JPS61153232A - Method for setting furnace temperature of continuous heating furnace - Google Patents

Abstract

PURPOSE:To calculate the furnace temp. to minimize the evaluation function defined by the prescribed equation and to set the furnace temp. of a continuous heating furnace in such a manner that the ejection temp. of each material to be heated attains a target temp. simultaneously while maintaining the low fuel consumption with the calculated furnace temp. as a set furnace temp. CONSTITUTION:The 1st term of the equation is the total sum of the value obtd. by multiplying the square of the difference between the slab temp. thetai and target ejection temp. thetaiREF at the ejection time tfi of each material to be heated, for example, a slab Si by a weight coefft. omegai with respect to m-pieces of the slabs S1-Sm. The 2nd term is the integration of the square sum of the fuel flow rate fj in the respective zones, for example, preheating zone, heating zone and soaking zone made as, for example, f1.f2.f3 for the time from the present time t0 till the intended ejection time tfm of the slab Sm. More specifically, the 1st term is the penalty term to express the deviation from the target temp. and the 2nd term is the penalty term to express the fuel consumption. The furnace temp. to minimize such evaluation function j is the optimum furnace temp.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a furnace temperature setting method for a continuous heating furnace for heating materials to be heated such as slabs, and in particular, to a method for setting a furnace temperature for a material to be heated that is continuously supplied to the furnace. 1. for heating to temperature. II tll
Regarding how to set the furnace temperature.

[Technical background of the invention and problems with the background art] Continuous heating furnaces (hereinafter referred to as heating furnaces) reduce the amount of fuel consumed to heat the material to be heated, such as slabs, while at the same time It must be heated to a certain temperature and operated to ensure the target production volume.

The problem when operating this heating furnace is how to set the furnace temperature when the load on the slabs in the furnace fluctuates, for example, when slabs of different dimensions are mixed in the same furnace. It becomes a problem. This will be explained using figures.

Figure 2 shows a basic continuous heating furnace, which has a pre-heating zone 111, a heating zone H2, and a soaking zone [13]. Although the lower part will be omitted and only the upper part will be explained for the sake of simplicity, the lower part is also symmetrically constructed in substantially the same way as the upper part.

The heating furnace has a thermometer 1, a burner 2, and a temperature control device 3.
A heating device with a furnace is provided and the furnace is thermally controlled. In the heating furnace, slabs 81 to 81 are placed from the extraction port to the charging port.
Slabs S to SN are arranged outside the furnace, and at every extraction pitch, the slab at the n+1 extraction port is extracted, and at the same time, the remaining slab rows move inside the furnace toward the extraction port. While slabs of a certain size are continuously charged, the furnace temperature setting remains constant and the furnace is in steady operation.

Now, as shown in Figure 3, slab S. If a slab with large dimensions is charged after +1, that is, if the operation becomes unsteady, how should the furnace temperature be set from time to time?
The problem is whether the extraction slab can be heated to the target temperature and the operation can be performed while minimizing fuel consumption.

If slabs not only with different slab dimensions but also with different extraction pitches and extraction target temperatures are charged, an unsteady operating state similar to the above will occur and similar problems will occur.

Further, the set furnace temperature of the multi-zone heating furnace cannot be set higher than the allowable upper limit due to restrictions on the heat resistance of the furnace wall.

Therefore, if the furnace temperature is set for only one slab that has come to the extraction port, if a slab of large size comes to the extraction port after a slab of small size, the slab of large size will come to the extraction port. Even if the furnace temperature is raised to the allowable upper limit, the temperature may fall below the extraction target temperature, so-called baking may result in a shortage. Therefore, it is necessary to perform so-called feedforward control, which predicts and calculates the furnace temperature at which all target slabs can be heated to the extraction target temperature. Furthermore, in a heating furnace, the fuel consumed in the soaking zone is a waste gas that flows into the downstream heating zone and preheating zone and contributes to the rise in furnace temperature. Therefore, in order to perform energy-saving operation, it is necessary to understand the relationship between each zone furnace temperature and each zone fuel flow rate.

As described above, it is necessary to set the furnace temperature in consideration of various conditions, but conventionally, the setting of the furnace temperature has relied on the experience and intuition of the heating furnace operator. However, in order to make detailed furnace temperature settings for the target slab row, it is necessary to know the dimension information, temperature information, extraction target temperature information, and extraction pitch information regarding the slab row. had its limits.

[Purpose of the invention]

The present invention has been made in consideration of these circumstances, and is a method for setting the furnace temperature of a continuous heating furnace to reduce fuel consumption and at the same time bring the extraction temperature of the heated material to the target temperature without relying on the intuition of the operator. The purpose is to provide a method.

[Summary of the invention]

The present invention is based on the evaluation function J1 defined by the following formula (where tfi is the extraction time of each slab Si, θ1 is the temperature (extraction temperature) of each slab S1 at the extraction time, and EF θ1 is the extraction time of each slab St). Target temperature, ωi is the weighting coefficient determined for each slab S1, m is the number of the last slab targeted by the front teeth, fj is the fuel 1 flow rate in 8 zones, k is the number of zones, to is the current time , tfm is the scheduled extraction time of slab 5Ill.) The furnace temperature that minimizes is calculated, and this calculated furnace temperature is set as the set furnace temperature.

(Example of the invention) First, the significance of equation (1) will be explained.

The first term of equation (1) is each heated 1F! For example, the square of the difference between the slab temperature θi at the extraction time tfi of the slab S and the extraction R It is.

The second term is the fuel flow rate in eight zones, such as the preheating zone, the heating zone, and the soaking zone, as fl, for example, f and f.

J 12 f3, the sum of squares is the current time t. It is obtained by multiplying the flI interval product by 9 from the slab SI extraction scheduled time tr-.

That is, the first term is a penalty ring that represents the deviation from the target temperature, and the second term is a penalty ring that represents fuel consumption.
The furnace temperature that minimizes this evaluation function J is the optimal temperature setting.

The temperature θi of each slab S1 can be determined as follows. First, for slabs that have not yet been charged into the heating furnace, they can be actually measured using a sensor (not shown) or estimated based on experience. On the other hand, the slab in the heating furnace can be pumped out based on the temperature at the time of charging, the furnace temperature, and the time the slab is in the furnace, and by using the following slab heat transfer calculation formula.

X(1-,,(θ(t)+273)) ・・・・・・・・・(2)(However, θ(t) is the slab temperature at the second time t, θ(t+Δ
, t) Slab temperature at two times (10Δt), ①: Furnace temperature 1. 2 Constants related to the properties and dimensions of the varnish slab. ) By using equation (2), the temperature of the slab in the furnace can be calculated moment by moment using the furnace temperature Tg of the corresponding zone.

In addition, the furnace temperature and fuel flow rate in eight zones, for example, the pre-heating zone, heating zone, and soaking zone, are set to Tgj, fj, for example, 1g3. ■, 2
．． T, 3. f4. When f and f3 are assumed, the relationship can be expressed as (Fl, F2.F3 represents a function).However, h, h2. h3 is the pre-heating zone, heating zone, and soaking zone at a certain assumed time (for example, the drawing time), respectively.
This is the average slab thickness of in-furnace slabs.

Furthermore, as a constraint, the allowable upper limit of the set furnace temperature is 0H.
Toj”oj□ to make it less than AX. ・・・・・・・・・(4)(j
For example, 1.2.3) must be satisfied.

That is, in order to find the minimum value of equation (1) according to the present invention, equations (2) and (3) must be used, and the limitations of equation (4) must be taken into account, but in either case, Let's evaluate the function ((
As a dynamic optimization problem that minimizes Equation 1), it can be solved by a well-known numerical method.

FIG. 1 shows an example of an apparatus used when the furnace temperature setting method according to the present invention is applied to the heating furnace shown in FIG. 2.

In the figure, 11 is a slab temperature calculation device that calculates the current temperature of all slabs.As mentioned earlier, for slabs that have not yet been charged into the heating furnace, the value detected by a sensor (not shown) or The estimated value is output. On the other hand, regarding the slab in the heating furnace, based on the temperature at the time of charging, the detected furnace temperature, and the time in the furnace of the slab, and formula (2), (3)
Calculate using the formula.

Reference numeral 12 denotes an extraction pitch calculation device that calculates the scheduled extraction time of all the slabs in the furnace according to the time required for the rear culm of the heating furnace, for example, the rolling culm.

Further, 13 is a memory table that stores slab information such as slab dimensions (for example, thickness) and target extraction temperature, and the stored data is updated sequentially.

14 is a future furnace temperature calculation device that calculates the furnace temperature required in the future;
Based on the slab temperature calculated by the device 11, the extraction pitch calculated by the device 12, and the slab information stored in the i-pull 13, the future furnace of the book that minimizes the evaluation function J of the above formula (1) Calculate the temperature.

Reference numeral 15 denotes a memory table for storing allowable furnace temperatures (upper limit values) that are permissible for operation, and when performing the above calculation, the arithmetic unit 14 stores the upper limit values or limiting conditions of the furnace temperature that can be set in the name book in the table 15. Take it from here and use it wisely. That is,
(4) so as to satisfy the condition of equation (4).

Reference numeral 16 denotes an output device that outputs the future furnace temperature calculated by the calculation device 14 to the furnace temperature control system as a furnace temperature set value.

Incidentally, the above calculations and furnace temperature setting are started each time one slab is extracted, or at regular intervals, or when a start signal G, which is generated when instructed by an operator, is given.

In the above embodiment, the heating furnace was composed of three zones: a pre-heating zone, a heating zone, and a soaking zone, but the application of the present invention is not limited to this.

〔Effect of the invention〕

As is clear from the explanation below, according to the furnace temperature setting method for a continuous heating furnace of the present invention, even for slab rows with different slab dimensions, extraction pitches, and extraction target temperatures, m Regarding the slab, the extraction temperature is the extraction target
The furnace temperature is set so that the heating furnace can operate stably.

Further, by adjusting the weighting coefficient of the evaluation function, it is possible to bake a specific slab to the extraction target temperature with high accuracy. Furthermore, since the furnace temperature is set so that the total fuel consumption flow rate is small, there is an advantage that energy-saving operation can be achieved.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of a furnace temperature setting device that implements the furnace temperature setting method of the present invention, and Figure 2 shows the furnace temperature I control system of a general continuous heating furnace and the arrangement of materials to be heated. The sectional view shown in FIG. 3 is an explanatory diagram showing a change in the arrangement state of the material to be heated. DESCRIPTION OF SYMBOLS 1... In-furnace wA thinning gauge, 2... Burner, 3... Furnace temperature control device, 11... Slab m* drilling device, 12...
Extraction pitch calculation device, 13... Slab information memory table, 14... Future furnace temperature calculation device, 15... Furnace temperature memory table, 16... Output device, G... Starting signal.

Claims (1)

[Claims] 1. In a continuous heating furnace consisting of a plurality of heating zones and heating a continuously supplied material to be heated to a target temperature at its extraction port, an evaluation function J defined by the following formula is used. , that is, j=Σ^m_i_=_1ω_i [θ_i(t_f_i)
-θ^R^E^F_i〕^2+∫^(t_f)_t_＿
oΣ＾k_i_=_1f^2_Jdt・・・・・・・・・
・(1) (where t_f_i is the extraction time of each slab S_i, θ_i is the temperature (extraction temperature) of each slab S_i at the extraction time, θ^R^E^F_i is the extraction target temperature ω of each slab S_i
_i is the weighting coefficient determined for each slab S_i, m is the number of the last slab to be considered, f_j is the fuel flow rate in each zone, k is the number of zones, t_o is the current time, t_f_m is the This is the scheduled extraction time of slab S_m. ) A furnace temperature setting method for a continuous heating furnace, characterized in that the furnace temperature is calculated to minimize the temperature, and the calculated furnace temperature is set as the set furnace temperature. 2. In the method described in claim 1, the slab in the heating furnace is based on the temperature at the time of charging, the furnace temperature, and the time the slab is in the furnace, and the following slab heat transfer calculation formula, That is, θ(t+Δt)=θ(t)+K_1{(T_g+273
)^4-(θ(t)+273)^4}×{1-K_2(
θ(t)+273)^3}・・・・・・・・・(2) (However, θ(t): slab temperature at time t, θ(t
+Δt): Slab temperature at time (t+Δt), T_g: Furnace temperature, K_1, K_2: Constants related to slab properties and dimensions. ) is used to calculate the slab temperature θ_i.