A method for operating a wide temperature difference denitrification catalyst at full load in a coal-fired power unit

Abstract

This disclosure relates to a method for operating a wide temperature difference denitrification catalyst in a coal-fired power unit at full load. The method includes: S1, determining the minimum continuous ammonia injection temperature (MOT) of the denitrification reactor; S2, switching the denitrification reactor between the normal operating state and the low-load operating state for denitrification treatment; and S3, shutting down the denitrification reactor under normal operating conditions. Based on the inlet and outlet flue gas parameters of the denitrification reactor, this disclosure determines the minimum continuous ammonia injection temperature, and then calculates the critical operating time (t) based on the initial potential energy and critical potential energy value of the denitrification reactor at time 0 under low-load operating conditions. max And based on the critical running time t max It can predict the operating time of the denitrification reactor under low load and normal operating conditions, thereby ensuring the safe and reliable operation of the wide temperature difference denitrification catalyst.

Description

Technical Field

[0001] This disclosure relates to the field of flue gas treatment, and more specifically, to a method for operating a wide temperature difference denitrification catalyst at full load in a coal-fired unit. Background Technology

[0002] With the increasing scale of new energy sources such as solar and wind power, coal-fired power plants are required to operate with flexibility and reliably at full load. However, the operating temperature window of denitrification catalysts used in coal-fired power plants is generally between 300 and 420°C. During start-up or deep peak shaving at low load, the inlet flue gas temperature of the denitrification reactor is lower than the lower limit of the operating temperature window (minimum continuous ammonia injection temperature), causing the power plant's denitrification unit to be unable to operate. To solve the denitrification problem under low load operation of coal-fired power plants, current technical approaches include economizer hot water recirculation, economizer segmentation, and flue gas bypass modification. These methods increase the inlet flue gas temperature of the denitrification reactor by reducing heat exchange. However, these technologies generally suffer from high modification costs, long construction periods, and reduced boiler thermal efficiency. Wide temperature difference denitrification catalysts, on the other hand, can operate under low load conditions during start-up or deep peak shaving of coal-fired power plants, i.e., when the inlet flue gas temperature of the denitrification reactor is lower than the operating temperature window of conventional catalysts. Wide temperature difference denitrification catalysts can operate safely both above and below the minimum continuous ammonia injection temperature, just like conventional catalysts. However, below the minimum continuous ammonia injection temperature, the activity of the wide temperature difference denitrification catalyst will continuously and reversibly decrease due to the effect of ammonium bisulfate. Under appropriate operating conditions, the activity of the wide temperature difference denitrification catalyst can be restored by increasing the load of the coal-fired unit and raising the flue gas temperature. However, if the operating method is inappropriate, fly ash and ammonium bisulfate can also cause irreversible deactivation of the wide temperature difference denitrification catalyst. Summary of the Invention

[0003] The purpose of this disclosure is to provide a method for operating a wide temperature difference denitrification catalyst at full load in a coal-fired unit, so as to solve the problem of irreversible deactivation of wide temperature difference denitrification catalysts caused by unsuitable operating methods in the prior art.

[0004] To achieve the above objectives, this disclosure provides a method for operating a wide temperature difference denitrification catalyst at full load in a coal-fired power unit. The method includes: S1, determining the minimum continuous ammonia injection temperature (MOT) of the denitrification reactor based on the parameters of the flue gas at the inlet and outlet of the reactor; when the inlet flue gas temperature (T1) of the denitrification reactor is lower than the MOT, it indicates that the denitrification reactor is operating at a low load; when the inlet flue gas temperature (T2) of the denitrification reactor is between the MOT and the full load temperature (T... full When the time interval is between, it indicates that the denitrification reactor is in normal operating condition;

[0005] S2. The denitrification reactor is operated alternately between the normal operating state and the low-load operating state to perform denitrification treatment;

[0006] Step S2 also includes:

[0007] S21. When the denitrification reactor is in the low-load operation state, the critical operating time t is calculated using Equation 1. max :

[0008]

[0009] Where A refers to the time constant, with units of h. -1 P0 represents the initial potential energy of the denitrification reactor at time 0 under low-load operation; P C The critical potential of the denitrification reactor is represented by the maximum permissible emission concentrations of NH3 and NO in the flue gas exiting the denitrification reactor.

[0010] S22, Based on the critical running time t max The first running time t1 and the second running time t2 are obtained; the first running time t1 is obtained at the critical running time t2. max The second running time t2 is greater than or equal to the first running time t1.

[0011] S23. After the denitrification reactor operates under the low-load operation state for a first operating time t1, it is switched to the normal operation state for a second operating time t2.

[0012] S3. Shut down the denitrification reactor under normal operating conditions.

[0013] Optionally, the first running time t1 and the critical running time t max The ratio of the first running time t1 to the second running time t2 is (0 to 0.95):1; the ratio of the first running time t1 to the second running time t2 is (0 to 1):1.

[0014] Optionally, the ratio of the critical potential Pc to the initial potential P0 of the denitrification reactor is (0.55 to 0.8):1.

[0015] Optionally, step S21 further includes: running the denitrification reactor under the low-load operating state for an initial test time t0 to obtain the reference relative potential function of the denitrification reactor; running the denitrification reactor under the low-load operating state to obtain the real-time relative potential function of the denitrification reactor; and differentiating the reference relative potential function with respect to time to obtain the first real-time derivative D. 1i The second real-time derivative D is obtained by differentiating the real-time relative potential function with respect to time. 2i Based on the first real-time derivative D within the same time period 1i Second real-time derivative D 2iFurther determine the operating time of the denitrification reactor under low load operation.

[0016] Optionally, the benchmark relative potential function is as shown in Equation 2:

[0017]

[0018] The real-time relative potential function is shown in Equation 3:

[0019]

[0020] Among them, t i The time t represents the real-time duration of the denitrification reactor during low-load operation. i A1 is any value between 0 and t1; A1 refers to the time constant of the reference relative potential function, in units of h. -1 A2 refers to the time constant of the real-time relative potential function, with units of h. -1 .

[0021] Optionally, the calculated value of the real-time relative potential function f2 is 0.55 to 1.

[0022] Optionally, step S23 further includes: when the first real-time derivative D 1i Less than the second real-time derivative D 2i When the denitrification reactor operates under low load for the first operating time t1, it switches to normal operating condition for the second operating time t2; when the first real-time derivative D 1i Greater than the second real-time derivative D 2i At that time, the denitrification reactor is directly switched to the normal operating state for a second operating time t2.

[0023] Optionally, before step S2, the wide temperature difference denitrification catalyst is installed in the denitrification reactor and then the reactor is started up, allowing the denitrification reactor to operate under full load conditions, and the full load temperature T of the inlet flue gas of the denitrification reactor is monitored. full The full-load temperature T full The temperature ranges from 360 to 400°C, and the minimum continuous ammonia injection temperature (MOT) is 290 to 320°C.

[0024] Optionally, the difference between the minimum continuous ammonia injection temperature MOT and the inlet flue gas temperature T1 of the denitrification reactor under low load operation is 10 to 40°C.

[0025] Optionally, step S3 further includes: directly shutting down the denitrification reactor when it is in normal operation; and directly switching the denitrification reactor to normal operation when it is in low-load operation, until the denitrification reactor resumes normal operation and is then shut down.

[0026] Using the above technical solution, after determining the minimum continuous ammonia injection temperature based on the inlet and outlet flue gas parameters of the denitrification reactor, the critical operating time t is obtained based on the initial potential energy and critical potential energy value of the denitrification reactor at time 0 under low load operation. max And based on the critical running time t max It can predict the operating time of the denitrification reactor under low load and normal operating conditions, thereby ensuring the safe and reliable operation of the wide temperature difference denitrification catalyst.

[0027] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0028] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 This is a graph showing the temperature, potential energy, and operating time of a wide temperature difference denitrification catalyst under full load in a coal-fired unit. Detailed Implementation

[0030] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0031] This disclosure provides a method for operating a wide temperature difference denitrification catalyst at full load in a coal-fired power unit. The method includes:

[0032] S1. Determine the minimum continuous ammonia injection temperature (MOT) of the denitrification reactor based on the parameters of the inlet and outlet flue gas. When the inlet flue gas temperature (T1) of the denitrification reactor is lower than MOT, it indicates that the denitrification reactor is operating at a low load. When the inlet flue gas temperature (T2) of the denitrification reactor is between MOT and the full load temperature (T...), it indicates that the denitrification reactor is operating at a low load. full When the time interval is between, it indicates that the denitrification reactor is in normal operating condition;

[0033] S2. The denitrification reactor is operated alternately between the normal operating state and the low-load operating state to perform denitrification treatment;

[0034] Step S2 also includes:

[0035] S21. When the denitrification reactor is in the low-load operation state, the critical operating time t is calculated using Equation 1. max :

[0036]

[0037] Where A refers to the time constant, with units of h. -1 P0 represents the initial potential energy of the denitrification reactor at time 0 under low-load operation; P C The critical potential of the denitrification reactor is represented by the maximum permissible emission concentrations of NH3 and NO in the flue gas exiting the denitrification reactor.

[0038] S22, Based on the critical running time t max The first running time t1 and the second running time t2 are obtained; the first running time t1 is obtained at the critical running time t2. max The second running time t2 is greater than or equal to the first running time t1.

[0039] S23. After the denitrification reactor operates under the low-load operation state for a first operating time t1, it is switched to the normal operation state for a second operating time t2.

[0040] S3. Shut down the denitrification reactor under normal operating conditions.

[0041] Using the above technical solution, after determining the minimum continuous ammonia injection temperature based on the inlet and outlet flue gas parameters of the denitrification reactor, the critical operating time t is obtained based on the initial potential energy and critical potential energy value of the denitrification reactor at time 0 under low load operation. max And based on the critical running time t max It can predict the operating time of the denitrification reactor under low load and normal operating conditions, thereby ensuring the safe and reliable operation of the wide temperature difference denitrification catalyst.

[0042] In step S1 of this disclosure, the accurate minimum continuous ammonia injection temperature (MOT) of the wide temperature difference denitrification catalyst of this application can be obtained based on the concentrations of nitrogen oxides, sulfur trioxide, and ammonia in the flue gas at the inlet and outlet of the denitrification reactor, and by using conventional methods in the art for determining the minimum continuous ammonia injection temperature (MOT) of the denitrification reactor.

[0043] The minimum continuous ammonia injection temperature (MOT) is 290–320°C.

[0044] In order to ensure that the potential decrease of the denitrification reactor equipped with the wide temperature difference denitrification catalyst is stable, the difference between the minimum continuous ammonia injection temperature MOT and the low load temperature T1 is kept stable at 10-40℃, preferably 10-25℃.

[0045] The parameters of the inlet flue gas entering the denitrification reactor disclosed herein include: a nitrogen oxide concentration of 200–800 mg / Nm³. 3 The concentrations of sulfur trioxide were 1.4–15 μL / L and ammonia concentrations were 85–500 mg / Nm³. 3 The parameters of the outlet flue gas treated by the denitrification reactor disclosed herein include: nitrogen oxide concentration of 0–50 mg / Nm³. 3 The concentrations of sulfur trioxide were 1.5–16 μL / L and ammonia concentrations were 0–2.28 mg / Nm³. 3 .

[0046] In the above embodiments, due to the influence of power grid dispatch and the performance limitations of the wide temperature difference denitrification catalyst, the denitrification reactor needs to operate under low load conditions for a period of time. This disclosure can accurately determine the minimum continuous ammonia injection temperature (MOT) of the wide temperature difference denitrification catalyst based on the parameters of the inlet and outlet flue gas, and determine the operating time of the denitrification reactor under low load conditions based on the difference between the obtained minimum continuous ammonia injection temperature (MOT) and the inlet flue gas temperature (T1), thus ensuring the performance of the wide temperature difference denitrification catalyst.

[0047] Before step S2, this disclosure involves installing a wide temperature difference denitrification catalyst in the denitrification reactor and starting it up. The reactor is then operated under high load Q for 8–36 hours, preferably 12–24 hours; wherein high load Q is full load Q. full 75% to 100%.

[0048] Among them, the full load temperature T full It is determined by the nature of the boiler; for example, the full-load temperature T of the boiler disclosed herein. full Between 360 and 400℃.

[0049] In step S2 of this disclosure, after the denitrification reactor has undergone high-load treatment, it can first be operated in normal operating condition for a period of time, and then switched to low-load operating condition for a period of time; or it can first be operated in low-load operating condition for a period of time, and then switched to normal operating condition for a period of time.

[0050] The denitrification reactor is equipped with detectors for nitrogen oxide concentration and ammonia slip concentration at the inlet and outlet to measure the nitrogen oxide concentration and ammonia slip concentration at the inlet and outlet of the denitrification reactor.

[0051] The inlet and outlet nitrogen oxide concentrations and ammonia slip concentrations at the initial test time t0 are measured; based on the above data and Equation 4, the initial potential energy P0 of the denitrification reactor at time 0 under low load operation is calculated:

[0052]

[0053] Where η represents the denitrification efficiency, expressed as a percentage, calculated using Equation 5; MR is the molar ratio of ammonia nitrogen compounds, calculated using Equation 6.

[0054]

[0055] Among them, C NOx,in This indicates the concentration of nitrogen oxides in the inlet flue gas, expressed in mg / Nm³. 3 C NOx,out This indicates the concentration of nitrogen oxides in the flue gas at the outlet, expressed in mg / Nm³. 3 .

[0056]

[0057] Among them, C NOx,in This indicates the concentration of nitrogen oxides in the inlet flue gas, expressed in mg / Nm³. 3 C NH3 This indicates the ammonia slip concentration in the flue gas at the outlet, expressed in mg / Nm³. 3 2.7 is the conversion factor.

[0058] The critical potential Pc of the denitrification reactor is obtained based on the national / local / industry emission limits for NO and NH3 in flue gas from coal-fired power plants and Equation 7:

[0059]

[0060] Where η represents the denitrification efficiency, in %; MR is the molar ratio of ammonia nitrogen compounds, and the denitrification efficiency η is calculated using Equation 8:

[0061]

[0062] Of these, 50 were NO from flue gas from coal-fired power plants. x The national standard emission limit shall not exceed 50 mg / Nm³. 3 C NOx，in NO at the inlet of the denitrification reactor x Concentration, in mg / Nm 3 ;

[0063] The molar ratio MR of ammonia nitrogen compounds is calculated using Equation 9:

[0064]

[0065] Among them, 2.28 is the industry emission limit for NH3 escape in flue gas from coal-fired power plants, which shall not exceed 2.28 mg / Nm³. 3 2.7 is the conversion factor, C NOx，in NO at the inlet of the denitrification reactor xConcentration, in mg / Nm 3 .

[0066] In one embodiment, based on the properties of the boiler of this application, the ratio of the critical potential energy Pc to the initial potential energy P0 of the denitrification reactor is limited to (0.55~0.8):1; and the critical operating time t can be calculated according to Equation 1. max Then, through the critical running time t... max Determine the first running time t1 and the second running time t2. The first running time t1 and the critical running time t... max The ratio of the first operating time t1 to the second operating time t2 is (0-0.95):1; the ratio of the first operating time t1 to the second operating time t2 is (0-1):1. In this embodiment, making the first operating time lower than the critical operating time can provide a certain buffer time for temperature rise, thereby improving the safety of the reactor's full-load operation.

[0067] During the denitrification process in step S2 of the denitrification reactor, the temperature T of the flue gas at the inlet and outlet of the denitrification reactor is monitored. i and temperature T i The corresponding potential is monitored.

[0068] Step S21 of this disclosure further includes: running the denitrification reactor under the low-load operation state for an initial test time t0, and predicting the benchmark relative potential function based on the benchmark relative potential within the initial test time t0.

[0069] In this embodiment, during the operation of the wide temperature difference denitrification catalyst within the initial test time t0, a series of baseline potential energy P values ​​are obtained based on the flue gas parameters at the inlet and outlet of the denitrification reactor at multiple time points, the denitrification efficiency, and the potential energy calculation formula. The ratio between the baseline potential energy P and the initial potential energy P0 is combined with the corresponding time to form a first data set, and data regression fitting is performed on the first data set to obtain the baseline relative potential energy function f1 of the denitrification reactor and the time constant A1 of the baseline relative potential energy function. The baseline relative potential energy function is shown in Equation 2.

[0070]

[0071] Among them, t i The time t represents the real-time duration of the denitrification reactor during low-load operation. i A1 is any value between 0 and t1; A1 refers to the time constant of the reference relative potential function, in units of h. -1 .

[0072] Step S22 further includes: obtaining a series of real-time potential P values ​​when the wide temperature difference denitration catalyst is running at the low load. i Numerical value; the real-time potential P i The ratio between the initial potential P0 and the corresponding time constitutes a second data set. Data regression fitting is then performed on this second data set to obtain the real-time relative potential function f2 of the denitrification reactor and the time constant A2 of the real-time relative potential function. The real-time relative potential function is shown in Equation 3.

[0073]

[0074] Among them, t i The time t represents the real-time duration of the denitrification reactor during low-load operation. i A1 is any value between 0 and t1; A2 refers to the time constant of the real-time relative potential function, in units of h. -1 .

[0075] Differentiating the benchmark relative potential function with respect to time yields the first real-time derivative D. 1i The second real-time derivative D is obtained by differentiating the real-time relative potential function with respect to time. 2i Based on the first real-time derivative D within the same time period 1i Second real-time derivative D 2i Further determine the operating time of the denitrification reactor under low load operation.

[0076] In the above embodiment, step S23 further includes: when the first real-time derivative D 1i Less than the second real-time derivative D 2i When the denitrification reactor operates under low load for the first operating time t1, it switches to normal operating condition for the second operating time t2 to restore the relative potential of the denitrification reactor to 1, and operates in this state for a period of time; when the first real-time derivative D 1i Greater than the second real-time derivative D 2i When the denitrification reactor is switched to the normal operating state for a second operating time t2, the relative potential of the denitrification reactor is restored to 1, and it operates in this state for a period of time.

[0077] The calculated value of the real-time relative potential function f2 is 0.55 to 1.

[0078] By implementing the above methods and monitoring the parameters of the inlet and outlet flue gas of the denitrification reactor in real time, the accuracy of the obtained real-time potential can be improved, further enhancing the safety and reliability of the wide temperature difference denitrification catalyst operation. Furthermore, by adopting the above operating method, the relative potential of the wide temperature difference denitrification catalyst can be restored to 1 after each low-load operation, enabling the catalyst to reach its expected lifespan and thus ensuring its safe and reliable operation. The expected lifespan is determined by the properties of the wide temperature difference denitrification catalyst and the properties of the flue gas being treated.

[0079] Step S3 of this disclosure further includes: after the denitrification reactor receives a shutdown signal, confirming whether the denitrification reactor is in normal operation or low-load operation; if the denitrification reactor is in normal operation, shutting it down directly; if the denitrification reactor is in low-load operation, switching it directly to normal operation until it resumes normal operation and then shutting it down. Here, "resumption of normal operation" means that the denitrification reactor's potential energy is restored to its state before the current low-load operation.

[0080] In this embodiment, distinguishing the operating states of the denitrification reactor can avoid the risk of deactivation of the wide temperature difference denitrification catalyst caused by directly shutting down the denitrification reactor under low load conditions.

[0081] In one embodiment, the method for operating a wide temperature difference denitrification catalyst at full load in a coal-fired unit includes:

[0082] S1. Determine the minimum continuous ammonia injection temperature (MOT) of the wide temperature difference denitrification catalyst based on the parameters of the inlet and outlet flue gas of the denitrification reactor. When the inlet flue gas temperature T1 of the denitrification reactor is lower than MOT, it indicates that the denitrification reactor is in a low-load operation state; when the inlet flue gas temperature T2 of the denitrification reactor is between MOT and the full-load temperature T... full When the time interval is between, it indicates that the denitrification reactor is in normal operating condition;

[0083] S2. Initial Start-up Operation: After the wide temperature difference denitrification catalyst is installed in the denitrification reactor, the coal-fired unit is ignited and started up. After the coal-fired unit load is increased to high load operation and maintained for 8 to 36 hours, the denitrification reactor is operated alternately between the normal operation state and the low load operation state to carry out denitrification treatment.

[0084] Step S2 also includes:

[0085] S21. Run the denitrification catalyst under low load for an initial test time t0. Based on the denitrification reactor potential calculation formula and real-time data such as denitrification efficiency and ammonia-nitrogen molar ratio during the initial test time t0, calculate the initial potential P0 and baseline potential P of the denitrification reactor at time 0 under low load operation. Then, perform data regression to obtain P / P0 = e^(-A1t). i ), to obtain the time constant A1; through the critical potential P C The critical running time t is calculated using the initial potential P0, the time constant A1, and Equation 1. max Simultaneously, the benchmark relative potential function f1 can be obtained, as shown in Equation 2:

[0086]

[0087]

[0088] Among them, t i The time t represents the real-time duration of the denitrification reactor during low-load operation. i A1 is any value between 0 and t1; A1 refers to the time constant of the reference relative potential function, in units of h. -1 .

[0089] S22, Based on the critical running time t max The first running time t1 is obtained, and the second running time t2 is obtained based on the first running time. The first running time t1 is at the critical running time t max In the following case, the second running time t2 is greater than the first running time t1;

[0090] S23. Run the denitrification reactor under low load for a first running time t1 to obtain the real-time relative potential function f2 of the denitrification reactor at t1:

[0091]

[0092] Among them, t i The time t represents the real-time time of the denitrification reactor under low-load operation. i A1 is any value between 0 and t1; A2 refers to the time constant of the real-time relative potential function, in units of h. -1 .

[0093] Differentiating the benchmark relative potential function with respect to time yields the first real-time derivative D. 1i The second real-time derivative D is obtained by differentiating the real-time relative potential function with respect to time. 2i ;

[0094] When the first real-time derivative D1i Less than the second real-time derivative D 2i When the denitrification reactor operates under low load for the first operating time t1, it switches to normal operating condition for the second operating time t2 to restore the relative potential of the denitrification reactor to 1, and operates in this state for a period of time; when the first real-time derivative D 1i Greater than the second real-time derivative D 2i When the denitrification reactor is switched to the normal operating state for a second operating time t2, the relative potential of the denitrification reactor is restored to 1, and it operates in this state for a period of time.

[0095] S3. When the denitrification reactor receives a shutdown signal, confirm whether the denitrification reactor is in normal operation or low-load operation. If the denitrification reactor is in normal operation, shut it down directly. If the denitrification reactor is in low-load operation, switch the denitrification reactor directly to normal operation until the denitrification reactor resumes normal operation and then shuts it down.

[0096] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0097] Example 1

[0098] The flue gas source is a 300MW coal-fired power unit: the SO3 concentration in the flue gas at the inlet of the SCR denitrification reactor is 9.1 μL / L, NO... x Concentration 350 mg / Nm 3 (Dry basis, standard state), Export NO x Maximum permissible concentration: 40 mg / Nm 3 (Dry basis, standard state), the maximum permissible concentration of NH3 is 2.28 mg / Nm³. 3 (Dry basis, standard condition), full-load operating temperature is 380℃.

[0099] S1. Based on the parameters of the inlet and outlet flue gas of the denitrification reactor, the minimum continuous ammonia injection temperature (MOT) for the wide temperature difference denitrification catalyst is determined to be 299℃. When the inlet flue gas temperature T1 of the denitrification reactor is lower than MOT, it indicates that the denitrification reactor is operating at a low load. When the inlet flue gas temperature T2 of the denitrification reactor is between MOT and the full load temperature T1, it indicates that the denitrification reactor is operating at a low load. full When the temperatures are between 289℃ and 330℃, it indicates that the denitrification reactor is in normal operating condition; where T1 is 289℃ and T2 is 330℃.

[0100] S2. Initial Start-up Operation: After the wide temperature difference denitrification catalyst is installed in the denitrification reactor, the coal-fired unit is ignited and started up, and the unit load is increased to full load 300MW and operated for 12 hours. At this time, the inlet flue gas temperature is about 380℃. The denitrification reactor is switched between the normal operation state and the low load operation state to carry out denitrification treatment.

[0101] Step S2 also includes:

[0102] S21. The denitrification catalyst is run under low load for an initial test period of 2 hours. Based on the denitrification reactor potential calculation formula and real-time data such as denitrification efficiency and ammonia-nitrogen molar ratio during the initial test period of 2 hours, the initial potential P0 and baseline potential P of the denitrification reactor at time 0 under low load operation are calculated, and then P / P0 = e^(-A1t) is obtained through data regression. i The time constant A1 was found to be 0.005; the critical potential P was obtained. C The critical running time t is calculated using the initial potential P0, the time constant A1, and Equation 1. max It is 120 hours;

[0103]

[0104] Simultaneously, the benchmark relative potential function f1 can be obtained, as shown in Equation 2:

[0105]

[0106] Among them, t i The time t represents the time the denitrification reactor operates at low load. i Any value between 0 and 24h;

[0107] S22, Based on the critical running time t max The first running time t1 is obtained as 24h, and the second running time t2 is obtained as 24h based on the first running time;

[0108] S23. Run the denitrification reactor under low load for 24 hours to obtain the real-time potential P. i and initial potential P0, and P through data regression i / P0=e^(-A2t i The time constant A2 was found to be 0.0038; subsequently, the real-time relative potential function f2 of the denitrification reactor over 24 hours was obtained.

[0109]

[0110] Among them, t i The time t represents the time the denitrification reactor operates at low load.i It can be any value between 0 and 24h.

[0111] Differentiating the benchmark relative potential function f1 with respect to time yields the first real-time derivative D. 1i for Differentiating the real-time relative potential function f2 with respect to time yields the second real-time derivative D. 2i for

[0112] The wide temperature difference denitration catalyst consistently exhibited D during 24 hours of low-load operation. 2i >D 1i After the wide temperature difference denitrification catalyst is operated at low load for 24 hours, the temperature of the inlet flue gas of the denitrification reactor is raised to 330°C by increasing the load of the coal-fired unit and then operated under normal operating conditions for 24 hours. This allows the relative potential of the denitrification reactor to be restored to 1, and it can be operated under this condition for a period of time.

[0113] S3. When the denitrification reactor receives a shutdown signal, confirm whether the denitrification reactor is in normal operation or low-load operation. If the denitrification reactor is in normal operation, shut it down directly. If the denitrification reactor is in low-load operation, shut it down after the relative potential of the denitrification reactor recovers to 1.

[0114] Example 2

[0115] The operation method of the wide temperature difference denitrification catalyst at full load in a coal-fired unit is the same as in Example 1, except that:

[0116] S1 and T1 are 272℃, and T2 is 350℃;

[0117] S21. The denitrification catalyst is run under low load for an initial test time of 1 hour; the critical relative potential is 0.69 and Equation 1 is as follows:

[0118]

[0119] The critical running time t is calculated using Equation 1. max It is 11 hours;

[0120] The baseline relative potential function f1 is obtained, and the baseline relative potential function f1 is shown in Equation 2:

[0121]

[0122] Among them, t i The time t represents the time the denitrification reactor operates at low load. i Any value between 0 and 8h;

[0123] S22, Based on the critical running time t max The first running time t1 is 8 hours and the second running time t2 is 8 hours.

[0124] S23. Run the denitrification reactor under low load for 8 hours, and obtain the real-time relative potential energy change function f2 of the denitrification reactor within 8 hours:

[0125]

[0126] Among them, t i The time t represents the time the denitrification reactor operates at low load. i Any value between 0 and 8h;

[0127] Differentiating the benchmark relative potential function f1 with respect to time yields the first real-time derivative D. 1i for Differentiating the real-time relative potential function f2 with respect to time yields the second real-time derivative D. 2i for

[0128] The wide temperature difference denitration catalyst consistently exhibited D during low-load operation for 8 hours. 2i >D 1i After the wide temperature difference denitrification catalyst is run at low load for 8 hours, the temperature of the flue gas at the inlet of the denitrification reactor is raised to 350°C and then run at normal operating temperature for 8 hours. This allows the relative potential of the denitrification reactor to be restored to 1, and the reactor can operate in this state for a period of time.

[0129] Example 3

[0130] The operation method of the wide temperature difference denitrification catalyst at full load in a coal-fired unit is the same as in Example 1, except that:

[0131] S1 and T1 are 260℃, and T2 is 380℃;

[0132] S21. The denitrification catalyst is operated under low load for an initial test time of 0.5 hours; the critical relative potential is 0.76 and Equation 1 is as follows:

[0133]

[0134] The critical running time t is calculated using Equation 1. max It takes 5.2 hours;

[0135] The benchmark relative potential function f1 is obtained, and the benchmark relative potential function f1 is shown in Equation 2:

[0136]

[0137] Among them, ti The time t represents the time the denitrification reactor operates at low load. i Any value between 0 and 5h;

[0138] S22, Based on the critical running time t max The first running time t1 is 5 hours and the second running time t2 is 7 hours.

[0139] S23. Run the denitrification reactor under low load for 5 hours, and obtain the real-time relative potential energy change function f2 of the denitrification reactor within 5 hours:

[0140]

[0141] Among them, t i The time t represents the time the denitrification reactor operates at low load. i Any value between 0 and 5h;

[0142] Differentiating the benchmark relative potential function f1 with respect to time yields the first real-time derivative D. 1i for Differentiating the real-time relative potential function f2 with respect to time yields the second real-time derivative D. 2i for

[0143] The wide temperature difference denitrification catalyst showed D after being operated at low load for 5 hours. 2i <D 1i Immediately increasing the load of the coal-fired unit raises the temperature of the inlet flue gas of the denitrification reactor to 380℃ and then operates normally for 7 hours, which can restore the relative potential of the denitrification reactor to 1 and operate in this state for a period of time.

[0144] Example 4

[0145] The operation method of the wide temperature difference denitrification catalyst at full load in a coal-fired unit is the same as in Example 1, except that the flue gas source is a 600MW coal-fired unit: the SO3 concentration in the flue gas at the inlet of the SCR denitrification reactor is 14μL / L, NO... x Concentration 300mg / Nm 3 (Dry basis, standard state), Export NO x Maximum permissible concentration: 30 mg / Nm 3 (Dry basis, standard state), the maximum permissible concentration of NH3 is 2.28 mg / Nm³. 3 (Dry basis, standard condition), the full-load operating temperature is approximately 380℃.

[0146] S1, the minimum continuous ammonia injection temperature MOT is 302℃, T1 is 275℃, and T2 is 330℃;

[0147] S2. Initial Start-up Operation: After the wide temperature difference denitrification catalyst is installed in the denitrification reactor, the coal-fired unit is ignited and started up, increasing the unit load to full load 600MW and running for 24 hours. At this time, the inlet flue gas temperature is about 380℃. The denitrification reactor is operated alternately between the normal operation state and the low load operation state to carry out denitrification treatment.

[0148] Step S2 also includes:

[0149] S21. Run the denitrification catalyst under low load for an initial test time of 1 hour. Calculate the baseline potential P of the denitrification reactor based on the denitrification reactor potential calculation formula and real-time data such as denitrification efficiency and ammonia-nitrogen molar ratio during the initial 1-hour test. Then, perform data regression to P / P0=e^(-A1t). i ), to obtain the time constant A1; through the critical potential P C The critical running time t is calculated using the initial potential P0, the time constant A1, and Equation 1. max It takes 16.4 hours;

[0150]

[0151] Simultaneously, the benchmark relative potential function f1 can be obtained, as shown in Equation 2:

[0152]

[0153] Among them, t i The time t represents the time the denitrification reactor operates at low load. i Any value between 0 and 12h;

[0154] S22, Based on the critical running time t max The first running time t1 is obtained as 12h, and the second running time t2 is obtained as 12h based on the first running time;

[0155] S23. Run the denitrification reactor under low load for 12 hours, and obtain the real-time relative potential energy function f2 of the denitrification reactor within 12 hours:

[0156]

[0157] Among them, t i The time t represents the time the denitrification reactor operates at low load. i It can be any value between 0 and 12h.

[0158] Differentiating the benchmark relative potential function f1 with respect to time yields the first real-time derivative D. 1i for Differentiating the real-time relative potential function f2 with respect to time yields the second real-time derivative D. 2i for

[0159] The wide temperature difference denitration catalyst consistently exhibited D during 12 hours of low-load operation. 2i >D 1i After the wide temperature difference denitrification catalyst is run at low load for 12 hours, the temperature of the flue gas at the inlet of the denitrification reactor is raised to 330°C and then run under normal operating conditions for 12 hours, which can restore the relative potential of the denitrification reactor to 1 and run under this condition for a period of time.

[0160] S3. When the denitrification reactor receives a shutdown signal, confirm whether the denitrification reactor is in normal operation or low-load operation. If the denitrification reactor is in normal operation, shut it down directly. If the denitrification reactor is in low-load operation, shut it down after the relative potential of the denitrification reactor recovers to 1.

[0161] Comparative Example 1

[0162] A 300MW coal-fired power unit: The SO3 concentration in the flue gas at the inlet of the SCR denitrification reactor is 12.7 μL / L, NO... x Concentration 450 mg / Nm 3 (Dry basis, standard state), Export NO x Maximum permissible concentration: 50 mg / Nm 3 (Dry basis, standard state), the maximum permissible concentration of NH3 is 2.28 mg / Nm³. 3 (Dry basis, standard condition), full-load operating temperature is 360℃.

[0163] S1. Based on the parameters of the inlet and outlet flue gas of the denitrification reactor, the minimum continuous ammonia injection temperature (MOT) of the wide temperature difference denitrification catalyst is determined to be 305℃.

[0164] S2. The coal-fired unit is ignited and started up, so that the wide temperature difference denitrification catalyst operates in the temperature range of 305-360℃. At this time, the inlet flue gas temperature of the denitrification reactor and its potential at each temperature are monitored in real time.

[0165] S21, a wide temperature difference denitrification catalyst, operates at the low load temperature of 270℃ at the inlet flue gas temperature of the denitrification reactor, resulting in a continuous decrease in the reactor's potential. After 24 hours of operation, the nitrogen oxide concentration at the reactor outlet exceeds 50 mg / Nm³. 3 (Dry basis, standard state), ammonia slip concentration higher than 2.28 mg / Nm³ 3 (Dry basis, standard conditions) The outlet flue gas concentration exceeds the standard, and operation cannot continue.

[0166] S22, increasing the load of the coal-fired unit to raise the inlet flue gas temperature of the denitrification reactor above the MOT temperature to 330℃, the denitrification reactor's potential slowly recovers, with a relative potential of 0.8 after 24 hours of operation. Continuing to extend the high-load operation time to 48 hours, the denitrification reactor's potential cannot recover to its initial normal operating potential.

[0167] S23, or continue to increase the load of the coal-fired unit to full load, the flue gas temperature at the inlet of the denitrification reactor to 360℃, the relative potential of the reactor still has not reached 1, which is not the potential during normal operation. Based on the regression of the potential data at this time, its operating life is 17400 hours, which is 5600 hours less than the initial expected life.

[0168] S3, after receiving a shutdown signal, the denitrification reactor will be shut down directly if the coal-fired unit is in normal operation.

[0169] According to the comparison of Examples 1-4 and Comparative Example 1, this disclosure determines the minimum continuous ammonia injection temperature based on the inlet and outlet flue gas parameters of the denitrification reactor to guide the normal operation of the wide temperature difference denitrification catalyst. When the wide temperature difference denitrification catalyst is running at low load, the time for low load operation and the time for high load treatment of the wide temperature difference denitrification catalyst are predicted based on the initial reference potential and critical potential of the denitrification reactor. This allows the relative potential of the reactor to be restored to 1 and operated in this state for a period of time, thereby ensuring the safe and reliable operation of the wide temperature difference denitrification catalyst.

[0170] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0171] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0172] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for operating a wide temperature difference denitrification catalyst at full load in a coal-fired power unit, characterized in that, The execution method includes: S1. Determine the minimum continuous ammonia injection temperature (MOT) of the denitrification reactor based on the parameters of the inlet and outlet flue gas. When the inlet flue gas temperature (T1) of the denitrification reactor is lower than MOT, it indicates that the denitrification reactor is operating at a low load. When the inlet flue gas temperature (T2) of the denitrification reactor is between MOT and the full load temperature (T...), it indicates that the denitrification reactor is operating at a low load. full When the time interval is between, it indicates that the denitrification reactor is in normal operating condition; S2. The denitrification reactor is operated alternately between the normal operating state and the low-load operating state to perform denitrification treatment; Step S2 also includes: S21. When the denitrification reactor is in the low-load operation state, the critical operating time t is calculated using Equation 1. max : Where A refers to the time constant, with units of h. -1 P0 represents the initial potential energy of the denitrification reactor at time 0 under low-load operation; P C The critical potential of the denitrification reactor is represented by the maximum permissible emission concentrations of NH3 and NO in the flue gas exiting the denitrification reactor. S22, Based on the critical running time t max The first running time t1 and the second running time t2 are obtained; the first running time t1 is obtained at the critical running time t2. max The second running time t2 is greater than or equal to the first running time t1. S23. After the denitrification reactor operates under the low-load operation state for a first operating time t1, it is switched to the normal operation state for a second operating time t2. S3. Shut down the denitrification reactor under normal operating conditions.

2. The operating method according to claim 1, characterized in that, The first running time t1 and the critical running time t max The ratio is (0~0.95):1; The ratio of the first running time t1 to the second running time t2 is (0~1):

1.

3. The operating method according to claim 1, characterized in that, The critical potential energy Pc to the initial potential energy P0 of the denitrification reactor is (0.55~0.8):

1.

4. The operating method according to claim 1, characterized in that, Step S21 further includes: running the denitrification reactor under the low-load operating state for an initial test time t0 to obtain the reference relative potential function of the denitrification reactor; The real-time relative potential function of the denitrification reactor is obtained under the low-load operation state. Differentiating the benchmark relative potential function with respect to time yields the first real-time derivative D. 1i The second real-time derivative D is obtained by differentiating the real-time relative potential function with respect to time. 2i ; Based on the first real-time derivative D within the same time period 1i Second real-time derivative D 2i Further determine the operating time of the denitrification reactor under low load operation.

5. The operating method according to claim 4, characterized in that, The benchmark relative potential function is shown in Equation 2: The real-time relative potential function is shown in Equation 3: Among them, t i The time t represents the real-time duration of the denitrification reactor during low-load operation. i A1 is any value between 0 and t1; A1 refers to the time constant of the reference relative potential function, in units of h. -1 A2 refers to the time constant of the real-time relative potential function, with units of h. -1 .

6. The operating method according to claim 5, characterized in that, The calculated value of the real-time relative potential function f2 is 0.55 to 1.

7. The operating method according to claim 4, characterized in that, Step S23 also includes: When the first real-time derivative D 1i Less than the second real-time derivative D 2i When the denitrification reactor operates under low load for the first operating time t1, it is switched to normal operating condition for the second operating time t2. When the first real-time derivative D 1i Greater than the second real-time derivative D 2i At that time, the denitrification reactor is directly switched to the normal operating state for a second operating time t2.

8. The operating method according to claim 1, characterized in that, Before step S2, the wide temperature difference denitrification catalyst is installed in the denitrification reactor and then the reactor is started up to operate under full load conditions. The full load temperature T of the inlet flue gas of the denitrification reactor is monitored. full ; The full load temperature T full The temperature ranges from 360 to 400°C, and the minimum continuous ammonia injection temperature (MOT) is 290 to 320°C.

9. The operating method according to claim 8, characterized in that, The difference between the minimum continuous ammonia injection temperature MOT and the inlet flue gas temperature T1 of the denitrification reactor under low load operation is 10-40℃.

10. The operating method according to claim 1, characterized in that, Step S3 also includes: When the denitrification reactor is shut down directly under normal operating conditions; When the denitrification reactor is operating at low load, it is directly switched to normal operation until it is shut down after it resumes normal operation.

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