JP5790329B2 - Exhaust gas treatment equipment - Google Patents

Description

  The present invention relates to an exhaust gas treatment apparatus that removes NOx contained in exhaust gas.

  Combustion exhaust gas (exhaust gas) is generated when fossil fuel is burned in an engine such as a ship or a vehicle. The exhaust gas generated as a result of burning such a fossil fuel contains nitrogen oxides (hereinafter simply referred to as NOx). Since NOx is an air pollutant, emission concentration and emission amount are regulated by international organizations, countries, and local governments. Therefore, when the concentration of NOx contained in the exhaust gas discharged from the engine is equal to or higher than a predetermined regulation value, it is necessary to remove NOx from the exhaust gas using an exhaust gas treatment device for removing NOx.

  As an exhaust gas treatment apparatus that removes NOx, there is a selective catalytic reduction denitration apparatus that includes a denitration catalyst that promotes NOx reduction and a reducing agent that reduces NOx. However, if the denitration catalyst is not at a certain high temperature (for example, about 270 ° C.), the NOx reduction efficiency is lowered. Further, since urea water is generally used as a reducing agent, the cost for urea water is increased, and the disposal of excess urea water is costly.

  Therefore, for example, the exhaust gas is absorbed in seawater, and the seawater is accommodated in an anode tank and a cathode tank separated by a permeable membrane, respectively, and electrolysis is performed, so that NOx is used using a solution generated in the anode tank. Has been disclosed (for example, Patent Document 1).

Japanese Patent No. 3829184

However, in the technique of Patent Document 1, magnesium ions (Mg ²⁺ ) and calcium ions (Ca ²⁺ ) contained in seawater are deposited in the cathode cell as scales (deposits) by electrolysis. More specifically, as shown in the following reaction formulas (1) and (2), Mg ²⁺ becomes magnesium hydroxide (Mg (OH) ₂ ), and Ca ²⁺ becomes calcium hydroxide (Ca (OH) ₂ ). And deposits in the cathode chamber.
Mg ²⁺ + 2OH ⁻ → Mg (OH) ₂
... Reaction formula (1)
Ca ²⁺ + 2OH ⁻ → Ca (OH) ₂
... Reaction formula (2)

  Then, the permeable membrane separating the anode tank and the cathode tank may be clogged by the deposited hydroxide (deposit). When the permeable membrane becomes clogged, it is necessary to replace the permeable membrane, which increases the maintenance cost. In addition, the amount of seawater that can be accommodated in the cathode tank is reduced by the amount of deposits, and the electrolysis efficiency may be reduced. For this reason, an apparatus for removing (collecting) deposits from the cathode chamber must be separately employed, resulting in high costs.

  Therefore, in view of such problems, the present invention devised the liquid stored in the cathode tank, thereby suppressing the generation of deposits in the cathode tank and removing NOx from the exhaust gas at low cost. An object is to provide a processing apparatus.

In order to solve the above problems, an exhaust gas treatment apparatus of the present invention comprises an anode tank in which seawater is accommodated and an anode is provided, and water in which Mg ²⁺ is 30 mg / L or less and Ca ²⁺ is 100 mg / L or less. An electrolytic cell in which a cathode cell, which is accommodated and provided with a cathode, is partitioned by an ion exchange membrane, a voltage application unit that performs electrolysis by applying a voltage to the anode and the cathode, and an exhaust gas containing at least NOx The Cl ₂ gas generated in the anode tank by the electrolysis and the anode solution generated in the anode tank by the electrolysis are introduced through different paths. 1 exhaust gas treatment section.

The exhaust gas further contains one or both of SOx and CO ₂ , and the cathode solution generated in the cathode chamber by introducing the gas that has passed through the first exhaust gas treatment unit and performing electrolysis You may provide the 2nd exhaust gas processing part in which is introduced.

  The voltage application unit may apply a voltage of 3.5V to 20V to the anode and the cathode. Further, the pH of the anode solution may be pH 1 to pH 6, and the pH of the cathode solution may be pH 7 to pH 14.

The voltage application unit may apply a voltage to the anode and the negative electrode using H ₂ generated in the cathode tank as a power source.

  The first exhaust gas treatment unit is a spray tower that sprays the anode solution on the introduced exhaust gas, and the second exhaust gas treatment unit is a spray tower that sprays the cathode solution on the gas that has passed through the first exhaust gas treatment unit. Good.

  According to the present invention, by devising the liquid stored in the cathode tank, it is possible to suppress the generation of deposits in the cathode tank and remove NOx from the exhaust gas at a low cost.

It is explanatory drawing for demonstrating the specific structure of the waste gas processing apparatus concerning embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(Exhaust gas treatment device 100)
FIG. 1 is an explanatory diagram for explaining a specific configuration of an exhaust gas treatment apparatus 100 according to the present embodiment. As shown in FIG. 1, the exhaust gas treatment apparatus 100 includes an electrolytic cell 110, a voltage application unit 130, a first exhaust gas treatment unit 150, and a second exhaust gas treatment unit 160. In FIG. 1, the flow of gas (gas) is indicated by broken-line arrows, and the flow of liquid is indicated by solid-line arrows.

  The electrolytic cell 110 includes an anode cell 112 and a cathode cell 114, and the anode cell 112 and the cathode cell 114 are partitioned by an ion exchange membrane 116.

  Seawater is fed into the anode tank 112 from a seawater source (not shown) through a pump 120a, a seawater introduction pipe 120b, and a valve 120c, and air is introduced from an air source (not shown) through a pump 122a, an air introduction pipe 122b, and a valve 122c. Is done.

  The anode tank 112 is provided with seawater and an anode 112a. The anode 112a is made of a conductive material that can be generally used as an electrode, such as titanium (Ti) coated with platinum (Pt).

Water is introduced into the cathode tank 114 from a water source (not shown) through a pump 124a, a water pipe 124b, and a valve 124c. Here, the Mg ²⁺ concentration contained in the water charged into the cathode tank 114 is 30 mg / L or less, preferably 20 mg / L or less, more preferably 10 mg / L or less. The lower the Mg ²⁺ concentration of the water charged into the cathode tank 114, the lower the amount of magnesium hydroxide produced when electrolysis is performed by the voltage application unit 130 described later. Further, the Ca ²⁺ concentration contained in the water charged into the cathode tank 114 is 100 mg / L or less, preferably 50 mg / L or less, more preferably 30 mg / L or less. The lower the Ca ²⁺ concentration of water charged into the cathode chamber 114, the lower the amount of calcium hydroxide that is generated when the voltage application unit 130 performs electrolysis.

  By reducing the amount of hydroxide (sediment) generated in this way, clogging of the ion exchange membrane 116 due to hydroxide can be reduced, and the exchange frequency of the ion exchange membrane 116 can be reduced. It becomes. In addition, since the amount of hydroxide generated is extremely small, the amount of water that can be accommodated in the cathode chamber 114 can be maintained, and the electrolysis efficiency can be stabilized.

In addition, the cathode tank 114 accommodates the water having the Mg ²⁺ concentration and the Ca ²⁺ concentration described above and is provided with a cathode 114a. The cathode 114a is made of copper (Cu), nickel (Ni), iron (Fe), titanium (Ti), tungsten (W), molybdenum (Mo), chromium (Cr), platinum (Pt), aluminum (Al), zinc It is composed of a material using one or more metals such as (Zn) and cadmium (Cd), or an alloy such as brass or high-strength brass.

The voltage application unit 130 includes a device that generates electric power using hydrogen (H ₂ ) as a power source, such as a hydrogen gas fuel cell or a hydrogen diesel generator, an anode 112 a provided in the anode tank 112, and a cathode tank Electrolysis is performed by applying a voltage to the cathode 114 a provided at 114.

Here, H ₂ supplied to the voltage application unit 130 is H ₂ gas (hereinafter simply referred to as H ₂ ) generated in the cathode chamber 114 described later. Thus, the voltage application unit 130, and H ₂ by configuring an apparatus for generating power as a power source, it is possible to effectively utilize the H ₂ produced at the cathode chamber 114.

  The voltage applied by the voltage application unit 130 to the anode 112a and the cathode 114a is 3.5V to 20V, preferably 3.5V to 15V, more preferably 3.5V to 10V. The voltage applied by the voltage application unit 130 to the anode 112a and the cathode 114a is changed from 3.5V to 20V, preferably from 3.5V to 15V, more preferably from 3.5V to 10V. The pH of the solution CS can be easily adjusted to a desired value.

When the voltage application unit 130 applies voltage to the anode 112a and the cathode 114a to perform electrolysis, the reactions shown in the following reaction formulas (3), (4), and (5) are performed in the anode tank 112.
2Cl ⁻ → Cl ₂ (g) + 2e ⁻
... Reaction formula (3)
2H ₂ O → O ₂ (g) + 4H ⁺ + 4e ⁻
... Reaction formula (4)
Cl ₂ + 2H ₂ O → 2HClO + 2H ⁺
... Reaction formula (5)

On the other hand, the reaction shown in the following reaction formula (6) is performed in the cathode chamber 114.
2H ₂ O + 2e ⁻ → H ₂ (g) + 2OH ⁻
... Reaction formula (6)
In the reaction formula, (g) represents gas.

Then, Cl ₂ (chlorine) gas and O ₂ (oxygen) gas are generated in the anode tank 112 (see the reaction formulas (3), (4), and (5)), and H ₂ (hydrogen) is generated in the cathode tank 114. (Refer to reaction formula (6)).

Then, Cl ₂ gas (hereinafter simply referred to as Cl ₂ ) and O ₂ gas (hereinafter simply referred to as O ₂ ) generated in the anode tank 112 stay in the gas retention space 112b and are then introduced from the air source. The air is pushed out by the air to be guided to the gas supply port 152 of the first exhaust gas processing unit 150 described later through the valve 140a and the gas pipe 140b. Further, the H ₂ gas generated in the cathode tank 114 stays in the gas retention space 114b and is then introduced into the voltage application unit 130 through the valve 142a and the gas pipe 142b.

  In addition, as the electrolysis progresses, the pH of the anode solution produced in the anode tank 112 tends to be acidic (see reaction formulas (4) and (5)), and the pH of the cathode solution produced in the cathode tank 114 is It tends to be alkaline (see reaction formula (6)).

  The anode solution AS generated by the voltage application unit 130 applying voltage to the anode 112a and the cathode 114a to perform electrolysis is supplied to a first exhaust gas, which will be described later, through a valve 144a, an anode solution circulation pipe 144b, and a pump 144c. It is supplied to the spray unit 156 of the processing unit 150.

  On the other hand, the cathode solution CS is supplied to the spray unit 166 of the second exhaust gas processing unit 160 described later through the valve 146a, the cathode solution circulation pipe 146b, and the pump 146c.

  The first exhaust gas processing unit 150 is, for example, a spray tower, and includes a main body 150a, a gas supply port 152, an exhaust gas introduction unit 154, and a spray unit 156.

  By configuring the first exhaust gas treatment unit 150 with a spray tower, it is possible to increase the superficial velocity (the flow rate of gas when it is assumed that there is no packing inside the tower) as compared with the bubble tower and the packed tower. This makes it possible to reduce the column diameter for achieving the same NOx removal rate. Therefore, the occupied volume of the first exhaust gas treatment unit 150 can be reduced, and the exhaust gas treatment apparatus 100 can be mounted even if the occupied volume of a ship or the like is limited.

The gas supply port 152 communicates with the gas retention space 112b of the anode tank 112 through the gas pipe 140b and the valve 140a, and Cl ₂ and O ₂ generated in the anode tank 112 pass through the gas supply port 152 in the main body 150a. To be supplied.

The exhaust gas introduction unit 154 includes a valve 154a and an exhaust gas introduction pipe 154b, and introduces the exhaust gas X1 containing NOx, SOx, and CO ₂ into the main body 150a.

The spray unit 156 communicates with the solution storage region 112c of the anode tank 112 through the pump 144c, the anode solution circulation pipe 144b, and the valve 144a, and introduces Cl ₂ and O ₂ supplied from the gas supply port 152 and exhaust gas. The anode solution AS is sprayed on the exhaust gas X1 introduced by the part 154.

Then, as shown in the following reaction formula (7), first, NOx in the exhaust gas X1 (here, NO is given as an example) and Cl ₂ react with each other in the main body 150a to form NOCl (nitrosyl chloride). Generated.
2NO (g) + Cl ₂ (g) → 2NOCl (g)
... Reaction formula (7)

  Then, when the anode solution AS is sprayed onto NOCl by the spraying unit 156, NOCl is absorbed (dissolved) in the anode solution AS.

  Here, the pH of the anode solution AS is pH 1 to pH 6, preferably pH 2 to pH 5, more preferably pH 2 to pH 4. Thus, when the pH of the anode solution AS is low, that is, when the anode solution AS is acidic, NOCl can be absorbed efficiently.

  In order to change the pH of the anode solution AS from pH 1 to pH 6, the voltage applied by the voltage applying unit 130 to the anode 112a and the cathode 114a may be set to 3.5V to 20V.

Thus, in the first exhaust gas treatment unit 150, NOx is removed from the exhaust gas X1, and SOx, CO ₂ , surplus Cl ₂ and O ₂ (hereinafter simply referred to as exhaust gas X2) are supplied to the valve 170a, the gas pipe Through 170b, the exhaust gas is introduced to an exhaust gas inlet 162 of the second exhaust gas processing unit 160 described later. The anode solution AS that has absorbed NOx is discharged to the outside through the valve 180a.

  The second exhaust gas treatment unit 160 is, for example, a spray tower, and includes a main body 160 a, an exhaust gas introduction port 162, and a spray unit 166.

By configuring the second exhaust gas treatment unit 160 with a spray tower, the superficial velocity can be increased as compared with the bubble tower and the packed tower, and the same removal rate of SOx, CO ₂ and Cl ₂ is achieved. Therefore, the tower diameter can be reduced. Therefore, the occupied volume of the second exhaust gas treatment unit 160 can be reduced, and the exhaust gas treatment apparatus 100 can be mounted even if the occupied volume of a ship or the like is limited.

  The exhaust gas inlet 162 communicates with the gas retention space 150b of the first exhaust gas treatment unit 150 through the gas pipe 170b and the valve 170a, and the exhaust gas X2 staying in the gas retention space 150b passes through the exhaust gas inlet 162 through the main body. Introduced in 160a.

  The spray unit 166 communicates with the solution storage region 114c of the cathode tank 114 through the pump 146c, the cathode solution circulation pipe 146b, and the valve 146a, and sprays the cathode solution CS onto the exhaust gas X2 introduced from the exhaust gas inlet 162.

Then, the cathode unit CS is sprayed onto the exhaust gas X2 by the spraying unit 166, so that SOx, CO ₂ , Cl ₂ , and O ₂ in the exhaust gas X2 are absorbed (dissolved) in the cathode solution CS.

Here, the pH of the cathode solution CS is pH 7 to pH 14, preferably pH 8 to pH 13, and more preferably pH 9 to pH 13. As described above, when the pH of the cathode solution CS is high, that is, when the cathode solution CS is alkaline, SOx, CO ₂ , and Cl ₂ can be efficiently absorbed. Further, since the cathode solution CS has a lower concentration of Cl ⁻ (chloride ion) than when the seawater is accommodated in the cathode tank, it is possible to absorb Cl ₂ more efficiently.

  In order to change the pH of the cathode solution CS from pH 7 to pH 14, the voltage applied by the voltage applying unit 130 to the anode 112a and the cathode 114a is preferably set to 3.5V to 20V.

In this way, in the second exhaust gas treatment unit 160, SOx and CO ₂ are removed from the exhaust gas X2, and excess Cl ₂ is also removed. The cathode solution CS that has absorbed SOx, CO ₂ , and Cl ₂ is discharged to the outside through the valve 182a. Further, the gas from which SOx, CO ₂ and Cl ₂ have been removed is released from a gas discharge port (not shown).

As described above, according to the exhaust gas treatment apparatus 100 according to the present embodiment, seawater that is easily available is stored in the anode tank 112, and Mg ²⁺ is 30 mg / L or less and Ca ²⁺ is 100 mg / L in the cathode tank 114. By storing water that is equal to or lower than L and performing electrolysis, it is possible to generate Cl ₂ in the anode tank 112 and to suppress the formation of deposits in the cathode tank 114. Therefore, it is possible to reduce the probability that the ion exchange membrane 116 is clogged.

In addition, with the configuration including the first exhaust gas treatment unit 150, the Cl ₂ generated in the anode tank 112 can be brought into contact with the exhaust gas X1, and NOx contained in the exhaust gas X1 can be decomposed, and the spraying unit 156 has a gas retention space. By spraying the anode solution AS to 150b, the NOx decomposition product (NOCl) can be dissolved in the anode solution AS and discharged.

Furthermore, with the configuration including the second exhaust gas treatment unit 160, SOx and CO ₂ contained in the exhaust gas X1 can be dissolved in the cathode solution CS and discharged. In addition, the second exhaust gas treatment unit 160 is configured such that not only the SOx and CO ₂ but also the amount of Cl ₂ supplied to the first exhaust gas treatment unit 150 is greater than the amount necessary for decomposing NOx of the exhaust gas X1. Excessive Cl ₂ generated in a large amount can be absorbed by the cathode solution CS, so that release of Cl _{2 to} the outside can be suppressed.

In this way, the exhaust gas treatment apparatus 100 devises the liquid stored in the cathode tank 114, thereby suppressing the generation of deposits in the cathode tank 114 and removing NOx, SOx, CO ₂ from the exhaust gas X1 at low cost. Is possible.

(Example)
Two liters of artificial seawater was stored in the cathode tank 114 and the anode tank 112, and the voltage application unit 130 applied a voltage of 4 V to the anode 112a and the cathode 114a. Then, Cl ₂ produced in the anode tank 112 was introduced into a spray tower (first exhaust gas treatment unit 150) capable of treating the exhaust gas X1 of about 0.3 m ³ / h.

As a result, the concentration of Cl ₂ produced in the anode tank 112 was 0.01% to 0.1%. Further, when this Cl ₂ was introduced into the first exhaust gas treatment unit 150, the NO removal rate in the first exhaust gas treatment unit 150 was 70%.

From this result, even when water with Mg ²⁺ of 30 mg / L or less and Ca ²⁺ of 100 mg / L or less is accommodated in the cathode tank 114, it is generated by electrolysis to accommodate seawater in the anode tank 112. The concentration of Cl ₂ is considered to be substantially equal. Therefore, the NOx removal rate of the first exhaust gas treatment unit 150 in the exhaust gas treatment device 100 is estimated to be about 70%.

Further, the exhaust gas X2 sent out from the first exhaust gas treatment unit 150 contained Cl ₂ in% order. Therefore, by providing the exhaust gas treatment device 100 with the second exhaust gas treatment unit 160, unreacted Cl ₂ can be removed in the first exhaust gas treatment unit 150, and release of Cl _{2 into} the atmosphere can be prevented.

On the other hand, as a result of the electrolysis, in the cathode tank 114, deposits were deposited in a dry weight of about 6 g (about 3 g with respect to 1 L of seawater). However, since the anode tank 112 of the exhaust gas treatment apparatus 100 contains water with Mg ²⁺ of 30 mg / L or less and Ca ²⁺ of 100 mg / L or less, magnesium hydroxide, which is the main component of the deposit, The amount of calcium hydroxide produced can be extremely reduced.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

For example, in the embodiment described above, a river is taken as an example of a water source that is introduced into the cathode tank 114 by the pump 124a and that has Mg ²⁺ of 30 mg / L or less and Ca ²⁺ of 100 mg / L or less. It is also possible to use tap water or industrial water. Further, the obtained fresh water may be introduced into the cathode tank 114 and the concentrated sea water may be introduced into the anode tank 112 using a seawater desalination apparatus. In this case, the concentration of Cl ⁻ (chloride ions) in the anode tank 112 can be made higher than that of seawater, and electric power necessary for electrolysis can be reduced as compared with the case of seawater.

In the above-described embodiment, the example in which H ₂ generated in the cathode tank 114 is introduced into the voltage application unit 130 through the valve 142a and the gas pipe 142b has been described. However, the present invention is not limited thereto, and H ₂ generated in the cathode chamber 114 can be once collected in a gas holder and purified, and then introduced into the voltage application unit 130.

Furthermore, in the above-described embodiment, the voltage application unit 130 configured by a device that generates electric power using hydrogen (H ₂ ) as a power source has been described as an example. However, the voltage application unit 130 only needs to be able to apply a voltage to the anode 112a and the cathode 114a, and may be, for example, a device that applies a voltage using a commercial power source.

  Further, in the above-described embodiment, the example in which the first exhaust gas processing unit 150 and the second exhaust gas processing unit 160 are configured by spray towers has been described. Also good.

  In addition to the positions shown in the exhaust gas treatment apparatus 100, a pump or a valve may be provided.

  The present invention can be used for an exhaust gas treatment apparatus that removes NOx contained in exhaust gas.

DESCRIPTION OF SYMBOLS 100 ... Exhaust gas treatment apparatus 110 ... Electrolytic cell 112 ... Anode cell 112a ... Anode 114 ... Cathode cell 114a ... Cathode 116 ... Ion exchange membrane 130 ... Voltage application part 150 ... 1st exhaust gas process part 160 ... 2nd exhaust gas process part

Claims (6)

The ion exchange membrane includes an anode tank in which seawater is contained and an anode is provided, and a cathode tank in which Mg ²⁺ is 30 mg / L or less and Ca ²⁺ is 100 mg / L or less and a cathode is provided. A partitioned electrolysis cell;
A voltage application unit that performs electrolysis by applying a voltage to the anode and the cathode;
The exhaust gas containing at least NOx is introduced, and the Cl ₂ gas generated in the anode tank by electrolysis and the anode solution generated in the anode tank by electrolysis are routed through the path. A first exhaust gas treatment unit introduced differently;
An exhaust gas treatment apparatus comprising: The exhaust gas further includes one or both of SOx and CO ₂ ,
2. A second exhaust gas treatment unit, wherein a gas that has passed through the first exhaust gas treatment unit is introduced and a cathode solution generated in a cathode tank by the electrolysis is introduced. Item 2. An exhaust gas treatment apparatus according to Item 1.   3. The exhaust gas treatment apparatus according to claim 1, wherein the voltage application unit applies a voltage of 3.5 V to 20 V to the anode and the cathode.   The exhaust gas treatment device according to any one of claims 1 to 3, wherein the anode solution has a pH of pH 1 to pH 6, and the cathode solution has a pH of pH 7 to pH 14. 5. The exhaust gas treatment apparatus according to claim 1, wherein the voltage application unit applies a voltage to the anode and the cathode using H ₂ generated in the cathode tank as a power source. 6. . The first exhaust gas treatment unit is a spray tower that sprays the anode solution on the introduced exhaust gas,
6. The exhaust gas treatment apparatus according to claim 2, wherein the second exhaust gas treatment unit is a spray tower that sprays the cathode solution onto the gas that has passed through the first exhaust gas treatment unit. .

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