JPH08100631A - Exhaust gas processing equipment - Google Patents

Abstract

PURPOSE: To provide an exhaust gas processing equipment which sufficiently secures the rates of denitration and desulfurization from exhaust gas, and moreover functions well at inexpensive running cost, and dispenses with a large quantity of water for processing, and can be composed in a small type. CONSTITUTION: A discharge device 1 to use a space between a discharge pole 1B and an earth pole 1A as an exhaust gas processing passage 5 is provided, and a pulse power source 2 for short pulse corona discharge is provided between the discharge pole 1B and the earth pole 1A in the discharge device 1, and a neutralizing solution supply means for supplying alkali-component solution onto the surface of the earth pole 1A of the discharge device 1 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to exhaust gas discharged from industrial furnaces and boilers that use heavy oil and coal as fuel, or internal combustion engines for ships, that is, nitrogen oxides (nitrogen monoxide, etc., hereinafter referred to as NOx). The present invention relates to an apparatus for purifying exhaust gas containing harmful gas components such as sulfur oxides (hereinafter referred to as SOx for sulfur dioxide).

[0002]

2. Description of the Related Art Conventionally, the following devices have been put into practical use as exhaust gas treatment devices.

A flue gas denitration device for removing NOx in exhaust gas is a method of reducing NOx to nitrogen and water with ammonia (or urea) and discharging it, and ammonia (NH) is contained in exhaust gas containing NOx. ₃ ) is added and uniformly mixed, and then introduced into a reactor and brought into contact with a denitration catalyst at a temperature of 300 to 400 ° C., whereby NOx in the exhaust gas is selectively reacted with ammonia to form harmless nitrogen. An apparatus for denitration by a selective catalytic reduction method that decomposes into water vapor is known.

As a flue gas desulfurization device for removing SOx in exhaust gas, a device for desulfurization by a wet lime gypsum method using limestone as an absorbent, a device for desulfurization by a wet caustic soda absorption method using caustic soda as an absorbent, an absorbent There are known devices for desulfurization by a wet magnesium hydroxide absorption method using magnesium hydroxide, devices for desulfurization by a dry activated carbon adsorption method, and the like.

[0005]

However, the conventional flue gas denitration apparatus described above has a drawback that the running cost is high because a denitration catalyst having a life of about 4 years is required for its high price. It was Moreover, since a reducing agent such as ammonia is required, when the exhaust gas source is a moving engine such as a marine internal combustion engine or a moving vehicle (hereinafter, these are collectively referred to as a moving source), the reducing agent is mounted. Also, there is a drawback in that replenishment is indispensable, which is a burden and is not suitable for a mobile source.

On the other hand, in the case of each of the above-mentioned conventional flue gas desulfurization devices of the wet absorption type, the exhaust gas is brought into contact with the absorbent liquid slurry in which the absorbent is dissolved, and the SOx in the exhaust gas is
Since it absorbs and removes water, it has a drawback that a large amount of water (fresh water) is required. Further, even in the case of the apparatus using the dry activated carbon adsorption method, it is necessary to secure a sufficient contact area between the activated carbon and the exhaust gas in order to satisfactorily remove SOx, so that there is a drawback that the entire apparatus becomes large.

A device that requires a large amount of water or a large-sized device as described above is extremely disadvantageous for a moving source from a loading surface or a mounting surface.

A first object of the present invention is to ensure a sufficient denitrification rate and desulfurization rate from exhaust gas, but at the same time the running cost is low and a large amount of water is not required for the treatment.
The point is to provide an exhaust gas treatment device that can be made compact.

A second object of the present invention is to provide an exhaust gas treating apparatus capable of simultaneously removing soot dust and hydrocarbons.

A third object of the present invention is to provide an exhaust gas treating apparatus which is very useful for a mobile generation source such as a marine internal combustion engine.

[0011]

According to a first aspect of the present invention, there is provided a feature of an exhaust gas treatment device, wherein a discharge device is provided which makes an exhaust gas treatment passage between a discharge electrode and a ground electrode. A pulse power supply for performing short pulse corona discharge is provided between the discharge electrode and the ground electrode, and a neutralizing solution supply means for supplying an alkaline component solution is provided on the surface of the ground electrode of the discharge device. .

A feature of the exhaust gas treating apparatus according to the second aspect of the present invention is that, in the first aspect of the present invention, a scrubber for cooling and cleaning the exhaust gas supplied to the discharge device is provided.

The feature of the exhaust gas treating apparatus according to the third invention of the present invention is the above-mentioned first invention and second invention.
In the invention, a means for using seawater for the alkaline component solution is provided as the solution supply means.

A feature of the exhaust gas treating apparatus according to the fourth invention of the present invention is the above-mentioned second invention and third invention.
In the present invention, as the scrubber, one using seawater as a cooling / cleaning liquid is provided.

[0015]

[Function] When corona discharge is carried out in exhaust gas containing NOx or SOx, oxidation radicals such as OH are generated to generate NOx.
It is known that SOx and SOx are oxidized to generate an acid.

That is, in terms of NOx, the oxidation reaction of NOx (NO and NO ₂ ) due to corona discharge is: NO + N → N ₂ + O (Equation 1) NO + O → NO ₂ ... (Equation 2) NO ₂ + OH → HNO ₃ (Equation 3), and at normal temperature, all of Equation 1, Equation 2, and Equation 3 have the same fast reaction rate. OH is generated by the bond dissociation of water vapor.

Therefore, NOx and SOx due to corona discharge
It can be seen that NOx and SOx in the exhaust gas can be removed by capturing and neutralizing the acid generated by the oxidation of the with an alkali.

Further, as corona discharge for oxidizing NOx and SOx, direct current corona discharge at a constant voltage (20 to 60 KV) and high voltage nonasecond pulse (rise time 50 to 500 nonasecond, cycle 5 to 5). Short pulse corona discharge (PPCP = Pulse CoronaIn) at 50 milliseconds and voltage of about 50 to 200 KV)
reduced Plasma Chemical Pro
cess) is known.

Further, for example, NO is converted to N by corona discharge.
NO to O ₂ and then to HNO ₃
In order to oxidize x and SOx, the generation of OH radical is indispensable, and this OH radical is generated by the bond dissociation of water vapor, and the energy required for it is 499 KJ /
mol, and when converted to the electron temperature in the electric field,
It is 5.17 eV.

By the way, in the DC corona discharge, in order to suppress the rise of the gas temperature, the voltage is constant and the electric field strength E is 1 to 1.
The acceleration of the emitted electrons is extremely small because the range is limited to 5 KV / cm, and the average electron temperature in the electric field is 1
It is eV or less, and as a result, OH radicals cannot be generated in the entire electric field, and there is only a possibility that OH radicals are locally generated only in the vicinity of the discharge electrode. That is, the generation region of non-equilibrium plasma (low temperature plasma) required to oxidize NOx and SOx is small, and the radical generation efficiency is poor.

On the other hand, in the short pulse corona discharge,
Because it discharges intermittently with an extremely short rise time and short cycle,
While suppressing a rise in gas temperature, a high voltage can be applied to instantaneously generate a high electric field in the range of 20 to 50 KV / cm, so that electrons can be given a large acceleration and velocity, and the electric field The average electron temperature can be 2 to 6 eV. As a result, OH radicals can be generated in a wide area within the electric field. That is, the non-equilibrium plasma generation region necessary for oxidizing NOx and SOx is large, and radicals can be efficiently generated to oxidize NOx and SOx.

That is, the number of radicals generated by energy input per 100 eV in the discharge field is 0.1 for N radicals, 0.1 for O radicals, and OH for DC corona discharge (E = 5 KV / cm). Radical is 0.1, short pulse corona discharge (E = 50KV / c
m), N radicals are 0.7, O radicals are 1.5,
The OH radical is 1.6.

Therefore, when the energy required for the oxidation treatment per NOx molecule in the discharge field is calculated based on the above-mentioned equations 1 to 3, for example, direct current corona discharge (E = 5 KV)
/ Cm), 0.1 (N + NO) → 0.1N ₂ + 0.05O ₂ 0.1 (O + NO) → 0.1NO ₂ 0.1 (OH + NO ₂ ) → 0.1HNO ₃ (N + O + OH) + 0.2NO → 0.1N ₂ +
It becomes 0.05O ₂ + 0.1HNO ₃ , and 0.2 NO can be processed with the input of 0.1 (N + O + OH) = 100 eV, and as a result, the energy required for the oxidation process per NO molecule is 500 eV. .

On the other hand, short pulse corona discharge (E = 50 KV
/ Cm), 0.7 (N + NO) → 0.7N ₂ + 0.35O ₂ 1.5 (O + NO) → 1.5NO ₂ 1.6 (OH + NO ₂ ) → 1.6HNO ₃ resulting in 0.7N + 1. 5O + 1.6OH + 2.2NO + 0.1
It becomes HNO _{2 and} 0.7N + 1.5O + 1.6OH = 100eV
Input of 2.3 NOx (2.2NO + 0.1HNO
₂ ) can be treated, and as a result, the energy required for the oxidation treatment per NOx molecule is 43.5 eV.

In short, comparing the direct current corona discharge with the short pulse corona discharge, the short pulse corona discharge shows that
Experimental results have shown that the same radical generation can be performed with a discharge input that is an order of magnitude less than that of DC corona discharge.

Therefore, according to the first aspect of the present invention, a discharge device for corona discharge and a pulse power source for applying a nonasecond pulse high voltage to cause short pulse corona discharge in the discharge device are provided. Since the short pulse corona discharge is performed in the exhaust gas treatment passage, non-equilibrium plasma that generates radicals is generated in a wide area of the exhaust gas treatment passage with a small amount of discharge input, and NOx and NOx contained in the exhaust gas are generated. SOx can be efficiently oxidized.

By providing a solution supply means and supplying the alkaline component solution to the surface of the ground electrode of the discharge device,
Since the acid generated by the oxidation of NOx or SOx is brought into contact with the alkaline component solution to be neutralized and taken into the alkaline component solution, NOx or SOx can be removed from the exhaust gas. .

As described above, NOx and SOx are oxidized by the short pulse corona discharge, and the acid produced by this oxidation is neutralized with the alkaline component solution to perform denitration and desulfurization. Therefore, a denitration catalyst is not required for denitration. Moreover, no water is required for desulfurization.

Then, NOx is generated by the short pulse corona discharge.
In the denitration and desulfurization performed by oxidizing or SOx and neutralizing the acid generated by this oxidation with an alkaline component solution, the denitration rate and desulfurization rate can be reduced to 0 by controlling the voltage applied by the discharge device.
It has been confirmed by experiments that control can be performed in a wide range of 90% or more.

Therefore, denitration can be performed efficiently, and as a result, the entire apparatus can be made compact for the performance of denitration and desulfurization.

Further, as a result of the experimental research conducted by the present inventor,
When the non-equilibrium plasma is generated by the short pulse corona discharge to oxidize NOx and SOx, the exhaust gas temperature is set to 100 ° C. or lower, preferably 75 ° C. or lower,
It was found that the oxidation treatment can be effectively performed.

Focusing on the above knowledge, in the second invention of the present invention, since the scrubber is provided to cool and wash the exhaust gas supplied to the discharge device, NOx and SOx by short pulse corona discharge are provided. When the exhaust gas contains soot and hydrocarbons, they can be removed while improving the oxidation treatment performance of the above.

In other words, N by short pulse corona discharge
A simple and inexpensive structure that only one scrubber is provided can be used while optimizing the oxidation treatment of Ox and SOx and removing soot and hydrocarbons.

In order to neutralize the acid generated by oxidizing NOx and SOx by short pulse corona discharge, weak alkaline water (for example, seawater or caustic soda of 0.02% or less) is used as an alkaline component solution. It was found that it was sufficient to use the one of the concentration).

That is, in the oxidation reaction of NOx (NO and NO ₂ ), 2 mol of NO in formulas 1 and 2 is used as HNO ₃ in formula _3.
Is produced in an amount of 1 mole, and the alkali that neutralizes 1 mole of NO becomes 1/2 mole.

Now, assuming that the NO (gas) concentration of the target gas is 2000 ppm, for example, the number of moles of NO per 1 m ³ of the target gas at room temperature is 2000 × 10 ⁻⁶ /22.4=90×10 ⁻³ mol. Therefore, the equivalent weight of the alkali that neutralizes this is ½ × 90 × 10 ⁻³ × 40 = 1.8 g in the case of caustic soda (40 g / mol). When the amount of treated water per 1 m ³ of the target gas at room temperature is 10 liters, the weight concentration of alkali required for neutralization is 1.8 / 10 ⁴ = 0.02%.

Focusing on the above points, in the third invention of the present invention, since seawater is supplied as the alkaline component solution, the acid generated by the oxidation of NOx or SOx by the short pulse corona discharge is surely performed. Of course, it can be neutralized, and when it is used for a marine internal combustion engine, the alkali component solution can be easily obtained at low cost.

According to the fourth aspect of the present invention, since the scrubber for using the seawater as the cooling / cleaning liquid is provided, the cooling / cleaning liquid can be easily obtained at low cost when used for a marine internal combustion engine.

[0039]

As described above, according to the first aspect of the present invention, denitration and desulfurization can be performed efficiently, and although the denitration performance and desulfurization performance are excellent, a denitration catalyst is not required and the input energy required for denitration and desulfurization is By synergy with the fact that there is less
It can be carried out at low cost, and the amount of water used is small, and in addition, it can be constructed in a compact size.
Since no reducing agent or a large amount of water is used and the size can be reduced, it is possible to provide an exhaust gas treatment device that can be easily implemented as a mobile source such as a marine internal combustion engine.

According to the second aspect of the present invention, further, not only dust and hydrocarbons in exhaust gas can be removed, but also initial denitration and desulfurization can be optimized at the same time, and a simple and inexpensive structure can be implemented. You can

According to the third aspect of the present invention, when it is used for a marine internal combustion engine, it is suitable for a marine internal combustion engine because the alkaline component solution is easily available.

According to the fourth aspect of the present invention, when it is used for a marine internal combustion engine, a cooling / cleaning liquid can be easily obtained, so that it is suitable for a marine internal combustion engine.

[0043]

EXAMPLE An example of application to an exhaust gas treatment apparatus for a marine internal combustion engine will be shown. As shown in FIG. 1, the exhaust gas treatment device is configured to include a discharge device 1, a pulse power supply 2, a solution supply means, and a scrubber 3.

The discharge device 1 has an exhaust gas inlet 4A at the bottom.
And a cylindrical ground electrode 1A in a vertical position and a discharge electrode 1B arranged in the center thereof are arranged side by side in parallel with each other. Is configured.

The ground electrode 1A, that is, the space between the ground electrode 1A and the discharge electrode 1B is formed in the exhaust gas treatment passage 5 which goes from the lower side to the upper side, and the exhaust gas treatment passage 5 has an exhaust gas inlet 4A at the lower end. Is also connected to the exhaust gas outlet 4B at the upper end. The discharge electrode 1B is supported on the top plate of the processing case 4 via the electric insulator 6 at the upper end portion, and is supported by the support member 7 at the lower end so as not to come into contact with the ground electrode 1A due to vibration. The support member 7 is attached to the processing case 4 via an electric insulator 8. The electric insulator 6 and the electric insulator 8 are housed in a box 9 to which a dry gas heated above the dew point is supplied. In addition, the discharge electrode 1B is formed with a plurality of discharge-inducing projections 1a at intervals in the longitudinal direction. That is, even if the middle of the discharge electrode 1B is slightly bent and the distance between the discharge electrode 1B and the ground electrode 1A becomes uneven, the discharge from the projection 1a is preferentially performed to discharge the discharge electrode 1B. It is configured to be performed over the entire length of 1B (the entire length of the exhaust gas treatment passage 5). The reason why the protrusion 1a is not formed on the ground electrode 1A but is formed on the discharge electrode 1B is that when the protrusion 1a is formed on the ground electrode 1A, the ground electrode 1A becomes dirty.

The pulse power supply 2 has a voltage waveform (that is, a voltage of 50 to 200 KV and a rise time of 50 as shown in FIG. 2 between the discharge electrode 1B and the ground electrode 1A of the discharge device 1.
˜500 ns, the period is 5˜50 ms) and a non-second pulse high voltage is applied to cause short pulse corona discharge, the electric field strength is about 20˜50 KV / cm, and the average electron temperature in the electric field is 2 to 6 eV.

Therefore, when an exhaust gas at 100 ° C. or lower, preferably 75 ° C. or lower is supplied into the exhaust gas treatment passage 5, the short pulse corona discharge by the discharge device 1 causes a non-equilibrium plasma (low temperature) in the exhaust gas treatment passage 5. If the exhaust gas contains NOx and SOx,
Radicals of N, S, and OH are generated, and NOx and SOx
Is oxidized to generate an acid. According to the experiment, when a metal tube having a diameter of 10 cm is used as the ground electrode 1A, the peak voltage applied to the discharge electrode 1B is 50 to 80 KVpp.

The solution supply means supplies an alkaline component solution to the surface of the ground electrode 1A (inner peripheral surface in contact with exhaust gas) to bring the acid generated by the short pulse corona discharge into contact with the solution for neutralization. A supply pipe 10 for supplying an alkaline component solution using a pump or the like, and a distribution pipe 11 for distributing and supplying the alkaline component solution supplied thereby to the upper end of each ground electrode 1A. Then, the alkali component solution is alkali caustic soda (40 g / mol)
In this case, the solution has a weight concentration of 0.02% or less, and seawater is used as the alkaline component solution in this example. The inner peripheral surface of the ground electrode 1A is formed as a smooth surface without unevenness so that the alkaline component solution flowing along the ground electrode 1A is prevented from scattering to the discharge electrode 1B side, or is extremely reduced. The reason is that the alkaline component solution flowing down along the inner peripheral surface of the ground electrode 1A is discharged from the discharge electrode 1B.
This is because if it scatters on, there is a risk of a short circuit in the current.

Therefore, the acid generated by the short pulse corona discharge is captured and neutralized by the alkaline component solution, and is discharged downward together with the alkaline component solution. As a result, NOx and SOx are removed from the exhaust gas. That is, denitration and desulfurization are performed. The removal rate by denitration and desulfurization can be adjusted by controlling the voltage applied to the discharge device 1. Normally, in denitration, a removal rate of about 80% can be easily achieved, and in desulfurization, a removal rate of about 90%. Can be easily achieved.

The scrubber 3 supplies 100 ° C. of the exhaust gas supplied to the discharge device 1 (in the case of the exhaust gas of a marine diesel engine, the exhaust gas temperature is about 250 to 400 ° C.).
A cyclone scrubber that cools to 75 ° C. or lower, and also removes soot and hydrocarbons (tar and the like) in the exhaust gas by the discharge device 1
It is located at the bottom of. Reference numeral 12 is a supply pipe for supplying seawater to the scrubber 3 as a cooling / cleaning liquid.

Therefore, when the exhaust gas contains soot dust and hydrocarbons, the soot dust and hydrocarbons can be removed, and the discharge electrode 1B and the ground electrode 1A are not contaminated with the soot dust and hydrocarbons. The short pulse corona discharge performance of can be favorably maintained.

At the lower part of the processing case 4, cooling by the alkaline component solution that has flowed down and the scrubber 3 is performed.
A drain port 13 for discharging the cleaning drain is formed. Reference numeral 14 is a drainage reservoir that receives the drainage from the drainage port 13.

[Other Embodiment] In the above embodiment, the discharge electrode 1B is used.
The number of pairs may be one, two, four or more.

Although the scrubber 3 is provided in the above embodiment, the scrubber 3 may be omitted if the exhaust gas does not contain soot dust or hydrocarbons. In this case, when the exhaust gas temperature is equal to or higher than the temperature suitable for the appearance of the non-equilibrium plasma state by the short pulse corona discharge, the exhaust gas is supplied to the discharge device 1 at the suitable temperature (100
It is preferable to implement by providing a cooler for cooling to ℃ or less, preferably 75 ℃ or less). Of course, in this case, it is only necessary to remove NOx and SOx.

In the above embodiment, the scrubber 3 is arranged below the discharge device 1, but the scrubber 3 may be installed at any place as long as it is an exhaust gas supply path to the discharge device 1.

Although a cyclone scrubber is shown as the scrubber 3 in the above embodiment, the scrubber 3 may be of a cyclone type or a sprinkling type.

In the above embodiment, seawater was used as the alkaline component solution, but the alkaline component solution may be a preparation solution in which an alkali such as caustic soda is dissolved.

In the above embodiment, seawater was used as the cooling / cleaning liquid, but the cooling / cleaning liquid may be other than seawater such as fresh water.

In the above embodiments, the exhaust gas treating apparatus for a marine internal combustion engine is shown, but the exhaust gas treating apparatus of the present invention can be applied to a boiler and an industrial furnace.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram.

FIG. 2 Waveform diagram of short pulse voltage

[Explanation of symbols]

 1 Discharge device 1A Ground electrode 1B Discharge electrode 2 Pulse power supply 3 Scrubber 5 Exhaust gas treatment passage

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01D 53/56 53/74 B01J 19/08 ZAB C 9342-4D F01N 3/04 ZAB Z B01D 53 / 34 129 C (72) Inventor Kiyoji Mizouchi 1-33 Dojimahama, Kita-ku, Osaka-shi, Osaka Prefecture Takuma Research Institute, Inc. (72) Kenyuki Onishi 1-3-23 Dojimahama, Kita-ku, Osaka-shi, Osaka Inside the Takuma Research Institute Co., Ltd. (72) Inventor Tomohisa Ota 1-33 Dojimahama, Kita-ku, Osaka City, Osaka Prefecture Inside the Takuma Research Institute Co., Ltd.

Claims (4)

[Claims] 1. A discharge device (1) for providing an exhaust gas treatment passage (5) between a discharge electrode (1B) and a ground electrode (1A) is provided, and the discharge electrode (1B) of the discharge device (1) is grounded. Pole (1
A pulse power source (2) for performing short pulse corona discharge is provided between the discharge device (A) and a neutralizing solution supply means for supplying an alkaline component solution to the surface of the ground electrode (1A) of the discharge device (1). Exhaust gas treatment equipment provided. 2. A scrubber (3) for cooling and cleaning exhaust gas supplied to the discharge device (1) is provided.
Exhaust gas treatment device described. 3. The exhaust gas treating apparatus according to claim 1, wherein the solution supply means is provided with means for using seawater for the alkaline component solution. 4. The exhaust gas treatment apparatus according to claim 2, wherein the scrubber (3) is provided with one that uses seawater as a cooling / cleaning liquid.