JPH0799245B2 - Boiler start control device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a boiler start-up control device, and more particularly to a boiler start-up control device suitable for realizing good start-up characteristics.

[Conventional technology]

The start-up of the boiler device is carried out in the order of starting the temperature rise and pressure increase of the boiler by supplying fuel from the fuel system to ignite the burner after completion of ignition preparation such as water filling and furnace purge.

[Problems to be Solved by the Invention]

However, in the conventional boiler start-up control device, no consideration has been given to how to reach the preset steam temperature target value and steam pressure target value in a short time with a minimum amount of fuel input. Therefore, there is a drawback that the amount of fuel input is large, or it takes time to start the boiler, resulting in poor efficiency as a boiler.

The object of the present invention is to eliminate such drawbacks of the prior art,
An efficient boiler start-up control device is provided.

[Means for Solving the Problems]

To achieve the above object, the present invention provides: a superheater; a first valve for extracting steam to the superheater;
The present invention is directed to a boiler start-up control device provided with a second valve for extracting steam from the superheater to a source other than its main supply destination and a third valve for controlling the fuel supply amount to the furnace.

And a temperature detector for detecting the steam temperature of the boiler predetermined part, a pressure detector for detecting the steam pressure of the boiler predetermined part, the steam temperature detected by the temperature detector and the steam detected by the pressure detector A target value calculator that outputs the boost rate target value and the temperature rise rate target value based on the pressure, the pressure rise target value, the temperature rise target value, the pressure rise limit value, and the temperature rise limit value, and the boost rate target value and the temperature rise rate. An optimum manipulated variable calculator for calculating the opening of the first valve, the second valve, and the third valve for realizing the target value under the condition of the minimum fuel input amount is provided. It is a thing.

Further, according to the present invention, the optimum manipulated variable calculator is configured to cause the first valve, the second valve, and the third valve to operate based on the boost rate target value and the temperature increase rate target value, and the actually measured steam pressure and steam temperature. It is characterized in that a parameter adaptive corrector for correcting a parameter when calculating the opening of the valve is provided.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a boiler start-up control device according to an embodiment. In the figure, 1 is a water wall that constitutes the furnace wall of the boiler furnace, 2
Is a burner, and 3 is a boiler water supply pump for supplying water to the water wall 1. Reference numeral 4 denotes a steam separator, which separates a steam mixture generated by heating the feed water by the water wall 1 into steam and moisture. 5 is a superheater for superheating the steam from the steam separator 4, 6
Is a economizer that preheats the water supply from the water supply pump 3, and 7 is a turbine that is connected to a generator. A turbine control valve 8 is interposed between the superheater 5 and the turbine 7 and controls the amount of steam from the superheater 5 to the turbine 7.

Reference numeral 9 is a superheater bypass valve that allows steam from the steam separator 4 to escape to a condenser or the like. This superheater bypass valve 9 has a large amount of low-temperature steam flowing into the superheater 5 at the time of startup, and
When the temperature rise of the outlet steam is hindered, it has a function of releasing such low temperature steam to reduce the amount of steam passing through the superheater 5 and increasing the outlet steam temperature of the superheater 5.

Reference numeral 10 is a turbine bypass valve that allows steam generated from the outlet of the superheater 5 to escape to a condenser or the like. This turbine bypass valve
10 has a function of releasing generated steam when the temperature of the generated steam has not been raised or boosted to such an extent that the generated steam can be ventilated to the turbine 7, and when the boiler load is low even after ventilation to the turbine 7. Since it becomes difficult to control the steam pressure by the amount of fuel input, it also has a function of contributing to the steam pressure control by letting the generated steam escape in this region.

11 is a fuel flow control valve, 12 is a steam pressure detector, 13 is a steam temperature detector, 14 is a target value calculator, 17 is a target value setting device for setting a steam pressure boosting target value, and 18 is a steam temperature raising target. Target value setter to set the value, 19 is a limit value setter to set the temperature rise rate limit value, 20 is a limit value setter to set the boost rate limit value, 25 is a steam temperature detector, 26 is a feed water temperature detection , 37 is an optimum manipulated variable calculator, 38 and 39 are integrators, 40 and 41 are signal subtractors, and 42 is a parameter adaptive modifier.

First, the definition of symbols used in the specification of the present invention will be described.

A: heat transfer area [m ^2] G _WW superheater 5: water supply amount of the water wall 1 [kg / S] G _e: amount of evaporation of the water wall 1 [kg / S] h '(P): saturated water Enthalpy [kcal / kg] (Function of P) h ″ (P): Saturated steam enthalpy [kcal / kg] (Function of P) H (P, T): Outlet steam enthalpy of superheater 5 [kcal / kg]
(Function of P, T) H _i (P, T _i ): Inlet steam enthalpy of superheater 5 [kcal / k
g] (function of P, T _i ): Rate of change of steam enthalpy at outlet of superheater 5 [kcal / k
gs] H _WW : Outlet fluid enthalpy of water wall 1 [kcal / kg] H _ECO (P, T _ECO ): Outlet water supply enthalpy of economizer 6 [kcal
/ kg] (function of P, T _ECO ) P: Steam pressure [kg / cm ² abs]: Rate of steam pressure change [kg / cm ² s] Q (x): Heat absorption of water wall 1 [kcal / S ] (Function of x) T: outlet steam temperature of superheater 5 [° C]: outlet steam temperature change rate of superheater 5 [° C / S] T _ECO : outlet water supply temperature of economizer 6 [° C] T _i : Inlet steam temperature of superheater 5 [° C] T _s (P): Saturated steam temperature [° C] (function of _P ) V _P : Volume in superheater 5 [m ³ ] V _T : Total volume of boiler steam part [ m ^3] x: fuel input amount [kg / S] x _min: fuel input amount lower limit value [kg / S] y: passing the steam flow [kg / S] y _min of the turbine bypass valve 10: passage of the turbine bypass valve 10 Minimum steam flow rate [kg / S] Z: Amount of steam passing through superheater bypass valve 9 [kg / S] U: Average heat transmission coefficient of superheater 5 [kcal / m ² s ° C] υ (P, T): Average vapor specific volume in superheater 5 [m ³ / kg] (P,
Function of T) Θ (x): Fuel gas temperature [° C] at inlet of superheater 5 (function of x) (∂T / ∂H) _{P, T} : Partial differential coefficient of steam temperature with respect to enthalpy (function of P, T) ) (∂P / ∂ρ) _{P, T} : Partial differential coefficient of steam pressure density (function of P, T) Among the above values, A, V _P , V _T are determined by the structure of the boiler, and G _WW , x _min and y _min are determined by the boiler design. See h '
(P), h "(P), H (P, T), H _i (P, T _i ), H _ECO (P,
T _ECO ), T _s (P), (∂T / ∂H) _{P, T} , (∂P / ∂
ρ) The functional form of _{P, T} , υ (P, T) is determined by the physical properties of water, and can be determined by using the steam table of the Japan Society of Mechanical Engineers, etc., as is known.

Although Q (x) and Θ (x) are complex functional forms that are affected by various factors due to their properties, they can be put to practical use if they are handled in a functional form that arranges the fuel injection amount x that has the largest contribution empirically. It is known that the value of U is also empirically known.

The relational expressions that hold between these variables will be described below.

For the superheater 5, it is known from the energy balance that the following equation holds.

= Υ (P, T) / V _P・ (∂T / ∂H) _{P, T}・ [y {H _i (P,
T _i ) −H (P, T)} + AU {Θ (x) −T}] (1) The following equation holds as the mass balance of the boiler steam section.

= (∂P / ∂ρ) _{P, T}・ 1 / V _T {G _e −y−Z} …… (2) where G _e = G _WW [(H _WW −h ′ (P)] / [h ″ (P) −h ′
(P)] (3) H _WW = H _ECO (P, T _ECO ) + Q (x) / G _WW (4) (2), (3), (4) Desired.

= 1 / V _T・ (∂P / ∂ρ) _{P, T}・ [−y−Z + {Q (x)
/ (H ″ (P) −h ′ (P)} + G _WW {H _ECO (P, T _ECO )
−h ′ (P)} / h ″ (P) −h ′ (P)] (5) Here, the parameters K _{1 to} K ₆ that do not depend on x, y, Z are defined as follows. .

K ₁ = {υ (P, T) / V _P・ (∂T / ∂H) _{P, T} } ・ {H (P,
T) −H _i (P, T _i )} (6) K ₂ = {υ (P, T) / V _P・ (∂T / ∂H) _{P, T} } Uα ……
(7) K ₃ = {υ (P, T) / V _P・ (∂T / ∂H) _{P, T} } UαT ……
(8) K ₄ = 1 / V _T・ (∂P / ∂ρ) _{P, T} …… (9) K ₅ = 1 / V _T・ (∂P / ∂ρ) _{P, T}・ (1 / {h ″ (P) −h ′
(P)} …… (10) K ₆ = 1 / V _T・ (∂P / ∂ρ) _{P, T}・ G _WW {h ′ (P) −H
_ECO (P, T _ECO )} / {h ″ (P) −h ′ (P)} …… (1
1) At this time, K _{1 to} K ₆ are detected from the detectors 12, 13, 25, 26 by P,
If signals f, g, p, and q corresponding to T, T _i , and T _ECO are input, other variables and function forms are known as described above, and can be calculated immediately.

Summarizing the equations (1) and (5), the definitions of x _min and y _min , and the condition that Z is positive, the fuel injection amount x, the turbine bypass valve 10 passing flow rate y, and the superheater bypass valve 9 passing flow rate Z are as follows. Satisfy the relational expression.

= −K ₁ y + K ₂ Θ (x) −K ₃ …… (12) ≦ K ₄ y + K ₅ Q (x) −K ₆ …… (13) x ≧ x _min …… (14) y ≧ y _min …… (15) And Z = 1 / K ₄ · {K ₅ Q (x) −− K ₆ } −y (16) Therefore, as the function of the optimum manipulated variable calculator 37, it is input from the target value calculator 14. By knowing the target value of by the signals a and b, in this case, find the pair of x and y that satisfy the equations (12) to (15) and the value of x is the minimum, and (16)
To obtain Z, and output the valve opening signals c, d, e corresponding to the obtained x, y, Z.

As shown in FIG. 1, the boiler starting control device according to the present invention mainly comprises a target value calculator 14, an optimum manipulated variable calculator 37, a parameter adaptive corrector 42, and a measurement error corrector 46. .

The target value calculator 14 is set by the steam pressure detector 12, the steam temperature detector 13, the boiler steam pressure signal f measured respectively, the superheater outlet steam temperature signal g, and the target value setters 17, 18. The steam pressure increase target value signal 1, the steam temperature increase target value signal m, the temperature increase rate limit value signal n and the pressure increase rate limit value signal o respectively set by the limit value setters 19 and 20 are input and measured. When the deviation between f and g of the target value and the target setting l and m is large, the step-up rate target value signal a and the temperature increase rate target value signal b, which are full of the limit values of n and o, are output respectively, and the deviation is zero or When it is small, zero or a small value a or b is output.

The optimum manipulated variable calculator 15 receives the boost rate target value signal a and the temperature rise rate target value signal b from the target value calculator 14, and opens the fuel flow control valve 11 that realizes these at the minimum fuel injection amount condition. Degree c,
The opening d of the turbine bypass valve 10 and the opening e of the superheater bypass valve 9 are calculated.

The a and b signals from the target value calculator 14 are integrated by the integrators 38 and 39 into α and β signals, and the measurement error corrector 46 performs correction assuming the measurement error and the like α ′ and β ′. After the signal is obtained, it is compared with the f and g signals by the signal subtractors 40 and 41 to generate deviation signals γ and δ, respectively, and the p, q, f, g, γ and δ signals are input, This is to have a parameter adaptive modifier 42 that modifies the parameters of the calculator 37 so that the equations in the calculator 37 match the characteristics of the controlled object.

Next, the functions of the optimum manipulated variable calculator 37 and the parameter adaptive modifier 42 will be described in detail.

In the optimum manipulated variable calculator 37, relational expressions (12), (13), (14), which are used when determining the fuel injection amount x, the turbine bypass valve 10 passing flow rate y, and the superheater bypass valve passing flow rate Z.
(15) and (16) were explained above. Although this equation (12) to the parameter K ₁ in _{(16), K 2, K} 3, K 4, K 5, K 6 is always given in parameter adaptive correction unit 42, the parameter K ₁ ~K ₆ Is originally a parameter in the calculator 37 and is corrected by the operation ε of the corrector 42.

The parameter adaptive corrector 42 uses K ₆ , K ₃ , K ₄ and K _{6 in the same} manner as in the petition invention (6), (8), (9) and (11), respectively.
According to the formula, the signals f, which correspond to the variables P, T, T _i , T _ECO in the formula in order,
The parameters of the calculator 37 are corrected by receiving g, p and q.

By the way, for K ₂ and K ₅ , these are the coefficients of Θ (x) and Q (x) in equations (12) and (13), respectively. As described above, Θ (x) and Q (x) are Certainly, the contribution of the fuel injection amount x is a large function, but it is affected by complicated influences such as the heat transfer tube metal temperature of the furnace water wall 1 and the difference in the ignition positions of the multiple burners 2, and the optimum manipulated variable calculator 37 It is considered that this accounts for most of the error in calculating the optimum manipulated variable. Therefore, if K ₂ and K ₅ are corrected according to the degree of deviation from the characteristics of the controlled object in the various equations of the calculator 37, the error in calculating the optimum manipulated variable can be eliminated.

This is done by modifying K ₂ and K ₅ according to the following equation.

K ₂ = {υ (P, T) / V _P・ (∂T / ∂H) _{P, T}・ Uα} ・ {1
_{+ Η T (ε T + 1} / τ T · ∫ε T dt)} ...... (17) K 5 = {1 / V T · (∂P / ∂ρ) P, T · 1 / h "(P) -h ′
(P)} · {1 + η _P (ε _P + 1 / τ _P · ∫ε _{P dt} )}
(18) Here, ε _P and ε _T are input by signals γ and δ, respectively,
η _P and η _T are parameter adaptive modified proportional sensitivities,
τ _P and τ _T are parameter adaptive modified integration times. That is, although K ₂ and K ₅ are basically calculated by the equations (7) and (10), the optimum manipulated variable calculator 37 is used to realize that they are given by the signals a and b of the target value calculator 14. Despite manipulating the controlled object, the measured values of P and T represented by f and g signals are compared with the integrated values of and represented by α and β signals, respectively, and if T exceeds T Then, the calculator 37
Θ (x) in the middle is corrected so as to increase K ₂ which is considered to be undersized than the characteristic of the controlled object. Similarly, if T exceeds, correction is performed so that the coefficient K ₅ of Q (x) is increased. This correction is performed by the deviation signals γ and δ in accordance with the idea of the proportional / integral adjuster to realize the adaptive correction of the parameters.

Next, it will be explained that the adaptive correction of the parameters described above is theoretically valid.

FIG. 2 illustrates the basic concept of adaptive correction according to the present invention, and the alternate long and short dash line 43 represents the plant to be controlled. Here, the plant is originally a black box, and what we can know is the manipulated variable vector U | that is the input of the plant and the observed value vector y | that is the output of the plant. Here, U | has at least fuel input amount x, turbine bypass amount y, superheater bypass amount Z as components, and y | is at least superheater outlet steam temperature T, steam pressure P, superheater inlet steam temperature T _i It has a charcoal outlet water temperature T _ECO as a component. That is, it is expressed by the following formula.

U | ＝ (x, y, Z ・ ・ ・ ・) …… (19) y | ＝ (P, T, T _i T _ECO・ ・ ・ ・) …… (20) The plant 43 is a black box, It is known that it is appropriate to consider a state quantity vector x that cannot be directly observed and assume a structure represented by the following equation. Where A,
B and C are vector functions.

In Fig. 2, the block diagram shown in the plant 43 is (21),
This is the expression (22).

Here, since A, B and C cannot be directly known, consider the observer shown by the chain line portion 44 in FIG. This is A, B, C
Estimate the structure of ,,, and think of. These satisfy the following relationships.

That is, the observer 44 receives the same manipulated variable vector U | Is output.

here Has, for each component of y |

If A, B, C assumed in the plant 43 and the ,, in the observer 44, are better approximated, y | Will be very close.

Then y | think of.

here, Consider a parameter adaptive modifier 42 that modifies the parameters ,, such that is a zero vector. This If is kept close to the zero vector, we are in the observer 44 and we know its structure, think that we can estimate A, B, C in the controlled plant 43 well. Good.

Now, the task of starting control given to us is to control the temperature rise rate and the pressure rise rate, in other words, the rate of change of the state quantity vector in the plant 43. To get closer to. here Is a vector with up ratio target value _r outputted from the target value calculator _14, the NoboriAtsushiritsu target value _r in the component.

For this purpose, the following can be considered. Since the structure of is known, its inverse function The structure of can also be known, and from equation (24), there is the following relationship.

Substituting this into Eq. (30), the inverse function from the known structure of U |

Known in A, B, C and observer of plant 43,
The objective is achieved by inputting the manipulated variable vector U | given by the equation (32) into the plant 43 on the assumption that are close to each other.
At this time, the rate of change in the state quantity of the plant 43 By substituting equation (32) into equation (21), it can be obtained as follows.

Consider the condition of the following equation for equation (34).

A, B, C (34) In this case, the following equation holds from the property of the inverse function.

Substituting Eqs. (35), (36), and (37) into Eq. (33), the following equation is obtained.

Equation (38) can be considered to be satisfied by equation (34). If the adaptive correction of, is properly performed by the parameter adaptive modifier 42, the manipulated variable vector U | Rate of change of state variables inside the plant when inputting to plant 43 Means to be matched.

The manipulated variable generator surrounded by the alternate long and short dash line 45 in Fig. 2 is (32)
The equation is expressed as a block diagram, and FIG. 2 reflects the above discussion as a whole. Therefore, we conclude that the intended purpose can be achieved by creating a control device according to the configuration of FIG. Here, in the observer 44 and in the manipulated variable generator, and have the same structure, the parameter adaptive modifier 42 simultaneously receives the same correction, and the necessary inverse function Will be requested at the same time.

By the way, since the observer 42 and the manipulated variable generator 45 shown in FIG. 2 have many common parts, they can be simplified by equivalent conversion.

FIG. 3 is common to the observer 42 and the manipulated variable generator 45 in FIG. It was intended to be shared by focusing on the fact that there is a certain amount.

FIG. 4 is an equivalent conversion of FIG. 3 utilizing the establishment of the following relational expression.

FIG. 5 is an equivalent conversion utilizing the establishment of the following relational expression in FIG.

Fig. 5 is much simpler than Fig. 2, but it is based on the equivalent transformation, so Fig. 2 and Fig. 5
The figures have exactly the same function.

In FIG. 5, if the portions surrounded by alternate long and short dash lines 37 and 46 are made to correspond to the optimum manipulated variable calculator 37 and the measurement error corrector 46 of FIG. 1, the apparatus configuration including the parameter adaptive corrector 42 is completely eliminated. It becomes the same, and it is proved that the control device of FIG. 1 according to the present invention has a theoretically valid configuration.

〔The invention's effect〕

As described above, the present invention increases the pressure based on the steam temperature detected from the temperature detector, the steam pressure detected from the pressure detector, the pressure increase target value and the temperature increase target value, the pressure increase limit value, and the temperature increase limit value. Target value calculator for outputting the rate target value and the temperature rise rate target value, and the first valve and the second valve for realizing the boost rate target value and the temperature rise rate target value under the condition of the minimum amount of fuel input. Since it is equipped with an optimum manipulated variable calculator that calculates the opening of the second valve and the third valve, the boiler can be efficiently started under the condition of the minimum amount of fuel input, and the cost can be reduced. .

Further, by providing the optimum manipulated variable calculator with a parameter adaptive corrector that corrects the parameters when calculating the openings of the first valve, the second valve and the third valve, This eliminates the problem of loss of optimality caused by deviation, and while monitoring the boiler state, always set the maximum temperature rise rate and pressure rise rate allowed for thermal stress restrictions to the lowest possible fuel injection amount. Can be achieved with.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a boiler start-up control device according to an embodiment of the present invention, FIG. 2 is an explanatory view showing a concept of adaptive correction of control device parameters, and FIG. 3 is an equivalent conversion of FIG. 4 and FIG. 4 are explanatory diagrams in which FIG. 3 is equivalently converted, and FIG. 5 is an explanatory diagram in which FIG. 4 is equivalently converted. 5 ... Superheater, 7 ... Steam turbine, 9 ... Superheater bypass valve, 10 ... Turbine bypass valve, 11 ... Fuel flow regulating valve, 12 ... Steam pressure detector, 13 ... Steam temperature detector ,14
...... Target value calculator, 17 …… Boost target value setter, 18 …… Rise temperature target value setter, 19 …… Rate rise rate limit value setter, 20 …… Rate rise rate limit value setter, 25… ... Steam temperature detector, 37 ... Optimal manipulated variable calculator, 42 ... Parameter adaptive corrector, a ... Boost target value signal, b ... Temperature increase target value signal, c ... Fuel flow control valve opening Signal, d ... Turbine bypass valve opening signal,
e ... Opening signal of superheater bypass valve, 1 ... Boost target value setting signal, m ... Temperature rising target value setting signal, n ... Temperature rising rate limit value signal, o ... Boosting rate limit value signal, K ₁ ~K ₆ ...... parameters.

Claims (2)

[Claims] 1. A superheater, a first valve for discharging steam to the superheater, a second valve for discharging steam from the superheater to a source other than its main supply destination, and a fuel supply amount to the furnace. In a boiler start-up control device including a third valve for controlling, a temperature detector for detecting a steam temperature of a boiler predetermined portion, a pressure detector for detecting a steam pressure of the boiler predetermined portion, and a temperature detector Outputs the boost rate target value and the ramp rate target value based on the detected steam temperature, the steam pressure detected from the pressure detector, the boost target value and the temperature rise target value, the boost limit value, and the temperature rise limit value. A target value calculator and the opening degrees of the first valve, the second valve, and the third valve for realizing the boost rate target value and the temperature rise rate target value under the condition of the minimum fuel injection amount It is equipped with an optimal manipulated variable calculator that Boiler start-up control device. 2. In the claim (1),
The optimum manipulated variable calculator calculates the opening degrees of the first valve, the second valve, and the third valve based on the boost rate target value and the temperature increase rate target value, the measured steam pressure and steam temperature. A boiler start-up control device, comprising a parameter adaptive corrector for correcting a parameter used in calculation.