JP4994434B2 - Performance recovery method for exhaust gas treatment equipment - Google Patents

Description

  The present invention relates to a method for recovering the performance of an exhaust gas treatment apparatus in which a honeycomb catalyst used for an exhaust gas treatment of an automobile or other reactions such as gas purification or synthesis is used for flue gas denitration particularly in a thermal power plant.

  Conventionally, boilers of thermal power plants using various fuels such as oil, coal and gas, various large boilers, and other waste incinerators have been equipped with flue gas denitration equipment that treats exhaust gas. Has a multi-layered denitration catalyst.

As a denitration catalyst, in general, TiO ₂ or the like is used as a carrier, V ₂ O ₅ or the like is used as an active component, and an oxide of tungsten or molybdenum is added as a co-catalyst component. VO _x -WO _y Composite oxides such as —TiO ₂ and VO _x —MoO _y —TiO ₂ are used.

  Further, as the catalyst shape, a honeycomb type or a plate type is generally used. For honeycomb type, after manufacturing honeycomb shape with substrate, coated type coated with catalyst component, kneaded type formed by kneading catalyst component on substrate, impregnation with honeycomb shaped substrate impregnated with catalyst component There are shapes. The plate-like material is a metal core or ceramic coated with a catalyst component.

  In any case, if such a denitration catalyst is used continuously, a substance that deteriorates the catalyst performance (hereinafter referred to as a deteriorated substance) adheres to or dissolves on the catalyst surface and inside, thereby reducing the catalyst performance. There is a problem of going.

  Therefore, various methods for regenerating the denitration catalyst have been studied in the past.

  For example, a method of polishing an inner surface of an exhaust gas passage with an abrasive (see Patent Document 1), a method of scraping off the surface portion of a deteriorated denitration catalyst to make a new catalytic active surface appear (see Patent Document 2, etc.), A method of physically removing a deteriorated part or a foreign substance and causing an active surface to appear, such as a method of removing a foreign substance by passing an accompanying gas through a through hole (see Patent Document 3, etc.).

  In addition, a method of washing with an acid having a pH of 5 or less, or an alkali having a pH of 8 or more (see Patent Document 4), washing with water or a dilute inorganic acid aqueous solution, and washing with a 0.1 to 5% by weight oxalic acid aqueous solution, Furthermore, the catalyst performance is restored by washing, such as washing with water to remove oxalic acid remaining on the catalyst (see Patent Document 5, etc.), washing with water at 50 ° C to 80 ° C and drying (see Patent Document 6, etc.) How to do is being studied.

  However, the method of physically polishing and the like has a problem that the operation is complicated and the denitration catalyst itself is cracked or destroyed by the regeneration operation.

  In the case of cleaning the denitration catalyst, generally, the alkaline component is removed by washing with an alkaline aqueous solution or hot water, and the heavy metal component mainly composed of vanadium is washed with an oxalic acid aqueous solution. Although it is said to be effective, cleaning methods using various cleaning components are still being studied because it is not sufficient.

  In addition, although an apparatus that can regenerate a deteriorated catalyst function while the catalyst is installed has been proposed (see Patent Document 7), it is expensive to install and install a new apparatus. There is a problem that it ends up.

  As described above, various types of reproduction methods have been studied, but all have some drawbacks, and no satisfactory one has been developed yet.

JP-A-1-119343 (Claims etc.) JP-A-4-197451 JP-A-7-116523 Japanese Patent Application Laid-Open No. 64-80444 JP-A-7-222924 JP-A-8-196920 JP 2000-325801 A

  In view of the above-described circumstances, the present invention provides a performance recovery method for an exhaust gas treatment apparatus that can recover the NOx removal performance of a deteriorated NOx removal catalyst at low cost without replacing and adding the deteriorated NOx removal catalyst. This is the issue.

  A first aspect of the present invention that solves the above-described problem is an exhaust gas treatment apparatus that has a gas flow path for passing a gas to be treated and that has a honeycomb catalyst that performs treatment on the side wall of the gas flow path installed in the exhaust gas flow path. A method for recovering performance, wherein the honeycomb catalyst is rearranged so that a predetermined range from the upstream side in the flow direction of the gas to be treated of the honeycomb catalyst is a deteriorated portion, and the deteriorated portion is moved from the inlet side of the exhaust gas passage. There is a method for recovering the performance of an exhaust gas treatment apparatus.

  In the first aspect, the honeycomb catalyst is rearranged so as to move the degraded portion of the honeycomb catalyst from the inlet side of the exhaust gas passage. Thereby, the site | part substantially related to denitration can be changed into the last use state, and denitration performance can be recovered | restored.

  According to a second aspect of the present invention, in the first aspect, the exhaust gas treatment apparatus is characterized in that the honeycomb catalyst is rearranged with the feeding direction reversed so that the deteriorated portion is located on the downstream side. It is in the performance recovery method.

  In the second aspect, the honeycomb catalyst is rearranged in the exhaust gas treatment apparatus so that the deteriorated portion is on the downstream side. Thus, the NOx removal performance can be easily recovered by reversing the arrangement direction of the honeycomb catalyst.

  According to a third aspect of the present invention, in the first or second aspect, the honeycomb catalyst is cut into a plurality of pieces in the flow direction, and the honeycomb catalyst is regenerated so that the deteriorated portion is not positioned at least on the most upstream side. It is in the performance recovery method of the exhaust gas treatment apparatus characterized by arranging.

  In the third aspect, when the honeycomb catalyst is rearranged in the exhaust gas treatment apparatus, the honeycomb catalyst including the deteriorated portion is not arranged on the most upstream side among the plurality of honeycomb catalysts cut in the flow direction. ing. The denitration performance can be reliably recovered also by the combination mode of the honeycomb catalyst thus cut.

  A fourth aspect of the present invention is the performance recovery method for an exhaust gas treatment apparatus according to any one of the first to third aspects, wherein the honeycomb catalyst is rearranged in a state where the deteriorated portion is removed. .

  In the fourth aspect, when the honeycomb catalyst is rearranged in the exhaust gas treatment apparatus, the degraded portion of the honeycomb catalyst is removed. Thereby, it is possible to recover the performance of the denitration catalyst which has been relatively easily and reliably deteriorated.

  According to a fifth aspect of the present invention, in any one of the first to third aspects, the range of the deteriorated portion of the side wall of the gas flow path of the honeycomb catalyst is polished, and the honeycomb catalyst is rearranged. In the method for recovering the performance of the exhaust gas treatment apparatus.

  In the fifth aspect, when the honeycomb catalyst is rearranged in the exhaust gas treatment apparatus, the range of the deteriorated portion generated on the side wall of the gas flow path is polished. As a result, only a predetermined range needs to be polished, and the polishing rate can be reduced as compared with the case of polishing the whole, so that the denitration catalyst can be prevented from being damaged.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the predetermined range is a range until the flow of exhaust gas sent into the gas flow path is rectified. The characteristic is a method for recovering the performance of an exhaust gas treatment apparatus.

  In the sixth aspect, the range until the exhaust gas entering from the inlet side of the gas flow path of the honeycomb catalyst is rectified is the target of the performance recovery process, and thereby, the portion that does not effectively contact the side wall of the gas flow path It is possible to reliably recover the NOx removal performance.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the predetermined range Lb (mm) is an inflow rate Uins (m / s), and an arbitrary honeycomb diameter is Ly (mm). In the method for recovering the performance of the exhaust gas treatment apparatus, the honeycomb diameter constant Lys is in a range specified by the following formula (A) when the constant Lys is 6 mm.

（ａは、ハニカム径が６ｍｍのハニカム触媒で流入速度が６ｍ／ｓの場合には、３〜５の範囲から選択される定数である。）

(A is a constant selected from the range of 3 to 5 when the honeycomb catalyst has a honeycomb diameter of 6 mm and the inflow rate is 6 m / s.)

  In the seventh aspect, the degradation site of the honeycomb catalyst can be identified stably and reliably, and the performance recovery process can be performed uniformly based on the result.

  An eighth aspect of the present invention is the performance recovery method for an exhaust gas treatment apparatus according to any one of the first to seventh aspects, wherein the honeycomb catalyst is a catalyst for flue gas denitration.

  In the eighth aspect, the honeycomb catalyst can be employed as a catalyst for flue gas denitration.

  According to a ninth aspect of the present invention, in the eighth aspect, the honeycomb catalyst is used in combination with a regeneration method in which the honeycomb catalyst is substantially immersed in regenerated water at room temperature without containing chlorine and a cleaning component, and then taken out and drained. There is a method for recovering the performance of an exhaust gas treatment apparatus.

  In the ninth aspect, by simply immersing the denitration catalyst in pure water at room temperature, it is possible to easily elute and remove the inhibitor that has deteriorated the denitration performance, and to recover the denitration performance. it can.

  The present invention is applicable to various honeycomb catalysts that have been used conventionally. Here, the honeycomb catalyst has a gas flow path having a polygonal cross section such as a quadrangle, a hexagon, or a triangle, and causes a catalytic reaction on the wall surface of the gas flow path. Is a cylindrical shape, or the whole having a gas flow path defined in a lattice shape having a quadrangular section, but is not limited thereto.

  In such a honeycomb catalyst, when gas enters the inside of the honeycomb lattice, gas turbulence occurs on the inlet side, and the probability that the reaction material collides with the wall surface (catalyst wall) of the gas flow path increases. On the other hand, gas turbulence converges while passing through the inside of the lattice, transitions to laminar flow, reduces the probability of collision of the gas flow channel wall with the reactant, and settles in the normal diffusion range It is expected to be.

More specifically, as the honeycomb-type denitration catalyst continues to be used, the catalyst surface is covered with coal ash and the like, and the reactant NH ₃ (ammonia) or NO _X approaches the catalyst. Since the adsorption of ammonia on the catalyst (reaction rate-determining) is hindered, it is presumed that the performance is lowered. As a result of investigating the catalyst surface of each part in the longitudinal direction after use based on such an assumption, the inlet side is violently covered and the performance is also significantly reduced, going to the outlet side As a result, it was found that the coating was not seen so much and the outlet side hardly contributed to the denitration reaction, and the present invention was completed. That is, the inventors have found that the deterioration of the catalyst is localized and occurs on the gas inlet side, and that the catalyst performance is dominated by the gas inlet side, thereby completing the present invention.

  That is, according to the present invention, the deterioration of the honeycomb catalyst occurs in a predetermined range which is a range from the inlet side to the flow of the exhaust gas sent into the gas flow path, and the downstream side of the range is almost in the reaction. It is based on the knowledge that it does not contribute. The predetermined range Lb (mm) will be described in detail later, but when the inflow rate is Uins (m / s), the arbitrary honeycomb diameter is Ly (mm), and the honeycomb diameter constant Lys is 6 mm, the following is given. It was also found that the range is specified by the formula (A).

（ａは、ハニカム径が６ｍｍのハニカム触媒で流入速度が６ｍ／ｓの場合には、３〜５の範囲から選択される定数である。）

(A is a constant selected from the range of 3 to 5 when the honeycomb catalyst has a honeycomb diameter of 6 mm and the inflow rate is 6 m / s.)

  Therefore, the honeycomb catalyst to which the present invention can be applied can be applied to a honeycomb catalyst having a length equal to or longer than the length of the above-described predetermined range, preferably at least twice the predetermined range that can be calculated by the above formula. In such a honeycomb catalyst, it is possible to recover the performance of the exhaust gas treatment apparatus by performing a performance recovery process on the used deteriorated denitration catalyst without replacing and adding the deteriorated denitration catalyst.

  Whether or not the performance recovery process is performed by the method of the present invention may be periodically determined according to the usage period of the denitration catalyst, but it is assumed that the period of deterioration differs depending on the usage conditions. Therefore, it is preferable to perform the performance recovery process when the deterioration state of the denitration catalyst is accurately grasped and the deterioration is more than a predetermined level.

For example, the measuring the concentration of NO _x and NH ₃ concentrations on the inlet side and the outlet side of the denitration catalyst, an inlet mole ratio = considering the inlet NH 3 _/ inlet NO _x measured NOx removal efficiency eta, to the NOx removal efficiency eta It is preferable to evaluate the performance of the denitration catalyst based on this. In such a method, since measuring the concentration of NO _x and NH ₃ to measure the concentration in view of the inlet mole ratio denitration ratio η at the entrance of the denitration catalyst, the denitration rate is improved as the molar ratio increases and absolute Can be reliably evaluated.

In this case, the denitration rate η may be measured based on the NO _x concentration, but is preferably measured based on the NH ₃ concentration. This is because the catalyst performance can be grasped more stably when the denitration rate η is measured not based on the NO _x concentration but on the NH ₃ concentration.

  Furthermore, in order to grasp the deterioration state of the catalyst more accurately, the catalyst may be actually sampled from a part of the denitration catalyst, and the performance of the sampling catalyst may be evaluated.

  The honeycomb catalyst of the present invention is not limited to a denitration catalyst such as an exhaust gas treatment device because the catalytic reaction is caused by the shape as described above. The present invention can be applied to all catalysts having a shape in which a substance that causes deterioration of the catalytic reaction is mixed in the reaction fluid.

  As described above, according to the present invention, by moving a portion including a specific range from the gas inlet side of the used denitration catalyst from the inlet side of the exhaust gas flow path of the exhaust gas treatment apparatus, It is possible to provide a performance recovery method for an exhaust gas treatment apparatus that can recover the denitration performance. This makes it possible to maintain the performance of the exhaust gas treatment device at a low cost without replacing and adding a deteriorated denitration catalyst.

It is a figure which shows the mode of the internal flow of a honeycomb catalyst. It is a figure which shows the relationship between the turbulent flow continuous distance by a simulation result, and Uin * Ly. It is a figure which shows the relationship between the turbulent flow continuous distance in an actual apparatus, and the contamination distance of a catalyst. It is a figure which shows an example of the performance recovery process of the catalyst concerning one Embodiment of this invention. It is a figure which shows the combination aspect of the cut | disconnected catalyst concerning one Embodiment of this invention. It is a figure which shows the excision state of the catalyst concerning one Embodiment of this invention. It is a figure which shows the performance recovery process by the grinding | polishing process concerning one Embodiment of this invention. It is a figure which shows schematic structure of the waste gas processing apparatus using the denitration catalyst to which this invention method is applied. It is a figure which shows the result of the test example 4 of this invention. It is a figure which shows the result of the test example 5 of this invention.

  The best mode for carrying out the present invention will be described below with reference to the drawings. The description of the present embodiment is an exemplification, and the configuration of the present invention is not limited to the following description. In the present embodiment, a case where the honeycomb catalyst is applied to a denitration catalyst of an exhaust gas treatment apparatus will be described as an example, but it is needless to say that the present invention is not limited to such use.

  In the method for recovering the performance of the exhaust gas treatment apparatus of the present invention, when the honeycomb catalyst is deteriorated, as described above, only the predetermined range on the inlet side is deteriorated, and the other ranges are hardly deteriorated. Based on the knowledge, the degraded part is rearranged to move from the entrance side.

  Here, the flow of the exhaust gas passing through the gas flow path of the honeycomb catalyst will be described with reference to the drawings. FIG. 1 is a view showing a state of exhaust gas flowing inside a honeycomb catalyst based on a simulation result. Note that the honeycomb catalyst 1 shown in FIG. 1 has a plurality of gas passages 1A penetrating through a substantially square columnar structure in the length direction, and the overall size is 600 mm × 6 mm × 6 mm. It is assumed that the channels 1a are formed with a pitch of 7 mm and a honeycomb diameter of 6 mm.

First, when the exhaust gas enters the gas flow path 1A from a wide space outside the honeycomb catalyst 1, the space ratio decreases from, for example, 1 to 0.64, and the exhaust gas is considerably disturbed in the gas flow path 1A. Passes in contact with the wall (catalyst wall). That is, the exhaust gas that has entered the gas flow path 1A is disturbed by friction with the catalyst wall ((A) in the figure), and coal ash contained in the exhaust gas and NH ₃ or NO _{X as} a reactant collide with the wall surface. (B in the figure).

The exhaust gas is gradually rectified as it passes through the gas flow path 1A, and NH ₃ or NO _X colliding with the wall surface is extremely reduced ((C) in the figure), and the gas flow path 1A. Most of the NH ₃ or NO _X passes through the boundary with the wall surface without contacting the wall surface ((D) in the figure). That is, after the exhaust gas is rectified, the denitration reaction is hardly performed.

  The turbulence of gas in a general honeycomb catalyst varies depending on the inflow speed ((V) in the figure) and the diameter of the gas flow path of the honeycomb catalyst, but as shown in FIG. In the honeycomb catalyst 1 in which the gas flow path 1A is formed at 6 mm), the turbulent flow region ((X) in the figure) extends from the gas inlet side to about 300 mm, and the wall in that range greatly contributes to the denitration reaction. It has become.

  Here, the following relationship could be estimated from the simulation results for the above-described turbulent region. In the simulation, the structure has a plurality of gas flow paths 1A penetrating in the lengthwise direction in a substantially quadrangular prism-shaped structure, the overall size is 600 mm × 6 mm × 6 mm, the gas flow paths 1a are 7 mm pitch, and the honeycomb diameter is Was used at a gas temperature of 350 ° C. In the following description, the turbulent flow continuous distance refers to a place where turbulent energy disappears when transitioning from turbulent flow to laminar flow.

  In this simulation, the turbulent flow continuous distance Lts when the fluid inflow velocity Uin was 4, 6, and 10 m / s was determined to be 50, 80, and 180 mm, respectively.

In general, the state of the fluid in the calculation is the Reynolds number Re (Re = Uin · Ly / νν = 5.67 × 10 ⁻⁵ m ² / S), which is a parameter using the inflow velocity Uin and the honeycomb diameter Ly. Constant).

  Therefore, in a honeycomb catalyst having a honeycomb diameter of 6 mm, the turbulent flow sustaining region Lts (mm) is determined by the product of the inflow velocity Uins (m / s) and the honeycomb diameter Lys (mm), as shown in FIG. The relationship between the product of the inflow velocity Uins and the honeycomb diameter Lys and the turbulent flow continuous distance Lts is obtained. As a result, it can be inferred from the approximate expression obtained from the least square method that the turbulent flow sustain distance Lts when the honeycomb diameter Lys is 6 mm is specified by the following expression (1).

  Here, when the honeycomb diameter Lys = 6 mm is a constant and the honeycomb diameter Ly (mm) is arbitrary, the turbulent flow sustaining distance Lt when the inflow velocity is Uin can be specified by the following formula (2). This is the general formula.

  Here, in order to compare the simulation result with the degradation site in the actual device, the turbulent flow sustaining region Lt and the degradation site in the actual device, that is, the size of the contamination range (stain distance) that is a factor of catalyst degradation. 3), the result shown in FIG. 3 was obtained. That is, in an actual apparatus, it is presumed that the turbulent flow is maintained for a long time with respect to the turbulent continuous distance Lt obtained from the above-mentioned simulation due to factors such as uneven inflow velocity and development of fluid turbulence.

In the case of specifying a predetermined range until rectification by an actual device, that is, a deteriorated part, it is necessary to multiply the expression (2) by a constant a, and the deteriorated part range Lb is expressed by the following formula ( It is estimated that it is specified in 3). The constant a is a constant selected from the range of 3 to 5 when the honeycomb catalyst has a honeycomb diameter of 6 mm (7 mm pitch) and the inflow speed is 6 m / s.
Lb = a · Lt (3)

  Here, in the above-described embodiment, a honeycomb catalyst having a honeycomb diameter of 6 mm (7 mm pitch) is used at 6 m / s. Therefore, when Lt = 80 mm and a≈3.8, the actual degradation site is about It corresponds to 300mm.

  As described above, in this embodiment, the predetermined range until the exhaust gas is rectified in the honeycomb catalyst 1, that is, the range from the inlet side of the gas flow path 1A to about 300 mm is greatly involved in the denitration reaction. Focusing on the fact that the used honeycomb catalyst is rearranged so that the 300 mm portion on the inlet side (hereinafter referred to as a deteriorated portion) is moved from the inlet side of the exhaust gas flow path of the exhaust gas treatment device. Perform performance recovery processing. Here, the rearrangement so that the deteriorated part is moved from the inlet side of the exhaust gas flow path means that the deteriorated part is removed from the inlet side and a part that is hardly deteriorated is arranged on the inlet side. The following aspects are conceivable.

  First, there is a method in which the honeycomb catalyst is rearranged with the feeding direction reversed so that the deteriorated portion is located on the downstream side. Such a method will be specifically described with reference to FIG.

  As shown in FIG. 4, the exhaust gas treatment apparatus 10 includes a honeycomb catalyst 1 in an apparatus main body 11, and a treated gas introduction pipe 12 is connected to one of the apparatus main bodies 11 and an exhaust gas pipe 13 is connected to the other. . Here, it is assumed that the honeycomb catalyst 1 uses the part A as the inlet side and the part B as the outlet side, and the predetermined range on the part A side is the deteriorated part X. Then, the honeycomb catalyst 1 is rearranged so that the feeding direction is reversed (hereinafter also referred to as reverse arrangement). This reverse arrangement means that the part B is on the inlet side and the part A is on the outlet side. As a result, in the exhaust gas treatment, since the portion B where little deterioration has occurred is the inlet side, the performance is remarkably recovered.

  In this case, the honeycomb catalyst 1 may be reversely arranged in the apparatus main body 11, but the gas to be treated introduction pipe 12 connected to the part A side and the exhaust gas pipe 13 connected to the part B side are exchanged. Thus, the flow of the gas to be processed itself may be reversed by connecting them, and it goes without saying that the effect is the same.

  The second method is to cut the honeycomb catalyst into a plurality of pieces in the flow direction and rearrange the honeycomb catalyst so that the deteriorated portion is not located at least on the most upstream side.

  Specifically, as shown in FIG. 5, the honeycomb catalyst 1 is assumed that the part A is used as the inlet side and the part B is used as the outlet side, and the predetermined range on the part A side is the deteriorated part X. May be rearranged so that the degradation site X is not located on the inlet side. That is, as shown in FIG. 5 (a), only the catalyst 1a including the deteriorated portion X may be reversely arranged and the portion C may be arranged on the inlet side, or FIG. 5 (b) or (c). ), The catalyst 1b on the outlet side may be disposed on the inlet side, and various other rearrangements are conceivable.

  When cut and rearranged in this way, the catalyst 1a and the catalyst 1b may be in close contact with each other or may be spaced apart from each other, but at the inlet side of the catalyst 1a or 1b arranged on the downstream side, Since it is considered that the flow of the processing gas is disturbed, it is expected that this portion will greatly contribute to the exhaust gas treatment, and the exhaust gas treatment capacity is expected to be improved from before the recovery. Therefore, as shown in FIG. 5 (b), the degradation site X may be arranged on the inlet side of the downstream catalyst 1a. For example, as shown in FIG. 5 (a) and (c), It is preferable to arrange a portion where no deterioration has occurred on the inlet side.

  Further, the honeycomb catalyst 1 may be cut and rearranged into three or more. For example, the same effect can be expected if the honeycomb catalyst 1 is cut to a predetermined length equivalent to the deteriorated portion X at least. In the case of cutting longer than the deteriorated portion X, if the length is doubled, there is an advantage that it can be reused by reverse placement.

  Third, there is a method in which the honeycomb catalyst is rearranged in a state in which the deteriorated portion of the honeycomb catalyst is removed.

  Specifically, as shown in FIG. 6, the honeycomb catalyst is considered that the portion A is used as the inlet side and the portion B is used as the outlet side, and the predetermined range on the portion A side is the deteriorated portion X. At least the deteriorated portion X of 1 is excised to make a catalyst 1c, and this catalyst 1c is rearranged and used in the same direction or in the opposite direction. In this case, the length of the honeycomb catalyst is shorter than before the recovery, but the range contributing to the performance of exhaust gas treatment is almost the predetermined range on the inlet side, so there is no problem in performance. Therefore, when degradation occurs again, the degradation site can be further cut and removed.

  Fourthly, a method is conceivable in which the range of the deteriorated portion of the side wall of the gas flow path of the honeycomb catalyst is polished and the honeycomb catalyst is rearranged.

  Specifically, as shown in FIG. 7, the honeycomb catalyst 1 is assumed that the part A is used as the inlet side and the part B is used as the outlet side, and the predetermined range on the part A side is the deteriorated part X. The abrasive is recovered only by shot blasting or the like only in the degraded portion X, and rearranged. The direction of rearrangement may be any of those shown in FIG. 7 (a) or (b), but it goes without saying that the reverse performance of FIG. 7 (b) allows a sufficient performance recovery. Absent. In this method, a conventionally known polishing process can be used. However, in the method of the present invention, it is not necessary to polish the entire longitudinal direction of the gas flow path of the honeycomb catalyst 1 as in the prior art, and only the degraded portion X needs to be polished. Therefore, the polishing process can be realized relatively easily.

  Further, the method of the present invention may be combined with a treatment for cleaning the honeycomb catalyst. That is, in the first method described above, after the honeycomb catalyst 1 is washed, it may be reversely arranged. In the second method, after the cutting, the catalyst 1a including the deteriorated portion X may be washed and used. Furthermore, in the fourth method, the cleaning process may be performed before or after the polishing process, and preferably the cleaning process may be performed after the polishing process.

  The cleaning treatment here is not particularly limited, but in the case of a denitration catalyst, particularly a denitration catalyst used in a flue gas denitration device of a coal fired boiler, regenerated water at room temperature without substantially containing chlorine and a cleaning component. For example, it is preferable to perform a washing process in which, after, for example, dipping in reclaimed water is immersed until foaming is completed, the water is taken out and drained. That is, in the case of such a catalyst, the catalytic activity can be sufficiently recovered by simply immersing it in pure water at room temperature, and the treated reclaimed water can be used repeatedly, and heavy metals are also included in the treatment. Therefore, there is an advantage that water treatment can be performed relatively easily.

  Furthermore, in the method of the present invention, in the exhaust gas treatment apparatus in which the honeycomb catalyst is arranged in multiple stages in the flow direction, the above-described recovery treatment can be applied to the honeycomb catalyst arranged in each stage. In addition, when applying the recovery process, the recovery process may be applied to the honeycomb catalyst arranged in all the stages. However, if the deterioration state is grasped for each stage, the stage where the deterioration has occurred. The recovery process may be applied only to the honeycomb catalyst.

(Example)
Hereinafter, as an exhaust gas treatment apparatus to which the method of the present invention is applied, a flue gas denitration apparatus provided in a thermal power plant is shown as an example, but the exhaust gas treatment apparatus of the present embodiment is not limited to this.

As shown in FIG. 8, the exhaust gas treatment apparatus 10A includes a gas introduction pipe 12A that is connected to the upstream side of the apparatus main body 11A and communicates with the boiler apparatus of the thermal power plant, and an exhaust gas pipe 13A that is connected to the downstream side. The apparatus main body 11A has an exhaust gas passage 110, and a plurality of layers, in this embodiment, four layers of denitration catalysts 14A to 14D are arranged at predetermined intervals in the middle of the apparatus main body 11A. ing. Each of the denitration catalysts 14A to 14D is provided so that the exhaust gas introduced from the treated gas introduction pipe 12A sequentially passes through the exhaust gas flow path 110, and is in contact with the passed exhaust gas to oxidize nitrogen contained in the exhaust gas. Things (NO _x ) are reduced. Note that NH ₃ is injected into the treated gas introduction pipe 12A communicating with the boiler device in accordance with the amount of exhaust gas from the boiler body.

Here, the type, shape, and the like of each of the denitration catalysts 14A to 14D are not particularly limited, but in general, the denitration catalysts 14A to 14D have a honeycomb structure in which TiO ₂ is used as a carrier and V ₂ O ₅ is used as an active component.

  In the present embodiment, a plurality of columnar honeycomb type denitration catalysts 14 having a plurality of gas flow passages 14a penetrating in the length direction in a substantially rectangular columnar structure are arranged side by side to combine each denitration catalyst 14A- 14D is configured. Each denitration catalyst 14 has a length of 860 mm, and a plurality of gas flow paths 14a are formed at a pitch of 7 mm, and corresponds to the honeycomb catalyst 1 shown in FIG.

  Further, the intervals between the denitration catalysts 14A to 14D are about a height that can be inspected by a person or about 2000 mm at which a sample catalyst can be taken out.

Here, in the denitration catalyst management unit 20, the denitration catalyst 14A~14D on the inlet side and the outlet side is provided with gas sampling means 15A to 15E, respectively gas sampling means 15A to 15E are concentration of NO _x measurement means 16A to 16E and NH ₃ concentration measuring means 17A to 17E, and these measurement results are collected in the denitration rate measuring means 18 for calculating the denitration rate and the denitration burden rate of each denitration catalyst 14A to 14D. It has become.

The gas sampling means 15A to 15E collect a desired amount of sampling gas through a sampling pipe at a desired timing, and the collected sampling gas is supplied to the NO _x concentration measuring means 16A to 16E and NH ₃ concentration measuring means 17A to 17E. To supply.

The sampling gas sampling by the gas sampling means 15A to 15E is not particularly limited, but is preferably performed during normal operation of the power plant, preferably at the rated load at which the gas amount is maximized. Further, even if the gas sampling interval is about 6 months at the maximum, it is sufficient for managing the performance of the denitration catalysts 14A to 14D. However, if the frequency is increased, the management accuracy is improved. For example, about once every 1 to 2 months. It is preferable to carry out at a frequency of In particular, in the downstream catalyst layer, the NH ₃ concentration decreases and the fluctuation range increases. Therefore, in order to improve management evaluation, the number of measurements of NH ₃ concentration is increased and the denitration rate is obtained from the average concentration. It is preferable to do so.

Further, the denitration rate measuring means 18 acquires the measurement results from the NO _x concentration measuring means 16A to 16E and the NH ₃ concentration measuring means 17A to 17E, and from these measurement results, the denitration rate and denitration of each of the denitration catalysts 14A to 14D. The burden rate is calculated.

Here, in consideration of the inlet molar ratio of each of the denitration catalysts 14A to 14D = inlet NH ₃ / inlet NO _x , the denitration rate η based on the NH ₃ concentration is calculated based on the following formula (4).

  The evaluation molar ratio is a molar ratio set for evaluating the denitration catalyst, and an arbitrary molar ratio can be set. For example, the operating molar ratio of the power plant is about 0.8, for example, 0.8. You only have to set it.

  In such an exhaust gas treatment apparatus 10A, since the deteriorated one of the four layers of the denitration catalysts 14A to 14D can be accurately grasped, the above-described deterioration of the denitration catalysts 14A to 14D is described above. Recovery processing can be performed.

  Hereinafter, tests using a performance test apparatus will be carried out. However, since the catalyst that can be installed in the apparatus is limited to a catalyst having a total length of 600 mm or less, a denitration catalyst cut out to 600 mm is used.

(Comparative test example)
Denitration obtained by cutting 600 mm from the inlet side with respect to the gas flow direction from a 860 mm long denitration catalyst that was deteriorated by use of an actual coal-fired power plant flue gas denitration device (configuration corresponding to the exhaust gas treatment device shown in FIG. 8) The catalyst (comparative test piece) is placed in the performance test apparatus as it is (same as the original state), and the molar ratio (inlet molar ratio = inlet NH ₃ / inlet NO _X ) is 0.54, 0.72, 0 Each denitration rate η was set to 0.87 and 0.98, and the inflow rate was 6 m / s, and was measured based on the NH ₃ concentration as shown in the above formula (4). The comparative test piece here corresponds to the honeycomb catalyst 1 before recovery shown in FIG. 4 and has not been subjected to any performance recovery processing.

(Test Example 1)
600 mm from the outlet side with respect to the gas flow direction was cut out from the denitration catalyst having a total length of 860 mm, which was deteriorated by using an actual coal-fired power plant flue gas denitration device (configuration corresponding to the exhaust gas treatment device shown in FIG. 8). The denitration catalyst (test piece 1) is reversed and installed in the performance test apparatus, and the molar ratio (inlet molar ratio = inlet NH ₃ / inlet NO _X ) is 0.57, 0.73, 0.87, and 0.98. Each denitration rate η was measured based on the NH ₃ concentration as shown in Equation (4) described above. The test piece 1 installed here corresponds to the recovered honeycomb catalyst 1 shown in FIG.

(Test Example 2)
600 mm from the outlet side with respect to the gas flow direction was cut out from the denitration catalyst having a total length of 860 mm, which was deteriorated by using an actual coal-fired power plant flue gas denitration device (configuration corresponding to the exhaust gas treatment device shown in FIG. 8). The denitration catalyst (test piece 2) is installed in the performance test apparatus in the same direction, and the molar ratio (inlet molar ratio = inlet NH ₃ / inlet NO _X ) is 0.54, 0.73, 0.87, 0.97. Each denitration rate η was measured based on the NH ₃ concentration as shown in the above-mentioned formula (4). The test piece 2 installed here corresponds to the state of the recovered honeycomb catalyst 1c shown in FIG. That is, it corresponds to the honeycomb catalyst 1c in which the deteriorated portion is removed and rearranged as it is.

(Test Example 3)
Similarly to Test Example 1, the gas removal direction was cut 600 mm from the outlet side, and the denitration catalyst (test piece 3) subjected to the cleaning treatment was reversed and installed in the performance test apparatus, and the molar ratio (inlet molar ratio = inlet) Each denitration rate η with NH ₃ / inlet NO _X ) of 0.54, 0.72, 0.89, and 0.99 was measured based on the NH ₃ concentration as shown in the above formula (4). That is, except for the cleaning treatment and the set value of the molar ratio, it is the same as in Test Example 1, and the test piece 3 is different from the test piece 1 in that the cleaning treatment is performed.

Here, Table 1 shows a comparison of measurement results of Test Examples 1 to 3 and Comparative Test Examples. In addition to the comparative test example, a new product as a comparative control product having a molar ratio (inlet molar ratio = inlet NH ₃ / inlet NO _X ) of 0.56, 0.76, 0.94, 1.12. Table 1 also shows each denitration rate η based on extrapolated values obtained by measuring between 100 mm and 500 mm in steps of 100 mm and extrapolating by the least square method.

  As a result, it was confirmed that the denitration catalysts in Test Examples 1 to 3 that had undergone some performance recovery treatment recovered the denitration rate compared to the denitration catalysts that had not been subjected to any performance recovery treatment as in the comparative test examples. It was. Furthermore, with respect to the denitration catalyst of Test Example 3, it was confirmed that the denitration rate recovered to a state close to a new product.

(Test Example 4)
For the new denitration catalysts of Comparative Test Example and Test Examples 1 to 3, the flow rate inside the honeycomb was 6 m / s at 360 ° C., the catalyst length (test piece length) was 600 mm, and the SV value was 99001 / h, each NOx removal rate with an AV value of 23.3 m ³ N / m ² , a molar ratio of 0.82 and a gas temperature of 360 ° C. was measured, and the performance recovery rates calculated based on the following formula (5) were compared. . The results are shown in Table 2 and FIG.

  In addition, the performance recovery rate of a new article which is a comparative product is based on an extrapolated value as in Test Example 3, and is calculated for a 500 mm specimen in addition to a specimen having a length of 600 mm.

  As a result, it was confirmed that the catalyst installed in reverse after cutting out 600 mm from the outlet side in the gas flow direction in Test Example 3 and performing the cleaning treatment exhibits a remarkable performance recovery rate.

(Test Example 5)
About the comparative test piece, the molar ratio was 0.6, 0.8, 1.0, and 1.2, and the reaction amount of NO _X per unit length was measured every 100 mm. The results are shown in Table 3 and FIG. Note that the data after 600 mm is a mathematical formula that combines the manufacturer's published data.

As a result, a state in which the tangent lines just overlap each other in the range of the catalyst length from 300 mm to 400 mm was recognized. Therefore, it can be inferred that both gas diffusion and NH ₃ adsorption are performed up to this range. When the catalyst length is 400 mm or more, a state in which the reaction amount of NO _X is drastically reduced is recognized, so that it can be assumed that only the reaction of gas diffusion is performed.

  The present invention can be applied to all catalysts having a shape in which a reacting fluid passes through the inside of the honeycomb and reacts, and further to all catalysts having a shape in which a substance that causes deterioration of the catalytic reaction is mixed in the reaction fluid. It is.

Claims (5)

An exhaust gas treatment apparatus having a gas flow path for passing a gas to be treated and a honeycomb catalyst for treating the gas to be treated by colliding a side wall of the gas flow path with the gas to be treated in the exhaust gas flow path. A performance recovery method,
The honeycomb catalyst is a single-layer catalyst for flue gas denitration, and there is no turbulent energy at the time of transition from a turbulent flow to a laminar flow in a predetermined range from the upstream side of the flow direction of the gas to be treated of the honeycomb catalyst. It is assumed that the deteriorated part is identified depending on the turbulent flow distance, and the deteriorated part is moved from the inlet side of the exhaust gas flow path, and the predetermined range from the inlet side of the exhaust gas flow path is a part other than the deteriorated part. Thus, when the honeycomb catalyst is rearranged, the performance is recovered by rearranging the honeycomb catalyst with the feeding direction reversed so that the deteriorated portion is located on the downstream side. Device performance recovery method. The method for recovering performance of an exhaust gas treatment apparatus according to claim 1 , wherein the range of the deteriorated portion of the side wall of the gas flow path of the honeycomb catalyst is polished and the honeycomb catalyst is rearranged. In the range 1 or 2, wherein said predetermined range, Ri range der to flow of the exhaust gas that is passed through feed to the gas flow path is rectified, the predetermined range Lb is, Lt the sustained turbulent flow distance In this case, Lb = a · Lt (a; constant) is specified, and the performance recovery method for the exhaust gas treatment apparatus is characterized. The predetermined range Lb (mm) according to any one of claims 1 to 3 , wherein the inflow velocity is Uins (m / s), the arbitrary honeycomb diameter is Ly (mm), and the honeycomb diameter constant Lys is 6 mm. In this case, the exhaust gas treatment device performance recovery method is within a range specified by the following formula (A).
Lb = a (Ly / Lys) · 22e ^{0.035 (Ly · Uin)} (A)
(A is a constant selected from the range of 3 to 5 when the honeycomb catalyst has a honeycomb diameter of 6 mm and the inflow rate is 6 m / s.) Any one of claims 1 to 4 , wherein the honeycomb catalyst is used in combination with a regeneration method in which the honeycomb catalyst is substantially immersed in regenerated water at room temperature without containing chlorine and a cleaning component, and then taken out and drained. A method for recovering the performance of an exhaust gas treatment apparatus.

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