JPH032213B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion control method for a multi-zone heating furnace. An energy-saving operation control method for a heating furnace is an important issue in furnace operation. Predetermine and memorize a temperature rise schedule curve that takes energy savings into consideration.
There is a method of controlling the furnace along a memorized curve. However, the temperature rise schedule curve suitable for energy conservation will vary depending on the operating status and operating plan of the furnace.
Further, the amount of fuel required to heat a certain piece of steel in the furnace to a predetermined temperature varies depending on not only the heating state of the piece of steel itself but also the heating state of other pieces of steel in the furnace and the scheduled heating curve. Therefore, even if the steel slab is heated according to the stored temperature increase schedule curve, a satisfactory energy saving effect cannot necessarily be obtained, and there is a problem that the steel billet cannot be heated to the scheduled extraction temperature. Furthermore, it is almost impossible to memorize in advance the temperature increase schedule curves for all possible state changes and all operational plans.

The present invention has been made to solve these problems. The present invention predicts the current heating state of a steel billet or a group of steel billets and the fuel flow rate required until it is extracted over the remaining furnace time, and increases the fuel flow rate so that the predicted fuel flow rate is minimized. This method finds the temperature schedule curve and performs control.

In particular, the remaining furnace time until extraction is divided into multiple time regions, and the furnace temperature in each of the divided time regions is used as an independent variable to search and determine a planned temperature increase curve that minimizes fuel consumption. be.

The combinations of billets charged into the heating furnace are not randomly charged, but billets of similar size and steel type are charged together, or billets of approximately the same temperature are charged together. , etc. In other words, there are several groups of billets in the furnace that are similar in size, steel type, charging temperature, etc.

In addition, if continuous casting equipment and heating furnace operations are closely linked, a certain amount of billets will arrive one after another from the continuous casting equipment, and the next group of billets will arrive after a certain period of time and be loaded. may be entered. That is, there are cases where the successive charging timing of one group of steel billets and the charging timing of the next group are relatively close to each other, and cases where they are significantly different from each other.
In such a case, the movement history of the steel billets in the furnace differs depending on the billet group to which each billet belongs.

If a preferable temperature-rise curve from an energy-saving perspective were determined for each billet, billets in the same group would have similar temperature-rise curves, and different groups would have different temperature-rise curves. have.

From the above-mentioned viewpoint, in the embodiment of the present invention, a case will be described in which the steel slabs in the furnace are divided into groups and a scheduled temperature increase curve for each group is determined. In the following, steel billet groups in the furnace will be named groups a, b, c, . . . from the extraction port to the charging port and will be described.

Next, regarding estimation of the steel billet temperature, it is assumed that the internal temperature distribution of the steel billet in the furnace can be determined by calculation. A method often used in conventional automatic combustion control is to calculate the amount of heat flowing in from the surface of a steel billet using a radiation model, and calculate the heat transfer inside the billet using a heat diffusion equation. (For example, the Iron and Steel Institute of Japan, Special Report No. 11, "Heat Transfer Experiments and Calculation Methods in Continuous Billet Heating Furnaces," published in May 1980, etc.) If the value of the furnace temperature history T around one piece is known, the current temperature of the steel piece can be found using the above method.
Furthermore, when the current billet temperature is known, the previous value of the billet temperature can be predicted by assuming the furnace temperature history around the billet since the present time. This predictive calculation is used in calculating the temperature increase schedule curve.

In the following, the average value of the steel billet temperature, the difference between the surface and internal temperatures will be expressed as Δθ, and the internal temperature distribution of the steel billet will be expressed as θ.

Furthermore, the amount of heat absorbed by the steel piece within a certain time will be expressed as q. The value of q can be easily determined by integrating the amount of inflow heat calculated using the above-mentioned radiation model within that time.

The schedule for moving the steel billet in the furnace can be determined by calculation if the information on the extraction plan for the steel billet is given. The extraction plan is usually given as the rolling production amount, but if it is not given, it may be estimated from the rolling results to date or a standard value may be used. Once the extraction plan is given, the average extraction pitch corresponding to the extraction amount is determined, and the extraction time of each steel slab is determined by assuming that the steel slabs will be extracted at that pitch in order starting from the extraction side. If there is an appropriate waiting time between the extraction of one group of billets and the next group of billets, the time of extraction of the billets of the subsequent group may be delayed by that amount.

If the walking beam that actually moves the billet is integrated, the movement pattern of the following billets in the furnace is automatically adjusted by moving so that the leading charge arrives at the extraction port by the scheduled extraction time. It's decided. Furthermore, even in furnaces with independent walking beams for each hearth zone, and in split-type moving hearth furnaces, if the rules for how to move the walking beams are taken into consideration, the subsequent The movement pattern of the steel slab in the furnace is determined (the specific calculation method is omitted because it is not related to the purpose of this application).

Once the movement pattern in the furnace is determined in this way,
Then it is easy to know how long each billet will stay in each zone in the furnace in the future.

Also, as shown in Figure 1, the steel slabs in the fourth zone from the extraction side of the heating furnace are grouped a, the steel slabs in the third zone are group b, and the steel slabs in the first zone are group d. (Figure 1 shows the case where there is no steel piece in the second band).

In addition, in the control method described below, the in-furnace time τz, which represents how many pieces of steel (or a group of steel pieces) exist in the furnace before being extracted, and the furnace zone residence time, which shows how much they stay in each zone, are used. Time is an important parameter, but its value can be predicted in advance. Although FIG. 1 shows an example of a split hearth, it goes without saying that the present invention is equally applicable to a conventional walking beam type furnace, that is, a continuous furnace in which the hearth is integrated.

In the present invention, the temperature rise curves of the steel slabs belonging to each group are calculated in order from the extraction side group to the charging side group. In the following, a method for calculating a temperature rise curve will be described using as an example the charge b retained in the (M-1)th zone as a general formula for a heating furnace consisting of M zones. It is assumed that charge a remains in the M-th zone, and the calculation of its temperature rise curve has been completed (the calculation method is essentially the same as that for charge b, but there are some things to note. There are some points (I'll get to that later).

Therefore, at the time of starting the calculation of charge b, the values of the optimum furnace temperature and fuel flow rate necessary for heating charge a in the M-th zone have already been calculated.

What must be noted when heating group b is that while group b exists in the (M-1) zone, high-temperature exhaust gas generated as a result of heating group a in the M zone will flow in. That is to say. Therefore, the fuel flow rate injected in the (M-1)th zone for heating group b becomes a different value depending on what kind of heating is performed in group a. If the calculation of the temperature increase schedule curve for group a is completed first, the sensible heat of the exhaust gas flowing out from the furnace zone M at each time is known, so as described below, the fuel required for heating charge b is Flow rate can be calculated.

First, the time that group b stays in the (M-1) band and M band is expressed as τ _b,M-1 and τ _b,M , and K _{M-1 and τ b,M} respectively.
Divide into K _M time domains. At this time, the future furnace temperature history until the extraction of group b is {T ⁽¹⁾ _M-1 , T ⁽¹⁾ _M-1 , ..., T ^(KM-1) _M-1 , T ⁽¹⁾ _M , ..., T ^(KM) _M }, which are collectively expressed as T _b . Here T ⁽¹⁾ _M-1 ,
..., T ^(KM-1) _M-1 is the temperature history in the (M-1) zone of group b, T ⁽¹⁾ _M , ...T ^(KM) _M is the temperature after advancing to the M-th zone Let T _b,M-1 and T _b,M be respectively in the history.

Below, the furnace temperature history is simply expressed as follows.

T _b = {T ^(K) | K = 1, ...K _M ′} K _M ′ = K _M-1 + _K At any time when M charge b is in furnace zone I (I = M-1, M) Calculate the fuel flow rate v ^(K) _b using the following formula.

v ^(K) _b = QT〓／Δτ＋QT〓／Δτ／H _L ′−T ^(K) / _M-1・C _g
w +C _gw (T〓−T〓)vT〓/H _L ′−T ^(K) / _M-1 C _gw …(1) (K=1,2,…,K _M ,…,K _M ′) [Q ^(K) _b : Heat received by the slab of group b in the K-th time region Q ^(K) _L : Heat loss of the associated furnace zone in the K-th time region ^(K) _M-1 , ^(K) _M :(M-th in the K-th time domain)
1) Temperature of the waste gas flowing out from the zone and the M-th zone Δτ: Time length of the K-th time region H _L ′, C _gw : Constant] Here, the second term on the right side is the term representing the influence of heating on group a. , when K≧K _M-1 +1 after the time when group b enters the M-th zone, v ^(K) _a =0.

Also, when K≧K _M-1 +1, ^(K) _M-1 is used instead of ^(K) _M-1 in the first term.

Furthermore, when 1≧K≧K _M-1 , ^(K) _M is a value determined by the heating of group a staying in the M-th zone, and this is determined when calculating the temperature rise curve of group a as described above. Assume that it is on. K≧K _M-1 +1
Then, ^(K) _M is a value that changes depending on the heating method of group b. The amount of heat received by group b Q ^(K) _b is the Kth
It can be easily determined as the sum of the amount of heat received by each slab, q, which can be determined by calculating the temperature of the slab in the time domain. The amount of heat loss Q ^(K) _L and the exhaust gas temperature ^(K) are linked to the furnace temperature T ^(K) by the following regression equation.

Q ^(K) _L =ξT ^(K) +η ...(2) ^(K) =αT ^(K) +β ...(3) Here, ξ, η, α, and β are regression coefficients determined experimentally.

From the above, if the furnace temperature {T ^(K) |K=1~ _{K M} ′} is given, the fuel flow rate v ⁽¹⁾ _b , v ⁽²⁾ _b ,...
…, v ^(KM ′ ⁾ _b can be calculated using equation (1).

At this time, the required fuel usage amount V _b when group b is heated at the planned furnace temperature history T _b can be calculated from the following equation.

V _b =v ⁽¹⁾ _b Δτ _M-1,b +...+V _b Δτ _M-1,b +...+
v ^(KM ′ ⁾ _b Δτ _M,b ……(4) Here Δτ _M-1,b ＝τ _b,M-1 ／K _M-1 ……(4′) Δτ _M,b ＝τ _b,M /K _M ……(4″) At this time, the problem is to find a heating method that minimizes V _b and a corresponding temperature rise curve, but in actual heating furnaces there are various operational constraints. Here, the main ones are expressed as the following constraint equations and reflected in the calculation of the temperature rise curve.

^L ≦≦ ^U (Extraction condition 1) ……(5) Δθ ^L ≦Δθ≦Δθ ^U (Extraction condition 2) ……(6) T ^L _K ≦T ^(K) ≦T ^U _K (Furnace temperature condition) …… (7) v ^L _K ≦v ^(K) _b ≦v ^U _K (Fuel flow rate condition) ……(8) (K=1~K _M ′) Here, the subscript L represents the lower limit value and U represents the upper limit value. . Equation (5) is a condition regarding the average value of the internal temperature of the steel slab during extraction, and Equation (6) is a condition regarding the temperature difference between the surface and interior of the steel slab during extraction.

Next, we will specifically describe the calculation algorithm for finding a heating method that minimizes the fuel flow rate under constraint conditions, using the furnace temperatures T ⁽¹⁾ , T ⁽²⁾ , ..., T ^(KM ′ ⁾ as independent variables. . The method described here first uses a nonlinear function
Start by finding the linear form of v ^(K) _b and Δθ. The reference value of the furnace temperature in the time division domain is T ⁰ _b = (T ⁽¹⁾ ₀ ,
T ⁽²⁾ ₀ , ..., T ^(KM ′ ⁾ ), and the furnace temperature that has slightly deviated from that temperature is expressed as T _b = (T ⁽¹⁾ , T ⁽²⁾ , ..., T ^(KM ′ ⁾⁾ . , the difference between the two is (ΔT ⁽¹⁾ , ΔT ⁽²⁾ , ..., ΔT ^(KM ′ ⁾
It is expressed as At this time, the function v ^(K) _b , , Δθ of T _b is
By performing linear approximation around T ^{0 b} , the following equation is obtained (how to determine T ⁰ _b will be described later).

= ₀ + _kM 〓 ^J=1 ′α _J・ΔT ^(J) ……(9) Δθ=Δθ ₀ + _kM 〓 ^J=1 ′β _J・ΔT ^(J) ……(10) Δ ^(K) _b = v ^(K) _b0 + _kM 〓 ^J=1 ′γ ^(K) _J ΔT ^(J) ……(11) (K=1~K _M ′ where ₀ , Δθ ₀ , v ^(K) _b0 is the furnace temperature T _b Means the average temperature of the billet when heated at ⁰ , the temperature difference between the inside and outside, and the fuel flow rate in each time domain, and α _J , β _J , γ ^(K) _J are coefficients that represent the magnitude of the influence of furnace temperature changes. (influence coefficient).

The value of each element of T ⁰ _b = {T ⁽¹⁾ ₀ , T ⁽²⁾ ₀ , ..., T ^(KM ′ ⁾ ₀ } should be selected as follows.

1≦K≦K _M-1 T ^(K) ₀ =T ⁽⁰⁾ _M-1 (Current furnace temperature in M-1 zone) K _M-1 +1≦K≦K _M ′ T ^(K) ₀ =T ⁽⁰⁾ _M (at the initial furnace temperature when group b enters the M zone, group a
(determined by temperature rise calculation).

If the values of α _J , β _J , γ ^(K) _J (K, J = 1 to K _M ) are known, when the furnace temperature in each time division zone changes by a certain value, the steel billet at the time of extraction The values of temperature, Δθ, and fuel flow rate v ^(K) _b can be determined from equations (9) to (11). The influence coefficients α _K , β _K , γ ^(K) _J can be calculated by the following procedure.

(i) Calculate the value of Δθ, v ^(K) _b when heated at the furnace temperature T ⁰ _b . The calculation results are ₀ , Δθ ₀ , v ^(K) _b0 (K=1~
_KM ).

(ii) When only the furnace temperature in the K-th time division zone increases by a predetermined temperature <ΔT>,
Find the value of Δθ, v ^(K) _b and use it as <>, <Δθ>, <
Let v ^(K) _b > (K=1 to K _M ′).

(iii) In this case, α _J , β _J , and γ ^(K) _J are calculated using the following equations.

α _J = (<>− ₀ )/<ΔT> …(12) β _J = (<Δθ>−Δθ ₀ )/<ΔT> …(13) γ ^(K) _J = (<v ^(K) _b > −v ^(K) _b0 )/<ΔT> (14) If the above calculation is performed for K=1 to K _M , all influence coefficients can be found.

When formulas (9) to (11) are replaced by formulas (4) to (8), the following formulas are obtained.

V _b =C ₀ +C ₁ t ₁ +……+C _KM ′t _KM ′ …(15) b ^L 〓≦α ₁ t ₁ +……+α _KM ′t _KM ′≦b ^U 〓 …(16) b ^L 〓〓≦β ₁ t ₁ ＋……＋β _KM ′t _KM ′≦b ^U 〓〓……（17
) O≦t _K ≦b ^U _t,K (J=1~ _{K M} ′) ……(18) b ^L _v,K ≦γ ^(K) ₁ t ₁ ＋……＋γ ^(K) _KM ′t _KM ′ ≦b ^U _v,K (K=1~ _{K M} ′...(19) Here, t _K =T ^(K) −T ^L _K (K=1~ _{K M} ′)...(20) Also, C _a ,...,C _KM ′,b ^L 〓,b ^U 〓,b ^L 〓〓,b ^U 〓〓
, b ^U _t ,
K, b ^L _v , K, b ^U _v , K are influence coefficients, T ⁰ _b , ₀ , Δθ ₀ ,
It is uniquely determined by applying v ^(K) _b0 to equations (4) to (11).

Equations (15) to (19) are variables {t ₁ , t ₂ , ..., t _KM ′}
Since this is _a linear _{relational expression} for do.

The method for solving this problem is well known and is not related to the essence of the present invention, so its explanation will be omitted. Let the solutions obtained using the linear programming method be {t ₁ ^* , t ₂ ^* , ..., t ^* _KM ′}. Applying this to equation (20) yields the optimal furnace temperature set {T ^(1)* , T ^(2)* , ..., T _(KM ′ _)* }.
Furthermore, we calculate the time change in the billet temperature when a representative billet is heated with this set of furnace temperatures, and calculate this change over time for group b.
Let the planned temperature increase curve θ* be θ ^* .

Figure 2 shows an example of the calculation results. Figure 2 shows K _M ′=
4, and a indicates the change in furnace temperature over time, that is, {T ^(1)* , ..., T ^(4)* }. b shows the temperature increase schedule curve θ ^* . Further, c indicates the time course of the fuel flow rate. The fuel v ^(K)* _b at each time is
T ^(K)* was calculated by applying equation (1).

In the above explanation, it is assumed that the temperature increase schedule curve for group a has been calculated in advance, and that the influence on the heating of group b can be known from the calculation results. On the other hand, group a staying in the Mth band
In this case, the temperature increase schedule curve can be calculated without considering the influence of heating in other groups. That is, in the Mth zone, the waste gas only flows out and does not flow in. Furthermore, since the M-th band is the final band, there is no possibility of moving to the next band and being affected by the heating of the preceding group there.

Therefore, when calculating the optimal temperature increase schedule curve by dividing the time until extraction of group a appropriately and using the M zone furnace temperature in each time division area as an independent variable, the calculation is easier than calculation for group b. become. for example
For the fuel equation (1), in the case of group b, it is sufficient to consider only the equation corresponding to the first term, and the current furnace temperature in the M-th zone may be used as the reference furnace temperature for linearization. The calculation procedure is the same as for group b, so it will be omitted.

A specific embodiment of the present invention will be described below with reference to FIG.

In Fig. 3, 1 is the heating furnace main body, 2 is the heating furnace flue 3, 3 _{~ 1} ~ 3 _{~ 3} is the split type moving hearth, 4 is the steel piece in the furnace, 5 is the burner, 6, 6 _{~ 1} ~ 6 ₃ represents a minor controller, 7, _{7 1} to 7 ₃ represent a furnace temperature detector, and 100 represents a combustion control device.

The steel slabs 4 charged into the heating furnace 1 are divided into moving hearths 3
It is heated while being transported by the beam through the furnace to the extraction port. The combustion control device 100 outputs the furnace temperature set value or fuel flow rate set value for each zone to the minor controller 6 so that the temperature of the steel billet 1 reaches a desired value. The minor controller 6 adjusts the opening degree of the burner 5 so that the furnace temperature or fuel flow rate matches a given set value. The air input from the burner is combusted by a fuel mixture in the furnace to heat the steel billets. The combustion control device 100 has a function of heating the steel billet in the furnace to the extraction temperature of the steel billet with a minimum amount of fuel input.

FIG. 4 shows the functional configuration of the combustion control device 100. In FIG. 4, 101 is an information management department, 102
Reference numeral 103 indicates a steel billet temperature calculation section, 103 a temperature rise curve calculation section, and 104 a control calculation section.

The information management unit 101 divides the steel pieces in the furnace into groups of divided hearth units. That is, when a plurality of steel billet groups in the first zone start moving to the second zone, this steel billet group is regarded as one group in subsequent heating.
If pieces of steel continue to be loaded after starting to move to the second zone, pieces of steel that are more than a certain distance away from the head of the group are considered to belong to another new group.

The second function of the information management unit 101 is to determine the timing for calculating the temperature increase schedule curve for each group. The heating furnace changes its operating plan depending on the operating state of the rolling mill on the outlet side of the heating furnace. When such a change in furnace operation occurs, the temperature increase schedule curve that was considered optimal until then does not necessarily match the actual situation. Commands calculation of temperature schedule curve. Further, even if an attempt is made to heat the steel billet according to the planned temperature increase curve, if the disturbance is large, the difference between the temperature of the steel billet and the planned temperature increase curve becomes large. In such a case, the optimal temperature increase curve for achieving the target temperature using the current heating state as a starting point will be different from the current temperature increase schedule curve. Therefore, the temperature increase schedule calculation unit 103 is configured to recalculate the temperature increase schedule curve after a certain period of time has elapsed since calculating the currently used temperature increase schedule curve.
issue instructions to. Furthermore, when a group moves from one zone to another, the projected temperature increase curve is recalculated.

As described above, when the occurrence of a predetermined event is detected, the information management unit 101 instructs the temperature increase expected curve 103 to calculate a temperature increase schedule curve. It goes without saying that the events are not limited to those described above.

A billet temperature calculation unit 102 calculates the current temperature of all billets in the furnace. In this calculation, the furnace temperature around the steel slab is determined from the furnace temperature in each zone (T^ ₁ , T^ ₂ , ..., T^ _N ) detected by the furnace temperature detector 7. For example, when a steel piece is located between the d-th and d+i-th furnace temperature detectors, the furnace temperature T around the steel piece is calculated using the following equation.

T^=(T^ _d+1 −T^ _d )・L ^l _d +T^ _d ...(21) L _d : Distance between furnace temperature detector d and (d+1) l: From furnace temperature detector d Distance to the steel billet Assume that the temperature of this steel billet has been heated at this T since the last time the temperature was calculated, and calculate the change in the temperature of the steel billet up to the present. This value becomes the starting point for the next billet temperature calculation and is further used as the initial value for the temperature increase schedule curve calculation. The specific calculation method uses the radiation model and thermal diffusion model as described above. As a result, the internal temperature distribution θ of the steel piece is obtained.

The temperature increase schedule calculation section 103 is the information management section 101
Upon receiving a command to calculate the planned temperature rise curve, the calculation starts immediately. The specific method was described in detail earlier.

The calculation flow for group b is shown in FIG. In steps 40, 70, and 130 in the figure, the temperature of the steel piece is calculated, but the details are omitted as described above.

Also, when calculating the fuel flow rate in steps 40 and 70, the value of the fuel flow rate input for group a in the extraction side band is required, but for this purpose, the temperature rise of group a must be determined prior to the calculation of group b. It is necessary to calculate the curve. This will be discussed later. Note that in the case of group a in the M-th zone, there is no inflow of waste gas, so calculation can be performed using the same flow as in FIG. 5, except that calculation of the fuel flow rate is simplified. It goes without saying that the calculation flow for group d is also exactly the same as that in FIG.

Next, the relationship between events detected by the information management section 101 and calculations by the temperature increase schedule curve calculation section 103 will be described.

As an example, first consider a case where extraction of steel billets from a heating furnace is stopped due to rolling trouble. At this time, when the operator inputs the scheduled stop time Δτz, the information management unit 101 receives this information and instructs the temperature increase schedule curve calculation unit 103 to calculate a temperature increase schedule curve. The temperature increase schedule curve calculation unit 103
Instead of the previous in-furnace time τz, τz + Δτz is regarded as the new in-furnace time, and the temperature increase schedule curve is calculated. Figure 6 shows the calculation results. is before the change, and is after the change. It can be seen that the fuel flow rate level has decreased and the temperature rise schedule curve is suitable for energy saving.

As another example, a case will be described in which the information management unit 101 detects that a certain period of time has passed since the previous calculation of the temperature increase schedule curve and issues a command to the temperature increase schedule curve calculation unit. Let us consider a case where the billet temperature is considerably lower than the planned temperature rise curve due to an unexpected disturbance.
At this time, the temperature increase schedule curve calculation unit 103 performs calculations using the current billet temperature as a starting point to reach the target temperature. The results of this calculation are shown in FIG. θ
*() indicates the old curve, and θ*() indicates the new temperature increase schedule curve.

The temperature increase schedule curve θ* for each group calculated by the temperature increase schedule curve calculation unit 103 is output to the control calculation unit 104. The control calculation unit 104 inputs this θ* and the temperature θ of each billet calculated by the billet temperature calculation unit 102, and sets the furnace temperature or fuel set value so that each billet is heated along θ*. Calculate. The calculation method is not related to the present invention and will therefore be omitted, but an example thereof is detailed in Japanese Patent Publication No. 49-29403.

Next, the effect of grouping the steel slabs in the furnace and determining the planned temperature increase curve in order from the furnace zone on the extraction side will be explained. Therefore, in the first case, group a is a collection of steel pieces with a thickness of 250 mm, and group b is a collection of steel pieces with a thickness of 200 mm.
Consider the case of a collection of mm steel pieces. On the other hand, the second
Assume that both groups a and b are a collection of steel pieces with a thickness of 200 mm. In other words, consider two cases in which the thicknesses of the groups on the extraction side of group b are different, 250 mm and 200 mm. At this time, the results calculated for the scheduled temperature increase curve of group b are
As shown in the figure. Although the first case reaches a higher temperature earlier than the second case, the fuel level is rather low. This is because in the first case, group a is thick, so the furnace temperature is raised to heat it. This can be considered to be because the temperature of the exhaust gas flowing into the position of group b becomes high as a result, and a large amount of heat flows into the position.

Next, we will briefly discuss how the number of divisions regarding the residence time of each band is specifically determined.
Figure 9 shows the number of divisions when billet group b stays in the (M-1) zone and M zone for 40 minutes each.
The calculation results are shown when K _M-1 and K _M are both set to 1, 3, and 5. Figure 9a shows the calculation results of the expected temperature rise curve, and Figure 9b
is the calculated value of the consumed fuel flow rate when the number of divisions of both bands K _M-1 and K _M are 1, 3, and 5, K = K _M-1 = K _M =
It is expressed in the form of a ratio, with the case of 1 being 100.

According to FIG. 9a, when K is 1, the temperature increase schedule curve becomes considerably large at the place of the furnace zone, whereas as K increases, a smooth temperature increase schedule curve is obtained. Also, according to FIG. 9b, K=1
The fuel consumption is the highest when K = 3 and 5.
There is not much difference in the case of The reason why the fuel consumption is large when K=1 is considered to be due to the calculation conditions such that the furnace temperature is kept at a certain high temperature while group b passes through the furnace zone (K=1). When a group of billets enters a new furnace zone, the temperature of the furnace in that zone is rapidly increasing.
(as shown in the figure). On the other hand, when K=3 and 5, the furnace temperature in the same furnace zone rises over several stages over time, so the thermal efficiency decreases due to rapid heating (mainly caused by the rise in exhaust gas sensible heat). It can be prevented.

If we thoroughly follow this idea, we will be able to obtain a temperature rise schedule curve in which the larger K is, the higher the energy-saving effect will be.However, as can be seen from Figure 9b, there is almost no difference even if K is increased beyond a certain point. . On the other hand, when K is increased, the above-mentioned influence coefficient increases rapidly, and the calculation time increases rapidly. For this reason, it is not preferable to make K too large. According to past experience, it is preferable to select K so that the division time Δτ is about 10 to 20 minutes, and the value of K is preferably about 2 to 4. This indicates that the response characteristic of the furnace is approximately 10 to 20 minutes, and there is no point in dividing the time into more detailed time periods.

Furthermore, when dividing the remaining residence time of the furnace zone to which it currently belongs by a certain value of K, if Δτ is smaller than the predetermined minimum division time Δτ _MIN , then
It is also effective to re-determine Δτ by setting the number of divisions to K-1. It will be clear from the above explanation that K should be 1 when the remaining residence time is smaller than Δτ _MIN .

Note that the energy saving effect of time division differs depending on the furnace zone. For furnaces where it is more effective to time-divide the zone on the extraction side, divide only the residence time of the zone closer to the extraction side, and calculate the planned temperature rise curve for the zone closer to the charging side without dividing the time. It's okay. By doing so, the influence coefficient calculation time can be shortened without sacrificing the energy saving effect too much.

In the previous example, θ, Δθ, v ^(K) _M were linearized to determine the optimal furnace temperature change and the corresponding temperature increase schedule curve θ*, but θ, Δθ, v ^(K) _M Since it is a nonlinear function of furnace temperature change, θ is calculated using nonlinear programming method.
* can be determined.

Further, θ* calculated in the present invention is not only used for control but also useful as driving guidance information for the operator.

As described above, according to the present invention, it is possible to calculate on-line a temperature increase schedule curve with a high energy-saving effect, taking into account changes over time in the furnace temperature of each zone through which a group of steel billets will pass from now on.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the split type moving hearth, Figure 2 a
b shows the time course of the furnace temperature, b shows the planned temperature increase curve, c shows the time course of the fuel flow rate, FIG. 3 shows an explanatory diagram of the entire control system according to the present invention, and FIG. 4 shows a block of the fuel control device Figure 5 shows the calculation flow for group b, Figure 6 shows the predicted fuel flow rate and billet temperature, and Figure 7 shows the temperature increase schedule calculated based on the current billet temperature. Figure 8 shows group b
FIG. 9 shows the relationship between the number of time divisions and the billet temperature and fuel flow rate in two cases of billet temperature and fuel flow rate for billet group b. 1...furnace body, 2...flue, 3 _~1 ~3 _~4 ...divided type moving hearth, 4...steel piece, 5...burner, 100
... Combustion control device, 101 ... Information management department, 10
2... Steel billet temperature calculation section, 103... Temperature increase schedule calculation section.

Claims (1)

[Claims] 1. A combustion control method for a heating furnace that has a plurality of furnace zones and transfers and heats a steel billet along a scheduled temperature rise curve,
The remaining furnace time of one steel billet or a group of steel billets adjacent to each other is divided into a plurality of time regions, and for each of a plurality of heating patterns given as a combination of furnace temperatures in each time region. The fuel consumption and extraction temperature of the steel billets are calculated, and the calculation results are used to calculate the remaining furnace time during which the temperature of the steel billet or group of billets is within a predetermined allowable range and the fuel consumption is minimized. calculate the optimum heating pattern for the steel billet, calculate the planned temperature increase curve for the steel billet or group of billets using the computed optimum heating pattern, and calculate the temperature increase curve for the billet or group of billets during the remaining furnace time. Or a combustion control method for a heating furnace, which is characterized by heating a group of steel slabs. 2. A heating furnace characterized by dividing the remaining furnace time in at least one furnace zone into a plurality of time regions when dividing the remaining furnace time according to claim 1 into a plurality of time regions. combustion control method. 3. When dividing the remaining furnace time into a plurality of time regions according to claim 1, the remaining furnace time is divided into a number of time regions that is equal to or greater than a predetermined minimum number of time regions. Combustion control method for heating furnace. 4. A combustion control method for a heating furnace, characterized in that the minimum time range according to claim 3 is determined based on the response time of the furnace. 5. A combustion control method for a heating furnace as set forth in claim 2, characterized in that only a predetermined furnace zone is divided into a plurality of time regions for a time period in which the furnace zone is occupied. 6. A heating furnace combustion control method as set forth in claim 1, characterized in that when dividing the remaining furnace time into a plurality of time regions, the remaining furnace time is divided within a range not exceeding a predetermined maximum number of divisions. 7. A combustion control method for a heating furnace, characterized in that the amount of fuel consumed in each heating pattern as set forth in claim 1 is calculated as a sum of calculations for each of the divided time regions. 8 In calculating the fuel consumption amount as set forth in claim 7, the fuel consumption amount in the divided time region of the furnace zone is calculated by taking into account the sensible heat of the exhaust gas flowing from the extraction side furnace zone adjacent to the furnace zone. A combustion control method for a heating furnace characterized by predictive calculation. 9. A combustion control method for a heating furnace according to claim 7, characterized in that the fuel consumption in the divided time domains is calculated sequentially from the steel slabs in the furnace zone on the extraction side of the furnace. 10. A combustion control method for a heating furnace, characterized in that the optimum heating pattern according to claim 1 is calculated by the following steps. (a) From the fuel consumption and the extraction temperature of the steel billet or steel billet group in the plurality of heating patterns determined by the calculation, calculate the fuel consumption or the extraction temperature for the change in the furnace temperature in the plurality of time-divided regions. Steps to derive the relationship as a linear form. (b) a step of calculating the optimum heating pattern using the derived linear form; 11. Using the calculation results of the fuel consumption and extraction temperature in the heating pattern given as a combination of the furnace temperatures of each time domain as set forth in claim 10, the change in the furnace temperature of the divided time domain is determined. Calculate the influence coefficient on the fuel consumption and extraction temperature, and use the calculated influence coefficient to set the furnace temperature to a given one based on the deviation from the predetermined reference value of the furnace temperature in each time division area. A combustion control method for a heating furnace, comprising predicting and calculating the fuel consumption amount and the extraction temperature.