Denitration control method for boiler flue gas

Abstract

The invention discloses a denitration control method for boiler flue gas. The method comprises the steps that a boiler is connected with the first ends of a plurality of flues, and the second ends of the flues are jointly connected to a chimney; the denitration control method for the boiler flue gas comprises a first control mode and a second control mode. The first control mode comprises the following steps: acquiring the oxynitride content of a flue outlet; the ammonia spraying amount of the flue is adjusted according to the relation between the content of the oxynitride at the flue outlet and the preset value of the oxynitride at the flue outlet; the second control mode comprises the following steps: acquiring the oxynitride content of the chimney inlet; the preset value of the oxynitride is updated according to the relation between the content of the oxynitride at the chimney inlet and the preset value of the oxynitride; the content of the oxynitride at the chimney inlet comprises the content of the oxynitride obtained by fitting the content of the oxynitride at the multiple flue outlets. According to the technical scheme provided by the embodiment of the invention, the stability of oxynitride concentration control can be improved, the risk of flue blockage is reduced, and maintenance is convenient.

Description

Technical Field

[0001] The invention relates to the technical field of automatic control of thermal power plants, and in particular to a denitration control method for boiler flue gas. Background Art

[0002] At present, most of the flue gas denitrification control technologies are based on modeling or predictive control methods of external controllers. Due to the large delay, time-varying, multivariable coupling, and large delay in the measurement of nitrogen oxides in the flue gas denitrification process, conventional control methods are difficult to achieve ideal control effects, which can easily cause excessive ammonia injection or poor ammonia injection stability, resulting in blockage of flues and other equipment. The modeling and predictive control methods based on external controllers have main control logics in the external machines, which have confidentiality measures for power plant maintenance personnel, and manufacturers need to be on-site for maintenance when problems occur; in addition, when the combustion system and flue gas system need to be modified, it is necessary to contact the manufacturer for optimization, which has poor maintainability and affects production efficiency. Summary of the invention

[0003] The present invention provides a boiler flue gas denitration control method to improve the stability of nitrogen oxide concentration control at the denitration outlet, reduce the ammonia escape rate and the risk of boiler flue clogging and shutdown, and facilitate maintenance and adjustment by power plant maintenance personnel.

[0004] According to one aspect of the present invention, a method for controlling denitration of boiler flue gas is provided, comprising: the boiler is respectively connected to first ends of a plurality of flues, and second ends of the plurality of flues are commonly connected to a chimney;

[0005] The boiler flue gas denitration control method includes a first control mode and a second control mode;

[0006] The first control mode includes:

[0007] Obtaining the nitrogen oxide content at the flue outlet;

[0008] adjusting the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxide at the flue outlet;

[0009] The second control mode includes:

[0010] Obtaining the nitrogen oxide content at the chimney inlet;

[0011] The preset value of nitrogen oxides is updated according to the relationship between the nitrogen oxide content at the chimney inlet and the preset value of nitrogen oxides.

[0012] Optionally, the method includes: a third control mode;

[0013] The third control mode includes:

[0014] Obtaining the ammonia content at the flue outlet;

[0015] The preset value of nitrogen oxides is corrected according to the relationship between the ammonia content at the flue outlet and the preset value of ammonia content at the flue outlet.

[0016] Optionally, the method further comprises: starting the first control mode alone;

[0017] Or, start the first control mode and the second control mode;

[0018] Or, start the first control mode and the third control mode;

[0019] Or, start the first control mode, the second control mode and the third control mode.

[0020] Optionally, adjusting the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and a preset value of nitrogen oxides at the flue outlet includes:

[0021] If the nitrogen oxide content at the flue outlet is less than the preset nitrogen oxide value, reducing the amount of ammonia sprayed into the flue;

[0022] If the nitrogen oxide content at the flue outlet is greater than the preset nitrogen oxide value, increasing the ammonia injection amount of the flue;

[0023] If the nitrogen oxide content at the flue outlet is equal to the preset nitrogen oxide value, the ammonia injection amount of the flue is controlled to remain unchanged.

[0024] Optionally, updating the preset value of nitrogen oxides according to the relationship between the nitrogen oxide content at the chimney inlet and the preset value of nitrogen oxides includes:

[0025] Based on the nitrogen oxide content at the chimney inlet and the current nitrogen oxide preset value, a PID algorithm is used to update the current nitrogen oxide preset value.

[0026] Optionally, correcting the preset value of nitrogen oxides according to the relationship between the ammonia content at the flue outlet and the preset value of ammonia content at the flue outlet includes:

[0027] Based on the ammonia content at the flue outlet and the preset ammonia content at the flue outlet, a correction amount of the current preset value of nitrogen oxides is calculated using a PID algorithm;

[0028] The current preset value of nitrogen oxides is updated according to the correction amount of the current preset value of nitrogen oxides.

[0029] Optionally, the method further comprises: after the preset value of nitrogen oxides is updated, adjusting the amount of ammonia sprayed into the flue according to the updated preset value of nitrogen oxides.

[0030] Optionally, the method further includes: if the difference between the nitrogen oxide content at the flue outlet and a preset value of nitrogen oxides at the flue outlet exceeds a first control threshold, shutting down the first control mode.

[0031] Optionally, the method further includes: if the difference between the nitrogen oxide content at the chimney inlet and the updated nitrogen oxide preset value exceeds a second control threshold, shutting down the second control mode.

[0032] Optionally, the method further comprises: if the difference between the ammonia content at the flue outlet and a preset value of the ammonia content at the flue outlet exceeds a third control threshold, shutting down the third control mode.

[0033] The technical solution provided by the embodiment of the present invention obtains the nitrogen oxide content at the flue outlet and adjusts the ammonia injection amount of the flue in combination with the preset value of nitrogen oxides at the flue outlet, thereby controlling the flue gas after denitrification treatment to meet the environmental protection emission standards; obtains the nitrogen oxide content at the chimney outlet and updates the preset value of nitrogen oxides at the single flue outlet in combination with the preset value of nitrogen oxides at the single flue outlet, thereby adjusting the standard of denitrification treatment of the single flue, so that the flue gas finally discharged from the chimney meets the environmental protection emission standards, thereby improving the stability of the nitrogen oxide concentration control at the flue denitrification outlet.

[0034] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 A schematic diagram of the structure of a boiler flue and chimney provided in an embodiment of the present invention;

[0037] Figure 2 A flow chart of a boiler flue gas denitrification control method provided in an embodiment of the present invention.

[0038] Figure 3A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention;

[0039] Figure 4 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention;

[0040] Figure 5 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention;

[0041] Figure 6 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention;

[0042] Figure 7 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention;

[0043] Figure 8 An operation logic diagram of multiple control modes of a boiler flue gas denitration control method provided by an embodiment of the present invention;

[0044] Fig. 9 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention;

[0045] Fig.10 An exit logic diagram of a first control mode of a boiler flue gas denitration control method provided by an embodiment of the present invention;

[0046] Fig.11 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention;

[0047] Fig.12 An exit logic diagram of a second control mode of a boiler flue gas denitration control method provided by an embodiment of the present invention;

[0048] Fig.13 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention;

[0049] Fig.14 An exit logic diagram of a third control mode of a boiler flue gas denitration control method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0051] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0052] Figure 1 A schematic structural diagram of a boiler flue and chimney provided in an embodiment of the present invention. Figure 2 This is a flow chart of a boiler flue gas denitration control method provided by an embodiment of the present invention. This embodiment is applicable to the case of boiler flue gas denitration control. The method can be executed by a denitration control device, which can be implemented in the form of hardware and / or software and configured in a distributed control system. Figure 1 and Figure 2 The boiler 100 is respectively connected to first ends of a plurality of flues 200 , and second ends of the plurality of flues 200 are commonly connected to a chimney 300 .

[0053] Specifically, the boiler 100 may be a coal-fired boiler of a thermal power plant. The coal in the boiler 100 converts chemical energy into heat energy through a combustion reaction to generate high-temperature and high-pressure steam. The boiler 100 is connected to a plurality of flues 200. The flue gas generated by the combustion reaction of the coal in the boiler 100 may be diverted through the plurality of flues 200 and then collected in a chimney 300 and then discharged into the air. For example, Figure 1 As shown, the boiler 100 is connected to two flues 200 , and the other ends of the two flues 200 are commonly connected to a chimney 300 .

[0054] The denitration control method of boiler flue gas includes a first control mode and a second control mode;

[0055] The first control mode includes:

[0056] S110, obtaining the nitrogen oxide content at the flue outlet;

[0057] Specifically, the first control mode may be a working mode for controlling the nitrogen oxide content in the flue gas at the outlet of a single flue 200. A CEMS (Continuous Emission Monitoring System) may be provided in the flue 200 and the chimney 300. A variety of gases are generated during the coal combustion reaction in the boiler 100, among which the main pollutant gas component is nitrogen oxide. Nitrogen oxides may be nitrogen oxides such as nitric oxide or nitrogen dioxide, for example. CEMS can effectively measure and monitor the content of various gases, and CEMS can be used to measure and monitor the nitrogen oxide content in the flue gas at the outlet of the flue 200. The nitrogen oxides in the flue gas will be denitrated after passing through the flue 200, and then collected in the chimney 300, and finally discharged into the air.

[0058] S120, adjusting the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxide at the flue outlet.

[0059] Specifically, the preset value of nitrogen oxides at the flue outlet can be a nitrogen oxide content value that meets environmental emission standards. An ammonia spraying device is provided in the flue 200. The ammonia spraying device can spray ammonia and a catalyst. Ammonia can produce a denitrification reaction with nitrogen oxides in the flue gas under the catalysis of the catalyst to produce nitrogen and water, thereby reducing the content of nitrogen oxides in the flue gas, so that the final exhaust gas meets the emission standards of environmental protection. The difference between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxides at the flue outlet can be used to adjust the ammonia spraying amount of the ammonia spraying device in the flue 200 accordingly, so that the nitrogen oxide content value in the flue gas after denitrification treatment in the flue 200 meets the emission standards of environmental protection.

[0060] The second control mode includes:

[0061] S130, obtaining the nitrogen oxide content at the chimney inlet;

[0062] Specifically, the second control mode may be a working mode for controlling and adjusting the preset value of nitrogen oxides at the outlet of a single flue 200. The flue gas generated by the boiler 100 will be collected in the chimney 300 after being diverted and denitrated through multiple flues 200. A CEMS may be provided in the chimney 300, so that the nitrogen oxide content at the inlet of the chimney 300 can be measured and monitored according to the CEMS provided in the chimney 300. After the flue gases after denitration treatment in multiple flues 200 are collected, the nitrogen oxide content in the flue gas flowing into the chimney 300 will change. Since the outlet of the chimney 300 is connected to the air, it is difficult to accurately measure the nitrogen oxide content at the outlet of the chimney 300. Therefore, the nitrogen oxide content at the chimney inlet is selected to be equivalent to the nitrogen oxide content in the flue gas finally discharged from the chimney 300 to the air.

[0063] S140: updating the preset value of nitrogen oxides according to the relationship between the nitrogen oxide content at the chimney inlet and the preset value of nitrogen oxides.

[0064] Specifically. The preset value of nitrogen oxides is the preset value of nitrogen oxides for a single flue 200 in the first control mode. Since the preset value of nitrogen oxides is the content value of nitrogen oxides that meets the environmental emission standards, and the nitrogen oxide content at the chimney inlet is the nitrogen oxide content in the flue gas finally discharged to the air; therefore, when there is a large gap between the preset value of nitrogen oxides and the nitrogen oxide content at the chimney inlet, it means that when the flue 200 performs denitration according to the current preset value of nitrogen oxides, the flue gas finally discharged by the chimney 300 cannot meet the environmental emission standards. Therefore, the preset value of nitrogen oxides for the flue 200 can be updated and set according to the nitrogen oxide content at the chimney inlet, thereby improving the stability of the control of nitrogen oxide concentration at the flue denitration outlet.

[0065] The technical solution provided by the embodiment of the present invention obtains the nitrogen oxide content at the flue outlet and adjusts the ammonia injection amount of the flue in combination with the preset value of nitrogen oxides at the flue outlet, thereby controlling the flue gas after denitrification treatment to meet the environmental emission standards; obtains the nitrogen oxide content at the chimney outlet and updates the preset value of nitrogen oxides at the single flue outlet in combination with the preset value of nitrogen oxides at the single flue outlet, thereby adjusting the standard of denitrification treatment of the single flue, so that the flue gas finally discharged from the chimney meets the environmental emission standards, thereby improving the stability of the nitrogen oxide concentration control at the flue denitrification outlet; at the same time, the technical solution provided by the embodiment of the present invention does not completely rely on the control logic of the external equipment, which is convenient for power plant maintenance personnel to perform maintenance and adjustment when modification is required.

[0066] Optionally, Figure 3 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention. Figure 3 The method further includes a third control mode;

[0067] S210, obtaining the nitrogen oxide content at the flue outlet;

[0068] S220, adjusting the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxides at the flue outlet.

[0069] S230, obtaining the nitrogen oxide content at the chimney inlet;

[0070] S240, updating the preset value of nitrogen oxides according to the relationship between the nitrogen oxide content at the chimney inlet and the preset value of nitrogen oxides;

[0071] The third control mode includes:

[0072] S250, obtaining the ammonia content at the flue outlet;

[0073] Specifically, the third control mode may be a working mode for controlling the ammonia content in the flue gas at the outlet of the flue 200. The ammonia content at the flue outlet can be obtained by the CEMS installed in the flue 200. When the flue gas is denitrated in the flue 200, the ammonia spraying device will spray ammonia, but not all of the sprayed ammonia will react with the nitrogen oxides in the flue gas, so the flue gas at the flue outlet contains some ammonia that does not participate in the denitrification reaction. This phenomenon is called ammonia escape. When the ammonia escape rate is too high, the ammonia that does not participate in the reaction is easily condensed and crystallized in the flue 200 or the chimney 300, thereby blocking the control valves and other equipment in the flue 200 or the chimney 300, affecting normal production, and even causing the risk of flue blockage and shutdown.

[0074] S260: Correct the preset value of nitrogen oxides according to the relationship between the ammonia content at the flue outlet and the preset value of ammonia content at the flue outlet.

[0075] Specifically, the preset value of the ammonia content at the flue outlet can be the ammonia content value in the flue gas at the flue outlet while ensuring that the escaped ammonia will not block the flue 200 and the chimney 300. When the ammonia content at the flue outlet exceeds a certain deviation from the preset value of the ammonia content at the flue outlet, the preset value of nitrogen oxides in the flue needs to be corrected. After the preset value of nitrogen oxides in the flue is corrected, the flue 200 will adjust the amount of ammonia sprayed during the denitrification process, thereby controlling the ammonia escape rate at the flue outlet and ensuring that the flue 200 and the chimney 300 will not be blocked or shut down.

[0076] Optionally, the method further includes: starting the first control mode alone; or starting the first control mode and the second control mode; or starting the first control mode and the third control mode; or starting the first control mode, the second control mode and the third control mode.

[0077] Specifically, the first control mode is the most basic working mode and can be used alone. After the first control mode is used, the second control mode can be selectively controlled to be used, or the third control mode can be controlled to be used, or both the second control mode and the third control mode can be used according to actual working conditions. When the first working mode is turned off, neither the second control mode nor the third control mode can be used.

[0078] Exemplarily, when the first control mode is turned on alone, the amount of ammonia sprayed in the flue 200 is adjusted to control the nitrogen oxide content in the flue gas at the flue outlet.

[0079] The second control mode is a working mode for controlling the preset value of nitrogen oxides at a single flue outlet. When both the first control mode and the second control mode are put into use, the nitrogen oxide content in the flue gas at a single flue outlet is first controlled by the first control mode, so that the flue gas after denitrification treatment in a single flue meets the environmental emission standards, and then the preset value of nitrogen oxides at a single flue outlet is updated and adjusted by the second control mode, thereby improving the stability of the control of nitrogen oxide concentration at the flue outlet.

[0080] The third control mode is a working mode for controlling the ammonia content in the flue gas at the flue outlet. When both the first control mode and the third control mode are put into use, the nitrogen oxide content in the flue gas at the outlet of a single flue is first controlled by the first control mode, so that the flue gas after denitrification treatment in a single flue meets the environmental emission standards, and then the preset value of nitrogen oxides at the outlet of a single flue is corrected and adjusted by the third control mode, thereby controlling the ammonia escape rate at the flue outlet and ensuring that the flue 200 and the chimney 300 will not be blocked or shut down.

[0081] When the first control mode, the second control mode and the third control mode are all put into use, the nitrogen oxide content in the flue gas at a single flue outlet is first controlled by the first control mode, and then the preset value of nitrogen oxides at a single flue outlet is updated and adjusted by the second control mode, and finally the updated preset value of nitrogen oxides in the second control mode is corrected and adjusted by the third control mode. When all three control modes are turned on, the stability of the control of nitrogen oxide concentration at the flue outlet can be improved, the ammonia escape rate and the risk of boiler flue blockage and shutdown can be reduced, and it is convenient for power plant maintenance personnel to perform maintenance and adjustment.

[0082] Optionally, Figure 4 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention. Figure 4 The method comprises:

[0083] S310, obtaining the nitrogen oxide content at the flue outlet;

[0084] S320, if the nitrogen oxide content at the flue outlet is less than the preset value of nitrogen oxides, reducing the amount of ammonia sprayed into the flue;

[0085] Specifically, when the nitrogen oxide content at the flue outlet is less than the preset value of nitrogen oxides, it means that the flue gas after denitration treatment in the flue 200 exceeds the environmental emission standard. Correspondingly, the flue gas will contain more ammonia that does not participate in the denitration reaction. Therefore, it is necessary to reduce the amount of ammonia sprayed by the ammonia spraying device in the flue 200 to prevent the ammonia escape rate from increasing and avoid the risk of blockage and shutdown of the flue 200 or chimney 300.

[0086] S330, if the nitrogen oxide content at the flue outlet is greater than the preset value of nitrogen oxides, increasing the amount of ammonia sprayed into the flue;

[0087] Specifically, when the nitrogen oxide content at the flue outlet is greater than the preset value of nitrogen oxide, it means that the flue gas contains a large amount of nitrogen oxide that has not been denitrified, and the flue gas after denitration in the flue 200 does not meet the environmental emission standards. Therefore, it is necessary to increase the ammonia injection amount of the ammonia injection device in the flue 200. After the ammonia injection amount is increased, the ammonia content in the flue 200 will increase, so that the nitrogen oxide in the flue gas reacts fully with the ammonia, so that the flue gas after denitration in the flue 200 meets the environmental emission standards.

[0088] S340, if the nitrogen oxide content at the flue outlet is equal to the preset value of nitrogen oxides, the ammonia injection amount of the flue is controlled to remain unchanged;

[0089] Specifically, when the nitrogen oxide content at the flue outlet is equal to the preset value of nitrogen oxides, it means that the denitration reaction in the flue is moderate, the ammonia content in the flue gas after denitration treatment will not cause an increase in the ammonia escape rate, and the nitrogen oxide content just meets the environmental emission standards. At this time, the ammonia injection amount of the flue can be controlled to remain unchanged.

[0090] S350, obtaining the nitrogen oxide content at the chimney inlet;

[0091] S360: Update the preset value of nitrogen oxides according to the relationship between the nitrogen oxide content at the chimney inlet and the preset value of nitrogen oxides.

[0092] Optionally, Figure 5 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention. Figure 5 The method comprises:

[0093] S410, obtaining the nitrogen oxide content at the flue outlet;

[0094] S420, adjusting the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxide at the flue outlet.

[0095] S430, obtaining the nitrogen oxide content at the chimney inlet;

[0096] S440: Based on the nitrogen oxide content at the chimney inlet and the current nitrogen oxide preset value, a PID algorithm is used to update the current nitrogen oxide preset value.

[0097] Specifically, after obtaining the nitrogen oxide content at the entrance of the chimney 300 through CEMS, the nitrogen oxide content at the entrance of the chimney can be subtracted from the current nitrogen oxide preset value of the flue 200 that needs to be adjusted to obtain an error value; then the error value is multiplied by the proportional gain coefficient of the PID algorithm to obtain a proportional term; then the error value is integrated to obtain an integral term, and the error value is differentiated to obtain a differential term; finally, the proportional term, the integral term and the differential term are added together as the updated nitrogen oxide preset value. By using the PID algorithm to update the current nitrogen oxide preset value, the degree of denitration treatment in a single flue 200 can be changed and adjusted in a timely manner, thereby improving the stability of the control of the nitrogen oxide concentration of the flue gas after denitration by a single flue 200. After the nitrogen oxide preset values ​​of each flue 200 are updated, it is further ensured that the nitrogen oxide content in the flue gas at the entrance of the chimney meets the environmental emission standards.

[0098] Optionally, Figure 6 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention. Figure 6 The method comprises:

[0099] S510, obtaining the nitrogen oxide content at the flue outlet;

[0100] S520: adjusting the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxide at the flue outlet.

[0101] S530, obtaining the nitrogen oxide content at the chimney inlet;

[0102] S540, updating the preset value of nitrogen oxides according to the relationship between the nitrogen oxide content at the chimney inlet and the preset value of nitrogen oxides;

[0103] S550, obtaining the ammonia content at the flue outlet;

[0104] S560, based on the ammonia content at the flue outlet and the preset ammonia content at the flue outlet, using a PID algorithm to calculate a correction amount of the current preset value of nitrogen oxides;

[0105] Specifically, after obtaining the ammonia content at the outlet of the flue 200 through CEMS, the ammonia content at the outlet of the flue 200 can be subtracted from the preset value of the ammonia content in the flue 200 to obtain an error value; then the error value is multiplied by the proportional gain coefficient of the PID algorithm to obtain a proportional term; then the error value is integrated to obtain an integral term, and the error value is differentiated to obtain a differential term; finally, the proportional term, the integral term and the differential term are added together as a correction amount for the current preset value of nitrogen oxides in the flue 200.

[0106] S570: Update the current preset value of nitrogen oxides according to the correction amount of the current preset value of nitrogen oxides.

[0107] Specifically, the correction amount of the current nitrogen oxide preset value of the flue 200 is added to the current nitrogen oxide preset value to obtain the updated nitrogen oxide preset value. It should be noted that when both the second control mode and the third control mode are turned on, the current nitrogen oxide preset value is first updated by the second control mode, and then the updated nitrogen oxide preset value is corrected by the third control mode, and the corrected nitrogen oxide preset value is used as the final updated nitrogen oxide preset value of the flue.

[0108] Optionally, Figure 7 A flow chart of another boiler flue gas denitration control method provided in an embodiment of the present invention. Figure 7 The method further comprises:

[0109] S610, obtaining the nitrogen oxide content at the flue outlet;

[0110] S620: Adjust the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxide at the flue outlet.

[0111] S630, obtaining the nitrogen oxide content at the chimney inlet;

[0112] S640, updating the preset value of nitrogen oxides according to the relationship between the nitrogen oxide content at the chimney inlet and the preset value of nitrogen oxides;

[0113] S650: After the preset value of nitrogen oxides is updated, the amount of ammonia sprayed into the flue is adjusted according to the updated preset value of nitrogen oxides.

[0114] Specifically, the updated nitrogen oxide preset value is used as the latest nitrogen oxide preset value of the flue 200, and the ammonia injection amount of the flue 200 is adjusted according to the latest nitrogen oxide preset value. This can not only ensure that the flue gas after denitrification treatment of a single flue 200 meets the environmental emission standards, but also ensure that the flue gas after multiple flues 200 are gathered into the chimney 300 also meets the environmental emission standards.

[0115] Figure 8 This is an operation logic diagram of multiple control modes of a boiler flue gas denitration control method provided by an embodiment of the present invention. Figure 8, A0 is the current preset value of nitrogen oxides at the flue outlet. When the first control mode is put into use alone, the preset value of nitrogen oxides A0 does not change. a is the measured nitrogen oxide content at the chimney inlet. When the second control mode is put into use, the PID algorithm is used to obtain the updated preset value of nitrogen oxides A according to the nitrogen oxide content a at the chimney inlet and the preset value of nitrogen oxides A0. B0 is the preset value of ammonia content at the flue outlet, and b is the measured ammonia content at the flue outlet. When the third control mode is put into use, the PID algorithm is used to obtain the correction amount of the preset value of nitrogen oxides according to the preset value of ammonia content B0 at the flue outlet and the ammonia content b at the flue outlet. Then, the correction amount of the preset value of nitrogen oxides is summed with the preset value of nitrogen oxides updated by the second control mode to obtain the final updated preset value of nitrogen oxides A. When the third control mode is turned off, the correction amount of the preset value of nitrogen oxides is zero.

[0116] Optionally, Fig. 9 A flow chart of another boiler flue gas denitrification control method provided in an embodiment of the present invention. Fig.10 The exit logic diagram of the first control mode of a boiler flue gas denitration control method provided by an embodiment of the present invention. Fig. 9 and Fig.10 The method further comprises:

[0117] S710, obtaining the nitrogen oxide content at the flue outlet;

[0118] S720, adjusting the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxides at the flue outlet;

[0119] S730: If the difference between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxide at the flue outlet exceeds a first control threshold, the first control mode is turned off.

[0120] Specifically, when the difference between the nitrogen oxide content N at the flue outlet and the preset value A0 of nitrogen oxides at the flue outlet exceeds the first control threshold, it means that the flue gas after denitrification treatment cannot be controlled to meet the environmental emission standards in the current state, and the first control mode needs to be turned off in time to avoid damage to the denitrification equipment in the flue 200 caused by continuous control.

[0121] In other embodiments, the first control mode can also be turned off based on other reference quantities. For example, when the operator determines that the nitrogen oxide content N1 measured at the inlet of the CEMS, or the nitrogen oxide content N2 measured at the outlet of the CEMS deviates greatly from the nitrogen oxide content in the actual working condition, the first control mode can be manually turned off. At this time, it may be due to a malfunction of the CEMS, resulting in a large deviation in the detected nitrogen oxide content. When the difference between the opening K0 of the ammonia injection valve in the flue 200 and the set opening K exceeds the error range, or the opening K0 of the ammonia injection valve cannot be adjusted, the first control mode can be turned off.

[0122] Optionally, Fig.11 A flow chart of another boiler flue gas denitrification control method provided in an embodiment of the present invention. Fig.12 The following is an exit logic diagram of the second control mode of a boiler flue gas denitration control method provided by an embodiment of the present invention. Fig.11 and Fig.12 The method further comprises:

[0123] S810, obtaining the nitrogen oxide content at the flue outlet;

[0124] S820. Adjust the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxides at the flue outlet.

[0125] S830, obtaining the nitrogen oxide content at the chimney inlet;

[0126] S840, updating the preset value of nitrogen oxides according to the relationship between the nitrogen oxide content at the chimney inlet and the preset value of nitrogen oxides;

[0127] S850: If the difference between the nitrogen oxide content at the chimney inlet and the updated nitrogen oxide preset value exceeds the second control threshold, the second control mode is turned off.

[0128] Specifically, when the difference between the nitrogen oxide content a at the chimney inlet and the updated nitrogen oxide preset value A exceeds the second control threshold, it means that the flue gas collected in the chimney 300 cannot be controlled to meet the environmental emission standards in the current state, and the second control mode needs to be turned off in time to avoid damage to the denitrification equipment caused by continuous control. It should be noted that when the first control mode is turned off, the second control mode is automatically turned off.

[0129] Optionally, Fig.13 A flow chart of another boiler flue gas denitrification control method provided in an embodiment of the present invention. Fig.14 The third control mode exit logic diagram of a boiler flue gas denitration control method provided by the embodiment of the present invention. Fig.13 and Fig.14 The method further comprises:

[0130] S910, obtaining the nitrogen oxide content at the flue outlet;

[0131] S920: Adjust the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxide at the flue outlet.

[0132] S930, obtaining the ammonia content at the flue outlet;

[0133] S940, correcting the preset value of nitrogen oxides according to the relationship between the ammonia content at the flue outlet and the preset value of ammonia content at the flue outlet;

[0134] S950: If the difference between the ammonia content b at the flue outlet and the preset value B0 of the ammonia content at the flue outlet exceeds a third control threshold, the third control mode is turned off.

[0135] Specifically, when the difference between the ammonia content b at the flue outlet and the preset value B of the ammonia content at the flue outlet exceeds the third control threshold, it means that the ammonia escape from the flue cannot be controlled in the current state, and the third control mode needs to be closed in time to avoid damage to the ammonia injection device caused by continuous control. It should be noted that when the first control mode is closed, the third control mode is automatically closed; the closing of the second control mode does not affect the normal use of the third control mode.

[0136] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0137] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A boiler flue gas denitrification control method, characterized in that: include: The boiler is respectively connected to the first ends of the plurality of flues, and the second ends of the plurality of flues are commonly connected to the chimney; The boiler flue gas denitration control method includes a first control mode and a second control mode; The first control mode includes: Obtaining the nitrogen oxide content at the flue outlet; adjusting the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxide at the flue outlet; The second control mode includes: Obtaining the nitrogen oxide content at the chimney inlet; The preset value of nitrogen oxides is updated according to the relationship between the nitrogen oxide content at the chimney inlet and the preset value of nitrogen oxides.

2. The boiler flue gas denitrification control method according to claim 1, characterized in that: include: The third control mode; The third control mode includes: Obtaining the ammonia content at the flue outlet; The preset value of nitrogen oxides is corrected according to the relationship between the ammonia content at the flue outlet and the preset value of ammonia content at the flue outlet.

3. The boiler flue gas denitrification control method according to claim 2, characterized in that: include: Enable the first control mode alone; Or, start the first control mode and the second control mode; Or, start the first control mode and the third control mode; Or, start the first control mode, the second control mode and the third control mode.

4. The boiler flue gas denitrification control method according to claim 1, characterized in that: Adjusting the ammonia injection amount of the flue according to the relationship between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxide at the flue outlet includes: If the nitrogen oxide content at the flue outlet is less than the preset nitrogen oxide value, reducing the amount of ammonia sprayed into the flue; If the nitrogen oxide content at the flue outlet is greater than the preset nitrogen oxide value, increasing the ammonia injection amount of the flue; If the nitrogen oxide content at the flue outlet is equal to the preset nitrogen oxide value, the ammonia injection amount of the flue is controlled to remain unchanged.

5. The boiler flue gas denitrification control method according to claim 1, characterized in that: Updating the preset value of nitrogen oxides according to the relationship between the nitrogen oxide content at the chimney inlet and the preset value of nitrogen oxides includes: Based on the nitrogen oxide content at the chimney inlet and the current nitrogen oxide preset value, a PID algorithm is used to update the current nitrogen oxide preset value.

6. The boiler flue gas denitration control method according to claim 2, characterized in that: Correcting the preset value of nitrogen oxides according to the relationship between the ammonia content at the flue outlet and the preset value of ammonia content at the flue outlet includes: Based on the ammonia content at the flue outlet and the preset ammonia content at the flue outlet, a correction amount of the current preset value of nitrogen oxides is calculated using a PID algorithm; The current preset value of nitrogen oxides is updated according to the correction amount of the current preset value of nitrogen oxides.

7. The boiler flue gas denitrification control method according to claim 2, characterized in that: include: After the nitrogen oxide preset value is updated, the ammonia injection amount of the flue is adjusted according to the updated nitrogen oxide preset value.

8. The boiler flue gas denitration control method according to claim 3, characterized in that: include: If the difference between the nitrogen oxide content at the flue outlet and the preset value of nitrogen oxide at the flue outlet exceeds a first control threshold, the first control mode is turned off.

9. The boiler flue gas denitration control method according to claim 8, characterized in that: include: If the difference between the nitrogen oxide content at the chimney inlet and the updated nitrogen oxide preset value exceeds a second control threshold, the second control mode is closed.

10. The boiler flue gas denitration control method according to claim 8, characterized in that: include: If the difference between the ammonia content at the flue outlet and the preset value of the ammonia content at the flue outlet exceeds a third control threshold, the third control mode is turned off.

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