JP3322817B2 - Drainless desulfurization method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-drainable desulfurization method and apparatus, and more particularly to a non-drainable desulfurization method in which ammonia is injected into a high-temperature gas containing sulfur oxides such as boiler combustion exhaust gas to desulfurize the gas. And equipment.

[0002]

2. Description of the Related Art By injecting ammonia into a high-temperature gas containing sulfur oxides, such as boiler flue gas,
In the desulfurization method for removing sulfur oxides as ammonia compounds in powder, the lower the gas temperature, the higher the reaction rate between sulfur oxides and ammonia. , A completely evaporating cooling tower for completely evaporating the sprayed water in the tower was installed, and the gas was cooled to about 50 ° C to 70 ° C. This is the same in the desulfurization method of irradiating an electron beam together with the injection of ammonia. On the other hand, when the concentration of the sulfur oxide is relatively high and / or when the irradiation amount of the electron beam is relatively large, for example, the heat of reaction between the sulfur oxide and ammonia and / or the gas generated by the heat generated by the electron beam irradiation are used. In order to suppress the decrease in the reaction rate due to the temperature rise, it is necessary to suppress the rise in the gas temperature by spraying and evaporating water in the reaction vessel after the above-mentioned gas cooling. (Hereinafter, the suppression of the temperature rise of the gas performed by the evaporation of the spray water in the reaction vessel is referred to as “secondary gas cooling” and the gas cooling performed prior thereto is referred to as “primary gas cooling”).

[0003] However, in the conventional system in which the primary gas is cooled in a completely evaporative cooling tower, the residence time of the gas is required to be about 10 to 30 seconds in order to completely cool the spray water in the tower. However, there has been a problem that the volume of the cooling tower is increased, and the construction cost and the installation space of the cooling tower are increased. As a measure for reducing the volume of the cooling tower of the complete evaporation type, there is a case where the particle size of the spray water droplet is reduced.
In this case, there is a problem that the power for atomization increases. When the primary gas cooling is performed by a method in which the gas is brought into contact with circulating cooling water (hereinafter, referred to as “water circulating cooling method”), the required residence time of the gas in the cooling unit is 0.
Although it is about 1 to 5 seconds, it is greatly reduced, but since sulfur oxides and dust etc. contained in the gas are collected in the circulating water, part of the circulating water is drained for stable gas cooling. In the conventional water circulation type cooling, this is turned into wastewater, and is discharged after being subjected to necessary treatment.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and reduces the required residence time of gas in a cooling section by performing primary gas cooling by a water circulation system. It is an object of the present invention to provide a non-drainage type desulfurization method and apparatus which can eliminate the generation of wastewater by completely evaporating the discharged water in the reactor and thereafter using it for cooling the secondary gas.

[0005]

According to the present invention, there is provided a desulfurization method for injecting ammonia into a high-temperature gas containing sulfur oxides and removing the sulfur oxides as an ammonia compound in a powder. After contacting the high-temperature gas with circulating cooling water and cooling, when injecting ammonia into the cooling gas, in the cooling gas, partially withdrawing the circulating cooling water, or further with the extracted cooling water Add water, before, simultaneously with, after injection of ammonia,
Alternatively, it is a non-drainage desulfurization method in which the mixture is sprayed with ammonia to suppress the temperature rise of the gas due to the heat of reaction, and to completely evaporate the extracted water. In the present invention, the water discharged from the circulating cooling water is preferably filtered before spraying, and the gas injected with ammonia can be irradiated with an electron beam, thereby improving the desulfurization rate. Can be.

Further, according to the present invention, in a desulfurization apparatus for injecting ammonia into a high-temperature gas containing sulfur oxide and removing the sulfur oxide as an ammonia compound in powder, the high-temperature gas is brought into contact with circulating cooling water for cooling. A gas cooling device to be injected, an ammonia injection device for injecting ammonia into the cooled gas, or before or in the same position as the ammonia injection device,
Alternatively, a non-drainable desulfurization apparatus provided with a spraying device for spraying into the gas a water withdrawn from the circulating cooling water of the gas cooling device or a diluent obtained by adding water thereto. Further, according to the present invention, in a desulfurization apparatus for injecting ammonia into a high-temperature gas containing a sulfur oxide and removing the sulfur oxide as an ammonia compound in a powder form, a gas cooling method in which the high-temperature gas is brought into contact with circulating cooling water for cooling A device, a mixing device that mixes with ammonia a withdrawal water from the circulating cooling water of the gas cooling device or a diluent obtained by adding water thereto, and a mixed water of ammonia and withdrawal water or a diluent solution with the cooled gas. This is a non-draining type desulfurization device provided with an ammonia water spray device for spraying.

Further, according to the present invention, in a desulfurization apparatus for injecting ammonia into a high-temperature gas containing sulfur oxide and removing the sulfur oxide as an ammonia compound in powder, the high-temperature gas is brought into contact with circulating cooling water for cooling. And a gas-liquid mixing and spraying device for mixing and spraying water extracted from the circulating cooling water of the gas cooling device or a diluent obtained by adding water thereto with ammonia or ammonia-mixed air. This is a wastewater desulfurization unit. In the non-draining desulfurization device, after the gas cooling device, it is preferable to provide a filtration device for filtering water extracted from the circulating cooling water of the device, an ammonia injection device for injecting ammonia, an ammonia water spray device or An electron beam irradiation device that irradiates the ammonia-added gas with an electron beam can be provided after the gas-liquid mixing and spraying device.

In the present invention, the amount of the circulating cooling water is adjusted so that the pH becomes 1 or more and 7 or less, preferably 1 or more and 6 or less, or ammonia, a sodium compound, a potassium compound, and a calcium compound. And at least one alkaline substance selected from magnesium compounds is injected to adjust the pH to 1 or more and 7 or less, preferably 1 or more and 6 or less. , Potassium compounds,
Inject or dilute one or more alkaline substances selected from calcium compounds and magnesium compounds with water
Is adjusted to 1 or more and 8 or less, preferably 1 or more and 7 or less. Further, soft water can be used as makeup water to be supplemented to the circulating cooling water of the gas cooling device. As the alkaline substance of the compound of sodium, potassium, calcium and magnesium, hydroxides, oxides and carbonates of these metals can be used.

[0009]

Next, the present invention will be described in detail.
Gas cooling can be performed by installing an independent gas cooling device upstream of the reactor, but since the required residence time is short, a gas cooling unit is provided on the upstream side of the ammonia injection part of the reactor. You can also. The amount of spray water required for secondary gas cooling depends on the gas temperature before secondary gas cooling, the gas temperature desired to be achieved by secondary gas cooling, the heat of reaction, and the amount of electron beam irradiation. Therefore, in order to completely eliminate the generation of drainage, it is necessary to reduce the amount of circulating water extracted to the amount required for spraying water for secondary gas cooling. If the amount of water to be withdrawn is equal to or less than the required amount of spray water, the water is sprayed after mixing the water with water. Conversely, if the amount of withdrawal is greater than the required amount of spray water, only a part of the withdrawal water will be sprayed and the rest will be drained. In this case, however, the amount of generated waste water can be reduced and it is effective. Generally, in order to completely evaporate the extracted water, it is necessary to spray as fine water droplets. Therefore, a nozzle having a small diameter of the liquid passing portion is often used as the spray nozzle. On the other hand, when the high-temperature gas containing sulfur oxides simultaneously contains dust, the dust is collected in the circulating cooling water in the water circulation type cooling. Therefore, in order to prevent dust from clogging the liquid passage portion of the nozzle, it is preferable to spray the filtered water after filtering it.

[0010] When the concentration of sulfur trioxide among the sulfur oxides in the gas is relatively high, if the water circulation type cooling is performed,
Sulfur trioxide dissolves into the circulating water, lowering the pH of the circulating water, and the corrosion of the gas cooling unit, the water circulation line, the circulating water extraction line, and the secondary gas cooling spray unit may proceed. This corrosion is likely to proceed when the pH is less than 1,
Is desirably maintained at 1 or more. This is done by increasing the amount of water withdrawn from the water circulation type cooling tower, or by injecting ammonia into the circulating cooling water and circulating it, or by extracting the circulating cooling water and then injecting ammonia into the withdrawn water. Alternatively, it is realized by dilution with water. This is to increase the amount of water withdrawn from the circulating cooling water, or to circulate or circulate after injecting an alkaline substance such as ammonia, sodium compound, potassium compound, calcium compound, or magnesium compound into the circulating cooling water. After extracting the cooling water, this is realized by injecting an alkaline substance such as ammonia, a sodium compound, a potassium compound, a calcium compound, or a magnesium compound, or diluting with water.

On the other hand, when the injection amount of an alkaline substance such as ammonia, a sodium compound, a potassium compound, a calcium compound or a magnesium compound is excessively increased, and the circulating cooling water is made alkaline, the high-temperature gas generates carbon dioxide like boiler combustion exhaust gas. In the case where carbon dioxide is included, carbon dioxide that is not originally intended to be removed is dissolved in the circulating cooling water. In addition, sodium compound, potassium compound,
When the circulating cooling water is made alkaline by injecting an alkaline substance such as a calcium compound or a magnesium compound, the circulating cooling water becomes an aqueous solution of a salt such as sodium sulfate, potassium sulfate, calcium sulfate or magnesium sulfate, and the extracted water is sprayed. And complete evaporation, the mixing amount of these salts with the ammonia compound, which is the main by-product of desulfurization, also increases. Therefore, the circulating cooling water has a pH of 1
It is desirably at least 7 and preferably at least 1 and at most 6. In addition, when an alkaline substance such as ammonia, a sodium compound, a potassium compound, a calcium compound, or a magnesium compound is injected into the extraction water from the circulating cooling water, the above-described problem does not occur. If the cooling water is made strongly alkaline, calcium and magnesium originally contained in the working water may be generated as scaling in the secondary gas cooling section, which may lead to blockage. Therefore, the pH of the withdrawal water is 1 or more and 8 or less,
It is desirable that the number be 1 or more and 7 or less.

When the extracted water is filtered, the pH is adjusted as required. In this case, the pH is preferably 1 or more and 8 or less, more preferably 1 or more and 7 or less. In addition, when injecting ammonia, sodium compound or potassium compound, if calcium and magnesium are removed in advance by softening the make-up water to the circulating cooling water, it will not be included in the withdrawal water.
It is more preferable for prevention of blockage. As a gas cooling method intermediate between the complete evaporation type cooling tower and water circulation type cooling, a method of spraying water in the tower and circulating and using un-evaporated water without removing the water is also conceivable, but in this method, If the amount of withdrawal is equal to or less than the amount required for secondary gas cooling, the drainage water can be eliminated by mixing the extracted water with water if necessary and using it as secondary gas cooling. . Further, when the amount of withdrawal is equal to or more than the required amount of spray water, only a part of the withdrawal water is sprayed, and the rest becomes waste water. In this case, too, the amount of generated waste water can be reduced, which is effective.

[0013]

The present invention will be described below in more detail with reference to examples. Reference Example 1 In the reference example shown in FIG. 3, 1,500 m ³ N / h of exhaust gas containing 850 ppm of sulfur oxides generated from the boiler 1 was used.
After cooling to 150 ° C. in the heat exchanger 2, the working water supplied from the spray pump 3 is sprayed by the one-fluid nozzle 6 and cooled to 60 ° C. in the complete evaporation type cooling tower 4 for complete evaporation. Lead to. On the other hand, ammonia 2.3 m ³ N / h supplied from the ammonia supply facility 9, the air 8.0 m ³ N /
and the mixed gas and water 1
8 kg / h was mixed in the gas-liquid mixing chamber of the two-fluid nozzle 11, sprayed and injected at the inlet of the reactor 5, and irradiated with an electron beam of 15 kGy from the electron accelerator 12. As a result, the reactor 5
The gas temperature at the outlet is 65 ° C and the sulfur oxide is 35 pp
m. In this case, neither the working water sprayed by the complete evaporation type cooling tower nor the working water sprayed at the reactor inlet was completely evaporated, so that no drainage was generated. A residence time of 20 seconds was required for evaporation.

Embodiment 1 In the embodiment shown in FIG. 1, the exhaust gas containing 850 ppm of sulfur oxides generated from the boiler 21 is 1,500 m ³ N / h.
Is cooled to 150 ° C. in the heat exchanger 22 and the circulation pump 2
The water is cooled to 50 ° C., which is the water saturation temperature, in a water circulation type cooling tower 24 that circulates the cooling water in 3, and is guided to a reactor 25. At this time, a pH meter 27 installed in the circulating water tank 26
The circulating water was withdrawn so that the pH became 0.5, and the working water was replenished with the liquid level gauge 28 in the circulating water tank 26 so that the liquid level became constant. As a result, the amount of water withdrawn was 2.5 kg / h. It became. After 2.5 kg / h of the extracted water is filtered by the filtration device 33, the extracted water is mixed with 7.5 kg / h of working water in the mixing water tank 34.
After being diluted to pH = 1.1, the ammonia 2.3 m ³ N / h supplied from the ammonia supply facility 29 was further added to
A gas mixed with 8.0 m ³ N / h of air in the line mixer 30 and a gas mixed in the gas-liquid mixing chamber of the two-fluid nozzle 31 were spray-injected at the inlet of the reactor 25. Then, the electron accelerator 32
15 kGy of electron beam from the reactor 25
The gas temperature at the outlet is 65 ° C and the sulfur oxide is 35 pp
m.

The water discharged from the circulating water tank was mixed with industrial water and sprayed, and completely evaporated in the reactor, so that no drainage was generated. Further, the residence time required for cooling to 50 ° C. in the water circulation type cooling tower was 0.5 seconds, which was significantly reduced as compared with the complete evaporation type cooling tower of Reference Example 1. At this time, the corrosion progressed at 0.5 mm / y in the circulating water extraction line 35 made of carbon steel through which the liquid of pH = 0.5 flowed, but the carbon steel through which the liquid of pH = 1.1 after dilution flowed Corrosion was not observed in the circulating water extraction line 36 manufactured by Toshiba Corporation. In addition, no corrosion was observed in the gas cooling section and the water circulation line of the water circulation type cooling tower having a resin lining on the surface in contact with the circulating water.

Example 2 A gas under the same conditions as in Example 1 was flowed through the same apparatus as shown in FIG. 1 and cooled to the same temperature in a heat exchanger 22 and a water circulation type cooling tower 24, respectively. lead. At this time, the pH is measured by a pH meter 27 installed in the circulating water tank 26.
= 1.0 and the replenishment of working water so that the liquid level becomes constant with the liquid level gauge 28 in the circulating water tank 26, the amount of water withdrawn is 8 kg / h. Was. After 8 kg / h of the extracted water is filtered by the filtration device 33, the water is mixed with 2 kg / h of working water in the mixing water tank 34 to dilute the pH to 1.1, and further, the ammonia supplied from the ammonia supply facility 29. 2.3 m ³ N / h and 8.0 m ³ N air
/ H and the gas mixed by the line mixer 30 and the gas mixed in the gas-liquid mixing chamber of the two-fluid nozzle 31, and sprayed and injected at the inlet of the reactor 25. Then, as a result of irradiating the electron beam from the electron accelerator 32 with 15 kGy, the gas temperature at the outlet of the reactor 25 became 65 ° C., and the sulfur oxide became 35 ppm. In this case, as in the case of Example 1, no drainage is generated,
The residence time in the water circulation type cooling tower was 0.5 seconds. In addition, not only the extracted liquid line 36 after dilution with water,
No corrosion was observed in the extraction liquid line 35 before dilution.

Embodiment 3 In the embodiment shown in FIG. 2, the exhaust gas containing 2,000 ppm of sulfur oxides generated from the boiler 41 is 1,500 m ³ N / h.
Is cooled to 150 ° C. in the heat exchanger 42 and the circulation pump 4
The water is cooled to 50 ° C., which is the water saturation temperature, in a water circulation type cooling tower 44 that circulates the cooling water in 3, and is guided to a reactor 45. At this time, a pH meter 47 installed in the circulating water tank 46
The circulating water was withdrawn so that the pH became 0.5, and the working water was replenished with the liquid level meter 48 of the circulating water tank 46 so that the liquid level became constant. As a result, the amount of withdrawn water became 10 kg / h. . After 10 kg / h of the extracted water was filtered by a filtration device 53, it was mixed with 14 kg / h of working water in a mixing water tank 54, and further adjusted to pH = 8.5 by injecting ammonia from an ammonia supply facility 49. The extracted water after the pH adjustment, a gas obtained by mixing 5.4 m ³ N / h of ammonia supplied from the ammonia supply facility 49 with 8.0 m ³ N / h of air in the line mixer 50 and a two-fluid nozzle 51 And mixed by spraying at the inlet of the reactor 45. On top of that, the electron beam is
As a result of the Gy irradiation, the gas temperature at the outlet of the reactor 45 was 65 ° C.
And the sulfur oxide content was 100 ppm.

Also in this case, no drainage was generated, and the residence time in the water circulation type cooling tower was 0.5 seconds. Also, pH =
0.5 circulating water drain line 55 made of carbon steel
The corrosion progressed at 0.5 mm / y.
No corrosion was observed in the circulating water extraction line 55 made of carbon steel through which the liquid of 8.5 flowed. On the other hand, in the gas-liquid mixing chamber of the two-fluid nozzle 51, scaling mainly containing calcium and magnesium occurred, and the nozzle was finally closed. For this reason, after cleaning the two-fluid nozzle, the amount of ammonia injected into the mixed water tank 54 was reduced, and pH =
7, the scaling in the gas-liquid mixing chamber of the two-fluid nozzle 51 did not occur.
No corrosion was observed in the circulating water extraction line 56 through which the liquid having the adjusted pH = 7 flowed.

[0019]

According to the present invention, the primary gas cooling is performed by the water circulation system, so that the required residence time of the gas in the cooling section is significantly reduced, and the extracted water is used for the secondary gas cooling. And after that, by completely evaporating, generation of wastewater can be eliminated. Further, by adjusting the amount of water used for cooling the secondary gas, it is possible to suppress an increase in the temperature of the gas due to the heat of reaction and an increase in the temperature due to the heat generated by electron beam irradiation.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a non-drainage type desulfurization device of the present invention.

FIG. 2 is a schematic configuration diagram showing another example of the non-drainage type desulfurization device of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional non-drainable desulfurization apparatus.

[Explanation of symbols]

1, 21, 41: boiler, 2, 22, 42: heat exchanger,
3: spray pump, 4: complete evaporation type cooling tower, 5, 25, 4
5: reactor, 6: one-fluid nozzle, 9, 29, 49: ammonia supply equipment, 10, 30, 50: line mixer, 1
1, 31, 51: two-fluid nozzle, 12, 32, 52: electron accelerator, 24, 44: water circulation type cooling tower, 26, 46:
Circulating water tank, 27, 47: pH meter, 28, 48: Liquid level meter,
33, 53: filtration device, 34, 54: mixed water tank

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-215335 (JP, A) JP-A-6-296825 (JP, A) JP-A-8-164324 (JP, A) WO 97/31702 (WO, A1) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 53/34

Claims (9)

(57) [Claims] In a desulfurization method for injecting ammonia into a high-temperature gas containing sulfur oxide and removing the sulfur oxide as a powdery ammonia compound, the high-temperature gas is cooled by contacting with circulating cooling water, When injecting ammonia into the cooling gas, a part of the circulating cooling water is extracted into the cooling gas, or water is further added to the extracted cooling water, and before and simultaneously with injection of ammonia. after, or ammonia mixed with and sprayed, no waste water type desulfurization process which comprises bringing emitted distilled the extraction water. 2. The non-drainage desulfurization method according to claim 1, wherein the extracted water from which the circulating cooling water is extracted is filtered and sprayed. 3. The non-drainage desulfurization method according to claim 1, wherein the gas into which the ammonia is injected is irradiated with an electron beam. 4. The non-drainage desulfurization method according to claim 1, wherein the amount of the circulating cooling water is adjusted so that the pH is 1 or more and 7 or less. 5. The extraction water from the circulating cooling water is adjusted to a pH of 1 to 8 by injecting or diluting at least one alkaline substance selected from ammonia, sodium compound, potassium compound, calcium compound and magnesium compound with water.
4. The non-drainage desulfurization method according to claim 1, wherein the method is adjusted as follows. 6. A desulfurizer for injecting ammonia into a high-temperature gas containing sulfur oxide and removing the sulfur oxide as a powdery ammonia compound, wherein the high-temperature gas is brought into contact with circulating cooling water to cool the gas. And, an ammonia injection device that injects ammonia into the cooled gas, and before, at the same position as, or after the ammonia injection device, water extracted from the circulating cooling water of the gas cooling device or water was added thereto. A non-drainable desulfurization device, comprising: a spray device for spraying the diluent into the gas. 7. A gas cooling device for injecting ammonia into a high-temperature gas containing sulfur oxide and removing the sulfur oxide as an ammonia compound in a powder form, wherein the high-temperature gas is brought into contact with circulating cooling water to cool the gas. And a mixing device that mixes the ammonia with the extracted water from the circulating cooling water of the gas cooling device or a diluent obtained by adding water to the ammonia, and the mixed gas of the ammonia and the extracted water or the diluent with the cooled gas. A non-drainage type desulfurization device comprising an ammonia water spray device for spraying. 8. A desulfurization apparatus for injecting ammonia into a high-temperature gas containing sulfur oxide and removing the sulfur oxide as a powdery ammonia compound, wherein the high-temperature gas is brought into contact with circulating cooling water for cooling. And a gas-liquid mixing / spraying device for spraying water extracted from the circulating cooling water of the gas cooling device or a diluent obtained by adding water thereto with ammonia or ammonia mixed air. No drainage desulfurizer. In free drainage type desulfurizing device of any one of claim 9 claim 6-8, ammonia injection unit for injecting ammonia, after aqueous ammonia spraying apparatus, or gas-liquid mixture spraying device, electrons in ammonia added gas A non-drainable desulfurization device comprising an electron beam irradiation device for irradiating a beam.