JPS5834528B2 - Blowing method of bottom blowing converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blowing method for a bottom-blowing converter, and particularly proposes a method that can perform effective and appropriate tuyere cooling even during blowing.

Recently, a new type of converter furnace has been put into practical use for steelmaking and refining, in which pure oxygen is directly blown into the steel bath through a number of holes buried in the bottom of the furnace.

This converter is a method of oxidizing and removing impurities such as C, Si, and P contained in steel by blowing pure oxygen, which is an oxidizing gas, into the furnace through the tuyeres.

However, since this oxidation reaction is an exothermic reaction, the molten steel around the tuyere becomes extremely hot, and the tuyere itself is exposed to a high-temperature atmosphere and suffers severe melting damage.

Conventionally, in the case of a converter where oxygen is injected from the bottom of the furnace, a hydrocarbon-based cooling gas pipe is placed around the refining gas pipe that conducts the oxidizing refining gas inside. The tuyere is cooled by providing a wall of heavy concentric pipes, flowing hydrocarbon (chemical formula: CnHm) from the cooling gas pipe, and utilizing the endothermic effect when this is thermally decomposed into C and H2 gas. Measures were taken to reduce the wear and tear.

However, the heat received during such a process is not necessarily constant because the heat generated by oxidation of iron and impurities is the main component.

In addition, recently, a powdered slag forming agent was mixed with the oxidizing gas, and -
This slag-forming agent also has the effect of acting as a separate coolant, but the amount used varies depending on the blowing conditions, so the heat receiving state of the so-called tuyeres is different from that of blowing. The reality is that it is not constant.

On the other hand, the flow rate of the hydrocarbon, which is the cooling gas mentioned above, is
They were using more than necessary to ensure safety, and as a result, a considerable amount was wasted.

On the other hand, for example, if the flow rate of cooling gas is excessive, it is not only uneconomical, but also causes excessive cooling, which causes the solidified shell (commonly known as matshu room) that adheres around the tuyere end to become abnormally large. Due to its unusual size, it may suddenly become missing or peel off.

In such a case, the tips of the linings are exposed, so that they wear out quickly and the area around the linings recedes into a concave shape, resulting in a shortened lifespan, which is an extremely undesirable situation.

From the above, in order to suppress the wear and tear of the tuyere, it is a good idea to stably generate a small but strong pine room at the top of the tuyere and thereby protect the tip of the tuyere.

For this purpose, it is desirable to constantly detect the temperature of the tuyere on the side that contacts the molten steel at the tip of the blade during blowing, and to perform converter blowing while controlling the cooling conditions so that the temperature remains at the desired value. .

The purpose of this invention is to achieve effective and appropriate cooling of the tuyere in the process of converter blowing, and the gist of this invention is to provide a thermometer at the tuyere of a so-called bottom-blowing converter. installation,
The temperature measuring device continuously measures the temperature at the tip of the tuyere, and blowing is performed while adjusting the composition and/or flow rate of the cooling gas in response to changes in the measured temperature.

The details of the configuration will be explained below with reference to the drawings and examples.

Converter blowing according to the present invention is a method of oxidizing and refining by blowing refining gas through a large number of tuyeres t buried in the furnace bottom 1.

The tuyere t is a concentric double pipe consisting of an inner pipe 2 and an outer pipe 3, and the outer pipe line 3a is filled with hydrocarbon-based cooling gas, and the inner pipe line 2a is filled with oxidizing refining gas such as pure oxygen. It is configured to allow gas to flow through it.

This tuyere t is naturally immersed in a steel bath during blowing, and is also buried in the furnace bottom 1.

Therefore, temperature measurements at the tip of the tuyere, which is under the most severe conditions, are usually extremely difficult.

Therefore, even though the heat receiving conditions at the tip of the tuyere fluctuated greatly during the blowing process, appropriate cooling of the tuyere was not performed.

Therefore, in this invention, the temperature of the tuyere t and its surroundings is measured by using a thermocouple between the outer circumference of the outer tube 3 and the bottom refractory, or within the cooling gas pipe (outer pipe) 3a.
The temperature around the tuyere was measured by providing a temperature sensing element such as the one shown in FIG.

Next, a method of temperature measurement and a blowing method that responds to the temperature will be explained.

FIG. 2 of the drawings shows an embodiment in which a thermocouple 4 is attached to the outside of the tuyere t to measure temperature.

To measure the temperature using the thermocouple 4, a groove 5 having a depth of about 1 mm and a width of about 5 mπ is provided along the tube axis direction on the outer surface of the outer tube 3 of the concentric double tube tuyere t.

When the tuyere t is attached to the hearth bottom 1, the diameter is 0.3 so that each temperature detection end is located every 40 mπ from the side that contacts the steel bath; that is, from the fire point side during blowing. A Pt/Pt-13Rh thermocouple 4 with a diameter of about φ was insulated through an alumina insulating tube.

The lead wire of the thermocouple 4 is usually connected to the barrel part (furnace body) 7.
It is taken out from between the joint flange 8 at the bottom of the furnace and to the outer periphery of the furnace as shown in Fig. 2, and connected to the compensating conductors 6. These compensating conductors 6 are connected to the front of the steelmaking furnace while being protected by a flexible tube that shields heat. The temperature was measured by electrically processing the thermoelectromotive force by connecting it to an amplification device and an indicator.

The measured temperature is monitored throughout the blowing period, and at the same time, the flow rate of hydrocarbon cooling gas is adjusted so that the temperature remains constant, or a mixture of hydrocarbon gas and inert gas such as N2 or Ar is used for cooling. By adjusting the composition while maintaining the sum of gas flow rates at a constant flow rate, unnecessary consumption of hydrocarbons, which has conventionally been observed, is suppressed.

At that time, the distance from the tip of the tuyere to the tip of the heating element 4 closest to it changes each time as the bottom refractory wears out, so the distance from the tip of the tuyere to the tip of the heating element 4 changes each time, so it is determined in advance according to the work standard that The above-mentioned method is used to memorize the thermocouple reading under the specified cooling conditions, and to maintain that temperature continuously during the entire period of blowing, from the peak decarburization period, the dephosphorization period, and the end of blowing. By adjusting the composition of the cooling gas under a constant flow rate condition, or by adjusting only the flow rate of the cooling gas, the tuyeres can be appropriately cooled according to the heat fluctuations in the furnace and the heat reception fluctuations of the tuyere t.

Note that the method of keeping the total flow rate of the cooling gas constant and changing its composition is (a) in response to the temperature (oxidation calorific value) around the siding, which fluctuates due to various factors during blowing. ,
It is a cooling gas that causes the necessary heat removal reaction (thermal decomposition reaction), and satisfies the following two points at the same time: (0) It can overcome the static pressure of molten steel and prevent molten steel from entering the outer pipe 3a. This is necessary control.

Therefore, when performing such control, for example, if the pressure is insufficient as a result of keeping the flow rate of gas other than hydrocarbon constant in order to obtain the desired heat removal effect, another gas may be used to
It is necessary to maintain a predetermined pressure inside a.

These gases include N2. An inert gas such as Ar is preferable, but CO gas, H2 gas, NH3 gas, etc. may also be used.

Furthermore, the above-mentioned temperature around the tuyere can also be measured using an optical element 9 as shown in FIG.

This optical element 9 is fixed in a magnetic tube 10 via a filler 11, and the magnetic tube 10 is inserted into a gas injection tube 13 having an inward injection port 12 at its tip.

This gas injection is performed in order to prevent (blow away) the powdered slag-forming agent that becomes a coolant mixed into the refining gas from interfering with the light-transmitting function of the optical element 9.

As shown in FIG. 4, the optical thermometer tube P including 9 optical elements is inserted into the refining gas introduction pipe below the tuyere T, and the optical element is installed facing the inside of the furnace. 9, the temperature of the spark point at the tip of the tuyere is detected as the amount of light received.

Note that the temperature around the cuffs detected through the light receiver 12, indicator 13, and recorder 14 is processed in the same manner as in the case of the thermal lightning pair described above.

Next, the temperature at the tip of the tuyere during blowing is measured using the optical temperature measuring tube P, and the relationship between the temperature and the cooling gas flow rate (propane flow rate ratio indicating the oxygen flow rate) adjusted according to the temperature will be shown. Examples will be described below.

However, in this embodiment, if the gas pressure in the cooling gas passage of the concentric double pipe panel is reduced too much, there is a risk of shallow pan formation, so Ar gas is mixed in to compensate for the reduction in propane, and the oxygen flow rate is This is an example in which the total cooling gas flow rate is 4% in terms of ratio.

In this example, the optical thermometer tube was attached to one of six tuyeres provided in a bottom blowing converter.

The tip of the optical thermometer, which is inserted into the tuyere through which oxygen gas for refining flows, is made of transparent quartz (4 mm φ x 200 mm).
) is the part covered by the optical fiber (
41n7ILφ×8000mm) is connected to the light receiver.

FIG. 5 of the drawings shows an example in which blowing was carried out while controlling the amount of cooling gas in accordance with the results of temperature measurement.

(The numerical value uses the average value of 10 heats) The erosion rate of the hearth refractory by implementing this invention is 2.7 mm/ch
zPropane consumption was 1,14 Nm3/steel.

On the other hand, the propane ratio according to the conventional method was a constant value of 3%, the welding speed of the bottom refractory was 3.5 mrn/ch, and the propane consumption was an average value of 1.93 Nm3/ for steel. The effects are obvious.

That is, according to the method of the present invention, an economical bottom-blowing converter blowing method can be provided in which the life of the bottom of the furnace can be extended and the amount of propane consumed can be reduced.

This extension of the hearth bottom life is due to the fact that the cooling of the siding becomes constant, the temperature of the surrounding refractory material does not change too rapidly during blowing, and the peeling of the hearth bricks due to spalling is reduced. It is thought that this is brought about by

As explained above, according to the present invention, it is possible to perform tuyere cooling that responds well to changes in the heat receiving state around the tuyere, and is also economical without wasting expensive cooling gas. On the other hand, since there is no supercooling, a stable tuyere tip state can be maintained.

Therefore, its feather life can be significantly extended.

[Brief explanation of the drawing]

Figure 1 of the drawings is an end view of the bottom blowing converter tuyere, Figure 2 is a cross-sectional view of the bottom of the bottom blowing converter furnace with a thermocouple attached, and Figure 3 is a partial cutaway of the optical thermometer tube. FIG. 4 is a schematic diagram showing a state in which an optical thermometer tube is attached to the bottom of the converter furnace, and FIG. 5 is a diagram showing an example of propane flow rate control with respect to tuyere tip temperature. T...Tuyere, P...Optical thermometer tube, 1.
...Hearth bottom, 2...Circular tube, 3...
Outer tube, 4... thermocouple, 5... groove, 6...
... Compensation lead wire, 7 ... Barrel part, 8.
...Flange portion, 9...Optical element, 10
...Magnetic tube, 11...Filling material, 12.
...Injection port, 13...Gas injection pipe.

Claims (1)

[Claims] 1 Hydrocarbon cooling gas is passed through the outer pipe of the concentric double pipe to cool the tuyere by its thermal decomposition action, while oxidizing refining gas is introduced into the inner pipe to cool the steel bath. In blowing in a bottom-blown converter that performs oxidation refining by blowing air into the interior, a temperature meter is attached to the tuyere tip, and the temperature at the tuyere tip is continuously measured by the temperature meter. A method for blowing in a bottom blowing converter, characterized by adjusting the composition and/or flow rate of cooling gas.