JPH10156193A - Activity regenerating method of for eliminating nitrogen oxides and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an activity regenerating method for regenerating the activity of a catalyst for regenerating nitrogen oxides by washing a spent catalyst for deNOx with a chemical relatively inexpensive and easily handleable and to provide a device therefor. SOLUTION: In the activity regenerating method of the deNOx catalyst regenerating the activity of the deNOx catalyst in which deNOx rate is deteriorated by sticking of Na and K contents thereto when used at a heavy oil burning boiler and increased in an SO3 conversion due to sticking of vanadium content contacted in a fuel, the deNO2 catalyst is washed with an inorg. alkali aq. soln. and an oxidizing agent soln.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for regenerating an activity of a denitration catalyst for cleaning a denitration catalyst of a denitration apparatus and regenerating the activity thereof. the Na, eluted K min, then aqueous NaOH the denitration catalyst from 0.1 to 10 percent, and 0.1 to 10% H ₂ O
_{The present} invention relates to a method and an apparatus for regenerating the activity of a denitration catalyst for regenerating a catalyst by washing with _two solutions to elute vanadium attached to the catalyst.

[0002]

BACKGROUND OF THE INVENTION Coal, in the boiler combustion system for a heavy oil as a fuel, for removing nitrogen oxides in exhaust gases (NO _X), the denitration apparatus is provided downstream of the boiler.
In the denitration apparatus, a denitration catalyst containing titanium oxide as a main component is formed in a honeycomb shape, and ammonia (reducing agent) is injected into exhaust gas upstream of the denitration catalyst, and the exhaust gas passes through the catalyst layer, NO _x (mainly NO) is reduced to nitrogen by ammonia to perform denitration (see FIG. 1).

[0003]

However, when a fuel such as heavy oil having a high sulfur content is used, vanadium (V) contained in the fuel flies in the exhaust gas and becomes a catalyst for the above-mentioned denitration apparatus. By adhering and accumulating, the SO ₃ conversion rate (the rate at which SO ₂ is converted to SO ₃ ) increases with time,
The SO ₃ concentration near the outlet of the denitration device increases. When the concentration of SO ₃ in the exhaust gas discharged from the denitration device rises, when the temperature of the exhaust gas falls below the acid dew point of SO ₃ , corrosion (acid corrosion) of the downstream duct and the like is caused and residual NH ₃
The SO ₃ and acidic ammonium sulfate produced by the reaction (NH ₄ HSO
₄ ) adheres to GAH or the like and causes dust clogging, and causes problems such as fume-like acidic ammonium sulfate that could not be completely removed by EP to form white smoke and be discharged from the chimney.

[0004] In addition, since alkali components such as Na and K in the boiler fuel adhere to and accumulate in the catalyst, there is a problem that the catalyst is poisoned and its denitration activity is reduced. And the denitration performance decreases due to the adhesion of the alkali,
The above-mentioned increase in the SO ₃ conversion rate due to the attachment of vanadium is a major factor in lowering the activity (performance) of the denitration catalyst.

[0005] Therefore, it is necessary to restore the denitration performance of the denitration catalyst whose activity has been reduced as described above. However, conventionally, it is general to simply replace the used catalyst with a new one to solve the problem. Was. However, in this case, there is a disadvantage that the economic burden is large.

Further, a method of regenerating the performance of a used catalyst by washing it with an organic acid or the like has been tried. However, the organic acid has a drawback that the wastewater treatment is not easy due to high COD (chemical oxygen demand). .

Accordingly, an object of the present invention is to provide a method and an apparatus for regenerating the activity of a denitration catalyst, in which a used denitration catalyst is washed with a relatively inexpensive and easy-to-treat agent to regenerate its activity.

[0008]

In order to achieve the above object, the invention according to claim 1 is characterized in that, when used in a heavy oil oil fired boiler or the like, Na and K adhere to the boiler to lower the denitration rate, in the active regeneration process of the denitration catalyst vanadium content adheres sO ₃ conversion rate to regenerate the the denitration catalyst increases contained in, and is configured to clean the denitration catalyst in the inorganic alkali aqueous solution and oxidizing agent solution .

According to a second aspect of the present invention, the denitration catalyst is washed with water before being washed with the aqueous inorganic alkali solution and the oxidizing agent solution to remove the Na and K components attached to the catalyst. .

According to a third aspect of the present invention, a 0.1-10% NaOH aqueous solution is used as the inorganic alkali aqueous solution, and a 0.1-10% H ₂ O ₂ solution is used as the oxidizing agent solution.

According to a fourth aspect of the present invention, there is provided a denitration catalyst regenerating apparatus for regenerating the activity of a denitration catalyst having an increased SO ₃ conversion rate due to the attachment of vanadium contained in a fuel. A cleaning tank filled with an inorganic alkali aqueous solution and an oxidizing agent solution, a cleaning liquid supply means for supplying the cleaning liquid with the inorganic alkali aqueous solution and the oxidizing agent solution, and a cleaning liquid circulating means for circulating the cleaning liquid. ing.

[0012]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

In a boiler combustion system using coal, heavy oil, gas, or the like as a fuel, nitrogen oxides (N
O _X) to remove the NOx removal device is provided downstream of the boiler.

FIG. 1 schematically shows such a denitration apparatus 1. A boiler or the like (not shown) is connected to the upstream side of the denitration device 1, and various downstream devices (an air heater, an EP, a desulfurization device, a chimney, etc.) are connected to the downstream side.

[0015] Inside the denitration apparatus 1, a denitration catalyst 2 mainly composed of titanium oxide is accommodated in a catalyst basket (not shown) and installed. Further, an NH ₃ injection device 3 is connected to the inlet of the denitration device 1 as shown in the figure.
The NH ₃ injection device 3 is configured to inject ammonia into exhaust gas introduced into the denitration device 1 via a duct at the entrance of the denitration device 1.

A cleaning tank 4 for cleaning a used denitration catalyst is installed adjacent to the denitration apparatus 1 (see FIG. 1). The cleaning tank 4 is connected to a cleaning liquid supply unit 5 that supplies an inorganic alkaline aqueous solution and an oxidizing agent solution to the cleaning tank 4 when cleaning (main cleaning) the denitration catalyst 2. In addition, this cleaning liquid supply means 5 is provided with an inorganic alkali aqueous solution supply means (not shown) for supplying an inorganic alkali aqueous solution.
Of course, it may be configured separately from an oxidant solution supply means (not shown) for supplying the oxidant solution. The cleaning tank 4 is provided with a cleaning liquid circulating means 7 for circulating the cleaning liquid in the cleaning tank 4 via a pump 8 as shown in the figure.

The cleaning tank 4 and the above-mentioned respective means 5, 7, and 8 accompanying the cleaning tank 4 are used as the denitration catalyst activity regeneration apparatus 10 of the present invention.
Is configured.

In this embodiment, a 0.1-10% NaOH aqueous solution is used as the inorganic alkali aqueous solution, and a 0.1-10% H ₂ O ₂ aqueous solution is used as the oxidizing agent solution.

Further, the denitration catalyst activity regenerating device 10 may be configured to be movable and may be moved to a position adjacent to the denitration device 1 only when the denitration catalyst 2 of the denitration device 1 is washed. is there. Alternatively, the denitration catalyst activity regenerating device 10 of the present invention may be installed at a location remote from the denitration device 1, and the denitration catalyst 2 removed from the denitration device 1 may be transferred to the denitration catalyst cleaning means 10 for cleaning.

Exhaust gas generated by burning the fuel is introduced into the denitration device 1. At this time, NH ₃ is injected into the exhaust gas by the NH ₃ injection device 3. The exhaust gas and NH ₃ introduced into the denitration device 1 come into contact with a denitration catalyst such as titanium oxide in the denitration catalyst 2. Then, by nitrogen oxides contained in the exhaust gas (NO _X) and NH ₃ comes into contact with the denitration catalyst, NO _X (mainly NO) is reduced to nitrogen by NH _3, denitration is performed.

The exhaust gas thus denitrated is introduced into subsequent devices (desulfurizer, chimney, etc.) and finally discharged to the atmosphere.

In the above-described denitration process, the vanadium (V) and alkali (Na, K) components contained in the fuel adhere to the denitration catalyst 2 of the denitration device 1, and as described above, Decreases the denitration activity.

Therefore, in the method for regenerating the activity of the denitration catalyst according to the present invention, the V and Na, K components (hereinafter, referred to as “V”) adhered to the denitration catalyst 2 by the denitration catalyst activity regeneration device 10 described above.
The activity of the denitration catalyst, whose activity (performance) has been reduced, is intended to be regenerated by washing and removing the Na component). Hereinafter, the method will be described.

First, the denitration catalyst 2 having a reduced catalytic activity due to the adhesion of V component, Na component, etc. is removed from the denitration device 1 by a crane or the like.
Then, as preparatory work before cleaning, dust removal by air blowing (air blowing) and preliminary cleaning with water are performed. Dust and the like adhering to the (denitration) catalyst 2 are removed by air blow, and Na is removed by preliminary washing with water.
Elutes alkaline components.

The catalyst 2 from which the dust and the Na content have been removed,
Next, it is moved into the cleaning tank 4. 0.1 in the form of an oxidizing agent aqueous solution (exemplary (0.1 to 10% NaOH aqueous solution in the present embodiment) inorganic alkali aqueous solution to 10% H ₂ O
₂ solution) is supplied into the cleaning tank 4 by the cleaning liquid supply means 5 as a cleaning liquid. At this time, it is a matter of course that the inorganic alkali aqueous solution and the oxidizing agent aqueous solution may be supplied into the cleaning tank 4 by separate supply means. The cleaning liquid supplied into the cleaning tank 4 is cleaned by the cleaning liquid circulating means 7.
The catalyst 2 is appropriately circulated through the pump 8, so that the catalyst 2 is effectively washed by the washing liquid (main washing).

In the above main cleaning, NaO was added to the cleaning tank 4.
When the H aqueous solution and the H ₂ O ₂ solution are supplied, an alkaline and oxidizing atmosphere is provided in the cleaning tank 4. In this alkaline and oxidizing atmosphere, vanadium is easily ionized as shown in FIG. 3, so that vanadium attached to the catalyst 2 is ionized and eluted,
As a result, V components and the like are removed from the catalyst 2. In addition, by the main cleaning, Na and the like which could not be completely removed by the preliminary cleaning are surely removed, and vanadium which has an undesirable effect similarly to VOSO ₄ (V ₂ O _5, etc.)
(Which may be attached to the catalyst 2) is also effectively removed.

In the main cleaning, NaO used for cleaning is used.
The concentration of the H aqueous solution and the H ₂ O ₂ solution is 0.1% as described above.
Desirably, it is about 10%. The washing time is 0.1 to 4
Time, the solid-liquid ratio (volume of (washing) solution / volume of catalyst) is 0.
A volume of 5 to 7 times is appropriate, but these conditions may be appropriately changed depending on the condition of the catalyst to be washed, the concentration of the washing solution, and the like. The temperature at the time of washing may be room temperature (that is,
Even at normal temperature, a sufficient cleaning effect can be obtained).

FIG. 2 shows that the main cleaning was performed at a solid-liquid ratio of 3, normal temperature,
The experimental results obtained when a 3% NaOH aqueous solution and a 1% H ₂ O ₂ solution were used and when a 6% NaOH aqueous solution and a 1% H ₂ O ₂ solution were used under the condition that the washing time was 2 hours were as follows. The graph also shows the denitration rate regeneration rate, SO ₃ conversion rate regeneration rate, catalyst V ₂ O ₅ cleaning rate, and Na ₂ O cleaning rate.

By the way,

[0030]

(Equation 1)

Is as follows.

As is clear from FIG. 2, in both cases, the denitration rate regeneration rate and the catalyst V ₂ O ₅ cleaning rate are 100% or more (that is, the catalyst is regenerated to be equal to or more than the fresh catalyst). Regarding the SO ₃ conversion rate and the regeneration rate, when a 6% NaOH aqueous solution and a 1% H ₂ O ₂ solution were used, a favorable result of 94.4% was obtained. (Note that when a 6% NaOH aqueous solution is used, Na
_{The 2} O cleaning rate is slightly lower than that when a 3% NaOH aqueous solution is used, but has no effect on the denitration regeneration rate as shown in FIG. 2).

That is, when the denitration catalyst is washed with an inorganic alkali aqueous solution and an oxidizing agent solution based on the method for regenerating the activity of the denitration catalyst of the present invention, the denitration rate is higher than that of the fresh catalyst, and the SO ₃ conversion rate is increased. Greatly decreases and SO
_{(3) Even at a} conversion rate, it almost completely returns to the fresh state before use (regenerated).

In the present embodiment, air blowing and pre-cleaning as preparatory work for the main cleaning are performed outside the cleaning tank 4, but after the catalyst 2 is set in the cleaning tank 4, the cleaning is performed. 4 may of course be performed. Also,
As the cleaning liquid circulating means 7 for circulating the cleaning liquid in the cleaning tank 4, other circulating means other than the circulation by the pump may be used.

The main cleaning is performed as described above, and the V content and N
After the removal of the a component and the like is completed, the denitration catalyst 2 is washed again with water. As a result, the sodium component that may have adhered to the denitration catalyst 2 (because the NaOH aqueous solution was used in the main cleaning) is washed away (rinse). When the rinsing is completed, it is taken out of the washing tank 4 by a crane or the like and dried (natural drying). The denitration catalyst 2 whose drying has been completed is installed in the denitration apparatus 1 again.

Various changes can be made to the above-mentioned rinsing and drying, such as performing drying in the washing tank 4 (with the rinse liquid removed) or performing drying quickly with a dryer (not shown). Some things are, of course.

As described above, according to the method for regenerating the activity of the denitration catalyst of the present invention and the apparatus for regenerating the activity of the denitration catalyst based on the method, the denitration catalyst of the denitration apparatus whose activity is reduced due to the adhesion of V and Na components is first treated with water To remove the Na content, etc., and then remove the V content by washing the catalyst with an inorganic alkali aqueous solution and an oxidizing agent solution, thereby lowering the SO ₃ conversion rate of the denitration catalyst and increasing the denitration rate. As a result, the activity (performance) of the catalyst can be almost completely recovered. That is, by the method for regenerating the activity of the denitration catalyst of the present invention, the (increased) SO ₃ conversion rate and the (decreased) of the used denitration catalyst whose performance has been reduced are reduced.
The denitration rate can be reduced or improved to about the same as the SO ₃ conversion rate and the denitration rate of a fresh denitration catalyst.

[0038]

As described above, according to the method and apparatus for regenerating the activity of the denitration catalyst according to the present invention, the following excellent effects can be obtained.

(1) The used denitration catalyst having an increased SO ₃ conversion rate due to the adhesion of vanadium is washed at room temperature with an aqueous solution of an inorganic alkali and an oxidizing agent so that the vanadium can be easily ionized. Elution from the catalyst. As a result, SO ₃ conversion of washed catalyst is decreased to substantially the same level as that of fresh denitration catalyst, thus, SO ₃
The corrosion of the duct and the generation of acidic ammonium sulfate caused by the increase in the amount of ammonium sulfate are prevented.

(2) Washing the used denitration catalyst with reduced denitration performance (ie, reduced activity) due to adhesion of an alkali component such as Na component with water, the alkali component is eluted and removed from the catalyst. Is done. As a result, the denitration rate of the washed catalyst is improved to the same level as or higher than that of a fresh denitration catalyst.

(3) The catalyst is converted to a general inorganic agent (for example, 0.1
By washing with to 10% NaOH and _{0.1 ~10% H 2 O 2)} , it can be cost savings over conventional methods of washing with organic acids.

(4) By washing the catalyst with 0.1 to 10% NaOH, V attached to the catalyst can be effectively removed not only from V ₂ O ₅ but also from VOSO ₄ .

(5) The catalyst is 0.1 to 10% NaOH and 0.1 to 10%.
When cleaning is performed using 10% H ₂ O ₂ , the cleaning can be performed at room temperature (that is, there is no need to heat), so that the cleaning process is easy. Further, in the case of washing with NaOH and H ₂ O ₂ as described above, the wastewater treatment after washing is easy, and also in this respect, organic acids (high COD value and large environmental load).
Is superior to the conventional method using

(6) The catalyst was 6% NaOH and 1% H ₂ O ₂
In the case of washing using, although the treatment after washing is simple (only rinsing with water and natural drying), an extremely high denitration rate regeneration rate (100%) and SO ₃ conversion rate regeneration rate (94.4
%) Is obtained. On the other hand, in the case of the conventional method using an organic acid or the like, in order to achieve a desired denitration rate regeneration rate, the washed catalyst is impregnated with a solution of a tungsten compound that is a catalytically active component to support the tungsten compound. In this respect, the method for regenerating the activity of the denitration catalyst of the present invention is more excellent.

[Brief description of the drawings]

FIG. 1 is a schematic view (partially sectional view) of an apparatus for regenerating the activity of a denitration catalyst of the present invention and a denitration apparatus accompanying the apparatus.

FIG. 2 shows a method for regenerating the activity of a denitration catalyst according to the present invention, in which NaOH aqueous solution and 1% H at different concentrations (3% and 6%) are used.
_When the denitration catalyst is washed using ₂ O ₂ , the denitration rate regeneration rate, SO ₃ conversion rate regeneration rate, catalyst V ₂ O ₅ cleaning rate and Na
It is a figure which shows a ₂ O cleaning rate.

FIG. 3 V ₂ O ₅ (and other vanadium oxides)
FIG. 4 is a diagram showing how is ionized with changes in pH and redox atmosphere.

[Explanation of symbols]

 2 denitration catalyst 4 cleaning tank 5 cleaning liquid supply means 7 cleaning liquid circulation means 10 denitration catalyst activity regeneration device

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01J 21/20 B01D 53/36 102E 38/48 (72) Inventor Junsei Senoo Harima Ishikawajima 3-2-16-1 Toyosu, Koto-ku, Tokyo Heavy Industries, Ltd. Toyosu General Office

Claims (4)

[Claims] 1. Use of heavy oil-fired boilers in N
In the method for regenerating the activity of a denitration catalyst, a denitration catalyst is reduced in which a and K components are attached and a denitration ratio is reduced, and a vanadium component contained in fuel is attached and an SO ₃ conversion is increased.
A method for regenerating the activity of a denitration catalyst, comprising washing the denitration catalyst with an aqueous solution of an inorganic alkali and an oxidizing agent. 2. The method for regenerating the activity of a denitration catalyst according to claim 1, wherein said denitration catalyst is washed with water before being washed with said inorganic alkali aqueous solution and oxidizing agent solution to remove Na and K components attached to said catalyst. . 3. The aqueous inorganic alkali solution of 0.1 to 10
% NaOH aqueous solution, 0.1 to 10% H
_{3. The} method for regenerating the activity of a denitration catalyst according to claim 1, wherein a ₂ O ₂ solution is used. 4. A denitration catalyst regenerating apparatus for regenerating the activity of a denitration catalyst having an increased SO ₃ conversion rate due to the attachment of vanadium contained in fuel, wherein the denitration catalyst is accommodated, and an inorganic alkaline aqueous solution and an oxidizing solution are oxidized. A denitration catalyst, comprising: a cleaning tank filled with a cleaning agent solution; a cleaning liquid supply unit for supplying an inorganic alkali aqueous solution and an oxidizing agent solution to the cleaning tank as a cleaning liquid; and a cleaning liquid circulation unit for circulating the cleaning liquid. Active regeneration device.