[0001] The present invention relates to a 5 denitration apparatus.
BACKGROUND ART
[0002] Various devices used for removing nitrogen oxides from combustion exhaust gas have been 10 proposed.
For example, Patent Document 1 discloses a denitration apparatus, characterized in that a reducing agent injection device is arranged upstream of a denitration reactor having a built-15 in catalyst layer, the reducing agent injected from the reducing agent injection device is reacted with nitrogen oxide in exhaust gas, a strainer grid that partitions the gas flow direction is arranged between the reducing agent 20 injection device and the catalyst layer, and a gas mixing promoter of the exhaust gas and the reducing agent is provided in at least one area of the strainer grid.
[0003] Patent Document 2 discloses a flue-gas 25 denitration apparatus, characterized in that a temperature of an exhaust gas is raised with a heat exchanger and the exhaust gas is reduced with a reducing agent to remove nitrogen oxides in the exhaust gas through a denitration catalyst, a 30 rectifying plate is installed upstream of the heat 2
exchanger, the heat exchanger is arranged so as to face the denitration catalyst, and the reducing agent is injected from a reducing agent injection tube inserted between the heat exchanger and the denitration catalyst. 5
[0004] Patent Document 3 discloses an ammonia gas injection device, characterized in that a plurality of mother pipes arranged perpendicular to the exhaust gas flow, a plurality of protruding pipes projecting from the side surface of the 10 mother pipe and nozzles are provided in an exhaust gas flow path, the nozzles open toward the downstream direction of the exhaust gas flow at an end portion of each of the protruding pipes, the distance between the center line of each 15 nozzle and the side surface of the mother pipe is larger than the outer diameter of the mother pipe, the nozzles are positioned so as to be located at each apex of a plurality of regular triangles adjacent to each other in a cross section 20 orthogonal to the exhaust gas flow, and an exhaust gas rectifier is set on the upstream side of the exhaust gas flow from the nozzle.
[0005] In Patent Document 4, described is a denitration agent injection device characterized 25 in that a denitration agent is injected into the exhaust gas flow to remove nitrogen oxides, a denitration agent supply pipe is arranged in the exhaust gas flow on the downstream side of the denitration agent injection pipe, the denitration 30 agent injection pipe and the denitration agent
3
supply pipe are connected, the denitration agent supply pipe is utilized as an element for supplying the denitration agent, heating the denitration agent and facilitating injection, denitration and mixing. 5
[0006] Patent Document 5 discloses an ammonia injection pipe characterized in that an ammonia injection nozzle portion is arranged in a waste gas, nitrogen oxide in the waste gas is reduced by spraying ammonia, and a pipe on the upstream 10 side of the ammonia injection nozzle portion is used as an ammonia heating unit to heat ammonia by heat possessed by the waste gas.
CITATION LIST 15
PATENT LITERATURES
[0007] [Patent Document 1] JP H10-165769 A
[Patent Document 2] JP H10-57770 A
[Patent Document 3] JP H08-89754 A
[Patent Document 4] JP S60-12120 A 20
[Patent Document 5] JP S56-10322 A
SUMMARY OF THE INVENTION
PROBLEMS TO BE RESOLVED BY THE INVENTION
[0008] An object of the present invention is to 25 provide a novel denitration apparatus.
MEANS FOR SOLVING THE PROBLEMS
[0009] The present invention includes the following aspects. 30
[0010] [1] A denitration apparatus, comprising 4
a reactor duct having a flow path for flowing an exhaust gas from a boiler,
a screen plate,
a denitration agent supply line system, and
a fixed bed, 5
wherein the fixed bed comprises a denitration catalyst,
the screen plate, the denitration agent supply line system and the fixed bed are set in this order along the flow of the exhaust gas in the 10 reactor duct,
the denitration agent supply line system comprises a heat exchange line for warming a denitration agent with the heat possessed by the exhaust gas, a transportation line for supplying 15 the denitration agent warmed by the heat exchange line to a nozzle, and the nozzle for injecting the denitration agent supplied through the transportation line into the reactor duct.
[0011] [2] A denitration apparatus, comprising 20
an entrance duct having a flow path for flowing an exhaust gas from a boiler in the horizontal direction,
a joint duct having a flow path for changing the flow of the exhaust gas from the horizontal 25 direction to the vertical direction,
a reactor duct having a flow path for flowing the exhaust gas in the vertical direction.
a screen plate,
a denitration agent supply line system, and 30
a fixed bed, 5
wherein the fixed bed comprises a denitration catalyst,
the screen plate, the denitration agent supply line system and the fixed bed are set in this order along the flow of the exhaust gas in the 5 reactor duct,
the denitration agent supply line system comprises a heat exchange line for warming a denitration agent with the heat possessed by the exhaust gas, a transportation line for supplying 10 the denitration agent warmed by the heat exchange line to a nozzle, and the nozzle for injecting the denitration agent supplied through the transportation line into the reactor duct.
[0012] [3] The denitration apparatus according to [1] 15 or [2], further comprising a structure for holding the screen plate, wherein the denitration agent supply line system is held by the structure for holding the screen plate.
[4] The denitration apparatus according to [1] 20 or [2], further comprising a structure for holding the screen plate and a structure for holding the denitration agent supply line system, wherein the denitration agent supply line system is held by the structure for holding the denitration agent 25 supply line system.
[5] The denitration apparatus according to any one of [1] to [4], wherein the denitration agent supply line system further comprises a baffle.
[6] The denitration apparatus according to any 30 one of [1] to [5], wherein at least a part of the
6
heat exchange line has fins.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0013] The denitration apparatus of the present invention can uniformly mix the exhaust gas and 5 the denitration agent, and the flow of the exhaust gas introduced into the fixed bed is unlikely to be biased, so that the denitration efficiency is extremely high. The denitration apparatus of the present invention is less likely to cause 10 occlusion of the fixed bed and uneven attrition of the fixed bed, can suppress equipment troubles due to the generation of ammonium sulfate, and can be stably operated for a long period of time.
In the denitration apparatus of the present 15 invention, the denitration agent is injected between the screen plate and the catalytic fixed bed, preferably at a place where the gas flow is not biased, so that the denitration agent is uniformly supplied to the catalytic fixed bed. 20 Moreover, the amount of denitration agent that slips through without reacting with the catalyst is small. As a result, it is not necessary to inject an excessive amount of the denitration agent far exceeding the stoichiometric ratio of 25 the denitration agent in the denitration reaction, and the running cost can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a diagram showing a first embodiment of 30 a denitration apparatus according to the present
7
invention.
FIG. 2 is a diagram showing a second embodiment of the denitration apparatus according to the present invention.
FIG. 3 is an oblique view showing an example of a 5 denitration agent supply line system (with fins).
FIG. 4 is a cross-sectional view showing an example of a denitration agent supply line system (with a gable baffle).
FIG. 5 is a cross-sectional view showing an 10 example of a denitration agent supply line system (with a wing baffle).
FIG. 6 is a diagram showing a third embodiment of the denitration apparatus according to the present invention. 15
FIG. 7 is an oblique view showing an example of a denitration agent supply line system (without fins).
EMBODIMENTS FOR CARRYING OUT THE INVENTION 20
[0015] Embodiments of the present invention will be specifically described with reference to the drawings. The scope of the present invention is not limited by the following embodiments.
[0016] FIG. 1 is a diagram showing a first 25 embodiment of the denitration apparatus according to the present invention. The denitration apparatus of the first embodiment comprises a reactor duct 6 having a flow path for flowing an exhaust gas from a boiler. A screen plate 3 30 comprising a plurality of louver plates, a 8
denitration agent supply line system 7, and a fixed bed 4 are set in this order along the flow of the exhaust gas in the reactor duct. The fixed bed comprises a catalyst for removing nitrogen oxides from the exhaust gas. The louver plate is 5 usually composed of a flat plate or the like. The denitration agent supply line system 7 comprises a heat exchange line 8 for warming the denitration agent with the heat possessed by the exhaust gas, a transportation line 9 for supplying the 10 denitration agent warmed by the heat exchange line to the nozzle, and a nozzle 10 for injecting the denitration agent supplied through the transportation line into the reactor duct.
[0017] FIG. 2 is a diagram showing a second 15 embodiment of the denitration apparatus according to the present invention. The denitration apparatus of the second embodiment comprises an entrance duct 1, a joint duct 2, a reactor duct 6, and an exit duct 5. The exhaust gas G from 20 the boiler flows in the order of the entrance duct 1, the joint duct 2, the reactor duct 6, and the exit duct 5.
[0018] In the denitration apparatus of the second embodiment, the entrance duct 1 has a flow path 25 through which the exhaust gas from the boiler flows in the horizontal direction. In FIG. 2, the wall constituting the upper side and the wall constituting the lower side of the flow path of the entrance duct 1 are drawn by a straight line 30 respectively. The cross-sectional shape of the
9
flow path of the entrance duct when viewed from the gas flow direction can be rectangular, trapezoidal, circular, elliptical or the like. Of these, a rectangle is preferable in terms of ease of processing. 5
[0019] In the denitration apparatus of the second embodiment, the joint duct 2 has a flow path that changes the flow of exhaust gas from the horizontal direction to the vertical direction. The joint duct shown in FIG. 2 changes the flow 10 downward, but may change the flow upward as shown in FIG. 6. The orientation of the joint duct can be appropriately selected in consideration of the installation space and layout of the denitration apparatus. In FIG. 2, the wall constituting the 15 upper side and the wall constituting the lower side of the flow path of the joint duct 2 are drawn by a straight line respectively. The walls constituting the upper side and the lower side of the flow path of the joint duct 2 may draw an 20 arc curve when viewed from the same viewpoint as in FIG. 2. Further, the wall constituting the lower side of the flow path of the joint duct 2 may be omitted, instead the wall constituting the lower side of the flow path of the entrance duct 25 1 and the wall constituting the side of the flow path of the reaction duct 6 close to the entrance duct 1 may be directly connected. The cross-sectional shape of the flow path of the joint duct 1 when viewed from the gas flow direction can be 30 rectangular, trapezoidal, circular, elliptical,
10
or the like. Of these, a rectangle is preferable in terms of ease of processing.
[0020] In the denitration apparatus of the second embodiment, the reactor duct 6 has a flow path through which the exhaust gas flows in the 5 vertical direction. In FIG. 2, the walls constituting the side of the flow path of the reactor duct 6 close to and away from the entrance duct are drawn by a straight line respectively. The cross-sectional shape of the flow path of the 10 reactor duct when viewed from the gas flow direction can be rectangular, trapezoidal, circular, elliptical or the like. Of these, a rectangle is preferable in terms of ease of processing. The size of the flow path cross 15 section of the reactor duct is preferably substantially the same from the inlet of the reactor duct, through the outlet of the catalytic fixed bed, to the outlet of the reactor duct. The outlet of the reactor duct is usually connected 20 to the inlet of the exit duct 5.
[0021] A screen plate 3, a denitration agent supply line system 7, and a catalytic fixed bed 4 are provided in the reactor duct. The screen plate 3 is arranged on the inlet side of the 25 reactor duct. A structure for holding the screen plate, such as a beam bridged in the reactor duct, is installed on the inlet side of the reactor duct (not shown). The screen plate is held in the reactor duct by the structure for holding the 30 screen plate. The catalytic fixed bed 4 is 11
arranged on the outlet side of the reactor duct. A structure for holding the catalytic fixed bed, such as a beam bridged in the reactor duct, is installed on the outlet side of the reactor duct (not shown). The catalytic fixed bed is held in 5 the reactor duct by the structure for holding the catalytic fixed bed. The denitration agent supply line system 7 is arranged between the screen plate and the catalytic fixed bed. The denitration agent supply line system is preferably arranged 10 closer to the screen plate than the catalytic fixed bed. The denitration agent supply line system may be held by the screen plate holding structure or the catalytic fixed bed holding structure described above. Alternatively, a 15 structure for holding the denitration agent supply line system, for example, a beam or the like bridged in the reactor duct, may be installed between the screen plate and the catalytic fixed bed to hold the denitration agent supply line 20 system in the reactor duct. The method of holding is not particularly limited, and for example, it may be placed on the holding structure installed below, suspended from the holding structure installed above, or mounted on the holding 25 structure installed aside.
[0022] The screen plate preferably comprises a plurality of louver plates. The plurality of louver plates are usually arranged so that the main surfaces are parallel to each other. In 30 order to fix such arrangement of multiple louver 12
plates, rod materials or plate materials (cross members) may be joined to each louver plate in a direction orthogonal to the main surface of each louver plate to form a grid. Outer frame members (end members) may be set at both ends of the 5 plurality of louver plates.
The screen plate is preferably installed on the inlet side of the flow path of the reactor duct 6 so that the main surface of the louver plate is substantially orthogonal to the gas flow 10 direction in the entrance duct 1 over the entire cross section of the flow path of the reactor duct and is substantially parallel to the gas flow direction in the reactor duct 6.
The installation of the screen plate is 15 performed at the inlet of the flow path of the reactor duct 6 as the following. A beam is bridged between the two facing insides the wall of the flow path, for example, in parallel or perpendicular to the gas flow direction in the 20 entrance duct 1 or in form of a grid. A screen plate unit is put on the beam or bridged between the beams. The screen plate is composed of the plurality of screen plate units. The screen plate unit may be composed of the louver plate and the 25 cross member or the end member joined in a ladder shape or a grid shape, a grating shape, or the like.
[0023] The denitration agent supply line system comprises a heat exchange line 8 for warming the 30 denitration agent with the heat possessed by the
13
exhaust gas, a transportation line 9 for supplying the denitration agent warmed by the heat exchange line to a nozzle, and the nozzle 10 for injecting the supplied denitration agent through the transportation line into the reactor duct. 5
[0024] The heat exchange line 8 is a pipe line in which heat transfer tubes are arranged so as to be orthogonal to the gas flow in the reactor duct. The heat exchange line may have one horizontal structure composed of heat transfer tubes 10 arranged in a zigzag shape, a spread shape sideways like skewered, or a comb shape. The heat exchange line 8 may have a plurality of the horizontal structures in vertically parallel or vertically staggered composed of heat transfer 15 tubes. As the heat transfer tube, a tube having a high thermal conductivity in the shape of a straight line or a curved line can be used. The cross-sectional shape of the heat transfer tube may be circular, polygonal, or the like. The 20 inside the wall of the heat transfer tube may be smooth, but may be grooved to improve thermal conductivity. A heat transfer tube having a spiral groove on the inside the wall is preferably used. The heat transfer tube may have fins 13 on 25 the outside of the wall. Examples of the fins can include plate fins, corrugated fins, slit fins, spiral fins, and aero fins. The fins are preferably arranged so that their main surface is parallel or perpendicular to the main surface of 30 the louver plate and substantially parallel to 14
the gas flow direction in the reactor duct 6. The end of the heat exchange line inlet is connected to a tube from a denitration agent tank outside the reactor duct, and the end of the heat exchange line outlet is connected to the end of 5 the transportation line inlet. As the denitration agent, one obtained by diluting ammonia gas with air is preferably used. It is preferable to warm the ammonia gas in the heat exchange line to a temperature at which ammonium 10 sulfate is not generated in the reactor duct.
[0025] The transportation line 9 is a pipe line in which the supply tubes are arranged so as to be orthogonal to the gas flow in the reactor duct. As the supply tube, a straight or curved tube can 15 be used. The cross-sectional shape of the supply tube may be circular, polygonal, or the like. The inside the wall of the supply tube is preferably smooth from the viewpoint of reducing pressure loss. The transportation line has preferably one 20 horizontal structure composed of supply tubes arranged in a zigzag shape, a spread shape sideways like skewered, or a comb shape. The transportation line can be installed in the reactor duct either at the same height level as 25 the heat exchange line, at a height level lower than the heat exchange line, or at a height level higher than the heat exchange line. It is preferable to install at a height level higher than the heat exchange line. The transportation 30 line is preferably arranged so that the
15
longitudinal direction of the supply tube is parallel or perpendicular to the main surface of the louver plate.
[0026] The nozzle 10 is not particularly limited in its shape as long as it can supply the 5 denitration agent into the reactor duct. At least one nozzle can be installed in the middle or at the end of the supply tube. The nozzle is preferably installed so that the denitration agent is supplied in the same direction as the 10 gas flow in the reactor duct. The nozzle is preferably installed so that the transportation line or the heat exchange line is arranged downstream of the nozzle, since the flow disturbance by the transportation line or the heat 15 exchange line uniformly mixes the supplied denitration agent and the exhaust gas. The number of nozzles installed is not particularly limited as long as the denitration agent can be uniformly supplied into the reactor duct. The 20 nozzles can also be installed in a staggered or parallel arrangement. The staggered arrangement, angle, etc. can be set as appropriate.
[0027] FIG. 3 is a conceptual diagram of the denitration agent supply line system 7 shown in 25 FIG. 2 when viewed from diagonally below. In the heat exchange line shown in FIG. 3, fins 13 are provided on a part of the outside of the heat transfer tube 8, and the heat transfer tubes 8 are piped in a zigzag shape. If the heat transfer 30 coefficient of the heat exchange line is
16
sufficiently large, the fins may not be provided as shown in FIG. 7. In the transportation line shown in FIG. 3, the supply tubes 9 are arranged in a spread shape sideways like skewered, and a plurality of nozzles 10 are installed in the 5 middle and at the ends of the supply tubes 9.
[0028] The denitration agent supply line system may further comprises a baffle. The baffle is not particularly limited by its shape, and may be, for example, a gable-shaped baffle extending 10 along the ridgeline of the supply tube in which the nozzle is installed (gable baffle 11, see FIG. 4), or a wing shaped baffle spread out both sides of the supply tube in which the nozzle is installed (wing baffle 12, see FIG. 5). 15
[0029] In the denitration apparatus of the present invention, nitrogen oxides come into uniform contact with the catalytic fixed bed together with the denitration agent, so that the reaction ratio in the catalytic fixed bed can be increased. In 20 addition, since the dust contained in the combustion exhaust gas comes into uniform contact with the catalytic fixed bed, local attrition of the catalytic fixed bed or local accumulation of dust on the catalytic fixed bed can be prevented, 25 and local deterioration of the catalyst can be suppressed. In the denitration apparatus of the present invention, suppressed can be the reaction between the sulfur component that may be contained in the combustion exhaust gas and ammonia which 30 is one of the denitration agents, and decreased
17
can be the production of ammonium sulfate.
EXPLANATION OF SYMBOLS
[0030] 1: Entrance duct
2: Joint duct 5
3: Screen plate
4: Catalytic fixed bed
5: Exit duct
6: Reactor duct
7: Denitration agent (NH3) supply line system 10
8: Heat exchange line
9: Transportation line
10: Nozzle
11: Gable baffle
12: Wing baffle 15
13: Fin
G: Exhaust gas

We Claim:

1. A denitration apparatus, comprising
a reactor duct having a flow path for flowing an exhaust gas from a boiler, 5
a screen plate,
a denitration agent supply line system, and
a fixed bed,
wherein the fixed bed comprises a denitration catalyst, 10
the screen plate, the denitration agent supply line system and the fixed bed are set in this order along the flow of exhaust gas in the reactor duct,the denitration agent supply line system comprises a heat exchange line for warming a 15 denitration agent with the heat possessed by the exhaust gas, a transportation line for supplying the denitration agent warmed by the heat exchange line to a nozzle, and the nozzle for injecting the denitration agent supplied through the 20 transportation line into the reactor duct.
2. A denitration apparatus, comprising
an entrance duct having a flow path for flowing an exhaust gas from a boiler in the horizontal 25 direction,
a joint duct having a flow path for changing the flow of the exhaust gas from the horizontal direction to the vertical direction,
a reactor duct having a flow path for flowing the 30 exhaust gas in the vertical direction, 19
a screen plate,
a denitration agent supply line system, and
a fixed bed,
wherein the fixed bed comprises a denitration catalyst, 5
the screen plate, the denitration agent supply line system and the fixed bed are set in this order along the flow of the exhaust gas in the reactor duct,
the denitration agent supply line system 10 comprises a heat exchange line for warming a denitration agent with the heat possessed by the exhaust gas, a transportation line for supplying the denitration agent warmed by the heat exchange line to a nozzle, and the nozzle for 15 injecting the denitration agent supplied through the transportation line into the reactor duct.
3. The denitration apparatus according to [1] or [2], further comprising a structure for holding 20 the screen plate, wherein the denitration agent supply line system is held by the structure for holding the screen plate.
4. The denitration apparatus according to [1] or 25 [2], further comprising a structure for holding the screen plate and a structure for holding the denitration agent supply line system, wherein the denitration agent supply line system is held by the structure for holding the denitration 30 agent supply line system. 20
5. The denitration apparatus according to any one of [1] to [4], wherein the denitration agent supply line system further comprises a baffle.
5
6. The denitration apparatus according to any one of [1] to [5], wherein at least a part of the heat exchange line has fins.