JP3857460B2 - Denitration control device - Google Patents

Description

ここで、右辺第１項の反応の総量Ｒは脱硝装置に流入したＮＯxが反応した量であるから、入口ＮＯx量と脱硝率ηの積に外ならない。
【００２３】
一方、注入ＮＨ₃は入口ＮＯxに対してモル比ＳＭの割合で設定されるから、入口ＮＯxに対応するモル比ＳＭと脱硝率ηの差分が第２項のリークＮＨ₃に外ならない。すなわち、

であるから、結局、

である。
【００２４】
ここで、左辺に関して、ｎ時間経過後のＮＨ₃流量をＧ_NH3 ^in,n、右辺に関して、ｎ分後の入口ＮＯxの予想値をＮＯxⁿ、モル比ＳＭをＳＭⁿ、とする。このとき左辺と右辺第１項は現時点値とｎ時間経過後の値との平均値で置き換えて以下を得る。
【００２５】

これから分かることは、ＳＭⁿをｎ時間経過後の必要脱硝率ηⁿを得るに必要なモル比に設定しておけば、上式で決まるｎ時間経過後の注入ＮＨ₃量Ｇ_NH3 ^in,nによって必要な脱硝率ηⁿを得られる、ということである。
【００２６】
実際に計算するには、ｎ時間経過後の吸着量Ｃ_NH3 ⁿと現時点で吸着量Ｃ_NH3が必要である。このためには、以下のような実験的に知られた触媒の特性を適用する。すなわち、
モル比ＳＭ＝ｆｕｎｃ１（吸着量Ｃ_NH3，入口ＮＯx，運転条件）
及び
脱硝率η＝ｆｕｎｃ２（モル比ＳＭ，運転条件）
との関数関係を利用する。ここで、ｆｕｎｃ１とｆｕｎｃ２は表示された引数の関数を表現する記号である。これにより、現時点の脱硝率ηから現時点のモル比ＳＭ従って吸着量Ｃ_NH3を知ることができ、また、ｎ時間経過後については必要な脱硝率ηⁿを設定しておけば対応して、必要モル比ＳＭⁿ、必要吸着量Ｃ_NH3 ⁿが推算出来る。
【００２７】
以上の関係から、ｎ時間経過後において必要な脱硝率ηⁿを得るためのＮＨ₃流量が計算でき、それは上式をｎ／２で除算することから、

である。
【００２８】
図２には、この必要ＮＨ₃流量補正器３００の内容を詳細に示す。
【００２９】
（１）脱硝率計算値３４５の入力による関数発生器の出力としてモル比ＳＭ４１０を計算する。入口ＮＯx流量１０４とこのモル比ＳＭ４１０との積３５１を乗算器にて算出する。ここで脱硝率計算値３４５は入口ＮＯx濃度１０１と出口ＮＯx濃度１０７を脱硝率計算器に入力し、その出力として算出される。
【００３０】
（２）一方、ｎ時間経過後の必要脱硝率３０１の入力による関数発生器の出力としてｎ時間経過後の必要モル比ＳＭⁿ４２０を計算する。入口ＮＯx流量１０４とこのモル比ＳＭⁿ４２０との積３５３を乗算器にて算出する。
【００３１】
（３）上記２つの量を加算器にて加算し量３５５を算出する。すなわち加算量３５５とは、

である。
【００３２】
（４）一方で入口ＮＯx濃度１０１と出口ＮＯx濃度１０７を吸着ＮＨ₃量推算器３７０に入力して得られた現時点の吸着ＮＨ₃量推算値３２１をｎ時間経過後の吸着ＮＨ₃必要量推算値３３０から差し引き、この３３０から３２１を差し引いた量３６１を予め適切な値に設定されている予測スパンｎ３０２の半分の量（ｎ／２）で除算器により除算した量が３６３である。すなわち、

ここで、ｎ時間経過後の吸着ＮＨ₃必要量予測値３３０はｎ時間経過後の必要脱硝率３０１を関数発生器に入力してその出力として計算される。
【００３３】
また、吸着ＮＨ₃推算器３７０の計算内容は次の通りである。まず、モル比ＳＭが吸着ＮＨ₃、入口ＮＯxから次の実験的に知られた関数で決まる。
【００３４】
モル比ＳＭ＝ｆｕｃｎ１（吸着ＮＨ₃，入口ＮＯx）
すなわち、吸着ＮＨ₃は入口ＮＯxとモル比ＳＭを与えれば逆にこの関数から計算できる。
【００３５】
吸着ＮＨ₃＝ｆｕｎｃ１^-1（モル比ＳＭ，入口ＮＯx）
一方、脱硝率ηがこのモル比ＳＭから決まり、
脱硝率η＝ｆｕｃｎ２（モル比ＳＭ）
であるから、これも逆に、
モル比ＳＭ＝ｆｕｃｎ２^-1（脱硝率η）
と計算することができる。
【００３６】
従って、吸着ＮＨ₃は結局、

のように脱硝率ηと入口ＮＯxが分かれば計算される。
【００３７】
図２中の吸着ＮＨ₃推算器３７０には入口ＮＯx濃度１０１と出口ＮＯx濃度１０７が入力されているが、この二つの量から脱硝率ηが算定され、これと入口ＮＯx濃度１０１とから上記ｆｕｎｃ３の関数によって吸着ＮＨ₃が推算されている訳である。
【００３８】
（５）以上の（３）の量３５５と（５）の量３６３との和が量４７０である。すなわち、和４７０とは、入口ＮＯx流量１０４と脱硝率計算値３４５或いはｎ時間経過後の必要脱硝率３０１とのそれぞれの積３５１及び３５３と、吸着ＮＨ₃量に関する量、すなわち、ｎ時間経過後の必要吸着ＮＨ₃量予量値３３０と現時点の吸着ＮＨ₃量の推算値３２１との差分３６１を予測スパンｎの半分３４０で除した量と、を総和した量である。すなわち、

（６）このようにして計算した総和４７０を現時点でのＮＨ₃流量１１２と比較し減算器にて差を計算し、この差分が、必要ＮＨ₃流量補正値３０２として、必要ＮＨ₃流量補正器３００からの出力となる。すなわち、

と算出される。
【００３９】
本発明の制御装置による脱硝制御の結果を図３に示す。従来方式による制御結果に比べ、ｎ時間経過後にて必要な吸着ＮＨ₃量をベースに制御しているので、過脱硝が防げ、出口ＮＯx濃度の下限からの逸脱は回避され（ａ点）、対応してＮＨ₃注入量も最適化されておりリークＮＨ₃量の上限からの逸脱の回避（ｂ点）、またＮＨ₃注入量の最大流量も抑制されて（ｃ点）いる。
【００４０】
【発明の効果】
本発明では、ｎ時間経過後の必要ＮＨ₃吸着量をベースに制御するので過脱硝が防げて、
（１）出口ＮＯx濃度の下限からの逸脱は回避され、対応してＮＨ₃注入量も最適化されており
（２）リークＮＨ₃量の上限からの逸脱は回避され、
（３）ＮＨ₃注入量の最大流量も抑制されている、という効果がある。
【図面の簡単な説明】
【図１】本発明の実施形態に係る脱硝制御装置の全体構成を示す図である。
【図２】図１の必要ＮＨ₃流量補正器の内容を詳細に示す図である。
【図３】本発明の実施形態に係る制御装置による脱硝制御の結果のトレンドを示す図である。
【図４】従来技術に係る制御装置による脱硝制御結果のトレンドを示す図である。
【図５】従来技術に係る脱硝制御装置の内容を示す図である。
【符号の説明】
１０１ 入口ＮＯｘ濃度
１０２ 空気流量
１０３ 燃焼排ガス流量
１０４ 入口ＮＯｘ流量
１０５ 出口ＮＯｘ濃度設定値
１０６ 必要モル比
１０７ 出口ＮＯｘ濃度
１０８ 出口ＮＯｘ濃度偏差
１０９ モル比修正量
１１０ 修正モル比
１１１ 必要ＮＨ₃流量
１１２ ＮＨ₃流量
１１３ ＮＨ₃流量偏差
１１４ ＮＨ₃流量調節量
１１５ 現時点計測ベースの必要ＮＨ₃流量
２０１ 関数発生器
２０２ 減算器
２０３ 調節器
２０４ 乗算器
２０５ 加算器
３００ 必要ＮＨ₃流量補正器
３０１ ｎ時間経過後の必要脱硝率
３０２ 予測スパンｎ
３１０ 必要ＮＨ₃流量補正値[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a denitration control apparatus suitable for optimally controlling a system having a large chemical reaction delay such as a denitration apparatus such as a coal fired boiler.
[0002]
[Prior art]
The technical background of the present invention will be described. The denitration device here is a device that injects NH ₃ as a reducing agent into exhaust gas and reacts NH ₃ injected on the installed catalyst with NO x in the exhaust gas to form nitrogen and water.
[0003]
NH ₃ + NO + 1/4 · O ₂ → N ₂ + 3/2 · H ₂ O
The reaction NOx in the exhaust gas is indicated by the above equation and NH ₃ to be injected, since the nitrogen and water, basically, NH ₃ amount to be injected, to inject an amount corresponding to the NOx amount to be processed Become. In addition to being used for the reaction with NOx, the injected NH ₃ is adsorbed by an amount capable of being adsorbed on the catalyst surface. Therefore, if it is injected beyond that, it will flow out from the apparatus as leak NH ₃ . On the other hand, if the amount of NH ₃ to be injected is insufficient with respect to the amount of NOx to be processed, NOx cannot be completely processed, and the outlet NOx concentration cannot be reduced to a predetermined value or less.
[0004]
FIG. 5 shows a system diagram of a control apparatus according to the related art relating to a denitration control system including the denitration control apparatus according to the present invention. The outlet NOx concentration 107 is compared with the outlet NOx concentration set value 105 by the subtractor 202a, and a deviation, that is, an outlet NOx concentration deviation 108 is output. The outlet NOx concentration deviation 108 is input to a PI (proportional / integral) regulator 203 a, and its output is a molar ratio correction amount 109.
[0005]
On the other hand, the required molar ratio 106 is calculated by inputting the outlet NOx concentration set value 105 to the function generator 201b, and the corrected molar ratio 110 is calculated by adding this and the previous molar ratio correction amount 109 by the adder 205c. . The corrected molar ratio 110 is multiplied by the inlet NOx flow rate 104 and the multiplier 204b to obtain the required NH ₃ flow rate 111.
[0006]
The NH ₃ flow rate 112 is compared with the necessary NH ₃ flow rate 111 by the subtractor 202b to calculate a deviation, that is, an NH ₃ flow rate deviation 113, and this is input to the PI controller 203c, whereby an NH ₃ flow rate adjustment amount 114 is obtained. Raru. Here, the inlet NOx flow rate 104 is calculated as a result of multiplying the inlet NOx concentration 101 and the combustion exhaust gas flow rate 103 by the multiplier 204a, and the combustion exhaust gas flow rate 103 is an output of the air flow rate 102 by the function generator 201a. .
[0007]
FIG. 4 shows the result of controlling the outlet NOx concentration according to the prior art. Since the outlet NOx concentration 501 is not the NH ₃ injection amount 503 corresponding to the NH ₃ adsorption amount, it may deviate greatly from the set range as indicated by point a. Further, the leak NH ₃ 502 also temporarily becomes considerably high due to excessive injection of the NH ₃ injection amount 503 as shown at point b. Furthermore, the NH ₃ injection amount 503 itself is also temporarily temporarily introduced in a considerably large amount as indicated by point c, causing waste and uneconomical factors.
[0008]
In FIG. 4, the time 500 (unit (sec)), the outlet NOx concentration 501, the setting lower limit 504 and the setting upper limit 505, and the leak NH ₃ amount 502 and the upper limit 506 (these 501, 502, 504 and 505 are units ( ppm)) and further, the NH ₃ injection amount 503 (unit (m ³ / h)) is a non-dimensional representation of the minimum value to the maximum value that can be taken from 0 to 100%.
[0009]
[Problems to be solved by the invention]
The feedback control device using the PI (proportional / integral) regulator 203a according to the prior art aims at asymptotically approaching the set value of the outlet NOx concentration, but NH ₃ injection according to the amount of NH ₃ adsorption on the catalyst. For this reason,
(1) Excessive removal of outlet NOx at the time of load reduction where the adsorption amount remains, deviation from the set range downward,
(2) Overshoot of leaked NH ₃ due to excessive NH ₃ injection,
(3) Generation of uneconomics due to excessive use of NH ₃ ,
Such problems arise.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention mainly adopts the following configuration.
[0012]
In a denitration control device that controls NH3 flow rate so that the NOx concentration of the catalyst falls within a predetermined range by injecting NH3 on the catalyst to react with NOx in the exhaust gas,
Based on the catalyst inlet NOx flow rate, the deviation between the outlet NOx concentration set value and the measured value, the current required NH3 flow rate is obtained,
A necessary NH3 flow rate corrector for correcting the necessary NH3 flow rate is provided so that the required denitration rate can be obtained at the time point when n hours have elapsed from the present time point,
The required NH3 flow rate corrector is
The reaction NOx flow rate obtained by multiplying the NOx flow rate by the inlet NOx flow rate and the NOx flow rate obtained by multiplying the NOx flow rate required by the NOx flow rate required by the inlet NOx flow rate. Add the NOx flow rate,
Subtract the estimated amount of NH3 adsorbed on the catalyst from the required amount of NH3 adsorbed on the catalyst when n hours elapse,
Obtaining a total value which is the sum of the added reaction NOx flow rate and the subtracted adsorbed NH3 amount divided by half the time interval n;
The total value is compared with the current NH3 flow rate to calculate a correction value for correcting the necessary NH3 flow rate.
[0013]
In the denitration control device,
The input to the required NH ₃ flow rate corrector includes the inlet NOx flow rate, the inlet NOx concentration, the outlet NOx concentration, the required denitration rate when n hours have elapsed from the present time, the predicted span n that determines the time point to be predicted, and the measured NH ₃ flow rate, denitration control device.
[0014]
In the denitration control device,
The necessary NH ₃ flow rate compensator includes a computing device for estimating the amount of adsorbed NH ₃ at the present time, a computing device for calculating the current denitration rate, and the adsorbed NH ₃ amount after n hours from the required denitration rate after n hours A denitration control device comprising a function generator for calculating a predicted value of the required amount of the catalyst.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
A denitration control apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a denitration control apparatus according to this embodiment. The difference between the prior art, in the calculation of the required flow rate _of NH ₃ 111, the required flow rate i.e. current measurement-based required NH ₃ flow rate 115 according to the prior art, required flow rate _of NH ₃ is the output from necessary NH ₃ flow corrector 300 An amount obtained by adding the correction value 310 by the adder 205d is set as the necessary NH ₃ flow rate 111.
[0016]
Here, 101 is the inlet NOx concentration, 102 is the air flow rate, 103 is the combustion exhaust gas flow rate, 104 is the inlet NOx flow rate, 105 is the outlet NOx concentration set value, 106 is the required molar ratio, 107 is the outlet NOx concentration, and 108 is the outlet NOx. Concentration deviation, 109 is the corrected molar ratio, 110 is the corrected molar ratio, 111 is the required NH ₃ flow rate, 112 is the NH ₃ flow rate, 113 is the NH ₃ flow rate deviation, 114 is the NH ₃ flow rate adjustment amount, and 115 is the current measurement base Required NH ₃ flow rate, 201 is a function generator, 202 is a subtractor, 203 is a regulator, 204 is a multiplier, 205 is an adder, 300 is a required NH ₃ flow rate corrector, 301 is a required denitration rate after elapse of n hours , 302 represents a predicted span n, and 310 represents a necessary NH ₃ flow rate correction value.
[0017]
The input to necessary NH ₃ flow corrector 300, inlet NOx flow 104, the inlet NOx concentration 101, the outlet NOx concentration 107, n time after the required denitrification rate 301, an expected span n302 and NH ₃ flow rate 112, need NH The output from the ₃ flow rate corrector 300 is a required NH ₃ flow rate correction value 310.
[0018]
Here, the basic concept of the features of the denitration control apparatus according to the embodiment of the present invention will be described.
[0019]
First, in order to compensate for a delay in the reaction time, the amount of NH ₃ injected at the current time is set so that the required denitration rate can be obtained n minutes after the current time. Its denitrification rate due to the use that the amount determined in relation to the adsorption amount of NH _3, based on the estimated value of the adsorption amount of NH ₃ at the present time, NH ₃ set amount, adsorption NH from the current time after n minutes Decide that the required amount of ₃ remains.
[0020]
It is assumed that the amount of NH ₃ adsorbed at the present time is the amount of C _{NH 3} per unit area on the catalyst surface. When NH ₃ is injected by G _NH3 ⁱⁿ per unit time in this state, the injected NH ₃ is once adsorbed on the catalyst surface and reacts with NOx there. Excess NH _{3 that} has not reacted with NOx leaks to the downstream (this is referred to as G _NH3 ^leak ) or is adsorbed on the catalyst surface.
[0021]
Therefore, considering the process between the present time and the lapse of n hours, the total amount of NH ₃ injected G _NH3 ⁱⁿ · n is the total amount R of reaction with NOx, the total amount of leak NH ₃ G _NH3 ^leak · n and the adsorbed NH Equal to the sum of ₃ increments. That is, if the amount of adsorbed NH ₃ after the elapse of n hours is C _NH3 ⁿ , the following equation holds.
[0022]

Here, the total amount R of the reaction in the first term on the right side is the amount of NOx that has flowed into the denitration device, and therefore does not deviate from the product of the amount of inlet NOx and the denitration rate η.
[0023]
On the other hand, since the injection NH ₃ is set at a ratio of the molar ratio SM to the inlet NOx, the difference between the molar ratio SM corresponding to the inlet NOx and the denitration rate η does not deviate from the leak NH ₃ in the second term. That is,

So, after all,

It is.
[0024]
Here, regarding the left side, the NH ₃ flow rate after elapse of n hours is G _NH3 ^{in, n} , and regarding the right side, the expected value of the inlet NOx after n minutes is NOx ⁿ and the molar ratio SM is SM ⁿ . At this time, the first term on the left side and the right side is replaced with the average value of the current value and the value after the lapse of n hours to obtain the following.
[0025]

It can be seen from this that if SM ⁿ is set to a molar ratio necessary for obtaining the required denitration rate η ⁿ after elapse of n hours, the amount of NH ₃ injected after elapse of n hours determined by the above equation G _NH3 ^{in, n} The necessary denitration rate η ⁿ can be obtained.
[0026]
To actually calculate the amount of adsorbed after n times C _NH3 ⁿ and at present it is necessary adsorption amount C _NH3. For this purpose, the following experimentally known characteristics of the catalyst are applied. That is,
Molar ratio SM = func1 (adsorption amount C _NH3 , inlet NOx, operating conditions)
And denitration rate η = func2 (molar ratio SM, operating conditions)
Use the functional relationship with. Here, func1 and func2 are symbols representing functions of the displayed arguments. As a result, the present molar ratio SM and the adsorption amount C _NH3 can be known from the present denitration rate η, and after n hours, the necessary denitration rate η ⁿ can be set correspondingly. The molar ratio SM ⁿ and the required adsorption amount C _NH3 ⁿ are estimated.
[0027]
From the above relationship, the NH ₃ flow rate for obtaining the required denitration rate η ⁿ after elapse of n hours can be calculated, because the above equation is divided by n / 2.

It is.
[0028]
FIG. 2 shows the details of the necessary NH ₃ flow rate corrector 300 in detail.
[0029]
(1) The molar ratio SM410 is calculated as the output of the function generator by inputting the denitration rate calculated value 345. A product 351 of the inlet NOx flow rate 104 and the molar ratio SM410 is calculated by a multiplier. Here, the denitration rate calculated value 345 is calculated as the output of the NOx concentration 101 and the NOx concentration 107 are input to the denitration rate calculator.
[0030]
(2) On the other hand, the required molar ratio SM ⁿ 420 after elapse of n hours is calculated as the output of the function generator by inputting the required denitration rate 301 after elapse of n hours. A product 353 of the inlet NOx flow rate 104 and the molar ratio SM ⁿ 420 is calculated by a multiplier.
[0031]
(3) The amount 355 is calculated by adding the above two amounts with an adder. That is, the addition amount 355 is

It is.
[0032]
(4) On the other hand, the adsorbed NH ₃ amount estimated value 321 obtained by inputting the inlet NOx concentration 101 and the outlet NOx concentration 107 to the adsorbed NH ₃ amount estimator 370 is used to estimate the required amount of adsorbed NH ₃ after n hours. The amount 361 obtained by subtracting from the value 330 and subtracting 321 from 330 is divided by a divider by a half amount (n / 2) of the predicted span n302 set to an appropriate value in advance, and is 363. That is,

Here, the predicted NH ₃ required amount predicted value 330 after elapse of n hours is calculated by inputting the required denitration rate 301 after elapse of n hours into the function generator.
[0033]
The calculation contents of the adsorption NH ₃ estimator 370 are as follows. First, the molar ratio SM is determined by the following experimentally known function from the adsorbed NH ₃ and the inlet NOx.
[0034]
Molar ratio SM = fucn1 (adsorption NH ₃ , inlet NOx)
That is, the adsorbed NH ₃ can be calculated from this function conversely if the inlet NOx and the molar ratio SM are given.
[0035]
Adsorption NH ₃ = func ^{1 −1} (molar ratio SM, inlet NOx)
On the other hand, the denitration rate η is determined from this molar ratio SM,
Denitration rate η = fucn2 (molar ratio SM)
So, on the contrary,
Molar ratio SM = fucn2 ⁻¹ (denitration rate η)
And can be calculated.
[0036]
Therefore, the adsorbed NH ₃ is

If the denitration rate η and the inlet NOx are known as shown in FIG.
[0037]
The inlet NHx concentration 101 and the outlet NOx concentration 107 are input to the adsorption NH ₃ estimator 370 in FIG. 2, and the NOx removal rate η is calculated from these two amounts, and the func3 is calculated from this and the inlet NOx concentration 101. Thus, the adsorbed NH ₃ is estimated by the function of
[0038]
(5) The sum of the amount 355 of (3) and the amount 363 of (5) is the amount 470. That is, the sum 470 is the products 351 and 353 of the inlet NOx flow rate 104 and the calculated denitration rate 345 or the required denitration rate 301 after elapse of n hours, and the amount related to the amount of adsorbed NH ₃ , that is, after elapse of n hours. The amount obtained by dividing the difference 361 between the required adsorption NH ₃ amount preliminary value 330 and the estimated value 321 of the current adsorption NH ₃ amount by the half 340 of the predicted span n. That is,

(6) The sum 470 calculated in this way is compared with the current NH ₃ flow rate 112, and a difference is calculated by a subtractor. This difference is used as the required NH ₃ flow rate correction value 302, and the required NH ₃ flow rate corrector. Output from 300. That is,

Is calculated.
[0039]
The result of the denitration control by the control device of the present invention is shown in FIG. Compared with the control result by the conventional method, control is based on the amount of adsorbed NH ₃ required after n hours has elapsed, thus preventing excessive denitration and avoiding deviation from the lower limit of the outlet NOx concentration (point a). The NH ₃ injection amount is also optimized, avoiding deviation from the upper limit of the leaked NH ₃ amount (point b), and the maximum flow rate of the NH ₃ injection amount is also suppressed (point c).
[0040]
【The invention's effect】
In the present invention, since it controls based on the required amount of NH ₃ adsorption after elapse of n hours, excessive denitration can be prevented,
(1) Deviation from the lower limit of the outlet NOx concentration is avoided, and correspondingly, the NH ₃ injection amount is also optimized. (2) Deviation from the upper limit of the leak NH ₃ amount is avoided,
(3) There is an effect that the maximum flow rate of the NH ₃ injection amount is also suppressed.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a denitration control apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing in detail the contents of the necessary NH ₃ flow rate corrector of FIG.
FIG. 3 is a diagram showing a trend of a result of denitration control by the control device according to the embodiment of the present invention.
FIG. 4 is a diagram showing a trend of a denitration control result by a control device according to a conventional technique.
FIG. 5 is a diagram showing the contents of a denitration control device according to the prior art.
[Explanation of symbols]
101 inlet NOx concentration 102 air flow 103 flue gas flow rate 104 inlet NOx flow rate 105 outlet NOx concentration setting 106 required molar ratio 107 outlet NOx concentration 108 outlet NOx concentration deviation 109 molar ratio necessary NH ₃ flow rate 112 NH correction amount 110 fixes the molar ratio 111 ₃ Flow rate 113 NH ₃ flow rate deviation 114 NH ₃ flow rate adjustment amount 115 Required NH ₃ flow rate based on current measurement 201 Function generator 202 Subtractor 203 Controller 204 Multiplier 205 Adder 300 Necessary NH ₃ flow rate corrector 301 After n hours elapse Required denitration rate 302 Expected span n
310 Required NH ₃ flow rate correction value

Claims (6)

In a denitration control device that controls NH3 flow rate so that the NOx concentration of the catalyst falls within a predetermined range by injecting NH3 on the catalyst to react with NOx in the exhaust gas,
Based on the catalyst inlet NOx flow rate, the deviation between the outlet NOx concentration set value and the measured value, the current required NH3 flow rate is obtained,
A necessary NH3 flow rate corrector for correcting the necessary NH3 flow rate is provided so that the required denitration rate can be obtained at the time point when n hours have elapsed from the present time point,
The required NH3 flow rate corrector is
The reaction NOx flow rate obtained by multiplying the NOx flow rate by the inlet NOx flow rate and the NOx flow rate obtained by multiplying the NOx flow rate required by the NOx flow rate required by the inlet NOx flow rate. Add the NOx flow rate,
Subtract the estimated amount of NH3 adsorbed on the catalyst from the required amount of NH3 adsorbed on the catalyst when n hours elapse,
Obtaining a total value which is the sum of the added reaction NOx flow rate and the subtracted adsorbed NH3 amount divided by half the time interval n;
The denitration control device, wherein the total value and the current NH3 flow rate are compared to calculate a correction value for correcting the necessary NH3 flow rate. In the denitration control apparatus according to claim 1,
The input to the required NH3 flow rate compensator is the inlet NOx flow rate, the inlet NOx concentration, the outlet NOx concentration, the required denitration rate when n hours have elapsed from the present time, the predicted span n that determines the time point to be predicted, and the measured NH3 flow rate The denitration control apparatus characterized by the above-mentioned. In the denitration control apparatus according to claim 1,
The required NH3 flow rate compensator is a calculation device that estimates the amount of adsorbed NH3 at the present time, a calculation device that calculates the current denitration rate, and the required amount of adsorbed NH3 after the elapse of n hours from the required denitration rate after the elapse of n hours A denitration control device comprising: a function generator that calculates a predicted value of. In the denitration control device according to claim 3,
The denitration control apparatus according to claim 1, wherein the input of the calculation device for estimating the amount of adsorbed NH3 at the present time is an inlet NOx concentration and an outlet NOx concentration, and the output is an estimated value of the amount of adsorbed NH3 at the present time. In the denitration control device according to claim 3,
The denitration control apparatus characterized in that the input of the arithmetic unit for calculating the present denitration rate is the inlet NOx concentration and the outlet NOx concentration, and the output is the present denitration rate. In the denitration control device according to claim 3,
The input of the function generator that calculates the predicted value of the required amount of adsorbed NH3 after elapse of n hours from the required denitration rate after elapse of n hours is the denitration rate required after elapse of n hours, and its output Is the amount of adsorbed NH3 required corresponding to the denitration rate after the elapse of n hours.

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