JPS59123706A - Treatment of desulfurized slag - Google Patents

Abstract

PURPOSE:To treat desulfurized lime slag and to make effective use of said slag by subjecting the slag to cooling by water spray and drying then screening the slag, subjecting the oversize to a magnetic sepn. and crushing treatment and using the treated slag together with blast furnace raw material and the undersize as a sintering raw material. CONSTITUTION:Desulfurized lime slag 2 generated in a desulfurizing stage for molten iron is taken in a molten slag pan 1, and is subjected to cooling by water spray to a satd. moisture condition. Moist slag 2' is fed out to the outdoors and is allowed to rest there so that the slag is dried to about 5-20% moisture. The dried slag is screened with a vibrating screen 3 and the oversize 2'' of 10-25mm. screen mesh is passed through a rotary drum 9 made of steel according to need whereby the slag is crushed. The crushed slag is treated with a magnetic separator 4 and a base metal 5 is recovered. The residual slag 6 of the separator 4 is passed through a crusher 7 according to need and thereafter the crushed slag is mixed with the undersize 2''' of the screen 3 and is utilized as a CaO source for a blast furnace raw material or sintering raw material 8.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a treatment method for effectively utilizing desulfurization slag generated in the desulfurization process of hot metal, and more specifically, to a method for manufacturing steel by softening hot metal in a converter. In the step immediately before the hot metal desulfurization, 1. Calcium compounds such as burnt lime are added to the hot metal, making it possible to effectively utilize the lime-based desulfurization slag generated when hot metal desulfurization is carried out. The aim is to provide a processing method for recovering the residue and utilizing the residue as a blast furnace raw material or sintering raw material.

(Prior art) A great deal of effort has been made in various fields for the treatment and effective use of blast furnace slag and converter slag, and in recent years there are prospects for their use.However, regarding the treatment and effective use of desulfurization slag No fundamental solution has been proposed yet.

JP-A-55-119137 only discloses a technique for recovering metal from soda ash desulfurization slag produced in a desulfurization process using soda ash.

The cause of this lies in the following points about lime-based desulfurization slag.

(1) Particle size distribution and chemical composition of lime-based desulfurization slag are shown in Table 1.
As shown in Figure 2, T
Difficulty in recovering active ingredients such as Fe and CaO.

Table 1 Particle size distribution and chemical composition of desulfurization slag 2 (2) Therefore, crushing and sieving are repeated, a portion of the iron content is recovered by magnetic separation, and most of the residue must be discarded.

(Object of the Invention) The present invention discloses the development results aimed at the effective use of desulfurization slag, which has been forced to be disposed of in large quantities as described above, through advantageous treatment.

(Structure of the Invention) This invention discharges lime-based desulfurization slag produced in the desulfurization process of hot metal into a slag pot, then cools it by pouring water until it reaches a moisture saturated state, and then discharges it outside to dry. The dried slag is sieved, placed on a sieve with a sieve mesh size of 10 to 25 mm, subjected to magnetic separation to recover the metal content, and then crushed and used as a sintering raw material together with the blast furnace raw material or the bottom of the sieve. It solves problems advantageously.

This invention aims to cool the molten slag discharged into the slag ladle in the above method by injecting water until it reaches a moisture saturated state, and by using this cooling process, magnetic separation of the desulfurized slag after drying is extremely effective. It originates from the discovery that things can become easier.

That is, the desulfurization slag that is discharged outdoors from the pot by using the above-mentioned water injection cooling becomes a coagulated lump or powder with a high water content, and the base metal is concentrated in the coarse particles.

Therefore, if the coarse grain portion is selected and subjected to magnetic separation, the ingots can be recovered efficiently, and the fine grain portion is advantageous in terms of processing because it contains very little ingots.

In this invention, after the above-mentioned cooling, the humid slag is dried outdoors, and the desulfurized slag that has been appropriately dried to a moisture content of about 5 to 20% is sent to the next culm sieve to the process.

If the moisture content is 5% or more in this sieving step, there will be no scattering of powder, and if the moisture content is less than 20%, the sieve will not be clogged, and the sieve material can be easily disposed of.

In addition, this sieve is used in the process as described above.
Noting that the grain part G has a high metal content, after drying, the desulfurization slag is classified into 0 to 2Q mrn culm and sieved.
) 11-grain powder (supplied as is as raw material for sintering equipment.

This sintering equipment is equipped with flue gas desulfurization equipment, so that active ingredients can be recovered without dispersing SOX into the atmosphere, and sintering productivity and quality can be improved.

On the other hand, the raw metal content is separated by coarse granulation, magnetic separation, and crushing treatment to recover the raw metal content, and the residue can be used as a raw material for sintering or a raw material for blast furnaces, together with the original fine grain content.

(Concrete example) The processing flow of desulfurization slag according to the present invention is shown in FIG. 1G.

The lime-based molten slag 2 separated and discharged from the hot metal ladle into the slag ladle 1 is cooled by completely injecting water into the slag ladle 1 until it is saturated with water (FIG. 1(a)). Moisture saturation means water-soaking, which means pouring water into the slag pot until it overflows.

After cooling, the moist slag 2' discharged to the outdoor yard is left for about a month in the sun to dry to a moisture content of 5 to 20% so that subsequent treatment is easy (Fig. 1 ('b)). .

Next, the desulfurized slag dried to a moisture content of about 5 to 20% is classified into an upper sieve portion 2' and a lower sieve portion 2'' using a vibrating sieve 3 having a mesh size of 10 to 2 Qim (FIG. 1(C)).

Slag whose moisture content is adjusted to the above range does not cause problems such as disposal or clogging of sieves.

Approximately 5 to 40% of the above sieving results in the top 2'
For this oversize, magnetic separator 4. In this example, the residue 6 is sized through a crusher 7 (Fig. 1(e)),
Lower sieve portion 2N in blast furnace raw material sieve Figure 1 (C)
It is mixed with undersize and used as a sintering raw material.

On the other hand, the sieve bottom fraction 2'', which is generated at 60 to 95%, is directly provided to the sintering raw material 8, and by making the sieve mesh the maximum particle size of the sintering raw material, a crushing culm is unnecessary.

Separation method of metal and residue in desulfurization slag G In case of trouble, the desulfurization slag that has been sieved as oversize with the vibrating sieve 3 is passed through a rotating drum 9 with fine cracks. Rotating drum 9 for sorting and collection
It is desirable to crush the residue inside the rotary drum 9, and the crushed slag from the rotating drum 9 can be passed through the magnetic separator 4 to be recovered as the bullion 5, and the residue 6 can be returned to the original sieve. (Fig. 1(d')) In this way, by disposing the rotating drum 9 between the magnetic separator 4 and the oversize of the upper sieve portion 2', it is also possible to increase the magnetic separator fraction.

Figure 2 shows an example of the results of a sintered steel test using desulfurization slag.

The desulfurization slag used as the sintering raw material is produced by preliminary treatment of hot metal for steelmaking, the chemical composition of which is shown in Table 3.
The chemical composition of the slag is shown in Table 4, and the percentage of coke addition is also listed.

Table 8 Table 4 This slag was immediately cooled by pouring water into a slag pot, and when it was left to pile up outdoors for one month, the moisture content became 7%. This dried slag is classified using a vibrating sieve with 15 mesh sizes,
The lower part of the sieve was left as is, and the upper part of the sieve was subjected to magnetic separation to recover iron (120"9/min), crushed with a crusher, and mixed with the lower part of the sieve.

These mixtures are 7.5% for the 0.8 mark in Table 4, with respect to the normal sintering raw materials used in the OL type sintering machine.
For those marked with △, the sintering pot test was conducted with the mixture so as to account for 5.0%.

As shown in Figure 2 ○ and Φ, an increase in the desulfurization slag mixing rate is due to a slight or slight decrease in the ventilation resistance before ignition expressed by the JPU index, a reduction in sintering time, and a reduction in reduced powder Improvements in drop strength (shutter value), production and yield are realized with a slight reduction in the conversion ratio RDI-3.

In this way, the method of the invention makes use of CaO in the desulfurization slag, helping to save limestone as a normal sintering raw material and blast furnace raw material. It can also significantly contribute to improving ore production efficiency.

As described above, according to the present invention, the treatment of lime-based desulfurization slag can be effectively utilized.

[Brief explanation of the drawing]

FIG. 1 is a processing flow diagram showing an embodiment of the present invention; FIG. 2 is a diagram showing the results of a sintered steel test. Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] 1. Discharge the lime-based desulfurization slag produced in the desulfurization process of hot metal into the slag ladle G, then cool it by pouring water until it reaches a moisture saturated state, then take it outside to dry, and then sieve the dried slag, A method for treating desulfurization slag, which comprises magnetically separating and crushing the upper part of a sieve having 10 to 25 mesh sizes, and providing it as a blast furnace raw material or a sintering raw material together with the lower part of the sieve.