CFB boiler flue gas denitration automatic control method and system

Abstract

The invention discloses a CFB boiler flue gas denitration automatic control method and system. The control method comprises the following steps: S1, monitoring and controlling a CFB boiler by taking an operator station display as a center; s2, a nitrogen oxide emission value of a boiler tail flue in the CFB boiler is collected in real time to serve as a feedback value; s3, the feedback value is compared with a set target emission value, and the deviation value of nitric oxide at the flue gas outlet and the change rate of the deviation value are calculated; s4, constructing a fuzzy relation between the three PID parameters and the deviation and the change rate of the deviation value, and obtaining a new PID parameter; s5, the stroke of an ammonia water pump is dynamically adjusted according to the new PID parameters, and the amount of the urea solvent sprayed into the boiler is controlled; and S6, the stroke of a dilution water pump and the flow of dilution water are regulated and controlled. By means of early warning, control over spraying of the reducing agent and burdening in the boiler is achieved, it is guaranteed that the denitration system can change along with changes of the boiler operation load, and long-term, reliable and safe operation of boiler denitration is achieved.

Description

Technical Field

[0001] The present invention relates to the field of boiler exhaust pollutant control and environmental protection, and in particular to a CFB boiler flue gas denitration automatic control method and system. Background Art

[0002] At present, coal combustion is an important factor leading to environmental pollution, but coal burning is still the main energy structure in my country. Coal meets more than 65% of my country's energy supply needs. Coal can produce a large amount of harmful gases during the combustion process, so it is particularly important to achieve efficient and clean combustion of coal. Fuel produces a large amount of flue gas pollutants during the combustion process. x It is an important factor affecting air pollution. It can not only produce photochemical smog under strong light, causing environmental pollution, but also NO x It is also an important cause of acid rain.

[0003] NOx is a general term for N2O, NO, NO3, NO2, etc. x It mainly refers to NO and NO2. NO2 itself is a highly toxic gas, 4 to 5 times more toxic than NO. When NO2 is exposed to strong light, it intervenes in photochemical reactions to form more harmful photochemical smog, which not only affects agricultural production, but also causes strong stimulation to the human body. It can also accelerate the aging of rubber products and corrode buildings, bringing serious impacts to people's lives. Acid rain has a direct impact on the agricultural ecosystem, which is manifested in affecting the germination rate of seeds, yellowing and even death of leaves, resulting in reduced crop yields; it also affects the ecological balance of aquatic organisms and even causes the death of some fish; and acid rain can accelerate the corrosion of materials and make various coatings lose their protective effects.

[0004] The unique structure of the CFB boiler helps the injected reducing agent and flue gas to mix evenly. Setting the injection point in the horizontal flue before the separator can significantly reduce the ammonia nitrogen ratio and reduce the amount of ammonia escape. The existing denitrification control system uses the NOx concentration at the outlet of the CFB boiler furnace as the control target. The flue gas flow represented by the unit load is multiplied by the flue gas inlet and outlet NOx concentrations. The flue gas volume measurement is determined according to the DCS boiler load or coal supply. The required denitrification dosage is calculated based on the ammonia nitrogen ratio, and the opening of the denitrification agent regulating valve is controlled to achieve control of the NOx content at the flue gas outlet. However, during the operation of the denitrification system, it was found that under PID control, the nitrogen oxide concentration at the flue gas outlet always overshoots from time to time, causing the outlet nitrogen oxide emission concentration to always exceed 50mg / Nm 3 , even up to 70mg / Nm 3The process from system overshoot to the final nitrogen oxide emission concentration reaching the environmental emission standard takes a long time, generally taking more than an hour. According to environmental protection requirements: The nitrogen oxide emission concentration of coal chemical enterprises must be reduced to 50mg / Nm 3 Once the emission exceeds the standard, the company will be fined by the Environmental Protection Bureau at the least, or the company will need to suspend production for rectification at the most serious. However, in the prior art, it is difficult to determine the parameters of the PID controller when dealing with time-varying parameters and numerous controlled objects. Therefore, the PID parameter tuning method has certain limitations and cannot solve the fundamental contradiction between dynamic performance and steady-state accuracy. In addition, the intervention means for early warning during the processing are not mature enough to meet the control of automated CFB boiler flue gas denitrification.

[0005] Currently, no effective solution has been proposed for the problems in the related technologies. Summary of the invention

[0006] In view of the problems in the related art, the present invention proposes a CFB boiler flue gas denitrification automatic control method and system to overcome the above technical problems existing in the existing related art.

[0007] To this end, the specific technical solution adopted by the present invention is as follows:

[0008] According to one aspect of the present invention, a CFB boiler flue gas denitrification automatic control method is provided, the control method comprising:

[0009] S1. Monitor and control the CFB boiler with the operator station display as the center;

[0010] S2, real-time collection of nitrogen oxide emission values ​​from the tail flue of the CFB boiler as feedback values;

[0011] S3. Compare the feedback value with the set target emission value, and calculate the deviation value of nitrogen oxides at the flue gas outlet and the rate of change of the deviation value;

[0012] S4, constructing the fuzzy relationship between the three PID parameters and the deviation and the change rate of the deviation value, and modifying the PID parameters online to obtain new PID parameters;

[0013] S5. Dynamically adjust the stroke of the ammonia pump according to the new PID parameters to control the amount of urea solvent sprayed into the boiler furnace;

[0014] S6. Regulate the stroke of the dilution water pump and the flow rate of the dilution water, and control the concentration of nitrogen oxides and ammonia escape concentration.

[0015] Furthermore, the monitoring and controlling of the CFB boiler centered on the operator station display includes the following steps:

[0016] S11, scanning the CFB boiler in real time to obtain the content of the oxide emission value of the boiler tail flue and the drum water level of the CFB boiler;

[0017] S12, performing data processing and timed tabulation on the content of nitrogen oxide emission values, and setting limit values ​​of nitrogen oxide emission values ​​and drum water level;

[0018] S13: When the water level in the drum exceeds the limit value, an alarm is automatically sounded and manual processing is performed;

[0019] S14. Set manual instructions to automatically complete the regulation of each local out-of-stock process or the start and stop of the auxiliary machine program, and realize early warning processing.

[0020] Furthermore, the automatic alarm is issued when the content of the drum water level exceeds the limit value, and the manual processing includes the following steps:

[0021] S131, real-time collection of the steam flow, feed water flow and steam drum position signal of the CFB boiler;

[0022] S132, converting the signal quantity into an input quantity through a converter, and changing the opening of the water valve according to the input quantity to adjust the water supply and stabilize the drum water level;

[0023] S133, when the water level deviates from the given value, the deviation from the given value is calculated to obtain the adjustment value of the water flow rate, and then the adjustment value is passed through the water flow regulator;

[0024] S134. Change the water supply flow rate through the actuator to restore the water level to a given value.

[0025] Furthermore, the construction of the fuzzy relationship between the three PID parameters and the deviation and the rate of change of the deviation value, and modifying the PID parameters online to obtain new PID parameters includes the following steps:

[0026] S41, using the deviation and the deviation value change rate as input variables of the fuzzy controller, and using the PID parameter change amount as the output variable of the fuzzy controller;

[0027] S42, selecting language variables describing input variables and output variables, formulating fuzzy subsets of fuzzy variables, and establishing fuzzy control rules;

[0028] S43. Output a new fuzzy set according to the fuzzy control rules.

[0029] Furthermore, the selecting of linguistic variables describing input variables and output variables, formulating fuzzy subsets of fuzzy variables, and establishing fuzzy control rules comprises the following steps:

[0030] S421, constructing the deviation, the deviation value change rate and the output variable into a fuzzy subset, and determining the shape of the fuzzy subset membership function curve;

[0031] S422, according to the membership function curve, obtain a membership value table of deviation and deviation change rate;

[0032] S423, finding the fuzzy relationship between the three PID parameters and the deviation and the deviation change rate, and continuously detecting the deviation and the deviation change rate during operation, and making online changes to the three parameters according to the fuzzy controller.

[0033] Furthermore, the control rule formula of the fuzzy controller is:

[0034] if E=E i andEC=EC j thenK x =K xij

[0035] In the formula, E is the deviation, EC is the deviation change rate, x is the PID parameter, K xij is the control rule, if is the fuzzy quantity, i, j are constants.

[0036] Furthermore, dynamically adjusting the stroke of the ammonia pump according to the new PID parameters to control the amount of urea solvent sprayed into the boiler furnace includes the following steps:

[0037] S51. According to the new PID parameters, the solid urea is diluted with water into a solution in a dissolving tank, and then filtered and fed into a storage tank through a delivery pump. The urea solvent in the storage tank is filtered and then fed into an addition pump.

[0038] S52, after being pumped into the flow control valve and flow meter, the metering solution is allowed to flow into the nozzle and controlled to be sprayed into the boiler;

[0039] S53, controlling the temperature of the denitrification, controlling the input amount of ammonia through a volume meter, obtaining the denitrification efficiency under different ammonia-nitrogen ratios, and determining the optimal ammonia-nitrogen ratio value;

[0040] S54, mix the nozzle and compressed air, and enter the decomposition furnace after atomization.

[0041] Furthermore, the method of controlling the temperature of the denitrification, controlling the input amount of ammonia through a volume meter, obtaining the denitrification efficiency under different ammonia-nitrogen ratios, and determining the optimal ammonia-nitrogen ratio value includes the following steps:

[0042] S521, controlling the temperature of the desoldering, increasing the particle size of the droplets, and increasing the penetration of the droplets into the furnace;

[0043] S522, controlling the injection speed of the urea solution and obtaining the denitrification efficiency under different ammonia nitrogen ratios.

[0044] Furthermore, the concentration of nitrogen oxides is controlled to be less than or equal to 100 mg / m 3 , and control the ammonia escape concentration to be less than or equal to 8mg / m 3 .

[0045] According to another aspect of the present invention, there is also provided a CFB boiler flue gas denitrification automatic control system, the system comprising: an early warning module, a collection module, a comparison module, a processing module, a spraying amount control module and an emission concentration control module;

[0046] The early warning module is used to monitor and control the CFB boiler with the operator station display as the center;

[0047] The collection module is used to collect the nitrogen oxide emission value of the tail flue of the CFB boiler in real time as a feedback value;

[0048] The comparison module is used to compare the feedback value with the set target emission value, and calculate the deviation value of nitrogen oxides at the flue gas outlet and the rate of change of the deviation value;

[0049] The processing module is used to construct a fuzzy relationship between the three PID parameters and the deviation and the rate of change of the deviation value, and to modify the PID parameters online to obtain new PID parameters;

[0050] The spraying amount control module is used to dynamically adjust the stroke of the ammonia pump according to the new PID parameters to control the amount of urea solvent sprayed into the boiler furnace;

[0051] The emission concentration control module is used to regulate the stroke of the dilution water pump and the flow rate of the dilution water, and to control the concentration of nitrogen oxides and the ammonia escape concentration.

[0052] The beneficial effects of the present invention are:

[0053] 1. The design of the CFB boiler flue gas denitrification control method of the present invention does not vary greatly with the project. The number of ammonia pumps and dilution water pumps is basically adjusted according to the number of boilers. If the electrical system and the automatic control system are integrated into a module and skid-mounted, it has great advantages, such as less floor space, making the system layout compact and orderly; standardized production can be achieved, the quality of the whole set is improved, the supply cycle is shortened, and the system cost is reduced; the on-site installation is simple and convenient, and the construction efficiency is improved; the control is relatively independent and the reliability is high.

[0054] 2. The present invention processes CFB boiler combustion and flue gas denitrification through FLUENT software, and obtains a linear relationship curve between unit load, oxygen content, water-coal ratio, primary and secondary air ratio and furnace outlet NOx content under variable operating conditions. At the same time, the influence of the number of urea spray guns, nitrogen-ammonia ratio and reducing agent flow rate on the final denitrification efficiency in the SNCR process is simulated, and the synergistic relationship between furnace denitrification and SNCR is pointed out, ensuring the maximum contact area between the reducing agent and the flue gas after furnace denitrification, reasonably controlling the chemical reaction balance, and the optimal contact position, so that the denitrification efficiency can achieve the best effect.

[0055] 3. The early warning part of the present invention adopts an independent DCS control system to realize automatic control of the injection of reducing agent in the furnace and the batching of the SNCR supply system, and ensure that the denitration system can change with the change of the boiler operating load, so that the boiler denitration system can operate safely for a long time and reliably. In order to ensure the reliability and high cost performance of the system, the SNCR injection system of each boiler is incorporated into the boiler DCS control system. Therefore, the SNCR injection system of each boiler adopts a remote I / 0 station. In principle, the DCS system CPU uses the original DCS CPU, and the workstation and system software also use the original equipment. During normal operation, the combustion system and SNCR operating condition data are recorded at intervals, including real-time thermal operation parameters and equipment operation status. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 paying creative work.

[0057] Figure 1 The present invention is a flowchart of a CFB boiler flue gas denitrification automatic control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0058] To further illustrate each embodiment, the present invention provides drawings, which are part of the disclosure of the present invention and are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, ordinary technicians in the field should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0059] According to an embodiment of the present invention, a CFB boiler flue gas denitrification automatic control method and system are provided.

[0060] The present invention is further described with reference to the accompanying drawings and specific embodiments. Figure 1 As shown, according to the automatic control method of flue gas denitrification of a CFB boiler according to an embodiment of the present invention, the control method includes:

[0061] S1. Monitor and control the CFB boiler with the operator station display as the center;

[0062] In one embodiment, the monitoring and control of the CFB boiler centered on the operator station display includes the following steps:

[0063] S11, scanning the CFB boiler in real time to obtain the content of the oxide emission value of the boiler tail flue and the drum water level of the CFB boiler;

[0064] S12, performing data processing and timed tabulation on the content of nitrogen oxide emission values, and setting limit values ​​of nitrogen oxide emission values ​​and drum water level;

[0065] S13: When the water level in the drum exceeds the limit value, an alarm is automatically sounded and manual processing is performed;

[0066] S14. Set manual instructions to automatically complete the regulation of each local out-of-stock process or the start and stop of the auxiliary machine program, and realize early warning processing.

[0067] In one embodiment, the automatic alarm is issued when the content of the drum water level exceeds the limit value, and the manual processing includes the following steps:

[0068] S131, real-time collection of the steam flow, feed water flow and steam drum position signal of the CFB boiler;

[0069] S132, converting the signal quantity into an input quantity through a converter, and changing the opening of the water valve according to the input quantity to adjust the water supply and stabilize the drum water level;

[0070] S133, when the water level deviates from the given value, the deviation from the given value is calculated to obtain the adjustment value of the water flow rate, and then the adjustment value is passed through the water flow regulator;

[0071] S134. Change the water supply flow rate through the actuator to restore the water level to a given value.

[0072] Specifically, the early warning part adopts an independent DCS control system to realize the automatic control of the injection of reducing agent in the furnace and the batching of the SNCR supply system, and ensure that the denitration system can change with the change of the boiler operating load. Make the boiler denitration system operate safely and reliably for a long time. In order to ensure the reliability and high cost performance of the system, the SNCR injection system of each boiler is incorporated into the boiler DCS control system. Therefore, the SNCR injection system of each boiler adopts a remote I / 0 station. In principle, the CPU of the DCS system uses the CPU of the original DCS, and the workstation and system software also use the original equipment. During normal operation, the combustion system and SNCR operating condition data are recorded at intervals, including real-time thermal operation parameters, equipment operation status, etc.

[0073] S2. Real-time collection of nitrogen oxide emission values ​​from the tail flue of the CFB boiler as feedback values.

[0074] S3. Compare the feedback value with the set target emission value, and calculate the deviation value of nitrogen oxides at the flue gas outlet and the rate of change of the deviation value.

[0075] S4, constructing the fuzzy relationship between the three PID parameters and the deviation and the change rate of the deviation value, and modifying the PID parameters online to obtain new PID parameters;

[0076] In one embodiment, the fuzzy relationship between the three PID parameters and the deviation and the rate of change of the deviation value is constructed, and the PID parameters are modified online to obtain new PID parameters, including the following steps:

[0077] S41, using the deviation and the deviation value change rate as input variables of the fuzzy controller, and using the PID parameter change amount as the output variable of the fuzzy controller;

[0078] S42, selecting language variables describing input variables and output variables, formulating fuzzy subsets of fuzzy variables, and establishing fuzzy control rules;

[0079] S43. Output a new fuzzy set according to the fuzzy control rules.

[0080] Specifically, PID control is the most typical control law in classical control theory. It can often obtain satisfactory results when controlling the controlled object, so it has been widely used in previous analog control systems. Through PID adjustment, the system deviation can be proportionally adjusted; the introduction of the integral link integrates the deviation, which improves the steady-state accuracy and anti-interference ability of the system; the introduction of the differential link can be used to overcome the inertial lag of the system, thereby improving the stability of the system. This greatly improves the performance and quality of control.

[0081] PID controller is a linear controller, which forms the control deviation e(t) based on the input value r(t) and the actual output value c(t), as shown in the formula: e(t) = r(t)-c(t)

[0082] The proportion, integral and differential of the deviation are linearly combined to form the control quantity to control the controlled object, so it is called PID controller. Its commonly used control law is:

[0083]

[0084] With the deviation e as the controller input and u as the controller output, the above formula can be written in the form of transfer function:

[0085]

[0086] Where u(t) is the output value of the controller at time t;

[0087] e(t) is the deviation at time t, that is, the difference between the target emission value and the feedback value;

[0088] k p is the proportionality coefficient;

[0089] T i is the integration time constant;

[0090] T d is the differential time constant;

[0091] t is the time.

[0092] The three parameters change with different control requirements, which is called parameter setting or parameter adjustment. The purpose of parameter setting is to make the whole system have the fastest dynamic response speed, the smallest overshoot and the smallest steady-state error.

[0093] In one embodiment, the steps of selecting linguistic variables describing input variables and output variables, formulating fuzzy subsets of fuzzy variables, and establishing fuzzy control rules include the following steps:

[0094] S421, constructing the deviation, the deviation value change rate and the output variable into a fuzzy subset, and determining the shape of the fuzzy subset membership function curve;

[0095] S422, according to the membership function curve, obtain a membership value table of deviation and deviation change rate;

[0096] S423, finding the fuzzy relationship between the three PID parameters and the deviation and the deviation change rate, and continuously detecting the deviation and the deviation change rate during operation, and making online changes to the three parameters according to the fuzzy controller.

[0097] In one embodiment, the control rule formula of the fuzzy controller is:

[0098] if E=E i andEC=EC j thenK x =K xij

[0099] In the formula, E is the deviation, EC is the deviation change rate, x is the PID parameter, K xij is the control rule, if is the fuzzy quantity, i, j are constants.

[0100] S5. Dynamically adjust the stroke of the ammonia pump according to the new PID parameters to control the amount of urea solvent sprayed into the boiler furnace;

[0101] In one embodiment, dynamically adjusting the stroke of the ammonia pump according to the new PID parameters to control the amount of urea solvent sprayed into the boiler furnace includes the following steps:

[0102] S51. According to the new PID parameters, the solid urea is diluted with water into a solution in a dissolving tank, and then filtered and fed into a storage tank through a delivery pump. The urea solvent in the storage tank is filtered and then fed into an addition pump.

[0103] S52, after being pumped into the flow control valve and flow meter, the metering solution is allowed to flow into the nozzle and controlled to be sprayed into the boiler;

[0104] S53, controlling the temperature of the denitrification, controlling the input amount of ammonia through a volume meter, obtaining the denitrification efficiency under different ammonia-nitrogen ratios, and determining the optimal ammonia-nitrogen ratio value;

[0105] S54, mix the nozzle and compressed air, and then enter the decomposition furnace after atomization.

[0106] Specifically, the selection of the injection point is an important part of the design. The injection position in the boiler should not only ensure that the flue gas temperature is within the temperature window reflected by the reducing agent, but also that the NOx concentration is appropriate and cannot be too low. The temperature of the flue gas in the boiler and the distribution of NOx need to be numerically simulated by CFD based on FLUENT (a popular commercial CFD software package in the world);

[0107] The basic steps of CFD numerical simulation using FLUENT are as follows:

[0108] 1. Establish geometric model and divide mesh according to geometric dimensions of boiler;

[0109] 2. Determine boundary conditions such as the velocity of the inlet medium based on the calculation conditions;

[0110] 3. Select a suitable model to simulate the combustion process;

[0111] 4. Perform post-processing analysis of the data.

[0112] In one embodiment, the step of controlling the temperature of the denitrification reactor, controlling the amount of ammonia input through a volume meter, obtaining the denitrification efficiency under different ammonia-nitrogen ratios, and determining the optimal ammonia-nitrogen ratio value comprises the following steps:

[0113] S521, controlling the temperature of the desoldering, increasing the particle size of the droplets, and increasing the penetration of the droplets into the furnace;

[0114] S522, controlling the injection speed of the urea solution and obtaining the denitrification efficiency under different ammonia nitrogen ratios.

[0115] S6. Regulate the stroke of the dilution water pump and the flow rate of the dilution water, and control the concentration of nitrogen oxides and ammonia escape concentration.

[0116] In one embodiment, the concentration of nitrogen oxides is controlled to be less than or equal to 100 mg / m 3 , and control the ammonia escape concentration to be less than or equal to 8mg / m 3 .

[0117] According to another embodiment of the present invention, there is also provided a CFB boiler flue gas denitrification automatic control system, the system comprising: an early warning module, a collection module, a comparison module, a processing module, a spraying amount control module and an emission concentration control module;

[0118] The early warning module is used to monitor and control the CFB boiler with the operator station display as the center;

[0119] The collection module is used to collect the nitrogen oxide emission value of the tail flue of the CFB boiler in real time as a feedback value;

[0120] The comparison module is used to compare the feedback value with the set target emission value, and calculate the deviation value of nitrogen oxides at the flue gas outlet and the rate of change of the deviation value;

[0121] The processing module is used to construct a fuzzy relationship between the three PID parameters and the deviation and the rate of change of the deviation value, and to modify the PID parameters online to obtain new PID parameters;

[0122] The spraying amount control module is used to dynamically adjust the stroke of the ammonia pump according to the new PID parameters to control the amount of urea solvent sprayed into the boiler furnace;

[0123] The emission concentration control module is used to regulate the stroke of the dilution water pump and the flow rate of the dilution water, and to control the concentration of nitrogen oxides and the ammonia escape concentration.

[0124] In summary, with the help of the above technical scheme of the present invention, the design of the CFB boiler flue gas denitrification control method of the present invention is not very variable with the project, and the number of ammonia pumps and dilution water pumps is basically adjusted according to the number of boilers. If the electrical system and the automatic control system are integrated into a module and skid-mounted, it has great advantages, such as less floor space, making the system layout compact and orderly; standardized production can be achieved, the quality of the whole set is improved, the supply cycle is shortened, and the system cost is reduced; the on-site installation is simple and convenient, and the construction efficiency is improved; the control is relatively independent and the reliability is high; the present invention processes the CFB boiler combustion and flue gas denitrification through FLUENT software, and obtains the linear relationship curve between the unit load, oxygen content, water-coal ratio, primary and secondary air ratio and the NOx content at the furnace outlet under variable working conditions, and at the same time simulates the influence of the number of urea spray guns, nitrogen-ammonia ratio, and reducing agent flow rate on the final denitrification efficiency in the SNCR process, points out the synergistic relationship between furnace denitrification and SNCR, ensures the maximum contact area between the reducing agent and the flue gas after furnace denitrification, reasonably controls the chemical reaction balance, and the optimal contact position, so that the denitrification efficiency can achieve the best effect. The early warning part of the present invention adopts an independent DCS control system to realize the automatic control of the injection of reducing agent in the furnace and the batching of the SNCR supply system, and ensure that the denitration system can change with the change of the boiler operating load. Make the boiler denitration system operate safely for a long time and reliably. In order to ensure the reliability and high cost performance of the system, the SNCR injection system of each boiler is incorporated into the boiler DCS control system. Therefore, the SNCR injection system of each boiler adopts a remote I / 0 station. In principle, the DCS system CPU uses the original DCS CPU, and the workstation and system software also use the original equipment. During normal operation, the combustion system and SNCR operating condition data are recorded at intervals, including real-time thermal operation parameters and equipment operation status.

[0125] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A CFB boiler flue gas denitrification automatic control method, characterized in that: The control method includes: S1. Monitor and control the CFB boiler with the operator station display as the center; S2, real-time collection of nitrogen oxide emission values ​​from the tail flue of the CFB boiler as feedback values; S3. Compare the feedback value with the set target emission value, and calculate the deviation value of nitrogen oxides at the flue gas outlet and the rate of change of the deviation value; S4, constructing the fuzzy relationship between the three PID parameters and the deviation and the change rate of the deviation value, and modifying the PID parameters online to obtain new PID parameters; S5. Dynamically adjust the stroke of the ammonia pump according to the new PID parameters to control the amount of urea solvent sprayed into the boiler furnace; S6. Regulate the stroke of the dilution water pump and the flow rate of the dilution water, and control the concentration of nitrogen oxides and ammonia escape concentration.

2. The automatic control method for flue gas denitrification of a CFB boiler according to claim 1, characterized in that: The monitoring and control of the CFB boiler centered on the operator station display includes the following steps: S11, scanning the CFB boiler in real time to obtain the content of the oxide emission value of the boiler tail flue and the drum water level of the CFB boiler; S12, performing data processing and timed tabulation on the content of nitrogen oxide emission values, and setting limit values ​​of nitrogen oxide emission values ​​and drum water level; S13: When the water level in the drum exceeds the limit value, an alarm is automatically sounded and manual processing is performed; S14. Set manual instructions to automatically complete the regulation of each local out-of-stock process or the start and stop of the auxiliary machine program, and realize early warning processing.

3. The automatic control method for flue gas denitrification of a CFB boiler according to claim 2, characterized in that: When the content of the drum water level exceeds the limit value, the alarm is automatically issued, and the manual processing includes the following steps: S131, real-time collection of the steam flow, feed water flow and steam drum position signal of the CFB boiler; S132, converting the signal quantity into an input quantity through a converter, and changing the opening of the water valve according to the input quantity to adjust the water supply and stabilize the drum water level; S133, when the water level deviates from the given value, the deviation from the given value is calculated to obtain the adjustment value of the water flow rate, and then the adjustment value is passed through the water flow regulator; S134. Change the water supply flow rate through the actuator to restore the water level to a given value.

4. The automatic control method for flue gas denitrification of a CFB boiler according to claim 1, characterized in that: The method of constructing the fuzzy relationship between the three PID parameters and the deviation and the rate of change of the deviation value, and modifying the PID parameters online to obtain new PID parameters comprises the following steps: S41, using the deviation and the deviation value change rate as input variables of the fuzzy controller, and using the PID parameter change amount as the output variable of the fuzzy controller; S42, selecting language variables describing input variables and output variables, formulating fuzzy subsets of fuzzy variables, and establishing fuzzy control rules; S43. Output a new fuzzy set according to the fuzzy control rules.

5. The automatic control method for flue gas denitrification of a CFB boiler according to claim 4, characterized in that: The step of selecting linguistic variables describing input variables and output variables, formulating fuzzy subsets of fuzzy variables, and establishing fuzzy control rules comprises the following steps: S421, constructing the deviation, the deviation value change rate and the output variable into a fuzzy subset, and determining the shape of the fuzzy subset membership function curve; S422, according to the membership function curve, obtain a membership value table of deviation and deviation change rate; S423, find the fuzzy relationship between the three PID parameters and the deviation and the deviation change rate, and continuously detect the deviation and the deviation change rate during operation, and make online changes to the three parameters according to the fuzzy controller.

6. The automatic control method for flue gas denitrification of a CFB boiler according to claim 5, characterized in that: The control rule formula of the fuzzy controller is: ifE=EiandEC=ECjthenKx=Kxij In the formula, E is the deviation, EC is the deviation change rate, x is the PID parameter, K xij is the control rule, if is the fuzzy quantity, i, j are constants.

7. The automatic control method for flue gas denitrification of a CFB boiler according to claim 1, characterized in that: The method of dynamically adjusting the stroke of the ammonia pump according to the new PID parameters to control the amount of urea solvent sprayed into the boiler furnace comprises the following steps: S51. According to the new PID parameters, the solid urea is diluted with water into a solution in a dissolving tank, and then filtered and fed into a storage tank through a delivery pump. The urea solvent in the storage tank is filtered and then fed into an addition pump. S52, after being pumped into the flow control valve and flow meter, the metering solution is allowed to flow into the nozzle and controlled to be sprayed into the boiler; S53, controlling the temperature of the denitrification, controlling the input amount of ammonia through a volume meter, obtaining the denitrification efficiency under different ammonia-nitrogen ratios, and determining the optimal ammonia-nitrogen ratio value; S54, mix the nozzle and compressed air, and then enter the decomposition furnace after atomization.

8. The automatic control method for flue gas denitrification of a CFB boiler according to claim 7, characterized in that: The method of controlling the temperature of the denitrification process, controlling the input amount of ammonia through a volume meter, obtaining the denitrification efficiency under different ammonia-nitrogen ratios, and determining the optimal ammonia-nitrogen ratio value comprises the following steps: S521, controlling the temperature of the desoldering, increasing the particle size of the droplets, and increasing the penetration of the droplets into the furnace; S522, controlling the injection speed of the urea solution and obtaining the denitrification efficiency under different ammonia nitrogen ratios.

9. The automatic control method for flue gas denitrification of a CFB boiler according to claim 1, characterized in that: The concentration of nitrogen oxides is controlled to be less than or equal to 100 mg / m 3 , and control the ammonia escape concentration to be less than or equal to 8mg / m 3 .

10. A CFB boiler flue gas denitrification automatic control system, used to implement the CFB boiler flue gas denitrification automatic control method according to any one of claims 1 to 9, characterized in that: The system includes: an early warning module, a collection module, a comparison module, a processing module, a spraying amount control module and an emission concentration control module; The early warning module is used to monitor and control the CFB boiler with the operator station display as the center; The collection module is used to collect the nitrogen oxide emission value of the tail flue of the CFB boiler in real time as a feedback value; The comparison module is used to compare the feedback value with the set target emission value, and calculate the deviation value of nitrogen oxides at the flue gas outlet and the rate of change of the deviation value; The processing module is used to construct a fuzzy relationship between the three PID parameters and the deviation and the rate of change of the deviation value, and to modify the PID parameters online to obtain new PID parameters; The spraying amount control module is used to dynamically adjust the stroke of the ammonia pump according to the new PID parameters to control the amount of urea solvent sprayed into the boiler furnace; The emission concentration control module is used to regulate the stroke of the dilution water pump and the flow rate of the dilution water, and to control the concentration of nitrogen oxides and the ammonia escape concentration.

Images