JPH02200760A - Strip temperature control method for heating furnace - Google Patents

Abstract

PURPOSE:To improve the responsiveness when parameter changes and to make uniform the strip temp. distribution in a thickness direction by computing the required fuel flow rate corresponding to the quantity of heat of which a strip is deprived, determining the fuel flow rate distribution pattern to respective burner groups and further determining the fuel flow rates to the respective burner groups. CONSTITUTION:The change in the respective parameters; the thickness, a width of the strip, a line speed, and target strip temp., is detected and the required total fuel flow rate Ft corresponding to the quantity of heat of which the strip is deprive is calculated, then the fuel flow rate distribution pattern to the respective burner groups is determined. Further, the fuel flow rates to the respective burner groups are determined by equation I. The fuel is passed at the above-mentioned flow rates to the respective burner groups for the prescribed period of time when the parameter changing part of the strip passes the burner groups in accordance with the determined fuel flow rates. In equation I, Fis is the optimum fuel flow rate (set value) of the i-th zone in the transverse direction of the strip; Ri is the constant to determine the fuel flow rate distribution pattern to the i-th zone (under the conditions expressed by equation II); N denotes the number of zones of the respective burner groups in the transverse direction of the strip.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a plate control force method for a heating furnace in which a plurality of burner groups are arranged in the width direction on seven consecutive plates.

[Conventional technology]

As an example of a heating furnace, a heating zone for alloying plating equipment will be explained with reference to FIGS. 3 to 7.

Fig. 3 is a block diagram of the zinc alloy plating equipment, Fig. 4 is an explanatory diagram of the heat cycle, Fig. 5 is a partial vertical cross-sectional view of the heating plate 1), and Fig. 6 is the vi-vq of Fig. 5. The sectional view and FIG. 7 are block diagrams of the plate temperature control system of the heating furnace of the heating zone.

First, in FIG. 3, after the strip 1 leaves the VT blunt furnace 2, it passes through a zinc bot 3 and is molten by -8. Furthermore, after controlling the adhesion amount using the gas blown out from the nozzle 4, the zero-alloy plating equipment enters the alloying plating equipment in the heating zone 51. A holding zone 6 and a cooling zone 7 are arranged in sequence. By carrying out one cycle as shown in FIG. 4, an alloy layer of zinc and the base steel sheet is formed. Figures 5 and 6 show the heating zone, which is a direct-fire heating type heating zone in which direct-fired burners 8 are arranged in a staggered manner in the plate advancing direction and plate width direction on the furnace wall 28 on the surface facing the strip. This is an example. In the heating zone, a conventional sheet temperature control system in the sheet width direction as shown in FIG. 7 has been constructed. Figure 7 shows an example where a direct-fired burner group is installed in five zones (zones ■, ■■, ■, ■, including the strip center section in the strip width direction), and the control loop is only for the right side from the center. (The same is true for the left side).

Fuel is supplied all at once to each direct-fired birch in the direction of board movement, and the flow rate is controlled2. A scanning plate thermometer 9 is installed at the outlet of the heating zone, and scans in the width direction of the plate at regular intervals to detect the plate temperature.

That is, the plate temperature corresponding to the burner position in each zone in the plate width direction is detected as shown in FIG. 7, and the plate temperature controller 10.
1). Send 4 on 12.

Plate temperature controller 10.1). 12 is plate temperature detection value a, 1)
．． c, the fuel flow rate detector is operated so that the temperature reaches a predetermined target temperature, and the fuel flow rate controllers 13, 14, respectively.
Send to 15th.

Note that the fuel flow rate detector may be calculated so that the plate temperature 1) node 1l1.12 is the plate temperature difference in the plate width direction -0, that is, a-b=o (ac-0).

The fuel flow 13M1 moderators 13, 14, 15 operate the control n valves 19, 20, 21, respectively, so that the fuel flow detected by the fuel flow detector 1617, 18 becomes equal to a predetermined value. In other words, a plate temperature feedback control system is configured to cascade control the fuel flow rate in accordance with the plate temperature detection value for each zone in the plate width direction, thereby controlling the plate temperature distribution in the plate width direction.

[Problem to be solved by the invention] The above conventional method has the following problems.

(1) In the direct-fire heating method, the strip is heated by radiation heat from the furnace wall heated by a direct-fire burner. Since the furnace wall has a large heat capacity, the response of the furnace is poor; for example, the time constant of the step response of the plate temperature to a salt flow rate of 1!4 takes about several minutes.

However, since the heating belt threading time is about a few seconds, for example, if the width of the trailing material changes at the seam between coils,
Since the heating amount distribution in the width direction of the sheet was inappropriate for the following material, there was a problem in that the sheet temperature distribution temporarily exceeded the allowable value (approximately ±10° C.).

(2) Even if the plate width is constant, the required amount of heat absorption Q from the strip, expressed by the following equation, changes, and the optimal heating distribution depending on Q changes, causing a similar problem.

Q,=V −D −W(TI−′TI)C,−r*−(
2) Here ■ Nistrip's linear speed 1'):
Plate thickness W: Strap width 'r,: Heating strip output cn Reheating target I Direct TI: Heating entry [J Plate temperature C1: Strimp specific heat T,; Strip specific weight Ql: Required amount of heat removal for entry trip [Task] Means for Solving the Problems] The present invention takes the following measures to solve the above problems.

(+) In a method for controlling the plate temperature of a heating furnace in which a plurality of burner groups are arranged in the width direction of the strip, and the plate temperature distribution in the strip width direction is uniform, the fuel flow rate of each burner group is detected. Thickness and width of the above strip 1. When the line speed, target board, and other parameters change, the changes in each bar meter are detected, and the required total fuel flow rate (
Ft) 杏f′A is calculated, and the fuel flow rate distribution pattern to each burner group is determined in advance in relation to the heat removal amount and plate width of the strip, and further, the claim (
jp! to each burner group using equation (1) described in 1). N: 1 flow rate was determined, and when the parameter changing portion of the strip passes through each burner group, the fuel flow rate was made to flow to each burner group for a predetermined period of time.

(2) Multiple bar holes in the width direction of the strip.
Group 4 arrangement L2, the plate temperature distribution in the width direction of the plate will be uniform.
) In a method for controlling the plate temperature of a heating furnace in which the fuel flow and quantity of each bar 1 to 1 group are produced in one sheet, the plate thickness, plate width of the strip,
When changing parameters such as line speed and target plate temperature,
.

The required total fuel flow according to the heat cover of the strip obtained from the same parameters by detecting the changes in each parameter.
(FL) to determine the fuel flow distribution pattern to each burner group associated with the heat removal amount and plate width of the strip in advance, and at a predetermined time point before the change of each parameter above, for a predetermined period of time. After red-filtration, the fuel flow rate detection value of each burner group is calculated from the detected value of the fuel flow rate of each burner group when the board temperature feedback control system in the board width direction, which operates the fuel flow rate of each burner group based on the board temperature detection value in the board width direction, is stabilized. The constant R1 that determines the fuel flow distribution pattern is calculated backward from the relationship of equation 1.1 described in claim (1), and the fuel flow distribution pattern F is sequentially corrected. From (1), calculate the fuel flow rate of each burner group by equation (1), and when the parameter changing part of the strip passes through each burner group, flow the fuel wit to each upper group of bars for a predetermined period of time. I declined.

[Effect]

By the means described in 1-, ζ in the inventions of 1-, (1) and (2) operate as in the following (1) and (2), respectively.

(1) Changes in the following parameters (repetition, thickness M, line speed, and board temperature of Strip II strip) are detected, and the required M value is calculated based on the required heat removal amount of the strip obtained from each parameter. , the fuel flow rate (Ft) is calculated.

Next, an optimal fuel flow distribution pattern for each burner group is determined in advance in relation to the necessary heat removal amount and plate width of the strip. Then, the optimal fuel flow rate to each burner group is determined by equation (1) above, and when the parameter changing part of the string passes through the burner group described in 1-, the flow rate is determined for each burner group for a predetermined period of time. L Q Appropriate fuel flow rate is reduced.

In this way, even when strip variations and meters change, each burner group burns at the optimum fuel flow rate, and the plate temperature distribution in the plate width direction becomes uniform.

(2) Strip thickness, width, and 1 line speed
Changes in parameters such as strip temperature and target plate temperature are detected, and a required total fuel flow rate (Ft) corresponding to the required heat removal amount of the strip obtained from each parameter is calculated. Next, the optimal fuel flow distribution pattern for each burner group is determined in advance, which is related to the required QiQ amount and strip width of the strip. -, at a predetermined time point before the change in each of the above parameters, after a predetermined period of time, the plate temperature in the plate width direction is controlled by the detected value of the & point in the plate width direction. When the feedback control system is stabilized, the constant R4 that determines the fuel flow distribution pattern is inverted by 1γ from the fuel flow rate detection values of each burner group using the above equation (1), and the optimal fuel flow distribution pattern is successively corrected. Ru. From this modified fuel flow rate distribution pattern, the optimal fuel flow rate to each burner group is determined using the equation (0), and when the parameter changing part of the strip passes through the upper group of each bar, each part/group is Note: The optimal fuel flow rate is applied.

In this way, even when the parameters of the strip change, each burner group burns at the optimum fuel consumption and one flow rate, and the strip temperature distribution in the strip width direction becomes uniform.

〔Example〕

An embodiment according to claims (1) and (2) of the present invention will be explained in Sections (1) and (2) of Section F with reference to FIGS. 1 and 2, respectively.

Note that the description of the portions described in the conventional example will be omitted to avoid redundancy, and the description will mainly focus on the portions related to the present invention.

(1) FIG. 1 is a configuration diagram of one embodiment, and FIG. 2 is an explanatory diagram of a fuel flowmeter distribution pattern of the same embodiment. However, in Fig. 1, as in Fig. 7 of the conventional example, the side half is explained, and the fuel flow rate of each burner in the plate advancing direction is not shown on the premise that it is controlled all at once. hand,
Each switch 25, 26, 27 receives one input signal from the scanning plate thermometer 9, and receives a signal 2 representing the optimum fuel flow rate from the arithmetic processing unit 22 as an input signal.
3. Receive 24125. Furthermore, a switching command is also received. In addition, their outputs are the fuel 14 flow rate controllers 13 and 14.1, respectively.
Sent to 5.

In the above configuration, the input data and output data of the arithmetic processing unit 22 are as follows.

(al Input data ■ Plate width ■ Plate temperature target value for plate thickness ■ Line speed detection value ■ Fuel flow rate detection value for each zone in the plate width direction ■ Plate temperature detection value in the plate width direction (b) Output Y-ta ■ In the plate width direction Optimal fuel $4 meteor setting for each zone ■ Cascade controller's 0N10FF switching command switch
Changes in the lip thickness, width, line speed, and target plate temperature are detected, and the processing unit 22 calculates the required strip stripping number obtained from each parameter.
ftQ, the total required fuel according to (formula (2) above) 21■ (
Ft) is calculated by the following (3) Take.

FL = Q, /η −・−・ (3) where η: constant Next, the required value of the above strip as shown in FIG. 2 in advance!
An optimal fuel flow distribution pattern, ie, RL, for each burner group is determined in relation to the E heat amount and the plate width.

FIG. 2 shows an example of the necessary heating cover and plate width of the strip and the fuel flow distribution pattern for each zone. Initially, it was set up as a target for the center. Also, Q s r + Q s
z, Q5j·W, , W, , W3 indicate dividing nodes, which are obtained in advance by heat transfer theory analysis or organizing experimental data. Furthermore, the optimal fuel iN and amount to be supplied to each burner group are determined by the formula (1.

When the parameter changing part of the burner passes through each burner group,
The switches 25, 26, and 27 are switched to turn off the phytback control system and output signals 23, 24, and 25 indicating the optimum fuel flow rates, respectively.

After that, after being held for a certain period of time, the switch 25.26.27
is switched to its original position, and the feedback control system is switched to O.
Return to N. The timing is, for example, when the plate temperature distribution detection value has been continuously within the allowable value for a predetermined period of time or more.

In this way, even when the strip parameters change, the strip temperature distribution in the width direction of the two strips remains uniform.

In addition, although the required total fuel: lXm1 F t was calculated|required by formula (2) and (3) above, it may be calculated|required from a more detailed heat balance formula as follows.

Integrate the heat transfer equation (4) below from x = 0 to N (furnace length) and calculate 7
, T for r@ at x = 1 to become the target plate temperature, ,
I'm looking for apricot. Substitute T into the heat balance equation (5) to obtain FL.

(T, +273)') −(4)FtCz
-Qs+Qi+C3FtTm -"" (5) where 'r1: Furnace temperature 1', Nislip temperature Q,: Furnace body dissipated heat C1~C1: Constant (2) Almost the same configuration as explained in section (1) above , changes in the parameters of strip thickness, strip width, 3.in speed, and target strip temperature are detected, and the arithmetic processing unit 2
In step 2, the required total fuel flow *CFt> according to the required heat removal IQ of the strip (formula (2) above) obtained from each of the same parameters is calculated. Next, an optimal fuel flow rate distribution pattern to each burner group is determined in advance in relation to the necessary heat removal amount and plate width of the F-street knob. −Jj, sheet temperature feedback in the sheet width direction that operates the fuel flow rate of each burner group in the sheet width direction based on the sheet temperature detection value in the sheet width direction after a predetermined time has elapsed at a predetermined time before the change of each of the above parameters; From the fuel flow rate detection values of each burner group mentioned above when the control system is stable, the following equations (6) and (7) can be calculated.
From this, the constant R, which determines the fuel flow rate distribution button, is calculated backwards.1. The optimal fuel flow pattern is successively modified.

L-"1 R1-L-L~Tobe-1 ΣV'1, where Fi(t): 1st zone fuel flow detection value y' at time j; 1st zone fuel flow rate f average value ΔL: sample Period (k-L) Δt: Sample time (when 0, the current time is 6) LΔt: PPJ calculation time of Fi(t) (for example, F
It is assumed to be approximately three times the fluctuation period of t(t). ) The correction is 1) D1 in the fuel 1 flow distribution pattern table.
The table usage is corrected by replacing the previous value with the current value in equation (7), or by replacing it with the weighted average of the previous value and the current value.

From this modified fuel flow rate distribution pattern, the optimum fuel flow rate to each burner group is determined by the above equation (1), and when the parameter changing section of the strip passes through each burner group, the switching device 25.26° 27 is switched, the feedback control system is turned OFF, and signals 23, 24.25 of the optimum fuel flow rate are outputted, and then after being held for a certain period of time, the switching devices 25, 26, and 27 are switched back to their original positions. The filled pack control system returns to ON.

The timing is, for example, when the plate temperature distribution detection value continues for a predetermined period of time or more and is within a permissible value.

In this way, even when the parameters of the strip change, the strip width distribution in the strip width direction remains uniform.

〔Effect of the invention〕

As explained above, according to the present invention, even when parameters such as sheet thickness and sheet width change in the sheet temperature distribution control method in the sheet width direction of a heating furnace, the responsiveness is improved and the sheet width is The plate temperature in the direction will be 4 degrees.

Therefore, the product 'a' and the yield direction J- can be measured.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a plate temperature control system of a heating furnace as an embodiment to which the method of the present invention is applied, Fig. 21>0 is an explanatory diagram of the fuel 'mF1 distribution pattern of the same embodiment, and Fig. 3 is a conventional example. Fig. 4 is an explanatory diagram of the complete cycle of the conventional alloying plating equipment, and Fig. 5 shows an example of the conventional heating furnace. Figure 6 is a partial cross-sectional view of the burner arrangement example of the heating zone of the alloy plating equipment in Japan, Figure 6 is a cross-sectional view of ■-Vl in Figure 5, and Figure 7 is the plate 4 control string of the heating furnace of the Confucian Song Dynasty. It is a diagram. I Strip, 10.1). 12- Board temperature 1! Fuel meter, 1.3.14.15-1 fuel flow rate, 23,
24. , 25-optimum fuel $4 kan 1) (setting value), 28
Furnace wall, 22-computation processing unit, 8--direct fire burner, 9-scanning plate thermometer (plate temperature detector), 5-heating zone. Agent: Patent Attorney Akigai Sakama (2 people) Figure 2 Figure 4 Figure 6

Claims (2)

[Claims] (1) In a heating furnace strip temperature control method in which a plurality of burner groups are arranged in the strip width direction and the fuel flow rate of each burner group is controlled so that the strip temperature distribution in the strip width direction is uniform. , When the above-mentioned strip thickness, width, line speed, and target strip temperature change, the required total fuel flow rate ( F_t) to obtain a fuel flow distribution pattern to each of the burner groups that is related in advance to the heat removal amount and plate width of the strip;
Further, the fuel flow rate to each burner group is determined by the following equation (1), and when the parameter changing part of the strip passes through each burner group, the fuel flow rate is caused to flow to the same burner group for a predetermined period of time. Method for controlling plate temperature in a heating furnace. F_i_s=(1+R_i)F_t/N(i=1~N)
...(1) Here, F_i_s: Optimal fuel flow rate for the first zone in the plate width direction (set value) F_t: Total fuel flow rate (obtained from operating conditions) R_i: Fuel flow rate to the first zone A constant that determines the distribution pattern (obtained from a table that shows the relationship between strip heat removal and plate width.) However, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ N: Number of zones in each burner group in the plate width direction (2) In a heating furnace strip temperature control method in which a plurality of burner groups are arranged in the strip width direction and the fuel flow rate of each burner group is controlled so that the strip temperature distribution in the strip width direction is uniform. , When the above-mentioned strip thickness, width, line speed, and target strip temperature change, the required total fuel flow rate ( F_t) to determine the fuel flow distribution pattern to each burner group that is related in advance to the heat removal amount and plate width of the strip, and at a predetermined time before the change of each parameter above, after a predetermined time has elapsed. , Claims from the detected value of the fuel flow rate of each burner group when the board temperature feedback control system in the board width direction that operates the fuel flow rate of each burner group based on the board temperature detection value in the board width direction is stabilized. (1) described in (1)
) is the constant R_ that determines the fuel flow distribution pattern from the relationship of the formula.
Reverse calculation of i and sequentially correct the above fuel flow distribution pattern,
From this modified fuel flow distribution pattern, the fuel flow rate to each burner group is determined by the formula (1) described in claim (1), and when the parameter changing part of the strip passes through each burner group, , a method for controlling plate temperature of a heating furnace, characterized in that the above-mentioned fuel flow rate is caused to flow to each burner group for a predetermined period of time.