JP2006320870A - Waste gas treatment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste gas treatment system capable of suppressing the cost without degrading the waste gas treatment efficiency therein. <P>SOLUTION: The waste gas treatment system has a passage to circulate a liquid absorbent to/from a scrubber 20, and a passage to circulate the liquid absorbent to/from an electrolysis vessel 50 separately from the passage in a storage tank 30. In other words, a waste gas generated in a combustion device 10 is fed to the scrubber 20, and absorbed in the liquid absorbent. The waste gas mainly contains SO<SB>x</SB>and NO<SB>x</SB>. The liquid absorbent in the scrubber 20 is fed to the storage tank 30, and subjected to the electrolysis treatment in the electrolysis vessel 50. A hypochlorous acid is generated in the liquid absorbent to oxidize nitrogen and sulfur in nitrogen oxides and sulfur oxides. The liquid absorbent in the electrolysis vessel 50 is further returned to the storage tank 30, and returned to the scrubber 20. The liquid absorbent in the storage tank 30 is adequately discharged from an overflow pipe 33. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an exhaust gas treatment system, and in particular, an exhaust gas treatment system for treating an exhaust gas containing sulfur oxide (SO _x ) and nitrogen oxide (NO _x ) generated when fuel is burned by absorbing it. About.

Conventionally, in the treatment of exhaust gas containing SO _x and NO _x that is generated when fuel is burned in a boiler or the like of a power plant, the exhaust gas is absorbed into an absorption liquid, and hypochlorine is further added to the absorption liquid. There was a process of oxidizing the components of the exhaust gas by adding a chemical such as acid soda.

In recent years, a technology has been disclosed in which exhaust gas is brought into contact with salt water, and voltage is applied to the salt water to generate hypochlorous acid to oxidize SO _x and NO _x in the exhaust gas. .

Specifically, for example, Patent Document 1 discloses a technique for installing an electrode in a scrubber where exhaust gas and salt water are brought into contact with each other, and a technique for supplying an alkaline solution obtained by electrolysis into the scrubber. Is disclosed.
JP 2004-89770 A

  The electrolytic treatment as described above makes it easy to treat exhaust gas because it is not necessary to use a difficult-to-handle chemical such as sodium hypochlorite.

  However, when the exhaust gas treatment system is configured such that an electrode is installed in the scrubber as described in Patent Document 1 or an alkaline solution is unilaterally supplied from the electrolytic cell into the scrubber, the scale of the system Therefore, there is a problem that the scale of the electrolysis system including the electrode must be increased accordingly, which increases the cost.

  The present invention has been conceived in view of such circumstances, and an object of the present invention is to suppress costs in an exhaust gas treatment system without reducing exhaust gas treatment efficiency.

  An exhaust gas treatment system according to the present invention includes an exhaust gas absorption part that introduces exhaust gas and an absorption liquid and brings them into gas-liquid contact, a storage tank that stores the absorption liquid introduced from the exhaust gas absorption part, and an inside of the storage tank An electrolytic bath that performs electrolytic treatment on the absorbent, a halogen ion supply that supplies a chemical that generates halogen ions in an aqueous solution to the electrolytic bath, and an absorbent between the exhaust gas absorber and the storage tank. And a second circulation part that circulates the absorbing liquid between the storage tank and the electrolytic cell.

  In addition, the exhaust gas treatment system according to the present invention may further include a filter that is in the second circulation unit and that filters the absorbent before being sent out from the storage tank and introduced into the electrolytic tank. preferable.

  Moreover, in the exhaust gas treatment system according to the present invention, it is preferable that the halogen ion supply unit supplies the chemical to the absorbent before passing through the filter and being introduced into the electrolytic cell.

  Moreover, in the exhaust gas treatment system according to the present invention, it is preferable that the exhaust gas absorbing section is introduced with exhaust gas generated by power generation in a generator.

  In addition, the exhaust gas treatment system according to the present invention further includes a power supply unit that supplies power generated in the generator to the electrolytic cell, the first circulation unit, and the second circulation unit. Is preferred.

  Moreover, in the exhaust gas treatment system according to the present invention, it is preferable that the exhaust gas absorption part is constituted by a scrubber.

  In the exhaust gas treatment system according to the present invention, it is preferable that the halogen ion supply unit supplies sodium chloride as the chemical.

  According to the present invention, since the first circulation part and the second circulation part are provided, the scale of the electrolytic cell is absorbed by the exhaust gas by keeping the circulation flow rate of the second circulation part lower than the first circulation flow rate. It can be kept small relative to the scale of the part. In addition, since the absorption liquid in the 1st circulation part is also circulated also in the 2nd circulation part containing an electrolytic cell, active oxygen species, such as hypochlorous acid, are nitrogen and sulfur in nitrogen oxide and sulfur oxide. Substances such as chlorine ions generated by oxidizing can be changed to active oxygen species by electrolysis again.

  Thereby, in the exhaust gas treatment system, the cost can be suppressed without reducing the exhaust gas treatment efficiency and by reducing the scale of the electrolytic cell.

  FIG. 1 schematically shows the configuration of an embodiment of an exhaust gas treatment system of the present invention. In FIG. 1, the flow of the solution containing the absorbing liquid is indicated by an arrow, and the flow of the gas containing the exhaust gas is indicated by a thicker arrow than the arrow indicating the flow of the solution.

  Referring to FIG. 1, the exhaust gas treatment system mainly includes a scrubber 20, a storage tank 30, a filter 40, an electrolytic tank 50, an NaOH aqueous solution tank 60, and an NaCl aqueous solution tank 70.

The exhaust gas generated in the combustion device 10 is introduced into the scrubber 20. In the scrubber 20, SO _x and NO _x soot in the exhaust gas are absorbed by the absorbing liquid, and the absorbing liquid is sent out to the storage tank 30. Examples of the combustion apparatus 10 include a power generation apparatus that is used for in-house power generation in a factory, such as oil as fuel.

The internal configuration of the scrubber 20 is schematically shown in FIG.
Referring to FIG. 2, the scrubber 20 includes a main body 21, an intake pipe 24 for introducing exhaust gas from the combustion device 10 into the main body 21, an exhaust hole 22 for appropriately discharging gas from the main body 21, and the main body 21. An introduction pipe 23 for introducing an absorption liquid from an absorption liquid source 80 such as groundwater into the upper part, a filler 26 located above the intake pipe 24 and below the introduction pipe 23, and the inside of the main body 21 A discharge pipe 25 for sending the solution to the storage tank 30 is provided.

The introduction tube 23 is formed with a plurality of holes for discharging the absorption liquid into the main body 21.
The filling material 26 is configured by laminating nonwoven fabrics, for example.

  Hereinafter, an exhaust gas treatment method in the exhaust gas treatment system of the present embodiment will be described with reference to FIGS. 1 and 2.

  The introduction pipe 23 introduces the NaOH aqueous solution in the NaOH aqueous solution tank 60 into the main body 21 by appropriately driving the pump 61 together with the absorbing liquid from the absorbing liquid source 80 when the valve 81 is opened.

  When the exhaust gas generated in the combustion device 10 is introduced into the main body 21, it comes into contact with the absorption liquid introduced from the introduction pipe 23 and is absorbed by the absorption liquid. The filler 26 is provided so that the exhaust gas and the absorbing liquid can easily come into contact with each other. Moreover, the absorption efficiency of the exhaust gas of the said absorption liquid becomes high by adding alkaline chemical | medical agents, such as NaOH aqueous solution, to an absorption liquid suitably.

  The absorbing liquid that has come into contact with the exhaust gas in the scrubber 20 is introduced into the storage tank 30 via the discharge pipe 25. The absorbing liquid introduced into the storage tank 30 is introduced into the electrolytic cell 50 through the filter 40 when the pump 32 is appropriately driven. Further, the aqueous solution of NaCl in the aqueous NaCl solution tank 70 is introduced into the electrolytic bath 50 by appropriately driving the pump 71.

  In the electrolytic cell 50, an anode electrode 52 and a cathode electrode 53 are installed so as to be immersed in the introduced absorbing liquid. The anode electrode 52 and the cathode electrode 53 are composed of, for example, an electrode made of a noble metal such as platinum or iridium or an electrode in which such a noble metal is coated on a metal. The electrolytic cell 50 is provided with a power source 51 for supplying power to these electrodes.

  Here, a chemical reaction that is considered to occur in the electrolytic cell 50 when power is supplied to the anode electrode 52 and the cathode electrode 53 will be described.

First, in the absorption liquid, the equilibrium shown in Formula (1) is established for water.
H ₂ O⇔H ⁺ + OH ⁻ (1)
Moreover, since sodium chloride is supplied as an agent for supplying chloride ions to the absorbing solution in the electrolytic cell 50, the equilibrium shown in the equation (2) is established for the sodium chloride.

NaCl Ｎａ Na ⁺ + Cl ⁻ (2)
Then, when electric power is supplied to the anode electrode 52 and the cathode electrode 53 and electrolysis is performed in the electrolytic cell 50, as shown in the formulas (3) to (5), the electricity of water is used in the vicinity of the anode electrode 52. Oxygen gas is generated by the decomposition, and chloride ions become chlorine gas. A part of the chlorine gas is hydrated to become hypochlorous acid.

2H ₂ O⇔O ₂ ↑ + 4H ⁺ + 4e ⁻ (3)
2Cl ⁻ Ｃｌ Cl ₂ ↑ + 2e ⁻ (4)
Cl ₂ + H ₂ O⇔H ⁺ + Cl ⁻ + HClO (5)
Also, electrolysis generates active oxygen species in addition to hypochlorous acid in the absorbing solution.

Then, the absorbing liquid containing active oxygen species is returned to the storage tank 30.
In the storage tank 30, by absorbing the exhaust gas, nitrous acid gas and sulfurous acid gas present in the absorbing liquid are oxidized by the active oxygen species contained in the absorbing liquid. As a result, the COD (Chemical Oxygen Demand) value of the absorbing solution is reduced, and the absorbing solution can be drained into a general sewer.

  Further, the absorption liquid in the storage tank 30 is mixed with the absorption liquid from the absorption liquid source 80 when the pump 31 is driven, and is introduced into the main body 21 of the scrubber 20 through the introduction pipe 23.

  In the exhaust gas treatment system described above, the pumps 31, 32, 61, 71 are appropriately driven by a drive unit (not shown). It is also conceivable to use electric power generated by the fuel device 10 as the driving force and the power source 51. That is, it is preferable that a control circuit or the like for supplying electric power generated by the fuel device 10 to the pump or power supply on the exhaust gas treatment system of the present embodiment is introduced into the exhaust gas treatment system. If comprised in this way, since the quantity of the waste gas which should be processed increases, so that the amount of electric power generated with fuel device 10 increases, the amount of power which an exhaust gas treatment system requires also increases. However, since the amount of electric power generated by the fuel device 10 is increased by that amount, the required amount of increase in electric power can be supplemented by the electric energy generated by the fuel device 10.

  And the 1st circulation part which circulates absorption liquid between an exhaust gas absorption part and a storage tank is comprised by the pump 31 driven in order to circulate absorption liquid between the scrubber 20 and the storage tank 30. FIG. In addition, a pump 32 that is driven to circulate the absorbing liquid between the storage tank 30 and the electrolytic cell 50, thereby forming a second circulation unit that circulates the absorbing liquid between the storage layer and the electrolytic cell. .

  Further, in the exhaust gas treatment system described above, by the NaCl aqueous solution tank 70 and the pump 71 which add the NaCl aqueous solution to the absorption liquid after being filtered by the filter 40 and before being introduced into the electrolytic cell 50, A halogen ion supply unit is configured. In addition, although the chemical | medical agent which a halogen ion supply part supplies is preferable from points, such as a price and ease of handling, it is not limited to this. If the chemical | medical agent which produces | generates a halogen ion in aqueous solution is supplied, the chemical | medical agent added may be potassium chloride and sodium bromide other than NaCl (sodium chloride), for example.

  Further, in the exhaust gas treatment system described above, the absorbing liquid sent to the storage tank 30 is sent back to the electrolytic tank 50 and then returned to the storage tank 30 or further returned to the scrubber 20. In addition, the density | concentration of the dissolved substance in an absorption liquid rises by circulating in this way. The absorbing liquid in the storage tank 30 is appropriately discharged from the overflow pipe 33, and new absorbing liquid is introduced from the absorbing liquid source 80 into the system.

  Moreover, in this Embodiment demonstrated above, in the storage tank 30, the path | route which circulates absorption liquid between the scrubbers 20 and the path | route which circulates absorption liquid between the electrolytic cells 50 separately from the said path | route are provided. It has been.

Thus, the flow rate of the absorbing liquid circulated between the scrubber 20 and the storage tank 30 in order to absorb the exhaust gas by the scrubber 20, and the circulation between the electrolytic cell 50 and the storage tank 30 in order to electrolyze the absorbing liquid. The flow rates of the absorbents to be made can be determined independently of each other. For example, the absorbing liquid can be circulated between the scrubber 20 and the storage tank 30 at 1 m ³ / min, while the absorbing liquid can be circulated between the electrolyzer 50 and the storage tank 30 at 10 L / min.

  As described above, since the path for circulating the feed water is independently provided in the electrolytic cell, in the exhaust gas treatment system of the present embodiment, the electrolytic cell is smaller than the scrubber (exhaust gas absorption unit). It can be.

  Further, in the present embodiment, since the absorption liquid subjected to the electrolytic treatment in the electrolytic cell can be circulated through the circulation path including the scrubber, in the electrolytic cell, the nitrogen and sulfur in the nitrogen oxide and sulfur oxide can be circulated. Active oxygen species that can be used for oxidation can be generated, and nitrogen and sulfur in nitrogen oxides and sulfur oxides can be oxidized.

  Furthermore, since the absorption liquid in the circulation path including the scrubber is also circulated in the path through the electrolytic cell, the active oxygen species such as hypochlorous acid oxidizes nitrogen and sulfur in the nitrogen oxide and sulfur oxide. The generated substance such as chlorine ions can be used again by changing it to active oxygen species by electrolysis. Thereby, it is possible to efficiently oxidize nitrogen and sulfur in nitrogen oxides and sulfur oxides absorbed as exhaust gas.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows typically the structure of one Embodiment of the waste gas processing system of this invention. It is a figure which shows typically the internal structure of the scrubber of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Combustion device, 20 Scrubber, 21 Main body, 22 Exhaust hole, 23 Introducing pipe, 24 Intake pipe, 25 Exhaust pipe, 26 Filling, 30 Storage tank, 31, 32, 61, 71 Pump, 40 Filter, 50 Electrolyzer , 51 power source, 52 anode electrode, 53 cathode electrode, 60 NaOH aqueous solution tank, 70 NaCl aqueous solution tank, 80 absorbent liquid source, 81 valve.

Claims (7)

An exhaust gas absorption part that introduces exhaust gas and absorption liquid and brings them into gas-liquid contact;
A storage tank for storing an absorption liquid introduced from the exhaust gas absorption unit;
An electrolytic cell that performs electrolytic treatment on the absorbing solution in the storage tank;
A halogen ion supply unit for supplying a chemical agent that generates halogen ions in an aqueous solution to the electrolytic cell;
A first circulation part for circulating an absorbent between the exhaust gas absorption part and the storage tank;
An exhaust gas treatment system including a second circulation unit that circulates an absorbing liquid between the storage tank and the electrolytic tank.   2. The exhaust gas treatment system according to claim 1, further comprising a filter that filters the absorption liquid that is in the second circulation unit and is sent out from the storage tank and before being introduced into the electrolytic tank.   The exhaust gas treatment system according to claim 2, wherein the halogen ion supply unit supplies the chemical to the absorbent before passing through the filter and being introduced into the electrolytic cell.   The exhaust gas treatment system according to any one of claims 1 to 3, wherein the exhaust gas absorption unit is introduced with exhaust gas generated by power generation in a generator.   The exhaust gas treatment system according to claim 4, wherein electric power generated in the generator is supplied to the electrolytic cell, the first circulation unit, and the second circulation unit.   The exhaust gas treatment system according to any one of claims 1 to 5, wherein the exhaust gas absorption unit is configured by a scrubber.   The exhaust gas treatment system according to any one of claims 1 to 6, wherein the halogen ion supply unit supplies sodium chloride as the medicine.

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