JP2007061667A - Flow velocity control device in high-dust denitration reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the gas flow velocity by reducing the sectional area in a low load condition to prevent any catalyst clogging by varying the exhaust gas passing sectional area of a denitration catalyst layer, and make the dust wear resistance retainment compatible with the dust clogging resistance with respect to a catalyst by changing the gas passing sectional area of the denitration reactor according to the boiler load factor. <P>SOLUTION: In this flow velocity control device, the exhaust gas passing sectional area of a denitration catalyst layer is varied by providing a damper 4 for blocking the exhaust gas directly on the upstream side of the denitration layer 2 in an exhaust gas flue, and controlling the blocking of the exhaust gas flow by the damper. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reactor used in a denitration method for injecting a reducing agent ammonia into an exhaust gas containing a large amount of dust, such as a coal-fired boiler, and selectively reducing and removing nitrogen oxides in the exhaust gas in the presence of a catalyst, More particularly, the present invention relates to a gas flow rate control device in an exhaust gas passage.

  In the denitration reactor for coal-fired boilers, because of the coal ash contained in the exhaust gas, the upper and lower limits of the exhaust gas flow velocity are set for the following reasons.

i) There is a possibility that the denitration catalyst may be blocked by ash, and in order to prevent this, the lower limit value of the flow velocity is set to about 1.0 [Nm / s].

ii) The upper limit of the flow velocity is set to about 2.5 [Nm / s] because there is a risk of catalyst wear due to ash collision.

  For this reason, in a coal-fired boiler with a normal denitration device, the load factor has to be increased to at least about 40%.

  Due to recent economic conditions, even coal-fired boilers are forced to cope with peak loads, and it is desired to reduce the nighttime load factor to about 15 to 20% or less.

  In view of these points, the present invention provides a denitration reactor capable of continuing the denitration operation without causing any catalyst clogging or catalyst deterioration even at a low boiler load.

  The invention according to claim 1 is a flow rate control device in a high dust denitration reactor characterized in that an exhaust gas passage cross-sectional area of a denitration catalyst layer is variable.

  In the invention according to claim 2, the exhaust gas passage cross-sectional area of the denitration catalyst layer is controlled by providing a damper that cuts off the exhaust gas immediately upstream of the denitration catalyst layer in the flue gas flue, and controlling the cutoff of the exhaust gas flow by the damper. It is a flow rate control device in a high dust denitration reactor characterized by being variable.

  The invention according to claim 3 is the flow rate control device in the high dust denitration reactor according to claim 2, wherein the damper is a swing type damper, a louver type damper or a guillotine type damper.

  The invention according to claim 4 is characterized in that a partition wall that divides the denitration catalyst layer into a plurality of sections is provided in the exhaust gas flow direction, and the exhaust gas flow between the sections is blocked by the partition walls. This is a flow rate control device in a high dust denitration reactor.

  When using any of the dampers, the following problems may occur due to a temperature drop in the closed side portion of the denitration catalyst layer.

(1) S0 of several tens of ppm or less A part of the exhaust gas containing is mixed into the closed side portion of the denitration catalyst layer, and local sulfuric acid corrosion occurs at this portion (temperature is about 170 ° C. or less).

(2) Similarly, under a situation where a part of the exhaust gas is mixed in the closed side portion of the denitration catalyst layer, the temperature becomes lower than the water condensation temperature (about 80 ° C. when the amount of water in the exhaust gas is 10%). Moisture condensation occurs.

(3) The catalytic activity is deteriorated by the condensed water of (2).

  In order to eliminate such a point, an inert gas that does not adversely affect the denitration catalyst, such as compressed air, nitrogen, or clean exhaust gas after passing through the desulfurization device, is supplied to the closed side portion of the denitration catalyst layer, and the pressure in this portion is reduced. Slightly higher than the gas passage side portion of the denitration catalyst layer (10 mmAq or more).

  According to the present invention, by making the exhaust gas passage cross-sectional area of the denitration catalyst layer variable, at the time of low load, the cross-sectional area can be reduced, the gas flow rate can be increased, and catalyst blockage can be prevented. Thus, by changing the gas passage cross-sectional area of the denitration reactor according to the boiler load factor, it is possible to achieve both maintenance of the catalyst's resistance to dust wear and resistance to dust blockage.

  Next, in order to explain the present invention specifically, some examples of the present invention will be given.

Example 1
In FIG. 1, a two-stage denitration catalyst layer (2) (3) is provided in a vertical denitration reactor (1) of a flue gas flue of a coal fired boiler. An upper swing damper (4) is arranged immediately upstream of the upstream denitration catalyst layer (2), and its upper end is swingable to the horizontal top wall of the flue gas flue via the upper horizontal support shaft (5). Installed. The denitration reactor (1) is provided with a vertical partition wall (6) that divides the upper and lower denitration catalyst layers (2) and (3) into left and right parts. The vertical partition wall (6) is made of the same material as the material of the denitration reactor (1) (equivalent material for general carbon steel such as SS400 or steel material having high temperature strength higher than that), and the thickness is about 6 mm.

  The upper swing damper (4) has its lower end raised from the fully closed state (close to the vertical shown by the solid line in FIG. 1) where it hits the upper end of the vertical bulkhead (6), and its lower end moved away from the upper end of the vertical bulkhead (6). The angle between the fully opened state (the state indicated by the chain line in FIG. 1) is swung. In the fully closed state of the upper swing damper (4), the right flow path of the upper and lower two-stage denitration catalyst layers (2) (3) is blocked, and the exhaust gas flows only through the left flow path. When the upper swing damper (4) is fully open, the exhaust gas flows to the left and right sides of the two-stage denitration catalyst layer (2) (3). By switching the swing type damper (4) between fully closed and fully open, the exhaust gas passage cross-sectional area of the denitration catalyst layer can be made variable. The partition wall blocks the exhaust gas flow between the compartments.

  A lower swing damper (7) is disposed immediately downstream of the vertical partition wall (6), and its upper end is swingably attached to the lower end of the vertical partition wall (6) via a lower horizontal support shaft (8). The lower swing damper (7) is fully closed (indicated by a solid line in FIG. 1) in synchronization with the fully closed state of the upper swing damper (4), and the upper swing damper (4) is fully opened. It swings so as to be fully open (a state indicated by a chain line in FIG. 1) synchronously.

  In the denitration catalyst layer (2) (3), as shown in FIG. 6, the gap between the catalyst frames (19), the inner wall of the reactor (18), the vertical partition walls and the catalyst frame (19) are provided so that the exhaust gas does not leak. And a gas seal mechanism (23) made of an inorganic fibrous material is provided in the upper part or the lower part of the catalyst frame (19) in the gap between the vertical partition wall and the beam (21), respectively.

  In the denitration reactor having the above-described configuration, the vertical swing dampers (4) (7) are normally fully opened. When the boiler load becomes low and the gas flow rate in the denitration reactor (1) falls below the specified value, the vertical swing damper (4) (7) is fully closed. In the fully closed state, the exhaust gas passage cross section of the upper and lower two-stage denitration catalyst layers (2) and (3) is reduced. In this state, the operation of the boiler and its denitration reactor is continued.

Example 2
In FIG. 2, in this embodiment, an upper partition plate (10) having a plurality of louvers (9) is provided across the upper end of the vertical partition wall (6) and the horizontal top wall of the flue gas flue. . Each louver (9) is attached to the opening of the upper partition plate (10) via a horizontal support shaft (11), and is provided to open and close the opening. A lower partition plate (13) having a plurality of louvers (12) is provided across the lower end of the vertical partition wall (6) and the side wall of the exhaust gas flue. Each louver (12) is attached to the opening of the lower partition (13) via a horizontal support shaft (23), and is provided to open and close the opening.

  Other configurations are the same as those of the first embodiment.

  In the denitration reactor configured as described above, the openings of the upper and lower partition plates (10) and (13) by the louvers (9) and (12) are opened and closed. In the fully closed state of the opening, the right flow path of the upper and lower two-stage denitration catalyst layers (2) (3) is blocked, and the exhaust gas flows only through the left flow path. When the opening is fully open, the exhaust gas flows to the left and right sides of the upper and lower two-stage denitration catalyst layers (2) and (3). By switching the louvers (9) and (12) between fully closed and fully open, the exhaust gas passage cross-sectional area of the denitration catalyst layer can be made variable. Usually, the openings of the upper and lower partition plates (10) and (13) are kept fully open. When the boiler load is low and the gas flow rate in the denitration reactor (1) is below the specified value, the openings of the upper and lower partition plates (10) and (13) are fully closed.

Example 3
3 to 5, in this embodiment, an upper guillotine damper (14) is provided which reaches the upper end of the vertical partition wall (6) from the horizontal top wall of the flue gas flue. That is, a slit-shaped opening (15) is opened in the horizontal top wall of the flue gas flue, and a pair of guide grooves (15) from the opening (15) to the upper end of the vertical partition wall (6) are formed on the inner walls of both sides of the flue gas flue. 16) is provided (see FIG. 4), and a lid (22) made of carbon steel for general use is attached to the outside of the opening (15) via a hinge (17) (see FIG. 5). When the body (22) closes the opening (15), the protrusion (22a) is fitted into the opening (15). Then, after the upper guillotine damper (14) completely enters the flow path from the outside of the exhaust gas flow path through the opening (15), the opening (15) is closed by the lid (22). Since the denitration reactor for coal-fired boilers is operated under negative pressure, there is a risk that outside air may be mixed into the exhaust gas flow path. However, the use of the lid configured as described above prevents outside air from being mixed, and exhaust gas leaks. You can also prevent.

  A lower guillotine damper (20) is provided across the lower end of the vertical partition wall (6) and the side wall of the flue gas flue.

  Other configurations are the same as those in the first embodiment.

  In the denitration reactor having the above-described configuration, the upper and lower guillotine dampers (14) and (20) are normally drawn out of the exhaust gas flow path so that the flow path is fully opened. When the boiler load is low and the gas flow rate in the denitration reactor (1) falls below the specified value, the upper and lower guillotine dampers (14) and (20) are introduced into the exhaust gas flow path and their tips are vertically aligned. It makes contact with the partition wall (6). In this state, the right channel of the upper and lower two-stage denitration catalyst layers (2) and (3) is blocked, and the exhaust gas flows only through the left channel.

1 is a vertical sectional view showing a flow rate control device in a high dust denitration reactor according to Example 1. FIG. 6 is a vertical sectional view showing a flow rate control device in a high dust denitration reactor according to Example 2. FIG. 6 is a vertical sectional view showing a flow rate control device in a high dust denitration reactor according to Example 3. FIG. It is sectional drawing which shows the guide mechanism of a guillotine type damper. It is a perspective view which shows opening of the waste gas flow path top wall, and its cover body. It is a vertical sectional view of a denitration reactor.

Explanation of symbols

(1) Denitration reactor
(2) (3) Denitration catalyst layer
(4) (7) Swing type damper
(5) Upper horizontal spindle
(6) Vertical bulkhead
(18) Reactor inner wall
(19) Catalyst frame
(21) Beam
(9) (12) Louver
(10) (13) Partition plate
(11) (23) Horizontal spindle
(14) (20) Guillotine damper
(15) Opening
(16) Guide groove
(17) Hinge
(22) Lid
(22a) Projection
(23) Gas seal mechanism

Claims (4)

A flow rate control device in a high dust denitrification reactor, wherein the exhaust gas passage cross-sectional area of the denitration catalyst layer is variable. A damper for blocking exhaust gas is provided in the exhaust gas flue immediately upstream of the denitration catalyst layer, and the exhaust gas cross-sectional area of the denitration catalyst layer is made variable by controlling the cutoff of the exhaust gas flow with the damper. Flow rate control device in high dust denitration reactor. 3. The flow rate control device in a high dust denitration reactor according to claim 2, wherein the damper is a swing damper, a louver damper or a guillotine damper. 4. A flow rate control in a high dust denitration reactor according to claim 2, wherein a partition wall for dividing the denitration catalyst layer into a plurality of sections is provided in the exhaust gas flow direction, and the exhaust gas flow between the sections is blocked by the partition walls. apparatus.

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