JP3362212B2 - Catalytic denitration equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic denitration device, and more specifically, it relates to an exhaust gas containing a large amount of solid matter such as combustion dust such as coal combustion exhaust gas, diesel engine exhaust gas, iron ore sintering furnace exhaust gas and the like. The present invention relates to a catalytic denitration device used for denitration.

[0002]

2. Description of the Related Art In a catalyst denitration apparatus for exhaust gas containing solid matter such as combustion dust, it is necessary to prevent the catalyst from being clogged by the solid matter, but a large number of vertical independent passages are used instead of the conventional granular catalyst. As a result, the honeycomb-shaped catalyst having the above has been used, and the blocking property of the catalyst has been remarkably improved. However, for example, in the case of an exhaust gas containing a large amount of solid matter such as combustion dust such as coal combustion exhaust gas, diesel engine exhaust gas, iron ore sintering furnace exhaust gas, etc., even with a honeycomb catalyst, the clogging by the solid matter is completely eliminated. It could not be prevented.

Therefore, in the conventional catalytic denitration device (31) used for denitration of exhaust gas as described above, as shown in FIG. 8, a sootbrow nozzle (32) is provided and the upper surface of the catalyst block (2) is provided. The dust accumulated on the air was blown off by high pressure steam or air from the nozzle (32).

[0004]

However, the above-mentioned conventional catalytic denitration device (31) has the following problems.

That is, when the reactor (7) of the device (31) is large, a large number of soot-blow nozzles (32) are provided on the upper surface of the catalyst block (2) or a large-sized one is installed. However, in any case, the catalyst block (2), the upstream duct (33) or the reactor should be installed.
Since a structure of a size that cannot be ignored can be placed inside (7), this not only increases the flow resistance of the exhaust gas, but also the dust accumulated on the nozzle (32) and its ancillary substances causes the catalyst block (2 ), The passage (16) of the catalyst (9) may be blocked. Therefore, the sootblow needs to be operated quite frequently, which is very uneconomical.

Further, the steam or air blown out from the sootblow nozzle (32) has a high pressure, and the dust blown off by the soot collides with the ceramic paper or the like constituting the catalyst (9) at a considerably high speed. Therefore, the catalyst (9) is required to have sufficient mechanical strength to withstand it. However, when increasing the mechanical strength of the catalyst (9), the porosity of the catalyst (9) is generally lowered, which causes a problem that the activity of the catalyst (9) is reduced.

[0007] Further, the sootblow not only costs the installation cost of the equipment, but also causes an increase in cost due to the enlargement of the reactor (7), further costs of high-pressure steam or air, and operating costs such as inspection and repair of mechanical equipment. Since it also costs, there was a problem from the economical point of view.

Therefore, in order to develop a catalytic denitration apparatus which does not require soot-blowing equipment having various problems as described above, the inventors of the present invention first of all, the dust accumulation state in the above-mentioned conventional apparatus (31), or dust. By catalyst
The occlusion condition of (9) was observed.

As a result, the channels (16) of the honeycomb catalyst (9)
A large amount of dust was accumulated and blocked near the entrance of the (see FIGS. 9 and 10). The cause is the passage (1
6) Dust of a size that does not easily pass through the inside, specifically, combustion dust in exhaust gas that is extremely slightly condensed,
Debris from the oxide layer on the duct (33) wall or reactor (7) wall,
The heat insulation / sealant pieces mixed in the exhaust gas will pass through the passage (16).
It is possible to get caught at the entrance of. Among them, most of the causes of accumulated dust are condensed combustion dust except when the reactor block (2) is initially filled with the catalyst block (2). That is, there is a place where combustion dust is accumulated above the entrance of the passage (16), and the combustion dust accumulated there is slightly condensed by being heated near the denitration reaction temperature for a long time. It is thought that the greatest cause of blocking the passage (16) is that it falls or flies.
Here, the duct (3
3) and each wall of the reactor (7), thermometer protection tube (34), soot blow nozzle (32), gas flow guide plate (35), upper end surface of catalyst block frame (8), and catalyst block (2 The upper end surface of the honeycomb-shaped catalyst (9) that constitutes

The cause of dust accumulation and clogging in the passage (16) may be that the outlet of the passage (16) is blocked by the catalyst block frame (8). Is only a design problem of the catalyst block (2) and can be easily solved. It is considered that the main cause is that dust having a size that cannot easily pass through the passage (16) is caught in the passage (16) as in the case of the entrance of the passage (16) described above.

As a result of the above consideration, in order to prevent the accumulation or clogging of dust in the catalyst block (2), first, the size of the catalyst block (2) must be such that it cannot easily pass through the passage (16). It was found that it is essential not to bring the dust of the above into the catalyst block (2). It is considered that this point can be solved by disposing a member that does not allow dust of such a size to pass therethrough above the catalyst block (2). However, it is unavoidable that dust accumulates on the upper end surface of the honeycomb catalyst (9) with a thickness of 1 mm or less, but dust accumulated in such a narrow place is generally unstable. Therefore, it is considered that if the flow of exhaust gas changes, it will easily fall off. That is, it is considered that the accumulation of dust on the upper end surface of the catalyst (9) can be prevented by changing the exhaust gas flow condition of the upstream side of the catalyst block (2) at an appropriate frequency such that condensation of accumulated dust can be ignored.

The present invention has been made on the basis of the above-mentioned findings, and overcomes various problems of the conventional apparatus using a sootblow to efficiently and economically block the passage of the catalyst block. It is an object of the present invention to provide a catalytic denitration device that can prevent the above.

[0013]

In order to achieve the above object, the catalytic denitration apparatus of the present invention has a strainer for preventing blockage of the passage above a catalyst block having a large number of vertical independent passages. It is characterized by being. The strainer may be a net-like strainer as well as a honeycomb-like one having a large number of vertical independent passages narrower than the passage of the catalyst block. With this strainer, it is possible to prevent dust of a size that cannot easily pass through the passage of the catalyst block from being introduced into the catalyst block.

In the above apparatus, the strainer is preferably a honeycomb-shaped one having a large number of vertical independent passages narrower than the passages of the catalyst block, and the base end of the strainer is rotated around the horizontal axis on the support frame. It is freely attached, and a cam for rocking the strainer is arranged at a required position on the lower surface of the strainer. As a result, the strainer is provided with a rectifying function, and the angle of the strainer with respect to the flow direction of the front flow gas is periodically changed, so that the exhaust gas flow state of the catalyst block front flow is changed, and as a result, the upper surface of the catalyst is changed. The accumulated dust is blown off by the wind pressure of the exhaust gas and falls.

The honeycomb-shaped strainer is preferably formed of a thin metal plate which is excellent in strength and hard to attach dust. In that case, it is necessary to appropriately select one having corrosion resistance according to the corrosive component in the exhaust gas. The thickness of the plate is preferably as thin as possible in terms of strength, whereby the flow resistance of exhaust gas and the accumulation of dust on the upper end surface of the strainer are reduced.

The cross-sectional shape of the passage of the honeycomb strainer is usually hexagonal, but it may be triangular or quadrangular. A strainer having a passage having a hexagonal cross section is formed, for example, by spot-welding a plurality of metal trapezoidal corrugated plates. A strainer having a passage having a triangular cross section is formed by alternately laminating metal flat plates and corrugated plates, for example. Further, the strainer having the passage having the quadrangular cross section is formed, for example, by spot-welding a plurality of metal corrugated plates.

The passage of the honeycomb strainer preferably has an equivalent diameter of its cross section which is not less than ⅓ and not more than ⅕ of the equivalent diameter of the passage of the catalyst block. As a result, it is possible to reduce the pressure loss due to the increase in the exhaust gas flow resistance and prevent the passage of the strainer from being blocked.

The length of the passage of the honeycomb strainer is preferably at least twice the equivalent diameter of the cross section of the passage and 1
It is set to 0 times or less, and more preferably 5 to 10 times the equivalent diameter of the cross section of the passage. Less than twice,
The strainer has insufficient strength. The longer the length of the strainer passage, the better the gas rectifying action,
It contributes to the change of the gas flow situation due to the change of the angle of the strainer with respect to the flow direction of the upstream gas. In addition, in the case where abrasion of the catalyst due to dust collision is a problem such as coal flue gas denitration, it is preferable to set the passage of the strainer to be long so that the gas flow entering the catalyst is completely rectified. However, if the diameter exceeds 10 times the equivalent diameter of the cross section of the passage, there is a risk of pressure loss and passage clogging due to an increase in exhaust gas flow resistance.

In the above apparatus, the accumulated dust removing sweeper is preferably movably provided along the upper surface of the strainer. This effectively prevents accumulation of dust on the upper end surface of the strainer and blockage of the strainer. As means for moving the sweeper along the upper surface of the strainer, for example, rails are laid on both edges of the upper surface of the strainer, and the sweeper provided with rollers is run on the rails. A metal brush is preferably used as the sweeper. By lightly sweeping the accumulated dust accumulated on the upper surface of the strainer with this metal brush, the accumulated dust shatters and falls.

[0020]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 shows a catalytic denitration apparatus (1) according to the present invention.
The apparatus (1) is provided with a number of vertical independent passages (narrower than the passage of the catalyst block (2) above the catalyst block (2) having a large number of vertical independent passages (16). The strainer (3) having 15) is arranged. One end of the strainer (3) is rotatably attached to the support frame (12) around the horizontal axis (4), and a cam (5) for swinging the strainer (3) is arranged on the lower surface of the other end. (See Figure 4). Above the strainer (3), a wire dust removing wire brush (6) is movably provided along the upper surface of the strainer (3) (see FIGS. 3 to 5).

A total of 15 catalyst blocks (2) were arranged in the vertical direction in the middle position of the inside of the rectangular tubular reactor (7) of the apparatus (1).
The catalyst beds are arranged in parallel in rows and three rows to form a catalyst bed (see FIG. 2). The overall size of the catalyst bed is 500 cm in width,
The depth is 300 cm and the height is 100 cm. Each catalyst block (2) is a block frame made of a stainless steel square tube.
A plurality of honeycomb catalysts (9) are filled in (8). The lower end of the block frame (8) of the catalyst block (2) is received by the shaped steel beam (10). At the upper end of the block frame (8) of the catalyst block (2), a dust accumulation prevention member (11) made of a triangular tube made of stainless steel having a sharp top is arranged.
The catalyst (9) is composed of a plurality of trapezoidal corrugated plates made of ceramic paper carrying denitration catalytic metal, and has a large number of vertical independent passages (16) having a hexagonal cross section (see FIG. 6). . The equivalent diameter of the cross section of the passage (16) is 7.8 mm.

A total of 15 strainers (3) are provided, and the strainers (3) are arranged above each catalyst block (2) at an interval of 15 cm. These strainers (3) are
It is fitted in the voids of the stainless steel lattice-shaped support frame (12) fixed to the wall surface of (7). Each strainer (3) comprises a stainless steel rectangular outer frame (13) and a passage forming part (14) provided inside the outer frame (13), and the passage forming part (14) has a thickness of 0. It is formed by spot welding a plurality of trapezoidal corrugated plates made of stainless steel of 05 mm, and each passage (15) has a hexagonal cross section. aisle
The equivalent diameter of the cross section of (15) was 6.1 mm, and the catalyst
It is about 4/5 of the equivalent diameter of the cross section of the passage (16) of (9). Moreover, the length of the passage (15) of the strainer (3) is 30 m.
m, which is about 5 times the equivalent diameter of the cross section of the passage (15).

One end of the strainer (3) is attached to the support frame (12) by a hinge so that the strainer (3) is rotatable about the horizontal axis (4). The cam (5) arranged on the lower surface of the other end of the strainer (3) can swing the other end of the strainer (3) up and down by 50 mm by the rotation of the cam shaft (17).

The wire brush (6) has a large number of thin wires (19) planted on the lower surface of the base (18) extending in the lengthwise direction of the strainer (3) (horizontal direction in FIG. 3). Rollers (20) are provided at both ends of the platform (18) so that they run on rails (not shown) provided at both edges of the upper surface of the rectangular frame (13) of the strainer (3). ing. The wire brush (6) is driven by pulling the wire from the outside of the reactor (7).

The operating conditions of the catalytic denitration device (1) are as follows.・ Processing gas amount 100,000 Nm ³ / h (coal boiler flue gas) ・ Dust concentration 10 g / m ³・ Strainer pressure loss 5 mmAq or less ・ Catalyst block pressure loss 60 mmAq or less ・ Reaction temperature 330 ° C ・ Denitration rate 90% (NH ₃ ratio) : 1.0) Dust clogging experiment 1 Air containing solids was passed through a strainer having a passage having a hexagonal cross section with dimensions (unit: mm) shown in FIG. 7, and the depositability of solids on the strainer was measured. did. As the solid material, coal boiler (powdered coal combustion) dust of 60 mesh or less is used, and 0.5 pieces of ceramic paper with a thickness of 0.5 mm is cut into this, and one piece of paper of 7 types is produced for each 1 g of dust. Were sequentially mixed. The solid matter concentration in the air stream was set to about 50 g / m ³ . 3 from the start of ventilation
Table 1 shows the blockage rate of the strainer passage after 0 minutes.

[0027]

[Table 1] As is clear from Table 1, solid materials having a size of two-thirds or less of the cross-sectional area of the passage do not cause clogging.

Dust clogging experiment 2 A catalyst having hexagonal cross-section passages having a size (unit: mm) shown in FIG. 6 was arranged below the strainer used in Experiment 1 at an interval of 30 mm, and in this state In the same manner as in Experiment 1, air containing solids mixed with seven kinds of paper pieces was passed through and the clogging rate of the catalyst passage was measured. The results are shown in Table 2.

[0029]

[Table 2] As is clear from the experimental results shown in Table 2, the function of the strainer hardly causes the clogging of the catalyst.

[0030]

According to the catalytic denitration apparatus of the present invention, the strainer can prevent dust of a size that cannot easily pass through the passage of the catalyst block from being introduced into the catalyst block. Further, by making the strainer a honeycomb shape having a rectifying action, and by periodically changing the angle of the strainer with respect to the flow direction of the front gas, the exhaust gas flow situation of the catalyst front flow changes,
Since the dust accumulated on the upper end surface of the catalyst is dropped by the wind pressure of the exhaust gas, it is possible to reliably prevent the accumulation of dust on the upper end surface of the catalyst. Further, the sweeper effectively prevents dust accumulation on the upper end surface of the strainer and blockage of the strainer.

Therefore, according to the catalytic denitration apparatus of the present invention, it is possible to efficiently and economically prevent the blockage of the passage of the catalyst block without using the sootblow equipment having various problems as described at the beginning. The stable operation is possible until the time of the next periodic repair.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the outline of a catalytic denitration apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view showing an outline of a catalytic denitration device of an example.

FIG. 3 is a plan view showing a strainer of the catalytic denitration apparatus of the embodiment.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

5 is a cross-sectional view taken along the line VV of FIG.

6A and 6B are a plan view and a side view showing the dimensions of the catalyst used in the dust clogging experiment 2 of the example.

7A and 7B are a plan view and a side view showing the dimensions of the strainer used in the dust blocking experiments 1 and 2 of the example.

FIG. 8 is a vertical cross-sectional view showing a conventional catalytic denitration device.

FIG. 9 is an enlarged vertical cross-sectional view showing a portion surrounded by an alternate long and short dash line in FIG.

10 is a vertical cross-sectional view showing, in an enlarged manner, a portion surrounded by the alternate long and short dash line in FIG.

[Explanation of symbols]

(1) ...... Catalytic denitration equipment (2) …… Catalyst block (3) ...... Strainer (4) ...... Horizontal axis (5) ...... Cam (6) ...... Wire brush (12) …… Support frame (15) …… Vertical independent passage (of strainer) (16) …… Vertical independent passage (of catalyst block)

Continuation of the front page (56) Reference JP-A-57-50532 (JP, A) JP-A-6-183750 (JP, A) Actually open Sho-58-195634 (JP, U) Actual-open Sho-58-23622 (JP , U) Actual Development Sho 59-146028 (JP, U) Actual Development 3-26322 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B01D 53/86

Claims (4)

(57) [Claims] 1. A above the catalyst block having a number of vertical independent passages, and closed preventing strainer same passage is arranged
The strainer is narrower than the passage of the catalyst block.
Made of honeycomb with a number of vertical independent passages,
The base end of the strainer is attached to the support frame so that it can rotate around a horizontal axis.
The strainer and attach it to the required position on the bottom of the strainer.
It is characterized in that a cam that swings it is arranged ,
Catalytic denitration equipment. 2. The equivalent diameter of the cross section of the strainer passage is one third of the equivalent diameter of the cross section of the catalyst block passage.
More than 5 minutes at 4 or less, the catalytic denitration apparatus according to claim 1. The length of 3. A strainer passage is less than 10 times 2 times the equivalent diameter of the cross section of the passage, according to claim 1
The catalytic denitration apparatus described. 4. A deposited dust removing sweeper is provided movably along the upper surface of the strainer device of claim 1, wherein.