JPH07265655A - Plasma-process waste gas purifying device - Google Patents

Abstract

PURPOSE:To improve the contact efficiency between plasma and waste gas by arranging the discharge electrode and counter electrode consisting of a mesh having a different density from each other in a flue to pass the whole amt. of waste gas. CONSTITUTION:A reactor formed by alternately providing plural discharge electrodes 13 and plural counter electrodes 14 and a high-voltage pulse power source 12 connected to the electrodes 13 and 14 are set in a flue 11. The discharge electrode 13 is formed with a coarse mesh and the counter electrode 14 with a dense mesh. The whole amt. of waste gas is passed through the electrodes 13 and 14. Consequently, a large-area plasma is produced close to the discharge electrode 13, the whole amt. of waste gas 15 is brought into contact with the plasma, and contact efficiency is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma method exhaust gas purifying apparatus which is one of means for purifying harmful substances contained in exhaust gas discharged from power generation boilers, various combustion engines, combustion furnaces and the like.

[0002]

2. Description of the Related Art A plasma method exhaust gas purifying apparatus is known (see Japanese Patent Laid-Open No. 63-500020), and its principle will be described with reference to FIG.

In FIG. 6, (1) shows a high voltage pulse generating power source for generating plasma, (2) shows a wire type discharge electrode, and (3) shows a plate type counter electrode. A pulse peak voltage of 1 kV to 500 Kv, a pulse frequency of 10 HZ to 250 HZ, and a pulse width of 1 nanosecond to between both electrodes (2) and (3).
10 microseconds, rise time 100 kV / nanoseconds ~
When a high voltage pulse of 100 V / nanosecond is continuously applied, a non-equilibrium plasma (4) is generated between the electrodes. This generated plasma (4) is a pulse streamer corona discharge between asymmetric electrodes, and most of the current is due to electrons. Exhaust gas containing harmful gas components in such a place (5)
Then, various radicals are generated by plasma (4). Radicals are generated between the electrodes.

Here, the pulse streamer corona discharge is
In addition to the feature of widening the radical generation region by the electronic current, the feature of suppressing generation of a large ionic current spark (that is, dielectric breakdown of the gap) due to formation of a conduction bridge by performing discharge in a short time. I also have. Further, the peak value Vp of the pulse power supply is equal to or higher than the voltage (several kV) required for the streamer corona discharge,
The pulse rise time Tr is the streamer formation speed (100
0 km / s) or more is required. Further, in order to enhance the exhaust gas treatment effect (accelerate the electrons in the streamer and activate the exhaust gas molecules by these electrons), ΔVp / ΔTr
A large value is desirable.

By reacting with the radicals, the harmful components in the exhaust gas are oxidized into CO ₂ , SO x into SO ₃ , and NO x into NO _2, and are transformed into a harmless form or a form easily collected. Further, when the gas to be treated is the exhaust gas from the refuse incinerator, dioxins and the like contained in the gas are decomposed and rendered harmless. When ammonia, lime, etc. are blown into the reactor where these reactions occur or in the downstream of the reactor, the SOx component and NOx component change to solids such as ammonium sulfate and ammonium nitrate or calcium sulfate and calcium nitrate. An exhaust gas purification is achieved by providing an electrostatic precipitator or a bag filter and collecting them.

[0006]

In the electrode shown in FIG. 6, the plasma is generated intermittently in the lengthwise direction of the wire type discharge electrode. Therefore, a sparse portion is formed in the plasma and the plasma and the exhaust gas are separated from each other. There was a problem that the contact efficiency was poor.

An object of the present invention is to provide a plasma method exhaust gas purifying apparatus capable of improving the contact efficiency between plasma and exhaust gas.

[0008]

A plasma method exhaust gas purifying apparatus according to the present invention is connected to both a reactor and a reactor in which at least one discharge electrode and at least one counter electrode are alternately provided inside a flue. Equipped with a high-voltage pulse generation power supply, the non-equilibrium plasma is generated by continuously applying a high-voltage pulse between both electrodes, and harmful gas components in the exhaust gas are removed while the exhaust gas passes through the reactor. In the plasma-type exhaust gas purifying apparatus that converts into a form that is easy to collect or a harmless form, the discharge electrode and the counter electrode are mesh-shaped electrodes having different densities, and are arranged in the flue so as to pass the entire amount of exhaust gas. It is characterized by that.

[0009]

In the plasma-type exhaust gas purifying apparatus according to the present invention, the discharge electrode and the counter electrode are mesh-shaped electrodes having different densities, and are arranged in the flue so as to pass the entire amount of exhaust gas. A large-area plasma is generated in the vicinity of the discharge electrode, and the entire amount of exhaust gas comes into contact with the plasma.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the left and right of FIG. 1 will be referred to as the left and right.

FIG. 1 shows a plasma-type exhaust gas purifying apparatus according to the present invention, and FIG. 2 shows the concept of a plasma generating electrode in this apparatus.

As shown in FIG. 1, the plasma method exhaust gas purifying apparatus has a reactor (in which a plurality of discharge electrodes (13) and a plurality of counter electrodes (14) are alternately provided inside a flue (11). Ten)
And a high voltage pulse power supply (12) connected to both electrodes (13) (14)
It has and.

As shown in FIG. 2, the discharge electrode (13) and the counter electrode (14) are both mesh electrodes, and the discharge electrode (13) is a coarse (large opening area) mesh, counter electrode ( 14)
Is a dense (large opening area) mesh. Both electrodes (1
3) and (14) are supported in an insulating material frame (16). Discharge electrode
(13) is composed of, for example, five vertical and horizontal wires made of conductive material, and the counter electrode (14) is made of, for example, 17 vertical and horizontal wires made of conductive material, and the discharge electrode (13) has an electrode area facing each other. The size is significantly smaller than the electrode area of the electrode (14). The discharge electrode (13) and the counter electrode (14) are arranged perpendicular to the flow direction of the exhaust gas (15). The discharge electrode (13) and the counter electrode (14) do not have to be perpendicular to the flow direction of the exhaust gas (15), and they are in the flue (11) so as to pass the entire amount of the exhaust gas (15). It should be arranged.

In the embodiment shown in FIG. 1, the number of electrodes (13) and (14) is nine in total, and these electrodes (13) and (14) respectively alternate with the exhaust gas ( They are arranged along the flow direction of 15). These electrodes (13) and (14) were sequentially numbered from the left to NO. 1 to NO. When it is distinguished as up to 9, the odd number is a dense mesh which becomes the counter electrode (14), and the even number is a coarse mesh which becomes the discharge electrode (13). The even-numbered electrodes (13) are connected to one end of the high-voltage pulse power supply (12) via the rotary switch (18), and the odd-numbered electrodes (14) are connected to each other by a conductive wire, and the conductive wire is It is connected to the other end of the high voltage pulse power supply (12).

The rotary switch (18) is a spark gap switch, and is a rotary bar (2) driven by a motor (19).
0) and two movable contacts on both ends of the rotating bar (20)
(21) and eight fixed contacts (22) arranged at equal intervals on the circumference around the center of rotation of the rotating bar (20) are provided to rotate the rotating bar (20). Accompanied by eight fixed contacts
The electric circuit between the opposing ones of (22) is a rotating bar (20)
It will be opened and closed via. Therefore, when the rotating bar (20) is driven by the motor (19), even numbered discharge electrodes
Plasma is sequentially generated between (13) and the counter electrodes (14) on the left and right sides of the (13). As the rotary switch (18), a spark gap switch driven by the motor (19) is desirable from the viewpoint of shortening the pulse rise time and narrowing the pulse width, but other switches are used. Good.

A plasma generation time chart in this apparatus is shown in FIG. When the rotary bar (20) is in the position shown in FIG. No. 2 discharge electrode (13) and NO. 1 and NO. Plasma is generated between the counter electrode 14 of FIG.
When the rotary bar (20) is rotated clockwise from this position, NO. No. 4 discharge electrode (13) and NO. 3 and NO. 5
Plasma is generated between the counter electrode (14) and the counter electrode (14). Similarly, as the rotary bar (20) is rotated in the clockwise direction, NO. No. 6 discharge electrode (13) and NO. 5 and NO. 7
Between the counter electrode (14) of NO. 8 discharge electrodes (13) and N
O. 7 and NO. N between the counter electrode (14) of N
O. No. 2 discharge electrode (13) and NO. 1 and NO. Plasma is sequentially generated between the counter electrode 14 and the counter electrode 14. NO. No. 2 discharge electrode (13) and NO. 1 and NO. 3 counter electrodes (14)
Since there is a limit to the number of times of switching by the rotating bar (20) between and, the interval of plasma generation is 4 milliseconds and the number of plasma generations is 250 times per second. Plasma is also generated once between the electrodes, and the number of plasma generations in the reactor is 10 per second.
00 times, that is, duty factor (DF) = 1 /
It will be 1000.

FIG. 4 shows a mesh-shaped discharge electrode having a coarse density.
(13) shows a discharge area (P1) having an ionizing ability in the vicinity, and FIG. 5 shows a discharge area having an ionizing ability in the vicinity of the wire type discharge electrode (2) in the conventional apparatus shown in FIG. (P2) is shown. As can be seen from FIG. 4 and FIG. 5, the discharge area (P2) having the ionizing ability in the conventional device is limited to the vicinity of the wire type discharge electrode (2), and therefore the exhaust gas
The contact area with (5) is very small, whereas the discharge area (P1) having the ionization capacity in the device of the present invention is almost the entire area near the mesh-shaped discharge electrode (13),
The contact area with (15) is large. Since the discharge and the counter electrodes (13) and (14) are both mesh-shaped, the pressure loss of the exhaust gas (15) flow is not much worse than that of the conventional one.

In the above embodiment, the total number of electrodes (13) and (14) is nine, but this number may be changed appropriately. When scaling up the above device, the electrodes (13) (1
It is sufficient to increase the number and area of 4) and it is possible to easily scale up.

[0019]

According to the plasma type exhaust gas purifying apparatus of the present invention, a large-area plasma is generated in the vicinity of the discharge electrode, and the entire amount of the exhaust gas comes into contact with the plasma, so that the contact efficiency between the exhaust gas and the plasma is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a plasma method exhaust gas purification apparatus according to the present invention.

FIG. 2 is a perspective view showing the concept of an electrode for plasma generation in the same apparatus.

FIG. 3 is a plasma generation time chart in the same apparatus.

FIG. 4 is a diagram schematically showing a discharge region in the same device.

FIG. 5 is a diagram schematically showing a discharge region in a conventional plasma-type exhaust gas purifying apparatus.

FIG. 6 is a perspective view showing the concept of electrodes for plasma generation in a conventional plasma-type exhaust gas purifying apparatus.

[Explanation of symbols]

 (10) Reactor (11) Flue (12) High-voltage pulse power supply (13) Discharge electrode (14) Counter electrode (15) Exhaust gas

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location B01D 53/56 53/60 53/74 B01D 53/34 132 A (72) Inventor Kenji Yasuda Nishi, Konohana-ku, Osaka 5-3-28 Kujo Inside Hitachi Shipbuilding Co., Ltd.

Claims (1)

[Claims] 1. A reactor provided with at least one discharge electrode and at least one counter electrode alternately provided inside a flue, and a high-voltage pulse generating power source connected to both electrodes, and between both electrodes. A plasma method in which a non-equilibrium plasma is generated by continuously applying a high-voltage pulse to the gas, and while the exhaust gas passes through the reactor, the harmful gas components in the exhaust gas are converted into a form that is easy to collect or a harmless form. In the exhaust gas purifying apparatus, the discharge electrode and the counter electrode are mesh-shaped electrodes having different densities from each other, and are arranged in the flue so as to pass the entire amount of the exhaust gas.