Method for operating wide-temperature-difference denitration catalyst in full load of coal-fired unit

Abstract

The invention relates to an operation method of a wide-temperature-difference denitration catalyst in a full load of a coal-fired unit. The operation method comprises the following steps: S1, determining the lowest continuous ammonia spraying temperature MOT of a denitration reactor; s2, switching the denitration reactor between the normal operation state and the low-load operation state so as to carry out denitration treatment; and S3, the denitration reactor is shut down in the normal operation state. After the minimum continuous ammonia spraying temperature is determined according to the inlet and outlet flue gas parameters of the denitration reactor, the critical operation time tmax is obtained according to the initial potential value and the critical potential value of the denitration reactor at 0 moment in the low-load operation state; the operation time of the denitration reactor in a low-load operation state and a normal operation state can be predicted according to the critical operation time tmax, so that safe and reliable operation of the wide-temperature-difference denitration catalyst can be guaranteed.

Description

Technical Field

[0001] The present disclosure relates to the field of flue gas treatment, and in particular, to a method for operating a wide temperature difference denitration catalyst within full load of a coal-fired unit. Background Art

[0002] At present, the scale of new energy sources such as solar energy and wind energy is expanding year by year, requiring coal-fired power plants to operate flexibly and reliably at full load. However, the operating temperature window of the denitrification catalyst used in coal-fired power plants is generally between 300 and 420°C. When the furnace is started or the deep peak load is operated at low load, the flue gas temperature at the inlet of the denitrification reactor is lower than the lower limit of the operating temperature window (the minimum continuous ammonia injection temperature), resulting in the inability to put the denitrification device of the power plant into operation. In order to solve the denitrification problem under low load operation of coal-fired power plants, the technical routes currently adopted include economizer hot water recirculation, economizer segmentation, flue gas bypass modification, etc., which increase the inlet flue gas temperature of the denitrification reactor by reducing heat exchange, but these technologies generally have problems such as high modification costs, long construction period, and reduced boiler thermal efficiency. The wide temperature difference denitrification catalyst can be operated when the inlet flue gas temperature of the denitrification reactor is lower than the operating temperature window of the conventional catalyst when the coal-fired power plant is started or the deep peak load is operated at low load. The wide temperature difference denitrification catalyst can be operated safely at a temperature higher than the minimum continuous ammonia injection temperature, the same as the conventional catalyst, and can also be operated at a temperature lower than the minimum continuous ammonia injection temperature. However, when the temperature is lower than the minimum continuous ammonia injection temperature, the activity of the wide temperature difference denitration catalyst will continue to decline reversibly due to the effect of ammonium bisulfate. Under the guidance of appropriate operation methods, the wide temperature difference denitration catalyst can be restored by increasing the load of the coal-fired unit and raising the flue gas temperature. However, if the operation method is not appropriate, fly ash and ammonium bisulfate will also cause irreversible deactivation of the wide temperature difference denitration catalyst. Summary of the invention

[0003] The purpose of the present disclosure is to provide a method for operating a wide temperature difference denitration catalyst within full load of a coal-fired unit, so as to solve the problem of irreversible deactivation of the wide temperature difference denitration catalyst caused by inappropriate operation mode in the prior art.

[0004] In order to achieve the above-mentioned object, the present disclosure provides a method for operating a wide temperature difference denitration catalyst in a full load of a coal-fired unit, the operating method comprising: S1, determining the minimum continuous ammonia injection temperature MOT of the denitration reactor according to the parameters of the flue gas at the inlet and outlet of the denitration reactor, when the inlet flue gas temperature T1 of the denitration reactor is lower than MOT, it indicates that the denitration reactor is in a low-load operation state; when the inlet flue gas temperature T2 of the denitration reactor is between MOT and the full-load temperature T full When , it indicates that the denitration reactor is in normal operation;

[0005] S2, operating the denitration reactor alternately between the normal operation state and the low-load operation state to perform denitration treatment;

[0006] Step S2 also includes:

[0007] S21, when the denitration reactor is in the low-load operation state, the critical operation time t is calculated by formula 1 max :

[0008]

[0009] Where A is the time constant, in h -1 ; P0 represents the initial potential of the denitration reactor at time 0 under low load operation; P C represents the critical potential of the denitrification reactor obtained by the maximum allowable emission concentration of NH3 and NO in the flue gas at the outlet of the denitrification reactor;

[0010] S22, according to the critical operation time t max A first running time t1 and a second running time t2 are obtained; the first running time t1 is within the critical running time t max Below; the second operating time t2 is greater than the first operating time t1;

[0011] S23, after operating the denitration reactor in the low-load operation state for at most a first operation time t1, switching to operating in the normal operation state for a second operation time t2;

[0012] S3, shutting down the denitration 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 (0~1):1.

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

[0015] Optionally, step S21 further includes: operating the denitration reactor for an initial test time t0 under the low-load operation state to obtain a reference relative potential function of the denitration reactor; operating the denitration reactor under the low-load operation state to obtain a real-time relative potential function of the denitration reactor; and differentiating the reference relative potential function with respect to time to obtain a first real-time derivative D 1i ; Derivative the real-time relative potential function with respect to time to obtain a second real-time derivative D 2i According to the first real-time derivative D at the same time 1i and the second real-time derivative D 2iThe time for which the denitration reactor operates under a low-load operation state is further determined.

[0016] Optionally, the reference relative potential function is as shown in Formula 2:

[0017]

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

[0019]

[0020] Among them, t i represents the real time when the denitration reactor is running at low load, t i is any value between 0 and t1; A1 refers to the time constant of the reference relative potential function, the unit is h -1 ; A2 refers to the time constant of the real-time relative potential function, the unit is h -1 .

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

[0022] Optionally, step S23 further includes: when the first real-time derivative D 1i is less than the second real-time derivative D 2i When the denitration reactor is operated in the low-load operation state for the first operation time t1, it is switched to the normal operation state for the second operation time t2; when the first real-time derivative D 1i is greater than the second real-time derivative D 2i When the denitration reactor is directly switched to the normal operation state, it operates for the second operation time t2.

[0023] Optionally, before step S2, a wide temperature difference denitration catalyst is installed in the denitration reactor and then the furnace is started, so that the denitration reactor is operated under full load conditions, and the full load temperature T of the inlet flue gas of the denitration reactor is monitored. full ; The full load temperature T full The minimum continuous ammonia injection temperature MOT is 290-320°C.

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

[0025] Optionally, step S3 also includes: when the denitration reactor is in normal operation, directly shutting down the furnace; when the denitration reactor is in low-load operation, directly switching the denitration reactor to normal operation, and shutting down the furnace after the denitration reactor resumes normal operation.

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

[0027] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0029] Figure 1 This is a graph of the temperature, potential and operating time of a wide temperature difference denitrification catalyst when the coal-fired unit is operating at full load. DETAILED DESCRIPTION

[0030] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0031] The present disclosure provides a method for operating a wide temperature difference denitration catalyst within full load of a coal-fired unit, the operating method comprising:

[0032] S1. Determine the minimum continuous ammonia injection temperature MOT of the denitrification reactor according to the parameters of the flue gas at the inlet and outlet 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 , it indicates that the denitration reactor is in normal operation;

[0033] S2, operating the denitration reactor alternately between the normal operation state and the low-load operation state to perform denitration treatment;

[0034] Step S2 also includes:

[0035] S21, when the denitration reactor is in the low-load operation state, the critical operation time t is calculated by formula 1 max :

[0036]

[0037] Where A is the time constant, in h -1 ; P0 represents the initial potential of the denitration reactor at time 0 under low load operation; P C represents the critical potential of the denitrification reactor obtained by the maximum allowable emission concentration of NH3 and NO in the flue gas at the outlet of the denitrification reactor;

[0038] S22, according to the critical operation time t max A first running time t1 and a second running time t2 are obtained; the first running time t1 is within the critical running time t max Below; the second operating time t2 is greater than the first operating time t1;

[0039] S23, after operating the denitration reactor in the low-load operation state for at most a first operation time t1, switching to operating in the normal operation state for a second operation time t2;

[0040] S3, shutting down the denitration reactor under normal operating conditions.

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

[0042] In step S1 of the present disclosure, the accurate minimum continuous ammonia injection temperature MOT of the wide temperature difference denitrification catalyst of the present application can be obtained according to the nitrogen oxide concentration, sulfur trioxide concentration and ammonia concentration of the flue gas at the inlet and outlet of the denitrification reactor and the conventional method in the art for determining the minimum continuous ammonia injection temperature MOT of the denitrification reactor.

[0043] Wherein, the minimum continuous ammonia injection temperature MOT is 290-320°C.

[0044] In order to ensure the stable reduction of the potential of the denitration reactor equipped with a wide temperature difference denitration catalyst, the difference between the minimum continuous ammonia injection temperature MOT and the low load temperature T1 is stabilized at 10-40°C, preferably 10-25°C.

[0045] The parameters of the inlet flue gas entering the denitration reactor disclosed in the present invention include: a nitrogen oxide concentration of 200 to 800 mg / Nm 3 , sulfur trioxide concentration is 1.4-15μL / L and ammonia concentration is 85-500mg / Nm 3 The parameters of the outlet flue gas treated by the denitration reactor disclosed in the present invention include: nitrogen oxide concentration of 0-50 mg / Nm 3 , sulfur trioxide concentration is 1.5~16μL / L and ammonia concentration is 0~2.28mg / Nm 3 .

[0046] In the above embodiment, affected by the grid dispatch and the performance limitation of the wide temperature difference denitration catalyst, the denitration reactor needs to operate for a period of time under low load operation. The present disclosure can accurately obtain the minimum continuous ammonia injection temperature MOT of the wide temperature difference denitration catalyst according to the parameters of the inlet and outlet flue gas, and determine the operation time of the denitration reactor under low load operation according to the difference between the obtained minimum continuous ammonia injection temperature MOT and the inlet flue gas temperature T1, which can ensure the performance of the wide temperature difference denitration catalyst.

[0047] Before performing step S2, the wide temperature difference denitration catalyst is installed in the denitration reactor and the denitration reactor is operated under high load Q for 8 to 36 hours, preferably 12 to 24 hours. The high load Q is the full load Q. full 75-100%.

[0048] Among them, the full load temperature T full is determined by the boiler properties. For example, the full load temperature T of the boiler disclosed herein is full Between 360 and 400°C.

[0049] When the present disclosure performs step S2, after the denitration reactor is treated with high load, the denitration reactor can be operated in a normal operating state for a period of time, and then switched to a low load operating state for a period of time; or the denitration reactor can be operated in a low load operating state for a period of time, and then switched to a normal operating state for a period of time.

[0050] Among them, nitrogen oxide concentration and ammonia escape concentration detectors are also provided at the inlet and outlet of the denitrification reactor to measure the nitrogen oxide concentration and ammonia escape concentration at the inlet and outlet of the denitrification reactor.

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

[0052]

[0053] Wherein, η represents the denitration efficiency, in %, which is calculated by Formula 5; MR is the molar ratio of ammonia nitrogen compounds, which is calculated by Formula 6:

[0054]

[0055] Among them, C NOx,in Indicates the concentration of nitrogen oxides in the inlet flue gas, in mg / Nm 3 , C NOx,out Indicates the nitrogen oxide concentration in the outlet flue gas, in mg / Nm 3 .

[0056]

[0057] Among them, C NOx,in Indicates the concentration of nitrogen oxides in the inlet flue gas, in mg / Nm 3 , C NH3 Indicates the ammonia escape concentration in the outlet flue gas, in mg / Nm 3 , 2.7 is the conversion factor.

[0058] The critical potential Pc of the denitrification reactor is obtained according to the national, local / industry emission limit standards for NO and NH3 in flue gas from coal-fired power plants and formula 7:

[0059]

[0060] Wherein, η represents the denitration efficiency, in %; MR is the molar ratio of ammonia nitrogen compounds, and the denitration efficiency η is calculated by formula 8:

[0061]

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

[0063] The molar ratio MR of the ammonia nitrogen compound is calculated by formula 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 / Nm 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, according to the properties of the boiler of the present application, the ratio of the critical potential Pc to the initial potential P0 of the denitration reactor is limited to (0.55-0.8):1; and the critical operation time t can be calculated according to formula 1 max Then, through the critical running time t max The first running time t1 and the second running time t2 are determined. The first running time t1 and the critical running time t2 max The ratio of the first operation time t1 to the second operation time t2 is (0-0.95): 1; the ratio of the first operation time t1 to the second operation time t2 is (0-1): 1. In this embodiment, making the first operation time lower than the critical operation time can provide a certain buffer time for the temperature increase, thereby improving the safety of the full load section operation of the reactor.

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

[0068] Wherein, step S21 of the present disclosure further includes: operating the denitration reactor in the low-load operation state for an initial test time t0, and performing a prediction based on the benchmark relative potential within the initial test time t0 to obtain a benchmark relative potential function.

[0069] In this embodiment, the wide temperature difference denitration catalyst is operated within the initial test time t0, and a series of reference potential P values ​​are obtained according to the flue gas parameters at the inlet and outlet of the denitration reactor, the denitration efficiency and the potential calculation formula at multiple time points; the ratio between the reference potential P and the initial potential P0 and the corresponding time form a first data set, and the first data set is subjected to data regression fitting to obtain the reference relative potential function f1 of the denitration reactor and the time constant A1 of the reference relative potential function; the reference relative potential function is shown in Formula 2:

[0070]

[0071] Among them, t i represents the real time when the denitration reactor is running at low load, t i is any value between 0 and t1; A1 refers to the time constant of the reference relative potential function, the unit is h -1 .

[0072] Wherein, step S22 further comprises: obtaining a series of real-time potentials P when the wide temperature difference denitration catalyst is operating at the low load. i Value; the real-time potential P i The ratio between the initial potential P0 and the corresponding time constitutes a second data set, and the second data set is subjected to data regression fitting to obtain the real-time relative potential function f2 of the denitration reactor and the time constant A2 of the real-time relative potential function; the real-time relative potential function is shown in Formula 3:

[0073]

[0074] Among them, t i represents the real time when the denitration reactor is running at low load, t i is any value between 0 and t1; A2 refers to the time constant of the real-time relative potential function, the unit is h -1 .

[0075] The reference relative potential function is derived with respect to time to obtain a first real-time derivative D 1i ; Derivative the real-time relative potential function with respect to time to obtain a second real-time derivative D 2i According to the first real-time derivative D at the same time 1i and the second real-time derivative D 2i The time for which the denitration reactor operates under a low-load operation state is further determined.

[0076] In the above embodiment, step S23 further includes: when the first real-time derivative D 1i is less than the second real-time derivative D 2i , the denitration reactor is operated in the low-load operation state for the first operation time t1, and then switched to the normal operation state for the second operation time t2, so that the relative potential of the denitration reactor is restored to 1, and is operated in this state for a period of time; when the first real-time derivative D 1i is greater than the second real-time derivative D 2i When the denitration reactor is directly switched to the normal operation state and operated for the second operation time t2, the relative potential of the denitration reactor is restored to 1, and the denitration reactor is operated for a period of time in this state.

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

[0078] Through the above implementation, by real-time monitoring of the parameters of the inlet and outlet flue gas of the denitration reactor, the accuracy of the obtained real-time potential can be improved, and the safety and reliability of the operation of the wide temperature difference denitration catalyst can be further improved. In addition, by adopting the above operation method, the relative potential of the wide temperature difference denitration catalyst can be restored to 1 after each low-load operation, and the wide temperature difference denitration catalyst can reach the expected life, thereby ensuring the safe and reliable operation of the wide temperature difference denitration catalyst; wherein the expected life is jointly determined by the properties of the wide temperature difference denitration catalyst and the properties of the flue gas being treated.

[0079] Step S3 of the present disclosure also includes: when the denitration reactor receives a shutdown signal, confirming whether the denitration reactor is in a normal operation state or a low-load operation state; if the denitration reactor is in a normal operation state, directly shutting down the furnace; if the denitration reactor is in a low-load operation state, switching the denitration reactor directly to a normal operation state until the denitration reactor is shut down after resuming normal operation. Resuming normal operation means that the potential of the denitration reactor is restored to the potential before the low-load operation.

[0080] In this embodiment, the working state of the denitration reactor is distinguished, so as to avoid the risk of deactivation of the wide temperature difference denitration catalyst caused by direct shutdown of the denitration reactor under low load operation.

[0081] In one embodiment, the operation method of the wide temperature difference denitration catalyst at full load of the coal-fired unit includes:

[0082] S1. Determine the minimum continuous ammonia injection temperature MOT of the wide temperature difference denitration catalyst according to the parameters of the flue gas at the inlet and outlet of the denitration reactor. When the inlet flue gas temperature T1 of the denitration reactor is lower than MOT, it indicates that the denitration reactor is in a low-load operation state; when the inlet flue gas temperature T2 of the denitration reactor is between MOT and the full-load temperature T full When , it indicates that the denitration reactor is in normal operation;

[0083] S2. First start-up operation: After the wide temperature difference denitration catalyst is installed in the denitration reactor, it is operated for the first time. The coal-fired unit is ignited and the coal-fired unit load is increased to high load operation and continued for 8 to 36 hours. Then, the denitration reactor is operated alternately between the normal operation state and the low load operation state to perform denitration treatment;

[0084] Step S2 also includes:

[0085] S21, operate the denitration catalyst under low load operation for the initial test time t0. According to the denitration reactor potential calculation formula and the real-time data such as the denitration efficiency and ammonia nitrogen molar ratio of the denitration reactor within the initial test time t0, calculate the initial potential P0 and the reference potential P of the denitration reactor at time 0 under low load operation, and through data regression P / P0=e^(-A1t i ), the time constant A1 is obtained; through the critical potential P C , initial potential P0, time constant A1 and formula 1 to calculate the critical operating time t max At the same time, the reference relative potential function f1 can be obtained, and the reference relative potential function f1 is shown in Formula 2:

[0086]

[0087]

[0088] Among them, t i represents the real time when the denitration reactor is running at low load, t i is any value between 0 and t1; A1 refers to the time constant of the reference relative potential function, the unit is h -1 .

[0089] S22, according to the critical operation time t max A first running time t1 is obtained and a second running time t2 is obtained according to the first running time. The first running time t1 is the critical running time t2. max Hereinafter, the second operating time t2 is greater than the first operating time t1;

[0090] S23, operating the denitration reactor under low load operation for a first operation time t1, so as to obtain a real-time relative potential function f2 of the denitration reactor at t1:

[0091]

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

[0093] The reference relative potential function is derived with respect to time to obtain a first real-time derivative D 1i ; Derivative the real-time relative potential function with respect to time to obtain a second real-time derivative D 2i ;

[0094] When the first real-time derivative D1i is less than the second real-time derivative D 2i , the denitration reactor is operated in the low-load operation state for the first operation time t1, and then switched to the normal operation state for the second operation time t2, so that the relative potential of the denitration reactor is restored to 1, and is operated in this state for a period of time; when the first real-time derivative D 1i is greater than the second real-time derivative D 2i When the denitration reactor is directly switched to the normal operation state and operated for the second operation time t2, the relative potential of the denitration reactor is restored to 1, and the denitration reactor is operated for a period of time in this state.

[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 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 down.

[0096] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0097] Example 1

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

[0099] S1. According to 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 299°C; when the inlet flue gas temperature T1 of the denitrification reactor is lower than MOT, it means 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 temperature is between 289℃ and 330℃, it indicates that the denitration reactor is in normal operation; T1 is 289℃ and T2 is 330℃;

[0100] S2. First start-up operation: After the wide temperature difference denitration catalyst is installed in the denitration reactor, it is operated for the first time. The coal-fired unit is ignited and the unit load is increased to 300MW at full load and operated for 12 hours. At this time, the inlet flue gas temperature is about 380°C; the denitration reactor is switched between the normal operation state and the low load operation state to perform denitration treatment;

[0101] Step S2 also includes:

[0102] S21, operate the denitration catalyst under low load operation for an initial test time of 2 hours. According to the denitration reactor potential calculation formula, as well as the real-time data such as denitration efficiency and ammonia nitrogen molar ratio within the initial test time of 2 hours, calculate the initial potential P0 and the reference potential P of the denitration reactor at time 0 under low load operation, and through data regression P / P0=e^(-A1t i ), the time constant A1 is 0.005; through the critical potential P C , initial potential P0, time constant A1 and formula 1 to calculate the critical operating time t max 120h;

[0103]

[0104] At the same time, a reference relative potential function f1 can be obtained, and the reference relative potential function f1 is shown in Formula 2:

[0105]

[0106] Among them, t i Indicates the time when the denitrification reactor is running at low load, t i Any value between 0 and 24 hours;

[0107] S22, according to the critical operation time t max The first running time t1 is obtained to be 24 hours, and the second running time t2 is obtained to be 24 hours according to the first running time;

[0108] S23, operating the denitration reactor under low load operation for 24 hours, and obtaining the real-time potential P i and initial potential P0, and after data regression P i / P0=e^(-A2t i ), the time constant A2 is 0.0038; furthermore, the real-time relative potential function f2 of the denitration reactor within 24 hours is obtained:

[0109]

[0110] Among them, t i Indicates the time when the denitrification reactor is running at low load, ti It is any value between 0 and 24 hours.

[0111] The reference relative potential function f1 is derived with respect to time to obtain the first real-time derivative D 1i for The real-time relative potential function f2 is derived with respect to time to obtain a second real-time derivative D 2i for

[0112] The wide temperature difference denitration catalyst is operated at low load for 24 hours and always shows D 2i >D 1i After the wide temperature difference denitration catalyst is operated at low load for 24 hours, the load of the coal-fired unit is increased to raise the temperature of the inlet flue gas of the denitration reactor to 330°C and then operate under normal operating conditions for 24 hours, the relative potential of the denitration reactor can be restored to 1, and it can operate in this state for a period of time.

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

[0114] Example 2

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

[0116] S1, T1 is 272℃, T2 is 350℃;

[0117] S21, the denitration catalyst is operated under low load for an initial test time of 1 hour; the critical relative potential is 0.69 and Formula 1 is as follows:

[0118]

[0119] The critical operating time t is calculated by formula 1. max 11h;

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

[0121]

[0122] Among them, t i Indicates the time when the denitrification reactor is running at low load, t i Any value between 0 and 8 hours;

[0123] S22, according to the critical operation time t max The first running time t1 is 8 hours and the second running time t2 is 8 hours;

[0124] S23, operating the denitration reactor under low load operation for 8 hours, and obtaining a real-time relative potential change function f2 of the denitration reactor within 8 hours:

[0125]

[0126] Among them, t i Indicates the time when the denitrification reactor is running at low load, t i Any value between 0 and 8 hours;

[0127] The reference relative potential function f1 is derived with respect to time to obtain the first real-time derivative D 1i for The real-time relative potential function f2 is derived with respect to time to obtain a second real-time derivative D 2i for

[0128] The wide temperature difference denitration catalyst is always D in low load operation for 8 hours 2i >D 1i After the wide temperature difference denitration catalyst is operated at low load for 8 hours, the temperature of the inlet flue gas of the denitration reactor is increased to 350°C and then operated normally for 8 hours, the relative potential of the denitration reactor can be restored to 1, and it can be operated in this state for a period of time.

[0129] Example 3

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

[0131] S1, T1 is 260℃, T2 is 380℃;

[0132] S21, the denitration catalyst is operated under low load for an initial test time of 0.5 h; the critical relative potential is 0.76 and formula 1 is as follows:

[0133]

[0134] The critical operating time t is calculated by formula 1. max 5.2h;

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

[0136]

[0137] Among them, ti Indicates the time when the denitrification reactor is running at low load, t i Any value between 0 and 5h;

[0138] S22, according to the critical operation time t max The first running time t1 is 5 hours and the second running time t2 is 7 hours;

[0139] S23, operating the denitration reactor under low load operation for 5 hours, and obtaining a real-time relative potential change function f2 of the denitration reactor within 5 hours:

[0140]

[0141] Among them, t i Indicates the time when the denitrification reactor is running at low load, t i Any value between 0 and 5h;

[0142] The reference relative potential function f1 is derived with respect to time to obtain the first real-time derivative D 1i for The real-time relative potential function f2 is derived with respect to time to obtain a second real-time derivative D 2i for

[0143] The wide temperature difference denitration catalyst was operated at low load for 5 hours and then D 2i <D 1i By immediately increasing the load of the coal-fired unit to raise the temperature of the inlet flue gas of the denitrification reactor to 380°C and then operating it in a normal operating state for 7 hours, the relative potential of the denitrification reactor can be restored to 1, and it can operate in this state for a period of time.

[0144] Example 4

[0145] The operation method of the wide temperature difference denitration catalyst in the full load of the coal-fired unit is the same as that 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 denitration reactor is 14μL / L, and the NO x Concentration 300mg / Nm 3 (dry basis, standard state), export NO x The maximum concentration allowed is 30 mg / Nm 3 (Dry basis, standard state), the maximum allowable concentration of NH3 is 2.28 mg / Nm 3 (dry basis, standard state), the full load operating temperature is about 380℃.

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

[0147] S2. First start-up operation: After the wide temperature difference denitration catalyst is installed in the denitration reactor, it is operated for the first time. The coal-fired unit is ignited and the unit load is increased to 600MW at full load and operated for 24 hours. At this time, the inlet flue gas temperature is about 380°C; the denitration reactor is operated alternately between the normal operation state and the low load operation state to perform denitration treatment;

[0148] Step S2 also includes:

[0149] S21, operate the denitration catalyst under low load for an initial test time of 1 hour. Calculate the baseline potential P of the denitration reactor according to the potential calculation formula of the denitration reactor and the real-time data such as the denitration efficiency and ammonia nitrogen molar ratio within the initial test time of 1 hour, and calculate the baseline potential P of the denitration reactor through data regression P / P0=e^(-A1t i ), the time constant A1 is obtained; through the critical potential P C , initial potential P0, time constant A1 and formula 1 to calculate the critical operating time t max 16.4h;

[0150]

[0151] At the same time, a reference relative potential function f1 can be obtained, and the reference relative potential function f1 is shown in Formula 2:

[0152]

[0153] Among them, t i Indicates the time when the denitrification reactor is running at low load, t i Any value between 0 and 12 hours;

[0154] S22, according to the critical operation time t max The first running time t1 is obtained to be 12 hours, and the second running time t2 is obtained based on the first running time to be 12 hours;

[0155] S23, operating the denitration reactor under low load operation for 12 hours, and obtaining the real-time relative potential function f2 of the denitration reactor within 12 hours:

[0156]

[0157] Among them, t i Indicates the time when the denitrification reactor is running at low load, t i It is any value between 0 and 12 hours.

[0158] The reference relative potential function f1 is derived with respect to time to obtain the first real-time derivative D 1i for The real-time relative potential function f2 is derived with respect to time to obtain a second real-time derivative D 2i for

[0159] The wide temperature difference denitration catalyst is always D in low load operation for 12 hours 2i >D 1i After the wide temperature difference denitration catalyst is operated at low load for 12 hours, the temperature of the inlet flue gas of the denitration reactor is increased to 330°C and then operated under normal operating conditions for 12 hours, the relative potential of the denitration reactor can be restored to 1, and it can be operated for a period of time in this state.

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

[0161] Comparative Example 1

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

[0163] S1. According to 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°C;

[0164] S2, the coal-fired unit is ignited and the wide temperature difference denitration catalyst is operated in the temperature range of 305-360°C. At this time, the inlet flue gas temperature of the denitration reactor and its potential at various temperatures are monitored in real time;

[0165] S21. The wide temperature difference denitration catalyst is operated at the low load temperature of 270°C at the inlet flue gas temperature of the denitration reactor, and the denitration reactor potential continues to decrease. After 24 hours of operation, the nitrogen oxide concentration at the outlet of the denitration reactor is higher than 50 mg / Nm 3 (dry basis, standard state), ammonia escape concentration is higher than 2.28mg / Nm 3 (dry basis, standard state), the outlet flue gas concentration exceeds the standard and cannot continue to operate;

[0166] S22, increase the load of the coal-fired unit, make the flue gas temperature at the inlet of the denitrification reactor higher than the MOT temperature to 330℃, the potential of the denitrification reactor slowly recovers, and the relative potential is 0.8 after 24 hours of operation. Continue to extend the high-load operation time to 48 hours, and the potential of the denitrification reactor cannot be restored to the potential during the initial normal operation.

[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 reaches 360℃, the relative potential of the reactor still does not reach 1, and cannot reach the potential during normal operation. The potential data at this time is regressed, and its operating life is 17,400 hours, which is 5,600 hours less than the initial expected life.

[0168] S3, after receiving the shutdown signal, the denitration reactor is directly shut down in normal operation.

[0169] According to the comparison between Examples 1 to 4 and Comparative Example 1, the present invention determines the minimum continuous ammonia injection temperature according to 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 operated at a low load, the low load operation time and high load treatment time of the wide temperature difference denitrification catalyst are predicted according to the initial baseline potential and critical potential of the denitrification reactor, so that the relative potential of the reactor can be restored to 1 and operate 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 the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

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

[0172] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for operating a wide temperature difference denitration catalyst at full load in a coal-fired unit, characterized in that: The operation method includes: S1. Determine the minimum continuous ammonia injection temperature MOT of the denitrification reactor according to the parameters of the flue gas at the inlet and outlet 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 , it indicates that the denitration reactor is in normal operation; S2, operating the denitration reactor alternately between the normal operation state and the low-load operation state to perform denitration treatment; Step S2 also includes: S21, when the denitration reactor is in the low-load operation state, the critical operation time t is calculated by formula 1 max : Where A is the time constant, in h -1 ; P0 represents the initial potential of the denitration reactor at time 0 under low load operation; P C represents the critical potential of the denitrification reactor obtained by the maximum allowable emission concentration of NH3 and NO in the flue gas at the outlet of the denitrification reactor; S22, according to the critical operation time t max A first running time t1 and a second running time t2 are obtained; the first running time t1 is within the critical running time t max Below; the second operating time t2 is greater than the first operating time t1; S23, after operating the denitration reactor in the low-load operation state for at most a first operation time t1, switching to operating in the normal operation state for a second operation time t2; S3, shutting down the denitration reactor under normal operating conditions.

2. The operating method according to claim 1, characterized in that: The first operating time t1 and the critical operating 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 ratio of the critical potential Pc to the initial potential P0 of the denitration reactor is (0.55-0.8):

1.

4. The operating method according to claim 1, characterized in that: Step S21 also includes: operating the denitration reactor for an initial test time t0 under the low-load operation state to obtain a reference relative potential function of the denitration reactor; Allowing the denitration reactor to operate under the low-load condition to obtain a real-time relative potential function of the denitration reactor; The reference relative potential function is derived with respect to time to obtain a first real-time derivative D 1i ; Derivative the real-time relative potential function with respect to time to obtain a second real-time derivative D 2i ; According to the first real-time derivative D at the same time 1i and the second real-time derivative D 2i The time for which the denitration reactor operates under a low-load operation state is further determined.

5. The operating method according to claim 4, characterized in that: The reference relative potential function is shown in Formula 2: The real-time relative potential function is shown in Formula 3: Among them, t i represents the real time when the denitration reactor is running at low load, t i is any value between 0 and t1; A1 refers to the time constant of the reference relative potential function, the unit is h -1 ; A2 refers to the time constant of the real-time relative potential function, the unit is 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 0.55-1.

7. The operating method according to claim 4, characterized in that: Step S23 also includes: When the first real-time derivative D 1i is less than the second real-time derivative D 2i When the denitration reactor is operated in the low-load operation state for the first operation time t1, it is switched to the normal operation state for the second operation time t2; When the first real-time derivative D 1i is greater than the second real-time derivative D 2i When the denitration reactor is directly switched to the normal operation state, the denitration reactor is operated for the second operation time t2.

8. The operating method according to claim 1, characterized in that: Before step S2, a wide temperature difference denitration catalyst is installed in the denitration reactor and then the furnace is started, so that the denitration reactor is operated under full load conditions, and the full load temperature T of the inlet flue gas of the denitration reactor is monitored. full ; The full load temperature T full The minimum continuous ammonia injection temperature MOT is 290-320°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 denitration reactor in the low-load operation state is 10-40°C.

10. The operating method according to claim 1, characterized in that: Step S3 also includes: When the denitration reactor is in normal operation, it is directly shut down; When the denitration reactor is in a low-load operation state, the denitration reactor is directly switched to a normal operation state until the denitration reactor resumes normal operation and then is shut down.

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