JPS63128110A - Injecting method for gas and powder into converter - Google Patents

Abstract

PURPOSE:To make the actuation of change-over valve smooth without any deterioration of molten steel quality by injecting powdered coal for fuel into molten steel by carrier gas at the time of operation of a converter and next at the time of blowing oxidizing gas by changing over supply of inert gas to supply of he oxidizing gas at the timing, when the flow rate of powdered coal becomes constant. CONSTITUTION:At the time of refining steel from molten iron and steel scrap as the raw material in the converter 1, the low-priced powdered coat for heating and raising the temp. of the molten steel in the converter 1 is injected into the molten steel in the furnace by the carrier gas, such as N gas, and next, the oxidizing gas, such as O2, is blown into the molten steel, to heat the raw material in the converter 1 using mush steel scrap and to raise the temp. by combustion heat of powdered coal. In this case, the quantity of powdered coat at the time of supplying the powdered coal into the converter 1 by N gas is measured by a flow metal 10, and when aflaining a constant value, the supply of powdered coal from a powder material dispenser 7 is stopped, and just after the remaining powdered coal is eliminated from the piping 3 by N gas, the change-over valve is changed over, to blow the O2 gas into the furnace. The working trouble of the change-over valve 5 caused by remaining powdered coal is prevented and also the deterioration of quality caused by in creasing N content in the molten steel by over-supplying N gas as carrier gas is prevent.

Description

[Detailed description of the invention] (Field of industrial application) In recent years, as the use of coal energy, which is cheaper than electric energy, has been reconsidered, it has become especially As an attempt to add carbon-containing fuel, etc., a technique has been put into practical use in which pulverized coal, oxidizing gas, etc. are directly blown into a molten iron bath.

The present invention relates to a method of blowing gas and powder into a molten iron bath charged into a converter for safer blowing of pulverized coal and the like.

(Prior art) Conventionally, the method of injecting powder such as pulverized coal or oxidizing gas into a molten iron bath charged in a converter requires piping for supplying powder and piping for supplying oxidizing gas. A piping switching method is known in which the pipes are connected via a switching valve and powder or oxidizing gas is alternately blown in by switching the switching valve.

In this regard, in Japanese Patent Publication No. 60-40487, a movable housing is provided which mainly has a supply pipe for an oxidizing gas such as 02, a fuel supply pipe for blowing powder such as pulverized coal together with an inert gas, and a siding pipe. A valve member is provided to control the gas pressure of the oxidizing gas supply pipe, and the fuel is supplied to the fuel supply pipe and the oxidizing gas is supplied to the gas supply pipe alternately through the tuyere vibrator. A device designed to blow into the molten iron bath has been proposed.

The device disclosed in Japanese Patent Publication No. 60-40487 uses a movable valve member provided in a housing to physically separate the coexistence of oxidizing gas and pulverized coal to prevent coal dust explosions. This system allows both oxidizing gas and pulverized coal to be injected through a single inlet. In addition, the blockage of the blowing port due to continuous blowing of only pulverized coal can be prevented.
This has the advantage that it can be prevented by the oxidative heating reaction caused by blowing in oxidizing gas.

By the way, the carrier gas is not always flowing through the fuel supply pipe of this device, and if the gear gas is stopped with powder remaining in the pipe, the powder remaining in the pipe will cause the fuel to move. There was a risk that switching between the fuel pipe and the oxidizing gas supply pipe using the valve member would become impossible, or the inside of the pipe would become clogged, making it impossible to restart the injection of fuel.

Therefore, when switching from the supply of powdered fuel to the supply of oxidizing gas using such a device, conventionally, after the powder has stopped being cut out from the powder dispenser, the carrier gas is allowed to flow for a certain period of time to drain the inside of the piping. A method was adopted in which the supply of oxidizing gas was started after purging the remaining powder.

(Problem to be solved by the invention) However, such a piping switching method does not transfer the powder remaining in the powder supply pipe to the carrier gas at the end of powder injection without any information regarding the amount of remaining powder. The system was designed to purge for a certain period of time, but there were the following problems.

That is, (1) if the purge time is too long, the amount of gas used increases, and furthermore, when a soluble gas such as nitrogen gas is used as the purge gas, the gas concentration in the steel increases.

(2) If the purge time is too short, powder may remain in the piping due to the barcine foot, making it impossible to switch the switching valve, or the powder injection piping cannot be used again due to piping blockage.

The object of the present invention is to provide a method for blowing gas and powder into a molten iron bath in a converter that is safe and advantageous in avoiding the troubles described above when blowing oxidizing gas and powder into a molten iron bath in a converter using a piping switching system. This is where we propose.

(Means for Solving the Problems) The present invention mainly includes a gas blowing system that controls the supply of oxidizing gas, and a powder blowing system that controls the supply of powder such as pulverized coal using a carrier gas such as an inert gas. , in a method of timely switching and blowing either gas or powder into the converter through a blowing port provided below the bath surface, when switching from the powder blowing system to the gas blowing system, the powder blowing system Measure the powder flow rate,
After stopping cutting out the powder from the powder dispenser, stopping the supply of the carrier gas when the powder flow rate reaches a certain value, and then blowing the oxidizing gas from the gas blowing system. This is a method for blowing gas and powder into a converter, which is characterized by:

(Function) When blowing oxidizing gas or powder into the converter using the piping switching method, especially when switching from blowing powder to blowing gas, cut out the powder from the powder dispenser after stopping it. Ascertain the time (to) until all the powder existing in the pipe from the position to the inlet of the converter is blown out, and then incorporate control logic to continue flowing the carrier gas until this time (70) has elapsed. This is considered to be advantageous in solving the conventional problems. However, the above time (70) varies depending on various factors such as the powder blowing speed.

Therefore, in reality, the value is larger than necessary in view of safety, resulting in an increase in the amount of gas used and a high gas concentration in the steel. Therefore, the means proposed in the present invention, when switching from powder blowing to gas blowing, accurately determines the time (to) required to blow all the powder remaining in the powder blowing pipe after stopping powder cutting. The powder flow rate value in the powder injection pipe is measured.

Then, when the flow rate value becomes lower than a preset value, the supply of the gas used for blowing the powder is stopped, and at the same time, the system switches to the oxidizing gas supply system and starts blowing the gas.

By switching between the powder blowing system and the gas blowing system in this manner, the amount of gas required for powder blowing can be greatly reduced, and clogging of piping, etc. can be easily prevented. Here, it is desirable that the powder flow rate value be measured particularly in the powder supply system closest to the inlet of the converter.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 schematically shows equipment for blowing gas and powder into a converter suitable for carrying out the present invention. In the figure, 1 is a converter, 2 is a gas and powder blowing port, 3 is a powder injection system that supplies powder such as pulverized coal using a carrier gas such as an inert gas (hereinafter referred to as powder injection piping)
, 4 is a gas blowing system that mainly controls the supply of oxidizing gas (
5 is a switching valve for switching between the powder blowing pipe 3 and the gas blowing pipe 4 (hereinafter referred to as gas blowing pipe).

Further, 6 is a carrier gas cutoff valve, 7 is a powder dispenser, 8 is a powder cutoff valve, 9 is a carrier gas bleed valve, 10 is a powder flow meter, 11 is a gas cutoff valve, 12 is a gas bleed valve, And 13 is a control device.

In this equipment, when powder is being blown into the converter 1, the powder cutoff valve 8, the carrier gas cutoff valve 6, and the gas bleed valve 12 are opened, and the carrier gas bleed valve 9 and the gas cutoff valve 11 are opened. is closed. When switching from powder blowing to gas blowing, first, the powder cutoff valve 5 is closed by a command from the control device 13. After closing the cutoff valve 5, when the powder flow rate measured by the powder flow meter 10 has decreased to a predetermined value, the gas bleed valve 12 is closed by a command from the control device 13, and this closed state is shown in the figure. After confirming with a limit switch etc. that the gas is not present, the gas cutoff valve 11 is opened. Next, the carrier gas cutoff valve 6 is closed and the carrier gas bleed valve 9 is opened according to a command from the control device 13. Then, the switching valve 5 is switched to the gas blowing pipe 4 side.

FIG. 2 shows the operational status of the response when switching from the powder blowing pipe 3 to the gas blowing pipe 4.

(Example) Using the equipment shown in Fig. 1, N2 gas 50 Nm'/ll1in, pulverized coal flow [3
The state in which fine powder was being blown into the converter 1 with the setting at 00 kg/win was switched to the gas blowing pipe 4 in order to blow oxygen gas into the converter 1. The powder flow rate that can be switched by the switching valve 5 was set to 20 kg/win.

First, about 40 seconds after the powder cutoff valve 8 was closed, the value measured by the powder flow meter IO decreased to 20 kg/ff1in. At this point, the answer was activated as shown in Figure 2. After switching to the gas blowing pipe 4, blow at at 50 Nm''/win for 5 minutes from the gas blowing pipe 4.Furthermore, switch the switching valve 5 again and N2
As a result of blowing pulverized coal together with the gas, it was confirmed that the N2 gas was flowing according to the set value (5ONm''/n+in).

For comparison, without applying the present invention, 15 seconds after closing the powder cutoff valve 8, the valve 1 was opened as shown in FIG.
2.11,6. When the switching valve 5 was switched to the gas blowing pipe 4 side by activating the answer in step 9, the switching valve 5 malfunctioned due to the powder remaining in the powder blowing pipe, and the gas from the gas blowing pipe 4 was turned off. The flow rate did not reach the set value of 50 Nm''/min, and in order to prevent leakage of molten iron from the inlet 2, the furnace had to be collapsed.

In addition, the blowing flow rate of pulverized coal was set to 150 kg/l1in.
When the switching valve 5 was operated in the same manner as in the above embodiment, the value measured by the powder flowmeter 10 became 20 kg/min about 17 seconds after closing the powder cut-off valve 5, and the switching valve The switch was successfully made without any malfunction or blockage of the piping. The difference in time between the present example and the previous example after the powder cut-off valve 8 is closed until the powder flow rate reaches the level at which the switching valve 5 can be switched is as follows.
This shows that the time required to purge the remaining powder inside the pipe 3 varies depending on the powder blowing flow rate before switching starts, which shows that the present invention is advantageous compared to the conventional switching method in which the purge time is constant. It shows that.

(Effects of the Invention) According to the present invention, the conventional problems that occurred when adopting a piping switching method in which powder and oxidizing gas are alternately blown into the molten iron bath in the converter can be easily solved. is possible,
It is possible to save carrier gas and prevent the carrier gas concentration in the steel from increasing more than necessary.Furthermore, there is no risk of switching valve malfunction or piping clogging, making it possible to achieve safer blowing.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the blowing method according to the present invention, and FIG. 2 is an explanatory diagram showing the operating state of answering. 1... Converter 2... Gas/powder blowing port 3... Powder blowing piping 4... Gas blowing piping 5... Switching valve 6... Carrier gas cutoff valve 7... Powder dispenser 8...Powder cut-off valve 9...Carrier gas bleed valve 10...Powder flow meter 11...Gas cutoff valve 1
2...Gas bleed valve 13...Control device patent applicant: Kawasaki Steel Co., Ltd. Applicant: Fuji Electric Co., Ltd.

Claims (1)

[Claims] 1. A gas blowing system that mainly controls the supply of oxidizing gas;
The powder injection system, which controls the supply of powder such as pulverized coal using a carrier gas such as an inert gas, is switched in a timely manner, and either gas or powder is introduced into the converter through the injection port provided below the bath surface. In the blowing method, when switching from the powder blowing system to the gas blowing system, measure the powder flow rate in the powder blowing system, stop cutting out the powder from the powder dispenser, and then change the powder flow rate. A method for blowing gas and powder into a converter, characterized in that the supply of carrier gas is stopped when the carrier gas reaches a certain value, and then the oxidizing gas is blown from the gas blowing system.