JPH0288710A - Method for changing over process gas in metallurgical furnace - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a process gas switching method in a metallurgical furnace, particularly in a bottom-blown converter, a top-bottom blowing converter, and other metallurgical furnaces in which various process gases are injected into molten metal for refining.
From the preceding gas that is currently supplying the process gas,
The present invention relates to an improvement in a process gas switching method in a metallurgical furnace, which is suitable for use when switching to a trailing gas that is about to be supplied.

[Conventional technology]

In bottom-blown converters, top-bottom blown converters, and other metallurgical furnaces, various process gases (e.g., oxygen gas, hydrocarbon gas) are added to molten metal such as hot metal for the purpose of refining the molten metal during operation. It's infused. When blowing process gas in this way, the gas to be blown from the inner tube and outer tube of the tuyere is switched as necessary depending on various conditions. In addition, when the tuyere is immersed in molten metal, in order to prevent the molten metal from entering the tuyere, process gas is applied to the tip of the tuyere while applying gas pressure that overcomes the static pressure of the molten metal. It is necessary to make a switch. Conventionally, various techniques have been proposed regarding such a method of switching the blown gas. For example, JP-A-57-894
17, by controlling the leading gas pressure, the opening degree of the flow rate control valve of the trailing gas system, and the trailing waste pressure to constant conditions, and controlling the waste switching by pressure control, it is possible to prevent pressure fluctuations from occurring at the tip of the tuyere. A method of switching over to bottom-blown gas in a converter is disclosed which prevents the intrusion of molten metal into the tuyeres. Here, FIG. 5 shows an example of the configuration of a control device for switching process gases using Siegen control, which is employed in equipment for supplying process gases to bottom-blowing converters. Fifth
In the control device shown in the figure, when a process necessary for process gas switching control is selected using the process selection push button 10, the step selection section 11 performs an operation based on the startup conditions from the startup condition holding display section 12 and the settings of the changeover switch 13. After a diagnostic check of the operation mode selected in the mode selection section 14 and the conditions stored in the converter state storage section 16, such as whether the converter is in a full or empty state, the process gas is Select the switching steps required for switching. This selected switching step determines the type of gas. The type of gas is transmitted to the step starting section 20. Next, when the step is started by the step starting section 20, the gas line selection section 22 selects the waste line to be used according to the determined type of gas,
Via the valve drive command unit 24, the cutoff valve 26A of the gas line that supplies the trailing waste is opened to start supplying the trailing gas, and after the switching condition of the step is satisfied, the gas line that supplies the leading gas is shut off. A process gas switching step is performed in which the valve 26B is closed and the supply of the preceding gas is stopped. In addition, in the figure, reference numeral 27 is a condition fulfillment determination unit that determines whether the switching condition of this step is satisfied in a procedure that will be described in detail later. A gas change command is transmitted to the step starting section 20. On the other hand, if the switching condition is satisfied, the switching step is stored in the step storage unit 30,
Moreover, the fact that the switching step has been completed is transmitted to the used waste line selection section 22. In addition, in FIG. 5, the reference numeral 32 is a process display section,
The process currently in progress is displayed by blinking (flickering) the indicator light 32A. Reference numeral 34 denotes a controller mode and flow rate setting section, which switches the process gas flow rate setting via a contact 36 and inputs a mode switching signal to the controller 38. The controller 38 controls the flow rate of the process gas using a flow control valve 40 according to the flow rate setting and mode.
In this case, the operation of the flow rate control valve 40 is controlled by the valve drive command section 2.
This is performed when an activation command is issued from 4 and the contact 42 is turned on. Furthermore, 44 is a limit switch for detecting the open/closed state of the shutoff valves 26A, 26B, etc., and detecting which process gas is being blown in, and 46 is an indicator light based on the output signal of this limit switch 44. Flashing 46A,
A display section 48 displays the type of gas being blown, a display section 48 indicates that the controller 38 is in operation by blinking the indicator light 48A, and 50 indicates the cutoff valves 26A, 26B,
This is a monitoring unit for monitoring the state of each waste valve such as the flow rate control valve 40 by comparing it with a step signal, flow rate, pressure, and status signal (detected as a contact signal of a limit switch, etc.). As shown in FIG. 6, the judgment procedure of the step establishment judgment unit 27 is to first judge whether T1 seconds have elapsed since the step start signal was input (Pl), and if T1 seconds have not elapsed, then continues this determination, and if T1 seconds have elapsed, it is determined whether the conditions for establishing the switching step are met (P2). If it is determined that the conditions for establishing the switching step are met,
The processing of the step storage section 30 shown in FIG. 5 is performed. on the other hand,
If the conditions for the establishment of the switching step are not met, it is determined whether or not the step is starting (P3). When the judgment result is negative, the waste changing section 28 shown in FIG.
Process. On the other hand, when the determination result is positive, it is determined whether T2 seconds have elapsed since the step start (P4). When the determination result is positive, the process of the gas changing section 28 is performed. On the other hand, if the determination result is negative, the process returns to P2 and the steps after P2 are executed again. Note that the monitoring unit 50 in FIG.
Even when a supervisory signal is output from , the steps from P2 onwards are executed to determine the step establishment condition. When switching the process gas as described above, the combinations of the leading gas and trailing gas to be switched exist, for example, depending on the type of operation process, the inner pipe and outer pipe of the bottom blowing tuyere, and the type of gas. , a shutoff valve 26A that is driven during switching;
The number of 26B varies depending on the plant, but the number is close to several tens to hundreds.Furthermore, the process gas to be supplied is not only a single type of gas but also a mixture of two or more types of gas. be. Therefore, the logic from the selection of one process to the determination of the opening/closing operation of the shutoff valve required for process gas switching is complicated, so the conventional process gas switching control device has become complicated and has a high capacity. However, there was a problem in that the cost was high.

[Problem to be solved by the invention]

The present invention has been made in order to solve the problems of the conventional technology, and it is possible to centralize and simplify the switching logic for switching process gases, and to set a free combination of process gases. An object of the present invention is to provide a process gas switching method in a metallurgical furnace.

[Means to achieve the task]

The present invention provides a method for switching the process gas supplied from the tuyere into the molten metal of a metallurgical furnace from the leading gas to the trailing gas. Classify the process gas into the necessary number of units depending on the type of process gas, and for each classified unit, determine how the flow rate of the process gas should change when switching the process gas.
The process gas is divided into four patterns: "start of flow", "m-continuation", "end of flow", and "irrespective of switching", and based on the contents of the flow rate change of each recognized pattern, process gas is By defining a slave sequence for controlling the switching of the tuyere and controlling the defined slave sequence with a master sequence depending on the type of tuyere and process gas, the process gas is switched.
The above-mentioned problem has been achieved.

[Operation and effects of the invention]

As a result of various studies, the inventors found that in a process gas supply device, when switching the currently supplied leading gas to the trailing gas to be supplied from now on, the inner and outer pipes of the tuyere and the type of process gas According to the above, the combination of leading gas and trailing gas is classified into the necessary number of units, and for each classified unit, the flow rate of each process gas, ``leading gas'' and trailing gas, is determined by gas switching. If you classify whether it changes,
The present invention was created by focusing on the fact that it is possible to distinguish and recognize four patterns: "start of flow,""continuation,""end of flow," and "irrespective of switching." That is, "start of flow" is a case where a predetermined process gas is not supplied as a leading gas but is supplied as a trailing gas, and the gas flow rate changes as shown in FIG. 1(A). Further, "continuation" refers to a case where a predetermined process gas is supplied as a leading gas and also as a trailing gas, and the gas flow rate changes as shown in FIG. 1(B). Furthermore, the "end of flow" is a case where a predetermined process gas is supplied as a leading gas but not as a trailing gas, and the gas flow rate changes as shown in FIG. 1(C). Moreover, "irrespective of switching" is a case where the predetermined process gas is not supplied as either the leading gas or the trailing gas, and the gas flow rate changes as shown in FIG. 1(D). Based on the results recognized in the four patterns as described above, a slave sequence for controlling process gas switching is defined for each unit. In the defined slave sequence, input condition signals include, for example, opening/closing conditions for each shutoff valve of the leading gas line and trailing gas line, each flow rate, and each pressure condition, and output control signals include, for example, There are commands to open and close the shutoff valve, and control commands to the flow control valve and pressure control valve. Is it possible to perform basic switching control of the process gas for each unit by the above slave sequence, or is it necessary to control the switching timing for each tuyere and the switching timing for the gas type in each tuyere. In this case, if the tuyere has a double tuyere structure having an inner tube and an outer tube, it is necessary to control the switching timing for each inner tube and outer tube. Therefore, in the present invention, the slave sequence is controlled by checking whether the switching conditions are satisfied in the master sequence for each type of tuyere and process gas,
I am trying to switch gases. Therefore, according to the present invention, appropriate process gas switching can be performed by a combination of patterned slave sequences, thereby simplifying the switching logic, and
You can easily switch between free combinations. Further, regarding the change in the logic of dregs switching, the four basic patterns do not change, and the change can be made by changing only the master sequence, making it possible to easily change the logic. Therefore, the capacity and number of control computers, such as microcomputers, used for gas switching are reduced, resulting in lower equipment costs and easier maintenance.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. In this embodiment, the present invention is applied to the process gas switching control device of the process gas supply equipment shown in FIG. 5 above. In this case, the configuration of each component device is as described above, so a description thereof will be omitted. In the embodiment, the trailing gas cutoff valve 26A, the flow rate control valve 4OA, the leading gas cutoff valve 26B, the flow rate control valve 40B, etc.
Execute the gas switching pattern shown in the figure. That is, for the "flow start" pattern shown in FIG. 1(A), the shutoff valve 26A of the trailing waste line is opened, and the necessary pressure control and flow rate control are performed by the flow rate control valve 4OA and the like. Also, regarding the "flow end" pattern shown in FIG. 1(C), while closing the preceding gas cutoff valve 26B,
Stop the pressure control and flow rate control of the preceding gas. Furthermore, the first
Regarding the "continuation" pattern shown in Figure (B), the same process gas is used as the trailing waste even after the leading gas is shut off. Furthermore, the "unrelated to switching" pattern shown in FIG. 1<D) indicates that the cutoff valves 26A and 26B are not operated and are not related to waste switching. Recognition of which of the four patterns described above the change in process gas flow rate at the time of gas switching belongs to is performed by logic as conceptually shown in FIG. 2. In this case, the leading gas and the trailing dregs similarly have three types of process gases (dregs type 1 to dregs type 3), and the flow rate change of the same type of process gas (gas type n) is
The switching pattern is determined by AND and NOT determination logic indicated by reference numerals 101 to 104 in the figure. The determination logic 101 determines whether the leading gas is cut off and the trailing gas is allowed to flow.
Determine when the flow begins. Further, the determination logic 102 determines whether both the leading gas and the trailing gas are flowing, and determines whether the gas type n is "continuing". Furthermore, the determination logic 103 determines whether the leading gas is flowing but the trailing gas is shut off, and determines whether the gas type n is "flowing complete". Further, the determination logic 104 determines that both the leading gas and the trailing gas are not flowing, and determines that the gas type n is "irrelevant to switching." Using the above logic, for example, when recognizing the case where gas type 2 of the leading gas is switched to gas type 1 of the trailing gas, gas type 1 is the pattern for "starting to flow", and gas type 2
is a pattern of "flow end", and gas type 3 is a pattern "irrelevant to switching". Next, when switching the process gas from gas type 2 to gas type 1 for both the inner tube and outer tube of the tuyere of a metallurgical furnace, Fig. 3 shows a time chart of the slave sequence for controlling the process gas of each male type. Shown below. Figure 3 (A) shows a time chart of the slave sequence of the inner tube, and Figure 3 (A) shows the time chart of the slave sequence of the inner tube.
B) shows a time chart of the slave sequence of the outer tube. As shown in FIGS. 3(A) and 3(B), gas type 1 in the inner tube is controlled in a pattern that starts flowing from time ti, and gas type 2 in the inner tube is controlled in a pattern that starts flowing from time tm. It is controlled by the following pattern. Also, gas type 1 in the outer tube is at time ti
The flow is controlled by the pattern of "starting to flow" from
is controlled in a pattern from time tm to "end of flow". However, when gas switching is controlled only by such slave sequences, each slave sequence performs condition judgment and control independently, and the timing of the switching operation between the inner and outer pipes and the switching between gas types are difficult. The timing of the operation is fixed at times tn and tm, and cannot be controlled to a desired timing. Therefore, the master sequence is used to control the timing of the slave sequence for the inner pipe, outer pipe, and waste type of the tuyere. An example of a time chart of this master sequence is shown in FIG. FIG. 4(A) shows a time chart of a master sequence for the inner tube of the tuyere, and FIG. 4(B) shows a time chart of a slave sequence controlled by the master sequence. The master sequence determines the start and end of the slave sequence, so that the flow of gas type 1 starts from time to in FIG.
The end of the flow of gas type 2 is at time tP in FIG. Since these times to and tp can be freely set in the master sequence, gas switching can be performed at desired timing. In the above embodiment, a case has been described in which the switching control of the leading gas and the trailing gas of three gas types is performed using the change pattern shown in FIG. 1, but the change pattern when implementing the present invention is And the number of gas species is not limited to those in the examples. In other words, the waste flow rate change in each change pattern does not rise in a step-like manner as shown in FIG.
The waste flow rate may be increased in stages. Furthermore, the number of types of process gas may be four or more. Further, the process gas may be a single type of waste or a mixture of a plurality of gases.

[Brief explanation of drawings]

FIGS. 1A to 1D are diagrams showing each side of the change pattern during gas switching according to the present invention, and FIG.
A block diagram to explain the change pattern recognition procedure,
FIG. 3 is a diagram showing an example of a time chart of a slave sequence, and FIG. 4 is a diagram showing an example of a time chart when controlling a slave sequence with a master sequence.
FIG. 5 is a block diagram showing an example of the configuration of a gas switching control device employed in general gas supply equipment to which the embodiment is applied, and FIG. 6 shows a procedure for determining step fulfillment conditions in the control device. FIG. DESCRIPTION OF SYMBOLS 18... Step selection part, 22... Use waste line selection part, 24... Valve drive command part, 26A, 26B... Shutoff valve, 36... Controller mode, flow rate setting part, 40... ...Flow control valve.

Claims (1)

[Claims] (1) In a method of switching the process gas supplied to molten metal in a metallurgical furnace via a tuyere from a leading gas to a trailing gas, the combination of leading gas and trailing gas at the time of process gas switching is Classify the process gas into the necessary number of units depending on the type of process gas, and for each classified unit, determine how the flow rate of the process gas should change when switching the process gas.
4: “Continue”, “End of flow”, and “Irrelevant to switching”
A slave sequence for controlling process gas switching is defined for each unit based on the content of the flow rate change of each recognized pattern. A process gas switching method in a metallurgical furnace, characterized in that the process gas is switched by controlling a master sequence according to the type of process gas.