on the measured sulfuric acid mist concentration (see FIG. 4).
[0042]
FIG. 3 shows a detailed diagram of the heat medium circulation system of the heat recovery unit 11 and the reheater 13 according to the present embodiment. The heat transfer tube 12 and the heat transfer tube 14 of the heat recovery unit 11 and the reheater 13 are connected annularly by heat medium circulation lines 15-1 and 15-2, and a circulation pump provided in the middle of the lines. 10, the heat medium is circulated in the heat transfer tubes 12 and 14. Fin tubes and the like are used for the heat transfer tubes 12 and 14 in order to improve the efficiency of heat exchange. The heat medium circulation pipe 15-2 is provided with a heat medium tank 26 for absorbing the expansion of the heat medium in the pipe.
[0043]
A specific method for controlling the exhaust gas temperature at the outlet of the electrostatic precipitator 4 is as follows.
A heat medium bypass line 16 is provided to control the exhaust gas temperature at the outlet of the heat collector 11, and the electric dust collector 4 is calculated based on a signal from a mist concentration meter 22 that measures the exhaust gas temperature at the outlet of the electric dust collector 4. The amount of heat recovery is controlled by adjusting the opening of the flow control valve 18 provided in the heat medium bypass line 16 so that the mist concentration at the outlet of the heat exchanger falls within the set range. A heat exchanger 19 is connected to the heat medium circulation line 15-2. Steam or cooling water is supplied from the supply pipe 20 to the heat recovery circuit 11 by adjusting the opening of the flow control valve 21. The temperature of the exhaust gas at the outlet is controlled to control the mist concentration at the outlet of the electrostatic precipitator 4.
[0044]
In the first embodiment, the exhaust gas temperature at the outlet of the electrostatic precipitator 4 is measured. However, when the exhaust gas temperature drop at the electric precipitator 4 is small, the exit of the heat recovery device 11 or the entrance of the electric precipitator 4 is performed. It is also possible to measure the temperature of the exhaust gas at this point instead. In the second embodiment, the mist concentration at the inlet of the chimney 8 can be measured instead of the mist concentration at the outlet of the electric precipitator 4.
[0045]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the sulfuric acid mist density | concentration in the exhaust gas exhausted from a chimney can be reduced economically. In addition, since the sulfuric acid mist is neutralized and neutralized with highly alkaline coal ash, corrosion of equipment can be prevented.
[Brief description of the drawings]
FIG. 1 is a basic system diagram of an exhaust gas treatment system according to an embodiment of the present invention.
FIG. 2 is a partial detailed structural view of the exhaust gas treatment system according to the first embodiment of the present invention.
FIG. 3 is a partial detailed structural view of an exhaust gas treatment system according to a second embodiment of the present invention.
FIG. 4 is a graph showing the relationship between the concentration of SO ₃ in exhaust gas and the dew point temperature of sulfuric acid in exhaust gas in the exhaust gas treatment system of the present invention.
FIG. 5 is a diagram showing the reactivity between SO ₃ -containing gas and coal ash.
[Explanation of symbols]
1: Boiler 2: Denitration device 3: Air preheater 4: Electric precipitator 5: Induction fan 6: Wet desulfurization device 7: Desulfurization fan 8: Chimney 10: Pump 11: Heat recovery unit 12: Heat transfer tube 13: Reheating 14: Heat transfer tube 15: Heat medium circulation line 16: Heat medium bypass line 17: Thermometer 18: Flow control valve 19: Heat exchanger 20: Supply pipe 21: Flow control valve 22: Mist concentration meter 25: Exhaust gas duct 26: Heat medium tank

Claims (16)

An air preheater for preheating combustion air of the combustion device with exhaust gas discharged from the combustion device,
A heat recovery unit comprising a heat transfer tube group for recovering heat of the exhaust gas at the outlet of the air preheater into a heat medium,
A dust collector for collecting dust in exhaust gas at the outlet of the heat recovery device,
A wet desulfurization device for removing sulfur oxides in the exhaust gas at the outlet of the dust collector,
A reheater comprising a heat transfer tube group for heating the exhaust gas at the outlet of the wet desulfurization device with a heat medium supplied from the heat recovery device,
Are arranged sequentially from upstream to downstream of the exhaust gas duct of the combustion device,
In an exhaust gas treatment device that connects a heat transfer tube provided in each of a heat recovery unit and a reheater and has a heat medium circulation line that circulates a heat medium therein,
The exhaust gas temperature control means at the outlet of the dust collector, wherein the dew point of the sulfuric acid (SO ₃ ) mist in the exhaust gas is between the exhaust gas temperature at the heat recovery device inlet and the exhaust gas temperature at the dust collector outlet. An exhaust gas treatment device characterized by being provided. The dew point of the sulfuric acid (SO ₃ ) mist in the exhaust gas is between the exhaust gas temperature at the inlet of the heat recovery unit and the exhaust gas temperature at the outlet of the dust collector, and is lower than the exhaust gas temperature at the outlet of the dust collector by 30%. 2. The exhaust gas treatment apparatus according to claim 1, further comprising a temperature control unit for exhaust gas at an outlet of the dust collector, the temperature of which is set to be higher than the temperature of the exhaust gas. The exhaust gas temperature control means at the outlet of the dust collector is a heat medium circulation flow rate adjusting means for a heat medium circulation line between the reheater and the heat recovery unit, or a means for cooling the heat medium, and heating the heat medium. The exhaust gas treatment device according to claim 1 or 2, wherein the exhaust gas treatment device is at least one of the following means. Heat is diverted from the heat medium circulation line between the reheater and the heat recovery unit to bypass only the heat medium circulation line passing through the heat transfer tube of the heat recovery unit, and heat is generated only in the heat transfer tube of the reheater. 4. A bypass line for circulating a medium is provided, and the outlet exhaust gas temperature control means of the dust collector is a means for adjusting a heat medium flow rate of the bypass line. Exhaust gas treatment equipment. An air preheater for preheating combustion air of the combustion device with exhaust gas discharged from the combustion device,
A heat recovery unit comprising a heat transfer tube group for recovering heat of the exhaust gas at the outlet of the air preheater into a heat medium,
A dust collector for collecting dust in exhaust gas at the outlet of the heat recovery device,
A wet desulfurization device for removing sulfur oxides in the exhaust gas at the outlet of the dust collector,
A reheater comprising a heat transfer tube group for heating the exhaust gas at the outlet of the wet desulfurization device with a heat medium supplied from the heat recovery device,
Are arranged sequentially from upstream to downstream of the exhaust gas duct of the combustion device,
In an exhaust gas treatment device that connects a heat transfer tube provided in each of a heat recovery unit and a reheater and has a heat medium circulation line that circulates a heat medium therein,
The collector to the dust outlet sulfate in the exhaust gas (SO ₃₎ sulfate (SO ₃₎ to measure the mist concentration provided mist densitometer, based on the measured value of the sulfuric acid (SO ₃₎ mist densitometer, sulfuric acid in the exhaust gas ( SO ₃ ) an exhaust gas temperature control means for the outlet of the dust collector is provided so that the dew point of the mist is between the exhaust gas temperature at the inlet of the heat recovery device and the exhaust gas temperature at the outlet of the dust collector. Waste gas treatment equipment. Based on the measured value of the sulfuric acid (SO ₃₎ mist densitometer, sulfuric acid in the exhaust gas (SO ₃₎ dew point of the mist, between the exhaust gas temperature in the dust collector outlet and the exhaust gas temperature at the heat recovery inlet 6. The exhaust gas treatment apparatus according to claim 5, further comprising an exhaust gas temperature control means for exiting the dust collector, wherein the temperature of the exhaust gas is 30 ° C. or more higher than the exhaust gas temperature at the exit of the dust collector. The exhaust gas temperature control means at the outlet of the dust collector is a heat medium circulation flow rate adjusting means for a heat medium circulation line between the reheater and the heat recovery unit, or a means for cooling the heat medium, and heating the heat medium. The exhaust gas treatment device according to claim 5, wherein the exhaust gas treatment device is any one or more of the means for performing the treatment. Heat is diverted from the heat medium circulation line between the reheater and the heat recovery unit to bypass only the heat medium circulation line passing through the heat transfer tube of the heat recovery unit, and heat is generated only in the heat transfer tube of the reheater. A bypass line for circulating a medium is provided, and the outlet exhaust gas temperature control means of the dust collector is a means for adjusting a flow rate of a heating medium in the bypass line. Exhaust gas treatment equipment. An air preheater for preheating combustion air of the combustion device with exhaust gas discharged from the combustion device,
A heat recovery unit comprising a heat transfer tube group for recovering heat of the exhaust gas at the outlet of the air preheater into a heat medium,
A dust collector for collecting dust in exhaust gas at the outlet of the heat recovery device,
A wet desulfurization device for removing sulfur oxides in the exhaust gas at the outlet of the dust collector,
A reheater comprising a heat transfer tube group for heating the exhaust gas at the outlet of the wet desulfurization device with a heat medium supplied from the heat recovery device,
Are arranged sequentially from upstream to downstream of the exhaust gas duct of the combustion device,
In the method of operating an exhaust gas treatment device provided with a heat medium circulating line for communicating a heat transfer tube provided in each of a heat recovery unit and a reheater and circulating a heat medium therein,
The outlet exhaust gas temperature of the dust collector is adjusted so that the dew point of the sulfuric acid (SO ₃ ) mist in the exhaust gas is between the exhaust gas temperature at the heat recovery unit inlet and the exhaust gas temperature at the dust collector outlet. An operation method of an exhaust gas treatment device, characterized by controlling. The dew point of the sulfuric acid (SO ₃ ) mist in the exhaust gas is between the exhaust gas temperature at the heat recovery device inlet and the exhaust gas temperature at the dust collector outlet, and is lower than the exhaust gas temperature at the dust collector outlet. The method for operating an exhaust gas treatment apparatus according to claim 9, further comprising means for controlling the temperature of the exhaust gas at the outlet of the dust collector, which is set to a temperature higher than 30 ° C. The outlet exhaust gas temperature of the dust collector may be adjusted by adjusting a heat medium circulation flow rate of a heat medium circulation line between the reheater and the heat recovery device, cooling the heat medium, or heating the heat medium. The method for operating an exhaust gas treatment device according to claim 9 or 10, wherein In the exhaust gas treatment device, the heat medium circulation line between the reheater and the heat recovery unit branches off from the heat medium circulation line passing through the heat transfer tube of the heat recovery unit, and the heat transfer tube of the reheater passes through the heat transfer line. A bypass line that circulates the heat medium only in
The method of operating an exhaust gas treatment apparatus according to any one of claims 9 to 11, wherein the temperature control of the exhaust gas at the outlet of the dust collector is performed by adjusting a flow rate of a heating medium in the bypass line. An air preheater for preheating combustion air of the combustion device with exhaust gas discharged from the combustion device,
A heat recovery unit comprising a heat transfer tube group for recovering heat of the exhaust gas at the outlet of the air preheater into a heat medium,
A dust collector for collecting dust in exhaust gas at the outlet of the heat recovery device,
A wet desulfurization device for removing sulfur oxides in the exhaust gas at the outlet of the dust collector,
A reheater comprising a heat transfer tube group for heating the exhaust gas at the outlet of the wet desulfurization device with a heat medium supplied from the heat recovery device,
Are arranged sequentially from upstream to downstream of the exhaust gas duct of the combustion device,
In the method of operating an exhaust gas treatment device provided with a heat medium circulating line for communicating a heat transfer tube provided in each of a heat recovery unit and a reheater and circulating a heat medium therein,
The sulfuric acid (SO ₃ ) mist concentration in the exhaust gas discharged from the dust collector is measured, and the dew point of the sulfuric acid (SO ₃ ) mist in the exhaust gas is determined based on the measured value of the sulfuric acid (SO ₃ ) mist concentration. The exhaust gas temperature at the outlet of the dust collector, which is between the exhaust gas temperature at the heat collector inlet and the exhaust gas temperature at the dust collector outlet, and is higher than the exhaust gas temperature at the dust collector outlet by 30 ° C. or more. A method for operating an exhaust gas treatment apparatus, comprising:
The sulfuric acid (SO ₃ ) mist concentration in the exhaust gas discharged from the dust collector is measured, and the dew point of the sulfuric acid (SO ₃ ) mist in the exhaust gas is determined based on the measured value of the sulfuric acid (SO ₃ ) mist concentration. A method for operating an exhaust gas treatment apparatus, comprising adjusting an exhaust gas temperature at an outlet of the dust collector so as to be in a state between an exhaust gas temperature at an inlet of a heat recovery device and an exhaust gas temperature at an outlet of the dust collector. The sulfuric acid (SO ₃ ) mist concentration in the exhaust gas discharged from the dust collector is measured, and the dew point of the sulfuric acid (SO ₃ ) mist in the exhaust gas is determined based on the measured value of the sulfuric acid (SO ₃ ) mist concentration. The exhaust gas temperature at the outlet of the dust collector, which is between the exhaust gas temperature at the heat collector inlet and the exhaust gas temperature at the dust collector outlet, and is higher than the exhaust gas temperature at the dust collector outlet by 30 ° C. or more. 14. The method for operating an exhaust gas treatment device according to claim 13, wherein: The outlet exhaust gas temperature of the dust collector is adjusted by adjusting a heat medium circulation flow rate of a heat medium circulation line between the reheater and the heat recovery unit, and cooling or heating the heat medium. Item 15. The method for operating an exhaust gas treatment device according to item 13 or 14. The heat medium is diverted from the heat medium circulation line between the reheater and the heat recovery device, bypasses the heat medium circulation line passing through the heat transfer tube of the heat recovery device, and is supplied only into the heat transfer tube of the reheater. A bypass line to circulate
The method according to any one of claims 13 to 15, wherein the control of the exhaust gas temperature at the outlet of the dust collector is performed by adjusting a flow rate of a heating medium in the bypass line.

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