JP2007181756A - Wastewater treatment method for flue gas desulfurization equipment - Google Patents

Wastewater treatment method for flue gas desulfurization equipment Download PDF

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JP2007181756A
JP2007181756A JP2006000532A JP2006000532A JP2007181756A JP 2007181756 A JP2007181756 A JP 2007181756A JP 2006000532 A JP2006000532 A JP 2006000532A JP 2006000532 A JP2006000532 A JP 2006000532A JP 2007181756 A JP2007181756 A JP 2007181756A
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liquid
flue gas
tank
solution
alkali
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Shigeaki Koike
重章 小池
Koichi Yasunaga
光市 安永
Katsuyuki Nakamura
勝幸 中村
Akiyoshi Miwa
昭義 三輪
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Eneos Corp
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Japan Energy Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment method for use in wastewater treatment for flue gas desulfurization equipment, the method by which the futile use of an alkali agent is prevented, the alkali agent being used for neutralizing absorbing solution which has absorbed sulfur oxides and is discharged, and trouble due to clogging of a filter for solid-liquid separation after the nuetralization is prevented. <P>SOLUTION: The wastewater treatment method is used for wet flue gas desulfurization equipment removing sulfur oxides by bringing flue gas containing sulfur oxides into contact with alkali absorbing solution. The method includes: an oxidation step of taking out the alkali solution which has absorbed sulfur oxides from an absorption tower, sending the solution to a first treating vessel, oxidizing and adjusting pH of the solution to ≤4; a neutralization step of sending the absorbing solution with pH adjusted to ≤4 to a second treatment vessel and adjusting the pH of the solution to 5-8 using an alkaline agent; and a solid-liquid separation step of filtering the neutralized absorbing solution. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、ボイラや加熱炉などの排ガス中に含まれる硫黄酸化物、特に亜硫酸ガス(SO)などの除去に適用される湿式排煙脱硫装置の廃水処理方法に関する。 The present invention relates to a wastewater treatment method for a wet flue gas desulfurization apparatus applied to the removal of sulfur oxides, particularly sulfurous acid gas (SO 2 ), contained in exhaust gas such as boilers and heating furnaces.

ボイラ等の排ガス中の硫黄酸化物を除去する排煙脱硫装置には、各種の方式があり、湿式法、乾式法及び半乾式法によるものに大別できるが、本発明の対象は湿式法による排煙脱硫装置における排水処理方法である。   There are various types of flue gas desulfurization apparatuses that remove sulfur oxides in exhaust gas from boilers and the like, and they can be roughly classified into wet methods, dry methods, and semi-dry methods, but the object of the present invention is based on wet methods. It is the waste water treatment method in a flue gas desulfurization apparatus.

湿式排煙脱硫の代表的な方法として水酸化マグネシウム法(水マグ法)が挙げられる。水マグ法は、例えば、ボイラや各種加熱炉などからの燃焼排ガスを脱硫吸収塔に供給し、水酸化マグネシウム水溶液(スラリー)などの吸収液と接触させて、排ガス中の硫黄酸化物を吸収液に物理的、化学的に取り込み、脱硫処理する。硫黄酸化物が除去された排ガスは排出口より、通常煙突を経由して大気に排出される。一方、排ガス中の硫黄酸化物を吸収した吸収液は、最終的には排水として、排水基準を遵守するよう適切に処理されて、河川や海域に放流される。   A typical method of wet flue gas desulfurization is a magnesium hydroxide method (water mug method). In the water mug method, for example, combustion exhaust gas from a boiler or various heating furnaces is supplied to a desulfurization absorption tower and brought into contact with an absorption liquid such as a magnesium hydroxide aqueous solution (slurry) to absorb sulfur oxide in the exhaust gas. It is physically and chemically incorporated into and desulfurized. The exhaust gas from which the sulfur oxide has been removed is discharged from the discharge port to the atmosphere, usually via a chimney. On the other hand, the absorption liquid that has absorbed sulfur oxides in the exhaust gas is finally treated as wastewater in order to comply with the drainage standards and discharged into rivers and sea areas.

排煙脱硫装置は、脱硫吸収塔と、硫黄酸化物を吸収した吸収液のCODやpHを調整する処理槽、さらに処理された吸収液(排水)中の固形分を除去するろ過器、COD調整のため酸化用空気を供給するブロワ、吸収液を循環するポンプ、処理槽からろ過器に吸収液を送るポンプなどから構成されている。脱硫吸収塔の内部には、排ガスと吸収液とを効果的に気液接触するための噴霧ノズル、さらには、棚段、充填層、スプレーノズル等があり、排ガスと吸収液とを効果的に接触するための噴霧ノズル、さらには充填層と、硫黄酸化物を吸収し、脱硫吸収塔底部の滞液部には、貯留する吸収液に空気を吹き込み撹拌及び酸化するための酸化用空気の曝気ノズルさらにはミキサーと、吸収液のpHを監視するpH計などが設けられている。   The flue gas desulfurization equipment includes a desulfurization absorption tower, a treatment tank that adjusts the COD and pH of the absorption liquid that has absorbed sulfur oxides, a filter that removes solid content in the treated absorption liquid (drainage), and COD adjustment. Therefore, it is composed of a blower for supplying oxidizing air, a pump for circulating the absorbing liquid, a pump for sending the absorbing liquid from the treatment tank to the filter, and the like. Inside the desulfurization absorption tower, there are spray nozzles for effective gas-liquid contact between the exhaust gas and the absorption liquid, as well as shelves, packed beds, spray nozzles, etc. An aeration of oxidizing air for agitating and oxidizing a spray nozzle for contact, further a packed bed, and absorbing sulfur oxide, blowing air into the absorbed liquid stored in the bottom of the desulfurization absorption tower A nozzle, a mixer, and a pH meter for monitoring the pH of the absorbing solution are provided.

脱硫吸収塔に導入された排ガスは、当該吸収塔の中で噴霧ノズルにより噴霧された吸収液と接触し脱硫される。一般的には、噴霧ノズル下部に設けられた気液接触部を流下する吸収液と上昇する排ガスとが向流で接触し、硫黄酸化物やダストを吸収液に吸収し、排ガスを脱硫する。脱硫後の排ガスには吸収液のミストなどが含まれるが、噴霧ノズル上部に設けられたデミスタで補集され、吸収液として回収、循環使用される。こうして、硫黄酸化物、ダストのどが除去された排ガスは排出口から煙突を経由して大気に放出される。   The exhaust gas introduced into the desulfurization absorption tower is desulfurized in contact with the absorbing liquid sprayed by the spray nozzle in the absorption tower. In general, the absorbing liquid flowing down the gas-liquid contact portion provided in the lower part of the spray nozzle and the rising exhaust gas come into contact with each other in a counterflow, so that sulfur oxide and dust are absorbed into the absorbing liquid, and the exhaust gas is desulfurized. The exhaust gas after desulfurization contains mist of the absorbing solution, but is collected by a demister provided on the upper part of the spray nozzle and recovered and recycled as the absorbing solution. In this way, the exhaust gas from which sulfur oxides and dust are removed is discharged from the discharge port to the atmosphere via the chimney.

また、硫黄酸化物を吸収した吸収液は、上記吸収塔底部に貯留され、吸収塔外部に設けられた循環ポンプにより、前記噴霧ノズルに循環供給され噴霧され、気液接触部を流下する。この間に排ガスと接触し、硫黄酸化物、ダスト等を吸収して吸収塔底部に落下して貯留される。吸収液は、このように循環使用されるため、循環液ともいうことがある。硫黄酸化物を吸収した吸収液は、吸収するにつれて、pHが低下し、硫黄酸化物の吸収能力が低下してゆく。そこで、通常、フレッシュなアルカリ成分を補給し、pHを一定に保つと共に、塩の析出を防止するに必要な循環液の抜き出しを行い、硫黄酸化物の吸収能力を保持するよう調整される。   Moreover, the absorption liquid which absorbed the sulfur oxide is stored in the bottom part of the absorption tower, is circulated and supplied to the spray nozzle by a circulation pump provided outside the absorption tower, and flows down the gas-liquid contact part. During this time, it comes into contact with the exhaust gas, absorbs sulfur oxides, dust, etc., falls to the bottom of the absorption tower and is stored. Since the absorption liquid is circulated and used in this way, it may be referred to as a circulation liquid. The absorption liquid that has absorbed sulfur oxides has a lower pH as it absorbs, and the absorption capacity of sulfur oxides decreases. Therefore, normally, fresh alkali components are replenished, the pH is kept constant, and the circulating fluid necessary for preventing salt precipitation is extracted to adjust the sulfur oxide absorption capacity.

この吸収塔へのアルカリ成分の供給を制御する方法は各種の方法があり、例えば、処理する排ガス中のSO濃度に応じて水酸化マグネシウムの注入量を調節する方法(特許文献1参照)や、処理する排ガス中のSO濃度に応じて酸化マグネシウム粉末を煙道内に粉体吹込む方法(特許文献2参照)などが提案されている。また、排煙脱硫装置において、酸化マグネシウムや軽焼マグネシウム粉を吸収剤として使用する方法なども提案されている(特許文献3、4)。 There are various methods for controlling the supply of the alkali component to the absorption tower. For example, a method of adjusting the injection amount of magnesium hydroxide according to the SO 2 concentration in the exhaust gas to be treated (see Patent Document 1), There has been proposed a method of blowing magnesium oxide powder into the flue according to the SO 2 concentration in the exhaust gas to be treated (see Patent Document 2). In addition, a method of using magnesium oxide or lightly burned magnesium powder as an absorbent in a flue gas desulfurization apparatus has been proposed (Patent Documents 3 and 4).

従来、排煙脱硫装置の循環液のpHは、排ガス中のSO濃度を排出基準に合わせるように、アルカリ成分を間欠又は連続的に注入して制御していた。
また、排煙脱硫装置において、SOの吸収反応は、亜硫酸塩を生成するかたちで進むが、硫黄酸化物を吸収した吸収液を公共用水域に放流するには、少なくともCOD、pHを規定の範囲内に調整することが求められる。このために、抜き出された循環液(吸収液)を処理する排水処理設備を吸収塔の後段に設置し、吸収液を酸化して亜硫酸イオンを硫酸イオンにしてCODを下げ、さらに、排水基準のpHを満足させるためにアルカリを添加してpH調整(中和)を同時に行なっていた。
しかしながら、酸化と中和を単一槽内で実施しているためか、使用する水酸化マグネシウムのリークによると思われるろ過による固液分離工程でフィルター目詰まり頻度が高く、運転員を煩わせていた。この煩わしさのメカニズム、原因ははっきりしてないが、中和を滴定点付近で行っているために、負荷変動による滴定量のずれに対し、水酸化マグネシウムの追従遅れで一部の水酸化マグネシウムがリークしていると思われる。
特開平9−66219号公報 特開平7−24252号公報 特開平7−60057号公報 特開平7−232029号公報
Conventionally, the pH of the circulating fluid in the flue gas desulfurization apparatus has been controlled by injecting an alkali component intermittently or continuously so that the SO 2 concentration in the exhaust gas matches the emission standard.
Further, in the flue gas desulfurization apparatus, the SO 2 absorption reaction proceeds in the form of sulfite, but at least COD and pH are specified in order to discharge the absorption liquid that has absorbed sulfur oxides into public water areas. Adjustment within the range is required. For this purpose, a wastewater treatment facility for treating the extracted circulating liquid (absorbing liquid) is installed at the rear stage of the absorption tower, oxidizing the absorbing liquid to convert sulfite ions to sulfate ions, and lowering the COD. In order to satisfy this pH, alkali was added to adjust the pH (neutralization) at the same time.
However, because the oxidation and neutralization are carried out in a single tank, the filter clogging frequency is high in the solid-liquid separation process by filtration, which seems to be due to leakage of magnesium hydroxide used, and the operator is troubled. It was. The mechanism and cause of this annoyance are not clear, but neutralization is performed near the titration point. Seems to be leaking.
JP-A-9-66219 Japanese Patent Laid-Open No. 7-24252 Japanese Patent Laid-Open No. 7-60057 Japanese Patent Laid-Open No. 7-232029

本発明は、上記課題を解決するものであり、排煙脱硫装置の排水処理において、排ガス中の硫黄酸化物を吸収した吸収液を排出する際の中和に用いるアルカリ剤、例えば水酸化マグネシウムの無駄な消費を防止するとともに、中和後、固液分離するフィルターの目詰まりによるトラブルを防止することが可能な排水処理方法を提供することを課題とするものである。   The present invention solves the above-mentioned problems, and in the wastewater treatment of the flue gas desulfurization apparatus, an alkaline agent used for neutralization when discharging the absorbing liquid that has absorbed the sulfur oxide in the exhaust gas, such as magnesium hydroxide. An object of the present invention is to provide a wastewater treatment method capable of preventing wasteful consumption and preventing troubles caused by clogging of a filter that is subjected to solid-liquid separation after neutralization.

本発明の排煙脱硫装置の排水処理方法は、
硫黄酸化物を含む排ガスをアルカリ吸収液と吸収塔内で接触して硫黄酸化物を除去する湿式排煙脱硫装置における排水処理方法であって、硫黄酸化物を吸収したアルカリ吸収液を吸収塔から抜き出して第1の処理槽に送り、酸化してpH4以下に調整する酸化工程と、pH4以下に調整された前記吸収液を第2の処理槽に送り、アルカリ剤を用いてpH5〜8に調整する中和工程と、中和された液をろ過する固液分離工程とを有することを特徴とする。
また、本発明の排煙脱硫装置の排水処理方法は、前記中和工程において使用するアルカリ剤は水酸化マグネシウムであることが好ましい。
The waste water treatment method of the flue gas desulfurization apparatus of the present invention,
A wastewater treatment method in a wet flue gas desulfurization apparatus that removes sulfur oxide by contacting exhaust gas containing sulfur oxide in an absorption tower with an alkali absorption liquid, wherein the alkali absorption liquid that has absorbed sulfur oxide is removed from the absorption tower. Extracted and sent to the first treatment tank, oxidized and adjusted to pH 4 or lower, and the absorption liquid adjusted to pH 4 or lower is sent to the second treatment tank and adjusted to pH 5 to 8 using an alkaline agent And a solid-liquid separation step of filtering the neutralized liquid.
Moreover, in the waste water treatment method for a flue gas desulfurization apparatus of the present invention, the alkali agent used in the neutralization step is preferably magnesium hydroxide.

本発明の排煙脱硫装置の排水処理方法は、吸収塔の後段に第1の処理槽として酸化槽、次いで第2の処理槽として中和槽を設置し、各槽のpHをそれぞれ所定範囲に制御することにしたことから、固液分離(ろ過)工程において、フィルター前後の差圧の上昇が少なく、しかもこの低い差圧上昇が長時間にわたって持続した。この結果、水酸化マグネシウム量の無駄な消費が削減、防止されるとともに、珪藻土などのろ過助剤を使用しなくても、中和槽後流に設置されるフィルターの目詰まりによるトラブルが回避され、処理効率が向上し、フィルターの交換頻度を低減することが可能となる。   The waste water treatment method of the flue gas desulfurization apparatus of the present invention includes an oxidation tank as a first treatment tank and a neutralization tank as a second treatment tank at the subsequent stage of the absorption tower, and the pH of each tank is kept within a predetermined range. Since it was decided to control, in the solid-liquid separation (filtration) process, the increase in the differential pressure before and after the filter was small, and this low differential pressure increase lasted for a long time. As a result, wasteful consumption of magnesium hydroxide is reduced and prevented, and troubles caused by clogging of filters installed downstream of the neutralization tank can be avoided without using filter aids such as diatomaceous earth. As a result, the processing efficiency is improved and the frequency of filter replacement can be reduced.

以下に本発明を、図面等を参照してより詳しく説明する。図1は本発明の排水処理方法が適用される排煙脱硫装置の一例を示す簡略化されたフローシートである。図1に示すように、通常、湿式排煙脱硫装置の脱硫吸収塔1(単に吸収塔ともいう。)には、その内部に上から、デミスタ5、循環液(吸収液)の噴霧ノズル4、気液接触部6、該気液接触部6の下部の側壁部に排ガスの吸入口2が設けられている。なお、デミスタ5の上部に脱硫された排ガスの排出口3が設けられ、普通煙突につながっている。また、脱硫吸収塔1の底部には、循環液を保持する貯留槽が設けられ、その側部には、補給されるフレッシュな水酸化マグネシウムスラリーの供給配管及び循環液を循環ポンプ7に導く配管が設けられており、さらに、撹拌及び貯留槽の循環液を酸化するための空気を供給する配管が貯留槽の側壁部を貫通するかたちで設けられ、貯留槽内部の空気供給配管には複数の酸化用空気の曝気ノズル8が配置されている。   Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a simplified flow sheet showing an example of a flue gas desulfurization apparatus to which the waste water treatment method of the present invention is applied. As shown in FIG. 1, normally, a desulfurization absorption tower 1 (also simply referred to as an absorption tower) of a wet flue gas desulfurization apparatus has a demister 5 and a circulating liquid (absorption liquid) spray nozzle 4 from above. The gas-liquid contact part 6 and the exhaust gas inlet 2 are provided in the side wall part below the gas-liquid contact part 6. In addition, the exhaust port 3 of the desulfurized exhaust gas is provided in the upper part of the demister 5 and is connected to a normal chimney. In addition, a storage tank for holding the circulating liquid is provided at the bottom of the desulfurization absorption tower 1, and a supply pipe for fresh magnesium hydroxide slurry to be replenished and a pipe for leading the circulating liquid to the circulation pump 7 at the side thereof. Furthermore, a pipe for supplying air for oxidizing the circulating liquid in the agitation and storage tank is provided in a form penetrating the side wall of the storage tank, and there are a plurality of air supply pipes in the storage tank. An aeration nozzle 8 for oxidizing air is arranged.

排ガスは、吸入口2から脱硫吸収塔1に導入され、気液接触部6を通過して、噴霧ノズル4から噴霧される吸収液と接触する。この間に、かかる接触により排ガス中のSOなどの硫黄酸化物は、吸収液に吸収されて、排ガスは、脱硫される。脱硫された排ガスは、噴霧ノズル4上部に設けられたデミスタ5で、同伴する飛沫などが捕捉され、落下して吸収液(循環液)として回収、再使用される。また、排ガス中のダストなども、気液接触部6からデミスタ5を通過する間に吸収液と接触して捕捉される。 The exhaust gas is introduced into the desulfurization absorption tower 1 from the suction port 2, passes through the gas-liquid contact portion 6, and comes into contact with the absorption liquid sprayed from the spray nozzle 4. During this time, sulfur oxides such as SO 2 in the exhaust gas are absorbed by the absorption liquid by such contact, and the exhaust gas is desulfurized. The desulfurized exhaust gas is captured by the demister 5 provided on the upper part of the spray nozzle 4, entrained splashes, etc., dropped and collected as an absorption liquid (circulating liquid) and reused. In addition, dust and the like in the exhaust gas are trapped in contact with the absorbing liquid while passing through the demister 5 from the gas-liquid contact portion 6.

脱硫吸収塔1底部の貯留槽に保持される吸収液(循環液)は、吸収塔1の外部に設けられた循環ポンプ7により、噴霧ノズルに導かれ、噴霧される。噴霧された吸収液は、気液接触部6を流下して、例えば充填層の充填物をくまなく湿らせるように、均一に分散、流下して、上昇してくる排ガスと接触し、硫黄酸化物などを吸収して、排ガスの脱硫を行っている。
脱硫吸収塔1として、気液接触部6に充填層を有するものを例示しているが、本発明は、脱硫吸収塔のタイプを特に限定するものでなく、排ガスと吸収液(循環液)とが効果的に気液接触されて、排ガス中の硫黄化合物が効率よく吸収液に移動するものであれば、どのようなタイプのものでも使用することができる。脱硫吸収塔として、充填物を有する充填塔のほかに、例えば、棚段塔、スプレー塔、濡れ壁塔、気泡塔、サイクロンスクラバなどを挙げることができる。
The absorption liquid (circulation liquid) held in the storage tank at the bottom of the desulfurization absorption tower 1 is guided to the spray nozzle by the circulation pump 7 provided outside the absorption tower 1 and sprayed. The sprayed absorption liquid flows down the gas-liquid contact section 6 and uniformly disperses and flows down, for example, so as to wet the packing in the packed bed all over, and comes into contact with the rising exhaust gas, and sulfur oxidation. Exhaust gas is desulfurized by absorbing substances.
Examples of the desulfurization absorption tower 1 include those having a packed bed in the gas-liquid contact portion 6, but the present invention does not particularly limit the type of the desulfurization absorption tower, and exhaust gas, absorption liquid (circulating liquid), Any type can be used as long as the gas is effectively brought into gas-liquid contact and the sulfur compound in the exhaust gas efficiently moves to the absorbing liquid. As a desulfurization absorption tower, besides a packed tower having a packing, for example, a plate tower, a spray tower, a wet wall tower, a bubble tower, a cyclone scrubber and the like can be mentioned.

硫黄酸化物などを吸収した吸収液は、デミスタ5で捕集されて落下する液体と共に、吸収塔1底部の貯留槽に集まる。貯留槽では、底部に複数の酸化用空気の曝気ノズル8が設けられており、空気をバブリングして吸収液を撹拌して、硫黄化合物のアルカリ中和物や亜硫酸を酸化することによって、特には、亜硫酸塩を硫酸塩に酸化することによって、吸収液の化学的酸素消費量(COD)の改善(低減)を図っている。
なお、排ガス中の硫黄酸化物の吸収能力を保持すために、フレッシュな水酸化マグネシウムスラリーがメイクアップされ、その量に相当する貯留槽の吸収液は、循環ポンプ7吐出で噴霧ノズルに供給される配管から分岐して、排出される。
湿式排煙脱硫において、水酸化マグネシウムスラリー以外のアルカリ吸収液も使用されるが、水酸化マグネシウムは最も一般的に使用されるアルカリ成分である。その他のアルカリ成分としては、水酸化カルシウム、水酸化ナトリウム、水酸化カリウム、酸化マグネシウム、酸化カルシウム、炭酸マグネシウム、炭酸カルシウム、炭酸ナトリウム、炭酸カリウムなどが挙げられる。これらのアルカリ成分は、通常はアルカリ水溶液のスラリーとして、典型的には水酸化マグネシウム水溶液のスラリーとして吸収塔に供給され、循環使用される。
The absorption liquid that has absorbed sulfur oxides and the like is collected in the storage tank at the bottom of the absorption tower 1 together with the liquid that is collected by the demister 5 and falls. In the storage tank, a plurality of aeration nozzles 8 for oxidizing air are provided at the bottom, and by specifically bubbling air and stirring the absorption liquid, the alkali neutralized product of sulfur compounds and sulfurous acid are oxidized, in particular. The chemical oxygen consumption (COD) of the absorbing solution is improved (reduced) by oxidizing sulfite to sulfate.
In order to maintain the ability to absorb sulfur oxides in the exhaust gas, a fresh magnesium hydroxide slurry is made up, and the amount of absorption liquid in the storage tank corresponding to that amount is supplied to the spray nozzle by discharging the circulation pump 7. Branches out from the pipe and is discharged.
In wet flue gas desulfurization, alkali absorbing liquids other than magnesium hydroxide slurry are also used, but magnesium hydroxide is the most commonly used alkali component. Examples of other alkali components include calcium hydroxide, sodium hydroxide, potassium hydroxide, magnesium oxide, calcium oxide, magnesium carbonate, calcium carbonate, sodium carbonate, and potassium carbonate. These alkali components are usually supplied to the absorption tower as a slurry of an alkaline aqueous solution, typically as a slurry of a magnesium hydroxide aqueous solution, and are used in a circulating manner.

吸収塔1のSOを吸収するエリアでは、次の反応が進む。
SO+HO→HSO
SO+Mg(OH)→MgSO+2H
MgSO+HSO→Mg(HSO
Mg(OH)+SO→MgSO+H
MgSO+SO+HO→Mg(HSO
In the area of the absorption tower 1 where SO 2 is absorbed, the next reaction proceeds.
SO 2 + H 2 O → H 2 SO 3
H 2 SO 3 + Mg (OH) 2 → MgSO 3 + 2H 2 O
MgSO 3 + H 2 SO 3 → Mg (HSO 3 ) 2
Mg (OH) 2 + SO 2 → MgSO 3 + H 2 O
MgSO 3 + SO 2 + H 2 O → Mg (HSO 3 ) 2

吸収塔下部の液中では
Mg(HSO+Mg(OH)→2MgSO+2H
SO+1/2O→HSO
SO+Mg(OH)→MgSO+2H
MgSO+1/2O→MgSO
の反応が起きている。
In the liquid at the bottom of the absorption tower, Mg (HSO 3 ) 2 + Mg (OH) 2 → 2MgSO 3 + 2H 2 O
H 2 SO 3 + 1 / 2O 2 → H 2 SO 4
H 2 SO 4 + Mg (OH) 2 → MgSO 4 + 2H 2 O
MgSO 3 + 1 / 2O 2 → MgSO 4
The reaction is happening.

水酸化マグネシウムがSOと反応してゆくと、循環液はSOを吸収して脱硫する能力が低下してゆくから、この脱硫能力を維持するために、フレッシュな水酸化マグネシウムスラリーがメイクアップされる。メイクアップ量は、排ガス中のSO濃度や流量、循環液のpH、流量などを目安にコントロールされ、特には脱硫処理後の排ガス中の硫黄濃度が所定の値以下になるよう調整される。吸収液の一部、すなわち、メイクアップ量に相当する量の吸収液は、吸収塔1から抜き出され、後段の排水処理設備としての第1の処理槽9である酸化槽に送られる。吸収塔1から抜き出されたスラリー(廃スラリー)は、亜硫酸水素マグネシウム(Mg(HSO)や亜硫酸マグネシウム(MgSO)を含有しているため、化学的酸素消費量(COD)が高く、そのまま公共用水域に放流することはできない。そのため、抜き出された循環液は、第1の処理槽9である酸化槽において、次の酸化反応を進めて、化学的酸素消費のない硫酸マグネシウム(MgSO)、硫酸(HSO)などのかたちに変換する。
Mg(HSO+1/2O→MgSO+HSO
SO+1/2O→HSO
Mg(HSO+O→MgSO+HSO
MgSO+1/2O→MgSO
MgSO+2H0→Mg(OH)+2H+2SO 2−
When magnesium hydroxide slide into reaction with SO 2, circulating fluid from slide into reduced ability to desulfurize absorbs SO 2, in order to maintain this desulfurization capability, fresh magnesium hydroxide slurry make-up Is done. Makeup amount, SO 2 concentration and the flow rate in the exhaust gas, pH of the circulating liquid is controlled flow rate and a guide, in particular is adjusted to the sulfur concentration in the exhaust gas after the desulfurization treatment is below the predetermined value. A part of the absorption liquid, that is, an amount of the absorption liquid corresponding to the makeup amount is extracted from the absorption tower 1 and sent to an oxidation tank which is a first treatment tank 9 as a waste water treatment facility at the subsequent stage. Since the slurry (waste slurry) extracted from the absorption tower 1 contains magnesium bisulfite (Mg (HSO 3 ) 2 ) and magnesium sulfite (MgSO 3 ), the chemical oxygen consumption (COD) is high. It cannot be discharged directly into public water areas. Therefore, the extracted circulating liquid advances in the next oxidation reaction in the oxidation tank which is the first treatment tank 9, and magnesium sulfate (MgSO 4 ) and sulfuric acid (H 2 SO 4 ) without chemical oxygen consumption. It transforms into the form.
Mg (HSO 3 ) 2 + 1 / 2O 2 → MgSO 4 + H 2 SO 3
H 2 SO 3 + 1 / 2O 2 → H 2 SO 4
Mg (HSO 3 ) 2 + O 2 → MgSO 4 + H 2 SO 4
MgSO 3 + 1 / 2O 2 → MgSO 4
MgSO 4 + 2H 2 0 → Mg (OH) 2 + 2H + + 2SO 4 2−

図1において、第1の処理槽9における廃スラリーの酸化は、吸収塔1の底部における酸化と同様に空気を曝気ノズル8より廃スラリーに吹き込んでバブリングし、撹拌して空気中の酸素で酸化を行っている。第1の処理槽9における酸化は、空気のバブリングに限らず、効率的に推進する方法であれば、どのような方法、手段で行っても良く、空気の替わりに酸素や、オゾンなどを吹き込む方法、あるいは過酸化水素を投入する方法などが挙げられる。空気を吹き込む方法は安全性が高く、操作が面倒ではないので、本発明で用いることのできる好ましい方法の一つである。   In FIG. 1, the oxidation of the waste slurry in the first treatment tank 9 is performed by blowing air into the waste slurry from the aeration nozzle 8 and bubbling, and agitating and oxidizing with oxygen in the air, similarly to the oxidation at the bottom of the absorption tower 1. It is carried out. The oxidation in the first treatment tank 9 is not limited to air bubbling, and may be performed by any method and means as long as it is an efficient propulsion method. Oxygen or ozone is blown in place of air. Or a method of adding hydrogen peroxide. The method of blowing air is one of the preferable methods that can be used in the present invention because it is highly safe and the operation is not troublesome.

本発明の排煙脱硫装置の排水処理方法では、上記第1の処理槽(酸化槽)9において吸収液を酸化してpH4以下、好ましくはpH3.5以下に調整する。酸化槽9における排液のpHが4を超えると、水酸化マグネシウムのリークが発生し、フィルターの目詰まりを起こしやすくなる。   In the wastewater treatment method of the flue gas desulfurization apparatus of the present invention, the absorbing solution is oxidized in the first treatment tank (oxidation tank) 9 to adjust to pH 4 or less, preferably pH 3.5 or less. If the pH of the effluent in the oxidation tank 9 exceeds 4, leakage of magnesium hydroxide occurs and the filter is likely to be clogged.

また、公共用水域へ放流する際にはCODの他に、環境への影響からpHを中性付近に制御することが望ましい。酸化槽9では酸化されてHSOが生成するため、酸化処理した吸収液(酸化処理液)のpHは酸性側に偏っている。そこで、本発明においては、酸化処理液を酸化槽9に続く第2の処理槽10である中和槽に送り、アルカリ剤で中和する中和工程が必須である。すなわち、本発明の排煙脱硫装置の排水処理方法は、この第2の処理槽10において、第1の処理槽9で酸化した酸化処理液に、アルカリ剤を適宜の濃度の水溶液ないしスラリーとして投入して、必要ならば、撹拌羽、空気バブリングなど公知の手段を用いて適宜撹拌、混合して中和する。中和後の液(中和処理液)のpHが、pH5〜8、好ましくはpH5.5〜7.5になるように調整する。pHがこの範囲にないと、公共用水域へ放流したときに環境に悪影響を及ぼすことが懸念される。 Moreover, when discharging into public water areas, it is desirable to control the pH in the vicinity of neutrality from the influence of the environment in addition to COD. Since the oxidation tank 9 is oxidized to produce H 2 SO 4 , the pH of the oxidized absorption liquid (oxidation treatment liquid) is biased toward the acidic side. Therefore, in the present invention, a neutralization step of sending the oxidation treatment liquid to the neutralization tank which is the second treatment tank 10 following the oxidation tank 9 and neutralizing with an alkaline agent is essential. That is, the waste water treatment method for the flue gas desulfurization apparatus of the present invention is such that in this second treatment tank 10, an alkaline agent is added as an aqueous solution or slurry of an appropriate concentration to the oxidation treatment liquid oxidized in the first treatment tank 9. If necessary, neutralization is performed by appropriately stirring and mixing using known means such as stirring blades and air bubbling. The pH of the liquid after neutralization (neutralization treatment liquid) is adjusted to pH 5-8, preferably pH 5.5-7.5. If the pH is not within this range, there is a concern that it may adversely affect the environment when released into public water bodies.

第2の処理槽(中和槽)10で使用するアルカリ(中和)剤は、脱硫吸収塔のアルカリ吸収液と同じものを、すなわち、水酸化マグネシウム、水酸化カルシウム、水酸化ナトリウム、水酸化カリウム、酸化マグネシウム、酸化カルシウム、炭酸マグネシウム、炭酸カルシウム、炭酸ナトリウム、炭酸カリウムなどを使用することができる。当該装置への腐食性、コスト、毒性等を考慮すると、水酸化マグネシウムが好ましい。水酸化マグネシウムは弱アルカリ性であるが、毒性、腐食性もほとんどなく、水酸化ナトリウムのような劇物でもないため、危険性がなく、取り扱いも容易である。また、アルカリ(中和)剤は、脱硫吸収塔のアルカリ吸収液と同じものを使用する必要はないが、同じものを用いれば、管理、取り扱いの利便性が高くなり、好都合である。   The alkali (neutralization) agent used in the second treatment tank (neutralization tank) 10 is the same as the alkali absorbent of the desulfurization absorption tower, that is, magnesium hydroxide, calcium hydroxide, sodium hydroxide, hydroxide. Potassium, magnesium oxide, calcium oxide, magnesium carbonate, calcium carbonate, sodium carbonate, potassium carbonate and the like can be used. In view of the corrosiveness, cost, toxicity, etc. of the apparatus, magnesium hydroxide is preferred. Magnesium hydroxide is weakly alkaline, but it is hardly toxic and corrosive. It is not a deleterious substance like sodium hydroxide, so there is no danger and it is easy to handle. Further, the alkali (neutralizing) agent need not be the same as the alkali absorbing liquid of the desulfurization absorption tower, but using the same agent is advantageous in terms of convenience in management and handling.

第2の処理槽で中和された中和処理液は、次いで固液を分離する固液分離工程に送られ、そこで、スケール、スラッジ分などの固体成分が除去される。スケール、スラッジ分が除去された中和処理液は、中和工程でpHも排水基準内にコントロールされているため、そのまま排水として、公共用水域に放流することができる。固液分離工程は、特にその種類を限定するものではなく、固体成分と液体成分が、面倒な操作を要せず、安価で、効率的に分離できれば、どのような固液分離設備や、装置を用いてもよく、公知のものを適宜選択して用いることができる。   The neutralized treatment liquid neutralized in the second treatment tank is then sent to a solid-liquid separation step for separating the solid and liquid, where solid components such as scale and sludge are removed. Since the neutralization treatment liquid from which the scale and sludge have been removed has its pH controlled within the drainage standard in the neutralization step, it can be discharged as it is to the public water area. The solid-liquid separation process is not particularly limited in its type, and any solid-liquid separation equipment or device can be used as long as the solid component and the liquid component can be separated efficiently without complicated operations. May be used, and known ones may be appropriately selected and used.

本発明においては、固形分を分離除去したいので、例えば、ミウラ化学装置(株)製の全自動ケーキ回収フィルター「ABC型」(Automatic Backwash Clean Filter)が好ましく用いることができる。このろ過装置は、特殊成型された断面星型円筒に円筒状のろ布をかぶせたフィルターエレメントを多数、垂直に、ろ過装置のケーシング内に配列されている。処理液は、フィルターエレメントの外側に供給され、ろ布を通過する間にろ過され、ろ液は円筒状エレメントの内部に進み、円筒の一方の開口(もう一端の開口は塞がれている)から、他のエレメントのろ液と一緒になってろ過装置から排出される。
ろ布の外側(エレメント表面)にはスケール、スラッジなどのケーキが堆積してゆくため、ろ過圧力(又はエレメント前後の差圧(ΔP))が上昇する。この圧力が所定の圧力に達したら、処理液の供給を止め、ろ過を中止して、液体の流れとは逆に、エレメント内部から外側に向かって適宜の流体を流す(逆ブローする)ことによって、ろ布外側表面に堆積したケーキを剥離する。剥離されたケーキは、公知の適宜な方法で、ろ過装置の外部に取り出されて廃棄される。逆ブローの流体としては空気が好ましく、フィルターのろ布の細孔内の固形物も除去され、フィルターは繰り返してろ過に供される。
ろ過装置では、ろ過と、逆ブローによるケーキの剥離とを順繰りに行い、ケーキの剥離の間は、ろ過することができないため、通常は、上流にバッファータンクを設けて、ケーキの剥離やろ布交換時に流出する処理液を一時的に貯蔵する。
In the present invention, since it is desired to separate and remove the solid content, for example, a fully automatic cake recovery filter “ABC type” (Automatic Backwash Clean Filter) manufactured by Miura Chemical Equipment Co., Ltd. can be preferably used. In this filtering device, a number of filter elements each having a specially shaped cross-sectional star-shaped cylinder covered with a cylindrical filter cloth are arranged vertically in the casing of the filtering device. The processing liquid is supplied to the outside of the filter element and filtered while passing through the filter cloth, and the filtrate proceeds to the inside of the cylindrical element, and one opening of the cylinder (the opening of the other end is blocked). From the filtration device together with the filtrate of the other elements.
Since cakes such as scale and sludge accumulate on the outside of the filter cloth (element surface), the filtration pressure (or differential pressure before and after the element (ΔP)) increases. When this pressure reaches a predetermined pressure, the supply of the processing liquid is stopped, the filtration is stopped, and an appropriate fluid is allowed to flow from the inside of the element to the outside (reverse blow), contrary to the flow of the liquid. The cake deposited on the outer surface of the filter cloth is peeled off. The peeled cake is taken out of the filtration device and discarded by a known appropriate method. Air is preferable as the reverse blow fluid, and solid matter in the pores of the filter cloth of the filter is also removed, and the filter is repeatedly subjected to filtration.
In the filtration device, filtration and peeling of the cake by reverse blow are performed in order, and filtration cannot be performed during the peeling of the cake. Therefore, usually a buffer tank is provided upstream to remove the cake or replace the filter cloth. Temporarily store the processing liquid that sometimes flows out.

本発明の排水処理方法においては、上記のように、排煙脱硫装置の吸収塔1の後段に第1の処理槽9として酸化槽と、第2の処理槽10として中和槽とを設置し、各槽においてpHを所定範囲に制御することした。これによって、固液分離工程におけるフィルターの目詰まりによるトラブルは解消され、アルカリ中和剤の消費量も低減することができた。これは、排煙脱硫装置の排水処理(酸化及び中和)を一つの処理槽で行っていた従来の方法において、無駄に消費された水酸化マグネシウムスラリーが、中和処理液の移送経路の詰まりや固液分離工程におけるフィルターの目詰まりによるトラブルを発生させていたためと考えられる。これらのトラブルは、本発明の廃水処理方法により、防止することが可能となり、さらに、水酸化マグネシウムの過剰添加、無駄な消費を防止することができた。   In the wastewater treatment method of the present invention, as described above, an oxidation tank as the first treatment tank 9 and a neutralization tank as the second treatment tank 10 are installed at the rear stage of the absorption tower 1 of the flue gas desulfurization apparatus. In each tank, the pH was controlled within a predetermined range. As a result, troubles caused by clogging of the filter in the solid-liquid separation step were eliminated, and the consumption of the alkali neutralizer could be reduced. This is because, in the conventional method in which the wastewater treatment (oxidation and neutralization) of the flue gas desulfurization apparatus is performed in one treatment tank, the waste magnesium hydroxide slurry is clogged in the transfer path of the neutralization treatment liquid. This is thought to be due to troubles caused by clogging of the filter in the solid-liquid separation process. These troubles can be prevented by the wastewater treatment method of the present invention, and excessive addition of magnesium hydroxide and wasteful consumption can be prevented.

以下に実施例及び比較例を用いて本発明をより詳細に説明する。なお、本発明は該実施例に限定されるものではない。   Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In addition, this invention is not limited to this Example.

本発明の排煙脱硫装置の排水処理方法のフローシートを図1に示す。図1に示す排煙脱硫装置の排水処理工程を、以下のように実行して、評価した。
SO濃度が2000〜3000ppmであり、ダスト分を約100mg/Nm含有する重質重油焚きボイラの排ガスを脱硫吸収塔1に吸入口2から導入した。排ガスは、気液接触部6を上昇する間に、噴霧ノズル4で噴霧され充填物表面を流下する水酸化マグネシウムを主成分とするスラリー状の吸収液と気液接触する。排ガス中のSOなどの硫黄酸化物等が吸収液に吸収されて排ガスから硫黄分が除去される。吸収塔上部から系外に排出される排ガスのSO濃度は60ppm以下、ダスト分は30mg/Nm以下に低減されていた。
The flow sheet of the waste water treatment method for the flue gas desulfurization apparatus of the present invention is shown in FIG. The waste water treatment process of the flue gas desulfurization apparatus shown in FIG. 1 was executed and evaluated as follows.
An exhaust gas from a heavy heavy oil fired boiler having an SO 2 concentration of 2000 to 3000 ppm and containing about 100 mg / Nm 3 of dust was introduced into the desulfurization absorption tower 1 from the inlet 2. While the exhaust gas ascends the gas-liquid contact portion 6, the exhaust gas comes into gas-liquid contact with a slurry-like absorption liquid mainly composed of magnesium hydroxide sprayed by the spray nozzle 4 and flowing down the surface of the filling. Sulfur oxides such as SO 2 in the exhaust gas are absorbed by the absorption liquid, and the sulfur content is removed from the exhaust gas. The SO 2 concentration of the exhaust gas discharged out of the system from the upper part of the absorption tower was reduced to 60 ppm or less, and the dust content was reduced to 30 mg / Nm 3 or less.

吸収液は、塔底の貯留槽に貯留され、塔外に設けられた循環ポンプ7で上記の噴霧ノズル4に送られ循環使用される。吸収塔底部の貯留槽には、吸収液に吸収された硫黄化合物を酸化するための空気を供給する配管とそれにつながる複数の曝気ノズルが設けられている。酸化用空気を曝気ノズルから吸収液に吹き込んで、バブリングし、撹拌して吸収液中の亜硫酸や亜硫酸のアルカリ中和物などを酸化する。
また、吸収塔底部の貯留槽には、吸収液の硫黄化合物の吸収性能を保持すために、フレッシュな水酸化マグネシウムスラリーを一定量供給し、その量に相当する量の吸収液を吸収塔から抜き出した。抜き出した吸収液のpHは6.0、SO 2−は0.5〜0.9重量%、スラッジ量は100〜300mg/Lであった。
The absorption liquid is stored in a storage tank at the bottom of the tower, and is sent to the spray nozzle 4 and circulated by a circulation pump 7 provided outside the tower. The storage tank at the bottom of the absorption tower is provided with piping for supplying air for oxidizing the sulfur compound absorbed in the absorption liquid and a plurality of aeration nozzles connected thereto. Oxidizing air is blown into the absorption liquid from the aeration nozzle, bubbled, and stirred to oxidize sulfurous acid or an alkali neutralized product of sulfurous acid in the absorption liquid.
In addition, a fixed amount of fresh magnesium hydroxide slurry is supplied to the storage tank at the bottom of the absorption tower in order to maintain the absorption performance of the sulfur compound in the absorption liquid, and an amount of absorption liquid corresponding to that amount is supplied from the absorption tower. Extracted. The extracted absorbing solution had a pH of 6.0, SO 3 2- of 0.5 to 0.9% by weight, and a sludge amount of 100 to 300 mg / L.

吸収塔から抜き出した吸収液は、第1の処理槽である酸化槽へ送り、そこで、酸化槽底部に設けられた曝気ノズルから空気を吹き込み、吸収液をエアーバブリング、撹拌して、吸収液を空気中の酸素で酸化して、pHが3.4〜3.6になるように制御した。次いで酸化された吸収液(酸化処理液)を第2の処理槽である中和槽に移送した。このとき、酸化処理液は、pHが3.5、SO 2−が0.0〜0.1重量%、ダスト量が100〜300mg/Lであった。 The absorption liquid extracted from the absorption tower is sent to the oxidation tank which is the first treatment tank, where air is blown from an aeration nozzle provided at the bottom of the oxidation tank, and the absorption liquid is air bubbled and stirred to absorb the absorption liquid. The pH was controlled to be 3.4 to 3.6 by oxidation with oxygen in the air. Subsequently, the oxidized absorption liquid (oxidation treatment liquid) was transferred to a neutralization tank which is a second treatment tank. At this time, the oxidation treatment liquid had a pH of 3.5, SO 3 2- of 0.0 to 0.1% by weight, and a dust amount of 100 to 300 mg / L.

中和層では、酸化槽でCODを改善するために特にSO 2−をSO 2−に変えてpHが約3.5まで低下した吸収液に、水酸化マグネシウムスラリーを添加し、空気をバブリングし撹拌してpHが7.0になるように中和した。中和実施後の吸収液(中和処理液)を、次いでろ過器へ送った。このとき、中和処理液は、pHが7.0、SO 2−が0.0〜0.1重量%、ダスト量が100〜300mg/Lであった。
ろ過器(ミウラ化学装置(株)製の全自動ケーキ回収フィルター)は、タイマー設定時間によりろ過運転からケーキ剥離運転、ろ過運転からケーキ剥離運転、に切り替える運転を交互に繰り返した。ろ過器のフィルター前後における差圧が0.2MPaに達するか、ろ過時間のタイマー設定は12時間とし、先にきたほうで、自動的にケーキ剥離運転に切り換わる。ケーキ剥離運転には通常30分程度を要した。予備基への切り替えは行わず、すなわち、ケーキ剥離運転期間中にはろ過を行わず、中和処理液はバッファータンクに貯蔵した。10ヶ月連続運転したが、ろ過器のフィルター前後における差圧は0.1MPaを超えることはなく、ろ液(排水)中のスラッジ量は14mg/L以下にろ過され、6ヶ月以上の連続運転においてもフィルター目詰まりによるトラブルは発生しなかった。
In the neutralization layer, in order to improve COD in the oxidation tank, magnesium hydroxide slurry is added to the absorbing solution whose pH is lowered to about 3.5 by changing SO 3 2− to SO 4 2− in particular, and air is supplied. Bubbling and stirring were performed to neutralize the pH to 7.0. The absorption liquid after neutralization (neutralization treatment liquid) was then sent to a filter. At this time, the neutralization treatment solution had a pH of 7.0, SO 3 2- of 0.0 to 0.1% by weight, and a dust amount of 100 to 300 mg / L.
The filter (a fully automatic cake recovery filter manufactured by Miura Chemical Equipment Co., Ltd.) alternately repeated a switching operation from a filtration operation to a cake peeling operation and a filtration operation to a cake peeling operation according to a timer setting time. The differential pressure before and after the filter of the filter reaches 0.2 MPa, or the filtration time is set to 12 hours, and automatically switches to the cake peeling operation when it comes first. The cake peeling operation usually took about 30 minutes. Switching to the preliminary group was not performed, that is, filtration was not performed during the cake peeling operation period, and the neutralized solution was stored in a buffer tank. Although operated continuously for 10 months, the differential pressure before and after the filter of the filter does not exceed 0.1 MPa, the amount of sludge in the filtrate (drainage) is filtered to 14 mg / L or less, and in continuous operation for 6 months or more There was no trouble caused by filter clogging.

比較例
前記実施例で用いた第1の処理槽である酸化槽と第2の処理槽である中和槽に替えて、1つの処理槽(酸化・中和槽)を用い、その酸化・中和槽の運転条件が、前記実施例と異なる以外は、実施例と同じ条件で排水処理を行った。吸収塔から抜き出した吸収液(pH=6.0、SO 2−=0.5〜0.9重量%、スラッジ量=100〜300mg/L)を、1つの処理槽(酸化・中和槽)でエアーバブリングによる吸収液の空気酸化と、水酸化マグネシウムスラリーによる中和処理を同時に実施した。酸化用空気の供給量は、実施例の酸化槽での供給量と同じ量に設定し、pHが実施例の中和槽と同様にpH7.0となるように水酸化マグネシウムスラリーを添加した。
酸化及び中和処理後の吸収液(酸化・中和処理液)を、実施例で用いたものと同じろ過器に送り、差圧設定及びタイマー設定は実施例と全く同じ条件で、固液分離処理を行った。ろ布交換後、1ヶ月以内にろ過圧力が0.15MPaを超えた。さらに、3ヶ月程度で、ケーキ剥離直後のろ過圧力が0.2MPaに達し所定の処理量が保てなくなり、ろ布交換を余儀なくされた。なお、ろ液中のスラッジ量は14mg/Lを超えることはなかった。
なお、pH、SO 2−濃度及びスラッジ量は、次の方法によって測定した。
pH:JIS K 0102のガラス電極法にて測定した。
SO 2−濃度:JIS K 0102のヨウ素滴定法にて測定した。
スラッジ量:JIS K 0102の懸濁物質の測定方法にて測定した。
Comparative Example Instead of the oxidation tank which is the first treatment tank and the neutralization tank which is the second treatment tank used in the above embodiment, one treatment tank (oxidation / neutralization tank) is used, and the oxidation / medium The wastewater treatment was performed under the same conditions as in the examples except that the operating conditions of the Japanese tank were different from those in the examples. Absorbing liquid (pH = 6.0, SO 3 2− = 0.5 to 0.9 wt%, sludge amount = 100 to 300 mg / L) extracted from the absorption tower is treated as one treatment tank (oxidation / neutralization tank) ), Air oxidation of the absorbing solution by air bubbling and neutralization treatment with magnesium hydroxide slurry were simultaneously performed. The supply amount of the oxidizing air was set to be the same as the supply amount in the oxidation tank of the example, and the magnesium hydroxide slurry was added so that the pH was 7.0 as in the neutralization tank of the example.
The absorption liquid after oxidation and neutralization treatment (oxidation / neutralization treatment liquid) is sent to the same filter as used in the example, and the differential pressure setting and timer setting are exactly the same as in the example. Processed. After replacement of the filter cloth, the filtration pressure exceeded 0.15 MPa within one month. Furthermore, in about 3 months, the filtration pressure immediately after the cake peeled reached 0.2 MPa, and the predetermined treatment amount could not be maintained, and the filter cloth had to be replaced. The amount of sludge in the filtrate did not exceed 14 mg / L.
The pH, SO 3 2− concentration and sludge amount were measured by the following methods.
pH: Measured by the glass electrode method of JIS K 0102.
SO 3 2− concentration: Measured by the iodine titration method of JIS K 0102.
Sludge amount: Measured by the suspended substance measurement method of JIS K 0102.

本発明の排水処理方法が適用される排煙脱硫装置の一例を示す簡略化されたフローシートである。It is the simplified flow sheet which shows an example of the flue gas desulfurization apparatus to which the waste water treatment method of this invention is applied.

符号の説明Explanation of symbols

1 脱硫吸収塔
2 吸入口
3 排出口
4 噴霧ノズル
5 デミスタ
6 気液接触部
7 循環ポンプ
8 曝気ノズル
9 第1の処理槽
10 第2の処理槽
11 ろ過器
12 廃液ポンプ

DESCRIPTION OF SYMBOLS 1 Desulfurization absorption tower 2 Intake port 3 Outlet 4 Spray nozzle 5 Demister 6 Gas-liquid contact part 7 Circulating pump 8 Aeration nozzle 9 1st processing tank 10 2nd processing tank 11 Filter 12 Waste liquid pump

Claims (2)

硫黄酸化物を含む排ガスをアルカリ吸収液と吸収塔内で接触して硫黄酸化物を除去する湿式排煙脱硫装置における排水処理方法であって、硫黄酸化物を吸収したアルカリ吸収液を吸収塔から抜き出して第1の処理槽に送り、酸化してpH4以下に調整する酸化工程と、pH4以下に調整された吸収液を第2の処理槽に送り、アルカリ剤を用いてpH5〜8に調整する中和工程と、中和された吸収液をろ過する固液分離工程とを含むことを特徴とする排煙脱硫装置の排水処理方法。   A wastewater treatment method in a wet flue gas desulfurization apparatus that removes sulfur oxide by contacting exhaust gas containing sulfur oxide in an absorption tower with an alkali absorption liquid, wherein the alkali absorption liquid that has absorbed sulfur oxide is removed from the absorption tower. Extracted and sent to the first treatment tank, oxidized and adjusted to pH 4 or lower, and the absorption liquid adjusted to pH 4 or lower is sent to the second treatment tank and adjusted to pH 5 to 8 using an alkaline agent. A wastewater treatment method for a flue gas desulfurization apparatus, comprising a neutralization step and a solid-liquid separation step of filtering the neutralized absorbent. 中和工程において使用するアルカリ剤が水酸化マグネシウムである請求項1に記載の排煙脱硫装置の排水処理方法。
The wastewater treatment method for a flue gas desulfurization apparatus according to claim 1, wherein the alkali agent used in the neutralization step is magnesium hydroxide.
JP2006000532A 2006-01-05 2006-01-05 Wastewater treatment method for flue gas desulfurization equipment Pending JP2007181756A (en)

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CN102698582A (en) * 2012-05-30 2012-10-03 艾淑艳 Ammonium bicarbonate desulfurization process and ammonium bicarbonate desulfurization process system
CN104162486A (en) * 2013-05-20 2014-11-26 上海三卿环保科技有限公司 Method for synchronously removing sulfur dioxide and fine particles in smoke through electrical charge and mist spray
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CN108046499A (en) * 2017-12-18 2018-05-18 宁波大学 It is a kind of using spray column as the desulfurization wastewater drying energy saving emission-reducing system of feeding chamber
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CN108159854A (en) * 2017-11-28 2018-06-15 江苏民生重工有限公司 A kind of coal-burning boiler wet desulfurization system
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JP2020089804A (en) * 2018-12-03 2020-06-11 住友金属鉱山株式会社 Detoxification method of exhaust gas containing sulfur dioxide
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Publication number Priority date Publication date Assignee Title
CN102698582A (en) * 2012-05-30 2012-10-03 艾淑艳 Ammonium bicarbonate desulfurization process and ammonium bicarbonate desulfurization process system
CN104162486A (en) * 2013-05-20 2014-11-26 上海三卿环保科技有限公司 Method for synchronously removing sulfur dioxide and fine particles in smoke through electrical charge and mist spray
CN104692516A (en) * 2015-03-19 2015-06-10 吉林大学 Device and method for synchronously removing ammonia nitrogen and sulfide of strong alkaline wastewater
CN105268305A (en) * 2015-11-23 2016-01-27 金川集团股份有限公司 Device and method for multistage cyclic absorption and desulfurization of active ore pulp
JP2017121604A (en) * 2016-01-06 2017-07-13 日新製鋼株式会社 Treatment method of hexavalent chromium-containing waste liquid
CN106268173A (en) * 2016-08-29 2017-01-04 合肥合意环保科技工程有限公司 A kind of method of flue gas desulfurization
CN106145230A (en) * 2016-08-30 2016-11-23 成都锐思环保技术股份有限公司 A kind of fume afterheat processes the system and method for desulfurization wastewater
KR101860295B1 (en) * 2017-10-18 2018-05-23 주식회사 방산테크 Treatment Apparatus of FGD Wastewater by using Vacuum Evaporation and Method Thereof
CN108159854A (en) * 2017-11-28 2018-06-15 江苏民生重工有限公司 A kind of coal-burning boiler wet desulfurization system
CN108046499A (en) * 2017-12-18 2018-05-18 宁波大学 It is a kind of using spray column as the desulfurization wastewater drying energy saving emission-reducing system of feeding chamber
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JP7196575B2 (en) 2018-12-03 2022-12-27 住友金属鉱山株式会社 Method for detoxifying exhaust gas containing sulfur dioxide
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