JPS62228419A - Apparatus for supplying powdery substance to vertical furnace - Google Patents

Abstract

PURPOSE:To stabilize supplying of powdery substance and prevent wear of each pipe of apparatus, by specifying an angle formed by aperture surface of an introducing pipe for powdery material with center axis of blowing pipe, moving velocity of powdery material in the introducing pipe and a distance from aperture of the introducing pipe to tuyere top end. CONSTITUTION:Powdery granule ore supplied from a hopper 1 is charged from tuyere into vertical furnace through a supplying pipe 3, the introducing pipe 4 and a blowing pipe 5. I this time, the angle theta3 formed by aperture surface of the pipe 4 with center axis of the pipe 5, the powder moving velocity V0 in the pipe 5 and the distance L from introducing pipe aperture to tuyere to end are determined so that a inequality I is satisfied. In the inequality, DE' is shown in a formula II, Wf: upper limit powder supplying velocity (kg/sec), V0: blowing air flow quantity (Nm<2>/sec), T: blowing air temp. ( deg.K), P: blowing air pressure (kg/m<2>), rho: blowing air density (kg/m<3>), mu: blowing air viscosity (kg/m.sec), Re: blowing air Reynolds number (-), D: tuyere diameter (m), L: aforesaid (m), theta3: aforesaid (degree), V0: aforesaid (m/sec), DE': effective eddy diffusion coefft. (m<2>/sec).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a powder supply device to a vertical furnace, and discloses the development results of a powder ore supply blowing device.

[Conventional technology]

In recent years, raw material ores mainly composed of various metal oxides, including iron ore, have become more powdery and granular ores than lumpy ores, and the proportion is expected to increase in the future. It will be done.

A common method for smelting using powder or granular ore is to pre-reduce the powder or granular ore using a fluidized bed, and then melt and reduce the pre-reduced ore in an electric furnace, converter or other melting furnace. . In this case, there are many methods in which a binder is added to the preliminary reduction, the agglomerates are agglomerated, and the agglomerates are melted and reduced in a blast furnace.

However, this method has the disadvantage that the agglomeration cost is extremely high. In addition, there are plans to use arc furnaces, plasma, or furnaces that use pure oxygen to melt and reduce the pre-reduced ore without agglomerating it, but these methods are currently not possible due to site conditions and power consumption. Application on an industrial scale has become difficult.

In response, the inventors continuously formed a packed bed of carbonaceous solid reducing agent inside a vertical furnace, while
Using the reducing exhaust gas discharged from the furnace through a plurality of tuyere groups arranged in stages, powder and granular ore are heated to 800°C to 410Q with flux added as necessary. We have proposed a method of melting and reducing by blowing into a vertical furnace while conveying a high-temperature air stream at 300°C (Registration No. 1240304).

Furthermore, the present inventors studied the injection conditions and found that even if the preliminary reduction treatment as described in 2 was omitted, powder and granular ore could be directly charged into a vertical furnace by injection of reactive gas under heating. , has also filed an application to advantageously perform direct melt reduction (Japanese Patent Application Laid-Open No.
9-105818).

In this case, since the powder is supplied by falling by gravity, it is necessary to set a large piping angle with respect to the water surface between the powder hopper installed at the top of the furnace and the tip of the tuyere. However, it is difficult to set the angle in the layout around the blast furnace. On the other hand, if it is too small, stable supply will be hindered, so it must be determined by considering the entire supply and blowing system. Furthermore, in a method like this, in which a huge amount of powder or granular ore is injected only through the tuyeres, the injection method using pressure feeding, which is conventionally used as an auxiliary supply in blast furnaces, reduces the amount of conveyed gas, pipe wear, etc. It is difficult to use it as is because of the problems that arise, and it is necessary to separately develop powder supply and blowing equipment suitable for this situation.

[Problem that the invention seeks to solve]

In the present invention, when powder is supplied to the tuyere of a vertical furnace such as a blast furnace, the powder hopper cannot be installed directly above the tuyere because of the poor environment near the tuyere. The purpose is to optimize the angles of the supply pipes, introduction pipes, and blower pipes that pass through, to stabilize powder supply when the supply speed to the introduction pipes is slow, and to prevent wear on each pipe. .

[Failure to solve the problem]

The technical means of the present invention are as follows.

The wall of the 8-air blowing pipe connected to the vertical blast furnace tuyere
In a device for supplying powder from an inlet pipe for blowing powder raw materials that protrudes diagonally through the center of the tuyere, the angle 0 between the opening surface of the inlet pipe and the central axis of the blower pipe and the angle in the inlet pipe. This is a powder supply device to a vertical blast furnace tuyere, characterized in that the powder moving speed UO and the distance from the introduction pipe opening to the tip of the tuyere satisfy the following formula.

Wf< [8,9X 10-IPDE AX (L 2
+D2 ) l/2 ]/Tl1exp[(■oII
T×(L(L2+D2)l/2)/L71X1
03 DE' ・D2 Pl However, DE' = 0.015 (2,5-1,5cosθ)
X e'X P (0,05UO O,07)x
(Re) 0815 X uL/ pWf: Upper limit powder supply rate [kg/5ec) vo: Blowing air 'f
ii, % (Nm'/sec: iT: Blowing air temperature [OK] P: Blowing air pressure [kg/Cm') ρ: Blowing air density [kg/m') End: Blowing air viscosity [kg/m'] fist5ec) Re: Reynolds number of the blowing air [-] ] D: Wing diameter (m) L: Distance from the center of the inlet pipe opening surface to the tip of the tuyere (m) θ: When the opening surface of the inlet pipe is Angle in contact with the central axis [degrees] UO: Powder movement speed in the introduction pipe [m/sec] DE': Effective eddy diffusion coefficient Crn'/5ee) Furthermore, as a preferred embodiment of the present invention, powder movement into the conduit is The method is characterized in that the flow rate of the carrier gas in the introduction pipe is set to be less than sm, sec and less than m/sec.

[Takeda]

First, the system of the melting mouth apparatus using the powder supply and blowing method of the present invention will be explained based on FIG. ■ is powder, granular η, stone supply hopper, 2 is quantitative cutting device, 3 is supply pipe, 4
7.7a is a group of multiple blades installed in the lower two stages of F. Through this group of tuyere , for example, by blowing high-temperature air under heating into the vertical furnace 8.
blue fire in the packed bed.

Powdered ore is discharged from the quantitative cutting device at the bottom of the supply hopper, falls freely within the supply pipe, and reaches the introduction pipe. Here, it is accelerated by a small amount of carrier gas, and flows down the inlet pipe having a predetermined slope to a certain depth, reaching the inside of the X-transmission pipe. It is diffused by the high-speed airflow in the blast pipe and blown into the blades, where it is melted and reduced through the sway section and the carbonaceous packed bed between the upper and lower tuyeres.

When blowing powder into the tuyere of a blast furnace, it is necessary that the injected powder melts sufficiently within the raceway at the tip of the tuyere. It is important to infuse it stably. This is because if an excessive amount is blown in, it becomes difficult to melt within the raceway, causing clogging of the packed bed and making smooth operation difficult.

Since the powder supply device of the present invention mainly uses free-fall supply using gravity, it does not require a large amount of carrier gas unlike the pressure-feeding method, but in order to stably supply powder, it is necessary to Basically, the mounting angle with respect to the direction must be greater than the angle of repose of the powder. As a result of experiments conducted by the inventors, the first
As shown in the figure, it was found from observation of the powder flow that the former angle (θ2) is preferably north of 50°. If the angle is 50° or more, there is no significant difference in the flow flowing downstream. Therefore, when installing this device in a blast furnace, the angle can be arbitrarily determined within the range of 50° to 90° with respect to the layout. Of course, it is also possible to combine a plurality of pipings in the range of 50° to 90°.

The latter angle (02) is limited to 35° or less due to the connection with the blow pipe and the distance from the tip of the tuyere, which will be described later, so that some powders do not flow down.

However, although the flow rate will be described later, by flowing an appropriate amount of conveyed waste, the powder that has reached the introduction pipe -L does not stay and flows down the slope in the introduction pipe as a powder flow to a predetermined depth.

The amount supplied to the inlet pipe is controlled by the valve rotation speed of a fixed-quantity cutting device provided at the bottom of the hopper.

The carrier gas should be allowed to flow at least as much as possible so that the powder does not accumulate, and even if the amount is more than this, it will not be necessary to supply it to the inlet pipe.
Since the amount of gas blown into the blade is determined by the cutting amount, the amount blown into the blade [I will not change, but it is preferable to keep it to the minimum necessary level in order to reduce the amount of gas flowing into the blast furnace. According to experiments on supplying and blowing various powders, this minimum flow rate increases as the angle of the powder becomes larger, as shown in FIG.

By setting 01.02 as shown in the north, it became possible to stably supply powder at 1.02 with sufficient consideration given to layout and h constraints. In addition, as a means to maintain the pressure in the hopper and the blade [J part] at the same pressure, it can be solved by installing a pipe connecting the lower part of the cutting device and the inside of the hopper. This is because the powder supply and blowing are controlled so that a space exists within the pipe.

The next remaining issue is how to prevent wear on the piping, especially the tuyeres.

In the present invention, the powder is supplied by falling by gravity, so the powder is not dispersed compared to a pressure-feeding method using airflow, so the powder and the carrier gas are separated, and the powder flow rate is 1. The speed is as slow as 1/10 to 1/100, which can be said to be extremely advantageous in terms of pipe wear countermeasures. The inside of the supply pipe is a free fall with a terminal velocity of 2 to 3 m/Sec, and U inside the introduction pipe. is 062~3
m/sec. Therefore, wear inside the supply pipe and introduction pipe is not a big problem. However, since the part from the confluence with the blow pipe to the tip of the tuyere is affected by air flow of 100 to 200 m/sec, wear inside the blow pipe, especially the introduction pipe, is not a big problem. Countermeasures against wear at the tip of the pipe and the tip of the tuyere inside the blast pipe must be considered.

The inventors conducted various model experiments and found that wear at the tip of the tuyere greatly affects the state of powder dispersion within the blast tube due to the shape of the aperture surface at the tip of the introduction tube, especially the relative angle to the central axis of the blast tube. It was discovered from the observation results of powder flow and the state of wear inside the piping that this had an effect.

When powder fluid is injected from one point in turbulent flow, the powder fluid gradually spreads and mixes due to eddy diffusion in the turbulent flow.The ratio of powder fluid to turbulent fluid at this time is shown by equation (1). It is known that

φcal= (Wf*Ustr)/(4πWa'*DB e5)exp (-U
str (S-1)/2DE)... (1) DE =0.0154 (Re) 0875/ 1...
...(2) Where, Wf: Powder injection speed [kg/5ec] Ustr: Turbulent flow speed [m/sec] Wa': Turbulent mass velocity [kg/rr1'・SeC] S:
fQ line length (m) See: Axial distance from the injection point [m] ρ: Density of turbulent fluid [kg/m') u,: Viscosity of turbulent fluid [kg/m@5ec) Re: Distance of turbulent fluid Reynolds number [-] DE: Eddy diffusion coefficient (rn'/5ec).

2. The eddy diffusion coefficient DE was determined using the equation (2) in L, and φcal was calculated by determining the correspondence with the wear condition in the piping.
It was found that 0x10-4 was the wear limit. Change the relative angle 03 and find the limit length that does not cause wear φ
='z, oxto-+ is calculated using equation (1), and as shown in Figure 5 (a), the relative angle 03 = 0, that is, the eddy diffusion coefficient DE is the minimum when installed on the same axial plane. Therefore, it becomes 0.014rn'/sec. Therefore, it became clear that it is best to align the aperture surface of the joint between the introduction pipe and the blower pipe with the central axis of the blower pipe. transport)
By changing the powder flow rate, the effect of flow rate UO on DE is reduced to 0.
As a result of investigation using the same method as in 3, it was found that the eddy diffusion coefficient DB increases as the UO increases, as shown in FIG. 5(b). From the above, we were able to obtain the experimental formula (3) for calculating the effective diffusion coefficient DE' by correcting the effects of 03 and UO.

DE' = 0.015 (2,5-1,5cos
θ)Xexp (0,05UO -0,07)X (R
e) 0815×g/p-(3) where, 0: Angle (O
≦θ≦90) UO: Powder supply speed Re in the introduction pipe + Reynolds number of blown air Tile: Viscosity of blown air p: Density of blown air.

Next, in order to determine the diameter of the blast pipe and the distance from the position of the tip of the tuyere to the tip of the opening surface of the inlet pipe, the relationship with the powder supply rate must be found. Given the obtained limit φ = 2.0X10-4 that does not cause wear, Wf
By calculating, equation (4) is obtained.

Wf = [8,9X I O-'FD+:X (
L2 + D2)! / 2] /T.ex
p [(V(, aTX (L (L2 +D2) I/2 'j/
1.71X103 DE @D2 F]...
...(4) By substituting DE' obtained by equation (3) into DE in equation (4), once the air blowing conditions and powder supply conditions are determined, the installation location of the tip of the introduction tube is determined.

An example is shown in FIG. 6, and the shaded area is the area where wear of the tuyere tip can be prevented.

The next problem is powder abrasion at the tip of the inlet tube.With the 0-piece method, the powder ejects at a slow speed, so it is greatly affected by the eddy current generated by the blown air at the tip of the inlet tube, and the particles fall onto the upper surface of the tip. This is a phenomenon that has not been observed in pumping systems with high extrusion flow speeds, which cause abrasion and erosion from the inner surface due to impact. As a result of intensive studies conducted by the present inventors through model experiments, it was found that increasing the flow rate of the carrier gas is effective in preventing the generation of vortices. However, it was also found that if the flow rate of the carrier gas is set too high, the flying angle of the particles becomes too downward, causing wear on the bottom of the blast tube. As a result of various studies, 5 m/s
Stable blowing was possible without abrasion at the tip of the introduction tube or around the tuyere at a speed of ec or more and less than 15 m/sec. The above relationship is shown in FIG.

As mentioned above, in the wooden sword method, which supplies powder to the blast furnace tuyere mainly by gravity fall, the angle between the supply pipe and the water surface is set at 50' or more, and the horizontal plane of the introduction pipe is set at an angle of 30 to 35°. The opening surface of the part where the pipe and the blower pipe join is aligned with the central axis of the blower pipe so that DE' is minimized, and the installation position is (3).
By keeping the formula (4) in the range that satisfies the equation, there will be no shelf blockage of the powder in the piping and wear of the tuyere tips, and by maintaining the carrier gas flow velocity between 5 m/sec and 15 m/S8C, the powder can be stabilized. The present invention, which has been shown to enable quantitative injection of powder, can be fully utilized as an auxiliary injection of powder in blast furnaces.

Due to uninvention, L/I7 as a gravity drop supply blowing method
Setting the piping installation angle with respect to the horizontal plane for the system as a whole, taking into account the two-sided nature of supply constraints and stable supply, and determining the shape and position of the attachment part with the blower pipe, taking into account the prevention of wear inside the blower pipe or tuyere. By configuring the settings, it is now possible to stably operate powder supply blowing, which is mainly based on gravity falling, using an extremely small amount of carrier gas, with minimal layout constraints. .

〔Example〕

Example I FIG. 1 shows a system diagram of the example. The specifications shown in the figure are as follows.

Supply pipe slope 0. =80°, 70' Inclination of introduction pipe θ2 = 35° Introductory tube opening angle θ3=0 Distance from the opening of the introduction pipe to the tuyere L=300mm Blower pipe inner diameter 2D = 100mm Powder injection experiments were conducted using this test furnace.

Powder: Three types of powder blast furnaces with angles of 35°, 37.5°, and 40°, respectively. Inner diameter of blast furnace + 1.2 m. Blowing tuyeres: 3 on the upper stage, 3 on the lower stage. Air blowing isl: 250 to 350 N rnj/h.
R wing [J temperature = 800°C Pressure crab 0.6 kg/Cm" Wing diameter: 50 φ mm Supply pipe inner diameter: 50 φ Introductory pipe inner diameter: 25 φ Carrier gas: N2 gas - Powder injection experiment was conducted using the test furnace described in The results of examining the supply pipe angle 01 and the introduction pipe angle θ2 are shown in FIG.

When 01 is less than 50°, the flow of the powder is unstable, and it sometimes stays in the tube, causing shelf suspension, whereas a value of 50° or more is preferable.

As a result of examining the carrier gas flow rate required for stable blowing of various powders,
By changing the curve as shown in FIG. 8 and flowing a carrier gas of a certain value or more according to the 5u angle of the powder, stable powder supply and blowing could be performed.

Example 2 A cold model with the same specifications as Example 1 was manufactured, and the tuyere blower pipe and tuyere were made of acrylic, and the aperture surface of the joint between the introduction pipe and the blower pipe was determined from the wear condition of the inner surface of the pipe. As a result of examining the installation angle 03 with respect to the center axis of the blower pipe, as shown in Fig. 5, it becomes the minimum at 03=O, and the eddy diffusion coefficient DB at this time is (
2) Determine from the formula DE=0. OL 4m'/s e
c, and substitute this value into equation (1) to obtain φcal=2.
0X10-4 was determined. When φcal=2.0X10-', no wear occurred inside the pipe, so φc
DE=0 at al=2.0X10-4 and o3=o
．． By substituting 014m'/s e c, Wf
= [8,82X I 0-3F A×(L 2 +
D2 ) l/2 ] /T@eXp[(volIT× (L (2nd + D2 ) l/2 )/9.57x
10-2] Changed.

This experimental formula shows that once the blowing conditions are determined, the L-limit powder blowing speed and the distance between the introduction pipe and the tip of the blowing tuyere are determined.

Next, the value that satisfies this formula L=O, 12m, D=0, 05
As a result of conducting a hot experiment in the blast furnace of Example 1 with mφ,
It was possible to stably inject powder into honey without wearing out the tuyeres.

Example 3 A cold model with the same specifications as Example 1 was manufactured, one tuyere of the tuyere blow pipe was made of acrylic, the carrier gas flow rate was changed, and the appropriate range of the carrier gas flow rate was examined based on the wear condition of the inner surface of the tube. As a result, when the speed is less than 5 m/sec, the ejected particles collide with the inner surface of the tip of the introduction tube, causing significant wear, and when the speed is more than 5 m/sec, the angle of the ejected particles gradually changes downward. As a result, the area around the blade [1] on the lower surface of the blower pipe began to wear out, and
It is not preferable because it becomes noticeable north of sec, therefore 5
It was found that a suitable range is m/sec or more and less than 15 m/sec.

〔Effect of the invention〕

The layout of the gravity drop supply blowing method, the entire system considering the constraints of h and stable supply, and 1. Setting the piping installation angle with respect to the water flow surface, setting the shape and position of the attachment part with the blast pipe in consideration of preventing wear inside the blast pipe or tuyere, and setting the carrier gas flow gutter that flows into the blow pipe to an appropriate level. By doing this, we were able to create a powder supply blowing device that uses gravity drop as its main method, with an extremely small amount of carrier gas, with minimal layout constraints, and stable blowing operation of vertical melting furnaces became possible. .

[Brief explanation of drawings]

Figure 1 shows (a) a system diagram of powder supply and blowing equipment, and (b)
Figure 2 is a system diagram showing an example of the powder blowing device layout; Figure 3 is a graph showing the influence of the piping installation angle on the powder blowing speed; Figure 4 is a diagram showing the arrangement around the inlet pipe and the blade. Figure 5 (a), a graph showing the relationship between the carrier gas to prevent the tip from wearing out, shows the angle θ3 at which the aperture surface of the joining part of the introduction pipe and the blower pipe touches the central axis of the blower pipe, and the equation (1). φcal
Figure 5(b) is a graph showing the relationship between the eddy diffusion coefficient DE' and the eddy diffusion coefficient DE' determined as =2-OXIO-4.
, and D6', and Figure 6 shows the relationship between the upper limit powder blowing speed Wf to prevent the tuyere tip from wearing out and the distance from the inlet pipe tip to the tuyere tip when the air blowing conditions are fixed. Figure 7 is a graph showing the relationship between powder extraction speed and rotary valve rotation speed, and Figure 8 is a graph showing the relationship between carrier gas minimum flow rate and upper limit blowing speed required for blowing various powders. be. l...Powdered acupuncture stone hopper 2...Quantitative cutting device 3.
...Supply pipe 4...Introduction pipe 5...Blower pipe 6...Carbonaceous solid reducing agent supply device 7..." Two-stage tuyere group 7a...Lower-stage tuyere group 8
・・・Vertical furnace

Claims (1)

[Scope of Claims] 1. Powder is supplied from an inlet pipe for blowing powder raw material that penetrates the wall of a hot air blowing pipe connected to a vertical blast furnace tuyere and protrudes obliquely to the center of the tuyere. In the device, it is confirmed that the angle θ formed by the aperture surface of the inlet pipe with the central axis of the blast pipe, the powder movement speed U_O in the inlet pipe, and the distance L from the inlet pipe aperture to the tip of the tuyere satisfy the following formula. Features: Powder feeding device to the vertical blast furnace tuyere. Wf<[8.9×10^-^1PD_E ×(L^2+D^2)^1^/^2] /T.exp[{Vo.T× (L-(L^2+D^2)^1^) /^2} /1.71×10^3D_E'・D^2P] However, D_E'=0.015(2.5-1.5cosθ)×e
xp(0.05U_O-0.07) ×(Re)0.875×μ/ρ Wf: Upper limit powder supply rate [kg/sec] V_O: Blow air flow rate [Nm^2/sec] T: Blow air temperature [＾0K] P: Blowing air pressure [kg/cm^2] ρ: Blowing air density [kg/m^3] μ: Blowing air viscosity [kg/m・sec] Re: Blowing air Reynolds number [-] D : Tuyere diameter [m] L: Distance from the center of the inlet tube aperture surface to the tip of the tuyere [m] θ: Angle at which the inlet tube aperture surface touches the central axis of the blast tube [degrees] U_O: Powder inside the inlet tube Body movement speed [m/sec] D_E': Effective eddy diffusion coefficient [m^2/sec]2 According to claim 1, the powder is moved into the introduction pipe by gravity fall. A device for feeding powder to the tuyere of a vertical blast furnace. 3. The powder supply device to the vertical furnace blast furnace tuyeres according to claim 1, wherein the flow velocity of the carrier gas in the introduction pipe is 5 m/sec or more and less than 15 m/sec.