JPS61199019A - Method for controlling continuous heating furnace - Google Patents

Abstract

PURPOSE:To permit the easy handling of the coefft. of heat transfer and to heat surely billets to a target temp. by determining set furnace temp. in accordance with the four factors; the present and future billet temps., future furnace temp. and target billet temp. by using functions to calculate the furnace temp. and billet temp. respectively. CONSTITUTION:The preset temp. and billet temp. are first calculated by present temp. calculation 1 in a function part 106 to set the furnace temp. with the billet information and actual fuel flow rate from an operation information control part 102 and a fuel flow rate control part 103 as inputs in the operation of a continuous heating furnace 101. The future furnace temp. and billet temp. are predicted in accordance with the calculated temps. The heating-up pattern is determined by taking energy economization, etc., into consideration in heating-up pattern calculation 3. The results of the calculations 1-3 (2 is future temp. calculation) are inputted and the set value of the furnace temp. is determined by furnace temp. setting calculation 4. The function part 106 applies the set value determined in the above-mentioned manner to a control part 103 which controls the fuel flow rate by heating with a burner 105 so that a furnace temp. measuring part 104 attains the set value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a method of controlling a continuous heating furnace.

[Conventional technology]

Conventionally, computer control of the baking temperature of steel slabs in a heating furnace in a continuous heating furnace control method has been described, for example, in Japanese Patent Laid-Open No. 56-7.
As shown in Publication No. 5527, the size of the steel billet is determined based on the temperature distribution in the furnace and the thickness of the steel billet at each position in the furnace from charging to extraction.

Determined by heat transfer calculation based on physical property values and accumulated in-furnace time, the width of the steel billet +3'A is determined to follow a certain temperature increase pattern.
A method is adopted in which the required temperature inside the furnace is set using the temperature and the current temperature, and the fuel flow rate is fully controlled so that the set value is achieved.

[Problem that the invention seeks to solve]

In the conventional continuous heating furnace control method as described above, the size and physical properties of the steel billet charged into the heating furnace are controlled.

The steel billet groups in the furnace can be divided into groups based on combinations of processed steel types (extraction temperature upper and lower limits for the 4 pieces, and soaking degree limits), or the steel billet groups in the furnace may span several dozen types due to high-mix low-volume production. Even if a preferable heating pattern for each piece of steel could be found from the perspective of energy saving, it would be difficult to bake each piece of steel according to that pattern. There are the following drawbacks when determining the required furnace temperature.

The amount of heat qA required to bake from the current billet temperature to the target temperature is qA = CP@G・(θe−θF)Δt =α,・(T'−TPzu...(1)A However, , CP: Specific heat G: @ Piece weight αA: Transfer coefficient θA: Target billet temperature T: Necessary set furnace temperature (absolute furnace temperature) TP: Calculate TA backward from the current billet temperature (l), or... ... (2) However, θgA: Necessary set furnace temperature A: Steel billet surface area Δt: The set furnace temperature can be determined by calculating θgA backward from the time step,
The heat transfer coefficient changes depending on the position in the furnace, temperature, combustion pattern, etc., and it is difficult to treat it as a constant. Therefore, it is not possible to accurately set the furnace temperature, and the problem often occurs that the steel slabs are not baked sufficiently.

This invention was made in order to solve such problems, and its purpose is to provide a control method for a continuous heating furnace that can easily handle heat transfer coefficients and reliably bake steel slabs to a target temperature. do.

[Means for solving problems]

The control method for a continuous heating furnace according to the present invention uses a function that calculates the furnace temperature and billet temperature, and is based on four elements: current and future billet temperatures, future furnace temperature, and target billet temperature. In addition to determining the set furnace temperature, the set furnace temperature of the steel billet at that setting position is recalculated by taking into account the furnace temperature setting position of the steel billet and the position of the control thermometer, and the new setting furnace temperature of each steel billet is determined. It is made to be warm.

[Effect]

In this invention, the current and future billet temperatures.

Since it uses four elements: future furnace temperature and target billet temperature, it is easy to handle the heat transfer coefficient.Furthermore, it uses a function to calculate the furnace temperature and billet temperature respectively, and calculates the heat transfer coefficient based on each of the above factors. In addition to determining the set furnace temperature, the furnace temperature setting position of the steel slab and the position of the control thermometer are taken into account, and the set furnace temperature of the steel slab at that setting position is recalculated to set a new setting for the valley slab. Since the temperature is kept at the furnace temperature, it is possible to reliably bake the steel billet to the target temperature.

〔Example〕

The control method of the present invention will be explained below. As shown in Figure 1, the heating furnace is divided into nine parts in the furnace length direction, and heat generation, radiation, and convection are calculated based on the actual fuel flow rate.

A heat balance equation that takes heat transfer into account is established, and the unsteady nonlinear simultaneous equations are converged using Newton's method to determine the furnace temperature distribution.

Based on this temperature, a known heat transfer difference equation is solved for all the steel materials present in the furnace to determine the temperature of the steel billet.

Since the movement schedule of the billet is known, the location of the billet in the future after Δ time can be predicted, and the furnace temperature mentioned above can be predicted.

By repeatedly calculating the billet temperature and movement calculation function in combination, it is possible to predict the future billet temperature and temperature distribution in the furnace when the current input fuel is maintained.

Furthermore, when the target temperature is determined based on the temperature increase pattern of the steel billet determined from the viewpoint of energy saving, etc., it becomes possible to bake the steel billet along the temperature increase pattern using the following formula.

The amount of heat required to bake Δ to the target temperature after a certain period of time can be found using the formula (11), and the amount of heat q required to bring Δ to the temperature θ7 after a certain period of time is q, = CP＠G・(θ2−θP ) Δt = α c Tg, 4 ++ TP4 )
...(81 However, 0XP: Future billet temperature T: I Furnace temperature (absolute temperature) g?).In the above formula (2), 1 formula (8), αF'':α, then the furnace temperature setting for the billet The value θgA is...@ (4).

By controlling the fuel flow i to achieve the set furnace temperature determined in this way, the temperature of the billet can be maintained as per the target, and the temperature can be baked to a good degree of hardness.
can be raised. FIG. 2 shows this state.

For example, according to equation (4), the collar temperature wave θ□ is the current temperature σ
If a case occurs where the future temperature θ2 is higher than 1 and lower than the current temperature θ2, then the current fuel flow M−? If maintained, the temperature increase will be lower than the target temperature increase pattern, so the current fuel flow rate will be increased. Also, in the opposite case to the above, that is, θ□×θ2. θF
) If a case of 6 F occurs, the temperature rise pattern will be higher than the current fuel flow rate, so
It will operate in the direction of lowering the current fuel flow rate.

In this way, the set temperature at the furnace temperature setting position for each slab can be determined, but in general, in a heating furnace, there are more calculation zones for the furnace temperature than the zones that can be controlled, and in order to reach the temperature at the set position,
For the first time, by calculating the temperature of the control zone and leaving it to the control zone,
Perform the first shift at that position by leaving the bed. Therefore, T=T+(Tg(j)-Tg(k))...
(5) gA gA However, T': Calculated set furnace temperature A Tg (, 1" Furnace temperature in the furnace temperature setting zone Ttdkl "Existence of a control thermometer that refers to the furnace temperature setting zone Since the furnace temperature distribution in the zone ( be.

The furnace temperature set values for the valleys and valleys of the steel billet were determined by the method described above, and based on these set values, the set values for each control band are determined by the following equations.

Here, C(□n) is the baking weight coefficient for each steel billet.If C(1) is all the same, each steel billet will be baked to the target temperature on average, and in terms of operation, If it is desired to preferentially fire a certain steel piece, it can be achieved by increasing the weight of C(□j) for that steel piece. Figure 6 shows this condition!!!4'c.

Next, heating furnace control based on an embodiment of the present invention will be explained with reference to FIG. 4. In FIG. Fuel flow control section, (10
1 is a furnace temperature measuring part such as a thermocouple, (105, l is a burner,
(106) is the furnace temperature setting function section. Furnace temperature setting function section (
10/)) is broadly divided into four functions: current temperature calculation (1), future rhA degree calculation +21. Temperature rise pattern meter
This is ts++ furnace temperature setting calculation (4). (1) The logic of (21) has the same logic, and has functions for calculating furnace temperature, billet temperature, and purchased billet movement.First, the operation information management section (1 (J2)) and the fuel (Calculate the temperature of the slab from 10 points. Based on these, predict the future furnace temperature and billet temperature, and in the rising pattern calculation (3), calculate the temperature rising pattern in consideration of energy saving etc. Decided.

The furnace temperature setting value is determined by the furnace temperature setting calculation (4) using the calculation result of (11 (21fa)) as input.The furnace temperature setting function section (106) thus determines the determined setting value total fuel flow rate control section (103). is heated by the burner (105), and the fuel flow rate is adjusted so that the furnace temperature measurement part (1) becomes the set value.

〔Effect of the invention〕

As explained above, this invention uses four elements: current and future billet temperature, future furnace temperature, and target billet temperature, making it easy to handle the heat transfer coefficient. The temperature calculation function is used to determine the set furnace temperature based on each of the above factors, and the furnace temperature setting position of the steel billet at the setting position is taken into consideration. Since the furnace temperature is recalculated and a new furnace temperature is set for each piece of steel, it is possible to reliably bake the copper piece to the target temperature.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the furnace temperature calculation zone division of the heating furnace, Figure 2 is a conceptual diagram of determining the furnace temperature set value, Figure 3 is a conceptual diagram of determining the correction value of the furnace temperature set value, and Figure 4 is a conceptual diagram of determining the correction value of the furnace temperature set value. FIG. 1 is an overall configuration diagram showing one embodiment of the present invention. (1): Current temperature calculation (2j: Future temperature reaction calculation (S)
: Temperature increase pattern calculation

Claims (2)

[Claims] (1) In a continuous heating furnace composed of multiple zones, it is equipped with a function to calculate the furnace temperature in the valley zone and the billet temperature in the furnace, and calculates the current billet temperature, future furnace temperature,
The set furnace temperature is determined using the above function based on the four elements of the future billet temperature and the target billet temperature determined from the perspective of energy saving, etc., and the furnace temperature setting position of the billet and control thermometer are determined. 1. A control method for a continuous heating furnace, characterized in that the set furnace temperature of the steel billet at the setting position is reconverted in consideration of the position of the steel billet, and the set furnace temperature of the steel billet is set as a new set furnace temperature of each billet. (2) Control of a continuous heating furnace according to claim 1, characterized in that the set furnace temperature is set to a weighted average value obtained by multiplying the furnace temperature setting value of each steel billet by a weighting coefficient for furnace temperature setting. Method.