JP2003144852A - Exhaust gas denitrification method and exhaust gas denitrification equipment for gas engine using digested gas as fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and surely remove the NOx in exhaust gas by preventing the degradation in the denitrification performance of a denitrification catalyst by the influence of the siloxane included in digested gas. SOLUTION: The exhaust gas denitrification equipment 1 has an adsorber 4 which is disposed at fuel piping (flow passage) 3 for feeding the digested gas to a gas engine 2, a denitrification reactor 6 which is connected by exhaust piping (flow passage) 5 to the gas engine 2, a pretreating reactor 7 which is disposed upstream of the denitrification reactor 6, a reducing agent feeder 8 which feeds a reducing agent for denitrification in the exhaust gas flowing in the exhaust piping 5, and a controller 9 which controls the gas engine 2, the denitrification reactor 6, the reducing agent feeder 8, or the like. The siloxane in the digested gas is adsorbed in the granular active carbon of the adsorber 4 and is mostly removed and the siloxane included in the unburned gas in the exhaust gas of the gas engine 2 is brought into contact with spherical alumina in the pretreating reactor 7 and is removed by oxidation and therefore the deterioration of the denitrification performance of the denitrification reactor 6 by the siloxane does not occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas denitration method and an exhaust gas denitration apparatus for removing nitrogen oxides from exhaust gas of a gas engine using digestion gas as a fuel.

[0002]

2. Description of the Related Art In a sewage treatment plant or the like, when a sewage sludge or the like is digested and digested gas generated from a waste landfill is used as a fuel to operate a gas engine, the motive power drives a power generator to obtain electric power. Is being done. In this gas engine, in order to remove nitrogen oxides in exhaust gas,
A denitration reactor filled with a denitration catalyst is provided in the exhaust gas passage.

[0003]

However, the digestive gas contains siloxane (organic silica), and this siloxane is a small amount of unburned gas that is discharged without burning in the combustion chamber of a gas engine. Since it passes through the denitration catalyst layer of the denitration reactor together with the exhaust gas while being contained therein, siloxane burns inside the denitration catalyst layer, and the silica oxide (Si ₂ O ₅ ) produced by this combustion denitrates. There is a problem that it remains inside the catalyst layer, which deteriorates the denitration catalyst and significantly reduces the denitration performance of exhaust gas in a short period of time. Therefore, in a gas engine that uses digestive gas as a fuel, it is possible to prevent the NOx removal performance of the NOx removal catalyst from being deteriorated due to the influence of siloxane contained in the digestion gas, and to reliably and reliably remove nitrogen oxides in exhaust gas. Realization of an exhaust gas denitration method and apparatus has been desired.

The present invention has been made in view of the above circumstances and prevents deterioration of the denitration performance of a denitration catalyst due to the influence of siloxane contained in a digestion gas, and stabilizes nitrogen oxides in exhaust gas. It is an object of the present invention to provide an exhaust gas denitration method and an exhaust gas denitration apparatus for a gas engine that uses digestion gas that can be reliably removed as a fuel.

[0005]

The present invention is characterized by the following points in order to solve the above problems. That is,
The exhaust gas denitration method for a gas engine using digestive gas as a fuel according to claim 1, wherein the exhaust gas of a gas engine using digestive gas as a fuel is passed through a denitration reactor filled with a denitration catalyst to reduce nitrogen oxides in the exhaust gas. In the denitration method of reducing and removing with a chemical agent, it is characterized in that the gas is supplied to the gas engine, the exhaust gas of the gas engine is passed through a packed bed of spherical alumina, and then passed through a packed bed of a denitration catalyst of a denitration reactor. .

According to a second aspect of the present invention, there is provided an exhaust gas denitration apparatus for a gas engine that uses digestive gas as a fuel. In a denitration device for reducing and removing substances with a reducing agent, an adsorber filled with activated carbon is provided in a flow path for supplying the digestion gas to a gas engine,
It is characterized in that a pretreatment reactor in which a pretreatment catalyst is filled is provided in a flow path of exhaust gas which connects the gas engine and a packed bed of the denitration catalyst in the denitration reactor.

An exhaust gas denitration apparatus for a gas engine using digested gas as a fuel according to a third aspect is the apparatus according to the second aspect, wherein the pretreatment reactor is a denitration reaction upstream of the packed bed of the denitration catalyst. It is characterized by being installed in a container.

An exhaust gas denitration device for a gas engine using digestive gas as a fuel according to a fourth aspect is the second or third aspect.
In the apparatus described in (1), the pretreatment catalyst is spherical alumina.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An exhaust gas denitration apparatus for a gas engine using digestive gas as a fuel according to an embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1
1 shows an exhaust gas denitration device for a gas engine using digestion gas as a fuel according to an embodiment of the present invention. The exhaust gas denitration device 1 of this gas engine includes a gas engine 2, an adsorber 4 provided in the middle of a fuel pipe (flow path) 3 for supplying digestive gas as fuel to the gas engine 2, and the gas engine 2. A denitration reactor 6 connected through the exhaust pipe (flow path) 5, a pretreatment reactor 7 provided at the lower part of the denitration reactor 6, and a denitration gas in the exhaust gas flowing through the exhaust pipe 5 for denitration. The main components are a reducing agent supply device 8 for supplying a reducing agent, and a control device 9 for controlling the gas engine 2, the denitration reactor 6, the reducing agent supply device 8 and the like.

The adsorber 4 is an adsorption layer in which a self-standing vertical cylindrical container 4a is filled with granular activated carbon (activated carbon) having a particle size of 4 mesh or more at a packing density of 0.4 to 0.45 g / l. (Filled bed of activated carbon) 4b is provided, and the digestion gas F discharged from the digestion treatment facility for sewage sludge is
The fuel pipe 3 is introduced from the upper portion through the upstream fuel pipe 3a, passes through the adsorption layer 4b and is discharged from the bottom portion, and is sent to the gas engine 2 through the downstream fuel pipe 3b. The upper and lower fuel pipes 3a and 3b are provided with filters 10 and 11 for removing foreign matters in the digestion gas F, respectively.

The denitration reactor 6 has a cell number in which a three-way catalyst containing titanium oxide or tungsten oxide as a main component as an active component is formed in a lattice in a self-supporting vertical tower 6a. 35, a denitration catalyst layer (filling layer of denitration catalyst) 6b having an opening of 3.65 mm is installed in two layers, the exhaust pipe 5 is connected near the bottom, and a damper 6c is provided at the top. A chimney 6d is provided. The pretreatment reactor 7 is provided on the lower side (upstream side) of the denitration catalyst layer 6b in the lower stage of the denitration reactor 6 and the column container 6 is provided.
The pretreatment reactor 7 is supported so as to be inclined to a,
For example, a pretreatment agent (pretreatment catalyst) made of spherical alumina whose main component is alumina oxide having a particle diameter of 5 mm is filled to form the pretreatment agent layer 7a.

Both ends of the pretreatment reactor 7 are opened so as to project outward from the container 6a so that the pretreatment agent can be introduced through the high-side opening and taken out through the low-side opening. The exhaust gas passing through the inside of the mounting container 6a can pass through the inside of the mounting container 6a. Lid plates are removably attached to the openings at the upper and lower ends of the pretreatment reactor 7.

The reducing agent supply device 8 is attached in the middle of the exhaust pipe 5 and the tank 12 that stores about 25% ammonia water (ammonium) as a reducing agent, and the ammonia water is exhausted from the exhaust pipe 5 by the exhaust pipe 5. A two-fluid spray nozzle 13 for spraying into the exhaust gas passing through the inside, a pump 15 for supplying ammonia water in the tank 12 to the two-fluid spray nozzle 13 through a reducing agent pipe 14, and a reducing agent on the downstream side of the pump 15. An air compressor 17 for supplying air into the reducing agent flowing through the pipe 14 through the air pipe 16 or directly supplying air to the two-fluid spray nozzle 13 through the branch pipe 16a is provided.

Further, a ventilation port 18 for introducing diluted air into the exhaust gas passing through the exhaust pipe 5 is provided downstream of the position of the two-fluid spray nozzle 13 in the exhaust pipe 5, and the ventilation port 18 is an air port. It is in communication with the blower 20 via a tube 19. Further, on the downstream side of the ventilation port 18 in the exhaust pipe 5, the opening degree of the opening communicating with the bypass exhaust pipe 21 connected to the chimney 6d and the downstream exhaust pipe 5a connected to the denitration reactor 6 is provided. A damper 22 for adjusting is provided.

In the exhaust gas passage between the denitration catalyst layer 6b in the lower stage of the denitration reactor 6 and the pretreatment reactor 7 and the exhaust passage of the chimney 6d, NOx.O ₂
Sensors 23 and 24 for detecting the respective values are provided, and the detection values of the sensors 23 and 24 are input to the NOx.O ₂ analyzer 25 for analysis, and based on the analysis result, the control device 9 causes the two-fluid spray. The reducing agent supplied to the nozzle 13, the flow rate of air, the flow rate of dilution air supplied to the vent hole 18, and the like are adjusted. Reference numerals 26a and 26b in the figure denote thermometers for detecting exhaust gas temperature, which are provided on the denitration catalyst layer 6b of the denitration reactor 6 and on the downstream side, respectively, and the detected values are input to the control device 9.

Next, the operation of the exhaust gas denitration apparatus 1 of the gas engine having the above-mentioned configuration and the exhaust gas denitration method will be described. When the gas engine 2 is started and the operation of the exhaust gas denitration device 1 is started in response to a command from the control device 9, the digestion gas F from the sewage sludge digestion treatment facility serves as fuel to the adsorber 4 through the fuel pipe 3. After that, the exhaust gas is supplied to the combustion chamber of the gas engine 2 and burned, and the exhaust gas thereof is introduced into the bottom portion of the denitration reactor 6 through the exhaust pipe 5, and further passes through the pretreatment reactor 7 and then the denitration catalyst layers 6b and 6b. It passes through and is emitted to the atmosphere from the chimney 6d.

Meanwhile, in the reducing agent supply device 8, the ammonia water in the tank 12 is sent to the reducing agent pipe 14 by the pump 15, and the air compressor 17
Since the air from is introduced into the reducing agent pipe 14 via the air pipe 16, the ammonia water in a gas-liquid mixed state is supplied to the two-fluid spray nozzle 13, and the exhaust gas passing from the two-fluid spray nozzle 13 through the exhaust pipe 5. Atomized ammonia water is sprayed on. As a result, the exhaust gas containing the mist-like ammonia water comes into contact with the denitration catalyst in the denitration catalyst layers 6b, 6b of the denitration reactor 6, and the nitrogen oxides in the exhaust gas are reduced by ammonia and removed (denitration), From the chimney 6d, exhaust gas whose nitrogen oxides are reduced to below the allowable value is discharged.

[0018] Then, NOx · O ₂ in the exhaust gas before and after denitration detected by the sensors 23 and 24 are analyzed by the NOx · O ₂ analyzer 25, the controller 9 operates based on the result, the The amount of ammonia water supplied to the two-fluid spray nozzle 13, the flow rate of air, the flow rate of dilution air supplied to the ventilation port 18, etc. are adjusted so that the nitrogen oxides in the exhaust gas discharged from the chimney 6d are always kept below a predetermined allowable value. Controlled to be.

In the denitration process of the exhaust gas, digestion gas containing siloxane (organic silica) is sent as fuel to the gas engine 2 side through the fuel pipe 3, but is adsorbed in the middle of the fuel pipe 3. Since the reactor 4 is provided and most of it is adsorbed and removed by the granular activated carbon filled in the adsorption layer 4b inside thereof, the amount of siloxane flowing into the combustion chamber of the gas engine 2 is reduced as much as possible. A small amount of siloxane that has entered the combustion chamber is burned there to become silica oxide (Si ₂ O ₅ ) and reaches the denitration reactor 6 through the exhaust pipe 5, but this silica oxide does not deteriorate the denitration catalyst.

However, since a small amount of unburned gas is also emitted from the gas engine 2, the siloxane contained in this unburned gas is sent to the denitration reactor 6 side through the exhaust pipe 5, but the denitration reaction occurs. Since the pretreatment reactor 7 is provided in the lower part of the reactor 6 (upstream side of the denitration catalyst layer), the siloxane in the unburned gas is treated with the pretreatment agent layer 7 a of the pretreatment reactor 7.
It contacts the spherical alumina inside and burns, adheres to the spherical alumina and is captured by the pretreatment agent layer 7a.

As a result, even if the digested gas F containing siloxane is supplied to the gas engine 2 through the fuel pipe 3 and the exhaust gas containing siloxane is discharged from the gas engine 2, the denitration catalyst layer 6b of the denitration reactor 6 will be described. Siloxane is effectively removed on the upstream side of the denitration catalyst layer 6b.
It remains in b and does not deteriorate the denitration catalyst, and the removal action of nitrogen oxides in the exhaust gas is stably performed.

In the pretreatment reactor 7, the pretreatment agent layer 7a is used.
Since silica oxide adheres to the spherical alumina of No. 1 and the siloxane trapping ability gradually deteriorates, the lid plates at the upper and lower open end portions of the pretreatment reactor 7 are removed, and the used spherical alumina is opened from the lower end opening. Is removed and replaced with new spherical alumina that is charged through the opening on the upper end side, and used spherical alumina is regenerated as necessary.

As described above, according to the exhaust gas denitration method of the gas engine using the digestion gas as the fuel according to this embodiment, the digestion gas F as the fuel is adsorbed by the adsorber 4 in the adsorption layer 4b filled with the granular activated carbon. It is supplied to the gas engine 2 after adsorbing and removing siloxane in the digested gas, and the exhaust gas of the gas engine 2 is passed through the spherical alumina pretreatment agent layer 7a of the pretreatment reactor 7 to obtain unburned gas in the exhaust gas. After removing the siloxane contained in the gas, it is passed through the denitration catalyst layer 6b of the denitration reactor 6 for removing nitrogen oxides in the exhaust gas, so that it is contained in the unburned gas in the exhaust gas of the gas engine 2. The amount of siloxane can be reduced in a gradeable manner, and siloxane contained in a small amount of unburned gas can also be efficiently removed by burning with a pretreatment agent made of spherical alumina. Therefore, it is possible to prevent the inconvenience that the denitration catalyst deteriorates due to the silica oxide generated by the combustion of the siloxane contained in the exhaust gas of the gas engine 2 in the denitration catalyst layer 6b and the denitration performance deteriorates. The nitrogen oxides in the exhaust gas can be removed stably and reliably.

Further, according to the exhaust gas denitration apparatus for a gas engine using digested gas as fuel according to the embodiment, the fuel pipe 3 for supplying the digested gas F to the gas engine 2 is provided with the adsorber 4 filled with granular activated carbon. A pretreatment reactor 7 filled with spherical alumina as a pretreatment agent is provided in the exhaust pipe 5 that connects the gas engine 2 and the denitration catalyst layer 6b of the denitration catalyst 6 for reducing and removing nitrogen oxides in the exhaust gas. So
Before being supplied to the combustion chamber of the gas engine 2, most of the siloxane in the digestion gas F can be adsorbed and removed by the activated carbon of the adsorber 4, and contained in the unburned gas in the exhaust gas of the gas engine 2. The amount of siloxane can be reduced to a small extent, and siloxane contained in a small amount of unburned gas can be burned and removed by the pretreatment agent in the pretreatment reactor 7.

Therefore, it is possible to prevent the disadvantage that the siloxane contained in the exhaust gas of the gas engine burns in the denitration catalyst layer 6b of the denitration reactor 6 and remains as silica oxide inside the denitration catalyst to deteriorate its denitration performance. Therefore, it is possible to easily realize an exhaust gas denitration device that can stably and reliably remove nitrogen oxides in exhaust gas by a denitration catalyst.

By the way, the exhaust gas discharged from the gas engine 2 (gas temperature 300 to 360 ° C., NOx1600) is continuously operated for 6 months or more at a load of 100% by using the digested gas as fuel and driving the power generator. ~ 250
(0 ppm) was denitrified by the exhaust gas denitration apparatus 1 and the denitration state was observed. The denitration rate by the fresh denitration catalyst at the start of denitration was 92.2%.
The denitration rate by the denitration catalyst after use for 9 months was 91.2.
%, And the decrease in the denitration rate was not so much recognized. In the visual inspection of the denitration catalyst after use, no clogging, cracking, bending, discoloration due to adhesion of silica oxide, etc. were observed, and the specific surface area was also the same as that of the fresh denitration catalyst (93 m ² / g).

On the other hand, when the amount of adhered Si of the spherical alumina filled in the pretreatment reactor 7 was analyzed, it was found that 0.028 wt% of fresh spherical alumina was used and 0.282 wt% of the used spherical alumina was used. And increased significantly. This is the result of the siloxane contained in the exhaust gas of the gas engine 2 burning in the pretreatment reactor 7 and adhering as silica oxide to the surface layer of the spherical alumina.

From the above, according to the exhaust gas denitration method and the exhaust gas denitration apparatus for the gas engine of the above-mentioned embodiment,
Even if the siloxane in the digested gas is sent to the denitration reactor 6 side with the exhaust gas of the gas engine 2, the siloxane is effectively captured and removed by the spherical alumina of the pretreatment reactor 7 on the upstream side of the denitration reactor 6. Therefore, it has been clarified that the denitration catalyst of the denitration reactor 6 is not deteriorated with time and the denitration performance is not deteriorated, and the denitration action is stably performed for a long period of time.

In the exhaust gas denitration apparatus 1 for a gas engine of the above-described embodiment, the pretreatment reactor 7 is incorporated in the denitration reactor 6 on the upstream side of the denitration catalyst layer 6b. 7 and the denitration reactor 6 can be easily manufactured as a single device, and the arrangement and piping of the devices constituting the exhaust gas denitration device 1 are easy, which is preferable, but not limited to this, and a pretreatment reactor 7 may be configured as a device independent of the denitration reactor 6, and may be installed on the upstream side of the denitration reactor 6 and connected to the denitration reactor 6 through an exhaust pipe.

Further, in the exhaust gas denitration apparatus 1 for a gas engine of the above-mentioned embodiment, since the pretreatment agent is spherical alumina containing alumina oxide as a main component, it is inexpensive and easily available. In addition, the strength and surface area of the pretreatment catalyst can be increased, so that the siloxane can be effectively burned and captured from the exhaust gas, and the pretreatment agent can be regularly replaced, regenerated, and operated easily. However, the pretreatment agent is not limited to spherical alumina, and may be pellet-shaped, honeycomb-shaped, or other-shaped alumina oxide. Not limited to alumina oxide, titanium oxide, tungsten oxide, vanadium oxide, copper oxide, etc. It may be an oxide of another metal.

[0031]

As described above, the present invention has the following excellent effects. According to the exhaust gas denitration method for a gas engine using digestion gas as a fuel according to claim 1, the exhaust gas of the gas engine is passed through the packed bed of spherical alumina and then through the packed bed of the denitration catalyst of the denitration reactor. Therefore, the siloxane contained in the unburned gas in the exhaust gas of the gas engine can be efficiently burned by the pretreatment catalyst made of spherical alumina. Therefore, it is possible to prevent the inconvenience that the denitration catalyst deteriorates due to the silica oxide generated by the combustion of the siloxane contained in the exhaust gas of the gas engine in the denitration catalyst layer, and the denitration performance decreases. It is possible to stably and reliably remove the nitrogen oxides.

According to the exhaust gas denitration apparatus for a gas engine using digested gas as a fuel according to the second aspect, an adsorber filled with activated carbon is provided in a flow path for supplying the digested gas to the gas engine, and the denitration reaction with the gas engine. Since a pretreatment reactor filled with a pretreatment catalyst was installed in the exhaust gas flow path that communicates with the packed bed of the denitration catalyst in the reactor, the siloxane in the digested gas is adsorbed before it is supplied to the combustion chamber of the gas engine. Most of it can be adsorbed and removed by the activated carbon of the above, and the siloxane contained in the unburned gas in the exhaust gas of the gas engine can be reduced to a small extent, and the siloxane contained in the unburned gas can also be pretreated. It can be removed by burning with the pretreatment catalyst. Therefore, it is possible to prevent the inconvenience that siloxane contained in the exhaust gas burns in the denitration catalyst layer of the denitration reactor and remains as silica oxide inside the denitration catalyst to lower its denitration performance. It is possible to easily realize an exhaust gas denitration device that can stably and reliably remove the nitrogen oxides.

According to the exhaust gas denitration apparatus for a gas engine using digestion gas as a fuel according to the third aspect, the pretreatment reactor comprises:
Since it was installed in the denitration reactor on the upstream side of the packed bed of the denitration catalyst, the pretreatment reactor and the denitration reactor can be easily manufactured as a single device, and the exhaust gas denitration device Placement and piping are easy.

According to the exhaust gas denitration apparatus for a gas engine using digestion gas as a fuel according to the fourth aspect, since the pretreatment catalyst is spherical alumina, the strength and surface area of the pretreatment catalyst can be increased and the exhaust gas Combustion of siloxane from,
The trapping can be effectively performed, and the periodical replacement of the pretreatment catalyst, the regeneration treatment, and the operation can be easily performed.

[Brief description of drawings]

FIG. 1 is a system diagram showing an exhaust gas denitration device of a gas engine using digestive gas as a fuel according to an embodiment of the present invention.

[Explanation of symbols]

1 Exhaust gas denitration device 2 Gas engine 3 Fuel pipe (flow passage) 4 Adsorber 4b Adsorption layer (activated carbon filling layer) 5 Exhaust pipe (flow passage) 6 Denitration reactor 6b Denitration catalyst layer (denitration catalyst filling layer) 7 Previous Treatment reactor 7a Pretreatment agent layer 8 Reducing agent supply device 9 Control device 12 Tank 13 Two-fluid spray nozzle 14 Reducing agent pipe 15 Pump 17 Air compressor 18 Vent port 20 Blower

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Claims (4)

[Claims] 1. A denitration method for removing exhaust gas of a gas engine using digestive gas as a fuel through a denitration reactor filled with a denitration catalyst to reduce and remove nitrogen oxides in the exhaust gas with a reducing agent. The exhaust gas denitration method for a gas engine using digested gas as a fuel, wherein the exhaust gas of (1) is passed through a packed bed of spherical alumina and then through a packed bed of a denitration catalyst of a denitration reactor. 2. A denitrification apparatus for removing exhaust gas of a gas engine using digestive gas as a fuel through a denitrification reactor filled with a denitrification catalyst to reduce nitrogen oxides in the exhaust gas by reducing with a reducing agent. A pretreatment reactor in which an adsorber filled with activated carbon is provided in a flow path for supplying gas to a gas engine, and a pretreatment catalyst is filled in a flow path of exhaust gas that connects the gas engine and a packed bed of the denitration catalyst in the denitration reactor. An exhaust gas denitration device for a gas engine that uses digestive gas as fuel. 3. The gas using digestion gas as a fuel according to claim 2, wherein the pretreatment reactor is installed in the denitration reactor upstream of the packed bed of the denitration catalyst. Exhaust gas denitration equipment for engines. 4. The exhaust gas denitration device for a gas engine using digestive gas as a fuel according to claim 2, wherein the pretreatment catalyst is spherical alumina.