JPH03270713A - Apparatus for treatment of nox gas - Google Patents

Abstract

PURPOSE:To enhance NOX treatment efficiency by integrally incorporating a plasma discharge system in a scrubber type NOX gas treatment apparatus. CONSTITUTION:In an NOX gas treatment apparatus, a reaction cylinder 1 in which an aqueous solution of an azide compound is charged under an acidic condition and the plasma generating pipe 5 fixed within the reaction cylinder 1 and equipped with a plasma generator A are provided. A flange part 3 having an introducing pipe 2 equipped with a spirally formed blade 9 and introducing a gaseous mixture consisting of NOX and one of air and oxygen connected thereto is connected to the upper part of the reaction cylinder 1 and a flange part 4 is connected to the lower part of the reaction cylinder 1. An exhaust port 13 is provided to the reaction cylinder 1 in order to reduce and remove NOX gas by reacting the aforementioned gaseous mixture with the azide compound. The NOX gas subjected to decomposition treatment is discharged to the outside of the reaction cylinder 1 as N2 gas from the exhaust port 13.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an apparatus for treating NOx gas, and more particularly to an apparatus for treating NOx gas in the exhaust gas of day-cell engines and gas turbine engines.

B1 Overview of the Invention The present invention provides a NOx gas processing apparatus in which a plasma generation tube equipped with a plasma generator is installed in the reaction tube into which an aqueous solution containing an azide compound dissolved under oxygen conditions is introduced. By directly combining the plasma and the azide compound and working synergistically, it is possible to reduce No. without using harmful and dangerous ammonia and to further downsize the processing equipment.

C1 Prior Art Conventionally, NOx gas treatment has been put to practical use as a flue gas denitrification technology. Flue gas denitrification methods are broadly divided into dry methods and wet methods, and the most advanced dry method is the selective catalytic reduction method. This method has the following three advantages.

(1) The system is simple.

(2) High denitrification rate is possible.

(3) No. is decomposed into harmless N2 and HtO, eliminating the need for discharge treatment.

In this selective catalytic reduction method, ammonia, hydrocarbons, and carbon oxides are used as reducing agents. Among these, ammonia selectively reacts with NOx even in the presence of oxygen, while other reducing agents react with oxygen. For this reason, particularly in the case of diesel and gas turbine engines, ammonia gas, which selectively reacts with NOx, can be used even if oxygen is present.

In addition, examples of catalysts used in this reaction include noble metals such as Pt, and various metal oxides supported on Al tos, T102, and the like. NO produced by combustion in diesel and gas turbine prime movers.

Most of the components are No, and NO is about 5%. For this purpose, NO is mixed with ammonia gas, and this mixed gas is catalytically reduced on a catalyst to be decomposed into N2, H, and O. This reaction formula is shown next.

Reaction formula: 4 N O+ 4 N H3+ Ot→4
Nt+ 6 HtO (related) However, the selective catalytic reduction method shown in the above reaction formula had the following problems.

(1) Harmful and dangerous ammonia gas must be used to decompose No.

(2) The performance of the reduction catalyst caused by ammonia gas deteriorates.

In particular, the reduction catalyst deteriorates due to the exhaust gas components, and therefore requires replacement, which is cumbersome to operate.

(3) The operating temperature range is limited.

That is, at high temperatures (approximately 1000° C.), sintering of catalyst components progresses, and catalyst performance deteriorates due to crystal phase transition. Also,
At temperatures below 320° C., ammonia gas and moisture react with exhaust gas containing SOx to produce compounds such as acidic ammonium sulfate, resulting in a decrease in denitrification performance.

For these reasons, the operating temperature range for the conventional reduction method is 3.
The temperature was 20-450°C. Therefore, the operating temperature range was limited and it was difficult to use at room temperature.

(4) It is difficult to downsize the entire processing device.

This means that from the above reaction formula, the reduction reaction of NOx is equimolar, so ammonia gas that is approximately equal to the amount of NOx must be injected into the exhaust gas in accordance with the denitrification rate. This is because the size of the device makes it difficult to downsize the entire device.

Therefore, as a result of intensive research to solve the above problems, the present inventors found that sodium azide (hereinafter referred to as NaN3) was used instead of the harmful and dangerous ammonia gas, and that a solution selected from oxygen and plasma treatment was used. The inventors have discovered that NOx gas can be significantly reduced by using at least one type of NOx gas, and have completed a method and apparatus for treating NOx gas (Japanese Patent Application Nos. 1-30236 and 2-29255).

That is, in the above application, the present inventors introduced NOx with NaN.
We have proposed a NOx gas processing device in which a processing device (hereinafter referred to as a scrubber type) and a plasma reaction tube equipped with a plasma generator (hereinafter referred to as a plasma discharge type) are separated or independent.

D0 Problems to be Solved by the Invention However, in the processing equipment according to the above application, the scrubber system is separated from the plasma discharge system, so the equipment itself is small enough to fully demonstrate the plasma effect and NaNs effect. There were also limits to this.

Therefore, the present invention was devised to solve the problems related to the above-mentioned application, and by integrating one type of scrubber of the NO8 treatment device with a plasma discharge method, the plasma effect and the NaN3 effect can be reduced. The purpose is to produce a more synergistic effect by integrating the two, thereby significantly improving the NOx treatment rate and further downsizing the NOx treatment device.

23 Means and Action for Solving the Problems As a result of intensive studies to solve the above problems, the inventors of the present invention have found that by incorporating a plasma discharge method into one type of scrubber of the Noe treatment equipment, the -layer NOx treatment rate can be increased. We have found that improvements can be made and have completed the NOx gas treatment device according to the present invention.

That is, the NOx gas processing apparatus according to the present invention includes: a reaction tube into which an aqueous solution containing NaN3 dissolved under acidic conditions is introduced; a plasma generation tube fixed in the reaction tube and equipped with a plasma generation device; an introduction tube connected to the reaction tube and equipped with a helical spring into the plasma generation tube for introducing a gas mixture of NOx and one selected from air and oxygen; and the gas mixture and the azide compound. by reacting the N
The solution is to include an exhaust port provided in the reaction column to reduce and remove Ox gas.

The present invention will be explained in more detail below.

The method for treating NOx gas used in the device according to the present invention is not intended to be particularly theoretical; however, NaN3 is dissolved in water, and the NOx is converted into N2+ by the reaction between this aqueous solution and NOx gas.
The principle is to chemically change it to H20.

That is, this reaction can be explained by the following three equations.

NO+NO! +→2HNO1・(1) 6 N a N3+ 6 Hcl→6 N3H+ 6
Nacl-(2)2 HNOt+ 6 N5H-10N
2+ 4 H2O... (3) Normally, it is very inefficient to absorb gas into a liquid. Above (formula is No, NO2
is absorbed into water to form HNO, and this reaction is the so-called rate-determining step that controls the overall reaction rate. Therefore, if it is ensured that the reaction at this stage is carried out efficiently, the reaction of the above formula (3) will proceed easily. This can be said to be the central problem that non-inventions seek to solve.

That is, in this method of treating NOx gas, the reaction of the above formula (1) can be made to proceed efficiently by using oxygen. In addition, air can be used as long as it contains oxygen, and the purpose of treating NO and gas can be sufficiently achieved using either of them, but in order to proceed with the above equation (1) more efficiently, the oxygen concentration must Higher is preferable.

Next, the reaction of formula (2) above is performed separately in advance, thereby converting NaN to NsH. At this time, acidic conditions are required to allow the reaction to proceed completely. This condition is preferably such that the pH is 3 or less, and it is sufficient to add a few drops of hydrochloric acid or the like.

Furthermore, the reaction of the above formula (3) is performed using the H obtained in the above formula (1).
NO, is reduced with N3H obtained in (2) above to produce N
It decomposes into 2, H, and O. The N treated in this way is discharged as a treatment gas.

Next, a Nox gas processing apparatus according to the present invention that can suitably implement this NOx gas processing method will be described.

All of the reactions (1) to (3) above proceed in a reaction column provided within this apparatus. An introduction tube is connected to this reaction column, and through this introduction tube, an aqueous solution of NaNs to which several drops of hydrochloric acid have been added is first introduced into the reaction column, and the reaction equation (2) above is allowed to proceed. Next, through this introduction pipe, NOx
A mixture of gas and one selected from air and oxygen is introduced and injected into the reaction cylinder from the outlet provided in the introduction pipe.
The reaction formulas (1) and (3) above are allowed to proceed. On this occasion,
A spirally formed spring is provided in the inlet pipe, and the mixed gas is raised along the spring to increase the contact time with the NaN3 aqueous solution, so that the reaction equations (1) and (3) above are sufficiently satisfied. Let it proceed.

Further, in the apparatus according to the present invention, in addition to oxygen, plasma generated by high frequency waves or the like is used to more efficiently proceed with the above equation (1). That is, this device activates a gas mixture of NOl, oxygen, and a selected type of air by plasma generated by so-called electrical energy such as high frequency by installing a plasma generation tube equipped with a plasma generation device in the reaction tube. This allows the reaction (1) above to proceed even more effectively. This means that the reaction in (1) above can proceed with oxygen alone, or that a synergistic effect occurs when plasma and oxygen combine, and NOx is almost completely converted into HNO.
This means that it can be converted into 2.

When performing this plasma discharge method, a spirally formed spring provided in the introduction tube is rotated, and Na containing the mixed gas is
Plasma discharge is performed directly into the NaN3 aqueous solution by raising the N3 aqueous limb above the set position of the plasma generator, and the mixed gas is sufficiently activated.

The NOx gas treated in this manner is discharged as N gas from an exhaust port provided in the reaction column.

F Example Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

FIG. 1 is a schematic diagram of a No. 1 gas treatment apparatus in which a scrubber type and a plasma discharge type are integrated, showing an embodiment of the present invention.

(A) In this configuration diagram, 1 is a reaction tube with one type of scrubber, 2 is an introduction tube for introducing a mixed gas of NO8 and oxygen, 3 and 4 are flange parts, 5 is a plasma generation tube, and 6 is for holding down the tube 5. Stopper 7 is a mixed gas blowing unit, 8 is a mixed gas blowing hole, 9 is a spring formed in a spiral step shape, 10 is ground, II is a wire terminal inlet,
12 is a plasma generation power source, 13 is an N exhaust port, and 14 is a NO exhaust port.

In the gas concentration measuring device, A indicates a high frequency electrode.

(B) ■First, a one-type scrubber type NOx gas treatment device will be explained. The reaction tube l is made of metal such as stainless steel in consideration of the injection of an aqueous solution containing NaN3 dissolved under acidic conditions and plasma discharge during NOx gas treatment, and a cylindrical shape is preferable from the viewpoint of reaction efficiency. .

Further, an introduction pipe 2 for introducing a mixed gas of NO8 and oxygen is connected to the upper part of the reaction cylinder 1 through a flange part 3, and a flange part 4 is connected to the lower part thereof.

Furthermore, a plasma generation tube 5 is provided within the reaction tube I and between the introduction tube 2, and this tube 5 is made of glass and has a cylindrical shape in consideration of rotating a spring 9 described later within the tube. is preferably fixed by an L-shaped linear stopper 6 attached to the flange portion 3. Further, a removable mixed gas blowing unit 7 is attached to the lower part of the introduction pipe 2. Since this unit 7 can be freely attached and detached, the amount of mixed gas blown out can be adjusted by changing the unit 7 according to the NO gas concentration. That is, this unit 7 has a structure in which a mixed gas blowing hole 8 is opened at the bottom thereof, and by changing the diameter of this hole, the blowing amount of the mixed gas can be adjusted. Further, a spring 9 formed in the shape of a spiral step is provided from slightly above the tip of the introduction tube, and has a structure that fits snugly into the inside of the tube 5. With this structure, the mixed gas is blown out through the blowing unit 7, and by rotating the spring, the mixed gas is raised along the spring, and the Na inside the reaction tube 1 is
It is possible to sufficiently eliminate the contact reaction between the N3 water solution and the tube 5.

A zero-order plasma discharge type plasma generation device will be described.

The plasma generator is provided as an electrode A in a cylindrical shape at an intermediate position of the plasma generating tube 5. The plasma generated by silent discharge from this electrode A is combined with oxygen and an azide compound such as NaN3 to decompose NOx gas into N and H2, and the inlet tube made of metal such as stainless steel 2 to the ground IO. As a result, NOx gas is almost completely decomposed into N and H3. This electrode A is connected to a plasma generation power source 2 installed outside the reaction tube 1 through a wire terminal inlet 11 provided in the flange portion 3 .

It should be noted that this electrode A is preferably a high frequency electrode or the like, but is not limited to this, but any electrode that generates electrical energy and generates plasma can be used. good.

The NOx residue thus decomposed is turned into N2 residue and is discharged from the exhaust port 13 to the outside of the reaction tube l.

(C) Next, the NOx gas treatment process in the NO and gas treatment apparatus according to the present invention will be explained.

(1) First, N a N 3 is dissolved in water, and after adding hydrochloric acid to this aqueous solution to adjust the pH to 3 or less, this aqueous solution is injected into the reaction column 1 in a single-type scrubber.

(2) Next, a mixed gas of NOx gas and oxygen is introduced into this solution through the introduction pipe 2 and is blown out into the pipe 5 from the blow-off hole 8.

■Furthermore, rotate the spring 9 formed in the shape of a spiral staircase,
Lift the gas mixture along the spring and add enough N a N 3
While diffusing into the solution, the solution is raised above the electrode A position of the tube 5.

(2) At this time, plasma is silently discharged between the electrode A and the introduction tube 2 to decompose NO and gas.

(2) Next, the decomposed N and gas are discharged from the exhaust port 13.

G1 Effects of the Invention (1) The present invention is integrally constructed so that a plasma discharge method is incorporated into a NOx gas treatment apparatus having one type of scrubber. Therefore, in the NO and gas treatment apparatus according to the present invention, the plasma effect and the effects of oxygen and NaN3 are integrated to produce a synergistic effect, which can significantly improve the NO and gas treatment rate, and further improve the NO3 treatment rate. Enables further miniaturization.

(2) Since the present invention is configured as described above, it produces the following effects.

According to the device according to Tadamizu's invention, NO, NO, etc. can be produced without using harmful and dangerous ammonia because it uses an azide compound.
Gas can be reduced.

(2) According to the device according to the present invention, oxygen and plasma act as reaction accelerators, and these act synergistically in combination, making it possible to significantly reduce NO, compared to the nitrogen oxide emission standard value.

(2) Since the apparatus according to the present invention does not require a reduction catalyst, the entire apparatus can be downsized and its operation can be simplified and convenient.

(2) According to the apparatus according to the present invention, the reduction reaction of NOx gas is possible at room temperature, and a heating device or the like is not required, making it possible to easily process NOx gas.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a NO8 gas processing apparatus according to the present invention, and FIG. 2 is a sectional view of a mixed gas blowing unit. 1. Reaction tube with one type of scrubber, 2. Inlet pipe for introducing stall gas, 5.. Plasma generation tube, 8. Blowout hole for mixed gas, 9.. Spring formed in the shape of spiral steps, 1.
:31;, exhaust port, A. High frequency electrode.

Claims (1)

[Claims] (1) A reaction tube into which an aqueous solution in which an azide compound is dissolved under acidic conditions is introduced, a plasma generation tube fixed within the reaction tube and equipped with a plasma generation device, and a plasma generation tube connected to the reaction tube within the plasma generation tube. and an inlet pipe for introducing a gas mixture of NO_x and one selected from air and oxygen, which is equipped with a spring formed in a helical shape;
An NO_x gas processing apparatus, comprising: an exhaust port provided in the reaction tube for reducing and removing O_x gas.