JP4716325B2 - Flue gas denitration device and operation method thereof - Google Patents

Flue gas denitration device and operation method thereof Download PDF

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JP4716325B2
JP4716325B2 JP2006108618A JP2006108618A JP4716325B2 JP 4716325 B2 JP4716325 B2 JP 4716325B2 JP 2006108618 A JP2006108618 A JP 2006108618A JP 2006108618 A JP2006108618 A JP 2006108618A JP 4716325 B2 JP4716325 B2 JP 4716325B2
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exhaust gas
denitration
reducing agent
gas
combustion
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敏通 和田
昌典 石崎
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Mitsubishi Power Ltd
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Babcock Hitachi KK
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description

本発明は排煙脱硝装置とその運転方法に係り、特に還元剤として尿素（水）を煙道中に直接噴霧するシステムを用いた排煙脱硝装置とその運転方法に関する。   The present invention relates to a flue gas denitration apparatus and its operation method, and more particularly to a flue gas denitration apparatus using a system in which urea (water) is directly sprayed into a flue as a reducing agent and its operation method.

従来技術を用いた排煙脱硝装置の系統を図３に示す。
排ガス発生源が、例えばボイラ等である場合には排ガスは節炭器１において熱回収され、脱硝入口ダクト２を通って脱硝反応器３へ導入される。途中排ガス中の窒素酸化物（以下ＮＯｘと記すことがある）の還元剤であるアンモニアガス（以下ＮＨ3と記すことがある）が還元剤注入管７の噴霧ノズル８から脱硝入口ダクト２内に注入される。脱硝反応器３の運用に対してはボイラ負荷が低くなるに従い脱硝入口ガス温度が低下するため、脱硝触媒の性能低下、さらには排ガス中の三酸化硫黄（以下ＳＯ3ということがある）が還元剤であるＮＨ3と反応し、酸性硫安(ＮＨ4ＨＳＯ4)が析出する（（１）式参照）。前記酸性硫安が脱硝反応器３内の脱硝触媒層９に付着することにより、急激な触媒性能劣化を招く。
ＮＨ3 ＋ＳＯ3 ＋ Ｈ2Ｏ → ＮＨ4ＨＳＯ4 （１） FIG. 3 shows a system of a flue gas denitration apparatus using a conventional technique.
When the exhaust gas generation source is, for example, a boiler, the exhaust gas is heat recovered in the economizer 1 and introduced into the denitration reactor 3 through the denitration inlet duct 2. On the way, ammonia gas (hereinafter also referred to as NH 3 ), which is a reducing agent of nitrogen oxides (hereinafter also referred to as NOx) in the exhaust gas, enters the denitration inlet duct 2 from the spray nozzle 8 of the reducing agent injection pipe 7. Injected. Since the denitrification inlet gas temperature in accordance with the boiler load is low for operation of the denitration reactor 3 is reduced, degradation of the denitration catalyst, more (hereinafter, sometimes referred to SO 3) sulfur trioxide in the exhaust gas reduction It reacts with the agent NH 3 to precipitate acidic ammonium sulfate (NH 4 HSO 4 ) (see formula (1)). The acidic ammonium sulfate adheres to the denitration catalyst layer 9 in the denitration reactor 3, thereby causing rapid catalyst performance deterioration.
NH 3 + SO 3 + H 2 O → NH 4 HSO 4 (1)

そのため通常脱硝装置を運用する負荷は上記した問題が発生しない温度域（通常２８０〜３００℃以上）で行われる。しかし低負荷運転されるボイラなどからの排ガス中のＮＯｘを除去することが環境対策上要求される場合、前記低負荷でも脱硝反応器３の入口ガス温度が高く維持できるように、節炭器１を迂回して排ガスをバイパスダクト５に導き、該バイパスダクト５から高温のままの排ガスを脱硝反応器３に導入する構成が採用されている。   Therefore, the load for operating the normal denitration apparatus is performed in a temperature range (usually 280 to 300 ° C. or higher) in which the above-described problem does not occur. However, when it is required for environmental measures to remove NOx in exhaust gas from a boiler or the like that is operated at a low load, the economizer 1 can maintain a high inlet gas temperature of the denitration reactor 3 even at the low load. A configuration is adopted in which the exhaust gas is led to the bypass duct 5, and the exhaust gas that remains at a high temperature is introduced from the bypass duct 5 into the denitration reactor 3.

この節炭器バイパスシステムはボイラなどの排ガス発生源の低負荷運転時のみ脱硝入口ガス温度を規定値以上に保つことができるようにバイパスダクト５にダンパ６の開閉をコントロールする運用がなされる。なお、図中の還元剤注入管７の噴霧ノズル８からバイパスダクト５までの脱硝入口ダクト２の前方側のダクト長さＬ１は節炭器バイパスガスと節炭器出口ガスが十分に混合するために必要なゾーンであり、還元剤注入管７の噴霧ノズル８から脱硝反応器３までの脱硝入口ダクト２の後方側のダクト長さＬ２は注入されたＮＨ3と排ガスを混合するために必要なゾーンである。 This economizer bypass system is operated to control the opening and closing of the damper 6 in the bypass duct 5 so that the denitration inlet gas temperature can be maintained at a specified value or higher only during low load operation of an exhaust gas generation source such as a boiler. Note that the duct length L1 on the front side of the denitration inlet duct 2 from the spray nozzle 8 to the bypass duct 5 of the reducing agent injection pipe 7 in the drawing is sufficiently mixed with the economizer bypass gas and the economizer outlet gas. The duct length L2 on the rear side of the denitration inlet duct 2 from the spray nozzle 8 of the reducing agent injection pipe 7 to the denitration reactor 3 is necessary for mixing the injected NH 3 and exhaust gas. It is a zone.

図４は排ガス中のＮＯｘの還元剤として尿素（水）を用いたシステムを示している。基本的な系統は図３と同じであるが、還元剤注入管７に導入された尿素水が噴霧ノズル８より脱硝入口ダクト２内に注入され、尿素水中の尿素は排ガス温度による高温条件と熱量により加水分解し、アンモニアガスを発生する（（２）式参照）機構が図３に示す系統とは異なる。
ＮＨ2ＣＯＮＨ2 ＋ Ｈ2Ｏ → ２ＮＨ3 ＋ＣＯ2 （２）
（尿素） （水） FIG. 4 shows a system using urea (water) as a reducing agent for NOx in exhaust gas. The basic system is the same as in FIG. 3, but the urea water introduced into the reducing agent injection pipe 7 is injected into the denitration inlet duct 2 from the spray nozzle 8, and the urea in the urea water has a high temperature condition and heat quantity depending on the exhaust gas temperature. Is different from the system shown in FIG. 3 in the mechanism of generating ammonia gas by hydrolysis (see equation (2)).
NH 2 CONH 2 + H 2 O → 2NH 3 + CO 2 (2)
(Urea) (Water)

図４において還元剤注入管７の噴霧ノズル８から脱硝反応器３までの脱硝入口ダクト２の後方側のダクトの長さＬ２’は噴霧注入された尿素水が加水分解反応して発生したＮＨ3と排ガスが混合するためのゾーンである。従って、直接アンモニアガスを注入する方式に比べ長さＬ２’は図３の前記長さＬ２より長くすることが必要である。
特開平８−２８１０７４号公報 特開２００３−３２８７３４号公報 In FIG. 4, the length L2 ′ of the duct on the rear side of the denitration inlet duct 2 from the spray nozzle 8 of the reducing agent injection pipe 7 to the denitration reactor 3 is NH 3 generated by the hydrolysis reaction of the sprayed urea water. And a zone for mixing exhaust gas. Therefore, it is necessary to make the length L2 ′ longer than the length L2 in FIG. 3 as compared with the method in which ammonia gas is directly injected.
JP-A-8-281074 JP 2003-328734 A

上記従来技術で図４に示す尿素水噴霧注入システムに対しては、注入された尿素水液滴が排ガス中で加水分解する段階で次に示すような種々問題が発生する。特に低負荷時の排ガス温度が低い条件下では問題が顕著化する。
１）水の噴霧状態が、例えば部分的な噴霧ノズルの詰まりで悪くなり液滴径が大きい場合、尿素水液滴の蒸発に要する時間が長くなり脱硝触媒層９に至るまでに完全に蒸発せず、触媒が濡れることにより触媒性能劣化を招く。 In the urea water spray injection system shown in FIG. 4 according to the above prior art, the following various problems occur at the stage where the injected urea water droplets are hydrolyzed in the exhaust gas. In particular, the problem becomes conspicuous under conditions where the exhaust gas temperature at low load is low.
1) When the spray state of water deteriorates due to, for example, partial clogging of the spray nozzle and the droplet diameter is large, the time required for the evaporation of urea water droplets becomes long, and the water is completely evaporated before reaching the denitration catalyst layer 9. However, the catalyst performance deteriorates when the catalyst gets wet.

２）尿素水を排ガスの持つ熱量で加水分解する際、特に低負荷で排ガス温度が低い条件下（一般的に３５０℃以下）では尿素の一部は完全にアンモニアガスまで分解せずにシアヌル酸等の中間生成物（固形物）１０（図４）を形成する。そのためＮＯｘの還元剤であるアンモニアガスが不足し、所定の脱硝性能が得られず、また尿素注入量と発生アンモニアガス間に相関性がなくなるため尿素注入量の制御が困難となる。特にこの現象は前記ダクト長さＬ１の距離を十分に確保しておかないと噴霧尿素水と節炭器バイパス高温ガスとの混合が十分でなくなり、脱硝入口ダクト２内の尿素注入部での排ガス温度のバラツキが生じ、その低温域で上記した諸問題が発生することになる。 2) When hydrolyzing urea water with the amount of heat of exhaust gas, especially under conditions of low load and low exhaust gas temperature (generally 350 ° C or less), part of urea does not completely decompose to ammonia gas, but cyanuric acid Etc., forming an intermediate product (solid) 10 (FIG. 4). Therefore, ammonia gas which is a reducing agent for NOx is insufficient, a predetermined denitration performance cannot be obtained, and since there is no correlation between the urea injection amount and the generated ammonia gas, it is difficult to control the urea injection amount. In particular, this phenomenon requires that the distance of the duct length L1 is not sufficiently secured, so that the mixing of the sprayed urea water and the economizer bypass hot gas becomes insufficient, and the exhaust gas at the urea injection portion in the denitration inlet duct 2 is lost. Variations in temperature occur, and the above-described problems occur at low temperatures.

本発明の課題は、低負荷時の排ガス温度が低い条件下でも、脱硝用の還元剤水液滴の蒸発が比較的速く行われ、また脱硝触媒層に到達するまでには完全にアンモニアガスになるようにした排煙脱硝装置とその運用方法を提供することである。   The problem of the present invention is that even when the exhaust gas temperature at low load is low, evaporation of the reducing agent water droplets for denitration is performed relatively quickly, and until the denitration catalyst layer is reached, ammonia gas is completely converted to ammonia gas. It is to provide a flue gas denitration apparatus and an operation method thereof.

本発明の上記課題は次の解決手段で解決される。
請求項１記載の発明は、燃焼装置から排出する排ガスの熱を回収する熱交換器を配置した排ガスの流路内の前記熱交換器の下流側に脱硝反応器を配置した排煙脱硝装置において、熱交換器を迂回して燃焼排ガスを脱硝反応器の前流側の排ガス流路に導く開閉自在の排ガスバイパス流路を設け、該バイパス流路からの排ガスを導入する排ガス流路内にガイドダクトを設け、該ガイドダクト内であってバイパス流路の下流又はガイドダクトの下流開口部近傍の排ガス流路に還元剤含有溶液の供給部を設けた排煙脱硝装置である。 The above-mentioned problems of the present invention are solved by the following solution means.
The invention according to claim 1 is a flue gas denitration apparatus in which a denitration reactor is disposed downstream of the heat exchanger in a flow path of exhaust gas in which a heat exchanger that recovers heat of exhaust gas discharged from a combustion apparatus is disposed. An openable exhaust gas bypass channel that bypasses the heat exchanger and leads the combustion exhaust gas to the exhaust gas channel on the upstream side of the denitration reactor is provided, and a guide is provided in the exhaust gas channel for introducing the exhaust gas from the bypass channel. A flue gas denitration apparatus in which a duct is provided, and a supply part for a reducing agent-containing solution is provided in an exhaust gas passage in the guide duct and downstream of the bypass passage or in the vicinity of the downstream opening of the guide duct .

請求項２記載の発明は、ガイドダクトと脱硝反応器の設置部の間の排ガス流路内にガス混合器を配置した請求項１記載の排煙脱硝装置である。   The invention described in claim 2 is the flue gas denitration apparatus according to claim 1, wherein a gas mixer is disposed in the exhaust gas flow path between the guide duct and the installation portion of the denitration reactor.

請求項３記載の発明は、還元剤含有溶液の供給部と脱硝反応器の設置部の間の排ガス流路の長さを還元剤から得られるガス成分と排ガスが十分混合する長さとする請求項１記載の排煙脱硝装置である。   According to a third aspect of the present invention, the length of the exhaust gas flow path between the supply part of the reducing agent-containing solution and the installation part of the denitration reactor is set such that the gas component obtained from the reducing agent and the exhaust gas are sufficiently mixed. 1.

請求項４記載の発明は、請求項１記載の排煙脱硝装置の運転方法において、燃焼装置が通常の負荷燃焼をしている場合には排ガスバイパス流路を閉じて燃焼排ガスを熱交換器が配置された排ガス流路内に流し、該排ガスに還元剤含有溶液の供給部から還元剤を注入して脱硝反応器に排ガスと還元剤成分を供給し、燃焼装置が低負荷燃焼をしている場合には燃焼排ガスを熱交換器を迂回する排ガスバイパス流路に流し、該排ガスバイパス流路から排ガス流路内に導入された排ガスに還元剤含有溶液の供給部から還元剤を注入して脱硝反応器に排ガスと還元剤成分を供給する排煙脱硝装置の運転方法である。   According to a fourth aspect of the present invention, in the operation method of the flue gas denitration apparatus according to the first aspect, when the combustion device is performing normal load combustion, the exhaust gas bypass passage is closed and the combustion exhaust gas is removed by the heat exchanger. The exhaust gas is flowed into the exhaust gas flow path, the reducing agent is injected into the exhaust gas from the supply part of the reducing agent-containing solution, the exhaust gas and the reducing agent component are supplied to the denitration reactor, and the combustion device performs low-load combustion. In this case, the combustion exhaust gas is caused to flow through an exhaust gas bypass passage that bypasses the heat exchanger, and denitration is performed by injecting the reducing agent from the supply portion of the reducing agent-containing solution into the exhaust gas introduced into the exhaust gas passage from the exhaust gas bypass passage This is a method of operating a flue gas denitration apparatus that supplies exhaust gas and a reducing agent component to a reactor.

（作用）
請求項１、４記載の発明によれば、燃焼排ガス発生源が低負荷運転されている場合に、排ガス温度が低い排煙脱硝装置の運用条件では排ガス流路内に配置された節炭器等の熱交換器をバイパスした高温排ガス中に尿素水を注入することで尿素水の加水分解をスムーズに行い、また前記燃焼排ガス発生源が高負荷時の排ガス温度が高い運用条件では、排ガスの節炭器バイパスを行わないで節炭器出口ガス中に尿素水を注入するようにしたものである。こうして、中間生成物が析出すると言われている約３５０℃以下での尿素水の排ガス流路への注入を避けることができる。 (Function)
According to the first and fourth aspects of the present invention, when the combustion exhaust gas generation source is operated at a low load, the economizer disposed in the exhaust gas flow path or the like under the operating conditions of the flue gas denitration apparatus having a low exhaust gas temperature. The urea water is smoothly hydrolyzed by injecting the urea water into the high-temperature exhaust gas bypassing the heat exchanger, and in the operating conditions where the combustion exhaust gas generation source has a high exhaust gas temperature when the load is high, the exhaust gas is saved. The urea water is injected into the economizer outlet gas without performing the carbonizer bypass. In this way, it is possible to avoid injection of urea water into the exhaust gas flow path at about 350 ° C. or less, where intermediate products are said to precipitate.

請求項２記載の発明によれば、節炭器をバイパスした高温ガスと節炭器出口排ガスと還元剤から得られるガス状の還元剤成分の混合が混合器で行えるので、排ガスバイパス流路を流れ出たバイパス排ガスと節炭器出口の排ガスを混合する混合ゾーンの確保が不要となるため脱硝装置のコンパクト配置が可能となる。   According to the invention described in claim 2, since the mixing of the gaseous reducing agent component obtained from the high temperature gas bypassing the economizer, the economizer outlet exhaust gas and the reducing agent can be performed by the mixer, the exhaust gas bypass channel is provided. Since it is not necessary to secure a mixing zone for mixing the flowing bypass exhaust gas and the exhaust gas at the economizer outlet, a compact arrangement of the denitration apparatus is possible.

請求項３記載の発明によれば、還元剤含有溶液の注入部と脱硝反応器の設置部の間の排ガス流路内の長さを還元剤から得られるガス状の還元剤成分と排ガスが十分混合する長さとしているので脱硝反応に支障がない。   According to the third aspect of the present invention, the gaseous reducing agent component obtained from the reducing agent and the exhaust gas are sufficiently long in the exhaust gas passage between the injection part of the reducing agent-containing solution and the installation part of the denitration reactor. There is no problem in the denitration reaction because the length is mixed.

請求項１、４記載の発明によれば、排ガス発生源が低負荷段階より還元剤含有溶液注入が可能となり、低負荷時に節炭器等の熱交換器を迂回する排ガスバイパス流路内を流れる排ガスの温度が高いため、排ガスバイパス流路内に尿素水などの還元剤含有溶液を注入する際に、還元剤含有溶液注入部の排ガス温度が低いことに起因するシアヌル酸等の中間生成物（固形物）の析出を防止でき、さらには脱硝反応器内の脱硝触媒の濡れ等の問題が解消でき、排ガス脱硝反応が確実に行える。   According to the first and fourth aspects of the present invention, the exhaust gas generation source can inject the reducing agent-containing solution from the low load stage, and flows in the exhaust gas bypass flow path that bypasses the heat exchanger such as a economizer when the load is low. Since the temperature of the exhaust gas is high, when injecting a reducing agent-containing solution such as urea water into the exhaust gas bypass channel, an intermediate product such as cyanuric acid due to the low exhaust gas temperature of the reducing agent-containing solution injection part ( Solid matter) can be prevented from being precipitated, and further problems such as wetting of the denitration catalyst in the denitration reactor can be solved, and the exhaust gas denitration reaction can be performed reliably.

請求項２記載の発明によれば、請求項１記載の発明の効果に加えて、排ガス発生源が高負荷時だけでなく、低負荷時においても高温の排ガス中で尿素水などの還元剤含有溶液からアンモニアがスムーズに生成するので、排ガスバイパス流路出口と脱硝反応器の間の排ガス流路に配置されたガス混合器でアンモニアと排ガスが十分混合することができ脱硝反応器内での排ガス脱硝反応が確実に行える。   According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, not only when the exhaust gas generation source is at a high load, but also at a low load, a reducing agent such as urea water is contained in the high temperature exhaust gas. Since ammonia is generated smoothly from the solution, the ammonia and exhaust gas can be sufficiently mixed in the gas mixer placed in the exhaust gas passage between the outlet of the exhaust gas bypass passage and the denitration reactor. Denitration reaction can be performed reliably.

請求項３記載の発明によれば、請求項１記載の発明の効果に加えて、排ガス発生源が高負荷時だけでなく、低負荷時においても高温の排ガス中で尿素水などの還元剤含有溶液からアンモニアがスムーズに生成するので、排ガスバイパス流路出口と脱硝反応器の間の排ガス流路の長さはアンモニアと排ガスが脱硝触媒の前流側で十分混合する長さの排ガス流路が確保できる長さがあればよく、還元剤含有溶液からアンモニアを生成するために長い排ガスダクトを必要としていた従来技術に比べて設備コストが少なくて良い。   According to the invention described in claim 3, in addition to the effect of the invention described in claim 1, not only when the exhaust gas generation source is at a high load, but also at a low load, a reducing agent such as urea water is contained in the high temperature exhaust gas. Since ammonia is generated smoothly from the solution, the length of the exhaust gas flow path between the exhaust gas bypass flow path outlet and the denitration reactor is long enough to mix ammonia and exhaust gas on the upstream side of the denitration catalyst. It is sufficient if the length can be ensured, and the equipment cost can be reduced as compared with the conventional technique that requires a long exhaust gas duct to generate ammonia from the reducing agent-containing solution.

本発明の実施例を図面と共に説明する。
図１に本実施例のフローを示す。ボイラなどの燃焼源から排出した排ガスを排ガス流路内に流すが、該排ガス流路には節炭器１などの熱交換器が配置され、該熱交換器で熱回収された排ガスは脱硝入口ダクト２を通り、脱硝触媒層９を備えた脱硝反応器３へ導入される。脱硝入口ダクト２の脱硝反応器３設置部の前流側では、排ガス中のＮＯｘの還元剤である尿素の水溶液が還元剤注入管７の噴霧ノズル８から注入される。また、節炭器１を迂回して排ガスをバイパスさせる開閉用のダンパ６を備えたバイパスダクト５を設けているので、ボイラなどの燃焼源の負荷が低くなって、排ガス温度が低下しても脱硝触媒の脱硝反応を維持するために、高温のままの排ガスを脱硝反応器３に導入することができる構成である。 Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a flow of this embodiment. Exhaust gas discharged from a combustion source such as a boiler flows into the exhaust gas flow path. A heat exchanger such as a economizer 1 is disposed in the exhaust gas flow path, and the exhaust gas heat recovered by the heat exchanger passes through the denitration inlet. It passes through the duct 2 and is introduced into a denitration reactor 3 having a denitration catalyst layer 9. On the upstream side of the denitration reactor 3 installation portion of the denitration inlet duct 2, an aqueous solution of urea, which is a reducing agent for NOx in the exhaust gas, is injected from the spray nozzle 8 of the reducing agent injection pipe 7. Moreover, since the bypass duct 5 provided with the damper 6 for opening and closing which bypasses the economizer 1 and bypasses the exhaust gas is provided, even if the load of the combustion source such as the boiler becomes low and the exhaust gas temperature decreases, In order to maintain the denitration reaction of the denitration catalyst, the exhaust gas at a high temperature can be introduced into the denitration reactor 3.

ボイラプラント負荷が低く、脱硝反応器３の入口での排ガス温度が低い場合には節炭器バイパスダクト５に導かれた高温ガスは脱硝入口ダクト２の内部で合流ゾーン形成のために設置されたガイドダクト１１を通して主流の排ガス流路内部に導入される。ガイドダクト１１は節炭器バイパスダクト５の出口部の脱硝入口ダクト２内に配置される。また脱硝入口ダクト２内のガイドダクト１１の後流側であって脱硝反応器３の前流側には混合器１２が配置されている。   When the boiler plant load is low and the exhaust gas temperature at the inlet of the denitration reactor 3 is low, the high temperature gas led to the economizer bypass duct 5 is installed inside the denitration inlet duct 2 to form a merge zone. The gas is introduced into the main exhaust gas passage through the guide duct 11. The guide duct 11 is disposed in the denitration inlet duct 2 at the outlet of the economizer bypass duct 5. A mixer 12 is disposed on the downstream side of the guide duct 11 in the denitration inlet duct 2 and on the upstream side of the denitration reactor 3.

また、図２に図１の要部拡大図（図２（ａ））と図２（ａ）のＡ−Ａ線矢視図（図２（ｂ））を示すように、前記合流ゾーンには、尿素水の還元剤注入管７およびノズル８が設けられている。
ボイラなどの燃焼源が低負荷で運用されている場合であって、排ガス温度が低い条件下でも、排ガスは節炭器バイパスダクト５を通り脱硝入口ダクト２に導入されるため、尿素が注入される合流ゾーンは脱硝反応の運用温度（触媒層９入口ガス温度）より高い温度となる。すなわち、この合流ゾーンでは節炭器１をバイパスした排ガスが優先的に導入されるため、節炭器１を経由した排ガス量と節炭器１をバイパスした排ガス量の割合は、全排ガスの平均的な混合割合に比べ、バイパスした排ガス量の割合が大きいことから高温条件となる。 In addition, as shown in FIG. 2 which is an enlarged view of the main part of FIG. 1 (FIG. 2A) and an AA arrow view of FIG. 2A (FIG. 2B), A reducing agent injection pipe 7 and a nozzle 8 for urea water are provided.
Even when a combustion source such as a boiler is operated at a low load and the exhaust gas temperature is low, the exhaust gas is introduced into the denitration inlet duct 2 through the economizer bypass duct 5 and therefore urea is injected. The joining zone has a temperature higher than the operating temperature of the denitration reaction (catalyst layer 9 inlet gas temperature). In other words, since the exhaust gas that bypasses the economizer 1 is preferentially introduced in this merging zone, the ratio of the amount of exhaust gas that passes through the economizer 1 and the amount of exhaust gas that bypasses the economizer 1 is the average of all exhaust gases. Since the ratio of the amount of exhaust gas bypassed is larger than the typical mixing ratio, it becomes a high temperature condition.

このような高温条件下の排ガス中に尿素水を注入することにより、従来尿素水注入部の排ガス温度が低いことに起因して問題となっていた尿素水の気化速度が遅いことによる不完全加水分解（中間生成物の析出）、さらには脱硝触媒層９の濡れ等の問題が解消できる。   By injecting urea water into the exhaust gas under such high temperature conditions, incomplete hydrolysis due to the slow vaporization rate of urea water, which has been a problem due to the low exhaust gas temperature of the conventional urea water injection section, Problems such as decomposition (precipitation of intermediate products) and wetting of the denitration catalyst layer 9 can be solved.

また本実施例を採用することにより、合流ゾーン部のガイドダクト１１から排出された高温の排ガス温度は、尿素水の注入により若干低下する（（２）式反応は吸熱反応である）が、合流ゾーン前後のダクト主流の排ガス温度は前記した排ガス温度より低いため、尿素水注入によりガイドダクト１１から排出された排ガス温度と合流ゾーン前流のダクト主流排ガス温度の差は小さくなる。そのため、合流ゾーンより短い混合距離で温度分布を小さく抑えることができる。 Further, by adopting this embodiment, the temperature of the high-temperature exhaust gas discharged from the guide duct 11 in the merging zone portion is slightly lowered by the injection of urea water (the (2) type reaction is an endothermic reaction). for ducts mainstream of the exhaust gas temperature before and after the zone is lower than the temperature of exhaust gas described above, the difference of the duct main exhaust gas temperature of the confluent zone before flow and discharged exhaust gas temperature from the guide duct 11 by the urea water injection is reduced. Therefore, the temperature distribution can be kept small with a mixing distance shorter than the merge zone.

次に、ボイラプラントの運転負荷が上昇し、節炭器１の出口排ガス温度が高くなり、脱硝反応の運用上問題がなくなり、節炭器バイパスダンパ６を閉とする運用に切り替わった場合について説明する。
この場合には、節炭器１を通る主流の排ガスはガイドダクト１１から尿素水注入部（還元剤注入管７の噴霧ノズル８付近）に流入するため、尿素水の気化およびその加水分解等を十分行うことができる温度雰囲気下にある。 Next, the operation load of the boiler plant increases, the exhaust gas temperature at the outlet of the economizer 1 becomes high, there is no problem in the operation of the denitration reaction, and the operation is switched to the operation where the economizer bypass damper 6 is closed. To do.
In this case, since the mainstream exhaust gas passing through the economizer 1 flows from the guide duct 11 into the urea water injection part (near the spray nozzle 8 of the reducing agent injection pipe 7), the urea water is vaporized and hydrolyzed. It is in a temperature atmosphere that can be performed sufficiently.

なお、尿素注入部以降の排ガス流路には必要に応じて、排ガスと尿素が加水分解して生成したアンモニアガスの混合を促進するための混合器１２が設置される場合もあるが、設置スペース的に可能ならば図１に示す尿素水の還元剤注入管７の設置部から脱硝触媒層９の設置部までの長さＬ２を長く確保して、この長さＬ２の領域内で尿素水から生成したアンモニアと排ガスを十分混合させ、前記混合器１２の設置を省略することも可能である。   In addition, although the mixer 12 for accelerating the mixing of the ammonia gas generated by the hydrolysis of the exhaust gas and urea may be installed in the exhaust gas flow path after the urea injecting portion, the installation space may be provided. If possible, a length L2 from the installation portion of the reducing agent injection pipe 7 of urea water shown in FIG. 1 to the installation portion of the denitration catalyst layer 9 is ensured to be long, and from the urea water in the region of this length L2. It is also possible to sufficiently mix the generated ammonia and exhaust gas and omit the mixer 12 installation.

なお、脱硝入口ダクト２の尿素水の注入部は、必ずしも上記の合流ゾーンのガイドダクト１１の設置部にある必要はなく、例えば図２のようにガイドダクト１１より若干後流側であってもよい。必要なことは尿素水の注入を節炭器１をバイパスした高温排ガスの流れ部で行うことである。   Note that the urea water injection part of the denitration inlet duct 2 does not necessarily have to be provided in the installation part of the guide duct 11 in the above-mentioned merging zone. For example, as shown in FIG. Good. What is necessary is that the urea water is injected in the flow portion of the high-temperature exhaust gas bypassing the economizer 1.

上記実施例では尿素水注入システムについて述べたが、アンモニア溶解水（安水）を直接バイパスダクト５に噴霧注入するシステムを用いてもよい。
すなわち、バイパスダクト５へのアンモニア溶解水の液滴注入に対しては、より高温度の排ガス中に注入するほうが気化時間が短くなること、高温ガスの温度が低下することで主流の低温ガス温度により近くなることから混合が有利となる等の共通した効果が得られる。 Although the urea water injection system has been described in the above embodiment, a system in which ammonia-dissolved water (an aqueous solution) is sprayed directly into the bypass duct 5 may be used.
That is, for injecting ammonia-dissolved water droplets into the bypass duct 5, the vaporization time is shorter when injected into the exhaust gas at a higher temperature, and the temperature of the high-temperature gas is reduced, so that the mainstream low-temperature gas is reduced. Since the temperature is closer, a common effect such as advantageous mixing can be obtained.

環境保全の見地から今後とも大気中への窒素酸化物の排出規制は厳しくなる方向にあり、脱硝装置が設置される立地条件も人家に近い場所へ設置されるケースも増加する可能性が高い。そのためアンモニアガスの取扱が制限されることが予想される。従い必然的に取り扱いが容易で安全性に対しても問題ない尿素を用いた脱硝装置の需要が増加すると考えられるが、本発明は前記立地条件に適合した排ガス中の窒素酸化物の除去を行う排煙脱硝装置として適用できる。 From the standpoint of environmental conservation, the emission regulations of nitrogen oxides into the atmosphere will continue to become stricter, and there is a high possibility that the location conditions for installing denitration equipment and cases where it is installed near people's houses will increase. Therefore, it is expected that handling of ammonia gas will be limited. Easy inevitably HANDLING Demand denitrification device using also no problem urea relative safety Ru is considered to increase, the present invention is the nitrogen oxide in the exhaust gas adapted to the site conditions Follow It can be applied as a flue gas denitration device that removes objects.

本発明の実施例の排煙脱硫装置の概略図である。It is the schematic of the flue gas desulfurization apparatus of the Example of this invention. 図１の変形例の要部拡大図（図２（ａ））と図２（ａ）のＡ−Ａ線矢視図（図２（ｂ））である。It is the principal part enlarged view (FIG. 2 (a)) of the modification of FIG. 1, and the AA arrow directional view (FIG.2 (b)) of FIG. 2 (a). 従来技術の排煙脱硝装置の系統図である。It is a systematic diagram of a conventional flue gas denitration apparatus. 従来技術の排煙脱硝装置の系統図である。It is a systematic diagram of a conventional flue gas denitration apparatus.

符号の説明Explanation of symbols

１ 節炭器 ２ 脱硝入口ダクト
３ 脱硝反応器 ４ 出口ダクト
５ 節炭器バイパスダクト ６ ダンパ
７ 尿素水導管 ８ 尿素水ノズル
９ 脱硝触媒層 １０ 中間生成物
１１ ガイドダクト １２ 混合器 1 economizer 2 denitration inlet duct 3 denitration reactor 4 outlet duct 5 economizer bypass duct 6 damper 7 urea water conduit 8 urea water nozzle 9 denitration catalyst layer 10 intermediate product 11 guide duct 12 mixer

Claims (4)

燃焼装置から排出する排ガスの熱を回収する熱交換器を配置した排ガスの流路内の前記熱交換器の下流側に脱硝反応器を配置した排煙脱硝装置において、
熱交換器を迂回して燃焼排ガスを脱硝反応器の前流側の排ガス流路に導く開閉自在の排ガスバイパス流路を設け、該バイパス流路からの排ガスを導入する排ガス流路内にガイドダクトを設け、該ガイドダクト内であってバイパス流路の下流又はガイドダクトの下流開口部近傍の排ガス流路に還元剤含有溶液の供給部を設けたことを特徴とする排煙脱硝装置。 In the flue gas denitration device in which a denitration reactor is disposed downstream of the heat exchanger in the exhaust gas flow path in which a heat exchanger that recovers the heat of the exhaust gas discharged from the combustion device is disposed,
An openable and closable exhaust gas bypass passage is provided that bypasses the heat exchanger and leads the combustion exhaust gas to the exhaust gas passage on the upstream side of the denitration reactor, and the guide duct is introduced into the exhaust gas passage for introducing the exhaust gas from the bypass passage. A flue gas denitration apparatus, characterized in that a reducing agent-containing solution supply unit is provided in an exhaust gas channel in the guide duct and downstream of the bypass channel or in the vicinity of the downstream opening of the guide duct . ガイドダクトと脱硝反応器の設置部の間の排ガス流路内にガス混合器を配置したことを特徴とする請求項１記載の排煙脱硝装置。   The flue gas denitration device according to claim 1, wherein a gas mixer is disposed in the exhaust gas flow path between the guide duct and the installation portion of the denitration reactor. 還元剤含有溶液の供給部と脱硝反応器の設置部の間の排ガス流路の長さを還元剤から得られるガス成分と排ガスが十分混合する長さとすることを特徴とする請求項１記載の排煙脱硝装置。   The length of the exhaust gas flow path between the supply part of the reducing agent-containing solution and the installation part of the denitration reactor is set to a length sufficient to mix the gas component obtained from the reducing agent and the exhaust gas. Flue gas denitration equipment. 請求項１記載の排煙脱硝装置の運転方法において、燃焼装置が通常の負荷燃焼をしている場合には排ガスバイパス流路を閉じて燃焼排ガスを熱交換器が配置された排ガス流路内に流し、該排ガスに還元剤含有溶液の供給部から還元剤を注入して脱硝反応器に排ガスと還元剤成分を供給し、
燃焼装置が低負荷燃焼をしている場合には燃焼排ガスを熱交換器を迂回する排ガスバイパス流路に流し、該排ガスバイパス流路から排ガス流路内に導入された排ガスに還元剤含有溶液の供給部から還元剤を注入して脱硝反応器に排ガスと還元剤成分を供給することを特徴とする排煙脱硝装置の運転方法。 The operation method of the flue gas denitration device according to claim 1, wherein when the combustion device is performing normal load combustion, the exhaust gas bypass channel is closed and the combustion exhaust gas is placed in the exhaust gas channel where the heat exchanger is arranged. Pour the reducing agent into the exhaust gas from the supply part of the reducing agent-containing solution to supply the exhaust gas and the reducing agent component to the denitration reactor,
When the combustion apparatus performs low load combustion, the combustion exhaust gas is caused to flow through an exhaust gas bypass passage that bypasses the heat exchanger, and the reducing agent-containing solution is added to the exhaust gas introduced into the exhaust gas passage from the exhaust gas bypass passage. A method for operating a flue gas denitration apparatus, characterized by injecting a reducing agent from a supply unit and supplying exhaust gas and a reducing agent component to a denitration reactor.
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