JP5060776B2 - Method and apparatus for recovering mercury from exhaust gas - Google Patents
Method and apparatus for recovering mercury from exhaust gas Download PDFInfo
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- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 title claims description 125
- 229910052753 mercury Inorganic materials 0.000 title claims description 121
- 238000000034 method Methods 0.000 title claims description 30
- 239000007789 gas Substances 0.000 claims description 81
- 239000000428 dust Substances 0.000 claims description 77
- 239000003054 catalyst Substances 0.000 claims description 46
- 238000011084 recovery Methods 0.000 claims description 19
- 238000001816 cooling Methods 0.000 claims description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 13
- 229910000041 hydrogen chloride Inorganic materials 0.000 claims description 13
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims description 13
- 239000007921 spray Substances 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 8
- 239000003795 chemical substances by application Substances 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 6
- 239000003990 capacitor Substances 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 229940008718 metallic mercury Drugs 0.000 claims description 4
- 230000001590 oxidative effect Effects 0.000 claims description 3
- 230000003647 oxidation Effects 0.000 description 8
- 238000007254 oxidation reaction Methods 0.000 description 8
- 239000012855 volatile organic compound Substances 0.000 description 6
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 4
- 239000000460 chlorine Substances 0.000 description 4
- 229910052801 chlorine Inorganic materials 0.000 description 4
- 239000002028 Biomass Substances 0.000 description 3
- 150000003863 ammonium salts Chemical class 0.000 description 3
- 239000004568 cement Substances 0.000 description 3
- RCTYPNKXASFOBE-UHFFFAOYSA-M chloromercury Chemical compound [Hg]Cl RCTYPNKXASFOBE-UHFFFAOYSA-M 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 229910010413 TiO 2 Inorganic materials 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- -1 conventionally Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000002906 medical waste Substances 0.000 description 2
- 239000010801 sewage sludge Substances 0.000 description 2
- 229910000505 Al2TiO5 Inorganic materials 0.000 description 1
- 229910010038 TiAl Inorganic materials 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 239000012320 chlorinating reagent Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- AABBHSMFGKYLKE-SNAWJCMRSA-N propan-2-yl (e)-but-2-enoate Chemical compound C\C=C\C(=O)OC(C)C AABBHSMFGKYLKE-SNAWJCMRSA-N 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000011949 solid catalyst Substances 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
-
- 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
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- Catalysts (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
- Treating Waste Gases (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Description
本発明は例えば石炭火力発電所や医療廃棄物焼却装置、下水汚泥焼却装置から出る排ガス中に含まれる水銀の除去方法および装置に関するものである。 The present invention relates to a method and apparatus for removing mercury contained in exhaust gas discharged from, for example, a coal-fired power plant, a medical waste incinerator, and a sewage sludge incinerator.
近年、環境中への水銀排出をさらに削減することが求められている。特に火力発電所や医療廃棄物焼却装置、下水汚泥焼却装置から発生する排ガス中に含まれる水銀が環境中に排出される水銀総量に占める割合が増加しつつあり、日本国内における各排出量は年間数トン〜十数トンにも達し、先行する欧米に続いてわが国でもその対策が急務となっている。 In recent years, there has been a demand for further reducing mercury emissions into the environment. In particular, the ratio of mercury contained in exhaust gas generated from thermal power plants, medical waste incinerators, and sewage sludge incinerators to the total amount of mercury discharged into the environment is increasing. Several tons and dozens of tons have been reached, and countermeasures are urgently required in Japan following the leading Western countries.
ガスおよびダストからの水銀除去方法として、従来、バイオマスを被処理物（例えば火力発電所における石炭）と混焼することでバイオマス中の塩素分を利用して排ガス中の塩素量を増加させて、水銀を酸化して排ガス中の水銀を除去する方法が提案されている（特許文献１）。同文献には、水銀酸化用触媒によって水銀を酸化すること、塩素量が不足した場合には塩化水素を排ガスに注入することが開示されている。 As a method for removing mercury from gas and dust, conventionally, biomass is co-fired with an object to be treated (for example, coal in a thermal power plant), and the amount of chlorine in the exhaust gas is increased by utilizing the chlorine content in the biomass. A method has been proposed in which mercury in the exhaust gas is removed by oxidizing oxygen (Patent Document 1). This document discloses that mercury is oxidized by a mercury oxidation catalyst, and that hydrogen chloride is injected into exhaust gas when the amount of chlorine is insufficient.
また、塩化水素等の塩素化剤を添加せずハニカム状等の固体触媒によって水銀を酸化し、アルカリ吸収液によって水銀を除去する方法も提案されている（特許文献２）。
特許文献１の方法では、混焼するバイオマスの組成が一定しないため、加えるべき塩素量の制御が困難であり、状況によっては多量のバイオマスを必要とし、その結果焼却残渣が著しく増加するという問題があった。 In the method of Patent Document 1, since the composition of the biomass to be co-fired is not constant, it is difficult to control the amount of chlorine to be added. It was.
また、特許文献２に示されるようなハニカム成形タイプの触媒では水銀除去性能は十分でなく、かつ劣化時の触媒交換に多大な労力と時間を要していた。
Further, the honeycomb forming type catalyst as shown in
本発明はこれらの問題を解決することを企図したもので、水銀含有排ガスの処理過程において塩化水素ガスを吹き込み、さらに該排ガス中に反応性に優れた粉体状の触媒を通過させることで排ガス中の水銀（主としてゼロ価のＨｇ）を高効率に酸化し、これを排ガスダスト中に取り込み、ダストは後段に設けた集塵機により分離除去し、得られたダスト中の水銀は加熱および湿式処理により、ほぼ全量金属状態で回収し、さらに処理後のダストはセメント原料をはじめとする再利用に供する。 The present invention is intended to solve these problems, and injecting hydrogen chloride gas in the process of treating the mercury-containing exhaust gas, and further passing the powdered catalyst having excellent reactivity into the exhaust gas, the exhaust gas. Mercury (mainly zero-valent Hg) is oxidized with high efficiency, and this is taken into exhaust gas dust. The dust is separated and removed by a dust collector provided at the subsequent stage, and the mercury in the obtained dust is heated and wet-treated. In addition, almost all of it is recovered in the metal state, and the dust after the treatment is further reused including cement raw materials.
本発明の第１のものは、排ガス中の水銀を酸化処理し、処理されたガスからダストを分離する水銀含有排ガスの処理工程と、分離されたダストから水銀を回収する水銀含有ダス
トの処理工程とからなる水銀回収方法であって、
水銀含有排ガスの処理工程は、排ガスに塩化水素を吹き込む段階と、同排ガスを粉体状の触媒と接触させて水銀を酸化する段階と、反応後のガスを集塵処理する段階と、回収ダストと使用済み触媒の混合物をダストと触媒に分離する段階と、分離触媒の少なくとも一部を反応器へ循環する段階とを含み、
水銀含有ダストの処理工程は、分離されたダストを加熱する段階と、加熱されたダストを水銀含有加熱ガスからフィルタで分離する段階と、フィルタ分離されたダストを冷却し処理灰を生じさせる段階と、フィルタ分離された水銀含有ガスを直接および／または間接的に冷却する段階と、冷却によって生じた水銀含有水を蓄え金属水銀を生成させる段階とを含む、
水銀含有排ガスからの水銀回収方法である。
According to a first aspect of the present invention, a mercury-containing exhaust gas treatment step of oxidizing mercury in exhaust gas and separating dust from the treated gas, and a mercury-containing dust treatment step of recovering mercury from the separated dust A mercury recovery method comprising:
The treatment process of the mercury-containing exhaust gas includes a stage in which hydrogen chloride is blown into the exhaust gas, a stage in which the exhaust gas is contacted with a powdered catalyst to oxidize mercury, a stage in which the gas after the reaction is collected, and a collected dust And separating the spent catalyst mixture into dust and catalyst, and circulating at least a portion of the separated catalyst to the reactor,
The process for treating mercury-containing dust includes a stage for heating the separated dust, a stage for separating the heated dust from the mercury-containing heated gas with a filter, and a stage for cooling the filtered dust to produce treated ash. Cooling the filtered mercury-containing gas directly and / or indirectly and storing the mercury-containing water produced by the cooling to produce metallic mercury,
This is a method for recovering mercury from mercury-containing exhaust gas.
第１発明において、粉体状の触媒の平均粒径は好ましくは５０〜１００μｍの範囲にある。 In the first invention, the average particle size of the powdered catalyst is preferably in the range of 50 to 100 μm.
回収ダストと使用済み触媒の混合物をサイクロン方式の分離機でダストと触媒に分離することが好ましい。 It is preferable to separate the mixture of recovered dust and used catalyst into dust and catalyst by a cyclone separator.
水銀含有ガスをスプレー塔で直接冷却し、および／または、少なくとも一基のコンデンサで間接的に冷却することが好ましく、最終段のコンデンサで水銀含有ガスを好ましくは温度５〜１０℃に冷却する。 The mercury-containing gas is preferably cooled directly in the spray tower and / or indirectly with at least one condenser, and the mercury-containing gas is preferably cooled to a temperature of 5 to 10 ° C. in the final stage condenser.
ドレンタンクに、アルカリ剤の添加によってｐＨ８〜１２に調整した水銀含有ドレンを蓄えることが好ましい。 It is preferable to store the mercury-containing drain adjusted to pH 8-12 by adding an alkaline agent in the drain tank.
本発明の第２のものは、排ガス中の水銀を酸化処理し、処理されたガスからダストを分離する水銀含有排ガスの処理装置と、分離されたダストから水銀を回収する水銀含有ダストの処理装置とからなる水銀回収装置であって、
水銀含有排ガスの処理装置は、排ガスに塩化水素を吹き込む塩化水素吹込み口と、同排ガスを粉体状の触媒と接触させて水銀を酸化する反応器と、反応後のガスを集塵処理する集塵機と、回収ダストと使用済み触媒の混合物をダストと触媒に分離する分離機と、分離された触媒の少なくとも一部を反応器へ循環する触媒循環路とを具備し、
水銀含有ダストの処理装置は、分離されたダストを加熱する加熱器と、加熱されたダストを水銀含有加熱ガスから分離するフィルタと、フィルタ分離されたダストを冷却し処理灰を生じさせる冷却器と、フィルタ分離された水銀含有ガスを冷却する直接および／または間接冷却手段と、冷却によって生じた水銀含有水を蓄え金属水銀を生成させるドレンタンクとを具備する、
水銀含有排ガスからの水銀回収装置である。
According to a second aspect of the present invention, a mercury-containing exhaust gas treatment device that oxidizes mercury in exhaust gas and separates dust from the treated gas, and a mercury-containing dust treatment device that recovers mercury from the separated dust A mercury recovery device comprising:
Mercury-containing exhaust gas treatment equipment includes a hydrogen chloride inlet for injecting hydrogen chloride into the exhaust gas, a reactor that oxidizes mercury by bringing the exhaust gas into contact with a powdered catalyst, and dust collection treatment of the gas after the reaction A dust collector, a separator that separates a mixture of recovered dust and used catalyst into dust and catalyst, and a catalyst circulation path that circulates at least a part of the separated catalyst to the reactor,
An apparatus for treating mercury-containing dust includes a heater that heats the separated dust, a filter that separates the heated dust from the mercury-containing heated gas, and a cooler that cools the filtered dust and generates treated ash. A direct and / or indirect cooling means for cooling the filtered mercury-containing gas, and a drain tank for storing mercury-containing water generated by the cooling and generating metallic mercury.
It is a mercury recovery device from mercury-containing exhaust gas.
第２発明において、好ましい分離機はサイクロン方式のものである。 In the second invention, a preferable separator is of a cyclone type.
好ましい直接冷却手段はスプレー塔であり、好ましい間接冷却手段はスプレー塔の後流に設けられた少なくとも一基のコンデンサであり、最終段のコンデンサは水銀含有ガスを好ましくは温度５〜１０℃に冷却する。 The preferred direct cooling means is a spray tower, the preferred indirect cooling means is at least one condenser provided downstream of the spray tower, and the last stage condenser preferably cools the mercury-containing gas to a temperature of 5 to 10 ° C. To do.
ドレンタンクは、アルカリ剤の添加によってｐＨ８〜１２に調整した水銀含有ドレンを蓄えるものであることが好ましい。 The drain tank is preferably one that stores mercury-containing drain adjusted to pH 8 to 12 by addition of an alkaline agent.
本発明によれば、排ガス中に塩化水素ガスを吹き込み、排ガスを粉体状の触媒に接触させることでガス状の水銀を高効率で酸化し、これをダスト中に取り込むことができる。処理排ガスは水銀を含まず、大気中へ放散することができる。 According to the present invention, gaseous mercury is blown into exhaust gas, and the exhaust gas is brought into contact with a powder catalyst, whereby gaseous mercury can be oxidized with high efficiency and taken into dust. The treated exhaust gas does not contain mercury and can be released into the atmosphere.
また、回収ダストから分離した触媒の少なくとも一部を反応器へ循環して再使用するので、ランニングコストが安くつく。 Further, since at least a part of the catalyst separated from the collected dust is circulated to the reactor and reused, the running cost is low.
次いでダスト中の水銀を加熱および湿式処理によりほぼ全量金属状態で回収することができる。他方、ダストから生じる処理灰はセメント原料等に再利用することができる。 The mercury in the dust can then be recovered almost in the metal state by heating and wet processing. On the other hand, the treated ash generated from dust can be reused as a cement raw material or the like.
つぎに、本発明を実施例に基づいて添付の図面を参照して具体的に説明する。 Next, the present invention will be specifically described based on embodiments with reference to the accompanying drawings.
実施例
本発明による水銀含有排ガスからの水銀の回収方法は、排ガス中の水銀を酸化処理し、処理されたガスからダストを分離する水銀含有排ガスの処理工程と、分離されたダストから水銀を回収する水銀含有ダストの処理工程とからなる。
Example A method for recovering mercury from a mercury-containing exhaust gas according to the present invention includes a mercury-containing exhaust gas treatment process in which mercury in the exhaust gas is oxidized and dust is separated from the treated gas, and mercury is recovered from the separated dust. A process for treating mercury-containing dust.
始めに、排ガス処理工程について、説明をする。 First, the exhaust gas treatment process will be described.
排ガス処理工程において、まず、ダストと水銀を含む排ガスに塩化水素を吹き込む。塩化水素の濃度は、表１に示すように排ガスに対して２０ｐｐｍ以上、望ましくは３０〜４０ｐｐｍとすることが好ましい。この塩化水素の吹き込みで排ガス中の水銀の約６０％程度を酸化することができる。塩化水素が２０ｐｐｍ以下であれば十分な酸化効果は得られず、４０ｐｐｍを超えると一定量以上の酸化は生じず、機器への悪影響が生じ、供給ガスが無駄になる。 In the exhaust gas treatment process, first, hydrogen chloride is blown into the exhaust gas containing dust and mercury. As shown in Table 1, the concentration of hydrogen chloride is 20 ppm or more, preferably 30 to 40 ppm with respect to the exhaust gas. About 60% of mercury in the exhaust gas can be oxidized by blowing hydrogen chloride. If hydrogen chloride is 20 ppm or less, a sufficient oxidation effect cannot be obtained, and if it exceeds 40 ppm, a certain amount or more of oxidation does not occur, adversely affects the equipment, and the supply gas is wasted.
次いで、排ガスを反応器に導いて粉体状の触媒と接触させる。粉体状の触媒は平均粒径５０〜１００μｍのものを使用することが好ましい。平均粒径が５０μｍ以下であれば、酸化率は良好なものの、管路の閉塞や後流での分離工程で問題が起こりやすく、１００μｍ以上であれば水銀酸化効果が得られにくい。触媒の使用温度すなわち反応器における反応温度は、望ましくは３００〜４００℃、より望ましくは３５０℃付近である。反応温度が後述する表１に示すように３００℃以下であれば、触媒の水銀酸化効果が得られず、４００℃を越えると後流での機器類に影響が生じる恐れがある。 Next, the exhaust gas is led to the reactor and brought into contact with the powdered catalyst. It is preferable to use a powdery catalyst having an average particle diameter of 50 to 100 μm. If the average particle size is 50 μm or less, the oxidation rate is good, but problems are likely to occur in the blockage of the pipeline and the separation process in the downstream, and if it is 100 μm or more, the mercury oxidation effect is difficult to obtain. The use temperature of the catalyst, that is, the reaction temperature in the reactor, is preferably 300 to 400 ° C, more preferably around 350 ° C. If the reaction temperature is 300 ° C. or less as shown in Table 1 described later, the mercury oxidation effect of the catalyst cannot be obtained, and if it exceeds 400 ° C., there is a risk of affecting downstream equipment.
好ましい触媒は金属酸化物（ＴｉＯ２、Ａ１２Ｏ３、ＺｒＯ２、ＳｉＯ２、ＭｇＯ）を１種以上含む材料およびムライト（３Ａ１２Ｏ３・２ＳｉＯ２）、コーディエライト（２ＭｇＯ・２Ａｌ２Ｏ３・５ＳｉＯ２）、チタン酸アルミニウム（ＴｉＡｌ２Ｏ５）などの化合物を担体とし、その表面に１種以上の活性金属（Ｐｔ、Ｒｕ、Ｒｈ、Ｐｄ、ｌｒ、Ｖ、Ｗ、Ｍｏ、Ｎｉ、Ｃｏ、Ｆｅ、Ｃｒ、Ｃｕ、Ｍｎ）を担持したものである。
Preferred catalysts are metal oxides (TiO 2, A1 2 O 3 ,
次いで、反応後のガスを集塵機で３００℃以下の温度で集塵処理して、使用済み触媒とダストの混合物を排ガスから回収する。処理ガスは煙突を経て大気中へ放散される。 Next, the gas after the reaction is collected by a dust collector at a temperature of 300 ° C. or lower, and a mixture of the used catalyst and dust is recovered from the exhaust gas. The process gas is emitted into the atmosphere through a chimney.
次いで、回収ダストと使用済み触媒の混合物を分離機でダストと触媒に分離する。好ましい分離機は、ダストと触媒の粒径差を利用したサイクロン方式のものである。 Next, the mixture of recovered dust and spent catalyst is separated into dust and catalyst by a separator. A preferred separator is a cyclone type utilizing a particle size difference between dust and catalyst.
分離機で分離された触媒の少なくともの一部を触媒循環路を経て反応器へ循環する。 At least a part of the catalyst separated by the separator is circulated through the catalyst circulation path to the reactor.
分離機で分離されたダストと触媒の残部を後流のダスト処理装置に送る。一方、取り出した触媒の量で反応器の上流側で新しい触媒を補充する。これにより、水銀酸化処理性能を維持することができる。 The dust separated by the separator and the remainder of the catalyst are sent to a dust treatment device in the downstream. On the other hand, a new catalyst is replenished upstream of the reactor with the amount of catalyst taken out. Thereby, mercury oxidation treatment performance can be maintained.
表１は、ＳｉＯ２担体にＷＯ３、Ｖ２Ｏ５およびＴｉＯ２を担持した触媒について、反応温度と水銀酸化率の関係を示すものである。
つぎに、上記処理ガスから分離されたダストから水銀を回収する水銀含有ダストの処理工程について、説明をする。 Next, a process for treating mercury-containing dust for recovering mercury from dust separated from the processing gas will be described.
水銀含有ダストを前段加熱器に導いて３５０〜４００℃に加熱する。これによりダスト中に含まれる水分、水銀、ＶＯＣ（揮発性有機化合物）、アンモニウム塩などを循環ガス中に放出させる。図２は、実際のダストを用いた水銀の揮散性を調べた結果を示す。これによると、加熱温度が３５０℃以上であれば、ダスト中に存在する水銀のほぼ全量を揮散させることができる。前段加熱器を経たダストはさらに後段加熱器で加熱され、次いで冷却器で冷却されることで以降のハンドリングに支障のないようにされる。こうしてダスト処理により最終的に処理灰が得られ、セメント原料等への再利用が可能である。 The mercury-containing dust is guided to a pre-stage heater and heated to 350 to 400 ° C. As a result, moisture, mercury, VOC (volatile organic compound), ammonium salt and the like contained in the dust are released into the circulating gas. FIG. 2 shows the results of examining the volatility of mercury using actual dust. According to this, when the heating temperature is 350 ° C. or higher, almost all of the mercury present in the dust can be volatilized. The dust that has passed through the pre-stage heater is further heated by the post-stage heater and then cooled by the cooler so that the subsequent handling is not hindered. In this way, the treated ash is finally obtained by the dust treatment and can be reused as a cement raw material or the like.
一方、前段加熱器においてダストから放出された水分、水銀、ＶＯＣ（揮発性有機化合物）、アンモニウム塩などを含むガスは、ダストフィルタを経てスプレー塔さらにコンデンサへ送られる。ダストフィルタには圧縮空気を供給して同空気によってエレメントの逆洗を行う。この空気は循環ファンにより加熱器、ダストフィルタ、スプレー塔、コンデンサを循環し、前述の水銀、ＶＯＣ、アンモニアのキャリアガスとして作用する。 On the other hand, gas containing moisture, mercury, VOC (volatile organic compound), ammonium salt, etc. released from dust in the pre-stage heater is sent to the spray tower and further to the condenser through the dust filter. Compressed air is supplied to the dust filter and the elements are backwashed with the same air. This air circulates in a heater, dust filter, spray tower, and condenser by a circulation fan, and acts as a carrier gas for mercury, VOC, and ammonia.
スプレー塔を通過した循環ガスは水分飽和状態になっているので、後流のコンデンサにおいて温度低下に伴い凝縮水となる。従ってコンデンサで塩類析出による閉塞といった問題を生じることが全くない。 Since the circulating gas that has passed through the spray tower is saturated with water, it becomes condensed water as the temperature decreases in the downstream condenser. Therefore, there is no problem of clogging due to salt precipitation in the capacitor.
高度な水銀回収効率を得るためにはコンデンサは、図１に示すように、２段階で設置するのが望ましい。すなわち、ガスをまず前段コンデンサで冷却水により３０〜４０℃にまで間接冷却し、次いで後段コンデンサでチラー水により５〜１０℃まで間接冷却する。 In order to obtain high mercury recovery efficiency, it is desirable to install the capacitor in two stages as shown in FIG. That is, the gas is first indirectly cooled to 30 to 40 ° C. with cooling water in the first stage condenser, and then indirectly cooled to 5 to 10 ° C. with chiller water in the second stage condenser.
図３は水銀における蒸気圧と温度との関係を示したものである。この図において、１ｏｇＰ（Ｐ：水銀の蒸気圧）が−１より大きければ、揮散がし易いことが文献（例；日立造船技報、３７巻、３号）より知られている。つまり、１ｏｇＰが−１より小さければ、水銀は液体状態で安定である。よって、本発明における冷却温度であれば、高い効率で水銀を回収することができる。 FIG. 3 shows the relationship between the vapor pressure and temperature in mercury. In this figure, it is known from the literature (eg, Hitachi Zosen Technical Report, Vol. 37, No. 3) that if 1 ogP (P: vapor pressure of mercury) is larger than -1, volatilization is easy. That is, if 1 ogP is less than -1, mercury is stable in the liquid state. Therefore, mercury can be recovered with high efficiency at the cooling temperature in the present invention.
コンデンサで凝縮した水分および水銀やＶＯＣはドレンタンクに入る。ドレンタンクでは水銀が金属状態で沈降分離するので、これを回収する。スプレー塔ではドレンタンクの上澄水（以下ドレン水と称する）が循環しており、このドレン水が循環ガスと気・液接触して循環ガス中に含まれる水溶性のＨｇＣｌ２をドレン水中に吸収除去する。ＨｇＣｌ２はドレンタンク内に滞留する間に還元され、やがて金属状態で沈降分離する。ドレン水のｐＨをアルカリ剤の添加によって好ましくは８〜１２、より望ましくは９〜１１に調整すると、ドレン水に取り込んだＨｇＣｌ２の還元およびアンモニウム塩の分解に好都合である。ドレン水のｐＨは高くても不都合はないがアルカリ剤を無駄に消費して不経済である。 Moisture, mercury and VOC condensed by the condenser enter the drain tank. In the drain tank, mercury settles and separates in a metallic state and is collected. In the spray tower, the supernatant water of the drain tank (hereinafter referred to as drain water) circulates, and this drain water comes into gas-liquid contact with the circulating gas and absorbs the water-soluble HgCl 2 contained in the circulating gas into the drain water. Remove. HgCl 2 is reduced while it stays in the drain tank, and eventually settles and separates in a metallic state. Adjusting the pH of the drain water to preferably 8 to 12 and more desirably 9 to 11 by adding an alkaline agent is advantageous for the reduction of HgCl 2 taken into the drain water and the decomposition of the ammonium salt. Although there is no problem even if the pH of the drain water is high, it is uneconomical because the alkali agent is consumed wastefully.
Claims (12)
水銀含有排ガスの処理工程は、排ガスに塩化水素を吹き込む段階と、同排ガスを粉体状の触媒と接触させて水銀を酸化する段階と、反応後のガスを集塵処理する段階と、回収ダストと使用済み触媒の混合物をダストと触媒に分離する段階と、分離触媒の少なくとも一部を反応器へ循環する段階とを含み、
水銀含有ダストの処理工程は、分離されたダストを加熱する段階と、加熱されたダストを水銀含有加熱ガスからフィルタで分離する段階と、フィルタ分離されたダストを冷却し処理灰を生じさせる段階と、フィルタ分離された水銀含有ガスを直接および／または間接的に冷却する段階と、冷却によって生じた水銀含有水をドレンタンクに蓄え金属水銀を生成させる段階とを含む、
水銀含有排ガスからの水銀回収方法。 A mercury recovery method comprising a mercury-containing exhaust gas treatment process for oxidizing mercury in exhaust gas and separating dust from the treated gas, and a mercury-containing dust treatment process for recovering mercury from the separated dust. ,
The treatment process of the mercury-containing exhaust gas includes a stage in which hydrogen chloride is blown into the exhaust gas, a stage in which the exhaust gas is contacted with a powdered catalyst to oxidize mercury, a stage in which the gas after the reaction is collected, and a collected dust And separating the spent catalyst mixture into dust and catalyst, and circulating at least a portion of the separated catalyst to the reactor,
The process for treating mercury-containing dust includes a stage for heating the separated dust, a stage for separating the heated dust from the mercury-containing heated gas with a filter, and a stage for cooling the filtered dust to produce treated ash. Cooling the filtered mercury-containing gas directly and / or indirectly and storing the mercury-containing water generated by the cooling in a drain tank to produce metallic mercury,
Mercury recovery method from mercury-containing exhaust gas.
The mercury recovery method according to any one of claims 1 to 5, wherein mercury-containing drain adjusted to pH 8 to 12 by adding an alkaline agent is stored in the drain tank.
水銀含有排ガスの処理装置は、排ガスに塩化水素を吹き込む塩化水素吹込み口と、同排ガスを粉体状の触媒と接触させて水銀を酸化する反応器と、反応後のガスを集塵処理する集塵機と、回収ダストと使用済み触媒の混合物をダストと触媒に分離する分離機と、分離された触媒の少なくとも一部を反応器へ循環する触媒循環路とを具備し、
水銀含有ダストの処理装置は、分離されたダストを加熱する加熱器と、加熱されたダストを水銀含有加熱ガスから分離するフィルタと、フィルタ分離されたダストを冷却し処理灰を生じさせる冷却器と、フィルタ分離された水銀含有ガスを冷却する直接および／または間接冷却手段と、冷却によって生じた水銀含有水を蓄え金属水銀を生成させるドレンタンクとを具備する、
水銀含有排ガスからの水銀回収装置。 A mercury recovery device comprising a mercury-containing exhaust gas treatment device that oxidizes mercury in exhaust gas and separates dust from the treated gas, and a mercury-containing dust treatment device that recovers mercury from the separated dust. ,
Mercury-containing exhaust gas treatment equipment includes a hydrogen chloride inlet for injecting hydrogen chloride into the exhaust gas, a reactor that oxidizes mercury by bringing the exhaust gas into contact with a powdered catalyst, and dust collection treatment of the gas after the reaction A dust collector, a separator that separates a mixture of recovered dust and used catalyst into dust and catalyst, and a catalyst circulation path that circulates at least a part of the separated catalyst to the reactor,
An apparatus for treating mercury-containing dust includes a heater that heats the separated dust, a filter that separates the heated dust from the mercury-containing heated gas, and a cooler that cools the filtered dust and generates treated ash. A direct and / or indirect cooling means for cooling the filtered mercury-containing gas, and a drain tank for storing mercury-containing water generated by the cooling and generating metallic mercury.
Mercury recovery equipment from mercury-containing exhaust gas.
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