Biomass blending combustion proportion metering method for biomass coupling power generation of pulverized coal fired boiler of power station

Abstract

The invention provides a biomass blending combustion proportion metering method for biomass coupling power generation of a pulverized coal fired boiler of a power station, and belongs to the technical field of renewable energy source and fossil fuel coupling power generation. Then establishing a mechanism model of the heat value of the in-furnace fuel for the biomass coupling power generation of the fuel boiler; determining a proportionality coefficient according to an auxiliary formula for calculating the heat value of the in-furnace fuel based on the actual load and the actual fuel consumption, and establishing a mathematical model of the heat value of the in-furnace fuel based on a mechanism model; performing primary correction by using the deviation between the actual main steam pressure of the current boiler and the sliding pressure target value; and for the air cooling unit, the measurement result needs to be corrected according to the fuel consumption corresponding to the unit target load converted by the back pressure of the steam turbine. The method is not influenced by specific model factors, is sensitive in response, can timely reflect instantaneous change conditions of coupling blending combustion and different types of in-furnace fuel heat values, is low in failure rate, is high in measurement precision, and has universality.

Description

Technical Field

[0001] This invention belongs to the field of renewable energy and fossil fuel coupled power generation technology, specifically relating to a biomass co-firing ratio metering method for biomass coupled power generation in a power plant pulverized coal boiler under the background of biomass coupled power generation technology. Background Technology

[0002] The carbon emission intensity of biomass power generation is only about 1.8% of that of coal combustion. The carbon emissions generated by biomass in the process of replacing coal combustion can be regarded as offsetting each other with the CO2 absorbed during its growth process. Therefore, co-firing biomass can significantly reduce the carbon emissions of coal power.

[0003] Due to factors such as limited co-firing sites, an imperfect biomass procurement system, and the reliability of biomass blending and conveying systems, thermal power plants face difficulties in effectively controlling the uniformity of fuel blending and co-firing. Because biomass and conventional coal differ significantly in fuel characteristics, direct coupling of biomass power generation with a large proportion of coal-fired units can have numerous impacts. Determining the biomass co-firing ratio first requires obtaining the calorific value of the coal fed into the furnace, and then determining the biomass feed rate based on the co-firing ratio. This aims to achieve efficient, stable, and sustainable biomass co-firing, continuously innovating technologies to promote coal-power-biomass co-firing technology, continuously increasing the biomass co-firing ratio, calculating emission reductions, and serving online monitoring of CO2 emission reductions, carbon trading, and subsidies. Carbon emission metering related to biomass co-firing in power plant pulverized coal boilers is a common challenge in the power industry's implementation of biomass co-firing, and it is widespread within thermal power plants.

[0004] Currently, the blending amount is measured using industrial analysis data and trace element data of coal and biomass. This requires complex analysis of coal and biomass or combustion products, which is limited by the timeliness and cost of measurement. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method for metering the biomass co-firing ratio in biomass co-generation of pulverized coal boilers in power plants, which is simple to implement and requires little initial investment.

[0006] Based on the above technical concept, the technical solution adopted by this invention is as follows:

[0007] A method for metering the biomass co-firing ratio in a pulverized coal boiler for biomass co-generation in a power plant, comprising the following specific steps:

[0008] S1 establishes a mechanism model for measuring the calorific value of fuel fed into the furnace under biomass co-generation technology by statistically analyzing real-time data, historical data, and unit performance test data at the unit site, and obtains the formula for calculating the calorific value of fuel fed into the furnace.

[0009] S2 combines real-time on-site data and test data, uses combustion principles and air-cooled unit characteristics to perform regression analysis, and corrects the unit load for the calculation formula of the calorific value of the fuel entering the furnace of the air-cooled unit.

[0010] S3 combines real-time field data, test data, and historical data, and uses the deviation between the directly obtained real-time main steam pressure and the main steam sliding pressure value to perform pressure correction on the formula for calculating the calorific value of the furnace.

[0011] S4 determines the proportionality coefficient Km through analysis and processing based on the mechanism model corrected in steps S2 and S3.

[0012] S5 combines the formula for calculating the calorific value of the fuel fed into the furnace from step S1, and uses the proportionality coefficient Km to improve the formula for calculating the calorific value of the fuel fed into the furnace, and calculates the calorific value of the fuel fed into the furnace.

[0013] S6 biomass briquettes are independently weighed, pulverized, and then fed into a dedicated biomass burner for combustion.

[0014] S7 is based on the fact that the carbon content, moisture, ash content and other characteristics of biomass vary greatly depending on the source. The calorific value of biomass fuel is obtained by testing the calorific value of biomass fuel and then weighting the calorific value.

[0015] S8 calculates the biomass blending ratio of the fuel entering the furnace based on steps S5, S6 and S7, using the biomass briquette fuel weight obtained in S6, the biomass fuel calorific value obtained in S7, the calorific value of the fuel entering the furnace, and the amount of fuel entering the furnace.

[0016] Based on the principle of carbon isotope mass conservation, the flue gas produced by S9 contains the weighted values ​​of carbon isotopes of different fuel components. After detecting the content of carbon isotopes in the flue gas at the tail flue, the mass ratio of biomass blending can be obtained, thus verifying the biomass blending ratio of the fuel entering the furnace.

[0017] Further defining the above technical solution, data correction is required during the unit load correction in step S2 and the pressure correction in step S3. The data correction method is as follows: in the actual solution, the average actual unit load and the average actual fuel input in the furnace over a 15-minute period are used as the calculation basis.

[0018] Further defining the above technical solution, the formula for calculating the calorific value of the fuel entering the furnace in step S1 is: Q = Km × calorific value of coal during the test, where Q is the calorific value of the fuel entering the furnace and Km is the proportional coefficient of the calorific value of the fuel entering the furnace.

[0019] Further defining the above technical solution, the specific steps for load correction of the air-cooled unit in S2 include:

[0020] S201 uses the deviation between the turbine back pressure and the test back pressure to correct the unit load, performs regression analysis, and obtains the regression relationship;

[0021] S202 corrects the calculation results of the formula for calculating the calorific value of the fuel entering the furnace based on the regression relationship.

[0022] Further defining the above technical solution, the specific steps of pressure correction in S3 include:

[0023] S301 acquires overpressure and underpressure data of main steam pressure and incremental data of calorific value of main steam during the calibration of the calorific value of the fuel entering the furnace.

[0024] S302 substitutes the parameters obtained in step S301 into the set algorithm and rules for processing to obtain the actual total fuel amount fed into the furnace after pressure correction.

[0025] S303 corrects the calculation result of the formula for calculating the calorific value of the fuel in the furnace by adjusting the actual total fuel quantity into the furnace after pressure correction obtained in step S302;

[0026] S304 independently measures the amount of biomass fuel fed into the furnace and tests the calorific value of the biomass fuel. The biomass fuel blending ratio of the fuel fed into the furnace is calculated by multiplying the amount of biomass fuel fed into the furnace by the calorific value of the biomass fuel and dividing the calorific value of the fuel fed into the furnace by the amount of fuel fed into the furnace.

[0027] S305 uses radioactive isotopes 14 When determining the biomass co-firing amount, representative flue gas samples need to be collected. The flue gas sampling point should be located in a horizontal flue before the electrostatic precipitator and after the air preheater. The length of the horizontal flue should be greater than 1 meter. The flue gas sampling adopts the isokinetic sampling method.

[0028] S306 utilizes the differences in flue gas composition produced after the combustion of biomass and coal to verify the rise and fall of the proportion of biomass blending in fuel.

[0029] Further defining the above technical solution, S8 utilizes the difference in flue gas composition generated after the combustion of biomass and coal, and the change in flue gas composition verifies the rise and fall of the biomass blending ratio in the fuel.

[0030] Further specifying the above technical solution, a system for measuring the calorific value of fuel entering the boiler in a power plant using a biomass co-firing ratio metering method for power generation via pulverized coal boilers includes a power plant DCS system, multiple pressure sensors arranged in the main steam pipeline of the boiler, a coal feed rate sensor for the coal mill, and a biomass fuel feed rate sensor. 14 C-sensor and CO2 sensor; the input terminals of the power plant's DCS system are respectively connected to the output terminals of the pressure sensor, the coal feed rate sensor of the coal mill, and the biomass feed rate sensor. 14 Connect C and CO2 output terminals.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] (1) High real-time performance: The measured value of the calorific value of the fuel entering the furnace is directly calculated by the DCS system, which is fast and solves the problem of matching the fuel entering the furnace with the measured calorific value. This is conducive to guiding operators to adjust and optimize automatic control.

[0033] (2) Good stability and high accuracy: Because the measurement method covers the entire combustion process of the fuel input in the furnace, the biomass co-firing ratio measurement accuracy of a power plant pulverized coal boiler biomass co-generation is more representative.

[0034] (3) Versatility: This technology is highly practical and requires no large capital investment. It can establish a mathematical model of the mechanism for measuring the calorific value of fuel entering the furnace using only existing DCS systems and conventional measurement points in thermal power plants. It is not limited by algorithms and has strong practicality in DCS systems. It can be directly promoted and can effectively control the biomass co-firing ratio and calculate emission reductions while ensuring the safe operation of the unit. It serves online monitoring of CO2 emission reductions, carbon trading, and government subsidies, and has significant social benefits. Because it requires a large number of experiments and long-term observations, the data is more comprehensive than other single algorithms. After comparison with hardware measurements, calibration and correction through unit performance tests, and model improvement, the parameters have stronger adaptability and higher accuracy.

[0035] Compared with other modeling methods, the modeling method used in this invention is simple in algorithm and has strong novelty and practicality in DCS systems. It has the characteristics of high sensitivity, good stability and strong versatility, and can be widely used in industrial boilers and other fields. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of the method of the present invention;

[0038] Figure 2 This is a system structure block diagram of the present invention. Detailed Implementation

[0039] The following is in conjunction with the appendix Figure 1-2 The present invention will be described in further detail below.

[0040] Example 1: This example provides a method for metering the biomass co-firing ratio in a pulverized coal boiler-biomass co-generation power plant, such as... Figure 1 As shown, the specific steps are as follows:

[0041] S1 establishes a mechanism model for measuring the calorific value of fuel fed into the furnace under biomass co-generation technology by statistically analyzing real-time data, historical data, and unit performance test data at the unit site, and obtains a formula for calculating the calorific value of fuel fed into the furnace. The formula for calculating the calorific value of fuel fed into the furnace in step S1 is: Q = Km × calorific value of coal during the test, where Q is the calorific value of fuel fed into the furnace and Km is the proportional coefficient of the calorific value of fuel fed into the furnace.

[0042] S2 combines real-time on-site data and experimental data, utilizes combustion principles and air-cooled unit characteristics to perform regression analysis, and corrects the unit load on the formula for calculating the calorific value of the fuel entering the furnace for the air-cooled unit. The specific steps for air-cooled unit load correction in S2 include:

[0043] S201 uses the deviation between the turbine back pressure and the test back pressure to correct the unit load, performs regression analysis, and obtains the regression relationship;

[0044] S202 corrects the calculation results of the formula for calculating the calorific value of the fuel entering the furnace based on the regression relationship;

[0045] S3 combines real-time on-site data, experimental data, and historical data, and uses the deviation between the directly obtained real-time main steam pressure and the main steam sliding pressure value to perform pressure correction on the formula for calculating the calorific value of the furnace feed. The specific steps of pressure correction in S3 include:

[0046] S301 acquires overpressure and underpressure data of main steam pressure and incremental data of calorific value of main steam during the calibration of the calorific value of the fuel entering the furnace.

[0047] S302 substitutes the parameters obtained in step S301 into the set algorithm and rules for processing to obtain the actual total fuel amount fed into the furnace after pressure correction.

[0048] S303 corrects the calculation result of the fuel calorific value calculation formula by adjusting the actual total fuel quantity into the furnace after pressure correction obtained in step S302. The specific calculation method is as follows:

[0049] Based on the actual pressure value obtained by the pressure sensor and the sliding pressure test value, calculate the main steam pressure deviation value: Main steam pressure deviation value = Actual pressure value - Sliding pressure test value; Calculate the pressure deviation correction fuel quantity coefficient according to Appendix 1 and Appendix 2;

[0050] S304 independently measures the amount of biomass fuel fed into the furnace and tests the calorific value of the biomass fuel. The biomass fuel blending ratio of the fuel fed into the furnace is calculated by multiplying the amount of biomass fuel fed into the furnace by the calorific value of the biomass fuel and dividing the calorific value of the fuel fed into the furnace by the amount of fuel fed into the furnace.

[0051] S305 uses radioactive isotopes 14 When determining the biomass co-firing amount, representative flue gas samples need to be collected. The flue gas sampling point should be located in a horizontal flue before the electrostatic precipitator and after the air preheater. The length of the horizontal flue should be greater than 1 meter. The flue gas sampling adopts the isokinetic sampling method.

[0052] S306 utilizes the difference in flue gas composition produced after the combustion of biomass and coal to verify the rise and fall of the biomass blending ratio in fuel by measuring changes in flue gas composition.

[0053] S4 determines the proportionality coefficient Km through analysis and processing based on the mechanism model corrected in steps S2 and S3.

[0054] S5 combines the formula for calculating the calorific value of the fuel fed into the furnace from step S1, and uses the proportionality coefficient Km to improve the formula for calculating the calorific value of the fuel fed into the furnace, and calculates the calorific value of the fuel fed into the furnace.

[0055] S6 biomass briquettes are independently weighed, pulverized, and then fed into a dedicated biomass burner for combustion.

[0056] S7 is based on the fact that the carbon content, moisture, ash content and other characteristics of biomass vary greatly depending on the source. By testing the calorific value of biomass fuel, the calorific value is weighted and averaged to obtain the calorific value of biomass fuel.

[0057] S8 calculates the biomass blending ratio of the fuel entering the furnace based on steps S5, S6 and S7, using the biomass briquette fuel weight obtained in S6, the biomass fuel calorific value obtained in S7, the calorific value of the fuel entering the furnace, and the amount of fuel entering the furnace. S8 uses the difference in flue gas composition produced after the combustion of biomass and coal to verify the rise and fall of the biomass blending ratio in the fuel.

[0058] Based on the principle of carbon isotope mass conservation, the flue gas produced by S9 contains the weighted values ​​of carbon isotopes of different fuel components. After detecting the content of carbon isotopes in the flue gas at the tail flue, the mass ratio of biomass blending can be obtained, thus verifying the biomass blending ratio of the fuel entering the furnace.

[0059] During the unit load correction in step S2 and the pressure correction in step S3, data correction is required. The data correction method is to use the average actual unit load and average actual fuel input over 15 minutes as the calculation basis in the actual scheme.

[0060] Appendix 1 f1 matrix

[0061]

[0062]

[0063] Appendix 2 f2 matrix

[0064] Serial Number load Main steam pressure 1 0 12.5 2 300 12.5 3 330 12.5 4 360 13.1 5 390 13.7 6 420 14.3 7 450 14.9 8 480 15.5 9 510 16.1 10 540 16.7 11 566.8 16.7 12 660 16.7

[0065] (1) Based on the main steam pressure deviation value and pressure deviation correction fuel quantity coefficient obtained in the above steps, calculate: Pressure deviation correction fuel quantity = Main steam pressure deviation value × Pressure deviation correction fuel quantity coefficient;

[0066] (2) Calculate the actual total fuel amount fed into the furnace after pressure correction = actual fuel amount fed into the furnace - fuel amount corrected for pressure deviation.

[0067] (3) The formula for calculating the proportional coefficient Km in step S3 is: Km = actual power-fuel ratio ÷ test power-coal ratio.

[0068] (4) Calculate the biomass blending ratio of the fuel entering the furnace by using the weight of biomass briquettes × calorific value of biomass fuel ÷ (calorific value of S303 fuel entering the furnace × amount of fuel entering the furnace).

[0069] (5) The difference in flue gas composition after the combustion of biomass and coal is used to verify the rise and fall of the proportion of biomass in the fuel.

[0070] Appendix 3 f3 Common Biomass and Coal 14 C content value

[0071]

[0072] In the above calculation, the biomass blending ratio of fuel entering the furnace is calculated as follows: biomass briquettes weight × biomass fuel calorific value ÷ fuel calorific value entering the furnace.

[0073] In a preferred embodiment of the present invention, the process of determining the calibration coefficient of the calorific value of the fuel entering the furnace is as follows: calibration tests are carried out under multiple operating conditions, the preliminary calibration coefficient of the calorific value of the fuel entering the furnace under each operating condition is calculated, and the average value of the preliminary calibration coefficients of the calorific value of the fuel entering the furnace is taken as the calibration coefficient.

[0074] Example 2: This example provides a system for measuring the calorific value of fuel entering the boiler in a power plant using a biomass co-firing ratio metering method for power generation from pulverized coal boilers. Figure 2 As shown, this includes the power plant's DCS system, multiple pressure sensors arranged in the boiler's main steam pipeline, coal feed rate sensors for the coal mill, and biomass fuel feed rate sensors for the boiler. 14 C-sensor and CO2 sensor; the input terminals of the power plant's DCS system are respectively connected to the output terminals of the pressure sensor, the coal feed rate sensor of the coal mill, and the biomass feed rate sensor. 14The C and CO2 output terminals are connected. The DCS system measures the calorific value of the fuel entering the furnace based on the output information from the pressure sensor, unit load sensor, and fuel quantity sensor, according to the above method.

[0075] In this embodiment, sensors for coal quantity, biomass quality, unit load, turbine back pressure, and main steam pressure are fixed sensors in the DCS, without adding new measuring points. Regular calibration and inspection of each sensor are required. The measurement system uses the formula for calculating the calorific value of the fuel entering the furnace to measure the calorific value, obtaining a comparison curve between the measured and actual values. The original unit coordinated control system was designed based on the type and calorific value of the coal. Calorific value and fuel quantity are the basis for control. After biomass co-firing, the calorific value changes, leading to changes in the regulation characteristics of the main steam pressure. In the coordinated control system, under the coordinated mode of furnace following, the fuel calorific value coefficient is used to determine the basic condition of the fuel entering the furnace. This improves the feedforward of the boiler fuel control system as the main adjustment means, and corrects the fuel command of the boiler control system as an extreme condition adjustment method. This allows the boiler combustion regulation system to quickly respond to load requirements based on the fuel calorific value, effectively improving the level of coordinated control.

[0076] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention, enabling those skilled in the art to understand and apply the invention. However, it should not be construed that the specific implementation of the invention is limited to these descriptions.

Claims

1. A biomass blending ratio metering method for a biomass coupled power generation of a power station pulverized coal boiler, characterized in that, The specific steps are as follows: S1, by statistical analysis of real-time data, historical data, and unit performance test data, a mechanism model for measuring the heat value of the fuel fed into the furnace under the condition of biomass coupled power generation technology is established, and a calculation formula for the heat value of the fuel fed into the furnace is obtained; S2, combined with real-time data and test data, regression analysis is performed by using the combustion principle and the characteristics of the air-cooled unit, and the calculation formula for the heat value of the fuel fed into the furnace of the air-cooled unit is corrected according to the unit load; S3, combined with real-time data, test data and historical data, the deviation of the directly obtained main steam real-time pressure and main steam sliding pressure value is used to correct the calculation formula for the heat value of the fuel fed into the furnace; S4, according to the mechanism model corrected in steps S2 and S3, the proportional coefficient Km is determined by analysis and processing; S5, combined with the calculation formula for the heat value of the fuel fed into the furnace in step S1, the calculation formula for the heat value of the fuel fed into the furnace is perfected by using the proportional coefficient Km, and the heat value of the fuel fed into the furnace is calculated; S6, the biomass briquette fuel is independently weighed and measured, and after being crushed, it is sent into a biomass special burner for combustion; S7, based on the characteristics of the carbon content, moisture content, ash content and other characteristics of biomass, which vary greatly due to different sources, the heat value of the biomass fuel is obtained by testing the heat value of the biomass fuel and performing weighted average on the heat value; S8, according to steps S5, S6 and S7, the biomass briquette fuel weight obtained in S6, the heat value of the biomass fuel obtained in S7, the heat value of the fuel fed into the furnace and the amount of fuel fed into the furnace are used to calculate the biomass blending ratio of the fuel fed into the furnace; S9, according to the principle of carbon isotope mass conservation, the carbon fourteen and carbon dioxide in the flue gas are the weighted values of the carbon isotopes of different fuel components, and after the content of carbon fourteen and carbon dioxide in the flue gas is detected in the tail flue, the mass ratio of biomass blending can be obtained, and the biomass blending ratio of the fuel fed into the furnace is verified.

2. The method according to claim 1, wherein the biomass blending ratio is measured by the biomass blending ratio metering method for the power plant pulverized coal boiler coupled with biomass power generation, characterized in that, In the process of unit load correction in step S2 and pressure correction in step S3, data correction is required; the method of data correction is that in the actual scheme, the average unit actual load and the average actual amount of fuel fed into the furnace in 15 minutes are used as the basis for calculation.

3. The method according to claim 1, wherein the biomass blending ratio is measured by the biomass blending ratio metering method for the power plant pulverized coal boiler coupled with biomass power generation, characterized in that, The calculation formula for the heat value of the fuel fed into the furnace in the mechanism model in step S1 is Q=Km×test coal heat value, wherein Q is the heat value of the fuel fed into the furnace, and Km is the proportional coefficient of the heat value of the fuel fed into the furnace.

4. The method according to claim 2, wherein the biomass blending ratio is measured by the biomass blending ratio metering method for the power plant pulverized coal boiler coupled with biomass power generation, characterized in that, The specific steps of air-cooled unit load correction in S2 include: S201, the unit load is corrected by the deviation of the back pressure of the steam turbine from the back pressure during the test, regression analysis is performed, and a regression relationship is obtained; S202, the calculation result of the calculation formula for the heat value of the fuel fed into the furnace is corrected according to the regression relationship.

5. The method according to claim 1, wherein the biomass blending ratio is measured by the biomass blending ratio metering method for the power plant pulverized coal boiler coupled with biomass power generation, characterized in that, The specific steps of pressure correction in S3 include: S301, in the calibration of the heat value of the fuel fed into the furnace, the overpressure and underpressure data of the main steam pressure and the heat value increment data of the fuel fed into the furnace are obtained; S302, the parameters obtained in step S301 are substituted into the set algorithm and rules for processing, and the actual total fuel amount fed into the furnace after pressure correction is obtained; S303, the actual total fuel amount fed into the furnace after pressure correction obtained in step S302 is used to correct the calculation result of the calculation formula for the heat value of the fuel fed into the furnace; S304, biomass fuel quantity into the furnace is independently metered, and the biomass fuel calorific value is detected, and the biomass blending combustion ratio of the fuel into the furnace is calculated by using the biomass fuel quantity into the furnace multiplied by the biomass fuel calorific value divided by the fuel calorific value into the furnace multiplied by the fuel quantity into the furnace; S305 with a radioisotope 14 When determining the biomass blending amount, representative flue gas samples need to be collected. The flue gas sampling point should be located in the horizontal flue after the air preheater and before the electric precipitator. The length of the horizontal flue should be greater than 1 meter. The flue gas sampling adopts the equal-speed sampling method. S306, the difference of the flue gas components generated after the biomass and the coal are combusted is used, and the change of the flue gas components verifies the increase and decrease of the biomass blending combustion ratio in the fuel.

6. The method according to claim 1, wherein the biomass blending ratio is measured. S8, the difference of the flue gas components generated after the biomass and the coal are combusted is used, and the change of the flue gas components verifies the increase and decrease of the biomass blending combustion ratio in the fuel.

7. A system for measuring the calorific value of a fuel fed to a furnace of a power plant using the method according to any one of claims 1 to 5, characterized in that, The power station DCS system, a plurality of pressure sensors arranged in the main steam pipeline of the boiler, a coal mill coal quantity sensor, a biomass fuel quantity biomass feeding quantity sensor, a carbon fourteen sensor and a carbon dioxide sensor are included; the input end of the power station DCS system is connected with the output end of the pressure sensor, the coal mill coal quantity sensor, the biomass feeding quantity sensor, the carbon fourteen and the carbon dioxide respectively.

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