JP2011177674A - Finishing flue gas desulfurization apparatus and exhaust gas treatment system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple finishing flue gas desulfurization apparatus and an exhaust gas treatment system using the same. <P>SOLUTION: The finishing flue gas desulfurization apparatus, which removes sulfur oxides from combustion exhaust gas beforehand by means of an existing desulfurization device thereafter further removing the remaining sulfur oxides to the extremely low concentration, includes a gas inlet part 12 which introduces combustion exhaust gas (exhaust gas) 11 including a trace quantity of sulfur oxides. It also includes: a desulfurization device body 15 provided with a finishing desulfurization part 14 which desulfurizes by bringing an absorbing solution 13 into contact with the sulfur oxides in the introduced combustion exhaust gas 11; a wet type electric dust collection part 16 which is provided at the rear-flow side of the finishing desulfurization part 14 in the finishing desulfurization device body 15 and removes soot and dust in the combustion exhaust gas after finishing desulfurization; a cooling part 17 which is provided at either front or rear of the wet type electric dust collection part 16 and cools the combustion exhaust gas; and a gas discharge part 19 which discharges the purifying combustion exhaust gas (purifying gas) 18 to the outside after dust removal and cooling. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a finish flue gas desulfurization apparatus and an exhaust gas treatment system using the same.

An example of the exhaust gas treatment system is shown in FIG. As shown in FIG. 6, the exhaust gas G from the boiler (coal-fired boiler) 101 is first guided to the air heater 103 and supplied to the boiler after nitrogen oxide (NOx) in the exhaust gas is removed by the denitration device 102. Heat the air. Thereafter, the exhaust gas G is introduced into a dry electric dust collector 104 to remove dust. Next, the exhaust gas G is introduced into the desulfurization apparatus 105 to remove sulfur oxides (SOx). Thereafter, the exhaust gas G is introduced into the CO ₂ recovery device 106 to remove carbon dioxide, and then the purified gas 112 is released from the chimney 111 to the atmosphere (for example, see Patent Document 1).

  There are various proposals as a method for simultaneously treating desulfurization and decarbonization (Patent Documents 2 to 4).

Japanese Patent Laid-Open No. 11-179147 Japanese Patent Laid-Open No. 06-86911 Japanese Patent Application Laid-Open No. 08-133365 JP 2003-53134 A

However, when the CO ₂ recovery device 106 is installed after desulfurization by the desulfurization device 105, if sulfur oxide or soot exceeding the allowable amount remains in the CO ₂ recovery device 106, for example, an amine-based absorption liquid is used as the CO ₂ absorption liquid. Is used, there is a problem that a running cost increases when reclaiming the absorption liquid corresponding to the deterioration or replenishing the new liquid, which is accumulated in the CO ₂ absorption liquid (for example, amine absorption liquid). .

Therefore, it is proposed to remove the dust using a filter when circulating the absorbing liquid in the CO ₂ recovery device 106, but there are the following problems.
1) When removing dust in the absorbent with a fiber-filled cartridge filter, there is a problem that the dust removal efficiency is low. Furthermore, there is a problem that the used cartridge filter needs to be disposed as waste, and the running cost increases.
2) For example, when using cellulose or diatomaceous earth as a precoat agent and removing dust in the absorbent with a precoat filter that removes dust, although the removal efficiency of dust is high, the used cartridge filter is disposed of as waste. There is a problem that the running cost increases. In addition, since the precoat agent contains the absorbing solution, there is a problem that the absorbing solution is lost.

  Therefore, the appearance of a finishing desulfurization apparatus that can further purify the target component in the exhaust gas to an extremely low concentration with respect to the exhaust gas G from which sulfur oxides have been removed in advance by the desulfurization apparatus 105 is desired.

  In view of the above problems, an object of the present invention is to provide a finish flue gas desulfurization apparatus and an exhaust gas treatment system using the same.

  1st invention of this invention for solving the subject mentioned above is the finishing flue gas desulfurization apparatus which removes further the remaining sulfur oxide to very low concentration after removing sulfur oxide from combustion exhaust gas, A finishing desulfurization apparatus main body having a gas introduction part for introducing combustion exhaust gas containing a small amount of sulfur oxide, and having a finishing desulfurization part for bringing the absorbing liquid into contact with the sulfur oxide in the introduced combustion exhaust gas for desulfurization; Provided on the downstream side of the final desulfurization unit in the main body of the final desulfurization unit, provided on either the front or back of the wet electrostatic precipitator for removing soot and dust in the combustion exhaust gas after the final desulfurization The finish flue gas desulfurization apparatus includes a cooling unit that cools the combustion exhaust gas, and a gas discharge unit that discharges the purified combustion exhaust gas after dust removal and cooling to the outside.

  According to a second invention, in the first invention, the finishing desulfurization part absorption liquid and the wet electrostatic precipitating part cleaning liquid are circulated independently, and the finishing desulfurization part absorption liquid is lime-absorbing. The finish flue gas desulfurization apparatus is characterized in that it is a liquid and the cleaning liquid of the wet electrostatic precipitator is a strong alkaline liquid.

  According to a third aspect of the present invention, there is provided the finished flue gas desulfurization apparatus according to the first aspect, wherein a part of the strong alkaline liquid of the wet electrostatic precipitator is supplied to the lime absorbing liquid of the final desulfurizer. is there.

  According to a fourth invention, in the first invention, the finishing desulfurization section absorption liquid and the wet electrostatic precipitating section cleaning liquid are both the same kind of strong alkali and the same concentration liquid, and are shared. In the featured flue gas desulfurization equipment.

  According to a fifth invention, in any one of the first to fourth inventions, a cooling device for cooling the purified gas is provided, and a part of the purified gas after cooling is used as the insulator seal gas of the wet electrostatic precipitator. It is in the finish flue gas desulfurization equipment characterized by

The sixth invention is a denitration device that removes nitrogen oxides in exhaust gas from boilers, a dust collector that removes soot and dust in the gas after nitrogen oxide removal, and sulfur oxides in the gas after dust removal A desulfurization apparatus for removing the sulfur oxide remaining in the exhaust gas after the desulfurization to a very low concentration, and recovering carbon dioxide in the purified gas. An exhaust gas treatment system comprising a CO ₂ recovery device.

According to the present invention, the concentration of sulfur oxides is extremely small, the accumulation of sulfur oxides and dust is reduced in the CO ₂ absorbing solution used in the CO ₂ recovery apparatus, it is possible to suppress the deterioration.

FIG. 1 is a schematic diagram of a finish flue gas desulfurization apparatus according to a first embodiment. FIG. 2 is a schematic diagram of a finish flue gas desulfurization apparatus according to a second embodiment. FIG. 3 is a schematic diagram of a finish flue gas desulfurization apparatus according to a third embodiment. FIG. 4 is a schematic diagram of another finish flue gas desulfurization apparatus according to the third embodiment. FIG. 5 is a schematic diagram of an exhaust gas treatment system according to a fourth embodiment. FIG. 6 is a diagram illustrating an example of an exhaust gas treatment system.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

A finish flue gas desulfurization apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a finish flue gas desulfurization apparatus according to a first embodiment.
As shown in FIG. 1, the final flue gas desulfurization apparatus 10A according to the first embodiment removes sulfur oxide from combustion exhaust gas in advance with an existing desulfurization apparatus (not shown), and then reduces the remaining sulfur oxide to an extremely low level. It is a finish flue gas desulfurization device that further removes to a concentration, and has a gas introduction part 12 for introducing combustion exhaust gas (exhaust gas) 11 containing a trace amount of sulfur oxide, and is absorbed by the sulfur oxide in the introduced combustion exhaust gas 11 A finishing desulfurization apparatus main body (hereinafter referred to as “apparatus main body”) 15 provided with a finishing desulfurization section 14 for desulfurization by contacting the liquid 13; and a finishing desulfurization section 14 in the finishing desulfurization apparatus main body 15, A wet electrostatic precipitator 16 that removes soot and dust in the exhaust gas after the final desulfurization, a cooling unit 17 that cools the exhaust gas, provided in either one of the front and rear of the wet electrostatic precipitator 16, and dust removal and cooling After The gas discharge portion 19 for discharging to the outside the combustion exhaust gas (purified gas) 18 is intended to provided.
In the present embodiment, the finishing desulfurization section 14 is supplied with lime (CaCO ₃ ) absorbing liquid through the circulation line L ₁ by the pump P ₁ as the absorbing liquid 13 for removing sulfur oxide of the lime gypsum method.
In addition, the wet electrostatic precipitator 16 is supplied with cleaning water 31 for the electrodes through a circulation line L ₂ by a pump P ₂ . The cooling unit 17 is supplied with cooling water 32 through a circulation line L ₃ by a pump P ₃ .
Reference numeral 21 denotes an insulator support, 22 an insulator, 23 a mist eliminator, 33 a Jinkasa chimney tray, 34 a dispersive chimney tray, and 35 to 37 nozzles.

  By using the finish flue gas desulfurization apparatus 10A according to the first embodiment, the exhaust gas 11 from which sulfur oxide has been removed in advance can be further desulfurized by the finish desulfurization unit 14, and most of the remaining sulfur oxide is removed. can do. Thereafter, the soot can be removed by the wet electrostatic precipitator 16 provided on the upper side of the finish desulfurizer 14.

Here, as the absorbing liquid 13 used in the finish desulfurization unit 14, NaOH, Na ₂ CO ₃ , NaHCO ₃ , Ca (OH) 2, Mg (OH) _{2 and the} like can be exemplified in addition to CaCO ₃ .
Further, examples of the cleaning water 31 used in the wet electrostatic precipitator 16 include Na ₂ CO ₃ and NaHCO _{3 in} addition to NaOH.
In the present embodiment, tanks for supplying the absorbing liquid 13 and the cleaning water 31 are omitted in the drawing.

Moreover, it is preferable that the finish desulfurization part 14 and the wet electric dust collection part 16 are made into a similar cross-sectional area (substantially the same cross-sectional structure or a similar cross-sectional structure).
This is because, if the structure is greatly widened or expanded, a portion where the gas flow rate is uneven is formed, and the contact efficiency between the exhaust gas and the electrode of the wet dust remover may be lowered, and the dust removal performance may be lowered.

Also, the preferred gas flow rate of the finishing desulfurization device is 2.0 to 3.8 m / s, and the preferred gas flow rate of the wet dust collection device is 2.0 to 3.0 m / s. For this purpose, it is preferable to adjust the gas flow rate passing through both in the range of 2.0 to 3.0 m / s. In addition, if necessary, a rectifying plate is provided at a place where drift in the tower is expected to occur in advance to suppress gas drift, or a partition-shaped jammer plate in the finishing desulfurization tower having a relatively fast gas flow velocity range. Or a suitable gas flow velocity zone may be optimally controlled.
For example, when supplying the exhaust gas 11 into the finish desulfurization section 14 at a relatively fast gas flow rate range (for example, about 3.0 m / s), by providing a partition-like jammer plate in the finish desulfurization tower, The suitable gas flow rate zone (for example, 2.5 m / s) of the wet electrostatic precipitator 16 can be optimally controlled, and as a result, good desulfurization treatment and dust removal treatment may be performed.

As a result, in the gas discharge unit 19, a highly purified purified gas 18 having a sulfur oxide concentration of 10 ppm or less (SO ₂ <1 to ₃ ppm, SO ₃ <1 to ₃ ppm) and a soot concentration of 10 mg / m ³ N or less. Can be obtained.

Thus, even when supplying a purge gas 18 to the CO ₂ recovery apparatus 106 which is installed in the subsequent stage of the finishing FGD 10A, the concentration of sulfur oxides is extremely low, CO ₂ absorbing solution (e.g. amine absorbent ) Accumulated in
As a result, it is possible to suppress a decrease in CO ₂ absorption performance due to deterioration of the CO ₂ absorbing solution.

In the present embodiment, the cooling unit 17 that cools the exhaust gas is provided on the downstream side of the wet electrostatic precipitator 16, but the present invention is not limited to this, and the upstream side of the wet electrostatic precipitator 16. You may make it provide in (between the finishing desulfurization part 14 and the wet electric dust collection part 16).
As the chimney tray for recovering the cooling water 32 provided at the lower part of the cooling unit 17, either a Jinkasa type chimney tray or a distributed type chimney tray may be used as long as a desired cooling effect can be obtained. However, the chimney tray that collects the washing water 31 in the lower part of the wet electrostatic precipitator 16 is preferably a distributed chimney tray in order to suppress the drift of the exhaust gas.

According to the present embodiment, the wet electrostatic precipitator 16 is provided on the upper side of the finish desulfurizer 14 so that the removal of soot and dust can be processed at the same time.
Moreover, in the finishing desulfurization part 14, a well-known watering type, jet type, filling type, liquid column type desulfurization apparatus can be used. By passing through the finish desulfurization section 14, the exhaust gas 11 is rectified, the rectified gas is supplied to the wet electric dust collection section 16, the contact efficiency with the electrode surface is improved, and the dust collection ability by rectification is improved. improves.

Moreover, the site area can be reduced by integrating the finish desulfurization section and the wet electric dust collection section.
In addition, since the conventional wet dust removal equipment is installed separately from other equipment, a connecting duct is required. At this time, when exhaust gas flows in through the connecting duct, it is necessary to connect with a bent duct or the like. Yes, as a result, drift occurs, and the dust removal performance in the wet dust collector decreases. However, this can be solved by using an integrated type.

Here, in the present embodiment, when the liquid desulfurization unit 14 is used in the finishing desulfurization section 14, for example, spray pipes of 200A to 350A are arranged at a pitch of about 0.5 m.
By using a liquid column type desulfurization apparatus in which such spray pipes are arranged at a pitch of about 0.5 m, this functions as a gas rectifying resistance structure, and the liquid falling to the pipe also contributes to resistance pressure loss. It will be.
For this reason, in this integrated structure equipment, due to the gas rectifying resistance effect in the finish desulfurization section 14, the drift of the gas introduced into the wet electrostatic precipitator 16 integrated in the upper part is suppressed. As a result, the dust collection performance in the dust collection unit 16 can be improved.

The decarburization equipment is expected to be applied to existing thermal power in addition to new thermal power due to increasing demand for CO ₂ reduction. At this time, by combining the wet electrostatic precipitator 16 and the finish desulfurizer 14 that have been separately provided in the same cross section, it is possible to install a decarburization / dust removal facility, which facilitates application.

  In the above embodiment, the wet electric dust collector is provided in one stage inside the apparatus main body 15. However, the present invention is not limited to this, and two stages may be provided continuously. Good.

A finish flue gas desulfurization apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a schematic diagram of a finish flue gas desulfurization apparatus according to a second embodiment.
As shown in FIG. 2, the finishing flue gas desulfurization apparatus 10B according to the second embodiment is configured to extract the cleaning water 31 used in the wet electric dust collection unit 16 through the line L _{4 in the} finishing flue gas desulfurization apparatus 10A according to the first embodiment. The cleaning water 31 is supplied into the absorption liquid (CaCO ₃ ) 13 stored on the lower side of the apparatus main body 15 as necessary. As the washing water 31, for example, by using a strong alkali agent such as NaOH, the desulfurization performance can be further improved.
The cleaning liquid 31 may be supplied while being monitored by the pH meter 41.
In particular, when the combustion exhaust gas (exhaust gas) 11 having a sulfur oxide concentration higher than the allowable value is introduced in the gas introduction unit 12, it becomes particularly effective, and the purified combustion exhaust gas (purified gas) in the gas discharge unit 19 is obtained. The concentration of sulfur oxide in 18 can be made extremely low.

  In general, when comparing the performance of lime gypsum method desulfurization method and strong alkali desulfurization method such as NaOH in equivalent molar amount, since the latter has no liquid side film resistance, the desulfurization performance becomes high, so the final desulfurization part When a strong alkali (for example, NaOH) is added to 14, this also contributes to an improvement in performance.

A finish flue gas desulfurization apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a schematic diagram of a finish flue gas desulfurization apparatus according to a third embodiment.
As shown in FIG. 3, the final flue gas desulfurization apparatus 10 </ b> C according to the third embodiment is the same as that of the final flue gas desulfurization apparatus 10 </ b> A according to the first embodiment. It is used as the absorbing liquid of the unit 14 and is shared as the absorbing / cleaning liquid 42.
As shown in FIG. 3, in the final flue gas desulfurization apparatus 10A of the first embodiment, the dispersive chimney tray 34 that collects the cleaning water 31 provided in the lower stage of the wet electrostatic precipitator 16 is removed, and the cleaning liquid is dropped as it is. To function as an absorbent.
The first and second orifices 43A and 43B are interposed in the lines L ₁₁ and L ₁₂ in order to set the supply amount of the strong alkaline liquid absorption / cleaning liquid 42 to a desired flow rate.

As a result, the cleaning water that contributes to the cleaning of the electrode in the wet electrostatic precipitator 16 can be used as it is as the absorbent of the finishing desulfurization unit 14.
In addition, since both the absorbing liquid in the finishing desulfurization unit 14 and the cleaning liquid in the wet electrostatic precipitator 16 are the same kind of strong alkali and the same concentration, both the cleaning water and the absorbing liquid can be shared and stored. Auxiliary facilities such as tanks and pumps can be shared.

  Further, in this example, only strong alkaline liquid such as NaOH is used as the absorbing liquid of the finishing desulfurization apparatus 14, and therefore there is no liquid side film resistance compared to the lime gypsum method, so the desulfurization performance is high. Thus, even if the concentration of the sulfur oxide in the gas introduction part 12 is high, good desulfurization performance is exhibited, and the concentration of sulfur oxide in the purified gas 13 in the gas discharge part 19 is 1 ppm or less. This will greatly contribute to the precise desulfurization of the steel.

Further, as shown in FIG. 4, in another finishing flue gas desulfurization apparatus 10D of the third embodiment, a purified gas cooling apparatus 45 for cooling purified gas 18 after precision desulfurization and precision dust removal, and a CO ₂ recovery apparatus are further provided. when providing a 106, a portion of the gas introduced into the CO ₂ recovering apparatus 106, via a line L _20, is supplied by the fan 46 as the seal gas 47 of the insulator 22 of the wet electrostatic precipitator 16. In other words, the seal gas 47 is supplied to the insulator chamber in which the insulator 22 is accommodated, and is constantly ventilated inside the wet electrostatic precipitator 16 to prevent the ingress of exhaust gas.
This eliminates the need for separately installed seal air fan equipment costs and electricity costs. Furthermore, since a part of the exhaust gas is circulated, it becomes a self-gas seal, and compared with the case where the total exhaust gas processing amount in the CO ₂ recovery device is covered with conventional air, for example, the gas processing amount is about It can be reduced by about 5%.

FIG. 5 shows a schematic configuration diagram of an exhaust gas treatment system according to an embodiment of the present invention.
As shown in FIG. 5, the exhaust gas treatment system 50 according to the fourth embodiment recovers the heat in the gas after removing the NOx removal device 102 that removes nitrogen oxide in the exhaust gas G from the boiler 101, for example. Air heater 103, electric dust collector 104 for removing dust in the gas after heat recovery, desulfurization device 105 for removing sulfur oxide in the gas after dust removal, and sulfur oxidation remaining in the exhaust gas 11 after desulfurization The finish desulfurization apparatus 10A according to the first embodiment that further removes substances to an extremely low concentration, the CO ₂ recovery apparatus 106 that recovers carbon dioxide in the purified gas 18, and the chimney 111 that discharges the CO ₂ recovered gas to the outside. It comprises.

Therefore, the purified gas 112 supplied to the CO ₂ recovery device 106 installed on the rear stage side of the final flue gas desulfurization device 10A has a very low concentration of sulfur oxides, and is circulated and used in the CO ₂ recovery device 106. Accumulation of sulfur oxides and soot and dust in the CO ₂ absorbing liquid (for example, amine absorbing liquid) is reduced, and deterioration can be suppressed.
As a result, reduction of CO ₂ absorption performance of the CO ₂ absorbing liquid due to the deterioration is reduced, it is possible to perform stable recovery of CO _2.

Further, in order to compensate for the decrease of CO ₂ absorption performance, the number of times the supply amount of the additional supply of CO ₂ absorption performance is reduced, there is no increase in the reclaiming frequency for recovery of CO ₂ absorption performance, in the exhaust gas treatment system Running costs can be reduced.

As described above, according to the finishing flue gas desulfurization apparatus according to the present invention, the concentration of sulfur oxides is extremely small, the accumulation of sulfur oxides and dust generation in CO ₂ absorbing solution used in the CO ₂ recovery system Therefore, deterioration can be suppressed.

10A-10D Finishing flue gas desulfurization equipment 11 Combustion exhaust gas (exhaust gas) containing a small amount of sulfur oxide
12 Gas introduction part 13 Absorbing liquid 14 Finishing desulfurization part 15 Finishing desulfurization equipment body (apparatus body)
16 Wet Electric Dust Collection Unit 17 Cooling Unit 18 Purified Combustion Exhaust Gas (Purified Gas)
19 gas exhaust unit 50 exhaust gas treatment system 101 boiler 102 denitration apparatus 103 air heater 104 electrostatic precipitator 105 desulfurizer 106 CO ₂ recovering apparatus 111 chimney G exhaust gas

Claims (6)

A finishing flue gas desulfurization device that further removes the remaining sulfur oxide to an extremely low concentration after removing the sulfur oxide from the combustion exhaust gas,
A finishing desulfurization apparatus main body having a gas introduction part for introducing combustion exhaust gas containing a small amount of sulfur oxide, and having a final desulfurization part for bringing the absorbing liquid into contact with the sulfur oxide in the introduced combustion exhaust gas to desulfurize;
A wet electrostatic precipitator that is provided on the downstream side of the finish desulfurization unit in the finish desulfurization apparatus body, and removes soot in the combustion exhaust gas after the finish desulfurization;
A cooling unit that is provided on either side of the wet electrostatic precipitator and cools the combustion exhaust gas;
A finishing flue gas desulfurization apparatus comprising a gas discharge unit that discharges purified combustion exhaust gas after dust removal and cooling to the outside. In claim 1,
The absorption liquid of the finishing desulfurization part and the cleaning liquid of the wet electrostatic precipitator are each circulated independently,
The absorption liquid of the finishing desulfurization part is a lime absorption liquid,
A finishing flue gas desulfurization apparatus, wherein the cleaning liquid of the wet electrostatic precipitator is a strong alkaline liquid. In claim 1,
A finishing flue gas desulfurization apparatus characterized in that a part of the strong alkaline liquid in the wet electrostatic precipitator is supplied to the lime absorbing liquid in the finishing desulfurizer. In claim 1,
A finishing flue gas desulfurization apparatus characterized in that both the absorbing liquid in the finishing desulfurization section and the cleaning liquid in the wet electrostatic precipitating section use the same kind of strong alkali and the same concentration, and share them. In any one of Claims 1 thru | or 4,
A finishing flue gas desulfurization device comprising a cooling device for cooling the purified gas, and using a part of the cooled purified gas as an insulator seal gas for a wet electric dust collector. A denitration device that removes nitrogen oxides in exhaust gas from boilers, a dust collector that removes soot and dust in the gas after removal of nitrogen oxides, a desulfurization device that removes sulfur oxides in the gas after dust removal, The finish flue gas desulfurization device according to any one of claims 1 to 5, further removing sulfur oxides remaining in the exhaust gas after desulfurization to an extremely low concentration, and a CO ₂ recovery device for recovering carbon dioxide in the purified gas. An exhaust gas treatment system comprising:

Images