An on-line calculation method and system for oxygen content of each part of a boiler flue

Abstract

The application discloses an online calculation method and system for oxygen content of each part of a boiler flue. The method establishes an oxygen content calculation model for each part of the boiler flue by measuring the oxygen content at a reference position and the design structure of the boiler, inputs the measured oxygen content data of the reference position of the boiler into the calculation model to obtain the oxygen content values of the rest positions of the boiler flue, and solves the practical problem of insufficient oxygen content online measuring instruments. The system comprises a data acquisition module, a first data processing module and a second data processing module which are connected in sequence. The calculation method does not need to perform heat balance calculation, greatly reduces the measuring points required for online calculation, has a simple calculation process, and has a certain precision in calculation result precision, so that online calculation of the oxygen content of each part of the boiler flue can be realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of thermal power plant boiler, and particularly relates to an online calculation method and system for oxygen content of each part of a boiler flue. BACKGROUND

[0002] The oxygen content of a boiler is an important parameter affecting the safety and economy of the operation of the boiler, and has an important influence on complete combustion of fuel, combustion stability, boiler efficiency, and coking performance of the tube wall. At present, in most cases, there is a lack of online data of oxygen content of each part of the boiler measured by measuring instruments in the DCS control system of the thermal power plant. Generally, when performing a boiler performance test (GB / T 10184-1988 Boiler Performance Test Procedure for Power Station), the oxygen content in the flue gas can be measured by installing paramagnetic oxygen content meters and zirconia oxygen content meters; however, this method requires strict requirements and installation of measuring instruments, and is difficult to apply in the daily operation process, thereby causing difficulties in real-time monitoring of real-time parameters of the oxygen content of each part and guiding the operation of the boiler unit. SUMMARY

[0003] In view of the problems existing in the current oxygen content statistics of the boiler, the present application provides an online calculation method and system for oxygen content of each part of a boiler flue, which has a simple calculation process and high accuracy of the calculation results, and can fully meet the engineering requirements.

[0004] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme:

[0005] An online calculation method for oxygen content of each part of a boiler flue, comprising the following steps:

[0006] Step 1: selecting a boiler oxygen content calculation reference point according to the actual situation on site, and measuring the oxygen content at the reference point Unit: %;

[0007] Step 2: determining the air leakage coefficient between the calculation reference point and the remaining points according to the recommended value of the air leakage coefficient or the air leakage test result of the boiler design;

[0008] Step 3: establishing an online calculation model for the oxygen content of each part of the boiler flue based on the oxygen content at the reference point and the air leakage coefficient between the reference point and the remaining points, and calculating the oxygen content of each part of the boiler flue.

[0009] The present application is further improved in that, in step 3, the calculation formula for the oxygen content of each part of the boiler flue is as follows:

[0010]

[0011] In the formula, Δα i The reference point is sequentially subjected to the flue air leakage coefficient of each part of the heating surface or the flue.

[0012] The further improvement of the present application is that the flue leakage coefficient of the reference point successively passing through each part of the heating surface or the flue is Δα i The relationship between the excess air coefficient α of each part of the flue and the reference point excess air coefficient α''0 is as follows:

[0013]

[0014] In the formula, α''0 is the reference point excess air coefficient.

[0015] The further improvement of the present application is that the flue leakage coefficient of the reference point successively passing through each part of the heating surface or the flue is Δα

[0016]

[0017] Approximately determined.

[0018] The further improvement of the present application is that the flue leakage coefficient is the ratio of the leakage air quantity to the theoretical air quantity.

[0019] An on-line calculation system of oxygen quantity of each part of a boiler flue comprises a data acquisition module, a first data processing module and a second data processing module connected in sequence;

[0020] The data acquisition module is used for acquiring oxygen quantity real-time measurement point data of a reference point.

[0021] The first data processing module is used for establishing an oxygen quantity calculation model of each part of the boiler flue to obtain an oxygen quantity calculation formula of each part of the boiler flue, and writing the flue leakage coefficient into the second data processing module according to a flue leakage test result or selecting a flue leakage coefficient recommended value according to a boiler design drawing.

[0022] The second data processing module is used for inputting the acquired oxygen quantity real-time measurement point data of the reference point into the oxygen quantity calculation model to calculate and obtain oxygen quantity calculation results of each part of the boiler flue.

[0023] The further improvement of the present application is that the oxygen quantity calculation formula of each part of the boiler flue is as follows:

[0024]

[0025] In the formula, Δα i The flue leakage coefficient of the reference point successively passing through each part of the heating surface or the flue is Δα.

[0026] The further improvement of the present application is that the flue leakage coefficient of the reference point successively passing through each part of the heating surface or the flue is Δα i The relationship between the excess air coefficient α of each part of the flue and the reference point excess air coefficient α''0 is as follows:

[0027]

[0028] In the formula, a"0 is the reference point excess air coefficient.

[0029] The further improvement of the present application is that when the boiler is running, the excess air coefficient of each part of the flue is according to the formula:

[0030]

[0031] Approximately determined.

[0032] Compared with the prior art, the present application has at least the following beneficial technical effects:

[0033] The present application provides an online calculation method and system for the oxygen content of each part of the boiler flue, mainly according to the calculation reference point oxygen content measurement value and the boiler flue leakage air coefficient set value, the accuracy of the two parameters will have an important influence on the accuracy of the calculation result, the present application greatly reduces the measurement points required for online calculation, the calculation process is simple, the calculation result precision has a certain precision, and the online calculation of the oxygen content of each part of the boiler can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The flow chart of the real-time calculation method for the oxygen content of each part of the boiler flue in the present application.

[0035] Figure 2 The structure diagram of the real-time calculation system for the oxygen content of each part of the boiler flue in the present application. DETAILED DESCRIPTION

[0036] In order for those skilled in the art to better understand the present application, the technical solutions in the examples of the present application will be described clearly and completely below in combination with the drawings in the examples of the present application. Obviously, the described examples are only a part of the examples of the present application, but not all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0037] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the examples of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0038] The application will be described in further detail below with reference to the drawings:

[0039] Referring to Figure 1 The application provides an online calculation method for oxygen content of each part of a boiler flue, which has simple calculation process and certain precision in calculation result, and can realize online calculation of oxygen content of each part of the boiler flue.

[0040] Specifically, the online calculation method for oxygen content of each part of the boiler flue comprises the following steps:

[0041] Step 1, measuring oxygen content of the boiler flue at a calculation reference point Unit: %;

[0042] Step 2, inquiring boiler design drawings to determine the equipment type and quantity between the point to be calculated and the calculation reference point, and selecting a corresponding air leakage coefficient according to the recommended value of the air leakage coefficient or the air leakage test result;

[0043] Step 3, establishing an online calculation model for oxygen content of each part of the boiler flue based on the oxygen content at the reference point and the air leakage coefficients between the reference point and the other points, and calculating the oxygen content of each part of the boiler flue.

[0044] When the boiler is running, the excess air coefficient of each part of the flue can be determined approximately according to the formula:

[0045]

[0046]

[0047] The relationship between the excess air coefficient of each part of the flue and the excess air coefficient α''0 of the reference point is as follows:

[0048]

[0049] In the formula, α''0 is the excess air coefficient of the reference point;

[0050] Δα i is the air leakage coefficient of each part of the flue in sequence from the reference point, and the air leakage coefficient refers to the ratio of the amount of air leakage to the theoretical air amount.

[0051] It should be noted that the excess air coefficient of the furnace outlet is not only related to the air amount sent into the furnace by the air blower, but also related to the air leakage coefficient of the furnace and the air leakage coefficient of the pulverizing system. For the air preheater: the pressure on the air side is higher than that on the flue gas side, so when the air flows through the air preheater, a part of the air will leak into the flue gas side.

[0052] According to the above theory, the excess air coefficient of the furnace outlet is calculated from the air side of the lowest air preheater as follows:

[0053] α''1=α' ky -Δα​ky + Δα l + Δα zf

[0054] wherein α' ky - the air side excess air ratio of the lowermost air preheater;

[0055] Δα ky - the air leakage factor of the entire air preheater;

[0056] Δα l - the air leakage factor of the furnace;

[0057] Δα zf - the air leakage factor of the pulverizing system.

[0058] If the oxygen content of the flue gas at any point is known, the above relationships can be solved simultaneously to approximately determine the oxygen content of the flue gas at each point;

[0059]

[0060] The recommended values of the air leakage factors of each section of the flue gas duct, the air leakage factors of various pulverizing systems, and the excess air ratio at the outlet of the furnace at the rated load are shown in Tables 1-2.

[0061] Table 1: Air leakage factors in each section of the flue gas duct at the rated load

[0062]

[0063]

[0064] Table 2: Average values of the air leakage factors of various pulverizing systems

[0065]

[0066] As shown in Figure 2 The present application provides an online calculation system for the oxygen content of each part of a boiler flue gas duct, which comprises a data acquisition module, a first data processing module, and a second data processing module.

[0067] The data acquisition module is used to acquire real-time measurement data of the oxygen content at a calculation reference point.

[0068] The first data processing module is used to establish an oxygen content calculation model for each part of the boiler flue gas duct to obtain an oxygen content calculation formula, and to write recommended values of the air leakage factors of the equipment between each sought point of the boiler flue gas duct into the second data processing module according to the boiler design drawings.

[0069] The second data processing module is used to input the acquired real-time measurement data of the oxygen content at the calculation reference point into the oxygen content calculation model to obtain calculation results of the oxygen content at each part of the boiler flue gas duct.

[0070] The calculation method of the present application mainly according to the calculation of the reference point oxygen content measured value and the boiler flue each part of the air leakage coefficient set value, the accuracy of the two parameters will have important influence on the accuracy of the calculation results.

[0071] Examples

[0072] Taking a 300MW unit of a certain plant as an example, the oxygen content of each part of the boiler flue is calculated by the method of the present application,

[0073] Position Leakage coefficient increment Δα Calculated value Measured value Relative deviation Low-temperature economizer outlet Reference point 3.3 High-temperature air preheater outlet (flue gas side) 0.03 3.74 3.72 0.54 Low-temperature air preheater outlet (flue gas side) 0.03 4.15 4.17 -0.47

[0074] In summary, the present application provides an online calculation method and system for the oxygen content of each part of the boiler flue, mainly according to the calculation of the reference point oxygen content measured value and the boiler flue each part of the air leakage coefficient set value, the accuracy of the two parameters will have important influence on the accuracy of the calculation results. The present application greatly reduces the measuring points required for online calculation, the calculation process is simple, the calculation result precision has certain precision, and the online calculation of the oxygen content of each part of the boiler can be realized.

[0075] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: the specific embodiments of the present application can still be modified or replaced by the equivalent, without departing from the spirit and scope of the present application, any modification or equivalent replacement should be covered within the protection scope of the claims of the present application.

Claims

1. An online calculation method for oxygen content in various parts of a boiler flue, characterized in that: The steps include: Step 1: Select the boiler oxygen calculation reference point according to the actual situation on site and measure the oxygen content at the reference point. ,unit:%; Step 2: Query the recommended value of the air leakage coefficient or the air leakage test results according to the boiler design, and determine the air leakage coefficient between the calculation reference point and the remaining points; Step 3: Based on the oxygen content at the reference point and the air leakage coefficient between the reference point and the remaining points, an online calculation model for the oxygen content in each part of the boiler flue is established to calculate the oxygen content in each part of the boiler flue. The calculation formula for the oxygen content in each part of the boiler flue is as follows: Where, ——The reference point passes through the flue leakage coefficient of each part of the heating surface or flue in sequence.

2. The online calculation method for oxygen content in various parts of a boiler flue according to claim 1 is characterized in that: The reference point passes through the flue air leakage coefficient of each part of the heating surface or flue in turn and excess air coefficient at various locations in the flue and the reference point excess air coefficient The relationship is as follows: Where, ——Excess air coefficient at the reference point.

3. The online calculation method for oxygen content in various parts of a boiler flue according to claim 2 is characterized in that: When the boiler is running, the excess air coefficient at each part of the flue is calculated according to the formula: Approximately determined.

4. The online calculation method for oxygen content in various parts of a boiler flue according to claim 1 is characterized in that: The flue air leakage coefficient refers to the ratio of the amount of air leaking into the flue to the theoretical amount of air.

5. An online calculation system for oxygen content in various parts of a boiler flue, characterized in that: It includes a data acquisition module, a first data processing module and a second data processing module connected in sequence; A data acquisition module is used to obtain real-time oxygen measurement point data for calculating the reference point; The first data processing module is used to establish a calculation model for the oxygen content of each part of the boiler flue to obtain a calculation formula for the oxygen content of each part of the boiler flue, select a recommended value of the air leakage coefficient according to the boiler design drawings, or write the air leakage coefficient into the second data processing module based on the air leakage test results; The second data processing module is used to input the obtained real-time measurement point data of the calculation reference point boiler oxygen content into the oxygen content calculation model to calculate the oxygen content calculation results of the remaining parts of the boiler flue. The calculation formula of the oxygen content of each part of the boiler flue is as follows: Where, ——The reference point passes through the flue leakage coefficient of each part of the heating surface or flue in sequence.

6. The online calculation system for oxygen content in various parts of a boiler flue according to claim 5 is characterized in that: The reference point passes through the flue air leakage coefficient of each part of the heating surface or flue in turn and excess air coefficient at various locations in the flue and the reference point excess air coefficient The relationship is as follows: Where, ——Excess air coefficient at the reference point.

7. The online calculation system for oxygen content in various parts of a boiler flue according to claim 6 is characterized in that: When the boiler is running, the excess air coefficient at each part of the flue is calculated according to the formula: Approximately determined.

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