JP2013112825A - Method for adjusting raw material for blowing in smelting-reduction furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a method for achieving a suitable form as a raw material for blowing in a smelting-reduction furnace by adjusting slurry to have appropriate constant concentration when metal powders are processed in a smelting-reduction furnace after generated in the state of slurry, dried, and granulated.SOLUTION: In the method for adjusting a raw material for blowing in a smelting-reduction furnace, metal powder-containing slurry obtained from dusts and scales generated in an iron-making factory are first received in a slurry receiving tank, then subjected to a dehydration process and then to concentration tuning in a slurry storage tank, and then dried and granulated, thereby producing the raw material for blowing in a smelting-reduction furnace, wherein the dehydration process is performed by parallel running of a wet cyclone and a centrifugal dehydrator.

Description

  The present invention dries and granulates metal powder containing slurry from steelmaking dust recovered from converter exhaust gas etc., pickling scale recovered from pickling process after steel rolling, etc. In particular, the present invention relates to a method for adjusting the concentration of the slurry to a concentration suitable for drying and granulating.

  Generally, it is known that steelmaking dust recovered from exhaust gas from a converter or the like is reused after being subjected to smelting reduction treatment in an electric furnace or the like. However, for example, in the case of an electric furnace, there is a problem that the exhaust gas recovery amount itself is small and the processing cost is high.

  In this regard, a method is also known in which metal iron-containing powder such as steelmaking dust is melted and reduced using a vertical furnace. However, steelmaking dust recovered from converter exhaust gas, pickling scale recovered from the pickling process after rolling steel, etc., are very fine and irregular, and are recovered in a slurry state. In addition, appropriate pretreatment is essential. In particular, the fine powder in the exhaust gas generated when scouring stainless steel or the like in a converter is very fine in particle size, so that the actual situation is that it must be recovered in a wet slurry state.

  Conventionally, there has been known a method of treating a slurry obtained from such steelmaking dust recovered from converter exhaust gas or pickling scale generated from a pickling process after rolling steel to obtain a raw material for a smelting reduction furnace. Yes. For example, in Patent Document 1, slurry derived from steelmaking dust is dehydrated to a constant concentration with a decanter and concentrated to a solid content concentration of about 60 mass%, and then sprayed into a high-temperature air stream using a spray dryer and dried and granulated. Thus, a method is disclosed in which physical agglomerated particles are produced and smelted and reduced as a blowing material for a smelting reduction furnace. Further, Patent Document 2 discloses a technology in which agglomerated particles derived from a steelmaking dust slurry are blown from the tuyere of a vertical smelting reduction furnace having a coke packed bed and having a two-stage tuyere, and this is smelted and reduced. Has been.

JP-A-5-311253 JP-A-5-331515

  In the case of the techniques described in Patent Documents 1 and 2, the dust (slurry 2) recovered from the exhaust gas of the converter passes through the slurry receiving tank 3 as shown in FIG. It is dehydrated by a centrifugal dehydrator 5 such as a decanter of the type to be dehydrated, adjusted to a slurry of an appropriate concentration in a slurry storage tank 6, and then sent to a spray dryer 7 to be dried by centrifugal spray drying. In this method, the pretreatment for granulating is performed, and then the pretreated particles are blown into the furnace from the upper tuyere 12a of the vertical smelting reduction furnace 12 to perform the smelting reduction process.

  The reason why such a treatment is performed prior to the smelting reduction treatment is as follows. First, the slurry generated from a converter or the like generally has a non-constant concentration. It is necessary to adjust to. However, when the metal powder-containing slurry is dehydrated using a screw decanter type centrifugal dehydrator or the like, there is a problem that the screw tip inside the centrifugal dehydrator is heavily worn and the maintenance cost of the centrifugal dehydrator is high. On the other hand, it is conceivable to remove moisture from the slurry using a pressure filtration device such as a filter press. However, steelmaking dust or the like tends to be agglomerated in the filter press. Therefore, there is no problem if it is used for a sintering raw material or the like, but it is unsuitable for processing a granulated product dried with a spray dryer in a smelting reduction furnace.

  Second, it may be possible to concentrate the slurry using a sedimentation device such as thickener, but it is difficult to stabilize the slurry concentration after treatment, and the construction of the thickener is also expensive. There's a problem.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and in particular, the metal powder generated in the slurry state is blown from the tuyere of the smelting reduction furnace after being dry granulated, and is smelted and reduced. At this time, the present invention proposes a method for easily making the slurry into a suitable form (particles) as a raw material for blowing the smelting reduction furnace by adjusting the slurry to an appropriate constant concentration.

As a method for solving the above-mentioned problems of the prior art and achieving the above object, in the present invention, first, a metal powder-containing slurry obtained from dust and scale generated in a steel factory is received in a slurry receiving tank. In the method of making the raw material for blowing the smelting reduction furnace by dehydrating and then adjusting the concentration in the slurry storage tank and then drying and granulating,
The present invention proposes a method for adjusting a raw material for blowing a smelting reduction furnace, wherein the dehydration process is performed by operating a wet cyclone and a centrifugal dehydrator in parallel.

In processing the method for adjusting the raw material for blowing the smelting reduction furnace,
(1) In the treatment with the wet cyclone during the dehydration treatment, the overslurry obtained by removing the coarse particles in the metal powder-containing slurry is returned to the dust generation source and / or the slurry receiving tank, Supplying an under slurry obtained by concentrating the coarse particles in the metal powder-containing slurry to the slurry storage tank;
(2) The metal powder-containing slurry is a mixture of a solid containing metal powder and a liquid, and the content ratio of the metal powder in the solid is 50 mass% or more,
(3) The slurry in the slurry receiving tank has a ratio of particles of 1 μm or more of 10 mass% or less.
(4) The amount of dust in the overslurry obtained by separating with the wet cyclone is obtained by separating with the wet cyclone in the concentrated slurry obtained by separating from the metal powder-containing slurry with a centrifugal dehydrator. Containing 0.5 times or more of the total amount of dust in the slurry for concentration adjustment from the under slurry and the slurry receiving tank,
(5) In the treatment with the centrifugal dehydrator, the concentrated slurry is supplied to the slurry storage tank, and at the same time, the supernatant obtained by separating from the metal powder-containing slurry is returned to the dust generation source and / or the slurry receiving tank. There is,
(6) The slurry in the slurry storage tank is mixed with the under slurry from the wet cyclone, the concentrated slurry from the centrifugal dehydrator, and the concentration adjusting slurry from the slurry receiving tank to adjust the concentration to 45 to 65 mass%. That it has been
However, it is considered to provide a more preferable problem solving means.

  According to the method of the present invention configured as described above, particularly during the pretreatment of the metal powder-containing slurry prior to the smelting reduction treatment, since the wear of the centrifugal dehydrator is reduced, the maintenance frequency and maintenance of the centrifugal dehydrator are reduced. Cost can be reduced. In addition, since the metal powder-containing slurry can be appropriately adjusted to a desired concentration, dry granulation of the metal powder-containing slurry is facilitated, and agglomerated particles (fine powder) suitable as a raw material for blowing in a smelting reduction furnace are obtained. Be able to get. As a result, the smelting reduction treatment of slurry derived from steelmaking dust can be performed at low cost.

It is a schematic diagram which shows the conventional embodiment which concentrates a slurry. It is a schematic diagram explaining an example of embodiment of this invention which concentrates a slurry. It is a contrast figure of the particle size distribution of the dust processed by the prior art example and this invention method.

  The inventors investigated the cause of severe wear of a centrifugal dehydrator used when dewatering a metal powder-containing slurry derived from steelmaking dust. As a result, a lot of metal powder is contained in coarse particles of 1 μm or more in steelmaking dust etc. in the slurry, and if the particles of 1 μm or more seem to exceed 10 mass%, the progress rate of wear is high. I found out.

  Therefore, in the present invention, the wet cyclone and the centrifugal dehydrator are operated in parallel, and at least part of the coarse particles (≧ 1 μm) of the slurry received in the slurry receiving tank from the dust generation source such as converter dust, By removing using a wet cyclone and refluxing the supernatant liquid (over slurry), the particle ratio of 1 μm or more of the dust particles in the slurry in the slurry receiving tank was reduced to 10 mass% or less. It has been found that this reduces the load on the centrifugal dehydrator, reduces the wear on the screw tip, and greatly reduces the maintenance cost of the centrifugal dehydrator.

  That is, with respect to the slurry in the slurry receiving tank, in order to reduce the particle size of 1 μm or more among the dust particles in the slurry to 10 mass% or less, the overslurry generated from the wet cyclone is refluxed and diluted. Is effective. For this purpose, the amount of dust in the overslurry is in the concentrated slurry obtained by dewatering with a centrifugal dehydrator, in the underslurry generated from the wet cyclone, and in the concentration adjusting slurry extracted from the slurry receiving tank, respectively. The total amount of dust contained is preferably 0.5 times (mass ratio) or more. The reason is that when the amount of dust in the overslurry is less than 0.5 times, the particle ratio of 1 μm or more entering the slurry receiving tank cannot be sufficiently diluted.

  On the other hand, the concentration-adjusted slurry stored in the slurry storage tank before dry granulation preferably has a concentration of 45 to 65 mass%. If the concentration (solid content concentration) of the slurry at this stage is less than 45 mass%, the concentration is too low, and it is difficult to form granular particles (aggregated particles) having an average particle diameter of about 60 μm even when properly dried with a spray dryer. . On the other hand, if the slurry concentration is too high and exceeds 65 mass%, clogging is likely to occur during processing with a spray dryer. Therefore, as the slurry concentration, it is preferable that the solid content is about 45 to 65 mass%, and the slurry is adjusted to such a concentration in the slurry storage tank and then transferred to the spray dryer of the next step. Is done.

  Next, the slurry whose concentration has been adjusted as described above is subjected to centrifugal spray drying using a centrifugal spray dryer. As a result of this treatment, the resulting dried granulated particles have a size within a particle size range of about 176 μm to 16 μm, and become granular particles having an average particle size of about 60 μm. Such particles are physically agglomerated particles that do not contain a binder and have a moisture content of less than 1 mass%. In addition, these particles have a substantially spherical shape and are very easy to handle, and can be said to be a suitable form to be blown together with hot air from the tuyeres of the smelting reduction furnace without causing clogging of the suction pipe or the hopper. . Since these physical agglomerated particles are excellent in fluidity, they are instantaneously melted when blown into a high-temperature raceway in a smelting reduction furnace and reduced in a short time in a reducing atmosphere of red hot coke. To produce metal.

  The metal powder-containing slurry mainly contains steelmaking dust (metal powder), and is a mixture of a solid substance containing the metal powder in the steelmaking dust and a liquid, and the metal in the solid substance It is effective to apply the present invention when the ratio of the powder is 50 mass% or more.

  Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to FIG. In this figure, the pre-treatment until the untreated slurry 2 containing the metal powder obtained from the dust generation source (steel mill, etc.) 1 is spray-dried with a spray dryer that is treated in a high-temperature air stream and granulated. An outline of the equipment is shown. In the figure, 3 is a slurry receiving tank, 4 is a wet cyclone, 5 is a centrifugal dehydrator (decanter), 6 is a slurry concentration adjusting storage tank (hereinafter simply referred to as “slurry storage tank”), and 7 is a spray dryer.

  Next, a method for concentrating untreated slurry containing metal powder using the equipment shown in FIG. First, the slurry in the slurry receiving tank 3 is poured into both the wet cyclone 4 and the centrifugal dehydrator 5 that are operated in parallel, and concentrated by performing each treatment.

  For example, in the dehydration treatment by the wet cyclone 4, the slurry is separated into an over slurry 8 (supernatant liquid) from which coarse particles are removed and an under slurry 9 in which the coarse particles are concentrated. While refluxing the dust generation source 1 and / or the slurry receiving tank 3, the underslurry 9 is extracted into the slurry storage tank 6 in the next step.

  The under-slurry 9 extracted from under the wet cyclone 4 is sent out toward a slurry storage tank 6 for storing the processed concentrated slurry in the next step using a general slurry extraction pump (not shown).

  On the other hand, the slurry in the slurry receiving tank 3 is also poured into a centrifugal dehydrator (decanter) 5 for dehydration. From the bottom of the centrifugal dehydrator 5, a concentrated slurry 10 having a concentrated solid content is generated, and this is extracted and stored in the slurry storage tank 6 using a slurry extraction pump.

  And in the slurry storage tank 6 into which both the under slurry 9 concentrated through the treatment of the wet cyclone 4 and the concentrated slurry 10 through the treatment of the centrifugal dehydrator 5 flow, the adjusted concentration slurry is stored. . That is, the slurry storage tank 6 preferably has a stirring function for stirring the slurry to make the slurry concentration uniform. As the agitation function, agitation methods such as agitation using an agitation blade and agitation by a circulation pump that circulates slurry inside can be applied. The stored slurry is sampled at any time to measure the solid content concentration (slurry concentration), and based on the measured value, the flow rate of the concentration adjusting slurry 13 directly sent from the slurry receiving tank 3 to the slurry storage tank 6 is controlled. Thus, the concentration-adjusted slurry described in (0014) to (0017) is stored.

  The slurry concentration at this time is measured by sampling the slurry in the tank, or using a turbidity measuring device such as an SS meter, or measuring the slurry density and showing a calibration curve indicating the relationship between concentration and density. It can be measured by using it and converting it to a concentration.

  On the other hand, the slurry in the slurry receiving tank 3 is preferably sampled periodically to measure the particle size distribution. The particle size distribution may be measured using a laser diffraction type particle size distribution measuring device or the like. The measurement frequency is, for example, once a week. The receiving tank extraction slurry 3a supplied to the centrifugal dehydrator 5 and the receiving tank supplied to the wet cyclone 4 so that the ratio of particles of 1 μm or more is 10 mass% or less. What is necessary is just to adjust the ratio of the extraction slurry 3b.

  As is clear from the above description, what is characteristic in the present invention is that the untreated slurry 2 is installed in parallel and can be operated simultaneously, that is, the wet cyclone 4 and one or more centrifuges. By operating the dehydrator 5 in parallel, the finer concentration of the slurry can be adjusted.

  The adjusted concentrated slurry in the slurry storage tank 6 is then sent to a spray drier 7 where it is dried and granulated (granulated), whereby the raw powder (granular form) for smelting reduction furnace blowing is used. ) And then blown into the upper tuyere 12a of the smelting reduction furnace 12 to perform the smelting reduction process.

  About the process of slurry concentration / drying / granulation treatment described above, each process is connected with necessary pipes, and each pipe has various on-off valves, flow meters, turbidimeters, etc. as necessary. Although these are disposed, existing ones are adopted.

Example 1
FIG. 3 shows the slurry in the slurry receiving tank in the conventional example in which the steelmaking dust slurry recovered from the converter is dehydrated only by the centrifugal dehydrator and in the invention example in which both the centrifugal dehydrator and the wet cyclone are operated in parallel and dehydrated. The particle size distributions of the particles are compared. For the particle size measurement, a Nikkiso laser diffraction particle size distribution measuring device (Microtrack) was used. The histogram shows the frequency for each particle size, and the curve shows the cumulative particle size curve.

  In the treatment in the conventional example, the ratio of particles of 1 μm or more was about 20%, but in the invention example, it was reduced to 9% by the reflux of the overslurry and the supernatant liquid and the adjustment by the concentration adjusting slurry 13. As a result, the maintenance frequency for repairing the wear of the screw tip of the centrifugal dehydrator has been once every month in the past, but every six months has become sufficient by applying the method of the present invention. In addition, the amount of dust in the overslurry for the six months is equal to the total amount of dust in the concentrated slurry obtained by separation with a centrifugal dehydrator, the underslurry obtained by separation with a wet cyclone, and the concentration adjusting slurry. On the other hand, it was 0.5 to 0.7 times.

(Example 2)
The equipment shown in FIG. 2 was used to dry-spray steelmaking dust recovered from the exhaust gas of a converter that refining stainless steel and granulate it. The slurry containing steelmaking dust was generated at 500 m ³ / day, and the solid content concentration (slurry concentration) of the untreated slurry 2 in the slurry receiving tank 3 was about 40 mass%. This untreated slurry 2 is poured into one wet cyclone 4 at 13.9 m ³ / hr and two centrifugal dehydrators 5 in 9 m ³ / hr-2 units for dehydration treatment. The under-slurry 9 and the concentrated slurry 10 generated by the treatment were extracted toward the slurry storage tank 6, and the slurry 7.6 m ³ / hr for concentration adjustment for dilution was poured from the slurry receiving tank 3 into the slurry storage tank 6.
On the other hand, the overslurry 8 was extracted from the wet sacron 4 and returned to the slurry receiving tank 3. Further, the supernatant liquid 11 was extracted from the centrifugal dehydrator 5 and refluxed to the dust generation source 1. The amount of the concentration adjusting slurry 13 was controlled based on the slurry concentration of the slurry storage tank 6 (concentration measurement by sampling). For example, a slurry extraction pump and a flow control valve (not shown) are used to finely adjust the slurry concentration in the slurry storage tank 6 so that the slurry concentrated to a predetermined concentration is supplied to the spray dryer 7. The slurry in the slurry storage tank 6 adjusted in this way had a concentration of about 56 mass%.

  With regard to the treated slurry whose concentration has been adjusted in this way, that is, the slurry in the slurry storage tank 6, a conventional example (Table 1) using only three centrifugal dehydrators 5 and a part (one) of the centrifugal dehydrators 5 are wet. Table 1 and Table 2 show the comparison of the slurry concentration, flow rate, specific gravity, and dust amount for the invention example (Table 2) used in combination with the cyclone 4 instead of the cyclone.

  Next, the concentrated treated slurry 14 was granulated by centrifugal spray drying using a spray dryer 7 to obtain granules (aggregated particles) having an average particle size of about 60 μm. This granulated product (dried granules) was blown from the upper tuyere 12a of the two-stage tuyere type smelting reduction furnace 12 filled with coke. In this vertical smelting reduction furnace 12, a coke packed bed is formed in the furnace by coke supplied from the top of the furnace, and high-temperature air sent from a hot air generator is blown into the furnace from two upper and lower tuyere. The format is The granulated product blown from the upper tuyere through the lance was melted and reduced in the furnace, descended in the furnace, and discharged from the outlet at the bottom of the furnace.

  In particular, when processing according to the method according to the present invention, compared with the processing according to the conventional method, blowing into the smelting reduction furnace can be facilitated, and at the pretreatment stage, the wear of the screw of the centrifugal dehydrator is reduced and maintenance is performed. In addition to reducing the maintenance costs, the slurry could be concentrated at a low cost.

  The above-described technique according to the present invention can be applied not only to the exemplified steelmaking (converter) dust-derived slurry but also to a scale and sludge generated from rolling and pickling processes as a dust generation source.

DESCRIPTION OF SYMBOLS 1 Dust generation source 2 Untreated slurry 3 Slurry receiving tank 3a, 3b Receiving tank extraction slurry 4 Wet cyclone 5 Centrifugal dehydrator 6 Slurry storage tank 7 Spray dryer 8 Over slurry 9 Under slurry 10 Concentrated slurry 11 Supernatant liquid 12 Melting reduction furnace 12a Melting Upper tuyere of reducing furnace 13 Concentration adjusting slurry 14 Treated slurry

Claims (7)

The metal powder-containing slurry obtained from the dust and scale generated in the steel factory is first received in the slurry receiving tank, then dehydrated, then the concentration is adjusted in the slurry storage tank, and then dried and granulated. In the method of making the raw material for smelting reduction furnace injection,
A method for adjusting a raw material for blowing a smelting reduction furnace, wherein the dehydration process is performed by operating a wet cyclone and a centrifugal dehydrator in parallel.   In the treatment with the wet cyclone during the dehydration treatment, the overslurry obtained by removing the coarse particles in the metal powder-containing slurry is returned to the dust generation source and / or slurry receiving tank, and at the same time contains the metal powder. The method for adjusting a raw material for blowing a smelting reduction furnace according to claim 1, wherein an under-slurry obtained by concentrating coarse particles in the slurry is supplied to a slurry storage tank. The metal powder-containing slurry is a mixture of a solid containing metal powder and a liquid, and the content ratio of the metal powder in the solid is 50 mass% or more. The preparation method of the raw material for smelting reduction furnace injection of description.   The method for adjusting a raw material for blowing a smelting reduction furnace according to any one of claims 1 to 3, wherein the slurry in the slurry receiving tank has a ratio of particles of 1 µm or more of 10 mass% or less.   The amount of dust in the overslurry obtained by separation with the wet cyclone is in the concentrated slurry obtained by separation from the metal powder-containing slurry with a centrifugal dehydrator, in the underslurry obtained by separation with the wet cyclone. 5 or more times the total amount of dust in the slurry for concentration adjustment from the slurry receiving tank. 5. The raw material for blowing the smelting reduction furnace according to claim 1, Adjustment method.   In the treatment with the centrifugal dehydrator, the concentrated slurry obtained by separating from the metal powder-containing slurry is supplied to the slurry storage tank, and at the same time, the supernatant liquid is returned to the dust generation source and / or the slurry receiving tank. The method for adjusting a raw material for blowing a smelting reduction furnace according to any one of claims 1 to 5.   The slurry in the slurry storage tank was adjusted to a concentration of 45 to 65 mass% by mixing the under slurry from the wet cyclone, the concentrated slurry from the centrifugal dehydrator, and the concentration adjusting slurry from the slurry receiving tank. The method for adjusting a raw material for blowing in a smelting reduction furnace according to any one of claims 1 to 6, wherein:

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