JPH01213A - How to operate a smelting reduction furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for operating a vertical smelting reduction furnace, and relates to an operation method for a furnace that produces molten metal by melting and reducing powdery ore containing metal oxides. Regarding the method.

[Conventional technology]

Most metal oxides such as iron ore as underground resources are in the form of powder rather than lumps, and it is expected that the number of powder ores will increase further in the future. Direct use of such ores in powder form is advantageous in terms of energy savings and manufacturing costs.

Conventionally, as a method of smelting and reducing fine ore, pre-reduced ore was heated in an electric furnace,
The method used was to melt and reduce in a melting furnace such as a converter.

In that case, there are many methods in which a binder is added to the pre-reduced ore to agglomerate it, and the agglomerate is melted and reduced in a melting furnace.However, in such a method, the equipment for agglomeration and processing ore costs are Not only does this require processing energy, but when firing after agglomeration, the cost of treating NOx, SOx, and dust in the gas discharged from the firing furnace is significant. .

Therefore, in Japanese Patent Publication No. 59-18452, a vertical furnace type smelting reduction furnace was proposed as a method for smelting and reducing fine ore.

According to the report, powdered ore was blown into the vertical furnace along with high-temperature air from at least the upper tuyere of the upper and lower tuyeres installed at the bottom of the furnace to blow in high-temperature air, and the furnace was filled. It is characterized by burning carbonaceous materials and melting and reducing them. In a vertical melting reduction furnace having upper and lower tuyeres, the carbonaceous material forming a packed layer between the upper and lower tuyeres burns and generates high temperatures. Therefore, the fine ore injected from the upper tuyere is heated and melted, and while it drips down the packed bed, it is directly reduced by the solid carbonaceous material to produce molten metal and slag, which accumulate at the bottom of the furnace.

In the above method, if the fine ore supplied from the upper tuyere does not melt quickly at the tip of the tuyere, it will not be able to drip into the lower area of the furnace, causing operational troubles. Problems are prevented by blowing in air or oxygen-enriched air.

Therefore, in the operation of the vertical smelting reduction furnace according to the above method, it is extremely important to maintain an appropriate balance with respect to various conditions such as air blowing conditions, ore injection conditions, two-stage tuyere spacing, and coke particle size. If the balance is disrupted, the melting state of the ore injected from the tuyere will change significantly, and if the result is excessive injection, the injected powder will not be able to melt sufficiently within the raceway at the tuyere end. , there is a risk that the molten material will remain near the tuyere, causing damage to the tuyere.

If the blowing amount is too low, the heat supply will be excessive and the metal [S
i], and as a result, the slag component changes significantly, deteriorating the sludge drainage performance and possibly resulting in the inability to operate.

In addition, the temperature of the gas at the top of the furnace rises significantly, leading to problems such as large energy losses.

In particular, when the production amount of metal must be changed due to production plans or requests from downstream processes,
The balance between the above conditions was easily disrupted, and in that case, there was no control index for selecting appropriate operating conditions, and operating conditions were selected through trial and error, so it took a long time to achieve stable operation. Meanwhile, metal production volume, metal [Sil]
However, there was a serious problem in that the temperature of the exhaust gas at the top of the furnace fluctuated greatly.

The present invention advantageously solves the above-mentioned problems in the prior art and provides a method for operating a vertical smelting reduction furnace that enables stable operation.

[Problem that the invention seeks to solve]

The present invention uses a vertical furnace having a plurality of tuyeres provided in at least two upper and lower stages to blow high-temperature air into a packed bed of a carbon-based solid reducing agent. The present invention proposes a method for operating a smelting reduction furnace, which is characterized in that the blowing conditions and ore supply conditions are controlled so that the blowing conditions and ore supply conditions are controlled in a method for producing molten metal by blowing it together with high-temperature air.

However, in the above formula, L: Melt production amount (rrI'/h) G: Generated gas rIL (Nrrf/h) SRCT=nIISRIIaTILH AT: Hearth cross-sectional area (rn’) , and L, G, and 5RCT are as shown in the following formulas.

L=CA+S+YM +YS However, C^: Amount of ash from combustion coke (mj/h) S: Amount of slag material (m”/h) YM: Metal depth in injected ore (mj/h) Ys: Gangue in injected ore minutes (m″/h), and furthermore, G=0.79V1 +2 (0,21VB +V,))
+22.4X However, va: blown air amount (Nrrf/h) vo: blown enrichment 0211 (Nm'/h)

n: Number of two-stage tuyere pairs 5R=0.0589DR2 U: Tuyere flow velocity (m/5ee) Dp Nikoke average diameter (m) DH double diameter (m) ε: Coke filling rate φ: Coke shape factor (0,7) H: Upper and lower tuyere spacing (m) Note that the coke filling rate ε is usually a value of about 0.5.

[Effect]

A type 1 smelting reduction furnace having upper and lower tuyeres, in which metal oxides such as fine ore are injected from at least the upper tuyere, forms a packed layer between the upper and lower tuyeres. The carbonaceous material is combusted by the air heated to 800-too many degrees Celsius, generating high temperatures. The fine ore injected from the upper tuyere is heated and melted, and while dropping through the packed bed, it is directly reduced by solid carbonaceous material to produce molten metal and slag.

In this case, hot air or oxygen-enriched air is also blown from the lower tuyere to promote melting and reduction so that the fine ore supplied from the upper tuyere quickly melts at the tip of the tuyere. The productivity of the above-mentioned vertical melting reduction furnace is influenced by the size of the raceway determined from the wind pattern and the reduction reaction rate determined from the effective interfacial area of the raceway of the upper and lower tuyeres.

The effective interfacial area of the raceway is determined by the size of the raceway, which is determined from the one-year-old air blast required to secure a certain production volume. determined by the distance between them.

When blowing powder into the tuyere, it is necessary that the injected powder melts sufficiently within the raceway at the tip of the tuyere.
For this purpose, it is important to always stably inject the most appropriate amount without injecting an excessive amount. If an excessive amount is injected, it becomes difficult to melt in the raceway, causing blockage of the packed bed.As a result, the flow of high-temperature gas from the lower tuyere becomes uneven, causing an increase in the top gas temperature and During[
This will lead to an increase in Sil, and in the worst case, the tuyere will be damaged by the molten material accumulated around the tuyere, making furnace operation difficult.

In addition, even if the injection amount is small, the heat of the high-temperature gas from the lower tuyere is not effectively utilized, leading to an increase in the top gas temperature and an increase in Sil in the metal, causing 5i02 in the slag to vaporize in the form of SiO. As a result, the slag components change significantly, resulting in a higher melting point, lowering the slag drainage performance, and in the worst case scenario, it may become difficult to operate the furnace.

Therefore, the furnace operation is stable and energy efficient,
In order to maintain this, it is important that the air blowing/blowing conditions are sufficiently consistent with the two-stage tuyere specifications and the coke diameter used. Therefore, the inventors of the present invention conducted extensive studies and conducted experiments.

Furnace operation will be extremely stable if the air blowing/blowing conditions are matched so that
il and furnace top gas temperature are determined by metal [Sil: 1 to 5% by weight,
It was found that the furnace top temperature was stable at 500 to 900°C.

In the above formula, L/G indicates solidification/vaporization, is a value similar to coke ratio, and is a factor for operating conditions, and is 5RCT/A.
T is composed of both an operating factor indicated by the raceway generation conditions and an equipment factor indicated by the two-stage tuyere spacing, tuyere diameter, hearth diameter, etc.

[Si1. Heat is oversupplied in the slag CaO/5i02 and under the furnace top gas, and the [Sil in the metal is as high as 5% or more, the 5i02 in the slag is significantly vaporized, and the CaO/
The increase in S i O2 causes an increase in the melting point of the slag, which reduces the ability to remove slag and there is a strong possibility that the slag will remain in the furnace, making the operation unstable. If it is more than 0.6, the powder will be injected too much, the molten material will accumulate in the raceway, the furnace operation will become unstable, and in the worst case, the tuyere will be damaged due to the molten material accumulated around the tuyere. There is a fear.

Note that the following formulas may be used to calculate L, G, and S ROT.

L=CA +S+YM +YS G=0.79VB + 2 (0.21Va+vo)
+ 22.4 h) Ys: Blown ore medium gangue content (tn'/h) va: Blowing air i1 (Nm''/
h) vo: Blast enrichment 021 (Nm″/h) U: Tuyere flow rate (m/5ec) DP: Coke average diameter (m) DH: Tuyere diameter (m) ε: Coke filling rate φ: Coke shape factor (0,7) Note that the coke filling rate (usually 0. The value is about 5.

〔Example〕

Figure 2 shows the process flow of the melting reduction furnace, and examples are shown in Figure 2.

Powdered metal oxide and solvent enter the hopper 1 at a predetermined mixing ratio, are cut out in an appropriate amount by the ore supply rate adjustment feeder 3, pass through the blowing pipe 4, and are fed into the smelting reduction furnace 5 through the upper tuyere 6. is blown into.

Coke is stored in a coke hopper 2 and charged into a melting reduction furnace 5 in an appropriate amount.

Next, in the process of sending the blast air from the blower blower 7 to the heat exchanger 9, an appropriate amount of oxygen is added via the oxygen flow rate regulator 8, and the air is sent to the #1 exchanger 9 where it is heated to ~1100°C. Hot air is blown through the pipe 10 into the melting reduction furnace 5 from the upper tuyere 6 and the lower tuyere 11, respectively.

Then, in the melting reduction furnace 5, the oxide is melted and reduced by the combustion heat and reducing gas generated when the oxygen in the blast air reacts with the carbon in the coke, as well as the contact between the oxide and the carbon, and the molten metal flows down. The tap hole 12 and the slag are discharged from the slag hole 13.

As an example, a melting reduction furnace with an inner diameter of 1.2 m was equipped with three upper and lower tuyeres each, and the interval between the upper and lower tuyeres was 1.0 m, the coke particle size was 15 mm, and the blowing Q was 1600 N. m”/hr, air temperature 9
The temperature was 00°C, the blowing pressure was 0.35 to 0.45 kg/Cm', the blowing tuyere diameter was 45 to 55 φmm, and the enriched oxygen was 1100 to 20 ONITf/hr.

The ores are A and B2 having the metal content and gangue content shown in Table 2.
Products with different mixing ratios of brands, injection volume 600-800
kg/hr (1) range, the flux used was limestone and silica sand, and a mixture of 1 part silica sand and 2 parts limestone was injected at a rate of 300 to 500 kg/hr. The ash content and fixed carbon content are shown in Table 3.

As shown in Figure 1, the results show that in metal [Sil] is stable at a low level of 1 to 5%, and slag C is stable.
aO/5i02 was 1.0 to 1.2, the slag removal performance was good, no slag remained in the furnace, and the furnace top gas temperature was 5.
We were able to secure a low level of 00 to 900°C.

CaO/SiO in the slag rises rapidly.
It was found from the tap slag balance that 2 also increased rapidly, the melting point increased rapidly, the slag removal performance deteriorated, and slag began to remain in the furnace. In addition, a large amount of dust was generated, and shelves were hanging inside the furnace, making furnace operation extremely unstable.

is less than 1%, and slag Cao/Sio2 is also 1. There is no problem with O, but when observing the inside of the furnace from the tuyere, molten material started to accumulate around the tuyere in the furnace, and it was obvious that the tuyere was in a state of excessive injection, causing the risk of damage to the tuyere due to the molten material. The situation became extremely dangerous.

Table 1 summarizes the results of these operations.

That is, in Example N001, only (B) brand ore was used as the ore, and the ore and flux were injected from 0.30 to 0.
．． This is an example in which the operation was controlled within the range of 32, and Example No.
Example No. 02 is an example of operation using both brands (A) and (B) as ore and controlling the blowing of ore and flux to 0.45 to 0.47. This is an example in which both brands (A) and (B) were used and the ore and flux blowing ratio was controlled to 0.55 to 0.60, and the operation was carried out under highly controlled conditions.

This is an example of an operation in which M was controlled to a level lower than the current limit, and a comparative example is an example of an operation in which M was controlled to a lower level.

Comparative Examples Nos. 3 to 5 are examples of conventional methods.

Production by blowing according to the unreleased IJ1 method and controlling the blowing conditions? Even if the metal content [Si1% and metal (T+st+] was carried out through trial and error, it is possible to significantly reduce the amount compared to the conventional method, Comparative Examples Nos. -L: Fluctuations in hairy slag basicity CaO/S i O2 can be suppressed to less than 1/l O, and the problem of residue has been solved.Furthermore, tuyere damage due to sagging of the tuyere of the melt can be suppressed. There was no sagging of the coke shelf in the furnace due to dust accompanying the vaporization of 5i02 in the slag due to excessive heat supply.

(Comparative Example No. 1) has a high [Si] value and its variation σtstt is on the order of 10 times that of the inventive example, and the slag <CaO/SL 02) is also higher than the inventive example 1.
It is on the order of 0 times, and the furnace top gas temperature is also 970 to 9.
The temperature was as high as 90°C. Furthermore, the shelf lifting frequency was 10 times/d, making stable operation impossible (Comparative Example No. 2)
As a result, metal [Si] and top gas temperatures remained low and stable, but one tuyere was damaged.

As shown in Tables 2 and 3 above, it is clear that the method of the present invention allows extremely stable furnace operation by adjusting the operating parameters.

〔Effect of the invention〕

As described above, according to the present invention, stable operation of the furnace without troubles such as shelf suspension and damage to tuyeres, reduction of the furnace top gas temperature, and metal [S
i] can be achieved at a low level of stability, which also contributes to reducing the cost of furnace operation.

[Brief explanation of drawings]

L 5RCT Figure 1 is an A7 graph showing the appropriate IF range of --- of the present invention, and Figure 2 is a flow sheet of the smelting reduction furnace process used to implement the method of the present invention. l...Ore hopper 2...Coke hopper 3...Ore supply amount adjustment feeder

Claims (1)

[Scope of Claims] 1. Ore containing metal oxides is produced using a vertical furnace having a plurality of tuyeres provided in at least two upper and lower stages that blows high-temperature air into a packed bed of a carbon-based solid reducing agent. A method for producing molten metal by blowing together high-temperature air from at least an upper tuyere, characterized by controlling air blowing conditions and ore supply conditions so that L/G・S_R_C_T/A_T=0.25 to 0.6. How to operate a smelting reduction furnace. However, L: Amount of melt produced (m^3/h) = C_A+S+Y_M+Y_S C_A: Amount of ash from combustion coke (m^3/h) S: Amount of slag forming material (m^3/h) Y_M: Injected ore Metal amount (m^3/h) Y_S: Injected ore medium gangue content (m^3/h) G: Generated gas amount (Nm^3/h) =0.79Va+2(0.21Va +Vo)+22.4X Va: Amount of blown air (Nm^3/h) Vo: Amount of enriched O_2 blown (Nm^3/h) X: Number of moles of oxygen in blown ore (kmol/h) S_R_C
_T=n・S_R・α_T・H n: Number of 2-stage tuyere pairs S_R=0.0589D_R^2 D_R=8.81×10^-^3×U/D_P^1^/
^2×D_HU: Tuyere flow rate (m/sec) D_P: Coke average diameter (m) D_H: Tuyere diameter (m) a_T=6(1-ε)/φ・D_P ε: Coke filling rate φ: Coke shape factor (0.7) H: Interval between upper and lower tuyeres (m) A_T: Hearth cross-sectional area (m^2)