JPH0647065B2 - Desulfurization and denitration equipment using corona discharge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is directed to desulfurization using a needle-shaped corona high-voltage discharge electrode.
Denitration equipment

(Prior Art) In recent years, environmental protection on a global scale has become a big problem, and therefore, a desulfurization / denitration technology that efficiently and economically removes nitrogen oxides and sulfur oxides that are the pollutants thereof Development is becoming an increasingly important international issue.

For desulfurization, a wet limestone-gypsum method has been put into practical use, and a direct desulfurization method for directly removing sulfur from fuel has also been developed.

As the denitration method, a selective catalytic reduction method using ammonia has been put into practical use. However, in any of the above methods, it is necessary to install a desulfurization and denitration device independently, and desulfurization and denitration cannot be performed efficiently and economically at the same time.

On the other hand, research on simultaneous electron beam irradiation and simultaneous desulfurization / denitration by pulse corona discharge as a method of simultaneously performing desulfurization / denitration is under way for exhaust gas at about 100 ° C. All of these methods generate highly active oxidizing radicals such as O, OH, and HO ₂ from flue gas by excited electrons by electron beam or corona discharge, and NO _x and SO _x are converted to nitric acid and sulfuric acid by the oxidizing radicals. It is oxidized and further neutralized with alkaline substances [NH ₃ and Ca (OH) ₂ etc.] and recovered as useful powdered fertilizers such as ammonium sulfate and ammonium nitrate.

(Problems to be solved by the invention) However, in the above-mentioned electron beam irradiation and the simultaneous desulfurization / denitration method by pulsed corona discharge, the amount of nitrogen oxides and sulfur oxides decreases with the increase in power due to DC corona discharge. However, when the applied voltage is increased under atmospheric pressure using a rod-shaped electrode that has been conventionally used as an electrode in this method, at some point the corona discharge transitions to arc discharge, and corona discharge does not increase any further. On the contrary, the transferred arc discharge locally heats the combustion gas, resulting in a drastic increase of nitrogen oxides. Therefore, in order to improve desulfurization / denitration performance,
It is necessary to increase the corona discharge input without reaching the arc discharge.

In order to solve the above problems, the inventors of the present invention have earnestly studied the shape of the electrode to be used, and as a result, when a needle-shaped electrode is used, more current, that is, electric power, can be obtained at the same voltage than that of a rod-shaped electrode. It was found that the useful corona discharge input can be high.

(Means for Solving Problems) The present invention is based on the above findings, and an outer peripheral ground electrode also serving as an introduction duct of exhaust gas to be desulfurized and denitrated, and a needle electrode installed in the outer peripheral ground electrode. It proposes a desulfurization / denitration device composed of and.

As the needle-shaped electrode, an electrode configured by extending a plurality of needle electrodes in a predetermined direction from the side surface of the structural electrode can be used.

(Operation) As described above, the desulfurization / denitration apparatus according to the present invention is configured by installing the needle electrode in the outer peripheral ground electrode of the exhaust gas, which also serves as the introduction duct. By using, the corona discharge power useful for desulfurization and denitration can be higher than that of the conventionally used needle electrode.

Further, the shape of the needle-shaped electrode can be freely selected according to the shape of the outer peripheral ground electrode.

Further, the needle-shaped electrode can be of a simple structure in which a plurality of needle electrodes are extended in a predetermined direction from the side surface of the structural electrode, and therefore can be easily manufactured and has no moving parts. There is no inconvenience in operation.

(Example) Hereinafter, the present invention will be described in detail based on an illustrated example.

Reference numeral 1 shows a needle-shaped electrode used in the present invention. Needle electrode 1
In this embodiment, a plurality of needle electrodes 4 each having an appropriate thickness and length are arranged in two or four directions from the side surface of a quadrangular prismatic structure electrode 3 having a current introduction terminal hole 2 at its tip. .

Here, the structure electrode 3 plays a role of supporting the plurality of needle electrodes 4 in an appropriate distribution and introducing a current into these needle electrodes 4, and the needles forming the needle electrodes 4 are The diameter is 1 mmφ, and the length is 20 mm so that the discharge input is maximized in consideration of the distance from the opposing ground electrode, and the distance between the needle electrodes 4 is about 30 mm. Needless to say, the present invention is not limited to this, and the length and shape of the needle electrode 4, the thickness, the interval between the needle electrodes 4 and the like can be freely selected according to the type of processing gas. A curved line or a polygonal line can be used as 1, and a finer needle electrode can be used if there is no problem in strength.

It should be noted that an electrode supporting hole 5 for inserting the needle-shaped electrode 1 into the opposing ground electrode and the supporting member 6 for the insulator is provided on the side surface of the structural electrode 3, but the current introducing terminal hole 2 is provided in the electrode supporting hole 5. When used in combination, the electrode supporting hole 5 is not particularly required.

FIG. 2 shows the present invention constructed by installing the above-mentioned needle-shaped electrode 1 in a square pole-shaped duct / opposite grounding electrode 8 which is provided with a high voltage power source 7 for corona discharge outside and which has both ends open. An example of such a desulfurization / denitration apparatus is shown. As is clear from this, the lead wire of the needle-shaped electrode 1 is connected to the opposite ground electrode 8 via the support 6 of the insulator. Is connected to the high-voltage power supply 7, and the combustion exhaust gas is introduced into the counter ground electrode 8 from the direction of arrow 9.

In this embodiment, the counter ground electrode 8 is in the shape of a quadrangular prism whose both ends are open. However, the present invention is not limited to this. For example, as shown in FIG. You may make it arrange | position the needle-shaped electrode 1 in 8.

FIG. 4 shows an example in which the desulfurization / denitration device 12 according to the present invention is installed in the cooling part of the combustion device including the burner 10 and the boiler 11. In this embodiment, desulfurization / denitration is performed in the low temperature part of the boiler 11. After the denitration device 12 is installed and the powder fertilizer produced by the desulfurization / denitration device 12 is removed by the electrostatic precipitator 13, the stack 14
I try to discharge more.

In the embodiment of FIGS. 2 and 3, the gap (Gap: discharge distance) between the tip of the needle electrode 4 and the opposing ground electrode 8 is 2 cm at which the discharge input is large and the voltage does not become so high. Ratio φ = 1, combustion gas amount GG = 2.06g / s approx. 1
Fig. 5 shows the relationship between the discharge input and the NO _x and NO concentrations at the outlet when discharge is carried out in the desulfurization / denitrification device 12 by adding 00 ppm of NO so that the inlet temperature is 150 ° C and the outlet temperature is 70 ° C. Shown in.

As is clear from the figure, when the desulfurization / denitration device according to the present invention is used, the denitration performance is remarkably improved as the corona discharge input amount increases.

Further, in FIG. 6, the conventional rod-shaped electrodes were set to discharge distances of 3 cm, 2 cm and 1 cm under the same conditions as in FIG. 5, and the needle electrodes used in the present invention were set to discharge distances of 3 cm, 2 cm and 1 cm. It shows the relationship between the discharge voltage and the discharge current in the case.

As is clear from the figure, when the corona power is applied to the needle-shaped electrode according to the present invention, a larger current, that is, power, can be obtained at the same voltage than the rod-shaped electrode. Therefore, a high corona discharge input, which is useful for desulfurization and denitration, can be obtained. It is estimated that the reason why the discharge power can be higher than that of the rod-shaped electrode is that the electric field is locally concentrated by the needle-shaped electrode and the current increases as compared with the rod-shaped electrode.

Furthermore, FIG. 7 shows the voltage-current waveform when the needle electrode is of positive polarity, and from now on, in addition to the DC component,
There are many pulsed discharges, and it is clear that the discharge input is increasing.

(Effects of the Invention) In summary, according to the present invention, it is possible to increase the input of corona discharge before the transition to arc discharge, and thus improve the desulfurization / denitration performance.

Further, according to the present invention, the needle electrode shape can be freely selected in consideration of the size and shape of the outer peripheral ground electrode which also serves as the exhaust duct.

Further, there is an advantage that no additional equipment is required for implementing the present invention.

[Brief description of drawings]

FIG. 1 is a perspective view of a needle-shaped electrode used in the present invention, and FIG.
FIG. 3 is a schematic configuration diagram showing an example of a desulfurization / denitration device according to the present invention, FIG. 3 is a schematic configuration diagram showing another example of a desulfurization / denitration device according to the present invention, and FIG. A diagram showing an example of a desulfurization / denitration method using such a device, FIG.
A figure showing the relationship between the NO _x and NO concentrations at the outlet with respect to the discharge input when 00 ppm NO is added and the temperature in the inlet is 150 ° C. and the outlet temperature is 70 ° C. when flowing through the desulfurization / denitration device 12. Sixth
The figure shows the discharge distance of 3 cm [curve: a], 2 cm [curve: b], 1 cm [curve:
c], and the needle electrode used in the present invention has a discharge distance of 3 cm [curve: d], 2 cmm [curve: e], 1 cm.
FIG. 7 is a diagram showing the relationship between discharge voltage and discharge current when [curve: f] is set, and FIG. 7 is a diagram showing voltage-current waveforms when the needle electrode has a positive polarity. In the figure, 1 is a needle electrode, 3 is a structural electrode, 4 is a needle electrode, 7 is a high-voltage power supply, and 8 is a counter ground electrode that also serves as a duct.

Continuation of the front page (56) Reference JP-A-61-15750 (JP, A) JP-A-51-56773 (JP, A) JP-A-51-56774 (JP, A) JP-A-61-71825 (JP , A)

Claims (1)

[Claims] 1. An outer peripheral ground electrode also serving as an introduction duct for exhaust gas to be desulfurized and denitrated, and a plurality of needle electrodes extending from two sides to four directions at predetermined intervals from the side surface of the structural electrode. The needle-shaped electrode is configured such that the tip of the needle electrode is directed toward the inner peripheral surface of the outer peripheral ground electrode, and a predetermined distance is provided between the tip and the inner peripheral surface of the outer peripheral ground electrode. A desulfurization / denitration device using corona discharge, which is installed in the outer circumference ground electrode so as to be maintained.