JPH0442449B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a blast furnace operating method that can control the Si concentration, S concentration, and Mn concentration in hot metal of a blast furnace under stable loading conditions. (Prior art and its problems) Si transfer into hot metal in a blast furnace is caused by SiO2 rather than slag metal reaction in the hearth pit.
Gas-mediated gas-metal reactions play a major role. Therefore, Si transfer into hot metal via SiO gas can be roughly divided into the following two processes ("Iron and Steel", Part 1).
58, 1972, p. 219). In other words, the main source of coke is ash in the high temperature, low oxygen partial pressure region near the raceway.
SiO by reaction of SiO ₂ with fixed carbon in coke
The gas generation process and the Si transfer process into the hot metal due to the reaction between the SiO gas contained in the ascending gas flow below the softening cohesive zone and the carbon in the dripping hot metal, and these processes can be described by the reaction equation. It can be expressed as follows. (SiO ₂ ) + C = SiO (g) + CO (g) ... SiO (g) + C = Si + CO (g) ... Here, () is a conventional notation that indicates that the compound is present in the slag. The underlined element name is a common notation to indicate that the element is present in the hot metal. Further, (g) is a common notation indicating that the compound is a gas. The following description uses the same notation. Therefore, as a method to control the Si concentration in hot metal, SiO
There are control of gas generation reaction and control of Si transfer reaction into hot metal. By the way, in actual blast furnace operation, the former control means include controlling the amount of SiO ₂ brought in before the tuyere by controlling the ash content in the coke, and controlling the SiO gas generation rate by controlling the temperature before the tuyere. There is. In addition, the latter control means include cohesive zone level management by coke ratio control based on charge distribution control, sinter reducibility, and cohesive zone level control by softening and cohesive property control. be. but,
Regarding the former control means, there are restrictions on controlling the amount of coke ash from the viewpoint of coking coal blending. Furthermore, the latter control means has almost reached its limit from the operational and raw material standpoints. In addition, as a method for controlling the Si concentration in hot metal, in addition to the above-mentioned control method based on the Si transfer mechanism into hot metal in the blast furnace, iron oxide is blown into the furnace from the blast tuyeres, and the following reaction is performed to control the Si concentration in the hot metal. A so-called in-furnace desiliconization means for oxidizing Si has been developed (Japanese Unexamined Patent Publication Nos. 56-29601 and 1982-77508). Si + 2 (FeO) = (SiO ₂ ) + 2Fe... In the case of this control means, if the above reaction is properly controlled, it is possible to control the Si concentration immediately before tapping, and the Si concentration in hot metal can be controlled. Easy to implement. However, the conventional method of controlling the Si concentration in hot metal by blowing iron oxide through the tuyere using gas transport has the following drawbacks. First, there were problems with the high cost of drying equipment and drying costs for the powder, and the problem of progressive wear on the piping, especially the distributor and bent pipe sections, making it difficult to operate stably over a long period of time. . Although this method is effective for reducing the Si concentration in hot metal, it does not lead to an increase in the Mn concentration in hot metal, so it leads to a reduction in the amount of slag forming agent used in the steelmaking process, but This will not lead to a reduction in the amount of iron used. On the other hand, regarding the S migration into the hot metal in the blast furnace, the coke gasified near the raceway and the S in the liquid combustion are vulcanized into the ore in the shaft section, and below the softened cohesive zone, the S is mainly transferred to the slag metal. It is known that desulfurization occurs through reactions. The S distribution reaction between slag metals is expressed by the following formula. S = (S) ... log (%S) ° / [%S] ° = -6888 / T + 1.152 + lo
gfs＋logCs−1/2logPo ₂ ... logCs＝1.35Ncao＋1/2NMgO/NSiO ₂ +1/3NAl ₂ O ₃
-6911/T-1.649... Here, T is temperature (K), fs is the activity coefficient of S in hot metal, and Cs is desulfurization capacity (Sulphide Capacity). Also, Ncao, NSiO ₂ , NAl ₂ O ₃ , NMgO
represents the mole fraction of that component in the slag.
By the way, in actual blast furnace operation, the means for reducing S in hot metal include increasing the hot metal temperature, reducing the amount of S charged, increasing the amount of slag, and adjusting the slag composition, that is, increasing CaO/SiO ₂ and decreasing Al ₂ O ₃ . , an increase in MgO is taken. However, there are restrictions on increasing the hot metal temperature because it leads to an increase in coke ratio and Si content in the hot metal. An increase in the amount of slag will cause an increase in the coke ratio, and if it is increased too much, the amount of residual pig iron slag will increase, and there is a risk of impurity due to unloading. Furthermore, regarding adjustment of the slag composition, in order to maintain stable operation, it is necessary to maintain the difference between the tapping temperature and the melting point of the final slag above a certain value. Here, as a measure to suppress the SiO gas generation reaction as a means for controlling Si in hot metal, it is also effective to reduce the activity σSiO ₂ of SiO ₂ in the slag. especially,
The area near the raceway is a high temperature, low oxygen partial pressure atmosphere.
In addition, due to the large amount of coke-derived slag, the activity of SiO ₂ in the slag, σSiO ₂ , is also high, and since this is an area where SiO gas is actively generated, the slag CaO/
Increasing SiO ₂ to lower σSiO ₂ of SiO ₂ in slag and reducing slag viscosity is as follows:
This is an effective means of controlling both the Si concentration in hot metal and the S concentration in hot metal. As mentioned above, as a means of reducing the activity σSiO ₂ of SiO ₂ in the slag near the raceway, quicklime is added during the coke manufacturing process to increase the activity of SiO 2 in the finished coke.
Attempts have been made to increase the CaO content (Coke Circulation, Vol. 17, 1968, 97
page). When 5 to 10% by weight of limestone is added to a highly fluid coal blend, it is possible to produce high-strength blast furnace coke by reducing the blending ratio of strongly caking coal, but coke productivity is considerably reduced. In addition, erosion of the silica bricks on the walls of coke ovens due to added limestone is a problem. In addition, the sintered ore ratio is 70% by weight or more, and the sintered ore is used in blast furnace operations where fuel is injected from the tuyere.
In order to reduce CaO/SiO ₂ to 0.6 to 1.0 and adjust the final slag amount and composition, there have been proposals for a method of injecting limestone powder through the tuyere (Japanese Patent Publication No. 32-2753, Japanese Patent Publication No. 32-2753, 39-28004). According to this method, a large amount of limestone powder can be injected from the tuyere, which is advantageous in reducing the Si and S concentrations in the hot metal.As for the properties of the sintered ore, the drop strength is improved, but the high temperature properties of the sintered ore are That is, reducibility,
This will cause deterioration of the softening and fusion properties, and there is a risk that blast furnace operations will experience irregular unloading. Furthermore, with this method,
Since limestone powder is injected through the tuyeres by gas transport, the cost of drying the powder is high, and since limestone powder is highly hygroscopic, it is prone to clogging pipes, which poses problems in the long term. Stable operation was difficult. Furthermore, although this method is effective as a method for reducing the Si concentration in hot metal, it does not lead to an increase in the Mn concentration in hot metal. This will not lead to a reduction in the amount of ferroalloy used. The present invention was made to solve the conventional problems in blast furnace operating methods aimed at reducing the amount of slag forming agents and ferroalloys used in the steelmaking process, and does not require powder drying. It is possible to inject steel stone powder, Mn ore powder, and slag-forming agent from the tuyere without causing pipe wear or pipe clogging, and obtains a large low-Si and low-S operation effect and Mn enrichment effect under stable loading conditions. The purpose of this study is to provide a method for operating a blast furnace that enables the following. (Means for Solving the Problems) The present invention involves sucking a mixture of iron ore powder, Mn ore powder, and a composite compound or mixed powder of a CsO source and/or MgO source through a blast furnace tuyere as a heavy oil slurry. This is a method of operating a blast furnace. In the present invention, the term "powder" refers to powder having a particle size of 5 mm or less. In the present invention, the reason why Mn ore powder injection was used in combination is as follows. An example of the composition of Mn ore powder is shown in Table 1 below, and as is clear from Table 1, the concentration of iron oxide is high as well as Mn oxide. This Mn
When ore powder is injected through the tuyere, the desiliconization reaction expressed by the following formula due to Mn oxides contained in the Mn ore powder and the desiliconization reaction expressed by the above formula due to iron oxides occur, and the Si in the pig iron volume is reduced. concentration decreases. Si + 2 (MnO) = (SiO ₂ ) + 2 Mn ... In addition, the Mn concentration in hot metal can be reduced by the desiliconization reaction using Mn oxide expressed by the above formula and the direct reduction reaction of Mn oxide expressed by the following formula. It will be enriched. (MnO)+C= Mn +CO(g)...

[Table] Next, in the present invention, the reason why a heavy oil slurry as a slag-forming agent consisting of a composite compound or mixed powder of iron ore powder, Mn ore powder, and a CaO source and/or a MgO source is adopted will be explained. First of all, using a heavy oil slurry eliminates the need to dry the powder, which is advantageous compared to gas transportation in terms of cost. Second, the problem of piping wear is eliminated, and powder can be stably supplied over a long period of time. On the other hand, blast furnace operation began in the 1960s, when heavy oil was removed from the tuyere.
By injecting a large amount of liquid fuel such as tar, efforts have been made to achieve low coke ratio and high iron production ratio operations. Later, in the early 1970s, the energy price system changed significantly due to the soaring price of crude oil, and all-coke operation became the mainstream for blast furnace operations. However, from the latter half of 1985, due to the effects of the strong yen and the reduction of crude oil prices in oil-producing countries, it became once again more advantageous in terms of cost to use heavy oil as an energy source in the steelmaking process and lower the coke ratio. There is.
Therefore, heavy oil slurry is very effective in the following points in terms of blast furnace operation. First of all, increasing the amount of hydrogen input by sucking heavy oil slurry is effective for low-Si operation due to the lower temperature in front of the tuyere, and also reduces the melting and dripping properties of ores because the hydrogen reduction reaction progresses at the bottom of the shaft. In addition, it greatly contributes to stabilizing unloading by reducing the amount of coke powder near the raceway. Second, in sucking the heavy oil slurry, the heavy oil is blown into the tuyere together with the powder, which also contributes to reducing the coke ratio of the blast furnace. (Function) The method of the present invention does not require powder drying because a complex compound or mixed powder of CaO source and/or MgO source is blown into the tuyere as a heavy oil slurry along with iron ore powder and Mn ore powder. Blowing from the tuyeres becomes possible without causing piping wear or piping blockage. (Example) Hereinafter, the method of the present invention will be explained based on the attached drawings. In the figure, 1 to 4 are service hoppers, and for example, ore powder stored in service hopper 1, Mn ore powder stored in service hopper 2, and service hoppers 3 and 4 are stored in service hoppers. The stored slag forming agents such as limestone and serpentine are fed into a mixing tank 9 via rotary feeders 5, 6 and 7, 8 provided at the bottom of each service hopper according to a predetermined cutting amount. It is supplied and mixed uniformly with heavy oil supplied from another line 10 in the mixing tank 9, and adjusted to a heavy oil slurry of a predetermined concentration. Thereafter, the slurry is sent from the lower part of the mixing tank 9 to the distributor 12 by the slurry pump 11, distributed and flowed to each tuyere 13, and blown into the furnace through the blow nozzle 14. 15 in the figure is a blast furnace. Although not shown, a heavy oil slurry blowing nozzle 14 is installed at each tuyere 13, and one or more distributors 12 are installed as necessary, and in some cases, in multiple stages. Further, a plurality of systems from the service hoppers 1 to 4 to the slurry pump 11 are installed as needed, one or more depending on the maximum tap direction and up to the number of tap ports. Furthermore, although not shown, there are service hoppers 3 and 4 for slag forming agent.
are installed for each mixing tank series depending on the type of sludge forming agent used. (Results of implementation) The results of implementation of the present invention in blast furnace A (inner volume 2700 m ³ ) are shown in Table 2 below. In addition, iron ore powder, Mn
The ore powder and slag forming agent powder used had the compositions shown in Table 1 above.

[Table] * Indicates the amount of powder in heavy oil slurry In Period A, iron ore powder was injected from the blast furnace tuyere using gas transport using a conventional method with the aim of reducing the Si concentration in hot metal. In this case, the amount of iron ore powder injected is 40Kg/P-T, and the Si concentration in the hot metal is 0.20.
However, the S concentration in the hot metal remained almost the same, and the number of slips did not decrease. In addition, due to the injection of powder by gas transport, troubles occurred due to piping abrasion, and transportation had to be stopped approximately four times a month and equipment repairs had to be carried out. On the other hand, in period B, the method of the present invention was applied, and iron ore powder, Mn Heavy oil slurry of ore powder and limestone powder was injected into the blast furnace tuyere. The amount of heavy oil slurry sucked is 75Kg/P-T, the amount of iron ore powder in the slurry is 20Kg/P-T, the amount of Mn ore powder is 25Kg/P-T, and the amount of limestone powder is 15Kg/P-T.
T, and the amount of heavy oil was set at 25Kg/P-T. The Si concentration in hot metal decreased to 0.18% by weight, the S concentration in hot metal decreased to 0.024% by weight, and the Mn concentration in hot metal decreased to 0.18% by weight.
Enriched to 0.87% by weight. Furthermore, since the blast furnace hydrogen input amount increased to 6.2 kg/PT, the unloading of the charge in the blast furnace became stable and the number of slips decreased. Furthermore, it led to a reduction in the coke ratio, and under these conditions a reduction in energy costs was achieved. In addition, since the method of the present invention adopts heavy oil slurry transportation,
Piping wear was significantly reduced, and continuous operation was possible without any equipment trouble during operation by inspecting the equipment once a month during the periodic blast furnace air shutdown. Although this example shows an example in which only limestone powder is used as the slag-forming agent, the same effect can be obtained even when a complex compound or mixture containing a CaO source and/or MgO source such as dolomite powder or serpentine powder is used. It worked. (Effects of the Invention) As explained above, the method of the present invention injects iron ore powder, Mn ore powder, and a complex compound or mixed powder with a CaO source and/or MgO source through the tuyere as a heavy oil slurry. There is no need for drying, and it is possible to blow through the tuyeres without causing piping wear or piping blockage. Therefore, under stable loading conditions, low Si concentration, low S concentration, and high
It becomes possible to produce hot metal with a high Mn concentration, which has a great effect on reducing the amount of slag forming agent and alloy used in the steelmaking process.

[Brief explanation of the drawing]

The drawing is a schematic diagram showing the configuration of an apparatus for carrying out the method of the present invention. 1 to 4 are service hoppers, 5 to 8 are rotary feeders, 9 is a mixing tank, 10 is a heavy oil supply line, 11 is a slurry pump, 12 is a distributor, 13 is a tuyere, 14 is a blowing nozzle, 15
is a blast furnace.

Claims (1)

[Claims] 1 Iron ore powder, Mn ore powder, CaO source and/or
A blast furnace operating method characterized by injecting a composite compound or mixed powder with an MgO source as a heavy oil slurry through the blast furnace tuyere.