JPH0826369B2 - Blast furnace powder injection operation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention aims to reduce the amount of slag forming agent used in the steelmaking process, and powder blast furnace operation for reducing Si concentration and S concentration in hot metal. Concerning the law.

[Prior Art] Conventionally, the operation mode of a blast furnace has been aimed at a liquid fuel injection operation aiming at a low coke ratio and a high tap ratio by injecting a large amount of liquid fuel such as heavy oil and tar from a tuyere. Was there. However, as the price of crude oil soared in the early 1950s, the energy price system changed significantly, and as a result, all coke operation became the mainstream of blast furnace operation.

Compared with liquid fuel injection operation, this all-coke operation has lower fuel cost, but the pre-tuyere temperature is higher and the amount of hydrogen input to the blast furnace is also lower, so unstable unloading and slippage occur. Frequent occurrence and Si in the hot metal
It also increases the concentration. This problem has been solved by using a large amount of humidity control, but instead, the problem of coke oven production capacity due to an increase in the coke ratio and the maximum blow-through unit due to an increase in the blower unit consumption are the maximum. There was a new problem that the tap ratio decreased.

Therefore, the number of blast furnaces that use pulverized coal as an inexpensive tuyere injection fuel has increased, and in this blast furnace, the reduction of the coke ratio has been achieved and the maximum tap ratio has increased. However, in the pulverized coal blowing operation as compared with the liquid fuel blowing operation, SiO ₂ derived from the pulverized coal undergoes the following reaction formula in Raceway near
There is a problem that SiO gas is generated and the Si concentration in the hot metal rises. Further, as compared with the all coke operation, during the pulverized coal blowing operation, S in the pulverized coal is gasified in the raceway, which causes a problem that the S concentration in the hot metal rises.
Therefore, the amounts of desulfurizing agent and slag-forming agent used in the steelmaking process increase.

SiO ₂ + C = SiO + CO ...... Therefore, the Si concentration and S in the hot metal during pulverized coal injection operation
A method has been developed which suppresses an increase in the concentration and positively achieves a low Si and low S operation (JP-A-57-137403).

This method involves blowing powdered limestone, slag-forming agent such as dolomite, etc. together with pulverized coal from the tuyere of the blast furnace, and reducing the activity of SiO ₂ in the tuyere slag to obtain the SiO ₂ of the above formula.
The gas generation reaction was suppressed to reduce the Si concentration in the hot metal.

[Problems to be solved by the invention]

However, this method has the following four problems.

Pulverized coal and slag powder require independent tuyere blowing systems (raw material hopper → intermediate tank → blowing tank), which complicates the equipment.

Pulverized coal and slag dust powder are blown into tuyeres from different systems, so the mixing in the pipe is not sufficient, and the pulverized coal / slag dust powder ratio varies from time to time and tuyere It becomes difficult to keep the combustibility of the coal and the slagging property of the pulverized coal ash and the slag-forming agent powder constant.

It is necessary to dry and crush the raw materials in separate equipment,
The equipment becomes complicated.

Since the carrier gas is cold air, gas transportation does not contribute to the improvement of the combustibility of pulverized coal.

Although it is in a field different from the blast furnace operating method targeted by the present invention, in order to improve the mixing property of the mixed powder, pulverized coal and iron oxide or reduced iron are blown in a fluidized state by gas inflow. There has been proposed a method of mixing in a mixing tank and blowing it into a blast furnace (Japanese Patent Laid-Open No. 62-77411). However, in the blast furnace operating method targeted by the present invention, the importance of mixing has not been sufficiently grasped and confirmed, and the effect of this method is unknown. Further, the above problems cannot be solved. There is also a problem that a fluidizing tank is required separately.

The present invention reduces the Si concentration and S concentration in hot metal,
In a blast furnace operating method for reducing the amount of desulfurizing agent and slag-forming agent used in the steelmaking process, the purpose is to solve all of the above-mentioned problems. A stable low Si and low S operation was realized under the operation of pulverized coal injection by relaxing the deviation of the powder mixture ratio and improving the combustibility of pulverized coal and the slagging property of pulverized coal ash and slag forming agent powder. The present invention provides a powder blowing operation method for the obtained blast furnace.

[Means for solving problems]

As shown in FIG. 1, the blast furnace powder blowing operation method according to the present invention uses a CaO source and / or a CaO source in a blast furnace operating method in which a powdered slag-forming agent is blown into the furnace from the blast furnace tuyere 21 into the furnace.
Alternatively, the slag forming agent 1 containing an MgO source is carried together with coal 2 into a crusher 9 having a facility 10 into which hot air generated in a hot blast furnace 10 in the range of 150 to 500 ° C. is introduced. The coal 2 and the slag forming agent 1 are crushed, mixed and dried at the same time, and the obtained mixed powder of the coal and the slag forming agent is tuyere 12 by gas transportation.
It is characterized in that it is blown into the furnace from.

[Action]

According to the present invention, firstly, 150 to 5 generated in the hot stove 10
Since the slag forming agent 1 and the coal 2 are cut out at the same time with respect to the crusher 9 into which the hot air in the range of 00 ° C. is introduced,
The raw materials can be crushed, mixed, and dried at the same time by one unit, which simplifies the facilities.

Secondly, since the slag-forming agent 1 and the coal 2 are gas-transported from the crusher 9 as a mixed powder to the blowing system, the blowing into the blast furnace can be performed with the mixed powder as it is. Therefore, it is not necessary to separately install the blowing system for the pulverized coal and the slag-forming powder, and the facility is simplified.

Thirdly, since the coal 2 and the slag-forming agent 1 are pulverized at the same time, a mixture having a sufficient degree of mixing can be obtained, and a powder mixture of pulverized coal / slag-forming agent powder having a small deviation with time and tuyere can be obtained. Can be supplied. Therefore, the combustibility of the pulverized coal and the slagging property of the pulverized coal ash content and the slag forming agent powder are improved, which leads to the improvement of the coke substitution ratio of the pulverized coal and the reduction efficiency of Si and S in the hot metal.

Fourth, since hot air in the range of 150 to 500 ° C. is introduced as the drying gas, the temperature of the powder carrying gas at the tip of the tuyere 12 rises, and the release of volatile matter is promoted. The combustibility of charcoal is improved. If the hot air temperature is less than 150 ° C, this effect is not sufficient, and if it exceeds 500 ° C, the pulverized coal is ignited to a high temperature, which may damage the crusher and the sending pipe.

〔Example〕

 An embodiment of the present invention will be described with reference to FIG.

The dolomite before crushing, slag-forming agent 1 such as limestone, etc. loaded in the yard, and the coal 2 before crushed loaded in the yard are conveyed through their own paths, respectively, and then the rising belt conveyor 3 and the left and right bidirectional belts. It is stored in the slag-making agent hopper 5 and the coal hopper 6 via the conveyor 4, respectively. At this time, the slag-forming agent 1 and the coal 2 are sorted and supplied from the bidirectional belt conveyor 4 to the respective hoppers 5 and 6 at different loading timings on the belt conveyor 3.

The slag-forming agent and the coal stored in the hoppers 5 and 6 are discharged by the rotary feeders 7 and 8 installed in the lower part of the popper, respectively, according to a predetermined cutting amount.
Simultaneously and continuously fed to the crusher 9.

The slag forming agent and the coal, which are simultaneously supplied in a predetermined ratio, are crushed and mixed in the crusher 9 and the crusher 9
Is dried by hot air having a predetermined temperature within the range of 150 to 500 ° C., which is sent from the hot air stove 10 attached to the. As this hot air, one obtained by burning B gas or the like generated in the steel mill may be used.

The mixed powder of the slag forming agent and coal pulverized to a predetermined particle size or less is gas-transported by the hot air from the hot air stove 10 to the blowing system toward the tuyere 12, and further passes through the distributor 11 to each tuyere 12.
Is distributed and gas is transported. Then, it is blown into the blast furnace 14 from the tuyere 12 through the blowing nozzle 13. In this case, hot air and / or cold air can be added through the pipe 15 in the blowing system after the crusher 9 if necessary.

Although not shown, the powder blowing nozzles 13 are arranged at each air blowing tuyere 12, and a plurality of distributors 11 may be installed, if necessary, in multiple stages.

Although not shown, the system from the yard of the slag slag 1 to the slag slag hopper 5 is also installed depending on the number of types of the slag slag to be used.

As the slag-forming agent, limestone, dolomite, etc. are used in the examples, but they may contain other CaO source or MgO source. Further, it may be a slag forming agent containing both CaO source and MgO source.

Below, the experimental results of the powder blowing operation of the blast furnace based on the present invention will be explained in comparison with the experimental results based on the conventional method. The results of the experiment are shown in Table 1, the composition of the coal and the slag-forming agent used in the experiment are shown in Table 2, and the particle size distribution is shown in Table 3.
Shown in the table. The blast furnace used in the experiment had a volume of 27
It is 00m ³ .

In Table 1, period A is an example by the conventional method. In this example, in order to reduce Si in the hot metal and S in the hot metal,
Pulverized coal and dolomite powder were supplied from different injection systems, and powder was injected from the tuyere of the blast furnace by gas transportation.

As a result of the implementation, Si in hot metal at a dolomite injection amount of 30 kg / _PT
The concentration decreased to 0.24% and the S concentration in the hot metal decreased to 0.024%. However, as a result of the powder sampling before the tuyere, the change in the mixing ratio of pulverized coal / dromite powder with time was ± 90.
%, The deviation for each tuyere direction was as high as ± 110%.

As a result, the combustibility of pulverized coal for each tuyere was not kept constant, and the coke substitution rate of pulverized coal was only 0.90.
Further, since the slagging properties of the pulverized coal and the slag-forming agent powder cannot be maintained together, the standard deviation of the Si concentration in the hot metal and the S concentration in the hot metal at each tapping is high, and sufficient low Si due to powder injection, The low S effect was not exhibited.

On the other hand, the period B is an example in which the method of the present invention is applied. In this example, the amount of dolomite blown in is 30 kg / _{PT, which} is the same as period A above.
Under the above conditions, coal and dolomite are cut out at the same time into a crusher in which hot air in the temperature range of 150 to 500 ° C is introduced, and both raw materials are simultaneously crushed, mixed, and dried, and then gas is transported from the tuyere of the blast furnace. Powder injection was carried out.

As a result of the implementation, the amount of dolomite injected was 30 kg / _PT , and the hot metal was
The Si concentration decreased to 0.16%, and the S concentration in the hot metal decreased to 0.021%. Then, as in the case of the conventional example, when powder sampling was performed just before the tuyere, the change in the mixing ratio of pulverized coal / dolomite powder with time was ± 10%, and the deviation for each tuyere direction was ± 20%.
And was greatly reduced.

As a result, the combustibility of pulverized coal in each tuyere was improved and made uniform by adding hot air as the transport gas, and the coke substitution rate of pulverized coal was improved to 1.05. In addition, the slagging properties of the pulverized coal and the slag forming powder are also kept constant, the standard deviation of the Si concentration in the hot metal and the S concentration in the hot metal for each tapping decreases, and low Si / low due to powder injection. The S effect was sufficiently exhibited.

Further, during the application period of the method of the present invention, the deviation of the mixing ratio of the pulverized coal / dromite powder in front of the tuyere was significantly alleviated, so the combustibility of the pulverized coal and the slagging property of the slag forming agent at each tuyere were reduced. Was made uniform, the number of slips in the blast furnace was reduced, and the unloading situation was stabilized.

[Effects of the Invention] As is apparent from the above-described examples, according to the present invention,
Under the pulverized coal blowing operation of a blast furnace, a slag-forming agent containing a CaO source and / or an MgO source is mixed with coal at 150 to 500 ° C.
Into a pulverizer into which hot air in the range is introduced, the pulverizer simultaneously pulverizes, mixes, and dries the coal and the slag-forming agent, and transports the obtained mixed powder of the coal and the slag-forming agent by gas. By blowing air into the furnace from the tuyere of the blast furnace, the effect of reducing Si in the hot metal and S in the hot metal can be achieved with a simple equipment arrangement, reducing the amount of smelting agent used in the steelmaking process and desulfurizing agent. It is possible to reduce the amount used.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an apparatus configuration suitable for carrying out the method of the present invention. In the figure, 1: Yard stacking agent, 2: Yard stacking coal, 3, 4: Belt conveyor, 5: Slaging agent hopper, 6: Coal hopper, 7,
8: rotary feeder, 9: crusher, 10: hot air oven, 11: distributor, 12: tuyere, 13: blowing nozzle, 14: blast furnace, 15: hot air and / or cold air additional piping.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Shimoda 1850 Minato, Wakayama, Wakayama Sumitomo Metal Industries, Ltd. Wakayama Works (56) Reference JP-A-57-137403 (JP, A) JP A 59-153812 (JP, A) JP-A-61-261408 (JP, A)

Claims (1)

[Claims] 1. In a blast furnace operating method in which a powdery slag-forming agent is blown into the furnace from the tuyere of a blast furnace, a slag-forming agent containing a CaO source and / or an MgO source is used together with coal in an amount of 150 to 500.
Carried into a pulverizer introduced with hot air in the range of ℃, the pulverizer simultaneously pulverize, mix and dry the coal and the slag-forming agent, and the obtained mixed powder of the coal and the slag-forming agent is vaporized. A blast furnace powder blowing operation method characterized by blowing into the furnace from the tuyere by transportation.