JP2014010145A - Device for detecting in-liquid ammonia and for controlling reaction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for continuously detecting ammonia in a sample water, and for controlling a reaction related to ammonia without using any barrier membrane or transparent gas tube or the like which is easily influenced by the dirt of the sample water.SOLUTION: A sample solution containing ammonia ion and alkaline solution are quantitatively and continuously sent to a vaporizer, and liquid phase part pH is set to pH 10.5-13, and a temperature is maintained to 50°C to 60°C, and vapor gas is sucked from a vapor phase above the vaporizer by an air pump, and recycled and aerated and stirred to the sample solution of the vaporizer, and the ammonia of the liquid phase part is vaporized, and subjected to vapor-liquid equilibrium, and the partial ammonia gas of the vapor phase is sucked, and ammonia is detected by an ammonia gas sensor, and a reaction related to ammonia is controlled. Furthermore, two detectors are installed, and mutually switched over and operated to prevent the sensitivity deterioration of the detectors.

Description

本発明は、液中アンモニアを検知し、反応を制御する装置に関する分野  The present invention relates to an apparatus for detecting ammonia in a liquid and controlling the reaction.

アンモニアは広く使われ、また他の物質から変化して生成されることもある、ごくありふれた物質の一つである。液中のアンモニア濃度を測定し、その値に基づいて反応を制御する装置は金属製錬、発電所、化学、肥料や排水処理工程など幅広い産業で求められている。従来、液中アンモニアを検知する方法としては、試料水にアルカリを添加混合してアンモニアイオン（ＮＨ_４ ^＋）をアンモニアガス（ＮＨ_３）にしたのち、
１）液中にアンモニアイオン電極を漬け、発生したアンモニアガスを隔膜電極によって 内部液の塩化アンモニウム溶液に吸収させ、内部液のｐＨ変化を検出し、アンモニ ア濃度を計測する。
２）試料液を、ガス透過チューブ（２重管）に通し、発生したアンモニアは２重管外側 のキャリアーの硫酸に吸収させ、アンモニアガスを分離抽出し、硫酸液の中和で生 じるキャリアーの導電率変化を計測する。
１）、２）が行われている。これらの方法は液中で隔膜やアンモニアガス透過チューブを使うため、膜の汚れによる測定精度が悪くなることや、２）の場合はシステムが複雑でタイムラグが大きいことなどから、濃度が変動する液中アンモニアイオンを安定して測定し、反応制御できる適切な装置はなかった。一方、別の手法として、試料水にアルカリを添加して発生するアンモニアガス濃度で試料中のアンモニア濃度を測定する方法が提案されている。この方法は基本的にはバッチ式で行われ、恒温槽内の測定セルに試料を導き、攪拌して、ガス化するアンモニアをアンモニアガス電極で測定して、測定値とあらかじめ用意していた検量線から試料水中のアンモニア濃度を算出する方法である。この方法は測定セル内でのアンモニア気化平衡に達するまでに時間がかかること、連続的な測定は出来ないことなどの問題点があり、液中アンモニアイオン濃度を連続的に計測し、液中アンモニアに係わる反応を制御する装置の開発が望まれている。Ammonia is one of the most common substances that are widely used and can be produced by transformation from other substances. Devices that measure the ammonia concentration in the liquid and control the reaction based on that value are required in a wide range of industries such as metal smelting, power plants, chemistry, fertilizers and wastewater treatment processes. Conventionally, as a method for detecting ammonia in a liquid, after adding alkali to sample water and mixing ammonia ion (NH ₄ ⁺ ) to ammonia gas (NH ₃ ),
1) Ammonia ion electrode is immersed in the solution, and the generated ammonia gas is absorbed by the ammonium chloride solution of the internal solution by the diaphragm electrode, and the pH change of the internal solution is detected and the ammonia concentration is measured.
2) The sample solution is passed through a gas permeation tube (double tube), and the generated ammonia is absorbed by sulfuric acid in the carrier outside the double tube, the ammonia gas is separated and extracted, and the carrier produced by neutralization of the sulfuric acid solution. Measure the change in conductivity.
1) and 2) are performed. Since these methods use a diaphragm or ammonia gas permeation tube in the liquid, the measurement accuracy due to the dirt on the film deteriorates. In the case of 2), the system is complex and the time lag is large. There was no suitable device that could stably measure ammonia ions and control the reaction. On the other hand, another method has been proposed in which the ammonia concentration in a sample is measured by the ammonia gas concentration generated by adding alkali to the sample water. This method is basically performed in a batch system, and a sample is introduced into a measurement cell in a thermostatic chamber, stirred, and ammonia to be gasified is measured with an ammonia gas electrode. This is a method for calculating the ammonia concentration in the sample water from the line. This method has problems such as it takes time to reach the ammonia vaporization equilibrium in the measurement cell, and continuous measurement is not possible, and the ammonia ion concentration in the liquid is continuously measured. Development of an apparatus for controlling the reaction related to the above is desired.

特開平６−１８４７４JP-A-6-18474 特開平７−３９３９５JP 7-39395 A 特開平１０−９６６９９JP-A-10-96699 特開２００３−１４７２２JP2003-14722 特開２００９−１９３４７JP2009-19347

従来の液中のアンモニア測定において、液中に隔膜などを浸漬して、アンモニアイオンとアルカリの反応を行うため、隔膜や透過チューブの汚れに起因する誤差が生じており、また、長時間の連続測定制御が困難であった。また、バッチ式で液中のアンモニアを気化させて、アンモニアガスを隔膜式電極で測定する方法はあるが、連続的にアンモニアガスを検知し、アンモニア反応を制御できる装置はなかった。  In the conventional measurement of ammonia in a liquid, a diaphragm or the like is immersed in the liquid and the reaction between ammonia ions and alkali causes an error due to contamination of the diaphragm or the permeation tube. Measurement control was difficult. Further, there is a batch type method in which ammonia in the liquid is vaporized and the ammonia gas is measured with a diaphragm electrode, but there is no apparatus that can detect ammonia gas continuously and control the ammonia reaction.

隔膜や透過チューブを使わず、連続的にアンモニアイオンを計測する方法を検討したところ、一定条件下で液中アンモニア濃度とそれに接する気相中のアンモニアガス濃度に相関があることが推定できた。そこで、試料水および一定濃度のアルカリを連続的に気化器に定量供給し、一定温度に維持し、気化器内を循環曝気攪拌したところ、供給液中のアンモニアイオン（ＮＨ_４ ^＋）がアンモニアガス（ＮＨ_３）になり、容易に気化平衡を保つことが判明した。それを、近年技術進歩が著しいガスセンサー技術（定電位電解式のアンモニアガスセンサー）を用いて連続的に測定すると、その濃度と試料水の液中アンモニア濃度との間に極めて高い相関関係があることが判明した。このことを利用し、水中アンモニア検知・反応制御装置を発明した。この装置によるとセンサーを液中に浸漬させる必要がないため、液中の汚れ成分は殆ど付着しない。システムは簡便で、タイムラグも少なく連続的にアンモニアイオンを検知し、安定な反応制御が行われる。When a method for measuring ammonia ions continuously without using a diaphragm or a permeation tube was examined, it was estimated that there was a correlation between the ammonia concentration in the liquid and the ammonia gas concentration in the gas phase adjacent to it under certain conditions. Therefore, when sample water and a certain concentration of alkali were continuously supplied to the vaporizer in a constant amount, maintained at a constant temperature, and aerated and agitated in the vaporizer, ammonia ions (NH ₄ ⁺ ) in the supply liquid were converted to ammonia gas. It became (NH ₃ ), and it was found that the vaporization equilibrium was easily maintained. When it is continuously measured using gas sensor technology (controlled potential electrolysis ammonia gas sensor), which has made remarkable technological progress in recent years, there is a very high correlation between the concentration and the ammonia concentration in the sample water. It has been found. Utilizing this fact, an in-water ammonia detection / reaction control device was invented. According to this apparatus, since it is not necessary to immerse the sensor in the liquid, the dirt component in the liquid hardly adheres. The system is simple, with little time lag, continuously detecting ammonia ions, and stable reaction control is performed.

図１に示す今回開発したアンモニア濃度の検知・制御装置はバッチ式ではなく連続的にアンモニア濃度を測定するもので、連続的に気化器２３に、サンプル槽から試料を定量供給して、同時に一定濃度の水酸化ナトリウムを苛性タンク３４より気化器に添加して、試料をアルカリ性（ｐＨ１０．５−１３、願わくば１２）にして、気化器の温度センサーの指示でＰＩＤ制御されたヒーターで加熱し、正確に一定温度（５０℃−６０℃、願わくば５５℃）に維持する。気化器の上部気相より配管４を通しエアーポンプで気相ガスを吸引し、配管５を通して気化器液中下部に排出する。気相ガスを循環曝気することにより、短時間で気液平衡状態にでき、アンモニアイオンをアンモニアガス化する。気相中のアンモニアはオートドレーン２５を通して２６または２７の定電位電解式のアンモニアガスセンサーで検知され、その濃度に比例した４−２０ｍＡ制御信号を出し、アンモニアと係わる反応を制御する。測定中のガスセンサーの感度を維持するため、２６，２７のセンサーは交互に使われるが、切り替え時には一定時間両方のセンサーにガスが送られる。交代する間隔および切り替え時に２重になる時間は任意に変えられる。切り替えは４個の電動弁で行われるが、試料ガスを吸わない時は外部新鮮空気を吸って検知部分をクリーニングする。  The ammonia concentration detection and control device developed this time shown in Fig. 1 is not a batch type, but measures the ammonia concentration continuously. The sample is continuously supplied to the vaporizer 23 from the sample tank and fixed at the same time. Concentration sodium hydroxide is added to the vaporizer from the caustic tank 34 to make the sample alkaline (pH 10.5-13, preferably 12) and heated with a heater controlled by PID according to the instructions of the vaporizer temperature sensor. Maintain at an exact constant temperature (50 ° C-60 ° C, preferably 55 ° C). The gas phase gas is sucked by the air pump from the upper vapor phase of the vaporizer through the pipe 4 and discharged to the lower part of the vaporizer liquid through the pipe 5. By circulating aeration of the gas phase gas, a gas-liquid equilibrium state can be achieved in a short time, and ammonia ions are converted into ammonia gas. Ammonia in the gas phase is detected by a constant potential electrolytic ammonia gas sensor 26 or 27 through the auto drain 25, and a 4-20 mA control signal proportional to the concentration is output to control the reaction related to ammonia. In order to maintain the sensitivity of the gas sensor during measurement, the sensors 26 and 27 are used alternately, but at the time of switching, gas is sent to both sensors for a certain period of time. The interval of alternation and the time of double at the time of switching can be arbitrarily changed. Switching is performed with four motor-operated valves. When the sample gas is not sucked, fresh fresh air is sucked to clean the detection portion.

気化器内の気化平衡を早めるため、気化器内循環空気量は、図１に示す検知器２６または２７内蔵のエアーポンプの吸引空気量０．５Ｌ／分程度と比べて、５Ｌ／分と多い。検知器の吸引空気量は外部の雰囲気ガスから気化器内に取り込んでいる。一方、体んでいる方のガスセンサーも雰囲気ガスを０．５Ｌ／分程度吸引している。そのため、雰囲気ガス中にアンモニアガスなど検知器と反応するガスが存在するとその影響を受ける。それを避けるために活性炭吸着装置２０または２１を通して、アンモニアなどのガスは取り除かれ、気化器またはガス検知器に雰囲気ガスが取り込まれるので検知器のゼロベース値は変動しない。  In order to accelerate the vaporization equilibrium in the carburetor, the amount of circulating air in the carburetor is as large as 5 L / min compared to the amount of air sucked by the air pump built in the detector 26 or 27 shown in FIG. . The amount of air sucked into the detector is taken into the vaporizer from the external atmospheric gas. On the other hand, the body gas sensor also sucks the atmospheric gas at about 0.5 L / min. Therefore, if there is a gas that reacts with the detector, such as ammonia gas, in the atmospheric gas, it is affected. In order to avoid this, the gas such as ammonia is removed through the activated carbon adsorption device 20 or 21, and the atmospheric gas is taken into the vaporizer or the gas detector, so that the zero base value of the detector does not change.

検知器２６、２７の導入口は気化器２３からオートドレー２５を通ってきた試料ガスと活性炭２０または２１を通ってきた雰囲気ガス（洗浄用ガス）とバルブ切り替えになっており、一定時間ごと、例えば１時間ごとに交互切り替えを行い、測定または洗浄し検知器の感度を維持し検知・制御を行う。  The inlets of the detectors 26 and 27 are valve-switched with the sample gas that has passed through the auto drain 25 from the vaporizer 23 and the atmospheric gas (cleaning gas) that has passed through the activated carbon 20 or 21, and at regular intervals. For example, by alternately switching every hour, measurement or cleaning is performed to maintain the sensitivity of the detector and perform detection and control.

検知器２６、２７で得られたアンモニアガス濃度はＰＩＤ２８に送られ、ＰＩＤ制御で設定値との差を修正するため、４−２０ｍＡの制御信号を出し、たとえば、反応槽へのアンモニア添加量を制御するなどして液中アンモニアと係わる反応を制御する。  The ammonia gas concentration obtained by the detectors 26 and 27 is sent to the PID 28, and in order to correct the difference from the set value by PID control, a control signal of 4-20 mA is issued, for example, the amount of ammonia added to the reaction tank The reaction related to ammonia in the liquid is controlled by controlling it.

試料液はポンプにてサンプル槽３２に運ばれ、オーバーフロー配管１１で廃水処理施設などに送られる。その一部を試料ポンプ３０で気化器に試料液を送る。この試料ポンプは流量を変化させることができ、試料液のアンモニア濃度や装置の状況をみて、流量を決める。常に一定流量で気化器に試料を送り込む必要がある。何故ならば、流量が変動した場合、気化器内のアンモニアの気化率も変化するため、常に一定の流量にすることが必要である。  The sample liquid is transported to the sample tank 32 by a pump and sent to a wastewater treatment facility or the like through the overflow pipe 11. A part of the sample liquid is sent to the vaporizer by the sample pump 30. This sample pump can change the flow rate, and the flow rate is determined in view of the ammonia concentration of the sample solution and the state of the apparatus. It is necessary to always send the sample to the vaporizer at a constant flow rate. This is because when the flow rate fluctuates, the vaporization rate of ammonia in the vaporizer also changes, so it is necessary to always maintain a constant flow rate.

産業界で液中のアンモニアを正確に測定し、安定してそれに係わる反応を制御する装置はなかった。液に浸漬する方式は隔膜などの膜を使うため、試料水の汚れなどの影響で感度を維持できなかった。一方、試料にアルカリを添加して、アンモニアガスにして測定する方法も、これまでは基本的にはバッチ式で、それを繰り返し、間欠的にアンモニアを測定する方法であるため、タイムラグが大きかった。また、検知方式も内部液の塩化アンモニア溶液に吸収させ内部液のｐＨ変化を測定する方法であった。
今回の開発装置は安定して連続的にアンモニアを検知・制御できるため、広範囲なアンモニアに係わる反応が制御できる（例えば、アナモックスにおけるアンモニアの添加等）。とりわけ微生物処理の硝化や脱窒処理工程では排水中に種々な物質が存在する悪条件下でアンモニアを正確に検知し、反応を制御することが難しかったが、この装置では容易に行える。There was no device in the industry that accurately measured ammonia in a liquid and stably controlled the reaction. The method of immersing in a liquid uses a membrane such as a diaphragm, so the sensitivity could not be maintained due to the influence of sample water contamination. On the other hand, the method of adding alkali to the sample and measuring it as ammonia gas has been basically a batch method, and it is a method of measuring ammonia intermittently by repeating it, so the time lag was large. . The detection method was also a method of measuring the pH change of the internal liquid by absorbing it in the ammonia chloride solution of the internal liquid.
The newly developed device can detect and control ammonia stably and continuously, so it can control a wide range of ammonia reactions (for example, adding ammonia in Anammox). In particular, in the nitrification or denitrification process of microbial treatment, it was difficult to accurately detect ammonia and control the reaction under adverse conditions in which various substances exist in the wastewater, but this apparatus can easily do this.

アンモニア検知・制御装置のフローシートAmmonia detection and control equipment flow sheet 気化温度とアンモニアガス濃度の関係Relationship between vaporization temperature and ammonia gas concentration 気化ｐＨとアンモニアガス濃度の関係Relationship between vaporization pH and ammonia gas concentration 液中アンモニア濃度とアンモニアガス濃度の関係Relationship between ammonia concentration in ammonia and ammonia gas concentration

気化温度とアンモニアガス濃度の関係を調べた。試料液中のアンモニア濃度は２０ｍｇ／Ｌ、ｐＨは１２．５として、気化温度を変え、１時間経過後のアンモニアガス濃度の値をプロットしたものを図−２に示した。図−２より気化温度とアンモニアガス濃度の間には明らかな関係が認められた。これはアンモニアの蒸気圧に関係していると考えられる。それ故、正確に測定するためには気化温度は一定に保つことが重要である。実用的な気化温度はガスセンサーの許容温度も考慮し、且つ、感度も高く保てる温度としては５５℃が最適と考えた。  The relationship between vaporization temperature and ammonia gas concentration was investigated. The ammonia concentration in the sample solution is 20 mg / L, the pH is 12.5, the vaporization temperature is changed, and the value of the ammonia gas concentration after 1 hour is plotted in FIG. From Fig. 2, a clear relationship was observed between the vaporization temperature and the ammonia gas concentration. This is considered to be related to the vapor pressure of ammonia. Therefore, it is important to keep the vaporization temperature constant for accurate measurement. The practical vaporization temperature was considered in consideration of the allowable temperature of the gas sensor, and 55 ° C. was considered optimal as the temperature at which high sensitivity can be maintained.

気化ｐＨとアンモニアガス濃度の関係を調べた。試料水のアンモニア濃度としては２０ｍｇ／Ｌ、気化温度としては５５℃、ｐＨを変化させ、１時間後の値をプロットし、図−３に示した。図−３より気化ｐＨとアンモニアの間には明らかな関係が認められ、気化ｐＨが１０．５以上では、アンモニアガス濃度はあまり変わらないため、アルカリの消費量も考慮してｐＨは１１が適当と考えた。  The relationship between vaporization pH and ammonia gas concentration was investigated. The ammonia concentration of the sample water was 20 mg / L, the vaporization temperature was 55 ° C., the pH was changed, and the values after 1 hour were plotted and shown in FIG. From Fig.3, there is a clear relationship between the vaporization pH and ammonia, and when the vaporization pH is 10.5 or higher, the ammonia gas concentration does not change much. I thought.

液中アンモニア濃度とアンモニアガス濃度の関係を調べた。気化温度としては５５℃、ｐＨを１１、１時間維持後の値を求めプロットし、図−４に示した。液中アンモニア濃度とアンモニアガス濃度の間には強い正の相関が認められたため、アンモニアガス濃度を検知することで、試料液中アンモニア濃度を算出できることが分かった。これにより、アンモニアガスセンサーで検知したアンモニアガス濃度に比例した制御信号を出すことで、アンモニアと係わる反応を制御できる装置が完成できた。  The relationship between the ammonia concentration in the liquid and the ammonia gas concentration was investigated. The vaporization temperature was 55 ° C., the pH was maintained at 11, and the value after maintaining for 1 hour was plotted and shown in FIG. Since a strong positive correlation was observed between the ammonia concentration in the liquid and the ammonia gas concentration, it was found that the ammonia concentration in the sample liquid can be calculated by detecting the ammonia gas concentration. As a result, a device capable of controlling the reaction related to ammonia was completed by issuing a control signal proportional to the ammonia gas concentration detected by the ammonia gas sensor.

Claims (3)

アンモニアイオンを含む試料液とアルカリ液をそれぞれ定量的且つ連続的に気化器に送液して液相部ｐＨをｐＨ１０．５−１３（願わくば１２）に調整すると共に、温度を５０℃−６０℃（願わくば５５℃）に調節・維持し、気化器上部の気相からエアーポンプにより吸引し、気化器の試料液へ循環曝気撹拌することで液相部のアンモニアを気化させて気液平衡させ、気化器内のアンモニアガスを含んだ気相の一部を吸引し、アンモニアガスセンサー（定電位電解式）でアンモニアを検知し、反応槽内の液中でアンモニアと係わる反応を制御できることを特徴とするアンモニア検知・制御装置。  The sample solution containing ammonia ions and the alkali solution are quantitatively and continuously sent to the vaporizer to adjust the pH of the liquid phase to pH 10.5-13 (preferably 12), and the temperature is 50 ° C.-60. Adjusted and maintained at ℃ (preferably 55 ℃), sucked from the gas phase above the vaporizer with an air pump, and circulated aerated and stirred into the sample liquid of the vaporizer to vaporize ammonia in the liquid phase and vapor-liquid equilibrium That the gas phase containing the ammonia gas in the vaporizer is sucked in, the ammonia is detected by an ammonia gas sensor (constant potential electrolysis), and the reaction related to ammonia can be controlled in the liquid in the reaction tank. Characteristic ammonia detection and control device. アンモニアガスセンサーなどの検出器の感度劣化を防ぐため、検出器を２台以上設置し、少なくても２台を交互に切り替え運転を行うことを特徴とする請求項１記載のアンモニア検知・制御装置。  2. The ammonia detection / control apparatus according to claim 1, wherein two or more detectors are installed to prevent sensitivity deterioration of a detector such as an ammonia gas sensor, and at least two of the detectors are alternately switched. . １台のアンモニアガスセンサーが試料ガスのアンモニア濃度検知動作中である時に、他方の１台は試料ガスとは別の外部新鮮空気を取り込むようにし、これをタイマーなどによって一定時間ごとに繰り返すこととし、長時間にわたって資料ガスに曝されるために発生する感度劣化を防止する構成にあって、外部新鮮空気を取り込む際に、事前に活性炭などの吸着剤で感度劣化の要因や外乱となるアンモニアガス等を吸着除去することを特徴とする請求項２記載のアンモニア検知・反応制御装置。  When one ammonia gas sensor is in the process of detecting the ammonia concentration of the sample gas, the other one takes in fresh fresh air that is different from the sample gas, and this is repeated at regular intervals by a timer or the like. In the configuration to prevent sensitivity deterioration that occurs due to exposure to the material gas for a long time, when taking in fresh external air, ammonia gas that becomes a factor of sensitivity deterioration or disturbance with an adsorbent such as activated carbon in advance The ammonia detection / reaction control apparatus according to claim 2, wherein the ammonia is adsorbed and removed.

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