CN103697958A - Real-time measurement method of mass flow of saturated steam of drum outlet of coal-fired unit - Google Patents

Abstract

The invention provides a real-time measurement method of the mass flow of the saturated steam of the drum outlet of a coal-fired unit. The real-time measurement method comprises step 1, establishing an overheated channel structure parameter database according to the operation design discipline of a boiler; step 2, combining with the information of an on-site plant-level monitoring information system server to perform real-time calculation on physical parameters of working mediums arranged in an overheated channel and at the drum outlet and the high pressure cylinder inlet at the current time k according to a working medium physical parameter library covering all conditions; step 3, establishing an overheated channel working medium mass balance model and combining with the main steam mass flow recorded in the plant-level monitoring information system server to calculate the mass flow Dbh of the saturated steam of the drum outlet. The real-time measurement method can be used for performing online measurement on the mass flow of the saturated steam of the drum outlet and can also be used for performing online estimation on the flue gas energy of the combustion chamber outlet and the real-time combustion power of the boiler.

Description

The real time measure method of coal-fired unit drum outlet saturated vapour mass rate

Technical field

The present invention relates to technical field of power generation, particularly, relate to a kind of real time measure method of the coal-fired unit drum outlet saturated vapour mass rate based on working medium mass balance in over-temperature channel.

Background technology

The saturated vapour mass rate of most of subcritical coal-fired unit drums outlets without direct measurement mechanism, but by the pressure-measuring-point of governing stage before and after high pressure cylinder, obtain governing stage front and back pressure reduction, after calculating, third party software obtains main steam mass rate, then be directly equivalent to the saturated vapour mass rate of drum outlet, after on-the-spot plant level supervisory information system server record, be uploaded to monitoring interface.

Yet the saturated vapour mass rate of drum outlet and the main steam mass rate of high pressure cylinder entrance have larger deviation in coal-fired unit.Main cause is that the over-temperature channel that connects drum outlet and high pressure cylinder entrance is that a volume is large, complex structure and operate the intermediate link of operating mode frequent variations, the dynamic perfromance of this intermediate link has directly caused the variation of drum outlet saturated vapour mass rate in time domain, to lag behind the variation that high pressure cylinder entrance goes out main steam mass rate, for example, for 300MW unit, be about 1-2 minute this retardation time, and in load alternation process, due to the impact of over-temperature channel heat interchanger and drum air-capacitor, dynamic deviation is also larger.In fact, the real-time calculating meeting of shortage drum outlet saturated vapour mass rate directly affects boiler side control (as drum three momentums are controlled) quality.

The retrieval of prior art is found, Chinese Patent Application No. 201210360382.X, open day 2012-12-26, recorded a kind of flexible measurement method of high pressure cylinder entrance main steam mass rate, the method be take Bei Nuli energy conservation equation as basis, utilize high pressure cylinder front and back first stage pressure measuring point, calculate in real time the mass rate of main steam; But this technology is only applicable to the calculating of the main steam flow in stable state when load, and to be defaulted as knownly, but in actual production process, often can only obtain the pressure and temperature of working medium, there is no density measurement.

Summary of the invention

For defect of the prior art, a kind of real time measure method that the object of this invention is to provide coal-fired unit drum outlet saturated vapour mass rate based on working medium mass balance in over-temperature channel, the method has been considered the dynamic perfromance of working medium mass change in over-temperature channel heat interchanger, take working medium physical parameter database and boiler side key equipment structural parameters database (in the present invention specifically refer to over-temperature channel structural database) for basic, calculate in real time the rate of change of working medium quality in over-temperature channel heat interchanger; Finally based on this rate of change and high pressure cylinder porch main steam mass rate measuring point accurate-metering drum outlet saturated vapour mass rate.

For realizing above object, the invention provides a kind of real time measure method of coal-fired unit drum outlet saturated vapour mass rate, the method concrete steps comprise:

Step 1: according to boiler operatiopn design discipline, set up over-temperature channel structural parameters database: described over-temperature channel structural parameters database comprises following information: over-temperature channel pipeline is along the total length L of Working fluid flow direction, and total length L is divided into the isometric short tube of n section; Over-temperature channel is along the heat exchanger tube sectional area distribution A (i) of Working fluid flow direction, the i.e. sectional area of i section short tube; The drum pressure p inscribing when plant level supervisory information system server real-time data base reads this _qb, superheated vapor pressure p _gr, superheat steam temperature T _gr, superheated vapor mass rate D _gr, Temperature of Working and the pressure at all measuring points place in over-temperature channel;

Step 2: according to the working medium physical parameter database that can cover full operation operating mode, the working medium state parameter of uploading in conjunction with on-the-spot plant level supervisory information system server is temperature, pressure, calculates in real time current time k, drum outlet saturated-steam temperature T _qb, each section of short tube Temperature of Working T of over-temperature channel _gzand pressure p (i) _gz(i), heat interchanger at different levels working medium density p everywhere _gz(i);

Step 3: set up over-temperature channel working medium mass budget model and calculate the working medium mass change in over-temperature channel, and in conjunction with the superheated vapor mass rate D being obtained by measuring point _gr, calculate in real time drum exit saturated vapour mass rate D _bh;

With moment t ₀for time zero, use the real-time computing technique of drum outlet saturated vapour mass rate, take time order and function as order, determine respectively t ₀, t ₀+ Δ t, t ₀+ 2 Δ t ..., t ₀during+n Δ t, inscribe corresponding saturated vapour mass rate D _bh(t ₀), D _bh(t ₀+ Δ t), D _bh(t ₀+ 2 Δ t) ..., D _bh(t ₀and draw D+n Δ t), _bhtime dependent trend curve.

Preferably, in step 2, each section of short tube Temperature of Working T of described over-temperature channel _gz(i) pressure p _gz(i) by the temperature T at over-temperature channel (take drum outlet as starting point, high pressure cylinder entrance is terminal) interior working medium measuring point place _gzand pressure p _gzlinear calculating obtains.

Preferably, in step 2, described heat interchanger at different levels working medium density p everywhere _gz(i) by each section of Temperature of Working T of current time k _gzand pressure p (i) _gz(i) calculate and obtain.

Preferably, in step 3, described over-temperature channel working medium mass budget model is specially:

$\frac{\mathrm{dM}}{\mathrm{dt}}=D_{\mathrm{bh}}-D_{\mathrm{gr}}$

$\frac{\mathrm{dM}}{\mathrm{dt}}\stackrel{\·}{=}M\left(k\right)-M(k-1)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ρ}}_{\mathrm{gz}}{\left(i\right)}^{\left(k\right)}A\left(i\right)\·0.1-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ρ}}_{\mathrm{gz}}{\left(i\right)}^{(k-1)}A\left(i\right)\·0.1$

$D_{\mathrm{bh}}=\frac{\mathrm{dM}}{\mathrm{dt}}+D_{\mathrm{gr}}$

In formula:

K is current time;

K-1 is last sampling instant;

M accumulates working medium gross mass in superheater system;

D _bhfor superheater system input working medium quality is drum saturated vapour flow;

D _grfor superheater system output working medium quality is main steam flow;

ρ _gz(i) ^(k)for current time k, the density of working medium in i section heat interchanger short tube;

ρ _gz(i) ^(k-1)for a upper sampling instant k-1, the density of working medium in i section heat interchanger short tube;

A (i) is the sectional area of i section heat interchanger short tube;

Dt is the differential of time.

The present invention can be for the on-line metering of coal-fired unit drum outlet saturated vapour mass rate, if be aided with suitable model further measure other heat transmission equipments as cross caloric receptivity, economizer caloric receptivity and the air preheater heat exchange models etc. of the passage of heat again, it can also be for furnace outlet flue gas energy and the real-time combustion power On-line Estimation of boiler.

Compared with prior art, the present invention has following beneficial effect:

With directly going out main steam flow with high pressure cylinder entrance and replace the method for drum outlet saturated vapour flow to compare in the past, the method has provided the soft measured value of the outlet of the drum under working medium mass conservation relation saturated vapour mass rate in meeting over-temperature channel, compares original scheme more accurate.In each saturated vapour mass flow measurement constantly, all working medium in over-temperature channel heat interchanger and high pressure cylinder entrance main steam measuring point information are united, obtain the saturated vapour mass rate of inscribing when corresponding.At next constantly, the mass conservation relation based on same can be measured saturated vapour mass rate, and it can reflect that with the difference of previous moment saturated vapour mass rate drum exports saturated vapour mass rate and measures over time truly, accurately.As a kind of flexible measurement method, the required measuring point data of saturated vapour mass rate all directly reads from plant level supervisory information system server real-time data base, the on-the-spot instrument that does not need additionally to increase measuring point, probe or costliness, only need in existing control system, increase corresponding software module, cost is low.The soft measurement of saturated vapour mass rate is that iteration is carried out, and only needs to preserve the result of a upper sampling instant (being the k-1 moment) in iteration, and EMS memory occupation is few, real-time.Simultaneously, by the working medium physical parameter database that can cover full operating mode, the method can accurately be followed the tracks of the variation of saturated vapour mass rate under different operating modes and loading condiction, the foundation of device structure parameter database makes the method can be generalized to very easily in the different boiler machine set control system of other device structures, for instructing burning adjusting and the optimal control of boiler, further improve whole unit performance, expanded application scope is wide.

Accompanying drawing explanation

By reading the detailed description of non-limiting example being done with reference to the following drawings, it is more obvious that other features, objects and advantages of the present invention will become:

Fig. 1 is boiler flue heat-exchange device distribution schematic diagram;

Fig. 2 over-temperature channel working medium actual internal area distributes;

The output of Fig. 3 working medium physical parameter database;

The soft measured value temporal evolution of Fig. 4 drum outlet saturated vapour mass rate curve map.

Embodiment

Below in conjunction with specific embodiment, the present invention is described in detail.Following examples will contribute to those skilled in the art further to understand the present invention, but not limit in any form the present invention.It should be pointed out that to those skilled in the art, without departing from the inventive concept of the premise, can also make some distortion and improvement.These all belong to protection scope of the present invention.

As shown in Figure 1, the coal-fired unit of certain 300MW of take is example, this natural circulation boiler model is HG-1025/17.3-WM18 type, and boiler is subcritical, Natural Circulation, resuperheat, " W " flame combustion mode, two arch list burner hearth, balanced ventilation, afterbody twin flue, gas baffle temperature adjustment, dry ash extraction, outdoor layout, all steel frame suspension type drum boiler.

The present embodiment provides a kind of real time measure method of the coal-fired unit drum outlet saturated vapour mass rate based on working medium mass balance in over-temperature channel, and concrete steps comprise:

Step 1: according to boiler operatiopn rules, set up major equipment structural parameters database, this database comprises following preset parameter information:

Superheater pipeline is along Working fluid flow direction as shown in solid arrow direction in Fig. 1, and its overall length is 396.7m, and total length L is divided into 3967 sections of isometric short tubes, and every section of short tube length setting is 0.1 meter;

Heat interchanger is along the heat exchanger tube sectional area distribution A (i) of Working fluid flow direction, i.e. the sectional area of i section short tube, and each major equipment sectional area A (i) distributes as shown in Figure 2;

From plant level supervisory information system server real-time data base, read relevant real time data, under the operating condition at current time k, main real time data is as follows:

Drum pressure 17.6MPa, high pressure cylinder entrance go out main steam flow 233.6kg/s, each section of short tube Temperature of Working of superheater at different levels (first 387.9 ℃ of superheater one-level attemperator, after superheater one-level attemperator 379.1 ℃, first 472.9 ℃ of superheater secondary attemperator, after superheater secondary attemperator 472.0 ℃, superheater outlet is 538.7 ℃) and pressure (superheater entrance is 17.459MPa, and superheater outlet is 16.605MPa).

Step 2: according to the working medium physical parameter database (Output rusults as shown in Figure 3) that can cover all operations were operating mode, the working medium state parameter (temperature, pressure) of uploading in conjunction with on-the-spot plant level supervisory information system server, calculates the saturated-steam temperature of k drum outlet constantly T in real time _qb(by current time k drum pressure p _qbcalculating acquisition), each section of short tube Temperature of Working T of over-temperature channel _gzand pressure p (i) _gz(i) (by the temperature T at measuring point place in over-temperature channel _gzand pressure p _gzlinear calculating acquisition), heat interchanger at different levels working medium density p everywhere _gz(i) (by each section of Temperature of Working T of current time k _gzand pressure p (i) _gz(i) calculate and obtain).

Described working medium physical parameter database, refer to can parallel calling according to having of water and steam thermodynamic properties industry formula (IAPWS-IF97) exploitation, the feature such as region automatic discrimination, batch processing computing for the working medium physical parameter database in line computation, can list of references: Wang Xuhui, in red, Hui Zhaoyu, Yuan Jingqi, for the working medium physical parameter database of thermoelectricity gamut emulation, control engineering, 2011; 18:131-133.

Step 3: set up over-temperature channel working medium mass budget model and calculate the working medium mass change in over-temperature channel, in conjunction with obtained superheated vapor mass rate D by measuring point _gr, calculate in real time drum exit saturated vapour mass rate D _bh;

The present embodiment interval of delta t=5s access time, calculates t=t ₀for drum outlet saturated vapour mass rate in 24 hours of time zero, at moment t=t ₀, t=t ₀+ 5, t=t ₀+ 10 ..., t=t ₀+ 86400, respectively repeat steps 1-3, obtain the soft measured value D of corresponding drum outlet saturated vapour mass rate _bh(t ₀), D _bh(t ₀+ 5), D _bh(t ₀+ 10) ..., D _bh(t ₀+ 86400); The soft measured value temporal evolution of drum outlet saturated vapour mass rate curve map as shown in Figure 4.

In the present embodiment step 3, described over-temperature channel working medium mass budget model is

$\frac{\mathrm{dM}}{\mathrm{dt}}=D_{\mathrm{bh}}-D_{\mathrm{gr}}$

$\frac{\mathrm{dM}}{\mathrm{dt}}\stackrel{\·}{=}M\left(k\right)-M(k-1)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ρ}}_{\mathrm{gz}}{\left(i\right)}^{\left(k\right)}A\left(i\right)\·0.1-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ρ}}_{\mathrm{gz}}{\left(i\right)}^{(k-1)}A\left(i\right)\·0.1$

$D_{\mathrm{bh}}=\frac{\mathrm{dM}}{\mathrm{dt}}+D_{\mathrm{gr}}$

In formula,

K is current time;

K-1 is the moment of last sampling;

M accumulates working medium gross mass in superheater system;

D _bhfor superheater system input working medium quality (being drum saturated vapour mass rate);

D _grfor superheater system output working medium quality (being main steam mass rate);

ρ _gz(i) ^(k)for current time k, the density of working medium in i section heat interchanger short tube;

ρ _gz(i) ^(k-1)for a upper sampling instant k-1, the density of working medium in i section heat interchanger short tube;

A (i) is the sectional area of i section heat interchanger short tube;

Dt is the differential of time.

The present invention can be for the on-line metering of coal-fired unit drum outlet saturated vapour mass rate, its measurement result can directly apply to drum feed water three momentums control in correction to outlet saturated vapour mass rate.If be aided with suitable model further measure other heat transmission equipments as cross caloric receptivity, economizer caloric receptivity and the air preheater heat exchange models etc. of the passage of heat again, it can also be for furnace outlet flue gas energy and the real-time combustion power On-line Estimation of boiler.

Above specific embodiments of the invention are described.It will be appreciated that, the present invention is not limited to above-mentioned specific implementations, and those skilled in the art can make various distortion or modification within the scope of the claims, and this does not affect flesh and blood of the present invention.

Claims (3)

1. a real time measure method for coal-fired unit drum outlet saturated vapour mass rate, is characterized in that, the method concrete steps comprise:

Step 1: according to boiler operatiopn design discipline, set up over-temperature channel structural parameters database; Described over-temperature channel structural parameters database comprises following information: over-temperature channel pipeline is along the total length L of Working fluid flow direction, and total length L is divided into the isometric short tube of n section; Over-temperature channel is along the heat exchanger tube sectional area distribution A (i) of Working fluid flow direction, the i.e. sectional area of i section short tube; The drum pressure p inscribing when plant level supervisory information system server real-time data base reads this _qb, superheated vapor pressure p _gr, superheat steam temperature T _gr, superheated vapor mass rate D _gr;

Step 2: according to the working medium physical parameter database that covers full operation operating mode, the working medium state parameter of uploading in conjunction with on-the-spot plant level supervisory information system server is temperature, pressure, calculates in real time current time k, drum outlet saturated-steam temperature T _qb, each section of short tube Temperature of Working T of over-temperature channel _gzand pressure p (i) _gz(i), heat interchanger at different levels working medium density p everywhere _gz(i);

Step 3: set up over-temperature channel working medium mass budget model and calculate the working medium mass change in over-temperature channel, and in conjunction with the superheated vapor mass rate D being obtained by measuring point _gr, calculate in real time drum exit saturated vapour mass rate D _bh;

With moment t ₀for time zero, use the real-time computing technique of drum outlet saturated vapour mass rate, take time order and function as order, calculate respectively t ₀, t ₀+ Δ t, t ₀+ 2 Δ t ..., t ₀during+n Δ t, inscribe corresponding saturated vapour mass rate D _bh(t ₀), D _bh(t ₀+ Δ t), D _bh(t ₀+ 2 Δ t) ..., D _bh(t ₀and draw D+n Δ t), _bhtime dependent trend curve;

In step 3, described over-temperature channel working medium mass budget model is specially:

$\frac{\mathrm{dM}}{\mathrm{dt}}=D_{\mathrm{bh}}-D_{\mathrm{gr}}$

$\frac{\mathrm{dM}}{\mathrm{dt}}\stackrel{\·}{=}M\left(k\right)-M(k-1)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ρ}}_{\mathrm{gz}}{\left(i\right)}^{\left(k\right)}A\left(i\right)\·0.1-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ρ}}_{\mathrm{gz}}{\left(i\right)}^{(k-1)}A\left(i\right)\·0.1$

$D_{\mathrm{bh}}=\frac{\mathrm{dM}}{\mathrm{dt}}+D_{\mathrm{gr}}$

In formula: k is current time;

K-1 is a upper sampling instant;

M accumulates working medium gross mass in superheater system;

D _bhfor superheater system input working medium quality is drum saturated vapour mass rate;

D _grfor superheater system output working medium quality is main steam mass rate;

ρ _gz(i) ^(k)for current time k, the density of working medium in i section heat interchanger short tube;

ρ _gz(i) ^(k-1)for a upper sampling instant k-1, the density of working medium in i section heat interchanger short tube;

A (i) is the sectional area of i section heat interchanger short tube;

Dt is the differential of time.

2. the real time measure method of coal-fired unit drum outlet saturated vapour mass rate according to claim 1, is characterized in that, in step 2, described working medium physical parameter database is by IF97 Formula.

3. the real time measure method of coal-fired unit drum outlet saturated vapour mass rate according to claim 1 and 2, is characterized in that, in step 2, and each section of short tube power pressure p of described over-temperature channel _gz(i) by the temperature T at measuring point place in over-temperature channel _gzand pressure p _gzlinear calculating obtains.

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