JPS61199020A - Method for controlling continuous heating furnace - Google Patents

Abstract

PURPOSE:To permit the easy handling of the coefft. of heat transfer and to control a continuous heating furnace so as to heat surely billets to a target temp. by determining set furnace temp. in accordance with furnace temp., future billet temp., future furnace temp. and target billet temp. 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 continuous heating furnace 10. The future furnace temp. and billet temp. are calculated in accordance with such calculation and a heating-up pattern is determined in heating-up pattern calculation by taking energy economization, etc. into consideration. The result of the calculations by present temp. calculation 1, future temp. calculation 2 and heating-up pattern calculation 3 are inputted and the set value of the furnace temp. is determined by furnace temp. setting calculation 4. The function part 106 controls the fuel flow rate by heating with a burner 105 so that a furnace temp. measuring part 104 attains the set value in the above-mentioned manner.

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 billets in a heating furnace was
For example, as shown in Japanese Unexamined Patent Publication No. 56-75527, the temperature of the steel billet at each position in the furnace from charging to extraction is determined based on the temperature distribution in the furnace, the size of the piece, its physical properties,
The required furnace temperature is determined by heat transfer calculation based on the cumulative in-furnace time, and the required furnace temperature is set using only the target temperature and current temperature of the billet so as to follow a certain temperature rise turn. [Problems to be solved by the invention] In the conventional continuous heating furnace control method as described above, in order to reach the target billet temperature The heat fqA is qA =
CPG (θ, -θAn Δt=αA*(TgA'-T
P')+1・a(1) However, CP: Specific heat G: Billet weight αA: Transfer coefficient θA = Target billet temperature θP: Current billet temperature TgA: Required set furnace temperature (absolute temperature) TP: Current billet temperature Temperature (TgA can be calculated backwards from the absolute temperature, or... (2) However, θ: Necessary set furnace temperature gmA: Slab surface area Δt Determine the set furnace temperature by calculating backwards TgA from 2-hour increments. However, 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 difficult to determine the set furnace temperature accurately, and the problem is that the steel billets are not baked sufficiently. there were.

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 to calculate the furnace temperature and billet temperature, and determines the set furnace temperature based on the current and future billet temperatures, future furnace temperature, and target billet temperature. It was designed to do so.

[Effect]

In this invention, the current and future billet temperatures.

Because it uses four elements: future furnace temperature and target billet temperature, it is easy to handle the heat transfer coefficient, and the function to calculate the furnace temperature and billet temperature respectively allows the set furnace temperature to be calculated based on each of the above factors. Since the temperature is determined, it is possible to reliably bake the steel piece to the target temperature.

〔Example〕

The control method of the present invention will be explained below. The heating furnace is divided into j parts in the furnace length direction as shown in Figure 1, 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 slabs present in the furnace to determine the temperature of the steel slabs.

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

By combining the billet temperature and movement calculation functions and performing repeated calculations, 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 equation.

The amount of heat required to bake Δ to the target temperature after a certain period of time is determined by equation (1), and the heat tqy required to bring Δ to a temperature θ2 after a certain period of time is qIP=CPIIG・(θ2−θF)Δt= αP (T
gP' - "P') ... (8) However, θ
IF = future billet temperature TgF:I Furnace temperature (absolute temperature) It is determined by: If α22α□ in the above equations (2) and 2 (8), the furnace temperature setting value θgA for the steel billet is -273,15・■(4) becomes.

By controlling the fuel flow rate so as to reach the set furnace temperature determined in this way, the steel billet temperature can be fired with high accuracy to the target temperature. FIG. 2 shows this state.

For example, according to equation (4), the target temperature θ6 is the current temperature θ
If a case occurs where the future temperature is higher than 2 υ but lower than the current temperature θa, in the future, if the current fuel flow rate is maintained, the temperature rise will be lower than the target temperature increase pattern, so the current fuel flow rate will be lower than the target temperature increase pattern. will act in the direction of increasing. Also, in the opposite case to the above, θ, θad F>
If case 02 occurs, if the current fuel flow rate remains unchanged, the temperature will become higher than the temperature increase pattern, so the current fuel flow rate will be lowered.

Next, the heating furnace control based on an embodiment of the present invention will be explained with reference to FIG. 3. In FIG. Control unit, (104
) is the furnace temperature measuring part such as a thermocouple, (105) is the burner s
(106) is a furnace temperature setting function section. The furnace temperature setting function section (106) is roughly divided into four functions: current temperature calculation (1);

These are future temperature calculation (2), temperature increase pattern calculation (8), and furnace temperature setting calculation (4). (1) The logic of (21) has almost the same logic and has functions for calculating furnace temperature, billet temperature, and billet movement. First, the operation information management department (102
) and the fuel flow rate control unit (103). Based on these, the future furnace temperature and billet temperature are predicted, and in temperature increase pattern calculation (8), the temperature increase pattern is determined by taking energy conservation measures, and the calculation results of (1), (2), and (8) are calculated. As an input, the furnace temperature setting value is determined by the furnace temperature setting calculation (4). In this way, the furnace temperature setting function section (106) gives the determined set value to the fuel flow rate control section (103), and the fuel is heated by the burner (105) so that the furnace temperature measurement section (104) reaches the set value. The flow rate is regulated.

〔Effect of the invention〕

As explained above, this invention uses not only the current and target billet temperatures but also the four elements of the future predicted billet temperature and furnace temperature to determine the furnace temperature setting value of the billet and heat the heating furnace. Since the method is controlled, it becomes possible to bake the steel billet in a targeted temperature increase pattern, and there are effects such as the possibility of controlling the heating furnace with high temperature control accuracy.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the division of furnace temperature calculation zones in a heating furnace, FIG. 2 is a conceptual diagram for determining a furnace temperature set value, and FIG. 3 is an overall configuration diagram showing one embodiment of the present invention. (1): Current temperature calculation (2): Future temperature calculation (8)
: Temperature increase pattern calculation

Claims (1)

[Claims] In a continuous heating furnace consisting of multiple zones, it is equipped with a function that calculates the furnace temperature of each zone and the billet temperature in the furnace, and calculates the current billet temperature, future furnace temperature, and future billet temperature. A control method for a continuous heating furnace, characterized in that a set furnace temperature is determined using the above function based on four elements of temperature and target billet temperature determined from the viewpoint of energy saving.