JPS6182213A - Process controlling method - Google Patents

Abstract

PURPOSE:To improve the energy efficiency of the whole furnace by executing a control so that the flow rate of a raw material is increased with respect to a pass whose efficiency is high, and said rate is decreased with respect to a pass whose efficiency is low, when heating the raw material flowing through channels (passes) of plural systems by a large-sized heating furnace. CONSTITUTION:A raw material from a raw material pipeline 22 is shunted to passes 22a, 22b and 22c of three systems and heated by a heating furnace 21, and thereafter, combined. Raw material temperatures T1-T3 in furnace outlets in each pass are detected by temperature transmitters 30-1-30-3, sent to a pass flow rate correcting and operating part 29, and a flow rate correcting quantity of each pass is derived. They are added to set values from ratio setting devices 24-1-24-3 by adders 28-1, 28-3, and go to control signals for adjusting an in-pass raw material flow rate at the inlet side of the heating furnace 21 by flow rate controllers 27-1-27-3.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention is a process in which raw ore is distributed into a plurality of channels, and the raw ore in each of the distributed channels is heat-treated in a heating furnace. The present invention relates to a process control method for controlling the humidity of raw materials after heat treatment to be equal to their respective set values.

[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.

Large-scale heating furnaces such as atmospheric distillation equipment and ethylene cracking furnaces often perform heat treatment using a multi-pass system in which raw materials are divided into multiple channels (hereinafter referred to as passes). .

The raw material after this heat treatment is processed in the downstream culm 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 is easily affected by temperature changes in the raw ore, flow rate balance of each pass, and changes in the combustion state of the furnace.
Difficult to control. Furthermore, the wasted time due to the long pass 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 into three paths 2a, 2b, and 2c, passed through the heating furnace 1, and then joined again. 3 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;
-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 attached to the paths 2a, 2C, 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 1.

6-1. ~6-3 are each of these flow rate transmitters 5-1°~5-
3, and the corresponding flow rate transmitter 5-1
．． A square root calculator that performs square root calculation processing on the output signal of ~5-3;
7-1. ~7-3 is a flow rate controller, and each of the paths 2a
, ~2C, and adjusts the in-pass flow rate of rough ore on the inlet side of heating furnace 1 to the flow rate in accordance with the control signal.

Said flow rate regulator 4-1. ~4-3 is a corresponding flow rate transmitter 5- given via the square root calculators 6-1 and ~6-3 based on the total amount of raw material flowing through the heating furnace per unit time given by the total raw material flow rate setting device 3. 1. '~5-3 output signals are compared, the deviation is outputted as a control signal, and this is used as a control signal for the corresponding flow rate controller 7~1. ~7-3.

8-1. ~8~3 are temperature transmitters, each of the paths 2a
, ~2C, and detects the temperature of the raw material in the path on the exit side of the heating furnace 1. Also,
9-1. ~9-3 is a temperature controller, which is provided corresponding to each of the paths 2a and ~2C, and compares the detected signal of the raw material temperature in the path with the preset raw material temperature in the outlet side path. , 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 are flow rate transmitters, 13-1. ~13-3 are square root calculators, 14-1. ~
14-3 is a control valve; 15-1. ~15-3 is a burner.

The fuel pipe 11 is connected to the three paths 2a of the raw material pipe 2.
, 2b, 2C, three systems of conduits 11a, ~1
1c, respectively, to a corresponding burner 15-1 . ~15-3. burner 15
-1. ~15-3 corresponds to paths 2a and ~2C of each system, one by one, and the corresponding paths 2a and ~2C of each system
heat up. Further, the flow rate transmitters 11-1. ~12-3 and the control valve 14-1. . . . . . . . . . . . . . . . . . . . . . . . . ~14
-3 adjusts the fuel flow rate in the corresponding pipe lines 11a to 11c to a flow rate according to the control signal. Further, the flow rate transmitter 11-1. ~12-3 are the corresponding pipe lines 11a and ~11C
Detects the fuel flow rate at and outputs a signal according to the detected amount.

Further, the square root calculation unit 13-'1. 13-3 are each flow rate transmitter 12-1. 12-3, and performs square root calculation processing on the output signal to linearly slice the flow rate controller 1o-i.

.about.10-3 are square root calculators 13-1. ~13-3, the detection signals obtained from the respective flow rate transmitters 12-"!, ~12-3 are transmitted to the corresponding temperature regulators 1t9-1.~
The control valve 14-1.9-3 is compared with the output of the control valve 14-1.A control valve 14-1. ~14-3.

The conventional apparatus having such a configuration supplies raw material to the heating furnace 1 through the raw ore pipe 2. This supplied rough stone is divided into three series, each with a pass 2a for each series.

~2C and sent into the heating furnace 1. that time,
The raw material flow rate of each path 2a to 2G is determined by the corresponding outflow transmitter 8-1. 8-3, and the detection signal is subjected to square root calculation processing and linearized by the corresponding square root calculators 6-1 to 6-3, and then sent to the corresponding flow rate controllers 4-1. ~ Sent to 4-3. The total amount of raw materials is m
The setting device 3 is set to 5, and each flow rate controller 4-1. ~
4-3 is given, each flow rate controller 4-1. ~4
-3 is a flow rate transmitter 8-1 corresponding to the set value of this total amount setting device 3 as a reference. The detection signals of the control valves 7-1 . . . . ~7-3.

As a result, each control valve 7-1. ~7-3 adjust 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 determined by a temperature transmitter 8-1 provided at the outlet side of the heating furnace in each pass. ~
8-3, and the corresponding temperature controller 9-
1. ~9-3.

Each temperature controller 9-1. ~9-3, the preset temperature and this temperature transmitter 8-1. -8-3 are compared, and the deviations thereof are outputted as control signals. This is then connected to the corresponding flow rate controller 10-1. ~10~
3 as a reference value.

Moreover, the flow rate controller 10-1. The flow rate transmitter 11-1.~10-3 is provided with three pipe lines 11a and ~11c of the fuel pipe 11. The detection outputs of the fuel flow rates in the corresponding pipes 11a and 11C are given from ~12-3, and therefore, the respective flow rate regulators 'to-1, ~1
0-3 compares the two and outputs a signal corresponding to the deviation from the reference value, respectively, and the flow rate controller 14-1. ~14-3.

This flow rate controller 10-'1. The flow rate controller 11-1. which received the signal of 10-3. ~14~3 The opening degree is adjusted to the opening degree corresponding to the received signal, and the conduit 11a.

The fuel flow rate at ~11c is adjusted to a flow rate commensurate with the opening degree.

The pipes 11a, .about.11C correspond to the three paths 2a, 2b, and 2c of the raw material pipe 2, and are connected to the corresponding burners 15-1.about.15-3 in the heating furnace 1, respectively. And burner 15-1. Since ~15-3 corresponds to paths 2a and ~2c of each system, one by one,
Burner 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 of ~15-3 are adjusted to 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. be.

Therefore, since there is no correction function for changes in efficiency due to changes in each pass over time and changes in efficiency due to changes in load flow rate, operation with low overall efficiency is forced. In other words, in a path with high thermal efficiency, the fuel flow rate is increased until the humidity at the furnace outlet of that path reaches the set temperature, and in a path with high thermal efficiency, the fuel flow rate is reduced, resulting in a large energy loss for the heating furnace as a whole. It had a 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. For low-value items, raw materials flow! , ~, - It is an object of the present invention to provide a process control method that improves the energy efficiency of a heating furnace as a whole by controlling so as to reduce the size of the heat sink.

[Summary of the Invention] In other words, in order to achieve the above object, the present invention is used in a process in which a raw material is distributed into a plurality of channels and then passed through a heating furnace to undergo heat treatment, and the raw material after the heat treatment in each of the channels is In a process control method that controls the amount of heat input into a heating furnace corresponding to each temperature, the temperature after heat treatment in each flow path is detected and the flow rate of raw material in each flow path is controlled to keep this temperature constant. This is a device that allows raw materials to flow through multiple channels (passes).
In a heating furnace, the raw material flow rate in each pass is adjusted so that the outlet temperature of each pass is adjusted to a predetermined value, without changing the sum of the raw material flow rates in each pass (total flow rate). According to its efficiency, the exit temperature of each pass is within a certain limit, so that the path with higher exit humidity increases the feedstock flow rate, and the pass with lower exit temperature decreases the feedstock flow rate.
The heating furnace can be operated efficiently by changing the flow rate ratio of each pass and increasing the flow rate for the more efficient pass.

[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 is shunted into three paths 22a, 22b, and 22C, passed through the heating furnace 1, and then joined again. 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; 24-1. 24-3 is a ratio setting device, and in order to proportionately distribute the set value to each path 22a, 22b, 22c, the set value is set at a ratio α1. α2. This is for multiplying by α3 and outputting the result. 25-1. 25-3 are flow rate transmitters, and these flow rate transmitters 25-1. ~25-
3 is attached to each of the paths 22a, 22c, respectively, and outputs a detection signal corresponding to the flow rate of raw material in the path on the inlet side of 21 of the heating furnace. 26-1.
26-3 are each of these flow rate transmitters 25-1. ~25-3
The corresponding flow rate transmitter 25-
a square root calculator for processing the output signals of 1, 25-3, 27-1. ~27-3 is a flow rate controller, which is installed corresponding to each of the paths 22a and ~22C,
The in-pass raw material flow rate on the inlet side of the heating furnace 21 is adjusted to a flow rate according to the control signal.

28-1. 28-3 is an adder, 29 is a path flow rate correction calculation unit, 301. ~30-3 is a temperature transmitter, which is installed corresponding to each of the paths 22a and ~22c,
This is to detect the temperature of the raw material 11.4 in the pass on the exit side of the heating furnace 21.

Said flow rate controller 27-1. ~27-3 is the ratio setting device 24-3, which is the ratio setting device 24-
1. ~24-3, each with a ratio α1. α2. Multiply by α3, add the outputs of the two path flow rate correction units based on the corrected output (individual path flow rate setting value), and control the added value tl
Corresponding flow transmitter 2 given via -3 as reference value
Compare the output signals of 5-1° to 25-3, output the deviation as a control signal, and send it to the corresponding flow controller 2-
7-1. ~Give to 27-3.

31 is a temperature transmitter, and each of the paths 22a.

It is installed at the outlet side AC point of ~22c, and the heating furnace 2
This is to detect the temperature of the combined raw material after passing through the path on the exit side of No. 1. Further, 32 is a temperature controller, which compares the signal of the combined raw material temperature detected by the temperature transmitter 31 with a preset raw material temperature in the output side path, and outputs the deviation. 33 is a flow rate controller, 34 is a fuel pipe for supplying fuel to the heating furnace 21, and 35 is this fuel pipe 3.
4, a flow rate transmitter for detecting the fuel flow rate; 36, a square root calculator that calculates the square root of the output of this flow rate transmitter 35 and performs linear razing; 37, which receives the output of this square root calculator 36 and adjusts the opening; a control valve for adjusting the fuel flow rate of 34, 38-
1. ~38-3 are supplied with fuel from the fuel pipe 34, and each path 22a in the furnace.

This is a burner that heats up to 22G.

Each of the fuel pipes 34 connects to a corresponding burner 15-1 in the heating furnace 1. ~15-3.

Burner 15-1. ~15-3 is the path 22a of each system, ~
22c, and heats paths 22a and 22G of each corresponding system, but the fuel supply amount is all -regulated, and here, as in the past, the heating temperature is controlled for each system. I won't do anything like that. However, the heating temperature may be controlled for each pass as in the conventional method.

Further, the path flow rate correction calculating section 29
0-1. After receiving the output of ~30-3, the heating efficiency in each path 22a and ~22C is known from each signal, and from this, the raw material flow rate is corrected according to the efficiency so that the outlet temperature in each path becomes a predetermined value. It has the function of calculating the amount (increase/decrease value). Specifically, the flow rate correction amount △ to obtain the flow rate adjustment amount of path j
Fj (j=1.2, 3..., n) uses the relationship shown in the first equation.

ΔFj=K・(Tj−T)...(1) However,
K is a correction coefficient, Tj is Pasco's furnace exit temperature, and K is the average furnace exit temperature.

Here, since ■ and F are constant, the sum of the flow rate correction amounts for each pass is O from the first equation. Therefore, ΔF1−ΔF2
=8FB =K (Tt -T)+K (T2 +T)
+K (T3 +T)=K ((TI +T2 +T
3)-3T)-〇...(1'
) Based on this relationship, the correction amount is Fj<j=1.2゜3,
..., n). The path flow rate correction calculation unit 29 that performs this calculation performs the calculation by software processing, which is shown in functional blocks as shown in FIG. 2.

In FIG. 2, 201 is an average calculation unit, and each pass 2
2a, ~22C outlet temperature T1. T2.

T3 is given to this average calculation section 201, where the average temperature T (= (T1 +T2 +T3) /3)
seek. 202-1. ~202-3 is a subtractor,
They are provided corresponding to each of the paths 22a and 22c, respectively, and are used to calculate the difference between the outlet temperature of each corresponding path and the average temperature calculated by the average calculating section 201. 2
03 is 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 provided corresponding to each of the paths 22a and ~22C, respectively, and receive the outputs of the corresponding subtracters 202-1~2013, and combine this with the proportionality constant given at the sampling timing. Multiply. 206. 206-3 are integral parts, and the corresponding multipliers 205-1. ~205-3
The outputs are integrated and the corresponding adders 28-1.
28-3.

These two path flow rate correction calculation units perform calculation processing according to a flowchart as shown in FIG. That is,
Interruptions are made sequentially, and it is determined in step ST1 whether or not it is the sampling period. Then, if it is the timing of the predetermined sampling period, the process moves to step ST2, and the temperature transmitter 3
0-1. ~Exit temperature Tt of each path detected at 30-3
, T2.

Enter T3. Upon receiving this, the average calculation unit 201 calculates the average temperature T (= (
TI +T2 +73)/3) is obtained, and the subtracter 202
-1. ~Give to 202-3. And then step ST
4, where each pass 22a.

22c, the difference between the outlet temperature of each corresponding path and the average temperature determined by the average calculation unit 201 is determined, and further, in step ST5, a proportionality constant K given at a predetermined timing is applied to the multiplication unit 205-1. After multiplying and correcting in 2o5-3, these are respectively applied to the integrating sections 206-1. ~2
Integrate at step 06-3 (step 5T6). This is applied to the corresponding adders 28-'l, .about.28-3, and the ratio setters 21-1. The correction amount is added to the flow rate set value for each pass given from ~24-3 to obtain a new flow rate set value Fcj (step 5T7).

This apparatus having such a configuration supplies raw materials to the heating furnace 21 through the raw material piping 22. The supplied raw material is divided into three lines and sent into the heating furnace 21 through separate paths 22a to 22c. At that time, each path 22
The raw material flow rates of 22G and 22G are determined by the respective flow rate transmitters 25-1.a and 22G. 25-3, and the detection signals are sent to the corresponding square root calculators 26-1. .about.26-3 and linearized, the corresponding flow rate controllers 27-1. ~27-3.

On the other hand, the total amount of raw materials is set by the 1-1 tal amount setter 3, and this set value is set by the ratio setter 24-1.

~24-3 is corrected by multiplying by a predetermined ratio and the adder 2B
-1, ~2B-3, the outputs of the two pass flow rate correction calculation units are added together, and then given to the corresponding flow m controllers 27-1, ~27-3 as the raw material flow rate reference value for each pass. Therefore, each flow rate controller 27-1. ~27-3 is a flow rate transmitter 25 corresponding to the output value of the adders 28-1~28-3 via the square root calculator 26-1~26-3.
The detection signals given from -1° to 25-3 are compared, the deviation thereof is determined, and the control amount is determined by the corresponding control valve 28-1. ~Give to 28-3. As a result, each of the control valves 29-L to 29-3 receives the controlled amount of tig,
Adjust the opening degree to adjust the flow rate of raw material in the path.

On the exit side of paths 22a and 22G, the temperature of the combined raw materials is detected by a temperature transmitter 31, and a temperature controller 32
given to. Then, the temperature controller 32 compares the preset temperature and the temperature detected by the temperature transmitter 31,
The deviation is output as a control amount, and this is sent to the flow controller 3.
3 as a reference value.

On the other hand, the flow rate controller 33 is given a fuel flow rate detection output from the flow rate transmitter 37 provided in the fuel pipe 34, and therefore, the flow rate controller 37 compares the two and calculates the deviation from the reference value. A signal is output and given to the flow rate controller 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.

Moreover, each pass 22a heated in the heating furnace 21.

The temperature of the raw material ~22c is determined by temperature transmitters 30-1, ~30- provided at the heating furnace outlet side position of each path 22a, ~22c.
3, and provided to two path flow rate correction calculation units. The path flow rate correction calculation unit 29 sequentially interrupts the temperature transmitter 3 at each timing of a predetermined sampling period.
0-1. ~Exit temperature T1 of each path detected at 30-3
．． T2.

Takes in the detection output of TE. Upon receiving this, the average calculation unit 2
01 is the average temperature T of the exit temperature of each given pass
(= (TI +T2 +T:l)/3), and the subtracter 202-1. ~Give to 202-3.

Then, for each of the paths 22a to 22c, the difference between the average temperature calculated by the average calculation unit 201 for the quality (exit) of the corresponding path is calculated, and this is multiplied by a proportionality constant K given at a predetermined timing by the unit 205. After multiplying and correcting by -1° to 205-3, the integral part 206-
1. - Integrate at 206-3. These are given to the corresponding adders 28-1 and ~28-3, where the constant value of the flow rate setting 21 for each pass given from the ratio setters 24-1 and ~24-3 is added to each pass. A new flow rate setting value (individual path flow rate setting value) Fcj is obtained by adding the correction amounts from the two path flow rate correction calculation units to the flow rate setting value for each flow rate.

In this way, the outlet humidity 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 in the outlet temperature for each pass with respect to the outlet average temperature. A new flow rate setting value (individual path flow rate setting value) Fcj that has been corrected for the increase/decrease in the raw material flow rate is successively obtained, and this is added to the reference value to become a new flow port setting value, so that the flow rate is at this set value. Adjust the raw material flow rate of the pass.

Therefore, the number of flow ports is increased in the more efficient path, and the flow rate is decreased in the less efficient path. As a result of this being repeated at a predetermined timing, the average temperature approaches the target pass outlet temperature as much as possible, and since the control is to increase 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 on the outlet side for the entire pass, and corrects the flow rate setting value of each corresponding pass to compensate for the difference between this average value and the raw material temperature on the outlet side for each pass. By doing so, the flow rate was increased in efficient paths and controlled to be suppressed in inefficient paths. 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 will 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, if we calculate the flow rate correction formula assuming that the raw material flow rate in each pass is almost equal, the average flow rate is F1 = F2 = F3 = F' = (Fl + F2 + F3)/3...
Assume (2).

Also, the average temperature T is T-(TI +T2 +T3)/3...(
3).

In pass j, if the raw material flow rate is the average value F and the furnace outlet temperature is Tj, then from the heat balance in passco (Tj - Ti>・F = (T - Ti) (F + ΔFJ) ... ( 4) However,
Ti is the raw material furnace inlet temperature. Therefore, the increase in the raw material flow rate in path j can be expressed as...(5).

The two path flow rate correction calculation units that realize this are shown in functional blocks as shown in FIG. The figure shows a configuration for executing the fifth equation, and in the figure, 201 is an average value calculation unit, and the outlet temperature T1 of each path 22a to 22c. T2
, Ta are input, and their average value is determined.

202-1. ~202-3 is a subtraction unit provided corresponding to each path 22a and ~22c, and each path 22
a.

~22c outlet temperature T1. T2 and Ta correspond to subtraction units 202-1. ~202-3. Further, the subtraction unit 202-1. ~202-3 input the average value of the pass outlet temperature from the average value calculating section 201, and each subtracting section 202-1°~202-3 subtracts this average value from the outlet temperature. As a result, each path 22a, ~
The difference between the pass exit temperature and the average value at 22C is determined. Reference numeral 203 denotes a subtraction unit, into which the output of the average value calculation unit 201 and the raw material inlet temperature T1 are input, and the raw material inlet temperature T with respect to the average value of the pass outlet temperature target value is calculated.
The difference from i is calculated.

204-1. 204-3 are division units provided corresponding to the paths 22a and 22c, respectively, and these division units 204-1. ~204-3 is the corresponding subtraction unit 20
2,1. The output of ~201-3 (the difference between the pass outlet temperature in the corresponding pass and the average value of all pass outlet temperatures) and the output of the subtraction unit 203 (the difference between the raw material inlet temperature Ti and the average value of the pass outlet temperature) are input. Here, each division unit 204-1. ~204-3 respectively divide the former with the numerator and the rear right as the denominator.

=25- 205 is an average value calculation unit, and each path 22a.

~22C flow rate Fi1. Fi2. Fi3 is input,
The average value of these is determined. Further, 206 is a sample period generating section. The average flow rate calculated by the average value calculating section 205 is sampled at a predetermined period by a sampling period generating section 206, and 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 then sent to the multiplying section 207-1. ~207-3.

Multiplication unit 207-1. ~207-3 is each path 22a, ~2
2c, respectively, and corresponding dividing units 204-1. The division results of ~204-3 are input. Therefore, multiplication m207-1. ~207-3 multiplies both at the predetermined period. As a result, the multiplier 2
From 07-1 to 207-3, the increase/decrease ΔFj in the raw material flow rate for each pass according to the heat balance is determined. 208-1.
.about.208-3 are integration sections, and multiplication sections 207-1. ~207-
3, and integrates the output of the corresponding multiplier.

Each integrating section 208-1. .about.208-3 are sent to the corresponding adders 28-1. ~28-3 and used to correct the reference value for flow rate control of each path.

In this way, it is possible to control the temperature at the predetermined pass outlet according to the heat balance by taking into account the inlet humidity, the average temperature at the outlet of all passes, the outlet temperature of each pass, and the average flow rate of the raw material, 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,
It is conceivable that there remains a problem as to whether or not the accuracy of the actual product outlet temperature is maintained.

Therefore, there is a control method that takes this into consideration, that is, the heat balance is kept constant for each pass while taking into account the raw material temperature at the confluence point so that the raw material temperature at the confluence point on the furnace exit side of each pass becomes the target value TO. A case in which the raw material flow rate is increased or decreased will be explained.

Now, each pass 22a, ~22C1) raw material flow rate and outlet temperature are Fj, Tj (j=1.2.3°...,
n), and the average temperature TO at the confluence point is determined as shown in Equation 6.

Next, if we increase the raw material flow rate of Pasco from Fj to Fj + ΔFj in order to set the Pasco outlet temperature Tj to the temperature Tn of the confluence point, then the additional cam "j is the amount of heat obtained at the pass outlet temperature Tj - (Tj - Ti>.Fi (7) Amount of heat when the pass exit temperature becomes the maximum - (TO - Ti) - (Fj + △Fj) - (8) Here, Ti is the inlet humidity 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 the 7th equation and the 8th equation, (Tj - T i )・Fj - (To - Ti) (Fj + ΔFj) ...
(9) 8Fj = ((Tj - To ) / (To - Ti)) · Fj ... 110) Therefore, from the 10th equation, ΔFj is the average temperature To of the confluence, the exit temperature Tj of Pasco, and the entrance of Pass j It can be determined from the temperature Ti and the raw material flow rate Fj of the pass j.

The path flow rate correction calculating section 29 that realizes this is shown in functional blocks as shown in FIG. The figure shows a configuration for executing the 10th equation, and in the figure, 301=1. ~30
1-3 is a multiplication unit provided corresponding to each path 22a, ~22C;
c flow rate Fi1°Fi2. Fiyo and each pass outlet temperature Tt, T2.

Tj is input, and the multipliers 301-1. ~301-3 multiplies these. The result is given to the addition section 302,
Here, the total amount of heat obtained is calculated. Also,
Flow rate Fi1. of each path 22a, to 22c. Fi2. Fi3
are added by the addition unit 303 to obtain the total flow rate.

The values of the adder 302 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 outlet average temperature T. This value is the subtraction part 2
0'5-. 1', ~20.5-3. This subtraction unit 205-1. ~205-3 are each path 22a.

~22c, and each path 2
2a and 22c to 22c respectively correspond to the outlet temperatures Tt and T2°Tj of the subtracting unit 305-1. ~305-3 is input. Therefore, the difference obtained by subtracting the outlet average temperature from the outlet temperature is obtained from the subtraction units 305-1 to 305-3. On the other hand, the outlet average temperature determined by the dividing section 304 is also given to the subtracting section 304, where the raw material inlet temperature T
The amount of heat received is determined by subtracting i. This value is calculated by the dividing unit 30'7-1. ~307-3.

Division unit 307-1. ~307-3 is the subtraction unit 305-
1. ~305-3, and the subtraction unit 3
05-1. The difference obtained by subtracting the average outlet temperature from the outlet temperature for each pass determined in steps 305-3 is input, and this is divided by the value (the amount of heat received by the raw material) determined by the subtraction unit 304. Each division value is determined by each division unit 307-
1. ~~ Multiplier 308 provided corresponding to 307-3
-1. ~308-3 is input.

Multiplication unit 308-1. ~308-3 has the corresponding path 22
a, ~22G flow rate Fi1, Fi2. Fi3 is provided, and this input is sampled at predetermined intervals by a sampling period generator 310.

Therefore, multipliers 308-1 to 308-3 multiply these inputs at predetermined time intervals. As a result, the multiplication unit 20
7-1. From ~207-3, the increase/decrease ΔFj in the raw material flow rate for each pass according to the heat balance is determined.

309-1. ~309-3 is an integration section and a multiplication section 3os-i
, ~308-3, and integrates the output of the corresponding multiplier.

Each integrating section 208-1. .about.208-3 are sent to the corresponding adders 28-1. 28-3 and used for correcting the reference value for outflow 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 changes over time and a combination of load changes.
In response to this complex variation in thermal efficiency, the heating furnace can always be operated at maximum thermal efficiency, and the overall thermal efficiency of the heating furnace can be maintained at its maximum. According to the present invention, it is possible to save energy dramatically compared to the conventional method, and the calculation method is also simple.
Further, the present invention has the advantage that it can be implemented even with a DDC level controller that controls each control section individually and independently.

[Effects of the Invention] As detailed above, the present invention allows raw materials to be passed through multiple lines of flow channels (
In a heating furnace where the raw material flow rate in each pass is adjusted so that the outlet temperature of each pass becomes a predetermined value, the sum of the raw material flow rates in each pass (total flow rate) does not change. In order to keep the outlet temperature of each pass within a certain limit value, the pass with the higher outlet temperature increases the raw material flow rate,
By reducing the raw material flow rate in the path with a low outlet temperature and allowing more raw material to flow in the path with higher efficiency, the furnace can always be operated at maximum thermal efficiency in response to complex fluctuations in thermal efficiency. It is an object of the present invention to provide a process control method that is capable of operating a heating furnace while maintaining its overall thermal efficiency to the maximum, and thus achieving dramatic energy savings compared to conventional methods. can.

[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 amount 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 amount calculating section, and FIG. 6 is a block diagram for explaining a conventional example. 21-... Heating furnace, 22a, ~22c... Pass, 2
3...Total raw material flow rate setting device, 24-1. ~24-
3...Ratio setter, 25-1. ~25-3.37...
・Flow rate transmitter, 2'l-1, ~ 27-3.33...Flow rate controller, 28-1. ~28-3... Adder, 29.
...Pass flow rate correction calculation section, 29-1. ~29-3.35
...Control valve, 30-1. ~30-3.31- Temperature transmitter, 32 Temperature controller, 34 Fuel pipe,
38-1. ~38-3...burner. Applicant's representative Patent attorney Takehiko Suzue 2nd Figure 2nd Figure 4th Figure TI T2 T3 Fi
t Fi2Fi3 JP-A-6L-82213 (11) TI T2 T3 Ti
Fir Fiz Fi32, Upper O 2nd year-, Lll.

Claims (4)

[Claims] (1) Used in a process in which raw materials with a constant total flow rate are distributed into multiple channels and passed through a heating furnace for heat treatment, and the furnace temperature is adjusted so that the raw material humidity after heat treatment in each of the channels reaches a predetermined value. In a process control method, the temperature after heat treatment in each flow path is detected, and a raw material flow rate correction amount corresponding to the difference is applied to each flow path in order to bring the raw material temperature after heat treatment closer to a predetermined target temperature. A process control method characterized in that the raw material flow rate of each channel is controlled using a raw material flow rate control reference value obtained by correcting the raw material flow rate correction amount. (2) Detect the temperature after heat treatment in each flow path, calculate the average temperature of the raw material after heat treatment in all flow paths, calculate the difference from this average temperature, and use this as the target temperature. From this, the amount necessary to reduce the temperature difference between the raw material temperature after heat treatment and the target temperature in each flow path is determined, and this is used as the raw material flow rate correction amount. Process control method described in Section. (3) Detect the raw material flow rate in each flow path and find their average value. Also, detect the furnace inlet temperature of the raw material, calculate the temperature ratio received in the furnace in each flow path, and correct the raw material flow rate. 2. The process control method according to claim 1, wherein the amount is proportional to the temperature ratio and the average flow rate. (4) Detect the raw material flow rate of each channel, and also detect the temperature of the raw material at the furnace inlet and the temperature of the raw material at the confluence on the outlet side of each channel, and from this, the ratio of the temperature received in the furnace in each channel 2. The process control method according to claim 1, wherein the raw material flow rate correction amount is set to a value proportional to this temperature ratio and the raw material flow rate value in each channel.