JP4026737B2

JP4026737B2 - Drain neutralization treatment method and neutralization treatment apparatus

Info

Publication number: JP4026737B2
Application number: JP12400699A
Authority: JP
Inventors: 茂小向; 嘉弘新谷; 大介越水
Original assignee: Tokyo Gas Co Ltd; Rinnai Corp
Current assignee: Tokyo Gas Co Ltd; Rinnai Corp
Priority date: 1999-04-30
Filing date: 1999-04-30
Publication date: 2007-12-26
Anticipated expiration: 2019-04-30
Also published as: JP2000312887A

Description

【０００１】
【発明の属する技術分野】
本発明は、酸性ドレンの中和処理に関し、特に潜熱回収用熱交換器を備えた燃焼装置を用いて天然ガス或いは都市ガス等を燃焼する際に発生する排ガスの酸性ドレンの中和に適した処理方法、及び処理装置に関する。
【０００２】
【従来の技術】
潜熱回収用熱交換器を備えた燃焼器は、民生用或は産業用の給湯器等に応用されている。図４にこのような給湯器の一般的な構成を示した。バーナ２で都市ガス等が燃焼され、発生した燃焼熱は第１段熱交換器３において水を所定温度まで加熱するために消費されるが、余剰の燃焼熱は第１段熱交換器３の上方に配設された第２段熱交換器４において、水管中の水を加熱するために使用される。
【０００３】
第２段熱交換器４において、燃焼排ガスが給水管から供給された冷水と熱交換する際に、排ガスの顕熱のみでなく排ガス中の水蒸気が保有している潜熱も回収され、高い熱交換効率が達成される。潜熱回収が行われる結果、排ガス中の水蒸気は凝縮して水滴５を生じ、集合してドレンとなるが、このドレンは排ガス中の硫黄酸化物（ＳＯ_Ｘと略記）や窒素酸化物（ＮＯ_Ｘと略記）等を吸収して、ＰＨが３程度の強酸性液体となっている。
【０００４】
強酸性のドレンをそのまま排出すると、排水管系統等に使用されている金属製品の腐蝕やコンクリート建造物の劣化等の被害、水質汚染等の環境問題を起こす原因となるため、排水基準で規定するＰＨ５−９の範囲に適合するように中和処理する必要がある。
【０００５】
従来、ドレンの中和処理方法として、第２段熱交換器４の下方に受け皿６を配設して水滴５を集め、例えば図４に示すように燃焼器内に、又は燃焼器外にアルカリ性中和剤等を充填した中和器９を設け、ドレン管７を通して中和器９にドレンを導いて中和処理する技術が提案されている（例えば特開平９−１５０１６３号、特開昭６０−９７０９４号等）。
【０００６】
最近、この受け皿に集めたドレンを燃焼器内の空間に配設した１槽の小型中和タンクへ導入し、この中和タンク内にイオン化傾向が水素を挟んで反対順位にある２本の金属電極を対向配置し、ドレンを電気分解することにより中和する画期的な技術が提案された（特開平８−１３６０５８号）。
【０００７】
【発明が解決しようとする課題】
上記電気分解方法では、燃焼器外の中和タンク設置や中和剤補給の必要がないため、煩雑な保守を要せず且つクリーンにドレンを中和できる。しかしながら、燃焼時即ちドレン発生中は第１電極に正の電圧、第２電極に負の電圧を印加し、逆に燃焼停止中即ちドレン非発生時には第１電極に負の電圧、第２電極に正の電圧を印加することとしているため、常に電力を消費することになる。
【０００８】
また、同一槽内に２本の電極が近接して配置されているため、陽極付近で電解されたドレンと陰極付近で電解されたドレンの混合が常に起こり、中和が比較的緩慢にしか進行しない。本発明は、酸性ドレンの直接電気分解におけるこのような問題点の改善を課題とするものである。
【０００９】
【課題を解決するための手段】
本発明によれば、陽極室と陰極室を別個に設け、両室を塩橋、隔膜若しくはイオン交換膜を介して接続し、ドレン発生時にのみ電圧印加することにより、酸性ドレンは発生中に陰極室において電気分解され、速やかに中和されたドレンが陰極室より排出されて上記課題が解決される。
【００１０】
即ち本発明は、電解質溶液または固体電解質を収納した第１電極室に塩橋、隔膜若しくはイオン交換膜を介して第２電極室を接続し、ドレンを第２電極室へ連続的または断続的に導入し、第１電極には正電圧を、第２電極には負電圧を印加してドレンを電気分解処理し、処理されたドレンを第２電極室から連続的または断続的に排出することを特徴とするドレンの中和処理方法の発明である。
【００１１】
また、第２の本発明は、ドレンを中和処理するための装置であって、少なくとも、第１電極と電解質溶液または固体電解質とを収納した第１電極室、この第１電極室と塩橋、隔膜若しくはイオン交換膜を介して接続され且つドレンの導入口及び排出口を有する第２電極室、この第２電極室に収納した第２電極、及びそれぞれ第１電極に正電圧、第２電極に負電圧を印加する電圧印加制御手段からなることを特徴とするドレン中和処理装置の発明である。
【００１２】
本発明において、第２電極室に酸性ドレンを導入して負電圧を印加すると、ドレン中の水素イオンが化学式１の陰極反応により水素ガスとなって除去されるため、ドレンのＰＨ値は酸性側からアルカリ性側へと変化する。中性付近のＰＨ値になった時点で、中和処理が済んだドレンを、例えばサイフォン等の移液手段により第２電極室から排出すると、環境基準に適合した排水処理が達成される。
【００１３】
【化１】
２Ｈ^＋＋２ｅ^-＝Ｈ_２
【００１４】
電解質溶液と第１電極とを収納した第１電極室では、正電圧を印加すると化学式２の陽極反応は左側へ進行して酸素が発生するが、イオン化反応の標準電極電位（Ｅ^Ｏ）が化学式２の反応のＥ^Ｏより大きな電極材料は溶解しない。
【化２】
Ｏ_２＋２Ｈ_２Ｏ＋４ｅ^-＝４ＯＨ^-
Ｅ^Ｏ＝０．４０１Ｖ
【００１５】
【発明の実施の形態】
本発明のドレン中和処理方法の一実施態様を示した図３を参照しながら、本発明の中和処理方法を説明する。第１電極室１１には導電率の高いＫ^＋イオンを高濃度で含有する飽和ＫＣｌ水溶液１５を入れ、アルミニウム棒１３を第１電極としてこの水溶液に浸し、固定する。第１電極１３に用いられる材料は、高い印加電圧を要しない材料であれば特に制約はない。電解質も、一般に用いられる導電率の高いＮａ^＋、Ｋ^＋等を含有する無機塩類であれば特に制約はない。
【００１６】
第２電極室１２にはドレンを導入する。図３では、ドレン管２１ｂを使用してドレンを導入する。また処理済みのドレンを第２電極室１２から随時排出するため、図３ではドレン管２１ａを使用する。ドレンが電気分解を受ける時間、即ちドレンが第２電極室１２に滞留する時間の調節を可能にするように、ドレン管２１ａに液深調節式のサイフォン管２０を接続している。第２電極室１２に白金棒１４を第２電極１４としてドレンに浸して固定する。更に、電気分解の進行に伴うドレンのＰＨ値変化を測定する便宜のためＰＨ計３３を、また排出する処理済みドレンのＰＨ値を均一化するため攪拌子３４を設けても良い。
【００１７】
両電極室１１及び１２をＵ字型塩橋１７或はＨ字型塩橋で接続する。塩橋電解質として、液間電位を小さくするＫＮＯ_３、ＫＣｌ等の濃厚水溶液をゼラチンで固化したものを充填する。なお、ゼラチン固化に代えて、塩橋１７の両端を多孔質の隔壁で閉鎖して水溶液の流出を止めても良い。または図１のドレン中和処理装置１０に示したように、塩橋１７に代えて、一般にこの分野で用いられる隔膜またはイオン交換膜を介して両電極室１１及び１２を接続しても良い。
【００１８】
ドレンを第２電極室１２に満たし、直流電圧０．５−３Ｖ程度の正電圧を第１電極１３に、また同じボルト数の負電圧を第２電極１４に印加する手段２９、例えばガルバノスタット、電池等を各電極に接続する。電圧を印加し、攪拌子３４を使用してドレンを攪拌しつつ時間の経過と共に第２電極室１２のＰＨ変化をＰＨ計３３により測定し、ＰＨ値が７になるまでの時間を計測する。次いで、ドレンのＰＨが中性付近になった時点でサイフォンが作用して中和済みのドレンが第２電極室１２から排出されるように、ドレン発生速度に対応してドレン滞留時間即ちドレン液面から第２電極室の底までの液深を、サイフォン管２０の長さを調節することにより調整する。一旦このように液深を調節して直流電圧を印加すると、ドレンが連続的に第２電極室１２に流入しても、所要の時間に亘り電気分解が行われ、ＰＨが７付近まで中和されたドレンがサイフォン作用により自動的に排出される。ドレン発生が停止した時点、或は暫くタイムラグを置いた後で、電圧印加を止める。
【００１９】
次に本発明の中和処理装置の実施形態について、本発明の一構成例を示した図２に沿って説明する。第１電極室１１には前記電解質溶液１５または固体電解質と第１電極１３とが収納され、絶縁封止材料２３ｂを用いて電解質１５を封止すると共に第１電極１３が固定されている。第１電極室１１の材料は、前記電解質１５に腐蝕されない材質であれば良い。
【００２０】
第２電極室１２には第２電極１４が収納され、絶縁封止材料２１ａで固定されると共に、下部にドレン導入口１９、比較的上部にドレン排出口１８が設けられている。前記の通り第２電極室１２内のドレン液深を最適に設定するため、ドレン液面からの深さの異なる複数ドレン排出口１８が設けられ、ドレンの流出位置を幾つか備えたサイフォン管２０が各ドレン排出口１８に接続されている。第２電極室１２に用いる材料は、ドレン１６に腐蝕されない材質であれば良い。ドレン導入口１９はドレン管１１ｂを介してドレン発生源（図示せず）に接続されている。ドレン排出口１８にはドレン管１１ａが接続されており、排水ピットへ中和処理済みドレンを導く。または、業務用大型給湯器のようにドレンの発生速度がかなり大きい場合には、上記サイフォンに代えて、ドレン排出口１８に流量制御用開閉弁を設けると共に第２電極室１２に液位計（図示せず）を設け、この液位計からの信号により開閉弁を自動的に開閉させ、中和処理済みドレンを断続的に第２電極室１２外へ排出しても良い。或は、家庭用小型給湯器のように燃焼器が比較的小型でドレンの発生速度が極く小さい場合には、開閉弁もサイフォンも設けず、中和処理済みドレンが自然に溢れ出るようにしても良い。
【００２１】
第１電極室１１と第２電極室１２をＨ字型塩橋１７を介して接続する。塩橋が液に浸る部位の末端には多孔性隔壁を設け、塩橋内にはＫＮＯ_３等の濃厚水溶液が充填されている。または塩橋に代えて、通常用いられるアスベスト膜等の隔膜或いはイオン交換膜（図示せず）等を用いて１槽を２室に分割して第１及び第２電極室として用いても良い。第１及び第２電極の材料は、通常用いられる黒鉛、鉛、アルミニウム等で良い。
【００２２】
両電極１３及び１４を導線等を用いて電圧印加手段２９に電気的に接続する。電圧印加手段２９は、ドレンの酸性度に対応した電流量を印加する可変電圧発生部２８、及び燃焼検出子（図示せず）からの信号２６を受けて燃焼の開始、停止に応じて上記可変電圧発生部をオン・オフする印加指令部２７から構成されている。燃焼停止後も第２電極室１２に滞留するドレンを充分に中和するため、印加指令部２７にはオン・オフにタイム・ラグを与える機能を付加しても良い。
【００２３】
［実施例１］
本発明の処理方法による中和性能を例示するため、図３に示された中和処理装置を用いて行った実施例を説明する。第１電極１３としてアルミニウム棒、電解質溶液１５として飽和ＫＣｌ水溶液、第２電極１４として白金棒、また酸性ドレン１６の模擬液として１ＮのＨＮＯ_３に数滴のＫＮＯ_３水溶液を添加したもの３００ｍｌを使用した。Ｕ字型塩橋１７にはＫＮＯ_３の６Ｎ溶液をゼラチンで固化したものを充填した。ガルバノスタット１９を用いて第１電極１３に正電圧、第２電極１４に負電圧を３Ｖ印加し、電流１０ｍＡを流した。通電開始と共に第２電極１４表面から発生する水素の気泡が観察された。マグネット撹拌子３４を用いて電解液１６を撹拌しながら電気分解を進めた。通電開始からの時間経過と共に上昇（アルカリ側に移行）するＰＨ値をＰＨ計３３により測定した結果を表１に示した。ＰＨが約４の酸性であったドレン模擬液１６が、通電から７分で中性となり、８分経過でアルカリ性となったので、７分前後の電気分解により排水基準ＰＨ＝５−９を満たし得ることが判る。
【００２４】
［比較例１］
上記実施例と同一の模擬液を使用し、容量３００ｍｌのビーカー１個に上記実施例と同一の両電極を２ｃｍ間隔で対向配置した以外は全く同様にして電気分解を行った。ＰＨ計による測定結果を表１に併せて示した。このように両電極が同一槽内に配置された従来の方法では、通電開始時に約４であったドレン模擬液のＰＨは、１０分間の通電後もなお約５．３に止まり、中和の進行が比較的遅いことが判る。
【００２５】
【表１】

【００２６】
【発明の効果】
本発明を用いれば、中和剤の補給なしに長期間、ドレンの中和を継続することができる。またドレンの発生量や発生源に応じて、電極室や電極の寸法を家庭用或は産業用に対応して拡大又は縮小できるので、広範囲な処理能力に応じて装置を製作することができる。しかも、電気分解の所要時間がかなり短いのでドレンを長時間滞留させる必要がなく、特に中和装置の小型化を容易に達成できる。
【００２７】
【図面の簡単な説明】
【図１】本発明の一構成例（隔膜型電解槽式中和処理装置）を組込んだ給湯器の概要を示す断面図である。
【図２】本発明の中和処理装置の一構成例を示す断面図である。
【図３】本発明の中和処理方法の一態様を示す説明図である。
【図４】従来の潜熱回収用熱交換器を備えた給湯器を説明する断面図である。
【符号の説明】
１燃焼器（給湯器）
２バーナ
３第１段熱交換器
４第２段熱交換器
５水滴
６受け皿
７ドレン管
８ファン
９中和器
１０ドレン中和処理装置
１１第１電極室
１２第２電極室
１３第１電極
１４第２電極
１５電解質溶液
１６ドレン
１７塩橋
１８ドレン排出口
１９ドレン導入口
２０サイフォン管
２１ａ、２１ｂドレン管
２２ａ、２２ｂ、２２ｃ液深調節用仕切弁
２３ａ、２３ｂ絶縁封止材料
２４水素放出口
２５通気口
２６燃焼検知子からの信号
２７印加指令部
２８可変電圧発生部
２９電圧印加手段
３３ＰＨ計
３４攪拌子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to neutralization treatment of acidic drain, and particularly suitable for neutralization of acidic drain of exhaust gas generated when natural gas or city gas is burned using a combustion apparatus equipped with a heat exchanger for recovering latent heat. The present invention relates to a processing method and a processing apparatus.
[0002]
[Prior art]
A combustor including a heat exchanger for recovering latent heat is applied to a hot water heater for consumer use or industrial use. FIG. 4 shows a general configuration of such a water heater. The city gas or the like is burned in the burner 2 and the generated combustion heat is consumed in the first stage heat exchanger 3 to heat the water to a predetermined temperature, but surplus combustion heat is consumed in the first stage heat exchanger 3. In the 2nd stage heat exchanger 4 arrange | positioned upwards, it is used in order to heat the water in a water pipe.
[0003]
In the second stage heat exchanger 4, when the combustion exhaust gas exchanges heat with the cold water supplied from the water supply pipe, not only the sensible heat of the exhaust gas but also the latent heat possessed by the water vapor in the exhaust gas is recovered, and high heat exchange is achieved. Efficiency is achieved. As a result of the latent heat recovery, the water vapor in the exhaust gas condenses to form water droplets 5 and collects to become drain, which is a sulfur oxide (abbreviated as SO _X ) or nitrogen oxide (NO _{X in the} exhaust gas). And a strong acid liquid with a pH of about 3.
[0004]
If draining strong acid drains as they are, it may cause environmental problems such as corrosion of metal products used in drainage pipes, deterioration of concrete structures, water pollution, etc. It is necessary to neutralize so as to meet the range of PH5-9.
[0005]
Conventionally, as a drain neutralization treatment method, a tray 6 is disposed below the second stage heat exchanger 4 to collect water droplets 5, and, for example, alkaline inside the combustor or outside the combustor as shown in FIG. There has been proposed a technique in which a neutralizer 9 filled with a neutralizing agent or the like is provided, and drainage is guided to the neutralizer 9 through a drain pipe 7 (for example, Japanese Patent Laid-Open No. 9-150163, Japanese Patent Laid-Open No. 60). -97094 etc.).
[0006]
Recently, the drain collected in this tray has been introduced into one small neutralization tank located in the space inside the combustor, and two metals with ionization tendencies in opposite order across hydrogen in this neutralization tank. An epoch-making technique has been proposed in which electrodes are arranged oppositely and neutralized by electrolyzing the drain (Japanese Patent Laid-Open No. 8-1336058).
[0007]
[Problems to be solved by the invention]
In the above electrolysis method, it is not necessary to install a neutralization tank outside the combustor or to supply a neutralizing agent, so that complicated maintenance is not required and the drain can be neutralized cleanly. However, a positive voltage is applied to the first electrode and a negative voltage is applied to the second electrode during combustion, i.e., during drain generation. Conversely, when combustion is stopped, i.e., when no drain is generated, a negative voltage is applied to the first electrode, Since a positive voltage is applied, power is always consumed.
[0008]
In addition, since the two electrodes are arranged close to each other in the same tank, mixing of the drained electrolysis near the anode and the drained electrolysis near the cathode always occurs, and the neutralization proceeds only relatively slowly. do not do. An object of the present invention is to improve such problems in the direct electrolysis of acidic drain.
[0009]
[Means for Solving the Problems]
According to the present invention, an anode chamber and a cathode chamber are provided separately, both chambers are connected via a salt bridge, a diaphragm, or an ion exchange membrane, and a voltage is applied only at the time of drain generation. The drain which has been electrolyzed in the chamber and quickly neutralized is discharged from the cathode chamber to solve the above-mentioned problem.
[0010]
That is, according to the present invention, the second electrode chamber is connected to the first electrode chamber containing the electrolyte solution or the solid electrolyte via the salt bridge, the diaphragm or the ion exchange membrane, and the drain is continuously or intermittently connected to the second electrode chamber. Introducing and applying a positive voltage to the first electrode and a negative voltage to the second electrode to electrolyze the drain, and discharging the treated drain continuously or intermittently from the second electrode chamber It is an invention of a drainage neutralization treatment method characterized.
[0011]
The second aspect of the present invention is an apparatus for neutralizing a drain, and includes at least a first electrode chamber containing a first electrode and an electrolyte solution or a solid electrolyte, and the first electrode chamber and a salt bridge. A second electrode chamber connected via a diaphragm or an ion exchange membrane and having a drain introduction port and a discharge port; a second electrode housed in the second electrode chamber; and a positive voltage and a second electrode respectively for the first electrode It is an invention of a drain neutralizing apparatus characterized by comprising a voltage application control means for applying a negative voltage to the drain.
[0012]
In the present invention, when acidic drain is introduced into the second electrode chamber and a negative voltage is applied, hydrogen ions in the drain are removed as hydrogen gas by the cathodic reaction of Chemical Formula 1, so that the pH value of the drain is on the acidic side. Changes from alkaline to alkaline. When the neutralized PH value is discharged from the second electrode chamber by a liquid transfer means such as a siphon when the PH value near neutrality is reached, wastewater treatment that meets environmental standards is achieved.
[0013]
[Chemical 1]
2H ⁺ + 2e ⁻ = H ₂
[0014]
In the first electrode chamber containing the electrolyte solution and the first electrode, when a positive voltage is applied, the anodic reaction of Chemical Formula 2 proceeds to the left to generate oxygen, but the standard electrode potential (E ^O ) of the ionization reaction is expressed by the chemical formula. An electrode material larger than ^EO of reaction 2 does not dissolve.
[Chemical 2]
O ₂ + 2H ₂ O + 4e ⁻ = 4OH ⁻
E ^O = 0.401V
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The neutralization treatment method of the present invention will be described with reference to FIG. 3 showing one embodiment of the drain neutralization treatment method of the present invention. A saturated KCl aqueous solution 15 containing high-conductivity K ⁺ ions at a high concentration is placed in the first electrode chamber 11, and an aluminum rod 13 is immersed in this aqueous solution as a first electrode and fixed. The material used for the first electrode 13 is not particularly limited as long as it does not require a high applied voltage. The electrolyte is not particularly limited as long as it is an inorganic salt containing Na ⁺ , K ⁺ or the like that is generally used and has high conductivity.
[0016]
Drain is introduced into the second electrode chamber 12. In FIG. 3, the drain is introduced using the drain pipe 21b. Further, in order to discharge the treated drain from the second electrode chamber 12 at any time, a drain pipe 21a is used in FIG. A liquid depth-adjustable siphon tube 20 is connected to the drain tube 21a so that the time during which the drain is electrolyzed, that is, the time during which the drain stays in the second electrode chamber 12 can be adjusted. A platinum rod 14 is immersed in a drain as the second electrode 14 and fixed in the second electrode chamber 12. Further, a PH meter 33 may be provided for the convenience of measuring the change in the PH value of the drain as the electrolysis progresses, and a stirrer 34 may be provided for making the PH value of the treated drain to be discharged uniform.
[0017]
Both electrode chambers 11 and 12 are connected by a U-shaped salt bridge 17 or an H-shaped salt bridge. As the salt bridge electrolyte, a solution obtained by solidifying a concentrated aqueous solution of KNO ₃ , KCl or the like with gelatin to reduce the liquid junction potential is filled. Instead of gelatin solidification, both ends of the salt bridge 17 may be closed with porous partition walls to stop the aqueous solution from flowing out. Alternatively, as shown in the drain neutralization processing apparatus 10 of FIG. 1, instead of the salt bridge 17, both electrode chambers 11 and 12 may be connected via a diaphragm or ion exchange membrane generally used in this field.
[0018]
Means 29 for applying a drain to the second electrode chamber 12 and applying a positive voltage of about 0.5-3V DC voltage to the first electrode 13 and a negative voltage of the same volt number to the second electrode 14, for example, galvanostat; A battery or the like is connected to each electrode. While applying voltage and stirring the drain using the stirrer 34, the PH change of the second electrode chamber 12 is measured with the passage of time by the PH meter 33, and the time until the PH value becomes 7 is measured. Next, when the pH of the drain becomes near neutral, the siphon acts to discharge the neutralized drain from the second electrode chamber 12, so that the drain residence time, that is, the drain liquid, corresponds to the drain generation rate. The liquid depth from the surface to the bottom of the second electrode chamber is adjusted by adjusting the length of the siphon tube 20. Once the liquid depth is adjusted in this way and a DC voltage is applied, even if drain continuously flows into the second electrode chamber 12, electrolysis is performed over a required time, and PH is neutralized to around 7. The drained water is automatically discharged by siphon action. The voltage application is stopped when drain generation stops or after a time lag.
[0019]
Next, an embodiment of the neutralization processing apparatus of the present invention will be described with reference to FIG. 2 showing one configuration example of the present invention. In the first electrode chamber 11, the electrolyte solution 15 or solid electrolyte and the first electrode 13 are accommodated, and the electrolyte 15 is sealed with an insulating sealing material 23b and the first electrode 13 is fixed. The material of the first electrode chamber 11 may be any material that is not corroded by the electrolyte 15.
[0020]
In the second electrode chamber 12, the second electrode 14 is accommodated and fixed with an insulating sealing material 21a, and a drain introduction port 19 is provided at the lower portion and a drain discharge port 18 is provided at a relatively upper portion. As described above, in order to optimally set the drain liquid depth in the second electrode chamber 12, a plurality of drain discharge ports 18 having different depths from the drain liquid surface are provided, and a siphon tube 20 having several drain outlet positions. Are connected to each drain outlet 18. The material used for the second electrode chamber 12 may be any material that is not corroded by the drain 16. The drain introduction port 19 is connected to a drain generation source (not shown) through a drain pipe 11b. A drain pipe 11a is connected to the drain discharge port 18 to guide the neutralized drain to the drain pit. Alternatively, when the drain generation speed is considerably high as in a large commercial water heater, a flow control opening / closing valve is provided at the drain outlet 18 instead of the siphon and a liquid level gauge ( (Not shown) may be provided, and the open / close valve may be automatically opened and closed by a signal from the liquid level gauge, and the neutralized drain may be intermittently discharged out of the second electrode chamber 12. Or, if the combustor is relatively small and the drain generation rate is extremely low, such as a small water heater for home use, neither the on-off valve nor siphon is provided, so that the neutralized drain overflows naturally. May be.
[0021]
The first electrode chamber 11 and the second electrode chamber 12 are connected via an H-shaped salt bridge 17. A porous partition wall is provided at the end of the portion where the salt bridge is immersed in the liquid, and the salt bridge is filled with a concentrated aqueous solution such as KNO ₃ . Alternatively, instead of the salt bridge, one tank may be divided into two chambers and used as the first and second electrode chambers using a generally used diaphragm such as an asbestos membrane or an ion exchange membrane (not shown). The material of the first and second electrodes may be commonly used graphite, lead, aluminum or the like.
[0022]
Both

electrodes

13 and 14 are electrically connected to the voltage applying means 29 using conducting wires or the like. The voltage application means 29 receives the signal 26 from the variable voltage generator 28 and the combustion detector (not shown) for applying a current amount corresponding to the acidity of the drain, and the above variable according to the start and stop of combustion. It is comprised from the application command part 27 which turns on and off a voltage generation part. In order to sufficiently neutralize the drain accumulated in the second electrode chamber 12 even after the combustion is stopped, the application command unit 27 may be provided with a function of giving a time lag to ON / OFF.
[0023]
[Example 1]
In order to illustrate the neutralization performance by the treatment method of the present invention, an example carried out using the neutralization apparatus shown in FIG. 3 will be described. Use aluminum rod as first electrode 13, saturated KCl aqueous solution as electrolyte solution 15, platinum rod as second electrode 14, and 300 ml of 1N HNO ₃ with a few drops of KNO ₃ aqueous solution added as simulated drain of acid drain 16 did. The U-shaped salt bridge 17 was filled with a 6N solution of KNO ₃ solidified with gelatin. A galvanostat 19 was used to apply a positive voltage of 3 V to the first electrode 13 and a negative voltage of 2 V to the second electrode 14 to pass a current of 10 mA. Hydrogen bubbles generated from the surface of the second electrode 14 with the start of energization were observed. Electrolysis was advanced while stirring the electrolyte solution 16 using the magnet stirrer 34. Table 1 shows the results of measuring the PH value, which increases (shifts to the alkali side) with the passage of time from the start of energization, using the PH meter 33. The drain simulation liquid 16, which had an acidic pH of about 4, became neutral after 7 minutes of energization, and became alkaline after 8 minutes. Therefore, electrolysis at around 7 minutes satisfied the drainage standard PH = 5-9. I know you get.
[0024]
[Comparative Example 1]
The same simulation solution as in the above example was used, and electrolysis was performed in exactly the same manner except that both electrodes identical to those in the above example were placed facing each other at a distance of 2 cm in one beaker having a capacity of 300 ml. Table 1 also shows the measurement results with the PH meter. Thus, in the conventional method in which both electrodes are arranged in the same tank, the pH of the drain simulation liquid, which was about 4 at the start of energization, still remains at about 5.3 after 10 minutes of energization, It can be seen that the progress is relatively slow.
[0025]
[Table 1]

[0026]
【The invention's effect】
If this invention is used, neutralization of drain can be continued for a long time without replenishment of a neutralizing agent. In addition, since the dimensions of the electrode chamber and the electrode can be enlarged or reduced in accordance with the amount or source of the drain, the apparatus can be manufactured according to a wide range of processing capabilities. In addition, since the time required for electrolysis is considerably short, it is not necessary to retain the drain for a long time, and in particular, the neutralization device can be easily downsized.
[0027]
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an outline of a water heater incorporating a configuration example (diaphragm electrolytic cell type neutralization treatment apparatus) of the present invention.
FIG. 2 is a cross-sectional view showing a configuration example of a neutralization processing apparatus of the present invention.
FIG. 3 is an explanatory view showing an embodiment of the neutralization treatment method of the present invention.
FIG. 4 is a cross-sectional view illustrating a conventional water heater provided with a latent heat recovery heat exchanger.
[Explanation of symbols]
1 Combustor (water heater)
2 Burner 3 First stage heat exchanger 4 Second stage heat exchanger 5 Water drop 6 Dish 7 Drain pipe 8 Fan 9 Neutralizer 10 Drain neutralization processing device 11 First electrode chamber 12 Second electrode chamber 13 First electrode 14 Second electrode 15 Electrolyte solution 16 Drain 17 Salt bridge 18 Drain outlet 19 Drain inlet 20 Siphon pipes 21a,

21b Drain pipes

22a, 22b, 22c Liquid depth adjusting gate valves 23a, 23b Insulating sealing material 24 Hydrogen outlet 25 Vent 26 Signal 27 from combustion detector Application command unit 28 Variable voltage generation unit 29 Voltage application means 33 PH meter 34 Stirrer

Claims

The second electrode chamber is connected to the first electrode chamber containing the electrolyte solution or the solid electrolyte via a salt bridge, a diaphragm or an ion exchange membrane, and the drain is continuously or intermittently introduced into the second electrode chamber. The drain is electrolyzed by applying a positive voltage to the electrode and a negative voltage to the second electrode, and the treated drain is discharged continuously or intermittently from the second electrode chamber. Neutralization method.

The drain is drainage that is condensed from flue gas generated by burning combustible gas, liquefied petroleum gas, or city gas obtained by separation from natural gas, methane hydrate, and a combustion device equipped with a heat exchanger for recovering latent heat. The neutralization method according to claim 1.

An apparatus for neutralizing drain, which is connected to at least a first electrode chamber containing an electrolyte solution or a solid electrolyte, and the first electrode chamber via a salt bridge, a diaphragm or an ion exchange membrane. And a second electrode chamber having a drain introduction port and a discharge port, a second electrode housed in the second electrode chamber, and a voltage application control means for applying a positive voltage to the first electrode and a negative voltage to the second electrode, respectively. A drain neutralization apparatus characterized by comprising:

The neutralization processing apparatus according to claim 3, wherein the drain is drain generated in a combustion apparatus including a heat exchanger for recovering latent heat.

4. A water heater provided with a latent heat recovery heat exchanger, comprising the drain neutralization apparatus according to claim 3, wherein the drain generated in the latent heat recovery heat exchanger is neutralized.