JPS61261407A - Operating method for blast furnace - Google Patents

Abstract

PURPOSE:To maintain the basicity of slag, the concn. of MgO and the content of S in a molten iron within set values and to stabilize the furnace condition of a blast furnace by controlling the charging rate of auxiliary raw materials such as dolomite with the furnace top temp. as an index in the stage of operating the blast furnace. CONSTITUTION:The basicity of molten slag and the MgO component in the molten slag are maintained at the adequate set values and the content of S in the molten iron is controlled so as not to exceed the set value in the stage of operating the blast furnace. The top gas temp. of the blast furnace is controlled to a 100-150 deg.C range and the dolomite consisting of CaCO3 and MgCO3 is added to the blast furnace raw material for the above-mentioned purpose. The CaCO3 and MgCO3 absorb the heat for thermal decomposition thereof to CaO and MgO to decrease the furnace top gas temp. to <=150 deg.C; at the same time the content of S in the molten iron is decreased by the increased basicity of the molten slag in the furnace and content of MgO therein. The charging of the dolomite is stopped to prevent the temp. decrease by the thermal decomposition of the dolomite when the furnace top gas temp. decreases to <=100 deg.C. The furnace top gas is thus held again at 100-150 deg.C and the furnace condition is stabilized.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention belongs to the field of blast furnace operation technology, and in particular, it is used to control the adjustment of furnace heat, hot metal and slag components. We propose a practical operating technology to realize this by direct input method.

(Prior art) In the case of general blast furnace operation, the ore that becomes the CaO source and MgO source used for the purpose of adjusting the hot metal and slag components is
As proposed in No. 6215, it is normal to include treated ore, such as sintered ore, or pellets. That is, Japanese Patent Application Laid-Open No. 47-27111
As disclosed in JP-A No. 49-24824, when raw auxiliary raw materials are directly charged into a blast furnace and the slag components, basicity, and MgO concentration are adjusted, they melt in the furnace. The amount of fuel that can be directly charged to the blast furnace in lump form is limited, and the amount of fuel that can be extracted is limited.
For example, heat must be guaranteed by increasing the amount of coke charged or raising the temperature of the air.

(Problems to be solved by the invention) As is clear from the above, directly charging raw ore (auxiliary raw material) that becomes a source of CaO and MgO into the blast furnace is effective in adjusting the components of hot metal and slag. However, pretreatment is usually carried out to reduce the furnace heat and increase the fuel ratio, but this has the problem of being uneconomical as extra energy is required at the processing ore manufacturing stage. Ta.

The purpose of the present invention is to overcome the problem of being uneconomical, to charge a large amount of raw ore as an auxiliary raw material without adversely affecting the furnace condition, and to ensure the furnace heat and hot metal/slag components. The goal is to propose technology that allows for precise adjustments.

(Means for Solving the Problems) The present invention solves the above problems by using CaO-based ores, M
In a method that adjusts the furnace heat and adjusts the composition of hot metal and slag by directly charging and pouring auxiliary materials such as gO-based ore into the blast furnace, the charging control of the auxiliary materials is carried out at the top of the blast furnace. A blast furnace operating method that is characterized by temperature-based operation is adopted.

In short, when the temperature at the top of the furnace is above a preset temperature level, the charging amount of auxiliary materials is controlled to adjust the composition of hot metal and slag, and when the temperature exceeds a certain level, This method attempts to adjust the furnace heat by increasing the amount of auxiliary materials charged.

(Function) According to the inventors' analysis of past blast furnace operation data, there is a clear relationship between the charging amount of dolomite and the furnace top temperature, as shown in Figure 1 (a). It turns out that there is a relationship.

In other words, dolomite is an ore represented by the molecular formula of CaCO2/MgCO3, and its heat of solution is 70.8Kc.
al/mol. As can be seen from FIG. 1(a), when 100 g/ch of dolomite is introduced into the blast furnace, the furnace top temperature decreases by about 5°C.

On the other hand, the amount of dolomite charged and basicity are shown in Figure 1-(b).
There is a relationship as follows, and the amount of dolomite charged is 100 kg.
/ch increases, the basicity increases by about 0.01. Also, MgO
Regarding the concentration, as shown in Fig. 1(c), if the amount of dolomite charged is increased by 100 kg/ch, the concentration will increase by 0.15%.

Because of this relationship, if the amount of dolomite charged is increased or decreased using the furnace top temperature as an index, the basicity and MgOtl
Therefore, based on these findings, the present invention increases or decreases the charging amount of auxiliary raw materials when the top temperature of the blast furnace is above a certain level. At the same time as adjusting the furnace heat, the hot metal and slag components were also adjusted. In the above explanation, dolomite is used as an example of the auxiliary raw material ore, but it goes without saying that other sources such as ash, jamonite, etc. can also be used as the CaO source and MgO source.

(Example) Regarding the operating method of the present invention, the internal volume is 2500 m'', the normal air blowing is N3N360ON/sin, and the air blowing temperature is about 1000°C.
, a blast furnace with a set furnace top temperature of 100°C to 150°C will be explained.

The auxiliary raw materials are stored in an ore storage tank and cut out as needed and charged into the blast furnace.

Figure 2 shows the furnace top temperature, dolomite charging amount, slag basicity, MgOtM degree in the ring, S concentration in the pig iron, before and after implementing the present invention.
It shows the changes in the contents in the blast furnace and the number of slips.

The upper limit of the set furnace top temperature is 150℃, the lower limit is 100℃,
Regarding the period A in the figure when the furnace top temperature exceeded 150°C, the amount of dolomite charged was increased until the furnace top temperature fell below 150°C. After that, the furnace top temperature reaches the set lower limit of 100.
The dolomite charge was maintained until the temperature dropped below ℃. During this period, the basicity and MgO concentration of the slag became high, and as a result, the 5t74 degree in the pig iron became a low level.

On the other hand, in period B, the furnace top temperature fell below the set lower limit of 100°C, so the dolomite charge amount was reduced, and then the dolomite charge amount was reduced until the furnace top temperature exceeded the set upper limit of 150°C. Maintained. During this period, slag basicity, MgO
T! JS degree decreased, and the S concentration in the pig iron increased. but,
The StJm degree was kept below the set upper limit. This is because the furnace conditions were stable, as can be seen from the change in the number of slips.

The same actions as in Period A were taken after Period C.

The stability of the furnace condition was shown by the fluctuation of the number of slips. After implementing the present invention, the number of slips was drastically reduced compared to before implementing the present invention, which shows that the present invention is highly effective.

(Effects of the Invention) As explained above, according to the present invention, by controlling the charging amount of auxiliary materials such as dolomite using the furnace top temperature as an index, it is possible to maintain the furnace condition stably, and also to maintain the fuel ratio. slag basicity, MgO'IM degree, and S in pig iron without increasing
It became possible to maintain the concentration within the set value. Therefore, in the conventional method, only 500 kg/ch of auxiliary raw materials such as dolomite, which is a CaO source and MgO source, could be directly charged into the blast furnace, whereas in the present method, 1500 kg/ch could be charged directly into the blast furnace.
Furthermore, since it is not necessary to include it in sintered ore in advance, it saves energy and is economically advantageous.

[Brief explanation of drawings]

(a), (b), and (c) in Fig. 1 are graphs showing the relationship between dolomite charging amount, furnace top temperature, slag basicity, and MgO concentration; This is a transition chart regarding blast furnace operation data. Figure 2 Period (month) My 04 crisis [%] 41%

[-] At the top of the furnace ('C)

Claims (1)

[Claims] 1. In a blast furnace operation method that adjusts the furnace heat and adjusts the hot metal and slag components by directly charging auxiliary materials such as CaO ore and MgO ore into the blast furnace,
A method for operating a blast furnace, characterized in that the charging of the auxiliary raw materials is controlled with consideration given to the temperature level at the top of the blast furnace.