JP2012196611A - Flue gas desulfurization apparatus and flue gas desulfurization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flue gas desulfurization apparatus of a water saving type which can reduce makeup water amount in the flue gas desulfurization apparatus at a low cost while maintaining desulfurization performance at the same degree as the present apparatus.SOLUTION: The flue gas desulfurization apparatus is provided with an absorption tower 4 in which flue gas discharged from a combustion device is introduced and absorption liquid is sprayed to absorb and remove sulfur oxides included in the flue gas, a mist eliminator 7 provided at an exit of the absorption tower 4 and a mist eliminator water-washing device 33 for water-washing the mist eliminator 7. In the flue gas desulfurization apparatus, two or more mist eliminators 7 are provided at an upstream side and a downstream side of a flue gas channel, washing water supply lines 37a, 37b for supplying washing water to respective mist eliminators 7a, 7b are provided at the mist eliminator water-washing device 33 and a seawater supply line 24 for supplying seawater is provided at the washing water supply line 37b at the downstream side of the flue gas channel. The mist eliminator 7b at the downstream side of the flue gas channel is washed by the seawater and thereby water amount supplied to the absorption tower 4 can be reduced.

Description

  The present invention relates to a flue gas treatment apparatus for purifying exhaust gas discharged from combustion equipment such as a boiler installed in a thermal power plant or factory, and in particular, sulfur oxidation contained in combustion exhaust gas such as a boiler. The present invention relates to a flue gas desulfurization apparatus and a flue gas desulfurization method that reduce harmful substances such as substances, hydrogen chloride, hydrogen fluoride and other acidic gases and dust, and trace components contained in fuel.

  In order to prevent air pollution, wet limestone-gypsum flue gas desulfurization devices have been widely put into practical use as devices for removing sulfur oxides in exhaust gas. FIG. 6 shows a general system of a wet type flue gas desulfurization apparatus in a thermal power generation facility. In addition, the same number is attached | subjected to the same apparatus (apparatus) in each figure.

  An exhaust gas containing sulfur oxides discharged from a combustion apparatus such as a boiler installed in a thermal power plant or factory is a gas gas heater (heat exchanger) 20 installed in the entrance flue 1 of the absorption tower 4 from the direction of arrow A. The heat of the exhaust gas is recovered and the gas temperature is lowered to 90-110 ° C. The exhaust gas whose gas temperature has dropped below a certain value is introduced from the gas inlet 3 into the absorption tower 4 of the wet flue gas desulfurization apparatus.

  The absorption tower 4 is composed of a liquid reservoir 5 and an absorption part (spray part) 6. In the absorption part 6, a spray header 8 provided with a plurality of spray nozzles 9 in a plurality of stages is installed vertically along the flow direction of the exhaust gas. By contacting the exhaust gas with a droplet of an absorbent such as limestone or lime-containing slurry sprayed as fine droplets from the spray nozzle 9, soot, hydrogen chloride (HCl), hydrogen fluoride ( Along with the acidic gas such as HF), sulfur oxide (SOx) in the exhaust gas is chemically absorbed and removed on the surface of the absorbing droplets of the spray nozzle 9.

  The liquid reservoir 5 is supplied with an absorbent from an absorbent slurry (mainly limestone slurry) supply line 16 according to the amount of sulfur oxide contained in the exhaust gas from the boiler or the like. The slurry-like absorption liquid in the liquid reservoir 5 is pressurized by the absorption liquid circulation pump 10 and supplied to the spray header 8 of the absorption part 6 at the upper part in the absorption tower 4 via the absorption liquid circulation pipe 13.

  Further, minute droplets (mist) accompanying the flow of the exhaust gas are removed by the mist eliminator 7 installed at the gas outlet 18 at the upper part of the absorption tower 4. The exhaust gas temperature that has passed through the mist eliminator 7 is normally a water saturated gas of about 50 ° C., but is reheated by passing through the gas gas heater 20 installed downstream of the exhaust gas flow path of the mist eliminator 7. That is, the exhaust gas that has passed through the mist eliminator 7 is reheated to about 90 to 100 ° C. by the heat of the inlet gas of the absorption tower 4 recovered by the gas gas heater 20, and flows from the outlet flue 2 in the direction of arrow B. Finally, after being introduced into a chimney (not shown), it is discharged into the atmosphere.

  The mist eliminator 7 installed at the outlet of the absorption tower 4 is provided with a water washing device 31 so that the absorption liquid circulating in the absorption tower 4 is scattered and adheres to the elements of the mist eliminator 7. The element is washed with industrial water as the washing water of the washing device 31.

Sulfur oxides such as sulfur dioxide (SO ₂ ) contained in exhaust gas discharged from boilers react with calcium compounds (limestone (CaCO ₃ ), etc.) contained in the absorption liquid, and calcium sulfite as an intermediate product (Including calcium bisulfite) and flows down to the liquid reservoir 5. On the other hand, the oxidizing air blower 17 forcibly supplies oxidizing air from the oxidizing air supply line 26 to the liquid reservoir 5, and gypsum as a reaction product is obtained by an oxidation reaction between the oxidizing air and calcium sulfite. a slurry _{(CaSO 4 · 2H 2 O)} .

  In this case, the oxidizing air supplied to the liquid reservoir 5 is refined by an oxidizing stirrer 15 that stirs the absorption liquid in the liquid reservoir 5, thereby increasing the utilization rate of the oxidizing air. . The absorbing liquid in the liquid reservoir 5 is approximately 50 ° C., but the air temperature at the outlet of the oxidizing air blower 17 is normally 120 to 150 ° C. When supplied to the liquid reservoir 5 as it is, Since repeated drying and wetting occurs at the end of the pipe inserted in the absorption liquid, the air at the outlet of the oxidizing air blower 17 is directly sprayed with industrial water to lower the air temperature to the water saturation temperature, and the liquid reservoir 5 To be supplied.

  The absorbent slurry in the liquid reservoir 5 is extracted from the liquid reservoir 5 to the gypsum dewatering equipment 12 according to the amount of gypsum produced by the absorption tower extraction pump 11 and dehydrated, and the gypsum 14 is recovered. On the other hand, the filtrate is stored in the filtrate collection tank 21, extracted by the filtrate pump 22, and discharged from the drainage line 23 to the outside of the wet flue gas desulfurization apparatus.

  In addition, makeup water for maintaining the balance of the amount of water in the entire equipment of the wet flue gas desulfurization apparatus is supplied from a liquid reservoir supply line 35 of the absorption tower 4 and a flush water supply line 37 of the mist eliminator 7.

  Particularly in areas where it is difficult to secure the amount of water used in thermal power plants, etc., it is essential to reduce the amount of makeup water used in wet flue gas desulfurization equipment. In order to reduce the amount of new water (industrial water) used in the wet flue gas desulfurization system, the water flow downstream side (absorption tower side) is used as flush water for the mist eliminator installed between the dust removal tower and the absorption tower. ) Is used to clean the mist eliminator, while the mist eliminator on the upstream side (dust removal tower side) of the mist eliminator is used to clean the mist eliminator. ing.

  In Patent Document 2 below, the exhaust gas before desulfurization is directly sprayed with a circulating coolant sprayer to increase the humidity, and then the exhaust gas is cooled in contact with the coolant indirectly with a heat exchanger, and then absorbed. The structure which wash | cleans waste gas with an agent slurry is disclosed. By providing a circulating coolant sprayer upstream of the exhaust gas flow path and a heat exchanger downstream, the outside of the heat exchanger is always moistened to reduce the amount of water loss and used in wet flue gas desulfurization equipment. The amount of makeup water is reduced.

  Furthermore, in the configuration described in Patent Document 3 below, a horizontally long and compact gas humidity control unit is provided in front of the horizontally long and compact absorption unit, and the waste water from the boiler and seawater are used as cooling water in the gas humidity control unit. This saves the amount of makeup water.

JP-A-55-106515 JP-A-6-134251 Japanese Patent Laid-Open No. 10-5538

  In the above-described prior art, when a boiler or the like is operated in a rated operation load zone (high load zone), the inlet gas temperature of the absorption tower is 90 to 110 ° C. even after the heat of the exhaust gas is recovered by the gas gas heater. And relatively hot. Therefore, the amount of evaporated water in the absorption tower increases, the liquid level in the liquid reservoir (liquid level) and the concentration of the absorbent slurry are kept constant, and the water amount balance of the entire wet flue gas desulfurization equipment is maintained. Therefore, there is a problem that a large amount of makeup water is required in the absorption tower.

  As a countermeasure, the capacity of the gas gas heater installed at the entrance of the absorption tower is made larger than before, and the amount of evaporated water in the absorption tower can be reduced by lowering the exhaust gas temperature at the entrance of the absorption tower. The amount of makeup water required for the entire facility can also be reduced.

  However, when the capacity of the gas gas heater is increased, the amount of evaporated water in the absorption tower is reduced when the boiler is operated in a low load zone due to the operating state of the thermal power generation facility. It becomes difficult to maintain the water volume balance of the entire facility. That is, by supplying the washing water of the mist eliminator and the air humidified water for oxidation of the absorption tower to the absorption tower, the amount of water supplied to the absorption tower becomes excessive with respect to the amount of water extracted from the absorption tower. There is a problem that it becomes impossible to maintain the water balance of the entire equipment of the flue gas desulfurization apparatus.

  On the other hand, the waste water from the mist eliminator is circulated and used as in the configuration described in Patent Document 1, or the amount of moisture loss is reduced by always keeping the outside of the heat exchanger wet as in the configuration described in Patent Document 2. Or, as in the configuration described in Patent Document 3, by using a compact configuration of the absorption unit and the gas humidity control unit and using waste water from the boiler and seawater as cooling water in the gas humidity control unit, Reduction is possible.

  However, in the configuration described in Patent Document 1, since fresh water is used for washing water of the mist eliminator on the downstream side of the gas flow, it can be said that the amount of new water used is still insufficient.

  Further, in the configuration described in Patent Document 2, the absorption liquid containing solid matter such as gypsum is sprayed upstream of the heat exchanger, and the outside of the heat exchanger is always moistened, but the gas temperature is relatively high. For this reason, a portion of repeated (wet and dry) occurs partially (locally), the corrosion of the equipment becomes significant, and clogging due to solid matter in the absorbing solution, and the deterioration of performance over time becomes a problem.

  Further, in the configuration described in Patent Document 3, the gas adjustment unit and the absorption unit are horizontally long and installed in the horizontal direction, so that the facility is low in the height direction, but conversely the installation area of the facility is large. There is a problem of becoming.

  In the configurations described in Patent Document 2 and Patent Document 3, although a water-saving effect is expected to some extent, no consideration is given to equipment that uses a relatively large amount of water such as flush water of a mist eliminator.

  An object of the present invention is to provide a water-saving and water-saving type flue gas desulfurization apparatus and a flue gas desulfurization method that can reduce the amount of makeup water in the flue gas desulfurization apparatus at a low cost while maintaining the desulfurization performance at the same level as the current situation. It is to be.

The object of the present invention can be achieved by adopting the following constitution.
The invention according to claim 1 absorbs sulfur oxides contained in the exhaust gas by introducing exhaust gas discharged from a combustion device including a boiler, spraying an absorption liquid on the exhaust gas and bringing it into gas-liquid contact, A flue gas provided with an absorption tower to be removed, a mist eliminator provided at an outlet of an exhaust gas flow path of the absorption tower and collecting mist discharged from the absorption tower, and a mist eliminator water washing device for washing the mist eliminator with water In the desulfurization apparatus, a plurality of the mist eliminators are provided on the upstream side and the downstream side of the exhaust gas flow path, a rinsing water supply unit that supplies water for rinsing to each mist eliminator is provided in the mist eliminator water washing apparatus, and the downstream side It is a flue gas desulfurization device provided with a seawater supply unit that supplies seawater to a flush water supply unit of a mist eliminator.

  According to a second aspect of the present invention, an exhaust gas cooler having a cooling medium pipe inside is provided at an inlet of the exhaust gas flow path of the absorption tower, and a seawater supply unit for supplying seawater to the cooling medium pipe is provided. The flue gas desulfurization apparatus according to claim 1.

  According to a third aspect of the present invention, an oxidation air supply section for supplying oxidation air to the absorption tower is provided, and an oxidation air cooler having a cooling medium pipe inside is provided in the oxidation air supply section. The flue gas desulfurization apparatus according to claim 1, further comprising a seawater supply unit configured to supply seawater to the cooling medium pipe.

  The invention according to claim 4 introduces the exhaust gas discharged from the combustion device including the boiler into the absorption tower, sprays the absorbing liquid, and makes the sulfur oxide contained in the exhaust gas come into gas-liquid contact with the exhaust gas. After absorption and removal, the mist discharged from the absorption tower is collected by a plurality of mist eliminators provided upstream and downstream of the outlet of the exhaust gas passage of the absorption tower, and the mist eliminator that has collected the mist is collected. A flue gas desulfurization method for washing with water, wherein sea water is used as flush water for the downstream mist eliminator.

The invention according to claim 5 is the flue gas desulfurization method according to claim 4, wherein the exhaust gas at the inlet of the absorption tower is cooled using seawater as a cooling medium.
The invention according to claim 6 supplies the oxidizing air to the absorption tower and cools the oxidizing air supplied to the absorption tower using seawater as a cooling medium. It is a flue gas desulfurization method.

(Function)
The above issues are the reduction of the amount of water washed by the mist eliminator installed at the outlet of the absorption tower, the reduction of the amount of evaporated water in the absorption tower of the flue gas desulfurization device, and the increase of the humidity of the oxidizing air supplied to the liquid reservoir of the absorption tower This can be solved by reducing the amount of water.

  As described above, for example, when the capacity of the gas gas heater installed at the inlet of the absorption tower is made larger than before, and the exhaust gas temperature at the inlet of the absorption tower is lowered, the boiler and the like are reduced depending on the operating state of the thermal power generation facility. Under the condition of operating in the load zone, there is a problem that it becomes difficult to maintain the water volume balance of the entire facility of the flue gas desulfurization apparatus.

  In the mist eliminator installed at the outlet of the absorption tower, the absorption liquid circulating through the absorption tower scatters and there are many deposits attached to the elements of the mist eliminator. And the washing drainage of the mist eliminator contains a large amount of solids such as gypsum. Therefore, it is necessary to return the washing waste water to the absorption tower and reuse it as make-up water, and to discharge and collect the solid matter from the gypsum extraction line.

  In the configuration described in Patent Document 2, seawater is used as the refrigerant of the heat exchanger. In the configuration described in Patent Document 3, seawater is used as cooling water for cooling the exhaust gas that passes through the duct portion of the gas humidity control unit. By using it, the amount of makeup water in the flue gas desulfurization apparatus is reduced.

  Since seawater contains a large amount of dissolved salts such as chlorine, seawater is not used as the make-up water for the absorption tower, but was used as cooling water for cooling the heat exchanger refrigerant and exhaust gas. Seawater is circulated and used as a refrigerant, or is directly discharged out of the flue gas desulfurization system.

  As described above, since the washing drainage of the mist eliminator contains a large amount of solids such as gypsum, it is necessary to collect the washing drainage and reuse it as an absorbent, or collect gypsum and the like. Therefore, seawater was unsuitable and not used for flushing drainage of the mist eliminator.

  However, the present inventors provide a plurality of mist eliminators on the upstream side and downstream side of the exhaust gas flow path, and use seawater only for washing water of the downstream mist eliminator, thereby supplying the entire equipment of the flue gas desulfurization apparatus. The present invention has been completed by finding that the amount of fresh water used can be greatly reduced.

  That is, according to the first or fourth aspect of the present invention, a plurality of mist eliminators for collecting the mist discharged from the absorption tower are provided on the upstream side and the downstream side of the exhaust gas flow path, and each mist eliminator water washing device has each mist eliminator. A flush water supply unit that supplies flush water to the eliminator and a sea water supply unit that supplies sea water to the flush water supply unit of the downstream mist eliminator are provided. By using this, the amount of new water (industrial water) supplied to the entire equipment of the flue gas desulfurization apparatus can be reduced.

  The mist eliminator on the upstream side of the exhaust gas flow channel has a large amount of absorbing liquid scattered from the absorption tower, so that the amount of deposits on the mist eliminator increases, and the washing waste water contains a large amount of solids such as gypsum. . Therefore, it is only necessary to return the washing effluent of the mist eliminator upstream of the exhaust gas passage to the absorption tower, reuse the washing effluent as make-up water for the absorption tower, and extract the solid matter from the absorption tower to collect the gypsum. .

  When seawater is also used for the washing water of the mist eliminator upstream of the exhaust gas flow path, the seawater contains a large amount of dissolved salts such as chlorine, so if the washing wastewater is returned to the absorption tower, the absorption tower The chlorine concentration in the absorption liquid circulating inside increases. Generally, when the chlorine concentration in the absorbing solution increases, the pH of the absorbing solution decreases and the desulfurization performance decreases. In addition, when draining the waste water from the mist eliminator to the outside of the flue gas desulfurization system, a large amount of solid matter is contained, and thus a waste water treatment facility is required.

  According to the present invention, the mist eliminator on the upstream side of the exhaust gas passage is washed with fresh water (industrial water), and the mist eliminator on the downstream side of the exhaust gas passage is washed with seawater. Most of the solid matter scattered from the absorption tower is collected by the mist eliminator on the upstream side of the exhaust gas flow path, and the amount of solid matter attached to the mist eliminator on the downstream side is small. Therefore, the flush water (seawater) of the mist eliminator on the downstream side of the exhaust gas flow path may be discharged as it is outside the system of the flue gas desulfurization device, so that no waste water treatment equipment is required or the waste water treatment equipment can be simplified. It becomes.

  In this way, the mist eliminator on the downstream side of the exhaust gas flow path is washed with seawater, so that the amount of water supplied to the absorption tower is reduced, and the flue gas desulfurization device is independent of the operating state and operating load of the boiler and the like. Boilers can be stably operated while maintaining the water balance of the entire facility. And it becomes possible to reduce the amount of makeup water required as the whole equipment of the flue gas desulfurization apparatus.

  According to the invention of claim 2 or claim 5, in addition to the action of the invention of claim 1 or claim 4, by providing a gas cooler at the inlet of the exhaust gas flow path of the absorption tower, Since the gas temperature at the inlet of the absorption tower is lowered, the amount of evaporated water in the absorption liquid circulating in the absorption tower is reduced, and the amount of makeup water necessary to maintain the balance of the total amount of flue gas desulfurization equipment is greatly increased. Savings.

  Further, by using seawater as a cooling medium for the gas cooler, new water can be further reduced, and by controlling the amount of cooling water (seawater) to the gas cooler, the inlet gas temperature of the absorption tower is predetermined. Value can be maintained. That is, it is possible to maintain the water amount balance of the entire equipment of the flue gas desulfurization apparatus at a temperature at which it can be maintained.

  Furthermore, according to the invention of claim 3 or claim 6, in addition to the action of the invention of claim 1 or claim 4, the oxidizing air supply unit for supplying oxidizing air to the absorption tower, By providing an air cooler for cooling the air for oxidation using seawater as the cooling medium in the air supply section for oxidation, the seawater is used as the cooling medium to cool the oxidation air supplied to the absorption tower and lower the temperature. By doing so, it becomes possible to reduce the humidified water for oxidizing air that has been sprayed directly on the oxidizing air.

  According to the present invention, the amount of washing water of the mist eliminator installed at the outlet of the absorption tower is reduced, the amount of evaporated water in the absorption tower of the flue gas desulfurization apparatus is reduced, and the amount of humidified water of the oxidizing air supplied to the absorption tower is reduced. Is possible. Specifically, the following effects are exhibited.

  According to the first or fourth aspect of the present invention, a plurality of mist eliminators for collecting the mist discharged from the absorption tower are provided on the upstream side and the downstream side of the exhaust gas flow path, and the mist eliminator on the downstream side of the exhaust gas flow path is provided. The amount of water supplied to the absorption tower can be reduced by using seawater for the washing water. Accordingly, the amount of new water (industrial water) supplied to the entire facility of the flue gas desulfurization apparatus can be reduced.

  According to the invention of claim 2 or claim 5, in addition to the effect of the invention of claim 1 or claim 4, by providing a gas cooler at the inlet of the exhaust gas passage of the absorption tower, Since the gas temperature at the inlet is lowered, the amount of evaporated water in the absorption liquid circulating in the absorption tower is reduced, and the amount of makeup water required to maintain the balance of the entire amount of flue gas desulfurization equipment is greatly reduced. I can plan. And the further reduction of new water can be aimed at by using seawater for the cooling medium of a gas cooler.

  According to the invention of claim 3 or claim 6, in addition to the effect of the invention of claim 1 or claim 4, the seawater is used as a cooling medium to cool the oxidizing air supplied to the absorption tower. Thus, by reducing the temperature, it is possible to reduce the oxidizing air humidified water in which fresh water is directly sprayed on the oxidizing air.

It is a figure which shows the system | strain of the wet flue gas desulfurization apparatus which is one Example of this invention. It is a figure which shows the system | strain of the wet flue-gas desulfurization apparatus which is another Example of this invention. It is a figure which shows the system | strain of the wet flue-gas desulfurization apparatus which is another Example of this invention. It is a figure which shows the system | strain of the wet flue-gas desulfurization apparatus which is another Example of this invention. It is a correlation diagram of the inlet gas temperature of an absorption tower, and the amount of evaporating water (necessary makeup water amount) in a wet flue gas desulfurization apparatus. It is a figure which shows the system | strain of the conventional wet flue gas desulfurization apparatus.

  Embodiments of the present invention are shown below.

  In FIG. 1, the system | strain of the wet flue gas desulfurization apparatus (wet limestone-gypsum method flue gas desulfurization apparatus) which is one Example of this invention is shown. In the wet flue gas desulfurization apparatus in FIG. 1, the description of members having the same reference numerals as those in the wet flue gas desulfurization apparatus in FIG. 6 is partially omitted.

  An exhaust gas containing sulfur oxides discharged from a combustion apparatus such as a boiler installed in a thermal power plant or factory is a gas gas heater (heat exchanger) 20 installed in the entrance flue 1 of the absorption tower 4 from the direction of arrow A. The heat of the exhaust gas is recovered and the gas temperature is lowered to 90-110 ° C. The exhaust gas whose gas temperature has fallen below a certain value is introduced from the gas inlet 3 into the absorption tower 4 of the wet flue gas desulfurization apparatus.

  The absorption tower 4 is composed of a liquid reservoir 5 and an absorption part (spray part) 6. In the absorption part 6, a spray header 8 provided with a plurality of spray nozzles 9 in a plurality of stages is installed vertically along the flow direction of the exhaust gas. By contacting the exhaust gas with a droplet of an absorbent such as limestone or lime-containing slurry sprayed as fine droplets from the spray nozzle 9, soot, hydrogen chloride (HCl), hydrogen fluoride ( Along with the acidic gas such as HF), sulfur oxide (SOx) in the exhaust gas is chemically absorbed and removed on the surface of the absorbing droplets of the spray nozzle 9.

  The liquid reservoir 5 is supplied with an absorbent from an absorbent slurry (mainly limestone slurry) supply line 16 according to the amount of sulfur oxide contained in the exhaust gas from the boiler or the like. The slurry-like absorption liquid in the liquid reservoir 5 is pressurized by the absorption liquid circulation pump 10 and supplied to the spray header 8 of the absorption part 6 at the upper part in the absorption tower 4 via the absorption liquid circulation pipe 13.

  Further, minute droplets (mist) accompanying the flow of the exhaust gas are removed by the mist eliminator 7 installed at the gas outlet 18 at the upper part of the absorption tower 4. The exhaust gas temperature that has passed through the mist eliminator 7 is normally a water saturated gas of about 50 ° C., but is reheated by passing through a gas gas heater (heat exchanger) 20 installed downstream of the mist eliminator 7 in the exhaust gas flow path. Is done. That is, the exhaust gas that has passed through the mist eliminator 7 is reheated to about 90 to 100 ° C. by the heat of the inlet gas of the absorption tower 4 recovered by the gas gas heater 20, and flows from the outlet flue 2 in the direction of arrow B. Finally, after being introduced into a chimney (not shown), it is discharged into the atmosphere.

  The mist eliminators 7a and 7b installed at the outlet of the absorption tower 4 are provided with a water washing device 33 so that the absorption liquid circulating in the absorption tower 4 is scattered and adheres to the elements of the mist eliminators 7a and 7b. The water washing device 33 will be described in detail later.

Sulfur oxides such as sulfur dioxide (SO ₂ ) contained in exhaust gas discharged from boilers react with calcium compounds (limestone (CaCO ₃ ), etc.) contained in the absorption liquid, and calcium sulfite as an intermediate product (Including calcium bisulfite) and flows down to the liquid reservoir 5. On the other hand, the oxidizing air blower 17 forcibly supplies oxidizing air from the oxidizing air supply line 26 to the liquid reservoir 5, and gypsum as a reaction product is obtained by an oxidation reaction between the oxidizing air and calcium sulfite. a slurry _{(CaSO 4 · 2H 2 O)} .

  In this case, the oxidizing air supplied to the liquid reservoir 5 is refined by an oxidizing stirrer 15 that stirs the absorption liquid in the liquid reservoir 5, thereby increasing the utilization rate of the oxidizing air. . The absorbing liquid in the liquid reservoir 5 is approximately 50 ° C., but the air temperature at the outlet of the oxidizing air blower 17 is normally 120 to 150 ° C. When supplied to the liquid reservoir 5 as it is, Since repeated drying and wetting occurs at the end of the pipe inserted in the absorption liquid, the air at the outlet of the oxidizing air blower 17 is directly sprayed with industrial water to lower the air temperature to the water saturation temperature, and the liquid reservoir 5 To be supplied.

  The absorbent slurry in the liquid reservoir 5 is extracted from the liquid reservoir 5 to the gypsum dewatering equipment 12 according to the amount of gypsum produced by the absorption tower extraction pump 11 and dehydrated, and the gypsum 14 is recovered. On the other hand, the filtrate is stored in the filtrate collection tank 21, extracted by the filtrate pump 22, and discharged from the drainage line 23 to the outside of the wet flue gas desulfurization apparatus.

  In addition, makeup water for maintaining the balance of the amount of water in the entire equipment of the wet flue gas desulfurization apparatus is supplied from a liquid reservoir supply line 35 of the absorption tower 4 and a flush water supply line 37 of the mist eliminator 7.

  According to this embodiment, a plurality of mist eliminators 7a and 7b, such as at least the mist eliminator 7a on the upstream side of the exhaust gas flow path and the mist eliminator 7b on the downstream side, are installed. The flush water supply lines 37a and 37b are provided, the sea water supply line 24 is connected to the downstream flush water supply line 37b of the downstream mist eliminator 7b, and the seawater and fresh water (industrial water) are switched as flush water. The water-washing device 33 having a configuration that can be supplied is provided.

  Switching between seawater and fresh water is performed by changing the seawater supply valve 24 and the downstream flush water supply line 37b of the downstream mist eliminator 7b to the seawater switching valve (seawater amount adjusting means) 38 and the downstream flush water supply. It is possible to adjust the supply amount of seawater and fresh water by operating a fresh water switching valve (new water amount adjusting means) 39 provided in the line 37b.

  Since a large amount of absorbing liquid scatters from the absorption tower 4 to the upstream mist eliminator 7a, the amount of deposits on the mist eliminator increases, and the washing waste water contains a large amount of solids such as gypsum. Therefore, the flush drainage of the upstream mist eliminator 7a is once returned to the absorption tower 4, the flush drainage is reused as makeup water for the absorption tower 4, and the solid matter is discharged from the gypsum extraction line 11 of the absorption tower 4 and absorbed. Collect the gypsum 14 in the liquid.

  On the other hand, when seawater is also used for the washing water of the upstream mist eliminator 7a, since the seawater contains a large amount of dissolved salt such as chlorine, the washing drainage of the upstream mist eliminator 7a is absorbed by the absorption tower. If it returns to 4, the chlorine concentration in the absorption liquid which circulates the inside of the absorption tower 4 will become high. Generally, when the chlorine concentration in the absorbing liquid increases, the pH of the absorbing liquid decreases and the desulfurization performance decreases. Moreover, when draining flush wastewater outside the wet flue gas desulfurization system, wastewater treatment equipment is required because it contains a large amount of solid matter.

  In this embodiment, the upstream mist eliminator 7 a is washed with fresh water (industrial water) from the upstream flush water supply line 37 a, and the downstream mist eliminator 7 b is washed with seawater from the seawater supply line 24. . Most of the solid matter scattered from the absorption tower 4 is collected in the mist eliminator 7a on the upstream side of the exhaust gas flow path, and the amount of solid matter attached to the mist eliminator 7b on the downstream side is small. Therefore, since the washing waste water (seawater) of the downstream mist eliminator 7b may be discharged as it is outside the wet flue gas desulfurization system, no waste water treatment facility is required, or the wet flue gas desulfurization device is simplified. Is possible.

The total amount of water washed in the mist eliminators 7a and 7b depends on the amount of exhaust gas from the boiler and the element configuration of the mist eliminators 7a and 7b, but is approximately 30 to 40 t / h in the case of a 1000 MW scale thermal power generation facility.
On the other hand, according to the present embodiment, by using seawater as the washing water of the downstream mist eliminator 7b, the amount of water of about 10 to 15 t / h can be saved.

  In this way, the mist eliminator 7b on the downstream side of the exhaust gas flow path is washed with seawater, so that the amount of water supplied to the absorption tower 4 is reduced, and wet flue gas regardless of the operating state and operating load of the boiler and the like. It is possible to stably operate boilers and the like while maintaining the water balance of the entire desulfurization equipment. And it becomes possible to reduce the amount of supplementary water required as the whole equipment of a wet flue gas desulfurization apparatus.

  In the present embodiment, the case where two mist eliminators 7a and 7b are provided is shown, but three or more mist eliminators may be provided. In the three cases, seawater may be used for washing water of the most downstream mist eliminator or the two downstream mist eliminators.

In FIG. 2, the system | strain of the wet flue gas desulfurization apparatus which is another Example of this invention is shown.
The wet flue gas desulfurization apparatus shown in FIG. 2 is provided with a gas cooler 25 on the upstream side of the exhaust gas flow path of the absorption tower 4 of the wet flue gas desulfurization apparatus in FIG. 1 and further adjusts the amount of cooling medium in the gas cooler 25. The other configuration is the same except that the control device 40 is provided.

An exhaust gas containing sulfur oxides discharged from a combustion apparatus such as a boiler installed in a thermal power plant or factory is a gas gas heater (heat exchanger) 20 installed in the entrance flue 1 of the absorption tower 4 from the direction of arrow A. The heat of the exhaust gas is recovered and the gas temperature is lowered to 90-110 ° C. The exhaust gas whose gas temperature has dropped below a certain value is introduced into a multi-tube gas cooler 25 provided on the upstream side of the exhaust gas passage of the absorption tower 4.
The gas cooler 25 has a seawater supply line 24 connected to a pipe 25a through which a cooling medium passes, and has a configuration that can supply seawater as a cooling medium (internal medium) of the gas cooler 25. Therefore, water from the outside of the absorption tower such as seawater flows from the seawater supply line 24 using the pipe inner surface of the gas cooler 25 as a cooling medium, and exhaust gas flows from the pipe outer surface.

  The temperature of the exhaust gas cooled by passing through the gas cooler 25 is measured by an absorption tower inlet gas thermometer 30. The controller 40 can control the amount of seawater supplied from the seawater supply line 24 to the gas cooler 25 so that the temperature measured by the absorption tower inlet gas thermometer 30 is maintained at a predetermined value of about 60 to 80 ° C. is there. The amount of seawater supplied from the seawater supply line 24 is adjusted by a supply amount adjusting means such as a seawater amount adjusting valve 42 provided at the entrance of the cooling medium pipe 25a.

  Then, the temperature measured by the absorption tower inlet gas thermometer 30 is input to the control device 40 as an electric signal, and an electric signal is sent from the control device 40 to the seawater amount adjusting valve 42 so that this temperature maintains a predetermined value. By outputting, the amount of seawater introduced into the cooling medium pipe 25a of the gas cooler 25 is determined.

  By controlling the amount of seawater supplied to the gas cooler 25 by the control device 40 in this way, the boiler maintains the water amount balance of the entire equipment of the wet flue gas desulfurization apparatus regardless of the operation state and operation load of the boiler and the like. And so on. And it becomes possible to reduce the amount of supplementary water required as the whole equipment of a wet flue gas desulfurization apparatus. Moreover, since the composition of the cooling medium inside the gas cooler 25 does not change before and after passing through the gas cooler 25, the drainage treatment of the used water is unnecessary.

  And the exhaust gas from the boiler etc. which passed the gas cooler 25 is introduce | transduced into the absorption tower 4 after that, and is contained in exhaust gas by the gas-liquid contact with absorption liquid similarly to the wet flue gas desulfurization apparatus of FIG. After removing the required amount of acidic gas such as sulfur oxide, hydrogen chloride, hydrogen fluoride, etc., it is discharged from the chimney.

 Conventionally, exhaust gas from boilers and the like installed in thermal power plants and factories is introduced into the absorption tower 4 while the exhaust gas temperature is relatively high, so there is a problem that the amount of evaporated water in the absorption tower 4 increases. there were. The amount of evaporated water in the absorption tower 4 depends on the exhaust gas composition such as the inlet gas temperature of the absorption tower 4, the amount of treated gas in the absorption tower 4, and the amount of water in the exhaust gas.

As an example, FIG. 5 shows a correlation diagram between the inlet gas temperature of the absorption tower 4 and the amount of evaporated water in the absorption tower 4 in a 1000 MW scale thermal power generation facility.
As apparent from FIG. 5, the amount of evaporated water of about 15 t / h is reduced by reducing the temperature of the absorption gas at the inlet 4 of the absorption tower 4 that is conventionally operated at about 90 ° C. by 10 ° C. Therefore, according to this embodiment, the gas cooler 25 is installed at the inlet of the absorption tower 4 and seawater is supplied as a cooling medium for the gas cooler 25, so that the required amount of makeup water for the entire wet flue gas desulfurization apparatus is obtained. Can be saved significantly.

In FIG. 3, the system | strain of the wet flue gas desulfurization apparatus which is another Example of this invention is shown.
The wet flue gas desulfurization apparatus shown in FIG. 3 is different in that the gas gas heater 20 is not provided on the upstream side of the exhaust gas flow path of the absorption tower 4 of the wet flue gas desulfurization apparatus in FIG. Therefore, explanation is omitted.

  Exhaust gas containing sulfur oxides discharged from a combustion apparatus such as a boiler installed in a thermal power plant or factory is a multi-tube gas cooler 25 installed at the gas inlet 3 of the absorption tower 4 from the direction of arrow A. To be introduced. In the multitubular gas cooler 25, the controller 40 controls the seawater supply line 24 to the gas cooler 25 so that the temperature measured by the absorption tower inlet gas thermometer 30 is maintained at a predetermined value of about 60 to 80 ° C. The amount of seawater supplied is controlled. The amount of seawater supplied from the seawater supply line 24 is adjusted by a supply amount adjusting means such as a seawater amount adjusting valve 42 provided at the entrance of the cooling medium pipe 25a.

Basically, the operational effects are the same as those of the second embodiment (FIG. 2), but the gas temperature at the inlet of the gas cooler 25 is increased to the extent that the gas temperature is not lowered by the gas gas heater 20 in advance. If it is not installed, more makeup water is required. By installing the gas cooler 25, the effect of reducing makeup water is enhanced.
According to this structure, although the capacity | capacitance (heat-transfer area) of the gas cooler 25 becomes large, since the gas gas heater 20 is not provided, it becomes a simple structure.

In FIG. 4, the system | strain of the wet flue gas desulfurization apparatus which is another Example of this invention is shown.
The wet flue gas desulfurization apparatus shown in FIG. 4 is different in that an air cooler 27 that cools the oxidizing air supplied to the absorption tower of the wet flue gas desulfurization apparatus shown in FIG. 1 is provided. is there.

  By installing an air cooler 27 in the oxidation air supply line 26 and connecting the seawater supply line 24 to a pipe 27a through which the cooling medium of the air cooler 27 passes, seawater is used as a cooling medium (internal medium) of the air cooler 27. The equipment configuration can supply.

  Normally, the outlet air temperature of the oxidizing air blower 17 is high-temperature air of 120 to 150 ° C. When supplied to the liquid reservoir 5 of the absorption tower 4 as it is, the end of the pipe interpolated in the absorbent in the liquid reservoir 5 Therefore, the air at the outlet of the oxidizing air blower 17 is supplied to the liquid reservoir 5 by reducing the air temperature to the water saturation temperature by direct spraying of industrial water. The amount of water sprayed at this time depends on the amount of oxidizing air determined in accordance with the amount of sulfur oxide to be removed, but in the case of a 1000 MW scale thermal power generation facility, it is about 1 to 2 t / h.

  However, according to the present embodiment, an air cooler 27 for cooling the oxidizing air is installed in the oxidizing air supply line 26, and seawater is used as a cooling medium for the air cooler 27. The amount of air humidified water for oxidation can be reduced, and the amount of water of about 1 to 2 t / h (industrial water amount, that is, seawater amount) can be saved. The amount of seawater used for the cooling medium of the air cooler 27 can be adjusted by a seawater amount adjusting valve 42 provided at the entrance of the cooling medium pipe 27a.

Further, a thermometer (not shown) for measuring the temperature of the oxidizing air is provided at the outlet of the oxidizing air blower 17, and the air cooler 27 is connected from the seawater supply line 24 so that the water saturation temperature is obtained by the measured value of the thermometer. It is good also as a structure which can be controlled by the control apparatus 40 (FIG. 2 etc.).
Moreover, you may provide the air cooler 27 which cools the air for oxidation in the wet flue gas desulfurization apparatus of FIG.2 and FIG.3. The installation of the air cooler 27 can further reduce the makeup water.

  And as shown in these Examples 1-4, according to this invention, the reduction of the amount of washing water of the mist eliminators 7a and 7b of the absorption tower 4, the reduction of the amount of evaporated water in the absorption tower 4, and the oxidation of the absorption tower 4 This makes it possible to reduce the amount of air-humidified water, which is expected to have a reduction effect on the amount of water required in the wet flue gas desulfurization apparatus, and is also useful in areas where it is difficult to secure the amount of water.

  Moreover, the above-mentioned Example etc. are applicable also when it is set as the horizontal flow type absorption tower which waste gas flows into a horizontal direction, or when it is set as a two-chamber type absorption tower.

  In wet flue gas desulfurization equipment and the like, it may be used as a technology that can reduce the amount of makeup water.

DESCRIPTION OF SYMBOLS 1 Inlet flue 2 Outlet flue 3 Absorption tower gas inlet part 4 Absorption tower 5 Absorption tower liquid storage part 6 Absorption tower absorption part (spray part)
7 Mist Eliminator 7a Upstream Mist Eliminator 7b Downstream Mist Eliminator 8 Spray Header 9 Spray Nozzle 10 Absorbing Liquid Circulating Pump 11 Absorbing Liquid Extraction Pump 12 Gypsum Dehydration Equipment 13 Absorbing Liquid Circulating Pipe 14 Gypsum 15 Oxidizing Stirrer 16 Absorbent Slurry Supply Line 17 Oxidizing air blower 18 Absorption tower gas outlet 20 Gas gas heater (heat exchanger)
21 Filtrate recovery tank 22 Filtrate pump 23 Drain line 24 Seawater supply line 25 Gas cooler 25a Cooling medium pipe 26 Oxidizing air supply line 27 Oxidizing air cooler 27a Cooling medium pipe 30 Absorption tower inlet gas temperature Total 31, 33 Flushing device 35 Liquid reservoir supply line 37 Flushing water supply line 37a Upstream flush water supply line 37b Downstream flush water supply line 38 Seawater switching valve 39 New water switching valve 40 Control device 42 Seawater amount adjustment valve

Claims (6)

An absorption tower for absorbing and removing sulfur oxides contained in the exhaust gas by introducing exhaust gas discharged from a combustion apparatus including a boiler, spraying an absorption liquid on the exhaust gas, and bringing it into gas-liquid contact, and the absorption In the flue gas desulfurization apparatus provided with the mist eliminator that is provided at the outlet of the exhaust gas flow path of the tower and collects the mist discharged from the absorption tower, and the mist eliminator water washing device that rinses the mist eliminator,
A plurality of the mist eliminators are provided on the upstream side and the downstream side of the exhaust gas flow path, and the mist eliminator flushing device is provided with a flush water supply unit for supplying flush water to each mist eliminator, and the downstream mist eliminator is flushed. A flue gas desulfurization apparatus comprising a seawater supply section for supplying seawater to a water supply section. An exhaust gas cooler having a cooling medium pipe inside is provided at the inlet of the exhaust gas flow path of the absorption tower,
The flue gas desulfurization apparatus according to claim 1, further comprising a seawater supply unit configured to supply seawater to the cooling medium pipe. An oxidizing air supply unit for supplying oxidizing air to the absorption tower is provided,
The oxidation air supply unit is provided with an oxidation air cooler having a cooling medium pipe inside,
The flue gas desulfurization apparatus according to claim 1, further comprising a seawater supply unit configured to supply seawater to the cooling medium pipe. The exhaust gas discharged from the combustion apparatus including the boiler is introduced into the absorption tower, sprayed with the absorbing liquid, and brought into gas-liquid contact with the exhaust gas, thereby absorbing and removing sulfur oxides contained in the exhaust gas, and then absorbing the absorption This is a flue gas desulfurization method in which mist discharged from the tower is collected by a plurality of mist eliminators provided upstream and downstream of the outlet of the exhaust gas passage of the absorption tower, and the mist eliminator collecting the mist is washed with water. And
A flue gas desulfurization method using seawater for washing water of the downstream mist eliminator.   The flue gas desulfurization method according to claim 4, wherein the exhaust gas at the inlet of the absorption tower is cooled using seawater as a cooling medium.   The flue gas desulfurization method according to claim 4, wherein the oxidizing air is supplied to the absorption tower, and the oxidizing air supplied to the absorption tower is cooled using seawater as a cooling medium.

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