JPH01123014A - Method for settling on pretreating plan in molten iron - Google Patents

Abstract

PURPOSE:To prevent excess refining of molten iron, to prevent waste use of treating agent for pre-refining and to reduce consumption of carbonic material for heat compensation in a converter by premeditatedly executing pre-refining of molten iron at the time of refining for steelmaking in the converter after pre-refining the molten iron from a blast furnace. CONSTITUTION:The molten iron from the blast furnace is received into mixing furnace and pre-refinings of desiliconization, desulfurization and dephosphorization are executed and also carbon content is reduced. This pre-refined molten iron is supplied into the converter and the remained molten iron in the mixing furnace is combined with the other molten iron as the raw material for the steel having the next other specification and supplied into the converter to refine it for steelmaking. In case the contained impurities (Si, P, S) in the next molten steel specification may be higher than them in the previous molten steel specification, as the quality of the molten iron, which the previous pre-refining has been executed, comes to the excess refining, the pre-refining is premeditatedly executed to the molten iron so as not to come to the excess pre-refining under consideration of the molten steel specification for producing in the converter. The waste consumption of pre-refining agent is reduced and also the adding quantity of the carbonic material for heat consumption based on insufficiency of carbon as the heat source at the time of refining in the converter is reduced and the cost for the steelmaking refining is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention improves the quality of hot metal by systematically carrying out pre-mIA treatment of hot metal before charging into a converter in an integrated blast furnace-converter ironmaking process. The present invention relates to a method for formulating a hot metal pretreatment plan that can prevent the pretreatment from being carried out to the extent that the pretreatment is carried out, thereby eliminating excessive consumption of pretreatment agents and carrying out economical hot metal pretreatment.

[Prior Art] In the blast furnace-converter integrated steelmaking method, the hot metal components (especially St, S, P,
C, etc.), and the chemical composition is not necessarily as suitable as vAA, and in mass-production converters, steel types with different chemical compositions are continuously melted.
In particular, in cases where the above-mentioned components in the molten steel are not adjusted after being tapped in a converter, such as in recent steelmaking processes, the hot metal should be pretreated to a degree that corresponds to the target composition at the time of being tapped in the converter. There is a need.

By the way, when transferring hot metal from a blast furnace to a converter,
Transfer containers such as pig iron mixers or ladles are used, but the amount of hot metal charged into these transfer containers is determined in order to improve the refractory life of the transfer container (total amount transported per generation), and to prevent the hot metal temperature from decreasing. From this point of view, operations and equipment plans are designed to charge as much hot metal as possible into the transport vessel. Therefore, for example, for a converter charging amount of 230 tons, the pig iron car loading amount is 290 tons.
The situation is like t. In addition, the amount of hot metal charged in the converter may vary depending on processing conditions such as main raw material balance and heat balance. It is difficult to maintain the ratio of 1:1 in actual operation. In the above example, at least the surplus hot water before and after Sot remains in the pig iron mixer car, which will be used for charging into the next rotary furnace, and the shortfall of 230-60 = 170 (t) will have to be replenished from the next pig iron mixer car. This is called Awaseyu.

When the hot metal pretreatment is carried out in a transport container, the amount of combined hot metal varies depending on various factors.
It is practically impossible to carry out preliminary treatment taking these into account and taking into account the combined amount of hot water. In other words, it has been difficult to predict the ratio of the combined hot water for each charge, so recent converter blowing operations do not take into account the removal of components to be pretreated (e.g., Si, S, P) in the converter. In this case, during pre-processing, excessive pre-processing that exceeds the target component value is inevitable, and it is not always possible to effectively utilize the excess water (60 tons in the previous example) after performing high-level pre-processing. If the next blowing goal is high (light pretreatment is fine), the pretreatment materials (flux and oxygen) required for the previous excessive pretreatment will have been wasted, which will be very uneconomical. there were. In addition, excessive pretreatment reduces the amount of carbon in the hot metal, and there is a problem in that it is necessary to take the trouble to replenish carbonaceous materials to compensate for the heat during converter blowing.

[Problems to be Solved by the Invention] In view of the above-mentioned circumstances, in the present invention, hot metal is pre-treated excessively by systematically pre-treating the hot metal before charging into the converter in the blast furnace-converter integrated iron manufacturing method. Therefore, a method for formulating a hot metal pretreatment plan that can avoid excessive consumption of pretreatment agents and carry out economical hot metal pretreatment was investigated.

[Means for Solving the Problems] The present invention, which has solved the above-mentioned problems, pre-processes each piece of hot metal that is sequentially brought in by a molten metal storage conveyance container in a batch manner, and then combines each piece of hot metal. When implementing the blast furnace-converter steel manufacturing method, which includes a distribution system that systematically produces molten steel with different contents of pre-processed components by charging it into a converter and refining it, the requirements are met based on the steel manufacturing specifications. The concentration of the components to be pretreated is planned for each unpretreated hot metal. On the other hand, for pretreated hot metal whose concentration of components to be pretreated is known, the remaining amount to be charged to the converter is predicted, and the remaining amount of the remaining hot metal is calculated. By successively repeating the process of correcting the planned concentration of the components to be pretreated in the unpretreated hot metal that has been selected to be used for mixing with hot metal, an appropriate reserve with no excess or deficiency can be obtained. The main purpose of this is to formulate a processing execution plan.

[Function] In the present invention, the main raw material blending plan and the transportation container distribution plan (here, the vehicle distribution plan is described assuming a pig iron mixing vehicle, but a ladle or other container can also be used), and the two are combined. By taking this into account and calculating, it is possible to bring the target content value of each component in the pretreated hot metal that is scheduled to be used as the next batching hot metal closer to the content standard value of each component in the converter, and by that much. It is now possible to prevent an increase in the basic unit of pretreatment agent due to overtreatment.

A specific embodiment of the hot metal pretreatment plan according to the present invention consists of two steps as described below, and will be explained here by taking sulfur as an example of the pretreatment component. Components other than sulfur, such as phosphorus and silicon, can also be controlled in the same way.

(1) Calculate the transportation container distribution plan (molten pig iron delivery order) as follows for transportation containers for which desulfurization treatment has already been completed and the components and temperature results after preliminary treatment are known.

Required amount of hot metal for the H-2 converter (target charging amount) Target sulfur content for the S-2 converter S: Sulfur content of the hot metal in the transfer container (actual value) h: Loading amount of hot metal in the transfer container i: Hot metal discharging order (i=1.2....) When α: remaining iron amount in the transport container (next combined drying schedule fit), (h+ -α) Si + [:H 凰 -(
h+ −α ) ]XS1+1 ≦ SI
) I 5... (1) However, h+-α) s+: Total sulfur amount in the hot metal charged from the i-th conveyance container to the converter [H+-(h+-a)] s++1: i+1-th Total sulfur amount S in the combined vortex charged from the transfer container,
) and...(3) (If the i+1st combined metal is less than half of the total charge in the converter, the hot metal in the converter is ranked higher than the pre-operation target sulfur content [low sulfur] (pre-treated to the same or lower sulfur content) (i11) When the combined metal to be added is more than half of the total charge amount of the converter, the target sulfur content of the hot metal in the converter before operation Among the transport containers that satisfy (h +++ l S +++ ) (pre-treated to the same or lower sulfur content), the transport containers with the highest sulfur content are preferentially dispatched. That is, those that have been pre-treated to excess quality are passed on to the next charge, and the one that has the lowest product quality achieved through pre-treatment within the above condition range is used as a combined quality. Here, H is a numerical value given from a cost-minimum main raw material composition calculation to obtain a predetermined blow-off temperature and components based on the hot metal temperature distribution.

(2) Based on the vehicle allocation plan that adopts the transport containers determined in (1) above, a matching plan with converter melting MFL for unpretreated transport containers and a target sulfur content after pretreatment. Determine the value.

The method is to determine the vehicle allocation in the converter according to the pig iron receiving type (including schedule) in the blast furnace, but for this vehicle allocation schedule, return to equation (1) above again and convert S +++ as an unknown quantity, The following equation (5) is derived.

(5) Then, the untreated transport container is subjected to preliminary treatment using SI+l that satisfies the above equation (5) as the sulfur content target value.

[Example] [S] standard value of unpretreated hot metal (%, target sulfur content of hot metal ) and the target production ratio of hot metal were sequentially planned, and hot metal pretreatment (desulfurization) was performed according to the present invention. Target [S
] Specification value (%), target production ratio (%) 1 Actual desulfurization hot metal production ratio (%) and desulfurization agent used (kg/l)
Shown in the table. Table 2 also shows examples processed using the conventional method.

Table 1 (Example) Target [S1 standard value average 01011% Actual desulfurization solution a [S] average 0.011% Table 2 (
Conventional example) Target [S] standard value average 0011% Actual desulfurized hot metal [S] average 0009% m in the example and conventional example from Tables 1 and 2
When calculating the amount of desulfurization agent used per tt (kg), the consumption amount of desulfurization agent in the example: 4.32X0.118 +2.93X0.165
+2.27X0.14+ 1.70X 0.07+ 1
．． 35X O, 507 = 2.11 (kg/l) Desulfurizing agent consumption in conventional example: 4.32xQ, 118 +2.93xO, 177+2.
27x0.173+ 1.90x Q, 029 + 1
．． 70x O, 118+ 1.35x Q, 4L5=
2.18 (kg/l), and the amount of desulfurizing agent saved is 2.18-2.11=0.07 (kg/l).

From the above results, in the example, there was less excessive desulfurization as in the conventional example, and the amount of desulfurization agent was 0.07 kg/
It saves l.

In addition, the actual desulfurized hot metal [S] average was 0.011% in the example and 0.009% in the conventional example compared to the target [S] standard value average of 0.011%. It turns out that it is not.

[Effects of the Invention] Since the present invention is configured as described above, pre-treatment of hot metal is carried out in a planned manner, thereby preventing pre-treatment of excessive quality, thereby preventing excessive use of pre-treatment agents. can. Therefore, the reduction in carbon content was also suppressed, and the amount of heat-compensating carbon material added to the converter could also be reduced.

Applicant: Kobe 8 Co., Ltd. steelworks

Claims (1)

[Scope of Claims] The components to be pretreated are prepared by pre-processing each piece of hot metal sequentially brought in by a molten metal storage conveyance container in batches, and then combining each piece of hot metal and charging it into a converter for refining. When implementing the blast furnace-converter steelmaking method, which includes a logistics system that systematically produces molten steel with different contents, the concentration of pretreatment target components required for each unpretreated hot metal is planned based on the steelmaking specifications. On the other hand, for the pretreated hot metal whose concentration of components to be pretreated is known, the remaining amount to be charged into the converter is predicted, and the unpretreated hot metal selected to be used for combining with the remaining hot metal is estimated. , a method for formulating a hot metal pretreatment plan, comprising formulating an appropriate pretreatment execution plan with no excess or deficiency by successively repeating the operation of correcting the planned concentration of the component to be pretreated in the hot metal. .