WO2017022520A1 - Method for inhibiting degradation of denitration device - Google Patents

Method for inhibiting degradation of denitration device Download PDF

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Publication number
WO2017022520A1
WO2017022520A1 PCT/JP2016/071551 JP2016071551W WO2017022520A1 WO 2017022520 A1 WO2017022520 A1 WO 2017022520A1 JP 2016071551 W JP2016071551 W JP 2016071551W WO 2017022520 A1 WO2017022520 A1 WO 2017022520A1
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coal
denitration
combustion boiler
coal ash
exhaust gas
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PCT/JP2016/071551
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French (fr)
Japanese (ja)
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敏和 吉河
健治 引野
啓一郎 盛田
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中国電力株式会社
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Publication of WO2017022520A1 publication Critical patent/WO2017022520A1/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C99/00—Subject-matter not provided for in other groups of this subclass
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J15/00—Arrangements of devices for treating smoke or fumes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J7/00—Arrangement of devices for supplying chemicals to fire
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L7/00—Supplying non-combustible liquids or gases, other than air, to the fire, e.g. oxygen, steam

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  • the present invention relates to a method for suppressing deterioration of a denitration apparatus. More specifically, the present invention relates to a method for suppressing deterioration of a denitration device that can suppress degradation of a denitration catalyst constituting the denitration device.
  • denitration equipment is installed at power plants to reduce and decompose nitrogen oxides.
  • a denitration catalyst containing an active component such as vanadium pentoxide is disposed, and denitration is realized by a reduction reaction at a high temperature by coexisting ammonia therein.
  • 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 large amount of soot immediately after burning coal in a boiler. In order to maintain the performance of the denitration apparatus, it is necessary to replace or regenerate a catalyst whose activity has decreased with a new catalyst.
  • Patent Document 1 discloses a method for replacing a denitration catalyst of a flue gas denitration apparatus filled with a plurality of stages of denitration catalysts, and a catalyst removal step of taking out a first-stage denitration catalyst located on the most upstream side. And a catalyst moving step for sequentially moving all the denitration catalysts in the second and subsequent stages to the upstream side of the first stage, and a catalyst for replenishing a new denitration catalyst in the most downstream stage that has been emptied through the catalyst moving process And a replenishment step.
  • a method for replacing the denitration catalyst is disclosed.
  • the present inventors have found that a deposit having a particle size far smaller than the conventional coal ash particle size range of several tens to hundreds of ⁇ m or less is a denitration catalyst. It was found that the surface of the catalyst was coated to form a coating layer, whereby contact between the denitration catalyst and the exhaust gas was hindered and the performance of the denitration catalyst was lowered.
  • an object of the present invention is to provide a method for suppressing deterioration of a denitration apparatus that can suppress degradation of the denitration catalyst by preventing deposits having a small particle diameter from covering the surface of the denitration catalyst.
  • the present invention relates to a pulverized coal machine that pulverizes coal to produce pulverized coal, a combustion boiler that burns the pulverized coal produced in the pulverized coal machine, and a pulverized powder in the combustion boiler that is disposed downstream of the combustion boiler.
  • a denitration device for removing nitrogen oxides contained in exhaust gas generated by combustion of charcoal and a method for suppressing deterioration of the denitration device in a coal-fired power generation facility, wherein a coal ash aggregation accelerator is added to the combustion boiler
  • the present invention relates to a method for suppressing deterioration of a denitration apparatus that promotes aggregation of fine coal ash and prevents adhesion of fine coal ash to a denitration catalyst.
  • the coal ash aggregation accelerator is preferably an alkali metal and / or salt thereof, an alkaline earth metal and / or salt thereof, or iron or a salt thereof.
  • coal ash aggregation accelerator in a range of 0.1% by mass to 10% by mass with respect to 100% by mass of the coal.
  • deterioration of the denitration catalyst can be suppressed by preventing deposits having a small particle diameter from covering the surface of the denitration catalyst.
  • the coal-fired power generation facility 1 includes a coal bunker 20, a coal feeder 25, a pulverized coal machine 30, a combustion boiler 40, and an exhaust passage 50 provided on the downstream side of the combustion boiler 40. , A denitration device 60 provided in the exhaust passage 50, an air preheater 70, an electric dust collector 90, a gas heater (for heat recovery) 80, an induction fan 210, a desulfurization device 220, a gas heater (for reheating) 230, desulfurization A ventilator 240 and a chimney 250.
  • the coal bunker 20 stores coal supplied from a coal silo (not shown) by a coal transportation facility.
  • 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.
  • the coal is pulverized to an average particle size of 60 ⁇ m to 80 ⁇ m.
  • the particle size distribution of pulverized coal is about 10 to 15% at 150 ⁇ m or more, 30 to 40% at 75 to 150 ⁇ m, and 45 to 60% at less than 75 ⁇ m.
  • a roller mill, a tube mill, a ball mill, a beater mill, an impeller mill, or the like is used 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 forcibly supplied air.
  • coal ash such as clinker ash and fly ash is generated and exhaust gas is generated.
  • clinker ash means the massive coal ash which fell to the bottom part of the combustion boiler 40 among the coal ash generate
  • Fly ash has a particle size (particle size of about 200 ⁇ m or less) of coal ash generated when pulverized coal is burned and blown up with combustion gas (exhaust gas) and circulated to the exhaust passage 50 side. Spherical coal ash.
  • the combustion boiler 40 will be described in detail with reference to 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 reversed into a U-shape.
  • a burner 41a for burning pulverized coal is disposed in the vicinity of the burner zone 41a 'inside the combustion boiler 40.
  • the 1st superheater 41b is arrange
  • the 2nd superheater 41c is arrange
  • a primary economizer 41d and a secondary economizer 41e are provided in two stages.
  • the economizer (also referred to as ECO) is a heat transfer surface group provided for preheating boiler feedwater using heat retained by exhaust gas.
  • 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, the second superheater 41c, The next economizer 41d and the secondary economizer 41e are sequentially passed.
  • the combustion gas exchanges heat by passing through a heat transfer surface group provided for preheating boiler feed water, and the temperature is lowered to about 450 ° C. to 500 ° C.
  • the time required for the exhaust gas to reach the economizer from the burner zone 41a ' is approximately 5 to 10 seconds.
  • the exhaust passage 50 is arranged on the downstream side of the combustion boiler 40 and distributes the exhaust gas generated in the combustion boiler 40 and the generated coal ash.
  • the denitration device 60, the air preheater 70, the gas heater (for heat recovery) 80, the electric dust collector 90, the induction ventilator 210, the desulfurization device 220, and the gas heater (for reheating) ) 230, the desulfurization ventilator 240, and the chimney 250 are arranged in this order.
  • the denitration device 60 removes nitrogen oxides in the exhaust gas.
  • the denitration device 60 injects ammonia gas as a reducing agent into the exhaust gas at a relatively high temperature (300 ° C. to 400 ° C.), and the action of the denitration catalyst converts nitrogen oxides in the exhaust gas into harmless nitrogen. Nitrogen oxides in the exhaust gas are removed by a so-called dry ammonia catalytic reduction method that decomposes into water vapor.
  • the denitration apparatus 60 includes a denitration reactor 61, a plurality of stages of denitration catalyst layers 62, 62, 62 disposed inside the denitration reactor 61, and upstream of the denitration catalyst layer 62.
  • a rectifying layer 63 to be disposed, a rectifying plate 64 disposed in the vicinity of the inlet of the denitration reactor 61, and an ammonia injection portion 65 disposed on the upstream side of the denitration reactor 61 are provided.
  • the denitration reactor 61 is a place for denitration reaction in the denitration apparatus 60.
  • the denitration catalyst layer 62 is disposed in the denitration reactor 61 in a plurality of stages (three stages in this embodiment) at predetermined intervals along the exhaust gas flow path.
  • the denitration catalyst layer 62 includes a plurality of honeycomb catalysts (not shown) as denitration catalysts.
  • the honeycomb catalyst is formed in a long shape (cuboid shape) in which a plurality of exhaust gas circulation holes extending in the longitudinal direction are formed.
  • the plurality of honeycomb catalysts are arranged so that the exhaust gas circulation holes are along the flow path of the exhaust gas.
  • As the honeycomb catalyst for example, a catalyst having a rectangular parallelepiped shape of 150 mm ⁇ 150 mm ⁇ 860 mm and 400 exhaust gas circulation holes (20 ⁇ 20) having openings of 6 mm ⁇ 6 mm is used.
  • 9000 to 10,000 honeycomb catalysts are installed in one denitration catalyst layer 62.
  • a honeycomb catalyst is formed by supporting a catalyst material such as vanadium or tungsten on a ceramic material such as titanium oxide or zirconium oxide and then performing extrusion molding.
  • the rectifying layer 63 is disposed on the upstream side of the denitration catalyst layer 62.
  • the rectifying layer 63 is composed of a metal member or the like having a plurality of openings formed in a lattice shape, and partitions the exhaust gas flow path in the denitration reactor 61.
  • the rectifying layer 63 rectifies the exhaust gas introduced through the exhaust passage 50 and introduced into the denitration reactor 61, and uniformly guides it to the denitration catalyst layer 62.
  • the rectifying plate 64 is disposed on the upstream side of the rectifying layer 63 in the vicinity of the inlet of the denitration reactor 61. More specifically, the rectifying 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 rectifying plate 64 adjusts the flow of exhaust gas at the bent portion of the exhaust passage 50 or the denitration reactor 61.
  • the ammonia injection part 65 is arranged upstream of the denitration reactor 61 and injects ammonia into the exhaust passage 50.
  • ammonia is injected into the high-temperature exhaust gas (300 ° C. to 400 ° C.) flowing through the exhaust passage 50 in the ammonia injection section 65.
  • the exhaust gas into which ammonia has been injected is rectified by the rectifying plate 64 and the rectifying layer 63 and introduced into the denitration catalyst layer 62.
  • 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 that has passed through the denitration device 60 and the combustion air sent from the push-in type ventilator 75 to cool the exhaust gas and heat the combustion air.
  • the gas heater 80 is disposed downstream of the air preheater 70 in the exhaust passage 50.
  • the exhaust gas recovered by the air preheater 70 is supplied to the gas heater 80.
  • the gas heater 80 further recovers heat from the exhaust gas.
  • the electrostatic precipitator 90 is disposed on the downstream side of the gas heater 80 in the exhaust passage 50.
  • the exhaust gas recovered in the gas heater 80 is supplied to the electric dust collector 90.
  • the electric dust collector 90 is a device that collects coal ash (fly ash) in exhaust gas by applying a voltage to electrodes.
  • the fly ash collected by the electric dust collector 90 is collected by the fly ash collection device 120.
  • the induction ventilator 210 is disposed on the downstream side of the electric dust collector 90 in the exhaust passage 50.
  • the induction ventilator 210 takes in the exhaust gas from which fly ash has been removed in the electrostatic precipitator 90 from the primary side and sends it to the secondary side.
  • the desulfurization device 220 is arranged on the downstream side of the induction fan 210 in the exhaust passage 50.
  • the desulfurization apparatus 220 is supplied with exhaust gas sent from the induction fan 210.
  • the desulfurization apparatus 220 sprays a mixed liquid of limestone and water on the exhaust gas, thereby absorbing the sulfur oxide contained in the exhaust gas into the mixed liquid to generate a desulfurized gypsum slurry, and dehydrating the desulfurized gypsum slurry. This produces desulfurized gypsum.
  • the desulfurized gypsum generated in the desulfurization apparatus 220 is recovered by a desulfurization gypsum recovery apparatus 222 connected to this apparatus.
  • the gas heater 230 is disposed downstream of the desulfurization device 220 in the exhaust passage 50.
  • the gas heater 230 is supplied with exhaust gas from which sulfur oxides have been removed in the desulfurization apparatus 220.
  • 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 electric dust collector 90 and the exhaust gas flowing between the desulfurization device 220 and the desulfurization ventilator 240 in the exhaust passage 50. It may be configured as a 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 in the gas heater 230 from the primary side and sends it to the secondary side.
  • the chimney 250 is arranged on the downstream side of the desulfurization ventilator 240 in the exhaust passage 50. Exhaust gas heated by the gas heater 230 is introduced into the chimney 250. The chimney 250 discharges exhaust gas.
  • the denitration catalyst is deteriorated by use and the denitration rate is lowered.
  • causes of deterioration of the denitration catalyst include thermal deterioration such as sintering, chemical deterioration due to poisoning of catalyst components, and physical deterioration due to the coal ash covering the catalyst surface.
  • the present inventors now have a much smaller particle size (1 ⁇ m or less, more specifically about several tens of nm) compared to the average particle size of coal ash, which is about several tens ⁇ m to one hundred ⁇ m. It has been found that deposits resulting from coal ash cover the surface of the denitration catalyst to form a coating layer, thereby inhibiting the contact between the denitration catalyst and the exhaust gas and reducing the performance of the denitration catalyst. Since the coal ash having such a small particle size has a small content, it has not been considered as a cause of deterioration of the denitration catalyst.
  • the present inventors promote the aggregation of coal ash having a small particle size by adding a coal ash aggregation accelerator to the combustion boiler 40 and burning the pulverized coal in the coal-fired power generation facility 1.
  • the inventors have found that the production of coal ash having a fine particle size can be suppressed, and have reached the present invention. That is, the present invention is a method for suppressing deterioration of a denitration catalyst in a coal-fired power generation facility, and includes a step of adding a coal ash aggregation accelerator to the combustion boiler 40.
  • the step of adding the coal ash aggregation accelerator to the combustion boiler 40 may be performed by adding the coal ash aggregation accelerator to the coal bunker 20 or by adding the coal ash aggregation accelerator directly to the combustion boiler 40. Also good.
  • the coal ash aggregation accelerator used in the present invention contains an alkali metal and / or a salt thereof, an alkaline earth metal and / or a salt thereof, or iron or a salt thereof.
  • the coal ash aggregation accelerator is preferably in the form of particles or powder. Specifically, the average particle diameter is preferably 1 ⁇ m to 100 ⁇ m, more preferably 5 ⁇ m to 70 ⁇ m.
  • coal ash aggregation promoter containing alkali metal and / or salt thereof, alkaline earth metal and / or salt thereof, or iron or salt thereof examples include limestone (CaCO 3 ) and slaked stone (Ca (OH) 2 ). , Quicklime (CaO), sodium oxide (Na 2 O), potassium oxide (K 2 O), magnesium oxide (MgO), iron oxide (Fe 2 O 3 ) and the like.
  • the ratio of the alkali metal, alkaline-earth metal, and iron with respect to coal may be 0.1 mass% or more and 10 mass% or less. If the ratio of alkali metal, alkaline earth metal and iron to coal is less than 0.1% by mass, the effect of agglomerating fine coal ash becomes insufficient, such being undesirable. Further, even if the ratio of alkali metal, alkaline earth metal and iron to coal exceeds 10% by mass, no significant improvement in the effect of agglomerating fine coal ash is observed, and the melting point of the surface of coal ash is large. Since descending may cause a large amount of coal ash to adhere to the inner wall of the combustion boiler 40 (slagging), it is not preferable.
  • the mechanism for suppressing the generation of fine particle size coal ash contained in the exhaust gas is as follows.
  • coal ash aggregation accelerator When the pulverized coal to which the coal ash aggregation accelerator is added burns in the combustion boiler 40, the melting point of the coal ash is lowered due to the presence of alkali metal, alkaline earth metal, or iron contained in the coal ash aggregation accelerator. That is, under the conditions of 1300 ° C. to 1500 ° C. inside the combustion boiler 40, coal containing silica and alumina as main components is added by adding a coal ash aggregation accelerator, which is a compound containing alkali metal, alkaline earth metal, or iron. The ash surface softens (melts) and the viscosity increases. Thereby, it is estimated that the fine coal ash particles having increased viscosity are aggregated to increase the particle size, and as a result, the production of fine coal ash having a particle size of 1 ⁇ m or less is suppressed.
  • a coal ash aggregation accelerator which is a compound containing alkali metal, al
  • the generation of fine coal ash is suppressed by utilizing the change in the viscosity of coal ash by adding the coal ash aggregation accelerator to the combustion boiler 40, and the denitration catalyst for the fine coal ash is used. Prevents adhesion to the surface. This prevents the coal ash having a fine particle diameter from covering the surface of the denitration catalyst, and suppresses the deterioration of the denitration catalyst.
  • Coal-fired power generation equipment 30 Pulverized coal machine 40 Combustion boiler 60 Denitration equipment

Abstract

Provided is a method for inhibiting the degradation of a denitration device, said method making it possible to inhibit the degradation of a denitration catalyst by preventing the surface of the denitration catalyst from becoming coated with sediment having an extremely small particle size. The method is for inhibiting the degradation of a denitration device 60 in a coal-fired power plant 1 provided with: a coal pulverizer 30 that pulverizes coal in order to produce pulverized coal; a combustion boiler 40 that burns the pulverized coal produced in the coal pulverizer 30; and a denitration device 60 that is arranged downstream from the combustion boiler 40 and that removes nitrogen oxides included in exhaust gas generated when the pulverized coal is burned in the combustion boiler 40. In the method, the agglomeration of extremely fine coal ash is promoted by adding a coal ash agglomeration promoter to the combustion boiler 40, and the extremely fine coal ash is thereby prevented from adhering to the denitration catalyst.

Description

脱硝装置の劣化抑制方法Denitration device degradation control method
　本発明は、脱硝装置の劣化抑制方法に関する。より詳しくは、脱硝装置を構成する脱硝触媒の劣化を抑制できる脱硝装置の劣化抑制方法に関する。 The present invention relates to a method for suppressing deterioration of a denitration apparatus. More specifically, the present invention relates to a method for suppressing deterioration of a denitration device that can suppress degradation of a denitration catalyst constituting the denitration device.
　石炭火力発電所では、石炭の燃焼に伴い窒素酸化物が発生するが、大気汚染防止法等により、窒素酸化物の排出は一定水準以下に抑えることが必要となっている。そこで発電所では、窒素酸化物を還元分解するために脱硝装置を設置している。この脱硝装置には、五酸化バナジウム等の活性成分を含む脱硝触媒が配置されており、ここにアンモニアを共存させることで、高温下の還元反応により脱硝を実現している。 In coal-fired power plants, nitrogen oxides are generated as coal is burned, but it is necessary to keep nitrogen oxide emissions below a certain level by the Air Pollution Control Law and other standards. Therefore, denitration equipment is installed at power plants to reduce and decompose nitrogen oxides. In this denitration apparatus, a denitration catalyst containing an active component such as vanadium pentoxide is disposed, and denitration is realized by a reduction reaction at a high temperature by coexisting ammonia therein.
　この脱硝触媒は、一般に３００℃～４００℃の高温雰囲気下で効率的に作動するため、ボイラにおいて石炭を燃焼させた直後の煤塵が非常に多く含まれた排ガスを脱硝させる必要がある。脱硝装置の性能を維持するために、活性が低下した触媒は、新品の触媒に取替えたり、再生したりする必要がある。 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 large amount of soot immediately after burning coal in a boiler. In order to maintain the performance of the denitration apparatus, it is necessary to replace or regenerate a catalyst whose activity has decreased with a new catalyst.
　例えば、下記の特許文献１には、脱硝触媒が複数段充填された排煙脱硝装置の脱硝触媒の交換方法であって、最上流側に位置する第１段目の脱硝触媒を取出す触媒取出し工程と、第２段目以降の全ての脱硝触媒を順次、１段上流側に移動させる触媒移動工程と、触媒移動工程により移動して空となった最下流段に新たな脱硝触媒を補充する触媒補充工程と、を含む脱硝触媒の交換方法が開示されている。 For example, the following Patent Document 1 discloses a method for replacing a denitration catalyst of a flue gas denitration apparatus filled with a plurality of stages of denitration catalysts, and a catalyst removal step of taking out a first-stage denitration catalyst located on the most upstream side. And a catalyst moving step for sequentially moving all the denitration catalysts in the second and subsequent stages to the upstream side of the first stage, and a catalyst for replenishing a new denitration catalyst in the most downstream stage that has been emptied through the catalyst moving process And a replenishment step. A method for replacing the denitration catalyst is disclosed.
特開２０１３－０５２３３５号公報JP 2013-052335 A
　しかしながら、そもそも、どのタイミングで脱硝触媒の取替えや再生を行うかについて、従来は知見がない。このため、現地での排ガス測定や実際に触媒サンプルを採取して触媒性能試験等を実施し、脱硝率の低下を測定しているのが現状である。石炭火力発電所の操業における脱硝触媒の機能の低下は長期間に亘って徐々に進行するものであるから、この劣化メカニズムを明らかにすることは、劣化予測や劣化抑制対策を講じる上で極めて重要である。 However, in the first place, there is no knowledge in the past regarding when to replace or regenerate the denitration catalyst. For this reason, the present situation is that the exhaust gas measurement at the site or the catalyst sample is actually collected and the catalyst performance test is carried out to measure the decrease in the denitration rate. Decreasing the function of denitration catalysts in the operation of coal-fired power plants gradually progresses over a long period of time, so it is extremely important to clarify this deterioration mechanism in order to predict deterioration and take measures to suppress deterioration. It is.
　本発明者らは、脱硝触媒の劣化メカニズムにつき鋭意検討した結果、従来の石炭灰の粒径である数十μｍ以上百μｍ以下程度の範囲に比べて遥かに小さい粒径の堆積物が脱硝触媒の表面を被覆して被覆層を形成し、それによって、脱硝触媒と排ガスの接触が阻害され脱硝触媒の性能が低下していることを見出した。 As a result of intensive investigations on the deterioration mechanism of the denitration catalyst, the present inventors have found that a deposit having a particle size far smaller than the conventional coal ash particle size range of several tens to hundreds of μm or less is a denitration catalyst. It was found that the surface of the catalyst was coated to form a coating layer, whereby contact between the denitration catalyst and the exhaust gas was hindered and the performance of the denitration catalyst was lowered.
　従って、本発明は、微小な粒径の堆積物が脱硝触媒の表面を被覆することを防ぐことで脱硝触媒の劣化を抑制できる脱硝装置の劣化抑制方法を提供することを目的とする。 Therefore, an object of the present invention is to provide a method for suppressing deterioration of a denitration apparatus that can suppress degradation of the denitration catalyst by preventing deposits having a small particle diameter from covering the surface of the denitration catalyst.
　本発明は、石炭を粉砕して微粉炭を製造する微粉炭機と、該微粉炭機において製造された微粉炭を燃焼させる燃焼ボイラと、該燃焼ボイラの下流側に配置され該燃焼ボイラにおいて微粉炭が燃焼されて発生した排ガス中に含まれる窒素酸化物を除去する脱硝装置と、を備える石炭火力発電設備における脱硝装置の劣化抑制方法であって、前記燃焼ボイラに石炭灰凝集促進剤を添加することで微小な石炭灰の凝集を促進し、脱硝触媒への微小な石炭灰の付着を防ぐ脱硝装置の劣化抑制方法に関する。 The present invention relates to a pulverized coal machine that pulverizes coal to produce pulverized coal, a combustion boiler that burns the pulverized coal produced in the pulverized coal machine, and a pulverized powder in the combustion boiler that is disposed downstream of the combustion boiler. A denitration device for removing nitrogen oxides contained in exhaust gas generated by combustion of charcoal, and a method for suppressing deterioration of the denitration device in a coal-fired power generation facility, wherein a coal ash aggregation accelerator is added to the combustion boiler The present invention relates to a method for suppressing deterioration of a denitration apparatus that promotes aggregation of fine coal ash and prevents adhesion of fine coal ash to a denitration catalyst.
　また、前記石炭灰凝集促進剤は、アルカリ金属及び／又はその塩類、アルカリ土類金属及び／又はその塩類、あるいは、鉄又はその塩類であることが好ましい。 Further, the coal ash aggregation accelerator is preferably an alkali metal and / or salt thereof, an alkaline earth metal and / or salt thereof, or iron or a salt thereof.
　また、前記石炭１００質量％に対して、前記石炭灰凝集促進剤を０．１質量％以上１０質量％以下の範囲で添加することが好ましい。 Moreover, it is preferable to add the coal ash aggregation accelerator in a range of 0.1% by mass to 10% by mass with respect to 100% by mass of the coal.
　本発明の脱硝装置の劣化抑制方法によれば、微小な粒径の堆積物が脱硝触媒の表面を被覆することを防ぐことで脱硝触媒の劣化を抑制できる。 According to the method for suppressing deterioration of a denitration apparatus of the present invention, deterioration of the denitration catalyst can be suppressed by preventing deposits having a small particle diameter from covering the surface of the denitration catalyst.
石炭火力発電設備の構成を示す図である。It is a figure which shows the structure of a coal thermal power generation equipment. 図１に示す燃焼ボイラの付近を拡大して示す図である。It is a figure which expands and shows the vicinity of the combustion boiler shown in FIG. 図１に示す脱硝装置を拡大して示す図である。It is a figure which expands and shows the denitration apparatus shown in FIG.
　以下、本発明の脱硝装置の劣化抑制方法の好ましい一実施形態について、図面を参照しながら説明する。まず、本発明の脱硝装置の劣化抑制方法が適用される石炭火力発電設備１の全体構成について、説明する。 Hereinafter, a preferred embodiment of a method for suppressing deterioration of a denitration apparatus of the present invention will be described with reference to the drawings. First, the overall configuration of the coal-fired power generation facility 1 to which the method for suppressing deterioration of a denitration apparatus of the present invention is applied will be described.
　石炭火力発電設備１は、図１に示すように、石炭バンカ２０と、給炭機２５と、微粉炭機３０と、燃焼ボイラ４０と、燃焼ボイラ４０の下流側に設けられた排気通路５０と、この排気通路５０に設けられた脱硝装置６０、空気予熱器７０、電気集塵装置９０、ガスヒータ（熱回収用）８０、誘引通風機２１０、脱硫装置２２０、ガスヒータ（再加熱用）２３０、脱硫通風機２４０、及び煙突２５０と、を備える。 As shown in FIG. 1, the coal-fired power generation facility 1 includes a coal bunker 20, a coal feeder 25, a pulverized coal machine 30, a combustion boiler 40, and an exhaust passage 50 provided on the downstream side of the combustion boiler 40. , A denitration device 60 provided in the exhaust passage 50, an air preheater 70, an electric dust collector 90, a gas heater (for heat recovery) 80, an induction fan 210, a desulfurization device 220, a gas heater (for reheating) 230, desulfurization A ventilator 240 and a chimney 250.
　石炭バンカ２０は、石炭サイロ（図示しない）から運炭設備によって供給された石炭を貯蔵する。給炭機２５は、石炭バンカ２０から供給された石炭を所定の供給スピードで微粉炭機３０に供給する。
　微粉炭機３０は、給炭機２５から供給された石炭を粉砕して微粉炭を製造する。微粉炭機３０においては、石炭は、平均粒径６０μｍ～８０μｍに粉砕される。また、微粉炭の粒度分布は、１５０μｍ以上が１０～１５％、７５μｍ～１５０μｍが３０～４０％、７５μｍ未満が４５～６０％程度となる。
　微粉炭機３０としては、ローラミル、チューブミル、ボールミル、ビータミル、インペラーミル等が用いられる。 The coal bunker 20 stores coal supplied from a coal silo (not shown) by a coal transportation facility. 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% at 150 μm or more, 30 to 40% at 75 to 150 μm, and 45 to 60% at 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.
　燃焼ボイラ４０は、微粉炭機３０から供給された微粉炭を、強制的に供給された空気と共に燃焼する。微粉炭を燃焼することによりクリンカアッシュ及びフライアッシュなどの石炭灰が生成されると共に、排ガスが発生する。
　尚、クリンカアッシュとは、微粉炭を燃焼させた場合に発生する石炭灰のうち、燃焼ボイラ４０の底部に落下した塊状の石炭灰をいう。また、フライアッシュとは、微粉炭を燃焼させた場合に発生する石炭灰のうち、燃焼ガス（排ガス）と共に吹き上げられて排気通路５０側に流通する程度の粒径（粒径２００μｍ程度以下）の球状の石炭灰をいう。 The combustion boiler 40 burns the pulverized coal supplied from the pulverized coal machine 30 together with the forcibly supplied air. By burning pulverized coal, coal ash such as clinker ash and fly ash is generated and exhaust gas is generated.
In addition, clinker ash means the massive coal ash which fell to the bottom part of the combustion boiler 40 among the coal ash generate | occur | produced when pulverized coal is burned. Fly ash has a particle size (particle size of about 200 μm or less) of coal ash generated when pulverized coal is burned and blown up with combustion gas (exhaust gas) and circulated to the exhaust passage 50 side. Spherical coal ash.
　図２を参照して、燃焼ボイラ４０について詳しく説明すると、図２において、燃焼ボイラ４０は全体として略逆Ｕ字状をなしており、図中矢印に沿って排ガス（燃焼ガス）が逆Ｕ字状に移動した後、２次節炭器４１ｅを通過後に、再度小さくＵ字状に反転する。 The combustion boiler 40 will be described in detail with reference to FIG. 2. 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 reversed into a U-shape.
　燃焼ボイラ４０の下方には、燃焼ボイラ４０の内部のバーナーゾーン４１ａ’付近で微粉炭を燃焼するためのバーナ４１ａが配置されている。また、燃焼ボイラ４０の内部のＵ字頂部付近には、第一の過熱器４１ｂが配置されており、更にそこから第二の過熱器４１ｃが続いて配置されている。更に、第二の過熱器４１ｃの終端付近からは、１次節炭器４１ｄ、２次節炭器４１ｅが２段階に設けられている。ここで、節炭器（ＥＣＯとも呼ばれる）は、排ガスの保有する熱を利用してボイラ給水を予熱するために設けられた伝熱面群である。 Below the combustion boiler 40, a burner 41a for burning pulverized coal is disposed in the vicinity of the burner zone 41a 'inside the combustion boiler 40. Moreover, the 1st superheater 41b is arrange | positioned near the U-shaped top part inside the combustion boiler 40, and also the 2nd superheater 41c is arrange | positioned from there. Furthermore, from the vicinity of the terminal 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 heat transfer surface group provided for preheating boiler feedwater using heat retained by exhaust gas.
　以上の燃焼ボイラ４０によれば、バーナーゾーン４１ａ’において微粉炭が燃焼される。微粉炭の燃焼温度は、１３００℃から１５００℃に及び、燃焼によって生成される石炭灰は、矢印の方向に沿って上昇して排ガスと共に第一の過熱器４１ｂ、第二の過熱器４１ｃ、１次節炭器４１ｄ、及び２次節炭器４１ｅを順次通過する。燃焼ガスは、ボイラ給水を予熱するために設けられた伝熱面群を通過することによって熱交換され、４５０℃～５００℃程度に温度が低下する。排ガスがバーナーゾーン４１ａ’から節炭器付近まで到達するまでに要する時間は、おおむね５秒から１０秒である。 According to the above combustion boiler 40, 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, the second superheater 41c, The next economizer 41d and the secondary economizer 41e are sequentially passed. The combustion gas exchanges heat by passing through a heat transfer surface group provided for preheating boiler feed water, and the temperature is lowered to about 450 ° C. to 500 ° C. The time required for the exhaust gas to reach the economizer from the burner zone 41a 'is approximately 5 to 10 seconds.
　排気通路５０は、燃焼ボイラ４０の下流側に配置され、燃焼ボイラ４０で発生した排ガス及び生成された石炭灰を流通させる。この排気通路５０には、上述のように、脱硝装置６０、空気予熱器７０、ガスヒータ（熱回収用）８０、電気集塵装置９０、誘引通風機２１０、脱硫装置２２０と、ガスヒータ（再加熱用）２３０、脱硫通風機２４０、及び煙突２５０がこの順で配置される。 The exhaust passage 50 is arranged on the downstream side of the combustion boiler 40 and distributes the exhaust gas generated in the combustion boiler 40 and the generated coal ash. In the exhaust passage 50, as described above, the denitration device 60, the air preheater 70, the gas heater (for heat recovery) 80, the electric dust collector 90, the induction ventilator 210, the desulfurization device 220, and the gas heater (for reheating) ) 230, the desulfurization ventilator 240, and the chimney 250 are arranged in this order.
　脱硝装置６０は、排ガス中の窒素酸化物を除去する。本実施形態では、脱硝装置６０は、比較的高温（３００℃～４００℃）の排ガス中に還元剤としてアンモニアガスを注入し、脱硝触媒との作用により排ガス中の窒素酸化物を無害な窒素と水蒸気に分解する、いわゆる乾式アンモニア接触還元法により排ガス中の窒素酸化物を除去する。 The denitration device 60 removes nitrogen oxides in the exhaust gas. In the present embodiment, the denitration device 60 injects ammonia gas as a reducing agent into the exhaust gas at a relatively high temperature (300 ° C. to 400 ° C.), and the action of the denitration catalyst converts nitrogen oxides in the exhaust gas into harmless nitrogen. Nitrogen oxides in the exhaust gas are removed by a so-called dry ammonia catalytic reduction method that decomposes into water vapor.
　脱硝装置６０は、図３に示すように、脱硝反応器６１と、この脱硝反応器６１の内部に配置される複数段の脱硝触媒層６２，６２，６２と、脱硝触媒層６２の上流側に配置される整流層６３と、脱硝反応器６１の入口付近に配置される整流板６４と、脱硝反応器６１の上流側に配置されるアンモニア注入部６５と、を備える。 As shown in FIG. 3, the denitration apparatus 60 includes a denitration reactor 61, a plurality of stages of denitration catalyst layers 62, 62, 62 disposed inside the denitration reactor 61, and upstream of the denitration catalyst layer 62. A rectifying layer 63 to be disposed, a rectifying plate 64 disposed in the vicinity of the inlet of the denitration reactor 61, and an ammonia injection portion 65 disposed on the upstream side of the denitration reactor 61 are provided.
　脱硝反応器６１は、脱硝装置６０における脱硝反応の場となる。
　脱硝触媒層６２は、脱硝反応器６１の内部に、排ガスの流路に沿って所定間隔をあけて複数段（本実施形態では３段）配置される。 The denitration reactor 61 is a place for denitration reaction in the denitration apparatus 60.
The denitration catalyst layer 62 is disposed in the denitration reactor 61 in a plurality of stages (three stages in this embodiment) at predetermined intervals along the exhaust gas flow path.
　脱硝触媒層６２は、脱硝触媒としての複数のハニカム触媒（図示せず）を含んで構成される。ハニカム触媒は、長手方向に延びる複数の排ガス流通穴が形成された長尺状（直方体状）に形成される。そして、複数のハニカム触媒は、排ガス流通穴が排ガスの流路に沿うように配置される。ハニカム触媒としては、例えば、１５０ｍｍ×１５０ｍｍ×８６０ｍｍの直方体形状で目開き６ｍｍ×６ｍｍの排ガス流通穴が４００個（２０×２０）形成されたものが用いられる。また、一層の脱硝触媒層６２には、例えば、９０００本から１００００本のハニカム触媒が設置される。
　ハニカム触媒は、バナジウムやタングステン等の触媒物質を酸化チタンや酸化ジルコニウム等のセラミック材料に担持させた後、押出成形することで形成される。 The denitration catalyst layer 62 includes a plurality of honeycomb catalysts (not shown) as denitration catalysts. The honeycomb catalyst is formed in a long shape (cuboid shape) in which a plurality of exhaust gas circulation holes extending in the longitudinal direction are formed. The plurality of honeycomb catalysts are arranged so that the exhaust gas circulation holes are along the flow path of the exhaust gas. As the honeycomb catalyst, for example, a catalyst having a rectangular parallelepiped shape of 150 mm × 150 mm × 860 mm and 400 exhaust gas circulation holes (20 × 20) having openings of 6 mm × 6 mm is used. In addition, for example, 9000 to 10,000 honeycomb catalysts are installed in one denitration catalyst layer 62.
A honeycomb catalyst is formed by supporting a catalyst material such as vanadium or tungsten on a ceramic material such as titanium oxide or zirconium oxide and then performing extrusion molding.
　整流層６３は、脱硝触媒層６２の上流側に配置される。整流層６３は、格子状に形成された複数の開口を有する金属部材等により構成され、脱硝反応器６１における排ガスの流路を区画する。整流層６３は、排気通路５０を流通し脱硝反応器６１に導入される排ガスを整流して脱硝触媒層６２に均等に導く。 The rectifying layer 63 is disposed on the upstream side of the denitration catalyst layer 62. The rectifying layer 63 is composed of a metal member or the like having a plurality of openings formed in a lattice shape, and partitions the exhaust gas flow path in the denitration reactor 61. The rectifying layer 63 rectifies the exhaust gas introduced through the exhaust passage 50 and introduced into the denitration reactor 61, and uniformly guides it to the denitration catalyst layer 62.
　整流板６４は、脱硝反応器６１の入口の近傍における整流層６３よりも上流側に配置される。より具体的には、整流板６４は、脱硝反応器６１又は排気通路５０の内壁における屈曲部分に配置され、内壁から内面側に突出する。整流板６４は、排気通路５０又は脱硝反応器６１における屈曲部分における排ガスの流れを整える。 The rectifying plate 64 is disposed on the upstream side of the rectifying layer 63 in the vicinity of the inlet of the denitration reactor 61. More specifically, the rectifying 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 rectifying plate 64 adjusts the flow of exhaust gas at the bent portion of the exhaust passage 50 or the denitration reactor 61.
　アンモニア注入部６５は、脱硝反応器６１の上流側に配置され、排気通路５０にアンモニアを注入する。 The ammonia injection part 65 is arranged upstream of the denitration reactor 61 and injects ammonia into the exhaust passage 50.
　以上の脱硝装置６０によれば、まず、アンモニア注入部６５において、排気通路５０を流通する高温の排ガス（３００℃～４００℃）にアンモニアが注入される。アンモニアが注入された排ガスは、整流板６４及び整流層６３により整流され、脱硝触媒層６２に導入される。 According to the above denitration apparatus 60, first, ammonia is injected into the high-temperature exhaust gas (300 ° C. to 400 ° C.) flowing through the exhaust passage 50 in the ammonia injection section 65. The exhaust gas into which ammonia has been injected is rectified by the rectifying plate 64 and the rectifying layer 63 and introduced into the denitration catalyst layer 62.
　脱硝触媒層６２においては、アンモニアを含む排ガスがハニカム触媒の排ガス流通穴を通過するときに、以下の化学反応式に従って、窒素酸化物とアンモニアとが反応し、無害な窒素と水蒸気に分解される。
　４ＮＯ＋４ＮＨ３＋Ｏ２→４Ｎ２＋６Ｈ２Ｏ
　ＮＯ＋ＮＯ２＋２ＮＨ３→２Ｎ２＋３Ｈ２Ｏ In the denitration catalyst layer 62, when the exhaust gas containing ammonia passes through the exhaust gas circulation hole of the honeycomb catalyst, the nitrogen oxide and ammonia react according to the following chemical reaction formula and are decomposed into harmless nitrogen and water vapor. .
4NO + 4NH 3 + O 2 → 4N 2 + 6H 2 O
NO + NO 2 + 2NH 3 → 2N 2 + 3H 2 O
　空気予熱器７０は、排気通路５０における脱硝装置６０の下流側に配置される。空気予熱器７０は、脱硝装置６０を通過した排ガスと押込式通風機７５から送り込まれる燃焼用空気とを熱交換させ、排ガスを冷却すると共に、燃焼用空気を加熱する。 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 that has passed through the denitration device 60 and the combustion air sent from the push-in type ventilator 75 to cool the exhaust gas and heat the combustion air.
　ガスヒータ８０は、排気通路５０における空気予熱器７０の下流側に配置される。ガスヒータ８０には、空気予熱器７０において熱回収された排ガスが供給される。ガスヒータ８０は、排ガスから更に熱回収する。 The gas heater 80 is disposed downstream of the air preheater 70 in the exhaust passage 50. The exhaust gas recovered by the air preheater 70 is supplied to the gas heater 80. The gas heater 80 further recovers heat from the exhaust gas.
　電気集塵装置９０は、排気通路５０におけるガスヒータ８０の下流側に配置される。電気集塵装置９０には、ガスヒータ８０において熱回収された排ガスが供給される。電気集塵装置９０は、電極に電圧を印加することによって排ガス中の石炭灰（フライアッシュ）を収集する装置である。電気集塵装置９０において捕集されるフライアッシュは、フライアッシュ回収装置１２０に回収される。 The electrostatic precipitator 90 is disposed on the downstream side of the gas heater 80 in the exhaust passage 50. The exhaust gas recovered in the gas heater 80 is supplied to the electric dust collector 90. The electric dust collector 90 is a device that collects coal ash (fly ash) in exhaust gas by applying a voltage to electrodes. The fly ash collected by the electric dust collector 90 is collected by the fly ash collection device 120.
　誘引通風機２１０は、排気通路５０における電気集塵装置９０の下流側に配置される。誘引通風機２１０は、電気集塵装置９０においてフライアッシュが除去された排ガスを、一次側から取り込んで二次側に送り出す。 The induction ventilator 210 is disposed on the downstream side of the electric dust collector 90 in the exhaust passage 50. The induction ventilator 210 takes in the exhaust gas from which fly ash has been removed in the electrostatic precipitator 90 from the primary side and sends it to the secondary side.
　脱硫装置２２０は、排気通路５０における誘引通風機２１０の下流側に配置される。脱硫装置２２０には、誘引通風機２１０から送り出された排ガスが供給される。脱硫装置２２０は、排ガスに石灰石と水との混合液を吹き付けることにより、排ガスに含有されている硫黄酸化物を混合液に吸収させて脱硫石膏スラリーを生成させ、この脱硫石膏スラリーを脱水処理することで脱硫石膏を生成する。脱硫装置２２０において生成された脱硫石膏は、この装置に接続された脱硫石膏回収装置２２２に回収される。 The desulfurization device 220 is arranged on the downstream side of the induction fan 210 in the exhaust passage 50. The desulfurization apparatus 220 is supplied with exhaust gas sent from the induction fan 210. The desulfurization apparatus 220 sprays a mixed liquid of limestone and water on the exhaust gas, thereby absorbing the sulfur oxide contained in the exhaust gas into the mixed liquid to generate a desulfurized gypsum slurry, and dehydrating the desulfurized gypsum slurry. This produces desulfurized gypsum. The desulfurized gypsum generated in the desulfurization apparatus 220 is recovered by a desulfurization gypsum recovery apparatus 222 connected to this apparatus.
　ガスヒータ２３０は、排気通路５０における脱硫装置２２０の下流側に配置される。ガスヒータ２３０には、脱硫装置２２０において硫黄酸化物が除去された排ガスが供給される。ガスヒータ２３０は、排ガスを加熱する。ガスヒータ８０及びガスヒータ２３０は、排気通路５０における、空気予熱器７０と電気集塵装置９０との間を流通する排ガスと、脱硫装置２２０と脱硫通風機２４０との間を流通する排ガスと、の間で熱交換を行うガスヒータとして構成してもよい。 The gas heater 230 is disposed downstream of the desulfurization device 220 in the exhaust passage 50. The gas heater 230 is supplied with exhaust gas from which sulfur oxides have been removed in the desulfurization apparatus 220. 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 electric dust collector 90 and the exhaust gas flowing between the desulfurization device 220 and the desulfurization ventilator 240 in the exhaust passage 50. It may be configured as a gas heater that performs heat exchange.
　脱硫通風機２４０は、排気通路５０におけるガスヒータ２３０の下流側に配置される。脱硫通風機２４０は、ガスヒータ２３０において加熱された排ガスを一次側から取り込んで二次側に送り出す。
　煙突２５０は、排気通路５０における脱硫通風機２４０の下流側に配置される。煙突２５０には、ガスヒータ２３０で加熱された排ガスが導入される。煙突２５０は、排ガスを排出する。 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 in the gas heater 230 from the primary side and sends it to the secondary side.
The chimney 250 is arranged on the downstream side of the desulfurization ventilator 240 in the exhaust passage 50. Exhaust gas heated by the gas heater 230 is introduced into the chimney 250. The chimney 250 discharges exhaust gas.
　次に、本発明の脱硝触媒の劣化抑制方法につき説明する。
　上述した石炭火力発電設備１では、脱硝触媒は、使用により劣化し脱硝率が低下していく。脱硝触媒の劣化の原因としては、シンタリング等の熱的劣化、触媒成分の被毒による化学的劣化、及び石炭灰が触媒表面を被覆することによる物理的劣化等が挙げられる。 Next, a method for suppressing deterioration of the denitration catalyst of the present invention will be described.
In the above-described coal-fired power generation facility 1, the denitration catalyst is deteriorated by use and the denitration rate is lowered. Causes of deterioration of the denitration catalyst include thermal deterioration such as sintering, chemical deterioration due to poisoning of catalyst components, and physical deterioration due to the coal ash covering the catalyst surface.
　本発明者らは、今般、石炭灰の平均的な粒径である数十μｍ以上百μｍ以下程度の範囲に比べて遥かに小さい粒径（１μｍ以下、より詳細には数十ｎｍ程度）の石炭灰に起因する堆積物が脱硝触媒の表面を被覆して被覆層を形成し、それによって、脱硝触媒と排ガスの接触が阻害され脱硝触媒の性能が低下していることを見出した。このような微小な粒径の石炭灰は含有量が少ないため、これまで脱硝触媒の劣化の原因とは考えられていなかった。 The present inventors now have a much smaller particle size (1 μm or less, more specifically about several tens of nm) compared to the average particle size of coal ash, which is about several tens μm to one hundred μm. It has been found that deposits resulting from coal ash cover the surface of the denitration catalyst to form a coating layer, thereby inhibiting the contact between the denitration catalyst and the exhaust gas and reducing the performance of the denitration catalyst. Since the coal ash having such a small particle size has a small content, it has not been considered as a cause of deterioration of the denitration catalyst.
　上記知見に基づき、本発明者らは、石炭火力発電設備１において、燃焼ボイラ４０に石炭灰凝集促進剤を添加して微粉炭を燃焼させることで、微小な粒径の石炭灰の凝集を促進して微小な粒径の石炭灰の生成を抑制できることを見出し、本発明に到達した。
　即ち、本発明は、石炭火力発電設備おける脱硝触媒の劣化抑制方法であって、燃焼ボイラ４０に石炭灰凝集促進剤を添加する工程を備えることを特徴とする。 Based on the above knowledge, the present inventors promote the aggregation of coal ash having a small particle size by adding a coal ash aggregation accelerator to the combustion boiler 40 and burning the pulverized coal in the coal-fired power generation facility 1. The inventors have found that the production of coal ash having a fine particle size can be suppressed, and have reached the present invention.
That is, the present invention is a method for suppressing deterioration of a denitration catalyst in a coal-fired power generation facility, and includes a step of adding a coal ash aggregation accelerator to the combustion boiler 40.
　この燃焼ボイラ４０に石炭灰凝集促進剤を添加する工程は、石炭灰凝集促進剤を石炭バンカ２０に添加して行ってもよく、石炭灰凝集促進剤を燃焼ボイラ４０に直接添加して行ってもよい。 The step of adding the coal ash aggregation accelerator to the combustion boiler 40 may be performed by adding the coal ash aggregation accelerator to the coal bunker 20 or by adding the coal ash aggregation accelerator directly to the combustion boiler 40. Also good.
　本発明において用いられる石炭灰凝集促進剤は、アルカリ金属及び／又はその塩類、アルカリ土類金属及び／又はその塩類、あるいは、鉄又はその塩類を含む。石炭灰凝集促進剤は、粒状又は粉末状であることが好ましく、具体的には、平均粒径が１μｍ～１００μｍであることが好ましく、５μｍ～７０μｍであることがより好ましい。 The coal ash aggregation accelerator used in the present invention contains an alkali metal and / or a salt thereof, an alkaline earth metal and / or a salt thereof, or iron or a salt thereof. The coal ash aggregation accelerator is preferably in the form of particles or powder. Specifically, the average particle diameter is preferably 1 μm to 100 μm, more preferably 5 μm to 70 μm.
　アルカリ金属及び／又はその塩類、アルカリ土類金属及び／又はその塩類、あるいは、鉄又はその塩類を含む石炭灰凝集促進剤としては、石灰石（ＣａＣＯ３）、消灰石（Ｃａ（ＯＨ）２）、生石灰（ＣａＯ）、酸化ナトリウム（Ｎａ２Ｏ）、酸化カリウム（Ｋ２Ｏ）、酸化マグネシウム（ＭｇＯ）、酸化鉄（Ｆｅ２Ｏ３）等が挙げられる。 Examples of the coal ash aggregation promoter containing alkali metal and / or salt thereof, alkaline earth metal and / or salt thereof, or iron or salt thereof include limestone (CaCO 3 ) and slaked stone (Ca (OH) 2 ). , Quicklime (CaO), sodium oxide (Na 2 O), potassium oxide (K 2 O), magnesium oxide (MgO), iron oxide (Fe 2 O 3 ) and the like.
　また、石炭灰凝集促進剤は、石炭に対するアルカリ金属、アルカリ土類金属及び鉄の割合が０．１質量％以上１０質量％以下となるように添加することが好ましい。
　石炭に対するアルカリ金属、アルカリ土類金属及び鉄の割合が０．１質量％未満であると、微小な石炭灰を凝集させる効果が不充分となるので好ましくない。また、石炭に対するアルカリ金属、アルカリ土類金属及び鉄の割合が１０質量％を超えても、微小な石炭灰を凝集させる効果に大きな向上は認められず、また、石炭灰の表面の融点が大きく降下することによって燃焼ボイラ４０の内壁への石炭灰の多量の付着（スラッギング）を起こすおそれがあるので、好ましくない。 Moreover, it is preferable to add a coal ash aggregation promoter so that the ratio of the alkali metal, alkaline-earth metal, and iron with respect to coal may be 0.1 mass% or more and 10 mass% or less.
If the ratio of alkali metal, alkaline earth metal and iron to coal is less than 0.1% by mass, the effect of agglomerating fine coal ash becomes insufficient, such being undesirable. Further, even if the ratio of alkali metal, alkaline earth metal and iron to coal exceeds 10% by mass, no significant improvement in the effect of agglomerating fine coal ash is observed, and the melting point of the surface of coal ash is large. Since descending may cause a large amount of coal ash to adhere to the inner wall of the combustion boiler 40 (slagging), it is not preferable.
　本発明における、排ガス中に含まれる微小な粒径の石炭灰の生成を抑制するメカニズムは、以下のとおりである。 In the present invention, the mechanism for suppressing the generation of fine particle size coal ash contained in the exhaust gas is as follows.
　石炭灰凝集促進剤が添加された微粉炭が燃焼ボイラ４０で燃焼すると、石炭灰凝集促進剤に含まれるアルカリ金属、アルカリ土類金属、又は鉄の存在により、石炭灰の融点が低下される。即ち、燃焼ボイラ４０の内部における１３００℃～１５００℃の条件において、アルカリ金属、アルカリ土類金属、又は鉄を含む化合物である石炭灰凝集促進剤の添加によって、シリカ、アルミナを主成分とする石炭灰の表面が軟化（溶融）し、粘性が高まる。これにより、粘性が高まった微小な石炭灰粒子が互いに凝集して粒径が増大し、その結果、粒径１μｍ以下の微小な石炭灰の生成が抑制されるものと推定される。 When the pulverized coal to which the coal ash aggregation accelerator is added burns in the combustion boiler 40, the melting point of the coal ash is lowered due to the presence of alkali metal, alkaline earth metal, or iron contained in the coal ash aggregation accelerator. That is, under the conditions of 1300 ° C. to 1500 ° C. inside the combustion boiler 40, coal containing silica and alumina as main components is added by adding a coal ash aggregation accelerator, which is a compound containing alkali metal, alkaline earth metal, or iron. The ash surface softens (melts) and the viscosity increases. Thereby, it is estimated that the fine coal ash particles having increased viscosity are aggregated to increase the particle size, and as a result, the production of fine coal ash having a particle size of 1 μm or less is suppressed.
　このように、本発明では、燃焼ボイラ４０に石炭灰凝集促進剤を添加することによる石炭灰の粘性の変化を利用して微小な石炭灰の生成を抑制し、微小な石炭灰の脱硝触媒の表面への付着を防いでいる。そして、これにより、微小な粒径の石炭灰が脱硝触媒の表面を被覆することを防ぎ、脱硝触媒の劣化が抑制される。 Thus, in the present invention, the generation of fine coal ash is suppressed by utilizing the change in the viscosity of coal ash by adding the coal ash aggregation accelerator to the combustion boiler 40, and the denitration catalyst for the fine coal ash is used. Prevents adhesion to the surface. This prevents the coal ash having a fine particle diameter from covering the surface of the denitration catalyst, and suppresses the deterioration of the denitration catalyst.
　１　石炭火力発電設備
　３０　微粉炭機
　４０　燃焼ボイラ
　６０　脱硝装置 1 Coal-fired power generation equipment 30 Pulverized coal machine 40 Combustion boiler 60 Denitration equipment

Claims (3)

  1. 　石炭を粉砕して微粉炭を製造する微粉炭機と、該微粉炭機において製造された微粉炭を燃焼させる燃焼ボイラと、該燃焼ボイラの下流側に配置され該燃焼ボイラにおいて微粉炭が燃焼されて発生した排ガス中に含まれる窒素酸化物を除去する脱硝装置と、を備える石炭火力発電設備における脱硝装置の劣化抑制方法であって、
    　前記燃焼ボイラに石炭灰凝集促進剤を添加することで微小な石炭灰の凝集を促進し、脱硝触媒への微小な石炭灰の付着を防ぐ脱硝装置の劣化抑制方法。     A pulverized coal machine that pulverizes coal to produce pulverized coal, a combustion boiler that burns the pulverized coal produced in the pulverized coal machine, and a pulverized coal that is disposed downstream of the combustion boiler and burns in the combustion boiler A denitration device for removing nitrogen oxides contained in the exhaust gas generated by the method, and a method for suppressing deterioration of the denitration device in a coal-fired power generation facility comprising:
    A method for suppressing deterioration of a denitration apparatus that promotes the aggregation of fine coal ash by adding a coal ash aggregation accelerator to the combustion boiler and prevents the adhesion of fine coal ash to the denitration catalyst.
  2. 　前記石炭灰凝集促進剤は、アルカリ金属及び／又はその塩類、アルカリ土類金属及び／又はその塩類、あるいは、鉄又はその塩類を含む請求項１に記載の脱硝装置の劣化抑制方法。 The method for suppressing deterioration of a denitration apparatus according to claim 1, wherein the coal ash aggregation accelerator includes an alkali metal and / or a salt thereof, an alkaline earth metal and / or a salt thereof, or iron or a salt thereof.
  3. 　前記石炭１００質量％に対して、前記石炭灰凝集促進剤を０．１質量％以上１０質量％以下の範囲で添加する請求項１又は２に記載の脱硝装置の劣化抑制方法。 The method for suppressing deterioration of a denitration apparatus according to claim 1 or 2, wherein the coal ash aggregation accelerator is added in a range of 0.1 mass% to 10 mass% with respect to 100 mass% of the coal.
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JPS51109279A (en) * 1975-03-24 1976-09-28 Hitachi Ltd
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JPS6348392A (en) * 1986-08-15 1988-03-01 Toa Netsuken Kk Method of controlling clinker ash of coal exhaust gas dust
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