JP3513163B2 - Method and apparatus for removing nitrogen oxides - Google Patents

Description

Detailed Description of the Invention

[0001]

This invention uses a solid reducing agent,
The present invention relates to a method and a device for reducing nitrogen oxide (NOx: NOx) in exhaust gas by bringing it into contact with a catalyst and reducing it with high efficiency.

[0002]

2. Description of the Related Art As a method for removing nitrogen oxides from exhaust gas discharged from a gas turbine, a gas engine, a diesel engine, a heating furnace, various boilers, etc., a selective reduction denitration method using ammonia as a reducing agent is used. Since it can selectively remove nitrogen oxides with high efficiency without being affected by oxygen concentration, it has been applied to denitration processes of various fixed sources so far. Ammonia is supplied in the form of liquid ammonia (liquid ammonium), ammonia water (ammonium), or the like.

In recent years, cogeneration systems driven by gas turbines, gas engines and diesel engines have tended to increase rapidly in coastal areas and urban areas from the viewpoints of global environmental protection and economic efficiency, and accompanying this, denitration process also occurs. It needs to be installed in a building or a residential area. In this case, liquid ammonia and ammonia water used as a reducing agent are poisonous and deleterious substances control methods,
Its use is restricted by regulations such as the High Pressure Gas Control Law and the Fire Service Law, and special attention must be paid to its handling, transportation, storage, etc. to prevent the leakage of offensive odors.

In order to solve the above problems, it is necessary to use a reducing agent which is easy to handle and highly stable, instead of ammonia. As a reducing agent having high stability and easy handling in U.S. Pat.
A NOx removal method using a solid reducing agent such as melamine or cyanuric acid in a solid or liquid state is disclosed. When the solid reducing agent is made into an aqueous solution, it is easy to handle for transportation, storage, etc. However, since the weight of water causes an extra load, it is handled as a high-concentration aqueous solution which is close to the saturated concentration and has a great cost advantage.

The solid reducing agent aqueous solution is sprayed into the exhaust gas flowing in the duct from a nozzle provided in the duct and mixed with the exhaust gas.

[0006]

The high-concentration solid reducing agent aqueous solution is supplied to the nozzle at a small flow rate because the solid reducing agent content is high, but moisture is evaporated by heat transfer from the high temperature exhaust gas to the inside of the nozzle. Then, the solid reducing agent is extremely easily crystallized or polymerized. As a result, the nozzle is clogged and the reducing agent aqueous solution cannot be supplied, and the function of the denitration equipment stops.

If the flow rate of the aqueous solution of solid reducing agent is low, sufficient spraying performance of the nozzle cannot be obtained, and the solid reducing agent will not be uniformly dispersed in the exhaust gas duct. As a result, NOx
The reduction reaction at the removal catalyst ends inadequately, the amount of unreacted ammonia increases, and the exhaust gas is discharged in a state containing ammonia. The present invention has been made in view of such circumstances, and it is possible to prevent clogging by a solid reducing agent or its reaction product in the inside and the tip of a nozzle, and to spray a solid reducing agent aqueous solution into exhaust gas stably and continuously. And at the same time uniformly mix the aqueous solution into the exhaust gas,
An object of the present invention is to provide a method and an apparatus for removing nitrogen oxides in exhaust gas with high efficiency and reducing the amount of unreacted ammonia.

[0008]

In order to solve the above-mentioned problems, the present invention sprays an aqueous solution of a solid reducing agent into a flowing exhaust gas and mixes the solid reducing agent into the exhaust gas to form a catalyst. In the method of selectively reducing and removing nitrogen oxides in exhaust gas in the presence, it is necessary to dilute the solid reducing agent aqueous solution stored at a high concentration with water during spraying before spraying. A characteristic nitrogen oxide removing method is provided.

In order to solve the above problems, the present invention provides
A nozzle for spraying the solid reducing agent aqueous solution onto the exhaust gas flowing in the duct from the upstream to the downstream of the exhaust gas flow in the duct for flowing the exhaust gas, and a catalyst for the reduction reaction of nitrogen oxides in the exhaust gas are provided. In the nitrogen oxide removing apparatus, which is provided sequentially, a reducing agent aqueous solution supply line is provided from the storage means for storing the solid reducing agent aqueous solution at a high concentration to the nozzle, A dilution line for supplying water for diluting the high-concentration aqueous solution is connected to the supply line, so that the high-concentration aqueous solution is diluted with water while being supplied to the nozzle. A characteristic nitrogen oxide removing device is provided.

In the present invention, as usual, exhaust gas discharged from a gas turbine, a gas engine, a diesel engine, a heating furnace, various boilers, etc. is made to flow in a duct.
The solid reducing agent aqueous solution is sprayed onto the exhaust gas flowing in the duct, and the nitrogen oxides in the exhaust gas are reduced and removed in the presence of a catalyst, and then the exhaust gas is discharged to the outside.

The solid reducing agent is a reducing agent which is solid at room temperature, and urea, melamine, ammonium carbonate, ammonium hydrogencarbonate, cyanuric acid and the like are used. In particular, when urea is used as a reducing agent and handled in an aqueous solution, it is easy to handle such as transportation and storage, and at the same time, it is inexpensive as compared with melamine, ammonium carbonate, ammonium hydrogencarbonate, cyanuric acid, etc. .

The concentration of the aqueous solution of solid reducing agent depends on the solid reducing agent used during storage, but it is usually at a saturation concentration of about 0 ° C. and is usually 30% by weight or more (for example, 30-40% by weight of the aqueous urea solution is used). %), Which is a high concentration, and conventionally, this high concentration aqueous solution was sprayed. Diluted. When the dilution ratio is less than the above range, the solid reducing agent concentration becomes high, so that it is supplied to the nozzle at a low flow rate, and as a result, the nozzle spraying performance decreases and the solid reducing agent becomes difficult to disperse in the exhaust gas. There is a possibility that the denitration efficiency may decrease, or that the solid reducing agent may crystallize in the nozzle inner tube due to heat transfer from the high-temperature exhaust gas, resulting in clogging of the nozzle.

In the present invention, water for diluting the high-concentration aqueous solution is supplied to the reducing-agent aqueous solution supply line provided from the storage means adapted to store the high-concentration aqueous solution of the solid reducing agent to the nozzle. The supply dilution line is connected. The high-concentration aqueous solution supplied from the reducing agent aqueous solution supply line joins with the water supplied from the dilution line to be diluted, and this diluted aqueous solution is sprayed from the nozzle. Industrial water, boiler water, pure water, tap water, etc. are used as the dilution water, but are not particularly limited.

The amounts of the high-concentration solid reducing agent aqueous solution and the dilution water to be supplied are taken into consideration to prevent the solid reducing agent from precipitating in the nozzle inner tube due to heat transfer from the exhaust gas and to uniformly mix the solid reducing agent into the exhaust gas. And set appropriately. In this invention,
Since the solid reducing agent aqueous solution having a larger amount of water than the conventional one, that is, the aqueous solution diluted as described above is supplied to the nozzle, the heat capacity is high and the flow rate is large.

In the present invention, the nozzle (solid reducing agent aqueous solution injection nozzle) may be installed near the center of the duct, but it is preferable to install it on the side peripheral surface of the duct to spray the solid reducing agent aqueous solution. As a result, it is possible to prevent blockage in the pipe up to the nozzle. When the nozzle is installed on the side peripheral surface of the duct, the sprayed solid reducing agent aqueous solution may not be uniformly mixed in the exhaust gas, but by devising the structure of the nozzle, the aqueous solution can be uniformly mixed.
That is, the nozzle has a double pipe structure composed of an inner pipe and an outer pipe, and while supplying the solid reducing agent aqueous solution to the inner pipe, it is possible to supply the spray gas for cooling between the inner pipe and the outer pipe. preferable. As a result, heat transfer from the outside of the nozzle to the inner tube of the nozzle is suppressed, and as a result, phenomena such as crystallization of the solid reducing agent at the tip of the nozzle and clogging of the nozzle due to reaction products are avoided.

Furthermore, by providing a structure in which the tip of the inner tube of the nozzle is made to protrude from the tip of the outer tube by 1 to 5 mm, it becomes possible to atomize the aqueous solution and spray it in the form of mist. This is preferable because homogenization of mixing is further promoted. When the protruding length of the tip of the inner tube of the nozzle is less than 1 mm, the droplets of the aqueous solution hang down along the outer wall of the inner tube, so that the solid reducing agent that has solidified accumulates between the outer tube and the inner tube, and the nozzle is clogged. There is a risk. On the other hand, if the projection length of the tip of the inner tube exceeds 5 mm, the dispersion of the aqueous solution in the exhaust gas may be deteriorated.

The nozzle is arranged so that the tip of the outer tube does not project into the duct from the inner peripheral surface of the duct, that is, in the same plane as the inner peripheral surface of the duct or at a position lower than the inner peripheral surface of the duct. It is good to be installed as described. If the tip of the outer tube projects from the inner peripheral surface of the duct, the cooling effect due to the atomizing gas flowing between the outer tube and the inner tube of the nozzle decreases, so the solid reducing agent precipitates in the inner tube at the tip of the nozzle.
It may solidify and block the nozzle.

The atomizing gas supplied between the inner tube of the nozzle and the inner tube and the outer tube is not particularly limited as long as it is a gas inert to the solid reducing agent such as nitrogen in addition to air and water vapor.
The number of nozzles to be installed may be either one or plural, but plural is preferable. With multiple nozzles,
The sprayed solid reducing agent aqueous solution is likely to be uniformly dispersed in the exhaust gas.

When a plurality of nozzles are provided on the side peripheral surface of the duct, it is preferable that the plurality of nozzles be arranged at substantially equal intervals along the circumference on the side peripheral surface of the duct. Usually, the duct is installed at each angle of 360 ° divided by the number of nozzles. For example, four nozzles are arranged at every 90 °. The nozzle may be oriented upstream, downstream, or at right angles to the exhaust gas flow, but from the viewpoint of uniform mixing of the solid reducing agent aqueous solution sprayed from the nozzle into the exhaust gas, The angle is preferably set in the range of 45 to 135 °.

When the solid reducing agent aqueous solution and the spray gas are simultaneously supplied into the nozzle inner pipe and the spray gas increases the passage speed of the aqueous solution into the nozzle inner pipe, heat transfer to the aqueous solution is effectively prevented, so that the nozzle tip Not only can the clogging of the part be prevented, but the dispersion of the aqueous solution in the exhaust gas can be improved. When the solid reducing agent aqueous solution injection nozzle is installed in the zone where the exhaust gas flow velocity in the exhaust duct is 15 m / s or more, the aqueous solution is more evenly dispersed in the exhaust gas, and thus a high denitration rate can be obtained. Good results are obtained. Since the flow velocity of the exhaust gas is usually changed by changing the cross-sectional area of the duct, it is preferable to install the nozzle on the duct side peripheral surface having a cross-sectional area suitable for such a flow velocity.

The speed of the solid reducing agent aqueous solution passing through the inside of the nozzle inner tube is preferably 0.1 m / s or more. Below this range, heat transfer from high-temperature exhaust gas may cause the solid reducing agent to crystallize or polymerize in the nozzle inner tube, resulting in clogging of the nozzle. The velocity of the atomizing gas passing between the inner pipe of the nozzle and the outer pipe is preferably set to a value 10 times or more the velocity of the aqueous solution passing through the inner pipe of the nozzle. Below this range, the dispersion of the solid reducing agent aqueous solution sprayed from the nozzle into the exhaust gas becomes poor, and at the same time, the cooling effect due to the spray gas flowing between the outer tube and the inner tube of the nozzle decreases, so the solid inside the nozzle inner tube The reducing agent may precipitate and solidify, and the nozzle may be clogged.

When both the solid reducing agent aqueous solution and the spray gas are supplied into the nozzle inner tube, the ratio of the aqueous solution to the spray gas is preferably 20 parts by volume or less of the spray gas to 1 part by volume of the aqueous solution. Even if the amount of the spray gas is increased beyond this range, the improvement of the NOx removal performance due to the improved dispersibility of the solid reducing agent aqueous solution in the exhaust gas cannot be expected. The method and apparatus of the present invention can be applied before or after desulfurization, and is usually installed before desulfurization when treating boiler exhaust gas.

[0023]

[Function] The solid reducing agent solution can be stored as a high-concentration aqueous solution having a high cost merit by diluting with water while the stored solid reducing agent aqueous solution is being sent for spraying, and high temperature exhaust gas Even if water is evaporated by heat transfer from the nozzle to the inside of the nozzle, the solid reducing agent is less likely to be crystallized or metamorphosed. As a result, the reducing agent aqueous solution can be continuously sprayed without blocking the nozzle, and the denitration equipment can be operated continuously for a long period of time. Moreover, since the flow rate of the solid reducing agent aqueous solution increases,
Sufficient spraying performance of the nozzle is obtained, and the solid reducing agent is easily uniformly dispersed in the exhaust gas duct. As a result, the amount of unreacted ammonia in the NOx removal catalyst is reduced.

A nozzle having a double pipe structure consisting of an inner pipe and an outer pipe, the tip of the inner pipe of which protrudes from the tip of the outer pipe by 1 to 5 mm, is installed on the side peripheral surface of the duct. When the solid reducing agent aqueous solution is sprayed on the exhaust gas by supplying the solid reducing agent aqueous solution into the inner pipe of the nozzle and supplying the atomizing gas between the inner tube and the outer tube, the nozzle produces a solid reducing agent precipitate or a reactant. It can be continuously sprayed for a long period of time without clogging, and the solid reducing agent aqueous solution is uniformly mixed in the exhaust gas.

When the nozzle is provided at the center of the duct, the solid reducing agent and its reactant are deposited and clogged in the nozzle and the pipe due to being exposed to the high temperature exhaust gas flow, but on the side peripheral surface of the duct. When the nozzle is installed, the solid reducing agent and its reaction product are not deposited, and maintenance of the nozzle is easy.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing the embodiments, but the present invention is not limited to the illustrated ones. FIG. 1 shows a nitrogen oxide removing apparatus 1 according to the present invention.
It is an example, and schematically shows a case where a solid reducing agent aqueous solution injection nozzle is installed in a region where exhaust gas flows at a flow velocity of 15 m / s or more. In the nitrogen oxide removing apparatus shown in FIG. 1, the exhaust gas from the gas turbine 1 which is the exhaust gas generation source flows in the duct 2. The duct 2 is a circular duct in this embodiment, and has a high flow velocity region 2a having the same diameter as the gas turbine 1 from the upstream side to the downstream side of the exhaust gas flow, an enlarged region 2b in which the diameter gradually increases, and a low flow velocity with a large diameter. It has a region 2c. Exhaust gas is usually 1 in the high velocity region 2a.
Flows at a flow velocity of 5 m / s or more, and is 5 to 1 in the low flow velocity region 2c.
The flow rate is 0 m / s. The nozzle 11 is provided in the high flow velocity region 2a, and the low flow velocity region 2c is provided.
An exhaust heat recovery boiler (waste heat boiler) 3, a denitration catalyst layer 4, and an economizer 40 are sequentially provided in the.

As shown in FIG. 3, a reducing agent aqueous solution supply line 33 is provided from the storage tank 10 in which the high concentration aqueous solution 23 of the solid reducing agent is stored to the nozzle 11. A dilution line 32 for supplying water 31 for diluting the high concentration aqueous solution 23 is connected to the reducing agent aqueous solution supply line 33. Storage tank 10 by pump 9
The high-concentration aqueous solution 23, which is supplied from the reducing agent aqueous solution supply line 33, joins the water 31 supplied from the water storage tank 30 through the dilution line 32 by the pump 39 on the way. The reducing agent aqueous solution thus diluted is sprayed from the nozzle 11 into the duct 2.

As shown in FIG. 1, the confluence of the dilution line 32 with the reducing agent aqueous solution supply line 33 is arranged downstream of the flow control valve (control valve) 8 for the following reason. It is easier to control the flow rate of the solid reducing agent aqueous solution in the state of a concentrated solution before dilution, and if diluted upstream of the flow rate control valve 8, it is necessary to control the concentration after dilution. The cost is that it is cheaper to provide the confluence of the dilution line 32 downstream of the flow control valve 8.

The exhaust gas flowing from the gas turbine 1 is mixed with the solid reducing agent deposited from the solid reducing agent aqueous solution sprayed from the nozzle 11. The solid reducing agent aqueous solution sprayed on the exhaust gas is thermally decomposed to produce ammonia. In this state, the exhaust gas passes through the exhaust heat recovery boiler 3 and the NOx removal catalyst layer 4 to be selectively reduced by nitrogen oxides and is removed. Then, the exhaust gas is guided to the chimney 5 via the economizer 40 and is then discharged to the outside. Is discharged. Exhaust heat recovery boiler 3 and economizer 4
0 is provided as needed.

The denitration catalyst layer 4 uses TiO ₂ as a carrier,
A catalyst that accelerates the reduction reaction of nitrogen oxides, such as a honeycomb catalyst made of V ₂ O ₅ and WO ₃ as an active component, is filled. The nozzle 11 has a duct 2 as shown in FIG.
The nozzle mounting seats 20 are installed at substantially equal intervals along the circumference of the side peripheral surface of the. Ie 4
One nozzle 11 is arranged every 90 °. The nozzle 11 is attached to the nozzle attachment seat 20 attached to the duct 2, as shown in FIG. Nozzle 11
Is attached to, for example, the flange of the mounting seat 20 so that the outer tube tip does not protrude into the duct from the inner peripheral surface of the duct 2.

4 and 5 each show an example of the nozzle 11. The nozzle 11 shown in FIG. 4 has a double pipe structure, and the solid reducing agent aqueous solution is supplied to the inside 13 of the nozzle inner pipe, and the spray gas 21 is supplied to the space 14 between the inner pipe and the outer pipe. The nozzle shown in FIG. 5 has a bifurcated inner pipe inlet portion 15 of a double-pipe structure, the solid reducing agent aqueous solution and the spray gas 21 are simultaneously supplied into the inner pipe 13, and the space between the inner pipe and the outer pipe 14 is sprayed. Gas 2
Only one is supplied. The tip of the inner tube projects from the tip of the outer tube by a length t. The length t is 1 to 5 mm as described above. Reference numeral 16 is a member that supports the inner pipe.

A predetermined amount of the spray gas 21 which is circulated in the nozzle inner pipe 13 and between the nozzle inner pipe and the outer pipe 14 is supplied through the flowmeter 6 and the flowmeter 7, respectively, and at the same time, the solid reducing agent aqueous solution 23 is stored in the storage tank. Liquid is sent from 10 by a pump 9, and a predetermined amount of injection is controlled by a flow rate control valve 8, and then it is supplied into the inner pipe of the nozzle shown in FIG. 4 or 5 and sprayed into the exhaust gas.

Reference numeral 26 is a gas line for supplying the spray gas to the space 14 between the inner pipe and the outer pipe, and 27 is a gas line for supplying the spray gas to the interior 13 of the inner pipe. Gas turbine 1
The concentration of nitrogen oxides (NOx) in the exhaust gas in the exhaust gas is N which is provided with a detection end upstream of the solid reducing agent aqueous solution injection nozzle 11.
The exhaust gas amount is measured by the Ox meter 24 and is determined by the output signal of the gas turbine 1.
The NOx amount obtained by determining the NOx amount from the concentration and the exhaust gas amount
A control signal based on the amount of solid reducing agent required according to the Ox value is sent from the control device 25 to the flow control valve 8, and the solid reducing agent aqueous solution is sprayed into the exhaust gas from the nozzle 11.

The nozzle 11 may be provided in the low flow velocity region 2c as shown in FIG. In this case, in order to uniformly mix the solid reducing agent in the exhaust gas, it is effective to install a dispersion plate for diffusing and mixing the solid reducing agent in the duct 2. In FIGS. 1 to 8, components having the same numbers are the same. In the present invention, the nozzle 1 having a double pipe structure
Instead of 1, a nozzle 100 having a single tube structure may be used as seen in FIG. High-concentration aqueous solution of solid reducing agent 2
A reducing agent aqueous solution supply line 33 is provided from the storage tank 10 storing 3 to the pipe 100a in the nozzle 100, and the water 31 stored in the water storage tank 30 is supplied to the line 33 to dilute the high-concentration aqueous solution 23. A dilution line 32 for connecting is connected. A line 27 for supplying gas such as air may be connected to the line 33, and in this case, gas is supplied to the reducing agent aqueous solution.

As shown in FIG. 7, the apparatus of the present invention may be one in which the nozzle 11 or 100 is attached to the pipe 102 installed across the inside of the duct 2. Figure 7
Among them, those having the same numbers as in FIGS. 1 to 5 are the same. Specific examples of the present invention will be shown below, but the present invention is not limited to the following examples.

Example 1 A denitration test was conducted using the apparatus shown in FIG. 1 in which the nozzle 11 shown in FIG. 4 was installed in the duct 2 as shown in FIGS. The high-concentration aqueous solution (40% by weight) supplied from the storage tank 10 in which 40% by weight of urea aqueous solution is stored by the pump 9 through the supply line 33 is supplied with the water supplied from the water storage tank 30 through the dilution line 32 by the pump 39 on the way. It is diluted by confluence with the duct 11 from the nozzle 11 as an aqueous urea solution having a concentration of 7% by weight.
Was sprayed in.

The tip of the inner tube of the nozzle is 2 more than the tip of the outer tube.
Using four nozzles 11 projecting mm, an aqueous urea solution diluted to a concentration of 7% by weight described above is used in an amount of 1.9 m / m3 so that the NH ₃ / NOx molar ratio is 0.9 on the ammonia conversion basis.
It is supplied to the inside 13 of the nozzle inner tube at a speed of s (the speed of passing through the inner tube of the nozzle 11) and at the same time between the outer tube 14 and the inner tube
Air is supplied to the inner pipe 13 at a speed that is 30 times the speed of the aqueous urea solution flowing in the inner pipe 13 (the speed passing through 14 between the nozzle outer pipe and the inner pipe), and the urea aqueous solution is continuously supplied from the nozzle 11 to the duct 2 It was sprayed on the exhaust gas inside and a denitration test was conducted under the conditions shown in Table 1.

[0038]

[Table 1] ────────────────────────────────── Exhaust gas Turbine exhaust gas (output 1000 kW) Fuel City gas ( 13A) Exhaust gas amount 14,200 Nm ³ / h Exhaust gas temperature 500 ° C. (nozzle installation part) 230 ° C. (catalyst inlet part) NOx concentration in exhaust gas 43 ppm VD (catalyst inlet part) Solid reducing agent urea Solid reducing agent amount NH ₃ / NOx = 0.9 (molar ratio) (However, ammonia conversion standard) SV (space velocity) 8,500 h ^-1 Exhaust gas flow velocity 25 m / s (in duct 2 at nozzle installation part) Nozzle installation angle Right angle to exhaust gas flow Catalyst V ₂ O ₅ —WO ₃ —TiO ₂ type honeycomb catalyst ─────────────────────────────────── , Urine over 1000 hours The nozzle was not clogged with the polymer of urea and urea, and the urea aqueous solution could be continuously supplied. The denitration rate is 89.5.
%, Unreacted ammonia was 0.2 ppm, and excellent results were obtained.

[0039]

According to the present invention, the amount of unreacted ammonia (leakage ammonia amount) in the exhaust gas is reduced, the cost is reduced by reducing the amount of the solid reducing agent aqueous solution used such as urea water, and the denitration performance is improved. To do.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of an embodiment of a nitrogen oxide removing device of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement state of nozzles in the apparatus shown in FIG.

FIG. 3 is an explanatory diagram showing a mounting state of nozzles in the apparatus shown in FIG.

FIG. 4 is a schematic sectional view of an example of a nozzle used in the present invention.

FIG. 5 is a schematic cross-sectional view of another example of the nozzle used in the present invention.

FIG. 6 is a schematic vertical sectional view of another embodiment of the nitrogen oxide removing device of the present invention.

FIG. 7 is still another one of the nitrogen oxide removing apparatus of the present invention.
It is a schematic longitudinal cross-sectional view of an example.

FIG. 8 is a schematic cross-sectional view of still another example of the nozzle used in the present invention.

[Explanation of symbols]

1 Gas turbine that is an exhaust gas source 2 ducts (exhaust gas flue) 3 Exhaust heat recovery boiler 4 DeNOx catalyst layer (DeNOx reactor) 5 chimney 6 gas flow meter 7 gas flow meter 8 Flow control valve 9 Solid reducing agent aqueous solution supply pump 10 Solid reducing agent aqueous solution storage tank 11 Solid reducing agent aqueous solution injection nozzle 13 Inside 14 Between inner pipe and outer pipe 23 High-concentration aqueous solution of solid reducing agent 24 NOx meter 25 Control device 26 gas lines 27 gas lines 30 water tank 31 Water for dilution 32 dilution line 33 Reducing agent aqueous solution supply line 39 Dilution water supply pump 40 economizer 100 nozzles

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Tanasawa               1-7-7 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa                 Tokyo Gas Co., Ltd. Production Technology Center               Within (72) Inventor Kenichiro Kobayashi               1-7-7 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa                 Tokyo Gas Co., Ltd. Production Technology Center               Within (72) Inventor Hiroaki Hayashi               1-2-2 Uchisaiwaicho, Chiyoda-ku, Tokyo               Nippon Shokubai Co., Ltd. Tokyo head office (72) Inventor Motonobu Kobayashi               992 Nishioki, Okihama, Aboshi-ku, Himeji City, Hyogo Prefecture               No. 1 inside Nippon Shokubai Catalysis Laboratory                (56) Reference JP-A-3-294591 (JP, A)                 Japanese Patent Laid-Open No. 4-16216 (JP, A)                 JP-A-58-223427 (JP, A)                 JP-A-53-63266 (JP, A)                 JP 62-289257 (JP, A)                 JP-A-59-120263 (JP, A)                 Actual Kaihei 4-4035 (JP, U)                 Actual Development Sho 54-139042 (JP, U)

Claims (7)

(57) [Claims] 1. In a duct, a solid reducing agent aqueous solution is sprayed onto flowing exhaust gas to mix the solid reducing agent with the exhaust gas, and nitrogen oxides in the exhaust gas are selectively reduced and removed in the presence of a catalyst. In the method, a double pipe consisting of an inner pipe and an outer pipe
It has a structure and its inner pipe tip is 1 to 5 mm deeper than the outer pipe tip.
Install the protruding nozzle on the side surface of the duct,
A solid reducing agent aqueous solution stored at a high concentration of 30% by weight or more is diluted with water while being fed for spraying and then supplied into the inner pipe of the nozzle and the inner pipe and the outer pipe.
Solid reducing agent water soluble by supplying atomizing gas between the tubes
A method for removing nitrogen oxides, which comprises spraying a liquid onto exhaust gas . 2. The method according to claim 1 , wherein the atomizing gas is supplied into the inner tube of the nozzle together with the solid reducing agent aqueous solution. 3. The process as claimed in claim 1 or 2 for spraying a solid reductant aqueous solution into the exhaust gas flowing at 15 m / s or more flow rates. 4. claims 1-3 solid reductant is urea
The method described in any of the above. 5. A nozzle for spraying a solid reducing agent aqueous solution onto the exhaust gas flowing in the duct from an upstream side to a downstream side of the exhaust gas flow, and a reduction reaction of nitrogen oxides in the exhaust gas. And a solid reducing agent aqueous solution is stored at a high concentration of 30% by weight or more, from the storage means to the nozzle, a reducing agent aqueous solution supply line is provided. In the nitrogen oxide removing device provided, a dilution line for supplying water for diluting the high concentration aqueous solution is connected to the reducing agent aqueous solution supply line, and the high concentration aqueous solution is supplied to the nozzle. It became diluted with water on the way
The nozzle has a double pipe structure consisting of an inner pipe and an outer pipe.
The inner tube tip should be projected 1-5 mm more than the outer tube tip
It is installed on the side peripheral surface of the duct,
A solid reducing agent aqueous solution supply line is provided in the inner tube of the nozzle.
Connected and supplied with solid reducing agent aqueous solution diluted with water
In addition, a spray gas is provided between the inner tube and the outer tube of the nozzle.
The first gas line that supplies gas
The nitrogen oxide removing apparatus is characterized in that the nitrogen oxides are supplied . 6. A second gas line for supplying the spray gas is connected to a solid reducing agent aqueous solution supply line so that the spray gas is supplied to the inner pipe of the nozzle together with the solid reducing agent aqueous solution diluted with water. The device according to claim 5, wherein: 7. The apparatus according to claim 5 , wherein the nozzle is installed in a region where the exhaust gas flows at a flow velocity of 15 m / s or more.