JPH04259318A - Lance for blowing oxygen - Google Patents

Abstract

PURPOSE:To secure oxygen gas quantity and to prevent erosion of refractory due to secondary combustion of CO gas near furnace opening hole by arranging plural steps of sub-nozzle group and specifying mutual parting angle to the sub-nozzles in the same step and interval at upper and lower positions. CONSTITUTION:Under condition of freely inserting a lance 2 into a converter 1, the sub-hole groups N1, N2 having plural sub-holes (n) on outer periphery at upper position of a mina hole Nm for injecting the oxygen gas, are arranged at two steps (plural steps). The mutual parting angle alpha to the sub-holes in the same step of sub-hole groups N1, N2 is made to >=30 deg.. Further, at the time of using R for average radius at center part of the converter, when (d) as diameter of the lance body, thetad and thetau respectively as an angle among the direction of the sub-hole (n1) in the sub-hole group N1 at the lower step and longitudinal direction axis of the lance body and that among the direction of the sub-hole (n2) in the sub-hole group N2 at the upper step and the longitudinal direction axis, are denoted, the interval L between the sub-hole groups N1 and N2 is set so as to satisfy L>=R(cotthetau-cotthetad)/3+pi/d/(360/alpha). By this method, the secondary combustion of CO gas is surely executed in the furnace.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen injection lance for secondary combustion, which ensures the combustion of unburned gas within a converter.

0002

[Prior Art] As is well known, an oxygen injection lance (hereinafter referred to as a lance) is inserted loosely into a converter, for example, and is used to refine hot metal in the converter, as well as as a hot metal reserve. It is also used in processing furnaces and melting reduction furnaces. Hereinafter, an example of such a lance will be explained based on FIG. 3, which is an explanatory diagram of the loosely fitted state of the lance and the converter, taking as an example the refining of hot metal in a converter. A lance 2 having the following configuration is loosely fitted into the furnace mouth 1a of the converter 1.

[0003] The details of the above-mentioned lance 2 include a main nozzle (hereinafter referred to as main hole) Nm that injects oxygen gas downward when loosely fitted into the converter 1, and a main nozzle (hereinafter referred to as main hole) Nm that injects oxygen gas downward. A plurality of sub nozzles (hereinafter referred to as
The structure is such that a sub nozzle group (hereinafter referred to as a sub hole group) N1 having a sub nozzle group (hereinafter referred to as a sub hole group) N1 is provided.

Therefore, while oxygen gas 3 is injected from the main hole Nm toward the molten bath contained in the converter 1,
Oxygen gas 3 is also injected outward in the radial direction of the lance 2 from the subhole n1 of the subhole group N1, and secondary combustible gas is generated based on combustion by the oxygen gas 3 injected from the main hole Nm. For example, carbon monoxide gas (hereinafter referred to as CO gas) is burned.

[0005]

[Problem to be Solved by the Invention] However, since the sub-hole groups of the lance having the above-mentioned configuration are arranged around the outer circumference at a position a predetermined distance from the main hole, the oxygen gas injected from each sub-hole is The amount of carbon monoxide gas supplied may be partially insufficient, and as a result, unreacted oxygen gas rises to the vicinity of the converter mouth, where CO
There was a problem with the gas burning.

As mentioned above, when CO gas is burned near the furnace mouth of the converter, it not only causes a decrease in refining efficiency due to the effective use of heat due to the secondary combustion reaction, a decrease in so-called heat transfer efficiency; This also led to increased erosion of nearby refractories, which increased running costs for the converter.

[0007] Therefore, the present invention reliably eliminates C in the converter.
The purpose of the present invention is to provide a lance that makes it possible to burn O gas.

[0008]

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned circumstances, and therefore, the lance according to the present invention has a main hole at the tip and a plurality of sub holes around the outer periphery. In a lance for secondary combustion equipped with a group of secondary holes,
A plurality of stages of the sub-hole groups are provided, the separation angle α between the sub-holes in each stage is at least 30 degrees, and the oxygen injection lance is loosely fitted within the average center of the converter. When the radius is R, the diameter of the lance body is d, and the angles between the longitudinal axis of the lance body and the orientation of the sub-holes of the sub-hole group in the vertical position relationship are θu and θd, respectively, the vertical positional relationship is The interval L between the steps of adjacent sub-hole groups in is L≧R(
cotθu − cotθd )/3+πd/(360/
It is characterized by satisfying the relationship α).

[0009]

[Function] According to the lance according to the present invention, in order to completely burn the downward CO gas, the vertical positional relationship is established between the sub-hole groups in multiple stages, each of which has sub-holes with a separation angle α of at least 30 degrees. The interval L between adjacent sub-hole groups in the lower sub-hole group is R, the average radius of the center of the converter is R, the diameter of the lance body is d, the longitudinal axis of the lance body and the sub-holes of the lower sub-hole group. When the angle with the direction is θd, and the angle with the direction of the sub-holes of the upper sub-hole group is θu, the interval L between adjacent sub-hole groups is L≧R(cotθu −cotθd)/3+πd/
It is set to satisfy (360/α).

As shown in FIG. 2, which explains the derivation of the mathematical formula, the above formula calculates the vertical distance between the position of the upper secondary hole n2 and the intersection of the line passing through its center and the R/3 line by L2.
, the position of the lower subhole n1, the line passing through its center, and R
When the vertical distance from the intersection with the /3 line is L1, and the distance between the above intersections is L3, L2
tanθu = R/3 to L2 = R/3×cotθu
and L1 tanθd = R/3 to L1
=R/3×cotθd is derived.

Next, from the relationship L+L1 =L2 +L3, L+R/3×cotθd =R/3×cotθ
By deriving and transposing u +L3, L=R/3
×cotθd +R/3×cotθu +L3, and assuming that L3 is larger than the arcuate distance between sub-holes of the same group on the outer periphery of the lance, that is, πd/(360/α), L3 is calculated as πd/(360/α). It can be derived by replacing α).

[0012] As can be well understood from the figure, R
Strictly speaking, /3 is the distance from the center of converter 1, but since d of the lance is sufficiently small compared to R of converter 1, R/3
is the distance from the outer circumference of the lance.

Therefore, as is well known, the separation angle α of the sub-holes
The larger the separation angle α, the better the contact between the oxygen gas and the CO gas. However, if the separation angle α is too large, the amount of oxygen gas required for secondary combustion of the CO gas will be insufficient. By making it 30 degrees, in the circumferential direction at the R/3 position, the amount of oxygen gas required for combustion of CO gas is ensured according to the separation angle of 30 degrees, and contact between oxygen gas and CO gas is ensured. Also, in the vertical direction of the R/3 position, the interval L between adjacent sub-hole groups in the vertical positional relationship is L.
Oxygen gas is dispersed between.

[0014]

[Example] An example of the lance according to the present invention is shown in FIG. 1, which is an explanatory diagram of a state in which the lance is loosely fitted into a converter, and FIG. 2, which is an explanatory diagram of formula derivation.
Hereinafter, the same parts as the conventional ones will be described using the same reference numerals. Reference numeral 1 shown in FIG. The lance 2 is inserted loosely.

By the way, CO gas generated by the reaction between the oxygen gas injected from the main hole Nm and carbon in the steel bath is supplied to the oxygen gas 3 for secondary combustion injected from the sub-holes of the sub-hole group. By doing so, it is preferable to promote the secondary combustion reaction of the CO gas near the steel bath surface inside the converter 1 in order to improve the heat transfer efficiency.

However, inside the converter 1,
As shown in the figure, gas, that is, CO gas, flows in the direction of the black arrow in the central area within 1/3 of the average radius R of the center of the converter 1, that is, R/3, centered on the lance 2. It flows as a downward flow 4. Such a downward flow 4 of CO gas is
As is well known, since oxygen gas is injected downward from the main hole Nm of the lance 2 at a high speed higher than the speed of sound, this is caused by the suction force caused by the downward jet flow of the oxygen gas 3.

On the other hand, from R/3 in the converter 1 to R
In the region up to, CO gas generated by the reaction between the oxygen gas injected from the main hole Nm and C in the steel bath flows as an upward flow 5 in the direction of the upward white arrow. From this, it is well understood that in order to improve the heat transfer efficiency, it is preferable to combust the CO gas as close to the steel bath surface as possible before the CO gas rises to the vicinity of the furnace mouth.

Therefore, if oxygen gas 3 for secondary combustion injected from each of the sub-holes of the sub-hole group is distributed and supplied to the descending flow 4 of CO gas, the CO gas in the descending flow 4 can be supplied to the steel bath. Focusing on the fact that combustion can be performed near the surface, the lance 2 having the configuration described below was developed.

The configuration of the lance 2 will be explained below based on FIG. 1. In the loosely fitted state of the lance 2 into the converter 1, a main hole Nm is provided for injecting oxygen gas downward, and a main hole Nm is provided.
A sub-hole group N1 is provided which has a plurality of sub-holes n1 arranged at a predetermined separation angle around the outer periphery at a predetermined distance above m. A sub-hole group N2 having holes n2 is provided. In other words, the structure is such that two stages of subhole groups N1 and N2 are provided.

[0020]Then, the separation angle α between the sub-holes n1 and n2 of the sub-hole groups N1 and N2 is
was set at 30 degrees or more, more specifically at 60 degrees. From the point of view of contact with CO gas, it is desirable that α be large, but if α is too large, it will not be possible to supply enough oxygen gas to completely burn CO gas, so in order to increase the amount of oxygen supplied, Since the number of holes had to be increased, the degree of contact between oxygen gas and CO gas deteriorated, and even though the amount of oxygen supplied increased, CO gas could not be completely combusted in the converter 1. It disappears.

[0021] This indicates that it is sufficient to have a large separation angle α between the subholes and to supply a large amount of oxygen. As a solution to this problem, the lance 2 is provided with two groups of sub-holes.

In this way, the sub-hole groups N1 and N2 in two stages
By providing this, in the past, the downward flow 3 of CO gas had only one opportunity to come into contact with the oxygen gas 3 injected from the sub-hole, but in this embodiment, there are two opportunities for contact. It becomes possible to burn the downward flow 3 of CO gas more effectively.

Furthermore, in order to completely burn the downward flow 3 of CO gas between the second-stage sub-hole groups N1 and N2, the distance L between these sub-hole groups N1 and N2 is set to the central part of the converter. The average radius is R, the diameter of the lance body is d, the angle between the longitudinal axis of the lance body and the direction of the sub-hole n1 of the lower sub-hole group N1 is θd, the sub-hole of the upper sub-hole group N2 is n
When the angle formed with the direction of 2 is θu, the subhole group N
1 and N2 is L≧R(cotθu −co
It was set to satisfy tθd)/3+πd/(360/α).

[0024] The above formula was derived by the procedure explained below. That is, as shown in FIG. 2, the upper sub-hole n
The vertical distance between the position of 2 and the intersection of the line passing through its center and the line R/3 is L2, and the distance between the position of the lower secondary hole n1 and the line passing through its center and the line R/3 is L2. The vertical distance to the intersection point is L1, and the distance between the above intersection points is L
3, L2 tanθu = R/3 to L
2=R/3×cotθu and L1 tan
From θd = R/3, L1 = R/3×cotθd is derived.

[0025] Also, since there is a relationship L+L1 =L2 +L3, from now on, L+R/3×cotθd =R/
By deriving and transposing 3×cotθu +L3, L=R/3×cotθd +R/3×cotθu
+L3 is derived, and L3 is the arc distance between the sub-holes of the same group on the outer periphery of the lance 2, πd/(360
/α), L3 is πd/(360/α
).

In this case, as is well understood from FIG. 2, strictly speaking R/3 is the distance from the center of the converter 1, but compared to the R of the converter 1, the distance of the lance 2 is Since d is sufficiently small, R/3 is taken as the distance from the outer periphery of the lance 2.

Therefore, at the R/3 position, the oxygen gas is dispersed in both the vertical direction and the circumferential direction, and the downward CO gas is almost completely combusted, and the furnace of the converter 1 is heated as before. CO gas no longer burns near the port 1a.

By the way, the larger the value of L is, the more advantageous it becomes to increase the secondary combustion efficiency of downward CO gas.
If the value of L becomes too large, the upper secondary hole n2 will move away from the steel bath surface, which will be disadvantageous in terms of heat transfer efficiency, so it is extremely important to select the most advantageous spacing L by considering each operating condition. becomes.

An example of the performance of the lance constructed as described above will be described below while comparing it with that of a conventional lance. In addition, the main hole conditions of the lance are that the number of main holes is 6, the opening angle of the main hole is 12 degrees, and the amount of oxygen gas fed to the lance is 20 degrees.
000 Nm3/hr, and the average inner radius R at the center of the converter 1 is 1950 mm, and the main hole and converter conditions are the same. Then, the secondary combustion reaction ratio and heat transfer efficiency were determined under the same hot metal conditions and blow-off conditions as shown in Table 2 using the sub-hole conditions shown in Table 1.

[0030]

[Table 1]

[0031]

[Table 2] In addition, the slag conditions include Ca per ton of hot metal.
7.6 kg of O, 5.3 kg of light calcined dolomite, and 2.2 kg of silica stone were added in advance. Under each of the above conditions, CO gas, CO
2 Gas, N2 gas, O2 gas, and Ar gas concentrations were continuously measured, and the influence of air inflow due to entrainment from the furnace mouth 1a of the converter 1 was converted and corrected by material balance calculation, and the The average value of the obtained exhaust gas composition values was determined.

[0032] Then, the heat transfer efficiency for each 30 charges is
Calculations were made by calculating the heat balance of the reaction in the furnace using actual values, and the results shown in Table 2 below were obtained. As a result, as can be well understood from Table 2 above, the lance of the present invention is not only superior to the conventional lance in terms of secondary combustion reaction ratio and heat transfer efficiency, but also superior to the conventional lance. In the lance of the present invention, melting loss of the refractory near the mouth of the converter was observed, whereas in the lance of the present invention, no melting loss of the refractory was observed.

[0033] In the above description, the case where the sub-hole group has two stages has been described as an example, but the number of stages of the sub-hole group may be greater than two stages. However, if the number of stages is increased, the sub-hole group in the uppermost stage will be separated from the steel bath, which will be disadvantageous from the viewpoint of heat transfer efficiency to the steel bath. Therefore, it is preferable to limit the number of stages to three at most.

[0034]

As described in detail above, according to the lance of the present invention, at a position R/3 from the center of the converter, the oxygen gas required for combustion of CO gas is reduced by a separation angle of 30 degrees in the circumferential direction. In addition, contact between oxygen gas and CO gas is ensured, and in the vertical direction, oxygen gas is dispersed between groups of sub-holes that are vertically adjacent to each other, so that CO gas does not flow inside the converter. This means that secondary combustion will occur more reliably than in the past, and is expected to have an extremely large effect on preventing erosion of refractories and improving heat transfer efficiency due to secondary combustion of CO gas near the furnace mouth of the converter. be able to.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a lance according to an embodiment of the present invention and a state in which the lance is loosely fitted into a converter.

FIG. 2 is an explanatory diagram of formula derivation.

FIG. 3 is an explanatory diagram of a conventional lance and a state in which the lance is loosely fitted into a converter.

[Explanation of symbols]

1... Converter, 1a... Converter mouth, 2... Lance, 3... Oxygen gas, 4... Downflow, 5... Upflow, d... Diameter of lance, L...
Distance between sub-hole groups in adjacent vertical positional relationship, N1
...lower sub-hole group, n1...lower sub-hole group, N2...upper sub-hole group, n2...upper sub-hole, Nm...main hole, R...average inner radius of the center of the converter, α...adjacent Separation angle of secondary hole,
θ...Angle between the lance and the direction of the subhole.

Claims (1)

[Claims] 1. An oxygen injection lance for secondary combustion comprising a main nozzle at the tip and a plurality of sub nozzles around the outer periphery, wherein the sub nozzle groups are provided in multiple stages, The separation angle α between the sub-nozzles in the sub-nozzle group at each stage should be at least 30 degrees, and the average inner radius of the center of the converter where the oxygen blowing lance is loosely fitted should be R, and the diameter of the lance body should be d. When the angles between the longitudinal axis of the lance body and the direction of the sub nozzles of the sub nozzle groups in the vertical position relationship are respectively θu and θd, the steps of the adjacent sub nozzle groups in the vertical position relationship The interval L between them is L≧R (
cotθu − cotθd )/3+πd/(360/
An oxygen injection lance characterized by satisfying the relationship α).