JPH08954A - Nitrogen oxide removal device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a nitrogen oxide removing device provided with a charge / discharge circuit with good energy efficiency that can convert charging energy into discharging energy without excess or deficiency. A nitrogen oxide removing device for removing NOx in exhaust gas, comprising a discharge part having linear electrodes and a plate electrode facing each other for generating discharge plasma, and applying a high voltage to the discharge part. In the nitrogen oxide removing apparatus having the charging / discharging circuit, a distributed constant system charging / discharging circuit in which coils and capacitors are arranged in steps is provided. Further, this distributed constant system charging / discharging circuit utilized any one of a charging resistor, a charging coil, a stray inductance or a voltage doubler circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrogen oxide removing apparatus for removing nitrogen oxides in exhaust gas discharged from a boiler for a power plant, a diesel engine, a gas turbine or various combustion furnaces. The present invention relates to a charging / discharging circuit (hereinafter referred to as “charging / discharging circuit”) for supplying electric power to a discharging unit.

[0002]

2. Description of the Related Art Conventionally, many attempts have been made to decompose NOx, which is a nitrogen oxide, by corona discharge of high voltage pulse, but the technique is NOx removal (for example, 90% removal).
The progress has been made toward reducing the exhaust gas absorption energy required for Moreover, the energy is close to the practical level. However, the charging / discharging circuit has a very poor conversion rate for converting charging energy into discharge energy which is exhaust gas absorption energy. Therefore, a charging / discharging circuit having a high conversion rate from charging energy to discharging energy has been required for practical use. Conventionally, as this type of charge / discharge circuit 1 ', a circuit as shown in FIG. 6 is known ("Control of NOx by Positive and Negative Pulsed").
Corona Discharges. "Senichi Masuda 1986 IEEE p117
3 ~ 1182). This rotates the rotary spark switch 14 by the synchronous motor 13, boosts the voltage from the voltage regulator 10 by the high voltage transformer 11, and
The high voltage rectified by 2 is used to generate a high voltage pulse between the terminals 19 and 19 by the pulse forming capacitor 15. In FIG. 6, reference numeral 16 is a coupling capacitor, 17 is a bias DIC high voltage, 18 is a test battery, 20 is a coil, and 21 and 22 are resistors.

[0003]

FIG. 7 is a simplified representation of the charging / discharging circuit 1'of FIG. 6, which is a lumped constant system charging / discharging circuit composed of a floating coil and a charging capacitor C. As shown in FIG. . Further, the discharge resistance R ₁ is used to shorten the high voltage discharge duration, thereby preventing the transition to arc discharge. However, in this circuit, as shown in FIG. 8, since the rising time 8 and the falling time 9 of the voltage waveform are longer than the discharge duration 7 of the high voltage, the energy consumption during discharge is reduced. Further, energy consumption in the discharge resistor R ₁ is also added, and a considerable amount of charging energy is lost in the charging / discharging circuit 1 '.

An object of the present invention is to provide a nitrogen oxide removing device equipped with an energy efficient charge / discharge circuit capable of converting charge energy into discharge energy without excess or deficiency.

[0005]

In order to solve the above problems, the nitrogen oxide removing apparatus of the present invention adopts a distributed constant type charge / discharge circuit in which a coil and a capacitor are properly combined instead of a lumped constant type circuit. did. That is, a nitrogen oxide removing device for removing nitrogen oxides in exhaust gas, wherein a discharge part provided with electrodes facing each other for generating discharge plasma, and a high voltage is applied to the discharge part charged from a high voltage power source. In the nitrogen oxide removing apparatus having the charging / discharging circuit, a distributed constant system charging / discharging circuit in which coils and capacitors are arranged in steps is provided.

Further, in the above invention, the distributed constant type charging / discharging circuit uses any one of a charging resistor, a charging coil, a stray inductance and a voltage doubler circuit.

[0007]

Since the nitrogen oxide removing apparatus of the present invention is provided with the distributed constant system charge / discharge circuit in which the coil and the capacitor are arranged in a stepwise manner, the plasma duration thereof is obtained by connecting a number of capacitors in parallel, The discharge voltage of the discharge part is maintained constant and continues. The rise and fall times have short voltage waveforms due to the effect of one small-capacity capacitor. The energy consumed in the discharge part is already 100% of the charged energy due to the plasma extinction voltage in the initial short time.
Reach near By this control, the discharge energy required for removing the nitrogen oxides can be supplied without excess or deficiency.

Further, in the above invention, since the distributed constant system charging / discharging circuit utilizes any one of the charging resistor, the charging coil, the stray inductance and the voltage doubler circuit, the generation of plasma by the corona discharge is stable. The discharge energy required for removing nitrogen oxides can be supplied without excess or deficiency.

[0009]

Embodiments of the nitrogen oxide removing apparatus according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is an electric circuit diagram showing an embodiment of the charging / discharging circuit of the nitrogen oxide removing apparatus according to the present invention, and FIG. 2 shows the relationship between the time of the charging / discharging circuit shown in FIG. Curve diagram,
3 to 5 are electric circuit diagrams showing other embodiments of the charging / discharging circuit of the nitrogen oxide removing apparatus according to the present invention.

In the embodiment of the present invention, a discharge portion provided with electrodes facing each other for generating discharge plasma by a high-voltage pulse for NOx which is a nitrogen oxide in exhaust gas flowing through a flow passage, is provided in the discharge portion. A nitrogen oxide removing device having a charging / discharging circuit that applies a high voltage to supply the electric power necessary for decomposing NOx in the exhaust gas flowing through this flow path without excess or deficiency.

FIG. 1 is an electric circuit diagram showing an embodiment of a charging / discharging circuit of the above nitrogen oxide removing apparatus. NOx in exhaust gas is shown in FIG.
It is used for a nitrogen oxide removing device that decomposes.
The charging / discharging circuit 1 is for applying a high voltage to a discharging portion 2 provided with electrodes 3 and 4 facing each other for generating discharge plasma. The charging / discharging circuit 1 includes the distribution system coil L.
_{It is} a distributed constant system charge / discharge circuit in which _{1 to} L ₈ and distributed system capacitors C _{1 to} C ₈ are arranged in steps. In the figure, S is a switch, R ₀ is a charging resistance, and R ₁ is a discharging resistance. In the embodiment of FIG. 1, the distributed capacitors are arranged in parallel in eight steps, but the number of steps is not limited to eight steps. Of course, the number of steps of the distributed capacitor and the distributed coil is determined so that the required duration is obtained. The rise time and the fall time are adjusted by the capacity of one capacitor, and the voltage maintaining time corresponding to the discharge duration is adjusted by the number of capacitors.

Further, the electrode 3 of the discharge part 2 is a linear electrode, and the electrode 4 is an opposing flat plate or a Chang-type electrode facing the electrode 3, but the present invention is not limited to this, and other types of electrodes may be used. It may be.

The nitrogen oxide removing apparatus of the present invention operates as follows. That is, the high voltage power source + HV is used when the switch S such as the spark switch and thyratron is in the open state.
The eight capacitors C _{1 to} C ₈ are charged by the charging resistor R ₀ . Next, since the capacitors C _{1 to} C ₈ are connected in parallel via the coils L _{1 to} L ₈ , the capacitors C _{1 to} C ₈ are
Energy is supplied to the discharge part in the order of C ₁ to C ₈ , and the discharge voltage in the discharge part is maintained at a high voltage for a certain period of time, and plasma is maintained for a certain period of time to decompose NOx which is a nitrogen oxide. The rising and falling times have a voltage waveform of a short time due to the effect of one small-capacity capacitor, so that the charging energy is converted into the discharging energy without excess or deficiency.

FIG. 2 is a curve diagram showing the relationship between the time of the charge / discharge circuit shown in FIG. 1 and the discharge voltage or energy consumed by the discharge section. The operation of the charging / discharging circuit shown in FIG. 1 will be further described. The horizontal axis represents time t [sec], the left vertical axis represents discharge voltage U [V], and the right vertical axis represents discharge part consumption energy E.
[J] is taken, and the discharge voltage curve 5 is represented by a solid line and the discharge portion energy consumption curve 6 is represented by a broken line. The energy consumption E at the discharge part is already 1 of the charging energy at a plasma extinction voltage of -20 [kv], as shown by the chain line.
It can be seen that it is close to 00 [%]. By this control, the discharge energy required for removing NOx can be supplied without excess or deficiency.

FIG. 3 is an electric circuit diagram showing another embodiment of the charging / discharging circuit of the nitrogen oxide removing apparatus according to the present invention. This embodiment is similar to the embodiment of FIG.
_{1 to} Cn and distributed system coils L _{1 to} Ln are arranged in steps, and a distributed constant system charge / discharge circuit 1 is provided with a charging coil L ₀ that is a charging coil. The same reference numerals and symbols are given to the same structures and operations as those in FIG. 1, and the description thereof will be omitted.

FIG. 4 is an electric circuit diagram showing still another embodiment of the charging / discharging circuit similar to FIG. This embodiment is similar to the embodiment of FIG. 1 in that the distribution system capacitors C _{1 to} Cn are arranged in steps, but the distribution system coils L ₁ , L ₂ ... And the charging resistance R _{0 of} FIG. The charging / discharging circuit 1 is a distributed constant system that does not include the charging coil L ₀ of No. 3 and uses a floating inductance. The same reference numerals and symbols are given to the same structures and operations as those in FIG. 1, and the description thereof will be omitted.

FIG. 5 is an electric circuit diagram showing still another embodiment of the charging / discharging circuit similar to FIG. Charging and discharging circuit 1 of this embodiment, like the embodiment of FIG. 1, the distribution system capacitor C ₁
The ~Cn and distribution system coil L ₁ Ln, each of the plus side and the minus side of the discharge portion is obtained by utilizing the voltage doubler circuit which is arranged in steps. As in the embodiment of FIG. 3, a charging coil L ₀ is provided. The same reference numerals and symbols are given to the same structures and operations as those in FIG. 1, and the description thereof will be omitted.

Although the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited only to those embodiments by that, and various modifications can be made without departing from the spirit of the present invention. In addition, it goes without saying that various modifications can be made.

[0019]

Since the nitrogen oxide removing apparatus of the present invention is provided with the distributed constant type charging / discharging circuit in which the coil and the capacitor are arranged in steps, the nitrogen oxide in the exhaust gas can be efficiently discharged by the discharge plasma by the high voltage. It is an energy-saving nitrogen oxide removing device that can be decomposed well, can shape an ideal pulse waveform according to plasma formation time, and can convert charging energy into discharge energy without excess or deficiency.

Further, in the above invention, the distributed constant type charging / discharging circuit uses any one of the charging resistor, the charging coil, the stray inductance and the voltage doubler circuit, so that the generation of plasma by the corona discharge is stable. The discharge energy required for removing nitrogen oxides can be supplied without excess or deficiency.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a charge / discharge circuit of a nitrogen oxide removing apparatus according to the present invention.

FIG. 2 is a curve diagram showing a relationship between time and discharge voltage or energy consumption of a discharge part of the charge / discharge circuit shown in FIG.

FIG. 3 is an electric circuit diagram showing another embodiment of the charge / discharge circuit of the nitrogen oxide removing apparatus according to the present invention.

FIG. 4 is an electric circuit diagram showing still another embodiment of the charging / discharging circuit similar to FIG.

FIG. 5 is an electric circuit diagram showing still another embodiment of the charging / discharging circuit similar to FIG.

FIG. 6 is an electric circuit diagram showing a charge / discharge circuit of a nitrogen oxide removing apparatus according to a conventional technique.

7 is an electric circuit diagram in which the charge / discharge circuit of FIG. 6 is simplified.

FIG. 8 is a voltage waveform curve diagram for explaining discharge duration when the charge / discharge circuit of FIG. 6 or 7 is used in a nitrogen oxide removing device.

[Explanation of symbols]

1 Charging / Discharging Circuit 2 Discharging Section 3 Linear Electrode 4 Opposing Plate Electrode L _{1 to} Ln Distribution System Coil C _{1 to} Cn Distribution System Capacitor S Switch + HV High Voltage Power Supply R ₀ Charging Resistance L ₀ Charging Coil

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B01J 19/00 C 0821-4D

Claims (2)

[Claims] 1. A nitrogen oxide removing apparatus for removing nitrogen oxides in exhaust gas, comprising: a discharge part provided with electrodes facing each other for generating discharge plasma; A nitrogen oxide removing device having a charging / discharging circuit for applying a voltage, comprising a distributed constant system charging / discharging circuit in which coils and capacitors are arranged in steps. 2. The nitrogen oxide according to claim 1, wherein the distributed constant type charging / discharging circuit uses any one of a charging resistor, a charging coil, a stray inductance, and a voltage doubler circuit. Removal device.