Method for evaluating maximum safe output of SCR denitration device based on measured data

Abstract

The application discloses a kind of based on measured data's SCR denitration device maximum safety output evaluation method, belong to power plant boiler flue gas denitration technical field, this method is by to the data under actual operation condition of actual test to the flow field of SCR denitration device, NO x Concentration field, NH3 concentration field, temperature field and other flue gas parameters, realize the uniformity optimum of reactor outlet NO x Concentration distribution by ammonia injection optimization adjustment, based on the measured data, the model of reactor outlet NO x Concentration-ammonia escape amount is used as the evaluation index of the maximum safety output of SCR denitration device, under the premise of ensuring that the ammonia escape concentration of the full cross section of the reactor outlet does not exceed the standard, the maximum safety output and the optimal control concentration of the SCR denitration device are analyzed, which meets the actual needs of operation and management, avoids the deviation problem of catalyst performance detection, and also avoids the problem of shutdown sampling and experiment frequency, and truly realizes online detection and evaluation under actual working conditions.

Description

Technical Field

[0001] This invention belongs to the field of flue gas denitrification technology for power plant boilers, specifically involving a method for evaluating the maximum safe output of an SCR denitrification device. The method analyzes and evaluates the maximum safe output of the SCR denitrification device based on actual on-site test data. Background Technology

[0002] After the full implementation of ultra-low emissions from coal-fired power units, NO x With increasingly stringent emission standards, SCR denitrification units face even greater challenges and operational pressures.

[0003] Driven by the rapid development of new energy sources and changes in the power structure, coal-fired power units are gradually transforming into functional and regulating types. The increasing frequency of deep peak shaving, start-up and shutdown peak shaving, and long-term low-load operation in coal-fired power units has led to significant deviations between the actual operating conditions and the design operating conditions of SCR denitrification devices in these units.

[0004] Currently, the performance evaluation of SCR denitrification catalysts is mainly achieved through periodic performance testing, which evaluates the performance and degradation of existing catalysts by periodically sampling and testing them. Traditional catalyst performance testing methods suffer from problems such as insufficient representativeness of test samples, limitations in sampling time and experiment frequency, and deviations between experimental and actual operating conditions, leading to significant discrepancies between the final performance evaluation results and reality. Furthermore, the purpose of SCR denitrification unit performance evaluation tests is to assess whether the main performance indicators of the unit can meet design requirements, and it cannot achieve the goal of evaluating the unit's maximum output, thus offering limited guidance for operation and management. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned shortcomings in existing technologies and methods, and to provide a systematic evaluation method for the maximum safe output of an SCR denitrification device based on measured data, under the background of "ultra-low emissions" and low-load, long-cycle on-grid operation of coal-fired power units. This method assesses the maximum safe output of the SCR denitrification device by analyzing the flow field, NO... x Actual measurements of concentration field, NH3 concentration field, temperature field, and other flue gas parameters yielded data under actual operating conditions. Ammonia injection was then used to optimize and adjust the reactor outlet NO levels. x The concentration distribution uniformity is optimal, and based on measured data, a method for determining the NO concentration at the reactor outlet is proposed. x The concentration-ammonia slip model serves as an evaluation index characterizing the maximum safe output of an SCR denitrification unit. Under the premise of ensuring that the ammonia slip concentration at the reactor outlet does not exceed the standard, it analyzes the maximum safe output and optimal control concentration of the SCR denitrification unit, which meets the actual needs of operation and management. It avoids the problem of operating condition deviation in catalyst performance testing, as well as the problems of shutdown sampling and experiment frequency, and truly realizes online detection and evaluation under actual operating conditions.

[0006] The technical solution adopted by this invention to solve the above problems is: a method for evaluating the maximum safe output of an SCR denitrification device based on measured data, comprising the following steps:

[0007] (1) Working condition selection

[0008] In order to accurately reflect the maximum safe output of the SCR denitrification unit under different operating conditions, evaluation tests were conducted under the conditions of lowest stable combustion, 50%, 75%, and 100% rated load.

[0009] (2) Flue gas parameter and component testing

[0010] 1) Flue gas flow rate

[0011] According to GB / T 16157—1996 "Methods for Determination of Particulate Matter and Sampling of Gaseous Pollutants in Exhaust Gas from Stationary Sources", a calibrated flue gas sampling gun and thermocouple were used to measure the flue gas velocity, pressure, temperature and oxygen content at each point using the grid method, and the flue gas flow rate was calculated.

[0012] The flue gas flow rate is calculated using the following formula:

[0013] Q=3600F×ω (1)

[0014] In the formula: Q is the flue gas flow rate, m 3 / h; F is the test cross-sectional area, m 2 ω is the average flue gas velocity at the test section, in m / s, calculated using the following formula:

[0015]

[0016] In the formula: K is the correction coefficient for the dynamic pressure measuring tube; ρ is the flue gas density under actual operating conditions, kg / m³. 3 Calculate using the following formula:

[0017]

[0018] P d To measure the average dynamic pressure of the flue gas at the test section, in Pa, it is calculated using the following formula:

[0019]

[0020] In the formula: ρ0 is the density of flue gas under standard conditions, kg / m³ 3 ;ρ t The density of flue gas under actual operating conditions is expressed in kg / m³. 3 ;P a The local atmospheric pressure is Pa; P j To test the flue gas static pressure at the cross-section, Pa; P bP represents standard atmospheric pressure, Pa; n is the total number of measuring points at the inlet (or outlet); di Let be the flue gas dynamic pressure at each measuring point, in Pa.

[0021] 2) Smoke composition

[0022] Flue gas composition (NO) x Since the concentration distribution of O2 is uneven, a grid method is used for testing. The grid layout is arranged in accordance with the requirements of GB / T 16157—1996 "Methods for Determination of Particulate Matter and Sampling of Gaseous Pollutants in Exhaust Gas from Stationary Sources".

[0023] The concentration of flue gas components is measured at each measuring point, and the arithmetic average of the flue gas component concentrations at each grid point is calculated. The result is the actual flue gas component concentration value of that cross section.

[0024] The measuring instrument is calibrated using a high-purity, qualified standard gas. During the measurement process, the instrument is calibrated using the standard gas at least once before and once after the test.

[0025] 3) Flue gas temperature

[0026] A rapid-response temperature probe thermocouple was used for testing, and the temperature values ​​at each measurement point were taken. The values ​​during the test were then averaged.

[0027] 4) Moisture content of flue gas

[0028] The moisture content of flue gas is calculated using the following formula:

[0029]

[0030] In the formula: X sw G represents the volume percentage of moisture in the exhaust gas, expressed as %; m V represents the weight of moisture absorbed by the absorbent tube, in grams. d The cumulative volume of dry flue gas extracted under the measured conditions is expressed in L; t r P represents the flue gas temperature before the flow meter, in °C. r B is the flue gas pressure before the flow meter, in Pa; a The pressure is atmospheric pressure, in Pa.

[0031] 5) Denitrification efficiency

[0032] Use NO x The testing instrument was calibrated using standard gas and O2 standard gas respectively. Then, measurements were taken in the denitrification inlet and outlet flues using the grid method. The test values ​​were averaged during the test, and the denitrification efficiency was calculated using the following formula:

[0033]

[0034] Where: η is the denitrification efficiency of the SCR flue gas denitrification device, %; C NOx-in NO at the reactor inlet x Concentration (standard state, dry basis, 6% O2), mg / m³ 3 C NOx-out NO at reactor outlet x Concentration (standard state, dry basis, 6% O2), mg / m³ 3 .

[0035] (3) Data processing

[0036] 1) Export NO x Relative standard deviation of concentration distribution

[0037] NO in the outlet flue gas was tested using a flue gas analyzer. x Concentration, calculated from multiple test points, outlet NO x The relative standard deviation of the concentration is used to characterize the NO concentration at the export site. x Non-uniformity of concentration distribution.

[0038]

[0039] In the formula: RSD is NO x Relative standard deviation of concentration distribution, %; x i NO at a single measuring point x Concentration value (standard state, dry basis, 6% O2), mg / m³ 3 ; For test section NO x Average concentration (standard state, dry basis, 6% O2), mg / m³ 3 .

[0040] 2) Relative standard deviation of NH3 concentration distribution at the outlet

[0041] A portable laser ammonia slip detector was used to test the NH3 concentration in the outlet flue gas. After multi-point testing, the relative standard deviation of the outlet NH3 concentration was calculated to characterize the non-uniformity of the outlet NH3 concentration distribution.

[0042]

[0043] Where: RSD 1 y represents the relative standard deviation of NH3 concentration distribution, in %; i The value of NH3 at a single measuring point is expressed in μL / L. For test section NO x Average concentration, μL / L;

[0044] (4) Ammonia injection optimization

[0045] The ammonia injection rate was adjusted based on the experimental results, and an optimized ammonia injection strategy compatible with different operating conditions was developed to ensure that the denitrification efficiency reached the design value. NO₂ levels at the reactor inlet and outlet were measured. x / O2 concentration, based on NO at the reactor outlet section x The NH3 concentration distribution was monitored, and the opening of the regulating valve of the ammonia injection grid at the denitrification inlet was repeatedly adjusted in a targeted manner to control the NO concentration at the reactor outlet. x The relative standard deviation of the concentration is controlled within 15%, and the NO concentration at the outlet of both denitrification reactors is achieved. x Average concentration and total NO emission x The relative deviation of concentration values ​​is within ±10%, and the ammonia slip concentration is controlled within 3 μL / L. Maximize the NO concentration at the reactor outlet. x Uniform distribution, improved denitrification system efficiency, reduced ammonia escape at denitrification outlet and ammonia consumption.

[0046] (5) Establish NO x -Ammonia slip relationship model

[0047] By optimizing and adjusting the ammonia injection, the NO content at the reactor outlet cross-section was increased. x Uniformity of concentration distribution should be ensured to minimize the possibility of excessive ammonia escape at the reactor outlet section.

[0048] 1) Test the same NO under different load conditions. x Concentration control concentration corresponds to the ammonia escape concentration.

[0049] 2) Under the same load conditions, test different NO x Concentration control concentration corresponds to the ammonia escape concentration.

[0050] 3) Based on the test results, establish NO x Concentration-ammonia slip relationship model.

[0051] (6) Assessment of the maximum safe output of SCR denitrification unit

[0052] Based on the NO established in step (5) x - An ammonia slip relationship model is used to characterize the output change of the SCR denitrification unit. The upper limit of ammonia slip in the relationship model corresponds to the NO... x The concentration control concentration is the minimum control concentration of the SCR denitrification device, which is the maximum safe output of the SCR denitrification device.

[0053] Compared with the prior art, the present invention has the following advantages and effects:

[0054] This invention proposes using NO at the outlet cross section of the SCR reactor. xThe average ammonia slip concentration at the SCR reactor outlet section under conditions where the relative standard deviation of concentration distribution is less than 20% is used as an evaluation index for the maximum safe output of the SCR denitrification unit, and is used to assess the performance of the SCR denitrification catalyst and NO. x The minimum and optimal control concentrations are evaluated and analyzed to meet the actual needs of operation and management, and the existing SCR denitrification performance and maximum safe output can be analyzed online.

[0055] This invention's method, based on field measurement data, fully leverages the flexibility and mobility of field testing, avoiding problems such as insufficient representativeness of catalyst samples, limited sampling timing, and restricted experimental frequency in laboratory catalyst performance testing. The proposed method for obtaining the maximum safe output evaluation index of the SCR denitrification unit is scientifically sound, highly operable, and fully considers the significant indicative value of high ammonia slip in evaluating SCR denitrification unit performance and its adverse effects on downstream facilities. Catalyst performance testing and output evaluation under different operating loads can be conducted without shutdown sampling, avoiding deviations between experimental and actual operating conditions. Furthermore, it better meets operational management requirements. Attached Figure Description

[0056] Figure 1 This is a flowchart of the evaluation method in an embodiment of the present invention.

[0057] Figures 2-5 This is the distribution diagram in Table 1 of the embodiments of the present invention.

[0058] Figures 6-9 This is the distribution diagram in Table 2 of the embodiments of the present invention.

[0059] Figures 10-13 This is the distribution diagram in Table 3 of the embodiments of the present invention.

[0060] Figures 14-17 This is the distribution diagram in Table 4 of the embodiments of the present invention.

[0061] Figures 18-21 This is the distribution diagram in Table 5 of the embodiments of the present invention.

[0062] Figures 22-25 This is the distribution diagram in Table 6 of the embodiments of the present invention.

[0063] Figure 26 NO is an embodiment of the present invention. x - Ammonia slip relationship model diagram. Detailed Implementation

[0064] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0065] Example

[0066] In this embodiment, taking the A-side reactor of the SCR denitrification system of a 600MW coal-fired unit as an example, the maximum safe output was evaluated through on-site testing, optimization, and data processing. This invention mainly consists of operating condition selection, flue gas parameter and component testing, data processing, ammonia injection optimization, and NO... x - This consists of several parts, including the establishment of an ammonia slip relationship model and the assessment of the maximum safe output of the SCR denitrification unit. Detailed procedures are as follows: Figure 1 As shown.

[0067] 1) A 600MW coal-fired unit has completed its flexibility retrofit, and the minimum stable combustion load under pure condensing conditions is 30% of the unit's rated load. Therefore, based on the actual operating conditions of the unit, maximum safe output assessment tests were conducted under operating conditions of 100%, 75%, 50%, and 30% of the rated load.

[0068] 2) According to GB / T 16157—1996 "Determination of Particulate Matter and Sampling Methods for Gaseous Pollutants in Exhaust Gas from Stationary Sources", the parameters and components of the flue gas at the reactor inlet and outlet were tested under four selected load conditions. These mainly included the flue gas velocity and distribution at the reactor inlet, and the inlet NO... x Concentration and distribution, export NO x Data on concentration and distribution, and NH3 concentration and distribution at the outlet are shown in Tables 1 to 4.

[0069] 3) Process the measured data according to the formula, and draw the inlet flue gas velocity distribution diagram and the inlet NO2 distribution diagram respectively. x Concentration distribution map, export NO x Concentration distribution map, outlet NH3 concentration distribution map, and calculate inlet NO. x Concentration, export NO x The relative standard deviation of the concentration and outlet NH3 concentration distribution is used to characterize the degree of unevenness in their respective distributions.

[0070] Table 1 Test data of reactor inlet velocity distribution

[0071]

[0072] Table 2 Reactor inlet NO x Concentration distribution test data table

[0073]

[0074]

[0075] Table 3 Reactor outlet NO x Concentration distribution test data table

[0076]

[0077]

[0078] Table 4. Test data on NH3 concentration distribution at reactor outlet

[0079]

[0080]

[0081] 4) Based on on-site measurement data and export NO x By analyzing the concentration and NH3 concentration distribution at the reactor outlet, the regulating valve of the ammonia injection grid at the denitrification inlet was repeatedly optimized and adjusted to ultimately control the NO concentration at the reactor outlet. x The relative standard deviation of the concentration was controlled within 20%, and the ammonia slip at each point was controlled within 3 μL / L. The optimized test data are shown in Tables 5 and 6.

[0082] Table 5. Optimized Export NO x Concentration distribution test table

[0083]

[0084] Table 6. Optimized NH3 Concentration Distribution at the Outlet - Test Table

[0085]

[0086]

[0087] 5) NO x The -NH3 relationship model was established, and after optimization and adjustment through ammonia injection, the NO concentration at the reactor outlet cross-section was increased. x The uniformity of concentration distribution will affect the NO concentration at the reactor outlet. x The relative standard deviation of the concentration was controlled within 20% under different operating conditions to minimize the possibility of excessive ammonia slip at the reactor outlet. Under these conditions, the following work was carried out:

[0088] ① Test the NO at the outlet of the same reactor under different load conditions. x Concentration control concentration corresponds to the ammonia slip concentration;

[0089] ② Under the same load conditions, test the NO at the outlet of different reactors. x Concentration control concentration corresponds to the ammonia slip concentration;

[0090] ③Based on the test results, establish NO x Concentration-ammonia slip relationship model.

[0091] NO x The concentration control concentration and corresponding ammonia slip concentration test data are shown in Table 7. (NO) x -Ammonia slip relationship model see Figure 26 .

[0092] Table 7 Different Export NO x Table of Controlled Concentrations Corresponding to NH3 Concentrations

[0093]

[0094]

[0095] 6) Assessment of the maximum safe output of the SCR denitrification unit, based on the NO established in step (5). x -NH3 relationship model to characterize NO at different outlets x The relationship model relates NO to the upper limit of ammonia slip of 3 μL / L under controlled concentration and different load conditions. x The concentration control concentration is the minimum control concentration of the SCR denitrification unit under different operating conditions, i.e., the maximum safe output of the SCR denitrification unit. This test unit operates at 100%, 75%, 50%, and 30% of its rated load. x The minimum controlled concentration is 13.1 mg / m³. 3 14.3 mg / m 3 16.2 mg / m 3 19.0 mg / m 3 .

[0096] Any content not described in detail in this specification is prior art known to those skilled in the art.

[0097] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the scope of protection of the present invention. Any modifications and refinements made by those skilled in the art without departing from the concept and scope of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for evaluating the maximum safe output of an SCR denitrification device based on measured data, characterized in that, Includes the following steps: (1) Selection of operating conditions; In order to accurately reflect the maximum safe output of the SCR denitrification unit under different operating conditions, evaluation tests were conducted under the conditions of lowest stable combustion, 50%, 75%, and 100% rated load. (2) Flue gas parameters and composition testing; 1) Flue gas flow rate; Using a calibrated flue gas sampling gun and thermocouples, the flue gas velocity, pressure, temperature and oxygen content at each point were measured using the grid method, and the flue gas flow rate was calculated. The flue gas flow rate is calculated using the following formula: ， In the formula: Q To handle flue gas flow rate, m 3 / h; F To test the cross-sectional area, m 2 ; ω To determine the average flue gas velocity (m / s) at the test section, the following formula is used: ， In the formula: K This is the correction factor for the dynamic pressure measuring tube; ρ The density of flue gas under actual operating conditions is expressed in kg / m³. 3 Calculate using the following formula: ， P d To measure the average dynamic pressure of the flue gas at the test section, in Pa, it is calculated using the following formula: ， In the formula: ρ 0 The density of flue gas under standard conditions is kg / m³. 3 ; ρ t The density of flue gas under actual operating conditions is expressed in kg / m³. 3 ; P a The local atmospheric pressure is in Pa. P j To test the static pressure of flue gas at the cross-section, Pa; P b Standard atmospheric pressure, Pa; n This represents the total number of measurement points for imports or exports. P di The dynamic pressure of the flue gas at each measuring point is Pa; 2) Smoke composition; The concentration distribution of flue gas components in the flue is uneven, so a grid method is used for testing; The concentration of flue gas components is measured at each measuring point, and the arithmetic average of the flue gas component concentrations at each grid point is obtained as the actual flue gas component concentration value of the test section. The measuring instrument is calibrated using a high-purity, qualified standard gas; the measuring instrument is calibrated using the standard gas during the measurement period, and is calibrated at least once before and after the test; 3) Flue gas temperature; The rapid-response temperature probe thermocouple was used to conduct the test according to the grid method. The temperature values ​​at each measurement point were taken and the values ​​during the test were averaged. 4) Moisture content of flue gas; The moisture content of flue gas is calculated using the following formula: ， In the formula: X sw The percentage by volume of moisture content in the exhaust gas, % G m The weight of moisture absorbed by the absorbent tube, in grams; V d The cumulative volume of dry flue gas extracted under the measured conditions is expressed in L. t r The flue gas temperature before the flow meter is given in °C. P r The pressure of the flue gas before the flow meter, in Pa; B a Atmospheric pressure, Pa; 5) Denitrification efficiency; Use NO x The testing instrument was calibrated using standard gas and O2 standard gas respectively. Then, measurements were taken at the inlet and outlet flues of the denitrification system using the grid method. The test values ​​were averaged during the experiment, and the denitrification efficiency was calculated using the following formula: ， In the formula: The denitrification efficiency of the SCR flue gas denitrification device is % NO at the reactor inlet x Concentration, mg / m³ 3 ; NO at reactor outlet x Concentration, mg / m³ 3 ; (3) Data processing; 1) Export NO x The relative standard deviation of the concentration distribution; NO in the outlet flue gas was tested using a flue gas analyzer. x Concentration, calculated from multiple test points, outlet NO x The relative standard deviation of the concentration is used to characterize the NO concentration at the export site. x Non-uniformity of concentration distribution; ， In the formula: RSD NO x Relative standard deviation of concentration distribution, % x i NO at a single measuring point x Concentration value, mg / m³ 3 ; For testing section NO x Average concentration, mg / m³ 3 ; 2) Relative standard deviation of NH3 concentration distribution at the outlet; A portable laser ammonia slip detector was used to test the NH3 concentration in the outlet flue gas. After multi-point testing, the relative standard deviation of the outlet NH3 concentration was calculated to characterize the non-uniformity of the outlet NH3 concentration distribution. ， In the formula: RSD 1 The relative standard deviation of NH3 concentration distribution is %; y i The value of NH3 at a single measuring point is expressed in μL / L. For testing section NO x Average concentration, μL / L; (4) Ammonia injection optimization; The ammonia injection rate was adjusted based on the experimental results, and an optimized ammonia injection strategy compatible with different operating conditions was developed to ensure that the denitrification efficiency reached the design value. NO₂ levels at the reactor inlet and outlet were measured. x / O2 concentration, based on NO at the reactor outlet section x The NH3 concentration distribution was monitored, and the opening of the regulating valve of the ammonia injection grid at the denitrification inlet was repeatedly adjusted in a targeted manner to control the NO concentration at the reactor outlet. x The relative standard deviation of the concentration is controlled within 20%, and the NO concentration at the outlet of both denitrification reactors is achieved. x Average concentration and total NO emission x The relative deviation of concentration values ​​is within ±10%, and the ammonia slip concentration is controlled within 3 μL / L; maximize the NO concentration at the reactor outlet. x Uniform distribution, improved denitrification system efficiency, reduced ammonia escape and ammonia consumption at the denitrification outlet; (5) Establish NO x -Ammonia slip relationship model; By optimizing and adjusting the ammonia injection, the NO content at the reactor outlet cross-section was increased. x The uniformity of concentration distribution will affect the NO concentration at the reactor outlet. x The relative standard deviation of the concentration was controlled within 20% under different operating conditions to minimize the local ammonia escape at the reactor outlet section. 1) Test the NO at the outlet of the same reactor under different load conditions. x Concentration control concentration corresponds to the ammonia slip concentration; 2) Under the same load conditions, test the NO at the outlet of different reactors. x Concentration control concentration corresponds to the ammonia slip concentration; 3) Based on the test results, establish NO x Concentration-ammonia slip relationship model; (6) Assessment of the maximum safe output of the SCR denitrification unit; Based on the NO established in step (5) x - An ammonia slip relationship model is used to characterize the output change of the SCR denitrification unit. The upper limit of ammonia slip in the relationship model corresponds to the reactor outlet NO. x The concentration control concentration is the minimum control concentration of the SCR denitrification unit, which is also the maximum safe output of the SCR denitrification unit; unit operating conditions at 100%, 75%, 50%, and 30% rated load. x The minimum controlled concentration is 13.1 mg / m³. 3 14.3 mg / m 3 16.2 mg / m 3 19.0 mg / m 3 .

Images