CN114367191A - Denitration control method - Google Patents

Denitration control method Download PDF

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Publication number
CN114367191A
CN114367191A CN202111616340.3A CN202111616340A CN114367191A CN 114367191 A CN114367191 A CN 114367191A CN 202111616340 A CN202111616340 A CN 202111616340A CN 114367191 A CN114367191 A CN 114367191A
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value
ammonia
ammonia injection
flow
coal
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CN114367191B (en
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王林
杨立兵
郝伟阳
杜继臻
周权
齐也平
陈永龙
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Guoneng Shenwan Anqing Power Generation Co ltd
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Guoneng Shenwan Anqing Power Generation Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8696—Controlling the catalytic process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/40—Nitrogen compounds
    • B01D2257/404—Nitrogen oxides other than dinitrogen oxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases

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Abstract

The application discloses denitration control method, including: acquiring an outlet NOx flow measured value, an outlet NOx flow set value and a unit load value; carrying out PID control according to the outlet NOx flow measured value and the outlet NOx flow set value to obtain the ammonia nitrogen molar ratio; the first ammonia spraying flow is obtained by multiplying the ammonia nitrogen molar ratio, the unit load value and the ammonia spraying coefficient value, the unit load value is inserted into the ammonia spraying adjusting process in advance, the lag influence brought by the related technology is reduced or even eliminated through feedforward adjustment of the unit load value, the speed of the denitration device responding to the change of the NOx flow is faster and more sensitive, the obtained first ammonia spraying flow and the NOx flow in the flue have higher matching degree, the NOx in the flue can be fully reduced, and the ammonia escape exceeding standard or the NOx concentration exceeding standard is effectively avoided.

Description

Denitration control method
Technical Field
The application relates to the technical field of denitration control of thermal power plants, in particular to a denitration control method.
Background
In order to prevent the environment pollution caused by excessive nitrogen oxide (NOx) generated after the coal in the boiler is combusted, a denitration device is usually arranged between the economizer and the air preheater in the boiler so as to carry out denitration treatment on the coal.
The denitration treatment is carried out by adding reducing agents such as ammonia gas and urea into flue gas in a flue so as to reduce nitrogen oxide (NOx). However, the denitration device and the denitration method adopted in the related technology have certain hysteresis, so that the denitration automatic input quality is poor, the ammonia injection flow is over-standard or insufficient for a long time, and the ammonia escape is over-standard or the NOx concentration is over-standard.
Disclosure of Invention
The application discloses a denitration control method, which aims to solve the problem that ammonia escapes or NOx concentration exceeds standard due to hysteresis of a denitration device.
In order to solve the above problems, the following technical solutions are adopted in the present application:
a denitration control method, comprising: acquiring an outlet NOx flow measured value, an outlet NOx flow set value and a unit load value;
carrying out PID control according to the outlet NOx flow measured value and the outlet NOx flow set value to obtain the ammonia nitrogen molar ratio;
and multiplying the ammonia nitrogen molar ratio, the unit load value and the ammonia spraying coefficient value to obtain a first ammonia spraying flow.
Further, the ammonia injection coefficient value comprises a steady-state ammonia injection coefficient value and a dynamic ammonia injection coefficient value, wherein the steady-state ammonia injection coefficient value is less than the dynamic ammonia injection coefficient value;
the step of multiplying the ammonia nitrogen molar ratio, the unit load value and the ammonia spraying coefficient value to obtain a first ammonia spraying flow comprises the following steps:
and judging whether the unit load value changes, if not, multiplying the ammonia nitrogen molar ratio, the unit load value and a steady-state ammonia spraying coefficient value to obtain a first ammonia spraying flow, and if so, multiplying the ammonia nitrogen molar ratio, the unit load value and a dynamic ammonia spraying coefficient value to obtain a first ammonia spraying flow.
Further, the determining whether the unit load value changes, if not, obtaining a first ammonia injection flow rate by multiplying the ammonia nitrogen molar ratio, the unit load value and a steady-state ammonia injection coefficient value, and if so, obtaining a first ammonia injection flow rate by multiplying the ammonia nitrogen molar ratio, the unit load value and a dynamic ammonia injection coefficient value further includes:
and if the load value of the unit is changed, adjusting PID control parameters according to the load value of the unit.
Further, the acquiring the outlet NOx flow measured value, the outlet NOx flow set value, and the unit load value further includes:
acquiring an inlet NOx flow measured value;
the PID control is carried out according to the outlet NOx flow measured value and the outlet NOx flow set value so as to obtain the ammonia nitrogen molar ratio, and the method further comprises the following steps:
and performing PID control according to the outlet NOx flow measured value, the outlet NOx flow set value and the difference value between the inlet NOx flow measured value and the outlet NOx flow set value to obtain the ammonia nitrogen molar ratio.
Further, the method further comprises:
acquiring a coal quantity feed-forward value;
inputting the coal amount feedforward value into a coal amount algorithm block for operation to obtain a coal amount ammonia injection adjustment value,
and adding the coal quantity ammonia injection adjustment value and the first ammonia injection flow to obtain a second ammonia injection flow.
Further, the method further comprises:
acquiring an oxygen amount feedforward value;
inputting the oxygen quantity feedforward value into an oxygen quantity algorithm block for operation to obtain an obtained oxygen quantity ammonia spraying adjustment value;
the step of adding the coal quantity ammonia injection adjustment value and the first ammonia injection flow to obtain the second ammonia injection flow further comprises the following steps:
and adding the coal quantity ammonia injection adjusting value, the oxygen quantity ammonia injection adjusting value and the first ammonia injection flow to obtain the second ammonia injection flow.
Further, the method further comprises:
acquiring an air volume feedforward value;
inputting the air volume feedforward value into an air volume algorithm block for operation to obtain an air volume ammonia injection adjusting value;
adding the coal amount ammonia injection adjustment value, the oxygen amount ammonia injection adjustment value and the first ammonia injection flow to obtain a second ammonia injection flow, wherein the second ammonia injection flow further comprises:
and adding the coal quantity ammonia injection regulating value, the oxygen quantity ammonia injection regulating value, the air quantity ammonia injection regulating value and the first ammonia injection flow to obtain the second ammonia injection flow.
Further, the method further comprises:
acquiring a feed-forward value of the coal mill;
inputting the feed-forward value of the coal mill into a coal mill algorithm block for operation to obtain an ammonia injection regulating value of the coal mill;
through coal volume ammonia injection regulating value, oxygen volume ammonia injection regulating value, air volume ammonia injection regulating value and first ammonia injection flow adds, in order to obtain the second ammonia injection flow still includes:
and adding the coal quantity ammonia injection regulating value, the oxygen quantity ammonia injection regulating value, the air quantity ammonia injection regulating value, the coal mill ammonia injection regulating value and the first ammonia injection flow to obtain a second ammonia injection flow.
Further, the method also comprises
Performing overrun-preventing operation according to the second ammonia injection flow to obtain a third ammonia injection flow;
and the third ammonia injection flow is less than or equal to the preset upper limit value of ammonia injection.
Further, the steady-state ammonia injection coefficient value is 2900, and the dynamic ammonia injection coefficient value is 3100.
The technical scheme adopted by the application can achieve the following beneficial effects:
the application discloses denitration control method, including: acquiring an outlet NOx flow measured value, an outlet NOx flow set value and a unit load value; carrying out PID control according to the outlet NOx flow measured value and the outlet NOx flow set value to obtain the ammonia nitrogen molar ratio; the first ammonia spraying flow is obtained by multiplying the ammonia nitrogen molar ratio, the unit load value and the ammonia spraying coefficient value, the unit load value is inserted into the ammonia spraying adjusting process in advance, the lag influence brought by the related technology is reduced or even eliminated through feedforward adjustment of the unit load value, the speed of the denitration device responding to the change of the NOx flow is faster and more sensitive, the obtained first ammonia spraying flow and the NOx flow in the flue have higher matching degree, the NOx in the flue can be fully reduced, and the ammonia escape exceeding standard or the NOx concentration exceeding standard is effectively avoided.
Drawings
FIG. 1 is a flow chart of a denitration control method in an embodiment disclosed herein;
FIG. 2 is a graph of measured outlet NOx flow versus time for an embodiment disclosed herein;
FIG. 3 is a graph of ammonia nitrogen mole ratio versus time for the examples disclosed herein;
FIG. 4 is a graph of unit load values versus time in an embodiment disclosed herein;
FIG. 5 is a graph of first ammonia injection flow rate versus time for an embodiment disclosed herein.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Technical solutions disclosed in the embodiments of the present application are described in detail below with reference to the accompanying drawings.
Referring to fig. 1, the denitration control method of the present application includes:
and acquiring an outlet NOx flow measured value, an outlet NOx flow set value and a unit load value.
And performing PID control according to the outlet NOx flow measured value and the outlet NOx flow set value to obtain the ammonia nitrogen molar ratio.
And multiplying the ammonia nitrogen molar ratio, the unit load value and the ammonia spraying coefficient value to obtain a first ammonia spraying flow.
In this application, the unit is usually a thermal power station unit, and needs to burn coal to operate, so that the unit generates a unit load value when operating, and also generates NOx correspondingly, where the NOx generated correspondingly when operating is recorded as a unit NOx flow measurement value PV ', and the unit load value is recorded as W, it can be known that the unit load value W is proportional to the unit NOx flow measurement value PV', for example: PV ═ WxawWherein a iswA value of a coefficient set artificially.
The NOx generated when the unit operates needs a certain time from the time when the NOx is input into the flue to the time when the NOx is detected at the outlet of the flue so as to obtain an outlet NOx flow measured value PV. Thus, the measured outlet NOx flow PV at time T does not represent the NOx produced during operation of the unit at that time, i.e. the measured outlet NOx flow PV does not correspond to the calculated unit NOx flow PV'.
The purpose of ammonia injection is to effectively reduce the NOx generated during the operation of the unit, so if the actual outlet NOx flow PV is used to convert the ammonia injection amount required at the time, the NOx generated during the operation of the unit cannot be effectively reduced, that is, the measured unit NOx flow PV' cannot be matched, a delay occurs, and the influence of the delay causes ammonia slip or NOx slip.
Therefore, the unit load value is required to be introduced to perform feedforward regulation on the ammonia injection amount so as to obtain a first ammonia injection flow, and the formula is as follows:
Q1＝W×a×M
in the formula, Q1 represents a first ammonia injection flow rate, M represents an ammonia nitrogen molar ratio, W represents a unit load value, a represents an ammonia injection coefficient value, and the ammonia injection coefficient value a is artificially set.
Wherein, the ammonia nitrogen molar ratio M is an outlet NOx flow measured value PV and an outlet NOx flow set value SP which are obtained through PID control, the outlet NOx flow measured value PV can be obtained through detecting the content of NOx at the outlet position of the flue, and the outlet NOx flow set value SP is set for people.
Therefore, when the load value W of the unit changes, the load value W acts on the ammonia amount in advance to play a role in feedforward regulation, so that the obtained first ammonia injection flow Q1 has higher matching degree with NOx generated during the operation of the unit, namely, a measured value PV' of the NOx flow of the unit, the NOx in a flue can be fully reduced, and the ammonia escape exceeding standard or the NOx concentration exceeding standard is effectively avoided.
Further, the measured outlet NOx flow value in the present application is usually measured by a CEMS meter, specifically, the CEMS meter is disposed at the outlet of the flue to obtain the measured outlet NOx flow value, and the measured outlet NOx flow value is usually a dynamic value that changes in real time. The outlet NOx flow set point SP is a predetermined constant value, for example, the outlet NOx flow set point should be smaller than the environmental standard emission value, and will not be described in detail herein.
Further, the PID control in the present application is realized by a PID controller, wherein the measured value of the outlet NOx flow and the set value of the outlet NOx flow are both input values of the PID controller, and the ammonia nitrogen molar ratio is an output value of the PID controller. It should be noted that the operation of the PID controller is a mature technology, and the required output values can be obtained by selecting appropriate input values, for example, in the present application, the input values are an outlet NOx flow measured value PV and an outlet NOx flow set value SP, and the output value is an ammonia nitrogen molar ratio M, which is not described in detail herein. The calculation process of the PID controller is well known in the art and will not be described herein.
In a more specific embodiment, the value of the ammonia injection coefficient can include a steady state value of the ammonia injection coefficient and a dynamic value of the ammonia injection coefficient, wherein the steady state value of the ammonia injection coefficient < the dynamic value of the ammonia injection coefficient;
the step of multiplying the ammonia nitrogen molar ratio, the unit load value and the ammonia spraying coefficient value to obtain a first ammonia spraying flow rate further comprises the following steps:
judging whether the unit load value changes or not, if not, multiplying the ammonia nitrogen molar ratio, the unit load value and the steady-state ammonia spraying coefficient value to obtain a first ammonia spraying flow rate:
Q1＝W×a1×M；
if the ammonia nitrogen ratio is changed, multiplying the ammonia nitrogen molar ratio, the unit load value and the dynamic ammonia spraying coefficient value to obtain a first ammonia spraying flow rate:
Q1＝W×a2×M。
in the formula, Q1 represents the first ammonia injection flow, W represents the unit load value, a1 represents the steady-state ammonia injection coefficient value, a2 represents the dynamic ammonia injection coefficient value, and M represents the ammonia nitrogen molar ratio. Wherein the steady-state ammonia spraying coefficient value a1 and the dynamic ammonia spraying coefficient value a2 are both set manually, and the setting principle is as follows:
referring to fig. 2 to 5, before time T, the unit load value W is Wei, the measured outlet NOx flow value PV is PVei, and the ammonia nitrogen molar ratio is Mei. At time T, the unit load value W increases to Wes, and is kept Wes after time T.
From the above, the NOx generated by the unit needs to be discharged through the flue, and can flow into the flue outlet after a certain time Δ T, so as to obtain the measured outlet NOx flow PV. That is, the actual value PV of the outlet NOx flow rate needs to be increased from PVei to PVes at the time T + Δ T, and the ammonia nitrogen molar ratio is obtained by PID control of the actual value of the outlet NOx flow rate, so the ammonia nitrogen molar ratio also needs to be increased from Mei to Mes at the time T + Δ T. Here, the outlet NOx flow rate measured value PVes corresponds to NOx generated when the unit load value is Wes, and it can be considered that the outlet NOx flow rate measured in the flue at time T + Δ T is equal to the NOx content generated when the unit load value is Wes at time T.
Before time T, since the unit load value W has not changed, the first ammonia injection flow rate is:
Q1＝Wei×a1×Mei＝Qei；
at time T, since the unit load value W changes, the first ammonia injection flow rate:
Q1＝Wei×a2×Mei＝Qes；
after time T, since the unit load value W has not changed, the first ammonia injection flow rate:
Q1＝Wes×a1×Mes＝Qes：
as can be seen from the above description, the first ammonia injection flow rate Q1 is used for reducing NOx generated by the plant, so the first ammonia injection flow rate Q1 should be changed along with the plant load value W, and since the plant load value W is always kept at Wes from time T (including time T), the first ammonia injection flow rate Q1 should also be kept constant from time T (including time T), that is, Q1 is Qes.
The ammonia nitrogen molar ratio M at the time T is Mei; and the ammonia nitrogen molar ratio does not rise to M-Mes until T + delta T, namely after the T.
Therefore, in order to ensure the constant first ammonia injection flow Q1 at and after time T
The dynamic ammonia spraying coefficient value a2 is selected at the time T to calculate a first ammonia spraying flow Q1,
after time T, for example, when the ammonia nitrogen molar ratio increases to M ═ Mes at time T + Δ T, the ammonia injection coefficient value should be decreased, so that the steady-state ammonia injection coefficient value a1 is selected. The first ammonia injection flow Q1 is regulated through the parameter control, so that the first ammonia injection flow Q1 is matched with the unit load value W.
The sensitivity of the denitration device is further improved by the control mode, different working conditions can be better adapted, the matching degree of the first ammonia spraying flow and the NOx flow in the flue is further improved, and the ammonia escape exceeding standard or the NOx concentration exceeding standard is further effectively avoided.
Further, the steady-state ammonia injection coefficient value a1 and the dynamic ammonia injection coefficient value a2 in the present application are summarized from practical working experience, and generally, the steady-state ammonia injection coefficient value a1 should be smaller than the dynamic ammonia injection coefficient value a2, for example, the steady-state ammonia injection coefficient value a1 is 2900; the dynamic ammonia injection coefficient value a2 is 3100, so that the obtained first ammonia injection flow rate Q1 can be matched with the NOx generated by the unit, namely the measured value PV' of the NOx flow rate of the unit.
Further, the fixed PID parameters cannot simultaneously meet the ammonia injection regulation under the conditions of stable unit load value and unit load value change. Therefore, judging whether the unit load value changes, if not, obtaining a first ammonia spraying flow rate by multiplying the ammonia nitrogen molar ratio, the unit load value and the steady-state ammonia spraying coefficient value, and if so, obtaining the first ammonia spraying flow rate by multiplying the ammonia nitrogen molar ratio, the unit load value and the dynamic ammonia spraying coefficient value, further comprising:
and if the load value of the unit is changed, adjusting the PID control parameter according to the load value of the unit. The PID control parameters to be adjusted comprise related parameters such as a proportional coefficient kp and an integral coefficient Ki which can influence the response sensitivity.
Specifically, when the plant load value is unchanged, the proportionality coefficient kp is 1 and the integral coefficient Ki is 0.3, and when the plant load value is changed, the proportionality coefficient kp is 1.2 and the integral coefficient Ki is 0.5. It can be seen that the change mode of the proportional coefficient kp and the integral coefficient Ki can increase the response sensitivity of the PID controller when the unit load value changes. Under the condition that the response sensitivity of the PID controller is increased, the calculation time of the PID controller for obtaining the ammonia nitrogen mole ratio according to the outlet NOx flow measured value and the outlet NOx flow set value is also faster, and the advantages of the setting are explained as follows:
as can be seen from the above, when the unit load value is not changed, the measured value of the unit NOx flow, the measured value of the outlet NOx, the ammonia nitrogen molar ratio, the first ammonia injection flow value, and the like are all in a steady state and are kept constant, so that the control proportional coefficient kp of the unit load value is 1 and the integral coefficient Ki is 0.3, and under such parameters, although the response sensitivity of the PID controller is low and the calculation time is long, the finally obtained first ammonia injection flow value can also be effectively matched with the measured value of the unit NOx flow, so as to achieve a good ammonia injection reduction effect. The response sensitivity of the PID controller is reduced, and the consumption of the PID controller can be reduced.
However, once the load value of the unit changes, the measured value of the NOx flow of the unit also changes, so that the proportional coefficient kp is 1.2 and the integral coefficient Ki is 0.5, and the PID controller has higher response sensitivity under the parameters, so that the calculation time of the ammonia nitrogen molar ratio is shortened, the influence caused by delay can be reduced, and the matching degree of the obtained first ammonia injection flow and the measured value of the NOx flow of the unit is higher.
By adopting the mode, the PID control parameters are adaptively adjusted along with the change of the unit load value, so that the ammonia injection adjustment can better meet the requirements under different working conditions, and the consumption of the PID controller is reduced. Therefore, the matching degree of the first ammonia injection flow and the NOx flow measurement value of the unit can be further improved, and the ammonia escape exceeding standard or the NOx concentration exceeding standard can be more effectively avoided.
Further, obtaining the outlet NOx flow measured value and the unit load value further includes:
and acquiring an inlet NOx flow measured value. Typically, a CEMS meter may be installed at the inlet of the flue to collect NOx to obtain an actual inlet NOx flow measurement.
Carrying out PID control according to the outlet NOx flow measured value and the outlet NOx flow set value to obtain the ammonia nitrogen molar ratio, and further comprising:
and performing PID control according to the outlet NOx flow measured value, the outlet NOx flow set value and the difference value between the inlet NOx flow measured value and the outlet NOx flow set value to obtain the ammonia nitrogen molar ratio.
In the mode, the difference value between the inlet NOx flow measured value and the outlet NOx flow set value is input into the PID controller to participate in PID control, and the ammonia nitrogen molar ratio output by the PID controller can be limited, namely the output ammonia nitrogen molar ratio does not exceed the upper limit value and does not exceed the lower limit value, so that the ammonia injection regulation overshoot is effectively prevented.
Specifically, when the unit load value W is not changed, the ammonia nitrogen molar ratio M output by the PID controller0The difference between the actual measured value of the inlet NOx flow and the set value of the outlet NOx flow is used as a reference value and is used as a bias value to be used as a variation range of the ammonia nitrogen molar ratio, for example, when the unit load value is not changed, the ammonia nitrogen molar ratio output by the PID controller is equal to M0And the difference between the measured inlet NOx flow and the set outlet NOx flow is delta M, so that the variation range of the ammonia nitrogen molar ratio is M0Plus or minus delta M, the upper limit value Tmax of the ammonia nitrogen molar ratio is equal to M0+ delta M, lower limit Tmin of ammonia nitrogen molar ratio being M0-ΔM。
Further, the denitration control method further includes:
and acquiring a coal quantity feed-forward value.
And inputting the coal quantity feedforward value into a coal quantity algorithm block for operation to obtain a coal quantity ammonia injection regulating value.
And adding the coal quantity ammonia injection adjustment value and the first ammonia injection flow to obtain a second ammonia injection flow.
Wherein, the feed-forward value QK of the coal amountmeiThe coal consumption in the working process of the unit can be determined by detecting the amount of the pulverized coal put into the unit or the coal consumption in the running process of the coal mill through a weighing device.
As is known, NOx generated during the operation of the unit is obtained by burning coal, and the purpose of injecting ammonia is to reduce the NOx generated by burning coal, and the NOx is recorded as an actual value PV of the NOx flow of the unit0′。
When the feed-forward value of the coal amount is changed, NOx generated by coal combustion corresponds to the actual value PV of the NOx flow of the unit0' will change directly without a time difference between the two.
And the feed-forward value of the coal quantity changes, the load value W of the unit also changes, but the changed feed-forward value of the coal quantity can be matched after a time period delta T. For example, the coal consumption of 8 tons corresponds to a unit load value of 8MKW, and when the coal consumption at time T is increased from 8 tons to 10 tons, the unit load value needs a Δ T time period to be increased from 8MKW to 10MKW, that is, when the coal consumption at time T is increased to 10 tons, the unit load value needs to be increased to 10MKW at time T + Δ T, so that the coal consumption at time T can be matched.
Therefore, if the ammonia amount is acted on in advance only by the unit load value W, the obtained first ammonia injection flow Q1 cannot be completely matched with the actual unit NOx flow PV0' therefore, it is necessary to continuously advance the feed forward value of the amount of coal to the amount of ammonia.
Specifically, firstly, the feed-forward value of the coal quantity is input into a coal quantity algorithm block to calculate to obtain the ammonia injection adjustment value of the coal quantity, namely
PENmei＝QKmei×amei；
In the formula, PENmeiIndicating the ammonia injection regulation value of coal quantity, QKmeiRepresenting a feed forward value of the coal amount, ameiRepresenting a coal quantity coefficient; wherein the coal amount coefficient ameiIs artificially set.
And then adding the coal quantity ammonia injection adjustment value and the first ammonia injection flow to obtain a second ammonia injection flow, namely:
Q2＝Q1+PENmei，
wherein Q1 is W × a × M, and Q1 represents the first ammonia injection flow rate; w represents a unit load value; a represents an ammonia injection coefficient value, and a is equal to a steady-state ammonia injection coefficient value a1 when the unit load value W is unchanged, and is equal to a dynamic ammonia injection coefficient value a2 when the unit load value W is changed; m represents the ammonia nitrogen molar ratio. Q2 represents the second ammonia injection flow rate at time T.
It can be seen that on the basis that the unit load value W acts on the ammonia amount in advance to play a role in feedforward regulation, the coal amount feedforward value QK is usedmeiThe ammonia amount is acted in advance, so that the obtained second ammonia injection flow Q2 and the actual unit NOx flow PV0The method has better matching degree, can further fully reduce the NOx in the flue, and more effectively avoids ammonia escape or excessive NOx concentration.
Further, the denitration control method further includes:
and acquiring a feed-forward value of the oxygen amount.
And inputting the oxygen quantity feedforward value into an oxygen quantity algorithm block for operation to obtain an oxygen quantity ammonia spraying adjustment value.
Adding the coal injection ammonia adjustment value and the first ammonia injection flow to obtain a second ammonia injection flow, wherein the second ammonia injection flow further comprises:
and adding the coal amount ammonia injection adjusting value, the oxygen amount ammonia injection adjusting value and the first ammonia injection flow to obtain a second ammonia injection flow.
In the method, the oxygen feed-forward value is also inserted into the ammonia injection regulation process in advance in consideration of the fact that the change of the coal consumption inevitably causes the change of the oxygen consumption. Specifically, the oxygen amount feedforward value is the oxygen consumption, so the oxygen amount feedforward value is firstly input into an oxygen amount algorithm block for calculation to obtain the ammonia injection flow rate which is required to be corrected and corresponds to the oxygen consumption in the current coal burning process, namely an oxygen amount ammonia injection regulation value:
PENy＝QKy×ay；
PEN in the formulayIndicating the ammonia injection regulation value of oxygen quantity, QKyRepresenting a feed-forward value of oxygen amount, ayRepresents an oxygen content coefficient; wherein the oxygen content coefficient ayIs artificially set.
Then, summing the coal amount ammonia injection adjustment value, the oxygen amount ammonia injection adjustment value and the first ammonia injection flow to obtain a second ammonia injection flow:
Q2＝Q1+PENmei+PENy；
it can be seen that the feed forward value QK is due to the oxygen amountyThe second ammonia injection flow Q2 and the actual unit NOx flow PV0The method has higher matching degree, can more fully reduce the NOx in the flue, and more effectively avoids the ammonia escape exceeding standard or the NOx concentration exceeding standard. Feed-forward value QK of oxygen amount in the applicationyCan be measured by a meter and is not detailed here.
Further, the denitration control method further includes:
and acquiring an air volume feedforward value.
And inputting the air volume feedforward value into an air volume algorithm block for operation to obtain an air volume ammonia injection regulating value.
Through coal volume ammonia injection regulating value, oxygen volume ammonia injection regulating value and the first ammonia injection flow add up to obtain the second ammonia injection flow still include:
and adding the coal quantity ammonia injection regulating value, the oxygen quantity ammonia injection regulating value, the air quantity ammonia injection regulating value and the first ammonia injection flow to obtain a second ammonia injection flow.
Similarly, considering that the change of the coal consumption also inevitably causes the change of the wind consumption, the air volume feed-forward value is also inserted into the ammonia injection regulation process in advance. Specifically, the air volume feedforward value is the air consumption, so the air volume feedforward value is firstly input into an air volume algorithm block for calculation to obtain the ammonia injection flow which is the air volume ammonia injection regulating value and needs to be corrected and corresponds to the current air consumption;
PENf＝QKf×af；
PEN in the formulafIndicating the air flow ammonia injection regulation value, QKfRepresenting feed forward value of air quantity, afRepresenting the air quantity coefficient; wherein the air volume coefficient afIs artificially set.
And then summing the coal quantity ammonia injection regulating value, the oxygen quantity ammonia injection regulating value, the air quantity ammonia injection regulating value and the first ammonia injection flow to obtain a second ammonia injection flow.
Q2＝Q1+PENmei+PENy+PENf；
It can be seen that the feed-forward value QK is due to the air quantityfThe second ammonia injection flow Q2 and the actual unit NOx flow PV0The method has higher matching degree, can more fully reduce the NOx in the flue, and more effectively avoids the ammonia escape exceeding standard or the NOx concentration exceeding standard. In the application, the air volume feedforward value can be obtained by measuring through an instrument, and the detail is not described here.
Further, the denitration control method further includes:
and acquiring a feed-forward value of the coal mill.
And inputting the feed-forward value of the coal mill into a coal mill algorithm block for operation so as to obtain an ammonia injection regulating value of the coal mill.
Through coal volume ammonia injection regulating value, oxygen volume ammonia injection regulating value, air volume ammonia injection regulating value and the first ammonia injection flow add up to obtain the second ammonia injection flow still include:
and adding the coal quantity ammonia injection regulating value, the oxygen quantity ammonia injection regulating value, the air quantity ammonia injection regulating value, the coal mill ammonia injection regulating value and the first ammonia injection flow to obtain a second ammonia injection flow.
The coal mill is a device for crushing and grinding coal blocks into coal powder, so that the change of the coal consumption also inevitably causes the change of the opening number of the coal mill, and the feed-forward value of the coal mill is also inserted into the adjustment process of ammonia injection in advance. Specifically, the coal mill feed-forward value is the coal mill opening number, so the coal mill feed-forward value is firstly input into the coal mill algorithm block for calculation to obtain the ammonia injection flow rate which is required to be corrected and corresponds to the current coal mill opening number, namely the coal mill ammonia injection regulation value:
PENmm＝QKmm×amm；
PEN in the formulammIndicating the coal pulverizer ammonia injection regulation value, QKmmRepresenting the feed-forward value of the mill, ammRepresenting the coal mill coefficient; wherein coefficient of coal mill ammIs artificially set.
And then summing the coal quantity ammonia injection regulating value, the oxygen quantity ammonia injection regulating value, the air quantity ammonia injection regulating value, the coal mill ammonia injection regulating value and the first ammonia injection flow to obtain a second ammonia injection flow.
Q2＝Q1+PENmei+PENy+PENf+PENmm；
It can be seen that PEN is a feed forward value for coal millsmmThe second ammonia injection flow Q2 and the actual unit NOx flow PV0The method has higher matching degree, can more fully reduce the NOx in the flue, and more effectively avoids the ammonia escape exceeding standard or the NOx concentration exceeding standard. The feed-forward value of the coal mill in the application can be obtained through measurement of a meter, and the detailed description is omitted.
Further, the denitration control method further includes:
performing overrun-preventing operation according to the second ammonia injection flow to obtain a third ammonia injection flow; specifically, the second ammonia injection flow is input into the overrun-prevention algorithm block for overrun-prevention operation, and the overrun-prevention algorithm block outputs a third ammonia injection flow:
when Q2 is less than or equal to Q0Q3 ═ Q2;
when Q2 > Q0When Q3 is Q0；
In the formula, Q0Represents the preset upper limit value of ammonia injection, Q2 represents the second ammonia injection flow rate, and Q3 represents the third ammonia injection flow rate. Preset upper limit Q of ammonia injection0Can be manually set according to the environmental protection standard, the rated power of the ammonia spraying device and the like.
The setting corrects the value of the second ammonia injection flow through the overrun-preventing operation, and the obtained third ammonia injection flow is less than or equal to the preset upper limit value of the ammonia injection, so that the ammonia injection flow can be prevented from exceeding the limit value, and the ammonia injection cost can be controlled.
Further, the denitration control method further includes:
and spraying ammonia according to the third ammonia spraying flow, inputting the sprayed ammonia gas into a urea distribution system, distributing in the urea distribution system to obtain a reducing agent, and inputting the reducing agent into the SCR reactor, thereby realizing the reduction of NOx in the flue.
In the embodiments of the present application, the difference between the embodiments is described in detail, and different optimization features between the embodiments can be combined to form a better embodiment as long as the differences are not contradictory, and further description is omitted here in view of brevity of the text.
The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims (10)

1. A denitration control method is characterized by comprising the following steps:
acquiring an outlet NOx flow measured value, an outlet NOx flow set value and a unit load value;
carrying out PID control according to the outlet NOx flow measured value and the outlet NOx flow set value to obtain the ammonia nitrogen molar ratio;
and multiplying the ammonia nitrogen molar ratio, the unit load value and the ammonia spraying coefficient value to obtain a first ammonia spraying flow.
2. The denitration control method according to claim 1,
the ammonia injection coefficient value comprises a steady-state ammonia injection coefficient value and a dynamic ammonia injection coefficient value, and the steady-state ammonia injection coefficient value is less than the dynamic ammonia injection coefficient value;
the step of multiplying the ammonia nitrogen molar ratio, the unit load value and the ammonia spraying coefficient value to obtain a first ammonia spraying flow comprises the following steps:
and judging whether the unit load value changes, if not, multiplying the ammonia nitrogen molar ratio, the unit load value and a steady-state ammonia spraying coefficient value to obtain a first ammonia spraying flow, and if so, multiplying the ammonia nitrogen molar ratio, the unit load value and a dynamic ammonia spraying coefficient value to obtain a first ammonia spraying flow.
3. The denitration control method according to claim 2,
the judging whether the unit load value changes or not, if not, obtaining a first ammonia spraying flow rate by multiplying the ammonia nitrogen molar ratio, the unit load value and a steady-state ammonia spraying coefficient value, and if so, obtaining the first ammonia spraying flow rate by multiplying the ammonia nitrogen molar ratio, the unit load value and a dynamic ammonia spraying coefficient value, further comprises:
and if the load value of the unit is changed, adjusting PID control parameters according to the load value of the unit.
4. The denitration control method according to claim 1,
the acquiring of the outlet NOx flow measured value, the outlet NOx flow set value and the unit load value further includes:
acquiring an inlet NOx flow measured value;
the PID control is carried out according to the outlet NOx flow measured value and the outlet NOx flow set value so as to obtain the ammonia nitrogen molar ratio, and the method further comprises the following steps:
and performing PID control according to the outlet NOx flow measured value, the outlet NOx flow set value and the difference value between the inlet NOx flow measured value and the outlet NOx flow set value to obtain the ammonia nitrogen molar ratio.
5. The denitration control method according to claim 1, further comprising:
acquiring a coal quantity feed-forward value;
inputting the coal amount feedforward value into a coal amount algorithm block for operation to obtain a coal amount ammonia injection adjustment value,
and adding the coal quantity ammonia injection adjustment value and the first ammonia injection flow to obtain a second ammonia injection flow.
6. The denitration control method according to claim 5, further comprising:
acquiring an oxygen amount feedforward value;
inputting the oxygen quantity feedforward value into an oxygen quantity algorithm block for operation to obtain an obtained oxygen quantity ammonia spraying adjustment value;
the step of adding the coal quantity ammonia injection adjustment value and the first ammonia injection flow to obtain the second ammonia injection flow further comprises the following steps:
and adding the coal quantity ammonia injection adjusting value, the oxygen quantity ammonia injection adjusting value and the first ammonia injection flow to obtain the second ammonia injection flow.
7. The denitration control method according to claim 6, further comprising:
acquiring an air volume feedforward value;
inputting the air volume feedforward value into an air volume algorithm block for operation to obtain an air volume ammonia injection adjusting value;
the step of adding the coal amount ammonia injection adjustment value, the oxygen amount ammonia injection adjustment value and the first ammonia injection flow to obtain the second ammonia injection flow further comprises the following steps:
and adding the coal quantity ammonia injection regulating value, the oxygen quantity ammonia injection regulating value, the air quantity ammonia injection regulating value and the first ammonia injection flow to obtain the second ammonia injection flow.
8. The denitration control method according to claim 7, further comprising:
acquiring a feed-forward value of the coal mill;
inputting the feed-forward value of the coal mill into a coal mill algorithm block for operation to obtain an ammonia injection regulating value of the coal mill;
the step of adding the coal quantity ammonia injection regulating value, the oxygen quantity ammonia injection regulating value, the air quantity ammonia injection regulating value and the first ammonia injection flow to obtain the second ammonia injection flow further comprises the following steps:
and adding the coal quantity ammonia injection regulating value, the oxygen quantity ammonia injection regulating value, the air quantity ammonia injection regulating value, the coal mill ammonia injection regulating value and the first ammonia injection flow to obtain a second ammonia injection flow.
9. The denitration control method according to claim 5, further comprising
Performing overrun-preventing operation according to the second ammonia injection flow to obtain a third ammonia injection flow;
and the third ammonia injection flow is less than or equal to the preset upper limit value of ammonia injection.
10. The denitration control method according to claim 2, wherein the steady-state ammonia injection coefficient value is 2900, and the dynamic ammonia injection coefficient value is 3100.
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Publication number Priority date Publication date Assignee Title
JPH08155267A (en) * 1994-12-01 1996-06-18 Tokyo Electric Power Co Inc:The Denitration control device
JP2005211750A (en) * 2004-01-28 2005-08-11 Babcock Hitachi Kk Method for controlling ammonia injection into catalytic denitrification equipment
CN106970692A (en) * 2017-03-31 2017-07-21 紫光华山信息技术有限公司 Rotation speed of the fan adjusting method and device
CN107243257A (en) * 2017-05-08 2017-10-13 浙江大学 It is adapted to the intelligence spray ammonia control system of full load
CN109062053A (en) * 2018-08-31 2018-12-21 江苏国信靖江发电有限公司 A kind of denitration spray ammonia control method based on multivariate calibration
CN112316718A (en) * 2020-11-13 2021-02-05 西安热工研究院有限公司 Denitration ammonia injection control system and method for W-flame boiler
CN112619394A (en) * 2020-11-24 2021-04-09 呼和浩特科林热电有限责任公司 Denitration ammonia injection self-adaptive control method and device and denitration system

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08155267A (en) * 1994-12-01 1996-06-18 Tokyo Electric Power Co Inc:The Denitration control device
JP2005211750A (en) * 2004-01-28 2005-08-11 Babcock Hitachi Kk Method for controlling ammonia injection into catalytic denitrification equipment
CN106970692A (en) * 2017-03-31 2017-07-21 紫光华山信息技术有限公司 Rotation speed of the fan adjusting method and device
CN107243257A (en) * 2017-05-08 2017-10-13 浙江大学 It is adapted to the intelligence spray ammonia control system of full load
CN109062053A (en) * 2018-08-31 2018-12-21 江苏国信靖江发电有限公司 A kind of denitration spray ammonia control method based on multivariate calibration
CN112316718A (en) * 2020-11-13 2021-02-05 西安热工研究院有限公司 Denitration ammonia injection control system and method for W-flame boiler
CN112619394A (en) * 2020-11-24 2021-04-09 呼和浩特科林热电有限责任公司 Denitration ammonia injection self-adaptive control method and device and denitration system

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