JP3887959B2

JP3887959B2 - Microwave concentration measurement method

Info

Publication number: JP3887959B2
Application number: JP21500098A
Authority: JP
Inventors: 和宏豊岡; 朋史宮下; 茂雄佐藤
Original assignee: Meidensha Corp
Current assignee: Meidensha Corp
Priority date: 1998-07-30
Filing date: 1998-07-30
Publication date: 2007-02-28
Anticipated expiration: 2018-07-30
Also published as: JP2000046757A

Description

【０００１】
【発明の属する技術分野】
本発明は、下水処理プラント、排水処理プラント、浄水処理プラントやそれらの汚泥処理プラントの処理工程における懸濁物質混合液中の懸濁物質の濃度をマイクロ波を利用して測定する方法に関する。
【０００２】
【従来の技術】
懸濁物質混合液中の懸濁物質の濃度測定方法には、主に、以下の方法がある。
【０００３】
（１）散乱光式測定方法…懸濁物質混合液に向けて照射する光が懸濁物質で散乱することで受光器に濃度に応じた受光量を得る。
【０００４】
（２）超音波式測定方法…懸濁物質混合液に向けて放射する超音波が懸濁物質で反射又は減衰することで超音波受信器に濃度に応じた受信量を得る。
【０００５】
（３）マイクロ波式測定方法…懸濁物質混合液に向けてマイクロ波を照射し、照射波と透過波の位相差又は透過強度もしくは反射強度に濃度に応じた値を得る。
【０００６】
上記の散乱光式測定方法は、懸濁物質の色による影響を受け易いため測定対象物の色が濃い場合に測定濃度範囲が小さくなる。また、懸濁物質混合液に対する光照射と受光のための検出窓の汚れが測定精度に影響し易くなる。
【０００７】
超音波式測定方法は、懸濁物質混合液中の気泡の影響を受け易い。この気泡の除去のため、加圧脱泡装置等の機械的な気泡除去装置を設ける方式があるが、この方式では大掛かりな測定装置になるし、メンテナンス性の問題がある。
【０００８】
マイクロ波式測定方法の透過方式の構成を図１０に示す。同図において、懸濁物質混合液輸送管１の所定部位に対向してガラスやセラミック製の窓を設ける。この窓にマイクロ波送信側の濃度計検出プローブ２と、マイクロ波受信側の濃度計検出プローブ３を設ける。４は両プローブ２、３に接続されるマイクロ波送受信器、５はマイクロ波の送信、受信波の位相差又は透過強度から、懸濁物質の濃度を得る濃度計変換器である。
【０００９】
位相差を利用したマイクロ波式濃度計は、清水（濃度０％）でのマイクロ波透過波の位相遅れと、懸濁物質混合液中の懸濁物質におけるマイクロ波透過波の位相遅れとの差（位相差）が、図１１に示すように懸濁物質の濃度と比例関係になることを利用して濃度を計測する。また、マイクロ波の照射強度に対する透過強度の比を検出して濃度を測定することができる。
【００１０】
他のマイクロ波式測定方法として、反射方式になる図１２に示す構成のものがある。同図においては、輸送管１内の懸濁物質混合液に対して１つのプローブ６からマイクロ波を照射すると共に懸濁物質からの反射波を検出し、この照射波と反射波との強度の比から濃度を測定する。
【００１１】
上記のプローブ２や６は、例えば、反射方式による測定方法での構造を図１３に示す。懸濁物質混合液輸送管１にフランジ７によってガラスやセラミック製の窓８を設け、この外側に設ける導波管９内にマイクロ波アンテナ１０を突出させ、マイクロ波送受信器４から同軸ケーブル１１を通したマイクロ波をアンテナ１０から放射又はマイクロ波を受信する。１２は、導波管９のマイクロ波周波数特性を決定するスタブである。
【００１２】
以上のような方式にされるマイクロ波式濃度測定方法は、懸濁物質の色の影響を受けにくく、濃度の測定範囲も広いとされている。さらに、マイクロ波電極になるアンテナ等は、懸濁物質と非接触にできること及び窓の汚れの影響が少ないため、メンテナンス性も高めることができる。さらにまた、マイクロ波は懸濁物質混合液中の気泡の影響も他の方法に比べて少ない。
【００１３】
【発明が解決しようとする課題】
（第１の課題）
従来の測定方法において、マイクロ波周波数は、導波管の構造で決まる周波数帯域に合わせた固定周波数とするため、導波管の伝送特性の微妙な変化で導波管におけるマイクロ波の透過・反射特性が変化して測定誤差が大きくなることがある。
【００１４】
本発明の目的は、導波管の伝送特性の微妙な変化による測定誤差の発生を少なくした濃度測定方法を提供することにある。
【００１５】
（第２の課題）
マイクロ波式測定方法は、懸濁物質混合液の温度や導電率の変化が濃度測定精度に影響を及ぼす。
【００１６】
そこで、これら要因による測定誤差を少なくするため、温度計や導電率計を使って懸濁物質混合液の温度や導電率を測定し、この測定値を基に濃度測定値を補正することが考えられるが、温度や導電率の変化に対するマイクロ波の透過・反射特性が不安定であるため、適正な補正特性を得て高い精度で補正するのが難しい。
【００１７】
本発明の目的は、懸濁物質混合液の温度や導電率による濃度測定値の補正を適正にできる濃度測定方法を提供することにある。
【００１８】
【００１９】
【００２０】
【００２１】
【００２２】
【００２３】
【課題を解決するための手段】
本発明は、マイクロ波式濃度測定方法において、ある周波数範囲又は複数の固定周波数におけるマイクロ波の反射強度又は透過強度の特性を検出し、この特性から各周波数における反射強度又は透過強度の積分値又は平均値を求めて濃度測定値を得ることにより、導波管の伝送特性の微妙な変化にも濃度測定誤差の発生を少なくしたもので、以下の方法を特徴とする。
【００２４】
懸濁物質混合液に向けて照射するマイクロ波の反射強度又は透過強度を検出して懸濁物質の濃度測定を行うマイクロ波式濃度測定方法において、
前記マイクロ波の周波数を走査し、
前記各周波数に対する反射強度又は透過強度の特性を求め、
前記特性から各周波数における反射強度又は透過強度の積分値又は平均値を求め、
前記積分値又は平均値とマイクロ波の検量線と比較することで懸濁物質の濃度を求めることを特徴とする。
【００２５】
【００２６】
上記のマイクロ波式濃度測定方法において、懸濁物質混合液の温度や導電率の測定により濃度測定値を補正するのに、温度又は導電率の変化に対して、ある周波数範囲又は複数の固定周波数におけるマイクロ波の反射強度又は透過強度の特性を検出し、この特性から各周波数における反射強度又は透過強度の積分値又は平均値を求めて温度又は導電率の補正特性を得、この補正特性を使用して濃度測定値を補正することにより、温度や導電率による濃度測定値の補正を適正にするもので、以下の方法を特徴とする。
【００２７】
懸濁物質混合液の温度又は導電率を変化させ、前記各温度又は導電率における前記マイクロ波の周波数を走査し、前記各周波数に対する反射強度又は透過強度の特性を求め、前記特性から各周波数における反射強度又は透過強度の積分値又は平均値を懸濁物質混合液の温度又は導電率に対する補正特性として求めておき、
前記補正特性から懸濁物質混合液の温度又は導電率の変化に応じて前記濃度を補正することを特徴とする。
【００２８】
また、前記までの積分値又は平均値は、導波管の主モード帯域全体での積分値又は平均値とすること、又は導波管のマッチング周波数付近のピークを含む半値幅の周波数範囲での積分値又は平均値とすること、又は導波管のマッチング周波数付近の複数の周波数での反射強度又は透過強度の積算値又は平均値とすることを特徴とする。
【００２９】
【００３０】
【００３１】
【００３２】
【００３３】
【発明の実施の形態】
（第１の実施形態）
図１は、本発明の実施形態を示すマイクロ波式濃度測定方法のデータ処理フローである。なお、マイクロ波の検出は、透過方式又は反射方式の何れかに限定されるものでない。
【００３４】
（Ｓ１）濃度測定に際して、マイクロ波の照射にはマイクロ波送受信器４が発生するマイクロ波周波数を導波管の周波数帯域内で走査（スキャン）させる。
【００３５】
（Ｓ２）上記の周波数走査による各周波数でのマイクロ波の反射強度又は透過強度をマイクロ波送受信器４で検出し、この検出値を基に懸濁物質濃度計変換器５等によって反射特性又は透過特性を求める。
【００３６】
（Ｓ３）上記の反射又は透過特性から各周波数における反射強度又は透過強度の特性の和を求める。この特性の和の演算は、反射強度又は透過強度の積分値又は平均値を求める。
【００３７】
（Ｓ４）上記の積分値又は平均値をそのときの検量線（マイクロ波照射量）と比較することにより、マイクロ波の照射強度に対する反射強度又は透過強度の相対値を求める。
【００３８】
（Ｓ５）上記の相対値から懸濁物質混合液の測定濃度を決定する。
【００３９】
以上までの処理において、処理Ｓ１におけるマイクロ波の走査について説明する。導波管は、図２に矩形導波管の周波数帯と内外径寸法例を示すように、その形状によって周波数帯が決まり、遮断周波数以上の周波数の電磁波を通過させることができる。しかし、高周波になると高次のモードが発生するため、一般に主モード帯域内で余裕をもって下記式の範囲になる波長λを持つ周波数が使われる。なお、下記式のａは、導波管の横幅寸法（ｍｍ）である。
【００４０】
［数１］
（ａ／0.95）＜λ＜（2ａ／1.3）
したがって、送受信器４は、この式で決まる周波数ｆ₁〜ｆ₂の範囲を含む周波数でマイクロ波を走査させる。
【００４１】
次に、処理Ｓ２，Ｓ３における反射又は透過特性及びその積分値又は平均値演算について説明する。
【００４２】
図３は、マイクロ波周波数の走査による反射強度又は透過強度の特性Ａを示す。この特性Ａに対して、反射又は透過強度の積分は、上記の式で決定した周波数ｆ₁〜ｆ₂（主モード帯全体）の範囲での反射又は透過強度の積分演算により求める。この積分は、図３の斜線部分の面積に相当する。
【００４３】
この積分演算は、アナログ積分回路を使って周波数ｆ₁〜ｆ₂までの反射・透過強度を連続的に積分演算する方法、又は各走査周波数における離散的な反射・透過強度をディジタル演算によって積算する方法で実現できる。また、平均値を求める場合には、アナログ演算では積分値を積分時間で割算することで求められ、ディジタル演算ではサンプル数で割算することで求められる。
【００４４】
図４は、反射・透過強度特性Ａのピークの半値幅の周波数範囲ｆａ〜ｆｂにおける反射又は透過強度の積分演算により求める場合を示す。導波管から懸濁物質混合液まで電気的にマッチングがとれていれば、周波数−反射・透過強度特性Ａには、ある周波数（マッチング周波数）付近で反射又は透過強度の急峻又は緩やかなピークが発生する。このピークにおける反射又は透過強度Ｓの半分の値Ｓ／２をとる周波数をｆａ，ｆｂとすると、この周波数ｆａ〜ｆｂの範囲で反射又は透過強度を積分する。この積分は、図４の斜線部分の面積に相当する。
【００４５】
この積分演算及び平均値演算は、上記の場合と同様に、反射・透過強度をアナログ演算又はディジタル演算すること及び割算によって実現できる。
【００４６】
図５は、複数の周波数（マッチング周波数付近に選択した周波数）における反射又は透過強度の和をとる場合を示す。同図では、特性Ａに対して、３つの周波数ｆａ，ｆｂ，ｆｃにおける反射又は透過強度Ｓａ，Ｓｂ，Ｓｃを積算する。これら積算結果は、上記の積分演算を簡略化したものになるが、従来の１つの周波数に固定した方法とは異なる。なお、平均値の演算には各強度を加算した数で割算することで求められる。
【００４７】
以上のように、本実施形態では、ある周波数範囲又は複数の固定周波数におけるマイクロ波の反射強度又は透過強度をそれぞれ検出し、これら検出値の積分値又は平均値から濃度測定値を得る。これにより、懸濁物質の濃度測定に際して、導波管の伝送特性の微妙な変化で反射又は透過強度の特性が変化するも、その積分値又は平均値をとることで特性変化分の影響を少なくすることができ、濃度測定誤差の発生を少なくすることができる。
【００４８】
図６は、反射強度のみから測定した濃度と、反射強度の積分値から測定した濃度とを示すと共に、その垂下特性と相関度を示し、反射強度のみからの測定では相関度Ｒ²＝0.7677であるのに対して、積分値からの測定では相関度Ｒ²＝0.9518の高い相関度を呈した。したがって、反射強度からの測定に比べて積分値からの測定の方が濃度との相関がよく、従来の固定周波数による反射又は透過強度からの測定に比べて測定精度を高めることができる。
【００４９】
（第２の実施形態）
図７は、本発明の実施形態を示すマイクロ波式濃度測定方法のデータ処理フローであり、同図が図１と異なる部分は、温度及び導電率の変化による濃度測定値の補正処理を追加した点にある。
【００５０】
温度・導電率補正処理Ｓ６では、懸濁物質混合液の温度や導電率の測定により濃度測定値を補正するのに、処理Ｓ１〜Ｓ４の処理と同様に、温度又は導電率の変化に対して、ある周波数範囲又は複数の固定周波数におけるマイクロ波の反射強度又は透過強度の積分値又は平均値を求め、これらから温度又は導電率の変化に対する補正特性を得ておき、この補正特性と温度又は導電率の測定値から濃度測定値を補正する。
【００５１】
すなわち、温度又は導電率の補正特性を得るのに、温度変化に対する反射又は透過強度の変化を測定して補正特性とするのではなく、温度変化に対する反射又は透過強度の積分値又は平均値の変化を測定して補正特性として求めておく。なお、積分値や平均値の演算は、第１の実施形態における濃度測定方法での演算と同様にできる。
【００５２】
図８は、温度変化に対する反射強度の変化と、反射強度積分値の変化を測定した場合を示し、その垂下特性（又は補正特性）及び相関度も併せて示す。図示のように、懸濁物質混合液の温度変化に対して、反射強度は相関度Ｒ²＝0.4582であるのに対し、反射強度積分値は相関度Ｒ²＝0.9822と高くなり、反射強度の積分値から補正特性を求める方が補正精度を高めることができる。
【００５３】
図９は、導電率変化に対する反射強度の変化と、反射強度積分値の変化を測定した場合を示し、その垂下特性（又は補正特性）及び相関度も併せて示す。図示のように、懸濁物質混合液の導電率変化に対して、反射強度は相関度Ｒ²＝0.7829であるのに対し、反射強度積分値は相関度Ｒ²＝0.9524と高くなり、反射強度の積分値から補正特性を求める方が補正精度を高めることができる。
【００５４】
これら温度又は導電率に対する相関性は、反射強度に限らず、透過強度に対しても同様に高いものを得ることができるし、積分値に代えて平均値とすることでも高い相関性を得ることができる。
【００５５】
以上のように、本実施形態では、温度又は導電率の変化に対して、マイクロ波の反射強度又は透過強度の積分値又は平均値から補正特性を得、この補正特性を使用して濃度測定値を補正することにより、濃度測定値の補正を適正にすることができる。
【００５６】
【００５７】
【００５８】
【００５９】
【００６０】
【００６１】
【００６２】
【００６３】
【００６４】
【００６５】
【００６６】
【００６７】
【００６８】
【００６９】
【００７０】
【００７１】
【００７２】
【発明の効果】
以上のとおり、本発明によれば、ある周波数範囲又は複数の固定周波数におけるマイクロ波の反射強度又は透過強度をそれぞれ検出し、これら検出値の積分値又は平均値から濃度測定値を得るようにしたため、導波管の伝送特性の微妙な変化にも濃度測定誤差の発生を少なくすることができる。
【００７３】
また、懸濁物質混合液の温度や導電率の測定により濃度測定値を補正するのに、温度又は導電率の変化に対して、ある周波数範囲又は複数の固定周波数におけるマイクロ波の反射強度又は透過強度の積分値又は平均値の変化から補正特性を得、この補正特性を使用して濃度測定値を補正するようにしたため、温度や導電率による濃度測定値の補正を適正にすることができる。
【００７４】
【００７５】
【図面の簡単な説明】
【図１】本発明の第１の実施形態を示すマイクロ波式測定方法のデータ処理フロー。
【図２】矩形導波管の寸法例。
【図３】第１の実施形態における反射・透過強度特性と積分範囲。
【図４】第１の実施形態における反射・透過強度特性と積分範囲。
【図５】第１の実施形態における反射・透過強度特性と積算位置。
【図６】第１の実施形態における反射強度と積分値の濃度との相関の比較。
【図７】本発明の第２の実施形態を示すマイクロ波式測定方法のデータ処理フロー。
【図８】第２の実施形態における反射強度と積分値の温度との相関の比較。
【図９】第２の実施形態における反射強度と積分値の導電率との相関の比較。
【図１０】マイクロ波式濃度測定方法における透過方式の測定原理。
【図１１】マイクロ波の位相差−濃度特性図。
【図１２】マイクロ波式濃度測定方法における反射方式の測定原理。
【図１３】マイクロ波式濃度測定方法におけるプローブの構成例。
【符号の説明】
１…懸濁物質混合液輸送管
２、３、６…プローブ
４…マイクロ波送受信器
５…濃度計変換器
９…導波管[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for measuring the concentration of suspended solids in a suspension mixed solution in a treatment process of a sewage treatment plant, a wastewater treatment plant, a water purification treatment plant, or a sludge treatment plant using a microwave.
[0002]
[Prior art]
There are mainly the following methods for measuring the concentration of the suspended substance in the suspended substance mixture.
[0003]
(1) Scattered light measurement method: The amount of light received in accordance with the concentration is obtained in the light receiver by scattering the light irradiated toward the suspension substance mixed solution from the suspension substance.
[0004]
(2) Ultrasonic measurement method: The amount of reception corresponding to the concentration is obtained in the ultrasonic receiver by reflecting or attenuating the ultrasonic wave radiated toward the suspension substance mixed solution by the suspension substance.
[0005]
(3) Microwave measurement method: Microwave is applied to the suspension substance mixed solution, and the phase difference between the irradiation wave and the transmitted wave, or the transmission intensity or reflection intensity is obtained according to the concentration.
[0006]
Since the above scattered light measurement method is easily affected by the color of the suspended substance, the measurement concentration range becomes small when the color of the measurement object is dark. In addition, contamination of the detection window for light irradiation and light reception on the suspension substance mixture tends to affect the measurement accuracy.
[0007]
The ultrasonic measurement method is easily affected by bubbles in the suspension material mixture. In order to remove the bubbles, there is a method in which a mechanical bubble removing device such as a pressure defoaming device is provided. However, this method has a large measuring device and has a problem of maintenance.
[0008]
The structure of the transmission method of the microwave measurement method is shown in FIG . In the figure, a window made of glass or ceramic is provided to face a predetermined portion of the suspended solid mixture transport pipe 1. A densitometer detection probe 2 on the microwave transmission side and a densitometer detection probe 3 on the microwave reception side are provided in this window. 4 is a microwave transmitter / receiver connected to both probes 2 and 3, and 5 is a densitometer converter that obtains the concentration of suspended substances from the phase difference or transmission intensity of microwave transmission and reception waves.
[0009]
The microwave densitometer using the phase difference is the difference between the phase lag of the microwave transmission in fresh water (concentration 0%) and the phase lag of the microwave transmission in the suspension in the suspension mixture. The concentration is measured by utilizing the fact that (phase difference) is proportional to the concentration of suspended solids as shown in FIG . Further, the concentration can be measured by detecting the ratio of the transmission intensity to the microwave irradiation intensity.
[0010]
As another microwave measurement method, there is a method shown in FIG . In the figure, a microwave is irradiated from one probe 6 to the suspended substance mixture in the transport pipe 1 and a reflected wave from the suspended substance is detected, and the intensity of the irradiated wave and the reflected wave is measured. The concentration is measured from the ratio.
[0011]
FIG. 13 shows the structure of the above-described probes 2 and 6, for example, by a measurement method using a reflection method. A window 8 made of glass or ceramic is provided in the suspension material mixture transport pipe 1 by a flange 7, a microwave antenna 10 is projected into a waveguide 9 provided outside this, and a coaxial cable 11 is connected from the microwave transceiver 4. The transmitted microwave is radiated from the antenna 10 or received. Reference numeral 12 denotes a stub that determines the microwave frequency characteristics of the waveguide 9.
[0012]
The microwave concentration measurement method employed as described above is not easily affected by the color of the suspended matter, and the concentration measurement range is wide. Furthermore, since the antenna or the like that becomes the microwave electrode can be made non-contact with the suspended substance and is less affected by dirt on the window, the maintainability can be improved. Furthermore, microwaves have less influence of bubbles in the suspension material mixture than other methods.
[0013]
[Problems to be solved by the invention]
(First issue)
In the conventional measurement method, the microwave frequency is a fixed frequency that matches the frequency band determined by the waveguide structure. Therefore, the transmission and reflection of microwaves in the waveguide are caused by subtle changes in the transmission characteristics of the waveguide. The characteristic may change and the measurement error may increase.
[0014]
An object of the present invention is to provide a concentration measurement method in which occurrence of measurement errors due to subtle changes in transmission characteristics of a waveguide is reduced.
[0015]
(Second problem)
In the microwave measurement method, changes in temperature and conductivity of the suspended solid mixture affect the concentration measurement accuracy.
[0016]
Therefore, in order to reduce measurement errors due to these factors, it is considered to measure the temperature and conductivity of the suspended solid mixture using a thermometer or conductivity meter and correct the concentration measurement value based on this measurement value. However, since the transmission and reflection characteristics of the microwave with respect to changes in temperature and conductivity are unstable, it is difficult to obtain an appropriate correction characteristic and correct it with high accuracy.
[0017]
The objective of this invention is providing the density | concentration measuring method which can correct | amend the density | concentration measured value by the temperature and electrical conductivity of a suspension substance liquid mixture appropriately.
[0018]
[0019]
[0020]
[0021]
[0022]
[0023]
[Means for Solving the Problems]
In the microwave concentration measurement method, the present invention detects a characteristic of microwave reflection intensity or transmission intensity in a certain frequency range or a plurality of fixed frequencies, and from this characteristic, an integrated value of reflection intensity or transmission intensity at each frequency or By obtaining an average value and obtaining a concentration measurement value, the occurrence of a concentration measurement error is reduced even for subtle changes in the transmission characteristics of the waveguide, and the following method is characterized.
[0024]
In the microwave concentration measurement method for measuring the concentration of suspended solids by detecting the reflection intensity or transmission intensity of the microwaves irradiated toward the suspended solid mixture,
Scanning the microwave frequency,
Obtain the characteristics of the reflection intensity or transmission intensity for each frequency,
Obtain the integrated value or average value of the reflection intensity or transmission intensity at each frequency from the characteristics,
It is characterized in that the concentration of suspended solids is determined by comparing the integrated value or average value with a calibration curve of microwaves.
[0025]
[0026]
In the above-mentioned microwave concentration measurement method, in order to correct the concentration measurement value by measuring the temperature and conductivity of the suspended solid mixture, a certain frequency range or a plurality of fixed frequencies can be used with respect to changes in temperature or conductivity. The characteristic of the reflection intensity or transmission intensity of microwaves is detected, and the integrated value or average value of the reflection intensity or transmission intensity at each frequency is obtained from this characteristic to obtain the correction characteristic of temperature or conductivity, and this correction characteristic is used. Then, by correcting the concentration measurement value, the correction of the concentration measurement value by temperature and conductivity is made appropriate, and the following method is characterized.
[0027]
Change the temperature or conductivity of the suspension material mixture, scan the frequency of the microwave at each temperature or conductivity, determine the reflection intensity or transmission intensity characteristics for each frequency, and determine the characteristics at each frequency from the characteristics. for temperature or conductivity of the integral value or the average value of the reflection intensity or transmitted intensity suspended solids mixture previously obtained as correction characteristic,
The concentration is corrected according to a change in temperature or conductivity of the suspension substance mixed solution based on the correction characteristic.
[0028]
Further, the integrated value or average value up to the above is the integrated value or average value over the entire main mode band of the waveguide, or in the frequency range of half width including the peak near the matching frequency of the waveguide. An integral value or an average value is used, or an integrated value or an average value of reflection intensity or transmission intensity at a plurality of frequencies near the matching frequency of the waveguide.
[0029]
[0030]
[0031]
[0032]
[0033]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a data processing flow of a microwave concentration measurement method showing an embodiment of the present invention. Note that the detection of microwaves is not limited to either the transmission method or the reflection method.
[0034]
(S1) In the concentration measurement, for microwave irradiation, the microwave frequency generated by the microwave transmitter / receiver 4 is scanned within the frequency band of the waveguide.
[0035]
(S2) The microwave reflection intensity or transmission intensity at each frequency by the frequency scanning described above is detected by the microwave transmitter / receiver 4, and based on the detected value, the reflection characteristic or transmission by the suspended substance concentration meter converter 5 or the like. Find characteristics.
[0036]
(S3) The sum of the reflection intensity or transmission intensity characteristics at each frequency is obtained from the above reflection or transmission characteristics. In the calculation of the sum of the characteristics, an integrated value or an average value of the reflection intensity or the transmission intensity is obtained.
[0037]
(S4) The relative value of the reflection intensity or the transmission intensity with respect to the irradiation intensity of the microwave is obtained by comparing the integrated value or the average value with the calibration curve (microwave irradiation intensity) at that time.
[0038]
(S5) The measured concentration of the suspended solid mixture is determined from the above relative values.
[0039]
In the above processing, the microwave scanning in the processing S1 will be described. As shown in FIG. 2, an example of the frequency band and inner and outer diameter dimensions of the rectangular waveguide, the frequency band is determined by the shape of the waveguide, and electromagnetic waves having a frequency equal to or higher than the cutoff frequency can pass therethrough. However, since higher-order modes are generated at higher frequencies, a frequency having a wavelength λ having a margin within the main mode band and having the following range is generally used. Note that “a” in the following formula is the width dimension (mm) of the waveguide.
[0040]
[Equation 1]
(A / 0.95) <λ <(2a / 1.3)
Therefore, the transceiver 4 scans the microwave at a frequency including the range of the frequencies f _{1 to} f ₂ determined by this equation.
[0041]
Next, the reflection or transmission characteristics and the integral value or average value calculation in the processes S2 and S3 will be described.
[0042]
FIG. 3 shows a characteristic A of reflection intensity or transmission intensity by scanning at a microwave frequency. For this characteristic A, the integration of the reflection or transmission intensity is obtained by the integral calculation of the reflection or transmission intensity in the range of the frequencies f _{1 to} f ₂ (the whole main mode band) determined by the above formula. This integration corresponds to the area of the hatched portion in FIG.
[0043]
In this integration calculation, a method of continuously integrating the reflection / transmission intensity at frequencies f _{1 to} f ₂ using an analog integration circuit, or a discrete reflection / transmission intensity at each scanning frequency is integrated by digital calculation. It can be realized by the method. In addition, when obtaining an average value, it is obtained by dividing an integral value by an integration time in an analog operation, and is obtained by dividing by an number of samples in a digital operation.
[0044]
FIG. 4 shows a case where the reflection / transmission intensity characteristic A is obtained by integral calculation of reflection or transmission intensity in the frequency range fa to fb having a half-value width of the peak. If the matching from the waveguide to the suspended solid mixture is electrically matched, the frequency-reflection / transmission intensity characteristic A has a steep or gentle peak of reflection or transmission intensity near a certain frequency (matching frequency). appear. Assuming that the frequency at which the half value of the reflection or transmission intensity S at the peak is S / 2 is fa and fb, the reflection or transmission intensity is integrated in the range of the frequencies fa to fb. This integration corresponds to the area of the hatched portion in FIG.
[0045]
The integration calculation and the average value calculation can be realized by analog or digital calculation and division of the reflection / transmission intensity as in the case described above.
[0046]
FIG. 5 shows a case where the sum of reflection or transmission intensities at a plurality of frequencies (frequency selected near the matching frequency) is taken. In the figure, the reflection or transmission intensities Sa, Sb, and Sc at the three frequencies fa, fb, and fc are integrated with respect to the characteristic A. These integration results are obtained by simplifying the integration calculation described above, but are different from the conventional method of fixing to one frequency. The average value is calculated by dividing each intensity by the added number.
[0047]
As described above, in the present embodiment, the reflection intensity or transmission intensity of microwaves in a certain frequency range or a plurality of fixed frequencies is detected, respectively, and a concentration measurement value is obtained from an integral value or an average value of these detection values. As a result, when measuring the concentration of suspended solids, the reflection or transmission intensity characteristics change due to subtle changes in the transmission characteristics of the waveguide. And the occurrence of density measurement errors can be reduced.
[0048]
FIG. 6 shows the density measured only from the reflection intensity and the density measured from the integrated value of the reflection intensity, and shows the drooping characteristic and the correlation. In the measurement only from the reflection intensity, the correlation R ^{2 is} 0.7677. On the other hand, the measurement from the integral value showed a high correlation degree of correlation R ² = 0.9518. Therefore, the measurement from the integral value has a better correlation with the concentration than the measurement from the reflection intensity, and the measurement accuracy can be improved as compared with the measurement from the reflection or transmission intensity by the conventional fixed frequency.
[0049]
(Second Embodiment)
FIG. 7 is a data processing flow of the microwave type concentration measuring method showing the embodiment of the present invention. In FIG. 7, a portion different from FIG. 1 is added with correction processing of the concentration measurement value due to changes in temperature and conductivity. In the point.
[0050]
In the temperature / conductivity correction process S6, the concentration measurement value is corrected by measuring the temperature and the conductivity of the suspended solid mixture. Then, the integrated value or average value of the reflection intensity or transmission intensity of the microwave in a certain frequency range or a plurality of fixed frequencies is obtained, and a correction characteristic for a change in temperature or conductivity is obtained from these, and the correction characteristic and the temperature or conductivity are obtained. The concentration measurement value is corrected from the rate measurement value.
[0051]
That is, in order to obtain a correction characteristic of temperature or conductivity, a change in the reflection or transmission intensity with respect to a temperature change is not measured by measuring a change in reflection or transmission intensity with respect to a temperature change. Is obtained as a correction characteristic. The calculation of the integral value and the average value can be performed in the same manner as the calculation in the concentration measurement method in the first embodiment.
[0052]
FIG. 8 shows a case where a change in the reflection intensity with respect to a temperature change and a change in the reflection intensity integrated value are measured, and the drooping characteristics (or correction characteristics) and the degree of correlation are also shown. As shown in the figure, the reflection intensity is correlated R ² = 0.4582 with respect to the temperature change of the suspended solid mixture, whereas the reflection intensity integrated value is high as correlation R ² = 0.9822. The correction accuracy can be improved by obtaining the correction characteristic from the integral value.
[0053]
FIG. 9 shows a case where the change in the reflection intensity with respect to the change in conductivity and the change in the reflection intensity integrated value are measured, and also shows the drooping characteristics (or correction characteristics) and the correlation. As shown in the figure, the reflection intensity is correlated R ² = 0.7829 with respect to the change in conductivity of the suspended solid mixture, whereas the integrated reflection intensity is as high as R ² = 0.9524. The correction accuracy can be improved by obtaining the correction characteristic from the integral value of.
[0054]
These correlations with respect to temperature or conductivity are not limited to reflection intensity, but can also be high with respect to transmission intensity, and high correlation can also be obtained by taking average values instead of integral values. Can do.
[0055]
As described above, in the present embodiment, a correction characteristic is obtained from an integrated value or an average value of microwave reflection intensity or transmission intensity with respect to a change in temperature or conductivity, and a concentration measurement value is obtained using this correction characteristic. By correcting this, it is possible to correct the correction of the density measurement value.
[0056]
[0057]
[0058]
[0059]
[0060]
[0061]
[0062]
[0063]
[0064]
[0065]
[0066]
[0067]
[0068]
[0069]
[0070]
[0071]
[0072]
【The invention's effect】
As described above, according to the present invention, the microwave reflection intensity or transmission intensity in a certain frequency range or a plurality of fixed frequencies is detected, and the concentration measurement value is obtained from the integrated value or average value of these detection values. The occurrence of concentration measurement errors can be reduced even with subtle changes in the transmission characteristics of the waveguide.
[0073]
In addition, in order to correct the concentration measurement value by measuring the temperature and conductivity of the suspended solid mixture, the reflected intensity or transmission of microwaves in a certain frequency range or multiple fixed frequencies with respect to changes in temperature or conductivity. Since the correction characteristic is obtained from the change of the integrated value or the average value of the intensity, and the concentration measurement value is corrected using the correction characteristic, the correction of the concentration measurement value by the temperature and conductivity can be made appropriate.
[0074]
[0075]
[Brief description of the drawings]
FIG. 1 is a data processing flow of a microwave measurement method according to a first embodiment of the present invention.
FIG. 2 is a dimension example of a rectangular waveguide.
FIG. 3 shows reflection / transmission intensity characteristics and integration ranges in the first embodiment.
FIG. 4 shows reflection / transmission intensity characteristics and integration ranges in the first embodiment.
FIG. 5 shows reflection / transmission intensity characteristics and integrated positions in the first embodiment.
FIG. 6 is a comparison of the correlation between the reflection intensity and the integrated density in the first embodiment.
FIG. 7 is a data processing flow of a microwave measurement method showing a second embodiment of the present invention.
FIG. 8 is a comparison of the correlation between the reflection intensity and the integrated value temperature in the second embodiment.
FIG. 9 is a comparison of the correlation between the reflection intensity and the integral conductivity in the second embodiment.
FIG. 10 shows the measurement principle of the transmission method in the microwave concentration measurement method .
FIG. 11 is a phase difference-concentration characteristic diagram of microwaves .
FIG. 12 shows a measurement principle of a reflection method in a microwave concentration measurement method .
FIG. 13 shows a configuration example of a probe in a microwave concentration measurement method .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Suspended substance mixed liquid transport tube 2, 3, 6 ... Probe 4 ... Microwave transmitter / receiver 5 ... Densitometer converter 9 ... Waveguide

Claims

In the microwave concentration measurement method for measuring the concentration of suspended solids by detecting the reflection intensity or transmission intensity of the microwaves irradiated toward the suspended solid mixture,
Scanning the microwave frequency,
Obtain the characteristics of the reflection intensity or transmission intensity for each frequency,
Obtain the integrated value or average value of the reflection intensity or transmission intensity at each frequency from the characteristics,
A microwave concentration measuring method, wherein the concentration of suspended solids is determined by comparing the integrated value or average value with a calibration curve of microwaves.

Change the temperature or conductivity of the suspension material mixture, scan the frequency of the microwave at each temperature or conductivity, determine the reflection intensity or transmission intensity characteristics for each frequency, and determine the characteristics at each frequency from the characteristics. for temperature or conductivity of the integral value or the average value of the reflection intensity or transmitted intensity suspended solids mixture previously obtained as correction characteristic,
2. The microwave concentration measuring method according to claim 1, wherein the concentration is corrected in accordance with a change in temperature or conductivity of the suspended solid mixture from the correction characteristic.

The integrated value or the average value is an integrated value or an average value over the entire main mode band of the waveguide, or an integrated value or an average in a frequency range of half width including a peak near the matching frequency of the waveguide. 3. The microwave concentration measurement according to claim 1, wherein the measured value is an integrated value or an average value of reflection intensity or transmission intensity at a plurality of frequencies near a matching frequency of the waveguide. Method.