JP2018094529A - Mercury removal method in waste incineration exhaust gas - Google Patents

Mercury removal method in waste incineration exhaust gas Download PDF

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JP2018094529A
JP2018094529A JP2016244259A JP2016244259A JP2018094529A JP 2018094529 A JP2018094529 A JP 2018094529A JP 2016244259 A JP2016244259 A JP 2016244259A JP 2016244259 A JP2016244259 A JP 2016244259A JP 2018094529 A JP2018094529 A JP 2018094529A
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exhaust gas
mercury
smoke
ozone
gas
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JP7244200B2 (en
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三島　俊一
Shunichi Mishima
俊一 三島
遠藤　正人
Masato Endo
正人 遠藤
山本　昌幸
Masayuki Yamamoto
昌幸 山本
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Metawater Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide a mercury removal method in waste incineration exhaust gas capable of removing mercury in waste incineration exhaust gas, efficiently in a smoke washing tower.SOLUTION: Ozone is supplied in a gaseous state to a humidifying cooling part 23 where an exhaust gas temperature is lowered to 100°C or lower, in a smoke washing tower 21 for washing waste incineration exhaust gas, and is brought into contact with exhaust gas, and thereby metal mercury in exhaust gas is converted into divalent mercury, dissolved into smoke washing water, and removed. Since contact between ozone and exhaust gas is carried out in a low temperature area, thermal decomposition of ozone is suppressed.SELECTED DRAWING: Figure 2

Description

本発明は、廃棄物焼却排ガス中の水銀を、オゾンを用いて効果的に除去する方法に関するものである。   The present invention relates to a method for effectively removing mercury in waste incineration exhaust gas using ozone.

廃棄物焼却炉の排ガス中には微量の水銀が含有されていることがあるため、排ガス処理工程において除去する必要がある。焼却排ガス中の水銀は、水に可溶なHgO、HgCl2等の二価水銀と、水に不溶な金属水銀である。このうち水に可溶な二価水銀は、洗煙処理塔において排ガスを洗煙水と接触させることによって除去することができる。しかし水に不溶な金属水銀は、洗煙処理塔で除去することは困難である。 Since a trace amount of mercury may be contained in the exhaust gas from the waste incinerator, it must be removed in the exhaust gas treatment process. Mercury in the incineration exhaust gas is divalent mercury such as HgO and HgCl 2 that is soluble in water and metallic mercury that is insoluble in water. Among these, divalent mercury that is soluble in water can be removed by bringing the exhaust gas into contact with the smoke-washed water in the smoke-washing treatment tower. However, it is difficult to remove metallic mercury that is insoluble in water using a smoke treatment tower.

そこで特許文献１に示されるように、触媒を用いて金属水銀を二価水銀に変換したうえ、吸収液と接触させて除去する方法が提案されている。しかしこの方法は排ガス処理設備中に新たに触媒反応設備を増設する必要があるため、排ガス処理設備が複雑化し設備コストが高くなるという問題がある。   Therefore, as disclosed in Patent Document 1, a method has been proposed in which metallic mercury is converted into divalent mercury using a catalyst and then removed by contact with an absorbing solution. However, since this method requires a new catalytic reaction facility to be added to the exhaust gas treatment facility, there is a problem that the exhaust gas treatment facility becomes complicated and the equipment cost increases.

そこで特許文献２に示されるように、排煙処理塔においてオゾンを用いて金属水銀を二価水銀に変換し、洗煙水で除去する方法も提案されている。この特許文献２の方法は、図４に模式的に示すように、洗煙処理塔１の下部から洗煙水を循環ポンプ２で汲み上げて洗煙処理塔１の上部に循環させる循環配管３中にオゾンを吹き込み、このオゾン水を洗煙処理塔の上部のノズル４から噴霧して排ガスと接触させ、二価水銀とするものである。この方法は特許文献１のように触媒反応設備を増設する必要がなく、洗煙処理塔にオゾン発生器を取り付けるだけでよい利点がある。   Therefore, as shown in Patent Document 2, a method of converting metal mercury into divalent mercury using ozone in a flue gas treatment tower and removing it with smoke washing water has also been proposed. As schematically shown in FIG. 4, the method of Patent Document 2 is configured in a circulation pipe 3 that draws smoke-washed water from the lower part of the smoke-washing treatment tower 1 with a circulation pump 2 and circulates it in the upper part of the smoke-washing treatment tower 1. Ozone is blown into this, and this ozone water is sprayed from the nozzle 4 at the top of the smoke-washing tower and brought into contact with the exhaust gas to form divalent mercury. This method has the advantage that it is not necessary to add a catalytic reaction facility as in Patent Document 1, and only an ozone generator may be attached to the smoke-washing treatment tower.

しかし一般に、洗煙処理塔の入り口部分における排ガス温度は200〜300℃であるから、オゾン水を排ガス中に噴霧してもオゾンは熱により直ちに分解してしまい、排ガス中の金属水銀を効率よく二価水銀に酸化することができない。また、下水処理場では洗煙水として下水処理水を使用しているが、この処理水中にはBODが15mg/L程度含有されているため、オゾンが洗煙水中のBODと反応して無駄に消費されてしまう。さらに、オゾンの水への溶解度は低い。このため、排ガス中の金属水銀を十分に酸化させるためには多量のオゾンと水とを添加しなければならず、ランニングコストが非常に高くなるという問題がある。このほか、オゾン水は循環配管の酸化腐食を促進するため、設備寿命の点でも問題がある。   However, in general, the exhaust gas temperature at the entrance of the smoke cleaning tower is 200 to 300 ° C, so even if ozone water is sprayed into the exhaust gas, the ozone is immediately decomposed by heat, and metal mercury in the exhaust gas is efficiently removed. It cannot be oxidized to divalent mercury. In addition, sewage treatment water is used as sewage water in the sewage treatment plant, but since this treatment water contains about 15 mg / L of BOD, ozone reacts with BOD in the shamwash water and is wasted. It will be consumed. Furthermore, the solubility of ozone in water is low. For this reason, in order to fully oxidize the metal mercury in the exhaust gas, a large amount of ozone and water must be added, and there is a problem that the running cost becomes very high. In addition, since ozone water promotes oxidative corrosion of the circulation pipe, there is a problem in terms of equipment life.

特開２００４−３１３８３３号公報JP 2004-313833 A ＷＯ２００５／００５０２５号公報WO2005 / 005025 Publication

従って本発明の目的は上記した従来の問題点を解決し、廃棄物焼却排ガス中の水銀を、洗煙処理塔において効率よく除去することができる廃棄物焼却排ガス中の水銀除去方法を提供することである。   Accordingly, an object of the present invention is to solve the above-mentioned conventional problems and to provide a mercury removal method in waste incineration exhaust gas that can efficiently remove mercury in waste incineration exhaust gas in a smoke-washing tower. It is.

上記の課題を解決するためになされた本発明の廃棄物焼却排ガス中の水銀除去方法は、廃棄物焼却排ガスを洗浄する洗煙処理塔の、排ガス温度を100℃以下にまで低下させたガスの増湿冷却部にオゾンをガス状態で供給して排ガスと接触させ、排ガス中の金属水銀を二価水銀に変換し、洗煙水に溶解させて除去することを特徴とするものである。   The mercury removal method for waste incineration exhaust gas according to the present invention, which has been made to solve the above-mentioned problems, is a method for removing smoke from a smoke cleaning tower for cleaning waste incineration exhaust gas by reducing the exhaust gas temperature to 100 ° C or lower. Ozone is supplied in a gaseous state to the humidified cooling section and brought into contact with the exhaust gas, and the metal mercury in the exhaust gas is converted to divalent mercury and dissolved in smoke-washed water to be removed.

なお、前記洗煙処理塔が下段のガス増湿冷却部とその上段の排ガス洗浄部、あるいはガス減湿冷却部とを備えたものであり、オゾンをガスの増湿冷却部の上部にガス状態で供給することが好ましい。また、前記洗煙処理塔の底部の洗煙水を循環ポンプで汲み上げ、下段のガス増湿冷却部で循環させることが好ましい。さらに、前記洗煙処理塔で処理された排ガス中の水銀濃度を測定し、オゾンの供給量を自動制御することが好ましい。   The smoke cleaning tower includes a lower gas humidification cooling section and an upper exhaust gas cleaning section, or a gas dehumidification cooling section, and ozone is in a gas state above the gas humidification cooling section. It is preferable to supply by. Further, it is preferable that the smoke-washing water at the bottom of the smoke-washing tower is pumped up by a circulation pump and circulated in the lower gas humidification cooling unit. Furthermore, it is preferable to measure the mercury concentration in the exhaust gas treated in the smoke washing tower and to automatically control the supply amount of ozone.

本発明の廃棄物焼却排ガス中の水銀除去方法によれば、洗煙処理塔の内部で金属水銀を酸化させて二価水銀とし、洗煙水に溶解させて除去することができる。このため洗煙処理塔にオゾン供給手段を組み込むだけでよく、触媒反応装置などを増設する必要がない。   According to the method for removing mercury from the waste incineration exhaust gas of the present invention, metallic mercury can be oxidized into divalent mercury inside the smoke washing tower and dissolved in smoke washing water for removal. For this reason, it is only necessary to incorporate ozone supply means in the smoke-washing tower, and there is no need to add a catalyst reaction device or the like.

また本発明の廃棄物焼却排ガス中の水銀除去方法によれば、洗煙処理塔の排ガス温度が100℃以下にまで低下するガスの増湿冷却部に、オゾンを供給して排ガスと接触させる。このようにオゾンガスと接触する排ガス温度が低下しているためにオゾンの熱分解が抑制され、特許文献２の方法に比べてオゾン供給量を削減することができる。   Further, according to the method for removing mercury from the waste incineration exhaust gas according to the present invention, ozone is supplied to the humidification cooling section of the gas where the exhaust gas temperature of the smoke treatment tower is lowered to 100 ° C. or less to contact the exhaust gas. As described above, since the exhaust gas temperature in contact with the ozone gas is lowered, the thermal decomposition of ozone is suppressed, and the ozone supply amount can be reduced as compared with the method of Patent Document 2.

また本発明の廃棄物焼却排ガス中の水銀除去方法によれば、オゾンをガス状態で供給するため、オゾンを水中に供給する場合に比べて、洗煙処理塔でのオゾンとガスの接触時間を長くすることができる。このため特許文献２の方法では水中で分解してしまうオゾン量が多く、大量のオゾンを供給しなければ、排ガス中の金属水銀を酸化させることができないが、本願発明では少量のオゾンで効率よく金属水銀を酸化させることができる。このため、ランニングコストを削減することが可能となる。   Further, according to the method for removing mercury from the waste incineration exhaust gas of the present invention, ozone is supplied in a gas state. Therefore, compared with the case of supplying ozone into water, the contact time between ozone and gas in the smoke treatment tower is reduced. Can be long. Therefore, in the method of Patent Document 2, the amount of ozone that decomposes in water is large, and unless a large amount of ozone is supplied, the metal mercury in the exhaust gas cannot be oxidized. Metallic mercury can be oxidized. For this reason, it becomes possible to reduce running cost.

焼却炉とその排ガス処理設備の全体構成図である。It is a whole block diagram of an incinerator and its waste gas treatment equipment. 実施形態の洗煙処理塔の模式的な断面図である。It is typical sectional drawing of the smoke-washing processing tower of embodiment. 他の実施形態の洗煙処理塔の模式的な断面図である。It is typical sectional drawing of the smoke-washing processing tower of other embodiment. 従来の洗煙処理塔における水銀除去技術の説明図である。It is explanatory drawing of the mercury removal technique in the conventional smoke-washing processing tower.

（全体構成）
以下に本発明の好ましい実施形態を説明するが、先ず図１により、焼却炉とその排ガス処理設備の全体構成について説明する。 (overall structure)
A preferred embodiment of the present invention will be described below. First, an overall configuration of an incinerator and its exhaust gas treatment facility will be described with reference to FIG.

図１は実施形態の全体構成図であり、１０は廃棄物を焼却する焼却炉である。この焼却炉１０は下部に流動空気供給手段１１を備え、流動媒体を流動させながら汚泥を焼却する流動床炉である。汚泥ポンプ１２により炉内に投入された脱水汚泥は850℃以上の高温で焼却され、発生した廃棄物焼却排ガス（排ガス）は流動空気予熱器１３に入る。なお、本発明においては焼却炉１０の種類は特に限定されるものではなく、ストーカー炉等の焼却炉を用いてもよい。前記したように、この排ガス中には廃棄物由来の水銀が、金属水銀及び二価水銀として微量含まれている。   FIG. 1 is an overall configuration diagram of an embodiment, and 10 is an incinerator for incinerating waste. The incinerator 10 includes a fluidized air supply means 11 in the lower part, and is a fluidized bed furnace that incinerates sludge while flowing a fluid medium. The dewatered sludge introduced into the furnace by the sludge pump 12 is incinerated at a high temperature of 850 ° C. or higher, and the generated waste incineration exhaust gas (exhaust gas) enters the fluidized air preheater 13. In the present invention, the type of the incinerator 10 is not particularly limited, and an incinerator such as a stalker furnace may be used. As described above, this exhaust gas contains a trace amount of mercury derived from waste as metallic mercury and divalent mercury.

流動空気予熱器１３は流動空気ブロワ１４により吹き込まれた空気を高温の排ガスとの熱交換によって予熱し、流動空気供給手段１１に供給する。流動空気予熱器１３を通過した排ガスは次に白煙防止器１５に入り、白煙防止ファン１６から供給される空気を加熱する。加熱された空気は白煙防止空気として煙突１７へ送られ、煙突１７から大気中に放出される排ガスを加熱し、白煙を防止する。これらの流動空気予熱器１３及び白煙防止器１５はともに、排ガスと空気との間で熱交換を行う熱交換器である。   The fluidized air preheater 13 preheats the air blown by the fluidized air blower 14 by heat exchange with high-temperature exhaust gas, and supplies the fluidized air supply means 11 with it. The exhaust gas that has passed through the fluidized air preheater 13 then enters the white smoke preventer 15 and heats the air supplied from the white smoke preventive fan 16. The heated air is sent to the chimney 17 as white smoke prevention air, and the exhaust gas discharged from the chimney 17 into the atmosphere is heated to prevent white smoke. Both the fluid air preheater 13 and the white smoke preventer 15 are heat exchangers that exchange heat between exhaust gas and air.

白煙防止器１５を通過した排ガスは、冷却塔１８において冷却される。冷却塔１８は冷却水を散水する散水ノズル１９を備えており、排ガスを200〜300℃まで冷却する。冷却水はすべて蒸発するため、排水は発生しない。この冷却塔１８は省略することもできる。冷却された排ガスは集塵機２０に送られ、ダストを除去される。   The exhaust gas that has passed through the white smoke preventer 15 is cooled in the cooling tower 18. The cooling tower 18 includes a watering nozzle 19 for spraying cooling water, and cools the exhaust gas to 200 to 300 ° C. Since all cooling water evaporates, there is no drainage. The cooling tower 18 can be omitted. The cooled exhaust gas is sent to the dust collector 20, where dust is removed.

この実施形態では集塵機２０は耐熱性に優れるセラミックフィルタを用いた構造のものであり、集塵機２０では排ガスの温度低下はほとんどないため、集塵機２０を通過した排ガス温度は200〜300℃である。排ガスは次に洗煙処理塔２１に送られて処理され、吸引ファン２２によって吸引されて煙突１７から大気中に放出される。本発明ではこの洗煙処理塔２１において水銀の除去を行う。以下に洗煙処理塔２１の構造と水銀除去方法を詳細に説明する。   In this embodiment, the dust collector 20 has a structure using a ceramic filter having excellent heat resistance, and since the exhaust gas temperature hardly decreases in the dust collector 20, the exhaust gas temperature passing through the dust collector 20 is 200 to 300 ° C. The exhaust gas is then sent to the smoke cleaning tower 21 for processing, sucked by the suction fan 22 and released from the chimney 17 into the atmosphere. In the present invention, mercury is removed in the smoke cleaning tower 21. Hereinafter, the structure of the smoke cleaning tower 21 and the mercury removal method will be described in detail.

（洗煙処理塔）
図２は本発明で用いられる洗煙処理塔２１の模式的な断面図である。塔体は下段のガス増湿冷却部２３とその上段のガス減湿冷却部２４とからなる２段構造である。下段のガス増湿冷却部２３は底部の洗煙水槽２５の水を循環ポンプ２６で汲み上げ、散水ノズル２７から散水し、塔体下部の排ガス供給口２８から送り込まれる排ガスを冷却する領域である。排ガス供給口２８から送り込まれる排ガス温度は200〜300℃であるが、塔体内部を上昇する間に冷却され、ガス増湿冷却部２３の上部では60〜100℃にまで冷却される。この位置には温度センサ２９が設置されており、排ガス温度が100℃以下に保たれるようにガス増湿冷却部２３の循環水量を制御している。なお温度センサ２９を省略し、入口側のガス温度とガス量とを計算により求めておき、その値から循環水量を制御してもよい。 (Smoke washing tower)
FIG. 2 is a schematic cross-sectional view of the smoke cleaning tower 21 used in the present invention. The tower has a two-stage structure including a lower gas humidification cooling unit 23 and an upper gas dehumidification cooling unit 24. The lower gas humidification cooling unit 23 is an area for pumping water from the bottom smoke washing water tank 25 with a circulation pump 26, sprinkling water from a water spray nozzle 27, and cooling exhaust gas sent from an exhaust gas supply port 28 at the lower part of the tower body. The exhaust gas temperature fed from the exhaust gas supply port 28 is 200 to 300 ° C., but is cooled while rising inside the tower body, and is cooled to 60 to 100 ° C. above the gas humidification cooling unit 23. A temperature sensor 29 is installed at this position, and the amount of circulating water in the gas humidification cooling unit 23 is controlled so that the exhaust gas temperature is kept at 100 ° C. or lower. Note that the temperature sensor 29 may be omitted, the gas temperature and the gas amount on the inlet side may be obtained by calculation, and the circulating water amount may be controlled based on these values.

上段のガス減湿冷却部２４はトレー３０を複数段備え、補給水をノズル３１，３２から供給する構造である。このうち、補給ノズル３１からは、補給水が常時供給されている。他方、補給ノズル３２からは、トレー３０及びデミスタ３４を洗浄する際に、必要に応じて補給水が供給される。排ガスはこれらのトレー３０の間を上昇する間に補給水と接触して洗浄され、含有ダスト、NOXやSOXなどが除去される。またガス減湿冷却部２４の上部にはアルカリ供給手段３３が設けられており、NaOHを散布している。これにより塔内水のpHをアルカリに保ち、ガス洗浄効率を高める。ガス減湿冷却部２４を通過した排ガスは塔体上端のデミスタ３４を通過し、40〜60℃で煙突１７に吸引される。 The upper gas dehumidifying / cooling section 24 includes a plurality of trays 30 and supplies makeup water from nozzles 31 and 32. Among these, the replenishing water is always supplied from the replenishing nozzle 31. On the other hand, when the tray 30 and the demister 34 are washed from the supply nozzle 32, supply water is supplied as necessary. Exhaust gas is washed in contact with the makeup water while rising between these trays 30, containing dust, such as NO X and SO X is removed. An alkali supply means 33 is provided above the gas dehumidifying / cooling unit 24 and sprays NaOH. As a result, the pH of the water in the tower is kept alkaline and the gas cleaning efficiency is increased. The exhaust gas that has passed through the gas dehumidifying cooling section 24 passes through the demister 34 at the upper end of the tower body, and is sucked into the chimney 17 at 40 to 60 ° C.

（水銀除去方法）
図２に示すように、このガス増湿冷却部２３の上部位置にはオゾン供給手段３５が設置されており、オゾンをガス状態で供給している。前記したように、排ガス供給口２８から送り込まれる排ガスの温度は200〜300℃であるが、ガス増湿冷却部２３を上昇する間に100℃以下にまで冷却される。本発明ではこの位置においてオゾンをガス状態で供給する。このためオゾンの熱分解が抑制され、オゾンは長時間にわたり塔内に滞留するので、排ガス中の金属水銀を酸化して二価水銀とし、排ガス中の二価水銀とともに、循環水中に溶解させて除去することができる。循環水中の水銀は後段の水処理設備で処理される。 (Mercury removal method)
As shown in FIG. 2, the ozone supply means 35 is installed in the upper position of this gas humidification cooling part 23, and ozone is supplied in a gas state. As described above, the temperature of the exhaust gas fed from the exhaust gas supply port 28 is 200 to 300 ° C., but is cooled to 100 ° C. or less while ascending the gas humidification cooling unit 23. In the present invention, ozone is supplied in a gaseous state at this position. For this reason, the thermal decomposition of ozone is suppressed, and ozone stays in the tower for a long time, so the metallic mercury in the exhaust gas is oxidized to divalent mercury and dissolved in the circulating water together with the divalent mercury in the exhaust gas. Can be removed. Mercury in the circulating water is treated at the subsequent water treatment facility.

またオゾンはガス状態で供給されるため長時間にわたり排ガスと混合、接触させることができる。しかもオゾン供給手段３５の天井部にはトレー３０があるため生成した二価水銀を速やかに水に溶解させることができる。さらにガス状のオゾンは水中のBODと反応しにくいので無駄に消費されることもない。   Moreover, since ozone is supplied in a gas state, it can be mixed and contacted with exhaust gas for a long time. Moreover, since the tray 30 is provided at the ceiling of the ozone supply means 35, the generated divalent mercury can be quickly dissolved in water. Furthermore, gaseous ozone does not react with BOD in water, so it is not wasted.

このため本発明によれば、循環水中のオゾンを従来のように水中に供給する方法に較べて、オゾン使用量を大幅に減少させることができる。本発明者が行ったモデル実験によれば、同一の水銀除去効果を得るために必要なオゾン供給量を、従来の約30％にまで減少させることができた。しかも循環水の配管がオゾンによって腐食することもない。   For this reason, according to this invention, compared with the method of supplying ozone in circulating water to water conventionally, the amount of ozone used can be reduced significantly. According to the model experiment conducted by the present inventor, the ozone supply amount necessary for obtaining the same mercury removal effect could be reduced to about 30% of the conventional amount. Moreover, the piping of the circulating water is not corroded by ozone.

また図１に示すように、煙突１７の出口において排ガス中の水銀濃度を水銀連続分析装置３６により連続分析し、水銀濃度に応じてオゾン発生装置３７からのオゾン供給量を制御するようにすれば、少ないオゾン量で排ガス中の金属水銀を効率よく除去することが可能となる。オゾン発生装置３７は多量の電力を消費するため、オゾン使用量の削減はランニングコストの削減に大きく寄与するものである。   As shown in FIG. 1, the mercury concentration in the exhaust gas is continuously analyzed at the outlet of the chimney 17 by the mercury continuous analyzer 36, and the ozone supply amount from the ozone generator 37 is controlled according to the mercury concentration. Therefore, it becomes possible to efficiently remove metallic mercury in the exhaust gas with a small amount of ozone. Since the ozone generator 37 consumes a large amount of electric power, the reduction of the amount of ozone used greatly contributes to the reduction of the running cost.

（他の実施形態）
以上に説明した実施形態は水が豊富にある下水処理場での使用を想定したものであり、上段のガス減湿冷却部２４に供給した水は下段のガス増湿冷却部２３に供給され、スクラバ排水となる。しかしゴミ処理場では下水処理場とは異なり水が豊富ではないため、水の使用量を極力少なくする必要がある。 (Other embodiments)
The embodiment described above is assumed to be used in a sewage treatment plant where water is abundant, and the water supplied to the upper gas dehumidification cooling unit 24 is supplied to the lower gas dehumidification cooling unit 23, Scrubber drainage. However, unlike a sewage treatment plant, water is not abundant at a garbage disposal plant, so it is necessary to reduce the amount of water used as much as possible.

図３はこのような水が豊富ではない処理場での使用を想定した洗煙処理塔２１の模式的な断面図である。この実施形態では洗煙処理塔２１の内部はガスを通過させることができる隔壁４０によって上段のガス減湿冷却部２４と下段のガス増湿冷却部２３に区画されている。オゾンは、ガス増湿冷却部２３の上部位置のオゾン供給手段３５からガス状態で供給される。下段のガス増湿冷却部２３では、底部の洗煙水槽２５の水を循環ポンプ２６で汲み上げ、散水ノズル２７から散水し、塔体下部の排ガス供給口２８から送り込まれる排ガスを冷却する。循環水の一部は洗煙排水槽４１に取り出され、排水される。   FIG. 3 is a schematic cross-sectional view of the smoke cleaning tower 21 intended for use in a treatment plant that is not rich in water. In this embodiment, the inside of the smoke cleaning tower 21 is divided into an upper gas dehumidifying cooling unit 24 and a lower gas humidifying cooling unit 23 by a partition wall 40 through which gas can pass. Ozone is supplied in a gas state from ozone supply means 35 at an upper position of the gas humidification cooling unit 23. In the lower gas humidification cooling unit 23, water in the bottom smoke washing water tank 25 is pumped by the circulation pump 26, sprayed from the water spray nozzle 27, and exhaust gas sent from the exhaust gas supply port 28 in the lower part of the tower body is cooled. A part of the circulating water is taken out to the smoke washing drain 41 and drained.

一方、上段のガス減湿冷却部２４については、減湿冷却槽４２において補給水とアルカリを混合し、ポンプ４３によってノズル４４から散水し、ガスを冷却する。補給水は隔壁４０によって受け止められ、減湿冷却槽４２に回収される。なおポンプ４３とノズル４４の間には、補給水を冷却する減湿用冷却器４５が設置される。このように上段のガス減湿冷却部２４についても補給水を無駄なく回収し、冷却したうえでガス冷却に循環使用している。この実施形態は補給水の使用法が異なるだけであり、オゾンによる水銀回収については前記した実施形態と同様である。   On the other hand, the upper gas dehumidifying cooling unit 24 mixes makeup water and alkali in the dehumidifying cooling tank 42, sprays water from the nozzle 44 by the pump 43, and cools the gas. The makeup water is received by the partition wall 40 and collected in the dehumidifying cooling tank 42. A dehumidifying cooler 45 that cools the makeup water is installed between the pump 43 and the nozzle 44. In this manner, the upper gas dehumidifying / cooling section 24 also collects makeup water without waste, cools it, and circulates it for gas cooling. This embodiment is different only in the use of makeup water, and the mercury recovery by ozone is the same as the embodiment described above.

以上に説明したように、本発明によれば、廃棄物焼却排ガス中の水銀を、洗煙処理塔において効率よく除去することができる。   As described above, according to the present invention, mercury in waste incineration exhaust gas can be efficiently removed in the smoke cleaning tower.

１ 洗煙処理塔
２ 循環ポンプ
３ 循環配管
４ ノズル
１０ 焼却炉
１１ 流動空気供給手段
１２ 汚泥ポンプ
１３ 流動空気予熱器
１４ 流動空気ブロワ
１５ 白煙防止器
１６ 白煙防止ファン
１７ 煙突
１８ 冷却塔
１９ 散水ノズル
２０ 集塵機
２１ 洗煙処理塔
２２ 吸引ファン
２３ ガス増湿冷却部
２４ ガス減湿冷却部
２５ 洗煙水槽
２６ 循環ポンプ
２７ 散水ノズル
２８ 排ガス供給口
２９ 温度センサ
３０ トレー
３１ ノズル
３２ ノズル
３３ アルカリ供給手段
３４ デミスタ
３５ オゾン供給手段
３６ 水銀連続分析装置
３７ オゾン発生装置
４０ 隔壁
４１ 洗煙排水槽
４２ 減湿冷却槽
４３ ポンプ
４４ ノズル
４５ 減湿用冷却器 DESCRIPTION OF SYMBOLS 1 Smoke-washing tower 2 Circulation pump 3 Circulation piping 4 Nozzle 10 Incinerator 11 Fluid air supply means 12 Sludge pump 13 Fluid air preheater 14 Fluid air blower 15 White smoke preventer 16 White smoke prevention fan 17 Chimney 18 Cooling tower 19 Watering Nozzle 20 Dust collector 21 Smoke washing tower 22 Suction fan 23 Gas humidification cooling unit 24 Gas dehumidification cooling unit 25 Smoke washing water tank 26 Circulation pump 27 Sprinkling nozzle 28 Exhaust gas supply port 29 Temperature sensor 30 Tray 31 Nozzle 32 Nozzle 33 Alkali supply means 34 Demister 35 Ozone supply means 36 Mercury continuous analyzer 37 Ozone generator 40 Bulkhead 41 Smoke-washing drainage tank 42 Dehumidifying cooling tank 43 Pump 44 Nozzle 45 Dehumidifying cooler

Claims (4)

廃棄物焼却排ガスを洗浄する洗煙処理塔の、排ガス温度を100℃以下にまで低下させたガス増湿冷却部にオゾンをガス状態で供給して排ガスと接触させ、排ガス中の金属水銀を二価水銀に変換し、洗煙水に溶解させて除去することを特徴とする廃棄物焼却排ガス中の水銀除去方法。   Supplying ozone in a gas state to the gas humidification cooling section of the smoke-washing tower that cleans the waste incineration exhaust gas whose exhaust gas temperature has been lowered to 100 ° C or less to bring it into contact with the exhaust gas. A method for removing mercury from waste incineration exhaust gas, which is converted to valence mercury and dissolved in smoke-washed water for removal. 前記洗煙処理塔が、下段のガス増湿冷却部とその上段のガス減湿冷却部とを備えたものであり、オゾンをガス増湿冷却部の上部に供給することを特徴とする請求項１に記載の廃棄物焼却排ガス中の水銀除去方法。   The smoke cleaning treatment tower includes a lower gas humidification cooling unit and an upper gas dehumidification cooling unit, and supplies ozone to an upper part of the gas humidification cooling unit. The method for removing mercury in waste incineration exhaust gas according to 1. 前記洗煙処理塔の底部の洗煙水を循環ポンプで汲み上げ、下段のガス増湿冷却部で循環させることを特徴とする請求項２に記載の廃棄物焼却排ガス中の水銀除去方法。   3. The method for removing mercury in waste incineration exhaust gas according to claim 2, wherein smoke cleaning water at the bottom of the smoke cleaning tower is pumped up by a circulation pump and circulated in a lower gas humidification cooling unit. 前記洗煙処理塔で処理された排ガス中の水銀濃度を測定し、オゾンの供給量を自動制御することを特徴とする請求項１〜３の何れかに記載の廃棄物焼却排ガス中の水銀除去方法。   The mercury concentration in the waste incineration exhaust gas according to any one of claims 1 to 3, wherein the mercury concentration in the exhaust gas treated in the smoke treatment tower is measured and the supply amount of ozone is automatically controlled. Method.
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