JPH0577958B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention provides a control system for intensively collecting dust from exhaust gas from the electric furnaces when systematically controlling the operation of a plurality of electric furnaces associated with a raw material charging yard. The present invention relates to an exhaust gas flow rate control method capable of quickly suctioning exhaust gas irregularly generated from the electric furnace and appropriately adjusting a damper and a blower in the system without causing disturbance to the entire system. . [Prior Art] In this type of conventional electric furnace control system, when centrally controlling the dust gas generated at multiple locations in the control system, it is necessary to perform necessary measures such as improving the environment of the dust gas generation source. In order to apply an appropriate suction force according to each required flow rate, the opening degree of a damper provided at an appropriate location within the control system is frequently adjusted. In this case, the specific exhaust gas generation forms stipulated for each operating period such as scrap charging, ignition, boring, melting, scouring, and furnace repair for each electric furnace are classified in advance based on past data. This is stored in a microcomputer, etc. installed in the control system, and the thus set and stored signals are used as control input signals for the control system. Damper opening is controlled, but especially in the operation of electric furnaces, even during the same operating period, for example, scrap may fall off or smoke may occur due to rapid oxidation reaction of charged raw materials. Moreover, since the generation of dust is completely irregular in terms of quantity and time, it is impossible to set the amount required for complete collection of dust in advance, However, the maximum value in the past was set for the corresponding operating period. However, with this method, under normal conditions without smoke generation, not only does over-collection of dust occur and the amount of dust collection power is excessive, but it also takes away more heat from the electric furnace than necessary, leading to an increase in the amount of melting power. This was not desirable from the point of view of energy saving. For this purpose, the set flow rate for each operating season is
It is desirable to set Q _E to the average value of past data or the maximum flow rate under normal conditions excluding the flow rate occurring during the abnormal phenomenon. Note that when the abnormal phenomenon occurs, the operator intervenes and performs manual operation to adjust the opening degree of the damper while monitoring the smoke generation state. However, for a preset flow rate,
While taking into account various factors that affect the actual suction air volume, such as the flow rate characteristics of the blower and damper or the pressure loss of the duct piping, the opening degree of each damper is manually adjusted to match the air volume required by each source. is extremely difficult and virtually impossible to determine. [Problems to be Solved by the Invention] The conventional methods described above have the following basic problems. These are also the problems to be solved by the present invention. (1) If the opening degree of the damper is changed by manual operation, the flow rate value of the system connected to the electric furnace cannot be determined. (2) Since concentrated dust collection is performed using one dust collector, changing the damper opening at one location will cause the flow rate values of all control systems to fluctuate, resulting in over-collection of dust in systems connected to different electric furnaces. As a result of excess heat or lack of heat, heat is lost and smoke generation occurs. (3) As a result, the amount of melting power in the electric furnace increases due to unnecessary suction force, and the operating cost increases due to unnecessary energy consumption. [Means for Solving the Problems] The present invention has been made to solve the various problems of the conventional methods described above, and the outline thereof is as follows. Data on the past exhaust gas generation flow rate of the target electric furnace system is classified in advance, and this is used as a setting signal to the microcomputer, which also functions as a selector for each operating period. Considering this setting signal, the flow rate characteristics of the damper in the system connected to each electric furnace (Fig. 2a) stored in advance in the microcomputer, and factors that affect the actual suction flow rate such as duct piping pressure loss, etc. , the damper opening degree of each of the systems is calculated so that the suction flow rate matches the required air volume of each generation source. When the opening degree of the damper is manually changed, the differential pressure before and after the damper in the corresponding system, the opening degree, etc. will be changed depending on the timing at which the drive signal to the control device of the changed damper is operated. Based on this, the flow rate of the system is calculated backward. This result is used as the required flow rate of the system, or the pressure in the corresponding electric furnace is detected, the set flow rate is increased as the pressure increases, and this increased flow rate is used as the required flow rate of the system. . By adding up the required flow rates for each system, the required flow rate for all control systems, that is, the set flow rate is determined. From this overall flow rate and the flow rate for each individual system, the flue pressure for each exhaust gas is determined, and the opening degree of the damper and the rotation speed of the blower for each system are determined to match the required flow rate of each system. Calculate and instruct. [Example] FIG. 1 is a diagram illustrating the configuration of an electric furnace control system for implementing the method of the present invention. In FIG. 1, an electric furnace 1, a plaque flange 2 between the electric furnace elbow and the dust collection duct, a dust collection duct branch pipe 3, a butterfly damper 6 for controlling electric furnace exhaust gas, and a thermometer 8 are shown.
are successively connected in series and guided to the main flue 11 to form one electric furnace system. Other electric furnace systems, etc. are also arranged in a similar manner.
The system relates to the raw material yard 21. A differential pressure transmitter 5 is provided to detect the differential pressure before and after the damper 6 for controlling electric furnace exhaust gas, and a pressure transmitter 4 is provided to detect the pressure up to the damper inlet. Dust collection duct branch pipe 3
It is connected to the. Further, a drive device 9 and an opening degree detector 10 are connected to the damper 6 for controlling electric furnace exhaust gas. The main flue 11 has a gas cooler 1
2. Bag filter 13, thermometer 14, blower 1
5 and the chimney 16 are sequentially assembled in series to form the main flue 11 as a whole. blower 15
is driven by an electric motor 20 via a hydraulic clutch 19. Further, the main flue 11 is connected to a plurality of dust collection duct branch pipes 3 for electric furnaces and a plurality of dust collection duct branch pipes 28 for a plurality of scrap charging raw material yards 21, and a local dust collection port 27 A damper 22 for on/off control is provided between the exhaust gas control damper 6 and the damper 6 for controlling exhaust gas. A differential pressure transmitter 17 for detecting the differential pressure before and after the gas cooler 12 and a differential pressure transmitter 18 for detecting the differential pressure before and after the bag filter 13 are connected to the main flue 11, respectively. A differential pressure transmitter 5, a pressure transmitter 4, a thermometer 8, which are connected to the branch pipes of each electric furnace and material charging yard.
differential pressure transmitters 17 and 18 connected to the main flue 11, an opening detector 10 for the exhaust gas control damper 6, an open/close signal 23 and an open command 24 for the damper 22 for on/off control, and a thermometer 14; blower 15
A variable output signal 25 of the hydraulic clutch 19 for changing the rotation speed of the hydraulic clutch 19 and a damper opening/closing output signal 29 are both connected to a microcomputer 26, and the microcomputer 26 inputs the respective input signals and
Various calculations are performed using predetermined data stored in advance. According to the method of the present invention, the following two functions are performed for the electric furnace control system as illustrated in FIG. 1. (1) When the damper 6 of the system in Fig. 1 is manually operated, the pressure at the damper inlet of the system, the differential pressure before and after the damper, the exhaust gas temperature, and the damper opening degree are determined by the microcomputer. 2
6, and the exhaust gas flow rate after the change in the system changed by the manual operation is calculated. (2) Next, the opening degree of the damper 6 and the rotation speed of the blower 15 of each system are calculated by adding the set flow rate of the different system and the flow rate of the changed system. First, function (1) will be explained. When the control system is in steady operation and is always automatically operated, past data regarding the generation form of the amount of exhaust gas generated from the corresponding electric furnace is stored in advance in the microcomputer.
The damper opening degree of each system is controlled according to these data, but for example, sudden smoke generation due to oxidation reaction of charging material, gaps in break flange or work opening in the furnace wall, etc. In the event that the electric furnace changes due to human factors or adhesion of scrap, etc. during operation, or smoke is generated due to changes in the pressure inside the electric furnace, the operator intervenes and takes appropriate measures while monitoring the smoke generation situation. The damper 6 is opened and closed manually. At this time, the following values are obtained according to the drive signal for the damper 6, which is operated by the operator's manual operation. 1 Value △P of the differential pressure transmitter provided to detect the differential pressure before and after the damper 6, 2 Value P ₁ of the pressure transmitter provided to detect the pressure loss on the input side of the damper 6, 3 Value of the pressure transmitter provided to detect the pressure loss on the input side of the damper 6. 6 opening degree y, 4 Exhaust gas temperature T passing through the damper 6 ₁₀ By knowing these values, the damper 6 temperature stored in advance in the microcomputer can be determined.
The CV value is calculated from the following equation (1) based on the flow rate characteristic CV (Fig. 2a). K ₁ y + K ₂ = og ₁₀ CV …(1) Where, y is the opening degree of the damper. On the other hand, the CV value can also be expressed by the following formula (1-1).

From equations (1) and (1-1), the flow rate Q _o of exhaust gas passing through the damper can be determined by equation (1-2). This is then taken as the required flow rate of the system.

[C] _Qo : Exhaust gas flow rate (Nm ³ /min) y: Damper opening (%) △P: Differential pressure before and after the damper (mmAq) P ₁ : Pressure before the damper (mmAq) r: Vs. Air specific gravity T ₁ : Exhaust gas temperature at damper passing point (°C) K ₁ , K ₂ , K ₃ : Constants Next, function (2) will be explained. In this function (2), the required flow rate Q _p of the entire control system is calculated by adding the flow rate Q o determined for the system and the set flow rate of other systems _.
is required. By the way, the blower in the control system has pressure-flow characteristics as illustrated in Fig. 2, and under the condition that this is operated at a constant rotation speed,
In the characteristic part of FIG. 2 where the flow rate is less than _c1 , that is, the characteristic part rising to the right, the blower pressure tends to increase as the air flow rate increases (called surging), so it generally becomes an unstable region. Further, the blower has a rated flow rate, and if the blower continues to operate at a flow rate higher than this flow rate, the drive motor will be overloaded, which may cause a burnout accident. Therefore, in order to avoid this problem, the following measures are taken. In other words, the newly determined required flow rate of the entire system
If Q _O is less than the blower's surging limit flow rate Q _S , the insufficient flow rate is determined by the following formula (1-3).
Calculate Q _{SS ,} and add the set flow rate Q _M and Q _SS of the material charging yard using equation (1-3) and calculate _the flow _rate of the material charging yard. Required flow rate
Let Q _a . Q _a = Q _M + Q _SS …(1-4) If the rated flow rate of the blower is exceeded, calculate the excessive flow rate Q _RR using formula (1-5), and calculate Q _RR = Q _O − Q _R ...(1-5) Using equation (1-6), Q _RR is subtracted from the set flow rate Q _M of the raw material charging yard to obtain the required flow rate Q _a of the raw material charging yard. Q _a = Q _M −Q _RR …(1-6) Here, the pressure-flow characteristic curve _a1 of the blower illustrated in Fig. 2 can be calculated by using the following equation (2). From the curve b ₁ corrected by the exhaust gas temperature T _O ,
Find the value of _P when Q is substituted with _Q , and use this as
This is the pressure value before the blower (see point a in Figure 1) when the required flow rate Q _O of the entire system is flowing. P=K・273/273+T _O Q ² …(2) In addition, point b (between gas cooler 12 and bag filter 13) in Figure 1 indicates the required flow rate of the entire control system before manual intervention by the operator. When Q _A is assumed, the pressure loss coefficient K _A of the bag filter 13 at this time is expressed by the following equation (3). △P _A1 = K _A Q ² _A , K _A = △P _A1 / ² / _A (3) △P _A1 is the differential pressure measured by the differential pressure transmitter 18 at that time. Therefore, the differential pressure ΔP ₁ in the bag filter 13 that will occur when the newly requested flow rate Q _O is supplied can be expressed by equation (4). △P ₁ = K _A Q ² _O …(4) Similarly, the differential pressure △P ₂ of the gas cooler 12 is (5)
It can be expressed by the formula. ΔP ₂ = K _B Q ² _O (5) K _B is the pressure loss coefficient of the gas cooler 12 with a flow rate of Q _A. As described above, the target pressure P ₃ at point c in FIG. 1 can be obtained from equation (6). P ₃ = P ₀ −△P ₁ −△P ₂ …(6) Since the branch pipes 3 and 28 of the electric furnace and material charging yard of each branch are all connected to the main flue 11, the control The whole system should be at the same pressure P ₃ . That is, by finding ΔP _Vi in equation (7) for each system, the target differential pressure before and after the damper can be found. P ₃ =K _Ei Q ² _Ei +△P _Vi ∴△P _Vi =P ₃ −K _Ei Q ² _Ei …(7) K _Ei : Pressure loss coefficient of each system branch pipe Q _Ei : Required flow rate of each system (Nm ³ /min) △P _Vi : Target differential pressure before and after the damper of each system (mm
Aq) i: Each system On the other hand, the flow rate characteristics of the damper can be expressed by equation (8). K _1i y _i + K _2i = log ₁₀ C _i …(8) K _1i , K _2i : Constant for each damper y _i : Opening degree of each damper (%) C _i : CV value of each damper Also, CV of the damper The value calculation formula can be expressed as equation (9).

[C] γ: Specific gravity to air T _Ei : Exhaust gas temperature of each system From equations (8) and (9) above, the required air volume Q _Ei of each system and the target differential pressure △P _Vi before and after the damper of each system are known. From both equations above, the damper opening y _i of each system is
Each can be obtained using equation (10). Note that C _i , K ₁ , K ₂ , K ₃ , γ, and K _Ei are set values stored in advance, and T _Ei is the actually measured exhaust gas temperature at thermometer 8 in FIG.

〔Effect of the invention〕

The present invention is a method for adjusting the flow rate of exhaust gas in a centralized precipitator having a plurality of electric furnaces as described above. To detect fluctuations in furnace pressure in certain cases and automatically adjust the dampers of other electric furnaces to the required flow rate without having to manually adjust and set the damper of the electric furnace. This allows smoke to be sucked out as quickly as possible. Therefore, according to the present invention, the complexity of manual operation is eliminated, and the electric furnace melting power consumption and dust collection operation cost can be reduced by preventing excessive dust collection, which is extremely effective. method can be provided.

[Brief explanation of drawings]

FIG. 1 is a relational connection diagram of a control system to which the method of the present invention is applied, FIG. 2 is a pressure-flow characteristic curve diagram of a blower in the system, and FIG. 2a is a flow characteristic diagram of a damper in the system. FIG. 3 is a flowchart for explaining the steps in the method of the present invention. 1...Electric furnace, 2...Break flange, 3...
...Dust collection duct branch pipe, 4...Pressure transmitter before damper, 5...Pressure transmitter before and after damper, 6...
Butterfly damper, 8... Thermometer, 9... Butterfly damper drive device, 10... Opening degree detector,
11...Main flue, 12...Gas cooler, 13...
... Bag filter, 14 ... Thermometer, 15 ... Blower, 16 ... Chimney, 17 ... Differential pressure transmitter before and after gas cooler, 18 ... Differential pressure transmitter before and after bag filter, 19 ... Variable speed hydraulic clutch, 20...
Motor, 21... Scrap charging material yard, 2
2...On-off damper, 23...On-off damper opening/closing signal, 24...On-off damper opening/closing command, 25...Clutch variable speed output signal, 26
... Microcomputer, 27 ... Local dust collection port, 28 ... Dust collection duct branch pipe for scrap charging material yard, 29 ... Damper opening/closing output signal, 3
0...Furnace pressure detector.

Claims (1)

[Claims] 1. The exhaust gas generated from each of the plurality of electric furnaces is guided to the main flue connected to the dust collection duct branch pipe for the scrap charging raw material yard of the scrap charging raw material yard, and this main smoke In an electric furnace control system in which a gas cooler, bag filter, blower, and chimney are arranged in sequence to perform concentrated dust collection, the irregular exhaust gas generation patterns for each furnace are classified in advance according to the operating period. , is a method of concentrated dust collection based on the set value, and when an abnormal situation exceeding the above-mentioned category set value occurs, (1) Manually adjust the flow rate adjustment means in any electric furnace system where the abnormal situation has occurred. The microcomputer reads the data regarding the opening degree of the flow rate regulating means, the pressure, the differential pressure, and the exhaust gas temperature. (2) calculating the required flow rate of the arbitrary electric furnace system from the pressure coefficient of the pressure coefficient, the flow rate characteristics of the flow rate adjustment means, and various constants; (2) calculating the required flow rate of the arbitrary electric furnace system and the set flow rate of other systems; is added to obtain the required total flow rate, and the data regarding the differential pressures of the gas cooler and bag filter installed in the main flue, and the exhaust gas temperature before the blower are loaded into the microcomputer, and the data about the blower temperature stored in advance in the microcomputer is read into the microcomputer. From the pressure-flow rate characteristics, the flow rate characteristics of the flow rate adjustment means, the pressure coefficients and various constants specific to each electric furnace system, the flow rate of the arbitrary electric furnace system calculated in the above (1) and the flow rate of other systems Calculate the required pressure up to the point where the main flue intersects with the branch pipe from each electric furnace at the set flow rate; (3) All the pressures of the individual electric furnace systems must match and the required pressure Calculate the opening degree of the flow rate adjustment means of each of the above systems so that the pressure exceeds the value above, and calculate the rotation speed of the blower so that the pressure does not fall below the pressure in front of the main flue blower. ) If the newly determined required flow rate of the entire system is less than the blower's surging limit flow rate, calculate the insufficient flow rate, add this insufficient flow rate to the set flow rate of the scrap charging material yard, and then start this scrap charging process. If the required flow rate of the entire system exceeds the rated flow rate of the blower, calculate the excessive flow rate and subtract the excessive flow rate from the set flow rate of the scrap charging raw material yard for scrap charging. (5) The instruction data regarding the opening degree and the rotation speed of the blower of the flow rate adjustment means of each of the above-mentioned systems calculated as described above is transmitted from the microcomputer to the flow rate adjustment means of each of the above-mentioned systems and the hydraulic pressure. A method for controlling the flow rate of exhaust gas in a concentrated dust collection system having a plurality of electric furnaces, characterized in that the output is output to a drive device of a clutch. 2 The exhaust gas generated from multiple electric furnaces is guided to the main flue connected to the dust collection branch pipe for the scrap charging raw material yard, and this main flue is equipped with a gas cooler, bag filter, etc. In an electric furnace control system that performs concentrated dust collection by sequentially arranging blowers and chimneys, the irregular exhaust gas generation patterns for each operating period of each furnace are classified in advance, and concentrated dust is collected based on the set values. A method for collecting dust, comprising: (1) detecting the furnace pressure of an electric furnace of an arbitrary system; The required increased flow rate is calculated from the calculated result and various constants stored separately, and the required increased flow rate is added to the value set in advance for the classification, and the required increased flow rate of the arbitrary system is calculated. (2) Add the required flow rate of the above arbitrary system and the set flow rate of other systems to obtain the required total flow rate, and calculate the differential pressure of the gas cooler and bag filter set in the main flue, and the pressure in front of the blower. Data regarding the exhaust gas temperature is loaded into a microcomputer, and the above (1) (3) Calculating the required pressure to the point where the main flue intersects with the branch pipe from each electric furnace at the flow rate of the arbitrary system calculated in paragraph ) and the set flow rate of other systems; Calculate the opening degree of the flow rate adjustment means for each electric furnace system so that the pressures in each electric furnace system are all the same and exceed the required pressure, and the pressure in front of the main flue blower is not lowered. (4) If the newly calculated required flow rate of the entire system is less than the blower's surging limit flow rate value, calculate the insufficient flow rate, and calculate the insufficient flow rate. and the set flow rate of the scrap charging material yard to determine the required flow rate of this scrap charging material yard.If the required flow rate of the entire system exceeds the rated flow rate of the blower, calculate the excessive flow rate and subtracting the excessive flow rate from the set flow rate of the yard to obtain the required flow rate of the scrap charging raw material yard; A method for controlling the flow rate of exhaust gas in a concentrated dust collection system having a plurality of electric furnaces, characterized by outputting instruction data from the microcomputer to the flow rate adjustment means of each of the systems and the driving device of the hydraulic clutch.