JP2864641B2 - NO ▲ lower x gas processing equipment - Google Patents

Description

BACKGROUND OF THE INVENTION Field of the A. industrial invention relates to apparatus of the NO _X gas, more particularly processor of the NO _X gas in the exhaust gas of a diesel engine and a gas turbine engine.

Overview B. INVENTION The present invention is in the processing apparatus of the NO _X gas, plasma and azide in the same reaction cylinder by providing a plasma generator into the reaction cylinder to inject aqueous solution of azide compound in oxygen conditions compound to enable further downsizing of the apparatus while reducing the no NO _X gas using harmful and dangerous ammonia by directly acting together synergistically.

C. Description of the Related Art conventionally, NO _X gas treatment is practically used as denitrification technology. The flue gas denitrification method is roughly classified into a dry method and a wet method, and the most advanced is the selective catalytic reduction method of the dry method. This method has the following three advantages.

(1) The system is simple.

(2) High denitration rate is possible.

(3) NO _X is decomposed into harmless N ₂ and H ₂ O, and no exhaust treatment is required.

In this selective catalytic reduction method, ammonia, hydrocarbon, and carbon monoxide are used as reducing agents. Reacts in this ammonia selectively to NO _X even coexist oxygen other reducing agent reacts with oxygen. For this reason, particularly in the case of diesel and gas turbine prime movers, ammonia gas that selectively reacts with NO _X is used even when oxygen coexists. Examples of the catalyst used in this reaction include a noble metal such as Pt and various metal oxides supported on Al ₂ O ₃ and TiO ₂ . The components of NO _X generated by the combustion of diesel and gas turbine prime movers are mostly NO and NO ₂
Is about 5%. Therefore, NO is mixed with ammonia gas, and this mixed gas is catalytically reduced on a catalyst to form N ₂ and H _2.
Decomposed into O. Next, this reaction formula is shown.

However, the selective catalytic reduction method shown in the above reaction scheme has the following problems.

(1) must be used toxic and hazardous ammonia gas to decompose NO _X.

(2) The performance of the reduction catalyst by ammonia gas is deteriorated.
In particular, since the reduction catalyst is deteriorated by the exhaust gas component, it requires replacement or the like, and its operation is troublesome.

(3) The operating temperature range is limited.

That is, at a high temperature (about 1000 ° C.), the sintering of the catalyst component proceeds, and the catalytic performance deteriorates due to the phase transition of the crystal. Also, 32
At 0 ° C. or lower, ammonia gas and moisture react with the exhaust gas containing SO _X to produce compounds such as acidic ammonium sulfate, which lowers the denitration performance. From these facts, the range of operating temperature in the conventional reduction method was 320 to 450 ° C. Therefore, the working temperature range is limited, and it is difficult to use at room temperature.

(4) It is difficult to reduce the size of the entire processing apparatus.

This means that since the reduction reaction of NO _X is equimolar from the above reaction formula, it is necessary to inject ammonia gas approximately equal to the amount of NO _X into the exhaust gas in accordance with the denitration rate. This is because it is difficult to reduce the size of the entire apparatus due to large size.

Therefore, the inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have been selected from using sodium azide (hereinafter, referred to as NaN ₃ ) instead of harmful and dangerous ammonia gas, and oxygen and plasma treatment. It found that can reduce significantly NO _X by using at least one, thereby completing the processing method and apparatus of the NO _X gas (Japanese Patent Application No. 1-30236 and No. 2-29255).

That is, the present inventors NO _X treatment apparatus was charged with NaN ₃ in the above application (hereinafter, referred to as a scrubber system) plasma reaction tube equipped with a plasma generator (hereinafter, referred to as plasma discharge system) and were each separated or independent NO _X with structure
A gas treatment unit was proposed.

D. Problems to be Solved by the Invention However, in the processing apparatus according to the above-mentioned application, since the scrubber method is separated from the plasma discharge method, the plasma effect and the NaN ₃ effect cannot be sufficiently exhibited, so that the apparatus itself can be reduced in size. Even had limitations.

Accordingly, the present invention was being developed to solve the problems related to the application, the plasma effect and NaN ₃ effect is integrated by the scrubber system of the NO _X processor are integrated with the plasma discharge system It produces an even more synergistic effect, which results in marked NO
_An object of the present invention is to improve the _X processing rate and further downsize the NO _X processing apparatus.

E. SUMMARY and effects the present inventors for solving the a result of intensive studies to solve the above problems, by incorporating a plasma discharge system to the scrubber system of the NO _X processor, the more NO _X treatment ratio found can be improved, thereby completing the processing apparatus of the NO _X gas according to the present invention.

That is, the processing apparatus of the NO _X gas according to the present invention, NO _X with a reaction tube to inject aqueous solution of NaN ₃ under acidic conditions, is connected to the reaction tube and the wings formed in helical An introduction pipe for introducing a mixed gas of a gas and one selected from air and oxygen, a plasma generation pipe suspended for performing plasma discharge in the introduction pipe, and reacting the mixed gas with the azide compound Let me say that
An exhaust port provided in the reaction tube in order to reduce and remove NO _X gas, to include are the possible solutions.

 Hereinafter, the present invention will be described in more detail.

The method of treating NO _X gas used in the apparatus according to the present invention is not particularly limited to theory, but dissolves NaN ₃ in water,
The principle is to chemically convert NO _X into N ₂ + H ₂ O by the reaction between this aqueous solution and NO _X gas.

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

_{NO + NO 2 + → 2HNO 2} ... (1) 6NaN 3 + 6Hcl → 6N 3 H + 6Nacl ... (2) 2HNO 2 + 6N 3 H → 10N 2 + 4H 2 O ... (3) Normally, to absorb the gas in the liquid is very efficient bad. The above equation (1) is a reaction in which NO and NO ₂ are absorbed into water to form HNO ₂ , and this reaction is a so-called rate-determining step that controls the overall reaction rate. Therefore, if the reaction at this stage can be carried out efficiently, the reaction of the above formula (3) proceeds easily. This can be said to be a central problem to be solved by the present invention.

That is, in this NO _X gas treatment method, the reaction of the above formula (1) can be efficiently advanced by using oxygen. Also, air can be used as long as it contains oxygen,
While any of the can processing purposes is sufficiently achieved of the NO _X gas be used, in order to proceed more efficiently equation (1) oxygen concentration is preferably higher.

Next, the reaction of the above formula (2) is separately performed in advance, whereby NaN ₃ is converted to N ₃ H. At this time, it is necessary to be under acidic conditions in order to make the reaction proceed completely. This condition is pH
Is desirably 3 or less, and it is sufficient to add a few drops of hydrochloric acid or the like.

Further, the reaction of the above formula (3) was obtained by the above formula (1).
HNO ₂ is reduced with N ₃ H obtained in the above (2) to reduce N ₂ and H ₂ O
Decompose into The N ₂ thus treated is discharged as a treated gas.

Next, a description will be given of a process apparatus of the NO _X gas according to the present invention that may be suitably implemented method of processing the NO _X gas.

All the reactions (1) to (3) proceed in a reaction tube provided in the apparatus. An introduction tube is connected to the reaction tube, and an aqueous solution of NaN ₃ to which a few drops of hydrochloric acid or the like are added is introduced into the reaction tube through the introduction tube, and the reaction formula (2) is advanced. Next, a mixed gas of NO _X and one selected from air and oxygen is introduced through the introduction pipe, and is injected into the reaction tube through a blowout port provided in the introduction pipe.
And (3). At this time, a spirally formed splash is provided in the inlet tube, the mixed gas is raised along the splash, the contact time with the NaN ₃ aqueous solution is lengthened, and the reaction equations (1) and (3) are sufficiently performed. Proceed to

Further, in the apparatus according to the present invention, the above-mentioned (1) is more efficiently achieved by using plasma by high frequency or the like in addition to oxygen.
Advance the expression. That is, by the apparatus comprising a plasma generator into the reaction cylinder, activating the gas mixture with one of NO _X and oxygen and air is selected by the plasma generated by a so-called electric energy such as high frequency, thereby the The reaction of (1) can proceed more effectively. This means that although the reaction of the above (1) proceeds with only oxygen, a synergistic effect is produced by the combination of plasma and oxygen, and NO _X can be almost completely converted to NHO ₂ .

In carrying out this plasma discharge method, a plasma generator, preferably a tension electrode having a thin metal projection provided around the electrode, is suspended in the introduction tube to sufficiently activate the mixed gas.

Treated in this way was NO _X gas is discharged as N ₂ from the exhaust port provided in the reaction tube as a N ₂ gas.

F. Embodiment Hereinafter, the present invention will be described based on an embodiment shown in the drawings.

Wherein FIG. 1 is a schematic configuration diagram of a processing device of the NO _X gas scrubber system and plasma discharge type are integrated showing an embodiment of the present invention.

(A) In this configuration diagram, 1 is a scrubber type reaction tube, 2 is an introduction pipe for introducing a mixed gas of NO _X and oxygen,
3 and 4 are flange portions, 5 is a tube, 6 is a stopper for holding down the tube 5, 7 is a mixed gas blowing unit, 8 is a mixed gas blowing hole, 9 is a spiral stepped splash, 10
Is ground, 11 is plasma generation power supply, 12 is N ₂ exhaust port, 13
Represents a NO ₂ gas concentration measuring instrument, and A represents a high-frequency electrode.

(B) will be described first NO _X gas treatment apparatus of the scrubber type. In the reaction tube 1 is NO _X gas treatment, considering that and the plasma discharge or the like to introduce the aqueous solution of NaN ₃ under acidic conditions are made of metal such as stainless steel, the cylindrical form is preferred from the reaction efficiency, etc. .

An upper part of the reaction tube 1 is connected to an introduction pipe 2 for introducing a mixed gas of NO _X and oxygen, and is connected by a flange part 3, and a lower part thereof is connected by a flange part 4.
Further, a tube 5 is provided in the reaction tube 1 and between the introduction tubes 2. The tube 5 is preferably made of glass and cylindrical in consideration of rotating a splash 9 described later in this tube. It is fixed by an L-shaped linear stopper 6 attached to the flange portion 3. A removable gaseous gas blowing unit 7 is attached to the lower part of the introduction pipe 2. The unit 7 can adjust the exhaust-gas mixture by changing the unit 7 according to the NO _X gas concentration for desorption can freely. That is, the unit 7 has a structure in which a mixed gas blowing hole 8 is formed at the bottom thereof, and the blowing amount of the mixed gas can be adjusted by changing the diameter of the hole. In addition, a sprinkle 9 formed in a spiral step shape from a little above the tip of the introduction tube is provided, and has a structure to fit into the inside of the tube 5 exactly. With such a structure, the gas mixture is blown through the blowout unit 7, it is raised along the mixed gas by rotating the blades to wings, catalytic reaction in the NaN ₃ solution and the tube 5 in the reaction cylinder 1 Can be performed sufficiently.

Next, a plasma generator of the plasma discharge system will be described.

The plasma generator is suspended as an electrode A at an intermediate position of the introduction pipe 2. Plasma generated by performing silent discharge by the electrodes A, coupled with oxygen, activates NO _X gas is discharged through the ground 10 through the inlet pipe 2 made of metal such as stainless steel. Thus NO _X gas is converted almost completely into HNO _2, azide compound in the scrubber system, for example, N ₂ almost completely due NaN ₃
It is decomposed into H _2. The electrode A is connected to a plasma generation power supply 11 installed outside the reaction tube 1 through the introduction pipe 2. The electrode A is preferably a high-frequency electrode or the like, but is not limited thereto. Any electrode may be used as long as it generates so-called electric energy and generates plasma.

The NO _X gas thus decomposed is converted into N ₂ gas and discharged from the exhaust port 13 to the outside of the reaction tube 1.

(C) then N in the processing apparatus of the NO _X gas according to the present invention
It explained O _X process gas.

First, dissolve NaN ₃ in water, add hydrochloric acid to this aqueous solution,
After adjusting the pH to 3 or less, this aqueous solution is injected into the reaction tube 1 in a scrubber system.

Next, a mixed gas of NO _X gas and oxygen is introduced into the solution through the introduction pipe 2.

At this time, by silent discharge plasma between the electrodes A and inlet tube 2, activates NO _X gas.

Activated NO _X gas is blown out from hole 8 through glass tube 5
Blow out inside.

Furthermore, the sprung 9 formed in a spiral stage is rotated,
While the mixed gas diffuses sufficiently NaN ₃ solution lifted along the wings, decomposing the NO _X gas.

Next, the decomposed N ₂ gas is discharged from the exhaust port 12.

G. Effect (1) The present invention is integrally formed to incorporate the plasma discharge system to the processing unit of the NO _X gas scrubber system. Thus processing apparatus of the NO _X gas according to the present invention further results in synergistic effects effects of plasma effect and the oxygen and NaN ₃ come together, thereby can improve significantly NO _X treatment rate, and more of the NO _X processor Can be downsized.

Further, the processing apparatus of the NO _X gas according to the present invention is the plasma generating apparatus is suspended as a needle-shaped electrode. Thus for the first gas mixture is introduced through the inlet pipe according to the apparatus according to the present invention may be directly activated by plasma discharge, NO _X gas after activation is almost completely decomposed with azide compound solution You.

In addition, since the apparatus according to the present invention is configured as described above, the untreated NO _X gas is not directly blown into the azide compound solution, so that the continuous treatment time of the azide compound solution becomes longer.

(2) Since the present invention is configured as described above, the following effects can be obtained.

According to the apparatus of the present invention can reduce the NO _X gas without the use of toxic and dangerous ammonia for using azide compound.

According to the apparatus according to the present invention, since oxygen and plasma act as reaction promoters, they further act synergistically to significantly reduce NO _X as compared with the nitrogen oxide emission reference value.

ADVANTAGE OF THE INVENTION According to the apparatus which concerns on this invention, since a reduction catalyst is not required, the whole apparatus can be miniaturized and its operation can also be simplified.

According to the apparatus according to the present invention enables the reduction reaction of the NO _X gas at room temperature, apparatus and the like for heating is unnecessary NO
_X gas can be easily processed.

[Brief description of the drawings]

Schematic structural view showing an example of a first figure processing apparatus of the NO _X gas according to the present invention, FIG. 2 is a sectional view of a gas mixture balloon unit. 1 ... Scrubber-type reaction tube, 2 ... Introducing tube for introducing mixed gas, 5 ... Tube, 8 ... Blow-out hole of mixed gas, 9 ... Spiral formed in spiral staircase, 12 ... N _2. Exhaust port, A: High frequency electrode.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshito Shoko 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Inside Meidensha Co., Ltd. (56) References JP-A-3-270713 (JP, A) JP-A-3-3- 270715 (JP, A) JP-A-3-270716 (JP, A) JP-A-3-270717 (JP, A) JP-A-3-232518 (JP, A) JP-A-2-211218 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B01D 53/34, 53/56

Claims (1)

(57) [Claims] A reaction tube to inject aqueous solution of azide compound, selected from the NO _X gas and air and oxygen having a wings formed is connected to the reaction tube and helically are at 1. A acidic conditions An introduction pipe for introducing a gaseous mixture of one kind, a plasma generator suspended for performing plasma discharge in the introduction pipe, and reacting the gaseous mixture with the azide compound to form the NO.
Processor of the NO _X gas, characterized in that it comprises a and an exhaust port provided in the reaction tube in order to reduce and remove _X gas.