JPH06221506A - Steam temperature control method of thermal power plant and device therefor - Google Patents

Abstract

PURPOSE:To permit following to the quick change of a load by a method wherein a PI regulating signal for a difference between the set value of gas temperature of a furnace and the operated value of gas temperature of the furnace is added as the feedback signal to the flow rate of fuel. CONSTITUTION:The gas temperature setting value 20 of a furnace is constituted of an output demand 5 through a function generator 8c while a difference 13c between the setting value 20 and the gas temperature operated value 19 of the furnace, which is operated as the output of the physical model 18 of the furnace, is obtained by a subtractor 2c. Then, the difference 13c is added to a fuel flow rate commanding value 15 of traditional technique by a PI regulator 6c through an adder 7d as a feedback signal 14c to operate a fuel flow rate commanding value 16. According to this method, the time lag of responce of a steam temperature with respect to the flow rate of fuel can be absorbed and the quick change of a load can be followed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for controlling a steam temperature of a boiler in a thermal power plant, and in particular, a physical model of a boiler furnace is incorporated in a control system to calculate a deviation between a calculated value of a furnace gas temperature and a set value. The present invention relates to a steam temperature control method and device for a thermal power plant, which can absorb the time delay of the boiler steam temperature by feeding back the flow rate command value and can control the steam temperature with good followability even for fast load changes. .

[0002]

2. Description of the Related Art A typical example of a conventional steam temperature control method is shown in FIG.
Shown in. In the figure, from the output demand (MWD) 5,
Main steam pressure set value (MSPD) 4 and main steam pressure (MSP) set by the transformer program setting device (FX) 3
From 1, and the deviation 13a is made by the subtractor (Δ) 2a,
This is made a feedback signal 14a by the PI adjuster (PI) 6a, which is used as the output demand 5 and the adder (Σ) 7
The boiler master (BM) 9 is configured by adding the value a. From this boiler master (BM) 9 to the function generator (F
X) 8a, the primary superheater outlet steam temperature set value 12
Is calculated and the deviation 13b is calculated by the subtractor 2b by comparing with the primary superheater outlet steam temperature (PSHOT) 17, and the deviation 13b becomes the feedback signal 14b by the PI controller 6b. On the other hand, from the boiler master (BM) 9 to the function generator (FX) 8b, the fuel flow rate advance value (JSPR
G) 11 is configured, and this is the boiler input acceleration signal (Bi
R) 10 and the adder 7b, and the added operation amount and the feedback signal 14b are added to the adder 7b.
The fuel flow rate command value (FRD) 16 is added by c.
As a conventional technique, for example, Japanese Patent Laid-Open No. 57-16719.
No. 61-70304, No. 61-2255.
No. 02 publication and the like.

[0003]

In the above-mentioned prior art, since the response of the steam temperature to the fuel flow rate is delayed with time, the deviation between the primary superheater outlet steam temperature and its set value is fed back to the fuel flow rate. However, there is a problem in that the control operation of the fuel flow rate is delayed after a rapid load change.

An object of the present invention is to solve the above-mentioned problems in the prior art, to absorb the time delay of the response of the steam temperature to the fuel flow rate, and to improve the controllability of the steam temperature even with a rapid load change. An object of the present invention is to provide an excellent method and apparatus for controlling the steam temperature in a thermal power plant.

[0005]

In order to achieve the above object of the present invention, in a method for controlling a steam temperature of a thermal power plant, an index of a manipulated variable is a gas temperature of a furnace which responds to a fuel flow rate with almost no time delay. Is used as.
That is, in the present invention, the physical model of the furnace is introduced to calculate and estimate the gas temperature of the furnace, and the deviation between this estimated value and the set value of the gas temperature of the furnace is fed back to the fuel flow rate for control. . As a result, it is possible to realize the control of the steam temperature of the thermal power plant which absorbs the response delay time of the steam temperature and can follow a rapid load change and which has extremely good controllability. The present invention, in the steam temperature control method of the furnace plant for correcting the fuel flow rate and controlling the steam temperature of the furnace in response to the load demand, the estimated gas temperature of the furnace calculated from the physical model of the furnace, and the furnace temperature Compare the gas temperature set values of the furnace set from the output demand,
This is a steam temperature control method for a thermal power plant in which the deviation is fed back to the fuel flow rate to control the steam temperature. Further, the present invention, in a steam temperature control device for a furnace plant equipped with means for correcting the fuel flow rate and controlling the steam temperature of the furnace according to the load demand, estimates the gas temperature of the furnace by calculation using a physical model of the furnace. Means, a furnace gas temperature setting means set from the output demand of the furnace, a means for obtaining a deviation by comparing the estimated furnace gas temperature value and the furnace gas temperature set value, and a PI adjustment signal for the deviation as feedback Then, the steam temperature control device for a furnace plant is provided with at least means for controlling the fuel flow rate by adding it to the fuel flow rate command value.

[0006]

When the PI adjustment signal of the deviation between the estimated value of the gas temperature of the furnace based on the physical model of the furnace and the set value of the gas temperature of the furnace is fed back to the control of the fuel flow rate, the fuel can be used even when the load fluctuation of the thermal power plant is fast. Since the time delay of the response of the steam temperature to the flow rate can be absorbed, the followability to the load change of the steam temperature is improved as compared with the conventional technique, and the control performance of the steam temperature can be further improved.

[0007]

Embodiments of the present invention will be described below in more detail with reference to the drawings. Differences from the prior art are as follows. That is, as shown in FIG. 1, the gas temperature set value 20 of the furnace from the output demand 5 is configured by the function generator 8c, and the calculated gas temperature 19 of the furnace is calculated as the output of the physical model 18 of the furnace. Deviation 13c
Is calculated by the subtracter 2c, and this is added as the feedback signal 14c by the PI controller 6c to the fuel flow rate command value 15 of the prior art by the adder 7d to calculate the fuel flow rate command value 16 of the present invention. The configuration of the physical model 18 of the furnace will be described below. Calculated furnace gas temperature (Tg)
19 is calculated by the following equation (1). Tg = F (Ff, Fa, Fgr, Fgas, Fa ₂ ) (Equation 1) (where Ff: fuel flow rate (22 in FIG. 1), Fa: air flow rate (23 in FIG. 1), Fgr: recirculation Gas flow rate (2 in Fig. 1)
4), Fgas: total gas flow rate (25 in FIG. 1), and Fa ₂ : two-stage combustion air flow rate (21 in FIG. 1) are shown. In addition to this, Tg is also calculated depending on the enthalpies and specific heats of fuel, air and gas, and also depends on the model parameters of the furnace. Next, a method of calculating the secondary superheater external gas temperature Tg will be described. First, a physical model of a furnace in which the furnace is divided into a burner area and a two-stage combustion area is described. The furnace is divided into a burner region and a two-stage combustion region, and the solution of the heat balance equation in both regions is the combustion gas temperature in the burner region and the two-stage combustion region. That is, the heat balance in the burner region is expressed by the following equation (Equation 2). QBin = QBout + QBtr (Equation 2) (where, QBin: heat input to burner area, QBout: heat output from burner area, QBtr: heat transfer quantity to water wall in burner area). The heat input amount QBin to the burner region is the heat generation amount QBgen of the fuel in the burner region and the sensible heat amounts of the air, the fuel and the recirculation gas, respectively, QBair, Qfuel and QBgr, i.
It is the total amount of n brought in. Of these, the amount of heat generated QBgen
Is determined depending on the combustion rate Fl. That is, it is expressed by the following equation (3). QBin = QBgen + QBair + Qfuel + QBgr, in (Equation 3) (where, QBin: heat input to burner area, QBgen: heat generation amount of fuel in burner area, QBair: sensible heat of air, Q
Bfuel: sensible heat amount of fuel, QBgr, in: sensible heat amount of recirculated gas. ) Also, the heat output QBout from the burner area is the sensible heat quantity of combustion gas, recirculation gas, and unburned gas, QBgas, QBgr, out, respectively.
And the total amount of Qubc taken out. That is, it is expressed by the following equation (4). QBout = QBgas + QBgr, out + Qubc (Equation 4) (wherein, QBout: heat output from burner area, QBgas: sensible heat of combustion gas, QBgr, out: sensible heat of recirculated gas, Qubc: sensible heat of unburned gas. Further, the amount of heat transfer QBtr from the flame in the burner area to the water wall in the burner area is the sum of the radiation QBrad and the heat transfer QBcv. Of these, the radiation QBrad is determined depending on the product F of the radiation rate and the view factor and the flame filling rate Fcg. That is, it is expressed by the following equation (5). QBtr = QBrad + QBcv (Equation 5) As described above, both sides of the heat balance equation in the burner region are functions of the combustion gas temperature TGB in the burner region, and TGB is calculated by solving this equation. That is, TGB is obtained as a function of the fuel flow rate, the air flow rate, the recirculation gas flow rate, and the two-stage combustion air flow rate. This function has parameters such as the combustion rate Fl, the product F of the emissivity and the number of forms, and the flame filling rate Fc.
g is included. These parameters are called "furnace model parameters". On the other hand, the heat balance in the two-stage combustion region is expressed by the equation (6). QYin = QYout + QYtr (Equation 6) (where, QYin: heat input to the second-stage combustion area, QYout: 2
Heat output from the staged combustion zone, QYtr: Heat transfer to the water wall in the two-staged combustion zone. ) Here, the heat input QYin to the two-stage combustion region is the heat generation amount QYgen of the unburned portion in the burner region and the sensible heat amount of the inflow gas from the burner region, that is, the heat output amount QBout from the burner region, 2
It is the sum total of the sensible heat amount QYair of the stage combustion air and the carried-in amount of the sensible heat amount QYgr, in of the recirculated gas. That is, it is expressed by the following equation (7). QYin = QYgen + QBout + QYair + QYgr, in (Equation 7) Further, the heat output amount QYout from the two-stage combustion region is the sum of the carried amount of the sensible heat amount QYgas of the combustion gas and the sensible heat amount QYgr, out of the recirculation gas. Of these, the amount of generated heat QYgen is determined depending on the combustion rate Fl. That is, it is expressed by the following equation (Equation 8). QYout = QYgas + QYgr, out (Equation 8) Furthermore, the amount of heat transfer QYtr from the flame in the second-stage combustion region to the water wall in the second-stage combustion region is the sum of the radiation amount QYrad and the heat transfer amount QYcv. Of these, the radiation QYrad is determined depending on the product F of the radiation rate and the view factor and the flame filling rate Fcg. That is,
It is expressed by the equation (9). QYtr = QYrad + QYcv (Equation 9) Thus, both sides of the heat balance equation in the two-stage combustion region are functions of the combustion gas temperature TGY in the two-stage combustion region and the combustion gas temperature TGB in the burner region, and TGB is the burner region. The heat balance equation can be calculated, and TGY can be calculated by solving this equation. That is, TGY is obtained in the form of the equation (1) as a function of the fuel flow rate, the air flow rate, the recirculation gas flow rate, and the two-stage combustion air flow rate. The combustion gas temperature TGY in the two-stage combustion region calculated as described above can be applied as the furnace gas temperature calculated value Tg, 19.

[0008]

As described in detail above, according to the steam temperature control apparatus for a thermal power plant of the present invention, the calculated gas temperature of the furnace, which is the output of the physical model of the furnace, and the set value of the gas temperature of the furnace. Since the PI adjustment signal of the deviation is added as a feedback signal to the fuel flow rate, it becomes possible to absorb the time delay of the response of the steam temperature to the fuel flow rate, and the controllability that can follow a rapid load change. It is possible to realize an extremely excellent steam temperature control device for a thermal power plant.

[Brief description of drawings]

FIG. 1 is a system diagram showing a configuration of a steam temperature control device for a thermal power plant exemplified in an embodiment of the present invention.

FIG. 2 is a system diagram showing a configuration of a conventional steam temperature control device for a thermal power plant.

[Explanation of Codes] 1 ... Main steam pressure 2a, 2b, 2c ... Subtractor 3 ... Transformation program setter 4 ... Main steam pressure set value 5 ... Output demand 6a, 6b, 6c ... PI regulator 7a, 7b, 7c, 7d ... Adder 8a, 8b, 8c ... Function generator 9 ... Boiler master 10 ... Boiler input acceleration signal 11 ... Fuel flow preceding value 12 ... Primary superheater outlet steam temperature set value 13a, 13b, 13c ... Deviation 14a, 14b, 14c ... Feedback signal 15 ... Conventional fuel flow rate command value 16 ... Fuel flow rate command value 17 ... Primary superheater outlet steam temperature 18 ... Physical model of furnace 19 ... Calculated gas temperature of furnace (Tg) 20 ... Gas temperature of furnace setpoint 21 ... two-stage combustion air flow rate (Fa ₂₎ 22 ... fuel flow (Ff) 23 ... air flow rate (Fa) 24 ... recycle gas flow rate (Fgr) 25 ... total gas flow rate (Fgas)

Claims (2)

[Claims] 1. A steam temperature control method for a furnace plant, which corrects a fuel flow rate according to a load demand and controls a steam temperature of a furnace, and a furnace gas temperature estimated value calculated and estimated from a physical model of the furnace, and a furnace. A method for controlling a steam temperature of a thermal power plant, comprising: comparing a gas temperature set value of a furnace set from the output demand of the above, and feeding back the deviation to the fuel flow rate to control the steam temperature. 2. A steam temperature control device for a furnace plant comprising means for controlling the fuel flow rate and controlling the steam temperature of the furnace according to the load demand, wherein the gas temperature of the furnace is estimated by calculation using a physical model of the furnace. Means, a furnace gas temperature setting means set from the output demand of the furnace, a means for obtaining a deviation by comparing the estimated furnace gas temperature value and the furnace gas temperature set value, and a PI adjustment signal for the deviation as feedback And at least means for controlling the fuel flow rate by adding the fuel flow rate command value to the steam temperature control apparatus for the furnace plant.