JPH0578370B2 - - Google Patents
Info
- Publication number
- JPH0578370B2 JPH0578370B2 JP63282597A JP28259788A JPH0578370B2 JP H0578370 B2 JPH0578370 B2 JP H0578370B2 JP 63282597 A JP63282597 A JP 63282597A JP 28259788 A JP28259788 A JP 28259788A JP H0578370 B2 JPH0578370 B2 JP H0578370B2
- Authority
- JP
- Japan
- Prior art keywords
- exhaust gas
- mercury
- concentration
- mercury concentration
- hypochlorite
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 claims description 33
- 229910052753 mercury Inorganic materials 0.000 claims description 33
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 claims description 26
- 238000000034 method Methods 0.000 claims description 15
- 238000004140 cleaning Methods 0.000 claims description 13
- 239000007800 oxidant agent Substances 0.000 claims description 8
- 238000013178 mathematical model Methods 0.000 claims 2
- 230000000694 effects Effects 0.000 claims 1
- 239000007788 liquid Substances 0.000 description 6
- 238000001816 cooling Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical compound ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Treating Waste Gases (AREA)
Description
［産業上の利用分野］
本発明は、ごみ焼却炉等から排出される排ガス
中の水銀濃度を制御する方法に関するものであ
る。
［従来の技術］
次亜塩素酸塩を添加した洗浄液と排ガスを接触
させて、排ガス中から水銀を除去する装置は以前
から考えられており、水銀除去方法に関する発明
として、洗浄液PHを所定の範囲に制御するもの、
次亜塩素酸塩が水銀と最もよく反応すべく、予冷
塔において排ガス温度を下げたのち、洗浄液と接
触させるものなどが提案されているが、いずれ
も、原ガス水銀濃度や原ガス還元成分濃度の変動
に対して、処理ガス水銀濃度を制御するものでは
ない。したがつて、処理ガス水銀濃度が作業環境
基準値（0.05mg／Ｎm3）を下廻る保証はなく、ま
た、原ガス水銀濃度が低い場合は、過剰な次亜塩
素酸塩を消費する可能性もある。
このようなプロセスに対して、最も一般的な制
御方法としては、処理ガス水銀濃度を計測し、こ
の値と目標値との偏差に応じて、操作量である次
亜塩素酸塩の流量を計算するPID制御方法が考え
られる。
［発明が解決しようとする課題］
しかしながら、このPID制御においては、次の
ような問題がある。
(1) 先ず、第１にはプロセスが有するむだ時間に
関するものである。第４図は次亜塩素酸塩の流
量に対する処理ガス水銀濃度のステツプ応答の
一例を示す線図である。第４図によれば、水銀
除去プロセスの動特性は、「むだ時間＋一次遅
れ」系で近似できることがわかる。第４図よ
り、むだ時間(L)≒3.5分、時定数(T)＝≒6.5分が
求められる。
このように、動特性がＬ／Ｔ≪１でない性質
をもつような制御対象を、汎用のPID制御で制
御することは困難で、PID制御で安定に運転す
るためには制御系のゲインを下げざるを得ず、
そのため偏差の解消に時間がかゝる。
(2) 第２のプロセスの非線形性の問題がある。第
５図は洗浄液中の酸化剤濃度に対する水銀除去
特性を示したもので、洗浄液中の酸化剤濃度が
高いほど水銀除去の割合が低下する非線形性が
あることがわかる。このため、制御系が不安定
にならないように、制御対象である水銀除去プ
ロセスのゲインが高いところで制御装置のゲイ
ンを調整しなければならない。この結果、処理
ガスの水銀濃度が低い領域では制御対象のゲイ
ンが低くなり、閉ループ系の一巡伝達関数のゲ
インが低下し、偏差の解消に時間がかゝる。
本発明は、上記の課題を解決すべくなされたも
ので、閉ループからのむだ時間が除外され、非線
形の問題も解消できる排ガス中の水銀濃度制御方
法をうることを目的としたものである。
［課題を解決するための手段］
先ず、制御対象である洗浄装置の動的モデルを
構成する。洗浄塔を循環している洗浄液ラインの
途中から添加される次亜塩素酸塩は、排ガス中の
水銀を除去する酸化剤となる。したがつて、次亜
塩素酸の流量が洗浄液中の酸化剤の濃度に関与
し、酸化剤が排ガス中の水銀と反応し、洗浄液中
に溶解して除去される。処理ガス中の水銀濃度
は、次亜塩素酸塩の流量、洗浄液中の酸化剤の濃
度と密接な関係があるので、この３つを変数とし
てモデル化すると、一般には非線形系であるた
め、ある定常点回りで線形化した次のように定式
化する。
ｄ／dtx1(t)
x2(t)＝
Ａ・x1(t)
x2(t)＋ｂ・ｕ（ｔ−Ｌ）
ｙ(t)＝Ｃ・x1(t)
x2(t)
……［１］
x1(t)：処理ガス水銀濃度［mg／Ｎm3］
x2(t)：洗浄液中の酸化剤濃度［ppm］
ｕ（ｔ−Ｌ）：次亜塩素酸塩流量［c.c.／min］
ｙ(t)：観測量
Ｌ：むだ時間［min］
Ａ，ｂ，ｃ：パラメータ
ここで、処理ガス水銀濃度目標値に、実際値が
追従するように制御装置内に目標値と実際値の偏
差の積分項を導入する。
ｄ／dtx3(t)＝ｒ(t)−x1(t) ……［２］
x3(t)：偏差積分値［mg／Ｎm3・min］
ｒ(t)：処理ガス水銀濃度目標値［mg／Ｎm3］
したがつて、［１］、［２］式を合わせた拡大系
は、次のように表現される。
[Industrial Field of Application] The present invention relates to a method for controlling mercury concentration in exhaust gas discharged from a garbage incinerator or the like. [Prior Art] A device for removing mercury from exhaust gas by bringing the cleaning solution containing hypochlorite into contact with the exhaust gas has been considered for some time. what is controlled by,
In order for hypochlorite to react best with mercury, methods have been proposed in which the temperature of the exhaust gas is lowered in a pre-cooling tower and then brought into contact with the cleaning solution. It does not control the mercury concentration in the treated gas due to fluctuations in mercury. Therefore, there is no guarantee that the mercury concentration in the treated gas will be below the working environment standard value (0.05 mg/Nm 3 ), and if the raw gas mercury concentration is low, there is a possibility that excessive hypochlorite will be consumed. There is also. The most common control method for such processes is to measure the mercury concentration in the treated gas and calculate the flow rate of hypochlorite, which is the manipulated variable, according to the deviation between this value and the target value. A PID control method can be considered. [Problems to be Solved by the Invention] However, this PID control has the following problems. (1) First, the first problem is the dead time that the process has. FIG. 4 is a diagram showing an example of the step response of the mercury concentration in the treated gas to the flow rate of hypochlorite. According to FIG. 4, it can be seen that the dynamic characteristics of the mercury removal process can be approximated by a "dead time + first-order lag" system. From Figure 4, dead time (L) = 3.5 minutes and time constant (T) = 6.5 minutes. In this way, it is difficult to control a controlled object whose dynamic characteristics are not L/T << 1 using general-purpose PID control, and in order to operate stably with PID control, the gain of the control system must be lowered. I had no choice but to
Therefore, it takes time to eliminate the deviation. (2) There is a problem with the nonlinearity of the second process. FIG. 5 shows the mercury removal characteristics with respect to the oxidizing agent concentration in the cleaning liquid, and it can be seen that there is a non-linearity in that the higher the oxidizing agent concentration in the cleaning liquid, the lower the mercury removal rate. Therefore, in order to prevent the control system from becoming unstable, the gain of the control device must be adjusted when the gain of the mercury removal process to be controlled is high. As a result, in a region where the mercury concentration of the process gas is low, the gain of the controlled object becomes low, the gain of the closed loop transfer function decreases, and it takes time to eliminate the deviation. The present invention was made to solve the above problems, and aims to provide a method for controlling mercury concentration in exhaust gas that eliminates dead time from a closed loop and can also solve nonlinear problems. [Means for solving the problem] First, a dynamic model of the cleaning device to be controlled is constructed. Hypochlorite, which is added midway through the cleaning liquid line circulating through the cleaning tower, acts as an oxidizing agent to remove mercury from the exhaust gas. Therefore, the flow rate of hypochlorous acid affects the concentration of the oxidizing agent in the cleaning liquid, and the oxidizing agent reacts with mercury in the exhaust gas, dissolves in the cleaning liquid, and is removed. The mercury concentration in the process gas is closely related to the flow rate of hypochlorite and the concentration of the oxidizing agent in the cleaning solution, so if these three are modeled as variables, it is generally a nonlinear system, so It is formulated as follows, linearized around a stationary point. d/dtx 1 (t) x 2 (t)= A・x 1 (t) x 2 (t)+b・u(t−L) y(t)=C・x 1 (t) x 2 (t) ...[1] x 1 (t): Treated gas mercury concentration [mg/Nm 3 ] x 2 (t): Oxidizing agent concentration in cleaning liquid [ppm] u (t-L): Hypochlorite flow rate [ cc/min] y(t): Observable quantity L: Dead time [min] A, b, c: Parameters Here, the target value is set in the control device so that the actual value follows the target value of the treated gas mercury concentration. We introduce an integral term for the deviation of the actual value. d/dtx 3 (t)=r(t)−x 1 (t)...[2] x 3 (t): Deviation integral value [mg/Nm 3・min] r(t): Treated gas mercury concentration target Value [mg/Nm 3 ] Therefore, the expanded system combining equations [1] and [2] is expressed as follows.
【表】
Ａ￣
ｂ￣
〓x１(t)〓
[Table] A￣
b￣
〓x １ (t)〓
Claims (1)
加した洗浄液と接触させて除去し、排出される排
ガス中の水銀濃度を制御する方法において、 排出される排ガス中の水銀濃度と添加する次亜
塩素酸塩の流量を測定して洗浄液中の酸化剤濃度
を測定又は推定し、添加する次亜塩素酸塩の流量
の変動が排出される排ガス中の水銀濃度変動に影
響するまでの無駄時間をＬとするとき、前記測定
又は推定量、排ガス中の水銀濃度、次亜塩素酸塩
流量及び排出される排ガス中の水銀濃度の目標値
を入力として、前記Ｌだけ後に排出される排ガス
中の水銀濃度とその目標値との偏差を数式モデル
により推定し、前記推定されたＬだけ後に排出さ
れる排ガス中の水銀濃度と目標値との偏差をゼロ
に制御するように次亜塩素酸塩の流量を操作する
ことを特徴とする排ガス中の水銀濃度制御方法。 ２ 数式モデルが線形モデルより構成され、該線
形モデルのパラメータが排出される排ガス中の水
銀濃度によつて変化するように構成された請求項
１記載の排ガス中の水銀濃度制御方法。[Scope of Claims] 1. A method for controlling the concentration of mercury in the exhaust gas by contacting it with a cleaning solution containing hypochlorite to remove mercury in the exhaust gas containing mercury, comprising: The oxidizing agent concentration in the cleaning solution is measured or estimated by measuring the mercury concentration and the flow rate of the added hypochlorite, and the fluctuation in the flow rate of the added hypochlorite is determined by the fluctuation in the mercury concentration in the exhaust gas. When L is the dead time until the effect occurs, input the measured or estimated amount, the mercury concentration in the exhaust gas, the hypochlorite flow rate, and the target value of the mercury concentration in the exhaust gas to be discharged, and after the above L. The deviation between the mercury concentration in the exhaust gas discharged and its target value is estimated by a mathematical model, and the deviation between the mercury concentration in the exhaust gas discharged after the estimated L and the target value is controlled to zero. A method for controlling mercury concentration in exhaust gas, characterized by manipulating the flow rate of hypochlorite. 2. The method for controlling mercury concentration in exhaust gas according to claim 1, wherein the mathematical model is composed of a linear model, and the parameters of the linear model are configured to change depending on the mercury concentration in the exhaust gas to be discharged.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63282597A JPH02191526A (en) | 1988-10-11 | 1988-11-10 | Method for controlling mercury concentration in exhaust gas |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25390988 | 1988-10-11 | ||
| JP63-253909 | 1988-10-11 | ||
| JP63282597A JPH02191526A (en) | 1988-10-11 | 1988-11-10 | Method for controlling mercury concentration in exhaust gas |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02191526A JPH02191526A (en) | 1990-07-27 |
| JPH0578370B2 true JPH0578370B2 (en) | 1993-10-28 |
Family
ID=17257741
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63282597A Granted JPH02191526A (en) | 1988-10-11 | 1988-11-10 | Method for controlling mercury concentration in exhaust gas |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02191526A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104801152A (en) * | 2014-01-27 | 2015-07-29 | 阿尔斯通技术有限公司 | Mercury re-emission control |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4395315B2 (en) | 2003-04-11 | 2010-01-06 | 三菱重工業株式会社 | Method and system for removing mercury from exhaust gas |
| JP2007050334A (en) * | 2005-08-17 | 2007-03-01 | Ishikawajima Harima Heavy Ind Co Ltd | Exhaust gas purification method and facility |
| US7524473B2 (en) * | 2007-03-23 | 2009-04-28 | Alstom Technology Ltd | Method of mercury removal in a wet flue gas desulfurization system |
| JP2009208078A (en) * | 2009-06-16 | 2009-09-17 | Mitsubishi Heavy Ind Ltd | Method for treating mercury in tail gas, and treatment system for tail gas |
| JP7324159B2 (en) * | 2020-02-13 | 2023-08-09 | 株式会社東芝 | Acid gas removal device and removal method |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60235630A (en) * | 1984-05-07 | 1985-11-22 | Kawasaki Heavy Ind Ltd | Desulfurization or denitration method of waste gas |
| JPS61234914A (en) * | 1985-04-08 | 1986-10-20 | Nippon Kokan Kk <Nkk> | Controlling method for exhaust gas denitration facility |
-
1988
- 1988-11-10 JP JP63282597A patent/JPH02191526A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60235630A (en) * | 1984-05-07 | 1985-11-22 | Kawasaki Heavy Ind Ltd | Desulfurization or denitration method of waste gas |
| JPS61234914A (en) * | 1985-04-08 | 1986-10-20 | Nippon Kokan Kk <Nkk> | Controlling method for exhaust gas denitration facility |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104801152A (en) * | 2014-01-27 | 2015-07-29 | 阿尔斯通技术有限公司 | Mercury re-emission control |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02191526A (en) | 1990-07-27 |
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