JPS6096703A - Operation of blast furnace - Google Patents

Abstract

PURPOSE:To restrain the occurrence and increment of adhesive matters on the furnace wall by removing the zinc and alkali group from a blast furnace by a method that when zinc and alkali contents in gas and ash of the furnace increase, the charge level is lowered and the admixture of CaCl2-NH4Cl is charged. CONSTITUTION:When analytical values of zinc and alkali group in the gas and ash of a blast furnace collected from inside the furnace increases, the furnace operation is carried out with decreased charge level, and, at the same time, CaCl2-NH4Cl admixture is charged. When chloride is charged, zinc and alkali group which are circulating inside the furnace are discharged from the furnace system as ZnCl, NaCl, KCl. By this method, zinc and alkali can be efficiently removed in a short time, deterioration of coke in the lower part of the furnace caused by the increase of alkali content circulating in the furnace can be prevented, the occurrence and increment of adhesive matters can be restrained, and existing adhesive matters become brittle, fall and can be removed. Consequently, the blast furnace operation can be stabilized.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a blast furnace operating method.

(Prior art and its problems) In the blast furnace, Zn and alkali are in their gas phase.

' It either circulates in the condensed phase temperature region or accumulates as a component in the furnace wall deposits. This deteriorates the air permeability inside the furnace, leading to unstable operation, and causes an increase in the high-f fuel ratio and an increase in the variation in Si in the pig iron.

In the latter case, Zn and alkali condense in the region with low relative τ′ quality, which acts as a binder of the charging material, generates and grows strong deposits on the furnace wall, and causes the Suspension belt,
This causes irregularities in unloading, making it impossible for the blast furnace to perform its original functions, and causing an increase in the blast furnace fuel ratio.

That is, the mechanism of occurrence of furnace wall deposits has been known from Japanese Patent Publication No. 42-26377 (Patent No. 518010). In other words, the deposits on the furnace wall are caused by zinc and alkalis introduced by ore that evaporate in the lower part of the furnace where the temperature is high, condense in the relatively low temperature parts called the shaft and the furnace belly, and this becomes a bond. It solidifies the charged ore and coke and forms a strong deposit. When this deposit occurs on the furnace wall and grows, it causes a mixed layer, which induces a drifting flow of the reducing gas and disturbs the balance of the cohesive zone in the circumferential direction, reducing the gas inside the furnace. Efficiency ηe.

C02 where the top of the furnace is in the air (@<rra.=7□□10,000,., Agesakaki...2 禰X100)
This causes a decrease in the temperature and increases the dispersion in the pig iron [8i].

In addition, if you force the operation with deposits forming and growing,
A large amount of gas ash comes out from the top of the furnace, which causes the raw material charges to become stuck and unloading irregularly, and the blast furnace cannot perform its original functions to its full potential, resulting in a significant increase in the blast furnace fuel ratio. .

For this reason, those skilled in the art have conventionally proposed the following methods for removing zinc and alkalis from the furnace.

A. Japanese Patent Publication No. 54-14562 (method for chloride volatilization of raw materials for iron making) b. Japanese Patent Publication No. 42-26377 (method for removing walls of blast furnaces) In method A above, non-ferrous metal washers such as ZN are removed in advance during pellet production to prevent them from entering the blast furnace. Specifically, As, Cu, Pb
, Zn, and other non-ferrous metals are added to ironmaking raw materials, kneaded and ground, granulated, dried, and fired in a rotary kiln.
Using a mixed chlorinating agent consisting of t2 and NH2Cl, All
This is a method in which nonferrous metals such as Cu, Pb, and zinc are simultaneously chlorinated and volatilized. Therefore, this method is intended to strengthen the pellets by chlorinating and volatilizing non-ferrous metals from the iron-making raw materials and performing high-temperature firing to remove S during the process of making pellets.

However, the content of non-ferrous metals in pellets is controlled (suppressed).
There is a management limit to doing so considering the current status of mineral resources.

Therefore, there is a limit to how much zinc etc. can be removed from the raw material and prevented from entering the blast furnace.

(Objective of the Invention) The object of the present invention is to reduce the amount of zinc circulating in the furnace, which is a factor in the generation of deposits on the furnace wall. The alkalis are discharged out of the blast furnace system and recovered to suppress the generation and growth of deposits on the furnace walls, and the generated deposits are removed, reducing the blast furnace fuel ratio over a long period of time.
The aim is to provide a blast furnace operating method that reduces the variation in pig iron [S, i].

(Structure and operation of the invention) In order to solve the above-mentioned difficulties, the present invention reduces the level of blast furnace charge when the analysis values of zinc and alkalis in blast furnace gas ash become high during blast furnace operation. Measured, and CaCA2-
The NH4Ct mixture is charged into the blast furnace, and zinc,
This is a blast furnace operating method characterized by removing alkalis.

As a result, in the present invention, the zinc and alkali IJ d circulating in the furnace, which are the cause of the generation of furnace wall deposits, are discharged to the outside of the blast furnace system.
We provide a blast furnace operating method that reduces the blast furnace fuel ratio and the variation in pig iron [Si] by recovering and suppressing the generation and growth of deposits on the furnace wall, and removing the deposits that have occurred. This is what I am trying to do.

By the way, the present invention and the above-mentioned known examples are distinguished from each other in the following points.

That is, both the present invention and the prior art (a) have the same concept of volatilizing Cact2-NH4C1 and dichloride to remove zinc, etc., but the present invention has the same conditions for adding this CaCl2 NH2Cl. This method is distinguished from the conventional method described above in that the material is reduced in size and charged into the blast furnace. That is, in the present invention, the above-mentioned CaC22-NH2Cl is charged into the blast furnace as a solid (lump) through the furnace top charging device.
'It has better reactivity than adding Cl2-NH2Cl, and the purpose of the invention can be achieved quickly. That is, inside the blast furnace, zinc is mainly discharged to the outside of the furnace together with dust through the furnace top. On the contrary, most of the alkali is contained in the slag and is discharged outside the furnace. Since ZnCL2 produced by the chlorination reaction has a boiling point of 730°C, it vaporizes and becomes cloudy compared to Zn (boiling point 907°C) and ZnO (melting point 1800°C), and its discharge to the outside of the furnace is promoted. Furthermore, NaCL also has a low melting point of 800° C. and is highly volatile, so the amount of NaCL discharged from the furnace increases. Similarly, KCl has a low melting point of 768°C.
Easier to drain.

Next, the reason for the 1st grade of the present invention will be described.

1) The reason why a CaCl2-NH4CL mixture was used as a chlorinating agent was for the following three reasons.

1)-(1) CaC22, NI (4Ct both ordinary Y crystal ~
It exists as a solid at temperatures of several hundred degrees Celsius, making it easy to store and photograph continuously.

1)-(2) NH2Cl sublimates at 335°C and becomes CaC
A2 melts at 774°C. Therefore, if a combination of a substance that volatilizes chloride quickly (NH4C2) and a substance that evaporates relatively slowly (CaCA2), the responsiveness and removal efficiency for chloride volatilization will deteriorate.

Figure 1 shows CaC4 in A blast furnace (1730+y+')
2 and N114Ct and the dezincification and dealkalization efficiency. The dezincing and alkali amounts are the average values for 3 days before and after repeated scale reduction. The mixing ratio of NH4Cl is 2
It can be seen that dezincification and dealkalization efficiency is maximum in the ratio 0 to 60.

1) - (:3) Are components other than chlorine discharged outside the furnace as blast furnace gas or slag, causing harmful effects and physical damage inside the furnace? Don't f.

NI (4CtI''i sublimes and is separated into NI3 and ct2, and NH5 is discharged outside the furnace together with the furnace gas.
ILC42 undergoes an oxidation reaction at high temperature, and C
CaC2z +1/202-+ CaO+ C12↑ which is separated into aO and ct2 enters the generated CaOu slag and is discharged together with the slag, and at the same time, the basicity increases and plowing is performed to lower the St in the pig iron.

2) Reasons for reducing the size of blast furnace charge The reason for implementing the reduced scale operation is considered as follows.

2)-(1) During the process of scale reduction, some zinc and alkali are evaporated and recovered in the gas ash.

2)-(2): With the reduction in size, the temperature near the surface of the raw material charge rises, and the temperature gradient in the height direction inside the charge increases, and accordingly, zinc and alkali, which are estimated from conventional blast furnace dismantling results, The area inside the furnace, which is at the concentration temperature (800 to 1300°C), can be kept to an extremely small range compared to normal operation. By narrowing the concentration range, the chloride removal reaction can proceed efficiently.

2)-(3): Reoxidation in which zinc and alkali chloride come into contact with the charge and react with it by reducing the size.

Traps caused by condensation can be suppressed.

Due to the three factors mentioned above, namely the increase in temperature, the reduction of the zinc and alkali enrichment area, and the suppression of re-oxidation and condensation by the charge, charging chloride in a reduced size will It was observed that the removal effect of zinc and alkali and the yield of chlorinating agent were significantly improved.

FIG. 1 shows that the effect of zinc and alkali removal was improved by increasing the scale reduction level.

3) Timing of start and end of chloride charging CaCA2-
NH4Cl starts to be added when the analysis value of zinc in the blast furnace gas ash increases. Figure 2 shows the changes in chloride input and the zinc and alkali concentrations in the dust in the B blast furnace (1150 m3).

When the zinc concentration increases (A), the first CaC6-NH4
As a result of CL injection, zinc and alkali concentrations increased, and after a while they decreased, so CaCl2-N
H4CA was added. After repeating this several times, a time (B) appeared where the zinc and alkali concentrations no longer increased even if CaC22-NH4Cl was added.

The charging of CaC22-NH4CL is completed at this timing, that is, when the zinc in the dust and the alkali IJ 14 degrees no longer increase even if CaCL2-NH4Ct is charged.

Next, embodiments of the present invention will be explained.

In the A blast furnace, which has a furnace capacity of 1,730 m3, the total amount of residual alkali in the furnace has increased rapidly, and irregularities in unloading for unknown reasons have begun to occur frequently. Initial zinc was collected from the furnace from the middle to the bottom of the shaft and charged to fc.

An increase in Alka IJit was also observed. For this reason, we conducted a reduced scale operation and added CaCl2-NH4CL,
zinc.

Alkali removal was performed. As a result, the total amount of residual alkali in the furnace has decreased to the previous level, the amount of zinc and alkali between the middle and lower shafts has decreased significantly, and the unexplained unloading irregularities (slips) have subsided, so the fuel ratio has also been adjusted to the latest level. It was possible to reduce p by 3.5 t'J/l compared to the 3-month average. (Effects of the invention) As described above, the present invention can: ■ Regularly discharge zinc and alkali during normal operation ■ Reduction Utilizing shaku operation, it is possible to discharge zinc and alkali efficiently in a short time ■ It is possible to prevent coke deterioration in the lower part of the furnace due to an increase in the amount of alkali circulating in the furnace ■ It is possible to prevent the formation and growth of deposits, and to remove existing deposits. It is possible to remove embrittlement and falling off. ■ With the stabilization of blast furnace operation, it is possible to improve the sulfur reduction efficiency in the furnace, reduce the variation in St in the pig iron, and reduce the blast furnace fuel ratio.

Since the present invention has the above-mentioned effects, it is a blast furnace operating method that has great industrial benefits.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between CaCl2 and NH4C1 mixing ratio, scale reduction level and amount of dezincification and dealkalization. Figure 2 is a graph showing the relationship between chloride input and amount of zinc and alkali in dust. The figure is a graph showing the relationship between the amount of alkali remaining in the furnace, the number of unloading cine sequences, and the fuel ratio, and FIG. 4 is a graph showing the relationship between scale reduction operation and operating specifications. Patent Applicant: Nippon Steel Corporation Fan 7 Mouth 2nd Illustration Engraved (Kasuna) 3rd Illustration 4 Illustration

Claims (1)

[Claims] During blast furnace operation, when the analysis values of zinc and alkalis in blast furnace gas ash were too high, the level of blast furnace charge was reduced.
A blast furnace operating method characterized in that a CaCl2-NH4CL mixture is charged into a blast furnace to remove zinc and alkalis from inside the blast furnace.