A method for sequential control of spray guns in a denitrification system

Abstract

This invention discloses a spray gun sequential control method for a denitrification system, relating to the field of denitrification. The method includes adjusting the air pressure of compressed air and urea solution within the spray gun and determining the atomization effect; during unit start-up and shutdown, determining the opening of the spray gun's flow control valve based on the nitrogen oxide emission rate, and adjusting the flow control valve opening in real time based on the difference between the current nitrogen oxide emission rate and the preset nitrogen oxide target emission rate; after a period of unit start-up and shutdown, determining the duration of nitrogen oxide emission exceeding the limit based on the load fluctuation range during the start-up and shutdown process; judging whether the duration of exceeding the limit meets the preset allowable duration of exceeding the limit; if so, adjusting the delay time of the spray gun flow control valve based on the difference between the duration of exceeding the limit and the preset allowable duration of exceeding the limit; judging whether to engage or disengage the spray gun based on the opening status of the spray gun flow control valve and determining the required number of engagements or disengagements; and determining the spray gun engagement / disengagement time point based on the catalyst temperature. This effectively prevents nitrogen oxide emissions from exceeding the limit during unit start-up and shutdown and improves urea utilization.

Description

Technical Field

[0001] This application relates to the field of denitrification technology, and more specifically, to a method for sequential control of spray guns in a denitrification system. Background Technology

[0002] Nitrogen oxide (NOx) treatment technologies mainly include low-NOx combustion technology, SNCR (Selective Non-Catalytic Reduction) technology, SCR (Selective Catalytic Reduction) technology, oxidation methods, and mixed powder technology. Currently, SCR denitrification technology is the most widely used denitrification technology in coal-fired power plants. The principle of this technology is to inject ammonia or urea into the boiler using a spray gun to mix it with NOx in the flue gas. Under the action of a catalyst, a redox reaction occurs, generating N2 and H2O, thereby achieving the goal of ultra-low NOx emissions.

[0003] However, gas turbine units are responsible for load shaving, so they start and stop relatively frequently. During the start-up and shutdown process, the unit load fluctuates greatly, and NOx emissions fluctuate with the changes in unit load and operating conditions. In this process, due to manual adjustment, the flow rate regulating valve of the urea solution in the spray gun is not adjusted in time, and the timing and quantity of the urea spray gun system are unclear. As a result, nitrogen oxides exceed the standard and urea solution is wasted during the start-up and shutdown phases.

[0004] Therefore, how to adjust the spray gun flow control valve in a timely manner during the start-up and shutdown of the unit, and how to promptly engage and disengage the spray gun to prevent excessive nitrogen oxide emissions and improve urea utilization rate, are currently technical problems that need to be solved. Summary of the Invention

[0005] This invention provides a method for sequential control of spray guns in a denitrification system, addressing the technical problems in existing denitrification systems where excessive nitrogen oxide emissions and low urea utilization rates occur during unit start-up and shutdown due to untimely adjustment of the spray gun flow control valve and untimely deployment and withdrawal of the spray guns. The method includes:

[0006] Adjust the air pressure of the compressed air and urea solution inside the spray gun, and determine the corresponding atomization effect;

[0007] During the start-up and shutdown phases of the unit, the emission of nitrogen oxides during the unit operation is monitored in real time. The opening of the flow control valve of the spray gun is determined based on the emission of nitrogen oxides, and the opening of the flow control valve of the spray gun is adjusted in real time based on the difference between the current emission of nitrogen oxides and the preset target emission of nitrogen oxides.

[0008] After the unit has been started and stopped for a period of time, the start and end times of the nitrogen oxide emission exceeding the standard are determined according to the load fluctuation range during the start and stop of the unit, and the duration of the exceedance is calculated.

[0009] Determine whether the duration of the exceedance meets the preset allowable duration of exceedance. If the duration of the exceedance is greater than the preset allowable duration of exceedance, calculate the delay time for adjusting the spray gun flow control valve based on the difference between the end time of the exceedance corresponding to the exceedance of nitrogen oxide emissions and the adjustment time of the spray gun flow control valve.

[0010] Calculate the difference between the duration of exceeding the standard and the preset allowable duration of exceeding the standard, and adjust the delay time of the regulating spray gun flow control valve according to the difference between the duration of exceeding the standard and the preset allowable duration of exceeding the standard;

[0011] Determine whether to engage or disengage the spray gun based on the opening of the spray gun flow control valve, and determine the required number of spray guns to engage or disengage.

[0012] The temperature of the catalyst during the reaction process is monitored in real time, and the timing of the spray gun's engagement and disengagement is determined based on the catalyst temperature. The spray gun is then engaged and disengaged in a timely manner according to the engagement and disengagement timing.

[0013] In some embodiments of this application, adjusting the air pressure of the compressed air and urea solution inside the spray gun and determining the corresponding atomization effect includes:

[0014] Different compressed air and urea solution pressures inside the spray gun correspond to different atomization effects. Adjust the compressed air and urea solution pressures inside the spray gun. When the atomization effect reaches the preset requirements, start the unit. When the boiler inlet flue gas temperature reaches the temperature required for the sequential start of the spray gun, close the flushing water valve of the spray gun in sequence and start the on / off valve and flow control valve of the spray gun.

[0015] In some embodiments of this application, the opening degree of the flow control valve of the spray gun is determined based on the emission amount of nitrogen oxides, including:

[0016] The corresponding urea injection amount is determined based on the amount of nitrogen oxides emitted in the boiler and the reaction ratio between nitrogen oxides and urea. The opening degree of the spray gun flow control valve is determined based on the urea injection amount, and the flow control valve of the spray gun is adjusted in real time based on the opening degree of the spray gun flow control valve.

[0017] In some embodiments of this application, the start and end times of nitrogen oxide emissions exceeding the standard are determined based on the load fluctuation range during unit start-up and shutdown, and the time interval of the exceedance is calculated, including:

[0018] The system detects the fluctuation range of the unit load during the start-up and shutdown process, and detects the fluctuation range of nitrogen oxide emissions within the unit load fluctuation range. Within the nitrogen oxide emission fluctuation range, it determines whether the nitrogen oxide emissions exceed the standard. If the nitrogen oxide emissions exceed the standard, the system records the start and end times of the exceedance and calculates the exceedance duration based on the start and end times of the exceedance.

[0019] In some embodiments of this application, the delay time for adjusting the spray gun flow control valve is calculated based on the difference between the start time of the nitrogen oxide emission exceeding the standard and the adjustment time of the spray gun flow control valve, including:

[0020] Let T1 be the onset time of nitrogen oxide emissions exceeding the standard, T2 be the time of exceeding the standard, T0 be the adjustment time of the spray gun flow control valve, and T′ be the delay time for adjusting the spray gun flow control valve.

[0021] T′=T0-T1;

[0022] Let the duration of exceeding the limit be L1, and the allowable duration of exceeding the limit be L2.

[0023] L1 = T2 - T1.

[0024] In some embodiments of this application, calculating the difference between the excessive duration and the preset allowable excessive duration, and adjusting the delay time of the regulating spray gun flow control valve based on the difference between the excessive duration and the preset allowable excessive duration, includes:

[0025] Let L′ be the difference between the duration of the exceedance and the preset allowable exceedance duration.

[0026] L′=L1-L2;

[0027] Let S be the amount of nitrogen oxide emissions within the time difference L′, where S is the difference between the actual excess emissions and the allowable excess emissions of nitrogen oxides during the start-up and shutdown of the unit.

[0028] The emission amount S of nitrogen oxides corresponding to the time difference L′ is determined based on the time difference L′, and the delay time T′ of the regulating spray gun flow control valve is adjusted based on the emission amount S of nitrogen oxides.

[0029] In some embodiments of this application, determining whether to engage or disengage the spray gun and determining the required number of spray guns to be engaged or disengaged based on the opening of the spray gun flow control valve includes:

[0030] The system presets a first threshold for the opening of the spray gun flow control valve and a second threshold for the opening of the spray gun flow control valve. When the opening of the spray gun flow control valve is lower than the preset first threshold, the spray gun is withdrawn. The number of spray guns to be withdrawn is determined based on the difference between the amount of urea injected into the boiler at this time and the actual amount of urea required.

[0031] When the opening of the spray gun flow control valve is higher than the preset second threshold of the spray gun flow control valve opening, the spray gun is engaged, and the number of spray guns to be engaged is determined based on the difference between the amount of urea already injected into the boiler and the actual amount of urea required.

[0032] In some embodiments of this application, determining the engagement / disengagement time of the spray gun based on the temperature of the catalyst, and engaging / disengaging the spray gun in a timely manner according to the engagement / disengagement time, includes:

[0033] A preset catalyst temperature threshold is set. When the catalyst temperature reaches the preset catalyst temperature threshold, the time point at which the spray gun is engaged is taken as the time point when the catalyst temperature reaches the preset catalyst temperature threshold. When the catalyst temperature is lower than the preset catalyst temperature threshold, the time point at which the spray gun is disengaged is taken as the time point when the catalyst temperature is lower than the preset catalyst temperature threshold.

[0034] Based on the deployment and withdrawal time of the spray gun and the required number of spray guns to be deployed and withdrawn, the spray guns are deployed and withdrawn in a timely manner. When it is necessary to withdraw the spray gun, the flow control valve of the spray gun is closed in sequence, the flushing water valve of the spray gun is opened to flush the spray gun, and the on / off valve of the spray gun solution is closed.

[0035] By applying the above technical solutions, the air pressure of compressed air and urea solution in the spray gun is adjusted and the atomization effect is determined. During the unit start-up and shutdown phase, the opening of the spray gun flow control valve is determined according to the nitrogen oxide emission, and the opening of the flow control valve is adjusted in real time according to the difference between the current nitrogen oxide emission and the preset nitrogen oxide target emission. After the unit has been started and stopped for a period of time, the duration of nitrogen oxide emission exceeding the standard is determined according to the load fluctuation range during the unit start-up and shutdown process. It is judged whether the duration of exceeding the standard meets the preset allowable duration of exceeding the standard. If it does, the delay time of the spray gun flow control valve is adjusted according to the difference between the duration of exceeding the standard and the preset allowable duration of exceeding the standard. It is judged whether to engage or disengage the spray gun according to the opening of the spray gun flow control valve and the required number of engagements or disengagements is determined. The timing of engaging or disengaging the spray gun is determined according to the temperature of the catalyst. This invention adjusts the urea injection rate of the spray gun based on changes in nitrogen oxide emissions, thereby adjusting the opening of the spray gun flow valve to ensure the effective utilization of urea solution. By adjusting the adjustment time of the spray gun flow control valve in real time, it ensures timely adjustment of the flow control valve, preventing waste of urea solution due to premature adjustment and excessive nitrogen oxide emissions due to delayed adjustment. Furthermore, it clarifies the timing and number of spray gun activation and deactivation, improving the stability of spray gun operation. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A schematic flowchart of a spray gun sequential control method for a denitrification system proposed in an embodiment of the present invention is shown. Detailed Implementation

[0038] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0039] Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] This application provides a method for sequential control of spray guns in a denitrification system, such as... Figure 1 As shown, the method includes the following steps:

[0041] Step S101: Adjust the air pressure of the compressed air and urea solution inside the spray gun, and determine the corresponding atomization effect.

[0042] In some embodiments of this application, adjusting the air pressure of the compressed air and urea solution inside the spray gun and determining the corresponding atomization effect includes:

[0043] Different compressed air and urea solution pressures inside the spray gun correspond to different atomization effects. Adjust the compressed air and urea solution pressures inside the spray gun. When the atomization effect reaches the preset requirements, start the unit. When the boiler inlet flue gas temperature reaches the temperature required for the sequential start of the spray gun, close the flushing water valve of the spray gun in sequence and start the on / off valve and flow control valve of the spray gun.

[0044] Step S102: During the unit start-up and shutdown phase, the amount of nitrogen oxide emissions during unit operation is detected in real time. The opening degree of the flow control valve of the spray gun is determined based on the amount of nitrogen oxide emissions, and the opening degree of the flow control valve of the spray gun is adjusted in real time based on the difference between the current amount of nitrogen oxide emissions and the preset target amount of nitrogen oxide emissions.

[0045] In some embodiments of this application, the opening degree of the flow control valve of the spray gun is determined based on the emission amount of nitrogen oxides, including:

[0046] The corresponding urea injection amount is determined based on the amount of nitrogen oxides emitted in the boiler and the reaction ratio between nitrogen oxides and urea. The opening degree of the spray gun flow control valve is determined based on the urea injection amount, and the flow control valve of the spray gun is adjusted in real time based on the opening degree of the spray gun flow control valve.

[0047] In this embodiment, the emission of nitrogen oxides (NOx) generated in the boiler is constantly changing. The urea injection rate is determined based on the NOx emission rate and the denitrification reaction ratio, ensuring that the amount of urea injected matches and changes accordingly with the fluctuating NOx emission. The valve opening of the injection gun changes with the constantly changing urea injection rate, thus requiring real-time adjustment to adapt to changes in the unit's operating conditions and to ensure effective utilization of the urea solution. Furthermore, the control of NOx emissions must also achieve a preset target emission value, necessitating further adjustment of the urea injection rate. Each difference between the current NOx emission rate and the preset NOx emission rate corresponds to a valve opening adjustment coefficient: Target flow valve opening = Actual flow valve opening * Valve opening adjustment coefficient.

[0048] It should be noted that the emission level of nitrogen oxides can also be replaced by the concentration of nitrogen oxides as a reference standard for adjusting the amount of urea injected.

[0049] Step S103: After the unit has been started and stopped for a period of time, determine the start and end time of the nitrogen oxide emission exceeding the standard based on the load fluctuation range during the unit's start and stop process, and calculate the duration of the exceedance.

[0050] In some embodiments of this application, the start and end times of nitrogen oxide emissions exceeding the standard are determined based on the load fluctuation range during unit start-up and shutdown, and the time interval of the exceedance is calculated, including:

[0051] The system detects the fluctuation range of the unit load during the start-up and shutdown process, and detects the fluctuation range of nitrogen oxide emissions within the unit load fluctuation range. Within the nitrogen oxide emission fluctuation range, it determines whether the nitrogen oxide emissions exceed the standard. If the nitrogen oxide emissions exceed the standard, the system records the start and end times of the exceedance and calculates the exceedance duration based on the start and end times of the exceedance.

[0052] In this embodiment, since the gas turbine unit is responsible for load peak shaving, the unit starts and stops relatively frequently. Frequent start and stop will cause large fluctuations in the unit load. Under low load and high load conditions, the combustion temperature will change significantly, which will cause large changes in nitrogen oxide emissions. During this process, there will be a momentary exceedance of nitrogen oxide emissions. Therefore, it is necessary to adjust the spray gun flow control valve in time to control the nitrogen oxide emissions.

[0053] In this embodiment, nitrogen oxide emissions are allowed to exceed the limit for a period of time during unit start-up and shutdown, but not exceeding the allowed overrun duration. During unit start-up, the unit load will continuously increase, and the allowed overrun duration is the duration from start-up to the unit reaching full load. During unit shutdown, the unit load will continuously decrease, and the allowed overrun duration is the duration from shutdown to the unit clearing the load. Since nitrogen oxide emissions will first increase and then decrease during the continuous increase or decrease of load, the overrun time will be concentrated within a certain period. The fluctuation range of nitrogen oxides within the unit load fluctuation range can be directly detected. Through image display, the overrun range of nitrogen oxide emissions within the nitrogen oxide fluctuation range and the starting time point corresponding to the overrun can be obtained, and the actual overrun duration can be calculated.

[0054] In this embodiment, if the flow control valve is adjusted before the start of the exceedance, urea solution will be wasted. If the flow control valve is adjusted after the end of the exceedance, nitrogen oxide emissions will exceed the limit due to failure to control them in time, and the duration of the exceedance will exceed the allowable duration. Therefore, the delay time of adjusting the spray gun flow control valve needs to be adjusted to minimize the delay time as much as possible.

[0055] Step S104: Determine whether the duration of exceeding the standard meets the preset allowable duration of exceeding the standard. If the duration of exceeding the standard is greater than the preset allowable duration of exceeding the standard, calculate the delay time for adjusting the spray gun flow control valve based on the difference between the start time of exceeding the standard corresponding to the nitrogen oxide emission exceeding the standard and the adjustment time of the spray gun flow control valve.

[0056] In some embodiments of this application, the delay time for adjusting the spray gun flow control valve is calculated based on the difference between the start time of the nitrogen oxide emission exceeding the standard and the adjustment time of the spray gun flow control valve, including:

[0057] Let T1 be the start time of the nitrogen oxide emission exceeding the standard, T2 be the end time of the exceedance, T0 be the adjustment time of the spray gun flow control valve, and T′ be the delay time for adjusting the spray gun flow control valve.

[0058] T′=T0-T1;

[0059] Let the duration of exceeding the limit be L1, and the allowable duration of exceeding the limit be L2.

[0060] L1 = T2 - T1.

[0061] Step S105: Calculate the difference between the excessive duration and the preset allowable excessive duration, and adjust the delay time of the regulating spray gun flow control valve according to the difference between the excessive duration and the preset allowable excessive duration.

[0062] In some embodiments of this application, calculating the difference between the excessive duration and the preset allowable excessive duration, and adjusting the delay time of the regulating spray gun flow control valve based on the difference between the excessive duration and the preset allowable excessive duration, includes:

[0063] Let L′ be the difference between the duration of the exceedance and the preset allowable exceedance duration.

[0064] L′=L1-L2;

[0065] Let S be the amount of nitrogen oxide emissions within the time difference L′, where S is the difference between the actual excess emissions and the allowable excess emissions of nitrogen oxides during the start-up and shutdown of the unit.

[0066] The emission amount S of nitrogen oxides corresponding to the time difference L′ is determined based on the time difference L′, and the delay time T′ of the regulating spray gun flow control valve is adjusted based on the emission amount S of nitrogen oxides.

[0067] In this embodiment, the actual duration of exceeding the standard corresponds to an actual amount of nitrogen oxide emissions, the allowable duration of exceeding the standard corresponds to an allowable amount of nitrogen oxide emissions exceeding the standard, and the duration difference L′ corresponds to the amount of nitrogen oxide emissions S.

[0068] It should be noted that the duration difference L′ is the sum of the difference between the time exceeding the standard and the preset allowable time exceeding the standard during the two processes of unit startup and shutdown. The nitrogen oxide emission S is the sum of the difference between the actual excess emission and the allowable excess emission during the two processes of unit startup and shutdown. The delay time T′ is the total delay time of the flow control valve during startup and shutdown. Since the nitrogen oxide emission S is the excess amount exceeding the allowable excess emission due to the adjustment time delay, the delay time can be adjusted according to the nitrogen oxide emission S.

[0069] In this embodiment, different nitrogen oxide emissions S correspond to different delay times, and the target delay time = delay time * time adjustment coefficient.

[0070] It should be noted that the method of adjusting the delay time is not limited to this. Other adjustment methods can be used based on historical experience or mathematical formulas to adjust the delay time as much as possible, so as to ensure that the excess time corresponding to the nitrogen oxide excess is within the allowable excess time as much as possible. When the delay time is zero, there is no excess of nitrogen oxides.

[0071] The beneficial effects of the above scheme are as follows: During unit start-up and shutdown, the opening of the spray gun flow control valve is adjusted in real time according to changes in the system response to control nitrogen oxide emissions and ensure they meet target emission values, thereby improving the utilization rate of urea solution and avoiding resource waste. Furthermore, the real-time adjustment of the spray gun flow control valve's adjustment time ensures that it is adjusted as promptly as possible, preventing nitrogen oxide emissions from exceeding allowable limits during unit start-up and shutdown, thus avoiding environmental pollution.

[0072] Step S106: Determine whether to engage or disengage the spray gun based on the opening of the spray gun flow control valve and determine the required number of spray guns to engage or disengage.

[0073] In some embodiments of this application, determining whether to engage or disengage the spray gun and determining the required number of spray guns to be engaged or disengaged based on the opening of the spray gun flow control valve includes:

[0074] The system presets a first threshold for the opening of the spray gun flow control valve and a second threshold for the opening of the spray gun flow control valve. When the opening of the spray gun flow control valve is lower than the preset first threshold, the spray gun is withdrawn. The number of spray guns to be withdrawn is determined based on the difference between the amount of urea injected into the boiler at this time and the actual amount of urea required.

[0075] When the opening of the spray gun flow control valve is higher than the preset second threshold of the spray gun flow control valve opening, the spray gun is engaged, and the number of spray guns to be engaged is determined based on the difference between the amount of urea already injected into the boiler and the actual amount of urea required.

[0076] In this embodiment, when it is detected that the flow control valve of a certain spray gun is too low, the amount of urea already injected into the boiler is higher than the actual required amount of urea, and the number of spray guns is more than the actual required number. The difference between the amount of urea already injected into the boiler and the actual required amount of urea is the excess amount of urea solution in the boiler. Different excess amounts of urea solution correspond to different numbers of spray guns that need to be withdrawn. Therefore, the number of spray guns that need to be withdrawn can be determined based on the difference between the amount of urea already injected into the boiler and the actual required amount of urea.

[0077] It should be noted that the method for determining the quantity of spray guns to be inserted is the same as the principle for determining the quantity to be withdrawn, so it will not be explained again.

[0078] Step S107: Real-time monitoring of the catalyst temperature during the reaction process; determination of the spray gun activation / deactivation time based on the catalyst temperature; and timely activation / deactivation of the spray gun based on the activation / deactivation time.

[0079] In some embodiments of this application, determining the engagement / disengagement time of the spray gun based on the temperature of the catalyst, and engaging / disengaging the spray gun in a timely manner according to the engagement / disengagement time, includes:

[0080] A preset catalyst temperature threshold is set. When the catalyst temperature reaches the preset catalyst temperature threshold, the time point at which the spray gun is engaged is taken as the time point when the catalyst temperature reaches the preset catalyst temperature threshold. When the catalyst temperature is lower than the preset catalyst temperature threshold, the time point at which the spray gun is disengaged is taken as the time point when the catalyst temperature is lower than the preset catalyst temperature threshold.

[0081] Based on the deployment and withdrawal time of the spray gun and the required number of spray guns to be deployed and withdrawn, the spray guns are deployed and withdrawn in a timely manner. When it is necessary to withdraw the spray gun, the flow control valve of the spray gun is closed in sequence, the flushing water valve of the spray gun is opened to flush the spray gun, and the on / off valve of the spray gun solution is closed.

[0082] In this embodiment, the temperature threshold of the catalyst is a reference point for the spray gun deployment and retraction time. This temperature threshold can be designed and adjusted according to the actual situation.

[0083] In this embodiment, when the spray gun is withdrawn, the flushing water valve needs to be opened to flush the spray gun to prevent the urea solution inside the spray gun from crystallizing and causing blockage.

[0084] The beneficial effects of the above scheme are: it clarifies whether the spray gun should be engaged or disengaged, the engagement and disengagement time, and the number of guns engaged or disengaged, thus avoiding the waste of urea solution and excessive nitrogen oxide emissions due to untimely engagement and disengagement, and further improving the stability of spray gun operation.

[0085] By applying the above technical solutions, the pressure of compressed air and urea solution in the spray gun is adjusted and the atomization effect is determined. During the unit start-up and shutdown phase, the opening of the spray gun flow control valve is determined based on the nitrogen oxide emission rate, and the flow control valve opening is adjusted in real time based on the difference between the current nitrogen oxide emission rate and the preset nitrogen oxide target emission rate. After the unit has been started and stopped for a period of time, the duration of nitrogen oxide emission exceeding the standard is determined based on the load fluctuation range during the unit start-up and shutdown process. It is judged whether the duration of exceeding the standard meets the preset allowable duration of exceeding the standard. If it does, the delay time of adjusting the spray gun flow control valve is adjusted based on the difference between the duration of exceeding the standard and the preset allowable duration of exceeding the standard. It is judged whether to engage or disengage the spray gun based on the opening of the spray gun flow control valve and the required number of engagements or disengagements is determined. The timing of engaging or disengaging the spray gun is determined based on the temperature of the catalyst. This invention adjusts the urea injection rate of the spray gun based on changes in nitrogen oxide emissions, thereby adjusting the opening of the spray gun flow valve to ensure the effective utilization of urea solution. By adjusting the adjustment time of the spray gun flow control valve in real time, it ensures timely adjustment of the flow control valve, preventing waste of urea solution due to premature adjustment and excessive nitrogen oxide emissions due to delayed adjustment. Furthermore, it clarifies the timing and number of spray gun activation and deactivation, improving the stability of spray gun operation.

[0086] Through the above description of the embodiments, those skilled in the art can clearly understand that the present invention can be implemented in hardware or by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of the present invention can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as a CD-ROM, USB flash drive, external hard drive, etc.) and includes several instructions to cause a computer device (such as a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for sequential control of spray guns in a denitrification system, characterized in that, The method includes: Adjust the air pressure of the compressed air and urea solution inside the spray gun, and determine the corresponding atomization effect; During the start-up and shutdown phases of the unit, the emission of nitrogen oxides during the unit operation is monitored in real time. The opening of the flow control valve of the spray gun is determined based on the emission of nitrogen oxides, and the opening of the flow control valve of the spray gun is adjusted in real time based on the difference between the current emission of nitrogen oxides and the preset target emission of nitrogen oxides. After the unit has been started and stopped for a period of time, the start and end times of the nitrogen oxide emission exceeding the standard are determined according to the load fluctuation range during the start and stop of the unit, and the duration of the exceedance is calculated. Determine whether the duration of the exceedance meets the preset allowable duration of exceedance. If the duration of the exceedance is greater than the preset allowable duration of exceedance, calculate the delay time for adjusting the spray gun flow control valve based on the difference between the start time of the exceedance corresponding to the exceedance of nitrogen oxide emissions and the adjustment time of the spray gun flow control valve. Calculate the difference between the duration of exceeding the standard and the preset allowable duration of exceeding the standard, and adjust the delay time of the regulating spray gun flow control valve according to the difference between the duration of exceeding the standard and the preset allowable duration of exceeding the standard; Determine whether to engage or disengage the spray gun based on the opening of the spray gun flow control valve, and determine the required number of spray guns to engage or disengage. The temperature of the catalyst during the reaction process is monitored in real time, and the timing of the spray gun's engagement and disengagement is determined based on the catalyst temperature. The spray gun is then engaged and disengaged in a timely manner according to the engagement and disengagement timing.

2. The spray gun sequential control method for the denitrification system according to claim 1, characterized in that, Adjust the air pressure of the compressed air and urea solution inside the spray gun, and determine the corresponding atomization effect, including: Different compressed air and urea solution pressures inside the spray gun correspond to different atomization effects. Adjust the compressed air and urea solution pressures inside the spray gun. When the atomization effect reaches the preset requirements, start the unit. When the boiler inlet flue gas temperature reaches the temperature required for the sequential start of the spray gun, close the flushing water valve of the spray gun in sequence and start the on / off valve and flow control valve of the spray gun.

3. The spray gun sequential control method for the denitrification system according to claim 1, characterized in that, The opening of the spray gun's flow control valve is determined based on the amount of nitrogen oxide emissions, including: The corresponding urea injection amount is determined based on the amount of nitrogen oxides emitted in the boiler and the reaction ratio between nitrogen oxides and urea. The opening degree of the spray gun flow control valve is determined based on the urea injection amount, and the flow control valve of the spray gun is adjusted in real time based on the opening degree of the spray gun flow control valve.

4. The spray gun sequential control method for the denitrification system according to claim 1, characterized in that, Based on the load fluctuation range during unit start-up and shutdown, determine the start and end times of nitrogen oxide emissions exceeding the standard and calculate the time interval of the exceedance, including: The system detects the fluctuation range of the unit load during the start-up and shutdown process, and detects the fluctuation range of nitrogen oxide emissions within the unit load fluctuation range. Within the nitrogen oxide emission fluctuation range, it determines whether the nitrogen oxide emissions exceed the standard. If the nitrogen oxide emissions exceed the standard, the system records the start and end times of the exceedance and calculates the exceedance duration based on the start and end times of the exceedance.

5. The spray gun sequential control method for the denitrification system according to claim 4, characterized in that, The delay time for adjusting the spray gun flow control valve is calculated based on the difference between the start time of the nitrogen oxide emission exceeding the standard and the adjustment time of the spray gun flow control valve. This includes: Let T1 be the start time of the nitrogen oxide emission exceeding the standard, T2 be the end time of the exceedance, T0 be the adjustment time of the spray gun flow control valve, and T′ be the delay time for adjusting the spray gun flow control valve. T′=T0-T1; Let the duration of exceeding the limit be L1, and the allowable duration of exceeding the limit be L2. L1 = T2 - T1.

6. The spray gun sequential control method for the denitrification system according to claim 5, characterized in that, Calculating the difference between the duration of exceeding the limit and the preset allowable duration of exceeding the limit, and adjusting the delay time of the regulating spray gun flow control valve based on the difference between the duration of exceeding the limit and the preset allowable duration of exceeding the limit, including: Let L′ be the difference between the duration of the exceedance and the preset allowable exceedance duration. L′=L1-L2; Let S be the amount of nitrogen oxide emissions within the time difference L′, where S is the difference between the actual excess emissions and the allowable excess emissions of nitrogen oxides during the start-up and shutdown of the unit. The emission amount S of nitrogen oxides corresponding to the time difference L′ is determined based on the time difference L′, and the delay time T′ of the regulating spray gun flow control valve is adjusted based on the emission amount S of nitrogen oxides.

7. The spray gun sequential control method for the denitrification system according to claim 1, characterized in that, Determine whether to engage or disengage the spray gun based on the opening of the spray gun flow control valve, and determine the required number of spray guns to engage or disengage, including: The system presets a first threshold for the opening of the spray gun flow control valve and a second threshold for the opening of the spray gun flow control valve. When the opening of the spray gun flow control valve is lower than the preset first threshold, the spray gun is withdrawn. The number of spray guns to be withdrawn is determined based on the difference between the amount of urea injected into the boiler at this time and the actual amount of urea required. When the opening of the spray gun flow control valve is higher than the preset second threshold of the spray gun flow control valve opening, the spray gun is engaged, and the number of spray guns to be engaged is determined based on the difference between the amount of urea already injected into the boiler and the actual amount of urea required.

8. The spray gun sequential control method for the denitrification system according to claim 7, characterized in that, Determining the timing of spray gun engagement and disengagement based on the temperature of the catalyst, and engaging and disengaging the spray gun promptly according to the engagement and disengagement timing, includes: A preset catalyst temperature threshold is set. When the catalyst temperature reaches the preset catalyst temperature threshold, the time point at which the spray gun is engaged is taken as the time point when the catalyst temperature reaches the preset catalyst temperature threshold. When the catalyst temperature is lower than the preset catalyst temperature threshold, the time point at which the spray gun is disengaged is taken as the time point when the catalyst temperature is lower than the preset catalyst temperature threshold. Based on the deployment and withdrawal time of the spray gun and the required number of spray guns to be deployed and withdrawn, the spray guns are deployed and withdrawn in a timely manner. When it is necessary to withdraw the spray gun, the flow control valve of the spray gun is closed in sequence, the flushing water valve of the spray gun is opened to flush the spray gun, and the on / off valve of the spray gun solution is closed.

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