JP2016022425A - Denitration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a denitration device capable of suppressing an increase in the pressure loss of flue gas due to clogging of lumps of ash on a denitration catalyst layer without disturbing a flow of the flue gas into the denitration catalyst layer.SOLUTION: A denitration device 1 in which denitration catalyst layers 30 reducing NOx in flue gas containing combustion ash are disposed horizontally, and an ash deposition protector 6 formed of a perforated body is disposed in a flow passage cross-section of an exhaust gas introduction flow passage for introducing the flue gas into the uppermost denitration catalyst layer, is configured so that the ash deposition protector 6 is formed to include a first perforated body 61 having an inclined surface 61a disposed in at least part of the flow passage cross-section; and a second perforated body 62 disposed in a lower end portion of the first perforated body and storing combustion ash dropped along the inclined surface 61a.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a denitration apparatus in which a denitration catalyst layer for reducing nitrogen oxide (NOx) in combustion exhaust gas containing combustion ash is disposed.

Nitrogen oxide (NOx) in combustion exhaust gas discharged from thermal power plants and various factories is a causative substance of photochemical smog and acid rain, and selective removal using ammonia (NH ₃ ) as a reducing agent as its removal technology A flue gas denitration method using a reduction reaction is used. As shown in the following formula (1), this selective catalytic reduction reaction is performed by injecting NH ₃ into NOx contained in the combustion exhaust gas and reducing it with a denitration catalyst.
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O (1)

  In particular, combustion exhaust gas from thermal power plants that use coal as fuel contains combustion ash, which may lead to clogging of the denitration catalyst layer and cause an increase in pressure loss and denitration performance over time. Is done. A so-called parallel flow type plate-like or honeycomb-like is used for the denitration catalyst layer of the exhaust gas containing high-concentration combustion ash using coal as fuel. Of these, the plate-like catalyst has the advantage that the pressure loss of the combustion exhaust gas is lower than that of the honeycomb-like catalyst, combustion ash is hardly deposited, and it is resistant to wear. On the other hand, the denitration device is formed by stacking a plurality of plate-like catalyst elements at a predetermined pitch in a frame body to form a unit, and stacking a plurality of them into blocks and arranging them in a hierarchical manner. Combustion exhaust gas is introduced from above the uppermost denitration catalyst layer of such a denitration device, is allowed to flow to the lowermost denitration catalyst layer, and is discharged to the exhaust gas treatment device in the next step. In this case, there is a problem that combustion ash accumulates on the uppermost denitration catalyst layer.

  Depending on the nature of the coal and the operating conditions of the boiler, a large ash mass represented by popcorn ash (a mass of ash of several to several tens mm) may be formed. Ash masses such as popcorn ash are more likely to clog the denitration catalyst layer than fine ash, and thus easily increase the pressure loss of the combustion exhaust gas. In particular, starting from clogging of ash blocks, fine ash is deposited in the denitration catalyst layer, which may spread the entire denitration catalyst layer.

  As a countermeasure for this, Patent Document 1 discloses that a flat ash accumulation protector composed of a perforated body such as a grating or a metal net is disposed upstream of the uppermost denitration catalyst layer, so Preventing lump accumulation is disclosed. Patent Documents 2 to 4 disclose that a ash lump is trapped and removed by providing a wire mesh or the like upstream of the denitration apparatus.

Japanese Examined Patent Publication No.59-4180 JP 2003-164729 A JP 61-1229029 A JP 2009-119384 A

  However, in the countermeasure disclosed in Patent Document 1, in the case of a denitration apparatus in which combustion exhaust gas containing combustion ash flows downward from above the denitration catalyst layer arranged in the horizontal direction, the combustion flowing into the uppermost denitration catalyst layer A flat ash accumulation protector is arranged to block the exhaust gas. Therefore, the ash mass can be prevented from falling onto the catalyst element, but the ash mass is deposited over a wide range on the ash accumulation protector, which may impede the flow of the combustion exhaust gas to the denitration catalyst layer. There is. In addition, the measures disclosed in Patent Documents 2 to 4 have a problem that not only a large-scale modification of the denitration apparatus is required, but also a general-purpose response according to the ash accumulation state is difficult.

  The problem to be solved by the present invention is to provide a denitration device that can suppress an increase in pressure loss of combustion exhaust gas due to clogging of the denitration catalyst layer by lumps of ash without hindering the inflow of combustion exhaust gas to the denitration catalyst layer. Is to provide.

  In order to solve the above-mentioned problems, the denitration apparatus of the present invention has an exhaust gas introduction system in which a denitration catalyst layer for reducing nitrogen compounds in combustion exhaust gas containing combustion ash is disposed horizontally, and the combustion exhaust gas is introduced into the uppermost denitration catalyst layer. An ash accumulation protector made of a perforated body is disposed on a flow path cross section of the flow path, and the ash deposition protector includes a first perforated body having an inclined surface disposed in at least a part of the flow path cross section, It consists of a 2nd perforated body which stores the said combustion ash which is arrange | positioned at the lower end part of the said 1st perforated body, and falls along the said inclined surface.

  According to this, by arranging the ash accumulation protector on the cross section of the exhaust gas introduction flow path, the mass of the combustion ash in the combustion exhaust gas is captured by the inclined surface of the first perforated body, and this is along the inclined surface. And can be stored in a reservoir formed by the second perforated body. Therefore, the combustion ash can be prevented from entering the denitration catalyst layer, and clogging of the denitration catalyst layer can be reduced. In addition, by dropping the combustion ash on the inclined surface of the first perforated body, it is possible to suppress the accumulation of the combustion ash mass on the inclined surface, so that the smooth inflow of the combustion exhaust gas to the denitration catalyst layer can be prevented for a long time. Can be maintained over time. Also, the maintenance of the ash accumulation protector can be reduced by simply removing the lump of combustion ash stored in the reservoir formed in the second perforated body when the denitration device is stopped during regular inspections, etc. can do.

  In this case, the first perforated body can be formed in a roof shape having at least a pair of inclined surfaces inclined with respect to the horizontal direction so as to be separated from each other as it goes in the flow direction of the combustion exhaust gas. The second perforated body can be formed in a frame shape surrounding the lower end of the first perforated body.

  According to the denitration apparatus of the present invention, it is possible to suppress an increase in the pressure loss of the combustion exhaust gas due to clogging of the denitration catalyst layer due to ash blocks without hindering the inflow of combustion exhaust gas to the denitration catalyst layer.

1 is a diagram schematically showing a denitration apparatus according to an embodiment of the present invention. It is a figure which shows the structure of the denitration catalyst layer arrange | positioned at the denitration reactor with which the denitration apparatus of one Embodiment of this invention is provided. It is a perspective view which shows the structure of the ash accumulation protector of one Embodiment of this invention. It is a figure which shows the storage aspect of the popcorn ash of the 2nd perforated body of an ash accumulation protector. It is a figure which shows an example of the deposition condition with respect to the denitration catalyst layer of the combustion ash in combustion exhaust gas.

  Hereinafter, a denitration apparatus of the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1, the denitration apparatus 1 includes an exhaust gas introduction duct 2, a denitration reactor 3, and exhaust gas discharge in order from the upstream side along the flow of combustion exhaust gas containing combustion ash discharged from a coal combustion facility or the like. A duct 4 is provided.

The exhaust gas introduction duct 2 is piped so that the flow of the combustion exhaust gas introduced into the denitration reactor 3 is vertically downward. The denitration reactor 3 is configured by horizontally arranging a denitration catalyst layer 30, and the flue gas flows through the denitration catalyst layer 30 from the upper side to the lower side, thereby removing nitrogen oxide (NOx) in the flue gas. , By selective catalytic reduction using ammonia (NH ₃ ) as a reducing agent. Ammonia necessary for the reduction reaction is injected into the combustion exhaust gas from a nozzle (not shown) provided upstream of the uppermost denitration catalyst layer 30. The combustion exhaust gas from which nitrogen oxides have been removed by the denitration reactor 3 is discharged from the exhaust gas discharge duct 4 and sent to an exhaust gas treatment device or the like in the next step.

  The denitration catalyst layer 30 disposed in the denitration reactor 3 is configured by assembling a large number of catalyst elements formed by supporting a catalyst component on a plate-like member. As shown in FIG. 2 (a), a plurality of catalyst elements 31 are accommodated in a rectangular tube-shaped frame 5 arranged at the same pitch (about 4 mm to 10 mm), and are first unitized. Then, as shown in FIGS. 2B and 2C, a plurality of catalyst units 32 are assembled as a set and are blocked. In this case, one catalyst block 33 is configured by stacking the catalyst units 32 vertically so that the arrangement directions of the catalyst elements 31 are orthogonal to each other. In the present embodiment, the catalyst block 33 is arranged in three stages at a predetermined interval in the vertical direction in the denitration reactor 3, and the three denitration catalyst layers 30 are formed by these catalyst blocks 33. The denitration catalyst layer 30 of each layer allows combustion exhaust gas to flow in from the upper opening of the catalyst block 33 and discharge from the lower opening.

  As shown in FIG. 1, the denitration apparatus 1 is provided with an ash accumulation protector 6 that prevents combustion ash from flowing into the denitration catalyst layer 30 and accumulating. 3 and 4 are schematic views showing the configuration of the ash deposition protector 6. As shown in FIG. 3, the ash accumulation protector 6 includes a first perforated body 61 and a second perforated body 62 formed of perforated members such as a grating 7 and a metal net 8.

  The first perforated body 61 is formed by using the grating 7 as a core material and a metal net 8 attached so as to cover the entire grating 7, and allows the combustion exhaust gas to pass through the holes (mesh) of the metal net 8 to remove the denitration. It is made to flow into the catalyst layer 30. On the other hand, the first perforated body 61 has a metal mesh 8 that is finer than the lump of ash having a large particle diameter of about several mm to several tens of mm (hereinafter referred to as popcorn ash) contained in the combustion exhaust gas. By sticking, it can be captured without passing through the popcorn ash.

  The first perforated body 61 is formed with an inclined surface 61a that captures popcorn ash and drops it along the inclination. In the present embodiment, a pair of inclined surfaces 61 a that are inclined with respect to the horizontal direction are formed in the first perforated body 61 so as to be separated from each other as it goes downward in the flow direction of the combustion exhaust gas. Each of the pair of inclined surfaces 61a extends in the shape of a rectangular flat plate, forms a so-called triangular roof type (inverted V shape), and covers the exhaust gas inlet of the catalyst block 33 that forms the uppermost denitration catalyst layer 30. It is like that. The inclination angles of these inclined surfaces 61a can be arbitrarily set, but popcorn ash in the combustion exhaust gas can easily fall along the inclined surface 61a and can be prevented from being deposited on the inclined surface 61a. It is preferable to set the angle around 45 ° (between about 40 ° and 50 °).

  At the lower end portion of the first perforated body 61, a second perforated body 62 for storing popcorn ash that falls along the inclined surface 61a is disposed. The second perforated body 62 rises from the lower end portions of the pair of inclined surfaces 61a, forms a pool portion 62a for storing popcorn ash between the inclined surfaces 61a, and connects between the raised portions. Then, it is formed in a frame shape surrounding the lower end portion of the first perforated body 61. In this case, the second perforated body 62 may be formed integrally with the first perforated body 61, or the second perforated body 62 formed separately from the first perforated body 61 may be used as the first perforated body 62. It may be assembled with the perforated body 61. In any case, the second perforated body 62 may be formed of the metal net 8 finer than the popcorn ash, like the first perforated body 61. Alternatively, the metal net 8 may be attached to the grating to form the second perforated body.

  The standing height of the second perforated body 62 can be arbitrarily set, but as shown in FIG. 4, the popcorn ash 9 that has dropped along the inclined surface 61a of the first perforated body 61 At 62a, the height is set such that it can be stored for a certain period of time (for example, the periodic inspection interval). In this case, the standing height may be set by predicting the content of the popcorn ash 9 in the combustion exhaust gas, but depending on the stored amount of the popcorn ash 9 at the time of internal inspection of the denitration device 1, for example, a rectangular tube shape The standing height may be appropriately extended by attaching the perforated body to the upper portion of the second perforated body 62.

  The ash accumulation protector 6 including the first perforated body 61 and the second perforated body 62 has a filter function of capturing the popcorn ash in the combustion exhaust gas while allowing the combustion exhaust gas to pass therethrough. The exhaust gas is introduced into the denitration catalyst layer 30 on the cross section of the exhaust gas introduction passage (a plane perpendicular to the axial direction of the exhaust gas introduction passage). In the present embodiment, the ash deposition protector 6 is disposed on the catalyst block 33 constituting the uppermost denitration catalyst layer 30 disposed so as to block the exhaust gas introduction flow path in the horizontal direction.

  Thus, only the popcorn ash 9 is captured by the inclined surface 61a of the first perforated body 61 and dropped along the inclined surface 61a without disturbing the inflow of the combustion exhaust gas into the denitration catalyst layer 30, and the second perforated It can be stored in the body 62. Therefore, the popcorn ash 9 can be prevented from entering the denitration catalyst layer 30, and clogging between the catalyst elements 31 can be reduced. Further, since the popcorn ash 9 can be prevented from being deposited on the inclined surface 61a of the first perforated body 61, the smooth inflow of the combustion exhaust gas to the denitration catalyst layer 30 can be maintained over a long period of time. That is, even if the combustion exhaust gas contains popcorn ash 9, an increase in the pressure loss of the combustion exhaust gas in the denitration catalyst layer 30 can be minimized, and a decrease in the denitration efficiency can be prevented. Further, the maintenance of the ash accumulation protector 6 only needs to remove the combustion ash stored in the pool portion 62a of the second perforated body 62 when the denitration apparatus 1 is stopped by periodic inspection or the like, thus reducing the maintenance load. be able to.

  For example, when it is predicted that ash masses such as popcorn ash 9 are included in the combustion exhaust gas at the design stage of the denitration device 1, when the denitration reactor 3 is filled with the denitration catalyst layer 30, If the ash accumulation protector 6 is disposed in advance on all or a part of the denitration catalyst layer 30, the popcorn ash 9 is prevented from being deposited on the denitration catalyst layer 30 from when the denitration reactor 3 is filled, and combustion exhaust gas is obtained. An increase in pressure loss can be reliably suppressed. Specifically, the accumulation amount distribution of the popcorn ash 9 is performed in advance using a simulation or the like, and the ash accumulation protector 6 is disposed on the catalyst block 33 where the accumulation amount is expected to be large.

  As an example, when the accumulation amount distribution of the popcorn ash 9 as shown in FIG. 5 is predicted, the ash accumulation protector 6 is disposed on the catalyst block 33 in the portion where the accumulation amount is large on both sides in the left-right direction in the same figure. That's fine. That is, since it is only necessary to arrange the ash accumulation protector 6 at the corresponding location, it is possible to prevent the popcorn ash 9 from being deposited on the denitration catalyst layer 30 easily and pinpointly in a relatively short construction period. In FIG. 5, a protector (filter member) 10 formed in a flat plate shape with a perforated member such as a grating or a metal net is disposed on the catalyst block 33 where the accumulation amount is expected to be small. That's fine. In this case, like the ash accumulation protector 6, the protector 10 is preferably formed of a perforated member having a smaller hole than the popcorn ash 9.

  On the other hand, even when the ash deposition protector 6 is not disposed when the denitration reactor 3 is filled with the denitration catalyst layer 30, a predetermined portion (catalyst of the denitration catalyst layer 30 at the time of the internal inspection of the denitration apparatus 1 or the like If the accumulation of combustion ash containing popcorn ash 9 is confirmed on the block 33), the ash accumulation protector 6 is placed on the catalyst block 33 where the combustion ash is remarkably deposited during the denitration period of the denitration apparatus 1 or the like. It is possible to prevent the combustion ash from being deposited on the subsequent denitration catalyst layer 30 simply by disposing it. In other words, since the ash accumulation protector 6 only needs to be placed after the fact, it can be used universally according to the actual ash accumulation situation, and it is burned at a low cost and with immediate effect without waste. It is possible to prevent ash accumulation. In this embodiment, the ash accumulation protector 6 has a simple configuration including only the first perforated body 61 and the second perforated body 62, thereby enabling such general-purpose correspondence. As an example, when the combustion ash accumulation state as shown in FIG. 5 is confirmed, the ash accumulation protector 6 is newly installed on the catalyst block 33 at the portion where the accumulation amount is large on both sides in the left-right direction as shown in FIG. Should be arranged.

  Although the present invention has been described based on one embodiment as shown in FIGS. 1 to 5, the above-described embodiment is merely an example of the present invention, and the present invention is only the configuration of the above-described embodiment. It is not limited to.

  For example, in the present embodiment described above, the first perforated body 61 of the ash accumulation protector 6 is formed with a pair of inclined surfaces 61a, but a pair of trapezoidal or triangular inclined surfaces are formed. In addition, the first perforated body may be a tetrahedron by forming another pair of inclined surfaces extending in a triangular shape between these inclined surfaces. It should be noted that the angle of inclination of the inclined surfaces with respect to the horizontal direction is not necessarily the same between the pair of inclined surfaces, regardless of whether they are a pair or two pairs. In addition, a vertical surface standing in the vertical direction and extending in a rectangular shape, and an inclined surface that is inclined so as to be separated from the vertical surface toward a downward direction that is a flow direction of the combustion exhaust gas are formed. The perforated body may be a so-called saw roof type.

  Further, in the present embodiment described above, the ash accumulation protector 6 is disposed on the catalyst block 33 constituting the uppermost denitration catalyst layer 30, but the upstream side of the uppermost denitration catalyst layer 30, for example, The ash accumulation protector 6 may be disposed in the exhaust gas introduction duct 2 or the like, and the ash accumulation protector 6 is disposed on the catalyst block 33 that constitutes the denitration catalyst layer 30 in the middle and lower stages in addition to the uppermost stage. Is also possible.

DESCRIPTION OF SYMBOLS 1 Denitration device 6 Ash accumulation protector 30 Denitration catalyst layer 61 1st hole body 61a Inclined surface 62 2nd hole body

Claims (2)

An ash deposit consisting of a perforated body in the cross section of the exhaust gas introduction flow path where the denitration catalyst layer that reduces the nitrogen compounds in the combustion exhaust gas containing combustion ash is horizontally arranged and introduces the combustion exhaust gas into the top denitration catalyst layer A protector,
The ash accumulation protector is disposed at a lower end portion of the first perforated body having an inclined surface disposed in at least a part of the cross section of the flow path, and falls along the inclined surface. A denitration apparatus comprising the second perforated body for storing the combustion ash. The first perforated body is formed in a roof shape having at least a pair of inclined surfaces inclined with respect to a horizontal direction so as to be separated from each other as it goes in a flow direction of the combustion exhaust gas,
2. The denitration apparatus according to claim 1, wherein the second perforated body is formed in a frame shape surrounding a lower end portion of the first perforated body.

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