JPH0374407B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a process in which a raw material is distributed into a plurality of channels, and the raw material in each of the distributed channels is heat-treated in a heating furnace. The present invention relates to a heating process control method that controls the raw material temperature after heat treatment to be equal to each corresponding set value.

[Technical background of the invention and its problems] In fields such as general chemistry and petrochemistry, heat treatment is performed as a basic unit operation worthy of raw materials.

As this heating furnace, an atmospheric distillation apparatus or an ethylene decomposition furnace is often used to heat-process the raw material using a multi-pass system in which the raw material is divided into a plurality of channels (hereinafter referred to as "passes").

The raw material after this heat treatment is processed in a downstream process to become a product. Therefore, the accuracy of temperature control at the outlet of the heating furnace is considered to be an important factor that affects the quality of the product.

Therefore, in the multi-pass, the flow rate of each pass and the fuel flow rate of the furnace are adjusted so that the furnace outlet temperature of each pass becomes a predetermined value.

However, the furnace outlet temperature depends on the temperature change of the raw material.
It is difficult to control as it is easily affected by the flow balance of each pass and changes in the combustion state of the furnace. Furthermore, by passing through a long path, dead time makes the furnace outlet temperature unstable.

Here, a conventional heating furnace control method will be explained with reference to FIG.

The figure shows an example of three paths, and 1 in the figure is a heating furnace. 2 is a raw material pipe, and this raw material pipe 2 is shunted to three systems of buses 2a, 2b, and 2c, passed through the heating furnace 1, and then joined again. 3
is a total raw material flow rate setting device that sets the total amount of raw material flowing through the heating furnace per unit time, and 4-1, ~4-
3 is a flow rate regulator. 5-1, ~5-3 are flow rate transmitters, and these flow rate transmitters 5-1, ~5-3
are respectively attached to the paths 2a, 2b, and 2c, and output a detection signal corresponding to the flow rate of the raw material in the path on the inlet side of the heating furnace 1. 6-1, ~ 6-3 are each of these flow rate transmitters 5-
7-1 and 7-3 are provided for flow rate adjustment. The flow rate of the raw material in the path on the inlet side of the heating furnace 1 is adjusted to the flow rate in accordance with the control signal.

The flow rate regulators 4-1, .
The output signals of the corresponding flow rate transmitters 5-1 and 5-3 given through the transmitters 1 and 6-3 are compared, and the deviation is outputted as a control signal, which is sent to the corresponding flow rate regulator 7-. 1, to 7-3.

Reference numerals 8-1 and 8-3 denote temperature transmitters, which are attached to the respective paths 2a and 2c to detect the temperature of the raw material in the path at the outlet side of the heating furnace 1. In addition, 9-1 and 9-3 are temperature controllers, which are provided corresponding to the paths 2a and 2c, respectively, and transmit the detected in-path raw material temperature signal to a preset outlet side path. Compare the internal raw material temperature and output the deviation. 10-1, ~
10-3 is a flow rate controller; 11 is a fuel pipe for supplying fuel to the heating furnace 1; 12-1, to 12;
-3 is a flow rate transmitter, 13-1, ~13-3 are square root calculators, 14-1, ~14-3 are flow rate control valves, 1
5-1 to 15-3 are burners.

The fuel pipe 11 is shunted into three pipe lines 11a to 11c corresponding to the three paths 2a, 2b, and 2c of the raw material pipe 2, and each branch is connected to a corresponding burner 15- in the heating furnace 1. 1, ~15-3
connected to. One burner 15-1, to 15-3 is associated with each path 2a, to 2c of each system, and heats the corresponding path 2a, to 2c of each system. Further, one flow rate transmitter 12-1, one to 12-3 and one control valve 14-1, one to 14-3 are associated with each of the three pipe lines 11a, to 11c. , the control valve 14-
1, ~14-3 are corresponding pipe lines 11a, ~11c
The fuel flow rate is adjusted to the flow rate according to the control signal. In addition, the flow rate transmitters 12-1 to 12-3
detects the fuel flow rate in the corresponding pipe lines 11a to 11c and outputs a signal corresponding to the detected amount.

In addition, the first-stage square root calculators 13-1, . The flow rate controller 10-
1, ~10-3 are square root calculators 13-1, ~13-
3 via respective corresponding flow transmitters 12-
The detection signals obtained from the temperature controllers 9-1 and 12-3 are compared with the outputs of the corresponding temperature controllers 9-1 and 9-3, and a control output corresponding to the deviation is generated to control the control valve 14-1. , ~14-3.

The conventional apparatus with such a configuration supplies raw materials to the heating furnace 1 through the raw material piping 2. This supplied raw material is divided into three lines, and each line passes 2
It is divided into streams a and 2c and sent into the heating furnace 1. At that time, the raw material flow rate of each path 2a, ~2c is detected by the corresponding flow rate transmitter 5-1, ~5-3, and the detection signal is square-rooted by the corresponding square root calculator 6-1, ~6-3. After being subjected to calculation processing and linearization, the corresponding flow rate regulator 4-1,
~ Sent to 4-3. The total amount of raw materials is set by the total amount setting device 3, and each flow rate controller 4-
1, to 4-3, each flow rate regulator 4-1, to 4-3 is set to the corresponding flow rate transmitter 5-1, to 5 based on the setting value of this total amount setting device 3.
Compare the detection signals of -3 and find the deviation,
The corresponding control valves 7-1, ~7 as control variables
-Give to 3. As a result, each control valve 7-1, ~
7-3 adjusts the opening degree by the received control amount to adjust the flow rate of the raw material in the path.

On the other hand, the temperature of the raw material heated in each pass in the heating furnace 1 is detected by temperature transmitters 8-1 to 8-3 provided at the outlet side of the heating furnace in each pass.
It is applied to the corresponding temperature controllers 9-1, 9-3. Each temperature controller 9-1, ~9-3 sets a preset temperature and this temperature transmitter 8-1, ~8-
3 and outputs the deviation as a control amount. This is then given as a reference value to the corresponding flow rate controllers 10-1 to 10-3.

Further, the flow rate controllers 10-1, 10-3 are connected to three systems of pipes 11a, 11c of the fuel pipe 11.
The flow rate transmitters 12-1, ~12- provided in
3 gives the detection output of the fuel flow rate in the corresponding pipe lines 11a, ~11c, respectively, and therefore, each flow rate controller 10-1, ~10-3 compares the two and determines the deviation from the reference value. A signal corresponding to the number of minutes is outputted and given to the flow rate control valves 14-1 to 14-3.

The flow rate control valves 14-1, 14-3 that receive the signals from the flow rate regulators 10-1, 10-3 are adjusted to have openings corresponding to the signals each received,
The fuel flow rate in the pipes 11a, 11c is adjusted to a flow rate commensurate with the opening degree thereof.

The pipe lines 11a, to 11c correspond to the three paths 2a, 2b, and 2c of the raw material pipe 2, and each corresponds to the corresponding burner 15- in the heating furnace 1.
1, to 15-3. The burners 15-1 and 15-3 are connected to paths 2a and 2a of each system.
Since the burners 15-1 and 2c correspond to each burner 15-1 and 2c, the burners 15-1 and 15-1 whose thermal power is adjusted by the above-mentioned flow rate adjustment
The heating temperatures of the paths 2a and 2c of the corresponding systems 5-3 are adjusted so as to reach the target outlet temperature.

In this way, in the past, the raw material flow rate was controlled to a target value, and the burner temperature was adjusted by applying feedback according to the raw material temperature at the outlet so that the raw material temperature at the outlet reached the target value. It is.

Therefore, efficiency changes due to changes in each path over time,
Since there is no correction function for changes in efficiency due to changes in load flow rate, operation with low overall efficiency is forced. In other words, in a path with poor thermal efficiency, the fuel flow rate will be increased until the furnace exit temperature of that path reaches the set temperature, and in a path with good thermal efficiency, the fuel flow will be operated at a low flow rate, resulting in a large energy loss for the heating furnace as a whole. It had the following defect.

[Object of the invention] The present invention has been made in view of the above circumstances, and its purpose is to increase the raw material flow rate for each pass according to its efficiency, and to increase the efficiency. The object of the present invention is to provide a heating process control method that improves the energy efficiency of the heating furnace as a whole by controlling the raw material flow rate to be small when the flow rate is low.

[Summary of the invention] That is, in order to achieve the above object, the present invention has the following features:
In a heating process control method used in a process in which raw materials are distributed into a plurality of channels and passed through a heating furnace to undergo heat treatment, and the furnace temperature is controlled so that the temperature of the raw materials after heat treatment in each of the channels becomes a predetermined value. , the temperature after heat treatment in each channel is detected, and the flow rate of the raw material in each channel is controlled to keep this temperature constant, and the raw material is divided into multiple series of channels (passes). The raw material is passed through the heating furnace, and the sum of the flow rates of each pass (total flow rate) is made so that the temperature at each outlet becomes a predetermined value.
According to the efficiency of each pass, a pass with a high outlet temperature increases the raw material flow rate, and a pass with a low outlet temperature decreases the raw material flow rate, so that the outlet temperature of each pass is within a certain value without changing the By changing the flow rate ratio and increasing the flow rate for the more efficient path, the heating furnace can be operated efficiently.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an apparatus to which the present invention is applied. The figure shows an example of three paths, and 21 is a heating furnace. Further, 22 is a raw material pipe, and this raw material pipe 22 has three paths 22a, 22b,
After being shunted to 22c and passed through the heating furnace 21,
be reunited. 23 is a total raw material flow rate setting device for setting the total amount of raw material flowing through the heating furnace per unit time;
Reference numerals 24-1 to 24-3 are ratio setting devices, which set the setting value of the total raw material flow rate setting device 23 in each pass 22.
In order to allocate proportionally to a, 22b, and 22c, the set values are multiplied by ratios α ₁ , α ₂ , and α ₃ and output. 25-1 and 25-3 are attached to the paths 22a, 22b, and 22c, respectively, and output a detection signal corresponding to the flow rate of the raw material in the path on the inlet side of the heating furnace 21. It is a flow rate transmitter. 26-1, ~26-3 are provided corresponding to each of these flow rate transmitters 25-1, ~25-3, and the corresponding flow rate transmitters 25-1, ~25-3 are provided.
a square root calculator that performs square root calculation processing on the output signal of No. 3;
Reference numerals 7-1 and 27-3 indicate flow rate controllers, which are installed in correspondence with the respective paths 22 and 22c, and adjust the flow rate of the raw material in the path at the inlet side of the heating furnace 21 according to a control signal. Adjust to.

28-1 and 28-3 are adders, 20 is a path flow rate correction calculation unit, and 30-1 and 30-3 are temperature transmitters, which are installed in correspondence with each of the paths 22a and 22c, This is to detect the in-pass raw material temperature on the exit side of the heating furnace 21.

The flow rate controllers 27-1, . The output corrected by multiplying the set ratios α ₁ , α ₂ , α ₃ (individual path flow rate set value) and the output of the path flow rate correction calculation unit 20 are added together to give the added value obtained as the control reference value. , the square root calculator 26-1, ~
A corresponding flow transmitter 25 provided via 26-3
-1 to 25-3 output signals are given. The flow rate controllers 27-1 and 27-3 are controlled based on the control reference value.
Compare the output signals of the corresponding flow rate transmitters 25-1 to 25-3, output the deviation as a control signal,
The corresponding flow rate control valves 29-1, ~29-3
give to

31 is a temperature transmitter, and each of the paths 22a,
It is attached to the confluence point on the exit side of the heating furnace 21 and detects the temperature of the combined raw materials after passing through the path on the exit side of the heating furnace 21. Further, 32 is a temperature controller, which compares the signal of the combined raw material temperature detected by the temperature transmitter 31 with the raw material temperature in the exit side path set in advance, and outputs the deviation.

33 is a flow rate controller, 34 is a fuel pipe for supplying fuel to the heating furnace 21, 37 is a flow rate transmitter for detecting the fuel flow rate in this fuel pipe 34, and 36 is an output of this flow rate transmitter 37. A square root calculator 35 performs calculations and linearizes.
control valves 38-1 to 38-3 that adjust the opening degree in response to the output of 6 and adjust the fuel flow rate of the fuel pipe 34;
A burner is supplied with fuel from the fuel pipe 34 and heats each path 22a, to 22c in the furnace.

The fuel pipes 34 are respectively connected to corresponding burners 38-1 to 38-3 in the heating furnace 21. The burners 38-1 and 38-3 heat the paths 22a and 22c of each system, but the fuel supply amount is the same for all, and here the burner temperature is controlled for each system as in the past. I don't.

However, the burner temperature may be controlled for each pass as in the conventional method.

Further, the path flow rate correction calculation unit 20 receives the outputs of the temperature transmitters 30-1 and 30-3, learns the heating efficiency in each path 22a and 22c from these signals, and uses this to determine the heating efficiency in each path 22a and 22c. It has a function of determining the raw material flow rate correction amount (increase/decrease value) necessary for the output temperature in each pass to reach a predetermined value.

Specifically, the flow rate correction amount ΔFj (j = 1, 2, 3, ..., n) for obtaining the flow rate adjustment amount of path j is the first
Use the relationship shown in the formula.

ΔFj=K·(Tj−) (1) where K is a correction coefficient, Tj is the furnace outlet temperature of pass j, and is the average temperature of the outlet temperatures of each pass.

Here, since is constant, the sum of the flow rate correction amounts for each pass is 0 from equation (1). Therefore, ΔF ₁ +ΔF ₂ +ΔF ₃ =K・(T ₁ −)+K・(T ₂ −)+
K・(T ₃ −)=K・{(T ₁ +T ₂ +T ₃ )−3}=0……(1′) Based on this relationship, the correction amount ΔFj (j=1, 2,
3,...,n). The path flow rate correction calculation unit 20 that performs this calculation performs the calculation by software processing, and if it is shown as a functional block, the second
It will look like the picture.

In FIG. 2, 201 is an average calculation unit, and the outlet temperatures T ₁ , T ₂ , T ₃ of each path 22a, to 22c are given to this average calculation unit 201, and the average temperature (=(T ₁ +T ₂ + T ₃ )/3).
202-1 and 202-3 are subtracters, which are provided corresponding to the respective paths 22a and 22c, and are used to calculate the average temperature calculated by the average calculation unit 201 corresponding to the exit temperature of the corresponding path. The purpose is to find the difference between Reference numeral 203 denotes a constant generator, which generates a proportionality constant.

204 is a sampling period generating section, and at the sampling timing given by this sampling period generating section 204, the proportionality constant is calculated by the multiplier 205-1,
~205-3. Multiplier 205-1,
~205-3 are respective paths 22a and ~22c
The subtracters 202-1 and 202-3 receive the outputs of the corresponding subtracters 202-1 and 202-3, respectively, and multiply the outputs by the proportionality constant given at the sampling timing.

206-1, .about.206-3 are integration sections, which integrate the outputs of the corresponding multipliers 205-1, .about.205-3, and integrate the outputs of the corresponding multipliers 205-1, .
1, to 28-3.

Such a path flow rate correction calculation section 20 performs calculation processing according to a flowchart as shown in FIG. In other words, sequential interrupts are applied and step ST1
It is determined whether or not it is the sample period. Then, if the timing of the predetermined sampling period is reached, the process moves to step ST2, and the temperature transmitters 30-1, .
−3 The outlet temperature of each path detected at T ₁ , T ₂ , T ₃
Enter.

Upon receiving this, the average calculation unit 201 calculates the average temperature (=T ₁ +T ₂ +
T ₃ )/3) and subtracters 202-1, ~20
Give to 2-3. Then, the process enters step ST4, where the difference between the outlet temperature of the corresponding path and the average temperature calculated by the average calculating section 201 is calculated for each of the paths 22a to 22c, and then step ST4 is performed.
In ST5, the proportional constant K given at a predetermined timing is corrected by the multipliers 205-1 and 205-3, and then the proportional constant K is corrected by the integrator 206-1 and 206-20, respectively.
Integrate in step 6-3 (step ST6).

The corresponding adders 28-1 and 28-2
8-3, where the ratio setters 24-1, ~2
The correction amount is added to the flow rate set value for each pass given in step 4-3 to obtain a new flow rate set value Fcj (step ST7).

This apparatus having such a configuration supplies raw materials to the heating furnace 21 through the raw material piping 22. This supplied raw material is divided into three systems, and each system passes 2
It is divided into streams 2a and 22c and sent into the heating furnace 21. At that time, the raw material flow rate of each path 22a, ~22c is determined by the corresponding flow rate transmitter 25-1, ~22c, respectively.
25-3, and the detection signal is subjected to square root calculation processing and linearized by the corresponding square root calculators 26-1 to 26-3, and then sent to the corresponding flow rate controllers 27-1 to 27-3. is sent.

On the other hand, the total amount of raw materials is determined by the total raw material flow rate setting device 23.
This setting value is set by ratio setting device 2.
After being corrected by multiplying by a predetermined ratio in steps 4-1 and 24-3 and added to the output of the pass flow rate correction calculation unit 20 in adders 28-1 and 28-3, the raw material flow rate standard for each pass is calculated. Since each flow rate controller 27-1, ~27-3 is given as a value to the corresponding flow rate controller 27-1, ~27-3, each flow rate controller 27-1, ~27-3 is given the output value of this adder 28-1, ~28-3. The detection signals given from the corresponding flow rate transmitters 25-1, 25-3 are compared via the square root calculators 26-1, 26-3, and the deviation is calculated as a control amount. Corresponding control valves 29-1, ~29-3, respectively
give to As a result, each control valve 29-1, ~2
9-3 adjusts the opening degree by the received control amount to adjust the flow rate of the raw material in the path.

On the exit side of the paths 22a and 22c, the temperature of the combined raw materials is detected by a temperature transmitter 31,
A temperature controller 32 is provided with the temperature controller 32 . Then, the temperature controller 32 compares the preset temperature and the temperature detected by the temperature transmitter 31, outputs the deviation as a control amount, and gives this to the flow controller 33 as a reference value.

On the other hand, the flow rate regulator 33 is given a detection output of the fuel flow rate from the flow rate transmitter 37 provided in the fuel pipe 34.
3 compares the two, outputs a signal corresponding to the deviation from the reference value, and supplies the signal to the control valve 35.

Thereby, the heating temperature on the furnace side is also controlled so as to reach the target temperature of the raw material at the outlet.

In addition, each pass 22a heated in the heating furnace 21,
The temperature of the raw material ~22c is determined by a temperature transmitter 30- installed at the heating furnace outlet side position of each pass 22a, ~22c.
1 to 30-3, respectively, and provided to the path flow rate correction calculation unit 20. The path flow rate correction calculation unit 20 successively interrupts the temperature transmitters 30-1 to 30 at each timing of a predetermined sampling period.
−3 The outlet temperature of each path detected at T ₁ , T ₂ , T ₃
Capture the detection output of

Upon receiving this, the average calculation unit 201 in the path flow rate correction calculation unit 20 calculates the average temperature (T ₁ +T ₂ +T ₃ )/3) of the exit temperatures of each given path, and subtractor 202-1, ~Give to 202-3.
Then, for each path 22a to 22c, the difference between the outlet temperature of the corresponding path and the average temperature calculated by the average calculating section 201 is calculated, and this is multiplied by a proportionality constant K given at a predetermined timing by the section 205-
After multiplying and correcting by 1 and 205-3 respectively, these are multiplied and corrected by integral parts 206-1 and 206, respectively.
Integrate by -3.

The corresponding adders 28-1 and 28-2
8-3, where the ratio setters 24-1, ~2
A new flow rate setting value (individual path flow rate setting value) is obtained by adding the flow rate setting amount for each pass given from 4-3 and adding the correction amount from the path flow rate correction calculation unit 20 to the flow rate setting value for each pass. ) Find Fcj.

In this way, the outlet temperature in each pass is monitored to determine the outlet average temperature of all passes, and based on this, the outlet temperature in that pass is required to compensate for the difference between the outlet temperature of each pass and the outlet average temperature. New flow rate setting value that corrects the increase/decrease in raw material flow rate (individual path flow rate setting value)
Fcj is determined one after another, this is added to the reference value as a new flow rate set value, and the raw material flow rate of the path is adjusted to the flow rate of this set value.

Therefore, the flow rate is amplified in the efficient path, and conversely, the flow rate is decreased in the inefficient path. As a result of this being repeated at a predetermined timing, the average temperature approaches the target path exit temperature as much as possible.
In addition, since the control increases the flow rate of the path with good heating efficiency, the efficiency of the entire heating furnace is also increased.

The above uses the average value of the raw material temperature at the outlet side for the entire pass, and corrects the flow rate setting value for each corresponding pass to compensate for the difference between this average value and the raw material temperature at the outlet side for each pass. By doing so, the flow rate was increased in the efficient path and controlled to be suppressed in the inefficient path. Therefore, although the configuration is simple, since the flow rate is not comprehensively monitored, there is a concern that the accuracy of the raw material flow rate may deteriorate.

Therefore, the following path flow rate correction control can be considered in consideration of this point.

The details will be explained below.

First, a case where the total flow rate is constant and the raw material flow rate is increased or decreased in each pass so that the heat balance is constant will be explained.

Now, a flow rate correction formula is determined assuming that the raw material flow rate in each pass is approximately equal. Here, it is assumed that the average flow rate is F ₁ =F ₂ =F ₃ ==(F ₁ +F ₂ +F ₃ )/3 (2).

From this, the average temperature is = (T ₁ + T ₂ + T ₃ )/3 (3).

In path j, the raw material flow rate is the average value,
Assuming that the furnace outlet temperature is Tj, from the heat balance in pass j, (Tj - Ti) = (-Ti) (+ΔFj) ... (4) where Ti is the raw material furnace inlet temperature. Therefore,
The increase in the raw material flow rate in pass j can be expressed as ΔFj=((Tj−)/(−Ti))····(5).

The path flow rate correction calculating section 20 that realizes this is shown in functional blocks as shown in FIG.

The figure shows the configuration for executing the fifth equation. In the figure, 201 is an average calculation unit, and each path 22
The outlet temperatures T ₁ , T ₂ , and T ₃ of points a and 22c are input, and their average value is determined. 202-1,
~202-3 is a subtraction unit provided corresponding to each path 22a, ~22c, and each path 22
The outlet temperatures T ₁ , T ₂ , T ₃ of a, ~22c are input to the corresponding subtraction units 202-1, ~202-3, respectively. In addition, subtraction units 202-1 to 202-3
The average value of the path outlet temperature is inputted from the average calculating section 201, and each subtracting section 202-1, .
202-3 subtracts this average value from the outlet temperature.

Thereby, the difference between the average value of the pass outlet temperatures in each of the passes 22a and 22c is determined.

Further, 203 in FIG. 4 is a subtraction section,
Here, the output of the average value calculating section 201 and the raw material inlet temperature Ti are input, and the difference between the raw material inlet temperature Ti and the average value of the pass output temperature target values is determined.

204-1, ~204-3 are each path 22a, ~
22c, and these dividing units 204-1 and 204-3 calculate the output of the corresponding subtracting units 202-1 and 202-3 (of the path exit temperature in the corresponding path). difference between the average value of all pass outlet temperatures) and the output of the subtraction unit 203 (raw material inlet temperature with respect to the average value of pass outlet temperatures)
(difference from Ti) is input, and each of the division units 204-1 to 204-3 divides the former with the numerator and the latter as the denominator, respectively.

205 is an average value calculation unit, and each path 22a,
The flow rates Fi ₁ , Fi ₂ , and Fi ₃ of ~22c are input, and their average value is determined. Further, 206 is a sample period generating section. The average flow rate obtained by the average value calculating section 205 is sampled at a predetermined period by a sampling period generating section 206, and
07-1, to 207-3.

The multipliers 207-1 to 207-3 are each 22a,
22c are provided, and the division results of the corresponding division units 204-1 and 204-3 are input. Therefore, the multipliers 207-1, . . .
207-3 multiplies both at the predetermined period.
As a result, the multipliers 207-1 to 207-3 obtain an increase/decrease ΔFj in the raw material flow rate for each pass according to the heat balance.

Integration sections 208-1 and 208-3 are provided corresponding to the multiplication sections 207-1 and 207-3, and integrate the outputs of the corresponding multiplication sections.

The outputs of the respective integrating sections 208-1, .about.208-3 are given to the corresponding adders 28-1, .about.28-3, and are used to correct the reference value for flow rate control of each path.

In this way, it is possible to control the temperature at a predetermined pass outlet according to the heat balance by taking into account the inlet temperature, the average temperature at the outlet of all passes, the outlet temperature of each pass, and the average flow rate of raw materials, resulting in higher precision. You will be able to control it.

However, even in this case, since the temperature of the raw material at the exit of each pass is mainly controlled, there may remain a problem as to whether or not the accuracy of the actual product exit temperature is maintained.

Therefore, a control method takes this into consideration. In other words, the temperature of the raw material at the confluence point on the furnace exit side of each pass is adjusted to the target average temperature _{of 0} in each pass while taking into consideration the raw material temperature at the confluence point. A case will be explained in which the flow rate of raw materials is increased or decreased so that the income and expenditure remain constant.

Now, the raw material flow rate and outlet temperature of each path 22a, ~22c are Fj, Tj (j=1, 2, 3,...,
n) and find the average temperature ₀ at the confluence point, the sixth
The formula is as follows.

₀ = ( _o 〓 ^j=1 Tj・Fj) / ( _o 〓 ^j=1 Fj) ...(6) Next, in order to make the outlet temperature Tj of flow path j the temperature of the confluence point ₀ , the raw material flow rate of path j is is increased from Fj to Fj + ΔFj, the increase ΔFj is the amount of heat obtained when the path exit temperature is Tj = (Tj − Ti)・Fj ...(7) When the exit temperature of path j becomes ₀ Calorific value = ( ₀ − Ti)・(Fj+ΔFj) ...(8) Here, Ti is the inlet temperature of the raw material.

Assuming that the heat exchange efficiency in the heating furnace of pass j does not change, according to the relationship of equation 7 = equation 8, (Tj − Ti)・Fj=( ₀ −Ti)・(Fj + ΔFj) ...(9) ΔFj = ( (Tj− ₀ )/( ₀ −Ti))・Fj……(10) Therefore, from equation 10, ΔFj is the average temperature at the confluence point.
₀ and the exit temperature Tj of path j and the inlet temperature of path j
Ti can be determined from the raw material flow rate Fj of pass j.

The path flow rate correction calculation unit 20 that implements this is shown in functional blocks as shown in FIG.

The figure shows the configuration for executing Equation 10, and in the figure, 301-1 to 301-3 indicate each path 22.
It is a multiplication unit provided corresponding to the paths 22a and 22c, and calculates the flow rates Fi ₁ , Fi ₂ , Fi ₃ of the corresponding paths 22a and 22c, and the outlet temperature T ₁ ,
T ₂ and T ₃ are input, and multiplication units 301-1, ~30
1-3 multiplies these. The result is the adder 3
02 and is added here to determine the total amount of heat obtained.

Moreover, the flow rate Fi ₁ of each path 22a, to 22c,
Fi ₂ and Fi ₃ are added by an adding unit 303 to obtain the total flow rate. The values of the adder 303 and the adder 303 are given to the divider 304, and the former (obtained total heat amount) is divided by the latter (total flow rate) to obtain the average temperature ₀ at the confluence point. This value is the subtractor 305-
1, ~305-3.

The subtraction units 305-1 and 305-3 are provided corresponding to each path 22a and 22c, respectively, and the outlet temperature T ₁ of each path 22a and 22c is
Subtraction unit 305-1 to which T ₂ and T ₃ respectively correspond,
~305-3 is input. Therefore, the subtraction unit 30
5-1 to 305-3, the difference obtained by subtracting the confluence point average temperature from the outlet temperature is obtained.

On the other hand, the confluence point average temperature determined by the division section 304 is also given to a subtraction section 306, where the raw material inlet temperature Ti is subtracted to determine the amount of heat received. This value is divided into division units 307-1, ~307-
given to 3.

The division units 307-1 and 307-3 are provided corresponding to the subtraction units 305-1 and 305-3, and each path calculated by the subtraction units 305-1 and 305-3 is The difference obtained by subtracting the confluence point average temperature from the outlet temperature is input, and this is divided by the value (the amount of heat received by the raw material) obtained by the subtraction unit 306. Each division value is calculated by each division unit 307-1,
Multiplying unit 308 provided corresponding to ~307-3
-1 to 308-3.

The multipliers 308-1 and 308-3 are given the flow rates Fi ₁ , Fi ₂ and Fi ₃ of the corresponding paths 22a and 22c, but this input is input to the sample period generator 31.
0 so that sampling is input at predetermined intervals. Therefore, the multipliers 308-1, 308-3
08-3 multiplies these inputs at predetermined time intervals. As a result, multipliers 308-1, 308-
3, the increase/decrease amount ΔFj of the raw material for each pass according to the heat balance is determined.

Integrating sections 309-1 and 309-3 are provided corresponding to the multiplication sections 308-1 and 308-3, and integrate the outputs of the corresponding multiplication sections. Each integrating section 309-1, ~309-3
The outputs are given to the corresponding adders 28-1 to 28-3 and used to correct the reference value for flow rate control of each path.

In this way, the most accurate outlet temperature control can be achieved.

The thermal efficiency of each pass in a multi-pass heating furnace changes in a complex manner due to a combination of changes over time and load changes. The heating furnace can be operated while maintaining the overall thermal efficiency of the heating furnace to the maximum. Therefore, according to the present invention as described above, energy saving can be achieved dramatically compared to the conventional method. In addition, the calculation method is simple,
Further, the present invention has the advantage that it can be implemented even with a DDC level regulator that controls each control section individually and independently.

[Effects of the Invention] As detailed above, the present invention divides the raw material into a plurality of channels (passes) and passes it through a heating furnace, adjusting the flow rate of the raw material in each pass so that the temperature at each outlet becomes a predetermined value. In a heating furnace designed to
In order to keep the outlet temperature of each pass within a certain limit value, the flow rate of raw material is increased in the path with a high outlet temperature, and the flow rate of raw material is decreased in the path with a low outlet temperature, so that more raw materials are flowed in the direction with higher efficiency. I did it like this,
The heating furnace can always be operated at maximum thermal efficiency in response to complex fluctuations in thermal efficiency, and the overall thermal efficiency of the heating furnace can be maintained to the maximum. It is possible to provide a heating process control method that is characterized by dramatically reducing energy consumption.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an apparatus to which the present invention is applied, FIG. 2 is a functional block diagram of a path flow rate correction calculating section, FIG. 3 is a flowchart showing an example of a processing procedure for path flow rate correction, and FIG. 5 and 5 are functional block diagrams showing other embodiments of the path flow rate correction calculating section, and FIG. 6 is a block diagram for explaining a conventional example. 10...Pass flow rate correction calculation unit, 21...Heating furnace, 22a, to 22c...Pass, 23...Total raw material flow rate setting device, 24-1, to 24-3...Ratio setting device, 25-1, ~25-3, 37...Flow rate transmitter, 27-1, ~27-3,33...Flow rate controller, 28-1, ~28-3...Adder, 29-
1,~29-3,35...Control valve, 30-1,~
30-3, 31...Temperature transmitter, 32...Temperature controller, 34...Fuel pipe, 38-1, ~38-3
...Burna.

Claims (1)

[Claims] 1. Raw materials having a constant total flow rate are distributed into a plurality of flow channels, passed through a heating furnace, and subjected to heat treatment, and the raw materials after the heat treatment in each of the flow channels are combined, and the temperature of the combined raw materials is adjusted. As a heating process control method to improve the thermal efficiency of a heating furnace, the temperature of the raw material after heat treatment in each flow path is detected, and these detected temperatures are used in the process of controlling the furnace temperature so that the In order to bring the raw material temperature after heat treatment in each flow path closer to this average temperature, the raw material flow rate correction amount corresponding to the difference was determined for each flow path, and this raw material flow rate correction amount was corrected. A heating process control method characterized by controlling the raw material flow rate of each channel using a raw material flow rate control reference value. 2. Find the average temperature of the raw material temperature after heat treatment in all channels from the detected temperature of the raw material after heat treatment in each channel, and find the difference between this average temperature and the temperature of the raw material after heat treatment in each channel. 2. The method of controlling a heating process according to claim 1, wherein an increase/decrease in the raw material flow rate necessary to reduce the temperature difference with respect to the average temperature is determined and used as the raw material flow rate correction amount. 3. Detect the raw material flow rate in each flow path and find their average value, and also detect the furnace inlet temperature of the raw material and the raw material temperature after heat treatment in each flow path, and calculate the raw material flow rate after heat treatment in each flow path. From the temperature, determine the average temperature of the raw material after heat treatment in all flow paths, determine the difference between the raw material temperature after heat treatment in each flow path and the average temperature, and calculate the difference between the average temperature and the furnace inlet temperature of the raw material. The ratio of the two temperature differences is determined for each flow path, and the raw material flow rate correction amount for each flow path is set to a value proportional to this ratio and the average flow rate value. Method for controlling the heating process described in Section 1. 4 Detect the raw material flow rate of each channel, and
The temperature of the raw material after heat treatment in each channel is detected, the amount of heat based on the flow rate and the temperature of the material is determined for each channel, and from these amounts of heat, the average temperature of the raw material temperature after heat treatment in all channels is determined. , find the difference between the average temperature and the temperature of the raw material after heat treatment in each channel, detect the furnace inlet temperature of the raw material, find the difference between the average temperature and the raw material inlet temperature, and calculate the difference between the two temperatures. The ratio of the raw material flow rate in each flow path is determined for each flow path, and the raw material flow rate correction amount for each flow path is set to a value proportional to the ratio of this temperature difference and the raw material flow rate value in each flow path. Method of controlling the heating process described.