KR0136199B1 - Air volume control system of a furnace - Google Patents

Abstract

In the oxygen gas and air concentration control system for controlling the air ratio by steel type in the continuous furnace, the first and second selectors (5, 6) are compared with the temperature set by the host computer and the operator and the current furnace temperature. Outputs and compares the outputs of the temperature controller 4, the temperature controller 4, the output of the second operator 2, and the third operator 3 with the output of the air flow sensor 21 and the gas to its small value. The second selector 6 for controlling the gas flow regulator 8 for controlling the valve 25 and the output of the temperature regulator 4 and the gas flow sensor 24 are compared and the large value of the first operator 1 is compared. It has a first selector (5) for controlling the air flow regulator (7) for controlling the air valve (22) through the second operator (2) having an output as an input, and a calculated value for general steel work and a calculated value for special steel work. Receives the values of the memory 18-20 and the oxygen sensor 27 which are provided to the 1-3 operators respectively. The oxygen receiver 10 for determining the oxygen concentration and selecting the first and second oxygen regulators 9 and 14 and the outputs of the first and second oxygen regulators 9 and 14 to the first operator 1. An oxygen output selection function switch 13 inputted together with the output of the oxygen contribution rate setter 16, and a digital I / O port 15 and a special steel work on function switch 11 through an input / output device 12; And a CPU7 (17) for controlling the oxygen output selection function switch (13) and the memory (18-20).

Description

Air ratio control system by steel type

1 is a block diagram of a continuous heating furnace and a conventional air ratio control system applied thereto

2 is a block diagram of an air ratio control system according to the present invention

3 is a detailed configuration diagram of the main part of the present invention system

4 is a flowchart of execution of FIG.

* Explanation of symbols for main parts of the drawings

1,2,3 Computer 4: Temperature controller

5, 6: Selector 7: Air flow regulator

8: Gas flow regulator 9, 14: oxygen regulator

10: oxygen receiver 11: special steel work on function switch

12: I / O device 13: output selection function switch

17: CPU 18, 20: Memory

21: Air flow sensor 22: Air valve

24: gas valve 25: gas flow sensor

27: oxygen sensor

The present invention relates to an air ratio adjusting device of a continuous furnace, and more specifically, to an air ratio control system for each type of furnace for setting the air ratio to steel grades and controlling the exhaust gas 02 concentration when general and special steel work is sequentially performed. will be.

When the work grade is changed during continuous operation of the furnace, the control of air ratio and exhaust gas oxygen concentration control system suitable for the grade should be performed continuously. At this time, it is necessary to efficiently manage the work and to be able to operate quickly, accurately and simply when resuming work after changing the work grade.

The air ratio indicates how many times the theoretical amount of air is required by the fuel. When the air ratio is excessively taken, the combustion gas amount increases, the energy loss from the exhaust gas increases, the combustion temperature decreases, and the heating capacity decreases. In addition, the excess oxygen also increases the emission of pollutants such as NOx SOx. On the other hand, if the air ratio is too small, the loss due to incomplete combustion increases, thereby reducing the combustion efficiency, that is, the conversion rate from chemical energy to thermal energy, and increasing emissions of carbon monoxide and unburned hydrocarbons.

In addition, surplus oxygen in the exhaust gas burnt in the furnace combines with iron and carbon components in the furnace to produce an oxidative reaction to generate scale on the surface of the material. It is necessary to control the optimum air ratio so as to improve the thermal efficiency and to always burn completely by controlling the air ratio so as not to generate excess oxygen in the exhaust gas. In order to minimize or minimize the oxidation reaction of the furnace material, air concentration and exhaust gas 02 concentration are controlled for the purpose of controlling the optimum air ratio and minimizing the oxidation of materials by measuring the excess oxygen concentration in the exhaust gas.

Of special steel, stainless steel is hard to oxidize, so oxidation does not occur well in furnace. Therefore, surface defects of materials that are not a problem in general steel work cause problems (not well generated in scale) in stainless steel work, and they are excessive in the furnace because they adversely affect the quality due to scale unevenness and poor peelability during material rolling. It is necessary to pursue productivity improvement and quality improvement by introducing air and generating surface defects in scale to remove surface defects and improve scale peelability. In addition, in an industrial combustion apparatus, fuel and air are separately supplied and mixed and combusted in a combustion chamber. In this case, it is difficult to uniformly mix fuel and air throughout the combustion chamber. Gas may be generated. Therefore, in the combustion device, it is common to supply more air volume than the theoretical air volume. The ratio between the actual air volume and the theoretical air volume is called the air ratio or the excess air machine number (symbol: m), and the excess air ratio is called u. In the control method applied to the normal combustion apparatus among the combustion air control systems, the quantitative control of supplying the combustion air was performed by setting the ratio between the fuel amount and the combustion air amount.

In recent years, 02 analyzers have been installed to measure the concentration of 02 in waste gas, and the 02 control system is applied to control the amount of combustion air according to the measurement results. The purpose of maintaining the proper combustion air ratio is the same, but the latter has been applied a lot because there is an advantage to consider the effects of the change in fuel properties, intrusion air.

In general, for example, the structure of a combustion control system of a conventional continuous heating furnace is shown in FIG. The operation shows that the temperature controller 4 inputs the current furnace temperature and input from the temperature sensor 28 of the heating table (preheating zone) according to the FCC (FURNACE CONTROL COMPUTER) or the driver set temperature for controlling the target temperature and furnace sulfur. Compare and adjust the set temperature and send the output signal to the second selector 6 which selects the smaller of the two input values. The first operator 1 sets the 02 regulator 9 control output signal and the The air ratio is calculated according to the air ratio setting value, and is output to the second operator 2 and the third operator 3. In the second operator 2, the gas flow rate with respect to the current air flow rate is determined by the air ratio state of the first operator 1. The gas flow rate setting value is output.

The second selector 6 selects a smaller value between the output value of the temperature controller 4 and the output value of the third operator 3 to set the set value of the gas flow regulator 8 so as to prevent the gas excess condition. The flow regulator 8 controls by comparing the set value with the current gas flow rate. In the first selector 5 which selects and outputs the larger value of the two input values, the output value of the temperature controller 4 is compared with the current gas flow rate, the large value is selected and output to the second operator 2, and the second operator 2 ) Sets the set value of the air flow regulator 7 after the gas air flow rate range correction for setting the air flow rate with the air ratio set in the first operator 1, and compares the set value with the current air flow rate in the air flow regulator 7. To control.

When changing the steel grade, the air ratio setting of the first operator (1), the second operator (2), and the third operator (3) should be changed from the general steel air ratio setting value to the air ratio setting value suitable for the work type, and one manual processing flow 3, the three calculators 1, 2, and 3 input the set values for the call grades to the first operator 1 in the input / output device 12, and then input the set values for the call grades to the second calculator 2. Subsequently, a set value corresponding to the calling steel grade is input to the third operator 3. However, when the air ratio is high, the concentration of 02 in the furnace exhaust gas increases, so that the measurement and control are not possible in the conventional 02 control loop, that is, the oxygen regulator 9 and the oxygen receiver 10, and the following problems occur.

First, when changing the air ratio set value, all eight sets of 24 air ratio settings must be changed, and thus, misoperation and missing points may occur. In addition, since one operator needs to load, extract, and operate the material, it is impossible to change the set value in a timely manner, and the repetitive operation time is lengthened. This makes it difficult to determine the 02 concentration in the furnace, which leads to excess air heat loss. In addition, the scale generation unevenness and excessiveness of the material surface due to the inhomogeneity in the furnace 02 causes scale peelability defects, quality defects, and work deterioration, and the operator has a heavy burden.

The present invention is to solve this problem, and when changing the working steel grade, it is possible to change the air ratio setting value of each unit at the same time and to expand and switch the 02 concentration control range in the furnace at the same time. It aims to provide stable operation and quality improvement by ensuring proper air ratio control and 02 concentration, and to provide air furnace control system for each steel type that can easily and accurately set air ratio and 02 control for steel type. .

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In general, the distribution of materials in the furnace can be divided into three zones: preheating zone, heating zone, and crack zones. The composition and operation of the air furnace and 02 control range are changed to values suitable for special steel according to the movement of the furnace materials. Since the working methods of the three zones are all the same, one example will be explained.

FIG. 2 compares the temperature set point set by the FCC upper computer and the driver with the current furnace temperature input through the temperature sensor 28 and sends the output signal to the small value selector 6 and the large value selector 5. 4), a small value selector 6 which selects and outputs a small value among the output value of the temperature controller 4 and the output value of the first operator 1 and sends it to the gas flow controller 8 set value; 4) The third operator (3) calculates the output of the large value selector (5) and the first operator (1) and the output of the large value selector (5), which selects and outputs a large value by comparing the output value with the value of the gas flow sensor (24). And a small value selector (6) by setting the gas flow rate according to the air ratio with the value of the second operator (2), the air flow sensor (21) and the value of the second operator (2) output to the air flow regulator (7). The gas flow sensor receives the output value of the third operator 3 and the small value selector 6 to (24) The gas flow regulator 8 which outputs a gas flow control signal compared with the output value, the gas valve 25 which receives the gas flow control signal, and controls the flow volume of a gas piping, and the current gas flow volume in a gas piping are detected. The gas flow sensor 21 to the gas flow regulator 8 and the large value selector 5, and the air flow sensor to detect the current air flow in the air pipe and send it to the air flow controller 7 and the third operator 3. (21) and the air flow regulator (7) which sends an output signal to the air flow valve (22) by comparing and controlling the signal of the air flow sensor (21) and the set value signal of the second operator (2), and the 02 concentration in the furnace. 02 (oxygen) receiver 10 for detecting and transmitting the signal, a first oxygen regulator 9 for adjusting 0-5% of receiving 02 concentration signal and controlling it during general steel work, and controlling during special steel work Select the second oxygen regulator 14 for the 02 concentration control of 0-25% and each 02 control system signal according to the type of steel 02 output selection function switch 13, 02 contribution ratio setter 16 for setting 02 control signal contribution, first operator 1 and first operator 1 for controlling selected 02 control signal and contribution ratio signal The second operator 2 for calculating the air ratio with the output value of the large value selector 5 and the third operator for calculating the gas air ratio with the signal of the air flow sensor 21 and the first operator 1 signal. (3), a function switch 11 for inputting a special steel working state, an input / output device 12 for receiving a special steel working temperature signal and outputting a digital input / output signal generation and a stainless steel working start signal of the CPU 17, Control of the digital I / O port 15 for receiving the digital output signal and controlling the 02 concentration receiver, and the 02 output selection function switch 13 for selecting the memory selection signal and the 02 controller signal of each operator according to the special steel work on signal. CPU 17 which generates a signal, and a calculator for general steel work The special steel is a memory (18,19,20) of each flight operation that stores a value calculator works.

Referring to the operation and effects of the present invention configured as described in detail as follows. First, when the special steel work on function switch 11 is operated, the input / output device 12 receives this signal and outputs a signal to the CPU 17 and the digital I / O port 15. Accordingly, the digital I / O port 15 generates the special steel working signal 1 so that the selection of the 02 output selection function switch 13 selects the second oxygen regulator 14 that adjusts 0-25% 02, thereby allowing the first operation unit to be selected. Send to (1). As shown in FIG. 3, the M12 value of the contents of the memory 18 of the first operator 1 is set by the memory selection signal 1 output from the CPU 17, and the second operator 2 stores the memory ( M22 is set among the contents of 19), and the third operator 3 sets the contents of M32 among the contents of the memory 20. That is, it operates in the same flow as the flowchart of FIG.

The setting values of M12, M22, and M32 of each calculator have a value (1.40) larger than the value (1.05) of the memory values M11, M21, and M31 for general steel work, so that the operation of the first operator 1 in FIG. As a result, 0-25% of the output value of the 02 02 controller 14 and the 02 contribution control unit 16 can be multiplied by this value and compared with the set value. The output value is larger, and the output value is larger than that of the general steel work, so that the larger value is added to the second summer (2).

(M * D) ± SV = DMV ............... ① M: 02 Controller output

D: 02 contribution rate

SV: set value

DMV: 1st operator output (air surplus = u)

Since the second operator 2 also has a large variation in the set value, the large value selector 5 calculates the value and the output value of the first operator 1 by the following calculation formula.

DMV * [(GFIC SH / AFIC SH) * M] * HMV ± SV = MV ........ ②

DMV: first operator output

GFIC SH: Upper limit of gas flow range

AFIC SH: Upper limit of air flow range

M: theoretical air ratio

HMV: Large value selector output

SV: second operator set value

MV: second operator output

The excess air ratio, that is, the gas / air range correction operation is performed on the output value of the first operator 1, and is compared with the set value. It is sent to 3 operators (3). Since the set value increased during the operation of stainless steel, the arithmetic output value of the first calculator 1 is smaller than the set value, and a large positive value is output to the air flow regulator 7, and this value becomes the set value of the air flow regulator 7. In the airflow regulator 7, when the airflow setting value is greater than the current airflow signal compared to the signal of the airflow sensor 21, that is, the airflow regulator plus the current airflow rate and the output value of the second operator 2, The flow regulating valve 22 is further opened to allow a large amount of air to be supplied. If this is expressed as a formula, it is as follows.

(MV ± ASV) ± APV = AMV ........... ③

MV: second operator output

ASV: Air Flow Controller Set Point

APV: Current Air Flow

AMV: Air flow regulator output

Since the set value of the third operator 3 also varies greatly, the current air flow rate signal of the air flow rate transmitter 22 and the output signal of the second operator 2 are calculated by the following equation.

DMV * [(GFIC SH / AFIC SH) * M] / AFIC PV ± SV = -RATIO MV ... ④

DMV: first operator output

GFIC SH: Gas Flow Regulator Range Upper Limit

AFIC SH: Upper limit of air flow regulator range

M: theoretical air ratio

AFIC PV: Current Air Volume

SV: Third Operator Set Point

MV: Third operator output

The gas excess value, that is, the gas / air range correction operation is performed on the output value of the first operator (1). Although the set value increased greatly, the air flow rate increased by the second operator (2), the air flow regulator (7), the air flow control valve (22), and the air flow sensor (21). The deviation of the calculated value is small.

The small value selector 6 selects and outputs a small value by comparing the value output from the temperature controller 4 with the value output from the third operator 3, and selects and outputs a small value so that the gas flow regulator 8 Minimize setpoint fluctuations and minimize gas flow fluctuations to prevent incomplete combustion due to the increase or decrease of gas volume to prevent the generation of pollutants. The value selected and output by the small value selector 6 is added to the set value of the gas flow controller 8, and the gas flow controller 8 compares the set value with the current gas flow rate of the gas flow sensor 24 and compares the operation output signal with gas. Output to the valve 25 so that the gas flow rate is added or subtracted. The calculation is as follows.

(LOMV ± GSV) ± GPV = GMV .......... ⑤

LOMV: small value selector output

GSV: Gas Flow Controller Set Point

GPV: Current Gas Flow

GMV: Gas flow controller output value

When the air flow rate is increased by changing the set value of each calculator according to the special steel work, the concentration of 02 in the exhaust gas caused by gas / air combustion in the furnace naturally increases as the air flow rate increases.

The increased 02 concentration in the exhaust gas is detected by the 02 sensor and 02 receiver 10 and output to the two first and second 02 regulators 9 and 14, and the 0-25% 02 regulator 14 selected during the special steel work is Control signal is output by the following formula with proper 02 concentration setting value suitable for special steel.

02PV ± 02SV = 02MV ............... ⑥

02PV: 02 concentration in exhaust gas

02SV: 02 Controller Set Point

02MV: 02 Controller Output

The output of the 02 regulator 14 is input to the first operator 1 via the 02 output selection function switch 13, and is then again calculated by the calculation formula ① of the first operator 1 and output to the next stage. Since the cycle has passed, the output value becomes small. That is, since the concentration of 02 in the exhaust gas is increased, the air increase signal is no longer output to the next stage, so that the concentration of 02 in the exhaust gas is constantly controlled to a value suitable for the special steel.

When the special steel work is resumed after the special steel work, the special steel work on function switch 11 is turned off in FIG. 2 and the input / output device 12 receives this signal and sends a signal to the CPU 17 and the digital I / O port 15. The special I / O port 15 generates a special steel workoff, that is, a general steel work signal 0, and the 02 output selector switch 13 selects 0-25%. The 02 controller 9 signal is output to the first operator 1 by causing the 02 controller 9 to be selected.

In Figure 3, the digital I / O port 15 generates the general steel work signal 0 by the memory selection signal 0 output from the CPU 17 so that the selection of the 02 output selection function switch 13 is 0-5% 02. The regulator is selected so that the 0-5% 02 regulator (9) output is sent to the first operator (1). In addition, the memory select signal 0 output from the CPU 17 sets the M11 of the contents of the memory 18 in the first operator 1, and sets the M21 of the contents of the memory 19 in the second operator 2. The third operator 3 sets the contents of M31 in the contents of the memory 20. This will be seen in the flow chart of FIG.

The memory data of each operator (1.2.3) can be changed by calling the memory addresses of addresses M11, M12, M21, M22, M31, and M32 from the input / output device 12 of FIG. The memory data is changed by converting it into bit data.

By the above-described action, it is possible to switch from general steel work to special steel work, and from special steel work to general steel work by one operation of special steel work on function switch 13, and the heating furnace is divided into three units. Therefore, it is possible to continuously measure and control the air ratio and 02 concentration in the furnace by changing 24 calculation set values and appropriate selection control of three 02 concentration measurement control controllers by changing three kinds of work grades.

As described above, the present invention can quickly set the proper air ratio and switch the 02 controller range for special steel work. Accurate and simple, it enables the operator to set air ratio, shorten operation time, prevent misoperation, omission, and reduce driver's anxiety, and to continuously measure and control 02 concentration during special steel work. The uniform effect of scale, improvement of peelability, improvement of thermal efficiency, improvement of quality and work rate, resetting of resumption of general steel after completion of special steel work, etc., can be easily operated.

Claims (1)

The temperature controller 4 compares and outputs the temperature set value set by the furnace control computer or the driver with the temperature sensor 28 which is input through the temperature sensor 28, and detects O ₂ concentration in the furnace and outputs an O ₂ concentration signal. An O ₂ (oxygen) receiver 10, a gas valve 25 for controlling the gas flow rate of the gas pipe flowing into the furnace, a gas flow sensor 24 for detecting and outputting the current gas flow rate in the gas pipe, and To control the air ratio by steel type in the continuous heating furnace having an air valve 22 for controlling the air flow rate of the air pipes introduced into the inside, and an air flow sensor 21 for detecting and outputting the current air flow rate of the air pipes. adjusted to control the general steel O ₂ concentration of 0-5% when working in, receives a special steel work or the selectively function to input switch 11 to general steel work, the O ₂ concentration signal to the control system of the air concentration signal To output Input of the first oxygen-regulator (9), a second oxygen regulator 14, the function switch (11) for receiving the O ₂ concentration signal outputs a signal for controlling the O ₂ concentration of 0-25% for special steel work O ₂ output selection function switch 13 for selecting and outputting any one of the O ₂ concentration control signals of the first and second oxygen regulators 9 and 14 and O ₂ contribution rate for setting and outputting the contribution rate of O ₂ concentration. A memory (18, 19, 20) for operating the setter (16) and the general steel work set point and the special steel work set point and outputting the general steel work set point or the special steel work set point in accordance with the input of the function switch (11); ₂ multiplies the O ₂ control signal of the output selection function switch 13 with the contribution ratio of the O ₂ contribution ratio setter 16 and compares the set value of the memory with a negative value greater than the set value, and a positive value to output an excess air ratio. Output value of the first operator (1) and the temperature controller (4) A first selector 5 for selecting and outputting a large value compared to the value of the gas flow sensor 24, and performing a gas / air range correction operation on the excess air rate of the first operator 1 and performing the first selector ( A second operator (2) which calculates and outputs an air ratio of a value that can be multiplied by the output value of 5) and compared with a set value of the memory to a value that is larger than a set value and a positive value to be equal to a set value, and the air flow sensor 21 The airflow regulator 7 outputs a signal for controlling the air valve 22 by comparing and subtracting and subtracting the signal of the second operator 2 with the air ratio signal, and outputting the gas to the output signal of the first operator 1. The air flow correction operation is performed and the signal of the air flow sensor 21 is divided to calculate and output a gas flow rate of a value that is larger than the set value compared to the set value of the memory and negative if smaller than the set value. Trioperator (3 ), A second selector 6 for selectively outputting a smaller value of the output value of the temperature controller 4 and the gas flow rate output value of the third operator 3, and an output value of the second selector 6. The gas flow regulator 8 outputs the gas valve control signal by comparing the output value of the gas flow sensor 24 with the set value, and the selection signal and O of each memory according to the input signal of the function switch 11. a furnace characterized in that the _second control signal comprises a CPU (17) for generating a control signal of the O ₂ output function selection switch 13 for selecting a steel type air ratio control system