JP2017077547A - Denitration method in incineration facility and system thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a denitration method in an incineration facility which can use hydrogen generated from incineration ash as a valuable substance, and can greatly reduce or can dispense with a purchasing expense of a medicine such as ammonia required for a denitration treatment, and to provide a system thereof.SOLUTION: There is provided a denitration system that includes: an ash cooling device 11 having a treatment tank having a role as a water tank for storing cooling water for cooling incineration ash from an incinerator 2 and a role as a hydrogen gas generating tank for generating hydrogen by reaction of the incineration ash and the cooling water; and an ammonia synthetic device 12 for synthesizing ammonia gas from hydrogen gas generated in a treatment tank in the ash cooling device 11 and nitrogen gas purified from air, where ammonia gas synthesized by the ammonia synthetic device 12 is sprayed into the incinerator 2 to subject the ammonia gas to a denitration treatment or supplying the ammonia to a denitration catalyst 8 as a reducer to subject the ammonia to the denitration treatment.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a denitration method and a system thereof in an incineration facility for incinerating general waste and industrial waste.

  Conventionally, in this type of incineration facility, for example, ammonia gas is supplied from a liquefied ammonia gas cylinder or the like to the incinerator or the denitration catalyst, or urea water is supplied to the incinerator or the denitration catalyst, A denitration method for removing nitrogen oxides (NOx) has been implemented.

  On the other hand, incineration ash generated with incineration of municipal waste, etc., tends to show alkalinity by generating hydroxide ions when in contact with water, and the incineration ash must contain metallic aluminum From the above, it is known that metal aluminum in the incineration ash reacts with water under alkaline conditions to generate hydrogen in the incineration ash cooling step or the like (see, for example, Patent Documents 1 and 2). It is considered that hydrogen gas recovered from incineration ash is used as fuel.

JP-A-4-265188 JP 11-141849 A

  However, in the above denitration method, ammonia gas or urea water must be purchased separately, and thus there is a problem that the purchase cost of ammonia gas or urea water increases.

On the other hand, the amount of hydrogen gas generated from the incinerated ash by reaction with water under alkaline conditions is determined under predetermined experimental conditions (8 to 45 L / kg-ash / 20 days, 40 ° C., shaking: 200 rpm, L / S ( Water / incineration ash weight ratio): 5), about 0.4 to 2.5L / kg-ash per day (waste generation amount is assumed to be 10t / day on a scale of 100t / day of waste treatment) The amount is 4 to 25 m ³ / day), and when recovered and used as fuel, there is a problem that only a small amount of heat can be obtained.
At present, hydrogen generated from incineration ash has no effective use, and if it stays in the ash cooler or ash pit, there is a risk of an explosion accident, so it is exhausted to an exhaust gas treatment facility or incinerator.

  The present invention has been made in view of the above-mentioned problems, and hydrogen generated from incineration ash can be used as a valuable material, greatly increasing the purchase cost of chemicals such as ammonia required for denitration treatment. It is an object of the present invention to provide a denitration method and system in an incineration facility that can be reduced or eliminated.

In order to achieve the object, the denitration method in the incineration facility according to the first invention is:
Hydrogen is generated by the reaction of the incineration ash generated when incinerators are incinerated with cooling water for cooling the incineration ash, and ammonia is synthesized from the generated hydrogen and nitrogen in the air, The synthesized ammonia is sprayed into the incinerator for denitration treatment, or supplied to a denitration catalyst that uses ammonia as a reducing agent installed in the middle of the flow path of exhaust gas from the incinerator for denitration treatment. It is what.

The denitration method in the incineration facility according to the second invention is as follows:
Hydrogen is generated by the reaction of the incineration ash generated when the waste is incinerated with the cooling water for cooling the incineration ash, and the generated hydrogen is in the middle of the flow path of the exhaust gas from the incinerator. The denitration treatment is performed by supplying hydrogen to a denitration catalyst using hydrogen as a reducing agent.

Next, the denitration system in the incineration facility according to the third invention is:
A hydrogen gas generation tank that contains cooling water for cooling the incineration ash generated when incinerator waste is incinerated and generates hydrogen by the reaction of the incineration ash and the cooling water, and the hydrogen gas generation tank An ammonia synthesizer that synthesizes ammonia from hydrogen generated in the air and nitrogen in the air,
Ammonia synthesized by the ammonia synthesizer is sprayed into the incinerator for denitration treatment, or supplied to a denitration catalyst using ammonia as a reducing agent installed in the flow path of exhaust gas from the incinerator. It is characterized by denitration treatment.

Moreover, the denitration system in the incineration facility according to the fourth invention is:
Comprising a hydrogen gas generation tank that contains cooling water for cooling the incinerated ash generated when the waste is incinerated in an incinerator and generates hydrogen by the reaction of the incinerated ash and the cooling water;
The hydrogen generated in the hydrogen gas generation tank is supplied to a denitration catalyst using hydrogen as a reducing agent installed in the middle of the flow path of the exhaust gas from the incinerator to perform a denitration process.

  According to 1st invention and 3rd invention, ammonia is synthesize | combined from the hydrogen generated by reaction of incineration ash and cooling water, and nitrogen in air, and the synthesized ammonia is sprayed in an incinerator. The denitration process is performed by the denitration process, or the denitration process is performed by supplying ammonia to the denitration catalyst that uses ammonia as the reducing agent, which is installed in the middle of the flow path of the exhaust gas from the incinerator. The purchase cost of chemicals such as ammonia required for the denitration treatment can be greatly reduced or eliminated.

  According to the second and fourth inventions, the hydrogen generated by the reaction between the incineration ash and the cooling water is supplied to the denitration catalyst using hydrogen as a reducing agent installed in the flow path of the exhaust gas from the incinerator. Therefore, the denitration process is performed, so that the same effects as those of the first invention and the third invention can be obtained, and the denitration process and system are compared with those of the first invention and the third invention. It can be simplified.

FIG. 1 is a schematic system configuration diagram of a waste incineration facility equipped with a denitration system according to the first embodiment of the present invention. FIG. 2 is a schematic system configuration diagram of a waste incineration facility equipped with a denitration system according to the second embodiment of the present invention.

  Next, a specific embodiment of a denitration method and its system in an incineration facility according to the present invention will be described with reference to the drawings.

[First Embodiment]
<Overview of incineration facilities>
In the incineration facility 1 shown in FIG. 1, waste such as municipal waste is burned in an incinerator 2. The exhaust gas generated by the combustion of the waste in the incinerator 2 is used for heat exchange in the boiler 3, and is used for heating water supply to the boiler 3 in the economizer 4, and then in the temperature reducing tower 5. After being cooled to a predetermined temperature, it is sent to a dust collector 6 using a bag filter. The exhaust gas from which dust has been removed by the dust collector 6 is heated by the exhaust gas heating device 7 and then sent to the catalyst denitration device 8. The exhaust gas denitrated by the catalyst denitration device 8 is discharged out of the system through a chimney 9 by an induction fan (not shown).

As the catalyst denitration device 8, a reaction between ammonia and NOx is caused on a denitration catalyst (component: titanium oxide, vanadium, etc.) using ammonia (NH ₃ ) as a reducing agent, and NOx is decomposed into N ₂ and H ₂ O. The format to be used is used.

  On the other hand, the incineration ash generated by the incineration of waste in the incinerator 2 reacts with the incineration ash and the cooling water, serving as a water tank for storing the cooling water for cooling the incineration ash from the incinerator 2. And introduced into the ash cooling device 11 including a treatment tank that also serves as a hydrogen gas generation tank for generating hydrogen.

  The ash cooling device 11 includes a wet type and a semi-wet type. In the wet type, the incineration ash from the incinerator 2 is cooled with cooling water in the treatment tank, and the cooled incineration ash is carried out to the ash pit by an ash conveyor installed at the bottom of the treatment tank. . On the other hand, in the semi-wet type, the incineration ash from the incinerator 2 is cooled with cooling water in the treatment tank, and the incinerated ash is drained with an ash pusher equipped with, for example, a hydraulic pusher while removing the ash pit. It is a method of carrying out to

  In the ash cooler 11, the incinerated ash charged into the treatment tank tends to show alkalinity by generating hydroxide ions when in contact with the cooling water, and the incinerated ash contains metallic aluminum. For this reason, when the incineration ash is cooled with cooling water, metal aluminum contained in the incineration ash and the cooling water react under alkaline conditions (pH> 12) to generate hydrogen gas.

An ammonia synthesizer 12 is installed downstream of the ash cooler 11. The ammonia synthesizer 12 includes hydrogen gas generated by the ash cooler 11 and nitrogen gas purified from air by the nitrogen gas generator 13. Is introduced.
Here, as the ammonia synthesizer 12, generally, a so-called Harbor Bosch method in which hydrogen and nitrogen are reacted on a catalyst mainly composed of iron under a high temperature and high pressure condition of a pressure of about 20 to 35 MPa and a temperature of about 500 ° C. A type that synthesizes ammonia is used, but from the viewpoint of energy saving and cost reduction, a type that synthesizes ammonia by reacting hydrogen and nitrogen in a normal pressure of 300 ° C with a ruthenium-supported electride catalyst. May be adopted.
Further, as the nitrogen gas generator 13, for example, an adsorbent such as molecular sieve charcoal is used, and high-purity nitrogen is generated from the air by utilizing the difference in adsorption speed due to the difference in the size of nitrogen and oxygen molecules in the air. A type of separation and purification is preferred.

Note that the amount of reducing agent (ammonia) necessary for an incineration facility with a waste disposal amount of 100 t / day is determined as an example.
Denitration pre 80ppm denitration after 30 ppm, when the amount of gas 24000m ³ _N -dry / h,
Denitration reaction 4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O
Ammonia synthesis N ₂ + 3H ₂ → 2NH ₃
Therefore, the required amount of ammonia is (80-30) /1000000×24000×24≈28.8 m ³ / day.
Assuming that the conversion rate of ammonia synthesis is 50%, the required amount of hydrogen is 28.8 ÷ 2 × 3 ÷ 0.5 = 86.4 m ³ / day.

As described above, the amount of hydrogen gas generated is small by just immersing the incinerated ash in the cooling water, and in the above example, it does not reach the amount of hydrogen (86.4 m ³ / day) necessary for producing ammonia used in the field. However, it is known that incinerated ash contains about 4 mass% of metallic aluminum on average, and the total amount of metallic aluminum contained in the incinerated ash is added to hydrogen gas by adding an alkali agent as in Patent Document 1. When used for generation, 500 m ³ of hydrogen gas is generated from 10 t of incineration ash according to the following reaction formula. Therefore, it is possible to increase the generation amount of hydrogen gas as required, and to generate the entire amount of hydrogen gas necessary for ammonia production from the incinerated ash.
2Al + 3H ₂ O → Al ₂ O ₃ + 3H ₂
2Al + 4H ₂ O → 2AlO (OH) + 3H ₂
2Al + 6H ₂ O → 2Al (OH) ₃ + 3H ₂
Here, when Al: 1 mol = 27 g → H ₂ : 1.5 mol = 33.6 L is generated, 10 t × 4% ÷ 27 g × 33.6 L≈500 m ³ −H ₂

  The ammonia gas synthesized by the ammonia synthesizer 12 is sprayed into the incinerator 2 or supplied to the catalyst denitration device 8 for denitration treatment. In this way, hydrogen generated from the incineration ash can be used as a valuable material, and the purchase cost of chemicals such as ammonia required for the denitration treatment can be greatly reduced or eliminated.

[Second Embodiment]
FIG. 2 shows a schematic system configuration diagram of a waste incineration facility equipped with a denitration system according to a second embodiment of the present invention. In the present embodiment, the same or similar parts as those of the first embodiment will be denoted by the same reference numerals in the drawings, and detailed description thereof will be omitted. The following description is specific to the present embodiment. The description will focus on this part.

In the first embodiment, hydrogen gas generated by the ash cooler 11 and nitrogen gas purified from air by the nitrogen gas generator 13 are introduced into the ammonia synthesizer 12 to synthesize ammonia gas, and the synthesized ammonia. Denitration treatment is performed by spraying gas into the incinerator 2 or by supplying the catalyst to a catalyst denitration apparatus 8 using ammonia as a reducing agent.
In contrast, in this embodiment, instead of the catalyst denitration device 8 using ammonia as a reducing agent in the first embodiment, the reaction is performed on a denitration catalyst (component: platinum, palladium, etc.) using hydrogen as a reducing agent. A catalytic denitration device 8A of the type that causes NOx to be decomposed and removed is employed, and denitration treatment is performed by directly supplying hydrogen gas from the ash cooling device 11 to the catalytic denitration device 8A.

The amount of necessary reducing agent (hydrogen) is obtained as an example in the same manner as described above.
Denitration reaction 2NO + 2H ₂ → 2H ₂ O + N ₂
Therefore, if the required amount of hydrogen is 28.8 m ³ / day and the required H ₂ / NO = 4, then 28.8 × 4 = 15.2 m ³ / day.
In conventional denitration catalysts, hydrogen is known to have no effect as a reducing agent when oxygen coexists, but in recent years, platinum and palladium are the main components, and hydrogen is used as a reducing agent even in the presence of oxygen. The development of catalysts that can do this is underway. At present, the catalyst cost is very high, but if the reduction performance is improved, the amount of catalyst used is reduced, so that the system is economically valid.

  According to this embodiment, the same effects as those of the first embodiment can be obtained, and the ammonia synthesizer 12 and the nitrogen gas generator 13 required in the first embodiment are not necessary. Therefore, the denitration system can be simplified as compared with the first embodiment.

  As mentioned above, although the denitration method and its system in the incineration facility of this invention were demonstrated based on several embodiment, this invention is not limited to the structure described in the said embodiment, It described in each embodiment. The configuration can be changed as appropriate within a range not departing from the gist, such as appropriately combining the configurations.

  The denitration method and system thereof in the incineration facility of the present invention can use hydrogen generated from incineration ash as a valuable material, greatly reducing or eliminating the purchase cost of chemicals such as ammonia required for denitration treatment. Therefore, it can be suitably used for NOx removal in an incineration facility that incinerates general waste and industrial waste, and has great industrial applicability. .

1, 1A Incineration facility 2 Incinerator 8, 8A Catalyst denitration equipment 11 Ash cooling device (hydrogen gas generation tank)
12 Ammonia synthesizer 13 Nitrogen gas generator

Claims (4)

  Hydrogen is generated by the reaction of the incineration ash generated when incinerators are incinerated with cooling water for cooling the incineration ash, and ammonia is synthesized from the generated hydrogen and nitrogen in the air, The synthesized ammonia is sprayed into the incinerator for denitration treatment, or supplied to a denitration catalyst that uses ammonia as a reducing agent installed in the middle of the flow path of exhaust gas from the incinerator for denitration treatment. Denitration method in an incineration facility.   Hydrogen is generated by the reaction of the incineration ash generated when the waste is incinerated with the cooling water for cooling the incineration ash, and the generated hydrogen is in the middle of the flow path of the exhaust gas from the incinerator. A denitration method in an incineration facility, characterized in that denitration treatment is performed by supplying hydrogen to a denitration catalyst using hydrogen as a reducing agent. A hydrogen gas generation tank that contains cooling water for cooling the incineration ash generated when incinerator waste is incinerated and generates hydrogen by the reaction of the incineration ash and the cooling water, and the hydrogen gas generation tank An ammonia synthesizer that synthesizes ammonia from hydrogen generated in the air and nitrogen in the air,
Ammonia synthesized by the ammonia synthesizer is sprayed into the incinerator for denitration treatment, or supplied to a denitration catalyst using ammonia as a reducing agent installed in the flow path of exhaust gas from the incinerator. A denitration system in an incineration facility characterized by denitration treatment. Comprising a hydrogen gas generation tank that contains cooling water for cooling the incinerated ash generated when the waste is incinerated in an incinerator and generates hydrogen by the reaction of the incinerated ash and the cooling water;
Denitration in an incineration facility characterized in that hydrogen generated in the hydrogen gas generation tank is supplied to a denitration catalyst using hydrogen as a reducing agent installed in the middle of the flow path of exhaust gas from the incinerator for denitration treatment system.

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