JPS59113113A - Method for controlling changeover of gas - Google Patents

Abstract

PURPOSE:To facilitate changeover of gases by setting beforehand the pressure control valve and flow rate control valve in a succeeding gas line at prescribed opening degrees, and opening successively the shutoff valves in the same line in accordance with a command for changeover. CONSTITUTION:The set flow rate values of both A and B gases are decreased down to around a lower limit as shown in the figure by flow rate control valves 23A, 23B, flow rates FA, FB by a command S1 for starting changeover from a control device in the stage of changing over the supply of both gaseous A and B gases to both A and C gases. On the other hand, the pressure control valve 18C and flow rate control valve 23C for the C gas is opened respectively at a present opening degree PS and therefore the pressure higher than the supply pressure Pc in the stage of use is supplied as the inlet pressure for the valve 23C. When the shutoff valve 25C for the C gas is opened by the command S1, the flow rate of the C gas shows a sharp rise as shown by the flow rate Fc and changes over easily to the B gas in a stable state. When the changeover is completed after a specified time T1, the control device generates a command S2 for completion of the changeover to shut off the shutoff valve 25B and to change the valves 18C, 23C, 23A to control to desired set values.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas switching control method when two or more gases are combined and fed, and in particular, it is easy to establish the flow rate of the trailing gas when switching from the leading gas to the trailing gas. The present invention relates to a gas switching control method that can be performed in a stable state.

When multiple gas lines are connected to one pipe and two or more gases are combined and fed from each gas line, one of these gases (leading gas) is used as a trailing gas. An operation is being performed to switch to a state where different types of gas are combined and fed. Such a gas switching operation is performed, for example, when switching the type of N gas to be blown below the surface of the molten metal in a metal refining furnace such as a bottom-blown converter, a top-bottom blowing converter, or a PH degassing furnace. The figure is a diagram illustrating the overall configuration of gas injection equipment that blows a plurality of types of gases below the surface of molten metal in a converter (metal smelting furnace).

In FIG. 1, a plurality of gases are blown below the surface of molten steel 2 stored in a converter 1 through tuyeres 3 provided at the bottom of the converter. In the illustrated example, the tuyere 3 is constructed of a double pipe consisting of an inner and outer pipe line 4.5. The outer pipe line 4 is provided with an A gas line 6 for supplying A gas. A B gas line 7 for feeding B gas and a C gas line 8 for feeding C gas are connected via a confluence point 9.10 and one pipe 11, and these three types Gases of various components can be injected by appropriately combining gases. On the other hand, similarly to the inner pipe line 5, there is a D gas line 12 for feeding D gas, an E gas line 13 for feeding E gas, and a line for feeding F gas. The F gas line 14 is connected through confluence points 15 and 16 and one pipe 17, and by appropriately combining these three types of gases, gases of various components can be blown from the tuyere 3 to create a vine-like flow. There is.

Each of the gas lines 6.7.8.12.13 and 14 has a similar configuration, and is provided with a pressure regulating valve, a flow regulating valve, a shutoff valve, etc., respectively. Corresponding parts in each gas line are therefore labeled using the same reference numerals separated by A-F for each gas line. Therefore, the A gas line 6 will be explained in detail below, and since the other gas lines are similar to this, detailed explanations thereof will be omitted.

A pressure regulating valve 18A is provided in the A gas thread path 6, so that the generated pressure (original pressure) of the A gas generation equipment is reduced to a predetermined pressure (supply pressure). A pressure detector 1.9A is provided immediately downstream of the pressure regulating valve 18A, and the actual supply pressure detected here is sent to the pressure regulator 2OA.
The drive signal from the pressure regulator controls the opening degree of the pressure regulating valve 18, thereby controlling the set value of the supply pressure. On the other hand, the detection signal from the supply pressure detector 19A is also input to a control section M (for example, a microcomputer) 21 for controlling the entire equipment.

Further, this control device 21 outputs a control signal for pressure adjustment to the pressure adjustment 1tt20A. With the above configuration, pressure control of A gas is performed.

As shown in the figure, a flow meter 2 is installed downstream of the pressure adjustment section.
2A and a flow control valve 23A are provided. Flow meter 2
The detection signal from 2A is input to a flow rate controller 24A, and the opening degree of the flow rate adjustment valve 23A is adjusted based on the signal from this flow rate controller, whereby the flow rate of gas A is controlled to a set value with the set flow rate as a target value. Ru. As in the previous case, flow meter 2
The detection signal of 2A is also input to the control device 21, and the flow rate adjustment signal from the control device 21 is input to the flow rate controller 2.
It is designed to be output to 4A. With this configuration, the flow rate of the A gas is controlled.

A cutoff valve 25A is provided downstream of the flow rate control section. This shutoff valve shuts off other gases from entering and mixing into the A gas line, and has two valves: fully open and fully closed.
Operates in position. Further, the fully closed and fully opened state of the shutoff valve 25A is detected by a limit switch, etc., and the signal is sent to the control device 2.
1 is input. On the other hand, the control device 21 outputs an opening/closing operation signal to the cutoff valve.

Each of the aforementioned gas paths also has substantially the same configuration as the A gas line path 6 described above. Therefore, the A gas line and the C gas line 8 meet at the confluence point 9, and the B
The gas line paths 7 are configured to merge at a merging point 10. The gases appropriately combined at the merging points 9 and 10 are blown into the molten steel 2 of the converter 1 from the tuyere 3 through the pipe 11. A pressure gauge 26 is provided in the conduit 11 to detect the pressure value at the confluence section and input the signal to the control device 21.

Gas switching when two or more types of gas are combined and fed is performed by the equipment as explained above. Taking as an example the case of switching B gas to C gas, leaving A gas unchanged, and thus supplying two types of gases, A gas and C gas, the conventional gas switching method will be described in the following. This will be explained with reference to the drawings and FIG.

When performing a gas switching operation, please follow the switching command S in Figure 2.
1, the flow rate settings of the flow rate control valves 23A and 23B for the A gas and B gas, which are the preceding gases, are lowered. This condition is shown by lines 23A and 23B in FIG.

On the other hand, the flow rate control valve 23C for C gas, which is the trailing gas, is in the second position.
As shown in the figure, it is preset to a predetermined opening degree in advance, and is kept open at a constant opening degree despite the switching start command S1. Further, based on the switching command S, the C gas shielding well 25C is opened as shown at 250 in FIG. 2 to enter gas switching. Similarly, the cutoff valve 25B for the preceding gas B is closed by the command of the switching end signal S, as shown at 25B in FIG.

However, when gas switching is started based on the switching start signal S, the supply pressure of C gas is equal to or higher than the set pressure value, so the pressure adjustment amount is 18C. is in a nearly fully closed state as shown at 180 in FIG. Therefore, even though the cutoff valve 250 is controlled to open as the cutoff valve 25C is opened and switching begins and the C gas supply pressure (feeding pressure) decreases as shown by Pc in FIG. Since there is a delay in the operation of 18C, the supply pressure Pc drops as shown in FIG. On the other hand, the pressure inside the confluence part, that is, the pipe 11, increases as shown by P in FIG. 2 due to the opening operation of the shutoff valve 25C and the generation of the flow rate of C gas (Pc in FIG. 2), that is, due to the influence of C gas. do. In addition, FA%FB in Figure 2 is A
The flow rates of gas and B gas are shown.

Therefore, in this state, the pressure difference between the upstream and downstream sides of the C gas flow rate control valve 23C, that is, the difference between the supply pressure Pc and the sum of the confluence pressure P and the pressure loss of the pipe line, orifice, etc., becomes small, and the C A situation arises in which it is difficult to secure the flow rate in the gas system path, and therefore switching is impossible.

In this case, if gas switching is stagnated until the flow rate of the trailing gas (C gas) is stabilized, the timing of gas switching will be impaired, and gas injection will continue depending on the operating conditions. Therefore, it becomes impossible to adjust the molten steel to the target composition or temperature.

A problem arises in that losses occur due to continued unnecessary gas injection.

An object of the present invention is to provide a gas switching control method that eliminates the drawbacks of the conventional gas switching control method as explained above and allows easy switching by stabilizing the flow rate establishment of trailing gas. That's true.

A feature of the present invention is that the pressure control valve and flow control valve of the trailing gas line are preset to a predetermined opening degree, and the flow rate setting value of the flow rate control valve of the leading gas line is reduced based on a switching command. The object is to achieve the above object by a control method in which the shutoff valve of the trailing gas line is opened at the same time as the switching of the trailing gas is established, and the shutoff valve of the leading gas line is closed.

That is, according to the present invention, in a gas switching control method when two or more gases are combined and fed, a pressure control valve, a flow rate control valve, and a cutoff valve are provided in each gas line, and the The pressure control valve and flow rate control valve of the leading gas line are preset to a predetermined opening degree, and the flow rate setting value of the flow rate control valve of the leading gas line is lowered based on the switching command. After confirming that the pressure and flow rate of the trailing gas and the pressure at the merging section have reached the specified values, close the shutoff valve of the leading gas line, and close the pressure regulating valve of the trailing gas line. and a gas switching control method characterized by starting set value control of a flow rate regulating valve.

The present invention will be described in detail below with reference to FIGS. 1 and 3.

Also in the following explanation, the above-mentioned conventional switching control (9) will be used.

Corresponding to the explanation of the method, from the state where A gas and B gas, which are leading gases, are fed, gas A is changed and continues to be fed, and gas B is changed to gas C, which is the trailing gas. An example of switching to a feeding state will be described.

FIG. 3 is a gas switching time chart corresponding to the above-mentioned FIG. 2, and illustrates the switching state when the present invention is implemented. Also, in FIG. 3, parts corresponding to each element in FIG. 2 are indicated by the same reference numerals, and
, and S indicate a command to start gas switching and a command to complete gas switching, and P indicates the pressure at the confluence section (for example, inside the pipe 11). In addition, 18A is the opening degree of the pressure regulating valve 18A, and PA is the opening degree of the pressure regulating valve 18A.
23A indicates the supply pressure in the gas system line, 23A indicates the opening degree of the flow rate control valve 23A, FA indicates the flow rate in the A gas system line, and 25A indicates the operation of the cutoff valve 25A (the upper line is open and the lower line is closed). The same symbols with symbols B and C added instead of symbol A (including the suffix) indicate the respective elements of B gas and C gas corresponding to the case of A gas.

(10) First, by the switching start command S from the control device 21, A
The flow rate setting values of gas and B gas are lowered to near the lower limits, respectively, as shown at 23A%FA, 23B, and FB in FIG. The purpose of this ramp-down setting is to facilitate the establishment of the flow rate of C gas, which is the trailing gas, while establishing the total flow rate of A and B gases, and the lower limit value is set in consideration of this.

On the other hand, the pressure regulating valve 18C for C gas is previously opened to a predetermined opening degree (preset opening degree indicated by PS in FIG. 3), as shown at 180 in FIG.

As a result, as shown in PC, the pressure on the generation side higher than the supply pressure during use is supplied as the inlet pressure of the flow rate control valve 23C. Moreover, this flow rate control valve 23C is designated as 23 in FIG.
As shown in 0, the opening degree is preset to a predetermined opening degree (PS opening degree).

According to the switching start command SI as shown in 25C! When the cutoff valve 25C opens, the original pressure of the C gas, which is higher than the supply pressure, is supplied to the flow rate control valve 23C, and since the flow rate control valve is at a preset opening degree, the flow rate of the C gas is as shown in FC. It shows a sudden rise (11).

In this way, the supply pressure Pc of C gas, which is the trailing gas, is maintained at a sufficiently high pressure and its flow rate FC also shows a sufficient rise, so even if the confluence pressure P rises to the state shown in FIG. The gas is supplied in a stable state and switches easily and stably from the preceding gas, B gas.

Before a certain period of time T has elapsed since the switching start command S,
The open state of the shutoff valve 25C, the flow rate Fc of the C gas, the pressure Pc of the C gas, the confluence part pressure P, etc. are detected to confirm the gas switching conditions, and when the gas switching is established, the control device 2
Switching completion command S from 1! is generated, and the following control is performed based on this.

(1) Close the cutoff valve 25B for B gas, which is the trailing gas (
(See 25B in Figure 3).

(2) Switch the C gas pressure control valve 18C from the preset opening degree to the desired pressure setting value control.

(3) Switch the C gas flow rate control valve 20 from the preset opening degree to the desired flow rate setting value control.

(12) (4) Switch the ramp-down setting of the A gas flow control valve 23A, which will continue to be used even after switching, to a predetermined (normal) flow rate set value control.

(5) The pressure regulating valve 18B and the flow regulating valve 23B of the preceding B gas, which are switched to C gas and are not used, are respectively switched to preset opening degrees.

With the above control, it is possible to easily, stably, and consistently perform the gas switching of switching B gas to C gas among the two types of gases, A gas and B gas, and avoid unstable switching as in the conventional technology. It is possible to prevent switching failure from occurring.

Similarly, if the gas switching conditions are not met, an alarm will be issued to notify the operator and the original A gas and B gas will be restored.
It is necessary to take abnormality countermeasures such as returning to the use of gas, but according to the embodiments described above, such countermeasures can be taken quickly and easily.

In the above embodiments, the case where one type of gas is switched to another gas is explained, but the control described above can also be applied when switching one type or two or more types of gases among three or more types of gas. Gas switching can be performed easily and stably by applying the method as is.

As is clear from the above description, the present invention provides a gas switching control method that can easily and stably switch the gas from the leading gas to the trailing gas.

[Brief explanation of drawings]

Fig. 1 is a system diagram illustrating equipment for blowing gas into molten steel in a converter suitable for applying the gas switching control method of the present invention;
The figure is a time chart illustrating the operation when a conventional gas switching control method is applied to the equipment shown in Fig. 1, and Fig. 3 is a time chart illustrating an example of the gas switching control method according to the present invention applied to the equipment shown in Fig. 1. 3 is a time chart illustrating the operation in this case. 1... converter, 2... molten steel, 3... siding,
6.7.8.12.13.14...Gas system line, 9.1
0.15.16...Confluence point, 11.17...Piping, 18A~18F'...Pressure control valve, 198~19F...Supply pressure detector, 2
1...Control device, 22A-22F...Flowmeter,
23A to 23F...Flow control valve, 25A to 25F...Shutoff valve, 26.27...Pressure gauge, Sl...Gas switching start command S,...Gas switching completion command, T,...・Gas switching time. Agent Tatsuyuki Unuma (and 2 others) Figure 2 Figure 3

Claims (1)

[Claims] (1) In a gas switching control method when two or more gases are combined and fed, a pressure control valve, a flow rate control valve, and a cutoff valve are provided in each gas line, and the trailing gas line is The pressure control valve and flow control valve of the preceding gas line are preset to a predetermined opening degree, and based on the switching command, the flow rate setting value of the flow rate control valve of the preceding gas line is lowered, and the cutoff valve of the following gas line is opened. After confirming that the pressure and flow rate of the trailing gas and the pressure at the convergence section have reached the predetermined values, close the cutoff valve of the trailing gas line and adjust the set values of the pressure control valve and flow rate control valve of the trailing gas line. A gas switching control method characterized by starting control.