JP6627312B2 - Coal-fired power plant - Google Patents

Description

  The present invention relates to a coal-fired power generation facility. More specifically, the present invention relates to a coal-fired power generation facility capable of suppressing deterioration of a denitration catalyst constituting a denitration device.

  In a coal-fired power plant, nitrogen oxides are generated by the burning of coal, but it is necessary to keep the emission of nitrogen oxides below a certain level by the Air Pollution Control Law. Therefore, power plants are equipped with denitration equipment to reduce and decompose nitrogen oxides. In this denitration apparatus, a denitration catalyst containing an active component such as vanadium pentoxide is disposed, and by coexisting ammonia here, denitration is realized by a reduction reaction at a high temperature.

  Since this denitration catalyst generally operates efficiently in a high-temperature atmosphere of 300 ° C. to 400 ° C., it is necessary to denitrate exhaust gas containing a very large amount of dust immediately after burning coal in a boiler. In order to maintain the performance of the denitration device, it is necessary to replace the catalyst with reduced activity with a new catalyst or to regenerate the catalyst.

  For example, Patent Literature 1 below discloses a method of replacing a denitration catalyst of a flue gas denitration apparatus in which a denitration catalyst is filled in a plurality of stages, and a catalyst removal step of removing a first-stage denitration catalyst located on the most upstream side. And a catalyst moving step of sequentially moving all the denitration catalysts of the second and subsequent stages to the first stage upstream, and a catalyst for replenishing a new denitration catalyst in the lowermost stage that has been moved and emptied by the catalyst moving step. A method for replacing a denitration catalyst including a replenishing step is disclosed.

JP 2013-052335 A

  However, in the first place, there is no knowledge about when to replace or regenerate the denitration catalyst. For this reason, the present situation is to measure the decrease in the denitration rate by measuring the exhaust gas on site or actually collecting a catalyst sample and conducting a catalyst performance test or the like. Since the deterioration of the function of the denitration catalyst in the operation of coal-fired power plants gradually progresses over a long period of time, it is extremely important to clarify this deterioration mechanism in predicting deterioration and taking measures to control deterioration. It is.

  The present inventors have conducted intensive studies on the deterioration mechanism of the denitration catalyst, and found that a deposit having a particle size much smaller than the range of the conventional coal ash having a particle size of about several tens μm to about 100 μm was obtained. It was found that the surface of was coated to form a coating layer, whereby the contact between the denitration catalyst and the exhaust gas was hindered, and the performance of the denitration catalyst was reduced.

  Accordingly, an object of the present invention is to provide a coal-fired power generation facility capable of suppressing deterioration of a denitration catalyst by preventing a deposit having a small particle size from covering the surface of the denitration catalyst.

  The present invention provides a pulverized coal machine that pulverizes coal to produce pulverized coal, a combustion boiler that burns pulverized coal produced in the pulverized coal machine, and a pulverized coal boiler that is disposed downstream of the combustion boiler. The present invention relates to a coal-fired power plant including a denitration device for removing nitrogen oxides contained in exhaust gas generated by burning coal, and a grounding member for grounding the denitration device.

  Further, the denitration device is a tubular casing having conductivity, and a plurality of honeycomb catalysts accommodated in the casing, wherein the plurality of elongated honeycombs are formed with a plurality of through holes extending in a longitudinal direction. A catalyst, a seal member disposed between the honeycomb catalysts arranged adjacent to each other in the short direction to prevent the inflow of exhaust gas, and a plurality of the honeycomb catalysts are a conductive carrier; And a catalyst material to be carried, and the seal member is preferably formed of a conductive member.

  Further, it is preferable that the coal-fired power generation facility further includes an ion generator that is disposed on the upstream side of the denitration apparatus and generates positive ions and negative ions.

  ADVANTAGE OF THE INVENTION According to this invention, the coal-fired power generation equipment which can suppress deterioration of a denitration catalyst by preventing that the deposit of a small particle size coats the surface of a denitration catalyst can be provided.

It is a figure showing composition of a coal-fired power generation facility concerning a 1st embodiment of the present invention. It is a figure which expands and shows the vicinity of the combustion boiler shown in FIG. It is a figure which expands and shows the vicinity of the denitration apparatus shown in FIG. It is a figure which shows typically the structure of the denitration catalyst layer which comprises a denitration apparatus. It is a figure which expands and shows the vicinity of the denitration apparatus which concerns on 2nd Embodiment.

Hereinafter, preferred embodiments of the coal-fired power generation facility of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the coal-fired power generation facility 1 of the first embodiment is provided on a coal bunker 20, a coal feeder 25, a pulverized coal machine 30, a combustion boiler 40, and a downstream side of the combustion boiler 40. Exhaust passage 50, a denitration device 60 provided in the exhaust passage 50, a grounding member 10, an air preheater 70, an electric precipitator 90, a gas heater (for heat recovery) 80, an induced draft fan 210, a desulfurization device 220, A gas heater (for reheating) 230, a desulfurization ventilator 240, and a chimney 250 are provided.

The coal bunker 20 stores coal supplied by a coal transportation facility from a coal silo (not shown). The coal feeder 25 supplies the coal supplied from the coal bunker 20 to the pulverized coal machine 30 at a predetermined supply speed.
The pulverized coal machine 30 pulverizes the coal supplied from the coal feeder 25 to produce pulverized coal. In the pulverized coal machine 30, the coal is pulverized to an average particle size of 60 μm to 80 μm. The particle size distribution of pulverized coal is about 10 to 15% for 150 μm or more, about 30 to 40% for 75 μm to 150 μm, and about 45 to 60% for less than 75 μm.
As the pulverized coal machine 30, a roller mill, a tube mill, a ball mill, a beater mill, an impeller mill, or the like is used.

The combustion boiler 40 burns the pulverized coal supplied from the pulverized coal machine 30 together with the forcedly supplied air. Combustion of the pulverized coal generates coal ash such as clinker ash and fly ash, and also generates exhaust gas.
The clinker ash is a lump of coal ash that has fallen to the bottom of the combustion boiler 40 among coal ash generated when pulverized coal is burned. Further, fly ash is a coal ash generated when pulverized coal is burned and has a particle size (particle size of about 200 μm or less) that is blown up together with a combustion gas (exhaust gas) and flows to the exhaust passage 50 side. It refers to spherical coal ash.

  Referring to FIG. 2, the combustion boiler 40 will be described in detail. In FIG. 2, the combustion boiler 40 has a substantially inverted U-shape as a whole, and the exhaust gas (combustion gas) is inverted U-shaped along the arrow in the figure. After passing through the secondary economizer 41e, it is again inverted into a small U-shape.

  Below the combustion boiler 40, a burner 41a for burning pulverized coal near the burner zone 41a 'inside the combustion boiler 40 is arranged. A first superheater 41b is arranged near the U-shaped top inside the combustion boiler 40, and a second superheater 41c is further arranged therefrom. Further, from the vicinity of the end of the second superheater 41c, a primary economizer 41d and a secondary economizer 41e are provided in two stages. Here, the economizer (also referred to as ECO) is a group of heat transfer surfaces provided for preheating boiler feedwater using heat of exhaust gas.

  According to the combustion boiler 40 described above, pulverized coal is burned in the burner zone 41a '. The combustion temperature of the pulverized coal ranges from 1300 ° C. to 1500 ° C., and the coal ash generated by the combustion rises along the direction of the arrow, and together with the exhaust gas, the first superheater 41b and the second superheater 41c, 1c. It sequentially passes through the next economizer 41d and the secondary economizer 41e. The combustion gas exchanges heat by passing through a group of heat transfer surfaces provided for preheating boiler feedwater, and the temperature is reduced to about 450 to 500 ° C. The time required for the exhaust gas to reach the vicinity of the economizer from the burner zone 41a 'is approximately 5 to 10 seconds.

  The exhaust passage 50 is disposed downstream of the combustion boiler 40, and allows exhaust gas generated in the combustion boiler 40 and generated coal ash to flow. As described above, the exhaust passage 50 includes a denitration device 60, a discharge device 10, a charging device 15, an air preheater 70, a gas heater (for heat recovery) 80, an electric dust collection device 90, an induced draft fan 210, a desulfurization device. 220, a gas heater (for reheating) 230, a desulfurization ventilator 240, and a chimney 250 are arranged.

  The denitration device 60 removes nitrogen oxides in the exhaust gas. In the present embodiment, the denitration apparatus 60 injects ammonia gas as a reducing agent into exhaust gas at a relatively high temperature (300 ° C. to 400 ° C.), and converts nitrogen oxides in the exhaust gas into harmless nitrogen by the action of the denitration catalyst. Nitrogen oxides in exhaust gas are removed by a so-called dry ammonia catalytic reduction method that decomposes into steam.

  As shown in FIG. 3, the denitration device 60 includes a denitration reactor 61, a plurality of stages of denitration catalyst layers 62, 62, and 62 disposed inside the denitration reactor 61, and an upstream side of the denitration catalyst layer 62. A rectifying layer 63 is disposed, a rectifying plate 64 disposed near an inlet of the denitration reactor 61, and an ammonia injection section 65 disposed upstream of the denitration reactor 61.

The denitration reactor 61 is a place for a denitration reaction in the denitration device 60.
The denitration catalyst layers 62 are arranged inside the denitration reactor 61 at a plurality of stages (three stages in the present embodiment) at predetermined intervals along the flow path of the exhaust gas.

  As shown in FIG. 4, the denitration catalyst layer 62 includes a plurality of honeycomb catalysts 622 as denitration catalysts. More specifically, the denitration catalyst layer 62 includes a plurality of casings 621, a plurality of honeycomb catalysts 622 contained in the plurality of casings 621, and a seal member 623.

  The casing 621 is formed of a rectangular tubular metal member whose one end and the other end are open. The casing 621 is disposed such that one open end and the other end face the flow path of the exhaust gas in the denitration reactor 61, that is, the exhaust gas flows through the inside of the casing 621. Further, the plurality of casings 621 are connected and arranged so as to be in contact with each other so as to close the flow path of the exhaust gas in the denitration reactor 61.

The honeycomb catalyst 622 is formed in a long shape (a rectangular parallelepiped shape) in which a plurality of exhaust gas flow holes 624 extending in the longitudinal direction are formed. The plurality of honeycomb catalysts 622 are arranged such that the direction in which the exhaust gas flow holes 624 extend is along the flow path of the exhaust gas. In the present embodiment, the plurality of honeycomb catalysts 622 are arranged inside the denitration reactor 61 while being housed in the casing 621.
In the present embodiment, the honeycomb catalyst 622 is formed by supporting a conductive substance such as vanadium or tungsten on a conductive carrier and extruding the catalyst. The conductive carrier can be constituted by mixing a conductive material such as a metal fiber or a conductive filler made of carbon black or metal with a ceramic material such as titanium oxide or zirconium oxide.

  The seal member 623 is disposed between the honeycomb catalysts 622 disposed adjacent to each other in the lateral direction, and prevents exhaust gas from flowing into a gap between the honeycomb catalysts 622 disposed adjacent to each other. In the present embodiment, the seal member 623 is formed of a conductive sheet-like member, and is formed at a predetermined length (for example, 150 mm from the end) at one end and the other end in the longitudinal direction of the honeycomb catalyst 622. It is wound.

  As the seal member 623, ceramic paper formed by mixing conductive fibers or conductive fillers with inorganic fibers and binders containing alumina or silica as a main component can be used.

  In the above-described denitration catalyst layer 62, as the honeycomb catalyst 622, for example, a catalyst having a rectangular parallelepiped shape of 150 mm x 150 mm x 860 mm and having 400 exhaust gas flow holes (20 x 20) with openings of 6 mm x 6 mm is used. As the casing 621, a casing capable of accommodating 72 honeycomb catalysts 622 (6 in length × 12 in width) is used. Then, 120 to 150 casings 621 are used for one denitration catalyst layer 62. That is, 9000 to 10000 honeycomb catalysts 622 are provided in one denitration catalyst layer 62.

  The rectification layer 63 is arranged on the upstream side of the denitration catalyst layer 62. The rectifying layer 63 is formed of a metal member or the like having a plurality of openings formed in a lattice, and divides a flow path of exhaust gas in the denitration reactor 61. The rectification layer 63 rectifies the exhaust gas flowing through the exhaust passage 50 and introduced into the denitration reactor 61, and uniformly guides the exhaust gas to the denitration catalyst layer 62.

  The rectifying plate 64 is arranged near the inlet of the denitration reactor 61 and on the upstream side of the rectifying layer 63. More specifically, the current plate 64 is disposed at a bent portion of the inner wall of the denitration reactor 61 or the exhaust passage 50, and protrudes from the inner wall to the inner surface side. The current plate 64 regulates the flow of the exhaust gas at the bent portion of the exhaust passage 50 or the denitration reactor 61.

  The ammonia injection section 65 is arranged on the upstream side of the denitration reactor 61 and injects ammonia into the exhaust passage 50.

  The grounding member 10 grounds the denitration device 60. In the present embodiment, the grounding member 10 is connected to each of the plurality of denitration catalyst layers 62, and grounds these plurality of denitration catalyst layers 62.

  According to the denitration apparatus 60 and the grounding member 10 described above, first, in the ammonia injection section 65, ammonia is injected into the high-temperature exhaust gas (300 ° C. to 400 ° C.) flowing through the exhaust passage 50. The exhaust gas into which ammonia has been injected is rectified by the rectifying plate 64 and the rectifying layer 63.

In the denitration catalyst layer 62, when the exhaust gas containing ammonia passes through the exhaust gas flow hole 624 of the honeycomb catalyst 622, the nitrogen oxide reacts with the ammonia according to the following chemical reaction formula to decompose into harmless nitrogen and water vapor. Is done.
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O
NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O

  By the way, the denitration catalyst is deteriorated by use and the denitration rate is lowered. Causes of the deterioration of the denitration catalyst include thermal deterioration such as sintering, chemical deterioration due to poisoning of the catalyst component, and physical deterioration due to coal ash covering the catalyst surface. The present inventors have recently found that the particle size of coal ash (1 μm or less, more specifically, several tens nm) is much smaller than the average particle size of coal ash in the range of several tens μm to 100 μm. It has been found that the deposits caused by the coal ash cover the surface of the denitration catalyst to form a coating layer, whereby the contact between the denitration catalyst and the exhaust gas is inhibited and the performance of the denitration catalyst is reduced. Since the content of the coal ash having such a small particle size is small, it has not been considered as a cause of deterioration of the denitration catalyst.

  Here, in the present embodiment, the denitration catalyst layer 62 is grounded by the grounding member 10. Thus, when the honeycomb catalyst 622 is charged due to friction with the exhaust gas flowing through the exhaust gas flow hole 624 of the honeycomb catalyst 622, the charge generated in the honeycomb catalyst 622 can be released via the grounding member 10. Therefore, when the exhaust gas containing coal ash passes through the exhaust gas passage hole 624 of the honeycomb catalyst 622, the coal ash (particularly, minute coal ash on which an electric force is likely to act) is electrically applied to the surface of the honeycomb catalyst 622. It prevents sticking. As a result, it is possible to prevent a coating layer caused by minute coal ash from being formed on the surface of the honeycomb catalyst 622 (denitration catalyst), so that deterioration of the honeycomb catalyst can be suppressed.

  Further, the denitration device 60 is configured to include a casing 621, a honeycomb catalyst 622, and a seal member 623, and the casing 621, the honeycomb catalyst 622, and the seal member 623 are all configured to have conductivity. . Thereby, the charges generated in the honeycomb catalyst 622 can be more appropriately released via the grounding member 10. Therefore, it is possible to more effectively prevent the formation of the coating layer caused by the minute coal ash on the surface of the honeycomb catalyst 622, and it is possible to further suppress the deterioration of the honeycomb catalyst 622.

  The air preheater 70 is disposed downstream of the denitration device 60 in the exhaust passage 50. The air preheater 70 exchanges heat between the exhaust gas passing through the denitration device 60 and the combustion air sent from the push-type ventilator 75, thereby cooling the exhaust gas and heating the combustion air.

  The gas heater 80 is disposed downstream of the air preheater 70 in the exhaust passage 50. The exhaust gas heat recovered in the air preheater 70 is supplied to the gas heater 80. The gas heater 80 further recovers heat from the exhaust gas.

  The electric precipitator 90 is disposed downstream of the gas heater 80 in the exhaust passage 50. The exhaust gas heat recovered by the gas heater 80 is supplied to the electric dust collector 90. The electric precipitator 90 is a device that collects coal ash (fly ash) in exhaust gas by applying a voltage to an electrode. The fly ash collected by the electric dust collector 90 is collected by the fly ash collecting device 120.

  The induction ventilator 210 is arranged downstream of the electric precipitator 90 in the exhaust passage 50. The induction ventilator 210 takes in the exhaust gas from which fly ash has been removed in the electric precipitator 90 from the primary side and sends it out to the secondary side.

  The desulfurization device 220 is arranged in the exhaust passage 50 on the downstream side of the induction ventilator 210. The exhaust gas sent from the induction ventilator 210 is supplied to the desulfurization device 220. The desulfurization device 220 sprays a mixed solution of limestone and water on the exhaust gas to absorb the sulfur oxides contained in the exhaust gas into the mixed solution to generate a desulfurized gypsum slurry, and performs a dehydration treatment on the desulfurized gypsum slurry. This produces desulfurized gypsum. The desulfurized gypsum generated in the desulfurization device 220 is recovered by a desulfurized gypsum recovery device 222 connected to the device.

  The gas heater 230 is disposed downstream of the desulfurization device 220 in the exhaust passage 50. The exhaust gas from which the sulfur oxides have been removed in the desulfurization device 220 is supplied to the gas heater 230. The gas heater 230 heats the exhaust gas. The gas heater 80 and the gas heater 230 are disposed between the exhaust gas flowing between the air preheater 70 and the electrostatic precipitator 90 and the exhaust gas flowing between the desulfurization device 220 and the desulfurization ventilator 240 in the exhaust passage 50. May be configured as a gas gas heater that performs heat exchange.

The desulfurization ventilator 240 is disposed downstream of the gas heater 230 in the exhaust passage 50. The desulfurization ventilator 240 takes in the exhaust gas heated by the gas heater 230 from the primary side and sends it to the secondary side.
The chimney 250 is disposed downstream of the desulfurization ventilator 240 in the exhaust passage 50. The exhaust gas heated by the gas heater 230 is introduced into the chimney 250. The chimney 250 discharges exhaust gas.

  According to the coal-fired power plant 1 of the first embodiment described above, the following effects can be obtained.

  (1) The coal-fired power generation facility 1 includes the grounding member 10 that grounds the denitration device 60 (denitration catalyst layer 62). Thus, when the honeycomb catalyst 622 is charged due to friction with the exhaust gas flowing through the exhaust gas flow hole 624 of the honeycomb catalyst 622, the charge generated in the honeycomb catalyst 622 can be released via the grounding member 10. Therefore, when the exhaust gas containing coal ash passes through the exhaust gas passage hole 624 of the honeycomb catalyst 622, the coal ash (particularly, minute coal ash on which an electric force is likely to act) is electrically applied to the surface of the honeycomb catalyst 622. It prevents sticking. As a result, it is possible to prevent a coating layer caused by minute coal ash from being formed on the surface of the honeycomb catalyst 622 (denitration catalyst), so that deterioration of the honeycomb catalyst can be suppressed.

  (2) The denitration device 60 is configured to include a casing 621, a honeycomb catalyst 622, and a seal member 623, and the casing 621, the honeycomb catalyst 622, and the seal member 623 are all configured to have conductivity. did. Thereby, the charges generated in the honeycomb catalyst 622 can be more appropriately released via the grounding member 10. Therefore, it is possible to more effectively prevent the formation of the coating layer caused by the minute coal ash on the surface of the honeycomb catalyst 622, and it is possible to further suppress the deterioration of the honeycomb catalyst 622.

  Next, a coal-fired power plant 1 according to a second embodiment of the present invention will be described with reference to FIG. The coal-fired power plant 1 according to the second embodiment is different from the first embodiment in that an ion generator 15 is provided.

As shown in FIG. 5, the ion generator 15 is disposed on the upstream side of the denitration device 60, and emits positive ions and negative ions toward coal ash contained in the exhaust gas. The ion generator 15 includes a plurality of discharge electrodes 151 and a charging unit 152.
The discharge electrode 151 includes a positive electrode and a negative electrode, and is disposed on the inner surface of the exhaust passage 50 or the denitration reactor 61. In the present embodiment, the discharge electrode 151 is constituted by the rectifying plate 64.
The charging unit 152 applies a high voltage to the discharge electrode 151 (rectifier plate 64).

According to the ion generator 15 described above, the corona discharge is generated from the discharge electrode 151 (rectifier plate 64) by applying a high voltage to the discharge electrode 151 (rectifier plate 64) by the charging unit 152. Accordingly, positive ions are generated by corona discharge generated from the positive electrode, and negative ions are generated by corona discharge generated from the negative electrode.
Here, the coal ash contained in the exhaust gas may be charged to the positive electrode or the negative electrode by frictional force or the like while flowing through the exhaust passage 50.

  Therefore, in the second embodiment, the coal-fired power plant 1 is configured to include the ion generator 15 arranged on the upstream side of the denitration device 60. As a result, the charged coal ash passing through the discharge electrode 151 (rectifying plate 64) is discharged by the positive and negative ions generated from the ion generator 15 and introduced into the denitration device 60 (denitration catalyst layer 62). Therefore, when the exhaust gas containing coal ash passes through the exhaust gas passage hole 624 of the honeycomb catalyst 622, the coal ash (particularly, minute coal ash on which an electric force is likely to act) is electrically applied to the surface of the honeycomb catalyst 622. It can be more effectively prevented from sticking.

Although the preferred embodiments of the coal-fired power plant 1 of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be appropriately modified.
For example, in the first embodiment and the second embodiment, the honeycomb catalyst is used as the denitration catalyst, but is not limited to this. That is, a plate-like catalyst formed by applying a catalytic substance to the surface of a net-like base material may be used as the denitration catalyst.

  In the first embodiment and the second embodiment, the seal member 623 is made of ceramic paper having conductivity. However, the present invention is not limited to this. That is, the seal member may be made of ceramic wool including a conductive member.

  Further, in the second embodiment, the discharge electrode 151 of the ion generator 15 is constituted by the rectifying plate 64, but is not limited to this. That is, the discharge electrode may be constituted by a rectifying layer. Further, the discharge electrodes may be arranged separately from the current plate.

DESCRIPTION OF SYMBOLS 1 Coal-fired power generation equipment 10 Grounding member 15 Ion generator 30 Pulverized coal machine 40 Combustion boiler 60 Denitration device 621 Casing 622 Honeycomb catalyst 623 Sealing member

Claims (2)

A pulverized coal machine that pulverizes coal to produce pulverized coal,
A combustion boiler for burning the pulverized coal produced in the pulverized coal machine,
A denitration device which is disposed downstream of the combustion boiler and removes nitrogen oxides contained in exhaust gas generated by burning pulverized coal in the combustion boiler,
A grounding member for grounding the denitration apparatus,
A coal-fired power plant comprising: an ion generator configured to generate positive and negative ions using a rectifying plate disposed upstream of the denitration device as a discharge electrode . A cylindrical casing having conductivity;
A plurality of honeycomb catalysts housed in the casing, a plurality of elongated honeycomb catalysts formed with a plurality of through holes extending in the longitudinal direction,
A seal member that is disposed between the honeycomb catalysts that are disposed adjacent to each other in the short direction and that prevents inflow of exhaust gas,
The plurality of honeycomb catalysts are configured to include a conductive carrier, and a catalyst substance supported on the conductive carrier,
The coal-fired power plant according to claim 1, wherein the seal member is configured by a conductive member.

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