JPS62164825A - Method for controlling combustion of heating furnace - Google Patents

Abstract

PURPOSE:To easily and stably control a furnace temp. and to minimize fuel consumption by determining the target heating up pattern of a non- representiative billet in accordance with the target heating up pattern of the representative billet of each billet group in the furnace and controlling the combustion in the heating furnace. CONSTITUTION:The billets in the multi-zone heating furnace are divided to continuous groups and the representative billet is set by each group. The present temps. of the above-mentioned representative billet and non-representative billet are designated as theta0, theta1, the intended time for extraction as t0, t1 and the target extraction temp. as thetaEXT. Further the coefft. alpha of temp. direction conversion is set at alpha=(thetaEXT-theta1)/(thetaEXT-theta0) and the coefft. beta of time direction conversion at beta=t1/t0. The target temp. pattern f0(t) set with the above-mentioned representative billet is converted to the time direction and g0(t)=f0(t/beta) is determined; further the time direction is converted to the temp. direction and f1(t)=(1-alpha).thetaEXT+alphaf0(t/beta) is determined. The combustion is controlled by determining the above-mentioned f1(t) as the target heating up pattern of the non- representative billet.

Description

[Detailed Description of the Invention] <Object of the Invention> Industrial Field of Application The present invention relates to a combustion control method for a heating furnace, and more particularly, the present invention relates to a combustion control method for a heating furnace that achieves stable furnace temperature control and contributes to energy saving. It concerns the control method.

In conventional multi-zone heating furnaces, the slabs in the furnace are divided into groups consisting of multiple slabs based on the steel type, heating regulation conditions, etc., and the furnace is calculated based on predictions for the representative slabs in each group. JP-A-58-2 discloses a method in which a target temperature increase pattern is calculated online based on internal movement schedules, heating regulations, etc., and the furnace temperature is controlled so that the billet temperature follows the temperature increase pattern.
It is known from No. 10121 and the like.

However, in order to calculate the temperature increase pattern online with these methods, an optimization problem that minimizes fuel consumption is solved, but a large amount of calculations must be performed online, and the n iF for all slabs
It is impossible to calculate the A pattern. On the other hand, the conventional method is to assume that the temperature difference between each piece of steel in the same group is not that large.
The temperature increase pattern calculated by δl for the representative slab is converted to the steel slabs in the group other than the representative slab, taking into account the difference in the remaining time between the representative slab and other slabs in the group, and converts the time direction. In addition, for continuous heating furnaces that can transport billets independently for each combustion zone, the temperature increase pattern of other billets is determined based on the temperature increase pattern of the representative billet. A method of determining the temperature from the current temperature ratio and remaining furnace time ratio with respect to other steel slabs is known from JP-A-59-14573 (No. 3).

However, with the method described above that only converts the time axis,
The temperature difference between each billet is not taken into account, and by the time the temperature increase pattern is determined, steel billets other than the representative billet will have been overheated and underheated compared to the temperature increase pattern, resulting in a stable condition. Accuracy of furnace temperature setting and extraction target temperature cannot be expected.

In actual operation, even steel pieces within the same charge may differ by several tens of degrees or more. Also, JP-A-59-14
In the method shown in No. 573G, the temperature increase pattern of the representative steel piece is determined depending on the relationship between the current temperature ratio of the representative steel piece and the non-representative steel piece and the slope of the stomach pattern at the time of extraction of the representative steel piece. It is easily proven that the temperature rise pattern of the non-representative steel piece obtained based on this has the Yang value. In other words, there are cases where the target temperature increase pattern of a non-representative steel piece goes through a temperature higher than the extraction target temperature before extraction, and then reaches the extraction target temperature, which is completely contrary to the idea of minimizing fuel consumption. be.

Problems to be Solved by the Invention The present invention aims to solve these problems.Specifically, it is possible to perform calculations easily, achieve stable furnace temperature control, and contribute to reducing fuel consumption. The purpose of the present invention is to provide a method for controlling combustion of a heating furnace.

<Structure of the Invention> Means for Solving the Problems and Their Effects The present invention provides a multi-zone heating furnace in which the steel slabs in the furnace are divided into a small number of successive steel slab groups, and each group is divided into a representative group. A steel billet is set, and based on the target temperature increase pattern obtained for the representative steel billet, the target temperature increase pattern of other steel billets in the group to which the representative billet belongs is determined by Target for extracting pieces: Calculated from the ratio of the difference between 8 degrees and the current temperature and the ratio of remaining furnace time from the current time to the scheduled extraction time.
It is characterized by controlling combustion in a one-heat furnace.

The structure and operation of the present invention will be explained below using the drawings.

Figure 1 is a graph showing the temperature increase pattern of a representative steel billet.
Figure 2 is a graph showing the temperature increase pattern of a representative steel billet and the temperature increase pattern of a non-representative steel billet converted from that temperature increase pattern in the time direction, and Figure 3 is a graph showing the temperature increase pattern of a non-representative steel billet converted in the time direction and temperature direction. 4 is a graph showing a temperature increase pattern of a non-representative steel piece;
The figure is a graph showing the temperature increase pattern of representative steel pieces and non-representative steel pieces.

Hereinafter, a method of calculating the temperature increase pattern of a non-representative steel billet from the temperature increase pattern of a representative steel billet in the present invention will be described.

Figure 1 shows the temperature increase pattern of a representative steel billet.

θEXT is extraction port 4! ! The temperature, θ0, is the current representative billet temperature, and to is the scheduled extraction time when the current time of the representative billet is O. In contrast, the current temperature of the non-representative steel piece is (7
Let t be the scheduled extraction time of jx.

First, the temperature direction conversion coefficient α, which is determined by the ratio of the difference between the current temperature and the extraction target temperature of the representative steel piece and the non-representative steel piece, and the time direction conversion coefficient β, which is determined from the ratio of the remaining short time, are defined as follows.

α=(OF:×T-θ, l/(OE×T-θQ)-・”
(11β=t, /L,...
・・・・・・・・・・・・・・・・・・・・・・・・(2)
If the temperature increase pattern of the representative steel piece is f, (t'l), the temperature increase pattern of the non-representative steel piece is determined by the following procedure.

(A) First, the temperature increase pattern of the representative steel piece is converted in the time direction, and a temperature increase pattern □(tl) having a residual time equal to the residual time of the non-representative steel piece is created.

Figure 2 shows f, (tl and g. Do of ([)) (tl=r, (j/β)...
・・・・・・・・・・・・・・・(3) Show the relationship.

+81 Next, convert 9° ([) into the temperature direction as shown below to make the current temperature match the temperature of the non-representative steel piece. That is, f, (t) found below becomes the temperature increase pattern of the non-representative steel piece.

f, (t)=(1-α)・0EXT+α(IQ (N
=(1-α)・θEXT+αfoft/β)・・・・・・
...(4) The relationship between the temperature increase pattern go (tl and the temperature increase pattern f, (t) of the non-representative steel piece is shown in Fig. 3. Also, the temperature increase pattern rr+ (t) of the representative steel piece and The temperature increase pattern r, (tl) of the non-representative steel piece is shown in Figure 4. (4)
The temperature increase pattern f, (t) of the non-representative steel piece shown in the formula is obtained by linearly converting the remaining short time difference from the temperature rise pattern of the representative steel piece in the time direction and interpolating it, and extracting the temperature difference from the target temperature. It is interpolated so that the ratio of is constant.

As described above, according to the present invention, one representative steel piece within a group
By determining the temperature increase pattern for only individual steel pieces, the temperature increase pattern of steel pieces within the same group can be more easily measured than the temperature increase pattern of representative steel pieces. In addition, the determined temperature increase pattern smoothly connects the current temperature of each billet to the extraction target temperature and has no extreme values, enabling stable furnace temperature control and minimizing fuel consumption. The pattern is sufficiently close to that of the previous model. As a result, it was possible to provide a combustion control method that stably controls the furnace temperature and contributes to energy savings. In addition, (Al, (B
The conversion of l in the time direction or the temperature direction may be performed first.

<Effects of the Invention> As explained above, the present invention divides the steel slabs in the furnace into a plurality of consecutive steel slab groups in a multi-zone heating furnace, and sets a representative steel slab for each group. , based on the target temperature increase pattern obtained for the representative steel billet, the target temperature increase pattern of other steel billets in the group to which the representative billet belongs is extracted as the target temperature of the representative steel billet and other steel billets. A combustion control method for a heating furnace, characterized in that the combustion in the heating furnace is controlled by determining from the ratio of the difference between This enabled stable furnace temperature control, provided a pattern that minimized fuel consumption, and provided a combustion control method that contributes to energy savings through smooth combustion.

[Brief explanation of drawings]

Fig. 1 is a graph showing the temperature increase pattern of a representative steel piece, Fig. 2 is a graph showing the temperature rise pattern of a representative steel piece and a temperature rise pattern of a non-representative steel piece obtained by converting the temperature rise pattern in the time direction. FIG. 3 is a graph showing a temperature increase pattern of a non-representative steel piece converted in the time direction and temperature direction, and FIG. 4 is a graph showing a temperature rise pattern of a representative steel piece and a non-representative steel piece.

Claims (1)

[Claims] In a multi-zone heating furnace, the steel slabs in the furnace are divided into groups of continuous steel slabs, a representative slab is set for each group, and the target temperature increase pattern is determined for the representative slab. , the target temperature increase pattern of other steel slabs in the group to which the representative steel slab belongs is determined by the ratio of the difference between the extraction target temperature and the current temperature of the representative steel slab and other steel slabs, and the scheduled extraction time from the current temperature. A combustion control method for a heating furnace, characterized in that the combustion in the heating furnace is controlled by determining from the ratio of remaining furnace time up to the remaining furnace time.