JPH0195202A - Method of predicting and controlling temperature of boiler steam - Google Patents

Abstract

PURPOSE: To accurately perform the prediction control of a steam temperature by obtaining the deviation value between an actual steam temperature and a set temperature value, adding a signal based on the deviation value to a signal from a prediction preceding signal generator and a signal based on the deviation value and creating this signal before a fuel starts to change. CONSTITUTION: The demand of each kind of fuel and a change target value are inputted to a prediction signal generator 4, and a prediction preceding signal with the two as variables is calculated before the fuel actually starts to change and is inputted to an adder 3 and is added to a signal based on the deviation between the actual steam temperature and the set steam temperature, thus creating this signal. Then, when the fuel is to be changed, the change in the fuel is started by a time delay after a fuel change push button is operated. However, a prediction preceding signal with the demand of each kind of fuel and a change target value as variables is created when a push button PB is operated in advance and is outputted as the command signal of an operation terminal at a point when at least a fuel change is started, thus accurately performing the prediction control of the steam temperature of a boiler corresponding to complex conditions without any time delay.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for predictively controlling the steam temperature of a boiler that receives and burns various byproduct gases as fuel in a steel mill or the like.

[Conventional technology]

A thermal power plant that uses byproduct gas from steel plants as fuel
As shown in Figure 3, steam temperature control is performed by feeding back the steam temperature (process value) and guiding it to the subtractor, comparing and subtracting it with the boiler steam temperature set value at and \, passing through the controller to the operating terminal. Generates a command value.

[Problem that the invention seeks to solve]

Conventional communal thermal power plants that use byproduct gas from steel plants as fuel accept a wide variety of fuels with different calorific values, and the power generation load fluctuates, making daily operation extremely complex and difficult to control. It's difficult. In particular, regarding steam temperature control, in the conventional foot-notch control as shown in Figure 3 above, the fuel change is fed back after the fuel change has started and a signal is output to the operating end, so time delays are avoided. Therefore, it was difficult to obtain sufficient controllability.

The present invention attempts to solve these problems.

[Means for solving problems]

The present invention provides a steam temperature control device for a boiler that receives and burns various by-product gases from steel works, etc., as fuel.
The deviation value between the actual steam temperature and the set temperature value set for Boi 2 is calculated, and the signal based on the above deviation value and the signal from the predictive advance signal generator using various fuel demands and change target values as variables are calculated. The main signal, which is the operating end command value, is created by adding it with an adder before the actual fuel change starts, and the above main signal is added to the boiler steam temperature at least by the time the fuel change starts. It is now transmitted as a control signal.

[Effect]

Set the variable names of state variables such as fuel flow rate to each fuel type.
X2. .・
..., yn, the following relationship holds between them.

Y□= fl (Xl * X2 * −* x!n)
(1) (1=1 to n) Equation (1) is a relational expression for setting the boiler outlet condition as a set value. In the present invention, this is stored as static characteristic data in a computer that executes steam temperature control.

On the other hand, when changing state variables such as the flow rate of each fuel, if the fuel change target values are x 7 , x :, .

Yr = fl (X: + X2 p - * xB)
(2) From equations (1) and (2) above, the manipulated variable y
The predicted preceding signal z1 of □ is obtained by the following equation.

zi=yi+Wi(yi yl) (3)
Here, Wl is an adjustment parameter that gives weight to how much the setting value change is applied, and this value can be set arbitrarily within the range of 0<W≦1.0! Ill be able to arrange it. This Norameter W
The value of □ is determined based on on-site test runs, etc.

When W□=O, the preceding signal z1 does not change even if the set value changes. In other words, the predicted advance signal will only change when the actual power generation amount, fuel flow rate, etc. change as the set value changes.
Become. When inverse Kw1=1, the predicted preceding signal changes immediately as the set value is changed.

In the present invention, as described above, the actual steam temperature is used as the process value, and the deviation from the set temperature value of the boiler 2 is determined.
A signal is output through a controller, etc.

On the other hand, the predictive advance signal transmitter outputs the advance signal shown in the above equation (3), which uses the demand signals of various fuels and their change target values as variables.

Both of the above signals are added by an adder to create the main signal, which is an instruction value to an operating end (for example, a spray water control valve or a control damper), before an actual fuel change starts.

The main signal created in advance as described above is transmitted to the operating end as a signal for controlling the steam temperature of the boiler at least until the time when the fuel change starts to control the boiler.

In this way, in the present invention, the fuel is changed by performing predictive control of the boiler in consideration of the predictive advance signal that uses the demand signals of various fuels prepared in advance and the change target value as variables. In this case, the operation end can be operated in advance, and sufficient controllability can be obtained without any time delay.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In Fig. 1, l is a subtracter, to which the actual steam temperature as a process value is fed back and the set value of the steam temperature is input. 3, the operating end command value is output.

On the other hand, in the prediction signal generator 4, the demand and change target value of various fuels are inputted, and the above (3) with both as variables is input.
) is calculated before the actual fuel change begins.

This signal is input to the adder 3, where it is added to the signal based on the deviation between the actual steam temperature and the set steam temperature to create the main signal. This added main signal output is used as an operating end command signal by the time when the fuel change starts at the latest, such as the spray valve of the superheater or reheater, burner tilt damper, gas distribution damper, etc. that controls the steam temperature of the boiler. is output to control the boiler.

When changing the fuel, for example, the fuel change is started with a time delay of T1 after the fuel change pushbutton PB is operated, as shown in FIG. In this embodiment, as described above, the predicted advance signal z1, which uses various fuel demands and change target values as variables, is created in advance at the time when the push button PB is operated, and this is operated at least until the time when the fuel change starts. Output as a command signal at the end.

For this reason, as shown in FIG. 2, the control end performs advance operation in accordance with the predicted advance signal z1 outputted to the control end in advance, and the boiler is controlled without time delay.

An example in which the present invention is applied to a boiler that uses byproduct gas in a steel mill as fuel is as follows.

The fuel is blast furnace gas (BF'G) as heavy oil gas fuel.
, coke oven gas, fpn gas (COG), and mixed gas of blast furnace gas or coke oven gas and converter gas (MXG).

Change width (KNm3/H/can) Change speed (KNm 1) B
P'0 50~300 10CO05~20
1 MX0 10 to 60 4 Load Rated 50% or more 3 MW/min The deviation from the set value of main steam temperature and reheat steam temperature can be suppressed to within 5% over the above load changes and fuel changes over the entire range. Ta.

〔Effect of the invention〕

In the present invention, a predicted advance signal that uses various fuel demands and change target values created in advance as variables is added to the deviation value between the actual steam temperature and the set temperature value, and this is calculated at least at the time when the fuel is started. By transmitting the boiler steam temperature as a control signal up to the maximum temperature, the operating end of the boiler can be activated in advance.

For this reason, in boilers that accept and burn a wide variety of byproduct gases from steel plants, etc., it is possible to accurately predict and control boiler steam temperature in response to complex conditions without time delay. .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a boiler steam temperature control device used in an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between predicted preceding signal z1 of the manipulated variable and time in the boiler steam temperature control device shown in FIG. A diagram showing the relationship, FIG. 3 is an explanatory diagram of a conventional boiler steam temperature control device.

Claims (1)

[Claims] In a steam temperature control device for a boiler that accepts and burns various byproduct gases as fuel, the deviation value between the actual steam temperature and the set temperature value of the boiler is determined, and the demand for various fuels and the change target value are calculated. The signal from the predicted preceding signal generator as a variable and the signal based on the above deviation value are added in an adder to create the main signal, which is the operating end command value, before the actual fuel change starts, and A method for predicting and controlling boiler steam temperature, characterized in that this signal is transmitted as a signal for controlling steam temperature in a boiler at least by the time when a change in fuel starts.