JPS6022049B2 - Furnace temperature setting control method for multi-zone heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to furnace temperature setting for a multi-zone heating furnace, and is particularly suitable for improving accuracy of slab extraction temperature.

In recent years, various attempts have been made to computer control multi-zone heating furnaces from the viewpoint of energy conservation. For example, Samurai Kosho No. 49-2 Aku No. 03 proposes a method for correcting the furnace temperature based on the deviation between the current slab temperature and the target value, and Samurai Kosho No. 51-305
No. 26 proposes a method for correcting the furnace temperature so that the predicted value of the slab temperature at the outlet of each furnace zone becomes the target temperature. These methods implicitly assume that the furnace temperature setting calendar will be reflected in the furnace overflow without any time delay, that there will be no interference between furnace zones, and that there will be no transient response of the furnace temperature. This differs from the actual change in furnace temperature. For this reason, there is no guarantee that the determined furnace temperature correction amount is correct, and the accuracy of the extraction temperature and the stability of the furnace temperature control system are lacking. In view of the drawbacks of the conventional method, an object of the present invention is to make it possible to provide an optimal furnace temperature setting value by taking into account dynamic changes in the furnace temperature of each furnace zone. The present invention calculates changes in furnace zone temperature due to fuel injection into each furnace zone and gas inflow from adjacent furnace bodies, predicts slab temperature based on this furnace zone temperature, and sets the predicted value to a target temperature given in advance. The feature is that it is controlled so that

FIG. 1 shows an example in which the present invention is applied to a three-zone heating furnace, in which 1 is the heating furnace main body, 2a to 2c are furnace temperature detection devices, 3 is a furnace temperature control device, and 4 is the invention of the present invention. 5 represents a storage unit for the current furnace temperature setting value, 6 a slab temperature prediction calculation unit 7 a furnace temperature setting evaluation calculation unit, 8 a furnace temperature setting correction calculation unit, 9 is a furnace temperature dynamic calculation section, 1
0' represents the output part of the furnace temperature set value, and 11 represents the calculation part of the current position of the slab temperature.

The furnace temperature setting device 4 inputs the current furnace temperature values detected by the furnace temperature detection devices 2a to 2c at regular intervals.

The slab temperature calculation unit 11 calculates, for each slab in the furnace, the change in slab temperature from the previous calculated slab temperature value to the present value based on the detected furnace temperature value. It is shown in the above-mentioned known example that the current slab temperature can be calculated using the heat conduction equation. Therefore, it is omitted here.
The slab temperature calculation unit 6 predicts and calculates the slab temperature after a certain period of time, assuming that the current slab furnace temperature continues. In other words, the slab temperature calculated by the slab current temperature calculation unit 11 is set to 0.
(x) (x is the distance taken in the thickness direction of the slab), using this as an initial value, calculate the slab temperature for a certain period of time 7o using the following heat conduction formula. a0 a26
...(1'a ke 1 a
4}. ... [2' phosphorus = 4. chick. cCG
{(T beef trunk) 4-(Misakiki 73) 4}
...[3' Assume that the average value of the slab temperature after o hours for the i-th slab obtained here is 8.

The furnace temperature setting evaluation calculation section 7 inputs the predicted temperature value 8i of each slab.

The temperature increase pattern op of each slab is given to the evaluation calculation section in advance as a function of position. Here, the tracking speed v is inputted from a tracking control device for in-furnace slabs (not shown), and 7 is obtained for N slabs in the furnace zone 1. Time later. Find /v. , from the given temperature increase pattern. Slab temperature after hours 8pi
is decided. Here, J,,A, is defined by the following equation. J,=
1■i-spi)2. ．．・{41i white・A.
=Kichii≧1. (Sui-8M) ---'5} The evaluation calculation section checks whether J is smaller than the target value, and if it is, the furnace temperature setting remains as it is and the calculation ends. .

If the condition is greater than that, repeat the furnace temperature setting procedure described below until this condition is satisfied. The furnace temperature setting correction calculation section 8 inputs J,,A, calculated by the evaluation calculation section 7 and calculates the next correction amount ΔTPI for the furnace temperature setting. △TP
・={Thousands of Kings ≦8≧ The proviso is a predetermined positive constant.

If TP, +ΔTP, exceeds the maximum value of the furnace zone temperature, TPI +ΔTPI is set to the maximum value. The fuel flow rate and furnace temperature dynamic calculation unit 9 calculates the amount of correction △ for this furnace temperature setting.
Input TP, (1=1 to 3) and calculate the temporal change in furnace temperature and fuel flow rate. The flow of this calculation is shown in FIG. In this figure, Gd(s) is the transfer function of the adjustment system for controlling the furnace temperature, Gp,(s) is the response transfer function of the furnace temperature to changes in fuel flow rate, K is the exhaust gas generation rate associated with unit fuel combustion, and Cr
is the calculation constant GP of the exhaust gas amount heat flowing out from the first furnace zone, (
s) is a transfer function representing the influence of gas flowing from the adjacent furnace zone onto the furnace overflow. That is, the furnace temperature dynamic calculation section shown in FIG. 1 corresponds to an approximate furnace simulator. Examples of each transfer function are shown below. Gq(S)=Kimo KP, GM(s)=▽Shimoichi KI=Cs Cx=(T, 1 TRM)・Cg Cb,=VG(1). Cg G town=. 10th magnitude ~ However, S represents a Laplace variable, and Kc,, Tcl
, KP1, TP1, Cs, Cg, Kql, and Tql are constants determined by the reactor structure and fuel type, and values determined experimentally in advance are used.

Further, as T, the current position of the furnace temperature is used, and VG(1) is the current position of the exhaust gas flow rate flowing out from the furnace zone 1. By inputting the furnace temperature correction amount (△TF,, △TP2, △TF3) determined by the furnace temperature setting correction calculation unit 8 into this dynamic calculation unit, it is possible to predict the furnace temperature change in response to the furnace temperature correction. . This time change will be referred to as a predicted furnace temperature pattern. The slab temperature prediction calculation unit 6 inputs the furnace temperature prediction pattern calculated by the dynamic calculation unit 9, and uses the current slab temperature as an initial value for that pattern for a certain period of time ↑.

Calculate the subsequent slab temperature. The furnace temperature setting evaluation calculation unit 7 calculates the furnace temperature setting (TP, △TP, , T
Evaluate whether P20△TP2, TP30△TP3) is appropriate. When a reasonable furnace temperature setting is obtained through the above manipulation, this is stored in the furnace temperature setting value output section 101,
It is output to the furnace temperature control devices 3a to 3c at appropriate timing.

The furnace temperature control devices 3a to 3c control the flow rate of fuel supplied to the furnace in order to control the furnace zone temperature detected by the furnace temperature detectors 2a to 2c to the furnace temperature set value. According to this embodiment, since the furnace temperature is set in consideration of the response of the furnace, the temperature of the slab can be accurately controlled to the target value.

Furthermore, if the slab temperature increase pattern used in this example is a temperature increase pattern that minimizes the fuel, this example has the characteristic of heating the slab along the overflow pattern, so that the fuel source is Units can be improved. Although this embodiment relates to a three-zone heating furnace, it can be applied regardless of the number of zones. In addition, in this example, the set furnace temperature is evaluated for a certain period of time 7. Although this was done from the predicted value of the slab temperature after , the slab temperature at the time when it reaches a suitable position in the furnace may be determined by taking into consideration the dynamics of the furnace temperature, and the furnace temperature setting may be evaluated from this value. Furthermore, in this example, the square deviation of the average temperature prediction value from the target value was used for N slabs as an evaluation of the set furnace temperature, but the following can also be used instead. , J;=Min{8i-opili=1,...,N
q} Alternatively, the slab surface temperature may be used instead of the average temperature, and it may be used in conjunction with one of the following evaluation functions regarding the temperature difference between the inside and outside of the extraction slab Δ8i to search for a set furnace temperature that satisfies both. Also good.

J′≦△8, (constant) However, J′=△ai (i is time T.

According to the present invention, the furnace temperature of the slab can be controlled with extremely high accuracy, and the fuel consumption rate can be improved.

[Brief explanation of drawings]

Fig. 1: An example of applying the present invention to a three-zone heating furnace; Fig. 2:
FIG. 2 shows a block diagram for calculating the furnace temperature characteristic used in the embodiment of the present invention. 1... Heating furnace main body, 2a-c... Furnace temperature detector, 3... Furnace temperature control device, 4... Furnace temperature setting device, 5. ...Current furnace temperature set value storage section, 6
... Slab temperature prediction calculation section, 9 ... Furnace temperature dynamic calculation section. Tsutomu's Leopard Z

Claims (1)

[Claims] 1. In a furnace temperature setting control method equipped with a furnace temperature control device that detects the furnace temperature of each furnace body and controls the furnace temperature to a predetermined target furnace temperature, The temperature of each furnace zone is set, and the actual furnace temperature relative to the set furnace temperature is determined by the fuel flow rate determined from the corresponding characteristics of the furnace temperature control device and the furnace zone, the amount of exhaust gas inflow from the adjacent furnace body, and the furnace temperature. predict the temporal change in furnace temperature using an approximate furnace simulator from the dynamic characteristics of the furnace, predict the slab temperature when heated at the predicted furnace temperature, and use the predicted slab temperature to A furnace temperature setting control method for a multi-zone heating furnace, comprising: correcting the furnace temperature setting value and heating a slab.