WO2009046628A1

WO2009046628A1 - Method of real-time on-line supervision for coal boiler efficiency

Info

Publication number: WO2009046628A1
Application number: PCT/CN2008/001670
Authority: WO
Inventors: Zhen Wang
Original assignee: Zhen Wang
Priority date: 2007-09-27
Filing date: 2008-09-27
Publication date: 2009-04-16
Also published as: CN101796346A; CN101796346B

Abstract

The invention discloses a method of real-time on-line supervision for coal boiler efficiency. The method includes the following steps: a) the first measuring step which is used to measure the component of O2 in flue gas in the period of outputting material; b) the second measuring step which is used to measure at least one of the following parameters: the coal supplying amount of milling system in the period of inputting material, the total air quantity in the period of inputting material and the flue gas amount in the period of outputting material; c)building positive definite equation or system of equations having exact solution according to the above measuring results without using outputting heat quantity as the measuring value, and computing at least one of the following parameters : heat output of the boiler, the representative value, the caloric value of the coal and the component of the coal, to obtain the real-time supervision data for coal boiler efficiency.

Description

Real-time monitoring method for coal-fired boiler performance

The invention relates to a real-time online monitoring method for operating performance of a large coal-fired boiler, and is mainly used in the technical field of real-time online monitoring and optimization control of fuel properties, heat balance, process efficiency and loss state by computer and online operation data of a large power station. Background technique:

With the development of IT and control technologies, products and services, real-time monitoring and optimization control of generator sets has become increasingly effective and valued. However, the calculation of the efficiency of the boiler is usually calculated using the coal quality data of the test. The prior art international invention patent application PCT/CN2005/000243 gives various positive definite mathematical models realized by various combinations of online measurement data, energy and material balance equations, coal quality equations, etc., to achieve boiler performance and A variety of methods for online measurement of coal quality. Since the mathematical model is positive definite, the calculation of this method is absolutely convergent and therefore an accurate method. However, it is usually necessary to use the boiler input and output heat balance as one of the qualification conditions, while solving the coal quality and boiler efficiency. Due to the fact that the boiler's input and output heat balance is still in dynamic unbalance during actual operation, there is a significant error in this method. And for real-time performance monitoring, this error is unacceptable. For example, in the process of increasing the power generation load, the calorific value of the coal is significantly reduced and the ash is significantly increased as a result of the monitoring of the method. In fact, this phenomenon is caused by an increase in the heat storage of the boiler during the process of increasing the load, but this part The heat is ignored in the calculation.

Since about 90% of the calorific value of coal is exported to the turbine as an effective heat absorption of the boiler; the basic principle of monitoring is to obtain the input heat of the coal according to the main heat component and the heat loss of the boiler; Some have reliable principle support and relatively reliable data sources. Therefore, the input and output heat balance of the boiler is the basic guarantee for the accuracy of the monitoring and is the most important limiting relationship. In other words, in order to get To reflect the monitoring results of the actual calorific value of coal, it is necessary to use the boiler input and output heat balance as one of the qualification conditions.

However, the boiler is a heat storage system, and the input and output heat balance process has a long delay, that is, when the input heat changes, the change amount is only immediately reflected in the heat storage change, and the output heat changes with the heat storage change due to The heat storage has a time constant and therefore does not change immediately, but produces a delay that may be as long as more than ten minutes. In addition, when the unit load is adjusted, the adjustment process is limited by the rate of load change. The time may be as long as several tens of minutes. During this process, the boiler load is always in the process of rising or falling, and its input and output heat and storage. The heat is also changing, the heat storage is not in equilibrium, and there is a significant deviation between input and output. At the same time, the adjustment of the load and thermal system during the operation of the generator set is continuous, and the thermal balance of the thermal system itself is a continuous and continuous dynamic process. Therefore, the boiler input and output heat balance calculation directly adopts the coal combustion heat release of the boiler as the boiler input heat, which is equal to the sum of the boiler loss and the steam output heat, which is equivalent to neglecting the change of the boiler heat storage, which may lead to the actual application. There is always a method error in the calculation results, which is more serious when the load is adjusted.

The above problems have led to the background technology being only applicable to strict steady state monitoring and not providing effective monitoring results for the changing process. The results of coal quality and efficiency monitoring can only reflect the long-term average level of steady-state operation. It is inaccurate for any actual operation process in which the system has dominant or implicit imbalance at any one time. In order to make the results more stable, the results cannot be filtered, and the delay of the monitoring results may be as long as several tens of minutes, thus seriously affecting the real-time and effectiveness of the monitoring results. For actual operation, such a long delay is equivalent to providing a coal shield one hour ago, and the efficiency error is also quite large due to the non-correspondence of coal quality, which makes the monitoring result almost meaningless. Therefore, the background art still has a large distance from the actual real-time needs of the project.

BACKGROUND OF THE INVENTION The above problems exist and represent the problems of performance monitoring, including coal quality monitoring techniques, which are ubiquitous in the art. That is, the following problems have not been solved: a) the real-time nature of online monitoring of coal quality; b) The measurement method of real-time combustion calorific value or heat absorption of the boiler, (so the boiler heat output cannot be replaced by the real-time heat absorption of the boiler, and the combined heat balance calculation of boiler efficiency and coal quality is performed);

c) Efficiency of boilers and units Since coal quality data is offline test data, or non-real-time data, real-time reference is not effective or even ineffective in real time.

As can be seen from the above, the level of skill in the art depends to a large extent on whether it is possible to overcome real-time obstacles.

The prior art is based on the following misconceptions:

d) Boiler heat absorption cannot be monitored in real time.

e) The heat generated by boiler combustion cannot be monitored in real time.

f) The heat output of the boiler must be relied on to effectively calculate the calorific value of the coal.

In fact, in the performance monitoring system, the manual input of coal quality data obtained through the acquisition is still considered to be a more stable and reliable technical solution. Therefore, another aspect of the problem is that the above-mentioned problems are generally unresolved in the field. Summary of the invention:

The object of the present invention is to propose a preferred solution based on the background art concept; provide a real-time monitoring method for coal-fired boiler performance, and solve the problem that the real-time performance of the prior art in boiler performance and real-time online monitoring of coal quality cannot meet the actual requirements; Under the dynamic conditions, accurately calculate the boiler efficiency, quickly and accurately reflect the changes in coal quality, including the calculation of real-time heat absorption of the boiler.

According to a first aspect of the present invention, a real-time online monitoring method for performance of a coal-fired boiler is provided, which comprises the steps of:

a) a measurement step for measuring the composition of the 02 of the flue gas during the output of the substance;

b) a second measuring step for measuring at least one of the amount of coal fed to the milling system during the input of the substance, the total amount of air during the input of the substance, and the amount of smoke during the output of the substance;

c) according to the above measurement and not using the boiler output heat as the measured value, Establish a corresponding positive definite equation or equation group with exact solution, and obtain real-time monitoring data of coal-fired boiler performance by solving at least one of boiler combustion heat, its representative quantity, coal calorific value and coal quality composition.

According to a second aspect of the present invention, in the real-time on-line monitoring method for the performance of a coal-fired boiler according to an aspect of the present invention, the second measuring step further comprises measuring the amount of coal fed, the total amount of air, and the amount of flue gas.

According to a third aspect of the present invention, in the real-time on-line monitoring method for the performance of a coal-fired boiler according to the second aspect of the present invention, the second measuring step further comprises: measuring a primary air volume of the milling system and an inlet and outlet temperature of the coal mill.

According to a fourth aspect of the present invention, in the real-time online monitoring method for the performance of a coal-fired boiler according to the first aspect of the present invention, the second measuring step comprises measuring the amount of flue gas, the CO 2 and H20 components of the flue gas, and calculating the flow rates of the C02 and the H20. And calculate the calorific value of combustion according to the approximate relationship between the calorific value of the unit <, H element combustion and the calorific value of coal combustion.

According to a fifth aspect of the present invention, in the real-time online monitoring method for the performance of a coal-fired boiler according to the first aspect of the present invention, the second measuring step includes measuring the amount of the flue gas, and calculating the amount of the flue gas generated by the actual combustion reaction, that is, the theoretical flue gas. The amount, and according to the approximate relationship between the theoretical amount of smoke and the amount of heat, calculate the calorific value or the theoretical amount of smoke as a representative amount of combustion exotherm.

According to a sixth aspect of the invention, in the real-time online monitoring method for the performance of a coal-fired boiler according to the first aspect of the invention, the second measuring step comprises measuring the total air volume, calculating the amount of air actually reflected, that is, the theoretical air amount, and passing the theory The approximate relationship between the amount of air and the amount of heat is used to calculate the amount of heat generated, or the theoretical amount of air is used as a representative amount of heat of combustion.

According to the seventh aspect of the present invention, in the real-time online monitoring method for the performance of the coal-fired boiler of the present invention, the material output component data and the boiler milling system data are measured by setting certain variables to be constants and using an elemental regression equation. Advantages of the invention and positive effects: The present invention solves and overcomes the present specification existing in the art and the prior art.

Prejudice and problems listed in the "Background" section a), b), c), d), e), f). Important technological advances in real-time monitoring of boiler and coal quality have been achieved.

The first aspect of the present invention proposes a monitoring method based on the background art, but does not use the boiler output heat (or the turbine cycle heat absorption) as an input, thereby avoiding heat and coal caused by the time lag effect caused by the heat storage of the steam water system. Deviation of the quality component.

The first aspect of the invention encompasses many different embodiments consisting of a combination of different variables, including measurements and given equations, and set constants.

An advantage of the second aspect of the present invention is that it takes full advantage of the measurement of the total amount of boiler process, forming a basic framework that is conducive to achieving the most reliable monitoring results. Compared with the embodiment of the present invention, the constraint of the flow rate such as the air volume or the flue gas is increased, and the heat of combustion of the boiler and the calorific value of the coal can be monitored quite effectively.

The advantage of the third aspect of the present invention is that the coal pulverization system is used to calculate the moisture of the coal under the condition that many generator sets do not have the flue gas CO 2 and/or H 20 measuring points, and the second aspect of the present invention cannot solve the coal quality component (especially Oxygen, moisture and ash) problems.

Some preferred simplifications are proposed in the fourth, fifth and sixth aspects of the invention, respectively. In the real-time performance monitoring of the generator set, the combustion heat release of the boiler is equivalent to the total energy consumption, so it is very important data. The advantages of the four, five, and six aspects of the present invention are not only easy to apply, but also have important advantages over known techniques, and can more effectively achieve monitoring of boiler combustion exotherm.

Known techniques, including calculating the exothermic value of boiler combustion by using the amount of coal fed and the calorific value of coal, or the background art's calculation of the exotherm of boiler combustion by the heat output of the boiler, can cause significant delays and deviations. With the fourth, fifth and sixth aspects of the invention, the calorific value of the boiler combustion is calculated, and the time delay is only a few seconds, so the real-time performance is better than the above two methods. At the same time, due to the relationship between the calorific value of coal and the theoretical amount of flue gas and the theoretical air volume, the relationship between the ratio and the mass is more stable and accurate. Therefore, the calorific value of the boiler combustion is calculated than the calculated face value of the coal amount and the calorific value of the coal. The method is more accurate. The representative amount of the heat of combustion described in the fourth, fifth, and sixth aspects of the present invention means an amount proportional to the heat of combustion. The advantage is that the amount can be used as a control system input signal to improve the accuracy and response speed of the amount of heat generated by the original control system.

The invention has the advantages that the coal quality component and/or the heat is calculated according to the material balance relationship of the boiler combustion process, and the heat balance of the boiler is calculated by relying on the boiler output heat, thereby realizing real-time monitoring of the boiler performance, including coal quality and combustion hair. Rapid monitoring of heat. The calculation result of the present invention can also be used to calculate the calorific value of coal and the efficiency of the boiler, so that the real-time heat absorption of the boiler can be calculated, and therefore the present invention solves the historical problem of calculation of the heat absorption of the boiler.

The present invention directly derives heat and coal quality components based on the material balance of the boiler, especially the change in total air volume or exhaust gas, and avoids the delay caused by utilizing the heat balance of the boiler based on the output heat of the boiler. Since the change in flue gas occurs substantially simultaneously with the combustion process of the boiler, the delay is two orders of magnitude smaller than the hysteresis of the boiler output heat, thus greatly improving the time response characteristics. The monitoring results are basically completely real-time for the operation, and there is no significant deviation due to violent operation, such as fuel addition, air volume, etc.

By using the output heat obtained by the invention, the heat of circulation of the steam turbine, that is, the heat output of the boiler, is corrected to obtain a more accurate heat absorption of the boiler, and the heat of the boiler is used instead of the original boiler heat output, and the international invention patent is applied. Application

In the course of the method in PCT/CN2005/000243, the monitoring results ensure both real-time and effectiveness in system adjustments and fluctuations, as well as long-term reliability and accuracy.

The boiler efficiency and coal quality calculation results obtained by applying the invention are not affected by the dynamic balance relationship of the thermal system and the heat storage change of the boiler, and have important value for the practical application of engineering technology and production process. For example, in the process of load adjustment or dynamics of the unit's thermal system, the monitoring results of coal quality and boiler efficiency are continuous and effective, so it can be used as a guide for every moment, even as a basis and signal for optimal control.

The heat absorption result of the boiler obtained by applying the invention can express the thermal system The level of stability has important reference value for the practical application of engineering technology and production process. For example, when the amount of coal is changed, if the heat absorption of the boiler does not change significantly, it indicates that the thermal system itself is stable, and the calorific value of the raw coal has changed.

For real-time performance monitoring, the ratio of the heat absorption of the boiler obtained by the present invention to the heat output of the boiler can be used to define the heat absorption coefficient of the boiler. Therefore, we can define: Unit real-time heat rate == raw coal heat · Raw coal flow / power generation

= boiler heat absorption coefficient · actual heat rate of the unit

Actual heat consumption rate of the unit = steam cycle heat rate / boiler efficiency

The real-time heat consumption rate of the unit is the ratio of the thermal energy input to the power generated by the unit at every moment. The actual heat consumption rate of the unit is the ratio of the thermal energy consumed by the unit to the generated power at all times.

In this way, we establish the different concepts of real-time heat consumption rate and actual heat rate of the unit through the boiler heat absorption coefficient, and correctly establish the relationship between the flow rate and heat generation of the raw coal and the heat rate of the unit. When assessing and accounting for unit efficiency, two different concepts of real-time heat rate and actual heat rate should be distinguished. Because there is an accurate relationship between the real-time heat rate and the calorific value and flow rate of raw coal, it is related to the actual heat rate and heat storage, but it does not represent the performance level of operation; there is no actual heat rate between the heat and the flow of raw coal. The exact relationship is also independent of heat storage, but it represents the level of performance of the operation.

The present invention includes both complete and simplified implementations, and the integrity of the simplified implementation may be relatively low, but may be more practical. For example, in the sixth aspect of the present invention, although it is impossible to monitor the composition of coal, practical experience has proved that the accuracy of monitoring the calorific value of coal is high and practical. Specific ways of implementing the invention:

There are many different embodiments of the present invention, wherein the simplified schemes given in the fourth, fifth and sixth aspects of the invention include the calorific value according to the unit (:, H element combustion, or the theoretical smoke generated according to the combustion of coal) Quantity, theoretical air volume, measuring coal combustion The amount of heat generated or its change, rate of change, can be assumed by the complete scheme by some variables including the elemental composition of the coal, and is achieved with reference to the following examples.

In the real-time online monitoring method for the performance of the coal-fired boiler of the present invention, only the composition of the 02 of the flue gas during the output of the material and the amount of coal supplied to the milling system during the input of the measuring substance, the total amount of the air during the input of the substance, and the substance are measured. One of the flue gas quantities in the output process, and based on the above measurement results and without using the boiler output heat as the measured value, establish a corresponding positive definite equation or equation group with an exact solution, by solving the boiler combustion heat, its representative amount, coal At least one of the calorific value and the coal quality component can obtain real-time monitoring data of the performance of the coal-fired boiler.

The invention adopts the measurement signals of the material input and output process of the boiler, and these signals may have shortcomings in reflecting the real-time state, reliability, stability, accuracy, etc., but a targeted solution can be adopted for different signals to improve the performance. High signal redundancy for critical data. For example, you can increase the number of smoke points. The weighing point of the coal feeder can be increased to four weighing rollers per coal feeder.

Since the object of the present invention is to achieve fast and real-time measurement of coal quality, boiler combustion conditions, boiler heat absorption and other performance indicators, and the purpose of the traditional smoke emission continuous monitoring system (CEMS) (measuring the emission level of pollutants) Differently, in order to ensure the real-time measurement of flue gas parameters, the flue gas component measuring device directly measured in the flue should be used as much as possible to avoid the delay caused by the sampling method of sampling sampling; in order to ensure real-time representativeness, it is better to wear A flue-type probe measures the composition and flow rate of the flue gas.

By using the output heat obtained by the invention, the heat of circulation of the steam turbine, that is, the heat output of the boiler, is corrected to obtain a more accurate heat absorption of the boiler, and the heat of the boiler is used instead of the original boiler heat output, and the international invention patent is applied. In the process of applying for the method of PCT/CN2005/000243, the monitoring results ensure the real-time and effectiveness of the system adjustment and fluctuation process, and ensure long-term reliability and accuracy. Therefore, it can be applied in combination with the method of the international invention patent application PCT/CN2005/000243, and under steady state conditions The system is calibrated to achieve calibration of the relevant measuring points.

The practical example given in the following examples has the advantage of being easy to converge, but the flow calculation is based on the amount of coal fed to the milling system. This program is a more complete solution to achieve more accurate monitoring results.

The ten conditions used in this embodiment of the element model scheme according to the present invention are:

1. Thermal balance of the milling system. Calculate _{Mar ar} .

2. The total input of coal is equal to the sum of elements and water and ash. See (2).

3. Measure the S0 _{2 of the} boiler flue gas, and obtain the expression of the S component in the coal and the S0 ₂ component in the flue gas. See (5).

4. A regression equation or empirical formula for the composition of an element (such as H, N). See (4).

5. Elements (for example, regression equations or empirical formulas for components between (:, O). See (3).

6. Measure the corresponding expression expressed by the composition of coal obtained from 0 _{2 of the} boiler flue gas. See (6), (7), (8), (9).

7. Measure the corresponding expression of the coal component obtained from C0 _{2 of the} boiler flue gas. See (10) and (11).

8. Measure the corresponding expression expressed by the coal component of the CO of the boiler flue gas. See (7) and (10).

9. Measure the corresponding expression expressed by the coal component of the boiler fly ash carbon content. See (8).

10. Measure the corresponding expression expressed by the composition of the coal obtained by H20 of the boiler flue gas. See (13) and (14). The Cfh measured by the carbon content of the fly ash is calculated according to the statistical law or average value of the carbon content C _lz of the fly ash share otfh slag, and the unburned carbon is calculated.

C _ub =A _ar [( la _fh )C _lz /( 1-C _lz )+a _fh C _fh /( 1-C _fh )] ( 1 ) According to the elemental composition expression of coal C _ar +H _ar +O _ar +N _ar +S _ar +A _ar =100-M _ar ( 2 ) An empirical formula between the elemental content of coal, for bituminous coal

N _ar =A ₂ H _ar +B ₂

Α ₂ =0·3, B ₂ =0. (4) Expression of dry smoke volume calculated by S element content

Relationship between dry flue gas volume and air excess coefficient

V _gy = ( V _gy °+ ( -1 ) V _gk ° ) ( 6 )

o is the air excess factor (the ratio of the total air volume to the dry air volume calculated from the actual burnout carbon)

=21/ ( 21-79 ( O ₂ -0.5CO ) /(100-(CO ₂ +SO ₂ +CO+O ₂ )) ) ( 7 ) V _gk ^e is considering the mechanical unburned carbon to apply the basic element The composition calculates the amount of dry air required for theoretical combustion.

Vg _k ⁰ =0.0889(C _ar +0.375S _ar )+0.265H _ar -0.0333O _ar -0.0889C _ub ( 8 ) V _gy ° is a theoretical combustion calculated by considering the mechanical unburned carbon and applying the basis element composition. Dry smoke volume.

V _gy ⁰ =0.0889C _ar +0.03331S _ar +0.2094H _ai .+0.008N _ar

-0.0263O _ar -0.0889C _ub ( 9 ) Relationship between smoke composition and fuel characteristic coefficient

CO ₂ +SO2+O2=21-P(CO ₂ +SO ₂ )-(0.605+ )CO ( 10 ) Fuel characteristic coefficient

P=2.35(H _ar -0.126O _ar +0.038N _ar )/(C _ar -C _ub +0.375S _ar ) ( 11 ) Empirical formula between low calorific value and elemental content of coal

Smoke moisture

H20=V _H2 o /( V _H 2o+ V _gy ) ( 13 ) VH2o=0.0124M _ar +0.1118H _ar +0.0161 V,

Various flue gas volumes

V _C0 =V _gy CO

V ₀₂ =V _gy O ₂

The above 18 equations have a total of 18 variables (C _ar , Har _ar , O _ar , N _ar , S _ar , A _ar , Vgk ⁰ , Vgy ⁰ , Vgy cc , β , C _ub , VR ₀₂ , V _N 2 , VO2 VCO,

V _H2 G, Qar, „et ) constitute the simultaneous combustion equations of the boiler.

Based on the calculated coal quality data and other results, the boiler efficiency and loss can be calculated to obtain the boiler heat absorption, including the corresponding results of the unit weight fuel and the total fuel.

Some data required in the scheme proposed in the fourth, fifth, and sixth aspects of the present invention, such as unit theoretical air volume, unit theoretical flue gas volume, unit flue gas containing C02 amount, and unit flue gas containing H20 amount, may be Test, experience or calculations are used, and the test data of the actual raw coal is preferred. While the invention has been described above, the foregoing description is for the purpose of illustration and description A person skilled in the art can make various changes to the invention without departing from the spirit of the invention, and the scope of the invention is defined by the appended claims.

Claims

Rights request

1. A real-time online monitoring method for coal-fired boiler performance, characterized by the following steps:

a) a first measuring step for measuring the composition of the 02 of the flue gas during the output of the substance;

b) a second measuring step for measuring at least one of the amount of coal supplied to the milling system during the input of the substance, the total amount of air during the input of the substance, and the amount of smoke during the output of the substance;

c) According to the above measurement results and without using the boiler output heat as the measured value, establish a corresponding positive definite equation or equation with accurate solution, by solving at least one of boiler combustion heat, its representative quantity, coal calorific value and coal quality component , real-time monitoring data on the performance of coal-fired boilers.

2. The real-time online monitoring method for coal-fired boiler performance according to claim 1, wherein the second measuring step measures the amount of coal fed, the total amount of air, and the amount of flue gas.

3. The real-time online monitoring method for coal-fired boiler performance according to claim 2, wherein the second measuring step further comprises: measuring a primary air volume of the milling system and a temperature at the inlet and outlet of the coal mill.

4. The real-time online monitoring method for coal-fired boiler performance according to claim 1, wherein the second measuring step measures the amount of flue gas, and also measures the CO2 and H20 components of the flue gas, calculates the flow rate of the C02 and H20, and according to the unit C. The approximate relationship between the calorific value of the combustion of the H element and the calorific value of the combustion of the coal, and the calorific value of the combustion is calculated.

5. The real-time online monitoring method for coal-fired boiler performance according to claim 1, wherein the second measurement step measures the amount of smoke, calculates the amount of smoke generated by the actual combustion reaction, that is, the theoretical amount of smoke, and according to the theoretical amount of smoke. The approximate relationship with the calorific value is calculated as the calorific value or the theoretical amount of flue gas as a representative amount of the calorific value of combustion.

6. The real-time online monitoring method for coal-fired boiler performance according to claim 1, wherein the second measuring step measures the total air volume, calculates the amount of air actually reacted, that is, the theoretical air amount, and passes between the theoretical air amount and the calorific value. The approximate relationship calculates the amount of heat generated, or the theoretical amount of air is used as a representative amount of heat of combustion.

The real-time online monitoring method for coal-fired boiler performance according to any one of claims 1 to 6, wherein the output component data is measured by setting certain variables as constants and using an elemental regression equation, and the boiler milling system data .