JPS60147817A - Method for controlling exhaust gas temperature of hot stove - Google Patents

Abstract

PURPOSE:To improve the temperature controllability of a hot stove in a method for controlling the exhaust gas temperature of the stove, by controlling the set value of a flow rate controller so that the exhaust gas temperature becomes the secondary upper limit at the time of completion of burning. CONSTITUTION:An M gas is supplied to a hot stove 3 from a pipeline 1 and its flow rate is inputted to a flow rate controller 6 as a flow rate signal Q from a flow meter 5. The temperature of exhaust gas is detected by a temperature detector 8 and transmitted to a computer 10 as a temperature signal T. The computer 10 calculates an estimated exhaust gas temperature at an expected burning completing time from the calculated result of a temperature rising speed and calculates a setting value S3 of the flow rate to the controller 6 so that the exhaust gas temperature becomes the secondary upper limit value at the expected burning completing time. The controller 6 performs a PID arithmetic to the deviation between the set value S3 of flow rate and the flow rate signal Q drom the flow meter 5 and controls the valve opening degree of a control valve 7 to bring the exhaust gas temperature at the time of completion of burning to the secondary upper limit value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the control of the exhaust gas temperature of a hot blast furnace (E, Tostop) in a blast furnace plant, and particularly to a control method that improves the controllability of the exhaust gas temperature.

Prior art: In conventional instrumentation methods for controlling the exhaust gas temperature of a hot air stove, a PID (proportional, integral, differential) calculation is performed on the deviation between the measured value of the exhaust gas temperature and the target exhaust gas temperature. Using this result, the flow rate of the mixed gas (hereinafter referred to as M gas), which is a mixture of B gas, which is the fuel gas generated from the blast furnace, and C gas, which is the fuel gas generated from the coke oven, to the blast furnace can be calculated using this result. was under control.

FIG. 1 is a schematic diagram showing a conventional embodiment of this type. In FIG. 1, 1 is a pipe through which M gas flows, and 2 is a pipe that sends air controlled to have a predetermined flow rate so as to provide optimal combustion conditions for M gas. 3 is a hot blast stove, and M gas is sent through pipe 1 and air is sent through piping 2. The M gas is combusted in the hot blast stove, and the heat generated at that time is stored in the heat storage bricks of the hot blast stove. The exhaust gas after combustion is discharged from the pipe 4. The piping 1 is provided with a flow meter 5 that measures the flow rate of M gas in the piping 1, and a flow rate signal Q detected here is input to a controller 6. Piping 1
A control valve 7 is also installed, and M is controlled by the output M of the controller 6.
The gas flow rate is controlled. A temperature detector 8 for measuring the temperature of the exhaust gas is installed in the pipe 4, and a temperature signal T detected here is input to a controller 9. A set value S, which is a control target for controlling the temperature of exhaust gas, is given to the controller 9, and the controller 9 performs calculations such as PID on the deviation between the set value S1 and the temperature signal T.

The result of the calculation is converted into a flow rate and the set value s of the controller 6 is
Given as 2. The initial condition of the set value s2 is such that as the deviation from the predetermined M gas, which is determined by the design conditions of the hot blast stove, becomes smaller, the set value S2 is lowered so that the opening degree of the control valve 7 becomes smaller.

In this way, the exhaust gas temperature of the hot stove is given in advance by the control operations of the controllers 6 and 9, which is the set value S of the exhaust gas temperature.
The opening degree of the control valve 7 is controlled so that the opening of the control valve 7 becomes 1.

In the conventional instrumentation described above, the M gas flow rate is controlled by performing PID calculation on the deviation between the set value and the measured value of the exhaust gas temperature, so it is possible to control the M gas flow rate from the change in the flow rate of the fuel gas to the change in the exhaust gas temperature, as in a hot blast furnace. Long response delay (30 minutes to 60 minutes)
) It is not possible to perform optimal control over the plant, and as a result, the exhaust gas temperature of the hot-blast stove may exceed the set value and damage the metal fittings that support the heat-storage bricks of the hot-blast stove, which is undesirable from a maintenance standpoint. Also, problems arise from the viewpoint of thermal efficiency and energy saving.

<Purpose of the Invention> In view of the above-mentioned prior art, an object of the present invention is to provide a control method that can save energy and protect the furnace body by improving the temperature controllability of a hot air stove that has a large response delay depending on the temperature. do.

OBJECTS OF THE INVENTION The configuration of the present invention to achieve this object relates to a method for controlling the exhaust gas temperature of a hot air stove, which includes measuring the exhaust gas temperature of a hot air stove heated by supplying fuel gas at a predetermined period, The rate of increase in the exhaust gas temperature is calculated from the time (3) when the exhaust gas temperature exceeds the primary upper limit, and then the predicted exhaust gas temperature at the scheduled combustion end time is estimated in mK, and when this calculation result exceeds the secondary upper limit. calculates an estimated rate of increase in the structure gas temperature such that the pre-exhaust gas temperature reaches the secondary upper limit value at the scheduled combustion end time, sets this as a target value, and calculates the rate of increase in the exhaust gas temperature between the target value and the exhaust gas temperature. A control calculation is performed on the deviation from the speed, and the flow rate □ of the fuel gas is controlled based on the calculation result.

<Embodiments> □ Hereinafter, embodiments of the present invention will be described based on the drawings. Similarly, parts having the same functions as those in the prior art are given the same reference numerals, and redundant explanations will be omitted.

Figure 2 is a professional diagram showing one embodiment of the present invention.

M gas is supplied to the hot air stove 5 through the pipe 1, and the amount thereof is inputted to the controller as a flow rate signal Q by the flow meter 5. on the other hand,
The temperature of the exhaust gas is detected by a temperature detector 8 and transmitted as a temperature signal T to a snoring machine 10. The computer performs predetermined calculations according to an exhaust gas degree control program to be described later, and provides the result to the controller 6 as a set value S3 of 6 in total in section t--(4). The controller 6 controls the control valve 7 so that the deviation between the set value S3 and the flow rate signal Q becomes zero. - FIG. 3 is an i-chart showing the exhaust gas temperature control program in the embodiment of FIG. 2.

The computer 10 reads the temperature signal T of the exhaust gas from the input reading device in the calculation unit at regular intervals, for example, every minute (step ■), and determines whether or not the predetermined primary upper limit of the temperature has been exceeded. is monitored in step ■.As a result, if the primary upper limit value exceeds 1?W, take 1 step. □Keep the opening of control valve 7 fixed. 1) From the point when the frost heave limit is exceeded, the rate of rise of the exhaust gas (mar) is increased at regular intervals in steps and steps.
t-calculate. From the calculation result of this temperature rise rate, the predicted exhaust gas temperature at the scheduled combustion end time is calculated in step (2). □Determine in step ■ whether the predicted exhaust gas temperature exceeds the predetermined secondary upper limit. If it does not exceed the secondary upper limit, proceed to step ■ and halt the initial flow rate.
do. When the secondary freezing upper limit value is exceeded, the process moves to step 2, where the rate of increase in exhaust gas temperature V is calculated so that the exhaust gas temperature reaches the secondary upper limit value at the scheduled combustion end time, and this upper valve speed V is set as the target value. In step ■, target value v8 and step ■
The deviation from the actually measured rate of increase in exhaust gas temperature V calculated in step 1 is calculated. Thereafter, at step (2), the calculation result at step (2) is converted into a flow rate, and the result is set as the flow rate setting value S3 (step [phase]) to the controller 6. The controller 6 performs PID calculation on the deviation between the flow rate set value S3 and the flow rate signal Q from the flow meter 5 to control the valve opening of the control valve 7, so that the exhaust gas temperature reaches the secondary 1 upper limit at the end of combustion. Pressure to maintain the value.

In addition, in order to estimate the rate of increase in temperature at which the temperature reaches the secondary upper limit when the exhaust gas is full at the scheduled combustion end time at the step, it is necessary to calculate the shadow of noise. In order to avoid #, instead of estimating the climbing speed based only on the current reading value, filtering is applied to make the climbing speed calculated based on the previous reading value contrary to the current estimation of the climbing speed. .

FIG. 4 is a characteristic diagram when the exhaust gas temperature is controlled according to the flowchart of FIG. 3. The horizontal axis shows the period from the start of combustion to the end of combustion, and the vertical axis shows both the M gas flow rate and the exhaust gas temperature. When the exhaust gas temperature is lower than the primary upper limit, a constant flow rate determined by the initial setting is maintained.
Once the primary upper limit value is exceeded, control by the exhaust gas temperature control program is started. Here, step ■ in Figure 3
Calculations from to (■) are performed, and if the actually measured temperature rise exceeds the secondary upper limit value at the combustion end time, a curve of the rate of increase in exhaust gas temperature that reaches the secondary upper limit value at the combustion end time is set as the target value. It has been shown that

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, the setting value of the controller is controlled so that the exhaust gas temperature reaches a predetermined secondary upper limit value at the combustion end time. As a result, it is possible to improve the temperature controllability even in a hot-blast stove that has a large response delay with respect to temperature, thereby contributing to energy saving and protecting the furnace body of the hot-blast stove.

(7)

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional embodiment, Fig. 2 is a program diagram showing an embodiment of the present invention, and Fig. 3 is a flowchart showing six exhaust gas temperature control programs in the embodiment of Fig. 2. , FIG. 4 is a characteristic diagram when the exhaust gas temperature is controlled by the 70-chart of FIG. 3. 1.2.4... Piping, 5... Hot stove, 5... Flow meter, 6.9... Controller, 7... Control valve, 8... Temperature detector, 10. ...Calculator, Q...Flow rate signal, T...
...Temperature □ signal, sl. 82, 8. ...Setting value. (8) ぢ Beast ζ Σ Button Ward Fee

Claims (1)

[Claims] The exhaust gas temperature of a hot stove heated by supplying fuel gas is measured at a predetermined period, and the exhaust gas temperature is calculated to estimate the exhaust gas temperature, and if this calculation result exceeds the secondary upper limit value, the above-mentioned Calculate an estimated rate of increase in the exhaust gas temperature such that the exhaust gas temperature reaches the secondary upper limit at the scheduled combustion end time, set this as a target value, and control the deviation between the target value and the rate of increase in the exhaust gas temperature. 1. A method for controlling exhaust gas temperature of a hot blast stove, comprising performing calculation and controlling the flow rate of the fuel gas based on the calculation result.