A thermal deviation calculation method based on real-time measurement data

Abstract

The invention discloses a thermal deviation calculation method based on real-time measurement data, including: S1: calculating the flue gas temperature non-uniformity coefficient of the pipe where the measuring point is installed, and then fitting the continuous distribution function of the flue gas temperature non-uniformity coefficient of all pipes; S2: using the continuous distribution function of the flue gas temperature non-uniformity coefficient and the heat load non-uniformity coefficient of the measuring point pipe, correcting and fitting the distribution function of the heat load non-uniformity coefficient along the width direction; S3: iterative calculation of the target calculation pipe outlet temperature: assuming the outlet specific volume of the target calculation pipe, calculating the flow deviation and the heat load deviation, and then calculating the outlet enthalpy value, calculating the outlet temperature according to the outlet enthalpy value and the outlet pressure, and calculating whether the difference between the outlet specific volume and the assumed value is within the error range, and outputting the outlet temperature when the error range is less than the preset value. Using the correlation between the outlet wall temperature and the heat load, a width direction heat load distribution that matches the actual operation is established to achieve soft measurement of the wall temperature of the heating surface in the furnace.

Description

Technical Field

[0001] The invention relates to the technical field of boilers, and in particular to a thermal deviation calculation method based on real-time measurement data. Background Art

[0002] The working environment of the high-temperature heating surface of the boiler, especially the final superheater and the final reheater, is particularly harsh. The explosion of the heating surface caused by overheating seriously affects the safe and stable operation of the boiler. The operation monitoring of the heating surface of the boiler in the existing power plant mainly relies on the measurement points outside the furnace, which are installed in the large package at the top of the boiler, and the ambient temperature is about 400 degrees Celsius. Since the flue gas temperature in the boiler furnace is higher than the long-term stable operating temperature of the general thermocouple, it is impossible to arrange thermocouples inside the boiler to monitor the actual wall temperature of the boiler heating surface for a long time. The power plant's monitoring of the temperature in the furnace is relatively simple and cannot achieve accurate monitoring. The actual temperature of the pipe in the furnace is much higher than the temperature measured in the large package at the top, which leads to bursting and leakage of the boiler during operation due to the overheating of the pipe wall in the furnace that cannot be grasped.

[0003] The temperature of the boiler heating surface inside the furnace is obtained through the thermal calculation results, and the temperature of the measuring point outside the furnace is set according to the empirical data of the actual temperature difference between the inside and outside of the furnace; for safety reasons, a large safety margin is reserved for the temperature setting.

[0004] The traditional wall temperature monitoring method only pays attention when the temperature exceeds the limit. The changes in low temperature data are basically ignored, and the relationship between wall temperature and pipeline heat transfer characteristics cannot be established. When the oxide layer thickens, the outlet temperature will drop due to the decrease in thermal conductivity, but this drop will not attract the attention of alarm and operators.

[0005] In the existing measurement scheme, only the outlet temperature at a limited number of measuring points can be monitored, and full coverage monitoring of the furnace and outlet wall temperature of all heating surface pipes cannot be achieved. In order to facilitate the monitoring and analysis of boiler operation conditions, the heat absorption deviation of the traditional calculation method uses the empirical formula of parabolic distribution or double hump distribution, which has a large error from the actual heat absorption deviation. Summary of the invention

[0006] To this end, the present invention provides a thermal deviation calculation method based on real-time measurement data to solve the problem that the empirical formula of the heat absorption deviation using parabolic distribution or double hump distribution in the prior art has a large error with the actual heat absorption deviation.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for calculating thermal deviation based on real-time measurement data comprises the following steps:

[0009] S1: Calculate the flue gas temperature non-uniformity coefficient of the pipe where the measuring point is installed, and then fit the continuous distribution function of the flue gas temperature non-uniformity coefficient of all pipes;

[0010] S2: Using the continuous distribution function of the flue gas temperature non-uniformity coefficient and the heat load non-uniformity coefficient of the measuring point pipeline, the distribution function of the heat load non-uniformity coefficient along the width direction is corrected and fitted;

[0011] S3: Iterative calculation of the target calculation tube outlet temperature: Assuming the outlet specific volume of the target calculation tube, calculate the flow deviation and heat load deviation, and then calculate the outlet enthalpy value. Calculate the outlet temperature based on the outlet enthalpy value and the outlet pressure, and calculate whether the difference between the outlet specific volume and the assumed value is within the error range. If it exceeds the range, use the calculated outlet specific volume to perform iterative calculation again until the error range is less than the preset value, and then output the outlet temperature.

[0012] Furthermore, step S1 includes: using formula (1) to calculate the temperature rise of the pipeline at each measuring point,

[0013] Δt i =t out -t in (1)

[0014] The flue gas temperature non-uniformity coefficient of the measuring point pipeline is calculated using formula (2):

[0015]

[0016] The continuous distribution function of the flue gas temperature non-uniformity coefficient is obtained by fitting the data of each discrete measuring point:

[0017] η i,x =a+bx+cx 2 +dx 3 +ex 4 (3)

[0018] In the formula, Δt i ,t out ,t in They are the temperature increase, outlet value and inlet value of the pipe equipped with measuring points, N represents the number of pipes involved in the calculation, a, b, c, d are model coefficients, and x is the distance from the left side of the furnace.

[0019] Further, step S2 includes: using the temperature of the inlet header and the outlet pipe wall temperature measurement point data to calculate the inlet enthalpy value and the outlet enthalpy value respectively, and using formula (4) to calculate the heat load unevenness coefficient of the measuring point pipe:

[0020]

[0021] In the formula, ρ irepresents the heat load unevenness coefficient of the i-th pipe; h i,out Indicates the outlet steam enthalpy; h i,in Indicates the inlet steam enthalpy; (h i,out -h i,in ) pj Represents the average steam enthalpy.

[0022] Furthermore, the actual values ​​of each discrete measuring point calculated by formula (4) are used to correct formula (3) to obtain the distribution function of the heat load unevenness coefficient along the width direction:

[0023] η r,x =A+Bx+Cx 2 +Dx 3 +Ex 4 (5).

[0024] Further, step S3 includes: assuming that the outlet specific volume v of the outlet pipe is p ; Use formula 6 to obtain the thermal deviation coefficient of other pipelines without installed measuring points:

[0025]

[0026] Where η r Indicates the thermal load deviation coefficient, η l Indicates the flow deviation coefficient;

[0027] Then use formula (7) to calculate the outlet enthalpy of the pipeline without measuring points:

[0028] h i,out =h i,in +ρ i *(h i,out -h i,in ) pj (7)

[0029] Where, the thermal load deviation coefficient η r Calculated by formula (5).

[0030] Furthermore, the flow deviation coefficient of the target calculation tube is calculated according to the following formula:

[0031] In the Z-type header connection system, any Δp h -Δp f The values ​​are:

[0032]

[0033] In the formula, X represents the distance from the calculation point to the header inlet, L represents the calculated length of the header, Indicates the relative position from the calculation point to the header inlet;

[0034] In the U-type header connection system, any Δp h -Δp f The values ​​are:

[0035]

[0036] In the formula, Δp hL Indicates the total pressure change in the collection header, Δp fL Indicates the total pressure change in the distribution header;

[0037] Other connection methods can be derived through the above two methods, and their flow deviation coefficient η l The calculation formula is:

[0038]

[0039] In the formula, v pj Represents the average specific volume in the average working condition pipe and the average specific volume of the inlet and outlet headers; v p represents the average value of the inlet and outlet specific volumes of the target calculation tube; ρv represents the average working fluid mass flow rate in the tube; Z pj The comprehensive coefficient of friction resistance and local resistance of the average working condition pipe; (Δp h -Δp f ) pj Indicates the growth value of the average working condition pipe inlet and outlet pressure difference; (Δp h -Δp f ) i Indicates the increase value of the inlet and outlet pressure difference of the target working condition pipe.

[0040] Furthermore, in step S2, the average enthalpy increase and the enthalpy value at the deviation pipe outlet are calculated according to the temperature, pressure, flow rate, pipeline and header size parameters of the inlet and outlet headers and the deviation pipe outlet wall temperature.

[0041] Furthermore, before step S1, the outlet pressure of this stage is calculated by a heat balance method according to the inlet pressure and temperature of the heating surface of the previous stage and the flow rate and temperature of the cooling water.

[0042] The present invention has the following advantages: the present invention utilizes the correlation between the outlet wall temperature and the heat load to establish a heat load distribution in the width direction that is more matched with the actual operation, and based on a small number of existing measuring points of the boiler, combined with the operating parameters of the boiler, performs real-time flow distribution calculation and thermal calculation on the heating surface of the boiler; obtains the working fluid temperature distribution along the heating surface pipeline from the inlet to the outlet, and then calculates the metal wall temperature in the furnace, thereby realizing soft measurement of the wall temperature of the heating surface in the furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0044] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0045] Figure 1 A calculation flow chart of a thermal deviation calculation method based on real-time measurement data provided by a specific embodiment of the present invention;

[0046] Figure 2 A schematic diagram of the structure of a measuring point pipeline and measuring point position of a thermal deviation calculation method based on real-time measurement data provided by a specific embodiment of the present invention;

[0047] Figure 3 A detailed flow chart of a thermal deviation calculation method based on real-time measurement data provided in a specific embodiment of the present invention.

[0048] Figure 2 Middle: 1- measuring point pipeline; 2- measuring point; 3- inlet header; 4- outlet header. DETAILED DESCRIPTION

[0049] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] The terms such as "upper", "lower", "left", "right", "middle", etc. cited in this specification are only for the convenience of description and are not intended to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as within the scope of implementation of the present invention without substantially changing the technical content.

[0051] like Figure 1As shown, a specific embodiment of the present invention provides a method for calculating thermal deviation based on real-time measurement data, comprising the following steps:

[0052] S1: Calculate the flue gas temperature non-uniformity coefficient of the pipe where the measuring point is installed, and then fit the continuous distribution function of the flue gas temperature non-uniformity coefficient of all pipes;

[0053] S2: Using the continuous distribution function of the flue gas temperature non-uniformity coefficient and the heat load non-uniformity coefficient of the measuring point pipeline, the distribution function of the heat load non-uniformity coefficient along the width direction is corrected and fitted;

[0054] S3: Iterative calculation of the target calculation tube outlet temperature: Assuming the outlet specific volume of the target calculation tube, calculate the flow deviation and heat load deviation, and then calculate the outlet enthalpy value. Calculate the outlet temperature based on the outlet enthalpy value and the outlet pressure, and calculate whether the difference between the outlet specific volume and the assumed value is within the error range. If it exceeds the range, use the calculated outlet specific volume to perform iterative calculation again until the error range is less than the preset value, and then output the outlet temperature.

[0055] The heat load distribution of the convection flue is uneven. It is generally believed that the distribution along the width of the furnace is symmetrical, with the highest heat load in the middle of the flue and the lowest heat load on both sides. However, in actual operation, the distribution of flue gas is affected by many factors and differs greatly from the ideal distribution. Studies have shown that there is a strong correlation between the superheater outlet temperature and the heat load distribution along the width of the superheater. A relatively accurate flue gas heat load distribution can be obtained by data fitting through the outlet temperature. The present invention utilizes the correlation between the outlet wall temperature and the heat load to establish a width-wise heat load distribution that matches the actual operation. On the basis of a small number of existing measuring points in the boiler (or adding a small number of measuring points), combined with the operating parameters of the boiler, real-time flow distribution calculations and thermal calculations are performed on the heating surface of the boiler; the working fluid temperature distribution along the heating surface pipeline from the inlet to the outlet is obtained, and then the metal wall temperature in the furnace is calculated to achieve soft measurement of the wall temperature of the heating surface in the furnace.

[0056] In an optional embodiment, S1 includes: using formula (1) to calculate the temperature rise of the pipeline at each measuring point,

[0057] Δt i =t out -t in (1)

[0058] The flue gas temperature non-uniformity coefficient of the measuring point pipeline is calculated using formula (2):

[0059]

[0060] The continuous distribution function of the flue gas temperature non-uniformity coefficient is obtained by fitting the data of each discrete measuring point:

[0061] η i,x =a+bx+cx 2 +dx 3 +ex 4 (3)

[0062] In the formula, Δt i ,t out ,t in They are the temperature increase, outlet value and inlet value of the pipe equipped with measuring points, N represents the number of pipes involved in the calculation, a, b, c, d are model coefficients, and x is the distance from the left side of the furnace.

[0063] In an optional embodiment, S2 includes: using the temperature of the inlet header and the outlet pipe wall temperature measurement point data to calculate the inlet and outlet enthalpy values ​​respectively, and using Formula 4 to calculate the heat load unevenness coefficient of the measuring point pipe:

[0064]

[0065] In the formula, ρ i represents the heat load unevenness coefficient of the i-th pipe; h i,out Indicates the outlet steam enthalpy; h i,in Indicates the inlet steam enthalpy; (h i,out -h i,in ) pj Represents the average steam enthalpy.

[0066] In an optional embodiment, since the outlet temperature distribution function and the distribution of the heat load unevenness coefficient are similar, the distribution form can be determined by formula (3), and the actual value of the discrete point calculated by formula (4) is used to correct formula (3) to obtain the distribution function of the heat load unevenness coefficient along the width direction:

[0067] η r,x =A+Bx+Cx 2 +Dx 3 +Ex 4 (5)

[0068] Research shows that there is a strong correlation between the superheater outlet temperature and the heat load distribution along the width direction of the superheater. Data fitting through the outlet temperature can obtain a relatively accurate flue gas heat load distribution. By using the actual value of the discrete point to correct formula (3), the distribution function of the heat load unevenness coefficient along the width direction can be obtained, and the heat load distribution in the width direction that matches the actual operation can be established. The wall temperature monitoring of the pipeline without the measurement point can be realized, and the over-temperature and pipe burst of the pipeline without the measurement point can be effectively avoided.

[0069] In an optional embodiment, S3 includes: assuming that the outlet specific volume v of the outlet pipe is p ; Use public

[0070] Formula 6 obtains the thermal deviation coefficient of other pipelines without installed measuring points:

[0071]

[0072] Where η r Indicates the thermal load deviation coefficient, η l Indicates the flow deviation coefficient;

[0073] Then use formula (7) to calculate the outlet enthalpy of the pipeline without measuring points:

[0074] h i,out =h i,in +ρ i *(h i,out -h i,in ) pj (7)

[0075] Where, the thermal load deviation coefficient η r Calculated by formula (5). By calculating the heat load deviation in the width direction and the flue gas flow direction, full coverage monitoring of the furnace and outlet wall temperature of all heating surface pipes can be achieved. Real-time monitoring of the boiler furnace wall temperature can be achieved. The actual operating temperature in the furnace can be accurately calculated to provide basic data for boiler operation and status evaluation.

[0076] In an optional embodiment, the flow deviation coefficient of the target calculation tube is calculated according to the following formula:

[0077] In the Z-type header connection system, any Δp h -Δp f The values ​​are:

[0078]

[0079] In the formula, X represents the distance from the calculation point to the header inlet, L represents the calculated length of the header, Indicates the relative position from the calculation point to the header inlet;

[0080] In the U-type header connection system, any Δp h -Δp f The values ​​are:

[0081]

[0082] In the formula, Δp hL Indicates the total pressure change in the collection header, Δp fL Indicates the total pressure change in the distribution header;

[0083] Other connection methods can be derived through the above two methods, and their flow deviation coefficient η l The calculation formula is:

[0084]

[0085] In the formula, v pj Represents the average specific volume in the average working condition pipe and the average specific volume of the inlet and outlet headers; v p represents the average value of the inlet and outlet specific volumes of the target calculation tube; ρv represents the average working fluid mass flow rate in the tube; Z pj The comprehensive coefficient of friction resistance and local resistance of the average working condition pipe; (Δp h -Δp f ) pj Indicates the growth value of the average working condition pipe inlet and outlet pressure difference; (Δp h -Δp f ) i Indicates the increase value of the inlet and outlet pressure difference of the target working condition pipe.

[0086] In an optional embodiment, in S2, the average enthalpy increase and the enthalpy value at the deviation pipe outlet are calculated based on the temperature, pressure, flow rate, pipeline and header size parameters of the inlet and outlet headers and the deviation pipe outlet wall temperature.

[0087] In an optional implementation scheme, in general, the temperature data of the inlet and outlet of the boiler heating surface are known, and there will be pressure data on one side (inlet or outlet). Before step S1, the outlet pressure of this stage is calculated by the heat balance method based on the inlet pressure and temperature of the previous stage heating surface and the flow rate and temperature of the cooling water.

[0088] The present invention relates to a specific device comprising: a temperature sensor, an acquisition card, and an interface machine; the temperature sensor is a high-temperature thermocouple installed on the collecting pipe of the boiler header; the acquisition card is TP1608P-AI-Z; the interface machine is an ordinary PC, and the data acquisition cycle is 30S. After real-time data is collected, the inlet and outlet enthalpy values ​​of the heating surface inlet header 3 and the outlet header 4 are calculated in real time, and the outlet enthalpy value of the measuring point pipeline 1 is calculated. The positions of the measuring point pipeline and the measuring point 2 are as follows: Figure 2 shown.

[0089] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for calculating thermal deviation based on real-time measurement data, characterized in that: The steps include: S1: Calculate the flue gas temperature non-uniformity coefficient of the pipe at the installation measuring point, and then fit the continuous distribution function of the flue gas temperature non-uniformity coefficient of all pipes; S2: using the continuous distribution function of the flue gas temperature non-uniformity coefficient and the heat load non-uniformity coefficient of the measuring point pipeline, correcting and fitting to obtain the distribution function of the heat load non-uniformity coefficient along the width direction; S3: Iterative calculation of the target calculation tube outlet temperature: Assuming the outlet specific volume of the target calculation tube, calculate the flow deviation and heat load deviation, and then calculate the outlet enthalpy value. Calculate the outlet temperature based on the outlet enthalpy value and the outlet pressure, and calculate whether the difference between the outlet specific volume and the assumed value is within the error range. If it exceeds the range, use the calculated outlet specific volume to perform iterative calculation again until the error range is less than the preset value, and then output the outlet temperature.

2. The method for calculating thermal deviation based on real-time measurement data according to claim 1, characterized in that: Step S1 includes: using formula (1) to calculate the temperature rise of the pipeline at each measuring point, Δt i =t out -t in (1) The flue gas temperature non-uniformity coefficient of the measuring point pipeline is calculated using formula (2): The continuous distribution function of the flue gas temperature non-uniformity coefficient is obtained by fitting the data of each discrete measuring point: η i,x =a+bx+cx 2 +dx 3 +ex 4 (3) In the formula, Δt i ,t out ,t in are respectively the temperature increase value, outlet value and inlet value of the pipeline equipped with the measuring point, N represents the number of pipelines involved in the calculation, a, b, c, d are model coefficients, and x is the distance from the left side of the furnace.

3. The method for calculating thermal deviation based on real-time measurement data according to claim 2, characterized in that: Step S2 includes: using the temperature of the inlet header and the outlet pipe wall temperature measurement point data to respectively calculate the inlet enthalpy value and the outlet enthalpy value, and using formula (4) to calculate the heat load unevenness coefficient of the pipe at the measurement point: In the formula, ρ i represents the heat load unevenness coefficient of the i-th pipe; h i,out Indicates the outlet steam enthalpy; h i,in Indicates the inlet steam enthalpy; (h i,out -h i,in ) pj Represents the average steam enthalpy.

4. The method for calculating thermal deviation based on real-time measurement data according to claim 3, characterized in that: The actual values ​​of each discrete measuring point calculated by formula (4) are used to correct formula (3) to obtain the distribution function of the heat load unevenness coefficient along the width direction: η r,x =A+Bx+Cx 2 +Dx 3 +Ex 4 (5)。 5. The method for calculating thermal deviation based on real-time measurement data according to claim 1, characterized in that: Step S3 includes: assuming that the outlet specific volume v of the outlet pipe is p ; Use formula 6 to obtain the thermal deviation coefficient of other pipelines without installed measuring points: Where η r Indicates the thermal load deviation coefficient, η l Indicates the flow deviation coefficient; Then use formula (7) to calculate the outlet enthalpy of the pipeline without measuring points: h i,out =h i,in +ρ i *(h i,out -h i,in ) pj (7) Where, the thermal load deviation coefficient η r Calculated by formula (5).

6. The method for calculating thermal deviation based on real-time measurement data according to claim 5, characterized in that: Calculate the flow deviation coefficient of the target calculation tube according to the following formula: In the Z-type header connection system, any Δp h -Δp f The values ​​are: In the formula, X represents the distance from the calculation point to the header inlet, L represents the calculated length of the header, Indicates the relative position from the calculation point to the header inlet; In the U-type header connection system, any Δp h -Δp f The values ​​are: In the formula, Δp hL Indicates the total pressure change in the collection header, Δp fL Indicates the total pressure change in the distribution header; Other connection methods can be derived through the above two methods, and their flow deviation coefficient η l The calculation formula is: In the formula, v pj Represents the average specific volume in the average working condition pipe and the average specific volume of the inlet and outlet headers; v p represents the average value of the inlet and outlet specific volumes of the target calculation tube; ρv represents the average working fluid mass flow rate in the tube; Z pj The comprehensive coefficient of friction resistance and local resistance of the average working condition pipe; (Δp h -Δp f ) pj Indicates the growth value of the average working condition pipe inlet and outlet pressure difference; (Δp h -Δp f ) i Indicates the increase value of the inlet and outlet pressure difference of the target working condition pipe.

7. The method for calculating thermal deviation based on real-time measurement data according to claim 1, characterized in that: In step S2, the average enthalpy increase and the enthalpy value at the deviation pipe outlet are calculated according to the temperature, pressure, flow rate, pipeline and header size parameters of the inlet and outlet headers and the deviation pipe outlet wall temperature.

8. The method for calculating thermal deviation based on real-time measurement data according to claim 1, characterized in that: Before step S1, the outlet pressure of this stage is calculated by heat balance method according to the inlet pressure and temperature of the heating surface of the previous stage and the flow rate and temperature of the cooling water.

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