CN1877193A - Method and apparatus for online monitoring tube wall temperature in boiler overheater and reheater - Google Patents

Abstract

The invention relates to a detecting method used to on-line detect the wall temperature and life consumption of the tubes of boiler over-heater and regenerator. Wherein, it inputs the temperature detected at the entrance external gas temperature detecting point and other parameters of boiler into the computer, to real-time calculate out the wall temperature of each section of tube, to judge if there is over heated and calculate out the life consumption and the smoke temperature difference, while the result will be displayed on the detector and recorded in the database.

Description

Wall temperature on-line monitoring method and device in the boiler superheater reheater stove

Technical field:

The present invention relates to electricity generation boiler and other boiler technology fields, belong to specifically and avoid boiler to be in operation taking place superheater or reheater that a kind of networked on-line monitoring and diagnosis device of pipe overtemperature demolition accident takes place too greatly because of thermal deviation.

Technical background:

In recent years, the many boilers of China, particularly jumbo homemade, import and introduction type electricity generation boiler are in operation pipe overtemperature (tube wall temperature is above the allowable temperature of the used steel) demolition accident of superheater or reheater take place too greatly because of thermal deviation.In power plant, a pipe explosion meeting causes the economic loss of millions of units in the boiler.So-called thermal deviation is too big, is meant that a pipe of superheater or reheater is organized between each sheet tube panel, and has big deviation with caloric receptivity or the steam flow between the pipe in parallel of each root in a slice tube panel.Little its outlet temperature of pipe of big pipe or steam flow that recepts the caloric will raise.The overtemperature tube burst accident will take place when vapor (steam) temperature is elevated to the allowable temperature that makes tube wall temperature surpass the pipe steel.Because the calculating accuracy of thermal deviation is not high in the boiler design, so the overtemperature tube burst accident of superheater and reheater is a lot of in the boiler of power plant and other purposes.

Summary of the invention:

The present invention relates to a kind of monitoring method, be specially adapted to the interior wall temperature of stove, cigarette temperature deviation and the life consumption of online each section of detection boiler superheater reheater pipe.

Superheater reheater regional area pipe is a boiler because of booster takes place overtemperature (wall temperature surpasses the allowable temperature of used metal material in the pipe stove), particularly the major accident reason of station boiler.Boiler generation superheater reheater overtemperature tube burst needs blowing out repairing at least 72 hours, and economic loss is huge.

Because technical complexity, can't in stove, install a large amount of pipe wall temperature measuring points, therefore before used monitoring method be at steam temperature measuring point outside the outlet installing stove of a part of pipe of boiler width, calculate by rule of thumb that the interior pipe wall temperature of stove has or not overtemperature.The shortcoming of this method is: (one) because the structure of each boiler and design parameter such as cigarette temperature, plume, steam pressure and steam flow rate all have difference, therefore by rule of thumb from stove outside in the steam temperature reckoning stove wall temperature error too big; (2) be difficult to accomplish that the outer temperature point of stove is just in time on the pipe of the highest temperature; Therefore (three) measured value does not have the record of system, can not calculate the life consumption of every section pipe, time of its inefficacy of expectability not, accomplishes real " repair based on condition of component " and " life-span monitoring ".

Shortcoming at above-mentioned prior art existence, characteristics of the present invention provide a kind of practicality, mobile and the flue gas HEAT TRANSFER LAW based on steam, gather the on-line monitoring method that relevant data calculated and showed and write down the gentle residual lifes of all pipeline section stove inwalls of superheater reheater in real time.

The key of loss mathematic(al) expectation is the interior wall temperature of the stove of pipe.Wall temperature is decided by following each factor in the stove of section of a pipe:

1. the steam flow in managing;

2. flue gas is to the various radiant heat transfer thermic loads of this pipe;

3. flue gas is to the convection heat transfer' heat-transfer by convection thermic load of this pipe;

4. tube wall is to the heat transfer coefficient of steam.

Because boiler is in operation and has various bias factors, as heat absorption deviation and steam flow deviation along each sheet screen of width; The length variation and the steam flow deviation of shielding each root pipe with a slice; And the radiant heat transfer and the convection heat transfer' heat-transfer by convection deviation of shielding each root pipe with a slice, therefore pipe is organized the outlet mean temperature of each sheet screen and all is different with the outlet temperature that a slice is shielded each root pipe.If these deviations in service will make some pipe generation overtemperature even booster greater than the numerical value of being considered in the design.This also is the reason in the design of heavy duty boiler generation overtemperature tube burst of some introduction types and import.

Description of drawings:

Fig. 1 is a systematic schematic diagram of the present invention.

Boiler real-time data base--data acquisition module---server (steam temperature computing module in the stove; Wall temperature computing module in the stove; Cigarette temperature deviation computing module; The life consumption computing module)--on-line monitoring real-time data base---record and demonstration

The specific embodiment:

This also is the reason in the design of heavy duty boiler generation overtemperature tube burst of some introduction types and import.

The present invention implements by following technical measures.

1. the various structured datas of monitoring pipe group are imported software for calculation, for example the internal diameter of the section length of the pipe number in the tube panel number of a pipe group, a slice screen, every pipe, caliber, material, import and export collection case and structure etc.;

2. with the outer temperature point of original stove on the boiler or install the outer temperature point of a small amount of stove additional, (for example per minute once) gathers these data and necessary boiler operating parameter (as the steam flow of boiler, pressure etc.) by software for calculation at regular intervals;

According to these measurement data in conjunction with the structured data of being stored, at the steam flow Di of pipeline section that line computation is calculated (kg/h);

$\mathrm{Di}=\sqrt{\mathrm{\ξo}/\mathrm{\ξ}}*\sqrt{\mathrm{vpj}/\mathrm{vi}}*\mathrm{Kl}---(\mathrm{kg}/h)$

In the formula: ξ o; The resistance coefficient of ξ--average tube; The resistance coefficient of computer tube

Vpj; The steam specific volume of vi--average tube; The steam specific volume of computer tube

Kl----calculates the flow deviation coefficient of screen

The steam enthalpy of pipeline section that line computation is calculated increase Δ i and calculation level vapor (steam) temperature t (℃);

$\mathrm{\Δi}=\frac{3.6K_r{K}_h{E}_{0}d{l}_i}{D_i}(\mathrm{\Σ}{q}_f{p}_i+q_p{\mathrm{\ξ}}_{1i}+q_d{\mathrm{\ξ}}_{2i})---(\mathrm{kJ}/\mathrm{kg})$

t＝tj+ΣΔi/R 〔℃〕

In the formula: Kr, Kh----width and height heat absorption deviation coefficient;

Li, E ₀, d---computer tube segment length, area conversion factor and tube outer diameter (m);

Before the qf, pi----screen, between screen back, screen, the screen radiant heat load (W/m of smoke-box down ²) and deviation factor;

Qp, qd, ξ 1i, gas radiation and advection heat load (W/m between ξ 2i---screen ²) and deviation factor;

Di,----calculates the steam flow (kg/h) of pipeline section;

Tj----computer tube inlet temperature (℃);

R----steam specific heat (kJ/kg/ ℃)

5. at the radiant heat of pipeline section that line computation is calculated load qf, advection heat load qd and total heat duties qm (W/m ²);

qf＝5.7*10 ^-8a*(ab+1)(T ⁴-Tb ⁴)/2 (W/m ²)

qd＝α(T-Tb) (W/m ²)

qm＝Kr*Kh*(qf+qd) (W/m ²)

In the formula: before a, ab----screen, between screen back, screen, the screen blackness of smoke-box down; The blackness of tube surface;

T; Before the Tb---screen, between screen back, screen, the screen temperature of flue gas down; The temperature of tube surface (K);

α----flue gas is to the coefficient of convective heat transfer (W/m of pipe ²H);

6. in the stove inner tubal wall temperature t of pipeline section that line computation is calculated _b(℃):

In the formula; Vapor (steam) temperature in the t------calculation level pipe, (℃);

J, hot current stabilizing factor of β----and caliber ratio;

δ, λ----pipe thickness (m) and metal heat-conducting coefficient, (W/ (mK));

α ₂Steam is to the exothermic coefficient (W/ (m of tube wall in----pipe ²K)).

The basis that life-span calculates is the accuracy of calculation of Wall Temperature in the stove.Since the boiler superheater reheater conduct heat and the deviation of steam aspect flowing very big, the temperature operating mode of each root pipe all was very different during each sheet tube panel and a slice were shielded.Be difficult to accomplish accurately calculate wall temperature in the stove in the general designing and calculating.Of the present invention in line computation, radiation between real-time service data such as steam flow, tube length, convection heat transfer' heat-transfer by convection, screen, screen previous irradiation, screen back radiation have been adopted, and width and 8 bias factors such as heat absorption highly, so the interior wall temperature of each point stove that calculates gained has very high accuracy.

Utilize the outer steam temperature measuring point of original pipe outlet stove on the boiler, or install the outer temperature point of a spot of stove additional, every certain time interval (for example one minute), database by boiler or additive method are gathered measured data and minority operational factor (as the boiler export steam flow, superheater and reheater outlet steam pressure and temperature etc.), just can be with steam temperature in several thousand the stove in online all pipeline sections of calculating each sheet screen of software for calculation, wall temperature and life consumption distribute and cigarette temperature deviation, make chart, record in addition, and show on the computer screen in all LANs.

Advantage of the present invention is: (one) does not add measuring point or needs only the outer measuring point of the stove that increases minute quantity; (2) at regular intervals together In time, shows and records wall temperature, life consumption and cigarette temperature deviation in the stove of all pipeline sections; (3) computational methods accuracy height calculates institute The wall temperature value error that gets is little; (4) just report to the police if any the overtemperature pipeline section; (5) have demonstration, record, statistics and history and recollect merit Can; (6) can instruct operation adjustment, maintenance and technological transformation.

Claims (2)

1. wall temperature and life consumption on-line monitoring method in the boiler superheater reheater stove is characterized by the outer temperature point data of a spot of stove and boiler operatiopn data are combined and import computer simultaneously, calculate in real time with the software for calculation of high accuracy.All pipes of superheater reheater that calculate distribute along wall temperature, cigarette temperature deviation and life consumption in the stove of each pipeline section of length, on computers by regular hour rule statistics, demonstration and record, reach on-line monitoring and have or not the overtemperature situation, instruct operation, the purpose of repair based on condition of component and life-span monitoring.

2. according to wall temperature and life consumption on-Line Monitor Device in a kind of boiler superheater reheater stove of claims 1 described method, it is by temperature point (1), temperature point measurement data and service data data acquisition software, (2) server end computer, (3) client computer (4) and online monitoring data storehouse (5) constitute.It is characterized by server end computer (2) wall temperature, life consumption and cigarette temperature deviation in the stove of each point that line computation is monitored simultaneously; Institute's data monitored can go up the requirement that shows and write down power plant's high-tech management of accomplishing repair based on condition of component and life-span monitoring in database (5) in each client computer (4) simultaneously.

Images