CN101832544B - Method for monitoring thermal deviation of final superheater and final reheater of power station boiler on line - Google Patents

Abstract

The present invention provides an online monitoring method for thermal deviation of a final superheater and a final reheater of a power station boiler, the steps of which are to first build an online monitoring device, then read online detection data, calculate the thermal deviation of each screen and each tube according to the read online monitoring data, and store and display the result. The advantages of the present invention are that it can realize fast online real-time calculation and online monitoring and control of thermal deviation of a final superheater and a final reheater of a boiler, realize safe operation of the final superheater and the final reheater of the boiler during service life, and extend the service life of the final superheater and the final reheater of the boiler.

Description

On-line monitoring method for thermal deviation of final superheater and final reheater of utility boiler

technical field

The invention relates to an on-line monitoring method for the thermal deviation of the final superheater and the final reheater of a power station boiler, belonging to the technical field of power station boilers.

Background technique

At present, my country's generating units have entered the development stage of large capacity and high parameters, and a batch of 600MW and 1000MW supercritical generating units have been put into operation one after another. With the increase of boiler parameters, especially the increase of steam temperature, some parameters different from subcritical parameters such as the overheating problem caused by scale in the tube become more prominent. A tube burst in a large-capacity supercritical boiler during operation will not only cause huge direct economic losses, but also cause the hidden danger of continuous tube burst due to the damage of a large area of tubes near the burst area, seriously affecting the safe operation of the boiler.

In order to slow down the formation speed of oxide scale in the final superheater and final reheater tubes and control the peeling of oxide scales to cause blockage and burst tubes, and effectively monitor the furnace wall temperature distribution of the final superheater and final reheater furnace tubes, A method is needed for on-line monitoring of thermal deviation of the superheater and reheater heating surface of the utility boiler.

Contents of the invention

The purpose of the present invention is to provide a method for on-line monitoring of thermal deviation of boiler superheater and reheater, realize on-line monitoring of thermal deviation of boiler final superheater and final reheater, and provide one or several thermal power plants The thermal deviation of the final stage superheater and final stage reheater of the unit boiler.

In order to achieve the above object, the technical solution of the present invention is to provide an on-line monitoring method for the thermal deviation of the final superheater and the final reheater of the utility boiler, characterized in that the steps are:

Step 1, the web server is connected with the client browser, the database server and the calculation server respectively, the database server is connected with the calculation server, and the database server is connected with the power plant DCS system or MIS system and online measuring points through the plant-level monitoring information system;

Step 2. The database server reads the online monitoring data of the boiler final stage superheater and final stage reheater every at least 30 seconds;

Step 3. Read the wall temperature data at the outlet of each screen and tube, the inlet steam temperature data and the main parameters of the boiler operation collected by online monitoring, and directly calculate the thermal deviation coefficient along the width of the furnace according to the definition of thermal deviation. Step 3 includes:

Step 3.1, calculate the non-uniform heat absorption coefficient K ₁ along the flue width direction, K ₁ =η _r *η _l , wherein, η _r is the heat deviation coefficient along the furnace width, and η _l is the steam flow deviation along the furnace width coefficient;

其中，h为计算点离屏底部的距离，T为屏的总高度；Step 3.2, calculate the non-uniform heat absorption coefficient K ₄ along the flue height direction,

Among them, h is the distance from the calculation point to the bottom of the screen, and T is the total height of the screen;

式中，ξ₀为平均阻力系数；ξ为计算管阻力系数；Step 3.3. Calculate the flow deviation of the same screen. The flow deviation of the same screen is defined as the ratio of the flow of a certain pipe in a screen to the average flow of each pipe in the screen. The calculation formula is

In the formula, _ξ0 is the average resistance coefficient; ξ is the calculation pipe resistance coefficient;

(i＝1，2，…，n)为第i根管的总折算阻力系数； ${\mathrm{\ξ}}_0={\left(\frac{\mathrm{no}}{\sqrt{1/{\mathrm{\ξ}}_1^z}+\sqrt{1/{\mathrm{\ξ}}_2^z}+......+\sqrt{1/{\mathrm{\ξ}}_{\mathrm{no}}^z}}\right)}^2,$ Among them, n is the number of parallel tubes forming a screen,

(i=1, 2, ..., n) is the total converted resistance coefficient of the i-th pipe;

其中，m为组成一根并联管的不同内径管段的数量，d₀为假想的统一管子内径，d_j为第j根管段的内径，

为第j根管段的摩擦系数；

Among them, m is the number of pipe sections with different inner diameters forming a parallel pipe, d ₀ is the inner diameter of a hypothetical unified pipe, and _dj is the inner diameter of the jth pipe section,

is the friction coefficient of the jth pipe section;

其中，υ₀为平均比容，g₀为平均管屏的流量；The average tube resistance ΔP ₀ is,

Among them, υ ₀ is the average specific volume, and g ₀ is the flow rate of the average tube panel;

Step 3.4, calculate the flow deviation between screens:

其中，g_i为计算管屏的流量，g₀为平均管屏的流量；Step 3.4.1. Knowing the pressure distribution curve of the inlet and outlet headers, first set the pressure difference value ΔP′ between the two headers. According to the position of each screen, the pressure difference ΔP _i of each screen can be obtained. According to the flow rate and pressure According to the difference relationship, the flow rate of each screen can be calculated according to the following formula:

Among them, g _i is the flow rate of the calculated tube panel, and _g0 is the flow rate of the average tube panel;

Step 3.4.2, total flow G'=∑g _i , where i=1,...,n, n is the total number of screens;

并回到步骤3.4.1，否则进入下一步；Step 3.4.3. Investigate the deviation between the calculated flow G' and the actual flow G. If |(G'-G)/G| does not meet the requirements, change ΔP' to ΔP" according to the following formula,

And go back to step 3.4.1, otherwise go to the next step;

Step 3.4.4, flow deviation between screens ξ _i = g _i /g ₀ ;

Step 3.5, calculate thermal deviation coefficient:

Δi_i为计算屏的焓增，i＝1，…，n，n为总屏数目，Δi₀为各屏焓增平均值；Thermal deviation coefficient of each screen

Δi _i is the enthalpy increase of the calculation screen, i=1,...,n, n is the total number of screens, and Δi ₀ is the average value of the enthalpy increase of each screen;

Step 4. Real-time display of thermal deviation curves of the final stage superheater and final stage reheater.

The present invention has the following characteristics:

1. Install computer software for on-line monitoring of the thermal deviation of the boiler’s final superheater and final reheater written in VB language on the calculation/application server for the online monitoring of the thermal deviation of the boiler’s final superheater and final reheater, according to The time interval set by the software reads the online monitoring boiler parameters from the database server, calculates the thermal deviation of the boiler in real time online, calculates and analyzes the results, and then sends them to the database server for storage and for the web server to call.

2. The database server stores two types of data:

The first type of data is the data of online monitoring of boiler parameters, including main steam pressure, main steam temperature, reheat steam pressure, reheat steam temperature, electrical load, final superheater outlet pressure, final superheater outlet temperature, high temperature Outlet temperature of reheater, outlet temperature of high-temperature reheater, temperature of installation measuring point of each panel and tube of final reheater, temperature of measuring point of each panel and tube of final superheater, etc.

The second type of data is the calculation result of the thermal deviation of the final superheater and the final reheater of the boiler.

3. The external system interface has two functions:

One is to store the monitoring values of boiler parameters into the database;

The second is to transmit the boiler operation control measures to the boiler control system.

4. Boiler automatic control system and parameter measuring point have two functions:

One is to provide parameters for boiler online monitoring;

The second is to guide the operation of the boiler based on the calculation results of the thermal deviation of the final superheater and the final reheater of the boiler to ensure that the final superheater and the final reheater of the boiler do not exceed the temperature and operate in a safe state.

5. The results of the online calculation of the thermal deviation of the final stage superheater and the final reheater of the boiler are published on the computer web browser. According to the request issued by the browser end user, that is, the technician of the power plant, the boiler terminal in the database server is called through the calculation/application server. The real-time calculation results of the thermal deviation of the first-stage superheater and the final-stage reheater will form the management results of the thermal deviation of the final-stage superheater and the final-stage reheater of the boiler on the web server, and return it to the browser end user to guide the operation of the boiler.

6. The client browser is used to view the thermal deviation online monitoring results of the boiler's final stage superheater and final stage reheater.

The method and system for on-line monitoring of the thermal deviation of the boiler final superheater and final reheater provided by the invention can realize online real-time calculation, online real-time monitoring and control of the thermal deviation of the boiler final superheater and final reheater. If the temperature of a certain tube panel of the boiler’s final superheater and final reheater exceeds the warning value, the temperature of the tube wall will be reduced through boiler operation adjustment, so that the boiler’s final superheater and final reheater tube wall will be in a safe state, reaching The technical effect of monitoring and controlling the thermal deviation of the boiler's final stage superheater and final stage reheater is realized.

The advantage of the present invention is that it can realize rapid online real-time calculation and online monitoring and control of the thermal deviation of the final superheater and the final reheater of the boiler, and realize the safe operation of the final superheater and the final reheater of the boiler during the service period , prolong the service life of the final stage superheater and the final stage reheater of the boiler.

Description of drawings

Fig. 1 is a block diagram of an on-line monitoring system for thermal deviation of a boiler final stage superheater and final stage reheater of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the examples.

Example

For a supercritical 600MW utility boiler final-stage superheater and final-stage reheater heating surface in a power plant, the thermal deviation online monitoring device was used to calculate the thermal deviation and start-up conditions of the final-stage superheater and final-stage reheater heating surface , and the historical optimal working condition.

As shown in Figure 1, the block diagram of the intelligent wall temperature management device of the boiler final stage superheater and the final stage reheater of the present invention, the boiler final stage superheater and the final stage reheater intelligent wall temperature management device are composed of computing server, database server, The plant-level monitoring information system (PI system) is composed of web server and user browser server. The web server is connected to the user-end browser, database server and computing server respectively. The computing server is connected to the database server. The database server is connected to the factory-level monitoring information system. Connect with power plant DCS system or MIS system and online measuring points.

For a supercritical 600MW boiler, the thermal deviation online monitoring device shown in Figure 1 is used for the final superheater and final reheater, and the method is as follows:

Step 1: Read the data of online measuring points on the heating surface of the boiler: the database server reads the data every Δτ=30s, and reads the main steam pressure, main steam pressure and Temperature, reheat steam pressure, reheat steam temperature, electrical load, final superheater outlet pressure, final superheater outlet temperature, high temperature reheater outlet temperature, final superheater partition screen inlet temperature, final reheat Real-time measurement data such as the temperature of the installation measuring point of each panel and each tube of the device, the temperature of each tube of each partition panel, the temperature of each panel and each tube of the panel superheater, and the temperature of each panel and each tube of the final superheater.

The second step: Calculate the thermal deviation coefficient of each screen and each tube according to the actual measurement data.

1. Non-uniform coefficient of heat absorption along the width direction of the flue

There is the following relationship between the non-uniform heat absorption coefficient K along the width direction of the flue, the heat deviation coefficient η _r along the furnace _width , and the steam flow deviation coefficient η _l along the furnace width: K ₁ = η _r * η _l

For the last-stage superheater of this boiler, the method of combining test data and theoretical analysis is proposed to determine the distribution of flue gas temperature along the width direction of the furnace.

2. Non-uniform coefficient of heat absorption along the height direction of the flue

Due to the deviation of flue gas flow along the screen height, there is a non-uniform heat absorption coefficient K ₄ along the height direction, and the heat absorption deviation coefficient K ₄ along the height is fitted:

${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; b</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; )</span>$

In the formula: a, b are the selection coefficients; h——the distance between the calculation point and the bottom of the screen; T——the total height of the screen.

3. Calculation of flow deviation on the same screen

The flow deviation of the same screen is defined as the ratio of the flow rate of a certain pipe in a screen to the average flow rate of each pipe in the screen ${\mathrm{\&eta;}}_l=\sqrt{\frac{{\mathrm{\&xi;}}_0}{\mathrm{\&xi;}}}$

In the formula: _ξ0 is the average resistance coefficient; ξ is the calculation pipe resistance coefficient.

第i根管的总折算阻力系数为

If a screen is composed of n parallel pipes, and each pipe is composed of m pipe sections with different inner diameters, for example, the inner diameter and friction coefficient of the i-th pipe are: d _j and

The total converted resistance coefficient of the i-th pipe is

In the formula: d ₀ is the inner diameter of the imaginary unified pipe

Then the average pipe resistance coefficient is ${\mathrm{\&xi;}}_0={\left(\frac{\mathrm{no}}{\sqrt{1/{\mathrm{\&xi;}}_1^z}+\sqrt{1/{\mathrm{\&xi;}}_2^z}+......+\sqrt{1/{\mathrm{\&xi;}}_{\mathrm{no}}^z}}\right)}^2$

The average pipe resistance ΔP ₀ can be obtained as: ${\mathrm{\&Delta;P}}_0=8.0{\mathrm{\&xi;}}_0{g}_0^2{\mathrm{\&upsi;}}_0/{\mathrm{\&pi;}}^2{d}_0^4$

In the formula: υ ₀ is the average specific volume, g ₀ is the flow rate of the average tube panel.

4. Calculation of flow deviation between screens

If the pressure distribution curve of the inlet and outlet headers is known, first set the pressure difference value ΔP′ between the two headers, and according to the position of each screen, the pressure difference ΔP _i of each screen can be obtained. According to the relationship between the flow rate and the pressure difference, The flow rate of each screen can be calculated according to the following formula: $g_i=\sqrt{{\mathrm{\&Delta;P}}_i/{\mathrm{\&Delta;P}}_0}\&Center\; Dot;g_0$

In the formula: g _i ——the flow rate of the calculated tube panel, g ₀ ——the flow rate of the average flow tube panel

Calculate the total flow as: G'=∑g _i , where i=1,...,n, n is the total number of screens;

Investigate the deviation between the calculated flow rate G' and the actual flow rate G, if |(G'-G)/G| does not meet the requirements (the judgment value of different parameter boilers is different, and the value is determined according to the specific boiler), change ΔP' to ΔP according to the following formula "

${\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; G</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}}^{<span\; class="notranslate">\; \&prime;</span>}$

Repeat the above steps until |(G′-G)/G| meets the requirements, and the flow deviation between screens can be obtained: ξ _i = g _i /g ₀

5. Calculation of thermal deviation coefficient:

Thermal deviation coefficient of each screen:

Δi _i ——the enthalpy increase of the calculated screen (i=1,...,n, n is the total number of screens), Δi ₀ ——the average value of the enthalpy increase of each screen;

The above values are considered in the enthalpy calculation formula, and the enthalpy calculation formula refers to the 97 water vapor parameter calculation standard.

Step 3: Calculate the thermal variation coefficient result and save it in the local database.

Service program timing trigger process: Initialize service program interval time. The operation completes the database transaction, and first inserts the latest row of data in the timetable, including the corresponding ID and current time. Calculate the thermal deviation coefficient of the final superheater and final reheater by calling the basic working condition information already collected in the database, and then save the calculated thermal deviation coefficient of the final superheater and reheater to the local relational database middle. By comparing the latest ID number after the completion of this calculation with the ID when the last calculation was completed, it is judged whether the data saving of this calculation process is successful. If not, write the abnormal reason and abnormal time to the text file.

Step 4: Display the basic working condition information and the over-temperature information of the last-stage superheater and final-stage reheater

The display program accesses the database, and calls the basic working condition parameters (electrical load, main steam flow, main steam pressure, main steam temperature, coal mill combination, exhaust gas temperature, etc.) in real time. The display program accesses the database in real time, counts and displays the maximum thermal deviation coefficient, the minimum thermal deviation coefficient, and the number of overheated tubes of the final superheater (these three parameters are obtained from the actual calculated thermal deviation coefficient, and the warning temperature of the pipe is exceeded The total number of tubes is called the number of over-temperature tubes), the maximum thermal deviation coefficient, the minimum thermal deviation coefficient, and the number of over-temperature tubes of the final reheater.

Step 5: Display the thermal deviation curve of the final stage superheater and final stage reheater in real time

The display program accesses the database in real time, calls the latest record in the thermal deviation coefficient table, and displays it in the form of a curve, and calls the display program again at 30-second intervals to refresh the display. When there are multiple measuring points installed on the same screen of the final superheater, there are multiple thermal deviation curves on the display interface, which are distinguished by different colors.

Step 6: Display the thermal deviation history curve of the final stage superheater and final stage reheater

The user selects "thermal deviation history curve" in the display interface, and then selects "pipe", "screen", "start time" and "end time", and the display program can access the database according to the user input conditions, call and display the data result set, and the user can You can view the thermal deviation history curve of this calculation point during this period.

Claims (2)

1. station boiler finishing superheater and final reheater method for online monitoring thermal deviations is characterized in that,

Step is:

Step 1, web page server is connected with user side browser, database server and calculation server respectively; Database server is connected with calculation server, and database server is connected through plant level supervisory information system and Power Plant DCS System or mis system and online measuring point;

Step 2, every boiler finishing superheater and the final reheater online monitoring data of reading at a distance from least 30 seconds of database server;

Step 3, read each pipe outlet wall temperature data of each screen that on-line monitoring collects, import steam temperature data and boiler operatiopn major parameter define according to thermal deviation and directly to calculate the thermal deviation coefficient along furnace width, and wherein, step 3 comprises:

Step 3.1, calculate heat absorption nonuniformity coefficient K along the flue width ₁, K ₁=η _r* η _l, wherein, η _rBe the thermal deviation coefficient along furnace width, η _lBe steam flow deviation factor along furnace width;

Step 3.2, calculate heat absorption nonuniformity coefficient K along the flue height direction ₄,

Wherein, h is the distance that calculation level leaves the screen bottom, and T is the total height of screen;

Step 3.3, calculating are with the screen flow deviation; With the ratio of average every pipe flow in the flow that is defined as a certain pipe in a slice screen that shields flow deviation and this screen, its computing formula is

In the formula, ξ ₀Be average resistance coefficient; ξ is the computer tube resistance coefficient;

${\mathrm{\&xi;}}_0={\left(\frac{n}{\sqrt{1/{\mathrm{\&xi;}}_1^z}+\sqrt{1/{\mathrm{\&xi;}}_2^z}+......+\sqrt{1/{\mathrm{\&xi;}}_n^z}}\right)}^2,$ Wherein, n is the parallel transistor quantity of composition one screen,

(i=1,2 ..., n) be total conversion resistance coefficient of i root pipe;

Wherein, m is the quantity of the different inner diameters pipeline section of a parallel transistor of composition, d ₀Be imaginary unified ips, d _jBe the internal diameter of j root pipeline section,

It is the coefficient of friction of j root pipeline section;

Average tube resistance Δ P ₀For, Wherein, υ ₀Be average specific volume, g ₀Flow for average tube panel;

Flow deviation between step 3.4, calculating screen:

The pressure distribution curve of step 3.4.1, known import and export collection case is set the pressure difference Δ P ' between two collection casees earlier, according to the position at each screen place, can respectively be shielded pressure differential deltap P _i, according to the relation of flow and pressure reduction, can calculate the flow of each sheet screen by following formula:

Wherein, g _iFor calculating the flow of tube panel, g ₀Flow for average tube panel;

Step 3.4.2, total flow G '=∑ g _i, wherein, i=1 ..., n, n are total screen number;

Step 3.4.3, investigate the deviation of calculated flow rate G ' and actual flow G; If | (G '-G)/G| do not meet the demands; Pressing following formula change Δ P ' is Δ P ";

also gets back to step 3.4.1, otherwise gets into next step;

Flow deviation ξ between step 3.4.4, screen _i=g _i/ g ₀

Step 3.5, calculating thermal deviation coefficient:

The thermal deviation coefficient of each sheet screen Δ i _iFor the enthalpy that calculates screen increases, i=1 ..., n, n are total screen number, Δ i ₀For each screen enthalpy increases mean value, the enthalpy computing formula is with reference to 97 water vapour calculation of parameter standards;

Step 4, show the thermal deviation curve of finishing superheater and final reheater in real time.

2. a kind of station boiler finishing superheater as claimed in claim 1 and final reheater method for online monitoring thermal deviations; It is characterized in that online monitoring data described in the step 2 comprises that main steam pressure, main steam temperature, reheated steam pressure, reheat steam temperature, electric load amount, finishing superheater outlet pressure, finishing superheater outlet temperature, high temperature reheater outlet temperature, finishing superheater divide each pipe of each screen of shield inlet temperature, final reheater that measuring point temperature is installed, divide that each sheet of shield is respectively managed the measuring point temperature, the measuring point temperature respectively managed by each screen of pendant superheater and each screen of finishing superheater is respectively managed the measuring point temperature.

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