Denitrification control method, system, medium and electronic equipment

Abstract

The present invention provides a denitration control method, system, medium and electronic equipment, which relates to the technical field of denitration in thermal power plants, including: using a boiler to provide a preset reaction temperature for a reactor; calculating the ammonia and NO x The molar ratio of NO at the reactor inlet x The flow rate of the ammonia in the reactor is multiplied by the molar ratio to determine a first flow rate of ammonia in the reactor. A PID controller is used to obtain a feedforward correction value and a differential value of the boiler load change rate in real time to determine a second flow rate of ammonia actually required to be introduced into the reactor. Based on the difference between the first and second flow rates, combined with the pressure, total flow rate, and temperature of the ammonia in the ammonia injection regulating valve, a third flow rate of ammonia required to be released from the ammonia injection regulating valve is determined, and the opening of the ammonia injection regulating valve is controlled based on the third flow rate. This invention solves the problem of hysteresis in existing denitration control methods.

Description

Technical Field

[0001] The present invention relates to the technical field of denitration control in thermal power plants, and in particular to a denitration control method, system, medium and electronic equipment. Background Art

[0002] In order to prevent excessive nitrogen oxides (NOx) from polluting the environment after coal combustion in the boiler, a denitrification device is often installed between the economizer and the air preheater to denitrify the coal.

[0003] Denitrification involves adding reducing agents such as ammonia and urea to the flue gas to reduce nitrogen oxides (NOx). Currently, most thermal power plants use a cascaded PID loop to control the NOx concentration at the SCR reactor outlet. This control strategy is effective in eliminating inertia.

[0004] However, simply using cascade PID can easily cause excessive ammonia injection, which can block the air preheater downstream of the flue gas. Furthermore, when the unit's load changes rapidly, it can easily cause a transient peak in NOx at the SCR outlet.

[0005] That is, the denitrification control method in the prior art has a certain hysteresis, which will result in poor quality of the automatic denitrification input, and further lead to excessive or insufficient ammonia injection flow for a long time, as well as excessive ammonia escape or excessive NOx concentration. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a denitration control method, system, medium and electronic equipment, which solve the problem that the denitration control method in the prior art has a certain hysteresis.

[0007] At least one embodiment of the present invention provides a denitration control method, comprising:

[0008] Using a boiler to provide a preset reaction temperature for the reactor;

[0009] Obtain ammonia and NO in the reactor x The molar ratio of

[0010] The reactor inlet NO x The flow rate of the ammonia gas in the reactor is multiplied by the molar ratio to determine the first flow rate of the ammonia gas in the reactor;

[0011] The feedforward correction value and differential value of the boiler load change rate are obtained in real time through the PID controller to determine the second flow rate of ammonia gas that actually needs to be introduced into the reactor;

[0012] According to the difference between the first flow rate and the second flow rate, combined with the pressure, total flow rate and temperature of the ammonia in the ammonia injection regulating valve, the third flow rate of ammonia that needs to be released from the ammonia injection regulating valve is determined, and the opening of the ammonia injection regulating valve is controlled according to the third flow rate to output ammonia to the reactor.

[0013] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0014] Because the present application adds the differential value of the boiler load change rate when using the PID controller to determine the second flow rate of ammonia that actually needs to be introduced into the reactor, the disturbance to the denitrification control system caused by boiler load changes or combustion fluctuations is reduced, thereby overcoming the lag of the denitrification control system to a certain extent.

[0015] In a denitration control method provided in one embodiment of the present invention, a third flow rate of ammonia gas to be released from the ammonia injection regulating valve is determined based on the difference between the first flow rate and the second flow rate, in combination with the pressure, total flow rate, and temperature of the ammonia gas in the ammonia injection regulating valve, and the opening of the ammonia injection regulating valve is controlled based on the third flow rate, including:

[0016] Obtaining a fitting curve of the opening change of the ammonia injection regulating valve and the flow rate of ammonia released from the ammonia injection regulating valve;

[0017] Based on the difference between the first flow rate and the second flow rate, combined with the pressure, total flow rate and temperature of the ammonia in the ammonia injection regulating valve, a third flow rate of ammonia that needs to be released from the ammonia injection regulating valve is determined, and the opening change of the ammonia injection regulating valve is determined and controlled in combination with the third flow rate and the fitting curve.

[0018] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0019] By obtaining the fitting curve, the fitting curve can be used to directly act on the ammonia injection regulating valve, so that the ammonia injection flow rate can be controlled more quickly and accurately.

[0020] In a denitration control method provided in one embodiment of the present invention, a boiler is used to provide a preset reaction temperature for a reactor, comprising:

[0021] NO at the outlet of the fitting reactor x The negative correlation between the flow rate and the inertia time of the air volume and fuel volume introduced into the boiler;

[0022] According to the actual NO x The inertia time of the air volume and fuel volume introduced into the boiler is corrected based on the flow rate and the negative correlation.

[0023] The corrected inertia time is used in combination with the air-coal cross signal strategy to control the air volume and fuel amount passing through the boiler so that the reactor reaches the preset reaction temperature.

[0024] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0025] By using the intelligent correction of the inertia time of the air volume and fuel amount fed into the boiler, the air volume and fuel amount fed into the boiler can be adjusted more quickly when the boiler load changes, thereby reducing the NO discharged from the reactor outlet. x The concentration remains stable.

[0026] In a denitrification control method provided in one embodiment of the present invention, the air-coal cross signal strategy includes:

[0027] When the load required by the boiler increases, the air volume introduced into the boiler is increased so that the air volume required by the current boiler load is greater than the fuel volume required by the current boiler load;

[0028] When the load required by the boiler decreases, the amount of fuel introduced into the boiler is reduced so that the air volume required by the current boiler load is greater than the amount of fuel required by the current boiler load.

[0029] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0030] Through the above strategy, the use of fuel can be minimized and energy can be saved while maintaining the required temperature of the reactor.

[0031] In a denitration control method provided in one embodiment of the present invention, ammonia and NO in the reactor are obtained. x The molar ratio includes:

[0032] Get the reactor inlet NO x The first concentration of and the second concentration of oxygen, as well as the NO at the reactor outlet x a third concentration of and a fourth concentration of oxygen;

[0033] According to the first concentration, the second concentration, the third concentration, the fourth concentration and the NO x The concentration setting value of ammonia and NO in the reactor is calculated. x molar ratio.

[0034] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0035] The NO at the first concentration, the second concentration, the third concentration, the fourth concentration, and the reactor outlet x The concentration setting value of ammonia and NO can be accurately obtained. xmolar ratio.

[0036] At least one embodiment of the present invention further provides a denitration control system, comprising:

[0037] The environmental control module uses a boiler to provide the reactor with a preset reaction temperature;

[0038] The first calculation module determines the ammonia and NO in the reactor x The molar ratio of

[0039] The second calculation module calculates the NO x The flow rate of is multiplied by the molar ratio to determine the first flow rate of ammonia required in the reactor;

[0040] The feedforward correction and differential module obtains the feedforward correction value and differential value of the boiler load change rate in real time through the PID controller to determine the second flow rate of ammonia actually required in the reactor;

[0041] The regulating valve control module determines a third flow rate of ammonia that needs to be released from the ammonia injection regulating valve based on the difference between the first flow rate and the second flow rate, combined with the pressure, total flow rate and temperature of the ammonia in the ammonia injection regulating valve, and controls the opening of the ammonia injection regulating valve according to the third flow rate to output ammonia to the reactor.

[0042] At least one embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores instructions, which, when executed on a terminal device, enable the terminal device to execute the steps of a denitrification control method as described above.

[0043] At least one embodiment of the present invention further provides an electronic device, comprising a memory, a processor, and a program stored in the memory and running on the processor, wherein the processor implements the steps of a denitrification control method as described above when executing the program. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of a denitrification control method according to the present invention;

[0045] Figure 2 The figure is a schematic flow chart of a denitrification control system according to the present invention. DETAILED DESCRIPTION

[0046] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0047] Furthermore, those skilled in the art may combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without mutual contradiction.

[0048] The control mode of denitrification system is generally divided into efficiency control mode and concentration control mode. From the perspective of economic operation, the latter is often used. First, the NO x / O2 analyzer measures NO x / O2 content, and then with the reactor outlet NO x The content setting value (can be set manually) calculates the ammonia and NO x The molar ratio of NO x The required NH3 flow rate is calculated by multiplying the calculated flow rate by the calculated molar ratio. The required calculated NH3 flow rate is then calculated using the feedforward correction value for the boiler load change rate. The actual NH3 flow rate is then calculated based on the actual NH3 pressure, flow rate, and temperature before the ammonia injection control valve. The calculated NH3 flow rate is compared with the actual NH3 flow rate, and the ammonia injection control valve opening is output after PID loop limiting.

[0049] At present, most thermal power plants use cascade PID controllers to control the NO x This control strategy has a certain effect on eliminating the inertia link. However, simply using a cascade PID controller can easily cause excessive ammonia injection, thereby blocking the air preheater downstream of the flue gas, and when the unit changes load quickly, it is easy to cause NO x There is a transient peak in concentration.

[0050] In view of the above situation, the present invention starts to deeply optimize the original logic to ensure that the SCR reactor outlet NO x The concentration is always better than the environmental protection index, and the ammonia injection flow is not too much, thereby reducing the occurrence of blockage of the flue gas downstream air preheater, and striving to improve the NO at the outlet of the SCR reactor by optimizing the existing logic. x The concentration is controlled to reduce the "overspray" and "underspray" of ammonia flow during the unit's load change process.

[0051] The present invention provides a denitrification control method, please refer to Figure 1 Shown, including:

[0052] Using a boiler to provide a preset reaction temperature for the reactor;

[0053] Determine the ammonia and NO in the reactor x The molar ratio of

[0054] The reactor inlet NO xThe flow rate of the ammonia gas in the reactor is multiplied by the molar ratio to determine the first flow rate of the ammonia gas in the reactor;

[0055] The feedforward correction value and differential value of the boiler load change rate are obtained in real time through the PID controller to determine the second flow rate of ammonia gas that actually needs to be introduced into the reactor;

[0056] According to the difference between the first flow rate and the second flow rate, combined with the pressure, total flow rate and temperature of the ammonia in the ammonia injection regulating valve, the third flow rate of ammonia that needs to be released from the ammonia injection regulating valve is determined, and the opening of the ammonia injection regulating valve is controlled according to the third flow rate to output ammonia to the reactor.

[0057] Since the present application uses the PID controller to determine the second flow rate of ammonia gas actually required to be introduced into the reactor, the differential value of the boiler load change rate is additionally added, thereby reducing the disturbance to the denitration control system caused by boiler load changes or combustion fluctuations, thereby overcoming the hysteresis of the denitration control system to a certain extent, and thus more quickly controlling the NO at the reactor inlet. x concentration.

[0058] Further, determining a third flow rate of ammonia gas to be released from the ammonia injection regulating valve based on the difference between the first flow rate and the second flow rate in combination with the pressure, total flow rate, and temperature of the ammonia gas in the ammonia injection regulating valve, and controlling the opening of the ammonia injection regulating valve based on the third flow rate, including:

[0059] Obtaining a fitting curve of the opening change of the ammonia injection regulating valve and the flow rate of ammonia released from the ammonia injection regulating valve;

[0060] Based on the difference between the first flow rate and the second flow rate, combined with the pressure, total flow rate and temperature of the ammonia in the ammonia injection regulating valve, the third flow rate of ammonia that needs to be released from the ammonia injection regulating valve is determined, and the opening change of the ammonia injection regulating valve is determined and controlled in combination with the third flow rate and the fitting curve.

[0061] Since the ammonia injection regulating valve operates very frequently, the linearity of the valve is generally not very good. If a single-loop PID is simply used to control the ammonia injection flow rate, the ammonia injection flow rate cannot be accurately controlled due to factors such as the idle stroke of the ammonia injection regulating valve. For this reason, the present invention fits the characteristic curve of the ammonia injection regulating valve to the ammonia flow rate, and directly acts on the ammonia injection regulating valve with this curve, so that the ammonia injection flow rate can be controlled more quickly and accurately.

[0062] Furthermore, a boiler is used to provide a preset reaction temperature for the reactor, including:

[0063] NO at the outlet of the fitting reactor x The negative correlation between the flow rate and the inertia time of the air volume and fuel volume introduced into the boiler;

[0064] According to the actual NOx The inertia time of the air volume and fuel volume entering the boiler is corrected based on the negative correlation between the flow rate and the fuel volume.

[0065] The corrected inertia time is used in combination with the air-coal cross signal strategy to control the air volume and fuel amount passing through the boiler so that the reactor reaches the preset reaction temperature.

[0066] By using the intelligent correction of the inertia time of the air volume and fuel amount fed into the boiler, the air volume and fuel amount fed into the boiler can be adjusted more quickly when the boiler load changes, thereby reducing the NO discharged from the reactor outlet. x The concentration remains stable.

[0067] Furthermore, the wind and coal cross signal strategy includes:

[0068] When the load required by the boiler increases, the air volume introduced into the boiler is increased so that the air volume required by the current boiler load is greater than the fuel volume required by the current boiler load;

[0069] When the load required by the boiler decreases, the amount of fuel introduced into the boiler is reduced so that the air volume required by the current boiler load is greater than the amount of fuel required by the current boiler load.

[0070] Through the above strategy, the use of fuel can be minimized and energy can be saved while maintaining the required temperature of the reactor;

[0071] The above strategy can ensure that the fuel in the furnace is fully burned, but it will increase the thermal NO x The amount of NO generated at the outlet of the SCR reactor will be affected by the change of boiler load. x The concentration shows an instantaneous peak. At this time, due to the NO x The concentration signal makes intelligent correction to the air-coal cross signal, i.e. NO x Concentration is used to correct the inertia time of the air flow and fuel quantity command signal (fitting the NO x The concentration is negatively correlated to the inertia time of the wind flow and fuel quantity command signal; and when the SCR reactor outlet NO x When the concentration exceeds a certain threshold, the inertia time can be quickly reduced to shorten the duration of the instantaneous peak and maintain NO x Stable concentration.

[0072] Specifically, obtain the ammonia and NO in the reactor x The molar ratio includes:

[0073] Get the reactor inlet NO xThe first concentration of and the second concentration of oxygen, as well as the NO at the reactor outlet x a third concentration of and a fourth concentration of oxygen;

[0074] According to the first concentration, the second concentration, the third concentration, the fourth concentration and the NO x The concentration setting value of ammonia and NO in the reactor is calculated. x molar ratio.

[0075] The NO at the first concentration, the second concentration, the third concentration, the fourth concentration, and the reactor outlet x The concentration setting value of ammonia and NO can be accurately obtained. x molar ratio.

[0076] The present invention also provides a denitrification control system, please refer to Figure 2 Shown, including:

[0077] The environmental control module uses a boiler to provide the reactor with a preset reaction temperature;

[0078] The first calculation module determines the ammonia and NO in the reactor x The molar ratio of

[0079] The second calculation module calculates the NO x The flow rate of the ammonia gas is multiplied by the molar ratio to determine the first flow rate of the ammonia gas required in the reactor;

[0080] The feedforward correction and differential module obtains the feedforward correction value and differential value of the boiler load change rate in real time through the PID controller to determine the second flow rate of ammonia actually required in the reactor;

[0081] The regulating valve control module determines a third flow rate of ammonia that needs to be released from the ammonia injection regulating valve based on the difference between the first flow rate and the second flow rate, combined with the pressure, total flow rate and temperature of the ammonia in the ammonia injection regulating valve, and controls the opening of the ammonia injection regulating valve according to the third flow rate to output ammonia to the reactor.

[0082] Furthermore, the regulating valve control module further includes:

[0083] Obtaining a fitting curve between the opening change of the ammonia injection regulating valve and the ammonia gas actually entering the reactor;

[0084] Based on the difference between the first flow rate and the second flow rate, combined with the pressure, total flow rate and temperature of the ammonia in the ammonia injection regulating valve, the third flow rate of ammonia that needs to be released from the ammonia injection regulating valve is determined, and the opening change of the ammonia injection regulating valve is determined and controlled in combination with the third flow rate and the fitting curve.

[0085] Furthermore, the environmental control module includes:

[0086] NO at the outlet of the fitting reactor x The negative correlation between the flow rate and the inertia time of the air volume and fuel volume introduced into the boiler;

[0087] According to the actual NO x The inertia time of the air volume and fuel volume entering the boiler is corrected based on the negative correlation between the flow rate and the fuel volume.

[0088] The corrected inertia time is used in combination with the air-coal cross signal strategy to control the air volume and fuel amount passing through the boiler so that the reactor reaches the preset reaction temperature.

[0089] Furthermore, the wind-coal cross signal strategy in the environmental control module includes:

[0090] When the load required by the boiler increases, the air volume introduced into the boiler is increased so that the air volume required by the current boiler load is greater than the fuel volume required by the current boiler load;

[0091] When the load required by the boiler decreases, the amount of fuel introduced into the boiler is reduced so that the air volume required by the current boiler load is greater than the amount of fuel required by the current boiler load.

[0092] Furthermore, the present invention also includes:

[0093] NO x / O2 analysis module, obtain NO at the reactor inlet x The first concentration of and the second concentration of oxygen, as well as the NO at the reactor outlet x a third concentration of and a fourth concentration of oxygen;

[0094] The first calculation module calculates the NO concentration at the reactor outlet according to the first concentration, the second concentration, the third concentration, the fourth concentration, and the NO concentration at the reactor outlet. x The concentration setting value of nitrogen and NO in the reactor is calculated. x molar ratio.

[0095] The present invention also provides a computer-readable storage medium, in which instructions are stored. When the instructions are executed on a terminal device, the terminal device executes the steps of the above-mentioned denitrification control method.

[0096] The present invention also provides an electronic device, comprising a memory, a processor, and a program stored in the memory and running on the processor. When the processor executes the program, the steps of the above-mentioned denitrification control method are implemented.

[0097] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A denitrification control method, characterized in that: include: Using a boiler to provide a preset reaction temperature for the reactor; Obtain ammonia and NO in the reactor x The molar ratio of The reactor inlet NO x The flow rate of the ammonia gas in the reactor is multiplied by the molar ratio to determine the first flow rate of the ammonia gas in the reactor; The feedforward correction value and differential value of the boiler load change rate are obtained in real time by the PID controller to determine the second flow rate of ammonia gas that actually needs to be introduced into the reactor; determining a third flow rate of ammonia gas to be released from the ammonia injection regulating valve based on the difference between the first flow rate and the second flow rate, in combination with the pressure, total flow rate, and temperature of the ammonia gas in the ammonia injection regulating valve, and controlling the opening of the ammonia injection regulating valve based on the third flow rate to output the ammonia gas to the reactor; Determining a third flow rate of ammonia gas to be released from the ammonia injection regulating valve based on a difference between the first flow rate and the second flow rate in combination with the pressure, total flow rate, and temperature of the ammonia gas in the ammonia injection regulating valve, and controlling the opening of the ammonia injection regulating valve based on the third flow rate, including: Obtaining a fitting curve of the opening change of the ammonia injection regulating valve and the flow rate of ammonia released from the ammonia injection regulating valve; and determining a third flow rate of ammonia gas to be released from the ammonia injection regulating valve based on the difference between the first flow rate and the second flow rate, in combination with the pressure, total flow rate, and temperature of the ammonia gas in the ammonia injection regulating valve; and determining and controlling a change in the opening of the ammonia injection regulating valve in combination with the third flow rate and the fitting curve; The boiler is used to provide the reactor with a preset reaction temperature, including: NO at the outlet of the fitting reactor x The negative correlation between the flow rate and the inertia time of the air volume and fuel volume introduced into the boiler; According to the actual NO x The inertia time of the air volume and fuel volume introduced into the boiler is corrected based on the flow rate and the negative correlation; The corrected inertia time is used in combination with the air-coal cross signal strategy to control the air volume and fuel volume passing through the boiler so that the reactor reaches the preset reaction temperature. The wind-coal cross signal strategy includes: When the load required by the boiler increases, the air volume introduced into the boiler is increased so that the air volume required by the current boiler load is greater than the fuel volume required by the current boiler load; When the load required by the boiler decreases, the amount of fuel introduced into the boiler is reduced so that the air volume required by the current boiler load is greater than the amount of fuel required by the current boiler load.

2. A denitration control method according to claim 1, characterized in that: Obtain ammonia and NO in the reactor x The molar ratio includes: Get the reactor inlet NO x The first concentration of and the second concentration of oxygen, as well as the NO at the reactor outlet x a third concentration of and a fourth concentration of oxygen; According to the first concentration, the second concentration, the third concentration, the fourth concentration and the NO x The concentration setting value of ammonia and NO in the reactor is calculated. x molar ratio.

3. A denitrification control system, characterized in that: include: The environmental control module uses a boiler to provide the reactor with a preset reaction temperature; The first calculation module determines the ammonia and NO in the reactor x The molar ratio of The second calculation module calculates the NO x The flow rate of is multiplied by the molar ratio to determine the first flow rate of ammonia required in the reactor; The feedforward correction and differential module obtains the feedforward correction value and differential value of the boiler load change rate in real time through the PID controller to determine the second flow rate of ammonia actually required in the reactor; a regulating valve control module that determines a third flow rate of ammonia gas to be released from the ammonia injection regulating valve based on a difference between the first flow rate and the second flow rate, in combination with the pressure, total flow rate, and temperature of the ammonia gas in the ammonia injection regulating valve, and controls an opening of the ammonia injection regulating valve based on the third flow rate to output the ammonia gas to the reactor; The regulating valve control module also includes: Obtaining a fitting curve between the opening change of the ammonia injection regulating valve and the ammonia gas actually entering the reactor; and determining a third flow rate of ammonia gas to be released from the ammonia injection regulating valve based on the difference between the first flow rate and the second flow rate, in combination with the pressure, total flow rate, and temperature of the ammonia gas in the ammonia injection regulating valve; and determining and controlling a change in the opening of the ammonia injection regulating valve in combination with the third flow rate and the fitting curve; The environmental control module includes: NO at the outlet of the fitting reactor x The negative correlation between the flow rate and the inertia time of the air volume and fuel volume introduced into the boiler; According to the actual NO x The inertia time of the air volume and fuel volume introduced into the boiler is corrected based on the flow rate and the negative correlation; The corrected inertia time is used in combination with the air-coal cross signal strategy to control the air volume and fuel volume passing through the boiler so that the reactor reaches the preset reaction temperature. The wind-coal cross signal strategy includes: When the load required by the boiler increases, the air volume introduced into the boiler is increased so that the air volume required by the current boiler load is greater than the fuel volume required by the current boiler load; When the load required by the boiler decreases, the amount of fuel introduced into the boiler is reduced so that the air volume required by the current boiler load is greater than the amount of fuel required by the current boiler load.

4. A computer-readable storage medium, characterized in that The computer-readable storage medium stores instructions, and when the instructions are executed on the terminal device, the terminal device executes the steps of the denitration control method according to claim 1 or 2.

5. An electronic device comprising a memory, a processor, and a program stored in the memory and running on the processor, characterized in that: When the processor executes the program, the steps of a denitrification control method as claimed in claim 1 or 2 are implemented.

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