CN110160041B - CFB boiler pollutant coupling control method and CFB boiler pollutant coupling control system - Google Patents

Abstract

The invention provides a CFB boiler pollutant coupling control method and a CFB boiler pollutant coupling control system. The method includes the following steps: S1, during the operation of the CFB boiler, establish a functional relationship between the emission concentrations of different pollutants, and the pollutants include sulfur dioxide and nitrogen oxides; S2, apply the functional relationship to the amount of oxygen and the amount of limestone added In the relationship with the pollutant emission concentration, the oxygen amount and the limestone addition amount when the pollutant emission concentration is the lowest are obtained and recorded as the optimal value; S3, the oxygen amount and the limestone addition amount are controlled at the optimal value. By obtaining the quantitative coupling relationship between the SO ₂ emission concentration and NO _x emission concentration of the CFB boiler, the optimal recommended values of the pollutant control concentration and the amount of limestone added are given, so that the SO ₂ emission concentration and NO _x emission concentration of the CFB boiler both reach the overall maximum. The figure of merit can guide the operation of CFB pollutant control, reduce the operation intensity of operators, and reduce the calcium-sulfur ratio of desulfurization in the furnace.

Description

CFB boiler pollutant coupling control method and CFB boiler pollutant coupling control system

technical field

The invention relates to the field of CFB boilers, in particular to a CFB boiler pollutant coupling control method and a CFB boiler pollutant coupling control system.

Background technique

At present, CFB boiler and generator sets often use in-furnace desulfurization to control SO ₂ emissions, that is, the limestone feeder frequency is automatically and manually controlled by the limestone adding system to adjust the limestone addition amount, and the calcium-sulfur molar ratio is adjusted to adjust SO ₂ emissions. In terms of denitrification in the furnace of the CFB unit, operating measures such as controlling the operating oxygen amount, bed temperature, and graded air distribution are adopted to reduce the _NOx emission concentration.

However, since the limestone added to the desulfurization in the CFB furnace has a certain catalytic effect on the formation of _NOx , and the increase in the amount of operating oxygen will also promote the desulfurization reaction, resulting in a decrease in the concentration of _SO2 emissions and an increase in the amount of _NOx emissions. Therefore, in actual operation, it is found that as the SO ₂ emission of the unit gradually decreases, the NO _x emission gradually increases, and the emission concentrations of the two show the effect of “one trade off and one trade off from the other”, as shown in Figure 1. The above problems bring great difficulties to the operation of controlling CFB pollutants.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a CFB boiler pollutant coupling control method and a CFB boiler pollutant coupling control system, so as to solve the problem of difficulty in controlling and operating CFB pollutants in the prior art.

In order to achieve the above object, according to one aspect of the present invention, a method for coupling pollutants of a CFB boiler is provided, comprising the following steps: S1, during the operation of the CFB boiler, establishing a functional relationship between the emission concentrations of different pollutants, The pollutants include sulfur dioxide and nitrogen oxides; S2, the functional relationship is applied to the relationship between the amount of oxygen, the amount of limestone added and the pollutant emission concentration, and the oxygen amount and the amount of limestone added when the pollutant emission concentration is the lowest is obtained and recorded as the optimal value; S3, the amount of oxygen and limestone added to the optimal value.

Further, the step of establishing the functional relationship includes: S11, establishing a first functional relationship C(NO _x )+K×C(SO ₂ )=M, wherein C(NO _x ) is the nitrogen oxide emission concentration, C( SO ₂ ) is the sulfur dioxide emission concentration; S12, the sulfur dioxide emission concentration and nitrogen oxide emission concentration at different time points under the same load are applied to the functional relationship to obtain K and M.

Further, step S11 includes: measuring the sulfur dioxide emission concentration and nitrogen oxide emission concentration of the CFB boiler under different loads, and drawing a relationship curve; respectively, performing data fitting on each relationship curve to obtain a plurality of sulfur dioxide emission concentrations and nitrogen oxides. The functional relationship of the emission concentration; according to the law between the functional relationships, the first functional relationship is obtained.

Further, the step of obtaining the optimal value of the oxygen amount and the amount of limestone added includes: S21, establishing a constraint condition according to the relationship between the sulfur dioxide emission concentration and the nitrogen oxide emission concentration, and applying the constraint condition to the functional relationship to obtain The optimal value of sulfur dioxide emission concentration; S22, the optimal value of sulfur dioxide emission concentration is applied to the relationship between oxygen amount, limestone addition amount and sulfur dioxide emission concentration, so as to obtain the optimal value of oxygen amount and the optimal value of limestone addition amount .

Further, the constraint condition is: control the emission concentration of nitrogen oxides to be 100-150 mg/Nm ³ .

According to another aspect of the present invention, a CFB boiler pollutant coupling control system is provided, which is electrically connected to the CFB boiler generator set, and the CFB boiler generator set includes a CFB boiler, a pollutant discharge pipeline communicated with the CFB boiler, and a limestone conveying system, The above-mentioned pollutant coupling control system further includes: a collection unit, connected with the pollutant discharge pipeline, for collecting the concentration of pollutants, and the pollutants include sulfur dioxide and nitrogen oxides; a first calculation unit, electrically connected with the collection unit, for establishing the functional relationship between the emission concentrations of different pollutants; the second calculation unit, electrically connected to the first calculation unit, is used for applying the functional relationship to the relationship between the oxygen amount, the amount of limestone added and the pollutant emission concentration to obtain the pollutant emission concentration The oxygen amount and the limestone addition amount when the emission concentration is the lowest shall be recorded as the optimal value; the control unit is electrically connected to the CFB boiler, the limestone conveying system and the second calculation unit respectively, and is used to control the oxygen amount and the limestone addition amount to the optimal value. value.

Further, the first calculation unit includes: a data fitting module, electrically connected to the acquisition unit, for establishing a first functional relationship C(NO _x )+K×C(SO ₂ )=M, where C(NO _{x )} ) is the emission concentration of nitrogen oxides, and C(SO ₂ ) is the emission concentration of sulfur dioxide; the first calculation module is electrically connected to the data fitting module, and is used to calculate the emission concentration of sulfur dioxide and nitrogen oxides at different time points under the same load The concentration is applied to the functional relationship to obtain K and M.

Further, the second calculation unit includes: a second calculation module, electrically connected to the first calculation module, for establishing a constraint condition according to the relationship between the sulfur dioxide emission concentration and the nitrogen oxide emission concentration, and applying the constraint condition to the functional relationship in order to obtain the optimal value of the sulfur dioxide emission concentration; the third calculation module, electrically connected with the second calculation module, is used for applying the optimal value of the sulfur dioxide emission concentration to the relationship between the oxygen amount, the amount of limestone added and the sulfur dioxide emission concentration , in order to obtain the optimal value of oxygen and the optimal value of limestone addition.

By applying the technical solution of the present invention, a coupling control method for pollutants of a CFB boiler is provided. By obtaining the quantitative coupling relationship between the SO ₂ emission concentration and the NO _x emission concentration of the CFB boiler, the optimal control concentration of pollutants and the amount of limestone added are given. The proposed value makes the SO ₂ emission concentration and NO _x emission concentration of the CFB boiler reach the overall optimal value, which guides the operation of CFB pollutant control, reduces the operation intensity of operators, reduces the calcium-sulfur ratio of desulfurization in the furnace, and improves the operation economy of the power plant.

Description of drawings

The accompanying drawings forming a part of the present invention are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation of the present invention. In the attached image:

Fig. 1 shows the schematic diagram of the relationship between CFB boiler pollutant emission concentration and oxygen amount in the prior art;

FIG. 2 shows a schematic flowchart of a method for coupling pollutants in a CFB boiler provided by an embodiment of the present invention;

3 shows a schematic diagram of the relationship between the nitrogen oxide emission concentration and the sulfur dioxide emission concentration in the CFB boiler pollutant coupling control method provided by the embodiment of the present invention;

4 shows a schematic flowchart of a method for coupling pollutants in a CFB boiler with a first functional relationship provided by an embodiment of the present invention;

Fig. 5 shows the quantitative relationship schematic diagram of SO emission concentration and limestone addition in the prior art _;

FIG. 6 shows a schematic flowchart of an implementation process of a CFB boiler pollutant coupling control system provided by an embodiment of the present invention.

Detailed ways

It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

In order to make those skilled in the art better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only Embodiments are part of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terms "first", "second" and the like in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence. It is to be understood that the data so used are interchangeable under appropriate circumstances for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having" and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those expressly listed Rather, those steps or units may include other steps or units not expressly listed or inherent to these processes, methods, products or devices.

As described in the background art, in the prior art, limestone added for desulfurization in the CFB furnace has a certain catalytic effect on the formation of NO _x , and at the same time, the increase in the amount of operating oxygen will also promote the desulfurization reaction, resulting in the reduction of SO ₂ emissions. The concentration also increases _NOx emissions, and the above problems bring greater difficulties to the operation of controlling CFB pollutants.

In order to solve the above technical problems, the present invention proposes a coupling control method for pollutants of a CFB boiler, as shown in FIG. 2, including the following steps: S1, during the operation of the CFB boiler, establish a function between the emission concentrations of different pollutants The pollutants include sulfur dioxide and nitrogen oxides; S2, the functional relationship is applied to the relationship between the amount of oxygen, the amount of limestone added and the pollutant emission concentration, and the oxygen amount and the amount of limestone added when the pollutant emission concentration is the lowest is obtained and recorded as Optimal value; S3, control the amount of oxygen and limestone added to the optimal value.

In the above-mentioned CFB boiler pollutant coupling control method of the present invention, by obtaining the quantitative coupling relationship between the SO ₂ emission concentration and the NO _x emission concentration of the CFB boiler, the optimal recommended value of the pollutant control concentration and the amount of limestone added is given, so that the CFB boiler can Both SO ₂ emission concentration and NO _x emission concentration reach the overall optimal value, which guides the operation of CFB pollutant control operation, reduces the operation intensity of operators, reduces the calcium-sulfur ratio of desulfurization in the furnace, and improves the operation economy of the power plant.

Exemplary embodiments of the CFB boiler pollutant coupling control method provided according to the present invention will be described in more detail below. These exemplary embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art.

In the process of field tests of multiple CFB power plants, the applicant analyzed the variation trends of SO ₂ and NO _x emission concentrations in multiple groups, and found that there is a strong negative correlation between the two, and the values of the two have a certain quantification. relation. As shown in Figure 1, the numerical changes of SO ₂ and NO _x emission concentrations are coupled with each other, with opposite trends, and there is a certain proportional relationship between the changes.

Then, through the data analysis of multiple groups under different loads on the 300MW CFB boiler generator set, it is concluded that the pollutant emission concentration has a certain relationship, as shown in Figure 3. By arranging the data, the functional relationship between the two is fitted as:

151MW load:

C(NOx)=-0.142C(SO ₂ )+142.17;

192MW load:

C(NOx)=-0.122C(SO ₂ )+132.17;

Among them, C(NO _x ) is the emission concentration of nitrogen oxides, and C(SO ₂ ) is the emission concentration of sulfur dioxide;

It can be seen that under different load conditions, when the oxygen content, the amount of limestone added and other factors change, although the concentrations of both are changing, there is always a proportional coefficient K that makes the NOx concentration and the SO after the ratio converted. ₂ The sum of the concentrations is equal to a constant M, the proportional coefficient K and the constant M change slightly with the load, and the change range is not large, that is, the relationship is as follows:

C(NO _x )+K×C(SO ₂ )=M, wherein C(NO _x ) is the emission concentration of nitrogen oxides, and C(SO ₂ ) is the emission concentration of sulfur dioxide.

Therefore, in the above step S1, as shown in FIG. 4, the step of establishing the above functional relationship may include: S11, establishing a first functional relationship formula C(NO _x )+K×C(SO ₂ )=M, where C (NO _x ) is the nitrogen oxide emission concentration, C(SO ₂ ) is the sulfur dioxide emission concentration; S12, the sulfur dioxide emission concentration and nitrogen oxide emission concentration at different time points under the same load are applied to the functional relationship to obtain K and M.

In a preferred embodiment, the above step S11 includes: measuring the sulfur dioxide emission concentration and nitrogen oxide emission concentration of the CFB boiler under different loads, and drawing a relationship curve; The functional relationship between the sulfur dioxide emission concentration and the nitrogen oxide emission concentration; the first functional relationship is obtained according to the law between the functional relationships.

After the above step S1, step S2 is performed: the functional relationship is applied to the relationship between the oxygen amount, the amount of limestone added and the pollutant discharge concentration, and the oxygen amount and the amount of limestone added when the pollutant discharge concentration is the lowest is obtained and recorded as the optimal value .

Under different coal combustion conditions, the data of SO ₂ emission concentration and NO _x emission concentration can be used for a period of time, input into the DCS of the power plant, and the values of K and M can be solved by calculation and fitting, and K and M can be applied to the amount of oxygen. , the relationship between the amount of limestone added and the pollutant emission concentration, the optimal value of the amount of operating oxygen and the amount of limestone added can be obtained. At the same time, quantitative description of the relationship between SO ₂ emission concentration and NO _x emission concentration can provide a reference for on-site adjustment of pollutant concentration operations, so that SO ₂ emission concentration and NO _x emission concentration can reach ideal values at the same time.

In a preferred embodiment, as shown in FIG. 4 , the step of obtaining the optimal value of the above-mentioned oxygen amount and the above-mentioned limestone addition amount includes: S21, establishing a constraint according to the relationship between the sulfur dioxide emission concentration and the nitrogen oxide emission concentration S22, apply the optimal value of sulfur dioxide emission concentration to the relationship between oxygen amount, limestone addition amount and sulfur dioxide emission concentration to obtain the optimal value of sulfur dioxide emission concentration; The optimum value of oxygen and the optimum amount of limestone added.

In the circulating fluidized bed, the limestone is first endothermically decomposed into CaO and CO ₂ , and then CaO reacts with SO ₂ to achieve desulfurization in the furnace. The reaction formula is as follows:

CaCO ₃ →CaO+CO ₂ ;

CaO+1/2O ₂ +SO ₂ →CaSO ₄ .

In CFB power plants, the amount of limestone added in the furnace is generally adjusted by controlling the frequency of the limestone feeder to control the SO ₂ emission concentration. There is a specific quantitative relationship between the SO ₂ emission concentration and the amount of limestone added, as shown in Figure 5; another On the one hand, the limestone desulfurization reaction requires oxygen consumption, and the increase of the oxygen content within a certain range is beneficial to the desulfurization reaction, thereby reducing the SO ₂ emission. There is also a quantitative relationship between the SO ₂ emission concentration and the oxygen amount, as shown in Figure 1.

In the actual operation of the CFB power plant, in order to control the _NOx emission up to the standard or cooperate with the SNCR denitrification system to achieve ultra-low _NOx emissions, while taking into account the combustion effect and operating economy, the _NOx at the furnace outlet can be controlled at 100mg/ ^Nm3 ~ 150mg/ Within the range of Nm ³ as the above constraint, the specific value C(NO _x ) can be selected and determined by each power plant according to the actual operating conditions on site. Substitute C(NO _x ) into the functional relationship determined by the present invention, the optimal target value C(SO ₂ ) of SO ₂ emission concentration under this operating condition can be obtained, thereby obtaining the optimal recommended target of limestone addition amount value. At the same time, quantitative optimization suggestions are made for the operating oxygen control value. And then achieve the effect of reducing the amount of limestone added, optimizing the amount of oxygen in operation, and improving the operation economy of the power plant.

According to another aspect of the present invention, a CFB boiler pollutant coupling control system is also provided, which is electrically connected to the CFB boiler generator set, and the CFB boiler generator set includes a CFB boiler, a pollutant discharge pipeline communicated with the CFB boiler, and a limestone conveying system. The above-mentioned pollutant coupling control system further includes a collection unit, a first calculation unit, a second calculation unit and a control unit.

Wherein, the above-mentioned collection unit is connected with the pollutant discharge pipeline, and is used to collect the concentration of pollutants, and the pollutants include sulfur dioxide and nitrogen oxides; the above-mentioned first calculation unit is electrically connected with the collection unit, and is used to establish a relationship between the discharge concentrations of different pollutants. The functional relationship between the above-mentioned second calculation unit and the first calculation unit is electrically connected to apply the functional relationship to the relationship between the amount of oxygen, the amount of limestone added and the pollutant discharge concentration to obtain the oxygen amount when the pollutant discharge concentration is the lowest and the amount of limestone added and recorded as the optimal value; the above control units are respectively electrically connected to the CFB boiler, the limestone conveying system and the second calculation unit to control the oxygen amount and the added amount of limestone to the optimal value.

In the above-mentioned CFB boiler pollutant coupling control system of the present invention, through the quantitative coupling relationship between the CFB boiler SO ₂ emission concentration and NO _x emission concentration, the optimal recommended value of the pollutant control concentration and the amount of limestone added is given, so that the CFB boiler SO _2. Both the emission concentration and _NOx emission concentration reach the overall optimal value, which guides the operation of CFB pollutant control, reduces the operation intensity of operators, reduces the calcium-sulfur ratio of desulfurization in the furnace, and improves the operation economy of the power plant.

Preferably, the above-mentioned first calculation unit includes a data fitting module and a first calculation module, and the data fitting module is electrically connected to the acquisition unit for establishing the first functional relationship C(NO _x )+K×C(SO ₂ ) =M, where C(NO _x ) is the emission concentration of nitrogen oxides, and C(SO ₂ ) is the emission concentration of sulfur dioxide; the first calculation module and the data fitting module are electrically connected to The sulfur dioxide emission concentration and nitrogen oxide emission concentration are applied in the functional relationship to obtain K and M.

Preferably, the above-mentioned second calculation unit includes a second calculation module and a third calculation module, the second calculation module is electrically connected to the first calculation module, and is used for establishing a constraint condition according to the relationship between the sulfur dioxide emission concentration and the nitrogen oxide emission concentration , and apply the constraint conditions to the functional relationship to obtain the optimal value of the sulfur dioxide emission concentration; the third calculation module is electrically connected to the second calculation module, and is used to apply the optimal value of the sulfur dioxide emission concentration to the amount of oxygen, the addition of limestone In order to obtain the optimal value of oxygen amount and the optimal value of limestone addition amount in the relationship between the amount and sulfur dioxide emission concentration.

The above-mentioned CFB boiler pollutant coupling control system of the present invention can also utilize the DCS control system in the existing CFB boiler generator set, as shown in Figure 6, in which a new data fitting calculation module is added, and its general formula is:

C(NO _x )+K×C(SO ₂ )=M (1)

Among them, C(NO _x ) is the emission concentration of nitrogen oxides, and C(SO ₂ ) is the emission concentration of sulfur dioxide. Its value can be obtained in real time from the existing pollutant measurement system of the power plant. By substituting multiple groups of C ( NO _x ), C(SO ₂ ) values, perform data fitting calculation, the specific values of K and M can be obtained, and formula (1) is determined accordingly. Take the specific values of K and M as K ₁ and M ₁ as an example , so the coupling relationship between the emission concentration of NO _x and SO ₂ for this period of time is obtained:

C(NOx)+K ₁ ×C(SO ₂ )=M ₁ (2)

Using the relational formula (2), the optimal control recommendation value of the current concentration and limestone addition amount can be obtained, and then displayed on the DCS screen or input into the automatic control system to realize the optimal coupling control of the pollutants of the CFB unit.

From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects:

By obtaining the quantitative coupling relationship between the SO ₂ emission concentration and NO _x emission concentration of the CFB boiler, the optimal recommended values of the pollutant control concentration and the amount of limestone added are given, so that the SO ₂ emission concentration and NO _x emission concentration of the CFB boiler both reach the overall maximum. The figure of merit can guide the operation of CFB pollutant control, reduce the operation intensity of operators, reduce the calcium-sulfur ratio of desulfurization in the furnace, and improve the operation economy of the power plant.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. A pollutant coupling control method for a CFB boiler is characterized by comprising the following steps:

s1, establishing a functional relation between emission concentrations of sulfur dioxide and nitrogen oxides in pollutants during operation of the CFB boiler, wherein the pollutants comprise the sulfur dioxide and the nitrogen oxides;

s2, applying the functional relation to the relation among oxygen quantity, limestone adding quantity and pollutant emission concentration to obtain the oxygen quantity and the limestone adding quantity when the pollutant emission concentration is lowest and recording as optimal values;

and S3, controlling the oxygen amount and the limestone addition amount at the optimal value, and mutually coupling the numerical changes of the emission concentrations of the sulfur dioxide and the nitrogen oxide in the functional relation, wherein the numerical changes have opposite trends, and the change amplitudes have a certain proportional relation.

2. The CFB boiler contaminant coupling control method of claim 1, wherein the step of establishing said functional relationship comprises:

s11, establishing a first functional relation C (NO)_x)+K×C(SO₂) Wherein, C (NO)_x) For the nitrogen oxide emission concentration, C (SO)₂) The sulfur dioxide emission concentration;

s12, the sulfur dioxide emission concentration and the nitrogen oxide emission concentration at different time points under the same load are applied to the functional relation to obtain K and M.

3. The CFB boiler contaminant coupling control method of claim 2, wherein said step S11 includes:

measuring the sulfur dioxide emission concentration and the nitrogen oxide emission concentration of the CFB boiler under different loads, and drawing a relation curve;

respectively carrying out data fitting on each relation curve to obtain a plurality of functional relation formulas of the sulfur dioxide emission concentration and the nitrogen oxide emission concentration;

and obtaining the first functional relation according to the rule among the functional relations.

4. A CFB boiler contaminant coupling control method according to any one of claims 1 to 3, wherein the step of obtaining optimal values of said oxygen amount and said limestone addition amount comprises:

s21, establishing a constraint condition according to the relation between the sulfur dioxide emission concentration and the nitrogen oxide emission concentration, and applying the constraint condition to the functional relation to obtain the optimal value of the sulfur dioxide emission concentration;

and S22, applying the optimal value of the sulfur dioxide emission concentration to the relation among oxygen quantity, limestone adding quantity and the sulfur dioxide emission concentration to obtain the optimal value of the oxygen quantity and the optimal value of the limestone adding quantity.

5. The CFB boiler contaminant coupling control method of claim 4, wherein the constraints are: controlling the emission concentration of the nitrogen oxide to be 100-150 mg/Nm³。

6. A CFB boiler contaminant coupling control system electrically connected to a CFB boiler generator set, the CFB boiler generator set including a CFB boiler, a contaminant discharge line in communication with the CFB boiler, and a limestone conveyance system, the contaminant coupling control system further comprising:

a collection unit in communication with the pollutant discharge line for collecting a concentration of the pollutant, the pollutant including sulfur dioxide and nitrogen oxides;

the first calculation unit is electrically connected with the acquisition unit and is used for establishing a functional relation between the emission concentrations of the sulfur dioxide and the nitrogen oxide;

the second calculation unit is electrically connected with the first calculation unit and is used for applying the functional relation to the relation among oxygen quantity, limestone adding amount and pollutant emission concentration to obtain the oxygen quantity and the limestone adding amount when the pollutant emission concentration is lowest and recording the oxygen quantity and the limestone adding amount as optimal values;

and the control unit is respectively and electrically connected with the CFB boiler, the limestone conveying system and the second calculation unit and is used for controlling the oxygen amount and the limestone adding amount to be in the optimal value, the numerical changes of the emission concentrations of the sulfur dioxide and the nitrogen oxide in the functional relation are mutually coupled, the trends are opposite, and the change amplitudes have certain proportional relation.

7. The CFB boiler contaminant coupling control system of claim 6, wherein the first calculation unit comprises:

a data fitting module electrically connected with the acquisition unit and used for establishing a first functional relation C (NO)_x)+K×C(SO₂) Wherein, C (NO)_x) For the nitrogen oxide emission concentration, C (SO)₂) The sulfur dioxide emission concentration;

and the first calculation module is electrically connected with the data fitting module and is used for applying the sulfur dioxide emission concentration and the nitrogen oxide emission concentration at different time points under the same load to the functional relation to obtain K and M.

8. The CFB boiler contaminant coupling control system of claim 7, wherein the second calculation unit comprises:

the second calculation module is electrically connected with the first calculation module and used for establishing a constraint condition according to the relation between the sulfur dioxide emission concentration and the nitrogen oxide emission concentration and applying the constraint condition to the functional relation so as to obtain the optimal value of the sulfur dioxide emission concentration;

and the third calculation module is electrically connected with the second calculation module and is used for applying the optimal value of the sulfur dioxide emission concentration to the relation among oxygen quantity, limestone addition and the sulfur dioxide emission concentration so as to obtain the optimal value of the oxygen quantity and the optimal value of the limestone addition.

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