JPH032931B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for controlling a heating furnace.

The semi-batch type multi-zone heating furnace is arranged as equipment downstream of the continuous casting machine, and 8 to 10 pieces of steel produced by the continuous casting machine are charged into the heating furnace as one charge. The charged charge is moved to each furnace zone by an independently movable walking beam, heated in each furnace zone, and baked by the scheduled extraction time.

Figure 1 shows the structure of a semi-batch type multi-zone heating furnace. There are 10 furnace zones in total: charging zone, first heating zone, second heating zone, third heating zone, and upper and lower zones of soaking zone. The difference from a general continuous heating furnace is that the charged charge is moved to a furnace zone in the downstream zone where no charge exists, and heating of the steel billet begins from that point. This is because the charge sent from the continuous casting machine is not continuous as in a continuous heating furnace, depending on the production capacity of the continuous casting machine and the type of steel manufactured. The operational status is detailed in JP-A-56-96031.

Figure 2 shows the third stage after the charging in the soaking zone has completed extraction.
The relationship between the actual temperature inside the furnace and the flow rate of the input fuel is shown when the charge in the heating zone begins to move and enters the soaking zone. The heating furnace control while the charge is stopped in the furnace zone is similar to a general continuous heating furnace, in which each billet in the charge is heated after a fixed period of time according to the heating pattern of the billet at a fixed time period. The control method is to make a prediction, determine the set value based on the current furnace atmosphere temperature of the controlled furnace zone, and output the furnace temperature set value to the control system. However, as shown in FIG. 2, while the charge is advancing to the next zone (while moving between furnace zones), the temperature of the steel billet in the charge is considerably lower than the ambient temperature of the furnace zone into which it enters, so the furnace temperature begins to drop rapidly. Therefore, in the control by setting the furnace temperature using a heating pattern, the furnace temperature is set at a fixed period, so when controlling to lower the actual furnace temperature, the setting is performed until the timing of the next set value output. A relationship of value > actual furnace temperature occurs. Therefore, the control system, which had previously been lowering the fuel flow rate, operates in the opposite direction to increase the fuel flow rate. Furthermore, even if the set value is output in a direction lower than the current furnace temperature at the next timing, a similar phenomenon will occur and the control will be hunting, causing black smoke to be generated. Then, when the furnace temperature has settled down to an almost constant value, the set fuel is held at a fairly high value. However, other problems may occur.

The object of the present invention is to
It is an object of the present invention to provide a method for controlling a heating furnace, which achieves optimum heating furnace control by using a fuel flow rate setting method, while eliminating waste of input fuel by using a furnace temperature setting method, in response to a phenomenon in which the temperature inside the furnace rapidly decreases.

That is, the present invention heats a plurality of steel billets in each furnace zone, extracts them into charge units after heating, and after the completion of the extraction, the subsequent charge moves to the next furnace zone. Temperature of multi-zone heating furnace,
In the fuel flow control method, while the charge is stopped in the furnace zone, the set temperature is determined by temperature prediction for each charge according to the heating pattern of each billet, and the atmosphere temperature in the furnace is controlled. While moving to the furnace zone, the input fuel is determined at fixed time intervals, regardless of the heating pattern of each billet, based on the target extraction temperature and the time in the furnace until extraction, and the fuel flow rate in each furnace zone is controlled. A method for controlling the temperature and fuel flow rate of a semi-batch multi-zone heating furnace is provided.

The present invention enables the furnace temperature to be lowered from the timing when the charge starts moving by understanding the amount of sudden decrease in furnace temperature that occurs while the charge is moving between furnace zones and the time required from the start of approach until it reaches a constant value. It is determined that the charge is moving until it reaches a certain value, and during that time, the control system is controlled by setting the fuel flow rate regardless of the heating pattern of the steel billet. This relationship is shown in FIG. The fuel flow rate set value is determined from the difference θ _r between the extraction target temperature and the current billet temperature at a certain periodic timing, and the remaining furnace time T _r
Calculate V _s and output to the control system. This control is repeated until the furnace temperature drops. However, if the fuel flow rate set value V _s is less than the lower limit value V _nio determined by the furnace zone, it is held at the lower limit value.

FIG. 4 shows a specific example according to the present invention.

101 is a movement signal from a walking beam, and 104 is a movement status determining device. The walking beam movement signal is input to the movement status determination device 104 at each pitch movement timing, and changes in the billet number and the position in the furnace of the steel billet at the beginning of each band are monitored, and it is checked whether the charge is stopped while the charge is moving or not. is determined and the result is stored in the movement status storage device 105. 107
is a set value calculation device that is operated by a timer 106 at regular intervals, and is operated by a movement status judgment SW (switch) 10.
8 is switched depending on the state of the movement status storage device 105. When the movement status determination SW 108 is stopped, the furnace temperature set value calculation device 109 operates and outputs the set furnace temperature TS to the control system by heating prediction according to the heating pattern.

Here, TS=T _p +ΔT _s …(1) ΔT _s : Range of furnace temperature fluctuation from the current furnace temperature due to heating pattern T _p : Current actual furnace temperature (input from furnace temperature detector 3) Movement status judgment SW 108 is moving In this case, the fuel flow rate set value calculation device 110 operates and calculates the fuel flow rate set value V _s based on the difference θ _r between the extraction target temperature and the current billet temperature, the remaining furnace time T _r , and a constant A determined by the furnace zone. Output to control system.

Here, VS=A・θ _r /T _r …(2) However, if VS<V _nio …(3), by setting VS=V _nio …(4) as the fuel flow rate setting value, the charge can be adjusted between the furnace zones. Enables optimal heating furnace control while moving.

[Brief explanation of the drawing]

Figure 1 shows the structure of a semi-batch multi-zone heating furnace and an example of charge inventory, and Figure 2 shows the relationship between the fuel flow rate and furnace temperature when the charge is moving between furnace zones using the furnace temperature setpoint method. FIG. 3 is a diagram showing the relationship between the furnace temperature and fuel flow rate according to the fuel flow rate setting method, and FIG. 4 is a block diagram of a concrete example of the fuel flow rate setting method and the furnace temperature setting method when the charge is moving. 1... Charging zone walking beam, 2... First heating zone walking beam, 3... Second heating zone walking beam, 4... Third heating zone walking beam, 5... Soaking zone walking beam, 6... Steel billet,
7... Charging machine, 8... Extraction machine, 9... First heating zone burner, 10... Second heating zone burner, 11... Third heating zone burner, 12... Soaking zone burner, 102... Fuel flow rate detector, 103... Furnace temperature detector.

Claims (1)

[Claims] 1. Control of a semi-batch type multi-zone heating furnace in which steel slabs are heated in each furnace zone in a plurality of charge units, and after heating, they are extracted into the charge units and transferred to the next furnace zone. In the method, while the charge unit is stopped in the furnace zone, a set temperature is determined by predicting the temperature of the charge unit according to the heating pattern of each billet, and the atmosphere temperature in the furnace is controlled; While the charge is moving to the next furnace zone, the temperature difference between the extraction target temperature from the next furnace zone of the charge and the current billet temperature and the temperature difference of the current billet temperature in the next furnace zone of the charge are calculated at regular intervals. A heating furnace control method, characterized in that the fuel input to the next furnace zone is determined based on time, and the fuel input to the next furnace zone is controlled.