JP2013086054A - Wet type limestone-gypsum method desulfurization apparatus using seawater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet type limestone-gypsum method desulfurization apparatus which sprays an absorbing solution of high limestone concentration, low Cl concentration and low temperature to an exhaust gas to effectively desulfurize the exhaust gas, and to reduce an amount of industrial water required for exhaust gas desulfurization by using seawater.SOLUTION: In order to remove a sulfur oxide-acidic gas contained in the exhaust gas 1 with limestone slurry 16, the wet type limestone-gypsum method desulfurization apparatus has an absorbing tower 4 consisting of a plurality of steps of spray parts 6 arranged in the flowing direction of the exhaust gas and a liquid storage 5, a slurry tank 24 for forming a limestone slurry 16 with a limestone 25 and water, and a plurality of circulation pumps 28, 29 for supplying the absorbing liquid in the liquid storage 5 to the plurality of steps of spray parts 6, respectively, wherein seawater 27 is used as water for forming the limestone slurry 16 and the limestone slurry 16 with seawater 27, is supplied to a suction side of the circulation pump 28 for supplying the absorbing liquid to the highest step of the spray parts 6. Seawater using and improvement of exhaust gas desulfurization are achieved at the same time by this constitution.

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 oxide contained in combustion exhaust gas such as a boiler. In a wet flue gas desulfurization device that reduces acid gases such as hydrogen chloride and hydrogen fluoride, and human harmful substances such as dust and trace components contained in fuel, efficient desulfurization, The present invention relates to a technique for reducing industrial water necessary for desulfurization.

  A general system of a wet type flue gas desulfurization apparatus in a thermal power generation facility is shown in FIG. Note that the same number is assigned to the same device in each drawing described later. In FIG. 5, the exhaust gas 1 discharged from a boiler or the like installed in a thermal power plant, a factory, or the like is pressurized by an exhaust gas fan 20 after dust in the exhaust gas is removed by an electric dust collector 19, and is absorbed by an absorption tower. The gas is introduced into the absorption tower 4 from the gas inlet 3.

  Limestone slurry 16 composed of limestone 25 and filtrate 18 is supplied to the liquid reservoir 5 of the absorption tower 4. The slurry-like absorption liquid in the liquid reservoir 5 of the absorption tower 4 is pressurized by the absorption liquid circulation pumps 28 and 29, and sulfur in the exhaust gas comes into contact with the absorption liquid sprayed from the spray nozzle 9 and the exhaust gas 1. Acid gases such as oxides, hydrogen chloride, and hydrogen fluoride are absorbed on the surface of the liquid droplets of the absorbing liquid. Thereafter, the mist accompanying the exhaust gas is removed by the mist eliminator 7 installed at the outlet of the absorption tower 4 and finally discharged from the chimney. Water loss due to evaporation or drainage inside the absorption tower is compensated by supplying industrial water 26 shown in FIG.

  The absorption tower liquid reservoir 5 becomes gypsum slurry by an oxidation reaction between the air from the oxidation air blower 17 and calcium sulfite generated from sulfur oxides. The absorbent slurry in the liquid reservoir 5 of the absorption tower 4 is extracted from the liquid reservoir 5 of the absorption tower 4 to the gypsum dewatering equipment 12 by the absorption tower extraction pump 11 according to the amount of gypsum produced. After being dehydrated at 12, it is recovered as a powder gypsum 14. Thus, in the desulfurization system shown in FIG. 5, industrial water is used as water necessary for desulfurization. As described above, as a means for removing sulfur oxides, acid gases, and the like contained in exhaust gas discharged from a boiler or the like, it is generally known as a wet desulfurization apparatus and has been put into practical use.

  Moreover, regarding said prior art, patent document 1 is mentioned as invention which utilizes seawater as absorption tower supplementary water, for example. According to Patent Document 1, when wet gas desulfurization treatment is performed on a gas containing sulfur oxides, seawater is used as moisture used for forming a calcium-based compound absorption liquid, and the pH of the absorption liquid is 4.5. It is disclosed that approximately 80% of high-quality makeup water necessary for wet flue gas desulfurization can be substituted with seawater by keeping the Mg concentration below 1,000 mg / L or lower in the absorption liquid. ing.

  Further, as a conventional technique for desulfurization / dedusting using limestone and seawater, for example, Patent Document 2 is cited. According to Patent Document 2, a primary desulfurization spray nozzle by spraying of limestone slurry and a position above the primary desulfurization spray nozzle are arranged. And a secondary desulfurization spray nozzle that sprays seawater, and further includes a seawater recovery unit for receiving the seawater sprayed from the secondary desulfurization spray nozzle and discharging it to the outside. However, it is disclosed that the remainder uses magnesium hydroxide or seawater.

JP-A-7-275648 JP 2001-170444 A

  By the way, in the prior art in the above-described wet flue gas desulfurization apparatus (see FIG. 5), the exhaust gas temperature discharged from the boiler or the like and the gas temperature at the absorption tower inlet are relatively high at 120 to 160 ° C. In order to maintain the liquid level and absorption liquid slurry concentration in the absorption tower liquid reservoir 5 constant and maintain the water balance of the entire desulfurization apparatus, the absorption tower increases. 4 has a problem that a large amount of industrial water 26 needs to be replenished.

  On the other hand, as disclosed in Patent Documents 1 and 2, when seawater is used as makeup water, the Cl concentration (chlorine concentration) in industrial water is several hundred ppm, whereas seawater The concentration of Cl in the reactor is about 20,000 ppm, and Cl in the desulfurization system is concentrated by evaporation of water in the absorption tower, resulting in a decrease in desulfurization performance (seawater is gradually concentrated when seawater is used as makeup water). However, when the concentration of chlorine contained in seawater increases and exceeds the limit, limestone solubility becomes insufficient and desulfurization performance decreases).

  The purpose of the present invention is to reduce the amount of industrial water required in a wet flue gas desulfurization device installed in a plant facility such as a thermal power plant, and suppress a decrease in desulfurization performance due to an increase in Cl concentration in the desulfurization device system. The object is to provide a wet limestone-gypsum desulfurization apparatus using seawater.

In order to solve the above problems, the present invention adopts the following configuration.
In order to remove sulfur oxide and acid gas contained in exhaust gas using limestone slurry, limestone is composed of an absorption tower composed of a spray part and a liquid storage part arranged in a plurality of stages in the exhaust gas flow direction, and limestone and water. A wet limestone-gypsum desulfurization apparatus comprising: a slurry tank that generates slurry; and a plurality of circulation pumps that respectively supply absorption liquid of the liquid reservoir to the plurality of stages of spray units, the limestone slurry The seawater is used as the water for generating water, and the limestone slurry using the seawater is connected to the suction side of the circulation pump that feeds the absorption liquid to the uppermost stage of the spray unit.

  Further, in the wet limestone-gypsum desulfurization apparatus using seawater, the amount of the spray composed of the absorption liquid and the limestone slurry to the uppermost stage of the spray part is composed of the absorption liquid to the spray parts other than the uppermost stage. Less than spray amount.

  According to the present invention, by supplying a limestone slurry mixed with seawater to the suction side of the circulation pump at the uppermost stage of the spray section of the absorption tower, it is possible to spray an absorption liquid having a high limestone concentration, a low Cl concentration, and a low temperature onto the exhaust gas. As a result, the exhaust gas can be efficiently desulfurized. Furthermore, industrial water required for exhaust gas desulfurization can be reduced by using seawater.

It is a block diagram which shows the system configuration | structure example in the wet limestone-gypsum method desulfurization apparatus using the seawater which concerns on embodiment of this invention. It is a block diagram which shows the other system | strain structural example in the wet limestone-gypsum method desulfurization apparatus using the seawater which concerns on embodiment of this invention. It is a characteristic view which shows the relationship between Cl density | concentration in a desulfurization apparatus system, and a limestone solubility. It is a table | surface explaining the influence on the amount of absorption liquids / gas amount (L / G) by the desulfurization apparatus which concerns on this embodiment compared with a comparative example. It is a block diagram which shows the example of a system | strain structure in the wet limestone-gypsum method desulfurization apparatus using industrial water regarding a prior art.

  A seawater-based wet limestone-gypsum desulfurization apparatus according to an embodiment of the present invention will be described below with reference to FIGS. The contents shown in each drawing are as described in the brief explanation column of the drawing. In the drawings, 1 is an exhaust gas from a boiler outlet, 2 is a desulfurizer gas outlet, 3 is a desulfurizer gas inlet, 4 is an absorption tower, 5 is an absorption tower liquid reservoir, 6 is an absorption tower spray section (absorption section), 7 Is a mist eliminator, 8 is a spray header, 9 is a spray nozzle, 10 is a bypass line, 11 is an absorption liquid extraction pump, 12 is a gypsum dewatering facility, 13 is an absorption liquid circulation pipe, 14 is gypsum, 15 is an agitator for oxidation, and 16 is limestone. Slurry, 17 is an oxidizing air blower, 18 is filtrate, 19 is an electric dust collector, 20 is an exhaust gas fan, 21 is a filtrate recovery tank, 22 is a filtrate pump, 23 is a drain line, 24 is a limestone slurry tank, and 25 is limestone. , 26 is industrial water, 27 is seawater, 28 is an absorption tower upper stage circulation pump, 29 is an absorption tower lower stage circulation pump, and 30 is an open / close valve.

  In FIG. 1, exhaust gas 1 from a boiler or the like installed in a thermal power plant or factory is introduced into an absorption tower 4 from an absorption tower gas inlet 3, and sulfur oxide, hydrogen chloride, or fluorine contained in the exhaust gas 1 is introduced. The basic structure is shown in which acidic gas such as hydrogen fluoride is absorbed and removed by the surface of the liquid droplet of the absorbing liquid circulating in the absorption tower 4. Here, in FIG. 1 representing this embodiment, the seawater 27 is used to generate the limestone slurry 16, and the suction of the circulation pump 28 that is fed to the uppermost stage of the spray section (absorption section) 6 of the absorption tower 4. The limestone slurry 16 is provided on the side. The desulfurization apparatus according to the present embodiment uses an exhaust gas flow system after the exhaust gas fan 20, a configuration system including an oxidation air blower 17, an absorption liquid extraction pump 11, and seawater 27 in FIG. 1. And a constituent system having the gypsum dewatering equipment 12 may be included in a broad sense.

  The system configuration shown in FIG. 1 will be described in more detail. Exhaust gas 1 discharged from a boiler or the like installed in a thermal power plant or factory is exhausted after dust in the exhaust gas is removed by an electric dust collector 19. The pressure is increased by the fan 20 and introduced into the absorption tower 4 from the absorption tower gas inlet 3. Here, the temperature of exhaust gas discharged from boilers installed in thermal power plants and factories varies depending on the fuel used, but in the case of coal-fired boilers, it is usually a relatively high temperature gas of 120 to 160 ° C. Temperature.

  The absorption tower 4 is composed of a liquid storage section 5 and a spray section (absorption section) 6. The liquid storage section 5 of the absorption tower 4 contains sulfur oxides, hydrogen chloride / hydrogen fluoride contained in the exhaust gas 1 from a boiler or the like. The limestone slurry 16 is supplied from the limestone slurry tank 24 in accordance with the amount of acid gas such as sulfur oxide (hereinafter also referred to as sulfur oxide). In the limestone slurry tank 24, the amount and concentration of the limestone slurry 16 are adjusted by the limestone 25 and the seawater 27. The slurry-like absorption fluid (fluid in which solid particles are suspended in the liquid) in the liquid reservoir 5 of the absorption tower 4 is pressurized by the absorption liquid circulation pumps 28 and 29 and passes through the absorption liquid circulation pipe 13. Then, it is supplied to the spray header 8 provided in multiple stages in the gas flow direction to the upper absorption section 6 in the absorption tower 4.

  Each spray header 8 is provided with a number of spray nozzles 9, and sulfur oxides and hydrogen chloride contained in the exhaust gas due to gas-liquid contact between the absorbing liquid sprayed from the spray nozzle 9 and the exhaust gas 1 from a boiler or the like. Acidic gas such as hydrogen fluoride is absorbed on the droplet surface of the absorbing liquid circulating in the absorption tower 4. Thereafter, the mist accompanying the exhaust gas (liquid fine particles dispersed in the gas) is removed by the mist eliminator 7 installed at the outlet of the absorption tower 4 and finally discharged from the chimney. Evaporation inside the absorption tower or water loss in the system due to drainage or the like can be compensated by supplying seawater 27 shown in FIG.

  The mist eliminator 7 installed at the outlet of the absorption tower 4 is provided with a water washing device so that the absorption liquid circulating through the absorption tower 4 scatters and adheres to the mist eliminator 7 element. The mist eliminator 7 element is washed with water.

  Sulfur oxide or the like contained in the exhaust gas 1 discharged from the boiler or the like reacts with the calcium compound in the absorption liquid, becomes calcium sulfite as an intermediate product, and flows down to the absorption tower liquid reservoir 5. On the other hand, air is forcibly supplied from the oxidizing air blower 17 to the absorption tower liquid reservoir 5, and a gypsum slurry is obtained as a reaction product by an oxidation reaction between the air and calcium sulfite. At this time, the oxidized air supplied to the absorption tower liquid reservoir 5 is refined by an oxidizer stirrer 15 for agitating the absorption liquid in the absorption tower liquid reservoir 5, thereby increasing the utilization rate of the oxidized air. ing.

  The absorption liquid in the liquid reservoir 5 of the absorption tower 4 is approximately 50 ° C., but the air temperature at the outlet of the oxidizing air blower 17 is normally 120 to 150 ° C., and the liquid reservoir 5 of the absorption tower 4 is used as it is. 1, since dry / wet repetition occurs at the end of the pipe inserted in the absorbent in the liquid reservoir 5 of the absorption tower 4, as shown in FIG. 1, the air at the outlet of the oxidizing air blower 17 is used as industrial water. The air temperature is lowered by the spraying 26 and supplied to the liquid reservoir 5 of the absorption tower 4.

  The absorbent slurry in the liquid reservoir 5 of the absorption tower 4 is extracted from the liquid reservoir 5 of the absorption tower 4 to the gypsum dewatering equipment 12 by the absorption tower extraction pump 11 according to the amount of gypsum produced. After being dehydrated at 12, it is recovered as a powder gypsum 14.

  As described above, in the configuration example of this embodiment shown in FIG. 1, the amount and concentration of the slurry-like limestone slurry 16 serving as the absorption liquid is adjusted by the limestone slurry tank 24, and the uppermost stage of the absorption tower spray unit 6. Is supplied to the suction side of the circulation pump 28 to be fed to the pump. And it is one of the characteristics of the said structural example to provide the line which can mix the seawater 27 used as makeup water in the path | route of this limestone slurry supply line. In the prior art, the exhaust gas 1 from a boiler or the like installed in a thermal power plant or factory is introduced into the absorption tower 4 at a relatively high exhaust gas temperature of 120 to 160 ° C. Therefore, the absorption tower 4 There is a problem that the amount of evaporated water increases. For this reason, a large amount of absorption water for the absorption tower is required. In this embodiment, the wet limestone-gypsum method is used even in an area where there is little industrial water that can be used by using seawater as supplementary water instead of industrial water. It is possible to utilize a desulfurization apparatus.

  Further, this configuration example shown in FIG. 1 will be described together with its functions and actions. Exhaust gas 1 from a boiler or the like is introduced into a spray section (absorption section) 6 of an absorption tower 4 and a liquid of limestone slurry 16 as an absorption liquid. By contacting the droplets with gas and liquid, sulfur oxides contained in the exhaust gas are taken into the absorbing solution and removed. The limestone slurry of the absorbent circulation pipe 13 contains gypsum 14 as a by-product in addition to sulfur oxide, and the pH is maintained at about 5.5 to 6.0. The gypsum generated in the retention part 5 has a system configuration that is continuously extracted by the gypsum dewatering equipment 12, and the gypsum concentration in the sprayed absorbent is approximately 20%.

  As for the desulfurization performance of the absorption liquid, the higher the limestone concentration, the higher the pH and the more favorable conditions. Therefore, supply the limestone slurry directly to the suction side of the circulation pump 28 to the top of the absorption tower spray section 6. Thus, the absorbing liquid having a high limestone concentration can be sprayed by the spray part (absorbing part) 6 so that the residence time becomes the highest, and can be efficiently desulfurized. In other words, connecting the supply line of the limestone slurry 16 to the suction side of the absorption tower circulation pump 28 makes it possible to spray an absorption liquid having a high limestone concentration. It can suppress desulfurization performance degradation by.

In addition, seawater (Cl concentration: about 20,000 ppm) is mixed as make-up water in the course of the limestone slurry supply line, so that the concentration of Cl (100,000 ppm) concentrated in the desulfurization system is reduced and the limestone solubility is reduced. It is possible to suppress the decrease and suppress the desulfurization performance deterioration. That is, by supplying seawater 27 (Cl concentration: about 20,000 ppm) as makeup water when supplying the limestone slurry 16, the Cl concentration (100,000ppm) in the absorption liquid concentrated in the system is reduced. This makes it possible to suppress a decrease in desulfurization performance when seawater 27 is used as makeup water. FIG. 3 shows the relationship between the Cl concentration in the desulfurization system and the solubility of limestone. When the Cl concentration (100,000 ppm) in the system is lowered by supplementing seawater 27 (Cl concentration: about 20,000 ppm), limestone dissolution occurs. This indicates that the desulfurization performance is improved.
Normally, the inside of the desulfurization system is maintained at about 50 ° C., but by supplying seawater at about 30 ° C. to the suction side of the circulating pump 28 at the top of the absorption tower spray section, the temperature of the absorption liquid is lowered and replenished. There exists an effect | action which suppresses the desulfurization performance fall at the time of using the seawater 27 as water. It is a well-known fact that the solubility of the gaseous sulfur oxide SOx in the absorbing solution is higher at lower temperatures, so that the desulfurization performance improves as the temperature of the absorbing solution decreases.

  As described above, the limestone slurry supply line of the wet flue gas desulfurization apparatus according to the present embodiment is connected to the suction side of the circulation pump at the uppermost stage of the spray tower, and seawater is supplied in the route of the limestone slurry supply line. By connecting in such a way as possible, spraying a high limestone concentration, low Cl concentration, low temperature absorption liquid and supplying seawater as make-up water can be achieved simultaneously.

  Next, an improvement example in the system configuration shown in FIG. 1 will be described. In the system of FIG. 1, the limestone slurry 16 is supplied to the suction side of the circulation pump 28, but the supply method is improved. That is, it is set as the improvement example which supplies the limestone slurry 16 to the inner peripheral wall side of the suction pipe of the circulation pump 28 (that is, the limestone slurry 16 is not supplied to the central portion of the pipe, but from a plurality of parts on the inner peripheral wall of the pipe. By supplying along the inner peripheral wall in the absorption liquid flow direction), it is possible to reduce the corrosive environment of the pump inlet due to the use of seawater.

  The reason for the reduction is that the seawater 27 having a Cl concentration of 20,000 ppm flows on the inner peripheral wall of the pipe, and further, the absorption liquid having a Cl concentration (100,000 ppm) concentrated in the system flows to the center of the pipe. This is because a limestone slurry layer having a low Cl concentration is formed on the inner peripheral wall, thereby mitigating corrosion caused by chlorine on the inner peripheral wall of the pipe and the pump inlet.

  Next, another system configuration example in the seawater-based wet limestone-gypsum desulfurization apparatus according to the present embodiment will be described with reference to FIG. 2, between the suction side of the uppermost pump 28 to which the limestone slurry 16 is supplied and the suction side of the other pumps 29,... Among the absorption tower circulation pumps 28, 29,. Each of the bypass lines 10 is provided, and an opening / closing valve (flow path on / off valve) is installed in each bypass line.

  When switching the circulation pump to be used in response to boiler load fluctuations (exhaust gas inflow fluctuations), for example, all circulation pumps are used for full load, but pump 28 is stopped for partial load. When the on-off valve 30 is turned on and the limestone slurry 16 is supplied to the pump 29, it is always possible to supply the highly efficient absorption liquid to the pump sprayed on the uppermost stage of the spray header in the circulating pump to be used.

  Next, FIG. 4 shows the efficient operation of the system configuration based on the difference in the amount of the circulating liquid absorbed by the uppermost pump 28 in the system configuration example in the seawater-based wet limestone-gypsum desulfurization apparatus according to the present embodiment shown in FIG. This will be described below with reference.

  In the system configuration of FIG. 1, by reducing the amount of circulation in the uppermost circulation pump 28 of the absorption tower as compared with the circulation line of the other stages, it is possible to spray an absorption liquid having a higher limestone concentration from the uppermost stage of the spray unit 6. It becomes a system configuration capable of efficient operation. FIG. 4 shows a system (comparative example) for supplying seawater as make-up water to a desulfurization apparatus as shown in Patent Document 1, and the effect on the amount of absorbed liquid / gas amount (L / G) of the system according to this configuration example Contrast. Here, the smaller amount of the absorbing liquid with respect to the same gas amount represents that the power of the exhaust gas fan 20 and the circulation pumps 28 and 29 is reduced (the smaller L / G is the more efficient the system configuration). Will be operational).

According to FIG. 4, in this configuration example and the comparative example, the liquid circulation rate is 30,000 [m ³ / h] in any case, and 200 [m ³ / h] is supplied as seawater as makeup water therein. To do. The in-system Cl concentration was set to 100,000 ppm. The number of spray stages is three, and the spray amount is sprayed equally at 10,000 [m ³ / h] in each stage in the comparative example case, and in the case of this configuration example, only the upper stage is 1,000 [m ³ / h]. ], And the other stages are set to the circulation amount (each 30,000-1,000 / 2 [m ³ / h]) that is evenly distributed. The flow rate adjustment shown in FIG. 4 at each stage of the spray amount can be performed by controlling each circulation pump as an example.

  Further, the ratio Qtop / Qtotal between the upper stage liquid circulation amount Qtop and the total liquid circulation amount Qtotal is shown in each case. Here, the RTU indicating the degree of influence on the desulfurization performance is increased by 5% by lowering the spray amount at the uppermost stage of the absorber and lowering the spray amount at the other stage and changing Qtop / Qtotal from 0.33 to 0.033. Overall, L / G can be reduced by 5%. This contributes to the improvement in the performance of the upper spray part absorbent by reducing the Cl concentration, increasing the limestone concentration, lowering the temperature of the absorbent, and the like.

According to FIG. 4, the amount of seawater (Cl concentration: 20,000 ppm) is the same in the present configuration example and the comparative example, and the upper spray amount is 10,000 in this configuration example as compared with the comparative example. Since [m ³ / h] is reduced to 1,000 [m ³ / h], the present configuration example is about 1,000 [m] of the absorbed liquid having a concentrated 100,000 ppm Cl concentration for the upper spray. ³ / h] is small, that is, since the Cl concentration is low, it is possible to suppress a decrease in desulfurization performance. Here, RTU is an abbreviation for Relative transfer unit, and represents a ratio of ATU (Actual transfer unit) which is an evaluation index of SO ₂ absorption performance. The RTU represents the ratio of the ATU between the two when representing the degree of influence of each influencing factor on the desulfurization performance or as an index representing the scale-up factor between the pilot device and the actual machine.

Next, the effect of the seawater-based wet limestone-gypsum desulfurization apparatus according to the embodiment of the present invention will be described below. According to the present embodiment, seawater can be used instead of industrial water as make-up water for the slurry tank 24. Therefore, it is difficult to secure industrial water by using seawater, such as the Middle East, Southeast Asia, and South America (this area However, it is an effective method for employing wet limestone-gypsum desulfurization. For example, when exhaust gas equivalent to 1,000 MW is treated by the wet limestone-gypsum method, industrial water of about 160 ton / h in total is installed without installing a gas gas heater (GGH) (not shown) provided on the gas input / output side of the desulfurization apparatus shown in the figure. Of these, water other than about 10 ton / h used for oxidizing air humidification at the outlet of the oxidizing air blower 15 and the sealing water of the pump 17 is supplemented with seawater, and the Cl concentration in the system is set to 100, When it is going to be maintained at 000 ppm, it is sufficient if there is about 200 ton / h seawater (corresponding to the seawater amount 200 m ³ / h shown in FIG. 4). The total supply water amount of 160 tons and 200 tons mentioned above changes because the Cl concentration in industrial water and seawater is different. To maintain the same Cl concentration in the system, the supply water amount and the drainage amount must be adjusted. This is because it must not.

  In addition, when installing a desulfurization unit in an existing thermal power plant, using seawater directly as make-up water is less expensive as a cost impact than securing necessary industrial water by adding a seawater desalination unit. .

  In areas where it is difficult to secure industrial water, a seawater desulfurization method that uses seawater as a desulfurization agent is being adopted, but the amount of wastewater is large and discharged to the ocean without sufficient wastewater treatment. There are concerns about contamination. In this embodiment, seawater is used as make-up water, but limestone is used as an absorbent and wastewater treatment equipment can be installed. Therefore, the system configuration can reduce the environmental burden compared to the seawater desulfurization method.

  As a method of replenishing seawater, by supplying from the suction tower circulation pump suction side together with limestone slurry, higher performance can be achieved by increasing the limestone concentration and decreasing the absorption solution Cl concentration (in the case of Cl concentration in the system: 100,000 ppm). It becomes possible to spray as an absorbing solution.

  In addition, the inside of the desulfurization system is normally maintained at about 50 ° C., but when the seawater at about 30 ° C. is supplied on the circulation pump suction side, the temperature of the absorption liquid is lowered and seawater 27 is used as makeup water. It has the effect of suppressing the desulfurization performance degradation.

  Then, by connecting the limestone slurry 16 supply pipe to the suction side of the absorption tower upper circulation pump 28, the residence time of the absorbent with high absorption performance becomes the longest (the time during which the absorbent is in contact with the exhaust gas becomes longer). ) In addition, by reducing the amount of circulation in the upper circulation pump 28 of the absorption tower as compared with the circulation line of the other stages, it is possible to spray an absorption liquid having a higher limestone concentration and a lower Cl concentration from the uppermost stage of the spray unit 6. This has the effect of more efficiently desulfurizing (see the description of FIG. 4).

  Furthermore, by supplying the limestone slurry to the circulation pump suction side at the uppermost stage of the absorption tower spray section, the gypsum concentration in the sprayed absorption liquid slurry is lowered, the gypsum concentration in the scattered mist is lowered, and the gypsum to the mist eliminator There is an effect that sticking can be reduced.

DESCRIPTION OF SYMBOLS 1 Boiler exit exhaust gas 2 Desulfurization apparatus gas exit part 3 Desulfurization apparatus (absorption tower) gas inlet part 4 Absorption tower 5 Absorption tower liquid storage part 6 Absorption tower spray part (absorption part)
7 Mist Eliminator 8 Spray Header 9 Spray Nozzle 10 Bypass Line 11 Absorption Liquid Extraction Pump 12 Gypsum Dehydration Equipment 13 Absorption Liquid Circulation Pipe 14 Gypsum 15 Oxidizing Stirrer 16 Limestone Slurry 17 Oxidizing Air Blower 18 Filtrate 19 Electric Dust Collector 20 Exhaust Fan 21 Filtrate recovery tank 22 Filtrate pump 23 Drain line 24 Limestone slurry tank 25 Limestone 26 Industrial water 27 Seawater 28 Absorption tower upper circulation pump 29 Absorption tower lower circulation pump 30 Open / close valve

Claims (4)

In order to remove sulfur oxide and acid gas contained in exhaust gas using limestone slurry, limestone is composed of an absorption tower composed of a spray part and a liquid storage part arranged in a plurality of stages in the exhaust gas flow direction, and limestone and water. A wet limestone-gypsum desulfurization apparatus comprising a slurry tank for generating slurry, and a plurality of circulation pumps for feeding the absorption liquid of the liquid reservoir to the plurality of stages of spray parts, respectively.
Seawater is used as water to generate the limestone slurry,
A wet limestone-gypsum desulfurization method using seawater, characterized in that the limestone slurry using the seawater is connected to the suction side of a circulation pump that feeds the absorbing liquid to the uppermost stage of the spray section. apparatus. In claim 1,
Wet water using seawater, characterized in that the amount of spray consisting of the absorbent and limestone slurry to the uppermost stage of the spray part is less than the amount of spray consisting of the absorbent to the spray part other than the uppermost stage. Limestone-gypsum desulfurization equipment. In claim 1 or 2,
The connection configuration for supplying the limestone slurry to the suction side of the circulation pump is configured to supply the limestone slurry along the inner peripheral wall in the absorption liquid flow direction from a plurality of peripheral wall portions of the suction side piping. Wet limestone-gypsum desulfurization equipment using seawater. In claim 1, 2 or 3,
Each of the plurality of circulation pumps is provided with a bypass line that connects between the suction side of the circulation pump that feeds liquid to the uppermost stage of the spray unit and the suction side of other circulation pumps, and each bypass line Each has an open / close valve,
A wet limestone-gypsum using seawater, wherein the on-off valve for each bypass line is selected and turned on / off when the circulation pump used for the inflow fluctuation of the exhaust gas is switched on / off. Process desulfurization equipment.

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