GB1568588A - Creación de Inventos y Patentes con Inteligencia Artificial

GB1568588A – Boilers with means for reducing and removing nitrogen oxides from combustion gases
– Google Patents

GB1568588A – Boilers with means for reducing and removing nitrogen oxides from combustion gases
– Google Patents
Boilers with means for reducing and removing nitrogen oxides from combustion gases

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Publication number
GB1568588A

GB1568588A
GB2807677A
GB2807677A
GB1568588A
GB 1568588 A
GB1568588 A
GB 1568588A
GB 2807677 A
GB2807677 A
GB 2807677A
GB 2807677 A
GB2807677 A
GB 2807677A
GB 1568588 A
GB1568588 A
GB 1568588A
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GB
United Kingdom
Prior art keywords
boiler
catalyst layer
gas
catalyst
reductant
Prior art date
1977-07-05
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Expired

Application number
GB2807677A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Hitachi Zosen Corp

Original Assignee
Hitachi Zosen Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1977-07-05
Filing date
1977-07-05
Publication date
1980-06-04

1977-07-05
Application filed by Hitachi Zosen Corp
filed
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Hitachi Zosen Corp

1977-07-05
Priority to GB2807677A
priority
Critical
patent/GB1568588A/en

1980-06-04
Publication of GB1568588A
publication
Critical
patent/GB1568588A/en

Status
Expired
legal-status
Critical
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Classifications

F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES

F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES

F23J15/00—Arrangements of devices for treating smoke or fumes

F23J15/02—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material

B—PERFORMING OPERATIONS; TRANSPORTING

B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL

B01D—SEPARATION

B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols

B01D53/34—Chemical or biological purification of waste gases

B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases

B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes

B01D53/9404—Removing only nitrogen compounds

B01D53/9409—Nitrogen oxides

B01D53/9431—Processes characterised by a specific device

F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

F22—STEAM GENERATION

F22B—METHODS OF STEAM GENERATION; STEAM BOILERS

F22B33/00—Steam-generation plants, e.g. comprising steam boilers of different types in mutual association

F22B33/18—Combinations of steam boilers with other apparatus

F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

F22—STEAM GENERATION

F22B—METHODS OF STEAM GENERATION; STEAM BOILERS

F22B37/00—Component parts or details of steam boilers

F22B37/008—Adaptations for flue gas purification in steam generators

Description

(54) IMPROVEMENTS RELATING TO BOILERS WITH MEANS
FOR REDUCING AND REMOVING NITROGEN OXIDES FROM
COMBUSTION GASES
(71) We, HITACHI SHIPBUILDING & ENGINEERING CO., LTD., of 914 Edobod l-chone, Nishi-ku, Osaka, Japan, a company organized under the laws of Japan, do hereby declare the invention for which we tray that a Patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: The put invention relates to a boiler containing a denitrator, and more particularly it relates to a boiler internally equipped with a reactor for reducing and removing nitrogen oxides contained in comSion gas.
Various combustion devices having boilers or waste heat boilers have a denitrator attached thereto for removing nitrogen oxides contained in exhaust gas. Conventionally, such a deitrator is disposed downstream of a dust collector, i.e., in the flue immediately up steam of a chimney. With this arrangement, however, since the temperature of the exhaust gas introduced into the denitrator is too low to cause denitration, it has been necessary to provide said denitrator with a temperature raising furnace and a rotary heat exchanger.
More particularly, the present invention relates to a denitrator which operates on the basis of dry type smoke denitration which is ane of the methods of removing nitrogen oxides (NOx) from exhaust gas. Of these methods one wih is based on a reaction with ammonia expsesd by the following formula is most effective.
4NH, + 6NO o 5N2 + 6H20
Such a reaction for denitration as exemplified by the above formula is caused by the action of a catalyst and the properties of the catalyst are the most important factors. Optimum reaction temperatures for such catalysts mostly are within a range of 350–500C. On the other hand, the temperature of exhaust gas from a boiler exit is about 200″C, which accounts for the necessity of providing a denitrator with additional means for raising waste gas temperature as described above.
Further, since the catalysts used in conventional denitrators are in the form of pellets, the construction is such that the catalyst layer is liable to have any soot contained in exhaust gas collected thereon. For this reason, it has been necessary to install the denitrator downstream of the dust collector, as described above, and hence it cannot be helped that the temperature of exhaust gas becomes further decreased.
Further, since the catalyst is in the form of pellets, no matter how much the catalyst layer is widened to reduce the thickness, it has been necessary to use a blower or the like since the pressure loss due to the catalyst layer is high. Further, this has been a cause of the denitrator having to be separately installed.
The present invention is based on the fact that in the comubstion gas channel in a boiler there is always a region where the temperature conditions are most suited for reduction of nitrogen oxides. The principal object of the invention is to install a denitration catalyst layer and, if necessary, means for feeding a reductant such as ammonia in said region having the optimum temperature conditions upstream of one of a plurality of heat exchangers in a combustion gas channel, thereby making it possible to remove nitrogen oxides without providing a separate temperature raising furnace, a rotary heat exchanger, a blower and a catalyst-layer-filled container, thereby reducing floor space for installation and saving cost of construction.
According to the invention there is provided a boiler containing a denitration catalyst layer disposed in an optimum catalytic reaction temperature region between two of said heat exchangers, said catalyst layer being constituted by a number of plate-like denitration catalyst units disposed with their plate surfaces extending along the direction of flow of combustion gas. Preferably, each catalyst unit comprises a plurality of shaped plates of wavy or corrugated form, which may be interleaved with flat plates, to form gas flow passages. The use of such plate-like catalyst units minimizes pressure loss and soot collection and facilitates soot blowing, which brings about the fact that no trouble will be caused even if the catalyst layer is not disposed downstream of the dust collector.
In one embodiment of the invention the denitrator is contained in the boiler, and the plate-like catalyst units are assembled as a block in a box with two opposed surfaces facing in the direction of gas flow which are open, such units being combined in a block to form said catalyst layer. Assembly of the catalyst layer and its maintenance, control and replacement of catalyst are very easy.
A waste heat boiler containing such a denitrator as described above, may be supplied with waste gas from a gas turbine, said denitrator catalyst layer and, if necessary, re
ductant feeding means being disposed between two of the heat exchangers, preferably a superheater and an evaporator.
An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a schematic view showing the outline of the construction of a waste heat boiler which is a type of boiler with which the invention is concerned, and also showing a preferred manner of use thereof.
Figure 2 is a sectional view taken along the line II–II of Figure 1;
Figure 3 is a perspective view of a catalyst unit;
Figure 4 is an enlarged plan view of a part of the catalyst unit; and
Figure 5 is a perspective view of a catalyst container into which catalyst units will be assembled.
Referring to Figure 1, the numeral 1 designates a waste heat boiler shown as an example of one of various boilers. The lower end of said boiler is formed with a combustion gas inlet 2 and the upper end with an outlet 3 to a flue 18. Disposed inside said boiler, in the direction of gas flow from bottom upward, are three heat exchangers, namely a superheater 4, an evaporator 5, and an economizes 6, in the order mentioned. Connected to the combustion gas inlet 2 is a waste gas channel 8 from a gas turbine, for example, in an electric power station, and in this case, the heat exchangers are usually so designed that combustion gas may have a temperature of about 6500C when entering the superheater 4, about 300″C when entering the evaporator 5 and about 2000C when entering the eco nozer 6. Therefore, it follows that the optimum reaction temperature region for the ckest exists exist between the superheater 4 and the evaporator 5. The numeral 9 designates a compressor for the gas turbine 7; 10, a naphta supplying device; 11, a turbine; and 12 designates an electric generator connected to the output shaft of the turbine 11. The heat exchangers 4, 5 and 6 in said waste heat boiler 1 are used for additional electric power generation by recovered heat. More particularly, there are provided an accumulator 13, a steam turbine 14 having its output shaft connected to a electric generator 15, and a steam condenser 16, and these units and said superheater 4, evaporator 5 and economizer 6 are connected together in the manner shown in Figure 1 to constitute a heat cycle engine.
Designated at 17 is a water replenishing pipe.
In the waste heat boiler 1 constructed in the manner described above, a denitration catalyst layer 20 is provided in the gas flow path downstream of the superheater 4 and upstream of the evaporator 5, and ammonia feeding means 21 for adding ammonia, which is a reductant, to combustion gas is provided upstream of said denitration catalyst layer 20, i.e., on the superheater 4 side. The ammonia feeding means 21, as shown in Figure 2, com- prises a plurality of injection pipes 22 extending into the gas channel of the waste heat boiler 1, and an ammonia supply unit 23 disposed outside the gas channel. The injection pipes 22 are each formed with a number of injection ports 22a, whereby ammonia can be uniformly added to waste gas. Further, the unit 23 comprises an ammonia gas bomb, replacing means and a pressure adjusting device therefor, and a gas leakage preventing device.
The denitration catalyst layer 20 is constituted by a number of plate-like denitration catalyst units disposed with their plate surfaces extending along the direction of flow of combustion gas. In a desired form, as shown in
Figures 3 and 4, there is used a honey-combshaped catalyst 25 which is a combination of plate-like catalyst bodies 25a and corrugated catalyst bodies 25b. Further, in this embodiment each catalyst 25 is formed into a unit 27 by being built in a box 26 whose two opposed surfaces facing in the direction of flow of gas are open, as shown. A predetermined number of such uits 27 are assembled into a framework 28 having support grids 29 at the lower, upstream end, and each framework 28 is arranged on a support frame in the waste heat boiler 1, thereby constituting the catalyst layer 20.
The catalyst 25, may be of the kind described in the applicant’s U.K. Patent No.
1,522,424 (24567/76) or modifications thereof, but the present invention is not concerned with the composition of the catalyst itself and hence catalysts known per se and catalysts of new compositions may be used
According to the arrangement described above, since the denitration catalyst layer 20 and ammonia feeding means 21 are disposed between the superheater 4 and the evaporator 5, i.e. in an optimum catalytic reaction temperature region there is no need to use a temperature raising furnaces rotary heat ex changes and catalyst-layer-filled container, and further, by forming the catalyst layer 20 using plate-like catalyist bodies, pressure loss in the catalyst layer is minimized and hence it is not necessary to use a separate blower for the denitrator. Further, even if the catalyst layer 20 is formed inside the boiler 1, there is no trouble. Moreover, this construction decreases the tendency of soot to collect thereon and facilitates soot blowing. Further, by forming a catalyst into a unit 27 and combining such units to form a catalyst layer, formation, exchange, raaiateccnce and control of the catalyst layer are greatly facilitated.
In the description of the embodiment, the boiler has been described as a waste heat boiler, specifically a waste heat boiler using waste gas from a gas turbine. The essence of the invention, however, lies in the formation of a catalyst layer, specifically a catalyst layer consisting of plate-like catalyst bodies in an optimum catalytic reaction temperature region in a, combustion gas channel, and, therefore, the invention is not limited to a waste heat boiler but is applicable to other boilers. Fur the the denitration has been described as a reaction with ammonia, which is most effec tice, but the invention is applicable to other factions for denitration employing other re ducisats such as carbon monoxide, hydrogen gas, methane gas and other hydrocarbons and catalysts. For example, catalysts desceSi in the applicant’s U.K Patent 1,442,788 and modifications thereof may be ui The described invention provides a boiler baving a plurality of heat exchanger stages sidi as a superheater, an evaporator and a perheater, disposed in a combustion gas channel between heat exchangers including an optimum catalyst reaction temperature region are a denitration catalyst layer crossing said chunnel and a reductant feeding device for adding a reductant such as ammonia gas at a point just upstream of the catalyst layer.
The denitration catalyst layer comprises a number of plate-like catalyst bodies whose plate surfaces exfBnd along the direction of flow of gas, and desirably it is honey-comb- shapes If the boiler is a waste heat boiler, the denitration catalyst layer will be disposed between the superheater and the evaporator.
WHAT WE CLAIM IS:
1. A boiler having a plurality of heat exchanger stages disposed in a combustion gas channel, wherein said boiler contains a denitrator comprising a denitration catalyst layer disposed in an optimum catalytic reaction temperature region between two of said heat exchangers, said catalyst layer being constituted by a number of plate-like denitration catalyst units disposed with their plate surfaces extending along the direction of flow of combustion gas.
2. A boiler according to claim 1, wherein each said catalyst unit comprises a plurality of plate numbers assembled to form a plurality of gas passages.
3. A boiler according to claim 2 wherein the catalyst unit comprises a plurality of shaped plates separated by flat plates to define the gas passages.
4. A boiler according to any one of claims 1 to 3, wherein said plate-like denitration catalyst units are assembled into a block having two opposed surfaces facing in the direction of flow of gas which are open, said catalyst layer consisting of a combination of such units.
5. A boiler according to any one of the preceding claims wherein there is provided reductant feeding means for adding a reductant to the combustion gas upstream of said catalyst layer.
6. A boiler as set forth in claim 5, wherein said reductant feeding means comprises a plurality of injection pipes extending into the gas channel and each having a number of reductant injecting ports, and a reductant feeding unit disposed outside the gas channel and communicating with said injection pipes.
7. A boiler as set forth in claim 5, wherein said reductant is ammonia gas.
8. A boiler as set forth in claim 5, wherein said reductant is CO H2 or a hydrocarbon or combination thereof.
9. A boiler according to any one of the preceding claims wherein said boiler is a waste heat boiler and said denitration catalyst layer is disposed between the superheater and evaporator of said waste heat boiler.
10. A boiler as set forth in claim 9, wherein said waste heat boiler is fed with waste gas from a gas turbine.
11. A boiler substantially as hereinbefore described, with reference to the accompanying drawings.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. between the superheater 4 and the evaporator 5, i.e. in an optimum catalytic reaction temperature region there is no need to use a temperature raising furnaces rotary heat ex changes and catalyst-layer-filled container, and further, by forming the catalyst layer 20 using plate-like catalyist bodies, pressure loss in the catalyst layer is minimized and hence it is not necessary to use a separate blower for the denitrator. Further, even if the catalyst layer 20 is formed inside the boiler 1, there is no trouble. Moreover, this construction decreases the tendency of soot to collect thereon and facilitates soot blowing. Further, by forming a catalyst into a unit 27 and combining such units to form a catalyst layer, formation, exchange, raaiateccnce and control of the catalyst layer are greatly facilitated. In the description of the embodiment, the boiler has been described as a waste heat boiler, specifically a waste heat boiler using waste gas from a gas turbine. The essence of the invention, however, lies in the formation of a catalyst layer, specifically a catalyst layer consisting of plate-like catalyst bodies in an optimum catalytic reaction temperature region in a, combustion gas channel, and, therefore, the invention is not limited to a waste heat boiler but is applicable to other boilers. Fur the the denitration has been described as a reaction with ammonia, which is most effec tice, but the invention is applicable to other factions for denitration employing other re ducisats such as carbon monoxide, hydrogen gas, methane gas and other hydrocarbons and catalysts. For example, catalysts desceSi in the applicant’s U.K Patent 1,442,788 and modifications thereof may be ui The described invention provides a boiler baving a plurality of heat exchanger stages sidi as a superheater, an evaporator and a perheater, disposed in a combustion gas channel between heat exchangers including an optimum catalyst reaction temperature region are a denitration catalyst layer crossing said chunnel and a reductant feeding device for adding a reductant such as ammonia gas at a point just upstream of the catalyst layer. The denitration catalyst layer comprises a number of plate-like catalyst bodies whose plate surfaces exfBnd along the direction of flow of gas, and desirably it is honey-comb- shapes If the boiler is a waste heat boiler, the denitration catalyst layer will be disposed between the superheater and the evaporator. WHAT WE CLAIM IS:

1. A boiler having a plurality of heat exchanger stages disposed in a combustion gas channel, wherein said boiler contains a denitrator comprising a denitration catalyst layer disposed in an optimum catalytic reaction temperature region between two of said heat exchangers, said catalyst layer being constituted by a number of plate-like denitration catalyst units disposed with their plate surfaces extending along the direction of flow of combustion gas.

2. A boiler according to claim 1, wherein each said catalyst unit comprises a plurality of plate numbers assembled to form a plurality of gas passages.

3. A boiler according to claim 2 wherein the catalyst unit comprises a plurality of shaped plates separated by flat plates to define the gas passages.

4. A boiler according to any one of claims 1 to 3, wherein said plate-like denitration catalyst units are assembled into a block having two opposed surfaces facing in the direction of flow of gas which are open, said catalyst layer consisting of a combination of such units.

5. A boiler according to any one of the preceding claims wherein there is provided reductant feeding means for adding a reductant to the combustion gas upstream of said catalyst layer.

6. A boiler as set forth in claim 5, wherein said reductant feeding means comprises a plurality of injection pipes extending into the gas channel and each having a number of reductant injecting ports, and a reductant feeding unit disposed outside the gas channel and communicating with said injection pipes.

7. A boiler as set forth in claim 5, wherein said reductant is ammonia gas.

8. A boiler as set forth in claim 5, wherein said reductant is CO H2 or a hydrocarbon or combination thereof.

9. A boiler according to any one of the preceding claims wherein said boiler is a waste heat boiler and said denitration catalyst layer is disposed between the superheater and evaporator of said waste heat boiler.

10. A boiler as set forth in claim 9, wherein said waste heat boiler is fed with waste gas from a gas turbine.

11. A boiler substantially as hereinbefore described, with reference to the accompanying drawings.

GB2807677A
1977-07-05
1977-07-05
Boilers with means for reducing and removing nitrogen oxides from combustion gases

Expired

GB1568588A
(en)

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Application Number
Priority Date
Filing Date
Title

GB2807677A

GB1568588A
(en)

1977-07-05
1977-07-05
Boilers with means for reducing and removing nitrogen oxides from combustion gases

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Priority Date
Filing Date
Title

GB2807677A

GB1568588A
(en)

1977-07-05
1977-07-05
Boilers with means for reducing and removing nitrogen oxides from combustion gases

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GB1568588A
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GB1568588A
(en)

1980-06-04

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GB1568588A
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1977-07-05
1977-07-05
Boilers with means for reducing and removing nitrogen oxides from combustion gases

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GB1568588A
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1977

1977-07-05
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GB2807677A
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