JP3757597B2

JP3757597B2 - Absorbent slurry flow rate control method and apparatus for flue gas desulfurization apparatus

Info

Publication number: JP3757597B2
Application number: JP01264998A
Authority: JP
Inventors: 訓木村
Original assignee: 石川島播磨重工業株式会社
Priority date: 1998-01-26
Filing date: 1998-01-26
Publication date: 2006-03-22
Anticipated expiration: 2018-01-26
Also published as: JPH11207141A

Description

【０００１】
【発明の属する技術分野】
本発明は、排煙脱硫装置の吸収剤スラリー流量制御方法及び装置に関するものである。
【０００２】
【従来の技術】
吸収剤として炭酸カルシウム（ＣａＣＯ₃）を用いた排煙脱硫装置は、一般に図４に示されるように、下部に吸収液１の液溜部１ａが形成され且つ上部に多数のスプレーノズル２が配設された吸収塔３と、該吸収塔３の液溜部１ａの吸収液１を汲み上げ前記スプレーノズル２から噴霧させて循環させる複数台の循環ポンプ４と、前記吸収塔３の液溜部１ａに酸化用の空気を供給する酸化空気ブロワ５とを備えてなる構成を有している。
【０００３】
前述の如き排煙脱硫装置の場合、吸収液１が循環ポンプ４の作動によりスプレーノズル２から噴霧されつつ循環しており、図示していない石炭焚ボイラ等から吸収塔３に送り込まれた排ガスは、前記スプレーノズル２から噴霧される吸収液１と接触することにより、ＳＯ₂（硫黄酸化物）が吸収除去された後、外部へ排出される。
【０００４】
一方、前記排ガスからＳＯ₂を吸収した吸収液１の一部は、吸収塔３の液溜部１ａの底部から石膏スラリーとして回収され、該石膏スラリーから水分が除去され石膏が生成されるようになっている。
【０００５】
又、前記吸収塔３には、必要に応じて適宜、流量調整弁８の開度を制御することにより、所要量の吸収剤スラリーが供給されるようになっているが、その制御系は、吸収塔３内における吸収液１のｐＨ（ペーハー）を検出するｐＨ計７と、脱硫ガス流量Ａを検出する脱硫ガス流量計９と、吸収塔入口ＳＯ₂濃度Ｂを検出する吸収塔入口ＳＯ₂濃度計１０と、吸収剤スラリー流量Ｄを検出する吸収剤スラリー流量計１２と、吸収剤スラリー濃度Ｅを検出する吸収剤スラリー濃度計１３とを備えると共に、前記脱硫ガス流量計９で検出された脱硫ガス流量Ａと、前記吸収塔入口ＳＯ₂濃度計１０で検出された吸収塔入口ＳＯ₂濃度Ｂと、前記ｐＨ計７で検出された吸収液１のｐＨと、前記吸収剤スラリー濃度計１３で検出された吸収剤スラリー濃度Ｅとに基づき、前記吸収液１のｐＨを設定ｐＨ値に保持するのに必要となる設定吸収剤スラリー流量２８（図５参照）を求め、前記吸収剤スラリー流量Ｄが設定吸収剤スラリー流量２８と等しくなるよう、前記流量調整弁８へ開度指令３２を出力する制御器６とを備えてなる構成を有している。
【０００６】
前記制御器は、図５に示される如く、前記吸収塔入口ＳＯ₂濃度計１０で検出された吸収塔入口ＳＯ₂濃度Ｂに対して設定脱硫率（例えば９０％）を掛けることにより、脱硫ＳＯ₂濃度１４を求めて出力する乗算器１５と、
前記脱硫ガス流量計９で検出された脱硫ガス流量Ａに対して前記乗算器１５から出力される脱硫ＳＯ₂濃度１４を掛けることにより、排ガス中から除去するＳＯ₂量１６を求めて出力する乗算器１７と、
該乗算器１７から出力されるＳＯ₂量１６に対して（吸収剤量／ＳＯ₂量）の値を掛けることにより、吸収剤量１８を求めて出力する乗算器１９と、
該乗算器１９から出力される吸収剤量１８に対して設定吸収剤過剰率（例えば１．０２）を掛けることにより、実際に必要となる必要吸収剤量２０を求めて出力する乗算器２１と、
予め設定された設定ｐＨ値（例えば５．０）と前記ｐＨ計７で検出された吸収液１のｐＨとの差を求め、ｐＨ偏差２２を出力する減算器２３と、
該減算器２３から出力されるｐＨ偏差２２を比例積分処理して該ｐＨ偏差２２をなくすための吸収剤量に換算した吸収剤換算量２４を出力する比例積分調節器２５と、
前記乗算器２１から出力される必要吸収剤量２０に対して前記比例積分調節器２５から出力される吸収剤量に換算した吸収剤換算量２４を加えることにより、ｐＨ考慮必要吸収剤量２６を求めて出力する加算器２７と、
該加算器２７から出力されるｐＨ考慮必要吸収剤量２６を前記吸収剤スラリー濃度計１３で検出された吸収剤スラリー濃度Ｅで割ることにより、設定吸収剤スラリー流量２８を求めて出力する除算器２９と、
該除算器２９から出力される設定吸収剤スラリー流量２８と前記吸収剤スラリー流量計１２で検出された吸収剤スラリー流量Ｄとの差を求め、吸収剤スラリー偏差３０を出力する減算器３１と、
該減算器３１から出力される吸収剤スラリー偏差３０を比例積分処理して該吸収剤スラリー偏差３０をなくすための流量調整弁８の開度指令３２を出力する比例積分調節器３３と
を備えてなる構成を有している。
【０００７】
前記排煙脱硫装置の運転時には、ｐＨ計７で検出された吸収液１のｐＨと、脱硫ガス流量計９で検出された脱硫ガス流量Ａと、吸収塔入口ＳＯ₂濃度計１０で検出された吸収塔入口ＳＯ₂濃度Ｂと、吸収剤スラリー流量計１２で検出された吸収剤スラリー流量Ｄと、吸収剤スラリー濃度計１３で検出された吸収剤スラリー濃度Ｅとが制御器６へ入力され、該制御器６の乗算器１５において前記吸収塔入口ＳＯ₂濃度計１０で検出された吸収塔入口ＳＯ₂濃度Ｂに対して設定脱硫率を掛けることにより、脱硫ＳＯ₂濃度１４が求められて乗算器１７へ出力され、該乗算器１７において前記脱硫ガス流量計９で検出された脱硫ガス流量Ａに対して前記乗算器１５から出力される脱硫ＳＯ₂濃度１４を掛けることにより、排ガス中から除去するＳＯ₂量１６が求められて乗算器１９へ出力され、該乗算器１９において前記乗算器１７から出力されるＳＯ₂量１６に対して（吸収剤量／ＳＯ₂量）の値を掛けることにより、吸収剤量１８が求められて乗算器２１へ出力され、該乗算器２１において前記乗算器１９から出力される吸収剤量１８に対して設定吸収剤過剰率を掛けることにより、実際に必要となる必要吸収剤量２０が求められて加算器２７へ出力される一方、減算器２３において予め設定された設定ｐＨ値と前記ｐＨ計７で検出された吸収液１のｐＨとの差が求められてｐＨ偏差２２が比例積分調節器２５へ出力され、該比例積分調節器（フィードバック制御演算を行なっている調節器）２５において前記減算器２３から出力されるｐＨ偏差２２が比例積分処理され該ｐＨ偏差２２をなくすための吸収剤量に換算した吸収剤換算量２４が加算器２７へ出力され、該加算器２７において前記乗算器２１から出力される必要吸収剤量２０に対して前記比例積分調節器２５から出力される吸収剤量に換算した吸収剤換算量２４を加えることにより、ｐＨ考慮必要吸収剤量２６が求められて除算器２９へ出力され、該除算器２９において前記加算器２７から出力されるｐＨ考慮必要吸収剤量２６を前記吸収剤スラリー濃度計１３で検出された吸収剤スラリー濃度Ｅで割ることにより、設定吸収剤スラリー流量２８が求められて減算器３１へ出力され、該減算器３１において前記除算器２９から出力される設定吸収剤スラリー流量２８と前記吸収剤スラリー流量計１２で検出された吸収剤スラリー流量Ｄとの差が求められ、吸収剤スラリー偏差３０が比例積分調節器３３へ出力され、該比例積分調節器３３において前記減算器３１から出力される吸収剤スラリー偏差３０が比例積分処理され該吸収剤スラリー偏差３０をなくすための開度指令３２が流量調整弁８へ出力され、該流量調整弁８の開度が調節され、前記吸収剤スラリー流量Ｄが設定吸収剤スラリー流量２８と等しくなるよう制御が行われ、これにより前記吸収液１のｐＨを設定ｐＨ値に保持するようになっている。
【０００８】
前述の如く、吸収塔３内における吸収液１のｐＨを設定ｐＨ値となるよう一定に制御し、排ガス中の硫黄分と吸収剤中のカルシウムとが正常に一対一で反応している限りは、未反応な吸収剤はほとんどゼロとなり、排ガスの脱硫が確実に行われるが、吸収剤の回りに硫黄分との反応を阻害する不純物が付着する等、なんらかの原因で排ガス中の硫黄分と吸収剤とが反応しなくなった場合（いわゆる吸収剤の活性低下が発生した場合）には、排ガスの脱硫が充分に行われなくなり、脱硫性能が低下する虞れがある。
【０００９】
このため、従来においては、吸収剤の活性低下を未然に防止するために、或いは吸収剤の活性低下が発生した場合にそれを解消するために、図４に示される如く、吸収塔３内に苛性ソーダ（ＮａＯＨ）等の中和剤を中和剤注入弁３４を適宜開いて注入することにより、吸収剤の活性低下をなくし、排ガス中の硫黄分と吸収剤との反応が促進されるようにしている。
【００１０】
【発明が解決しようとする課題】
ところで、苛性ソーダ等の中和剤は吸収剤と同様にアルカリであって、ｐＨを上げる効果があるため、前述の如く中和剤を吸収塔３内に注入した場合、吸収塔３内における吸収液１のｐＨが急激に上昇する一方、前記中和剤の吸収塔３内への注入を停止した場合には、吸収塔３内における吸収液１のｐＨが急激に下降してしまい、吸収塔３内における吸収液１のｐＨが不安定となり、脱硫性能も変動してしまうという欠点を有していた。
【００１１】
本発明は、斯かる実情に鑑み、中和剤の吸収塔内への注入時並びに注入停止時における吸収液のｐＨの変動を抑制し得、脱硫性能の安定化を図り得る排煙脱硫装置の吸収剤スラリー流量制御方法及び装置を提供しようとするものである。
【００１２】
【課題を解決するための手段】
本発明は、吸収剤として炭酸カルシウムを用いた吸収液と排ガスとを吸収塔内で接触させることにより、排ガス中に含まれる硫黄酸化物を吸収除去すると共に、吸収塔内における吸収液のｐＨに応じて吸収塔内へ供給される吸収剤スラリーの流量を調整するようにし、更に、吸収剤の活性低下をなくすために中和剤を吸収塔内へ注入し、該中和剤の吸収塔内への注入時並びに注入停止時における吸収液のｐＨの変動を抑制するために前記吸収剤スラリーの流量を調整するようにした排煙脱硫装置の吸収剤スラリー流量制御方法であって、
検出された脱硫ガス流量と吸収塔入口ＳＯ₂濃度とに基づき実際に必要となる必要吸収剤量を求め、検出された中和剤注入流量に基づいて求めた吸収剤減算量を前記必要吸収剤量から差し引いて補正吸収剤量を求めると共に、予め設定された設定ｐＨ値と検出された吸収液のｐＨとのｐＨ偏差をなくすための吸収剤換算量を求め、前記補正吸収剤量に吸収剤換算量を加えてｐＨ考慮必要吸収剤量を求め、該ｐＨ考慮必要吸収剤量と検出された吸収剤スラリー濃度とに基づき、前記中和剤注入流量を考慮した上で前記吸収液のｐＨを設定ｐＨ値に保持するのに必要となる設定吸収剤スラリー流量を求め、検出された吸収剤スラリー流量が設定吸収剤スラリー流量と等しくなるよう、制御を行うことを特徴とする排煙脱硫装置の吸収剤スラリー流量制御方法にかかるものである。
【００１３】
又、本発明は、吸収剤として炭酸カルシウムを用いた吸収液と排ガスとを吸収塔内で接触させることにより、排ガス中に含まれる硫黄酸化物を吸収除去すると共に、吸収塔内における吸収液のｐＨに応じて吸収塔内へ供給される吸収剤スラリーの流量を調整するようにし、更に、吸収剤の活性低下をなくすために中和剤を吸収塔内へ注入し、該中和剤の吸収塔内への注入時並びに注入停止時における吸収液のｐＨの変動を抑制するために前記吸収剤スラリーの流量を調整するようにした排煙脱硫装置の吸収剤スラリー流量制御装置であって、
吸収塔内における吸収液のｐＨを検出するｐＨ計と、脱硫ガス流量を検出する脱硫ガス流量計と、吸収塔入口ＳＯ₂濃度を検出する吸収塔入口ＳＯ₂濃度計と、吸収剤スラリー流量を検出する吸収剤スラリー流量計と、吸収剤スラリー濃度を検出する吸収剤スラリー濃度計と、吸収塔内へ注入される中和剤注入流量を検出する中和剤注入流量計と、吸収塔内へ供給される吸収剤スラリー流量を調節する流量調整弁と、
前記脱硫ガス流量と前記吸収塔入口ＳＯ₂濃度とに基づき実際に必要となる必要吸収剤量を求め、前記中和剤注入流量に基づいて求めた吸収剤減算量を前記必要吸収剤量から差し引いて補正吸収剤量を求めると共に、予め設定された設定ｐＨ値と前記吸収液のｐＨとのｐＨ偏差をなくすための吸収剤換算量を求め、前記補正吸収剤量に吸収剤換算量を加えてｐＨ考慮必要吸収剤量を求め、該ｐＨ考慮必要吸収剤量と前記吸収剤スラリー濃度とに基づき、前記中和剤注入流量を考慮した上で前記吸収液のｐＨを設定ｐＨ値に保持するのに必要となる設定吸収剤スラリー流量を求め、前記吸収剤スラリー流量が設定吸収剤スラリー流量と等しくなるよう、前記流量調整弁へ開度指令を出力する制御器と
を備えたことを特徴とする排煙脱硫装置の吸収剤スラリー流量制御装置にかかるものである。
【００１４】
上記手段によれば、以下のような作用が得られる。
【００１５】
本発明の排煙脱硫装置の吸収剤スラリー流量制御方法においては、検出された脱硫ガス流量と吸収塔入口ＳＯ₂濃度とに基づき実際に必要となる必要吸収剤量が求められ、検出された中和剤注入流量に基づいて求めた吸収剤減算量が前記必要吸収剤量から差し引かれて補正吸収剤量が求められると共に、予め設定された設定ｐＨ値と検出された吸収液のｐＨとのｐＨ偏差をなくすための吸収剤換算量が求められ、前記補正吸収剤量に吸収剤換算量が加えられてｐＨ考慮必要吸収剤量が求められ、該ｐＨ考慮必要吸収剤量と検出された吸収剤スラリー濃度とに基づき、前記中和剤注入流量を考慮した上で前記吸収液のｐＨを設定ｐＨ値に保持するのに必要となる設定吸収剤スラリー流量が求められ、検出された吸収剤スラリー流量が設定吸収剤スラリー流量と等しくなるよう、制御が行われる。
【００１６】
又、本発明の排煙脱硫装置の吸収剤スラリー流量制御装置においては、制御器において、脱硫ガス流量計で検出された脱硫ガス流量と吸収塔入口ＳＯ₂濃度計で検出された吸収塔入口ＳＯ₂濃度とに基づき実際に必要となる必要吸収剤量が求められ、中和剤注入流量計で検出された中和剤注入流量に基づいて求めた吸収剤減算量が前記必要吸収剤量から差し引かれて補正吸収剤量が求められると共に、予め設定された設定ｐＨ値とｐＨ計で検出された吸収液のｐＨとのｐＨ偏差をなくすための吸収剤換算量が求められ、前記補正吸収剤量に吸収剤換算量が加えられてｐＨ考慮必要吸収剤量が求められ、該ｐＨ考慮必要吸収剤量と前記吸収剤スラリー濃度とに基づき、前記中和剤注入流量を考慮した上で前記吸収液のｐＨを設定ｐＨ値に保持するのに必要となる設定吸収剤スラリー流量が求められ、前記吸収剤スラリー流量が設定吸収剤スラリー流量と等しくなるよう、前記流量調整弁へ開度指令が出力され、該流量調整弁の開度が調節され、前記吸収剤スラリー流量が設定吸収剤スラリー流量と等しくなるよう制御が行われる。
【００１７】
この結果、本発明の排煙脱硫装置の吸収剤スラリー流量制御方法及び装置においては、中和剤注入流量を考慮した上で前記吸収液のｐＨが設定ｐＨ値に保持される形となるため、中和剤を吸収塔内に注入した場合に、吸収塔内における吸収液のｐＨが急激に上昇したりすることがなくなると共に、前記中和剤の吸収塔内への注入を停止した場合に、吸収塔内における吸収液のｐＨが急激に下降してしまうようなこともなくなり、吸収塔内における吸収液のｐＨの変動が抑えられ、脱硫性能も安定する。
【００１８】
【発明の実施の形態】
以下、本発明の実施の形態を図示例と共に説明する。
【００１９】
図１及び図２は本発明を実施する形態の一例であって、図中、図４及び図５と同一の符号を付した部分は同一物を表わしており、基本的な構成は図４及び図５に示す従来のものと同様であるが、本図示例の特徴とするところは、図１及び図２に示す如く、吸収塔３内へ注入される中和剤注入流量Ｃを検出する中和剤注入流量計３５と、該中和剤注入流量計３５で検出された中和剤注入流量Ｃに基づき吸収剤減算量３６を求めて出力する関数発生器３７と、該関数発生器３７から出力される吸収剤減算量３６が変化した場合に、その変化率を設定値以下の範囲内に制限する処理を行って吸収剤減算量３６’を出力する変化率制限器３８と、乗算器２１から出力される必要吸収剤量２０から前記吸収剤減算量３６’を差し引いて補正吸収剤量２０’を加算器２７へ出力する減算器３９とを追加装備した点にある。
【００２０】
前記関数発生器３７には、図３に示すような関数が入力されており、該関数は、中和剤注入流量Ｃの増減に対し略比例させて吸収剤減算量３６を増減させることを表わしている。
【００２１】
尚、例えば、吸収塔３へ中和剤として２５％濃度の苛性ソーダ（ＮａＯＨ）をＱ₀［ｋｇ／ｈ］注入している場合、吸収剤減算量３６（Ｑ₁［ｋｇ／ｈ］）は、
【数１】
Ｑ₁＝（Ｑ₀×０．２５×１００）／（２×４０）［ｋｇ／ｈ］
という計算式によって求めることもできる。
【００２２】
これは、吸収塔３へ流入してくるＳＯ₂によって生じるＨ₂ＳＯ₄を１［ｍｏｌ］中和するためには、吸収剤がＣａＣＯ₃の場合１［ｍｏｌ］で足りるのに対し、ＮａＯＨの場合２［ｍｏｌ］が必要となり、２５％濃度の苛性ソーダ中にはＮａＯＨが
（Ｑ₀×０．２５×１０００）／４０［ｍｏｌ］
含まれており（但し、４０はＮａＯＨの分子量である。）、これを吸収剤としてのＣａＣＯ₃量に換算すると
【数２】

となるためである。（但し、１／２は中和に必要なＮａＯＨとＣａＣＯ₃のｍｏｌ数の比であり、又、１００はＣａＣＯ₃の分子量である。）
【００２３】
次に、上記図示例の作動を説明する。
【００２４】
排煙脱硫装置の運転時には、ｐＨ計７で検出された吸収液１のｐＨと、脱硫ガス流量計９で検出された脱硫ガス流量Ａと、吸収塔入口ＳＯ₂濃度計１０で検出された吸収塔入口ＳＯ₂濃度Ｂと、吸収剤スラリー流量計１２で検出された吸収剤スラリー流量Ｄと、吸収剤スラリー濃度計１３で検出された吸収剤スラリー濃度Ｅと、中和剤注入流量計３５で検出された中和剤注入流量Ｃとが制御器６へ入力され、該制御器６の乗算器１５において前記吸収塔入口ＳＯ₂濃度計１０で検出された吸収塔入口ＳＯ₂濃度Ｂに対して設定脱硫率を掛けることにより、脱硫ＳＯ₂濃度１４が求められて乗算器１７へ出力され、該乗算器１７において前記脱硫ガス流量計９で検出された脱硫ガス流量Ａに対して前記乗算器１５から出力される脱硫ＳＯ₂濃度１４を掛けることにより、排ガス中から除去するＳＯ₂量１６が求められて乗算器１９へ出力され、該乗算器１９において前記乗算器１７から出力されるＳＯ₂量１６に対して（吸収剤量／ＳＯ₂量）の値を掛けることにより、吸収剤量１８が求められて乗算器２１へ出力され、該乗算器２１において前記乗算器１９から出力される吸収剤量１８に対して設定吸収剤過剰率を掛けることにより、実際に必要となる必要吸収剤量２０が求められて減算器３９へ出力される。
【００２５】
制御器６の関数発生器３７においては、中和剤注入流量計３５で検出された中和剤注入流量Ｃに基づき吸収剤減算量３６が求められて変化率制限器３８へ出力され、該変化率制限器３８において前記関数発生器３７から出力される吸収剤減算量３６が変化した場合に、その変化率を設定値以下の範囲内に制限する処理が行われて吸収剤減算量３６’が前記減算器３９へ出力され、該減算器３９において前記乗算器２１から出力される必要吸収剤量２０から前記吸収剤減算量３６’が差し引かれて補正吸収剤量２０’が加算器２７へ出力される。
【００２６】
又、制御器６の減算器２３においては、予め設定された設定ｐＨ値と前記ｐＨ計７で検出された吸収液１のｐＨとの差が求められてｐＨ偏差２２が比例積分調節器２５へ出力され、該比例積分調節器２５において前記減算器２３から出力されるｐＨ偏差２２が比例積分処理され該ｐＨ偏差２２をなくすための吸収剤換算量２４が前記加算器２７へ出力され、該加算器２７において前記減算器３９から出力される補正吸収剤量２０’に対して前記比例積分調節器２５から出力される吸収剤換算量２４を加えることにより、ｐＨ考慮必要吸収剤量２６が求められて除算器２９へ出力され、該除算器２９において前記加算器２７から出力されるｐＨ考慮必要吸収剤量２６を前記吸収剤スラリー濃度計１３で検出された吸収剤スラリー濃度Ｅで割ることにより、設定吸収剤スラリー流量２８が求められて減算器３１へ出力され、該減算器３１において前記除算器２９から出力される設定吸収剤スラリー流量２８と前記吸収剤スラリー流量計１２で検出された吸収剤スラリー流量Ｄとの差が求められ、吸収剤スラリー偏差３０が比例積分調節器３３へ出力され、該比例積分調節器３３において前記減算器３１から出力される吸収剤スラリー偏差３０が比例積分処理され該吸収剤スラリー偏差３０をなくすための開度指令３２が流量調整弁８へ出力され、該流量調整弁８の開度が調節され、前記吸収剤スラリー流量Ｄが設定吸収剤スラリー流量２８と等しくなるよう制御が行われる。
【００２７】
この結果、前記中和剤注入流量Ｃを考慮した上で前記吸収液１のｐＨが設定ｐＨ値に保持される形となるため、中和剤を吸収塔３内に注入した場合に、吸収塔３内における吸収液１のｐＨが急激に上昇したりすることがなくなると共に、前記中和剤の吸収塔３内への注入を停止した場合に、吸収塔３内における吸収液１のｐＨが急激に下降してしまうようなこともなくなり、吸収塔３内における吸収液１のｐＨの変動が抑えられ、脱硫性能も安定する。
【００２８】
こうして、中和剤の吸収塔３内への注入時並びに注入停止時における吸収液１のｐＨの変動を抑制し得、脱硫性能の安定化を図り得る。
【００２９】
尚、本発明の排煙脱硫装置の吸収剤スラリー流量制御方法及び装置は、上述の図示例にのみ限定されるものではなく、本発明の要旨を逸脱しない範囲内において種々変更を加え得ることは勿論である。
【００３０】
【発明の効果】
以上、説明したように本発明の排煙脱硫装置の吸収剤スラリー流量制御方法及び装置によれば、中和剤の吸収塔内への注入時並びに注入停止時における吸収液のｐＨの変動を抑制し得、脱硫性能の安定化を図り得るという優れた効果を奏し得る。
【図面の簡単な説明】
【図１】本発明を実施する形態の一例の全体概要構成図である。
【図２】本発明を実施する形態の一例の制御ブロック図である。
【図３】図２に示す関数発生器に設定されている関数を表わす線図である。
【図４】従来例の全体概要構成図である。
【図５】従来例の制御ブロック図である。
【符号の説明】
１吸収液
３吸収塔
６制御器
７ｐＨ計
８流量調整弁
９脱硫ガス流量計
１０吸収塔入口ＳＯ₂濃度計
１２吸収剤スラリー流量計
１３吸収剤スラリー濃度計
２０必要吸収剤量
２０’ 補正吸収剤量
２２ｐＨ偏差
２４吸収剤換算量
２６ｐＨ考慮必要吸収剤量
２８設定吸収剤スラリー流量
３２開度指令
３５中和剤注入流量計
３６’ 吸収剤減算量
３７関数発生器
３８変化率制限器
３９減算器
Ａ脱硫ガス流量
Ｂ吸収塔入口ＳＯ₂濃度
Ｃ中和剤注入流量
Ｄ吸収剤スラリー流量
Ｅ吸収剤スラリー濃度[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an absorbent slurry flow rate control method and apparatus for a flue gas desulfurization apparatus.
[0002]
[Prior art]
As shown in FIG. 4, a flue gas desulfurization apparatus using calcium carbonate (CaCO ₃ ) as an absorbent is generally formed with a liquid reservoir 1a of the absorbent 1 at the bottom and a number of spray nozzles 2 at the top. Absorbing tower 3 provided, a plurality of circulation pumps 4 for pumping up the absorbing liquid 1 in the liquid reservoir 1 a of the absorbing tower 3 and spraying it from the spray nozzle 2, and a liquid reservoir 1 a of the absorbing tower 3 And an oxidizing air blower 5 for supplying the air for oxidation.
[0003]
In the case of the flue gas desulfurization apparatus as described above, the absorbing liquid 1 is circulated while being sprayed from the spray nozzle 2 by the operation of the circulation pump 4, and the exhaust gas sent to the absorption tower 3 from a coal fired boiler or the like not shown is The SO ₂ (sulfur oxide) is absorbed and removed by contact with the absorbing liquid 1 sprayed from the spray nozzle 2 and then discharged to the outside.
[0004]
On the other hand, a part of the absorbing liquid 1 that has absorbed SO ₂ from the exhaust gas is recovered as gypsum slurry from the bottom of the liquid reservoir 1a of the absorption tower 3, and water is removed from the gypsum slurry so that gypsum is generated. It has become.
[0005]
The absorber 3 is supplied with a required amount of absorbent slurry by appropriately controlling the opening degree of the flow rate adjusting valve 8 as necessary. A pH meter 7 that detects the pH (pH) of the absorbent 1 in the absorption tower 3, a desulfurization gas flow meter 9 that detects the desulfurization gas flow rate A, and an absorption tower inlet SO ₂ that detects the absorption tower inlet SO ₂ concentration B. A densitometer 10, an absorbent slurry flow meter 12 that detects the absorbent slurry flow rate D, and an absorbent slurry concentration meter 13 that detects the absorbent slurry concentration E, and are detected by the desulfurization gas flow meter 9. The desulfurization gas flow rate A, the absorption tower inlet SO ₂ concentration B detected by the absorption tower inlet SO ₂ concentration meter 10, the pH of the absorbent 1 detected by the pH meter 7, and the absorbent slurry concentration meter 13 Absorbent slurry concentration detected in Based on the above, a set absorbent slurry flow rate 28 (see FIG. 5) required to maintain the pH of the absorbent 1 at the set pH value is obtained, and the absorbent slurry flow rate D is set to the set absorbent slurry flow rate 28. A controller 6 that outputs an opening degree command 32 to the flow rate adjusting valve 8 is provided so as to be equal.
[0006]
As shown in FIG. 5, the controller multiplies the absorption tower inlet SO ₂ concentration B detected by the absorption tower inlet SO ₂ concentration meter 10 by a set desulfurization rate (for example, 90%), thereby desulfurizing SO 2. A multiplier 15 for obtaining and outputting _two concentrations 14;
Multiplication for obtaining and outputting the SO ₂ amount 16 to be removed from the exhaust gas by multiplying the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9 by the desulfurization SO ₂ concentration 14 output from the multiplier 15. Container 17;
A multiplier 19 that obtains and outputs an absorbent amount 18 by multiplying the SO ₂ amount 16 output from the multiplier 17 by a value of (absorbent amount / SO ₂ amount);
A multiplier 21 that obtains and outputs the necessary amount 20 of the absorbent that is actually required by multiplying the amount of absorbent 18 that is output from the multiplier 19 by a set absorbent excess rate (for example, 1.02); ,
A subtractor 23 for obtaining a difference between a preset pH value (for example, 5.0) set in advance and the pH of the absorbent 1 detected by the pH meter 7 and outputting a pH deviation 22;
A proportional-plus-integral controller 25 for outputting an absorbent conversion amount 24 converted to an absorbent amount for eliminating the pH deviation 22 by proportionally integrating the pH deviation 22 output from the subtractor 23;
By adding an absorbent conversion amount 24 converted to the amount of absorbent output from the proportional-plus-integration controller 25 to the required amount of absorbent 20 output from the multiplier 21, the pH-considered required absorbent amount 26 is obtained. An adder 27 to obtain and output;
A divider that obtains and outputs a set absorbent slurry flow rate 28 by dividing the absorbent-considered absorbent amount 26 output from the adder 27 by the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13. 29,
A subtractor 31 for calculating a difference between the set slurry flow rate 28 outputted from the divider 29 and the absorbent slurry flow rate D detected by the absorbent slurry flow meter 12 and outputting an absorbent slurry deviation 30;
And a proportional integral controller 33 for outputting an opening degree command 32 of the flow rate adjusting valve 8 for eliminating the absorbent slurry deviation 30 by proportionally integrating the absorbent slurry deviation 30 output from the subtractor 31. It has the composition which becomes.
[0007]
During the operation of the flue gas desulfurization apparatus, the pH of the absorption liquid 1 detected by the pH meter 7, the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9, and the absorption tower inlet SO ₂ concentration meter 10 were detected. The absorption tower inlet SO ₂ concentration B, the absorbent slurry flow rate D detected by the absorbent slurry flow meter 12, and the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13 are input to the controller 6, By multiplying the absorption tower inlet SO ₂ concentration B detected by the absorption tower inlet SO ₂ concentration meter 10 in the multiplier 15 of the controller 6 by the set desulfurization rate, the desulfurization SO ₂ concentration 14 is obtained and multiplied. The desulfurization gas flow rate A detected by the desulfurization gas flow meter 9 in the multiplier 17 is multiplied by the desulfurization SO ₂ concentration 14 output from the multiplier 15 to be removed from the exhaust gas. SO ₂ amount 6 is outputted to the multiplier 19 is determined by applying against SO ₂ amount 16 outputted from the multiplier 17 in this multiplier 19 the value of (absorbent weight / SO ₂ volume), absorbent The amount 18 is obtained and output to the multiplier 21. In the multiplier 21, the necessary amount of absorption that is actually required is obtained by multiplying the absorbent amount 18 output from the multiplier 19 by the set absorbent excess rate. While the dosage 20 is obtained and output to the adder 27, the difference between the preset pH value preset in the subtractor 23 and the pH of the absorbing liquid 1 detected by the pH meter 7 is obtained to determine the pH deviation. 22 is output to the proportional-plus-integral adjuster 25, and the proportional-plus-integral adjuster (the adjuster that performs feedback control calculation) 25 performs proportional-integral processing on the pH deviation 22 output from the subtractor 23, and the pH deviation 22 is reduced. Na Absorbent conversion amount 24 converted to an absorbent amount for output is output to an adder 27, and from the proportional integral controller 25 to the required absorbent amount 20 output from the multiplier 21 in the adder 27. By adding the absorbent conversion amount 24 converted to the output absorbent amount, a pH-considered absorbent amount 26 is obtained and output to the divider 29, and is output from the adder 27 in the divider 29. By dividing the pH-required absorbent amount 26 by the absorbent slurry concentration meter 13 detected by the absorbent slurry concentration meter 13, a set absorbent slurry flow rate 28 is obtained and output to the subtractor 31. The difference between the set absorbent slurry flow rate 28 output from the divider 29 and the absorbent slurry flow rate D detected by the absorbent slurry flow meter 12 is obtained, and the absorbent slurry The deviation 30 is output to the proportional-plus-integral controller 33, and the proportional-plus-integral regulator 33 performs proportional-integral processing on the absorbent slurry deviation 30 output from the subtractor 31 to eliminate the absorbent slurry deviation 30. 32 is output to the flow rate adjusting valve 8, the opening degree of the flow rate adjusting valve 8 is adjusted, and the control is performed so that the absorbent slurry flow rate D becomes equal to the set absorbent slurry flow rate 28. The pH is maintained at the set pH value.
[0008]
As described above, as long as the pH of the absorption liquid 1 in the absorption tower 3 is controlled to be a set pH value, the sulfur content in the exhaust gas and the calcium in the absorbent are normally reacted one-on-one. However, the amount of unreacted absorbent is almost zero, and the exhaust gas is reliably desulfurized, but impurities that inhibit the reaction with the sulfur are attached around the absorbent, and the sulfur content in the exhaust gas is absorbed for some reason. When the agent no longer reacts (so-called a decrease in the activity of the absorbent occurs), the exhaust gas is not sufficiently desulfurized and the desulfurization performance may be reduced.
[0009]
Therefore, in the prior art, in order to prevent the decrease in the activity of the absorbent, or in order to eliminate the decrease in the activity of the absorbent, as shown in FIG. By injecting a neutralizing agent such as caustic soda (NaOH) by appropriately opening the neutralizing agent injection valve 34, the activity of the absorbent is reduced and the reaction between the sulfur content in the exhaust gas and the absorbent is promoted. ing.
[0010]
[Problems to be solved by the invention]
By the way, the neutralizing agent such as caustic soda is alkali like the absorbent and has the effect of raising the pH. Therefore, when the neutralizing agent is injected into the absorption tower 3 as described above, the absorbent in the absorption tower 3 While the pH of 1 suddenly rises, when the injection of the neutralizing agent into the absorption tower 3 is stopped, the pH of the absorption liquid 1 in the absorption tower 3 drops rapidly, and the absorption tower 3 In this case, the pH of the absorbent 1 becomes unstable, and the desulfurization performance fluctuates.
[0011]
In view of such circumstances, the present invention is a flue gas desulfurization apparatus that can suppress fluctuations in the pH of the absorbing liquid when the neutralizing agent is injected into the absorption tower and when the injection is stopped, and can stabilize the desulfurization performance. It is an object of the present invention to provide an absorbent slurry flow rate control method and apparatus.
[0012]
[Means for Solving the Problems]
The present invention absorbs and removes sulfur oxides contained in the exhaust gas by bringing the absorption liquid using calcium carbonate as the absorbent into contact with the exhaust gas in the absorption tower, and adjusts the pH of the absorption liquid in the absorption tower. Accordingly, the flow rate of the absorbent slurry supplied into the absorption tower is adjusted, and a neutralizing agent is injected into the absorption tower in order to eliminate the decrease in the activity of the absorbent. An absorbent slurry flow rate control method for a flue gas desulfurization apparatus that adjusts the flow rate of the absorbent slurry in order to suppress fluctuations in the pH of the absorbent liquid at the time of injection into and at the time of injection stop,
Based on the detected desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration, the necessary amount of absorbent that is actually required is obtained, and the subtracted amount of absorbent obtained based on the detected neutralizer injection flow rate is used as the necessary absorbent. The amount of the corrected absorbent is calculated by subtracting from the amount, and an equivalent amount of the absorbent for eliminating the pH deviation between the preset pH value set in advance and the detected pH of the absorbing solution is obtained. Add the conversion amount to obtain the pH-required absorbent amount, and based on the pH-required absorbent amount and the detected absorbent slurry concentration, consider the neutralizer injection flow rate and adjust the pH of the absorbent. A flue gas desulfurization apparatus characterized in that a set absorbent slurry flow rate required to maintain a set pH value is obtained, and control is performed so that the detected absorbent slurry flow rate becomes equal to the set absorbent slurry flow rate. Absorbent slurry flow It relates to a control method.
[0013]
Further, the present invention absorbs and removes sulfur oxides contained in the exhaust gas by bringing the absorption liquid using calcium carbonate as the absorbent into contact with the exhaust gas in the absorption tower. The flow rate of the absorbent slurry supplied into the absorption tower is adjusted according to the pH, and a neutralizing agent is injected into the absorption tower to eliminate the decrease in the activity of the absorbent, and the neutralizing agent is absorbed. An absorbent slurry flow control device of a flue gas desulfurization device that adjusts the flow rate of the absorbent slurry in order to suppress fluctuations in the pH of the absorbent at the time of injection into the tower and at the time of injection stop,
A pH meter for detecting the pH of the absorption liquid in the absorption tower, the desulfurization gas flow meter for detecting the desulfurized gas flow rate, and the absorption tower inlet SO ₂ concentration meter for detecting the absorption tower inlet SO ₂ concentration, the absorbent slurry flow rate An absorbent slurry flow meter for detecting, an absorbent slurry concentration meter for detecting the concentration of the absorbent slurry, a neutralizer injection flow meter for detecting the flow rate of the neutralizer injected into the absorption tower, and the absorption tower A flow rate adjusting valve for adjusting the flow rate of the supplied absorbent slurry;
The actual search of necessary absorbent amount required based on the desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration, minus the absorbent subtraction amount determined on the basis of the neutralizing agent infusion rate from the necessary absorbent amount To obtain a corrected absorbent amount, and determine an absorbent equivalent amount for eliminating a pH deviation between a preset pH value set in advance and the pH of the absorbent, and add the absorbent equivalent amount to the corrected absorbent amount. A pH-required absorbent amount is obtained, and based on the pH-required absorbent amount and the absorbent slurry concentration, the pH of the absorbent is maintained at a set pH value in consideration of the neutralizer injection flow rate. And a controller that outputs an opening degree command to the flow rate adjustment valve so as to obtain a set absorbent slurry flow rate required for the flow rate, and to make the absorbent slurry flow rate equal to the set absorbent slurry flow rate. Absorption of flue gas desulfurization equipment Those according to slurry flow controller.
[0014]
According to the above means, the following operation can be obtained.
[0015]
In the absorbent slurry flow rate control method of the flue gas desulfurization apparatus of the present invention, the required amount of absorbent that is actually required is determined based on the detected desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration. The absorbent subtraction amount obtained based on the sump injection flow rate is subtracted from the necessary absorbent amount to obtain the corrected absorbent amount, and the pH between the preset set pH value and the detected pH of the absorbent solution Absorbent equivalent for eliminating deviation is determined, and the amount of absorbent in consideration of pH is calculated by adding the amount of equivalent of absorbent to the corrected amount of absorbent, and the detected amount of absorbent in consideration of the pH in consideration of the necessary amount of absorbent. Based on the slurry concentration, the set absorbent slurry flow rate required to maintain the pH of the absorbent at the set pH value in consideration of the neutralizer injection flow rate is obtained, and the detected absorbent slurry flow rate Set absorbent To be equal to Larry flow control.
[0016]
Further, in the absorbent slurry flow control device of the flue gas desulfurization apparatus of the present invention, in the controller, the desulfurization gas flow rate detected by the desulfurization gas flow meter and the absorption tower inlet SO detected by the absorption tower inlet SO ₂ concentration meter. _{2 The} required amount of absorbent that is actually required is calculated based on the concentration, and the subtracted amount of absorbent determined based on the neutralizer injection flow rate detected by the neutralizer injection flow meter is subtracted from the required amount of absorbent. The corrected absorbent amount is obtained, and an equivalent amount of absorbent for eliminating a pH deviation between the preset pH value set in advance and the pH of the absorbent detected by the pH meter is obtained. The amount of the absorbent in consideration of the pH is obtained by adding the amount of the absorbent in consideration of the pH, and the amount of the absorbent in consideration of the neutralizing agent injection flow rate based on the amount of the pH-considered necessary absorbent and the concentration of the slurry of the absorbent. At the set pH value An opening command is output to the flow rate adjustment valve so that a set absorbent slurry flow rate required for the flow rate is obtained, and the absorbent slurry flow rate becomes equal to the set absorbent slurry flow rate. Control is performed so that the absorbent slurry flow rate becomes equal to the set absorbent slurry flow rate.
[0017]
As a result, in the absorbent slurry flow rate control method and apparatus of the flue gas desulfurization apparatus of the present invention, since the pH of the absorbent is maintained at the set pH value in consideration of the neutralizer injection flow rate, When the neutralizer is injected into the absorption tower, the pH of the absorption liquid in the absorption tower does not increase rapidly, and when the injection of the neutralizer into the absorption tower is stopped, The pH of the absorption liquid in the absorption tower is not suddenly lowered, the fluctuation of the pH of the absorption liquid in the absorption tower is suppressed, and the desulfurization performance is stabilized.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
1 and 2 show an example of an embodiment of the present invention. In the figure, the same reference numerals as those in FIGS. 4 and 5 denote the same components, and the basic configuration is shown in FIGS. Although it is the same as the conventional one shown in FIG. 5, the feature of this example is to detect the neutralizing agent injection flow rate C injected into the absorption tower 3 as shown in FIG. 1 and FIG. The sum generator injection flow meter 35, the function generator 37 for obtaining and outputting the absorbent subtraction amount 36 based on the neutralizer injection flow rate C detected by the neutralizer injection flow meter 35, and the function generator 37 A change rate limiter 38 for outputting an absorbent subtraction amount 36 ′ by performing a process of limiting the change rate within a range equal to or less than a set value when the output amount of the absorbent subtraction amount 36 changes, and a multiplier 21. Is subtracted from the absorbent subtraction amount 36 'from the necessary absorbent amount 20 output from the corrected absorbent amount 20'. Lies in that additionally equipped with a subtracter 39 for outputting to the adder 27.
[0020]
A function as shown in FIG. 3 is input to the function generator 37, and this function indicates that the absorbent subtraction amount 36 is increased or decreased in proportion to the increase or decrease of the neutralizing agent injection flow rate C. ing.
[0021]
For example, when 25% concentration of caustic soda (NaOH) is injected into the absorption tower 3 as Q ₀ [kg / h], the absorbent subtraction amount 36 (Q ₁ [kg / h]) is
[Expression 1]
Q ₁ = (Q ₀ × 0.25 × 100) / (2 × 40) [kg / h]
It can also be calculated by the following formula.
[0022]
This is because, in order to neutralize 1 [mol] of H ₂ SO ₄ generated by SO ₂ flowing into the absorption tower 3, 1 [mol] is sufficient when the absorbent is CaCO ₃ , whereas NaOH In this case, 2 [mol] is required, and NaOH is (Q ₀ × 0.25 × 1000) / 40 [mol] in 25% caustic soda.
It is included (however, 40 is the molecular weight of NaOH). When this is converted into the amount of CaCO ₃ as an absorbent,

It is because it becomes. (However, 1/2 is the ratio of the number of moles of NaOH and CaCO ₃ required for neutralization, and 100 is the molecular weight of CaCO _3. )
[0023]
Next, the operation of the illustrated example will be described.
[0024]
During operation of the flue gas desulfurization apparatus, the pH of the absorbent 1 detected by the pH meter 7, the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9, and the absorption detected by the absorption tower inlet SO ₂ concentration meter 10. With the tower inlet SO ₂ concentration B, the absorbent slurry flow rate D detected by the absorbent slurry flow meter 12, the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13, and the neutralizing agent injection flow meter 35 The detected neutralizing agent injection flow rate C is input to the controller 6, and with respect to the absorption tower inlet SO ₂ concentration B detected by the absorption tower inlet SO ₂ concentration meter 10 in the multiplier 15 of the controller 6. By multiplying the set desulfurization rate, the desulfurization SO ₂ concentration 14 is obtained and output to the multiplier 17, and the multiplier 15 is applied to the desulfurization gas flow rate A detected by the desulfurization gas flow meter 9 in the multiplier 17. desulfurization SO ₂ concentration of 14 output from By multiplying, SO ₂ amount 16 to be removed from the exhaust gas is output to the multiplier 19 is determined with respect to SO ₂ amount 16 outputted from the multiplier 17 in the multiplier 19 (absorbent amount / SO ₂ ), the amount of the absorbent 18 is obtained and output to the multiplier 21. In the multiplier 21, the set absorbent excess rate with respect to the amount of absorbent 18 output from the multiplier 19 , The required amount of absorbent 20 that is actually required is obtained and output to the subtractor 39.
[0025]
In the function generator 37 of the controller 6, the absorbent subtraction amount 36 is obtained based on the neutralizing agent injection flow rate C detected by the neutralizing agent injection flow meter 35, and is output to the change rate limiter 38. When the absorbent subtraction amount 36 output from the function generator 37 is changed in the rate limiter 38, processing for limiting the change rate to a range equal to or less than the set value is performed, and the absorbent subtraction amount 36 ′ is obtained. Output to the subtractor 39, and the subtractor 39 subtracts the absorbent subtraction amount 36 ′ from the required absorbent amount 20 output from the multiplier 21 to output the corrected absorbent amount 20 ′ to the adder 27. Is done.
[0026]
Further, in the subtractor 23 of the controller 6, the difference between the preset pH value set in advance and the pH of the absorbent 1 detected by the pH meter 7 is obtained, and the pH deviation 22 is transferred to the proportional integral controller 25. The proportional deviation adjuster 25 outputs the pH deviation 22 output from the subtractor 23 to the proportional integration process, and the absorbent conversion amount 24 for eliminating the pH deviation 22 is output to the adder 27. By adding the absorbent conversion amount 24 output from the proportional-plus-integral controller 25 to the corrected absorbent amount 20 ′ output from the subtractor 39 in the device 27, the pH-required absorbent amount 26 is obtained. The output is taken to the divider 29, and the pH-required absorbent amount 26 outputted from the adder 27 in the divider 29 is divided by the absorbent slurry concentration E detected by the absorbent slurry concentration meter 13. Thus, the set absorbent slurry flow rate 28 is obtained and output to the subtractor 31, and the set absorbent slurry flow rate 28 output from the divider 29 and the absorbent slurry flow meter 12 are detected in the subtractor 31. The difference from the absorbent slurry flow rate D is obtained, and the absorbent slurry deviation 30 is output to the proportional-plus-integral adjuster 33, and the absorbent slurry deviation 30 output from the subtractor 31 in the proportional-plus-integral adjuster 33 is proportional to integral. An opening command 32 for processing and eliminating the absorbent slurry deviation 30 is output to the flow regulating valve 8, the opening of the flow regulating valve 8 is adjusted, and the absorbent slurry flow D is set to the set absorbent slurry flow 28. Control is performed so that
[0027]
As a result, since the pH of the absorption liquid 1 is maintained at the set pH value in consideration of the neutralization agent injection flow rate C, when the neutralization agent is injected into the absorption tower 3, the absorption tower The pH of the absorption liquid 1 in the absorption tower 3 does not increase rapidly, and when the injection of the neutralizing agent into the absorption tower 3 is stopped, the pH of the absorption liquid 1 in the absorption tower 3 rapidly increases. , The fluctuation of the pH of the absorbent 1 in the absorption tower 3 is suppressed, and the desulfurization performance is stabilized.
[0028]
In this way, fluctuations in the pH of the absorbent 1 when the neutralizing agent is injected into the absorption tower 3 and when the injection is stopped can be suppressed, and desulfurization performance can be stabilized.
[0029]
In addition, the absorbent slurry flow rate control method and apparatus of the flue gas desulfurization apparatus of the present invention is not limited to the above illustrated examples, and various modifications can be made without departing from the scope of the present invention. Of course.
[0030]
【The invention's effect】
As described above, according to the absorbent slurry flow rate control method and apparatus of the flue gas desulfurization apparatus of the present invention, it is possible to suppress fluctuations in the pH of the absorbent when the neutralizer is injected into the absorption tower and when the injection is stopped. It is possible to achieve an excellent effect that the desulfurization performance can be stabilized.
[Brief description of the drawings]
1 is an overall schematic configuration diagram of an example of an embodiment for carrying out the present invention;
FIG. 2 is a control block diagram illustrating an example of an embodiment of the present invention.
FIG. 3 is a diagram representing a function set in the function generator shown in FIG. 2;
FIG. 4 is an overall schematic configuration diagram of a conventional example.
FIG. 5 is a control block diagram of a conventional example.
[Explanation of symbols]
1 absorbing fluid 3 absorption tower 6 controller 7 pH eight flow regulating valve 9 desulfurized gas flowmeter 10 absorption tower inlet SO ₂ concentration meter 12 absorbent slurry flow meter 13 absorbent slurry concentration meter 20 must absorbent amount 20 'corrected absorption Agent amount 22 pH deviation 24 Absorbent conversion amount 26 Absorbable amount required for pH consideration 28 Set absorbent slurry flow rate 32 Opening command 35 Neutralizer injection flow meter 36 'Absorbent subtraction amount 37 Function generator 38 Change rate limiter 39 Subtractor A Desulfurization gas flow rate B Absorption tower inlet SO ₂ concentration C Neutralizer injection flow rate D Absorbent slurry flow rate E Absorber slurry concentration

Claims

Absorption liquid using calcium carbonate as an absorbent and exhaust gas are contacted in the absorption tower to absorb and remove sulfur oxides contained in the exhaust gas, and the absorption tower according to the pH of the absorption liquid in the absorption tower The flow rate of the absorbent slurry supplied to the inside is adjusted, and in order to eliminate the decrease in the activity of the absorbent, a neutralizing agent is injected into the absorption tower, and the neutralizing agent is injected into the absorption tower. And an absorbent slurry flow rate control method for a flue gas desulfurization apparatus that adjusts the flow rate of the absorbent slurry in order to suppress fluctuations in the pH of the absorbent when injection is stopped,
Based on the detected desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration, the necessary amount of absorbent that is actually required is obtained, and the subtracted amount of absorbent obtained based on the detected neutralizer injection flow rate is used as the necessary absorbent. The amount of the corrected absorbent is calculated by subtracting from the amount, and an equivalent amount of the absorbent for eliminating the pH deviation between the preset pH value set in advance and the detected pH of the absorbing solution is obtained. Add the conversion amount to obtain the pH-required absorbent amount, and based on the pH-required absorbent amount and the detected absorbent slurry concentration, consider the neutralizer injection flow rate and adjust the pH of the absorbent. A flue gas desulfurization apparatus characterized in that a set absorbent slurry flow rate required to maintain a set pH value is obtained, and control is performed so that the detected absorbent slurry flow rate becomes equal to the set absorbent slurry flow rate. Absorbent slurry flow Control method.

Absorption liquid using calcium carbonate as an absorbent and exhaust gas are contacted in the absorption tower to absorb and remove sulfur oxides contained in the exhaust gas, and the absorption tower according to the pH of the absorption liquid in the absorption tower The flow rate of the absorbent slurry supplied to the inside is adjusted, and in order to eliminate the decrease in the activity of the absorbent, a neutralizing agent is injected into the absorption tower, and the neutralizing agent is injected into the absorption tower. And an absorbent slurry flow rate control device of the flue gas desulfurization device that adjusts the flow rate of the absorbent slurry in order to suppress fluctuations in the pH of the absorbent when injection is stopped,
A pH meter for detecting the pH of the absorption liquid in the absorption tower, the desulfurization gas flow meter for detecting the desulfurized gas flow rate, and the absorption tower inlet SO ₂ concentration meter for detecting the absorption tower inlet SO ₂ concentration, the absorbent slurry flow rate An absorbent slurry flow meter for detecting, an absorbent slurry concentration meter for detecting the concentration of the absorbent slurry, a neutralizer injection flow meter for detecting the flow rate of the neutralizer injected into the absorption tower, and the absorption tower A flow rate adjusting valve for adjusting the flow rate of the supplied absorbent slurry;
The actual search of necessary absorbent amount required based on the desulfurization gas flow rate and the absorption tower inlet SO ₂ concentration, minus the absorbent subtraction amount determined on the basis of the neutralizing agent infusion rate from the necessary absorbent amount To obtain a corrected absorbent amount, and determine an absorbent equivalent amount for eliminating a pH deviation between a preset pH value set in advance and the pH of the absorbent, and add the absorbent equivalent amount to the corrected absorbent amount. A pH-required absorbent amount is obtained, and based on the pH-required absorbent amount and the absorbent slurry concentration, the pH of the absorbent is maintained at a set pH value in consideration of the neutralizer injection flow rate. And a controller that outputs an opening degree command to the flow rate adjustment valve so as to obtain a set absorbent slurry flow rate required for the flow rate, and to make the absorbent slurry flow rate equal to the set absorbent slurry flow rate. Absorption of flue gas desulfurization equipment Slurry flow controller.